基于超声衰减谱和相速度的颗粒粒径测量

超声波在颗粒两相体系中传播,包含了大量颗粒粒径信息,结合理论模型,通过提取超声波有效衰减谱和相速度谱分析了颗粒的粒径分布。实验中,对体积分数为10%的3种不同粒径分布的聚苯乙烯-水悬浊液,通过双样法和插入取代法（单样法）分别获得宽带超声波衰减谱与相速度谱,以ECAH模型为理论基础,并分别用Twomey、ORT和Davidon-Fletcher-Powell优化算法,反演出悬浊液颗粒粒径分布。测量结果与显微镜图像法结果进行对比,中位径误差小于15%,表明了利用超声波衰减谱法（UASA）和相速度谱法（UPVSA）测量悬浊液颗粒粒径分布的可行性与可靠性。     

高频宽带超声衰减谱表征纳米颗粒粒度的方法

为研究纳米颗粒粒度的表征,在"长波长"条件下,通过提高超声波频率、增加频带宽度以及提高纳米颗粒悬浊液中超声波检测的稳定性等技术手段,实现了纳米级颗粒粒度分布的准确测量。实验中,采用中心频率50MHz宽频超声换能器,通过缓冲块内一次回波校验和变声程方法,以体积分数0.5%的纳米银-水悬浊液为验证性测量对象,获得了频率为25～62MHz的宽带声衰减谱。粒度反演过程中,采用McClementsBLBL理论模型结合最优正则化算法,将实测声衰减谱进行反演计算获得了纳米银颗粒的粒度分布,并证实了在50MHz频率下的理论测量下限可以达到5nm。与CPS离心沉降纳米颗粒测量仪、TEM图像等结果相比较,表明超声衰减谱法测量纳米颗粒的结果是可信的。     

Optical characterization of concentrated dispersions: applications to laboratory analyses and on‐line process monitoring and control

Light scattering methods are often used to study the stability of suspensions or emulsions and to estimate the dispersed phase properties such as particle size and volume fraction. However, such optical methods often require a previous dilution of the dispersion because of a limited measurement range, and are then unable to give information about the real physical state of dense heterogeneous media. A new technology based on multiple light scattering analysis and called Turbiscan has been recently developed by a French company, Formulaction, to fill this gap and to characterize both diluted and concentrated dispersions. In the first part, we review the physical concepts of multiple light scattering by dispersions. In relation to the optical analyser Turbiscan, we present physical and statistical models for the radiative transfer in dense suspensions. In the second part, we investigate the influence of particle volume fraction and particle size (polystyrene latex bead suspensions) on the backscattered and transmitted light fluxes measured by Turbiscan. The experimental data are compared with results from the physical models. In the last section, we use the optical analyser Turbiscan Lab to detect and characterize various concentrated dispersions destabilization (coalescence, flocculation, creaming and sedimentation), and then the Turbiscan On Line to monitor and characterize an emulsification process under ultrasonic agitation. Copyright © 2004 Society of Chemical Industry     

Further observations on the rheological behaviour of dense suspensions

The literature and recent WSL results on suspensions of spherical particles are surveyed and summarised. It is concluded that the steady shear properties of a dense suspension is not characterised by an unique viscosity or flow curve, but rather it is described by a wide viscosity distribution or a shear stress - shear rate flow band whose mean and standard deviation are functions of solids concentration, particle size distribution and viscometric geometry and dimensions. The standard deviation (or data spread) increases with solids concentration and with decreasing viscometer gap to particle diameter ratio. This property is due to poor sample reproducibility in respect of solids concentration and particle size distribution and the inherent two-phase nature of suspension which gives rise to particle migration and consequently non-uniform packing density or structure in a sample. Because a dense suspension is increasingly sensitive to these factors as concentration is increased, the standard deviation can be very large. Because the details of packing structure vary with flow, the viscosity distribution or flow band depends on viscometric flow geometry and measuring element dimensions. The implications of this conclusion on the study and characterisation of dense suspension property and the prediction of its behaviour in industrial handling and process equipment are discussed.     

纳米级碳酸钙悬浊液粒度分布的有效测定

利用超声衰减法对纳米级碳酸钙悬浊液中颗粒粒度分布进行了分析，为纳米颗粒悬浊液粒度分布的测量提供了新方向。实验结果表明，表面改性能够很好地改善纳米级碳酸钙在水中的润湿性及分散性，是实现纳米级碳酸钙悬浊液粒度分布有效测定的关键因素。另外，样品透射电镜分析结果表明，基于声衰减原理的声波粒度仪较好地反映了纳米级碳酸钙悬浊液中颗粒粒度分布情况。     

基于超声波阻抗谱的颗粒粒径表征方法

研究超声反射波谱与颗粒粒径及浓度之间的关系并发展一种基于超声波阻抗谱的颗粒粒径表征方法。对超声波波动理论模型适当变形,建立超声阻抗谱与颗粒粒径及浓度之间的关系;进一步通过数值模拟分析超声阻抗谱对颗粒浓度及粒径变化的敏感性;实验中使用中心频率10~100MHz超声波换能器,利用自发自收模式对超声波在缓冲层与介质界面上的反射波信号进行测量并分析,对体积中位径分别为7.69、21.58、66.64mm的聚苯乙烯悬浮液进行实验,获得阻抗谱并与数值模拟结果对比,根据实验阻抗谱进行数据反演获得样品颗粒粒度分布,并与图像分析结果进行了对比,结果显示,本方法可有效分辨3种颗粒样品的粒径。     

一种纳米颗粒粒度分布的非接触测量方法

研究了基于高频宽带超声衰减谱非接触式方法测量纳米颗粒悬浊液中颗粒相粒度分布问题. 通过理论分析和数值计算,选择ECAH模型作为反演计算的理论模型. 以1%(j)的纳米银水悬浊液作为实验样品,采用标称中心频率为50 MHz的超声换能器和变声程脉冲回波法进行了非接触测量,获得了可利用的高频宽带(10~50 MHz)超声衰减谱,结合理论模型和最优正则化算法反演出纳米颗粒的粒度分布. 实验结果与透射电子显微镜法和高速离心沉降法的测定结果吻合较好,表明该方法可测量悬浊液中纳米颗粒粒度分布.     

Mechanics and Microstructures of Concentrated Particle Gels

It is often assumed that the viscoelastic properties of dense colloids are determined by the colloid volume fraction, the interaction potential, as well as the particle size distribution and shape. The dependence of the viscoelastic behavior of particle suspensions and gels on these parameters has been widely studied, and is well understood in many cases. In contrast, our knowledge on the influence of microstructure on mechanical and rheological properties, in particular for high solid loading suspensions as used in ceramic processing, is much less developed. This aspect has been the focus of recent experiments, which show that small changes in microstructure can have dramatic effects on the mechanics and dynamics of concentrated colloidal gels. In this article, we attempt to give an overview of the influence of microstructure on the mechanical and rheological properties of colloidal systems. Particular attention is given to colloidal particle gels at high volume fractions.     

Effect of different types of carbon black on the mechanical and acoustic properties of ethylene–propylene–diene rubber

The effects of the incorporation of different types of carbon black as fillers on some selected physical and mechanical properties of ethylene–propylene–diene rubber (EPDM) based compounds were studied with the results of density, ultrasonic wave velocity, and tensile measurements. Ultrasonic wave velocities (both longitudinal and shear) were measured at frequencies up to 4 MHz at room temperature. The density, ultrasonic attenuation coefficient, and tensile strength results showed that rubber mixes containing general‐purpose furnace (GPF) black at a concentration of 25 phr had the best physical and mechanical properties. These results were interpreted to be due to the better compatibility of GPF black, which, because of its particle size and structure, filled the interstitial spaces in EPDM and provided better reinforcement of the elastomer. The use of a nondestructive technique such as ultrasonic measurement presents a new possibility for testing rubber and plastic products more efficiently. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A neural network-based soft sensor for particle size distribution using image analysis

Many industrial processes require on-line measurement of particle size and particle size distribution for process monitoring and control. The available techniques for reliable on-line measurement are, however, limited. In this paper, based on the captured surface images of randomly disarranged ore particles, the image uniformity was characterized. Particle size distribution was then investigated by applying a neural network-based modeling with the obtained image uniformity. The proposed soft sensor provides an improved prediction model and can be used for real time measurement of particle size distribution in the industrial operations.     

Complementary analysis techniques applied on optimizing suspensions of yttria stabilized zirconia

Three different polymers with different functional groups and similar molecular weight were tested as dispersing agents for suspensions of yttria stabilized zirconia in ethanol: polyvinyl pyrrolidone, polyethylene imine, polyvinyl butyral/acetal. The stability of the system was assessed considering, in details, all the processing steps, including suspension de-agglomeration, slurry manipulation, quality of sintered tapes microstructure, and final layer leak tightness. Different analytical techniques were used to monitor ceramic de-agglomeration and stability as a function of time, for different types of dispersing agent and to optimize the dispersants concentration: Electrokinetic Sonic Amplitude was used to obtain zeta potential, Multiple Light Scattering for evaluating sedimentation rate, and multi-wavelength laser light scattering for measuring particle size distribution. All the results agree upon excellent performance of polyvinyl pyrrolidone and polyethylene imine as dispersing agents. The stability and dispersing power were finally utilized for preparing concentrated suspensions for tape casting and subsequently to sinter the tapes into dense ceramic pieces.     

Effect of Ultrasonication on the Microstructure and Tensile Elongation of Zirconia-Dispersed Alumina Ceramics Prepared by Colloidal Processing

To obtain dense, fine-grained ceramics, fine particles and advanced powder processing, such as colloidal processing, are needed. Al₂O₃ and ZrO₂ particles are dispersed in colloidal suspensions by electrosteric repulsion because of polyelectrolyte absorbed on their surfaces. However, additional redispersion treatment such as ultrasonication is required to obtain dispersed suspensions because fine particles tend to agglomerate. The results demonstrate that ultrasonication is effective in improving particle dispersion in suspensions and producing a homogeneous fine microstructure of sintered materials. Superplastic tensile ductility is improved by ultrasonication in preparing suspensions because of the dense and homogeneous fine microstructure.     

大型喷雾粒径分布的图像法测量

雾化技术在能源、化工等领域应用广泛,研究雾化机理和优化雾化喷嘴性能的前提是对其雾化液滴尺寸及粒度分布进行准确有效的测量和表征。目前常用的雾化液滴粒度测量技术,如基于光散射或衍射原理的激光粒度仪和相位多普勒分析仪等,能够较准确地测量粒径分布比较窄、最大粒度在2000 μm以下的喷雾,但对含特大颗粒且粒径分布很宽的喷雾,往往难以得到可靠结果甚至不可能进行测量。本文提出了用图像法测量这类大流量喷雾,构建了图像法测量系统,编写了图像处理程序,经标定实验后,采用该系统对某喷嘴喷雾液滴粒径分布及规律进行了测量研究。研究结果表明图像法可用于大型喷雾液滴粒度及分布的测量。     

Particle grinding by high‐intensity ultrasound: Kinetic modeling and identification of breakage mechanisms

High‐intensity ultrasound, is sought as a means to break particles. A horn‐type ultrasonic transducer is used to apply HIU into a suspension of alumina particles causing breakage to occur. The rate of particle breakage is monitored continuously via in‐line laser‐based particle chord length measurement. Kapur function analysis is used to arrive at the grinding kinetics under variations of ultrasonic power, particle loading, temperature of the suspension and particle size. The first Kapur function increases monotonically with increase in input ultrasonic power. Increasing temperature also increases the first Kapur function but an optimum in the range investigated (10–50°C) is observed near 25°C. An exponential relation is found for the variation of first Kapur function with particle size, this being unique to ultrasound‐mediated particle breakage. The breakage mechanism is attributed mainly to particle abrasion. Different breakage mechanisms are observed at different temperatures. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Specific features of cellular detonation in polydisperse suspensions of aluminum particles in a gas

Formation of cellular detonation in polydisperse suspensions of fine aluminum particles in oxygen is studied by methods of numerical modeling. The influence of the particle size distribution on the character and scale of cellular structures is analyzed. The transition of plane to cellular detonation is modeled by two methods: development of small perturbations on the front and passing of the detonation front through a discontinuity of the channel cross section. The character of the cellular structures is independent of the method of their formation and displays signs of degeneration in polydisperse mixtures. As the scatter in the particle size increases, cellular detonation transforms to plane detonation. Stable propagation of a plane detonation wave is observed in mixtures with significant differences in the particle size. The critical share of the dominating fraction for complete degeneration in suspensions with three and five fractions of particles is identical.     

Separation of liquid-liquid and liquid-solid heterogeneous systems in single-flow vortex separators

A method for calculating the efficiency of single-flow vortex separators intended for removing liquid and solid suspensions from industrial waste is proposed. The method reveals a relationship between the efficiency of separation of heterogeneous systems and the particle size distribution of the dispersed phase, its flow rate parameters, and the geometry of the apparatus.     

Traditional and new applications for kaolin, smectite, and palygorskite: a general overview

Clays have been and continue to be one of the more important industrial minerals. Clays and clay minerals are widely utilized in many facets of our society. They are important in geology, agriculture, construction, engineering, process industries, and environmental applications. Traditional applications are many. Some of the more important include ceramics, paper, paint, plastics, drilling fluids, foundry bondants, chemical carriers, liquid barriers, decolorization, and catalysis.Research and development activities by clay scientists in academia, government, and industry are continually resulting in new and innovative clay products Many of these new applications are the result of improved processing, which provides clays of higher purity, more precise particle size and distribution, whiter and brighter color, modified surface chemistry, and other physical and chemical modifications. Some new and improved clay products include tailored or engineered paper coating kaolins, enhanced paint thickeners, nanocomposites for plastics, pillared clays as special absorbents and catalysts, clays for liquid fertilizer suspensions, clays for absorption of animal wastes, calcined kaolins with high brightness and low abrasion, faster casting clays, and clays with a very high modulus of rupture.Improvement of mining and processing techniques will lead to the continued growth of traditional clay applications and to the development of new and innovative clay products. Value added products are the wave of the future for the traditional industrial clay minerals.     

Nanomilling in stirred media mills

This paper investigates the production of stable nanoparticle suspensions. The experimental set-up allows the online measurement of the most important electrochemical properties and the particle size distribution of the product suspension as well as an adjustment of the pH-value for stabilization during the comminution process. Electrostatic stabilization is a strong tool to produce stable nanoparticle suspensions for sparingly soluble oxide components. In this contribution the influence of different operational parameters at stable suspensions properties on the grinding result in the nanometer size range is presented. In addition to alumina, the concept of electrostatic stabilization during wet grinding of nanoparticles is also applied to tin oxide.     

旋管动态过滤的研究进展

综述了近年来旋管动态过滤技术的主要研究成果 ,展望了其应用前景。提出采用高频超声波断层扫描技术在线测定沉积颗粒的粒度分布特性 ,是研究旋管过滤中颗粒沉积机理的一种有效方法     

On-line measurement of partical size distribution and partical concentration in suspensions by ultrasonic spectrometry

The principle of ultrasonic spectrometry is based on the measurement of the ultrasonic extinction caused by the presence of particles. From measurements at different frequencies and with the knowledge of the ultrasonic extinction cross section of the particles, a system of linear equations can be established and solved to obtain the particle size distribution and particle concentration. With an experimental apparatus covering the frequency range from 1.7 MHz to 81 MHz, particles ranging from 20 to 1000 μm in diameter may be analyzed. The measurements can be carried out with particle concentrations as high as 10% by volume.