共查询到20条相似文献,搜索用时 437 毫秒
1.
Akira Watanabe Yoshimitsu Takeuchi Goji Saeki 《Journal of the American Ceramic Society》1990,73(10):3094-3095
Crystal growth of rod-shaped β-LiAlO2 was previously reported by us, and the rod-shaped β-LiAlO2 crystals were 1.5 μ in diameter and 10 to 15 μm long. In the present study needle-shaped β-LiAlO2 crystals which were thinner and had larger aspect ratios (length/diameter) than the rodshaped β-LiAlO2 crystals were grown by using LiOH–Al2 O3 –Al(OH)3 –NaOH as the raw material. These crystals were 0.7 to 1 μm in diameter, 9 to 13 μm long, and had aspect ratios of about 10 to 13. 相似文献
2.
Byong-Taek Lee Rajat Kanti Paul Hyun-Jin Hong Kap-Ho Lee 《Journal of the American Ceramic Society》2009,92(4):911-915
Using a multipass extrusion process, continuous porous Al2 O3 body (∼41% porosity) was produced and used as a substrate to fabricate continuous porous TiO2 /Al2 O3 composite membrane. The diameter of the continuous pores of the porous Al2 O3 body was about 150 μm. The TiO2 nanopowders dip coated on the continuous pore-surface Al2 O3 body existed as rutile and anatase phases after calcination at 520°C in air. However, after aging of the fabricated continuous porous TiO2 /Al2 O3 composite membrane in 20% NaOH at 60°C for 24 h, a large number of TiO2 fibers frequently observed on the pore surface. The diameter of the TiO2 fibers was about 150 nm having a high specific surface area. However, after 48-h aging period, the diameter of the TiO2 fibers increased, which was about 3 μm. Most of the TiO2 fibers had polycrystalline structure having nanosized rutile and anatase crystals of about 20 nm. 相似文献
3.
Yiquan Wu Larry L. Hench Jing Du Kwang-Leong Choy Jingkun Guo 《Journal of the American Ceramic Society》2004,87(10):1988-1991
Hydroxyapatite (Ca10 (PO4 )6 (OH)2 , HA) fibers were prepared by electrospinning a precursor mixture of Ca(NO3 )2 ·4H2 O and (C2 H5 O)3 PO with a polymer additive, followed by a thermal treatment. The X-ray diffraction (XRD) analysis of the annealed composite fibers revealed that pure HA phase could be obtained by annealing at 600°C for 1 h. The scanning electron microscopy (SEM) analysis showed the surface of as-electrospun composite fibers with an average diameter of 50 μm was smooth due to the amorphous nature of the polymer. However, the surface of the calcined HA fibers was rough because of the complete removal of the polymer. The pure HA fibers obtained by electrospinning in this work were up to 10 mm in length and 10–30 μm in diameter and the hydroxyapatite grain size was ∼1 μm in the HA fibers. 相似文献
4.
Akira Watanabe Yoshimitsu Takeuchi Goji Saeki 《Journal of the American Ceramic Society》1987,70(10):268-C
LiAlO2 crystals are obtained conventionally in the form of powder. In a few publications, crystal growth of rod-shaped LiAlO2 has been described, but the fiber length was very short, <4 μm. In the present study, rod-shaped β-LiAIO2 crystals 10 to 15 μm long were grown using LiOH-AI2 O3 NaOH as the raw material. 相似文献
5.
Yoshio Ota Saburo Inui Tetsushi Iwashita Toshihiro Kasuga Yoshihiro Abe 《Journal of the American Ceramic Society》1996,79(11):2986-2988
Solid and/or hollow CaF2 fibers were prepared from aragonite whiskers. Aragonite (CaCO3 ) whiskers with diameters of ∼2 μm were converted into CaF2 fibers without deformation by treatment with HF aqueous solution. The resultant CaF2 fibers were polycrystalline with large specific surface areas of ∼60 m2. g−i , and they densified when heated at 800°C. The thickness of the CaF2 reaction layer can be controlled by the concentration of the HF aqueous solution used. Hollow CaF2 fibers were successfully prepared when CaCO3 whiskers covered with CaF2 were leached with HC1. 相似文献
6.
Young-Min Kim Seong-Hyeon Hong Doh-Yeon Kim 《Journal of the American Ceramic Society》2000,83(11):2809-2812
The effect of TiO2 /SiO2 addition on the grain growth of alumina was reinvestigated. TiO2 promoted the grain growth, but there was no abnormal grain growth. However, codoping of TiO2 and SiO2 resulted in a duplex microstructure consisting of large platelike grains, ∼800 μm long and ∼100 μm thick, and fine matrix grains. The observed anisotropic abnormal grain growth was explained in terms of liquid formation during heat treatment. 相似文献
7.
Emission properties of PbO–Bi2 O3 –Ga2 O3 glasses doped with Ho3+ were investigated for fiber-optic amplification at the 1.18 μm wavelength region. When the glasses were doped with Ho3+ ions only, there was a weak emission at 1.18 μm with a lifetime of ∼200 μs. However, when Yb3+ ions were codoped, the lifetime of the 1.18 μm emission increased to 630 μs together with a significant increase in intensity. A similar enhancement in the intensity and lifetimes was realized for the 2.05 μm emission. These effects are due to energy transfer from the Yb3+ :2 F5/2 to the Ho3+ :5 I6 level. Devitrification of the ternary PbO–Bi2 O3 –Ga2 O3 glasses was efficiently suppressed by adding 10 mol% GeO2 . Optimum Ho3+ concentration was ∼0.4 mol%, whereas Yb3+ ions can be added up to the solubility limit. 相似文献
8.
Youren Xu Chao M. Huang Waltraud M. Kriven Avigdor Zangvil 《Journal of the American Ceramic Society》1994,77(8):2213-2216
The microstructure of a pressureless sintered (1605°C, 90 min) O'+β' SiAlON ceramic with CeO2 doping has been investigated. It is duplex in nature, consisting of very large, slablike elongated O' grains (20–30 μm long), and a continuous matrix of small rodlike β' grains (< 1.0 μm in length). Many α-Si3 N4 inclusions (0.1–0.5 μm in size) were found in the large O' grains. CeO2 -doping and its high doping level as well as the high Al2 O3 concentration were thought to be the main reasons for accelerating the reaction between the α-Si3 N4 and the Si-Al-O-N liquid to precipitate O'–SiAlON. This caused the supergrowth of O' grains. The rapid growth of O' crystals isolated the remnant α–Si3 N4 from the reacting liquid, resulting in a delay in the α→β-Si3 N4 transformation. The large O' grains and the α-Si3 N4 inclusions have a pronounced effect on the strength degradation of O'+β' ceramics. 相似文献
9.
Myeong-Heon Um Chul-Tae Lee Hidehiro Kumazawa 《Journal of the American Ceramic Society》2001,84(5):1181-1183
TiO2 fibers were formed by thermal treatment of layered H2 Ti4 O9 (hydrous titanium dioxide) and KHTi4 O9 synthesized by ion-exchange reactions. The calcination of the former at 900° and 1050°C for 3 h yielded TiO2 fibers with anatase and rutile phases, whose length and diameter were 15–20 and 2–5 μm and 10–15 and 3–5 μm, respectively. The thermal treatment of the latter at temperatures of 250° to 500°C yielded pure K2 Ti8 O17 , which tended to decompose to K2 Ti6 O13 and TiO2 at temperatures >600°C. At 1050°C, K2 Ti6 O13 phase was formed with rutile TiO2 fibers, whose length and diameter were 10–20 and 1–3 μm, respectively. 相似文献
10.
Ken-ichi Noda Wataru Sakamoto Toshinobu Yogo Shin-ichi Hirano 《Journal of the American Ceramic Society》1997,80(9):2437-2440
Crack-free and dense KTiOPO4 (KTP) fibers could be successfully synthesized through metallo-organics. A homogeneous, drawable KTP precursor solution was prepared from the reaction of (n BuO)2 P(O)(OH), Ti(OEt)4 , and KOEt. KTP precursor fibers crystallized to a single-phase KTP at 650°C for 0.5 h. KTP fibers were a few centimeters in length and 10–150 μm in diameter. The density of the KTP fibers was higher than 2.97 g/cm3 (>98% of theoretical density). 相似文献
11.
Toshio Shimoo Yoshiaki Morisada Kiyohito Okamura 《Journal of the American Ceramic Society》2003,86(5):838-845
Three types of polycarbosilane-derived SiC fibers (Nicalon, Hi-Nicalon, and Hi-Nicalon S) with different SiO2 film thicknesses ( b ) were subjected to exposure tests at 1773 K in an argon-oxygen gas mixture with an oxygen partial pressure of 1 Pa. The suppression effect of a SiO2 coating on active oxidation was examined through TG, XRD analysis, SEM observation, and tensile tests. All the as-received fibers were oxidized in the active-oxidation regime. The mass gain and the SiO2 film development showed a suppression of active oxidation at b values of ≧0.070 μm for Nicalon, ≧0.013 μm for Hi-Nicalon, and ≧0.010 μm for Hi-Nicalon S fibers. Considerable strength was retained in the SiO2 -coated fibers. For Hi-Nicalon fibers, the retained strength was 71%–90% of the strength in the as-received state (2.14–2.69 GPa). 相似文献
12.
Yoshihito Mizoguchi Masahiro Kagawa Yasuhiko Syono Toshio Hirai 《Journal of the American Ceramic Society》2001,84(3):651-653
Thin films of yttrium aluminum garnet (YAG, Y3 Al5 O12 ) and yttrium iron garnet (YIG, Y3 Fe5 O12 ) were synthesized on single-crystal Al2 O3 substrates by a modification of spray pyrolysis using a high-temperature inductively coupled plasma at atmospheric pressure (spray–ICP technique). Using this technique, films could be grown at faster rates (0.12 μm/min for YAG and 0.10 μm/min for YIG) than using chemical vapor deposition (0.005–0.008 μm/min for YAG) or sputtering (0.003–0.005 μm/min for YIG). The films were dense and revealed a preferred orientation of (211). The growth of YIG was accompanied by coprecipitation of α-Fe2 O3 . The coprecipitation, however, could be largely suppressed by preliminary formation of a Y2 O3 layer on the substrate. 相似文献
13.
Preliminary results indicate that large strains (∼80%) and strain rates (0.001 s−1 ) can be obtained without tearing (or cracking) in fine-grain ZrO2 (0.3 μm) and Al2 O3 /ZrO2 (1 μm) ceramics. Alumina develops crystallographic and morphological texture as previously reported by Heuer et al.1 相似文献
14.
Susan R. Loehr Ki-Ho Chung Cornelius T. Moynihan 《Journal of the American Ceramic Society》1988,71(1):46-C-
A comparative study of infrared absorption due to H2 O and D2 O impurities in a fluorozirconate glass (53ZrF4 ·20BaF2 ·4LaF3 ·3AlF3 ·20NaF) was carried out. The H2 O and D2 O were introduced into the glass by reaction of the surface at 260°C with H2 O and D2 O vapor entrained in a stream of N2 . Reaction with H2 O produced IR absorption bands at 2.9 μm (O–H stretch) and 6.1 μm (H2 O bend). Reaction with D2 O produced bands at 3.9 μm (O–D stretch) and 8.3 μm (D2 O bend). The ratios of the corresponding D2 O/H2 O peak frequencies are 0.74 for both the stretching and bending vibrations, in good agreement with the value of 0.727 predicted from the difference in the OH and OD reduced masses. 相似文献
15.
High-Strength Zirconia Fibers 总被引:1,自引:0,他引:1
David B. Marshall F. F. Lange Peter D. Morgan 《Journal of the American Ceramic Society》1987,70(8):187-C
Fine-grained polycrystalline zirconia fibers have been formed from an acetate precursor. The fibers contained a Y2 O3 additive, which inhibited grain growth (grain size ≤0.5 μm) and allowed the tetragonal phase to be retained at room temperature. Fibers with diameters in the range 2 to 5 μm had strengths in the range 1.5 to 2.6 GPa. 相似文献
16.
Ya-Feng Yang Hui-Yuan Wang Ru-Yi Zhao Yun-Hong Liang Qi-Chuan Jiang 《International Journal of Applied Ceramic Technology》2009,6(3):437-446
The composites synthesized with three kinds of B4 C particles mainly consist of TiC, TiB2 , and the alloy austenite containing Ni element. Ceramic particulate sizes in the composites synthesized with ∼3.5 and ∼45 μm B4 C particles are larger than that synthesized with ∼140 μm B4 C particle. No pores are found between the reinforcing region and matrix in the composites synthesized with ∼3.5 and ∼45 μm B4 C particles, while some large pores exist in the composites synthesized with ∼140 μm B4 C particle. With the decrease of B4 C particle size, the pores in the composites become fewer and the hardness and wear resistance of the composites increase. 相似文献
17.
MANFRED KAHN 《Journal of the American Ceramic Society》1971,54(9):455-457
Effects of grain size and grain growth in Nb-doped BaTiO3 on temperature and frequency dependencies of the dielectric constant were investigated. When 0.65 μm powder is sintered to an average grain size of 1 μm, two dielectric constant peaks indicate the presence of Nb-free BaTiO3 and of Nb-containing material. Single peaks are observed above room temperature after additional grain growth or when 0.07 μm powder is sintered to an average grain size of 1 μm. The Curie point of pure BaTiO3 with 1 μm grains is 4 to 6°C lower than that of material with grains >10 μm. Thermodynamically, this behavior is accounted for by a phase inversion stress ∼ the room-temperature stress. 相似文献
18.
Paul w. France Stephen F. Carter John R. Williams 《Journal of the American Ceramic Society》1984,67(11):c243-c244
Molecular ion absorption due to NH4+ was observed in fluoride glass infrared fibers. The absorption has a double peak at 2.96 and 3.04 μm, and vibrational assignments were made by analogy with other host materials. The position of these peaks could influence the minimum-loss wavelength. 相似文献
19.
Magnesium orthosilicate (forsterite) whiskers were synthesized by an oxidation-reduction reaction in the present investigation. These whiskers were rectangular parallelepipeds, with long sides in a cross-sectional view from two to ten times as long as the short sides, and measuring from several micrometers to 200 μm wide and ∼15 mm in the elongated direction. The Mg2 SiO4 elongation was on the c-axis. The growth mechanism of the whiskers was investigated on the basis of chemical thermodynamics, and the present study revealed that the Mg2 SiO4 whiskers grew by a VS (vapor-solid) mechanism . 相似文献
20.
Wei Zhao Jing Ya Ying Xin Lie E Dan Zhao Heping Zhou 《Journal of the American Ceramic Society》2009,92(7):1607-1609
Textured 0.94Na0.5 Bi0.5 TiO3 –0.06BaTiO3 (NBT–6BT) ceramics were fabricated by templated grain growth (TGG) using anisotropically shaped Na0.5 Bi0.5 TiO3 (NBT) templates. Platelet NBT was synthesized by the topochemical technique, using precursor Na0.5 Bi4.5 Ti4 O15 (NBIT). The NBT particles have an average length of 10–15 μm and a thickness of 1 μm, which are suitable templates for obtaining textured ceramics (especially NBT-based ceramics) by the TGG process. This study revealed that the NBT templates are effective in inducing grain orientation in NBT–6BT ceramics. For NBT–6BT ceramics textured with 5 vol% NBT templates, a Lotgering factor of 0.87 and a d 33 of 299 pC/N are given. 相似文献