Homogenous distribution of the particles

The reaction is carried out in the cast iron kettle A, which holds 7 5 litres and is fitted with the helical agitator B which imparts an ascending motion to the mass, so that a homogeneous distribution of the particles in the liquid is obtained. The kettle is closed at the top with a lid, in the centre of which is the agitator gear, and which also has a charging hole C for the diphenylamine hydrochloride and arsenious oxide. Above this hole a hopper is... 

In order to eliminate large (>200 nm) particles the powders were separated in alcohol. The mixing of different powders in order to obtain composites was performed here. The ultrasonic mixing during liquid evaporation provided the homogeneous distribution of the particles and prevented the formation of hard aggregates. 

Mixing of fluids is necessary in many chemical processes. It may include mixing of liquid vith liquid, gas with liquid, or solids with liquid. Agitation of these fluid masses does not necessarily imply any significant amount of actual intimate and homogeneous distribution of the fluids or particles, and for this reason mixing requires a definition of degree and/or purpose to properly define the desired state of the system. 

However, there may be good reasons why a catalyst should not consist of particles that are too small, as we saw in the beginning of this chapter, e.g. to avoid pressure gradients in the reactor. Based on an analysis such as the above, one can decide whether it makes sense to use support particles that contain a homogeneous distribution of the catalytic phase. With expensive noble metals, one might perhaps decide to use an egg-shell type of arrangement, where the noble metal is only present on the outside of the particles. 

Morphological analysis of the nanoparticle suspensions by SEM showed a homogeneous distribution of spheroidal particles with diameters less than 1 pm embedded in a continuous matrix (Figure 4) consisting of polymeric material not incorporated within the microspheres. 

The size distributions of the particles in cloud samples from three coral surface bursts and one silicate surface burst were determined by optical and electron microscopy. These distributions were approximately lognormal below about 3/x, but followed an inverse power law between 3 and ca. 60 or 70p. The exponent was not determined unequivocally, but it has a value between 3 and 4.5. Above 70fi the size frequency curve drops off rather sharply as a result of particles having been lost from the cloud by sedimentation. The effect of sedimentation was investigated theoretically. Correction factors to the size distribution were calculated as a function of particle size, and theoretical cutoff sizes were determined. The correction to the size frequency curve is less than 5% below about 70but it rises rather rapidly above this size. The corrections allow the correlation of the experimentally determined size distributions of the samples with those of the clouds, assuming cloud homogeneity. 

A flame reactor is an excellent means for preparing pure or mixed oxides in the form of nonporous particles. The absence of porosity allows an average homogeneous irradiation of the particles. The morphologies (spheres, polyhedra) and the particle sizes (usually with a narrow distribution) can be mastered by adjusting the temperature, the flow rates (H2 and 02), and the concentration(s) of the compound(s) employed to generate the oxide. In the particular case of Ti02, anatase samples whose rutile content is very low can be produced. Consequently, the effect of the surface area S on the photocatalytic activity can be determined, in principle. 

It has also been observed that employing, at near-saturation, a catalyst precursor that does not crystallize at all but rather forms a coating on the support surface, can lead to a homogeneous distribution of small particles — a case in point being the application of an iron EDTA complex at alkaline pH to produce, after calcination, small (2-5 nm) Fe203 particles homogeneously distributed through SiC>2 extrudates. 

Typical SEM micrographs of cryogenically fractured surfaces show an homogeneous distribution of the rubber particles for both DZ and NZ materials (Fig. 3). In Table I are reported the specific surface of the nylon/particle interface and the mean free path within the rubber phase. It appears that the rubber particles are by far finer in the NZ blend even though the number of particles is underestimated for this material due to the presence of very small particles and the poor contrast between the rubber and the nylon. 

The water content in the studied material is approximately 90%. For the present research work the black liquor were dried up to 100% content of solids. This drying stage needs to be gradual and carefully controlled in order to reach an homogeneous distribution of the inorganic compounds inside the solid matrix. After drying, the solids were ground, sieved under a particle size of 53 pm mesh and kept in a fiirnace at 105 C. 

Cryptocrystalline natural graphite is also beneficiated using flotation, but this is complicated by its small particle size and the resulting more homogeneous distribution of the accompanying minerals. Oils are preferred as flotation media. 

The particles of the bed of an analytical column are held by the column wall and by the porous frits at the column top and column end. Specific frit systems have been developed by column manufacturers to enable a homogeneous distribution of the flow across the column. Wide bore preparative columns contain distributors at both ends for optimum sample distribution. Both the quality of the frits and the distributors significantly affect the performance of a chromatographic column. While for analytical columns the bed is supported by friction between the column wall and the packed particles, the particles of wide bore preparative columns are subjected to a much higher mechanical stress. 

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