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Glossary of Terms in Powder & Bulk Technology

3. Powder Properties

Written by Lyn Bates edited by mhd on 18. Sep. 2022
absolute powder density The mass of powder per unit of absolute powder volume.
absolute powder volume The volume occupied by the solid content of a powder, excluding all pores and voids.
absorption (1) Penetration of a substance, usually a fluid, into the body of another.
absorption (2) The attachment of water molecules to the surface of particles
aerated bulk density (See density, aerated bulk)
agglomerate An accumulated cluster of many particles that are rigidly bonded together by inter-particle forces, partial fusion, sintering or by growing together, such that they act as a single, larger particle.
apparent powder density The mass of powder per unit of apparent powder volume.
apparent powder volume The total volume occupied by solid matter, including open and closed pores.
bed porosity (See powder bed porosity)
blinding The building up of small particles on a screening surface reducing the aperture size or closing them completely.
bulk A mass of particles.
coefficient of compressibility The secant slope, for a given pressure increment, of the pressure-void ratio curve.

av = (L 2 F –1 )

Where a stress-strain curve is used, the slope of this curve is equal to av/(1+e).
coefficient of consolidation A coefficient, defined as

av (L 2 T –1 )

utilised in the theory of consolidation containing the physical constant of the loose solid affecting its volume change:

cv = k(1+e)/ avlw

where:
- k = coefficient of permeability, LT
- e = Voids ratio
- av = coefficient of compressibility, (L 2 F –1 )
- lw = unit weight of water, FL-3
coefficient of friction μ, The relationship between normal stress and the corresponding shear stress at which sliding takes place between two surfaces. (Between a loose solid and a contact surface, this behaviour is referred to as wall friction). See static friction and dynamic friction.
coefficient of permeability The rate of passage of a fluid under laminar flow conditions through a unit cross section of a media under a unit pressure drop at standard temperature conditions.
coefficient of uniformity Cu (D), The ratio D60/D10, where D60 is the particle diameter corresponding to 60 % finer on the cumulative particle-size distribution curve, and D10 is the particle diameter corresponding to 10 % finer on the cumulative particle-size distribution curve.
compression ratio The ratio of the loose poured density to the pressed density.
dynamic friction The frictional resistance to sustained sliding. See friction.
friability The tendency of particles and granules to break down in size during handling and storage under the influence of light physical forces.
gravel Mineral particles greater in size than 2000 microns

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