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71.
72.
水泥是建筑工程材料的基石,对于混凝土的性能有着直接的影响,因此我国有着严格规定,限制使用的水泥材料中氯离子含量。《铁路混凝土工程施工质量验收标准》[1]与《通用硅酸盐水泥》[2]中要求w(Cl-)≤0.06%。准确测量水泥中氯离子含量同时进行不确定度评定变得具有意义,许多研究者进行了不同材料的氯离子检测的不确定度评定研究[3-4]。本文基于国家标准《水泥化学分析方法》[5]中氯离子含量检测的基准法,即:硫氰酸铵容量法,设计评定流程,找到最终影响不确定度的主要因素。 相似文献
73.
采用图像分析技术对4种不同方法制备的球形Ti-6Al-4V粉末进行粒形的定量分析,分别测量了粉末的球形度、椭圆率、赘生物指数及粗糙度。结果表明:4种方法制备的粉末平均球形度均在90%以上。等离子旋转电极雾化法(PREP)、等离子火炬雾化法(PA)、等离子惰性气体雾化法(PIGA)、电极感应熔炼气雾化法(EIGA)制得粉末球形度依次降低,粗糙度依次增加。PREP、PA、EIGA、PIGA法制得粉末的表面卫星球粘附依次增加。对于PREP法制得粉末,粉末粒径范围越细,球形度越高,平均粗糙度越小。粉末粒形指标的差异与其制备方法的原理有关。采用图像分析技术可以实现对金属粉末粒形指标的科学定量分析。 相似文献
74.
Santosh K. Gupta Maya Abdou Partha S. Ghosh Jose P. Zuniga Ezhilarasan Manoharan HyeongJun Kim Yuanbing Mao 《Journal of the American Ceramic Society》2020,103(1):235-248
Unveiling the underlying mechanisms of properties of functional materials, including the luminescence differences among similar pyrochlores A2B2O7, opens new gateways to select proper hosts for various optoelectronic applications by scientists and engineers. For example, although La2Zr2O7 (LZO) and La2Hf2O7 (LHO) pyrochlores have similar chemical compositional and crystallographic structural features, they demonstrate different luminescence properties both before and after doped with Eu3+ ions. Based on our earlier work, LHO-based nanophosphors display higher photo- and radioluminescence intensity, higher quantum efficiency, and longer excited state lifetime compared to LZO-based nanophosphors. Moreover, under electronic O2−→Zr4+/Hf4+ transition excitation at 306 nm, undoped LHO nanoparticles (NPs) have only violet blue emission, whereas LZO NPs show violet blue and red emissions. In this study, we have combined experimental and density functional theory (DFT) based theoretical calculation to explain the observed results. First, we calculated the density of state (DOS) based on DFT and studied the energetics of ionized oxygen vacancies in the band gaps of LZO and LHO theoretically, which explain their underlying luminescence difference. For Eu3+-doped NPs, we performed emission intensity and lifetime calculations and found that the LHOE NPs have higher host to dopant energy transfer efficiency than the LZOE NPs (59.3% vs 24.6%), which accounts for the optical performance superiority of the former over the latter. Moreover, by corroborating our experimental data with the DFT calculations, we suggest that the Eu3+ doping states in LHO present at exact energy position (both in majority and minority spin components) where oxygen defect states are located unlike those in LZO. Lastly, both the NPs show negligible photobleaching highlighting their potential for bioimaging applications. This current report provides a deeper understanding of the advantages of LHO over LZO as an advanced host for phosphors, scintillators, and fluoroimmunoassays. 相似文献
75.
Dongqing Wang Mao Chen Yang Jiang Shuai Wang Zhixing Zhao Tim Evans Baojun Zhao 《Journal of the American Ceramic Society》2020,103(12):7299-7309
Phase equilibria and liquidus temperatures in the CaO–SiO2–Al2O3–MgO system at a CaO/SiO2 weight ratio of 0.9 in the liquid phase have been experimentally determined employing high-temperature equilibration and quenching technique followed by electron probe X-ray microanalysis. Isotherms at 1573, 1623, 1673, and 1773 K were determined and the primary phase fields of wollastonite, melilite, olivine, periclase, spinel, and corundum have been located. Compositions of the olivine and melilite solid solutions were analyzed and discussed. Comparisons between the newly constructed diagram, existing data, and FactSage predicted phase diagrams were performed and differences were discussed. The present study will be useful for guidance of industrial practices and further development of thermodynamic modeling. 相似文献
76.
Hong Fang Lihai Wang Weijie Kuai Juan Du Guicheng Jiang Xiaoyan Lu Minglei Zhao Chunming Wang Wenbin Su Limei Zheng Chunying Wang Chunlei Wang 《Journal of the American Ceramic Society》2020,103(5):3257-3264
Domain wall motions mainly affect all kinds of properties of ferroelectric materials, such as piezoelectricity, dielectric response, and mechanical loss, and the extrinsic contributions associated with domain wall motions have always been an important issue. In this study, the reversible and irreversible extrinsic contributions to the dielectric properties of [011]C-oriented 0.27Pb(In1/2Nb1/2)O3-0.46Pb(Mg1/3Nb2/3)O3-0.27PbTiO3:Mn single crystals have been extracted by the Rayleigh analysis. We found that in the unpoled samples, the extrinsic contributions of reversible and irreversible domain wall motions to dielectric properties significantly reduced, whereas after poling, only the irreversible extrinsic contribution decreased. The pinning effect in the 2R domain structure is much weaker than that in the 4R domain structure, leading to the low enhancement of Qm and a slight decrease in piezoelectricity caused by acceptor doping in 2R domain structure. This study explores the domain wall dynamics of acceptor-doped single crystals and mainly guides on further performance optimization in PbTiO3-based relaxor single crystals. 相似文献
77.
This work aims to investigate the unsteady conjugate interphase mass transfer between a stationary deformed drop and the modest extensional flow in a cross-intersected 2D channel. It is very difficult to accurately quantify the transient mass transfer rate of solute in such a geometry. Therefore, we established a mathematical model on the basic of the Stokes equation and solved it by the boundary element method, which could deal precisely with a two-phase flow system with a deformable interface; meanwhile, the convection-diffusion equation was solved by the finite difference method to calculate the unsteady conjugate interphase mass transfer. The simulation results showed that the mass transfer rate, analyzed and characterized in terms of mean concentration variation and Sherwood number Sh, was affected by capillary number Ca, Peclet number Pe, viscosity ratio λ , interior-to-exterior diffusivity ratio K, distribution coefficient m, and wall effect factor W. 相似文献
79.
丝网分离器在工业中有着广泛地应用。本文针对液滴撞击网丝的动态过程,采用CLSVOF方法对单个液滴撞击干燥网丝的问题进行数值模拟,经过合理的简化,建立了气流扰动下单液滴撞击干燥扁网丝面的二维数学模型,分析了液滴撞击角和撞击位置对液滴撞击行为特性的影响。数值计算的结果表明:液滴撞击到干燥网丝上分为铺展和飞溅2个过程,撞击角越小,上铺展半径越大,下铺展半径越小,分离的二次液滴体积越大;液滴撞击网丝的位置离网丝边缘越近,越容易产生二次液滴,二次液滴的总体积越多。 相似文献
80.
Junsong Zhang Yinong Liu Lishan Cui Shijie Hao Daqiang Jiang Kaiyuan Yu Shengcheng Mao Yang Ren Hong Yang 《Advanced materials (Deerfield Beach, Fla.)》2020,32(18):1904387
Nanosized materials are known to have the ability to withstand ultralarge elastic strains (4–10%) and to have ultrahigh strengths approaching their theoretical limits. However, it is a long-standing challenge to harnessing their exceptional intrinsic mechanical properties in bulk forms. This is commonly known as “the valley of death” in nanocomposite design. In 2013, a breakthrough was made to overcome this challenge by using a martensitic phase transforming matrix to create a composite in which ultralarge elastic lattice strains up to 6.7% are achieved in Nb nanoribbons embedded in it. This breakthrough was enabled by a novel concept of phase transformation assisted lattice strain matching between the uniform ultralarge elastic strains (4–10%) of nanomaterials and the uniform crystallographic lattice distortion strains (4–10%) of the martensitic phase transformation of the matrix. This novel concept has opened new opportunities for developing materials of exceptional mechanical properties or enhanced functional properties that are not possible before. The work in progress in this research over the past six years is reported. 相似文献