Size distribution measurement of floating particles in the Allen region by a buoyancy weighing-bar method

The particle size distributions of spherical or cylindrical solid particles in the Allen region were measured using a buoyancy weighing-bar method. The particle size distribution obtained in the buoyancy weighing-bar method agrees with those measured by a laser diffraction/scattering method and a sieving method. The present study demonstrates that a buoyancy weighing-bar method is suitable for measuring the particle size distribution of a floating solid in the Allen region.     

The method to determine the optimum refractive index parameter in the laser diffraction and scattering method

It is the most important and difficult problem to decide the refractive index of sample particles in particle size distribution measurements using the laser diffraction and scattering method. In this study, the method to decide both particle size distribution and refractive index of particle is investigated. The new method to determine the refractive index of particles is applied for several sample powders (polystyrene latex, glass beads, etc.) and the usefulness of this new method is confirmed.     

空心玻璃微珠对阻尼固体浮力材料力学性能影响研究

通过空心玻璃微珠（HGB）的体积分数、粒径、偶联剂改性等系列实验,总结分析了空心玻璃微珠对阻尼固体浮力材料力学性能的影响。结果表明,随着空心玻璃微珠体积分数的增加,浮力材料的吸水率逐渐增大,而密度、压缩强度和阻尼损耗因子逐渐降低;随着空心玻璃微珠粒径的增大,浮力材料的吸水率和阻尼损耗因子逐渐增加,而密度、压缩强度逐渐减小;添加偶联剂可有效改善空心玻璃微珠与环氧树脂的界面结合性,提高浮力材料的性能。      

中空玻璃微珠粒度分布分形特征及其与空隙率关系的研究

为研究中空玻璃微珠粒度分布分形特征与空隙率的关系,测量了6种中空玻璃微珠的粒度累积分布,用统计学概念与分形理论分别考察了中空玻璃微珠的粒度分布法则及其分形特征。结果表明:中空玻璃微珠粒度累积频率与相应的上限粒径的对数值有良好的线形关系,粒度符合对数正态分布法则;各中空玻璃微珠的粒度累积频率与粒径与最大粒径比值的双对数值呈线形关系,相关系数在0.95～0.98之间,强的相关表明各中空玻璃微珠的粒度分布的分形结构是客观的;随着中空玻璃微珠粒度分布分形维的增加,其空隙率减少。     

树脂基深水浮力材料压缩性能研究

为探究空心微珠填充量对树脂基深水浮力材料压缩性能的影响以及材料压缩破坏机理,基于Mori-Tanaka及Turesanyi方法对空心微珠填充环氧树脂基深水浮力材料的有效弹性模量及压缩强度进行了理论预测.制备了空心微珠填充环氧树脂基深水浮力材料,对不同空心微珠填充比的材料体系进行了单轴压缩试验,并通过扫描电镜观察了材料断裂面微观形貌.结果表明:随着空心微珠填充量增加,材料体系耐压强度降低,模量上升,且实验结果与理论预测吻合情况较好;空心微珠破损是深水浮力材料破坏的根本因素.     

一种新型隔热涂料的制备及性能研究

以苯丙乳液为成膜剂,硅烷偶联剂处理后的中空玻璃微珠为功能隔热填料合成新型的隔热涂料。结果表明,用硅烷偶联剂预处理中空玻璃微珠后涂料附着力能提高1个级别;涂层导热系数随中空玻璃微珠粒径的增加呈现先减小后增大的趋势,当中空玻璃微珠的粒径为58μm左右时导热系数比其它粒径制得涂料的导热系数降低6%～28%;随涂膜厚度的增加,隔热效果增强,但当涂膜厚度增大到0.3mm时,继续增加涂膜厚度,隔热效果几乎不再增强;当中空玻璃微珠含量小于10%时,热反射率随中空玻璃微珠在隔热涂料中含量的增加显著增加,超过10%后,热反射率增加速率减缓,当达到12%时,涂料的热反射率值最高,继续增加玻璃微珠含量,热反射率几乎不增加。     

Comparative Nanoparticle Size Characterization of EEW Alumina Using Various Measurement Techniques

Modern material science is paying more attention on the development of nanomaterials for superior properties in various fields of applications like mechanical, thermal, electronic, bio-medical etc. For such applications, determination of nanoparticle sizes along with their distribution is important for attaining the desired properties. Particle sizes along with the crystallite sizes of oxides, non-oxides and metallic nanopowders produced by different processes can be determined by different techniques which includes x-ray diffraction/neutron diffraction (XRD/ND), transmission electron microscopy/field emission scanning electron microscopy (TEM/FESEM), Brunauer-Emmett-Teller (BET) surface area method, small angle neutron scattering (SNAS), dynamic light scattering (DLS), static light scattering (SLS), etc. For average nano-metric particle size determination, DLS is the most frequently used technique that gives a distribution that approximates the exact binomial distribution of large numbers of nanoparticulates with varying particle size under investigation (Gaussian distribution). However, the other techniques mainly give either localized distribution of the particles under observation or the distribution derived from type II isotherm. In this investigation, nano-alumina powder produced by the electrical explosion of wire technique (EEW) is used for comparative evaluation of particle size analysis by DLS measurement technique for nanoparticles vis-à-vis to other techniques like XRD (for crystallite size), FESEM, BET, and TEM. The superiority of the DLS technique has been discussed in details with respect to the unique features of its Gaussian distribution nature.     

Regimes of segregation and mixing in combined size and density granular systems: an experimental study

Granular segregation in a rotating tumbler occurs due to differences in either particle size or density, which are often varied individually while the other is held constant. Both cases present theoretical challenges; even more challenging, however, is the case where density and size segregation may compete or reinforce each other. The number of studies addressing this situation is small. Here we present an experimental study of how the combination of size and density of the granular material affects mixing and segregation. Digital images are obtained of experiments performed in a half-filled quasi-2D circular tumbler using a bi-disperse mixture of equal volumes of different sizes of steel and glass beads. For particle size and density combinations where percolation and buoyancy both contribute to segregation, either radial streaks or a “classical” core can occur, depending on the particle size ratio. For particle combinations where percolation and buoyancy oppose one another, there is a transition between a core composed of denser beads to a core composed of smaller beads. Mixing can be achieved instead of segregation if the denser beads are also bigger and if the ratio of particle size is greater than the ratio of particle density. Temporal evolution of these segregated patterns is quantified in terms of a “segregation index” (based on the area of the segregated pattern) and a “shape index” (based on the area and perimeter of the segregated pattern).     

Comparison of Particle Size Distributions Measured Using Different Techniques

In this article, particle size distributions (PSDs) measured by different techniques, including image analysis (IA), laser diffraction (LD), ultrasonic attenuation spectroscopy (UAS), and focused-beam reflectance measurement (FBRM), are compared for spherical glass beads and nonspherical silica flakes. It is shown that particle shape strongly affects the results obtained by different techniques. For spheres, the PSDs obtained by IA, LD, and UAS agree well. There is no consistent result among different particle measurement techniques for nonspherical particles. The conversion between PSDs obtained by IA, LD, and UAS has been based on particle shape factors. Caution must be exercised when a measured chord length distribution (CLD) is used to indicate the PSD during a process because the CLD result obtained by FBRM is complex, depending not only on the PSD, but also on particle optical properties and shape.     

Multiple light scattering in laser particle sizing

Multiple light scattering is an important issue in modern laser diffraction spectrometry. Most laser particle sizers do not account for multiple light scattering in a disperse medium under investigation. This causes an underestimation of the particle sizes in the case of high concentrations of scatterers. The retrieval accuracy is improved if the measured data are processed with multiple-scattering algorithms that treat multiple light scattering in a disperse medium. We evaluate the influence of multiple light scattering on light transmitted by scattering layers. The relationships among different theories to account for multiple light scattering in laser particle sizing are considered.     

Comparison of Particle Size Distributions Measured Using Different Techniques

ABSTRACT

In this article, particle size distributions (PSDs) measured by different techniques, including image analysis (IA), laser diffraction (LD), ultrasonic attenuation spectroscopy (UAS), and focused-beam reflectance measurement (FBRM), are compared for spherical glass beads and nonspherical silica flakes. It is shown that particle shape strongly affects the results obtained by different techniques. For spheres, the PSDs obtained by IA, LD, and UAS agree well. There is no consistent result among different particle measurement techniques for nonspherical particles. The conversion between PSDs obtained by IA, LD, and UAS has been based on particle shape factors. Caution must be exercised when a measured chord length distribution (CLD) is used to indicate the PSD during a process because the CLD result obtained by FBRM is complex, depending not only on the PSD, but also on particle optical properties and shape.     

Particle size determination in aluminum hydroxide suspensions using near-infrared transmittance spectroscopy

A new method for particle size determination in polystyrene and aluminum hydroxide suspensions using near-infrared transmittance spectroscopy is described. Mono-dispersed polystyrene particle size standards were used to establish the calibration model. The particle sizes used in the study are similar to the wavelength range of 700-1300 nm, where light scattering is wavelength dependent. The wavelength dependency of near-infrared (NIR) absorbance is found to be linear with the particle size when the analysis is based on the same spectrum starting point (the same absorbance at 700 nm). Partial least squares regression (PLSR) is applied to model this linear relationship. Compared to laser diffraction (LD) the NIR method has similar accuracy and precision in the measurement of particles with a uniform size. For a sample containing multiple sizes of particles, the mean size measured by the NIR method is shown to be weighted by the particle mass. The application of the model to aluminum hydroxide suspension shows that the NIR method is suitable for the detection of particle size changes during the production process and storage. The advantages of the NIR method are that no knowledge of the refractive index and the concentration of a sample are necessary and that the method is fast and easy to operate.     

空心微球/环氧树脂复合泡沫塑料的抗压性能与破坏机制

以环氧树脂为基体, 不同粒径空心玻璃微球为填充体, 制备了轻质高强复合泡沫塑料。通过单轴准静态压缩试验研究了空心微球的粒径大小对复合泡沫塑料的抗压性能的影响, 并采用SEM对复合泡沫塑料的微观结构进行观测。通过随机空间分布法建立了空心玻璃微球/环氧树脂复合泡沫塑料的实体模型, 并且使用有限元分析软件对复合泡沫塑料在1 kPa载荷下的应力分布进行了分析。结果表明, 在相同体积含量下, 当空心微球的粒径从30 μm增大到120 μm时, 复合泡沫塑料的抗压强度无明显变化。有限元分析的结果表明, 在复合泡沫塑料中主要承载部分为空心微球, 空心微球上的应力大于树脂基体上的应力。最大应力分布在空心微球的内壁, 结合SEM图像可推测, 空心微球在破裂之前受到充分的挤压, 并且从内壁产生裂纹。     

The effect of initial parameters on particle size distribution inverted using the laser diffraction technique and a non-linear iterative method

The Twomey non-linear iteration (NLI) method is known by the simple algorithm. However, the performance of the inversion is strongly depended on parameters of the NLI algorithm. Major parameters in the algorithm are the initial size distribution, weight parameter, and the number of iteration. In the study, we show how values of initial parameters affect to the result of size distribution in the algorithm by the laser diffraction scattering method. Computer simulations and experimental method are carried out to observe the influence of the parameters in the algorithm. Scattering pattern is calculated by Mie scattering model in the range of 5.0 × 10^?4 ? 2.5 rad. Experimental results were measured mono-distribution polystyrene latex (50 μm) and poly-distribution glass beads (3–30 μm, and 10–100 μm). The number of iteration is a most influence parameter in the NLI algorithm. If the number of iteration is too high for calculation, calculated result will lose the smoothness. We also introduced a new parameter C (combination of the sum of residual squares of scattering signals and sum of secondary differentiation of size distribution) to monitor the suitable stop criterion for the NLI method. The parameter C is a useful index for the poly dispersion sample to find the suitable stop criterion.     

石墨微粉形状参数分布的研究

采用激光衍射法和沉降法的粒度分析结果,研究了石墨微粉颗粒的形状及其参数分布,给出了３ 种石墨微粉产品的长径比随粒径变化的分布曲线。通过对曲线的分析,可提取与颗粒制备机理有关的信息。本文从一个角度证明了颗粒的粒度分析与形状分析是相互影响、相互依存、不可分割的整体     

Particle shape effects on particle size measurement for crushed waste glass

Recently, narrow particle size distributions, as measured by sieve analysis, of crushed waste glass were used as a replacement for Portland cement in concrete. Their chemical reactivity was successfully studied as a function of this measure of particle size. Differences between sieve analysis and laser diffraction measures of particle size prompted this current re-analysis. Extremely careful sieving was used to divide the crushed waste glass particles into 0–25 μm, 25–38 μm, and 63–75 μm sieve size ranges, but laser diffraction did not agree with these particle size cutoffs. We use these same materials to try and understand the discrepancies between particle size as measured by laser diffraction and sieve analysis by using X-ray computed tomography followed by spherical harmonic analysis to measure the three-dimensional particle shape and size, as well as the length (L), width (W), and thickness (T) of each particle. We show how laser diffraction and X-ray CT results, along with sieve analyses, can be quantitatively related for these crushed waste glass particles in the approximate size ranges considered. In contrast to previous speculation, the particle width W does not have to correspond closely to the sieve opening – the correspondence depends on overall particle shape. In addition, we demonstrate how many particles are needed to analyze in order to achieve stable averages and distributions of the L/W, W/T, and L/T aspect ratios, which approximately define particle shape. These results have implications for how particle size is measured and interpreted in the cement and concrete and other industries.     

Laser Heating Tunability by Off‐Resonant Irradiation of Gold Nanoparticles

Temperature changes in the vicinity of a single absorptive nanostructure caused by local heating have strong implications in technologies such as integrated electronics or biomedicine. Herein, the temperature changes in the vicinity of a single optically trapped spherical Au nanoparticle encapsulated in a thermo‐responsive poly(N‐isopropylacrylamide) shell (Au@pNIPAM) are studied in detail. Individual beads are trapped in a counter‐propagating optical tweezers setup at various laser powers, which allows the overall particle size to be tuned through the phase transition of the thermo‐responsive shell. The experimentally obtained sizes measured at different irradiation powers are compared with average size values obtained by dynamic light scattering (DLS) from an ensemble of beads at different temperatures. The size range and the tendency to shrink upon increasing the laser power in the optical trap or by increasing the temperature for DLS agree with reasonable accuracy for both approaches. Discrepancies are evaluated by means of simple models accounting for variations in the thermal conductivity of the polymer, the viscosity of the aqueous solution and the absorption cross section of the coated Au nanoparticle. These results show that these parameters must be taken into account when considering local laser heating experiments in aqueous solution at the nanoscale. Analysis of the stability of the Au@pNIPAM particles in the trap is also theoretically carried out for different particle sizes.     

不同方法测试粒度分布的比较研究

介绍了不同原理仪器粒度测试结果间存在差异的原因以及对测试结果准确性应如何评价。用筛分法和激光法对氧化铝样品进行测试对比,初步分析结果间的差异。结果表明,筛分法和激光法测试粒度分布在质量(体积)累积分布达到50%时,测试结果相差最小,不同的粒度组成、颗粒的形状都会造成两种方法测试结果的差异。     

FRICTION LOSSES FOR FLOW OF SLURRIES IN PIPELINE BENDS, FITTINGS, AND VALVES

Resistance coefficients for flow of suspensions of well defined glass beads of narrow size fractions in 1-inch and 2-inch straight pipes, in standard 45^°, 90^° and 180^° bends, in 90^° smooth bends of various curvature radii, and also in gate and globe valves were measured. The measurements were made for two sizes of fine glass beads, -325 mesh and -200-325 mesh, covering wide ranges of turbulent Reynolds number and solids concentrations from 0 to 50 weight percent.

These friction loss data were analyzed with regard to the effects of Reynolds number and suspended solids concentration, and the calculated resistance coefficients were compared with those estimated from available design procedures recommended for turbulent single-phase Newtonian flow. Within the range of particle sizes examined in this work no particle size effects could be discerned. The effects of Reynolds number and suspended solids concentration on the friction loss measurement were calculated.     

激光光散射法在超细粉粒度测试中的应用

介绍了激光光散射的基本原理及其在粉体测试领域中的应用,分析了激光粒度测试仪的基本组成和工作原理,通过不同仪器间粒度测试的对比实验及准确度,精密度实验,并对误差进行了分析,指出激光光散射法是一种高效,快速、准确的现代粒度测试方法。