共查询到20条相似文献,搜索用时 31 毫秒
1.
Takashi Uchino Tetsuo Sakka Koukichi Hotta Matae Iwasaki 《Journal of the American Ceramic Society》1989,72(11):2173-2175
Attenuated total reflectance Fouriertransform infrared (ATR-FTIR) spectra were measured in the region from 4300 to 400 cm−1 for a hydrated Na2 O–SiO2 glass containing 35 wt% water. The Si–OH bending vibration mode was observed. It was found that the incorporated water, molecular water as well as hydroxyls, affected the Si–O vibrations. The effect of incorporated water upon the glass structure is discussed. 相似文献
2.
S.J. ROTHMAN T.L.M. MARCUSO L.J. NOWICKI P.M. BALDO A. W. McCORMICK 《Journal of the American Ceramic Society》1982,65(11):578-582
The diffusion of Cs+ , Rb+ , and K+ ions was measured in three grades of vitreous SiO2 by the radiotracer-sectioning technique or Rutherford, backscattering spectroscopy. The values of the diffusion coefficient, D , at 1000°C decrease strongly with increasing ionic radius, changing by about two and one-half orders of magnitude per row of the periodic table. The difference between DCs and DRb is largely in the preexponential factor Do in the Arrhenius expression rather than in the activation enthalpy Q . The values of D are much smaller than the tracer D values for the alkali metal ion in homogeneous Rb or Cs silicate glasses. Residual metallic impurities in the SiO2 decrease both Q and Do for the diffusion of Rb. The results are analyzed in terms of the interstitial structure of vitreous SiO2 . 相似文献
3.
Francisco del Monte Willa Larsen John D. Mackenzie 《Journal of the American Ceramic Society》2000,83(6):1506-1512
Metastable tetragonal ZrO2 phase has been observed in ZrO2 –SiO2 binary oxides prepared by the sol–gel method. There are many studies concerning the causes of ZrO2 tetragonal stabilization in binary oxides such as Y3 O2 –ZrO2 , MgO–ZrO2 , or CaO–ZrO2 . In these binary oxides, oxygen vacancies cause changes or defects in the ZrO2 lattice parameters, which are responsible for tetragonal stabilization. Since oxygen vacancies are not expected in ZrO2 –SiO2 binary oxides, tetragonal stabilization should just be due to the difficulty of zirconia particles growing in the silica matrix. Furthermore, changes in the tetragonal ZrO2 crystalline lattice parameters of these binary oxides have recently been reported in a previous paper. The changes of the zirconia crystalline lattice parameters must result from the chemical interactions at the silica–zirconia interface (e.g., formation of Si–O–Zr bonds or Si–O− groups). In this paper, FT-IR and 29 Si NMR spectroscopy have been used to elucidate whether the presence of Si–O–Zr or Si–O− is responsible for tetragonal phase stabilization. Moreover, X-ray diffraction, Raman spectroscopy, and transmission electron microscopy have also been used to study the crystalline characteristics of the samples. 相似文献
4.
Masayoshi Ohashi Kazuo Nakamura Kiyoshi Hirao Shuzo Kanzaki Stuart Hampshire 《Journal of the American Ceramic Society》1995,78(1):71-76
Homogeneous Y-Si-O-N glasses containing 15 or 20 eq% nitrogen (N) were prepared from compositions with Y/Si ratios in the vicinity of that of the lowest eutectic point on the Y2 O3 –SiO2 phase diagram. The liquidus on the phase diagram shifted toward lower temperatures by incorporation of N. The density, the elastic moduli, and the glass transition temperature of the Y-Si-O-N glasses increased with incorporation of N. This is due to the closer packing of atoms in the glasses by the substitution of N, which is in three-fold coordination with Si, for O which is in two-fold coordination, and the stronger covalent nature of the Si–N bond compared with the Si–O bond. The coefficient of thermal expansion of the Y-Si-O-N glasses increased with increasing Y content, because the discontinuity of the glass network developed with increasing nonbridging anions by the introduction of Y. In contrast, the glass transition temperature and the elastic moduli increased with Y content due to the high coordination of Y for O, and the relatively high cationic field strength of Y. Furthermore, the effect of cationic field strength on properties of Ln-Si-O-N glasses (Ln = lanthanides or Y) is discussed. 相似文献
5.
Tetsuji Yano Shuichi Shibata Terutaka Maehara 《Journal of the American Ceramic Society》2006,89(1):89-95
Structural equilibria of alkali silicate glasses and melts are investigated based on the Q n fractions ( n =number of bridging oxygen in SiO4 tetrahedron) obtained from high-temperature Raman spectra. A mathematical treatment of the entropy of mixing, Δ S mix , of structural groups of Q n is conducted and applied to the investigation of phase transformation and phase separation. Characteristics of Q n traces and the counter-map of Δ S mix on Q n diagram are found to possess useful information to understand their mechanisms. An extended Q n diagram is also proposed to understand the melt structure and properties for the wide composition range. 相似文献
6.
Takahiro Takada Sea Fue Wang Shoko Yoshikawa Sei-Joo Jang Robert E. Newnham 《Journal of the American Ceramic Society》1994,77(9):2485-2488
The effects of glass additions on the properties of (Zr,Sn)TiO4 as a microwave dielectric material were investigated. The (Zr,Sn)TiO4 ceramics with no glass addition sintered at 1360°C gave Q = 4900 and K = 37 at 7.9 GHz . Several glasses, including SiO2 , B2 O3 , 5ZnO–2B2 O3 , and nine commercial glasses, were tested during this study. Among these glasses, (Zr,Sn)TiO4 sintered with ZnO-B2 O3 –SiO2 (Corning 7574) showed more than 20% higher density than that of pure (Zr,Sn)TiO4 sintered at the same temperature. A 5-wt% addition of SiO2 , to (Zr,Sn)TiO4 , when sintered at 1200°C, gave the best Q : Q = 2700 at 9 GHz. Results of XRD analysis and scanning electron microscopy and the effect of glass content are also presented. 相似文献
7.
Laurent Cormier Daniel R. Neuville Georges Calas 《Journal of the American Ceramic Society》2005,88(8):2292-2299
The anomalous behavior of the glass transition temperature ( T g ) in low silica calcium aluminosilicate glasses has been related to the structural modifications observed by neutron and X-ray diffraction. The diffraction data indicate that Al and Si are in tetrahedral sites and that Ca atoms are in distorted octahedral sites. By subtracting the correlation functions for glasses at constant SiO2 or constant Al2 O3 content, we have shown that Si and Al atoms are introduced in a different way within the glass structure. Si is present in various Q n sites, while Al resides in Q3 and Q4 sites for glasses with high CaO content and enters fully polymerized Q4 sites with increasing SiO2 or Al2 O3 content. The higher proportion of Al in Q3 positions at high CaO content yields a depolymerization of the network. The lower connectivity will contribute to a decrease of the viscosity, which may be at the origin of the decrease of T g for glasses at low silica content. 相似文献
8.
Teiichi Hanada Akihiro Ando Setsuhisa Tanabe Naohiro Soga 《Journal of the American Ceramic Society》1992,75(12):3417-3420
Amorphous films in the system SiO2 –AlPO4 were prepared by means of the rf-sputtering method, and their physical properties, such as density, refractive index, and temperature coefficient of Young's modulus, and infrared spectra were measured. Also, the K α X-ray emission spectra of silicon and aluminum were measured in order to investigate the coordination state of these cations in the amorphous films. The density and the refractive index were close to those of amorphous SiO2 and AlPO4 and the compositional dependence showed a small deviation from linearity. The temperature coefficients of Young's modulus were positive for all of the samples. The infrared absorption spectra of all of the samples were similar to those of SiO2 glass and amorphous AlPO4 film, and there was no evidence of the presence of P═O bonds. The coordination states of silicon and aluminum ions in the present amorphous films were the same as those in fused silica and AlPO4 crystal, respectively. The results of the properties, infrared absorption spectra, and X-ray emission spectra suggest that SiO4 tetrahedrons and AlO4 –PO4 connecting tetrahedral dimers constitute the network of the present amorphous films. A small deviation of the physical properties from an additive rule was thought to result from the difference in the bond character between the newly formed Si–O–Al and Si–O–P bonds and the bonds in the end members, Si–O–Si and Al–O–P. 相似文献
9.
Atsumi Nitta Terumi Miura Takayuki Komatsu Kazumasa Matusita 《Journal of the American Ceramic Society》1989,72(1):163-165
Glass-forming regions, valence states, and viscosities in SiO2 –PbO systems containing various transition-metal oxides as a third component were investigated. The glasses were prepared by melting in an open atmosphere. The glass-forming regions ranged as follows: MnO≡ZnO > FeO1.5 >NiO. The ratios Fe2+ /(Fe2+ + Fe3+ ) and Mn3+ / (Mn3+ + Mn2+ ) in the glasses were determined by chemical analysis. The Fe2+ / (Fe2+ + Fe3+ ) ratio in SiO2 –PbO–FeO1.5 glasses ranged from 0.016 to 0.050. The Mn3+ / (Mn3+ + Mn2+ ) ratio in SiO2 –PbO–MnO glasses ranged from 0.056 to 0.30. The fraction of manganese (III) ions in the glasses varies considerably with the glass composition. The effects of transitionmetal oxides on the viscosity are discussed. 相似文献
10.
Setsuhisa Tanabe Kazuyuki Hirao Naohiro Soga 《Journal of the American Ceramic Society》1992,75(3):503-506
The elastic properties, molar volume, and glass transition temperature ( T g ) of rare-earth-containing aluminosilicate glasses were investigated in the compositions of SiO2 –LnAlO3 and SiO2 –Ln3/4 Al5/4 O3 , where Ln is Y, La, Nd, Eu, or Yb. The molar volume decreased with decreased ionic size of the Ln3+ ion, and T g and elastic moduli increased in the same order. The Yb-containing glasses showed the highest Young's modulus among all the oxide glasses, even higher than the highest value ever known for glass containing Y2 O3 , as expected from the smaller ionic radius of Yb3+ than that of Y3+ . The bulk modulus was found to be almost proportional to the inverse four-thirds power of the molar volume of glasses in each composition, indicating that Ln3+ ions can substitute for each other without changing the glass structure except for the size of the local structure around themselves. From the comparison of these properties, the structural role of rare-earth ions in these glasses is discussed. 相似文献
11.
Anna Musinu Giorgio Piccaluga Mauro Magini 《Journal of the American Ceramic Society》1988,71(5):256-C
The radial distribution functions of ZnO–K2 O–SiO2 glasses with 7 and 10 wt% ZnO are compared with that of the corresponding K2 O–SiO2 matrix leading to "difference distribution curves'representative of the zinc structural arrangement. Analysis of the curves indicates that Zn2+ ions are prevalent (65% to 80%) in the glasses in tetracoordinated form. 相似文献
12.
Masao Morishita Alexandra Navrotsky Martin C. Wilding 《Journal of the American Ceramic Society》2004,87(8):1550-1555
The relative partial molar enthalpies, Δ SiO2 , of SiO2 in SiO2 –M2 O (M = Li, Na, K and Cs) binary and SiO2 –CaO–Al2 O3 ternary melts were directly measured by drop-solution calorimetry at 1465 K and 1663 K. Δ SiO2 changes from exothermic to endothermic as silica content increases, confirming the tendency toward immisciblity seen from activity measurements. It is concluded that Δ SiO2 is negative due to acid-base reactions and charge-coupled substitutions when the melt is composed of fewer Q 4 and more Q 3 and Q 2 species, but positive due to structural strain when the melt is composed of mostly Q 4 species. The Δ SiO2 obtained by calorimetry is a useful measure of basicity, when comparing different alkali and alkaline earth oxides. 相似文献
13.
Masayuki Nogami Yoichi Goto Toshihiro Kasuga 《Journal of the American Ceramic Society》2003,86(9):1504-1507
The effect of zirconium ions on glass structure and proton conductivity was investigated for sol-gel-derived P2 O5 –SiO2 glasses. Porous glasses were prepared through hydrolysis of PO(OCH3 )3 , Zr(OC4 H9 )4 , and Si(OC2 H5 )4 . Chemical bonding of the P5+ ions was characterized using 31 P-NMR spectra. The phosphorous ions, occurring as PO(OH)3 in the ZrO2 -free glass, were polymerized with one or two bridging oxygen ions per PO4 unit with increased ZrO2 content. The chemical stability of these glasses was increased significantly on the addition of ZrO2 , but the conductivity gradually decreased from 26 to 12 mS/cm at room temperature for 10P2 O5 ·7ZrO2 ·83SiO2 glass. A fuel cell was constructed using 10P2 O5 ·5ZrO2 ·85SiO2 glass as the electrolyte; a power of ∼4.5 mW/cm2 was attained. 相似文献
14.
Shimin Liu Gaoling Zhao Wangle Ruan Zhiwang Yao Tingting Xie Ji Jin Hao Ying Jianxun Wang Gaorong Han 《Journal of the American Ceramic Society》2008,91(8):2740-2742
Eu2 O3 -doped aluminoborosilicate glasses were prepared in air at high temperature. Luminescence measurements were used to investigate a valence change from Eu3+ to Eu2+ ions in the aluminoborosilicate glasses. The results showed that the doped Eu3+ ions were partially reduced to Eu2+ in the Eu2 O3 :RO–Al2 O3 –B2 O3 –SiO2 (RO=CaO, SrO, BaO, Li2 O) glasses, but not in the Eu2 O3 :RO–Al2 O3 –B2 O3 –SiO2 (RO=Na2 O, K2 O) glasses. The changes of Eu reduction with different RO components were discussed with the variation of optical basicity of RO and with different valency of R cations. The effects of co-doping BaO and ZnO in aluminoborosilicate glasses on Eu reduction were also investigated and discussed. 相似文献
15.
Shinji Kondoh Yuji Iwamoto Koichi Kikuta Shin-ichi Hirano 《Journal of the American Ceramic Society》1999,82(1):209-212
Mesoporous silica films with one-dimensional through channels perpendicular to the substrate surface have been fabricated successfully by a novel process, which was a combination of eutectic decomposition of amorphous films and subsequent chemical etching. In the case of the Fe–Si–O system, amorphous precursor films annealed under oxidizing conditions were decomposed to a regular array of needlelike hematite (Fe2 O3 ) crystals with a diameter of ∼4 nm surrounded by an amorphous silica matrix. Then, hematite crystals were preferentially removed by chemical etching. The pore surface areas of the remaining mesoporous SiO2 films were found to be more than 1000 m2 /g by an isothermal N2 gas adsorption and desorption measurement. 相似文献
16.
The leaching kinetics of lead glasses (25 to 35 mol% PbO-75 to 65 mol% SiO2 ; some with K2 O and A12 O3 , additions) were determined in 10% acetic acid. Except for a ternary glass (SiO2 -PbO-K2 O) which had a linear dependence on time, all compositions exhibited a linear dependence on the square root of time for the amount of Pb and K removed. Increasing the SiO2 : PbO ratio or the Al2 O3 content improved the durability whereas adding K2 O to a binary PbO-Si02 glass greatly increased the corrosion rate. Activation energies for the rates of Pb and K removal were determined for three compositions and it was deduced that the diffusion of H+ controlled the leaching for binary and 4-component glasses whereas dissolution of the silica network was rate-controlling for the ternary. 相似文献
17.
G. H. BEALL B. R. KARSTETTER H. L. RITTLER 《Journal of the American Ceramic Society》1967,50(4):181-190
Metastable solid solutions with the β-quartz structure can be crystallized from most glasses in the system SiO2 -Mg(AlO2 )2 -LiAlO2 as well as from many containing the additional components Zn(AlO2 )2 Al(AlO2 )3 , Li2 ZnO2 , and Li2 BeO2 . Internal nucleation is afforded by additions of ZrO2 or TiO2 . Either transparent or opaque crystalline materials can be formed from glasses containing about 70% SiO2 . The transparency is due to a combination of low birefringence in the major stuffed β-quartz phase and minute crystal size. Thermal expansions vary from -20 to +50 × 10−7 /°C. Thermal stability is highly variable. Breakdown products include spinel, cordierite, β-spodumene, willemite, mullite, and cristobalite. Magnesian compositions can be strengthened by a 2Li+ ⇌ Mg2+ ionexchange reaction. Abraded flexural strengths range from 30,000 to 160,000 psi. 相似文献
18.
YOSHIRO ISHII KAZUO ARAI HIROSHI NAMIKAWA MITSUHIRO TANAKA AKIRA NEGISHI TAKASHI HANDA 《Journal of the American Ceramic Society》1987,70(2):72-77
Cerium-activated silica (SiO2 ) glasses were prepared by plasma torch chemical vapor deposition (CVD). In Ce-doped SiO2 glasses, most Ce exists as Ce4+ ions; the remaining small amount of Ce3+ ions exhibits a broad fluorescence spectrum with a large Stokes shift, ∼9600 cm-1 , from the excitation spectrum peak of 324 nm. Aluminum and phosphorus codoping considerably increases the Ce3+ ratio and shifts the peaks of both spectra to shorter wavelengths. P codoping is the more effective way to achieve this result and in some cases produces an absorption spectrum similar to that of a Ce-doped phosphate glass. These findings are consistent with the solvatiorn shell model for codoping, as previously proposed. To codope P, a soot remelting method was devised to deal with the highly volatile P2 O5 . 相似文献
19.
Shankar Krishnan J. Richard K. Weber Stuart Ansell April D. Hixson Paul C. Nordine 《Journal of the American Ceramic Society》2000,83(11):2777-2780
We report the first measurements of the structure factor, S ( Q ), and the pair distribution function, G ( r ), of Al6 Si2 O13 (3:2 mullite) in the normal and supercooled liquid states in the temperature range 1776–2203 K. Measurements are obtained by synchrotron X-ray scattering on levitated, laser-heated liquid specimens. The S ( Q ) shows a prepeak at 2.0 Å−1 followed by a main peak at 4.5 Å−1 and a weak feature at 8 Å−1 . The G ( r ) shows a strong (Si,Al)–O correlation at 1.80 Å at high temperature that moves to 1.72 Å as the liquid is supercooled. The second and third nearest neighbor peaks at 3.0 and 4.25 Å sharpen with supercooling. The short-range structure of the high-temperature liquid is similar to the corresponding glasses produced by rapid quenching. Supercooling causes an increase in the concentration of tetrahedral Si4+ ions, which is manifested by the large shift in the first peak to lower ionic distance, r , values in G ( r ). The increase in tetrahedrally coordinated Si4+ ions is offset by an increase in octahedral Al3+ ions. The clustering of the SiO4 4− tetrahedral units results in increased viscosity of the liquid at temperatures below the melting point, which is consistent with Al6 Si2 O13 being a fragile liquid. 相似文献
20.
F. Momo A. Sotgiu E. Baiocchi A. Montenero 《Journal of the American Ceramic Society》1981,64(6):93-c-
EPR spectra of lead silicate glasses doped with small amounts of V2 O5 were studied at −150°C to room temperature. Only the glasses with the higher SiO2 contents produced EPR signals. The spin Hamiltonian parameters are characteristic of the V(IV) species in axial symmetry. The values of g, g ⊥, A, and B indicate that V(IV) is present as VO2plus; in a tetragonally distorted octahedral site. This ion probably does not enter the SiO2 network but rather behaves as a modifier cation. 相似文献