Temperature pressure-composition

One of the most useful features of metal-hydrogen systems are their pressure-composition-temperature data, P-C-T. Such relationships for palladium-hydrogen are shown in Figure 1. For compositions and temperatures within the envelope, two solid phases coexist, as required by the phase rule. The lower hydrogen-content a-phase represents solution of hydrogen into the metal, and the higher hydrogen-content jS-phase is the hydride. Both a and (3 are... 

Figure 1. Pressure-composition-temperature relationships for palladium-hydrogen (43)...

Pressure-composition-temperature and thermodynamic relationships of of the titanium-molybdenum-hydrogen (deuterium) system are reported. 0-TiMo exhibits Sieverts Law behavior only in the very dilute region, with deviations toward decreased solubility thereafter. Data indicate that the presence of Mo in the 0-Ti lattice inhibits hydrogen solubility. This trend may stem from two factors for Mo contents >50 atom %, an electronic factor dominates whereas at lower Mo contents, behavior is controlled by the decrease in lattice parameter with increasing Mo content. Evidence suggests that Mo atoms block adjacent interstitial sites for hydrogen occupation. Thermodynamic data for deuterium absorption indicate that for temperatures below 297°C an inverse isotope effect is exhibited, in that the deuteride is more stable than the hydride. There is evidence for similar behavior in the tritide. 

Pressure-composition-temperature (P-C-T) relationships were reported for hydrogen and deuterium in a-titanium. Both systems obey Sieverts Law in the dilute region (10) i.e., the square root of equilibrium pressure is linearly proportional to the solute content. McQuillan (3) extended the hydrogen P-C-T data into the 7-phase. For a maximum equilibrium hydrogen pressure of 500... 

Here x represents a vector of n continuous variables (e.g., flows, pressures, compositions, temperatures, sizes of units), and y is a vector of integer variables (e.g., alternative solvents or materials) h(x,y) = 0 denote the to equality constraints (e.g., mass, energy balances, equilibrium relationships) g(x,y) < 0 are the p inequality constraints (e.g., specifications on purity of distillation products, environmental regulations, feasibility constraints in heat recovery systems, logical constraints) f(x,y) is the objective function (e.g., annualized total cost, profit, thermodynamic criteria). 

With Th carbides, two carbohydride phases, ThjCHj and ThjCH, are obtained by heating the carbide in Hj gas at 0.1 MPa and 850°C. Pressure-composition isotherms show that these are definite phases, not solid solutions. The ThjCHj is hexagonal and the ThjCH monoclinic (probably distorted hexagonal). These are stable compounds extrapolation of the pressure-composition-temperature data to RT indicates dissociation pressures of ca. 10 and 10 Pa, respectively. However, the hexagonal ThjCHj transforms to a cubic phase at 380°C. 

EDAX Energy dispersive analysis of X-ray PCT Pressure composition temperature... 

LIB] Libowitz, G. G., A pressure-composition-temperature study of the Zr-H system at high hydrogen contents, J. Nucl. Mater., 5, (1962), 228. Cited on page 131. 

The parameter au cty is defined as representing the situation for the maximum possible evaporation rate resulting from a given set of environmental pressure, composition, temperature, and flow conditions. 

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