Modelling of structure forming in structural steels

The study showed that the influence of alloying elements on the secondary structure formation of the steels containing from 0.19 to 0.37 wt. % carbon; 0.82-1.82 silicon; 0.63-3.03 manganese; 1.01-3.09 chromium; 0.005-0.031 nitrogen; up to 0.25 wt.% vanadium and austenite grain size is determined by their change in the content of vanadium nitride phase in austenite, its alloying and overheating above tac3, and the dispersion of ferrite-pearlite, martensitic and bainitic structures is determined by austenite grain size and thermal kinetic parameters of phase transformations. Analytical dependencies are defined that describe the experimental data with a probability of 95% and an error of 10% to 18%. An analysis results of studying the structure formation of structural steel during tempering after quenching show that the dispersion and uniformity of the distribution of carbide and nitride phases in ferrite is controlled at complete austenite homogenization by diffusion mobility and the solubility limit of carbon and nitrogen in ferrite, and secondary phase quantity in case of the secondary phase presence in austenite more than 0.04 wt. %. Equations was obtained which, with a probability of 95% and an error of 0.7 to 2.6%, describe the real process.

Thermal Analysis On The Kinetics Of Magnesium-Aluminum Layered Double Hydroxides In Different Heating Rates

The thermal decomposition of magnesium-aluminum layered double hydroxides (LDHs) was investigated by thermogravimetry analysis and differential scanning calorimetry (DSC) methods in argon environment. The influence of heating rates (including 2.5, 5, 10, 15 and 20K/min) on the thermal behavior of LDHs was revealed. By the methods of Kissinger and Flynn-Wall-Ozawa, the thermal kinetic parameters of activation energy and pre-exponential factor for the exothermic processes under non-isothermal conditions were calculated using the analysis of corresponding DSC curves.

Experimental Determination of Thermal Kinetic Parameters in Case Study of Tubes with Smooth and Structured Surface

Thermal kinetic parameters are very often used in the engineering practice for the simplified design of the heat exchangers. These thermal kinetic parameters must be determined from the experimental measurement. This contribution is aimed on the calculation of thermal kinetic parameters from the experimental measurements of heat exchanger water steam / hot water. In this case study are tested and compared tubes with the smooth and structured surface. Obtained results can be directly used in the engineering practice.

Synthesis and Characteristics of Energetic Materials Based on 1,2-Dinitroguanidine

A series of energetic salts based on 1,2-dinitroguanidine were successfully synthesised and fully characterised using 1H NMR, 13C NMR, and IR spectroscopy, mass spectrometry, elemental analysis, and differential scanning calorimetry. The results show that all the salts possess higher detonation properties (detonation pressures and velocities ranging from 24.8 to 30.3 GPa and 7665 to 8422 m s–1, respectively) than those of trinitrotolouene (TNT, 2,4,6-trinitromethylbenzene). The thermal stability and thermal kinetic parameters were also investigated to give a better understanding of the physical and chemical properties of these energetic salts.

Note. Kinetic parameters of Bacillus stearothermophilus spores under isothermal and non-isothermal heating conditions Nota. Parámetros cinéticos del tratamiento isotérmico y no isotérmico de esporas de Bacillus stearothermophilus

Thermobacteriological studies using Bacillus stearotherrnophilus spores were carried out by heating the spores under isothermal and non-isothermal conditions followed by an isothermal period. Ex perimental data obtained after isothermal heating were analyzed using a two-step linear regression procedure and a one-step nonlinear regression method. Results obtained using both analytical tech niques were close, but the 90% interval of confidence for predictions was lower when the one-step nonlinear regression was used. These results indicated the convenience of using the one-step nonlin ear regression method to obtain thermal kinetic parameters for bacterial spores. Also, the parameters obtained by a non-isothermal program followed by an isothermal heating period were similar to those obtained after isothermal heating. Nevertheless, the joint confidence regions at 90% did not overlap, indicating that there are significant differences. The z values obtained under isothermal (7.0 °C) and non-isothermal (8.5 °C) conditions are close and characteristic for this microorganisms.