The specific surface area refers to the total area of a unit mass of material. There are two types of external surface area and internal surface area. National standard unit m2/g. Ideal non-porous material only has external surface area, such as Portland cement, some clay mineral powder, etc.; porous and porous materials have external surface area and internal surface area, such as asbestos fiber, rock (mine) Cotton, diatomaceous earth, etc. The measurement methods include a volume adsorption method, a weight adsorption method, a flow adsorption method, a gas permeable method, and a gas adhesion method. The specific surface area is one of the important indicators for evaluating the utilization of catalysts, adsorbents and other porous materials such as asbestos, mineral wool, diatomaceous earth and clay minerals. The specific surface area of asbestos has obvious influence on its thermal properties, adsorption capacity, chemical stability and degree of cotton opening.
The fineness is the degree to which the powdery substance is finely dispersed in the binder, expressed in microns. The larger the fineness modulus, the thicker the sand. Ordinary concrete sand has a fineness modulus ranging from 3.7 to 1.6, preferably medium sand, or coarse sand plus a small amount of fine sand in a ratio of 4:1.
The specific surface area and fineness are proportional. The finer the fineness, the larger the specific surface area, but the surface integral is several types such as BET SATA. The key is that some materials have small or empty surfaces, which may be fine overall. The degree of increase is doubled, the specific surface area is increased a lot, and sometimes the area of the particle size distribution is different, which will lead to different results, such as 80 nm square hole sieve for testing: although the fineness of the ore powder is small, the particle distribution is concentrated. Such as mainly distributed around 60 microns. The fineness of the stone powder is large, but if the particles are evenly distributed, such as: 10 to 80 microns, the ratio of the stone powder is larger than that of the ore.
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