Carbide light

Fig. 9-15. Carbides (light areas) in an iron-nickel alloy. The dark line is the contamination mark made by translating the specimen slowly past the electron beam. (Courtesy of Birks and Brooks, Rev. Sci. Instr., 28, 709.)...

Edmond, J., Suvorov, A., Waltz, D. Carter, C. (1997). 6H-Silicon Carbide Light Emitting Diodes and UV Photodiodes. Phsyica Status Solidi (a), Vol. 162, p. 481... 

Figure 16.4 Photomicrograph of a WC-Co cemented carbide. Light areas are the cobalt matrix dark regions are the particles of tungsten carbide. lOOx.

Silicon is important to plant and animal life. Diatoms in both fresh and salt water extract Silica from the water to build their cell walls. Silica is present in the ashes of plants and in the human skeleton. Silicon is an important ingredient in steel silicon carbide is one of the most important abrasives and has been used in lasers to produce coherent light of 4560 A. 

Lithium Acetylide. Lithium acetyhde—ethylenediamine complex [50475-76-8], LiCM7H -112X01120112X112, is obtained as colodess-to-light-tan, free-flowing crystals from the reaction of /V-lithoethylenediamine and acetylene in an appropriate solvent (131). The complex decomposes slowly above 40°O to lithium carbide and ethylenediamine. Lithium acetyhde—ethylenediamine is very soluble in primary amines, ethylenediamine, and dimethyl sulfoxide. It is slightly soluble in ether, THF, and secondary and tertiary amines, and is insoluble in hydrocarbons. 

For erosive wear. Rockwell or Brinell hardness is likely to show an inverse relation with carbon and low alloy steels. If they contain over about 0.55 percent carbon, they can be hardened to a high level. However, at the same or even at lower hardness, certain martensitic cast irons (HC 250 and Ni-Hard) can out perform carbon and low alloy steel considerably. For simplification, each of these alloys can be considered a mixture of hard carbide and hardened steel. The usual hardness tests tend to reflect chiefly the steel portion, indicating perhaps from 500 to 650 BHN. Even the Rockwell diamond cone indenter is too large to measure the hardness of the carbides a sharp diamond point with a light load must be used. The Vickers diamond pyramid indenter provides this, giving values around 1,100 for the iron carbide in Ni-Hard and 1,700 for the chromium carbide in HC 250. (These numbers have the same mathematical basis as the more common Brinell hardness numbers.) The microscopically revealed differences in carbide hardness accounts for the superior erosion resistance of these cast irons versus the hardened steels. 

Cihal and Prazak determined the resistance of 18/8 stainless steel to this type of corrosion. They claimed that the technique could be used on steels which are difficult to test by other methods, including steels of low carbon content, and steels in which stabilising elements are present. By means of potentiostatic curves and light etching at constant potential they confirmed that the extent of intergranular corrosion depended upon the amount of precipitated chromium carbide. 

A vapor phase process for deparaffmization of light gas oils performed by the BP works in this way The gas oil, boiling range 230-320°C, is passed over a 5-A molecular sieve at 320°C and a pressure of 3.6 bar. The space velocity is 0.63 vol liquid gas oil per vol molecular sieve and per hour, [liquid hourly space velocity (lhsv) = 0.63] the adsorption period takes 6 min. Together with the gas oil vapor 120 vol N2 per vol liquid gas oil is led over the sieve as carrier and purge gas. After the adsorption period the loaded molecular sieve is purged at the same temperature with pure N2 for 6 min. Subsequently, the adsorbed /z-alkanes are desorbed by 1 vol liquid /z-pentane per vol molecular sieve and per hour. The /z-pentane is recovered from the /z-alkane//z-pentane mixture by simple distillation [15]. The IsoSiv process of the Union Carbide Corporation works in a similar way [16]. The purity of the isolated /z-alkanes is >98%. 

The Lawrie Tea Processor (LTP) is used in Africa to macerate lightly withered leaf. A hammer mill, in which final particle size can be controlled by degree of wither and adjustment of the tungsten-carbide-tipped beaters, is essential. 

As these experiments indicate, polysilanes can in some cases be converted to silicon carbide directly, without the necessity for formation of polycarbosilane, fractionation, or oxidation. For example, polysilastyrene copolymers can be formed into films or fibers and then crosslinked by irradiation with UV light. The crosslinked polysilane forms silicon carbide when heated to 1100°C in vacuum. (1U This method can be used in a "printing" mode, if a film of polysilane is cast onto a ceramic or metal substrate, then... 

The first synthetic polymers to be used as paint varnishes were acrylic and vinylic resins. Poly(vinyl acetate) (PVAc), commercialized under the name Mowilith by Hoechst and Vinylite by Union Carbide, has been used in conservation as an adhesive since 1932 and in 1937 it was proposed as a picture varnish by Stout and Cross [63]. PVAc was soon rejected as a varnish because, despite its light stability and good solubility in organic solvents, it demonstrated poor optical properties in terms of colour saturation and the tendency to pick up dirt due to its low glass transition temperature. 

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