The poor corrosion and wear resistances of Mg alloys seriously limit their potential applications in various industries.The conventional epoxy coating easily forms many intrinsic defects during the solidification proc...The poor corrosion and wear resistances of Mg alloys seriously limit their potential applications in various industries.The conventional epoxy coating easily forms many intrinsic defects during the solidification process,which cannot provide sufficient protection.In the current study,we design a double-layer epoxy composite coating on Mg alloy with enhanced anti-corrosion/wear properties,via the spin-assisted assembly technique.The outer layer is functionalized graphene(FG)in waterborne epoxy resin(WEP)and the inner layer is Ce-based conversion(Ce)film.The FG sheets can be homogeneously dispersed within the epoxy matrix to fill the intrinsic defects and improve the barrier capability.The Ce film connects the outer layer with the substrate,showing the transition effect.The corrosion rate of Ce/WEP/FG composite coating is 2131 times lower than that of bare Mg alloy,and the wear rate is decreased by~90%.The improved corrosion resistance is attributed to the labyrinth effect(hindering the penetration of corrosive medium)and the obstruction of galvanic coupling behavior.The synergistic effect derived from the FG sheet and blocking layer exhibits great potential in realizing the improvement of multi-functional integration,which will open up a new avenue for the development of novel composite protection coatings of Mg alloys.展开更多
Poly （ glycidyl methacrylate ） / silica （PGMA/silica） composite nanoparticles , containing epoxy functional groups on the surface, were synthesized via emulsion polymerization. With batch process, high yield and b...Poly （ glycidyl methacrylate ） / silica （PGMA/silica） composite nanoparticles , containing epoxy functional groups on the surface, were synthesized via emulsion polymerization. With batch process, high yield and binding efficiency （ both around 90% ） were achieved. The amount of crosslinked GMA was approximately 8wt%- 14wt% to the polymerized monomer. It was found that both the encapsulating ratio and the number of the original silica beads per composite particles altered with the amount of silica added. The obtained particles, with their average particle size of about 60- 70 nm, had a spherical shape and a clear core- shell structure.展开更多
Density functional theory and GGA-PW91 exchange correlation function were performed to simulate the bonding behavior of hydroxyl and epoxy groups on the graphene surface. We compared the different binding energies for...Density functional theory and GGA-PW91 exchange correlation function were performed to simulate the bonding behavior of hydroxyl and epoxy groups on the graphene surface. We compared the different binding energies for two epoxy groups, as well as one hydroxyl group and one epoxy group on all possible positions within a 6-fold ring, respectively. The calculated results suggest that two oxygen-containing groups always tend to bind with the neighboring carbon atoms at the opposite sides. Moreover, two hydroxyl groups on the meta position are unstable, and one of the hydroxyl groups easily migrates to the para position. In contrast to the disperse arrangement, the aggregation of multiply hydroxyl groups largely enhances the binding energy of every hydroxyl group. It is worth noting that the binding sites and hydrogen bonds play an important role in stability. Our work further points out the number of oxygen-containing groups and the location of oxide region largely influence the electronic properties of graphene oxide.展开更多
Epoxidation of the carbon-carbon double bonds on unsaturated rubber macromolecules can produce novel modified rubber species with special properties,and construct eco-friendly crosslinking pathway via the reaction of ...Epoxidation of the carbon-carbon double bonds on unsaturated rubber macromolecules can produce novel modified rubber species with special properties,and construct eco-friendly crosslinking pathway via the reaction of epoxide groups to solve the problems brought by conventional sulfur vulcanization system.In this contribution,a novel modified product of isobutylene isoprene rubber(IIR),epoxyfunctionalized IIR(EIIR)was successfully prepared by in situ epoxidation technique for the first time,and the crosslinking of EIIR was achieved by the reaction of oxirane groups with maleic anhydride(MAH)without additional additives.The reaction conditions for preparing EIIR were optimized through systematic research on the epoxidation process.Under optimal condition,the degree of epoxidation of the rubber reached around 99%without side reactions.The obtained EIIR/carbon black composites cured by MAH had excellent mechanical properties comparable to those of IIR composites.More importantly,compared with IIR composites,the air-tightness of the EIIR composites was improved by about 50%,and the flexural fatigue life of first-level cracks and sixth-level cracks was increased by several times.The significant improvement of these properties is of great significance for the application safety and energy saving of IIR materials.展开更多
Glass fibers(GFs)/epoxy laminated composites always present weak interlaminar shear strength(ILSS)and low cross-plane thermal conductivity coefficient(λ⊥).In this work,silica-sol,synthesized from tetraethyl orthosil...Glass fibers(GFs)/epoxy laminated composites always present weak interlaminar shear strength(ILSS)and low cross-plane thermal conductivity coefficient(λ⊥).In this work,silica-sol,synthesized from tetraethyl orthosilicate(TEOS)and KH-560 via sol-gel method,was employed to functionalize the surface of GFs(Si-GFs).Together with a spherical boron nitride(BNN-30),the thermally conductive BNN-30/Si-GFs/epoxy laminated composites were then fabricated.Results demonstrate that Si-sol is beneficial to the improvement of mechanical properties for epoxy laminated composites(especially for ILSS).The BNN-30/Si-GFs/epoxy laminated composites with 15 wt%BNN-30 fillers display the optimal comprehensive properties.In-planeλ(λ//)andλ⊥reach the maximum of 2.37 and 1.07 W.m-1.K-1,146.9%and 132.6%higher than those of SiGFs/epoxy laminated composites(λ//=0.96 W.m-1.K-1 andλ⊥=0.46 W.m-1K-1),respectively,and also about 10.8 and 4.9 times those of pure epoxy resin(λ//=λ⊥,0.22 W.m-1.K-1).And the heat-resistance index(THRI),dielectric constant(ε),dielectric loss(tanδ),breakdown strength(E0),surface resistivity(ρs)as well as volume resistivity(ρv)are 197.3℃,4.95,0.0046,22.3 kV.mm-1,1.8×1014Ω,and 2.1×1014Ω.cm,respectively.展开更多
Two-dimensional Ti_(3)C_(2)T_(x) flakes have great application potential in various areas due to their optical,electronic,electrochemical and mechanical properties,but their anti-corrosion and wear-resistance performa...Two-dimensional Ti_(3)C_(2)T_(x) flakes have great application potential in various areas due to their optical,electronic,electrochemical and mechanical properties,but their anti-corrosion and wear-resistance performance were not well understood.The difficulties in achieving good dispersity and interface interaction of inorganic additives in organic coatings hinder the incorporation of Ti_(3)C_(2)T_(x) into the epoxy coating.Here,few-layered Ti_(3)C_(2)T_(x) sheets with amino-functionalization were prepared,and as reinforced-additives were added into the waterborne epoxy coating.Anti-corrosion and tribological properties of as-prepared composite coatings were investigated in detail.The results reveal that the composite coating with 0.5 wt.%amino-functionalized Ti_(3)C_(2)T_(x) sheets shows excellent corrosion protection(the lowest frequency impedance was 3.12×10^(9) cm^(2))and wear resistance(wear rate was reduced by 72.74%).The greatly improving performance of composite coatings mainly depends on:(a)good dispersity and compatibility of amino-functionalized Ti_(3)C_(2)T_(x) in organic matrix,(b)high adhesion strength between coating and metal substrate and(c)the intrinsic properties of Ti3C2Tx sheets.The work provides a good path for applications of MXene as multifunctional additives.展开更多
The surface flashover of epoxy resin(EP) composites is a pivotal problem in the field of highvoltage insulation.The regulation of the interface between the filler and matrix is an effective means to suppress flashover...The surface flashover of epoxy resin(EP) composites is a pivotal problem in the field of highvoltage insulation.The regulation of the interface between the filler and matrix is an effective means to suppress flashover.In this work,nano ZnO was fluorinated and grafted using lowtemperature plasma technology,and the fluorinated filler was doped into EP to study the DC surface flashover performance of the composite.The results show that plasma fluorination can effectively inhibit the agglomeration by grafting –CFxgroups onto the surface of nano-ZnO particles.The fluorine-containing groups at the interface provide higher charge binding traps and enhance the insulation strength at the interface.At the same time,the interface bond cooperation caused by plasma treatment also promoted the accelerating effect of nano ZnO on charge dissipation.The two effects synergistically improve the surface flashover performance of epoxy composites.When the concentration of fluorinated ZnO filler is 20%,the flashover voltage has the highest increase,which is 31.52% higher than that of pure EP.In addition,fluorinated ZnO can effectively reduce the dielectric constant and dielectric loss of epoxy composites.The interface interaction mechanism was further analyzed using molecular dynamics simulation and density functional theory simulation.展开更多
基金the National Natural Science Foundation of China(Grant number 51771178)Shaanxi Outstanding Youth Fund project(Grant number 2021JC-45)+2 种基金Key international cooperation projects in Shaanxi Province(Grant number 2020KWZ-007)the Major Program of Science and Technology in Shaanxi Province(Grant number20191102006)Open Fund of State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body(Grant number 32115019)。
文摘The poor corrosion and wear resistances of Mg alloys seriously limit their potential applications in various industries.The conventional epoxy coating easily forms many intrinsic defects during the solidification process,which cannot provide sufficient protection.In the current study,we design a double-layer epoxy composite coating on Mg alloy with enhanced anti-corrosion/wear properties,via the spin-assisted assembly technique.The outer layer is functionalized graphene(FG)in waterborne epoxy resin(WEP)and the inner layer is Ce-based conversion(Ce)film.The FG sheets can be homogeneously dispersed within the epoxy matrix to fill the intrinsic defects and improve the barrier capability.The Ce film connects the outer layer with the substrate,showing the transition effect.The corrosion rate of Ce/WEP/FG composite coating is 2131 times lower than that of bare Mg alloy,and the wear rate is decreased by~90%.The improved corrosion resistance is attributed to the labyrinth effect(hindering the penetration of corrosive medium)and the obstruction of galvanic coupling behavior.The synergistic effect derived from the FG sheet and blocking layer exhibits great potential in realizing the improvement of multi-functional integration,which will open up a new avenue for the development of novel composite protection coatings of Mg alloys.
文摘Poly （ glycidyl methacrylate ） / silica （PGMA/silica） composite nanoparticles , containing epoxy functional groups on the surface, were synthesized via emulsion polymerization. With batch process, high yield and binding efficiency （ both around 90% ） were achieved. The amount of crosslinked GMA was approximately 8wt%- 14wt% to the polymerized monomer. It was found that both the encapsulating ratio and the number of the original silica beads per composite particles altered with the amount of silica added. The obtained particles, with their average particle size of about 60- 70 nm, had a spherical shape and a clear core- shell structure.
基金supported by the Foundation of State Key Laboratory of Coal Combustion of Huazhong University of Science and Technology(FSKLCC1110)the Natural Science Foundation of Fujian Province(2012J01032,2012J01041)
文摘Density functional theory and GGA-PW91 exchange correlation function were performed to simulate the bonding behavior of hydroxyl and epoxy groups on the graphene surface. We compared the different binding energies for two epoxy groups, as well as one hydroxyl group and one epoxy group on all possible positions within a 6-fold ring, respectively. The calculated results suggest that two oxygen-containing groups always tend to bind with the neighboring carbon atoms at the opposite sides. Moreover, two hydroxyl groups on the meta position are unstable, and one of the hydroxyl groups easily migrates to the para position. In contrast to the disperse arrangement, the aggregation of multiply hydroxyl groups largely enhances the binding energy of every hydroxyl group. It is worth noting that the binding sites and hydrogen bonds play an important role in stability. Our work further points out the number of oxygen-containing groups and the location of oxide region largely influence the electronic properties of graphene oxide.
基金the National Key Research and Development Program of Chinathe National Natural Science Foundation of China(Nos.2022YFB3704800,2022YFB3704802 and 52273051)the Fundamental Research Funds for the Central Universities(No.JD2221)。
文摘Epoxidation of the carbon-carbon double bonds on unsaturated rubber macromolecules can produce novel modified rubber species with special properties,and construct eco-friendly crosslinking pathway via the reaction of epoxide groups to solve the problems brought by conventional sulfur vulcanization system.In this contribution,a novel modified product of isobutylene isoprene rubber(IIR),epoxyfunctionalized IIR(EIIR)was successfully prepared by in situ epoxidation technique for the first time,and the crosslinking of EIIR was achieved by the reaction of oxirane groups with maleic anhydride(MAH)without additional additives.The reaction conditions for preparing EIIR were optimized through systematic research on the epoxidation process.Under optimal condition,the degree of epoxidation of the rubber reached around 99%without side reactions.The obtained EIIR/carbon black composites cured by MAH had excellent mechanical properties comparable to those of IIR composites.More importantly,compared with IIR composites,the air-tightness of the EIIR composites was improved by about 50%,and the flexural fatigue life of first-level cracks and sixth-level cracks was increased by several times.The significant improvement of these properties is of great significance for the application safety and energy saving of IIR materials.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51973173 and 51773169)Natural Science Basic Research Plan for Distinguished Young Scholars in Shaanxi Province of China(No.20191C-11)+1 种基金Funuaneilal Resealuh Funds fur te Centual Univel sities(No.310201911py010)and Fund Project of Basic and Applied Basic Research in Guangdong Province of China(No.2019B1515120093).
文摘Glass fibers(GFs)/epoxy laminated composites always present weak interlaminar shear strength(ILSS)and low cross-plane thermal conductivity coefficient(λ⊥).In this work,silica-sol,synthesized from tetraethyl orthosilicate(TEOS)and KH-560 via sol-gel method,was employed to functionalize the surface of GFs(Si-GFs).Together with a spherical boron nitride(BNN-30),the thermally conductive BNN-30/Si-GFs/epoxy laminated composites were then fabricated.Results demonstrate that Si-sol is beneficial to the improvement of mechanical properties for epoxy laminated composites(especially for ILSS).The BNN-30/Si-GFs/epoxy laminated composites with 15 wt%BNN-30 fillers display the optimal comprehensive properties.In-planeλ(λ//)andλ⊥reach the maximum of 2.37 and 1.07 W.m-1.K-1,146.9%and 132.6%higher than those of SiGFs/epoxy laminated composites(λ//=0.96 W.m-1.K-1 andλ⊥=0.46 W.m-1K-1),respectively,and also about 10.8 and 4.9 times those of pure epoxy resin(λ//=λ⊥,0.22 W.m-1.K-1).And the heat-resistance index(THRI),dielectric constant(ε),dielectric loss(tanδ),breakdown strength(E0),surface resistivity(ρs)as well as volume resistivity(ρv)are 197.3℃,4.95,0.0046,22.3 kV.mm-1,1.8×1014Ω,and 2.1×1014Ω.cm,respectively.
基金the National Natural Science Foundation of China(Nos.51705435 and 51575459)the Key Project of Sichuan Department of Science and Technology(Nos.2018JZ0048 and 2019YFG0292)。
文摘Two-dimensional Ti_(3)C_(2)T_(x) flakes have great application potential in various areas due to their optical,electronic,electrochemical and mechanical properties,but their anti-corrosion and wear-resistance performance were not well understood.The difficulties in achieving good dispersity and interface interaction of inorganic additives in organic coatings hinder the incorporation of Ti_(3)C_(2)T_(x) into the epoxy coating.Here,few-layered Ti_(3)C_(2)T_(x) sheets with amino-functionalization were prepared,and as reinforced-additives were added into the waterborne epoxy coating.Anti-corrosion and tribological properties of as-prepared composite coatings were investigated in detail.The results reveal that the composite coating with 0.5 wt.%amino-functionalized Ti_(3)C_(2)T_(x) sheets shows excellent corrosion protection(the lowest frequency impedance was 3.12×10^(9) cm^(2))and wear resistance(wear rate was reduced by 72.74%).The greatly improving performance of composite coatings mainly depends on:(a)good dispersity and compatibility of amino-functionalized Ti_(3)C_(2)T_(x) in organic matrix,(b)high adhesion strength between coating and metal substrate and(c)the intrinsic properties of Ti3C2Tx sheets.The work provides a good path for applications of MXene as multifunctional additives.
基金supported by Beijing Natural Science Foundation (No. 3222057)National Natural Science Foundation of China (Nos. 52277147 and 52007065)。
文摘The surface flashover of epoxy resin(EP) composites is a pivotal problem in the field of highvoltage insulation.The regulation of the interface between the filler and matrix is an effective means to suppress flashover.In this work,nano ZnO was fluorinated and grafted using lowtemperature plasma technology,and the fluorinated filler was doped into EP to study the DC surface flashover performance of the composite.The results show that plasma fluorination can effectively inhibit the agglomeration by grafting –CFxgroups onto the surface of nano-ZnO particles.The fluorine-containing groups at the interface provide higher charge binding traps and enhance the insulation strength at the interface.At the same time,the interface bond cooperation caused by plasma treatment also promoted the accelerating effect of nano ZnO on charge dissipation.The two effects synergistically improve the surface flashover performance of epoxy composites.When the concentration of fluorinated ZnO filler is 20%,the flashover voltage has the highest increase,which is 31.52% higher than that of pure EP.In addition,fluorinated ZnO can effectively reduce the dielectric constant and dielectric loss of epoxy composites.The interface interaction mechanism was further analyzed using molecular dynamics simulation and density functional theory simulation.
