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1.
BaFe12O19 hexaferrite films have been produced on thermally oxidized single-crystal silicon (SiO2/Si) substrates by sequential ion-beam sputtering of BaFe2O4 and α-Fe2O3 targets in an argon-oxygen atmosphere. Their crystal structure has been studied, and the origin of the impurity phases forming during heat treatment has been identified. The results show that heat treatment may lead to the formation of eutectic melts. As a result, the hexaferrite films may contain spherulites. 相似文献
2.
The dc conductivity of the glasses in the Fe2O3-Bi2O3-K2B4O7 system was studied at temperatures between 223 and 393 K. At temperatures from 300 to 223 K, T–1/4 (T is temperature) dependence of the conductivity was found, however, both Mott variable-range hopping and Greaves intermediate range hopping models are found to be applicable. Mott and Greaves parameters analysis gave the density of states at Fermi level N (EF) = 3.13 × 1020–21.01 × 1020 and 1.93 × 1021–16.39 × 1021 cm–3eV–1 at 240 K, respectively. The variable-range hopping conduction occurred in the temperature range T = 300–223 K, since WD was found to be large (WD = 0.08–0.14 eV for these glasses) and dominated the conduction at T < 300 K. 相似文献
3.
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
4.
Differential thermal analysis and x-ray diffraction data indicate that the ZnO B2O3-CuO B2O3 join of the ternary system CuO-B2O3-ZnO is pseudobinary, with eutectic phase relations and a liquid-liquid miscibility gap in the composition range 25–35 mol % CuO.Translated from Neorganicheskie Materialy, Vol. 41, No. 3, 2005, pp. 339–340.Original Russian Text Copyright © 2005 by Kasumova, Bananyarly.This revised version was published online in April 2005 with a corrected cover date.This revised version was published online in April 2005 with a corrected cover date. 相似文献
5.
Semih Seyyidoğlu Macit Özenbaş Necmeddin Yazıcı Ayşen Yılmaz 《Journal of Materials Science》2007,42(15):6453-6463
In this study, ZrP2O7 was synthesized by the solid state reaction of ZrO2 and NH4H2PO4 at 900 °C. Then, in set 1; 10, 5, 1, 0.5, 0.1, 0.05, 0.03% previously prepared Sr2P2O7 were doped into ZrP2O7, and Sr2P2O7 slightly affect the unit cell parameter of cubic ZrP2O7 (a = 8.248(6)–8.233(8) Å). The reverse of this process was also applied to Sr2P2O7 system (set 2). ZrP2O7 changes the unit cell parameters of orthorhombic Sr2P2O7 in between a = 8.909(5)–8.877(5) Å, b = 13.163(3)–13.12(1) Å, and c = 5.403(2)–5.386(4) Å. Analysis of the vibrations of the P2O 7 4? ion and approximate band assignments for IR and Raman spectra are also reported in this work. Some coincidences in infrared and Raman spectra both sets were found and strong P–O–P bands were observed. Surface morphology, EDX analysis, and thermoluminescence properties of both sets were given the first time in this paper. 相似文献
6.
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
7.
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
8.
Gadolinium doped bismuth borate glasses containing up to 30 mol% Y2O3 were prepared by fast melt quenching method. The effect of yttrium on the local order in 3B2O3 · Bi2O3 and B2O3 · Bi2O3 glass matrices, particularly on the bismuth sites, was investigated by infrared (IR) spectroscopy and electron paramagnetic
resonance (EPR) of Gd3+ ions. The IR results show that the local structure is more ordered in the glass system with higher bismuth content and the
progressive addition of yttrium increases the local disorder in both bismuth–borate glass matrices. The EPR results indicate
that Gd3+ ions occupy both bismuth and yttrium sites and reflect the same structural disorder like that suggested by IR results. 相似文献
9.
Wookyung Sung Jinho Kim Seongjin Hwang Hyungsun Kim 《Journal of Materials Science》2008,43(12):4016-4021
The properties of the composite, having a complicated microstructure, are decided by many factors such as those of glass matrix,
crystal phases, fillers, and holes. We investigated how the addition of ceramic fillers to the glass matrix affects the mechanical
and etching properties of the glass composite by forming new crystal phases. Different amounts of two fillers, ZnO and Al2O3, were added to a glass frit consisting of Bi2O3–ZnO–B2O3. It was sintered at 550 °C for 30 min. Based on the results of this study, the porosity and degree of crystallization of
the composites could be controlled by adjusting the content of the ZnO and Al2O3 fillers. Therefore, porosity and degree of crystallization formed by the reaction between a glass matrix and fillers influence
the mechanical and etching properties of the composite. 相似文献
10.
FTIR spectroscopy has been employed to investigate the structure of CaF2–B2O3 glasses. It is proposed that CaF2 partially modifies the borate network forming
\textCa 1 / 2 2+ [\textBO 3 / 2 \textF] - {\text{Ca}}_{ 1 / 2}^{ 2+ } [{\text{BO}}_{ 3 / 2} {\text{F]}}^{ - } units. The rest of CaF2 is assumed to build an amorphous network formed of CaF4 tetrahedra. Analysis of density and molar volume revealed that the volume of CaF4 tetrahedron in the studied glasses is slightly greater than that in the crystalline form. Data of density, molar volume,
and electric conductivity have been correlated with the glass structure. As far as the authors know, CaF2–B2O3 glasses are investigated for the first time. 相似文献
11.
Laura Londaitzbéhère Sylvie Lartigue-Korinek Leo Mazerolles 《Journal of Materials Science》2017,52(10):5489-5502
New compositions in the melt-grown eutectic ceramics field are investigated for thermomechanical applications. This paper is focused on the Al2O3–Sm2O3–(ZrO2) system. The studied compositions give rise to interconnected microstructures without anisotropy along the growth direction. At variance with the binary eutectic Al2O3–SmAlO3, the homogeneity of the microstructure of the Al2O3–SmAlO3–ZrO2 ternary eutectic is less sensitive to the growth rate. Interfaces between the alumina and perovskite phases are investigated by high-resolution transmission electron microscopy (TEM). They are semi-coherent. In stepped interfaces, the facets are parallel to dense planes of each phase. The steps have a dislocation character and may accommodate both misfits. The ternary eutectic displays a very good creep behaviour with strain rates very close to those obtained on other previously studied eutectics in the Al2O3–RE2O3(RE = Y, Gd, Er)–ZrO2 systems. The deformation micromechanisms are analysed by TEM in the three eutectic phases. After creep, dislocations are present in every phase. The activation of unusual slip systems (pyramidal slip in the alumina phase) shows that high local stresses can be reached. The presence of dislocation networks with low energy configurations is consistent with predominance of dislocation climb processes controlled by bulk diffusion. 相似文献
12.
D. S. Lipatov A. N. Guryanov M. V. Yashkov M. M. Bubnov M. E. Likhachev 《Inorganic Materials》2018,54(3):276-282
An all-vapor phase MCVD process has been proposed for the fabrication of fiber preforms with a Yb2O3–Al2O3–P2O5–SiO2 multicomponent glass core. We have investigated the tubular preform collapse into a rod and demonstrated approaches capable of preventing P2O5 losses in the central part of the core during the collapse process. Preforms with a flat, perfect step-index profile have been fabricated. 相似文献
13.
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
14.
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
15.
I. V. Kulbakin A. A. Solovieva S. V. Fedorov V. V. Artemov V. V. Belousov 《Inorganic Materials》2018,54(10):1055-1061
A NiV2O6–25 wt % V2O5 molten-oxide material has been prepared and characterized, and its transport properties (electrical conductivity, oxygen ion transport number, and oxygen permeability) have been studied in the temperature range 680–700°C. The results demonstrate that the molten-oxide membrane material obtained possesses high selective oxygen permeability (KO2 = (2.5–5.6) × 10–10 mol/(cm s) in the range 680–740°C and \(\frac{{{j_{{O_2}}}}}{{{j_{{N_2}}}}}\) ~ 1500) and can be used in separators for the preparation of extrapure oxygen from air. 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.
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
18.
HIMANSHU TRIPATHI AREPALLI SAMPATH KUMAR S P SINGH 《Bulletin of Materials Science》2016,39(2):365-376
The aim of the present investigation was to study the role of Al2O3 in the Li2O–CaO–P2O5–SiO2 bioactive glass for improving the bioactivity and other physico-mechanical properties of glass. A comparative study on structural and physico-mechanical properties and bioactivity of glasses were reported. The structural properties of glasses were investigated by X-ray diffraction, Fourier transform infrared spectrometry, scanning electron microscopy and the bioactivity of the glasses was evaluated by in vitro test in simulated body fluid (SBF). Density, compressive strength, Vickers hardness and ultrasonic wave velocity of glass samples were measured to investigate physical and mechanical properties. Results indicated that partial molar replacement of Li2O by Al2O3 resulted in a significant increase in mechanical properties of glasses. In vitro studies of samples in SBF had shown that the pH of the solution increased after immersion of samples during the initial stage and then after reaching maxima it decreased with the increase in the immersion time. In vitro test in SBF indicated that the addition of Al2O3 up to 1.5 mol% resulted in an increase in bioactivity where as further addition of Al2O3 caused a decrease in bioactivity of the samples. The biocompatibility of these bioactive glass samples was studied using human osteoblast (MG-63) cell lines. The results obtained suggested that Li2O–CaO–Al2O3–P2O5–SiO2-based bioactive glasses containing alumina would be potential materials for biomedical applications. 相似文献
19.
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
20.
xV2O5·(100 − x)[0.7P2O5·0.3CaO] glass system was obtained for 0 ≤ x ≤ 35 mol% V2O5. In order to obtain information regarding their structure, several techniques such as X-Ray diffraction, FT-IR, and EPR spectroscopies
were used. X-Ray diffraction patterns of investigated samples are characteristic of vitreous solids. FT-IR spectra of 0.7P2O5·0.3CaO glass matrix and its deconvolution show the presence in the glass structure of all structural units characteristic
to P2O5. Their number are increasing for x ≤ 3 mol% V2O5 then, for higher content of vanadium ions, the number of phosphate structural units are decreasing leading to a depolymerization
of the structure. The structural units characteristic to V2O5 were not evidenced but their contribution to the glass structure can be clearly observed. EPR revealed a well resolved hyperfine
structure (hfs) typical for vanadyl ions in a C4v symmetry for x ≤ 3 mol% V2O5. For 5 < x < 20 mol% V2O5 the spectra show a superposition of two EPR signals one due to a hfs structure and another consisting of a broad line typical
for associated V4+–V4+ ions. For x ≥ 20 mol% V2O5 only the broad line can be observed. The composition dependence of the line-width suggests the presence of dipole–dipole
interaction between vanadium ions up to x ≤ 5 mol% V2O5 and superexchange interactions between vanadium ions for x > 5 mol% V2O5. 相似文献