High-Temperature Environment

Ceramic matrices are usually chosen on their merits as high temperature materials reinforcements are added to improve their toughness, reUabiUty, and damage tolerance. The matrix imparts protection to the reinforcements from chemical reaction with the high temperature environment. The principal concerns in choosing a matrix material are its high temperature properties, such as strength, oxidation resistance, and microstmctural stabiUty, and chemical compatibihty with the reinforcement. 

Scott latex-coated products are designed for high temperature environments and long cycle crops such as commercial ornamental production and specialty agriculture. 

A PFBC boiler is visually similar to an AFBC boiler. The combustor is made of water-wall tubing, which contains the high-temperature environment, but the whole assembly is placed within a pressure vessel. Unlike an AFBC unit, there is no convection pass, as the flue-gas temperature must be maintained at boiler temperature to maximize energy recovery by the expansion turbine. There is an economizer after the turbine for final heat recoveiy. A simplified schematic is presented in Fig. 27-49. An 80-MWe demonstration plant, operating at 1.2 MPa (180 psia), began operation in 1989 with a power producdion intensity of 3 MWe/m (1 MWe/3.5 fU). By 1996, five units of this size had been construcded, and a 320-MWe unit is planned to commence operation in 1998. 

Kalen, B., and O Broin, A. E., Emtrol Corporation, A Unique Solution-Cyclone Support in a High-Temperature Environment, presented at Katalistik s 8th Annual FCC Symposium, Budapest, Hungary, June 1, 1987. 

Since 1950, plastics have been development for uses in very high temperature environments. By 1954, it was demonstrated that plastic materials were suitable for thermally protecting structures during intense propulsion heating. This discovery, at that time, became one of the greatest achievements of modern times, because it essentially initially eliminated the thermal barrier to hypersonic atmospheric flight as well as many of the internal heating problems associated with chemical propulsion systems. 

A corrosion inhibitor that is the adduct of a carbonyl compound, an amine, and a thiocyanate has been described [1431]. The product provides protection against ferrous corrosion in severe environments. 500 ppm by weight is sufficient. The inhibitor is employed in wells producing both oil and water and in high-temperature environments around 120° C. 

G. M. Graham, S. J. Dyer, and P. Shone. Potential application of amine methylene phosphonate based inhibitor species in HP/HT (high pres-sure/high temperature) environments for improved carbonate scale... 

The purpose of the various Ingredients Is to provide desirable fluid properties at different times 1n the treatment. For example, the crosslinker system may be designed to have a low reaction rate while the fluid 1s at low temperatures (such as those found 1n the mixing tanks and before the fluid has traveled very far Into the fracture). Then as the fluid temperature Increases above a threshold value, the crosslinking rate accelerates and changes the rheology of the fluid to one more desirable 1n the low-shear, but high-temperature, environment of the fracture. 

The synthesis of chalcogenides such as those of the rare earth elements has traditionally been performed through the reaction of rare earth metals or oxides with a molten or vaporous chalcogen source in a high-temperature environment. Soft synthetic methods utilizing lower temperature conditions, such as hydrothermal or flux syntheses, can allow access also to thermodynamically metastable phases. Flux syntheses of R chalcogenides via an alkali poly-chalcogenide flux have been shown to be extremely versatile for the preparation of many new structures, some of which cannot be obtained by direct synthesis from the elements. 

Kaufmaim RS (1989) Equilibrium exchange models for chlorine stable isotope fractionation in high temperature environments. In Proc 6 Int S>mp Water-Rock Interaction. Miles DL (ed) p 365-368 Kaufmann RS, Frape SK, Fritz P, Bentley H (1987) Chlorine stable isotope composition of Canadian Shield brines. In Saline Water and Gases in Crystalline Rocks, Fritz P, Frq)e SK (eds) Geological Association of Canada Special Paper 33 89-93... 

IRON ISOTOPE VARIATIONS IN HIGH TEMPERATURE ENVIRONMENTS... 

To prove or disprove such a modified superheated-liquid model, experiments are necessary to delineate the rates and products of reaction between molten metals and water in a high-temperature environment with and without substrates which could participate in the reaction. 

A broader, more generie name for fuel eells operating at the temperatures described in this seetion would be "ceramie" fuel eells. The electrolyte of these eells is made primarily from solid ceramie material to smvive the high temperature environment. The eleetrolyte of present SOFCs is oxygen ion conducting. Ceramic cells eould also be proton eonducting. 

Carbon monoxide (CO) and hydrocarbons such as methane (CH4) can be used as fuels in SOFCs. It is feasible that the water gas shift involving CO (CO + H2O H2 + CO2) and the steam reforming of CH4 (CH4 + H2O 3H2 + CO) occur at the high temperature environment of SOFCs to produce H2 that is easily oxidized at the anode. The direct oxidation of CO in fuel cells also is well established. It appears that the reforming of CH4 to hydrogen predominates in... 

On the other hand, since most of these reactions are thermally activated, their kinetics are accelerated by the rise in temperature in an Arrhenius-like manner. Therefore, within a much shorter time scale, the adverse effect of these reactions could become rather significant during the storage or operation of the cells at elevated temperatures. In this sense, the long-term and the thermal stability of electrolytes can actually be considered as two independent issues that are closely intertwined. The study of temperature effects on electrolyte stability is made necessary by the concerns over the aging of electrolytes in lithium-based devices, which in practical applications are expected to tolerate certain high-temperature environments. The ability of an electrolyte to remain operative at elevated temperatures is especially important for applications that are military/space-related or traction-related (e.g., electric or hybrid electric vehicles). On the other hand, elevated tem-... 

A fourth process for catalyst decay involves the structural modification or sintering of the catalyst surface caused by exposure of the catalyst to extreme conditions. This type of decay is dependent on the time that the catalyst spends in the high temperature environment, and since it is unaffected by the materials in the gas stream we call it independent deactivation. 

A diesel fuel stabilizer containing a blend of amines, polyamines, and alkyl ammonium alkyl phosphate as specified under MIL-S-53021 is recommended for federal diesel fuel oil. This stabilizer is to be used at a treat rate of 25 lb/1,000 barrels. It is not intended for use in routine applications, but for situations where increased stability protection is required. Typical applications include fueled equipment undergoing long-term storage in a warehouse or depot, prepositioned equipment or equipment maintained in a high-temperature environment. 

Inflammability or Flammability (latter is preferred in modern usage). The ease with which a material (gas, liquid or solid) will ignite, either spontaneously (pyrophoric), from exposure to a high-temperature environment (autoignition), or to a spark or open flame. It also involves the rate of spreading of a flame once it has started. The more readily ignition occurs, the more flammable the material less easily ignited materials are said to be combustible, but the line of demarcation is often indefinite, and depends on the state of subdivision of the material as well as on its chemical nature... 

TATB is an explosive which is resistant to high temperatures, and therefore used in high-temperature environments or where safety from accidental fires is important. TATB is extremely insensitive to initiation by shock and requires a large amount of booster to initiate it. TATB is therefore regarded as an insensitive explosive and will most likely replace HMX and RDX in future explosive compositions. However, the cost of TATB is five to ten times greater than the cost of HMX. 

The CBI process is an endothermic, physical-chemical bonding of metal ions to alumina-silicate crystals in a high temperature environment. The process is accomplished in two stages proportioning and mixing of the additive material with the metal sludge and thermal processing. 

Both of these copper-based lithium primaries are manufactured as button and bobbin-configured cylindrical cells. Copper oxyphosphate cells find particular application in high temperature environments. 

It is costly to make and fabricate because temperature in excess of 1800°C is required lo manufacture it. However, its refractory character coupled with its very high resistance to thermal shock makes it ideal for special laboratory equipment, windows in high-temperature environments, and instruments. 

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