Solid surface sheet area of atoms or molecules on a solid surface in general is not easy to move, their location is the position at which the generated surface, they do not have the same energy, so the solid surface is uneven. Since the size of the contact surfaces of different preparation conditions, solids and gases (surface area) may be very different. Or finely divided solid porous solid surface area in two parts, the inner surface of the wall by their internal surface of the pores and cracks formed includes an inner surface and an outer surface; refers to an outer surface of the solid particles of the external geometric area.
Atoms or molecules on a solid surface in general is not easy to move, their location is the position at which the generated surface, they do not have the same energy, so the solid surface is uneven. Since the size of the contact surfaces of different preparation conditions, solids and gases (surface area) may be very different. Or finely divided solid porous solid surface area in two parts, the inner surface of the wall by their internal surface of the pores and cracks formed includes an inner surface and an outer surface; refers to an outer surface of the solid particles of the external geometric area. The sum of the surface area to external surface area of the total surface area. It is known as the ratio of external surface area of rough factor, obviously, solid surface roughness factor of a minimum of 1. In order to measure and compare the size of the adsorbent or catalyst surface area. The total surface area is referred to the provisions of one gram of solid surface area.
Determination of surface area are: direct determination of particle size of the solid particles to calculate the external surface area of the sedimentation method; optical microscopy and electron microscopy; X-ray width method; direct determination of the outer surface of the transmission method. However, these methods can not be measured of the inner surface of the solid.
Cryogenic gas adsorption method is the determination of the total surface area of the solid most commonly used method, the basic point is: determine the absorption of the amount of adsorbent adsorbate gas at different relative pressure applied BET two constant equation (see multi-molecular layer adsorption) Calculation the surface covered with the adsorbent adsorbate monolayer amount (monolayer adsorption capacity), and then the specific surface area can be obtained according to the cross-sectional area of each adsorption and sorbent mass molecular weight.
Cross-sectional area of each of the adsorbed molecules σ can be calculated as: where Μ is adsorbate molecular weight; N is the Avogadro number; d is a liquid (or solid) adsorbate density.
Dye adsorption method is a simple method for the determination of crude porous solid surface area, according to this law: Some solid can selectively adsorb certain dyes from the solution reached saturation, according to the concentration absorption solution before and after the change, you can obtained monolayer adsorption capacity is then calculated based on the specific surface area per sectional area of the dye molecules may. The disadvantage of this method is: dye molecules on the surface sheet of the orientation to have a certain hypothesis, but still solvent adsorption even when adsorption; pores in the area because of the dye molecules can not enter but could not be measured.
 |
| acrylic solid surface sheet |
没有评论:
发表评论