C and Above

NASA Glenn Research Center 21000 Brookpark Road Cleveland, Ohio 44135 Phone 216-433-55al4 James.A.DiCarlo NASA.gov 

As structural materials for high-temperature components in advanced engines forpower and propulsion, fiber-reinforced ceramic matrix composites (CMC) offer a variety ofperfor-mance advantages overthe best metallic alloys with current stractural capability to 1100°C. 

TABLE I. Key CMC Property Goals, Controlling Factors, and Demonstration Tests for 

CMC Demonstration Tfest (Typically conducted on specimens from thin CMC panels) 

High tensile Proportional Limit Stress (PLS) after CMC processing (allows high CMC design stress and high environmental resistance) 

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Psychrometrics. Psychrometrics is the branch of thermodynamics that deals specifically with moist air, a biaary mixture of dry air and water vapor. The properties of moist air are frequentiy presented on psychrometric charts such as that shown ia Figure 2 for the normal air conditioning range at atmospheric pressure. Similar charts exist for temperatures below 0°C and above 50°C as well as for other barometric pressures. AH mass properties ate related to the mass of the dry air. 

Because PTFE resins decompose slowly, they may be heated to a high temperature. The toxicity of the pyrolysis products warrants care where exposure of personnel is likely to occur (120). Above 230°C decomposition rates become measurable (0.0001% per hour). Small amounts of toxic perfiuoroisobutylene have been isolated at 400°C and above free fluorine has never been found. Above 690°C the decomposition products bum but do not support combustion if the heat is removed. Combustion products consist primarily of carbon dioxide, carbon tetrafluoride, and small quantities of toxic and corrosive hydrogen fluoride. The PTFE resins are nonflammable and do not propagate flame. 

C or higher for the kaolin-based products to 1425°C and above for the zirconium-containing materials. At temperatures above 1000°C these ceramic fibers tend to devitrify and partially crystallize. Specially prepared ceramic fibers are used to protect space vehicles on re-entry and can withstand temperatures above 1250°C (see Ablative materials Refractory fibers). 

Measurements of stress relaxation on tempering indicate that, in a plain carbon steel, residual stresses are significantly lowered by heating to temperatures as low as 150°C, but that temperatures of 480°C and above are required to reduce these stresses to adequately low values. The times and temperatures required for stress reUef depend on the high temperature yield strength of the steel, because stress reUef results from the localized plastic flow that occurs when the steel is heated to a temperature where its yield strength is less than the internal stress. This phenomenon may be affected markedly by composition, and particularly by alloy additions. 

The primary use for methyl bromide is in the extermination of insect and rodent pests. Methyl bromide is used in space and stmctural fumigation except in California. The material is suitable for the fumigation of food commodities such as dried fmits, grain, flour, and nuts, and the faciHties in which these foods are processed or stored, as weU as for tobacco and many kinds of nursery stock. The usual dosage is 2—4 kg/28 m for 12—24 h. In soil fumigation methyl bromide controls weed seeds, nematodes, wireworms, and soil fungi. The usual dosage is 0.5—1 kg/9 m for 24 h at 16°C and above (82). 

Typical positive temperature coefficient (PTC) device behavior for a doped polycrystaHine BaTiO thermistor is presented in Figure 4. At temperatures below - 100° C and above - 200° C the material shows the expected negative resistivity vs temperature associated with semiconductors as expressed by ... 

Membrane Reactor. Another area of current activity uses membranes in ethane dehydrogenation to shift the ethane to ethylene equiUbrium. The use of membranes is not new, and has been used in many separation processes. However, these membranes, which are mostly biomembranes, are not suitable for dehydrogenation reactions that require high temperatures. Technology has improved to produce ceramic and other inorganic (90) membranes that can be used at high temperatures (600°C and above). In addition, the suitable catalysts can be coated without blocking the pores of the membrane. Therefore, catalyst-coated membranes can be used for reaction and separation. 

Uncharged azoles not containing oxygen or sulfur are often resistant to attack by hydroxide ions at temperatures up to 100 °C and above. However, neutral azoles react with hydroxide ions under extreme conditions, e.g. 1-substituted imidazoles such as (153) at 300°C give the corresponding imidazolinone (154) 80AHC(27)24l). 

The sulphation of cobalt oxide, CoO, follows the parabolic law up to 700°C and above 850°C, proceeding by outward diffusion of cobalt and oxygen ions through a sulphate layer which is coherent up to about 700°C. The mechanism... 

The polymer melts at 216°C and above this temperature shows better cohesion of the melt than PTFE. It may be processed by conventional thermoplastics processing methods at temperatures in the range 230-290°C. Because of the high melt viscosity high injection moulding pressures are required. 

Allyl esters undergo rearrangement reactions at 300°C and above. Two examples are shown, one of which is degenerate, since the product and reactant are identical ... 

Polyfluoroalkyl- andperfluoroalkyl-substituted CO and CN multiple bonds as dipolarophiles. Dmzo alkanes are well known to react with carbonyl compounds, usually under very mild conditions, to give oxiranes and ketones The reaction has been interpreted as a nucleophilic attack of the diazo alkane on the carbonyl group to yield diazonium betaines or 1,2,3 oxadiazol 2 ines as reaction intermediates, which generally are too unstable to be isolated Aromatic diazo compounds react readily with partially fluorinated and perfluorinated ketones to give l,3,4-oxadiazol-3-ines m high yield At 25 °C and above, the aryloxa-diazolines lose nitrogen to give epoxides [111]... 

Cyclic heating tests on electrically heated nickel-chromium and nickel-chromium-iron wires in nitrogenshowed that the lives to burn-out were at least as good as those obtained in air. The same was true in ammonia at 1 050°C, but at 1 150°C and above the life was less in ammonia than in air (Table 7.30) indicating, as would be expected, that it is atomic nitrogen which is most effectively absorbed. 

Fig. 17. CP-MAS 13C-NMR spectra of threodiisotactic poly(l, 2-dimethyltetrame-thylene) below, c), and above the glass transition, b), in comparison to the spectrum in CDC13 solution at 303 K, a). The chemical shifts given at the signals refer to TMS = 0 ppm. (Ref. 32))...

Curiously, very little TiC was observed at any stage of the treatment it does not appear to be an intermediate to alloy phase formation. A significant amount of alloy phase appears only at 900°C and above. At 1200°C, Pt3Ti is the predominant Ti phase present. 

Figure 5 shows a series of infrared spectra taken during the TPR of NO with CH4. At temperatures less than 350 °C the spectra in Figure 5 are virtually identical to those for NO TPR seen in Figure 4. Above 350 °C the nitrosyl bands are more intense in the presence of CH4. A new peak appears at 2270 cm when the temperature is raised to 400 °C and above, and another one appears at 2173 cm at 450 °C. Neither of these bands was observed when the reaction mixture was passed over Na-ZSM-5. When 5NO was substituted for NO, the two bands appeared at 2256 cm- and 2144 cm, and when 3CH4 was substituted for 12CH4, the bands shifted to 2237 cm and 2132 cm-. Based on previous studies [32-34], the band at 2270 cm- is best attributed to NCO species adsorbed at Al + sites. The observed shift in the...

The reaction of vinyl chloride becomes violent at 90°C and above when oxygen is present. 

Magnesium combuste above 900 C with carbon dioxide. The ignition takes place at a temperature of 780°C and above if water traces are present. This behaviour thus does not allow use of extinguishers containing carbon dioxide for magnesium fires. 

Magnesium combusts when it is heated in air at a temperature of 520°C and above. The magnesium/liquid oxygen mixture is explosive. 

Texturized or denatured WPl retained its native protein value, functionality, and digestibility when extruded below 50 °C changes in functionality occur at 65 °C and above. Through careful selection of extrusion conditions of temperature and moisture, TWPs with unique functionality can be produced. The degree of texturization increased with increasing temperature, but temperatures higher than 100 °C may be needed to form fibrous structures with WPl. 

Hydroboration is thermally reversible. B-H moieties are eliminated from alkyl-boranes at 160° C and above, but the equilibrium still favors of the addition products. 

To study the factors leading to the unusual hydrolytic stability of polydimethacrylamides, we synthesized poly[N-(4-sulfophenyl)di-methacrylamide] (PSPDM) (IV). PSPDf s water soluble, in contrast to the previously studied polymers. The hydrolytic stability of PSPDM was studied in acidic, neutral, and basic aqueous solutions at 90 C and above. The results of these experiments will be described. 

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