Silicate heat capacity

Brunauer and co-workers [129, 130] found values of of 1310, 1180, and 386 ergs/cm for CaO, Ca(OH)2 and tobermorite (a calcium silicate hydrate). Jura and Garland [131] reported a value of 1040 ergs/cm for magnesium oxide. Patterson and coworkers [132] used fractionated sodium chloride particles prepared by a volatilization method to find that the surface contribution to the low-temperature heat capacity varied approximately in proportion to the area determined by gas adsorption. Questions of equilibrium arise in these and adsorption studies on finely divided surfaces as discussed in Section X-3. 

Study of hydrated kaolinites shows that water molecules adsorbed on a phyllosilicate surface occupy two different structural sites. One type of water, "hole" water, is keyed into the ditrigonal holes of the silicate layer, while the other type of water, "associated" water, is situated between and is hydrogen bonded to the hole water molecules. In contrast, hole water is hydrogen bonded to the silicate layer and is less mobile than associated water. At low temperatures, all water molecules form an ordered structure reminiscent of ice as the temperature increases, the associated water disorders progressively, culminating in a rapid change in heat capacity near 270 K. To the extent that the kao-linite surfaces resemble other silicate surfaces, hydrated kaolinites are useful models for water adsorbed on silicate minerals. 

Table 6.9 Parameters for calculation of heat capacity of silicate melts (1) after Carmichael et al. (1977) and Stebbins et al. (1984) (2) model of Richet and Bottinga (1985)...

Table 6.9 lists the parameters of the model of Carmichael et al. (1977) for the heat capacity of silicate melts, recalibrated by Stebbins et al. (1984) and valid for the T range 1200 to 1850 K. To obtain the heat capacity of the melt at each T condition, within the compositional limits of the system, it is sufficient to combine linearly the molar proportions of the constituent oxides multiplied by their respective Cp values (cf equation 6.69). 

Like heat capacity, the molar volume of chemically complex silicate melts may also be obtained through a linear combination of the molar volumes of molten oxide components—i.e.,... 

Richet P. and Bottinga Y. (1985). Heat capacity of aluminium-free liquid silicates. Geochim. 

Robinson G. R. Jr. and Haas I L. Jr. (1983). Heat capacity, relative enthalpy and calorimetric entropy of silicate minerals An empirical method of prediction. Amer. Mineral, 68 541-553. 

Stebbins I F, Carmichael I. S. E. and Moret L. K. (1984). Heat capacities and entropies of silicate liquids and glasses. Contrib. Mineral Petrol, 86 132-148. 

Direct observations of Tm (P) and AV may be made in a sapphire optical cell with simple screw-press pump by measuring the offset in the pressure versus volume curve. AH can be measured at room pressure using a simple differential calorimeter comprised of two paper nut cups outfitted with kitchen thermistors and containing water in one and a standard solid material in the other for which the heat capacity curve is known. Direct observations of pressure-release freezing of water (as compared to pressure-release melting in silicates) may be observed in such an optical pressure cell by sudden release of pressure. 

Owing to their polymeric nature, many silicate compounds and systems tend to form glasses. When cooling rapidly from the molten state, a part of the sample crystallizes, while the other part remains glassy. This is the main disadvantage while measuring their heat capacity, heat content, enthalpy of fusion, and mixing. 

The Barin tables are far more complete in coverage than any of the sources described above. All of the natural elements and their compounds are included. In addition to the substance types listed in USBM Bull 677, the Barin tables include a large number of ternary oxides - aluminates, arsenates, borates, chromates, molybdates, nitrates, oxy-halides, phosphates, titanates, tungstates, selenates, vanadates, zirconates, etc. - as well as cyanides, hydroxides, complex silicates and inter-metallic compounds. The only substances not included by Barin, for which tables can be found elsewhere, are the ionized-gas species and a limited number of gas species important only at very high temperatures, which are listed in the JANAF tables. For each table Dr. Barin gives references for each of the major thermochemical values employed (enthalpy of formation and entropy at 298 K, and heat capacity). Like the USBM Bulletins, no attempt is made to discuss the choice between conflicting data sources. 

VIC/D0U] Victor, A. C., Douglas, T. B., Physical properties of high temperature materials. Part VI. Enthalpy and heat capacity of magnesium oxide, zirconium oxide, and zirconium silicate from 0 to 900°C, Natl.Bur. Stand., Annu. Rep.fU.S.), (1961). Cited on pages 217,218. 

The mean isobaric specific heat capacities Cp (2Q°C 100 °C) listed in Table 3.4-16c were measured from the heat transfer from a hot glass sample at 100 °C into a liquid calorimeter at 20°C. The values of Cp 20°C 100 °C) and also of the true thermal capacity Cp 20 °C) for silicate glasses range from 0.42 to 0.84 J/gK. 

Pot life and exotherm. Fillers can increase pot life and lower exotherm of epoxy systems. Fillers reduce the reactant concentration in the formulation and act as a heat sink. Generally, they have higher heat capacities than the epoxy resins. They are also better heat conductors than the resins, and thus help to dissipate exotherm heat more readily. Commonly used fillers are silica, calcium carbonate, alumina, lithium aluminum silicate, and powdered metals. 

Geiger C, Kolesov BA. Microscopic-macroscr ic relationships in silicates Examples from IR and Raman spectroscopy and heat capacity measurements. In European notes in mineralogy—energy modeUng in minerals, vol. 4 2002. p. 347-87. 

The heat capacity of various zeolites relative to quartz at different temperatures were calculated. All the siliceous zeolites show the same behaviour at different temperatures (Figure 9). Cancrinite and sodalite (not shown) have a much higher heat capacity when compared to other zeolites. This is probably due to their greater stability as shown in Figure 7. The non-siliceous zeolites show that the overall heat capacity is much higher although less stable than siliceous ones. 

Moore and Sharp have found that the mean heat capacity (cal/g) for various silicate... 

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