Showing 3 results for Powders
A. Najafi, F. Golestani-Fard, H. R. Rezaie, N. Ehsani,
Volume 8, Issue 2 (6-2011)
Abstract
Abstract: SiC nano particles with mono dispersed distribution were synthesized by using of silicon alkoxides and phenolic resin as starting materials. After synthesis of sample, characterizations of the obtained powder were investigated via Fourier Transform Infrared Spectroscopy (FTIR) with 400-4000 cm-1, X-ray Diffractometry (XRD), Laser Particle Size Analyzing (LPSA), Si29 NMR analysis, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). FTIR and Si29 NMR results of the gel powder indicated that Si-O-C bonds were formed due to hydrolysis and condensation reactions . FTIR results showed a very strong peak for heat treated powder at 1500°C after carbon removal which is corresponded to Si-C bond. Obtained pattern from X-ray diffractometry showed that the final products contain -SiC phase with poly crystalline planes and little amounts of residual carbon. PSA results showed that the average particles size were 50.6 nm with monosized distribution. Also microstructural studies showed that the SiC nano powders have semi spherical morphology with mean particles size of 30-50 nm and also there are some agglomerates with irregular shape.
Razieh Khoshhal, Seyed Vahid Alavi Nezhad Khalil Abad,
Volume 21, Issue 0 (3-2024)
Abstract
This study utilized aluminum, copper powder according to the stoichiometric ratio of Al₂Cu, and calcium powder in relation to the eutectic composition of Al-Ca at the ratio of 5.5 atomic percent. Two samples were prepared, one without calcium and another with calcium, and were analyzed to determine the impact of calcium on the formation of copper aluminide. Samples were subjected to thermal treatment at temperature of 400, 600, and 800ºC. The obtained results indicated that disappearance of Al₂Cu phase at 800ºC in calcium-free sample and existence of Al₂Cu phase in calcium sample indicating a possible role of calcium in stabilization of Al₂Cu phase. Furthermore, it was concluded that calcium influences phase formation. There was higher diffusion of aluminum in to copper resulting in formation of Al₄Cu₉ not only in the sample with calcium, but also in calcium-free sample. One more finding of the research is that calcium influences microstructure and its homogenization as well. In particular, it was found that calcium-containing sample has the least number of pores and was uniform in the structure.
Amir Hojjati Lemraski, Ali Sedaghat Ahangari Hossein Zadeh, Rahim Naghizadeh, Hudsa Majidian,
Volume 21, Issue 4 (12-2024)
Abstract
Cordierite ceramics are of interest for various applications due to their properties such as low thermal expansion coefficient and high thermal shock resistance. However, due to the narrow range of sintering temperature, attempts have been made to synthesize it using different additives. In this way, titania and tialite have been added in different amounts to the initial raw material mixture (talc, kaolin, and synthetic alumina). In this research, the initial powders (talc, kaolin, and synthetic alumina) were mixed in a planetary ball mill using different amounts of TiO2 and tialite. The mixtures were sintered at 1250, 1300, and 1350 °C for 3 h. X-ray diffractometry and fluorescence, thermal analysis, microstructural observation, density, and cold compressive strength (CCS) were used to evaluate the sintered samples. Phase analysis revealed the presence of the cordierite phase along with small amounts of spinel. With increasing sintering temperature and titania addition, the amount of spinel decreased and the amount of cordierite phase increased. The real density increased with increasing titania additive content, but at higher titania contents, microcracks were observed in the SEM micrographs. By adding 15 wt% of tialite to the initial batch, the compressive strength has been increased by 88% compared to the pure cordierite sample.
