Powder compaction controlling

The success of compression agglomeration depends on the effective utilization and transmission ofthe applied external force and on the ability of the material to form and maintain interparticle bonds during pressure compaction (or consolidation) and decompression. Both these aspects are controlled in turn by the geometiy of the confined space, the nature of the apphed loads and the physical properties of the particulate material and of the confining walls. (See the section on Powder Mechanics and Powder Compaction.)... 

Fig. 6.5. The shock-compression conditions imposed on powder compacts preserved for post-shock analysis are controlled by details of the shock-recovery fixtures. In all the work of Chap. 6, the Sandia Bear and Bertha fixtures are used. The fixtures represent a standardized system that is highly reproducible and has been subject to extensive numerical simulation.

If the transport process is rate-determining, the rate is controlled by the diffusion coefficient of the migrating species. There are several models that describe diffusion-controlled processes. A useful model has been proposed for a reaction occurring at the interface between two solid phases A and B [290]. This model can work for both solids and compressed liquids because it doesn t take into account the crystalline environment but only the diffusion coefficient. This model was initially developed for planar interface reactions, and then it was applied by lander [291] to powdered compacts. The starting point is the so-called parabolic law, describing the bulk-diffusion-controlled growth of a product layer in a unidirectional process, occurring on a planar interface where the reaction surface remains constant ... 

The tableting indices methods, summarized in Table 1, require powder compacts that are prepared under carefully controlled conditions so that they are essentially free of flaws (4,7). These compacts are the samples used for indentation hardness and TS measurements. 

Stress transmission in powders controls flow out of hoppers, feeders, filling of tubes, and compaction problems such as tableting and roll pressing. (See Powder Compaction. )... 

J.P. van Houten, On the Control of Powder Compact Microstructure through Methods of Wet Consolidation, Thesis, Delft University 1995. 

Moon, J. et al.. Slurry chemistry control to produce easily redispersible ceramic powder compacts, J. Am. Ceram. Soc., 83. 2401. 2000. 

Atmosphere. The effect of atmosphere can be critical to the densifica-tion of a powder compact. In some cases, the atmosphere can enhance the diffusivity of a rate-controlling species, e.g., by influencing the defect structure. In other cases, the presence of a certain gas can promote coarsening by enhancing the vapor pressure and totally... 

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