Laser particle sizer performance characteristics at home and abroad

[Abstract] The development stages of particle size detection can be roughly divided into microscope method, sedimentation method and laser method. The current popular laser particle size test is divided into dry method and wet method, of which wet method occupies a considerable proportion. There are three factors that play a decisive role in obtaining accurate test results: one is the choice of solvent; the other is the effect of ultrasonic waves; the third is the setting of the refractive index of the material.

1 Introduction

According to the introduction of relevant Japanese literature, the purpose of powder measurement is divided into three categories: ① study the measured value of physical properties; ② predict the fluidity and dispersibility of powder from the measured value of physical properties; ③ measure the physical properties of powder, Effective management of product quality (such as effective evaluation of the degree of crushing) can be implemented.

Microscopic method, image analysis method, current detection method, sedimentation method (light passing method, X-ray passing method, pipette method), laser diffraction scattering method and photon correlation method can be used for the determination of powder particle size distribution. Among them, the laser particle size Tester integrates laser technology, modern photoelectric technology , electronic technology, precision machinery and computer technology, and has the advantages of fast measurement speed, large dynamic range, easy operation and good repeatability . In the laser Mie scattering method, the astigmatism of tiny particles is collected by a photocell, and the light is converted into a pulsating voltage for detection. Using this pulsating voltage, the particle diameter of monodisperse spherical particles can be obtained. In the Fraunhofer diffraction method, the intensity distribution of the diffracted light has nothing to do with the chemical composition, refractive index and other properties of the particles, but has a great relationship with the geometric factors such as the size and shape of the particles. The diffraction ring of the particles is not affected by the movement of the particles The influence of the diffraction ring is always centered on the optical axis, and the measured light intensity has a certain proportional relationship with the number of particles. Using this diffraction ring, the particle size distribution of the particle group can be measured.

2 Comparison of performance characteristics of laser particle size analyzers at home and abroad

The domestically produced laser particle size analyzers are known to be quite influential, such as "European and American grams" in Zhuhai, "Micro-Nano" in Jinan, "Jingxin" in Chengdu, Sichuan, and "Baite" in Dandong. Imported laser particle size analyzers mainly include CILAS from France, HORIBA, Daojin andセイシン from Japan, Malvern from the United Kingdom, COULTER and BROOKHAVEN from the United States, SYMPATEC from Germany and a company . From its structure, it is roughly divided into three parts: range, laser light source, and Detector. Among them, the Detector has developed from a circle, a semicircle, and then to a fan .

20 years ago, it was the era of sedimentation particle size analyzers. Due to the restrictions on the export of technical products in the Chinese market by European and American countries, the related products were actively traded in the Chinese market. At this time, the related products in CHINA were still very immature. The "Riqing" enterprise has achieved excellent marketing performance in CHINA. Later, with the introduction of the laser method and the relaxation of European and American countries' policies towards CHINA , European and American manufacturers entered the Chinese market one after another, and at the same time, high-level competition also kicked off. The British Malvern particle size analyzer adopts He-Ne light source (advantage: not affected by ambient temperature. Disadvantage: life is shorter than that of semiconductor type, measuring range: 0.02-2 000 μm, built-in small-angle laser light scattering method) full-scale Mie theory, The theory of Mie light scattering is very complicated, and the amount of data processing is large . The circulation pipe is an ordinary plastic pipe. Built-in non-uniform cross-arranged three- dimensional sector detection system with extremely high resolution and no signal blind spots. Equivalent to 175 in ring or cross star shape and 93 in semicircular arrangement, the direct detection angle can reach 135°, and the sampling rate is 1,000 times per second. The Coulter particle size analyzer in the United States adopts Fraunhofer and Mei's theory , double-lens patented technology, polarized light intensity difference patented technology, and 132 Detectors (the number is not the decisive factor for evaluating its detection quality, but also its shape. Generally speaking, the larger the size, the better the detection effect and the higher the cost), the circulation tube is a silicone tube. The measuring range is 0.04～2 000μm.

The particle size analyzer of France Silas company adopts semiconductor laser tube and optical fiber laser light source, the measuring range is 0.04-2 500 μm, and the built-in peristaltic pump has a very low replacement cost, which is the Achilles heel for centrifugal pumps.

Germany's new Batako particle size analyzer uses a helium light source and uses the Fraunhofer principle with a measuring range of 0.1-3 500 μm. Built-in 31 sensors , dry test is its unique technology, with less sample consumption and good repeatability. During the wet test, the sealing ring of the circulation pipe and the centrifugal pump can be replaced according to the requirements of the solvent used.

The particle size analyzer produced by Riqing Enterprise uses a semiconductor light source with a light wavelength of 670nm, 55 built-in sensors, and a semicircular design. Circulation pipes and centrifugal pumps have weak resistance to organic solvent corrosion. After tracking and observation tests , the sealing rings of the centrifugal pumps cannot withstand the infiltration of organic solvents for a long time and are easily damaged. Comparing the domestic Jinan micro-nano particle size analyzer with Riqing's instrument, the repeatability of the micro-nano instrument test is excellent , and its characteristics are as follows: ①Professional testing principle: full-range Mie scattering theory; ②Excellent resolution: 0.1～300μm The measurement range is divided into 3 levels (0.1～40μm, 0.6～120μm, 1～300μm); ③The test operation is simple and fast, and the output data is rich and intuitive; ④Sample preparation is effective and convenient: simple operation, convenient cleaning, and avoid the occurrence of rescattering ; ⑤ Reliable test standard: Calibrate with national particle size standard GBW (E) 120 000.

The laser particle size analyzer produced by Japan HORIBA company has a range of 0.02-2 000 μm, built-in 12 independent large-angle Detectors and a ring Detector (divided into 75 units), He-Ne laser, in order to better capture small particles Scattered light, especially built-in tungsten lamp, its wavelength is shorter than that of He-Ne laser, which can accurately detect small particle signals. The circulation system adopts a high-output centrifugal pump, and all parts in contact with the liquid are made of anti-corrosion and anti-rust materials (such as stainless steel, PTFE resin and glass, etc.), and the design concept is very forward-looking. It can also be customized according to the requirements of users.

3 Conclusion

CHINA's particle size analyzer market can be said to be crowded, as a buyer , it is subject to various factors, but one thing needs to be seriously considered, that is, when wet testing is required, once the choice of solvent is determined, the relative The circulation part of the particle size analyzer is investigated. At present , Nissan HORIBA particle size analyzers are mainly resistant to corrosion by organic solvents. The related performance of the particle size analyzers of Jinan Micro-Nano Company is also recognized.

[references]

[1] Zhang Lanying, Wang Faping, et al. Effects of Micronized Preparations of Crude Medicinal Materials on Drug Effects [J]. CHINA Powder Technology, 2001, (1): 38-41.

[2] Feng Ruitang, Li Peizhen. Expanding the measuring range of Fischer micropowder particle size analyzer[J]. Powder Metallurgy , 2001,11(5).

[3] Xu Feng, Cai Xiaoshu, et al. Discussion on Fraunhofer Diffraction Theory [J]. CHINA Powder Technology, 2003, 9(2).