a novel trend in producing ceramic based nanocomposite ... · mohamed. m. el-sayed & mohamed m....
TRANSCRIPT
------------- Journal of Sebha University - (Pure and Applied Sciences) - Vol. 8 No.2 (2009) --------------- 5
--------------------------------------------------------------------------------------------------------------------------------
A Novel Trend In Producing Ceramic Based Nanocomposite Material using α-
Al2O3 Powder and FeCl2 Solution as Starting Materials Mohamed. M. EL-Sayed & Mohamed M. Saleh
Sebha University, Sebha
E-mail: [email protected] or [email protected] --------------------------------------------------------------------------------------------------------------------------------
Abstract In recent years, it has been established that the incorporation of nano metallic particles
into a ceramic matrix lead to enhanced fracture properties. Alumina-iron nanocomposite powders
are prepared by a two-step process. In the first step, -alumina-ferrous chloride powder mixture
was formed by mixing -alumina powders with ferrous chloride solution followed by drying in
an oven at 60 oC for 24 h. In the second step, the ferrous chloride in the dry power mixture was
selectively reduced to iron particles. A reduction temperature of 750 oC for 15 min in dry H2 was
chosen based on the thermodynamic calculations The concentration of iron in ferrous chloride
solution was calculated to give 20 vol.% Fe in the final composite product. Two techniques were
used to produce composite bulk materials. The alumina-iron nanocomposite powders were
divided to two batches. The first batch of the produced mixture was hot pressed at 1400 C and
27 MPa for 30 min in a graphite die. To study the effect of oxygen on the Al2O3/Fe interface
bonding and mechanical properties of the composite, the second batch was heat treated in air at
700 C for 20 min to partially oxidize the iron particles before hot pressing Characterization of
the composites was undertaken by conventional density measurements, X-ray diffractometry
(XRD), Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and
electron probe microanalysis (EPMA). The mechanical properties of the produced composites are
also investigated. The suggested processing route (mixing, reduction and hot pressing) produces
ceramic-metal nanocomposite much tougher than the virgin alumina. The fracture strength of the
produced Al2O3/Fe nanocomposite is nearly twice that of the pure alumina. The presence of
spinal phase, FeAl2O4, as thick layer around the iron particles in the alumina matrix has a
detrimental effect on interfacial bonding between iron and alumina and the fracture properties of
the composite.
Key Words: Ferrous chloride, reduction, alumina-iron nanocomposite, spinal phase. --------------------------------------------------------------------------------------------------------------------------------
1. Introduction The application of ceramics as
engineering parts is handicapped by their
brittleness. It is well accepted that the
fracture toughness and in some cases
fracture strength of a brittle, ceramic
material can be increased through the
addition of a dispersed second phase. One
approach to this involves the introduction of
a ductile metallic phase into the oxide
ceramic matrix. This metallic phase can be
continuous along the grain boundaries of the
ceramic grains[1-5], or it can be highly
dispersed with a particulate morphology[6-11].
Of course, the processing of this material is
difficult, especially in the latter case, where
one desires a uniform dispersion of fine
-------------------------------------------------------------------------- Mohamed. M. EL-Sayed & Mohamed M. Saleh.
6 ------------- Journal of Sebha University - (Pure and Applied Sciences) - Vol. 8 No.2 (2009) ---------------
metallic particles within a fine-grained
ceramic matrix[12].
The toughening mechanisms of the
ceramic-metal composites have already been
investigated[6,11,13] and the enhancement is
believed to be produced by the plastic
inclusions which bridge the crack and are
stretched as it opens, absorbing energy
which contributes to the toughness.
Nevertheless, some interface conditions have
to be fulfilled in order for the plastic
deformation to be fully exploited[14-16].
Two main difficulties in the ceramic-
metal composites still remain and restrict
their use for structural application. The first
difficulty is the poor interfacial cohesion
between the metallic particles and the
ceramic matrix and the second is the highly
non-uniform and large metallic particles
dispersion often associated with a high
content of pores[17], where large amounts of
metal phase often interfere with the sintering
mechanisms. It has been proposed to reduce
such unfavourable characteristics by a
reduction of the mean grain size to the
nanometer region[8,18,19]. Both, the
achievable regularity of metallic dispersion
and the interfacial cohesion may be affected
by the grain size. Recently, many research
results showed that the toughness of ceramic
materials can be increased by utilizing nano
powder as starting materials[20-22].
Applications such as high
temperature engine components, catalysts
and alloys resistant to high temperature
oxidation have placed increasing emphasis
on metal-ceramic interfacial phenomena.
Although great studies have been made in
these areas[23,24], more work is needed before
a general understanding of these phenomena
can be reached.
Chemical reaction at ceramic-metal
interfaces can result in the formation of
intermediate phases and this may have a
marked effect on the interfacial properties
and thus on the final properties of the
produced composites. The reaction products
at alumina-metal interfaces are normally
spinel-type compounds. In alumina-metal
composites, the metal is either separated
from the alumina matrix by a double oxide
phase or is directly in contact with the
alumina. Systems Al2O3-MAl2O4-M, where
M stands for metal, are likely to exist when
the MO oxide is easy to form and is then
able to react with alumina to form an
MAl2O4 spinel phase. For example, such
systems were observed with M = Cu[25],
Mg[26], Ni[16]. Factors determining the effect
of interphase formation on bond strength
involve the extent of reaction, thickness of
reaction product, the mechanical properties
of the interphase, the stability of the
interphase, and its compatibility with the
metal and the ceramic.
As it was reported[12] that the mixing
of alumina powder and iron powder is
difficult due to both the tendency of
agglomeration of soft iron powders at higher
content and the difference in densities.
Therefore, the main aims of the present work
were to suggest a new technique to
overcome this problem and to produce
alumina-iron nanocomposite. Alumina-iron
nanocomposite powders are prepared by a
selective reduction process in which powder
mixture of -alumina and ferrous chloride
solution; as a source of iron, is reduced
selectively to produce -alumina-iron
mixture. The concentration of iron in Fecl2
solution was calculated to give 20 vol.% Fe
in the final composite. Microstructure and
-------------------------------------------------------------------------------- A Novel Trend In Producing Ceramic Based
------------- Journal of Sebha University - (Pure and Applied Sciences) - Vol. 8 No.2 (2009) ---------------7
mechanical properties of the produced
composites by hot pressing are examined.
The effect of heat treatment in presence of
oxygen on the formation of the spinel phase
and mechanical properties of the composite
are also investigated.
2. Experimental Procedures
2.1 Fabrication of the composites α-alumina powder (100 nm average
particle size and 99.99 % purity) was mixed
with ferrous chloride solution (as a source
material for iron) in a small hand mixer for
30 min. To achieve homogenous mixture of
α-alumina and ferrous chloride before
reduction and hot pressing. The wet α-
Al2O3/FeCl2 mixture was dried in an oven at
a temperature of 60 oC for 24 h, and then
crushed and sieved to less than 30 m in
grain size. It was observed that the color of
the dry blend was yellow-green. The dry
powder mixture was then reduced using
hydrogen gas with a flow rate of 5 L/min in
a quartz tubular reducing furnace, 4 cm in
diameter and 1.5 m in length at a
temperature of 750 oC for 15 min. The
reduced powder mixture was furnace cooled
to room temperature under a dry hydrogen
atmosphere before removal from the furnace
to the hot pressing step. The color of the
powder mixture after reduction process is
completely changed to slivery-gray,
indicating the complete reduction of ferrous
chloride and good dispersion of iron
particles throughout α-alumina.
Two techniques were used to produce
composite bulk materials. The alumina-iron
nanocomposite powders were divided for
two batches. Batch one of the produced
mixture was hot pressed at 1400 C and 27
MPa for 30 min in a graphite die of diameter
42.5 mm. The heating rate of hot-pressing
was 20 C min-1. The die was prevented
from oxidation by an inert argon atmosphere.
Batch two was heat treated in air at 700 C
for 20 min to partially oxidize the iron
particles before hot pressing to study the
effect of oxygen on the Al2O3/Fe interface
bonding and mechanical properties of the
produced composite. For comparison
monolithic alumina specimens were also
fabricated using the same method and the
same powder. Throughout the article
samples prepared from batch one is called
composite I, whereas, samples produced
from batch two is called composite II
2.2 Characterization of powders and
composites
The hot-pressed bodies were cut into
bars (5×5×30 mm) using a diamond cut-off
wheel and ground with diamond metal
bonded plates and SiC abrasive papers with
different grit up to 1500, following by
polishing on felt-cloth with diamond paste to
0.5 m surface finish. The densities of the
hot-pressed samples were measured using
Archimeds’principle in toluene, and the
theoretical density was calculated by the law
of mixture. Phase identification of powders
and the final composite was determined
using X-ray diffractometey (XRD) on a
D/Max-RB X-ray diffractrometer.
Transmission electron microscopy (TEM)
was used to measure and analyze the
powders size and morphology of the reduced
iron particles. Hardness (HV10) was
obtained with Vickers diamond indenter
using a 98 N load and a loading time of 15
sec. The harness value was taken as an
average of 10 readings. The fracture strength
of the composites was evaluated using a
three-point bending test at ambient
conditions with span 24 mm and cross head
-------------------------------------------------------------------------- Mohamed. M. EL-Sayed & Mohamed M. Saleh.
8 ------------- Journal of Sebha University - (Pure and Applied Sciences) - Vol. 8 No.2 (2009) ---------------
speed 0.5 mm min-1. Microstructure
observations of the polished surfaces, the
fracture surfaces and the crack propagation
behaviour of the produced composites were
investigated using a Stereoscan 360
(Cambridge, UK) scanning electron
microscope (SEM) working at 20 Kv. The
surfaces were coated with gold using a Joel
fine coater machine (JFC-1200) to avoid
charging during the SEM observations.
Electron probe micro analysis (EPMA) was
used to analyze the distribution elements of
composite II. The fracture toughness was
measured using the indentation strength by
bending (ISB) method[27].
3. Results and Discussion:
The chemical reaction for the reduction of
ferrous chloride by hydrogen gas can be
represented as:
1...........)(
)()()( 22
gasHCl
solidFegasHsolidFeCl Heat
Based on the thermodynamics
calculation (see appendix A) and the given
data in Table 1[28], the equilibrium
temperature for reaction in Eq.1 was found
to be 615 oC (888 K). Since the reduction of
ferrous chloride by hydrogen is endothermic
reaction (H888 K = 146.23 KJ.mol-1), a
temperature higher than the calculated
equilibrium temperature is required for the
reaction to proceed in the direction of iron
formation. In the present work the
temperature of reduction chosen to be 750 oC.
Table 1 Values of the standard free energy change, enthalpy change and entropy
for FeCl2 (s), HCl (g), H2 (g) and Fe(s) [28].
Materials )( 1
298
molkJ
H o
k
)( 1
298
molkJ
G o
K
)( 11
298
kmolJ
S o
k 22 cTTcbTaCp
a 310b 510c c
FeCl2 (s) -342.25 -303.49
120.1 79.25 8.70 -4.90 ---
HCl (g) -92.31 -95.23
186.6 26.53 4.60 2.59 ---
H2 (g) 0.00 0.00
130.6 27.28 3.26 0.50 ---
Fe (s) 0.00 0.00
27.15 17.49 24.77 --- ---
The XRD profiles that were
registered for the starting mixture of -
alumina and ferrous chloride before
reduction, after reduction in a H2 gas at 750
for 15 min, and after heat treating the
reduced mixture in air at 700 oC for 20 min
are given in Fig 1. The XRD pattern before
reduction, contains only the characteristic
peaks for -Al2O3 and FeCl2.4H2O, line a in
Fig.1. After reduction at 750 C for 15 min,
The FeCl2.4H2O peaks are not observed,
whereas the peaks for -Al2O3 and Fe are
found, line b in Fig.1, indicating complete
reduction of FeCl2.4H2O phase to iron phase
according to Eq.1.
-------------------------------------------------------------------------------- A Novel Trend In Producing Ceramic Based
------------- Journal of Sebha University - (Pure and Applied Sciences) - Vol. 8 No.2 (2009) ---------------9
Fig.1 XRD profiles for the starting mixture of -alumina and ferrous chloride
before reduction (line a), after reduction in a H2 gas at 750 for 15 min (line b),
and after heat treating the reduced mixture in air at 700 oC for 20 min (line c).
Some iron particles that collected by
magnetic field form the reduced alumina-
ferrous chloride mixture is investigated using
TEM to determine their morphological
(particle size and shape) properties, Fig.2. As
it is shown in Fig.2, the size of the produced
iron powders in the range of 50 -110 nm and
the particles shows the spherical shape.
Fig.2 Typical morphology of the iron powders (TEM)
10 20 30 40 50 60 70 80
2, °
Inte
nsity
, Arb
itrar
y un
itsFe
Spinel
(a)
(b)
(c)
Fe2Cl2.4H2O
-Al2O3
-------------------------------------------------------------------------- Mohamed. M. EL-Sayed & Mohamed M. Saleh.
10 ------------- Journal of Sebha University - (Pure and Applied Sciences) - Vol. 8 No.2 (2009) ---------------
The XRD pattern of hot-pressed
composite of the reduced mixture, composite
I, gives the same characteristic peaks that
given in line b, Fig.1, indicating there is no
reaction product between -Al2O3 and Fe
during the consolidation process. Typical
microstructure for the composite I is shown
in Fig.3. The iron areas have bright contrast
whereas, the alumina grains are dark. Iron
particles appear to be uniformly distributed
in the alumina matrix. The materials are
homogeneous in that the volume fraction of
metal is constant everywhere in the
specimen. Coalescence of the initial iron
nano-particles in the chemically synthesized
powder occurs during the thermal
consolidation and micrometer size metal
particles with a complex morphology are
formed. Nevertheless, a large amount of
finer-scale particulates have also been
retained and a wide distribution of shape and
size is observed, Fig.3 (b).
The XRD profiles that were
registered for powders of batch two, after
heat treated in air at 700 C for 20 min
shows the peaks of -Al2O3, Fe and FeAl2O4
spinel phase, as shown in Fig.1 (line c). The
same peaks are also observed after hot-
pressing. The appearance of the FeAl2O4
spinel phase in batch two after treating and
in its composite is due to the presence of
oxygen in the surrounding atmosphere.
Fig.3 (a) Low and (b) high magnification SEM photomicrographs showing the
microstructure of composite I .
The photomicrograph in Fig.4 shows
typical microstructure for the composite II.
Three distinguished regions are observed:
alumina (dark regions), iron (light regions)
and spinel (gray regions). Open porosity can
be observed at the Al2O3/FeAl2O4 and
FeAl2O4/Fe interfaces, Fig.4 (b). It was
reported that the presence of spinel phase is
expected with oxygen presence in the
environmental production operation of the
composite and its thickness depends on the
time and temperature of processing[16,31]. It
was observed in Fig.4 (b) also, some iron
particles that completely changed to the
spinal phase due to the sensitivity of the
reduced iron particles to oxygen in air during
heat treatment at 700 oC for 20 min. Hence,
the oxygen partial pressure in this region was
-------------------------------------------------------------------------------- A Novel Trend In Producing Ceramic Based
------------- Journal of Sebha University - (Pure and Applied Sciences) - Vol. 8 No.2 (2009) ---------------11
high enough such that the conditions for
spinel formation were satisfied. Figure 5
shows the distribution map of the constituent
elements for composite II, i.e. iron,
aluminum, oxygen as shown in Figs.5 (b),
Fig.5 (c), and Fig.5 (d), respectively. It can
be seen that the gray areas corresponding to
spinel have a depleted amount of iron and
aluminum. The spinel is associated with the
iron particles and has formed as a result of
the additional oxygen in the system. The
central region in Figure 5 (a) shows very
little porosity and any porosity that does
exist appears to be associated with the spinel
regions. The fact that most of the iron was
consumed in the process of spinel formation
in many regions suggests that the conditions
for spinel formation were not optimized
Fig.4 (a) Low and (b) high magnification SEM photomicrographs
showing the microstructure of composite II .
Fig 5. Electron probe chemical analysis showing the distribution map of the constituent
elements for the composite II; (a) same as b in Fig.4, but higher magnification (b)
iron, (c) aluminum and (d) oxygen.
-------------------------------------------------------------------------- Mohamed. M. EL-Sayed & Mohamed M. Saleh.
12 ------------- Journal of Sebha University - (Pure and Applied Sciences) - Vol. 8 No.2 (2009) ---------------
Densities, mean values of hardness,
fracture strength and fracture toughness of
the alumina and composites are given in
Table 2. Relative density of composite I is
slightly higher than that of the hot-pressed
monolithic alumina. Nevertheless, the final
density of both composite and the monolithic
alumina is higher than 99.4 % of the
theoretical value. It can be concluded that
the hot-pressing technique in the present
study succeeded to consolidate a monolithic
ceramic and ceramic/metal nanocomposites
and produce nearly full dense materials.
Relative sintered density of composite II
gives a lower value around 96.5 %. This
decrease in density may be attributed to of
the presence of porosity associated with the
formation of iron aluminate spinal
phase[16,29].
The hardness values of all the
composite specimens are lower than that of
pure alumina. The lower hardness values of
the composites could be explained by
addition of ductile iron particles to the
matrix. The fracture strength of the produced
composite I is higher than that of the
alumina and the produced composite II. It is
reasonable to expect the increase of the
fracture strength with decreasing the grain
size, as suggested by Petch for brittle metals,
and by the Griffith criterion for brittle
fracture[30]. The strengthening of composite I
is, therefore, explained as being mainly
attributed to the refinement of matrix grains
by the nano-sized iron dispersion at the grain
boundary and the toughness improvement.
This results is in a good agreement with that
obtained by Sung –Tag Oh et al.[8] for the
alumina/copper system. The two composites
have been found to be tougher than the
virgin alumina matrix. Significant
improvement of fracture toughness was
observed for composite I, as shown in Table
2. Toughness of composite I is twice as high
as than that of the alumina, whereas,
toughness of composite II is improved only
by 50 % over that of the pure alumina
specimens. The lower fracture toughness of
composite II is ascribed to the lack of ductile
iron particles in the microstructure due to the
fact that they were consumed in the process
of forming the brittle spinel phase.
Table 2 Relative density and mechanical properties of the composites and the
aluminamonolithic.
Material Density
(% theoretical)
Hardness
(GPa)
Fracture strength
(MPa)
Fracture toughness
(MPa m1/2
)
Pure alumina 99.4 20.1 400 3.4
Composite I 99.6 14.8 780 8.1
composite II 96.5 15.3 470 5.1
Scanning electron micrographs of the
fracture surfaces for the composite I and the
composite II are shown in Figs.6 and 7,
respectively. As shown in Fig.6 (a) iron
particles that have been deformed plastically
can be observed in some areas, and these
-------------------------------------------------------------------------------- A Novel Trend In Producing Ceramic Based
------------- Journal of Sebha University - (Pure and Applied Sciences) - Vol. 8 No.2 (2009) ---------------13
particles contribute more to toughening.
However, there are also cavity sites on the
fracture surface, indicating pull out of some
iron particles. The main toughening
mechanisms in such type of composite are
crack deflection and plastic deformation of
the metal particles. Figure 8 also shows
cavity sites on the fracture surface,
indicating pull out of iron particles and
spinel phase. Pull out of iron particles
seriously restricts the plastic deformation of
the iron during the fracture of the composite
II. Microcracks could be observed on the
fracture surface of composite II, as shown in
Fig.7 (a).
Fig.6 SEM photomicrograph showing the fracture surface of composite I
Fig.7 (a) Low and (b) high magnification SEM photomicrographs
showing the fracture surface of composite II
However, very little iron particles that
have been deformed plastically can be
observed, and these particles slightly
improve the toughness. The toughening
mechanisms, which are observed to occur in
this composite, include mainly the crack
deflection mechanism. In the region where
spinel phase exists, the indentation crack
goes through the spinel phase, or along the
interface between the iron and the spinel as
shown in Fig.8 indicating poor bonding at
the FeAl2O4/Fe and FeAl2O4/Al2O3
interfaces. Therefore, it can be concluded
that, the spinel regions are detrimental to the
toughness of the composite II, as they would
provide a preferential fracture path for a
propagating crack producing a more brittle
material. The poor bonding between
spinel/alumina and spinel/metal is also
observed in other ceramic/metal systems[16,
29]. Trumble and Ruhle[29], in a study of
spinel interphase formation at diffusion-
-------------------------------------------------------------------------- Mohamed. M. EL-Sayed & Mohamed M. Saleh.
14 ------------- Journal of Sebha University - (Pure and Applied Sciences) - Vol. 8 No.2 (2009) ---------------
bonded Al2O3/nickel interfaces, have
observed the existence of physical gaps
along the spinel layer and, thus, proposed
that this is the origin of the weakness of the
spinel/nickel interface. In contrast to their
observation, Sun and Yeomans[31], reported
that the spinel/nickel interface is quite
intimate, and no physical gap has been
observed. In the present work, both
phenomenon are observed between the
spinel/alumina and the spinel/iron interfaces.
Thus, the spinel/iron interface may be
intrinsically weak, or the weakness may be
due to the residual thermal stress because of
the difference in coefficient of thermal
expansion (CTE) between spinel and iron.
Because the CTE of spinel is almost the
same as that of alumina[32], thermal stresses
at the spinel/iron and Al2O3/iron interfaces
should be very similar. Thus, the spinel/iron
interface may be considered to be
intrinsically weak. Thick layer of spinel has
a detrimental effect on the mechanical
properties in many systems[29, 31].
Fig.8 (a) Low and (b) high magnification SEM photomicrographs
of indentation cracks propagation in the composite II
The effect of a very thin layer of spinel
(such as one atomic layer) on the bonding
between iron and Al2O3 is unclear and
difficult to control, however some authors
consider it to be beneficial for the bonding
between nickel and alumina in the
alumina/nickel composite[33]. In fact, the
phenomena of the spinel phase formation
and the factors affecting are not well
understood till now and need more research.
Moreover, it is difficult to control the
thickness of spinel phase in all the areas of
the hot pressed specimens, because of the
oxygen partial pressure gradient from the
outer surface to the inner surface of the
specimen.
4. Conclusions (1) A novel processing route consists of
mixing -alumina powder with
ferrous chloride solution followed by
drying and reduction at 750 oC for 15
min in a dry hydrogen atmosphere
successfully produced -alumina-
iron powder mixture, where nano-
sized iron particles are
homogenously and highly distributed
in the alumina matrix.
(2) Hot pressing of the formed powder
mixture at 1400 C and 27 MPa for
30 min in a graphite die produce
ceramic-metal nanocomposite with
fracture strength and fracture
-------------------------------------------------------------------------------- A Novel Trend In Producing Ceramic Based
------------- Journal of Sebha University - (Pure and Applied Sciences) - Vol. 8 No.2 (2009) ---------------15
toughness that are twice as high as
those of the monolithic alumina. In
other words, this technique offers a
new nano composite material with
fracture strength of 780 MPa and
fracture toughness of 8.1 MPam1/2,
that can be the perfect candidate in
many structural and engineering
applications.
(3) Heat treatment of the -Al2O3-Fe
powder mixture in air at 700 oC for
20 min produces powder mixture
mainly consists of -Al2O3, Fe and
FeAl2O4 spinel.
(4) Hot pressing of the -Al2O3-Fe-
FeAl2O4 powder mixture produces
composite with fracture strength and
fracture toughness that are slightly
higher than those of the monolithic
alumina.
(5) The presence of spinal phase,
FeAl2O4, as thick layer around the
iron particles in the alumina matrix
has a detrimental effect on interfacial
bonding between iron and alumina
and the fracture properties of the
composite.
Appendix : Calculation of reduction
temperature of ferrous chloride: Based on the thermodynamics
aspects and from the given data in Table 1,
the free energy change (Go) for the
reduction of ferrous chloride to iron
according to Eq.1 can be calculated using
Eq. 2 to be: 113.03 KJ.mol-1
)2(22
298o
Fe
o
FeCl
o
HCl
o
Feko GGGGG
This means that the reaction is not
spontaneous and need energy to start. The
enthalpy change (Ho) for the reduction
reaction gives a value of 157.63 KJ.mol-1
using Eq.3:
)3(222298
o
H
o
FeCL
o
HCL
o
Fe
o
k HHHHH
and the entropy change gives a value of 149.65 J.mol-1.K-1 using Eq.4.
)4(222298
o
H
o
FeCL
o
HCL
o
Fe
o
k SSSSS
Change of specific heat at constant pressure (CP) can be calculated using Eq.5 to be:
o
H
o
FeCL
o
HCL
o
Fe
o
k CpCpCpCpCp22
2298
= -35.98 + 0.02201 T + 9.578 10-5 T-2 (5)
At the reduction temperature T:
)6(298
298 dtCHHT
K
P
o
KT
)7(298
298 dtT
CSS
T
K
Po
KT
For the reduction of ferrous chloride by
hydrogen to start G in the general form of
thermodynamic second law (Eq.8) should be
less than zero and HT has a positive value .
)8(TT STHG
-------------------------------------------------------------------------- Mohamed. M. EL-Sayed & Mohamed M. Saleh.
16 ------------- Journal of Sebha University - (Pure and Applied Sciences) - Vol. 8 No.2 (2009) ---------------
At G = 0 and substituting in Eq.8 using Eqs 6 and 7, then:
)9(0)()(298
298
298
298
dtT
CSTdtCH
T
K
Po
K
T
K
P
o
K
On solving Eq.9 by substituting the value of
CP (Eq.5) and integrating the equation as a
function of T, the theoretical value of the
reduction temperature of ferrous chloride to
iron particles is obtained to be 615 oC.
--------------------------------------------------------------------------------------------------------------------------------
دام مسحوق طريقة مبتكرة إلنتاج المواد المركبة النانومترية ذات األرضيه السيراميكيه باستخ
أكسيد األلومنيوم ومحلول كلوريد الحديدوز كمواد أولية صالح محمد مفتاح، محمد محمد عبد المنعم السيد
كلية الهندسة ـ جامعة سبها --------------------------------------------------------------------------------------------------------------------------------
ملخصال
سبها خواص جديدة مثل مقاومتها أوضحت األبحاث الحديثة أن إضافة المواد الفلزية النانومتريه الى المواد السيراميكية يك
لالنهيار المفاجئ وذلك بتحسين المتانة مع الحفاظ على خواصها األصيلة مما يفتح مجاالت إستخدام جديدة للمواد المركبة
الناتجة. وتهدف هذه الدراسة إلى تحضير و إنتاج المواد المركبة النانومترية ذات األرضية السيراميكية بطريقة اختزال منتقاه
لخليط مسحوق أكسيد األلومنيوم مع محلول كلوريد الحديدوز والذى يتم فيه إختزال األخير بواسطة الهيدروجين الجاف الى حديد
بالحجم من الحديد. وأختيرت درجة %20بحجم حبيبات فائقة الدقة )نانومتر( وتم الخلط على أساس إنتاج مواد مركبه تحوي
دقيقه. هذا وتم إنتاج 15ناءا على حسابات الديناميكا الحرارية وتم اإلختزال عند زمن درجه مئوية ب 750حرارة اإلختزال
جو خامل عند درجة حرارة فينوعين من المواد المركبة: النوع األول تم كبس الخليط الناتج من اإلختزال مباشرة على الساخن
النوع الثانى من المواد المركبة تم معالجة الخليط الناتج من فيميجابسكال, و 27دقيقة و ضغط 30درجة مئوية وزمن 1400
دقيقة و ذلك قبل كبسه على الساخن بهدف دراسة 20درجة مئوية و لمدة 700الهواء عند درجة حرارة فياإلختزال حراريا
ميكانيكية للمواد المركبة الناتجة. تأثير األكسجين على قوة الربط بين الحديد و أكسيد األلومنيوم وبالتالي تأثيره على الخواص ال
( XRDهذا ولتقيم سلوك وخواص المخلوط الناتج من اإلختزال وكذا المواد المركبة تم استخدام األشعة السينية )
( وتم رصد تواجد عناصر األلومنيوم TEM( والميكروسكوب اإللكتروني النافذ )SEMوالميكروسكوب اإللكتروني الماسح )
إختبار EPMAالمواد المركبة الناتجة بواسطة جهاز التحليل اإللكتروني ) فين والحديد واألكسجي ( هذا وتم أيضا
الخواص الميكانيكية للمواد المركبة. ولقد أوضحت النتائج أن طريقة اإلنتاج المقترحة )خلط ثم اختزال ثم كبس على الساخن(
بالحجم( فائقة الدقة ومتجانسة التوزيع مع %20تحوى مواد فلزيه )إنتاج مواد مركبه ذات أساس سيراميكى و فينجحت
تحسين المتانة و مقاومة الكسر كما وجد أيضا أن وجود تفاعل كيميائي بين أكسيد الحديد و أكسيد األلومنيوم وتكون الطور
4O2FeAl ة الناتجة.صورة طبقه سميكة يضعف المتانة و مقاومة الكسر ويعجل بانهيار المواد المركب في --------------------------------------------------------------------------------------------------------------------------------
References
1. Han D. and J. J. Mecholsky: 1990,J. Mater.
Sc., 25, 4949.
2. Flinn B. D., C. S. LO, F. W. Zok and A. G.
Evans: 1993, J. Amer. Ceram. Soc., 76, 369.
3. Sun X. and J. A. Yeomans: J. Meter. 1996,
Sci. Technol., 12, 124.
4. El-Sayed Seleman M. M., F. Zhang, X.
Sun and L. Zuo: 2000, in Proc. of the
ICCE/7, Ed. D. Hui, Denver, Colorado, 783.
5. Zhang F.: 2001 Ph.D. Thesis,
Northeastern University, China,.
6. El-Sayed Seleman M. M.: 2005, in Proc.
of the 9th International Conference of
-------------------------------------------------------------------------------- A Novel Trend In Producing Ceramic Based
------------- Journal of Sebha University - (Pure and Applied Sciences) - Vol. 8 No.2 (2009) ---------------17
Petroleum,Mining and Metallurgical
Engineering , February, Cairo, 110.
7. Schicker S., D. E. Garcia, J. Bruhn, R.
Janssen and N. Claussen: 1997, J. Amer.
Ceram. Soc., 80, 2294.
8. Tag Oh S., T. Sekino and K. Niihara:
1998, J. Eur. Ceram. Soc., 18, 495.
9. Chou W. B. and W. H. Tuan: 1995, J.
Eur. Ceram. Soc., 15, 291.
10. Chakraborty A., S. V. Kamat, R. Mitra
and K. K. Ray : 2000, J. Mater. Sci., 35,
3827.
11. El-Sayed Seleman M. M.: 2003, in
Proc. of the 5th Egyptian-Syrian Conference
on
Chemical and Petroleum Engineering, Suez,
Egypt, October, 849.
12. Breval E., G. Dodds, and C. G. Pantano:
1985, Mat. Res. Bull., 20, 1191.
13. Ashby M. F., F. G. Blunt and M.
Bannister: 1989, Acta Metall., 37, 1847.
14. Xiao L. and R. Abbaschian: 1992,
Metall. Trans., 23 A, 2863.
15. Zhang X., G. Lu, M. J. Hoffmann and R.
Metselaar: 1995,J. Eur.Ceram. Soc., 15, 225.
16. Sun X. and J. A. Yeomans: 1996 , J.
Meter. Sci. Technol., , 12, 421.
17. Breval E., Z. Deng, S. Chiou and C. G.
Pantano : 1992, J. Mater. Sci, 27, 1464.
18. Nalwa H. S.: 2002, Nanostructured
Materials and Nanotechnology, Academic
Press, San Diego, California, USA, 70.
19. Rousset A.: 1994, J. of Solid State
Chemistry, 111, 164.
20. Han Y., Q. Xian, X. Wang, Y. Jiang and
Y. Liang: 2001, J. Mater. Sci. Technol., 17
Suppl.1 , 52.
21. Matsunaga T., U. Leela-Adisorn, Y.
Kobayashi, S. Choi and H. Awaji: 2005, J.
Eur. Ceram. Soc., , 113, 123.
22. Majumdar R : 2008 , Nanotechnology :
Basic Science and Emerging Technologies,
1st ed., Cyber Tech Publications, New Delhi.
23. Devaux X., Ch. Laurent, M. Brieu and A.
Rousset: 1992, J. of Alloys and Compounds,
188, 179.
24. Smith M. A. and D. P. Pope: 1991,
Materials Science and Engineering, A145,
79.
25. Wlosinski W. K.: 1984, in Sintered
Metal Ceramic Composite, ed. by G. S.
Upadhyaya, Elsevier, Amsterdam, 483.
26. 1992, S. Antolin and A. S. Nagelberg: J.
Am. Ceram. Soc., 75 [2], 447.
27. Chantikul P., G. R. Anstis, B. R. Lawn
and D. B. Marshall: 1981, J. Amer. Ceram.
Soc., 64, 539.
28. Smith J. M., H. C. Van Ness and M. M.
Abbott: 2001. Introduction to Chemical
Engineering Thermodynamics, 6th ed.,
McGraw-Hill, New York,
29. Trumble K. P. and M. Ruhle: 1991, Acta
Metall. Mater., 39(8), 1915.
30. Kingery W. D., H. K. Bowen, and D. R.
Uhlmann: 1976, Interduction to ceramics, 2nd
edn., John Wiley and Sons, New Yyork, 765.
31. Sun X. and J. A. Yeomans: J. Am.
Ceram Soc., 1996, 79 [10], 2705.
32. Touloukian Y.S., R. K. Kirby, R. E.
Talor and P. D. Desai: 1977,
Thermophysical Properties of Matter Vol.12,
IFI / plenum, New Yourk,.
33. Bailey F.P. and W. E. Borbidge: 1981, In
Surface and Interface in Ceramic and
Ceramic Metal Systems, eds. By J. Pask and
A. Evans, Plenum Press, New York, 525