Casting techniques metals

Slip casting of metal powders closely follows ceramic slip casting techniques (see Ceramics). SHp, which is a viscous Hquid containing finely divided metal particles in a stable suspension, is poured into a plaster-of-Paris mold of the shape desired. As the Hquid is absorbed by the mold, the metal particles are carried to the wall and deposited there. This occurs equally in all directions and equally for metal particles of all sizes which gives a uniformly thick layer of powder deposited at the mold wall. 

Conventional machining operations are used preferably from the same plastic to be used in the product (Chapter 8, SECONDARY EQUIPMENT). Different casting techniques are used that provide low cost even though they are usually labor intensive. The casting of unfilled or filled/reinforced plastic used include TS polyurethane, epoxy, structural foam, and RTV silicone. Also used are die cast metals. 

Metal Casting Techniques. Many ancient cast metal objects were made by the cire perdue (lost wax) casting process, which involves pouring molten metal into a one-piece mold and letting it solidify modem fakes are usually cast in two halves that are then joined. A casting fin, or a fine line of filed solder on a cast object, usually reveals that the casting is modem. 

Finally, metal- and resin-bonded composites are also classified as particulate composites. Metal-bonded composites included structural parts, electrical contact materials, metal-cutting tools, and magnet materials and are formed by incorporating metallic or ceramic particulates such as WC, TiC, W, or Mo in metal matrixes through traditional powder metallurgical or casting techniques. Resin-bonded composites are composed of particulate fillers such as silica flour, wood flour, mica, or glass spheres in phenol-formaldehyde (Bakelite), epoxy, polyester, or thermoplastic matrixes. 

Different foundry casting techniques are used. Included are plastic-based binders mixed with sand. Various types of molds and cores are produced that include no-bake or cold-box, hot-box, shell, and oven-cured. Usual binders are phenolic, furan, and thermoset polyester. There is the foundry shell casting, also called dry-mix casting. It is a type of process used in the foundry industry, in which a mixture of sand and plastic (phenolic, thermoset polyester, etc.) is placed on to a preheated metal pattern (producing half a mold) causing the plastic to flow and build a thin shell over the pattern. Liquid plastic pre-coated sand is also used. After a short cure time at high temperature, the mold is stripped from its pattern and combined with a similar half produced by the same technique. Finished mold is then ready to receive the molten metal. Blowing a liquid plastic/sand mix in a core-box also produces shell molds. 

As more sophisticated metal hydrides are developed (nanocrystalline, multicomponent systems, composites and nanocomposites, graphite/metals or similar hybrid systems, clusters, etc.), it is important to be a vare that, for practical applications, a large volume of material should be processed in a fast, inexpensive and reliable vay, for example casting. Techniques such as cold vapor deposition may be impossible to scale up but this does not mean they should be discarded as a means of studying new metal hydrides. On the contrary, laboratory techniques allow much better control of the end product and permit the elaboration of new compounds. Once an attractive compound is found then another challenge w ill have to be faced scaling up the synthesis. In this respect, it is important for the community of metal hydrides researchers to also study large-scale production techniques in order to make the transition from laboratory to industrial scale easier. 

Spin-casting techniques have also been used to prepare imprinted thin films. Makote and Collinson recently prepared metal oxide thin films imprinted with recognition sites for dopamine [18], The dopamine template was loaded at 4 mole % in a sol with a 10 1 ratio of tetramethoxysilane and phenyltrimethoxysilane. The prepared film had a thickness of ca. 450 nm. CV analysis found that 90% of the templates could be removed by washing the films with pH 7 phosphate buffer. The opened receptor sites offered selective binding for related molecules containing catechol amines, such as dopamine, epinephrine and norepinephrine, as determined by CV. The use of phenyltrimethoxysilane turns out to be an essential ingredient for the gel matrix and is believed to provide some complementary affinity for the catechol amines via hydrophobic and/or 7i-stacking interactions. 

Silanes are often used to modify metal oxide surfaces, especially those rich in hydroxyl groups, to enable a broad range of functionalities such as hydrophilicity, immobilization of therapeutic agents, polymers, and cells, and the creation of model surfaces [67-72]. The easiest methods of deposition of silane compounds involve dipping or solution casting techniques. Other methods for depositing silanes include microwave and vapor deposition techniques [70, 71, 73]. 

William Hyde Wollaston first described this type of adhesion experiment in 1829. He was interested in making dense and strong wires from platinum and other rare metals, such as palladium and osmium, which he had just diseovered. Platinum is so hard and refractory that it is extremely difficult to work by ordinary melting and casting techniques. Wollaston prepared the platinum in fine particle form by precipitating the metal from an acid solution which had been used to remove impurities. This produced a muddy mixture of water and particles which were cleaned by washing, then dispersed by milling in a wooden mortar and pestle. Wood was used to limit contamination since it would burn out later. 

K. R. Forwald, G. Schussler, (1992) Aspects upon silicon metal casting techniques , in Silicon for the Chemical Industry, ed. H. A. 0ye, H. Rong, Institute of Inorganic Chemistry, NTH, Trondheim, p. 39-46, ISBN 82-90265-10-7. 

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