共查询到20条相似文献,搜索用时 31 毫秒
1.
Junqing Hu Qingyi Lu Kaibin Tang Shuhong Yu Yitai Qian Guien Zhou Xianming Liu 《Journal of the American Ceramic Society》2000,83(2):430-432
A benzene–thermal reaction of TiCl4 and NaN3 at 350°–380°C was conducted for the preparation of nanocrystalline TiN. Powder X-ray diffractometry patterns indicated that the powder was cubic-phase TiN with a lattice constant a = 4.23656 Å. Transmission electron microscopy images showed the TiN powders consisted of uniform spherical particles with an average diameter of 50 nm. The binding energies of Ti 2 p 3/2 and N 1 s core levels at the positions of 454.85 and 397.1 eV, respectively, and the Ti:N atomic ratio of 1.08:1.00 were detected by X-ray photoelectron spectra. A possible formation mechanism of TiN was proposed. 相似文献
2.
Shuichi Kawano Junichi Takahashi Shiro Shimada 《Journal of the American Ceramic Society》2003,86(9):1609-1611
Nano-sized TiO2 powders were prepared by controlled hydrolysis of TiCl4 and Ti(O-i-C3 H7 )4 solutions and nitrided in flowing NH3 gas at 700°–1000°C to form TiN. Nano-sized TiN was densified by spark plasma sintering at 1300°–1600°C to produce TiN ceramics with a relative density of 98% at 1600°C. The microstructure of the etched ceramic surface was observed by SEM, which revealed the formation of uniformly sized 1–2 μm grains in the TiCl4 -derived product and 10–20 μm in the Ti(O-i-C3 H7 )4 -derived TiN. The electric resisitivity and Vickers micro-hardness of the TiN ceramics was also measured. 相似文献
3.
Nanocrystalline aluminum nitride (AlN) with surface area more than 30 m2 /g was synthesized by nitridation of nanosized δ-Al2 O3 particles using NH3 as a reacting gas. The resulting powders were characterized by CHN elemental analysis, X-ray diffraction (XRD), Fourier transform infrared spectra, X-ray photoelectron spectra, field-emission scanning electron microscopy, transmission electron microscopy, and Brunauer–Emmett–Teller surface area techniques. It was found that nanocrystalline δ-Al2 O3 was converted into AlN completely (by XRD) at 1350°–1400°C within 5.0 h in a single-step synthesis process. The complete nitridation of nanosized alumina at relatively lower temperatures was attributed to the lack of coarsening of the initial δ-Al2 O3 powder. The effect of precursor powder types on the conversion was also investigated, and it was found that α-Al2 O3 was hard to convert to AlN under the same conditions. 相似文献
4.
Preparation of Titanium Nitride/Alumina Laminate Composites 总被引:2,自引:0,他引:2
Jing-Xian Zhang Zheng-Ren Huang Dong-Liang Jiang Shouhong H. Tan Zhijian Shen Mats Nygren 《Journal of the American Ceramic Society》2002,85(5):1133-1138
A preparation route for TiN/Al2 O3 laminate composites has been described. A water-based process using Al2 O3 and TiN slurries with solids contents of 40 and 35 vol%, respectively, was used to make TiN and Al2 O3 tapes. The removal of the binder was monitored by weight-loss measurements in a thermogravimetry unit. Bodies composed of Al2 O3 and TiN tapes were densified at temperatures of 1400° and 1500°C using the Spark Plasma Sintering® (SPS) technique. Densities of >98% of the theoretical densities were approached. Crack-free and almost fully densified TiN/Al2 O3 compacts were prepared by heating the burned-out green bodies to the final sintering temperature (1500°C) at a rate of 100°C/min, and with a holding time of 5–10 min, under a pressure of 75 MPa. The microstructures of the obtained compacts were studied using scanning electron microscopy. Grain sizes in the sintered Al2 O3 and TiN compacts were similar to those of the precursor powders. Hardness and indentation fracture toughness were measured at room temperature, and the monolithic compacts as well as the laminate composites exhibited anisotropic mechanical behavior; i.e., the cracks propagated much more easily in a direction parallel to the laminas than perpendicular to them. 相似文献
5.
Jingguo Li Lian Gao Jing Sun Qinghong Zhang Jingkun Guo Dongsheng Yan 《Journal of the American Ceramic Society》2001,84(12):3045-3047
Nanocrystalline TiN powder has been synthesized by the direct nitridation of nanocrystalline TiO2 powder. Powder XRD patterns indicated that the TiN nanocrystalline powder could be obtained by nitridation at 800°C for 5 h. TEM micrographs showed that the synthesized TiN powders consisted of uniform spherical particles with an average diameter of ∼20 nm. The effect of the nitridation temperature and holding time on the powder properties is discussed. 相似文献
6.
Yuan Zhao Lian-Jun Wang Guo-Jun Zhang Wan Jiang Li-Dong Chen 《Journal of the American Ceramic Society》2007,90(12):4040-4042
A mixture of Zr, B4 C, and Si powders was adopted to synthesize a ZrB2 –SiC composite using the spark plasma sintering–reactive synthesis (SPS–RS) method. SPS treatments were carried out in the temperature range of 1350°–1500°C under a varying pressure of 20–65 MPa with a 3-min holding time. A dense (∼98.5%) ZrB2 –SiC composite was successfully fabricated at 1450°C for 3 min under 30 MPa. The microstructure of the composite was investigated. The in situ formed ZrB2 and SiC phases dispersed homogeneously on the whole. The grain size of ZrB2 and SiC was <5 and 1 μm, respectively. A number of in situ formed ultrafine SiC particles were observed entrapped in the ZrB2 grains. 相似文献
7.
Ling-Feng He Yi-Wang Bao Yan-Chun Zhou 《Journal of the American Ceramic Society》2009,92(11):2751-2758
ZrO2 –Al2 O3 nanocrystalline powders have been synthesized by oxidizing ternary Zr2 Al3 C4 powders. The simultaneous oxidation of Al and Zr in Zr2 Al3 C4 results in homogeneous mixture of ZrO2 and Al2 O3 at nanoscale. Bulk nano- and submicro-composites were prepared by hot-pressing as-oxidized powders at 1100°–1500°C. The composition and microstructure evolution during sintering was investigated by XRD, Raman spectroscopy, SEM, and TEM. The crystallite size of ZrO2 in the composites increased from 7.5 nm for as-oxidized powders to about 0.5 μm at 1500°C, while the tetragonal polymorph gradually converted to monolithic one with increasing crystallite size. The Al2 O3 in the composites transformed from an amorphous phase in as oxidized powders to θ phase at 1100°C and α phase at higher temperatures. The hardness of the composite increased from 2.0 GPa at 1100°C to 13.5 GPa at 1400°C due to the increase of density. 相似文献
8.
Shuichi Kawano Junichi Takahashi Shiro Shimada 《Journal of the American Ceramic Society》2003,86(4):701-705
TiN-coated Si3 N4 particles were prepared by depositing TiO2 on the Si3 N4 surfaces from Ti(O- i -C3 H7 )4 solution, the TiO2 being formed by controlled hydrolysis, then subsequently nitrided with NH3 gas. A homogeneous TiO2 coating was achieved by heating a Si3 N4 suspension containing 1.0 vol% H2 O with the precursor at 40°C. Nitridation successfully produced Si3 N4 particles coated with 10–20 nm TiN particles. Spark plasma sintering of these TiN/Si3 N4 particles at 1600°C yielded composite ceramics with a relative density of 96% at 25 vol% TiN and an electrical resistivity of 10−3 Ω·cm in compositions of 17.5 and 25 vol% TiN/Si3 N4 , making these ceramics suitable for electric discharge machining. 相似文献
9.
A TiN precursor solution was synthesized by galvanostatic electrolysis of Ti metal and isopropylamine at a current density of 50 mA·cm−2 at room temperature. TiN films were prepared by dip-coating of the precursor solution on a Si wafer, followed by two-stage heat treatment at 400°C and a fixed temperature of 800–1200°C in flowing N2 , N2 /NH3 , or NH3 gas. The TiN films were characterized by XRD, chemical analysis, XPS, and electrical resistivity measurements. The TiN films were composed of uniform grains 20 to 200 nm in size with thicknesses ranging from 300 to 400 nm at temperatures of 800–1200°C. The effect of the heat treatment atmosphere (N2 and NH3 ) on the impurity content, crystallinity, particle size, and electrical resistivity is discussed. 相似文献
10.
Naonori Sakamoto Masahito Hori Yuki Matsuyama Naoki Wakiya Hisao Suzuki 《Journal of the American Ceramic Society》2009,92(S1):S189-S191
12CaO·7Al2 O3 (C12A7) composed of nanosize cage structure can clathrate oxygen radicals (O− ) and has a high potential to application of strong oxidizing catalysis. In the present report, we demonstrate a fabrication route to C12A7 fine powders by Chemical Solution Deposition method in order to enhance the catalytic reactivity. Aluminum sec-butoxide, calcium nitrate tetrahydrate, acetylacetone, 2-methoxyethanol, and nitric acid were used as raw materials. Precursor solution was dried and annealed at 800°–900°C in air or O2 atmosphere. Crystalline C12A7 powders were obtained by annealing at 900°C in O2 atmosphere. Scanning electron microscope and transmission electron microscope images of the obtained powders revealed C12A7 particles were sintered and formed several micrometer particles with many pores. BET specific surface area of the powders was 4.2 m2 /g. Possibility for synthesizing C12A7 powder with higher specific surface area by the solution process was indicated. 相似文献
11.
Xiaogang Yang Cun Li Lihua Yang Yan Yan Yitai Qian 《Journal of the American Ceramic Society》2003,86(1):206-208
Titanium nitride (TiN) particles (8 nm) were prepared via a reduction-nitridation route in an autoclave at 500°C, using TiCl4 , NH4 Cl, and metal Na as reactants. X-ray powder diffraction indicated that the product was a NaCl-type of TiN with a cell constant a = 4.242 Å. Transmission electron microscopy images showed that the TiN particles were 5–10 nm. Raman spectra showed the defect-induced first-order shifts in the TiN nanocrystals. 相似文献
12.
Joanna McKittrick Carlos F. Bacalski G. A. Hirata Kevin M. Hubbard S. G. Pattillo Kenneth V. Salazar M. Trkula 《Journal of the American Ceramic Society》2000,83(5):1241-1246
The purpose of this study was to identify and correlate the microstructural and luminescence properties of europium-doped Y2 O3 (Y1– x Eu x )2 O3 thin films deposited by metallorganic chemical vapor deposition (MOCVD), as a function of deposition time and temperature. The influence of deposition parameters on the crystallite size and microstructural morphology were examined, as well as the influence of these parameters on the photoluminescence emission spectra. (Y1– x Eu x )2 O3 thin films were deposited onto (111) silicon and (001) sapphire substrates by MOCVD. The films were grown by reacting yttrium and europium tris(2,2,6,6-tetramethyl–3,5-heptanedionate) precursors with an oxygen atmosphere at low pressures (5 torr (1.7 × 103 Pa)) and low substrate temperatures (500°–700°C). The films deposited at 500°C were smooth and composed of nanocrystalline regions of cubic Y2 O3 , grown in a textured [100] or [110] orientation to the substrate surface. Films deposited at 600°C developed, with increasing deposition time, from a flat, nanocrystalline morphology into a platelike growth morphology with [111] orientation. Monoclinic (Y1– x Eu x )2 O3 was observed in the photoluminescence emission spectra for all deposition temperatures. The increase in photoluminescence emission intensity with increasing postdeposition annealing temperature was attributed to the surface/grain boundary area-reduction effect. 相似文献
13.
Jingguo Li Lian Gao Jingkun Guo Dongsheng Yan 《Journal of the American Ceramic Society》2002,85(3):724-726
A novel method for the preparation of TiN–Al2 O3 nanocomposites was developed. TiN–Al2 O3 nanocomposite powders were prepared by the direct nitridation of TiO2 –Al2 O3 nanocomposite powders that were derived from the simultaneous hydrolysis of tetra-butyl titanate and precipitation of aluminum nitrate. Dense sintered bodies of these TiN–Al2 O3 nanocomposite powders were obtained by hot pressing at 1450°–1650°C and 30 MPa for 60 min. The resistivity of nanocomposite reaches a minimum (1.5 × 10−3 Ω·cm) at 25 vol% TiN additions. The percolation concentration of nanocomposite is ∼10 vol% TiN. 相似文献
14.
Yoshiho Ito Shiro Shimada Michio Inagaki 《Journal of the American Ceramic Society》1995,78(10):2695-2699
Ba1– x Pb x TiO3 powder with a fixed composition was prepared by the reaction of BaTiO3 powders with molten PbCl2 at various PbCl2 /BaTiO3 molar ratios at 600° and 800°C in a nitrogen atmosphere. When 0.1 μm powder was used, the reaction was finished when x = 0.9. Two phases of BaTiO3 and a solid solution of Ba1– x Pb x TiO3 coexisted, but the final phase gave a solid solution of Ba1– x Pb x TiO3 at 800°C. When 0.5 μm powder was used, the two phases coexisted in the products at 600°C at PbCl2 /BaTiO3 = 1.0. A sintered compact of Ba1– x Pb x TiO3 powders solid solution was prepared by hot isostatic pressing, and its dielectric constant was measured in the temperature range 20°–550°C. 相似文献
15.
Hisayuki Suematsu Mamoru Mitomo Terence E. Mitchell John J. Petrovic Osamu Fukunaga Naoki Ohashi 《Journal of the American Ceramic Society》1997,80(3):615-620
Single crystals of α-Si3 N4 were annealed at 2000°–2150°C. The β phase was detected after annealing at 2150°C only when the crystals were surrounded by MgO·3Al2 O3 or Y2 O3 powders. On the other hand, no evidence of the α–β transformation was found when the crystals were annealed without additives. The solution–precipitation mechanism was concluded to be the dominant factor in the α–β transformation of Si3 N4 . 相似文献
16.
Yougojoti Nayak Raghunath Rana Swadesh Pratihar Santanu Bhattacharyya 《International Journal of Applied Ceramic Technology》2008,5(1):29-36
Hydroxyapatite (HA)–YTZP (2, 5, 7.5, and 10 wt% ZrO2 ) composite powders prepared from inorganic precursors were characterized by FTIR, DSC/TG, XRD, and TEM. The calcined powders had HA and t / c -ZrO2 , which undergo structural changes between 650°C and 1050°C. TEM of calcined powder showed larger HA particles (100 nm) and smaller ZrO2 particles (≤50 nm). HA and HA–2 wt% ZrO2 -sintered samples had 98% density and it was (90–95%) for HA–5, 7.5, and 10 wt% ZrO2 . The bending strength of HA–2wt% ZrO2 composites was 72 MPa. The grain sizes of HA showed a refinement with ZrO2 addition. 相似文献
17.
Reaction and Formation of Crystalline Silicon Oxynitride in Si–O–N Systems under Solid High Pressure
Ya-Li Li Fen Zheng Yong Liang Xian-Feng Ma Suo-Jing Cui Takamasa Ishigaki 《Journal of the American Ceramic Society》2001,84(4):875-877
Oxidized amorphous Si3 N4 and SiO2 powders were pressed alone or as a mixture under high pressure (1.0–5.0 GPa) at high temperatures (800–1700°C). Formation of crystalline silicon oxynitride (Si2 ON2 ) was observed from amorphous silicon nitride (Si3 N4 ) powders containing 5.8 wt% oxygen at 1.0 GPa and 1400°C. The Si2 ON2 coexisted with β-Si3 N4 with a weight fraction of 40 wt%, suggesting that all oxygen in the powders participated in the reaction to form Si2 ON2 . Pressing a mixture of amorphous Si3 N4 of lower oxygen (1.5 wt%) and SiO2 under 1.0–5.0 GPa between 1000° and 1350°C did not give Si2 ON2 phase, but yielded a mixture of α,β-Si3 N4 , quartz, and coesite (a high-pressure form of SiO2 ). The formation of Si2 ON2 from oxidized amorphous Si3 N4 seemed to be assisted by formation of a Si–O–N melt in the system that was enhanced under the high pressure. 相似文献
18.
Shu-Hong Yu Lei Shu Yong-Sheng Wu Jian Yang Yi Xie Yi-Tai Qian 《Journal of the American Ceramic Society》1999,82(2):457-460
Uniform nanocrystalline β-In2 S3 powders have been prepared by reacting the reagents at 140°C for 12 h using an organothermal process in nonaqueous solvents. XRD patterns and TEM images showed that the average particle sizes of the powders prepared in toluene and 1,2-dimethoxyethane (DME) were 8 and 16 nm, respectively. The particle sizes of nanocrystalline β-In2 S3 powders synthesized by the organothermal process can be controlled by choosing different solvents. The specific surface areas of the products obtained in toluene and DME, which were measured by the BET method, were 74.92 and 36.20 m2 /g, respectively. The products were analyzed by XPS, atomic absorption, and IR. The formation process of the nanocrystalline β-In2 S3 has been discussed. 相似文献
19.
Yosuke Matsumoto Ken Hirota Osamu Yamaguchi Suguru Inamura Hiroki Miyamoto Nobuaki Shiokawa Kazuhiro Tsuji 《Journal of the American Ceramic Society》1993,76(10):2677-2680
Amorphous Al2 O3 –ZrO2 composite powders with 5–30 mol% ZrO2 have been prepared by adding aqueous ammonia to the mixed solution of aqueous aluminum sulfate and zirconium alkoxide containing 2-propanol. Simultaneous crystallization of γ-Al2 O3 and t -ZrO2 occurs at 870°–980°C. The γ-Al2 O3 transforms to α-Al2 O3 at 1160°–1220°C. Hot isostatic pressing has been performed for 1 h at 1400°C under 196 MPa using α-Al2 O3 – t -ZrO2 composite powders. Dense ZrO2 -toughened Al2 O3 (ZTA) ceramics with homogeneous-dispersed ZrO2 particles show excellent mechanical properties. The toughening mechanism is discussed. The microstructures and t / m ratios of ZTA are examined, with emphasis on the relation between strength and fracture toughness. 相似文献
20.
New titanium–niobium oxynitride (Ti1− z Nb z O x N y ) powders were synthesized by ammonolysis of nanosized TiO2 /Nb2 O5 composite powders at 700°–900°C for 5 h. The products were characterized by X-ray diffraction (XRD), chemical analysis, and transmission electron microscopy. The results indicated that the as-synthesized powders were pure cubic structures with sizes of 30–60 nm. With increasing value of z , XRD peaks of Ti1− z Nb z O x N y powders tended to shift toward low 2θ angle and the cell parameter showed a linear increase. 相似文献