Powder packing density

Jia, X. Gan, M. Williams, R.A. Rhodes, D. (2007) Validation of a digital packing algorithm in predicting powder packing densities. Powder Technology 174, 10-13. 

Moderate Less restriction of substrate shape and roughness high powder packing density of deposited layers favorable for lowering sintering temperature manufacturability is easy fast deposition rates thickness of films variable... 

Tap Density. Tapping a mass of loose powder, or more specifically, the appHcation of vibration to the powder mass, separates the powder particles intermittently, and thus overcomes friction. This short-time lowering of friction results in an improved powder packing between particles and in a higher apparent density of the powder mass. Tap density is always higher than apparent density. The amount of increase from apparent to tap density depends mainly on particle size and shape (see Table 4). 

DpopE related to SpQpp, which is in turn related to the closeness of packing of the powder. The number of particles adjacent to a given particle is represented by The maximum packing density for monosize spheres occurs at hexagonal close packing, where = 12 and = 0.2595 for... 

From isotherm measurements, usually earried out on small quantities of adsorbent, the methane uptake per unit mass of adsorbent is obtained. Sinee storage in a fixed volnme is dependent on the uptake per unit volume of adsorbent and not on the uptake per unit mass of adsorbent, it is neeessary to eonvert the mass uptake to a volume uptake. In this way an estimate of the possible storage capacity of an adsorbent can be made. To do this, the mass uptake has to be multiplied by the density of the adsorbent. Ihis density, for a powdered or granular material, should be the packing (bulk) density of the adsorbent, or the piece density if the adsorbent is in the form of a monolith. Thus a carbon adsorbent which adsorbs 150 mg methane per gram at 3.5 MPa and has a packed density of 0.50 g/ml, would store 75 g methane per liter plus any methane which is in the gas phase in the void or macropore volume. This can be multiplied by 1.5 to convert to the more popular unit, V/V. 

Brown et al. [494] developed a method for the production of hydrated niobium or tantalum pentoxide from fluoride-containing solutions. The essence of the method is that the fluorotantalic or oxyfluoroniobic acid solution is mixed in stages with aqueous ammonia at controlled pH, temperature, and precipitation time. The above conditions enable to produce tantalum or niobium hydroxides with a narrow particle size distribution. The precipitated hydroxides are calcinated at temperatures above 790°C, yielding tantalum oxide powder that is characterized by a pack density of approximately 3 g/cm3. Niobium oxide is obtained by thermal treatment of niobium hydroxide at temperatures above 650°C. The product obtained has a pack density of approximately 1.8 g/cm3. The specific surface area of tantalum oxide and niobium oxide is nominally about 3 or 2 m2/g, respectively. 

Size, Particle Size Distribution, and Packed Density of Powdered Materials , MIL-STD-1233 (March 1962) 3) Anon, EngDesHdbk, Pro-... 

Powdered Teflon for use in pyrots is covered by US Mil Spec MIL-P-48296IPA) (1 May 1974), Polytetrafluoroethylene (TFE) . Three classes of material are specified (1,2 3). The requirements are purity, 99.4% min infrared spectrum, peaks consistent with figure shown color, TFE shall be opaque and the color shall range from white to gray moisture, 0.05% max ash, 0.1% max mp, 337° 10°C packing density, Class 1 — 1.18 0.13g/cc, Class 2 - 1.25 0.02g/cc, Class 3- 1.14 0.09g/cc particle size by sieve analysis, Class 1 — 95 15 microns, Class 2 — 237 27 microns, Class 3 — 200 30 microns particle size distribution by sieve analysis, as specified in Table 1... 

The bulk density of a powder is calculated by dividing its mass by the volume occupied by the powder (Abdullah Geldart, 1999). Tapped bulk density, or simply tapped density, is the maximum packing density of a powder achieved under the influence of well-defined, externally applied forces (Oliveira et al., 2010). Because the volume includes the spaces between particles as well as the envelope volumes of the particles themselves, the bulk and tapped density of a powder are highly dependent on how the particles are packed. This fact is related to the morphology of its particles and such parameters are able to predict the powder flow properties and its compressibility. 

In general, the material density of porous solids decreases with the development of porosity, as it can be seen in Figure 4 for various powdered activated carbons, where tap and packing density values are plotted versus the micropore volume. 

Figure 4. Density of the powder activated carbons (packing density ( ) and tap density ( )) versus the total micropore volume Vpp (N2).

From the above it can be said that MOF-5 s density goes from around 0.3 g cm"3 (packing density) up to a maximum value of 0.59 g cm 3 (crystal density), giving values of volumetric uptake capacity at 77 K and 4 MPa from 15.6 g L 1 up to 30.6 g L 1. The more realistic value of volumetric uptake capacity (15.6 g L 1) obtained using the MOF s packing density is lower than those obtained in the present study for powder activated carbons, as one can see in Figure 5. 

Parallel investigations of amorphous silica and quartz were executed by Stober (173, 218, 219, 225) with many reactions. No essential difference in reaction behavior and in the packing density of the surface groups was observed. Of course, quantitative measurements were not as accurate with quartz powder as with high surface area Aerosil. 

The coercive force of a powder is an extrinsic property, which is influenced by many factors such as size and shape and packing density. Maghemite particles prepared from directly precipitated spindle-type hematite particles showed a tendency of increase in coercive force with decrease in particle size, and increase in their aspect ratios (31). However, a quantitative relationship between the coercive force and size and/or aspect ratio is still not available. 

The foregoing treatment assumes that at least one of the reactants is a single crystal and the reactant/product geometry is well-defined. Many technologically important ceramic reactions, on the other hand, are usually carried out between polycrystalline powders. The reaction kinetics in these cases depend on several physical factors such as particle size, packing density, porosity, and so on. Jander (1927) and Carter (1961) have proposed models for powder reactions making several simplifying assumptions. 

Bulk density, or packing density, includes all pores and voids (interparticle spaces) in its calculation. This value depends on the form of the particle (powder, tablets, or extmdates) and the packing procedure. It is extensively used in reactor designing since this value connects the solid volume with that of the reactor. 

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