共查询到20条相似文献,搜索用时 46 毫秒
1.
Moo-Chin Wang Wang-Long Li Chih-Wei Cheng Kuo-Ming Chang Yong-Feng Chen Chi-Shiung Hsi 《Materials Chemistry and Physics》2010
The phase transformation and crystallization kinetics of (1 − x)Li2O–xNa2O–Al2O3–4SiO2 glasses have been studied by using differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron diffraction (ED) analysis. The crystallization temperature at the exothermic peak increases from 1171 to 1212 K when the Na2O content increases from 0 to 0.6 mol. The crystalline phase is composed of spodumene crystallization when the Na2O content increases from 0 to 0.6 mol. The activation energy of spodumene crystallization decreases from 444.0 ± 22.2 to 284.0 ± 10.8 kJ mol−1 when the Na2O content increases from 0 to 0.4 mol. Moreover, the activation energy increases from 284.0 ± 10.8 to 446.0 ± 23.2 kJ mol−1 when the Na2O content increases from 0.4 to 0.6 mol. The crystallization parameters m and n approach 2, indicating that the surface nucleation and two-dimensional growth are dominant in (1 − x)Li2O–xNa2O–Al2O3–4SiO2 glasses. 相似文献
2.
H. Doweidar 《Journal of Materials Science》2009,44(11):2899-2906
Refractive index and molar refraction of Li2O–, Na2O–, CaO–, and BaO–Ga2O3–SiO2 glasses have been used to test the validity of a structural model of silicate glasses containing Ga2O3 glasses. Ga2O3 enters these types of glass in a similar manner as Al2O3. It is assumed that, for (SiO2/Ga2O3) >1 and (Ga2O3/R2O) ≤1, Ga2O3 associates primarily with modifier oxides to form GaO4 units. The rest of modifier oxide forms silicate units with non-bridging oxygen ions. Silicate structural units have the
same factors as found for binary alkali- and alkaline earth silicate glasses. Differences between experimental and model values
suggest another structure for (Ga2O3/SiO2) ≥1. 相似文献
3.
CoFe2−xSmxO4 (x = 0–0.2) nanofibers with diameters about 100–300 nm have been prepared using the organic gel-thermal decomposition method. The composition, structure and magnetic properties of the CoFe2−xSmxO4 nanofibers were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, inductive coupling plasma mass analyzer and vibrating sample magnetometer. The CoFe2−xSmxO4 (x = 0–0.2) nanofibers obtained at 500–700 °C are of a single spinel structure. But, at 800 °C with a relatively high Sm content of 0.15–0.2 the spinel CoFe2−xSmxO4 ferrite is unstable and the second phase of perovskite SmFeO3 occurs. The crystalline grain sizes of the CoFe2−xSmxO4 nanofibers decrease with Sm contents, while increase with the calcination temperature. This grain reduction effect of the Sm3+ ions doping is largely owing to the lattice strain and stress induced by the substitution of Fe3+ ions with larger Sm3+ ions in the ferrite. The saturation magnetization and coercivity increase with the crystallite size in the range of 8.8–57.3 nm, while decrease with the Sm content from 0 to 0.2 owing to a smaller magnetic moment of Sm3+ ions. The perovskite SmFeO3 in the composite nanofibers may contribute to a high coercivity due to the interface pinning, lattice distortion and stress in the ferrite grain boundary fixing and hindering the domain wall motion. 相似文献
4.
H1−xLaNb2−xMoxO7 was prepared by solid-state reaction followed by an ion-exchange reaction. Pt was incorporated in the interlayer of H1−xLaNb2−xMoxO7 by the stepwise intercalation reaction. The H1−xLaNb2−xMoxO7 showed hydrogen production activity and the activities were greatly enhanced by Pt co-incorporating. The x value in H1−xLaNb2−xMoxO7 had an important effect on the photocatalytic activity of the catalyst. When the x = 0.05, the H1−xLaNb2−xMoxO7/Pt showed a photocatalytic activity of 80 cm3 h−1 g−1 hydrogen evolution rate in 10 vol.% methanol solution under irradiation from a 100 W mercury lamp at 333 K. 相似文献
5.
High-quality and large-size lead-free (1 − x)Na0.5Bi0.5TiO3–xBaTiO3 single crystals (x = 0, 0.025, 0.0325 and 0.05) were grown using Czochralski method. The obtained samples were of pure perovskite structure with rhombohedral symmetry at room temperature. Thermal expansion, heat capacity, ferroelectric and dielectric properties were measured in a wide temperature range. The broad anomalies observed in thermal expansion and heat capacity were corresponded to structural, ferroelectric and dielectric anomalies, related to temperature features of polar regions and formation of a long-range order ferroelectric phase. The Burns temperature was found to increase with increasing BaTiO3 content. At low-frequency (100 Hz–100 kHz) the samples showed diffuse phase transitions. The obtained results were discussed in terms of local electric and strain fields caused by a difference in ionic radii between (Na,Bi) and Ba ions. 相似文献
6.
7.
Moo-Chin Wang Huy-Zu Cheng Huey-Jiuan Lin Chien-Fu Wang Chi-Shiung Hsi 《Materials Chemistry and Physics》2013
The crystallization behavior and magnetic properties of 10Li2O–9MnO2–16Fe2O3–25CaO–5P2O5–35SiO2 (10LFS) glass have been studied using differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), transmission electron microscopy (TEM) and selected area electron diffraction (SAED) to observe the crystallization behavior and a superconducting quantum interference device (SQUID) for measurements of the magnetic properties. The DTA shows that the 10LFS glass has one broad exothermic peak at approximately 674 °C and one sharp (the highest) exothermic peak at 764 °C. When the 10LFS glass crystallized at 850 °C for 4 h, the crystalline phases identified by XRD were lithium silicate (Li2SiO3), β-wollastonite (β-CaSiO3), lithium orthophosphate (Li3PO4), magnetite (FeFe2O4) and triphylite (Li(Mn0.5Fe0.5)PO4). The SEM surface analysis revealed that the β-wollastonite and lithium silicate have a lath morphology. The TEM microstructure examination showed that the largest FeFe2O3 particles have a size of approximately 0.3 μm. When the 10LFS glass was heat treated at 850 °C for 16 h and a magnetic field of 1000 Oe was applied, a very small remnant magnetic induction of 0.01 emu g−1 and a coercive force of 50 Oe were obtained, which revealed an inverse spinel structure. 相似文献
8.
The microwave dielectric properties of the (1 − x)(Mg0.95Co0.05)2TiO4–xCa0.8Sm0.4/3TiO3 ceramic system prepared by mixed oxide route have been investigated. The crystal structures and the microstructures of the ceramics were characterized by means of X-ray and SEM, respectively. The microwave dielectric properties are strongly related to the density and the matrix of the specimen. Combining (Mg0.95Co0.05)2TiO4 (spinel structure) and Ca0.8Sm0.4/3TiO3 (perovskite structure) forms a two-phase system and leads to a near-zero τf. With increasing x, the Q × f of the specimen decreased, whereas its ?r increased due to a compositional variation. A new microwave dielectric 0.8(Mg0.95Co0.05)2TiO4–0.2Ca0.8Sm0.4/3TiO3, possessing excellent microwave dielectric properties with a dielectric constant (?r) of 20.84, a Q × f of 112,600 GHz (where f = 9.1 GHz, is the resonant frequency) and a τf value ∼0.8 ppm K−1 at 1573 K/4 h, is proposed as a candidate material for GPS patch antennas and 3G passive components. 相似文献
9.
Atiar Rahaman Molla Anal Tarafder Basudeb Karmakar 《Journal of Materials Science》2011,46(9):2967-2976
Glasses were prepared by the melt-quench technique in the K2O–SiO2–Bi2O3–TiO2 (KSBT) system and crystallized bismuth titanate, BiT (Bi4Ti3O12) phase in it by controlled heat-treatment at various temperature and duration. Different physical, thermal, optical, and
third-order susceptibility (χ3) of the glasses were evaluated and correlated with their composition. Systematic increase in refractive index (n) and χ3 with increase in BiT content is attributed to the combined effects of high polarization and ionic refraction of bismuth and
titanium ions. Microstructural evaluation by FESEM shows the formation of polycrystalline spherical particles of 70–90 nm
along with nano-rods of average diameter of 85–90 nm after prolonged heat treatment. A minor increase in dielectric constants
(εr) has been observed with increase in polarizable components of BiT in the glasses, whereas a sharp increase in εr in glass–ceramics is found to be caused by the formation of non-centrosymmetric and ferroelectric BiT nanocrystals in the
glass matrix. 相似文献
10.
Y. Y. Chen P. C. Chen C. B. Tsai K. I. Suga K. Kindo 《International Journal of Thermophysics》2009,30(1):316-324
Thermometers consisting of RuO2–Al2O3 composite thin films were prepared by RF sputtering. It was found that different electrode-patterning techniques have dissimilar
effects on the magnetoresistance (MR) and the temperature coefficient of resistance (TCR). In general, the thermometers with
electrodes fabricated by photo-resist lithography exhibit superior performance compared to those with electrodes prepared
using a metal mask. By adjusting the relative compositions of RuO2 and Al2O3, the thermometers can be applied to a wide temperature range from 60 mK to 500 K. In a pulsed magnetic field up to 55 T,
the MR at 4.2 K of a typical thermometer for the temperature range from 1.4 K to 300 K increases linearly with magnetic field
to a maximum of ~15 %, corresponding to a temperature deviation of ~−4 %. As frequency increases from dc to 1.9 MHz, the MR
decreases from −13 % to ~ − 0.5 % at T = 1.3 K and H = 55 T. By integrating the thermometer with a heater on a sapphire chip, a micro-calorimeter can be developed and successfully
used to measure the heat capacity of small mg-sized sample. The RuO2–Al2O3 composite film can also be employed as an infrared bolometer operated at room temperature. 相似文献
11.
Manish S. Jayswal D.K. Kanchan Poonam Sharma Nirali Gondaliya 《Materials Science and Engineering: B》2013,178(11):775-784
Silver ion conducting super-ionic glass system xPbI2–(100 − x) [Ag2O–2(V2O5–B2O3)], where, 5 ≤ x ≤ 25, were prepared via melt quenching route and -characterized by XRD and DSC. Their electrical properties were measured by impedance spectroscopy in the frequency range of 2 MHz to 20 Hz from 30 to 120 °C. The electrical relaxation mechanism has been studied using AC conductivity, dielectric modulus function and frequency dependent dielectric permittivity over a wide range of frequency and temperature. Two different scaling approaches for AC conductivity as well as dielectric permittivity spectra were used to understand the nature of relaxation processes. 相似文献
12.
13.
A magnetic SO42−/ZrO2–B2O3–Fe3O4 solid superacid catalyst is prepared via a simple chemical co-precipitation approach. The obtained materials were characterized in detailed by X-ray powder diffraction, thermogravimetric analysis–different scanning calorimetry, Fourier transform infrared spectroscopy (FTIR), electron microscopy (SEM and TEM), and Mossbauer spectra. Powder X-ray diffraction patterns show that in this composite oxide the transformation temperature of ZrO2 from tetragonal to monoclinic phase is higher compared to the pristine SO42−/ZrO2 material. The introduction of Fe3O4 endows the superacid with a super-paramagnetic property while in a ferromagnetic state after calcination. The superacid exhibits high catalytic activity in forming ethyl acetate by esterification. 相似文献
14.
Min Wang Ruzhong Zuo Weiqing Meng Yi Liu 《Journal of Materials Science: Materials in Electronics》2011,22(7):843-848
The CaO–B2O3–SiO2 glass/CaSiO3 ceramic (CBS/CS) composites were fabricated via sol–gel processing routes. Their densification behavior, structures and dielectric
properties were investigated. The precursors of CBS glass and CS ceramic filler were firstly obtained via individual soft
chemical route and then mixed together in various proportions. The results indicated that the structures of CBS/CS composites
are characteristic of CS and CaB2O4 (CB) ceramic phases distributed in the matrix of glass phase at 800–950 °C. The CS ceramic phase not only acts as fillers,
but nuclei for the crystallization of CBS glass as well such that the CS content exhibits an effect on the densification and
dielectric properties of the composites. The CBS/CS composites with 10% CS sintered at 850 °C own dielectric properties of
εr < 5 and tanδ = 6.4 × 10−4 at 1 MHz. 相似文献
15.
The influence of SrO (0·0–5·0 wt%) on partial substitution of alpha alumina (corundum) in ceramic composition (95 Al2O3–5B2O3) have been studied by co-precipitated process and their phase composition, microstructure, microchemistry and microwave dielectric
properties were studied. Phase composition was revealed by XRD, while microstructure and microchemistry were investigated
by electron-probe microanalysis (EPMA). The dielectric properties by means of dielectric constant (ε
r
), quality factor (Q × f) and temperature coefficient of resonant frequency (τ
f
) were measured in the microwave frequency region using a network analyser by the resonance method. The addition of B2O3 and SrO significantly reduced the sintering temperature of alumina ceramic bodies to 1600 °C with optimum density (∼ 4g/cm3) as compared with pure alumina powders recycled from Al dross (3·55g/cm3 sintered at 1700 °C). 相似文献
16.
Ivana R?sslerová Ladislav Koudelka Zdeněk ?erno?ek Petr Mo?ner Ludvík Bene? 《Journal of Materials Science》2011,46(20):6751-6757
Thermal properties and crystallization of glasses from PbO–MoO3–P2O5 ternary system were studied in three compositional series (100 − x)[0.5PbO–0.5P2O5]–xMoO3 (A), 50PbO–yMoO3–(50 − y)P2O5 (B), and (50 − z)PbO–zMoO3–50P2O5 (C). Glass transition temperature, crystallization temperature, coefficient of thermal expansion, and dilatation softening
temperature of the studied glasses were determined by differential thermal analysis and dilatometry. Crystallization products
of annealed glass samples were investigated by X-ray diffraction and Raman spectroscopy. X-ray diffraction analysis of crystallized
glasses revealed the formation of PbP2O6, Pb3P4O13, and PbMoO4 in the samples of the B series. In the series A and C in the samples with a high MoO3 content, crystalline compounds of Pb(MoO2)2(PO4)2 and (MoO2)(PO3)2, respectively, were identified. Raman spectra of crystalline samples confirmed the results of X-ray diffraction measurements
and provided also information on thermal stability of glasses and formation of glass-crystalline phases in the studied glass
series. 相似文献
17.
Bo Li Shuren Zhang Ying Yuan Xiaohua Zhou Longcheng Xiang 《Journal of Materials Science》2009,44(18):4993-4998
The low-fired (ZnMg)TiO3–TiO2 (ZMT–TiO2) microwave ceramics using low melting point CaO–B2O3–SiO2 as sintering aids have been developed. The influences of Mg substituted fraction on the crystal structure and microwave properties
of (Zn1−x
Mg
x
)TiO3 were investigated. The result reveals that the sufficient amount of Mg (x ≥ 0.3) could inhibit the decomposition of ZnTiO3 effectively, and form the single-phase (ZnMg)TiO3 at higher sintering temperatures. Due to the compensating effect of rutile TiO2 (τf = 450 ppm/°C), the temperature coefficient of resonant frequency (τf) for (Zn0.65Mg0.35)TiO3–0.15TiO2 with biphasic structure was adjusted to near zero value. Further, CaO–B2O3–SiO2 addition could reduce the sintering temperature from 1150 to 950 °C, and significantly improve the sinterability and microwave
properties of ZMT–TiO2 ceramics, which is attributed to the formation of liquid phases during the sintering process observed by SEM. The (Zn0.65Mg0.35)TiO3–0.15TiO2 dielectrics with 1 wt% CaO–B2O3–SiO2 sintered at 950 °C exhibited the optimal microwave properties: ε ≈ 25, Q × f ≈ 47,000 GHz, and τf ≈ ± 10 ppm/°C. 相似文献
18.
In this article, the wetting of 23 wt% CaO–15 wt% Al2O3–62 wt% SiO2 molten glass on polycrystalline silicon carbide is studied under air at temperatures between 1,100 and 1,590 °C. Wetting
experiments are performed by the sessile drop technique. Good wetting (final contact angle lower than 50°) is observed regardless
of the experimental temperature when it is higher than 1,300 °C. Moreover, some specific experiments of wetting of glass on
platinum, silica and monocrystalline SiC substrates are also performed. The character of molten glass spreading on silicon
carbide (reactive or non-reactive) as well as the role of the atmosphere on interfacial interactions with SiC are identified
and discussed. 相似文献
19.
Solid solutions of (1 − x)BaTiO3–xK0.5Bi0.5TiO3 were prepared by the solid state reaction technique. Samples were sintered in reducing atmosphere of N2/H2 in the temperature range 1100–1240 °C with subsequent oxidation at 700 °C. Phase composition and crystal structure were investigated by X-ray powder diffractometry (XRPD). It was shown that all samples of (1 − x)BaTiO3–xK0.5Bi0.5TiO3 (0 ≤ x < 0.4) exhibit a tetragonal structure at room temperature, the parameters a and c decrease with increasing x. With increasing x the Curie temperature of solid solutions (1 − x)BaTiO3–xK0.5Bi0.5TiO3 (0.1 ≤ x < 0.4) increases from 150 to 220 °C. The values of potential barriers at grain boundaries were calculated on the basis of Heywang model. With increasing x, the potential barrier at grain boundaries increases. It was shown that the grain size decreases with increasing the bismuth–potassium titanate content. The complex impedance results indicate that the grain boundary and the outer layer region, located between the boundary and the core of the grain, make a contribution to the positive temperature coefficient of resistance (PTCR) effect in (1 − x)BaTiO3–xK0.5Bi0.5TiO3 solid solutions. With increasing x ρmax increases due to an increase in potential barrier at grain boundaries. 相似文献
20.
Feifei Chen Baoan Song Changgui Lin Shixun Dai Junwen Cheng Jong Heo 《Materials Chemistry and Physics》2012
Glass-forming region of Bi2O3–GeO2–TiO2 (BGT) pseudo-ternary system was determined by using melt-quench method. A series of high transparent glass samples were selected and their structural characteristics were investigated by FT-IR and Raman spectra. By employing Z-scan and optical Kerr shutter techniques with femtosecond laser pulses as excitation source, third-order optical nonlinearities (TON) of the BGT glasses as well as the TON response time were investigated at wavelength of 800 nm. The ultrafast nonlinear response and high figure of merit suggest great potentials of BGT glasses in applications of all-optical switching or related optical devices. 相似文献