Resin matrix carbon brush composites(RMCBCs)are critical materials for high-powered electric tools.However,effectively improving their wear resistance and heat dissipation remains a challenge.RMCBCs prepared with flak...Resin matrix carbon brush composites(RMCBCs)are critical materials for high-powered electric tools.However,effectively improving their wear resistance and heat dissipation remains a challenge.RMCBCs prepared with flake graphite powders that were evenly loaded with tungsten copper composite powder(RMCBCs-W@Cu)exhibited a low wear rate of 1.63 mm^(3)/h,exhibiting 48.6%reduction in the wear rate relative to RCMBCs without additives(RMCBCs-0).In addition,RMCBCs-W@Cu achieved a low friction coefficient of 0.243 and low electric spark grade.These findings indicate that tungsten copper composite powders provide particle reinforcement and generate a gradation effect for the epoxy resin(i.e.,connecting phase)in RMCBCs,which weakens the wear of RMCBCs caused by fatigue under a cyclic current-carrying wear.展开更多
In order to reduce the amount of volumetric shrinkage that occurs in dental composites as a result of curing,a new kind of dental matrix resin combining bisphenol-S-bis（3-meth acry late-2-hydroxy propyl）ether（BisS-...In order to reduce the amount of volumetric shrinkage that occurs in dental composites as a result of curing,a new kind of dental matrix resin combining bisphenol-S-bis（3-meth acry late-2-hydroxy propyl）ether（BisS-GMA） with the expanding monomer unsaturated spiro orthoesters 2-methylene-1,4,6-trispiro[4,4] nonane （SOE） was prepared,with triethylene glycol dimethacrylate （TEGDMA） as diluent.CQ （camphorquinone） of 1wt% and DMAEMA （2-（dimethylamino） ethyl meth acrylate） of 2wt% were used as photoinitiation system to initiate the copolymerization of the matrix resins.The performance including volumetric shrinkage,degree of conversion and condition of the ring-opening reaction of SOE,as well as curing time and the tensile bond strength were investigated respectively by the dilatometer,Fourier transfer infrared,the universal testing machine,and so on.The ring-opening polymerization of SOE occurred.Meanwhile,the obtain copolymers were crosslinked.The matrix resin containing BisS-GMA and SOE showed a reduced amount of volumetric shrinkage at 1.52%,which is a promising strategy for obtaining a polymer with a low amount of volumetric shrinkage.Furthermore,the other properties were not compromised.展开更多
The purpose of this study was to use. a three-component photoinitiation system comprising 1wt% CQ （camphorquinone）, 2wt% DMAEMA （2-（dimethylamino） ethyl meth acrylate） and 2wt% ph^2I^＋PF6^- （diphenyliodonium h...The purpose of this study was to use. a three-component photoinitiation system comprising 1wt% CQ （camphorquinone）, 2wt% DMAEMA （2-（dimethylamino） ethyl meth acrylate） and 2wt% ph^2I^＋PF6^- （diphenyliodonium hexafluorophosphate） to initiate the copolymerization of the matrix resins which combine bisphenol-S-bis （3-methacrylate-2-hydroxy propyl） ether （BisS-GMA） with the expanding monomer unsaturated spiro orthoesters 2-methylene-l,4,6-tdspiro[4,4] nonane （MTOSN）, for minimizing the volumetric shrinkage that generally occurs during polymerization. It was hypothesized that MTOSN would expand volumetrically during polymerization under the three-component photoinitiator system and further reductions in volumetric shrinkage would be obtained. The performance study which consists of degree of conversion and condition of the ring-opening reactions of MTOSN, volumetric shrinkage and mechanical properties including tensile bond strength, compressive strength and Vicker＇s hardness were carried out respectively by Fourier transfer infrared, the dilatometer and the universal testing machine. The results supported that the dental composites based on the expanding monomer and three-component photoinitiator system engendered a greater decrease of volumetric shrinkage and better mechanieal properties.展开更多
The new chelate resins, abbreviated as PNBMZs and PBBMZs based on epoxide polymer, were synthesized by polycondensation of N,N-diglycidyl-4-glycidyloxyaniline or 1,4-bis（2,3-epoxypropyl）benzene with the primary amin...The new chelate resins, abbreviated as PNBMZs and PBBMZs based on epoxide polymer, were synthesized by polycondensation of N,N-diglycidyl-4-glycidyloxyaniline or 1,4-bis（2,3-epoxypropyl）benzene with the primary amine group of 1,3-bis（benzimidazol-2yl）propylamine （BBPAH）. The ion exchangers contain 2.71-3.23 mmol of the ligand contents per gram of the resin. Batch extraction capacities were determined for the metal chloride salts in buffer solutions in the pH range from -1 to 6.0. The chelate resins were very selective for Cu^2＋, Zn^2＋, Cd^2＋ in the presence of other divalent transition metal ions. The maximum uptake capacities of PNBMZ （synthetic molar ratio = 1：1.5） under non-competitive condition were found to be 0.94 mmol/g for Cu^2＋ at pH = 2, 1.3 mmol/g for Cd^2＋ at pH = 1 and 1.75 mmol/g for Zn^2＋ at pH = -1 respectively. While in the case of PBBMZ, it was 1.39 mmol/g for Cd〉 at pH = 1. The metal-uptake behaviors for both of them showed strong pH dependence, and their extraction capacities increase with decreasing pH. The uptake of Cu^2＋ by the resin PNBMZs at pH = 1 was found to be rather fast with t1/2 = 18 min. Metal-uptake experiments under competitive conditions also confirm that the chelate resins have a high selectivity for Cu^2＋, Zn^2＋, Cd^2＋ and the contrary pH dependence.展开更多
The boron content of uranium fuel samples with boron concentrations in the range of 0.05–10 μg/g was determined using inductively coupled plasma optical emission spectrometry(ICP-OES) after the uranium was separated...The boron content of uranium fuel samples with boron concentrations in the range of 0.05–10 μg/g was determined using inductively coupled plasma optical emission spectrometry(ICP-OES) after the uranium was separated by cation exchange. The samples were dissolved in 3 M HNO_3 on a hot plate at 150℃ and evaporated to near dryness. The residues were redissolved in 0.2 M HNO-_3 and passed through a column loaded with Dowex 50WX8-400 resin. Uranium was adsorbed on the resin,while boron was easily eluted with 0.2 M HNO_3. The boron content of the effluent was determined using ICPOES. Several strategies were employed to improve the reliability of the experimentally determined boron content.The addition of mannitol and proper control of the evaporation process were shown to be effective in preventing boron loss during sample dissolution and evaporation. The memory effect was eliminated by flushing the system with 1.5% ammonia for 30 s between successive sample runs,and the matrix match method was used to eliminate the matrix effect arising from mannitol during the ICP-OES analysis. The accuracy of the results of the analysis was determined by addition recovery tests and by comparison with the results of three Chinese certified reference materials(GBW04242, GBW04243, and GBW04232). Using the method we developed, the limit of detection for boron was as low as 0.05 μg/g in uranium fuel samples, and the relative standard deviations for 0.1–0.5 g uranium samples with 0.05–2 μg/g of boron were within 9%.展开更多
An experimental procedure was designed to monitor the preform thickness change real-time throughout the vacuum assisted resin infusion( VARI) process. Two kinds of liquid with different viscosity were infused with dif...An experimental procedure was designed to monitor the preform thickness change real-time throughout the vacuum assisted resin infusion( VARI) process. Two kinds of liquid with different viscosity were infused with different post-filling time. The variation of the part thickness during the VARI process was studied. And the effect of the post-filling time on the part thickness was investigated.The results indicate that the compaction behavior of the preform can be divided into three stages,and the fiber volume fraction varies with the post-filling time in a similar sinusoid form. In addition,the post-filling should be overtime for the greatest fiber volume fraction,and when the resin is infused with higher viscosity,the greatest fiber volume fraction is higher.展开更多
基金Projects(51772081,51837009,51971091)supported by the National Natural Science Foundation of ChinaProject(HFZL2018CXY003-4)supported by the Industry-University-Research Cooperation of AECC,ChinaProject(kq1902046)supported by the Major Science and Technology Projects of Changsha City,China。
文摘Resin matrix carbon brush composites(RMCBCs)are critical materials for high-powered electric tools.However,effectively improving their wear resistance and heat dissipation remains a challenge.RMCBCs prepared with flake graphite powders that were evenly loaded with tungsten copper composite powder(RMCBCs-W@Cu)exhibited a low wear rate of 1.63 mm^(3)/h,exhibiting 48.6%reduction in the wear rate relative to RCMBCs without additives(RMCBCs-0).In addition,RMCBCs-W@Cu achieved a low friction coefficient of 0.243 and low electric spark grade.These findings indicate that tungsten copper composite powders provide particle reinforcement and generate a gradation effect for the epoxy resin(i.e.,connecting phase)in RMCBCs,which weakens the wear of RMCBCs caused by fatigue under a cyclic current-carrying wear.
基金Funded by the National Natural Science Foundation of China(No.50673065)
文摘In order to reduce the amount of volumetric shrinkage that occurs in dental composites as a result of curing,a new kind of dental matrix resin combining bisphenol-S-bis（3-meth acry late-2-hydroxy propyl）ether（BisS-GMA） with the expanding monomer unsaturated spiro orthoesters 2-methylene-1,4,6-trispiro[4,4] nonane （SOE） was prepared,with triethylene glycol dimethacrylate （TEGDMA） as diluent.CQ （camphorquinone） of 1wt% and DMAEMA （2-（dimethylamino） ethyl meth acrylate） of 2wt% were used as photoinitiation system to initiate the copolymerization of the matrix resins.The performance including volumetric shrinkage,degree of conversion and condition of the ring-opening reaction of SOE,as well as curing time and the tensile bond strength were investigated respectively by the dilatometer,Fourier transfer infrared,the universal testing machine,and so on.The ring-opening polymerization of SOE occurred.Meanwhile,the obtain copolymers were crosslinked.The matrix resin containing BisS-GMA and SOE showed a reduced amount of volumetric shrinkage at 1.52%,which is a promising strategy for obtaining a polymer with a low amount of volumetric shrinkage.Furthermore,the other properties were not compromised.
基金Funded by the National Natural Science Foundation of China(No.50673065)
文摘The purpose of this study was to use. a three-component photoinitiation system comprising 1wt% CQ （camphorquinone）, 2wt% DMAEMA （2-（dimethylamino） ethyl meth acrylate） and 2wt% ph^2I^＋PF6^- （diphenyliodonium hexafluorophosphate） to initiate the copolymerization of the matrix resins which combine bisphenol-S-bis （3-methacrylate-2-hydroxy propyl） ether （BisS-GMA） with the expanding monomer unsaturated spiro orthoesters 2-methylene-l,4,6-tdspiro[4,4] nonane （MTOSN）, for minimizing the volumetric shrinkage that generally occurs during polymerization. It was hypothesized that MTOSN would expand volumetrically during polymerization under the three-component photoinitiator system and further reductions in volumetric shrinkage would be obtained. The performance study which consists of degree of conversion and condition of the ring-opening reactions of MTOSN, volumetric shrinkage and mechanical properties including tensile bond strength, compressive strength and Vicker＇s hardness were carried out respectively by Fourier transfer infrared, the dilatometer and the universal testing machine. The results supported that the dental composites based on the expanding monomer and three-component photoinitiator system engendered a greater decrease of volumetric shrinkage and better mechanieal properties.
文摘The new chelate resins, abbreviated as PNBMZs and PBBMZs based on epoxide polymer, were synthesized by polycondensation of N,N-diglycidyl-4-glycidyloxyaniline or 1,4-bis（2,3-epoxypropyl）benzene with the primary amine group of 1,3-bis（benzimidazol-2yl）propylamine （BBPAH）. The ion exchangers contain 2.71-3.23 mmol of the ligand contents per gram of the resin. Batch extraction capacities were determined for the metal chloride salts in buffer solutions in the pH range from -1 to 6.0. The chelate resins were very selective for Cu^2＋, Zn^2＋, Cd^2＋ in the presence of other divalent transition metal ions. The maximum uptake capacities of PNBMZ （synthetic molar ratio = 1：1.5） under non-competitive condition were found to be 0.94 mmol/g for Cu^2＋ at pH = 2, 1.3 mmol/g for Cd^2＋ at pH = 1 and 1.75 mmol/g for Zn^2＋ at pH = -1 respectively. While in the case of PBBMZ, it was 1.39 mmol/g for Cd〉 at pH = 1. The metal-uptake behaviors for both of them showed strong pH dependence, and their extraction capacities increase with decreasing pH. The uptake of Cu^2＋ by the resin PNBMZs at pH = 1 was found to be rather fast with t1/2 = 18 min. Metal-uptake experiments under competitive conditions also confirm that the chelate resins have a high selectivity for Cu^2＋, Zn^2＋, Cd^2＋ and the contrary pH dependence.
文摘The boron content of uranium fuel samples with boron concentrations in the range of 0.05–10 μg/g was determined using inductively coupled plasma optical emission spectrometry(ICP-OES) after the uranium was separated by cation exchange. The samples were dissolved in 3 M HNO_3 on a hot plate at 150℃ and evaporated to near dryness. The residues were redissolved in 0.2 M HNO-_3 and passed through a column loaded with Dowex 50WX8-400 resin. Uranium was adsorbed on the resin,while boron was easily eluted with 0.2 M HNO_3. The boron content of the effluent was determined using ICPOES. Several strategies were employed to improve the reliability of the experimentally determined boron content.The addition of mannitol and proper control of the evaporation process were shown to be effective in preventing boron loss during sample dissolution and evaporation. The memory effect was eliminated by flushing the system with 1.5% ammonia for 30 s between successive sample runs,and the matrix match method was used to eliminate the matrix effect arising from mannitol during the ICP-OES analysis. The accuracy of the results of the analysis was determined by addition recovery tests and by comparison with the results of three Chinese certified reference materials(GBW04242, GBW04243, and GBW04232). Using the method we developed, the limit of detection for boron was as low as 0.05 μg/g in uranium fuel samples, and the relative standard deviations for 0.1–0.5 g uranium samples with 0.05–2 μg/g of boron were within 9%.
基金The Fundamental Research Funds for the Central Universities,China(No.2232014D3-26)Innovation Fund of the Chinese National Engineering Research Center,China(No.SAM C14-JS-15-049)Science and Technology Commission of Shanghai Municipality,China(No.14DZ1100402)
文摘An experimental procedure was designed to monitor the preform thickness change real-time throughout the vacuum assisted resin infusion( VARI) process. Two kinds of liquid with different viscosity were infused with different post-filling time. The variation of the part thickness during the VARI process was studied. And the effect of the post-filling time on the part thickness was investigated.The results indicate that the compaction behavior of the preform can be divided into three stages,and the fiber volume fraction varies with the post-filling time in a similar sinusoid form. In addition,the post-filling should be overtime for the greatest fiber volume fraction,and when the resin is infused with higher viscosity,the greatest fiber volume fraction is higher.
