不同速度及载荷作用下焦粉润滑特性的试验研究

将焦粉导入摩擦副间,研究不同速度及载荷作用下钢、焦粉、耐火砖三体接触状态下焦粉润滑特性. XRD测试结果表明焦粉微晶结构发生石墨化.通过对比无润滑及焦粉润滑对摩擦界面的影响,进一步验证了焦粉具有良好的润滑性能.此外,通过改变试验的速度及载荷,探究不同速度及载荷作用下粉末层成形机理及焦粉润滑特性.结果表明:载荷为5 MPa,速度分别为0.05、0.20和0.40 m/s时,速度越大,粉末层越厚,焦粉润滑性能越好;而速度为0.55 m/s时,由于速度过大,焦粉被抛出摩擦界面,表面发生严重磨损,并引发振动发生.速度为0.40 m/s,载荷分别为5和15 MPa时,载荷越大,越不利于形成粉末层,载荷分别为20和25 MPa时,粉末层发生不同程度的破坏,表面磨损严重.     

活性粉末混凝土力学性能及冻融性能研究

活性粉末混凝土具有优异的力学性能和耐久性,本文按照正交设计方法设计了9组不同配合比的活性粉末混凝土,通过试验研究了其基本力学性能及抗冻融性能,分析了水胶比、硅灰水泥比和钢纤维含量等因素对活性粉末混凝土力学性能及抗冻融性能的影响规律。研究表明,水胶比是影响活性粉末混凝土力学性能及抗冻融性能最主要的因素,钢纤维含量对活性粉末混凝土抗折和劈裂强度影响较为显著,对其抗压强度和抗冻融性能的影响不明显。本文根据试件破坏的现象对钢纤维作用的机理做了初步的探讨。     

FLOW PROPERTIES OF COHESIVE NANOPOWDERS

The fundamentals of cohesive powder consolidation and flow behaviour using a reasonable combination of particle and continuum mechanics are explained.By means of the model “stiff particles with soft contacts”,the influence of elastic-plastic repulsion in particle contacts is demonstrated.With this as the physical basis,the stationary yield locus,instantaneous yield loci and consolidation loci,flow function and compression function are presented.The flow properties of a very cohesive titania nanopowder (ds=200nm) are shown.These models are used to evaluate shear cell test results as constitutive functions for computer aided apparatus design for reliable powder flow.     

基于二肽的相选择胶凝剂对水中油污和有毒染料的清污性能

设计合成了一系列相选择胶凝剂(3a-3e),并通过¹H和¹³C核磁共振波谱和质谱对其结构进行了表征。 在有机溶剂和水的混合体系中对目标化合物进行相选择凝胶性能试验,结果表明化合物3c在粉末状态下表现出出色的相选择胶凝能力,在室温下可通过摇晃从油水两相体系中快速除去苯、甲苯、二甲苯和汽油。 另外,实验证明以3d-苄醇凝胶作为吸附剂可以实现有毒染料溶液的有效吸附,而且通过紫外-可见光谱实验可以对其清除效果进行量化。 操作简单和高效除污等优点表明这些二肽胶凝剂在污水纯化处理中具有广阔的应用前景。     

MULTI-SCALE AGGREGATION OF PARTICLES IN GAS-SOLIDS FLUIDIZED BEDS

The multi-scale characteristics of clusters in a fast fluidized bed and of agglomerates in a fluidized bed of cohesive particles are discussed on the basis of large amounts of experiments.The cluster size and concentration are dominated by the local voidage of the bed.A cluster consists of many sub-clusters with different sizes and discrete par-ticles,and the sub-cluster size probability density distribution appears as a negative exponential function.The agglom-erates in a fluidized bed of cohesive particles also possess the multi-scale nature.The large agglomerates form a fixed bed at the bottom,the medium agglomerates are fluidized in the middle,and the small agglomerates and discrete parti-cles become the dilute-phase region in the upper part of the bed.The agglomerate size is mainly affected by cohesive forces and gas velocity.The present models for prediction the size of clusters and agglomerates can not tackle the in-trinsic mechanism of the multi-scale aggregation,and a challenging problem for establishing mechanistic model is put forward.     

X射线衍射法钾混盐无标样定量相分析

采用EVD、TOPAS应用软件和TOPAS结构数据库以及无机晶体结构数据库,对一些混合盐样品(如钾混盐、尾矿等)进行了X射线粉末衍射无标样定量相分析全谱拟合模拟研究。在用Rietveld分析法对上述样品中无机盐成分的X射线衍射谱进行模拟过程中,选择基本参数函数为峰形函数,并通过March-Dolase择优取向校正拟合,提高了拟合精度。测得钾混盐样品中钾盐镁矾相含量为72.44%,岩盐相含量为27.56%,误差值Rwp(17.45),Rp(12.21)和拟合度S(4.91)均有所降低。     

MICROSTRUCTURE AND CHARACTERISTICS OF MECHANICALLY ACTIVATED W-Cu POWDER

Introduction Tungsten-copper alloy powders are used in many fields on account of the high electric and thermal conductivities of copper and high melting point of tungsten. W-Cu pow-ders, as prepared conventionally by means of infiltration, has the disadvantage of inhomogeneity in microstructure, and are difficult to work with after sintering. Increasing the particle activity of these powders tends to accelerate the sintering process, lower the sintering temperature and improve their properties…     

2003 Asian Particle Technology Symposium

The 2nd Asian Particle Technology Symposium (APT2003), held from Dec. 17 to 19, 2003 in Penang Island, Malaysia,was attended by 178 participants from 17 countries, mainly the Asia Pacific but also including the Middle East, Europe,and USA. The symposium was chaired by Prof. Wan Ramli Wan Daud. The main objectives of the symposium were:     

Numerical investigation into the influence of the punch shape on the mechanical behavior of pharmaceutical powders during compaction

During the production of pharmaceutical tablets using powder compaction, certain common problems can occur, such as sticking, tearing, cutting, and lamination. In the past, the compressibility of the powder was calculated only along the axis of the device; consequently, critical areas of the material throughout the volume could not be identified. Therefore, finite element method （FEM） can be used to predict these defects in conjunction with the use of an appropriate constitutive model. This article summarizes the current research in the field of powder compaction, describes the Drucker-Prager Cap model calibration procedure and its implementation in FEM, and also examines the mechanical behavior of powder during compaction. In addition, the mechanical behavior of pharmaceutical powders in relation to changes in friction at the wall of the system is examined, and the dependence of lubrication effect on the geometry of the compaction space is also investigated. The influence of friction on the compaction process for the flat-face, fiat-face radius edge, and standard convex tablets is examined while highlighting how the effects of friction change depending on the shape of these tablets.     

SAB-16型介孔材料的制备、表征及表面改性——介绍一个材料化学综合实验

介绍了一个材料化学综合实验——SBA-16型介孔材料的制备、表面改性以及修饰。该实验将化学反应热力学、动力学以及表面吸附等相关物理化学理论知识与仪器分析相结合,学生不仅可以通过材料的制备过程了解材料形成的原理,还可以在材料的表征过程中学习X射线粉末衍射、透射电子显微镜、氮气吸附/脱附仪以及吸附重量分析仪等的使用方法,提升实验操作技能,培养学生解决问题的能力和创新意识。