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The increase in operating temperature contributes to improving the performance and fuel utilization efficiency of gas turbines. However, it also places thermal barrier coatings (TBCs) in a more demanding working environment, requiring higher sintering resistance and better mechanical properties. In the present study, HfO2 was introduced into the dual‐phase LaYbZr2O7 system as a doping oxide to form the LaYb(HfxZr1−x)2O7 system. The research concentrated on its phase composition, mechanical properties, and thermophysical properties. The results show that substituting Hf for Zr does not alter the dual‐phase structure of the system. The mutual inhibition between the two phases and the inherent material‐binding capability of Hf further reduce the grain size compared to pure LYZO. Additionally, the presence of Hf reduces the tendency of Frenkel defect formation and cation migration frequency, effectively inhibiting ion diffusion and thereby suppressing the densification and shrinkage trends of the material. The system retains relatively high hardness, fracture toughness, and low elastic modulus of the LYZO matrix, with a decrease in thermal conductivity and an increase in infrared reflectivity. These results suggest that Hf doping enhances the sintering resistance of LYZO material, making them promising for high‐temperature TBCs. Our study presents a viable approach to enhance the sintering resistance of LYZO, and this methodology can be extrapolated to other rare‐earth zirconates. [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]

Hybridization of natural fibers with ceramic materials for reinforcing composites allows the optimization of the properties of these materials. For this reason, the present study aims to investigate physical, mechanical, water absorption, swelling and thermal properties as well as morphological characteristics of a hybrid Paederia foetida fibers–alumina powder (PFs–Al2O3)‐reinforced epoxy composite. Epoxy resin served as the matrix, while PFs and Al2O3 were employed as reinforcement. Five types of composites were fabricated using the hot‐pressing technique. The corresponding ratios of PFs:Al2O3 volume fractions (%) considered here were 0:40 (SFA), 10:30 (SFB), 20:20 (SFC), 30:10 (SFD) and 40:0 (SFE). The results reveal that the density of the hybrid PFs–Al2O3 composites decreased for increasing volume fractions of PFs: from 2.173 g cm−3 of SFA to 1.042 g cm−3 of SFE. The highest values of tensile strength (i.e. 49.085 MPa), tensile elastic modulus (i.e. 1.431 GPa) and impact strength (24 kJ m−2) were obtained for the SFD composite material with 30% volume fraction of PFs and 10% volume fraction of Al2O3: this happened because interface bonds between PFs, Al2O3 and epoxy phases achieved their optimal configuration. Overall, mechanical properties of the hybrid PFs–Al2O3‐reinforced epoxy composites were superior to those of composites reinforced only by PF fibers or only by Al2O3. Water absorption and swellability reached their maximum values at the steady state occurring after tested samples remained immersed in water for 820 h. The SFE composite reinforced only by PFs presented the highest water absorption and swelling (i.e. 6.034% and 5.81%, respectively) while for all other hybrid composites (SFD, SFC and SFB) these two quantities remained below 5%. Density and volume fraction of voids of hybrid PFs–Al2O3‐reinforced composites were consistent with the corresponding properties of the composites reinforced only by Al2O3 or PFs. SFD was also the most thermally stable material. Scanning electron microscopy observations of fractured surfaces indicated that the microstructure of the PFs–Al2O3‐reinforced epoxy composites presents several voids, fiber pullouts and transverse fibers, which together optimize the mechanical response of the composite material. Remarkably, the SFD composite material was highly competitive with the most recently developed hybrid composites employing natural reinforcements. © 2024 Society of Industrial Chemistry. [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]

Waste management and recycling have led to numerous studies on particleboard production. This study attempted to use milled corncob (MCC) and waste ceramic tiles (WCTs) to produce particleboard. The MCC (100−70 wt.%) and WCT (0–30 wt.%) were mixed at different ratios, mixed and compressed at a pressure of 0.25 MPa using urea formaldehyde (UF) resin as adhesive. The physicomechanical and thermal properties of the particleboards produced were investigated. The physical properties (bulk density, water absorption, and thickness swelling) improved with composite particleboard compared to the 100% MCC particleboard. The increase in WCT yielded improved density and lowered the particleboard's water absorption and thickness swelling. The mechanical tests showed that MOE values were below the recommended standard, which makes them unsuitable for structural use. However, MOR revealed values above the recommended standard. The thermal conductivity of the particleboards was reduced with increased WCT, and the required standard was found to be met. Hence, the particleboards produced are found helpful as thermal wall insulators. Based on the experiments done, sample R7 (70% MCC and 30% WCT) was considered the most preferable since it achieved the most preferable physicomechanical and thermal conductivity performance. The particleboards produced are recommended for wall partitioning and other internal and external purposes. [ABSTRACT FROM AUTHOR]

Energy efficient buildings, propulsion components and thermal protection systems require materials with high thermal protective properties. Traditional polymer composites or ceramic materials have limited comprehensive applications because of their poor thermal protective properties or poor processability. Herein, a novel fire resistant and thermally insulating polymer/ceramic hybrid ceramifiable composite was developed based on low temperature sintering principle and foaming on fire strategy. Specifically, the influences of raw materials of low temperature ceramics, such as glass frit, phosphate, etc, on the properties of ceramifiable ethylene-vinyl acetate (EVA) composites were investigated. Its fire resistance and thermal insulation properties were evaluated by simulating different sintering environments. The results show that the ceramifiable composite exhibits the highest improvement in fire resistance because a crystalline phase was formed at high temperatures. Gas evolution from the thermal decomposition of ammonium polyphosphate (APP) and EVA contributes to the formation of the porous structure in ceramic residues. The optimal system can resist above 1000 °C flame for 30 min without disintegration, and the temperature of the unfired side was maintained around 200 °C. The reliability of the strategy was verified by the effective medium theory model. [Display omitted] [ABSTRACT FROM AUTHOR]

AlN is regarded as a promising ceramic material for high performance structural and high temperature applications due to its superior properties such as high thermal conductivity, excellent stability and wear resistance. However, challenges remain in fabricating AlN ceramics with high strength and high thermal shock resistance. In this work, AlN/YAlO 3 composites with different YAlO 3 contents (3–10 wt%) were prepared by a simple pressureless sintering method, and the impact of YAlO 3 content on mechanical properties and thermal shock resistance of AlN/YAlO 3 composites was investigated. Results show that the grain growth of AlN is inhibited and the densification is improved with the addition of 3 wt% and 5 wt% YAlO 3. Hence, the flexural strength and fracture toughness of AlN/YAlO 3 composites are improved due to the grain refinement and compactness enhancement, and the highest value, 369 MPa and 3.84 MPa m1/2, are reached by the AlN-5 wt% YAlO 3 composite. Moreover, the thermal shock resistance was assessed through theoretical forecast and cyclic thermal shock tests over a temperature range between 1000 °C and 1600 °C. Comparing with pure AlN, the thermal stress damage resistance parameters (R IV ) of AlN/YAlO 3 composites were increased, while their residual strengths and retention ratios after 10–50 cycles of thermal shock tests maintained a higher level as well. Microstructure analysis revealed that the thermal shock resistance of AlN/YAlO 3 composites was evidently improved attributing to various strengthening mechanisms such as crack deflection, crack branching and microcrack toughening. [ABSTRACT FROM AUTHOR]

Clays from Alhabia (Almería, Spain) have been investigated in this work using several analytical techniques: X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), thermal analysis (Thermogravimetry, TG, and its first derivative, DTG), Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS). Texture characteristics (granulometry) and plasticity have been examined. The main ceramic properties (firing shrinkage, water absorption, bulk density, open porosity, flexural strength and thermal conductivity) have been determined using pressed and fired clay samples. Thus, the mineralogical, chemical, textural and ceramic features of these clays have been evidenced for the first time. The mineralogical analysis by XRD indicated that the clay samples are constituted by a mixture of chlorite and illite, as main clay minerals, being quartz and other minerals in lower relative proportion (calcite, gypsum and hematite). This finding is important because the investigations on chlorite-illite-calcitic clays are very scarce. The chemical analysis by XRF showed that silica and alumina are predominant, as expected by the mineralogy, with medium contents of calcium oxide, from calcite, and alkalis, from illite, being ∼8 and ∼5%, respectively, besides iron and titanium oxides (∼8%). The particle size analysis showed 71.76% of "clay fraction" (<2 μm) and 21.66% of silt fraction (2–50 μm). The plasticity index (Atterberg) was 14.3%, with acceptable moulding and extrusion properties. Thermal analysis by TG/DTG indicated a weight loss associated to dehydroxylation of structural water of the clay minerals and decarbonation of calcite by progressive heating. After the characterization of raw clays, the next step was the determination of ceramic properties of mixed and ground clays after firing using pressed bodies. For this purpose, two firing temperatures were selected (900 and 1100 °C) for 1 h. The examination of the resultant fired bodies indicated that porous ceramic materials (∼36% open porosity and ∼22% of water absorption capacity) can be obtained by firing at 900 ᵒC, with small variations in dimensions (<0.8% at 1100 °C). The porosity changed at relatively lower values by firing at 1100 °C (∼34–35%), being associated to the presence of decomposed calcite. Bulk density was found almost constant from 900 to 1100 °C, with a maximum value of ∼1.67 g/cm3 at 1100 °C. Flexural strength reached a maximum value of 34.47 MPa at 1100 °C for the ground sample. Finally, thermal conductivity after firing the clay bodies was found almost constant at 900 and 1100 °C (0.457 and 0.479 W/mK, respectively). Taking into account these results, the main applications of the Alhabia clays have been evaluated. These clays can be used for the fabrication of porous ceramic supports and tiles by firing at 900 °C. Firing the clays at higher temperature (1100 °C) is of great interest for the fabrication of ceramic tiles and ceramic bricks of higher flexural strength with variable porosity and practically constant in dimensions. It is economically important although at higher processing costs. Finally, it can be emphasized that this work is a contribution of a better scientific knowledge of chlorite-illite-calcitic clays as ceramic raw materials. [ABSTRACT FROM AUTHOR]

Ultra high temperature ceramics (UHTC) with good mechanical properties and thermal physical properties, including high melting point (>30000C), high conductivity, high thermal conductivity, high thermal shock resistance rate, provides a sharp leading edge and smooth surface of a new generation of aerospace vehicle design to the aerospace industry; Due to ultra-high temperature ceramic materials with high strength, oxidation resistance and thermal shock resistance, it can be applied to extreme environments such as hypersonic flight, atmospheric reentry and rocket propulsion system, and have been widely used in key components of aircraft front cone, engine, wing and engine hot end. Based on the application of ultra-high temperature superconducting materials in practical application, the solid modeling of ultra-high temperature superconducting front-end components of ultra-high speed aircraft wing is carried out by using ABAQUS software, the ultra-high temperature thermal field of loaded aircraft flying at ultra-high speed is simulated, the stress-strain field at the flange is obtained, and the thermal mechanical coupling analysis is carried out. [ABSTRACT FROM AUTHOR]

h-BN is a two-dimensional ceramic material with a lamellar structure, known for its typical orientation characteristics on mechanical and thermal properties. By optimizing the size and arrangement of h-BN grains in the matrix, the anisotropic characteristics of h-BN ceramics can be fully utilized to obtain ceramic materials with high thermal conductivity or high strength. In order to study the effect of grain orientation distribution on the mechanical and thermal properties of materials, the index of orientation distribution (IOP) was used to quantitatively characterize the orientation degree of h-BN grains and analyzed the effect of h-BN grain size on material properties. The results show when the initial h-BN size is 13.50 μm, the ceramic has the highest orientation degree/-507, and the mechanical and thermal properties show obvious anisotropy. While the related properties of BN-YAG ceramics varies significantly with the decrease of initial h-BN grain size. [ABSTRACT FROM AUTHOR]

In the present work, carbon nanotube (CNT)‐reinforced alumina nanocomposite ceramics were investigated about their electrical and, for the first time in such detail, thermal conductivity. Therefore, two different alumina powders with varying CNT‐contents were processed by pressureless sintering and hot pressing to achieve CNT/alumina composite ceramics with varying porosity and CNT‐content between 0 and 5 wt.% CNTs. A significant influence of the grain size on percolation threshold of the electrical conductivity was detected. The coarser CT 3000 SG‐based ceramic showed a threshold of <0.25 wt.%, which is the lowest reported threshold in literature. Pore orientation in the hot‐pressed materials shows a significant influence on the electrical and thermal conductivity of the composite, causing anisotropic properties. Both, electrical and thermal conductivity are higher parallel to the pore structure and perpendicular to the press‐direction, respectively, with electrical conductivity being up to three times and thermal conductivity up to 30% higher parallel to the pore structure. Unlike electrical conductivity, thermal conductivity decreases significantly with increasing CNT‐content. As two influences, CNT‐content and porosity, interact, each of them was analyzed separately in order to measure the isolated influence of CNT‐content on thermal conductivity at constant porosity. It was shown, that thermal conductivity decreases considerably with increasing CNT‐content even at constant porosity, because of a disturbed crystal structure due to a finer grain structure with more grain boundaries. This behavior is contrary to the expected, and sometimes reported, effect of CNTs. The combination of an increasing CNT‐content and the related increase in porosity causes a strongly decreasing thermal conductivity of the material from 35 W/m∙K for pure alumina to 10 W/m∙K for alumina with 5 wt.% CNTs. The presented results in this and other previously published investigations from the authors show that CNT/alumina‐nanocomposites have the potential of combining outstanding mechanical properties and electrical conductivity, which can be used as high performance electrically conductive ceramic material for a wide range of applications. [ABSTRACT FROM AUTHOR]

The high-entropy ceramic materials (Zr 0.25 Ce 0.25 Hf 0.25 Y 0.25)O 1.875 (H-0) and (Zr 0.2 Ce 0.2 Hf 0.2 Y 0.2 RE 0.2)O 1.8 (H-RE) (RE = La, Nd and Sm) with fluorite structure and homogeneous element distribution were prepared. With fluorite structure, fine grain size and high density, the H-0 and H-RE ceramics displayed low thermal conductivity, suitable thermal expansion coefficient, high hardness and fracture toughness. The effect of La, Nd and Sm on the mechanical, heat conductivity and heat expansion properties of high entropy ceramics were discussed. The single-phase high-entropy ceramic materials in this work are very suitable for application as thermal barrier materials. [ABSTRACT FROM AUTHOR]

Epoxy composites with glass fiber reinforcement can be found in the automotive and aerospace industries. In this study, the properties of the epoxy matrix were enhanced by processing composites filled with ceramic particles of silicon carbide (SiC). At first, SiC-filled E-glass fiber-reinforced epoxy composites/sandwich structures were processed using the hand layup technique. Next, processed composites were characterized using a tensile tester and an Izod impact tester to determine the best mixing ratio of ceramic-embedded epoxy composites. The highest mechanical properties were obtained according to ASTM D638 and D256 standards. Next, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), analysis of differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) were carried out respectively to find out the presence of functional groups, surface morphology, crystallographic structure, glass transition temperature (Tg) and thermal/material stability of processed composites. In the end, the study elaborates that the mechanical properties of epoxy matrix composites were improved by the addition of SiC ceramic fillers, and among processed composites, 10% SiCE composite carried the highest properties, including the Tg value of 62.8 °C, 69.87 MPa for tensile strength and 57.12 kJ m−1 for impact strength. [ABSTRACT FROM AUTHOR]

The temperature dependence of thermal conductivity and specific heat for detonated nanodiamond ceramics is investigated on specially designed experimental setups, implementing the uniaxial stationary heat flow method and the thermal relaxation method, respectively. Additionally, complementary studies with a commercial setup (Physical Property Measurement System from Quantum Design operating either in Thermal Transport or Heat Capacity Option) were performed. Two types of samples are under consideration. Both ceramics were sintered at high pressures (6–7 GPa) for 11–25 s but at different sintering temperatures, namely 1000 °C and 1600 °C. The effect of changing the sintering conditions on thermal transport is examined. In thermal conductivity κ(T), it provides an improvement up to a factor of 3 of heat flow at room temperature. The temperature dependence of κ(T) exhibits a typical polycrystalline character due to hindered thermal transport stemming from the microstructure of ceramic material but with values around 1–2 W/mK. At the lowest temperatures, the thermal conductivity is very low and increases only slightly faster than linear with temperature, proving the significant contribution of the scattering due to multiple grain boundaries. The specific heat data did not show a substantial difference between detonated nanodiamond ceramics obtained at different temperatures unlike for κ(T) results. For both samples, an unexpected upturn at the lowest temperatures is observed—most likely reminiscent of a low-T Schottky anomaly. A linear contribution to the specific heat is also present, with a value one order of magnitude higher than in canonical glasses. The determined Debye temperature is 482 (±6) K. The results are supported by phonon mean free path calculations. [ABSTRACT FROM AUTHOR]

Highly optically transparent polycrystalline fluorapatite ceramics with hexagonal crystal structures were fabricated via a liquid-phase synthesis of fluorapatite powder, followed by spark plasma sintering (SPS). The effect of sintering temperature, as observed using a thermopile, on the optical transmittance and microstructure of the ceramics was investigated in order to determine suitable sintering conditions. As a result, high optical transmittance was obtained in the SPS temperature range of 950–1100 °C. The highest optical transmittance was obtained for the ceramic sample sintered at 1000 °C, and its average grain size was evaluated at only 134 nm. The grain size dramatically increased with temperature, and the ceramics became translucent at SPS temperatures above 1200 °C. The mechanical and thermal properties of the ceramics were measured to evaluate the thermal shock parameter, which was found to be comparable to or slightly smaller than that of single-crystal fluorapatite. This transparent polycrystalline fluorapatite ceramic material should prove useful in a wide range of applications, for example as a biomaterial or optical/laser material, in the future. Furthermore, the knowledge obtained in this study should help to promote the application of this ceramic material. [ABSTRACT FROM AUTHOR]

The way to achieve better energy efficiency in buildings is to improve their thermal insulation properties. This can be done by increasing the porosity of the ceramic materials by introducing pore-forming additives to the clay for production of lightweight ceramic panels. Compositions and properties of lightweight ceramic panels from marl clay and rice husks as lightweight aggregate were investigated. The lightweight ceramic panels from marl clay and rice husks with sizes 5x5x1 cm were produced by dry pressing and following firing at 1000°C. The influence of the amount of rice husks of 15, 30, 50 and 65 mass % on the properties of light ceramic samples fired at 1000°C has been established. Apparent density, apparent porosity, thermal conductivity and compressive strength were measured. The thermal conductivity is reduced from 1.0 W mK-1 (in ceramic panels without rice husks) to 0.6 W mK-1 (ceramic panels with 30 mass % rice husks) at standard compressive strength of 10 MPa. This quantity of rice husks is recommended for the composition of light porous ceramic materials for heat isolation in intelligent house. [ABSTRACT FROM AUTHOR]

Carbon‐fiber‐reinforced carbon–silicon carbide (C/C–SiC) composites were prepared by impregnating carbon fibers with ethynylphenyl‐terminated poly(silylene–acetylene) (EPTSA) as a single‐source precursor with subsequent hot pressing and pyrolysis. The structural evolution, crystallization behavior, and graphitization of bulk C–SiC ceramics, as well as their mechanical properties and ablation behavior, were investigated. The EPTSA precursor starts to transform into inorganic SiC ceramic materials at 800°C, which is characterized by an amorphous structure with weight loss, shrinkage, and densification between 800 and 1000°C. The formation of SiC crystals inhibited the growth of the graphitic structure between 1000 and 1200°C. As the temperature was raised, both graphite and SiC crystals continued to grow, and the crystalline forms became more complete. The carbon‐fiber cloth (T300CF)‐reinforced C–SiC composite (T300CF/C–SiC) prepared using polymer infiltration and pyrolysis (PIP) exhibited excellent mechanical properties. After five PIP cycles, the flexural strength, flexural modulus, and interlaminar shear strength of the T300CF/C–SiC composite reached 169 MPa, 32.5 GPa, and 9.38 MPa, respectively. In addition, the chopped‐carbon‐fiber‐reinforced C–SiC composite fabricated using the PIP process demonstrated good oxyacetylene‐torch ablation properties. [ABSTRACT FROM AUTHOR]

Fabrication of ceramic materials containing high amount of porosity with controlled size and structure is a critical factor for various applications. In this study, porous alumina ceramics were prepared by addition of 5–30 vol% carbon black (CB) powders with different specific surface area (SSA) into the alumina matrix as a pore forming agent and application of partial sintering via spark plasma sintering (SPS) technique. After removal of CB particles from the ceramic structures, physical, mechanical, and thermal properties of the porous alumina ceramics were investigated. The open porosity level was detected between 38.48 and 59.81% depending on the type and amount of CB removed. The compressive strength of the sintered samples was measured as ∼150 MPa, which is ∼3 times higher than that of the conventionally sintered samples thanks to the strong neck formation between grains. The large pores formed by removal of CB agglomerates in case of using CB powders with SSA of 107 and 254 m2/g resulted in a change in thermal conduction mechanism from lattice vibration to thermal convection. [ABSTRACT FROM AUTHOR]

Thermoelectric materials can easily realize energy savings by converting untapped waste heat into electricity. Unfortunately, however, the coupling of the thermoelectric parameters limits the conversion efficiency. Herein, we fabricated titanium oxide ceramic thermoelectric materials using a simple one-step solid-state reaction between TiO2 and starch at high temperature, and improved the electrical and thermal transport properties simultaneously by adjusting the amount of starch during preparation. With increasing starch, the electrical conductivity and power factor increased and the thermal conductivity decreased significantly. The samples mixed with 7 wt% starch showed rather low thermal conductivity (less than 2.0 W m−1 K−1) and a dimensionless figure of merit (ZT) close to 0.14K at 973 K. When the samples were sintered in an argon atmosphere, the starch was carbonized in situ into carbon and provided a reducing atmosphere, leading to the appearance of oxygen vacancies in the lattice of titanium oxide. The oxygen vacancies increased with increasing starch in the mixture during preparation, which resulted not only in a narrower band gap of titanium oxide but also enhanced phonon scattering. [ABSTRACT FROM AUTHOR]

A novel negative thermal expansion (NTE) material composed of Sm0.85Sr0.15MnO3-δ was synthesized using the solid-state method. By allowing Sr2+ to partially replace Sm3+ in SmMnO3, the ceramic material Sm0.85Sr0.15MnO3-δ exhibits NTE properties between 360K and 873K, and its average negative thermal expansion coefficient was −10.08 × 10−6/K. The structure of Sm0.85Sr0.15MnO3-δ is orthogonal, the space group is pbnm, the morphology is regular, and the grain size is uniform. The results of X-ray diffraction and XPS (X-ray photoelectron spectroscopy) suggest that the NTE phenomenon is related to the electron transfer of Mn ions. With the increase in temperature, Mn4+ is rapidly transformed into Mn3+, accompanied by Mn4+O6 octahedron distortion and oxygen defects. It was found that the sample volume continually decreased at the same time. [ABSTRACT FROM AUTHOR]

Phenolic impregnated carbon ablator (PICA) as a typical lightweight ceramic ablative material is widely used in thermal protection systems (TPS). However, the rigidity and poor mechanical property of the existing PICA limit its application in flexible TPS. For the purpose of solving these problems, a novel lightweight, flexible, and heat‐insulated PICA material is first successfully fabricated using resorcinol‐formaldehyde (RF) aerogel as matrix and flexible carbon fiber felt as reinforcement through vacuum impregnating and ambient pressure drying. The prepared composites have relatively low densities (0.20 ~ 0.27 g/cm3) and low thermal conductivities (~0.11 W/[m·K]) at room temperature. The flexible PICA has adjustable flexibility through changing the RF concentration of impregnated sols and exhibits excellent folding endurance, which can be folded more than 500 times without fracture. The material can recover to its original shape without fracture when the compressive strain is up to 60%, which shows high compressive resilience properties. The result of the back‐face temperature test indicates the prepared flexible PICA composite has improved thermal insulation property at high temperature by impregnating with RF aerogels. These results demonstrate the flexible PICA prepared in this work is a promising material that can be used in the flexible thermal protection field of aerospace. [ABSTRACT FROM AUTHOR]

The additive composition of an AlN ceramic substrate material was optimized to achieve high strength and thermal conductivity. MgO-CaO-Al 2 O 3 -SiO 2 (MCAS) glass and Y 2 O 3 were used as basic additives for improved sintering properties and thermal conductivity, thereby allowing for AlN to be sintered at a relatively low temperature of 1600 °C without pressurization. Yttria-stabilized zirconia (YSZ) was added (0–3 wt%) to further improve the strength of the AlN ceramic. YSZ and Y 2 O 3 reacted with AlN to produce ZrN, Y 4 Al 2 O 9 , and Y 3 Al 5 O 12 secondary phases. The formation of these yttrium aluminate phases improved the thermal conductivity by removing oxygen impurities, while ZrN formed at the AlN grain boundaries provided resistance to grain boundary fractures for improved strength. Overall, the AlN ceramic with 1 wt% MCAS, 3 wt% Y 2 O 3 , and 1 wt% YSZ exhibited excellent thermal and mechanical properties, including a thermal conductivity of 109 W/mK and flexural strength of 608 MPa. [ABSTRACT FROM AUTHOR]

CeO 2 and Sc 2 O 3 co-stabilized ZrO 2 ceramics have attracted much attention as potential thermal barrier coatings (TBCs) materials for applications above 1300 °C. In this study, a series of Sc 0.04 Ce x Zr 0.96-x O 1.98 (SCZ, x = 0.08, 0.10, 0.12, 0.16) ceramic materials were synthesized with the solid-state method and their phase stability, microstructures and thermo-physical properties were systemically investigated by x-ray diffraction (XRD), Raman spectra, field emission scanning electron microscopy (SEM), thermal dilatometer, laser flash apparatus (LFA), and Vickers hardness tester. The results showed that Sc 0.04 Ce 0.12 Zr 0.84 O 1.98 (4S12CZ) and Sc 0.04 Ce 0.16 Zr 0.80 O 1.98 (4S16CZ) ceramic materials still maintained stable tetragonal phase structure after 100 h high temperature treatment at 1500 °C. SCZ had a high thermal expansion coefficient (TEC), low thermal conductivity, and high fracture toughness. The TEC of the ceramics increased with CeO 2 addition because lattice energy reduced with increasing substitution of Zr4+ by bigger Ce4+ while thermal conductivity decreased due to the increase of lattice distortion. Compared with 4S12CZ, 4S16CZ exhibited a higher fracture toughness of 6.48 ± 0.04 MPa m1/2 and showed the better anti-sintering property. Besides, the thermal conductivity, TEC and thermal cycling lifetime of 4S16CZ were optimal. The comprehensive performance of 4S16CZ suggested it could be explored as a promising TBC material for high-temperature application. [ABSTRACT FROM AUTHOR]

• The CaO-MgO-SiO 2 -Al 2 O 3 -CaF 2 (CMSAC) glass was first used as a sintering aids for Al 2 O 3 to enhance the flexural strength of composites. • The CMSAC glass/Al 2 O 3 ceramic can be densified when sintered at 910 °C and has good dielectric and mechanical properties. • The CMSAC glass/Al 2 O 3 ceramic has a high flexural strength of 310±14 MPa, which is higher than most LTCC materials reported previously. • The excellent mechanical properties are mainly attributed to three aspects: grain refinement, improved fracture energy, and the synergistic effect of the relative contents of Al 2 O 3 and the CMSAC glass. A high flexural strength low temperature co-fired ceramic material was obtained by mixing the CaO-MgO-SiO 2 -Al 2 O 3 -CaF 2 glass and Al 2 O 3 by the weight percentage of x Al 2 O 3 +(1- x)CaO-MgO-SiO 2 -Al 2 O 3 -CaF 2 (x = 30, 35, 40 and 45 wt.%). The sintering behavior, crystalline component, mechanical, electrical and thermal properties were investigated in depth. The X-ray diffraction data demonstrated that Al 2 O 3 , CaMgSi 2 O 6 , and Mg 2 SiO 4 were formed during the sintering process. The glass/ceramic composites with 35 wt.% Al 2 O 3 sintered at 910 °C for 2 h exhibited excellent mechanical properties, with a flexural strength of 310±14 MPa. The excellent mechanical properties are mainly attributed to the following three aspects: grain refinement, improved fracture energy, and the synergistic effect of the relative contents of Al 2 O 3 and the CaO-MgO-SiO 2 -Al 2 O 3 -CaF 2 glass. The results suggest that the CaO-MgO-SiO 2 -Al 2 O 3 -CaF 2 glass/Al 2 O 3 composites can be regarded as promising candidates for low temperature co-fired ceramic substrate applications. [ABSTRACT FROM AUTHOR]

• NdHfO composites materials and NdHfO "stuffed" pyrochlore solid solutions. • Thermal conductivity, luminescence, and oxygen ion conductivity were studied. • (Nd 2- x Hf x)Hf 2 O 7+ x /2 (x = 0.2) composite shows the lowest thermal conductivity. • (Nd 2- x Hf x)Hf 2 O 7+ x /2 (x = 0.2, 0.32) composites show the highest conductivity. • Narrow-band luminescence of the NdHfO composites has been observed. The phase composition, microstructure, electrical and thermal conductivity of Nd 2± x Hf 2± x O 7±δ ceramic materials have been studied. (Nd 2- x Hf x)Hf 2 O 7+ x /2 (x = 0.2, 0.32, 0.39) composites, containing 4–16 wt% HfO 2 , have the highest conductivity and the brightest narrow-band luminescence among materials under study. The (Nd 2- x Hf x)Hf 2 O 7+ x /2 (x = 0.2) composite, containing ∼ 4 wt% HfO 2 , is shown to have the lowest thermal conductivity: 1.52 W m–1 K–1 at 300 K. XRD and Raman spectroscopy results show that (Nd 2- x Hf x)Hf 2 O 7+ x /2 (x = 0.2, 0.32, 0.39, 1.14) are composites consisting of a mixture of pyrochlore solid solutions with Hf on the Nd site and two HfO 2 polymorphs (m - HfO 2 and γ 2 - HfO 2 nanodomains). The properties of the (Nd 2- x Hf x)Hf 2 O 7+ x /2 (x = 0.2, 0.32, 0.39, 1.14) composites are compared to that of the Nd 2 (Hf 2- x Nd x)O 7- x /2 (x = 0, 0.1) pyrochlores, and the best properties were shown by the (Nd 2- x Hf x)Hf 2 O 7+ x /2 (x = 0.2, 0.32) composites. [Display omitted] [ABSTRACT FROM AUTHOR]

Boride ceramics are materials of choice in extreme conditions. Among them, titanium borides have many applications due to their high hardnesses and melting points. The behavior of titanium borides may not be easily studied at very high pressures and temperatures by experimental means. Alternatively, molecular dynamics (MD) is a powerful computational tool to investigate the desired behavior of materials in certain conditions. In this study, we develop an interatomic potential for the Ti B system based on the second nearest-neighbor modified embedded atom method (2NN-MEAM) formulation. With the developed potential, MD simulations reproduce many physical, mechanical, and thermal properties of titanium borides with good accuracy. As an application of the developed potential, a series of nanoindentation simulations is also conducted to investigate the temperature dependence of the nanohardness of TiB 2 up to 1500 K. The results illustrate a linear dependence between nanohardness and temperature. [Display omitted] • We developed a 2NN-MEAM interatomic potential for the Ti B system. • The predicted properties of titanium borides agree with the experimental data. • Nanoindentation simulations of TiB 2 are performed at various temperatures. • Our simulations predict a linear decline of the nanohardness of TiB 2 in 0 K ∼ 1500 K. [ABSTRACT FROM AUTHOR]

Zirconium dioxide (ZrO2) is one of the ceramic materials with high potential in many areas of modern technologies. ZrO2 doped with 8 wt.% (~4.5 mol%) Y2O3 is a commercial powder used for obtaining stabilized zirconia materials (8 wt.% YSZ) with high temperature resistance and good ionic conductivity. During recent years it was reported the co-doping with multiple rare earth elements has a significant influence on the thermal, mechanical and ionic conductivity of zirconia, due complex grain size segregation and enhanced oxygen vacancies mobility. Different methods have been proposed to synthesize these materials. Here, we present the hydrothermal synthesis of 8 wt.% (~4.5 mol%) YSZ co-doped with 4, 6 and 8 wt.% La2O3, Nd2O3, Sm2O3 and Gd2O3 respectively. The crystalline phases formed during their thermal treatment in a large temperature range were analyzed by X-ray diffraction. The evolution of phase composition vs. thermal treatment temperatures shows as a major trend the formation at temperatures >1000 °C of a cubic solid solutions enriched in the rare earth oxide used for co-doping as major phase. The first results on the thermal conductivities and impedance measurements on sintered pellets obtained from powders co-doped with 8 wt.% Y and 6% Ln (Ln = La, Nd, Sm and Gd) and the corresponding activation energies are presented and discussed. The lowest thermal conductivity was obtained for La co-doped 8 wt.% YSZ while the lowest activation energy for ionic conduction for Gd co-doped 8 wt.% YSZ materials. [ABSTRACT FROM AUTHOR]

Octalithium plumbate (Li 8 PbO 6) is a candidate for use as a breeder material in future D-T tokamak fusion reactor designs. Key to the development of a breeder blanket is the characterisation of candidate materials. Therefore, density functional theory (DFT) simulations are used to examine the fundamental elastic, electronic and thermal properties of Li 8 PbO 6. A comparison is made between two different DFT simulation packages to demonstrate the validity of the results given in this article and as compensation for a lack of experimental data to compare to in the literature. Finally, formation energies are calculated for lithium vacancy defects as well as tritium accommodated as substitutional defects on the lithium site, as these are expected to be some of the most common types of defect in the breeder blanket during reactor operation. [ABSTRACT FROM AUTHOR]