共查询到20条相似文献,搜索用时 31 毫秒
1.
Masanobu Kamitakahara Masakazu Kawashita Noboru Miyata Tadashi Kokubo Takashi Nakamura 《Journal of the American Ceramic Society》2004,87(2):235-239
It has been shown that polydimethylsiloxane (PDMS)–CaO–SiO2 –TiO2 and poly(tetramethylene oxide) (PTMO)–CaO–TiO2 hybrids form apatite on their surfaces in a simulated body fluid (SBF) and show mechanical properties similar to those of human cancellous bones. In the present study, changes, caused by soaking in SBF, were measured in the mechanical properties of PDMS–CaO–SiO2 –TiO2 hybrids with different CaO and TiO2 contents and PTMO–CaO–TiO2 hybrids with different CaO contents. Significant decreases in the strength and strain at failure of the hybrids were observed for the PDMS–CaO–SiO2 –TiO2 hybrids with high CaO or TiO2 contents and PTMO–CaO–TiO2 hybrids with a high CaO content after soaking in SBF for 4 w. This indicates that incorporation of a large amount of CaO component into the hybrids should result in the deterioration of the hybrids in the body environment. 相似文献
2.
Jau-Ho Jean Yu-Ching Fang Steve X. Dai David L. Wilcox Sr. 《Journal of the American Ceramic Society》2001,84(6):1354-1360
The devitrification kinetics and mechanism of a low-dielectric, low-temperature, cofirable K2 O–CaO–SrO–BaO–B2 O3 –SiO2 glass-ceramic have been investigated. Crystalline phases including cristobalite (SiO2 ) and pseudowollastonite ((Ca,Ba,Sr) SiO3 ) are formed during firing. Activation energy analysis shows that the nucleation of the crystalline phases is controlled by phase separation of the glass. The crystallization kinetics of both cristobalite and pseudowollastonite obey Avrami-like behavior, and the results show an apparent activation energy close to that of the diffusion of alkaline and alkali ions in the glass, suggesting that diffusion is rate limiting. The above conclusion is further supported by analysis of measured growth rates. 相似文献
3.
The phase relations of the systems ZrO2 –TiO2 and ZrO2 –TiO2 –SiO2 were investigated. X-ray diffraction techniques served as the principal means of analysis. The binary system ZrO2 –TiO2 was found to be one of partial solid solutions with no intermediate compounds. A eutectic point was found to exist at 50 to 55 weight % ZrO2 and 1600°C. A preliminary investigation of the ternary system ZrO2 –TiO2 –SiO2 , although not extensive, resulted in a better understanding of this system, with a fairly accurate location of some of its boundary lines. A eutectic point was located at 2% ZrO2 , 10% TiO2 , and 88% SiO2 at approximately 1500°C. 相似文献
4.
A furnace for use in conjunction with the X-ray spectrometer was developed which was capable of heating small powdered specimens in air to temperatures as high as 1850°C. This furnace was also used for the heating and quenching of specimens in air from temperatures as high as 1850°C. An area of two liquids coexisting between 20 and 93 weight % TiO2 above 1765°± 10°C. was found to exist in the system TiO2 –SiO2 , which is in substantial agreement with the previous work of other investigators. The area of immiscibility in the system TiO2 –SiO2 was found to extend well into the system TiO2 –ZrO2 –SiO2 . The two liquids were found to coexist over a major portion of the TiO2 (rutile) primary-phase area with TiO2 (rutile) being the primary crystal beneath both liquids. The temperature of two-liquid formation in the ternary was found to fall about 80°C. with the first additions of ZrO2 up to 3%. With larger amounts of ZrO2 the change in the temperature of the boundary of the two-liquid area was so slight as to be within the limits of error of the temperature measurement. Primary-phase fields for TiO2 (rutile), tetragonal ZrO2 , and ZrTiO4 were found to exist in the system TiO2 –ZrO2 –SiO2 . SiO2 as high cristobalite is known to exist in the system TiO2 –ZrO2 –SiO2 . 相似文献
5.
Hyunho Shin Sang-Gon Kim Jong-Sung Park Jae-Sul An Kug Sun Hong Hyungsun Kim 《Journal of the American Ceramic Society》2006,89(10):3258-3261
The influence of co-additions of crystalline TiO2 and SiO2 fillers (10 wt% addition in total) to BaO–ZnO–B2 O3 –SiO2 glass on resultant properties was investigated from the viewpoint of applying the material to the barrier ribs of plasma display panels. The substitution of SiO2 for TiO2 reduced the dielectric constant significantly, while it maintained high optical reflectance and appropriate coefficient of thermal expansion (CTE) in the case when TiO2 alone was used. A 5–7.5 wt% SiO2 addition with 2.5–5 wt% TiO2 under the constraint of 10 wt% total fillers demonstrated an optical reflectance of about 55%, a CTE of about 8.3 × 10−6 K−1 (compatible with glass panels), and a dielectric constant of about 7.5, which are promising properties for the barrier rib application. 相似文献
6.
Wei Chen Xiaoming Tao Junying Zhang Qi Fang Jun Yang 《Journal of the American Ceramic Society》2005,88(11):2998-3002
SiO2 –TiO2 –methylcellulose (MC) composite materials processed by the sol-gel technique were studied for optical waveguide applications. Dense, crack-free and homogeneous films as thick as 2 μm were obtained via the organic binder MC-assisted sol–gel process and single coating with low-temperature treatment. Light waveguiding in such hybrid film was demonstrated at a wavelength of 650 nm. About 1.1 dB/cm or lower propagation loss for the SiO2 (80 mol%)–TiO2 (20 mol%)–MC (22 wt%) film can be achieved. The effects of thermal treatment on the structure and properties of the gel films were also investigated. 相似文献
7.
Cristina Siligardi Luca Lusvarghi Monia Montorsi Cecilia Vernia 《Journal of the American Ceramic Society》2008,91(3):990-995
In this work several complementary techniques have been employed to carefully characterize the sintering and crystallization behavior of CaO–Al2 O3 –ZrO2 –SiO2 glass powder compacts after different heat treatments. The research started from a new base glass 33.69 CaO–1.00 Al2 O3 –7.68 ZrO2 –55.43SiO2 (mol%) to which 5 and 10 mol% Al2 O3 were added. The glasses with higher amounts of alumina sintered at higher temperatures (953°C [lower amount] vs. 987°C [higher amount]). A combination of the linear shrinkage and viscosity data allowed to easily find the viscosity values corresponding to the beginning and the end of the sintering process. Anorthite and wollastonite crystals formed in the sintered samples, especially at lower temperatures. At higher temperatures, a new crystalline phase containing ZrO2 (2CaO·4SiO2 ·ZrO2 ) appeared in all studied specimens. 相似文献
8.
Mohsen Mahmoudysepehr Vahak K. Marghussian 《Journal of the American Ceramic Society》2009,92(7):1540-1546
Zirconolite (CaZrTi2 O7 ) is a mineral that has a high containment capacity for actinides and lanthanides and is considered to be a good candidate for the immobilization of radioactive wastes. The glass–ceramic technique seems to be a very suitable and convenient method to produce zirconolite crystals by precipitating them in a specific glass matrix. In this study, development of a new zirconolite-based glass–ceramic belonging to SiO2 –PbO–CaO–ZrO2 –TiO2 –(B2 O3 –K2 O) system was investigated. The presence of PbO, together with B2 O3 and K2 O, allowed the preparation of a X-ray diffraction (XRD) amorphous glass with a relatively high concentration of ZrO2 and TiO2 , which was successfully converted to a glass–ceramic containing 34 wt% of zirconolite after heating at 770°C for 4 h. Differential thermal analysis, XRD, scanning electron microscope, and energy dispersive X-ray spectroscopy were used to determine the crystallization conditions, identify the crystallized phases, determine their compositions and quantities and observe and analyze the microstructures. The zirconolite crystals showed a platelet morphology with a monoclinic structure characterized by a =1.246 nm, b =0.7193 nm, c =1.128 nm, and β=100.508°. 相似文献
9.
Masayuki Fujimoto Tomoya Ohno Hisao Suzuki Hiroshi Koyama Junzo Tanaka 《Journal of the American Ceramic Society》2005,88(11):3264-3266
We characterized SiO2 –TiO2 nano-hybrid particles, prepared using the sol–gel method, using high-resolution transmission microscopy. A few nanometer-ordered TiO2 anatase crystallites could be observed on the monodispersed SiO2 nanoparticle surface. The quantum size effect of the TiO2 anatase crystallites is attributed to the blue shift of the absorption band. The rough surface of the SiO2 –TiO2 nano-hybrid particles was derived from the developed growth planes of the TiO2 anatase crystallites, grown from fully hydrolyzed Ti alkoxide that did not react with acetic acid during the crystallization process at 600°C thermal annealing. 相似文献
10.
Results of a study of phase equilibria in the system CaO–TiO2 –SiO2 are presented. A prominent feature of the liquidus surface is a large two-liquid region which appears on the equilibrium diagram as a broad band extending from the SiO2 -CaO side to the SiO2 -TiO2 side of the triangle. Evidence for the liquid immiscibility and the significance of the resulting large high-temperature liquidus region in silicate technology are discussed. Representative paths of crystallization of liquids in the system under equilibrium conditions are outlined. It is shown that solid solution in the system is virtually nonexistent except for the small-scale substitution of Ti4+ for Si4+ in wollastonite. Indices of refraction of glasses are given. Composition and temperature are listed for the twelve liquidus ternary invariant points. 相似文献
11.
Equilibrium relations in the system NiO–TiO2 –SiO2 in air have been investigated in the temperature range 1430° to 1660°C. The most conspicuous feature of the phase relations is the existence of a cation-excess spinel-type phase, in addition to NiO and NiTiO3 , on the liquidus surface and at subsolidus temperatures down to 1430°C. Three invariant points have been located on the liquidus. There is a peritectic at 1540°C characterized by coexisting NiO ( ss ), spinel( ss ), cristobalite, and liquid of composition 47 wt% NiO, 29 wt% TiO2 , and 24 wt% SiO2 . Two eutectics are present, one at 1480°C, with spinel( ss ), NiTiO3 , cristobalite, and liquid (42 wt% NiO, 43 wt% TiO2 , and 15 wt% SiO2 ), as the coexisting phases. The other is at 1490°C with NiTiO3 , rutile, cristobalite, and liquid (32 wt% NiO, 56 wt% TiO2 , and 12 wt% SiO2 ). A liquid miscibility gap extends across the diagram from the two bounding binary systems NiO–SiO2 and TiO2 –SiO2 . 相似文献
12.
13.
Badri Rangarajan Tom Shrout Michael Lanagan 《Journal of the American Ceramic Society》2009,92(11):2642-2647
Nucleation and crystallization kinetics of fresnoite (Ba2 TiSi2 O8 ) crystals in BaO–TiO2 –SiO2 glasses have been explored for dielectric applications. The volume fractions crystallized at different temperatures and times were tracked by XRD analysis. The activation energy of crystallization was estimated from DTA results to be about 528 kJ/mol, which is consistent with the value obtained by XRD results. The Avrami parameter values calculated at different temperatures from DTA results were found to be between 3.2 and 3.9, indicating that the growth is three dimensional and the mechanism of growth is interface-controlled. Additionally, because of compositional similarities, the dielectric contrast between the glass (ɛr ∼15) and the resulting glass–ceramic (ɛr ∼18) was minimal. 相似文献
14.
The dissolution of MgO in CaO–"FeO"–CaF2 –SiO2 slags has been studied in the temperature range 1573°–1673° K under static conditions. The concentration profiles of Mg in the product Mg1-x Fex O solid-solution layer as well as slag were determined by EDS analysis. From this, the diffusivities of MgO in the slag and the. interdiffusivities in solid solution were estimated. The dissolution of MgO in CaO–"FeO"–CaF2 –SiO2 slags increased with CaF2 content. 相似文献
15.
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
16.
Data obtained by quenching, thermal, and high-temperature X-ray techniques are presented for the three binary systems CaF2 –BeF2 , MgF2 –BeF2 , and LiF–MgF2 . The systems CaF2 –BeF2 and MgF2 –BeF2 are presented as weakened models of the systems ZrO2 –SiO2 and TiO2 –SiO2 , respectively. The compound CaBeF4 is a model of ZrSiO4 (zircon). New data obtained for the system LiF–MgF2 explain many discrepancies among the results of previous authors. Solid solution is almost complete between LiF and MgF2 at elevated temperatures, but a small gap occurs at the eutectic (735°C.) with extensive exsolution at lower temperatures. 相似文献
17.
In this work the corrosion behaviors of zirconia refractory (partially MgO-stabilized zirconia) was investigated in CaO–SiO2 –MgO–CaF2 slag with varying CaF2 content at 1873 K. To figure out the corrosion mechanism, the characteristics of present slag at high temperature were examined in terms of melting temperature and vaporization behaviors. Corrosion experiment and melting temperature measurement were carried out by heating microscope (HM) and the vaporization phenomenon was investigated by thermo gravimetry–differential scanning calorimetry. After experiment, the corroded interfaces of zirconia refractory by slag were analyzed by scanning electron microscope-energy dispersive spectroscopy and electron probe microanalysis. With an addition of CaF2 , three different layers were formed at the interface of slag and zirconia refractory. Furthermore, the corrosion behaviors of zirconia refractory were found to be continuously accelerated with an increase of CaF2 which facilitated the dissolution of intermediate compound. On the other hand, melting temperature of CaO–SiO2 –MgO–CaF2 slag showed no continuous decrease with an increase of CaF2 . Also, considerable vaporization of fluoride gas was occurred in high CaF2 containing slag during HM experiment which might cause a gradual change of slag composition and also environmental pollution. From the results, present study suggested that a proper amount of CaF2 should be added when it is used for enhancing refining capacity of slag in order not to cause any severe damage of zirconia-based refractory by slag. 相似文献
18.
Sang-Gon Kim Jong-Sung Park Jae-Sul An Kug Sun Hong Hyunho Shin Hyungsun Kim 《Journal of the American Ceramic Society》2006,89(3):902-907
Various types of crystalline ceramic fillers (TiO2 , ZrO2 , Al2 O3 , MgO, and cordierite) were added to BaO–ZnO–B2 O3 –SiO2 (BZBS) glass (5–20 wt%), and the resultant dielectric constant, coefficient of thermal expansion (CTE), and optical reflectance were investigated for the application of the composites to the barrier ribs in plasma display panels. All the investigated fillers were partially dissolved into the glass at the fabrication temperature (575°C), and the residual fillers were aligned along the boundaries of sintered glass frits. By considering all aspects of the properties, the addition of TiO2 fillers of about 10 wt% to BZBS glass was the most desirable of the types of fillers investigated. The addition of TiO2 filler (10 wt%) yielded 61% in optical reflectance, 8.3 × 10−6 K–1 in coefficient of thermal expansion, and 15.5 in dielectric constant, which were properties comparable with the currently used Pb-based barrier ribs. 相似文献
19.
Bertha Alicia Vázquez Angel Caballero Pilar Pena 《Journal of the American Ceramic Society》2003,86(12):2195-2199
Compatibility relations of Al2 O3 in the quaternary system Al2 O3 –CaO–MgO–SiO2 were studied by firing and quenching followed by microstructural and energy-dispersive X-ray examination. A projection of the liquidus surface of the primary phase volume of Al2 O3 was constructed in terms of the CaO, SiO2 , and MgO contents of the mixtures recalculated to 100 wt%. Two invariant points, where four solids coexist with a liquid phase, were defined, and the positions of the isotherms were tentatively established. The effect of SiO2 , MgO, and CaO impurities on Al2 O3 growth also was studied. 相似文献
20.
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