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  • Comparison of Six Methods for Making Silicon Nitride Powder

    The basic principle of the preparation of silicon nitride powder is to produce silicon nitride powder with high purity and specific crystal phase (α phase or β phase) by chemical reaction between nitrogen compounds and silicon compounds under suitable temperature and atmosphere.
     
    In the actual preparation process, there are the following difficulties:
     
    ① The temperature window of powder preparation is narrow. If the temperature is too low, the reaction is incomplete; if the temperature is too high, silicon nitride is easy to decompose.
     
    ② The preparation of powder requires high purity of atmosphere. In fact, compared with N element, Si element prefers to combine with O element; if oxygen is mixed in the atmosphere, Si powder is easy to "derail" to form silica.
     
    ③ It is very difficult to obtain the specific crystal phase with high purity. The preparation method and process conditions, the type and amount of raw materials and additives have a direct impact on the crystal phase composition of silicon nitride products, which requires strict screening and control.
     
    There are six methods to prepare silicon nitride powder. Their advantages and disadvantages are analyzed as follows:
     
    Direct nitriding
    Under the condition of 1300 ℃, the silicon powder with 0.125%Ca was added to react with nitrogen to form silicon nitride powder with α phase content up to 99%.
    Advantages: low cost, simple process, convenient for large-scale production;
    Disadvantages: high temperature and long time; powder is easy to agglomerate, and impurities are easy to be introduced into the crushing process.
     
    Carbothermal reduction
    Silicon nitride powder was prepared from carbon powder and quartz powder at 1500 ℃ in sufficient nitrogen atmosphere.
    Advantages: low raw materials, simple process, continuous production;
    Disadvantages: product purity is not high, easy to introduce impurities.
     
    Gas phase method
    Silicon nitride powder was prepared by the reaction of silicon tetrachloride and ammonia at 1100-1500 ℃.
    Advantages: high purity and ultra-fine powder can be prepared;
    Disadvantages: high cost, low yield, not easy to produce.
     
    Self propagating method
    Silicon nitride powder was prepared by self propagating process with silicon powder and nitrogen as raw materials and ammonium chloride as additive.
    Advantages: short time, high purity and activity;
    Disadvantages: high equipment requirements, uncontrollable process.
     
    Thermal decomposition method
    Silicon nitride powder can be prepared by heating the reaction product of silicon tetrachloride and excess anhydrous ammonia at high temperature.
    Advantages: high purity and ultra-fine powder can be prepared;
    Disadvantages: complex equipment and process, difficult to mass production.
     
    Sol gel method
    Using silica sol, urea and carbon black as raw materials, 50-80nm silicon nitride powder was prepared at 1500 ℃.
    Advantages: it is easy to produce high-purity and ultra-fine powder;
    Disadvantages: high cost and long cycle.
    If you have any questions, please email us. If you need to buy powder, you can also go to the powder page to buy. We (AEM) provide tantalum powder, niobium powder, hafnium powder, molybdenum powder, chromium powder, etc. The specific powder products are shown in the table below.
    Tantalum Powder
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