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1.
Keisuke Yasuda Toshiyuki Masui Takahiro Miyamoto Nobuhito Imanaka 《Journal of Materials Science》2011,46(11):4046-4052
Catalytic combustion of methane was investigated on Pt and PdO-supported CeO2–ZrO2–Bi2O3/γ-Al2O3 catalysts prepared by a wet impregnation method in the presence of polyvinylpyrrolidone. The catalysts were characterized
by X-ray fluorescence analysis, X-ray powder diffraction, X-ray photoelectron spectra, transmission electron microscopy, and
BET specific surface area measurements. The Pt/CeO2–ZrO2–Bi2O3/γ-Al2O3 and PdO/CeO2–ZrO2–Bi2O3/γ-Al2O3 catalysts were selective for the total oxidation of methane into carbon dioxide and steam, and no by-products such as HCHO,
CO, and H2 were obtained. The catalytic activities of the PdO/CeO2–ZrO2–Bi2O3/γ-Al2O3 catalysts were relatively higher than those of the Pt-supported catalysts, due to the facile re-oxidation of metallic Pd
into PdO based on lattice oxygen supplied from the CeO2–ZrO2–Bi2O3 bulk. A decrease in the calcination temperature during the preparation process was found to be effective in enhancing the
specific surface area of the catalysts, whereby particle agglomeration was inhibited. Optimization of the PdO amount and calcination
temperature enabled complete oxidation of methane at temperatures as low as 320 °C on the 11.6 wt% PdO/CeO2–ZrO2–Bi2O3/γ-Al2O3 catalyst prepared at 400 °C. 相似文献
2.
3.
A new method has been proposed for the synthesis of catalytically active 80 wt % SnO2 + 20 wt % CeO2 materials supported on glass fiber, which involves the use of an ethanolic film-forming solution based on cerium(III) nitrate and salicylic acid, with the addition of tin(IV) chloride. We have studied the morphology of the materials thus prepared and assessed their catalytic activity for the deep oxidation of methane. The results indicate that the appreciable catalytic activity of the materials is ensured by their uniform distribution over the support surface and the small oxide aggregate size ( 10 μm), which is due to the use of the filmforming solution of the proposed composition. 相似文献
4.
E. V. Dudnik A. V. Shevchenko A. K. Ruban V. P. Red’ko L. M. Lopato 《Inorganic Materials》2008,44(4):409-413
Using hydrothermal treatment of coprecipitated hydroxides, we have prepared nanocrystalline ZrO2-rich ZrO2-Y2O3-CeO2-Al2O3 powder. The effect of heat treatment on the properties of the powder has been studied in the temperature range 400–1300°C. The powder has been shown to have a metastable phase composition, which is attributable to structural and size factors and also to the fact that the ZrO2 and Al2O3 crystallites inhibit the growth of each other. Sintering the powder under various conditions, we have obtained ceramics with fracture toughnesses from 6.4 to 16.8 MPa m1/2. 相似文献
5.
L. I. Podzorova A. A. Il’icheva O. I. Pen’kova V. P. Sirotinkin O. S. Antonova A. A. Konovalov 《Inorganic Materials》2018,54(5):454-459
We have studied phase formation in calcium-modified Al2O3–ZrO2–CeO2 nanopowders during sol–gel synthesis. The results demonstrate that heat treatment of the nanopowders first leads to the formation of a zirconium dioxide-based solid solution stabilized with cerium cations. Raising the heat treatment temperature helps the crystallization of corundum, a stable phase of aluminum oxide, to reach completion. In the temperature range 1400–1550°C, we observe the formation of a second aluminum-containing phase: calcium cerium hexaaluminate consisting of long prismatic grains. 相似文献
6.
M. Alfano G. Di Girolamo L. Pagnotta D. Sun J. Zekonyte R. J. K. Wood 《Journal of Materials Science》2010,45(10):2662-2669
In this study, ceria–yttria co-stabilized zirconia (CYSZ) free-standing coatings, deposited by air plasma spraying (APS),
were isothermally annealed at 1315 °C in order to explore the effect of sintering on the microstructure and the mechanical
properties (i.e., hardness and Young’s modulus). To this aim, coating microstructure, before and after heat treatment, was
analyzed using scanning electron microscopy, and image analysis was carried out in order to estimate porosity fraction. Moreover,
Vickers microindentation and depth-sensing nanoindentation tests were performed in order to study the evolution of hardness
and Young’s modulus as a function of annealing time. The results showed that thermal aging of CYSZ coatings leads to noticeable
microstructural modifications. Indeed, the healing of finer pores, interlamellar, and intralamellar microcracks was observed.
In particular, the porosity fraction decreased from ~10 to ~5% after 50 h at 1315 °C. However, the X-ray diffraction analyses
revealed that high phase stability was achieved, as no phase decomposition occurred after thermal aging. In turn, both the
hardness and Young’s modulus increased, in particular, the increase in stiffness (with respect to “as produced” samples) was
equal to ~25%, whereas the hardness increased to up to ~60%. 相似文献
7.
Wilfried Hermes Stefan Linsinger Sudhindra Rayaprol Selcan Tuncel Rolf-Dieter Hoffmann Reinhard K. Kremer Ove Jepsen Rainer Pöttgen 《Journal of Superconductivity and Novel Magnetism》2011,24(5):1585-1592
The intermetallic compounds RE
2Cu2Mg and RE
2Pd2Mg (RE=La, Ce) were prepared and characterized by magnetic susceptibility and heat-capacity measurements. They crystallize with
an ordered U3Si2 type structure (space group P4/mbm) and the cerium compounds contain stable trivalent cerium ions, which undergo antiferromagnetic ordering at ∼7.5 and ∼4 K,
respectively. In high magnetic fields Ce2Cu2Mg exhibits spin reorientation with critical field strength of 40 kOe at 5 K. The data are compared to the non-magnetic isotypic
compounds La2
T
2Mg (T=Cu, Ni, Pd) and to the already reported intermediate valent Ce2Ni2Mg. 相似文献
8.
E. V. Dudnik A. V. Shevchenko A. K. Ruban Z. A. Zaitseva L. M. Lopato 《Inorganic Materials》2008,44(5):510-514
We have studied the evolution of nanocrystalline 80 wt % Al2O3-20 wt % ZrO2〈CeO2, Y2O3〉 powder prepared through hydroxide coprecipitation followed by hydrothermal decomposition of the hydroxides and firing at temperatures from 400 to 1300°C. α-Al2O3 has been shown to form at 850°C. The metastable phase F-ZrO2 persists up to this temperature. The variation in the morphology of the powder is topologically continuous. The processes induced by heat treatment of the nanocrystalline powder are interpreted in terms of the evolution of an open system. 相似文献
9.
E. N. Galashov V. V. Atuchin T. A. Gavrilova I. V. Korolkov Y. M. Mandrik A. P. Yelisseyev Zhiguo Xia 《Journal of Materials Science》2017,52(22):13033-13039
Garnet phosphor Y3Al5O12:Ce3+ is prepared in the Y2O3–Al metal–CeO2 ternary system by the solid-state reaction method in the air. For the first time, metal Al is used as a source of aluminum for the reaction instead of traditional oxide Al2O3. It is shown that the chemical reaction can be realized at lower temperatures and without use of special reducing atmosphere. The structural and spectroscopic properties of the prepared powder phosphor are very close to those earlier reported for the Y3Al5O12:Ce3+ single crystal. 相似文献
10.
Song Chen Shuren Zhang Xiaohua Zhou Bo Li 《Journal of Materials Science: Materials in Electronics》2011,22(3):238-243
The low-temperature co-fired ceramic (LTCC) composites containing quartz based on the eutectic system BaO–Al2O3–SiO2–B2O3 are fabricated at the sintering temperature below 980 °C. Preparation process and sintering mechanism were described and
discussed, respectively. The results indicated that the addition of quartz to the eutectic system can availably improve dielectric
properties of the LTCC composites. In addition, The LTCC composites with optimum compositions, which were obtained by the
regulation of an Al2O3 content in the composite, can express excellent dielectric properties (permittivity: 5.94, 5.48; loss: 7 × 10−4, 5 × 10−4), considerable CTE values (11.7 ppm. °C−1, 10.6 ppm. °C−1) and good mechanical properties (128 MPa,133 MPa). 相似文献
11.
Wenbo Yue Xiaoxiang Xu Zixue Su John T. S. Irvine Yongcun Zou Yunling Liu Wuzong Zhou 《Journal of Materials Science》2012,47(5):2146-2154
Two mesoporous oxide composites of Nd2O3–SiO2 and NdOCl–SiO2 were synthesized using SBA-15 as a template and neodymium nitrate or neodymium chloride as a precursor. The porous Nd2O3–SiO2 with a SBA-15-like structure has amorphous walls and the porous NdOCl–SiO2 with a replicated structure of SBA-15 has crystalline walls. These porous materials were characterized by X-ray diffraction,
transmission electron microscopy and nitrogen adsorption/desorption. They exhibited significant proton conductivities in the
presence of moisture at low temperatures and the highest conductivity observed was 4.55 × 10−4 S/cm at 47 °C in wet air (RH = 28.6%). 相似文献
12.
T. N. Kol’tsova 《Inorganic Materials》2010,46(3):242-250
The phase equilibria in the “CaAl2Si3O10”-Na2Al2Si3O10-H2O system are analyzed using structural and thermal analysis data, and the ideal gonnardite structure is modeled. The results
suggest that, to ensure a better correlation with the structures of the zeolites in this series, a new structural model of
the gonnardite-based solid solution must be selected, with the structure rotated through 45° about the c axis in the ab plane. 相似文献
13.
Shaaban M. Salem E. M. Antar A. G. Mostafa S. M. Salem S. A. El-badry 《Journal of Materials Science》2011,46(5):1295-1304
(10Li2O–20GeO2–30ZnO–(40-x)Bi2O3–xFe2O3 where x = 0.0, 3, 6, and 9 mol%) glasses were prepared. A number of studies, viz. density, differential thermal analysis, FT-IR spectra,
DC and AC conductivities, and dielectric properties (constant ε′, loss tan δ, AC conductivity, σ
ac, over a wide range of frequency and temperature) of these glasses were carried out as a function of iron ion concentration.
The analysis of the results indicate that, the density and molar volume decrease with an increasing of iron content indicates
structural changes of the glass matrix. The glass transition temperature T
g and onset of crystallization temperature T
x increase with the variation of concentration of Fe2O3 referred to the growth in the network connectivity in this concentration range, while glass-forming ability parameter ΔT decrease with increase Fe2O3 content, indicates an increasing concentration of iron ions that take part in the network-modifying positions. The FT-IR
spectra evidenced that the main structural units are BiO3, BiO6, ZnO4, GeO4, and GeO6. The structural changes observed by varying the Fe2O3 content in these glasses and evidenced by FTIR investigation suggest that the iron ions play a network modifier role in these
glasses while Bi2O3, GeO2, and ZnO play the role of network formers. The temperature dependence of DC and AC conductivities at different frequencies
was analyzed using Mott’s small polaron hopping model and, the high temperature activation energies have been estimated and
discussed. The dielectric constant and dielectric loss increased with increase in temperature and Fe2O3 content. 相似文献
14.
Hui-Juan Wang Tilman Zscheckel Bo-Tao Li Hui-Xing Lin Christian Bocker Christian Rüssel Lan Luo 《Journal of Materials Science》2017,52(3):1330-1347
Crystallization and microstructure of glasses with the molar compositions 1MgO·1.2Al2O3·2.8SiO2·1.2TiO2·xLa2O3 (x = 0.1 and 0.4) were thermally treated at different temperatures in the range from 950 to 1250 °C and then analyzed by X-ray diffraction and scanning electron microscopy, in combination with energy-dispersive X-ray spectroscopy and electron backscatter diffraction. It was found that the microstructure is first homogeneous with the precipitation of randomly distributed crystals and then indialite domains with embedded perrierite and rutile crystals are formed. For higher temperatures or prolonged times, more domains appear and expand into the bulk of the sample. Finally, the entire sample consists of the indialite domains and the boundaries that are enriched in rutile, perrierite, and magnesium aluminotitanate. Nevertheless, very distinct differences are observed between the samples with different La2O3 concentrations. For the sample with x = 0.4, the domains were detected at lower temperatures, while the quantity and size of the domains increase faster due to the promoted precipitation of indialite. For the sample with x = 0.1, in addition to the domain boundaries, secondary boundaries between the “regions” (assemblages of the domains) are observed in a larger length scale. The average size of the crystalline phases found between the “regions” is larger than that typically observed at the domain boundaries. The sizes of the crystals at the boundaries decrease with higher concentrations of La2O3, and the crystals (especially perrierite) within the domains become larger, resulting in a more homogeneous microstructure. This results in better dielectric properties, i.e., much higher quality factor for the sample with x = 0.4 in comparison to that with x = 0.1 after heat-treatment at 1150 or 1250 °C. 相似文献
15.
F. M. Sadygov T. M. Il’yasly G. T. Ganbarova V. P. Zlomanov I. I. Aliev 《Inorganic Materials》2017,53(7):665-669
We have studied phase relations in the Sb2Se3–Nd2Se3 system and mapped out its T–x phase diagram using differential thermal analysis, X-ray diffraction, microstructural analysis, microhardness tests, and density measurements. The system contains one compound, with the composition NdSbSe3, which melts incongruently at 865 K and crystallizes in orthorhombic symmetry with the following lattice parameters: а = 12.77(1) Å, b = 14.08(1) Å, and c = 5.82(5) Å (Z = 8, ρmeas = 6.20 g/cm3, ρx = 6.38 g/cm3). At room temperature, the Nd2Se3 solubility in Sb2Se3 is 5 mol % and the Sb2Se3 solubility in Nd2Se3 is 2.5 mol %. The Sb2Se3–Nd2Se3 system has a eutectic located at 15 mol % Nd2Se3, with a melting point at 755 K. The electrical conductivity and thermoelectric power of the (Sb2Se3)1–x (Nd2Se3) x solid solutions have been measured as functions of temperature. 相似文献
16.
Ekkehard Krüger 《Journal of Superconductivity and Novel Magnetism》2010,23(2):213-223
It is shown that the ceramic superconductor YBa2Cu3O7 as well as the superconducting intermetallic compound MgB2 possesses a narrow, partly filled “superconducting band” with Wannier functions of special symmetry in their band structures.
This result corroborates previous observations about the band structures of numerous superconductors and non-superconductors
showing that evidently superconductivity is always connected with such superconducting bands. These findings are interpreted
in the framework of a nonadiabatic extension of the Heisenberg model. Within this new group-theoretical model of correlated
systems, Cooper pairs are stabilized by a nonadiabatic mechanism of constraining forces effective in narrow superconducting
bands. The formation of Cooper pairs in a superconducting band is mediated by the energetically lowest boson excitations in
the considered material that carry the crystal-spin angular momentum 1⋅ℏ. These crystal-spin-1 bosons are proposed to determine whether the material is a conventional low-T
c or a high-T
c superconductor. This interpretation provides the electron–phonon mechanism that enters the BCS theory in conventional superconductors. 相似文献
17.
A. Bachvarova-Nedelcheva R. Iordanova L. Aleksandrov Y. Dimitriev M. AtaaLLa 《Journal of Materials Science》2011,46(22):7177-7183
The purpose of this work is to study the optical properties and crystallization of glasses in the ternary system Bi2O3–MoO3–B2O3. In order to verify the obtaining of bismuth borate crystal phases several glass compositions have been selected for crystallization.
The obtained samples were characterized by X-ray diffraction, scanning electron microscopy and UV–Vis spectroscopy. The UV–Vis
spectroscopy showed that the obtained glasses are transparent in the visible region. The values of optical band gap (E
opt) and changes in cut-off (λc) depending on composition are reported. It was established that the increase in the MoO3 content led to decreasing the transmittance of the glasses. Moreover, the absorption edge shifts towards longer wavelength. 相似文献
18.
Susumu Ikeno Kenji Matsuda Toshimasa Matsuki Toshiaki Suzuki Noriaki Endo Tokimasa Kawabata Yasuhiro Uetani 《Journal of Materials Science》2007,42(14):5680-5685
The formation mechanism of spinels on Al2O3 particles in the Al2O3/Al–1.0 mass% Mg2Si alloy composite material has been investigated by transmission electron microscopy (TEM) in order to determine the crystallographic
orientation relationship. A thin sample of the Al2O3/Al–Mg–Si alloy composite material was obtained by the FIB method, and the orientation relationship between Al2O3 and MgAl2O4, which was formed on the surface of Al2O3 particles, was discovered by the TEM technique as follows:
At the interface between the Al2O3 and the matrix the MgAl2O4 (spinel) crystals had facets of {111} planes. Spinels were not grown as thin films, but as particles consisting of {111}
planes. They grow towards both the matrix and the Al2O3 particles. 相似文献
19.
L. V. Morozova M. V. Kalinina M. Yu. Arsent’ev O. A. Shilova 《Inorganic Materials》2017,53(6):640-647
We have studied the influence of cryochemical and ultrasonic processing on the formation, structure, particle size, and thermal decomposition of xerogels in the ZrO2〈Y2O3〉–Al2O3 (20 wt %) system. Nanopowders of tetragonal-zirconia-based solid solutions with a high degree of tetragonality (c/a = 1.4366) have been synthesized. Al2O3 has been shown to slow down t-ZrO2 crystallite growth in the temperature range 600–1400°C. We have optimized nanopowder consolidation conditions, obtained nanoceramics stable to low-temperature “aging” in a humid medium, and investigated their physicochemical and mechanical properties. 相似文献
20.
X. Mantzouris G. Triantafyllou F. Tietz P. Nikolopoulos 《Journal of Materials Science》2008,43(22):7057-7065
Mixed oxides in the binary Y2O3–CeO2 (YC) and ternary Y2O3–CeO2–TiO2 (YCT) systems as well as the corresponding Ni cermets were evaluated in terms of application as anodes in solid oxide fuel
cells (SOFCs) between 650 and 900 °C. X-ray diffraction (XRD) analysis of the YCT powders calcined up to 1,400 °C showed the
cubic fluorite structure of YC and also the formation of an additional phase with pyrochlore structure. The thermal expansion
of the ceramics measured in air and Ar/4% H2 showed no significant differences in the temperature range of 25–800 °C. The absolute values of the total electrical conductivity
of the ceramics measured between 450 and 900 °C in Ar/4% H2 increased by about 1–2 orders of magnitude compared to those measured in air. Ni/Y0.20Ce0.80O1.9 and Ni/Y0.20C0.75Ti0.05O1.9 cermets with 40 vol% Ni exhibited improved long-term stability regarding their electrical conductivity after annealing at
1,000 °C. The diffusion coefficient of Ce in the 8YSZ electrolyte was measured by compatibility tests. Electrochemical measurements
on single SOFCs showed high polarization resistance at the anode/electrolyte interface. 相似文献