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The corrosion resistance of Ti 3 AlC 2 is an indispensable characteristic in its practical applications, and the focus of this study is to optimize its mechanical and corrosion properties by introducing metal ions at the M-sites of Ti 3 AlC 2. Utilizing Ti/Al/C/Zr/Mo/Cr powders, (Ti 0.8 X 0.2) 3 AlC 2 solid solutions were synthesized via reactive hot pressing, with XRD and SEM analyses confirming the formation of MAX phases. Results revealed varying degrees of influence on the properties of Ti 3 AlC 2 due to different doping elements. Among these, Zr-doped samples exhibited superior mechanical properties, boasting excellent hardness (511 Hv), flexural strength (386.57 MPa), and fracture toughness (10.24 MPa m1/2). Additionally, all (Ti 0.8 X 0.2) 3 AlC 2 samples formed n-type semiconductor passive layers in 3.5% NaCl solution, demonstrating outstanding corrosion resistance. Further investigation revealed that the enhancement in mechanical properties stems from solid solution strengthening and lattice distortion induced by different metallic elements. Meanwhile, the corrosion resistance is primarily attributed to alterations in electron distribution resulting from doping elements. These stable materials could find applications in electroplating wastewater treatment, where materials with excellent mechanical properties and corrosion resistance are required. It is anticipated that further modifications of MAX phase materials through doping will meet these additional requirements. [ABSTRACT FROM AUTHOR]

Currently, materials that absorb electromagnetic waves (EMW) are being increasingly studied and used. In particular, numerous attempts have been made to improve the performance of EMW-absorbing ceramics, but little attention was paid to the effect of doping on their relevant properties. In this work, Ti 3 AlC 2 , a typical MAX-phase ceramic, was doped with different elements (Zr, Mo, Cr, Fe and Ni) at the M site via a pressure-free reactive sintering. Phase and microstructure analysis show that the doped Ti 3 AlC 2 samples possess high purities and typical layered structures. It was noticed that (Ti 0.8 Zr 0.2) 3 AlC 2 demonstrates the lowest reflection loss (−48.0 dB at the thickness of 1.62 mm) and a maximum effective absorption bandwidth of 3.9 GHz. Elemental doping has been proved to alter the dielectric and magnetic properties of Ti 3 AlC 2 , and the boosted EMW absorption performance was found to be originated from the improved impedance matching. Here, we systematically investigated the influence of different dopants on the EMW absorption characteristics of Ti 3 AlC 2 , which provides significant insights for the future design of novel EMW-absorbing materials. [ABSTRACT FROM AUTHOR]

How to deal with the brittleness of ceramic materials is always one of the hot topics in the field of materials science. Design of layered ceramics with textured structure is one of the effective methods to improve their fracture toughness. The introduction of additives as interlayer phases can balance fracture toughness and flexural strength. However, the research about addition of interlayer phases and their mechanisms in the layered ceramics is still limited. In this work, nacre-like alumina ceramics were successfully fabricated by freeze casting followed by hot pressing. Silicon nitride was incorporated as the interlayer phase, and the effect on the mechanical properties of the nacre-like alumina was investigated. The addition of silicon nitride was beneficial to improvement of interlayer bonding between the alumina layers due to formation of sialon phase, leading to increase of flexural strength but decease of fracture toughness. When the content of silicon nitride was 3.3 wt%, flexural strength and fracture toughness of the sample was 468 MPa and 6.2 MPa m1/2, respectively. Compared with the sample without silicon nitride, the flexural strength was enhanced significantly. Additionally, both flexural strength and fracture toughness were improved as compared the sample without any additives. This work can provide available references for design and fabrication of high-strength and high-toughness ceramics by properly tuning the layer structure and interlayer phase composition. [ABSTRACT FROM AUTHOR]

High-entropy RE 3 MO 7 -type ceramics with multiple cations at RE and M sites have been successfully fabricated via solid-state reaction method. The microstructure and thermal properties of two compositions, namely (Y 1/3 Yb 1/3 Er 1/3) 3 (Nb 1/2 Ta 1/2)O 7 and (Y 1/3 Yb 1/3 Er 1/3) 3 (Nb 1/3 Ta 1/3 Mo 1/3)O 7 , are studied. The XRD Rietveld refinement, transmission electron microscopy and scanning electron microscopy results demonstrate that the samples have pure disordered defective fluorite structure with highly homogeneous composition. These high entropy ceramics exhibit good thermal stability, high thermal expansion coefficients (11.1–11.5 × 10−6 K−1, 1000 °C), and low thermal conductivities (0.91–1.16 W m−1 K−1, 30–1000 °C), which make them promising for applications as thermal barrier coating materials. [ABSTRACT FROM AUTHOR]

Synergic effect of graphene oxide (GO) and silicon nitride whisker (Si 3 N 4 w) on the mechanical properties of nacre-like alumina was investigated in this study. A comprehensive analysis on the composites, including microstructure, relative densities, flexural strength and fracture toughness, was carried out. The experimental results showed that, GO promoted the fracture toughness of the composites, but reduced the flexural strength slightly; while adding a certain amount of Si 3 N 4 w improved both flexural strength and fracture toughness. With the incorporation of GO and Si 3 N 4 w, the highest flexural strength reached 520 MPa and the fracture toughness reached 9.59 MPa m1/2. Microstructure observation revealed that the enhanced mechanical properties were ascribed to the synergistic toughening mechanisms induced by the nacre-like structure of alumina, GO pull-out, Si 3 N 4 w pinning and pull-out. [ABSTRACT FROM AUTHOR]

Boron nitride nanosheets (BNNSs) with relatively low dielectric constant and excellent mechanical strength were employed for fabrication of BNNSs/fused silica (FS) composites. High-temperature mechanical behavior and microstructural evolution of the composites were investigated. The addition of BNNSs can improve the mechanical properties of FS efficiently, and the reinforcement from BNNSs can be preserved during the high temperature service. The flexural strength of BNNSs/FS composites exhibited anomalous gains at certain high temperature range, which can be explained by the softening of FS matrix, the heal of defect tips, and the reinforcement from BNNSs. [ABSTRACT FROM AUTHOR]

Abstract Boron nitride nanosheets (BNNSs) have attracted increasing attention in the field of two-dimensional materials. In the paper, the BNNSs/alumina composites were fabricated by a flocculation method and hot pressing. It is found that the BNNSs were dispersed uniformly in the alumina matrix by the flocculation technique via pH adjustment. The experimental results showed that with the increasing BNNSs content, the density of the composites decreased. Compared with the monolithic alumina, bending strength of the composite with 1.0 wt% BNNSs was increased by 58.6%; while the fracture toughness was increased slightly. The addition of BNNSs changed the fracture pattern, refined the grains of composites and inhibited abnormal grain growth, which contributed to the improvement of mechanical properties of the composites. [ABSTRACT FROM AUTHOR]

Binderless cemented carbide has garnered attention for its exceptional hardness and suitability in extreme service conditions. The absence of a metal binder, however, leads to inadequate fracture toughness, which limits its broader application. This study explores the influence of SiC whisker on the microstructure and mechanical properties of WC-Al 2 O 3 -ZrO 2 binderless cemented carbide, utilizing a combination of experimental method and Density Functional Theory (DFT) calculations. The inclusion of 1 wt% SiC whisker resulted in a notable increase in fracture toughness, reaching an impressive toughness of 16.4 ± 0.5 MPa⋅m1/2, while maintaining a high Vickers hardness of 19.4 GPa. DFT calculations provided insights into the interface energy, cohesive energy, and charge density differences at the WC/SiC interface. This work also presents two models depicting the behavior of whiskers during fracture, based on the observed microstructure and computational findings. Overall, the present work offers significant insights and practical guidance for advancing binderless cemented carbide technologies. [ABSTRACT FROM AUTHOR]

The incorporation of a significant amount of organic materials in the fabrication process of Al 2 O 3 ceramics using digital light processing (DLP) 3D printing technology leads to a noticeable reduction in mechanical properties compared to those prepared using traditional methods. To enhance its mechanical performance of Al 2 O 3 ceramics, the addition of MgO and MgO-Y 2 O 3 sintering additives, along with a three-step curing method, has resulted in significant improvements. Al 2 O 3 ceramics fabricated with the addition of MgO exhibited a flexural strength of 454.2 MPa, Vickers hardness of 20.24 GPa and apparent porosity of 0.15 %. Similarly, the addition of MgO-Y 2 O 3 yielded Al 2 O 3 ceramics with a flexural strength of 491.6 MPa, Vickers hardness of 20.91 GPa, and apparent porosity of 0.11 %. These values exceed the typical flexural strength of Al 2 O 3 ceramics prepared using traditional methods. This research provides a fundamental basis for the production of high performance, dense, and complex shaped Al 2 O 3 ceramics using DLP 3D printing technology. [ABSTRACT FROM AUTHOR]

The incorporation of a significant amount of organic materials in the fabrication process of Al 2 O 3 ceramics using digital light processing (DLP) 3D printing technology leads to a noticeable reduction in mechanical properties compared to those prepared using traditional methods. To enhance its mechanical performance of Al 2 O 3 ceramics, the addition of MgO and MgO-Y 2 O 3 sintering additives, along with a three-step curing method, has resulted in significant improvements. Al 2 O 3 ceramics fabricated with the addition of MgO exhibited a flexural strength of 454.2 MPa, Vickers hardness of 20.24 GPa and apparent porosity of 0.15 %. Similarly, the addition of MgO-Y 2 O 3 yielded Al 2 O 3 ceramics with a flexural strength of 491.6 MPa, Vickers hardness of 20.91 GPa, and apparent porosity of 0.11 %. These values exceed the typical flexural strength of Al 2 O 3 ceramics prepared using traditional methods. This research provides a fundamental basis for the production of high performance, dense, and complex shaped Al 2 O 3 ceramics using DLP 3D printing technology. [ABSTRACT FROM AUTHOR]

Core-shell hierarchical structured composites have demonstrated great advantages in numerous energy storage devices. In particular, structured composites with rationally structural components and controllable morphology are the most effective in enhancing electrochemical properties. In this work, MnO 2 @NiCo 2 O 4 @Ti 3 SiC 2 /CC (carbon cloth) core-shell hierarchical structured composites were designed and successfully synthesized via electrospinning followed by a two-step hydrothermal reaction. The Ti 3 SiC 2 /CC nanofibers and core-shell nanoarrays were able to improve the specific capacitance and cycling stability. In the three-electrode system, the specific capacitance of MnO 2 @NiCo 2 O 4 @Ti 3 SiC 2 /CC was observed as 1938.2 F/g at a current density of 1 A/g, while the rate capability retention was observed as 81.7% between 1 and 10 A/g. Furthermore, a superior cycling stability was observed following 5000 cycles with a specific capacitance retention rate of 55.4%. Employing MnO 2 @NiCo 2 O 4 @Ti 3 SiC 2 /CC as the all solid-state supercapacitor positive electrode exhibited a high energy density of 58.0 W h/kg at the power density of 800 W/kg. Results demonstrate the potential of the MnO 2 @NiCo 2 O 4 @Ti 3 SiC 2 /CC as an electrode material with phenomenal electrochemical properties for supercapacitors. [ABSTRACT FROM AUTHOR]

Abstract Graphene oxide (GO) is one of the most important ceramic-toughening candidates due to its outstanding physical and chemical properties. In this paper, nacre-like alumina ceramics reinforced with GO have been prepared by freeze casting followed by hot pressing. The experimental results showed that a laminated structure with homogeneous distribution of GO was obtained in the composites. Microstructural analysis, relative densities, flexural strength and fracture toughness of the samples were investigated to reveal the effect of GO. Higher flexural strength and fracture toughness (~380 MPa and ~7.5 MPa m1/2, respectively) were achieved and the multiple length-scale toughening mechanisms of composites contributed to the improved mechanical properties. The results show that it is a promising method to enhance the mechanical properties of nacre-like alumina by the addition of GO. [ABSTRACT FROM AUTHOR]

Abstract Bimetallic carbides with high activity and stability are promising potential materials for energy-storage application. However, the researches about Fe 2 MoC as electrode material on supercapacitors are comparatively weak, and the processing methods of Fe 2 MoC were also relatively few. Herein, a simple hydrothermal method, combining with carbothermic treatment at 900 °C, is explored to fabricate molybdenum iron carbon (Fe 2 MoC) successfully. Chitosan is not only a carbon source, but also a chelating agent to form bimetallic carbide rather than two separated monometallic carbide during the high-temperature treatment. Fe 2 MoC nanoparticles possessing large specific surface, high activity, stability and small resistance were the promising candidate for electrode material. Systematic electrochemical characterizations have verified the Fe 2 MoC (chitosan as carbon source) possesses a specific capacitance (97.7 F/g at a current density of 0.5 A/g), high rate capability (97.0% capacitance retention from 0.5 to 10 A/g) and cycling stability (83.9% capacitance retention after 1000 cycles) in 1 M KOH. In addition, it offers the energy density of 6.74 Wh/kg at a power density of 21 kW/kg. In view of the low-cost and excellent performance, Fe 2 MoC will hold great promise in energy-storage field for supercapacitors. [ABSTRACT FROM AUTHOR]

Well-dispersed boron nitride nanosheets (BNNSs) reinforced fused silica composites were successfully fabricated by surface modification assisted flocculation method. Surface modification can enhance the performance of flocculation process. BNNSs were homogeneously mixed with fused silica through the electrostatic interaction between hydroxylated BNNSs with negative charge and amino-modified fused silica with positive charge. The BNNSs can act as excellent nanofillers for enhancing the mechanical properties of fused silica composites. Approximately 74% and 48% increases in flexure strength and fracture toughness can be achieved for the 1.5 wt% BNNSs/fused silica composite, respectively. The toughening mechanisms were analyzed by microstructural characterization, especially for pull-out mechanism. [ABSTRACT FROM AUTHOR]

The microstructure and mechanical properties of (Hf 0.2 Nb 0.2 Ta 0.2 Ti 0.2 Zr 0.2)B 2 high-entropy boride (HEB) were first predicted by first-principles calculations combined with virtual crystal approximation (VCA). The results verified the suitability of VCA scheme in HEB studying. Besides, single-phase (Hf 0.2 Nb 0.2 Ta 0.2 Ti 0.2 Zr 0.2)B 2 ceramics were successfully fabricated using boro/carbothermal reduction (BCTR) method and subsequent spark plasma sintering (SPS); furthermore, the effects of different amounts of B 4 C on microstructure and mechanical properties were evaluated. Due to the addition of B 4 C and C, all samples formed single-phase solid solutions after SPS. When the excess amount of B 4 C increased to 5 wt%, the sample with fine grains exhibited superior comprehensive properties with the hardness of 18.1 ± 1.0 GPa, flexural strength of 376 ± 25 MPa, and fracture toughness of 4.70 ± 0.27 MPa m1/2. Nonetheless, 10 wt% excess of B 4 C coarsened the grains and decreased the strength of the ceramic. Moreover, the nanohardness (34.5–36.9 GPa) and Young's modulus (519–571 GPa) values with different B 4 C contents just showed a slight difference and were within ranges commonly observed in high-entropy diboride ceramics. [ABSTRACT FROM AUTHOR]

Uniformly dispersed boron nitride nanosheets (BNNSs) reinforced silicon nitride (Si 3 N 4) composites were prepared by surface modification assisted flocculation combined with SPS sintering. In order to improve the dispersibility of the BNNSs in the composites, the liquid phase stripped BNNSs are surface functionalized by a two-step covalently modification. The amino-modified BNNSs (NH 2 -BNNSs) and Si 3 N 4 powders have opposite surface potential, mixed evenly by electrostatic interaction during flocculation. The results showed that mechanical properties of Si 3 N 4 composites were obviously enhanced by adding NH 2 -BNNSs. The fracture toughness and bending strength of Si 3 N 4 composites added 0.75 wt% NH 2 -BNNSs were increased by 34% and 28%, respectively, compared with monolithic Si 3 N 4. Toughening mechanisms are synergistic action of the torn, pull-out or bridging of BNNSs and crack deflection mechanisms with microstructural analyzes. The dielectric properties of the Si 3 N 4 ceramics are also improved after the addition of NH 2 -BNNSs. [ABSTRACT FROM AUTHOR]

Boron nitride nanosheets (BNNSs)/magnesium oxide (MgO) composites were prepared via hot pressing. Mechanical properties of MgO ceramics were improved obviously in virtue of adding BNNSs. The bending strength of the 1 wt% BNNSs/MgO composite increased by about 85% than that of the monolithic MgO. The fracture toughness increased by 34% with the addition of 1.5 wt% BNNSs. Microstructural analyzes have shown that the toughening mechanisms are combinations of the pull-out and bridging of BNNSs, crack deflection, and crack bypassing mechanisms. The addition of a small amount of BNNSs don't destroy the excellent dielectric properties of composites. The dielectric constant of the sample doped with 1 wt% BNNSs was about 9.5 in the whole X-band and the vast majority of P-band, and the loss tangent was less than 5 × 10−3 in 10–15.8 GHz. [ABSTRACT FROM AUTHOR]