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A high-entropy silicide (HES), (Ti 0.2 Zr 0.2 Nb 0.2 Mo 0.2 W 0.2 )Si 2 with close-packed hexagonal structure is successfully manufactured through reactive spark plasma sintering at 1300 °C for 15 min. The elements in this HES are uniformly distributed in the specimen based on the energy dispersive spectrometer analysis except a small amount of zirconium that is combined with oxygen as impurity particles. The Young’s modulus, Poisson’s ratio, and Vickers hardness of the obtained (Ti 0.2 Zr 0.2 Nb 0.2 Mo 0.2 W 0.2 )Si 2 are also measured.

The growing demand for composite materials capable of enduring prolonged loads in high-temperature and aggressive environments presents pressing challenges for materials scientists. Ceramic materials composed of silicon carbide largely possess high mechanical strength at a relatively low density, even at elevated temperatures. However, they are inherently brittle in nature, leading to concerns about their ability to fracture. The primary objective of this study was to develop a novel technique for fabricating layered composite materials by incorporating SiC-based ceramics, refractory metals, and their silicides as integral constituents. These layered composites were produced through the liquid-phase siliconization method applied to metal–carbon blanks. Analysis of the microstructure of the resultant materials revealed that when a metal element interacts with molten silicon, it leads to the formation of a layer of metal silicide on the metal’s surface. Furthermore, three-point bending tests exhibited an enhancement in the bending strength of the layered composite in comparison to the base silicon carbide ceramics. Additionally, the samples demonstrated a quasi-plastic nature during the process of destruction.

Thermoelectric materials-based devices are used to convert heat energy into electrical energy. Magnesium silicide-based thermoelectric-based devices are considered commercially viable due to their low cost compared to other contemporary materials. The current study investigates the influence of Sb doping on the thermoelectric properties of the Mg2.15Si0.28Sn0.714Sb0.006 (Sample-A) compound with an excess Mg content (7.5 mol %). The excess Mg induces point defects through interstitial Mg and Si/Sn vacancies, significantly enhancing the electron concentration (ne). Moreover, Sb is recognized as an effective single-electron donor in Mg2Si-based materials, leading to notable increases in ne and electrical conductivity. Consequently, in the current investigation, excess Mg combined with appropriate Sb doping, resulted in the selection of Mg2.15Si0.28Sn0.714Sb0.006 (Sample-A), which exhibited high ne and superior thermoelectric performance. Further, the current study was extended by incorporating 3 vol.% of reduced graphene oxide (rGO) into Mg2.15Si0.28Sn0.714Sb0.006 + 3 vol.% rGO (Sample-B) to enhance mechanical performance and reduce thermal conductivity (k). Consequently, Sample-B showed a ∿ 28% increase in fracture toughness (from 1.48 to 1.9 MPa√m) and a ∿ 137% improvement over conventional Mg2Si. Moreover, the inclusion of rGO resulted in a substantial reduction in k ∿ 40% in the mid-temperature range, due to intensified phonon scattering caused by the higher interface density within the matrix. However, adding more than 3 vol.% rGO negatively impacts both thermoelectric and mechanical properties by obstructing the charge carriers. Therefore, achieving an optimal balance between rGO addition and compositional modulation is essential to enhance both thermoelectric and mechanical performance in these composites.

The growing demand for composite materials capable of enduring prolonged loads in high-temperature and aggressive environments presents pressing challenges for materials scientists. Ceramic materials composed of silicon carbide largely possess high mechanical strength at a relatively low density, even at elevated temperatures. However, they are inherently brittle in nature, leading to concerns about their ability to fracture. The primary objective of this study was to develop a novel technique for fabricating layered composite materials by incorporating SiC-based ceramics, refractory metals, and their silicides as integral constituents. These layered composites were produced through the liquid-phase siliconization method applied to metal–carbon blanks. Analysis of the microstructure of the resultant materials revealed that when a metal element interacts with molten silicon, it leads to the formation of a layer of metal silicide on the metal’s surface. Furthermore, three-point bending tests exhibited an enhancement in the bending strength of the layered composite in comparison to the base silicon carbide ceramics. Additionally, the samples demonstrated a quasi-plastic nature during the process of destruction.

Thermoelectric materials convert heat into electricity and can provide solid-state cooling for spot-sized refrigeration. One important barrier for adopting these materials beyond niche applications is their low efficiency. He and Tritt review the mechanisms and strategies for improving thermoelectric efficiency. They discuss how to report material performance and highlight the most promising materials. With new materials and strategies for performance enhancement, thermoelectrics are poised to alter the renewable energy landscape. Science , this issue p. eaak9997 High-performance thermoelectric materials lie at the heart of thermoelectrics, the simplest technology applicable to direct thermal-to-electrical energy conversion. In its recent 60-year history, the field of thermoelectric materials research has stalled several times, but each time it was rejuvenated by new paradigms. This article reviews several potentially paradigm-changing mechanisms enabled by defects, size effects, critical phenomena, anharmonicity, and the spin degree of freedom. These mechanisms decouple the otherwise adversely interdependent physical quantities toward higher material performance. We also briefly discuss a number of promising materials, advanced material synthesis and preparation techniques, and new opportunities. The renewable energy landscape will be reshaped if the current trend in thermoelectric materials research is sustained into the foreseeable future.

Refractory metal (RM) M5Si3 silicides are desirable intermetallics in metallic ultra-high temperature materials (UHTMs), owing to their creep properties and high Si content that benefits oxidation resistance. Of particular interest is the alloyed Nb5Si3 that forms in metallic UHTMs with Nb and Si addition. The choice of alloying elements and type of Nb5Si3 that is critical for achieving a balance of properties or meeting a property goal in a metallic UHTM is considered in this paper. Specifically, the different types of alloyed “normal” Nb5Si3 and Ti-rich Nb5Si3, namely “conventional”, “complex concentrated” (CC) or “high entropy” (HE) silicide, in metallic UHTMs with Nb and Si addition were studied. Advanced metallic UHTMs with additions of RMs, transition metals (TMs), Ge, Sn or Ge + Sn and with/without Al and with different Ti, Al, Cr, Si or Sn concentrations were investigated, considering that the motivation of this work was to support the design and development of metallic-UHTMs. The study of the alloyed silicides was based on the Nb/(Ti + Hf) ratio, which is key regarding creep, the parameters VEC and Δχ and relationships between them. The effect of alloying additions on the stability of “conventional”, CC or HE silicide was discussed. The creep and hardness of alloyed Nb5Si3 was considered. Relationships that link “conventional”, CC or HE bcc solid solution and Nb5Si3 in the alloy design methodology NICE (Niobium Intermetallic Composite Elaboration) were presented. For a given temperature and stress, the steady state creep rate of the alloyed silicide, in which TMs substituted Nb, and Al and B substituted Si, depended on its parameters VEC and Δχ and its Nb/(Ti + Hf) ratio, and increased with decreasing parameter and ratio value, compared with the unalloyed Nb5Si3. Types of alloyed Nb5Si3 with VEC and Δχ values closest to those of the unalloyed Nb5Si3 were identified in maps of alloyed Nb5Si3. Good agreement was shown between the calculated hardness and chemical composition of Nb5Si3 and experimental results.

The influence of simple and transition metal impurities, as well as interstitial impurities (B, C, and N), on the oxygen adsorption on the Ti.sub.5Si.sub.3 titanium silicide surface has been studied using the of projector augmented wave method within the electron density functional theory. It has been shown that titanium-substituting impurities belonging to the latter halves of the 3d-5d periods cause most significant changes in the adsorption energy. In addition, simple metals and interstitial impurities reduce the oxygen-surface interaction. By analyzing local electron densities of states, charge density difference distribution, charge transfer, and the overlap population of oxygen bonds to nearest-neighbor atoms, we have revealed special aspects of impurity influence on chemical bonding between the titanium silicide surface and oxygen. Factors responsible for an increase/decrease in the adsorption energy of oxygen on the doped surface are discussed. A correlation between the change in adsorption energy and the electronegativity of impurities has been found.

Refractory metal (RM) M[sub.5]Si[sub.3] silicides are desirable intermetallics in metallic ultra-high temperature materials (UHTMs), owing to their creep properties and high Si content that benefits oxidation resistance. Of particular interest is the alloyed Nb[sub.5]Si[sub.3] that forms in metallic UHTMs with Nb and Si addition. The choice of alloying elements and type of Nb[sub.5]Si[sub.3] that is critical for achieving a balance of properties or meeting a property goal in a metallic UHTM is considered in this paper. Specifically, the different types of alloyed “normal” Nb[sub.5]Si[sub.3] and Ti-rich Nb[sub.5]Si[sub.3], namely “conventional”, “complex concentrated” (CC) or “high entropy” (HE) silicide, in metallic UHTMs with Nb and Si addition were studied. Advanced metallic UHTMs with additions of RMs, transition metals (TMs), Ge, Sn or Ge + Sn and with/without Al and with different Ti, Al, Cr, Si or Sn concentrations were investigated, considering that the motivation of this work was to support the design and development of metallic-UHTMs. The study of the alloyed silicides was based on the Nb/(Ti + Hf) ratio, which is key regarding creep, the parameters VEC and Δχ and relationships between them. The effect of alloying additions on the stability of “conventional”, CC or HE silicide was discussed. The creep and hardness of alloyed Nb[sub.5]Si[sub.3] was considered. Relationships that link “conventional”, CC or HE bcc solid solution and Nb[sub.5]Si[sub.3] in the alloy design methodology NICE (Niobium Intermetallic Composite Elaboration) were presented. For a given temperature and stress, the steady state creep rate of the alloyed silicide, in which TMs substituted Nb, and Al and B substituted Si, depended on its parameters VEC and Δχ and its Nb/(Ti + Hf) ratio, and increased with decreasing parameter and ratio value, compared with the unalloyed Nb[sub.5]Si[sub.3]. Types of alloyed Nb[sub.5]Si[sub.3] with VEC and Δχ values closest to those of the unalloyed Nb[sub.5]Si[sub.3] were identified in maps of alloyed Nb[sub.5]Si[sub.3]. Good agreement was shown between the calculated hardness and chemical composition of Nb[sub.5]Si[sub.3] and experimental results.

Extreme ultraviolet (EUV) pellicles must withstand intense thermal stress during exposure due to their limited heat dissipation, which results from their ultrathin geometry and the vacuum environment within EUV scanners. To address this challenge, we investigated the crystalline phase-dependent emissivity of nanometer-thick molybdenum disilicide (MoSi[sub.2]) membranes. Membranes exhibiting amorphous, hexagonal, and tetragonal phases were independently prepared via controlled annealing, and their thermal radiation properties were evaluated using heat-load testing under emulated EUV scanner conditions. The Hall effect measurements revealed distinct variations in carrier density and mobility across phases, which were theoretically correlated with emissivity using the Lorentz–Drude model. The results demonstrate that emissivity increases in the hexagonal phase due to increased carrier density and reduced scattering, offering improved thermal radiation performance. These findings establish the phase engineering of conductive silicides as a viable strategy for enhancing radiative cooling in EUV pellicles and offer a theoretical framework applicable to other high-temperature nanomaterials.