Thermal conductivity of indium at high pressures and temperatures under shock compression

The results of investigations of the electrical and thermal conductivity of indium in the pressure range up to 27 GPa and at temperatures up to 1000 K are presented. In this pressure range, the electrical resistance of indium samples is measured under multishock compression. The equation of state constructed for indium is used to calculate the evolution of the thermodynamic parameters of indium in shock wave experiments; then, the dependences of the electrical resistivity and thermal conductivity coefficient on the volume and temperature are determined. It is demonstrated that, in the pressure and temperature ranges under investigation, the thermal conductivity coefficient of indium does not depend on temperature and its threefold increase is caused only by the change in the volume under compression.     

Equation of state of solids from high-pressure isotherm

A new variant of the method of finding the equation of state in the Mie–Grüneisen form is presented. It is based only on high-pressure isotherms of solids. Using this procedure, the semiempirical equation of state and shock adiabats of solids may be found at high pressures and high temperatures. The method is tested on periclase MgO within the range of shock pressures up to 300–500 GPa.     

Mathematical simulation of the shock compression of porous molybdenum using a heterogeneous model

The shock compression of a heterogeneous material is numerically simulated. The physical model used for the simulation is based on a layered model of a porous material and consists of a set of thin matrix plates with a known equation of state that are separated by filler layers also with a known equation of state. The model is intended to calculate the parameters (pressure, temperature, mass velocity) of shock compression of the matrix and the filler of heterogeneous materials during their one-dimensional shock compression in terms of a developed hydrodynamic code. The adequacy of the proposed model is tested on porous molybdenum during shock-wave loading to a pressure of 15–70 GPa and a temperature of 4000 K.     

Electrophysical properties of calcium at high pressures and temperatures

Electrical resistivity of two crystal phases of shock-compressed calcium and its melt was measured in a range of high pressures (10–50 GPa) and temperatures (800–1600 K). The thermodynamic equilibrium curves were constructed for different calcium phases and the shape of Hugoniot adiabat was determined in the region where it intersects the equilibrium curves. It is shown that sharp kinks observed earlier in the Hugoniot adiabat in shock experiments were caused not by the jumplike electronic transitions but by the intersections of the adiabat and the phase-equilibrium and melting curves. The electronic spectra of the calcium crystal phases were calculated using the electron-density functional method; the computational results are used to explain the observed behavior of the Ca resistivity under compression.     

Magnetic Transformations and Polymorphic Transition of Ferromagnetic Steels under Shock-Wave Loading

Technical Physics - A method for recording magnetic transformation is presented for ferromagnetic steels under shock-wave loading. The operation of the magnetic transformation gauge is considered...     

Similarity criteria for Debye temperatures of simple solids at compression

A similarity criterion for the volume dependence of Debye temperatures of simple solids at compression is presented. It is shown that the volume dependences of the characteristic Debye temperatures of various solids fall on a single common curve in dimensionless coordinates. The validity of the model is tested on examples of solids with various types of interatomic forces – molecular crystal, ionic crystal, metals and covalent crystal.     

Polymorphic transformations in nanostructured anatase (TiO2) under high-pressure shock compression

The action of dynamic pressure and temperature on polymorphic transformations in nanostructured (grain size of 8–20 nm) anatase (TiO₂) is studied. The dynamic pressure of a loading pulse (10–45 GPa) is measured with a manganin gauge. The temperature of shock-compressed specimens, which is varied by varying the initial temperature and initial porosity, is found to fall into the range 500–2500 K. It is shown that as the temperature and shock compression pressure rise, the nanostructured anatase turns into a nanoanatase-nanocolumbite or columbite-rutile mixture or into almost impurity-free (pure) nanocolumbite or impurity-free microcrystalline rutile.