几种常用的粉体粒度测试方法.docx

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Title: An Overview of Commonly Used Methods for Particle Size Analysis of Powders
Introduction:
Particle size analysis of powders is a key parameter that influences the performance and quality of various industrial processes. Testing the particle size distribution is essential for process optimization, quality control, and material characterization. This paper provides an overview of some commonly used methods for determining the particle size of powders. The methods covered include sieving, sedimentation, laser diffraction, microscopy, and dynamic light scattering.
1. Sieving:
Sieving is one of the oldest and simplest methods for particle size analysis. In this method, a sample is passed through a series of sieves with different mesh sizes. The particles are retained on the sieves and their mass or weight percentage is recorded. The results are then used to calculate the particle size distribution by plotting a cumulative particle size distribution curve. Sieving is a widely used method for coarse powders with particle sizes larger than 45 μm.
2. Sedimentation:
Sedimentation methods, such as the hydrometer method and the pipette method, rely on the principles of gravity sedimentation. In the hydrometer method, a sample is dispersed in a liquid medium and allowed to settle under gravity. The settling velocity is measured using a hydrometer, and the particle size distribution is calculated based on Stokes' law. The pipette method involves withdrawing a known volume of settled particles from the bottom of a sedimentation column and analyzing them.
3. Laser diffraction:
Laser diffraction is a widely used and highly accurate method for particle size analysis. It is based on the principle that when a laser beam passes through a suspension of particles, the intensity of light scattered by the particles is inversely proportional to their size. By measuring the scattered light at various angles, the particle size distribution can be determined. Laser diffraction is suitable for a wide range of particle sizes, from sub-micrometer to several millimeters.
4. Microscopy:
Microscopy techniques, such as optical microscopy and electron microscopy, provide direct visual information about particle size and shape. Optical microscopy involves magnifying the samples and measuring the dimensions of individual particles using a calibrated eyepiece or software. Electron microscopy, such as scanning electron microscopy (SEM) or transmission electron microscopy (TEM), allows for higher magnification and provides more detailed information about particle morphology and structure.
5. Dynamic light scattering (DLS):
DLS, also known as photon correlation spectroscopy, measures the fluctuations in scattered light caused by Brownian motion of particles in a suspension. This information is used to calculate the particle size distribution. DLS is particularly suitable for sub-micrometer particles in the colloidal range, where other techniques might be limited.
Conclusion:
Particle size analysis is vital for understanding and optimizing the performance of powders in various industries. This paper has discussed five commonly used methods for particle size analysis: sieving, sedimentation, laser diffraction, microscopy, and dynamic light scattering. Each method has its benefits and limitations, and the choice of method depends on the size range of the particles, the required accuracy, and the specific sample properties. Researchers and industry professionals should carefully consider the appropriate method for their application, considering factors such as cost, time, and sample preparation requirements.