Shape-forming process

Superplastic forming is used to produce complex-shaped components and unitized structures. Superplasticity has emerged as an attractive, commercial, cost-effective, near-net shape forming process. Superplastic deforma-... 

Richerson, D.W. (2006) Modem Ceramic Engineering, 3rd. edition, CRC Press, Boca Raton, FL. Chapter 13 describes the important shape-forming processes. 

The effects of all the membrane preparation steps (from the powder particle morphology and size distribution, starting composition and membrane shape-forming process and the subsequent thermal treatment) on the structure and permeation behaviour of the resulting... 

K. A. Blakely, The Critical Role of Raw Material Suppliers in Market Development pp. 21-27 in Ceramic Transactions, Vol. 62, Science, Technology and Commercialization of Powder Synthesis and Shape Forming Processes. Edited by J. J. Kingsley, C. H. Schilling, and J. H. Adair. The American Ceramic Society, Westerville, OH, 1996. 

The system described here is chemically extremely simple and easy to handle but gives rise to complex coupled physical processes. The surfactant concentration, used here as a control parameter, induces an amazing range of shapes and motion patterns. Coupled to these shape-forming processes is the emission of very small but macroscopic droplets. This system is the first example of such a sequence of highly ordered patterns induced by coupled hydrodynamic instabilities. The resulting structures show very efficient motility, internal agitation and dispersion properties. 

Aluminum alloys are commercially available in a wide variety of cast forms and in wrought mill products produced by rolling, extmsion, drawing, or forging. The mill products may be further shaped by a variety of metal working and forming processes and assembled by conventional joining procedures into more complex components and stmctures. 

Hydrolysis of aluminum alkoxides is also used commercially to produce precursor gels. This approach avoids the introduction of undesirable anions or cations so that the need for extensive washing is reduced. Although gels having surface area over 800 m /g can be produced by this approach, the commercial products are mosdy pseudoboehmite powders in the 200 —300 m /g range (28). The forming processes already described are used to convert these powders into activated alumina shapes. 

A considerable amount of information has been reported regarding mass transfer between a single fluid phase and solid particles (such as those of spherical and cylindrical shape) forming a fixed bed. A recent review has been presented by Norman (N2). The applicability of such data to calculations regarding trickle-flow processes is, however, questionable, due to the fundamental difference between the liquid flow pattern of a fixed bed with trickle flow and that of a fixed bed in which the entire void volume is occupied by one fluid. 

Many process response curves have an S-shaped form, as given in Fig. 2.19. 

Organometallic polymer precursors offer the potential to manufacture shaped forms of advanced ceramic materials using low temperature processing. Polysilazanes, compounds containing Si-N bonds in the polymer backbone, can be used as precursors to silicon nitride containing ceramic materials. This chapter provides an overview of the general synthetic approaches to polysilazanes with particular emphasis on the synthesis of preceramic polysilazanes. 

Hollow sand casting is a relatively simple process for making cast metal objects that for thousands of years was the most widely used of all casting methods. For the most basic castings, the molds are made from ordinary silica sand mixed with water so as to keep the sand particles compacted together to maintain the required hollow-shaped form. The hot, fluid... 

Extruders play a key role in many conversions processes we use them to melt solid polymers and pump the resulting molten material to a die or a mold. After the molten polymer has been molded to the desired shape, it is cooled to form a solid product. We can feed the output of an extruder to continuous forming processes to create films, pipes, and fibers. Alternatively, we can employ discontinuous molding processes to create discrete items, such as soda bottles, lenses for single use cameras, or bathtubs. 

Figure 1.7. Shapes of solidified droplets (particles) generated in powder production and spray forming processes, (a) Spherical shape gas-atomized gold alloy particles (b) near-spherical and dendritic shapes water-atomized bronze particles (c) irregular and porous (spongiform) shapes water-atomized zinc particles (d) irregular aggregates water-atomized copper particles (Cour. tesy of Atomizing Systems Ltd., UK.)...

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