TY - JOUR A1 - Yao, Dongxu A1 - Xia, Y. A1 - Zuo, K.-h. A1 - Jiang, D. A1 - Günster, Jens A1 - Zeng, Y.-P. A1 - Heinrich, J.G. T1 - Porous Si3N4 ceramics prepared via partial nitridation and SHS N2 - Porous Si3N4 ceramics were prepared via partial nitridation and self-propagating high temperature synthesis (SHS) process. Raw Si and additive Y2O3 were mixed and molded under 10 MPa into a compact, the compact was partial nitridation at 1300 °C to form a porous Si/Si3N4, and then it was buried in a Si/Si3N4 bed for SHS to obtain porous Si3N4 with rod-like β-Si3N4 morphology. The processing combined the advantages of the nitridation of Si and SHS with low cost, low shrinkage and time saving. Porous Si3N4 with a porosity of 47%, a strength of 143 MPa were obtained by this method. KW - Si3N4 KW - Strength KW - Porosity PY - 2013 U6 - https://doi.org/10.1016/j.jeurceramsoc.2012.08.033 SN - 0955-2219 SN - 1873-619X VL - 33 IS - 2 SP - 371 EP - 374 PB - Elsevier CY - Oxford AN - OPUS4-31282 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yao, Dongxu A1 - Xia, Y. A1 - Zuo, K.-h. A1 - Jiang, D. A1 - Günster, Jens A1 - Zeng, Y.-P. A1 - Heinrich, J.G. T1 - The effect of fabrication parameters on the mechanical properties of sintered reaction bonded porous Si3N4 ceramics N2 - Porous silicon nitride ceramics were prepared via sintered reaction bonded silicon nitride at 1680 °C. The grain size of nitrided Si3N4 and diameter of post-sintered ß-Si3N4 are controlled by size of raw Si. Porosity of 42.14–46.54% and flexural strength from 141 MPa to 165 MPa were obtained. During post-sintering with nano Y2O3 as sintering additive, nano Y2O3 can promote the formation of small ß-Si3N4 nuclei, but the large amount of ß-Si3N4 (>20%) after nitridation also works as nuclei site for precipitation, in consequence the growth of fine ß-Si3N4 grains is restrained, the length is shortened, and the improvement on flexural strength is minimized. The effect of nano SiC on the refinement of the ß-Si3N4 grains is notable because of the pinning effect, while the effect of nano C on the refinement of the ß-Si3N4 grains is not remarkable due to the carbothermal reaction and increase in viscosity of the liquid phase. KW - Porous ceramics KW - Silicon nitride KW - Reaction bonding KW - Anisotropic grain growth KW - Ceramic PY - 2014 U6 - https://doi.org/10.1016/j.jeurceramsoc.2014.06.018 SN - 0955-2219 SN - 1873-619X VL - 34 IS - 15 SP - 3461 EP - 3467 PB - Elsevier CY - Oxford AN - OPUS4-32542 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - 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 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. KW - Silicon nitride KW - Graded PY - 2015 U6 - https://doi.org/10.1016/j.matlet.2014.11.067 SN - 0167-577x SN - 1873-4979 VL - 141 SP - 138 EP - 140 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-35177 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yao, Dongxu A1 - Wirth, Cynthia A1 - Zeng, Y.-P. A1 - Jiang, D. A1 - Günster, Jens A1 - Heinrich, J. T1 - Near zero shrinkage porous Al2O3 prepared via 3D-printing and reaction bonding N2 - Porous Al2O3 with high porosity (~45%), remarkable flexural strength (~70 MPa), and low dimensional change (~1–2%), was produced by indirect 3D printing and reaction bonding. Coarse Al with good flowability was carried out printing green body. The green body was heat treated to get fully oxidized, volume expansion during oxidation simultaneously formed strong neck bonding, not only brought good strength, but also restricted shrinkage. Porous Al2O3 with architecture of macro pores designed by 3D printing and micro pores in the strut formed by packing of particles was obtained. The near zero shrinkage can facilitate precise design of product with complex shape. KW - Al2O3 reaction bonding PY - 2015 U6 - https://doi.org/10.1016/j.matlet.2015.02.037 SN - 0167-577x SN - 1873-4979 VL - 147 SP - 116 EP - 118 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-34960 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -