Recently, WSe2 as a typical transition metal dichalcogenide compound has attracted extensive attention due to its potential applications in electronic and optoelectronic devices. However, WSe2 alone cannot be directly used as a photocatalyst due to its inferior performance possibly caused by the strong recombination of photogenerated electron–hole pairs. Here a novel C fibers@WSe2 nanoplates core–shell composite (NPCSC) was successfully synthesized via facile, one-step thermal evaporation, in which numerous WSe2 thin nanoplates were in situ, densely and even vertically grown on the surface of the C fibers. Such composite presents highly solar-driven photocatalytic activity and stability for the degradation of various organic aqueous dyes including methylene blue and rhodamine B, and highly harmful gases like toluene, showing the great potential for environmental remediation by degrading toxic industrial chemicals using sunlight. Under simulated sunlight irradiation, comparing with commercially available WSe2 powder, the as-synthesized C fibers@WSe2 NPCSC presents significantly enhanced reaction rate constants by a factor of approximately 15, 9, and 3 for the degradation of aqueous methylene blue, aqueous rhodamine B, and gaseous toluene, respectively, due to the effective separation of photogenerated electron–hole pairs promoted by the rapid transfer of photogenerated electrons through C fibers. Moreover, this one-step thermal evaporation is an easy-handling, environmentally friendly, and low-cost synthesis method, which is suitable for large-scale production.Keywords: C fiber; composite; in situ synthesis; mechanism; solar-driven photocatalysis; WSe2 nanoplates;

Lead-free 0.912Ba0.97TiO3–0.088(Bi0.5Na0.5)TiO3–xTa2O5 (0 ≤ x ≤ 0.005) ceramics with positive temperature coefficient of resistivity (PTCR) were prepared by solid reaction sintering of high-purity metal oxides and carbonates reagents. The doping effect of Ta5+ ions on the microstructure and electrical properties of the samples was investigated. X-ray diffraction analysis indicated that all the samples were of a single tetragonal perovskite structure with the calculated c/a value first increased and then decreased with increasing x. The Raman shift at 305 cm−1 became strong firstly and then declined, and the broad band at 722 cm−1 narrowed initially and then broadened with the increase in Ta5+ content. The Curie temperature raised first and then decreased, presenting the highest value up to 170 °C for the samples with x = 0.001. Moreover, after the incorporation of Ta5+ ions, the PTCR (defined by the resistivity jump with the ratio of maximum to minimum ones) decreased first and then increased, presenting the best PTCR performance for the samples with x = 0.005. And with increasing x, the room temperature resistivity decreased first and then increased, displaying the lowest room temperature resistivity for the samples with x = 0.003.

•Novel carbon fibers @ semiconductors nanostructures core–shell composites.•General, low-cost, and environmentally friendly synthesis method.•Highly efficient solar-driven photocatalysts for environmental pollutants.•Mechanism for improved photocatalytic activity.The photocatalytic activity of transition metal dichalcogenides (TMDCs) can be improved by loading them on carbon materials, which can reduce the recombination of photogenerated electrons and holes. However, the already existing approaches to producing carbon–TMDC nanocomposites have been complicated and time-consuming, and have involved the use of organic solvents or sometimes of dangerous chemicals. Here, we report a one-step strategy for the large-scale in situ synthesis of C fibers@MX2 (M = W or Mo; X = S or Se) nanoplates core–shell composites simply by heating mixtures of cheap polyacrylonitrile fibers and metal oxides in S or Se vapor. The photocatalytic performance of the as-synthesized composites was evaluated by the degradation of methylene blue, rhodamine B, Cr(VI), and E. coli. Surprisingly, such composites exhibited greatly improved photocatalytic activity and excellent stability under full-spectrum light irradiation. This strategy is a general, low-cost, and environmentally friendly solution for the synthesis of highly efficient semiconductor photocatalysts for industrial applications.Download high-res image (61KB)Download full-size image

Uniform CdS coated AuAg alloyed double-walled nanotubes were successfully fabricated by solvothermal process using Ag nanowires as the template. UV–vis-NIR extinction spectra revealed that the obtained double-walled nanotubes can present an enhanced light absorption ability compared with both pure AuAg alloyed nanotubes and CdS nanowires. Photocurrent and electrochemical impedance spectroscopy measurements indicated that such double-walled structure could significantly extend the lifetime of photo-generated carriers and increase the light-harvesting efficiency of CdS, due to the low charge transfer resistance and a high carrier transfer rate of the double-walled structure. The growth mechanism of such kind of nanotubes was also proposed.Download high-res image (67KB)Download full-size image

Ni-Zn ferrites with a nominal composition of Ni0.5Zn0.5HoxFe2-xO4 (x = 0–0.06) were prepared by conventional solid state reaction through using analytical-grade metal oxides powders as raw materials. The phase composition, microstructure, magnetic properties and dielectric performance of the as-prepared samples were investigated. The doped Ho3+ ions could enter into the crystal lattice of the resultant spinel ferrites, causing the expansion of the unit cell, reaching a saturated state when x = 0.015; and the additional Ho3+ ions would form a foreign HoFeO3 phase at the grain boundary. The grain size and densification of the samples initially decreased after a small amount of Ho3+ ions was doped, but then increased with more Ho3+ ions added. The saturation magnetization decreased gradually with increasing substitution level of Ho3+ ions. The Curie temperature and coercivity raised initially and declined later with increasing content of Ho3+ ions in the samples, reaching their maximums of 305 °C with x = 0.015 and 2.99 Oe with x = 0.03, respectively. The variation of complex permeability versus Ho3+ ions substitution level presented an opposite trend to that of coercivity. The dielectric loss increased slightly after the introduction of a small amount of Ho3+ ions, but reduced significantly with more Ho3+ ions doped.

Novel AuAg@CdS double-walled nanotubes (DWNTs) were successfully fabricated through a three-step solvothermal method, starting with silver nanowires as the template. In the DWNTs, a uniform layer of a CdS shell is coated onto the AuAg nanotubes, finally forming the one-dimensional nanocomposites. Nonlinear optical analysis indicated that the plasmon–exciton interaction in the AuAg@CdS DWNTs induced an obviously saturated absorption response under visible light excitation, in contrast to individual AuAg nanotubes and CdS shells. Furthermore, the effective nonlinear absorption coefficient of the AuAg@CdS DWNTs was 7 times larger than that of the CdS shell, which was attributed to the local field enhancement effect. Such a unique morphological configuration and optical properties make AuAg@CdS DWNTs an ideal candidate for next generation nano-photonic devices employed as a mode-locking element, optical switch, and so on.

In this paper, the thermoanalytical investigations on structure and chemical transformation of the Cs–P–W oxides are reported. The thermal decomposition and chemical transformations of solid Cs–P–W oxides prepared through evaporating the mixture solution containing a certain amount of Cs2CO3, (NH4)2HPO4 and (NH4)6PW7O24·6H2O were analyzed using the TG/DTA and X-ray diffraction during heating process at a rate of 5 °C min−1. The results showed that the W/Cs molar ratio significantly influences on the structure and chemical transformation of the Cs–P–W oxides. Besides, the influence of the support on the structure transformation is also investigated and found that the cesium tungsten oxides (CsW2O6) and cesium phosphotungstate salts (CsxH3−xPW12O40) are formed on the surface of γ-Al2O3 and SiO2, respectively, due to different interactions of component with supports.

Two-dimensional layered chalcogenide WS2, similar to graphene, is considered to be very interesting for materials scientists. However, to make it a useful material platform, it is necessary to develop sophisticated synthesis methods to control its morphology. In this paper, we present a simple approach to prepare various morphologies of WS2 nanostructures by direct thermal evaporation of WO3 and S powders onto Si substrates sputtered with W film without using any nanostructured W-contained precursors and highly toxic sulfide gases. This method can produce bulk quantities of pure hexagonal, horizontally grown WS2 nanoplates, vertically grown nanoplates, and nanoplate-formed flowers simply by tuning the distance between the substrate and source powders. The synthesis mechanism and morphology evolution model were proposed. Moreover, when employed as a thin-film anode material, the Li-ion battery with as-prepared, vertically grown WS2 nanoplates presented a rechargeable performance between 3 and 0.01 V with a discharge capacity of about 773 mAh/cm3 after recycling three times, much better than its already-reported counterparts with randomly distributed WS2 nanosheet electrodes, but the battery with horizontally grown WS2 nanoplates could not show any charge–discharge cycling property, which could be attributed to the different structures of WS2 anodes for Li+ ion intercalation or deintercalation.

Bifunctional catalysts Cs–P/γ-Al2O3 were developed and firstly applied in a one-step synthesis of methyl acrylate using methyl acetate (Ma) and formaldehyde (FA). The catalysts were prepared using impregnation and characterized with X-ray diffraction, transmission electron microscopy, thermogravimetry and differential thermal analysis, nitrogen adsorption–desorption, ammonia- and carbon dioxide-temperature programmed desorption methods. The catalytic performance was evaluated using a fixed-bed microreactor. Experimental results indicated that the P loading had significant influence on the catalytic activity by modifying the acid–base surface properties of the catalyst. The process optimization using response surface methodology was performed and the interactions of operational variables including the Ma/FA molar ratio, reaction time and temperature were elucidated. Then the kinetics of the aldol condensation reaction was studied using a pseudo-homogeneous kinetic model. In addition, the lifetime of optimum Cs10%–P5%/γ-Al2O3 catalyst was evaluated over a continuous period of 400 h, and did not exhibit an obvious decrease in efficiency.

•Bimetallic CuPt alloy nanoparticles with different morphologies have been prepared.•The seed-mediated growth is used as synthetic approach.•The morphology and electronic coupling have effect on the electrochemical property.•The dendritic CuPt alloy nanoparticles display superior electrocatalytic activity.Mastery over the morphology of nanomaterials usually enables control of their properties and enhancement of their usefulness for a given application. Herein, we report a seed-mediated approach for the fabrication of bimetallic copper–platinum (CuPt) alloy nanoparticles with different morphologies. This strategy involves the first synthesis of Cu seed particles with multiple twins, and subsequent nucleation and growth of Pt metal. Then upon the Cu/Pt molar ratios in the synthesis, the rapid interdiffusion of Cu and Pt atoms results in the formation of bimetallic CuPt alloy nanoparticles with polyhedral, stellated, or dendritic morphologies. It has been found that both the morphology and electronic coupling effect between Cu and Pt components have significant effect on the electrochemical property of the alloy particles. In particular, the dendritic CuPt alloy nanoparticles display the highest specific activity for methanol oxidation reaction (MOR) due to their abundant atomic steps, edges, and corner atoms in the dendritic structure, while the polyhedral CuPt alloy particles show best carbon monoxide (CO) tolerant behavior due to the strong electronic donation effect from Cu to Pt atoms.

•ZnxCd1−xS whiskers in silica matrix with novel rib-like structures were reported.•Novel photoluminescence was presented.•Growth mechanism was proposed.ZnxCd1−xS whiskers in silica matrix with novel rib-like structure have been synthesized in high yield by a solid–vapor decomposition route. The whiskers are composed of ZnxCd1−xS rod-arrays grown closely parallel to each other with uniform diameter and length. The photoluminescence spectrum of the whiskers revealed a strong blue light emission peak at 469 nm and a weak one at 533 nm, suggesting their potential applications in short wavelength optoelectronic nanodevices.

•Branched FeWO4@FeS core–shell nanostructures were reported.•Simple and feasible synthesis method was presented.•Growth mechanism was proposed.Branched FeWO4@FeS core–shell nanostructures were synthesized on silicon substrates sputtered with approximately 5 nm of iron thin film via thermal evaporation of WO3 and S powder at 1050 °C in a tube furnace. Both the trunk and branch of the nanostructures are of uniform morphology and well-crystalline structure with diameters in the range of 100–400 nm and lengths up to tens of micrometers. It was proposed that the growth mechanism of the nanostructures was a combination of the classic vapor–liquid–solid and vapor–solid processes.

•Sn0.95-x(Mn0.05,Lix)O2 (0 ≤ x ≤ 0.08) with well retained host structure was prepared.•Sensitivity to Li+ doping level on structure and magnetism evolutions was found.•Sn0.95-x(Mn0.05,Lix)O2 is ferromagnetic at 5 K, but paramagnetic at room temperature.•The saturation magnetization reaches a maximum of Ms = 1.06 μB/Mn when x = 0.06.Sn0.95-x(Mn0.05,Lix)O2 (0 ≤ x ≤ 0.08) with well retained host structure was prepared by using conventional solid sintering method. The structure and magnetism evolutions actually show sensitivity to the Li doping level, although the precise position and real content of Li were hard to be determined by powder X-ray diffraction. The measured magnetic susceptibility indicates that Sn0.95-x(Mn0.05,Lix)O2 is ferromagnetic at 5 K, but paramagnetic at room temperature. The saturation magnetization changes with Li doping level, reaching its maximum of Ms = 1.06 μB/Mn when x = 0.06. Li ions can effectively mediate the density of carriers in Sn0.95Mn0.05O2, further enhancing the magnetic moment at low temperature.

•Binderless WC–ZrC cemented carbides were fabricated.•The addition amount of ZrC nano-powder on WC cemented carbides was optimized.•The addition effect of ZrC nano-powder on WC cemented carbides was investigated.•Combining enhancement mechanisms were proposed.Binderless tungsten carbide with varied amounts of ZrC nano-powder (0–9 wt.%) were prepared by spark plasma sintering at 1600 °C under an applied pressure of 50 MPa. The effect of ZrC nano-powder addition on the densification behavior, phase composition, microstructure and mechanical properties of the composites were investigated. With appropriate amount of ZrC nano-powder, the coarsening and abnormal growth of WC grains were suppressed, resulting in more homogeneous microstructure of the materials. The Vickers hardness, flexural strength and fracture toughness of the as-prepared composites first increased and then decreased with increasing addition fraction of ZrC nano-powder. When the added fraction of ZrC nano-powder was 1 wt.%, the hardness and fracture toughness reached their maximum values of about 2800 HV10 and 8.1 MPa·m1/2, respectively. When the added fraction of ZrC nano-powder was 3 wt.%, the flexural strength presented its maximum value of about 1100 MPa.

Phase transfer techniques possess remarkable advantages for the synthesis of inorganic nanomaterials. In contrast to the abundant reports on the preparation of noble metal nanoparticles using phase transfer, the number of semiconductor nanocrystals syntheses based on phase transfer techniques is still limited. Herein, we report a systematic study of the phase transfer-based synthesis of HgS nanocrystals, including the tuning of their morphology/shape by either solvent choice or temperature. This strategy involves the transfer of Hg(II) ions from aqueous solution to toluene, oleic acid or oleylamine and subsequent sulfidation at room or elevated temperature. Furthermore, we have extended this phase-transfer based strategy to the fabrication of HgS–Au nanocomposites. The studies in this work might provide a facile route for producing HgS nanocrystals with desirable properties and offer an effective strategy to investigate the influence of the morphology of HgS on the physical/chemical properties of various HgS-based materials.

•FeWO4/FeS core/shell nanorods were reported.•Simple and feasible synthesis method was presented.•Growth mechanism was proposed.FeWO4/FeS core/shell nanorods were fabricated on silicon substrate sputtered with approximately 5 nm of iron thin film via simple thermal evaporation of WO3 and S powders at 1000 °C in a tube furnace. The as-prepared nanorods are of uniform morphology in large scale with a diameter of 175±60 nm and a length of 1.4±0.5 μm. Both the core and shell are of well-crystalline structure. Raman spectroscopy revealed that the active optical phonon modes positioned at 873, 820, 690, 322 and 300 cm−1 were assigned to FeWO4, and that at 214 cm−1 to FeS. The growth mechanism of the nanorods was also proposed.

There are many elaborate masterpieces exist in natural world. Learning from nature, people developed serial intelligent biomimetic devices. Biomimetic smart nanochannels received widespread attention for mimicking biological processes in bodies. Excellent stability, tailorable surface characteristics and nano-size effects rend polymer single nanochannel an ideal candidate for constructing sensitive and reproducible biosensors. Nanochannels are responsive for special analytes while appropriate recognition elements are modified in channels wall. In this review, we summarized recent works in contructing biosensors that are using polymer single nanochannels for detecting various analytes.

Ultrafine WC–Ni based cemented carbides with varying fraction of SiC nano-whiskers were fabricated by hot-press sintering at 1400 °C for 60 min under a sintering pressure of 20 MPa and with the assistance of VC and TaC as WC grain growth inhibitors. X-ray diffraction analysis reveals that no SiC phase can be detected. Scanning electron microscopy examination indicates that the sintered samples have WC grains with a mean size of about 400 nm; with small amount of SiC nano-whisker, the samples can be consolidated; but as the added fraction of SiC nano-whisker increases, the agglomeration and inhomogeneous dispersion of the SiC whisker become more and more serious. With increasing added fraction of SiC nano-whisker, the flexural strength and Vickers hardness of the samples first increase and then decrease, indicating that an appropriate addition amount of SiC nano-whisker could improve the mechanical properties of the samples. When the SiC nano-whisker added fraction is 0.53 wt.% and 0.42 wt.%, the flexural strength and Vickers hardness of the samples reach their maximum values of about 1700 MPa and 1910 HV, respectively. The fracture toughness of the samples reaches its highest value of 15 MPa·m1/2 when the added fraction of SiC nano-whisker is 0.53 wt.%.Highlights► WC-Ni based cermets with SiC nano-whisker were fabricated. ► Enhanced cermet mechanical properties were achieved. ► Combining enhancement mechanisms were proposed.

Cemented carbide is an old and well-known WC-based hardmetal, which has been widely applied in geo-engineering as drill buttons and various wear-resistant parts. In order to extend the service life of cemented carbide components and enhance their efficiency for rock drilling under various conditions, the recent research efforts have focused on their failure mechanisms and developing nanostructured, functionally graded and Co-free cemented carbides. With the advance in synthesizing nanosized powders and advent of electric field assisted fast sintering techniques, the consolidation of nanostructured and Co-free cemented carbides and even pure WC materials has been possible; and because of their high hardness and wear resistance, they are much promising in geo-engineering drilling. Functionally graded cemented carbide provides a combination of high wear resistance and toughness in a single component, which is also much favorable for geo-engineering drillers. In addition, by replacing the binder phase Co with Ni or carbide binder, and even without binder phase, the corrosion and oxidation of the resultant materials can be significantly improved without considerable deterioration of fracture toughness.Highlights► To sum up the applications of cemented carbide in geo-engineering. ► To clarify the failure mechanisms of cemented carbide in geo-engineering. ► To review the efforts in developing new conceptual cemented carbide hardmetals.

In order to improve the performances of TiCN-based cermets, researchers have paid much attention directly towards developing various new spices of cermets. The present review will try to sum up the efforts in designing and tailing in compositions and microstructures of TiCN-based cermets in recent years aiming at enhanced cermet properties. The relationship between the cermet constituents and their mechanical properties and wear resistance, as well as the advances in the synthesis of TiCN powders and preparation of TiCN-based cermets were included. Special emphasis was paid on the preparation of ultrafine/nano TiCN-based cermets possessing enhanced hardness, mechanical strength, toughness and wear resistance, which has led to a very recent surge of interest in the development of TiCN-based cermets. In particular, it has been possible to obtain dense TiCN-based cermets with ultrafine- and/or nano-structures by means of fast sintering techniques, such as spark plasma sintering, microwave vacuum sintering and so on.Highlights► To sum up the recent efforts in designing and tailing advanced TiCN-based cermets ► To clarify the relationship between cermet constituents and service performance ► To review the advances in synthesis of nano TiCN powders ► Ultrafine/nano TiCN-based cermets with nano TiCN powders ► Dense ultrafine/nano TiCN-based cermets with fast sintering techniques

•Ultrafine binderless WC-based cemented carbides with AlN nano-powder were fabricated.•The addition effects of AlN nano-powder on WC cemented carbides were investigated.•Combining enhancement mechanisms was proposed.Ultrafine binderless WC-based cemented carbides with varied amounts of AlN nano-powder (0–16 wt.%) were fabricated by spark plasma sintering at 1600 °C under a pressure of 50 MPa with the assistance of VC and TaC as WC grain growth inhibitors. The densification behavior, phase composition, microstructure and mechanical properties of the as-prepared samples were investigated. During sintering, rapid sample shrinkage started at about 1050 °C and ended at about 1550 °C. X-ray diffraction analysis revealed that an appropriate addition amount of AlN nano-powder would be of help to limit the formation of W2C phase and promote the formation of solid solution phase of (V,W)C2 during sintering. As the added fraction of AlN nano-powder increased, the relative density of the samples initially increased and then decreased, reaching its maximum of about 99.6% when 3–5 wt.% AlN nano-powder was added. Scanning electron microscopy examination indicated that the average size of WC grains in the samples was about 0.7 μm and with increasing added fraction of AlN nano-powder, the abnormal growth of WC grains was suppressed and their sizes were somewhat reduced. Both the sample hardness and flexural strength first increased and then decreased with increasing added fraction of AlN nano-powder, reaching the maximum hardness of about 2400 HV10 with 3 wt.% AlN nano-powder and maximum flexural strength of about 1250 MPa with 5 wt.% AlN nano-powder, respectively. However, the fracture toughness slightly decreased from 7.5 to 6.3 MPa·m1/2 with increasing added fraction of AlN nano-powder.

SnO2–Ta2O5 based varistors doped with 0–2.0 mol% of ZnO were prepared by sintering the samples at 1450 °C for 2 h with conventional ceramic processing method. The doping effect of ZnO on the microstructural and electrical properties of the as-prepared SnO2–Ta2O5 based varistor ceramics was investigated. The change in SnO2 lattice parameter and EDX analysis both confirmed the doping of Zn ions into SnO2 grains, although the identified phase was only SnO2 (cassiterite) by X-ray diffraction in detection limit. The microstructure observation indicated that the doped ZnO can facilitate the sintering of the varistor ceramics. The measured electric-field/current-density characteristics of the samples revealed that the nonlinear exponents and varistor voltage increased with increasing doping amount of ZnO when the ZnO content was no more than 0.5 mol%; and more addition of ZnO would cause a decrease in nonlinear exponent and varistor voltage of the ceramic varistors.Highlights► SnO2–Ta2O5–ZnO varistors. ► Doping effect of ZnO on SnO2–Ta2O5 based varistors. ► Optimizing doping of ZnO in SnO2–Ta2O5 based varistors.

Tree-like branched α-Si3N4 single-crystalline nano/submicron-structures were successfully synthesized in one step simply by catalytic pyrolysis of a powder mixture of an amorphous preceramic polymer (polyhydridomethylsilazane) and FeCl2 (as catalyst). The growth processes of the trunks and branches of the as-prepared structures were both controlled by vapor-liquid-solid mechanism. The luminescent behavior of the structures was also reported and discussed. An intensive photoluminescence, with peaks at 1.82, 2.16, 2.78, 3.24 and 3.97 eV, was observed.Graphical abstract

TiCN-based cermets with different amounts of SiC nano-whisker were prepared by spark plasma sintering at 1350 °C with an initial pressure of 30 MPa and a holding time of 8 min. The microstructural and mechanical properties of the as-prepared samples were investigated. The addition of SiC nano-whisker has a significant effect on the cermets, resulting in 6% increase in Vickers hardness and 63% increase in flexural strength, respectively, when 2.5 wt.% of SiC nano-whisker was added, as compared with its counterpart without whisker. X-ray diffraction analysis revealed that no SiC peaks were detected but some peaks of new hard phases due to the reactions of SiC with the cermet matrix. The resultant hard phases were present normally in the grain boundary in the cermets on the basis of observation by transmission electron microscopy, and they are responsible for the hardness increase of the as-obtained cermets. The observation by scanning electron microscopy on the microstructure indicated that the fracture mechanism of the as-obtained cermets was mainly inter-granular of TiCN grains.Highlights► TiCN-based cermets with SiC nano-whisker were fabricated. ► Combining enhancement method from sparking plasma sintering, reaction hardening, and whisker reinforcement. ► Detailed fracture mechanism was discussed.

With VC and TaC as WC grain growth inhibitors, ultrafine WC–Ni cemented carbides with different fractions (6–10 wt%) of binder metal nickel were fabricated by utilizing high energy milling together with spark plasma sintering. In the obtained samples, only WC and Ni phases were detected in X-ray diffraction limit. The microstructure of the specimens was examined on fractural, polished, and polished/etched surfaces by scanning electron microscopy, and the results revealed that the average WC grain size of the WC–Ni cemented carbides was about 330 nm, and there were lots of micro-pores in the samples. The relative density of the samples was all higher than 92%. But the measurement of hardness and flexural strength indicated that the existence of micro-pores had no significant influence on the performance of the obtained materials. On the basis of observation on the micro-fracture surface of the samples, it was found that fractures occurred along the binder metal, and the obtained ultrafine WC–Ni cemented carbides showed a very short binder mean free path (about 22 nm), thus resulting in excellent performance in mechanical strength.Graphical abstractHighlights► Ultrafine WC–Ni cemented carbides with average WC grain size of about 330 nm prepared by combination of sparking plasma sintering and grain growth inhibitors. ► Very short mean free path of about 22 nm for crack in metal binder of the obtained materials. ► Higher hardness than those of WC–Co cemented carbide counterparts sintered by rapid sintering. ► Observation of fracture along metal binder and no carbon–carbon fracture face.

ZnO–Pr6O11 based varistor ceramics doped with 0–2.0 mol% SnO2 were fabricated by sintering samples at 1300 °C for 2 h with conventional ceramic processing method. X-ray diffraction analysis indicated that the doped SnO2 reacted with praseodymium oxides during sintering, generating Pr2Sn2O7 phase. Through scanning electron microscopy, it was found that the doping of SnO2 played a role against the growth of ZnO grains. Capacitance–voltage analysis revealed that the doped SnO2 acted as a donor in the varistor. The measured electric-field/current-density characteristics of the samples showed that the varistor voltage increased with the increase of SnO2 doping content, when the SnO2 content was no more than 1.0 mol%; with the SnO2 content up to no more than 0.5 mol%, the doping of SnO2 could increase the nonlinear coefficient; but, when the SnO2 doping content was further increased, the nonlinear coefficient and varistor voltage of the samples decreased, and the leakage current increased.Highlights► ZnO–Pr6O11 based varistor ceramic materials ► Eliminating the few drawbacks due to the high volatility and reactivity of Bi2O3 during liquid sintering by Pr6O11 substituting Bi2O3 ► Doping effect of SnO2 on ZnO–Pr6O11 based varistor ceramic materials ► Optimizing doping of SnO2 in ZnO–Pr6O11 based varistor ceramic materials.

An empirical function was proposed to describe the continuous stiffness curves, i.e., Er2/H versus h (where Er is the reduced modulus, H is the composite hardness and h is the indenter penetration depth), measured with nanoindentation tests for titanium films on glass substrate. By analyzing the variations of the parameters included in this empirical equation with film thickness, the physical meanings of this empirical equation were discussed. It was shown that the mechanical properties of the substrate and the film may be extracted from such analyses.

Ultrafine WC–Ni–VC–TaC cemented carbides with different amounts of cubic boron nitride (cBN) were fabricated by spark plasma sintering, and the microstructure and mechanical properties of the as-prepared cermets were investigated. Scanning electron microscopy observations showed that the size of WC grains in the cermet samples was 0.2–0.4 μm. After the addition of cBN, the samples were still quite dense with the highest relative density of almost 98% when the addition fraction of cBN was 50 vol.%, although some micropores might exist in the samples. X-ray diffraction results indicated that no phase transformation of cBN was detected. The relative density and hardness of the cemented carbides increased with the addition fraction of cBN, but their strength decreased. When the fraction of cBN increased from 0 up to 50 vol.%, the hardness of the samples increased from 2100 to 3200 HV, but the flexural strength decreased from 1950 to 1250 MPa.Research highlights► Ultrafine WC–Ni–VC–TaC–cBN cemented carbides were fabricated. ► Almost full dense cermet of high hardness and high strength. ► Combining enhancement method from sparking plasma sintering, WC grain growth inhibitor and addition of superhard materials.

Wear behaviors of hardmetal YG8B were examined in detail through a modified wet sand rubber rimmed wheel test system ASTM B611 using drilling fluids (slurries) with three types of coarse angular sands, SiC, Al2O3 and SiO2, respectively, and an extremely long sliding distance up to more than 60 km was adopted. Under the same condition, the volume loss of hardmetals was positively correlated with the hardness of abrasives, their concentration in slurry and the duration of testing, respectively. But the wear rate was influenced by them in complicated ways. It was positively correlated with the hardness of abrasives and their concentration in slurry. However, it changed in different ways with sliding distance while different abrasive slurries were used. Through morphology observation on the abraded surfaces, the wear mechanism of hardmetals was proposed, which included WC grain fracture, fragmentation and pullout, microcutting, plastic deformation, groove, and binder removal. And when SiC and Al2O3 were used as abrasive, different abraded surface areas on the samples showed different wear mechanisms, but no obvious difference was observed among them with SiO2 as abrasive. The change of abrasive concentration in the slurry had no obvious effect on the wear mechanism.Highlights► Using a modified wet sand rubber rimmed wheel test system ASTM B611 to evaluate the abrasive wear behavior in drilling fluids. ► Three kinds of coarse angular sands, SiC, Al2O3 and SiO2, of different hardness were used. ► Extremely long sliding distance experiment condition was built, which was up to more than 60 km. ► Different abraded areas of the hardmetal have different wear mechanisms. ► New wear model was proposed.

W-doped Ni–Zn ferrites with a nominal composition of Ni0.5Zn0.5WxFe2−xO4 (where x = 0, 0.02, 0.04, 0.06, and 0.08) were prepared by one-step synthesis through the incorporation of WO3 into the raw powders. The magnetic and dielectric properties of the as-prepared Ni–Zn ferrites were investigated. All samples have a typical spinel cubic structure. With increasing amount of W ions doped, the lattice constant decreases, while the grain size increases. The density and diameter shrinkage of the samples raise with small amount of W ions doped, but drop down with large amount of W ions doped. However, an uneven abnormal growth and closed pores were observed when too much of WO3 was added. The saturation magnetization of the samples increases with small amount of W ions doped, but decreases with large amount of W ions doped, and the coercivity shows an opposite trend. The Curie temperature raises with increasing amount of W ions doped. Both the real and imaginary parts of permeability of the ferrites decrease with increasing amount of W ions doped, while the natural resonance changes very little. Both the dielectric constant and dielectric loss present a decrease with small amount of W ions doped, but increase with large amount of W ions doped.Highlights► One-step direct synthesis of Ni–Zn ferrites. ► Doping of W ion into Ni–Zn ferrites. ► Magnetic and dielectric properties of doped Ni–Zn ferrites.

The doping effect of Fe2O3 on the microstructural and electrical properties of ZnO–Pr6O11 based varistor ceramic materials was investigated. Fe2O3 doping would inhibit the growth of ZnO grains, whose average sizes were found to decrease from 3.0 to 2.7 μm with the doping level of Fe2O3 increased from 0 to 1 mol%. When the doping level of Fe2O3 was 0.005 mol%, the varistors exhibited the optimum nonlinear electrical characteristics with nonlinear coefficient of about 26, breakdown voltage of approximately 571 V/mm and leakage current of less than 65 μA. With higher doping level of Fe2O3, more Fe atoms would segregate at grain boundaries, providing more extra electrical carriers, decreasing the resistances of the grain boundaries, and PrFeO3 would be formed, destroying the construction of grain boundaries. Therefore, the nonlinear electrical properties of the resultant varistor materials were deteriorated.Research highlights▶ ZnO–Pr6O11 based varistor ceramic materials. ▶ Eliminating the few drawbacks due to the high volatility and reactivity of Bi2O3 during liquid sintering by Pr6O11 substituting Bi2O3. ▶ Optimizing doping of Fe2O3 in ZnO–Pr6O11 based varistor ceramic materials.

The microstructural and electrical properties of ZnO–Pr6O11 based varistors, which are composed of ZnO–Pr6O11–Co3O4–TiO2 with different doping amounts of TiO2, were investigated. Through X-ray diffraction and scanning electron microscopy analyses, it was found that TiO2 acted as an inhibitor of ZnO grain growth in varistor ceramics, resulting in the decrease of ZnO grain size with more TiO2 doped, due to the formation of more second phases such as PrTiO3, Zn2TiO4 and even Pr2Ti2O7 at the grain boundaries, which would exert more intensive pinning effects on the ZnO grain growth. Doping with appropriate amount of TiO2 can improve the nonlinear property, and decrease the leakage current of the as-prepared ZnO–Pr6O11 based varistors. The samples’ varistor voltage and nonlinear exponents can be enhanced till no more than 1.0 mol% TiO2 doped. The maximal values of varistor voltage and nonlinear exponents acquired in this work were 90.2 V/mm and 15, respectively. The obtained materials might be much promising in application of varistors for devices working under low voltages.

We reported a simple, large-scale, and controllable growth method for network-like branched single-crystalline Si3N4 nanostructures by catalyst-assisted pyrolysis of a polysilazane. The templates were a silicon wafer deposited with a 5 nm Fe film. The processes simply involved in thermal cross-linking of the polymer precursor, crushing of the solidified preceramic polymer chunks into fine powder, and thermal pyrolysis of the powder under the protection of ultra-high purity nitrogen. The collected white network-like branched nanostructures were formed through “metal-absorption on the surface of nanostructures” model by vapor-liquid-solid mechanism. Microstructure characterizations indicate that the nanostructures are single-crystalline hexagonal α-Si3N4. The reaction mechanism of Si3N4 nanonetworks was also proposed.

Large-scale synthesis of clustered one-dimensional amorphous silica nanowires was achieved by simple thermal pyrolysis of an amorphous preceramic powder from perhydropolysilazane on alumina wafers coated with catalyst FeCl2. Scanning electron microscopy and transmission electron microscopy observations showed that the silica nanowires had smooth surface, and lengths of hundreds of micrometers and diameters in the range of 30–40 nm. Energy dispersive X-ray spectroscopy revealed that these nanowires consisted of Si and O elements in an atomic ratio of approximately 1:2, consistent with the stoichiometric formula SiO2. The two amorphous bulges in Raman spectrum at the centers of around 260 cm−1 and 800 cm−1 were identified to be those of amorphous silica. The growth mechanism of the as-produced silica nanowires could be attributed to vapor–liquid–solid mechanism. These results provide an alternative and simple preparation procedure for nanostructures with controlled morphology, and it will be helpful to understand the growth mechanism of one-dimensional SiO2 nanostructures.

Bundled one-dimensional Si3N4 single-crystalline nanowires are successfully synthesized by pyrolysis of a polymer precursor using Fe as catalyst. The average diameter of the obtained Si3N4 nanowires is about 200 nm, and the nanowires have perfect single-crystalline structure. Intense photoluminescence was observed centered at 1.83, 2.79, 3.24, and 3.74 eV. The nanowires could be useful in the fabrication of optoelectronic nanodevices and nanocomposites.

Ni-Zn ferrites of nominal composition Ni0.5Zn0.5SmxFe2-xO4 (x=0–0.1) were prepared by a conventional two-steps solid sintering method. The effect of Sm3+ doping on the microstructural, magnetic and dielectric properties of the as-prepared Ni-Zn ferrites were investigated. The main phase of all the samples was ferrite spinel, and the samples doped with Sm3+ ions contained a small amount of a foreign SmFeO3 phase as well. And the doping of Sm3+ resulted in the increase of lattice constant. The grain size, density and densification of the ferrites initially decreased after Sm3+ doping, but then increased with more Sm3+ doped. With increasing substitution level, x, the saturation magnetization of the as-prepared ferrites decreased, while the coercivity increased. The Curie temperature raised initially and decreased later with increasing content of Sm3+ in the samples, reaching a maximum of 274 °C when x=0.025. The initial permeability of the ferrites first decreased and then increased with increasing doping amount of Sm3+ ions. The introduction of Sm3+ ions into Ni-Zn ferrite would lead to the reduced dielectric loss in the frequency range of 1–100 MHz, but the dielectric loss raised when more Sm3+ was added in the frequency range of 100–1000 MHz. When x=0.05, the dielectric loss reached the lowest value.

Bifunctional catalysts Cs–P/γ-Al2O3 were developed and firstly applied in a one-step synthesis of methyl acrylate using methyl acetate (Ma) and formaldehyde (FA). The catalysts were prepared using impregnation and characterized with X-ray diffraction, transmission electron microscopy, thermogravimetry and differential thermal analysis, nitrogen adsorption–desorption, ammonia- and carbon dioxide-temperature programmed desorption methods. The catalytic performance was evaluated using a fixed-bed microreactor. Experimental results indicated that the P loading had significant influence on the catalytic activity by modifying the acid–base surface properties of the catalyst. The process optimization using response surface methodology was performed and the interactions of operational variables including the Ma/FA molar ratio, reaction time and temperature were elucidated. Then the kinetics of the aldol condensation reaction was studied using a pseudo-homogeneous kinetic model. In addition, the lifetime of optimum Cs10%–P5%/γ-Al2O3 catalyst was evaluated over a continuous period of 400 h, and did not exhibit an obvious decrease in efficiency.

Phase transfer techniques possess remarkable advantages for the synthesis of inorganic nanomaterials. In contrast to the abundant reports on the preparation of noble metal nanoparticles using phase transfer, the number of semiconductor nanocrystals syntheses based on phase transfer techniques is still limited. Herein, we report a systematic study of the phase transfer-based synthesis of HgS nanocrystals, including the tuning of their morphology/shape by either solvent choice or temperature. This strategy involves the transfer of Hg(II) ions from aqueous solution to toluene, oleic acid or oleylamine and subsequent sulfidation at room or elevated temperature. Furthermore, we have extended this phase-transfer based strategy to the fabrication of HgS–Au nanocomposites. The studies in this work might provide a facile route for producing HgS nanocrystals with desirable properties and offer an effective strategy to investigate the influence of the morphology of HgS on the physical/chemical properties of various HgS-based materials.