共查询到20条相似文献,搜索用时 15 毫秒
1.
MURLI H. MANGHNANI 《Journal of the American Ceramic Society》1972,55(7):360-365
Ultrasonic interferometry was used to measure elastic-wave velocities and moduli in six Na2 O-TiO2 -SiO2 glasses; three glasses contained 20 mol% TiO2 and three 25 mol% TiO2 . The elastic moduli and their pressure derivatives varied systematically with the SiO2 /Na2 O molar ratio of the glasses. In the group of glasses which contained 20 mol% TiO2 , dK/dP ( K =bulk modulus) decreased linearly from 4.85 to 2.59 as the SiO2 /Na2 O ratio increased; in the other group, dK/dP decreased from 4.00 to 3.05. Similarly, dμ/dP (μ=shear modulus) decreased with the SiO2 /Na2 O ratio, but somewhat non-linearly. The extrinsic and intrinsic contributions to the temperature dependencies of the elastic moduli are evaluated in light of the measured pressure dependencies of these moduli. 相似文献
2.
AKIO MAKEHIMA YOSHIAKI TAMURA TERUO SAKAINO 《Journal of the American Ceramic Society》1978,61(5-6):247-249
Glasses in the system Al2 O3 -Y2 O3 -SiO2 , containing TiO2 and La2 O3 , were investigated. Glasses of high refractive index and elastic modulus were developed. The observed Young's and shear moduli of these glasses show good agreement with theoretical values. Agreement was also found between the observed and calculated values of refractive index when the Appen's empirical coefficients were used. 相似文献
3.
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
4.
PETER C. SCHULTZ 《Journal of the American Ceramic Society》1976,59(5-6):214-219
A series of glasses in the TiO2 -SiO2 system was prepared by the flame hydrolysis boule process. Clear glasses containing as much as 16.5 wt% TiO2 were obtained. More TiO2 caused opacity due to phase separation and anatase/rutile crystallization during glass boule formation. Glasses in the 12 to ∼17 wt% TiO2 range were metastable and showed structural rearrangements on heat treatment at temperatures as low as 750CEC (∼200° below the annealing point). These changes were accompanied by large changes in thermal expansion. Thermal treatment can be designed to produce almost any desired expansion between α-200+700 =−5 × 10-7 /°C and +10 × 10-7 /°C. Zero expansion between 0 and 550°C was obtained. Evidence that these changes are due to phase separation and anatase formation is presented. Viscosity data in the glass transition range, refractive index, and density are also presented. 相似文献
5.
Teiichi Hanada Yoshinari Kato Setsuhisa Tanabe Naohiro Soga 《Journal of the American Ceramic Society》1992,75(9):2335-2338
Amorphous films in the system AlPO4 –TiO2 were prepared by an rf-sputtering method, and their physical properties, such as density, refractive index, and thermal expansion coefficient, and the infrared absorption spectra were measured. The thermal expansion coefficient increased linearly with increasing TiO2 content. The results of the molar refractivity and the infrared absorption spectra indicated that the coordination number of titanium ions in these films is higher than that in SiO2 –TiO2 glasses with a negative thermal expansion, in which Ti4+ ions are tetrahedrally coordinated. In order to confirm the coordination state of the titanium ions in these amorphous films, titanium K -band emission spectra were obtained by X-ray emission spectroscopy, revealing sixfold coordination. The higher coordination state of Ti4+ was considered to account for these amorphous films not exhibiting negative thermal expansion, as in the SiO2 –TiO2 system. 相似文献
6.
An investigation was made of the effect of TiO2 on the glassforming region and on the physical properties of glasses in the system Na2 O-B2 O3 -SiO2 TiO2 . Glasses containing up to 45 mole % TiO2 may be formed with an alkali content of 30 mole %. At lower alkali contents (10 mole % Na2 O) glasses may be formed containing up to 22 mole % TiO2 . The way in which the coefficient of linear thermal expansion and the transformation and softening temperatures are affected by TiO2 additions has been determined. 相似文献
7.
Bh. V. JANAKIRAMA RAO 《Journal of the American Ceramic Society》1964,47(9):455-463
Glasses corresponding to mole formulas R2 TiO3 and R2 Ti2 O5 were prepared in 1- to 5-g quantities by quenching in a platinum crucible. K2 O, Rb2 O, and Cs2 O formed fairly stable glasses with TiO2 . On heat treatment, these glasses nucleated readily and formed opal-like glasses. Li2 O and Na2 O, however, did not form glasses with TiO2 in 1-g quantities. Hygroscopicity increased with the alkali content and decreased with the increase in TiO2 concentration. The refractive indices of the glasses ranged from 1.66 to 1.90. These facts indicate that TiO2 is a glass former in its own right and that Ti4+ exists in sixfold coordination in these glasses. 相似文献
8.
W. ZDANIEWSKI 《Journal of the American Ceramic Society》1975,58(5-6):163-169
Crystallization sequences of glasses with compositions in the tridymite primary phase field of the MgO-Al2 O3 -SiO2 system were studied by DTA, X-ray diffraction, and other techniques. Crystallization was catalyzed by the addition of 7 wt% of either ZrO2 or TiO2 . Up to 10 wt% CeO2 was also added to some glasses. Metastable solid solutions with the high-quartz structure exhibiting varying lattice parameters commonly occurred at low temperatures, transforming into a high cordierite at higher temperatures. Depending on the composition and heat treatment, other phases also appeared, e.g. Ce2 Ti2 O4 (Si2 O7 ). The rate of crystallization was markedly dependent on the catalyst. Colloidal precipitation of the catalyst accompanied by bulk crystallization of the glass was observed with ZrO2 , but no crystalline TiO2 was detected. In the presence of CeO2 , TiO2 was a more effective catalyst than ZrO2 . Although CeO2 lowered the melting temperatures of the glass-ceramics, it increased the stability of the glasses and inhibited volume nucleation, causing coarse structures to form on crystallization. 相似文献
9.
Guangxiu Cao Yaogang Li Qinghong Zhang Hongzhi Wang 《Journal of the American Ceramic Society》2010,93(1):25-27
La-doped TiO2− x F x (La–TiO2− x F x ) powders were prepared by the sol–gel method. X-ray diffraction results showed that La efficiently inhibited grain growth. X-ray photoelectron spectroscopy spectra revealed that La2 O3 and O–Ti–F bonds have formed, the La2 O3 maintained the high surface area of TiO2− x F x after calcination at a temperature above 500°C, while the O–Ti–F bonds increased the oxidation potential of the photogenerated hole in the valence band. The UV-vis spectroscopy of the La–TiO2− x F x showed that the presence of intraband gap states was likely responsible for its absorption of visible light. When the molar ratios of La and F to Ti were 1.5:100 and 5:100, respectively, and calcined at 500°C, the photocatalytic degradation rate of methylene blue over La–TiO2− x F x was about 1.5 times higher than that of F-doping TiO2 . 相似文献
10.
Shoji Nagaoka Masanori Nagata Kenji Arinaga Kiyoshi Shigemori Makoto Takafuji Hirotaka Ihara 《Coloration Technology》2007,123(6):344-350
In order to develop environmentally friendly coloured materials, cellulose composite spherical microbeads hybridised with titanium dioxide (TiO2 ) particles and inorganic pigment were prepared by a phase-separation method using viscose and an aqueous solution containing sodium polyacrylate. Findings regarding the relationships between cellulose xanthate and the electronic characteristics of TiO2 particles used in the cellulose/inorganic material composite sphering process are also reported. These findings suggest that the location of TiO2 particles in cellulose microbeads is related to electrical repulsion between the xanthate (CSS− ) group and TiO2 . The use of TiO2 powder as colour pigment is limited, as its colour is white. The cellulose composite spherical microbeads covered with TiO2 and Fe2 O3 particles were developed by addition of iron oxide (Fe2 O3 ). Their surfaces were viewed by laser microscope and using SEM images. These composite microbeads retained the photocatalytic property of TiO2 . Cellulose/TiO2 /Fe2 O3 composite spherical microbeads with both colour function and photocatalytic properties were successfully prepared. 相似文献
11.
Toshihiro Kasuga Yoshimasa Hosoi Masayuki Nogami Mitsuo Niinomi 《Journal of the American Ceramic Society》2001,84(2):450-52
Calcium phosphate invert glasses, which contain P2 O7 2− and PO4 3− ions, have been prepared via the addition of a small amount of TiO2 . The formation of bonelike calcium phosphate apatite on the surface of the phosphate invert glasses was examined in simulated body fluid (SBF) at a temperature of 37°C. Soaking for 20 d resulted in the deposition of leaflike apatite particles on 6CaO·3P2 O5 ·TiO2 invert glass (based on molar ratio). The glass had much-greater chemical durability against SBF, in comparison with a metaphosphate glass; P ions were not dissolved excessively from the 6CaO·3P2 O5 ·TiO2 glass, so the apatite formation was not suppressed. 相似文献
12.
The crystallization of several Nb2 O5 -catalyzed glasses in the Na2 O.Al2 O.SiO2 system was studied using DTA, X-ray diffraction, and electron microscopy. The Nb2 O5 was an effective nucleation catalyst; fine-grained body-nucleated glass-ceramic materials containing hexagonal nepheline and NaNbO3 were obtained. The crystallization sequence and final crystalline phases in these compositions were quite different from those found in the equivalent TiO2 analogs. The addition of small amounts of carbides and nitrides at the expense of oxides in the initial glass batch markedly affected the final crystalline phases. 相似文献
13.
Xinhua Liang David M. King Peng Li Alan W. Weimer 《Journal of the American Ceramic Society》2009,92(3):649-654
Atomic layer deposition (ALD) has been successfully utilized for the conformal and uniform deposition of ultrathin titanium dioxide (TiO2 ) films on high-density polyethylene (HDPE) particles. The deposition was carried out by alternating reactions of titanium tetraisopropoxide and H2 O2 (50 wt% in H2 O) at 77°C in a fluidized bed reactor. X-ray photoelectron spectroscopy confirmed the deposition of TiO2 and scanning transmission electron microscopy showed the conformal TiO2 films deposited on polymer particle surfaces. The TiO2 ALD process yielded a growth rate of 0.15 nm/cycle at 77°C. The results of inductively coupled plasma atomic emission spectroscopy suggested that there was a nucleation period, which showed the reaction mechanism of TiO2 ALD on HDPE particles without chemical functional groups. TiO2 ALD films deposited at such a low temperature had an amorphous structure and showed a much weaker photoactivity intensity than common pigment-grade anatase TiO2 particles. 相似文献
14.
Bh. V. JANAKIRAMA RAO 《Journal of the American Ceramic Society》1963,46(3):107-114
By a progressive weight percent substitution of TiO2 for SiO2 at various rations of concentration of K2 O and PbO, the entire region of glass formation in the quaternary system K2 O–PbO–SiO2 –TiO2 was covered with 51 glass compositions. The properties of these glasses were determined and studied with respect to the role of TiO2 in the system. The results indicated that the dielectric constant increased progressively with increasing TiO2 concentration whereas the dissipation factor showed an overall decrease, when measured at 1 Mc and 25°C. Density and the refractive index increased progressively with increasing TiO2 concentration but deviated from the additive relation. Chemical durability, expansivity, and softening temperature vs. composition curves showed definite inflections. The effect of TiO2 on oxygen packing indicated that Ti4+ strengthens the network in lower concentrations and weakens the network in higher concentrations in this system. It appears to be likely that Ti4+ changes its coordination number form 4 to 6. 相似文献
15.
CHANDRA S. RAY WENHAI HUANG DELBERT E. DAY 《Journal of the American Ceramic Society》1987,70(8):599-603
The kinetics of crystallization of a 25Li2 O · 75SiO2 (wt%) glass doped with Pt, Cu, Au, TiO2 , and P2 O5 were studied using nonisothermal techniques. The activation energy, E , and the frequency factor, v , for the overall crystallization process depended directly on the critical cooling rate for the glass formation, Rc , of these glasses. The crystallization kinetics of several other glasses in the lithia-silica system were also studied as a function of composition, critical cooling rate, and liquidus temperature, Tm . E and v for these glasses were more dependent on the liquidus temperature than on Rc . 相似文献
16.
Yingying Lv Yan Ding Jiahong Zhou Wenmin Xiao Yuying Feng 《Journal of the American Ceramic Society》2009,92(4):938-941
The doping of titanium dioxide (TiO2 ) with various metal or nonmetal elements has been considered as an effective strategy to extend the photoactive wavelength region to visible light. In this paper (nitrogen [N] and sulfur [S])-codoped anatase TiO2 nanoparticles were prepared via a sol–gel route, followed by a heat treatment at elevated temperatures. The as-prepared samples were extensively characterized by X-ray diffraction, UV–Vis absorption spectroscopy, and X-ray photoelectron spectroscopy. The N, S-codoped TiO2 nanoparticles showed a strong visible light absorption and exhibited an enhanced photocatalytic activity for the degradation of methylene blue as compared with the pure, N- or S-doped TiO2 under either UV light or solar light irradiation. 相似文献
17.
Gao Tang Zhiyong Yang Lan Luo Wei Chen 《Journal of the American Ceramic Society》2008,91(5):1686-1689
The glass-forming region of the GeSe2 –Ga2 Se3 –PbI2 system was determined and homogeneous glasses were prepared. The maximum dissolvable PbI2 can be up to 50 mol%. The structures of glasses were characterized by Raman spectroscopy. The thermal, optical, and some basic physical properties of the glasses were investigated. The results show that GeSe2 –Ga2 Se3 –PbI2 glasses have a wide region of transmission window (0.7–16 μm) and high refractive index (∼2.5) with the addition of PbI2 . The glasses have good glass-forming ability and high glass transition temperatures. Consequently, these novel glasses may be promising candidate materials for infrared optics and nonlinear optical field. 相似文献
18.
Setsuhisa Tanabe Naohiro Saga Kazuyuki Hirao Teiichi Hanada† 《Journal of the American Ceramic Society》1990,73(6):1733-1736
SiO2 –Al2 O3–Eu2 O3 glasses were prepared for the composition 50siO2 ·(50 – x )Al2 O3·x Eu2 O3 , and their density, sound velocity, and elastic modulus were measured. The chemical shift of the AIK a band emission spectra and the isomer shift of 151 Eu by Mössbauer effect were obtained to determine the coordination states of Al3+ and Eu3+ ions in these glasses. It was found that the coordination number of Eu3+ ions was 12 and that the average coordination number of A13+ ions was almost 5 in these glasses. By introducing Eu2 O3 , the packing of constituent ions was strongly enhanced and the elastic modulus increased in this system. The compositional dependence of the molar volume and elastic modulus were explained by these states of high coordination number for Eu3+ and low coordination number for Al3+ ions compared with those in the corresponding M2 O3 crystals. 相似文献
19.
Anatase nanocrystalline titanium dioxide (TiO2 ) with high photocatalytic activities was prepared by hydrothermal crystallization with the addition of acetic acid. The presence of acetic acid could arrest the growth of the nanocrystallites during the hydrothermal processes and be propitious to form nanocrystallites with round edges and corners. This morphology of (TiO2 ) had more active sites in the photocatalytic process and showed high photocatalytic activity in the degradation of the methylene blue in the aqueous solution. 相似文献
20.
Oxyfluoronitride Glasses with High Elastic Modulus and Low Glass Transition Temperatures 总被引:1,自引:0,他引:1
Amir Reza Hanifi Annaïk Genson Michael J. Pomeroy Stuart Hampshire 《Journal of the American Ceramic Society》2009,92(5):1141-1144
The preparation and properties of novel calcium aluminosilicate glasses containing both nitrogen and fluorine are reported. Nitrogen increases Young's modulus and microhardness of oxide glasses by ∼25%. However, one of the major disadvantages of the use of oxynitride glasses for high-stiffness applications is the fact that nitrogen also increases glass viscosity. Melting temperatures of the order of ∼1700°C are required to achieve sufficiently low viscosities for glass forming and drawing processes. Fluorine substitution for oxygen in Ca–Si–Al–O–N glasses yields significant decreases in glass transition temperature and glass melting temperature as well as increasing nitrogen solubility to levels much higher than that previously reported for glasses made by melting CaO, SiO2 , Si3 N4 , and Al2 O3 powder mixtures. The important effect that N results in increased elastic modulus is not diminished by the addition of fluorine. Thus, it is possible to produce novel oxyfluoronitride glasses with a high elastic modulus but melting and working can be carried out at more conventional glass processing temperatures. 相似文献