[en] Ultrasound techniques are capable of monitoring changes in the time-of-flight as a material is exposed to different thermal environments. The focus of the present study is to identify the phase of a material via ultrasound compression wave measurements in a through transmission experimental setup as the material is heated from a solid to a liquid and then allowed to re-solidify. The present work seeks to expand upon the authors’ previous research, which proved this through transmission phase monitoring technique was possible, by considering different experimental geometries. The relationship between geometry, the measured speed of sound, and the temperature profile is presented. The use of different volumes helps in establishing a baseline understanding of which aspects of the experiment are geometry dependent and which are independent. The present study also investigates the relationship between the heating rate observed in the experiment and the measured speed of sound. Lastly, the trends identified between the experimental geometry, heat rate and ultrasound wave speed measurement assist in providing a baseline understanding of the applicability of this technique to various industries, including the polymer industry and the oil industry.

[en] Highlights: • Heating rate and washing affected the porosity and chemistry of N/S-carbon. • FE for CO₂ reduction increased upon N and S-doping. • FE did not directly depend on the porosity and surface chemistry of N/S- carbons. • Relative dispersion of N/S groups on the surface strongly affected CO₂ reduction. The catalytic activity for CO₂ electrochemical conversion into CO on N-doped carbons has been previously suggested to be enhanced by introducing a sulfur co-dopant to the carbon matrix. In this study, nitrogen and sulfur-codoped porous carbons were synthesized by a high temperature treatment of commercial wood-based carbon impregnated with thiourea. By slightly changing synthesis conditions, three different carbons were obtained and used as electrocatalysts for reduction of CO₂. Detailed analyses of chemistry and texture showed differences in the amounts of N and S heteroatoms, in the speciation of surface groups, and in porosity. The best preforming sample had the highest dispersion/lowest density of nitrogen-containing groups and the low dispersion/high density of thiophenic groups. The dependence of the Faradaic efficiency for CO reduction on the ratio of the density of nitrogen groups to that of sulfur showed a linear decrease with an increase in the ratio, supporting the previously suggested enhancing effect of the high dispersion of N-containing catalytic centers and their activation by sulfur co-doping on CO₂ electroreduction. The results also indicated that the catalytic activity of pyridinic groups is more positively affected by sulfur co-doping than is that of quaternary nitrogen species.

[en] Highlights: • Fe₃O₄ magnetic nanoparticles with small size (6.5 ± 2 nm) were synthesized by one-step carbothermal synthesis method, and heat generation was spontaneous under alternating magnetic field. • Fe₃O₄ nanoparticles possess a very strong saturation magnetization of 90.2 emu/g. • The optimum specific absorption rate (SAR) is 43.5 W/g at 15 mT and 245.6 kHz. • The maximum intrinsic loss power (ILP) value is 3.8 nHm²/kg⁻¹. -- Abstract: Induction heating Fe₃O₄ nanoparticles are commonly used in magnetic hyperthermia. For the best comprehensive efficiency, particles are needed which possess the highest possible heating rates/specific absorption rate when being exposed to a magnetic field. In this paper, a fail one-step carbothermal reduction method for magnetic nanoparticles is optimized towards yielding Fe₃O₄ nanoparticles with small-size (6.5 ± 2 nm), strong magnetism (90.2 emu·g⁻¹), and high heating rates. The parameters of alternating magnetic field are studied in depth to understand how to produce the best heating rates. Hyperthermia measurements were performed under an alternating magnetic field with a frequency of 165.3 kHz, 245.6 kHz and calculated the specific absorption rate. The optimum specific absorption rate is 43.5 W·g⁻¹ at 15 mT and 245.6 kHz. The maximum intrinsic loss power (ILP) value is 3.8 nHm²·kg⁻¹.

[en] The influence of varied process parameters involving three levels of temperature, pressure, heating rate and dwell time on the microstructure, densification and microhardness of spark plasma sintered Ti-6Al-4V/h-BN binary composite was studied. Taguchi design method was adopted to randomize the SPS process parameter levels. The microstructure was analyzed by optical microscopy, densification was determined based on the principle of Archimedes and Vickers microhardness tester was used to evaluate the microhardness of the sintered composite. The consolidation of Ti-6Al-4V powder and nanoparticles of 3 wt.% of h-BN via SPS produced nearly full theoretical densification of 99.77% and the sintered composite gave a microhardness value of 710.37 HV which is more than 200% that of the monolithic alloy. The best combination of relative densification and microhardness were obtained at the sintering parameters of 1000 °C of temperature, 40 MPa of pressure, 100 °C/min heating rate and 15 min of dwell time. Generally, it was found that improved microstructure, densification and microhardness were influenced by the high temperature of sintering and low rate of heating that gave room for adequate diffusional mass transport resulting in solid bonding between the particles of the matrix and the ceramic reinforcement. (paper)

[en] NSSS of TR-1 000 PB is a 1000 MW (e) plant with gas-cooled (C02) heavy water reactor the main equipment of which is contained within the vessel of restressed reinforced concrete. In project of TR-1000 PB NSSS the principle of inherent and passive safety is used as much as possible and the version is given how to localize the molten fuel in the special catcher within the prestressed reinforced concrete vessel with long-term passive heat removal

[en] Nominally undoped p-GaS layered single crystals were grown using the Bridgman technique. Thermally stimulated current measurements in the temperature range 10–300 K were performed at a heating rate of 0.10 K/s. The analysis of the data revealed six trap levels at 0.05, 0.06, 0.12, 0.63, 0.71, and 0.75 eV. The calculations for these traps yielded 1.2×10^-21, 2.9×10^-23, 2.4×10^-21, 8.0×10^-9, 1.9×10^-9 and 4.3×10^-10 cm² for the capture cross sections and 1.6×10¹³, 5.0×10¹², 7.3×10¹², 1.2×10¹⁴, 8.9×10¹³ and 2.6×10¹³ cm^-3 for the concentrations, respectively.

[en] Highlights: • Thermal effects lead to an increase in the heating rate of the biomass layer. • Pyrolysis of straw over 290 °C is accompanied by the exothermic effect. • The maximum temperature rise during straw pyrolysis is noted at 365 °C. • The exothermic effects of straw and peat pyrolysis are 1475 kJ/kg and 862 kJ/kg respectively. -- Abstract: The desire to increase the role of renewable biomass resources in the energy sector sets the task of finding promising areas for its resource-efficient use. Pyrolytic conversion (pyrolysis) of biomass can be considered as one of such directions. The efficiency of pyrolysis depends on the possibility of its implementation in the autothermal mode. In this regard, the purpose of this work is to study the thermal conversion of biomass in the process of slow low-temperature pyrolysis in relation to its implementation in a fixed bed reactor. Physical experiment methods, differential thermal analysis and electron scanning microscopy were used in the work. As a result of the study, it was shown that in the process of straw and peat low-temperature pyrolysis (heating rate of 10 °C/min) a thermal exothermic decomposition effect was observed when the reactor was heated to 500 °C. This effect led to an increase in the rate of heating of the biomass bed. Moreover, in the case of straw pyrolysis, the temperature in the bed began to exceed the temperature of the reactor wall (up to 55–60 °C) when heated above 303 °C. The total values of the exothermic effect of straw and peat pyrolysis in the temperature range of 170–600 °C were 1,475 kJ/kg and 862 kJ/kg, respectively (based on the dry mass of the feedstock). The scanning microscopy method shows the change in the biomass structure during the pyrolytic decomposition process.

[en] The methods of optically stimulated luminescence (OSL) measurements used until recently, used optical stimulation with a constant energy and a constant or linearly increased flux of stimulation photons. During such a stimulation the ratio of probabilities of the optical release of electrons from different traps is constant and it is hard to separate the signals of different origins. It was shown recently that advantageous changes of the probability ratio during the OSL experiments, and more information about traps can be obtained by optical stimulation with the increasing stimulation energy. This method, however, needs a strong tuneable light source that supplies a stable flux of photons and because of that it cannot find a wide application. Inducing the appropriate changes of the probabilities of the optical release of electrons from traps by increasing the sample temperature during the optical stimulation with a constant stimulation band do not face such obstacles. Such a stimulation can be realised by means of the standard OSL readers after a slight modification and offers the possibility for direct estimation of optical trap depth. The simulations of the OSL process during linear heating show that the experimental parameters such as the heating rate, the stimulation light intensity and the stimulation energy strongly affect the shape of the OSL curve and can be the very useful tools for the OSL process regulation. By this kind of stimulation one can reach very deep traps that are not detectable by thermoluminescence measurements below 500 °C. The resolution of the OSL signal originating from different traps is remarkable.

[en] We report a spurious thermoluminescence (TL) present in three types of calcite powders which also show regenerated TL (RTL). The amount of RTL was found on storage time and on the heating rate used during TL readout. Different heating rates during TL readout caused profound changes in the measured TL spectra in the range 400-650 nm. These changes can be explained by manganese ions moving into and out of clusters during the heating process. (author)

[en] Solar wind protons undergo significant heating during the expansion of the solar wind and turbulence plays an important role in this process. It is believed that the energy is injected from the energy-containing range into the inertial range and then transferred to dissipate into heat eventually. However, the energy injection process in the heliosphere remains unclear. Here we analyze this process. We utilize Helios 2 and Ulysses measurements of the fast solar wind at different radial distances from 0.29 to 4.8 au. We obtain the perpendicular heating rate based on the gradient of the magnetic moment. We estimate for the first time the energy supply rate due to the sweeping of low-frequency break based on the identification of low-frequency break and the corresponding power spectra density profile. We find that the energy supply rate is comparable to the perpendicular heating rate of protons, which support the idea that low-frequency range becomes part of the inertial range as the solar wind turbulence ages. These results help us understand the energy supply process from the energy-containing range and the heating process of solar wind protons.