Research And Preparation Of Low-temperature And Low-expansion Ceramics Coating

Missile radome is utilized to make radar aerial system work safely, whose properties have great effect on missiles control and guide precision. Quartz ceramic radome and quartz with quartz fibers radom are researched in many ways, which have easy to absorb moisture and low thermal expansion. Quartz fibers are easy to embrittlement in the high temperature that reduce the mechanical properties of materials. In order to obtain a kind of ceramic radome coating material that can dramproof well and have a transmission rate of electromagnetic wave and have low-temperature and low thermal expansion coefficient, we used Li₂O-Al₂O₃-SiO₂(LAS) ceramic material as the origination in this study. As to produce the coating material, we used the technique which is combined low-temperature sintering and ceramic glaze spray painting, the coating can matching well with SiO2 sandwich layer. Main research contents are as follows.1. The fonnula composes of low-temperature and low thermal expansion coefficient ceramic coatings were determined. Spodumene and eucryptite provide the low thermal expansion of ceramic coating.Low temperature frit reduced the sintering temperature of ceramic coating. Heat treatment temperature impacts on the thermal expansion coefficient of spodumene and eucryptite ceramics that the thermal expansion coefficient is declined by the increase of the heat treatment temperature.2. The preparation process of low-temperature ceramic coating was studied. Sintering system was developed with the DTA curve of coating and the maximum sintering temperature was 650℃with holding 1h by experimental.3. Department of the spodumene coating with 5% of the negative thermal expansion material ZrW₂O₈ can reduce the thennal expansion coefficient. The sintreing temperature of ceramic coating has no effect with ZrW₂O₈.4. Department of the eucryptite coating with nucleation agent TiO2 can refine the crystalloid of coating. The best heat treatment is crystallization at 810℃with holding 1h. The crystal particles become bigger and the thennal expansion coefficient decrease with TiO2 increasing.Combination of XRD, SEM, mechanical properties testing act, we studied that the phase composition and microstructure of the LAS ceramic coating with sintering. The results show that:the main phase of LAS ceramic coating are spodumene crystal phase and eucryptite crystal phase. The crystal of coating is clear by sintered at low temperature. The coating has good mechanical properties and able to meet the quartz ceramic radome waterproof requirements.