共查询到20条相似文献,搜索用时 156 毫秒
1.
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
2.
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
3.
S. Bindra Narang Shalini Bahel S. Dash 《Journal of Materials Science: Materials in Electronics》2010,21(11):1186-1190
The influences of Bi substitution on microwave dielectric properties of Ba4(La0.5Sm0.5)9.33Ti18O54 solid solutions were investigated. Dielectric ceramics with general formula Ba4(La(0.5−z)Sm0.5Bi
z
)9.33Ti18O54, z = 0.0–0.2 were prepared by conventional solid state route. The structural analysis of all the samples was carried out by
X-ray diffraction and scanning electron microscopy. The dielectric properties were investigated as a function of Bi contents
using open-ended coaxial probe method in the frequency range 0.3–3.0 GHz at room temperature. Dielectric constant varies from
83 to 88 and loss tangent from 2.1 × 10−3 to 5.5 × 10−3 at 3 GHz with temperature coefficient of resonant frequency changing from 106.7 to −8.4 ppm/oC as Bi contents increases from
z = 0.00–0.20. It has been found that dielectric constant and temperature coefficient of resonant frequency improve whereas
loss tangent is adversely affected with increase in Bi substitution. 相似文献
4.
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
5.
Rajendra Kumar Singh A. Srinivasan G. P. Kothiyal 《Journal of materials science. Materials in medicine》2009,20(1):147
Magnetic bioglass ceramics (MBC) are being considered for use as thermoseeds in hyperthermia treatment of cancer. While the bioactivity in MBCs is attributed to the formation of the bone minerals such as crystalline apatite, wollastonite, etc. in a physiological environment, the magnetic property arises from the magnetite [Fe3O4] present in these implant materials. A new set of bioglasses with compositions 41CaO · (52 ? x)SiO2 · 4P2O5 · xFe2O3 · 3Na2O (2 ≤ x ≤ 10 mol% Fe2O3) have been prepared by melt quenching method. The as-quenched glasses were then heat treated at 1050°C for 3 h to obtain the glass-ceramics. The structure and microstructure of the samples were characterized using X-ray diffraction and microscopy techniques. X-ray diffraction data revealed the presence of magnetite in the heat treated samples with x ≥ 2 mol% Fe2O3. Room temperature magnetic property of the heat treated samples was investigated using a Vibrating Sample Magnetometer. Field scans up to 20 kOe revealed that the glass ceramic samples had a high saturation magnetization and low coercivity. Room temperature hysteresis cycles were also recorded at 500 Oe to ascertain the magnetic properties at clinically amenable field strengths. The area under the magnetic hysteresis loop is a measure of the heat generated by the MBC. The coercivity of the samples is another important factor for hyperthermia applications. The area under the loop increases with an increase in Fe2O3 molar concentration and the. coercivity decreases with an increase in Fe2O3 molar concentration The evolution of magnetic properties in these MBCs as a function of Fe2O3 molar concentration is discussed and correlated with the amount of magnetite present in them. 相似文献
6.
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
7.
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
8.
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
9.
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
10.
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
11.
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
12.
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
13.
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
14.
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
15.
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
16.
Mechanical treatment of Fe2O3, Al and Fe powder mixtures was carried out in a high energy ball mill to synthesize Fe3Al–Al2O3 intermetallic matrix nanocomposite. Different compositions including 3Fe + Al, Fe2O3 + 2Al, 3Fe2O3 + 8Al and Fe2O3 + 3Al+Fe were chosen in this study. Phase development and structural changes occurring during ball milling were investigated
by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The results showed that during MA, Fe2O3, Al, and Fe react to give a nanocrystalline Fe3Al intermetallic compound matrix. The presence of pure Fe in initial powder mixture changed the modality of mechanochemical
process from sudden to gradual reaction. The Fe3Al–Al2O3 compound had a finer microstructure and particles size compared to the Fe3Al compound. 相似文献
17.
Bo Li Quanyin Long Dinan Duan 《Journal of Materials Science: Materials in Electronics》2016,27(3):2206-2211
BaO–B2O3–SiO2–Al2O3 (BBSA) glass/silica composites synthesized by solid-state reaction method were developed for CBGA packages, and the effects of sintering temperature (900–950 °C) on the phase transformation, microstructure, thermal, mechanical and electrical properties were investigated. XRD results show that the major phases quartz and cristobalite, and the minor phase BaSi2O5 are detected in BBSA composites. Furthermore, it was found that the quartz phase transforms to cristobalite phase at 930–940 °C. The formation of cristobalite phase with higher coefficient of thermal expansion (CTE) led to the increase of CTE value of BBSA composites. However, excessive cristobalite phase content would degrade the mechanical properties and the linearity of thermal expansion of the ceramics. BBSA composites sintered at 920 °C exhibited excellent properties: low dielectric constant and loss (εr = 6.2, tanδ = 10?4 at 1 MHz), high bending strength (179 MPa), high CTE (12.19 ppm/°C) as well as superior linearity of the thermal expansion. 相似文献
18.
In view of the potential engineering applications requiring machinability and wear resistance, the present work focuses to
evaluate hardness property and to understand the damage behavior of some selected glass–ceramics having different crystal
morphologies with SiO2–MgO–Al2O3–K2O–B2O3–F composition, using static micro-indentation tests as well as dynamic scratch tests, respectively. Vickers hardness of up
to 5.5 GPa has been measured in glass–ceramics containing plate like mica crystals. Scratch tests at a high load of 50 N in
artificial saliva were carried out in order to simulate the crack–microstructure interaction during real-time abrasion wear
and machining operation. The experimental observations indicate that the novel “spherulitic-dendritic” shaped crystals, similar
to the plate like crystals, have the potential to hinder the scratching induced crack propagation. In particular, such potential
of the ‘spherulitic-dendritic’ crystals become more effective due to the larger interfacial area with the glass matrix as
well as the dendritic structure of each mica plate, which helps in crack deflection and crack blunting, to a larger extent.
While modest damage tolerant behavior is observed in case of ‘spherulitic-dendritic’ crystal containing material, severe brittle
fracture of plate like crystals were noted, when both were scratched at 50 N load. 相似文献
19.
S. M. Abo-Naf R. L. Elwan M. A. Marzouk 《Journal of Materials Science: Materials in Electronics》2012,23(5):1022-1030
SiO2–PbO–Bi2O3 glasses having the composition of 35SiO2–xPbO–(65−x)Bi2O3 (where x = 5, 10, 15, 20, 25, 35, 45; in mol%) have been prepared using the conventional melting and annealing method. Density, molar
volume and Vickers microhardness of the prepared glasses were measured. Infrared (IR) and UV–visible spectroscopic techniques
were used for structural studies of these glasses. Density as well as the microhardness increase systematically and, conversely,
the molar volume decreases with increasing the lead oxide content. This behavior can be explained by the correlation with
the glass structure. Increasing the lead oxide content (≥20 mol%) increases the network former PbO4 groups which can play an important role in increasing the connectivity and compactness of the glass matrix via increasing
the cross-linking with the other constituent silicate and bismuthate structural units. The increased compactness may explain,
in turn, the increase of the density and microhardness. IR spectra reinforce the idea that bismuth participates in the glassy
network predominantly as BiO6 octahedral structural units. UV–VIS optical absorption spectra revealed UV-charge transfer absorption bands related to the
contribution of Pb2+ ions in the region 350–385 nm; in addition to the extrinsic absorption of trace iron impurities in the range 220–290 nm.
In the visible region, three optical bands in the ranges 415–435, 605–650 and 880–890 nm were correlated with the contribution
of electronic transitions in Bi3+ ions. Calculation of the optical mobility gap and the width of the energy tail of glass from the UV–VIS absorption indicated
a slight increase followed by a decrease in their values. The behavior change occurred at the glass in which PbO content is
20 mol% where lead oxide starts to participate into the glassy matrix as a network former. The combination of analytical FTIR
and UV–visible spectroscopy provided a consistent picture of structure–property relations in this glass system. 相似文献
20.
In this work, we have described the antibacterial activities of Fe3O4 nanoparticles with different organic parts, including Humic acid (HA), Nicotinic acid (Nico) and Histidine (His), and the antibacterial activity of MnFe2O4 nanoparticles coated with PANI and SiO2 against different bacteria and some standard antibacterial drugs. The present study revealed that the newly fabricated various Fe3O4 and MnFe2O4 nanocomposites, when combined with some different organic parts, are superiour antibacterial agents. Also, the synthesized nanocomposites can be easily separated from aqueous solution by magnetic filtration without any contamination of the medium. 相似文献