Consolidated particles

A transmission electron microscope (TEM) observation of the Z1O2 nanocrystallites obtained at 500°C is given in Fig. 13. Homogenous, quite spherical, consolidated particles of about 5-6 nm in size can be observed. This clearly shows that, to maintain nanoporosity inside the membrane, an upper limit for membrane sintering exists. Because these results, a zirconia nanofil-ter has been obtained by coating a 1 pm thick layer on a microfiltration zirconia layer. The separation performance of this membrane, characterized with model solutes in aqueous media, is in the nanofiltration range [26]. 

The contact relations of cohesive soil particle before consolidation are side-side, side-face. After consolidation the contact relations is transition for the side-face, face-face. Due to the consolidation, particles contact more closely and pores trend to be homogeneous. 

D. L. Dauplaise and M. F. Wemeke, Proceedings of the Consolidation and Dewatering of Fine Particles Conference, University of Alabama, Tuscaloosa, Ala., 1982, pp. 90-113. 

Vibr toiy Consolidation. Powders are vibrated in a mold or other container in which they will be sintered, or in a metal container that will be used for extmsion or other metalworking process (31). Vibratory consoHdation produces packings of UO2 particles up to 95% of theoretical density. 

Metal-Matrix Composites. A metal-matrix composite (MMC) is comprised of a metal ahoy, less than 50% by volume that is reinforced by one or more constituents with a significantly higher elastic modulus. Reinforcement materials include carbides, oxides, graphite, borides, intermetahics or even polymeric products. These materials can be used in the form of whiskers, continuous or discontinuous fibers, or particles. Matrices can be made from metal ahoys of Mg, Al, Ti, Cu, Ni or Fe. In addition, intermetahic compounds such as titanium and nickel aluminides, Ti Al and Ni Al, respectively, are also used as a matrix material (58,59). P/M MMC can be formed by a variety of full-density hot consolidation processes, including hot pressing, hot isostatic pressing, extmsion, or forging. 

FIG. 19-26 Movement of particles in a jig. a) Displacement of the bed as a function of time, (h) Starting position of particles, (c) After dilation. (d) After differential initial acceleration, (e) After hindered settling, (f ) After consolidation trickling. 

Particle size and friction strongly interact with hinder viscosity to control consolidation. Feed particle size maybe increased and fine tail of distrihiition removed. 

The typical value of porosity for a clean, consolidated, and reasonably uniform sand is 20%. The carbonate rocks (limestone and dolomite) normally exhibit lower values, e.g., 6-8%. These are approximate values and do not fit all situations. The principal factors that complicate intergranular porosity magnitudes are uniformity of grain size, degree of cementation, packing of the grains, and particle shape. 

The particle size of powder most often used for consolidation is —200 mesh (74 /xm sieve aperture), and the most widely practised method of consolidation is hot pressing in vacuo. 

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