Nano - composites: a state of the art review

N. Crainic1, A. T. Marques

2

1Politehnic University of Timisoara (NATO grant holder at INEGI),

Mechanical Faculty, B-dul M. Viteazul Nr. 1, Ro 1900 Timisoara, Romania

2INEGI-DEMEGI-FEUP, Faculdade de Engenharia da Universidade do Porto

Rua Dr. Roberto Frias, s/n 4200-465 Porto, Portugal

Keywords: Nano � Composites, Nano � Clay Composites, Nano � Particles Technological

Applications, Commercial Applications

Abstract

In recent years there has been an increased interest in the use of nano � composites for different

applications. Bearing in mind certain technological applications, a state of the art review has been

carried out and will be described in this paper. Although for commercial applications what is more

developed refers to nano � clay composites, other types will be evaluated as possible interest as

final products. Moreover, the use of nano � particles as an aid for processing of composite materials

will also be discussed.

1. Introduction

The nanotechnology is a reality, at least for researchers in the academic world that work in the

different disciplines to a nanometer scale, even though they don't call their own work

nanotechnology. A set of pre-selected domains has been considered within the nanotechnology.

They are the following: nano electronic, electronic quantic and electronic molecular, materials nano

structure, molecular nanotechnology, components for computers, physical mesoscopic/technology,

chemistry macro molecular.

The general domain of nanotechnology is possible to be subdivided in two branches: technology of

the miniaturization of the macroscopic technology and molecular nanotechnology. The former is

more developed, but the molecular nanotechnology begins at this moment.

2. Nanoclay Structures and applications

An essential property of clays is their interaction with organic molecules. An early use of clays was

to mix them with the sheep�s wool in order to extract the natural greases and oils so that the refined

wool could be made into clothing. The subject today is a particular type of clay that can be

chemically-modified with a variety of different chemistries to make the clay complexes compatible

with organic monomers and polymers: we call them Nanoclays, which in combination with

monomers or polymers form nanocomposites.

The essential raw material for a nanoclay is montmorillonite, a 2-to-1 layered smectite clay with a

layered structure. Individual layer thicknesses are just one nanometer, but surface dimensions are

generally 100 to more than 1,000 nanometers.

The intercalated molecules expand the layers to the point that the individual layer can be separated

by mechanical shear. Thermoplastic and thermosets can be employed. The specific chemistries

designed and employed are necessarily a function of the host polymer's unique chemical and

physical characteristics.

In the engineering plastics arena, a set of automotive components can be considered, making use of

lightweight, impact and scratch-resistant, and higher heat distortion performance characteristics.

Impermeable, transparent sheets are created when individual clay platelets, one nanometer thin but

with surface dimensions extending to one micron (1000 nanometers), are fully dispersed

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(exfoliated) into a host polymer. The key to exfoliation is the definition of polymer-compatible

chemistries to intercalate the individual clay sheets.

With surface areas of 750 m2/gram, small amounts of nanoclays can have large effects on

theological, structural, thermal, and barrier characteristics of the base polymer. Edison Polymer

Innovation Corporation (EPIC) - Nanocomposite Consortium, proposes to organize an industry-

sponsored consortium to perform research in the area of polymer nanocomposites and applications

with significant opportunity for commercial impact. The ability of nanoparticles to alter the

performance of polymers is dramatic in the areas of reinforcement, gas diffusion, electro-optical

behavior and high temperature durability.

Polymer nanocomposites are a class of materials that have properties offering significant

commercial potential. Polymer nanocomposites are generally defined as the combination of a

polymer matrix resin and inorganic particles, which have at least one dimension (i.e. length, width,

or thickness) in the nanometer size range. Typical of this class of materials is the nanocomposite,

which Toyota discovered in the 1980's, which is a polyamide 6 (from Caprolactam) having

dispersed ion-exchanged montmorillonite as the reinforcement. This material is commercially

available and has been used to mold engine covers on some models of Toyota vehicles.

Several benefits of such a nanocomposite that have been identified include:

- efficient reinforcement with minimal loss of ductility and impact strength; heat stability;

flame resistance; improved gas barrier properties; improved abrasion resistance; reduced

shrinkage and residual stress and altered electronic and optical properties.

The other research activities concerning polymer/clay nanocomposites have a big development with

respect to produce them and, at the same time, to search for applications. They are the following:

1. Intercalation complexes of clay minerals with fullerene and polymers as materials for electrodes

for secondary lithium batteries. [1.]

2. Water-insoluble oligomers or polymers adsorbed onto the external surface of exfoliated layered

materials and nanocomposites. [2.]

3. Gas barrier resin composition, multiplayer structure and its production. [3.]

4. Preparation of film capable to keep transparency and surface smoothness of a resin of its own,

developing excellent modulus of elasticity, dimensional stability, gas barrier properties, etc., useful

in the field of food packaging material, liquid crystal board, etc., by adding a prescribed silane clay

composite to a specific resin [4.]

5. Polyolefin nanocomposites. The present invention is a nanocomposite, which is a dispersion of

nanofiller particles derived from layered metal oxides or metal oxide salts. The nanocomposite is

advantageously prepared by first swelling an untreated clay in water, then removing the water to

form an organophilic clay that is dispersible in non-polar organic solvents. The organophilic clay

can then be treated with an alkyl aluminoxane and subsequently a catalyst to form a complex that

promotes olefin or styrenic polymerization and platelet dispersion. The nanocomposite can be

prepared directly by in situ polymerization of the olefin or the styrene at the nanofiller particles

without shear, without an ion exchange step, and without the need to incorporate polar substituents

into the polyolefin or polystyrene. [5.].

6. Polyester nanocomposites with dispersed expanded cation-exchanged clay materials for high gas

barrier applications. The polyester composite materials exhibit lower gas permeability and can be

used for forming packages or containers with improved gas barrier properties, e.g., for foods, soft

drinks and medicines. [6.]

7. Thermoplastic resin compounds containing clay composite with excellent mechanical properties,

heat resistance, and ease of molding. The clay composite is formed by introducing a certain silane

compound into a swellable silicate. The clay composite is prepared by increasing the bottom

spacing of the swell able silicate and then introducing the silane compound. It is dispersed in the

form of a nombre of very small layers, separetes from one another, in the resin of the thermoplastic

resin compound. [7.]

3. Carbon Nanotubes and applications

Key Engineering Materials Vols. 230-232 657

Since their discover in 1991 by Iijima [8.], Carbon Nanotubes have been the object of an intense

activity. It goes beyond their numerous potential applications, the interest of nanotubeses lies in

their internal structure itself. They are shapes of the coaxial cylinders, every cylinder being formed

by the physical fitness of tube in a graphite plan. Their diameter is typically nanometric, of some

nanometers for mono partitions until several tenths of nanometers for multi-layers, while their

length can reach several microns [9.].

The research activities concerning Carbon Nanotubes have a big development with respect to

produce them and, at the same time, to search for applications. They are the following:

1. The carbon nanotube-metal-oxide composites are electrical conductors owing to the

percolation of the carbon nanotubes. Carbon nanotube-metal-oxide composite have been

prepared by hot-pressing the corresponding composite powders, in which the carbon

nanotubes, mostly single or double-walled, are very homogenously dispersed between the

metal-oxide grains [10.].

2. Nanotube composites for tailored electromagnetic (EM) radiation shielding. EM radiation

shielding nanotube-based materials could be developed for incorpotation into non-metalic

composites. The principle would be the use of ordered high conductivity carbon nanotubes

to tailor the shielding for controlled respose to electromagnetic radiation, including control

of polarization, frequency, and amplitude response [11.].

3. The feasibility of the hot filament assisted chemical vapor deposition (HFCVD) technique to

syntetize carbon nanostructures on catalyst particles was investigated using an atmosphere

of methane dilued in hydrogen. The peculiarity of the HFCVD technique appears to be its

ability to favor a whisker like growth mode of carbone nanostructures for a particular range

of the deposition parameters [12.].

4. Magnetic Fluids and composites technologies

4.1. Magnetic Fluids - a special category of nanomaterials

Magnetic fluids, also known as Ferro fluids, are ultrastable colloidal suspension of ferro/or

ferromagnetic particles � e.g., magnetic (Fe3O4) � in various carrier liquids. The ultra fine magnetic

particles, of (30 � 150)�, �integrate� themselves in the structure of the carrier liquid and together

with Brownian motion, ensure indefinitely the colloid stability even in strongly non-uniform

magnetic fields. The medium behaves like a quasi-homogeneous strongly magnetizable liquid due

to the presence of approximately (1017

� 1018

) magnetic particles in one cubic centimeter and

combines the properties of magnetic materials with those of fluids in a rather spectacular way. [13.]

The magnetic fluids are magnetically perfect soft materials and thus they lack hysterezis in practical

cases. When a magnetic field is applied, the fluid acquires a magnetic moment due to the orientation

of the magnetic materials with those of fluids in rather spectacular forms. New technologies and

devices have their origin in various basic phenomena related to magnetic fluids: control and

positioning; passive levitation; auto levitation; surface instability; controllable jet; rotary motion.

[14.]

4.2. The use of Magnetic Fluid with RTM - Resin Transfer Moulding process

The future of the magnetic nanofluides presence in the mass of the composite can be analyzed for

potential applications in aeronautics or can be frequently used to promote the RTM process. [15.]

The main objectives of the research are the speed up of production rates of RTM, plus the guarantee

of complete filling and homogenization of the pre-forms and reduction in costs through increased

reliability. Moreover, it is the intention of this research to study mechanisms of cure, which apply

the potential of magneto fluid nano materials to the cure mechanisms of the resin.

The use of magnetic fields to evaluate, through NDT, the quality of the products made by RTM, as

well as to increase the potential applications of composite materials where magnetism is important

658 Advanced Materials Forum I

(such as radar, magnetic levitation trains, kinetic energy accumulators and electric engine rotors),

are amongst other objectives to pursue.

A new RTM concept is envisaged where the combination of magneto fluid nano materials with

Peristaltic motion will be used to reduce pressure and increase speed of filling.

In the field of applications, one can imagine a situation where, through numerical modeling and as

an answer to the requirements, it will be possible to apply a magnetic field, which, together with the

Peristaltic motion, will adequate/orient the materials where they are needed.

As health and safety objective, we can underline the search for new cure mechanisms avoiding the

need for certain type of reactive monomers which can be dangerous for the persons working with

this material, and also not environmental friendly.

5. Conclusions

The enormous potential of nanocomposites has been identified. With imagination and heavy

research work, it may be possible to use nanomagnetic fluids with the RTM process, enhancing its

capabilities.

Bibliography

1. Ishikawa, Toshihide; Nakayama, Atsuyoshi; Ishida, Tadashi - Intercalation complexes of clay minerals with

fullerene and polymers as materials for electrodes for secondary lithium batteries 1997. -:

http://www.patents.ibm.com/details?&pn=JP09132695A2 2. Serrano, Fernando; Beall, Gary W.; Cruz, Hannah - Water-insoluble oligomers or polymers adsorbed onto the

external surface of exfoliated layered materials and nanocomposites �1998.

http://www.patents.ibm.com/patlist?icnt=EP&patent_number=822163&x=25&y=10

3. Itada Mitsuyoshi � Gas barrier resin compodsition, multilayr structure and its production � 1998.

http://www.patents.ibm.com/details?&pn=JP10231434A2

4. Suzuki, Noriyuki � Laminar inorganic substance containing resin film � 1999.

http://www.patents.ibm.com/details?&pn=JP11071509A2

5. ALEXANDRE, Michael, DUBOIS, Philippe, JEROME, Robert, GARCIA-MARTI, Miguel, SUN, Tao,

GARCES, Juan, M, MILLAR, Dean, M, KUPERMAN, Alex - Polyofelin naocomposites �

1999.http://www.patents.ibm.com/details?&pn=WO09947598A1

6. Barbee, Robert Boyd, Matayabs Cristopher, Jr., Trexler, Jack Wesley, Jr., Piner, Rodney Layne � Polymers

nanocomposites with dispersed expanded cation-exchanged clay materialsfor high gas barier application � 1999. http://www.patents.ibm.com/details?pn=WO09932403A1

7. Suzuki, Noriyuki; Oohara, Youichi - Thermoplastic resin comps containing clay composite and mfg thereof

with excellent mechanical properties, heat resistance, and molding � 1997.

http://www.patents.ibm.com/details?&pn=WO09743343A1

8. Iijima S., Nature 354 (1991) 56.

9. Cecile NAUD, Giancarlo FAINI, Dominique MAILL, Hubert PASCARD � Quantum interference in carbon

nanotubes � C. R. Acad. Sci. Paris, t . 327, Serie II b, p. 945-992, 1999.

10. E. Flahaut, A. Peigney, Ch. Laurent, Ch Marliere, F. Chastel and A. Rousset � Carnon nanotube-metal-oxide

nanocomposites: microstructure, electrical conductivity and mechanical properties � Acta Materialia, 48

(2000) 3803 � 3812.

11. H. Daniel WAGNER � Carbon Nanotube Composites for Tailored EM Radiation Shielding, see: www.aro.ncren.net/arowash/rt/a_1page 8.htm

12. A. M. Bonnot, M. Deldem, E. Beaugmon, T. Fournier, M.C. Schoulder, M. Mermoux � Crabon nanostructure

and diamond rowth by HFCVD: role of the substate preparation ond synthesis condition � Diamond and

Related Materials 8 (1999) 631-635.

13. V. Sofonea, L. Veckas, E. Hegedus - Magneto-Optical effects induced in a magnetic fluid layr by thermally

released supermasive magnetic monopoles � Europhysics Letters 23 (1993), 604-614.

14. Ioan Anton, Ladislau Vekas � Magnatic Fluids a special category of nanomaterials � Proprety and

Applilactions � Romanian Academy � Timisoara Branch Center for Fundamental and Advanced Technical

Research, 2000.

15. A T Marques. N Crainic � Research concerning the behaviour of nanocomposites, how to obtain it,

characteristics and ways of predicting, their properties � INEGI � CEMACOM � Report 1. INVOTAN -

PROGRAMA DE COOPERACAO �OUTREACH�, 2001.

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