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Fe-Al intermetallic compounds have great potential to replace nickel-based superalloys in industry, which is attributed to their attractive properties such as low density,high specific strength,good high-temperature oxidation and corrosion resistance and especially low cost.In this paper, important advances in the application of first-principles calculations to study the effect of element doping and microalloying on the brittleness at room temperature, high-temperature strength, interface bonding, high-temperature oxidation resistance and corrosion resistance of Fe-Al intermetallic compounds and coatings were comprehensively reviewed.A theoretical calculation scheme for first-principles research on the chloride salt corrosion resistance mechanism of B2 type Fe-Al alloy was designed,and the development directions for the application of first-principles calculations to study Fe-Al alloy and coatings were prospected.

A series of Sr0.7Ba0.3Nb2O6−δ/x wt. % Ti (x = 1, 3, 5, and 10) composite ceramic thermoelectric materials were prepared, and the mechanism for improving their thermoelectric properties was explored. The experimental results demonstrate that nano-additive titanium powder undergoes oxidation to form TiO2 during sintering. However, under annealing in a reducing atmosphere, oxidation reactions further deplete the lattice oxygen, leading to an increased generation of oxygen vacancies and enhanced carrier concentration, ultimately leading to successful resistivity reduction. The samples consistently exhibit low thermal conductivity values below 2.0 W m−1 K−1 due to crystal defects, complex structure, and phonon scattering at the grain boundaries. The sample doped with 5 wt. %. Ti exhibits the lowest resistivity and highest PF value (409.3 μW/m K2 at 1073 K). Consequently, the figure of merit of Sr0.7Ba0.3Nb2O6−δ with 5 wt. % Ti attains its maximum value of 0.30 at 1073 K, representing a 50% increase compared to that of the undoped sample Sr0.7Ba0.3Nb2O6−δ (0.20 at 1073 K). [ABSTRACT FROM AUTHOR]

As concentrated solar power (CSP) systems evolve, the new generation of CSP systems will utilize chloride molten salts, which are cost-effective and have high operating temperatures, but are highly corrosive. In order to reduce the corrosiveness of chloride salts, we investigated the addition of different levels of Mg to chloride salts to study the effect on corrosion. In this paper, the corrosion behavior of 310S stainless steel with aluminum in high-temperature molten salt NaCl-KCl-MgCl2 was studied. By adding different contents of magnesium corrosion inhibitor, the corrosion mechanism and the effect of the corrosion inhibitor were explored. The results show that the lowest corrosion rate of 6.623 mm/y was obtained for the aluminum-formed 310S with 0.05 wt.% Mg. However, the corrosion rate rises when the Mg content exceeds 0.05 wt.% compared to the corrosion rate of corroded specimens without Mg. Changing the added Mg content does not affect the corrosion products. For 310S stainless steel with aluminum, its corrosion inhibition was best achieved by adding 0.05 wt.% Mg to the chloride molten salt. [ABSTRACT FROM AUTHOR]

Photocatalytic technology is a novel approach that harnesses solar energy for efficient energy conversion and effective pollution abatement, representing a rapidly advancing field in recent years. The development and synthesis of high-performance semiconductor photocatalysts constitute the pivotal focal point. Oxygen vacancies, being intrinsic defects commonly found in metal oxides, are extensively present within the lattice of semiconductor photocatalytic materials exhibiting non-stoichiometric ratios. Consequently, they have garnered significant attention in the field of photocatalysis as an exceptionally effective means for modulating the performance of photocatalysts. This paper provides a comprehensive review on the concept, preparation, and characterization methods of oxygen vacancies, along with their diverse applications in nitrogen fixation, solar water splitting, CO2 photoreduction, pollutant degradation, and biomedicine. Currently, remarkable progress has been made in the synthesis of high-performance oxygen vacancy photocatalysts and the regulation of their catalytic performance. In the future, it will be imperative to develop more advanced in situ characterization techniques, conduct further investigations into the regulation and stabilization of oxygen vacancies in photocatalysts, and comprehensively comprehend the mechanism underlying the influence of oxygen vacancies on photocatalysis. The engineering of oxygen vacancies will assume a pivotal role in the realm of semiconductor photocatalysis. [ABSTRACT FROM AUTHOR]

Gradient induced unusual strain hardening achieves the equilibrium of the strength and plasticity of alloys, and is an important strategy for the optimization of the mechanical properties of metals and alloys. The segregation of solute elements can greatly improve the grain boundary stability, inhibit grain coarsening and promote the mechanical strength of the alloy. In our efforts, the segregation structure of the solute element Co was designed and added to the gradient nano Ni–Co alloy, and the two strengthening strategies were applied simultaneously in one structure. The mechanical strength of the alloy achieved a second increase based on the unique combination of gradient induced strain hardening and high plasticity, especially the yield strength of alloy increase amplitude reach to 42%. This provides a positive direction for the alloy strengthening strategy. In the process of secondary strengthening, the micro-mechanism is divided into two stages: in the first stage, the gradient strain provides the alloy with geometrically necessary dislocations and a multi-axial stress state, and the existence of large numbers of geometrically necessary dislocations creates good conditions for the second stage strengthening. In the second stage, the solute segregation induced stable grain boundaries produce a strong pinning effect on the geometrically necessary dislocation, which realizes the coupling of grain boundary strengthening and dislocation strengthening. This provides a new strengthening strategy and positive theoretical guidance for the experimental preparation of advanced alloys with excellent properties. [ABSTRACT FROM AUTHOR]

Nano ZrC powder was prepared by salt assisted combustion synthesis process. The effect of raw material ZrO2 particle size on the microstructure of nano ZrC powder and its mechanism were studied. The results show that in ZrO2-Mg-C system, with the decrease of ZrO2 original particle size (200→10 nm), the reaction activity of carbon zirconium system increases and the free carbon content in ZrC decreases gradually. The average particle size of ZrC powder decreases with the decrease of ZrO2 particle size. When ZrO2 with particle size of 10 nm is added, the average particle size of ZrC powder is 48 nm, and the spherical like morphology tends to be more uniform. The particle size of raw material ZrO2 decreases and the specific surface area increases, which improve the reaction activity and carburizing speed, so as to reduce the influences of reaction time and reaction temperature on crystal growth, and obtain high-purity nano ZrC powder with uniform distribution. [ABSTRACT FROM AUTHOR]

Using an appropriate heat treatment process to control the precipitation of the σ phase, while regulating the alloy structure and grain size, is one of the effective ways to obtain good comprehensive properties of duplex stainless steel (DSS). Herein, the feasibility and preparation parameters of micro/nanostructure 2205 DSS prepared by the aluminothermic reaction are explored. The microstructure and properties are further controlled by isothermal treatment at 1000 °C for a different time. The results show that the volume percentages of α and γ phases in the 1.0 h isothermal treated steel obtain a maximum value and a minimum value, corresponding to 60% and 36%, respectively. The evolution of microstructure with isothermal treatment also affects the content and morphology of the precipitated σ phase, which changes from continuous precipitation to granular precipitation at the α/γ phase boundaries, and its volume percentage obtains a minimum value when the isothermal treatment is performed for 1.0 h. With the increase of heat treatment time, the average grain size and volume fraction of nanocrystals increase gradually. Corresponding to the changes in microstructure and grain size, the maximum values of Vickers hardness and tensile properties of the alloy are obtained after 1.0 h isothermal treatment. [ABSTRACT FROM AUTHOR]