Applied Science and Advanced Materials International

Vol. 1 Issue 1 (September – October, 2014) ISSN: 2394-3173

Editorial Advisory Board

Prof. Madhab Ranjan Panigrahi Orissa Engineering College Bhubaneswar 751 007 Dr Swaminathan Sivaram National Chemical Laboratory Dr Homi Bhabha Road Pune 411 008 Dr. Swapan Kumar Dolui Department of Chemical Sciences School of Science and Technology

Tezpur University Napaam, Sonitpur, Assam–784 028 Dr. Sabbu Thomas Mahatma Gandhi University Priyadarshini Hills, Kottayam-686560 Kerala, India Dr. Amulya Kumar Panda National Institute of Immunology JNU Complex New Delhi – 110 067

Editorial Board

Dr. Pulickel Ajayan Rice University Houston, Texas,USA Dr. Ganesh Chandra Sahoo Central Glass and Ceramic Research Institute Kolkata Dr. Dipul Kalita CSIR-North Eastern Institute of Science and Technology Jorhat, Assam

Dr. Prakash P. Wadgaonkar National Chemical Laboratory Pune Dr. Maya Nayak Orissa Engineering College Bhubaneswar Dr. Balbir Singh Kaith National Institute of Technology Jalandhar

Editor: Dr. Biranchinarayan Tosh

E.mail: bntosh.chm@oec.ac.in Fax: 0091-06758-239723 Phone: 239737; 9437560248 Website: www.oec.ac.on

Published by Dr. Biranchinarayan Tosh on behalf of Hiranya Kumar Centre for Research & Development, Orissa Engineering College, Bhubaneswar 751 007 Applied Science and Advanced Materials International is issued bimonthly by HKCR&D – OEC and assumes no responsibility for the statements and opinions advanced by the contributors. The editorial staff in the work of examining papers received for publication is assisted, in an honorary capacity, by a large number of distinguished scientists and engineers. Communications regarding contributions for publication in the journal should be addressed to the Editor, Applied Science and Advanced Materials International, Hiranya Kumar Centre for Research and Development, Orissa Engineering College, Bhubaneswar 751 007 Correspondence regarding subscriptions and advertisements should be addressed to the Sales & Distribution Officer, Hiranya Kumar Centre for Research and Development, Orissa Engineering College, Bhubaneswar 751 007 Annual Subscription: Rs 1600.00 $ 300.00* Single Copy: Rs 320.00 $ 60.00* (*Inclusive of first class mail) For inland outstation cheques, please add Rs 50.00 and for foreign cheques, please add $ 10.00. Payments in respect of subscriptions and advertisements may be sent by cheque/bank draft, payable to Hiranya Kumar Centre for Research and Development, Orissa Engineering College, Bhubaneswar 751 007. Bank charges shall be borne by subscriber. Claims for missing numbers of the journal will be allowed only if received within 3 months of the date of issue of the journal plus the time normally required for postal delivery of the journals and the claim. © 2014 Hiranya Kumar Centre for Research and Development, Orissa Engineering College, Bhubaneswar 751 007

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Published by Dr. B Tosh on behalf of HKCR&D, OEC, Bhubaneswar 751 007 and printed at Devee Printers, Nuapatna, Cuttack - 754035

Applied Science and Advanced Materials International Vol. 1 Issue 1 (September – October, 2014)

CONTENTS

Editorial 2

Papers

Novel Composite Materials from Polymeric Waste and Modified Agro-Fiber 3

Himadri Das, Dipanka Dutta, Pallav Saikia, Dipul Kalita and Tridip Goswami

Clarification of tannery wastewater from beam house operation using ceramic 12

MF membrane

Ganesh C. Sahoo, Sourja Ghosh, Swachchha Majumdar and Sibdas Bandyopadhyay

Synthesis, Structural and Electrical Properties of Cu doped ZnO nanoparticles 16

Bikramkeshari Das, Tanushree Das,KajalParashar,S.K.S.Parashar

Low Density Polyethylene/Layered Silicate Nanocomposites: Influence of 21

MAH-g-PE as Compatibiliser on the Morphology, Physical Properties and

Crystallization Characteristics.

Sanghamitra Parija

Impedance Spectroscopy Of Zn0.98Nd0.02O Ceramic By High Energy Ball Milling 28

Tanushree Das, Bikram keshari Das, Kajal Parashar, S. K. S. Parashar,

Sequence Based Prediction of Kink in Transmembrane Helices by 32

Neural Network Method

N Mishra, A Khamari, M R Panigrahi, J K Meher, M K Raval

Author Index 37

Keyword Index 38

2

Applied Science and Advanced Materials International Vol. 1 Issue 1 (September – October, 2014)

Editorial…….

It was 2007, when I had a visit to National Chemical Laboratory, Pune where I had a

fruitful discussion with the then Director, Dr. Swaminathan Sivaram to open a new branch or

carry out research work on Advanced Materials at OEC. In the same year “Hiranya Kumar

Centre for Research and Development” was established in OEC to carry out research on

different thrust areas. The earlier concept was boosted after seven years, when Dr. Madhab

Ranjan Panigrahi, Director Academic/Principal, OEC, discussed with me to publish some in-

house journals. As a result of which, OEC now comes out with two new buds, “Applied Science

and Advanced Materials International” and “International Journal of Energy, Sustainability

and Environmental Engineering”.

While writing the editorial of the first issue, I wish to express my greatest respect to all

members of the editorial advisory board, especially to Dr. S. Sivaram and Dr. M. R. Panigrahi;

all members of the editorial board, especially to Dr. Prakash P. Wadgaonkar, Dr. G. C. Sahoo

and Dr. D. Kalita, whose constant moral support guided me to place the journals before you in

the present format.

I acknowledge to all the contributors, authors, who published their papers in our journal

and respond to my mails immediately for any help during editorial work.

A scientific journal’s greatest responsibility is to ensure that all contributions accepted

for publications are rigorously, but fairly reviewed. We gratefully acknowledge the valued

support of all scientists who have reviewed papers for our journal.

We wish you a very happy Foundation Day and welcome the submission of excellent

articles for the next issue.

Biranchinarayan Tosh

Editor

Applied Science and Advanced Materials International

Vol. 1 (1), September 2014, pp. 3-11

Novel Composite Materials from Polymeric Waste and Modified Agro-Fiber

Himadri Das, Dipanka Dutta, Pallav Saikia, Dipul Kalita* &Tridip Goswami

Cellulose Pulp & Paper Division

CSIR-North East Institute of Science and Technology, Jorhat-785006, Assam, India

Received 01 August 2014; accepted 28 August 2014

Abstract In the present study, an effort has been made to develop a quality composite material using coir fibre and waste

polyethylene by improving the surface properties of coir fibre with the help of chemical treatment under controlled

conditions. Chemical constituents of untreated and treated fibre were analysed by TAPPI standard method. Structural

analyses of these fibres were carried out by FTIR, Electron microscopy, Powder-XRD and Thermogravimetric analysis.

From powder-XRD crystallinity index was found to be higher for chemically modified fiber than untreated fibers. The

characteristics properties i.e. water absorption, total swelling values of the composite board made from different chemically

treated fibers reduced drastically and the mechanical strength properties i. e. ultimate tensile strength (UTS) and modulus of

rupture (MOR) increase significantly. Surface modifications of coir fiber increased the adhesion of fiber matrix which

improves the quality characteristics properties of the composite material.

Keywords Fibers, Composite, Electron microscopy, Modulus of rupture, Coir

In recent years, the use of lignocellulosic fibres or

plant fibres as a replacement for synthetic fibre such

as carbon, aramid, glass fibres in composite and

various areas of engineering have received increasing

attention in light of the growing environmental

awareness throughout the World. The use of natural

fibres as reinforcing materials in both thermoplastic

and thermoset matrix composites provides positive

environmental benefits with respect to ultimate

disposability and best utilization of raw materials1,2

.

Most of the developing countries are very rich in

agricultural fibre and a large part of agricultural waste

is being used as a fuel. India produces more than 400

million tonnes of agricultural waste annually and has

got a very large percentage of total world production

of rice husk, jute, stalk, baggase, groundnut shell and

coconut fibre etc3. These fibres often contribute

greatly to the structural performance of the composite

when used in plastic composites, can provide

significant reinforcement3. Natural fibres are very

attractive for composite materials because of their

advantages compared to synthetic fibres as it causes

lower levels of skin irritation and respiratory

problems during handling, reducing tool wear during

the processing, good recyclability, abundant supply,

low cost, low density, high specific strength to weight

ratio, non-toxicity and biodegrability4-6

. Bio

composite from plant and wood based fibres are used

in a different range of products, including aerospace

materials, automobile industry, building materials

etc7. Plastic materials are indispensable in our

livelihood but they are an important source of

environmental pollution. In order to reduce the

environmental pollution generated from the waste

polyethylene a suitable wood substitute composite

material can be developed from the mixture of natural

fibre and polyethylene waste material. Using biomass

fibres to reinforce plastics has several advantages

over synthetic fibre. They are low cost, low density,

have a high specific strength and modulus

comparatively easy to process due to their

nonabrasive, biodegradable and environment friendly

in nature. The efficiency of the fibre reinforced

composite depends on the fibre-matrix interface and

the ability to transfer stress from the matrix to the

fibre. This stress transfer efficiency plays a dominant

Corresponding Author:

Dipul Kalita

e-mail: dipulklta@gmail.com

4 Appl Sci Adv Mater Int, September 2014

role in determining the mechanical properties of the

composite8.

Coir is an important agro-fibre extracted from the

exocarp of the fruit of coconut palm (Cocosnucifera

L.). It mainly consists of lignin and cellulose. Lignin

is the main constituent and responsible ingredient for

the stiffness of the fibre. It is also responsible partly

for the natural colour of the fibre. Coir fibres are stiff

coarse, resilient, pliable and quite resistant to

bacterial attack. These fibres are widely available in

India, Srilanka, Malaysia, Indonesia and Philippines.

The performance of coir as reinforcement in polymer

composite is not satisfactory comparable to other

natural fibre, because of its low cellulose content,

brittle nature and high microfibrillar angle9. The

efficiency of coir as a reinforcement can be induced

by enhancing the interfacial adhesion between coir

and the polymer matrix. In order to improve the

mechanical properties of these composites, chemical

treatment has been considered as a good technique to

modify the fibre surface to obtain better adhesion

between the fibre and the matrix. Rout et al. (2001)9

studied the influence of fibre treatments (alkali,

blenching, vinyl grafting) on the performance of

coconut coir polyester composites. Rahman and

Khan8 subjected coconut coir fibres to alkali

treatment 5-50% for 0.5 h at temperatures ranging

from 0-100 °C. In the present study, various chemical

treatments like alkali, hydrochloric acid, ethanol-

benzene, acetic acid treatment has been done under

different conditions, in order to improve compatibility

of coir fibres, which are polar and hydrophilic due to

the presence of hydroxyl groups with non-polar and

hydrophobic thermoplastic matrix material. The

surface modification of coir fibres improves adhesion

of fibre-matrix interfaces in a composite, which in

turn improve the mechanical properties of the

composite9-12

.

The suitability of natural fibre composite in a

certain engineering application mainly depends on the

mechanical properties of composite. Therefore, the

present study has been conducted to study the

mechanical properties and in particular the interfacial

performance of composite based on coir fibres and

waste polyethylene as matrix. Ultimate tensile

strength (UTS) and modulus of rupture (MOR) are

two of the mechanical tests that can be made to find

significant basic mechanical properties of natural

fibre composites. Surface modification of coir fibre

by chemical treatment and its effect on mechanical

properties were studied and compared with untreated

fibre.

Experimental Procedure

Materials

Coir fibres were collected from the local market of

Jorhat, Assam. The fibres were cut to a length of

0.005-0.015m. The fibres were rinsed with water to

remove dust and impurities and then boiled in 40ml

of water per 1g fibre at room temperature and also for

killing the bacteria.13

.The polyethylene begs were

collected from the household waste, segregated,

cleaned with warm water. After these processes the

fibres and waste polyethylene were rinsed in tap

water and allowed to dry under sun. The dried fibres

were subjected to various chemical treatments like

sodium hydroxide, acetic acid, hydrochloric acid,

ethanol-benzene solution. All the chemicals were

purchased from spectrochem.

Proximate chemical constituents of coir fibre, was

carried out using the analytical method suggested by

Technical Association of Pulp and Paper Industry

(TAPPI, T-21 cm-86, T-222 om-83, USA) and

standard method of biochemical analysis. The fibres

were washed, dried in oven for 6-8 h at 40±5 °C

temperatures and then powdered in a Wiley mill. The

powder was then screened with 40 and 60 BSS mesh

and the powder fraction passed through 40 BSS mesh

and retained on 60 BSS mesh was taken for different

chemical analysis.

Lignin content was determined by Technical

Association of Pulp and Paper Industry (TAPPI, T-

222 om-83) standard method. Cellulose and

hemicelluloses content was determined by Standard

Methods of Biochemical Analysis by S.R.

Thimmaiah14

.

FT-IR studies were conducted by using a Perkin-

Elmer system 2000 FT-IR Spectrophotometer.

Powder XRD diffractions were carried out on a

Rigaku, UltimaIV X-ray diffractometer from 2-80°

2θ, using CuKα source (=1.54 Ǻ). The crystallinity

index (CI) was calculated using the following

equation, where I002 is the maximum intensity of the

I002 lattice reflection and I101 is the maximum intensity

of X-ray scattering broad band, due to amorphous

region of the sample. This method was developed by

Segal et al. 1959 15

and it is widely used for the study

of natural fibres.

CI (%) = [(I002─I101)/I002] ×100

The fibre samples were characterized for their

thermal stability using a thermogravimetric analyser

(TGA), TA, SDQ600. The samples were heated from

5

Das et al.: Novel Composite Materials

20 °C to 1000 °C at a heating rate of 10 °C/min under

a nitrogen environment flow of 100 ml/min.

Scanning Electron Microscopy (SEM) images were

analysed with JSM-6360 (JEOL). Tensile strength of

five composite specimens was analysed at 25 °C and

55% RH using Universal Testing Machine (UTM)

INSTRON Make, Model 5594. Ultimate tensile

strength, maximum load, tensile modulus values were

calculated by the software Merlin software version

V22054. The values of elongation at break were

calculated using the following equation: Tensile Strength

Elongation at break (%) = × 100

Tensile Modulus

For determination of Modulus of Rupture (MOR),

3 point flexural test additional attachment was used.

The MOR was then calculated using the following

equation and expressed in MPa by Equation: 3PL

R = (MPa)

2bd2

Where,

P - Maximum load applied on the test specimen (N)

L –Support span (mm)

b - Width of specimen tested (mm)

d –Thickness of specimen tested (mm)

Treatment of Coir Fibre

Screened coir fibres were treated with15% NaOH

solution at 100 °C for 4 h, 1.5 % HCl at 65 °C for 3 h,

1:1 ethanol-benzene solution at 80 °C for 6 h and

50% acetic acid solution at 100 °C for 3 h. After the

treatments, the fibres were washed properly with

distilled water and dried under sunlight.

Composite Board Preparation

Boards were made in the laboratory using untreated

and chemically treated fibre and polyethylene waste

cuttings. Polyethylene bags (PE) of lower density

were considered for the present investigation. The

wastes PE were first screened and after removal of

dust and foreign particles, these were washed with

water, dried under sunlight and cut in a chopping

machine. The cut pieces obtained from the chopper

were mixed with coir fibre for making the boards.

The size of the particles maintained at 0.01-0.0115 m

in length and 0.005- 0.0075 m width.

Approximately 0.5 kg of coir fibre was taken and

mixed with 0.25 kg of waste polyethylene (PE) bag

cuttings. These were mixed with coir fibres in such a

way that the cut pieces were uniformly distributed all

around the fibre mass. The mixture was put into the

wooden mould size 0.3 × 0.3 m and hot pressed at

115 ± 5 °C for 20 min and at 4.903 ± 5 N/mm2

pressure. A releasing agent was spread on both sides

of the fibre mass before hot pressing. After that, the

pressure was released from the hot press and the

board was kept for some time in open air for

conditioning. The properties of the boards made from

each treated coir fibre and PE waste bag cuttings were

studied.

Results and discussion

Fibre Characterization

The surface treatment of the coir fibre was carried out

by hydrochloric acid, acetic acid, ethanol-benzene

and sodium hydroxide at different concentrations

under controlled condition.

Table 1 shows the chemical constituents of both

untreated and treated coir fibre. It has been observed

from the Table 1 that the lignin content was recorded

40% for hydrochloric acid treated fibre, while 39%,

35% and 24% recorded for acetic acid, ethanol-

benzene and sodium hydroxide treated fibre

respectively. In case of untreated fibre lignin content

was recorded 44%. The higher lignin content makes

the fibre more rigid and stiff compare to other natural

fibre. Lignin provides plant tissue and individual

fibres with compressive strength and protects the

carbohydrates from chemical and physical damage16

.

But after treatment removal of lignin decreases

rigidity and stiffens of the fibre and enhanced the

surface roughness which will ultimately help in

compatibility of fibre to bond with the polyethylene

matrix for making composites. Hemicellulose content

of untreated fibre was recorded 18%, while after

chemical treatment it was reduced to 8% in

hydrochloric acid treatment, 15% in acetic acid

treatment, 13% in ethanol-benzene treatment and 6%

after sodium hydroxide treatment. Among all the

treatments, alkali treatments remove higher

percentage of hemicellulose content and as a result

showed a greater exposure of cellulose has taken

place and thereby increase in thermal stability.

Hemicellulose is strongly bound to cellulose fibrils by

hydrogen bonds. Hemicellulosic polymers are

branched, fully amorphous and have a significantly

lower molecular weight than cellulose. Because of its

open structure containing many hydroxyl and acetyl

groups, hemicelluloses is partly soluble in water and

hygroscopic17

.

6 Appl Sci Adv Mater Int, September 2014

So also, cellulose content was recorded 36.36 %

for untreated fibre, while 36.53 %, 37.21%, 37.50%

and 38.53 % for hydrochloric acid, acetic acid,

ethanol-benzene, and sodium hydroxide treated

respectively. Presence of hydroxyl groups of the

cellulose in coir is responsible for its inherent

hydrophilic nature. Treatments were done to reduce

the number of free hydroxyl groups of cellulose. This

would result in the reduction of the polarity of

cellulose molecules and in the improvement of its

compatibility with the thermosetting matrix used in

composites18

. Among all the treatment used for

modification of surface properties of coir fibre, the

alkali treatment showed better result in terms of

quality and strength. Chemical treatment decreases

the amorphous region of the fibres resulting in the

increase in crystalline portion. Because of higher

crystallinity of cellulose improves the bonding

property as well as ultimate tensile strength.

The treatment process removed lignin,

hemicellulose and other soluble parts like wax, tannin

and other non-cellulosic polysaccharides on the

surface of the fibre and made the fibre soft to adhere

easily with the polyethylene matrix been observed.

The fibrils get separated from each other because of

lignin, the cementing component had been removed

by the action of chemical treatment, leading to an

increase of the surface area and potentially improving

the fibre-matrix adhesion in composite.

The FTIR spectra (Fig. 1) of treated and untreated

coir fibre showed a broad and intense band centring

at ~3400 cm-1

due to the hydrogen bonded O-H

stretching vibration from the cellulose. The IR band at

~2925 cm-1

for untreated fibre is assigning to -

CH2antisymmetric stretching. This band at ~2925 cm-

1 shifted to ~2900 cm

-1 for treated coir fibre with

decrease in intensity, which concluded that carbon

atoms attached to carbon or hydrogen (-C-C- or –C-

H) decrease. The untreated coir fibre also showed an

absorption band at ~1735 cm-1

due to -C=O stretching

of the carbonyl and acetyl groups in the 4-O-methyl-

glucuronoacetyl xylan component of hemicelluloses

in coir fibre. The band is disappeared for the treated

fibre indicating removal of hemicelluloses

component. The treated and untreated fibre also

showed an absorption band at ~1607 cm-1

due to

adsorbed water molecule. The intensity of this band

increased upon treatment under controlled condition.

The band at ~1510 cm-1

for untreated fibre due to

presence of aromatic rings of lignin which shifted to

~1498 cm-1

with decrease in intensity for treated fibre

indicating partial removal of the lignin. A band at

~1250 cm-1

was observed for untreated coir fibre

which may be attributed to -C-O-C- bond in the

cellulosic chain. This band shifted to ~1258 cm-1

for

treated fibre indicating the change in the bonding

environment due to dissolution of hemicelluloses

during treatment.

Fig. 1 – FT-IR spectra of untreated and treated coir fiber

The effect of chemical treatment on surface

properties of fibre was examined under scanning

electron microscopy. Fig. 2 compares SEM of

untreated and treated coir fibre. SEM image of

untreated fibres Fig. 2(a) indicate that fibre surface

was covered with a layer of substances like oils,

waxes and extractives, part of natural constituents of

fibres. This layer was also observed by Vilay et al.19

Table 1 Chemical constituents of untreated and treated coir fibre

Particulars

Untreated

(%)

HCl treated

(%)

CH3COOH

treated (%)

Alcohol-benzene

treated (%)

NaOH

treated (%)

Ash 2.00 5.00 4.00 3.00 4.00

Cellulose 36.36 36.53 37.21 37.50 38.53

Lignin 44.00 40.00 39.00 35.00 24.00

Hemicelluloses 18.00 8.00 15.00 13.00 6.00

7

Das et al.: Novel Composite Materials

in the analysis of untreated sugarcane bagasse

micrographs and by Huang Gu5 in the analysis of the

tensile behaviour of brown coir fibre. But after

treatment Fig. 2(b)-(e) showed the pits and globular

marks which reveal chemical treatments removes

extractives, waxes and oils from fibre surfaces and it

increases the overall roughness of surface. With the

removal of these substances it indicates the presence

of parenchyma cells that are the natural constituents

of lignocellulosic fibres as well as the presence of

globular protusions, which are fatty deposits called

“tylose”19

. The presence of pits and globular marks

after chemical treatment are important for an increase

in the effective surface area and higher increase of the

roughness, consequently improving mechanical

bonding with the polymer matrix 20, 21

. For untreated

condition, poor adhesion between the fibre and

polyethylene matrix leads to existence of debonding

gap around the fibre. Partial removal of lignin, silica

and pith from the fibre helped in better bonding

between fibre and matrix and improved the surface

properties of fibre.

Fig. 2 – SEM image of a) Untreated b) Acetic acid treated

c) Alcohol-benzene treated d) HCl treated and e) NaOH

treated coir fibre

The TGA curves of untreated and treated coir fibre

are shown in Fig. 3. Two prominent weight loss were

invariably found for all the fibres. One was around

30-138 °C and other is around 220-457 °C. The

lower temperature thermal peak may be accounted for

evaporation of absorbed and crystal water molecule

associated with the cellulose fibre22

. The weight loss

occurred in this stage were 7.81% for untreated fibre,

14.45% for NaOH, 10.66% for acetic acid, 10.30%

hydrochloric acid and11.20% for ethanol-benzene

treated fibre respectively. The weight loss due to

moisture was found higher for treated fibre than

untreated one because, the treated fibre contains more

pores which substantiate the finding from SEM

image. Control treatment of coir fibre leads to

removal of fatty wax materials, pectins as well as

hemicelluloses ultimately makes the fibre more

hydrophilic in nature. Therefore, moisture loss is

easier and weight loss is more compared to untreated

one. The main degradation peak occurred 220-4570C.

It has been observed that for untreated fibre the

weight loss between 221-397 °C is 50.82%, which

may be assign for degradation hemicelluloses and α-

cellulose 23

. The main degradation peak was observed

60.99% for sodium hydroxide treated, 66.10% for

acetic acid treated, 68.00% for hydrochloric acid

treated, 62.85% for ethanol benzene treated

respectively in the temperature range 227-457 °C.

The degradation temperature for treated fibres shifted

to higher temperature well over 221°C to 457 °C

compared to the untreated fibre (397 °C) indicating

the higher thermal stability of treated fibre.

Fig. 3 – TGA of untreated and treated fiber

XRD studies of different treated and untreated

fibres were carried out to investigate the crystalline

behaviour of coir fibre (Figure 4). XRD analysis

showed two main peaks representing the planes 101

and 002 at 2θ around 16° and 22.4° respectively,

characteristic of cellulose crystalline phase of the

fibre21,24,25

. Crystallinity index (CI) was calculated

8 Appl Sci Adv Mater Int, September 2014

according to Equation 1, it was found 27.16 % in

case of untreated fibre whereas, it was recorded 30.07

%, 32.5 %, 28.71 % and 33.87 %, for acetic acid,

hydrochloric acid, ethanol- benzene, sodium

hydroxide treatment respectively. The higher CI of

treated fibre than untreated one due to removal of

residual lignin increased the exposure of the cellulose,

resulting in the crystalline index. X-ray graph shows

that the chemically treated fibre peaks were more

intense than untreated fibres i.e. treatments were able

to remove part of the amorphous material covering

the fibre.

Fig. 4 – X-ray diffraction spectra of untreated and treated

coir fibre

Characterization of Composite Boards

Table 2 represents the mechanical and physical

properties of composite boards made from both

untreated and chemically treated fibre using waste

polyethylene. Mechanical strength properties of

composite board viz. ultimate tensile strength (Fig. 5)

was recorded 3.099 MPa for untreated fibrewhich

attributed to lower crystallinity and considerably high

microfibrillar angle, while 6.345 MPa for NaOH

treated fibre. The minimum tensile strength 4.304

MPa was recorded in the composite board made of

HCl treated fibre among all treatment. Tensile

strength of composites made from treated fibre has

been improved and was capable of withstanding more

strain at maximum tensile stress. Composite made of

untreated fibre showed rapid decline of tensile stress

after attaining the ultimate strength. Likewise,

ethanol-benzene and acetic acid treated fibre

composite showed similar trend. Tensile strength

property of the HCl treated fibre composite showed

less tensile strength with high ductility. The

elongation at break (Fig. 6) of composite board found

maximum prepared from NaOH treated fibre. It was

visibly pronounced when treated with NaOH,

associated with the high lignin content and

consequently with the high values of microfibrillar

angles5. The coir fibre exhibited greater improvement

of tensile strength due to removal of hemicelluloses

and impurities from the coir fibre after the fibre

treatment. Cellulose content is responsible for a

consistent increased in tensile strength and elastic

modulus without exhibiting a decrease of the

elongation to break5. Modulus of rupture (MOR)

increased leading chemical treatment under controlled

conditions (Figure 7). MOR was recorded maximum

(15.4 MPa) for composites made from sodium

hydroxide treated fibre followed by acetic acid treated

(12.35 MPa), ethanol-benzene (11.62 MPa) and

hydrochloric acid treated (11.79 MPa) fibre

composite. During the progress of compression load,

the composite were not broken suddenly at certain

point but it could sustain the maximum load with

more extension.

Mechanical properties of composites were

strongly influenced by adhesion between the matrix

and fibre. The effects of the different chemical

treatments on the surface of fibre and the adhesion

between fibres and matrix were observed by scanning

electron microscope. SEM image of fracture surface

after tensile and compression test of untreated and

treated coir fibre composite are shown in Fig. 8-9. In

the case of the untreated fibres Fig. 8(a) & 9(a), they

seem to detach from the polymer matrix and have

relatively large pull-outs compared to other treated

fibres due to the poor interfacial adhesion with the

Table 2 Mechanical and physical properties of composite boards

Sample Density

(g/mm2)

UTS (MPa) MOR( MPa)

Untreated 0.733 3.099 ± 0.130 10.83 ± 0.459

HCl treated 0.740 4.304 ± 0.132 11.79 ± 0.459

Acetic acid treated 0.742 5.158 ± 0.168 12.35 ± 0.455

Alcohol-benzene

treated

0.771 4.853 ± 0.140 11.62 ± 0.500

NaOH treated 0.914 6.345 ± 0.093 15.4 ± 0.512

9

Das et al.: Novel Composite Materials

matrix. It is due to the presence of impurities like

waxy layer over the coconut fibre causes the poor

bonding. But after treatment Fig. 8(b) & 9(b), it was

observed that the fracture surfaces are uneven matrix

cracking and less void formation takes place due to

the good laminar bond between treated coir fibre and

binding matrix.

Fig. 5 – Tensile strength properties of treated coir

polyethylene composite board

Fig. 6 – Elongation at break of untreated and treated coir

polyethylene composite board.

Fig. 7 – 3-point flexural test (MOR) of treated coir

polyethylene composite board

Fig. 8 – SEM image of fracture surface of (a) Untreated

coir fiber composites after tensile test (b) Treated coir fiber

composites after tensile test

Fig. 9 – SEM image of fracture surface of a) Untreated coir

fibre composites after compression test b) Treated coir

fibre composites after compression test

Fig. 10 – Water absorption test of untreated and treated coir

polyethylene composite board

Fig. 11 – Total swelling test of untreated and treated coir

polyethylene composite board

10 Appl Sci Adv Mater Int, September 2014

Fig. 10 and Fig. 11 depict the water absorption and

swelling properties of composites. Water absorption

value of composite board was determined by

immersing the samples in distilled water for 24 h at

room temperature, after every 24 h the composite

board was taken out and excess of water on the

surface was removed. Three replicate data were

recorded and the average results were presented. The

water absorption was found higher in the boards made

from untreated fibre (8.07 %) due to less compactness

of the composite board. SEM micrograph of the

surface of untreated and treated coconut fibre (Fig. 2)

also support this statement. Figure 2a exhibits the

SEM micrograph of the untreated single fibre surface,

which indicates that it is full of randomly distributed

organic materials, whereas after treatment, the

hemicellulose and lignin are removed and pits are

revealed on the surface of the fibre (Fig. 2b-e)9,26

.

This statement was also supported by FTIR that

shows the peak at 1735 cm-1

(-C=O stretching of the

carbonyl and acetyl groups hemicelluloses) and

disappears after treatment. The fibre after

modification shows significant changes in water

absorption. Minimum water absorption was recorded

5.89 % in the composites made from sodium

hydroxide treated fibre while the composite made

from hydrochloric acid and acetic acid treated fibre

show 6.82 % and 6.38 %. Because of treatments

coating the fibre surface, therefore decreasing the

water absorption of the composites themselves 19, 27

.

The reaction result can be seen from FTIR, which is

shown at peak ~2925 cm-1

for untreated fibre is

assigning to -CH2antisymmetric stretching. This band

at ~2925 cm-1

shifted to ~2900 cm-1

for treated coir

fibre with decrease in intensity, which concluded that

carbon atoms attached to carbon or hydrogen (-C-C-

or –C-H) decrease.The reduction of water uptake by

the composite made from sodium hydroxide treated

fibre is due to the mechanical bonding between

cellulose and polyethylene matrix at higher

temperature and higher compactness of the

composites. By replacing some of the hydroxyl

groups on the cell wall polymers with bonded

chemical groups (e.g. NaOH), hygroscopicity of the

lignocellulosic material are reduced 28

. Total swelling

value (Figure 11) due to surface absorption was

recorded 5.16 %, 2.24 %, 3.47 %, 3.45 % and 4.82 %

in untreated, sodium hydroxide, hydrochloric acid,

acetic acid and ethanol benzene treated fibre board

respectively. The swelling of the fibre caused by

water uptake, which fills gaps and enhance the

friction between the fibre and polyethylene matrix.

Untreated coir fibre boards have more void space than

treated one so that more water can absorbed and

causes swelling.

Conclusions The adhesion properties of coir fibre as such with

polyethylene material are very poor. However, these

properties can be enhanced by applying chemical

treatments to the fibre. From the above study it is

revealed that treated coir fibre is found suitable for

mixing with waste polyethylene for making

composite. Chemical treatments improve the fibre

properties which ultimately enhance mechanical

strength to the finished product. Among the

chemicals, NaOH treated coir fibre composites were

found better in all the quality characteristics.

Therefore, it can be concluded modified coir fibre

may suitably be used for development of composite

material for building and furnishing material in near

future.

Acknowledgements The authors are grateful to the Director, CSIR-North

East Institute of Science and Technology, Jorhat for

his kind permission to publish this paper. They are

also thankful to Coir Board for the financial assistant

to carry out the research work at CSIR-NEIST,

Jorhat.

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Applied Science and Advanced Materials International

Vol. 1 (1), September 2014, pp. 12 -15

Clarification of tannery wastewater from beam house operation using ceramic

MF membrane

Ganesh C. Sahoo*, Sourja Ghosh, SwachchhaMajumdar and SibdasBandyopadhyay

Ceramic Membrane Division, CSIR-Central Glass & Ceramic Research Institute

196 Raja S. C. Mullick Road, Jadavpur, Kolkata 700032

Received16 August 2014; accepted 30 August 2014

Abstract Clarification study of sectional stream and composite effluent from beam house operation of tannery

industry was carried out using tubular ceramic membrane following cross-flow membrane filtration (CMF) technique.

In order to minimize the interaction between foulants and membrane layer, composite effluent was also pretreated and

membrane filtered using the same technique. Two types of pretreatment viz gravity settling and chemical treatment

under optimized dose followed by gravity settling were studied. Sectional stream, composite effluent and pretreated

supernatants were analyzed before and after membrane filtration study. Zirconia and alumina coated membrane over

low-cost clay-alumina based membrane support were used. Physical properties of the elements were also determined.

Membrane flux varied from 25 to 350 l/m2h depending on the feed turbidity and membrane type at 1.2 bar, and

permeate turbidity down to 1 NTU was achieved with 99% removal.

Keywords Tannery wastewater, beam house, pretreatment, cross-flow membrane filtration, tubular ceramic

membrane, flux, turbidity.

Processing of leather in tannery industry generates

wastewater at various stages like soaking, bating,

liming, deliming, pickling, skin degreasing, tanning

etc. are called ‘Beam House’ operation. Effluent

contains two types of contaminants viz. chemical

contaminants like sodium chloride, sodium

sulphide, lime, chromium etc. and organic matters

like, proteins, fats, coloring compounds etc. with

high biological and chemical oxygen demand.

Developments are being carried out to reduce water

consumption during the leather processing, adopt

green process without toxic chemicals and recovery

and reuse of wastewater.

Existing treatment processes include treatment

of effluent with the chemicals like sodium

hydroxide, magnesium oxide, etc, which results a

sludge and liquor. In the common effluent treatment

plant (CETP), the effluent generated from different

sectional streams are mixed and subjected to

primary, secondary and tertiary treatment steps to

recover and reuse of tannery wastewater.

Microfiltration (MF), ultrafiltration (UF),

nanofiltration (NF) and reverse osmosis (RO)

membranes have been used for clarification of

various effluent streams of the ‘beam house’ have

been examined extensively1. Application of UF and

RO for treatment of effluents from liming,

degreasing2,3

, soaking, bating and pickling1 steps

has been reported. CSIR-CGCRI, Kolkata have

been working on development of low-cost clay-

alumina based ceramic membranes, their

characterization and application for wastewater

treatment4-8

. Porous ceramic membranes have

excellent chemical resistance, operable at higher

temperature, stability to organic solvents, are

expected to be used in the separation and filtration

of both aqueous and non-aqueous solutions9-15

.

Objective of the present study is clarification of

sectional stream and composite effluent from ‘beam

house’ operation using tubular ceramic membrane

following cross-flow membrane filtration (CMF)

technique. Minimization of membrane fouling by

pretreatment of effluentwas also carried out. Two

types of pretreatment were studied viz. gravity

settling and chemical treatment under optimized

dose followed by gravity settling.

Corresponding Author:

Ganesh C. Sahoo

e-mail: gcsahoo07@gmail.com

13 Sahoo et al.: Clarification of Tannery Waste Water

Experimental Procedure Physical properties of 200 mm long ceramic

elements were determined using buoyancy method

(Table 1). Waste water from various tannery

operations and membrane permeate samples were

characterized w.r.t. turbidity (NTU), total dissolved

solid (TDS), pH and conductivity (mS/cm) using

Turbidity Meter and Multiparameter, HACH Co.,

USA (Table 2). Composite sample (CTE) was

prepared by mixing 4-sectionalstreams viz. 1st

soaking, 2nd

soaking, 3rd

soaking and liming at a

fixed volume ratio (2:2:2:1.5). Pretreatment

condition of CTE was optimized. Pretreatment of

composite sample was done by gravity settling for

24 hours of raw effluent and chemical treatment

followed by gravity settling for 24 hours.

Optimization of chemical pretreatment of composite

sample was done on the basis of lowering of

supernatant turbidity by varying coagulant dose at a

fixed flocculent concentration (1.0 ml/l). CMF

study was carried out at variable transmembrane

pressure (TMP) and at constant transmembrane

pressure of 1.2 bar for two hrs. A feed of 40 l batch

of 4-sectional streams was treated using 19-channel

ceramic membrane. Clarification study of CTE and

supernatants of composite samples (SCTE) using

single-channelsupport, alumina and zirconia coated

membranes was donefor 10 L batch.

Results & Discussion

Properties of sectional streams, composite effluent

and pretreated effluents are given in Table-2.

Particle size distribution study shows that average

particle size ranges from 0.1 to 90 m (Fig. 1) can

be separated using microfiltration membrane.

Microfiltration of sectional streams of 40 l batch in

bench scale unit using 19-channel ceramic element

showed that permeate flux (70 – 170 l/m2h, LMH)

and turbidity were varied according to feed turbidity

and permeate turbidity down to 16 NTU was

achieved at 1.2 bar TMP from feed of 150 NTU

(Fig. 2). Apparent porosity of single Channel

elements are higher compare to 19-channel element

as shown in Table 1.

Table 1Properties of Ceramic Elements.

Properties 19-channel

element

Single channel

element

Zirconia coated

membrane

Alumina coated

membrane

Outer diameter (mm) 35 36 36 36

Channel diameter (mm) 4.2 29 29 28

Tube length (mm) 200 200 200 200

Dry weight (g) 313.4 160.6 162.3 163.8

Bulk density (g/cc) 2.4 2.1 2.2 2.1

Apparent porosity (%) 23 36.1 36.8 37.7

Water absorption (%) 9.6 17.0 17.1 17.9

Table 2 Properties of sectional streams and composite of beam house operation.

Properties Sectional Stream Composite (2:2:2:1.5)

First

Soaking

Second

Soaking

Third

Soaking Liming

As such

Pretreated

Settling Chemical

treatment &

settling

Turbidity (NTU) 553 146 112 6,000 1241 160 30.2

TDS (g/l) 48.4 33.7 8.1 18.3 13.3 14.0 16.4

pH 6.7 7.8 7.6 12.5 7.5 8.4 7.1

Conductivity (mS/cm) 74.0 6.8 15.1 29.6 30.2 29.4 27.7

DO (ppm) 8.6 8.5 10.9 7.6 --- --- ---

BOD (g/l) - 2.3 - 6.1 --- --- ---

COD (g/l) - 0.8 - 4.5 --- --- ---

Av. Particle size (m) 9.9 24.8 89.6 0.1 6.3 --- ---

14 Appl Sci Adv Mater Int, September 2014

Fig. 1 Particle size distribution of tannery wastewater

samples collected from different stages of operation

using Zetasizer Nano-S (Malvern, UK).

Fig. 2 Membrane flux comparison with feed turbidity for

different sectional stream using 19-channel ceramic MF

membrane.

Crossflow membrane filtration of composite sample

for 10 l batch showed similar membrane flux of 80

LMH at 1.2 bar TMP at the initial stage using

single-channel membranes, but it came down to ~

45 LMH within 1.5 hrs of filtration may be due to

membrane fouling (Fig. – 3). Performance of

zirconia coated membrane element was found to be

better w. r. t. flux and turbidity removal (98%) as

shown in the Fig. - 3.

Fig. 3 Change in permeate flux and turbidity through

various single channel tubular ceramic elements at 1.2

bar TMP using lab unit.

Optimization of chemical pretreatment of

composite sample was performed by measuring the

turbidity of supernatant with varying coagulant dose

at a fixed flocculent concentration (1.0 ml/l).

Supernatant turbidity obtained was minimum (~25

NTU) for coagulant dose of 1.0 g/l as shown in

figure 4. Turbidity down to 30 NTU was achieved

at optimized chemical doses.

Fig. 4 Variation of turbidity in supernatant with variation

of coagulant dose.

Settling velocity (cm/s) was calculated (cm/s)

and plotted against time (hr) up to 40 hrs as shown

in fig. 5. The result shows that settling occurred

within 4 hrs under optimized doses of coagulant and

flocculant.

Fig. 5 Compression of settled mass with time during

coagulation of the composite tannery effluent.

Fig. 6 Variation of permeate flux and turbidity with time

of composite tannery effluent obtained after various

pretreatment through alumina coated ceramic membrane

at 1.2 bar TMP using lab unit.

15 Sahoo et al.: Clarification of Tannery Waste Water

Alumina coated membrane provided comparable

flux (25 LMH at 1.2 bar TMP) using composite

sample and gravity settled supernatant of composite

sample, and much higher flux (350 LMH at 1.2

bar TMP) using chemically treated supernatant

while permeate turbidity down to 1 NTU was

achieved using both type of pretreatment methods

as shown in Fig. 6.

Conclusion

Pretreatment of composite effluent from beam

house operation may be an alternative method of

clarification using ceramic membrane from the

points of turbidity removal and permeate

throughput. Membrane permeate of sectional stream

may be recycled after addition of balanced amount

of chemical to the same operation or to the

operation using similar chemicals. Solid waste

generated may be used as wealth such as fertilizer,

adsorbent preparation etc.

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February 12-13, 2004.

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Applied Science and Advanced Materials International

Vol. 1 (1), September 2014, pp. 16-20

Synthesis,Structural and Electrical Properties of Cu doped ZnO nanoparticles

Bikramkeshari Das*, Tanushree Das,KajalParashar,S.K.S.Parashar

Nano Sensor Lab, School of Applied Sciences, KIIT University, Bhubaneswar-751024,Odisha, India.

Received 21 August 2014; accepted 3September 2014

Abstract Single phaseZn0.99Cu0.01O ceramic nanopowder was successfully synthesized by solid state reaction

technique. X-ray diffraction studies of synthesized powder reveals single phase, hexagonal wurtzite structure and

belongs to space group of p63mc. No secondary peak in the XRD pattern shows the incorporation of Cu2+

ion into the

ZnO lattice rather than the interstitial one. Compare with pure ZnO(50nm),the average crystallite size of Zn0.99Cu0.01O

(55nm) is higher. The substitution of Cu in ZnO results in contraction of the atoms. Electrical properties of the material

has been studied by using Impedance Spectroscopy in the frequency range100Hz-1MHz and temperature range (3000c-

5000c) follow non-Debye relaxation process. The ac conductivity of Zn0.99Cu0.01O . lesser than ZnO which follow

universal power law s

dcac A within frequency range 1kHz to 1MHz.

Keywords XRD, Impedance Spectroscopy, Zn 0.99Cu0.01O , ac conductivity

ZnO is a well known of the II–VI compound

semiconductor which has a large direct band gap of

3.37 eV and high exciton binding energy of 60

meV, excellent chemical and thermal stability1-3

. It

has a stable wurtzite structure with lattice spacing a

= 0.325 nm and c = 0.521 nm and composed of a

number of alternating planes with tetrahedrally co-

ordinated O2-

and Zn2+

ions, stacked alternately

along the c-axis4. Furthermore, ZnO semiconductor

material has generated a lot of interest among

researchers and technologists for device

applications. For its unique properties, low cost and

environmental friendliness5 and optical properties

can be tuned by quantum confinement effects at

nano sizes6. Thus, zinc oxide can be a promising

candidate for novel applications such as UV

detectors7, field emission devices

8, high sensitivity

gas sensors9,biosensors

10,dye-sensitized solar

cells11

, photoluminescent materials12

, photocatalytic

degradation of pollutants13

and antibacterial

purposes14

,piezoelectric devices and spintronics4

These important properties make ZnO has a great

potential in the field of nanotechnology. Nano zinc

oxide is non-toxic, with wide band gap has also

been identified as a promising semiconductor

material for exhibiting ferromagnetism (RTFM) at

room temperature when doped with most of the

transition metal elements15

. Properties of ZnO can

be tuned, by doping with various metal atoms to suit

specific needs and applications16

. Doping is a

widely used means to tailor the band structures of

bulk semiconductors, facilitating the construction of

various devices essential for the development of

microelectronics17

.The metal doping induces drastic

changes in optical, electrical and magnetic

properties of ZnO by altering its electronic

structure. Many authors have reported the changes

induced by incorporation of transition metal ions

into ZnO lattice18-20

.Some reports addressed room-

temperature ferromagn- etic behaviour of transition

metal[Fe, Mn, Ni, Co, Cr] doped semiconductor

oxides,20-22

and the behaviour of ferromagnetism is

caused mainly by intrinsic defects or impurity

phases or ferromagnetic precipitates23-

24.Substitution of copper into the ZnO lattice has

shown to improve properties such as photocatalytic

activity, gas sensitivity and magnetic semi

conductivity25-28

. Copper doped zinc oxide

Zn0.95Fe0.03Cu0.02O was found to exhibit

ferromagnetic performance at room temperature 29

.But this Cu incorporation reduced the saturation

magnetization of Fe doped ZnO magnetic

semiconductors. Photoluminescence (PL) of Cu

doped ZnO nanocrystals were found to show

pronounced UV emission and negligible visible

emission with peak positions coinciding with that of

Corresponding Author:

Bikramkeshari Das

e-mail:vdmscchem@yahoo.co.in

17 Das et al.: Synthesis, Structural and Electrical Properties

undopedZnO30

. Among transition metals,Cu is an

especially interesting dopant because that Cu-

related compounds are not strongly ferromagnetic.

Recently, a few research groups have synthesized

and studied the physical properties of Zn1−xCuxO

thin films31-35

. Several methods are available for the

synthesis of ZnO nanoparticles,such as a chemical

or physical method37

hydrothermal process38

sol−gel

method39

and co-precipitation method40

.However,

there are still much less report on Cu doped ZnO36

.

Owing to the importance of Cu doped ZnO

nanoparticlecs, the current study involves the

analysis of phase, structure and electrical properties

of Zn1-xCuxO with x = 0, 0.01 by solid state reaction

route.

Experimental procedure Cu doped ZnO ceramic powder abbreviated as

Zn0.99Cu0.01O was prepared by using a simple solid

state reaction technique. High purity precursor ZnO

and CuO were weighted according to their atomic

ratio, used as a raw material to achieve the desired

product .The sample was prepared by thoroughly

grinding these powders in an agate mortar and was

calcined at 8500C for 2hr with a heating rate of

20C/min using air atmosphere. The calcined powder

was mixed with PVA which act as a binder to make

pellet at a pressure of 437Mpa using hydraulic

press. Finally,the pellet was sintered at 10000C for

2hr in air atmosphere and was coated with silver

paste on both sides heated at 7000C for 15 minute.

Crystal structure,phase identification and unit

cell parameters of Zn0.99Cu0.01O was investigated by

using XRD. The electrical properties were analysed

by using a computer cotrolled analyzer (Hioki LCR

Hi-tester-3532-50) as a function of temperature,(30

– 5000C) over a wide range of frequency ( 100Hz-

1MHz).

Result and Discussion

Structural Analysis Fig. 1 illustrates the XRD patterns of ZnO and

Zn0.99Cu0.01O ceramic nanopowder calcined at

8500C for 2hr.The XRD patterns of

Zn0.99Cu0.01Oshows the reflection planes indexed to

wurtzite hcp structure of ZnO(space group of

p63mc, JCPDS:36-1451).No extra peak in the

pattern shows the formation of single phase5. This

indicates that Cu2+

ion successfully occupy the

lattice site rather than interstitial one. This is due to

the fact that ionic radius of Cu2+

(0.73Å) is very

close to that of Zn2+

(0.74Å),due to which Cu can

easily penetrate into ZnO crystal lattice17

.

Fig. 1 (a)X-ray diffraction patterns of ZnO and

Zn0.99Cu0.01O nanoparticles; (b) Rietveld refinement plot

of ZnO; (c)Zn 0.99 Cu0.01 O nanoparticle

18 Appl Sci Adv Mater Int, September 2014

The average crystallite size has been estimated by

Debye-Scherrer equation17

d=0.9λ/βcosθ

Where d is the average crystallite size, λ is the

wavelength of the incident X-ray beam, θ is the

Braggs diffraction angle and β is the angular width

of the diffraction peak at the half-maximum in

radians on 2θ scale.The average crystallite sizes of

the samples havebeen found to be 50nm(ZnO) and

55nm(Zn0.99Cu0.01O) respectively.

The Lattice parameters are calculated by

Rietveld refinement using Maud software. For ZnO

the values are a=3.2493Å, c=5.2056Å and

microstrain=35.4 x 10-4

and for Zn0.99Cu0.01O the

values are, a=3.2504Å,c=5.2060Å, microstrain =

81.03 x 10-4

respectively. From Fig-1(c),it can be

seen that the fit between observed and calculated

profiles is very good inZn0.99Cu0.01O which

indicates that Cu occupying Zn sites confirms that

Cu is indeed substituting Zn in the formation of

Zn0.99Cu0.01O41

.It is observed from a-value that the

base atoms along X and Y axis lies closer to each

other in ZnO then Zn0.99Cu0.01O and also from c-

value there is a elongation of base atom along Z-

axis of Zn0.99Cu0.01O then pure ZnO.

Impedance Analysis Complex impedance spectroscopy(CIS) is anon-

destructive method to study the microstructure and

electrical properties of solids. It is a powerful

technique for the characterization of grain and grain

boundaries in ceramics42

. Measurement of

impedance parameter helps in the identification of

various electrical parameters appropriate for the

system43

. Polycrystalline materials usually shows

both grain and grainboundary effects with different

time constants, leading to two successive

semicircles43

. The semicircular pattern in the

impedance spectrum is representative of electrical

process taking place in the material which can be

thought of as resulting from the cascanding effect

of a parallel combination of resistive and

capacitance elements arising due to the bulk

properties of the material and the grainboundary

effects. The high frequency semicircle is due to the

bulk property of the material and the low frequency

semicircle to be due to grain boundary effects42

.

Fig2 shows the variation of real part of impedance

Z' with frequency, imaginary part of impedance

with Z" with frequency and real part w.r.t.

imaginary part ( Z' vs Z'') at different temperature

(3000c-500

0c) in ZnO and Zn0.99Cu0.01O.

From Fig. 2, it can be shown that, for both the

sample, the magnitude of Z' decreases with increase

in temperature, indicating increase in ac

conductivity, further at law frequencies the value of

Z' decreases with rise in temperature, showing

negative temperature co-efficient of resistance

(NTCR) effect45

. The value of Z' for all temperature

may merge after1MHz for Zn0.99Cu0.01O due to the

release of space charge45

.

The plot of imaginary part of impedance Z'' with

frequency shows the Z'' peak shifts to the higher

frequencies with increasing temperature and

existing of peak broadening indicating the

relaxation process in the system43

. The relaxation

species may possibly be electrons at low

temperature and defects at high temperature43

.

From Z' Vs Z'' it was observed that Zn0.99Cu0.01O

follow the non-Debye relaxation phenomena, ZnO

it does not have any clear semicircular arcs at

different temperature. The semicircular arcs are

generated during the temperature interval between

3000C – 375

0C indicates the major contribution of

grain boundary resistance. Again the magnitude of

semicircular arc decreases with increase in

temperature for both ZnO and Zn0.99Cu0.01O

indicates temperature dependant nature.

Fig. 2 CIS plots ofZnO and Zn0.99Cu0.01Onanoarticles

19 Das et al.: Synthesis, Structural and Electrical Properties

AC Conductivity The variation of AC Conductivity as a function of

temperature(1kHz-1MHz) at a temperature range

3000C – 500

0Cfor ZnO and Zn0.99Cu0.01O is shown

in Fig 3. The conductivity is found to be frequency

independent in low frequency regions and is

illustrated as dc conductivity.AC conductivity

measurement is an important tool for studying the

transport properties of materials45

. The frequency

dependent AC conductivity can be described by

Jonscher's power law as follows45

.

s

dcac A

Where n is a frequency exponent in the range 0

and 1

σdc is temperature dependent dc conductivity

related to the drift mobility of the charge carrier A

is a temperature dependent constant.

The AC conductivity value increases with

increase in temperature indicates the electrical

conduction in the material. The electrical

conduction in the sample is a thermally activated

process result by the release of space charge.

Further, one more possible reason is the native point

defects in ZnO(oxygen and zinc interstial)46

.The

increasing conductivity w.r.t temperature indicates

the negative temperature co-efficient of

resistance(NTCR). From graph it was found that

AC conductivity decreases with Cu doping to ZnO.

Conclusion Zn0.99Cu0.01O polycrystalline nanopowder was

synthesized by solid state reaction method.The

incorporation of Cu2+

ion into ZnO lattice rather

than the interstitial was observed from XRD

analysis. Contraction of base atom along all axis

was observed from Rietveld analysis.CIS plot of

Cu2+

doped ZnO shows relaxation phenomena in the

material.Increasing AC conductivity in ZnO

thanZn0.99Cu0.01O was observed due to release of

space charge and native point defect in ZnO.

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100 1000 10000 100000

0.0

5.0x10-2

1.0x10-1

1.5x10-1

2.0x10-1

2.5x10-1

ZnO

300 0C 325

0C

350 0C 375

0C

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(ac

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AC

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(ac

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100 1000 10000 100000

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20 Appl Sci Adv Mater Int, September 2014

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Applied Science and Advanced Materials International

Vol. 1 (1), September 2014, pp. 21-27

Low Density Polyethylene/Layered Silicate Nanocomposites: Influence of MAH-g-

PE as Compatibiliser on the Morphology, Physical Properties and Crystallization

Characteristics.

Sanghamitra Parija

Templecity Institute of Technology & Engineering, F-II, Knowledge campus, Khordha-752057

Received 11 August 2014; accepted 25 August 2014

Abstract In the present investigation nanocomposites have been prepared from the LDPE, octa decyl amine modified

montmorillonite (Nanomer 1.30P grade) and maleic anhydride grafted polyethylene (EpoleneE-142 ) as reinforcement and

compatibiliser. LDPE along with three different nanomer loading (1,3 and 5 wt %) were melt intercalated with and without

compatibiliser. Different material properties i.e. melt behavior, mechanical properties and thermal characteristics were

assessed and compared with the virgin polymer. The TEM analysis of the uncompatibilised and compatibilised hybrids was

carried out to evaluate the clay dispersion in the resulted hybrids. It is observed that the nanomer addition leads to decrease

in MFI and shear rate with increase in viscosity of base polymer. The nanocomposites show improved mechanical

properties as compared to the virgin polymer. However, the elongation at break decreased significantly with the increased

addition of nanomer. Experimental findings revealed that MAH-g-PE being used as a compoatibiliser is instrumental in the

property enhancement of the resulted hybrids. Compatibilised LDPE/layered silicate hybrid showed improved thermal

stability and crystallization characteristics as compared to the base polymer.

Key words Montmorillonite, Viscosity, E-142, intercalation, Nanocomposites, Compatibiliser,

The polymer melt intercalation of mica type layered

silicate is a viable approach to the synthesis of a

variety of polymer/layered silicate

nanocomposites1-5

. Since 1996 the preparation of

intercalated nanocomposites without in situ

intercalative polymerization became the mainstream

of the nanotechnology after being reported by

Giannelis and co workers6,7

. The melt intercalation

involves mixing the layered silicate with the base

polymer above its softening temperature. Interest in

polyolefin nanocomposites has gained a large

momentum due to their promise of improved

performance in packaging applications8-12

. The

polyolefin nanocomposites preparation by melt

compounding is considerably more difficult due to

the weak interaction between the mineral surface

and the low energy material i.e. polyolefin.

Grafting of pendant anhydride groups has been used

successfully for the chemical modification of these

resins to overcome the poor phase adhesion in

polyolefin/clay systems. The role of maleated

polyolefin in preparation of polyolefin-based

nanocomposites has already been well described by

various researchers 13-23.

As low-density polyethylene found rapid

acceptance because of its high toughness, tensile

strength, puncture resistance and elongation at break

it can be used as base polymer for nanocomposites

preparation. In this communication nanocomposites

from LDPE and organophilic montmorillonite

(Nanomer 1.30P) were prepared by implementing

melt intercalation technique. Comparative accounts of

the melt flow characteristics; mechanical properties &

analytical characterization of the virgin and resulted

hybrids were carried out. The influence of epolene-

C16 (maleic anhydride grafted PE) as compatibiliser

on the mechanical performance, thermal

Corresponding Author:

Sanghamitra Parija

e-mail: drsparija@gmail.com

22 Appl Sci Adv Mater Int, September 2014

characteristics and melt behavior of nanocomposites

were also evaluated.

Experimental Procedure

Materials

Low density polyethylene (Grade: with MFI 4.0 and

density 0.925 gm/cc from IPCL Ltd. (India) was used

as base polymer for the study.

Octa- decyl amine modified montmorillonite

(Nanomer -1.30P) with specific gravity 1.7g/cm3, 70-

75% montmorillonite clay and 25-30% octa -decyl

amine obtained from Nanocor Inc. U.S.A., was used

as reinforcing filler.

Maleic anhydride (MA) grafted Polyethylene (E-

142) with <1wt% MA content, acid number 5 and

Mw = 16,000 obtained from Eastman Chemicals Co.,

Germany was used as compatibiliser without further

modification.

Nanocomposite Preparation

Nanomer was kept in vacuum oven at 80°C for 2 h in

order to remove the absorbed moisture. The

nanocomposites samples were prepared in two stages.

At the first stage different LDPE/layered silicate

hybrids were prepared by melt compounding

technique taking three different weight percentage of

nanomer (1,3 and 5%), pre-weighed quantity of

LDPE with and without compatibiliser. Melt

intercalation was done at 50rpm rotor speed by using

torque rheometer (Haake Rheocord 9000,Germany)

having sigma roller rotors blades and a chamber size

of 69 cm3

volumetric capacities. The compounding

temperature was 160°C for a period of 15 min in all

the cases.

Subsequently these premixes were brought to

room temperature and separately molded by

compression molding using a 100T press, Delta

Malikson, India, for 10 minutes at 160°C with

molding tonnage of 10T to produce sheets of 3±

0.1mm thickness. Virgin LLDPE was compression

moulded under similar conditions of temperature for

comparison of mechanical properties. A Counter cut-

Copy milling machine 6490(CEAST, Italy) was used

for the preparation of test specimens from the sheets

as per ASTM-D-638, 790 and 256 using calibrated

templates24

.

Melt Flow Characteristics

The melt behavior of the nanocomposites as well as

virgin polymer was studied by melt flow index tests

using MFI tester (CEAST, Italy) as per the ASTM-D-

123824

. The molten sample was allowed to flow

through a standard die (2.095 mm diameter, length

8mm) keeping the temperature at 190°C and load 2.16

Kg. The MFI, shear rate and viscosity of the samples

were measured at a constant shear stress

Mechanical Property Evaluation

The specimens were prepared and subjected to the

influence of standard laboratory temperature of 23±1°

and relative humidity of 55±2% for 24 hours to bring

the materials into equilibrium before testing as per

ASTM- D-61824

to analyze various mechanical

properties with testing condition of 23± 1°C and

55±2% RH.

Tensile Properties

Specimens of virgin LLDPE, uncompatibilised and

compatibilised nanocomposites having dimensions

165x12.7x3mm were subjected to tensile tests as per

ASTM-D-63824

using universal testing machine

(UTM), LR-100K (Lloyd Instruments Ltd, U. K.) at

100 mm/min crosshead speed and 50mm gauge

length.

Flexural Modulus

The specimens of virgin, uncompatibilised and

compatibilised hybrids with 80 X 12.7 X 3mm

dimensions were subjected to flexural testing as per

ASTM-D-790 under three point bending using

universal testing machine (UTM) LR 100K Lloyds

Instruments Ltd. UK. The tests were carried out with

span length of 50mm and crosshead speed of

1.3mm/min.

Impact Strength

The izod impact strength of the nanocomposites and

virgin LLDPE was determined from the specimen

having dimensions 63.5X12.7X3mm with a V notch

with notch depth of 2.54mm and notch angle of 45° as

per ASTM-D- 256 by using Impactometer 6545

(CEAST, Italy).

Each mechanical data reported was the average of

five tests of the same specimen.

Thermal Characteristics Measurement

Differential Scanning Calorimetric (DSC) Analysis

Melting and isothermal crystallization behavior of the

nanocomposites and virgin LDPE were carried out by

differential scanning calorimeter (DSC, Perkin Elmer-

Pyris-6- USA). Samples with <5mg weight was

heated for the non-isothermal changes the samples

23 Parija S: Low Density Polyethylene/Layered Silicate Nanocomposites

from 50 to 225°C at the rate of 10°C/min under

nitrogen atmosphere. For isothermal change the

sample was kept at 225°C for 5 minutes in order to

remove the thermal history and then subjected to

cooling to 50°C at the rate of -10°C/min for the

crystallization temperature. For isothermal change the

samples were kept at 50°C for 5 minutes and then

heated up to 225°C for the melting point.

Thermo Gravimetric Analysis (TGA)

The TGA analysis of nanocomposites and virgin

polymer was studied in order to analyze the effect of

nanomer and compatibiliser on the thermal stability of

the base polymer by using a thermo gravimetric

analyzer (Mettle 4000). The samples of <10mg

weight were heated from 50°C to 600°C at the rate of

20°C/minutes under a protective nitrogen atmosphere.

The weight loss percentage was measured and

compared with the virgin polymer.

Nanocomposite Microstructure

Nanocomposite microstructure was investigated by

transmission electron microscopy using TEM –

Philips CM-20. Specimens of 75nm were cut from the

middle section of a compression-molded bar by using

a reichert microtome under cryogenic conditions and

then the film was retrieved onto Cu grids.

Results and Discussion

Melt behavior

The MFI, shear rate and viscosity data of the

LDPE/Clay nanocomposites and virgin polymer were

showed a decreased MFI and shear rate with

increased viscosity along with the increase in

nanoclay addition. The increase in viscosity is

attributed to the added nanoclay, a particulate filler

leading to the confinement of the polymer chains

those intruded in to the inter layer galleries of the

layered silicates

thereby affecting the flow

characteristics of the base polymer25

. Experimental

findings revealed that the melt behavior of the

resulted hybrids was not changed appreciably by the

addition of nanomer thereby unaffecting the

processibility of the base polymer.

The compatibilised nanocomposites showed

increased shear rate with decreased viscosity as

compared to the uncompatibilised one. The decrease

in viscosity is observed due to the increasing amount

of MAH-g-PE in the compatibilised LDPE/clay

hybrids containing low molecular weight oligomeric

fraction thereby increasing the flow of the LDPE.

Mechanical Properties

Tensile Properties

The tensile properties of the nanocomposites were

illustrated in Fig 1. It is well observed that the

nanocomposites show improved strength and modulus

values with reduced elongation at break than the

virgin LDPE. However, the strength and modulus of

the LDPE/ Clay hybrid has been increased up to 3%

nanomer loading (13.72%, 5.17% for 1% and

43.85%, 10.01 increment in tensile strength and

tensile modulus respectively for 3%) then decreased

for further increasing the clay loading to 5% (38.55 &

0.0% increment in tensile strength and modulus

respectively). The increment in strength and modulus

is attributable to the reinforcing and toughening

characteristics of dispersed nanolayers with high

aspect ratio. With large number of reinforcing

nanoclay platelets present in the polymer matrix

which act as efficient stress transfer agents in

nanocomposites induce plastic deformation into the

host polymer. It is expected that the macromolecules

contacted to the solid silica would have different

responses from those matrix because of the

mechanical displacement resulting from elongation,

which is responsible for the increased modulus of

nanocomposites26

. For higher percent clay loadings

corresponding strength and modulus of the hybrids

started to decrease mainly because of the

agglomeration of clay particles27,28

.

Fig. 1 Effect of nanomer loading on modulus of elasticity

of nanocomposites

Compatibilised nanocomposites showed linear

improvement in tensile modulus than the

uncompatibilised one (Fig. 2) up to 2% compatibiliser

loading and thereafter decreased drastically with

increase in epolene loading. The improvement is

attributable to the reinforcing effect of intercalated

nanolayers achieved through strong hydrogen

0

50

100

150

200

0 2 4 6

Nanomer(wt%)

Ela

sti

c M

od

ulu

s(M

Pa)

0

50

100

150

200

0 2 4 6

Nanomer(wt%)

Ela

sti

c M

od

ulu

s(M

Pa)

24 Appl Sci Adv Mater Int, September 2014

bonding between the OH groups of the maleic

anahydride group of MAH-g-PE and the oxygen of

the silicates thereby increasing the inter gallery space

of the nanoclay29

. At higher epolene loading the

nanocomposites showed decreased tensile modulus

due to the introduction of appreciable amount of low

molecular weight (MA-g-PE) fraction into the hybrid.

Fig. 2 Effect of epolene loading on modulus of elasticity of

nanocomposites

Flexural Modulus

Fig. 3 Effect of nanomer loading on Flexural modulus of

nanocomposites

The reinforcing benefit of nanomer loading on the

flexural modulus of the nanocomposites was reported

in Fig. 3. The nanocomposites showed increment in

flexural modulus (57.6,192.6 and 157% increment)

than the neat polymer for 1, 3 and 5% nanomer

loading respectively. However, modulus value

lowered for 5% than 3% clay loading. Increased

modulus for 1 and 3% nanomer loading is attributable

to the high stiffness of nanolayers with high aspect

ratio and anisotropy, which is acting as stress transfer

medium in the nanocomposites. The entanglement of

the polymer chain intruded into the inter gallery is

responsible for induced plastic deformation in the

hybrids. Similar observations were observed for other

nanocomposite systems30

. The toughness of

nanocomposites at higher nanomer loading might be

decreased due to the nanoparticle clusters inhibiting

plastic deformation of matrix by the constraining

effect of nanomer agglomerates31

.

Fig. 4 Effect of epolene loading on Flexural modulus of

nanocomposites

Compatibilised nanocomposites showed improved

flexural modulus (Fig. 4), which increased linearly

(4.19 increment for 1 % and 32.7increment for 2 %

respectively) with the epolene loading up to 2%

thereafter decreased drastically for further increasing

the MAH-g-PE. The improvement in toughness is

attributable to the reinforcing effect of separated

nanolayers achieved through intercalation of the

intruding MA-PE groups in the inter gallery space of

nanoclay inducing plastic deformation of the polymer

matrix. . However, at higher epolene loading the

nanocomposites showed decreased flexural modulus,

which is attributed to the introduction of appreciable

amount of low molecular weight (MA-PE) fraction

with lower toughness into the hybrid.

Impact Strength

The Impact strength (IS) values of nanocomposites

were shown in Fig. 5. IS increased by 43.8% than the

virgin LDPE for 1% nanomer and it is further

increased by 48.8% for 3% nanomer and then the

increment was reduced to 45.7% for 5% namomer

loading. The increment in impact strength suggested

that the resistance to crack propagation is enhanced

owing to the extensive plastic deformation of the

matrix bound to the nanomer. Circles of matrix

around the nanoparticles agglomerates, which was

proved to be substantially critical for consuming

failure energy45, t

is clearly a function of rate of

loading due to the viscoelastic nature of the inter

25 Parija S: Low Density Polyethylene/Layered Silicate Nanocomposites

phase. The decreased impact strength at higher clay

loading (5%) is attributed to detrimental effect of

nanomer clusters leading to non-uniform dispersion

of clay nanolayers in polymer matrix 32

.

Fig. 5 Effect of nanomer loading on impact strength of

nanocomposites

Fig. 6 Effect of epolene loading on Impact strength of

nanocomposites

The influence of added compatibiliser on the

impact strength was represented in Fig. 6. It is

observed that the impact strength of the

compatibilised nanocomposites improved linearly

(2.82% for 1% and 42.7% for 2%) with

compatibiliser addition up to 2% epolene and after

that the hybrids with higher epolene content showed

detrimental decrease in impact strength. The

improvement in IS might be due to the chain

entanglement by the intruded MAH-g-PE

macromolecules forming H-bonding with the oxygen

atom of the silicate tetrahedra inside the inter gallery

space of the clay. The interaction between the

grafted polymer and the base polymer also

contributed significantly towards the strength

increment33

. At higher epolene loading the

nanocomposites show decreased impact strength due

to the presence of appreciable amount of low

molecular weight (MAH-g- PE) fraction, which is

responsible for the decreased impact strength of the

hybrid.

Thermal Characteristics

Melting Point

Fig. 7 DSC Thermograms of nanocomposites for melting

behavior(Tm)

Melting point of LDPE, uncompatibilised and

compatibilised hybrids were reported in Fig. 7.

Uncompatibilised and compatibilised nanocomposites

showed higher melting point than the virgin polymer,

which is due to the higher thermal resistance of the

nanoclay. However, the difference in melting point

between both hybrids and virgin polymer were not

significant. This insignificant change in the melting

point is attributed to ineffectiveness of the nano filler

in changing the crystallite size of the base polymer34

.

Crystallization Characteristics

The crystallization exotherms of pure LDPE,

LDPE/Org-MMT and LDPE/MAH-g-PE/Org -MMT

systems were also reported. It is observed that the

LDPE/Clay nanocomposites exhibits a narrow

isothermal crystallization peak as compared to LDPE.

The crystallization process of LDPE seems to be

accelerated in the presence of clay platelets as

evidenced by the reduced peak width. The

crystallization temperature (Tc) of the

nanocomposites shifted to the higher side. The Tc for

the uncompatibilised nanocomposites is higher than

that of pure LDPE, which is explained by the

heterogeneous nucleation effect of the org-MMT

particle on the LDPE macromolecule segments35

.

Melted LDPE macromolecules can easily which leads

to the crystallization of LDPE molecules at a higher

26 Appl Sci Adv Mater Int, September 2014

temperature. From the result it is well observed that

the LDPE/MAH-g-PE/Org-MMT nanocomposites

showed higher Tc value than the uncompatibilised

one. The difference in crystallization temperature

between the LDPE/Org-MMT and LDPE/MAH-g-

PE/LDPE indicates the synergistic heterogeneous

nucleus effect of MAH-g-PE and Org-MMT on the

crystallization temperature of LDPE.

Thermal Stability

The dispersion of the clay is known to improve the

thermal stability of polymers. Fig. 8 presented the

results of the TGA analysis of LDPE samples. The

LDPE/clay hybrid showed increased thermal stability

than the pure LDPE. The increased thermal stability

of the uncompatibilised hybrid is due to the

introduction of inorganic clay with good thermal

stability as well as the interaction between the clay

particles and the polymer matrix36,37

.

Improved thermal stability of nanocomposites has

been attributed to the decreased permeability of

oxygen by the intercalated clay. Ogata et el reported

that the clay seemed to hinder the degradation of the

PLA hybrids at low temperature38

. The thermal

stability of the compatibilised nanocomposites was

more than the virgin and uncompatibilised one. The

higher thermal stability of the compatibilised hybrid

is attributed to the synergistic effect of the inherent

high heat resistance of the clay and the increased

interfacial interaction resulted between the clay

nanolayers, grafted polymeric fraction and the base

polymer. These results are in good agreement with the

PP/clay nanocomposites reported by Zanetti et al39

and Hambir et al40

.

Fig. 8 TGA Thermograms of nanocomposites

Nanocomposites Microstructure

The internal structure of the nanocomposites in the

nanometer scale was directly observed via TEM

analyses. Fig. 9a and b showed the result of the TEM

bright field images of the uncompatibilised as well as

compatibilised nanocomposites. It is revealed that the

clay layers are stacked to form intercalated structure

in case of uncompatibilised nanocomposites

contributing to the reduced benefits of the nano filler.

On the other hand the TEM image revealed that

layered silicates with smaller stacks were dispersed to

give a well interacted with strong flocculation

structure giving good adhesion between the nano

layers, LDPE and MAH-g-LDPE in case of

compatibilised hybrid.

Fig. 9 TEM micrograph of nanocomposites

Conclusion The incorporation of org-MMT in the LDPE matrix

leads to concurrent improvement in the mechanical

properties of the organoclay /LD hybrid for a

relatively lower nanomer loading (3%) without

affecting the processibility of the base polymer.

LDPE showed marginal decrease in MFI, shear rate

and increased viscosity with nanomer addition. The

nanomer as well as compatibiliser loading play

important roles in producing LDPE/ layered silicate

nanocomposites with superior mechanical properties

through intercalation of base polymer in the inter

gallery space of the layered silicates by mechanical

shear.

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Proc, 57 (1997) 513.

2 Gilman W J, Appl Clay Sci, 15 (1999) 31.

3 Vaia R A, Price G, Ruth P N, Nguyen H & Lichetenhan

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Mater, 8 (1996) 1728.

5 Okamoto M, Moitra S, Taguchi H, Kim Y H & Kotaka

T, Polymer, 41 (2000) 3887.

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6 Frones T D, Yoon P J, Keskula J H & Paul D R,

Polymer, 42 (2001) 9929.

7 Vaia R A, Jandt K D, Kramer E J and Giannelis E P,

Chem Mater, 8 (1996) 2628

8 Liu L M, Qu Z N & Zau X G, J Appl Polym Sci, 63

(1997) 137.

9 Zhang Q & Fu Q, Polym Int, 49 (2000) 1561.

10 Reichert P, Nitz H, Klinke S, Brangsch R, Thomann R

and Mulhaupt R, Macromol Mater Eng, 275 (2000) 8.

11 Fisher H, Geigens L, & Koster T, Nanocomposites from

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Applied Science and Advanced Materials International

Vol. 1 (1), September 2014, pp. 28-31

Impedance Spectroscopy Of Zn0.98Nd0.02O nano Ceramic By

High Energy Ball Milling

Tanushree Das*, Bikram keshari Das, Kajal Parashar, S.K.S. Parashar,

Nano Sensor Lab, School of Applied Sciences, KIIT University, Bhubaneswar-751024,Odisha, India.

Received 21 August 2014; accepted 5 September 2014

Abstract The electrical properties of Zn0.98Nd0.02O nano ceramic synthesized by high energy ball milling technique

was investigated by Impedance spectroscopy in the frequency range 100Hz to 1MHz and temperature range 3000c-

5000c.Complex Impedance Spectroscopy(CIS) plot reveals the presence of both bulk and grain boundary effect,

Negative temperature co-efficient of resistance (NTCR) and follow non-Debye relaxation phenomena. Variation of

AC conductivity as a function of frequency increases with increase in temperature.

Keywards Zn0.98Nd0.02O,Impedance spectroscopy,AC conductivity

The promise of nanocrystals as a technological

material for applications including wavelength

tuneable lasers1, bioimaging

2, and solar cells

3 may

ultimately depend on tailoring their behaviour by

adding impurities through doping. Impurities are

reported to modify electronic, electrical, optical,

and magnetic properties of bulk semi-conductors.

Zinc oxide (ZnO) is an important semiconductor

material both in the form of a ceramic or a powder.

Intrinsically, ZnO is a n-type semiconducting

compound with a wide band gap energy of about

3.37 eV and a large exciton binding energy of 60

meV at room temperature4. Due to its unique

properties, ZnO can be used for many applications

including the production of paint5, ceramics

6,

photocatalysis7 and electronics

8.It is well known

that ZnO nanoparticles can be fabricated through

two major routes, namely (1) the top-down route

that includes conventional9, mechanochemical

10 and

mechanical milling11

and (2) the bottom-up route

that includes solvothermal12

,sol–gel13

and

precipitation methods14

. Both these major routes

have different advantages and disadvantages; but

each can be used to produce high quality ZnO

nanoparticles. Rare earth elements(REEs), such as

Eu,Er,and Gd,are characterized by abundant energy

levels and multi-substrate and exhibit very sharp

and temperature independent luminescence in the

ultra violet(UV) and visible light range15–17

. REEs

such as Eu, Er and Tb doped into the ZnO

semiconductor can be tuned over the entire

ultraviolet(UV) and visible light range18–20

. For

example, Eu doped ZnO exhibits red light15

, while

Er doped ZnO exhibits a green emission21

. REE

Gd3+

is of particular interest because its scintillation

properties22

, which allow it to be used to make

phosphor films23-24

. Amornpitoksuk et al.25

investigated the effects of Ag doped ZnO

nanoparticles, prepared by a precipitation method,

on their structural, photocatalytic and antibacterial

properties. They reported that the particle sizes

decreased, and the photocatalytic efficiency for

degradation of methylene blue increased as a

function of the Ag concentration. Benhebal et

al.26

showed that the band gap energy was reduced

when ZnO was doped with 10% lithium, sodium or

potassium due to an increase in its crystallinity. The

Na- and Li-doped ZnO particles also had an

improved efficiency to degrade phenol and benzoic

acid, but the K-doped ZnO particles had reduced

degradation efficiency. Anandan et al. prepared La-

doped ZnO nanoparticles by a co- precipitation

method and they showed that the rate of degradation

of monocrotophos in aqueous solution for La doped

ZnO nanoparticles increased with an increase of the

La content up to 0.8 wt% and then decreased27

. In

addition, the properties of other metal dopants such

Corresponding Author:

Tanushree Das

e-mail:vdmscchem@yahoo.co.in

29 Das et al.: Impedance Spectroscopy

as Al, Ta, Sn, Cu, Cd, Pd, Cr and Mn on the ZnO

properties were also investigated28-35

.

Through mechanical milling technique, the

particle size down can easily reduce to nanoscale

level, the solubility limit of doping metal can be

extended at low temperature and amorphous phase

can be easily produced36

.It appears from our

literature survey that synthesis of Zn0.98Nd0.02O

material by ball milling and its electrical

characterization through Impedance analysis have

received little attention. In view of this, we have

carried out complex Impedance spectroscopy

studies on Zn0.98Nd0.02O with an aim to investigate

the picture of electrical properties prepared by high

energy ball milling.

Experimental Procedure Nanocrystalline Zn0.98Nd0.02O ceramic was

synthesized by high energy ball milling

technique(HEBM, PM 400Retsch,Germany). High

purity ZnO and Nd2O3 used as a raw material was

weighed according to their atomic ratio. The

powder was milled in tungsten carbide vials with

tungsten carbide balls by taking ball to powder ratio

10:1 for 10 hr at 300rpm in wet milling condition. It

is well known that the proper choice of milling

parameters such as milling time, ball to powder

mass ratio and rotation speed have major role in the

preparation of ZnO nanoparticles37

.The mixture was

milled for 1hr, alternating with a stop of 30 min to

prevent over heating and to reduce engine wear.

Generation of heat during mill is due to the kinetic

energy of grinding medium and secondly due to the

exothermic process occurring during milling38

.The

mixture powder was calcined at 11000C at a heating

rate of 20c per minute to obtain the desired product.

The calcined powder was pressed into circular disc

(pellet) using PVA as binder. The role of PVA is to

reduce the brittleness and to have better

compactness among the granuals of the material.

Finally the pellet was sintered at 12000C for 2 hr

and coated

with silver paste on both side and heated at 7000C

for 15min, for electrical measurement. The

electrical properties of sintered sample was

characterized by computer controlled Impedance

analyser (Hioki LCR Hi-tester-3532-50).

Result and Discussion

Impedance analysis

Impedance spectroscopy is an experimental tool for

the characterization of electrical behaviour of

electrochemical cells or electronic materials. It is an

important technique in view of its simplicity and

clarity in describing the electrical processes

occurring in a system on applying an ac signal as

input perturbation. The output response, when

plotted in a complex plane plot, appears in the form

of a succession of semicircles representing electrical

phenomena due to bulk material, grain boundary

effect and interfacial phenomena if any. In view of

this specialty, CIS makes it possible to separate the

contribution due to different components in a

polycrystalline sample, that of course have different

time constants, in the frequency domain. The

frequency dependent properties of a material is

normally described in terms of any of the formalism

expressed as: 39

Complex impedance,

Z* = Z'− jZ "= Rs– j/ωCs

Complex admittance,

Y*= Y'+ jY" = 1/Rp+ jωCp= G(ω) + jB(ω)

Complex permittivity (dielectric constant),

ε* = ε' − jε"

Complex modulus,

M*= 1/ε*= M '+ jM"= jωC0Z*

and tan δ = −Z'/Z" = Y'/y" = ε "/ε' = M" /M'

where (Z',Y', ε', M') and (Z", Y", ε", M") are the

real and imaginary components of impedance,

admittance,permittivity and modulus respectively,

G: conductance, B:susceptance,and tan δ: dielectric

loss. They are interrelated with each other.

Fig. 1 shows the variation of real part of

impedance (Z') wit frequency at different

temperature (3000C - 500

0C). It is observed that, the

curves display decrease in the value of Z' with the

increase in both frequency as well as temperature,

indicating an increase in AC conductivity with the

rise in temperature and frequency 40

. Again, at low

frequencies the value of Z' decreases with rise in

temperature40

.

Fig. 2 shows the variation of imaginary part of

impedance (Z'') with frequency at different

temperature. This plot is most suitable for

evaluation of relaxation frequency.Each

semicircular arc in the impedance has a

characteristics peak occurring at a unique relaxation

frequency(ωmax) attributed to electrical phenomena

due to different components in the sample. It can be

expressed as: 39

ωmaxRC= ωmaxτ= 1

⇒ ωmax = 1/τ = 1/RC

⇒ fmax = 1 / 2πτ= 1 / 2πRbCb

Relaxation frequency and hence relaxation time

(τ) is a parameter that depends only on the intrinsic

properties of the material and not on the sample

geometrical factors. The term intrinsic properties of

the material refer to the properties attributed to

structure/microstructure (i.e. grain interior or bulk,

grain boundary, etc.). It can be seen that, The

magnitude value of resonance frequency decreases

30 Appl Sci Adv Mater Int, September 2014

and shifting towards high frequency side with

increase in temperature. This indicates the

temperature dependence of electrical relaxation

phenomena of the material. Again a typical peak

broadening is observed with rise in temperature

suggesting a spread of relaxation time40

.

Fig. 1 Variation of real part of impedance(Z') of

Zn0.98Nd0.02O with frequency at different temperature.

Fig. 2 Variation of imaginary part (Z'') of impedance of

Zn0.98Nd0.02O with frequency at different temperature.

Fig-3 shows the CIS plot(z' vs z'' ) of

Zn0.98Nd0.02O nano ceramic measured at different

temperature( 3000c- 500

0c ). The complex

impedance spectrum comprised at high frequency

semicircle as well as low frequency semicircle, This

is due to contribution of both bulk and grain

boundary effects. The proposed material

Zn0.98Nd0.02O has semicircular arc and plots with

centre located below the real axis, describe non-

Debye relaxation.

AC conductivity

Conductivity analysis provides significant

information related to transport of charge carriers,

i.e electron/hole or cations /anions that

predominates the conduction process and their

response as a function of temperature and

frequency41

. Fig-4 shows the variation of AC

conductivity of Zn0.98Nd0.02O as a function of

frequency at different temperature. The frequency

dependent conductivity of material exhibit both low

and high frequency dispersion phenomena. This

follows the Jonscher's power law42

. s

dcac A

Where s is frequency exponents in the range of

0<n<1.Both the σdc and Aare thermally activated

quantities and indicate that the conduction is a

thermally activated process.From fig it is observed

that the AC conductivity value increases with

increase in temperature, indicating electrical

conduction in the material. The increasing

conductivity w.r.t. temperature indicates the

negative temperature co-effecient of resistance of

(NTCR) behaviour due to the grain and grain

boundary resistance.

Fig. 3 Variation of (Z' and Z'') of impedance of

Zn0.98Nd0.02O with frequency at different temperature

Fig. 4 Variation of Ac conductivity of Zn0.98Nd0.02O as a

function of frequency at different temperature

100 1000 10000 100000 1000000

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000 Zn0.98

Nd0.02

O,12000C Sint

Z'

Frequency(Hz)

3000c

3250c

3500c

3750c

4000c

4250c

4500c

4750c

5000c

100 1000 10000 100000 1000000

0

-500

-1000

-1500

-2000

-2500Zn

0.98Nd

0.02 O,1200

0C Sint

Frequency(Hz)

3000c

3250c

3500c

3750c

4000c

4250c

4500c

4750c

5000c

Z''

0.0 2.0x103

4.0x103

6.0x103

8.0x103

1.0x104

1.2x104

0.0

-2.0x103

-4.0x103

-6.0x103

-8.0x103

-1.0x104

-1.2x104

Zno.98

Nd0.02

O,12000c sint 300

0c

3250c

3500c

3750c

4000c

4250c

4500c

4750c

5000c

Z''

Z'

100 1000 10000 100000 1000000

-2.0x10-2

0.0

2.0x10-2

4.0x10-2

6.0x10-2

8.0x10-2

1.0x10-1

1.2x10-1

1.4x10-1 Zn

0.98Nd

0.02 O,1200

0C Sint

Frequency(Hz)

3000c

3250c

3500c

3750c

4000c

4250c

4500c

4750c

5000c

Ac C

on

du

cti

vit

y

31 Das et al.: Impedance Spectroscopy

Conclusion Nanocrystalline Zn0.98Nd0.02O ceramic synthesized

by high energy ball milling technique. From the

Impedance spectroscopic studies the material

showed relaxation effects which are non- Debye

type and NTCR effect The relaxation frequencies

shifted to higher frequency side with increase in

temperature. The CIS plots reveals the contribution

of both bulk and grain boundary effect.The AC

conductivity increases with increase in temperature.

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Applied Science and Advanced Materials International

Vol. 1 (1), September 2014, pp. 32-36

Sequence Based Prediction of Kink in Transmembrane Helices by Neural

Network Method

N. Mishra1, A. Khamari

2, M. R. Panigrahi

3, J. K. Meher

4, M. K. Raval

5

1Dept of Chemistry, Rajendra College, Balangir, Odisha, India -767002 2Dept of Physics, Rajendra College, Balangir, Odisha, India – 767002

3Department of Chemical Engineering, Orissa Engineering College, Bhubaneswar, India

4Dept of Computer Science and Engineering, Vikash College of Engg for Women, Bargarh, India-768028

5Department of Chemistry, Gangadhar Meher College, Sambalpur, Odisha, India – 768004,

Received 01 September 2014; accepted 10 September 2014

Abstract The kinks (bends) in helices play an important role in functions of transmembrane proteins. Kinked helices

are believed to be required for appropriate helix-helix and protein-protein interaction in membrane protein complexes.

Therefore, knowledge of kink and its prediction from amino acid sequences is of great help in understanding the

function of proteins. However, determination of kink in transmembrane α-helices is a computationally intensive task. In

this paper we have developed Neural Network method based on radial basis function for prediction of kink in the

helices with a prediction efficiency of 85%. A feature vector generated using three physico-chemical properties such as

alpha propensity, coil propensity, and EIIP constituted in kinked helices contains most of the necessary information in

determining the kink location. The proposed method captures this information more effectively than existing methods.

Keywords Kink, Transmembrane α-helices, RBF, Feature vector, Physico-chemical properties.

Knowledge of segments of transmembrane proteins

and the bends in helices help in the study of tertiary

structure and hence understanding the role played

by that protein. 20-30% of all the proteins in any

organism are membrane proteins. These are of

particular importance because they form targets for

over 60% of drugs on the market. Transmembrane

α-helix bundle is a common structural feature of

membrane proteins except porins, which contains

β-barrels. Membrane spanning α-helices differ

from their globular counterpart by the presence of

helix breakers, Pro and Gly, in the middle of

helices. Pro is known to induce a kink in the

helix1,2

. A hypothesis suggests that Pro is

introduced by natural mutation to have a bend and

later further mutated leaving the bend intact for

required function during the course of evolution3.

The role of Pro and kinks in transmembrane helices

were extensively investigated both experimentally

and theoretically to unravel the nature's

architectural principles2,4

. Another observation

suggest induction of kink at the juncture of α-

helical and 310 helical structure in a

transmembrane helix2-6

. Mismatch of

hydrophobicity of lipid bilayer and peptide may

also result in distortion of α-helical structure7.

Sequences of straight and kinked helices were

further subjected to machine learning to develop a

classifier for prediction of kink in a helix from

amino acid sequences. Support vector machine

(SVM) method8 projects that helix breaking

propensity of amino acid sequence determines kink

in a helix. DWT has been applied on

hydrophobicity signals in order to predict

hydrophobic cores in proteins10

. Protein sequence

similarity has also been studied using DWT of a

signal associated with the average energy states of

all valence electrons of each amino acid11

. Wavelet

transform has been applied for transmembrane

structure prediction12

. Signal processing methods

Corresponding Author:

N Mishra

e-mai: nibedita1976@yahoo.com

A Khamari

e-mai: akkhamari@gmail.com

M R Panigrahi

e-mail: madhaba_r@yahoo.com

J K Meher

e-mail: jk_meher@yahoo.co.in

M K Raval

e-mail: mraval@yahoo.com

33 Mishra et al.: Sequenced Based Prediction of Kink

such as Fourier transform and wavelet transform

can identify periodicities and variations in signals

from a background noise. The presence of kink in

amino acid sequence is determined effectively in

transform domain analysis13

.

Kinked and straight helix of protein Type-4

Pilin and Chlorophyll A-B binding protein

respectively are shown in Fig.1.

Fig. 1 Backbone representation of (a) kinked helix of

type-4 pilin protein (2pil) (b) straight helix (second helix)

of chlorophyll a-b binding protein (1rwt

A kink in a helix may be formed by helix-helix

interaction. In such cases the intrinsic kink forming

or helix breaking tendency may not be required.

Even a helix forming tendency may be overridden.

This possibility clamps a theoretical limit to predict

a kink with high accuracy. Hence there is a need to

develop advanced algorithm for faster and accurate

prediction of kink in transmembrane helices. This

motivates to develop novel approach based radial

basis function neural network (RBFNN) to

effectively predict kink in transmembrane α-helices.

Materials and Methods

Database.

List of transmembrane proteins and their coordinate

files were obtained from the Orientation of Proteins

in Membranes (OPM) database at College of

Pharmacy, University of Michigan

(http://www.phar.umich.edu).

Determination of α-helical regions.

Dihedral angles were computed using

MAPMAK from coordinate files and listed for each

residue along with assignment of conformational

status of the residue namely right or left helical, β-

strand. Molecular visual tools RasMol were used to

visually confirm the transmembrane α-helical

regions.

Computation of helix axis.

Helix axis was computed from the approximate

local centroids θi’(xi0,yi

0,zi

0) of the helix by taking

a frame of tetrapeptide unit [9].

(1)

where xi, yi, and zi are the coordinates of Cα atoms

of the tetrapeptide frame. Unit vector in the

direction of resultant of vectors θ'iθ'i+1 yields

direction cosines (l, m, n) of axis of helix (A). The

axis pass through the centroid of the helix θ0 = (X

0,

Y0, Z

0).

(2)

where n is the number of residues in a helix.

Refined local centers θi of helix are then calculated

for each Cα by computing the foot of perpendicular

drawn from Cαi to A.

Location of hinges.

Hinges were located in a helix by a distance

parameter d(CiNi+4), where Ci is the backbone

carbonyl carbon of ith residue and Ni+4 is backbone

peptide nitrogen of i+4th residue [9]. Value of

d(CiNi+4) beyond the range 4.227±0.35$ Å reflects

a hinge at the ith residue in the helix. Hinge was

quantified by two parameters kink and swivel [3].

Calculation of Feature Parameters Here physico-chemical properties of amino

acids are used to draw the feature vector. These are alpha, coil and Electron ion pseudpotential interaction potential (EIIP) as shown in Table 1.

Radial basis function neural network

classifier (RBFNNC). In this paper we have introduced a low complexity radial basis function neural network (RBFNN) classifier to efficiently predict the sample class [14,15] . The potential of the proposed approach is evaluated through an exhaustive study by many benchmark datasets.

The experimental results showed that the proposed method can be a useful approach for classification. A radial basis function network is an artificial neural network that uses radial basis functions as activation functions. It is a linear

3

03

03

0

4

1 ,

4

1 ,

4

1 i

i

ii

i

i

ii

i

i

ii zzyyxx

n

i

i

n

i

i

n

i

i zn

Zyn

Yxn

X1

0

1

0

1

0 1 ,

1 ,

1

34

Appl Sci Adv Mater Int, September 2014

combination of radial basis functions. The radial basis function network (RBFNN) is suitable for function approximation and pattern classification problems because of their simple topological structure and their ability to learn in an explicit manner. In the classical RBF network, there is an input layer, a hidden layer consisting of nonlinear node function, an output layer and a set of weights to connect the hidden layer and output layer. Due to its simple structure it reduces the computational task as compared to conventional multi layer perception (MLP) network. The structure of a RBF network is shown in Fig. 1.

Table 1 Physicochemical parameters of amino acid

residues used in algorithm for prediction of Ni-binding

sites in proteins

Amino acid Alpha Coil EIIP

A 1.372 0.824 0.0373

R 0.694 0.893 0.0959

N 0.473 1.167 0.0036

D 0.416 1.197 0.1263

C 1.021 0.953 0.0829

Q 0.765 0.947 0.0761

E 0.704 0.761 0.0058

G 0.913 1.251 0.0050

H 1.285 1.068 0.0242

L 1.471 0.810 0.0000

I 1.442 0.886 0.0000

K 0.681 0.897; 0.0371

M 1.448 0.810 0.0823

F 1.459 0.797 0.0946

P 0.526 1.540 0.0198

S 0.903 1.130 0.0829

T 0.910 1.148 0.0941

W 1.393 0.941 0.0548

Y 0.907 1.109 0.0516

V 1.216 0.772 0.0057

In the RBFNN based classifier, an input vector x is used as input to all radial basis functions, each with different parameters. The output of the network is a linear combination of the outputs from radial basis functions.

For an input feature vector x, the output y of the jth

output node is given as.

Fig.1 The structure of a RBF network

k

2k

x(n) CN N

2

j kj k kj

k 1 k 1

y w w e

(3)

The error occurs in the learning process is

reduced by updating the three parameters, the

positions of centers (Ck), the width of the Gaussian

function (σk) and the connecting weights (w) of

RBFNN by a stochastic gradient approach as

defined below:

ww(n 1) w(n) J(n)w

(4)

k k c

k

C (n 1) C (n) J(n)C

(5)

k k

k

(n 1) (n) J(n)

(6)

Where, 21J(n) e(n)

2

, e (n)=d(n) - y(n)

is the error, d(n) is the target output and y(n) is the predicted output. w C and are the learning parameters of the RBF network.

Simulation Studies and Discussions In order to compare the efficiency of the proposed

method in predicting the class of the kink data we

have used standard datasets. All the datasets

categorized into two groups: binary class to assess

the performance of the proposed method. The

dataset consists of amino acid sequences of 9

characters. 400 sequences from kink dataset and

400 sequences from non-kink dataset are taken as

35 Mishra et al.: Sequenced Based Prediction of Kink

training set. The feature selection process proposed

in this paper includes alpha, coil and EIIP as shown

in the Table 1. To implement the RBFNN classifier,

we first read in the file of protein sequence which is

represented with numerical values. The

performance of the proposed feature extraction

method is analyzed with the neural network

classifiers: RBFNN. The leave one out cross

validation (LOOCV) test is conducted by

combining all the training and test samples for the

classifiers with datasets [16]. LOOCV is a

technique where the classifier is successively

learned on n-1 samples and tested on the remaining

one. i.e., it removes one sample at a time for testing

and takes other as training set. It involves leaving

out all possible subsets so the entire process is run

as many times as there are samples. This is repeated

n times so that every sample was left out once.

Repeating these procedure n times gives us n

classifiers in the end. Our error score is the number

of mispredictions. Out of 400 sequences from kink

dataset all 400 samples are detected as true positive

whereas out of all 400 sequences from non-kink

dataset,all 400 samples are detected as true

negative. The prediction accuracy has been analyzed in

terms of two measuring parameters such as accuracy (A), precision (P) and recall (R). These are defined in terms of four parameters true positive (tp), false positive (fp), true negative (tn) and false negative (fn). tp denotes the number of kinks and are also predicted as kinks, fp denotes the number of actually Non-kinks but are predicted to be kinks, tn is the number of actually Non kinks and also predicted to be kinks, and fn is the number of actually kinks and predicted to be Non kinks.

Accuracy

The accuracy of prediction of kinks in amino acid sequence is defined as the percentage of kinks correctly predicted of the total sequences present. It is computed as follows:

(7)

Precision

Precision is defined as the percentage of kinks

correctly predicted to be one class of the total kinks

predicted to be of that class. It is computed as:

(8)

Recall

Recall is defined as the percentage of the kinks that

belong to a class that are predicted to be that class.

Recall is computed as:

(9)

A query sequence of 35 kink samples and 35 non-

kink samples are tested for validation and the result

obtained is shown in table 2.

Table 2 Measuring parameters for prediction

accuracy

Actual

Predicted

Kink Non-kink

Kink 30 (tp) 5 (fp)

Non-kink

6(fn) 29 (tn)

The accuracy, precision and recall are 0.85,

0.84, and 0.84 respectively. The accuracy of sequence based classifiers reported so far is about 85%. Hence the present classifier appears to have high accuracy compared to existing sequence based classifiers.

Conclusion

Neural network approach based on radial basis

function plays a vital role in the prediction of kink

in transmembrane α-helix. The proposed method is

not only fast but also has improved accuracy (85%)

as compared to SVM learning system (80%)

reported by us earlier8. However prediction of kink

in a helix depends on the features of amino acid

sequence. Feature vector with propensities of

residues in helix and coil along with EIIP are only

used for numerical representation in the present

study. Although kink prediction has its own

limitations, the present work is primary report in

the area of helix kink prediction from amino acid

sequence based on neural network algorithms.

Acknowledgment

The authors wish to thank management members

and the principal of the college for all kinds of

supports to complete this work.

nnpp

np

ftft

ttA

pp

p

ft

tP

np

p

ft

tR

36

Appl Sci Adv Mater Int, September 2014

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Applied Science and Advanced Materials International Vol. 1 Issue 1 (September – October, 2014)

Author Index

Bandyopadhyay, S 12

Das, B K 28

Das, B 16

Das, H 3

Das, T 28

Das, T 16

Dutta, D 3

Ghosh, S 12

Goswami, T 3

Kalita, D 3

Khamari, A 32

Majumdar, S 12

Meher, J K 32

Mishra, N 32

Panigrahi, M R 32

Parashar, K 16

Parashar, K 28

Parashar, S K S 16

Parashar, S K S 28

Parija, S 21

Raval, M K 32

Sahoo, G C 12

Saikia, P 3

Applied Science and Advanced Materials International Vol. 1 Issue 1 (September – October, 2014)

Keyword Index

Ac conductivity 16, 28

Beam house 12

Coir 3

Compatibiliser 21

Composite 3

Cross-flow membrane filtration 12

E-142 21

Electron microscopy 3

Feature vector 32

Fibers 3

Flux 12

Impedance Spectroscopy 16, 28

Intercalation 21

Kink 32

Modulus of rupture 3

Montmorillonite 21

Nanocomposites 21

Physico-chemical properties 32 Pretreatment 12

RBF 32

Tannery wastewater 12

Transmembrane α-helices 32

Tubular ceramic membrane 12

Turbidity 12

Viscosity 21

XRD 16

Zn 0.99Cu0.01O 16

Zn0.98Nd0.02O 28