注浆成型结合真空发泡法制备梯度多孔氮化硅陶瓷

通过注浆成型结合真空发泡制备出具有明显梯度结构的多孔氮化硅陶瓷。该工艺在浆料中加入发泡剂, 然后注入底部为石膏的模具中, 抽真空保压并恒温保存, 浆料在低压下会形成孔径梯度结构。研究发现, 气压对样品的梯度结构有较明显影响, 随着气压由80 kPa降低到9 kPa, 样品气孔率由59.01%提高到80.85%, 当气压为80 kPa时, 样品无宏观梯度结构, 随着气压的降低, 梯度结构趋于明显。压汞法测试表明, 9 kPa气压制备的样品孔径分布比较分散, 具有0.5、20、30、40、60、100和200 μm等多种气孔孔径值。该工艺具有简易、廉价, 孔径分布和气孔率可调的优点, 可实现大尺寸、复杂形貌材料的制备, 为梯度多孔材料的制备方法提供了新思路。

Gradient Porous Silicon Nitride by Slip Casting and Vacuum Foaming

Gradient porous silicon nitride was fabricated by a combination method of slip casting and vacuum foaming. Firstly, foaming agent was added into Si₃N₄ aqueous slurry, then the uniformly stirred slurry was poured into the mold with plaster as base. Under low pressure and steady temperature, a green body with gradient pores was formed. Based on our research, the gradient structure and porosity were greatly influenced by the vacuum pressure. With the pressure decrease from 80 kPa to 9 kPa, the porosity increased from 59.01% to 80.85% and the gradient structure became more noticeable. When the pressure was 80 kPa, the sample obtained a uniform pore structure. After the pressure being decreased to 9 kPa, the sample obtained dispersed pore size distribution including values of 0.5, 20, 30, 40, 60, 100 and 200 μm measured through mercury intrusion method. Gradient porous ceramics with adjustable porosity and pore size distribution, as well as achievable complex shape and large scale, may fabricate through this simply and low cost method.