Highly efficient and green ammonia production is an important demand for modern agriculture.In this study,a two-step ammonia production method is developed using a gliding arc discharge in combination with Cu/Cu_(2)O ...Highly efficient and green ammonia production is an important demand for modern agriculture.In this study,a two-step ammonia production method is developed using a gliding arc discharge in combination with Cu/Cu_(2)O electrocatalysis.In this method,NO_(x)is provided by the gliding arc discharge and then electrolyzed by Cu/Cu_(2)O after alkaline absorption.The electrical characteristics,the optical characteristics and the NO_(x)production are investigated in discharges at different input voltage and the gas flow.The dependence of ammonia production through Cu/Cu_(2)O electrocatalysis on pH value and reduction potential are determined by colorimetric method.In our study,two discharge modes are observed.At high input voltage and low gas flow,the discharge is operated with a stable plasma channel which is called the steady arc gliding discharge mode(A-G mode).As lowering input voltage and raising gas flow,the plasma channel is destroyed and high frequency breakdown occurs instead,which is known as the breakdown gliding discharge mode(B-G mode).The optimal NO_(x)production of 7.34 mmol h^(-1)is obtained in the transition stage of the two discharge modes.The ammonia yield reaches0.402 mmol h^(-1)cm^(-2)at pH value of 12.7 and reduction potential of-1.0 V versus reversible hydrogen electrode(RHE).展开更多
Methanol synthesis from hydrogenation of CO2 is investigated over Cu/ZnO/Al2O3 catalysts prepared by decomposition of M（Cu,Zn）-ammonia complexes （DMAC） at various temperatures.The catalysts were characterized in d...Methanol synthesis from hydrogenation of CO2 is investigated over Cu/ZnO/Al2O3 catalysts prepared by decomposition of M（Cu,Zn）-ammonia complexes （DMAC） at various temperatures.The catalysts were characterized in detail,including X-ray diffraction,N2 adsorption-desorption,N2O chemisorption,temperature-programmed reduction and evolved gas analyses.The influences of DMAC temperature,reaction temperature and specific Cu surface area on catalytic performance are investigated.It is considered that the aurichalcite phase in the precursor plays a key role in improving the physiochemical properties and activities of the final catalysts.The catalyst from rich-aurichalcite precursor exhibits large specific Cu surface area and high space time yield of methanol （212 g/（Lcat·h）;T=513 K,p=3MPa,SV=12000 h-1）.展开更多
A series of polymer- supported Pd -Fe2O3 composite catalysts were prepared and their hydrogenation property mas investigated. It was found that the above catalysts have good catalytic hydrogenation activity for carbon...A series of polymer- supported Pd -Fe2O3 composite catalysts were prepared and their hydrogenation property mas investigated. It was found that the above catalysts have good catalytic hydrogenation activity for carbon - carbon double bonds systems and reusability. Furthermore, XPS and IR spectra shouted that active component in the composite catalysts is atomic Pd(0). An addition of a small amount of Fe2O3 has a promotive action upon hydrogenation activity of the catalysts, which indicated that there are some strong interactions (electron transfer) between Pd(0) and Fe(Ⅲ) species. Based on these results, a possible catalytic hydrogenation mechanism was also suggested.展开更多
The preferred internal oxidation of aluminum in Cu Al alloy was used to obtain in situ Al 2O 3/Cu composites. The reinforcement particles were mainly γ Al 2O 3, some θ Al 2O 3 and a little α Al 2O 3. Thermodynamics...The preferred internal oxidation of aluminum in Cu Al alloy was used to obtain in situ Al 2O 3/Cu composites. The reinforcement particles were mainly γ Al 2O 3, some θ Al 2O 3 and a little α Al 2O 3. Thermodynamics analyses show that the chemical reactions are 3Cu 2O+2Al=6Cu+Al 2O 3 or 3CuO+2Al=3Cu+Al 2O 3. A related equilibrium diagram was drawn. The experiments and investigation show that the formation rate of Al 2O 3 was controlled by the diffusion of oxygen in matrix.展开更多
2-D nanosheet Cu2O doped CuO coating poly m-phenylenediamine and melamine/graphene/carbon fibers composite(CuxO/MPM/GFs)was firstly fabricated by compound electrochemical method.CuxO/MPM/GFs was successfully used to t...2-D nanosheet Cu2O doped CuO coating poly m-phenylenediamine and melamine/graphene/carbon fibers composite(CuxO/MPM/GFs)was firstly fabricated by compound electrochemical method.CuxO/MPM/GFs was successfully used to the recovery of iodide(I-)from salt water by lower potential-aided sorption and desorption processes.The potential-aided recovery of I-at CuxO/MPM/GFs was characterized by FE-SEM,XRD,IR,Raman,XPS,UV-vis and electrochemical techniques in detail.The maximal adsorption capacity of 86.82 mg·g^-1 could be obtained with a pseudo-second-order model at 0.8 V for 210 min in pH 5.0,0.1 mol·L^-1 NaCl,and the process accompanied the generation of CuI,CuO and I5-.The I-could be quickly desorbed from the electrode with a transfer of CuI to Cu2O by cycle voltammetry from-1.0 to 0.5 V for 90 cycles in pH 9.0,0.1 mol·L^-1 KNO3.Thus,CuxO/MPM/GFs was renewable in the continuous electrochemical-adsorption-desorption processes.展开更多
To improve the denitrification performance of carbon-based materials for sintering flue gas,we prepared a composite catalyst comprising coconut shell activated carbon(AC)modified by thermal oxidation air.The microstru...To improve the denitrification performance of carbon-based materials for sintering flue gas,we prepared a composite catalyst comprising coconut shell activated carbon(AC)modified by thermal oxidation air.The microstructure,the specific surface area,the pore volume,the crystal structure,and functional groups presented in the prepared Cu2O/AC catalysts were thoroughly characterized.By using scanning electron microscopy(SEM),nitrogen adsorption/desorption isotherms,Fourier-transform infrared(FTIR)spectroscopy and X-ray diffractometry(XRD),the effects of Cu2O loading and calcination temperature on Cu2O/AC catalysts were investigated at low temperature(150℃).The research shows that Cu on the Cu2O/AC catalyst is in the form of Cu2O with good crystalline performance and is spherical and uniformly dispersed on the AC surface.The loading of Cu2O increases the active sites and the specific surface area of the reaction gas contact,which is conducive to the rapid progress of the carbon monoxide selective catalytic reduction(CO-SCR)reaction.When the loading of Cu2O was 8%and the calcination temperature was 500℃,the removal rate of NOx facilitated by the Cu2O/AC catalyst reached 97.9%.These findings provide a theoretical basis for understanding the denitrification of sintering flue gas.展开更多
Alumina dispersion strengthened copper composite （nano-Al2O3/Cu composite） was recently emerged as a kind of potentially viable and attractive engineering material for applications requiring high strength, high ther...Alumina dispersion strengthened copper composite （nano-Al2O3/Cu composite） was recently emerged as a kind of potentially viable and attractive engineering material for applications requiring high strength, high thermal and electrical conductivities and resistance to softening at elevated temperatures. The nano-Al2O3/Cu composite was produced by internal oxidation. The microstructures of the composite were analyzed by the TEM and its hot deformation behavior was investigated by means of continuous compression tests performed on a Gleeble 1500 thermo-simulator. Making use of the modified algorithm-Levenberg-Marquardt （L-M） algorithm BP neural network, a model for predicting the flow stresses during hot deformation was set up on the base of the experimental data. Results show that the microstructures of the composite are characterized by uniform distribution of nano-Al2O3 particles in Cu-matrix. The sliding of dislocations is the main deformation mechanism. The dynamic recovery is the main softening mode with the flow stress decreasing gently from 500℃ to 850 ~C. The recrystallization of Cu-matrix can be retarded late into as high as 850 ℃, when it happens only partially. The well-trained BP neural network model can accurately describe the influence of the temperature, strain rate, and true strain on the flow stresses, therefore, it can precisely predict the flow stresses of the composite under given deforming conditions and provide a new way to optimize hot deforming process parameters.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
This work concerns with the high temperature deformation of internally oxidized Al2O3/Cu composites. The investigation revealed that dispersive alumina can obstruct dislocation sliding and define the subgrain size the...This work concerns with the high temperature deformation of internally oxidized Al2O3/Cu composites. The investigation revealed that dispersive alumina can obstruct dislocation sliding and define the subgrain size thereby improve significantly the strength of the materials at high temperature. The sliding of dislocations is a main deformation mechanism in the given temperature range. The sliding of grain boundary and diffusive creep play important roles at high temperature and low strain rate. The dispersoids can raise the recrystallization temperature to higher than 1223 K. Dynamic recovery is a main softening way under the experimental conditions. Higher deformation rate and lower deformation temperature imply a higher flow stress.展开更多
面向国家绿色低碳战略目标,变革化石资源合成氨技术路线变得尤为迫切,开发可再生能源制“绿氨”将成为合成氨领域未来的重要发展方向.将工业废水中的硝酸根(NO_(3)-)电催化还原为氨(NO_(3)RR),既可有效回收氨,又能消除硝酸根污染影响.然...面向国家绿色低碳战略目标,变革化石资源合成氨技术路线变得尤为迫切,开发可再生能源制“绿氨”将成为合成氨领域未来的重要发展方向.将工业废水中的硝酸根(NO_(3)-)电催化还原为氨(NO_(3)RR),既可有效回收氨,又能消除硝酸根污染影响.然而,NO_(3)RR涉及缓慢的八电子转移过程,含有多种反应中间体,其反应机理复杂不明.此外,水系电解液中存在的析氢竞争反应也为高效NO_(3)RR催化剂的开发设计带来了巨大的挑战.为突破高效催化剂的发展瓶颈,本文通过理论模拟,在低成本的催化剂上设计了高效的NO_(3)RR催化活性位点,并利用简单的制备策略合成了目标催化剂.同时,结合原位表征技术,阐明了NO_(3)RR的反应路径及催化机理.本文通过密度泛函理论(DFT)计算发现,Cu/TiO_(2)催化剂上的Cu-O-Ti-O_(v)结构具有较好的NO_(3)-还原活性,该结构不仅能够促进反应中间体NOx-的吸附和活化,还能有效抑制竞争析氢反应,从而降低NO_(3)RR的反应能垒.在该结构上,NO_(3)RR的反应路径为:NO_(3)^(*)→NO_(2)^(*)→HONO^(*)→NO^(*)→*NOH→*N→^(*)NH→*NH2→*NH_(3)→NH_(3).基于理论计算结果,分别采用浸渍法和尿素水解法制备了系列富含Cu-O-Ti-O_(v)结构的Cu/TiO_(2)催化剂.氮气等温吸附-脱附曲线、拉曼光谱(Raman)、电子顺磁共振波谱、X射线光电子能谱(XPS)和傅立叶红外光谱等结果发现,相比于采用浸渍法制备的系列Cu/TiO_(2)催化剂,采用尿素水解法制备的Cu/TiO_(2)(CT-U)催化剂具有更大的比表面积以及更多的Cu-O-Ti-O_(v)位点,说明尿素水解法可提高Cu颗粒在TiO_(2)载体表面的分散度,增强Cu颗粒与TiO_(2)载体之间的相互作用,提高Cu/TiO_(2)催化剂表面的Cu-O-Ti-O_(v)位点含量.将以上制备出的催化剂应用于催化NO_(3)RR中,结果表明,在-1.0 V vs.RHE还原电位下,CT-U催化剂上氨产率可达3046.5μg h^(-1) mgcat^(-1),高于大多数文献报道结果.循环稳定性测试结果表明,在Cu/TiO_(2)催化剂上构建Cu-O-Ti-O_(v)位点还能显著抑制电催化反应过程中Cu物种从Cu/TiO_(2)催化剂上溶出,从而显著增强催化剂的稳定性.此外,设计制备了不含氧空位的Cu/TiO_(2),TiO_(2)-x,Cu,Cu_(2)O以及CuO催化剂,并将其用于催化NO_(3)RR.结果发现,上述催化剂上的氨产率皆明显低于CT-U催化剂,说明Cu,Ti以及O_(v)构成的Cu-O-Ti-O_(v)结构具有较好的催化协同作用,从而显著提升了NO_(3)RR反应活性.最后,通过原位Raman及原位XPS表征检测反应中间体,验证了由DFT模拟出的NO_(3)RR反应路径.综上,通过在Cu/TiO_(2)催化剂上理论指导构建Cu-O-Ti-O_(v)活性位点,实现了NO_(3)RR性能的有效提升.Cu-O-Ti-O_(v)结构中的多位点协同作用不仅促进了NO_(x)-的吸附和活化,而且抑制了电催化过程中Cu物种从催化剂上的溶出,从而提高了催化剂的稳定性.本研究为设计高效稳定的NO_(3)RR催化剂提供了新思路.展开更多
Two Al2O3/Cu composites containing 0.24 wt.% Al2O3 and 0.60 wt.% Al2O3 separately are prepared by internal oxidation. Effects of sliding speed and pressure on the frictional characteristics of the composites and coppe...Two Al2O3/Cu composites containing 0.24 wt.% Al2O3 and 0.60 wt.% Al2O3 separately are prepared by internal oxidation. Effects of sliding speed and pressure on the frictional characteristics of the composites and copper against brass are investigated and compared. The changes in morphology of the sliding surface and subsurface are examined with scanning electron microscope （SEM） and energy dispersive X-ray spectrum （EDS）. The results show that the wear resistance of the Al2O3/Cu composites is superior to that of copper under the same conditions, Under a given electrical current, the wear rate of Al2O3/Cu composites decreases as the Al2O3-content increases, However, the wear rates of the Al2O3/Cu composites and copper increase as the sliding speed and pressure increase under dry sliding condition. The main wear mechanisms for Al2O3/Cu composites are of abrasion and adhesion; for copper, it is adhesion, although wear by oxidation and electrical erosion can also be observed as the speed and pressure rise.展开更多
The Cu2O/SiC photocatalyst was obtained from SiC nanoparticles （NPs） modified by Cu2O. Their photocatalytic activities for reducing CO2 to CH3OH under visible light irradiation have been investigated. The results in...The Cu2O/SiC photocatalyst was obtained from SiC nanoparticles （NPs） modified by Cu2O. Their photocatalytic activities for reducing CO2 to CH3OH under visible light irradiation have been investigated. The results indicated that besides a small quantity of 6H-SiC, SiC NPs mainly consisted of 3C-SiC. The band gaps of SiC and Cu2O were estimated to be about 1.95 and 2.23 eV from UV-Vis spectra, respectively. The Cu2O modification can enhance the photocatalytic performance of SiC NPs, and the largest yields of methanol on SiC, Cu2O and Cu2O/SiC photocatalysts under visible light irradiation were 153, 104 and 191μmol/g, respectively.展开更多
文摘Highly efficient and green ammonia production is an important demand for modern agriculture.In this study,a two-step ammonia production method is developed using a gliding arc discharge in combination with Cu/Cu_(2)O electrocatalysis.In this method,NO_(x)is provided by the gliding arc discharge and then electrolyzed by Cu/Cu_(2)O after alkaline absorption.The electrical characteristics,the optical characteristics and the NO_(x)production are investigated in discharges at different input voltage and the gas flow.The dependence of ammonia production through Cu/Cu_(2)O electrocatalysis on pH value and reduction potential are determined by colorimetric method.In our study,two discharge modes are observed.At high input voltage and low gas flow,the discharge is operated with a stable plasma channel which is called the steady arc gliding discharge mode(A-G mode).As lowering input voltage and raising gas flow,the plasma channel is destroyed and high frequency breakdown occurs instead,which is known as the breakdown gliding discharge mode(B-G mode).The optimal NO_(x)production of 7.34 mmol h^(-1)is obtained in the transition stage of the two discharge modes.The ammonia yield reaches0.402 mmol h^(-1)cm^(-2)at pH value of 12.7 and reduction potential of-1.0 V versus reversible hydrogen electrode(RHE).
基金supported by the National Basic Research Program of China (No. 2011CB201404)the financial support of the State Key Laboratory for Oxo Synthesis and Selective Oxidation (OSSO) of China
文摘Methanol synthesis from hydrogenation of CO2 is investigated over Cu/ZnO/Al2O3 catalysts prepared by decomposition of M（Cu,Zn）-ammonia complexes （DMAC） at various temperatures.The catalysts were characterized in detail,including X-ray diffraction,N2 adsorption-desorption,N2O chemisorption,temperature-programmed reduction and evolved gas analyses.The influences of DMAC temperature,reaction temperature and specific Cu surface area on catalytic performance are investigated.It is considered that the aurichalcite phase in the precursor plays a key role in improving the physiochemical properties and activities of the final catalysts.The catalyst from rich-aurichalcite precursor exhibits large specific Cu surface area and high space time yield of methanol （212 g/（Lcat·h）;T=513 K,p=3MPa,SV=12000 h-1）.
文摘A series of polymer- supported Pd -Fe2O3 composite catalysts were prepared and their hydrogenation property mas investigated. It was found that the above catalysts have good catalytic hydrogenation activity for carbon - carbon double bonds systems and reusability. Furthermore, XPS and IR spectra shouted that active component in the composite catalysts is atomic Pd(0). An addition of a small amount of Fe2O3 has a promotive action upon hydrogenation activity of the catalysts, which indicated that there are some strong interactions (electron transfer) between Pd(0) and Fe(Ⅲ) species. Based on these results, a possible catalytic hydrogenation mechanism was also suggested.
文摘The preferred internal oxidation of aluminum in Cu Al alloy was used to obtain in situ Al 2O 3/Cu composites. The reinforcement particles were mainly γ Al 2O 3, some θ Al 2O 3 and a little α Al 2O 3. Thermodynamics analyses show that the chemical reactions are 3Cu 2O+2Al=6Cu+Al 2O 3 or 3CuO+2Al=3Cu+Al 2O 3. A related equilibrium diagram was drawn. The experiments and investigation show that the formation rate of Al 2O 3 was controlled by the diffusion of oxygen in matrix.
基金supported by the National Natural Science Foundation of China(U1407110)Anhui Province Key Research and Development Plan(JZ2018AKKG0332)。
文摘2-D nanosheet Cu2O doped CuO coating poly m-phenylenediamine and melamine/graphene/carbon fibers composite(CuxO/MPM/GFs)was firstly fabricated by compound electrochemical method.CuxO/MPM/GFs was successfully used to the recovery of iodide(I-)from salt water by lower potential-aided sorption and desorption processes.The potential-aided recovery of I-at CuxO/MPM/GFs was characterized by FE-SEM,XRD,IR,Raman,XPS,UV-vis and electrochemical techniques in detail.The maximal adsorption capacity of 86.82 mg·g^-1 could be obtained with a pseudo-second-order model at 0.8 V for 210 min in pH 5.0,0.1 mol·L^-1 NaCl,and the process accompanied the generation of CuI,CuO and I5-.The I-could be quickly desorbed from the electrode with a transfer of CuI to Cu2O by cycle voltammetry from-1.0 to 0.5 V for 90 cycles in pH 9.0,0.1 mol·L^-1 KNO3.Thus,CuxO/MPM/GFs was renewable in the continuous electrochemical-adsorption-desorption processes.
基金Open Fund of Key Laboratory of Ministry of Education for Metallurgical Emission Reduction and Comprehensive Utilization of Resources,China(No.JKF19-08)General Project of Science and Technology Plan of Yunnan Science and Technology Department,China(No.2019FB077)+1 种基金Industrialization Cultivation Project of Scientific Research Fund of Yunnan Provincial Department of Education,China(No.2016CYH07)Top Young Talents of Yunnan Ten Thousand Talents Plan,China(No.YNWR-QNBJ-2019-263)。
文摘To improve the denitrification performance of carbon-based materials for sintering flue gas,we prepared a composite catalyst comprising coconut shell activated carbon(AC)modified by thermal oxidation air.The microstructure,the specific surface area,the pore volume,the crystal structure,and functional groups presented in the prepared Cu2O/AC catalysts were thoroughly characterized.By using scanning electron microscopy(SEM),nitrogen adsorption/desorption isotherms,Fourier-transform infrared(FTIR)spectroscopy and X-ray diffractometry(XRD),the effects of Cu2O loading and calcination temperature on Cu2O/AC catalysts were investigated at low temperature(150℃).The research shows that Cu on the Cu2O/AC catalyst is in the form of Cu2O with good crystalline performance and is spherical and uniformly dispersed on the AC surface.The loading of Cu2O increases the active sites and the specific surface area of the reaction gas contact,which is conducive to the rapid progress of the carbon monoxide selective catalytic reduction(CO-SCR)reaction.When the loading of Cu2O was 8%and the calcination temperature was 500℃,the removal rate of NOx facilitated by the Cu2O/AC catalyst reached 97.9%.These findings provide a theoretical basis for understanding the denitrification of sintering flue gas.
基金Henan Innovation Project for University Prominent Research Talents (2007KYCX008)Henan Major Science and Technol-ogy Project (0523021500)+1 种基金Henan University of Science and Technology Major Pre-research Foundation (2005ZD003)Henan University of Science and Technology Personnel Scientific Research Foundation
文摘Alumina dispersion strengthened copper composite （nano-Al2O3/Cu composite） was recently emerged as a kind of potentially viable and attractive engineering material for applications requiring high strength, high thermal and electrical conductivities and resistance to softening at elevated temperatures. The nano-Al2O3/Cu composite was produced by internal oxidation. The microstructures of the composite were analyzed by the TEM and its hot deformation behavior was investigated by means of continuous compression tests performed on a Gleeble 1500 thermo-simulator. Making use of the modified algorithm-Levenberg-Marquardt （L-M） algorithm BP neural network, a model for predicting the flow stresses during hot deformation was set up on the base of the experimental data. Results show that the microstructures of the composite are characterized by uniform distribution of nano-Al2O3 particles in Cu-matrix. The sliding of dislocations is the main deformation mechanism. The dynamic recovery is the main softening mode with the flow stress decreasing gently from 500℃ to 850 ~C. The recrystallization of Cu-matrix can be retarded late into as high as 850 ℃, when it happens only partially. The well-trained BP neural network model can accurately describe the influence of the temperature, strain rate, and true strain on the flow stresses, therefore, it can precisely predict the flow stresses of the composite under given deforming conditions and provide a new way to optimize hot deforming process parameters.
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The work was financiaIly supported hy the NaturalScience Foundation of Hebei Province (No.94087) alld Pd-ucation Conlmittee of
文摘This work concerns with the high temperature deformation of internally oxidized Al2O3/Cu composites. The investigation revealed that dispersive alumina can obstruct dislocation sliding and define the subgrain size thereby improve significantly the strength of the materials at high temperature. The sliding of dislocations is a main deformation mechanism in the given temperature range. The sliding of grain boundary and diffusive creep play important roles at high temperature and low strain rate. The dispersoids can raise the recrystallization temperature to higher than 1223 K. Dynamic recovery is a main softening way under the experimental conditions. Higher deformation rate and lower deformation temperature imply a higher flow stress.
文摘面向国家绿色低碳战略目标,变革化石资源合成氨技术路线变得尤为迫切,开发可再生能源制“绿氨”将成为合成氨领域未来的重要发展方向.将工业废水中的硝酸根(NO_(3)-)电催化还原为氨(NO_(3)RR),既可有效回收氨,又能消除硝酸根污染影响.然而,NO_(3)RR涉及缓慢的八电子转移过程,含有多种反应中间体,其反应机理复杂不明.此外,水系电解液中存在的析氢竞争反应也为高效NO_(3)RR催化剂的开发设计带来了巨大的挑战.为突破高效催化剂的发展瓶颈,本文通过理论模拟,在低成本的催化剂上设计了高效的NO_(3)RR催化活性位点,并利用简单的制备策略合成了目标催化剂.同时,结合原位表征技术,阐明了NO_(3)RR的反应路径及催化机理.本文通过密度泛函理论(DFT)计算发现,Cu/TiO_(2)催化剂上的Cu-O-Ti-O_(v)结构具有较好的NO_(3)-还原活性,该结构不仅能够促进反应中间体NOx-的吸附和活化,还能有效抑制竞争析氢反应,从而降低NO_(3)RR的反应能垒.在该结构上,NO_(3)RR的反应路径为:NO_(3)^(*)→NO_(2)^(*)→HONO^(*)→NO^(*)→*NOH→*N→^(*)NH→*NH2→*NH_(3)→NH_(3).基于理论计算结果,分别采用浸渍法和尿素水解法制备了系列富含Cu-O-Ti-O_(v)结构的Cu/TiO_(2)催化剂.氮气等温吸附-脱附曲线、拉曼光谱(Raman)、电子顺磁共振波谱、X射线光电子能谱(XPS)和傅立叶红外光谱等结果发现,相比于采用浸渍法制备的系列Cu/TiO_(2)催化剂,采用尿素水解法制备的Cu/TiO_(2)(CT-U)催化剂具有更大的比表面积以及更多的Cu-O-Ti-O_(v)位点,说明尿素水解法可提高Cu颗粒在TiO_(2)载体表面的分散度,增强Cu颗粒与TiO_(2)载体之间的相互作用,提高Cu/TiO_(2)催化剂表面的Cu-O-Ti-O_(v)位点含量.将以上制备出的催化剂应用于催化NO_(3)RR中,结果表明,在-1.0 V vs.RHE还原电位下,CT-U催化剂上氨产率可达3046.5μg h^(-1) mgcat^(-1),高于大多数文献报道结果.循环稳定性测试结果表明,在Cu/TiO_(2)催化剂上构建Cu-O-Ti-O_(v)位点还能显著抑制电催化反应过程中Cu物种从Cu/TiO_(2)催化剂上溶出,从而显著增强催化剂的稳定性.此外,设计制备了不含氧空位的Cu/TiO_(2),TiO_(2)-x,Cu,Cu_(2)O以及CuO催化剂,并将其用于催化NO_(3)RR.结果发现,上述催化剂上的氨产率皆明显低于CT-U催化剂,说明Cu,Ti以及O_(v)构成的Cu-O-Ti-O_(v)结构具有较好的催化协同作用,从而显著提升了NO_(3)RR反应活性.最后,通过原位Raman及原位XPS表征检测反应中间体,验证了由DFT模拟出的NO_(3)RR反应路径.综上,通过在Cu/TiO_(2)催化剂上理论指导构建Cu-O-Ti-O_(v)活性位点,实现了NO_(3)RR性能的有效提升.Cu-O-Ti-O_(v)结构中的多位点协同作用不仅促进了NO_(x)-的吸附和活化,而且抑制了电催化过程中Cu物种从催化剂上的溶出,从而提高了催化剂的稳定性.本研究为设计高效稳定的NO_(3)RR催化剂提供了新思路.
基金National Natural Science Foundation of China (50432020)Henan Innovation Project for University Prominent Re- search Talents (2007KYCX008)+3 种基金Henan Education Department Science and Technology Project (2007430004)Henan Plan Project for College Youth Backbone TeacherHenan University of Science and Technology Major Pre-research Foundation (2005ZD003)Henan University of Science and Technology Personnel Scientific Research Foundation (of023)
文摘Two Al2O3/Cu composites containing 0.24 wt.% Al2O3 and 0.60 wt.% Al2O3 separately are prepared by internal oxidation. Effects of sliding speed and pressure on the frictional characteristics of the composites and copper against brass are investigated and compared. The changes in morphology of the sliding surface and subsurface are examined with scanning electron microscope （SEM） and energy dispersive X-ray spectrum （EDS）. The results show that the wear resistance of the Al2O3/Cu composites is superior to that of copper under the same conditions, Under a given electrical current, the wear rate of Al2O3/Cu composites decreases as the Al2O3-content increases, However, the wear rates of the Al2O3/Cu composites and copper increase as the sliding speed and pressure increase under dry sliding condition. The main wear mechanisms for Al2O3/Cu composites are of abrasion and adhesion; for copper, it is adhesion, although wear by oxidation and electrical erosion can also be observed as the speed and pressure rise.
基金supported by the National Natural Science Foundation of China (Grant No. 20906034)the Key Academic Program of the 3rd Phase "211 Project" of South China Agricultural University (Grant No. 2009B010100001)China Postdoctoral Science Foundation (Grant No. 20080430820)
文摘The Cu2O/SiC photocatalyst was obtained from SiC nanoparticles （NPs） modified by Cu2O. Their photocatalytic activities for reducing CO2 to CH3OH under visible light irradiation have been investigated. The results indicated that besides a small quantity of 6H-SiC, SiC NPs mainly consisted of 3C-SiC. The band gaps of SiC and Cu2O were estimated to be about 1.95 and 2.23 eV from UV-Vis spectra, respectively. The Cu2O modification can enhance the photocatalytic performance of SiC NPs, and the largest yields of methanol on SiC, Cu2O and Cu2O/SiC photocatalysts under visible light irradiation were 153, 104 and 191μmol/g, respectively.
