Facile preparation of cost-effective and durable porous carbon-supported non-precious-metal/nitrogen electrocatalysts for oxygen reduction reaction(ORR)is extremely important for promoting the commercialized applicati...Facile preparation of cost-effective and durable porous carbon-supported non-precious-metal/nitrogen electrocatalysts for oxygen reduction reaction(ORR)is extremely important for promoting the commercialized applications of such catalysts.In this work,the FeCl3-containing porphyrinato iron-based covalent porous polymer(FeCl3·FeP or-CPP)was fabricated in-situ onto porous corncob biomass supports via a simple one-pot method.Subsequent thermal-reduction pyrolysis at 700℃-900℃with CO2 gas as an activating agent resulted in Fe2O3-decorated and N-doped graphitic carbon composite Fe2O3@NC&bio-C with a high degree of graphitization of Fe-involved promotion during pyrolysis(Fe2O3=FeCl3·FePor-CPP derived Fe2O3;NC=N-doped graphene analog;bio-C=the corncob-derived hierarchically porous graphitic biomass carbon framework).The derivedα-Fe2O3 andγ-Fe2O3 nanocrystals(5-10 nm particle diameter)were all immobilized on the N-doped bio-C micro/nanofibers.Notably,the Fe2O3@NC&bio-C obtained at the pyrolysis temperature of 800℃(Fe2O3@NC&bio-C-800),exhibited unusual ORR catalytic efficiency via a 4-electron pathway with the onset and half-wave potentials of 0.96 V and 0.85 V vs.RHE,respectively.In addition,Fe2O3@NC&bio-C-800 also exhibited a high and stable limiting current density of-6.0 mA cm-2,remarkably stability(larger than 91%retention after 10000 s),and good methanol tolerance.The present work represents one of the best results for iron-based biomass material ORR catalysts reported to date.The high ORR activity is attributed to the uniformly distributedα-Fe2O3 andγ-Fe2O3 nanoparticles on the N-enriched carbon matrix with a large specific surface area of 772.6 m^2 g^-1.This facilitates favor faster electron movement and better adsorption of oxygen molecules on the surface of the catalyst.Nevertheless,comparative studies on the structure and ORR catalytic activity of Fe2O3@NC&bioC-800 with Fe2O3@bio-C-800 and NC&bio-C-800 clearly highlight the synergistic effect of the coexisting Fe2O3 nanocrystals,NC,and bio-C on the ORR performance.展开更多
The microstructure and slag erosion fractal dimension of reaction interface of β-Sialon-Al2O3 brick used in 300 Mt iron ladle of Baosteel have been studied by SEM and XRD. The results indicated that β-Sialon-Al2O3 b...The microstructure and slag erosion fractal dimension of reaction interface of β-Sialon-Al2O3 brick used in 300 Mt iron ladle of Baosteel have been studied by SEM and XRD. The results indicated that β-Sialon-Al2O3 brick exhibited excellent slag resistance. The main wear mechanism of β-Sialon-Al2O3 brick is mainly from the spalling caused by thermal mechanical stress and attacked by slag secondly.展开更多
The process of electrodepositing Fe-Cr2O3 composite coating on polyacrylonitrile （PAN）-based carbon fibers and its catalytic graphitization were studied. Carbon fibers with and without electrodeposited Fe-Cr2O3 comp...The process of electrodepositing Fe-Cr2O3 composite coating on polyacrylonitrile （PAN）-based carbon fibers and its catalytic graphitization were studied. Carbon fibers with and without electrodeposited Fe-Cr2O3 composite coating were heat treated at different temperatures and the structural changes were characterized by XRD, Raman spectroscopy and SEM. The results indicate that Fe-Cr2O3 composite coating exhibits a significant catalytic effect on graphitization of carbon fibers at low temperatures. When the Fe-Cr2O3-coated carbon fibers were heat treated at 1 300℃ the interlayer spacing （doo2） and ratio of relative peak area （AD/AG） reach 3.364/k and 0.34, respectively. Whereas, the extent of graphitization of pristine carbon fibers is comparatively low even after heat treatment at 2 800℃ and the values of doo2 and AD/AG are 3.414 A and 0.68, respectively. The extent of graphitization of carbon fibers increases not only with the increase of the catalyst gross but also the Cr2O3 content in Fe-Cr2O3 coating. The catalytic effect of Fe-Cr2O3 composite coating accords with the dissolution-precipitation mechanism.展开更多
13 kinds of iron ores （6 from Australia and 7 from Brazil） were studied on their properties concerning CW （Combined Water） decomposition, FezO3 decomposition and softening-melting in air atmosphere through the cha...13 kinds of iron ores （6 from Australia and 7 from Brazil） were studied on their properties concerning CW （Combined Water） decomposition, FezO3 decomposition and softening-melting in air atmosphere through the characterization method of TG-DSC （Thermogravimetry-Differential Scanning Caloremetry ）. The experimental results of the Australian ores and Brazilian ores differ in terms of the initial temperature, temperature range and endothermic amount of CW decomposition,and besides, the content of CW. It is estimated that for every percent increase of CW content in sintering raw material, the extra thermal amount absorbed in the process is about 1.83 x 104 kJ, which equals to the thermal capacity of 0.625 kg of standard coal burning up completely. As to the decomposition of Fe203 ,the initial temperatures, terminal temperatures and temperature ranges of the Australian and Brazilian ores are quite close. However, the endothermic amount of Fe2O3 decomposition of the two turns out rather different： the endothermic capacity of Fe2O3 decomposition of the Australian ores is greater than that of the Brazilian ores. Furthermore, the liquid amount generated in the softening-melting process is closely related to the SiO2 content in iron ore. The higher SiO2 content the ore contains, the more liquid volume it will generate in the softening-melting process of iron ore.展开更多
Carbon-containing Al2O3 refractory crucibles and pure Al2O3 refractory crucible were fabricated to study the effect of carbon-containing Al2O3-C refractories on aluminum and carbon pick-up of iron.Refractory crucibles...Carbon-containing Al2O3 refractory crucibles and pure Al2O3 refractory crucible were fabricated to study the effect of carbon-containing Al2O3-C refractories on aluminum and carbon pick-up of iron.Refractory crucibles with pure iron powder were placed in a vacuum induction furnace and heated at 1600℃ for regular time under flowing argon atmosphere.The Al and C contents of iron samples were analyzed,and iron samples were also investigated using a field scanning electron microscope equipped with energy-dispersive spectroscope.The results showed that carbon materials did affect the interac?tion of(Al2O3-C)/Fe system,carbothermal reduction in alumina occurred in the reaction system and the extent of reactions depended on the kinds of carbon materials.展开更多
Metal-free catalyst for photocatalytic production of H_(2)O_(2)is highly desirable with the long-term vision of artificial photosynthesis of solar fuel.In particular,the specific chemical bonds for selective H_(2)O_(2...Metal-free catalyst for photocatalytic production of H_(2)O_(2)is highly desirable with the long-term vision of artificial photosynthesis of solar fuel.In particular,the specific chemical bonds for selective H_(2)O_(2)photosynthesis via 2e–oxygen reduction reactions(ORR)remain to be explored for understanding the forming mechanism of active sites.Herein,we report a facile doping method to introduce boron-nitrogen(B–N)bonds into the structure of graphitic carbon nitride(g-C_(3)N_(4))nanosheets(denoted as BCNNS)to provide significant photocatalytic activity,selectivity and stability.The theoretical calculation and experimental results reveal that the electron-deficient B–N units serving as electron acceptors improve photogenerated charge separation and transfer.The units are also proved to be superior active sites for selective O_(2)adsorption and activation,reducing the energy barrier for*OOH formation,and thereby enabling an efficient 2e–ORR pathway to H_(2)O_(2).Consequently,with only bare loss of activity during repeated cycles,the optimal H2O2 production rate by BCNNS photocatalysts reaches 1.16 mmol·L^(–1)·h^(–1)under 365 nm-monochrome light emitting diode(LED365nm)irradiation,increasing nearly 2–5 times as against the state-of-art metal-free photocatalysts.This work gives the first example of applying B–N bonds to enhance the photocatalytic H_(2)O_(2)production as well as unveiling the underlying reaction pathway for efficient solar-energy transformations.展开更多
The rotary hearth furnace iron nugget process has advantages of short reaction time, high-quality reduced product and wide adaptability of raw materials and meets the trend in ecofriendly development of iron and steel...The rotary hearth furnace iron nugget process has advantages of short reaction time, high-quality reduced product and wide adaptability of raw materials and meets the trend in ecofriendly development of iron and steel industry. Although the rotary hearth furnace iron nugget process cannot replace blast furnace process, which is affected by production scale, thermal efficiency and technical maturity, it is still a feasible technology for iron production. In order to realize the efficient utilization of high Al2O3 iron ore resources, preparation of iron nuggets with high Al2O3 iron ore was studied. Using iron concentrate as raw material, the effects of slag basicity, Al2O3 and MgO on melting separation of iron ore–coal composite pellets, such as the melting separation temperature, the melting separation time, the morphology of melting separated product, and the recovery rate of iron nugget, were studied. The results showed that relatively low or high liquidus temperature of slag had a negative effect on reduction and melting separation of iron ore–coal composite pellets. The increase in fluidity index of slag resulted in a decline in the melting separation temperature and time of iron ore–coal composite pellets. Optimum basicity to produce iron nuggets using iron ore–coal composite pellets was 0.8–1.0, 0.4 and 0.8 for iron concentrate containing 2, 4 and 6–10 wt.% Al2O3, respectively. Corresponding liquidus temperature and fluidity index of slag were 1300–1475 C and above 4.5, respectively. Under this condition, the lowest melting separation temperature and the shortest melting separation time of iron ore–coal composite pellets were 1375 C and 7 min, respectively. The recovery rate of metallic iron in the form of iron nugget could reach about 94%.展开更多
基金the National Natural Science Foundation of China(Nos.21771192,21631003,21871024)the Major Program of Shandong Province Natural Science Foundation(No.ZR2017ZB0315)+2 种基金Fundamental Research Funds for the Central Universities(Nos.18CX06001A,19CX05001A)Research Foundation from China University of Petroleum(East China)(No.Y1510051)Taishan Scholar Program of Shandong Province(ts201712019,ts201511019).
文摘Facile preparation of cost-effective and durable porous carbon-supported non-precious-metal/nitrogen electrocatalysts for oxygen reduction reaction(ORR)is extremely important for promoting the commercialized applications of such catalysts.In this work,the FeCl3-containing porphyrinato iron-based covalent porous polymer(FeCl3·FeP or-CPP)was fabricated in-situ onto porous corncob biomass supports via a simple one-pot method.Subsequent thermal-reduction pyrolysis at 700℃-900℃with CO2 gas as an activating agent resulted in Fe2O3-decorated and N-doped graphitic carbon composite Fe2O3@NC&bio-C with a high degree of graphitization of Fe-involved promotion during pyrolysis(Fe2O3=FeCl3·FePor-CPP derived Fe2O3;NC=N-doped graphene analog;bio-C=the corncob-derived hierarchically porous graphitic biomass carbon framework).The derivedα-Fe2O3 andγ-Fe2O3 nanocrystals(5-10 nm particle diameter)were all immobilized on the N-doped bio-C micro/nanofibers.Notably,the Fe2O3@NC&bio-C obtained at the pyrolysis temperature of 800℃(Fe2O3@NC&bio-C-800),exhibited unusual ORR catalytic efficiency via a 4-electron pathway with the onset and half-wave potentials of 0.96 V and 0.85 V vs.RHE,respectively.In addition,Fe2O3@NC&bio-C-800 also exhibited a high and stable limiting current density of-6.0 mA cm-2,remarkably stability(larger than 91%retention after 10000 s),and good methanol tolerance.The present work represents one of the best results for iron-based biomass material ORR catalysts reported to date.The high ORR activity is attributed to the uniformly distributedα-Fe2O3 andγ-Fe2O3 nanoparticles on the N-enriched carbon matrix with a large specific surface area of 772.6 m^2 g^-1.This facilitates favor faster electron movement and better adsorption of oxygen molecules on the surface of the catalyst.Nevertheless,comparative studies on the structure and ORR catalytic activity of Fe2O3@NC&bioC-800 with Fe2O3@bio-C-800 and NC&bio-C-800 clearly highlight the synergistic effect of the coexisting Fe2O3 nanocrystals,NC,and bio-C on the ORR performance.
文摘The microstructure and slag erosion fractal dimension of reaction interface of β-Sialon-Al2O3 brick used in 300 Mt iron ladle of Baosteel have been studied by SEM and XRD. The results indicated that β-Sialon-Al2O3 brick exhibited excellent slag resistance. The main wear mechanism of β-Sialon-Al2O3 brick is mainly from the spalling caused by thermal mechanical stress and attacked by slag secondly.
基金Project(2006CB600903) supported by the National Basic Research Program of China
文摘The process of electrodepositing Fe-Cr2O3 composite coating on polyacrylonitrile （PAN）-based carbon fibers and its catalytic graphitization were studied. Carbon fibers with and without electrodeposited Fe-Cr2O3 composite coating were heat treated at different temperatures and the structural changes were characterized by XRD, Raman spectroscopy and SEM. The results indicate that Fe-Cr2O3 composite coating exhibits a significant catalytic effect on graphitization of carbon fibers at low temperatures. When the Fe-Cr2O3-coated carbon fibers were heat treated at 1 300℃ the interlayer spacing （doo2） and ratio of relative peak area （AD/AG） reach 3.364/k and 0.34, respectively. Whereas, the extent of graphitization of pristine carbon fibers is comparatively low even after heat treatment at 2 800℃ and the values of doo2 and AD/AG are 3.414 A and 0.68, respectively. The extent of graphitization of carbon fibers increases not only with the increase of the catalyst gross but also the Cr2O3 content in Fe-Cr2O3 coating. The catalytic effect of Fe-Cr2O3 composite coating accords with the dissolution-precipitation mechanism.
文摘13 kinds of iron ores （6 from Australia and 7 from Brazil） were studied on their properties concerning CW （Combined Water） decomposition, FezO3 decomposition and softening-melting in air atmosphere through the characterization method of TG-DSC （Thermogravimetry-Differential Scanning Caloremetry ）. The experimental results of the Australian ores and Brazilian ores differ in terms of the initial temperature, temperature range and endothermic amount of CW decomposition,and besides, the content of CW. It is estimated that for every percent increase of CW content in sintering raw material, the extra thermal amount absorbed in the process is about 1.83 x 104 kJ, which equals to the thermal capacity of 0.625 kg of standard coal burning up completely. As to the decomposition of Fe203 ,the initial temperatures, terminal temperatures and temperature ranges of the Australian and Brazilian ores are quite close. However, the endothermic amount of Fe2O3 decomposition of the two turns out rather different： the endothermic capacity of Fe2O3 decomposition of the Australian ores is greater than that of the Brazilian ores. Furthermore, the liquid amount generated in the softening-melting process is closely related to the SiO2 content in iron ore. The higher SiO2 content the ore contains, the more liquid volume it will generate in the softening-melting process of iron ore.
基金This project was supported by the National Natural Science Foundation of China(Grant No.51572203).
文摘Carbon-containing Al2O3 refractory crucibles and pure Al2O3 refractory crucible were fabricated to study the effect of carbon-containing Al2O3-C refractories on aluminum and carbon pick-up of iron.Refractory crucibles with pure iron powder were placed in a vacuum induction furnace and heated at 1600℃ for regular time under flowing argon atmosphere.The Al and C contents of iron samples were analyzed,and iron samples were also investigated using a field scanning electron microscope equipped with energy-dispersive spectroscope.The results showed that carbon materials did affect the interac?tion of(Al2O3-C)/Fe system,carbothermal reduction in alumina occurred in the reaction system and the extent of reactions depended on the kinds of carbon materials.
基金supported by the Jiangsu Provincial Double-Innovation Doctor Program(JSSCBS20210996).
文摘Metal-free catalyst for photocatalytic production of H_(2)O_(2)is highly desirable with the long-term vision of artificial photosynthesis of solar fuel.In particular,the specific chemical bonds for selective H_(2)O_(2)photosynthesis via 2e–oxygen reduction reactions(ORR)remain to be explored for understanding the forming mechanism of active sites.Herein,we report a facile doping method to introduce boron-nitrogen(B–N)bonds into the structure of graphitic carbon nitride(g-C_(3)N_(4))nanosheets(denoted as BCNNS)to provide significant photocatalytic activity,selectivity and stability.The theoretical calculation and experimental results reveal that the electron-deficient B–N units serving as electron acceptors improve photogenerated charge separation and transfer.The units are also proved to be superior active sites for selective O_(2)adsorption and activation,reducing the energy barrier for*OOH formation,and thereby enabling an efficient 2e–ORR pathway to H_(2)O_(2).Consequently,with only bare loss of activity during repeated cycles,the optimal H2O2 production rate by BCNNS photocatalysts reaches 1.16 mmol·L^(–1)·h^(–1)under 365 nm-monochrome light emitting diode(LED365nm)irradiation,increasing nearly 2–5 times as against the state-of-art metal-free photocatalysts.This work gives the first example of applying B–N bonds to enhance the photocatalytic H_(2)O_(2)production as well as unveiling the underlying reaction pathway for efficient solar-energy transformations.
基金The authors would like to express their gratitude for the financial support of Fundamental Research Funds for the Central Universities (FRF-TP-18-008A2)the National Natural Science Foundation of China (51804024)+1 种基金the China Postdoctoral Science Foundation (2016M600919)the State Key Laboratory of Advanced Metallurgy of University of Science and Technology Beijing (41618022).
文摘The rotary hearth furnace iron nugget process has advantages of short reaction time, high-quality reduced product and wide adaptability of raw materials and meets the trend in ecofriendly development of iron and steel industry. Although the rotary hearth furnace iron nugget process cannot replace blast furnace process, which is affected by production scale, thermal efficiency and technical maturity, it is still a feasible technology for iron production. In order to realize the efficient utilization of high Al2O3 iron ore resources, preparation of iron nuggets with high Al2O3 iron ore was studied. Using iron concentrate as raw material, the effects of slag basicity, Al2O3 and MgO on melting separation of iron ore–coal composite pellets, such as the melting separation temperature, the melting separation time, the morphology of melting separated product, and the recovery rate of iron nugget, were studied. The results showed that relatively low or high liquidus temperature of slag had a negative effect on reduction and melting separation of iron ore–coal composite pellets. The increase in fluidity index of slag resulted in a decline in the melting separation temperature and time of iron ore–coal composite pellets. Optimum basicity to produce iron nuggets using iron ore–coal composite pellets was 0.8–1.0, 0.4 and 0.8 for iron concentrate containing 2, 4 and 6–10 wt.% Al2O3, respectively. Corresponding liquidus temperature and fluidity index of slag were 1300–1475 C and above 4.5, respectively. Under this condition, the lowest melting separation temperature and the shortest melting separation time of iron ore–coal composite pellets were 1375 C and 7 min, respectively. The recovery rate of metallic iron in the form of iron nugget could reach about 94%.
