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Loghman Estarki Mohammad Reza,Abedi Vellashani Faezeh,Moinifard Farzad,Milani Mostafa,Kumar Anjan,Ghazi Mohammad Reza,Sardarian Mehran 한국세라믹학회 2022 한국세라믹학회지 Vol.59 No.6
To produce transparent alumina pieces, alpha-alumina nanoparticles with diff erent amounts of MgO sintering aid were dispersed in a paraffi n-polypropylene-based binder system. The alumina-binder feedstock was optimized for the powder injection molding (PIM) method. After binder removal, the green body piece was sintered through the spark plasma sintering method. Rheometric tests, Vickers measurement, three-point bending fl exural test, and Archimedes test were used for the feed fl uidity, hardness, fl exural strength, and density of the sintered pieces, respectively. Next, IR and visible transmission of SPSed bodies were measured. The results showed that a combination of PIM and SPS methods with 500 ppm sintering aid causes higher IR and visible transmission than the sample with 600 ppm sintering aid. In addition, the hardness of as- obtained transparent alumina was in the range of 16–16.5 GPa. The fl exural strength of the as-obtained transparent sample (with 500 ppm MgO) was more than SPSed with 600 ppm MgO sintering aid.
Fatemeh Davar,Mohammad Reza Loghman-Estarki,Rouholah Ashiri 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.21 No.1
The aim of this work is to synthesis and characterization of cadmium sulfide/ thioglycolic acidnanocomposite and its conversion to pure CdS nanoparticles. The products were characterized by X-raydiffraction (XRD), SEM, TEM, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared(FTIR) spectra. The CdS/organic nanocomposite was decomposed into pure wurtzite CdS nanoparticlesthrough hydrothermal treatment at 200 8C. UV–vis spectra were used to study the optical properties ofCdS/organic nanocomposites and pure CdS. It was found that the absorption maximum of the CdS/TGAnanocomposite was significantly blue-shifted as compared to pure CdS nanoparticles.
Ghasemi Arman,Ramazani Mazaher,Bakhshi Saeed Reza,Al-Khafaji Ali Hussein Demin,Zahabi Saeed,Loghman Estarki Mohammad Reza,Zamani Abbas 한국세라믹학회 2023 한국세라믹학회지 Vol.60 No.4
This research aims to fabricate and develop a composite brake disc made of carbon/silicon carbide. For this purpose, the first silicon carbide nanoparticles were ultrasonicated with alumina sintering aid and carbon fi ber (between 10 and 20%) with different lengths of 3 mm, 10 mm, and 15 mm. Next, the fi nal Cf/SiC composite bulk was made-up via the spark plasma sintering (SPS) method. After that, the effect of different lengths of carbon fiber was explored on the porosity, coefficient of friction, fracture toughness, thermal conductivity, and microhardness of samples. The results showed that the density of sintered samples with a carbon fiber length of 10 mm was higher than that of samples with fiber lengths of 3 and 15 mm. Also, the hardness (25.79 GPa) and fracture toughness (5.72 MPa.m 1/2) of this sample were higher than those of the samples sintered with carbon fiber lengths of 3 and 15 mm. Further, this sample with the maximum density showed a coefficient of friction (COF) of 0.43. Since for aeroplane brake discs, the COF should be between 0.3 and 0.4, and the porosity of sam- ples should range within 3–5%, the samples sintered with the carbon fiber length of 10 mm had the nearby features to the preferred air brake disc indices.
Effect of Al on Structural and Magnetic Characteristics of CoCrFeNiMnAlx High Entropy Alloys
Majid Tavoosi,Ali Ghasemi,Gholam Reza Gordani,Mohammad Reza Loghman-Estarki 한국재료학회 2023 한국재료학회지 Vol.33 No.3
This research examines the effect of adding aluminum on the structural, phasic, and magnetic properties of CoCrFe NiMnAlx high-entropy alloys. To this aim, the arc-melt process was used under an argon atmosphere for preparing cast samples. The phasic, structural, and magnetic properties of the samples were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrational magnetometry (VSM) analyses. Based on the results, the addition of aluminum to the compound caused changes in the crystalline structure, from FCC solid solution in the CoCrFeNiMn sample to CoCrFeNiMnAl BBC solid solution. It was associated with changes in the magnetic property of CoCrFeNiMnAlx high-entropy alloys, from paramagnetic to ferromagnetic. The maximum saturation magnetization for the CoCrFeNiMnAl casting sample was estimated to be around 79 emu/g. Despite the phase stability of the FCC solid solution with temperature, the solid solution phase formed in the CrCrFeNiMnAl high-entropy compound was not stable, and changed into FCC solid solution with temperature elevation, causing a reduction in saturation magnetization to about 7 emu/g.