The identification of particles using diagrams and distributions of shape indices

Using five kinds of real powder paricles, we obtained their shape indices from their pictures, attempted to identify the powder particles morphologically and studied the distribution functions of particle shapes and their relationships. The results were indicated as the follwing.It is possible to identify powder particles on the diagrams of the shape indices. The distributions of the shape indices are expressed by some distribution functions. The sample material and the particle size of sample particles affect the distribution of the shape indices in a different way. The distributions of two characteristic diameters and the distribution of shape index defined by ratio of these diameters are accurately connected by an equation.     

华能南京电厂粉煤灰中微珠特征及形成机理探讨

本文利用现代分析技术，对华能南京电厂粉煤灰中玻璃微珠的一些物理性质和微结构特征，如形貌、粒径分布、颗粒类型、矿物相种类和含量、漂珠的丰度、微珠的密度和壳壁厚度以及热稳定性等，进行了详细研究，并对空心微珠和成因机制进行了讨论。     

形状记忆功能纤维及纺织品

形状记忆功能纺织品的开发是近年来在纺织材料学中研究较热门的新兴技术。介绍了该材料国内外的研究进展,对形状记忆合金类、形状记忆聚合物类和形状记忆水凝胶类功能纺织品进行了概述;并对各种不同类别的形状记忆功能纺织品的形变机理和适用领域进行了详细阐述,最后展望了形状记忆功能纺织品的未来。     

Spherical particles for automotive powder coatings

Clear powder coatings that consist of spherical particles with a narrow particle size distribution were produced via a suspension method that involves the agglomeration and unification of smaller particles. These powder coatings have the advantages of excellent powder flowability and high transfer efficiency. This behavior is attributable to the spherical particle shape and absence of finer particles. This production method has been developed for thinner film build clear coats with improved surface smoothness as compared to powder coatings produced by conventional methods.     

A simple feature-space representation of particle shape

Particle shape information is needed to describe the behavior of particles in both industrial processes and in products. It is also needed to predict the sedimentary properties of particles in fluids, and the transport characteristics of particles in streams, river, and on beaches.In this paper, a new method of representing particle shape is suggested, which takes into account the form and roundness features of the particles. These features are represented in three-dimensional space utilizing triaxial contour diagrams in the horizontal planes, and roundness in the vertical plane.Data are presented for a beach sand which has been mechanically shape classified, and the potential of the method for related fine particle applications is then discussed.     

板蓝根颗粒的X-射线衍射Fourier指纹图谱分析

采用粉末X-射线衍射Fourier指纹图谱法,建立了中成药板蓝根颗粒的分析鉴别新方法.通过对3种板蓝根中药材和9种板蓝根颗粒进行分析鉴定,分别获得它们的对照X-射线衍射Fourier指纹图谱及特征标记峰值.结果表明,X-射线衍射Fourier指纹图谱是一种鉴定中药材和中成药的便捷方法.     

Study of ageing of dry powder inhaler and metered dose inhaler by atomic force microscopy

Investigation by atomic force microscopy (AFM) is necessary for the analysis of the interaction between grains of powder used in dry powder inhalers (DPIs) in controlled atmosphere and metered dose inhalers (MDIs) in liquid phase. Measurements of nanonewton forces leading the powder cohesion resulting between active substances were performed. We have developed a protocol based on standard analysis: Scanning Electron Microscopy (SEM) and nano-analysis. This paper deals with the direct analysis of morphology evolution performed over three months in controlled atmosphere at various relative humidities (RH) and temperatures for DPIs and in a mimetic HFA134a liquid for MDIs in order to understand the behaviour of a binary mixing. Atomic force microscopy was also employed to characterize the interactions between particles.In this study, colloid probe AFM has been used to measure adhesive forces between drug particles in a controlled atmosphere for DPIs and in a liquid medium for MDIs. A link connecting the colloidal powder quality and particle-particle interactions is extracted from this study.     

Measurement and statistical analysis of shape of particles comminuted by a screen mill

Soma sands with particle sizes of 500 to 710 μm were comminuted by a screen mill. The impact velocity of the hammers was set at 32.3, 61.6 and 91.0 m/s, respectively, and products with sizes of about 10 to 350 μm were obtained. The rectangular co-ordinates of the periphery of particle projections were measured by a digitizer. Sixteen kinds of shape index were determined from each set of periphery data. These indices could be reduced by factor analysis to four main shape characteristic factors: elongation, global roughness, surface roughness and angularity, respectively. They contained about 85% of the information of the sixteen shape indices and expressed well the characteristics of comminuted particle shape. Several small particles comminuted at low impact velocity (32.3, 61.6 m/s) had large values of the first factor and high elongated shape. In the other cases, no appreciable differences in shape as characterized by the four factors were observed between the original particles and the comminuted particles of size approximately 10 to 350 μm.     

颗粒形状对全散射法测量颗粒物质量浓度的影响

燃煤电厂排放颗粒物作为大气颗粒物主要来源之一受到广泛关注,实现颗粒物质量浓度的精确在线监测意义重大。激光全散射法作为一种常用的颗粒物质量浓度在线监测方法,受颗粒特性影响较大,易造成较大的测量偏差。为探究颗粒形状对全散射法测量的影响,搭建了全散射法测试台架,并采用球形二氧化硅颗粒对测试系统进行标定,标定结果显示,球形二氧化硅颗粒质量浓度与消光程度高度线性相关,相关系数R2>0.99,测量浓度与真实浓度偏差仅为1.8%。进一步采用633 nm与532 nm波长激光分别对3种非球形(棱形、不规则和片状)二氧化硅颗粒进行测试试验。测试结果显示,3种形状颗粒物的质量浓度与消光程度均高度相关,R2均高于0.99;3种形状颗粒物质量浓度的测量值与真实值偏差与颗粒形状及激光波长相关,对比发现,入射波长为633 nm时,不规则、棱形和片状颗粒的质量浓度测量值与真实值的测量偏差分别为16.1%、27.4%和36.6%;入射波长为532nm时,3种颗粒质量浓度的测量偏差分别为4.8%、11.4%和17.4%;颗粒形状一致条件下,532 nm入射波长时的测量偏差明显较小,通过波长的选择可降低颗粒形状变化造成的测量偏差。     

Characterizing residence times of powder samples on sieves

Recently developed in the author's laboratory, particle chromatography is the most powerful technique in existence both for characterizing and separation particles in the 1 μ to 1 cm size range. Operating on the principle that for a given size seive, a particle of a given shape has a fixed residence time, cascading the particles through n identical sieves separates particles on the basis of shape. The first of a family of instruments, using this new technique, is called the Sieve Cascadograph, and is specifically designed to characterize naturally occurring and manufactured powders such as abrasives and comminuted material, food grains such as wheat and corn, and naturally occurring materials such as sand and soils. Capable of separating particles with subtle differences in shape, the Sieve Cascadograph is a good laboratory or quality control instrument for quantitative differentiation between similar powder samples.     

Three-dimensional shape analysis of coarse aggregates: New techniques for and preliminary results on several different coarse aggregates and reference rocks

The shape of aggregates used in concrete is an important parameter that helps determine many concrete properties, especially the rheology of fresh concrete and early-age mechanical properties. This paper discusses the sample preparation and image analysis techniques necessary for obtaining an aggregate particle image in 3-D, using X-ray computed tomography, which is then suitable for spherical harmonic analysis. The shapes of three reference rocks are analyzed for uncertainty determination via direct comparison to the geometry of their reconstructed images. A Virtual Reality Modeling Language technique is demonstrated that can give quick and accurate 3-D views of aggregates. Shape data on several different kinds of coarse aggregates are compared and used to illustrate potential mathematical shape analyses made possible by the spherical harmonic information.     

Synthesis of Colloidal Cobalt Nanoparticles with Controlled Size and Shapes

A method of producing high quality magnetic colloidal dispersions by the rapid pyrolysis of cobalt carbonyl in an inert atmosphere was employed to produce monodispersed, stabilized, defect-free -cobalt nanocrystals with spherical shapes and sizes ranging from 3 to 17 nm, as well as cubic and rod-like shaped particles. The size distribution and the shape of the nanocrystals were controlled by varying the surfactant composition (oleic acid, phosphonic oxides and acids), its concentration and the reaction temperature. These particles have been observed to produce 2D self-assemblies when evaporated at low rates in a controlled atmosphere. A combination of X-ray powder diffraction; transmission electron microscopy; and SQUID magnetometry has been used to characterize both the dispersed nanocrystals and the assembled superlattices.     

Dynamic viscoelastic properties and thermal properties of Ni powder–epoxy resin composites

The composite materials containing metal Ni powder of 5–15 μm in size were prepared by use of the matrix epoxy resin of glycidyl amine crosslinked with bis-4-amino-3-methylcyclohexyl methane and 2,4-diamine 3,5-dimethyltoluene. Dynamic viscoelastic properties of the composites at various volume fraction (Φ_p) of Ni powder have been measured over the temperature range from 30 to 300°C. The peak temperatures in dynamic loss modulus–temperature diagrams of the composite increased with increasing Φ_p, although the peak position was abruptly shifted to lower temperatures in the range of Φ_p more than 0.245. At this high concentration of Φ_p, agglomeration of the particles occurring in the composite lead to reduction of the interaction between Ni particle and epoxy resin. Parallel studies on the thermal conductivity (λ) of the composites materials showed that the value of λ at Φ_p = 0.245 increased by approximately 7 times that of the original epoxy resin. The shape of Ni particles also affected the thermal durabilities of the composites; the rough surface of Ni powder yields a higher storage modulus of the composite than that of the materials containing the powder with a smooth surface, which had been brought through a ball-milling process. The finding suggested that the increasing in specific surface area of the powder improved the thermal durability of the composites as well as their mechanical properties. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2593–2598, 1998     

Shape memory polyester-based nanomaterials: cutting-edge advancements

ABSTRACT

Shape memory polymers have gained immense importance across technical industries ranging from aerospace and electronics to biomedical fields. This article presents state-of-the-art overview of versatile shape memory polyesters and derived nanocomposites. Shape memory polyesters such as polylactic acid, polyhydroxyalkanoate, polycarbonate, and polyester blends have been identified. Shape memory polyesters have also been reinforced with nanoreinforcements including fullerene, graphene, carbon nanotube, and polyhedral oligomeric silsesquioxane (POSS). Consequently, different groups of stimuli-responsive polyester nanocomposites have been discussed such as polyester/graphene, polyester/carbon nanotube, polyester/fullerene, and polyester/POSS. Future development of shape memory polyesters may reveal superior electrical, mechanical, and thermal performance for technical applications.     

Morphology-Dependent Dye-Removal Mechanism as Observed for Anatase-Titania Photocatalyst

Nanotubes of anatase-titania with very high specific surface-area have been synthesized via hydrothermal using the as-received powder of anatase-titania particles, having lower specific surface-area, as a precursor. Various analytical techniques have been used to characterize the as-received powder and hydrothermally processed nanotubes of anatase-titania for their morphology, size, structure, specific surface-area, pore size distribution, photoabsorption, and photoluminescence properties. The dye adsorption and photocatalytic activity of as-received powder and nanotubes of anatase-titania have been studied using the methylene blue as a model catalytic dye agent. It has been shown that, due to higher specific surface-area, the dye removal using the nanotubes of anatase-titania is primarily via surface-adsorption mechanism in the dark; while, that using the anatase-titania particles is via photocatalytic degradation mechanism under ultraviolet-radiation exposure. Hence, the mechanism of dye removal from an aqueous solution using the anatase-titania appears to be highly morphology-dependent.     

邻苯二甲酸酯类化合物生物降解的电性拓扑研究

计算了9种邻苯二甲酸酯的两类拓扑指数值:(1)基于原子类型特征的电性拓扑状态指数(En);(2)自分子拓扑图的邻接矩阵衍生的分子连接性指数(mXtv).这些拓扑指数被用于关联9种邻苯二甲酸酯的生物降解速率常数(Kb)及其半衰期(lnt1/2),经向后逐步回归与偏最小二乘法,建立了定量结构-生物降解相关(QSBR)模型,其四元最佳方程的相关系数(R2)依次为0.995、0.986.这两个方程的平均估算误差接近实验误差,并通过Jackkn ife的逐一剔除法证明有良好的可靠性与稳定性.结果表明,这些模型能够较好地解释邻苯二甲酸酯的生物降解性的递变规律.     

Effect of Activated Carbon Bed on Binder Removal from Ceramic Injection Moldings

Weight losses during the binder removal from ceramic injection moldings that have been placed in beds of activated carbon powder and two types of alumina powder were compared. The effect of the specimen size and shape on debinding in a bed of activated carbon was investigated. Because of the structure of its particles, activated carbon powder allowed binder losses in ceramic moldings that consisted of submicrometer-sized particles to increase at a temperature of 130°C. The binder loss in a bed of activated carbon was dependent on the ratio of surface area to volume of the body that was extracted. Renewal of the sorption abilities of the bed of activated carbon after saturation with binder increased the rate of binder removal.     

Formselektive Katalyse in Zeolithen

Shape selective catalysis in zeolites . In recent years, shape selective catalysis has become an important field of heterogeneous catalysis. Shape selectivity can arise if the pore width of the catalyst resembles the dimensions of molecules or transition states involved in the catalytic reaction. Up till now, zeolites are employed almost exclusively as shape selective catalysts. Examples of the different kinds of shape selectivity are given. The classification of Weisz and Csicsery is presented. More recent concepts are discussed. Measures for a control of shape selectivity are outlined. For a routine characterization of shape selective catalysts, certain test reactions are shown to be useful tools; the two most important examples are the determination of the constraint index and the hydroconversion of long chain n-alkanes.     

Periodic solutions in a porous catalyst pellet—homoclinic orbits

The analysis performed as well as extensive numerical simulations have revealed the possibility of the generation of homoclinic orbits as a result of homoclinic bifurcation in the model which describes transport phenomena and chemical reaction in a porous catalyst pellet. A method has been proposed for the development of a special type of diagrams—the so-called bifurcation diagrams. These diagrams comprise the locus of homoclinic orbits together with the lines of limit points bounding the region of multiple steady states as well as the locus of the points of Hopf bifurcation. Thus, they define a set of parameters for which homoclinic bifurcation can take place. They also make it possible to determine conditions under which homoclinic orbits are generated.Two kinds of homoclinic orbits have been observed, namely semistable and unstable orbits. It is found that the character of the homoclinic orbit depends on the stability features of the limit cycle which is linked with the saddle point.Very interesting dynamic phenomena are associated with the two kinds of homoclinic orbits; these phenomena have been illustrated in the solution diagrams and phase diagrams.     

Silicon Particle Formation by Pyrolysis of Silane in a Hot Wall Gasphase Reactor

The formation of silicon powder by pyrolysis of silane diluted in argon at different concentrations has been studied. A hot wall gasphase reactor was used for the thermal decomposition of SiH₄ at 1000 °C and atmospheric pressure. The composition, morphology, size, and shape of the particles produced has been studied utilizing electron microscopy, X‐ray diffraction, infrared spectroscopy, and BET gas adsorption. Depending on the experimental conditions, agglomerates of polycrystalline, sintered particles have been obtained, which are composed of nanocrystallites of about 25 nm in size.