Minimum sintering temperature

Table 9. Dependency of Minimum Sintering Temperature on the Electronic Structure of Crystalline Material...

Compo, P., Pfeffer, R., and Tardos, G. I., Minimum Sintering Temperatures and Defluidization Characteristics of Agglomerating Particles, Powder Technology, 51(1) 87-103 (1987)... 

Sintering is a thermodynamically favorable process which decreases the catalyst surface area. Although the catalyst soHd nature and the environment to which the catalyst is exposed influence the process, the sintering phenomenon is basically dominated by temperature. The minimum sintering temperature can be estimated from the melting temperature of the solid (Tmeitmg) expressed in Kelvin ... 

Compo P, Pfeffer R, Tardos GI. Minimum sintering temperatures and defluidization characteristics of fluidizable particles. Powder Tech 51 85-101, 1987. 

Compo P, Tardos GI, Mazzone D, Pfeffer R. Minimum sintering temperatures of fluidizable particles. Part Charact 1 171-177, 1984. 

It was also found [8] that the sintering conditions have significant effects on the resistivity of the Smo.iCeo.gOi.g material. As shown in Fig. 4, the overall resistivity decreases with lower sintering temperature and attains a minimum at the sintering temperature of 1100-1200 °C, which is about 31 ohm-cm at 700 °C measurement. This makes the Smo.2Ceo.801,9 material capable of working as SOFC s electrolyte at temperatures lower than 700 C to avoid possible reduction of cerium (4+) and thus suitable for intermediate-temperature SOFC. 

Using the dilatometer technique, a small sample of powder (about 1 -2 grams) is heated at constant rate in the apparatus depicted schematically in Fig. 43. Dilatation of the sample is measured by a linear voltage transducer (LVDT) contraction of the sample indicates particle-particle surface flattening and defines the minimum softening point ox sintering temperature, Ts. In... 

It was also shown both theoretically and experimentally (Tardos et al., 1985a,b) that there is a strong correlation between the excess temperature above the minimum sintering point, T-Ts, and the excess gas velocity above minimum fluidization conditions (measured below the sintering point) U-lJm required to maintain fluidization. A general correlation was developed between the excess temperature and the excess gas velocity, which takes the form... 

There is a significant difference in the form of Eq. (46) for amorphous and crystalline materials (Compo et al., 1987 and 1990) for the first group, a slight increase in temperature above minimum sintering results in a significant increase in excess gas velocity as can be seen in both, the value of the... 

With the new types of ceramics (e.g, oxide, carbide, etc,), the aim is to achieve the maximum possible density, i.e. a minimum porosity of sintered ware, which is needed for the achievement of optimum properties. At the same time, however, it is necessary to eliminate excessive growth of crystals which hinders elimination of pores and impairs the properties. For this reason the lowest possible sintering temperature should be chosen. 

Ceramic bond formation and grain growth by diffusion are the two prominent reactions for bonding at the high temperature (1100 to 1370°C, or 2000 to 2500°F, for iron ore) employed. The minimum temperature required for sintering may be measured by modern dilatometry techniques, as well as by differential scanning calorimetry. See Compo et al. [Powder Tech., 51(1), 87 (1987) Paiticle Characterization, 1, 171 (1984)] for reviews. 

Decomposition Flame Arresters Above certain minimum pipe diameters, temperatures, and pressures, some gases may propagate decomposition flames in the absence of oxidant. Special in-line arresters have been developed (Fig. 26-27). Both deflagration and detonation flames of acetylene have been arrested by hydrauhc valve arresters, packed beds (which can be additionally water-wetted), and arrays of parallel sintered metal elements. Information on hydraulic and packed-bed arresters can be found in the Compressed Gas Association Pamphlet G1.3, Acetylene Transmission for Chemical Synthesis. Special arresters have also been used for ethylene in 1000- to 1500-psi transmission lines and for ethylene oxide in process units. Since ethylene is not known to detonate in the absence of oxidant, these arresters were designed for in-line deflagration application. 

Acetylene may propagate decomposition flames in the absence of any oxidant above certain minimum conditions of pressure, temperature, and pipe diameter. Acetylene, unlike most other gases, can decompose in a detonative manner. Among the different types of flame arresters that have proven successful in stopping acetylene decomposition flames are hydraulic (liquid seal) flame arresters, packed beds, sintered metal, and metallic balls (metal shot). 

This material sinters at a temperature above about 125°C and melts at 130 to 135 C UV absorption X maximum 255 m/j, X minimum 240 m/j. It contains one ester group and no N-methyl groups. 

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