High temperature thermodynamics of the zirconium-aluminum system

Experiments have been performed to help elucidate the high temperature phase diagram features and thermodynamic properties of the zirconium-aluminum system. The principal methods used were combinations of high temperature Knudsen effusion, heat treatment, and X-ray powder diffraction experiments performed with zirconium-aluminum samples in the composition range 0 \u3c X(,Al) \u3c 0.75. The results of these experiments confirmed in some respects the phase diagram features of Potschke and Schubert,(\u271) two previous investigators. In particular, X-ray powder diffraction experiments performed on samples in the composition range 0.50 \u3c X(,Al) \u3c 0.60 quenched from 800-1400(DEGREES)C indicate that ZrAl is stable below 1250(DEGREES)C, Zr(,4)Al(,3) below 1000(DEGREES)C, and Zr(,5)Al(,4) above about 1100(DEGREES)C;Aluminum vapor pressures were measured over compositions corresponding to mixtures of two solid phases between the com- positions ZrAl(,3) and Zr(,5)Al(,3), and as a function of composition over the solid solution of aluminum in bcc zirconium using a combined mass-loss-mass-spectrometric Knudsen effusion technique. In order to successfully measure the low aluminum pressures (less than (TURN)10(\u27-8) atm) over the more zirconium-rich samples it was necessary to use a small computer to signal average the mass-spectrometer signal. Data collected over 7 two-phase regions and the solid solutions were used to calculate enthalpies of formation at 298 K of seven zirconium-aluminum compounds. The heat of formation values (kcal/mole) obtained were: ZrAl(,3) = -38.96, ZrAl(,2) = -32.86, Zr(,2)Al(,3) = -56.12, ZrAl = -21.36, Zr(,5)Al(,4) = -93.76, Zr(,3)Al(,2) = -48.78, and Zr(,5)Al(,3) = -74.57;A nonrelativistic, nonself-consistent band structure calculation for the compound Zr(,2)Al was performed in an attempt to provide insight;into the type of chemical bonding occurring in zirconium-aluminum compounds; *DOE Report IS-T-1148. This work was performed under contract No. W-7405-Eng-82 with the U.S. Department of Oil, Gas, and Energy;(\u271)Potschke, M; Schubert, K. Z. Metallkde 1962, 53, 548

Leveraging mobile health technology and research methodology to optimize patient education and self-management support for advanced cancer pain

Funding: National Institutes of Health [R21 NR017745, PI, Enzinger]; Friends of Dana-Farber Cancer Institute. Availability of data and material: The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.Peer reviewedPostprin

Observation of the Dynamic Beta Effect at CESR with CLEO

Using the silicon strip detector of the CLEO experiment operating at the Cornell Electron-positron Storage Ring (CESR), we have observed that the horizontal size of the luminous region decreases in the presence of the beam-beam interaction from what is expected without the beam-beam interaction. The dependence on the bunch current agrees with the prediction of the dynamic beta effect. This is the first direct observation of the effect.Comment: 9 page uuencoded postscript file, postscritp file also available through http://w4.lns.cornell.edu/public/CLNS, submitted to Phys. Rev.

High temperature thermodynamics of the zirconium-aluminum system

Experiments have been performed to help elucidate the high temperature phase diagram features and thermodynamic properties of the zirconium-aluminum system. The principal methods used were combinations of high temperature Knudsen effusion, heat treatment, and X-ray powder diffraction experiments performed with zirconium-aluminum samples in the composition range 0 < X(,Al) < 0.75. The results of these experiments confirmed in some respects the phase diagram features of Potschke and Schubert,('1) two previous investigators. In particular, X-ray powder diffraction experiments performed on samples in the composition range 0.50 < X(,Al) < 0.60 quenched from 800-1400(DEGREES)C indicate that ZrAl is stable below 1250(DEGREES)C, Zr(,4)Al(,3) below 1000(DEGREES)C, and Zr(,5)Al(,4) above about 1100(DEGREES)C;Aluminum vapor pressures were measured over compositions corresponding to mixtures of two solid phases between the com- positions ZrAl(,3) and Zr(,5)Al(,3), and as a function of composition over the solid solution of aluminum in bcc zirconium using a combined mass-loss-mass-spectrometric Knudsen effusion technique. In order to successfully measure the low aluminum pressures (less than (TURN)10('-8) atm) over the more zirconium-rich samples it was necessary to use a small computer to signal average the mass-spectrometer signal. Data collected over 7 two-phase regions and the solid solutions were used to calculate enthalpies of formation at 298 K of seven zirconium-aluminum compounds. The heat of formation values (kcal/mole) obtained were: ZrAl(,3) = -38.96, ZrAl(,2) = -32.86, Zr(,2)Al(,3) = -56.12, ZrAl = -21.36, Zr(,5)Al(,4) = -93.76, Zr(,3)Al(,2) = -48.78, and Zr(,5)Al(,3) = -74.57;A nonrelativistic, nonself-consistent band structure calculation for the compound Zr(,2)Al was performed in an attempt to provide insight;into the type of chemical bonding occurring in zirconium-aluminum compounds; *DOE Report IS-T-1148. This work was performed under contract No. W-7405-Eng-82 with the U.S. Department of Oil, Gas, and Energy;('1)Potschke, M; Schubert, K. Z. Metallkde 1962, 53, 548.</p

The activity of cobalt and silicon in the Co - Si system with special focus on the {alpha} - Co solid solution

The activities of cobalt and silicon at 1463 K have been determined across the whole composition range in the Co - Si system, including the {alpha} - Co solid solution, for which no activity data were previously available. Simple and reactive Knudsen effusion mass spectroscopy employed in this work were shown to successfully overcome problems normally encountered in studying high-temperature solid binary systems, such as slow equilibration and low partial pressures of the components. The composition dependence of the cobalt activities within the {alpha} - Co solid solution phase was used to calculate the self-interaction coefficients of silicon in {alpha} - Co: ln {gamma}{sub Si} = 10.4 {+-} 0.2 and {epsilon}{sub Si}{sup (Si)} = 18.6 {+-} 0.8. The regular solution model was shown to be a fairly good description of the {alpha} - Co solid solution, with an energy parameter Z{sub CoSi} of -120 {+-} 5 kJ{center_dot}mol{sup -1}. The results compare well with literature data on similar systems, such as Fe - Si and Ni - Si