Indexes Objectively Reflecting Performance Evaluation of Technical Rubber Goods

AbstractIn order to choose a characteristic index which objectively reflects performance evaluation of technical rubber goods, accelerated thermal-oxidative ageing of rubbers was carried out. It has been demonstrated that as the index accountable for maintaining workability the rate of set at compressing or tension relaxing at pressing of technical rubber goods in a statically deformed state is usually taken. Besides, breaking elongation or tensile strength of technical rubber goods in a free state can be taken as an index, as well. It has been educed that the most sensitive index which reflexes the structural changes in the rubber of the rubber-cord casing (RCC) during the process of ageing is breaking elongation, the value of which is drastically dropping in the initial period of the thermal ageing and monotonously changing thereafter

A Dynamical Mean Field Theory for the Study of Surface Diffusion Constants

We present a combined analytical and numerical approach based on the Mori projection operator formalism and Monte Carlo simulations to study surface diffusion within the lattice-gas model. In the present theory, the average jump rate and the susceptibility factor appearing are evaluated through Monte Carlo simulations, while the memory functions are approximated by the known results for a Langmuir gas model. This leads to a dynamical mean field theory (DMF) for collective diffusion, while approximate correlation effects beyond DMF are included for tracer diffusion. We apply our formalism to three very different strongly interacting systems and compare the results of the new approach with those of usual Monte Carlo simulations. We find that the combined approach works very well for collective diffusion, whereas for tracer diffusion the influence of interactions on the memory effects is more prominent.Comment: 13 pages LaTeX and 6 PostScript figures, style files included. To appear in Surface Science Letter

Phase diagrams of the terminating oxygen layer on MXenes M2CO sheets (M = Ti, V, Nb)

In this work we have studied the behavior of oxygen adsorbed on the MXenes M2CO (M=Ti, V, Nb) surface by the density functional theory and Monte Carlo methods. An approximation for the lateral interactions potential has been constructed that has the form of a pair potential. We have carried out the quantitative assessment of the errors of the pair potential. Using SuSMoST program we have constructed isotherms of adsorption. The results showed a non-trivial phase behavior of the adlayer: we observed three phases characterized by the 1/3, 1/2 and 2/3 coverage. It has been predicted that complete oxygen removal from the MXenes surface is possible at temperatures above 500 K

Non-Arrhenius Behavior of Surface Diffusion Near a Phase Transition Boundary

We study the non-Arrhenius behavior of surface diffusion near the second-order phase transition boundary of an adsorbate layer. In contrast to expectations based on macroscopic thermodynamic effects, we show that this behavior can be related to the average microscopic jump rate which in turn is determined by the waiting-time distribution W(t) of single-particle jumps at short times. At long times, W(t) yields a barrier that corresponds to the rate-limiting step in diffusion. The microscopic information in W(t) should be accessible by STM measurements.Comment: 4 pages, Latex with RevTeX macro

Surface hydrogenation of oxygen terminated MXenes M2CO2 (M = Ti, V, Nb)

We have investigated reduction of MXenes M2CO2 (M = Ti, V, Nb) surface by hydrogen using density functional theory and statistical physics methods. We have approximated lateral interactions between adsorbed hydrogen with simple pairwise potential. We have confirmed model stability via cross-validation. Adsorption isotherms are calculated using Metropolis Monte Carlo method. We have built analytical Langmuir-like approximation of calculated isotherms. Ordered phases with 1/3 and 2/3 ML coverage are visually observed at low temperatures. At temperatures above 300 K no obvious plateau is observed, and intermediate phases does not exist. We compared adsorptive properties of MXenes at the same external conditions

Innovation engineering education: experience of OmSTU

The article presents the experience of Omsk State Technical University in training of engineering specialists for high-tech economy sectors. The system of innovation engineering education applied in OmSTU includes creation of innovation research-and-production educational centres (resource centres), the program of elite engineering education with aprofound fundamental component, integrated educational programs, the basic departments at research institutes and enterprises

SuSMoST: Surface Science Modeling and Simulation Toolkit

We offer the scientific community the Surface Science Modelling and Simulation Toolkit (SuSMoST), which includes a number of utilities and implementations of statistical physics algorithms and models. With SuSMoST one is able to predict or explain the structure and thermodynamics properties of adsorption layers. SuSMoST automatically builds formal graph and tensor-network models from atomic description of adsorption complexes. So it can be routinely used for a wide class of adsorption systems. SuSMoST aids ab initio calculations of interactions between adsorbed species. In particular it generates surface samples considering symmetry of adsorption complexes. Using methods of various nature SuSMoST generates representative samples of adsorption layers and computes its thermodynamics quantities such as mean energy, coverage, density, heat capacity. From these data one can plot phase diagrams of adsorption systems, assess thermal stability of self-assembled structures, simulate thermal desorption spectra, etc.<br /

Estimation of in-use Guaranteed Rubber Lifetime test methods

AbstractWith the purpose to estimate the existing methodologies of in-use guaranteed rubber life-time test, the processing of the accelerating rubber ageing results according to State Standard GOST, ISO and Research and Production Enterprise “Progress” methodology is carried out. It is shown that the experimental results analysis provides us with the similar picture, but analytical prognostic method is more advantageous because of its flexibility. Improving of the methods of processing experimental data of rubber accelerated ageing is in the scope of interest of modern mathematical modeling, which lets using more complex functions, reflecting the properties of rubber behaviour in the whole analyzed temperature and time interval without any rejection of experimental data. Such modelinglets more precisely predict rubber behaviour in different operating conditions and carry out computations in conditions of complex temperature-and-time model of rubber products storage and exploitation