CN105217634B - A kind of preparation method of silicon carbide nanotube - Google Patents

Abstract

The invention discloses a method for preparing silicon carbide nanotubes, which comprises the following steps: adding an octaalkyltrimethylammonium bromide solution dropwise to a halloysite suspension in a water bath, and then adding acetone dropwise after the dropwise addition , continue to stir under the same conditions after the dropwise addition, and finally centrifuge, wash, dry and grind; put the powder in a tube furnace for carbonization under the protection of _N2 , put the carbonized solid into a bottle, and add hydrochloric acid solution, stirring, solid-liquid separation, washing, and drying; the obtained particles are placed in a tube furnace, under the protection of argon, the temperature is programmed to be calcined and then cooled to room temperature, and the calcined product is soaked in a mixture of hydrofluoric acid and hydrochloric acid. In the mixed acid, the unreacted silicon dioxide is washed away, washed and dried with deionized water, and the silicon carbide nanotube is obtained. The method uses silicon in the halloysite as a raw material, fully utilizes the tubular structure of the halloysite, has cheap raw material source, controllable process, and is easy to realize industrial production.

Description

A kind of preparation method of silicon carbide nanotube

technical field

The invention belongs to the technical field of nanomaterial preparation, and in particular relates to a method for preparing silicon carbide nanotubes.

Background technique

Silicon carbide (SiC), commonly known as corundum, gemstone name drill pith, is a ceramic-like compound formed by bonding silicon and carbon. Silicon carbide exists in nature as a rare mineral such as moissanite. Silicon carbide powder has been widely used as abrasive since 1893. Sintering silicon carbide powder can produce hard ceramic-like silicon carbide particles, which can be used in materials that require high durability, such as automobile brake pads, clutches and bulletproof vests, in materials such as light-emitting diodes, early radio detectors, etc. It is also used in the manufacture of similar electronic devices. Silicon carbide is widely used today in the manufacture of high-temperature, high-voltage semiconductors.

At present, the main methods for preparing SiC nanomaterials include template growth method, carbothermal reduction method, chemical vapor deposition method and organic precursor pyrolysis method, etc.

The preparation methods of two-dimensional SiC nanomaterials mainly have the following problems: (1) high temperature (template method, laser ablation method, arc discharge method, thermal evaporation method, carbothermal reduction method) or high pressure (solvent (2) the product often contains metal impurities (such as metal vapor-liquid-solid (VLS) catalytic growth method) or the surface is coated with SiO ₂ layer (laser ablation method, arc discharge method, carbon thermal method) reduction method), the morphology is not uniform; (3) the yield is low (template method, solvothermal method). These problems restrict the preparation of high-purity two-dimensional SiC nanomaterials and the study of their intrinsic properties, and are not conducive to the large-scale production of two-dimensional SiC nanomaterials. Therefore, the development of new low-cost and high-purity two-dimensional SiC nanomaterials preparation technology is of great significance to promote the research, large-scale production and application of two-dimensional SiC nanomaterials in related high-tech fields.

Halloysite is also known as kaolinite. The chemical composition is the same as that of kaolinite, with the same ratio of 1:1 SiO ₂ /Al ₂ O ₃ , and the lamellar structure is curled into SiO ₂ in the outer layer and Al ₂ O ₃ in the inner layer, so the halloite nanotubes have Very similar surface properties to SiO2, similar inner layer properties to Al ₂ O ₃ . Generally speaking, halloysite nanotubes are formed by curling multiple kaolin sheets and are natural multi-walled nanotubes with an outer diameter of 20-100nm, an inner diameter of 5-30nm, and a length of 150nm-2μm. The main difference between halloysite and kaolin in terms of crystal structure is a tubular structure and a sheet structure. Halloysite nanotubes are formed by kaolinite sheets curled under natural conditions, showing a microtubular structure.

Contents of the invention

In order to overcome the defects of the above-mentioned prior art, the present invention provides a method for preparing silicon carbide nanotubes with cheap raw materials and low environmental pollution, comprising the following steps:

(1) Add dropwise octaalkyltrimethylammonium bromide solution containing 8-16mmol to the suspension containing 10g of halloysite in a water bath at 60-65°C, the octaalkyltrimethylammonium bromide solution The concentration is 1-4mol/L, stirring continuously during the dropping process, and then adding 7-9 mL of acetone dropwise after the dropping is completed, continuing to stir for 2-3 hours under the same conditions after the dropping, centrifuging, and using Wash with deionized water for 4 to 5 times, dry at 100 to 105°C, and grind the solid into 50 to 80 mesh powder. During this process, the cationic surfactant is fixed to the halloysite surface as a single molecule through electrostatic interaction ;

(2) Put the powder in a tube furnace with _N2 protection, carbonize at 500-800°C for 4-6 hours, then continue to pass _N2 to cool to room temperature, the organic matter is carbonized at high temperature, and a carbonaceous layer is formed on the surface of halloysite ;

(3) Put 2 to 4 g of the carbonized solid into a bottle, add 10 to 15 mL of hydrochloric acid solution with a concentration of 20 to 40%, stir for 20 to 30 hours, dissolve the alumina structure in the halloysite, and separate the solid and liquid , washed with deionized water, and dried at a constant temperature of 60-70°C for 5-6 hours to obtain carbon-silicon-bonded particles of silicon oxide coated with a carbon layer;

(4) Put the carbon-silicon bonded particles in a tube furnace, under the protection of argon, raise the temperature to 600°C at a heating rate of 10-15°C/min, keep the temperature constant for 60-120min, and continue to heat up at a rate of 10-15°C /min, heat up to 1400-1500°C, keep the temperature constant for 240-360min, then cool down to 300-400°C, feed air, calcine for 60-120min, cool to room temperature, soak the calcined product in a mixture of hydrofluoric acid and hydrochloric acid In the acid, the molar ratio of hydrofluoric acid to hydrochloric acid is 0.5-10:1, the mixed acid treatment time is 4-24h, and the unreacted silica is washed away, and after washing with deionized water to pH = 7, 80-105°C drying to obtain silicon carbide nanotubes.

The beneficial effects of the present invention are:

Compared with the prior art, the present invention has the following characteristics and advantages: (1) the organic matter coated on the surface of the nanotube-shaped material is used as the carbon source, and the special structure of the halloysite has a large specific surface area and a regular tubular shape. Features: First, a carbon layer is obtained on the surface of halloysite, which is beneficial to the full contact between the reactant silicon source and the carbon source, and the reaction is complete. (2) Using silicon in halloysite as a raw material, making full use of the tubular structure of halloysite, and maximizing the use of carbon and silicon sources. (3) The source of raw materials is cheap, the process is controllable, and it is easy to realize industrial production.

detailed description

Example 1

In a water bath at 65°C, add dropwise an octaalkyltrimethylammonium bromide solution containing 16 mmol to the suspension containing 10 g of halloysite, the concentration of the octaalkyltrimethylammonium bromide solution being 1 mol/L, drop Stir continuously during the addition process, then add 9 mL of acetone dropwise after the dropwise addition, continue to stir for 3 h under the same conditions after the dropwise addition, centrifuge, wash the obtained solid with deionized water for 5 times, and dry at 105°C. The solid is ground into 80-mesh powder, during which the cationic surfactant is fixed to the surface of halloysite as a single molecule through electrostatic interaction; the powder is placed in a tube furnace and protected by _N2 , and carbonized at 800°C 6h, then continue to pass _N2 to cool to room temperature, the organic matter is carbonized at high temperature, and a carbonaceous layer is formed on the surface of the halloysite; put 4g of the carbonized solid into the bottle, add 15mL of 40% hydrochloric acid solution, and stir for 30h , dissolve the aluminum-oxygen structure in the halloysite, separate the solid from the liquid, wash with deionized water, and dry at a constant temperature of 70°C for 6 hours to obtain carbon-silicon-bonded particles of silicon oxide coated with a carbon layer; place the carbon-silicon-bonded particles in a tube In the type furnace, under the protection of argon, the temperature was raised to 600°C at a heating rate of 15°C/min, and the temperature was kept constant for 120 minutes. Air was introduced, calcined for 120min, cooled to room temperature, and the calcined product was soaked in the mixed acid of hydrofluoric acid and hydrochloric acid, the molar ratio of hydrofluoric acid and hydrochloric acid was 10:1, the mixed acid treatment time was 24h, and the The unreacted silicon dioxide was washed with deionized water until pH = 7, and then dried at 105° C. to obtain silicon carbide nanotubes.

Example 2

Add dropwise octaalkyltrimethylammonium bromide solution containing 8mmol to the suspension containing 10g halloysite in a water bath at 60°C, the concentration of octaalkyltrimethylammonium bromide solution is 4mol/L, drop Stir continuously during the addition process, and then add 7 mL of acetone dropwise after the dropwise addition, continue to stir for 2 h under the same conditions after the dropwise addition, centrifuge, wash the obtained solid with deionized water 4 times, and dry at 100 ° C. The solid is ground into a 50-mesh powder, during which the cationic surfactant is fixed as a single molecule on the halloysite surface through electrostatic interaction; the powder is placed in a tube furnace and protected by _N2 , and carbonized at 500 °C 4h, then continue to pass _N2 to cool to room temperature, the organic matter is carbonized at high temperature, and a carbonaceous layer is formed on the surface of the halloysite; put 2g of the carbonized solid matter into a bottle, add 10mL of 20% hydrochloric acid solution, and stir for 20h , dissolve the aluminum-oxygen structure in the halloysite, separate the solid from the liquid, wash with deionized water, and dry at a constant temperature of 60°C for 5 hours to obtain carbon-silicon-bonded particles of silicon oxide coated with a carbon layer; place the carbon-silicon-bonded particles in a tube In the type furnace, under the protection of argon, the temperature was raised to 600°C at a heating rate of 10°C/min, and the temperature was kept constant for 60 minutes. Air was introduced, calcined for 60 minutes, cooled to room temperature, and the calcined product was soaked in the mixed acid of hydrofluoric acid and hydrochloric acid, the molar ratio of hydrofluoric acid and hydrochloric acid was 0.5:1, and the mixed acid treatment time was 4 hours, and washed off The unreacted silicon dioxide was washed with deionized water until pH = 7, and then dried at 80° C. to obtain silicon carbide nanotubes.

Example 3

In a water bath at 65°C, add 10 mmol of octaalkyltrimethylammonium bromide solution dropwise to the suspension containing 10 g of halloysite, the concentration of octaalkyltrimethylammonium bromide solution is 2 mol/L, drop Stir continuously during the addition process, then add 9 mL of acetone dropwise after the dropwise addition, continue to stir for 3 h under the same conditions after the dropwise addition, centrifuge, wash the obtained solid with deionized water for 5 times, and dry at 105°C. The solid is ground into 80-mesh powder, during which the cationic surfactant is fixed to the surface of halloysite as a single molecule through electrostatic interaction; the powder is placed in a tube furnace and protected by _N2 , and carbonized at 800°C 6h, and then continue to pass _N2 to cool to room temperature, the organic matter is carbonized at high temperature, and a carbonaceous layer is formed on the surface of the halloysite; put 3g of the carbonized solid matter into a bottle, add 10mL of 30% hydrochloric acid solution, and stir for 30h , dissolve the aluminum-oxygen structure in the halloysite, separate the solid from the liquid, wash with deionized water, and dry at a constant temperature of 70°C for 6 hours to obtain carbon-silicon-bonded particles of silicon oxide coated with a carbon layer; place the carbon-silicon-bonded particles in a tube In the type furnace, under the protection of argon, the temperature was raised to 600°C at a heating rate of 15°C/min, and the temperature was kept constant for 120 minutes. Air was introduced, calcined for 120 minutes, cooled to room temperature, and the calcined product was soaked in the mixed acid of hydrofluoric acid and hydrochloric acid, the molar ratio of hydrofluoric acid and hydrochloric acid was 5:1, and the mixed acid treatment time was 24 hours, and washed off The unreacted silicon dioxide was washed with deionized water until pH = 7, and then dried at 105° C. to obtain silicon carbide nanotubes.

Claims (1)

1. a preparation method of silicon carbide nanotubes is characterized in that comprising the steps successively: (1) Add dropwise octaalkyltrimethylammonium bromide solution containing 8-16mmol to the suspension containing 10g of halloysite in a water bath at 60-65°C, the octaalkyltrimethylammonium bromide solution The concentration is 1-4mol/L, stirring continuously during the dropping process, and then adding 7-9 mL of acetone dropwise after the dropping is completed, continuing to stir for 2-3 hours under the same conditions after the dropping, centrifuging, and using Wash with deionized water for 4 to 5 times, dry at 100 to 105°C, and grind the solid into 50 to 80 mesh powder. During this process, the cationic surfactant is fixed to the halloysite surface as a single molecule through electrostatic interaction ; (2) Put the powder in a tube furnace with _N2 protection, carbonize at 500-800°C for 4-6 hours, then continue to pass _N2 to cool to room temperature, the organic matter is carbonized at high temperature, and a carbonaceous layer is formed on the surface of halloysite ; (3) Put 2 to 4 g of the carbonized solid into a bottle, add 10 to 15 mL of hydrochloric acid solution with a concentration of 20 to 40%, stir for 20 to 30 hours, dissolve the alumina structure in the halloysite, and separate the solid and liquid , washed with deionized water, and dried at a constant temperature of 60-70°C for 5-6 hours to obtain carbon-silicon-bonded particles of silicon oxide coated with a carbon layer; (4) Put the carbon-silicon bonded particles in a tube furnace, under the protection of argon, raise the temperature to 600°C at a heating rate of 10-15°C/min, keep the temperature constant for 60-120min, and continue to heat up at a rate of 10-15°C /min, heat up to 1400-1500°C, keep the temperature constant for 240-360min, then cool down to 300-400°C, feed air, calcine for 60-120min, cool to room temperature, soak the calcined product in a mixture of hydrofluoric acid and hydrochloric acid In the acid, the molar ratio of hydrofluoric acid to hydrochloric acid is 0.5-10:1, the mixed acid treatment time is 4-24h, and the unreacted silica is washed away, and after washing with deionized water to pH = 7, 80-105°C drying to obtain silicon carbide nanotubes.