纳米氮化硅制备天线罩材料介电性能的研究

RESEARCH ON THE DIELECTRIC PROPERTIES OF RADOME MATERIAL MADE WITH NANOMETER SILICON NITRIDE

以国产纳米氮化硅粉为原料 ,经凝胶注模成型后在流动的高纯N2 作为控制气氛的条件下 ,于 15 10℃常压烧结出相对密度为 0 .72 ,结构均一 ,抗弯强度达 89MPa且具有良好介电性能的Si3N4天线罩材料。研究了原料的纯度、烧结温度、埋烧气氛对瓷体介电性能的影响。结果表明 :纳米粉原料中含有大量的SiO2 ,可以促进坯体的烧结 ,同时对瓷体的介电性能有较大的影响。因坯体收缩 ,在致密化以前 ,其介电常数随烧结温度的升高而增大。当温度高于 15 10℃时 ,随着烧结温度的升高 ,原料中氮化的Si—O数增加 ,瓷体的宏观缺陷增加 ,相对密度降低 ,因此瓷体的介电常数趋于减小。在 15 10℃烧结温度下 ,若不加埋料时 ,坯体中有的Si—O不能被氮化 ;用石墨粉作埋料 ,则发生渗碳现象 。

Radome materials with uniform structure, good relative density of 0.72, good fracture strength of 89 MPa and excellent dielectric properties were prepared, taking home-made nanometer silicon nitride powder as raw material and sintering the green bodies at 1510°C under flowing pure nitrogen after gel casting. The influence of purity of the starting material, sintering temperature and atmosphere on dielectric properties of sintered bodies were studied. It is suggested that SiO2 exists in the feed may promote the sintering, and it also seriously affect dielectric properties. The dielectric constant increases and SiO2 is nitridized further with the increase of sintering temperature before densification. Macroscopic defect increases and relative density and dielectric constant reduce gradually at above 1510°C. SiO2 can not be nitridized sufficiently when the green body was not embedded. When graphite powder is used to embed green bodies, carbon crystals come out, which damages dielectric properties of Si3N4 radome greatly.