Surface reconstruction of electrocatalysts has been widely witnessed during the electrochemical processes.Here,NiS_(2),NiSe_(2), and Se doped NiS_(2)(Se-NiS_(2)) are fabricated for oxygen evolution reaction(OER) throu...Surface reconstruction of electrocatalysts has been widely witnessed during the electrochemical processes.Here,NiS_(2),NiSe_(2), and Se doped NiS_(2)(Se-NiS_(2)) are fabricated for oxygen evolution reaction(OER) through a mild sulfuration and/or selenylation process of Ni(OH)_(2) supported on carbon cloth(CC).Through careful in-situ Raman spectroscopy and ex-situ X-ray photoelectron spectroscopy,surface reconstruction of NiS_(2),NiSe_(2),and Se-NiS_(2) during the OER process has been revealed.A potentialdependent study shows that Se-NiS_(2) undergoes surface evolution at lower potentials and requires the lowest potential for conversion to NiOOH as a highly OER-active species,accompanied by the leaching of SO_(4)^(2-) and SeO_(4)^(2-) that can again be adsorbed on the catalyst surface to enhance the catalytic activity.Density functional theory(DFT) calculations confirm that Se-NiS_(2) is more susceptible to surface oxidation through the OER process.Therefore,Se-NiS_(2) exhibits outstanding OER activity and stability in alkaline conditions,requiring an overpotential of 343 mV at a current density of 50 mA cm^(-2).A novel insight is provided by our work in understanding the surface reconstruction and electrocatalytic mechanism of Ni-based chalcogenides.展开更多
In-situ HVEM observation on phase transition of the YBa_2Cu_3O_(7-x) superconducting compound in pro- cess of heating was carried out,and high temperature X-ray diffraction analysis in air and X-ray diffraction phase ...In-situ HVEM observation on phase transition of the YBa_2Cu_3O_(7-x) superconducting compound in pro- cess of heating was carried out,and high temperature X-ray diffraction analysis in air and X-ray diffraction phase analysis for the sample treated in vacuum condition were made.The results showed that the temperature of phase transition is related to oxygen content in the sample and in general,is 100℃ to 120℃ lower in vacu- um condition than in air.At 320℃ to 350℃ twin bands begin to disappear,and some Cu_2O are formed on the surface of the sample and transit from orthorhombic YBa_2Cu_3O_(7-x) to arthorhombic Y_2BaCuO_5 compound. This transition was completed at about 500℃.Above 900℃,this compound consists of the Y_2BaCuO_5, BaCuO_2,Y_2O_3 and some other minor compounds.No phase transition was observed during cooling the sample.展开更多
The Al2O3 abrasion-resistant ceramics is successfully prepared by using waste aluminum sludge as the main raw material with the addition of a little clay, talc and barium carbonate. The crystal structure and microstru...The Al2O3 abrasion-resistant ceramics is successfully prepared by using waste aluminum sludge as the main raw material with the addition of a little clay, talc and barium carbonate. The crystal structure and microstructure of ceramic are characterized by means of XRD, SEM, etc., and the physical and mechanical properties are also tested. The results show that besides the phase of corundum, a little mullite, Mg-Al spinel and hyalophane phases also exist in the product. These phases are produced via reaction in-situ, which can inhibit the overgrowth of Al2O3 grain in grain boundary, and improve the integral property of the material.展开更多
Si3N4-Si2N2O composites were fabricated with amorphous nano-sized silicon nitride powders by the liquid phase sintering ( LPS ). The Si2 N2O phase was generated by an in-situ reaction 2 Si3 N4 ( s ) + 1.5 02 ( g...Si3N4-Si2N2O composites were fabricated with amorphous nano-sized silicon nitride powders by the liquid phase sintering ( LPS ). The Si2 N2O phase was generated by an in-situ reaction 2 Si3 N4 ( s ) + 1.5 02 ( g ) = 3 Si2 N2O ( s ) + N2 ( g ) . The content of Si2 N2 O phase up to 60% in the volume was obtained at a sintering temperature of 1 650℃ and reduced when the sintering temperature increased or decreased, indicating the reaction is reversible. The mass loss, relative density and average grain size increased with increasing the sintering temperature. The average grain size was less than 500 nm when the sintering temperature was below 1 700 ℃. The sintering procedure contains a complex crystallization and a phase transition : amorphous silicon nitride→equiaxial α- Si3 N4→ equiaxial β- Si3 N4→ rod- like Si2 N2O→ needle- like β- Si3N4 . Small round-shaped β→ Si3 N4 particles were entrapped in the Si2 N2O grains and a high density of staking faults was situated in the middle of Si2 N2O grains at a sintering temperature of 1 650 ℃. The toughness inereased from 3.5 MPa·m^1/2 at 1 600 ℃ to 7.2 MPa· m^1/2 at 1 800 ℃ . The hardness was as high as 21.5 GPa (Vickers) at 1 600 ℃ .展开更多
A γ-Al2O3 particles reinforced Al-Si alloy matrix composite was fabricated by adding NH4Al(SO4)2 to molten aluminum alloy. TEM observation shows that in-situ γ-Al2O3 particles are generally spherical and uniformly...A γ-Al2O3 particles reinforced Al-Si alloy matrix composite was fabricated by adding NH4Al(SO4)2 to molten aluminum alloy. TEM observation shows that in-situ γ-Al2O3 particles are generally spherical and uniformly distributed in the matrix. The results of dry sliding wear tests show that the wear resistance of the composites increases with increasing mass fraction, and the volume loss is considerably lesser than that of the matrix and is lesser than that of the composites by adding γ-Al2O3 particles directly.展开更多
LiMn2O4/Li4Ti5O12 composite was synthesized by in-situ composite technique using LiMn2O4,lithium acetate,tetrabutyl titanate as starting materials and characterized by various electrochemical methods in combination wi...LiMn2O4/Li4Ti5O12 composite was synthesized by in-situ composite technique using LiMn2O4,lithium acetate,tetrabutyl titanate as starting materials and characterized by various electrochemical methods in combination with X-ray diffractometry(XRD), infrared(IR)spectroscopy and scanning electron microscopy(SEM).The results show that Li4Ti5O12 is coated on the surface of crystalline LiMn2O4 to form LiMn2O4/Li4Ti5O12 composite.The structure of LiMn2O4 does not change due to the introduction of Li4Ti5O12.By being coated with Li4Ti5O12,the rate capability and high temperature cyclability of LiMn2O4 is improved greatly.At room temperature,the discharge capacity of LiMn2O4/Li4Ti5O12 composite is more than 108.4 mA·h/g and the capacity loss per cycle is only 0.053%after 20 cycles at 2.0C.While at 55℃,the discharge capacity of LiMn2O4/Li4Ti5O12 composite is more than 109.9 mA·h/g and the capacity loss per cycle is only 0.036%after 60 cycles at 1.0C.展开更多
Silver as a highly conductive metal is usually doped in YBa2Cu3O7-x superconductor bulks to improve critical current density of YBa2Cu3O7-x superconductor.The valuable metal elements silver,yttrium,barium and copper i...Silver as a highly conductive metal is usually doped in YBa2Cu3O7-x superconductor bulks to improve critical current density of YBa2Cu3O7-x superconductor.The valuable metal elements silver,yttrium,barium and copper in waste YBa2Cu3O7-x/Ag composite superconductor bulks were recovered,respectively.Silver was recovered with process at first,the waste was dissolved by nitric acid and silver chloride was precipitated by adding chloride acid,then silver pig was obtained by melting silver chloride together with sodium carbonate at 1 000℃.The effective factors on recovery ratio and purity of silver were studied.The chemical analysis proves that the purity of silver ingot is 95.86%.The recovery ratio of silver is calculated to be 92.56%.The loss of silver may be due to the loss of silver chloride during filtering and the volatilization of silver when silver chloride and sodium carbonate are smelted at high temperature.For other three metal elements,Y3 +,Ba 2+and Cu 2+,in the surplus waste liquid after recovering silver, they were separated with the sequence of barium,copper and then yttrium step by step.First,sulfate acid was used to precipitate barium sulfate.Then,sodium sulfide was added to the surplus solution so that copper could be separated as copper sulfide.During this separation procedure,it was important to control the pH value to be 1-2.After that,oxalic acid was added into the surplus solution to obtain yttrium oxalate.Finally,yttrium oxide was formed by burning yttrium oxalate.The XRD results indicate that the final products are all single-phase compounds as BaSO4,CuS and Y2O3,respectively.展开更多
With the development of stable alkali metal anodes,V_(2)O_(5) is gaining traction as a cathode material due to its high theoretical capacity and the ability to intercalate Li,Na and K ions.Herein,we report a method fo...With the development of stable alkali metal anodes,V_(2)O_(5) is gaining traction as a cathode material due to its high theoretical capacity and the ability to intercalate Li,Na and K ions.Herein,we report a method for synthesizing structured orthorhombic V_(2)O_(5) microspheres and investigate Li intercalation/deintercalation into this material.For industry adoption,the electrochemical behavior of V_(2)O_(5) as well as structural and phase transformation attributing to Li intercalation reaction must be further investigated.Our synthesized V_(2)O_(5) microspheres consisted of small primary particles that were strongly joined together and exhibited good cycle stability and rate capability,triggered by reversible volume change and rapid Li ion diffusion.In addition,the reversibility of phase transformation(a,e,d,c and xLixV_(2)O_(5))and valence state evolution(5+,4+,and 3.5+)during intercalation/de-intercalation were studied via in-situ X-ray powder diffraction and X-ray absorption near edge structure analyses.展开更多
Hydrodeoxygenation of furfural(FF)into 2-methylfuran(MF)is a significant biomass utilization route.However,designing efficient and stable non-noble metal catalyst is still a huge challenge.Herein,we reported the N,O c...Hydrodeoxygenation of furfural(FF)into 2-methylfuran(MF)is a significant biomass utilization route.However,designing efficient and stable non-noble metal catalyst is still a huge challenge.Herein,we reported the N,O co-doped carbon anchored with Co nanoparticles(Co-SFB)synthesized by employing the organic ligands with the target heteroatoms.Raman,electron paramagnetic resonance(EPR),electrochemical impedance spectroscopy(EIS),and X-ray photoelectron spectroscopy(XPS)characterizations showed that the co-doping of N and O heteroatoms in the carbon support endows Co-SFB with enriched lone pair electrons,fast electron transfer ability,and strong metal-support interaction.These electronic properties resulted in strong FF adsorption as well as lower apparent reaction activation energy.At last,the obtained N,O co-doped Co/C catalyst showed excellent catalytic activity(nearly 100 mol%FF conversion and 94.6 mol%MF yield)and stability for in-situ dehydrogenation of FF into MF.This N,O co-doping strategy for the synthesis of highly efficient catalytic materials with controllable electronic state will provide an excellent opportunity to better understand the structure-function relationship.展开更多
The upland agricultural soils in North China are distributed north of a line between the Kunlun Mountains, the Qinling Mountains and the Huaihe River. They occur in arid, semi-arid and semi-humid regions and crop prod...The upland agricultural soils in North China are distributed north of a line between the Kunlun Mountains, the Qinling Mountains and the Huaihe River. They occur in arid, semi-arid and semi-humid regions and crop production often depends on rain-fed or irrigation to supplement rainfall. This paper summarizes the characteristics of gross nitrogen(N) transformation, the fate of N fertilizer and soil N as well as the N loss pathway, and makes suggestions for proper N management in the region. The soils of the region are characterized by strong N mineralization and nitrification, and weak immobilization and denitrification ability, which lead to the production and accumulation of nitrate in the soil profile. Large amounts of accumulated nitrate have been observed in the vadose-zone in soils due to excess N fertilization in the past three decades, and this nitrate is subject to occasional leaching which leads to groundwater nitrate contamination. Under farmer's conventional high N fertilization practice in the winter wheat-summer maize rotation system(N application rate was approximately 600 kg ha–1 yr–1), crop N uptake, soil residual N, NH_3 volatilization, NO_3~– leaching, and denitrification loss accounted for around 27, 30, 23, 18 and 2% of the applied fertilizer N, respectively. NH_3 volatilization and NO_3~– leaching were the most important N loss pathways while soil residual N was an important fate of N fertilizer for replenishing soil N depletion from crop production. The upland agricultural soils in North China are a large source of N_2O and total emissions in this region make up a large proportion(approximately 54%) of Chinese cropland N_2O emissions. The “non-coupled strong ammonia oxidation” process is an important mechanism of N_2O production. Slowing down ammonia oxidation after ammonium-N fertilizer or urea application and avoiding transient high soil NH4+ concentrations are key measures for reducing N_2O emissions in this region. Further N management should aim to minimize N losses from crop and livestock production, and increase the recycling of manure and straw back to cropland. We also recommend adoption of the 4 R(Right soure, Right rate, Right time, Right place) fertilization techniques to realize proper N fertilizer management, and improving application methods or modifying fertilizer types to reduce NH_3 volatilization, improving water management to reduce NO_3~– leaching, and controlling the strong ammonia oxidation process to abate N_2O emission. Future research should focus on the study of the trade-off effects among different N loss pathways under different N application methods or fertilizer products.展开更多
A new process of extracting vanadium from the stone coal vanadium ore in Fangshankou, Dtmhuang area of Gansu Province, China was introduced. Various leaching experiments were carried out, and the results show that the...A new process of extracting vanadium from the stone coal vanadium ore in Fangshankou, Dtmhuang area of Gansu Province, China was introduced. Various leaching experiments were carried out, and the results show that the vanadium ore in Fangshankou is difficult to process due to its high consumption of acid and the high leaching rate of impurities. However, the leaching rate can be up to 80% and the content of V2O5 in the residue can be between 0.22%-0.25% in the process of ore fme grinding→oxidation roasting→mixing and ripening→aqueous leaching→P2O4 solvent extraction→sulfuric acid stripping→oxidation and precipitation→decomposition by heat. Also, the quality of flaky V205 produced by this process can meet the requirements of GB3283--87. The total leaching rate of vanadium is 70%. Also, three types of wastes are easy to treat. The vanadium extraction process is better in relation to the aspect of environmental protection than the sodium method.展开更多
β-Ga2O3 cone-like nanowires have been in-situ grown on the surface of gallium grains and films by heating gallium substrates at 750-1000℃ for 2h in air.The controllable synthesis of β-Ga2O3 nano-wires with differen...β-Ga2O3 cone-like nanowires have been in-situ grown on the surface of gallium grains and films by heating gallium substrates at 750-1000℃ for 2h in air.The controllable synthesis of β-Ga2O3 nano-wires with different diameters and lengths was achieved by adjusting the heating temperature and time.The as-synthesized products were characterized by means of X-ray diffraction,scanning electron mi-croscopy and transmission electron microscopy.The results showed that the β-Ga2O3 nanowires are single crystalline with a monoclinic structure and have a controllable diameter and length in the range of 30-100nm and 0.5-1.5μm,respectively.A possible mechanism was also proposed to account for the formation of β-Ga2O3 cone-like nanowires.Photoluminescence spectra of the β-Ga2O3 nanowires obtained at different temperatures were measured at room temperature,and a strong blue photolumi-nescence with peaks at 430 and 460nm and a weak red photoluminescence with peak at 713nm were observed.The blue light emission intensity decreases with increasing the reaction temperature,how-ever,the red light emission intensity hardly changes.The blue and red light emissions originate from the recombination of an electron on an oxygen vacancy with a hole on a gallium-oxygen vacancy pair and the nitrogen dopants,etc.,respectively.展开更多
V2O5 flower-like structures assembled by thin nanosheets were in-situ growth on ceramic tubes by hydrothermal process.The structural characterization indicates that V2O5 flower-like structures is orthogonal diamond ph...V2O5 flower-like structures assembled by thin nanosheets were in-situ growth on ceramic tubes by hydrothermal process.The structural characterization indicates that V2O5 flower-like structures is orthogonal diamond phase,which entirely covered on the surface of ceramic tubes.TMA sensing measured results revealed that the sensor based on V2O5 flower-like structures exhibited fast reversible and response,good selectivity to TMA and good stability at 200℃.The good sensing performance may be ascribed to flower-like structure s and directly growth sensing film on the ceramic tube without structure damage.Our works give a simple in-situ growth flower-like structures route on sensing device,which exhibits potential application for detecting trace amounts of TMA gas.展开更多
基金supported by the financial support from the National Natural Science Foundation of China (21871065, 22071038, 22209129)the Heilongjiang Touyan Team (HITTY20190033)the Interdisciplinary Research Foundation of HIT (IR2021205)。
文摘Surface reconstruction of electrocatalysts has been widely witnessed during the electrochemical processes.Here,NiS_(2),NiSe_(2), and Se doped NiS_(2)(Se-NiS_(2)) are fabricated for oxygen evolution reaction(OER) through a mild sulfuration and/or selenylation process of Ni(OH)_(2) supported on carbon cloth(CC).Through careful in-situ Raman spectroscopy and ex-situ X-ray photoelectron spectroscopy,surface reconstruction of NiS_(2),NiSe_(2),and Se-NiS_(2) during the OER process has been revealed.A potentialdependent study shows that Se-NiS_(2) undergoes surface evolution at lower potentials and requires the lowest potential for conversion to NiOOH as a highly OER-active species,accompanied by the leaching of SO_(4)^(2-) and SeO_(4)^(2-) that can again be adsorbed on the catalyst surface to enhance the catalytic activity.Density functional theory(DFT) calculations confirm that Se-NiS_(2) is more susceptible to surface oxidation through the OER process.Therefore,Se-NiS_(2) exhibits outstanding OER activity and stability in alkaline conditions,requiring an overpotential of 343 mV at a current density of 50 mA cm^(-2).A novel insight is provided by our work in understanding the surface reconstruction and electrocatalytic mechanism of Ni-based chalcogenides.
基金supported by the National Scientific Foundation of China(NSFC,Project no.21306119)the Provincial Natural Science Foundation of Sichuan(2013FZ0034 and 2013JY0150)the Outstanding Young Scientist Foundation of Sichuan University(2013SCU04A23)
文摘In-situ HVEM observation on phase transition of the YBa_2Cu_3O_(7-x) superconducting compound in pro- cess of heating was carried out,and high temperature X-ray diffraction analysis in air and X-ray diffraction phase analysis for the sample treated in vacuum condition were made.The results showed that the temperature of phase transition is related to oxygen content in the sample and in general,is 100℃ to 120℃ lower in vacu- um condition than in air.At 320℃ to 350℃ twin bands begin to disappear,and some Cu_2O are formed on the surface of the sample and transit from orthorhombic YBa_2Cu_3O_(7-x) to arthorhombic Y_2BaCuO_5 compound. This transition was completed at about 500℃.Above 900℃,this compound consists of the Y_2BaCuO_5, BaCuO_2,Y_2O_3 and some other minor compounds.No phase transition was observed during cooling the sample.
基金This project was sponsored by "863" Project (No. 2003AA322020)
文摘The Al2O3 abrasion-resistant ceramics is successfully prepared by using waste aluminum sludge as the main raw material with the addition of a little clay, talc and barium carbonate. The crystal structure and microstructure of ceramic are characterized by means of XRD, SEM, etc., and the physical and mechanical properties are also tested. The results show that besides the phase of corundum, a little mullite, Mg-Al spinel and hyalophane phases also exist in the product. These phases are produced via reaction in-situ, which can inhibit the overgrowth of Al2O3 grain in grain boundary, and improve the integral property of the material.
基金Funded by the National Science Foundation of China ( No.50375037)
文摘Si3N4-Si2N2O composites were fabricated with amorphous nano-sized silicon nitride powders by the liquid phase sintering ( LPS ). The Si2 N2O phase was generated by an in-situ reaction 2 Si3 N4 ( s ) + 1.5 02 ( g ) = 3 Si2 N2O ( s ) + N2 ( g ) . The content of Si2 N2 O phase up to 60% in the volume was obtained at a sintering temperature of 1 650℃ and reduced when the sintering temperature increased or decreased, indicating the reaction is reversible. The mass loss, relative density and average grain size increased with increasing the sintering temperature. The average grain size was less than 500 nm when the sintering temperature was below 1 700 ℃. The sintering procedure contains a complex crystallization and a phase transition : amorphous silicon nitride→equiaxial α- Si3 N4→ equiaxial β- Si3 N4→ rod- like Si2 N2O→ needle- like β- Si3N4 . Small round-shaped β→ Si3 N4 particles were entrapped in the Si2 N2O grains and a high density of staking faults was situated in the middle of Si2 N2O grains at a sintering temperature of 1 650 ℃. The toughness inereased from 3.5 MPa·m^1/2 at 1 600 ℃ to 7.2 MPa· m^1/2 at 1 800 ℃ . The hardness was as high as 21.5 GPa (Vickers) at 1 600 ℃ .
基金the Key Project of Ministry of Education of China (No.105055).
文摘A γ-Al2O3 particles reinforced Al-Si alloy matrix composite was fabricated by adding NH4Al(SO4)2 to molten aluminum alloy. TEM observation shows that in-situ γ-Al2O3 particles are generally spherical and uniformly distributed in the matrix. The results of dry sliding wear tests show that the wear resistance of the composites increases with increasing mass fraction, and the volume loss is considerably lesser than that of the matrix and is lesser than that of the composites by adding γ-Al2O3 particles directly.
基金Project(20376086)supported by the National Natural Science Foundation of ChinaProject(2005037700)supported by Postdoctoral Science Foundation of China+2 种基金Project(07JJ3014)supported by Hunan Provincial Natural Science Foundation of ChinaProject(07A058)supported by Scientific Research Fund of Hunan Provincial Education DepartmentProject(2004107)supported by Postdoctoral Science Foundation of Central South University
文摘LiMn2O4/Li4Ti5O12 composite was synthesized by in-situ composite technique using LiMn2O4,lithium acetate,tetrabutyl titanate as starting materials and characterized by various electrochemical methods in combination with X-ray diffractometry(XRD), infrared(IR)spectroscopy and scanning electron microscopy(SEM).The results show that Li4Ti5O12 is coated on the surface of crystalline LiMn2O4 to form LiMn2O4/Li4Ti5O12 composite.The structure of LiMn2O4 does not change due to the introduction of Li4Ti5O12.By being coated with Li4Ti5O12,the rate capability and high temperature cyclability of LiMn2O4 is improved greatly.At room temperature,the discharge capacity of LiMn2O4/Li4Ti5O12 composite is more than 108.4 mA·h/g and the capacity loss per cycle is only 0.053%after 20 cycles at 2.0C.While at 55℃,the discharge capacity of LiMn2O4/Li4Ti5O12 composite is more than 109.9 mA·h/g and the capacity loss per cycle is only 0.036%after 60 cycles at 1.0C.
基金Project(50702012)supported by the National Natural Science Foundation of ChinaProject(20060145030)supported by Doctoral Foundation of Chinese Education Ministry
文摘Silver as a highly conductive metal is usually doped in YBa2Cu3O7-x superconductor bulks to improve critical current density of YBa2Cu3O7-x superconductor.The valuable metal elements silver,yttrium,barium and copper in waste YBa2Cu3O7-x/Ag composite superconductor bulks were recovered,respectively.Silver was recovered with process at first,the waste was dissolved by nitric acid and silver chloride was precipitated by adding chloride acid,then silver pig was obtained by melting silver chloride together with sodium carbonate at 1 000℃.The effective factors on recovery ratio and purity of silver were studied.The chemical analysis proves that the purity of silver ingot is 95.86%.The recovery ratio of silver is calculated to be 92.56%.The loss of silver may be due to the loss of silver chloride during filtering and the volatilization of silver when silver chloride and sodium carbonate are smelted at high temperature.For other three metal elements,Y3 +,Ba 2+and Cu 2+,in the surplus waste liquid after recovering silver, they were separated with the sequence of barium,copper and then yttrium step by step.First,sulfate acid was used to precipitate barium sulfate.Then,sodium sulfide was added to the surplus solution so that copper could be separated as copper sulfide.During this separation procedure,it was important to control the pH value to be 1-2.After that,oxalic acid was added into the surplus solution to obtain yttrium oxalate.Finally,yttrium oxide was formed by burning yttrium oxalate.The XRD results indicate that the final products are all single-phase compounds as BaSO4,CuS and Y2O3,respectively.
基金supported by both the Technology Innovation Program(20004958,Development of ultra-high performance supercapacitor and high power module)funded by the Ministry of Trade,Industry and Energy(MOTIE)the R&D Convergence Program(CAP-15-02-KBSI)of the National Research Council of Science&Technology,Republic of Korea。
文摘With the development of stable alkali metal anodes,V_(2)O_(5) is gaining traction as a cathode material due to its high theoretical capacity and the ability to intercalate Li,Na and K ions.Herein,we report a method for synthesizing structured orthorhombic V_(2)O_(5) microspheres and investigate Li intercalation/deintercalation into this material.For industry adoption,the electrochemical behavior of V_(2)O_(5) as well as structural and phase transformation attributing to Li intercalation reaction must be further investigated.Our synthesized V_(2)O_(5) microspheres consisted of small primary particles that were strongly joined together and exhibited good cycle stability and rate capability,triggered by reversible volume change and rapid Li ion diffusion.In addition,the reversibility of phase transformation(a,e,d,c and xLixV_(2)O_(5))and valence state evolution(5+,4+,and 3.5+)during intercalation/de-intercalation were studied via in-situ X-ray powder diffraction and X-ray absorption near edge structure analyses.
基金supported by the National Key R&D Program of China(2021YFC2103704)the National Natural Science Foundation of China(22022812,21978259)+1 种基金Key R&D Program of Zhejiang(2022C01208)Institute of Zhejiang University-Quzhou S&T Planed Projects(IZQ2021KJ1001)。
文摘Hydrodeoxygenation of furfural(FF)into 2-methylfuran(MF)is a significant biomass utilization route.However,designing efficient and stable non-noble metal catalyst is still a huge challenge.Herein,we reported the N,O co-doped carbon anchored with Co nanoparticles(Co-SFB)synthesized by employing the organic ligands with the target heteroatoms.Raman,electron paramagnetic resonance(EPR),electrochemical impedance spectroscopy(EIS),and X-ray photoelectron spectroscopy(XPS)characterizations showed that the co-doping of N and O heteroatoms in the carbon support endows Co-SFB with enriched lone pair electrons,fast electron transfer ability,and strong metal-support interaction.These electronic properties resulted in strong FF adsorption as well as lower apparent reaction activation energy.At last,the obtained N,O co-doped Co/C catalyst showed excellent catalytic activity(nearly 100 mol%FF conversion and 94.6 mol%MF yield)and stability for in-situ dehydrogenation of FF into MF.This N,O co-doping strategy for the synthesis of highly efficient catalytic materials with controllable electronic state will provide an excellent opportunity to better understand the structure-function relationship.
基金supported by the National Natural Science Foundation of China (41471190)the National Key Research and Development Program of China (2016YFD0800102)+2 种基金the Special Fund for the Agricultural Public Welfare Profession of China (201503106)the Newton Fund, United Kingdom (BB/N013484/1)the GEF on the ‘Towards INMS’
文摘The upland agricultural soils in North China are distributed north of a line between the Kunlun Mountains, the Qinling Mountains and the Huaihe River. They occur in arid, semi-arid and semi-humid regions and crop production often depends on rain-fed or irrigation to supplement rainfall. This paper summarizes the characteristics of gross nitrogen(N) transformation, the fate of N fertilizer and soil N as well as the N loss pathway, and makes suggestions for proper N management in the region. The soils of the region are characterized by strong N mineralization and nitrification, and weak immobilization and denitrification ability, which lead to the production and accumulation of nitrate in the soil profile. Large amounts of accumulated nitrate have been observed in the vadose-zone in soils due to excess N fertilization in the past three decades, and this nitrate is subject to occasional leaching which leads to groundwater nitrate contamination. Under farmer's conventional high N fertilization practice in the winter wheat-summer maize rotation system(N application rate was approximately 600 kg ha–1 yr–1), crop N uptake, soil residual N, NH_3 volatilization, NO_3~– leaching, and denitrification loss accounted for around 27, 30, 23, 18 and 2% of the applied fertilizer N, respectively. NH_3 volatilization and NO_3~– leaching were the most important N loss pathways while soil residual N was an important fate of N fertilizer for replenishing soil N depletion from crop production. The upland agricultural soils in North China are a large source of N_2O and total emissions in this region make up a large proportion(approximately 54%) of Chinese cropland N_2O emissions. The “non-coupled strong ammonia oxidation” process is an important mechanism of N_2O production. Slowing down ammonia oxidation after ammonium-N fertilizer or urea application and avoiding transient high soil NH4+ concentrations are key measures for reducing N_2O emissions in this region. Further N management should aim to minimize N losses from crop and livestock production, and increase the recycling of manure and straw back to cropland. We also recommend adoption of the 4 R(Right soure, Right rate, Right time, Right place) fertilization techniques to realize proper N fertilizer management, and improving application methods or modifying fertilizer types to reduce NH_3 volatilization, improving water management to reduce NO_3~– leaching, and controlling the strong ammonia oxidation process to abate N_2O emission. Future research should focus on the study of the trade-off effects among different N loss pathways under different N application methods or fertilizer products.
文摘A new process of extracting vanadium from the stone coal vanadium ore in Fangshankou, Dtmhuang area of Gansu Province, China was introduced. Various leaching experiments were carried out, and the results show that the vanadium ore in Fangshankou is difficult to process due to its high consumption of acid and the high leaching rate of impurities. However, the leaching rate can be up to 80% and the content of V2O5 in the residue can be between 0.22%-0.25% in the process of ore fme grinding→oxidation roasting→mixing and ripening→aqueous leaching→P2O4 solvent extraction→sulfuric acid stripping→oxidation and precipitation→decomposition by heat. Also, the quality of flaky V205 produced by this process can meet the requirements of GB3283--87. The total leaching rate of vanadium is 70%. Also, three types of wastes are easy to treat. The vanadium extraction process is better in relation to the aspect of environmental protection than the sodium method.
基金Supported by the National Natural Science Foundation of China(Grant No. 20573072)Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20060718010)
文摘β-Ga2O3 cone-like nanowires have been in-situ grown on the surface of gallium grains and films by heating gallium substrates at 750-1000℃ for 2h in air.The controllable synthesis of β-Ga2O3 nano-wires with different diameters and lengths was achieved by adjusting the heating temperature and time.The as-synthesized products were characterized by means of X-ray diffraction,scanning electron mi-croscopy and transmission electron microscopy.The results showed that the β-Ga2O3 nanowires are single crystalline with a monoclinic structure and have a controllable diameter and length in the range of 30-100nm and 0.5-1.5μm,respectively.A possible mechanism was also proposed to account for the formation of β-Ga2O3 cone-like nanowires.Photoluminescence spectra of the β-Ga2O3 nanowires obtained at different temperatures were measured at room temperature,and a strong blue photolumi-nescence with peaks at 430 and 460nm and a weak red photoluminescence with peak at 713nm were observed.The blue light emission intensity decreases with increasing the reaction temperature,how-ever,the red light emission intensity hardly changes.The blue and red light emissions originate from the recombination of an electron on an oxygen vacancy with a hole on a gallium-oxygen vacancy pair and the nitrogen dopants,etc.,respectively.
基金financially supported by the National Natural Science Foundation of China(Nos.61973223,61673367 and 51674067)Liao Ning Revitalization Talents Program(No.XLYC1807198)。
文摘V2O5 flower-like structures assembled by thin nanosheets were in-situ growth on ceramic tubes by hydrothermal process.The structural characterization indicates that V2O5 flower-like structures is orthogonal diamond phase,which entirely covered on the surface of ceramic tubes.TMA sensing measured results revealed that the sensor based on V2O5 flower-like structures exhibited fast reversible and response,good selectivity to TMA and good stability at 200℃.The good sensing performance may be ascribed to flower-like structure s and directly growth sensing film on the ceramic tube without structure damage.Our works give a simple in-situ growth flower-like structures route on sensing device,which exhibits potential application for detecting trace amounts of TMA gas.