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This paper describes the fabrication and characterization of porous SiC ceramics derived from highly-filled preceramic papers. The SiC ceramics were obtained by spark plasma sintering of stacked preceramic papers at temperatures of 2100 and 2200 °C under pressures of 5–60 MPa for 10 min. The microstructure and phase composition were analyzed by scanning electron microscopy and X-ray diffraction, respectively. Gas permeation tests were performed using hydrogen permeation cell at room temperature. It is revealed that the porosity of sintered SiC can be varied from 9 to 45 % depending on the sintering parameters. The shrinkage of the materials during spark plasma sintering occurs in four stages. The linear shrinkage value of the material increases from 7 to 47 % at 2100 °C and from 20 to 50 % for the samples sintered at 2100 and 2200 °C, respectively. Correlation dependencies between porosity and mechanical properties of the fabricated SiC were established. The obtained porous SiC ceramics exhibit high bending strength of 165 MPa and gas permeation flux of 78 molH 2 /m2/s at the porosity of 36 % that make it suitable for ceramic-based membranes. [ABSTRACT FROM AUTHOR]

The ceramic materials studied in this paper consist of finely dispersed crystalline phases embedded in a glassy matrix, which is similar to glass-ceramic materials, porcelain, and VC products. The strength depends then not only on the properties of the individual crystalline phases but also on their interactions and the matrix. Differences in mechanical properties for materials with similar chemical compositions are most likely related to diverging microstructures. Crystal orientation, grain-size distribution and shape, the ratio of the glass matrix to the crystalline phase, and homogeneity control the flexural strength of glass-ceramic materials. The subject of the study is whiteware ceramic materials from the SiO 2 –Al 2 O 3 –Na 2 O–K 2 O–MgO–SrO system, fired similarly to the regime used for VC products. The effect of the type of alkali oxide and the share of SrO were tested. This paper presents the results of hot-stage microscopy, X-ray diffraction (XRD), scanning electron microscopy with a micro-analyzer (SEM-EDS) and biaxial flexural strength measurements. Additionally, nanoindentation technique was used to access local mechanical properties. [ABSTRACT FROM AUTHOR]

The present paper investigates the effect of carbon nanofibers (CNFs) on the microstructure and mechanical properties of Carbon fiber reinforced carbon and silicon carbide binary matrix (C/C–SiC) composite prepared by using the reactive melt infiltration technique. The CNFs used in this paper were generated through in-situ reaction in the pores of C/C preforms using the chemical vapor deposition. Results indicate introducing additional carbon sources in the form of CNFs in the C/C preform can remarkably improve the permeability of molten Si, resulting in higher density and more uniform microstructure of the RMI-deriver C/C–SiC composites. Consequently, the in-situ formation of CNFs reduces the residual Si content by 64.71% and increases the mechanical strength and modulus at room temperature by [22.31% and 17.89%] and after heat treatment at 1500 °C by [35.6% and 47.48%] with respect to no-CNF containing composites due to a lower amount of residual Si content and additional reinforcement effect of the unreacted CNFs. [ABSTRACT FROM AUTHOR]

This paper presents an overview of recent works on microscale mechanical and other properties of silicon nitride (Si 3 N 4) determined by microcantilever bending tests and their relationships with the processing and microstructures. We first focus on deformation behaviors and fracture strength of Si 3 N 4 single crystals. β-Si 3 N 4 single crystals are plastically deformed at room temperature under high bending stress, and the yield stress depends on the crystal orientation. The critical resolved share stress of the primary slip system is determined to be below 1.5 GPa from the yield stress. Next, we address microscale mechanical properties of Si 3 N 4 polycrystalline ceramics. Emphasis is placed on their grain-boundary strength or toughness in conjunction with intergranular glassy film (IGF) which is determined by processing parameters such as sintering additives. Assessment is made on two cases of fractures at the IGF-grain interface and that within the IGF, and in each of the cases, effects of rare earth oxide additives are discussed. In Si 3 N 4 ceramics doped with Al 2 O 3 , β-SiAlON layer forming on β-Si 3 N 4 grains enhances the microscale grain-boundary strength. Finally, we shed light on microscale property-degradation behaviors of Si 3 N 4 ceramics, including the deterioration due to the contact with molten Al and the corrosion in sulfuric acid solution. The variation of the microscale properties appears in very short periods compared to the macroscale approaches, demonstrating the advantage in terms of rapid assessment of time-dependent degradation behaviors. [ABSTRACT FROM AUTHOR]

This paper aims to study the effects of Si 3 N 4 whisker (β-Si 3 N 4 w) and MXene (Ta 3 C 4 T x) on the densification, microstructure and mechanical properties of Si 3 N 4 ceramics. In this research, Al 2 O 3 , Y 2 O 3 and CaF 2 are utilized as ternary composite sintering additives, and fast hot press sintering off 1750 °C and 30 MPa is conducted. The β-Si 3 N 4 w and Ta 3 C 4 T x are well dispersed in the ceramic matrix, resulting in the achievement of a high-density, high-toughness Si 3 N 4 ceramic. The microstructure observation shows that the uniform addition of whiskers leads to a significant increase in rod-shaped Si 3 N 4 grains. When 10 wt% of β-Si 3 N 4 w are added, the bending strength of 577.1 MPa and the fracture toughness of 7.6 MPa m1/2 are obtained. By introducing 0.5 wt% Ta 3 C 4 T x along with 10 wt% β-Si 3 N 4 w simultaneously, much higher bending strength and fracture toughness are achieved, with the bending strength being 743.9 MPa and the fracture toughness being 9.7 MPa m1/2. This demonstrates that the synergistic effect of β-Si 3 N 4 w and Ta 3 C 4 T x plays a significant role in enhancing the fracture toughness of Si 3 N 4 ceramics. This research paves a new way to prepare high-toughness Si 3 N 4 ceramics by fully utilizing of toughening agents and their coupling mechanisms. [ABSTRACT FROM AUTHOR]

The development of a high-power and long-life thermionic ceramic cathode poses significant challenges, namely the need for high electron emission capacity at low temperature and excellent machinability. In this paper, the first-principles method was used to obtain the (La 0.5 Ba 0.5)B 6 with the lowest work function, and (La 0.5 Ba 0.5)B 6 –ZrB 2 composite with high relative density of 98.08 % was prepared by spark plasma sintering (SPS) at T = 1800 °C, under which the densification mechanism transformed from the particle rearrangement into the grain boundary diffusion, and the corresponding apparent activation energies were 282.75 kJ/mol and 466.54 kJ/mol, respectively. The maximum current density of 12.93 A/cm2 at T = 1500 °C of the composite was higher than that of 11.71A/cm2 at T = 1600 °C of LaB 6 , which can be attributed to the high Fermi level and weak electronic constraints of (La 0.5 Ba 0.5)B 6. The practical work function distribution (PWFD) of 0.36 eV indicated the composite had excellent emission uniformity. [ABSTRACT FROM AUTHOR]

Currently, the encapsulation of SiC/SiC has been a key technical challenge limiting further application, and YAS-based glass offered a possible solution. In this paper, different CaO-doped Y 2 O 3 –Al 2 O 3 –SiO 2 (YAS) glass solders were prepared and employed to join SiC/SiC. The joints were all structurally dense with the room temperature shear strengths higher than or equal to ∼51.7 MPa. Notably, joints containing 3.0 wt% CaO exhibited increased shear strength of ∼57.1 MPa, and the shear strength at 1200 °C was about 15.8 MPa in an air environment, meeting the requirements of the LOCA conditions. Optimal performance was achieved by using 3.0 % CaO-doped YAS glass to encapsulate SiC/SiC cladding, yielding a continuous, dense encapsulation region with predominantly small closed pores (≤1.0 mm3). Glass infiltration was found in both the end plug and cladding wall. The joints did not leak after 72h of holding pressure at 15 MPa, indicating their excellent air tightness. [ABSTRACT FROM AUTHOR]

The preparation of cubic boron nitride (CBN) grinding tools using laser cladding has the advantages of strong bonding, short time consumption and customizable abrasive arrangement. In this paper, a two-step laser cladding method was used to prepare CBN abrasive blocks with the aim of reducing laser damage to CBN grits during the laser cladding process. The cross-sectional morphology of CBN abrasive blocks under different laser power conditions was characterized, and the relationship among laser power, preparation method, and forming quality of Cu–Sn–Ti/CBN cladding layer was investigated. Then, the microstructure at the Cu–Sn–Ti/CBN interface under different laser power conditions was characterized, and the main phase compositions at the Cu–Sn–Ti/CBN interface were analyzed. Finally, the grinding tests were carried out on CBN abrasive blocks. The results show that as the laser power increases from 250 W to 400 W, the fracture ratio of CBN grits increases dramatically from 4.3 % to 17.3 %. TiN, TiB 2 , and TiB compounds are all detected at the Cu–Sn–Ti/CBN interface under different laser power conditions. The mass loss of the TC4 wheel caused by the CBN abrasive block initially increases and then decreases as the laser power increases from 250 W to 400 W. The CBN abrasive block has the optimum material removal performance at the laser power of 300 W using two-step laser cladding. The results provide a theoretical basis for the preparation of high-performance CBN grinding tools using laser cladding. [ABSTRACT FROM AUTHOR]

With the increase in train speed and axle weight, the quality and service life of the rail (U71Mn steel) are more demanding. Aiming at the excellent properties of nickel/nickel-based alloys and ceramic materials, this paper prepares TiC/Ni45 composite coatings for rail repair by in-situ synthesis of ceramic phases using laser cladding technology. The effects of in-situ synthesized TiC on the physical phase, microstructure, microhardness and wear resistance were investigated and discussed in detail. The results show that the reaction of in-situ synthesized TiC can proceed positively, and the microstructure of the cladding layer mainly consists of the segregation of Cr, TiC particles, and substrate phase. With the increase of nickel-coated graphite and titanium powder, the average microhardness value of the cladding layer increased, and the average friction coefficient and wear volume decreased. When the mass fraction of (Ti + C) reaches 15 wt%, the average friction coefficient of the cladding layer reaches the minimum value. When the mass fraction reaches 20 wt%, the average microhardness of the cladding layer reaches 2.65 times that of the substrate, and the wear mechanism is transformed from mainly adhesive wear to abrasive, oxidative, and fatigue wear. [ABSTRACT FROM AUTHOR]

Doping refractory metal silicates into the matrix of C/SiC composites is an effective means to improve their oxidation resistance. Previous studies have demonstrated that doping HfSiO 4 matrix availably enhanced the oxidation resistance of C/SiC composites, but the high raw material cost of HfSiO 4 limits its widespread application. This paper attempts to introduce ZrSiO 4 matrix, which has lower raw material cost and similar properties to HfSiO 4 , into C/SiC matrix through the same process. To clarify whether the microstructure of the refractory metal silicate doped matrix significantly impacts the oxidation behavior of C/SiC composites, the preparation temperature of ZrSiO 4 was increased to 1100 °C. The densification effect, oxidation behavior, and related mechanisms of C/SiC composites doped with ZrSiO 4 matrix were investigated and compared in detail with the previously studied C/SiC composites doped with HfSiO 4 matrix. Results show that the oxidation resistance behavior of C/SiC composites is relatively sensitive to the microstructure of the refractory metal silicate-doped matrix. At lower preparation temperatures of refractory metal silicates, the particle size of the composite matrix is significantly refined, which is conducive to improving the matrix densification degree of the composites and protecting more carbon fibers from erosion by the oxidizing environment, thus achieving a better oxidation resistance modification effect. [ABSTRACT FROM AUTHOR]

Ultra-High Performance Concrete (UHPC), with its excellent tensile properties, can be used as an alternative to decorative materials that are heavy in cross-section, enabling architectural decoration field to develop in the direction of light weight and changeable shape. However, the extremely low water-binder ratio of UHPC produces obvious autogenous shrinkage, which leads to the development of many micro-cracks. When the micro-cracks develop to a certain extent, they can have a very negative impact on the finishing of the architecture. This paper studies the influence of medium-burnt quicklime dosing on the hydration process and mechanical properties of UHPC cured at room temperature and elucidates the mechanism by which medium-burnt quicklime reduces autogenous shrinkage in UHPC. The results show that the crystal growth pressure generated by the hydration of f-CaO (free calcium oxide) can significantly compensate the autogenous shrinkage of UHPC. The dosage of 3 % medium-burnt quicklime can make the mechanical properties and shrinkage properties of UHPC reach the relative optimum, and the autogenous shrinkage of UHPC can be reduced to 181.36 με. Although the medium-burnt quicklime reduces the hydration products by delaying the hydration of UHPC, it also can reduce the porosity and the percentage of the multi-harmful pores, and refine the pore aperture. In addition, the interfacial transition zone between the UHPC matrix and the steel fibres can be reduced due to the extrusion of Ca(OH) 2 crystal growth pressure on the surrounding crystals, resulting in a tighter lapping between the crystals. [ABSTRACT FROM AUTHOR]

Solar thermal power generation is an important direction of energy utilization, and thermal storage materials are the key to ensure the continuous use of energy. In this paper, forsterite - zirconia composite ceramics were prepared by adding different contents of 3Y–ZrO 2 and their physical properties, phase composition, microstructure thermal shock resistance and thermal physical properties were studied. The results showed that the water absorption, bulk density and bending strength of sample A3 sintered at 1600 °C (59.10 wt% fused magnesia, 40.90 wt% quartz and 30 wt% 3Y–ZrO 2) were 0.35 %, 3.27 g/cm3 and 83.66 MPa, respectively. The crystal phase of sample A3 was forsterite and c-ZrO 2. Mg2+ and Y3+ replace Zr4+, formed oxygen vacancy in the anion position, distort the coordination layer and release some interlayer stress to promote the stability of c-ZrO 2. In the sintering process, the zirconia solid solution existed in the form of second phase, which reduced the growth rate of periclase, facilitated the pore discharge in the sample and promotes sintering. The thermal conductivity of forsterite - zirconia composite ceramics at room temperature was 5.52 W/(m·K). At 1000 °C, the specific heat capacity and heat storage density were 1.09 J/(g·K) and 1062.36 kJ/kg, respectively. The forsterite - zirconia composite ceramic prepared in this study was suitable for high temperature environment, its heat storage capacity was excellent, and it was suitable for high temperature heat storage system. [ABSTRACT FROM AUTHOR]

3D printing is an excellent choice for manufacture of ceramic cores; however, the inter-layer structures in 3D printed sample leads to anisotropy in microstructure and properties. In this paper, silica-based ceramic cores were prepared by digital light processing, and metallic Si powder was employed as mineralizer to relieve the anisotropy. The metallic Si powder converts into SiO 2 in oxidation reaction with significant volume expansion, which inhibits the shrinkage rate and partly fills the interlayer gaps of the ceramic core. Meanwhile, the metal Si powder leads to lower curing thickness in 3D printing, and thicken the interlayer gaps. Due to the cooperation of the oxidation reaction and decreased curing thickness by the metallic Si powder, the 0.4 wt% of metallic Si powder reduced the anisotropy in structure and mechanical property due to the alleviated inter-layer structure and the interlayer and intralayer strengths show optimal values of 11.4 MPa and 17.2 MPa at room temperature, respectively. This work inspires new guidance to 3D printing of ceramic cores with uniform microstructure and excellent mechanical properties. [ABSTRACT FROM AUTHOR]

Insulators are vital components used in electrical transmission lines. It's crucial to keep their production cost low since they are widely used in electricity transmission. Instead of expensive alumina-based insulators, we can make cheaper ones using clay and bauxite found in nature. Adding more alumina makes them stronger, which is important for high voltage transmission. This paper aims to study the production process of bauxite-based insulators. We examined the insulators' structure using SEM images and EDAX spectrum analysis to see their formations, porosity ratio, and density. This research helps us learn more about these insulators and how they can be used effectively for high voltage transmission lines. [ABSTRACT FROM AUTHOR]

In this paper, by adding Co, Mo, and Ni metal binder and using spark plasma coupling high-frequency induction (SP–HF) sintering technology, high-entropy (W,Nb,Mo,Ta,Ti)C cermet with good performance was successfully prepared at 1350 °C. The sintering temperature was much lower than that of the solid-state sintering temperature adopted for high-entropy carbide ceramics (about 2000 °C) while maintaining high hardness and fracture toughness. The effects of sintering temperature, holding time and sintering pressure on the mechanical properties of high-entropy (W,Nb,Mo,Ta,Ti)C cermet were investigated. The experimental results show that the SP-HF sintering can promote the liquid phase flow inside the high-entropy (W,Nb,Mo,Ta,Ti)C cermet and improve the density. The high-frequency induction sintering effect of the high-intensity magnetic metal binder phase (Co, Ni) promotes the rapid diffusion of the constituent phases using the vacancy mechanism and the metal liquid phase, which helps to form a high-entropy cermet solid solution at a lower temperature. The different high-entropy effects of the inner and outer layers of high-entropy (W,Nb,Mo,Ta,Ti)C cermet materials play a role in strengthening and toughening the materials, and effective solid solution strengthening is the main reason for improving mechanical properties. The mechanical properties of high-entropy (W,Nb,Mo,Ta,Ti)C cermet are the optimized at 1350 °C, holding time of 8 min, and sintering pressure of 35 MPa. The Vickers hardness, fracture toughness, and flexural strength are 18.38 ± 0.19 GPa, 9.65 ± 0.25 MPa · m1/2 and 970 ± 30 MPa, Vickers hardness was measured at 49 N load. [ABSTRACT FROM AUTHOR]

Zirconolite (CaZrTi 2 O 7) glass-ceramic is considered as a potential stable matrix for the immobilization of Pu or minor actinides (Np, Am, Cm). In this work, the phase combination and evolution of glass (SiO 2 –Al 2 O 3 –Na 2 O–CaO–ZrO 2 –TiO 2 –B 2 O 3) with La as an actinide surrogate were investigated during the process of heating and cooling. By employing controlled cooling process, the zirconolite glass-ceramic with a controllable crystal size was successfully fabricated in borosilicate glass. The results demonstrate that heating and cooling exhibit distinct phase combinations. Both crystallization temperature and duration exert a significant influence on the composition of crystalline phases and microstructure. During the cooling of the melt, an increased degree of supercooling leads to an enhanced crystallization of zirconolite and a significant reduction in crystal size. The experimental results demonstrate that the optimal condition for preparing zirconolite glass-ceramic is held at 950 °C, for 4 h by one-step method, at which time the crystal exhibits a slender acicular morphology with a size of about 30 μm. Most of the simulated nuclides are enriched in crystals, and the rest are dissolved in glass. Zirconolite exhibits thermodynamic instability at elevated temperatures (1000 °C–1100 °C). Following the phase transformation, a proportion of Zr sequestered by titanite, while any excess Zr is either remain dissolved in the glass or gets precipitated as baddeleyite. For La, Al and other elements previously fixed in zirconolite, they are re-released to the glass and partially fixed by titanite, which may be detrimental to the long-term release behavior of the waste forms. In the aqueous durability test, both zirconolite glass-ceramic and phase transformation samples exhibited a low leaching rate, with LR Si , LR Zr , and LR La values of approximately 5 × 10−3, 4 × 10−6, and 6 × 10−6 g·m−2·d−1, respectively, after 28 days of leaching. By controlling the cooling process (one-step method), this paper provides useful information on the preparation of zirconolite glass-ceramic. [ABSTRACT FROM AUTHOR]

The paper uncovers microstructural evolution and bonding mechanism of yttrium iron garnet ferrite (YIG) and magnesium titanate ceramic (MTC) brazed by bismuth-based glass ceramic. The resulting mechanical and dielectric properties of the proposed YIG/MTC joint were investigated in detail. The reaction mechanism was thoroughly studied. Micro and nano CoFe 2 O 4 were generated in the glass seam. Besides, a CoFe 2 O 4 reaction layer was formed at the interface of MTC/glass ceramic. The atoms stacked along the plane (220), and a complete coherent boundary was emerged between the CoFe 2 O 4 reaction layer and MTC ceramic subsequently. YBO 3 clusters were formed at YIG/glass interface and Bi 9 Ti 3 Fe 5 O 27 stripe phases were generated in the glass matrix. The joint shear strength increased with the brazing temperature increasing, and reached a maximum value of 72 MPa at 800 °C. The dielectric constant of YIG/MTC joint varied from 16.5 to 17.9, and the dielectric loss tangent was nearly 0.001 at higher frequency. [ABSTRACT FROM AUTHOR]

Ti 3 SiC 2 , as one of the most typical MAX ceramics, has been extensively studied as a potential high-temperature structural material. However, the restrictive relations between strength and toughness of Ti 3 SiC 2 and Ti 3 SiC 2 -based materials have hampered their industrial applications. Herein, we reported the successful fabrication of Ti 3 SiC 2 –(Ti 3 SiC 2 –C f) functionally graded materials (FGM) via hot-press sintering Ti 3 SiC 2 and short C f -derived preceramic papers. The microstructure evolution as well as the effect of sintering temperature on phase composition and interfacial reaction were investigated. Flexural strength and fracture toughness from ambient temperature to 1000 °C of the graded composites were determined to evaluate the mechanical performance. The results have shown that chemical reactions occurred between carbon fibers and Ti 3 SiC 2 matrix, which leads to the formation of SiC interfaces with strong covalent bonds. The newly developed Ti 3 SiC 2 –(Ti 3 SiC 2 –C f) graded composite materials exhibited excellent comprehensive performance as compared to that of monolithic Ti 3 SiC 2. The flexural strength and fracture toughness of the graded composite at room temperature can be reached to 526 MPa and 7.46 MPa m1/2, respectively. However, there is no significant change in flexural strength and fracture toughness from RT to 1000 °C. The fracture micrographs also reveal that fiber breaking、pulling out and debonding are the primary mechanisms that contribute to the superior mechanical properties of composites. The exceptional performance demonstrated in Ti 3 SiC 2 –(Ti 3 SiC 2 –C f) graded materials also makes them attractive choices for a variety of heatproof devices in aerospace sectors. [ABSTRACT FROM AUTHOR]

In this paper, a series of AlN–Al nanocomposite films are prepared by reactive magnetron sputtering. The effects of N 2 flow rate on the microstructure and mechanical properties of the films are studied. The formation and evolution mechanism of the nanocomposite structure are revealed. The results show that with the decrease of N 2 flow rate, the microstructure goes through three stages: pure AlN, amorphous Al surrounded nanocrystalline AlN and AlN nanoparticle reinforced Al matrix composite. Benefiting from the good wettability of Al on AlN ceramics, the film deposited at 6 sccm N 2 flow rate forms a nanocomposite structure of about 8 nm AlN grains wrapped by 1–2 nm amorphous Al. The hardness of the films increases first and then decreases with the decrease of N 2 flow rate, ranging from 4 GPa to 25 GPa. The toughness of the films is analyzed by the ratio of H/E, H3/E2, the normalized plastic depth (δ H) and the morphology of large load indentation. The results show that the toughness of the nanocomposite film obtained at 6 sccm N 2 flow rate is significantly improved while maintaining the hardness equivalent to that of pure AlN film. The improvement in toughness comes from the microcracks initiated in AlN hindered by the surrounding Al phase. [ABSTRACT FROM AUTHOR]

Calcium-magnesium-alumina-silicate (CMAS) resistance has become a key parameter to evaluate the properties of thermal barrier coating (TBC) materials. The CMAS corrosion behavior of BMT ceramic as a novel candidate material for TBC is poorly understood. In this paper, the solid-state sintering process was used to prepare the BMT bulks, and the evolution of microstructure, phase composition, thermophysical properties, and mechanical properties of the BMT bulks exposed to CMAS corrosion were studied. The results indicate that obvious elemental interdiffusion between the CMAS melt and BMT occurred at 1250 °C, which changed the original phase composition and formed multiple substances including Ba(Al, Ca)Si 2 O 8 , Ba 2 MgSi 2 O 7 , BaTa 2 O 6 , Ba 2 Si 4 O 10 , etc. The microstructure of BMT also underwent changes due to differences in the diffusion coefficients of different elements. As corrosion time prolongs, an obvious porous columnar reaction layer formed on the sample surface, causing the CMAS melt to sustainably corrode the deep BMT, resulting in intragranular corrosion. In terms of properties, the thermophysical and mechanical properties of the BMT bulks corroded by CMAS deteriorated. The thermal conductivity at 1100 °C increased from 1.43 W m−1 · k−1 to 1.67 W m−1 · k−1. The average coefficient of thermal expansion at 200–1400 °C decreased from 11.60 × 10−6 K−1 to 10.95 × 10−6 K−1. The hardness dropped by 21 % compared to the original BMT bulk. Therefore, it is necessary to improve the CMAS resistance of BMT ceramic in future studies. [ABSTRACT FROM AUTHOR]

ZrO 2 –Al 2 O 3 -A 3 S 2 (3Al 2 O 3 ·2SiO 2) composites are ideal Casting filter materials with excellent mechanical properties and thermal shock resistance. In this paper, 3Y–ZrO 2 (3 mol% Y 2 O 3 -stabilized ZrO 2) was added to kaolin and α-Al 2 O 3 to prepare ZrO 2 –Al 2 O 3 -A 3 S 2 composites by pressureless sintering. The results showed that when the addition amount of 3Y–ZrO 2 is 15 wt%, the bending strength and fracture toughness of the composites sintered at 1600 °C are 152.51 MPa and 3.52 MPa m1/2, respectively. The bending strength increased to 161.83 MPa after 30 thermal shocks (1100 °C to room temperature), with an increase rate of 6.11 %. The ZrO 2 crystals are evenly distributed between corundum and mullite crystals, effectively preventing abnormal growth of corundum and mullite crystals, and a small number of pores exist in the samples, which could act as a "buffer zone" to prevent the expansion of cracks in the thermal shock, resulting in high mechanical strength and excellent thermal shock resistance for composites. [ABSTRACT FROM AUTHOR]

Calcium-magnesium-alumina-silicate (CMAS) resistance has become a key parameter to evaluate the properties of thermal barrier coating (TBC) materials. The CMAS corrosion behavior of BMT ceramic as a novel candidate material for TBC is poorly understood. In this paper, the solid-state sintering process was used to prepare the BMT bulks, and the evolution of microstructure, phase composition, thermophysical properties, and mechanical properties of the BMT bulks exposed to CMAS corrosion were studied. The results indicate that obvious elemental interdiffusion between the CMAS melt and BMT occurred at 1250 °C, which changed the original phase composition and formed multiple substances including Ba(Al, Ca)Si 2 O 8 , Ba 2 MgSi 2 O 7 , BaTa 2 O 6 , Ba 2 Si 4 O 10 , etc. The microstructure of BMT also underwent changes due to differences in the diffusion coefficients of different elements. As corrosion time prolongs, an obvious porous columnar reaction layer formed on the sample surface, causing the CMAS melt to sustainably corrode the deep BMT, resulting in intragranular corrosion. In terms of properties, the thermophysical and mechanical properties of the BMT bulks corroded by CMAS deteriorated. The thermal conductivity at 1100 °C increased from 1.43 W m−1 · k−1 to 1.67 W m−1 · k−1. The average coefficient of thermal expansion at 200–1400 °C decreased from 11.60 × 10−6 K−1 to 10.95 × 10−6 K−1. The hardness dropped by 21 % compared to the original BMT bulk. Therefore, it is necessary to improve the CMAS resistance of BMT ceramic in future studies. [ABSTRACT FROM AUTHOR]

ZrO 2 –Al 2 O 3 -A 3 S 2 (3Al 2 O 3 ·2SiO 2) composites are ideal Casting filter materials with excellent mechanical properties and thermal shock resistance. In this paper, 3Y–ZrO 2 (3 mol% Y 2 O 3 -stabilized ZrO 2) was added to kaolin and α-Al 2 O 3 to prepare ZrO 2 –Al 2 O 3 -A 3 S 2 composites by pressureless sintering. The results showed that when the addition amount of 3Y–ZrO 2 is 15 wt%, the bending strength and fracture toughness of the composites sintered at 1600 °C are 152.51 MPa and 3.52 MPa m1/2, respectively. The bending strength increased to 161.83 MPa after 30 thermal shocks (1100 °C to room temperature), with an increase rate of 6.11 %. The ZrO 2 crystals are evenly distributed between corundum and mullite crystals, effectively preventing abnormal growth of corundum and mullite crystals, and a small number of pores exist in the samples, which could act as a "buffer zone" to prevent the expansion of cracks in the thermal shock, resulting in high mechanical strength and excellent thermal shock resistance for composites. [ABSTRACT FROM AUTHOR]

Based on the improvement of the phase transition temperature of Ti by Al element and the excellent strengthening effect of TiC particles, this paper selects Ti 2 AlC as the precursor, striving to improve the high-temperature performance of the Ti matrix. The composites with 1–10 vol% Ti 2 AlC addition were fabricated by hot-pressing sintering. And a detailed study was conducted on the reaction process, microstructure, room and high temperature compression properties of the composites. The experimental results show that the separation of Al elements at the A-position occurs at around 700 °C in Ti 2 AlC, and the Al element is homogenized in the matrix during the subsequent sintering process. Micron sized TiC particles are mainly distributed at the Ti grain boundaries, while the content of sub-micron sized TiC particles entering the crystal increases with the increasing Ti 2 AlC addition. The interface mismatch between TiC and Ti is small, and the bonding is well. These microstructures enable composite materials to exhibit excellent mechanical properties, with 10 vol% Ti 2 AlC/Ti composite having a yield strength of 1858 MPa and an ultimate strength of 2200 MPa at room temperature, and maintaining a yield strength of 602 MPa and an ultimate strength of 1264 MPa at 500 °C. [ABSTRACT FROM AUTHOR]

ZrO 2 –Al 2 O 3 (ATZ) ceramics are attracting high interest in biomedical applications because of their desirable mechanical performance and biocompatibility. However, strength and toughness are mutually exclusive in structural ceramics. In this paper, based on digital light processing, novel textured ATZ ceramics with obvious crystallographic orientations were fabricated by incorporating Al 2 O 3 platelets with a high aspect ratio and equiaxed particles into the ZrO 2 matrix. The optimized fracture toughness of 16.9 ± 0.8 MPa m1/2 was achieved in the textured ATZ ceramic, which was about 67.3 % higher than non-textured ZrO 2 ceramics, without sacrificing strength. The coupling toughening effects of macrolayer structure, equiaxed and platelet-shaped Al 2 O 3 particles, and ZrO 2 particles were responsible for the enhanced mechanical performance. The macroscale toughening of 3D-printed lamellar architecture led to effective energy dissipation. Additionally, the crack deflection and crack branching induced by dual-morphology Al 2 O 3 particles, accompanied by the phase transformation of the ZrO 2 matrix, were significant microscopic toughening mechanisms. [ABSTRACT FROM AUTHOR]

ZrO 2 –Al 2 O 3 (ATZ) ceramics are attracting high interest in biomedical applications because of their desirable mechanical performance and biocompatibility. However, strength and toughness are mutually exclusive in structural ceramics. In this paper, based on digital light processing, novel textured ATZ ceramics with obvious crystallographic orientations were fabricated by incorporating Al 2 O 3 platelets with a high aspect ratio and equiaxed particles into the ZrO 2 matrix. The optimized fracture toughness of 16.9 ± 0.8 MPa m1/2 was achieved in the textured ATZ ceramic, which was about 67.3 % higher than non-textured ZrO 2 ceramics, without sacrificing strength. The coupling toughening effects of macrolayer structure, equiaxed and platelet-shaped Al 2 O 3 particles, and ZrO 2 particles were responsible for the enhanced mechanical performance. The macroscale toughening of 3D-printed lamellar architecture led to effective energy dissipation. Additionally, the crack deflection and crack branching induced by dual-morphology Al 2 O 3 particles, accompanied by the phase transformation of the ZrO 2 matrix, were significant microscopic toughening mechanisms. [ABSTRACT FROM AUTHOR]