Highly oriented poly(vinylidene fluoride)(PVDF)ultrathin films with differentβ-phase contents were prepared using the melt-draw method.The effect ofβ-phase content onα-βphase transition of highly oriented PVDF ult...Highly oriented poly(vinylidene fluoride)(PVDF)ultrathin films with differentβ-phase contents were prepared using the melt-draw method.The effect ofβ-phase content onα-βphase transition of highly oriented PVDF ultrathin films induced by stretching was investigated using transmission electron microscopy(TEM)and Fourier transform infrared(FTIR)spectroscopy.The results show that stretching can enhance the crystallinity and increase the average thickness of the lamellae.A fullα-βphase transition can be achieved for PVDF ultrathin films of 20.6%βphase stretched to aλ(stretching ratio)of 1.5,while fewαphases still exist for ultrathin films of 35.0%βphase,together with bent and tilted lamellae.Compared to thicker PVDF films undergoing stretching-inducedα-βphase transition,the higherα-βphase transition efficiency of the PVDF ultrathin films can be attributed to the parallel aligned lamellar structure.Moreover,a higherβ-phase content can suppressα-βphase transition because of the stress concentration effect ofβ-phase.Ultimately,these results provide valuable insights into the stretching-inducedα-βphase transition of PVDF ultrathin films.展开更多
This paper details an investigation of the effects of oxide stringers on theβ-phase depletion behaviour in thermally sprayed CoNiCrAlY coatings.Vacuum Plasma Sprayed(VPS)Co NiCrAlY coatings,which are free of oxide st...This paper details an investigation of the effects of oxide stringers on theβ-phase depletion behaviour in thermally sprayed CoNiCrAlY coatings.Vacuum Plasma Sprayed(VPS)Co NiCrAlY coatings,which are free of oxide stringers,are used as the reference materials in comparison with High-Velocity Oxy-Fuel(HVOF)sprayed CoNiCrAlY coatings during isothermal oxidation at 1100℃.An outer layer of spinel oxides and an inner layer of alumina are formed in the as-sprayed coatings,while only a single alumina scale is found in the heat-treated coatings.Lessβ-phase depletion occurred in the HVOF coatings than in the VPS coatings.It was found that theβphases tend to coalesce at the oxide stringers in the HVOF coatings,which is likely due to the internal oxide particles and stringers acting as short diffusion barriers to tie up theβphase and inhibit theβ-phase depletion.展开更多
In this paper,low temperature plasma is used to modify the surface of barium titanate（BaTiO3）nanoparticles in order to enhance the interfacial compatibility between ferroelectric poly（vinylidene fluoride）（PVDF） ...In this paper,low temperature plasma is used to modify the surface of barium titanate（BaTiO3）nanoparticles in order to enhance the interfacial compatibility between ferroelectric poly（vinylidene fluoride）（PVDF） and BaTiO3 nanoparticles.The results demonstrate that oxygenic groups are successfully attached to the BaTiO3 surface,and the quantity of the functional groups increases with the treatment voltage.Furthermore,the effect of modified BaTiO3 nanoparticles on the morphology and crystal structure of the PVDF/BaTiO3 membrane is investigated.The results reveal that the dispersion of BaTiO3 nanoparticles in the PVDF matrix was greatly improved due to the modification of the BaTiO3 nanoparticles by air plasma.It is worth noting that the formation of a β-phase in a PVDF/modified BaTiO3 membrane is observably promoted,which results from the strong interaction between PVDF chains and oxygenic groups fixed on the BaTiO3 surface and the better dispersion of BaTiO3 nanoparticles in the PVDF matrix.Besides,the PVDF/modified BaTiO3 membrane at the treatment voltage of 24 k V exhibits a lower water contact angle（≈68.4°） compared with the unmodified one（≈86.7°）.Meanwhile,the dielectric constant of PVDF/BaTiO3 nanocomposites increases with the increase of working voltage.展开更多
As a representative piezoelectric polymer,poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP)has been widely used in sensors transducers and actuators.In this paper,gold nanoparticles(AuNPs)are prepared and dop...As a representative piezoelectric polymer,poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP)has been widely used in sensors transducers and actuators.In this paper,gold nanoparticles(AuNPs)are prepared and doped into the PVDF-HFP solution to enhance the piezoelectric property of electrospun PVDF-HFP nanowires.The results indicate that proper amounts of AuNPs within the nanowires can improve the piezoelectric phase in PVDF-HFP.Then,a nanogenerator was prepared using the PVDF-HFP/Au nanowires to verify the increase in piezoelectric performance.Experimental results show that compared with PVDF-HFP n anoge nerator without AuNPs doping,the output voltage is in creased by about two times,while the output current is doubled for the PVDF-HFP/Au nano generator.Furthermore,systematic molecular dyn amics(MD)simulations are conducted to elucidate the physical mechanism of AuNPs enhanced β-phase formation in PVDF-HFP.Our results show that the adsorption and electrostatic interaction between the AuNPs and the PVDF chains promote the electroactive β-phase formation,and also significa ntly in crease the ten sion and poling effect during electrospin ning process,which is the origin of the enhanced elec-troactive phase formation in electrospun PVDF-HFP nanowires.展开更多
Poly(vinylidene fluoride)(PVDF)is the most attractive piezoelectric polymer for application in flexible sensors.To attain excellent piezoelectric properties,a substantial amount of spontaneous polarβ-phase content is...Poly(vinylidene fluoride)(PVDF)is the most attractive piezoelectric polymer for application in flexible sensors.To attain excellent piezoelectric properties,a substantial amount of spontaneous polarβ-phase content is highly desired.Nevertheless,the current reported manufacturing methods to increaseβ-phase contents are inconvenient and complex,hindering progress in PVDF's application.This work proposes a folding-hot-pressing method to fabricate highβ-phase-content PVDF films.Structural characterization indicates that the films haveαandβphases and the folding-hot-pressing process transforms theαphase into theβphase.Due to the 97.5%β-phase content and aligned structure,a piezoelectric constant of 20 pC/N is achieved in the three-times folded film.Furthermore,the process method enhances the tensile strength(126.2 MPa)of the films,with a low Young's modulus(0.87 GPa)remaining,making the films applicable for flexible piezoelectric sensors.Additionally,sensors based on the achieved films were assembled and applied for human physiological activity monitoring.This work offers a scalable new melt-processing strategy for developing high-performance PVDF-based piezo-electric composite films for wearable electronic devices.展开更多
Among all the phase morphologies of poly(9,9-di-n-octylfluorenyl-2,7-diyl)(PFO),the𝛽phase exhibits a zigzag coplanar arrangement with the highest conjugation degree.As a result,the𝛽-phasePFO has extrao...Among all the phase morphologies of poly(9,9-di-n-octylfluorenyl-2,7-diyl)(PFO),the𝛽phase exhibits a zigzag coplanar arrangement with the highest conjugation degree.As a result,the𝛽-phasePFO has extraordinary prop-erties,including enhanced charge carrier mobility.In this work,we report the formation of high-𝛽-phase PFO in nanoparticles(NPs)due to the synergistic effect of the slow crystallization of PFO in nanodroplet confinement and polystyrene(PS)blending.The𝛽-phase content of PFO can be flexibly tuned by varying the NP size,molec-ular weight(M w),or relative PS content in the NPs.The novel systems demonstrated in this study are likely to provide valuable insights into the𝛽-phase formation mechanism of PFO.As a proof of concept,we further demonstrate that NPs of PFO:PS(1:8)with a higher𝛽-phase content lead to improved photocatalyst efficiency at lower material costs,allowing for novel designs of efficient and visible-light-driven photocatalytic NPs.展开更多
A stable δ- and β-bismuth trioxide was prepared at room temperature by vacuum vapor-phase oxidation. The average crystal size of products was 14.6 nm (by XRD), the d(0.5) value was in the range from 62 nm to 69 nm, ...A stable δ- and β-bismuth trioxide was prepared at room temperature by vacuum vapor-phase oxidation. The average crystal size of products was 14.6 nm (by XRD), the d(0.5) value was in the range from 62 nm to 69 nm, and geometric standard deviation(GSD) was from 1.42 to 1.64. The results show that δ-Bi2O3 is formed when quenching rates is rapid and β-Bi2O3 is formed when it is slow. The size of grains increases with rising reaction temperature, flow rate of carrier gas, residual pressure of system and longer growing time of grains.展开更多
In the current work, a custom-made vibration injection molding device that can provide oscillatory pressure was utilized to create an injection-molded hierarchical structure. Growth competition among α, β, and γ ph...In the current work, a custom-made vibration injection molding device that can provide oscillatory pressure was utilized to create an injection-molded hierarchical structure. Growth competition among α, β, and γ phases in the injection-molded structure can be studied because of the presence of this hierarchical structure, wherein shish-kebab and spherulite layers were arranged alternately along the thickness direction. The γ crystals only existed in layers subjected to high pressure and shear stress, whereas β crystals formed between the shear layers. The change in trend of the γ fraction was similar to that of parent-to-daughter ratio. In addition, this hierarchical and alternating crystal structure can sharply increase the mechanical properties.展开更多
This paper reported an effectiveness of pre-cold rolling-induced{332}／113[twins combined with subsequent isothermal x-phase formation for enhancement of uniform elongation in a b-type Ti–15Mo alloy with high yield s...This paper reported an effectiveness of pre-cold rolling-induced{332}／113[twins combined with subsequent isothermal x-phase formation for enhancement of uniform elongation in a b-type Ti–15Mo alloy with high yield strength level.Mechanical{332}／113[twins were induced by cold rolling with an thickness reduction of 5%,which had little effect on x-phase precipitation after aging at 573 K for 3.6 ks.Twinning after the cold rolling was further activated during tensile deformation,even with the presence of isothermal x-phase.This combination of twins and x-phase enhanced uniform elongation from 0 to 9%at yield strength level of 890 MPa.The high yield strength was mainly dominated by dislocation slip due to the isothermal x-phase formation,and early onset of plastic instability after yielding was hindered due to the pre-cold rolling-induced twins.Dynamic microstructural refinement was induced by further twinning activation during deformation,which resulted in high work hardening rate corresponding enhancement of uniform elongation.展开更多
基金financially supported from the National Natural Science Foundation of China(Nos.52203026 and 52027804)。
文摘Highly oriented poly(vinylidene fluoride)(PVDF)ultrathin films with differentβ-phase contents were prepared using the melt-draw method.The effect ofβ-phase content onα-βphase transition of highly oriented PVDF ultrathin films induced by stretching was investigated using transmission electron microscopy(TEM)and Fourier transform infrared(FTIR)spectroscopy.The results show that stretching can enhance the crystallinity and increase the average thickness of the lamellae.A fullα-βphase transition can be achieved for PVDF ultrathin films of 20.6%βphase stretched to aλ(stretching ratio)of 1.5,while fewαphases still exist for ultrathin films of 35.0%βphase,together with bent and tilted lamellae.Compared to thicker PVDF films undergoing stretching-inducedα-βphase transition,the higherα-βphase transition efficiency of the PVDF ultrathin films can be attributed to the parallel aligned lamellar structure.Moreover,a higherβ-phase content can suppressα-βphase transition because of the stress concentration effect ofβ-phase.Ultimately,these results provide valuable insights into the stretching-inducedα-βphase transition of PVDF ultrathin films.
基金supported by Zhejiang Provincial Natural Science Foundation under Grant No.LQ18E010002Natural Science Foundation of China under Grant No.51901107+1 种基金Ningbo Natural Science Foundation under Grant No.2018A610168,2019A610176Zhejiang Qianjiang Talent Scheme under Grant No.QJD1803012。
文摘This paper details an investigation of the effects of oxide stringers on theβ-phase depletion behaviour in thermally sprayed CoNiCrAlY coatings.Vacuum Plasma Sprayed(VPS)Co NiCrAlY coatings,which are free of oxide stringers,are used as the reference materials in comparison with High-Velocity Oxy-Fuel(HVOF)sprayed CoNiCrAlY coatings during isothermal oxidation at 1100℃.An outer layer of spinel oxides and an inner layer of alumina are formed in the as-sprayed coatings,while only a single alumina scale is found in the heat-treated coatings.Lessβ-phase depletion occurred in the HVOF coatings than in the VPS coatings.It was found that theβphases tend to coalesce at the oxide stringers in the HVOF coatings,which is likely due to the internal oxide particles and stringers acting as short diffusion barriers to tie up theβphase and inhibit theβ-phase depletion.
基金financial support from the Opening Project of the State Key Laboratory of Polymer Materials Engineering (Sichuan University) (Grant No.Sklpme2015-4-24)the Provincial Department of Education Science General Foundation of Liaoning (Contract No.L2015017)
文摘In this paper,low temperature plasma is used to modify the surface of barium titanate（BaTiO3）nanoparticles in order to enhance the interfacial compatibility between ferroelectric poly（vinylidene fluoride）（PVDF） and BaTiO3 nanoparticles.The results demonstrate that oxygenic groups are successfully attached to the BaTiO3 surface,and the quantity of the functional groups increases with the treatment voltage.Furthermore,the effect of modified BaTiO3 nanoparticles on the morphology and crystal structure of the PVDF/BaTiO3 membrane is investigated.The results reveal that the dispersion of BaTiO3 nanoparticles in the PVDF matrix was greatly improved due to the modification of the BaTiO3 nanoparticles by air plasma.It is worth noting that the formation of a β-phase in a PVDF/modified BaTiO3 membrane is observably promoted,which results from the strong interaction between PVDF chains and oxygenic groups fixed on the BaTiO3 surface and the better dispersion of BaTiO3 nanoparticles in the PVDF matrix.Besides,the PVDF/modified BaTiO3 membrane at the treatment voltage of 24 k V exhibits a lower water contact angle（≈68.4°） compared with the unmodified one（≈86.7°）.Meanwhile,the dielectric constant of PVDF/BaTiO3 nanocomposites increases with the increase of working voltage.
基金the National Natural Science Foundation of China(Grant Nos.12075191 and 11972272).
文摘As a representative piezoelectric polymer,poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP)has been widely used in sensors transducers and actuators.In this paper,gold nanoparticles(AuNPs)are prepared and doped into the PVDF-HFP solution to enhance the piezoelectric property of electrospun PVDF-HFP nanowires.The results indicate that proper amounts of AuNPs within the nanowires can improve the piezoelectric phase in PVDF-HFP.Then,a nanogenerator was prepared using the PVDF-HFP/Au nanowires to verify the increase in piezoelectric performance.Experimental results show that compared with PVDF-HFP n anoge nerator without AuNPs doping,the output voltage is in creased by about two times,while the output current is doubled for the PVDF-HFP/Au nano generator.Furthermore,systematic molecular dyn amics(MD)simulations are conducted to elucidate the physical mechanism of AuNPs enhanced β-phase formation in PVDF-HFP.Our results show that the adsorption and electrostatic interaction between the AuNPs and the PVDF chains promote the electroactive β-phase formation,and also significa ntly in crease the ten sion and poling effect during electrospin ning process,which is the origin of the enhanced elec-troactive phase formation in electrospun PVDF-HFP nanowires.
基金Independent Innovation Projects of the Hubei Longzhong Laboratory,Grant/Award Numbers:2022ZZ-34,2022ZZ-35Science Fund for Distinguished Young Scholars of Hubei Province,Grant/Award Number:2021CFA067+1 种基金Open Fund of Sanya Science and Education Innovation Park of Wuhan University of Technology,Grant/Award Numbers:2021KF0022,2021KF0013,2020KF0026Key Research and Development Program of Hubei Province,Grant/Award Number:2021BAA214。
文摘Poly(vinylidene fluoride)(PVDF)is the most attractive piezoelectric polymer for application in flexible sensors.To attain excellent piezoelectric properties,a substantial amount of spontaneous polarβ-phase content is highly desired.Nevertheless,the current reported manufacturing methods to increaseβ-phase contents are inconvenient and complex,hindering progress in PVDF's application.This work proposes a folding-hot-pressing method to fabricate highβ-phase-content PVDF films.Structural characterization indicates that the films haveαandβphases and the folding-hot-pressing process transforms theαphase into theβphase.Due to the 97.5%β-phase content and aligned structure,a piezoelectric constant of 20 pC/N is achieved in the three-times folded film.Furthermore,the process method enhances the tensile strength(126.2 MPa)of the films,with a low Young's modulus(0.87 GPa)remaining,making the films applicable for flexible piezoelectric sensors.Additionally,sensors based on the achieved films were assembled and applied for human physiological activity monitoring.This work offers a scalable new melt-processing strategy for developing high-performance PVDF-based piezo-electric composite films for wearable electronic devices.
文摘Among all the phase morphologies of poly(9,9-di-n-octylfluorenyl-2,7-diyl)(PFO),the𝛽phase exhibits a zigzag coplanar arrangement with the highest conjugation degree.As a result,the𝛽-phasePFO has extraordinary prop-erties,including enhanced charge carrier mobility.In this work,we report the formation of high-𝛽-phase PFO in nanoparticles(NPs)due to the synergistic effect of the slow crystallization of PFO in nanodroplet confinement and polystyrene(PS)blending.The𝛽-phase content of PFO can be flexibly tuned by varying the NP size,molec-ular weight(M w),or relative PS content in the NPs.The novel systems demonstrated in this study are likely to provide valuable insights into the𝛽-phase formation mechanism of PFO.As a proof of concept,we further demonstrate that NPs of PFO:PS(1:8)with a higher𝛽-phase content lead to improved photocatalyst efficiency at lower material costs,allowing for novel designs of efficient and visible-light-driven photocatalytic NPs.
基金Project(03SSY4056) supported by the Bureau of Science and Technology of Hunan Province, China Project(04C034) supported by the Bureau of Education of Hunan Province, China
文摘A stable δ- and β-bismuth trioxide was prepared at room temperature by vacuum vapor-phase oxidation. The average crystal size of products was 14.6 nm (by XRD), the d(0.5) value was in the range from 62 nm to 69 nm, and geometric standard deviation(GSD) was from 1.42 to 1.64. The results show that δ-Bi2O3 is formed when quenching rates is rapid and β-Bi2O3 is formed when it is slow. The size of grains increases with rising reaction temperature, flow rate of carrier gas, residual pressure of system and longer growing time of grains.
文摘In the current work, a custom-made vibration injection molding device that can provide oscillatory pressure was utilized to create an injection-molded hierarchical structure. Growth competition among α, β, and γ phases in the injection-molded structure can be studied because of the presence of this hierarchical structure, wherein shish-kebab and spherulite layers were arranged alternately along the thickness direction. The γ crystals only existed in layers subjected to high pressure and shear stress, whereas β crystals formed between the shear layers. The change in trend of the γ fraction was similar to that of parent-to-daughter ratio. In addition, this hierarchical and alternating crystal structure can sharply increase the mechanical properties.
基金financially supported by the National Natural Science Foundation of China (Grant No. 51471040)
文摘This paper reported an effectiveness of pre-cold rolling-induced{332}／113[twins combined with subsequent isothermal x-phase formation for enhancement of uniform elongation in a b-type Ti–15Mo alloy with high yield strength level.Mechanical{332}／113[twins were induced by cold rolling with an thickness reduction of 5%,which had little effect on x-phase precipitation after aging at 573 K for 3.6 ks.Twinning after the cold rolling was further activated during tensile deformation,even with the presence of isothermal x-phase.This combination of twins and x-phase enhanced uniform elongation from 0 to 9%at yield strength level of 890 MPa.The high yield strength was mainly dominated by dislocation slip due to the isothermal x-phase formation,and early onset of plastic instability after yielding was hindered due to the pre-cold rolling-induced twins.Dynamic microstructural refinement was induced by further twinning activation during deformation,which resulted in high work hardening rate corresponding enhancement of uniform elongation.
