The size of the particle also affects the rate of sintering of the polymer powder. However, the powder having an average particle diameter less than 10 μm is also unsuitable for the SLS process because such powder is adhesive on the rolls due to static electricity generated by friction during the spreading process, which makes it difficult to spread the powder. Therefore, the average particle size of the powder for SLS generally does not exceed 100 μm, otherwise, the formed part will have a very significant step part and the surface is very rough. At the same time, reducing the particle size of the powder can reduce the roughness of the single-layer powder after the powder spreading, so that the surface finish of the formed part can be improved. When the particle size of the powder is reduced, the SLS parts can be manufactured at a smaller slice thickness, which can reduce the staircase effect and improve the forming precision. The thickness of the slice should not be smaller than the particle size of the powder. In the SLS-forming process, the slice thickness of the powder and the surface finish of each layer are determined by the particle size of the powder. The spray drying method and the solvent precipitation method usually can be used to obtain near-spherical powder with small particle size, and the low-temperature pulverization method can be used to obtain only irregular powder of large particle size. The particle size of the powder usually depends on the powdering method. The particle size of the powder affects the surface finish, precision, sintering rate and powder layer density of the SLS parts. Ying Chen, in Materials for Additive Manufacturing, 2021 2.1.3.2.2 Influence of particle size on selective laser sintering processing For the present study three different sets of measurements were performed for each identified AP powder. This scattering is captured by an array of detectors. The dispersed powder scatters laser light at angles that are inversely proportional to the size of the particles, i.e., large particles scatter light at small forward angles, whereas small particles scatter light at wider angles. The vacuum draws the powder sample into the instrument where the dispersed powder passes through the laser beam. A representative powder sample was placed in the feeder unit and a vacuum was switched on. Different lenses such as R1, R3, and R5 were used based on the anticipated particle size range of AP powder. Simultaneous diffraction on more than one particle results in a superposition of the diffraction patterns of the individual particles as long as the particles are moving and the diffraction between them is averaged out.įor accurate analysis, wet mode was used for particle size measurement and dispersion liquid for wet analysis was made by mixing CCl 4 and isobutanol in 60:40 (v/v).
Diffraction of the laser light results from the interaction of the light with the particles and can be described mathematically by Fraunhofer or Mie theory.
Sympatec make the Hellos model and this was used for analysis. Particle size of different grades of AP was measured through a laser diffraction-based particle size analyzer. Kandasubramanian Balasubramanian, in Nanomaterials in Rocket Propulsion Systems, 2019 3.2.2 Measurement of Particle Size of Ammonium Perchlorate Powder Through Laser Diffraction
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