Sintering and Melting

Recently this problem has been circumvented by the synthesis of so-called plugs which are in effect conventional resins that have been sintered and melt fused with a polyalkene (Fig. 1.11) [55]. Each cylindrical plug is 7 mmxlO mm and the level of polyalkene employed is low enough for much of the interstitial space between the resin beads to be retained hence providing ready access by solvent and reagents to the core of the plug. 

Di-iodo-3 3 -dinitro-4 4 -dihydroxyarsenobenzene is suspended in ether and treated mth iodine, when the arsine di-iodide is produced. The latter is then hydrolysed with aqueous sodium bicarbonate, the oxide being obtained as an orange-yellow powder, sintering and melting indefinitely between 170 and 210 C. It is sparingly soluble in water, more soluble in alcohol, acetone, ether, benzaldehyde, or pyridine. 

The industrial manufacture of aluminum hydroxide and aluminum oxide currently proceeds almost exclusively by the Bayer process i.e. by wet digestion of bauxite. The sinter- and melt-digestion processes with sodium carbonate and/or lime only have minor industrial importance. 

Nd-Fe-B magnets. Both quantities are of approximately the same size in SmCo5 magnets, whereas Dc exceeds the grain diameter in melt-spun Nd-Fe-B. For this reason the coercivity mechanism in sintered and melt-spun magnets will be discussed separately, together with the corresponding microstructures. 

While most calcium aluminate cements are produced from limestone and alumina (see section 9.5), high purity, refractory-grade material is made by at least one producer using ground quicklime as the source of calcium. The quicklime and alumina are blended and fed to a rotary kiln, where they sinter and melt at over 1500 °C. The molten calcium aluminate (about 70 % AI2O3 and 28 % CaO) is cooled in a rotating cylinder to produce a clinker, which is subsequently ground to substantially less than 90 pm [32.6]. 

Preliminary experiments that have been carried out at the Radium Institute have proved the possibility of a successful synthesis of plutonium-doped ceramics without the use of hot pressing. Now we are considering an application of methods of sintering and melting ... 

Direct Tooling by sintering and melting of metals can be regarded as the most important process to make tool components to be integrated in the final tools. 

Materials for sintering and melting are plastics, metals, or ceramics. Plastics may be unfilled or filled with glass or aluminum spheres or egg-shaped geometries to improve properties like durability and thermal resistance. Also nanoscale particles are used. Unfilled plastics are mostly commodities like semicrystalline polyamides from the PAl 1 or PA12 type or amorphous plastics like polystyrene (PS). Engineering plastics like PEEK are available. 

The sol-gel method makes it possible to prepare refractory materials at considerably lower temperatures than the conventional method of sintering and melt-quenching. Fully sintered mullite ceramics of the composition 3AI2O3 2Si02 are prepared by sol-gel method (Pask, 1987 Ismail, 1987). Alumina-sihcarefractory fibers (Sosman, 1988) and Si02 fibers (Taneda, 1988) are also prepared. 

The processes that are most suitable for rapid tooling, especially the sintering and melting process (see Section 4.7.3.2), only use as much material as necessary for the production of the component. Isolated geometries as free-standing domes and the like are therefore both produced faster and with less material consumption than with erosive or machining processes. 

Sintering and melting processes can process all the materials that behave as a thermoplastic and are available as a powder. They allow the production of internal cavities. The components do not require support structures. The processes are single-stage processes. The components are directly applicable after low rework, if the surface quality is accepted. The relatively rough surface is therefore one of the biggest disadvantages of the procedure. Especially for metal components, the rework becomes complex and also affects the accuracy. 

Components made from plastic, metal, and ceramics can be produced with sintering and melting processes. 

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