双组份室温加成型硅橡胶口腔印模材料的制备

以自制乙烯基硅油为基胶、自制含氢硅油为交联剂、铂配合物为催化剂、高纯度硅微粉为填料、多乙烯基化合物为抑制剂等,通过实验制得双组份室温加成型硅橡胶口腔印模材料.研究了各组分对硅橡胶印模材料硫化化时间、细微复制、力学性能的影响.并制备了与国外产品性能相当的产品.     

Preparation of Li_4Ti_5O_(12) submicrospheres and their application as anode materials of rechargeable lithium-ion batteries

We report on the preparation of spinel Li4Ti5O12 submicrospheres and their application as anode materials of rechargeable lithium-ion batteries. The spinel Li4Ti5O12 submicrospheres are synthesized with three steps of the hydrolysis of TiCl4 to form rutile TiO2, the hydrothermal treatment of rutile TiO2 with LiOH to prepare an intermediate phase of LiTi2O4+δ, and the calcinations of LiTi2O4+δ to obtain spinel Li4Ti5O12. The as-prepared products are investigated by X-ray powder diffraction (XRD), scanning el...     

参加国家金标准物质定值测试工作的研究报告

近20年来,武警黄金指挥部测试中心参加了12个国家矿石金、12个国家痕量金分析标准物质定值测试工作.该文对取样量、样品均匀性检验、样品焙烧、分析方法的选取、样品稳定性检验等技术进行了总结,并对今后金标准物质的研制提出了建议.     

检测/校准实验室仪器设备及标准物质期间核查实施方法

对检测/校准实验室仪器设备及标准物质期间核查的具体实施进行了讨论,重点介绍编写期间核查作业指导书需明确的内容,包括明确核查对象、确定核查项目、选择核查方法、规定核查间隔、获取核查判据及如何判定对核查不合格的处置.指出既能利用期间核查确保仪器设备及标准物质的可靠性,又不浪费人力物力的措施.     

介孔L材料CMK-3对甲基紫的吸附性能

合成了高度有序的具有二维六方(P6mm)结构的介孔碳材料CMK-3;利用X射线衍射分析了CMK-3的晶体结构,利用氮气吸脱附(BET)试验测定了孔体积;测定了CMK-3对水溶液中甲基紫的吸附行为,考察了不同pH、温度及浓度下水溶液中甲基紫的静态吸附行为,并分析了酸性、中性、碱性条件下吸附剂对甲基紫和罗丹明B混合溶液的竞...     

Preparation, characterization and application of a new stir bar sorptive extraction based on poly(vinylphthalimide-co-N,N'-methylenebisacrylamide) monolith

In this study, a new stir bar sorptive extraction (SBSE) coating based on poly(vinylphthalimide-co-N,N'-methylenebisacrylamide) monolith (SBSE-VPMB) was prepared. The influences of the contents of monomer in polymerization mixture and the percentage of porogen solvent on the extraction performance were investigated thoroughly. Several characteristic techniques, such as elemental analysis, scanning electron microscopy, mercury intrusion porosimetry and infrared spectroscopy, were used to characterize the monolithic material. The analysis of oxfendazole (OFZ) and mebendazole (MBZ) in milk and honey samples by the combination of SBSE with HPLC with diode array detection was selected as paradigms for the practical evaluation of the new coating. Under the optimized extraction conditions, the limits of detection (S/N=3) for OFZ and MBZ were 0.23-0.60 μg/L in milk and 0.24-1.08 μg/L in honey, respectively. The method also showed good linearity, repeatability, high feasibility and acceptable recoveries for real samples. At the same time, the extraction performance and the distribution coefficients (K(VPMB/W)) of OFZ and MBZ on SBSE-VPMB were compared with other SBSEs based on porous monoliths and commercial SBSE.     

High-rate cathode based on Li3V2(PO4)3/C composite material prepared via a glycine-assisted sol–gel method

Carbon-coated monoclinic Li₃V₂(PO₄)₃ (LVP/C) cathode material has been successfully prepared by a novel glycine-assisted sol–gel method. The product is investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM) and electrochemical method. In the range of 3.0–4.3 V, the LVP/C electrode presents excellent rate capability. It is 125.4 mAh g^{− 1} that can be delivered at 1 C charge–discharge rate and 99.5 mAh g^{− 1} is still obtained at 20 C charge–discharge rate. These results demonstrate that the carbon-coated LVP/C composite material prepared via a glycine-assisted sol–gel method has great potential for use in high-power lithium ion batteries.     

On the thermodynamic consistency of the equivalence principle in continuum damage mechanics

We consider theories of continuum damage mechanics involving damage effect variables of different tensorial ranks. It turns out that orthotropic damage together with the use of Lemaitre's equivalence principle for the elastic part does not allow thermodynamic potentials such as the free enthalpy to exist. As the existence of these potentials is, however, a strict thermodynamic requirement, a theory employing orthotropic damage in this way is inconsistent. We show that the use of a rank-4 damage effect variable allows a consistent use of the equivalence principle.     

Characterization of heterogeneous solids via wave methods in computational microelasticity

Real solids are inherently heterogeneous bodies. While the resolution at which they are observed may be disparate from one material to the next, heterogeneities heavily affect the dynamic behavior of all microstructured solids. This work introduces a wave propagation simulation methodology, based on Mindlin's microelastic continuum theory, as a tool to dynamically characterize microstructured solids in a way that naturally accounts for their inherent heterogeneities. Wave motion represents a natural benchmark problem to appreciate the full benefits of the microelastic theory, as in high-frequency dynamic regimes do microstructural effects unequivocally elucidate themselves. Through a finite-element implementation of the microelastic continuum and the interpretation of the resulting computational multiscale wavefields, one can estimate the effect of microstructures upon the wave propagation modes, phase and group velocities. By accounting for microstructures without explicitly modeling them, the method allows reducing the computational time with respect to classical methods based on a direct numerical simulation of the heterogeneities. The numerical method put forth in this research implements the microelastic theory through a finite-element scheme with enriched super-elements featuring microstructural degrees of freedom, and implementing constitutive laws obtained by homogenizing the microstructure characteristics over material meso-domains. It is possible to envision the use of this modeling methodology in support of diverse applications, ranging from structural health monitoring in composite materials to the simulation of biological and geomaterials. From an intellectual point of view, this work offers a mathematical explanation of some of the discrepancies often observed between one-scale models and physical experiments by targeting the area of wave propagation, one area where these discrepancies are most pronounced.     

Phase boundaries as agents of structural change in macromolecules

We model long rod-like molecules, such as DNA and coiled-coil proteins, as one-dimensional continua with a multi-well stored energy function. These molecules suffer a structural change in response to large forces, characterized by highly typical force-extension behavior. We assume that the structural change proceeds via a moving folded/unfolded interface, or phase boundary, that represents a jump in strain and is governed by the Abeyaratne–Knowles theory of phase transitions. We solve the governing equations using a finite difference method with moving nodes to represent phase boundaries. Our model can reproduce the experimental observations on the overstretching transition in DNA and coiled-coils and makes predictions for the speed at which the interface moves. We employ different types of kinetic relations to describe the mobility of the interface and show that this leads to different classes of experimentally observed force-extension curves. We make connections with several existing theories, experiments and simulation studies, thus demonstrating the effectiveness of the phase transitions-based approach in a biological setting.