• TECHNOLOGIES

    Kinetic and equilibrium study of the CO2 adsorption on activated carbon

    Machines. Technologies. Materials., Vol. 15 (2021), Issue 8, pg(s) 299-302

    The presented research are concerned with the modelling of isotherms and chemical kinetics of mass transport for the CO2 adsorption on activated carbon, taking place in the fluidized and fixed bed. To determine the nature of CO2 binding under low-pressure conditions, adsorption complex and thermodynamic effects occurring during the process, four isothermal models were used: Langmuir, Freundlich, Temkin and Halsey. The evaluation of the factors affecting the course and rate of CO2 binding was based on four kinetic models, i.e. pseudo-first-order (PFO), pseudo-second-order (PSO), intraparticle diffusion (IPD) and the Elovich model. The validation of mathematical models showed that the linearized Freundlich and Halsey isotherms models are best suited to empirical data. In the case of process kinetics, the analysis showed that the non-linearized pseudo-first-order model (PFO) proved to be unrivalled in fitting to experimental data. The comparison of two types of tested beds suggested faster kinetics for a fluidized bed, while a larger amount of CO2 at equilibrium was adsorbed by the fixed bed.

  • Fundamental properties of crystalline nano-structures caused by mechanical and thermodynamical excitations

    Materials Science. Non-Equilibrium Phase Transformations., Vol. 5 (2019), Issue 2, pg(s) 32-36

    Mechanical or thermodynamic excitations in solid state physics – phonons, cause all fundamental physical properties of materials and always are present, regardless of what is the main carrier of transport properties and ordering (for example, in electroconductivity, it can be electrons / holes, ions, etc., and in magnetism – magnons). In particular, phonons play a different and more subtle role in low-dimensional nano-scale samples, because they, due to the confinement effects, influence the creation of completely unusual and altered characteristics in relation to large (bulk) samples of exactly the same material. Therefore, the possible phonon spectra and states in model of crystal nanostructures: ultrathin films, nano-wires and quantum dots were founded in the paper. The most noticeable phenomenon is the consequence of the dimensional quantization, but also the shape of the boundary surfaces, as well as the presence of the environment surrounding the nano-pattern. In addition to the analysis of the microscopic properties of the phonon subsystem, the calculation of the temperature dependence of the thermal capacity and entropy of these nano systems was also calculated and performed by comparisons with the same for bulk structure.

  • Fatigue analysis approaches for vehicle components made of rubber

    Trans Motauto World, Vol. 4 (2019), Issue 1, pg(s) 16-19

    Generally, the most frequently used structural materials are metals which have high strength and stiffness. However, there are many cases, when other important properties come to the fore as well as high deformation by elastic behavior, high viscosity namely good damping effect. Vehicle components made of rubber usually exhibit large deformations. One of the most important properties of rubber is the ability to withstand large strains without permanent fractures. This feature makes it ideal for many engineering applications. On the other hand, the task becomes more complicated because of some features of rubber parts. The temperature of rubber increases significantly after deformations. Material properties of rubber change after these above mentioned temperature changes. Thus it is necessary to understand the mechanics underlying the failure process. This paper summarizes the applied equations and the basic physical laws which are responsible for the theoretical background of the strain and temperature changes and the analysis approaches that are available for predicting fatigue life in rubber, especially in vehicle components made of rubber.

  • TRANSPORT TECHNICS. INVESTIGATION OF ELEMENTS. RELIABILITY

    THEORETICAL AND NUMERICAL ASPECTS REGARDING THE THERMOELASTIC BEHAVIOUR OF RUBBERLIKE POLYMERS

    Trans Motauto World, Vol. 3 (2018), Issue 1, pg(s) 15-18

    Vehicle components made of rubber usually exhibit large deformations. Cyclic finite deformations may induce increasing temperature in hyperelastic materials. This case – where changes in deformation and in temperature occur simultaneously – is called coupled thermomechanical problem. Both the mechanical and thermal processes have their own governing equations, that is why special techniques are needed for the computation. A special technique will be presented for solving coupled problems, this is operator split method. The goal of this paper is to show how to solve the coupled thermomechanical problem by the principle of virtual power and the principle of virtual temperature, and how to apply them together.

  • THERMODYNAMIC ANALYSIS OF FRICTION AND WEAR OF ULTRAFINE- GRAINED MATERIALS

    Machines. Technologies. Materials., Vol. 9 (2015), Issue 11, pg(s) 13-16

    The conditions are substantiated for the loss of thermodynamic stability of a tribosystem and for its adaptation with a decreasing wear rate at the moving frictional contact of parts from materials with an ultrafine-grained structure produced by equal-channel angular pressing. The regularities of the influence of the structure’s dispersion degree and the friction contact’s temperature on the tribotechnical characteristics of ultrafine-grained materials are established theoretically and experimentally.