S. F. Dunaev

Thermodynamics and amorphization of the copper–zirconium alloys

The vapour composition and the thermodynamic properties of Cu–Zr alloys in the liquid and solid states have been studied by Knudsen-cell mass spectrometry over the temperature (701–1823 K) and composition (5.1–97.3 mol% Zr) intervals. The accessible temperature range has been enhanced by chemically generating volatile substances directly in the cell. For this purpose, the samples have been mixed with powdered fluorides of magnesium, calcium, sodium or potassium. Reduction reactions occurring in the cell produced zirconium fluorides, which have been examined with the mass spectrometer. The thermodynamic functions of formation of all crystalline phases in the Cu–Zr system have been determined. A representative file of experimental data has been obtained for the Cu–Zr melt. It comprises about 1100 values of the activities of both components at various concentrations and temperatures. The concentration and temperature dependences of the thermodynamic functions of the Cu–Zr melt have been described using the associated-solution concept with allowance for CuZr and Cu2Zr association types. The phase equilibria computed on the basis of the obtained thermodynamic properties and the developed model are shown to agree with the available experimental data. The nature of the interparticle interaction in the Cu–Zr system has been analysed and the behaviour of the thermodynamic functions accompanying the process of transition of the Cu–Zr melt into the amorphous state was considered. Quantitative agreement with the independent experimental results was obtained.

Surface state of sacrificial copper electrode by electropolishing in hydrophobic ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide.

Anodic dissolution of natural surface-oxidized, air-annealed, cathodically reduced, and cathodically deposited copper in hydrophobic ionic liquid 1-buthyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide under galvanostatic conditions by means of gravimetric measurements was studied. The resulting samples were mirror-like oxide-free copper pattern. The mechanism of the electropolishing of oxidized copper surface was considered. The consequent anodic reactions Cu2O - 1e = Cu(+) + CuO, CuO - 2e = Cu(2+) + O, and Cu - 1e = Cu(+) take place. The electropolishing itself occurs over oxygen-free copper surface due to competitive residual water discharge in the pits and copper dissolution on the roughness.

Thermodynamic Properties of Melts and Phase Equilibria in the Copper–Zirconium System

The vapor composition over and thermodynamic properties of Cu–Zr melts (5.1–85.0 at. % Zr) are studied by Knudsen cell mass spectrometry between 1191 and 1823 K. The data set obtained comprises more than 1100 activity values for various compositions and temperatures. The thermodynamic behavior of Cu–Zr melts is described in terms of the associated-solution approach with an accuracy no worse than the experimental accuracy. The melts are shown to contain two molecular species: CuZr and Cu2Zr. The contributions of different types of chemical bonding to the Gibbs energy and enthalpy of formation of Cu–Zr melts are asymmetrical and shifted from the equiatomic composition in opposite directions: the extremum of covalent bonding is shifted to the Cu-rich side, while metallic bonding is more significant in Zr-rich alloys. The rapid temperature variation of covalent bonding leads to a large excess heat capacity CpE of the melts and a negative excess entropy ΔfSE, which rapidly drops with decreasing temperature. It is shown that not only CpE and ΔfSE but also their temperature variations are governed by the parameters of association reactions and depend more strongly on the entropy than on the enthalpy of complex formation. This indicates that, in the general case, the glass-forming capabilities of melts are independent of the interparticle interaction and accounts for the pronounced tendency of Cu–Zr melts toward amorphization.

Crystal structure and phase transitions of ternary compounds in the thulium–silver–tin system

The existence of the TmAgSn compound in the Tm–Ag–Sn system in the form of two polymorphs was confirmed. The high-temperature phase crystallizes with the LiGaGe type (P63mc, Z = 2), and the lowtemperature one with the ZrNiAl type (

Thermodynamic Properties and Amorphization of Zr–Si Melts

P\overline 6 2m

Phase equilibria in Al-Ni-Zr system at 1123 K

, Z = 3). A new ternary compound TmAgSn2 was found to exist (Cu3Au type,

Synthesis of Nanotitania on the Surface of Titanium Metal in Ionic Liquids: Role of Water Additions

Pm\overline 3 m