The document summarizes research on synthesizing alumina-zirconia nanocomposites using a sol-gel process with organometallic precursors. Key findings include:
1) Alumina-zirconia nanopowders were successfully synthesized via a sol-gel process using aluminum butoxide and zirconium propoxide precursors.
2) Characterization of the nanopowders found them to have ultrafine particle sizes less than 10 nm based on BET surface area analysis and TEM imaging.
3) Parameters like solvent, precursor concentration, temperature, and pH were varied to study their effects on the sol-gel process and resulting particle size.
Synthesis and characterization of ZnO nanoparticles via aqueous solution, sol...iosrjce
ZnO nanoparticles were synthesized by aqueous solution method, sol-gel method and hydrothermal
method.The synthesized particles were characterized by XRD ,SEM ,EDX and UV .The X-ray diffraction studies
reveals that the synthesized ZnO nanoparticles have wurtzite structure and the particle size varies from 13 to 18
nm. Scanning Electron Microscopic investigation reveals that the surface morphology of ZnO nanoparticle is
spherical in hydrothermal process and varies to flower like arrangement in aqueous solution and sol-gel
process. The UV-Visible spectrum of the nanoparticles shows a blue shift compared to that of the bulk sample.
Presented in the 15th NCB International Seminar held from 05.12.- to 08.12.2017, the Indian organization for research and technological development under the administrative control of the Ministry of Commerce and Industry of the Government of India held the 15th edition of the NCB International Seminar, which again took place at the Manekshaw Centre in New Delhi.Was the 1st presenter in the Technical session:'Other Building Materials & Binders' held in Ashoka Convention Hall.Due to other important commitments Mr. Suresh Prabhu, Minister of Commerce and Industry, Government of India, was unable to attend the NCB International Seminar personally. Nevertheless he was able to welcome the delegates and to hold his inaugural address via video live stream. Regarding the technological development of the cement industry, one of the main challenges for the future perspective will be the limited materials. To help cope with the future challenges he confirmed the support of the Ministry of Commerce and Industry.
Synthesis of ZnO Nanoparticles using wet chemical method and its characteriza...Govind Soni
This is very intersting power point on ZnO NPs synthesized by me GOVIND SONI and my lab partnes KAUSHAL ,SANEHA & DINESH under the guidance of our PhD scholar Mr.SAHIL & Ms.KIRTI in the CYRSTAL LAB of DR.BINAY KUMAR in Department of Physics & Astrophysics .This presentation basically covers the Introduction to Nanoscience and Nanotechnology and synthesis of Zinc oxide nanoparticles using wet chemical method . its characterization has been done in Msc finals Nanoscience lab using X-Ray Diffraction and Particle size Analyzer.This presentation also contains an advance topic on introduction to Spintronics which is basically the study of internsic spin of electronics and its magnetic moment.I hope it will be an important tool to know about Nanoworld .
Synthesis and characterization of ZnO nanoparticles via aqueous solution, sol...iosrjce
ZnO nanoparticles were synthesized by aqueous solution method, sol-gel method and hydrothermal
method.The synthesized particles were characterized by XRD ,SEM ,EDX and UV .The X-ray diffraction studies
reveals that the synthesized ZnO nanoparticles have wurtzite structure and the particle size varies from 13 to 18
nm. Scanning Electron Microscopic investigation reveals that the surface morphology of ZnO nanoparticle is
spherical in hydrothermal process and varies to flower like arrangement in aqueous solution and sol-gel
process. The UV-Visible spectrum of the nanoparticles shows a blue shift compared to that of the bulk sample.
Presented in the 15th NCB International Seminar held from 05.12.- to 08.12.2017, the Indian organization for research and technological development under the administrative control of the Ministry of Commerce and Industry of the Government of India held the 15th edition of the NCB International Seminar, which again took place at the Manekshaw Centre in New Delhi.Was the 1st presenter in the Technical session:'Other Building Materials & Binders' held in Ashoka Convention Hall.Due to other important commitments Mr. Suresh Prabhu, Minister of Commerce and Industry, Government of India, was unable to attend the NCB International Seminar personally. Nevertheless he was able to welcome the delegates and to hold his inaugural address via video live stream. Regarding the technological development of the cement industry, one of the main challenges for the future perspective will be the limited materials. To help cope with the future challenges he confirmed the support of the Ministry of Commerce and Industry.
Synthesis of ZnO Nanoparticles using wet chemical method and its characteriza...Govind Soni
This is very intersting power point on ZnO NPs synthesized by me GOVIND SONI and my lab partnes KAUSHAL ,SANEHA & DINESH under the guidance of our PhD scholar Mr.SAHIL & Ms.KIRTI in the CYRSTAL LAB of DR.BINAY KUMAR in Department of Physics & Astrophysics .This presentation basically covers the Introduction to Nanoscience and Nanotechnology and synthesis of Zinc oxide nanoparticles using wet chemical method . its characterization has been done in Msc finals Nanoscience lab using X-Ray Diffraction and Particle size Analyzer.This presentation also contains an advance topic on introduction to Spintronics which is basically the study of internsic spin of electronics and its magnetic moment.I hope it will be an important tool to know about Nanoworld .
Synthesis and characterization of pure zinc oxide nanoparticles and nickel do...eSAT Journals
Abstract In this paper, Zinc oxide nanoparticles are synthesized by simple wet chemical precipitation method. Zinc nitrate and sodium hydroxide are used as the starting materials.Zinc oxide nanoparticles are formed at a very low temperature of the order of 800C. Nickel doped zinc oxide nanoparticles are synthesized in two steps. In first step precipitate is obtained by reduction of mixture of zinc nitrate, ferric nitrate and starch by sodium hydroxide solution while in second step the given precipitate is thermally decomposed at high temperature of the order of 4000C. The crystallinity of the synthesized nanoparticles is then confirmed by X ray diffraction spectroscopy (XRD).The elemental composition of the powder is detected by Energy Dispersive X ray spectroscopy (EDAX). The morphology of the powder is investigated by Scanning Electron Microscopy (SEM). Magnetic characterization of nickel doped zinc oxide nanoparticles is done by Squid Magnetometer. Low temperature magnetization behavior revealed ferromagnetic behavior of sample. Key Words: Zinc oxide nanoparticles, Nickel doped ZnO, Antibacterial activity, Squid magnetometer, SEM
Fundamentals, synthesis and applications of Al2O3-ZrO2 compositesTANDRA MOHANTA
When the word “Ceramic” comes to our mind, we usually associate them with plates, saucers, cups and mugs. But, the word “Ceramic” encompasses more than just the word “plates” or “saucers”. Indeed, ceramic materials are hard and inherently brittle, but this is just the tip of the iceberg. They have multifarious properties and have acquired a status of high technical importance in the field of scientific research. Ceramics are the soul of the modern day’s structural applications owing to their high mechanical and thermal stability under different challenging conditions. They exhibit remarkable properties such as high hardness, high wear resistance, high corrosion resistance, high elastic modulus, high melting point and the ability to retain high strength at elevated temperatures. Alumina (Al2O3) is one such remarkable ceramic material known for its unique optical, mechanical and electrical properties. But the brittle nature of Al2O3 limits its use in certain engineering applications. Therefore, the strength of Al2O3 and Al2O3- based ceramics can be enhanced by tailoring the microstructural design through the application of strategic techniques that may involve secondary phase particle inclusion (such as Zirconia, ZrO2)
Diffusion Dynamics of Metal Ions Uptake at the CarboxylatedEpichlorohydrin Re...IJERA Editor
Investigation into the diffusion dynamics of Mn2+ , Fe2+ and Pb2+ ions uptake from aqueous solution by chemically modified red onion skin extract was carried out. The polyhydroxylic extract of red onion skin was utilized in the synthesis of carboxylated-epichlorohydrin red onion skin extract resin (CERR). The fourier transform infrared spectra of red onion skin extract and CERR exhibited variations in bond interactions which was ascribed to the structural modification of the extract to yield CERR. Predictions of the mechanism of diffusion dynamics were carried out by applying the data resolved from the fractional attainment of equilibrium at varied times into the Vermeulen diffusion models within the temperature range of 29 to 70°C. The predominance of film diffusion mechanism was established from the smaller values of its diffusion coefficients as compared to those of particle diffusion. The film diffusion coefficient values were lowest at 29°C, indicating the most probable temperature condition for optimum exchange result with the CERR. Deductions from utilizing the Arrhenius type temperature dependence equation gave negative values of activation energy (-7.223 kJ/mol for Mn2+ , -6.898 kJ/mol for Fe2+ and -13.957 kJ/mol for Pb2+ ions); which suggests that increase in temperature from 29 to 70°C, lowered the rate of the exchange reaction.
Influence of reaction medium on morphology and crystallite size of zinc oxidejournal ijrtem
ABSTRACT : Zinc oxide nanoparticles were prepared by reacting zinc chloride and sodium hydroxide in different mediums such as chitosan, poly vinyl alcohol, ethanol and starch. The materials were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD) studies, transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). Elemental analysis was done by energy dispersive X-ray Analysis (EDAX).
KEY WORDS : Nano zinc oxide, morphology, crystallite size
Synthesis and characterization of pure zinc oxide nanoparticles and nickel do...eSAT Journals
Abstract In this paper, Zinc oxide nanoparticles are synthesized by simple wet chemical precipitation method. Zinc nitrate and sodium hydroxide are used as the starting materials.Zinc oxide nanoparticles are formed at a very low temperature of the order of 800C. Nickel doped zinc oxide nanoparticles are synthesized in two steps. In first step precipitate is obtained by reduction of mixture of zinc nitrate, ferric nitrate and starch by sodium hydroxide solution while in second step the given precipitate is thermally decomposed at high temperature of the order of 4000C. The crystallinity of the synthesized nanoparticles is then confirmed by X ray diffraction spectroscopy (XRD).The elemental composition of the powder is detected by Energy Dispersive X ray spectroscopy (EDAX). The morphology of the powder is investigated by Scanning Electron Microscopy (SEM). Magnetic characterization of nickel doped zinc oxide nanoparticles is done by Squid Magnetometer. Low temperature magnetization behavior revealed ferromagnetic behavior of sample. Key Words: Zinc oxide nanoparticles, Nickel doped ZnO, Antibacterial activity, Squid magnetometer, SEM
Fundamentals, synthesis and applications of Al2O3-ZrO2 compositesTANDRA MOHANTA
When the word “Ceramic” comes to our mind, we usually associate them with plates, saucers, cups and mugs. But, the word “Ceramic” encompasses more than just the word “plates” or “saucers”. Indeed, ceramic materials are hard and inherently brittle, but this is just the tip of the iceberg. They have multifarious properties and have acquired a status of high technical importance in the field of scientific research. Ceramics are the soul of the modern day’s structural applications owing to their high mechanical and thermal stability under different challenging conditions. They exhibit remarkable properties such as high hardness, high wear resistance, high corrosion resistance, high elastic modulus, high melting point and the ability to retain high strength at elevated temperatures. Alumina (Al2O3) is one such remarkable ceramic material known for its unique optical, mechanical and electrical properties. But the brittle nature of Al2O3 limits its use in certain engineering applications. Therefore, the strength of Al2O3 and Al2O3- based ceramics can be enhanced by tailoring the microstructural design through the application of strategic techniques that may involve secondary phase particle inclusion (such as Zirconia, ZrO2)
Diffusion Dynamics of Metal Ions Uptake at the CarboxylatedEpichlorohydrin Re...IJERA Editor
Investigation into the diffusion dynamics of Mn2+ , Fe2+ and Pb2+ ions uptake from aqueous solution by chemically modified red onion skin extract was carried out. The polyhydroxylic extract of red onion skin was utilized in the synthesis of carboxylated-epichlorohydrin red onion skin extract resin (CERR). The fourier transform infrared spectra of red onion skin extract and CERR exhibited variations in bond interactions which was ascribed to the structural modification of the extract to yield CERR. Predictions of the mechanism of diffusion dynamics were carried out by applying the data resolved from the fractional attainment of equilibrium at varied times into the Vermeulen diffusion models within the temperature range of 29 to 70°C. The predominance of film diffusion mechanism was established from the smaller values of its diffusion coefficients as compared to those of particle diffusion. The film diffusion coefficient values were lowest at 29°C, indicating the most probable temperature condition for optimum exchange result with the CERR. Deductions from utilizing the Arrhenius type temperature dependence equation gave negative values of activation energy (-7.223 kJ/mol for Mn2+ , -6.898 kJ/mol for Fe2+ and -13.957 kJ/mol for Pb2+ ions); which suggests that increase in temperature from 29 to 70°C, lowered the rate of the exchange reaction.
Influence of reaction medium on morphology and crystallite size of zinc oxidejournal ijrtem
ABSTRACT : Zinc oxide nanoparticles were prepared by reacting zinc chloride and sodium hydroxide in different mediums such as chitosan, poly vinyl alcohol, ethanol and starch. The materials were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD) studies, transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). Elemental analysis was done by energy dispersive X-ray Analysis (EDAX).
KEY WORDS : Nano zinc oxide, morphology, crystallite size
A NOVEL PRECURSOR IN PREPARATION AND CHARACTERIZATION OF NICKEL OXIDE (NIO) A...antjjournal
Synthesis of Nickel Oxide (NiO) nanoparticles and cobalt oxide (CO3O4) materials synthesis by aqueous chemical growth (ACG) Techniques. Oxide based material having a wide band gap, and suitable for optical devices,Optoelectronic devices, UV photodetector, and Light emitting diode LEDs. The analysis
and characterizationof Nickel Oxide (NiO) and cobalt oxide (CO3O4) nanoparticles by(1) X-ray diffraction (XRD), (2) Scanning electron microscopy (SEM), and (3) Ultraviolet–visible (UV–Vis) spectroscopy.
The sol-gel route is a simple chemical m
through bonding of atoms at the scale of 10
fabrication of oxides of metals chemically.
chemical & optical are enhanced
that, the relative surface area of the
with the bulk material. Controlling the annealing temperature would result in various
micro structures for the compound being produced.
acid solution was formed by stirring
minutes and subsequently annealed at 400°C.
particles decreased along with
increase of the silica content in the mixture.
Short Notes for Understanding the Basics of Nano TechnologyEditor IJCATR
In this paper, the basic terms and definitions of nano technology was discussed. The characteristics, advantages and
disadvantages of nano technology were discussed. Applications of nano technology were also mentioned. This paper would be useful
to young engineers to study the fundamentals of nano particles. Two approaches used for nano technology were also elaborated.
Synthesis and Characterization of High Quality Mesoporous Material SBA-16 wit...iosrjce
IOSR Journal of Applied Physics (IOSR-JAP) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of physics and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in applied physics. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Just basics of mesoporous materials!!The Break through came around 1992 by both Japanese and Mobil scientist on the soft template based synthesis of mesoporous materials
Electrospun Nanofibers Reinforced Aluminium Matrix Composites, A Trial to Imp...IJAMSE Journal
A comparison between TiO2 nanofibers and carbon nanofibers as fibers reinforced metal matrix composites with respect to mechanical properties improvements have been made in this paper. Al and Mg have been chosen as metal matrices. The used carbon and ceramic nanofibers (Titanium Oxide) were successfully synthesized using electrospinning technique. Various weight percentage of calcined
electrospun TiO2 and carbon nanofibers (1, 3, 5 and 10%) were mixed with metal matrix and fabricated by route of powder metallurgy using High Frequency Induction heat Sintering (HFIHS). Mechanical properties of the sintered composites have been investigated. The manufactured pellets were tested for compression test, hardness and microstructures by the field emission scanning electron microscopes (FESEM), which reveals the homogeneous distribution of nanofibers in the Al/Mg matrices. In addition,
energy-dispersive X-ray spectroscopy (EDS) was employed to obtain the chemical analysis of each composite. The result shows that, the ultimate compressive strength increased to 415 MPa at 5% TiO2, which is 13.5% more than the pure Al. The hardness increased up to 64% in case of using the ceramic nanofibers as reinforcement. While using CNFs as reinforcement to the Al matrix deteriorates the
mechanical properties.
2. SYNTHESIS OF ALUMINA–ZIRCONIA 653
applications. The present work is aimed to do the same for
a cutting tool material; however, it also attempts to make
a realistic target of applying it and close the gap between
properties and actual application.
Alcohol-based solgel processes can have homogeneity on
a molecular scale (when using organometallic precursors).
In the case of inorganic salt precursor this solgel process
requires ability to coprecipitate to maintain homogeneity on
an atomic scale. For Alumina–Zirconia system the inorganic
salts do not coprecipitate.
Solgel process, being a popular as well as versatile
process, has been used in multiple studies and material
systems. It has been used to make ceramics at low
temperature—say, to coat on polymer or maintain single
phase without phase separation or to prevent phase
coarsening. It has also been used to produce nearly full
density at low temperature due to high surface area
of solgel product. Some have used solgel to vary and
control composition. It can be a good process to obtain
uniform dispersion of a second molecular species/second
phase. The solgel process can enable the tailoring of
particle/coating size. Other studies have used solgel to
overcome agglomeration and enable scaling-up. Another
study has used solgel to synthesize sol stable for long
periods of time. The present study aims to incorporate most
of these features in a single process.
Solgel being the low temperature process, it offers
the greatest scope for the smallest nanosize material.
Also, organometallics are expected to produce narrow size
distribution. Organometallic precursors are also of very high
purity. This is the first time nanomaterial is produced from
organometallics. These precursors would lead to lowest
nanosize.
Composite nanopowder from organometallics would be a
major breakthrough for a number of reasons. The problem of
agglomerations of two different phases would be overcome.
A molecular level mixing would lead to complete mixing
of two phases. Because they are mixed at molecular
level coarsening of both phases during sintering would be
avoided. This would enable a nano/nano composite of very
fine phase size. Also a room temperature process that can
be scaled up would be possible. The actual reaction would
be a few hours and other steps such as calcination can be
split into separate operations of a few hours each.
Hence, the material development began with the synthesis
of composite nanopowder.
Synthesis of nanopowder
The composite alumina zirconia nanopowders were
synthesized by the solgel process using the organometallic
precursors aluminium secondary butoxide and zirconium
n-propoxide.
Initial Solgel Synthesis
Aluminium secondary butoxide is dissolved in a solvent
containing acetyl acetone. The solution is raised to
appropriate temperature and pH additives incorporated.
This is hydrolyzed by addition of a distilled water and
anhydrous solvent mixture and stirred for one hour in
ambient environment. Subsequently, zirconium n-propoxide
is added and stirred for two hours. Finally, a water and
solvent mixture containing water is added in a continuous
stream under vigorous stirring. This leads to the formation
of a clear yellowish sol [4].
The sol obtained was dried in an oven at 110 C for four
or more hours to cause gellation and drying of the gel.
The dried gel was calcined at 500 C for two hours to
produce powders. The organic residues decompose and
burn at 500 C, hence, the choice of this temperature for
calcination.
The calcined powder was then milled in a planetary mill
to break the lumps of powder. The milling was carried out
for five hours at 100rpm.
Extended Studies on Solgel
It was realized that a number of variables influence the
solgel synthesis. These include temperature, concentration
[5], pH [6], and solvent type [5]. Concentration is an
important factor. It comprises of concentration of precursor
and concentration of water. Extended studies were carried
out to qualitatively study the nature of the solgel process.
These factors were varied in a number of experiments
and the result on the nanopowder—its particle size
was measured. However, the concentration was varied
systematically. The objective was to develop a qualitative
understanding of the nature of the solgel process in terms
of the influence of the variables.
Characterization of composite
alumina–zirconia nanopowders
Various studies were carried out to characterize the
properties of the composite nanopowders. Apart from the
powder particle size, the nature of the processing method
and an insight into how it affects the powder was also
obtained.
Brunauer, Emmett, and Teller (BET) Surface Area
The powders were studied by the BET method to find
the surface area per unit mass. The method involves the
adsorption of a monolayer of gas atoms on the powder.
The BET procedure was carried out using the equipment
sorptomatic, carlo Erba strumentazinone.
The BET surface area was them used to calculate the
average particle size. The relation between surface area and
particle size is [7]:
d = Ks/ S (1)
where d = particle size, meter, Ks = shape factor = 6, S =
surface area (in m2
/kg , = density, kg/m3
Transmission Electron Microscopy
Transmission Electron Microscopy (TEM) was used to
characterize the solgel nanopowder. The particle size of
the nanopowder was analyzed. A phillips CM12 STEM
120kV instrument was used. The magnifications ranged
from 45,000X to 1,00,000X. Different methods were used
for sample preparation. The first method used a solder metal
3. 654 S. K. MALHOTRA ET AL.
Table 1.—BET surface area and corresponding particle size.
Sample Solvent Concentration (M) R/H Temperature (C) pH H2O:MOR ratio BET surface aream2
/gm D(nm)
Old T0 E 0 381 2 45 7 1 170 8 45
Old T2 40E + 60A 0 76 5 37 7 1 204 7 05
Old T3 70E+30A 0 381 10 45 9 1 212 6 79
Old T4p 25E+75A 1 523 5 37 9 1.5 214 6 74
Old T6 90E+10A 0 381 2 30 7 1 183 7 88
T19 10E+19A 0 76 5 30 2 1 150 9 57
Debsi But 1 52 2 30 7 1 243 5 89
Sysc But 0 76 2 30 7 1 209 6 89
SysRH But 1 523 5 30 7 1 151 9 50
E = ethanol, A = acetone, But = butanol, R/H = ratio of volume of alcohol, R-OH to the volume of water (H-OH), MOR = Metal
alkoxide.
to incorporate powder, then hot pressing and thinning by
electropolishing.
The second method ultrasonicated the powder in a
Schoeller & Co. ultrasonic agitator in acetone medium. The
frequency of the instrument was 30kHz. A drop of the
suspension was placed on a carbon-coated grid and allowed
to dry. This was observed in the TEM.
Diffuse Reflectance Spectroscopy (DRS)
Diffuse Reflectance Spectroscopy was carried out to
analyze the particle size of the nanopowder [8]. The
instrument used was Varian Cary Model No. 5E UV-NIR
spectrophotometer. The two sources used were a tungsten
lamp for the range 2500 to 400nm and a deuterium lamp
for the region 400 to 200nm.
The powder was mixed with silica (SiO2) and pressed into
a pellet by application of medium pressure. The spectrum
was then obtained for the UV to near IR region. This,
on comparison with data reported in literature, led to an
estimate of particle size.
Qualitative Optical Absorption
Optical absorption spectroscopy is a method used to
characterize materials by measuring the absorption of light
as the wavelength of the incident monochromatic beam is
varied. The instrument used in the present study is model
No. U3400 of Hitachi Ltd., Japan. It uses a double beam to
measure the incident and transmitted beam intensities. The
source of light is a tungsten filament lamp for the visible and
near infrared ranges (350nm to 2.5 m). The detector is a
photomultiplier in the visible range and a photoconductor in
the near infrared region. A hydrogen (deuterium) lamp is the
source for the near ultraviolet wavelengths (350–200nm).
The old T0 powder was impregnated in araldite resin to
produce a polymer film that was transparent. A blank film of
the same material was also made to check for the absorption
by the matrix.
Particle size of synthesized nanopowders
The results of the particle size analysis of the nano-
powders by various methods were encouraging. They
demonstrated the accuracy and suitability of different and
interdisciplinary methods of particle size analysis. The
widely divergent methods and modifications in view of the
present requirements were proved to be correct by the results
(Table 1).
Old T0 powder had a particle size of 8.45nm. All the
synthesis experiments led to very high surface area and
very fine nanosize less than 10nm. Hence, the successful
synthesis of nanopowders, of very fine nanosize has been
demonstrated (Fig. 1).
TEM showed particle size of 8nm (Fig. 2).
The DRS showed no feature up to 1000nm. The above
is the spectrum for 800nm to 200nm.
The diffuse reflectance spectra (DRS) of old T0 powder
shows a shoulder at 340nm. K. G. Kanade and colleagues
[9] have reported an absorption edge at 351nm for Zirconia
powder of 20nm particle size. This absorption is due to
surface defect abundance of high surface area nanopowders.
Hence the data is relevant to crystalline as well as
amorphous nanopowders. The powder in present study has
an absorption shoulder at 340nm. This is clearly less than
351nm. The particle size in probably less then 10nm.
Figure 1.—TEM photograph of old T0.
4. SYNTHESIS OF ALUMINA–ZIRCONIA 655
Figure 2.—Diffuse reflectance spectrum of old T0 in the band 200 to 800nm.
Qualitative Optical Absorption
The optical absorption led to qualitative information on
the nanopowder particle size. According to literature [10]
alumina film of 7nm has an absorption edge at 280nm. The
powder from solgel synthesis old T0 showed no absorption
upto 300nm. This shows that the powder is nanosize and
that of size less than 10nm.
Thus all the characterisation methods led to an identical
particle size around 8.5nm.
Analysis of solgel process by artificial
neural networks (ANN)
ANN was used to analyse the nature of the solgel process.
This included the variables that affect the process and the
extent of influence of different variables. The procedure was
carried out in Matlab 6.5 using the ANN tool Box.
The results showed that hydrophobic nature of the solvent
was the only important factor when it was present and,
by itself, it led to very high surface area i.e., very small
particle size. In the absence of hydrophobic solvent, basic
pH, high water to alkoxide ratio, and low hydrogen bonding
increased surface area. In presence of hydrophobic solvent,
other factors were not important. They could not improve
the results of hydrophobic solvent.
Fabrication and characterization of bulk
nano/nano composite
The nano/nano composites were fabricated from
synthesised debsiM nanopowder having a particle size of
5.9nm. The powders were cold pressed with 1.73 tonnes
load corresponding to a pressure of 150MPa. This pressure
was chosen based on a previous study [11]. Three green
Table 2.—Size of nanophases of bulk nano/nano alumina–zirconia composite.
-Al2O3 dimension m-ZrO2 dimension
Sample name Temperature ( C) Time (minutes) (024) (104) (211) (¯1 02) (¯1 11) (022)
CTC 4402 800 C 120 5.5 23 29 5.5 23 29
METTHIRU 800 C 30 3.5 20 27 3.5 3nm & 20nm 27
9902ATHIRUN 750 C 30 2.25 17 24 2.25 17 24
compacts were made, one weighing 1gm and two weighing
0.75gm each.
Time–temperature studies were carried out to fabricate
nano/nano composite. The first sample from 1gm powders,
CTC 4402, was sintered/crystallized at 800 C for two hours.
Each of the other two compacts had been made from 0.75gm
powder each. The first one, METTHIRU, was sintered at
800 C for 30 minutes. The second, 9902 ATHIRUN, was
sintered at 750 C for 30 minutes.
All the three samples were characterized using XRD. The
phase size was determined from peak broadening using the
relation [12]:
d = 0 9 / B cos (2)
where d = phase size, = wavelength of X-ray = 1.542Å,
B = full width at half maximum in radians, and =
position of the X-ray peak.
The XRD was carried out on a SHIMADZU XD-D1
X-ray diffractometer.
Because the sample was a regular circular disk the
dimensions were measured to obtain its volume, then, from
the weight of the piece, the apparent density was calculated.
This on comparison with the reference density gave the
porosity.
Nanosintering results
The XRD results of bulk sintered nano/nano composites
(Table 2).
Nanosintering involved on one hand, the separation of
Alumina and Zirconia phases from the molecular mixture
of them in the solgel nanopowder [13]. In another way,
the separated Alumina and Zirconia phases crystallize.
High temperature with long sintering time as well as low
temperature with less hold time are inadequate. We should
enable diffusion with high temperature, but we should not
allow too much time since the phases will be of coarse sizes
(due to more diffusion [14]). Thus the sintering process
must be optimized.
The density measurement showed 60% porosity. The
green compact was 100% dense, but at high temperature of
sintering they loose molecular water so much that it leads
to 60% porosity. The solgel nanoparticle have Aluminium
(Al) and Zirconium (Zr) along on the surface of the particle
forming Al(OH)3 and Zr(OH)4. On sintering at 800 C the
hydroxyl groups are volatilized and the hydroxides of Al
and Zr convert to respective oxides loosing mass. This leads
to 60% porosity.
Thus the time–temperature studies led to an in-depth
understanding of the nature of the phenomena involved in
5. 656 S. K. MALHOTRA ET AL.
sintering of nanopowders. The sintering was also optimized
through these studies.
The indentation method for measuring
mechanical properties
The sample METTHIRUN processing was optimal
leading to best nano-nano composite phase sizes. Hence it
was studied to obtain the mechanical properties. This was
implemented by the indentation method using the hardness
tester Wolpert Vickers Hardness Tester-Amsler Diamond
Tester 2RC. A load of 5kg was used. The vickers hardness
was calculated [4]:
The elastic modulus was calculated using the relation
[15]:
e = K5N cot 1
he
h
(3)
where K5 = constant depending on shape and material of
indenter = 0.35, N = constant calculated from elastic and
plastic penetration, and K5 = 0 76, 1 = angle of Vickers
diamond indenter = 68 , he = h ⇒ he/h = 1 .
Elastic modulus,
E = −1 08 1 − 1 − 2 2
1 ×
HV
e
(4)
where 1 =Poisson’s ratio = 0 2 (for ceramic), HV =
Vickers Hardness.
The fracture toughness was calculated from the lengths
of the two diagnols of vickers diamond indentation and
average crack length at each vertex of the indentation. A
number of relations were used for obtaining the fracture
toughness.
Mechanical properties of bulk nano/nano
composites
The data from the indentation are:
Load diagonal diagonal Average crack length
d1 d2 at each corner
5kg 0.4mm 0.4mm 125µm
The hardness is 58VHN (=0 142GPa). The elastic modulus
was calculated as 419.66GPa.
The fracture toughness from the various relations are:
Relation I [19] II [20] III [21] IV [22] V [23] VI [23] VII [23]
KIC
(MPa
√
m) 26.65 29.42 30.90 20.08 34.52 34.95 26.89
Thus the fracture toughness KIC is about 30MPa
√
m.
Conclusions
Composite nanopowder and bulk nano/nano composites
were developed by controlling the diffusion processes.
Nanopowders were successfully synthesised from high
purity organometallic precursors.
Following conclusions can be drawn from the above
work:
1. The presence of hydrophobic solvent was found to be an
important factor leading to very fine nanosize.
2. Different methods of particle size estimation led to
consistent estimate of particle size (6–10nm range).
3. The yield was 40–50% and bulk nano/nano composites
produced by cold pressing and sintering had high elastic
modulus and very high fracture toughness.
4. Artificial Neural Network analysis showed that, in
the presence of hydrophobic solvent, it was the only
important factor. However, in its absence other factors
led to very fine nanosize.
The high hardness was acceptable in view of very high
porosity (nano materials have inverse Hall–Petch relation
[16]). Reference 24 says that ZrO2 of nanosize has inverse
Hall-Petch relation. Other authors have said ceramics have
inverse Hall-Petch relation and metals have traditional Hall–
Petch relation. The high elastic modulus is an indication of
high strength. The processing by hot pressing may improve
all properties to unprecedented high levels.
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