Hydroscopicity - particles

Visibility is also affected by alteration of particle size due to hydroscopic particle growth, which is a function of relative humidity. In Los Angeles, California, the air, principally of marine origin, has numerous sea salt particles. Visibility is noticeably reduced when humidity exceeds about 67%. In a study of visibility related to both relative humidity and origin of... 

Even the void fraction together with particle size distribution does not provide all of the necessary information on the kind of flow. The mutual forces between distinct particles depend not only on the distance between the particles but also on the surface properties of the particles. The strength of the attractive forces between particles depends on conditions. For instance, the moisture content of the solid is essential for determining the attractiv c forces between particles, especially for hydroscopic materials such as wood. Airflow between particles usually tends to separate particles, whereas the surface forces, adhesion forces, tend to bring them together. 

Solid particles are not readily wettable when air is entrapped because the contact angle widens. Hydroscopic (or water-miscible) materials such as glycerin, alcohol, and glycol penetrate the spaces occupied by air and displace it. During the dispersion process, the hydroscopic materials separate the agglomerates and coat the particles so that water can flow into and wet the particles. 

Depending on the character of the inflaming material, the conditions of the pyrolysis process and the properties of the EC- residence medium, their surface can be covered with adsorbed substances. Often these ate hydrophobic, incompletely burnt, hydrocarbons. However, the cover may happen to be hydroscopic (due to adsorption of atmospheric gases), ready to form hydrogen and coordinate bonds. Pure EC is absolutely inert at usual temperatures. This is an hydrophobic, insoluble substance (it may be oxidized at about 600 C or in the atmosphere of F2, but such conditions do not occur in the real atmosphere). EC is capable of reacting with radicals, which may be essential from the viewpoint of the chemical reactions taking place in the atmosphere. The EC catalytic activity in reactions of atmospheric SO2 oxidation has been reported in [29]. These reactions can be driven by two mechanisms dry (in the presence of water) and moist , when an EC particle is filmed with water. The moist mechanism is more effective [10]. 

Atmospheric corrosion rates will tend to increase with winds directly from the ocean to the site, the lower the elevation, and the closer the ocean is to the specimen as shown in Table 2. The direction and velocity of the wind can affect the accumulation of entrained seawater-related particles on specimen surfaces. Generally, the closer the site to the ocean in the face of a prevailing wind the greater the corrosion rate of metals and alloys. Magnesium and calcium chlorides are hydroscopic and tend to keep surfaces wet or moist. Sulfur dioxide lowers the critical humidity required to activate corrosion [fO] and increases the aggressiveness of the marine atmospheric environment such as found in an industrial marine environment versus a rural marine environment (Table 2). The dew-point temperature and the component/specimen temperature wiU influence the rate of corrosion. 

Hygroscopic inorganic/organic composite membranes, in which the ionomer or polymer is blended with hydroscopic inorganic particles so that the membranes will remain hydrated at higher operating temperatures. 

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