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The (TiZrHfNbTaMo)C‐15 wt.% Co ceramics with excellent comprehensive properties were successfully prepared by vacuum liquid phase sintering. The effects of WC content on the grain size, microstructure, and mechanical properties were investigated. The results showed that WC was dissolved into (TiZrHfNbTaMo)C phase to form a seven‐component solid solution, and the independent WC phase disappeared. The addition of WC improved the wettability between the ceramic phase and the metal phase and promoted the densification of the ceramics. In addition, WC played a role in refining grains and inhibiting the grains growth to a certain extent. The comprehensive properties of ceramics were improved by solid solution strengthening and high entropy effect. When the WC content was 5 wt.%, the toughness reached the maximum of 9.41 ± 0.15 MPa·m1/2, and the hardness of the ceramic with 10 wt.% WC achieved the highest value of 18.18 ± 0.20 GPa. [ABSTRACT FROM AUTHOR]

This study prepared textured (Ti1/3Zr1/3Hf1/3)B2 medium‐entropy ceramics for the first time that maintain enhanced flexural strength up to 1800°C using single‐phase (Ti1/3Zr1/3Hf1/3)B2 powders, slip casting under a strong magnetic field, and hot‐pressed sintering methods. Effects of WC additive and strong magnetic field direction on the phase compositions, orientation degree, microstructure evolution, and high‐temperature flexural strength of (Ti1/3Zr1/3Hf1/3)B2 were investigated. (Ti1/3Zr1/3Hf1/3)B2 grain grows along the a,b‐axes, resulting in a platelet‐like morphology. Pressure parallel and perpendicular to the magnetic field direction can promote the orientation degree and hinder the texture structure formation, respectively. Reaction products of W(B,C) and (Ti,Zr,Hf)C between (Ti1/3Zr1/3Hf1/3)B2 and WC additive can efficiently refine the (Ti1/3Zr1/3Hf1/3)B2 grain size and promote grain orientation. (Ti1/3Zr1/3Hf1/3)B2 ceramics doped with 5 vol.% WC yielded a Lotgering orientation factor of 0.74 through slip casting under a strong magnetic field (12 T) and hot‐pressed sintering at 1900°C. Furthermore, cleaning the boundary by W(B,C) and introducing texture can enhance the grain‐boundary strength and improve its high‐temperature flexural strength. The four‐point flexural strength of textured (Ti1/3Zr1/3Hf1/3)B2‐5 vol.% WC ceramics was 770 ± 59 MPa at 1600°C and 638 ± 117 MPa at 1800°C. [ABSTRACT FROM AUTHOR]

Background and Objectives: The sticky surface of cooked noodles seriously reduces consumer acceptance. This study investigates the effects of 12 wheat flour samples with different farinograph and pasting characteristics on the texture, sensory properties, and surface tackiness of recooked frozen cooked noodles (FCNs). Findings: The recooked FCNs made of flour sample 1# with long dough stability time (DST) and high farinograph quality number (FQN) had a low surface tackiness (411 g) and high evaluation score (87). Meanwhile, wheat flour (sample 12#) with high peak viscosity (PV) had a proper degree of starch gelatinization, which would bring a low surface tackiness to FCNs. FCNs (sample 1#) had a high water‐holding capacity (T21 = 0.14 ms) and low unbound water content (A23 = 1.38%), and they had a dense internal gluten network structure. Conclusions: The dense structure formed by protein and starch contributed to reducing the surface tackiness of FCNs after recooking and storing. Noodles factories should choose wheat flour which has long DST, high FQN, and high PV as raw material when producing FCNs. Significance and Novelty: This study provides important information on choosing wheat flours suitable for making FCNs of high quality. [ABSTRACT FROM AUTHOR]

Herein, CoCrxCuFeMnNi (x = 0, 0.5, 1.0, 1.5, and 2.0, in molar ratio) high‐entropy alloys (HEAs) are prepared through vacuum hot‐pressing sintering. The influences of Cr content on the microstructure and the corrosion behavior in 3.5% NaCl solution are studied. The alloys are mainly composed of two face‐centered cubic (FCC) phases, namely, Cr–Co–Fe–Mn–Ni (or Co–Fe–Mn–Ni)‐rich FCC1 phase and Cu–Mn–Ni‐rich FCC2 phase. With the increase of Cr content, The FCC1‐phase area expands and the FCC2 phase area shrinks. In 3.5% NaCl solution, the corrosion current density (icorr) and average corrosion rate (Vcorr) of the HEAs decrease with the increase in Cr content. The icorr and Vcorr of Cr2.0 alloy are lower at 1.87 × 10−6A cm−2 and 0.02 mm year−1, respectively. The increase of transfer resistance (Rp) and decrease of relative thickness (CPE1−1) of the passivation film indicate that the more difficult it is for ions in the corrosive medium to pass through the capacitor layer, the better the corrosion resistance of the alloy. Improvement of the corrosion resistance is mainly due to the formation of denser Cr2O3 passivation film and reduction of the segregation degree of Cu in the FCC2 phase. [ABSTRACT FROM AUTHOR]

It is thought that the sintering of high‐entropy (HE) ceramics is generally more difficult when compared to that of the corresponding single‐component ceramics. In this paper, we report a novel approach to densify the HE carbide ceramics at relatively low temperatures with a small amount of silicon. Reactive spark plasma sintering (SPS) was used to densify the ceramics using powders of HE carbide and silicon as starting materials. Dense ceramics can be obtained at 1600 ‐1700°C. X‐ray diffraction analysis reveals that only non‐stoichiometric HE carbide phase with carbon vacancy and SiC phase exist in the obtained ceramics. The in‐situ formed SiC phase inherits the morphology of the starting silicon powder owing to the slower diffusion of silicon atoms compared to that of the carbon atoms in HE carbide phase. The mechanical properties of the prepared ceramics were preliminarily studied. [ABSTRACT FROM AUTHOR]

We report for the first time the synthesis of a core‐shell structured composite powder with a core of Zr(Ti,Ta)C and a shell of Ti,Ta(Zr)C at 1700°C and investigate the formation mechanism for the core‐shell structure. The medium‐entropy (Ti,Zr,Ta)C ceramics with fine grains (1.1 ± 0.4 μm) and relative density of 94.8% was prepared by hot‐pressing at 2100°C. The flexural strength of (Ti,Zr,Ta)C at 1000°C (493 ± 21 MPa) was close to the room temperature (511 ± 52 MPa). As the temperature increased from 1600°C to 1800°C, the flexural strength was increased significantly, with an ultra‐high flexural strength of 725 ± 32 MPa at 1800°C. The existence of the core‐shell structure in the powder suppressed the grain growth due to the sluggish diffusion effect. The ultra‐high strength of (Ti,Zr,Ta)C ceramics was attributed to its fine microstructures, high fracture toughness, and the reinforced the grain boundary strength. [ABSTRACT FROM AUTHOR]

Medium‐entropy (Ti,Zr,Hf)C ceramics were prepared by hot pressing a dual‐phase medium‐entropy carbide powder with low oxygen content (0.45 wt%). The results demonstrate that the medium‐entropy (Ti,Zr,Hf)C ceramics sintered at 2100°C had a relative density of 99.2% and an average grain size of 1.9 ± 0.6 μm. The flexural strength of (Ti,Zr,Hf)C carbide ceramics at room temperature was 579 ± 62 MPa. With an increase in temperature to 1600°C, the flexural strength showed an increase up to 619 ± 57 MPa, and had no significant degradation even up to 1800°C. The high‐temperature flexural strengths of (Ti,Zr,Hf)C were obviously higher than those of the monocarbide ceramics (TiC, ZrC, and HfC). The primary strengthening mechanism in (Ti,Zr,Hf)C could be attributed to the high lattice parameter mismatch effects between TiC and ZrC, which not only inhibited the fast grain coarsening of (Ti,Zr,Hf)C ceramics, but also increased the grain‐boundary strength of the obtained ceramics. [ABSTRACT FROM AUTHOR]

Abstract: A volatility diagram of zirconium carbide (ZrC) at 1600, 1930, and 2200°C was calculated in this work. Combining it with the existing volatility diagrams of ZrB2 and SiC, the volatility diagram of a ternary ZrB2‐SiC‐ZrC (ZSZ) system was constructed in order to interpret the oxidation behavior of ZSZ ceramics. Applying this diagram, the formation of ZrC‐corroded and SiC‐depleted layers and the oxidation sequence of each component in ZSZ during oxidation and ablation could be well understood. Most of the predictions from the diagrams are consistent with the experimental observations on the oxidation scale of dense ZrB2‐SiC‐ZrC ceramics/coatings after oxidation at 1600°C or ablation at 1930 and 2200°C. The reasons for the discrepancy are also briefly discussed. [ABSTRACT FROM AUTHOR]

Dense, highly textured Zr B2 and Zr B2- Mo Si2 ceramics were fabricated via a strong magnetic field alignment method followed by spark plasma sintering. Unlike with the previous studies, which only focused on the alignment of single-phase particles, both Zr B2 and Mo Si2, which exhibited a magnetic anisotropy, have been aligned in this study. The alignment of Mo Si2 in the same direction of Zr B2 enhanced the degree of orientation of Zr B2, decreased the grain size, but increased the aspect ratio of the platelet Zr B2 grains. The microstructure and anisotropic mechanical properties as well as the oxidation resistance in different directions were discussed. [ABSTRACT FROM AUTHOR]

HfC-30 vol% SiC ceramics with a relative density of 99.7% was obtained by pressureless sintering at 2300°C for 0.5 h. The resultant ceramics showed fine microstructure with HfC grain size around 1 μm. The hardness (20.5 ± 0.2 GPa), bending strength (396 ± 56 MPa), and fracture toughness (2.81 ± 0.18 MPa·m1/2) of HfC-30 vol% SiC ceramics were at least 20% higher than those of monolithic HfC ceramics. The influences of SiC particle size, volume fraction, and the oxide impurity on the microstructure evolution of HfC-based ceramics were examined. The results indicate that SiC addition and the oxygen impurity introduced by ball milling play opposite roles in the HfC grain growth during sintering. The oxide impurity introduced by ball milling caused the HfC grain coarsening, whereas SiC particles inhibited the grain growth of HfC significantly. [ABSTRACT FROM AUTHOR]

Influence of boron on densification and microstructure of zirconium diboride ( ZrB2) ceramics using pressureless sintering has been studied. The ZrB2 powders were synthesized by borothermal reduction of ZrO2 with three different ZrO2/ B ratios to produce powders nominally phase pure or that contained excess boron. The as-synthesized powders were then densified by heating to temperatures from 1800°C to 2200°C. The incorporation of 1.2 wt% excess boron increased relative density from ~54.3% to ~96.1% by reacting with and removing oxide impurities ( ZrO2 and B2 O3) after sintering at 2000°C, whereas it also led to an exaggerated grain growth from 1-3 to 20-80 μm presumably due to high grain-boundary mobility. The faster grain growth resulted in the formation of intragranular pores and prevented the ZrB2 ceramics from reaching full density. By the incorporation of 3 wt% excess boron, a fully dense ZrB2 ceramics with relative density of ~99.7% and grain size of 5-10 μm was obtained at 2000°C. The full densification was attributed to the synergistic effects of boron through oxide impurities removal and grain- growth inhibition. [ABSTRACT FROM AUTHOR]

The influence of carbon impurities on phase composition, microstructure, and mechanical properties of hot-pressed ZrB2-SiC ceramics was studied. Carbon was either present in the starting ZrB2 powders or introduced due to the carbon-rich sintering environment. Carbon present in the starting ZrB2 powders removed the inherent oxygen impurities to enable ceramics that appeared phase pure by X-ray diffraction, had smaller average grain sizes, and had higher Vickers' hardness, but lower fracture toughness. Carbon introduced from the sintering environment led to the formation of secondary ZrC, allowed the microstructure to coarsen, and decreased the fracture toughness. This study showed that ZrB2-SiC ceramics with refined microstructure could be obtained by introducing carbon impurities in the starting ZrB2 powders, whereas the densification should be carried out at lower temperature to avoid the carbon uptake from sintering environment. [ABSTRACT FROM AUTHOR]

Binderless tungsten carbide ceramics were produced by reactive spark plasma sintering, using tungsten nitride and carbon black as starting materials. The phase and microstructure evolution during the sintering process was investigated. It was found that the tungsten nitride decomposed into nano tungsten with a particle size of about 25 nm firstly, and then reacted with carbon black to form carbides. Due to the high activity of the in situ formed carbides, samples could be densified at a temperature as low as 1350°C. The bulk carbides possessed an average grain size of 270 nm and Vickers' hardness of 25.4 GPa. [ABSTRACT FROM AUTHOR]

A ZrB2–SiC–ZrC composite was prepared from a mixture of zirconium, silicon, and B4C via reactive hot pressing at a relatively low temperature (1800°C) for 60 min under 20 MPa in an argon atmosphere. The relative density was 96.8%, the micro-hardness (Hv10) was 16.7 GPa, and the fracture toughness was 5.1 MPa·m1/2. The presence of ZrC was helpful for the densification process and improved the mechanical properties of the composite. A model of the microstructure development of the composite was proposed to explain the phase distribution. [ABSTRACT FROM AUTHOR]