The products were analyzed by transmission electron microscope in Tsinghua University Analysis and Testing Center. Nano-zinc oxide particles are spherical, with uniform particle size distribution, with an average particle size of 20~30 nm and all below 50 nm. The BET specific surface area of nano-zinc oxide powder is more than 35m2/g through the test of specific surface area and pore size analyzer. In addition, rod-shaped nano-zinc oxide can be prepared by adjusting the preparation process parameters. This product has been tested and identified by Institute of Microbiology, China Academy of Sciences. The results showed that adding 0.5%~ 1% nano-zinc oxide to the bacteria-rich medium could effectively inhibit the growth of Escherichia coli, and the bacteriostatic rate was over 99.9%.
Nano-zinc oxide has large specific surface area, large surface energy and easy agglomeration. On the other hand, the surface polarity of nano-zinc oxide is strong, and it is not easy to disperse evenly in organic media, which greatly limits its nano-effect. Therefore, the dispersion and surface modification of nano-zinc oxide powder has become a necessary treatment means before nano-materials are applied to the matrix.
In the study of specific surface area of nano-zinc oxide and related data reports, only the results of BET method are true and reliable, because the standards for measuring specific surface area at home and abroad are based on BET method. Please refer to (GB. T 19587-2004)—— A method for measuring the specific surface area of solid materials based on the BET principle of gas adsorption. There is a special specific surface area tester to test the specific surface area, and the dynamic nitrogen adsorption method is relatively mature in China.
Nano-dispersion refers to the technology of reducing aggregates of various forms composed of dry nanoparticles into primary particles in a specific liquid medium (such as water) by using various principles, methods and means, and making them stably and uniformly distributed in the medium. The surface modification of nano-powder is an extension of nano-dispersion technology, that is, according to the needs of application, the dispersed nano-particles are coated with a film of suitable substances or dispersed in soluble solid carriers. After surface modification, a series of surface properties such as adsorption, wetting and dispersion of nano-dry powder will change, and it can be automatically or easily dispersed in a specific medium, which is very convenient to use. Generally speaking, there are three methods to modify nanoparticles: 1. Uniformly coating a layer of other substances on the surface of nanoparticles, thus changing the surface properties of nanoparticles; 2. Use charge transfer complexes (such as silane, titanate and other coupling agents, stearic acid, silicone and so on). ) as a surface modifier, chemical adsorption or chemical reaction is carried out on the surface of nanoparticles; 3. Surface modification of nanoparticles by high-energy means such as corona discharge, ultraviolet ray, plasma and radiation.
According to the requirements of different application fields, suitable surface modifiers or surface modification processes are selected to modify the surface of nano-zinc oxide, improve its surface properties and increase the compatibility between nano-particles and matrix, so as to be applied in various fields and improve the performance and technical indicators of products.