The Experts below are selected from a list of 531 Experts worldwide ranked by ideXlab platform
Yong Yang - One of the best experts on this subject based on the ideXlab platform.
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tuning carburization behaviors of metallic iron catalysts with potassium promoter and co syngas c2h4 c2h2 gases
Journal of Catalysis, 2019Co-Authors: Liwei Niu, Xingwu Liu, Jinjia Liu, Xi Liu, Xiaodong Wen, Yong YangAbstract:Abstract Iron carbide phase formation during carburization of α-Fe catalysts were studied using in situ XRD, where the effect of varying carbon chemical potentials of CO/syngas/C 2 H 4 /C 2 H 2 gases and potassium promoter on the carburization behaviors was studied. The actual carburization capability of these gases follows an order of 2% CO/He 2 H 4 /He 2 /He 2 H 2 /He, which does not correlate well with the theoretical carbon chemical potential. In addition, the carburization rate and the formation of carbon-rich iron carbides are favored by potassium under CO or syngas, while inhibited by potassium under C 2 H 4 or C 2 H 2 . Temperature programmed carburization together with pulse experiments and DFT calculations indicate that the potassium promoter could weaken the adsorption ability of the C 2 H 4 and C 2 H 2 and thus reduce their carburization capabilities.
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tuning carburization behaviors of metallic iron catalysts with potassium promoter and co syngas c2h4 c2h2 gases
Journal of Catalysis, 2019Co-Authors: Liwei Niu, Xingwu Liu, Jinjia Liu, Xi Liu, Xiaodong Wen, Yong YangAbstract:Abstract Iron carbide phase formation during carburization of α-Fe catalysts were studied using in situ XRD, where the effect of varying carbon chemical potentials of CO/syngas/C2H4/C2H2 gases and potassium promoter on the carburization behaviors was studied. The actual carburization capability of these gases follows an order of 2% CO/He 2H4/He
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effect of carburization protocols on molybdenum carbide synthesis and study on its performance in co hydrogenation
Catalysis Today, 2016Co-Authors: Yong YangAbstract:Abstract Molybdenum carbides were prepared under different carburization conditions. The role of carburization protocol was studied while their CO hydrogenating performances were evaluated in a fixed-bed reactor at 280 °C, 3.1 MPa, and H2/CO = 2.0. The structure of the carbides mainly depended on the type and concentration of carbon source while the crystallite size depended on carbon source and temperature. The surface area, morphology and surface carbon deposition phenomenon of the carbides were sensitive to heating rate and holding time other than the above factors. Though the bulk structure was the same at a carburization temperature range from 630 to 760 °C, the carburization degree of the carbides was changing continuously. This diversity led the bond strength of molecular adsorbed CO weaken at a higher carburization temperature while the adsorptive strength of H2 was hardly changed. Both the adsorptive quantities of CO and H2 followed the same trend, with the highest amount on the carbide prepared at 630 °C. The activities of the catalysts correlated well with their adsorptive quantities of CO and H2, and the product selectivity was related to their hydrogenation capacity.
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effect of manganese on an iron based fischer tropsch synthesis catalyst prepared from ferrous sulfate
Fuel, 2007Co-Authors: Yong Yang, Chenghua Zhang, Haijun Wan, Zhichao Tao, Hongwei XiangAbstract:The effects of manganese on the textural properties, bulk and surface phase compositions, reduction/carburization behaviors and surface basicity of an Fe–Mn–K/SiO2 catalyst prepared from ferrous sulfate were investigated by N2 physisorption, Mossbauer spectroscopy, X-ray photoelectron spectroscopy (XPS), H2 (or CO) temperature-programmed reduction (TPR) and CO2 temperature-programmed desorption (TPD). The Fischer–Tropsch synthesis (FTS) performance of the catalysts with different contents of manganese was studied in a slurry-phase continuously stirred tank reactor. The characterization results suggested that the added manganese suppressed the crystal growth of hematite and the catalyst reduction from FeO to Fe in H2. An appropriate amount of manganese improved the FTS activity, increased the surface basicity and enhanced the carburization of the catalyst. However, the excessive addition of manganese retarded the catalyst carburization in CO and syngas due to the high enrichment of manganese on the catalyst surface. At the same time, the addition of manganese suppressed the formation of CH4 and shifted the selectivity to heavy hydrocarbons (C12+).
Yawei Peng - One of the best experts on this subject based on the ideXlab platform.
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effect of low temperature surface carburization on stress corrosion cracking of aisi 304 austenitic stainless steel
Surface & Coatings Technology, 2017Co-Authors: Yawei Peng, Chaoming Chen, Jianming Gong, Yong Jiang, Zhe LiuAbstract:Abstract The effect of low-temperature surface carburization on the stress corrosion cracking (SCC) behavior of AISI 304 austenitic stainless steel in boiling magnesium chloride (MgCl2) solution at 155 ± 1 °C was investigated. The SCC tests were carried out for untreated and carburized AISI 304 with varying four-point bend loading. In order to elucidate the influence of low-temperature surface carburization on SCC resistance, optical microscope (OM), scanning electron microscope (SEM), X-ray diffractometry (XRD) and residual stress analyzer were used. The results show that the tensile stress on the surface of untreated four-point bend loaded AISI 304 and the occurrence of pits during SCC tests had bad influence on the SCC resistance. The surface of carburized four-point bend loaded AISI 304 was in a state of compressive stress over the whole loading range due to the presence of carburization-induced huge compressive residual stress. The chloride-induced SCC resistance of AISI 304 can be obviously improved by low-temperature surface carburization due the carburization-induced compressive residual stress and the improved pitting corrosion resistance. The carburization-induced compressive residual stress was the dominant reason for the improvement of SCC resistance. No relaxation happened in carburization-induced compressive residual stress and the phase of the expanded austenite was stable during SCC tests.
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the effect of plastic pre strain on low temperature surface carburization of aisi 304 austenitic stainless steel
Surface & Coatings Technology, 2016Co-Authors: Yawei Peng, Jianming Gong, Yong Jiang, Dongsong RongAbstract:Abstract In this paper, the influence of plastic pre-strain on low-temperature surface carburization of AISI 304 austenitic stainless steel was investigated. The materials were strained to different degrees of engineering strain including 5%, 10%, 15%, 20% and 25%. Low-temperature surface carburization of the pre-strained specimens was performed at 470 °C for 30 h. In order to elucidate the effect of plastic pre-strain on low-temperature surface carburization, optical microscopy (OM), X-ray diffractometer (XRD), scanning electron probe micro-analyzer (EPMA), microhardness tester and residual stress analyzer were used. Meanwhile, dislocation density and the martensite volume fraction of the pre-strained specimens were quantitatively measured by means of XRD analysis. Based on the experimental results, the role of dislocations and martensite on carbon diffusion and related phase transformation during low-temperature surface carburization was discussed. The results show that the thicknesses of the carburized layers are independent of the pre-strain degree. Dislocations and strain-induced martensite almost have no effect on the growth of the carburized layers at the given carburizing temperature. Increasing dislocation density does not promote the development of carbides formation, while strain-induced martensite does. Due to the supersaturated carbon atoms introduced into the materials during carburization, strain-induced martensite transforms into austenite. As a result of carburization, an outstanding strengthening layer of the material develops, and plastic pre-strain has no effect on strengthening of carburization.
Xi Liu - One of the best experts on this subject based on the ideXlab platform.
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reduction and carburization of iron oxides for fischer tropsch synthesis
Journal of Energy Chemistry, 2020Co-Authors: Monia Runge Nielsen, Xi Liu, Asger Barkholt Moss, Anton Simon Bjornlund, Axel Knopgericke, Alexander Yu Klyushin, Jandierk Grunwaldt, Thomas L SheppardAbstract:Abstract The activation of iron oxide Fischer–Tropsch Synthesis (FTS) catalysts was investigated during pretreatment: reduction in hydrogen followed by carburization in either CO or syngas mixture, or simultaneously reduction and carburization in syngas. A combination of different complementary in situ techniques was used to gain insight into the behavior of Fe-based FTS catalysts during activation. In situ XRD was used to identify the crystalline structures present during both reduction in hydrogen and carburization. An increase in reduction rate was established when increasing the temperature. A complete reduction was demonstrated in the ETEM and a grain size dependency was proven, i.e. bigger grains need higher temperature in order to reduce. XPS and XAS both indicate the formation of a small amount of carbonaceous species at the surface of the bulk metallic iron during carburization.
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tuning carburization behaviors of metallic iron catalysts with potassium promoter and co syngas c2h4 c2h2 gases
Journal of Catalysis, 2019Co-Authors: Liwei Niu, Xingwu Liu, Jinjia Liu, Xi Liu, Xiaodong Wen, Yong YangAbstract:Abstract Iron carbide phase formation during carburization of α-Fe catalysts were studied using in situ XRD, where the effect of varying carbon chemical potentials of CO/syngas/C 2 H 4 /C 2 H 2 gases and potassium promoter on the carburization behaviors was studied. The actual carburization capability of these gases follows an order of 2% CO/He 2 H 4 /He 2 /He 2 H 2 /He, which does not correlate well with the theoretical carbon chemical potential. In addition, the carburization rate and the formation of carbon-rich iron carbides are favored by potassium under CO or syngas, while inhibited by potassium under C 2 H 4 or C 2 H 2 . Temperature programmed carburization together with pulse experiments and DFT calculations indicate that the potassium promoter could weaken the adsorption ability of the C 2 H 4 and C 2 H 2 and thus reduce their carburization capabilities.
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tuning carburization behaviors of metallic iron catalysts with potassium promoter and co syngas c2h4 c2h2 gases
Journal of Catalysis, 2019Co-Authors: Liwei Niu, Xingwu Liu, Jinjia Liu, Xi Liu, Xiaodong Wen, Yong YangAbstract:Abstract Iron carbide phase formation during carburization of α-Fe catalysts were studied using in situ XRD, where the effect of varying carbon chemical potentials of CO/syngas/C2H4/C2H2 gases and potassium promoter on the carburization behaviors was studied. The actual carburization capability of these gases follows an order of 2% CO/He 2H4/He
Liwei Niu - One of the best experts on this subject based on the ideXlab platform.
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tuning carburization behaviors of metallic iron catalysts with potassium promoter and co syngas c2h4 c2h2 gases
Journal of Catalysis, 2019Co-Authors: Liwei Niu, Xingwu Liu, Jinjia Liu, Xi Liu, Xiaodong Wen, Yong YangAbstract:Abstract Iron carbide phase formation during carburization of α-Fe catalysts were studied using in situ XRD, where the effect of varying carbon chemical potentials of CO/syngas/C 2 H 4 /C 2 H 2 gases and potassium promoter on the carburization behaviors was studied. The actual carburization capability of these gases follows an order of 2% CO/He 2 H 4 /He 2 /He 2 H 2 /He, which does not correlate well with the theoretical carbon chemical potential. In addition, the carburization rate and the formation of carbon-rich iron carbides are favored by potassium under CO or syngas, while inhibited by potassium under C 2 H 4 or C 2 H 2 . Temperature programmed carburization together with pulse experiments and DFT calculations indicate that the potassium promoter could weaken the adsorption ability of the C 2 H 4 and C 2 H 2 and thus reduce their carburization capabilities.
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tuning carburization behaviors of metallic iron catalysts with potassium promoter and co syngas c2h4 c2h2 gases
Journal of Catalysis, 2019Co-Authors: Liwei Niu, Xingwu Liu, Jinjia Liu, Xi Liu, Xiaodong Wen, Yong YangAbstract:Abstract Iron carbide phase formation during carburization of α-Fe catalysts were studied using in situ XRD, where the effect of varying carbon chemical potentials of CO/syngas/C2H4/C2H2 gases and potassium promoter on the carburization behaviors was studied. The actual carburization capability of these gases follows an order of 2% CO/He 2H4/He
Jianming Gong - One of the best experts on this subject based on the ideXlab platform.
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effect of low temperature surface carburization on stress corrosion cracking of aisi 304 austenitic stainless steel
Surface & Coatings Technology, 2017Co-Authors: Yawei Peng, Chaoming Chen, Jianming Gong, Yong Jiang, Zhe LiuAbstract:Abstract The effect of low-temperature surface carburization on the stress corrosion cracking (SCC) behavior of AISI 304 austenitic stainless steel in boiling magnesium chloride (MgCl2) solution at 155 ± 1 °C was investigated. The SCC tests were carried out for untreated and carburized AISI 304 with varying four-point bend loading. In order to elucidate the influence of low-temperature surface carburization on SCC resistance, optical microscope (OM), scanning electron microscope (SEM), X-ray diffractometry (XRD) and residual stress analyzer were used. The results show that the tensile stress on the surface of untreated four-point bend loaded AISI 304 and the occurrence of pits during SCC tests had bad influence on the SCC resistance. The surface of carburized four-point bend loaded AISI 304 was in a state of compressive stress over the whole loading range due to the presence of carburization-induced huge compressive residual stress. The chloride-induced SCC resistance of AISI 304 can be obviously improved by low-temperature surface carburization due the carburization-induced compressive residual stress and the improved pitting corrosion resistance. The carburization-induced compressive residual stress was the dominant reason for the improvement of SCC resistance. No relaxation happened in carburization-induced compressive residual stress and the phase of the expanded austenite was stable during SCC tests.
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the effect of plastic pre strain on low temperature surface carburization of aisi 304 austenitic stainless steel
Surface & Coatings Technology, 2016Co-Authors: Yawei Peng, Jianming Gong, Yong Jiang, Dongsong RongAbstract:Abstract In this paper, the influence of plastic pre-strain on low-temperature surface carburization of AISI 304 austenitic stainless steel was investigated. The materials were strained to different degrees of engineering strain including 5%, 10%, 15%, 20% and 25%. Low-temperature surface carburization of the pre-strained specimens was performed at 470 °C for 30 h. In order to elucidate the effect of plastic pre-strain on low-temperature surface carburization, optical microscopy (OM), X-ray diffractometer (XRD), scanning electron probe micro-analyzer (EPMA), microhardness tester and residual stress analyzer were used. Meanwhile, dislocation density and the martensite volume fraction of the pre-strained specimens were quantitatively measured by means of XRD analysis. Based on the experimental results, the role of dislocations and martensite on carbon diffusion and related phase transformation during low-temperature surface carburization was discussed. The results show that the thicknesses of the carburized layers are independent of the pre-strain degree. Dislocations and strain-induced martensite almost have no effect on the growth of the carburized layers at the given carburizing temperature. Increasing dislocation density does not promote the development of carbides formation, while strain-induced martensite does. Due to the supersaturated carbon atoms introduced into the materials during carburization, strain-induced martensite transforms into austenite. As a result of carburization, an outstanding strengthening layer of the material develops, and plastic pre-strain has no effect on strengthening of carburization.