V. L. Gilyarov

Thermal expansion of the skeleton of chain molecules in polymer crystals

The expansion of the carbon skeleton of molecules in crystallites and the longitudinal contraction of the crystallite lattice in poly(ethylene) (PE) and poly(caproamide) (PCA) with an increase in the temperature are measured using IR and Raman spectroscopy and x-ray diffraction. The thermal expansion of the carbon skeleton due to transverse vibrations is theoretically calculated within the atomic chain model. The theoretical and experimental data on the thermal expansion of the carbon skeleton are in good agreement.

Energy features of an adiabatically loaded anharmonic oscillator

An excited anharmonic oscillator is considered under conditions of adiabatic (i.e., slow, as compared to the oscillation period) loading with an external force tending to a constant value at long times. The energy characteristics of the adiabatically loaded anharmonic oscillator, such as the instantaneous energy of the oscillator, the maximum kinetic (oscillation) energy, and the kinetic and potential energies averaged over the period, are analytically calculated as a function of the steady-state force. The analytical results are confirmed by the data of numerical calculations. It is established that the external force gives rise to a redistribution of the average kinetic and potential components of the initial energy of the anharmonic oscillator and that the transferred energy portions at a small external force considerably exceed the average work done by the external force.

On elementary events in the electrical failure kinetics of polymers

The kinetics of electrical failure of poly(ethylene terephthalate) under different experimental conditions is studied. Process variables are the film thickness, electrode configuration and material, presence of partial discharges, and field application conditions. It is found that the potential barrier for elementary events, which controls the failure kinetics, is nearly the same irrespective of the process, 1.1–1.3 eV. The control process is discussed.

Energetics of the thermoelastic effect in solids

The dependence of the temperature on the external adiabatic deformation is determined for a one-dimensional model of a solid — chains of atoms with an anharmonic interaction. The resulting dependences of the average kinetic and potential components of the internal energy on this deformation are compared with a model of adiabatic loading of a single oscillator.

Energy features of a loaded quantum anharmonic oscillator

A quantum anharmonic oscillator in the ground state has been considered under the conditions of loading with an external force. The wave functions have been calculated for different forces, and the eigenvalues of the energy of the system have been determined as a function of the load. It has been established that the zero-point energy of the oscillator varies linearly with a variation in the force (decreases under tension and increases under compression) and that the average kinetic and potential components of the energy are also characterized by linear variations.

Effect of mechanical loading on the kinetics of electrical breakdown in polymers

The decrease in the electrical lifetime (time of expectation of a breakdown in an electric field of constant polarity) under tensile loading of disoriented polyethylene, Teflon, and lavsan films in the range of 100–300 K is studied. It is found that tensile loading decreases the depth of intermolecular electron traps due to an increase in the spacing of chain molecules in amorphous regions of polymers. This accelerates the hopping (from one trap to another) transport of electrons, leading to the formation of critical (breakdown) volume charges.

Characteristics of elementary acts in the mechanical fracture kinetics of polymers

The main characteristics of elementary acts in the mechanical fracture kinetics of oriented polymers, namely, the initial potential barrier U0 and the activation volume VA, are determined. The values of U0 And VA are obtained from analyzing the temperature and force dependences of the life of polymers with allowance for the actual stresses (overstresses) applied to chain molecules, which are found by IR spectroscopy. The values obtained (U0 ≈ 4 eV, VA ≈ 0.03 nm3) agree satisfactorily with the dissociation energy and activation volume of the fluctuation breaking of covalent skeleton bonds in polymer molecules.

Negative longitudinal expansion and the amplitude of longitudinal vibrations in poly(ethylene) crystals

The experimental temperature dependences of the thermal expansion coefficient and the mean-square amplitude of atomic vibrations in the longitudinal direction (along the axes of chain molecules) in poly(ethylene) crystals of different sizes are measured using x-ray diffraction in the temperature range 5–350 K. Theoretical calculations of the temperature dependences of the thermal expansion coefficient and the mean-square amplitude of atomic vibrations in poly(ethylene) crystals are carried out. It is shown that the results of calculations are in good agreement with experimental data. The temperature ranges in which the quantum character of lattice dynamics affects the thermal expansion coefficient and the mean-square amplitude of vibrations are determined. It is revealed that the shear longitudinal modes play an important role in the lattice dynamics of crystals with a chain structure.

Analysis of energy distribution in a loaded quantum anharmonic oscillator in a wide temperature range

Analysis of the energy distribution in an ensemble of quantum anharmonic oscillators loaded by an external force in a wide temperature range (from T = 0) is carried out using a general approach based on the virial theorem. At T = 0, anharmonic effects are observed: a linear variation of zero-point energy of an oscillator under loading (energy decrease during extension and increase under compression) and a linear variation of the average kinetic and potential energy components. At high temperatures, at which the dynamics of the oscillators becomes classical, the anharmonic effects are manifested in a linear variation in the vibrational energy and a linear variation in the average kinetic and potential energy components upon an increase in force. Mutually compensating variation in the average kinetic and potential energy components of the internal dynamic energy of an oscillator (energy redistribution upon loading) takes place both at low and high temperatures.

Formation mechanism for nanodefects on surfaces of loaded metals

Tunneling profilometry is used to investigate the shape and orientation of defects that form at the surfaces of Cu, Au, Mo and Pd under loading. The defects have the shape of an indented prism. The value of the angles at the tip of the defects coincide with the angles between glide planes, while the orientation of the walls coincide with the orientation of these planes. At the edges of the defects there exist “swellings” caused by expulsion of material at the surface. Based on these results, the creation of these defects is explained by the exit of dislocations as they burst through barriers formed at intersecting glide planes.