Thermodynamic properties of uranium-bismuth alloys were determined by measuring the vapor pressure of bismuth in equilibrium with the condensed phase. Classical methods based on the rate of sublimation, rate of evaporation or rate of effusion could not be used since each method requires an accurate knowledge of the molecular weight of the vapor. The molecular weight of bismuth is not accurately known, but the presence of Bi and Bi, species has been established. An optical absorption technique was used to determine the concentration of each species independently. Briefly, this method consists of measuring concentrations in a vapor by the quantity of light absorbed at certain characteristic frequencies by the species in the vapor. The amount of each species present, which is related to the pressure, was determined by measuring the diminution of intensity at 3067 and 2731 A. The amount of radiation absorbed was found to be dependent on the thickness of the vapor space and the concentration of the bismuth vapor. The thermodynamic activity of bismuth was measured at temperatures from 725 to 875°C in the regions: U,Bi, + UBi,, UBi, + liquid and the one-phase, liquid region. In order to obtain measurable quantities in the regions UBi + U and UBi + U,B i, it was necessary to work at temperatures from 800 to 1000°C. From a measure of the activity of bismuth, the activity of uranium was calculated for the entire system. The liquid uranium-bismuth alloys were found not to be regular solutions. The Henry's law parameter (3.49 x 10m3 at 1064°K) was found to be valid for uranium concentrations of less than 2 mole n/o uranium. From a complete knowledge of the activities of uranium and bismuth in the system the partial molar quantit,ies and integral molar quantities were calculated at five temperatures: 1018, 1041, 1064, 1089 and 1115°K. PROPRIETER THERMODYNAMIQUES D'ALLIAGES URANIUM-BISMUTH Les proprietes t,hermodynamiques d'alliages uranium-bismuth ont et& determinees par la mesure de la pression de vapeur de bismut en Bquilibre avec la phase condensee. Des methodes classiques basees sur la vitesse de sublimation, la vitesse d'evaporation ou la vitesse de degagement ne pouvaient pas etre employees puisque chaque methode necessite une connaissance exacte du poids moleculaire de la vapeur. Lo poids moleculaire du bismuth n'est pas exactement cunnu mais la presence des especes Bi et Bi, a Stir Btablie. Une technique d'absorption optique a et& employee pour determiner la concentration de chaque espece independamment. Cette methode consiste brievement it mesurer les concentrations dans un gaz par la quantite de lumiero absorb&e par les especes dans le baz b des frequences caracteristiques determinces. La quantite de chaque espece presente, qui depend de la pression, etait determinee en mesurant la diminution de l'intensite Q 3067 et 2731 A. On a trouve que la partie du rayonnement absorb& tlependait de I'epaisseur de l'espace gazeux et de la concentration de la vapeur de bismuth. L'activite thermodynamique du bismuth a et& mesuree ...

employing a solid oxide electrolyte in the temperature range 650"-1150°C was carried out to gain structural information on glassy carbons. The measured Gibbs free enerav change vields configurational (residual quantities at zero Kelvin) enthalpy and __ _.entropy differences, which represent a two parameter measure of the structural differences between a given-glassy carbon and graphite, since the above reaction involves vanishingly small differences in composition, specific heat, and hence vibrational contributions. Many of the experimental and commercially available samples of glassy carbons studied exhibited at elevated temperature thermodynamic carbon activities lower than graphite. For various samples studied, the zero point entropy varied from 3.1 to 11.3 Cal/g-mole-"K. The thermodynamic parameters are correlated with X-ray and densAy measurements. The configurational enthalpy and entropy changes are interpreted in terms of strain related and atomic disorder parameters. respectively.

SummaryThe carbonization of certain polymers under carefully controlled conditions yields glassy carbon bodies which may have potential application in the dental profession. Considerable evidence is now available for the good compatibility of a variety of carbonaceous materials with tissue and bone. Many carbons remain relatively inert in the human environment compared to metals and polymers. Disordered carbons with strengths exceeding that of graphite are commercially available with elastic modulus in the same range as that reported for bone(m3 X lo6 psi). The object of this study was to determine mechanical properties and characterize the structure of a new porous glassy carbon material.Compressive and tensile strength data were obtained for carbon samples with a wide range of pore structures. A scanning electron microscope and a mercury porosimeter were used to observe variations in pore structures. The porous materials tested exhibited compressive strength values up to 48,000 psi and ultimate tensile strength values up to 7,500 psi. Sonic modulus values from 1 to 4.6 x 106 psi have been measured. Some carbon samples had interconnected porosity exceeding 50% and median pore diameters greater than 50 p . Material with an interconnected mean pore size as small as 46 A has also been produced.Preliminary animal implant studies are in progress.

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