METHOD OF PRODUCING COVER OF ANTENNA DOME OUT OF REACTION BONDED SILICON NITRIDE Russian patent published in 2012 - IPC C04B35/591 C04B41/84 

FIELD: metallurgy.

SUBSTANCE: method involves preparation of thermoplastic slurry of silicon particles with accelerator nitridation accelerator (Fe₂O₃, Ni or NiO) in amount of 0.1-3 wt % with an average powder mixture particle size of 1.5-3 micron, moulding of a workpiece by hot casting under pressure into a thermostated casting mould with two independent circuits of heating and cooling of the punch and matrix. In the process of casting the matrix temperature reaches 30-35 °C, and the punch - 50-55 °C, when a workpiece is taken out the temperature of the punch decreases to 30-35 °C due to cooling. Nitridation is conducted in the temperature range of 1000-1500 °C in a granular filling made of silicon nitride, located on the outer surface of the workpiece. After nitriding the products are impregnated with organosilicon compounds in two stages. After the first stage the product is heat treated in two stages at temperatures of 700 and 1300 °C, respectively.

EFFECT: production of high-quality large-sized covers of antenna domes from silicon nitride with a set of properties required for radiotransparent materials and products: high strength, next to zero porosity, dielectric characteristics stable over a wide temperature range including low dielectric losses.

2 cl, 3 ex