Microscopic Solids

Recall that for a heterogeneous catalytic reactor we had to consider the microscopic concentration profiles around and within a catalyst particle and then elirninate them in terms of the macroscopic position variable z in the reactor design ecpaations (mass transfer limits and effectiveness factors). 

In aU these examples the external and internal surface areas of the sohd increases 

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Aerosol a mixture of microscopic solid or liquid particles in a gaseous medium. Smoke, haze, and fog are aerosol examples. 

The separation of suspensions is the selective removal of suspended solids, say, by the ordinary processes of filtration. Application can also made to the separation of colloidal suspensions of minute or microscopic solid particles, and even of emulsions, the suspension of minute immiscible liquid droplets within another liquid phase. A distinguishing feature of ordinary filtration is usually that the discharged liquid phase does not form a continuum on the downflow or reject side of the membrane, or filter, and more or less exists at atmospheric pressure. If otherwise, if a contiunuum is formed, the process is more that of reverse osmosis, also called hyperfiltration. In common use, notably for the upgrading or desalination of salt water or brackish water, reverse osmosis is a subject for special consideration. 

One of the most influential innovations in the history of LbL technology so far must be LbL assembly on a colloidal particle with subsequent hoUow capsule preparation [220-223]. In the first decade of LbL technology, researchers regularly assembled films on a flat solid support of visible dimensions. However, the mechanism of the LbL assembly does not exert any limitations on the size of supports or their shape. Therefore, LbL assembly on microscopic solid surfaces dispersed in solution is reasonable, opening the way to fabrication of both three-dimensional structures and nano/micro-sized objects through the LbL process. As shown in Fig. 8, the concept of the assembly is simple. LbL films are assembled sequentially on a colloidal core in a similar way to conventional LbL assembly on a flat plate. Dissolution of the central particle core upon exposure of the particles to appropriate solvents then results in hollow capsules. 

Any of these substances can be a solid, a liquid, a gas, a vapour (which is the gaseous phase of a liquid or solid material at ambient temperature and pressure), an aerosol (a dispersion of microscopic solid or liquid particles in a gaseous medium), a smoke (an aerosol usually of carbon particles with less than 0.1 [xm diameter), or a fog (a visible liquid aerosol). 

A beauty of the diamond anvil cell is it is hard enough to flatten almost anything including polymers, powders, particles, fibers, paint chips, and elastomers. The cell turns an infrared microscope into an almost universal sampling accessory for solids in some labs they analyze all their macroscopic and microscopic solid samples this way. In labs without an IR microscope the diamond anvil cell can be used to analyze solids by placing it in a beam condenser mounted in the FTIR sample compartment. 

Particulate matter (PM) from fuel combustion is a mixture of microscopic solids, liquid droplets, and particles with solid and liquid components suspended in air. Solid particles, such as soot or black carbon, are referred to as non-volatile particles. Volatile PM is comprised of inorganic acids (and their corresponding salts, such as nitrates and sulphates), and organic chemicals limn incomplete fuel combustion. 

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