共查询到20条相似文献,搜索用时 31 毫秒
1.
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
2.
Glass samples of the system (15Li2O–30ZnO–10BaO–(45 − x)B2O3–xCuO where x = 0, 5, 10 and 15 mol%) were prepared by using the melt quenching technique. A number of studies, viz. density, differential
thermal analysis, FT-IR spectra, a.c. conductivity and dielectric properties (constant εφ, loss tan δ, a.c. conductivity,
σac, over a wide range of frequency and temperature) of these glasses were carried out as a function of copper ion concentration.
The analysis of the results indicate that the density increases while molar volume decreases with increasing of copper content
indicates structural changes of the glass matrix. The glass transition temperature, T
g, and crystallization temperature, T
c, increase with the variation of concentration of CuO referred to the growth in the network connectivity in this concentration
range, while glass-forming ability parameter (T
c − T
g) decreases with increasing CuO content, indicates an increasing concentration of copper ions that take part in the network-modifying
positions. The FT-IR spectra evidenced that the main structural units are BO3, BO4, and ZnO4. The structural changes observed by varying the CuO content in these glasses and evidenced by FTIR investigation suggest
that the CuO plays a network modifier role in these glasses while ZnO plays the role of network formers. The dielectric constant
decreased with increase in temperature and CuO content. The variation of a.c. conductivity with the concentration of CuO passes
through a maximum at 5 mol%. In the high temperature region, the a.c. conduction seems to be connected with the mixed conduction
viz., electronic conduction and ionic conduction. 相似文献
3.
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
4.
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
5.
6.
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
7.
Changrong Zhou Xinyu Liu Weizhou Li Changlai Yuan Guohua Chen 《Journal of Materials Science》2009,44(14):3833-3840
Lead-free piezoelectric ceramics (1 − x − y)Bi0.5Na0.5TiO3–xBi0.5K0.5TiO3–yBiCoO3 (x = 0.12–0.24, y = 0–0.04) have been fabricated by a conventional solid-state reaction method, and their structure and electrical properties
have been investigated. The XRD analysis shows that samples with y ≤ 0.03 exhibit a pure perovskite phase and very weak impurity reflections can be detected in the sample with y = 0.04. With x increasing from 0.12 to 0.24 and y increasing from 0 to 0.04, the ceramics transform gradually from a rhombohedral phase to a tetragonal phase and rhombohedral–tetragonal
phase coexistence to a pseudocubic phase, respectively. The morphotropic phase boundary (MPB) of the system between rhombohedral
and tetragonal locates in the range of x = 0.18–0.21, y = 0–0.03. The ceramics near the composition of the MPB have good performances with piezoelectric constant d
33 = 156 pC/N and electromechanical coupling factor k
p = 0.34 at x = 0.21 and y = 0.01, which attains a maximum value in this ternary system. Adding content of BiCoO3 leads to a disappearance of the response in the curves of dielectric constant-temperature to the ferroelectric–antiferroelectric
transition. The temperature dependence of dielectric properties suggests that the ceramics are relaxor ferroelectrics. The
results show that (1 − x − y)Bi0.5Na0.5TiO3–xBi0.5K0.5TiO3–yBiCoO3 ceramics are good candidate for use as lead-free ceramics. 相似文献
8.
Feng Ni Laihui Luo Xiaoyin Pan Yuepin Zhang Hongbing Chen 《Journal of Materials Science》2012,47(7):3354-3360
Lead-free piezoelectric ceramics (1 − x)Bi0.5(Na0.84K0.16)0.5TiO3–xBa0.77Ca0.23TiO3 (BNKT–xBCT, x = 0–0.04) were synthesized by conventional solid-state reaction method. The piezoelectric, dielectric, and ferroelectric
characteristics of the ceramics are investigated and discussed. The XRD results show that Ba0.77Ca0.23TiO3 (BCT) has diffused into Bi0.5(Na0.84K0.16)0.5TiO3 (BNKT) lattices to form a new solid solution. It is shown that moderate additive of BCT (x ≤ 0.025) in BNKT–xBCT ceramics can enhance their piezoelectric and ferroelectric properties. Three dielectric anomalies are observed in BNKT–xBCT (x ≤ 0.03) ceramics. The piezoelectric measurements and P–E hysteresis loops reveal that BNKT–0.025BCT ceramic has the highest piezoelectric performance and strongest ferroelectricity
in all the samples. Piezoelectric constants d
33, k
p, and k
t of 175 pC/N, 29.1, and 54% are, respectively, achieved. Remnant polarization P
r and coercive field E
c reach 28.3 μC/cm2 and 24.2 kV/cm, respectively. 相似文献
9.
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
10.
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
11.
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
12.
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
13.
Bi4Ti3O12–(Ni0.5Zn0.5)Fe2O4 dielectric–ferromagnetic ceramic composites synthesized with nanopowders
Bi4Ti3O12 and (Ni0.5Zn0.5)Fe2O4 nanopowders were prepared by co-precipitation and hydrothermal methods, respectively. It was found that ethanolamine is effective as a precipitating agent in the synthesis of Bi4Ti3O12 nanopowders via co-precipitation, and it also plays an important role in the synthesis of (Ni0.5Zn0.5)Fe2O4 nanopowders. Bi4Ti3O12–(Ni0.5Zn0.5)Fe2O4 multiferroic ceramics were obtained by sintering the as-prepared nanopowders. Lower sintering temperatures (800–900 °C) were available when compared with the traditional solid state method and ceramic composites with higher density and limited interfacial reaction were obtained. The ceramics also showed lower dielectric loss and higher magnetic moments. Both the ferroelectric and magnetic phases preserve their individual properties in bulk composite form and thus, these types of composite ceramics appear to be good candidate multiferroic materials. 相似文献
14.
M. H. Shaaban 《Journal of Materials Science》2012,47(15):5823-5832
Glasses with composition (70 − x) B2O3·15Bi2O3·15LiF·xNb2O5 with x = 0–1.0 mol% were prepared by conventional glass-melting technique. The molar volume V m values decrease and the glass transition temperatures T g increase with increase of Nb2O5 content up to 0.2 mol%, which indicates that Nb5+ ions act as a glass former. Beyond 0.2 mol% Nb2O5 the V m increases and the T g decreases, which suggests that Nb5+ ions act as a glass modifier. The FTIR spectra suggest that Nb5+ ions are incorporated into the glass network as NbO6 octahedra, substituting BO4 groups. The temperature dependence of the dc conductivity follows the Greaves variable range hopping model below 454 K, and follows the small polaron hopping model at temperatures >454 K. σ dc, σ ac conductivity and dielectric constant (ε) decrease and activation energy for dc conduction ΔE dc which increases with increasing Nb2O5 content up to 0.2 mol%, whereas σ dc, σ ac and (ε) increase and ΔE dc decreases with increasing Nb2O5 content beyond 0.2 mol%. The impedance spectroscopy shows a single semicircle or arcs which indicate only the ionic conduction mechanism. The electric modulus formalism indicates that the conductivity relaxation is occurring at different frequencies exhibit temperature-independent dynamical process. The (FWHM) of the normalized modulus increases with increase in Nb2O5 content suggesting that the distribution of relaxation times is associated with the charge carriers Li+ or F− ions in the glass network. 相似文献
15.
The effects of the annealing of 20BaO–30V2O5–50Bi2O3 glass on the structural and electrical properties were studied by scanning electron micrographs (SEM), X-ray diffraction (XRD), differential scanning calorimeter (DSC) density (d) and dc conductivity (σ). The XRD and SEM observations have shown that the sample under study undergoes structural changes: from amorphous at the beginning, to partly crystalline after nanocrystallization at crystallization temperature (Tc) for 1 h and to colossal crystallization after the annealing at the same temperature for 24 h. The average size of these grains after nanocrystallization at Tc for 1 h was estimated to be about 25–35 nm. However, the glass heat treated at Tc = 580 °C for 24 h the microstructure changes considerably. The nanomaterials obtained by nanocrystallization at Tc for 1 h exhibit giant improvement of electrical conductivity up to four order of magnitude and better thermal stability than the as-received glass. The major role in the conductivity enhancement of this nanomaterial is played by the developed interfacial regions “conduction tissue” between crystalline and amorphous phases, in which the concentration of V4+–V5+ pairs responsible for electron hopping is higher than inside the glassy matrix. The annealing at Tc for 24 h leads to decrease of the electronic conductivity. This phenomena lead to disappearance of the abovementioned “conduction tissue” for electrons and substantial reduction of electronic conductivity. The high temperature (above θ/2) dependence of conductivity could be qualitatively explained by the small polaron hopping (SPH) model. The physical parameters obtained from the best fits of this model are found reasonable and consistent with the glass compositions. 相似文献
16.
As technology evolves towards the design of small size – high efficiency devices there is a necessity for the development of solid, stable electrolytes that can be fabricated in various shapes. Accordingly, a glass system of xB2O3·0.4Li2O·(0.6 − x)P2O5 with 0 ≤ x ≤ 0.6 mol%, was prepared by melting the raw materials at 1200 °C and rapidly cooling the melts at room temperature. The samples were afterwards heat treated to develop crystalline structures, for better identification of the units that build up the network. 相似文献
17.
18.
Bi-metallic corrosion resistant steel pipes were produced through explosive welding process. The weldability window of the
stainless steel pipe (inner pipe) and the carbon steel pipe (outer pipe) was determined by the use of available semi-empirical
relations. The impact velocity of the pipes as the most important collision parameter was calculated by the finite element
simulation. Direct effect of the explosive mass reduction on the bonding interface of the pipes was studied. Optical microscopy
study showed that a transition from a wavy interface to a smooth one occurs with decrease in explosive load. 相似文献
19.
By using Au58.74Ni36.50V4.76 at.% filler alloy, a reliable Si3N4/Si3N4 joint was brazed at 1,423 K for 60 min in vacuum. The microstructure of the joint was investigated and analyzed by scanning
electron microscope with energy dispersive spectroscopy, transmission electron microscopy, and X-ray diffraction. The results
indicate that the joint consists of three main phases: a continuous VN reaction layer between filler alloy and Si3N4 ceramic; an Au[Ni] solid solution as the matrix of the joint; and Ni[Si,V] solid solution particles distributed homogeneously
in the Au[Ni] solid solution. The mechanism of formation of the interfacial structure is discussed. 相似文献
20.
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