Pyrolysis has the potential of transforming waste into recyclable products. Pyrolytic carbon black (PCB) is one of the most important products from the pyrolysis of used tires. Techniques for surface modifications of ...Pyrolysis has the potential of transforming waste into recyclable products. Pyrolytic carbon black (PCB) is one of the most important products from the pyrolysis of used tires. Techniques for surface modifications of PCB have been developed. One of the most significant applications for modified PCB is to reinforce the rubber matrix to obtain high added values. The transverse relaxation and the chain dynamics of vulcanized rubber networks with PCB and modified PCB were studied and compared with those of the commercial carbon blacks using selective 1H transverse relaxation (T2) experiments and dipolar correlation effect (DCE) experiments on the stimulated echo. Demineralization and coupling agent modification not only intensified the interactions between the modified PCB and the neighboring polyisoprene chains, but also increased the chemical cross-link density of the vulcanized rubber with modified PCB. The mechanical testing of the rubbers with different kinds of carbon blacks showed that the maximum strain of the rubber with modified PCB was improved greatly. The mechanical testing results confirmed the conclusion obtained by nuclear magnetic resonance (NMR). PCB modified by the demineralization and NDZ-105 titanate coupling agent could be used to replace the commercial semi-reinforcing carbon black.展开更多
The relationship among heating rate, mechanical properties, microstructure and texture of Al-Mg-Si-Cu alloy during solution treatment was investigated through tensile test, scanning electron microscope, X-ray diffract...The relationship among heating rate, mechanical properties, microstructure and texture of Al-Mg-Si-Cu alloy during solution treatment was investigated through tensile test, scanning electron microscope, X-ray diffractometer and EBSD technology. The experimental results reveal that there is a non-monotonic relationship among solution heating rate, mechanical properties, microstructure and texture. As the solution heating rate increases, the strength variations are dependent on the tensile direction;work hardening exponent n decreases first, and then increases;plastic strain ratio r increases first, and then decreases, and finally increases. The final microstructure and texture are also affected by heating rate. As heating rate increases, the microstructure transforms from elongated grain structure to equiaxed grain structure, and the average grain size decreases first, and then increases, and decreases finally. Although the texture components including CubeND{001}<310> and P{011}<122> orientations almost have no change with the increase of heating rate, the texture intensity and volume fraction decrease first, and then increase, and finally decrease. Both microstructure and texture evolutions are weakly affected by heating rate. Improving heating rate is not always favorable for the development of fine equiaxed grain structure, weak texture and high average r value, which may be related to the recrystallization behavior.展开更多
This article mainly discussed bulk material lHvl^ared by powder metallurgy, and the commercial 2024 aluminum alloy powder and FeNiCrCoA13 high entropy alloy powder （both produced by argon gas atomization process） we...This article mainly discussed bulk material lHvl^ared by powder metallurgy, and the commercial 2024 aluminum alloy powder and FeNiCrCoA13 high entropy alloy powder （both produced by argon gas atomization process） were ball-milled for different hours. The prepared powder was consolidated by hot extrusion method. The microstruetures of the milled powder and bulk alloy were examined by X - Ray Diffraction （XRD）, Scanning Electron Microscopy （SEM） and Transmission Electron Microscopy （TEM）. The thermal stability was tested by differential scanning calorimetry （DSC）. Mechanical properties of the extruded alloy were examined by Vickers hardness tester and mechanical testing machine. The results show that after milling, the mixed particle sizes and microstructures of the alloy powder change obviously. The compressive strength of the extruded alloy has reached 580 MPa under certain conditions of milling time and composition.展开更多
AIM:To compare the effectiveness of argon plasma coagulation (APC) and heater probe coagulation (HPC) in non-variceal upper gastrointestinal bleeding.METHODS:Eighty-five (18 female,67 male) patients admitted for acute...AIM:To compare the effectiveness of argon plasma coagulation (APC) and heater probe coagulation (HPC) in non-variceal upper gastrointestinal bleeding.METHODS:Eighty-five (18 female,67 male) patients admitted for acute gastrointestinal bleeding due to gastric or duodenal ulcer were included in the study.Upper endoscopy was performed and HPC or APC were chosen randomly to stop the bleeding.Initial hemostasis and rebleeding rates were primary and secondary end-points of the study.RESULTS:Initial hemostasis was achieved in 97.7% (42/43) and 81% (36/42) of the APC and HPC groups,respectively (P < 0.05).Rebleeding rates were 2.4% (1/42) and 8.3% (3/36) in the APC and HPC groups,respectively,at 4 wk (P > 0.05).CONCLUSION:APC is an effective hemostatic method in bleeding peptic ulcers.Larger multicenter trials are necessary to confirm these results.展开更多
Poly （methyl methacrylate） is widely used as denture base material. During fabrication of a denture, the physical and mechanical properties are influenced by cure condition. Each cure cycle or fabrication technique ...Poly （methyl methacrylate） is widely used as denture base material. During fabrication of a denture, the physical and mechanical properties are influenced by cure condition. Each cure cycle or fabrication technique is attempts to optimize the properties for a given application. The aim of this study was to compare two types of commercially available denture base materials （heat-cure and self-cure） in their mechanical properties. The samples were prepared according to the daily routine work for sample preparation in dental laboratories. After reaching dough stage the mix packed into dumbbell shaped of stainless steel mould and pressed in a hydraulic bench press for 25 mins at room temperature. For heat cure the polymerization cycle was carried out using water bath, while self cure was done at room temperature. The impact strength was evaluated using Charpy impact test. The hardness test was conducted using a calibrated Vickers hardness tester machine. The lowest impact strength was observed in self-cure denture base material （self cure material 6.2 kJ/m^2 while heat cure 12.69 kJ/m^2. It appears that the tendency of heat cure to fracture was lower than self-cure denture base materials. Heat cure denture base material has significantly higher hardness test values than self-cure denture base material. The observed VHN value of the heat-cure was 20.09 g/mm^2 while the self-cure value was 12.7 g/mm^2. This is may be due to the plasticizer effect of residual monomer which was higher in self curing material as reported in previous work. Generally, the heat cure material showed better properties compared to self cure material.展开更多
Hot stamping 22MnB5 steel plate with ultra-high strength has been widely used for body structural members in consideration of automobile safety and lightweight.This paper presents a verification program of simulating ...Hot stamping 22MnB5 steel plate with ultra-high strength has been widely used for body structural members in consideration of automobile safety and lightweight.This paper presents a verification program of simulating and testing pole impact in order to verify if the front crossbeam reinforcement assembly can meet the design requirements,reduce the overall vehicle simulation and test cost and shorten the operation period.In the same condition,the simulation proved conforming to the design requirements;however,the bumper cracked at the impacting point in the course of pole impact test.The analysis of the crack by optical microscope,Vickers and scanning electron microscope indicates that mixture of ferrite,bainite and martensite was produced in the weld heat-affected zone of the 340/590DP tow hook holder and the 22MnB5 front crossbeam;therefore,their hardness and mechanical property were reduced obviously,so that they fractured when impacted.No welding process with continuous weld but spot welding or other bonding method may be employed for the reason that the capacity of the 22MnB5 steel plate in the weld heat-affected zone was reduced obviously.展开更多
Semisolid processing is now a commercially successful manufacturing route to produce net-shape parts in automotive industry. The conspicuous results of alloy optimization with thermodynamic simulations for semisolid p...Semisolid processing is now a commercially successful manufacturing route to produce net-shape parts in automotive industry. The conspicuous results of alloy optimization with thermodynamic simulations for semisolid processing of commercial AM60 alloy were present. The results indicate that the available processing temperature range of AM60 alloy is 170 ℃. The temperature sensitivity of solid fraction decreases with increasing solid fraction or with decreasing temperature above eutectic reaction temperature of AM60 alloy. When the solid fraction φs is 0.4, corresponding processing temperature is 603.8 ℃ and the sensitivity -dφs/dT is 0.0184. The effects of various alloying elements on the solidification behavior and SSM processability of AM60 alloy were calculated with Pandat software.展开更多
The use of CO_(2) as monomer to synthesize polymer materials is an important and potential applications topic from the viewpoint of green and sustainable chemistry.A new kind of CO_(2)-based polyurea(PUa)was synthesiz...The use of CO_(2) as monomer to synthesize polymer materials is an important and potential applications topic from the viewpoint of green and sustainable chemistry.A new kind of CO_(2)-based polyurea(PUa)was synthesized by polycondensation of CO_(2) with 4,7,10-trioxa-1,13-tridecanediamine and tris(2-aminoethyl)amine(TAEA).TAEA was used as cross-link reagent.The mechanical properties of PUa were significantly improved by inserted the crosslink agent of TAEA.The formed slight cross-linked PUa exhibited excellent mechanical properties with tensile strength of 26.8 MPa,elongation at break of 34%and Young’s modulus of 351 MPa.Moreover,it could be remolded for 3 times without obvious change in the mechanical properties,which are ascribed to the hydrogen bonding interaction among the main chains and the slight cross-linked structure.In addition,the synthesized CO_(2)-based PUa is of outstanding thermal performance with an initial decomposition temperature above 300℃,besides it is tolerance for a variety of organic solvents.展开更多
基金Project supported by the National Natural Science Foundation of China (Nos. 20490200 and 20176051), and the Project Based Per-sonnel Exchange Program with the China Scholarship Council and the German Academic Exchange Service
文摘Pyrolysis has the potential of transforming waste into recyclable products. Pyrolytic carbon black (PCB) is one of the most important products from the pyrolysis of used tires. Techniques for surface modifications of PCB have been developed. One of the most significant applications for modified PCB is to reinforce the rubber matrix to obtain high added values. The transverse relaxation and the chain dynamics of vulcanized rubber networks with PCB and modified PCB were studied and compared with those of the commercial carbon blacks using selective 1H transverse relaxation (T2) experiments and dipolar correlation effect (DCE) experiments on the stimulated echo. Demineralization and coupling agent modification not only intensified the interactions between the modified PCB and the neighboring polyisoprene chains, but also increased the chemical cross-link density of the vulcanized rubber with modified PCB. The mechanical testing of the rubbers with different kinds of carbon blacks showed that the maximum strain of the rubber with modified PCB was improved greatly. The mechanical testing results confirmed the conclusion obtained by nuclear magnetic resonance (NMR). PCB modified by the demineralization and NDZ-105 titanate coupling agent could be used to replace the commercial semi-reinforcing carbon black.
基金The authors are grateful for the financial supports from the Science Challenge Project(TZ2018001)the State Key Laboratory of Advanced Metals and Materials University of Science and Technology Beijing,China(2019-Z02)+3 种基金the National Natural Science Foundation of China(52075272)the Key Laboratory of Impact and Safety Engineering,Ministry of Education,Ningbo University,China(CJ201912)the Ningbo Natural Science Foundation,China(2018A610174)the K.C.Wong Magna Fund from Ningbo University,China.
文摘The relationship among heating rate, mechanical properties, microstructure and texture of Al-Mg-Si-Cu alloy during solution treatment was investigated through tensile test, scanning electron microscope, X-ray diffractometer and EBSD technology. The experimental results reveal that there is a non-monotonic relationship among solution heating rate, mechanical properties, microstructure and texture. As the solution heating rate increases, the strength variations are dependent on the tensile direction;work hardening exponent n decreases first, and then increases;plastic strain ratio r increases first, and then decreases, and finally increases. The final microstructure and texture are also affected by heating rate. As heating rate increases, the microstructure transforms from elongated grain structure to equiaxed grain structure, and the average grain size decreases first, and then increases, and decreases finally. Although the texture components including CubeND{001}<310> and P{011}<122> orientations almost have no change with the increase of heating rate, the texture intensity and volume fraction decrease first, and then increase, and finally decrease. Both microstructure and texture evolutions are weakly affected by heating rate. Improving heating rate is not always favorable for the development of fine equiaxed grain structure, weak texture and high average r value, which may be related to the recrystallization behavior.
文摘This article mainly discussed bulk material lHvl^ared by powder metallurgy, and the commercial 2024 aluminum alloy powder and FeNiCrCoA13 high entropy alloy powder （both produced by argon gas atomization process） were ball-milled for different hours. The prepared powder was consolidated by hot extrusion method. The microstruetures of the milled powder and bulk alloy were examined by X - Ray Diffraction （XRD）, Scanning Electron Microscopy （SEM） and Transmission Electron Microscopy （TEM）. The thermal stability was tested by differential scanning calorimetry （DSC）. Mechanical properties of the extruded alloy were examined by Vickers hardness tester and mechanical testing machine. The results show that after milling, the mixed particle sizes and microstructures of the alloy powder change obviously. The compressive strength of the extruded alloy has reached 580 MPa under certain conditions of milling time and composition.
文摘AIM:To compare the effectiveness of argon plasma coagulation (APC) and heater probe coagulation (HPC) in non-variceal upper gastrointestinal bleeding.METHODS:Eighty-five (18 female,67 male) patients admitted for acute gastrointestinal bleeding due to gastric or duodenal ulcer were included in the study.Upper endoscopy was performed and HPC or APC were chosen randomly to stop the bleeding.Initial hemostasis and rebleeding rates were primary and secondary end-points of the study.RESULTS:Initial hemostasis was achieved in 97.7% (42/43) and 81% (36/42) of the APC and HPC groups,respectively (P < 0.05).Rebleeding rates were 2.4% (1/42) and 8.3% (3/36) in the APC and HPC groups,respectively,at 4 wk (P > 0.05).CONCLUSION:APC is an effective hemostatic method in bleeding peptic ulcers.Larger multicenter trials are necessary to confirm these results.
文摘Poly （methyl methacrylate） is widely used as denture base material. During fabrication of a denture, the physical and mechanical properties are influenced by cure condition. Each cure cycle or fabrication technique is attempts to optimize the properties for a given application. The aim of this study was to compare two types of commercially available denture base materials （heat-cure and self-cure） in their mechanical properties. The samples were prepared according to the daily routine work for sample preparation in dental laboratories. After reaching dough stage the mix packed into dumbbell shaped of stainless steel mould and pressed in a hydraulic bench press for 25 mins at room temperature. For heat cure the polymerization cycle was carried out using water bath, while self cure was done at room temperature. The impact strength was evaluated using Charpy impact test. The hardness test was conducted using a calibrated Vickers hardness tester machine. The lowest impact strength was observed in self-cure denture base material （self cure material 6.2 kJ/m^2 while heat cure 12.69 kJ/m^2. It appears that the tendency of heat cure to fracture was lower than self-cure denture base materials. Heat cure denture base material has significantly higher hardness test values than self-cure denture base material. The observed VHN value of the heat-cure was 20.09 g/mm^2 while the self-cure value was 12.7 g/mm^2. This is may be due to the plasticizer effect of residual monomer which was higher in self curing material as reported in previous work. Generally, the heat cure material showed better properties compared to self cure material.
基金"Twelfth Five-year Plan"for Sci & Tech Research of China(No.2011BAG03B02No.2011BAG03B06)
文摘Hot stamping 22MnB5 steel plate with ultra-high strength has been widely used for body structural members in consideration of automobile safety and lightweight.This paper presents a verification program of simulating and testing pole impact in order to verify if the front crossbeam reinforcement assembly can meet the design requirements,reduce the overall vehicle simulation and test cost and shorten the operation period.In the same condition,the simulation proved conforming to the design requirements;however,the bumper cracked at the impacting point in the course of pole impact test.The analysis of the crack by optical microscope,Vickers and scanning electron microscope indicates that mixture of ferrite,bainite and martensite was produced in the weld heat-affected zone of the 340/590DP tow hook holder and the 22MnB5 front crossbeam;therefore,their hardness and mechanical property were reduced obviously,so that they fractured when impacted.No welding process with continuous weld but spot welding or other bonding method may be employed for the reason that the capacity of the 22MnB5 steel plate in the weld heat-affected zone was reduced obviously.
基金Project(50964010) supported by the National Natural Science Foundation of ChinaProject(090WCGA894) supported by the International S&T Cooperation Program of Gansu Province,China
文摘Semisolid processing is now a commercially successful manufacturing route to produce net-shape parts in automotive industry. The conspicuous results of alloy optimization with thermodynamic simulations for semisolid processing of commercial AM60 alloy were present. The results indicate that the available processing temperature range of AM60 alloy is 170 ℃. The temperature sensitivity of solid fraction decreases with increasing solid fraction or with decreasing temperature above eutectic reaction temperature of AM60 alloy. When the solid fraction φs is 0.4, corresponding processing temperature is 603.8 ℃ and the sensitivity -dφs/dT is 0.0184. The effects of various alloying elements on the solidification behavior and SSM processability of AM60 alloy were calculated with Pandat software.
文摘The use of CO_(2) as monomer to synthesize polymer materials is an important and potential applications topic from the viewpoint of green and sustainable chemistry.A new kind of CO_(2)-based polyurea(PUa)was synthesized by polycondensation of CO_(2) with 4,7,10-trioxa-1,13-tridecanediamine and tris(2-aminoethyl)amine(TAEA).TAEA was used as cross-link reagent.The mechanical properties of PUa were significantly improved by inserted the crosslink agent of TAEA.The formed slight cross-linked PUa exhibited excellent mechanical properties with tensile strength of 26.8 MPa,elongation at break of 34%and Young’s modulus of 351 MPa.Moreover,it could be remolded for 3 times without obvious change in the mechanical properties,which are ascribed to the hydrogen bonding interaction among the main chains and the slight cross-linked structure.In addition,the synthesized CO_(2)-based PUa is of outstanding thermal performance with an initial decomposition temperature above 300℃,besides it is tolerance for a variety of organic solvents.
