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1.
Jaturong Jitputti Thitima Rattanavoravipa Surawut Chuangchote Sorapong Pavasupree Yoshikazu Suzuki Susumu Yoshikawa 《Catalysis communications》2009,10(4):378-382
Monodispersed flower-like titanate superstructure was successfully prepared by simple hydrothermal process without any surfactant or template. N2-sorption analysis, scanning electron microscopy (SEM), and X-ray diffraction (XRD) observation of as-synthesized product revealed the formation of flower-like titanate with diameter of about 250–450 nm and BET surface area (SBET) of 350.7 m2 g?1. Upon thermal treatment at 500 °C, the titanate nanosheets were converted into anatase TiO2 with moderate deformation of their structures. The as-prepared flower-like titanate showed high photocatalytic activity for H2 evolution from water splitting reaction. Moreover, the sample heat treated at 500 °C exhibited higher photocatalytic activity than that of commercial TiO2 anatase powder (ST-01). 相似文献
2.
A novel template- and organic-free synthesis of TiO2 nanostructures with controlled phase and morphology was realized through batch supercritical hydrothermal treatment (400 °C) of titanate nanotubes (TNTs) with H2O2 in NaOH aqueous solution. Well-defined 3D titanate hierarchical spheres (THSs), 2D multilayered titanate nanosheets (TNSs), and 1D monodisperse anatase nanorods (ANRs) exposing (0 1 0) facets were prepared in 15 min by slightly varying the NaOH solution pH. Specifically, the obtained Na/H-THSs (without/with HCl neutralization) exhibited highly porous structures with large specific surface area (109 m2 g−1 and 196 m2 g−1, respectively). Temperature-dependent phase and morphology evolutions of products under subcritical condition (200 and 300 °C) were investigated. The formation of the TiO2 nanostructures from TNTs was proposed mainly following a dissolution–nucleation-growth mechanism, suggesting that both supercritical temperature and NaOH solution pH were determinant factors governing the nucleation and growth process and thus the phase and morphology. 相似文献
3.
《Ceramics International》2016,42(11):12623-12629
In this work, electrohydrodynamic atomization deposition, combined with mechanical polishing, was used for the fabrication of dense and even PZT thick films. The PZT slurry was ball-milled and the effect of milling time on the characteristics of the deposited films was examined. A time of 50 h was found to be the optimum milling time to produce dense films. It was found that the PZT thick films presented rough surface after deposition. In order to overcome this drawback the mechanical polishing process was employed on the deposited films. After the mechanical polishing the roughness (Ra) and peak-to-peak height (Rz) of the film surface were decreased from 422 nm to 23 nm and from 5 µm to 150 nm, respectively. Subsequently, an increase of ~10 pC N−1 on piezoelectric constant (d33, f) was obtained. In addition, it was observed that the d33 was increased from 57 pC N−1 to 89 pC N−1 when the thickness was increased from 10 µm to 80 µm. 相似文献
4.
Lead zirconium titanate [Pb(ZrxTi1?x)O3 or PZT] thin films were prepared by the thermal annealing of multilayer films composed of binary oxide layers of PbO, ZrO2 and TiO2. The binary oxides were deposited by metal organic chemical vapor deposition. An interdiffusion reaction for perovskite PZT thin films was initiated at approximately 550 °C and nearly completed at 750 °C for 1 h under O2 annealing atmosphere. The composition of Pb/Zr/Ti in perovskite PZT could be controlled by the thickness ratio of PbO/ZrO2/TiO2 where the contribution of each binary oxide at the same thickness was 1:0.55:0.94. The electrical properties of PZT (Zr/Ti = 40/60, 300 nm) prepared on a Pt-coated substrate included a dielectric constant ?r of 475, a coercive field Ec of 320 kV/cm, and remnant polarization Pr of 11 μC/cm2 at an applied voltage of 18 V. 相似文献
5.
《Ceramics International》2016,42(11):13262-13267
Barium zirconate titanate (BaZr0.2Ti0.8O3, BZT) 250 nm thick thin films were fabricated by pulsed laser deposition and the influence of the substrate temperature on their preferred orientation, microstructure, morphology and dielectric properties was investigated. Dielectric measurements indicated the (1 1 0)-oriented BZT thin films deposited at 750 °C to show good dielectric properties with high dielectric constant (~500 at 100 kHz), low loss tangent (<0.01 at 100 kHz), and superior tunability (>70% at 400 kV/cm), while the largest figure of merit was 78.8. The possible microstructural background responsible for the high dielectric constant and tenability is discussed. In addition, thin films deposited at 750 °C with device quality factor of 8738 and dielectric nonlinearity coefficient of 1.66×10−10 J/C4m5 were demonstrated. 相似文献
6.
《Inorganic chemistry communications》2008,11(10):1159-1161
Thin films of halide free Cu–Co mixed metal oxide have been prepared at 390 °C from the heterobimetallic complex Co4(THF)4(TFA)8(μ-OH)2Cu2(dmae)2 · 0.5C7H8 (1) [dmae = N,N-dimethylaminoethanol ((CH3)2NCH2CH2O−), TFA = triflouroacetate (CF3COO−), THF = tetrahydrofurane (C4H8O)] which was prepared by the reaction of [Cu(dmae)Cl]4 and Co(TFA)2 · 4H2O. The precursor was characterized for its melting point, elemental composition, FTIR and X-ray single crystal structure determination. Thin films grown on glass substrate by using AACVD out of complex 1 were characterized by XRD and SEM. TGA and AACVD experiments reveal it to be a suitable precursor for the deposition of halide free Cu–Co mixed-metal oxide thin films at relatively low temperatures. 相似文献
7.
We have investigated the processing of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 (denoted PMN–PT) thick films using an electrophoretic deposition process (denoted EPD), with the PMN–PT particles suspended in an ethanol-based suspension. The zeta-potential and the viscosity were measured to identify the conditions for the preparation of a stable suspension suitable for the EPD. The applied voltage, the deposition time, the chemical composition of the suspension and the concentration of the powder were investigated in order to obtain a high-quality PMN–PT deposit with a target thickness of about 50 μm. The PMN–PT thick films prepared from stoichiometric and PbO-excess suspensions by sintering at 950 and 1100 °C were examined by X-ray powder-diffraction analysis and scanning electron microscopy. The highest functional response was obtained for a homogeneous, dense, crack-free PMN–PT thick film prepared from a PMN–PT suspension with excess PbO. The film was deposited at a constant voltage of 10 V and for a time of 120 s, followed by sintering at 1100 °C in a PbO-rich atmosphere. The film's properties were as follows: a dielectric permittivity ? of 20,250 at a Tm of 172 °C, a remanent polarization of 17 μC/cm2 and a coercive field of 5 kV/cm. 相似文献
8.
《Journal of the European Ceramic Society》2007,27(13-15):3793-3797
Porous Pb(ZrxTi1−x)O3(PZT) thick films that had been prepared by tape casting were densified by microwave energy. The microwave absorption effect is substantially correlated with the film thickness. In microwave-processed PZT thick films, rapid particle necking causes densification with no grain growth nearly in a short treatment time of 20 min at 820 °C. The same porous PZT thick films are difficult to densify in a conventional process. A 30-μm-thick PZT thick film has a pure perovskite structure. Self-supporting PZT thick films with a crack-free and uniform microstructure formed in a microwave process have larger coercive field than conventionally processed bulk PZT. The polarization, 14 μC/cm2, of PZT thick films in a microwave process exceeds that, 7 μC/cm2, of PZT bulk formed in a conventional process. 相似文献
9.
《Journal of the European Ceramic Society》1999,19(1):75-79
The effects of H2O in the EtOH–H2O disperse medium on the electrophoretic deposition (EPD) of CaSiO3 fine powder were investigated. Fine CaSiO3 powder with average diameter of 1·7 μm was prepared by the coprecipitation method. It was deposited on a stainless steel substrate by EPD in the disperse media with various H2O concentrations (0–20·2 mass%) under a DC field of 50 V. The amount of the CaSiO3 deposition increased with increasing H2O up to 11·2 mass% but decreased rapidly beyond this concentration. The surface potential of the powder showed a similar trend as the amount of deposition against H2O concentration. The effect of H2O was summarized as follows: (1) the addition of positive charge on the surface of CaSiO3 particles (2) the neutralization of the surface charge by OH− caused by the dissolution of CaSiO3 in the H2O. 相似文献
10.
Lead-free ferroelectric K0.5Na0.5NbO3 (KNN) films with different thicknesses were prepared by polyvinylpyrrolidone (PVP)-modified chemical solution deposition (CSD) method. The KNN films with thickness up to 4.9 μm were obtained by repeating deposition-heating process. All KNN thick films exhibit single perovskite phase and stronger (1 1 0) peak when annealed at 650 °C. The variation of dielectric constant with thickness indicates that there exists a critical thickness for the dielectric constant in the KNN films which should lie in 1.3–2.5 μm. The similar trend is observed for the ferroelectric and piezoelectric properties of KNN films. Both the remnant polarization Pr and the piezoelectric coefficient d33 of KNN thick films increase with the film thickness and become saturated after the critical thickness. 相似文献
11.
Haibo Zhang Shenglin Jiang Jianzhong Xiao Koji Kajiyoshi 《Journal of the European Ceramic Society》2010,30(15):3157-3165
Sodium–potassium bismuth titanate (NKBT) thick films with thickness of 40 μm were prepared by screen printing. To improve the homogeneity, the sintering aids were added into the pastes as a chemical liquid-phase doping method. The results show that the addition of Bi–Li sintering aids was beneficial for both the reduction of the sintering temperature and the improvement of the electrical performance of the thick films. The thick films containing 5 wt.% Bi–Li sintering aids demonstrated optimal dielectric properties with the maximum dielectric constant of 725 and minimum dielectric loss of 2.5%. Moreover, the NKBT thick films containing 3 wt.% Bi–Li sintering aids sintered at 950 °C exhibited the remanent polarization of 19.6 μC/cm2, room-temperature pyroelectric coefficient of 1.56 × 10?4 C/(m2 °C), figure of merit for specific detectivity of 0.48 × 10?5 Pa?0.5, and effective longitudinal piezoelectric coefficient of 88 pm/V, which are comparable to that of the high-temperature sintered thick films without sintering aids. 相似文献
12.
《Journal of the European Ceramic Society》2014,34(5):1063-1072
For the very first time, dense and thick films of Ti3SiC2, a popular MAX-phase material, were elaborated on glass substrates by the aerosol deposition method (ADM) at RT. The influence of some processing parameters on the deposition rate and morphology of the films was studied. The films revealed an adhesive interface with the substrate and a dense internal microstructure with nanocrystallites resulting from a high fragmentation of the initial powder at the impact. The film surface showed different types of structuration, from a flat to a rough one with the presence of craters, whose deepness and diameter were linked to the film thickness. The deposition rate and film morphology were both influenced by the distance of projection and the carrier gas flow. Films with thicknesses ranging from 0.1 to 16 μm were thus obtained with a high deposition rate reaching 4 μm min−1, with a roughness, Ra, lower than 300 nm. 相似文献
13.
《Diamond and Related Materials》1999,8(7):1272-1276
Homoepitaxial diamond films with atomically flat surface were grown using the microwave plasma chemical vapor deposition method at a low CH4 concentration of less than 0.05% in a CH4 and H2 mixed gas system. In Ib (001) diamond substrates having misorientation angles of 0.5°, atomic force microscope image on the surface of film grown at 0.025% CH4 concentration showed that the films had atomically flat surface with mean roughness of 0.04 nm in area as large as 4×4 mm2 (the whole region of the substrate). 相似文献
14.
《Carbon》2014
C58 fullerene cages made by electron-impact induced fragmentation of C60 fullerenes have been assembled into several micron thick solid films by low energy cluster beam deposition onto inert substrates held at room temperature under ultrahigh vacuum. The resulting as-prepared material, RT-C58, behaves as an amorphous wide-band semiconductor. Nanoindentation was used to measure its mechanical properties revealing that RT-C58 has a higher elastic modulus E and hardness H than the reference carbon allotropes solid C60 and Highly Ordered Pyrolytic Graphite (HOPG): E(RT-C58) = 14 GPa and H(RT-C58) = 1.2 GPa. This effect can be explained by the unique intrinsic “functionalization” of C58 cages: they comprise reactive surface sites constituted by annelated pentagon rings which give rise to covalently stabilized oligomers, –C58–C58–C58, under our deposition conditions. Annealing, thick RT-C58 films up to 1100 K in ultrahigh vacuum results in HT-C58, a new material with considerably modified electronic and vibrational properties compared to the as-prepared RT-C58 film. The associated molecular transformations, including also partial cage–cage coalescence reactions, raise the overall mechanical hardness of the material: H(HT-C58) = 3.9 GPa. 相似文献
15.
Seon Mi Kong Rong Fan Sung Hee Jung Chee Won Chung 《Journal of Industrial and Engineering Chemistry》2013,19(4):1320-1324
Cu(In1?xGax)Se2 (CIGS) thin films were prepared using a single quaternary target by RF magnetron sputtering. The effects of deposition parameters on the structural, compositional and electrical properties of the films were examined in order to develop the deposition process without post-deposition selenization. From X-ray diffraction analysis, as the substrate temperature and Ar pressure increased and RF power decreased, the crystallinity of the films improved. The scanning electron microscopy revealed that the grains became uniform and circular shape with columnar structure with increasing the substrate temperature and Ar pressure, and decreasing the RF power. The carrier concentration of CIGS films deposited at the substrate temperature of 500 °C was 2.1 × 1017 cm?3 and the resistivity was 27 Ω cm. At the substrate temperature above 500 °C, In and Se contents in CIGS films decreased due to the evaporation and it led to the deterioration of crystallinity. It was confirmed that CIGS thin films deposited at optimal condition had similar atomic ratio to the target value even without post-deposition selenization process. 相似文献
16.
Dušan A. Pejaković Jochen Marschall Mekha R. George Bridget R. Rogers Wesley R. Nieveen Vasil Pajcini 《Journal of the European Ceramic Society》2010,30(11):2289-2300
Carbon-rich ceramics are an emerging class of materials with attractive high-temperature properties, including resistance to crystallization, dense microstructure, and low porosity. We explored direct synthesis of carbon-rich hafnia, which is known to form as a compact interlayer in the oxide scales of oxidized hafnium carbide. The material was synthesized by pulsed laser deposition, using pure HfO2 targets in C2H2 background gas at low pressures. Stable films up to 700 nm thick and with high molar fractions (~0.1–0.45) of carbon were obtained. The predominant chemical bonding of Hf and O atoms is that of oxygen-deficient HfO2, while carbon is present in elemental or hydrogenated forms. Annealing at 600 °C leads to loss of most of the hydrogen from the films, which is accompanied by enhanced sp2 bonding of carbon. The films have amorphous, compact, and finely grained microstructure. Carbon molar fractions higher than ~0.2 inhibit microcrystallinity to at least 600 °C. 相似文献
17.
B. Barbier C. Combettes S. Guillemet-Fritsch T. Chartier F. Rossignol A. Rumeau T. Lebey E. Dutarde 《Journal of the European Ceramic Society》2009,29(4):731-735
Dielectric properties of CaCu3Ti4O12 (CCTO)-based ceramics and thick films (e ~50 μm) prepared from powders synthesized by a soft chemistry method (co-precipitation) are presented and discussed. The characteristics of pellets and thick films are compared.The pellets exhibit high values of the dielectric permittivity (?r ~1.4 × 105) and relatively small dielectric losses (tan δ ~0.16) at 1 kHz and room temperature. These properties are independent of the nature of the metallization of the electrodes. In addition, the dielectric permittivity decreases when the diameter of the electrodes of the pellets increases, while the losses remain constant. This result, which is strongly related to the nature of the dielectric material in between the electrodes, constitutes a strong indication that the high dielectric permittivity values observed in this material are not related to an interfacial (electrode material) related mechanism but is an internal barrier layer capacitor (IBLC) type.Very high values of the dielectric permittivity of CCTO thick films are measured (?r ~5 × 104). The differences in dielectric permittivity between thick films and dense pellets may be attributed to the difference in grain size due to different CuO contents, and to the different reactivity of the materials. 相似文献
18.
《Ceramics International》2017,43(17):15010-15017
During the last decade, fabrication of high-quality graphene films by chemical vapor deposition (CVD) for nanoelectronics and optoelectronic applications has attracted increasing attention. However, processing of large-area monolayer and defect-free graphene films is still challenging. In this work, we have studied the effect of processing conditions on the self-limited growth of graphene monolayers on copper foils during low pressure CVD both experimentally and theoretically based on thermokinetics and kinetics of Langmuir adsorption. The effect of copper pre-treatment, growth time, and carbon potential of the atmosphere (indicated by the methane-to-hydrogen gas ratio, r) on the quality of graphene nanosheets (number of layers, surface roughness and the lateral size) were studied. Microscopic studies show that careful pre-treatment of the copper foil by electropolishing provides a suitable condition for the self-limited growth of graphene with minimum surface roughness and defects. Raman spectroscopy and atomic force microscopy determine that the number of graphene sheets decreases with increasing the carbon potential while smother surfaces are attained. Large-area monolayer graphene films are obtained at relatively high carbon potential (r=1) and controlled growth time (10 min) at 1000 °C. Measurement of the electrical response of the prepared monolayer graphene films on SiO2 (300 nm)/Si substrates in a field effect transistor (FET) device shows a high mobility of 2780 cm2 V−1 s−1. Interestingly, the device exhibits p-type semiconducting behavior with the Dirac point at a gate voltage of 25 V. The finding show a great promise for graphene-based FET devices for future nanoelectronics. 相似文献
19.
《Dyes and Pigments》2008,76(3):693-700
Synthesis and the characterization of TiO2:5%Co (green), TiO3:5%Fe (brown-reddish), TiO2:2%Cr (brown), Al2O3:5%Co (blue), Al2O3:5%Fe (brown-reddish) and Al2O3:2%Cr (light green) nanometric pigment powders using polymeric precursor (modified Pechini's method) is reported. Colored thick films were deposited on amorphous quartz substrates by electron beam physical vapor deposition (EB-PVD) using pellets of the pigment powders as target. The evaporation process was carried out in vacuum of 4 × 10−6 Torr and the amorphous quartz substrates were kept at 350 °C during deposition. The TiO2-based pigment powders presented crystalline anatase phase and the Al2O3-based pigment powders showed corundum phase, investigated by X-ray diffraction (XRD). The average particle size of the pigment powders was about 20 nm, measured by scanning electron microscopy with field emission gun (SEM-FEG). Diffuse reflectance spectra and colorimetric coordinates L1, a1, b1 using the CIE-L1a1b1 method are shown for the pigment powders, in the 350–750 nm range. The colored thick films were characterized by transmittance (UV–Vis) and atomic force microscopy (AFM). The average film roughness was ∼5.5 nm and the average grain size obtained in the films was around 75 nm. Films with thickness from 400 nm to 690 nm were obtained, measured by talystep profiler. Transmission spectra envelop method has been used to obtain refractive index and thickness of the Al2O3 colored thick films. 相似文献
20.
G. Balakrishnan S. Tripura Sundari R. Ramaseshan R. Thirumurugesan E. Mohandas D. Sastikumar P. Kuppusami T.G. Kim J.I. Song 《Ceramics International》2013,39(8):9017-9023
Aluminum oxide (Al2O3) thin films were deposited on silicon (100) and quartz substrates by pulsed laser deposition (PLD) at an optimized oxygen partial pressure of 3.0×10?3 mbar in the substrate temperatures range 300–973 K. The films were characterized by X-ray diffraction, transmission electron microscopy, atomic force microscopy, spectroscopic ellipsometry, UV–visible spectroscopy and nanoindentation. The X-ray diffraction studies showed that the films deposited at low substrate temperatures (300–673 K) were amorphous Al2O3, whereas those deposited at higher temperatures (≥773 K) were polycrystalline cubic γ-Al2O3. The transmission electron microscopy studies of the film prepared at 673 K, showed diffuse ring pattern indicating the amorphous nature of Al2O3. The surface morphology of the films was examined by atomic force microscopy showing dense and uniform nanostructures with increased surface roughness from 0.3 to 2.3 nm with increasing substrate temperature. The optical studies were carried out by ellipsometry in the energy range 1.5–5.5 eV and revealed that the refractive index increased from 1.69 to 1.75 (λ=632.8 nm) with increasing substrate temperature. The UV–visible spectroscopy analysis indicated higher transmittance (>80%) for all the films. Nanoindentation studies revealed the hardness values of 20.8 and 24.7 GPa for the films prepared at 300 K and 973 K respectively. 相似文献