Physicochemical characterization of Baizhi particles by ultrafine pulverization

Baizhi, as a medicinal plant, has been demonstrated to be useful for the treatment of aches and pains in China. The physicochemical characterization of Baizhi particles is greatly influenced by ultrafine pulverization. To study the physicochemical characterization of Baizhi, the raw plant material of Baizhi was ground to 6 μm particles by a high speed centrifugal sheering （HSCS） pulverizer. The micron particles were characterized by optical microscopy and scanning electron microscopy （SEM）. Imperatorin is one of the active ingredients of Baizhi, and its extraction yield is determined to evaluate the chemical characterization of Baizhi powder. Imperatorin was analyzed by high performance liquid chromatography （HPLC）. The results show that after ultrafine pulverization, the plant cell walls are broken into pieces and the extraction yield of imperatorin is increased by 11.93% compared with the normal particles.

Spherical modification of tungsten oxide powder and its mechanism analysis

Owing to its high production costs, complexity of equipment, and difficulty in controlling parameters, spherical or subglobose tungsten powder preparation method cannot meet the demand of industrial production. Tungstic oxide powder was treated by particle composite system and its effects were studied. Morphologies of par- ticles were investigated by scanning electron microscopy （SEM）. Particle size analysis was carried out and the related mechanism was discussed. The results show that the processing effect is best when the rotational speed is set at 4,000 r.min-1 for 15 rain： the powder particles become nearly spherical and their sharp edge angles are rounded off and reshaped. When the processing time is 60 min, the powders smash to pieces because of too much energy inputting. So the test results, such as grain size distribution, can be explained well. Nearly spherical tungsten powder is obtained after reduction at 780 ℃ for 2 h and its flow ability is significantly improved.

Spherical modification of tungsten powder by particle composite system

Owing to contradiction between increasing demand of spherical tungsten powder and limitation of traditional manufacturing technology,a novel preparation method was developed to sphericize the polygonal tungsten powder by means of modification of particle composite system.Tungsten powder particles were modified by par-ticle composite system,and detailed characterization by scanning electron microscopy(SEM)was studied.Particle size distribution and function mechanism were analyzed,and the internal relationship between average diameter and processing time was discussed.The results show that the spherical tungsten powder with an average diameter of 6.41μm is obtained from polyhedral tungsten powder with an average diameter of 7.50μm.The spherical effect could be achieved(sharp edge angles of particles are rounded off and reshaped)when the processing time is over 30 min.The relationship between average diameter(d)and pro-cessing time can be described by the exponential decay model,which provides a good interpretation for the process of modification.The relationship between them can be expressed by the equation d=1.87406exp(-x/8.92718)+6.4182.The proposed method could readily enable large-scale production of spherical tungsten powder.