Zirconium diboride (ZrB₂)–silicon carbide (SiC) composites are promising candidates for ultra-high temperature applications, yet optimizing their densification and mechanical performance without sintering additives remains a challenge. This study systematically investigates the independent and combined effects of three critical spark plasma sintering (SPS) parameters, that is, temperature, applied pressure, and dwell time, on the densification behavior, microstructure, and mechanical properties of ZrB₂–20 vol% SiC composites. Building upon prior work on powder preparation effects (e.g., Tungsten Carbide (WC) vs. ZrO₂ milling), this research uniquely focuses on how precise control of sintering conditions alone can tailor final material characteristics. The results demonstrate that optimizing sintering parameters yields significant property enhancement, achieving a maximum relative density of 99.2% (at 2100°C, 65 MPa, 15 min) and peak flexural strength of 516 MPa (at 2000°C, 65 MPa, 60 min). Hardness and fracture toughness reached 17.08 GPa and 3.85 MPa m^1/2, respectively, under optimized conditions. Through detailed microstructural and performance analysis, this work explains the fundamental role of individual sintering parameters in governing densification kinetics and mechanical outcomes. The findings offer practical guidance for additive-free, energy-efficient processing of ZrB₂–SiC ceramics for advanced aerospace and thermal protection systems.

Zirconium carbide (ZrC) is a candidate material for extreme environments due to its exceptional thermal and mechanical properties. However, its oxidation behavior, particularly the formation of the Zr–C–O layer, requires further clarification. In this study, we investigated the oxidation of spark plasma sintered ZrC under varying temperatures and oxygen partial pressures, revealing a double-layer oxide scale. At the interface between ZrC and the Zr–C–O layer, we identified previously unreported oxidation front stripes composed of cubic zirconia, along which elliptical submicropores formed, suggesting preferential CO₂ release pathways. The Zr–C–O layer itself was significantly enriched with amorphous free carbon. Based on these findings, we developed a phenomenological model that incorporated the formation of the compact Zr–C–O layer to predict oxide scale growth. This multiscale approach provides new insights into ZrC oxidation mechanisms and supports the design of oxidation-resistant ceramics for aerospace and nuclear applications.

ZrC Ultra-High Temperature Ceramic is a promising material for future extreme environment applications. However, its susceptibility to oxidation at elevated temperatures poses a significant challenge. There remains unresolved controversy in literature regarding its oxidation kinetics and activation energies. The temperature, oxygen pressure and time effects on the oxidation and passivation of ZrC are still not fully understood. To address these questions, we fabricated near-stoichiometric ZrC ceramic via spark plasma sintering (SPS) and for the first time investigated the temperature-oxygen pressure-time (T-P-t) dependent oxidation kinetics of SPS-sintered ZrC. A three-stage oxidation mechanism including a passivation stage was reported. The study also revealed the complexity of activation energy dependence on temperature and pressure within the 3D T-P-t space. Additionally, it uncovered the conditions necessary to maintain the passivation of ZrC. These findings provide valuable insights for future design of oxidation-resistant ZrC and carbides, paving the way for advancements in materials for extremes.

This study investigates the impact of different powder milling methods on the densification and mechanical properties of ZrB₂-SiC ceramic composites processed via spark plasma sintering (SPS). Powders were prepared using two ball milling techniques: tungsten carbide (WC) and conventional ZrO₂. The densification behavior during SPS was monitored, and the sintered samples were evaluated for their relative density, hardness, fracture toughness, and flexural strength. Results show that WC milling significantly enhances densification, achieving 99.2 % relative density at 2100 °C/65 MPa/15 min, compared to 96.5 % for ZrO₂-milled samples. This improvement is due to WC's sintering aid effect, which promotes grain boundary diffusion and particle packing. However, ZrO₂-milled composites exhibit superior hardness (17.38 GPa) and fracture toughness (3.97 MPa m¹/²), attributed to their refined grain structure and the absence of softer ZrO₂ phases. Conversely, WC-milled samples show slightly higher flexural strength (384–516 MPa), likely due to the transformation toughening effect of the secondary ZrO₂ phase. Overall, WC milling improves densification and flexural strength, while ZrO₂ milling yields finer-grained composites with higher hardness and toughness, making it better suited for wear-resistant and mechanically demanding applications.

As with many tasks in engineering, structural design frequently involves navigating complex and computationally expensive problems. A prime example is the weight optimization of laminated composite materials, which to this day remains a formidable task, due to an exponentially large configuration space and non-linear constraints. The rapidly developing field of quantum computation may offer novel approaches for addressing these intricate problems. However, before applying any quantum algorithm to a given problem, it must be translated into a form that is compatible with the underlying operations on a quantum computer. Our work specifically targets stacking sequence retrieval with lamination parameters, which is typically the second phase in a common bi-level optimization procedure for minimizing the weight of composite structures. To adapt stacking sequence retrieval for quantum computational methods, we map the possible stacking sequences onto a quantum state space. We further derive a linear operator, the Hamiltonian, within this state space that encapsulates the loss function inherent to the stacking sequence retrieval problem. Additionally, we demonstrate the incorporation of manufacturing constraints on stacking sequences as penalty terms in the Hamiltonian. This quantum representation is suitable for a variety of classical and quantum algorithms for finding the ground state of a quantum Hamiltonian. For a practical demonstration, we performed numerical state-vector simulations of two variational quantum algorithms and additionally chose a classical tensor network algorithm, the DMRG algorithm, to numerically validate our approach. For the DMRG algorithm, we derived a matrix product operator representation of the loss function Hamiltonian and the penalty terms. Although this work primarily concentrates on quantum computation, the application of tensor network algorithms presents a novel quantum-inspired approach for stacking sequence retrieval.

In the past decades, Zirconia (ZrO₂) has emerged as a promising technical ceramic, both as high temperature structural material and electrolyte for fuel cells, etc. The traditional synthesis of ZrO₂ with spark plasma sintering (SPS) usually requires a sintering temperature as high as 1200 °C. General interest in lowering the sintering temperature to reduce energy consumption and thermal stresses has led to research on two promising routes – cold sintering via temperature-dependent chemical reactivity and sintering aids, which facilitates mass transport and improves densification. Here we combine both by developing a single-step sintering process benefitting from both water vapor through the in-situ conversion of Zr(OH)₄ to ZrO₂ and liquid phase Bi₂O₃ as a sintering aid. The resultant ZrO₂ has a relative density above 80% with a sintering temperature as low as 900 °C, significantly higher than that of ZrO₂ without sintering aids, which had a relative density of 54%, both sintered at 50 MPa. The dependence of porosity of sintered samples as a function of sintering pressure (range: 50 MPa–300 MPa) and temperature (range 400 °C–1200 °C) is mapped out as guidance for further material property design. A linear relationship between hardness and relative density was found, with a maximal hardness of 6.6 GPa achieved in samples with 30% porosity. In addition to sintered density, phase stabilization of tetragonal ZrO₂ is enhanced at sintering temperature of 900 °C with water vapor and Bi₂O₃, respectively.

SnSe is a promising thermoelectric material due to its low toxicity, low thermal conductivity, and multiple valence band structures, which are ideal for high electronic transport properties. The multiple valence band structure has attracted many attempts to engineer the carrier concentration of the SnSe via doping, to place its fermi level at a position where the maximum number of valence bands can participate in the electronic transport. Up until now, ~5 × 10¹⁹ cm^-3 was the highest carrier concentration achieved in SnSe via doping. Recently, introducing SnSe₂ into SnSe was found to effectively increase the carrier concentration as high as ~6.5 × 10¹⁹ cm^-3 (at 300 K) due to the generated Sn vacancies. This high carrier concentration at 300 K, combined with the reduction in lattice thermal conductivity due to SnSe₂ micro-domains formed within the SnSe lattice, improved the thermoelectric performance (zT) of SnSe – xSnSe₂ as high as ~2.2 at 773 K. Here, we analyzed the changes in the electronic band parameters of SnSe as a function of temperature with varying SnSe₂ content using the Single Parabolic Band (SPB) model. According to the SPB model, the calculated density-of-states effective mass and the fermi level are changed with temperature in such a way that the Hall carrier concentration (n_H) of the SnSe – xSnSe₂ samples at 773 K coincides with the optimum n_H where the theoretically maximum zT is predicted. To optimize the n_H at high temperatures for the highest zT, it is essential to tune the 300 K n_H and the rate of n_H change with increasing temperature via doping.