Xiaolei Su
材料科学技术（英文）
The SiC powders by Al or N doping have been synthesized by combustion synthesis, using Al powder and NH4Cl powder as the dopants and polytetrafluoroethylene as the chemical activator. Characterization by X-ray diffraction, Raman spectrometer, scanning electron microscopy and energy dispersive spectrometer demonstrates the formation of Al doped SiC, N doped SiC and the Al and N co-doped SiC solid solution powders, respectively. The electric permittivities of prepared powders have been determined in the frequency range of 8.2−12.4 GHz. It indicates that the electric permittivities of the prepared SiC powders have been improved by the pure Al or N doping and decrease by the Al and N co-doping. The paper presents a method to adjust dielectric property of SiC powders in the GHz range.
关键词:
Silicon carbide
Xiaolei Su
材料科学技术（英文）
The SiC powders by Al or N doping have been synthesized by combustion synthesis, using Al powder and NH4Cl powder as the dopants and polytetrafluoroethylene as the chemical activator. Characterization by X-ray diffraction, Raman spectrometer, scanning electron microscopy and energy dispersive spectrometer demonstrates the formation of Al doped SiC, N doped SiC and the Al and N co-doped SiC solid solution powders, respectively. The electric permittivities of prepared powders have been determined in the frequency range of 8.2−12.4 GHz. It indicates that the electric permittivities of the prepared SiC powders have been improved by the pure Al or N doping and decrease by the Al and N co-doping. The paper presents a method to adjust dielectric property of SiC powders in the GHz range.
关键词:
Silicon carbide
Xiaolei Su
材料科学技术（英文）
The nonstoichiometric β-SiC powders were synthesized via combustion reaction of Si and C system in a 0.1 MPa nitrogen atmosphere, using Teflon as the chemical activator. The prepared powders were invistigated by XRD and Raman spectra. The results indicates that the cell parameters of all the prepared β-SiC powder
are smaller than the standard value of β-SiC because of generation of CSi defects. The complex permittivity of prepared products was carried out in the frequency range of 8.2−12.4 GHz. It shows that the dielectric property of prepared β-SiC powder decrease with increasing PTFE content. The effect of CSi defects on dielectric property of -SiC powder has been discussed.
关键词:
Silicon carbide
Wen ZHANG
材料科学技术（英文）
Macroporous silicon nitride (Si3N4) ceramics with high strength, uniform structure and relatively high porosity were obtained by gelcasting and carbonthermal reaction in a two-step sintering technique. Microstructure and composition were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD). Open porosity, pore size distribution and basic mechanical performance were measured by Archimedes method, mercury intrusion porosimetry and three-point bending methods, respectively. SEM and TEM results revealed that pores were formed by elongated β-Si3N4. SADP measurement proved the formation of SiC particles. The SiC granules were beneficial for the formation of high ratio elongatedβ-Si3N4, and at proper amount, they also acted as reinforcement phase. Thermodynamic analysis indicated that the mechanisms of the reactions were mainly associated with liquid-solid reaction and gas-liquid reaction.
关键词:
Ceramics
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null
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null
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null
Xinwen ZHU
,
Dongliang JIANG
,
Shouhong TAN
材料科学技术（英文）
An innovative approach has been developed to fabricate reticulated porous ceramics (RPCs) with uniform macrostructure by using the polymeric sponge as the templates. In this approach, the coating process comprises of two stages. In the first stage, the thicker slurry was used to coat uniformly the sponge substrate. The green body was preheated to produce a reticulated perform with enough handling strength after the sponge was burned out. In the second stage, the thinner slurry was used to coat uniformly the preform. The population of the microscopic and macroscopic flaws in the structure is reduced significantly by recoating process. A few filled cells and cell faces occur in the fabrication and the struts were thickened. A statistical evaluation by means of Weibull statistics was carried out on the bend strength data of RPCs, which were prepared by the traditional approach and innovative approach, respectively. The result shows that the mechanical reliability of RPCs is improved by the innovative approach. This innovative approach is very simple and controlled easily, and will open up new technological applications for RPCs.
关键词:
Reticulated porous ceramics
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null
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null
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null
,
null
姚旺
,
张宇民
,
韩杰才
,
查炎峰
,
周玉锋
,
韩媛媛
,
曲伟
无机材料学报
doi:10.3724/SP.J.1077.2009.00301
借助X射线衍射方法测量了反应烧结碳化硅(RBSiC)材料的磨削表面的残余应力状态，并根据断裂力学评价了磨削引入的裂纹尺寸，分析了RBSiC的弯曲强度受磨削引入裂纹和残余应力的影响.研究表明，由于磨削过程中与磨削方向有关的机械载荷占主导作用，使磨削后的表面残余应力具有方向依赖性.砂轮轴向进给从0.90μm/s增加到1.35μm/s，磨削表面的残余压应力数值降低，计算得到的磨削引入的裂纹尺寸增大，导致强度下降.
关键词:
碳化硅
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grinding
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residual stress
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crack
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strength
唐春玖
,
符连社
,
新型炭材料
研究了衬底温度、核化密度、衬底表而预处理等工艺参数对微波等离子体化学气相沉积法在硅片上同时生长碳化硅和金刚石的影响.采用扫描电镜、X-射线衍射、喇曼光谱和红外光谱对样品进行了表征.结果表明:从高核化密度生长的金刚石膜中探测不到碳化硅;不论对硅衬底进行抛光预处理还是未抛光预处理,从低核化密度牛长的金刚石厚膜中总能探测到碳化硅.碳化硅生长在硅衬底上未被金刚石覆盖的地方,或者是在金刚石晶核之间的空洞处.碳化硅形成和金刚石生长是同时发生的两个竞争过程.此研究结果为制备金刚石和碳化砟复合材料提供了一种新的方法.
关键词:
碳化硅
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金刚石厚膜
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红外光谱
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微波等离子体气相化学沉积
张国权
,
彭家喜
,
孙天军
,
王树东
催化学报
doi:10.1016/S1872-2067(12)60639-1
采用等体积浸渍法制备了Ni/SiC甲烷化催化剂,研究了SiC载体表面氧化程度对催化剂低温活性和高温稳定性的影响,并采用热重-差示扫描量热、N2物理吸附、傅立叶变换红外光谱、氨程序升温脱附、X射线衍射、氢程序升温还原和氢化学吸附技术对样品进行了表征.结果表明,随着载体氧化温度的提高,催化剂的比表面积和镍分散度降低,但还原性和反应稳定性提高.未氧化载体所负载催化剂的高温稳定性最差,其原因在于载体对镍粒子的固定作用最弱.负载于500和700℃处理的SiC载体上的催化剂具有较好的低温活性和高温稳定性,这是因为适度氧化后的载体能较好地分散并固定镍粒子.900℃处理的载体因过度氧化形成了低活性的氧化层,使负载的镍粒子变大,因而催化剂的低温活性最差.
关键词:
甲烷化
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碳化硅
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表面氧化
,
镍
,
高温稳定性
