Manipulation of upconversion property and enhancement of sensitivity by tailoring the local structure

Tailoring the local crystal environment around the activators is one of an important way to enhance the upconversion (UC) luminescence intensity. Herein, we substitute the Y³⁺ lattice with La³⁺ ion gradually in Y₂Ti₂O₇:Yb³⁺, Er³⁺ phosphor and investigate the effect of La³⁺ concentration on the UC luminescent properties as well as the temperature sensing behaviors. During the phase transformation process from cubic Y₂Ti₂O₇ to monoclinic La₂Ti₂O₇, the La³⁺ ions also play an important role on the adjustment of size and morphology of particles. Furthermore, the cooperation of La³⁺ ion is in favor of the crystal growth toward the easy growth directions. The UC luminescence intensities can be enhanced efficiently with the increasing of La³⁺ concentration. The sensitivity for temperature sensing can be improved by the increasing of La³⁺ concentration in the Y₂Ti₂O₇ and La₂Ti₂O₇ two-phase coexistence system and the maximum S_A is 45.3 × 10⁻⁴ K⁻¹ at 410K when the La³⁺ concentration is 80%. The maximum S_A and corresponding temperature can be adjusted by controlling the La³⁺ concentration, which means that (Y_0.94-xLa_x)₂Ti₂O₇: Er³⁺/Yb³⁺ phosphors may be applicable to different working environment.     

钢管混凝土叠合柱在深圳某工程中的应用

钢管混凝土叠合柱是在钢管混凝土柱的截面中部设置钢管混凝土的一种叠合构件,已形成我国自主开拓的一种结构体系。本文介绍了圆形截面叠合柱在住宅公寓及办公楼中的应用,主要包括了叠合轴压比的计算、叠合柱与混凝土梁相接时的节点处理、叠合柱与钢梁相接时的节点处理等。     

Influence of AlF3 Concentration on Microstructures and Energy Storage Properties of Barium Strontium Titanate Glass Ceramics

The effect of AlF₃ concentration on the microstructures and energy storage properties of barium strontium titanate glass ceramics was studied. Scanning electron microscopy investigations revealed that the addition of AlF₃ significantly changed the microstructure morphology of the glass ceramics. Dielectric measurements indicated that the dielectric constant has a maximum value at 2 mol% AlF₃ concentration. Using polarization‐electric field measurements, the energy storage properties were found to be influenced strongly by the AlF₃ concentration. The correlation between the microstructure and the dielectric property in the barium strontium titanate glass ceramics with different AlF₃ concentrations was qualitatively discussed.     

基于AVC理论的南京桦墅村生产性景观评价模型的研究

为了促进我国乡村一二三产业的融合发展,对以农业为主导的乡村生产性景观进行合理有效的评价,是乡村景观设计策略的重要组成部分.文章基于AVC理论,从吸引力(Attraction)、生命力(Vitality)、承载力(Capacity)3方面,以层次分析法及专家咨询法选取了8个评价因素层、28个指标层,以定性与定量相结合的方...     

Polytypism of SiC and interfacial structure in SiCp/Al composites

In the present work, the polytypism of SiC and the interfacial structure between SiC and Al were investigated using X-ray diffraction (XRD) and high resolution transmission electron microscopy (HREM). It was approved that 15R could be juxtaposed with 6H stacking sequences in the same SiC reinforcement and a structural transformation zone was also observed. The Al₄C₃ compound can nucleate on SiC at the SiC/Al interface with the growth orientation parallel to the C axis of SiC. Mechanisms for the observed phenomena were also discussed in detail.     

Preparation and characterization of Ce0.8Sm0.2O1.9(SDC)–carbonates composite electrolyte via molten salt infiltration

Ce_0.8Sm_0.2O_1.9 (SDC)–carbonates composite electrolytes for SOFCs have been prepared for the first time via molten salt infiltration approach by infiltrating LiNaCO₃ molten carbonates into porous SDC ceramic. A range of techniques including XRD, SEM, Mercury Porosimeter and A.C. impedance, have been employed to characterize SDC and composite electrolytes. It has been found that the porous SDC shows a monomodal pore size distribution with average pore size of 300 nm. SDC–carbonates composite electrolytes via molten salt infiltration show a kind of SDC/carbonates co-continuous composite structure, with one SDC ceramic skeleton of bonded grains surrounded by carbonates phase. Both phases provide a continuous pathway for ionic transport and a large interfacial surface area. SDC–carbonates composite electrolytes prepared by molten salt infiltration have a higher mechanical strength than that of mixing–pressing composite electrolytes. Moreover, they show higher conductivity and lower activation energy than that of mixing–pressing composite electrolytes according to the measurements of AC impedance in the temperature range of 350 °C–650 °C.     

PC600LC-6型挖掘机主泵液压控制系统功能及原理研究

液压挖掘机是水电施工中最常用的设备之一.目前,液压挖掘机都是集光、机、电、液压等先进技术于一体.尤其是其液压系统,机构复杂.当设备液压系统发生故障时,如果不充分掌握其液压原理,难以进行准确的故障诊断,给设备维修带来困难.     

电子封装用金刚石/铜复合材料界面与导热模型的研究进展

金刚石/铜复合材料具有高热导率、高强度、热膨胀系数可调的优点,是极具发展潜力的新一代电子封装材料。针对复合材料两相界面结合较差的问题,目前主要采用添加活性元素在界面处生成碳化物层的方法来改善。论述了活性元素添加的两种手段,即基体合金化和金刚石表面金属化的研究进展,并归纳了金刚石/铜复合材料导热模型的发展情况,最后提出了金刚石/铜复合材料在界面研究中面临的挑战和其未来努力的方向。     

Adsorption of copper ions from aqueous solution by citric acid modified soybean straw

The objectives of the present study were to convert soybean straw to a metal ion adsorbent and further to investigate the potential of using the adsorbent for the removal of Cu(2+) from aqueous solution. The soybean straw was water or base washed and citric acid (CA) modified to enhance its nature adsorption capacity. The morphological and chemical characteristics of the adsorbent were evaluated by spectroscopy and N(2)-adsorption techniques. The porous structure, as well as high amounts of introduced free carboxyl groups of CA modified soybean straw makes the adsorbent be good to retain Cu(2+). The adsorption capacities increased when the solution pH increased from 2 to 6 and reached the maximum value at pH 6 (0.64 mmol g(-1) for the base washed, CA modified soybean straw (CA-BWSS)). The Cu(2+) uptake increased and percentage adsorption of the Cu(2+) decreased with the increase in initial Cu(2+) concentration from 1 mM to 20 mM. Both the Langmuir and Freundlich adsorption isotherms were tested, and the Freundlich model fited much better than the Langmuir model. It was found that CA-BWSS have the highest adsorption capacity of the four kinds of pretreated soybean straw.