Structural Distortion and Defects in Ti_3AlC_2 irradiated by Fe and He Ions

Ti_3AlC_2 samples are irradiated in advance by 3.5 MeV Fe-ion to the fluence of 1.0×10~(16) ion/cm~2,and then are implanted by 500 keV He-ion with the fluence of 1.0×10~(17) ion/cm~2 at room temperature.The irradiated samples are investigated by grazing incidence x-ray diffraction(GIXRD) and transmission electron microscopy(TEM).GIXRD results show serious structural distortion,but without amorphization in the irradiated samples.Fe-ion irradiation and He-ion implantation create much more serious structural distortion than single Fe-ion irradiation.TEM results reveal that there are a large number of defect clusters in the damage region,and dense spherical He bubbles appear in the He depositional region.It seems that the pre-damage does not influence the growth of He bubbles,but He-ion implantation influences the pre-created defect configurations.     

Effect of microstructure on ~3He migration in TiT_(1.9) films

Two kinds of films were prepared to study the effect of microstructure on helium migration in Ti tritides. Both films showed different release behaviors and helium bubble distributions. In the film consisting of columnar grains, a twolayered structure was observed. Inclusions with a strip feature were found at the grain boundary, and no helium bubbles were distributed in these inclusions. However, helium preferred to migrate to the boundaries of these inclusions. Bubble linkage as a ribbon-like feature developed parallel to the film surface in the film consisting of columnar grains. More cracks were developed at the grain boundaries of the film consisting of columnar grains, although the helium content in the film consisting of columnar grains was less than that in the film consisting of equiaxed grains. A surface region with a small number of bubbles, or "depleted zone", was observed near the surface. The cracks extending to the film surface were the pathways of the critical helium released from the film. The helium migration was strongly influenced by the grain microstructure.     

金属有机框架离子交换得到的镍单位点催化剂用于二氧化碳电催化还原

正电催化还原二氧化碳制备碳氢化合物或液体燃料等是CO_2化学利用的重要途径,也是CO_2反应化学的主要内容~(1–4)。过渡金属单原子结构催化剂由于其独特的电子和几何特性,其在一些重要的化学反应中通常会表现与传统的纳米粒子或者原子簇完全不同的催化性能~(5–8)。但是,过渡金属单原子结构催化剂的制备以及电催化二氧化碳还     

水汽和空气焙烧制备LaY沸石的SiCl4气相超稳研究

为了考察不同焙烧条件制备的LaY沸石在SiCl₄气相超稳后性能的差异,采用离子交换和氨水沉淀相结合的方法将La离子负载到NaY沸石上,经水蒸汽焙烧或空气焙烧得到不同La负载量的LaYS和LaYB沸石,再经过SiCl₄气相超稳改性得到DLaYS和DLaYB沸石.XRD数据表明水蒸汽焙烧能使沸石发生更为明显的骨架脱铝;不同La负载量的LaY沸石经SiCl₄气相超稳改性都能顺利实现晶胞收缩.XRF数据表明气相超稳和洗涤过程伴随着稀土La的大量流失,DLaYB沸石中的La流失量相对较小.NH₃-TPD和Py-IR数据表明La负载量相同时,DLaYS沸石的总酸量少于DLaYB沸石的总酸量.固定流化床重油催化裂化评价结果显示,与参比催化剂相比,DLaYS催化剂和DLaYB催化剂都具有汽油收率高、柴油收率低,及总轻质油收率高的特点.La负载量相同时,DLaYS催化剂的汽油收率低于DLaYB催化剂.     

基于时分复用的多点式环形腔光纤电流传感器

为实现输电线路上的多点电流监测,利用通信用普通单模光纤,设计基于时分复用的多点式光纤环形腔结构电流传感器.多路传感系统共用一套光源、检测设备和数字信号处理系统,在节约成本的同时,提高了利用率.实验中选用双路全光纤电流传感器结构,在两个不同的点同时测量电流,其中一测量点对0~600A范围内的电流进行测量,另一测量点对0~1 500A范围内的电流进行测量.对实验数据进行线性拟合,结果表明:循环次数取8比较合适,此时系统具有比取2时高约3~4倍的灵敏度;两个测量点光信号的偏振态与电流之间有良好的线性关系,两个传感单元的灵敏度不同,而且相互之间没有串扰是各自独立的传感系统.     

斜靠式拱桥结构侧倾失稳分析的Ritz法

采用Ritz法,首次推导了主拱肋拱脚铰接、稳定拱肋拱脚固接边界条件下,斜靠式拱桥的侧倾失稳临界荷载系数的计算公式,并通过有限元法验证了该计算公式的正确性.进一步分析了稳定拱肋弯曲变形能和扭转变形能、主拱肋与稳定拱肋间横撑切向和径向弯曲变形能及吊杆非保向力位势和桥面系侧向弯曲变形能对斜靠式拱桥侧倾失稳临界荷载系数λcr的影响.研究结果表明:稳定拱肋的侧向弯曲变形能对斜靠式拱桥侧倾失稳临界荷载系数λcr有一定的影响,而扭转变形对侧倾失稳临界荷载系数λcr影响甚微;若忽略横撑的所有变形能,侧倾失稳临界荷载系数λcr降低65％～83％,即横撑对斜靠式拱桥侧倾失稳临界荷载系数λcr的影响非常显著;随着稳定拱肋倾角的增加,侧倾失稳临界荷载系数λcr呈增大趋势,且增设稳定拱肋对提高斜靠式拱桥的侧向稳定性大有帮助.     

Ag/Bi2S3/Bi2WO6复合催化剂合成及光催化性能研究

以硝酸铋、钨酸钠和硫脲为起始原料,采用一步水热法成功合成Bi2 S3/Bi2 WO6光催化剂,采用光还原法在Bi2S3/Bi2 WO6表面沉积贵金属Ag.采用XRD、XPS、FESEM、TEM和UV-Vis-DRS等手段对Bi2S3/Bi2WO6和Ag/Bi2S3/Bi2WO6进行表征,并以罗丹明B和苯酚作为模型污染物对其光催化性能进行研究.结果证明,耦合Bi2S3可以提高Bi2WO6催化剂的光催化活性,Ag沉积使得其光催化性能进一步提高,且Ag的沉积量与催化剂的活性关系密切,其中5; Ag/Bi2S3/Bi2WO6的光催化效果最好.此外,结合活性物种检测和能带结构分析,对Ag/Bi2S3/Bi2WO6的光催化活性增强机理进行了分析.     

沉管隧道横向动力响应分析的多体动力学方法

沉管隧道横向地震响应分析是沉管隧道结构抗震设计的重点.根据沉管隧道的结构特点和接头剪力键的节点构造,建立了沉管隧道的多刚体-剪切铰-黏性阻尼铰多体动力学模型,并应用多体动力学中的离散时间传递矩阵法(multibody system discrete time transfer matriX method,MS—DT-TMM)建立了数学模型及表达式,同时编写Matlab程序进行求解实现.设定算例分别采用MS—DT—TMM和传统有限元法(finite element method,FEM)对沉管隧道横向地震响应进行对比分析,两者吻合较好,表明MS—DT-TMM应用于沉管隧道横向动力响应分析的可行性和有效性.     

Sm3+掺杂棒状BiPO4微晶的制备及其光催化活性增强机理

以Sm(NO3)3、NH4H2PO4和Bi(NO3)3为原料,采用水热法合成了Sm3+掺杂棒状BiPO4光催化剂.采用XRD、SEM、UV-Vis吸收光谱、BET比表面积测试等手段对其组成、晶型、粒径、形貌及比表面积等进行了表征,并以金卤灯模拟可见光,以甲基橙和邻硝基苯酚为模型污染物,对其光催化性能进行了评价和分析.XRD和SEM分析表明,Sm3+掺杂进入BiPO4的晶格,导致其晶胞参数发生变化,但对其物相结构和形貌的影响不明显;UV-Vis吸收光谱测试表明,Sm3+掺杂使BiPO4在紫外光区的吸收减弱,可见光区略有增强.光催化实验表明,Sm3+掺杂后BiPO4的光催化活性与掺杂量密切相关,当Sm3掺杂量为0.75at;时光催化活性提高较显著.根据实验结果和文献报道,论文对Sm3+掺杂后BiPO4活性提高机理进行了探讨,认为Sm3+掺杂后BiPO4光生电子-空穴分离效率提高是影响其活性的主要因素.     

基于TPRA—tree面向预言查询的时空索引

基于TPR-tree典型的移动对象索引方法,提出了TPRA—tree．TPRA—tree从频繁更新的移动对象运动方向的角度进行构造,减少了结点面积,减小了结点间重叠．实验结果表明：TPRA-tree的更新和与查询性能优于TPR-tree．