Papers by Keyword: Microcrystalline

Abstract: In the paper, a novel perovskite microcrystalline with a capsule-free cavity box structure was creatively prepared through solvent thermal reaction, and the composition and structure of CH₃NH₃PbI₃ perovskite microcrystalline were further characterized by scanning electron microscope (SEM) and energy dispersive X-ray (EDX) element mapping. The SEM results show that the grain size of the prepared CH₃NH₃PbI₃ perovskite microcrystalline is more than 100 μm. Furthermore, X-ray diffraction (XRD) analysis was used to characterize the material decomposition of perovskite microcrystals before and after 150 d of air aging. The XRD results indicate the prepared perovskite microcrystalline could be stably preserved in the air for 150 d without degradation. Our method provides technical guidance for further enriching the morphology of CH₃NH₃PbI₃ perovskite microcrystalline.

Abstract: An extensive study was made of the boundary area microstructure between the matrix and dense inner sublayers of the ceramic coating formed on AZ91 magnesium alloy substrate by micro-arc oxidation(MAO).The coating was prepared in an alkaline electrolytic solution composed of 5-20g/l of NaH₂PO₄, 1-5g/l of NaOH, 5-8g/l of KF; 0.5-2g/l of Na₃C₆H₅O₇, and 0.5-2g/l of EDTA , employing a constant-current controlled AC power supply with a current density of 10-30A/dm²; and the microstructure of the coatings was characterized using transmission electron microscopy(TEM) and scanning electron microscopy(SEM). It was found that (1) the main constituent of the coating adjacent to the boundary was microcrystalline and nanocrystalline; (2) the microhardness of the coating adjacent to the boundary was improved than that of the matrix. It was due to the formation of the intermixing of Mg and MgO and their grains were refined, these leaded to fine-crystal strengthen.

Abstract: SrWO₄ octahedrons, flowers, bundles, ellipsoids and dendrites had been successfully synthesized via surfactant-assisted method. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), photo-luminescent spectra techniques (PL) and fourier transrform infrared spectrometer (FTIR). By through various comparison experiments, it can be found that some related experimental parameters including the reagent concentration, [Sr²⁺]/[WO₄^2-] molar ratio (R), aging temperature and the pH value had great influences on morphology of the products.

Abstract: Ca(MoO₄)_x(WO₄)_(1-x) solid solution microcrystallines were synthesized by hydrothermal method at 120 °C; the crystal structure, surface morphology and room temperature photoluminescence properties of the as-synthesized microcrystallines were investigated by through X-ray diffraction (XRD), scanning electron micrograph (SEM), Fourier transform infrared spectroscopy (FT-IR) and fluorescence analysis (FA), respectively. Our results show that the obtained Ca(MoO4)x(WO4)(1-x)microcrystallines are single-phase scheelite structure with tetragonal symmetry. The grain size of the Ca(MoO4)x(WO4)(1-x) microcrystallines gradually increases with the increasing x (except x=0) and their agglomeration also becomes serious with x increasing. Under excited by 245 nm or 280 nm ultraviolet light (UV-light) at room temperature, the emission spectra of the Ca(MoO4)x(WO4)(1-x) microcrystallines vary slightly from 410nm to 490nm with increasing x. Whereas the emission intensity of Ca(MoO4)x(WO4)(1-x) microcrystallines changed markedly, and it increases with the increasing x (x＞0).

Abstract: The oxidation behavior of thin layers of Fe-15Cu-5Al-0.3Y alloy with grain size in nanometer range, prepared by magnetron sputtering deposition on cast alloy of the same composition, was studied at700oC in 0.1MPa O2. The scales grown on the coatings consist of two layers. The outer layer is composed of an external continuous Fe oxides scale free from copper and aluminum oxides. The inner layer is very complicated, with formation of dark oxides of Fe and Al, coupled with light un-oxidized Cu-rich stringers elongated perpendicularly to the alloy surface. Some degree of internal oxidation of Fe and Al is also present within the coating layer. A grain size reduction can effectively promote the selective external oxidation of Fe.

Abstract: In this paper microcrystalline CBN abrasives are prepared with CBN powders and vitrified bond additives by pressureless sintering method. Mechanical properties of the products are measured by using single particle compressive strength tester and three-point bending strength tester. The effects of vitrified bond additives, the CBN powders particle size and the sintering temperature on the performance of microcrystalline CBN abrasives are investigated. The microstructure characteristics of microcrystalline CBN abrasives are examined. The results showed that the performance and microstructure of microcrystalline CBN abrasives are significantly influenced by particle size of CBN powder and the addition amount of vitrified bond.