A “crystalline” and flexible film with high transparency was developed by uniaxially drawing of fluorinated copolymer. For the practical use of “crystalline” film-type optical waveguide in the near future, an accurate control of the solid-state structure is indispensable because of the necessity of reducing light refraction at the crystalline/amorphous interface. In the present study, changes in the lamella arrangement and molecular mobility in the amorphous region upon fixed annealing and free shrinkage after drawing poly[tetrafluoroethylene-co-(perfluoroethylvinylether)] (abbrev. PFA) transparent crystalline films were investigated by using small-angle X-ray scattering (SAXS) method and dynamic viscoelastic measurement. The PFA was crystallized as a lamella crystal in the films and formed a thicker lamella. Upon the drawing of the PFA films, four-point SAXS diagrams developed in the photograph at through direction to the film, which implied that a particular type of layer structure, an alternately tilted lamella arrangement known as the herringbone, was formed. From the result of SAXS measurements, it is found that changes in lamella arrangement with shrinkage. From the result of dynamic viscoelastic measurement, it is found that fixed annealing film was formed rigid amorphous fraction. In contrast, free shrinkage film disorganized the rigid amorphous fraction.
We investigated the two-dimensional polymorphisms in organized molecular films of dialkylammonium-M bis(1, 3-dithiole-2-thione-4, 5-dithiolate) (abbrev. (dmit)2, M = Ni) charge-transfer complexes using the surface pressure-area (π-A) isotherm, in-plane and out-of plane X-ray diffractions (XRD). Out-of plane and in-plane XRD measurements revealed that transition of molecular arrangement in layer structure along the c-axis and packing mode of molecules in ab-plane were occurred in organized film, respectively. In addition, arrangement of metal(dmit)2 unit in complexes were changed from a high density packing to a low density packing in two-dimensional plane with decrease of subphase temperature. These structural changes appear to be caused by weakening of π-π interaction between metal(dmit)2 units based on decrease of mobility. These results were associated with expansion behavior of monolayer on the water surface at low temperature. On the other hand, metal(dmit)2 units of complex having longer alkyl chain form the low density packing at almost all temperature region. As a reason of this phenomenon, enhancement of van der Waals interaction between alkyl chains with increase of number of carbons is suggested. Consequently, these two-dimensional polymorphic behaviors are based on the competition between van der Waals interaction of alkyl chain and π-π interaction between functional groups.
We constructed two-dimensional integrated single particle layer on the water surface of aromatic polyamides (poly-(N-alkylated benzamides) abbrev. PABAn n: carbon number of side-chains) having both a rigid main-chain and a flexible side-chain with different lengths. Further, the build-up particle layers with highly regular arrangement along the c-axis are formed by Langmuir-Blodgett (LB) method. Molecular orientation and surface morphology of organized particle films of PABAn were investigated by performing surface pressure-area (π-A) isotherm, in-plane and out-of plane X-ray diffraction (XRD), and atomic force microscopy (AFM) measurements. These single particle layers of several aromatic polyamides on the water surface were highly condensed at 15 ℃. Results of out-of plane XRD measurement of multi-particle layers showed that the PABA, particle layers showed large periodicities of 50-60 Å at 15 ℃. From these experimental findings, it was concluded that the polymer synthesis method employed in the present study can be directly used to control their surface morphologies, behavior of two-dimensional integration and multi-particle layer formation.
Hybridization with Ca2Nb3O5− (CNO) nanosheets maybe effective for immobilizing positively charged functional organic molecules on various inorganic materials. To prove this hypothesis, amphiphilic cyanine dyes have been spread on to the surface of a diluted CNO colloidal suspension. The dyes have formed Langmuir films with enlarged molecular areas due to the hybridization. The hybrid Langmuir films have been transferred on to solid substrates by means of the conventional vertical dipping method. Spectroscopic characterization of the obtained Langmuir-Blodgett films has suggested that organic-inorganic sandwiched structures are realized.
We investigated the molecular arrangement and surface morphology of organized molecular films of the 3-arm comb polymer containing metal ion us surface pressure-area (π-A) isotherm, inductively-coupled plasma mass spectrometry (ICP-MS), in-plane and out-of plane X-ray diffraction (XRD), and atomic force microscopy (AFM). From the result of WAXD measurement of the corresponding monomer in bulk, the long hydrocarbon chains are packed hexagonally in solid-state. Compared with their monolayer on the distilled water as subphase, that of this compound on buffer solution containing Cd2+ ion is remarkably expanded at 15°C. It is found that highly ordered layer structures and two-dimensional lattices are constructed in the organized molecular films of Cd-bridged comb polymer using in-plane and out-of plane XRD. Further, surface morphology of the LB films fabricated from the monolayers on buffer solution including Cd2+ formed flat and smooth domains by metal-scavenging.
We investigated formation of ultrathin hybrid films composed of a biodegradable polymers (ex. poly(ethylene succinate), poly(L-lactide), and poly(ε-caprolactone)) and organo-modified montmorillonite nanosheet at an air/water interface. When a chloroform solution of the biodegradable polymer was spread onto a surface of an pure water in a Langmuir trough, a mixed monolayer of biodegradable polymer was formed by hybridization with the clay nanosheets at the air/water interface. These results indicated that some ammonium cations spread onto the clay suspension were dissolved into the aqueous subphase before the hybridization with the clay nanosheets. The hybrid monolayers were transferred onto a mica substrate by Langmuir-Blodgett method to form a mixed monolayer. Interestingly, the densities of dimethyl dioctadecyl (DMDO) ammonium determined by the thermogravimetric analysis were constant in the hybrid multilayers prepared from the clay suspensions at the same concentration, regardless of the concentrations of the amphiphilic ammonium salt solutions. Out-of plane and in-plane XRD profiles of the films showed that the cations of DMDO would lie down on the clay layer in the hybrid film.
Integration of organic and inorganic material is a promising method for obtaining unusual functional material. Recently, we developed a new fabrication method through a combination of Langmuir-Blodgett (LB) and self-assembled monolayers (SAMs) techniques. Using this method, an enzyme of glucose oxidase was chemically bonded with –COOH terminal group of SAM. After that, Prussian Blue nano-clusters were electrostatically immobilized in the octadecyltrimethylammonium LB film. The amperometric glucose biosensor prepared with this method showed a stable linear relationship and a high stability of the sensor performance depending on the glucose concentration at a low potential range. It was found that the current density was affected by the molecular aliphatic chain length in the SAMs layer.
Highly conductive films made of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT/PSS) were prepared by casting the PEDOT/PSS aqueous dispersion of colloidal particles containing ethylene glycol (EG). By addition of 3% of EG, the electrical conductivity was significantly increased from 3 to 430 S/cm. The EG was crucially important for (i) removal of the insulating PSS from the surface of the PEDOT/PSS particles, (ii) crystallization of PEDOT molecules, and (iii) aggregation of the particles, which improved both intra- and inter-particle transfer of charge carriers. A further increase of the EG concentration, however, decreased the conductivity, which was due to the morphological inhomogeneity by the phase segregation.
Epitaxial growth of organized molecular films of alkylammonium-Au bis(1, 3-dithiole-2-thione-4, 5-dithiolate) ((dmit)2) charge-transfer complex on fluorinated copolymer as template estimated by in-plane X-ray diffraction (XRD). In the single crystal, didodecylammonium-Au(dmit)2 molecules packed triclinic lattice. From the in-plane XRD measurement of multilayers on hydrogenated solids, alkyl-chains of this complex also formed triclinic system. The orthorhombic packing of this complex film formed on fluorinated crystalline polymer as substrate. This structural transition is induced by crystal structure of fluorinated copolymer as template. On the other hand, disordered molecular arrangement in these two-dimensional films formed on the amorphous fluorinated copolymer.
The saturated acetone: OrangeII solution was coated on SiO2 surface. Pure Ni metal was used as a catalyst that was deposited on the SiO2 before the OrangeII coating. The sample after annealing showed thin graphite layer formation. Raman spectroscopy measurements suggested that the OrangeII organic solution resolved on the Ni layer surface and formed graphite thin layers. Our results could provide an easy way to produce graphene sheet with low cost.
Composite nanoparticles composed of fullerene C60 and zinc phthalocyanine (ZnPc) were synthesized by injecting their mixed N-methyl-2-pyrrolidone (NMP) solution into water. The nanoparticles have heterojunction structures according to charge-transfer (CT) absorption band of the mixed NMP solution and superior photoanodic current of the composite nanoparticles. The nanoparticles were used as visible-light-responsive photocatalysts without bias potential to decompose organic compounds to CO2, and heterojunctions are proved to be critical to enhance the photocatalytic activity of the nanoparticles.
The significant enhancement of fluorescent quantum yields for CdTe nanocrystals (from 1 to 60 %) through chemical surface modifications is described, enabling us to synthesize monolayer-functionalized nanocrystals with controlled flurescent properties. Several detailed structural characterization for the purified nanocrystals upon reaction revealed that the process relies on the surface chemical attachment of thiolate ligands on the nanocrystal surface, probably with a defect site at the nanocrystal surface being compensated, allowing an increase in the probability of radiative recombination of excitons generated in the nanocrystals. The surface of the obtained nanocrystals could be further modified with other type of molecules through ligand exchange reaction without significant changes in structural and optical characteristics of the nanocrystals.
In this study, Al doped ZnO(Al:ZnO) nanorods were synthesized on the conductive ITO glass substrate using hydrothermal method, and its piezoresistive properties were measured. Electrical impedance of the Al:ZnO nanorods have decreased compared to the undoped nanorods. However, the shape of the nanorod became more slender and inclined to the substrate if more than 1% aluminum ion was mixed to the reactive solution. Piezoresistive change ratio of the Al:ZnO nanorods was almost the same with undoped sample, which agrees with the results of Ga doped ZnO nanorods in our previous study.
Furnace temperature monitoring system with USB transducers was developed. The data were acquired automatically, transferred to PC, and analyzed. Temperatures of five points were measured simultaneously by the system. From the monitored temperatures, temperature distribution was drawn. When the set temperature is 500℃, the difference between set and real temperature is -45～+35℃. When the set temperature is 700℃, the difference between set and real temperature is -11.8～ +35.9℃. In the process of fine ceramics preparation such as high-TC superconductors, the difference between the set and real temperature should be controlled within ±5℃. The optimum area in the furnace was confirmed.
To fabricate the heterojunction, copper oxide (Cu2O) layers were deposited by the chemical bath deposition technique using aqueous solutions containing CuSO4 and Na2SO3 without and with adding a small amount of ethylendiamine (EDA). The counterpart of the heterojunction, i.e., a ZnO layer was deposited by electrochemical deposition. Indium-tin-oxide (ITO) coated glass sheet was used as a substrate, and both the substrate (ZnO/Cu2O/ITO) and superstrate (Cu2O/ZnO/ITO) structures were fabricated. The Cu2O films were crystalline with a cubic crystal structure, had Cu/O ratios of 1.7 - 2, and consisted of octahedral particles, whose size was reduced by addition of EDA. The Cu2O layers exhibited p-type conductivity and phtosensitivity. Rectification properties and week photovoltaic effects were observed for the heterojunctions fabricated using the solution with EDA.
Magnesium oxide (MgO) thin films are often used as protective layers of dielectrics in an AC-plasma display panel (AC-PDP) to improve the discharge characteristics and lifetime of the panel, because of their physical stability, high transmittance and secondary electron emission coefficient. Conventional MgO thin films which are typically deposited by electron beam deposition in vacuum, act as gas getters in the panel. In this study we investigated the surface morphology, chemical species for consistency and outgassing impurities of protective MgO thin films, along with PDP manufacturing steps, by photoelectron spectroscopy in air (PESA) and Kelvin probe force microscopy (KPFM). We prepared metal oxide films, that is, MgO thin films, on SiO2/Si substrates by coating using the metal organic decomposition (MOD) process. High-quality of MgO thin films on SiO2/Si substrates were successfully obtained by heating at a temperature of 900 ℃. A surface potential was induced on a MgO thin film by ultra violet (UV) light irradiation. KPFM showed that a very high surface potential exists, probably due to the high secondary electron emission from the MgO surface induced by UV light irradiation.
An intermediate-temperature (400-600℃) operation of solid oxide fuel cells (SOFCs) is considered to be one of the solutions for reducing a SOFC apparatus cost. In order to achieve this, we proposed to use proton conductive thin films as an electrolyte. As a substrate is required a fuel gas permeability, porous substances are used as substrate, in general. However, this makes depositing solid electrolyte quite difficult. In this paper, we will mention our proposals for avoiding this difficulty. One of our proposals is a direct deposition on a polished porous substrate by liquid-delivery metal-organic chemical vapor deposition (LD-MOCVD). The other is a sol-gel deposition of SZYO thin films on Pd plated porous substrate. Based on these new SOFC structures, we believe we can obtain good SOFC operations in a near future.
H2 permselective silica hybrid membranes were successfully prepared by using a novel deposition method. H2/SF6 permeances ratio was over 3000 through the membrane prepared by a PrTMOS/O3 counter diffusion CVD method at 270°C. H2 permeance through this membrane was 9.1 x 10-7 mol m-2 s-1 Pa-1 that is two orders higher than that through a silica membrane prepared by a TMOS/O2 counter diffusion CVD method at 600 °C. A high H2 permeance membrane was obtained from high O3 concentration during the deposition. Effects of deposition temperatures were investigated. Deposition temperature was important parameter to control pore size of the membrane. H2 permselctive membrane was obtained at 240°C deposition, while N2 permselective membrane was obtained at 270°C deposition. Pore size of the membranes increased with increasing the deposition temperatures upto270°C. C3H6/C3H8gas separation and C6H6/C6H12pervaporation separation were investigated using PrTMOS membranes by changing deposition conditions. The maximum C3H6/C3H8permeance ratio was 12.1 at the 320 °C permeation test. On the other hand, the maximum C6H6/C6H12separation factor was 113 at the 320 °C deposition by changing O3 flow rate. All the selectivities were considered to be a molecular sieving mechanism. Many types of the membranes were obtained by controlling the pore sizes of the membranes.
Pd membranes show high H2 permselectivity. In this study, ceramic particles were co-deposited in a Pd thin film to reduce Pd amounts of the thin films. Additives for ceramic particles were investigated. Pd films were prepared by using an electroplating at 0.20 A cm-2. CTAB (Cetyl trimethyl ammonium bromide: +), PEG (polyethylene glycol: ±), TPAOH (tetrapropyl ammonium hydroxide: +), BTMAOH (benzyltrimethylammonium hydroxide: +) and SDS (Sodium Dodecyl Sulfate: -) were employed for additives. Effects of charge and viscosity of the additives were tested using LTA zeolites (about 1 μm) for ceramic particles. Pd thin films were characterized by using surface and bulk EDX. LTA ratio for CTAB is much higher than those of PEG and SDS. Positive charge is effective for co-deposition, because Pd ion is also positively charged. LTA ratio for CTAB is also higher than those of TPAOH and BTMAOH. The charge of the additives must be key factor of the co-deposition. Surface ratio increased for TPAOH and BTMAOH samples. However, no relationship was found between surface ratios and the viscosity of the electrolyte.
Palladium membranes are useful to produce pure hydrogen by allowing only hydrogen to pass through. However, palladium, a platinum group metal, is limited in resources and expensive. Therefore, alternative membranes are intensively being developed including other metal membranes, porous ceramic membranes, etc. Comparison among them is essential in the development but difficult because these membranes obey different permeation laws. To overcome this difficulty, pressure-dependent permeance is applied to membranes of different thicknesses and different materials: pure palladium membranes 50 μm and 200 μm thick, a pure niobium membrane, and a silica membrane without pressure dependence in permeance. The result demonstrates that pressure-dependent permeance can describe hydrogen permeation flux more precisely than the conventional square-root law and that it enables comparison among membranes with different thicknesses made of different materials. Suitable operating pressure conditions for each membrane are proposed according to the comparison.
For use in a microwave heating system, a pore-filling type Pd membrane was prepared. This membrane was constructed by embedding Pd nanoparticles in micropores of an alumina support tube. Pd loading of 0.10 g/m2 was sufficient for both microwave heating and stopping gas leak. The amount of Pd converted into an equivalent thickness gives a thin metal membrane of 0.07 μm, suggesting a reduction in the amount of Pd in comparison with conventional thin membranes. The Pd membrane was easily heated to 700 K by microwave radiation. The temperature was precisely controlled by changing the microwave power, indicating effective control of the H2 permeation rate. In addition, this Pd membrane can be used as a catalytic membrane. As the model reaction, hydrogenation of benzene and toluene were demonstrated under microwave radiation.
In this work, H2 permeation through Pd-based membranes is analyzed and discussed in presence of inhibition by CO and concentration polarization. Here, a complex hydrogen permeation model is used to evaluate the combined effect of these two phenomena by means of the following coefficients: Concentration Polarization Coefficient (CPC), Inhibition Coefficient (IC) and a novel overall Permeation Reduction Coefficient (PRC). The latter (PRC) takes into account the permeation rate decrease due to mass transfer resistance (polarization) and competitive CO adsorption (inhibition) on the active sites on membrane surface. According to their definition, when polarization and/or inhibition are relevant, CPC and/or IC tend to the unity, pushing also PRC to the same behaviour. On the contrary, when both are negligible, PRC approaches to zero. An important aspect arising from this study is that the polarization and inhibition effects on the overall permeance reduction are not simply additive, because it is found that CPC is lower in presence of inhibition. The present approach is general and provides a useful method to distinguish and quantify the negative effects of polarization and inhibition. Therefore, it can be applied also to other membrane-aided separation systems different from the here-considered one.
Electroless Pd plating at different deposition temperatures was investigated to control Pd deposition behavior for preparing a much thinner Pd membrane to reduce Pd usage and achieve high hydrogen permeation flux. The deposition temperature directly influenced on the membrane thickness uniformity and defect formation. In our experimental condition, a thin Pd electroless-plated membrane with a thickness of 3 μm could be prepared at 333 K using a formic acid bath. It was found that this membrane showed no leakage of helium and high H2 permeation flux. The rate-limiting step of Pd deposition during the electroless plating must be one of the important factors for preparing the thinner Pd plating membrane with no pinholes.
We report magnetic properties of Cd6RE (RE= Tb, Sm) single-grained crystalline approximants. Magnetic susceptibilities show that various long-range magnetic orders occur at low temperatures for the compounds made of RE icosahedra: Cd6Tb shows three types of antiferromagnetic orders with temperature and Cd6Sm exhibits also three types of magnetic orders with temperature, i.e., one antiferromagnetic and two types of ferrimagnetic orders.
This paper describes the effects of the drying conditions of titania-silica (TiO2-SiO2) sol on the dispersibility of the hybrid particles. The hybrid sol of SiO2 nano-particles coated with TiO2 was prepared by a sol-gel process with controlled chemical modification (CCM). The effects of the initial pressure of supercritical drying (SCD) and the zeta potential in the sol on the dispersibility of the particles were investigated to obtain the well-dispersed TiO2-SiO2 hybrid particles. As a result, well-dispersed TiO2-SiO2 hybrid particles were successfully prepared by controlling the initial pressure of SCD and/or the zeta potential.
Boron nitride (BN) and titanium nitride (TiN) films which were made from stable oxide raw materials such as boric oxide and titania were synthesized on metallic substrates by using pulsed DC plasma chemical vapor deposition (PDCVD). Hydrogen gas was used as reducing gas for oxides in the process of CVD. Meantime, nitrogen gas nitrides the reduced materials on the surface of the substrate. In the plasma process when we used only nitrogen gas, both boric oxide and titania were not changed to nitride. However, when we used both nitrogen and hydrogen gases in the process, nitride films were synthesized on them. TiN grain size grew and degree of crystalline improved with increasing current density during the process. In case of BN, hexagonal h-BN was transformed into cubic c-BN under high current density. When the gas mixture ratio was H2 / N2 = 2.0, friction of BN films were improved, and the film was composed of 10μm diameter of island structure on the substrate.
A durability of an electrochromic switchable mirror glass was evaluated in the accelerated degradation test with a constant temperature of 40°C and a relative humidity of 80% for improvement of the durability in the environment. A fluorocarbon polymer was also developed as a surface coating layer of the device to avoid environmental negative impact. Although the conventional device without surface coating rapidly degraded in the test, the device with surface coating exhibited high durability under high temperature and high relative humidity conditions and excellent optical switching properties with high transmittance of around 52.2% in the transparent state. Therefore, we achieved to develop the device with high durability in the environment.
Transition metal doped CuO has been studied to realize the new room temperature ferromagnetic materials for the spintronics devises. Commercial transition metal oxides and CuO were used as the precursors, and they were mechanically milled by the planetary ball mill with WC vial and balls at 500 rpm for 15 minutes. V, Mn and Fe were successfully doped into CuO. These samples showed various magnetic properties at room temperature.
Recentry, from a point of environmental problems, oxygen gas sensors attract attention of controlling the exhaust gas. The Ga2O3 has an oxygen detection characteristic at temperatures more than 900℃, so this material atracts much attention as an oxygen sensor at high temperature. The β-Ga2O3 films were prepared by the RF magnetron sputtering method. The effects of Ar:O2 flow ratio, RF power, and thickness of films on the crystal and oxygen sensing properties were investigated. As a result, the superior crystal properties were obtained at the Ar:O2 flow ratio of 5:1. It was found that the oxygen sensitivity depended on the film thickness.
In order to obtain excellently heat-resistant and transparent polymer materials, the fully aromatic polysilarylenesiloxanes were synthesized via the solution polymerization and the melt-condensation from the corresponding disilanol monomer. And the thermal properties of these polymers were investigated by using DSC and TGA. The polymer synthesized via the solution polymerization showed good solubility in various organic solvents, and 116℃ of glass transition temperature, Tg, and 529℃ of 5% weight loss temperature, Td5. On the other hand, the product obtained by the melt-condensation polymerization partially dissolved in organic solvent, and showed 93℃ of Tg. Polyaryleneoxysiloxane was also prepared from 4,4’-dihydroxytetraphenylmethane and dichlorodiphenylsilane, and showed 137℃ of Tg, while polyaryleneoxysiloxane was easily hydrolyzed in homogeneous solution containing a base etc.
This research was designed for planning a progress of photocatalytic properties of TiO2 thin films prepared by RF magnetron sputtering method with depositing Pt particles on top. The films prepared without heating substrate showed anatase structure. The organic-decomposition properties of TiO2 thin films with Pt deposition showed large decomposition rate compared with these without Pt deposition. But optically excited hydrophilicity characteristics were descreased in the case of Pt deposition
To determine the location of molecules during endocytosis process inside cells, a new nanoparticle-type fluorescence probe whose fluorescence behavior can change in response with surrounding pH was prepared. The nanoparticles was composed of quantum dot (QD) core and block-type water-soluble phospholipid polymer with pH responsible poly(2-diethylamino methacrylate (DEAEMA)) segment as a shell. A small amount of fluorescent dye was bound to the polymer. For detecting the pH circumstances during endocytosis process, fluorescence resonance energy transfer (FRET) mechanism between QD as a donor and a fluorescent dye as an accepter was used. The block-type phospholipid polymer was synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization method to control molecular weight and polymer sequence. After solubilizing QD into water by the polymers to form nanoparticles, Alexa 594 cadaverine was immobilized on the nanoparticles. It was observed the change in fluorescence spectra dramatically in the pH range between pH 7.06 and pH 7.45. This was due to the morphology of the block-type phospholipid polymer chains was dramatically changed in this pH range. The poly(DEAEMA) segment in the polymer was shrunken at pH 7.45, while the segment was stretched below pH 7.06 related to the protonation of the polymer. The nanoparticles were added in the culture medium under HeLa cell culturing, the nanoparticles were accepted cell-uptake. During this process, the fluorescence property was changed. We considered that this fluorescence change is corresponded to uptake of the nanoparticles into endosome. Thus, the nanoparticles are good pH probe to detect the location of molecules inside of cells.
FeSix films were deposited on Si (100) substrates by RF-sputtering method at room temperature using FeSi2 and FeSi3 targets. After deposition, post-annealing was carried out at temperatures in the range of 500-900℃ in a quartz furnace for 1 h in Ar ambient. XRD measurements revealed that an annealing temperature of 900℃ was required for the FeSix films deposited with an FeSi2 target to be completely transformed to β-FeSi2 phase and that the FeSix films deposited with an FeSi3 target were completely transformed to β-FeSi2 phase after annealing at as low as 500℃. Although the FeSix film deposited with an FeSi2 target was transformed to β-FeSi2 phase after annealing at 900℃, it had many cracks on the surface due to high temperature annealing. On the other hand, the β-FeSi2 film deposited with an FeSi3 target had no cracks on the surface after annealing at 500℃. In summary, crack-free β-FeSi2 films on silicon were successfully obtained by controlling the composition of a sputtering target.
The synthesis of TiO2 nanostructures with uniform shape and the proper orientation is a vital task in ensuring their ability to function properly in their applications . Therefore, much effort has been dedicated to discovering an effective method to synthesize TiO2 nanostructures. In this preliminary work, TiO2 nanostructures were successfully synthesized by a simple precipitation technique. This solution-based technique offers many advantages such as composition modifications, low cost, relatively low temperatures and implementation into large-scale production. A variety of TiO2 nanostructures can be obtained by changing the growth temperature and time . In this study, TiO2 nanostructures were grown on a TiO2 template at various growth temperatures ranging from 60℃ to 140℃. The surface topography and morphology of TiO2 films were investigated by atomic force microscopy (AFM). The phase of the TiO2 nanostructures and their surface roughness properties were evaluated by Raman spectroscopy and a surface profiler (SP), respectively.
We have studied theoretically thermal and mechanical properties of nanoporous materials. The thermal conductivity has been estimated with special attention to phonon scattering by nanometer-sized pores. It is shown that the thermal conductivity of a material having several nanometer-sized pores decreases steeply with increasing porosity. The bulk modulus of model nanoporous materials has been calculated using an interatomic potential. It is shown that the bulk modulus of a material having several nanometer-sized pores decreases moderately with increasing porosity. From our theoretical consideration we discuss how we optimize thermal and mechanical properties of nanoporous materials.
Crystal structures and dielectric, polarization, and piezoelectric properties of x(Bi0.5K0.5)TiO3-(1−x)BiFeO3 ceramics were investigated. The results obtained using x-ray and neutron powder diffractions show that a morphotropic phase boundary between the rhombohedral (ferroelectric) and pseudo-cubic (ferroelectric) phases is present in 0.4 ＜ x ＜ 0.43. Ceramics with x = 0.4 exhibited a large remanent polarization of 52 μC/cm2 at 25 ℃ (1Hz). In addition, ceramics with x = 0.4 showed a relatively large electric-field-induced strain (Smax/Emax = 250 pm/V) at a high temperature of 200 ℃. Transmission electron microscopy for x = 0.4 provides evidence of polar nanosized domains with R3c rhombohedral structure. It is suggested that the presence of the nanosized domains is the origin of relaxor-like dielectric behavior.