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Recently, semiconducting metal oxide (SMO) gas sensors have attracted the attention of researchers for high conductivity, labile features by environment, low cost, easy preparation, etc. However, traditional SMOs have some defects such as higher operating temperature and lower response value, which greatly limit their application in the field of gas sensor. In this work, the carbon nitride decorated ball-flower like Co₃O₄ composite was successfully synthesized via a facile hydrothermal method, the composition and morphology of the as-synthesized samples were studied by the techniques of X-ray powder diffraction (XRD), Field-emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), Fourier transform infrared spectrometer (FT-IR) and N₂-sorption. As a consequence, the pure Co₃O₄ and the carbon nitride decorated Co₃O₄ both possess ball-flower like structure, and the as-synthesized carbon nitride decorated Co₃O₄ composite exhibits significant sensing properties to ethanol which is 1.6 times higher than that of pure Co₃O₄, furthermore, the composite possesses high selectivity and stability towards ethanol detection., Competing Interests: The authors declare no conflict of interest.

Flower-like SnO₂/g-C₃N₄ nanocomposites were synthesized via a facile hydrothermal method by using SnCl₄·5H₂O and urea as the precursor. The structure and morphology of the as-synthesized samples were characterized by using the X-ray powder diffraction (XRD), electron microscopy (FESEM and TEM), and Fourier transform infrared spectrometer (FT-IR) techniques. SnO₂ displays the unique 3D flower-like microstructure assembled with many uniform nanorods with the lengths and diameters of about 400-600 nm and 50-100 nm, respectively. For the SnO₂/g-C₃N₄ composites, SnO₂ flower-like nanorods were coupled by a lamellar structure 2D g-C₃N₄. Gas sensing performance test results indicated that the response of the sensor based on 7 wt. % 2D g-C₃N₄-decorated SnO₂ composite to 500 ppm ethanol vapor was 150 at 340 °C, which was 3.5 times higher than that of the pure flower-like SnO₂ nanorods-based sensor. The gas sensing mechanism of the g-C₃N₄nanosheets-decorated SnO₂ flower-like nanorods was discussed in relation to the heterojunction structure between g-C₃N₄ and SnO₂., Competing Interests: The authors declare no conflict of interest.

The NaHCO 3 /red-mud (RM) composite powders were successfully prepared by the solvent-anti-solvent method for methane explosion suppression. The RM was used as a carrier, and the NaHCO 3 was used as a loaded inhibitor. The NaHCO 3 /RM composite powders showed a special core-shell structure and excellent endothermic performance. The suppression properties of NaHCO 3 /RM composite for 9.5% CH 4 explosion were tested in a 20L spherical explosion vessel and a 5L Perspex duct. The results showed that the NaHCO 3 /RM composite powders displayed a much better suppression property than the pure RM or NaHCO 3 powders. The loading amount of NaHCO 3 has an intensive influence on the inhibition property of NaHCO 3 /RM composite powders. The best loaded content of NaHCO 3 is 35%. It exhibited significant inhibitory effect that the explosion max-pressure declined 44.9%, the max-pressure rise rate declined 96.3% and the pressure peak time delayed 366.7%, respectively., (Copyright © 2017 Elsevier B.V. All rights reserved.)

SnO₂/graphitic carbon nitride (g-C₃N₄) composites were synthesized via a facile solid-state method by using SnCl₄·5H₂O and urea as the precursor. The structure and morphology of the as-synthesized composites were characterized by the techniques of X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), thermogravimetry-differential thermal analysis (TG-DTA), X-ray photoelectron spectroscopy (XPS), and N₂ sorption. The results indicated that the composites possessed a two-dimensional (2-D) structure, and the SnO₂ nanoparticles were highly dispersed on the surface of the g-C₃N₄ nanosheets. The gas-sensing performance of the samples to ethanol was tested, and the SnO₂/g-C₃N₄ nanocomposite-based sensor exhibited admirable properties. The response value (Ra/Rg) of the SnO₂/g-C₃N₄ nanocomposite with 10 wt % 2-D g-C₃N₄ content-based sensor to 500 ppm of ethanol was 550 at 300 °C. However, the response value of pure SnO₂ was only 320. The high surface area of SnO₂/g-C₃N₄-10 (140 m²·g -1 ) and the interaction between 2-D g-C₃N₄ and SnO₂ could strongly affect the gas-sensing property., Competing Interests: The authors declare no conflict of interest.

The SnO₂/g-C₃N₄ composites were synthesized via a facile calcination method by using SnCl₄·5H₂O and urea as the precursor. The structure and morphology of the as-synthesized composites were characterized by the techniques of X-ray diffraction (XRD), the field-emission scanning electron microscopy and transmission electron microscopy (FESEM and TEM), energy dispersive spectrometry (EDS), thermal gravity and differential thermal analysis (TG-DTA), and N₂-sorption. The analysis results indicated that the as-synthesized samples possess the two dimensional structure. Additionally, the SnO₂ nanoparticles were highly dispersed on the surface of the g-C₃N₄ nanosheets. The gas-sensing performance of the as-synthesized composites for different gases was tested. Moreover, the composite with 7 wt % g-C₃N₄ content (SnO₂/g-C₃N₄-7) exhibits an admirable gas-sensing property to ethanol, which possesses a higher response and better selectivity than that of the pure SnO2-based sensor. The high surface area of the SnO2/g-C3N4 composite and the good electronic characteristics of the two dimensional graphitic carbon nitride are in favor of the elevated gas-sensing property.

We selected, as the objects of our research, lignite from the Beizao Mine, gas coal from the Caiyuan Mine, coking coal from the Xiqu Mine, and anthracite from the Guhanshan Mine. We used the mercury intrusion method and the low-temperature liquid nitrogen adsorption method to analyze the structure and shape of the coal pores and calculated the fractal dimensions of different aperture segments in the coal. The experimental results show that the fractal dimension of the aperture segment of lignite, gas coal, and coking coal with an aperture of greater than or equal to 10 nm, as well as the fractal dimension of the aperture segment of anthracite with an aperture of greater than or equal to 100 nm, can be calculated using the mercury intrusion method; the fractal dimension of the coal pore, with an aperture range between 2.03 nm and 361.14 nm, can be calculated using the liquid nitrogen adsorption method, of which the fractal dimensions bounded by apertures of 10 nm and 100 nm are different. Based on these findings, we defined and calculated the comprehensive fractal dimensions of the coal pores and achieved the unity of fractal dimensions for full apertures of coal pores, thereby facilitating, overall characterization for the heterogeneity of the coal pore structure.