Powder performance specifications

Metal or metal oxides may be added to perform specific functions. Brass chips and copper powder are frequently used in heavy-duty organics where these metaUics act as scavengers to break up undesirable surface films. Zinc chips used in Class A organics contribute significantly to recovery of normal performance following fade. Aluminum is also used. Most of these inorganic materials tend to detract from antinoise properties and mating surface compatibihty. 

Data on reduction of these metals (Ta, Mo, W, Zr, Hf) from chlorides in arc discharges in hydrogen (Case, 1967 Chizhikov etal., 1976) are summarized in Table 7-4. The table proves that hydrogen conversion of chlorides into pnre metals can be quite high in arc discharges, up to 98%. Metals produced in these experiments are in powder form. Specific surface areas of the powder can be different - from 0.6 to 13 m /g - which is due to differences in methods of separation of gas and the powder. When the separation is performed at temperatures exceeding 600-700 K, agglomeration of particulates takes place and the specific surface area of the powder decreases. 

Treatment of high-density PE film and powder with specific surface area 2 m /g has also been performed using low-pressure continuous RF discharge (Vasilets et al., 1979 Ponomarev, 1982 Ponomarev Vasilets, 2000 Vasilets, 2005). The voltage amplitude in this case was... 

In the United States, a number of physical tests are performed on siUcon carbide using standard AGA-approved methods, including particle size (sieve) analysis, bulk density, capillarity (wettabiUty), friabiUty, and sedimentation. Specifications for particle size depend on the use for example, coated abrasive requirements (134) are different from the requirements for general industrial abrasives. In Europe and Japan, requirements are again set by ISO and JSA, respectively. Standards for industrial grain are approximately the same as in the United States, but sizing standards are different for both coated abrasives and powders. 

In the second part of the 20th century, the tantalum capacitor industry became a major consumer of tantalum powder. Electrochemically produced tantalum powder, which is characterized by an inconsistent dendrite structure, does not meet the requirements of the tantalum capacitor industry and thus has never been used for this purpose. This is the reason that current production of tantalum powder is performed by sodium reduction of potassium fluorotantalate from molten systems that also contain alkali metal halides. The development of electronics that require smaller sizes and higher capacitances drove the tantalum powder industry to the production of purer and finer powder providing a higher specific charge — CV per gram. This trend initiated the vigorous and rapid development of a sodium reduction process. 

The change from zinc sheet to zinc powder improved the high-current performance of the cell significantly but it increased the corrosion problems (a larger specific surface means a higher corrosion rate). 

The above findings are quite significant since they indicate a clear way to design solvent evaporation in the bed when the binder is a solution or the cooling time when the binder is a melt. One has to stress, however, that the above estimates are probably not very general and may require corrections for different pairs of powders and binders. Since the experimental procedure and the instrument are quite simple and straightforward to use, such measurements should be easy to perform for each specific case. 

Materials purchased for the purpose of mixing with other materials in the preparation of pharmaceutical products are called raw materials. Pharmaceutical companies often purchase solid raw materials as powders in large drums. Quality assurance laboratories require samples of the material in the drums for the purpose of performing quality tests to see if the raw materials meet the specifications required for the company s products. 

Some quality factors, especially secondary ones, depend directly on material or structural attributes of the product. These product quality factors are often arbitrary and can only be qualitatively evaluated by panels of consumers or experts. Convenience for use, product stability, and ability for human skin protection are all examples of these quality factors. Each arbitrary performance index has specific relationships with the material/structural attributes. In such cases, the desirable quality factor can be realized by directly changing the formulation without concerning any of the performance indices. An example can be that to make a laundry detergent product more convenient to use, the product form can be changed from powder to tablet. Another example is that to make a highly biodegradable product, surfactants with less branching should be used. 

ENDOR experiments can be performed in liquid solution, in which only the isotropic hfc s (Ajso) are detected. They are proportional to the spin density at the respective nucleus. Erom the assigned isotropic hfc s a map of the spin density distribution over the molecule can be obtained. In frozen solutions and powders the anisotropic hf interactions can also be determined. Eurthermore, the method allows the detection of nuclear quadrupole couplings for nuclei with 1 1. For dominant g anisotropy as found in many metal complexes the external magnetic field can be set to several specific g values in the EPR, thereby selecting only those molecules that have their g tensor axis along the chosen field direction. In such orientation-selected spectra only those hf components are selected that correspond to this molecular orientation ( single crystal-like ENDOR ). 

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