What Is Specific Surface Area?

Specific surface area refers to the total area per unit mass of material. The unit is m ² / g. It usually refers to the specific surface area of solid materials, such as powder, fiber, granules, flakes, lumps and other materials.

Explanation: Specific surface area refers to the total area per unit mass of material. There are two types of external surface area and internal surface area. National standard unit m ² / g. Ideal non-porous materials have only external surface areas, such as

Method summary: The specific surface area testing methods are mainly divided into continuous flow method (ie dynamic method) and static capacity method.

The dynamic method and the static capacity method are the main specific surface testing methods commonly used.

The dynamic method is to install the powder sample to be tested in a U-shaped sample tube, and make a mixed gas containing a certain proportion of the adsorbent flow through the sample, and determine the adsorption of the adsorbent molecule (N2) by the measured sample according to the change in gas concentration before and after adsorption the amount.

The static method is divided into a gravimetric method and a volume method according to different methods for determining the adsorption amount. The gravimetric method is based on the change in the weight of the sample before and after adsorption to determine the amount of adsorbed molecules (N2) adsorbed by the test sample. Due to the low resolution, poor accuracy, and high equipment requirements, such defects are rarely used; the volume method is to wait The powder sample is placed in a certain volume of a closed test tube sample tube, and a certain pressure of adsorbent gas is injected into the sample tube. The adsorption of the adsorbent molecule (N2) by the measured sample is determined according to the pressure or weight change before and after adsorption. the amount;

Comparing the two methods, the dynamic method is more suitable for testing fast specific surface area test and small specific surface area samples with small and medium adsorption amount (for samples with medium and large adsorption amount,

There are about a dozen currently valid national standards for specific surface area testing in China. Here are a few commonly used national standard methods:

GB / T 19587-2004 "Determination of specific surface area of solid matter by gas adsorption BET method"

GB / T 13390-2008 "Determination of specific surface area of metal powders by nitrogen adsorption method"

GB / T 7702.20-2008 "Determination of specific surface area of coal-based granular activated carbon test method"

GB / T 6609.35-2009 "Methods for chemical analysis and determination of physical properties of alumina-Part 35: Determination of specific surface area-Nitrogen adsorption method"

SY / T 6154-1995 "Determination of Static Nitrogen Adsorption Capacity by Specific Surface and Pore Size Distribution of Rocks"