Z. Liu
,
Y. Y. Xu
,
Z.G. Wang
,
Y. Wang
,
and Z. Y. Liu State Key Laboratory for Fatigue and Fracture of Materials
,
Institute of Metal Research
,
Tile Chinese Academy of Sciences
,
Shenyang 110015
,
China School of Material Science and Engineering
,
Shenyang Technical University
,
Shenyang 110023
,
China
金属学报(英文版)
Fully reversed total strain-controlled low-cycle fatigue tests were conducted at room temperature in air to study fatigue behavior of AZ91HP in as high pressure die casting and subsequently heat treatments. All the specimens in different heat histories exhibited cyclic strum hardening in different degrees. It was difficult to distinguish the fatigue behaviors of the die-casting specimens from the solution-aging specimens. However the solution treated specimens showed longerfatigue life at high strum amplitude and shorter fatigue life at low strain amplitude than die-casting and the solution-aging specimens though they had the lowest yield strength with higher strain hardening. Fatigue fracture surfaces for strain amplitude larger than 0.005 showed very similar to those of the monotonic tensile tests. The SEM examination revealed that regions of fatigue crack growth and final fracture could be characterized by quasi-cleavage mech anisms, but some shallow dimples, slip bands and secondary cracks were found on the fracture surface in the fracturs crack growth areas.
关键词:
low-cycle fatigue
,
null
,
null
,
null
J. Li
,
Z.G. Wang
,
Y.Q. Lai
,
Y.Y. Wu
,
S.L. Ye
,
null
,
null
,
null
,
null
,
null
,
null
金属学报(英文版)
Inert anode has been a hot issue in the aluminum industry for many decades. In this article, with the help of FEA (finite element analysis) software Ansys, a model was developed to simulate the thermal stress distribution working condition of an inert anode. To reduce its thermal stress, the effect of some parameters on the thermal stress distribution was investigated, including the anode height, the anode radius, the hole depth, the hole radius, the radius of inner chamfer, and outer chamfer. The results showed that in the actual working condition of an inert anode, there existed a large axial tensile stress near the tangent interface between the anode and bath, which was the major cause of anode breaking. Increasing the anode height and reducing the hole depth properly seemed to be beneficial for the stress distribution. With the increase of anode radius, the stress distribution became better first and then deteriorated, the reasonable value was between 0.045 to 0.06m. The hole radius had a significant effect on the stress and a smaller radius would reduce the thermal stress. The effect of the radius of the inner chamfer and the outer chamfer was less than other parameters.
关键词:
inert anode
,
null
,
null
刘亚男
,
王瑞霞
,
杨正坤
,
杜虹
,
姜一帆
,
申丛丛
,
梁况
,
徐安武
催化学报
doi:10.1016/S1872-2067(15)60985-8
随着科学技术的不断进步和经济的快速发展,人类对自然资源的需求量越来越大,在开发利用自然资源的同时,大量的有机污染物也随之进入自然环境.这些物质不仅污染环境、破坏生态,更对人类的生活和健康带来了巨大的威胁.研究证实,半导体光催化剂在光照条件下可以破坏有机污染物的分子结构,最终将其氧化降解成CO2、H2O或其它不会对环境产生二次污染的小分子,从而净化水质.近年来,有关光催化降解有机污染物的报道日益增多. ZnO作为一种广泛研究的光催化降解材料,因其无毒、低成本和高效等特点而具有一定的应用前景.但是ZnO较大的禁带宽度(3.24 eV)导致其只能吸收紫外光部分,而对可见光的吸收效率很小,极大地制约了其实际应用.除此之外, ZnO受光激发产生的电子-空穴分离效率较低、光催化过程中的光腐蚀严重也是制约其实际应用的重要因素.为了提高ZnO的光催化活性和稳定性,本文合成了用g-C3N4修饰的氧空位型ZnO(g-C3N4/Vo-ZnO)复合催化剂,在有效调控ZnO半导体能带结构的同时,通过负载一定量的g-C3N4以降低光生电子-空穴对的复合速率和反应过程中ZnO的光腐蚀,增强催化剂的光催化活性和稳定性.本文首先合成前驱体Zn(OH)F,然后焙烧三聚氰胺和Zn(OH)F的混合物得到g-C3N4/Vo-ZnO复合催化剂,并采用电子顺磁共振波谱(EPR)、紫外-可见光谱(UV-vis)、高分辨透射电镜(HRTEM)和傅里叶变换红外光谱(FT-IR)等表征了它们的结构及其性质. EPR结果表明,ZnO焙烧后具有一定浓度的氧空位,导致其禁带宽度由3.24 eV降至3.09 eV,因而提高了ZnO对可见光的吸收效率. UV-vis结果显示, Vo-ZnO复合g-C3N4后对可见光的吸收显著增强. HRTEM和FT-IR结果均表明, g-C3N4纳米片和Vo-ZnO颗粒之间通过共价键形成了强耦合,这对g-C3N4/Vo-ZnO复合催化剂中光生载流子的传送和光生电子-空穴对的有效分离起到重要作用.可见光催化降解甲基橙(MO)和腐殖酸(HA)的实验进一步证明, g-C3N4/Vo-ZnO复合材料具有较好的光催化活性,优于单一的g-C3N4或Vo-ZnO材料.同时还发现, g-C3N4的负载量对光催化活性有显著影响,当氮化碳的负载量为1 wt%时,所制材料具有最高的光催化活性：可见光照射60 min后,MO降解率可达到93%, HA降解率为80%.复合材料光催化活性的增强一方面是因为氧空位的形成减小了ZnO的禁带宽度,使得ZnO对可见光的吸收能力大大增强；另一方面, g-C3N4和Vo-ZnO的能带符合了Z型催化机理所需的有效能带匹配,使得光生电子-空穴对得到了有效的分离,从而提高了光催化活性.降解MO的循环实验表明, g-C3N4/Vo-ZnO催化剂具有很好的稳定性且不容易发生光腐蚀.与此同时,我们对比了用不同方法制备的g-C3N4/ZnO材料的催化性能.结果显示,本文制备的g-C3N4/Vo-ZnO复合材料具有更好的降解效率.总体而言,对于降解有机污染物, g-C3N4/Vo-ZnO可能是一个更为有效可行的催化体系.此外,本文也为设计与制备其他新型光催化剂提供了一条新的思路.
关键词:
氧空位氧化锌
,
石墨化氮化碳
,
复合光催化剂
,
光降解
,
Z型
何科林
,
谢君
,
罗杏宜
,
温九青
,
马松
,
李鑫
,
方岳平
,
张向超
催化学报
doi:10.1016/S1872-2067(17)62759-1
光催化技术是目前解决能源和环境问题最具前景的手段之一,因此寻找高效光催化剂已成为光催化技术的研究热点.而在众多半导体催化剂中,廉价、环保且性能稳定的g-C3N4光催化剂在太阳光开发利用方面尤其引人关注.然而,由于g-C3N4的比表面小,活性位点少,以及光生电子/空穴对易复合等不足,严重导致其较低的光催化量子效率.因此,构造Z型体系和负载助催化剂等策略被广泛应用于提高g-C3N4光催化效率.在过去几年中,TiO2,Bi2WO6,WO3,Bi2MoO6,Ag3PO4和ZnO已经被成功证实可以与g-C3N4耦合而构造Z型光催化剂体系.其中,WO3/g-C3N4光催化剂体系,具有可见光活性的WO3导带中的光生电子和g-C3N4价带中的光生空穴容易实现Z型复合,从而保留了WO3的强氧化能力和g-C3N4的高还原能力,最终大幅度提高了整个体系的光催化活性.在g-C3N4的各种产氢助催化剂中,由于常用的Pt,Ag和Au等贵金属的高成本和低储量等问题严重限制了它们的实际应用,所以近年来各种非贵金属助催化剂(包括纳米碳,Ni,NiS,Ni(OH)2,WS2和MoS2等)得到了广泛的关注.我们采取廉价且丰富的Ni(OH)x助催化剂修饰g-C3N4/WO3耦合形成的Z型体系,开发出廉价高效的WO3/g-C3N4/Ni(OH)x三元产氢光催化体系.在该三元体系中,Ni(OH)x和WO3分别用于促进g-C3N4导带上光生电子和价带的光生空穴的分离及利用,从而使得高能的g-C3N4的光生电子在Ni(OH)x富集并应用于光催化产氢,而高能的WO3的光生空穴被应用于氧化牺牲剂三乙醇胺,最终实现了整个体系的高效光催化产氢活性及稳定性.我们通过直接焙烧钨酸铵和硫脲制备出WO3纳米棒/g-C3N4,并采用原位光沉积方法将Ni(OH)x纳米颗粒负载到WO3/g-C3N4上.随后,我们采取X射线衍射(XRD)、高分辨透射电子显微镜(HRTEM)、X射线光电子能谱分析(XPS)和比表面和孔径分布等表征手段来研究光催化剂的结构与形貌;采取紫外-可见漫反射表征方法来研究其光学性能;采取荧光光谱,阻抗和瞬态光电流曲线等表征手段来测试光催化剂的电荷分离性能;采取极化曲线和电子自旋共振谱等表征手段来证明光催化机理;采取光催化分解水产氢的性能测试来研究光催化剂的光催化活性与稳定性.XRD,HRTEM和XPS表征结果,表明WO3为有缺陷的正交晶系的晶体,直径为20–40纳米棒且均匀嵌入在g-C3N4纳米片上;Ni(OH)x为Ni(OH)2与Ni的混合物,其Ni(OH)2与Ni的摩尔比为97.4 : 2.6,Ni(OH)x粒径为20–50 nm且均匀分散在g-C3N4纳米片上,WO3/g-C3N4/Ni(OH)x催化剂界面之间结合牢固,其中WO3和Ni(OH)x均匀分布在g-C3N4上.紫外-可见漫反射表征结果表明,随着缺陷WO3的负载量增加,复合体系的吸收边与g-C3N4相比产生明显的红移,而加入Ni(OH)x助催化剂使得催化剂体系的颜色由黄变黑,明显地增加了可见光的吸收.荧光光谱,阻抗和瞬态光电流曲线结果表明,WO3和Ni(OH)x的加入能有效地促进光生电子/空穴的分离.极化曲线结果表明,掺入WO3和Ni(OH)x能降低g-C3N4的析氢过电位,从而提高光催化剂表面的产氢动力学.?O2?和?OH 电子自旋共振谱表明成功形成了WO3/g-C3N4 耦合Z 型体系.光催化分解水产氢的性能测试表明,20%WO3/g-C3N4/4.8%Ni(OH)x产氢效率最高(576 μmol/(g?h)),分别是g-C3N4/4.8%Ni(OH)x,20%WO3/g-C3N4和纯g-C3N4的5.7,10.8和230倍.上述结果充分证明,Ni(OH)x助催化剂修饰和g-C3N4/WO3 Z型异质结产生了极好的协同效应,最终实现了三元体系的极高的光催化产氢活性.
关键词:
光催化产氢
,
稳定的Ni(OH)x催化剂
,
g-C3N4
,
Z型体系
,
异质结
郑锡涛
,
李泽江
,
杨帆
复合材料学报
针对Z-pin增强复合材料层合板,开展了断裂韧性的试验研究.研究选取了3种Z-pin直径(0.28、0.52、0.80 mm)且每种直径下分别以3种分布形式(5×5、8×8、10×10)排布Z-pin的增强方式,为了确定比较基准,试验中同时测试了不含Z-pin的复合材料层合板试样.通过Z-pin拔出试验测试了3种直径Z-pin从基体拔出过程中的载荷-位移关系.利用双悬臂梁试验和端部开口弯曲试验分别测试了不含Z-pin和含Z-pin试样的Ⅰ型断裂应变能释放率GIC、Ⅱ型断裂应变能释放率GⅡC.试验结果表明:与不含Z-pin的结构相比,Z-pin增强试样的Ⅰ型断裂应变能释放率GIC增大了83%～1110%,Ⅱ型断裂应变能释放率GⅡC增大了23%～438%;在相同Z-pin体积含量下,与增大Z-pin直径相比,增大Z-pin分布密度能更有效地提高复合材料层合板的断裂韧性.
关键词:
Z-pin增强
,
Ⅰ型断裂
,
Ⅱ型断裂
,
应变能释放率
,
断裂韧性
Journal of Alloys and Compounds
The EPR g factors g(x), g(y) and g(z) and the local structures for the orthorhombic Nd3+ centers in YAG, YGG and LuGG garnets are studied by using the perturbation formulas of the g factors for a 43 ion in orthorhombic symmetry. In these formulas, the contributions to the g factors arising from the second-order perturbation terms and the admixture of various energy levels are considered. Based on the analyses of the g factors, we find that the polar angles theta'(j) of the impurity-ligand bonds related to the Z-axis of the crystals in these Nd3+ centers are smaller than the host angles theta(j) in pure crystals, whereas the azimuthal angles phi'(j) related to the X-axis in the impurity centers are larger than the corresponding phi(j) in the hosts. The calculated g factors, particularly their anisotropies Delta g [= g(z) - (g(x) + g(y))/2] and delta g (= g(x) - g(y)) for Nd3+ in the gamets based on the above local angles show reasonable agreement with the observed values. (c) 2004 Elsevier B.V. All rights reserved.
关键词:
electron paramagnetic resonance (EPR);defect structure;crystal-field;and spin hamiltonians;Nd3+;garnets;crystal-field;substituted garnets;superposition-model;magnetic-properties;neodymium;laser;parameters;calcium;cerium;ion
王晓旭
,
陈利
材料工程
doi:10.3969/j.issn.1001-4381.2011.11.001
通过单根Z-pin从复合材料层合板中拔出的试验方法,测试了Z-pin的拔出强度,计算了Z-pin的临界埋入深度,并引入抗拉强度利用率概念来表征Z-pin的抗拉强度在拔出过程中的利用程度.结果表明,直径0.50mm和0.28mm的Z-pin临界埋入深度分别约为5.1mm和3.1mm.当Z-pin的埋入深度小于临界埋入深度时,Z-pin从层板中拔出；Z-pin拔出强度与埋入深度成正比,与Z-pin的直径成反比；当Z-pin的埋入深度大于临界埋入深度时,Z-pin发生断裂,Z-pin的抗拉强度利用率达到100％.最后提出了提高抗拉强度利用率的建议.
关键词:
Z-pin
,
拔出强度
,
复合材料
,
拔出试验
,
抗拉强度
