Ultrafine WC-Co-VC cemented carbides are used extensively in a variety of industrial environments due to their excellent mechanical properties and outstanding wear resistance.Co content affects the service performance...Ultrafine WC-Co-VC cemented carbides are used extensively in a variety of industrial environments due to their excellent mechanical properties and outstanding wear resistance.Co content affects the service performance of the cemented carbides.In the present study,the influ-ences of Co content on microstructure,physical,and mechanical properties were investigated systematically.Ultrafine WC-Co-VC cemented carbides with Co content varying from 4 wt%and 7 wt%and assistance of VC(0.35 wt%)as inhibitor of WC grain growth were prepared.The physical and mechanical properties were tested and the microstructure characteristics were observed by optical microscope(OM)and scanning electron microscopy(SEM).From the results,it is found that with Co content increasing,both the cobalt magnetism and bending strength increase,while the coercive force,Rockwell hardness,density,and abrasive wear resistance decrease.In addition,the OM and SEM results show that the increase of Co content in WC-Co-VC cemented carbides tends to reduce the quantity and size of micro-pores,and make the fracture mode change from brittle fracture to ductile fracture.展开更多
Systematical researches were accomplished on WC-Co with different Co contents(6%,10%and 12%,mass fraction).Based on the XPS and EDX,from orthogonal pretreatment experiments,it is indicated that the acid concentration,...Systematical researches were accomplished on WC-Co with different Co contents(6%,10%and 12%,mass fraction).Based on the XPS and EDX,from orthogonal pretreatment experiments,it is indicated that the acid concentration,the time of the acid pretreatment and the original Co content have significant influences on the Co-removal depth(D).Moreover,the specimen temperature,original Co content and Co-removal depth dependences of the Co evolution in nucleation,heating(in pure H2 atmosphere)and growth experiments were discussed,and mechanisms of Co evolutions were summarized,providing sufficient theoretical bases for the deposition of high-quality diamond films on WC-Co substrates,especially Co-rich WC-Co substrates.It is proven that the Co-rich substrate often presents rapid Co diffusion.The high substrate temperature can promote the Co diffusion in the pretreated substrate,while acts as a Co-etching process for the untreated substrates.It is finally found that the appropriate Co-removal depth for the WC-12%Co substrate is 8-9μm.展开更多
The thermal expansion behavior of sintered Nd–Fe–B magnets is a crucial parameter for production and application.However, this aspect has not been thoroughly investigated. In this study, three different sintered Nd...The thermal expansion behavior of sintered Nd–Fe–B magnets is a crucial parameter for production and application.However, this aspect has not been thoroughly investigated. In this study, three different sintered Nd–Fe–B magnets with varying Co content(Co = 0, 6, 12 wt%) were prepared using the conventional powder metallurgy method, and four magnets oriented under different magnetic fields were prepared to compare. The thermal expansion behavior for the magnets was investigated using a linear thermal dilatometry in the temperature range of 20℃–500℃. It was found that, the coefficient of thermal expansion(CTE) increases with the increase of Co contents, while the anisotropy of thermal expansion decreases.The introduction of Co leads to continuous changes from negative to positive thermal expansion in the vertically oriented direction, which is important for the development of zero thermal expansion magnets. The thermal expansion of nonoriented magnets was found to be isotropic. Additionally, the anisotropy of thermal expansion increases with the increase of orientation degree. These results have important implications for the development of sintered Nd–Fe–B with controllable CTE.展开更多
The Co content dependence of crystal structure and specific magnetization of Fe1-xCox-SiO2granular solid prepared by the sol-gel method have been studied. It is found that the crystal structure, Iattice parameter and ...The Co content dependence of crystal structure and specific magnetization of Fe1-xCox-SiO2granular solid prepared by the sol-gel method have been studied. It is found that the crystal structure, Iattice parameter and specific magnetization of the FeCo alloy particles depend on the Co content.展开更多
In order to improve the cyclic stability of La-Mg-Ni system （Ce2Ni7-type） alloy electrode, small amount of Co was added in La0.75Mg0.25Ni3.5 alloy. The effect of Co on electrochemical performance and microstructure ...In order to improve the cyclic stability of La-Mg-Ni system （Ce2Ni7-type） alloy electrode, small amount of Co was added in La0.75Mg0.25Ni3.5 alloy. The effect of Co on electrochemical performance and microstructure of the alloys were investigated in detail. XRD results showed that the alloys had multiphase structure composed of （La, Mg）2Ni7, LaNi5 and small amount of LaNi2 phases. The discharge capacity of the alloys first increased and then decreased with increasing Co content. At a discharge current density of 900 mA/g, the HRD of the alloy electrodes increased from 81.3% （x=0） to 89.2 % （x=0.2）, and then reduced to 87.8 % （x=0.6）. After 60 charge/discharge cycles, the capacity retention rate of the alloys enhanced from 52.67% to 61.32%, and the capacity decay rate of the alloys decreased from 2.60 to 2.05 mAh/g per cycle with increasing Co content. The obtained results by XPS and XRD showed that the fundamental reasons for the capacity decay of the La-Mg-Ni system （Ce2Ni7-type） alloy electrodes were corrosion and oxidation as well as passivation of Mg and Lain alkaline solution.展开更多
In this paper, Ni/Zr–Yb–O catalysts with different sodium contents are prepared by a co-precipitation method, using aqueous Na2CO3 solution as a precipitant, and the effect of sodium on the catalyst structure and ca...In this paper, Ni/Zr–Yb–O catalysts with different sodium contents are prepared by a co-precipitation method, using aqueous Na2CO3 solution as a precipitant, and the effect of sodium on the catalyst structure and catalytic performance for syngas methanation is extensively investigated using five Ni/Zr–Yb–O catalysts, containing 0, 0.5, 1.5,4.5 and 13.5 wt% Na^+, those are denoted as Cat-1, Cat-2, Cat-3, Cat-4 and Cat-5 respectively. It is found that the interaction between Ni and support determines the catalytic performance of Ni/Zr–Yb–O and the residual sodium content negatively affects the interaction between Ni and support. Cat-1 exhibits an excellent catalytic performance.During a long run time of 380 h, no deactivation is observed and both CO conversion and CH4 selectivity maintain a level above 90%. However, Cat-3 and Cat-5 suffer rapid deactivation under the same reaction condition. The characterization results indicate the strong interaction between Ni and support enables Cat-1 to possess well dispersed Ni species, resistance to sintering and carbon deposition and thus the excellent catalytic performance. However, the presence of sodium ions over Ni/Zr–Yb–O degrades the interaction between Ni and support and the catalytic performance, especially for the stability. The relative weak interaction between Ni and support results in severe sintering of both ZrO2 and Ni under the reaction condition, carbon deposition and the poor catalytic performance.展开更多
The effects of single surfactant hexadecylpyridinium bromide（HPB） and cetyltrimethylammonium bromide（CTAB） and the combination of HPB and CTAB on the Cr nanoparticle content in the Ni-Cr film prepared by codeposit...The effects of single surfactant hexadecylpyridinium bromide（HPB） and cetyltrimethylammonium bromide（CTAB） and the combination of HPB and CTAB on the Cr nanoparticle content in the Ni-Cr film prepared by codeposition were investigated. Single HPB/CTAB addition inhibited the oxidation and amorphous transformation of the Cr nanoparticles in the plating bath and effectively stabilized the Cr nanoparticles content at approximately 10 mass% as a function of time. Moreover, the combination of HPB and CTAB formed a cylindrical micelle structure on the Cr nanoparticle surface, which prompted the formation of a layer of NiCr2O4. As a result, the Cr nanoparticle content increased sharply to 20 mass%.展开更多
The content of noble metal loading and the reduction process of the catalysts are important factors influence the economic indicator and catalytic performance for industrial catalysis. In the present work, Pd/CeO2NT (...The content of noble metal loading and the reduction process of the catalysts are important factors influence the economic indicator and catalytic performance for industrial catalysis. In the present work, Pd/CeO2NT (Pd supported on the CeO2 nanotubes) catalysts are prepared with the hydrothermal synthesized CeO2NT and glutathione (GSH) reduced Pd nanoparticles via impregnation. The content of Pd loading as well as the catalysts reduction temperature are optimized to the CO oxidation reduction. Our results show that the best Pd loading is 1.5%Pd/CeO2NT. The catalysts reduced at 350 ℃ for 2 h prior to catalytic reaction perform the best toward CO oxidation, which reaches completely CO conversion at 70 ℃. The XRD, Raman, H2-TPR, TEM, BET and XPS characterization reveal that the excellent catalytic performance of 350 °C 1.5%Pd/CeO2NT sample can be attributed the high Pd^0 species and oxygen vacancy in the sample, which are important factors influence the activity of the catalysts.展开更多
Sweetpotato （Ipomoea batatas （L.） Lam.） breeding is challenging due to its genetic complexity. In the present study, interval mapping （IM） and multiple quantitative trait locus （QTL） model （MQM） analysis wer...Sweetpotato （Ipomoea batatas （L.） Lam.） breeding is challenging due to its genetic complexity. In the present study, interval mapping （IM） and multiple quantitative trait locus （QTL） model （MQM） analysis were used to identify QTLs for starch content with a mapping population consisting of 202 F1 individuals of a cross between Xushu 18, a cultivar susceptible to stem nematodes, with high yield and moderate starch, and Xu 781, which is resistant to stem nematodes, has low yield and high starch content. Six QTLs for starch content were mapped on six linkage groups of the Xu 781 map, explaining 9.1-38.8% of the variation. Especially, one of them, DMFN 4, accounted for 38.8% of starch content variation, which is the QTL that explains the highest phenotypic variation detected to date in sweetpotato. All of the six QTLs had a positive effect on the variation of the starch content, which indicated the inheritance derived from the parent Xu 781. Two QTLs for starch content were detected on two linkage groups of the Xushu 18 map, explaining 14.3 and 16.1% of the variation, respectively. They had a negative effect on the variation, indicating the inheritance derived from Xu 781. Seven of eight QTLs were co-localized with a single marker. This is the first report on the development of QTLs co-localized with a single marker in sweetpotato. These QTLs and their co-localized markers may be used in marker-assisted breeding for the starch content of sweetpotato.展开更多
The high-N-content, the cup-stacking and the macroscopic nitrogen doped carbon nanotubes（NCNT）were synthesized via an easily manufactured catalytic chemical vapor deposition（CCVD） method. Nitrogen physisorption, t...The high-N-content, the cup-stacking and the macroscopic nitrogen doped carbon nanotubes（NCNT）were synthesized via an easily manufactured catalytic chemical vapor deposition（CCVD） method. Nitrogen physisorption, transmission electron microscopy（TEM）, thermogravimetric analysis（TGA）, X-ray diffraction（XRD） and X-ray photoelectron spectroscopy（XPS） were used to characterize the as-obtained NCNTs. High reaction temperatures were found to be the key point to the formation of inner-cup-stacking NCNTs. However, the synthesis of the outer-cup-stacking NCNT needs special demands not only to the reaction temperature but also to the catalyst and the carrier gas. The possibility of CO oxidation by NCNT was proved to be very small, and the outer-cup-stacking NCNT showed obvious advantage in the oxidative dehydrogenation（ODH） of butene to butadiene compared to a bamboo-like NCNT with an even higher N content.展开更多
Content analysis of scientific papers emanating from Antarctic science research during the 25 years period （1980-- 2004） has been carried out using neural network based algorithm-CATPAC. A total of 10 942 research a...Content analysis of scientific papers emanating from Antarctic science research during the 25 years period （1980-- 2004） has been carried out using neural network based algorithm-CATPAC. A total of 10 942 research articles published in Science Citation Indexed （SCI） journals were used for the study. Normalized co-word matrix from 35 most-used significant words was used to study the semantic association between the words. Structural Equivalence blocks were constructed from these 35 most-used words. Four-block model solution was found to be optimum. The density table was dichotomized using the mean density of the table to derive the binary matrix, which was used to construct the network map. Network maps represent the thematic character of the blocks. The blocks showed preferred connection in establishing semantic relationship with the blocks, characterizing thematic composition of Antarctic science research. The analysis has provided an analytical framework for carrying out studies on the con- tent of scientific articles. The paper has shown the utility of co-word analysis in highlighting the important areas of research in Antarctic science.展开更多
基金financially supported by the National Natural Science Foundation of China (No.51074189)
文摘Ultrafine WC-Co-VC cemented carbides are used extensively in a variety of industrial environments due to their excellent mechanical properties and outstanding wear resistance.Co content affects the service performance of the cemented carbides.In the present study,the influ-ences of Co content on microstructure,physical,and mechanical properties were investigated systematically.Ultrafine WC-Co-VC cemented carbides with Co content varying from 4 wt%and 7 wt%and assistance of VC(0.35 wt%)as inhibitor of WC grain growth were prepared.The physical and mechanical properties were tested and the microstructure characteristics were observed by optical microscope(OM)and scanning electron microscopy(SEM).From the results,it is found that with Co content increasing,both the cobalt magnetism and bending strength increase,while the coercive force,Rockwell hardness,density,and abrasive wear resistance decrease.In addition,the OM and SEM results show that the increase of Co content in WC-Co-VC cemented carbides tends to reduce the quantity and size of micro-pores,and make the fracture mode change from brittle fracture to ductile fracture.
基金Projects(51275302,51005154)supported by the National Natural Science Foundation of ChinaProject(2015M580327)supported by the China Postdoctoral Science FoundationProject(2016T90370)supported by the China Postdoctoral Science Foundation Special Funded Project
文摘Systematical researches were accomplished on WC-Co with different Co contents(6%,10%and 12%,mass fraction).Based on the XPS and EDX,from orthogonal pretreatment experiments,it is indicated that the acid concentration,the time of the acid pretreatment and the original Co content have significant influences on the Co-removal depth(D).Moreover,the specimen temperature,original Co content and Co-removal depth dependences of the Co evolution in nucleation,heating(in pure H2 atmosphere)and growth experiments were discussed,and mechanisms of Co evolutions were summarized,providing sufficient theoretical bases for the deposition of high-quality diamond films on WC-Co substrates,especially Co-rich WC-Co substrates.It is proven that the Co-rich substrate often presents rapid Co diffusion.The high substrate temperature can promote the Co diffusion in the pretreated substrate,while acts as a Co-etching process for the untreated substrates.It is finally found that the appropriate Co-removal depth for the WC-12%Co substrate is 8-9μm.
基金the National Key Research and Development Program of China (Grant No. 2021YFB3502900)the National Natural Science Foundation of China (Grant No. 51871063)+1 种基金the Key Technology Research and Development Program of Shandong Province, China (Grant No. 2019JZZY020210)the Major Projects in Inner Mongolia Autonomous Region, China。
文摘The thermal expansion behavior of sintered Nd–Fe–B magnets is a crucial parameter for production and application.However, this aspect has not been thoroughly investigated. In this study, three different sintered Nd–Fe–B magnets with varying Co content(Co = 0, 6, 12 wt%) were prepared using the conventional powder metallurgy method, and four magnets oriented under different magnetic fields were prepared to compare. The thermal expansion behavior for the magnets was investigated using a linear thermal dilatometry in the temperature range of 20℃–500℃. It was found that, the coefficient of thermal expansion(CTE) increases with the increase of Co contents, while the anisotropy of thermal expansion decreases.The introduction of Co leads to continuous changes from negative to positive thermal expansion in the vertically oriented direction, which is important for the development of zero thermal expansion magnets. The thermal expansion of nonoriented magnets was found to be isotropic. Additionally, the anisotropy of thermal expansion increases with the increase of orientation degree. These results have important implications for the development of sintered Nd–Fe–B with controllable CTE.
文摘The Co content dependence of crystal structure and specific magnetization of Fe1-xCox-SiO2granular solid prepared by the sol-gel method have been studied. It is found that the crystal structure, Iattice parameter and specific magnetization of the FeCo alloy particles depend on the Co content.
基金the National Natural Science Foundation of China (50701011)Natural Science Foundation of Inner Mongolia, China (200711020703)Science and Technology Planned Project of Inner Mongolia, China (20050205)
文摘In order to improve the cyclic stability of La-Mg-Ni system （Ce2Ni7-type） alloy electrode, small amount of Co was added in La0.75Mg0.25Ni3.5 alloy. The effect of Co on electrochemical performance and microstructure of the alloys were investigated in detail. XRD results showed that the alloys had multiphase structure composed of （La, Mg）2Ni7, LaNi5 and small amount of LaNi2 phases. The discharge capacity of the alloys first increased and then decreased with increasing Co content. At a discharge current density of 900 mA/g, the HRD of the alloy electrodes increased from 81.3% （x=0） to 89.2 % （x=0.2）, and then reduced to 87.8 % （x=0.6）. After 60 charge/discharge cycles, the capacity retention rate of the alloys enhanced from 52.67% to 61.32%, and the capacity decay rate of the alloys decreased from 2.60 to 2.05 mAh/g per cycle with increasing Co content. The obtained results by XPS and XRD showed that the fundamental reasons for the capacity decay of the La-Mg-Ni system （Ce2Ni7-type） alloy electrodes were corrosion and oxidation as well as passivation of Mg and Lain alkaline solution.
基金Supported by the National Natural Science Foundation of China(21673187,21336009,21576228)National Key Technology Support Program of China(2014BAC10B01).
文摘In this paper, Ni/Zr–Yb–O catalysts with different sodium contents are prepared by a co-precipitation method, using aqueous Na2CO3 solution as a precipitant, and the effect of sodium on the catalyst structure and catalytic performance for syngas methanation is extensively investigated using five Ni/Zr–Yb–O catalysts, containing 0, 0.5, 1.5,4.5 and 13.5 wt% Na^+, those are denoted as Cat-1, Cat-2, Cat-3, Cat-4 and Cat-5 respectively. It is found that the interaction between Ni and support determines the catalytic performance of Ni/Zr–Yb–O and the residual sodium content negatively affects the interaction between Ni and support. Cat-1 exhibits an excellent catalytic performance.During a long run time of 380 h, no deactivation is observed and both CO conversion and CH4 selectivity maintain a level above 90%. However, Cat-3 and Cat-5 suffer rapid deactivation under the same reaction condition. The characterization results indicate the strong interaction between Ni and support enables Cat-1 to possess well dispersed Ni species, resistance to sintering and carbon deposition and thus the excellent catalytic performance. However, the presence of sodium ions over Ni/Zr–Yb–O degrades the interaction between Ni and support and the catalytic performance, especially for the stability. The relative weak interaction between Ni and support results in severe sintering of both ZrO2 and Ni under the reaction condition, carbon deposition and the poor catalytic performance.
文摘The effects of single surfactant hexadecylpyridinium bromide（HPB） and cetyltrimethylammonium bromide（CTAB） and the combination of HPB and CTAB on the Cr nanoparticle content in the Ni-Cr film prepared by codeposition were investigated. Single HPB/CTAB addition inhibited the oxidation and amorphous transformation of the Cr nanoparticles in the plating bath and effectively stabilized the Cr nanoparticles content at approximately 10 mass% as a function of time. Moreover, the combination of HPB and CTAB formed a cylindrical micelle structure on the Cr nanoparticle surface, which prompted the formation of a layer of NiCr2O4. As a result, the Cr nanoparticle content increased sharply to 20 mass%.
基金the National Natural Science Foundation of China(Nos. 21868016, 21366020 and 21875096) Natural Science Foundation of Jiangxi Province (Nos. 20181BAB203016,20122BAB203009)the Key Laboratory of Jiangxi Province for Environment and Energy Catalysis of Jiangxi Province (No. 20181BCD40004)
文摘The content of noble metal loading and the reduction process of the catalysts are important factors influence the economic indicator and catalytic performance for industrial catalysis. In the present work, Pd/CeO2NT (Pd supported on the CeO2 nanotubes) catalysts are prepared with the hydrothermal synthesized CeO2NT and glutathione (GSH) reduced Pd nanoparticles via impregnation. The content of Pd loading as well as the catalysts reduction temperature are optimized to the CO oxidation reduction. Our results show that the best Pd loading is 1.5%Pd/CeO2NT. The catalysts reduced at 350 ℃ for 2 h prior to catalytic reaction perform the best toward CO oxidation, which reaches completely CO conversion at 70 ℃. The XRD, Raman, H2-TPR, TEM, BET and XPS characterization reveal that the excellent catalytic performance of 350 °C 1.5%Pd/CeO2NT sample can be attributed the high Pd^0 species and oxygen vacancy in the sample, which are important factors influence the activity of the catalysts.
基金supported by the China Agriculture Research System(CARS-11,Sweetpotato)the National High-Tech R&D Program of China(2012AA101204)
文摘Sweetpotato （Ipomoea batatas （L.） Lam.） breeding is challenging due to its genetic complexity. In the present study, interval mapping （IM） and multiple quantitative trait locus （QTL） model （MQM） analysis were used to identify QTLs for starch content with a mapping population consisting of 202 F1 individuals of a cross between Xushu 18, a cultivar susceptible to stem nematodes, with high yield and moderate starch, and Xu 781, which is resistant to stem nematodes, has low yield and high starch content. Six QTLs for starch content were mapped on six linkage groups of the Xu 781 map, explaining 9.1-38.8% of the variation. Especially, one of them, DMFN 4, accounted for 38.8% of starch content variation, which is the QTL that explains the highest phenotypic variation detected to date in sweetpotato. All of the six QTLs had a positive effect on the variation of the starch content, which indicated the inheritance derived from the parent Xu 781. Two QTLs for starch content were detected on two linkage groups of the Xushu 18 map, explaining 14.3 and 16.1% of the variation, respectively. They had a negative effect on the variation, indicating the inheritance derived from Xu 781. Seven of eight QTLs were co-localized with a single marker. This is the first report on the development of QTLs co-localized with a single marker in sweetpotato. These QTLs and their co-localized markers may be used in marker-assisted breeding for the starch content of sweetpotato.
基金financial support from the National Natural Science Foundation of China(Nos.21133010,21473223,51221264,21261160487,21411130120,21503241,91545119 and 91545110)the“Strategic Priority Research Program”of the Chinese Academy of Sciences(Grant No.XDA09030103)the CAS/SAFEA International Partnership Program for Creative Research Teams
文摘The high-N-content, the cup-stacking and the macroscopic nitrogen doped carbon nanotubes（NCNT）were synthesized via an easily manufactured catalytic chemical vapor deposition（CCVD） method. Nitrogen physisorption, transmission electron microscopy（TEM）, thermogravimetric analysis（TGA）, X-ray diffraction（XRD） and X-ray photoelectron spectroscopy（XPS） were used to characterize the as-obtained NCNTs. High reaction temperatures were found to be the key point to the formation of inner-cup-stacking NCNTs. However, the synthesis of the outer-cup-stacking NCNT needs special demands not only to the reaction temperature but also to the catalyst and the carrier gas. The possibility of CO oxidation by NCNT was proved to be very small, and the outer-cup-stacking NCNT showed obvious advantage in the oxidative dehydrogenation（ODH） of butene to butadiene compared to a bamboo-like NCNT with an even higher N content.
文摘Content analysis of scientific papers emanating from Antarctic science research during the 25 years period （1980-- 2004） has been carried out using neural network based algorithm-CATPAC. A total of 10 942 research articles published in Science Citation Indexed （SCI） journals were used for the study. Normalized co-word matrix from 35 most-used significant words was used to study the semantic association between the words. Structural Equivalence blocks were constructed from these 35 most-used words. Four-block model solution was found to be optimum. The density table was dichotomized using the mean density of the table to derive the binary matrix, which was used to construct the network map. Network maps represent the thematic character of the blocks. The blocks showed preferred connection in establishing semantic relationship with the blocks, characterizing thematic composition of Antarctic science research. The analysis has provided an analytical framework for carrying out studies on the con- tent of scientific articles. The paper has shown the utility of co-word analysis in highlighting the important areas of research in Antarctic science.
