1.1 This test method covers the determination of particle size distribution of advanced ceramic powders. Experience has shown that this test method is satisfactory for the analysis of silicon carbide, silicon nitride, and zirconium oxide in the size range of 0.1 up to 50 m. 1.1.1 However, the relationship between size and sedimentation velocity used in this test method assumes that particles sediment within the laminar flow regime. It is generally accepted that particles sedimenting with a Reynolds number of 0.3 or less will do so under conditions of laminar flow with negligible error. Particle size distribution analysis for particles settling with a larger Reynolds number may be incorrect due to turbulent flow. Some materials covered by this test method may settle in water with Reynolds number greater than 0.3 if large particles are present. The user of this test method should calculate the Reynolds number of the largest particle expected to be present in order to judge the quality of obtained results. Reynolds number (Re) can be calculated using the flowing equation Re = D3 00g182 (1) where D= the diameter of the largest particle expected to be present, in cm, = the particle density, in g/cm3, 0= the suspending liquid density, in g/cm3, g= the acceleration due to gravity, 981 cm/sec2, and = the suspending liquid viscosity, in poise. A table of the largest particles that can be analyzed with a suggested maximum Reynolds number of 0.3 or less in water at 35C is given for a number of materials in Table 1. A column of the Reynolds number calculated for a 50m particle sedimenting in the same liquid system is given for each material also. Larger particles can be analyzed in dispersing media with viscosities greater than that for water. Aqueous solutions of glycerine or sucrose have such higher viscosities. 1.2 The procedure described in this test method may be applied successfully to other ceramic powders in this general size range, provided that appropriate dispersion procedures are developed It is the responsibility of the user to determine the applicability of this test method to other materials. Note however that some ceramics, such as boron carbide and boron nitride, may not absorb X-Rays sufficiently to be characterized by this analysis method. 1.3 The values stated in cgs units are to be regarded as the standard, which is the long-standing industry practice. The values given in parentheses are for information only. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific hazard information is given in Section 7.
Keywordsadvanced ceramics; particle size distribution; gravity sedimentation; silicon carbide; silicon nitride; zirconium oxide
The title and scope are in draft form and are under development within this ASTM Committee.Back to Top
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