Avinash Balakrishnan | Amrita Vishwa Vidyapeetham (original) (raw)

Papers by Avinash Balakrishnan

Metals and Materials International, 2010

In this work, the sintering behaviour of hydroxyapatite (HA) at different temperatures was studie... more In this work, the sintering behaviour of hydroxyapatite (HA) at different temperatures was studied. Nano HA powders synthesized by sol-gel technique were uniaxially pressed at 30 MPa into pellets and cold isostatically pressed at 200 MPa. The pellets were sintered in air at temperatures ranging from 900 °C to 1400 °C with a holding time of 2 h. It was observed that, at a sintering temperature of 1200 °C when the material was composed of pure HA phase, the samples exhibited densities of > 98.5 % of the theoretical value and possessed a hardness value of 5.89 GPa. Decomposition of HA into the secondary phases of TCP and CaO was found to occur at 1300 °C and 1400 °C, respectively. Changes in the microstructure, relative density and hardness of the sintered HA ceramics with the sintering temperature were also analyzed. The variation in the hardness was found to be dependent on the relative density up to a threshold grain size limit of 2 μm. However, beyond this threshold, no correlation existed between the two properties. Porosity and grain size were found to play an important role in determining the properties of the sintered HA compacts.

Journal of Materials Research, 2007

ABSTRACT

Materials Science and Technology, 2008

ABSTRACT

Journal of Alloys and Compounds, 2010

This investigation was aimed to study the effect of nickel addition on the sintering behaviour of... more This investigation was aimed to study the effect of nickel addition on the sintering behaviour of Ti 3 SiC 2 powder under pressureless conditions. Nearly pure bulk Ti 3 SiC 2 ceramic with relative density of ∼98.5% was produced at 1500 • C by sintering of Ti 3 SiC 2 powder while using 1 wt.% nickel as a sintering aid. The activation energy of sintering of Ti 3 SiC 2 powder was determined to be 351 ± 5 kJ/mol, which was decreased slightly to 305 ± 10 kJ/mol when nickel (1 wt.%) was added. Sintering of Ti 3 SiC 2 powder was found to be controlled by mixed mode of mechanisms, i.e., the interface reactions and diffusion of Si atoms. The mechanism was changed to liquid phase sintering due to melting of Ni-based compounds in the sample sintered with Ni. The reaction of Ni with Ti 3 SiC 2 helped to decrease the grain growth rate. The hardness (Vickers), flexural strength and fracture toughness of the sintered Ti 3 SiC 2 -1Ni sample were found to be 3.4 GPa, 311 ± 22 MPa and 2.8-6.4 MPa m 1/2 , respectively.

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007

A low thermal expansion glass was melted on the sintered alumina. The molten glass penetrated int... more A low thermal expansion glass was melted on the sintered alumina. The molten glass penetrated into the surface region of the alumina along the grain boundaries. Thermal and elastic properties mismatch between the glass-penetrated surface region and the interior of alumina produced residual compression in the surface region during cooling. The glass penetration improved the strength by about 53% and also there was a significantly improvement in the thermal shock resistance of the alumina. The observed enhancement in the strength was found to be almost equal to the residual stress generated as a result of thermal and elastic properties mismatch.

Journal of Materials Science-materials in Medicine, 2008

The in vitro response of the mouse fibroblast cell line 3T3 on the surface of ultrafine grained t... more The in vitro response of the mouse fibroblast cell line 3T3 on the surface of ultrafine grained titanium [produced by a severe plastic deformation (SPD) process] has been studied in this work. SPD Ti showed much higher strength than the coarse grained Ti and equivalent to that of Ti–6Al–4V alloy. Better cell proliferation was observed on SPD Ti compared to conventional Ti and Ti–6Al–4V alloy. This could be attributed to the increased surface free energy by reduction in the grain size and possibly the presence of a large number of nano size grooves at the triple point junctions in SPD Ti sample. There was no significant difference in the results of cytotoxicity tests of fine and coarse grained materials.

Journal of The European Ceramic Society, 2011

The present work describes the processing of alumina fiber reinforced alumina ceramic preforms co... more The present work describes the processing of alumina fiber reinforced alumina ceramic preforms consisting of chopped Al 2 O 3 fibers (33 wt%) and Al 2 O 3 (67 wt%) fine powders by slip casting. The preforms were pre-sintered in air at 1100 • C for 1 h. A lanthanum based glass was infiltrated into these preforms at 1250 • C for 90 min. Linear shrinkage (%) was studied before and after glass infiltration. Pre-sintered and infiltrated specimens were characterized by scanning electron microscopy, energy dispersive X-ray, X-ray diffraction, porosimetry and flexural strength. The alumina preforms showed a narrow pore size distribution with an average pore size of ∼50 nm. It was observed that introducing Al 2 O 3 fibers into Al 2 O 3 particulate matrix produced warp free preforms with minor shrinkage during pre-sintering and glass infiltration. It was observed that the infiltration process fills up the pores and considerably improves the strength and reliability of alumina preform.

Bulletin of Materials Science, 2009

This work studies the effect on the mechanical properties of alumina-10 wt% zirconia (3 mol% yttr... more This work studies the effect on the mechanical properties of alumina-10 wt% zirconia (3 mol% yttria stabilized) composite by infiltrating glass of a higher thermal expansion (soda lime glass) on the surface at high temperature. The glass improved the strength of composite at room temperature as well as at high temperature. This could be attributed to the drastic drop in the coefficient of thermal expansion due to the compositional change in the soda lime glass during infiltration. There was a significant improvement in the Weibull modulus after glass infiltration. Glass infiltrated samples showed better thermal shock resistance. The magnitude of strength increment was found to be in the order of the surface residual stress generated by thermo-elastic properties mismatch between the composite and the penetrated glass.

Journal of Materials Research, 2009

ABSTRACT

Particuology, 2009

In the present study hydroxyapatite (HA) nano-hexagonal rods with 70-90 nm diameter and 400-500 n... more In the present study hydroxyapatite (HA) nano-hexagonal rods with 70-90 nm diameter and 400-500 nm length are synthesized using a simple sol-gel route with calcium nitrate and potassium dihydrogenphosphate as calcium and phosphorus precursors respectively. Deionized water was used as a diluting media for HA sol preparation and ammonia was used to adjust the pH = 9. After aging, the HA gel was dried at 60 • C and calcined at different temperatures ranging from 300 to 700 • C. The dried and calcined powders were characterized for phase composition using X-ray diffractrometry, elemental dispersive X-ray and Fourier transform infrared spectroscopy. Rietveld analysis showed the calcined HA powders of high purity with a hexagonal unit cell structure. Calcination yielded HA nanopowders of increased particle size and crystallinity with increase in temperature. The particle size and morphology was studied using transmission electron microscopy. The aspect ratio (length to diameter ratio) of HA nanorods was measured to be between 6 and 7.

Materials Letters, 2010

Hydroxypropylcellulose (HPC) and polyethylene oxide (PEO) were dissolved in water in order to be ... more Hydroxypropylcellulose (HPC) and polyethylene oxide (PEO) were dissolved in water in order to be electrospun. The electrospun membranes showed porous structure with fibers having diameter of 255 ± 65 nm. Synthesized silver nanoparticles of 5-8 nm were embedded into the HPC/PEO matrix to improve the strength. It was seen that the embedding of silver particles into the polymer matrix improved the membrane strength ∼ 4 times.

Biomedical Materials, 2007

This work attempts to understand the in vitro biocompatibility of ultrafine grained titanium prep... more This work attempts to understand the in vitro biocompatibility of ultrafine grained titanium prepared by the ECAP route. The results obtained from the mouse fibroblast cell line 3T3 showed a better cell adherence and cell proliferation on ECAP titanium specimen compared to the coarse grain Grade-2 Ti and Ti6Al4V alloy. This could be attributed to the increased surface energy and grain boundary energy and possibly the presence of a large number of nano-size conical groove-like structures (at triple point junctions of grain boundaries on the surface) in the ECAP Ti specimen compared to the coarse grain Grade-2 Ti and Ti6Al4V alloy.

Korean Journal of Materials Research, 2008

In this study, calcium titanate (CaTiO 3 ) gel was prepared by mixing calcium nitrate and titaniu... more In this study, calcium titanate (CaTiO 3 ) gel was prepared by mixing calcium nitrate and titanium isopropoxide in 2-methoxy-ethanol. CaTiO 3 gel was single-layer coated on Ti-6Al-4V using a sol-gel dip-coating technique. The coating was calcined at 750 o C in air by utilizing a very slow heating rate of 2 o C/min. The crystalline phases of the coating were characterized by x-ray diffraction using a slow scan rate of 1 o /min. The morphology of the coating was analyzed by scanning electron microscopy. The corrosion behavior of Ti-6Al-4V samples coated with CaTiO 3 films were tested in an artificial saliva solution by potentiodynamic polarization and were quantified by the Tafel extrapolation method. The electrochemical parameters showed a considerable increase in the corrosion resistance for the CaTiO 3 -coated Ti-6Al-4V samples compared to bare substrates.

Materials Letters, 2009

Nano hydroxyapatite (HA) powder was successfully synthesized from biowaste chicken eggshells. The... more Nano hydroxyapatite (HA) powder was successfully synthesized from biowaste chicken eggshells. The nanopowders were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), particle size distribution (PSD) analyzer, and Fourier transform infrared spectroscopy (FT-IR) techniques. Selected area electron diffraction (SAED) analysis during TEM showed the particles to be polycrystalline in nature. The resulting HA powder exhibited an average size of~35 nm with a narrowly distributed particle size range from 5 to 90 nm. XRD and FT-IR analysis showed that the powders produced were of high purity. The present study provides a simple sol-gel precipitation method to obtain nano HA powders of high purity from biowaste chicken eggshells.

Journal of Materials Processing Technology, 2009

This study investigates the effect of a low expansion glass (Mg 3 Al 2 Si 6 O 18 ) treatment on t... more This study investigates the effect of a low expansion glass (Mg 3 Al 2 Si 6 O 18 ) treatment on the surface fracture toughness of sintered alumina. The surface fracture toughness was determined by direct indentation method (Vickers indentations), carried out at different loads ranging from 9.8 to 196 N. The crack lengths on the surface at each load were found to be decreased (8-12%) by glass treatment and the corresponding crack resistance values increased by about 17-20%. Both sintered and glass treated specimens showed rising trend in crack resistance values as the indentation load was increased. There was also a significant increase in the Weibull modulus value of crack resistance. Improved properties of glass treated sample were attributed to the formation of a relatively larger process zone surrounding the crack, crack arrest behavior due to the compressive stresses and the crack bridging phenomena. The compressive stresses were generated from the thermo-elastic properties mismatch: (a) between the glass and the ceramic in the glass infiltrated zone, and (b) the glass-ceramic composite layer and the ceramic substrate.

Journal of Materials Processing Technology, 2009

This work attempts to improve the mechanical properties of alumina-10 wt% zirconia (3 mol% yttria... more This work attempts to improve the mechanical properties of alumina-10 wt% zirconia (3 mol% yttria stabilized) composite by infiltrating a glass (magnesium aluminum silicate glass) of lower thermal expansion on the surface at high temperature. The glass improved the strength of the composite at room temperature as well as at higher temperatures. There was a significant improvement in the Weibull modulus after the glass infiltration. Glass-infiltrated samples showed better thermal shock resistance. The magnitude of strength increment was found to be in the order of the surface residual stress generated by thermo-elastic properties mismatch between the composite and the infiltrated glass.

Dental Materials, 2010

d e n t a l m a t e r i a l s 2 6 ( 2 0 1 0 ) 100-104 a v a i l a b l e a t w w w . s c i e n c e... more d e n t a l m a t e r i a l s 2 6 ( 2 0 1 0 ) 100-104 a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . i n t l . e l s e v i e r h e a l t h . c o m / j o u r n a l s / d e m a Hardness Dental ceramics Vickers indentation Lamellar rod Palmqvist crack a b s t r a c t

Journal of Alloys and Compounds, 2010

Forsterite (FS) nanopowders (∼27 nm) were synthesized using a sol-gel route with magnesium nitrat... more Forsterite (FS) nanopowders (∼27 nm) were synthesized using a sol-gel route with magnesium nitrate hexahydrate and tetra ethyl ortho-silicate as magnesium and silicon precursors, respectively. Nitric acid was used as a catalyst. After aging, the FS gel was calcined at 800 • C for 30 min. The calcined powders were characterized for phase composition using X-ray diffractrometry and fourier transform-infrared spectroscopy. The particle size and morphology was studied using transmission electron microscopy. The particle size distribution analysis of FS powders showed skewed distribution plot with particle size ranging from 5-90 nm. This study showed that high phase purity and narrowly distributed FS nanoparticles could be obtained using this simple sol-gel technique.

Journal of Materials Science & Technology, 2010

The present study focuses on the relationship of hardness with grain size for commercially pure t... more The present study focuses on the relationship of hardness with grain size for commercially pure titanium (Cp-Ti) and ultra fine grained titanium (UFG-Ti) produced by equal channel angular process (ECAP) of Cp-Ti). Vickers and Knoop indentations of UFG-Ti at different loads was ∼2.5 times harder than those of Cp-Ti. Xray diffraction (XRD) analysis showed peak broadening in UFG-Ti due to reduced grain size and micro-lattice strains. Scanning electron microscopy (SEM) revealed that ECAP had reduced the grain size of Cp-Ti by ∼10 times. Weibull statistics showed UFG-Ti with lower dispersion in hardness values compare to Cp-Ti indicating a more uniform microstructure.

Materials Research Bulletin, 2010

Metals and Materials International, 2010

In this work, the sintering behaviour of hydroxyapatite (HA) at different temperatures was studie... more In this work, the sintering behaviour of hydroxyapatite (HA) at different temperatures was studied. Nano HA powders synthesized by sol-gel technique were uniaxially pressed at 30 MPa into pellets and cold isostatically pressed at 200 MPa. The pellets were sintered in air at temperatures ranging from 900 °C to 1400 °C with a holding time of 2 h. It was observed that, at a sintering temperature of 1200 °C when the material was composed of pure HA phase, the samples exhibited densities of > 98.5 % of the theoretical value and possessed a hardness value of 5.89 GPa. Decomposition of HA into the secondary phases of TCP and CaO was found to occur at 1300 °C and 1400 °C, respectively. Changes in the microstructure, relative density and hardness of the sintered HA ceramics with the sintering temperature were also analyzed. The variation in the hardness was found to be dependent on the relative density up to a threshold grain size limit of 2 μm. However, beyond this threshold, no correlation existed between the two properties. Porosity and grain size were found to play an important role in determining the properties of the sintered HA compacts.

Journal of Materials Research, 2007

ABSTRACT

Materials Science and Technology, 2008

ABSTRACT

Journal of Alloys and Compounds, 2010

This investigation was aimed to study the effect of nickel addition on the sintering behaviour of... more This investigation was aimed to study the effect of nickel addition on the sintering behaviour of Ti 3 SiC 2 powder under pressureless conditions. Nearly pure bulk Ti 3 SiC 2 ceramic with relative density of ∼98.5% was produced at 1500 • C by sintering of Ti 3 SiC 2 powder while using 1 wt.% nickel as a sintering aid. The activation energy of sintering of Ti 3 SiC 2 powder was determined to be 351 ± 5 kJ/mol, which was decreased slightly to 305 ± 10 kJ/mol when nickel (1 wt.%) was added. Sintering of Ti 3 SiC 2 powder was found to be controlled by mixed mode of mechanisms, i.e., the interface reactions and diffusion of Si atoms. The mechanism was changed to liquid phase sintering due to melting of Ni-based compounds in the sample sintered with Ni. The reaction of Ni with Ti 3 SiC 2 helped to decrease the grain growth rate. The hardness (Vickers), flexural strength and fracture toughness of the sintered Ti 3 SiC 2 -1Ni sample were found to be 3.4 GPa, 311 ± 22 MPa and 2.8-6.4 MPa m 1/2 , respectively.

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007

A low thermal expansion glass was melted on the sintered alumina. The molten glass penetrated int... more A low thermal expansion glass was melted on the sintered alumina. The molten glass penetrated into the surface region of the alumina along the grain boundaries. Thermal and elastic properties mismatch between the glass-penetrated surface region and the interior of alumina produced residual compression in the surface region during cooling. The glass penetration improved the strength by about 53% and also there was a significantly improvement in the thermal shock resistance of the alumina. The observed enhancement in the strength was found to be almost equal to the residual stress generated as a result of thermal and elastic properties mismatch.

Journal of Materials Science-materials in Medicine, 2008

The in vitro response of the mouse fibroblast cell line 3T3 on the surface of ultrafine grained t... more The in vitro response of the mouse fibroblast cell line 3T3 on the surface of ultrafine grained titanium [produced by a severe plastic deformation (SPD) process] has been studied in this work. SPD Ti showed much higher strength than the coarse grained Ti and equivalent to that of Ti–6Al–4V alloy. Better cell proliferation was observed on SPD Ti compared to conventional Ti and Ti–6Al–4V alloy. This could be attributed to the increased surface free energy by reduction in the grain size and possibly the presence of a large number of nano size grooves at the triple point junctions in SPD Ti sample. There was no significant difference in the results of cytotoxicity tests of fine and coarse grained materials.

Journal of The European Ceramic Society, 2011

The present work describes the processing of alumina fiber reinforced alumina ceramic preforms co... more The present work describes the processing of alumina fiber reinforced alumina ceramic preforms consisting of chopped Al 2 O 3 fibers (33 wt%) and Al 2 O 3 (67 wt%) fine powders by slip casting. The preforms were pre-sintered in air at 1100 • C for 1 h. A lanthanum based glass was infiltrated into these preforms at 1250 • C for 90 min. Linear shrinkage (%) was studied before and after glass infiltration. Pre-sintered and infiltrated specimens were characterized by scanning electron microscopy, energy dispersive X-ray, X-ray diffraction, porosimetry and flexural strength. The alumina preforms showed a narrow pore size distribution with an average pore size of ∼50 nm. It was observed that introducing Al 2 O 3 fibers into Al 2 O 3 particulate matrix produced warp free preforms with minor shrinkage during pre-sintering and glass infiltration. It was observed that the infiltration process fills up the pores and considerably improves the strength and reliability of alumina preform.

Bulletin of Materials Science, 2009

This work studies the effect on the mechanical properties of alumina-10 wt% zirconia (3 mol% yttr... more This work studies the effect on the mechanical properties of alumina-10 wt% zirconia (3 mol% yttria stabilized) composite by infiltrating glass of a higher thermal expansion (soda lime glass) on the surface at high temperature. The glass improved the strength of composite at room temperature as well as at high temperature. This could be attributed to the drastic drop in the coefficient of thermal expansion due to the compositional change in the soda lime glass during infiltration. There was a significant improvement in the Weibull modulus after glass infiltration. Glass infiltrated samples showed better thermal shock resistance. The magnitude of strength increment was found to be in the order of the surface residual stress generated by thermo-elastic properties mismatch between the composite and the penetrated glass.

Journal of Materials Research, 2009

ABSTRACT

Particuology, 2009

In the present study hydroxyapatite (HA) nano-hexagonal rods with 70-90 nm diameter and 400-500 n... more In the present study hydroxyapatite (HA) nano-hexagonal rods with 70-90 nm diameter and 400-500 nm length are synthesized using a simple sol-gel route with calcium nitrate and potassium dihydrogenphosphate as calcium and phosphorus precursors respectively. Deionized water was used as a diluting media for HA sol preparation and ammonia was used to adjust the pH = 9. After aging, the HA gel was dried at 60 • C and calcined at different temperatures ranging from 300 to 700 • C. The dried and calcined powders were characterized for phase composition using X-ray diffractrometry, elemental dispersive X-ray and Fourier transform infrared spectroscopy. Rietveld analysis showed the calcined HA powders of high purity with a hexagonal unit cell structure. Calcination yielded HA nanopowders of increased particle size and crystallinity with increase in temperature. The particle size and morphology was studied using transmission electron microscopy. The aspect ratio (length to diameter ratio) of HA nanorods was measured to be between 6 and 7.

Materials Letters, 2010

Hydroxypropylcellulose (HPC) and polyethylene oxide (PEO) were dissolved in water in order to be ... more Hydroxypropylcellulose (HPC) and polyethylene oxide (PEO) were dissolved in water in order to be electrospun. The electrospun membranes showed porous structure with fibers having diameter of 255 ± 65 nm. Synthesized silver nanoparticles of 5-8 nm were embedded into the HPC/PEO matrix to improve the strength. It was seen that the embedding of silver particles into the polymer matrix improved the membrane strength ∼ 4 times.

Biomedical Materials, 2007

This work attempts to understand the in vitro biocompatibility of ultrafine grained titanium prep... more This work attempts to understand the in vitro biocompatibility of ultrafine grained titanium prepared by the ECAP route. The results obtained from the mouse fibroblast cell line 3T3 showed a better cell adherence and cell proliferation on ECAP titanium specimen compared to the coarse grain Grade-2 Ti and Ti6Al4V alloy. This could be attributed to the increased surface energy and grain boundary energy and possibly the presence of a large number of nano-size conical groove-like structures (at triple point junctions of grain boundaries on the surface) in the ECAP Ti specimen compared to the coarse grain Grade-2 Ti and Ti6Al4V alloy.

Korean Journal of Materials Research, 2008

In this study, calcium titanate (CaTiO 3 ) gel was prepared by mixing calcium nitrate and titaniu... more In this study, calcium titanate (CaTiO 3 ) gel was prepared by mixing calcium nitrate and titanium isopropoxide in 2-methoxy-ethanol. CaTiO 3 gel was single-layer coated on Ti-6Al-4V using a sol-gel dip-coating technique. The coating was calcined at 750 o C in air by utilizing a very slow heating rate of 2 o C/min. The crystalline phases of the coating were characterized by x-ray diffraction using a slow scan rate of 1 o /min. The morphology of the coating was analyzed by scanning electron microscopy. The corrosion behavior of Ti-6Al-4V samples coated with CaTiO 3 films were tested in an artificial saliva solution by potentiodynamic polarization and were quantified by the Tafel extrapolation method. The electrochemical parameters showed a considerable increase in the corrosion resistance for the CaTiO 3 -coated Ti-6Al-4V samples compared to bare substrates.

Materials Letters, 2009

Nano hydroxyapatite (HA) powder was successfully synthesized from biowaste chicken eggshells. The... more Nano hydroxyapatite (HA) powder was successfully synthesized from biowaste chicken eggshells. The nanopowders were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), particle size distribution (PSD) analyzer, and Fourier transform infrared spectroscopy (FT-IR) techniques. Selected area electron diffraction (SAED) analysis during TEM showed the particles to be polycrystalline in nature. The resulting HA powder exhibited an average size of~35 nm with a narrowly distributed particle size range from 5 to 90 nm. XRD and FT-IR analysis showed that the powders produced were of high purity. The present study provides a simple sol-gel precipitation method to obtain nano HA powders of high purity from biowaste chicken eggshells.

Journal of Materials Processing Technology, 2009

This study investigates the effect of a low expansion glass (Mg 3 Al 2 Si 6 O 18 ) treatment on t... more This study investigates the effect of a low expansion glass (Mg 3 Al 2 Si 6 O 18 ) treatment on the surface fracture toughness of sintered alumina. The surface fracture toughness was determined by direct indentation method (Vickers indentations), carried out at different loads ranging from 9.8 to 196 N. The crack lengths on the surface at each load were found to be decreased (8-12%) by glass treatment and the corresponding crack resistance values increased by about 17-20%. Both sintered and glass treated specimens showed rising trend in crack resistance values as the indentation load was increased. There was also a significant increase in the Weibull modulus value of crack resistance. Improved properties of glass treated sample were attributed to the formation of a relatively larger process zone surrounding the crack, crack arrest behavior due to the compressive stresses and the crack bridging phenomena. The compressive stresses were generated from the thermo-elastic properties mismatch: (a) between the glass and the ceramic in the glass infiltrated zone, and (b) the glass-ceramic composite layer and the ceramic substrate.

Journal of Materials Processing Technology, 2009

This work attempts to improve the mechanical properties of alumina-10 wt% zirconia (3 mol% yttria... more This work attempts to improve the mechanical properties of alumina-10 wt% zirconia (3 mol% yttria stabilized) composite by infiltrating a glass (magnesium aluminum silicate glass) of lower thermal expansion on the surface at high temperature. The glass improved the strength of the composite at room temperature as well as at higher temperatures. There was a significant improvement in the Weibull modulus after the glass infiltration. Glass-infiltrated samples showed better thermal shock resistance. The magnitude of strength increment was found to be in the order of the surface residual stress generated by thermo-elastic properties mismatch between the composite and the infiltrated glass.

Dental Materials, 2010

d e n t a l m a t e r i a l s 2 6 ( 2 0 1 0 ) 100-104 a v a i l a b l e a t w w w . s c i e n c e... more d e n t a l m a t e r i a l s 2 6 ( 2 0 1 0 ) 100-104 a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . i n t l . e l s e v i e r h e a l t h . c o m / j o u r n a l s / d e m a Hardness Dental ceramics Vickers indentation Lamellar rod Palmqvist crack a b s t r a c t

Journal of Alloys and Compounds, 2010

Forsterite (FS) nanopowders (∼27 nm) were synthesized using a sol-gel route with magnesium nitrat... more Forsterite (FS) nanopowders (∼27 nm) were synthesized using a sol-gel route with magnesium nitrate hexahydrate and tetra ethyl ortho-silicate as magnesium and silicon precursors, respectively. Nitric acid was used as a catalyst. After aging, the FS gel was calcined at 800 • C for 30 min. The calcined powders were characterized for phase composition using X-ray diffractrometry and fourier transform-infrared spectroscopy. The particle size and morphology was studied using transmission electron microscopy. The particle size distribution analysis of FS powders showed skewed distribution plot with particle size ranging from 5-90 nm. This study showed that high phase purity and narrowly distributed FS nanoparticles could be obtained using this simple sol-gel technique.

Journal of Materials Science & Technology, 2010

The present study focuses on the relationship of hardness with grain size for commercially pure t... more The present study focuses on the relationship of hardness with grain size for commercially pure titanium (Cp-Ti) and ultra fine grained titanium (UFG-Ti) produced by equal channel angular process (ECAP) of Cp-Ti). Vickers and Knoop indentations of UFG-Ti at different loads was ∼2.5 times harder than those of Cp-Ti. Xray diffraction (XRD) analysis showed peak broadening in UFG-Ti due to reduced grain size and micro-lattice strains. Scanning electron microscopy (SEM) revealed that ECAP had reduced the grain size of Cp-Ti by ∼10 times. Weibull statistics showed UFG-Ti with lower dispersion in hardness values compare to Cp-Ti indicating a more uniform microstructure.

Materials Research Bulletin, 2010