TY - JOUR A1 - Yao, Dongxu A1 - Xia, Y. A1 - Zuo, K.-h. A1 - Zeng, Y.-P. A1 - Jiang, D. A1 - Günster, Jens A1 - Heinrich, J.G. T1 - Gradient porous silicon nitride prepared via vacuum foaming and freeze drying T2 - Materials letters N2 - Gradient porous silicon nitride (Si3N4) was fabricated by a novel vacuum foaming and freeze drying process. Aqueous Si3N4 slurries were foamed at vacuum pressure of 50–90 kPa, the green body was obtained by the freeze drying process, a gradient pore structure with porosities of 72–90% was achieved after pressureless sintering at 1680 °C. The porosity was increased with decreasing vacuum pressure. The pore structure consists of large pores (~100 μm) on top, medium pores (~45 μm) on the wall of the large pores, and small pores (~0.7 μm) in the matrix. Such gradient porous Si3N4 with macro- and micro-pores has potential application as high temperature filters. PB - Elsevier B.V. CY - Amsterdam KW - Silicon nitride KW - Graded PY - 2015 UR - https://opus4.kobv.de/opus4-bam/frontdoor/index/index/docId/35177 AN - OPUS4-35177 SN - 0167-577x SN - 1873-4979 VL - 141 SP - 138 EP - 140 AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany