Effects of ultrasound on the strength and reliability of slip-cast ceramic

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Effects of Particle Size and Molecular Weight of Polyethylenimine on Properties of Nanoparticulate Silicon Dispersions

The effect of particle size on the zeta potential and theology of nanoparticulate SiO2 dispersions stabilized with the polymer polyethylenimine (PEI) was investigated experimentally, The particle size and molecular weight of the polymer had only a small influence on the amount of PEI needed and the achieved zeta potential of the suspensions. The polymer concentration range within which a stable dispersion could be produced was very narrow for the smallest particle size. Higher-molecular-weight PEI was more suitable to stabilize small particle dispersions. Under optimum conditions, Newtonian flow behavior was achieved for dispersions of 20 nm particles with a solids content as high as 25 vol%

Characterization of Hardness and Stiffness of Ceramic Matrix Composites through Instrumented Indentation Test

The determination of the hardness allows useful qualitative conclusions regarding the mechanical properties of materials. It is one of the most economical characterization methods, since this can be carried out with little effort on small specimens. However, due to the heterogeneous structure containing hard and brittle ceramic phases the determination of hardness of ceramic matrix composites (CMCs) is a challenge and has thus rarely been investigated. In this work, the hardness and the stiffness in out of plane orientation are investigated on Liquid Silicon Infiltrated (LSI) C/C-SiC composites. For hardness tests a hemispherical indenter is used in order to evaluate residual indentation. The load-unload curve generated during the indentation process was analyzed to determine the hardness and stiffness. The employed experimental procedure is expected to be applicable to other CMCs with similar microstructure

Filtration behavior of nanoparticulate ceria slurries

The influence of poly(acrylic acid) (PAA) concentration and molecular weight on the filtration behavior of CeO2 slurries with 20 nm particle size was studied. Low-viscosity suspensions could be produced by adsorbing a monolayer of PAA that covered the nanoparticles. For all suspensions investigated, the cake permeability was lower than predicted by the Kozeny-Carman equation and decreased with increased filtration pressure because of the presence of a compressible PAA layer 3-5 nm thick on the surface of the particles. The permeability of the nanoparticulate cakes decreased with increased polymer addition because of clogging