Powder layering pelletization

To increase thermal conductivity of powder layer metal powders of copper, aluminium are added. Composites are compacted in pellets, which can be sintered in addition. Their main characteristics are coefficient of effective thermal conductivity and coefficient of gas-permeability. The weight fraction of powder in such compacts serves as the controlled parameter, and it has the optimum, when gas-permeability does not worsen sharply at acceptable thermal conductivity. Encapsulation of hydride powder by material with high thermal conductivity followed by compaction of pellets and their sintering is also used. 

With a double-walled centrifugal granulator, the process is carried out with the inner wall in the open or closed position (Fig. 2)P With powder layering, the inner wall is closed so that simultaneous application of liquid and powder could proceed until the pellets have reached the desired size. The inner wall is then raised, and the spheres enter the drying zone. The pellets are lifted by the fluidization air up and over the inner wall back into the forming zone. The cycle is repeated until the desired residual moisture level in the pellets is achieved. 

Jan, S. Goodhart, E.W. Dry powder layering. In Pharmaceutical Pelletization Technology Ghebre-Sellassie, I., Ed. Marcel Dekker, Inc. New York, 1989 182-183. 

Fig. 22 Pellets prepared by different methods. Cross-sectional view of a pellet prepared by powder layering (A), cross-sectional view of a pellet prepared by extrusion/spher-onization (B), and size and shape of pellets prepared by extrusion/spheronization (C).

Pellets. Pellets are mainly prepared by four different methods powder layering, rotating fluidized bed, extrusion/spheronization, and the agglomeration method. The oldest one is the so-called. 

They are harder compared with pellets produced by powder layering. Their appearance is similar to pellets obtained by fluidized-bed granulation using the so-called rotating fluidized bed. " Owing to the fact that ideally round pellets are desired, several attempts were made to quantify their roundness. " The spherical agglomeration is a completely different method that is employed to develop pellets that are round and uniform in size. In this, particles are agglomerated in suspension. ... 

Nastruzzi, C Cortesi, R. Esposito, E. Genovesi, A. Spa-doni. A. Vecchio, C. Menegatti, E. Influence of formulation and process parameters on pellet production by powder layering technique. AAPS Pharm. Sci. Tech. 2000,1 (2), 1-22. 

Reactions of nanoscale materials are classified with respect to the surrounding media solid, liquid, and gas phases. In the solid phase, nanoscale crystals are usually connected with each other to form a powder particle (micron scale) or a pellet (milli scale) see Figure 14.1. Two or more materials (powder or pellet) are mixed and fired to form a new material. The nanosized structure is favored, due to the mixing efficiency and high reaction rate. Alloys (metals), ceramics (oxides), cement (oxides), catalysts (metals and oxide), cosmetics (oxides), plastics (polymers), and many functional materials are produced through solid reaction of nanoscale materials. One recent topic of interest is the production of superconductive mixed oxides, where control of the layered stracture during preparation is a key step. 

Variations of this cell design include 1) the use of a two-layer pellet with diserete electrolyte and cathode layers formed into one part and 2) the use of a homogeneous pellet that has the electrolyte and cathode powders blended together (depolarizer-electrolyte-binder or DEB pellet). A typical Li/FeS2 cell, as illustrated in Fig. 2. Ad, is made up of the following ... 

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