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Exploring new applications of negative thermal expansion (NTE) materials is a recent research hotspot. In this work, the IV A element Sn was used to tailor the thermal expansion and dielectric properties of NTE material ZrMgMo 3 O 12 , and the samples Zr 1–x Sn x MgMo 3 O 12 (x = 0.05, 0.10, 0.15, 0.20, 0.25) can be used in the field of high-frequency dielectric ceramics. Both the substitution amount of Sn and sintering temperature have a certain effect on the properties of Zr 1-x Sn x MgMo 3 O 12. The coefficients of thermal expansion (CTE) can be adjusted between near zero thermal expansion (ZTE) (−0.24 × 10−6/K−1) and NTE (−8.16 × 10−6/K−1) and become larger toward negative as the amount of Sn increased under the same sintering temperature. The dielectric constants of Zr 1-x Sn x MgMo 3 O 12 can be adjusted in the range of 130∼155, which are about 25 times than ZrMgMo 3 O 12. The dissipation factors of Zr 1-x Sn x MgMo 3 O 12 were adjustable between 4.37 × 10−4 and 5.54 × 10−4, meeting the application requirements of high-frequency dielectric ceramics. This research shows that Sn can adjust the thermal expansion properties and significantly improves the dielectric properties of ZrMgMo 3 O 12 , so that Zr 1-x Sn x MgMo 3 O 12 materials have high value in the field of high-frequency dielectric ceramics. [ABSTRACT FROM AUTHOR]

Thermal camouflage technology can effectively hide an object by lowering its infrared emissivity and reducing its surface temperature. So far, it has been a challenge to realize thermal camouflage at high-temperatures with a single material. Here, we report a Ti 3 AlC 2 MAX phase material that exhibits excellent thermal camouflage properties from room temperature to 500 °C, and maintains a low emissivity of 0.25 at 500 °C, which is difficult to achieve for most metals due to the rapid increase in emissivity caused by oxidation. The thermal camouflage mechanism of Ti 3 AlC 2 was analyzed on the basis of experimental results and first-principles calculations, providing a feasible approach to select other MAX phases (such as Ti 3 SiC 2 , Cr 2 AlC, and Ti 2 AlC) with attractive thermal camouflage performance. Ti 3 AlC 2 and other MAX phases are promising candidates for thermal camouflage applications due to their low emissivity, high-temperature stability, good oxidation resistance and ease of fabrication. [ABSTRACT FROM AUTHOR]

This work investigates the behavior and properties of corundum and mullite ceramics at high temperatures and during very long exposures in a controlled atmosphere. The motivation of the work lies primarily in advanced applications in nuclear energy technology, specifically in the search for materials for helium-cooled reactors of the 4th generation. The studied ceramic samples Al63, Al70, Al76, Al96, Al100, where the number indicates the mass percentage of Al 2 O 3 , were exposed for 1000 h at a temperature of 900 °C in gaseous atmospheres of helium, nitrogen and air. The properties of the exposed and unexposed samples were evaluated by measuring the bending strength at room temperature (CMOR), hot modulus of rupture at high temperature (HMOR), and isothermal creep, BET method, and using electron microscopy. The color changes induced by the reducing atmosphere and temperature were also interpreted using a simple thermochemical model. The CMOR measurement results show that all ceramic samples do not significantly change their properties due to long-term exposure. The detected deviations in the exposed samples from the unexposed ones can be considered random caused by the inherent heterogeneous structure. A similar conclusion also applies in the case of the HMOR measurement results, except for the results for the Al63 sample, where the drop in the strength of the exposed samples by approx. 37 MPa (20 %) may be related with the highest proportion of polyvalent oxide admixtures of all studied ceramics, i.e. 1.01 wt % Fe 2 O 3 and 0.52 wt % TiO 2. The change in color indicates that the iron and titanium present are being reduced. However, none of the conducted experiments indicate that changes in the redox state associated with the formation of oxygen vacancies would significantly reduce strength at high temperatures or increase creep in mullite ceramics. [ABSTRACT FROM AUTHOR]

The concurrent enhancement of toughness, electrical conductivity, and thermal stability in polycrystalline diamond composites represents a formidable challenge. Here, a novel diamond-TiC composites (referred to as DTC) with high fracture toughness and conductivity were synthesized through a high-temperature and high-pressure reaction sintering process utilizing two precursors: diamond mixtures containing TiH 2 and Ti-coated diamonds. On the one hand, the inherent bonding and encasing of TiC onto the diamond matrix form a heterogeneous structure, providing high strength and excellent fracture toughness up to 11.6 MPa·m1/2. On the other hand, the established oxygen barrier and current pathway offer a thermal stability of 765 °C and high conductivity up to 837 S·m−1. Remarkably, this rare combination of mechanical, electrical, and thermal properties has been realized within a single material under relatively moderate sintering conditions, thus positioning diamond-TiC composites as a promising ceramic for electrical applications in high-stress environments. [ABSTRACT FROM AUTHOR]

Si3N4 ceramics with high mechanical properties and thermal conductivity, exhibiting fine and bimodal microstructure, were prepared by adjusting the Er2O3/MgO ratio and hot‐pressing sintering at 1800°C for 4 h. The microstructure, grain distribution, lattice oxygen content, mechanical properties, and crack propagation process of the sintered bulk samples were systematically investigated. It was found that a low Er2O3/MgO ratio contributed to the densification of Si3N4 ceramics, whereas a high Er2O3/MgO ratio favored the grain growth of Si3N4 ceramics. In this research, the grain size distribution and average diameters as well as their impact on mechanical properties were examined. When the ratio of Er2O3/MgO was 3:1, Si3N4 had a larger average diameter and higher thermal conductivity, but the mechanical properties were somewhat reduced. When the ratio of Er2O3/MgO was 2:2, the sample displayed enhanced mechanical performance, which can be explained by the formation of a bimodal structure. The research indicates that it is feasible to control the microstructure and optimize the mechanical properties of Si3N4 ceramics by tailoring the sintering additives. [ABSTRACT FROM AUTHOR]

Porous SiC ceramics with three different pore sizes (∼7, ∼45, and ∼98 μm) and two different porosities (∼54% and ∼63%) were prepared to investigate the effects of pore size on electrical and thermal properties of the porous ceramics. With an increase in pore size from ∼7 to ∼98 μm at the same porosity (∼54%), the electrical and thermal conductivities of the porous ceramics increased from ∼1.01 to ∼2.30 Ω−1·cm−1 and ∼14.3 to ∼26.2 W·m−1K−1, respectively. Similar trends have been obtained in the ceramics with ∼63% porosity. The porous SiC ceramic with larger pore size has smaller pore/strut interface area at the same porosity, which leads to less carrier scattering and phonon‐pore scattering at the pore/strut interfaces, resulting in higher electrical and thermal conductivities, respectively. These results suggest that the electrical and thermal properties of porous SiC ceramics can be successfully tuned by adjusting the pore size and porosity depending on the application. [ABSTRACT FROM AUTHOR]

In the thermal protection system of spacecraft, the bolts connecting the ceramic to the internal superalloy need to have low thermal conductivity and high strength. Two dense high entropy fluorite oxides (Zr 1/7 Hf 1/7 Ce 1/7 Y 2/7 La 2/7)O 2-δ (ZHCYL) and (Zr 1/8 Hf 1/8 Ce 1/8 Y 1/4 La 1/4 Pr 1/8)O 2-δ (ZHCYLP) were designed and synthesized by using the synergistic effect of plasma-assisted ball milling and spark plasma sintering(SPS). Through the synergistic effect of lattice distortion and oxygen vacancy guided by entropy regulation, ZHCYLP synthesized in this study has lower thermal conductivity(1.13 W·m−1·K−1), higher high temperature strength(192 MPa at 1000 °C) and high temperature phase stability up to 1600 °C than 8YSZ ceramics. The thermo-mechanical coupling finite element analysis results of high temperature bending test show that the variation trend of the maximum stress value of the sample is consistent with the experimental results. This shows that the mechanical and thermal properties of high entropy oxides can predict the variation trend of the maximum stress value in high temperature bending tests. It opens up a new way for designing and synthesizing high entropy oxide materials with low thermal conductivity and high strength which can be applied in the field of heat protection and load bearing. [ABSTRACT FROM AUTHOR]

Ceramic fibers are an important thermal insulation material that are not only widely used in extreme conditions, but also play an important role in energy conservation and energy efficiency for sustainable development. However, the practical application of conventional ceramic fibers has a high thermal conductivity in high-temperature environments, which hinders their widespread application. Here, a novel lamellar structured porous SiTiOC/C composite ceramic materials was designed and prepared with excellent thermal insulating properties. The unique microstructure endowed the porous SiTiOC/C composite ceramic materials with a high IR refractive index (93.81%) and an ultra-low thermal conductivity (0.0562 W·m−1 K−1 at 600 ℃). In addition, the porous SiTiOC/C composite ceramic materials not only exhibited excellent mechanical properties (4.46 MPa at 800 ℃), but also demonstrated impressive oxidation resistance and thermal stability. In summary, the proposed porous SiTiOC/C composite ceramic materials provide a reference for the development of high-temperature insulation with good mechanical properties. [ABSTRACT FROM AUTHOR]

Ceramic aerogels are promising candidates for high-temperature thermal resistance and thermal insulation materials. However, their application can be restricted by their brittleness when exposed to harsh conditions. Herein, this study has developed a novel synthesis process based on a sol-gel method and carbothermal reduction-nitridation to produce a porous TiN composite aerogel from an organic/inorganic hybrid. The resulting TiN displays a polyhedral particle size of around 30–60 nm with nanoscale pores. In addition, the TiN aerogel demonstrates a high BET-specific surface area of 653.42 m2/g and a very low thermal conductivity of 0.046 W/(m·K). Furthermore, the TiN aerogel composite displays a good thermal difference with no shrinkage and cracks of the morphology during the butane blazing torch at 1300 °C for 10 min under air environment, demonstrating its excellent thermal insulation property and anti-oxidation characteristics. The gas-solid reaction mechanism of TiN aerogel based on the Gibbs free energy calculations is also proposed. [ABSTRACT FROM AUTHOR]

Alumina‐based porous ceramics were fabricated via the starch consolidation casting route, using titanium oxide as a sintering additive. Alumina‐titania‐starch slurries with starch contents of 2.5, 5, 7.5, and 10 wt% relative to the alumina‐titania system were prepared. Titania was added to the slurries in proportions of 0, 1, 3, and 5 wt%, relative to alumina. The effects of starch and titania contents in the green bodies on the linear and volumetric shrinkage, as well as the total and open porosities of the sintered alumina product, were investigated. The effect of titania addition on mechanical, electrical, and thermal properties of the obtained porous alumina ceramics was studied. Microstructure and pores morphology were characterized by SEM. The alumina‐based ceramics obtained had external porosities that varied between 54 and 76 vol%. Thermal conductivities as low as 0.06–0.1 W/m.K were achieved and the volume electrical resistivity ranged from 3.6 to 600 GΩ·m, while compressive strengths up to 2.8 MPa for a titania ratio of 1 wt% were attained. [ABSTRACT FROM AUTHOR]

(KMg)3+ co-doped Sc 2 W 3 O 12 ceramics have been prepared via co-precipitation method. Effects of (KMg)3+ co-doping amount and sintering temperature on the phase constitution, microstructure, morphology, and negative thermal expansion (NTE) performance of K x Mg x Sc 2- x W 3 O 12 (0 ≤ x ≤ 1.25) ceramics were studied. Results indicate that: Sc3+ cations can be substituted by (KMg)3+ dual-cations and a composition-induced structural phase transition was observed in K x Mg x Sc 2- x W 3 O 12. For x ≤ 0.25, orthorhombic Sc 2 W 3 O 12 gradually changed into hexagonal K x Mg x Sc 2- x W 3 O 12 and coexisted. Single phase K x Mg x Sc 2- x W 3 O 12 with hexagonal symmetry can be prepared for 0.25 < x ≤ 1. When x ≥ 1.25, (KMg)3+ substitution reaches its solid solution limit in Sc 2 W 3 O 12 , and impurity MgWO 4 formed in the samples. As co-doping amount x increased, the NTE performance of the K x Mg x Sc 2- x W 3 O 12 (0 ≤ x ≤ 1) ceramics gradually enhanced. The coefficient of thermal expansion (CTE) of K x Mg x Sc 2- x W 3 O 12 (0 ≤ x ≤ 1) ceramics enhanced from −2.14 × 10−6 °C−1 to −19.68 × 10−6 °C−1 in 30–700 °C. With the increase of sintering temperature from 800 to 1100 °C, the grains grew up and the density of the K 0.75 Mg 0.75 Sc 1.25 W 3 O 12 ceramics increased as well, and the NTE performance was also improved. The linear CTE of K 0.75 Mg 0.75 Sc 1.25 W 3 O 12 ceramics enhances from −2.15 × 10−6 °C−1 to −14.70 × 10−6 °C−1 in 30–700 °C. [ABSTRACT FROM AUTHOR]

Lightweight phenolic matrix composites are highly potential in ablative thermal protective materials for future aerospace vehicles, and hybrid modification is considered as one of effective ways to improve the oxidation and ablation resistance of phenolic matrix. Herein, the co-continuous silica zirconium hybrid phenolic resin (SZRx) was synthesized, which can be used to prepare lightweight ablation resistant aerogel composites by the sol-gel method. The SZRx aerogel showed stable porous structure and excellent hydrophobicity, and the silicon zirconium hybrid greatly improved the high temperature carbon residue and oxidation resistance of phenolic resin. The SZRx aerogel composites also possessed excellent integrated characteristics of heat protection and insulation, with a linear ablation rate as low as 0.032 mm/s and a back temperature below 200 °C. The synergistic effect of silicon and zirconium formed the multiphase ceramic layer (C, SiO 2 , SiC and ZrO 2) with the sea-island-like structure on the surface of the composite material, which can effectively resist high-temperature ablation and aerodynamic exfoliation. This can indicate that silicon zirconium dual element hybrid phenolic resin is the highly competitive matrix for lightweight and ablation resistant composite materials. [Display omitted] [ABSTRACT FROM AUTHOR]

In pursuing enhanced performance for electronic applications, we synthesized ferroelectric materials, specifically Ba(1-x)Nd2x/3TiO3 (BNdTx) nanoceramics, utilizing solid-state reaction techniques coupled with microwave heating treatment. Our investigation involved varying Nd3+-doping levels (x = 0%, 2%, 4%, and 8%) to tailor the material's properties. XRD analysis confirmed the presence of a single-phase tetragonal perovskite structure (space group P4mm). A comprehensive examination of the partial density of states for both undoped and Nd3+-doped BaTiO3 was undertaken to discern the impact of Nd3+-doping on the energy bands. Microscopic analysis revealed the presence of pores in the samples, accompanied by a reduction in grain size with increasing Nd3+ content. The introduction of Nd3+ induced a shift in the Curie temperature (TC) towards room temperature. Simultaneously, the dielectric characteristics exhibited a consistent value above 1900, with a low loss of less than 5% observed across a range of temperatures (30–100 °C). Notably, the sample with x = 4% demonstrated thermally stable dielectric properties, suggesting its potential suitability as a material for Multilayer Ceramic Capacitor (MLCC) applications. Integrating microwave sintering and ball milling techniques is a significant development in advanced materials engineering, specifically in producing Multi-Layer Ceramic Capacitors (MLCC). The practical implementation of these novel methodologies is essential in decreasing particle size, which is a critical determinant in improving thermal stability. Ball milling further refines the particle size distribution, whereas microwave sintering guarantees a more uniform and fine-grained microstructure through its rapid and effective heating capabilities. The capacitors acquire enhanced thermal stability and a more refined material granularity through this synergistic combination. By achieving a more uniform and compact ceramic structure, these processes result in a finer particle size, enhancing the overall performance and dependability of MLCC capacitors. The increasing need for miniaturized and high-performance electronic components has focused on utilizing microwave sintering and ball milling. These processes are at the forefront of technological advancements in the pursuit of improved thermal properties and increased efficiency in manufacturing MLCC capacitors. [ABSTRACT FROM AUTHOR]

Ceramic thermal barrier coatings (TBCs) with high toughness and low thermal conductivity are important for developing aero engines with high thrust‐to‐weight ratio and thermal efficiency. In this work, the properties of tantalate Y1/6Yb5/6TaO4 (YYT) were optimized by introducing 8 wt.% yttria‐stabilized zirconia (8YSZ), synthesized using spark plasma sintering, as a second‐phase ceramic. The highest toughness (3.57 MPa m1/2) of the YYT/8YSZ composite ceramics was due to multiple toughening mechanisms. The underlying mechanisms of these processes were revealed based on the microstructures and residual stress of the YYT/8YSZ composite ceramics. A shift from an intergranular fracture to a transgranular fracture was caused by the difference between soft‐grain YYT and hard‐grain 8YSZ, which consumed the fracture energy. Furthermore, the formation of microcracks, crack deflection, bridging, and branching were analyzed based on the differences in Young's moduli and thermal expansion coefficients of YYT and 8YSZ. Internal defects and weak connections between the YYT and 8YSZ grains reduced the thermal conductivity of the composites until it reached its lowest value at 1.4 W m−1 K−1. The studied toughening mechanisms could be applied to various composites. Moreover, herein, we provide a new strategy to design and synthesize TBCs with enhanced performance. [ABSTRACT FROM AUTHOR]

In this study, a highly dense GdB 6 bulk ceramic material was fabricated using one-step in-situ reaction spark plasma sintering technology. The sample with a relative density of 96.7 % and a purity of 96.9 wt% was successfully obtained by sintering at 1800 °C for 30 min under a uniaxial pressure of 50 MPa. The Vickers hardness, elastic modulus and fracture toughness of the as-obtained GdB 6 bulk ceramics were 18.9 GPa, 209 GPa and 1.6 MPa·m1/2, respectively. The thermal conductivity of GdB 6 at room temperature was 28.68 W·m−1·K−1, 70 % of which was mainly attributed to phonon vibration, while the remaining 30 % to the electrical thermal conductivity. In addition, the as-obtained GdB 6 ceramics showed no phase transformation after heat treatment at a relatively high temperature of 2100 °C for 20 min in Ar atmosphere. The highly covalent octahedral boron framework played a critical role in maintaining the phase stability of the GdB 6 crystal lattice. This suggested that GdB 6 ceramics could be used as potential ultra-high temperature ceramics for aerospace applications and high-power vacuum electronic devices operated at high temperatures. [ABSTRACT FROM AUTHOR]

Rare earth compounds (RE 2 O 3), typically Eu 2 O 3 and Gd 2 O 3 , are considered as absorbing materials due to their long chain neutron absorbing ability and high efficiency of neutron absorption. In this paper, a specifically designed x Eu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 (x = 0.6, 0.7, 0.8, 0.85) composite ceramics with excellent thermal properties were synthesized through direct thermal decomposition reactions followed a high-temperature sintering method under vacuum conditions. X-ray diffraction (XRD) and Raman spectroscopy analysis indicated that the obtained ceramics consisted of monoclinic Eu 2 O 3 and fluorite Gd 2 Zr 2 O 7 phases. The hardness of x Eu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 ceramics (x = 0.8, 0.85) have no significantly changes in the test temperature range (25–350 °C). The thermal expansion coefficients (TECs) (7.3–10 ×10-6 K-1) are lower than Dy 2 TiO 5 (9.3–10.4 ×10-6 K-1), and the thermal expansion rate changes linearly with the increase of temperature, which indicates that the x Eu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 ceramics exhibit excellent high temperature phase stability. Furthermore, the range of thermal conductivities is from 0.96 W·m-1·K-1 to 2.02 W·m-1·K-1 (25–800 °C), which is higher than Dy 2 TiO 5 (0.27–0.55 W/m·K, 220–650 °C). Compared with the state-of-art Dy 2 TiO 5 ceramics, x Eu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 have superior thermal properties and are therefore expected to be the next generational of neutron absorbent materials used in ash rod. [ABSTRACT FROM AUTHOR]

This study utilizes modulation of ionic disorder and electronegativity differences for targeted component design of high-entropy ceramic compositions. A series of novel multicomponent ceramics with the general formula (LaGdYSm) x 2 Yb x 1 Zr 2 O 7 (x 1 +4x 2 = 2, x 1 = 0.6,0.4,0.2,0) were prepared by solid-state reaction. The evolution patterns of their microstructures were analyzed using XRD and TEM, and the anti-sintering ability and thermophysical properties were evaluated. The results confirm that the multicomponent ceramics gradually transform from the coexistence of pyrochlore/fluorite dual-phase structure to pyrochlore structure with the tuning of the size disorder degree. After 50h of exposure to air at 1500 °C, the ceramics retained excellent phase stability. Segregation of La and Yb elements with large differences in radius size occurs, forming a mixture of the La-rich pyrochlore and the Yb-rich fluorite phases. The specimen with the maximum size disorder exhibits the lowest grain growth rate and the greatest thermal insulation properties. Large lattice distortions and sluggish diffusion effects are responsible for the mutual inhibition of grain growth in the two-phase coexistence zone. The thermal insulation properties of the ceramics show well correlated with the degree of the size disorder, further validating the effectiveness of the component design. Meanwhile, the thermal expansion coefficients of prepared ceramic can reach 11.49 × ∼11.58 × 10−6 K−1 at 1000–1100 °C. The customization principles used in this work fill a gap in the compositional design methodology for multicomponent lanthanum zirconate-based high-entropy ceramics. It is essential for developing rare-earth zirconates with tunable thermophysical properties in the area of thermal barrier coatings. [ABSTRACT FROM AUTHOR]

Zirconium carbide (ZrC) ceramics have a high melting point, low neutron absorption cross section, and excellent resistance to the impact of fission products and are considered to be one of the best candidate materials for fourth-generation nuclear energy systems. ZrC ceramics with a high relative density of 99.1% were successfully prepared via pressureless sintering using a small amount of MoSi2 as an additive. The influence of the MoSi2 content on the densification behavior, microstructure, mechanical properties, and thermal properties of ZrC ceramics was systematically investigated. The results show that the densification of ZrC was significantly enhanced by the introduction of MoSi2 due to the formation of a liquid phase during sintering. In addition, the ZrC grains were refined due to the pinning effect of the generated silicon carbide. The flexural strength and Vickers hardness of ZrC ceramics with 2.5 vol% MoSi2 sintered at 1850 °C were 408 ± 12 MPa and 17.1 GPa, respectively, which were approximately 30% and 10% higher compared to the samples without the addition of MoSi2. The improved mechanical properties were mainly attributed to the high relative density (99.1%) and refined microstructure. [ABSTRACT FROM AUTHOR]

Al 2 O 3 /B 2 O 3 powder mixtures prepared at various ratios from 10.7 to 54.1 wt% B 2 O 3 were used to synthesize Al 18 B 4 O 33 powders by solid state calcination at 1300 °C for 1 h. Al 18 B 4 O 33 formation was completed at 44 wt% B 2 O 3 instead of stoichiometric ratio of 13.17 wt% B 2 O 3. In other words, B 2 O 3 -rich liquid phase accelerated Al 18 B 4 O 33 crystallization. Al 18 B 4 O 33 particles were not acicular in shape when first formed, but they were fully acicular for the 44 wt% and the 54.1 wt% B 2 O 3 mixtures. Anorthite-based glass and CaO were selected to induce liquid phase sintering. CaO considerably improved densification to 95.4 % relative density at 1350 °C. Both glass and mullite also enhanced densification to 94.8 %. Epitaxial nucleation of mullite on Al 18 B 4 O 33 particles resulted in a solid solution as well. Dielectric, mechanical and thermal properties of the samples were investigated and evaluated for possible applications. [ABSTRACT FROM AUTHOR]

An additively manufactured reaction‐bonded silicon carbide ceramic composite is fabricated using a bimodal powder feedstock and the binder‐jetting printing technique. On fabricating, the ceramic is investigated to report its composition, mechanical, and thermal properties at room temperature and high temperatures (up to 750∘C$^{\circ }C$). The ceramic has a density of 2.76 g/cc, and shows a hardness of 21.74 GPa, and a flexure strength of 207.5 MPa at room temperature. The mechanical property of flexure strength is used to estimate its failure probability under applied stress, using a Weibull distribution. The mechanical properties and failure probabilities are compared with those of conventionally fabricated reaction‐bonded silicon carbide ceramics reported in the literature. These ceramics were fabricated using methods such as slip‐casting, compacting, and tape‐casting. The comparison is used to elucidate the advantages and areas of improvement of the present additive manufacturing technique for reaction‐bonded ceramics. [ABSTRACT FROM AUTHOR]

Recently, CaO‐doped (≤4 mol.%) tetragonal zirconia (CaSZ) ceramic was recommended as a potential alternative to yttria‐stabilized ZrO2 (YSZ). Here, we investigate the limits of starting particle sizes on the stability of tetragonal (t) phase and other associated benefits on measured properties. Synthesized CaSZ powders calcined with different temperatures were used as a mono‐sized or mixed (i.e., two different calcination temperatures) batch fraction for making dense CaSZ ceramic. The mixed‐batch powders were found to be far more efficient in stabilizing the t‐phase in ceramic. Compared to YSZ, CaSZ recorded remarkable enhancement in toughness (up to 8.3 MPa m$\sqrt {\mathrm{m}} $). Contrary to YSZ, CaSZ ceramic demonstrated outstanding thermal stability. [ABSTRACT FROM AUTHOR]

High-entropy carbide ceramic materials exhibited excellent thermal and mechanical properties, making them highly sought after in high-temperature applications. However, the oxidation resistance of high-entropy carbide ceramic needed to be further improved. This work unraveled the oxidation behavior and mechanism of high-entropy carbide ceramic by introducing the Cr 3 C 2. The results indicated that the oxidation rate of (TiZrTaNbCr)C initially decreased with temperature up to 900 °C, followed by an increased with further temperature rise up to 1100 °C. At 800 and 900 °C, the parabolic oxidation rate constants were 0.70 and 0.17 mg2cm−4min−1, respectively. And the minimum thickness of oxidized layer was 60 µm at 900 °C for 120 min. This unusual phenomenon suggested the formation of different oxidation products. Specifically, the CrNbO 4 and Nb 2 Zr 6 O 17 oxide layer were formed at 900 °C, leading to an increased resistance to oxygen diffusion. Subsequently, loose oxidation products of Nb 2 O 5 were formed after 1000 °C, hindering the oxidation resistance. In the current study on oxidation resistance of high entropy carbides, this work showed a competitive performance. Overall, this study illustrated the oxidation mechanism and behavior of (TiZrTaNbCr)C and proposed a new avenue for the design of high-entropy ceramic components. [ABSTRACT FROM AUTHOR]

The (1−x)CaO-B2O3-SiO2(CBS)/xMg2SiO4 composites were prepared and the influence of CBS crystallizable glass content on the sintering properties, dielectric properties, and thermal properties of the composites were investigated. The primary crystal phases in the CBS/Mg2SiO4 composites were CaMgSi2O6 and CaB2O4. An appropriate amount of Mg2SiO4 reduced the crystallization temperature of the composite. For x = 0.30, a sintering temperature of 890°C with a holding time of 60 min resulted in a bulk density of 2.645 g/cm3, dielectric constant of 6.6, and dielectric loss of 2.54 × 10−3 at 10 kHz. Prolonged holding time promotes grain growth; when extended from 60 min to 180 min for x = 0.30, the permittivity increased from 6.5 to 6.6 and Q×f increased from 10,100 GHz to 15,700 GHz when x = 0.30 at 13 GHz. The CTE of 70 wt.% CBS + 30 wt.% Mg2SiO4 composite was 9.5 ppm/°C, which approached the value of a circuit board for a ceramic ball grid array package (CBGA). [ABSTRACT FROM AUTHOR]

The mechanical and thermal properties of ZrC x are strongly dependent on the composition and microstructure. In the present study, densified ZrC x (x = 0.5, 0.7 and 1.0) with relative density in the range of 99.2–99.7% have been prepared by a combination of spark plasma sintering (SPS) and vacuum arc melting (VAM). Both the Young's modulus and Vickers hardness monotonically increase with increasing C/Zr ratio. The maximum Young's modulus and Vickers hardness values of 488.1 ± 13.4 GPa and 28.8 ± 1.7 GPa, respectively, for dense ZrC have been obtained. With increasing the C/Zr ratio, the thermal conductivity of ZrC x increases. The thermal conductivity ZrC ranged from 25.17 W/m/K to 43.85 W/m/K from ambient to 1200 °C. Owing to the higher density of ZrC x , the present thermal conductivities and Young's modulus of ZrC x are higher than those of the previous studies. The present results are beneficial to design and preparation of ZrC x ceramics. [ABSTRACT FROM AUTHOR]

A novel NbSi 2 /Nb 2 O 5 -SiO 2 /MoSi 2 multilayer thermal protection ceramic coating is designed and fabricated via halide-activated pack cementation and liquid-plasma-assisted particle deposition and sintering technology, endowing the coating with multiple high-temperature protective properties. The incorporation of MoSi 2 nanoparticles not only gives superior high-temperature oxidation resistance/hot corrosion resistance of coating by forming a dense SiO 2 barrier layer, but also promotes passive radiative heat dissipation. When NbSi 2 /Nb 2 O 5 -SiO 2 /MoSi 2 coating was prolonged exposure to air at 1250 °C for 50 h of oxidation and at 900 °C for 100 h of corrosion, the mass gains are only 0.37 mg/cm2 and − 0.52 mg/cm2, respectively. The multilayer coating exhibits enhanced emissivity (>0.88) over the thermal infrared range of 3–20 µm, due to the lattice vibrational absorption-matching synergy of Nb 2 O 5 , SiO 2 , and MoSi 2 , as well as the mutual doping of SiO 2 /Nb 2 O 5 , mismatch of atoms at the interface, and a high degree of lattice distortion within the coating. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide, due to its structure, exhibits anisotropic properties, which are particularly evident in electrical and thermal conductivity. This study focuses on examining the influence of reduced graphene oxide in silicon carbide on these properties in directions perpendicular and parallel to the direction of the aligned rGO flakes in produced composites. Reduced graphene oxide is characterized by very high in-plane thermal and electrical conductivity. It was observed that the addition of rGO increases thermal conductivity from 64 W/mK (reference sample) up to 98 W/mK for a SiC–3 wt.% rGO composite in the direction parallel to the rGO flakes. In the perpendicular direction, the values were slightly lower, reaching up to 84 W/mK. The difference observed in electrical conductivity values is more significant and is 1–2 orders of magnitude higher for the flakes' alignment direction. The measured electrical conductivity increased from 1.2710−8 S/m for the reference SiC sinter up to 1.55 × 10−5 S/m and 1.2410−4 S/m for the composites with 3 wt.% rGO for the perpendicular and parallel directions, respectively. This represents an enhancement of four orders of magnitude, with a clearly visible influence of the anisotropy of the rGO. The composite's enhanced electrical and thermal conductivity make it particularly attractive for electronic devices and high-power applications. [ABSTRACT FROM AUTHOR]

Polycrystalline samples of (1-x)K 0.5 Bi 0.5 TiO 3 - xBaTiO 3 [(1-x)KBT - xBT] were synthesized using a solid-state reaction pathway. X-ray diffraction analysis confirmed the presence of a single-phase perovskite structure. To explore relaxation and conduction mechanisms, complex impedance spectroscopy was employed. Reduction in Curie temperature was observed as BT content increased. The grain and grain boundary contributions to relaxation was examined through complex impedance and modulus plots and quantified via fitting experimental data to an equivalent circuit model. Examination of the Complex impedance spectra uncovered the existence of dielectric relaxation characteristic of a non-Debye nature. Furthermore, the activation energy determined suggests commonalities in governing the conduction and relaxation processes in relation to temperature-dependent conductivity and relaxation time. A negative temperature coefficient of resistance behaviour was obtained from the temperature-dependent conductive study. Dielectric spectra revealed that these ceramic capacitors are useful in reduction of signal interference, signal attenuation and impedance matching circuits applications. [ABSTRACT FROM AUTHOR]

The chemical corrosion resistance properties of newly developed oxide (mullite-, cordierite)-bonded SiC ceramics prepared using mixture of waste fly ash and metal oxide additives were investigated in environments containing Na2SO4 at temperature 1000 °C for 8 h. The thermal shock resistance to cooling were evaluated as a function of quenching cycles. The changes in weight, flexural strength, and morphology due to thermal and chemical corrosion were examined. The mechanisms of flexural strength degradation due to chemical and thermal corrosion were analyzed, and the results were compared with literature data. In the hot corrosion by Na2SO4, the cordierite component was severely attacked in the cordierite-bonded SiC ceramics resulted ~ 34% strength degradation after 8 h corrosion; on the contrary, mullite-bonded SiC ceramics exhibited ~ 4% improvement of flexural strength. The chemical and thermal shock resistance results suggest a potential advantage of porous SiC ceramics prepared using waste fly ash for several industrial applications. [ABSTRACT FROM AUTHOR]

Mullite fiber-based porous ceramics is one of the most commonly used high-temperature insulation materials. However, how to further reduce the thermal conductivity and improve the strength of such materials has been a challenge in the field of high-temperature insulation. In this paper, mullite micro/nano fiber-based porous ceramic was prepared by introducing mullite nanofibers into mullite microfiber-based porous ceramics and the effect of microfiber/nanofiber weight ratio on the samples properties were characterized and analyzed. Results showed that the compressive strength and high-temperature thermal insulation properties of the porous ceramics increased significantly with an increase in the nanofiber content. For the porous ceramics with similar density (about 0.50 g/cm3), the compressive strength of the sample with a microfibers/nanofibers weight ratio of 1:2 was 1.43 MPa, which was much higher than that of the porous ceramics prepared with only microfibers (0.26 MPa). Meanwhile, the backside thermal equilibrium temperature of the sample with a microfiber/nanofiber weight ratio of 1:2 at 900 °C environment was 355.8 °C, which was much lower than that of the porous ceramic prepared with only microfibers (476.5 °C). In addition, in order to investigate the temperature resistance of mullite micro/nano fiber-based porous ceramics, the sintering temperatures was increased from 1400 °C to 1500 °C. Results shows that the high-temperature thermal insulation performance of mullite micro/nano fiber-based porous ceramics with high mullite nanofiber content decays more seriously. The back-temperature test showed that the thermal equilibrium temperature of the samples with a mullite micron/nanofiber weight ratio of 1:1 in 900 °C environment increased rapidly from 386.3 °C to 454.2 °C when the sintering temperature was increased from 1400 °C to 1500 °C. The preparation of mullite micro/nanofiber-based porous ceramics provides a new strategy to improve the performance of fiber-based porous ceramics. [ABSTRACT FROM AUTHOR]

Ni-containing SiOC bulk ceramics have been prepared by spark plasma sintering at 1300 °C from polysiloxane at Ar atmosphere in the present work. The microstructure and properties of SiOC ceramics with different Ni content were studied. The resultant Ni-containing SiOC ceramics consists of in situ formed turbostractic layer carbon, CNTs (C nanotubes) and SiC crystals which dispersed in the SiOC matrix. With increasing content of Ni, the Ni-containing SiOC ceramics displayed less porosity. And the increasing Ni improved the mechanical, thermal and friction properties of SiOC ceramics. Ni-containing SiOC ceramics developed a carbon friction layer, which enhanced abrasion resistance to provide friction materials with stable friction coefficients and low abrasion values. A decrease in wear mass, from 2.06 to 0.18 mg was observed as the Ni content increasing from 0 to 2 wt%. The primary wear mechanisms of SiOC ceramics were recognized as abrasive wear, fatigue wear, and adhesion wear. [ABSTRACT FROM AUTHOR]

Entropy plays a crucial role in designing new functional materials or enhancing material performance. The design of high entropy ceramics (HECs) introduces a larger composition space, thus the understanding of the correlation between the composition, entropy effect, and the performance of HECs is becoming increasingly important. In this work, to pursue superior properties, a series of CeNbO 4 -based solid solution ceramics with a maximum of 9 species cations in a single sublattice were synthesized by using high entropy configuration strategy. The interaction of composition, size disorder, and configurational entropy on the properties of HECs was emphasized. The potential conflict between high resistivity and low material constant of thermosensitive ceramics was overcome and thus achieving excellent thermal sensitivity properties having an extremely wide temperature range from room temperature to 1623 K and long-term high-temperature stability. This will bring innovative prospects for the design and application of high-temperature functional ceramics. [ABSTRACT FROM AUTHOR]

Piezoelectric ceramics with excellent piezoelectric properties and a high Curie temperature are important for numerous electromechanical devices in a broad range of temperature environments. In this work, the relaxor ferroelectric Pb(Yb1/2Nb1/2)O3 end member was selected to be introduced into a BiScO3-PbTiO3 high-temperature piezoelectric ceramic to reduce the dielectric loss and improve the piezoelectric properties while slightly reducing the Curie temperature. The phase structure and dielectric, ferroelectric and piezoelectric properties of 0.025Pb(Yb1/2Nb1/2)O3-(0.975 − x)BiScO3-xPbTiO3 (0.60 ≤ x ≤ 0.63) ceramics were systematically analyzed, and the best electrical properties were observed in the morphotropic phase boundary region x = 0.61 with d33 = 370 pC/N, kp = 44%, Pr = 33.9 μC/cm2. Importantly, no significant depolarization was observed in the x = 0.61 ceramic from room temperature to 290 °C, demonstrating its good thermal stability and potential applications in a wide range of temperature environments. [ABSTRACT FROM AUTHOR]

• A high energy density (W) value of 7.82 J/cm3 with energy storage efficiency (η) of 81.8% is acquired simultaneously. • A splendid thermal stability (Δ W rec : ∼ 2.9 %, Δ η : ∼ 3.9 %) within the temperature range of 20 ℃-100 ℃. • Further analysis of the influence of NaNbO 3 in KNN ceramics is investigated on the phase structure and microstructure. • Detailed discussions of evolution of domain structure and its influence on the energy storage properties after doping NaNbO 3. The advancement of high energy storage properties and outstanding temperature stability ceramics plays a decisive role in the field of pulsed power systems. The multi-component optimization strategy is conducted by introducing Li+, Bi(Ni 1/2 Zr 1/2)O 3 and NaNbO 3 into KNN-based ceramics. An excellent energy storage (W) of 7.82 J/cm3 along with a large efficiency (η) of 81.8 % is achieved at the breakdown strength (BDS) of 500 kV/cm for the ceramics. Simultaneously, the remarkable energy storage thermal stability (Δ W rec : ∼ 2.9 %, Δ η : ∼ 3.9 %) is acquired in the range from 20 ℃ to 100 ℃. The splendid charging-discharging performances (discharge energy density W d = 1.78 J/cm3, current density C D = 1376 A/cm2, power density P D = 124 MW/cm3) are also realized in the ceramics after doping. By investigating the evolution of crystal structure and domain structure, complex impedance and first-principle calculations, the internal mechanism of obtaining superior energy storage properties is analyzed. Thus, this research proves that the ceramics can effectively broaden the temperature range of the applications for the pulsed power systems while maintaining high energy storage properties, which offers a valuable approach for the improvement of dielectric capacitors. [ABSTRACT FROM AUTHOR]

• A silicate thermal insulation coating was prepared using water glass, etc. • The properties and structures of the coating were analyzed by various methods. • The coating formed a Si-O three-dimensional network structure at high temperatures. • The optimal preparation parameters and thermal insulation efficiency were determined. Thermal insulation slurry was fabricated using sodium silicate water glass (SSWG) as the film-forming material and hollow glass microspheres (HGM) as thermal insulation fillers. The thermal insulation slurry was coated on 316L stainless steel to fabricate a silicate thermal insulation coating. The results show that SiO 2 phase is formed by SSWG in the thermal insulation coating after sintering at 680 ℃. Through polymerization and dehydration reactions between Si-OH groups, the Si-O three-dimensional network structure develops at 680 ℃. The optimal value of SSWG to aggregate mass ratios is 2.00. Under this condition, the silicate thermal insulation coating exhibits smooth surface, continuous and dense microstructure, high Shore hardness of 50.1 HSD, remarkable thermal insulation efficiency of 21 % at 260 ℃, and excellent resistance to drop and thermal shock tests without any noticeable cracks or detachment. [ABSTRACT FROM AUTHOR]

This study explores the influence of processing methods on the connectivity of a ceramic component and its effect on the dielectric and thermal properties in Li 2 MoO 4 -polytetrafluoroethylene (LMO-PTFE) composites. Three processing cases were examined: cold sintering (case 1), dry pressing and subsequent thermal annealing (case 2), and cold sintering and subsequent thermal annealing (case 3). The processing methods change the connectivity of ceramic grains, the crystallinity of PTFE, and the dielectric properties of these composites. The microstructure analysis shows that CSP increases the LMO domain size via the dissolution and precipitation steps. The connected LMO grains increases the transport length of Li ions under electric field and manifests the space charge polarization in the dielectric measurments. More connected LMO grains of the composites also enhance thermal transport, while phonon scattering of discrete LMO particles lowers the thermal conductivity of the composites. • Processing methods change the connectivity of a ceramic component in a polymer matrix. • Cold sintering process increases the ceramic domain size in the ceramic-polymer composite. • The connected ceramics grains increase the transport length of Li ions under electric field. • Thermal conductivity can be enhanced by a chain of connected ceramic grains. • This study contributes to the rational design of high-performance dielectric composites. [ABSTRACT FROM AUTHOR]

Perovskite lanthanum chromate (LaCrO 3) has been widely investigated for applications as functional material, its properties can be finely tuned through doping. This study explores the effect of Al3+ doping on the structure and electrical properties of La 0.9 Sr 0.1 Cr 1- x Al x O 3 ceramics. Our findings reveal that Al3+ doping significantly influences the consistency of grain size and electrical transport properties of these ceramics. As x increases, the grain size decreases and obtains its minimum at x = 0.5. Compared to the undoped La 0.9 Sr 0.1 CrO 3 , Al3+ doping significantly reduces the resistivity. For x = 0.3, the resistivity obtains its minimum 142.60 Ω cm at −75 °C, while the B -value is reduced to 405 K. These results demonstrate the potential of Al3+ doping in enhancing the thermal sensing properties of LaCrO 3 ceramics and understanding of semiconductor behavior for electron device applications. Al3+ doping in La 0.9 Sr 0.1 CrO 3 ceramics reduces grain size and lowers resistivity, thereby increasing their potential for thermistor and semiconductor applications. [Display omitted] •Sr and Al co-doping alters LaCrO 3 ceramics, enabling thermistor functionality for temperature control. •Study reveals conduction via Cr3+ – Cr4+ small-polaron hopping and grain boundary effects. •Al3+ doping reduces grain size, while Sr–Al co-doping distorts octahedral structures. •Resistivity changes attributed to Cr element retention, promoting polaron hopping. [ABSTRACT FROM AUTHOR]

[Display omitted] • The material properties discount calculation method based on fiber distribution was proposed; • The node heat transfer judgment and coupling technique based on the fiber diameter was proposed; • The number of meshes required for composite modeling can be significantly reduced based on the MPDCM and NGTJCT; • The modulus, strengths, and thermal conductivities of 3D SCf/UHTCMCs were evaluated. Conducting precise and consistent research into the mechanical and thermal properties of 3D short fiber-reinforced ultra-high temperature ceramic matrix composites (SC f /UHTCMCs) is essential for the lightweight design optimization of structures operating under extreme loads. While the current use of one-dimensional elements to simplify fiber solids addresses the mesh quantity and quality issues stemming from the demand for periodic cell size, it fails to accurately predict the mechanical and thermal properties of SC f /UHTCMCs. This research developed material models featuring fiber volume fractions ranging from 0 to 15%, derived from statistical data on the aspect ratio distribution of short fibers. Addressing the unique characteristics of SC f /UHTCMCs, we proposed the Material Properties Discount Calculation Method (MPDCM), which leverages fiber distribution to calculate the mechanical properties and thermal conductivity of composite materials. Furthermore, we introduced the Node Heat Transfer Judgment and Coupling Technique (NGTJCT), rooted in fiber diameter, to address the issue of unrealistic heat transfer between fiber nodes and matrix nodes in numerical assessments. Utilizing both MPDCM and NGTJCT allows for a substantial reduction in the required mesh count for composite modeling, while adhering to the dimensional needs of periodic cells and facilitating rapid and precise numerical analysis of 3D short fiber-reinforced composites. The outcomes of this research have the potential to overcome the existing bottleneck in the numerical analysis of SC f /UHTCMCs, minimize the necessity for complex experimental procedures in material performance studies, and lay the groundwork for engineering optimization design. [ABSTRACT FROM AUTHOR]

Addition of Na 2 O to SiO 2 –CaO–P 2 O 5 glass-ceramics significantly impacts in-vivo dissolution and structural network modifications. However, achieving a vitreous state in sol-gel derived quaternary oxide powders, like the 45S5 bioglass containing high amounts of Na 2 O, is challenging. Synthesis of (69.5-x)SiO 2 -24..5CaO-6P 2 O 5 -xNa 2 O (x = 0, 2, 4, 8, 12, 16, 20, and 24.5 wt.%) ceramic powders has been carried out followed by heat-treatment between 500 °C and 700 °C. Structural characterization revealed that the vitreous state could be stabilized for Na 2 O content up-to 12wt.%. For higher Na 2 O content, the network transformed to a glass-ceramic state with the crystallization of combeite phase. In-vitro tests exhibited hydroxyapatite layer formation (Ca/P = 1.67) on all samples in simulated body fluid, regardless of structure. Samples were non-toxic to MG-63 osteoblast cells. The devitrification, bioactivity and associate properties of the quaternary system as a function of Na 2 O content is discussed with respect to envisaged biomedical applications. [Display omitted] • Selective heat-treatment of (69.5-x)SiO 2 24·5CaO6P 2 O 5 xNa 2 O sol-gel powders yielded bioactive glass and glass-ceramic. • Glassy state can be preserved up to x ≤ 12, beyond which crystallization occurs. • High Na 2 O bioceramics show bimodal pore distribution for optimal bone regeneration. • Glass-ceramic with Hench composition exhibited the best bioactivity. [ABSTRACT FROM AUTHOR]

• Study highlights the influence of Li doping on BaTiVO 3 ceramic. • Materials are having BaTiO 3 and an un-identified crystallographic phases. • The ECE is observed above room temperature in all the samples. • The maximum ΔS i.e. 0.355 J/KgK is achieved at about 80 °C with electric field of 20 kV/cm. • The maximum specific heat value corresponding to x = 0.05 sample is 626.59 J/kgK. The present work reveals the electrocaloric, structural, thermal, and other physical properties of Ba 1−x Li x Ti 0.975 V 0.025 O 3±δ (0 < x ≤ 0.05) ceramics synthesized via the solid-state chemical reaction method. X-ray studies reveal the presence of BaTiO 3 phase in all the samples, wherein the phase fraction of BaTiO 3 decreases with increasing Li content. Besides this, the replacement of lighter weight Li-atoms in place of Ba-atoms increases porosity and consequently decreases the density of the samples. However, the molar volume increases while inter-ionic distance decreases due to the small size of Li-atoms as compared with Ba-atoms. In this series, the sample with x = 0.05 exhibited a maximum change in entropy i.e., ΔS = 0.728 JK−1 kg−1 and the largest change in temperature i.e., ΔT = 0.422 K at 90 °C with the application of a 20 kV/cm electric field. Moreover, the x = 0.05 ceramic has the largest value of specific heat i.e., 626.59 JK−1 kg−1 as discovered during DSC investigations. In the present study, Li- and V- are attributing to good sintering and Li- in place of Ba- is enhancing electrocaloric properties in BaTiO 3 ceramic. [ABSTRACT FROM AUTHOR]