Heat capacity experiments

Measurements of heat capacity jumps at the glass-transition temperatures, Tg, in the matrix material and the composites, carried out from heat-capacity experiments, were intimately related to the extent of the mesophase thickness. Further accurate measurements of the overall longitudinal elastic modulus of the composites and the... 

Low temperature heat capacity experiments with huckminsterfullerene, Ceo, indicate that this substance does not follow the Dehye equation, but requires a more complex model. See W. P. Beyermann, et al. Phys. Rev. Lett. 68, 2046 (1992). 

Figure 14. Proposed low-coverage melting phase diagram of N2 on graphite according to an improved incipient triple-point model [261] (solid lines) and the density functional treatment [305] (dashed lines). Dots indicate the location of the coexistence boundary from heat capacity experiments. (Adapted from Fig. 3 of Ref. 261.)...

The heat capacity of polyoxymethylene, determined as above [6], is shown in Fig. 4 along with experimental values [14]. It is worth noting that the heat capacity experiments must be performed on specimens that are semicrystalline. Extrapolations are made vs crystallinity to arrive at the values tabulated and shown as experimental. Thus there can be uncertainties due to the extrapolation process and therefore the calculated values form a valuable check on the experimental ones. 

Returning to the Gd case, reports from heat capacity experiments both in zero and applied magnetic fields, indicated a complex low temperature behaviour with at least two transitions in zero field, at 0.9 K and 0.6 Neutron diffraction data, taken on a GdiTiiOy sample... 

High-resolution x-ray scattering and heat capacity experiments have been used to investigate the critical behaviour near the nematic-smectic A phase transition. 

It is manifestly impossible to measure heat capacities down to exactly 0 K, so some kind of extrapolation is necessary. Unless were to approach zero as T approaches zero, the limiting value of C T would not be finite and the first integral in equation (A2.1.71) would be infinite. Experiments suggested that C might... 

Sengers and coworkers (1999) have made calculations for the coexistence curve and the heat capacity of the real fluid SF and the real mixture 3-methylpentane + nitroethane and the agreement with experiment is excellent their comparison for the mixture [28] is shown in figure A2.5.28. 

In this book we have decided to concentrate on purely synthetic applications of ionic liquids, just to keep the amount of material to a manageable level. FFowever, we think that synthetic and non-synthetic applications (and the people doing research in these areas) should not be treated separately for a number of reasons. Each area can profit from developments made in the other field, especially concerning the availability of physicochemical data and practical experience of development of technical processes using ionic liquids. In fact, in all production-scale chemical reactions some typically non-synthetic aspects (such as the heat capacity of the ionic liquid or product extraction from the ionic catalyst layer) have to be considered anyway. The most important reason for close collaboration by synthetic and non-synthetic scientists in the field of ionic liquid research is, however, the fact that in both areas an increase in the understanding of the ionic liquid material is the key factor for successful future development. 

Bomb calorimeter. The heat flow, q, for the reaction is calculated from the temperature change multiplied by the heat capacity of the calorimeter, which is determined in a preliminary experiment... 

To find the heat capacity, Ccai, the experiment is repeated using the same bomb and the same amount of water. This time, though, we carry out a reaction for which the amount of heat evolved is known the temperature increase is again measured carefully. Suppose the reaction is known to evolve 93.3 kj of heat and the temperature rises from 20.00°C to 30.00°C. It follows that... 

The heat capacity for liquid Pu02 has been estimated (21) as 96 J mol-l K- assuming no electronic contribution. If an electronic contribution is found by experiment to be present, the liquid heat capacity would be increased. 

We can calculate the heat capacity of a substance from its mass and its specific heat capacity by using the relation C = m X Cs. If we know the mass of a substance, its specific heat capacity, and the temperature rise it undergoes during an experiment, then the heat supplied to the sample is... 

This is because the heat capacity of a wall of finite thickness is several orders of magnitude higher than that of the hot combustion products. However, some researchers did observe a small effect of the properties of the wall [17] on the quenching distance. This was interpreted in terms of some residual catalytic activity of the wall surface, poisoned by the combustion products from the preceding experiments [18]. With respect to this explanation, the surface of any material moistened through the condensation of the water vapor produced in the reaction is supposed to have very similar, low activity. 

Figure 11. Displayed are the TLS heat capacities as computed from Eq. (29) appropriate to the experiment time scales on the order of a few microseconds, seconds, and hours. A value of c = 0.1 was used here. If one makes an assumption on the specific value of Aq, it is possible to superimpose the Debye contribution on this graph, which would serve as the lowest bound on the total heat capacity. As checked for Aq = cod. the phonon contribution is negligible at these temperatures.

Section V, other quantum effects are indeed present in the theory and we will discuss how these contribute both to the deviation of the conductivity from the law and to the way the heat capacity differs from the strict linear dependence, both contributions being in the direction observed in experiment. Finally, when there is significant time dependence of cy, the kinematics of the thermal conductivity experiments are more complex and in need of attention. When the time-dependent effects are included, both phonons and two-level systems should ideally be treated by coupled kinetic equations. Such kinetic analysis, in the context of the time-dependent heat capacity, has been conducted before by other workers [102]. 

We must stress, however, that the Black-Halperin analysis has been conducted for only a single substance, namely, amorphous silica, and systematic studies on other materials should be done. The discovered numerical inconsistency may well turn out to be within the deviations of the heat capacity and conductivity from the strict linear and quadratic laws, repsectively. Finally, a controllable kinetic treatment of a time-dependent experiment would be necessary. 

---