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Porous morphology and total porosity produced in sintered ceramic tapes was controlled by the amount and distribution of pyrolyzable graphite particles added to a colloidal suspension during a tape casting operation. A conceptual model of the green tape microstructure was used to explain the influence of graphite and tape formulation on sintering characteristics. The creation of a connected, open porous network in the sintered body was the result of graphite particle percolation within the green body. Additional voidage introduced by particle bridging was the source of excess porosity and also resulted in a bimodal pore size distribution. Sintering shrinkage was determined by the ceramic packing density, which was primarily determined by the tape formulation. 相似文献
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Michael W. Murphy Timothy R. Armstrong Peter A. Smith 《Journal of the American Ceramic Society》1997,80(1):165-170
The effects of process additives, ball milling, and solids loading were evaluated for tape casting suspensions of glycinenitrate-synthesized La0.7 Ca0.31 CrO3 powder. An optimized formulation was obtained based on rheological characterization, electrokinetic sonic amplitude measurements, qualitative examination of green tapes, and the sintered microstructure. The tape casting formulation incorporated 66:34 methyl ethyl ketone/ethyl alcohol solvent, an aliphatic phosphate ester dispersant, and 80 wt% (35 vol%) solids. The best binder/plasticizer system was 12 wt% (15 vol%) poly(isobutyl methacrylate) and 5 wt% (6.3 vol%) benzyl butyl phthalate plasticizer (binder:plasticizer = 2.3). Cast tapes were sintered at 1300°C for 2 h, producing a bulk density of 96.2% theoretical, with linear shrinkage of 22% and an approximate grain size of 1.3 μm. 相似文献
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Zhihui Lü Dongliang Jiang Jingxian Zhang Qingling Lin 《Journal of the American Ceramic Society》2009,92(10):2212-2217
Aqueous tape casting of ZrB2 powder with sintering additives was investigated. The dispersion of ZrB2 suspensions in aqueous media was studied and characterized in terms of zeta potential, sedimentation, and rheological measurements. A well-stabilized suspension with a high solid content (up to 45 vol%) was prepared in the alkaline pH region with 0.4 wt% Lopon 885 as the dispersant. Several suspensions with different compositions of binder and plasticizer were prepared for comparison. Crack-free green tapes with a maximum thickness of approximately 250 μm were obtained with a binder content of 18–23 wt%. The green tapes had high qualities, such as homogeneity, good flexibility, and a smooth surface. Results showed that the slurries at selected formulations met the needs of the tape-casting process. 相似文献
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Cathleen M. Gustafson Rollie E. Button Ronald J. Kerans 《Journal of the American Ceramic Society》1995,78(5):1423-1424
A method has been developed to fabricate borosilicate glass matrix composites reinforced with monofilament SiC fibers by tape casting. Green matrix tapes are laminated with fiber mats of a uniform fiber spacing. The resulting laminate is sintered at 710°C to >98% relative density and HIP-consolidated to full density. The final specimens contain a high volume fraction of fibers (>35 vol%) in a uniform array. A variation of this technique can be used to mount "microcomposites" (i.e., coated fibers) in a glass matrix to facilitate fabrication of push-out test specimens. 相似文献
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低温共烧CBS基片的流延成型及其性能的研究 总被引:1,自引:0,他引:1
选用4种分散剂(三乙醇胺,磷酸三丁酯,蓖麻油和三油酸甘油酯),通过对分散剂的用量、固含量对浆料流变性能、流延生坯及烧结体性能的研究。分析了分散剂及固含量对流延浆料及陶瓷性能的影响。实验结果表明:以磷酸三丁酯为分散剂,当浆料的固含量为55%时,制备的料浆不仅分散性好而且稳定。流延所得烧结体介电常数为6.47、介质损耗为1.1×10-3。烧结后的样品中主要包含CaSiO3、CaB2O4和SiO2晶相。达到了LTCC材料的要求。 相似文献
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Konjhiparambil V. Arunkumar Rani N. Panicker Kalarickal G. Vasanthakumari Mathew Satheesh Natarajan Raghu Nelliparampil V. Unnikrishnan 《International Journal of Applied Ceramic Technology》2010,7(6):902-908
Dispersion behavior of TiO2 in different solvent systems in combination with two different dispersants was studied and optimized for the dispersion of TiO2. Based on sedimentation, viscosity, and rheological characteristics, zeotropic ethanol: xylene with a ratio of 50:50 along with 1 wt% menhaden fish oil is found to be the best solvent–dispersant combination for TiO2. Tape casting slurry was optimized using polyethylene glycol 400 and benzyl butyl phthalate as plasticizers and polyvinyl buyral as the binder. Cyclohexanone was used as homogenizer. TiO2 tapes were obtained by double doctor blade tape casting process. As cast tapes were dried in air at room temperature. The results show that it is possible to obtain homogenous defect-free green tapes of 58.7% solid loading and green density of 55% having thickness of ∼90 μm. 相似文献
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Mullite and ZrO2 -mullite ceramics have been prepared by tape casting mixtures of Al2 O3 , quartz, and ZrO2 powders and subsequent reaction sintering. Tape casting leads to homogeneous, high-density green materials with good sinterability. The design of a thermal cycle which favors densification with respect to mullitization allows the preparation of nearly dense, nearly fully reacted materials at sintering temperatures below 1600°C. ZrO2 additions limit grain growth, but the ZrO2 content must not be too high when a high tetragonal:monoclinic ratio is required. 相似文献
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Nurcan Calis Acikbas Ender Suvaci Hasan Mandal 《Journal of the American Ceramic Society》2006,89(10):3255-3257
Functionally graded SiAlON ceramics (FG-SiAlONs) were successfully prepared by the tape casting and lamination approach. Non-aqueous SiAlON slurries with five different α to β-SiAlON ratios (85α:15β, 70α:30β, 55α:45β, 40α:60β, and 25α:75β) were prepared by a 66 methyl ethyl ketone/34 ethanol (vol%) mixture. Phase and microstructure analyses incorporation with hardness measurements clearly show that the FG-SiAlONs, prepared by tape casting, exhibit a continuous and gradual change in composition and hardness. Thus, the tape casting approach is a viable method to produce FG-SiAlONs with a precisely controlled composition, and subsequently properties, as a function of position. 相似文献
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Xiao-Jun Luo Bao-Lin Zhang Wen-Lan Li Han-Rui Zhuang 《Journal of the American Ceramic Society》2005,88(2):497-499
A direct comparison of aqueous and non-aqueous tape casting was investigated. Aqueous and non-aqueous formulations were developed for tape casting of aluminum nitride (AlN) powder. The oxygen content of the AlN powder in aqueous ball-milling media had a slight increase, but it did not almost influence the thermal conductivity of AlN substrate. The solid loading of aqueous AlN slurry was higher than that of the non-aqueous one, but its viscosity was lower than that of non-aqueous AlN slurry. Under the same burnout program, the residual carbon content in aqueous AlN green sheet was lower than that of the non-aqueous one. The thermal conductivity of the aqueous AlN substrate sintered at 1850°C for 3 h was 138 W·(m·K)−1 , which was close to 142 W·(m·K)−1 of the non-aqueous AlN substrate. 相似文献
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Michael G. Pontin Fred F. Lange Antonio J. Sánchez-Herencia Rodrigo Moreno 《Journal of the American Ceramic Society》2005,88(10):2945-2948
Thin ceramic layers have been fabricated by dipping green tapes of alumina, formed by the doctor-blade casting method, into aqueous slurries containing mixtures of alumina and either unstabilized zirconia (MZ–ZrO2 ) or mullite. It was observed that the formation of a thin layer on the surface of the tape is governed by both liquid entrainment and slip-casting mechanisms, and was accelerated by increasing the withdrawal rate, immersion time, or volume fraction of solids in the slurry used for dip coating. By modifying these parameters, layers as thin as 2 μm and as thick as 108 μm were easily formed. Layer formation was found to be strongly influenced by the structure of the tape surface. Layers formed on the top surface of the tape were found to be as much as 48% thicker than those formed on the bottom surface. This difference appears to be related to the smaller amount of porosity on the bottom surface of the tape. Evidence suggests that the polymer binder, used for doctor-blade casting, concentrated on the bottom of the tape as evaporation occurred from the top surface. The lower porosity on the bottom reduced the casting rate during dip coating and produced significantly thinner layers, relative to the top surface. 相似文献
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The source of water and its effect on rheological and green tape properties of tape cast barium titanate were studied. The total water content, as well as the source, affect the slip rheology, green density, tensile strength, and strain to failure in the unsintered body. Sources of the water were broken down into contributions from the barium titanate powder surface versus from the solvent or ceramic additives. Water adsorbed on the powder surface was generally beneficial compared to water entering through the solvent. For carefully dried systems, below 0.15 wt% total water, properties change dramatically with small changes in water content. Thus, less stringent processing requirements can be used to achieve reproducibility at water contents above 0.15 wt%. 相似文献
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Fabrication of Oriented SiC-Whisker-Reinforced Mullite Matrix Composites by Tape Casting 总被引:1,自引:0,他引:1
Dense SiC-whisker-reinforced mullite composites with up to 50 vol% whiskers can be obtained by tape casting and hot pressing. The tape casting process results in high degrees of SiC whisker orientation as determined visually and by X-ray diffraction. The ability to achieve dense composites with as much as 50 vol % whiskers is attributed to the higher percolation threshold of aligned whiskers. The factors affecting the degree of whisker orientation during tape casting are described using a fluid dynamics model derived from Jeffery's equations and show that the orientation of anisometric particles is enhanced primarily by the casting rate and particle aspect ratio. 相似文献
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水基流延工艺制备陶瓷材料的研究 总被引:7,自引:0,他引:7
流延法作为制备片层材料的重要工艺已经被陶瓷研究者广泛应用.但是,有机流延体系带来的环境污染、毒性及易燃性等问题已被社会所关注.因此,研究无毒、无污染的水基流延工艺已得到材料界的广泛重视.本文主要概述了国内外水基流延工艺的研究现状,重点介绍了PVA体系、丙烯酰胺凝胶流延体系、纤维素类粘结剂体系及乳胶体系的不同特点;从粘结剂、分散剂、增塑剂等多个角度分析了影响水基流延工艺的技术因素,并提出了很好的解决方法,最后介绍了乳胶体系水基流延工艺在制备片状或层状陶瓷材料方面的应用. 相似文献
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Particle Orientation During Tape Casting in the Fabrication of Grain-Oriented Bismuth Titanate 总被引:1,自引:0,他引:1
Hidenori Watanabe Toshio Kimura Takashi Yamaguchi 《Journal of the American Ceramic Society》1989,72(2):289-293
Slurries containing platelike Bi4 Ti3 O12 particles have been tape cast to prepare green sheets with aligned particles. The slurries contain well-dispersed particles and show nearly Newtonian flow behavior. The effect of slurry composition and casting conditions on the particle orientation has been examined. The particle orientation in the green sheet is determined mainly by powder content; other parameters, such as binder content, casting speed, and blade opening, have little effect. The interaction between particles is a main cause for particle alingnment. The slurry with a large powder content is favorable for preparing dense grain-oriented ceramics. 相似文献
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Kevin P. Plucknett Carlos H. Cáceres David S. Willinson 《Journal of the American Ceramic Society》1994,77(8):2137-2144
Ceramic films, containing AI2 O3 , with up to 40 vol% ZrO2 , have been fabricated using the tape casting process. Finer powders (average mean diameter of 250–300 nm) than have generally been reported for tape casting were used in this study. The optimum formulation for tape casting is affected substantially by decreasing particle size. For example, the amount of dispersant needed is increased. Moreover, the amount of plasticizer/binder must be increased so as to maintain the solids content in the dried tapes below a critical level (about 55 vol% in this case), which decreases with particle size. Rheological studies on the effectiveness of menhaden fish oil and phosphate ester as dispersants show that phosphate ester can be used in lower concentrations, for the preparation of higher solids loading slurries, and was therefore selected for further study. The amount of dispersant required to obtain minimum slurry viscosity was found to be primarily dependent upon the effective particle surface area, defined as that available to the dispersant molecules. In the case of particles composed of agglomerated crystallites (such as the ZrO2 , powder used here), this may be considerably less than that measured by nitrogen absorption. Moreover, the porous internal structure of such powders is filled with solvent, which increases the effective solids loading of the slurry, and thus its viscosity. Particle morphology also influences the packing efficiency; i.e., the green density decreases as ZrO2 , is added. 相似文献