Powder generation, control

In the absence of air, TEE disproportionates violently to give carbon and carbon tetrafluoride the same amount of energy is generated as in black powder explosions. This type of decomposition is initiated thermally and equipment hot spots must be avoided. The flammability limits of TEE are 14—43% it bums when mixed with air and forms explosive mixtures with air and oxygen. It can be stored in steel cylinders under controlled conditions inhibited with a suitable stabilizer. The oxygen content of the vapor phase should not exceed 10 ppm. Although TEE is nontoxic, it may be contaminated by highly toxic fluorocarbon compounds. 

The main purpose of pesticide formulation is to manufacture a product that has optimum biological efficiency, is convenient to use, and minimizes environmental impacts. The active ingredients are mixed with solvents, adjuvants (boosters), and fillers as necessary to achieve the desired formulation. The types of formulations include wettable powders, soluble concentrates, emulsion concentrates, oil-in-water emulsions, suspension concentrates, suspoemulsions, water-dispersible granules, dry granules, and controlled release, in which the active ingredient is released into the environment from a polymeric carrier, binder, absorbent, or encapsulant at a slow and effective rate. The formulation steps may generate air emissions, liquid effluents, and solid wastes. 

A third approach is to use a stoichiometric amount of preformed lithium naphthalide. This approach allows for very rapid generation of the metal powders as reductions are diffusion controlled. Very low to ambient temperatures can be used for the reduction. In some cases the reductions are slower at low temperatures due to low solubility of the metal salts. 

In order to generate proper size distribution of graphite powder, the milling parameters are adjusted. Changes in particle size distributions for the end-products are controlled with laser particle size analyzers (example Microtrac-XlOO, of Microtrac, Inc., Montgomeryville, PA, USA). 

Main uses. Caesium metal is used in the production of vacuum tubes as a scavenger to reduce residual gaseous impurities after the tubes have been sealed. Cs may be generated in situ by heating a pellet of caesium chromate mixed with a metal powder (Zr, Ca, Ba). Cs metal is used as the propellant in ion thrusters (employed in satellites for orientation control) it is ionized in a vacuum chamber, the Cs+ are then accelerated through a nozzle (high specific impulse because of high atomic mass). 

Dry powder inhalers are generally described as breath actuated devices, because the inspiratory airstream releases the dose from the dose system and supplies the energy for the generation of fine drug particles from the powder formulation. Because the efficiency of dose release and powder disintegration increases with increasing inspiratory flow rate for most DPIs, these devices would be better described as breath controlled devices. In Section 3.9, the effect of resistance and clinical conditions on the flow curve and relevant flow parameters for DPIs are discussed. 

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