Coated Crucible

Mix and put them in a wide, red hot iron pot, and stir the mixture constantly, until it be burnt into a matter of an ash grey colour, which is to be then removed from the fire, ground into powder, and put into a coated crucible lute to this crucible another inverted over it, and perforated in the bottom with a small hole, and apply the fire, which is to be raised gradually to a white heat, and kept in that increased state for two hours lastly, grind the matter, when cold, into a very fine powder. 

In the block casting process, source silicon is melted in a first quartz crucible and poured into a second, nitride-coated crucible. Heaters are used to control cooling to produce columnar grains. Relative to Bridgeman, faster solidification is possible but at the expense of smaller grains. 

Lithium fluoride may be used in the preparation of single crystals for optical, photoelectric and dielectric studies, as well as for coating crucibles used in melting Li metal. 

LaSe is prepared from the elements in corundum coated crucibles placed in a quartz ampule at 1000 to 1100°C and 10 Torr, followed by an additional heat treatment at 1100°C for 50 to 60 h, Yarembash etal. [6]. More convenient preparation for the golden yellow or bronze-colored compound are given on p. 7. 

The extraction of titanium is still relatively costly first the dioxide Ti02 is converted to the tetrachloride TiCl4 by heating with carbon in a stream of chlorine the tetrachloride is a volatile liquid which can be rendered pure by fractional distillation. The next stage is costly the reduction of the tetrachloride to the metal, with magnesium. must be carried out in a molybdenum-coated iron crucible in an atmospheric of argon at about 1100 K ... 

Calcination is performed in crucibles made of platinum or related metals. Tantalum or niobium oxide can be successfully used in the manufacturing of such crucibles. Frolov et al. [505, 506] developed a method for coating various ceramic materials with tantalum or niobium oxide using an optical furnace. 

Beryllium Oxide (Bromellite). BeO, mw 25.01, white amorph powd, mp 2530°, bp ca 3900°, d 3.01g/cc. Sol in coned acids and alkalies. V si sol in w. Prepn is by burning BeC03 at 900° in a Pt crucible to the oxide. It is used in nuclear reactor fuels and moderators as well as in powder metallurgy, ceramics, fuel cells and coatings (see above)... 

Diffusion, corrosion Crucibles Ion barriers (sodium) Fiber coatings Reaction vessels... 

The synthetic method used in preparing a particular boride phase depends primarily on its intended use. Whereas for basic research borides of high purity are desirable, for industrial applications, e.g., in coatings, tools and crucibles, as a refining agent in metallurgy or in control rods in nuclear energy plants, pure borides are unnecessary. 

Pulse-mode pyrolyzers include resistively-heated electrical filaments or ribbons and radio frequency induction-heated wires [841,842,846,848,849]. The filament or ribbon-type pyrolyzers are simple to construct. Figure 8.45, and typically consist of an inert wire or ribbon (Pt or Pt-Rh alloy) connected to a high-current power supply. Samples soluble in a volatile solvent are applied to the fileutent as a thin film. Insoluble materials are placed in a crucible or quartz tube, heated by a basket-lilce shaped or helical wound filiunent. The coated filament is contained within a low dead volume chamber through which the carrier gas flows, sweeping the pyrolysis products onto the column. The surface temperatui of the filament is raised rapidly from ambient temperature to He equilibrium pyrolysis temperature. This... 

Silicon nitride (Si N ), resistant to oxidation, is an excellent coating for metals, as well as an adhesive and abrasive, and it is used in high-temperature crucibles. It has proven useful as heat-resistant substance for the nozzles on rocket engines. 

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