Ethane chemical looping oxidative dehydrogenation(CL-ODH)to ethylene is a new technology for ethylene preparation.Fe_(2)O_(3)/MgO oxygen carrier was prepared using the co-precipitation method.The influence of added Ni...Ethane chemical looping oxidative dehydrogenation(CL-ODH)to ethylene is a new technology for ethylene preparation.Fe_(2)O_(3)/MgO oxygen carrier was prepared using the co-precipitation method.The influence of added NiO and its different loadings on Fe_(2)O_(3)/MgO were investigated.Then,a series of oxygen carriers were applied in the CL-ODH of the ethane cycle system.Brunauer-Emmett-Teller(BET),X-ray diffractometry(XRD),X-ray photoelection spectroscopy(XPS),and H2-temperature programmed reduction(TPR)were used to characterize the physicochemical properties of these oxygen carriers.It was confirmed that an interaction between NiO and Fe_(2)O_(3) occurred based on the XPS and H2-TPR results.Based on the CL-ODH activity performance tests conducted in a fixed-bed reactor,it was revealed that ethylene selectivity was significantly improved after NiO addition.Fe_(2)O_(3)-10%NiO/MgO showed the best activity performance with 93%ethane conversion and 50%ethylene selectivity at a reaction temperature of 650℃,atmospheric pressure,and space velocity of 7500 mL/(g·h).展开更多
光电化学(PEC)分解水是一种清洁可持续的获取氢燃料的方法,其中产氧半反应(OER)是制约整个水分解过程效率的关键步骤.因此,光阳极的性能是决定太阳能到氢能转化效率的关键因素.在各种水氧化光阳极材料中,赤铁矿(α-Fe_(2)O_(3))因具有...光电化学(PEC)分解水是一种清洁可持续的获取氢燃料的方法,其中产氧半反应(OER)是制约整个水分解过程效率的关键步骤.因此,光阳极的性能是决定太阳能到氢能转化效率的关键因素.在各种水氧化光阳极材料中,赤铁矿(α-Fe_(2)O_(3))因具有良好的化学稳定性、合适的带隙(~2.1 eV)、无毒、储量丰富等优点而成为最有前途的光阳极材料之一.然而,α-Fe_(2)O_(3)丰富的受体表面态和缓慢的水氧化动力学导致光生电荷复合严重,限制了其在光电化学中的实际应用.因此,有必要对α-Fe_(2)O_(3)进行表面工程设计以提高水氧化效率.本文提出了一种新方法,以金属有机框架(Ti-MOFs)为模板,在Ti-Fe_(2)O_(3)表面煅烧合成TiO_(2)层,然后将富活性位点的ZIF-67加载在TiO_(2)/Ti-Fe_(2)O_(3)上作为助催化剂,制备出具有较好光电化学性能的ZIF-67/TiO_(2)/Ti-Fe_(2)O_(3)复合光阳极.X射线衍射、高分辨透射电镜、X射线光电子能谱和拉曼光谱等表征结果证实成功合成了ZIF-67/TiO_(2)/Ti-Fe_(2)O_(3).同时,氮气等温吸附脱附曲线和表面接触角测试结果表明,MOFs衍生的TiO_(2)为介孔材料.采用表面光伏技术、光致发光光谱、飞秒-瞬态吸收光谱和电化学阻抗谱分析,研究了光生电荷的分离和复合行为.结果表明,MOFs衍生的TiO_(2)不仅可以作为钝化层有效抑制了表面复合,还作为Ti-Fe_(2)O_(3)的电子阻挡层,显著减少了电子向表面的流失,从而大大提高了Ti-Fe_(2)O_(3)表面和体相的电荷分离效率.进一步的累积电荷量测试、电化学阻抗谱和Bode图分析显示,负载MOFs衍生TiO_(2)后,可以明显促进光生空穴向电解质的注入,其多孔结构也可以增加反应接触面积,这有利于光生电荷在固液界面传输.此外,理论计算结果表明,Ti-Fe_(2)O_(3)水氧化速控步骤的能垒(ΔG=3.38 eV)明显高于TiO_(2)(ΔG=1.67 eV),说明OER更容易在TiO_(2)/Ti-Fe_(2)O_(3)表面发生,这与其光电流密度结果一致.为进一步提高反应活性和加快水氧化动力学,负载助催化剂ZIF-67后,ZIF-67/TiO_(2)/Ti-Fe_(2)O_(3)复合光阳极实现了较好的光电化学性能,其在1.23 V vs.RHE时光电流密度高达4.04 mA cm^(‒2),是Ti-Fe_(2)O_(3)的9.3倍,并且复合光阳极的入射光子电流转换效率和空穴注入效率分别达到93%(390 nm)和91%.综上所述,本研究通过MOFs衍生的TiO_(2)和ZIF-67助催化剂改性α-Fe_(2)O_(3)光阳极,显著提升了其光电化学水氧化性能.其中,MOFs衍生TiO_(2)不仅优化了电荷分离,还促进了光生空穴的注入,从而显著提高其光电化学水氧化性能.本研究为构筑高性能的有机-无机杂化光阳极提供了新思路.展开更多
Fe_(2)O_(3)/ZnO/Ag ternary composite photocatalytic material was prepared by simple hydrothermal method,and its structure and photocatalytic properties were studied.The experimental results show that Fe_(2)O_(3)/ZnO/A...Fe_(2)O_(3)/ZnO/Ag ternary composite photocatalytic material was prepared by simple hydrothermal method,and its structure and photocatalytic properties were studied.The experimental results show that Fe_(2)O_(3)/ZnO/Ag exhibits better photocatalytic performance.After two hours of UV irradiation,the degradation rates of orange Ⅱ and methyl orange reached 91.9% and 75.9%,respectively.The design and preparation of the photocatalyst provide a theoretical basis for the practical application of photocatalytic technology.展开更多
Satellited CoNiCrAlY–Al_(2)O_(3)feedstocks with 2wt%, 4wt%, and 6wt% oxide nanoparticles and pure CoNiCrAlY powder were deposited by the high-velocity oxy fuel process on an Inconel738 superalloy substrate. The oxida...Satellited CoNiCrAlY–Al_(2)O_(3)feedstocks with 2wt%, 4wt%, and 6wt% oxide nanoparticles and pure CoNiCrAlY powder were deposited by the high-velocity oxy fuel process on an Inconel738 superalloy substrate. The oxidation test was performed at 1050℃ for 5, 50, 100,150, 200, and 400 h. The microstructure and phase composition of powders and coatings were characterized by scanning electron microscopy and X-ray diffraction, respectively. The bonding strength of the coatings was also evaluated. The results proved that with the increase in the percentage of nanoparticles(from 2wt% to 6wt%), the amount of porosity(from 1vol% to 4.7vol%), unmelted particles, and roughness of the coatings(from 4.8 to 8.8 μm) increased, and the bonding strength decreased from 71 to 48 MPa. The thicknesses of the thermally grown oxide layer of pure and composite coatings(2wt%, 4wt%, and 6wt%) after 400 h oxidation were measured as 6.5, 5.5, 7.6, and 8.1 μm, respectively.The CoNiCrAlY–2wt% Al_(2)O_(3)coating showed the highest oxidation resistance due to the diffusion barrier effect of well-dispersed nanoparticles. The CoNiCrAlY–6wt% Al_(2)O_(3)coating had the lowest oxidation resistance due to its rough surface morphology and porous microstructure.展开更多
The effects of Fe2O3 content on the microstructure and mechanical properties of the CaO-Al2O3-SiO2 system were investigated by differential thermal analysis（DTA）, X-ray diffraction（XRD）, scanning electron microsc...The effects of Fe2O3 content on the microstructure and mechanical properties of the CaO-Al2O3-SiO2 system were investigated by differential thermal analysis（DTA）, X-ray diffraction（XRD）, scanning electron microscopy（SEM）, electron spin resonance（ESR）, and Mssbauer spectroscopy. The results show that the addition of Fe2O3 does not affect the main crystalline phase in the prepared glasses, but it reduces the crystallisation peak temperature, increases the crystallisation activation energy, and reduces the crystal granularity. The ESR results indicate that Fe2O3 can promote crystallization, as it leads to the phase separation of the CaO-Al2O3-SiO2 system due to axial distortion. Moreover, Fe2O3 alters the network structure of the CaO-Al2O3-SiO2 system, allowing Fe3＋ to enter octahedral sites that exhibit higher symmetry than tetrahedral sites. All of these factors are favourable to increasing the bending strength. The Mssbauer results reveal that there are two types of coordination for both Fe3＋ and Fe2＋ and the bending strength of the CaO-Al2O3-SiO2 system increases with the amount of six-coordinate Fe3＋. The increasing interaction between Fe3＋ and Fe2＋ can also enhance the bending strength of the CaO-Al2O3-SiO2 system. The microhardness of the CaO-Al2O3-SiO2 system was determined to be HV 896.9 and the bending strength to be 217 MPa under the heat treatment conditions of nucleation temperature of 700 °C and nucleation time of 2 h, crystallization temperature of 910 °C and crystallization time of 3 h.展开更多
Al_(2)O_(3)–SiO_(2)sols were synthesized by using aluminum chloride hex hydrate and tetraethoxysilane(TEOS)as precursors,deionized water and ethanol mixture as the solvent,and propylene oxide as the coagulant aids.Al...Al_(2)O_(3)–SiO_(2)sols were synthesized by using aluminum chloride hex hydrate and tetraethoxysilane(TEOS)as precursors,deionized water and ethanol mixture as the solvent,and propylene oxide as the coagulant aids.Alumina coatings were prepared on the surfaces of hollow quartz filament fiber,then a new lightweight and thermal insulating material were successfully prepared by impregnatingAl_(2)O_(3)–SiO_(2)sol into a needle fabric made by coated hollow quartz filament fiber.The coated quartz fiber,aerogels and composites were characterized by Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),energy dispersive spectroscopy(EDS),nitrogen adsorption-desorption(BET),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and tensile tests.The effects of different fiber and calcination temperatures on the microstructures and properties ofAl_(2)O_(3)–SiO_(2)composite aerogels were investigated.The test results indicate that the mechanical properties of the aerogels are improved by introducing quartz filament fabrics and the introduction of alumina coating improves the thermal stability of the material.Compared to other fibers,Al_(2)O_(3)-coated hollow quartz fiber has significant advantages as reinforcement for composite,and their tensile strength is well retained after high temperature heat treatment.展开更多
文摘Ethane chemical looping oxidative dehydrogenation(CL-ODH)to ethylene is a new technology for ethylene preparation.Fe_(2)O_(3)/MgO oxygen carrier was prepared using the co-precipitation method.The influence of added NiO and its different loadings on Fe_(2)O_(3)/MgO were investigated.Then,a series of oxygen carriers were applied in the CL-ODH of the ethane cycle system.Brunauer-Emmett-Teller(BET),X-ray diffractometry(XRD),X-ray photoelection spectroscopy(XPS),and H2-temperature programmed reduction(TPR)were used to characterize the physicochemical properties of these oxygen carriers.It was confirmed that an interaction between NiO and Fe_(2)O_(3) occurred based on the XPS and H2-TPR results.Based on the CL-ODH activity performance tests conducted in a fixed-bed reactor,it was revealed that ethylene selectivity was significantly improved after NiO addition.Fe_(2)O_(3)-10%NiO/MgO showed the best activity performance with 93%ethane conversion and 50%ethylene selectivity at a reaction temperature of 650℃,atmospheric pressure,and space velocity of 7500 mL/(g·h).
文摘光电化学(PEC)分解水是一种清洁可持续的获取氢燃料的方法,其中产氧半反应(OER)是制约整个水分解过程效率的关键步骤.因此,光阳极的性能是决定太阳能到氢能转化效率的关键因素.在各种水氧化光阳极材料中,赤铁矿(α-Fe_(2)O_(3))因具有良好的化学稳定性、合适的带隙(~2.1 eV)、无毒、储量丰富等优点而成为最有前途的光阳极材料之一.然而,α-Fe_(2)O_(3)丰富的受体表面态和缓慢的水氧化动力学导致光生电荷复合严重,限制了其在光电化学中的实际应用.因此,有必要对α-Fe_(2)O_(3)进行表面工程设计以提高水氧化效率.本文提出了一种新方法,以金属有机框架(Ti-MOFs)为模板,在Ti-Fe_(2)O_(3)表面煅烧合成TiO_(2)层,然后将富活性位点的ZIF-67加载在TiO_(2)/Ti-Fe_(2)O_(3)上作为助催化剂,制备出具有较好光电化学性能的ZIF-67/TiO_(2)/Ti-Fe_(2)O_(3)复合光阳极.X射线衍射、高分辨透射电镜、X射线光电子能谱和拉曼光谱等表征结果证实成功合成了ZIF-67/TiO_(2)/Ti-Fe_(2)O_(3).同时,氮气等温吸附脱附曲线和表面接触角测试结果表明,MOFs衍生的TiO_(2)为介孔材料.采用表面光伏技术、光致发光光谱、飞秒-瞬态吸收光谱和电化学阻抗谱分析,研究了光生电荷的分离和复合行为.结果表明,MOFs衍生的TiO_(2)不仅可以作为钝化层有效抑制了表面复合,还作为Ti-Fe_(2)O_(3)的电子阻挡层,显著减少了电子向表面的流失,从而大大提高了Ti-Fe_(2)O_(3)表面和体相的电荷分离效率.进一步的累积电荷量测试、电化学阻抗谱和Bode图分析显示,负载MOFs衍生TiO_(2)后,可以明显促进光生空穴向电解质的注入,其多孔结构也可以增加反应接触面积,这有利于光生电荷在固液界面传输.此外,理论计算结果表明,Ti-Fe_(2)O_(3)水氧化速控步骤的能垒(ΔG=3.38 eV)明显高于TiO_(2)(ΔG=1.67 eV),说明OER更容易在TiO_(2)/Ti-Fe_(2)O_(3)表面发生,这与其光电流密度结果一致.为进一步提高反应活性和加快水氧化动力学,负载助催化剂ZIF-67后,ZIF-67/TiO_(2)/Ti-Fe_(2)O_(3)复合光阳极实现了较好的光电化学性能,其在1.23 V vs.RHE时光电流密度高达4.04 mA cm^(‒2),是Ti-Fe_(2)O_(3)的9.3倍,并且复合光阳极的入射光子电流转换效率和空穴注入效率分别达到93%(390 nm)和91%.综上所述,本研究通过MOFs衍生的TiO_(2)和ZIF-67助催化剂改性α-Fe_(2)O_(3)光阳极,显著提升了其光电化学水氧化性能.其中,MOFs衍生TiO_(2)不仅优化了电荷分离,还促进了光生空穴的注入,从而显著提高其光电化学水氧化性能.本研究为构筑高性能的有机-无机杂化光阳极提供了新思路.
基金Funded in Part by the 14th Five Year Plan Hubei Provincial Advantaged Characteristic Disciplines(Groups) Project of Wuhan University of Science and Technology(No.2023A0203)the Natural Science Foundation of Hubei Province(No.2022CFA003)。
文摘Fe_(2)O_(3)/ZnO/Ag ternary composite photocatalytic material was prepared by simple hydrothermal method,and its structure and photocatalytic properties were studied.The experimental results show that Fe_(2)O_(3)/ZnO/Ag exhibits better photocatalytic performance.After two hours of UV irradiation,the degradation rates of orange Ⅱ and methyl orange reached 91.9% and 75.9%,respectively.The design and preparation of the photocatalyst provide a theoretical basis for the practical application of photocatalytic technology.
文摘Satellited CoNiCrAlY–Al_(2)O_(3)feedstocks with 2wt%, 4wt%, and 6wt% oxide nanoparticles and pure CoNiCrAlY powder were deposited by the high-velocity oxy fuel process on an Inconel738 superalloy substrate. The oxidation test was performed at 1050℃ for 5, 50, 100,150, 200, and 400 h. The microstructure and phase composition of powders and coatings were characterized by scanning electron microscopy and X-ray diffraction, respectively. The bonding strength of the coatings was also evaluated. The results proved that with the increase in the percentage of nanoparticles(from 2wt% to 6wt%), the amount of porosity(from 1vol% to 4.7vol%), unmelted particles, and roughness of the coatings(from 4.8 to 8.8 μm) increased, and the bonding strength decreased from 71 to 48 MPa. The thicknesses of the thermally grown oxide layer of pure and composite coatings(2wt%, 4wt%, and 6wt%) after 400 h oxidation were measured as 6.5, 5.5, 7.6, and 8.1 μm, respectively.The CoNiCrAlY–2wt% Al_(2)O_(3)coating showed the highest oxidation resistance due to the diffusion barrier effect of well-dispersed nanoparticles. The CoNiCrAlY–6wt% Al_(2)O_(3)coating had the lowest oxidation resistance due to its rough surface morphology and porous microstructure.
基金Project(50974090)supported by the National Natural Science Foundation of ChinaProjects(JCYJ20140418182819155,JCYJ20130329113849606)supported by the Shenzhen Dedicated Funding of Strategic Emerging Industry Development Program,China
文摘The effects of Fe2O3 content on the microstructure and mechanical properties of the CaO-Al2O3-SiO2 system were investigated by differential thermal analysis（DTA）, X-ray diffraction（XRD）, scanning electron microscopy（SEM）, electron spin resonance（ESR）, and Mssbauer spectroscopy. The results show that the addition of Fe2O3 does not affect the main crystalline phase in the prepared glasses, but it reduces the crystallisation peak temperature, increases the crystallisation activation energy, and reduces the crystal granularity. The ESR results indicate that Fe2O3 can promote crystallization, as it leads to the phase separation of the CaO-Al2O3-SiO2 system due to axial distortion. Moreover, Fe2O3 alters the network structure of the CaO-Al2O3-SiO2 system, allowing Fe3＋ to enter octahedral sites that exhibit higher symmetry than tetrahedral sites. All of these factors are favourable to increasing the bending strength. The Mssbauer results reveal that there are two types of coordination for both Fe3＋ and Fe2＋ and the bending strength of the CaO-Al2O3-SiO2 system increases with the amount of six-coordinate Fe3＋. The increasing interaction between Fe3＋ and Fe2＋ can also enhance the bending strength of the CaO-Al2O3-SiO2 system. The microhardness of the CaO-Al2O3-SiO2 system was determined to be HV 896.9 and the bending strength to be 217 MPa under the heat treatment conditions of nucleation temperature of 700 °C and nucleation time of 2 h, crystallization temperature of 910 °C and crystallization time of 3 h.
文摘Al_(2)O_(3)–SiO_(2)sols were synthesized by using aluminum chloride hex hydrate and tetraethoxysilane(TEOS)as precursors,deionized water and ethanol mixture as the solvent,and propylene oxide as the coagulant aids.Alumina coatings were prepared on the surfaces of hollow quartz filament fiber,then a new lightweight and thermal insulating material were successfully prepared by impregnatingAl_(2)O_(3)–SiO_(2)sol into a needle fabric made by coated hollow quartz filament fiber.The coated quartz fiber,aerogels and composites were characterized by Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),energy dispersive spectroscopy(EDS),nitrogen adsorption-desorption(BET),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and tensile tests.The effects of different fiber and calcination temperatures on the microstructures and properties ofAl_(2)O_(3)–SiO_(2)composite aerogels were investigated.The test results indicate that the mechanical properties of the aerogels are improved by introducing quartz filament fabrics and the introduction of alumina coating improves the thermal stability of the material.Compared to other fibers,Al_(2)O_(3)-coated hollow quartz fiber has significant advantages as reinforcement for composite,and their tensile strength is well retained after high temperature heat treatment.
