检索结果-南通市图书馆

Preparation and Properties of sintering additives Coated Si_3N_4 from Heterogeneous Nucleation Processing

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2002年第1期18卷 34-36页

作者： Juxian ZHANG, Jinjun FENG and Longqiao GAOBeijing Vacuum Electronics Research Institute, 100016 Beijing, China[ Manuscript received January 18, 2001, in revised form April 24, 2001] Beijing Vacuum Electron. Res. Inst. Beijing 100016 China

The sintering additives such as Al2O3 and/or Y2O3 were coated on the surfaces of Si3N4 particles via heterogeneous nucleation processing using a buffered pH solution as the precipitation reagent. They nucleated and grew only on the surfaces of Si3N4 and did not form sol particles in solution by TEM observation. The isoelectric point (IEP) of coated Si3N4 was different from that of as-received Si3N4. The IEP of AI(OH)3-coated Si3N4 occurred at pH8.4, which is close to that of alumina. When AI(OH)3-coated Si3N4 particles were coated with Y(OH)3, the IEP of coated Si3N4 powder shifted from pH8.4 to pH9.2, similar to that of yttria. In addition, the rheological data showed that Al2O3 and/or Y2O3 coated Si3N4 suspension is nearly Newtonian and that added Si3N4 suspension shows a shear rate thinning behavior.

关键词： Si3N4 powder sintering additives Zeta potential Rheological property

Effect of sintering additives on Properties of Si_3N_4BN Composites Fabricated via Die Pressing and Precursor Infiltration and Pyrolysis Route

在线全文

学校读者我要写书评

暂无评论

Journal of Wuhan University of Technology(Materials Science) 2014年第5期29卷 891-894页

作者：刘坤张长瑞 LI Bin WANG Siqing CAO Feng Science and Technology on Advanced Ceramic Fibers and Composites Laboratory College of Aerospace Science and Engineering National University of Defense Technology

The Si3N4-BN composites have been prepared via die pressing and precursor infiltration and pyrolysis route using borazine as precursor, and the effect of sintering additives on properties of the composites has been investigated. After sintering additives are adopted, the a to β phase transition of Si3N4 and the mechanical properties of the composites at both room temperature and high temperature are all increased with small extent. When using Y2O3＋Al2O3 as additives, the phase transition of Si3N4 and the mechanical properties of the composites have better results. The β-Si3N4 content is 17.47%. The flexural strength, elastic modulus and fracture toughness of the composites are 188.74 MPa, 84.34 GPa and 2.96 MPa.m1/2, respectively. After exposed at 1 000 ℃ in the air for 15 min, the flexural strength of the composites is 154.62 MPa with a residual ratio of 81.92%. The elongated β-Si3N4 grains appear in all composites with different sintering additives. Relatively more rod like β-Si3N4 grains can be observed in composites with Y2O3＋Al2O3 as additives, making it to possess better mechanical properties.

关键词： silicon nitride boron nitride borazine composites sintering additives

Effects of sintering additives on Preparation of CaF_2 Transparent Ceramics

在线全文

学校读者我要写书评

暂无评论

Journal of Wuhan University of Technology(Materials Science) 2011年第6期26卷 1179-1183页

作者：智广林 State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology

The effects of different sintering addictives on the preparation of CaF2 transparent ceramics were studied. Transparent CaF2 ceramics were fabricated by vacuum sintering and hot isostatic pressing （HIP） method, using CaF2 nanopowders synthesized by chemical precipitation method as raw materials. The nanopowders and transparent ceramics were studied using X-ray diffraction, transmission electron microscopy （TEM）, scanning electron microscopy （SEM） and spectrophotometer. The experimental results indicated that the obtained nanopowders presented normal distribution with grain size about 30 nm; transmittance of CaF2 transparent ceramics was 39% and 26% at 1100 nm for LiF and NaF as sintering addictives, respectively, with corresponding mean grain size 188 μm and 44 μm. Loss of transmission could be attributed to the residual closed porosity. sintering mechanism was liquid-phase sintering at pre-stage, then solid-phase sintering at later stage, as well as solid solution of lithium ions and sodium ions in the CaF2 lattice structure.

关键词： CaF2 sintering additives transparent ceramics transmittance solid solution

Novel Phenomenon on Valence Unvariation of Doping Ion in Yb:YAG Transparent Ceramics Using MgO additives

在线全文

学校读者我要写书评

暂无评论

Journal of Wuhan University of Technology(Materials Science) 2013年第2期28卷 320-324页

作者：卢忠文卢铁城 WEI Nian MA Benyuan ZHANG Wei LI Feng GUAN Yongbing Department of Physics Key Laboratory of Radiation Physics and Technology of Ministry of Education Sichuan University International Center for Material Physics Chinese Academy of Sciences

Yb：YAG nanopowders were synthesized by the alcohol-water co-precipitatlon method adding MgO as sintering additives. Appropriate amount of MgO adding can restrict the agglomeration and reduce the particle size of Yb：YAG powders. When the MgO content was 0.04wt%, well-dispersed Yb：YAG powders with ellipsoidal particles of less than 100 nm diameter were obtained. The experimental results showed the valence variation of doping ion Yb〉 would not appear when adding MgO as sintering additives, so ceramics showed colorless transparent instead of green due to Yb^2＋ color center using traditional SiO2 as additives. The transmission of the sintered Yb：YAG ceramics can reach 80.6% even without annealing. Ceramic morphology showed that the grains had uniform-distribution with the size of 10 iam or so, and no impurity and pore existed in the grain boundary and crystalline while using optimal sintering conditions.

关键词： Yb:YAG MgO transparent ceramics sintering additives valence unvariation

Effect of sintering Additive on the Properties of Sialon-SiC by Gelcasting

在线全文

学校读者我要写书评

暂无评论

China's Refractories 2004年第4期13卷 17-20页

作者： BUJinglong YUZhidong WANGRuisheng WANGZhifa WANGRonglin SONGHuanqiao SUNJialin SchoolofMaterialScience HebeiPolytechnicUniversityTangshanHebei063009；SchoolofMaterialScienceUniversityofScienceandTechnologyBeijingBeijing100083 TangshangUniversity TangshanHebei063000 SchoolofMaterialScience HebeiPolytechnicUniversityTangshanHebei063009 SchoolofMaterialScience UniversityofScienceandTechnologyBeijingBeijing100083

sintering additives to gelcasting Sialon-SiC were decided by the optimizing experiments. The results show that Sialon-SiC can be sintered under 1450℃ and sintering temperature decreases by 100℃, when 2%～3% TiO 2 o... 详细信息

关键词： Gelcasting SiAlON-SiC sintering additives

Porous TiN Ceramics Fabricated by Carbothermal Reduction Method

在线全文

学校读者我要写书评

暂无评论

Porous TiN Ceramics Fabricated by Carbothermal Reduction Met...