Coarse fraction matrix

Three grades of grain size compositions with sizes 5-10 mm, 0.5-5 mm, and below 0.5 mm (80 % were below 0.075 mm) were investigated, and the only variable was a changing amount of fine fraction [61]. It was considered that the coarse fractions form the frame of the structure, while the fine fraction fills in the cavities in the frame. On filling in the cavities in the frame, it was possible to follow the change of the frame structure to a matrix structure when the coarse particles do not contact each other but only fine particles have contact. The amounts of the finegrained fraction were 15 %, 30 %, 40 %, and 60 % in the trials. 

The quality of separation depends on several factors. One point is the size and size distribution of the matrix beads. Small beads of same size increase fractionation efficacy, but also increase the flow resistance therefore, fractionations should be made with beads characterized as medium, fine, or superfine, whereas group separations are mostly successful with coarse media. 

Karanasiou AA, Siskos PA, Eleftheriadis K (2009) Assessment of source apportionment by Positive Matrix Factorization analysis on fine and coarse urban aerosol size fractions. Atmos Environ 43 3385-3395... 

Studies have also shown that, since the amount of reinforcement added affects all mechanical and thermal properties, there is an optimum volume fraction of particle or whisker reinforcement that should be added to the matrix material to ensure superior resistance to thermal shock (Becher, 1981 Jia etal., 1996 Sbaizero and Pezzotti, 2003 Pettersson and Johnson, 2003). The shape of the reinforcement also plays an important role in determining behaviour under thermal shock. Sbaizero and Pezzotti (2003) showed that the use of coarse and elongated particles resulted in better CMC performance compared with the use of fine-grained particles. 

The behavior of Co-based wear resistant alloys is based on a coarse dispersion of hard carbide phases embedded in a tough Co-rich metallic matrix. The volume fraction of the hard carbide phase is comparatively high e.g., at 2.4wt%C the carbide content is 30wt%. The carbide phases are M7C3 (Cr7C3 type) and MgC (WgC type). Table 3.1-85 lists characteristic properties of Co-based hard facing alloys the compositions of which are listed Table 3.1-83. 

When the sintering data for ceramic matrices with controlled amounts of rigid inclusions are compared with the predictions of the rule of mixtures, drastic deviations are found, particularly for polycrystalline powder matrices. Figure 11.15 shows the sintering data for a polycrystalline ZnO powder matrix (particle size —0.4 xm) with different amounts of coarse, inert SiC inclusions (size = 14 p.m) (26). The inclusions severely reduce the densification of the composite relative to that for the free ZnO matrix, and for inclusion volume fractions v, greater than —20 vol%, densification is almost completely inhibited. Data for a soda-lime glass powder (particle size = 4 pim) containing controlled amounts of coarse, inert SiC inclusions (particle size = 35 p.m) are shown in Fig. 11.16 (27). The... 

In ordinary concretes, Portland cement combined with sand and water is used as the matrix or the binder. The inclusions are composed of coarse aggregate made of natural stones with specially selected grain fractions. Under the term concrete-like composites falls a large group of materials which, with respect to ordinary concretes, all constituents may be replaced by other materials. Not only are Portland cements used as binders but also for other types of hydraulic cements, bitumens, polymers and resins. The natural stone grains are replaced by various kinds of artificial lightweight... 

As might be expected, spheroidized steels are extremely ductile, much more than either fine or coarse pearlite (Figure 10.30h). In addition, they are notably tough because any crack can encounter only a very small fraction of the brittle cementite particles as it propagates through the ductile ferrite matrix. 

Advanced refractory castables usually display a broad particle size distribution and, therefore, contain a large fraction of micron- and submicron-sized particles (0.1-100 p,m) in combination with coarse aggregates (> 100 xm). Consequently, aspects of the surface chemistry and, thus, the dispersion state of the smaller particles (matrix) in water also play a major role in the processing and final properties of these refractory materials (10-15). 

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