Particle cracking

The mechanisms of comminution are complex involving breakage along particle cracks and fissures etc., and depend on the hardness and structure of the feed particle. The Institution of Chemical Engineers (London) produced a major report on comminution (IChem, 1975), which was followed by reviews by Bemrose and Bridgwater (1987), Prior etal. (1990) and Jones (1997). These reviews included sections on both the fundamental and practical aspects of comminution and attrition in process equipment, test methods and an extensive list of references. 

It is appropriate to emphasize again that mechanisms formulated on the basis of kinetic observations should, whenever possible, be supported by independent evidence, including, for example, (where appropriate) X-ray diffraction data (to recognize phases present and any topotactic relationships [1257]), reactivity studies of any possible (or postulated) intermediates, conductivity measurements (to determine the nature and mobilities of surface species and defects which may participate in reaction), influence on reaction rate of gaseous additives including products which may be adsorbed on active surfaces, microscopic examination (directions of interface advance, particle cracking, etc.), surface area determinations and any other relevant measurements. 

Cavitation collapse will generate shock waves which can cause particle cracking through which the leaching agent can enter the interior of particle by capillary action... 

Because this kind of reaction takes place at low temperatures, thermal oscillations do not essentially contribute to backbone stretching. In fact, Ea is zero in this case. When Ea of bond scission is less than that required to form the active particles, cracking exhibits the character of a mechanically activated chemical reaction—chain scission in active particles takes place. There is a cause-and-effect relationship between the strain processes (which are cumulative in the deformed fragment to activate the backbone) and the destruction processes. 

Using alloys with micro-, nano-, or subnanoparticle sizes makes it possible to enhance lithium alloy cyclability. With such morphology, relatively large dimensional changes of the crystallites do not cause particle cracking since the absolute changes in the particle dimensions are small (138]. 

Polypropylene, fracture toughness, elastic modulus, filler particle, crack resistance, debonding, cavitation, process zone, silica, calcium carbonate. 

Figure IS shows the spatial distribution of volatile flux in a 2 mm particle. All the solid curves for time 3.92s to time 5.797s give a flat profile on the right hand side. For the moment specified by each curve, the primary decomposition has finished locally in the outer layers. This is also the case for a larger particle of 10 mm diameter. Thus, it is suggested that the secondary reaction plays a negligible role during this stage. In other word, volatile interior-particle crack during cellulose pyrolysis is not in jortant under the fluidized-bed condition. From the model prediction, 0.088% of volatile undergoes the secondary crack inside a 2 mm particle, and about 2% for a 10 mm particle.

The mechanical strength of the filler particle may be lower than the adhesive bond strength between the filler and the matrix. This effect is illustrated in Figure 7.30. Concentrated stress causes particle cracking. An SEM micrograph of this event is illustrated in Figure 7.31. 

The adhesion between the matrix and the filler has an important influence on the mechanism of failure. In polyester filled with quartz, uncoupled (low adhesion) quartz was delaminated from the matrix if the quartz particles were in the path of the crack growth. Silane coupled quartz particles showed many instances of particle cracking on the pathway of crack growth. Apparently, adhesive forces were higher than the cohesion of filler material. ... 

In view of the particle cracking observed in most composite specimens, we focus attention on the microstress the PSZ phase, and suppose that fracture occurs when a latent... 

Magnetic particles Cracks, laps, voids, porosity and inclusions Castings. forgingSi and extrusions Simple inexpensive detects shallow subsurface flaws as well as surface flaws Useful for ferromagnetic materials only surface preparation required, irrelevant indications often occur operator-dependent... 

Thirty slag particles of size 40 to 150 mm are immersed in water at 20 C 2°C for 2 days. If one or two particles crack or disintegrate, the test is repeated for another 30 particles. If a particle cracked or disintegrated again, the slag does not pass the test. 

Figure 5.9 Sequence of micrographs from an in situ deformation test of HIPS crack propagation in crazes and crack stop at rubber particles crack starts from above deformed SDS in HEM...

Keywords linear elastic fracture mechanics, critical strain energy release rate, precipitating elastomers, hyperbranched molecules, preformed rubber particles, core-shell latex particles, treated rubber, precipitating thermoplastic particles, preformed thermoplastic particles, crack bridging, shear banding, cavitation. 

Upon impact, this kinetic energy can be used to shatter or deform the abrasive particle, crack or deform old paint, or chip away rust. The behavior of the abrasive, as that of the old coating, depends in part on whether it favors plastic or elastic deformation. 

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