Characterization at High Temperature

High temperature mechanical characterization was performed on the PAIC compositions with Al/Si = 0.05 and 0.1. The elastic modulus has been measured in air at various temperatures between 800 and 1400°C by four point bend tests (40 X 20 mm) with a 0.2 mm min deformation rate. E has been calculated, through the standard equation valid for rectangular bars, by measuring the displacement with a LVDT. All the ceramic samples obtained by pyrolysis at 1000°C have been pre-annealed at 1400°C for 1 h in argon atmosphere, before the high temperature tests. This treatment lead to the crystallization of microcrystalline pSiC with a minor amount of aSiC. Aluminum atoms are present both as a solid solution of AI2OC in aSiC and in the residual amorphous phase. 

The results of the elastic modulus measurements are reported in Table 2. The evolution of the elastic modulus with the temperature for the Al/Si = 0.05 composition is reported in Fig. 12. It can be noticed that the elastic modulus is constant up to 

6 Polymer to Ceramic Transformation Processing of Ceramic Bodies and Thin Films 

1100°C. Above this temperature the slight decrease of E is probably related to the viscous deformation of the amorphous silicon oxycarbide phase that shows a glass transition temperature of 1300°C [76]. 

In this work, crack-free, dense (up to 92% theoretical density), amorphous SiAlOC ceramic components with good mechanical properties have been obtained at low temperature (T = 1000°C) by direct pyrolysis of pre-ceramic green bodies. 

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Hardesty, D. R. and Pohl, J. H., "The Combustion of Pulverized Coals-An Assessment of Research Needs, Proceedings of the 10th Materials Research Symposium on Characterization at High Temperature Vapor and Gases, National Bureau of Standards Special Publication 561, 1979, p. 1407. 

G. Simon and A. R. Bunsell, Creep behaviour and structural characterization at high temperatures of Nicalon SIC fibres. J. Mater. Sci., 19.3658-70 (1984). 

The hydroformylation of allylic alkenes is characterized, at high temperatures, by competing isomerization [22]. Significant regioselectivity ratios for the hydroformylation of the sole terminal double bond have been obtained by carrying out the reaction at partial substrate conversion, when the starting terminal alkene is still present in excess relative to that resulting from isomerization [22b]. In 1 -hexene hydroformylation the amount of... 

A lubricant should be characterized by its viscosity at low temperature (-18°C) to account for its behavior during cold weather starting and by its viscosity at high temperature (100°C). Values of these two viscosities are based on the SAE classification. See Chapter 6. 

Thousands of compounds of the actinide elements have been prepared, and the properties of some of the important binary compounds are summarized in Table 8 (13,17,18,22). The binary compounds with carbon, boron, nitrogen, siUcon, and sulfur are not included these are of interest, however, because of their stabiUty at high temperatures. A large number of ternary compounds, including numerous oxyhaUdes, and more compHcated compounds have been synthesized and characterized. These include many intermediate (nonstoichiometric) oxides, and besides the nitrates, sulfates, peroxides, and carbonates, compounds such as phosphates, arsenates, cyanides, cyanates, thiocyanates, selenocyanates, sulfites, selenates, selenites, teUurates, tellurites, selenides, and teUurides. 

Hard-burned lime is a quicklime that is calcined at high temperature and is generally characterized by relatively high density and moderate-to-low chemical reactivity. 

In principle, it is possible to obtain ECC in the absence of molecular orientation if the crystallization is carried out very slowly at high temperatures close to the melting temperature. Thus, Mandelkern obtained polyethylene crystals similar to ECC in their thermodynamic characteristics by a 40 days crystallization of an isotropic melt28. These experiments also characterize one of the possible paths of the generation of order in polymers order through fluctuations 29 (see below). 

It can be shown that high temperature levels and R-A have virtually no broadening effect on CCD dispersion because 3 has a small temperature coefficient, which frequently even takes on negative values causing drift dispersion to actually lessen at high temperatures. Figures 7 and 8 show the smallness and direction (improvement) of temperature effect on drift, and the ability of 3k to characterize direction (see crossover in Figure 7... 

Several studies have been published to assess the kinetics of polymerization reactions at high temperatures. (irZ) However, most of these studies only describe experiments conducted at isothermal conditions. Only a few papers are based on adiabatic runaways. This paper is one of the first studies based on "first principles" characterizing adiabatic runaway reactions. 

Isotropic carbon is obtained by the pyrolysis of a hydrocarbon, usually methane, at high temperature (1200-1500°C) in a fluidized bed on a graphite substrate.Under these conditions, a turbostratic structure is obtained which is characterized by very little ordering and an essentially random orientation of small crystallites. In contrast to graphite which is highly anisotropic, such a structure has isotropic properties (see Ch. 7). Isotropic carbon is completely inert biologically. Its properties are compared to alumina, another common implant material, in Table 17.8. Notable is its high strain to failure. 

Both rolling resistance and heat buildup are related to hysteresis that is the amount of energy that is converted to heat during cychc deformation. It is well known that hysteresis of tread compounds, characterized by the loss factor, tan 8, at high temperature, is a key parameter. It not only governs heat buildup of the compounds under dynamic strain but also shows a good correlation with the... 

Recently characterization of bimetallic nanoparticles by EXAFS were extensively reported [122-124,176], Structural transformation of bimetallic Pd/Pt nanoparticles, which were prepared by a sequential loading of H2PtClg onto the Pd loaded catalyst, was investigated with EXAFS at high temperatures [176], The results of EXAFS at Pd K and Pt L-III edges showed that Pt was surface-enriched or anchored on the Pd metal core with an increase of the Pt content. The structure of the obtained bimetallic Pd/Pt nanoparticles seemed to be retained upon heating up to 1273 K under ambient condition [176], Pt/ Au bimetallic nanoparticles can be prepared by polyol method and stabilized by PVP [122], XANES and EXAFS studies were also performed on the samples and their results supported the idea of a Pt-core/Au-shell structure with the elements segregated from each other [122],... 

The Okuaizu geothermal system is characterized by high temperatures (maximum 340°C), high salinity (about 2 wt% total dissolved solids (TDS)) and large amounts of non-condensable gases (1 wt% CO2 and 200 ppm H2S). The pH of the hydrothermal solution measured at 25°C is 6.44 (Table 2.6). However, the pH of the original fluid in the reservoir is computed to be 4.05. This pH as well as alkali and alkali earth element concentrations are plotted near the equilibrium curve of albite, K-mica, anhydrite and calcite (Fig. 2.19) (Seki, 1991). 

Gonsalves, K. Agarwal, R. presentation at "High Temperature Structural Composites Synthesis, Characterization Properties" Symposium May 87, sponsored by MRS, NJ. 

We can further characterize polymers into thermoplastics and thermosets . Thermoplastics consist of linear or lightly branched chains that can slide past one another under the influence of temperature and pressure. These polymers flow at high temperatures which facilitates their molding into useful products. Thermosets consist of a network of interconnected chains whose positions are fixed relative to their neighbors. Such polymers do not flow when heated. 

Vapor quenching provides a method of bridging the miscibility gap which exists in many alloy systems, and makes a range of novel alloys available for study. Such films, of course, would not be ideal for catalytic studies. They could not be used at high temperatures, and indeed the heat of reaction might be sufficient to induce a transformation to a more stable structure. In addition, characterization by X-ray diffraction would be difficult, even for the crystalline films, because of line broadening by the small crystallites. Nevertheless, alloy films which are metastable above room temperature can be prepared, and their high surface area would... 

Based upon raw material and intended application, the manufacturing of activated carbon falls into two mam categories thermal activation and chemical activation. In general, thermal activation involves the heating/gasification of carbon at high temperatures [13], while chemical activation is characterized by the chemical dehydration of the raw material at significantly lower temperatures [11,14],... 

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