排序方式: 共有50条查询结果,搜索用时 15 毫秒
41.
研究了柱状莫来石弥散四方氧化锆多晶陶瓷(MDZ)在含质量分数2%SiO2磨粒的5%NaOH溶液中的摩擦磨损性能.结果表明:在100~500N载荷范围内,莫来石质量分数为15%的15MDZ的耐磨性明显优于莫来石质量分数为20%的20MDZ;含莫来石弥散相的Y-TZP的力学性能有所降低,但15MDZ陶瓷在500N载荷下的耐磨性能优于Y-TZP;MDZ复合陶瓷主要呈现擦伤和塑性变形特征,而3Y-TZP陶瓷在相同试验条件下主要呈现塑性变形和断裂特征;柱状莫来石可阻碍裂纹扩展、阻止晶界滑移、抑制ZrO2晶粒异常长大、提高MDZ陶瓷的致密度,从而改善MDZ复会陶瓷的抗磨性能。 相似文献
42.
Hierarchical ZSM-11 with intergrowth structures: Synthesis,characterization and catalytic properties
Qingjun Yu Chaoyue Cui Qiang Zhang Jing Chen Yang Li Jinpeng Sun Chunyi Li Qiukai Cui Chaohe Yang Honghong Shan 《Journal of Energy Chemistry》2013,22(5):761-768
Hierarchical ZSM-11 microspheres with intercrystalline mesoporous properties and rod-like crystals intergrowth morphology have been synthesized using a spot of tetrabutylammonium as a single template. XRD, FTIR, SEM, TEM and N2 adsorption analysis revealed that each individual particle was composed of nanosized rod crystals inserting each other and the intercrystalline voids existing among rods gave a significant mesopore size distribution. Steam treatment result demonstrated the excellent hydrothermal stability of samples. Various crystallization modes including constant temperature crystallization (one-stage crystallization) and two-stage temperature-varying crystallization with different 1st stage durations were investigated. The results suggested that the crystallization modes were mainly responsible for the adjustable particle size and textural properties of samples while the small amount of tetrabutylammonium bromide was mainly used to direct the formation of both ZSM-11 framework and its intergrowth morphology. Furthermore, the performance of optimal ZSM-11 as an active component for the catalytic pyrolysis of heavy oil was also investigated. Compared with the commercial pyrolysis catalyst, the hierarchical ZSM-11 catalyst exhibited a high selectivity to desired products (LPG + gasoline + diesel), as well as a much lower dry gas and coke yield, plus a high selectivity and yield of light olefins ( ) and very poor selectivity to benzene. Therefore, fully open micropore-mesopore connectivity would make such hierarchically porous ZSM-11 zeolites very attractive for applications in clean petrochemical catalysis field. 相似文献
43.
通过水热法合成棒状纳米Ce O2(Ce O2-R),并将Pt纳米颗粒负载于Ce O2表面,制得甲醇燃料电池的阳极催化剂Pt/Ce O2-R.通过结构与形貌表征,结果表明,Pt/Ce O2-R中Ce O2的暴露晶面为(111)和(002)晶面,改变了Pt周围的电子结构,进而降低了Pt-COads的键能,释放出更多的活性位.另外,Pt纳米颗粒在Ce O2-R表面分散更均匀.利用电化学工作站测试阳极催化剂Pt/Ce O2-R在酸性溶液中的电化学性能,证明Pt/Ce O2-R催化剂的甲醇电氧化性能与抗CO毒害能力较颗粒状Ce O2负载Pt催化剂(Pt/Ce O2-P)都有很大的提高,证明Ce O2-R作为Pt纳米颗粒的载体用于直接甲醇燃料电池的阳极反应具有发展潜力. 相似文献
44.
45.
We study the organization of spherocylindrical molecules inside a freely rotating right circular cylindrical domain at the gas/liquid interface. The analysis is made under the assumption that the molecules are rigid and close packed, and that they are oriented parallel to each other. The direction and angle of their common orientation are completely arbitrary. We obtain exact analytic expressions for the lattice of molecular centers and its boundaries as a function of molecular dimensions, molecular orientation, and domain size. As a first application, we derive the number of molecules in a domain, and the packing fraction. The results obtained are essential when attempting to analytically model a Langmuir film where the global order of the film is less than the local order of the domains. 相似文献
46.
47.
分子磁体的设计与合成一直是当今物理和化学的热门研究课题. 受分子磁体启发, 通过引入叠氮磁耦合基团以及长链棒状配体4,4'-二咪唑联苯(L), 我们构筑了三个磁性化合物[Co2(N3)4(L)2.5]∞(1), [Ni2(N3)3(NO3)(L)2.5]∞(2)和[Mn2(N3)4(L)2.5]∞(3). 结构分析显示, 这是三个同构化合物, 展现了一种基于线性叠氮四核单元的二维层网络. 有意义的是, 这种线性叠氮四核单元还未曾被人报道. 磁性研究表明, 三个化合物都是铁磁耦合, 这是由于EO-叠氮所导致的. 通过拟合实验数据, 我们得到了三个化合物的磁耦合常数, 进一步验证了上面磁构相关性的讨论. 相似文献
48.
Yuki Arakawa Yukito Sasaki Naoki Haraguchi Shinichi Itsuno Hideto Tsuji 《Liquid crystals》2018,45(6):821-830
We synthesised a novel family of liquid crystalline 1,4-phenylene bis(4-alkylthio benzoates), of which homologues with different alkyl chain lengths of 1–8 were designed, to investigate the structure–property relationship. The mesogenic incidence and tendency were found to be strongly dependent on the carbon numbers in the terminal alkyl chains. Even members formed widely monotropic or enantiotropic nematic (N) phases compared to odd members that showed either none or monotropic-narrower ones. The temperature dependence of birefringence (Δn) for the hexylthio homologue was evaluated and compared to that for a hexyloxy counterpart. It was found that the hexylthio homologue exhibited higher Δn values than the hexyloxy counterpart over the entire range of near TIN–T. In addition, wide-angle X-ray diffraction measurements, using magnetically aligned specimens, found enhanced cybotactic nematic tendency with smectic (Sm) A-like temperature dependence for the hexylthio analogue, due to the intermolecular attractive S···S interaction, in comparison with the hexyloxy analogue exhibiting N phase with clear Sm C-type clusters. We revealed the actual benefits of alkylthio groups in the fluid N phase. 相似文献
49.
利用水热法合成了一维棒状BiPO4微晶,在此基础上采用浸渍-被烧法进行g-C3N4量子点表面修饰获得新颖的g-C3N4/BiPO4异质结。借助X射线衍射(XRD)、场发射扫描电镜(FE-SEM)、透射电镜(HRTEM)、能谱(EDS)、紫外-可见漫反射(UV-Vis-DRS)等测试手段对所得样品的相组成、形貌和谱学特征进行了表征。选择罗丹明B(RhB)和苯酚作为模型污染物研究了所得在可见光下的催化活性。结果表明,样品16%(w/w) g-C3N4/BiPO4对RhB降解的速率常数分别是纯和的g-C3N4和BiPO4的16倍和4.6倍。g-C3N4量子点与BiPO4之间形成异质结,抑制了光生电子-空穴对的复合,从而提高了催化剂的活性。自由基捕获实验进一步表明,超氧负离子自由基(·O2-)是催化降解RhB和苯酚的主要活性物种。 相似文献
50.
通过湿化学法在70℃低温条件下,制备了亚微米棒状ZnO。利用紫外可见吸收光谱(UV-Vis),扫描电镜(SEM),X射线粉末衍射(XRD)以及拉曼光谱对棒状ZnO进行了表征。采用密度泛函(DFT/B3LYP)方法,以6-311G*为基组研究了结晶紫(CV)的理论平衡构型,同时以CV作为探针分子,检测了亚微米棒状ZnO的表面增强拉曼(SERS)活性。结果表明:亚微米棒状ZnO为六方纤锌矿结构,具有很高纯度和结晶度。CV在ZnO表面的拉曼增强因子可达1.2×102,其增强机理主要来源于化学增强。 相似文献