High temperature capability

Because of their low thermal conductivity, high temperature capability, low cost, and neutron tolerance, carbon materials make ideal thermal insulators in nuclear reactor environments. For example, the HTTR currently under construction in Japan, uses a baked carbon material (Sigri, Germany grade ASR-ORB) as a thermal insulator layer at the base of the core, between the lower plenum graphite blocks and the bottom floor graphite blocks [47]. 

Flush aerodynamic Restores full strength high-temperature capability Time consuming usually limited to depot requires refrigeration Time consuming High... 

Intermetallic alloys (compounds) are becoming of increasing interest as materials which possess significantly enhanced high temperature capabilities compared to many conventional metallic alloys. However, they suffer intrinsic problems associated with low-temperature ductility and fracture toughness. Two types of... 

The particulates drift to the wall of the separator, where they aggregate with other particulates and precipitate into a collection hopper. The acoustic barrier particulate separator differs from other separators by combining both high-efficiency and high-temperature capabilities. 

Both gas turbine and process heat versions of the HTGR are based on the demonstrated high-temperature capability of the fuel and core structure. However, some development in the metallic components, such as the turbine, hot duels and intermediate heat exchanger is necessary, Present commercial alloys would have limited lifetime under service conditions at 1650°F (899°C) and above. However, currently envisioned advancements in ceramics and carbon-carbon composites indicate that high-temperature nonmctallic substitutes for metallic alloys will soon be available. These materials advances are the key to making future application of the IITGR a reality. 

Epoxy-phenolic adhesives are made by blending epoxy resins with phenolic resins to improve the high-temperature capabilities of the standard epoxy resins. Developed in the early 1950s, they were the first high-temperature epoxy adhesives to become commercially available.2,3... 

The oxide and ceramic binders have been studied by several research groups, but do not seem to have been much used in practice or made commercially available. They are a rather heterogeneous group with considerable theoretical potential, being capable of withstanding temperatures of the order of 1000° compared with 400°C for molybdenum disulphide. There has therefore been a tendency to use the ceramics and oxides themselves as lubricants to retain the best high-temperature capabilities. 

However, in view of the high-temperature capabilities of thermoplastic materials based on aromatic rings linked by thermally and oxidatively stable units such as ether, ketone, sulfone, or direct bonds,3 we have attempted to develop linear, carborane-copolymers of this same general type. We here describe synthetic and crystallographic studies of such materials, and report on their potential applications in membrane separation and in ceramic-precursor chemistry. 

Ordered polymer films made from poly benzthiazole (PBZT) and poly benzoxazole (PBO) can be used as substrates for multilayer printed circuit boards and advanced interconnects to fill the current need for high speed, high density packaging. Foster-Miller, Inc. has made thin substrates (0.002 in.) using biaxially oriented liquid crystal polymer films processed from nematic solutions. PBZT films were processed and laminated to make a substrate with dielectric constant of 2.8 at 1 MHz, and a controllable CTE of 3 to 7 ppm/°C. The films were evaluated for use in multilayer boards (MLBs) which require thin interconnect substrates with uniform controllable coefficient of thermal expansion (CTE), excellent dielectric properties, low moisture absorption, high temperature capability, and simple reliable processing methods. We found that ordered polymer films surpass the limitations of fiber reinforced resins and meet the requirements of future chip-to-chip interconnection. 

Despite the addition of anti-oxidants, di-ester-based lubricants are limited in their high-temperature capabilities by a P-hydrogen abstraction. The structure of the di-ester molecule allows it to form a hydrogen-bonded, six-membered, ring. This results in the breakdown of the molecule into an alkene and aldehyde, which then leads to further chemical breakdown as follows ... 

An overview of capillary gas chromatography is presented. Selected environmental applications, such as PCB s in water, PAH s in airborne particulate matter, and TCDD s at the part-per-trillion level illustrate the separation and analysis of complex mixtures. The chromatographic performance, characteristics, and trade-offs of packed and capillary columns are described in terms of permeability and efficiency, sample capacity, choice of stationary phase, high temperature capabilities, quantitative accuracy, and the development of GC separation methods. 

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