Advanced micro/nanofabrication of functional materials and structures with various dimensions represents a key research topic in modem nanoscience and technology and becomes critically important for numerous emerging ...Advanced micro/nanofabrication of functional materials and structures with various dimensions represents a key research topic in modem nanoscience and technology and becomes critically important for numerous emerging technologies such as nanoelectronics, nanopho- tonics and micro/nanoelectromechanical systems. This review systematically explores the non-conventional material processing approaches in fabricating nanomaterials and micro/nanostructures of various dimensions which are challenging to be fabricated via conventional approaches. Research efforts are focused on laser-based techniques for the growth and fabrication of one-dimensional （1D）, two-dimensional （2D） and three-dimensional （3D） nanomaterials and micro/nanostructures. The following research topics are covered, including： 1） laser-assisted chemical vapor deposition （CVD） for highly efficient growth and integration of 1D nanomaterial of carbon nanotubes （CNTs）, 2） laser direct writing （LDW） of graphene ribbons under ambient conditions, and 3） LDW of 3D micro/nanostructures via additive and subtractive processes. Comparing with the conventional fabrication methods, the laser-based methods exhibit several unique advantages in the micro/nanofabrication of advanced functional materials and structures. For the 1D CNT growth, the laser-assisted CVD process can realize both rapid material synthesis and tight control of growth location and orientation of CNTs due to the highly intense energy delivery and laser-induced optical near-field effects. For the 2D graphene synthesis and patterning, roomtemperature and open-air fabrication of large-scale graphene patterns on dielectric surface has been successfully realized by a LDW process. For the 3D micro/nanofabrica- tion, the combination of additive two-photon polymeriza- tion （TPP） and subtractive multi-photon ablation （MPA） processes enables the fabrication of arbitrary complex 3D micro/nanostructures which tional fabrication methods are challenging for conven- Considering the numerous unique advantages of laser-based techniques, the laser- based micro/nanofabrication is expected to play a more and more important role in the fabrication of advanced functional micro/nano-devices.展开更多
The present study clarifies the role of Mn in cementite on the driving force of cementite dissolution and the growth of austenite. From an experimental study, the effects of manganese composition and temperature on th...The present study clarifies the role of Mn in cementite on the driving force of cementite dissolution and the growth of austenite. From an experimental study, the effects of manganese composition and temperature on the cementite dissolution were shown. From a theoretical analysis based on thermodynamic and kinetics considerations, a criterion for the change from fast to slow regime of cementite dissolution was proposed. This criterion is in good agreement with the experimental results. It can be easily calculated and can define the composition and temperature ranges where the cernentite dissolution is slow or fast.展开更多
Conventional lithographic printing processes using porous alumina for offset applications generally use "wet" routes. Recently "dry" processes have been developed which are based on a heat-induced ...Conventional lithographic printing processes using porous alumina for offset applications generally use "wet" routes. Recently "dry" processes have been developed which are based on a heat-induced hydrophilic/oleophilic conversion of one or more layers of the coating so that a stronger affinity to-wards ink or water fountain is created at the exposed areas with respect to the surface of the unex-posed coating. Treatments involving rf plasma-enhanced fluorination (PEF) constitute exceptional tools for modifying the surface properties of materials. Many advantages of these techniques can be indeed outlined, when compared to more conventional methods: room-temperature reactions, chemical modi-fications limited to surface only without changing the bulk properties, possible non-equilibrium reac-tions. The influence of PEF treatments on porous alumina layer used in printing plates has been tested with various fluorinated gases (CF4, C3F8 and C4F8) and characterized by XPS. The hydrophobic prop-erties of the fluorinated layer have been deduced from contact angle measurements. Using C4F8 rf-PEF treatment, the outmost surface of the hydrophilic alumina substrate used for lithographic printing is hydrophobized, or in other words, the hydrophilic substrate is converted into a support with hydro-phobic properties. Once being hydrophobized, the surface layer may be rendered hydrophilic using a heat pulse, thus giving rise to switchable hydrophobic-hydrophilic properties of the material.展开更多
This review will deal with several types of free charge localization in oxides and their consequences on the effective dielectric spectra of such materials.The first one is the polaronic localization at the unit cell ...This review will deal with several types of free charge localization in oxides and their consequences on the effective dielectric spectra of such materials.The first one is the polaronic localization at the unit cell scale on residual impurities in ferroelectric networks.The second one is the collective localization of free charge at macroscopic interfaces like surfaces,electrodes and grain boundaries in ceramics.Polarons have been observed in many oxide perovskites mostly when cations having several stable electronic configurations are present.In manganites,the density of such polarons is so high as to drive a net lattice of interacting polarons.On the other hand,in ferroelectric materials like BaTiO_(3)and LiNbO_(3),the density of polarons is usually very small but they can influence strongly the macroscopic conductivity.The contribution of such polarons to the dielectric spectra of ferroelectric materials is described.Even residual impurities as for example Iron can induce well-defined anomalies at very low temperatures.This is mostly resulting from the interaction between localized polarons and the highly polarizable ferroelectric network in which they are embedded.The case of such residual polarons in SrTiO_(3)will be described in more detail,emphasizing the quantum polaron state at liquid helium temperatures.Recently,several nonferroelectric oxides have been shown to display giant effective dielectric permittivity.It is first shown that the frequency/temperature behavior of such parameters is very similar in very different compounds(donor-doped BaTiO_(3),CaCu_(3)Ti_(4)O_(12),LuFe_(2)O_(4),Li-doped NiO,etc.).This similarity calls for a common origin of the giant dielectric permittivity in these compounds.A space charge localization at macroscopic interfaces can be the key for such extremely high dielectric permittivity.展开更多
文摘Advanced micro/nanofabrication of functional materials and structures with various dimensions represents a key research topic in modem nanoscience and technology and becomes critically important for numerous emerging technologies such as nanoelectronics, nanopho- tonics and micro/nanoelectromechanical systems. This review systematically explores the non-conventional material processing approaches in fabricating nanomaterials and micro/nanostructures of various dimensions which are challenging to be fabricated via conventional approaches. Research efforts are focused on laser-based techniques for the growth and fabrication of one-dimensional （1D）, two-dimensional （2D） and three-dimensional （3D） nanomaterials and micro/nanostructures. The following research topics are covered, including： 1） laser-assisted chemical vapor deposition （CVD） for highly efficient growth and integration of 1D nanomaterial of carbon nanotubes （CNTs）, 2） laser direct writing （LDW） of graphene ribbons under ambient conditions, and 3） LDW of 3D micro/nanostructures via additive and subtractive processes. Comparing with the conventional fabrication methods, the laser-based methods exhibit several unique advantages in the micro/nanofabrication of advanced functional materials and structures. For the 1D CNT growth, the laser-assisted CVD process can realize both rapid material synthesis and tight control of growth location and orientation of CNTs due to the highly intense energy delivery and laser-induced optical near-field effects. For the 2D graphene synthesis and patterning, roomtemperature and open-air fabrication of large-scale graphene patterns on dielectric surface has been successfully realized by a LDW process. For the 3D micro/nanofabrica- tion, the combination of additive two-photon polymeriza- tion （TPP） and subtractive multi-photon ablation （MPA） processes enables the fabrication of arbitrary complex 3D micro/nanostructures which tional fabrication methods are challenging for conven- Considering the numerous unique advantages of laser-based techniques, the laser- based micro/nanofabrication is expected to play a more and more important role in the fabrication of advanced functional micro/nano-devices.
文摘The present study clarifies the role of Mn in cementite on the driving force of cementite dissolution and the growth of austenite. From an experimental study, the effects of manganese composition and temperature on the cementite dissolution were shown. From a theoretical analysis based on thermodynamic and kinetics considerations, a criterion for the change from fast to slow regime of cementite dissolution was proposed. This criterion is in good agreement with the experimental results. It can be easily calculated and can define the composition and temperature ranges where the cernentite dissolution is slow or fast.
文摘Conventional lithographic printing processes using porous alumina for offset applications generally use "wet" routes. Recently "dry" processes have been developed which are based on a heat-induced hydrophilic/oleophilic conversion of one or more layers of the coating so that a stronger affinity to-wards ink or water fountain is created at the exposed areas with respect to the surface of the unex-posed coating. Treatments involving rf plasma-enhanced fluorination (PEF) constitute exceptional tools for modifying the surface properties of materials. Many advantages of these techniques can be indeed outlined, when compared to more conventional methods: room-temperature reactions, chemical modi-fications limited to surface only without changing the bulk properties, possible non-equilibrium reac-tions. The influence of PEF treatments on porous alumina layer used in printing plates has been tested with various fluorinated gases (CF4, C3F8 and C4F8) and characterized by XPS. The hydrophobic prop-erties of the fluorinated layer have been deduced from contact angle measurements. Using C4F8 rf-PEF treatment, the outmost surface of the hydrophilic alumina substrate used for lithographic printing is hydrophobized, or in other words, the hydrophilic substrate is converted into a support with hydro-phobic properties. Once being hydrophobized, the surface layer may be rendered hydrophilic using a heat pulse, thus giving rise to switchable hydrophobic-hydrophilic properties of the material.
文摘This review will deal with several types of free charge localization in oxides and their consequences on the effective dielectric spectra of such materials.The first one is the polaronic localization at the unit cell scale on residual impurities in ferroelectric networks.The second one is the collective localization of free charge at macroscopic interfaces like surfaces,electrodes and grain boundaries in ceramics.Polarons have been observed in many oxide perovskites mostly when cations having several stable electronic configurations are present.In manganites,the density of such polarons is so high as to drive a net lattice of interacting polarons.On the other hand,in ferroelectric materials like BaTiO_(3)and LiNbO_(3),the density of polarons is usually very small but they can influence strongly the macroscopic conductivity.The contribution of such polarons to the dielectric spectra of ferroelectric materials is described.Even residual impurities as for example Iron can induce well-defined anomalies at very low temperatures.This is mostly resulting from the interaction between localized polarons and the highly polarizable ferroelectric network in which they are embedded.The case of such residual polarons in SrTiO_(3)will be described in more detail,emphasizing the quantum polaron state at liquid helium temperatures.Recently,several nonferroelectric oxides have been shown to display giant effective dielectric permittivity.It is first shown that the frequency/temperature behavior of such parameters is very similar in very different compounds(donor-doped BaTiO_(3),CaCu_(3)Ti_(4)O_(12),LuFe_(2)O_(4),Li-doped NiO,etc.).This similarity calls for a common origin of the giant dielectric permittivity in these compounds.A space charge localization at macroscopic interfaces can be the key for such extremely high dielectric permittivity.
