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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]

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]

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]

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]

Densification behavior, mechanical and thermal properties of ZrC 1 − x ceramics with various C/Zr ratios of 0.6–1.0 have been investigated by two-step reactive hot pressing of ZrC and ZrH 2 powders at 30 MPa and 1500–2100 °C. The two-step reactive hot pressed ZrC 1 − x ceramic has a higher relative density (> 95.3%) than that (91.9%) of stoichiometric ZrC sintered at 2100 °C. A cubic Zr 2 C-type ordered phase forms in the ZrC 1 − x sample obtained at a ZrC/ZrH 2 molar ratio of 0.6 at a relatively low temperature of 1100 °C. The decrease in C/Zr ratio is beneficial to densification of ZrC 1 − x ceramic, however, excess grain growth occurs after sintering above densification temperature. The elastic modulus and Vickers hardness decrease with decreasing the C/Zr ratio. With decreasing the C/Zr ratio, both thermal conductivity and specific heat decrease due to the enhanced scattering of conducting phonons and electrons by carbon vacancies. [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]

A conventional solid-phase sintering process was used to fabricate the (1 −x)Na0.5Bi0.5TiO3-xBaTiO3ceramics (x= 0, 0.04, 0.06, 0.08 and 0.1). X-ray measurements showed that all samples have a perovskite structure. The bulk density of the obtained samples exceeds 95% of the theoretical density. The thermal (DSC, dilatometry) and dielectric properties of these ceramics were investigated in a wide temperature range. Anomalies of the thermal expansion strain were observed at the temperatures which are not related to any phase transitions. The transition temperatures observed by means of thermal measurements are in good agreement with those obtained from dielectric studies. [ABSTRACT FROM PUBLISHER]

Ba(Sr 1/3 Ta 2/3)O 3 (BST) ceramic was synthesized by a solid-state reaction method. The phase stability, microstructural evolution, and mechanical and thermal properties of the BST ceramic were investigated and characterized to evaluate the potential application of BST as a top coating material for thermal barrier coatings (TBCs). The results show that BST can maintain a stable hexagonal perovskite structure up to 1600 °C. Anisotropic growth of the grains above 1400 °C was observed. Its low elastic modulus and high fracture toughness suggest a high damage tolerance for the BST ceramic. In addition, the moderate coefficient of thermal expansion and superior heat insulation capability of the BST ceramic provide this ceramic the potential to serve as a top coating material of TBCs at higher temperature. [ABSTRACT FROM AUTHOR]

Green ceramic bodies based on mullite were infiltrated with SiO (TEOS precursor) solution using a sol-gel technique and sintered at 1,300 °C. Previously, the green bodies had been prepared with the molding method, using corn flour as the pore-forming agent with a concentration in mass percent of 10, 15, and 20, and then they were sintered. Infiltrated ceramic material was evaluated to determine the relationship between, morphology, porosity, thermal properties, and crystalline characteristics by scanning electron microscopy, X-ray diffraction, porosimetry by N at 77 K, and thermal analysis using laser flash technique. The presence of SiO together with magnesium (talc powder) gives a cordierite crystalline phase, which is considered presenting thermal stability. Infiltration process changes the surface area, which is reduced by 93 %, and the pore size value reaches 1.98 nm, changing from open to closed structure. In spite of porosity change, thermal conductivity increases in the majority of the samples. This phenomenon obeys the complex system involved in the study, such as closed porosity, microstructure, tortuosity, geometry, and the anisotropy of mullite bonds, accompanied by the infiltrant liquid (SiO). [ABSTRACT FROM AUTHOR]

In this paper, a method is described to study the geometry and thermal properties of grain boundaries in a polysilicon sample. This method is based on the Photothermal Deflection Technique called “Photothermal Imaging.” In order to be able to heat the sample by a very low laser beam power (2 mW), the sample is immersed in a cell filled with paraffin oil. The comparison of the experimental curves of amplitude and phase of the photothermal signal variations versus the displacement x of the sample to the corresponding theoretical ones allows obtaining thermal properties of the grain boundaries and their dimension. [ABSTRACT FROM AUTHOR]

High density reduced graphene oxide (rGO) reinforced aluminum nitride (AlN) composites were successfully fabricated by the one-step spark plasma sintering (SPS) method. Raman spectra showed that the raw material of GO was thermal reduced to rGO during the SPS process, and the reduction of GO can be strongly affected by the carbonaceous atmosphere. With the rGO content increasing (0–2 wt %), the dispersion of rGO and relative density of the composites decreased, decreasing the elastic modulus and hardness accordingly. However the flexural strength had a slight increase when rGO content was ≤1 wt%, and the fracture toughness increased from 3.5 to 5.2 MPa m 1/2 with the rGO due to the crack bridging and pulling out of rGO. The thermal conductivity of the composites was low and sharply decreased from 92.5 to 37.4 W m −1 K −1 with the addition of rGO, which are attributed to the low crystalline quality and high vacancy defects in rGO and the increase of interfacial thermal resistance. [ABSTRACT FROM AUTHOR]

Abstract Two different SiC ceramics with a new additive composition (1.87 wt% Y 2 O 3 –Sc 2 O 3 –MgO) were developed as matrix materials for fully ceramic microencapsulated fuels. The mechanical and thermal properties of the newly developed SiC ceramics with the new additive system were investigated. Powder mixtures prepared from the additives were sintered at 1850 °C under an applied pressure of 30 MPa for 2 h in an argon or nitrogen atmosphere. We observed that both samples could be sintered to ≥99.9% of the theoretical density. The SiC ceramic sintered in argon exhibited higher toughness and thermal conductivity and lower flexural strength than the sample sintered in nitrogen. The flexural strength, fracture toughness, Vickers hardness, and thermal conductivity values of the SiC ceramics sintered in nitrogen were 1077 ± 46 MPa, 4.3 ± 0.3 MPa·m1/2, 25.4 ± 1.2 GPa, and 99 Wm−1 K−1 at room temperature, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Ultra‐high temperature ceramics (UHTCs) exhibit a unique combination of excellent properties that makes them promising candidates for applications in extreme environments. Various UHTCs are needed due to diverse harsh conditions that UHTCs are faced with in different applications. Due to structural similarity to ZrB2, possible high melting point and possible protective oxide scale formed in oxygen rich and water vapor environments, REAlB4 (RE: rare‐earth) is suggested a good candidate for UHTCs. In the present work, temperature‐dependent mechanical and thermal properties of both α‐YAlB4 (YCrB4 type, space group Pbam) and β‐YAlB4 (ThMoB4 type, space group Cmmm) were investigated by first principles calculations in combination with quasi‐harmonic approach. Due to the structural similarity between α‐YAlB4 and β‐YAlB4, their properties are very similar to each other, which are approximately transverse isotropic with properties in (001) plane being almost the same and differing from properties out of (001) plane. The results reveal that resistance to normal strain in (001) plane (~460 GPa) is higher than that along [001] direction (~320 GPa) and thermal expansion in (001) plane (~10 × 10−6 K−1) is lower than that along [001] direction (~17 × 10−6 K−1), which is because the stiff boron networks are parallel to (001) plane. The average thermal expansion coefficient is around 12 × 10−6 K−1, which is fairly high among UHTCs and compatible with metallic frameworks. The combination of high thermal expansion coefficient and protective oxidation scale forming ability suggest that REAlB4 is promising for practical applications not only as high‐temperature structural ceramic but also as oxidation resistant coating for alloys. [ABSTRACT FROM AUTHOR]

Rare-earth ( RE) monosilicates are promising candidates as environmental barrier coating ( EBC) materials for ceramic matrix composites for aerospace applications. Five rare-earth monosilicate materials have been investigated: Y2SiO5, Gd2SiO5, Er2SiO5, Yb2SiO5, and Lu2SiO5 produced from RE oxides and silica starting materials pressed and sintered at 1580°C under flowing air. Relative densities above 94% were obtained for all samples and ceramics were made containing 85-100 wt% of the RE monosilicate according to X-ray diffraction ( XRD) with RE disilicates as the second phase in the Gd, Yb, and Lu silicate systems. Microstructures were characterized using scanning electron microscopy and XRD, and thermal properties measured including specific heat, thermal expansion, and thermal diffusivity. For the first time, specific heat capacity values are reported for the monosilicates [0.45-0.69 J·(g·K)−1]. Thermal expansion coefficients ( TECs) of the dense samples ranged between 5.9 and 10.3 × 10−6 K−1 measured for 473 to 1473 K. All EBCs have low thermal conductivities [1.8 W·(m·K)−1 or less] making them excellent EBC insulators. [ABSTRACT FROM AUTHOR]

The development of high-power piezoelectric ceramics with superior piezoelectric properties and broad temperature usage ranges is vital for the thriving progress of electromechanical applications. However, achieving high piezoelectricity, high mechanical quality factor, and temperature stability often presents a trade-off. In this study, we present an advanced ceramic material with excellent high-power piezoelectric properties and superior temperature stability. The piezoelectric coefficient d 33 reaches 348 pC N−1, the electromechanical coupling factor k p is 54%, the mechanical quality factor Q m is 1501, the dielectric loss tanδ is 0.35%, and the d 33 variation is less than 10% within 25–210 °C in 0.05Pb(Mg1/3Nb2/3)O 3 -0.05Pb(Mn 1/3 Sb 2/3)O 3 -0.9Pb 0.95 Sr 0.05 (Zr 0.48 Ti 0.52)O 3 ceramic. The excellent piezoelectricity is attributed to the enhancement of intrinsic ionic displacement and reversible domains wall motion because of symmetry-conforming short-range distribution of oxygen vacancy, while the high Q m is a result of increased domain size and oxygen vacancy. The outstanding temperature stability is related to the stable non-180°domains structure due to the oxygen vacancy pinning effect. These properties hold great potential for advanced applications, particularly for piezoelectric high-power applications requiring constant d 33 over a broad temperature range. [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 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]

In this study, the PPS/MWCNTs/AlN composite was prepared with poly(phenylene sulfide) (PPS), covalent functionalized multi-walled carbon nanotubes (fMWCNTs), and aluminum nitride (AlN) via melt-blending techniques. The AlN is a fascinating non-oxidizing ceramic material having the highest thermal conductivity among the ceramic materials. In order to introduce the functional groups on the surface of the AlN particles, a silane coupling agent was used as it is able to graft with the functional groups on the covalent functionalized MWCNTs. The silanization reaction of the AlN was confirmed qualitatively and quantitatively by FT-IR (Fourier Transform Infrared Spectroscopy), and XPS (X-ray Photoelectron Spectroscopy). The grafting reaction of the AlN particles on the MWCNTs was confirmed using UV-Vis (Ultraviolet-Visible Spectroscopy), FE-SEM (Field-Emission Scanning Electron Microscopy) and FE-TEM (Field-Emission Transmission Electron Microscopy) images. The grafting reaction was accomplished by observing the change of the transmittance, the morphology of the AlN particle bonded to the MWCNTs. For the morphological changes of the fractured surface of the PPS/MWCNTs/AlN composites by FE-SEM, the hybrid filler was homogeneously dispersed on the PPS matrix when the AlN particle was grafted on the MWCNTs. The homogeneous distribution of the hybrid filler acts as a heat transfer path, which led the higher thermal properties, such as thermal conductivity, thermal resistance, and melting temperature than those of not grafted MWCNTs. [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]

Porous mullite-corundum refractory ceramics were produced by a patented slurry slip casting method from compositions based on commercially available α-Al 2 O 3 and γ-Al 2 O 3 , fused SiO 2 and kaolin. Pores were formed as a result of a chemical reaction of aluminium with water. The influence of usage of raw materials and doping additives such as micro-size ZrO 2 and WO 3 on the sintering temperature, formation of crystalline phases, linear thermal expansion, thermal conductivity and thermal shock resistance of mullite-corundum ceramic was studied. The best thermal shock resistance and, simultaneously, lower thermal conductivity was achieved for the samples doped with WO 3 . This was due to the influence of micro-sized WO 3 on the change in γ-Al 2 O 3 modification to α-Al 2 O 3 and on the structure of mullite ceramics. [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]

A new lightweight and thermal insulating material was successfully prepared by impregnating Al 2 O 3 –SiO 2 aerogel into a porous mullite–zirconia fiber network with a quasi-layered microstructure. The microstructures, thermal and mechanical properties of the porous mullite–zirconia ceramics were investigated before and after the impregnating of Al 2 O 3 –SiO 2 aerogel. It was observed that the mullite and zirconia fibers combined well with aerogels. Compared with fibrous porous mullite-zirconia ceramics, the Al 2 O 3 –SiO 2 aerogel/porous mullite–zirconia composite exhibited higher compressive strength (i.e. 1.36 MPa in the z direction) and lower thermal conductivity (i.e. 0.052 W/(m·K)). The present work provides an efficient way to fabricate highly porous ceramics with high strength and ultra-low thermal conductivity, which find potential use in high-temperature thermal insulation materials. [ABSTRACT FROM AUTHOR]

Thermal energy storage (TES) has been identified as a breakthrough concept in development of renewable technologies. However, the main challenges are related to the development of competitive heat storage materials. Despite the number of studies on heat storage materials, the determination of new alternatives for next generation technologies is still open. In this regard, this paper presents the results of an experimental study of the physical, thermal and mechanical properties of SiC-doped ceramics as potential materials for TES applications. Two kinds of SiC additives (high and low densities) were incorporated with different percentages into the clay matrix in order to produce ceramics via the extrusion process. The addition of low-density SiC (true density 3.16 g cm−3) led to the increasing of porosity with large pore sizes and the decreasing of bulk density. Therefore, the thermal and mechanical properties are decreased up to − 50% for flexural strength and − 15% for thermal conductivity when 20 mass% of low-density SiC was used. On the other hand, when high-density SiC (true density 3.42 g cm−3) was used, properties of the clay ceramic were strongly improved: i.e., increase in the bulk density, decrease in the porosity, increase in the thermal conductivity and increase in the flexural strength. The best material was found with the addition of 20 mass% of high-density SiC which had a thermal conductivity of 1 W m−1 K−1, a specific heat capacity of 0.62 kJ kg−1 K−1 and a mechanical strength of 19.6 MPa. It also showed a high thermal stability after 20 successive heating/cooling cycles. Hence, this study provided a useful insight into how the SiC modified the microstructure and properties of fired clay ceramics. Thus, the current results suggest that clay ceramics with high-density SiC addition are promising materials for thermal energy storage applications. [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]

Ceramic cores have been designed with compounds based on fused silica due to its excellent thermal stability and chemical inertness against molten metals. To endure the high temperatures present during investment casting, mineralizers have been widely used to enhance the flexural strength and shrinkage of ceramic cores. In this study, we demonstrated a silica-based ceramic core with silicon carbide as a mineralizer for improving the mechanical and thermal properties. The SiC in the silica-based ceramic cores can enhance the mechanical properties (i.e., flexural strength and linear shrinkage) by playing a role as a seed for the crystallization of fused silica to cristobalite. The SiC also improves the thermal conductivity due to its higher value compared with fused silica. The results suggest that using the optimal amount of silicon carbide in silica-based ceramic cores can provide excellent mechanical properties of flexural strength and linear shrinkage and improved thermal conductivity. [ABSTRACT FROM AUTHOR]

Porous ZrB 2 –SiC (ZS) ceramics with different volume fractions of porosity, i.e. 8.7%, 17.9% and 27.3% and different mean pore diameter, i.e. 2.21, 3.65 and 4.23 μm, were fabricated using partial hot pressing, in order to investigate the effect of the porosity and pore size on their mechanical and thermal properties as well as thermal shock performance. Particular emphasis was placed in the study on thermal shock fracture resistance. The critical temperature difference, Δ T c , of porous ZS herein was found to increase slightly with increasing porosity. This phenomenon is inconsistent with most previous researches on other material systems. However, it was well explained from the viewpoints of both physical properties and microstructures of the material, which provides new perspectives and a deeper understanding of how porosity and pore-size affect Δ T c . The Δ T c was also observed to increase as pore size decrease. It could tailor the thermal shock resistance of ZS ceramic and obtain porous ZS ceramic with both high thermal shock fracture resistance and high thermal shock damage resistance, using the above porosity and pore-size dependence of physical properties. [ABSTRACT FROM AUTHOR]

The present research studied a set of phyllite clays from several deposits in southeast Spain. These phyllite clays have traditionally been used as sealing material to impermeabilize roofs, embankments, ponds, construction and waste landfill, with recent applications in the preparation of new mortars. However, studies on thermal behaviour and ceramic properties of phyllite clays have been scarce. The present research showed a summary of previous characterization studies on representative phyllite clays from these deposits with additional results. Mineralogical, by X-ray diffraction, and chemical, by X-ray fluorescence characterization of these samples were summarized. Thermal analysis methods (DTA–TG and thermal diffractometry) were applied to achieve a more complete mineralogical characterization. Several phyllite clay samples were selected for a ceramic study by firing pressed powdered samples up to 1300 °C. Sintered or vitrified materials, with porosities almost zero, were obtained from these phyllite clays after firing at 1100–1200 °C, with apparent densities between 2.1 and 2.4 g cm−3. Higher firing temperatures (> 1250 °C) produced deformation and expansion of the ceramic bodies. These results allowed obtain the vitrification temperature (Tv) and the temperature of the maximum bulk density (Td). According to the previous mineralogical and chemical characterization and the values of these parameters, the phyllite clay samples were classified in three varieties, as follows: (1) Micaceous, characterized by predominant layer silicates, mainly muscovite or illite, alkaline elements (mainly K2O higher than 3.5 mass%) and lower values of both Tv and Td, (2) Quartzitic, with predominant quartz and SiO2 and intermediate values of Tv and Td, and (3) Carbonaceous, characterized by predominant dolomite, medium contents of CaO and MgO and higher values of both Tv and Td. These results are interesting for the application of these phyllite clays as ceramic raw materials. [ABSTRACT FROM AUTHOR]

Thermal barrier coating (TBC) system is an essential technology in many fields associated to high temperatures. The main function of these TBCs is to protect the metallic parts against high temperatures over 1000 °C. However, degradation occurs both in thermal and mechanical performances during service. Thus, understanding the underlying degradation and failure mechanisms of TBCs is significant to assess and further enhance the durability and reliability of TBCs. Regarding the durability of TBCs, this paper reviews different failures mechanisms of TBCs caused by residual stresses, phase transformations, sintering, hot corrosion attack and oxidation. Subsequently, some methods are summarized to alleviate the undesirable effects of the causes, so as to extend the lifetime of TBCs. Regarding the thermal barrier performance of TBCs, the neoteric advances to resist degradation in thermal conductivity of TBCs are reviewed. In addition, some new ceramic materials with superior intrinsic properties are introduced for ultra-high temperature applications. In brief, this review correlates the microstructure and properties of TBCs for finer interpretation and degradation-resistant design on their thermal and mechanical properties, which would benefit the advanced TBCs in future engineering applications. [ABSTRACT FROM AUTHOR]

Spark plasma sintering (SPS) has been employed to consolidate a micron-sized zirconium carbide (ZrC) powder. ZrC pellets with a variety of relative densities are obtained under different processing parameters. The densification kinetics of ZrC powders subjected to conventional hot pressing and SPS are comparatively studied by applying similar heating and loading profiles. Due to the lack of electric current assistance, the conventional hot pressing appears to impose lower strain rate sensitivity and higher activation energy values than those which correspond to the SPS processing. A finite element simulation is used to analyze the temperature evolution within the volume of ZrC specimens subjected to SPS. The control mechanism for grain growth during the final SPS stage is studied via a recently modified model, in which the grain growth rate dependence on porosity is incorporated. The constant pressure specific heat and thermal conductivity of the SPS-processed ZrC are determined to be higher than those reported for the hot-pressed ZrC and the benefits of applying SPS are indicated accordingly. [ABSTRACT FROM AUTHOR]

The basic goal of this article was thermal diffusivity characterization of ceramic materials used in thermal barrier coating (TBC) systems for depositions of the insulation layer and characterization of the materials' morphology and remanufacturing process. The base material was oxide 8YSZ (ZrO2 × 8Y2O3), which is usually dedicated to deposition of an insulating top layer in TBC systems. The data related to thermal properties such as thermal diffusivity and thermal conductivity are widely presented in the literature, but there is lack of information about the morphological form of investigated materials, and the presented results vary widely. Data on thermal properties based on the literature sources are inadequate for the real morphological form of materials used in the experiment (e.g., massive or single crystalline material vs. plasma-sprayed coatings), which consequently gives an unsatisfactory accuracy of the obtained numerical simulations by MES methods. This article presents the characterization of thermal diffusivity of the commercial 8YSZ ceramic material synthesized or remanufactured by different routes, which is investigated in the forms of pressed powder pellet (two commercial nano-sized powders with different morphologies), sintered pellets (one commercial powder, solid-state co-precipitated reacted powder of 8YSZ type), and a two-layered coating system of In625 + NiCrAlY/8YSZ type. The range of analysis included morphological investigations of different types of powders in initial conditions and after remanufacturing (sintering, thermal spraying) as well as the thermal diffusivity analysis by the laser flash method. The obtained data were corrected by porosity factor and compared to each other. The best similarity for obtained thermal diffusivity data was found for commercial powers of HOSPTM type after pressing and sintering processes and calculated (2-layered model) value of thermal diffusivity for two-layered system of In625/8YSZ TBS system. The results showed that there are significant differences in thermal diffusivity values for materials with different morphological forms. [ABSTRACT FROM AUTHOR]

A 2 B 2 O 7 -type rare earth zirconates have been intensively investigated as potential thermal barrier coating (TBC) materials due to their low thermal conductivities and high stability at high temperature. In this work, mixing La 3+ and Yb 3+ with a large difference in atomic radii at A site formed a quasi-eutectoid mixture of La 2 Zr 2 O 7 -rich pyrochlore phase and Yb 2 Zr 2 O 7 -rich fluorite phase. The competition between these two phases in grain growth effectively reduces the grain size down to 0.8–1 μm, giving rise to improved mechanical properties comparing with the single-phase materials, including a higher hardness, a higher fracture toughness and a lower elastic modulus. Furthermore, a significantly low thermal conductivity was found, as the small and heavy Yb 3+ ions that dissolve in the La 2 Zr 2 O 7 -rich pyrochlore could “rattle” in the lattice and strongly scatter the heat-carrying phonons. Considering the comprehensively improved mechanical and thermal properties, the quasi-eutectoid (La 1− x Yb x ) 2 Zr 2 O 7 ceramic can be considered as a potential TBC material. [ABSTRACT FROM AUTHOR]

Aluminium titanate (AT) (Al2TiO5) is a promising engineering material because of its low thermal expansion coefficient, excellent thermal shock resistance, good refractoriness and non-wetting with most metals. Functionally graded material (FGM) is generally a paniculate composite with continuously varying volume fractions. FGMs are alternative materials for dental implants, building materials and ballistic protection. It has been of great interest to future engines, internal combustion engines, metal cutting and other high temperature engineering application. There has been a demand for an adequate disc brake that requires less maintenance in the automotive manufacturing industry. FGM, the next evolution of layered structure, consists of graded compositions that are dispersed across the ceramic which produces a gradual improvement in the properties across the ceramic at a steady pace. [ABSTRACT FROM AUTHOR]

This research study investigates the potential use of traditional raw materials to synthesize new ceramic composite materials that can be used in different industrial applications. The composite materials were developed through mechanical activation, carbonization, and reactive sintering techniques. Natural zeolite from Tokaj region, alumina from Motim, and sawdust were used as starting raw materials. Stoichiometric amounts of the raw materials were mixed and milled in planetary ball milling followed by uniaxially pressing to produce cylindrical ceramic discs. The produced green ceramics were then sintered in an electric laboratory kiln under an oxygen-free environment at 1200 °C. In-situ carbonization of the sawdust was confirmed via X-ray diffraction. The thermal properties were also investigated by derivatography. The produced ceramic specimens were tested on microstructural characteristics, porosity, density, and water absorption. [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]

β-Lu 2 Si 2 O 7 is a promising candidate in the third generation of environmental barrier coating (EBC) materials for silicon-based ceramics due to its excellent high temperature environmental durability. However, the high temperature thermal and mechanical properties of β-Lu 2 Si 2 O 7 are seldom reported, which hinders the design and evaluation of its EBC applications. In this paper, pure and dense β-Lu 2 Si 2 O 7 sample was successfully fabricated and its mechanical properties, including Young's modulus, bulk modulus, shear modulus, Poisson's ratio, flexural strength, fracture toughness and hardness were investigated. The ball indentation test reveals that the main deformation mechanisms of β-Lu 2 Si 2 O 7 at room temperature are deformation twinning and dislocation glide, which indicate that β-Lu 2 Si 2 O 7 is a damage tolerant ceramic. In addition, the thermal expansion coefficient and thermal shock resistance were measured at high temperatures. β-Lu 2 Si 2 O 7 possesses excellent high temperature elastic stiffness up to 1470 °C, and the critical temperature difference for thermal shock resistance is 270 K. [ABSTRACT FROM AUTHOR]

Spectral emissivity of surface materials has a strong impact on thermal properties of systems that are exposed in the ambient environment. While the solar spectrum heating up the surface ranges from 200 to 2,500 nm, the atmospheric transmission spectrum allowed for infrared cooling ranges from 8 to 14 µm. However, conventional surface materials have emissivity values that are either high or low throughout the spectrum. For example, ceramic materials are typically emissive and metallic materials are typically reflective and not emissive. Here, we show that surface materials with artificial periodicities can have a selectively controlled emissivity and that the surface morphology can transform ceramic materials to be reflective or metallic materials to be emissive. As a model system, we use microscale tree-like structures, or briefly micro-trees, to demonstrate wide variations of morphology-driven emissivity spectra. Our computation based on the rigorous coupled-wave analysis shows that optimal designs of micro-trees can act as a nearly perfect reflector or a black body depending on the spectral range and offer radiative cooling or heating capabilities beyond the limits of conventional materials. For cooling, metallic micro-trees provide a surface temperature 10 K lower than that of bare metallic surfaces in a normal ambient condition, and for heating, ceramic micro-trees provide a surface temperature 8 K higher than that of bare ceramic materials. The morphology-driven emissivity of micro-trees can offer a net cooling power of 136 W/m2 or a net heating power of 12 W/m2 depending on the application without requiring any active devices, and these results guide optimal designs of artificial materials for thermal management. [ABSTRACT FROM AUTHOR]

The use of ceramic cutting tools is limited due to their inherent brittleness. In this paper, metal phase Co is considered to strengthen Si 3 N 4 based ceramic tool materials. The effects of Co on room-temperature and high-temperature mechanical properties and thermal shock resistance of the material are studied. Compared with the composite without Co, the addition of Co can improve room-temperature fracture toughness of Si 3 N 4 based ceramic material at the cost of reducing its hardness. The flexural strength decreases a little in accordance with the reduced relative density. As the testing temperature increases, the fracture toughness first increases gradually and then decreases sharply while the flexural strength decreases gradually. Due to the oxidation inhibition effect, the Co-containing composite maintains higher flexural strength and fracture toughness than the Co-free composite at the specified test temperatures. The critical thermal shock temperature difference of the composite with Co is higher than that without Co, although before reaching the difference its residual bending strength is lower due to pores and thermal mismatch effect. The addition of Co can also inhibit the growth of thermal shock microcracks and improve the thermal fatigue resistance of Si 3 N 4 ceramic material. [ABSTRACT FROM AUTHOR]

The prospects for using ceramic composite materials in place of metallic materials in heat-loaded units in advanced aircraft are examined. The manufacture of silicon carbide based ceramic composite materials, reinforced with filamentary crystals (whiskers), by means of hot-pressing and spark plasma sintering using oxide and nitride sintering additives was investigated. A complex of physical-mechanical and thermal properties of composites was investigated. [ABSTRACT FROM AUTHOR]

As polymers have the ability to be easily molded in to any shape, they have a wide range of applications in industry. Composites prepared by dispersing ceramics in to polymer matrix have higher thermal conductivity than the original polymer, and they still retain their high electrical resistance. In this work, polyvinyl butyral (PVB) is chosen as the polymer matrix. Ceramic nanoparticles like boron nitride (BN), zinc oxide (ZnO) and silicon carbide (SiC) are used as fillers. Polymer composites with different filler loading ratio (wt %) are prepared and their thermal and electrical properties are analyzed. FT–IR, XRD and TGA characterizations are also performed on the composites. The results indicated that PVB composite with hexagonal boron nitride (h–BN) showed the best improvement in thermal conductivity up to 0.5194 W m −1 .K −1 which is an increase of 131.87%, and volume resistivity of composites remained high, above the 10 10 Ω–cm level. [ABSTRACT FROM AUTHOR]

This paper presents the results of a combined experimental and theoretical study on a clay ceramic used for building applications. The thermal and mechanical properties of the clay ceramic were improved by addition of organic additives. The organic additives consisted of Olive Stone Flour (OSF), with round-shape particles of 55 µm, and Wheat Straw (WS), with 877 µm particles in the form of fibers. It was found that the combustion of OSF and WS resulted in a porosity formation during the firing process. The morphology of these pores corresponded to that of the organic additives. Therefore, the addition of small OSF particles decreased the median pore size of the clay ceramic. It improved the mechanical strength of the clay ceramic by 12% for an 8 wt% addition of OSF. On the other hand, the WS fibers increased the clay ceramic anisotropy. This resulted in a 41% improvement of the thermal conductivity using an 8 wt% addition of WS. Finally, a model was developed from these experimental results to predict the thermal conductivity and the mechanical strength of the clay ceramic with other organic additives. They were predicted from the parameters of the organic additives (i.e., true density, swelling degree, particle size distribution, particle shape factor). The predictions indicated that the thermal conductivity is improved by 50% with a 25% improvement of the mechanical strength using small organic fibers, which is a step forward in the development of fired clay bricks that can be used for both insulation and structure purposes in building applications. [ABSTRACT FROM AUTHOR]

Low softening point temperature glassy frit, reinforcing silica, wollastonite and dicumyl peroxide were incorporated into ethylene-propylene-diene (EPDM) rubber matrix in different amounts in order to obtain ceramifiable composites. Kinetics of vulcanization of the mixes was measured. Mechanical properties, micromorphology, thermal properties and combustibility of the vulcanizates were studied as well as compression strength of the ceramic residue obtained after heat treatment. Studies show that optimal amount of glassy frit from the point of view of ceramification effectiveness in dispersed mineral phase is 40% wt. [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]

A new low-lead content 0.975BaTiO3-0.025PbZn1/3Nb2/3O3(0.975BT-0.025PZN) ceramic with a high relative density and good mechanical quality was fabricated by the SPS method. X-ray diffraction measurements showed that the obtained specimen possesses a pure perovskite structure. The composition undergoes a sequence of phase transitions as pure BT. Dielectric studies revealed that the dielectric permittivity decreases at its maximum and the phase transitions shift after PZN-doping of BT. In addition, the dielectric dispersion and polarization increases and decreases, respectively. Possible reasons for the observed properties change are discussed. The results show that the investigated ceramic is a promising low-lead material for electronic applications. [ABSTRACT FROM PUBLISHER]

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]

Solid oxide electrolytes showing proton transport are extensively studied materials, which can be utilised in different types of highly efficient energy systems such as solid oxide fuel cells, solid oxide electrolysis cells, membrane converters and sensors. Here we present the results of a study of the functional properties of LaYO3-based materials, which exhibit higher chemical stability than the more well known proton-conducting electrolytes, cerates and zirconates of alkaline earth elements. The structural, ceramic, thermal and electrical properties of La0.9Sr0.1YO3–δ have been thoroughly studied depending on the partial Y substitution with some lanthanides (10 mol.% of Yb, Dy, Ho). According to the experimental data, La0.9Sr0.1Y0.9Yb0.1O3−δ can be considered a promising alternative to the basic oxide because of its better transport properties and the fact that there are no detrimental changes in other functional characteristics. [ABSTRACT FROM AUTHOR]