Size methods spherical agglomeration

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. ... 

At the simplest level, the rate of flow-induced aggregation of compact spherical particles is described by Smoluchowski s theory [Eq. (32)]. Such expressions may then be incorporated into population balance equations to determine the evolution of the agglomerate size distribution with time. However with increase in agglomerate size, complex (fractal) structures may be generated that preclude analysis by simple methods as above. 

Synthetic hydroxyapatites were prepared by the method of Hayek and co-workers (7, 8), modified to produce a product of small particle size. The products were isolated by washing the gel slurry with water until free of nitrate ion. The resultant suspensions were then spray-dried with a Minor Type 53 Niro Atomizer (Copenhagen, Denmark). The resultant dry products were in the form of porous, spherical polycrystalline agglomerates of 5 to 8 fi average diameter. The specific surfaces of these products ranged from 104 to 180 meter2/gram. 

Nanopowders of nonstoichiometric tungsten oxide W03 x were synthesized by EEC-method. According to the TEM data (Fig. 1) the mean size of nanoparticles is 10-35 nm, size distribution is normal (Gaussian). The nanoparticles have spherical shape, well-defined crystalline structure, their agglomeration is almost absent. The macropowders of stoichiometric tungsten oxide W03 was obtained at combustion of metal in oxygen. The macropowders of stoichoimetric (sample MS) and the nanopowders of nonstoichiometric (sample NN) tungsten oxides were examined conditioned on air (samples MSI and NN1 respectively) and annealed on air at 563 K (samples MS2 and NN2 respectively). 

Redispersible spherical BT nanoparticles with a narrow size distribution and a lower hydroxyl content were produced by our novel method, which we call the ambient condition sol (ACS) process, to produce pure crystalline nanometer-sized g-p 56-58 controlled particle size with a uniform distribution in the 50 to 100 nm size range from different refluxing media (e.g., water, butanol, toluene) was rapidly produced. During the process, a polymeric surface modifier can be added to protect the surface from agglomeration and to promote redispersibility after drying. The ACS process is similar to hydrothermal synthesis, but without applying pressure. 

In the case of fumed powders, the results of particle size analysis depend veiy strongly on the characterization method. Each method measures a different particle property, from which sphere equivalent diameters are calculated. The underlying models assume homogeneous, spherical particles, which does not apply to the porous aggregates and agglomerates of these materials. 

Shape is often also an important characteristic. In many cases spherical products of size enlargement are desired. This approximate shape can be obtained with all growth agglomeration methods. On the other hand, unless extremely accurate feed control can be established in some tabletting machines, spherical products cannot be produced with pressure agglomeration equipment. The nearest approximation would be lens- or almond-shaped compacts. 

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