Heat capacities of iron disulfides Thermodynamics of marcasite from 5 to 700 K, pyrite from 300 to 780 K, and the transformation of marcasite to pyrite

The heat capacity of purified natural marcasite has been determined by adiabatic-shield calorimetry in the region 5 to 700 K where it transforms to pyrite exothermically. Values of thermodynamic functions at 298.15 K are Cp, {So(T) - So(0)}, and {Ho(T) - Ho(0)} are 14.92 calth K-1 mol-1, 12.88 calth K-1 mol-1, and 2328 calth mol-1, respectively, for marcasite (FeS2). Our earlier measurements on pyrite have been extended to 770 K, and show that the heat capacity of marcasite is slightly higher than that of pyrite over the entire range of mutual existence. The transformation to pyrite is significantly exothermic at 700 K, [Delta]Ht = - (1.05 +/- 0.05) kcalth mol-1, and correspondingly, Ho(T = 0, marcasite) - Ho(T = 0, pyrite) = (0.99 +/- 0.05) kcalth mol-1. Marcasite is thus metastable with regard to pyrite over the whole temperature region and owes its formation and persistence to kinetic factors. At 298.15 K the standard enthalpies, entropies, and Gibbs energies of formation for FeS2 phases are:Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/21922/1/0000329.pd

Heat capacity and thermodynamic properties of FeSb2 from 5 to 1021.2 K Enthalpy of decomposition

The heat capacity of FeSb2 has been measured by adiabatic-shield calorimetry from 5 to 1021.2 K. At the latter temperature the phase decomposes into the FeSb phase and an antimony-rich melt. The heat capacity increases regularly over the entire temperature range, except for a high value at 898 K which is related to the fusion of a small amount of antimony. The enthalpy of peritectic decomposition of FeSb2 at 1021.2 K is (12910 +/- 30) calth mol-1. Thermodynamic functions have been evaluated and the values of Cp, {So(T) - So(0)}, and -[{Go(T) - Ho(0)}/T] at 298.15 and 1000 K are 19.08, 25.98, 12.881, and 24.80, 51.01, and 32.25 calth K-1 mol-1, respectively. The present results together with the Gibbs free energy of formation values from the literature give the formation values:Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23070/1/0000644.pd

Heat capacity and thermodynamic properties of ditungsten carbide, W2C1-x, from 10 to 1000 K

Thermodynamic properties of tungsten carbide, W2C0.833, have been derived from heat capacities measured by adiabatic calorimetry in the range 10-1000 K on a sample rich in this phase. The standard entropy of W2C0.833 was found to be 75.80 J K-1 mol-1 at 298.15 K and 159.8 J K-1 mol-1 at 1000 K. Thermodynamic formation values for W2C0.833 were deduced from the reported coexistence of this phase with tungsten and tungsten monocarbide at about 1550 K.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27259/1/0000268.pd

Heat capacity and thermodynamic properties of CrSb2 from 5 to 1050 K. Magnetic transition and enthalpy of decomposition

The heat capacity of CrSb2 has been measured by adiabatic calorimetry from 5 to 991.3 K. At the latter temperature the CrSb2-phase decomposes into the CrSb-phase and an antimonyrich melt. The heat capacity of the two-phase mixture was measured from 991.3 to 1050 K. The heat capacity of CrSb2 shows a small sharp [lambda]-type transition with a maximum at 274.1 K where the change from the antiferromagnetic to the paramagnetic state occurs. The low entropy of the clearly cooperative part of the transition, [Delta]St = 0.12 calth K-1 mol-1, shows that this contribution is only a small part of the total. From an estimate of the lattice heat capacity of CrSb2 outside the [lambda]-transition region we find an excess heat capacity amounting to about 1.7 calth K-1 mol-1 at 300 K, 1.6 calth K-1 mol-1 at 500 K, and 1.1 calth K-1 mol-1 at 800 K, which we attribute to the population of excited electronic states in CrSb2. The total transitional entropy amounts to about 2.6 calth K-1 mol-1 at 900 K only slightly more than the R 1n 3 (= 2.17 calth K-1 mol-1) expected from randomization of two unpaired spins per chromium atom. The enthalpy of the peritectic decomposition of CrSb2 at 991.3 K is (8325 +/- 20) calth mol-1.The high heat capacity above 991 K is presumably related to the solution of CrSb(s) in the melt. Thermodynamic functions have been evaluated and the values of Cp, {So(T)-So(0)}, and -{Go-Ho(0)}/T at 298.15 K are (19.66+/-0.02), (27.46+/-0.03), (14.009+/-0.014) calth K-1 mol-1. CrSb2 loses antimony on approaching the peritectic temperature and the composition of the decomposing phase is in the range CrSb1.90 to CrSb1.95. To explore further the homogeneity range of the CrSb2-phase some heat-capacity measurements on CrSb1.85 have also been carried out. Combination of the present results with standard Gibbs energies of formation at 850 K from the literature gives for CrSb2.00:Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22711/1/0000266.pd

Heat capacity of MnAs0.88P0.12 from 10 to 500 K: Thermodynamic properties and transitions

The heat capacity of MnAs0.88P0.12 has been measured by adiabatic shield calorimetry from 10 to 500 K. It is shown that very small energy changes are connected with two magnetic order-order transitions, indicating that these can be regarded as mainly "noncoupled" magnetic transitions. At higher temperatures contributions to the excess heat capacity arises from a magnetic order-disorder transition, a conversion from low- to high-spin state for manganese, and a MnP- to NiAs-type structural transition. The observed heat capacity is resolved into contributions from the different physical phenomena, and the character of the transitions is discussed. In particular it is substantiated that the dilational contribution, which includes magnetoelastic and magnetovolume terms as well as normal anharmonicity terms, plays a major role in MnAs0.88P0.12. The entropy of the magnetic order-disorder transition is smaller than should be expected from a complete randomization of the spins, assuming a purely magnetic transition. Thermodynamic functions have been evaluated and the respective values of Cp, {SOm(T) - SOm(0)}, and -{GOm(T) - HOm(0)}/T at 298.15 K are 68.74, 72.09, and 32.30 J K-1 mole-1, and at 500 K 56.05, 108.12, and 56.64 J K-1 mole-1.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26552/1/0000091.pd

Current state of quality of life and patient-reported outcomes research

The 5th EORTC Quality of Life in Cancer Clinical Trials Conference presented the current state of quality of life and other patient-reported outcomes (PROs) research from the perspectives of researchers, regulators, industry representatives, patients and patient advocates and health care professionals. A major theme was the assessment of the burden of cancer treatments, and this was discussed in terms of regulatory challenges in using PRO assessments in clinical trials, patients' experiences in cancer clinical trials, innovative methods and standardisation in cancer research, innovative methods across the disease sites or populations and cancer survivorship. Conferees demonstrated that PROs are becoming more accepted and major efforts are ongoing internationally to standardise PROs measurement, analysis and reporting in trials. Regulators are keen to collaborate with all stakeholders to ensure that the right questions are asked and the right answers are communicated. Improved technology and increased flexibility of measurement instruments are making PROs data more robust. Patients are being encouraged to be patient partners. International collaborations are essential, because this work cannot be accomplished on a national level

Size Dependence of a Temperature-Induced Solid–Solid Phase Transition in Copper(I) Sulfide

Determination of the phase diagrams for the nanocrystalline forms of materials is crucial for our understanding of nanostructures and the design of functional materials using nanoscale building blocks. The ability to study such transformations in nanomaterials with controlled shape offers further insight into transition mechanisms and the influence of particular facets. Here we present an investigation of the size-dependent, temperature-induced solid-solid phase transition in copper sulfide nanorods from low- to high-chalcocite. We find the transition temperature to be substantially reduced, with the high chalcocite phase appearing in the smallest nanocrystals at temperatures so low that they are typical of photovoltaic operation. Size dependence in phase trans- formations suggests the possibility of accessing morphologies that are not found in bulk solids at ambient conditions. These other- wise-inaccessible crystal phases could enable higher-performing materials in a range of applications, including sensing, switching, lighting, and photovoltaics

Triuranium heptaoxides: Heat capacities and thermodynamic properties of [alpha]- and [beta]-U3O7 from 5 to 350[deg]K

Low temperature heat capacities have been measured by adiabatic calorimetry on two phases with composition UO2.33 designated [alpha]- and [beta]-U3O7. They were obtained by oxidation of UO2 at 135 and 165[deg]C, respectively. [beta]-U3O7 was subsequently heat treated at 225[deg]C. Both substances possess UO2-like structures, apparently tetragonally deformed, with c/a = 0.986 for the face-centered uranium lattice of [alpha]-U3O7 and c/a = 1.031 for that of [beta]-U3O7. Both have normal and almost equal heat capacities over the measured range, except for a small lambda-type anomaly at 30.5[deg]K in [alpha]-U3O7. At 298.15[deg]K the values of the practical entropy, S0, and the free energy function, -(F0-H00)/T, are 19.73 and 9.66 cal gfw-1[deg]K-1 for [alpha]-UO2.333, and 19.96 and 9.77 cal gfw1[deg]K-1 for [beta]-UO2.333, respectively. These new data are correlated with structural and magnetic properties and thermodynamic data for other uranium oxides.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32328/1/0000398.pd

Alpha Ferric Oxide: Low Temperature Heat Capacity and Thermodynamic Functions

ABS>The heat capacity of synthetic alpha ferric oxide was determined at 5 to 350 K. The experimental technique is described, and the heat capacity and molal thermodyamic functions are tabulated. The heat capacity vs. temperature is shown graphically. (J.R.D.

Uranium chalcogenides--II Heat capacities and thermodynamic properties of US2 and US3 from 5 to 350[deg]K

Heat capacity measurements and calculations of thermodynamic properties have been carried out for the compounds US2 and US3 from 5 to 350[deg]K. The temperature dependence of the heat capacities is of normal sigmate type, except that for US2 the rise in heat capacity in the region 10 to 20[deg]K is more rapid than expected. Comparison of the US2 data with those on US and US3 indicates the presence of a Schottky-type transition in US2 with a maximum of about 0[middle dot]5 cal mole-1 [deg]K-1 at 25[deg]K.Values of the heat capacity (Cp), entropy (S[deg] - S[deg]0), and Gibbs energy function [-(G[deg] - G[deg]0)/T] at 298[middle dot]15[deg]K are 17[middle dot]86, 26[middle dot]42, and 14[middle dot]01 for US2 and 22[middle dot]85, 33[middle dot]09, and 17[middle dot]45 for US3, respectively, in cal mole-1[deg]K-1.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33134/1/0000520.pd