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。     

测量范围设定对激光粒度检测结果的影响

激光粒度测试仪在微粉行业得到广泛的应用，正确的使用，结合扫描电镜可以给出粉体颗粒大小的准确量度。引起粒度测量的误差原因很多，本文中讨论激光粒度仪测量范围的设定对粒度测量结果的影响。     

激光粒度测试的非理想聚焦问题研究

激光粒度测试系统是建立在理想聚焦条件的数学模型之上的,实际的测量系统通过光学准直光阑系统来逼近理想条件,大大增加了系统和应用成本.本文针对不满足理想条件时的情况,建立了对应的非理想聚焦散射模型,进行了数值模拟研究,以期得到误差定量的描述和找出误差的软件修正方法.研究表明非理想聚焦的效果等效于降低大颗粒的分辨率并使小颗粒粒度分布变宽.本文根据非理想聚焦散射模型建立了非理想聚焦模型软件修正方法,可以大幅度的减少非理想聚焦引起的测量误差.     

Mie理论在静态光散射粒度测量的应用下限研究

测量下限是光散射颗粒测试技术的关键问题。本文通过理论分析、比较归一化散射光强的分布图和构造方差函数F(d)对颗粒散射光的光强分布进行了定性和定量的讨论,对Mie散射向Rayleigh散射趋近的情况进行了分析,讨论了散射光光强大小的分布,分析了测量不同粒径的颗粒的可行性,最终得到在入射光源是波长为0.6328μm的He-Ne激光器的情况下,当粒径d取200nm以上时,不同粒径颗粒的M ie散射光强分布有较大差别,适合用静态光散射的方法来判断颗粒粒径。     

激光法检测粒度的探试

粒度检测大致可分为显微镜法、沉降法、激光法。现在流行的激光法的测试方法有干湿两种，湿法检测占有相当比重。对获取准确测试结果起决定性作用的有三大因素，即溶媒的选择、超声波的作用和物质折射率的设定。用有机溶剂汽油做溶媒对青霉素粒度的检测，经实践发现其对循环泵及循环管部分材质的要求甚为严格。     

激光粒度法测试结果与库尔特法、沉降法的比较

分别采用马尔文激光粒度仪、库尔特颗粒粒度计数仪、岛津离心粒度分析仪对玻璃微珠、聚苯乙烯微球、钨粉、氧化铝微粉、二氧化硅微粉等6种不同类型的粉末进行了测试,并对几种测试方法所得的结果进行比较。结果表明:激光法测试的结果重复性较好;对于粒径范围窄的球形粉体,几种仪器测得的中位径具有可比性,粒度分布曲线也相似;对于粒径范围较宽的球形粉体和不规则形状粉体,测得的中位径和粒度分布曲线一般没有可比性。     

激光粒度测量中的一种无模式综合反演算法

在目前常用的激光粒度仪无模式反演算方法的优点和缺点基础上,为了实现各种方法的稳定性与准确性的统一,本文中提出一种综合的无模式反演算法——二阶段迭法算法,综合采用了改进共轭梯度法和松弛迭代法各自的优点,在稳定性和准确性方面得到了一定程度的改进。经计算机模拟测量误差实验及国家标准颗粒实验的双重验证:该算法对单峰和多峰的分布具有较准确的分辨能力,且对噪声信号的抗干扰能力较强。     

中国粒度测试技术研发基地 中国激光粒度仪专业制造商

经过一年的筹备和建设，丹东百特5500平方米的仪器生产和研发基地于2007年12月正式竣工并投入使用，这是百特公司十几年不懈努力跃上的一个新台阶。     

高次衍射对激光粒度分析的影响

本文介绍了激光闰原理及高次衍射现象产生的原因,从理论上推导了高次衍射哟度的分布公式,分析了高次衍射对激光测粒度产生的影响,讨论了获得了最大有效信号强度时颗粒在分散相中的最佳体积浓度。     

Rise-2008型激光粒度仪／粒度分析仪

工作原理： Rise-2008型激光粒度分析仪采用全量程米氏散射理论，充分考虑到被测颗粒和分散介质的折射率等光学性质，根据大小不同的颗粒在各角度上散射光强的变化反演出颗粒群的粒度分布数据。     

The development of the measurement of particle concentration using a commercial laser diffraction particle size analyzer

A laser diffraction particle size analyzer based on the Fraunhofer diffraction theory has the advantages of real-time measurement of particle size distribution over a broad range. However, the dispersed particle number concentration is not displayed in commercially available analyzers. The method of measuring the dispersed particle number concentration was investigated for different particles having various shapes, i.e. spherical, cubical and prismoidal with a log-normal distribution, by considering the characteristics of the measured voltage of the set detector in relation to the diffracted light intensity using a commercial laser diffraction particle size analyzer. As a result, an approximate equation for the particle number concentration was proposed expressing the measured median diameter and the highest voltage measured by the detector. This equation was applicable to particles having various shapes, i.e. spherical, cubical and prismoidal. Furthermore, this technique can be used for the continuous measurement of the particle number concentration of growing crystals in the crystallizer for crystallization operation.     

Particle size measurement of standard reference particle candidates with improved size measurement devices

In order to prepare standard reference particles, experimental and theoretical studies have been conducted on particle size measurement of two kinds of spherical glass beads. The sheath flow- type electrical sensing zone method and the revised sedimentation balance method were used for the measurement. The data were compared with those obtained by the microscopic method with a sample size greater than 10 000. The particle size distributions obtained by use of the sheath flow- type electrical sensing zone method and microscopic method are nearly equal for the two kinds of glass beads. However, deviations of less than 5% were observed between the improved sedimentation balance and microscopic methods. The experimental data of the microscopic method are within the 95% reliability region of the sheath flow-type electrical sensing zone method.     

Research on ultrafine particle size measurement using small amounts of data

The paper puts forward a new method of ultrafine particle size measurement using small amounts of data of a dynamic light-scattering signal, and establishes an arithmetic model of the measurement by wavelet package transform. First, through the wavelet package transform, the ultrafine particle dynamic light-scattering signals were decomposed into multifrequency bands. Then, the noise of signals of different frequency bands were removed and the power spectrum of the wavelet packet coefficients of each frequency band was calculated. Finally, the ultrafine particle size distribution information could be deduced from inversing the power spectrum. The standard polystyrene particles of 100, 300, and 400 nm were measured using this method, and the inversion results indicated that this method can effectively remove noise and improve the accuracy of particle size measurement using small amounts of data.     

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.     

影响总氮准确测定的因素研究

实验表明测定总氮所用的消解剂K2S2O8在波长220nm处有很强的吸收峰,如果其在消解过程中不能完全分解,就会对比色测定严重干扰．通过对不同的消解方式,消解时间、温度等条件的研究,得到消除K2S2O8干扰的条件。     

影响总氮准确测定的因素研究

实验表明测定总氮所用的消解剂K2S2O8在波长220nm处有很强的吸收峰,如果其在消解过程中不能完全分解,就会对比色测定严重干扰.通过对不同的消解方式,消解时间、温度等条件的研究,得到消除K2S2O8干扰的条件。     

共轴两焦面探测信号的激光粒度测试

为了提高激光粒度仪测量宽分布范围粒径的能力,根据衍射原理,提出扩大测试动态范围的方法.该方法使用共轴的双透镜,在两个焦平面同时探测信号,将这些信号合成后经数据处理得到粒子尺寸分布.模拟计算表明,使用两个100mm焦距的透镜和两个32环的多元探测器可测量粒径为l～2000 μm的颗粒,动态范围为2000∶1.这种方法在不需更换镜头、不改变探测器轴向位置的情况下可以测量较大量程内的粒径分布.     

Automatic particle size distribution measurement by sedimentation from a starting layer

The VS-3 sedimentometer is described, which measures directly the mass of the particles of each size sedimenting from an initial layer. The basic theoretical concepts are given. If one is to extend the particle size range as determined with it, one needs to use not only the classical Stokes law but also other mathematically justified laws, in particular Klyachko's formula, to describe the sedimentation of large particles. The metrological characteristics have been evaluated. Translated from Izmeritel'naya Tekhnika, No. 3, pp. 65–68, March, 2000.     

In situ particle size measurements using a two-color laser scattering technique

We have developed a technique using light scattered from individual particles in the near-forward direction to measure particle size in the range of 10-200 microm. This technique uses the Mie scattering theory to relate the measured light intensity to particle size based on calibration techniques employing pinholes and water droplets of known size. We have applied a unique two-color optical arrangement to minimize the edge effect which can cause incorrect size measurements for particles that pass through the edge of the laser beam focal volume. In this paper we describe our experimental technique and the results of size measurements obtained with this technique for water droplets and pulverized coal particles.