G.C.Ji
金属学报(英文版)
Based on the energy conservation, the elastic energy linked to the compliance change, non-elastic energy dissipated by irreversible deformation and the resistance for crack propagation were quantitatively characterized by evaluation the load/qoad point displacement curves tested by three points bend experiment with single notch beam at 1300℃. The cracks length was determined by compliance calibration curves. It is shown by experimental results that the compliance of 3D-C/SiC composites changes with the cracks can be described by third order polynomial. The variation of crack advancing resistance with non-dimensional equivalent crack length presents a convex curve. The crack advancing resistance increases firstly and then decreases with the non-dimensional equivalent crack length, finally is in comparatively low level. The maximum values of crack advancing resistance are 269.73k J/m^2 for nondimensional equivalent crack length of 0.318 and original notch length of 0.35mm, and 138.65kJ/m^2 for non-dimensional equivalent crack length of 0.381 and original notch length of 2.06mm, respectively.
关键词:
fracture resistance
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null
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null
张淑佳
,
卢炎麟
,
任立义
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洪起超
金属学报
对20 g钢高温断裂韧性随加载速率的变化规律进行了实验研究.在400℃和500℃下,分别测量了几种加载速率下20 g钢的Ji值.实验结果表明:Ji值随应变速率的增大而有较大幅度的降低;在同一应变速率下,400℃时的Ji值小于500℃时的Ji值;400℃时裂纹扩展比500℃时更快.因此,当温度在400℃附近时更应注意避免超载.
关键词:
断裂韧性
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null
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null
周光明
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梁中全
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赵谦
宇航材料工艺
doi:10.3969/j.issn.1007-2330.2004.05.005
研究了C/G(碳/玻)层内混杂单向复合材料的力学性能,对其拉伸、弯曲、层间剪切、振动阻尼等性能进行了实验研究,并与同样铺层的纯C、G复合材料进行了对比分析.研究表明:C/G层内混杂复合材料可充分利用C、G纤维的各自优点,改善单一材料的模量、强度、断裂韧性、振动阻尼特性等力学性能,模量预测值与实验值较为接近,强度因影响因素较多,二者存在一定的差异,力学性能随C、G体积分数的变化符合混合律,说明了实验方法的合理性.通过C、G相对体积分数的合理设计可满足结构的实际要求.
关键词:
层内混杂
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复合材料
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力学性能
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实验
杭祖圣
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谈玲华
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黄玉安
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应三九
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徐复铭
功能材料
在半封闭系统中采用直接热解三聚氰胺的方法制备了C3N4,XRD、XPS及元素分析的结果证明了产物是类石墨相C3N4(g-C3N4).用热分析(TG/DTG)研究了g-C3N4的热分解过程.通过迭代法计算了热分解反应活化能Ea,采用积分法结合36种动力学函数来判断g-C3N4热分解的机理函数.计算结果表明,g-C3N4的平均热分解活化能Ea为178.59kJ/mol,可能的动力学函数积分形式是g(a)=[-In(1-a)]4,指前因子A为21.67s-1,对应的热分解动力学方程为:dα/dT=(21.67/β)exp(-178.59×103/RT)×1/4(1-α)[-ln(1-α]-3
关键词:
非等温热重法
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g-G3N4
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热分解动力学
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迭代法
Xifeng Lu Qilong Wang Deliang Cui
材料科学技术（英文）
g-C3N4/TiO2 composite were prepared by hydrolysis of Ti(OC4Hn 9 )4 and the precursors of g-C3N4 at room temperature and annealing in nitrogen atmosphere. X-ray diffraction results revealed that all the products were anatase structure. The chemical nature of O, N of the g-C3N4/TiO2 were identified by X-ray photoelectron spectroscopy, presenting N-Ti-O and N-Ti-N doping status of the composite. The g-C3N4/TiO2 composite showed better photocatalytic activity for the UV and visible-light degradation of Rhodamine B.
关键词:
Composite materials
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Chemical synthesis
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X-ray photoelectron spectroscopy (XPS)
楚增勇
,
原博
,
颜廷楠
无机材料学报
doi:10.15541/jim20130633
利用光催化剂将太阳能转化为人类可以直接利用的能量，并用其解决地球资源的枯竭和生存环境的恶化是可再生清洁能源研究的一个方向。g-C3N4的独特结构赋予其良好的光催化性能，使之成为光催化领域的研究热点。目前在光催化领域， g-C3N4主要用于催化污染物分解、水解制氢制氧、有机合成及氧气还原。在实际应用中，为进一步提高 g-C3N4的光催化效果，科研工作者开发了多种改进方法，例如物理复合改性、化学掺杂改性、微观结构调整等。本文主要论述了 g-C3N4在光催化领域的应用以及光催化性能的改进方法，简要阐述了光催化和各种改进方法的机理，分析了目前g-C3N4在光催化领域面临的问题和挑战，展望了g-C3N4的应用前景。
关键词:
g-C3N4
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光催化
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改进方法
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综述
郑小刚
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杜京城
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李子黎
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付孝锦
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由耀辉
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刘勇
人工晶体学报
采用浸渍法制备不同掺杂量的负载型光催化剂Ni/g-C3N4,并考察其在可见光照下对亚甲基蓝的光降解性能.利用XRD、FT-IR、SEM、TEM、XPS、N2-sorption和ICP-OES等手段表征Ni/g-C3N4样品.研究表明,Ni/g-C3N4催化剂的光催化活性随着金属镍粒子掺杂量的增加而增大,随着亚甲基蓝浓度的增大而减小,其中金属镍掺杂量4.0wt%的样品4-Ni/g-C3N4表现出优异的光催化活性和光降解稳定性.这是由于4-Ni/g-C3N4样品的光降解过程中产生了超氧自由基、羟基自由基和空穴等活性物质,其中超氧自由基起主导作用.金属Ni0离子在光生电子作用下生成Ni2+,O2分子得到电子生成O2·-自由基.这些活性物质的产生有助于光生电子-空穴对的分离和抑制其复合速率,从而实现可见光下高效催化降解亚甲基蓝.
关键词:
Ni/g-C3N4
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掺杂效应
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亚甲基蓝
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光降解性能
Thin Solid Films
The SiO(2)-Al(2)O(3)-ZrO(2)-CaO-ZnO glass-ceramic composite coatings (GC), nanocrystalline NiCoCrAlY coating, and their combinations (bi-layer GC/NiCoCrAlY) were prepared on K38G specimens. The thicknesses of the glass-ceramic coatings and the NiCoCrAlY coatings were about 10 mu m and 20 mu m, respectively. Cyclic oxidation tests were carried out at 1100 degrees C for 120 cycles. Microstructures of the specimens before and after oxidation tests were characterized by SEM, EDS and XRD. The glass-ceramic coatings with or without a NiCoCrAlY intermediate layer improved the isothermal and cyclic oxidation resistance of the Ni-base superalloy K38G at 1100 degrees C, and performed better than the NiCoCrAlY coatings. An alumina layer formed at the glass/metal interfaces of the specimens coated by the glass-ceramic coatings with or without a NiCoCrAlY intermediate layer. The NiCoCrAlY intermediate layer was beneficial to the cyclic oxidation resistance of the glass-ceramic coatings. (C) 2011 Elsevier B.V. All rights reserved.
关键词:
Glass-ceramic coating;NiCoCrAlY;Cyclic oxidation;Magnetron sputtering;resistance;microstructure;scales
