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Uses of aluminium (Al)-based metal matrix composites (MMCs) have been emerging in variety of applications since several decades. Hence, in the present study, hybrid Al-MMCs were developed using rice husk-extracted highly pure silica (SiO2) and commercial graphite (Grt) as reinforcing materials by powder metallurgical route followed by unique re-sintering. Effect of reinforcements on mechanical as well as thermal properties of Al-MMCs has been determined in this study by various tests. The microscopy, spectroscopy, and X-ray diffraction studies were conducted to characterize the purity and homogeneity of the composites. The hybrid MMCs had shown excellent physical and mechanical properties in terms of surface strength along with being light mass. The Vickers hardness (up to 250 MPa) and compressive strength (up to 341 MPa) of the hybrid nanocomposites has increased significantly on the addition of reinforcements. Thermal properties, including conductivity and linear expansion, were found to be lower for the composites compared to pure Al. Hence, the newly developed rice husk-extracted pure silica and graphite-reinforced hybrid Al-MMCs, particularly the samples of 5SiO2/5Grt/90Al (mass%), can be used as reliable potential materials for several advanced applications including, engine piston, automobile, aviation, and spacecraft components where both mechanical and thermal properties play vital role. [ABSTRACT FROM AUTHOR]

Purpose: Recently, titanium (Ti) and its alloys have been widely used in dental and surgical implants in the last few decades. However, there is a loosening effect over a long period usage. Therefore, the present study aimed to increase life of an implant by its surface modification. Methods: In present study, sol-gel process has been applied to create tantalum pentoxide (Ta2O5) layer coating on Ti-substrate. In this technique, polyethylene glycol (PEG) plays an important role to form uniform porous coating, which can have potential application in formation of strong bonding to the natural bone. Results: Microstructural, elemental, structural and binding energy results showed that the material with 100% PEG-enhanced sol-gel Ta2O5 with spin coating onto Ti substrate followed by an optimized sintering temperature (500 °C) has better porous structure than that of 5% PEG-enhanced sol-gel Ta2O5 coating, and would be suitable for tissue in-growth properties. Conclusions: Therefore, it was concluded that the present spin coated 100% PEG-enhanced Ta2O5 coating onto Ti, having the most suitable morphology with enhanced roughness, could be noteworthy for potential tissue in-growth and it could provide desired bonding at the interface of Ti-implant coating and host tissues in biomedical applications. [ABSTRACT FROM AUTHOR]

Armalcolite, a rare ceramic mineral and normally found in the lunar earth, was synthesized by solid-state step-sintering. The in situ phase-changed novel ceramic nanocrystals of Ca-Mg-Ti-Fe based oxide (CMTFOx), their chemical reactions and bonding with polydimethylsiloxane (PDMS) were determined by X-ray diffraction, infrared spectroscopy, and microscopy. Water absorption of all the CMTFOx was high. The lower dielectric loss tangent value (0.155 at 1 MHz) was obtained for the ceramic sintered at 1050 °C (S1050) and it became lowest for the S1050/PDMS nanocomposite (0.002 at 1 MHz) film, which was made by spin coating at 3000 rpm. The excellent flexibility (static modulus ≈ 0.27 MPa and elongation > 90%), viscoelastic property (tanδ = E"/E': 0.225) and glass transition temperature (Tg: ―58.5 °C) were obtained for S1050/PDMS film. Parallel-plate capacitive and flexible resistive humidity sensors have been developed successfully. The best sensing performance of the present S1050 (3000%) and its flexible S1050/PDMS composite film (306%) based humidity sensors was found to be at 100 Hz, better than conventional materials. [ABSTRACT FROM AUTHOR]

The complex architecture of the cortical part of the bovine-femur was examined to develop potential tissue engineering (TE) scaffolds. Weight-change and X-ray diffraction (XRD) results show that significant phase transformation and morphology conversion of the bone occur at 500-750°C and 750-900°C, respectively. Another breakthrough finding was achieved by determining a sintering condition for the nucleation of hydroxyapatite crystal from bovine bone via XRD technique. Scanning electron microscopy results of morphological growth suggests that the concentration of polymer fibrils increases (or decreases, in case of apatite crystals) from the distal to proximal end of the femur. Energy-dispersive analysis of X-ray, Fourier transform infrared, micro-computer tomography, and mechanical studies of the actual composition also strongly support our microscopic results and firmly indicate the functionally graded material properties of bovine-femur. Bones sintered at 900 and 1000°C show potential properties for soft and hard TE applications, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Hydroxyapatite (HAp) is a potential material for various biomedical applications. In the present study, an attempt has been made to synthesize this material using simpler and cheaper method of solid-state-reaction process. Samples were prepared by mixing the ingredients and then sintering the cold compacted pellets at various temperatures from 500 to 1250°C. X-ray diffraction, thermo-gravitometric and differential thermal analysis and Fourier transform infrared (FTIR) spectroscopy techniques were used for structural characterization of the samples. It was found that Monetite phase of hydroxyapatite forms in the unsintered powder. Upon heating up to 1250°C, samples undergo several structural transformations with final structure being α-tri calcium phosphate (TCP) after sintering at 1250°C. Presence of various chemical groups in the samples was analyzed using Fourier transform infrared spectrometry and the results are in accordance with the literature. Mechanical tests showed that increasing compaction pressure during cold pressing improves mechanical strength of sintered product by reducing overall porosity. Compressive, tensile and bending strength, bulk modulus (in compression), and microhardness values were found to improve after resintering the pellets at 1250°C, which were previously sintered at the same temperature. It was also found that the mechanical properties of synthesized HAp were better as compared to the natural products. In vitro biological studies in a simulated body fluid showed around 15–20% change in the surface roughness of the samples albeit with negligible weight gain in dry state. [Copyright &y& Elsevier]