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In order to induce bone regeneration several natural and synthetic materials have been proposed. However, single-phase scaffolds present some insurmountable disadvantages such as poor mechanical strength or brittleness and too low or too high degradation rate. In order to overcome these drawbacks, composite systems can be an interesting and promising option. In the present work a novel hybrid porous scaffold for bone tissue engineering is proposed. Chitosan/Forsterite (Ch/FS) composite scaffolds were prepared by freeze-drying method using a chitosan/forsterite ratio of 90/10. The FS nanopowder (Mg2SiO4) is synthesized using a simple solgel based method. The FS composition was checked by XRD analysis. The macrostructure of the Ch/FS scaffolds were analyzed by SEM, the FS distribution within the chitosan matrix observed by EDS, the mechanical strength measured by compression test in PBS and the biocompatibility of the composite on human osteosarcoma cell line (MG-63) verified by MTT assay after 48 hours. The porosity appears interconnected and with a pore size ranging from 1 to 100 μm. The FS is overall distributed within the chitosan matrix. The compression strength of composite scaffolds increased with respect to the pure chitosan scaffolds of more than two times (from 0.8 to 1.9 KPa) and the composites did not show any toxicity effect on human osteosarcoma cells.

In the present work Collagen/Hydroxyapatite microsphere (Col/mHA) scaffold with a multiscale porosity was prepared. Col/mHA composite scaffold was prepared by freeze-drying/dehydrothermal crosslinking method. The HA microspheres (mHA) were obtained by spray drying of nanohydroxyapatite slurry prepared by precipitation technique. XRD analysis revealed that the microspheres were composed only of pure HA phase and EDS analysis revealed that Ca/P ratio was 1.69. The obtained microspheres had an average diameter 6 microns, specific surface area of 40 m2/g by BET analysis and BJH analysis shows meso porous structure having an average pore diameter 16nm. SEM analysis shows that the obtained Col/mHA scaffold had a macro porosity ranging from micron to 200 microns with meso porous mHA embedded in the collagen matrix.

In the present work Collagen/Hydroxyapatite microsphere (Col/mHA) scaffold with a multiscale porosity was prepared. Col/mHA composite scaffold was prepared by freezedrying/ dehydrothermal crosslinking method. The HA microspheres (mHA) were obtained by spray drying of nano hydroxyapatite slurry prepared by precipitation technique. XRD analysis revealed that the microspheres were composed only of pure HA phase and EDS analysis revealed that Ca/P ratio was 1.69. The obtained microsphere had an average diameter 6 microns, specific surface area of 40 m2/g by BET analysis and BJH analysis shows meso porous structure having an average pore diameter 16nm. SEM analysis shows that the obtained Col/mHA scaffold had a macro porosity ranging from micron to 200 microns with meso porous mHA embedded in the collagen matrix.

The present study provides the first reports on the electrospinning of TiO2–ZnO–graphene composite nanofibers for photovoltaic and biomedical applications. These nanofibers were characterized by spectroscopic and microscopic techniques to evaluate the morphologies and phases. The fiber diameter was found to be ∼210 nm. The graphene content was maintained in the range of 0.2–0.7 weight percent. It was observed that when the graphene content was increased beyond 0.7 weight percent, the continuous fiber morphology was lost. Raman spectroscopy was used to confirm the presence of graphene. Conductivity studies showed a ∼9 times increase in conductance values for the TiO2–ZnO–graphene system as compared to TiO2–ZnO nanofibers. Employing these TiO2–ZnO–graphene fiber composites as photoanodes in dye sensitized solar cells, an efficiency of 3.7% was attained. Antibacterial studies performed on two bacterial strains, namely E.coli and S. aureus, have shown that these composite fibers can be used effectively for antibacterial wound dressing applications.

In this work a novel three-dimensional ostechondral substitute is proposed that is made of an inorganic/organic hybrid material, namely collagen/hydroxyapatite. The two components of the substitute have been characterized separately. The inorganic part, a hydroxyapatite scaffold, was fabricated by a polymer sponge templating method using a reactive sub-micron powder synthesized in our laboratory by hydroxide precipitation sol-gel route. The organic part, a collagen scaffold, was fabricated by a freeze-dying technique varying design parameters. Both the parts were analysed by scanning electron microscopy and their mechanical properties assessed by compression tests. The hydroxyapatite scaffold showed a high and highly interconnected porosity and a mechanical strength equal to 0.55 MPa, higher than those reported in literature. The collagen scaffolds were seeded by chondrocytes, processed for histology analysis and tested in compression. The biological tests proved the ability of the scaffolds to be positively populated by chondrocytes and the mechanical analysis showed that the mechanical strength of the scaffolds significantly increased after 3 weeks of culture.

Hydroxyapatite (HA) macrochanneled porous scaffolds were produced by polymer sponge templating method using a reactive submicrometer powder synthesized by hydroxide precipitation sol–gel route. The microstructure of the fine HA powder was carefully investigated and developed in order to optimize the mechanical properties and phase stability of sintered scaffold. The templating method ensured a highly interconnected macrochanneled porous structure with over 500 μm mean pore size and 90% porosity. The high reactivity of the powder led to an efficient sintering mechanism with a high and crack-free linear shrinkage (19 ± 2%) and a significant BET specific surface area reduction (from 12 to 0.33 m2/g). The powder does not dissociate into secondary phases during sintering. Despite the extreme porosity, the scaffolds had high mechanical performance (compressive strength ∼0.51 MPa, Weibull modulus 4.15) compared with literature data and with scaffolds similarly prepared from high-quality commercial HA powder.

The present study demonstrates an approach for fabricating fiber-reinforced ceramic matrix composites (CMCs) involving the coating of 2-dimensional woven alumina fibers with zirconia layer by sol gel, followed by impregnation of these coated fibers with alumina matrix and pressureless sintering. To emphasize the benefits of the zirconia coating on these CMCs, a reference sample without interfacial coating layer was prepared. The zirconia-coated CMCs showed superior flexural strength and thermal shock resistance compared with their uncoated counterparts. Foreign object damage tests carried out on the ZrO2 coated CMCs at high impact speed showed localized damage without any shattering.

In the present study, we have produced a sodium carboxymethylcellulose (CMC) hydrogel from a bacterial cellulose etherification reaction with chloroacetic acid in an alkaline medium. Bacterial cellulose (BC) was synthesized via economical and environmentally friendly methods using the Gluconacetobacter xylinus bacterium. After purification, freeze-drying, and milling, BC microparticles were dispersed in NaOH solution for different time periods before the etherification reaction. This has allowed the understanding of the alkalinization effect on BC modification. All synthesized CMC were soluble in water, and FTIR and XRD analyses confirmed the etherification reaction. The bath of BC in NaOH solution affects both molecular weight and degree of substitution. SEM analysis revealed the change of BC microstructure from fibrous-like to a smooth, uniform structure. The CMC-0 h allowed the production of crosslinked hydrogel after dehydrothermal treatment. Such hydrogel has been characterized rheologically and has shown a water absorption of 35 times its original weight. The optimization of the CMC produced from BC could pave the way for the production of ultrapure hydrogel to be applied in the healthcare and pharmaceutical industry.

Magnesium (Mg)- and silicon (Si)-substituted hydroxyapatite (HA) scaffolds were synthesized using the sponge replica method. The influence of Mg2+ and SiO44− ion substitution on the microstructural, mechanical and biological properties of HA scaffolds was evaluated. All synthesized scaffolds exhibited porosity &gt, 92%, with interconnected pores and pore sizes ranging between 200 and 800 μm. X-ray diffraction analysis showed that β-TCP was formed in the case of Mg substitution. X-ray fluorescence mapping showed a homogeneous distribution of Mg and Si ions in the respective scaffolds. Compared to the pure HA scaffold, a reduced grain size was observed in the Mg- and Si-substituted scaffolds, which greatly influenced the mechanical properties of the scaffolds. Mechanical tests revealed better performance in HA-Mg (0.44 ± 0.05 MPa), HA-Si (0.64 ± 0.02 MPa) and HA-MgSi (0.53 ± 0.01 MPa) samples compared to pure HA (0.2 ± 0.01 MPa). During biodegradability tests in Tris-HCl, slight weight loss and a substantial reduction in mechanical performances of the scaffolds were observed. Cell proliferation determined by the MTT assay using hBMSC showed that all scaffolds were biocompatible, and the HA-MgSi scaffold seemed the most effective for cell adhesion and proliferation. Furthermore, ALP activity and osteogenic marker expression analysis revealed the ability of HA-Si and HA-MgSi scaffolds to promote osteoblast differentiation.

Silica cryogel-glass fiber composites with a high specific surface area and high mesoporosity were fabricated via a simple still original drying technique. By applying vacuum at ambient temperature, the system evolution has been monitored and represented in the water phase diagram. The ratio of solvent/silica loading significantly affected the porous structure and thermal insulating properties of the blanket. From the results of BET surface area, apparent density and porosity studies, the microstructures and specific surface areas of the composites were greatly affected by changing the silica amount in the sol. The microstructure of silica cryogel blanket exhibits a porous structure consisting of glass fibers of diameter ~7 μm interconnected with solid silica clusters (5–20 μm). Silica cryogel-glass fiber blankets with low densities from 0.13–0.24 g/cm 3 and thermal conductivity as low as 0.02–0.035 W/mK were obtained using this cost effective, hazardous free and time saving method. The pH of the silica sol influenced the gelling property and the thermal conductivity of the composites.

This research is focused on sodium silicate bonded silica aggregates for making sustainable construction materials such as bricks and precast products. Different compositions are investigated to produce castable mortars. The mortars are cured at temperatures ranging from 150 to 300 °C and characterized, in particular microstructural and mechanical properties are investigated. Very high compressive strength of 100 MPa and elastic modulus of 5 GPa are obtained for samples with optimized compositions and heat treatments. Solubility and degradation study of the samples in water demonstrate that alkali silicates are prone to be soluble if not treated at 200 °C or above. Transformation of Si–OH to Si–O–Si not only increases the strength but also makes it insoluble in water. It is concluded that sodium silicate bonded bricks and blocks are very promising and affordable materials for construction. They represent an alternative to Portland cement concrete bricks and to sintered clay bricks, providing higher strength and representing an eco-friendly material.

Transparent nanocomposite films were prepared using bacterial cellulose (BC) as reinforcement and diethylene glycol bis(allyl carbonate) polymer (DEAC) as matrix by vacuum infiltration and UV polymerization. The BC/DEAC nanocomposites exhibit excellent transparency up to 88% at wavelength of 550 nm. The uniform dispersion of resin in BC 3D network was evidenced from SEM and ATR-FTIR analyses, confirms the complete photo-polymerization of diethylene glycol bis(allyl)carbonate monomer to Poly (diethylene glycol bis(allyl carbonate) in BC network. The BC/DEAC composites have good mechanical properties, reaching a tensile strength of 130 MPa and a Young’s Modulus of 6.4 GPa. Applying a micromechanic modeling approach, the elastic modulus of the composite was used in order to determine the average aspect ratio of BC fibers. These flexible transparent BC/DEAC composite films can be considered as functional films for optoelectronics application.

Wollastonite/hydroxyapatite composite scaffolds are proposed as bone graft. An investigation on scaffold with varying reinforcing wollastonite content fabricated by polymeric sponge replica is reported. The composition, sintering behavior, morphology, porosity and mechanical strength were characterized. All the scaffolds had a highly porous well-interconnected structure. A significant increase in mechanical strength is achieved by adding a 50% wollastonite phase. The most mechanically resistant (50/50) wollastonite/hydroxyapatite scaffolds were soaked in both simulated body fluid (SBF) and Tris–HCl solution in order to assess bioactivity and biodegradability. A carbo-hydroxyapatite layer formed on their surfaces when immersed in SBF. The biodegradability tests reveals that the composite scaffold shows a higher degradation rate compared to pure hydroxyapatite used as comparison. These results demonstrate that the incorporation of a 50% of wollastonite phase in hydroxyapatite matrix is effective in improving the strength and the bioactive and biodegradable properties of the porous scaffolds.

Biomimetic scaffolds with a structural and chemical composition similar to native bone tissue may be promising for bone tissue regeneration. In the present work hydroxyapatite mesoporous microspheres (mHA) were incorporated into collagen scaffolds containing an ordered interconnected macroporosity. The mHA were obtained by spray drying of a nano hydroxyapatite slurry prepared by the precipitation technique. X-ray diffraction (XRD) analysis revealed that the microspheres were composed only of hydroxyapatite (HA) phase, and energy-dispersive x-ray spectroscopy (EDS) analysis revealed the Ca/P ratio to be 1.69 which is near the value for pure HA. The obtained microspheres had an average diameter of 6 μm, a specific surface area of 40 m(2)/g as measured by Brunauer-Emmett-Teller (BET) analysis, and Barrett-Joyner-Halenda (BJH) analysis showed a mesoporous structure with an average pore diameter of 16 nm. Collagen/HA-microsphere (Col/mHA) composite scaffolds were prepared by freeze-drying followed by dehydrothermal crosslinking. SEM observations of Col/mHA scaffolds revealed HA microspheres embedded within a porous collagen matrix with a pore size ranging from a few microns up to 200 μm, which was also confirmed by histological staining of sections of paraffin embedded scaffolds. The compressive modulus of the composite scaffold at low and high strain values was 1.7 and 2.8 times, respectively, that of pure collagen scaffolds. Cell proliferation measured by the MTT assay showed more than a 3-fold increase in cell number within the scaffolds after 15 days of culture for both pure collagen scaffolds and Col/mHA composite scaffolds. Attractive properties of this composite scaffold include the potential to load the microspheres for drug delivery and the controllability of the pore structure at various length scales.

The present work describes the processing of alumina fiber reinforced alumina ceramic preforms consisting of chopped Al2O3 fibers (33 wt%) and Al2O3 (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 Al2O3 fibers into Al2O3 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.

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. © 2009 Elsevier B.V. All rights reserved.

In this work, we synthesized porous nanohydroxyapatite/collagen composite scaffold (nHA-COL), which resemble extracellular matrices in bone and cartilage tissues. Nano hydroxyapatite (nHA) was successfully nucleated in to the collagen matrix using hen eggshell as calcium biogenic source. Porosity was evaluated by apparent and theoretical density measurement. Porosity of all scaffolds was in the range of 95-98%. XRD and TEM analyses show the purity and size of nucleated HA around 10 nm and selected area electron diffraction (SAED) analysis reveals the polycrystalline nature of nucleated HA. SEM analysis reveals (i) all the scaffolds have interconnected pores with an average pore diameter of 130 micron and (ii) aggregates of hydroxyapatite were strongly embedded in the collagen matrix for both composite scaffolds compared with pure collagen scaffold. EDS analysis shows the Ca/P stoichiometric ratio around 1.67 and FTIR reveals the chemical interaction between the collagen molecule and HA particles. The testing of mechanical properties evidenced that incorporation of HA resulted in up to a two-fold increase in compressive modulus with high reinforcement level (similar to 7 kPa for 50HA-50COL) compared to pure collagen scaffold.

Bottom ash from coal-fired power plants is a potential raw material for the production of ceramic tiles, bricks and blocks for various applications. In this work we are presenting a novel microwave method to utilize the bottom ash to produce thermal insulating bricks. Foam samples were prepared by microwave foaming of the mortar prepared by milling the bottom ash, sodium silicate and NaOH. The microwave foaming ability of different slurry compositions and the physical and mechanical properties of the foamed samples were evaluated. FTIR analysis reveals that the degree of geopolymerization increases with increasing fraction of sodium silicate. Foams with low bulk density, high porosity, low thermal conductivity and compressive strengths were obtained by this method. With varying the bottom ash to sodium silicate ratio, it is possible to modulate the physical and mechanical properties of the insulating bricks.

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. © 2010 Elsevier B.V. All rights reserved.

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. © 2010 Elsevier B.V. All rights reserved.

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. © 2009 Elsevier B.V. All rights reserved.

The research was carried out to develop geopolymers mortars and concrete from fly ash and bottom ash and compare the characteristics deriving from either of these products. The mortars were produced by mixing the ashes with sodium silicate and sodium hydroxide as activator solution. After curing and drying, the bulk density, apparent density and porosity, of geopolymer samples were evaluated. The microstructure, phase composition and thermal behavior of geopolymer samples were characterized by scanning electron microscopy, XRD and TGA-DTA analysis respectively. FTIR analysis revealed higher degree of reaction in bottom ash based geopolymer. Mechanical characterization shows, geopolymer processed from fly ash having a compressive strength 61.4 MPa and Young's modulus of 2.9 GPa, whereas bottom ash geopolymer shows a compressive strength up to 55.2 MPa and Young's modulus of 2.8 GPa. The mechanical characterization depicts that bottom ash geopolymers are almost equally viable as fly ash geopolymer. Thermal conductivity analysis reveals that fly ash geopolymer shows lower thermal conductivity of 0.58 W/mK compared to bottom ash geopolymer 0.85 W/mK.

Nano sized hydroxyapatites with silicon substitution of three different silicon concentrations were successfully prepared first time by a rapid microwave assisted synthesis method, with a time saving and energy efficient technique. The effects of the Si substitution on crystallite size, particle size and morphology of the powders were investigated. The crystalline phase, microstructure, chemical composition, and morphology and particle size of hydroxyapatite and silicon substituted hydroxyapatites were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and dynamic light scattering. The crystallite size and particle size decreases with increase in silicon content and particle morphology spheroidal for pure hydroxyapatite changes to elongated ellipsoidal crystals while silicon substitution increases. Fourier Transform Infrared Spectroscopy analysis reveals, the silicon incorporation to hydroxyapatite lattice occurs via substitution of silicate groups for phosphate groups. Substitution of phosphate group by silicate in the apatite structure results in a small increase in the lattice parameters in both a-axis and c-axis of the unit cell.

The main objective of the present study was to develop a high-strength machinable ceramic based on zirconia (ZrO2) and magnesium aluminum silicate (Mg3Al2Si6O18; MAS) glass system through pressure-less sintering. Pressure-less sintering of ZrO2, 3 mol% yttria-stabilized (YSZ) was carried out at 1450°C in air, using 10 wt% MAS glass as a sintering additive. The influence of glass on the microstructure and mechanical properties of the composite was investigated. The presence of glass into the ZrO2 matrix was substantiated using scanning electron microscopy (SEM). X-ray diffractometry (XRD) revealed no crystalline phases other than tetragonal ZrO2. The flexural strength of the composite was found to be ~30% higher than YSZ. The apparent crack resistance was determined by Vickers microindentations carried out at different loads ranging from 9.8 to 196 N. The apparent crack length on the surface at each load was found to be decreased (6–21%) in YSZ and the corresponding crack-resistance values increased by about 5–20%. Both YSZ and composite showed rising trend in crack-resistance values as the indentation load was increased. Improved properties of composite sample were attributed to the formation of a relatively larger process zone surrounding the crack, crack-arrest behavior due to the localized compressive stresses, and the crack-bridging phenomena.

β-Tricalcium phosphate (β-TCP) nano powders (∼80 nm) were synthesized using a simple sol-gel route with calcium nitrate and potassium dihydrogenphosphate as calcium and phosphorus precursors, respectively. Double distilled water was used as a diluting media for β-TCP sol preparation and ammonia was used to adjust the pH. After aging, the β-TCP gel was dried at 40 °C and calcined to different temperatures ranging from 200 to 800 °C. The dried and calcined powders were characterized for phase composition using X-ray diffractrometry (XRD) and Fourier transform-infrared spectroscopy (FT-IR). The particle size and morphology was studied using Transmission electron microscopy (TEM). Calcination revealed that with increase in temperature, both the crystallinity and crystallite size of β-TCP particles increased. Particle size distribution analysis of the calcined β-TCP at 800 °C showed a narrow skewed distribution plot centered between 70 and 80 nm. This value was in closed agreement with particle size values obtained from XRD analysis (83 ± 6 nm). The present study showed that narrowly distributed, high crystalline, pure β-TCP could be obtained using this simple technique for biomedical applications. © 2009 Elsevier B.V. All rights reserved.

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 μn. 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. ©KIM and Springer.

Silver (Ag) nanoparticles (∼6 nm) were synthesized using a novel dialysis process. Silver nitrate was used as a starting precursor, ethylene glycol as solvent and hydroxy propyl cellulose (HPC) introduced as a capping agent. Different batches of reaction mixtures were prepared with different concentrations of silver nitrate (AgNO3). After the reduction and aging, these solutions were subjected to ultra-violet visible spectroscopy (UVS). Optimized solution, containing 250 mg AgNO3 revealed strong plasmon resonance peak at ∼410 nm in the spectrum indicating good colloidal state of Ag nanoparticles in the diluted solution. The optimized solution was subjected to dialysis process to remove any unreacted solvent. UVS of the optimized solution after dialysis showed the plasmon resonance peak shifting to ∼440 nm indicating the reduction of Ag ions into zero-valent Ag. This solutionwas dried at 80 8C and the resultant HPC capped Ag (HPC/Ag) nanoparticles were studied using transmission electron microscopy (TEM) for their particle size and morphology. The particle size distribution (PSD) analysis of these nanoparticles showed skewed distribution plot with particle size ranging from 3 to 18 nm. The nanoparticles were characterized for phase composition using X-ray diffractrometry (XRD) and Fourier transform infrared spectroscopy (FT-IR). © 2010 Elsevier Ltd. All rights reserved.

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. X-ray 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. © 2010 The Chinese Society for Metals.

Hydroxyapatite (HA) nano powders (20-60 nm) were synthesized using a sol-gel route with calcium nitrate and phosphoric acid as calcium and phosphorus precursors, respectively. Double distilled water was used as a diluting media for HA sol preparation and ammonia was used to adjust the pH. After aging, the HA gel was dried at 65°C and calcined to different temperatures ranging from 200-800°C. The dried and calcined powders were characterized for phase composition using X-ray diffractometry, elemental dispersive X-ray and Fourier transform infra-red spectroscopy. The particle size and morphology were studied using transmission electron microscopy. Calcination revealed HA nano powders of increased particle size and crystallinity with increase in temperature. For all calcinations temperatures, the particle size distribution analysis of HA powders showed skewed distribution plot. At temperature of 700°C and above, formation of CaO was noticed which was attributed to phosphorous volatilization. This study showed that high purity HA with varying degrees of crystallinity could be obtained using this simple technique. © Indian Academy of Sciences.