A number of CaHfO_(3)modified BiFeO_(3)-0.33BaTiO_(3)(BF-0.33BT-xCH)lead-free piezoceramics were fabri-cated through the solid-state sintering method and comprehensively investigated in this work.Under the optimal sin...A number of CaHfO_(3)modified BiFeO_(3)-0.33BaTiO_(3)(BF-0.33BT-xCH)lead-free piezoceramics were fabri-cated through the solid-state sintering method and comprehensively investigated in this work.Under the optimal sintering temperature,all compositions display a typical perovskite structure in a pseudo-cubic phase with slightly larger lattice parameters as the CH content increases.The electrical resistivity is highly enhanced due to the addition of CH.Microstructures,including the grain morphology,core-shell structure,and chemistry inhomogeneities,are demonstrated upon different BF-0.33BT-xCH composi-tions.In particular,the core-shell structures with non-uniform element distributions in the compositions can be eliminated by adding sufficient CH content(x>0.05).The highest saturation polarization(40.1 mC/cm^(2)),remnant polarization(26.8 mC/cm^(2)),and converse piezoelectric coefficient(290 pm/V)are achieved in the BF-0.33BT-0.01CH piezoceramic,which are significantly enhanced in comparison with the undoped BF-0.33BT piezoceramic.With further increasing the CH content,the piezoelectric properties of BF-0.33BT-xCH ceramics decline rapidly,and they start to exhibit characteristics of relaxor ferroelectrics.展开更多
Metallic nanostructures are becoming increasingly important for both fundamental research and practical devices.Many emerging applications employing metallic nanostructures often involve unconventional substrates that...Metallic nanostructures are becoming increasingly important for both fundamental research and practical devices.Many emerging applications employing metallic nanostructures often involve unconventional substrates that are flexible or nonplanar,making direct lithographic fabrication very difficult.An alternative approach is to transfer prefabricated structures from a conventional substrate;however,it is still challenging to maintain high fidelity and a high yield in the transfer process.In this paper,we propose a high-fidelity,clean nanotransfer lithography method that addresses the above challenges by employing a polyvinyl acetate(PVA)film as the transferring carrier and promoting electrostatic adhesion through triboelectric charging.The PVA film embeds the transferred metallic nanostructures and maintains their spacing with a remarkably low variation of<1%.When separating the PVA film from the donor substrate,electrostatic charges are generated due to triboelectric charging and facilitate adhesion to the receiver substrate,resulting in a high large-area transfer yield of up to 99.93%.We successfully transferred the metallic structures of a variety of materials(Au,Cu,Pd,etc.)with different geometries with a<50-nm spacing,high aspect ratio(>2),and complex 3D structures.Moreover,the thin and flexible carrier film enables transfer on highly curved surfaces,such as a single-mode optical fiber with a curvature radius of 62.5μm.With this strategy,we demonstrate the transfer of metallic nanostructures for a compact spectrometer with Cu nanogratings transferred on a convex lens and for surface-enhanced Raman spectroscopy(SERS)characterization on graphene with reliable responsiveness.展开更多
In this study,2-[2-(2-methoxyethoxy)ethoxy]acetic acid(MEEAA)was used to modify the surface of barium titanate nanoparticles(BT NPs)to enhance the compatibility and dispersion of the BT ceramic fillers in polymer matr...In this study,2-[2-(2-methoxyethoxy)ethoxy]acetic acid(MEEAA)was used to modify the surface of barium titanate nanoparticles(BT NPs)to enhance the compatibility and dispersion of the BT ceramic fillers in polymer matrix.A uniform coating layer with a thickness about 2 nm was formed on the surface of BT after modification.The poly(vinylidene fluoride)-hexafluoropropene[P(VDF-HFP)]composites filled with MEEAA-modified BT NPs achieved higher permittivity(∼13 at 3.0 vol%filler)and discharged energy density than that of the untreated BT filled composite.The maximum discharge energy density of 7.8 J/cm^(3)was obtained in the nanocomposites with 3 vol%MEEAA-modified BT NPs at electric field of 425 kV/mm,which is 77%higher than that of 4.4 J/cm^(3)of pure P(VDF-HFP)film at electric field of 420 kV/mm.展开更多
基金supported by the Science,Technology and Innovation Commission of Shenzhen Municipality,grants No:RCBS20210706092341001 and No:JCYJ20220531095802005.
文摘A number of CaHfO_(3)modified BiFeO_(3)-0.33BaTiO_(3)(BF-0.33BT-xCH)lead-free piezoceramics were fabri-cated through the solid-state sintering method and comprehensively investigated in this work.Under the optimal sintering temperature,all compositions display a typical perovskite structure in a pseudo-cubic phase with slightly larger lattice parameters as the CH content increases.The electrical resistivity is highly enhanced due to the addition of CH.Microstructures,including the grain morphology,core-shell structure,and chemistry inhomogeneities,are demonstrated upon different BF-0.33BT-xCH composi-tions.In particular,the core-shell structures with non-uniform element distributions in the compositions can be eliminated by adding sufficient CH content(x>0.05).The highest saturation polarization(40.1 mC/cm^(2)),remnant polarization(26.8 mC/cm^(2)),and converse piezoelectric coefficient(290 pm/V)are achieved in the BF-0.33BT-0.01CH piezoceramic,which are significantly enhanced in comparison with the undoped BF-0.33BT piezoceramic.With further increasing the CH content,the piezoelectric properties of BF-0.33BT-xCH ceramics decline rapidly,and they start to exhibit characteristics of relaxor ferroelectrics.
基金supported by the Research Grants Council of the Hong Kong Special Administrative Region (Awards No.17207419,17209320,C7018-20G,and AoE/P-701/20)the Platform Technology Funding programme,and the Seed Funding Programme for Basic Research (202011159235 and 202010160046)of the University of Hong KongShenzhen Government (Grant No.K20799112).
文摘Metallic nanostructures are becoming increasingly important for both fundamental research and practical devices.Many emerging applications employing metallic nanostructures often involve unconventional substrates that are flexible or nonplanar,making direct lithographic fabrication very difficult.An alternative approach is to transfer prefabricated structures from a conventional substrate;however,it is still challenging to maintain high fidelity and a high yield in the transfer process.In this paper,we propose a high-fidelity,clean nanotransfer lithography method that addresses the above challenges by employing a polyvinyl acetate(PVA)film as the transferring carrier and promoting electrostatic adhesion through triboelectric charging.The PVA film embeds the transferred metallic nanostructures and maintains their spacing with a remarkably low variation of<1%.When separating the PVA film from the donor substrate,electrostatic charges are generated due to triboelectric charging and facilitate adhesion to the receiver substrate,resulting in a high large-area transfer yield of up to 99.93%.We successfully transferred the metallic structures of a variety of materials(Au,Cu,Pd,etc.)with different geometries with a<50-nm spacing,high aspect ratio(>2),and complex 3D structures.Moreover,the thin and flexible carrier film enables transfer on highly curved surfaces,such as a single-mode optical fiber with a curvature radius of 62.5μm.With this strategy,we demonstrate the transfer of metallic nanostructures for a compact spectrometer with Cu nanogratings transferred on a convex lens and for surface-enhanced Raman spectroscopy(SERS)characterization on graphene with reliable responsiveness.
基金supported by the National Natural Science Foundation of China(no.51377157)the Guangdong Innovative Research Team Program(no.2011D052)+1 种基金the Guangdong Provincial Key Laboratory(2014B030301014)the Shenzhen Key Fundamental Program(JCYJ20160608160307181).
文摘In this study,2-[2-(2-methoxyethoxy)ethoxy]acetic acid(MEEAA)was used to modify the surface of barium titanate nanoparticles(BT NPs)to enhance the compatibility and dispersion of the BT ceramic fillers in polymer matrix.A uniform coating layer with a thickness about 2 nm was formed on the surface of BT after modification.The poly(vinylidene fluoride)-hexafluoropropene[P(VDF-HFP)]composites filled with MEEAA-modified BT NPs achieved higher permittivity(∼13 at 3.0 vol%filler)and discharged energy density than that of the untreated BT filled composite.The maximum discharge energy density of 7.8 J/cm^(3)was obtained in the nanocomposites with 3 vol%MEEAA-modified BT NPs at electric field of 425 kV/mm,which is 77%higher than that of 4.4 J/cm^(3)of pure P(VDF-HFP)film at electric field of 420 kV/mm.
