Powders characteristics

In precipitation reactions, powder characteristics depend on the speed of the nucleation of particles and their growth due to the mass flow to the surfaces. In freeze drying and spray drying, powder characteristics primarily depend on the size of droplets, which in turn is determined by the parameters of a nozzle and characteristics of the flow of a carrier gas. Both these methods enable one to obtain powders with very high surface area. 

Solid state reactions are also very common in producing oxide materials and are based on thermal treatment of solid oxides, hydroxides and metal salts (carbonates, oxalates, nitrates, sulphates, acetates, etc.) which decompose and react forming target products and evolving gaseous products. Solid-state chemistry states that, like in the case of precipitation, powder characteristics depend on the speed of the nucleation of particles and their growth however, these processes in solids are much slower than in liquids. 

E. Antolini, R. R. Passos, and E. A. Ticianelli. Effects of the carbon powder characteristics in the cathode gas diffusion layer on the performance of polymer electrolyte fuel cells. Journal of Power Sources 109 (2002) 477-482. 

The respirable powders of a DPI cannot be characterized adequately by single-particle studies alone bulk properties must also be assessed since they contribute to ease of manufacture and affect system performance. Primary bulk properties include particle size, particle size distribution, bulk density, and surface area. These properties, along with particle electrostatics, shape, surface morphology, etc., affect secondary bulk-powder characteristics such as powder fiow, handling, consolidation, and dispersibility. 

Bulk Powder Characteristics Data for Sorbitol Lots... 

The typical processing conditions and powder characteristics are shown in Table 8.1.6 and Table 8.1.7, respectively. The compaction property of this powder was... 

Schmidt PC, Rubensdorfer CJW. Evaluation of Ludipress as a multipurpose excipient for direct compression. Part I powder characteristics and tableting properties. Drug Dev Ind Pharm 1994 20 2899-2925. 

The surface oil content of the three encapsulated orange oils ranged from 102 (powder A) to 909 (powder C) mg/100 g powder, which corresponded to 0.67(powder A) and 7.10 (powder C) oil. Powders B and C had about 2 1/2 and 9 times surface oil as compared to powder A. This was not expected since powders with larger diameters had less calculated surface area as shown in Table I. It is therefore speculated that other powder characteristics, e.g. surface morphology, may play an important role on the oil retention properties and should be further studied. 

Kim Y. S., 1976, Effects of powder characteristics, in F. F. Y. Wang (Ed.), Treatise of Materials Science and Technology, Vol. 9 Ceramic Fabrication Processes, Academic Press, New York. 

Table 7. Typical Si3N4 powder characteristics (From different commercial data sheets)...

Powder characteristics of a physico-chemical nature, such as solubility, wettability, dispersability, and measures of the instant properties of powders (sludge, slowly dispersible particles, hot water sediment and coffee test), are determined by a variety of empirical physical tests, some of which incorporate subjective elements. These and the other tests for whole milk powders identified above are described in detail by Westergaard (1994) and Pisecky (1997). 

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