Papers by Keyword: Whisker

Abstract: To reinforce the mullite/Al₂O₃ composite ceramics through formation of mullite whiskers, the composite ceramics were prepared by pressureless sintering using different AlF₃ content. The microstructure, porosity, fracture toughness and thermal shock resistance of the composite ceramics were investigated. The results show that the addition of AlF₃ can promote the mullite whisker formations, and the whiskers with the size of 3～10μm in diameter and a length-diameter ratio of 10～15 are obtained by sintering at 1600°C with the AlF₃ content of 5wt%. Fracture toughness and thermal shock resistance of the composite ceramics are improved by the formation of mullite whisker. The fracture toughness of 4.79MPa•m^1/2 can be obtained, and the 95.18% flexural strength remained after thermal shock.

Abstract: The magnesium hydroxide whiskers,its length being about 30μm and its diameter being about 3μm, was prepared by hydrothermal conditions. The effect of preparation technology, which includes the reaction temperature and reaction time, was discussed according to the results of XRD, TEM, and SEM. Moreover, the mechanism of the preparation of magnesium hydroxide whiskers was studied.

Abstract: Al₂O₃-SiCw (SiC whisker) powders were plasma sprayed on carbon steel under the electrostatic field. Effect of voltage on the microstructure and mechanical properties of the coatings was investigated. The erosion resistance was measured on the rotating disk erosion tester. The micro hardness and fracture toughness were obtained by the indentation method. It is found that the phase composition is unchanged for the coatings deposited in the presence or absence of electrostatic field while the grain size of coatings varies with the voltage. The porosity of coatings increases with the voltage slightly at first, and then a decrement tendency can be found. The erosion weight loss shows the similar trends with the porosity under the influence of voltage. The fracture toughness is the lowest when the voltage is 10 kV, and it is the highest for coatings deposited under no electrostatic field. The measurement of hardness yields the similar results though the voltage is different. The deflection behaviour of whiskers under the electrostatic field affects the deposition of molten powder and then the microstructure and properties of plasma sprayed coatings.

Abstract: Zircon whiskers were synthesized via non-hydrolytic sol-gel process combined with molten salt method by using anhydrous zirconium tetrachloride as zirconium source, TEOS as silicon source, anhydrous ethanol as solvent, and sodium molybdate as molten salt. The effects of heat treatment mode and cooling rate on the synthesis of zircon whiskers have been studied by means of XRD, FE-SEM, TG and TEM. The results indicate that well-developed whiskers can be prepared through heat treating the sample at 850°C for 3 h followed by a furnace cooling process. The zircon whiskers which were fabricated by this heat treatment mode grew along the [001] direction and showed diameter of 50~100 nm and aspect ratio of 20~30.

Abstract: Silicon nitride whiskers or rod-like crystals have a wide range application due to its excellent mechanical properties and high temperature performance. Two different silicon powders with different size (mesh 200 and mesh 300, respectively) were chosen to prepare rod-like Si₃N₄ crystals by SHS method and the effects of silicon particle size on the morphology of rod-like Si₃N₄ crystals were investigated. The results indicate that rod-like Si₃N₄ crystals could be formed with either kind of silicon powders when no more than 9wt% extra Y₂O₃ was introduced, which could effectively promote the growth of rod-like Si₃N₄ crystals. The residual free silicon was detected when using coarse silicon powders, while the silicon could be reacted completely with nitrogen gas when using fine silicon powders. The morphology of samples with coarse Si powders as starting materials is more uniform and regular than that of fine Si powders samples. Fine silicon powders are not ideal candidates for forming uniform and regular rod-like Si₃N₄ crystals.

Abstract: Basic magnesium chloride whisker is described as a cheap and available whisker material. The preparation and application prospect of basic magnesium chloride whisker were introduced in this paper, and the use of abundant concentrated seawater or brine resources in the preparation of basic magnesium chloride whisker was prospected.

Abstract: Using melamine and aluminum nitrate as raw material, we prepared aluminum nitride whiskers by precursor method and studied the effect of reactants and concentration to AlN precursor. The results showed that when the Molar ratio is 1:3, and the concentration is 0.2mol/l, whisker precursor produced is relatively uniform and have large length diameter ratio.

Abstract: The study investigates the influence of different fraction of Mg₂B₂O5 whiskers (5, 10, 15 and 20vol.% ) on the microstructure of the hot extruded composite as well as on the mechanical properties in the same condition. The results indicate that the process is available for producing the composite, image analysis shows the whisker tends to cluster together with increasing content of reinforcement. When the content of the reinforcement is 10%, the composites exhibit the best mechanical properties, meanwhile, it demonstrate cluster is unfavorable to the improvement of properties of materials. The ductile failure of 6061Al matrix, the reinforcement fracture and the whisker-matrix interface debonding acted as the main mechanism of fracture nucleation.

Abstract: Metal-organic chemical vapor deposition (MOCVD) method has been applied to grow nanostructured ZnO films on Si (100) substrate at temperatures ranging from 200 to 550 °C. The as-prepared films were characterized by XRD, SEM, XPS analysis. The growth rate of ZnO films increases with increasing the deposition temperatures. The deposition temperatures have a drastic effect on the crystallinity and morphology of the nanostructured ZnO. Whisker shaped ZnO is formed at a temperature of 350 °C. The deposition time also affects the morphology of the particles. At 400 °C, sample with one hour deposition forms whisker shaped ZnO nanostructures whereas that of with two hours deposition forms flower-like nanostructures.

Abstract: Hydroxyapatite is well used as bone repair materials. Degradation property and biological activity can be further improved by addition Zn into the HAP crystals. Zinc-doped hydroxyapatite whiskers with different content of Zn were prepared with calcium nitrate, Zinc nitrate and diammonium phosphate at the degree of 95°C. Zinc-doped hydroxyapatite whiskers were characterized by XRD, FT-IR, SEM and EDS. It was indicated that zinc can be doped in hydroxyapatite with proper process and zinc-doped hydroxyapatite whiskers were produced successfully.