Showing 7 results for Borhani
S. R. Bakhshi, M. Salehi, H. Edris, G. H. Borhani,
Volume 29, Issue 1 (Jun 2010)
Abstract
In this study, Mo-14Si-10B and Mo-57Si-10B (at%) elemental powders were separately milled using an attritor mill. Mechanically alloyed powders were agglomerated and annealed. Then, powders of Mo-Si-B as alloyed (with composites) and agglomerated (without composites) were plasma sprayed onto plain carbon steels. The samples, both coated and non-coated, were subjected to isothermal oxidation tests. Metallurgical characteristics of powders and coatings were evaluated by SEM and XRD. Plasma-sprayed Mo-Si-B coatings (with phases of MoSi2, Mo5Si3, MoB and Mo5SiB2) greatly improved the oxidation resistance of the plain steel substrates, but plasma-sprayed Mo-Si-B coatings (without any phases) did not significantly improve the oxidation rate of substrates. Also, the kinetics and composition of the oxide-scale have been found to depend on the alloy composition.
P. Safaie, G. H. Borhani, S. R. Bakhshi,
Volume 33, Issue 1 (Journal of Advanced Materials- Summer 2014)
Abstract
In this study, pure powders such as molybdenum, silicon, aluminum and titanium carbide were utilized to produce MoSi2 compound, MoSi2 /20 Vol % TiC composite, MoSi2-x Al alloyed compound and MoSi2-x Al/20 Vol % TiC alloyed composite. The initial powders were mixed in specified ratios, and then, were activated by mechanical milling. Milled powders were compacted, synthesized and sintered in the temperature range of 1100 -1400 oC. SEM was used to investigate the microstructural change and XRD for identification of phases. Effect of aluminum addition on phase formation was investigated. Addition of aluminum by over 9 atomic percent resulted in the formation of Mo(Si,Al)2 in alloyed matrix.
M. Khajelakzay, S. R. Bakhshi, G.h. Borhani,
Volume 34, Issue 4 (Journal of Advanced Materials-winter 2016)
Abstract
In this study, synthesis of silicon nitride by mechanical alloying and the effects of important parameters of milling time and heat treatment temperature, time and rate are presented. Silicon micro powder and nitrogen gas were used as precursor materials. Synthesized phases, morphology and particle size were investigated by X-ray diffraction pattern (XRD) and Field emission scanning electron microscopy (FE-SEM), respectively. X-ray fluorescence analysis (XRF) was used for silicon nitride purity investigation.The optimum sample was produced at 30 h milling time, heat treatment at 1300 ℃ and 22 ℃/min heating rate conditions. X-ray fluorescence analysis showed more than 98% purity.
M. Bahrami, G.h. Borhani, S.r. Bakhshi, A. Ghasemi,
Volume 35, Issue 3 (Journal of Advanced Materials-Fall 2016)
Abstract
Organic–inorganic hybrid coatings were prepared by sol–gel method and deposited on aluminum alloy 6061. Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy and Scanning Electron Microscopy (SEM) were used for structural study of the hybrid coatings. Adhesive strength of sol–gel coatings to the substrate was evaluated quantitatively and qualitatively. Corrosion behavior of the samples was studied by cyclic potentiodynamic and linear polarization tests. Results showed that adhesion strength of the coatings to the substrates was increased with increasing tetrapropoxide of zirconium (TPOZ) and cerium content. Corrosion tests showed that corrosion current density of coated samples were decreased three to seven orders of magnitude in comparison with uncoated aluminum alloy 6061. Decreasing in corrosion current density and increasing in polarization resistance was observed by increasing zirconia and cerium content. Unlike the uncoated aluminum alloy 6061, the crack-free coatings did not show pitting tendency.
M. Tavoosi, S. Rizaneh, G. H. Borhani,
Volume 36, Issue 1 (Journal of Advanced Materials-Spring 2017)
Abstract
Investigating the effect of Al2O3-TiB2/Fe complex reinforcement (CCMR) on the mechanical properties of aluminum composites was the goal of this study. For this purpose, the Al2O3-TiB2/Fe reinforcement powders were synthesized during milling and subsequent annealing. Different volume percentages of the produced reinforcement powders (1.25, 2.5 and 5 vol.%) were added to aluminum matrix, milled for 10 h and then hot extruded. The structural phasic and mechanical investigations of the specimens were carried out using X-ray diffraction, scanning electron microscopy and tensile test. The results showed that the metallic component (Fe rich phase) in this new type of reinforcement stuck the ceramic parts (Al2O3-TiB2) to aluminium matrix, and has an importance role in the flexibility of the product. The best volume percentage of CCMR in aluminium matrix was about 2.5%. This nanocomposite had a combination of strength and ductility of about 500 MPa and 6%, respectively.
S. Borhani Esfahani, H. R. Salimi Jazi, M. H. Fathi, A. Ershad Langroudi, M. Khoshnam,
Volume 40, Issue 1 (Journal of Advanced Materials-Spring 2021)
Abstract
In this research, a kind of environmentally-friendly inorganic-organic hybrid nanocomposite coating based on silica containing titania/silica core/shell nanoparticles was synthesized and characterized for conservation of facade tiles in historical buildings. The matrix of the composite was prepared by sol-gel process via two methods of ultrasonic and reflux stirring. Tetraethyl orthosilicate (TEOS) and poly-dimethyl siloxane hydroxy-terminated (PDMS-OH) were used for the formation of silica network and creation of flexibility and hydrophobicity, respectively. Titania nanoparticles were used in the form of titania/silica core/shell as ultraviolet absorber. The synthesized nanocomposite was applied on the microscope slides and tiles by dip coating technique. The properties of nanoparticles and coatings were characterized by Fourier-transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM) and water contact angle measurement. The results revealed that formation of titania/silica core/shell structure was successful. The investigation of PDMS content effect on transparency, cohesion and hydrophobicity of the coating confirmed that the optimum content of this siloxane was around 20 wt.%. In general, the results showed that the silica-based hybrid nanocomposite reinforced with TiO2/SiO2 core/shell nanoparticles could produce a transparent and hydrophobic coating for tile and glass protection.
B. Sharifian, G. H. Borhani, E. Mohammad Sharifi,
Volume 41, Issue 2 (Journal of Advanced Materials-Summer 2022)
Abstract
In this study, mechanically milled (MM) Al-24TiO2-20B2O3 powder in molten Al7075 matrix was used in order to fabricate in-situ TiB2 and Al2O3 reinforcements in Al7075 matrix. Differential thermal analysis (DTA) examination was adopted to find reaction temperature between milled Al, TiO2, and B2O3 powders. X-Ray Diffraction (XRD) patterns showed the existence of TiB2 and Al2O3 peaks (750 °C at Ar atmosphere) in MM powder. Scanning Electron Microscopy (SEM) results revealed the uniform distribution of TiO2 and B2O3 particles in the aluminum matrix. 6 wt.% MM powder was added to molten Al7075 at 750 °C. The molten Al7075/TiB2-Al2O3 composite was poured in copper mold. The stir casted composites were hot extruded at 465 °C with extrusion ratio of 6:1 and ram speed of 5 mm/s. The microstructures (optical microscopy and TEM) and mechanical properties (hardness and tensile testing) of samples were evaluated. TEM results showed that in-situ TiB2 nanoparticles were formed. The tensile strength of extruded Al7075/TiB2-Al2O3 composite was reached the value of 496 MPa. This result was around four times greater than that of the as cast Al7075 alloy.
