To develop a high performance gray cast iron with high tensile strength and thermal conductivity, multivariable analysis of microstructural effects on properties of gray cast iron was performed. The concerned paramete...To develop a high performance gray cast iron with high tensile strength and thermal conductivity, multivariable analysis of microstructural effects on properties of gray cast iron was performed. The concerned parameters consisted of graphite content, maximum graphite length, primary dendrite percentage and microhardness of the matrix. Under the superposed influence of various parameters, the relationships between thermal conductivity and structural characteristics become irregular, as well as the effects of graphite length on the strength. An adaptive neuro-fuzzy inference system was built to link the parameters and properties. A sensitivity test was then performed to rank the relative impact of parameters. It was found that the dominant parameter for tensile strength is graphite content, while the most relative parameter for thermal conductivity is maximum graphite length. The most effective method to simultaneously improve the tensile and thermal conductivity of gray cast iron is to reduce the carbon equivalent and increase the length of graphite flakes.展开更多
Atmospheric exposure tests including two experimental stages of high temperature-spraying water cycle and heating-refrigeration cycle were carried out on three currently used ETIS of expanded polystyrene（EPS） board,...Atmospheric exposure tests including two experimental stages of high temperature-spraying water cycle and heating-refrigeration cycle were carried out on three currently used ETIS of expanded polystyrene（EPS） board,polystyrene granule mortar and polyurethane foam in order to study the weatherablility of external thermal insulation system（ETIS）.The change rules of adhesive strength were hereby studied at different time period of atmospheric exposure tests.The experimental results show that the adhesive strength of three kinds of ETIS changes a little during high temperature-spraying water cycle,but the adhesive strength of ETIS with EPS board decreases significantly after heating-refrigeration cycle.The lowering rate of adhesive strength with painting finishes is obviously faster than that of tile finishes for ETIS of EPS board during heating-refrigeration cycle.The weatherability of ETIS with EPS board is worse than the other two,and ETIS of polystyrene granule mortar and polyurethane foam are more suitable than ETIS of EPS board in cold area.展开更多
Using the detection principle of infrared thermal imaging technique and the detection principle of DRH thermal conductivity tester laboratory,we investigated the infrared thermal image inspection,coefficient of therma...Using the detection principle of infrared thermal imaging technique and the detection principle of DRH thermal conductivity tester laboratory,we investigated the infrared thermal image inspection,coefficient of thermal conductivity,apparent density,and compressive strength test on C80 high-strength concrete（HSC） in the presence and absence of polypropylene fibers under completely heated conditions.Only slight damages were detected below 400 ℃,whereas more and more severe deterioration events were expected when the temperature was above 500 ℃.The results show that the elevated temperature through infrared images generally exhibits an upward trend with increasing temperature,while the coefficient of thermal conductivity and apparent density decrease gradually.Additionally,the addition of polypropylene fibers with appropriate length,diameter,and quantity contributes to the improvement of the high-temperature resistance of HSC.展开更多
The specimens were prepared with high alumina fiber accounting for 0. 5% , 10% or 15% by mass of the total amount of amorphous silica and high alumina fiber, using phenolic resin as binder, and extra-adding 0 or 0. 5%...The specimens were prepared with high alumina fiber accounting for 0. 5% , 10% or 15% by mass of the total amount of amorphous silica and high alumina fiber, using phenolic resin as binder, and extra-adding 0 or 0. 5% ZnO as sunscreen to cut the cost of SiO2 nanoporous insulation board. The hot volume stability and thermal conductivity （flat plate method ） of the specimens were tested and multi-Jimetion simulation equipment was used to study the thermal insulation performante. The results show that： （1） with high alumina fiber addition increasing, the linear shrinkage rate decreases, but thermal eonductivity changes a little; （2） adding ZnO can decrease thermal conductivity obviously; （3）for the specimen with ZnO and 15% of high alumina fiber, its cold face temperature hardly rises during the simulation experiment at 1 000 ℃ for 2 h, and the cold face temperature of the specimen with the smallest thickness of 2 cm doesn＇t exceed 180 ℃.展开更多
A significant number of fire-induced power disruptions are observed in several countries every year. The faults are normally phase-to-phase short circuiting or conductor-to-ground discharges at mid-span region of the ...A significant number of fire-induced power disruptions are observed in several countries every year. The faults are normally phase-to-phase short circuiting or conductor-to-ground discharges at mid-span region of the high-voltage transmission system. In any case, the wildfire plumes provide a conductive path. The electrical conductivity is due to intense heat in combustion zone of the fire which creates ion and electrons from flame inherent particulates. Increase in the ion concentration increases the electrical conductivity of the fire plume. The main purpose of this study was to measure dielectric breakdown electric field for vegetation and hydrocarbon flames. The experimental data is needed for validation of simulation schemes which are necessary for evaluation of power grid systems reliability under extreme wildfire weather conditions. In this study, hydrocarbon and vegetation fuels were ignited in a cylindrically shaped steel burner which was fitted with type-K thermocouples to measure flame temperature. The fuels consisted of dried weeping wattle (Peltophorum africanum) litter, butane gas and candle wax. Two pinned copper electrodes supported by retort stands were mounted to the burner and energized to a high voltage. This generated a strong electric field sufficient to initiate dielectric breakdown in the flames. Breakdown electric field strength (Ecrit) obtained from the experiment decreased from 10.5 to 6.9 kV/cm for the flames with temperature range of 1003 to 1410 K, respectively.展开更多
The use of coconut shell particulates to enhance the insulating refractory properties of Ukpor, Osiele and Kankara fireclays in Nigeria was studied in this paper. The chemical analysis of the raw materials was conduct...The use of coconut shell particulates to enhance the insulating refractory properties of Ukpor, Osiele and Kankara fireclays in Nigeria was studied in this paper. The chemical analysis of the raw materials was conducted using Atomic Absorption spectrometer. The samples used for different tests were prepared by mixing the clay, bentonite and coconut shell, of grain sizes of 212 - 600 μm. The prepared samples were air and oven dried for 24 hours at room temperature and at 110°C respectively. The samples were then fired at different temperatures in the range of 950°C to 1200°C at 50°C interval and at 2.5°C/min. The fired samples were investigated for their physical, insulating (thermal) and mechanical properties. Micro-structural examination was also carried out. The results indicate that clays with 25 wt% - 30 wt% coconut shell and grain sizes of 212 - 300 μm fired at 1150°C - 1200°C possess enhanced mechanical, physical and insulating (thermal) properties. The SEM micrograph revealed the formation of mullite phase in the bricks fired at 1150°C. Thus, high quality refractory bricks with enhanced insulating properties could be produced from Ukpor, Osiele and Kankara fire-clays blended with coconut shell particulates.展开更多
To optimize their Al_(2)O_(3)-SiO_(2) raw materials,anorthite based insulation refractories were prepared by the in-situ sintering process combined with the foaming method after sintering at 1350℃for 3 h,using green ...To optimize their Al_(2)O_(3)-SiO_(2) raw materials,anorthite based insulation refractories were prepared by the in-situ sintering process combined with the foaming method after sintering at 1350℃for 3 h,using green and pollution-free kaolin,kyanite,andalusite and sillimanite as Al_(2)O_(3)-SiO_(2) raw materials,respectively,and industrial CaCO_(3) as the CaO source.Effects of Al_(2)O_(3)-SiO_(2) raw material types on the physical properties,phase composition and microstructure were investigated.The results are as follows.All samples prepared by different Al_(2)O_(3)-SiO_(2) raw materials have hexagonal flake anorthite and a small amount of mullite and corundum.Their bulk density and thermal conductivity decrease in the order of using kaolin,andalusite,kyanite and sillimanite as the Al_(2)O_(3)-SiO_(2) raw material,but their apparent porosity increases.Moreover,in the sample with kaolin,the bonding between anorthite crystals on the pore walls is closer than that of the other samples,which is conducive to increasing the cold crushing strength.The bonding between anorthite crystals on pore walls gradually decreases in the order of using kyanite,andalusite and sillimanite as the Al_(2)O_(3)-SiO_(2) raw material,thus their cold crushing strength decreases accordingly.In comprehensive consideration,the properties of the sample from kyanite are the optimal.Its apparent porosity,thermal conductivity and cold crushing strength are 84.6%,0.141 W·m^(-1)·K^(-1) and 1.89 MPa,respectively.展开更多
To solve the problem of over-high density of lightweight insulation refractory bricks prepared with fly ash, new lightweight insulation refractory materials with density 〈 0. 89 g · cm^-3 were .synthesized using...To solve the problem of over-high density of lightweight insulation refractory bricks prepared with fly ash, new lightweight insulation refractory materials with density 〈 0. 89 g · cm^-3 were .synthesized using pyrophyl-lite, .fly ash, and Suzhou clay as the main starting materials and saw dast as the pore forming substance, and controlling the addition of the pyrophyllite （20%, 30% , and 40% by mass ） and the treating temperature （1 250, 1 300, 1 350, and 1 400 ℃ ）. The synthesized materials were characterized by the XRD, SEM and the thermal conductivity measuring in.strument. The results show at pyrophyllite addition of 30% and treat temperature of l 400 ℃ , the material can achieve linear shrinkage of 6. 6%, apparent porosity of 57%, bulk density of 0. 75 g · cm^-3, compressive strength of 2.7 MPa, and thermal conductivity at 350 ℃ of 0. 152 -0. 216 W·（ m·K）^-1.This indicates that the pyrophyllite decomposition at high temperatures forms mullite and amorphous quartz introducing volume expansion, which counteracts some shrinkage at high temperatures. So it is feasible to use pyrophyllite, fly ash waste and clay to prepare lightweight insulation refractory materials.展开更多
文摘To develop a high performance gray cast iron with high tensile strength and thermal conductivity, multivariable analysis of microstructural effects on properties of gray cast iron was performed. The concerned parameters consisted of graphite content, maximum graphite length, primary dendrite percentage and microhardness of the matrix. Under the superposed influence of various parameters, the relationships between thermal conductivity and structural characteristics become irregular, as well as the effects of graphite length on the strength. An adaptive neuro-fuzzy inference system was built to link the parameters and properties. A sensitivity test was then performed to rank the relative impact of parameters. It was found that the dominant parameter for tensile strength is graphite content, while the most relative parameter for thermal conductivity is maximum graphite length. The most effective method to simultaneously improve the tensile and thermal conductivity of gray cast iron is to reduce the carbon equivalent and increase the length of graphite flakes.
基金Funded by the Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20050487017)
文摘Atmospheric exposure tests including two experimental stages of high temperature-spraying water cycle and heating-refrigeration cycle were carried out on three currently used ETIS of expanded polystyrene（EPS） board,polystyrene granule mortar and polyurethane foam in order to study the weatherablility of external thermal insulation system（ETIS）.The change rules of adhesive strength were hereby studied at different time period of atmospheric exposure tests.The experimental results show that the adhesive strength of three kinds of ETIS changes a little during high temperature-spraying water cycle,but the adhesive strength of ETIS with EPS board decreases significantly after heating-refrigeration cycle.The lowering rate of adhesive strength with painting finishes is obviously faster than that of tile finishes for ETIS of EPS board during heating-refrigeration cycle.The weatherability of ETIS with EPS board is worse than the other two,and ETIS of polystyrene granule mortar and polyurethane foam are more suitable than ETIS of EPS board in cold area.
基金Funded by the National Natural Science Foundation of China(No.51278325)the Shanxi Province Natural Science Foundation(No.2011011024-2)
文摘Using the detection principle of infrared thermal imaging technique and the detection principle of DRH thermal conductivity tester laboratory,we investigated the infrared thermal image inspection,coefficient of thermal conductivity,apparent density,and compressive strength test on C80 high-strength concrete（HSC） in the presence and absence of polypropylene fibers under completely heated conditions.Only slight damages were detected below 400 ℃,whereas more and more severe deterioration events were expected when the temperature was above 500 ℃.The results show that the elevated temperature through infrared images generally exhibits an upward trend with increasing temperature,while the coefficient of thermal conductivity and apparent density decrease gradually.Additionally,the addition of polypropylene fibers with appropriate length,diameter,and quantity contributes to the improvement of the high-temperature resistance of HSC.
基金support of the National Natural Science Foundation of China(No.51402265,51202225,and 51272240)
文摘The specimens were prepared with high alumina fiber accounting for 0. 5% , 10% or 15% by mass of the total amount of amorphous silica and high alumina fiber, using phenolic resin as binder, and extra-adding 0 or 0. 5% ZnO as sunscreen to cut the cost of SiO2 nanoporous insulation board. The hot volume stability and thermal conductivity （flat plate method ） of the specimens were tested and multi-Jimetion simulation equipment was used to study the thermal insulation performante. The results show that： （1） with high alumina fiber addition increasing, the linear shrinkage rate decreases, but thermal eonductivity changes a little; （2） adding ZnO can decrease thermal conductivity obviously; （3）for the specimen with ZnO and 15% of high alumina fiber, its cold face temperature hardly rises during the simulation experiment at 1 000 ℃ for 2 h, and the cold face temperature of the specimen with the smallest thickness of 2 cm doesn＇t exceed 180 ℃.
文摘A significant number of fire-induced power disruptions are observed in several countries every year. The faults are normally phase-to-phase short circuiting or conductor-to-ground discharges at mid-span region of the high-voltage transmission system. In any case, the wildfire plumes provide a conductive path. The electrical conductivity is due to intense heat in combustion zone of the fire which creates ion and electrons from flame inherent particulates. Increase in the ion concentration increases the electrical conductivity of the fire plume. The main purpose of this study was to measure dielectric breakdown electric field for vegetation and hydrocarbon flames. The experimental data is needed for validation of simulation schemes which are necessary for evaluation of power grid systems reliability under extreme wildfire weather conditions. In this study, hydrocarbon and vegetation fuels were ignited in a cylindrically shaped steel burner which was fitted with type-K thermocouples to measure flame temperature. The fuels consisted of dried weeping wattle (Peltophorum africanum) litter, butane gas and candle wax. Two pinned copper electrodes supported by retort stands were mounted to the burner and energized to a high voltage. This generated a strong electric field sufficient to initiate dielectric breakdown in the flames. Breakdown electric field strength (Ecrit) obtained from the experiment decreased from 10.5 to 6.9 kV/cm for the flames with temperature range of 1003 to 1410 K, respectively.
文摘The use of coconut shell particulates to enhance the insulating refractory properties of Ukpor, Osiele and Kankara fireclays in Nigeria was studied in this paper. The chemical analysis of the raw materials was conducted using Atomic Absorption spectrometer. The samples used for different tests were prepared by mixing the clay, bentonite and coconut shell, of grain sizes of 212 - 600 μm. The prepared samples were air and oven dried for 24 hours at room temperature and at 110°C respectively. The samples were then fired at different temperatures in the range of 950°C to 1200°C at 50°C interval and at 2.5°C/min. The fired samples were investigated for their physical, insulating (thermal) and mechanical properties. Micro-structural examination was also carried out. The results indicate that clays with 25 wt% - 30 wt% coconut shell and grain sizes of 212 - 300 μm fired at 1150°C - 1200°C possess enhanced mechanical, physical and insulating (thermal) properties. The SEM micrograph revealed the formation of mullite phase in the bricks fired at 1150°C. Thus, high quality refractory bricks with enhanced insulating properties could be produced from Ukpor, Osiele and Kankara fire-clays blended with coconut shell particulates.
基金This work was supported by the National Natural Science Foundation of China(5180021223)Henan Provice Science&Technology Programs(232102231046 and 232102231051)Cultivation Programme for Yong Backbone Teachers in Henan University to Technology(2142121).
文摘To optimize their Al_(2)O_(3)-SiO_(2) raw materials,anorthite based insulation refractories were prepared by the in-situ sintering process combined with the foaming method after sintering at 1350℃for 3 h,using green and pollution-free kaolin,kyanite,andalusite and sillimanite as Al_(2)O_(3)-SiO_(2) raw materials,respectively,and industrial CaCO_(3) as the CaO source.Effects of Al_(2)O_(3)-SiO_(2) raw material types on the physical properties,phase composition and microstructure were investigated.The results are as follows.All samples prepared by different Al_(2)O_(3)-SiO_(2) raw materials have hexagonal flake anorthite and a small amount of mullite and corundum.Their bulk density and thermal conductivity decrease in the order of using kaolin,andalusite,kyanite and sillimanite as the Al_(2)O_(3)-SiO_(2) raw material,but their apparent porosity increases.Moreover,in the sample with kaolin,the bonding between anorthite crystals on the pore walls is closer than that of the other samples,which is conducive to increasing the cold crushing strength.The bonding between anorthite crystals on pore walls gradually decreases in the order of using kyanite,andalusite and sillimanite as the Al_(2)O_(3)-SiO_(2) raw material,thus their cold crushing strength decreases accordingly.In comprehensive consideration,the properties of the sample from kyanite are the optimal.Its apparent porosity,thermal conductivity and cold crushing strength are 84.6%,0.141 W·m^(-1)·K^(-1) and 1.89 MPa,respectively.
基金financial support from the National Nature Science Foundation of China(51502213)
文摘To solve the problem of over-high density of lightweight insulation refractory bricks prepared with fly ash, new lightweight insulation refractory materials with density 〈 0. 89 g · cm^-3 were .synthesized using pyrophyl-lite, .fly ash, and Suzhou clay as the main starting materials and saw dast as the pore forming substance, and controlling the addition of the pyrophyllite （20%, 30% , and 40% by mass ） and the treating temperature （1 250, 1 300, 1 350, and 1 400 ℃ ）. The synthesized materials were characterized by the XRD, SEM and the thermal conductivity measuring in.strument. The results show at pyrophyllite addition of 30% and treat temperature of l 400 ℃ , the material can achieve linear shrinkage of 6. 6%, apparent porosity of 57%, bulk density of 0. 75 g · cm^-3, compressive strength of 2.7 MPa, and thermal conductivity at 350 ℃ of 0. 152 -0. 216 W·（ m·K）^-1.This indicates that the pyrophyllite decomposition at high temperatures forms mullite and amorphous quartz introducing volume expansion, which counteracts some shrinkage at high temperatures. So it is feasible to use pyrophyllite, fly ash waste and clay to prepare lightweight insulation refractory materials.
