To improve the ablation resistance of carbon/carbon(C/C)composites,a SiC/ZrC-ZrB2 double layer coating was fabricated by pack cementation and slurry-sintering method.The ablation resistance of the SiC/ZrC-ZrB2 coating...To improve the ablation resistance of carbon/carbon(C/C)composites,a SiC/ZrC-ZrB2 double layer coating was fabricated by pack cementation and slurry-sintering method.The ablation resistance of the SiC/ZrC-ZrB2 coating was tested under plasma flame above 2300°C.The results indicate that the SiC/ZrC-ZrB2 double layer coating exhibits superior ablation resistance than the ZrC-ZrB2 single layer coating.After being ablated under the plasma flame for 20 s,the mass and linear ablation rates of the ZrC-ZrB2 coating are 0.89 mg/s and 15.3μm/s,while those for SiC/ZrC-ZrB2 coating are 0.09 mg/s and 24.15μm/s,respectively.During ablation,the SiC inner layer can generate SiO2 glass and result in the formation of ZrO2-SiO2 molten film.Compared with the ZrO2 molten film formed on the ZrC-ZrB2 coating surface,the ZrO2-SiO2 molten film with lower oxygen diffusion rate and viscosity enables the SiC/ZrC-ZrB2 coating to have better self-healing ability.Therefore,the enhanced ablation resistance of the SiC/ZrC-ZrB2 coating can be attributed to the formation of dense ZrO2-SiO2 molten film under the plasma flame.展开更多
Energy saving has been an important concept in modern industry especially to the countries and regions with energy shortage such as China and Japan. Utilization of Coal-Water Slurry （CWS） can improve the burning eff...Energy saving has been an important concept in modern industry especially to the countries and regions with energy shortage such as China and Japan. Utilization of Coal-Water Slurry （CWS） can improve the burning efficiency of coal and reduce the pollutions of soot, sulfide and the nitride by burning lump coal directly. The CWS is a promising energy saving technique and the effectual substitute of oil. The study on the preparation and application of the CWS has made progresses in many aspects. The present paper studied the basal problems for applying the CWS on the rotary kilns during the calcining-dolomite process in the magnesium factory, summarized the key points for the application process of the CWS and gave the corresponding solutions.展开更多
The paper reports the effects of surface fractal structures on the rheological behavior and combustion kinetics of raw brown coal and three modified coal water slurries （CWSs）. The results show that the fractal stru...The paper reports the effects of surface fractal structures on the rheological behavior and combustion kinetics of raw brown coal and three modified coal water slurries （CWSs）. The results show that the fractal structures and physicochemical properties of samples are dependent on various modification processes. The apparent viscosities of the coal water slurries increase with increasing surface fractal dimensions （D）, especially with decreasing shear rates. Fur- thermore, it has been proved that the ignition temperatures and apparent activation energies of modified CWSs are lower than that of raw coal water slurry. Compared with the traditional qualitative analysis of the effect of pore structures on CWSs properties, D can more efficiently indicate the quantificational effect of pore structures on the rheological behavior and combustion kinetics of CWSs.展开更多
Ce-ZrO2 and ZrO2/CePO4 ceramic system was joined in the green body by using mixed powder. Three kinds of systems are discussed. The microstructure and bending strengths of the joint were investigated and it is found t...Ce-ZrO2 and ZrO2/CePO4 ceramic system was joined in the green body by using mixed powder. Three kinds of systems are discussed. The microstructure and bending strengths of the joint were investigated and it is found that the Ce-ZrO2 and 30%CePO4/ZrO2 ceramics can be well joined in the green body. A joint with high mechanical property and good microstructure can be obtained after sintering without applied pressure. Complexly shaped ceramic components can be created by the technique of green state joining. A new way to produce them is provided and the cost is reduced due to the simplicity of the process.展开更多
Circulating fluidized bed combustion （CFBC） ash can be potentially used as supplementary cementitious materials for concrete production due to its desirable pozzolanic activity. The adsorption properties of CFBC ash...Circulating fluidized bed combustion （CFBC） ash can be potentially used as supplementary cementitious materials for concrete production due to its desirable pozzolanic activity. The adsorption properties of CFBC ash-cement pastes were studied, and ordinary pulverized coal combustion （PCC） fly ash-cement pastes were used as control. The water-adsorption and superplasticizer （SP）-adsorption properties of the pastes were evaluated by water demand and UV-visible absorption spectroscopy respectively. The results show that CFBC ash-cement system has greater compressive strength as compared with PCC fly ash-cement system at a given curing age, although the water demand of the former is significantly higher than that of the latter. CFBC ash-cement pastes possess higher adsorption ability of aliphatic SP than PCC fly ash-cement pastes and the adsorption amount increases with an increase in ash replacement ratio. CFBC ash- cement pastes exhibit lower workability with higher slump loss. It is concluded that CFBC ash can be potentially used as supplementary cementitious material in concrete production, but the mix design of CFBC ash concrete needs to be appropriately adjusted. It is suggested that CFBC ash is used for the production of the concrete needing low flowability.展开更多
To design an effective and realistically applicable sinter bonding process for power devices,we proposed a two-step process using a 200 nm Cu-particle-based paste to form a bondline having high-temperature sustainabil...To design an effective and realistically applicable sinter bonding process for power devices,we proposed a two-step process using a 200 nm Cu-particle-based paste to form a bondline having high-temperature sustainability and superior thermal conductance.This process involved rapid pressure-assisted sinter bonding in air followed by pressureless annealing in a nitrogen atmosphere.In the case of a paste prepared with a mixture of 20 wt.%malic acid and 80 wt.%ethylene glycol,sinter bonding at 300℃and 5 MPa for only 30 s resulted in a sufficient shear strength of 23.1 MPa.The shear strength was significantly enhanced to 69.6 MPa by the additional pressureless aging for 30 min.Therefore,the two-step sinter bonding process is expected to provide an outstanding production rate as a next-generation sinter bonding process.展开更多
基金Project(51304249)supported by the National Natural Science Foundation of ChinaProject(14JJ3023)supported by the Science Foundation of Hunan Province,China。
文摘To improve the ablation resistance of carbon/carbon(C/C)composites,a SiC/ZrC-ZrB2 double layer coating was fabricated by pack cementation and slurry-sintering method.The ablation resistance of the SiC/ZrC-ZrB2 coating was tested under plasma flame above 2300°C.The results indicate that the SiC/ZrC-ZrB2 double layer coating exhibits superior ablation resistance than the ZrC-ZrB2 single layer coating.After being ablated under the plasma flame for 20 s,the mass and linear ablation rates of the ZrC-ZrB2 coating are 0.89 mg/s and 15.3μm/s,while those for SiC/ZrC-ZrB2 coating are 0.09 mg/s and 24.15μm/s,respectively.During ablation,the SiC inner layer can generate SiO2 glass and result in the formation of ZrO2-SiO2 molten film.Compared with the ZrO2 molten film formed on the ZrC-ZrB2 coating surface,the ZrO2-SiO2 molten film with lower oxygen diffusion rate and viscosity enables the SiC/ZrC-ZrB2 coating to have better self-healing ability.Therefore,the enhanced ablation resistance of the SiC/ZrC-ZrB2 coating can be attributed to the formation of dense ZrO2-SiO2 molten film under the plasma flame.
文摘Energy saving has been an important concept in modern industry especially to the countries and regions with energy shortage such as China and Japan. Utilization of Coal-Water Slurry （CWS） can improve the burning efficiency of coal and reduce the pollutions of soot, sulfide and the nitride by burning lump coal directly. The CWS is a promising energy saving technique and the effectual substitute of oil. The study on the preparation and application of the CWS has made progresses in many aspects. The present paper studied the basal problems for applying the CWS on the rotary kilns during the calcining-dolomite process in the magnesium factory, summarized the key points for the application process of the CWS and gave the corresponding solutions.
文摘The paper reports the effects of surface fractal structures on the rheological behavior and combustion kinetics of raw brown coal and three modified coal water slurries （CWSs）. The results show that the fractal structures and physicochemical properties of samples are dependent on various modification processes. The apparent viscosities of the coal water slurries increase with increasing surface fractal dimensions （D）, especially with decreasing shear rates. Fur- thermore, it has been proved that the ignition temperatures and apparent activation energies of modified CWSs are lower than that of raw coal water slurry. Compared with the traditional qualitative analysis of the effect of pore structures on CWSs properties, D can more efficiently indicate the quantificational effect of pore structures on the rheological behavior and combustion kinetics of CWSs.
文摘Ce-ZrO2 and ZrO2/CePO4 ceramic system was joined in the green body by using mixed powder. Three kinds of systems are discussed. The microstructure and bending strengths of the joint were investigated and it is found that the Ce-ZrO2 and 30%CePO4/ZrO2 ceramics can be well joined in the green body. A joint with high mechanical property and good microstructure can be obtained after sintering without applied pressure. Complexly shaped ceramic components can be created by the technique of green state joining. A new way to produce them is provided and the cost is reduced due to the simplicity of the process.
基金the National Nature Science Foundation of China （51272222）.
文摘Circulating fluidized bed combustion （CFBC） ash can be potentially used as supplementary cementitious materials for concrete production due to its desirable pozzolanic activity. The adsorption properties of CFBC ash-cement pastes were studied, and ordinary pulverized coal combustion （PCC） fly ash-cement pastes were used as control. The water-adsorption and superplasticizer （SP）-adsorption properties of the pastes were evaluated by water demand and UV-visible absorption spectroscopy respectively. The results show that CFBC ash-cement system has greater compressive strength as compared with PCC fly ash-cement system at a given curing age, although the water demand of the former is significantly higher than that of the latter. CFBC ash-cement pastes possess higher adsorption ability of aliphatic SP than PCC fly ash-cement pastes and the adsorption amount increases with an increase in ash replacement ratio. CFBC ash- cement pastes exhibit lower workability with higher slump loss. It is concluded that CFBC ash can be potentially used as supplementary cementitious material in concrete production, but the mix design of CFBC ash concrete needs to be appropriately adjusted. It is suggested that CFBC ash is used for the production of the concrete needing low flowability.
基金the Materials&Components Technology Development Program(10080187)the Ministry of Trade,Industry&Energy(MI,Korea).
文摘To design an effective and realistically applicable sinter bonding process for power devices,we proposed a two-step process using a 200 nm Cu-particle-based paste to form a bondline having high-temperature sustainability and superior thermal conductance.This process involved rapid pressure-assisted sinter bonding in air followed by pressureless annealing in a nitrogen atmosphere.In the case of a paste prepared with a mixture of 20 wt.%malic acid and 80 wt.%ethylene glycol,sinter bonding at 300℃and 5 MPa for only 30 s resulted in a sufficient shear strength of 23.1 MPa.The shear strength was significantly enhanced to 69.6 MPa by the additional pressureless aging for 30 min.Therefore,the two-step sinter bonding process is expected to provide an outstanding production rate as a next-generation sinter bonding process.
