Fabricating process

The pre-mixed molding materials contain randomly arranged fibers. They give properties approximately equal in all directions though with 

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It is estimated that there are in USA about 80,000 injection molding machines (IMMs) and about 18,000 extruders operating. This difference in the amount of machines is due the fact that there is more activity (product design, R8cD, fabrication, etc.) required with injection molding (IM). 

If an extruder can be used to produce products it has definite operating and economical advantages compared to IM. It requires detailed process control. IM requires more sophisticated process control to fabricate many thousands of different complex and intricate products. 

While the processes differ, there are elements common to many of them. In the majority of cases, TP compounds in the form of pellets, granules, flake, and powder, are melted by heat so they can flow. 

Pressure is often involved in forcing the molten plastic into a mold cavity or through a die and cooling must be provided to allow the molten plastic to harden. With TSs, heat and pressure also are most often used, only in this case, higher heat (rather than cooling) serves to cure or harden the TS plastic, under pressure, in the mold. When liquid TPs or TSs plastics incorporate certain additives, heat and/or pressure need not necessarily be used. 

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There have been numerous efforts to inspect specimens by ultrasonic reflectivity (or pulse-echo) measurements. In these inspections ultrasonic reflectivity is often used to observe changes in the acoustical impedance, and from this observation to localize defects in the specimen. However, the term defect is related to any discontinuity within the specimen and, consequently, more information is needed than only ultrasonic reflectivity to define the discontinuity as a defect. This information may be provided by three-dimensional ultrasonic reflection tomography and a priori knowledge about the specimen (e.g., the specimen fabrication process, its design, the intended purpose and the material). A more comprehensive review of defect characterization and related nondestructive evaluation (NDE) methods is provided elsewhere [1]. 

Greskovioh C 1976 Milling Ceramic Fabrication Processes, Treatise on Materials Science and Technology vo 9, ed F F Y Wang (New York Aoademio) pp 15-33... 

Brindiey G W 1960 ion exchange in ciay minerais Ceramic Fabrication Processes ed W D Kingery (New York Wiiey) pp 11-23... 

Fig. 7. Fabrication process for MLC capacitors. Steps are (a) powder (b) slurry preparation (c) tape preparation (d) electroding (e) stacking (f) lamination (g) dicing (h) burnout and firing and (i) termination and lead attachment.

M. H. Leipold, "Hot Pressing," ia F. F. Y. Wang, ed.. Treatise on Materials Science and Technology, Vol. 9 (Ceramic Fabrication Processes), Academic Press, New York, 1976. 

For high temperature fuel ceUs, there is stiU a strong need to develop lower cost materials for ceU components. In the case of SOFCs, improved fabrication processes and materials that permit acceptable performance in fuel ceUs at lower operating temperatures are also highly desirable. 

Etching. After a resist is patterned on a wafer, the exposed or unwanted substrate is removed by etching processes. Subsequentiy the resist is removed, leaving a desired pattern in a functional layer of the integrated circuit. Etching is performed to pattern a number of materials in the IC fabrication process, including blanket polysiHcon, metal layers, and oxide and nitride layers. The etch process for each material is different, and adapted to the material requirements of the substrate. 

There are several important fabrication processes for metal-matrix composites. 

The cost of a PV device is determined by several factors. These include the kind of materials used and the amount of materials requited, choice of substrates, device design, and fabrication processes. Crystalline devices ate generally mote efficient, but thin-film devices ate anticipated to cost less in flat-plate configurations. The use of concentrated light permits retention of efficiency with simultaneous reduction in cost. 

Antioxidants (qv) are used to prevent thermal and oxidative degradation of nylon in manufacturing, post-fiber and fabric processing, and final use. 

Methacrylate monomers are most effective with derivatives of bisphenol A epoxy dimethacrylates, in which the methacrylate—methacrylate cross-linking reaction proceeds at a much faster pace than with styrene monomer. This proves beneficial in some fabrication processes requiring faster cure, such as pultmsion and resin-transfer mol ding (RTM). 

Catalyst Selection. The low resin viscosity and ambient temperature cure systems developed from peroxides have faciUtated the expansion of polyester resins on a commercial scale, using relatively simple fabrication techniques in open molds at ambient temperatures. The dominant catalyst systems used for ambient fabrication processes are based on metal (redox) promoters used in combination with hydroperoxides and peroxides commonly found in commercial MEKP and related perketones (13). Promoters such as styrene-soluble cobalt octoate undergo controlled reduction—oxidation (redox) reactions with MEKP that generate peroxy free radicals to initiate a controlled cross-linking reaction. 

Some fabrication processes, such as continuous panel processes, are mn at elevated temperatures to improve productivity. Dual-catalyst systems are commonly used to initiate a controlled rapid gel and then a fast cure to complete the cross-linking reaction. Cumene hydroperoxide initiated at 50°C with benzyl trimethyl ammonium hydroxide and copper naphthenate in combination with tert-huty octoate are preferred for panel products. Other heat-initiated catalysts, such as lauroyl peroxide and tert-huty perbenzoate, are optional systems. Eor higher temperature mol ding processes such as pultmsion or matched metal die mol ding at temperatures of 150°C, dual-catalyst systems are usually employed based on /-butyl perbenzoate and 2,5-dimethyl-2,5-di-2-ethyIhexanoylperoxy-hexane (Table 6). 

The channel conductance (p 7j, g /U g) is proportional to the ratio of width to length for the channel, IU E. is deterrnined by the fabrication process, and E by photoHthography leaving the layout (HUE) to be adjusted by the circuit designer to achieve an appropriate trade-off between circuit speed and area. For k g small compared with V g — Up, the channel conductance is a constant, increasing with U g — Up. 

This article focuses primarily on the properties of the most extensively studied III—V and II—VI compound semiconductors and is presented in five sections (/) a brief summary of the physical (mechanical and electrical) properties of the 2incblende cubic semiconductors (2) a description of the metal organic chemical vapor deposition (MOCVD) process. MOCVD is the preferred technology for the commercial growth of most heteroepitaxial semiconductor material (J) the physics and (4) apphcations of electronic and photonic devices and (5) the fabrication process technology in use to create both electronic and photonic devices and circuits. 

As with any other fabrication process, masks are needed to define the features to be etched. It is common that the etch used for the semiconductor also etches the masking material. For this reason many different masks are used in etching, including photoresist, dielectric films, and metals. Masking can be a complex issue, especially when very deep etches (>5 fim) are performed with high aspect ratios (148). 

During the fabrication process the surface of the semiconductor is etched and metal contacts are deposited. These features can represent a topographical challenge to subsequent metal wiring levels. For this reason it is important that the dielectric film used tends to smooth out such discontinuities as metal and etched edges (150,217). Additional appHcations for spin-on dielectrics include forming integrated microlenses for optoelectronics (218). 

Blow Molding. Blow mol ding is a multistep fabrication process for manufacturing hoUow symmetrical objects. The granules are melted and a parison is obtained by extmsion or by injection mol ding. The parison is then enclosed by the mold, and pressure or vacuum is appHed to force the material to assume the contour of the mold. After sufficient cooling, the object is ejected. 

J. H. Jean and T. A. Ring, in R. W. Davidge, ed.. Novel Ceramic Fabrication Processes and Applications, Institute of Ceramics, Stoke-on-Trent, U.K, 1986, pp. 11-33. 

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