Ultra-fine metal powder

Two slightly different laser desorption/ionisation methods were developed simultaneously by Karas and Hillenkamp [1] and Tanaka et al. [2]. Whereas Karas and Hillenkamp used small organic matrix molecules to assist and facilitate the desorption and ionisation of analytes (MALDI), Tanaka et al. used ultra-fine metal powders and glycerol. Zumbiihl et al. first analysed natural triterpenoid resins, dammar and mastic, both... 

Sol-gel processes have several advantages over other techniques for the synthesis of nano-scale metal oxides. Because the process begins with a relatively homogeneous mixture, the resulting product is generally a uniform ultra-fine porous powder. Sol-gel processing also has the advantage that it can be scaled up to accommodate industrial-scale production. 

Despite Tab. 7.2, powders can be the preferred product form for various applications, due, for example, to their high volume-specific surface area and the resulting high reactivity. Even ultra-fine powders can be produced in spray fluidized beds. For this purpose, one follows Fig. 7.1c. However, the coating is created with the sole purpose of its subsequent in situ destruction by particle-particle collisions. The material created by attrition is now the real product of the process, which is carried out of the fluidized bed by the gas and can be collected in a cyclone or in filter bags. The core particles are carriers for the coating and, simultaneously, the promoters of its destruction, so that they have to be heavy and rigid. Metallic carrier particles can be heated by wall contact or by induction, so that the creation of ultra-fine powder can be combined with its thermal treatment. 

Sodium powder is prepared by melting S g of carefully cleaned cut sodium metal in 250 mL of boiling xylenes. After removal of the heating bath a slow stream of nitrogen is passed over the solvent, and a high speed stirrer (20,000 rpm, e.g., Ultra-Turrax, model T 18/10) is introduced and run for 15 s. The finely divided metal is filtered and washed (three l5-mL portions of pentane) under inert gas and sucked dry. It can be stored in a dry box for months without loss of activity. ... 

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