Silica specific surface area test

SiO2 is also called silica. It is widely distributed in nature, such as quartz and quartz sand. White or colorless, with a high iron content is light yellow. Density 2.2 ~ 2.66. Melting point 1670 ℃ (scale quartz); 1710 ℃ (cristobalite). It has a boiling point of 2230 ° C and a relative dielectric constant of 3.9. It is insoluble in water, slightly soluble in acid, and can act with molten alkali when in granular state. Used for making glass, water glass, pottery, enamel, refractory, ferrosilicon, molding sand, elemental silicon, etc

use

Silicone standard solution. Preparation materials for water glass and silicon compounds. As a masking film and a protective layer for impurity diffusion in transistors and integrated circuits, a silicon dioxide film is made as an integrated circuit device. Glass industry.

nature

Physical properties

Silica, also known as silica, has the chemical formula SiO? (The specific surface area of ​​silica is tested by 3H-2000 series automatic nitrogen adsorption specific surface area tester,

The professional manufacturer of silica specific surface area test, Beside, has high test accuracy and good repeatability, providing professional pre-sale technical support and high-quality after-sales service. However, there are crystalline silica and amorphous silica in the world. Species. Sandy silica.

Due to their different crystal structures, crystalline silica is divided into three types: quartz, scale quartz and cristobalite. Pure quartz is a colorless crystal, and large and transparent prismatic quartz is called crystal. If the crystals containing trace impurities have different colors, there are amethyst, tea crystal, and ink crystal. Ordinary sand is fine quartz crystal, with yellow sand (more iron impurities) and white sand (less impurities, more pure). In silicon dioxide crystals, the 4 valence electrons of silicon atoms form 4 covalent bonds with 4 oxygen atoms, the silicon atoms are located in the center of the regular tetrahedron, the 4 oxygen atoms are located at the 4 vertices of the regular tetrahedron ? Is the simplest formula for the composition, and only represents the ratio of the number of silicon and oxygen atoms in the silicon dioxide crystal. Silica is an atomic crystal.

The bond energy of the Si—O bond in SiO? Is high, and the melting point and boiling point are high (melting point 1723 ° C, boiling point 2230 ° C).

Diatomite existing in nature is amorphous silica, which is the remains of diatoms of lower aquatic plants. It is a white solid or powder, porous, light and soft solid, with strong adsorption.

The specific surface area of ​​silica is an important parameter. The specific surface area is the surface area per gram of solid material, the unit is m2 / g; the national standard for silica specific surface area test is the low-temperature nitrogen adsorption BET multi-point method based on BET theory (GB / T 19587-2004). The main points of measuring the specific surface area by the nitrogen adsorption BET multipoint method are: in the range of 5-30% nitrogen partial pressure, the amount of nitrogen adsorbed by the adsorbent (powder to be measured) is measured at different nitrogen partial pressure points to make adsorption For the isotherm, the saturated adsorption amount of the monolayer corresponding to the surface of the adsorbent when the monolayer is covered with nitrogen molecules is calculated by the BET formula, and the specific surface area of ​​the adsorbent can be calculated. The 3H-2000BET-A silica specific surface area test is a high-precision analytical instrument based on the national specific surface test standard, and has 7 domestic leading technologies; such as the only integrated in-situ purge processing function in China, which is aimed at chromatographic comparison The problem of purge treatment between different nitrogen partial pressure points for surface testing makes the purge treatment between different nitrogen partial pressure points more convenient and efficient, reducing the impact of continuous testing on accuracy; the only program-controlled wind and heat assist in China The decoupling device can ensure sharp and rapid desorption peaks and reduce background errors after full automation; the only chromatographic concentration detection system in China improves the detection accuracy of nitrogen partial pressure by 10 times relative to the flow method; six-port valve sampler Program control, the only domestic quantitative control program switching function; the only domestic particle size report and other functions; while the instrument parameter software is displayed, the large-screen LCD hardware display on the instrument makes the instrument's working status parameters clear and the operation is more reliable; and liquid nitrogen Temperature monitoring, detector gas cut-off protection, detector thermostat, and sound prompts for important links make 3H-2000BET-A 2 The silicon oxide specific surface area test achieves and partially surpasses the performance of similar foreign instruments in terms of test accuracy, stability, safety, and ease of operation. The 3H-2000 series silica specific surface area test has a large number of customers in China and is the silica specific surface area. Test well-known brands.

Chemical properties

The academic nature is relatively stable. Do not dissolve in water nor react with water. It is an acidic oxide and does not react with normal acids. Gaseous hydrogen fluoride reacts with silicon dioxide to form gaseous silicon tetrafluoride. Reacts with hot concentrated strong alkaline solution or molten alkali to form silicate and water. It reacts with various metal oxides to form silicate at high temperature. Used in the manufacture of quartz glass, optical instruments, chemical vessels, ordinary glass, refractory materials, optical fibers, ceramics, etc. Silica is inactive in nature. It does not interact with halogens, hydrogen halides, sulfuric acid, nitric acid, and perchloric acid (except hot concentrated phosphoric acid) other than fluorine and hydrogen fluoride. Common concentrated phosphoric acid (or pyrophosphoric acid) can corrode silica at high temperature and generate heteropoly acid [2]. At high temperature, molten borate or boric anhydride can corrode silica. In view of this property, boric acid Salt can be used as a flux in the firing of ceramics. In addition, hydrogen fluoride can also dissolve the acid of silicon dioxide to form fluorosilicic acid that is easily soluble in water: SiO? + 4HF = SiF4 ↑ + 2H? O

Acid-oxygen connectivity:

Silica and alkaline oxides

SiO? + CaO = (high temperature) CaSiO3

Silica can be dissolved in concentrated strong alkali solution: SiO? + 2NaOH = Na2SiO3 + H? O

(Reason for alkali-containing reagent bottle cannot use glass stopper and rubber stopper)

At high temperatures, silicon dioxide can be reduced by carbon, magnesium, and aluminum: SiO? + 2C = (high temperature) Si + 2CO ↑ If c is excessive, the reaction occurs: Si + C = high temperature = SiC (corundum)

Silicic anhydride: silicon dioxide (SiO2).

Silica does not react with water, that is, it does not generate silicic acid in contact with water, but it is artificially specified that silica is an anhydride of silicic acid

application

Silica is the raw material for manufacturing glass, quartz glass, water glass, optical fiber, important parts of the electronics industry, optical instruments, handicrafts and refractory materials. It is also an important material for scientific research. When the silica crystal is perfect, it is crystal; silica gel is agate after dehydration; silica gel containing water becomes solid when it becomes solid; when the silica crystal grains are less than a few microns, they form chalcedony, flint, and secondary Quartzite. Silica

Mineral resources with very stable physical properties and chemical properties. The crystal belongs to the oxide mineral of the trigonal system, that is, low-temperature quartz (a-quartz), which is the most widely distributed mineral species in the quartz family of minerals. Quartz in a broad sense also includes high-temperature quartz (b-quartz). Quartz blocks, also known as silica, are mainly raw materials for producing quartz sand (also known as silica sand), as well as raw materials for quartz refractories and sintered ferrosilicon.

Glass and glass lettering

The main raw materials of flat glass, float glass, glass products (glass jars, glass bottles, glass tubes, etc.), optical glass, glass fiber, glass instruments, conductive glass, glass cloth and special anti-radiation glass. Special use: Glass lettering: First coat a layer of paraffin wax on the glass bottle, then engrave the words with a sharp tool, and then use hydrofluoric acid to smear the wax on the lettering again. Wait for a moment for the lettering to appear. Principle: Hydrofluoric acid corrodes silica.

Ceramics and refractories

Raw materials and glazes for porcelain, high-silica bricks, ordinary silica bricks and silicon carbide for kilns.

metallurgy

Raw materials or additives and fluxes for silicon metal, ferrosilicon alloy and silicon aluminum alloy.

building

Concrete, cementitious materials, road construction materials, artificial marble, cement physical performance testing materials (ie cement standard sand), etc.

Chemical industry

Raw materials such as silicon compounds and water glass, fillers for sulfuric acid towers, and amorphous silica can be used as adsorbents.

mechanical

The main raw material of foundry sand, abrasive materials (sandblast, hard abrasive paper, sandpaper, emery cloth, etc.). .

electronic

High-purity metal silicon, optical fiber for communication, etc.

Rubber, plastic

Adding silica to rubber can improve the wear resistance of rubber. It can reduce tire rolling resistance and improve tire wear resistance and wet skid resistance. The tensile strength, tear strength, wear resistance, etc. of the compound using silica are improved.

coating

Filler (can improve the weather resistance of the coating), can be used to produce matting agent, can also be used as a coating thickener.

Food, medicine

In the food industry, it is mainly used to prevent powdered food from agglomerating and agglomerating, to maintain free-flowing food additives or to absorb liquid spices, fats, vitamins, etc., to make it into a powder, such as powdered fats, solid spices and Products such as solid wine. (Example: milk powder)

In medicine production, it can be used as glidant, catalyst carrier, etc.

Therefore, the silica specific surface area test needs to be tested with the 3H-2000 series automatic nitrogen adsorption specific surface area tester.The 3H-2000 series silica specific surface area tester can fully meet the needs of silica testing. Professional manufacturer of the instrument, Beside, the silica specific surface area tester has high test accuracy, fast speed, and good repeatability. It has obtained many national technical patents, providing professional pre-sale technical support and high-quality after-sale service.