The present day weapon technology demands novel energetic materials that exhibit simultaneous high explosive yield and reduced sensitivity.This article demonstrates application of spray evaporation to prepare reduced ...The present day weapon technology demands novel energetic materials that exhibit simultaneous high explosive yield and reduced sensitivity.This article demonstrates application of spray evaporation to prepare reduced sensitive co-crystals of high performance nitramine explosives like HMX and CL-20 with a relatively less insensitive explosive 1,1-diamino-2,2-dinitroethylene or FOX-7.Stronger intermolecurar hydrogen bonding in FOX-7 is responsible for limited solubility in nost of o rganic solvents.Large solubility differences of FOX-7 with HMX and CL-20 restricts ifs co-crystallization through classical methods that yields thermodynamically favorable product.Spray flash evaporation,a kinetic crystallization method,has been therefore adopted and could successfully produce CL-20/FOX-7(2:1) and HMX/FQX-7(4:1) co-crystals.The fine powdered materials obtained were characterized by SEM,powder XRD,Raman spectro scopy,DSC-TGA etc.Multipoint Raman spectra showed consistent occurrence of spectral features indicating stoichiometric co-existence of ingredients in the crystal lattices.DSC analysis showed absence of all thermally assisted solidsolid phase transformation in the co-crystals as they were observed in pristine materials.The thermal stability calculated in terms of activation barrier fordecomposition,revealed the CL-20/FOX-7 co-crystal to be interlediately stable on comparison to their constituents while,the HMX/FOX-7 co-crystal is more stable.Compared to pure HMX and CL-20,both the co-crystals have shown higher insensitivity to impact force,suggesting them to be suitable for future generation insensitive munitions.展开更多
Organic Rankine cycle(ORC)is widely used for the low grade geothermal power generation.However,a large amount of irreversible loss results in poor technical and economic performance due to its poor matching between th...Organic Rankine cycle(ORC)is widely used for the low grade geothermal power generation.However,a large amount of irreversible loss results in poor technical and economic performance due to its poor matching between the heat source/sink and the working medium in the condenser and the evaporator.The condensing temperature,cooling water temperature difference and pinch point temperature difference are often fixed according to engineering experience.In order to optimize the ORC system comprehensively,the coupling effect of evaporation and condensation process was proposed in this paper.Based on the laws of thermodynamics,the energy analysis,exergy analysis and entropy analysis were adopted to investigate the ORC performance including net output power,thermal efficiency,exergy efficiency,thermal conductivity,irreversible loss,etc.,using geothermal water at a temperature of 120℃as the heat source and isobutane as the working fluid.The results show that there exists a pair of optimal evaporating temperature and condensing temperatures to maximize the system performance.The net power output and the system comprehensive performance achieve their highest values at the same evaporating temperature,but the system comprehensive performance corresponds to a lower condensing temperature than the net power output.展开更多
The mesoporous Ti O2 has been synthesized by evaporation induced self assembly(EISA) method. The thermogravimetric/differential scanning calorimetric(TG/DSC), X-ray diffraction(XRD), high-resolution transmission elect...The mesoporous Ti O2 has been synthesized by evaporation induced self assembly(EISA) method. The thermogravimetric/differential scanning calorimetric(TG/DSC), X-ray diffraction(XRD), high-resolution transmission electron microscopy(HR-TEM) and N2 adsorption desorption and adsorption are used to study the effects of the synthesized process condition on the microstructure of the as-synthesized mesoporous Ti O2. The photocatalytic performances of as-synthesized samples are evaluated by the degradation of the formaldehyde under ultraviolet light irradiations. The results demonstrate that the as-synthesized mesoporous Ti O2 are anatase with the uniform size about 20-40 nm. The sample is prepared using cetyltrimethyl ammonium bromide(CTAB) as the template with average pore size distribution of 8.12 nm, specific surface area of 68.47 m2/g and pore volume of 0.213 m L/g. The samples show decomposition of formaldehyde 95.8% under ultraviolet light irradiations for 90 min. These results provide a basic experimental process for preparation mesoporous Ti O2, which will posses a broad prospect in terms of the applications in improving indoor air quality.展开更多
Polyfunctional aziridine/polyester microcapsules as control-release waterborne cross-linker were synthesized by multiple emulsion-solvent evaporation method. The results show that,a lower surface free energy with shel...Polyfunctional aziridine/polyester microcapsules as control-release waterborne cross-linker were synthesized by multiple emulsion-solvent evaporation method. The results show that,a lower surface free energy with shell polyester is more favourable for the formation of microcapsules. Full encapsulating microcapsules are synthesized with the polyester with a surface free energy of 34.5 mJ/m2. Shell-to-core feeding mass ratio has a significant influence on the morphology and core content of the resulting microcapsules. Well defined spherical microcapsules with uniform shell thickness and core content at around 22% are produced at a shell-to-core mass ratio of 1:1. When 2.5% of colloid stabilizer is used,hollow spherical microcapsules are obtained. A high solvent evaporation rate results in wrinkling and porosity of the microcapsules,and an evaporation rate equivalent to solvent elimination in about 2 h provides a uniform rate of surface hardening. The characterization of the microcapsules by SEM and FTIR demonstrates that polyfunctional aziridine is encapsulated at the centre of the microcapsule. The microcapsules synthesized can be broken at a high shear rate.展开更多
The boiling heat transfer of evaporation cooling in a billet reheating furnace was simulated.The results indicate that the bubbles easily aggregate inside of the elbow and upper side of the horizontal regions in theπ...The boiling heat transfer of evaporation cooling in a billet reheating furnace was simulated.The results indicate that the bubbles easily aggregate inside of the elbow and upper side of the horizontal regions in theπshaped support tubes.The circulation velocity increasing helps to improve the uniformity of vapor distribution and decrease the difference of vapor volume fraction between upper and down at end of the horizontal sections.With the increase of circulation velocity,the resistance loss and the circulation ratio both increase,but the former will decrease with the increase of work pressure.展开更多
基金Defense Research&Development Organization(DRDO),India for financial support towards this study。
文摘The present day weapon technology demands novel energetic materials that exhibit simultaneous high explosive yield and reduced sensitivity.This article demonstrates application of spray evaporation to prepare reduced sensitive co-crystals of high performance nitramine explosives like HMX and CL-20 with a relatively less insensitive explosive 1,1-diamino-2,2-dinitroethylene or FOX-7.Stronger intermolecurar hydrogen bonding in FOX-7 is responsible for limited solubility in nost of o rganic solvents.Large solubility differences of FOX-7 with HMX and CL-20 restricts ifs co-crystallization through classical methods that yields thermodynamically favorable product.Spray flash evaporation,a kinetic crystallization method,has been therefore adopted and could successfully produce CL-20/FOX-7(2:1) and HMX/FQX-7(4:1) co-crystals.The fine powdered materials obtained were characterized by SEM,powder XRD,Raman spectro scopy,DSC-TGA etc.Multipoint Raman spectra showed consistent occurrence of spectral features indicating stoichiometric co-existence of ingredients in the crystal lattices.DSC analysis showed absence of all thermally assisted solidsolid phase transformation in the co-crystals as they were observed in pristine materials.The thermal stability calculated in terms of activation barrier fordecomposition,revealed the CL-20/FOX-7 co-crystal to be interlediately stable on comparison to their constituents while,the HMX/FOX-7 co-crystal is more stable.Compared to pure HMX and CL-20,both the co-crystals have shown higher insensitivity to impact force,suggesting them to be suitable for future generation insensitive munitions.
基金Project(2018YFB1501805)supported by the National Key Research and Development Program of ChinaProject(51406130)supported by the National Natural Science Foundation of ChinaProject(201604-504)supported by the Key Laboratory of Efficient Utilization of Low and Medium Grade Energy(Tianjin University),China
文摘Organic Rankine cycle(ORC)is widely used for the low grade geothermal power generation.However,a large amount of irreversible loss results in poor technical and economic performance due to its poor matching between the heat source/sink and the working medium in the condenser and the evaporator.The condensing temperature,cooling water temperature difference and pinch point temperature difference are often fixed according to engineering experience.In order to optimize the ORC system comprehensively,the coupling effect of evaporation and condensation process was proposed in this paper.Based on the laws of thermodynamics,the energy analysis,exergy analysis and entropy analysis were adopted to investigate the ORC performance including net output power,thermal efficiency,exergy efficiency,thermal conductivity,irreversible loss,etc.,using geothermal water at a temperature of 120℃as the heat source and isobutane as the working fluid.The results show that there exists a pair of optimal evaporating temperature and condensing temperatures to maximize the system performance.The net power output and the system comprehensive performance achieve their highest values at the same evaporating temperature,but the system comprehensive performance corresponds to a lower condensing temperature than the net power output.
基金Projects(51102026,51272032) supported by the Program for the National Natural Science Foundation of ChinaProject(11A014) supported by the Scientific Research Fund of Hunan Provincial Education DepartmentProject supported by the Aid Program for Science and Technology Innovative Research Team in Higher Educational Instituions of Hunan Province,China
文摘The mesoporous Ti O2 has been synthesized by evaporation induced self assembly(EISA) method. The thermogravimetric/differential scanning calorimetric(TG/DSC), X-ray diffraction(XRD), high-resolution transmission electron microscopy(HR-TEM) and N2 adsorption desorption and adsorption are used to study the effects of the synthesized process condition on the microstructure of the as-synthesized mesoporous Ti O2. The photocatalytic performances of as-synthesized samples are evaluated by the degradation of the formaldehyde under ultraviolet light irradiations. The results demonstrate that the as-synthesized mesoporous Ti O2 are anatase with the uniform size about 20-40 nm. The sample is prepared using cetyltrimethyl ammonium bromide(CTAB) as the template with average pore size distribution of 8.12 nm, specific surface area of 68.47 m2/g and pore volume of 0.213 m L/g. The samples show decomposition of formaldehyde 95.8% under ultraviolet light irradiations for 90 min. These results provide a basic experimental process for preparation mesoporous Ti O2, which will posses a broad prospect in terms of the applications in improving indoor air quality.
基金Project(50903031) supported by the National Natural Science Foundation of ChinaProject(2009ZM0046) supported by the Fundamental Research Funds for the Central Universities in ChinaProject(N9100240) supported by the Foundation for Distinguished Young Talents in Higher Education of Guangdong Province, China
文摘Polyfunctional aziridine/polyester microcapsules as control-release waterborne cross-linker were synthesized by multiple emulsion-solvent evaporation method. The results show that,a lower surface free energy with shell polyester is more favourable for the formation of microcapsules. Full encapsulating microcapsules are synthesized with the polyester with a surface free energy of 34.5 mJ/m2. Shell-to-core feeding mass ratio has a significant influence on the morphology and core content of the resulting microcapsules. Well defined spherical microcapsules with uniform shell thickness and core content at around 22% are produced at a shell-to-core mass ratio of 1:1. When 2.5% of colloid stabilizer is used,hollow spherical microcapsules are obtained. A high solvent evaporation rate results in wrinkling and porosity of the microcapsules,and an evaporation rate equivalent to solvent elimination in about 2 h provides a uniform rate of surface hardening. The characterization of the microcapsules by SEM and FTIR demonstrates that polyfunctional aziridine is encapsulated at the centre of the microcapsule. The microcapsules synthesized can be broken at a high shear rate.
基金Project(51171041) supported by the National Natural Science Foundation of China
文摘The boiling heat transfer of evaporation cooling in a billet reheating furnace was simulated.The results indicate that the bubbles easily aggregate inside of the elbow and upper side of the horizontal regions in theπshaped support tubes.The circulation velocity increasing helps to improve the uniformity of vapor distribution and decrease the difference of vapor volume fraction between upper and down at end of the horizontal sections.With the increase of circulation velocity,the resistance loss and the circulation ratio both increase,but the former will decrease with the increase of work pressure.
