Modern microwave methods in solid state inorganic materials chemistry: from fundamentals to manufacturing

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Influence of tin content on spectral selectivity and thermal conductivity of Sn–Al2O3 solar selective absorber

Abstract The tin-pigmented aluminium oxide film (Sn–Al2O3) based solar selective absorber was successfully prepared with three different contents of tin by an anodization process. The phase and morphology of the Sn–Al2O3 were measured by X-ray diffractometer and a scanning electron microscope equipped with an energy dispersive X-ray analyser. The reflectance (R) of the coating was determined by Ultraviolet–visible-near infrared spectrophotometer in the wavelength interval of 300–2500 nm and the Fourier transform infrared spectrophotometer in the wavelength of infrared region (2500–25,000 nm). As a result, aluminium and tin phases were detected at the coating surface. The Al2O3 films were formed and compacted as a barrier on the Al substrate. The compositions of the oxide film composed of tin (Sn), aluminium (Al) and oxygen (O) elements. With increasing Sn content, the solar absorptance (α sol) gradually increased, but it has little effect on the thermal emittance (ε therm). The thermal conductivity of Sn–Al2O3 samples decreased with increasing Sn content as a result of the increasing thickness of the Sn layer at the interface leading to obstruct the free electrons and phonon contributions. The present result suggests that the increasing Sn content in the Sn–Al2O3 coating can enhance the solar selectivity properties and a good solar absorber material

Influence of Ni–Al coating thickness on spectral selectivity and thermal performance of parabolic trough collector

Abstract This study investigates the influence of Ni–Al coating thickness on the spectral selectivity and thermal performance of a parabolic trough collector (PTC). Three thicknesses of Ni–Al coating for use as solar absorber material were successfully prepared on the outer surface of a stainless steel 316L (SS) tube by flame spray. The phase, morphology, and reflectance (R) of the Ni–Al coatings were characterized using several techniques. The PTC and solar receiver tube were specially designed and constructed for observing the collector thermal performance by following ASHRAE 93-1986. Looking at the results, the actual average thicknesses of the three Ni–Al coatings turn out to be 195, 215, and 299 μm. The morphology and chemical composition of all three thicknesses are similar. The chemical composition in the cross-sectional view exhibits non-uniform distribution. The three thicknesses of the coating are composed of NiO and Al2O3 phases, which also corresponded to the results of SEM–EDX mapping. The differences in a solar absorptance (α) of the three thicknesses of Ni–Al coating are not statistically significant, with an average α value of 0.74–0.75. However, there are differences in thermal efficiency of the PTC depending on the thickness of the Ni–Al coating. Of the three samples, the thickest one (299 µm) demonstrates the highest ability to convert solar radiation into thermal energy

Enhancing durability of concrete mixtures with supplementary cementitious materials: A study on organic acid corrosion and physical abrasion in pig farm environments

This study assessed concrete durability in pig farm environments, focusing on resistance to organic acid corrosion and physical abrasion. It used supplementary cementitious materials like silica fume (SF), coal fly ash (CFA), and bagasse fly ash (BFA) to improve concrete resilience. The research involved casting and testing concrete samples for compressive strength, acid corrosion resistance, abrasion resistance, and their combined effects. A custom apparatus simulated corrosion and abrasion cycles typical in pig farm flooring. Results showed that a combination of SF, CFA, and BFA significantly enhanced compressive strength, especially with extended curing. Additionally, these materials improved concrete's resistance to acid corrosion, physical abrasion, and their combined effects. The replacement of 30 wt% of cement with CFA and BFA in concrete significantly reduced mass loss due to acid corrosion to less than 10%, whereas the control mix exhibited a mass loss exceeding 24%. Additionally, concrete with 30 wt% CFA or BFA replacement exhibited a minimal combined mass loss, decreasing to less than 2.5% due to acid corrosion and physical abrasion, as opposed to the 16% observed in the control mixture

Performance Comparison of Ferrite and Nanocrystalline Cores for Medium-Frequency Transformer of Dual Active Bridge DC-DC Converter

This article reports an investigation into ferrite and nanocrystalline materials for the medium-frequency transformer of a dual active bridge DC-DC converter, which plays a key role in the converter’s efficiency and power density. E65 MnZn ferrite cores and toroidal and cut nanocrystalline cores are selected for the construction of 20-kHz transformers. Transformer performance is evaluated with a 1.1-kW (42–54 V)/400 V dual active bridge DC-DC converter with single-phase shift and extended phase shift modulations. The experimental results indicate that the toroidal nanocrystalline transformer had the best performance with an efficiency range of 98.5–99.2% and power density of 12 W/cm3, whereas the cut-core nanocrystalline transformer had an efficiency range of 98.4–99.1% with a power density of 9 W/cm3, and the ferrite transformer had an efficiency range of 97.6–98.8% with a power density of 6 W/cm3. A small mismatch in the circuit parameters is found to cause saturation in the nanocrystalline toroidal core, due to its high permeability. The analytical and experimental results suggest that cut nanocrystalline cores are suitable for the dual active bridge DC-DC converter transformers with switching frequencies up to 100 kHz