Study On Preparation Processing Of Aluminum Nitride Whisker

With modern high technology development, the excellent performance of new ceramic composite, metal composite and resin composite more and more attracted scientists'great concern in the world. Whiskers are one of materials for enhancing the strong in the preparation of various composite. The rapid development of new composite in recent years greatly contributed to various whiskers to developing.Whiskers are single crystals of crystal perfection, and the atoms are arranged in high degree of order. Whiskers have fine characteristics, such as a high breaking strength and large elastic modulus, resistant to temperature and corrosion and so on. Therefore, using of the excellent mechanical, physical and chemistry properties of whiskers, these materials which are composited with the glass, ceramic, metals, polymers, not only improve the strength and toughness of body materials, but also can change their physical and chemistry performance, increase their function.Aluminum nitride material is one of new greatly developing materials in recent years because of good physical and chemistry properties such as high thermal conductivity, fine electric insulativity, small thermal expansion coefficient and so on. Aluminum nitride whiskers not only have inherent characteristics of aluminum nitride materials, but also have larger length-diameter ratio, complete crystal structure, fewer internal defects, and their strengths and modulus are high quality. Hence, aluminum nitride whisker is one ideal improving toughness material of high-powered nitrogen compounds and ceramic composite's materials. The text prepared aluminum nitride whiskers with precursor method and carbothermic method respectively, and analyzed the effects of technological conditions on the phase constitution and surface topography of whiskers.With C3H6N6 and A1(NO3)3·9H2O as the main raw materials, we prepared aluminum nitride whiskers using precursor method. And studied of influences which different materials proportion, concentration and response duration made to presoma. We studied of influences which not doping carbon, doping carbon in solid phase. doping carbon in liquid phase, nitriding temperature and the soaking time in decarburization made to aluminum nitride whiskers. We also analyzed the phase constitution and surface topography of aluminum nitride whiskers and presoma, using x-ray diffraction, scanning the electron microscope and optical microscopes.Results show that when materials proportion of C3H6N6/Al(NO3)3·9H2O=1:3 and the concentration of 0.2mol/L, the synthesis of aluminum nitride whisker presoma is the highest rate, and we can get slender and well-distributed size presoma with diameter of 1-2μm and length of about 80μm. The basic ingredients of samples prepared with carbon in solid phase and in liquid phase are AIN, and the latter have high purity and fine crystallinity. Raising the nitriding temperature is good for the whiskers to form. By 1800℃nitriding, produce a large number of AIN whiskers. Whiskers are long cylindrical and have smooth surface, with diameter of about 1μm and length of 10 to 20μm. By 700℃decarburizing for 240min, we can get high purity of aluminum nitride whiskers.Withγ-Al2O3,α-Al2O3, Al(OH)3 and activated charcoal as the main raw materials, prepared aluminum nitride whiskers using carbothermic method. We analyzed the effects of different aluminum sources, ball milling time and nitriding temperature on preparation of aluminum nitride whiskers. We also analyzed the phase constitution and surface topography of aluminum nitride whiskers, using x-ray diffraction and scanning the electron microscope.Results show that the samples prepared withγ-Al2O3 andα-Al2O3 as aluminum sources can compose AIN, but have many Al2O3. The basic ingredients of samples prepared with Al(OH)3 as aluminum sources are AIN. Extending ball milling time can promote to prepare aluminum nitride whiskers by carbothermic method. The samples prepared after ball milling for 24h are chiefly AIN and the formation rate is close to 100%. Raising the nitriding temperature is good for carrying on of carbothermic reaction and the whiskers to form. AIN whiskers prepared by 1800℃nitriding are stocky rhoptry with diameter of 1-2μm and length of 20 to 30μm.