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1.
In order to obtain oxide films using catalytic chemical vapor deposition (Cat-CVD), oxidation experiments for catalyzers of Alumel, Al Chrom-O, Chromel, Hastelloy C-276, Kanthal, Kovar, Inconel-600, Inconel-601, Inconel X-750, Iron Chrome 30, Moleculoy, Monel, Ni, Nickel Chrome, Pt, SUS-304, SUS-316, Super Invar, and Ti have been carried out. The electric resistance measured for each metal heated at 900 °C, exposed for 30 min in O2 atmosphere, have revealed that Alumel, Al Chrom-O, Chromel, Hastelloy C-276, Kanthal, Inconel-600, Inconel-601, Inconel X-750, Iron Chrome 30, Moleculoy, Ni, Nickel Chrome, Pt, SUS-304, and SUS-316 are in resistance to oxidation.  相似文献   

2.
The X-ray photoelectron spectroscopy (XPS) measurements have been used to reveal the compositions of alumina (Al2O3) films formed on Si wafers using tri-methyl aluminium (TMA) and molecular oxygen (O2) with catalytic chemical vapour deposition (Cat-CVD). The atomic ratio (O/Al) for Al2O3 samples formed at substrate temperature of 200-400 °C has been obtained to be 1.4 which is close to stoichiometry. The increase of growth rate at substrate temperatures below 200 °C and above 400 °C can be attributed to formation of aluminum oxides with non-stoichiometry and metallic aluminum incorporated in the films resulting from deficient oxygen. Angle resolved XPS measurements have revealed that the alumina/Si interface with no SiO2 film has been obtained at substrate temperatures below 200 °C.  相似文献   

3.
We report the structural and optical properties of nanocrystalline thin films of vanadium oxide prepared via evaporation technique on amorphous glass substrates. The crystallinity of the films was studied using X-ray diffraction and surface morphology of the films was studied using scanning electron microscopy and atomic force microscopy. Deposition temperature was found to have a great impact on the optical and structural properties of these films. The films deposited at room temperature show homogeneous, uniform and smooth texture but were amorphous in nature. These films remain amorphous even after postannealing at 300 °C. On the other hand the films deposited at substrate temperature TS > 200 °C were well textured and c-axis oriented with good crystalline properties. Moreover colour of the films changes from pale yellow to light brown to black corresponding to deposition at room temperature, 300 °C and 500 °C respectively. The investigation revealed that nanocrystalline V2O5 films with preferred 001 orientation and with crystalline size of 17.67 nm can be grown with a layered structure onto amorphous glass substrates at temperature as low as 300 °C. The photograph of V2O5 films deposited at room temperature taken by scanning electron microscopy shows regular dot like features of nm size.  相似文献   

4.
Jiahai Bai 《Materials Letters》2009,63(17):1485-1488
Novel cobalt oxide doped ZnFe2O4-Fe2O3-ZnO mixed oxides with the Zn/Fe molar ratio of 1/2 were synthesized with a citric acid complex method. The effects of cobalt oxide and calcination temperature on phase composition and photocatalytic activity of the mixed oxides were investigated. X-ray diffraction (XRD) analysis revealed that there were mainly ZnFe2O4, α-Fe2O3, amorphous ZnO and Fe2O3 in the 6 mol% cobalt oxide doped products calcined at 500 °C. 5-10 mol% cobalt oxide doping could significantly enhance the formation of ZnFe2O4 and altered the phase composition of the mixed oxides. Experimental results showed that cobalt oxide doping could remarkably improve the photocatalytic activity of the mixed oxides for phenol degradation. The 6 mol% cobalt oxide doped mixed oxides calcined at 500 °C exhibited better photocatalytic activity as compared with other samples.  相似文献   

5.
The chlorination process in aluminum production by carbothermic-chlorination reduction of Al2O3 under vacuum has been investigated by XRD, SEM and thermodynamic analysis. The results of thermodynamic calculations indicated that the chlorination of Al4C3 or Al4O4C possibly proceeded at temperature 1300 °C under 5-50 Pa. The experiment results showed that aluminum could be produced by the chlorination of Al4C3 or Al4O4C and the decomposition of AlCl(g). According to the analysis of experiment results, Al4C3 and Al4O4C were the main reactants participated in chlorination process in aluminum production by carbothermic-chlorination reduction of Al2O3 under vacuum. AlCl(g) generated in chlorination of Al4C3 or Al4O4C would decompose into Al and AlCl3(g), and then aluminum product would condense in condensation tower.  相似文献   

6.
A novel technique of mixing individual hydroxide is employed to prepare La0.65Sr0.35MnO3 (LSMO) at low temperature. Freshly prepared lanthanum and manganese hydroxides are mixed thoroughly with strontium hydroxide in stoichiometric ratio and heated at different temperatures ranging from 100 to 500 °C for 6 h. At 500 °C, formation of La0.65Sr0.35MnO3 was confirmed by the X-ray diffraction studies (XRD). This is the lowest temperature so far reported in the literature. The particle size and morphology were investigated by scanning electron microscopy (SEM).  相似文献   

7.
A modified sol-gel procedure, based on the esterification reaction, was used to prepare the Bi2O3 precursor, which was then heated to 400 or 500 °C. β-Bi2O3 obtained at 400 °C showed well-shaped plate-like particles. The mixture β-Bi2O3/α-Bi2O3, obtained by prolonged heating at 400 °C, yielded pseudospherical particles having about 100 nm in size and much larger particles, as found by FE SEM. α-Bi2O3 obtained at 500 °C consisted of particles of varying shapes and sizes. Vitrification of α-Bi2O3 was also observed. XRD showed a small fraction of unidentified phase(s) in these samples. Different microstructures were obtained when the precipitation from aqueous Bi(NO3)3 solution with tetramethylammonium hydroxide at pH ∼ 14 was used. The precipitation at pH ∼ 3.5 yielded cloverleaf-like particles of good uniformity, which were assigned to BiOOH (isomorphous with (La0.26Bi0.24)Bi0.5OOH. It was found that these particles were made up of much smaller primary BiOOH particles.  相似文献   

8.
High-Tc screen-printed Ho-Ba-Cu-O films were prepared on YSZ substrates by a melt processing method. The films were fired at Ts = 1000-1050 °C for 5 min and cooled to 450 °C by two steps in flowing O2. The maximum critical current density Jc (77 K, 0 T) of 2.0 × 103 A cm− 2 was only attained under much limited firing conditions; Ts = 1020 °C and cooled to 800 °C at a cooling rate of 400 °C h− 1.  相似文献   

9.
SiC films were synthesized by hot-wire chemical vapor deposition using a tungsten filament and a gas mixture of SiF4 and CH4. The etching of the substrate instead of the film growth occurred on the samples prepared using only source gases without H2 dilution. The atomic or molecular hydrogen was believed to control the density of radicals containing F in a gas phase or on a growth surface. Polycrystalline 3C-SiC(111) films were successfully obtained at substrate temperatures lower than 500 °C by using H2 dilution. The growth mode limited by source-gas supply was found to be important to obtain polycrystalline SiC films. The SiC film grown at higher deposition pressure was amorphous and contained no Si-Hx bonds but 6% fluorine. In SiF4/CH4/H2 system, the radicals containing F are considered to play very important roles in the reactions both on a growth surface and in a gas-phase.  相似文献   

10.
Hongrui Peng 《Materials Letters》2009,63(16):1404-1406
MnV2O6 nanostructures including nanorods, nanobelts, and nanosheets, have been synthesized by a facile hydrothermal reaction between Mn(CH3COO)2·4H2O and commercial V2O5. The synthesized products are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The influences of synthetic parameters, such as, reaction time, temperature and medium, on the morphologies of the resulting products have been investigated. As the reaction temperatures increase from 120 °C to 180 °C, MnV2O6 nanorods and nanobelts are obtained, respectively. The time-dependent experimental results at 180 °C reveal that the sizes of MnV2O6 nanobelts increase gradually with the reaction proceeding. Interestingly, as the reaction is carried out with the aid of H2O2 solution, flower-like MnV2O6 nanosheets are formed.  相似文献   

11.
LiOH·H2O, Ni(CH3COO)2·4H2O and NH4VO3 were used to synthesize nano-crystalline LiNiVO4 by hydrothermal process in deionized water at 150 °C for 2 h and subsequent calcination at 300-600 °C for 6 h. By using an X-ray diffractometer (XRD), a transmission electron microscope (TEM) and a selected area electron diffraction (SAED) method, nano-crystalline LiNiVO4 with inverse spinel structure was detected. The stretching vibration of VO4 tetrahedrons analyzed by a Fourier transform infrared spectrometer (FTIR) was split into three bands at 661, 746 and 835 cm− 1, and that analyzed by a Raman spectrometer was detected at 823.9 and 787.7 cm− 1. The thermogravimetric and differential thermal analyses (TGA and DTA) show two discrete weight losses at 25-117 °C and 117-600 °C and four endothermic peaks at 84, 145, 202 and 372 °C, corresponding to the evaporation of water and the decomposition of inorganic and organic compounds.  相似文献   

12.
L.H. Jiang  C.Y. Li  J.Q. Hao 《Materials Letters》2007,61(29):5107-5109
Borates LiSr4(BO3)3 were synthesized by high-temperature solid-state reaction. The thermoluminescence (TL) and some of the dosimetric characteristics of Ce3+-activated LiSr4(BO3)3 were reported. The TL glow curve is composed of only one peak located at about 209 °C between room temperature and 500 °C. The optimum Ce3+ concentration is 1 mol% to obtain the highest TL intensity. The TL kinetic parameters of LiSr4(BO3)3:0.01Ce3+ were studied by the peak shape method. The TL dose response is linear in the protection dose ranging from 1 mGy to 1 Gy. The three-dimensional thermoluminescence emission spectra were also studied, peaking at 441 and 474 nm due to the characteristic transition of Ce3+.  相似文献   

13.
Al foil was coated with niobium oxide by cathodic electroplating and anodized in a neutral boric acid solution to achieve high capacitance in a thin film capacitor. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) revealed the niobium oxide layer on Al to be a hydroxide-rich amorphous phase. The film was crystalline and had stoichiometric stability after annealing at temperatures up to 600 °C followed by anodizing at 500 V, and the specific capacitance of the Nb2O5-Al2O3 composite oxide was approximately 27% higher than that of Al2O3 without a Nb2O5 layer. The capacitance was quite stable to the resonance frequency. Overall, the Nb2O5-Al2O3 composite oxide film is a suitable material for thin film capacitors.  相似文献   

14.
Nanoporous titanium dioxide (TiO2) based conductometric sensors have been fabricated and their sensitivity to hydrogen (H2) gas has been investigated. A filtered cathodic vacuum arc (FCVA) system was used to deposit ultra-smooth Ti thin films on a transducer having patterned inter-digital gold electrodes (IDTs). Nanoporous TiO2 films were obtained by anodization of the titanium (Ti) thin films using a neutral 0.5% (wt) NH4F in ethylene glycol solution at 5 V for 1 h. After anodization, the films were annealed at 600 °C for 8 h to convert the remaining Ti into TiO2. The scanning electron microscopy (SEM) images revealed that the average diameters of the nanopores are in the range of 20 to 25 nm. The sensor was exposed to different concentrations of H2 in synthetic air at operating temperatures between 100 °C and 300 °C. The sensor responded with a highest sensitivity of 1.24 to 1% of H2 gas at 225 °C.  相似文献   

15.
Polycrystalline half-metallic Fe3O4 films with 1 μm in thickness were synthesized on glass substrates directly by electroless plating in aqueous solution at 90 °C without heat treatment. The films have single pure spinal phase structure and the well-crystallized columnar grains grow perpendicularly to the substrates, as revealed by XRD, XPS and SEM. At room temperature, the films exhibit negative magnetoresistance (MR) ratio of about −5.1%, which is ascribed to intergranular tunneling of spin polarized electrons of Fe3O4. The resistivity R of the films with 1 μm in thickness at room temperature is about 5.2 × 10−1 Ω cm. The cation distribution and the arrangement of the magnetic moments of the plated Fe3O4 ferrite thin films are different from that of the bulk materials, which is likely to be one of the reasons for the modification of R and MR properties.  相似文献   

16.
TiO2 thin films were prepared by DC reactive magnetron sputtering in a mixture of oxygen and argon on glass and oxidized silicon substrates. The effect of post-deposition annealing (300 °C, 500 °C and 700 °C for 8 h in air) on the structural and morphological properties of TiO2 thin films is presented. In addition, the effect of Pt surface modification (1, 3 and 5 nm) on hydrogen sensing was studied. XRD patterns have shown that in the range of annealing temperatures from 300 °C to 500 °C crystallization starts and the thin film structure changes from amorphous to polycrystalline (anatase phase). In the case of samples on glass substrate, optical transmittance spectra were recorded. TiO2 thin films were tested as sensors of hydrogen at concentrations 10,000-1000 ppm and operating temperatures within the 180-200 °C range. The samples with 1 nm and in particular with 3 nm of Pt on the surface responded to hydrogen fast and with high sensitivity.  相似文献   

17.
Thin films of nominal composition Ni-25at%Al have been sputter deposited from a target of the intermetallic compound Ni3Al at different substrate deposition temperatures. The film deposited on an unheated substrate exhibited a strongly textured columnar growth morphology and consisted of a mixture of metastable phases. Nanoindentation studies carried out on this film exhibited a strong strain hardening tendency. In contrast, the film deposited at 200 °C exhibited a recrystallized non-textured microstructure consisting of grains of a partially ordered Ni3Al phase. At higher deposition temperatures (∼400 °C), larger grains of the bulk equilibrium, long-range ordered, Ll2 Ni3Al phase were observed in the film. Unlike the film deposited on an unheated substrate, the films deposited at elevated temperatures did not exhibit any dependence of the hardness on the indentation depth and, consequently no strain hardening. The average hardness of the film deposited at 200 °C was higher than the one deposited at 400 °C. In addition to monolithic Ni-25Al thin films, multilayered Ni/Ni3Al thin films were also deposited. Multilayers deposited non-epitaxially on unheated substrates exhibited a strong {111} fiber texture while those deposited epitaxially on (001) NaCl exhibited a {001} texture. Free-standing multilayers of both types of preferred orientations as well as of different layer thicknesses were deformed in tension untill fracture. Interestingly, the {111} oriented multilayers failed primarily by a brittle fracture while the {001} multilayers exhibited features of ductile fracture.  相似文献   

18.
Spinel Fe2VO4 was synthesized by solid state method and its properties were characterized using XRD, SEM, TG-DSC and specific surface area measurements. The average size of the particles was 500 nm. TG-DSC test demonstrated that the Fe2VO4 was thermally stable in nitrogen atmosphere within 300 °C. Lithium insertion into the sample at room temperature and 55 °C has been investigated and the highest discharge capacity approached 250 mAh/g at an average voltage of 0.6 V vs Li+/Li. Capacity retention was unexpectedly good at 1C discharge rate at room temperature and 55 °C. At 5C discharge rate, the specific capacity was still 136 mAh/g. The results show that the Fe2VO4 is a promising anode material due to its high specific capacity, thermal stability and rate performances.  相似文献   

19.
The electrical properties of alumina films formed at substrate temperatures as low as 27 °C using tri-methyl aluminum (TMA) and molecular oxygen (O2) by catalytic chemical vapor deposition (Cat-CVD) have been investigated by capacitance-voltage (C-V), current-voltage (I-V) measurements and X-ray photoelectron spectroscopy (XPS). Substrate temperature dependence of dielectric constant and leakage current of the films has been explained on the basis of deficiency in oxygen. Interface trapping density of the order of 109 ev− 1cm− 2 has been obtained. Angle resolved XPS measurements have revealed that the direct bonding of alumina and Si was realized with very small interface trapping density.  相似文献   

20.
The microstructure evolutions of Ni-Cr-W based superalloy during thermal exposure have been investigated systematically. M6C carbides in the alloy decompose into M23C6 carbides at temperatures from 650 to 1000 °C due to its high content of Cr. The M6C carbides decompose dramatically from 800 to 900 °C. At temperatures up to 1000 °C, a few M23C6 carbides form on the surface of M6C carbides. The decomposition behavior of primary M6C can be explained by the following reaction: M6C → M23C6 + Me (W, Ni, Cr, Mo). At temperatures below 900 °C, coarse lamellar M23C6 carbides precipitate at the grain boundaries. The carbide lamellae line almost perpendicular to the grain boundaries. While the temperature is above 1000 °C, discrete M23C6 carbides precipitate at the grain boundaries. Moreover, there are lots of small M23C6 particles precipitated around M6C carbides from 650 to 1000 °C.  相似文献   

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