Amin Bahrami

Manufacturing Wear-Resistant 10Ce-TZP/Al2O3 Nanoparticle Aluminum Composite by Powder Metallurgy Processing

Aluminum matrix composites (AMCs) are candidate materials for total joint arthroplasty, dental prostheses, cutting tools, and biomedical gadgets owing to their strength, machinability, dimension accuracy, and wear resistance. A novel method for manufacturing new generation of AMCs by addition of 10Ce-TZP(tetragonal zirconia polycrystal)/Al2O3 nanoparticles to aluminum via powder metallurgy is devised. Aqueous combustion synthesis is used for dispersoid production and milling–compaction–sintering for AMC fabrication. Effects of 10Ce-TZP/Al2O3 content on hardness, erosion, and wear resistance are investigated. Scanning electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction, and pin-on-disk analyses are used to explore worn interface, morphology, mechanism of abrasion, and resistance to wear. By addition of 7 wt% dispersoid, considerable increase in hardness and resistance to wear are achieved.

Eco-fabrication of hierarchical porous silica monoliths by ice-templating of rice husk ash

In this study, within a sustainable chemistry approach, a clean and eco-friendly synthesis process of silica monoliths compatible with environmental limitations is developed. Rice husk (RH), a surplus agricultural byproduct, was used to engineer monoliths with a hierarchical pore structure. Amorphous and crystalline silica powders were extracted from rice husk and ice-templated using water as a liquid vehicle. The effect of silica crystallinity and silica content, as well as processing parameters such as the freezing rate and sintering temperature on the microstructural characteristics and mechanical properties of the obtained monoliths were investigated. Depending on the freezing regime, microstructural analysis confirmed the formation of macropores with lamellar or honeycomb-like structures. By varying the processing parameters, the pore size, wall thickness and porosity can be tailored. While monoliths from crystalline rice husk ash (CRHA) show higher mechanical strength, monoliths from amorphous rice husk ash (ARHA) possess a high specific surface area, demonstrating aligned nano-channels and non-uniform mesoporosity.

Effect of sintering temperature on tribological behavior of Ce-TZP/Al2O3-aluminum nanocomposite

10Ce-TZP/Al2O3 nanoparticles as reinforcement can be a good substitute in aluminum matrix composites prepared through powder metallurgy. In this work, the effects of sintering temperature on the hardness, friction, and wear characteristics of Al-10Ce-TZP/Al2O3 composites have been investigated. Ce-TZP/Al2O3 nanocomposites were synthesized by the aqueous combustion method. About 7u2009wt% 10Ce-TZP/Al2O3-aluminum composites in the form of cylindrical samples were prepared at the sintering temperatures of 400℃, 450℃, and 500℃ under an applied pressure of 600u2009MPa for 60u2009min. The experimental results show that the distribution of Ce-TZP/Al2O3 nanocomposite into the metal matrix is homogenous and that at 450℃ the hardness and wear resistance improved considerably. Formation of an oxide layer is a manifestation that in nanocomposites produced at 450℃, worn surfaces were smoother and the total depth of deformations were not severe.

Bilayer graded Al/B4C/rice husk ash composite: Wettability behavior, thermo-mechanical, and electrical properties:

In this study, wettability behavior of B4C substrate as well as B4C/crystalline rice husk ash and B4C/amorphous rice husk ash substrates with two aluminum alloys were studied. The electrical resistivity, thermal expansion coefficients, and thermal diffusivity of bilayer Al/B4C/rice husk ash composite fabricated by one-step pressureless infiltration were measured and the obtained data were systemically analyzed using the Taguchi method and analysis of variance. Boron carbide substrates after addition of amorphous or crystalline rice husk ash display good wettability with molten aluminum alloys. The results show that, electrical resistivity of Al/B4C/rice husk ash composites is mainly influenced by initial preform porosity, while the coefficient of thermal expansion of composites is determined by the chemical composition of infiltrated alloys. The measured values for coefficient of thermal expansion (10.5u2009×u200910−6/℃) and electrical resistivity (0.60u2009×u200910−5u2009Ω.m) of Al/B4C/rice husk ash composites, fabricated according to analysis of variances optimal conditions are in good agreement with those of the projected values (11.02u2009×u200910−6/℃ and 0.65u2009×u200910−5u2009Ω.m, respectively). The difference between the corresponding values obtained from verification tests and projected values, for electrical resistivity and coefficient of thermal expansion are less than 5%. Finally, as a material selection approach, the strengths and weaknesses of the composites have been graphed in the form of radar diagrams.