Volume 112, Issue 6

In this study, YAlO 3 (YAP) was produced at low temperatures by a powder sintering process. Al 2 O 3 –Y 2 O 3 powder mixtures were subjected to heat treatment at different temperatures. The relationship between the sintering temperature and the emergence of new phases was investigated via X-ray diffraction, and supported by energy dispersive X-ray spectroscopy. The crystallization of the monoclinic yttrium aluminum oxide (Y 4 Al 2 O 9 ) occurred at 1 000 °C, whereas the yttrium aluminum perovskite (YAlO 3 ) crystallization occurred at 1 100°C. Energy dispersive X-ray spectroscopy analysis showed yttrium content in the sample containing Al 2 O 3 –YAlO 3 powder sintered at 1100 °C, associated with the YAlO 3 phase formed at this temperature. Brunauer–Emmett–Teller surface analysis showed a significant decrease in the pore volume of the sample sintered at 1 100°C.

In this work, Al/Cu core–shell particles were successfully synthesized through an optimized galvanic replacement method. For this purpose, a uniform and dense copper layer was deposited on aluminum particles in an alkaline solution. The effects of four deposition factors, i. e. (i) molar ratio EDTA-2Na/CuSO 4 · 5H 2 O, (ii) molar ratio CuCl 2 /Al powder, (iii) pH and (iv) temperature were systematically studied and optimized using the Taguchi orthogonal (L9) method. It was observed that molar ratio EDTA-2Na/CuSO 4 · 5H 2 O and temperature are the most affecting factors in the deposition process. By increasing their levels, copper deposition increases within a specified time. The X-ray diffraction and scanning electron microscopy/ energy-dispersive X-ray spectroscopy results revealed the formation of homogeneous nanostructured Cu shells around Al particles. The results revealed that to achieve maximum copper deposition on Al powder; molar ratio EDTA-2Na. 2H 2 O/CuSO 4 . 5H 2 O, molar ratio CuCl 2 /Al powder, pH and temperature of the deposition bath should be 2.0, 0.05, 8.8 and 55 °C, respectively.

In the present study, BaTiO 3 nanospheres with a uniform particle size of around 100 nm were prepared by a hydrothermal route using Ba(OH) 2 .8H 2 O and TiO 2 nanoparticles. Experimental results revealed that the main influencing factors for the formation of BaTiO 3 nanospheres were molar Ba/Ti ratio ( R Ba/Ti ), hydrothermal temperature, and time. Highly-dispersed BaTiO 3 nanospheres (100 nm) were obtained under the optimum hydrothermal conditions at temperature = 200°C, time = 12 h, and R Ba/Ti = 1.5. Under these optimum conditions, BaTiO 3 ceramics were synthesized from the as-prepared BaTiO 3 nanospheres, and their structural, microstructural, and electrical properties were investigated. The BaTiO 3 ceramics exhibited a high dielectric constant of 7300 at a Curie temperature of 125 °C, great density (ρ), 5.83 g cm –3 ; large dielectric constant at room temperature e r = 3586 and tan d = 0.03, high remanant polarization P r = 10.6 μC cm –2 , low coercive field E c = 4.5 kVcm –1 .

Corrugated-surface silver powders were prepared for front contact pastes of silicon solar cells. The effects of using different pH controlling agents on the powder diameter, morphology, and conversion of silver ions to silver powders were investigated. Silver powders with wrinkled surface and 100% conversion were prepared, and ground by using spiral jet milling and tumbling ball milling, respectively. Silver powders ground by using spiral jet milling had better size distribution, higher tap density, and corrugated surface, the tap density of silver powders ground by using spiral jet milling was 6.52 g cm –3 . The silver powders were used to prepare front contact pastes of silicon solar cells, the aspect ratio of printed gridlines was 0.34.

Reduced graphene oxide has attracted great interest for application as microwave absorbing materials during recent years. Barium ferrite (BaFe 12 O 19 ) is also a hard magnetic material with microwave absorbing properties. In this research, Zn-doped barium ferrite/reduced graphene oxide nanocomposites were synthesized and their magnetic and microwave absorption properties were studied. Phase analysis, particle morphology, magnetic properties, and microwave absorption properties were investigated by means of X-ray diffraction, field-emission scanning electron microscopy, vibrating sample magnetometry, and vector network analysis, respectively. Electron microscopy images showed that reduced graphene oxide nanosheets are decorated with barium ferrite nanoparticles. Zn-doping in the reduced graphene oxide/BaFe 12- x Zn x O 19 ( x = 0.0, 0.2, 0.4, and 0.6) nanocomposites caused an increase in the saturation magnetization from 30.76 to 32.69 emu g –1 for Zn = 0.4. Maximum reflection loss was increased from –7.39 dB to –13.50 dB by Zn doping for x = 0.4 in the nanocomposite consisting of 10 wt.% of reduced graphene oxide/BaZn 0.4 Fe 11.6 O 19 . The microwave absorption characteristics are discussed based on the permittivity and permeability values of the nanocomposites.

The use of ceramic particles in the matrix of alloy coatings during the electroplating process has received considerable attention. These particles can create properties such as high corrosion resistance, insolubility, high-temperature stability, strong hardness, and self-lubrication capability. Herein, an Ni–P–W–TiO 2 coating was deposited on an AISI 304L steel substrate using the electroplating method. Electroplating was performed at current densities of 10, 15, 20, and 25 mA · cm –2 , and the effect of current density on microstructure, corrosion behavior, and wear behavior was investigated. The coatings were characterized by means of scanning electron microscopy. To investigate corrosion resistance, potentiodynamic polarization and electrochemical impedance spectroscopy tests were performed in a 3.5% NaCl aqueous solution. A pin-on-disk test was conducted to test the wear resistance of uncoated and coated samples. Sample micro-hardness was also measured by Vickers hardness testing. Examination of the microstructure revealed that the best coating was produced at a current density of 20 mA · cm –2 . The results of potentiodynamic polarization and electrochemical impedance spectroscopy tests were consistent with microscopic images. The coating created at the current density of 20 mA · cm –2 had the highest corrosion resistance compared to other coated and non-coated samples. Furthermore, the results of the wear test showed that increasing the current density of the electroplating path up to 20 mA · cm –2 enhances micro-hardness and wear resistance.

In recent years, minimum quantity lubrication machining has played a critical role in extending tool life, improving surface finish, and reducing tool wear during the machining of hardened steel. The reported investigation involved the utility of Hardox 500 steel for the machining process while the cubic boron nitride coated tool performed the function of removing the material. The investigation was carried out by adopting two different techniques to predict the responses, viz., the response surface methodology and the artificial neural network. These techniques have been employed to predict the possible responses in investigating machining characteristics. Also, due consideration has been made concerning the reduction of tool-tip temperature and surface roughness. The entire investigation was carried out using three different environments. They are dry machining, wet, and minimum quantity lubrication. A scanning electron microscope was used for examining the morphology of the worn tool surface.

This study was carried out to remove iron from kaolin using a biological method by two different species of Bacillus sp . and the combination of A. niger isolated from pistachio skin & Bacillus subtilis and comparing them with the control sample. The experiments were carried out for Bacillus sp . at 30 °C and 25 °C and for the combination of A. niger & Bacillus subtilis at 27 °C. The concentration of dissolved iron increased with increasing temperature in the samples treated with Bacillus sp . X-ray fluorescence spectroscopy results of the samples at 25 °C showed a reduction of 31.1% in Fe 2 O 3 and Fe content and a reduction of 37% at 30 °C after 28 days. Therefore, iron removal by Bacillus subtilis at 30 °C achieves better performance than at 25 °C. X-ray fluorescence spectroscopy results of the samples treated with the combination of A. niger & Bacillus subtilis show a decrease of 49% in Fe 2 O 3 and Fe content at 27 °C after 14 days. The results of colour measurement showed that kaolin powder treated with the combination of A. niger & Bacillus subtilis at 27 °C had the highest degree of whiteness compared to other samples.

Biomedical titanium alloys with elastic moduli close to that of cortical bone have gained great attention in the field of bone implantation. A low modulus is desirable in an implant to prevent stress shielding, which usually leads to critical clinical issues, such as bone resorption and implant loosening. The use of β-type titanium with nontoxic alloying elements, such as niobium, as a novel candidate of implant material for replacing failed hard tissues has shown great potential. This review describes a titanium implant application alloyed with niobium and the mechanical properties and bioactivity of various titanium alloys sintered at different temperatures.