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A method for low-temperature crystallization of silicon oxide in a molten salt system

A technology for crystallization of silicon oxide and silicon oxide, applied in silicon oxide and other directions, can solve problems such as equipment damage and difficult quantification of reactions, and achieve the effects of reducing synthesis temperature, short reaction time and simple preparation

Active Publication Date: 2017-05-03
SHANGHAI UNIV OF ENG SCI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the high pressure conditions required by hydrothermal will inevitably cause some damage to the equipment, and the reaction is difficult to quantify

Method used

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  • A method for low-temperature crystallization of silicon oxide in a molten salt system
  • A method for low-temperature crystallization of silicon oxide in a molten salt system
  • A method for low-temperature crystallization of silicon oxide in a molten salt system

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0025] Press molten salt NaNO 3 , Accurately weigh 10.0g for grinding, take uncalcined mesoporous silica SBA-15 as raw material, weigh 0.2g, add it to the ground molten salt system, and continue grinding to make the mesoporous silica SBA-15 uniform Dispersed in molten salt. Put the mixed powder into the corundum crucible and put it into the high temperature zone of the tube furnace. Under normal pressure in the air, the reaction temperature is 450°C, and the holding time is 6 hours. After the reaction, the molten salt is dissolved and removed with deionized water, centrifuged, and dried at 80°C for 4 hours. figure 1 a is the wide-angle X-ray diffraction pattern of the product after heat preservation at 450°C for 6 hours. The result shows that the product remains amorphous without crystallization at 450°C.

Embodiment 2

[0027] Press molten salt NaNO 3 , Accurately weigh 10.0g for grinding, take uncalcined mesoporous silica SBA-15 as raw material, weigh 0.2g, add it to the ground molten salt system, and continue grinding to make the mesoporous silica SBA-15 uniform Dispersed in molten salt. Put the mixed powder into the corundum crucible and put it into the high temperature zone of the tube furnace. Under normal pressure in the air, the reaction temperature is 500°C, and the holding time is 2 hours. After the reaction, the molten salt is dissolved and removed with deionized water, centrifuged, and dried at 80°C for 4 hours. figure 1 b is the wide-angle X-ray diffraction pattern of the product after holding at 500°C for 2 hours. The results show that it has not crystallized into an amorphous structure after holding at 500°C for 2 hours.

Embodiment 3

[0029] Press molten salt NaNO 3 , Accurately weigh 10.0g for grinding, take uncalcined mesoporous silica SBA-15 as raw material, weigh 0.2g, add it to the ground molten salt system, and continue grinding to make the mesoporous silica SBA-15 uniform Dispersed in molten salt. Put the mixed powder into the corundum crucible and put it into the high temperature zone of the tube furnace. Under normal pressure in the air, the reaction temperature is 500°C, and the holding time is 4 hours. After the reaction, the molten salt is dissolved and removed with deionized water, centrifuged, and dried at 80°C for 4 hours. figure 1 c is the wide-angle X-ray diffraction pattern of the product after being kept at 500°C for 4 hours. The results show that crystallization has begun after being kept at 500°C for 4 hours, but the amorphous structure accounts for the majority.

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Abstract

The invention relates to a method for crystallizing silicon oxide at a low temperature in a molten salt system. The method comprises the following steps: (1) adding silicon oxide into a molten salt system, and grinding to obtain mixed powder so as to evenly disperse silicon oxide in molten salt; (2) making mixed powder carry out molten salt reactions for 4 to 6 hours at a temperature of 500 DEG C under a normal pressure in the air; (3) after the reactions, dissolving molten salt by deionized water to remove molten salt, carrying out centrifugation, drying to obtain crystallized silicon oxide, and recycling the molten salt. Compared with the prior art, a method for crystallizing silicon oxide at a low temperature in a molten salt system is provided for the first time, the reaction temperature is prominently reduced, cristobalite is prepared, moreover, in the provided method, the reactions are carried out uniformly, and the provided method has the advantages of low reaction temperature, short reaction time, high crystallization degree, simple preparation, low cost, and environment-friendliness, and has a good application prospect.

Description

Technical field [0001] The invention relates to a method for crystallization of silicon oxide, in particular to a method for low-temperature crystallization of silicon oxide in a molten salt system. Background technique [0002] Silicon oxide is one of the most abundant materials on the earth, and there are three main forms of existence: quartz (density = 2.65g·cm -3 , trigonal), phosphorite (density=2.27g·cm -3 ,cell monoclinic), and cristobalite (density=2.32g·cm -3 , tetragonal). Under normal pressure, quartz exists stably at 1143K, the stable range of phosphorite is 1143-1743K, and cristobalite is 1743-1973K. Silicon oxide is commonly used in the field of semiconductor devices. Due to its small pore size, mesoporous silica is widely used in petroleum decomposition or material exchange. However, its amorphous pore wall structure results in poor hydrothermal stability, which greatly limits its application. Therefore, the hole wall crystallization of mesoporous silicon oxid...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01B33/113
Inventor 胡桂青姚宝殿于治水
Owner SHANGHAI UNIV OF ENG SCI
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