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1.
Highly crystallized BaWO4 films have been prepared on a tungsten substrate in an alkaline solution containing barium ions by an electrochemical method with a constant direct current density of 1 mA/cm2 at room temperature (25°C). The average grain size was about 13 μm, and the thickness about 9 μm after a treatment time of 35 min. The dependence of cell voltage on deposition time was divided into three steps: conduction, anodic oxidation, and breakdown steps. The BaWO4 film formed during the first step. Electrochemical dissolution of metal tungsten occurred with an accompanying positive change of overpotential in the first step. The crystallization of BaWO4 was characterized by three-dimensional nucleation. In the second step, an amorphous tungsten oxide film formed, thereby increasing the potential. An electrical breakdown occurred in the third step, and the breakdown voltage (about 90 V) was practically the same as those of anodic tungsten oxide films. 相似文献
2.
Films of a complete series of solid-solution oxides, Ba1-χ Srχ WO4 (O ≥ X ≥ 1), have been prepared on tungsten substrates in an electrolytic solution containing Ba2+ and Sr2+ ions by an electrochemical method at room temperature (25°C). The composition X could easily be controlled by the concentrations of Ba and Sr species in the starting solutions. X-ray diffraction and X-ray photoelectron spectroscopy analyses showed that a complete series of well-crystallized solid-solution oxides was formed even at room temperature. 相似文献
3.
Masahiro Yoshimura Mitsuhiro Ohmura Woo-Seok Cho Masatomo Yashima Masato Kakihana 《Journal of the American Ceramic Society》1997,80(9):2464-2466
A complete series of well-crystallized solid-solution Sr1– X -CaX MoO4 films has been prepared on molybdenum substrates in an electrolytic solution containing Sr2+ and Ca2+ ions by an electrochemical method at room temperature (25°C). The peak positions of excitation and emission of the Sr1–X CaX MoO4 solid-solution films were independent of the Ca content: 285 ± 2 nm for excitation and 536 ± 2 nm for emission at liquid-nitrogen temperature (−196°C). 相似文献
4.
Woo-Seok Cho Masatomo Yashima Masato Kakihana Akihiko Kudo ¶ Tadayoshi Sakata Masahiro Yoshimura 《Journal of the American Ceramic Society》1997,80(3):765-769
Crystallized luminescent calcium molybdate (CaMoO4 ) film has been prepared on a molybdenum substrate in an alkaline solution containing calcium ions by active electrochemical dissolution of molybdenum at room temperature (25°C). The dissolution rate became faster with an increase of pH value. A high concentration of calcium (0.02M) and a high pH value (13) favored the reaction of film formation. The film showed only a single green emission at 536 nm with the excitation of 285 nm at liquid-nitrogen temperature (-196°C), strongly suggesting that it consisted of well-crystallized defect-free crystals. 相似文献
5.
The Klc values for (100), (110), and (111) single-crystal MgAl2 O4 as well as those for polycrystalline MgAl2 O4 with transgranular and intergranular fractures are presented and discussed on the basis of their elastic moduli. It is observed that the single-crystal toughnesses are directly related to the elastic modulus. Polycrystalline and single-crystal toughnesses are comparable; however, the intergranular fracture has the lowest toughness. 相似文献
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7.
Masanori Hirano Mikimasa Imai Michio Inagaki 《Journal of the American Ceramic Society》2000,83(4):977-979
ZnGa2 O4 fine particles with a single phase of spinel were synthesized from a mixed solution of gallium sulfate and zinc sulfate in the presence of aqueous ammonia under hydrothermal conditions above 180°C. The effects of treatment temperature and ZnO/Ga2 O3 molar ratio in the starting solution on the crystallite size, morphology, lattice parameter, and chemical composition of the ZnGa2 O4 spinel particles were examined. Spinel with different morphologies, cubic nanoparticles, and elongated rodlike particles were thought to be formed based on the structure of amorphous gallium hydroxide and needlelike GaO(OH) particles, respectively. By treatment at a higher temperature, these particles with nonstoichiometric composition grew large and thick, and their composition approached ZnO/Ga2 O3 = 1. With an increase in the starting ZnO/Ga2 O3 molar ratio, the lattice parameter of the synthesized ZnGa2 O4 spinel approached the reported value for the stoichiometric composition and reached a = 0.8335 nm at ZnO/Ga2 O3 = 1.95 by treatment at 240°C for 50 h. 相似文献
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9.
We report for the first time the synthesis of Li4 SiO4 by the modified combustion method, a rapid chemical process that takes 5 min for completion. This method uses nonoxidizer compounds instead of nitrate mixtures, which are not always commercially available.
The effects of the following parameters on the production of Li4 SiO4 were studied: (1) different lithium hydroxide:silicic acid:urea (LiOH:H2 SiO3 :CH4 N2 O) molar ratios; (2) the presence of air flow in the furnace chamber; and (3) the furnace heating temperature. It was found that LiOH:H2 SiO3 :CH4 N2 O molar ratios 6:1:3 heated at 1100°C in the presence of additional air in the muffle chamber formed the best precursors to produce Li4 SiO4 . 相似文献
The effects of the following parameters on the production of Li
10.
Hiroya Yamashita Toshinobu Yoko Sumio Sakka 《Journal of the American Ceramic Society》1991,74(7):1668-1674
Li2 B4 O7 films, a promising material for surface acoustic wave devices, were prepared by the sol—gel method using metal alkoxide precursors as starting materials. The Li2 B4 O7 films on silicon (100) and (111) single crystals prepared from a coating solution to which acetic or hydrochloric acid was added were highly oriented along the (122) plane, whereas those without acid additive were randomly oriented. The results were interpreted based on the basic sol-gel chemistry and the lattice matching between the film and substrate. 相似文献
11.
Heon-Jin Choi Ki-Min Lee Gyeung-Ho Kim June-Gunn Lee 《Journal of the American Ceramic Society》2001,84(1):242-244
Spinel LiMn2 O4 as a cathode material for lithium secondary batteries has been synthesized by a mechanochemical process, and its electrochemical properties have been characterized. Highly disordered nanocrystalline LiMn2 O4 powders have been prepared by the mechanochemical processing of Li2 O and MnO2 powder mixtures for 24 h. Electrochemical characterization of mechanochemically processed powder has shown that the intercalation of Li+ takes place with an initial capacity of 167 mA·h/g in the 2.5–4.3 V range and has better capacity retention as compared to the well-ordered crystalline LiMn2 O4 powders. The better capacity retention of the mechanochemically processed LiMn2 O4 powder may be attributed to the highly disordered structure that could accommodate the Jahn–Teller distortion of the spinel structure during Li+ intercalation around the 3 V region. 相似文献
12.
Marin Cernea Elena Chirtop Dana Neacsu Iuliana Pasuk Sergiu Iordanescu 《Journal of the American Ceramic Society》2002,85(2):499-503
A barium titanate precursor with a barium:titanium ratio of 1:4 was prepared by controlled coprecipitation of mixed barium and titanium species with an ammonium oxalate aqueous solution at pH 7. The results of thermal analysis and IR measurement show that the obtained precursor is a mixture of BaC2 O4 ·0.5H2 O and TiO(OH)2 ·1.5H2 O in a molar ratio of 1:4. Crystallized BaTi4 O9 was obtained by the thermal decomposition of a precipitate precursor at 1300°C for 2 h in air. The dimensions of the powder calcined at 1000°C are between 100 and 300 nm. The grain dimensions of the sintered sample for 2 h at 1300°C are of the order of 10 to 30 μm. Dielectric properties of disk-shaped sintered specimens in the microwave frequency region were measured using the TE011 mode. Excellent microwave characteristics for BaTi4 O9 —ɛ= 38 ± 0.5, Q = 3800–4000 at 6–7 GHz and τ f = 11 ± 0.7 ppm/°C—were found. 相似文献
13.
Si3 N4 /MoSi2 and Si3 N4 /WSi2 composites were prepared by reaction-bonding processes using as starting materials powder mixtures of Si-Mo and Si-W, respectively. A presintering step in an At-base atmosphere was used before nitriding for the formation of MoSi2 and WSi2 ; the nitridation in a N2 -base atmosphere was followed after presintering with the total stepwise cycle of 1350°C × 20 h +1400°C × 20 h +1450°C × 2 h. The final phases obtained in the two different composites were Si3 N4 and MoSi2 or WSi2 ; no free elemental Si and Mo or W were detected by X-ray diffraction. 相似文献
14.
Yoshiaki Kinemuchi Ping Hua Xiang Hisashi Kaga Koji Watari 《Journal of the American Ceramic Society》2007,90(9):2753-2758
The preferred orientation of thick films prepared by paste printing is rarely observed because of their bulky polycrystalline nature. We found that a Bi4 Ti3 O12 thick film with a thickness of ca. 20 μm showed c -axis-preferred orientation. Initially, the texture of the screen-printed film was found to have a random orientation, which was attributed to the equiaxed particle shape of the raw powder synthesized by the co-precipitation method. During subsequent heating, c -axis orientation emerged in which the degree of orientation was proportional to the film density. Analysis of the orientation distribution revealed that the progress of texturing was attributed to the film deformation, indicating that anisotropic shrinkage and morphological changes in particles during heating influenced the preferred orientation. 相似文献
15.
A highly stable, water-based barium titanate BaTiO3 , BT, sol was synthesized using a sol–gel route through a chelate lactate technique. Dried BT precursor powders were measured by thermal gravimetry–differential thermal analysis and X-ray diffraction. It was found that BT powders first converted into barium carbonate BaCO3 , Ti complex, and intermediate phase Ba2 Ti2 O5 CO3 , and then transformed into perovskite phase BaTiO3 . The crystallization temperature was about 550°C. The low-voltage etched aluminum foils were covered with BT sol by dip coating, and then annealed at 600°C for 30 min in air. After that, the samples were anodized in a 15 wt% aqueous solution of ammonium adipate. The voltage–time variations during anodizing were monitored, and the electrical properties of the anodic oxide film were examined. It was shown that the specific capacitance, the product of specific capacitance and withstanding voltage, and leakage current of samples with a BT coating were about 48.93%, 38.50%, and 167% larger than that without a BT coating, respectively. 相似文献
16.
Tongjun Liu Zhengguo Jin Jingxia Yang Lirui Feng 《Journal of the American Ceramic Society》2008,91(6):1939-1944
Nanocrystalline SnO2 films were prepared from SnC2 O4 by a sol–gel route. A clarified and stable Sn-containing sol was obtained by dissolving and chelating SnC2 O4 with C6 H8 O7 and H2 C2 O4 in a C6 H8 O7 /triethanolamine (TEA) mixing aqueous solution with a pH of 6.5–7.0. The chelation and condensation reactions were deducted based upon infrared, Raman, and X-ray photoelectron spectra analysis. Results illuminated that a number of ionized-state carboxyl groups and active tin hydrate were produced in the mixing solution by amido association of TEA with H on –COOH of H3 L and H2 C2 O4 , supplying a precondition for tin sol formation. X-ray diffraction and field emission scanning electron microscope analysis indicated that SnO2 film had a rutile structure and consisted of nanocrystals with a mean size of about 7 nm. Film thickness could be controlled by the number of dip coating—annealing cycles according to 30–45 nm/cycle for a Sn concentration of 0.25 mol/L. 相似文献
17.
I. Prakash P. Muralidharan N. Nallamuthu N. Satyanarayana M. Venkateswarlu David Carnahan 《Journal of the American Ceramic Society》2006,89(7):2220-2225
NiAl2 O4 /SiO2 and Co2+ -doped NiAl2 O4 /SiO2 nanocomposite materials of compositions 5% NiO – 6% Al2 O3 – 89% SiO2 and 0.2% CoO – 4.8% NiO – 6% Al2 O3 – 89% SiO2 , respectively, were prepared by a sol–gel process. NiAl2 O4 and cobalt-doped NiAl2 O4 nanocrystals were grown in a SiO2 amorphous matrix at around 1073 K by heating the dried gels from 333 to 1173 K at the rate of 1 K/min. The formations of NiAl2 O4 and cobalt-doped NiAl2 O4 nanocrystals in SiO2 amorphous matrix were confirmed through X-ray powder diffraction, Fourier transform infrared spectroscopy, differential scanning calorimeter, transmission electron microscopy (TEM), and optical absorption spectroscopy techniques. The TEM images revealed the uniform distribution of NiAl2 O4 and cobalt-doped NiAl2 O4 nanocrystals in the amorphous SiO2 matrix and the size was found to be ∼5–8 nm. 相似文献
18.
Jun Zhou Junfeng Ma Chong Sun Lijin Xie Zhongqiang Zhao Hua Tian Yonggang Wang Jiantao Tao Xiaoyi Zhu 《Journal of the American Ceramic Society》2005,88(12):3535-3537
Nickel ferrite (NiFe2 O4 ) nanoparticles were successfully synthesized via a hydrothermal process and characterized by X-ray diffraction and transmission electron microscope techniques. The effects of reaction temperature, holding time, and RH ratio (isopropyl alcohol/water) were discussed. The NiFe2 O4 nanoparticles could be obtained at 60°C within 3 h. The crystallization of the spinel ferrites was promoted by the increase in reaction temperature, holding time, and RH ratio. 相似文献
19.
Un-Yeon Hwang Hyung-Sang Park Kee-Kahb Koo 《Journal of the American Ceramic Society》2004,87(12):2168-2174
The synthesis of spherical BaTiO3 particles was attempted by a new technique, the "gel–sol method," at 45°C. The (Ba–Ti) gel used as a starting material was prepared by aging mixtures of titanyl acylate with a barium acetate aqueous solution ([glacial acetic acid (AcOH)]/[titanium isopropoxide (TIP)] = 4, [barium acetate]/[TIP] = 1) at 45°C for 48 h. Potassium hydroxide (KOH) was used as a catalyst for the formation of BaTiO3 . Powder X-ray diffractometry (XRD) results and Fourier-transform infrared (FT-IR) measurements for the (Ba–Ti) gel showed that the gel was amorphous, but the spatial arrangement of barium and titanium in the (Ba–Ti) gel is similar to that in crystalline BaTiO3 particles. Fully crystallized spherical BaTiO3 powder with a particle size of 40–250 nm formed at the very low reaction temperature of 45°C. Scanning electron microscopy images showed that the final particles formed via aggregation of the fine particles that seem to be the primary particles of bulk (Ba–Ti) gel. From the XRD, FT-IR, and Raman spectroscopy analysis, it was found that the crystal structure of the as-prepared particles continuously transformed from cubic to tetragonal as the calcination temperature increased, and high crystalline tetragonal BaTiO3 phase was obtained at 1000°C after 1 h of heat treatment. 相似文献
20.
Jong-Jin Choi Jungho Ryu Byung-Dong Hahn Woon-Ha Yoon Dong-Soo Park 《Journal of the American Ceramic Society》2008,91(8):2756-2758
Metallic conductive LaNiO3 thick films with a thickness of 0.5–10 μm were fabricated by a room-temperature-operating powder deposition process—aerosol deposition method. The coated LaNiO3 layers were fairly dense without pores or cracks, and maintained their phase stability due to low-temperature consolidation. The as-deposited LaNiO3 film consisted of ∼10-nm-diameter grains, with a sheet resistance of 10–100 Ω/□, while the post-annealed LaNiO3 film had a sheet resistance of 4.45 Ω/□, which is the lowest value ever reported for an LaNiO3 film. This excellent conductivity result was attributed to the high crystal stability and dense microstructure. 相似文献