Method for preparing mullite crystal whisker by non-hydrolytic sol-gel process

Abstract

The invention discloses a method of preparing porzite whiskers by a non-hydrolyzed sol-gel technology. The method comprises the following steps: using an anhydrous aluminum source and an anhydrous silicon source as precursors and using low-carbon alcohol or ether as an oxygen donor to prepare porzite xerogel powder; then adding a certain amount of fluoride as a whisker catalyst and calcining a closed crucible to prepare the high-purity and white porzite whiskers which have the diameter of 0.2 micron to 2 micron, a slenderness ratio up to 60 to 70 and do not comprise mingled particles. Compared with the prior art, the invention has the advantages of simple technology, convenient operation, low whisker preparation temperature and high whisker yield.

Description

technical field [0001] The invention relates to a method for preparing mullite whiskers by using a non-hydrolytic sol-gel process, and belongs to the technical field of new materials. Background technique [0002] Mullite whiskers not only have the properties of high temperature resistance, wear resistance and oxidation resistance, but also have the characteristics of high temperature strength, small high temperature creep, small thermal expansion and good thermal shock resistance. Therefore, it is an excellent It can be used as a reinforcement for metals, polymers, ceramic-based materials, etc. Not only that, but it can also be used at higher temperatures and harsher oxidation conditions than non-oxide whiskers. [0003] At present, many literatures at home and abroad have reported the preparation methods of mullite whiskers, mainly including mineral decomposition method, molten salt method, ion doping method, Al 2 o 3 -SiO 2 Powder calcination method and traditional hy...

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Problems solved by technology

[0006] Comparing the above five methods, it is not difficult to see that: the mineral method is used to prepare whiskers. Since the minerals contain flux impurities, after calcination, in order to obtain high-purity mullite whiskers, the product must be pickled. However, in the pickling process The mullite whiskers with small size will be dissolved to a certain extent in the medium, so the glass phase must be quickly removed by microwave corrosion technology, the process is complicated, and the aspect ratio of the prepared whiskers is not high, and the ion doping method is also Also there is above-mentioned problem; Although the raw material that Chinese patent report adopts is cheap, needs to adopt high-energy ball milling process, and cost is higher

The preparation of mullite whiskers by the molten salt method requires washing of the sintered samples. The process is quite complicated, and there will be waste liquid treatment problems during the washing process.

[0007] Al 2 o 3 -SiO 2 Because the raw materials used in the powder calcination method are alumina and silicon oxide, although the cost of the raw materials is low, it is difficult to achieve uniform mixing of the two during the mixing process, so the shape and composition of the prepared whiskers are not uniform enough, and segregation is prone to occur

Although high-purity mullite whiskers can be prepared by the traditional hydrolysis sol-gel method, this method generally uses silicon alkoxides, aluminum alkoxides or aluminum inorganic salts as precursors. Due to the different hydrolysis rates of different metal alkoxides, it is difficult for the polycondensation products to achieve random and uniform distribution of M-O-M and M'-O-M' homogeneous bonds, and it is also difficult to form M-O-M' heterogeneous bonds, resulting in condensation The components in the glue cannot be uniformly mixed at the atomic level, resulting in a higher oxide synthesis temperature

For example, the temperature for synthesizing mullite by hydrolytic sol-gel method is usually above 1200°C. At this time, the mullite sample begins to sinter, the growth of mullite grains is hindered, and the size of the prepared mullite whiskers is small. Difficult to synthesize high quality mullite whiskers

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