碳-蒙脱石二维纳米复合粉体制备与提纯

以聚乙烯醇、钙基蒙脱石为原料,通过溶液插层、碳化和气流粉碎工艺和技术制备碳-蒙脱石二维纳米粉体。物相和粒径分析结果表明:在钙基蒙脱石、聚乙烯醇、水的质量比为5∶5∶90的反应体系中,获得层间距d(001)=2.11 nm的聚乙烯醇-蒙脱石插层型复合粉体;400℃碳化该复合粉体获得具有三明治结构特征的碳-蒙脱石复合粉体(d(001)=1.56 nm);将碳-蒙脱石复合粉体气流粉碎可得含碳质量分数为6%左右,平均片径约为2μm,厚度小于30 nm的碳-蒙脱石二维纳米粉体,以管状、单片和多片层堆积等形态存在于体系中。通过梯度离心分离法可以提取不同片径的碳-蒙脱石二维纳米复合粉体。     

On an Effect of Fine Ceramic Particles on the Structure of Aerogels

The addition of ferroelectric microparticles embedded in a nanostructured silica aerogel modifies the dry gel microstructure in a measurable way. The pore size distribution changes as well as the specific surface area. This indicates a possible positive effect of particles on the gelation characteristics. These modifications were observed in solutions gelling during a sounding rocket experiment in which approximately three minutes microgravity provided sufficient time for a convection and sedimentation free gelation to occur. The paper describes the synthesis procedures and the microstructures obtained for the gels under microgravity conditions.     

研磨介质对片状羰基铁结构及电磁性能的影响

分别以直径为6、1.5 mm的ZrO2磨球作为搅拌磨研磨介质制备片状羰基铁,对比研究这两种磨球对制备片状羰基铁的结构及电磁性能的影响。结果表明:采用直径为6 mm的ZrO2磨球所制备的羰基铁粉颗粒具有片状结构;而采用直径为1.5 mm的ZrO2磨球制备的羰基铁粉颗粒形状不规则,表面粗糙。研磨24 h时,采用直径为6 mm的ZrO2磨球所制备片状羰基铁粉微波吸收材料在2~18 GHz频段的反射率超过-15 dB的带宽为5 GHz,最大反射率为-30 dB。     

PBT树脂对核壳粒子增韧聚碳酸酯结构与性能的影响

合成了甲基丙烯酸甲酯-丁二烯-苯乙烯-甲基丙烯酸环氧丙酯(MBS-g-GMA)核壳粒子用于聚碳酸酯(PC)的增韧,并在PC/MBS-g-GMA共混物中引入聚对苯二甲酸丁二醇酯(PBT)以提高性能。PBT的加入使MBS-g-GMA在PC中分散更均匀;共混物缺口冲击强度进一步提高,PBT质量分数为20%时,冲击强度接近700J/m;PBT提高了PC/MBS-g-GMA共混物的熔体流动速率,使加工性能得到改善。断裂形态表明,PBT加入后共混物应力发白区尺寸增加,剪切屈服更明显,共混物韧性提高。     

Effect of Pulse Flows of Charged Particles on the Structure and Mechanical Properties of Metals

We investigate the effect of pulse flows of hydrogen, helium, and hydrogen–helium plasma of a specific power of 20–30 GW/m² on the surface structure and mechanical properties of vanadium, niobium, and Kh16N15M3B and Kh18N10T austenitic stainless steels. Plasma bunches acted for 2 sec with an average energy of particles of 2 keV. Tests of samples made of austenitic steels for tension showed that irradiation up to doses of 10¹⁸ cm^–2 strengthens them by a factor of 1.8 and decreases the relative elongation by a factor of 2.3–2.7. A layer-by-layer electron-microscopic analysis revealed that a cellular structure is formed in the surface layer 25 m in thickness as a result of irradiation, which explains the change in mechanical characteristics of the steels.     

Dependence of the Electronic Structure of a Graphene Nanoribbon on the Concentration of Adsorbed Particles

Technical Physics Letters - The effect of the indirect exchange of particles adsorbed on a graphene nanoribbon on the width of the induced energy gap and the effective mass of carriers is studied....     

Facile Growth of Porous Hierarchical Structure of ZnO Nanosheets on Alumina Particles via Heterogeneous Precipitation

ZnO nanosheets and nanoflakes were grown on alumina particles in the absence of surfactants via heterogeneous precipitation using urea, zinc acetate and bayerite as precursors. Thermo-gravimetric analysis （TGA）, X-ray diffraction （XRD） and Fourier transform infrared spectroscopy （FTIR） were used and the results indicated the formation of only two phases： wurtzite-type ZnO and γ-Al2O3. ZnO nanoflakes were grown on alumina particles in the samples with ZnO content of 40 and 60 wt%, By increasing the ZnO content to 80 wt%, a porous hierarchical structure of ZnO with nanosheet arrays appeared. Both of these nanoflakes and nanosheets were about 40-80 nm in thickness and about 1-2 μm in diameter. It was proposed that Zns（CO3）2（OH）6 nuclei undergo higher growth rates in thin sheets at edges of bayerite particles with a higher surface energy. The Brunauer-Emmett-Teller （BET） measurements proved a reachable high surface area for hierarchical structures of ZnO nanosheets, which could mainly be attributed to their unique growth on alumina particles. Also, UV absorption results revealed that ZnO--Al2O3 compositions still show the UV characteristic absorption of ZnO, which can evidence the presence of photocatalytic properties in ZnO-Al2O3 compositions.     

Development of High Strength Magnesium Based MMC Reinforced with SiC Particles for Satellite Structure Applications

The appearance of Metal Matrix Composites has opened a new area in structural design. The possibility of tailoring mechanical properties of structural metals reinforced with particles or fibers into specific spacecraft applications is very appealing. This paper deals with such a MMC, which is based on a magnesium alloy matrix and SiC reinforcement. The technology used is a commercial semi‐solid die‐casting, which promises a cost‐effective solution. The results of the first stage of this research are discussed with a focus on the satellite structure design application. The next steps of this investigation are also presented.     

微乳液的结构及其在制备超细颗粒中的应用

本文对微乳液的结构及特征作了概括的论述，着重对Ｗ／Ｏ微乳液制备超细颗粒的研究进行了评述，包括超细催化剂粒子、半导体粒子、磁性材料、陶瓷材料、感光材料等，分析了微乳液滴中超细颗粒的形成机理，讨论了用该法制备超细颗粒的影响因素，提出了这一研究领域的研究方向。     

颗粒分散

对颗拉在液体介质和空气介质中的分散过程进行了综述,概述了增强微细颗粒分散的手段在于合适的分散剂和高效的分散机械,并叙述了几种评价分散效果的方法,指出了颗粒分散研究存在的问题和发展方向.     

复杂质量结构产品参数设计的粒子群优化算法

首先提出了质量结构的概念,以质量结构模型表征复杂产品的质量特征,并基于产品的质量结构建立复杂产品系统参数设计模型,调用改进的粒子群优化算法求解,从而完成了复杂质量结构产品参数设计过程,为复杂质量结构产品的参数设计提供了一种新的思路。最后以气动换向装置的参数设计为例说明了所提方法的应用过程,验证了其可行性和有效性,得到设计参数的最优组合为换向活塞直径25.4851mm、气缸内气压3.2MPa及换向行程51.8mm。     

Classification of Fine Particles

ABSTRACT

Experimental results with two new classifiers for in-line and off-line operation are presented. The first type is a cyclone classifier, in which the vortex finder is exchanged with an impeller wheel enabling cut sizes between 5 and 100 µm. The second classifier is a high-end model, aiming at cut sizes in the range of l µm This classifier consists of a flat housing with tangential feed of product and secondary air. Experimental results with limestone, powder paint, and talcum are presented. The influence of main parameters such as air flow rate, circumferential velocity, and mass loading on the grade efficiency, as well as fines and coarse yield, will be discussed.     

Sampling Mixtures of Particles

Approximations are obtained for the second order moments of the distribution of volumes of differently sized particles in a sample. The sampler is filled randomly from a mixture of such particles. Some earlier results in the literature are modified and extended by use of a renewal theory technique based on Laplace transforms.     

固体颗粒的分散

详细阐述了固体颗粒分散的原理及实践。指出了颗粒分散研究所存在的问题和解决的办法。     

颗粒的表面粗糙度

收集了颗粒表面粗糙度的7种定义，对其适用性进行了定量评估。     

纳米陶瓷粉体的制备

纳米陶瓷是一种新型纳米材料,是现代陶瓷技术发展的最新领域。纳米陶瓷具有一些普通陶瓷所没有的优越性,如高硬度、高韧性、低温超塑性、易加工性等。为了使纳米陶瓷具有优良的性能,必须要有高纯度、化学组成均匀、颗粒大小能满足要求且粒度分布较窄的纳米陶瓷粉体作为原料。本文中主要介绍了纳米陶瓷粉体的制备方法:固相法、液相法和气相法,并分析比较了不同方法的优点与不足。     

颗粒粒度对碳化钨颗粒增强铁基复合材料界面的影响EI北大核心CSCD

采用常压烧结方法成功制备了碳化钨颗粒增强铁基复合材料,研究了碳化钨颗粒粒度对复合材料组织、界面及力学性能的影响。结果表明：随着碳化钨颗粒粒度的减小,颗粒熔解程度增大,主要熔解的是W2C,WC熔解的数量较少;界面主要的反应产物为Fe3W3C,Fe3W3C含量随着颗粒粒度的减小而增加,界面随着颗粒粒度的减小由连续变成间断,直至不存;颗粒粒度越大,材料的硬度及压缩强度均提高;当颗粒粒度为380-550μm时,反应生成物Fe3W3C与碳化钨颗粒体积比为1∶1,界面呈连续状,复合材料具有较好的综合性能。     

磁性高分子复合微球的制备

通过选用含有乙烯基的有机硅烷偶联剂对自制的纳米Fe3O4进行表面修饰后,采用悬浮聚合法成功制备了单分散磁性高分子复合微球,并重点研究了分散剂浓度、搅拌速度、磁含量等因素对制备的磁性高分子复合微球的影响.结果表明,合适的分散剂浓度和搅拌速度可以获得球径分布良好的磁性高分子复合微球,微球的磁感应强度可以通过改变Fe3O4磁性粒子的含量进行调节.