Viscosity and electrical resistivity of liquid cunial, cunialco, cunialcofe alloys of equiatomic compositions

The kinematic viscosity and electrical resistivity of equiatomic liquid alloys CuNiAl, CuNiAlCo, CuNiAlCoFe has measured during heating of the sample to 2070 K and subsequent cooling. We consider CuNiAl, CuNiAlCo, CuNiAlCoFe alloys of equiatomic compositions as the multi-principal element alloys (MPEAs), the complex concentrated alloys (CCAs), the high-entropy alloys (HEAs). The measuring results of the vickosity and the resistivity are discussed on base the available microgeterogenity concept. We searched the temperatureT*of the heating a melt for destroy of microheterogeneity. T* is the temperature of the beginning of the matching portion of the temperature dependence of the viscosity and resistivity which is obtained by heating and cooling. All the investigated melts demonstrated different temperature dependence of viscosity for heating and cooling. The temperature T*=1800 K were determined only for liquid alloy CuNiAl of equiatomic composition. For alloys CuNiAlCo, CuNiAlCoFe the coinciding part of the temperature dependences of the viscosity which are obtained by heating and cooling is absent. The results of viscosity are discussed within the theory of absolute reaction rates. Entropy of activation of viscous flow and free activation energy of viscous flow were determined by analyzing the temperature dependences of kinematic viscosity. The increasing of components quantity in the alloy leads to the increasing of the free activation energy of viscous flow and the volume per structural unit of the melt (ion, atom, or cluster). The measuring results of resistivity were interpreted using the Nagel-Tauc model. The temperature coefficient of resistivity (characteristic of the structural state of the melt) was determined. The temperature dependences of the CuNiAl liquid alloy resistivity measured upon heating to 2070 K and subsequent cooling do not coincide.The value of T*temperature for alloy CuNiAl of equiatomic composition is 1850 K. For CuNiAlCo, CuNiAlCoFe alloys the temperature dependences of the resistivity which are obtained by heating and cooling are coinciding. This means that destroy of microheterogeneity for melts after heating up to 2070K did not occur. The temperature coefficient of resistivity of the CuNiA liquid alloy irreversibly decreases when it heated to a temperature of 1850 K.This is evidence of the destruction of microheterogeneity with the formation of a homogeneous solution at the atomic level. The increasing of components quantityin the alloy leads to a decreasingof thetemperature coefficient of the resistivity (in cooling moda). According to the ideas of Nagel and Tauk, an irreversible decrease of the temperature coefficient of the specific resistance of the melt indicates an increase in the volume per structural unit of the melt (ion, atom, or cluster). © 2019, Technical University of Kosice. All rights reserved.Authors are grateful for the support of experimental works by Act 211 Government Russian Federation, contract 02.A03.21.0006

Adhesive coatings based on aligned arrays of carbon nanostructures

This work was financially supported by Russian Foundation for Basic Research (projects 16-29-14023 and 18-32-00652) and Internal grant of the Southern Federal University (project VnGr-07/2017-26)

Study of the dependence of Young's modulus of vertically aligned carbon nanotubes on their aspect ratio

The reported study was funded by RFBR according to the research projects No.16-29-14023 ofi_m, No.18-32-00652 and by grant of the Southern Federal University (project No. VnGr-07/2017-26)

Investigation of the effect of upper electrode material on the memristor properties of strained carbon nanotubes

The reported study was funded by RFBR according to the research project No. 16-29-14023 ofi_m

Study of the electromechanical properties of aligned carbon nanotubes coated with ZnO using atomic force microscopy

The reported study was funded by RFBR according to the research projects No. 18-32-00652 mol_a, No.18-29-11019 mk and by grant of the Southern Federal University (project No. VnGr-07/2017-26)

Anharmonic vs. relaxational sound damping in glasses: II. Vitreous silica

The temperature dependence of the frequency dispersion in the sound velocity and damping of vitreous silica is reanalyzed. Thermally activated relaxation accounts for the sound attenuation observed above 10 K at sonic and ultrasonic frequencies. Its extrapolation to the hypersonic regime reveals that the anharmonic coupling to the thermal bath becomes important in Brillouin-scattering measurements. At 35 GHz and room temperature, the damping due to this anharmonicity is found to be nearly twice that produced by thermally activated relaxation. The analysis also reveals a sizeable velocity increase with temperature which is not related with sound dispersion. This suggests that silica experiences a gradual structural change that already starts well below room temperature.Comment: 13 pages with 8 figure

COMBINED FEMORAL FIXATION TECNIQUE IN HAMSTRING TENDON ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION: ASESSMENT OF TUNNEL WIDENING

Purpose – to assess the influence of combined femoral fixation technique during arthroscopic ACL reconstruction on the femoral tunnel widening at long term follow-up.Material and methods. 99 patients with primary hamstring tendon (HT) ACL reconstruction performed in 2007-2008 were analyzed. In the study group (42 patients) on the femoral side a combined cortical suspension (Endobutton CL, Smith & Nephew) and transverse (Rigid Fix, Depuy Mitek) fixation of graft was used. In control group, isolated cortical suspension fixation (Endobutton CL, Smith & Nephew) was used. On the tibial side for graft fixation a biodegradable screw (Biointrafix, DePuy Mitek) was used in all cases. Tunnel widening was calculated in percentage against primary tunnel diameter created during the surgery. MRI data were exported to eFilm (Merge Healthcare software), measurement of femoral tunnel diameters was performed on T1 sequences in coronal and sagittal planes on three different levels.Results. The mean age at the last follow up in the study group was 38.9±1.4, in control group – 38,6±1,08. The median time from surgery to follow up was 9 years and 4 months in the study group and 8 years 7 months in the controls. The incidence of graft failure in the study group was reported as 14.3%, while in the control group as 17,5%. The median femoral tunnel widening was larger in the control group at the joint aperture and midsection levels both in coronal and sagittal plane, although there was no statistically significant differences (p>0,05).Conclusion. The combination of cortical suspension and transverse HT femoral graft fixation technique is likely to reduce tunnel enlargement at the long term follow-up. However further research and larger sample groups are required

Asymptotics of Eigenvalues and Eigenfunctions for the Laplace Operator in a Domain with Oscillating Boundary. Multiple Eigenvalue Case

We study the asymptotic behavior of the solutions of a spectral problem for the Laplacian in a domain with rapidly oscillating boundary. We consider the case where the eigenvalue of the limit problem is multiple. We construct the leading terms of the asymptotic expansions for the eigenelements and verify the asymptotics

Piezoelectric effect in non-uniform strained carbon nanotubes

Экспериментально установлено, что неравномерно деформированные углеродные нанотрубки (УНТ) обладают поверхностным потенциалом, значение которого зависит от величины деформации. Оценено значение пьезоэлектрического коэффициента УНТ, которое составило 0,107±0,032 Кл/м2.We have experimentally established that non-uniformly strained carbon nanotubes have a surface potential the value of which depends on the magnitude of the deformation. The value of the piezoelectric coefficient of car on nanotu es was estimated to e 0.107 ± 0.032 C/m2.Работа выполнена при финансовой поддержке РФФИ (проекты № 16-29-14023 офи_м и №16-37-00101 мол_а)