WC-6MoxC-0.47Cr3C2-0.28VC binderless carbide was prepared by hot pressing （1700 °C, 20 MPa）. The sample was observed and analyzed by scanning electron microscopy, energy dispersive X–ray spectroscopy and X–ra...WC-6MoxC-0.47Cr3C2-0.28VC binderless carbide was prepared by hot pressing （1700 °C, 20 MPa）. The sample was observed and analyzed by scanning electron microscopy, energy dispersive X–ray spectroscopy and X–ray diffraction. The results show that during the hot pressing process, W atoms dissolve substantially into the MoxC crystal lattices; whilst, the reverse dissolution of Mo atoms into the WC crystal lattices takes place. Consequently, the main phase and binder phase structure are formed. The phase compositions of the main phase and binder phase are a WC-based solid solution containing Mo and a Mo2C-based solid solution containing W, respectively. The isotropic dissolution and precipitation of W and Mo atoms do not result in substantial carbide coarsening. The mechanism for the densification was discussed.展开更多
WC-Co alloys have enjoyed great practical significance owing to their excellent properties during the past decades.Despite the advantages,however,recently there have been concerns about the challenges associated with ...WC-Co alloys have enjoyed great practical significance owing to their excellent properties during the past decades.Despite the advantages,however,recently there have been concerns about the challenges associated with the use of Co,i.e.price instability,toxicity and properties degeneration,which necessitates the fabrication of binderless tungsten carbide(BTC).On the other hand,BTC or BTC composites,none of them,to date has been commercialized and produced on an industrial scale,but only used to a limited extent for specialized applications,such as mechanical seals undergoing high burthen as well as high temperature electrical contacts.There are two challenges in developing BTC:fully densifying the sintered body together with achieving a high toughness.Thus,this review applies towards comprehensively summarize the current knowledge of sintering behavior,microstructure,and mechanical properties of BTC,highlighting the densification improving strategies as well as toughening methods,so as to provide reference for those who would like to enhance the performance of BTC with better reliability advancing them to further wide applications and prepare the material in a way that is environment friendly,harmless to human health and low in production cost.This paper shows that the fabrication of highly dense and high-performance BTC is economically and technically feasible.The properties of BTC can be tailored by judiciously selecting the chemical composition coupled with taking into careful account the effects of processing techniques and parameters.展开更多
Shaped binderless ZSM-11 zeolite catalysts were synthesized via a dry-gel conversion technique from 70ZSM-11/30 SiO;mix extrudates. 1,6-hexanediamine combined with tetrabutylammonium bromide was proved to be the best ...Shaped binderless ZSM-11 zeolite catalysts were synthesized via a dry-gel conversion technique from 70ZSM-11/30 SiO;mix extrudates. 1,6-hexanediamine combined with tetrabutylammonium bromide was proved to be the best structure directing agent for the synthesis of the binderless ZSM-11 catalyst, without adding other alkaline materials. The 70HZSM-11/30 SiO;mix serials materials crystallized for different times were detected by X-ray diffraction（XRD）, nuclear magnetic resonance（NMR）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, scanning transmission electron microscopy–energy dispersive spectroscopy（STEM–EDS） techniques, and so on. In order to investigate the possible crystallization mechanism, the textural and structural properties of 70HZSM-11/30 SiO;mix serials samples were further characterized by N;adsorption–desorption. Acid properties were determined by temperature-programed desorption of NH;（NH;-TPD） and pyridine adsorption-infrared（Py-IR） measurements. In the alkylation of benzene with dimethyl ether, the serials catalysts exhibited different benzene conversions. 70HZSM-11/30 SiO;mix showed the lowest benzene conversion while sample 70HZSM-11/30 SiO;mix-6.5h synthesized only for 6.5h displayed a higher benzene conversion, even higher than the value over 70HZSM-11/30Al;O;mix. Extending the crystallization time, the obtained samples displayed the increased benzene conversion in general under the same reaction conditions. In the end, the relation of physicochemical properties with the reaction performance was investigated.展开更多
A shaped binderless and two binder‐containing ZSM‐11 zeolite catalysts were prepared and characterized by powder X‐ray diffraction, N2 adsorption‐desorption, and pyridine adsorption‐infrared measurements. The bin...A shaped binderless and two binder‐containing ZSM‐11 zeolite catalysts were prepared and characterized by powder X‐ray diffraction, N2 adsorption‐desorption, and pyridine adsorption‐infrared measurements. The binderless catalyst was synthesized using a dry‐gel conversion technique, inwhich 1,6‐hexanediamine and tetrabutylammonium bromide were used as structure‐directingagents and no other alkaline materials were added. The catalytic performance of the zeolites in the direct amination of isobutene to tert‐butylamine was evaluated in a fixed‐bed reactor. By virtue of its high crystallinity as well as its good mechanical strength, the shaped binderless ZSM‐11 catalyst showed a higher rate of formation of tert‐butylamine than did the binder‐containing catalysts.展开更多
Owing to the absence of metal binder, binderless cemented carbides have higher wear, corrosion, and oxidation resistance. WC-0.3VC- 0.5Cr3C2 powders with an average particle size of 200 nm and a little amount of activ...Owing to the absence of metal binder, binderless cemented carbides have higher wear, corrosion, and oxidation resistance. WC-0.3VC- 0.5Cr3C2 powders with an average particle size of 200 nm and a little amount of active element were consolidated by spark plasma sintering. The sintered microstructure revealed that the average WC grain size was 0.24μm, which was almost consistent with the initial free powder. The results of XRD showed that W2C phase was formed. Nearly complete densification of ultrafine binderless cemented carbide was achieved by sintering at 1400℃ for 120 s under 50 MPa. The resulting hardness and the fracture toughness were 28.18 GPa and 6.05 MPa·m1/2, respectively.展开更多
Binderless zeolite is considered to be a potential alternative for binder-containing zeolite in the industrial applications of adsorptive separation process. Synthesized binderless zeolite and commercial binder-contai...Binderless zeolite is considered to be a potential alternative for binder-containing zeolite in the industrial applications of adsorptive separation process. Synthesized binderless zeolite and commercial binder-containing product were used in adsorptive separation of n-paraffins from a model oil, with their performance compared. It is indicated that the binderless zeolite exhibits by 25%-35% higher in saturated adsorption capacity and by 115%-130% more adsorption amount at the breakthrough point with much shorter length of mass-transfer zone. Adsorptive separation of n-paraffins from naphtha was carried out in a fixed-bed adsorber containing the synthesized binderless zeolite 5 A under the operating conditions covering a feed space velocity of 90 h-1 and an adsorption temperature of 573 K. As compared to original naphtha, the raffinate shows by 34 units more in research octane number and by around 10% more of potential aromatic content, while the desorption oil exhibits by 13.3% more ethylene yield and by 11.7% higher in total olefins yield.展开更多
Experiment of adding B 4C, SiC, and Si powders to improve oxidation resistance of the C/C composites was carried out. The results show that the increase of oxidation resistance is remarkable when the contents of B 4C,...Experiment of adding B 4C, SiC, and Si powders to improve oxidation resistance of the C/C composites was carried out. The results show that the increase of oxidation resistance is remarkable when the contents of B 4C, SiC, and Si powders are 10%, 10%, and 5% in the composites, respectively. The regularities and mechanism of the effects of the ceramic powders on the oxidation resistance of the composites were also discussed.展开更多
Despite its considerable potential,oil palm trunk(OPT)remains underutilized,largely owing to the cyclical replanting process that occurs every 25–30 years.This study aimed to address this issue by developing an ecofr...Despite its considerable potential,oil palm trunk(OPT)remains underutilized,largely owing to the cyclical replanting process that occurs every 25–30 years.This study aimed to address this issue by developing an ecofriendly oriented strand board(OSB)using vascular bundles(VBs)from oil palm,both in binderless form and with the incorporation of natural adhesives made from sucrose and ammonium dihydrogen phosphate(ADP).The VB was extracted from OPT using a pressure cooker and mixed with a sucrose-ADP solution at various ratios.The mixture was then pressed at temperatures of 180°C and 200°C for 10 min to form boards,which were evaluated based on the Japanese Industrial Standard(JIS)A 5908 for particleboards.Binderless OSB was also manufactured without the use of any adhesive components.Fourier-transform infrared(FTIR)spectroscopy was conducted to evaluate the VB and its board.The results indicated that the mechanical properties of the binderless OSB met the JIS A 5908 Type 8 requirements.Furthermore,the addition of sucrose-ADP improved the physical and mechanical properties of the board,with an optimal sucrose-to-ADP ratio of 85:15.The OSB with the best properties met the JIS A 5908 Type 13 requirements.The FTIR results indicated that carbonyl groups,furan rings,and lignin played important roles in the bonding properties of the OSB.In conclusion,this research demonstrated the potential of VBs as a raw material for producing environmentally friendly OSB,both in binderless form and with the use of sucrose-ADP.展开更多
The latest research progress of binderless board was summarized in the view of the existing binderless technology at home and abroad,and according to the bonding mechanism of binderless board,the problems an d questio...The latest research progress of binderless board was summarized in the view of the existing binderless technology at home and abroad,and according to the bonding mechanism of binderless board,the problems an d questions in its manufacture and application at present were summed up,at last,the effect of bindless board forming process on the development of artificial board industry in China was prospected.展开更多
基金Project (51074189) supported by the National Natural Science Foundation of ChinaProject (20100162110001) supported by Research Fund for the Doctoral Program of Higher Education of ChinaProject (2011BAE09B02) supported by the National Key Technology R&D Program of China
文摘WC-6MoxC-0.47Cr3C2-0.28VC binderless carbide was prepared by hot pressing （1700 °C, 20 MPa）. The sample was observed and analyzed by scanning electron microscopy, energy dispersive X–ray spectroscopy and X–ray diffraction. The results show that during the hot pressing process, W atoms dissolve substantially into the MoxC crystal lattices; whilst, the reverse dissolution of Mo atoms into the WC crystal lattices takes place. Consequently, the main phase and binder phase structure are formed. The phase compositions of the main phase and binder phase are a WC-based solid solution containing Mo and a Mo2C-based solid solution containing W, respectively. The isotropic dissolution and precipitation of W and Mo atoms do not result in substantial carbide coarsening. The mechanism for the densification was discussed.
基金the China Postdoctoral Science Foundation (No. 2019M663685)
文摘WC-Co alloys have enjoyed great practical significance owing to their excellent properties during the past decades.Despite the advantages,however,recently there have been concerns about the challenges associated with the use of Co,i.e.price instability,toxicity and properties degeneration,which necessitates the fabrication of binderless tungsten carbide(BTC).On the other hand,BTC or BTC composites,none of them,to date has been commercialized and produced on an industrial scale,but only used to a limited extent for specialized applications,such as mechanical seals undergoing high burthen as well as high temperature electrical contacts.There are two challenges in developing BTC:fully densifying the sintered body together with achieving a high toughness.Thus,this review applies towards comprehensively summarize the current knowledge of sintering behavior,microstructure,and mechanical properties of BTC,highlighting the densification improving strategies as well as toughening methods,so as to provide reference for those who would like to enhance the performance of BTC with better reliability advancing them to further wide applications and prepare the material in a way that is environment friendly,harmless to human health and low in production cost.This paper shows that the fabrication of highly dense and high-performance BTC is economically and technically feasible.The properties of BTC can be tailored by judiciously selecting the chemical composition coupled with taking into careful account the effects of processing techniques and parameters.
基金supported by K.C.Wong Education FoundationDalian Eminent Young Scientist Program(2015R009)Natural Science Foundation of Heilongjiang Province(No.B2015006)
文摘Shaped binderless ZSM-11 zeolite catalysts were synthesized via a dry-gel conversion technique from 70ZSM-11/30 SiO;mix extrudates. 1,6-hexanediamine combined with tetrabutylammonium bromide was proved to be the best structure directing agent for the synthesis of the binderless ZSM-11 catalyst, without adding other alkaline materials. The 70HZSM-11/30 SiO;mix serials materials crystallized for different times were detected by X-ray diffraction（XRD）, nuclear magnetic resonance（NMR）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, scanning transmission electron microscopy–energy dispersive spectroscopy（STEM–EDS） techniques, and so on. In order to investigate the possible crystallization mechanism, the textural and structural properties of 70HZSM-11/30 SiO;mix serials samples were further characterized by N;adsorption–desorption. Acid properties were determined by temperature-programed desorption of NH;（NH;-TPD） and pyridine adsorption-infrared（Py-IR） measurements. In the alkylation of benzene with dimethyl ether, the serials catalysts exhibited different benzene conversions. 70HZSM-11/30 SiO;mix showed the lowest benzene conversion while sample 70HZSM-11/30 SiO;mix-6.5h synthesized only for 6.5h displayed a higher benzene conversion, even higher than the value over 70HZSM-11/30Al;O;mix. Extending the crystallization time, the obtained samples displayed the increased benzene conversion in general under the same reaction conditions. In the end, the relation of physicochemical properties with the reaction performance was investigated.
基金supported by K.C.Wong Education Foundation, Hong Kong (201611)Youth Innovation Promotion Association, CAS (20120155)~~
文摘A shaped binderless and two binder‐containing ZSM‐11 zeolite catalysts were prepared and characterized by powder X‐ray diffraction, N2 adsorption‐desorption, and pyridine adsorption‐infrared measurements. The binderless catalyst was synthesized using a dry‐gel conversion technique, inwhich 1,6‐hexanediamine and tetrabutylammonium bromide were used as structure‐directingagents and no other alkaline materials were added. The catalytic performance of the zeolites in the direct amination of isobutene to tert‐butylamine was evaluated in a fixed‐bed reactor. By virtue of its high crystallinity as well as its good mechanical strength, the shaped binderless ZSM‐11 catalyst showed a higher rate of formation of tert‐butylamine than did the binder‐containing catalysts.
文摘Owing to the absence of metal binder, binderless cemented carbides have higher wear, corrosion, and oxidation resistance. WC-0.3VC- 0.5Cr3C2 powders with an average particle size of 200 nm and a little amount of active element were consolidated by spark plasma sintering. The sintered microstructure revealed that the average WC grain size was 0.24μm, which was almost consistent with the initial free powder. The results of XRD showed that W2C phase was formed. Nearly complete densification of ultrafine binderless cemented carbide was achieved by sintering at 1400℃ for 120 s under 50 MPa. The resulting hardness and the fracture toughness were 28.18 GPa and 6.05 MPa·m1/2, respectively.
基金financially supported by the Natural Science Foundation of Shanghai(Grant 16ZR1408100)the National Natural Science Foundation of China(Grant 91634112 and 21878097)the Open Project of State Key Laboratory of Chemical Engineering(SKL-ChE-16C01)
文摘Binderless zeolite is considered to be a potential alternative for binder-containing zeolite in the industrial applications of adsorptive separation process. Synthesized binderless zeolite and commercial binder-containing product were used in adsorptive separation of n-paraffins from a model oil, with their performance compared. It is indicated that the binderless zeolite exhibits by 25%-35% higher in saturated adsorption capacity and by 115%-130% more adsorption amount at the breakthrough point with much shorter length of mass-transfer zone. Adsorptive separation of n-paraffins from naphtha was carried out in a fixed-bed adsorber containing the synthesized binderless zeolite 5 A under the operating conditions covering a feed space velocity of 90 h-1 and an adsorption temperature of 573 K. As compared to original naphtha, the raffinate shows by 34 units more in research octane number and by around 10% more of potential aromatic content, while the desorption oil exhibits by 13.3% more ethylene yield and by 11.7% higher in total olefins yield.
文摘Experiment of adding B 4C, SiC, and Si powders to improve oxidation resistance of the C/C composites was carried out. The results show that the increase of oxidation resistance is remarkable when the contents of B 4C, SiC, and Si powders are 10%, 10%, and 5% in the composites, respectively. The regularities and mechanism of the effects of the ceramic powders on the oxidation resistance of the composites were also discussed.
基金The authors are grateful to the Directorate General of Higher Education,Research,and Technology of Ministry of Education,Culture,Research,and Technology of the Republic of Indonesia and Universitas Gadjah Mada(Indonesian Collaborative Research Project-World Class University Program:No.1566/UN1/DITLIT/Dit-Lit/PT.01.03/2022).
文摘Despite its considerable potential,oil palm trunk(OPT)remains underutilized,largely owing to the cyclical replanting process that occurs every 25–30 years.This study aimed to address this issue by developing an ecofriendly oriented strand board(OSB)using vascular bundles(VBs)from oil palm,both in binderless form and with the incorporation of natural adhesives made from sucrose and ammonium dihydrogen phosphate(ADP).The VB was extracted from OPT using a pressure cooker and mixed with a sucrose-ADP solution at various ratios.The mixture was then pressed at temperatures of 180°C and 200°C for 10 min to form boards,which were evaluated based on the Japanese Industrial Standard(JIS)A 5908 for particleboards.Binderless OSB was also manufactured without the use of any adhesive components.Fourier-transform infrared(FTIR)spectroscopy was conducted to evaluate the VB and its board.The results indicated that the mechanical properties of the binderless OSB met the JIS A 5908 Type 8 requirements.Furthermore,the addition of sucrose-ADP improved the physical and mechanical properties of the board,with an optimal sucrose-to-ADP ratio of 85:15.The OSB with the best properties met the JIS A 5908 Type 13 requirements.The FTIR results indicated that carbonyl groups,furan rings,and lignin played important roles in the bonding properties of the OSB.In conclusion,this research demonstrated the potential of VBs as a raw material for producing environmentally friendly OSB,both in binderless form and with the use of sucrose-ADP.
文摘The latest research progress of binderless board was summarized in the view of the existing binderless technology at home and abroad,and according to the bonding mechanism of binderless board,the problems an d questions in its manufacture and application at present were summed up,at last,the effect of bindless board forming process on the development of artificial board industry in China was prospected.
