Substrates, low-temperature

More generally for the manufacturing sector flexible is synonymous of rollable , thus the development of deposition techniques fully compatible with plastic substrates, low temperature processes and solution processable materials, and suitable for flexible substrates for roll-to-roll manufacturing technologies is mandatory. 

Properties and Reactions. The products of photo-oxidation of 1,4-dithian, which involved singlet oxygen and presumably the intermediacy of per-sulphoxides, depended critically upon the solvent, temperature, and concentration of substrate, low temperature and aprotic solvents favouring the... 

Multi-chip module (substrate low-temperature, co-fired ceramic, LTCC)... 

On the lower end of the temperature capability, the glass transition temperature can be important. When the temperatme drops below the glass transition of the sealant, the sealant acts like an adhesive rather than a sealant, restricting the movement of the substrates. Low temperatures also cause the sealant in butt joints to be loaded in tension due to thermal contraction of the substrates. When the temperature drops below the glass transition of the sealant, the tensile stress in the sealant, the bondlines, and the substrates increases tremendously. This can result in failure of any of the three. 

Grignard reagent comes from the substitution products it gives with various reactive substrates. When the low-temperature adduct is heated in an autoclave at 90 to 170 C for 3 to 6 hr, it does not rearrange to 2-ethylthiazole (12) as is the case in the pyridine series (436). 

The thermal protection system of the space shutde is composed mainly of subliming or melting ablators that are used below their fusion or vaporization reaction temperatures (42). In addition to the carbon-carbon systems discussed above, a flexible reusable surface insulation composed of Nomex felt substrate, a Du Pont polyamide fiber material, is used on a large portion of the upper surface. High and low temperature reusable surface insulation composed of siHca-based low density tiles are used on the bottom surface of the vehicle, which sees a more severe reentry heating environment than does the upper surface of the vehicle (43). 

Ethylene vinyl acetate copolymer (EVA) forms a soft, tacky film with good water-vapor barrier but very poor gas-barrier properties. It is widely used as a low temperature initiation and broad-range, heat-sealing medium. The film also serves for lamination to other substrates for heat-sealing purposes. 

Low temperature (It) tars of Eischer-Tropsch (ET) fractions provide reasonable substrates for growth of yeast for human or animal food supplements. Yeast growth yields were 99.8% (ET fraction), 95.2 and 84.2% (It tar) of those from a petroleum-derived paraffin fraction (63) (see Eoods, nonconventional). 

Because di-/ fZ-alkyl peroxides are less susceptible to radical-induced decompositions, they are safer and more efficient radical generators than primary or secondary dialkyl peroxides. They are the preferred dialkyl peroxides for generating free radicals for commercial appHcations. Without reactive substrates present, di-/ fZ-alkyl peroxides decompose to generate alcohols, ketones, hydrocarbons, and minor amounts of ethers, epoxides, and carbon monoxide. Photolysis of di-/ fZ-butyl peroxide generates / fZ-butoxy radicals at low temperatures (75), whereas thermolysis at high temperatures generates methyl radicals by P-scission (44). 

The borides are extremely hard (9.8—29 GPa (1000—3000 kgf/mm ) Knoop) and, in the case of molybdenum, >39 GPa (4000 kfg/mm ) (see Hardness). However, oxidation resistance is usually poor unless a subsequent coating is formed, such as silicidi ing or chromizing, which imparts oxidation resistance. SiUcides are generally very oxidation resistant, but not as hard as borides. SiUcide coatings formed on molybdenum (51 pm in 3 h) at 675°C have superior oxidation resistance. At these low temperatures, the molybdenum substrate does not embrittle and the coatings are quite flexible. 

LB films of 1,4,8,11,15,18-hexaoctyl-22,25-bis-(carboxypropyl)-phthalocyanine (2), an asymmetrically substituted phthalocyanine, were stable monolayers formed at the water—air interface that could be transferred onto hydrophilic siUca substrates (32—34). When a monolayer film of the phthalocyanine derivative was heated, there was a remarkable change in the optical spectmm. This, by comparison to the spectmm of the bulk material, indicated a phase transition from the low temperature herringbone packing, to a high temperature hexagonal packing. 

Plasticizers and Processing Aids. Petroleum-based oils are commonly used as plasticizers. Compound viscosity is reduced, and mixing, processing, and low temperature properties are improved. Air permeabihty is increased by adding extender oils. Plasticizers are selected for their compatibihty and low temperature properties. Butyl mbber has a solubihty parameter of ca 15.3 (f /cm ) [7.5 (cal/cm ) ], similar to paraffinic and naphthenic oils. Polybutenes, paraffin waxes, and low mol wt polyethylene can also be used as plasticizers (qv). Alkyl adipates and sebacates reduce the glass-transition temperature and improve low temperature properties. Process aids, eg, mineral mbber and Stmktol 40 ms, improve filler dispersion and cured adhesion to high unsaturated mbber substrates. 

Unsubstituted 3-alkyl- or 3-aryl-isoxazoles undergo ring cleavage reactions under more vigorous conditions. In these substrates the deprotonation of the H-5 proton is concurrent with fission of the N—O and C(3)—-C(4) bonds, giving a nitrile and an ethynolate anion. The latter is usually hydrolyzed on work-up to a carboxylic acid, but can be trapped at low temperature. As shown by Scheme 33, such reactions could provide useful syntheses of ketenes and /3-lactones (79LA219). 

Cathodoluminescence microscopy and spectroscopy techniques are powerful tools for analyzing the spatial uniformity of stresses in mismatched heterostructures, such as GaAs/Si and GaAs/InP. The stresses in such systems are due to the difference in thermal expansion coefficients between the epitaxial layer and the substrate. The presence of stress in the epitaxial layer leads to the modification of the band structure, and thus affects its electronic properties it also can cause the migration of dislocations, which may lead to the degradation of optoelectronic devices based on such mismatched heterostructures. This application employs low-temperature (preferably liquid-helium) CL microscopy and spectroscopy in conjunction with the known behavior of the optical transitions in the presence of stress to analyze the spatial uniformity of stress in GaAs epitaxial layers. This analysis can reveal,... 

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