Fired substrate

Beta-amylases (EC 3.2.1.2) (Fig. 34A,B) are exo-enzymes that attack fire substrate from the nonreducing end and hydrolyze a-(l—>4) glueosidie linkages. Maltose (disaccharide) molecules are successively detached from the non-reducing end during hydrolysis by beta-amylase. In addition, glucan (1 4)-a-glucosidases (EC 3.2.1.3,... 

In the subsequent sections, properties of a few compositions are presented in order to make a case for a non-fired substrate approach as an alternative to firing. Fused silica and... 

Furthermore, when the finished fired substrate is heated and cooled repeatedly, if the mismatch between the thermal expansion of the dissimilar materials is significant, it has been pointed out that cracking and so on may occur between the dissimilar materirds. 

Coating Theory. This theory includes fire retardants which form an impervious skin on the fiber surface. This coating may be formed during normal chemical finishing, or subsequently when the fire retardant and substrate are heated. It excludes the air necessary for flame propagation and traps any tarry volatiles produced during pyrolysis of the substrate. Examples of this type of agent include the easily fusible salts such as carbonates or borates. 

Metal powder—glass powder—binder mixtures are used to apply conductive (or resistive) coatings to ceramics or metals, especially for printed circuits and electronics parts on ceramic substrates, such as multichip modules. Multiple layers of aluminum nitride [24304-00-5] AIN, or aluminay ceramic are fused with copper sheet and other metals in powdered form. The mixtures are appHed as a paste, paint, or slurry, then fired to fuse the metal and glass to the surface while burning off the binder. Copper, palladium, gold, silver, and many alloys are commonly used. 

Cordierite [12182-53-5] Mg Al Si O g, is a ceramic made from talc (25%), kaolin (65%), and Al O (10%). It has the lowest thermal expansion coefficient of any commercial ceramic and thus tremendous thermal shock resistance. It has traditionally been used for kiln furniture and mote recently for automotive exhaust catalyst substrates. In the latter, the cordierite taw materials ate mixed as a wet paste, extmded into the honeycomb shape, then dried and fired. The finished part is coated with transition-metal catalysts in a separate process. 

Other small molecule species decompose and volatilise. The glass frit fuses, wetting the surface of the functional phase, providing adhesion and sealing of the composite to the substrate. Because of the screen printing process, resolution is modest. Fired film thicknesses, which range from 10 to 50 p.m (0.4 to 2.0 mils), are large compared to thin-fHm microelectronics. Some photosensitive pastes are also ia use. 

Cera.mic, The ceramic substrate is made from a mixture of siUcon dioxide, talc, and kaolin to make the compound cordierite [12182-53-5]. Cordierite possesses a very low coefficient of thermal expansion and is thermal-shock resistant. The manufacturing process involves extmding the starting mixture (which is mixed with water and kneaded into a sort of dough) through a complex die to form the honeycomb stmcture. The extmded piece is dried and fired in a kiln to form the cordierite. The outside or circumferential dimension is formed by the die, and the length is cut later with a ceramic saw. 

E-beam is a relatively cold process and so is more suitable for heat-sensitive substrates. UV lamps emit about one third UV light and the rest is visible and IR. Consequently substrates can get very hot, even causing fires if they become stuck beneath the lamp. Safety shutters which close if the line stops are installed on many UV bulbs. 

Once a fire has started, control of the fire can be accomplished in several ways through water systems (by reducing the temperature), carbon dioxide or foam systems (by limiting oxygen), or through removal of the substrate (by shutting off valves or other controls). Chapter 4 provides detailed discussion on the theories of fire and specific information on hydrocarbons, as well as chemical specific fire characteristics. 

The catalyst is normally contained on a ceramic substrate. These ceramics are extruded in a malleable state and then fired in ovens. The process consists of... 

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