Single component powders

In addition to single-component powders, gas-phase synthesis can be used to produce composite powders, such as SiC and BN. An example of an apparatus used for this particular synthesis, which is representative of the apparatuses used for most gas-phase synthesis of particles, is shown in Figure 7.38. 

To conclude, we venture to state that the problem of how to determine accurate optical constants from measurements on particulate samples, in contrast with homogeneous solids and liquids, has not been solved in general, even for single-component powders. This does not mean that there have not... 

For a single component powder cohesion normally implies that the bulk powder has a developed macro-structure which inhibits flow, and when flow does occur it will be of an erratic or stick-slip type. On a smaller scale the same powder could well develop micro-structures of small agglomerates, grits or... 

The sodium and potassium silicates are available as two-component systems filler and binder with the setting agent in the filler. Sodium and potassium silicates are referred to as soluble silicates because of their solubility in water. This prevents their use in many dilute acid services while they are not affected by strong concentrated acids. This disadvantage becomes an advantage for formulating single component powder systems. All that is required is the addition of water at the time of use. The fillers of these materials are pure silica. 

Indexings and Lattice Parameter Determination. From a powder pattern of a single component it is possible to determine the indices of many reflections. From this information and the 20-values for the reflections, it is possible to determine the unit cell parameters. As with single crystals this information can then be used to identify the material by searching the NIST Crystal Data File (see "SmaU Molecule Single Stmcture Determination" above). 

The testing procedures used in this work have all been well described in the literature (4) and are focused on understanding the compression behavior of the powder samples and the mechanical properties of the resulting compacts. These methods are summarized in Table 1. For brevity, we have limited our initial studies to single component systems, but recognize that more work is needed in the future to understand the complex behavior of multicomponent mixtures. The current work should provide a sound basis for further work on such systems. It is intended that this treatise will enable pharmaceutical formulation scientists to better understand the similarities and differences between the most common grades and types of excipients, and will facilitate the rational selection of excipients for use in the development of immediate release tablet formulations. 

Wurster DE, Majuru S, Oh E. Prediction of the Hiestand bonding indices of binary powder mixtures from single-component bonding indices. Pharma Dev Technol 1999 4 65-70. 

In Anglo-Saxon countries nitrocellulose powders are known as single base powders, i.e. made of only one explosive component. 

Magnetic single-component developers in which magnetic powder is comprised in the toner itself, and... 

The term crystallization describes the production of a solid, single-component, crystalline phase from a multicomponent fluid phase. The importance of crystallization lies primarily in the purification achieved during the process and in the physical properties of the product. A crystalline powder is easily handled, stable, and often possesses good flow properties and an attractive appearance. 

Many ceramic powders are based on the precipitation of single component materials from solution. The example of AI2O3 has already been noted, but most of the high purity powders such as metal carbonates used in the electronic ceramics industry are prepared from soluble salts in solutions. High quality Fc203 powder, used by the pigment and magnetic ceramic industries, is prepared by precipitation from iron sulfate or chloride solutions. 

Vapor decomposition is a powder preparation technique useful in a few cases when a vapor phase precursor exists (often an organometallic compound) which can be decomposed to the desired composition . The vapor decomposition usually takes place at elevated temperatures. Single component oxide powders of high purity can be prepared by vapor decomposition of metal alkoxides for example, Zr02 is prepared by pyrolyzing zirconium tetra-t-butoxide. ... 

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