Acidic-and alkalic-hydrolyses are selective in breaking functional bonds and falling off pharmacological moieties of antibiotics in production wastewater in comparison with advanced oxidation processes.Elevating tempe...Acidic-and alkalic-hydrolyses are selective in breaking functional bonds and falling off pharmacological moieties of antibiotics in production wastewater in comparison with advanced oxidation processes.Elevating temperature can accelerate hydrolytic kinetics and improve efficiency.In this work,magnetic sulfonated polypropylene resin(Fe_(3)O_(4)@PS-S)composites were reported for acidic-thermal hydrolysis of tylosin by employing the acidic feature of sulfonic group,the dielectric effect of resin,and the magnetic-loss effect of magnetite under microwave irradiation.As observed,a rapid and complete mitigation 100 mg/L of tylosin was achieved within 15 min by the catalysts.Acidic cleavage of tylosin was fulfilled by sulfonic groups in the composites,and microwave thermal accelerated the hydrolysis reactions due to the dielectric and magnetic-loss effects.Differentiating the dielectric and magnetic-loss effects through electromagnetic analyses indicated that the latter contributed more in converting microwave energy to heat.The interactions under multiple operational conditions were quantitatively fitted using the Behnajady model and visually demonstrated,which indicated that a synergic effect of microwave thermal-and acidichydrolyses contributed to the efficient mitigation of tylosin.The transformation products were identified and the pathways were supposed.Cleaving deoxyaminosugars groups and destructing lactone structures led to reduced antibacterial potential and toxicity reduction.The acute toxicity of tylosin and transformation products to fish,daphnia,and green algae were all classified as non-toxic.This work suggested that this synergistic acid-thermal hydrolytic method is attractive and promising in pretreating tylosin production wastewater in field.展开更多
In this study,a novel microwave-water cooling-assisted mechanical rock breakage method was proposed to address the issues of severe tool wear at elevated temperatures,poor rock microwave absorption,and excessive micro...In this study,a novel microwave-water cooling-assisted mechanical rock breakage method was proposed to address the issues of severe tool wear at elevated temperatures,poor rock microwave absorption,and excessive microwave energy consumption.The investigation object was sandstone,which was irradiated at 4 kW microwave power for 60 s,180 s,300 s,and 420 s,followed by air and water cooling.Subsequently,uniaxial compression,Brazilian tension,and fracture tests were conducted.The evolution of damage in sandstone was measured using active and passive nondestructive acoustic detection methods.The roughness of the fracture surfaces of the specimens was quantified using the box-counting method.The damage mechanisms of microwave heating and water cooling on sandstone were discussed from both macroscopic and microscopic perspectives.The experimental results demonstrated that as the duration of the microwave irradiation increased,the P-wave velocity,uniaxial compressive strength(UCS),elastic modulus(E),tensile strength,and fracture toughness of sandstone exhibited various degrees of weakness and were further weakened by water cooling.Furthermore,an increase in the microwave irradiation duration enhanced the damaging effect of water cooling.The P-wave velocity of the sandstone was proportional to the mechanical parameters.Microwave heating and water cooling weakened the brittleness of the sandstone to a certain extent.The fractal dimension of the fracture surface was correlated with the duration of microwave heating,and the water-cooling treatment resulted in a rougher fracture surface.An analysis of the instantaneous cutting rate revealed that water cooling can substantially enhance the efficiency of microwave-assisted rock breakage.展开更多
Few-layer graphenes were fabricated from expandable graphite by rapid microwave exfoliation. Expandable graphite was irradiated in a domestic microwave in full power for 3 min, then soaked in mixed strong hydrogen nit...Few-layer graphenes were fabricated from expandable graphite by rapid microwave exfoliation. Expandable graphite was irradiated in a domestic microwave in full power for 3 min, then soaked in mixed strong hydrogen nitrate and sulfuric acid with volume ratio of 1：1 for 24 h and re-irradiated, thus few-layer graphene sheets were obtained. Specimens gained from every step were selectively characterized by different techniques, such as SEM, XRD, Raman, AFM, XPS, FTIR and combustion elemental analysis. The results show that expandable graphite with loose, porous and worm-like morphology forms instantaneously in microwave irradiation with crackling sound and sparkles, which manifests physical exfoliation of graphene sheets. Few-layer graphene sheets with a dozen or more layers and average thickness of about 4.7 nm are obtained eventually after sequential treatment of microwave irradiation, mixed acid soaking and second microwave irradiation. The as-prepared few-layer graphenes still have high crystallinity and high purity with traces of oxide groups and without serious unrecoverable oxidation damage.展开更多
Fully-coupled thermo-mechanical simulations are implemented in COMSOL Multiphysics to investigate micro-scale stress-strain variability in pegmatite specimens subjected to thermal loading using microwaves. Thermally-i...Fully-coupled thermo-mechanical simulations are implemented in COMSOL Multiphysics to investigate micro-scale stress-strain variability in pegmatite specimens subjected to thermal loading using microwaves. Thermally-induced compressive and tensile stresses increase as the microwave irradiation duration increases. The dielectric constant, coefficient of expansion, and type and size of mineralogical boundary have significant impacts on the responses of the rock to microwave irradiation. The maximum principal stress of the chlorite is the smallest, indicating that the chlorite experiences the most damage under microwave irradiation, followed by the quartz. The maximum principal stress values of plagioclase and orthoclase are larger, indicating that they are likely to incur the least damage. Where quartz or chlorite is dominant, the resulting von Mises stresses are consistently higher after 120 s of microwave irradiation. The rate of generation of von Mises stresses increases most rapidly along the interface between quartz and plagioclase, and the interface between quartz and orthoclase, followed by the interface between quartz and chlorite, and finally the interface between plagioclase and orthoclase. The presented modeling approach provides a practical method to investigate stress-strain relationships within mineralogical boundaries inside a rock thin section.展开更多
In this work we prepared several CeO2-TiO2 catalysts for the NH3-SCR reactionusing co-precipitation with assistance of microwave irradiation.The catalytic NH3-SCR activities over CeO2-TiO2 catalysts at low temperature...In this work we prepared several CeO2-TiO2 catalysts for the NH3-SCR reactionusing co-precipitation with assistance of microwave irradiation.The catalytic NH3-SCR activities over CeO2-TiO2 catalysts at low temperatures are largely enhanced by the treatment of microwave irradiation,the operation temperature window is also broadened.For better understanding the promotion mechanism,the catalyst prepared by conventional co-precipitation with and without microwave irradiation treatment was characterized with H2-TPR,NH3-TPD,XPS,XRD and BET.Microwave irradiation treatment accelerates the crystallite rate of CeO2-TiO2 catalysts,and greatly enlarges their surface area by adjusting their microstructures.The resistance to SO2 and H2O is also improved via regulating the hierarchical pore structure by the microwave irradiation.Microwave irradiation treatment can also improve the redox property and increase the acid sites over the catalyst surfaces.The result of in situ DRIFTS suggests that the microwave irradiation treatment generates more Br?nsted acid sites on CeO2-TiO2-2 h catalyst,helpful in SCR reactions.XPS results show that after microwave irradiation on the CeO2-TiO2 catalysts,the surface demonstrates an elevated concentration of chemisorbed oxygen,consequently leading to better oxidation of NO to NO2.Additionally,the molar ratio of Ce3+/Ce4+has been elevated after being treated by microwave irradiation,a vital factor in enhancing the NH3-SCR activities.展开更多
Ultra-fine Ce:YAG phosphors were prepared by homogeneous precipitation under microwave irradiation method . The formation of Ce: YAG was investigated by means of XRD and DTA/TG. The purified YAG crystallized phase was...Ultra-fine Ce:YAG phosphors were prepared by homogeneous precipitation under microwave irradiation method . The formation of Ce: YAG was investigated by means of XRD and DTA/TG. The purified YAG crystallized phase was obtained at a lower temperature (1100℃). Basically spherical Ce:YAG powders were indicated from TEM images, and the size of the particles is about 80 nm. Two peaks of 436 and 473 nm can be seen from the excitation spectrum in the range of 402 -510 nm. A broad emission band located at 480 ~ 630 nm shows the phosphors prepared by this method have good emission properties.展开更多
Microwave assisted leaching of complex copper sulphide concentrate with ferric chloride was investigated, and its mechanism was analyzed. The results show that the leaching rate by microwave irradiation heating is mu...Microwave assisted leaching of complex copper sulphide concentrate with ferric chloride was investigated, and its mechanism was analyzed. The results show that the leaching rate by microwave irradiation heating is much faster than that by conventional heating.展开更多
A facile and efficient method for the preparation of 2-non-substituted quinoline-4-carboxylic acids is described via the Pfitzinger reaction of isatins with sodium pyruvate following consequent decarboxylation under m...A facile and efficient method for the preparation of 2-non-substituted quinoline-4-carboxylic acids is described via the Pfitzinger reaction of isatins with sodium pyruvate following consequent decarboxylation under microwave irradiation.展开更多
The effects of oxidant dosage,oxidation temperature and time on the degradation of soda lignin by hydrogen peroxide with and without the presence of microwave irradiation were investigated.It is found that the oxidati...The effects of oxidant dosage,oxidation temperature and time on the degradation of soda lignin by hydrogen peroxide with and without the presence of microwave irradiation were investigated.It is found that the oxidative degradation of lignin includes the cleavage of ether bond inβ-O-4 structure,the partial destruction of aromatic ring,and the re-condensation of the degraded lignin.Compared to the conventionally heated oxidation of lignin,the microwave irradiation efficiently facilitates the degradation of the lignin with high molecular weight and the re-condensation of that with low molecular weight at a low oxidant dosage,low oxidation temperature,or a short oxidation time,which leads to the formation of the degraded lignin with narrower molecular weight distribution and lower molecular weight.Additionally,the lignin degraded in the presence of microwave irradiation has the characteristics of higher content of phenolic hydroxyl group,lower content of methoxyl group,and lower degree of condensation,which enhances the reactivity of lignin.Therefore,the oxidative degradation of lignin assisted by microwave irradiation may be a new pretreatment approach for efficiently utilizing the soda lignin.展开更多
The larch wood was treated by microwave irradiation under different radiant intensity and treating duration. The microwave-treated wood specimens together with the un-treated for comparison were impregnated by water i...The larch wood was treated by microwave irradiation under different radiant intensity and treating duration. The microwave-treated wood specimens together with the un-treated for comparison were impregnated by water in pressure vessel and then tested for permeability, mechanical properties and microstructure change by SEM to study the modification performance of microwave treatment on larch wood. The results showed that under suitable conditions of microwave treatment the permeability of larch wood was improved without noticeable decreasing of the modulus of rupture （MOR） and the modulus of elasticity （MOE）. The radial parenchyma and some pit membrane were ruptured, and tiny cracks were formed in the cell walls. The formation of tiny cracks in the cell walls serves as man-made channels of gas and liquid and this contribute to improve the permeability of the wood.展开更多
The effect and mechanism of microwave irradiation on vanadium leaching were studied via a comparison between microwave heating and conventional heating. The results show a synergistic effect of microwave irradiation a...The effect and mechanism of microwave irradiation on vanadium leaching were studied via a comparison between microwave heating and conventional heating. The results show a synergistic effect of microwave irradiation and calcium fluoride （CaF2） on the vana- dium leaching efficiency. It is confirmed that the vanadium leaching process can be improved by microwave irradiation when CaF2 is present. The leaching rate of vanadium under microwave irradiation is increased by 8%-15% when 5wt% CaF2 is added; by contrast, in the absence of CaF2, the leaching rate is almost unaffected compared to that by conventional heating. Morphological analysis reveals that the particles are gradually eroded by acid under microwave irradiation, whereas some of the fine particles in samples subjected to conventional heating are tightly covered by a flocculent silicate product. Moreover, a large amount of A1 and V and a small amount of Si are dissolved from samples under microwave heating, as revealed by the elemental analysis of leachates. Fourier transform infrared spectroscopic analysis also indicates a higher mass transfer coefficient in the diffusion layer of the raw material by microwave irradiation. When CaF2 is present, the reaction energy barrier is lowered and the leaching process is controlled by the tightly covered product layer, resulting in a prominent effect of mi- crowave irradiation.展开更多
Blue-green luminescent BaAl2O4：Eu2＋,Dy3＋ phosphor powders were synthesized via combustion synthesis method assisted by microwave irradiation in air. The phosphors were characterized by X-ray diffraction （XRD）, sc...Blue-green luminescent BaAl2O4：Eu2＋,Dy3＋ phosphor powders were synthesized via combustion synthesis method assisted by microwave irradiation in air. The phosphors were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and fluorescence spectrophotometer. The XRD results revealed that when the concentration of urea was over 3 times higher than theoretical quantities, a BaAl2O4 single hexagonal phase was obtained. The SEM results revealed that the surface of the BaAl2O4：Eu2＋,Dy3＋ powder samples showed lots of voids and pores. The BaAl2O4：Eu2＋,Dy3＋ phosphors exhibited a broad emission band of main peak at 496 nm and a shoulder peak at 426 nm under excitation of 337 nm. The BaAl2O4：Eu2＋,Dy3＋ phosphors at the Eu2＋ concentration of 1 mol.% showed the strongest luminescent intensity. Long afterglow phosphorescence was observed in the dark with naked eyes after the removal of the excitation source.展开更多
Nano-TiO2 was employed for the separation and preconcentration of thallium.It was found that the adsorption ratio of thallium ions was more than 98% at pH 4.5 and the desorption ratio reached 99% under microwave irrad...Nano-TiO2 was employed for the separation and preconcentration of thallium.It was found that the adsorption ratio of thallium ions was more than 98% at pH 4.5 and the desorption ratio reached 99% under microwave irradiation for 3 min at 350 W.The adsorption equilibrium was well described by the Langmuir isotherm model with a maximum adsorption capacity of 4.09 mg/g[（20±0.1） °C].The nano-TiO2 was successfully applied to the determination of element thallium in the certified reference material polymetallic nodule and water samples.展开更多
Biodegradable poly(epsilon-caprolactone-co-p-dioxanone)(PCDO) random copolymers have been synthesized by ring-opening polymerization of epsilon-caprolactone(CL) and p-dioxanone(PDO) under microwave irradiation.The eff...Biodegradable poly(epsilon-caprolactone-co-p-dioxanone)(PCDO) random copolymers have been synthesized by ring-opening polymerization of epsilon-caprolactone(CL) and p-dioxanone(PDO) under microwave irradiation.The effects of irradiation time and different CL/PDO molar feed ratios on the microwave-assisted ring-opening polymerization(MROP) of PCDO have been discussed.The resultant products were characterized by ~1H NMR,GPC and DSC.It was found that the polymerization was completed within 20 min at 140℃.In th...展开更多
In this paper, the characteristics of the preparation of novolacs for the shell process under microwaveirradiation are investigated. Both polymerization and dehydration of the resins under microwave irradiation are co...In this paper, the characteristics of the preparation of novolacs for the shell process under microwaveirradiation are investigated. Both polymerization and dehydration of the resins under microwave irradiation are comparedwith those under conventional heating and further analysis is made. The results show that compared with those underconventional heating, the polymerization and dehydration time under microwave irradiation are shortened by 85.2% and80.7% respectively; On the other hand, the polymerization and dehydration under microwave irradiation lead to aremarkable increase in flow distance of the resins. Furthermore, the polymerization under microwave irradiation leads toreduced cure time, while the dehydration under microwave irradiation causes a slight increase in cure time.展开更多
This study is a part of an overall research project on the effects of microwave(MW)irradiation on rocks for assisted rock breaking systems as well as mineral processing at McGill University.For the first time,this pap...This study is a part of an overall research project on the effects of microwave(MW)irradiation on rocks for assisted rock breaking systems as well as mineral processing at McGill University.For the first time,this paper highlights a comprehensive investigation on the effects of microwave irradiation on Canadian kimberlites.Potential contribution to the continuous rock excavation and rock weakening effect prior to implementation of mechanical techniques was explored.Two different kimberlite rocks,i.e.volcaniclastic kimberlite(VK)and hypabyssal kimberlite(HK),and granite samples were studied.Some important physical properties of the rock samples were measured including rock quality designation(RQD),specific gravity,porosity,and specific heat capacity.Rock samples were treated for various exposure times using a multi-mode MWunit at different power levels ranging from 2 kW to 15 kW.The effect of MW irradiation on rock samples was investigated.The results indicate that the mechanical properties including unconfined compressive strength(UCS)and Brazilian tensile strength(BTS)were significantly dropped as a result of MWirradiation.Finally,the effect on rock abrasivity using the Cerchar abrasivity index(CAI)has also been discussed.展开更多
The technique of microwave irradiation induced free radical bulk- polyaddition reactions in porous wood flour was used to modify wood flour. The behaviors of the modified wood flour under microwave irradiation, such a...The technique of microwave irradiation induced free radical bulk- polyaddition reactions in porous wood flour was used to modify wood flour. The behaviors of the modified wood flour under microwave irradiation, such as thermal stability and moisture sorption properties, were studied. A kind of semiinterpenetrating polymer network wood four （Semi-IPN-WF） can be formed through polymerization of MMA in the porous wood flour by microwave irradiation, and the thermal decomposition temperature of the semi-IPN-WF is considerably increased. PVC/Semi-IPN-WF composites were prepared by melt mixing in double rolls, which exhibit improved rheological properties, lower water sorption properties and outstanding mechanical performances.展开更多
Microwave irradiation can accelerate the rate of the synthetic reaction of α,β-unsaturated ketones by using KF-Al2O3 as catalyst. The rate enhancement of the reaction is 360-860 fold.
A facile,rapid and efficient method for the synthesis of molecular tweezers containing chiral unsymmetrical urea unit in solvent-free conditions using microwave was reported.
基金supported by the National Natural Science Foundation of China(Nos.51978052 and 22306012)the National Key Research and Development Program of China(No.2023YFC3711300)the Guangdong Basic and Applied Basic Research Foundation(No.2022A1515110578).
文摘Acidic-and alkalic-hydrolyses are selective in breaking functional bonds and falling off pharmacological moieties of antibiotics in production wastewater in comparison with advanced oxidation processes.Elevating temperature can accelerate hydrolytic kinetics and improve efficiency.In this work,magnetic sulfonated polypropylene resin(Fe_(3)O_(4)@PS-S)composites were reported for acidic-thermal hydrolysis of tylosin by employing the acidic feature of sulfonic group,the dielectric effect of resin,and the magnetic-loss effect of magnetite under microwave irradiation.As observed,a rapid and complete mitigation 100 mg/L of tylosin was achieved within 15 min by the catalysts.Acidic cleavage of tylosin was fulfilled by sulfonic groups in the composites,and microwave thermal accelerated the hydrolysis reactions due to the dielectric and magnetic-loss effects.Differentiating the dielectric and magnetic-loss effects through electromagnetic analyses indicated that the latter contributed more in converting microwave energy to heat.The interactions under multiple operational conditions were quantitatively fitted using the Behnajady model and visually demonstrated,which indicated that a synergic effect of microwave thermal-and acidichydrolyses contributed to the efficient mitigation of tylosin.The transformation products were identified and the pathways were supposed.Cleaving deoxyaminosugars groups and destructing lactone structures led to reduced antibacterial potential and toxicity reduction.The acute toxicity of tylosin and transformation products to fish,daphnia,and green algae were all classified as non-toxic.This work suggested that this synergistic acid-thermal hydrolytic method is attractive and promising in pretreating tylosin production wastewater in field.
基金the financial support provided by the National Natural Science Foundation of China(Grant No.52274105)the China Scholarship Council(Grant No.202306370184)。
文摘In this study,a novel microwave-water cooling-assisted mechanical rock breakage method was proposed to address the issues of severe tool wear at elevated temperatures,poor rock microwave absorption,and excessive microwave energy consumption.The investigation object was sandstone,which was irradiated at 4 kW microwave power for 60 s,180 s,300 s,and 420 s,followed by air and water cooling.Subsequently,uniaxial compression,Brazilian tension,and fracture tests were conducted.The evolution of damage in sandstone was measured using active and passive nondestructive acoustic detection methods.The roughness of the fracture surfaces of the specimens was quantified using the box-counting method.The damage mechanisms of microwave heating and water cooling on sandstone were discussed from both macroscopic and microscopic perspectives.The experimental results demonstrated that as the duration of the microwave irradiation increased,the P-wave velocity,uniaxial compressive strength(UCS),elastic modulus(E),tensile strength,and fracture toughness of sandstone exhibited various degrees of weakness and were further weakened by water cooling.Furthermore,an increase in the microwave irradiation duration enhanced the damaging effect of water cooling.The P-wave velocity of the sandstone was proportional to the mechanical parameters.Microwave heating and water cooling weakened the brittleness of the sandstone to a certain extent.The fractal dimension of the fracture surface was correlated with the duration of microwave heating,and the water-cooling treatment resulted in a rougher fracture surface.An analysis of the instantaneous cutting rate revealed that water cooling can substantially enhance the efficiency of microwave-assisted rock breakage.
基金Project(51274248)supported by the National Natural Science Foundation of China
文摘Few-layer graphenes were fabricated from expandable graphite by rapid microwave exfoliation. Expandable graphite was irradiated in a domestic microwave in full power for 3 min, then soaked in mixed strong hydrogen nitrate and sulfuric acid with volume ratio of 1：1 for 24 h and re-irradiated, thus few-layer graphene sheets were obtained. Specimens gained from every step were selectively characterized by different techniques, such as SEM, XRD, Raman, AFM, XPS, FTIR and combustion elemental analysis. The results show that expandable graphite with loose, porous and worm-like morphology forms instantaneously in microwave irradiation with crackling sound and sparkles, which manifests physical exfoliation of graphene sheets. Few-layer graphene sheets with a dozen or more layers and average thickness of about 4.7 nm are obtained eventually after sequential treatment of microwave irradiation, mixed acid soaking and second microwave irradiation. The as-prepared few-layer graphenes still have high crystallinity and high purity with traces of oxide groups and without serious unrecoverable oxidation damage.
基金supported by the US National Science Foundation (CMMI award 1550307)the China Scholarship Council for financial support as a visiting scholar at the Colorado School of Mines (Grant No. 201706375077)
文摘Fully-coupled thermo-mechanical simulations are implemented in COMSOL Multiphysics to investigate micro-scale stress-strain variability in pegmatite specimens subjected to thermal loading using microwaves. Thermally-induced compressive and tensile stresses increase as the microwave irradiation duration increases. The dielectric constant, coefficient of expansion, and type and size of mineralogical boundary have significant impacts on the responses of the rock to microwave irradiation. The maximum principal stress of the chlorite is the smallest, indicating that the chlorite experiences the most damage under microwave irradiation, followed by the quartz. The maximum principal stress values of plagioclase and orthoclase are larger, indicating that they are likely to incur the least damage. Where quartz or chlorite is dominant, the resulting von Mises stresses are consistently higher after 120 s of microwave irradiation. The rate of generation of von Mises stresses increases most rapidly along the interface between quartz and plagioclase, and the interface between quartz and orthoclase, followed by the interface between quartz and chlorite, and finally the interface between plagioclase and orthoclase. The presented modeling approach provides a practical method to investigate stress-strain relationships within mineralogical boundaries inside a rock thin section.
基金Project supported by the National Natural Science Foundation of China(21577005)the National Key Research and Development Program of China(2016YFB0600400)
文摘In this work we prepared several CeO2-TiO2 catalysts for the NH3-SCR reactionusing co-precipitation with assistance of microwave irradiation.The catalytic NH3-SCR activities over CeO2-TiO2 catalysts at low temperatures are largely enhanced by the treatment of microwave irradiation,the operation temperature window is also broadened.For better understanding the promotion mechanism,the catalyst prepared by conventional co-precipitation with and without microwave irradiation treatment was characterized with H2-TPR,NH3-TPD,XPS,XRD and BET.Microwave irradiation treatment accelerates the crystallite rate of CeO2-TiO2 catalysts,and greatly enlarges their surface area by adjusting their microstructures.The resistance to SO2 and H2O is also improved via regulating the hierarchical pore structure by the microwave irradiation.Microwave irradiation treatment can also improve the redox property and increase the acid sites over the catalyst surfaces.The result of in situ DRIFTS suggests that the microwave irradiation treatment generates more Br?nsted acid sites on CeO2-TiO2-2 h catalyst,helpful in SCR reactions.XPS results show that after microwave irradiation on the CeO2-TiO2 catalysts,the surface demonstrates an elevated concentration of chemisorbed oxygen,consequently leading to better oxidation of NO to NO2.Additionally,the molar ratio of Ce3+/Ce4+has been elevated after being treated by microwave irradiation,a vital factor in enhancing the NH3-SCR activities.
基金Project supported by Foundation for the Excellent Middle-Aged or Young Scientists of Shandong Province (02BS049)
文摘Ultra-fine Ce:YAG phosphors were prepared by homogeneous precipitation under microwave irradiation method . The formation of Ce: YAG was investigated by means of XRD and DTA/TG. The purified YAG crystallized phase was obtained at a lower temperature (1100℃). Basically spherical Ce:YAG powders were indicated from TEM images, and the size of the particles is about 80 nm. Two peaks of 436 and 473 nm can be seen from the excitation spectrum in the range of 402 -510 nm. A broad emission band located at 480 ~ 630 nm shows the phosphors prepared by this method have good emission properties.
文摘Microwave assisted leaching of complex copper sulphide concentrate with ferric chloride was investigated, and its mechanism was analyzed. The results show that the leaching rate by microwave irradiation heating is much faster than that by conventional heating.
基金the National Basic Research Program(No.2003CB515400),administered by the Ministry of Science and Technology of China.
文摘A facile and efficient method for the preparation of 2-non-substituted quinoline-4-carboxylic acids is described via the Pfitzinger reaction of isatins with sodium pyruvate following consequent decarboxylation under microwave irradiation.
基金Supported by the National Natural Science Foundation of China（20876064） the Natural Science Foundation of Guangdong Province（9151064101000082） the Guangdong Provincial International Cooperation Fund（2008B05010006）
文摘The effects of oxidant dosage,oxidation temperature and time on the degradation of soda lignin by hydrogen peroxide with and without the presence of microwave irradiation were investigated.It is found that the oxidative degradation of lignin includes the cleavage of ether bond inβ-O-4 structure,the partial destruction of aromatic ring,and the re-condensation of the degraded lignin.Compared to the conventionally heated oxidation of lignin,the microwave irradiation efficiently facilitates the degradation of the lignin with high molecular weight and the re-condensation of that with low molecular weight at a low oxidant dosage,low oxidation temperature,or a short oxidation time,which leads to the formation of the degraded lignin with narrower molecular weight distribution and lower molecular weight.Additionally,the lignin degraded in the presence of microwave irradiation has the characteristics of higher content of phenolic hydroxyl group,lower content of methoxyl group,and lower degree of condensation,which enhances the reactivity of lignin.Therefore,the oxidative degradation of lignin assisted by microwave irradiation may be a new pretreatment approach for efficiently utilizing the soda lignin.
基金This paper was supported by Science Fund for Distin-guished Young Scholars, Heilongjiang Province (No. JC04-01)
文摘The larch wood was treated by microwave irradiation under different radiant intensity and treating duration. The microwave-treated wood specimens together with the un-treated for comparison were impregnated by water in pressure vessel and then tested for permeability, mechanical properties and microstructure change by SEM to study the modification performance of microwave treatment on larch wood. The results showed that under suitable conditions of microwave treatment the permeability of larch wood was improved without noticeable decreasing of the modulus of rupture （MOR） and the modulus of elasticity （MOE）. The radial parenchyma and some pit membrane were ruptured, and tiny cracks were formed in the cell walls. The formation of tiny cracks in the cell walls serves as man-made channels of gas and liquid and this contribute to improve the permeability of the wood.
基金financially supported by the National Natural Science Foundation of China(Nos.51474162 and 51404174)the Research Project of the Ministry of Education of China(No.213025A)
文摘The effect and mechanism of microwave irradiation on vanadium leaching were studied via a comparison between microwave heating and conventional heating. The results show a synergistic effect of microwave irradiation and calcium fluoride （CaF2） on the vana- dium leaching efficiency. It is confirmed that the vanadium leaching process can be improved by microwave irradiation when CaF2 is present. The leaching rate of vanadium under microwave irradiation is increased by 8%-15% when 5wt% CaF2 is added; by contrast, in the absence of CaF2, the leaching rate is almost unaffected compared to that by conventional heating. Morphological analysis reveals that the particles are gradually eroded by acid under microwave irradiation, whereas some of the fine particles in samples subjected to conventional heating are tightly covered by a flocculent silicate product. Moreover, a large amount of A1 and V and a small amount of Si are dissolved from samples under microwave heating, as revealed by the elemental analysis of leachates. Fourier transform infrared spectroscopic analysis also indicates a higher mass transfer coefficient in the diffusion layer of the raw material by microwave irradiation. When CaF2 is present, the reaction energy barrier is lowered and the leaching process is controlled by the tightly covered product layer, resulting in a prominent effect of mi- crowave irradiation.
基金supported by the National Natural Science Foundation of China (60477034)
文摘Blue-green luminescent BaAl2O4：Eu2＋,Dy3＋ phosphor powders were synthesized via combustion synthesis method assisted by microwave irradiation in air. The phosphors were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and fluorescence spectrophotometer. The XRD results revealed that when the concentration of urea was over 3 times higher than theoretical quantities, a BaAl2O4 single hexagonal phase was obtained. The SEM results revealed that the surface of the BaAl2O4：Eu2＋,Dy3＋ powder samples showed lots of voids and pores. The BaAl2O4：Eu2＋,Dy3＋ phosphors exhibited a broad emission band of main peak at 496 nm and a shoulder peak at 426 nm under excitation of 337 nm. The BaAl2O4：Eu2＋,Dy3＋ phosphors at the Eu2＋ concentration of 1 mol.% showed the strongest luminescent intensity. Long afterglow phosphorescence was observed in the dark with naked eyes after the removal of the excitation source.
基金Supported by the Excellent Talents Project(No.2009R30)Innovation Team Project(No.2007T053)of the Education Department of Liaoning Province,China
文摘Nano-TiO2 was employed for the separation and preconcentration of thallium.It was found that the adsorption ratio of thallium ions was more than 98% at pH 4.5 and the desorption ratio reached 99% under microwave irradiation for 3 min at 350 W.The adsorption equilibrium was well described by the Langmuir isotherm model with a maximum adsorption capacity of 4.09 mg/g[（20±0.1） °C].The nano-TiO2 was successfully applied to the determination of element thallium in the certified reference material polymetallic nodule and water samples.
文摘Biodegradable poly(epsilon-caprolactone-co-p-dioxanone)(PCDO) random copolymers have been synthesized by ring-opening polymerization of epsilon-caprolactone(CL) and p-dioxanone(PDO) under microwave irradiation.The effects of irradiation time and different CL/PDO molar feed ratios on the microwave-assisted ring-opening polymerization(MROP) of PCDO have been discussed.The resultant products were characterized by ~1H NMR,GPC and DSC.It was found that the polymerization was completed within 20 min at 140℃.In th...
文摘In this paper, the characteristics of the preparation of novolacs for the shell process under microwaveirradiation are investigated. Both polymerization and dehydration of the resins under microwave irradiation are comparedwith those under conventional heating and further analysis is made. The results show that compared with those underconventional heating, the polymerization and dehydration time under microwave irradiation are shortened by 85.2% and80.7% respectively; On the other hand, the polymerization and dehydration under microwave irradiation lead to aremarkable increase in flow distance of the resins. Furthermore, the polymerization under microwave irradiation leads toreduced cure time, while the dehydration under microwave irradiation causes a slight increase in cure time.
基金The financial support from the Natural Sciences and Engineering Research Council of Canada(NSERC)and our industrial partners,DeBeers,Metso,and Argex companies as well as PhD scholarship to Mr.Samir Deyab from the department of mining engineering,Tripoli University are gratefully acknowledged.
文摘This study is a part of an overall research project on the effects of microwave(MW)irradiation on rocks for assisted rock breaking systems as well as mineral processing at McGill University.For the first time,this paper highlights a comprehensive investigation on the effects of microwave irradiation on Canadian kimberlites.Potential contribution to the continuous rock excavation and rock weakening effect prior to implementation of mechanical techniques was explored.Two different kimberlite rocks,i.e.volcaniclastic kimberlite(VK)and hypabyssal kimberlite(HK),and granite samples were studied.Some important physical properties of the rock samples were measured including rock quality designation(RQD),specific gravity,porosity,and specific heat capacity.Rock samples were treated for various exposure times using a multi-mode MWunit at different power levels ranging from 2 kW to 15 kW.The effect of MW irradiation on rock samples was investigated.The results indicate that the mechanical properties including unconfined compressive strength(UCS)and Brazilian tensile strength(BTS)were significantly dropped as a result of MWirradiation.Finally,the effect on rock abrasivity using the Cerchar abrasivity index(CAI)has also been discussed.
基金Funded by the Natural Science Foundation of Hubei Province (No. 2003ABA084)
文摘The technique of microwave irradiation induced free radical bulk- polyaddition reactions in porous wood flour was used to modify wood flour. The behaviors of the modified wood flour under microwave irradiation, such as thermal stability and moisture sorption properties, were studied. A kind of semiinterpenetrating polymer network wood four （Semi-IPN-WF） can be formed through polymerization of MMA in the porous wood flour by microwave irradiation, and the thermal decomposition temperature of the semi-IPN-WF is considerably increased. PVC/Semi-IPN-WF composites were prepared by melt mixing in double rolls, which exhibit improved rheological properties, lower water sorption properties and outstanding mechanical performances.
文摘Microwave irradiation can accelerate the rate of the synthetic reaction of α,β-unsaturated ketones by using KF-Al2O3 as catalyst. The rate enhancement of the reaction is 360-860 fold.
文摘A facile,rapid and efficient method for the synthesis of molecular tweezers containing chiral unsymmetrical urea unit in solvent-free conditions using microwave was reported.
