共查询到20条相似文献,搜索用时 46 毫秒
1.
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
2.
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
3.
Herein, we report the results of the in vitro dissolution tests, which were carried out by immersing the selected glass-ceramic samples in artificial saliva (AS) for various time periods of up to 42 days. In our experiments, the SiO(2)-MgO-Al(2)O(3)-K(2)O-B(2)O(3)-F glass ceramics with different crystal morphology and crystal content were used and a comparison is also made with the baseline glass samples (without any crystals). The bioactivity of the samples was probed by measuring the changes in pH, ionic conductivity and ionic concentration of AS following in vitro dissolution experiments. High resistance of the selected glass-ceramic samples against in vitro leaching has been demonstrated by minimal weight loss (<1%) and insignificant density change, even after 6 weeks of dissolution in artificial saliva. While XRD analysis reveals the change in surface texture of the crystalline phase, FT-IR analysis weakly indicated the Ca-P compound formation on the leached surface. The experimental measurements further indicate that the leaching of F(-), Mg(2+) ions from the sample surface commonly causes the change in the surface chemistry. Furthermore, the presence of (Ca, P, O)-rich mineralized deposits on the leached glass-ceramic surface as well as the decrease in Ca(2+) ion concentrations in the leaching solutions (compared to that in the initial AS solution) provide evidences of the moderate bioactive or mild biomineralisation behaviour of investigated glass-ceramics. 相似文献
4.
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
5.
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
6.
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
7.
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
8.
Tulyaganov DU Agathopoulos S Valerio P Balamurugan A Saranti A Karakassides MA Ferreira JM 《Journal of materials science. Materials in medicine》2011,22(2):217-227
New compositions of bioactive glasses are proposed in the CaO–MgO–SiO2–Na2O–P2O5–CaF2 system. Mineralization tests with immersion of the investigated glasses in simulated body fluid (SBF) at 37°C showed that
the glasses favour the surface formation of hydroxyapatite (HA) from the early stages of the experiments. In the case of daily
renewable SBF, monetite (CaHPO4) formation competed with the formation of HA. The influence of structural features of the glasses on their mineralization
(bioactivity) performance is discussed. Preliminary in vitro experiments with osteoblasts’ cell-cultures showed that the glasses
are biocompatible and there is no evidence of toxicity. Sintering and devitrification studies of glass powder compacts were
also performed. Glass-ceramics with attractive properties were obtained after heat treatment of the glasses at relatively
low temperatures (up to 850°C). 相似文献
9.
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
10.
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
11.
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
12.
Sabrina Seidel Marc Dittmer Wolfgang Wisniewski Wolfram Höland Christian Rüssel 《Journal of Materials Science》2017,52(4):1955-1968
High-strength, colorless glass–ceramics in the MgO/Al2O3/SiO2 system with high concentrations of ZrO2 and a great potential for technical application, e.g., as high-performance hard disc substrates, are investigated. ZrO2 concentrations from 6 to 9 mol% are added to a stoichiometric cordierite glass to investigate the influence of the concentration of the nucleating agent on the crystallization behavior and the mechanical properties. The phase formation and the microstructure of the glass–ceramics are studied using X-ray diffraction and scanning electron microscopy including electron backscatter diffraction. It is shown that the volume crystallization of ZrO2, a low-/high-quartz solid solution (low-/high-QSS), and spinel is accompanied by the surface crystallization of indialite. This phase offers a much smaller coefficient of thermal expansion than the other crystal phases, which may induce high compressive stresses in the surface layer of the glass–ceramics after cooling and seems to result in excellent mechanical properties of the material. Biaxial flexural strengths of up to 1 GPa were measured. Higher ZrO2 concentrations reduce the surface crystallization of indialite and decrease the mean size of the crystals resulting in a higher translucency. The volume-crystallizing phases and the mechanical properties of the glass–ceramics do not seem to be significantly affected by the analyzed ZrO2 concentrations. 相似文献
13.
This paper presents a detailed study of phase formation processes in the AgNO3–Sb2O3–MoO3 system during heating in air. The compositions of the solid-state reaction products have been determined using thermogravimetry and qualitative X-ray diffraction. The results demonstrate that, at a final heat treatment temperature of 1023 K, synthesis yields a range of Ag2–xSb2–xMo x O6 compounds with the pyrochlore structure and 0.0 ≤ x ≤ 2.0. The structural parameters of the synthesized phases have been refined by the Rietveld method in space group Fd3?m and their electrical conductivity has been measured. 相似文献
14.
A. V. Logvinova B. G. Bazarov Yu. L. Tushinova J. G. Bazarova 《Inorganic Materials》2017,53(12):1286-1292
We have studied phase relations in the K2MoO4–Ln2(MoO4)3–Zr(MoO4)2 (Ln = La–Lu, Y) systems by the method of “intersecting cuts,” identified pseudobinary joins in their composition triangles, and constructed their phase compatibility diagrams. The systems have been shown to contain new ternary molybdates with the general formula K5LnZr(MoO4)6 (Ln = Dy–Lu and Y). The thermal characteristics of the synthesized compounds have been studied by differential scanning calorimetry in the temperature range 25–700°C. The new ternary molybdates crystallize in a trigonal structure (sp. gr. R\(\bar 3\)c, Z = 6). 相似文献
15.
The Tl2Te–Tl5Te3–Tl9TbTe6 system has been studied using differential thermal analysis, X-ray diffraction, and microhardness measurements. We have mapped out a number of vertical sections, the 680 K isothermal section of its phase diagram, and projections of its polythermal projections of its liquidus and solidus surfaces. The field of solid solutions with the Tl5Te3 structure (δ-phase) has been shown to account for more than 90% of the area of the composition triangle. Tl2Te-based solid solutions (α-phase) exist in a narrow composition region. 相似文献
16.
Bin Li Wenqin Luo Yongya Wang Yanhui Zhang Haiyan Wu 《Journal of Materials Science》2018,53(11):8030-8038
The glass and glass ceramics containing SiO2–CaO–Fe2O3–P2O5 were prepared by sol–gel method. The influence of the Fe contents on the crystallization and local structure of the glass and glass ceramics was systematically investigated. The crystal structure of the glass ceramics was identified by XRD characterization. Hematite phase can be precipitated from the glass matrix in all glass ceramics with various Fe contents, and the crystallographic parameters of hematite were determined by XRD Rietveld refinement. The crystallization kinetics of the glasses was investigated in detail. Relative low activation energies were obtained at low Fe contents. The local structure evolution of the glass and glass ceramics has been studied in-depth by means of FTIR and Mössbauer spectroscopy. Fe element is present both as network former and network modifier which significantly influenced the crystallization activation energies of the glasses. The results of this work may be of great significance for the material design and practical applications of bioactive magnetic glass ceramics for hyperthermia. 相似文献
17.
L. T. Denisova L. A. Irtyugo Yu. F. Kargin L. G. Chumilina N. V. Belousova V. M. Denisov N. A. Galiakhmetova 《Inorganic Materials》2017,53(3):300-306
The compounds BiVO4, Bi4V2O11, and Bi12V2O23 have been prepared by solid-state synthesis using stoichiometric mixtures of Bi2O3 and V2O5. The effect of temperature on the heat capacity of the synthesized bismuth vanadates has been studied by differential scanning calorimetry in the range 350–950 K. The C p (T) curves have extrema at 531.7 K for BiVO4 and at 725.2 and 852.8 K for Bi4V2O11, which are due to polymorphic transformations of these compounds. 相似文献
18.
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
19.
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
20.