Layered particle-reinforced

A layered particle-reinforced bionanocomposite, also known as a layered polymer nanocomposite (LPN), can be classified into three subcategories depending on how the particles are dispersed in the matrix. Intercalated nanocomposites are produced when polymer chains are intercalated between sheets of the layered nanoparticles, whereas exfoliated nanocomposites are obtained when there is separation of individual layers, and flocculated or phase-separated nanocomposites are produced when there is no separation between the layers due to particle-particle interactions. This last class of composites is often named microcomposites as the individual laminas do not separate, thus acting as microparticles dispersed in the polymeric matrix. Their mechanical and physical properties are poorer than exfoliated and intercalated nanocomposites [17, 20, 21, 36, 37]. Figure 11.1 shows a schematic drawing of the structure of layered nanocomposites. 

Exfoliating layered particles such as the clays, mica, or graphite is being used to provide very effective reinforcement of elastomers at loading levels much smaller than in the case of solid particles such as carbon black and silica [228-231]. Other properties can also be substantially improved, including increased resistance to solvents, and reduced permeability and flammability. 

Influence of the gradient layer on reinforcement increases essentially at percolation of particle-coating layers (connected by tacking or intersection). 

Xu, J., Zhuo, C., Han, D., Tao, J., Liu, L.L., Jiang, S., 2009. Erosion—corrosion behaviour of nano-particle-reinforced Ni matrix composite alloying layer by duplex surface treatment in aqueous slurry environment. Corrosion Science 542, 457. 

The results obtained by Kuila et al. and Acharya et al. [63,64] from the EVA elastomer blended with lamellar-like Mg-Al layered double hydroxide (LDH) nanoparticles demonstrate that MH nanocrystals possess higher flame-retardant efficiency and mechanical reinforcing effect by comparison with common micrometer grade MH particles. Kar and Bhowmick [65] have developed MgO nanoparticles and have investigated their effect as cure activator for halogenated mbber. The results as shown in Table 4.2 are promising. 

Perforated plate distributors are widely used in industry because they are cheap and relatively easy to manufacture. Simple perforated plate-type distributors suffer from particles passing back through to the plenum despite mean gas velocities well above the settling velocity for the particles. This is because of imbalances in gas flow between the orifices, which is difficult to eliminate. Hence, such plates take the form of either a layer of mesh sandwiched between two perforated plates or two staggered perforated plates without a mesh screen (Kunii and Levenspiel, 1991). However, these structures often lack rigidity and need to be reinforced or sometimes curved (concave to the bed) to withstand heavy loads. The diameter of the orifices in a perforated plate distributor varies from 1 or 2mm in small beds used for research or very small-scale production to 50 mm in very large chemical reactors. Most food applications are likely to use apertures of intermediate size. 

There are several methods of layering in common use ( ) thick layers shrunk together (2) thin layers, each wrapped over the other and the longitudinal seam welded by using the prior layer as backup and (3) thin layers spirally wrapped. The code rules are written for either thick or thin layers. Rules and details are provided for all the usual welded joints and nozzle reinforcement. Supports for layered vessels require special consideration, in that only the outer layer could con-triDute to the support. For lethal service only the inner shell and inner heads need comply with the requirements in Subsec. B. Inasmuch as radiography would not be practical for inspection of many of the welds, extensive use is made of magnetic-particle and ultrasonic inspection. When radiography is required, the code warns the inspector... 

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