Nano silicon dioxide (English Name: nano silicon dioxide) is an inorganic chemical material, commonly known as white carbon black. Due to its ultra-fine nanometer size and size range of 1~100nm, it has many unique properties, such as anti ultraviolet optical properties, which can improve the aging resistance, strength and chemical resistance of other materials. It is widely used. Nano silica is amorphous white powder, non-toxic, tasteless and pollution-free. Its microstructure is spherical, in flocculent and reticular quasi granular structure. Its molecular formula and structural formula are SiO2, insoluble in water.


Nano is a scale of 10 meters. Nano materials mean that at least one dimension in three-dimensional space is in the range of nano size, that is, the range of 1~100 nanometers. Nano materials have small size effect, surface effect and macroscopic quantum drug effect, so they show many unique properties and have broad application prospects in catalysis, light filtering, light absorption, medicine, magnetic media and new materials.


Main purpose

Nano silicon dioxide has a wide range of uses. Generally, the added weight is 0.5-2%, and individual product systems can reach more than 10%. The key to the performance of the product is to fully disperse it into the system. When using, according to different systems, nano silica is pre dispersed in water, acetone, alcohol or other solvents. For oily systems, auxiliary agents can be used for pretreatment. It is mainly used in the following fields,


(1) Electronic packaging materials

By fully dispersing the nano silica after surface activity treatment in the silicone modified epoxy resin packaging adhesive matrix, the curing time of the packaging material can be greatly shortened (2.0-2.5h), and the curing temperature can be reduced to room temperature, so that the sealing performance of the device can be significantly improved and the service life of the device can be increased.

(2) Resin composite

The properties of resin based materials can be improved by fully and uniformly dispersing nano silica particles into resin materials. Including: a improving strength and elongation; B improve wear resistance and surface finish of materials; C. aging resistance.


(3) Plastics

The use of nano silicon dioxide can make the plastic more dense because of its light transmission and small particle size. After adding silicon dioxide to polystyrene plastic film, its transparency, strength, toughness, waterproof performance and anti-aging performance can be improved. The main technical indexes (water absorption, insulation resistance, compressive residual deformation, flexural strength, etc.) of the common plastic polypropylene modified by nano silicon dioxide have reached or exceeded the performance indexes of the engineering plastic nylon 6.

(4) Paint
It can improve the poor suspension stability, thixotropy, weather resistance and washing resistance of the coating, greatly improve the bonding strength between the coating and the wall, increase the hardness of the coating, and improve the self-cleaning ability of the surface.

(5) Rubber
Silica is known as white carbon black. After adding a small amount of Nano-SiO2 to ordinary rubber, the strength, wear resistance and anti-aging properties of the product can reach or exceed those of high-grade rubber products, and the color can remain unchanged for a long time. Nano modified color EPDM waterproof coiled material has significantly improved its wear resistance, tensile strength, bending resistance and aging resistance, and has bright colors and excellent color retention effect.

(6) Color (dye)
The surface modification of organic pigments (dyes) by adding nano-SiO2 not only greatly improves the anti-aging performance of pigments (dyes), but also improves the brightness, hue, saturation and other indicators to a certain extent, which greatly broadens the grade and application range of organic pigments (dyes).


(7) Ceramics
Replacing nano-a1203 with nano-SiO2 can not only play the role of nano particles, but also be the second phase particles, which can improve the strength, toughness, hardness, elastic modulus and other properties of ceramic materials,.

Nano SiO2 is used to composite ceramic substrate, which improves the compactness, toughness and smoothness of the substrate, and greatly reduces the sintering temperature.


(8) Sealant, adhesive
With the addition of nano-SiO2, a layer of organic material is coated on its surface to form a network structure and a silica structure, which makes it hydrophobic, can inhibit the colloid flow, accelerate the curing speed, improve the bonding effect, and increase the sealing and anti-seepage properties of the product.

(9) FRP products

The grafting and bonding between nano particles and organic polymers increase the toughness, tensile strength, impact strength and heat resistance of the materials.

(10) Drug carrier
The nano-SiO2 can play a good slow-release effect.

(11) Cosmetics
Nano Si02 is an inorganic component, which is easy to be compatible with other components of cosmetics. It is non-toxic and tasteless. It is white in itself, with strong UV reflection ability and good stability. It will not decompose, change color or react with other components in the formula after being irradiated by UV light, laying a good foundation for the upgrading of sunscreen cosmetics.

(12) Antibacterial material
Taking advantage of the huge specific surface area, surface multi mesoporous structure, super adsorption capacity and strange physical and chemical properties of nano Si02, functional ions such as silver ions are uniformly designed into the mesoporous surface of nano si0x, and nano antibacterial powder with high efficiency, durability, high temperature resistance and broad-spectrum antibacterial is developed, which can be widely used in bill, medical and health care, chemical building materials, household appliances, functional fibers, plastic products and other industries.


manufacturing method
The preparation methods of Nano-SiO2 can be divided into physical method and chemical method.

(1) Physical method
Physical method generally refers to mechanical crushing method. Superfine SiO2 products with particle size of 1~5 μ M can be obtained by crushing SiO2 aggregates with super air mill or high-energy ball mill. This method is simple but easy to bring in impurities The powder characteristics are difficult to control, the preparation efficiency is low and the particle size distribution is wide.


(2) Chemical method
Pure and uniform ultrafine SiO2 particles can be prepared by chemical method. Chemical methods include chemical vapor deposition (CVD) method, liquid phase method, ion exchange method, precipitation method and sol gel method. The main production methods are gas phase method with silicon tetrachloride as raw material, precipitation method with sodium silicate and inorganic acid as raw material and sol gel method with silicic acid vinegar as raw material.