Easysizer20型激光粒度仪测定炭素粉末粒度分析

在电碳工业研究中,炭素粉末粒度的分析是炭素材料的重要技术指标之一,是炭素制品研究人员对工艺创新,提高产品质量的重要保证。本文通过激光粒度分析仪对石墨粉粒度测量进行的重复性试验,测试结果分析表明：激光粒度仪适合碳素粉末的粒度测量,同时讨论了激光粒度仪测量误差的主要来源,即来自仪器测量本身与测试前样品处理过程两个方面,其中样品处理过程是粒度测量中误差的主要来源。     

微米级多孔陶瓷的研究

本研究以石英和长石为主要原料，通过控制石英和长石的粒度和配比，研制出一种高强度的微米级多孔陶瓷，并讨论了管料粒径和烧成温度与其性能之间的关系。     

Near‐Infrared and Visible Absorption Spectroscopy of Nano‐Energetic Materials Containing Aluminum and Boron

Near‐infrared and visible absorption spectra are measured for nano‐energetic materials consisting of thirteen different types of Al or B nano‐particles in the 30 nm to 1 μm size range embedded in nitrocellulose or Teflon oxidizers, using an integrating sphere absorption spectrometer. The Al nano‐particle absorption is generally similar to the spectra of bulk Al, but the absorption strength is size‐dependent and up to twelve times more intense. Absorption coefficients are determined as a function of nano‐particle loading. For Al particles where the size is known, per particle cross sections are also determined. The ratio of cross section to volume decreases with increasing particle size. The implications of these measurements for nano‐sized energetic material analysis and for laser‐ignition experiments are briefly discussed.     

不同粒径纳米碱式碳酸锌的制备

以碳酸钠和氯化锌为原料,研究了直接沉淀法制备不同粒径的纳米碱式碳酸锌的工艺条件,讨论了工艺条件对粒径的影响规律。实验结果表明：采用直接沉淀法可以制备出平均粒径为7-16nm的纳米碱式碳酸锌;反应条件对纳米碱式碳酸锌的粒径有显著影响,反应物浓度越大,纳米粒子的粒径越大;反应温度越高,纳米粒子的粒径越小。     

超声波沉淀法制备不同粒径的纳米氧化锌

以硫酸锌和草酸为原料,采用超声波沉淀法,研究了不同粒径的纳米氧化锌的制备,讨论了不同工艺条件对粒径的影响规律。实验结果表明,采用超声波沉淀法可以制备出平均粒径为21～47nm的纳米氧化锌;反应条件对纳米氧化锌的粒径有显著影响:纳米氧化锌的粒径随草酸与硫酸锌配比的增大而增大,而随反应温度的升高而减小;并且沉淀剂的加入方式对所制备的纳米氧化锌的粒度也有较大影响:一次性将草酸沉淀剂倾倒入锌盐溶液比缓慢滴加所得微粒的粒径较小。     

有机/无机杂化渗透汽化优先透醇膜研究进展

渗透汽化优先透醇膜分离技术可有效解决燃料乙醇和丁醇生产中发酵产率较低的瓶颈问题,受到广泛关注。膜材料的选择与改性以及膜结构的构建是提高透醇性能的关键。有机/无机杂化膜可以实现有机和无机材料的优势互补,被认为是未来分离膜领域最重要的发展方向之一。本文扼要回顾了用于优先透醇渗透汽化分离的有机无机杂化材料,结合本文作者课题组的研究工作,重点阐述了杂化粒子的结构、粒径、界面相容性、纳微分散、负载量等因素对渗透汽化传递过程的作用机制,进一步对近年来发展的成膜新方法进行了总结。在此基础上,提出今后有机/无机杂化渗透汽化优先透醇膜研究的主要方向是发展新型纳米级、超疏水并与有机聚合物具有高度界面相容性的无机粒子,以及构建高负载量的纳微结构与超亲醇表面。     

自烧结炭材料的制备和性能研究

考察了球磨时间对生焦粉的粒度、粒度分布、挥发分含量的影响．以及生焦粉的上述物性参数对自烧结炭材料性能的影响，并初步分析了其影响机制。     

System development for size exclusion chromatography of starch hydrolysates

A system for the aqueous size exclusion chromatography (SEC) of starch hydrolysates has been developed. Sepharose CL is the chromatographic support material, and aqueous sodium hydroxide solution is the eluent. Various factors affecting the resolution of the proposed system are discussed. Support materials having small particle size and narrow particle size distribution are necessary for maximizing separation efficiency. The ionic strength of the eluent, however, has a negligible effect on separation efficiency. The fractionation range of the system has been broadened by connecting in series columns containing two different Sepharose-CL gel types according to the bimodal pore size distribution concept. Well-characterized sodium polystyrene sulfonate and dextran standards are used to calibrate this SEC system. The Coll–Prusinowski calibration procedure leads to a linear calibration curve over a wide molecular weight domain.     

Mechanism of Toughening in Rubber Toughened Polyolefin—A Review

The recent advances and theories in the studies of the toughening mechanism have been reviewed to explain the effect of rubber particles in different rubber modified Polyolefin materials. To elucidate toughening effect, major theories e.g., critical particle distance, particle size, micro deformation by stress field of rubber, shear yielding and crazing phenomena has been reviewed. Based on these theories, variety of blends of rubber modified Polyolefin materials has been compared but no one of these provided adequate information to be considered as total theory of toughening. To achieve the objective of toughening, it is important to maintain critical particle size, uniform particle distribution and good interfacial adhesion by inclusion of suitable compatibilizer in the matrix. Particular attention has been paid to study the type of morphology and bimodal distribution of rubber particles to elucidated toughening effect. Rubber particle cavitation, which comes from micro-voids and rubber phase interface are then further discussed.     

可控热膨胀聚合物复合材料的挑战和机遇(英文)

负热膨胀(negative thermal expansion,NTE)材料可作为填料制备可控热膨胀复合材料.高质量聚合物复合材料的研发面临诸多挑战,包括NTE 填料与基体材料的相容性,NTE相的稳定性,颗料形貌和尺寸的控制及其对混合稗度的影响.本文对影响聚合物复合材料成型中存在的诸多可能存 在的问题进行了述评,讨论了对有望用作填料的NTE材料的要求,即对NTE填料颗粒尺寸和相容性进行合成控制.通过晶体前驱体到目标NTE相 的拓扑转变,可实现对颗粒尺寸的最优控制.     

纳米TiO_2光触媒的制备及应用研究

以尿素为均匀沉淀剂、硫酸氧钛为原料制备粒径可控、分散性良好的纳米二氧化钛粉体。系统地研究了制备条件对粒径大小、粒子形貌的影响,探讨了均匀沉淀法形成纳米二氧化钛粉体的机理、晶体成长和晶型转化动力学以及光催化性能,并列举了作为光触媒的应用实例。     

电炉渣水分对水泥易磨性影响研究

对水泥不同孔径筛筛余物进行了化学成分分析,并结合水泥原材料化学成分、易磨性能,分析了不同粒径范围水泥原材料的分布情况及造成其区别的主要原因;探讨了混合材电炉渣水分对水泥易磨性的影响.     

微胶囊红磷阻燃剂的白度化研究

对微胶囊红磷阻燃剂的白度化进行了研究，探讨了囊材、囊材含量、粒径分布等因素对白度化的影响。结果表明，囊材中，以蜜胺树脂包覆的微胶囊红磷白度化效果最好，其含量的15%时，白度可达46.38%，且在囊材含量小于50%时，囊材含量越高白度效果越好。粒径分布窄的材料要比粒径分布宽的白度化效果好。     

Particle formation from solution in a gas fluidized bed. I

The mechanism of particle formation from solutions in a fluidized bed is discussed and information relating to particle size changes and the bringing about of steady-state conditions is presented. The experimental apparatus and methods are shown, followed by the results obtained with different model materials with and without solid material addition. It is proved that steady-state conditions can be created irrespective of the model material used by adding solid material to the system.     

Detailed study of distribution patterns of polycyclic aromatic hydrocarbons and isocyanates under different fire conditions

This study has examined the distribution patterns between gas phase and particle phase of some chemical compounds produced in fires. It has also addressed the question of the distribution of individual particle‐associated species between the different size‐ranges of particles. The chemical compounds studied and discussed in this paper are polycyclic aromatic hydrocarbons (PAHs), and isocyanates. The steady‐state tube furnace, ISO/TS 19700, was chosen as the physical fire model in order to study the production of particles from different types of fire exposure, that is, oxidative pyrolysis, well‐ventilated flaming fires and under‐ventilated flaming post‐flashover fires. Two materials were chosen for investigation, a polyvinyl chloride ( PVC) carpet and a wood board. The particle production from the two materials investigated varied concerning both the amounts produced and the particle size distributions. The analysis of PAHs showed that volatile PAHs were generally dominant. However, when the toxicity of the individual species was taken into account, the relative importance between volatile and particle‐associated PAHs shifted the dominance to particle‐bound PAH for both materials. The substantial degradation in the tests of the low polyurethane content of the PVC carpet, and the (4,4′‐methylenediphenyl diisocyanate)‐based binder in the wood board resulted in no or very small amount of quantifiable diisocyanates. Copyright © 2013 John Wiley & Sons, Ltd.     

适于配制高性能混凝土的硅酸盐水泥及其胶凝材料的最佳颗粒级配

根据国内外学者关于硅酸盐水泥及其胶凝材料最佳颗粒级配的论述,进一步探讨其颗粒分布,理顺和阐明硅酸盐水泥最佳颗粒级配与胶凝材料最佳颗粒级配之间的关系和不同点,从而为配制高性能混凝土提供在硅酸盐水泥及其胶凝材料颗粒级配方面的一些理论根据。     

Reference materials of defined particle size certified recently by the community bureau of reference of the european economic community

Some results from an international projects, supported by the Community Bureau of Reference of the European Economic Community, on the certification of five reference materials of defined particle size covering the overall range 0.35 – 650 μm are presented and discussed. Four of the reference materials were certified with respect to the mass distributions of the Stokes' diameters measured by an agreed gravitational sedimentation (Andreasen pipette) method. The coarsest of the reference materials was certified with respect to the mass distribution of the volume diameters of the particles using sieves, the ‘cut sizes’ of which were calibrated with respect to their equivalent volume diameters.Data were also obtained using several other methods, including X-ray gravitational sedimentation, sedimentation balance, centrifugal sedimentation, electrical sensing zone and photo-sedimentation methods. These were not used for certification but are presented for comparison purposes and to indicate the usefulness of the certified reference materials for the checking and calibration of many particle sizing techniques.     

Effect of Particle Size on the Room-Temperature Crystal Structure of Barium Titanate

The room-temperature tetragonal-to-cubic transformation in BaTiO₃ powders with decreasing particle size has been carefully studied, using materials prepared mainly by hydrothermal methods. Hydrothermal BaTiO₃ powders exhibited a more uniform particle size distribution than oxalate-route powders, with X-ray diffraction and electron microscopy indicating that powders 0.19 μm in size were fully cubic while powders 0.27 μ were completely tetragonal (within a 5% detection limit for cubic material) at room temperature. The tetragonal-to-cubic transformation temperature was also found to lie in the range of 121°± 3°C for BaTiO₃ powders with room-temperature ( c/a ) values > 1.008. No transformation could be detected using differential scanning calorimetry for BaTiO₃ particles with a ( c/a ) > 1.008 at room temperature. BaTiO₃ powder with a particle size just too small (0.19 μm) to be tetragonal at room temperature remained cubic down to 80 K. Different models for the cubic-to-tetragonal room-temperature transformation are discussed. Hydroxyl ions do not appear to greatly affect the cubic-to-tetragonal transformation, which appears to be essentially dependent on particle size. It is concluded that a model based on surface free energy, as previously discussed for the monoclinic-to-tetragonal transformation at room temperature of fine ZrO₂ particles, is consistent with the experimental data.     

一步法制备含羟基聚氨酯水分散体

以甲苯二异氰酸酯(TD I)、聚酯二醇和二羟甲基丙酸(DMPA)等为原料,采用一步法工艺制备了含羟基聚氨酯水分散体,探讨了聚酯二醇的种类、DMPA含量和NCO/OH摩尔比、中和剂及用量等对水分散体稳定性的影响,利用红外和粒度分析等方法表征了该体系的结构和胶粒尺寸。实验结果表明,随着亲水性离子用量增加,水分散体的粒径变小,稳定性增强,且在同样条件下采用不同的聚酯二醇制备的分散体粒径有一定的差异;采用JS307-110和JS308-110为原料时,最佳的NCO/OH摩尔比分别为0.91和0.85左右,其分散体粒径分别为60 nm和90 nm;采用三乙胺为中和剂,中和度为90%~100%时可得到稳定的水分散体。     

碳热还原法制备碳化硼粉末的工艺研究

采用碳热还原法制备了碳化硼粉末样品,讨论了硼碳比、煅烧合成和粉碎过程等工艺参数对其粉末性能的影响。借助XRD分析手段测试了其成分,并用化学方法分析了粉末的总碳含量,用激光粒度分布仪测试了其粒度分布。实验结果表明:以工业用硼酸和炭黑为原料,在1700～1850℃、保温0.5～1h煅烧合成能制得纯度较高的碳化硼粉末。其总碳含量为20.7%,接近理论值。中位径为32.56μm,经球磨粉碎后,其中位径可以达到2.42μm。