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Lu Y.,China University of Mining and Technology | Qin B.,China University of Mining and Technology | Qin B.,Key Laboratory of Gas and Fire Control for Coal Mines | Jia Y.,China University of Mining and Technology | And 2 more authors.
Advances in Cement Research | Year: 2015

Thermal insulation and setting properties are considered to be two significant parameters when inorganic solidified foam (ISF) is applied to control and extinguish coal fires. Based on studies concerning the thermal properties of porous media and experimental research on the relationship between porosity and the addition of aqueous foam, an equation describing the change in thermal conductivity with aqueous foam volume is deduced and then amended. Microscopic analysis of the process of setting is conducted by scanning electron microscopy. The results show that the coagulation of a single bubble wall and bubbles connecting with each other lead the ISF to lose fluidity gradually. A loss of fluidity time (LFT) index is then proposed on the basis of field process requirements and the aforementioned microscopic analysis, and a home-made instrument to test LFT is developed. Effects of aqueous foam volume and accelerator type, along with its addition quantity, on the LFT of ISF are investigated. The relationship equation provides a theoretical foundation for steerable adjustment of the LFT. Furthermore, under the restriction of cost, thermal conductivity threshold and LFT, the parameters of the feasible construction state areas of four different accelerators were compared; in this study AC3 was found to be the most appropriate accelerator. Source


Cheng J.-J.,China University of Mining and Technology | Cheng J.-J.,Australian National University | Zhou F.-B.,China University of Mining and Technology | Zhou F.-B.,Key Laboratory of Gas and Fire Control for Coal Mines
Journal of Thermal Analysis and Calorimetry | Year: 2016

Influence of expandable graphite on flame retardancy and mechanical properties of organic–inorganic hybrid material based on sodium silicate and polyisocyanate has been investigated. The results of mechanical measurement show that adding expandable graphite decreases the maximum of the compressive strength from 5.98 to 1.49 MPa. The thermal property is evaluated by thermal conductivity test, thermogravimetric analysis. The results indicate that adding the expandable graphite increases thermal conductivity of composite and lowers maximum heat release rate. The material with expandable graphite has better flame retardancy than original material with an obvious decrease in heat release rate, fire spread and thermal decomposition rate. What is more, intumescent graphite has the obvious effect to suppress flame and prevent the composite from fire. Scanning electron microscope shows that many large particles and gaps appear after compression deformation. © 2016 Akadémiai Kiadó, Budapest, Hungary Source


Cheng J.-J.,China University of Mining and Technology | Cheng J.-J.,Australian National University | Zhou F.-B.,China University of Mining and Technology | Zhou F.-B.,Key Laboratory of Gas and Fire Control for Coal Mines
Journal of Thermal Analysis and Calorimetry | Year: 2016

To improve the flame-retardant properties of polymer materials, an organic–inorganic hybrid material was obtained by various mixed ratios of sodium silicate solution and polyisocyanate. The chemical structure of materials was characterized by Fourier transform infrared spectroscopy, and the microstructures were observed by scanning electron microscope. The influence of various ratios of polyisocyanate and sodium silicate on the flame-retardant properties of hybrid materials was emphatically investigated. The results showed that Si–O and Si–O–Si bonds were introduced into the hybrid materials and the surfaces were rougher than that of rigid polyurethane. The hybrid materials had better flame-retardant properties than the rigid polyurethane with an obvious decrease in heat release rate, spread rate of fire, decomposition rate and increase in residue and LOI value. When the hybrid materials were burning, less carbon dioxide and carbon monoxide were produced. In addition, the TG curve showed that the mass of hybrid materials decreased more slowly than the mass of the rigid polyurethane. So the hybrid materials showed excellent flame-retardant properties. © 2016, Akadémiai Kiadó, Budapest, Hungary. Source


Zhou F.,Key Laboratory of Gas and Fire Control for Coal Mines | Zhou F.,China University of Mining and Technology | Sun Y.,Henan Polytechnic University | Li H.,China University of Mining and Technology | Yu G.,Coal Mine Gas Control National Engineering Research Center
Zhongguo Kuangye Daxue Xuebao/Journal of China University of Mining and Technology | Year: 2016

Low gas drainage concentration was caused by the leak in the borehole and the leakage fracture around the borehole. Based on the multi-physics field coupling theory, the mathematical model considering the leak in the borehole and the leakage fracture around the borehole was established for analyzing borehole leakage mechanism. The model was solved by COMSOL Multiphysics software. The results show that the bigger the width of the leakage fracture in the mining area is, the faster the decay rate of the gas drainage concentration is. The leakage fracture characteristic is an important factor to influence the concentration of gas drainage. In order to ensure sealing quality and improve the gas drainage results, the modern hole sealing technology not only needs to achieve the sealing in the borehole, but also seal the the leakage fracture field of coal mass around the borehole. Accordingly, two new fracture sealing technologies, namely bag-type grouting hole sealing and secondary hole sealing, were introduced emphatically in this paper with their application effects. © 2016, China University of Mining and Technology. All right reserved. Source


Cheng J.-J.,China University of Mining and Technology | Shi B.-B.,China University of Mining and Technology | Zhou F.-B.,China University of Mining and Technology | Zhou F.-B.,Key Laboratory of Gas and Fire Control for Coal Mines | Chen X.-Y.,China University of Mining and Technology
Journal of Applied Polymer Science | Year: 2014

Rigid polyurethane foam (RPUF) composites filled with expandable graphite (EG), hollow glass microspheres (HGM), and glass fibers (GF) have been synthesized and characterized by limiting oxygen index, radiation ignition, compressing and torsion testing, and scanning electron microscopy. The results indicate HGM and GF benefit to the mechanical properties, while EG is good for flame retardancy. Proper ingredient of additive can lead to good flame retardancy and mechanical properties of the RPUF. © 2013 Wiley Periodicals, Inc. Source

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