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The effects of CaO/SiO 2 ratio (basicity) and CaCl 2 addition amount on the properties of CaO–MgO–Al 2 O 3 –SiO 2 –CaCl 2 glass-ceramics (GC) were investigated. When sintered at 825 °C, the increase in basicity from 0.35 to 0.75 reduced the porosity of GCs from 1.1 to 0.8 vol%, but the increase of CaCl 2 addition amount from 5 to 10 wt% increased the porosity from 0.8 to 7.0 vol%. The main crystalline phase of GC changed from augite (Ca(Mg 0 · 7 Al 0.3) (Si 1 · 7 Al 0.3)O 6) to Ca 10 Al 12 Cl 2 Si 5 O 37 by increasing the CaCl 2 addition amount to 7.5 wt%. The increase in CaCl 2 addition had adverse effects on the bending strength and Vickers hardness, while the rise in basicity deteriorated the bending strength but had little impact on the Vickers hardness. This study may have a guiding significance for preparing slag-based GCs and treating CaCl 2 -containing wastes. [ABSTRACT FROM AUTHOR]

The microstructures and mechanical properties of two new aerospace Al-6.00 Mg-0.40Mn-0.12Zr (wt%) alloy sheets, containing 0.10 wt% Sc (low content) and 0.25 wt% Er(cheap), respectively, were investigated by tensile tests and electron microscopy methods. The results showed that microalloying elements were present in the form of core-shell-structured secondary Al 3 (Sc 1−x Zr x) and Al 3 (Er 1−x Zr x) nanoparticles, whose cores were enriched in Sc and Er, respectively. Stable core-shell structured nanoparticles enabled the annealed sheets to retain a completely non-recrystallized structure and strong β-fiber rolling textures. The ultimate tensile strength (UTS), yield strength (YS) and elongation to failure (El f) of the annealed sheets reached 422 ± 1 MPa, 312 ± 6 MPa, and 20.7 ± 1.5% in the Al-Mg-Mn-Sc-Zr alloy, and 404 ± 5 MPa, 283 ± 7 MPa, and 24.2 ± 0.9% in the Al-Mg-Mn-Er-Zr alloy, respectively, both exhibiting high strength and superior ductility. The mean diameters of the spheroidal Al 3 (Sc 1−x Zr x) and Al 3 (Er 1−x Zr x) particles were 12.1 ± 4.2 nm and 20.2 ± 8.4 nm, respectively, meantime, the number densities of the Al 3 (Sc 1−x Zr x) and Al 3 (Er 1−x Zr x) precipitates were (7.7 ± 3.2) × 1013 m2 and (6.4 ± 1.9) × 1012 m2. The higher number density and the smaller particle sizes of the Al 3 (Sc 1−x Zr x) leaded to the higher strength of the Al-Mg-Mn-Sc-Zr alloy. The main strengthening mechanisms from the secondary Al 3 (Sc 1−x Zr x)/Al 3 (Er 1−x Zr x) nanoparticles were associated with the direct Orowan precipitation strengthening and sub-structure strengthening. Based on the results of this paper, enhanced mechanical properties and a reduced cost can be simultaneously achieved with the new Al-Mg-Mn-Zr alloys with low Sc contents or inexpensive Er addition, offering great potential for the development of new high-strength micro-alloyed Al Mg alloys in industrial applications. Unlabelled Image • Successfully prepare two new Al-Mg-Mn alloys with secondary Al 3 (Sc 1−x Zr x) and Al 3 (Er 1−x Zr x) nanoparticles • Characterize the microstructure evolution of new alloy sheets during their preparations • Clarify the existing forms of the combined additions of low-content Sc and Zr or Er and Zr • Discuss the potential for developing new cost competitive Al-Mg-Mn-Sc-Zr/ Al-Mg-Mn-Er-Zr alloys [ABSTRACT FROM AUTHOR]

Abstract In the present work, the hydrogen reduction of commercial MoO 2 with the assistance of molten salt has been investigated at 720–850 °C. In the case of no salt addition, the prepared Mo particles maintained the big platelet shape of raw MoO 2 powders. However, after adding a small amount of salt (0.1% NaCl KCl binary salt, MgCl 2 KCl binary salt, or LiCl mono salt), Mo nanoparticles were prepared successfully. It was found that a small amount of molten salt can help Mo to nucleate dispersedly and its growth via chemical vapor transport (CVT) mechanism can be controlled by reducing temperature. At 750 °C, when the NaCl KCl binary salt was used, the obtained Mo nanoparticles had both good dispersion and small average size of about 70 nm. Kinetics analyses indicated that the rate controlling step for the hydrogen reduction of MoO 2 was the interface chemical reaction, and after adding salt, the reaction rate constant decreased dramatically, relative to that without salt. The extracted activation energies for pure MoO 2 , MoO 2 with 0.1% NaCl KCl binary salt and MoO 2 with 0.1% LiCl mono salt were 76.13 kJ/mol, 117.45 kJ/mol and 97.23 kJ/mol, respectively. Highlights • Mo nanoparticles were prepared via salt-assisted reduction of MoO 2 by H 2. • The addition of salt can help Mo to nucleate dispersedly. • Chemical reaction is the rate controlling step, and salt decreases ate constant. [ABSTRACT FROM AUTHOR]

This is the first comprehensive review on inherent anisotropic features of transition metal diboride (MB 2 ) and their implementation for tailoring the microstructure and properties of MB 2 -based Ultra-high temperature Ceramics (UHTCs). The emphasis is on the processing approaches, microstructures, and properties of self-reinforced and/or textured MB 2 -based composites with elongated MB 2 grains. The crystal structure characteristics and grain growth behaviour of MB 2 are also critically reviewed. Benefiting from the tailored microstructure, the MB 2 -based ceramics exhibit some improved properties. Considering the success of Si 3 N 4 ceramics in the field of structural ceramics, it is expected that the potential MB 2 -based ceramic composites with abundant elongated MB 2 grains, textured structures, and controlled grain boundaries would possess improved fracture toughness, thermal shock resistance, and reliable high-temperature properties, which are desired for their practical applications. Accordingly, microstructure designing and tailoring provide an important perspective for the future development of UHTCs. [ABSTRACT FROM AUTHOR]

In this paper, a novel process about the silicothermic reduction of molybdenum disulfide was proposed to prepare molybdenum silicides. This new method has a short process, which is beneficial for energy saving, environmental protection and cost reduction relative to the traditional methods by using pure molybdenum and silicon as the raw materials. It was found that the phase compositions and microstructures of products were greatly influenced by the molar ratio of Si to MoS 2 and temperature. From the experimental results, it was concluded that MoSi 2 , Mo 5 Si 3 and Mo 3 Si can be prepared when the temperature was above 1100 °C, 1300 °C and 1500 °C, and the Si/MoS 2 molar ratio was 4, 2.6 and 7/3, respectively. When the Si/MoS 2 molar ratio was less than 4 and the temperature was below 1100 °C, only one Mo-Si compound (MoSi 2 ) was generated; while above 1200 °C, the excessive MoS 2 could react with MoSi 2 to generate Mo 5 Si 3 , but Mo 5 Si 3 can't react with excessive MoS 2 below 1300 °C; until above 1400 °C, Mo 5 Si 3 and MoS 2 can react to generate Mo 3 Si. However, even at 1600 °C, excessive MoS 2 couldn't react with Mo 3 Si but can be decomposed. Besides molybdenum silicides, other products SiS or SiS 2 can also be generated. SiS could escape from sample at 1100 °C in the form of gas while SiS 2 couldn't. Both the increases of temperature and molar ratio of Si to MoSi 2 were beneficial for the decrease of the residual sulfur content in the final products. From the experimental results, it was found that as increasing the temperature or the molar ratio of Si to MoS 2 from 7/3 to 4, the grain size of products increased and the sintering phenomenon among grains was more and more obvious. [ABSTRACT FROM AUTHOR]

Lightweight Al 2 NbTi 3 V 2 Zr alloy was fabricated through mechanical milling and vacuum hot pressing. The effects of milling on the microstructure, phase evolution, and hardness of the fabricated alloy were investigated. High-energy (HE) milling decreased the size of crystalline grains and activated the powders for subsequent sintering. HE-annealed powders at above 900 °C and all sintered bulks consisted of body-centered cubic (BCC) and intermetallics α and β. Low-energy (LE) milling only provided homogeneity to the powders. LE bulks exhibited a microstructure similar to that of HE bulks at 1450 °C–1550 °C. The hardness of the HE bulk was higher than that of the LE bulk and exhibited a peak value of 781 HV at 1250 °C. All Al 2 NbTi 3 V 2 Zr bulks possessed low density ranging from 5.05 g/cm 3 to 5.25 g/cm 3 . Two empirical equations for hardness of the bulks were proposed for the BCC matrix bulks and simple cubic matrix bulks respectively and the estimated results are consistent with the experimental measurements. [ABSTRACT FROM AUTHOR]

SiC and ZrC were used to tailor microstructures and improve properties of hot-pressed ZrB 2 -based ceramics. Grain growth kinetics and microstructural stability during annealing were studied. Compared with ZrC, SiC grains grew slower and were more effective to inhibit ZrB 2 grain growth. ZrB 2 –20SiC–20ZrC (number in vol%) had the finest and the most stable microstructure, indicating synergistic effects of SiC and ZrC on grain growth. Also, ZrC and SiC played different roles on mechanical properties. Thermal residual stresses on SiC particles decreased from ∼800 MPa in ZrB 2 –SiC to ∼400 MPa in ZrB 2 –SiC–ZrC, due to the plastic deformation of ZrC. Crack deflection around ZrC grains was the major toughening mechanism (∼1 MPa m 1/2 ) in ZrB 2 –ZrC-based ceramics. The flexural strengths of ZrB 2 –SiC–ZrC were improved to 800 MPa, due to smaller SiC cluster sizes and lower residual stresses. ZrB 2 –20ZrC had the largest Weibull modulus of 14.1, and the modulus decreased with an increase in SiC content. [ABSTRACT FROM AUTHOR]

Despite of good oxidation resistance and ablation resistance, challenge to densify and tendency to loss high temperature (H.T.) strength have limited its potential applications in aerospace for HfB 2 –SiC ceramic. In this work, dense HfB 2 –SiC ceramic with improved H.T. flexural strength was prepared using WC as sintering aid. Pure HfB 2 –SiC ceramic exhibited creep deformation at 1600 °C with measured strength value of 389 ± 82 MPa, whereas WC doped sample showed much higher flexural strength of 658 ± 69 MPa with linear elastic behavior prior to fracture. In addition to clean grain boundary, the addition of 5 vol.%WC into HfB 2 –SiC ceramic promoted the formation of fine (Hf,W)B 2 , (Hf,W)C and WB precipitates. This combinative effect is responsible for its excellent H.T. mechanical property of WC doped HfB 2 –SiC ceramic. [ABSTRACT FROM AUTHOR]

Highlights: [•] Fine-grained Mo–12Si–8.5B alloys were prepared by hot pressing sintering. [•] The microstructure control is achieved by mechanical alloying process. [•] The yield stress and especial the flexure strength of alloys are superior. [ABSTRACT FROM AUTHOR]

Abstract: Binderless WC ceramics were prepared by reactive spark plasma sintering, using tungsten trioxide, tungsten and carbon black as the starting materials. Phase assemblages and microstructure of the as-sintered ceramics were investigated. It was found that graphite existed as an impurity phase due to the volatilization of WO3, and W could compensate for the WO3 loss to form WC with a single phase. Benefiting from the enhanced sinterability, WC ceramics with high relative density and good hardness could be obtained at temperature as low as 1500°C. [Copyright &y& Elsevier]

ZrB2–20vol% SiC (ZS) ceramics based on ZrB2 starting powders obtained by different boro/carbo-thermal reductions involving ZrO2 +B4C, ZrO2 +B4C+C, and ZrO2 +B, were fully densified by hot pressing at 1900–2000°C. The flexural strength of these ZS ceramics was measured from room temperature up to 1600°C. At 1600°C, the flexural strength of the ceramics is 460±31, 471±32 and 345±11MPa, respectively. The evolution of the strength as function of temperature is explained in terms of the differences in oxygen content, nature of fracture, grain sizes, grain boundary phases and microstructural defects. [ABSTRACT FROM AUTHOR]

ZrB2–SiC–ZrN composites were fabricated by reactive hot pressing using Zr, Si3N4, and B4C powders as starting materials. Sintering was conducted at temperatures of 1800 to 2000°C under a load of 20MPa in Ar atmosphere. The composite was densified at 2000°C. The in situ formed BN flakes which distributed uniformly at the grain boundaries were identified by X-ray diffraction and scanning electron microscopy. The formation of h-BN phase and its effect on the mechanical properties of the composite are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Fully dense titanium nitride (TiN) ceramic was irradiated using a 100keV Ar ion beam at 600°C and at target fluences of 3×1017 ionscm−2, corresponding to 115 displacements per atom (dpa). X-ray diffraction and transmission electron microscopy were performed to evaluate the irradiation damage in the TiN. The lattice parameter increased and the lattice expanded by 0.19% after irradiation due to interstitial atoms and vacancies in Ar-irradiated TiN. Hills, bubbles and dislocations were observed. It is noteworthy that many TiN grains pulled out after irradiation and that amorphization of oxide grain boundaries was observed using high-resolution transmission electron microscopy, which indicates that the oxygen-containing impurities are potentially fatally dangerous to the radiation resistance property of TiN and other candidate materials. [Copyright &y& Elsevier]

Abstract: The densification of hot-pressed ZrN ceramics doped with Zr or Ti have been investigated at 1500–1700°C. It is shown that either Zr or Ti additive can facilitate the densification process. ZrN with 20mol% Zr or Ti (named ZNZ and ZNT) sintered at 1700°C can achieve above 98% relative densities whereas densification temperature up to 2000°C is necessary for pure ZrN. The densification improvements are attributed to solid solution of Zr or Ti into ZrN to form non-stoichiometric ZrN1−x or (Zr, Ti)N1−x . The microstructures and mechanical properties of ZNZ and ZNT samples have been examined. Large grain size and flat fracture surface existed in ZNT sample sintered at 1700°C, which lead to poor toughness as low as 2.3MPam1/2. On the contrary, the fracture toughness of ZNZ sample sintered at 1700°C was up to 5.9MPam1/2, attributed to fine and uniform grain size distribution. [Copyright &y& Elsevier]

Abstract: Zirconium carbide and hafnium carbide ceramics were prepared by reactive spark plasma sintering, using oxides and carbon black as the raw materials. The phase and microstructure evolution during the sintering process was investigated. It was found that ZrC and HfC powder intermediates were formed at 1750 and 1800°C, respectively. Due to the high sinterability of the in situ formed carbide particles, samples with a fine microstructure could be densified at a relatively low temperature. [Copyright &y& Elsevier]

Abstract: Four-point flexure creep deformation of ZrB2–30vol% SiC ceramics in argon atmosphere under a static load of 19MPa for 0–100h at 1500 and 1600°C was investigated. The strain rate at 1600°C was 3.7 times higher than that at 1500°C. Microstructural evolution during creep consisted of nucleation and growth of triple-point cavitations which were always associated with SiC particles. Due to the low stress, only isolated cavitations were nucleated, and no microcracks were formed. For up to 100h at 1500 and 1600°C, the grains maintained their size and shape. The cavitations in both size and number showed no obvious difference from 26 to 100h at 1500°C, whereas that showed a significant increase from 26 to 100h at 1600°C. Present study suggested that ZrB2–30vol% SiC exhibited relatively good microstructural stability and creep resistance at 1500°C in argon atmosphere. [Copyright &y& Elsevier]

The initial stage of oxidation process of HfB2–20 vol.% SiC composite at 1500°C in air was investigated. With no holding, the oxide scale is composed of a discontinuous SiO2-rich glass layer and an imperfect SiC-depleted layer. Detailed analysis showed that the imperfect SiC-depleted layer contained an HfB2 matrix with partially oxidized HfB2 and SiC particles enclosed in graphite, which revealed that the formation of the SiC-depleted layer during oxidation resulted from the active oxidation of SiC with C as an initial product. [ABSTRACT FROM AUTHOR]

Abstract: Mo–Si alloy sheets with different silicon content were fabricated by powder-metallurgical and thermo-mechanically processing. The effect of Si content and annealing temperature on microstructure and hardness of the Mo–Si alloys were studied by using optical microscopy (OM), transmission electron microscopy (TEM) and Vickers hardness tester, respectively. The results indicated that the presence of Si can effectively refine the grain sizes and improve the hardness of Mo–Si alloys. Si can also increase the recrystallization temperature of alloys and play a significant role in restraining the grain growth at high temperatures. Increasing the annealing temperature, the microstructure of Mo–Si alloy sheets is gradually coarsened and changed from fibrous to equiaxed structure, causing reduction in hardness. The hardening effect in the Mo–Si alloys came from the refined grain strengthening, solid solution strengthening, and second phase particle strengthening, which are closely dependent on the Si content and annealing temperature. [Copyright &y& Elsevier]

Abstract: Oxidation behavior and effect of oxidation on the room-temperature flexural strength were investigated for ZrB2–10vol% SiC (ZB10S) and ZrB2–30vol% SiC (ZB30S) in air at 1500°C with times ranging from 0.5h to 10h. The oxide scale of both ZB10S and ZB30S was composed of an outer glassy layer and an inner extended SiC-depleted layer. The changes in weight gain, glass layer thickness, and extended SiC-depleted layer thickness with oxidation were measured. Analysis suggested that the extended SiC-depleted layer was most indicative for evaluating the oxidation resistance. Compared to the ZB10S, the improved oxidation resistance in ZB30S was attributed to the viscosity increase of glassy layer and the lower number of ZrO2 inclusions in the glassy layer. Because of the healing of surface flaws by the glassy layer, the strength increased significantly by ∼110% for ZB10S and by ∼130% for ZB30S after oxidation for 0.5h. [Copyright &y& Elsevier]

A pressureless sintering process with two pre-sintering heat treatments was developed for the densification of HfB2. The use of two isothermal holdings, at 1650 and 2000°C, prior to the final sintering temperature (2200°C) proved to be more effective at removing oxygen impurities and rearranging the initial powder compact microstructure. The mechanical properties of HfB2 with 2wt.%B4C, including hardness (19.5GPa), E modulus (529GPa) and strength (469MPa), were comparable to hot-pressed samples or higher than the values using other sintering aids. [Copyright &y& Elsevier]

Abstract: The isothermal oxidation of ZrB2 powder was carried out in the range of 650–800°C in a flowing air using thermogravimetric analysis (TGA). The evolution of the phase characterization and morphology of ZrB2 powder oxidized at 700°C for varying durations was studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The excellent fit of TG curves by multiple-law model suggests that the oxidation of ZrB2 powder in air follows para-linear kinetics, and based on the fitted results, oxidation mechanisms can also be obtained. The reaction product of ZrB2 powder with oxygen is metastable tetragonal ZrO2 at 700°C, and the tetragonal phase transforms to the monoclinic phase with oxidation. The oxidation of ZrB2 powder is associated with surface microcrack formation, which is attributed to volume expansion resulting from oxidation of ZrB2 to tetragonal ZrO2 and tetragonal-to-monoclinic phase transformation of ZrO2. In the last stage of oxidation, each ZrB2 particle breaks into fragments. [Copyright &y& Elsevier]

Abstract: Lanthanum oxide doped molybdenum alloy wires with different diameters were prepared by using the powder metallurgy method and press working technology. The strength were experimentally determined and related to the microstructures. The effects of the oxides mass fractions and wires diameter on the microstructures and on the mechanical properties of the molybdenum alloy wires were quantitatively investigated. Results showed that the microstructure of the doped molybdenum alloy wires will be refined with increasing the oxides mass fractions and reducing wire diameter, resulting in the increase in the yield strength. The quantitative relationships between the yield strengths and the volume fraction of lanthanum oxide particles and the subgrain sizes were presented. Calculations show that the lanthanum oxide particles strengthening effect, fine substructural strengthening effect and dislocation strengthening effect are the main strengthening mechanisms of the lanthanum oxide doped molybdenum alloy wires. [Copyright &y& Elsevier]

Abstract: The Berry phase of a bipartite system described by a Heisenberg XXZ model driven by a one-site magnetic field is investigated. The effect of the Dzyaloshinski–Moriya (DM) anisotropic interaction on the Berry phase is discussed. It is found that the DM interaction affects the Berry phase monotonously, and can also cause sudden change of the Berry phase for some weak magnetic field cases. [Copyright &y& Elsevier]

Four kinds of composites, ZrB2–SiC, ZrB2–SiC–ZrC, ZrB2–SiC–ZrN and ZrB2–SiC–AlN, were synthesized in situ via reactive hot pressing (RHP) and reactive spark plasma sintering (R-SPS), using Zr, Si, B4C, BN and Al as raw materials. The synthesis process plays a critical role in the microstructural features of the composites obtained. The R-SPS process can lead to a more homogeneous and finer microstructure due to its high heating rates and short holding time, while the RHP process is likely to result in coarse microstructures due to a long enough holding time for grains growth. [Copyright &y& Elsevier]

The site-directed covalent immobilization of amino-terminated DNA oligonucleotides on microstructured patterns at silicon surfaces generated by the methodology of electron beam (EB) lithography was investigated. The microstructured patterns characterized by scanning electron microscopy (SEM) revealed remarkably regular in size and shape. After treatment with different time of activation (10 s and 30 min), self-assembled layers of 3-aminopropyltriethoxysilane (APTES) on silicon surfaces characterized by X-ray photoelectron spectroscopy (XPS) were demonstrated to obtain similar N 1s peaks. The immobilization specificity was evaluated by means of 5′ amino-modified oligonucleotides labeled with Cy 5 at its 3′ end attached onto microstructured patterns. The high-density DNA array (40,000 spots per cm2) was achieved, and the resulting array exhibited the specific binding due to DNA–DNA interaction. Additional studies indicated hardly visible signals when non-complementary probes were immobilized on the microstructured patterns. The deposition of DNA in a microstructure array using this technique is precise and homogeneous, showing the potential for high-density information storage and the miniaturization for biosensors and biochips. [Copyright &y& Elsevier]

Hexagonal graphitic boron nitride (h-BN) composites show excellent corrosion and thermal shock resistance, good mechanical tolerance and machinability, especially Si3N4–BN and Sialon–BN composites; they have already been used as break rings for horizontal continuous casting of steel. However, the strength of the conventionally processed BN composites were remarkably degraded by the addition of BN due to the poor densification behavior and the existence of large BN flakes or agglomerates of BN flakes that acted as fracture flaws. This means that BN dispersoids with fine particle size and homogeneous distribution are the key factors to obtain high strength composites. By in situ process, such microstructural features can be realized. In this work, by using the proposed in situ reactions, synthesis, microstructures and properties of various in situ nonoxide-boron nitride (Nobn) composites including SiC–BN, Si3N4–BN, AlN–BN, Sialon–BN and Alon–BN composites were investigated. For some Nobn composite systems, due to the large volume expansion during the reaction processes, near-net shape sintering can be realized. For example, the sintering shrinkage of AlN-30 vol.% BN was 3.1% and that of Alon-21 vol.% BN was 4.2%. This will be an advantage for the fabrication of large and complicated products. [Copyright &y& Elsevier]

The AlCrMoZrTi/(AlCrMoZrTi)N multilayer high-entropy nitride ceramic films (HENCFs) fabricated by reactive RF magnetron sputtering presented (200) preferentially oriented FCC crystal structures. With the increase in the modulation period, the nitrogen content and surface roughness of the multilayer films gradually increased, the template effect between the nanocrystalline and amorphous forms was weakened, and the multilayer interface structure decreased. The S4 film with a modulation period of 1500 nm had the highest hardness and modulus (16.6 and 225.7 GPa, respectively) and the highest H/E* and H3/E*2 values. The results of friction experiments showed that the S1 film with the smallest modulation period had a stable friction coefficient and small wear rate on both Si and Cu substrates, and it exhibited the best friction and wear performance due to its low surface roughness, high toughness and compressive yield resistance, and dense multilayer structure. The friction mechanisms of the HECNFs on Si and Cu substrates were mainly adhesive wear, abrasive wear, and a small amount of oxidative wear. [ABSTRACT FROM AUTHOR]

Abstract: Sodium iron silicate (NaFe(III)[SiO3]2) nanorods have been synthesized using iron nitrate (Fe(NO3)3) and sodium silicate (Na2SiO3) solutions by means of hydrothermal method. The mixture solution is processed in hydrothermal autoclave first at 180–200 °C for two days and then dried at 70 °C to obtain nanotructured NaFe(III)[SiO3]2. It was revealed that NaFe(III)[SiO3]2 nanorod with the average diameter of ~15 nm and length of several hundreds nm was confirmed by X-ray power diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Cyclic voltammeter (CV) and electrochemical impedance spectra (EIS) investigations show that this kind of NaFe(III)[SiO3]2 nanostructures have evident and stable electrochemical redox behavior between potential range of −0.1–0.55 V in alkaline solution. [Copyright &y& Elsevier]

Abstract: Pure molybdenum and molybdenum alloys doped with two- or three-components rare earth oxide particles were prepared by powder metallurgy. Both the tensile property and fracture toughness of the pure molybdenum and multi-components rare earth oxide-doped molybdenum alloys were determined at room temperature. The multi-components rare earth oxide-doped molybdenum alloys are fine grained and contain a homogeneous distribution of fine particles in the submicron and nanometer size ranges, which is why the molybdenum alloys have higher strength and fracture toughness than pure molybdenum. Quantitative analysis is used to explain the increase in yield strength with respect to grain size and second phase strengthening. Furthermore, the relationship between the tensile properties and microstructural parameters is quantitatively established. [Copyright &y& Elsevier]

• SiO 2 -CaO-Al 2 O 3 -Na 2 O typed glass ceramics were synthesized. • Hardness of sample gradually decreased with the increase of temperature. • Flexural strength of sample first increased and then decreased with temperature. • Hardness and flexural strength have maximum values as prolonging sintering time. • CaO/SiO 2 ratio has a significant effect on the composition of crystalline phase. The SiO 2 -CaO-Al 2 O 3 -Na 2 O glass ceramics were prepared by the melting-sintering method. For samples with a CaO/SiO 2 ratio of 0.23, wollastonite was the only crystal phase after heat treatment for 2h in the temperature range of 800–1000 °C, and a maximum flexural strength of 99.39 MPa can be achieved at 900 °C. When the sintering time was extended from 2 h to 40 h at 800 °C, the metastable phase Na 2 CaSiO 4 first appeared, but then disappeared as the heat treatment continued. The maximum hardness and flexural strength were achieved at the sintering time of 20 h in this case. Furthermore, when the CaO/SiO 2 ratio was increased from 0.23 to 0.45 under the same heat treatment conditions (800 °C for 20 h), the main crystalline phase transformed from wollastonite to Na 2 CaSiO 4 , besides nepheline (NaAlSiO 4) and SiO 2. The existence of the nepheline enhanced the mechanical properties of glass ceramics. [ABSTRACT FROM AUTHOR]

In this work, dense TiB 2 -B 4 C based ceramics with different amounts of h BN additions were spark plasma sintered at 1700−1850 °C through in-situ reactions involving with TiC x N 1-x (x = 0.5 and 0.7) and boron. The molar Gibbs' free energy of TiCN is lower than that of TiC and TiN, thereby the boronizing of TiCN is more favorable in multiple steps which suppressed the combustion process in the TiCN-B system. Taking advantage of this, the reaction rate in the TiCN-B system was dragged to accompany with that of densification, resulting that nanometric TiB 2 grains were gradually produced and microstructures composed of B 4 C- h BN reinforcement and TiB 2 – h BN(C) matrix were finally built. Although h BN additions reduce the Young's modulus, TiB 2 -B 4 C composites with 17.4 vol% h BN additions densified at 1700 °C still exhibit excellent mechanical properties. The present study suggests solid solution powders are a class of promising reactants for achieving nanoceramics with better performance. [ABSTRACT FROM AUTHOR]

In this article, ultrafine-grained W–Ni–Fe composite with medium W content was successfully fabricated via methods composed of spray-drying, two-stage reduction and low-temperature sintering. It is noticed that the variation of matrix phase fractional volume was effective to tailor the microstructure, mechanical performance and deformation behavior. The microstructure of the medium heavy alloy (MHA) underwent the obvious change from traditional coarsen W grains (>40 μm) to those with sizes of only 3.5 μm, accompanied by a large number of nanosized W precipitate. The two main fracture types of MHA are the W cleavage fracture and matrix phase ductile rupture. The additions of Mo and La 2 O 3 revealed three kinds of strengthening effects, including fine-grained, solid-solution and dispersion strengthening. Experimental results showed that a significant enhancement in tensile properties (∼972.5 MPa and 26.5%) were benefitted from the cooperation of multiple strengthening and plasticized mechanisms, and the detailed effects of deformed twinning and precipitation strengthening were analyzed. The current findings demonstrated that MHA possessed an outstanding combination of strength and ductility and was a promising alternative to conventional tungsten heavy alloys (WHAs) for a more extensive range of applications. • Ultrafine-grained W–Ni–Fe alloy with medium W content was fabricated successfully. • The MHA possessed a superior combination of excellent strength and good ductility. • The interfacial bonding characteristics among W, matrix and La 2 O 3 were analyzed. • The formation process of the transition interfacial layer is elaborated. • The precipitation of nanosized W grains and deformed twin strengthened the MHA. [ABSTRACT FROM AUTHOR]

zirconium oxycarbide (ZrC x O y ) ceramics were hot pressed using ZrC-5ZrO 2 and ZrC-5ZrO 2 -5Zr (number in mol%) mixtures as starting powders, and the solid solution and densification processes were investigated. When 5 mol% ZrO 2 were added to ZrC matrix, ZrC x O y and CO were formed during the reaction between ZrC and ZrO 2 occurred above 1600 °C. And the sintered ZrC x O y ceramic had numerous pores. However, the co-doping of ZrO 2 and Zr could reduce the reaction temperatures and CO amounts in ZrC-5ZrO 2 -5Zr system, resulting in a near fully dense ZrC x O y ceramic. The chemical composition of obtained ZrC x O y ceramics were also calculated according to oxygen content and reaction processes. [ABSTRACT FROM AUTHOR]

Ultrafine WC-VC/Cr 3 C 2 composite powders with uniform distribution of V/Cr were synthetized by a novel method composed of carbothermic reduction of the mixture of WO 3 and V 2 O 5 /Cr 2 O 3 at 1050 °C and the following carburization process at 1300 °C under hydrogen atmosphere. The effects of addition amount of VC or Cr 3 C 2 on the phase constitution, particle size and micromorphology of WC-VC/Cr 3 C 2 composite powders were investigated. The results revealed that W, C, V/Cr elements were evenly distributed in the WC-VC/Cr 3 C 2 composite powders. Moreover, the particle size of WC-0.5wt.%VC composite powder was obviously smaller than that of pure WC powder, but decreased slightly with the further increase of VC content. Furthermore, it was found that the inhibition result of Cr 3 C 2 on WC grain growth was significantly worse than that of VC. In terms of micromorphology, pure WC and WC-VC powder had the round shaped WC particles originated from the isotropic growth, while there were triangular prism shaped WC particles because of the faceting of WC particles caused by the minimization of surface energy in WC-Cr 3 C 2 composite powders. Moreover, there were also a few WC particles with the layer-by-layer microstructure owing to the anisotropic growth under the action of Cr 3 C 2. • Ultrafine WC-VC/Cr 3 C 2 powders were prepared by reduction‑carbonization process. • Particle size of WC-VC was obviously smaller than that of pure WC powder. • WC and WC-VC powders had round shaped WC particles resulted from the isotropic growth. • WC-Cr 3 C 2 powder show triangular prism shaped WC particles because of the faceting of WC. [ABSTRACT FROM AUTHOR]

Combining spray drying and in-situ synthesized technology, WC-10Co cemented carbides with uniform composition was prepared by vacuum sintering to investigate the effects of different CeO 2 contents (0 wt%, 0.5 wt%, 1 wt%, 2 wt%, 4 wt%) as well as co-doping with CeO 2 and VC on the microstructure and mechanical properties. With increasing CeO 2 addition from 0 wt% to 0.5 wt%, the WC grain size decreased from 0.79 ± 0.35 μm to 0.62 ± 0.24 μm. The hardness, fracture toughness and transverse rupture strength (TRS) of the alloy with 0.5 wt% CeO 2 all reached the maximum values of 1752 ± 28 HV 30 , 18.50 ± 0.35 MPa·m1/2 and 2245 ± 35 MPa, respectively, which indicated that the mechanical properties of cemented carbide could be simultaneously improved by adding 0.5 wt% CeO 2 to refine the WC grains. However, as the CeO 2 content increased to 4 wt%, the hardness gradually decreased, while the fracture and TRS all slightly decreased first and then tended to be stable. Moreover, the corrosion resistance of alloys first increased and then decreased with the increase of CeO 2 content. The 0.5 wt% CeO 2 alloy had the best corrosion resistance. After adding 0.5 wt% VC, the grain size of alloys became smaller and distribution of Co binder was more uniform. Compared to the samples with only added CeO 2 , the alloy with co-addition of 0.5 wt% CeO 2 and 0.5 wt% VC exhibited the best comprehensive mechanical properties. The hardness, fracture toughness and TRS of the alloy with co-addition of 0.5 wt% CeO 2 and 0.5 wt% VC were 1987 ± 44 HV 30 , 16.10 ± 0.34 MPa·m1/2 and 2023 ± 78 MPa, respectively. [Display omitted] • Ultrafine-grained WC-10Co alloy was prepared by spray drying and in-situ synthesis. • Adding CeO 2 was beneficial to improve the comprehensive properties of the alloy. • The refinement effect of co-doping was better than that of adding only CeO 2. [ABSTRACT FROM AUTHOR]

The effect of temperature on the passive film structure and corrosion performance of CoCrFeMoNi HEA was studied. The results indicated that the passive films exhibited a bilayer structure, where Co and Mo were segregated in the outer film, while Cr was enriched in the inner layer. The content of Fe and Mo species in the passive films decreased with rising temperature, leading to the passive film degradation. The CPT of the HEA was 50–60 ℃. The HEA suffered from selective dissolution of FCC phase below 50 ℃ during the potentiodynamic polarization tests, while pitting corrosion occurred above 60 ℃. • Cr and Mo was enriched in the passive films of the HEA. • Distribution of cation elements within the bi-layered passive films was discussed. • The content of Fe and Mo species in the passive films decreased with raising temperature. • Selective corrosion of the (Cr, Mo)-depleted FCC phase was found. • The CPT value of the HEA was between 50 and 60 ℃. [ABSTRACT FROM AUTHOR]

SiC and HfC were used to tailor microstructures and improve properties of hot pressed HfB 2 -based ceramics. SiC and HfC particle, as the second phase, could hinder grain growth of HfB 2 . Compared with HfC, SiC grains grew slower, which was more effective to hinder grain growth of HfB 2 . The ternary ceramics HfB 2 –20vol%HfC–20vol%SiC had the finest microstructure, indicating the effect of SiC and HfC on grain growth. Several SiC clusters were found on related fracture surfaces. Large SiC clusters can cause high levels of residual stress and stress concentration, which are harmful to mechanical properties of boride-SiC ceramics. The predominant fracture mode of HfB 2 –20vol%SiC was transgranular, however, in HfB 2 –10vol%HfC–10vol%SiC and HfB 2 –20vol%HfC–20vol%SiC ceramics, the dominating fracture mode shift from transgranular to intergranular. With the incorporation of HfC, the fracture toughness of HH10S10 and HH20S20 increased to 4.34 MPa m 1/2 and 5.05 MPa m 1/2 , which were 17.3% and 26.7% higher than HS20 (3.72 MPa m 1/2 ), respectively. The flexural strengths of HfB 2 –HfC–SiC ceramics were improved to ~750 MPa, which were about 1.3 times higher than that of HfB 2 –20SiC. [ABSTRACT FROM AUTHOR]

New low-loss NiZrNb 2 O 8 microwave dielectric ceramics were synthesized via conventional mixed oxide route. The morphology, crystal structure and microwave dielectric properties were investigated. It exhibited a monoclinic wolframite crystal structure, with the space group of P2/c ( C 2 h 4 ) . The lattice energy was carried out to evaluate the structural stability and sintering characteristics. Two kinds of grain shapes in dense samples, with similar elements ratios, were observed. Variations in the dielectric constant (ε r ) were analyzed by relative density and porosity-corrected polarizability. The quality factor (Q × ƒ) was correlated with packing fraction and grain growth. The temperature coefficient of resonant (τ ƒ ) was depended on the dielectric constant. The typical microwave dielectric properties of NiZrNb 2 O 8 were ε r = 23.77, Q × ƒ = 40280 GHz, τ ƒ = −27.5 ppm/°C, sintered at 1200 °C. [ABSTRACT FROM AUTHOR]

The Al-27Si alloy was prepared using spray deposition and subsequently incorporated into Mg-Li alloy by vacuum melting furnace to produce a novel Mg-8Li-3Al-0.3Si (LA83–0.3Si) duplex alloy. The effect of final rolling deformation (30%, 40%, 50% and 60%) on the microstructure, mechanical properties, work hardening, and softening behavior was researched. Results indicated that the LA83–0.3Si alloy mainly comprised of α-Mg, β-Li, AlLi, and Mg 2 Si phases. The rolling deformation process induced elongation of the α-Mg and β-Li phase along rolling direction, facilitating the formation of α/β laminar structure, notably enhancing the strength and ductility. Increased final rolling deformation further prompted the formation of the α/β laminar structure and refined the precipitates. Consequently, the LA83–0.3Si alloy's strength progressively increased while elongation slightly diminished. At 60% deformation, the ultimate tensile strength of the LA83–0.3Si alloy reached 331 MPa, with the elongation sustained to 10.9%. The rolling process led to a reduction in the work hardening rate and an increase in the softening rate. With the increase of the final rolling deformation, the work hardening rate decreases and the softening rate further increases. However, the work hardening rate increases, and the softening rate decreases due to the decreasing of the hardness ratio of α-Mg and β-Li phases at 60% deformation. [Display omitted] • The low-sized granular Mg 2 Si phase was formed by adding Al-27Si master alloy prepared by spray deposition to Mg-Li alloy. • The highest strength of the alloy sheet with large final rolling deformation is 331 MPa, and the EL is maintained at 10.9%. • The layer structure weakens the hardening behavior of Mg-Li alloy and improves the softening behavior. [ABSTRACT FROM AUTHOR]

Toughened ZrB 2 –SiC composites have been prepared by an introduction of amorphous carbon spheres. After hot pressing, microstructure observation showed that the carbon phases were present in the form of thin layer at grain boundaries, or in the form of agglomerates at the multigrain junctions. The carbon spheres led to significant improvement of fracture toughness from 4.96 ± 0.46 MPa m 1/2 to 7.52 ± 0.19 MPa m 1/2 . The toughening mechanism was attributed to the weak interfaces, which occurred due to the presence of carbon layer formed at grain boundaries after sintering. [ABSTRACT FROM AUTHOR]

Two different modes of placing powders in a graphite die were used in a spark plasma sintering system: loading a conductive green body (zirconium nitride, ZrN, or titanium nitride, TiN) into a non-conductive bed (boron nitride) or loading the ZrN or TiN powders into the die directly. The ceramics obtained, which had completely different morphologies, have been characterized in this work. Through experimental and theoretical analysis, possible formation mechanisms of microstructural differences have been proposed. [Copyright &y& Elsevier]

ZrB2-20vol% SiC composites added with 3vol% Yb2O3 were hot-pressed at 1900°C, and then heat-treated at 2000°C in argon. The effect of heat treatment on phase composition, microstructure, and mechanical properties of the composites was investigated. Results showed that the high temperature heat treatment led to the depletion of Yb-containing phases by decomposition or evaporation, the formation of some pores at multiple-grain junctions, significant microstructural coarsening with the increase of ZrB2 grain size from ∼1.9μm to ∼4.8μm, and the change of fracture mode from mixed inter/transgranular to fully transgranular. In addition, Vickers' hardness, fracture toughness and flexural strength were severely degraded after heat treatment. [ABSTRACT FROM AUTHOR]

W-Cu immiscible bimetallic composite is an electrically and thermally conductive material with high temperature service potential. In present work, to improve its load bearing capacity, Ti and Zr were introduced to enhance the W-Cu interfacial bond strength and to achieve solid solution reinforcement. By infiltration of Cu-Ti/Zr alloy with different compositions into the W skeleton, both the strength and hardness were enhanced without sacrificing ductility. The Ti/Zr incorporation transformed the incoherent interface of W-Cu to a (W-Ti/Zr)-(Cu-Ti/Zr) semi-coherent interface. By utilizing the EDS technique, significant compositional interdiffusion between immiscible metals was revealed. Moreover, the introduction of Ti/Zr purified grain boundaries by capturing the reactive oxygen to generate TiO 2 and ZrO 2 , which inhibited W-Ti/Zr grain growth by Zenner pinning. As the alloy content rose from 0 wt% to 5 wt%, the average grain size of the W-Ti/Zr (or W) alloy decreased from 2.14 µm to 1.40 µm. It is noteworthy that the alloying with 2.50 wt% Ti reached peak microhardness (417 HV), bending strength (1546 MPa), and ultimate tensile strength (532 MPa). However, the presence of Cu-Ti/Zr solid solution and oxide particles increased the scattering effect of electrons in the Cu matrix, leading to a falling in electrical conductivity. • Well-bonded W-Cu-Ti/Zr alloys were fabricated by skeleton infiltration strategy. • The W-Cu-Ti/Zr alloys possessed high strength and great strain-to-failure. • Second-phase particles affected microstructure and overall mechanical properties. • Multiple strengthening mechanisms of W-Cu-Ti/Zr were analyzed in detail. [ABSTRACT FROM AUTHOR]

Abstract: This work reported submicrometric HfB2powder synthesis by a new borothermal reduction route using HfO2 and boron as raw materials. The particle size of HfB2 powders by conventional borothermal reduction was ~2.1μm. HfB2 particle coarsening mainly depended on the presence of B2O3 product. To obtain HfB2 powders with small particle size, new borothermal reduction route was developed. This route included the borothermal reduction of HfO2 with boron at 1100°C, washing by hot water, and the removal of residual B2O3 at 1550°C, namely, two-step reduction plus intermediate water-washing. Based on the new route, the particle size of HfB2 powders decreased to ~0.8μm. Finally, the hot-pressing densification of the synthesized powders was studied. [Copyright &y& Elsevier]

Abstract: This work investigated high-temperature four-point bending deformation of hot-pressed ZrB2 ceramics with WC additive at 1900°C for 0–60min in argon atmosphere under a static load of 25MPa. After 60min bending deformation, about 8% strain was achieved without apparent macroscopic cracks, suggestive of superplastic behavior at 1900°C. The tensile side and the compressive side of the deformed samples exhibited different microstructural characteristics. On the tensile side, many cavities were observed at the multigrain junctions and the fracture surface was relatively flat. On the compressive side very few cavities occurred and some large cracks were present on the fracture surface. The presence of a secondary W-containing phase formed by the addition of WC, prohibited the coalescence of cavities by its plastic deformation. [Copyright &y& Elsevier]

Abstract: The microstructural evolution of ZrB2–20vol% MoSi2 composites during heat treatment with and without pressure at 2000°C for 1h in argon was investigated. Results showed the materials exhibited a multiphase layered structure after heat treatment without pressure. From surface to center, the layered structure consisted of (1) a Mo layer, (2) a Si layer, (3) a ZrB2–MoSi2 layer and (4) a partially MoSi2-depleted ZrB2 layer. The formation mechanism of layered structure was analyzed. After heat treatment with pressure, the materials with high toughness mainly contained ZrB2 phase. [Copyright &y& Elsevier]

Abstract: This work compared phase composition, microstructures and mechanical properties of ZrB2—20vol.% SiC—5vol.%Yb2O3 prepared by hot pressing (HP) and spark plasma sintering (SPS) in vacuum. Despite the same raw material composition, the two densification techniques led to the appearance of different secondary phases. The HP ceramics had coarsened microstructure, predominantly intergranular fracture characteristic and high fracture toughness. The SPS ceramics exhibited refined microstructure, transgranular fracture model and high bending strength. [Copyright &y& Elsevier]

Abstract: Experiments and numerical simulations with Phase Field Model and Finite Element Analysis were carried out to investigate the phase separation dynamic properties and the corresponding thermal aging degradation mechanism. Experimental results from transmission electron microscopy and atomic force microscopy show that thermal aging causes the Cr-rich phase precipitate and form clusters. A phase field dynamic model was developed with constitutive relations and empirical potential functions to investigate the phase separation dynamics in the ferrite phase. Numerical results integrated with cell dynamical system method show clearly the micro structure morphology and the phase separation coarsening with aging time. The evolution process of the phase separation was quantitatively illustrated and reproduced macroscopically. The scattering pattern becomes clearer and the corresponding radius becomes smaller along with the increasing aging time. The average characteristic length increases firstly then decreases and enters a more stable stage. With the increment of the local Cr concentration, the evolution of the phase morphology was quite different. Finite Element Analysis simulation results with the Gurson–Tvergaard–Needleman void model show that the damage initiated more easily in the ferrite matrix for the Cr atoms forming clusters with increasing aging time. The phenomenological simulations with Phase Field Model and Finite Element Analysis were in remarkably good agreement with experimental results and analytical considerations. [Copyright &y& Elsevier]

The influence of the spark plasma sintering (SPS) heating rate on densification, microstructure and strength of ZrB2–20vol.% SiC composites with or without 5vol.% Yb2O3 addition was assessed. A low heating rate promoted densification, induced grain growth and slightly increased the strength in the Yb2O3-free ceramics, whereas the low heating rate inhibited the densification, maintained the grain size and greatly decreased the strength in the Yb2O3-doped composites. [Copyright &y& Elsevier]