热氧化处理对氮化硅粉料表面可溶性离子的影响

选用一种商业氮化硅粉料,研究了可溶性高价反离子对其水中分散性能的影响,并研究了粉料表面的几种可溶性金属离子在热氧化处理过程中的变化规律.研究发现,初始氮化硅粉料分散性能的限制性因素是可溶性（Ca^2＋＋Mg^2＋）的浓度过高所致.一价可溶性离子Na^＋和K＋非常稳定,热氧化处理基本上不改变其在氮化硅颗粒表面的存在状态.对于Ca^2＋,Mg^2＋和Fe^3＋而言,热氧化处理显著改变了其在氮化硅颗粒表面的存在状态,由可溶性的高价反离子变成了难溶性的氧化物.对Fe元素而言,除了变成难溶性的氧化物外,在热氧化过程中还发生了由氮化硅粉料表面向颗粒内部的扩散.

Influence of Thermal Oxidation on the Soluble Ions of Silicon Nitride Powder

For a kind of commercial silicon nitride powder,the effect of thermal oxidation on soluble metal ions at the particles surface,as well as the contributing factor for poor aqueous dispersibility of the as-received powder,is studied in this paper.It is shown that it is the high concentration of soluble(Ca~(2+)+Mg~(2+)) that deteriorates the aqueous dispersibility of the as-received powder.The state of soluble univalent ions of Na+ and K+ is very stable and almost unaffected by thermal oxidation treatment.For Ca~(2+),Mg~(2+) and Fe~(3+),however,transitions from the soluble high valence counter-ions to insoluble oxide species are completed through thermal oxidation.In addition to formation of insoluble species,diffusion of Fe3+ from particle surface into the bulk of silicon nitride powder is also found after thermal oxidation treatment.