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High-entropy alloys (HEAs) are composed of 5–35 at% of five or more elements, have high configurational entropy, do not form intermetallic compounds, and have a single-phase face-centered cubic structure or body-centered cubic structure. In particular, refractory HEAs (RHEAs), based on refractory materials with excellent mechanical properties at high temperatures, have high strength and hardness at room temperature and excellent mechanical properties at low and high temperatures. In this study, the Ti-Nb-Cr-V-Ni-Al RHEAs were deposited using direct energy deposition (DED). In the microstructure of Ti-Nb-Cr-V-Ni-Al, the sigma, BCC A2, and Ti2Ni phases appeared to be different from the BCC A2, BCC B2, and Laves phases predicted in the phase diagram. This microstructure was similar to that of the casted Ti-Nb-Cr-V-Ni-Al and had a constructed fine grain size. It was found that the growth of these microstructures was due to the DED process, which has a fast solidification rate. The fine grain size caused high hardness, and the microhardness of the Ti-Nb-Cr-V-Ni-Al was measured to be about 900 HV. In addition, in order to analyze the thermal properties of Ti-Nb-Cr-V-Ni-Al composed of the refractory material, the heat-affected zone (HAZ) was analyzed through a preheating test. The HAZ was decreased, owing to the high thermal diffusivity of Ti-Nb-Cr-V-Ni-Al.

Using machine learning models, this study innovatively introduces multi-element compositions to optimize the performance of spinel refractories. A total of 1120 spinel samples were fabricated at 1600 °C for 2 h, and an experimental database containing 112 data points was constructed. High-throughput performance predictions and experimental verifications were conducted, identifying the sample with the highest hardness, (Al2Fe0.25Zn0.25Mg0.25Mn0.25)O4 (1770.6 ± 79.1 HV1, 3.35 times that of MgAl2O4), and the highest flexural strength, (Al2Cr0.5Zn0.1Mg0.2Mn0.2)O4 (161.2 ± 9.7 MPa, 1.4 times that of MgAl2O4). Further analysis of phase composition and microstructure shows that the mechanism of hardness enhancement is mainly the solid solution strengthening of multi-element doping, the energy dissipation of the large-grain layered structure, and the reinforcement of the zigzag grain boundary. In addition to solid solution strengthening and a compact low-pore structure, the mechanism of improving bending strength also includes second-phase strengthening and phase concentration gradient distribution. This method provides a promising way to optimize the performance of refractory materials.

Recent developments in electronic, nuclear, and defense applications have resulted in new challenges and opportunities for refractory metals and ceramics with excellent corrosion resistance and high-temperature performance. There are also effective additives for alloy and composite systems to improve their functional and structural properties in corrosive or elevated temperature environments. However, common drawbacks like room temperature brittleness and low fracture toughness prevent the use of refractory materials in applications that need high mechanical reliability. Here, Ren et al discuss the experimental and theoretical advancements in refractory materials.

Lightweight refractory materials with thermal insulation properties and erosion resistance are advantageous for high-temperature applications. Lightweight zirconia refractories were prepared using starch as a pore-forming agent, basic magnesium carbonate as a stabilizer, and nano-zirconia as an additive. The effects of the nano-zirconia content on the pore and thermal insulation properties of the lightweight zirconia refractories were investigated based on the porosity, phase composition, microstructure, and thermal conductivity. Nano-zirconia was shown to have a high surface energy, and its addition effectively increased the driving force for sintering, reduced the sintering temperature, and promoted the sintering reaction, thereby reducing the apparent porosity and improving the density of the prepared material. Owing to the superplasticity of nano-zirconia, the surface stress caused plastic deformation between particles, which increased the migration rate of grain boundaries and trapped more gas inside the material before it diffused to the surface, thereby enhancing the closed porosity of the material. The presence of closed pores could extend the thermal conduction path, decrease the conduction rate, and hinder the conduction effect to effectively reduce the thermal conductivity of the material. At a nano-zirconia content of 0.75 wt.%, the prepared lightweight zirconia had the highest closed porosity and the lowest thermal conductivity. The apparent porosity, closed porosity, and total porosity of the material were 2.8%, 7.0%, and 9.8%, respectively, and the thermal conductivity at 800 °C was 1.37 W m −1  K −1 .

Corundum–mullite refractory material is an important material in rotary kiln incinerators due to its excellent properties, e.g., high temperature stability and chemical resistance, etc. However, in the process of use, the complexity of the sintering process will inevitably produce a large amount of spent corundum–mullite refractory material. Therefore, it is important to study the failure mechanism of corundum–mullite refractory material to prolong its service life. In this manuscript, the scrapping mechanism for the corundum–mullite refractory material was studied by XRD, XPS, SEM-EDS, FTIR, etc. The results indicate that chemical corrosion caused by impurity elements, such as Fe, Ca, Mg, Ti, etc., is one of the important scrapping mechanisms. The corundum structure remains stable throughout the service life, while mullite exhibits the opposite phenomenon. The Al-O-Si bonds in the mullite structure are depolymerized by impurity elements to release free tetrahedral structures, including the [AlO4] tetrahedron and [SiO4] tetrahedron. In the intervention of iron, the free tetrahedra, including [AlO4], [FeO4], and [SiO4] can bond with each other by sharing bridging oxygen (BO), probably forming Fe-O(BO)-Si, Fe-O(BO)-Al, and Al-O(BO)-Si in an Al2O3-SiO2-Fe2O3-MexOy (Me = Ca, Mg, Ti, etc.)-based amorphous phase. These findings provide theoretical support for prolonging the service life of refractory materials in rotary kiln incinerators.

Recent interest in compact nuclear reactors for applications in space or in remote locations drives innovation in nuclear fuel design, especially non-oxide ceramic nuclear fuels. This work details neutronic modeling designed to support the development of a new nuclear fuel concept based on a mixture of thorium and uranium nitride. A Monte Carlo N-Particle Version 6.2 (MCNP-6) model of a compact 10 MWe reactor design which incorporates (ThxU1_x)N fuel is presented. In this context, a \"compact\" reactor is a completely assembled reactor which may be emptied of coolant and transported by specialized commercial vehicle, deployed by a C130J aircraft, or launched into space. Core geometry, reflector barrels, and the heat exchange zones are designed to support reduction of overall reactor volume of core components while maintaining criticality with a fixed total fuel mass of 4500 kg. Dense mixed nitrides of thorium nitride (ThN) additions in uranium nitride (UN) in 5 wt.% increments between 0.05 < x < 0.5 have been considered for calculation of kœ and keffective. ThN additions in UN results in a slight increase in the magnitude of the temperature coefficient of reactivity, which is negative by design. The isotopic distribution of the principal actinide inventory as a function of burnup, time, and initial fuel composition is presented and discussed within the context of the proliferation risk of this core design.

The global reliance on coal-fired power generation continues to produce vast quantities of fly ash, exceeding 500 million tons annually, with limited recycling rates. Given its high silica (SiO2) and alumina (Al2O3) contents, fly ash represents a promising alternative raw material for sustainable refractory production. In this study, four aluminosilicate refractory castables were formulated using bauxite, calcined flint clay, kyanite, calcium aluminate cement, and microsilica, in which the fine fraction of flint clay was partially replaced by 0, 5, 10, and 15 wt.% fly ash. The specimens were dried at 120 °C and sintered at 850, 1050, and 1400 °C for 4 h. Their physical and mechanical properties were systematically evaluated, while phase evolution and microstructural development were analyzed through X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results revealed that the incorporation of 10 wt.% fly ash (10FAC) provided the optimal balance between densification and strength, achieving compressive strengths of 45.0 MPa and 65.3 MPa after sintering at 1050 °C and 1400 °C, respectively. This improvement is attributed to the formation of a SiO2-rich liquid phase derived from fly ash impurities, which promoted the in-situ crystallization of acicular secondary mullite and enhanced interparticle bonding among corundum grains. The 10FAC castable also exhibited only a slight increase in apparent porosity (26.39%) compared with the reference (25.74%), indicating effective sintering without excessive vitrification. Overall, the study demonstrates the technical viability of using fly ash as a sustainable substitute for flint clay in refractory castables. The findings contribute to advancing circular economy principles by promoting industrial waste valorization and resource conservation, offering a low-carbon pathway for the development of high-performance refractory materials for structural and thermal applications in energy-intensive industries.

The publication presents general information on calcium zirconate and the physical/chemical characteristics of products based thereon. The main fields of application of ceramic and refractory materials based on CaZrO 3 are also considered.

The publication presents general information on calcium zirconate and the physical/chemical properties of products based on it. Methods for CaZrO 3 production, such as solid phase synthesis, electric arc fusion, codeposition, hydrothermal synthesis, etc. are studied.

This paper presents the results of the studies of refractory materials produced by the company Keralit, the Borovichi Refractories Plant, and Scientific and Technical Center Bakor (STC Bakor) and intended for the roof of an EP-6 electric furnace for high-level waste vitrification. These studies determined the strength properties and acid resistance of these materials when exposed to nitric-acid in vapor and solution forms. The results of the studies show that the optimum materials for constructing the melter roof are MKRTU-50 and MKV-65 produced by the Borovichi Refractories Plant and STC Bakor, respectively.