Comparison of the melting point of silicon carbide and silicon dioxide

Silicon carbide is commonly known as corundum, chemical formula SiC, colorless crystal, blue-black when containing impurities. The structure is similar to that of diamond, with each silicon atom surrounded by 4 carbon atoms, and each carbon atom surrounded by 4 silicon atoms, forming a "giant molecule". The hardness is second only to diamond, with a density of grams3 and a melting point of about 2700 (decomposition and sublimation).

The chemical properties are stable, and it does not react with chlorine, oxygen, sulfur, and strong acids at high temperatures, but it can react with alkalis.

Chemically stable silicon carbide generally does not produce carbon dioxide and carbon monoxide.

Silica is also known as silica and has the chemical formula SiO2. There are two types of silica in nature: crystalline silica and amorphous silica.

Crystalline silica is divided into three types: quartz, lemostomatite and cristobalite due to different crystal structures. Pure quartz is a colorless crystal, and a large and transparent prismatic quartz is called a crystal. If the crystal containing trace impurities has different colors, there are amethyst, citrine, ink quartz, etc.

Ordinary sand is fine quartz crystals, with yellow sand (more iron impurities) and white sand (less impurities, purer). In the silicon dioxide crystal, the 4 valence electrons of the silicon atom and the 4 oxygen atoms form 4 covalent bonds, the silicon atom is located in the center of the regular tetrahedron, the 4 oxygen atoms are located on the 4 apex angles of the regular tetrahedron, the whole crystal is a giant molecule, SiO2 is the simplest expression of the composition, not a single silica molecule, but only the ratio of the number of atoms of silicon and oxygen in the silica crystal.

The bond energy of Si—O bond in SiO2 is very high, and the melting point and boiling point are high (melting point 1723, boiling point 2230).

Diatomaceous earth existing in nature is amorphous silica, which is the remains of diatoms of lower aquatic plants, which is white solid or powdery, porous, light and soft solid, and has strong adsorption.

The smaller the radius, the stronger the covalent bond and the higher the melting and boiling point of the atomic crystal"You lose a big premise in this sentence, and that is"The structure is similar".It is only on this premise that that sentence is correct. Such as diamond, crystalline silicon, silicon carbide, these three atomic crystal structures are similar, when comparing their melting and boiling points, you can look at the radius.

The smaller the radius, the stronger the covalent bond and the higher the melting boiling point.

This is not the case for SiO2, because the SiO2 crystal structure is very different from the previous 3 crystals.

Both crystals are atomic crystals and have tetrahedral structures, if this problem occurs in secondary school, it can only be inferred from the atomic radius, the atomic radius of oxygen is smaller than that of carbon, and the C-O bond is shorter and stronger than the C-Si bond, so the SiO2 melting point is higher. I didn't find any data either.

Silicon carbide decomposes at 2500 degrees Celsius under atmospheric pressure, and the melting point of silica is about 2000 degrees Celsius.

SilicaThe melting point is between 1600-1700°C.

Different forms of silica have different melting points, with a melting point of 1670 (squamolite (cristobalite quartz).

The melting point and hardness of silica are very large, because silica is an atomic crystal, and the melting point and hardness of atomic crystals are very large.

SiO2 is also known as silica. It is widely distributed in nature, such as quartz and quartz sand.

Wait. White or colorless, with a higher iron content being pale yellow. Density, melting point 1670 (lemosmosilica).

1710 (cristobalt). Boiling point 2230. Insoluble in water and acids (except hydrofluoric acid, which can work with melt and alkalis when particles.) It is used for making glass and water glass.

Pottery, enamel.

Refractories, ferrosilicon, molding sand, elemental silicon, etc.

Silica Chemistry:

The chemical properties are relatively stable. Does not react with water. It is an acidic oxide and does not react with ordinary acids. Hydrofluoric acid reacts with silica to form gaseous silicon tetrafluoride. Silicates and water are formed by reacting with a hot, concentrated alkali solution or molten alkali.

It reacts with a variety of metal oxides at high temperatures to form silicate. The nature of silica is not active, it is not compatible with the removal of fluoride and hydrogen fluoride.

other halogens.

Hydrogen halide as well as sulfuric acid and nitric acid.

Perchloric acid action (except for hot concentrated phosphoric acid).

Common concentrated phosphoric acid (or pyrophosphoric acid) can corrode silica at high temperatures to form heteropolyacids, and molten borate or boric anhydride can also corrode silica at high temperatures, in view of this property, borate can be used as a flux in ceramic firing, in addition to hydrogen fluoride can also make silica dissolved acids to produce fluorosilicic acid that is easily soluble in water.

The above content refers to Encyclopedia-Silica.

<> these two substances are atomic crystals, it is the covalent bond that determines their melting and boiling point, which can be judged by the bond energy of the covalent bond, and the bond energy is inversely proportional to the bond length, and the bond length is equal to the sum of the two atomic radii of the bond, so it can be compared with the atomic radius of carbon, oxygen, and silicon. Therefore, it can be seen that the carbon-silicon bond energy is greater than the oxy-silicon bond energy, and the melting and boiling point of silicon carbide is greater than that of silicon dioxide. The specific data is that the melting point of silicon dioxide is about 1723 degrees Celsius, and the melting point of silicon carbide is about 2700 degrees Celsius.

The melting point of silica is 1723. Physical. Density:.

Melting Point: 1723.

Boiling point 2230.

Refractive index:. Change when heated: It melts with a strong base when heated to form silicate.

Solubility: insoluble in water, can react with HF to form gaseous SIF4.

Substance use. Silica is a raw material for the manufacture of glass, quartz glass, water glass, optical fibers, important components of the electronics industry, optical instruments, handicrafts and refractory materials, and is an important material for scientific research.

When silica crystallizes perfectly, it is crystal; After silica gelatinization and dehydration, it is agate; The aqueous colloids of silica become opal when solidified; When the silica grains are less than a few microns, chalcedony, flint, and secondary quartzite are formed.

The physical and chemical properties are very stable mineral resources, and the crystal belongs to the trigonal crystal system of oxide minerals, that is, low-temperature quartz (quartz), which is the most widely distributed mineral species in the quartz group of minerals.

The above content refers to Encyclopedia-Silica.

High temperature and high pressure catalyst, silicon and carbon monoxide2c

sio2=si

2CO This is a redox reaction, and there are many factors depending on the oxidation product or reduction product, among which the strength of oxidation reduction is the main factor. In this reaction, the reduction of carbon and the oxidation of silica are relatively weak, and carbon dioxide cannot be generated.

Silicon is +4 valence, which becomes later 0 valence, and carbon is first oxidized to +2 valence from 0 valence, which means that the oxidation capacity of silica is relatively small, and it can only oxidize carbon to carbon monoxide!

This reaction is a reaction in the dry state, not a solution state, so it does not conform to the law of displacement. It is correct that silicon is more reducible than carbon, but at high temperature and in the dry state, the reaction between carbon and silicon dioxide is a reaction that conforms to the law that "high boiling point substances can be qualitatively replaced by low boiling point substances". In SiO2, C, Si, Co, only Co is gaseous and has the lowest boiling point, so the reaction can take place:

sio2+2c

High temperature = = si+

When there is an excess of 2Co carbon, the generated Si and C can continue to be synthesized into silicon carbide: Si + C = = High temperature = SiC

The melting point of silicon dioxide is 1713 and that of silicon carbide is 2700.

The melting point of silicon carbide is much higher than that of silicon dioxide, reaching 2700, while the melting point of silicon dioxide is only 1713. This is because silicon carbide has stronger chemical bonds than silicon dioxide, so it requires a higher temperature to melt.

Difference Between Silicon Dioxide and Silicon Carbide:

1. Chemical composition.

The chemical formula of silicon dioxide is SiO2 and the chemical formula of silicon carbide is SiC.

2. Structure. Silica is composed of silicon and oxygen atoms, in which the silicon atoms and four oxygen atoms form a tetrahedral structure. Silicon carbide is a crystal composed of carbon and silicon atoms, where the carbon and silicon atoms form a hexagonal lattice structure.

3. Physical properties.

Silica is a white powder, tasteless, odorless, non-toxic, insoluble in water, but soluble in hydrofluoric acid and alkaline solutions. Silicon carbide is a black crystal with very high hardness, harder than steel, and is also a good thermal conductive material and corrosion resistant material.

4. Application. Silica is widely used in the manufacture of glass, ceramics, cement, electronic devices and other fields. Silicon carbide is commonly used in the manufacture of high-temperature materials, semiconductor devices, abrasives and stoves. <>

Melting Point: 1723 degrees Celsius;

Introduction: Silicon carbide is commonly known as corundum, colorless crystal, blue-black jujube segment when containing impurities, similar in structure to diamond, each silicon atom is surrounded by 4 carbon atoms, and each carbon atom is surrounded by 4 silicon atoms to form a "giant molecule; The hardness is only second to diamond, the density is grams per cubic centimeter, the chemical properties are stable, and it does not react with chlorine, oxygen, sulfur and strong acids at high temperatures, but it can react with alkali.

Silica is colorless, solid at room temperature, insoluble in water, insoluble in acid. However, it is soluble in hydrofluoric acid-grade hot concentrated phosphoric acid, which can work with molten alkalis. The melting point is between 1,600 degrees Celsius and 1,700 degrees Celsius.

Silicon crystal is a gray-black solid with metallic luster, with high hardness, brittleness, and inactive chemical properties at room temperature. It is the most important photovoltaic material. The melting point is about 1,400 degrees Celsius.