Differential thermal analysis high pressure

The apparatus used are mostly stirred-tank-, tubular-, and differential recycle reactors. Also, optical cells are used for spectroscopic measurements, and differential thermal-analysis apparatus and stopped flow devices are applied at high pressures. 

The best evidence so far for the glassy nature of HDA was provided (1) by measurements of the dielectric relaxation time under pressure at 140 K [206, 251], (2) by the direct vitrification of a pressurized liquid water emulsion to HDA [252], and (3) by a high-pressure study of the glass >liquid transition using differential thermal analysis (DTA) [253], We note here that these studies probe structurally relaxed HDA (eHDA) rather than unrelaxed HDA. It is possible that structurally relaxed HDA behaves glass like, whereas structurally uHDA shows a distinct behavior. Thus, more studies are needed in the future, which directly compare structurally relaxed and unrelaxed HDA. 

FIGURE 1 shows the equilibrium pN2 - T curves for AIN, GaN and InN. The curve for AIN was calculated by Slack and McNelly [6], The one for GaN was determined by Karpinski and Porowski [5] based on gas pressure and Bridgman anvil experiments performed by Karpinski et al [4], The curve for InN was obtained by Grzegory et al [7] and follows from differential thermal analysis (DTA) and annealing of InN at high N2 pressure. The curves for GaN and InN deviate from linear dependence at... 

Busing, D., Jenau, M., Reuter, J., Wurflinger, A. and Tamarit, J. L. (1995). Differential thermal-analysis and dielectric studies on 2-methyl-2-nitro-propoane under high-pressure. Z. Natur. A. J. Phys. Sci., 50, 502-4. [239]... 

The decomposition temperatures of hydrates were measured by means of differential thermal analysis (DTA) under the conditions of excess gas in a stainless steel flask that was developed specially for the investigation of hydrate formation with a gaseous guest at high hydrostatic pressure. The hydrate decomposition temperature was measured with a chromel-alumel thermocouple to the accuracy of 0.3 K. The thermocouple was calibrated with the use of temperature standards. Pressure was measured with a Bourdon-tube pressure gauge. The error of the pressure measurements did not exceed 0.5 %. This procedure was described in more detail previously.The gases used in the investigation... 

Abe, A., Hiejima, T., Takeda, T., and Nakafuku, C., Orientational order and thermodynamic properties of main chain trimer liquid crystals a combined use of NMR, PVT and high-pressure differential thermal analysis. Polymer, 44, 3117-3123 (2003). 

Maeda, Y., Furuya, H., and Abe, A., High pressure differential thermal analysis of dimer hquid crystals a,(W-bis[(4,4 -cyanobiphenylyl)oxy]alkanes, Liq. Cryst, 21, 365-371 (1996). 

HAT Hata, K., The sorption properties of supercritical carbon dioxide in poly(ethylene glycol) and poly(ethylene oxide) with high-pressure thermogravimetiy-differential thermal analysis (Jap.), Kobunshi Ronbunshu, 58, 714, 2001. 

The slope of the phase boundary curve dpidt can be estimated from the Ttr - Pit plot obtained by using a PVT or high-pressure differential thermal analysis (DTA) method [118,119]. The volume-dependent entropy (correction for the volume change) ASy, the transition entropy (AStr)p under ordinary pressure, and the constant-volume entropy (AStr)v obtained therefrom are arranged in this order in Tables 2,3, and 4. 

High pressure DTA measurements. Differential Thermal Analysis (DTA) is a version of the method of parameter -property curves in which the thermal effect is a measured property of a system and temperature or time are the parameters ( Therm.anal. in Table 1.1). 

Differential scanning calorimetry (DSC) is the main approach used today for studying thermal properties of foods (phase transitions, reactions, and specific heats). Older systems, such as containers fitted with sensors that follow the rising temperature of a heating bench, autoclaves with additional pressure sensors, or (high pressure) differential thermal analysis (DTA) instruments, are still useful. Modulated DSC is also applied today to food studies [4-9],... 

A Raemy, M Ottaway. The use of high pressure DTA, heat flow and adiabatic calorimetry to study exothermic reactions. J Thermal Anal 37 1965-1971 (1991). A Raemy, J Loliger. Self-ignition of powders studied by high pressure differential thermal analysis. Thermochim Acta 85 343-346 (1985). 

The employment of high pressure is also indispensable to elucidate the phase situation of liquid crystals. Their rich polymorphism is most conveniently studied by high-pressure differential thermal analysis (DTA). " Not only may the phase behavior of the substance studied change significantly under pressure (pressure-induced and pressure-limited phases may occur), but also several peculiarities have been detected in liquid crystal phases, such as reentrant and tricritical phenomena. Also the properties of ferroelectric and polymeric liquid crystals are markedly altered under pressure. 

Reuter, J. Buesing, D. Tamarit, J. L. Wiirflinger, A. High-pressure differential thermal analysis of the phase behavior in some rm-butyl compounds, J. Mater. Chem. 1997,7,41 6. This paper also discusses some phenomenological theories of crystal melting (like the Pople-Karasz theory, 1961) that take into account orientational disorder in the solid, based on ideas presented in 1939 by Lennard-Jones and Devonshire. The essential parameter of such a theory is the ratio of the barriers to reorientation and to diffusion, which is also a measure for the anisotropy in molecular shape. 

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