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Ceramic Suspension (ceramic + suspension)
Selected AbstractsThe Effect of Electric Field on Pressure Filtration of Ceramic SuspensionsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2009Yoshihiro Hirata The consolidation behavior of Al2O3 and indium tin oxide (ITO, 90% In2O3,10% SnO2) particles 150,200 nm in size was examined using a pressure filtration apparatus at a constant compressive rate under an electric field. The relation of applied pressure (,Pt) with volume of dehydrated filtrate (Vf) was compared with the established filtration theory (theory I) for a well-dispersed suspension and the newly developed filtration theory (theory II) for a flocculated suspension. The experimental results without polyelectrolyte dispersant deviated from theory I when ,Pt exceeded a critical pressure (,Ptc). This deviation is associated with the phase transition from a dispersed suspension to a flocculated suspension at ,Ptc. A good agreement was shown between the developed theory II and experimental results after the phase transition. When a dispersant (polyacrylic ammonium, PAA) was added to alumina, ITO, or Al2O3,ITO mixed powder suspensions, the consolidation behavior of the particles was controlled by the dissociation and amounts of adsorbed and free PAA. The addition of a large amount of highly charged PAA enhanced the repulsive interaction between PAA-adsorbed particles, and the consolidation behavior was explained by theory I. The adsorption of neutral PAA on the particles reduced the repulsive interaction, and the consolidation behavior was well explained by theory II. The phase transition from dispersed to flocculated suspension was very sensitive to the electric field during the pressure filtration. The ,Ptc for the suspension with and without PAA decreased drastically when a low electric field was applied. The final packing density of the flocculated particles was greatly increased by the application of a weak electric field. However, the dense structure under high pressure was relaxed to a low-density structure when the stored elastic strain energy was released. [source] Fabrication of Al2O3/SiC Composite Microcomponents using Non-aqueous Suspension,ADVANCED ENGINEERING MATERIALS, Issue 1-2 2009Hany Hassanin This paper introduces a new process for fabrication of high resolution Al2O3/SiC composite microcomponents using softlithography and non-aqueous ceramic suspension. Polysilazane is used to provide both binding force and SiC composition. The shape retention and dimensions of the microcomponents were analyzed using a scanning electron microscope. Surface roughness, shrinkage, and density of the resultant sintered components were also discussed. [source] Lost Mold Rapid Infiltration Forming of Mesoscale Ceramics: Part 1, FabricationJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2009Nicholas E. Antolino Free-standing mesoscale (340 ,m × 30 ,m × 20 ,m) bend bars with an aspect ratio over 15:1 and an edge resolution as fine as a single grain diameter (,400 nm) have been fabricated in large numbers on refractory ceramic substrates by combining a novel powder processing approach with photoresist molds and an innovative lost-mold thermal process. The colloid and interfacial chemistry of the nanoscale zirconia particulates has been modeled and used to prepare highly concentrated suspensions. Engineering solutions to challenges in mold fabrication and casting have yielded free-standing, crack-free parts. Molds are fabricated using high-aspect-ratio photoresist on ceramic substrates. Green parts are formed using a rapid infiltration method that exploits the shear thinning behavior of the highly concentrated ceramic suspension in combination with gelcasting. The mold is thermally decomposed and the parts are sintered in place on the ceramic substrate. Chemically aided attrition milling disperses and concentrates the as-received 3Y-TZP powder to produce a dense, fine-grained sintered microstructure. Initial three-point bend strength data are comparable to that of conventional zirconia; however, geometric irregularities (e.g., trapezoidal cross sections) are present in this first generation and are discussed with respect to the distribution of bend strength. [source] Preparation of Ceramic Well Plates for Combinatorial Methods Using the Morphogenic Effects of Droplet DryingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2006Yong Zhang When droplets of a ceramic suspension dry on a non-wetting substrate, powder migrates to the periphery and builds there a wall of powder. This intriguing phenomenon, which is a nuisance in some processes, can be used to make arrays of ceramic wells on a ceramic substrate. These wells can, after sintering, be used to hold ceramic samples made from powder by controlled mixing of ceramic inks or could be made from ceramics that act as heterogeneous catalysts and used to hold reactants. The well plates can even be made from electrically conducting ceramics so that electrical property measurements can be made with a ground electrode. [source] Particle Redistribution During Dendritic Solidification of Particle SuspensionsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2006Noah O. Shanti Solidification of the liquid medium in ceramic suspensions containing less than a critical volume fraction powder leads to the formation of particle-free dendrites of the frozen medium. These particle-free dendrites create, after sublimation of the frozen vehicle, large dendrite pores. We define the conditions under which particle-free dendrites form, and relate the size and volume fraction of the dendrites to the volume fraction powder and the solidification rate. [source] Yodel: A Yield Stress Model for SuspensionsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2006Robert J. Flatt A model for the yield stress of particulate suspensions is presented that incorporates microstructural parameters taking into account volume fraction of solids, particle size, particle size distribution, maximum packing, percolation threshold, and interparticle forces. The model relates the interparticle forces between particles of dissimilar size and the statistical distribution of particle pairs expected for measured or log-normal size distributions. The model is tested on published data of sub-micron ceramic suspensions and represents the measured data very well, over a wide range of volume fractions of solids. The model shows the variation of the yield stress of particulate suspensions to be inversely proportional to the particle diameter. Not all the parameters in the model could be directly evaluated; thus, two were used as adjustable variables: the maximum packing fraction and the minimum interparticle separation distance. The values for these two adjustable variables provided by the model are in good agreement with separate determinations of these parameters. This indicates that the model and the approximations used in its derivation capture the main parameters that influence the yield stress of particulate suspensions and should help us to better predict changes in the rheological properties of complex suspensions. The model predicts the variation of the yield stress of particulate suspensions to be inversely proportional to the particle diameter, but the experimental results do not show a clear dependence on diameter. This result is consistent with previous evaluations, which have shown significant variations in this dependence, and the reasons behind the yield stress dependence on particle size are discussed in the context of the radius of curvature of particles at contact. [source] Analytical Electron Microscopy Study of Green Ceramics Formed from Aqueous Suspensions Using the Hydrolysis-Assisted Solidification ProcessJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2002a Novak During the hydrolysis-assisted solidification (HAS) of aqueous ceramic suspensions, aluminum hydroxides are formed that bind the ceramic particles into a stiff wet body. Transmission electron microscopy investigations of HAS-processed Al2O3 and ZrO2 green parts after drying revealed that the secondary phase is amorphous and distributed uniformly around the host ceramic particles. The estimated thickness of this layer was 3,5 nm. Moreover, areas of a few tens of nanometers in size were found at three-particle junctions that contained an amorphous phase and individual nanocrystals of boehmite. [source] | ||||||||||