Tungsten Metal Powder

Measuring particle size and growing single crystals 

A typical PSD for a tungsten metal powder where the large particles have been removed is shown as follows. In this ease, the PSD is suitable and particles larger than about 5 n appear to have suceessfiiUy removed. 

Note that we can easily determine the spread of the particles as well as the average size. It is these two parameters whieh are most important in the selection (and modification) of tungsten metal powders to be used to manufacture filaments used in all electronic equipment. Let us now examine a method of calculating a PSD. 

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Ferro tungsten Tungsten metal powder Tungsten carbide powder Tungsten e scrap Other tungsten materials Total... 

Tungstic oxide —- Hydrogen reduction — Tungsten metal powder Figure 5.39 Processing of tungsten resources. 

B430 (Particle Distribution of Tungsten Metal Powder by Turbidimetry) ... 

Oxidation of Tungsten Metal Powder. Tungsten powder, of average grain size > 1 pm, reacts like bulk tungsten. Finer powder qualities, depending on grain size and preparation method, can be pyrophoric. 

The capability of retaining water vapor within the layer is to a certain extent the reason why it can be used as a steering parameter for the final tungsten metal powder properties. The water vapor retention capacity of the layer depends on the layer height and its porosity. The layer height can be chosen within limits in connection with the temperature. The porosity depends on the oxide powder properties. The macroporosity is a consequence of the agglomerate size of the oxide powder (which is related to the size of the crystallized APT particles prior to decomposition) and the microporosity is due to... 

A Hydrogen peroxide is used to dissolve tungsten metal powder samples for analytical... 

The goal of this step—in the classical process achieved by tungstic acid precipitation and successive dissolution by ammonia—is almost total separation of sodium ions, which have been necessary for dissolution but which interfere in the further production steps to tungsten metal powder. Their concentration will be decreased quite effectively from approx. 70g/l to less than lOmg/1. 

Table 13 shows the required particle size distribution, detd in accordance with ASTM procedure B430 (Particle Distribution of Tungsten Metal Powder by Turbidimetry) ... 

Fifty grams of tungsten metal powder is placed in the reactor tray in as thin a layer as possible. The tray is... 

Starting materials, tungsten(VI) chloride [cat. 74-2350] Strem Chemical Co., Newburyport, MA and 12-pm tungsten metal powder, 99.9% (cat. 26,751-1) Aldrich Chemical Co., Milwaukee, WI, were used as received. Both the tungsten metal and tungsten(VI) chloride are air-sensitive and should be manipulated under inert atmosphere. 

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