Improving the breakdown strength of rutile capacitor by gelcasting

摘要: Gelcasting, one of the colloidal in-situ forming techniques, has been highly concerned and utilized in many sorts ceramic material systems [1–3], for homogeneous microstructures bodies can be assured by this low-cost near-net-shape molding process [4–8]. Thus parts exhibit good mechanical performances high reliability [9, 10]. Because power large breakdown strength, rutile capacitors have widely used frequency appliances such as broadcast emitters, radars, welding machines smelting furnaces. There are more than hundred kinds products with various sizes complex shapes. In past decades, shape size were made extrusion then machining. First, mixture a definite composition obtained ball-milling, was filtered day, aged month, mixed vacuum. Second, after extruded, cylindric green rolled, dried two weeks. Next, means machining, possessed desired shape. Finally, through sintering some sequent process, capacitor prepared. The whole procedure needed half months, machining resulted great deal environment pollution waste starting materials. Furthermore, traditional capacitors, bottleneck, which results from size, components raw materials, greatly impairs their functional properties, so strength generally reached only 15 KV/mm. A new route preparing gelcasting, indicated Fig. 1, developed. By route, not production cycle decreased to three weeks, but also dust caused eliminated due insitu forming. cost reduced improved. And particularly, voltage is improved original KV/mm 22 shown Table I. commercial powder additives industrial purity, Shanghai, China. following our work: deionized water conductivity 1.02 μS·cm−1, acrylamide (AM) monomer, methylenebisacrylamide (MBAM) crosslinker, (NH4)2S2O8 initiator, N,N,N′,N′tetraethylmethylenediamine (TEMED) catalyst PMAA-NH4 dispersant. pre-calcined at 900 ◦C ball-milled 50 h. particle distribution measured an X-ray centrifugal sedimentation technique (Instrument type: BI-XDC, Brookhaven Instrument Co., USA) 2. volume moment mean diameter 1.8 μm. concentrated 53 vol% suspension low viscosity successfully apparent rotating viscometer (model NSX-11, Chengdu Plant, People’s Republic China). Microstructures sintered observed S450 SEM Hitachi Japan. well dispersed premixed solution up acrylamide, water, N,N′-methylenbisacrylamide aid PMAA-NH4, ball-milling It seen 3 that strikingly