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g–C3N4 nanosheets were first synthesized by calcining the mixture of hydrochloric acid-pretreated melamine and ammonium chloride. Then, by the aiding of solvothermal method and hydrofluoric acid as morphology modifier, 001-TiO2/g–C3N4 (TCN-X, X = 5 , 3, 2, 1) nanocomposites were synthesized using g–C3N4 nanosheets and tetrabutyl titanate, with the mass ratio of g–C3N4 to TiO2 was 5:1, 3:1, 2:1 and 1:1, respectively. The as-synthesized samples were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscopy, Fourier transform infrared spectroscopy, nitrogen adsorption–desorption method, ultraviolet–visible diffuse reflectance spectrum, photoluminescence spectrum, etc. Their photocatalytic properties were evaluated under visible light irradiation with rhodamine B (RhB) as the target pollutant. The results reveal that the TCN-3 composites had a large specific surface area of 67.38 m2/g and consisted of g–C3N4 nanosheets and anatase TiO2 crystals about 10–20 nm in size. The (001) crystal planes of TiO2 can be easily observed in TCN-X composites. All TiO2/g–C3N4 composites exhibited excellent photocatalytic activity compared with the pure g–C3N4 did. The photocatalytic property of TCN-X samples varied with the mass ratio of g–C3N4to TiO2, and TCN-3 presented the optimum photocatalytic performance. In total, 50 mg of TCN-3 completely degraded 50 mL and 100 mL of RhB solution (10 mg/L) in 15 min and 40 min, respectively. The reaction rate constant of TCN-3 was 6.7 times as large as that of pure g–C3N4. TCN-3 also presented outstanding activity for the photocatalytic degradation of the colorless tetracycline solution. The significant improvement in photocatalytic activity of TCN-3 was attributed to the evenly distribution of TiO2 on g–C3N4, the enhanced specific surface area and the construction of 001-TiO2/g–C3N4 heterojunction between the g–C3N4 nanosheets and the (001) crystal planes of anatase TiO2, which greatly reduced the recombination rate of the photo-generated electron and hole. In this work, the g–C3N4 nanosheets were obtained by simple mixing and calcination of ammonium chloride and acid-treated melamine. Then, using tetrabutyl titanate as the precursor and hydrofluoric acid to expose the 001 crystal face of TiO2, 001-TiO2/g–C3N4 composite materials with different mass ratios were synthesized by simple hydrothermal method. The composite exhibited excellent photocatalytic performance and degraded RhB within 15 min. The rate constant of TiO2/g–C3N4 composite is 6.7 times that of pure g–C3N4. [ABSTRACT FROM AUTHOR]

ZnSn(OH)6 regular octahedrons were successfully synthesized through a simple hydrothermal method using an aqueous solution containing ZnO flower-like structures, SnCl4·5H2O, and NaOH. Phase structure, morphology and microstructure of the samples were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Parameters in preparation process such as the ratios of Sn4+/OH-, the molar ratio of Zn/Sn and reaction time were discussed. Results show that the obtained samples are comprised of ZnSn(OH)6 regular octahedrons with about 2 μm in side length and ZnSn(OH)6 urchins-like structures. ZnSn(OH)6 urchins-like structures preferentially grow on the edges and corners of regular octahedrons. Morphology of the products is susceptible to the ratios of Sn4+/OH-. A relatively low concentration of OH- is favored to obtain ZnSn(OH)6 regular octahedrons with urchins-like structures on the surface, while a high concentration of OH- results in a handful of regular octahedrons without urchins-like structures on the surface. When the molar ratio of Zn/Sn changes to 1:2 or 2:1, the edges and corners of regular octahedrons become coarse and urchins-like structures disappear from the surface. More urchins-like structures form on the surface of regular octahedrons and the edges and corners of regular octahedrons become coarsened with the increase of reaction time. Moreover, the possible mechanism for ZnSn(OH)6 regular octahedrons is discussed. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Ti 3 AlC 2 was used as the additive to fabricate a novel (Zr 0 · 2 Ta 0 · 2 Nb 0.2 Hf 0.2 Mo 0.2)B 2 -based (HEBTAC) ceramic using spark plasma sintering at 1900 °C. The as-prepared HEBTAC ceramic sample consists of (Ti, Zr, Hf, Ta, Nb, Mo)B 2 , multiscale (Zr, Hf, Ta, Nb, Mo)C, and Al 2 O 3 phases, which are produced by the decomposition of Ti 3 AlC 2 and subsequent exchange reaction & solid solution reactions during the sintering process. The relative density, hardness, fracture toughness, and flexural strength of the HEBTAC ceramic sample are 99.43 %, 27.92 ± 1.87 GPa, 5.84 ± 0.14 MPa m1/2, and 629 ± 8.7 MPa, respectively, which are even better than the same class of high-entropy diboride ceramics previously published. Solid-solution strengthening, dislocation strengthening and nano-HEC strengthening existed in the ceramic sample contribute to its excellent mechanical properties. The in situ formed Al 2 O 3 and (Zr, Hf, Ta, Nb, Mo)C effectively enhances the toughness of the HEBTAC ceramic sample through the synergistic effect of intrinsic and extrinsic toughening. This study presents a new approach for reactive sintering densification of high-entropy diborides with both high strength and high toughness. [ABSTRACT FROM AUTHOR]

Melamine pretreated with hydrochloric acid was mixed with diatomite-based porous ceramics (Ф 18 × 6 mm in size) and then heated from room temperature through an intermediate holding temperature up to 550 °C and calcined for 2 h to obtain g-C 3 N 4 /diatomite-based porous ceramic composites (xHCN/D, x = 310, 355, 400, representing the holding temperature in the intermediate stage). The samples were characterized by XRD, FT-IR, SEM, UV–Vis, PL, etc.. Rhodamine B (RhB) solution was used as the target pollutant to evaluate the photocatalytic activity of the samples. The results show that the phase composition of xHCN/D composites included g-C 3 N 4 and those in diatomite-based porous ceramic. The photocatalytic activity of xHCN/D composites were better than that of 355CN/D composite synthesized under the same condition as 355HCN/D but using pristine melamine, although the loading rates of g-C 3 N 4 on xHCN/D were much smaller than that on 355CN/D. The photocatalytic activity of xHCN/D changed with the variation of x, and 355HCN/D exhibited the optimum photocatalytic performance as well as excellent cycling stability and recoverability. 355HCN/D (1 g) degraded 86.74% of RhB molecules (2 mg/L, 100 mL) in 200 min, whose reaction rate constant was 1.45 times that of 355CN/D. In addition, the photocatalytic activity of 355HCN/D particles (3–4 mm in size) was superior to that of 355HCN/D disc. The enhanced UV–visible light absorption ability, narrowed band gap and the decreased photo-generated electron-hole recombination rate of 355HCN/D were ascribed to the significantly reduced size and appropriate amount of g-C 3 N 4 sheets loaded uniformly on the surface of diatomite-based porous ceramic, due to the synergistic action of acid-treating to melamine and holding at an intermediate temperature. This work provides a strategy for preparing high performance photocatalysts with a facile separation and recycle ability. [ABSTRACT FROM AUTHOR]

Vermiculite/g-C 3 N 4 /BiOBr composite (MCVB-X, X = 20, 50, 70, 90) with significantly improved photocatalytic performance was prepared by in-situ growing 20 wt%, 50 wt%, 70 wt%, 90 wt% of BiOBr nanosheets, respectively, on the surface of vermiculite/g-C 3 N 4 composite (MVC). With the increasing of BiOBr content, the photocatalytic performance of MCVB-X composites enhanced gradually. After 180 min of photocatalytic reaction under the visible light irradiation, the degradation rate of tetracycline (TC) by MCVB-50, which contained 50 wt% of BiOBr, reached 91.34 %, which was close to that of pure BiOBr and much higher than those of MVC and bulk g-C 3 N 4 (CN). The reaction rate constant (k) (0.0131 min−1) of MVCB-90 was 38.53 times and 6.24 times that of CN and MVC, respectively, which was also greater than that of pure BiOBr nanosheets (0.0098 min−1). The main reason for the significant improvement of photocatalytic performance of MCVB-X composites was that the construction of g-C 3 N 4 /BiOBr heterojunction promoted the separation and migration of photogenerated carriers and reduced the recombination rate of photogenerated electron-hole pairs. The agglomeration of BiOBr nanosheets was inhibited and contributed to the adsorption of pollutants. Moreover, the band structure, main active species (⋅O 2 −) and photocatalytic degradation mechanism were proposed. [Display omitted] • Vermiculite/g-C 3 N 4 /BiOBr composite was synthesized via an in-situ synthesis method. • Light absorption ability, charge transfer and separation efficiency were improved. • Photocatalytic activity of vermiculite/g-C 3 N 4 /50 wt%BiOBr was close to BiOBr nanosheet. • Vermiculite/g-C 3 N 4 /90 wt%BiOBr degraded 96.55 % of TC after photocatalysis for 180 min. • Reaction rate constant was 4.88 and 1.42 times that of g-C 3 N 4 and vermiculite/g-C 3 N 4. [ABSTRACT FROM AUTHOR]

A new high-entropy monoboride (Mo 0.2 Ta 0.2 Ni 0.2 Cr 0.2 W 0.2)B ceramic with a WB-type orthogonal structure was designed and synthesised by in-situ reactive hot pressing at 2000 °C and 30 MPa for 1.5 h under an argon atmosphere. The microstructure of the sintered samples was comprehensively characterised, and the formation of a high-entropy monoboride (Mo 0.2 Ta 0.2 Ni 0.2 Cr 0.2 W 0.2)B ceramic was confirmed. Owing to the high density of the dislocations and strengthening metal-boron bonds, the high-entropy (Mo 0.2 Ta 0.2 Ni 0.2 Cr 0.2 W 0.2)B ceramic exhibited a hardness of 48.51 ± 4.07 GPa, which enabled it to be classed as a new superhard material. In addition, the thermal conductivity (2.05 ± 0.10 W/(m·K) at 400 °C) and electric conductivity (132.30 S/cm) were determined. [ABSTRACT FROM AUTHOR]

Nitrogen-defect g-C 3 N 4 /vermiculite composites (gCVx, x = 0.1, 1, 3, 4) with high efficient photocatalytic performance were constructed by a wet chemical method cooperating with the calcination process, as well as using the pre-expanded vermiculite and the melamine pre-treated by hydrochloric acid solutions of 0.1, 1, 3, 4 mol/L, respectively. Micron-sized g-C 3 N 4 sheets with nitrogen defects were synthesized and uniformly distributed in the gCVx composites. Photocatalytic performance was evaluated by degrading Rhodamine B (RhB) aqueous solution. The results indicated that photocatalytic activities of gCVx increased firstly and then dropped down gradually with the increase of HCl concentration. gCV3 achieved the maximum degradation rate of 97.90 % for RhB after photocatalysis for 20 min, whose degradation rate constant was 14.9 times than that of bulk g-C 3 N 4. gCV3 also exhibited the highest photocatalytic activity toward degrading the tetracycline and phenol solutions. The excellent photocatalytic performance was ascribed to the enhanced amounts of active sites, increased specific surface area, improved visible light absorption ability, accelerated charge transfer and separation efficiency of photogenerated-carriers, which resulted from the synergistic effect between vermiculite and nitrogen defects in g-C 3 N 4 , as well as the mutual electrostatic repulsion between the negative-charged vermiculite and the photo-induced electron from the nitrogen-defect g-C 3 N 4. [Display omitted] • Nitrogen-defect g-C 3 N 4 /vermiculite composites were constructed by a novel method. • Light absorption ability, charge transfer and separation efficiency were improved. • 97.90 % RhB molecules were degraded after photocatalysis for 20 min. • Reaction rate constant was 14.9 times than that of g-C 3 N 4. • ·O 2 − and h+ played a mainly major role during the degradation of RhB. [ABSTRACT FROM AUTHOR]

ZrSi 2 and SiC are good candidates to improve both sinterability and mechanical properties of ZrB 2 ceramics, which were synthesized simultaneously by an in-situ reaction of ZrC and Si additives during the sintering processing in this work. The ZrB 2 ceramic composites with different amount of ZrSi 2 and SiC were fabricated by reactive spark plasma sintering (RSPS) method. X-ray diffraction, scanning microscopy and Archimedes's method are used to characterize the phase, microstructure and density of the composites. Meanwhile, fracture toughness and flexural strength of the obtained composites were investigated too. It's found that a fully dense composite can be achieved at 1500 °C by SPS. Both fracture toughness and flexural strength of ZrB 2 ceramics increased with increasing the concentration of ZrSi 2 and SiC additives and reached a maximum of 7.33 ± 0.24 MPa·m 1/2 and 471 ± 15 MPa, respectively, with the ZrSi 2 + SiC content of 30 wt%. [ABSTRACT FROM AUTHOR]

Abstract: In this work, triclinic WO3 nanoplates and WO3 nanoparticles were comparatively investigated as sensing materials to detect acetone vapors. Single-crystalline WO3 nanoplates with large side-to-thickness ratios were synthesized via a topochemical conversion from tungstate-based inorganic–organic hybrid nanobelts, and the WO3 nanoparticles were obtained by calcining commercial H2WO4 powders at 550°C. The acetone-sensing properties were evaluated by measuring the change in electrical resistance of the WO3 sensors before and after exposure to acetone vapors with various concentrations. The WO3 nanoplate sensors showed a high and stable sensitive response to acetone vapors with a concentration range of 2–1000ppm, and the sensitivity was up to 42 for 1000ppm of acetone vapor operating at 300°C. The response and recovery times were as short as 3–10s and 12–13s, respectively, for the WO3 nanoplate sensors when operating at 300°C. The acetone-sensing performance of the WO3 nanoplate sensors was more excellent than that of the WO3 nanoparticle sensors under a similar operating condition. The enhancement of the WO3 nanoplate sensors in the acetone-sensing property was attributed to the poriferous textures, single-crystalline microstructures and high surface areas of the aggregates consisting of WO3 nanoplates, which were more favorable in rapid and efficient diffusion of acetone vapors than the WO3 nanoparticles. [Copyright &y& Elsevier]

Abstract: The aim of this paper was to provide a convincing experimental research to demonstrate a dissolution–reorganization mechanism for the formation of tungstate-based inorganic–organic hybrid nanobelts by comparatively investigating the reaction behaviors of H2WO4 and H2W2O7·xH2O with n-alkylamines (C m H2m+1NH2, m =4–10). The formation of tungstate-based hybrid nanobelts derived from the reactions between n-alkylamines and H2WO4 with single-octahedral W–O layers was investigated with a detailed comparison with those between n-alkylamines and H2W2O7·xH2O with double-octahedral W–O layers. H2WO4 and H2W2O7·xH2O reacted with n-alkylamines, respectively, in reverse-microemulsion-like media. The obtained products were characterized by XRD, FT-IR, TG–DTA and SEM. The results indicated that the products derived from H2WO4 and those from H2W2O7·xH2O were similar in compositions, microstructures and morphologies. The structural analysis indicated the products were tungstate-based inorganic–organic hybrid one-dimensional belts with highly ordered lamellar structures by alternately stacking organic n-alkylammonium bilayers and inorganic single-octahedral W–O layers. The n-alkyl chains in the above hybrid nanobelts from H2WO4 and H2W2O7·xH2O took on a bilayer arrangement with tilt angles of 65° and 74°, respectively. The similarities in the microstructures of the products from H2W2O7·xH2O and H2WO4 demonstrated that the double-octahedral W–O layers of H2W2O7·xH2O were decomposed during the reactions. The changes of inorganic W–O layers and the morphologic changes of the tungstic-acid precursors before and after the reactions corroborated the dissolution–reorganization mechanism. [Copyright &y& Elsevier]

Abstract: A novel pseudo-morphotactic transformation route was developed to synthesize polycrystalline β-W2N nanoplates by thermally treating tungstate-based inorganic–organic hybrid nanobelts with a lamellar microstructure in an NH3 flow. The tungstate-based hybrid nanobelts were formed in a water-in-oil-microemulsion-like “commercial H2WO4 powders/n-octylamine/heptane” reaction system. The as-obtained hybrid nanobelts were thermally treated in an NH3 atmosphere at 650–800°C for 2h to form cubic β-W2N nanoplates. XRD, SEM, TEM, FT-IR and TG-DTA were used to characterize the precursors and their final products. The polycrystalline β-W2N nanoplates derived from hybrid nanobelts, with side lengths of several hundred nanometers, consist of small nanocrystals with an average grain size of 3.2nm. The formation of β-W2N nanoplates involved two steps: decomposing tungstate-based hybrid nanobelts into WO y and W species and then nitridizing the active W-containing species to β-W2N nanocrystals in an NH3 flow. The platelike morphology of the β-W2N nanocrystals was inherited from the precursor of tungstate-based inorganic–organic hybrid nanobelts. [Copyright &y& Elsevier]

Abstract: The intercalation compounds of kaolinite/potassium acetate were prepared by grinding and aging mixtures of potassium acetate and kaolinite from coal measures. The techniques of XRD, ICP-AES, IR, DSC, SEM and particle-size distribution analysis were used to characterize the microstructure and stability of the as-obtained intercalation compounds. The basal spacing increased from 0.72nm for the raw kaolinite to 1.42nm for the intercalation compound. The intercalation compounds were very stable in the anhydrous ethanol at room temperature, whereas deintercalation occurred when the as-obtained intercalation compounds were treated with water or heated at 296°C. [ABSTRACT FROM AUTHOR]

Abstract: Double-layer glass-ceramic/ceramic tiles made from bauxite tailings and red mud were prepared using a single firing powder processing route. The influence of the preparation method used for the green bodies on the microstructure and mechanical properties of the final products was investigated. The macroscopic appearance, microstructure, and mechanical properties indicated that the production of double-layer glass-ceramic/ceramic tiles may be an attractive method for recycling industrial waste into building materials. [Copyright &y& Elsevier]

Abstract: Sintering behavior and crystallization of glass–ceramic using bauxite tailings as one constituent were investigated. Different heat-treatment schedules were used to study their sintering effect on the glass powder-coated tiles. The results show that different heat-treatment schedule will result different crystal shape of the glass–ceramic. It was found that applying a two-stage heat-treatment schedule, first sintered at the crystallization temperature and then sintered at a higher temperature can make the glass–ceramic-coating layer bond strongly with the tile body. [Copyright &y& Elsevier]

Three phase nanocomposites g-C 3 N 4 /rGO/TiO 2 were synthesized successfully under hydrothermal reaction conditions using g-C 3 N 4 nanosheets as matrix, as well as TiO 2 sol and graphene oxide as the precursors of nano-size anatase and reduced graphene oxide (rGO), respectively. The photocatalytic performance of samples was investigated by degrading Rhodamine B (RhB) solution under sunlight irradiation with a xenon lamp. The results show that g-C 3 N 4 /rGO/TiO 2 three-phase composite nanomaterial was successfully prepared. g-C 3 N 4 /rGO/TiO 2 exhibited a satisfactory photocatalytic activity and cycle stability when the mass ratio of g-C 3 N 4 nanosheets (0.6 g) to nano-TiO 2 (0.2 g) was 3:1, the mass of GO was 0.002 g, the hydrothermal temperature and time were 160 °C and 6 h, respectively. When photocatalysis for 60 min, the degradation rate of RhB solution (100 mL, 10 mg/L) by g-C 3 N 4 /rGO/TiO 2 (100 mg) reached 99.63%. Main reasons for these results lie in the significantly improved separation efficiency of photogenerated electron-hole pairs due to the construction of g-C 3 N 4 /TiO 2 heterojunction, the enhanced optical absorption and the increased specific surface area. [Display omitted] • g-C 3 N 4 /rGO/TiO 2 nanocomposite was prepared by a facile process. • The g-C 3 N 4 nanosheets were below 10 nm and the diameter of nano-TiO 2 was about 10 nm. • g-C 3 N 4 /rGO/TiO 2 nanocomposite exhibited excellent photocatalytic activity and degraded RhB within 50 min under visible light. • Rate constant value of g-C 3 N 4 /rGO/TiO 2 is 8.99 times higher than that of common g-C 3 N 4. [ABSTRACT FROM AUTHOR]

g-C 3 N 4 /vermiculite composites were synthesized by calcining the wet-mixed mixture of melamine and pre-expanded vermiculite, which pre-heated from different particle size of vermiculite (30–60, 60–100, 100–200 and 200 mesh). Pre-heating destroyed the crystal structure of vermiculite and enlarged its interlayer space, which was beneficial to the synthesis of g-C 3 N 4 nano-sheets or nano-particles. With the decrease of the particle size of vermiculite, the dispersity of vermiculite and g-C 3 N 4 in g-C 3 N 4 /vermiculite composite improved and the specific surface area of the composites increased gradually, but the agglomeration of g-C 3 N 4 enhanced a little due to the lowered expanding degree of vermiculite. The photocatalytic performance of the g-C 3 N 4 /vermiculite composite enhanced firstly, and then dropped down as vermiculite particles were smaller than 100 mesh. g-C 3 N 4 /vermiculite composite synthesized from vermiculite of 60–100 mesh exhibited the optimum photocatalytic activity. It degraded 95.68% of Rhodamine B molecules in aqueous solution (100 mL, 10 mg/L) after photocatalysis for 90 min, and its reaction rate constant was about 2.7 times as large as that of the pure g-C 3 N 4. The weakened agglomeration, the closely contacted interface between g-C 3 N 4 and vermiculite, the enhanced separation efficiency of photo-generated carriers and the narrowed the band gap were responsible for the excellent photocatalytic performance of this g-C 3 N 4 /vermiculite composite. Image 1 • Nano g-C 3 N 4 formed in g-C 3 N 4 /vermiculite composite by the adding of pre-expanded vermiculite. • Particle size of vermiculite affects the microstructure and photocatalytic activity of composite. • High performance g-C 3 N 4 /vermiculite was synthesized from vermiculite of 60–100 mesh. • Rate constant value of g-C 3 N 4 /vermiculite was 2.7 times as large as that of pure g-C 3 N 4. [ABSTRACT FROM AUTHOR]

The effects of high-energy ball milling (HEBM) on the sintering ability and microstructure of hafnium diboride (HfB 2) ultrahigh-temperature ceramics (UHTCs) were investigated. After HEBM, the average particle size range of the HfB 2 ceramics decreased to 10–20 nm with a slight alteration in the crystal structure. The microscopic grains of the sintered samples were homogeneous and fine in size. WC removed oxide impurities on the surface of the HfB 2 particles by reacting with the oxide impurities, which further improved the sintering ability of the HfB 2 ceramics. The densification mechanism of the HfB 2 ceramics was also investigated, and nearly fully dense HfB 2 (99.1%) was fabricated by reactive spark plasma sintering (R–SPS) at 2100 °C for 35 min under a pressure of 40 MPa. HEBM increased the surface energy of the fine particles, which provided a sufficient driving force to improve the sintering ability and significantly increase the densification of HfB 2. • HfB 2 ceramics with nearly full density (99.1% relative density) has been successfully prepared. • The high energy ball mill slightly causes lattice distortion and improves sintering property. • Study of the mechanism of densification and grain coarsening of HfB 2 during SPS. [ABSTRACT FROM AUTHOR]