Graphite Crucible Purification via Vacuum Thermal Treatment
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Solution Overview
Problem
Current methods for producing high-purity graphite, such as the hydrofluoric acid and chlorination roasting methods, involve the use of corrosive and toxic chemicals, leading to high production costs and environmental concerns.
Innovation Solution
A method for purifying graphite that involves placing the material in a graphite crucible within a heating furnace under high vacuum and high temperature conditions, without using chlorine or hydrofluoric acid, allowing for the volatilization or carbonization of metal impurities and the growth of silicon carbide crystals to achieve high-purity graphite and silicon carbide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hydrofluoric acid method or chlorination roasting method is used to purify graphite, then graphite purity can be improved, but production cost increases and environmental problems arise due to strong corrosivity and toxicity
Solution Approach 1:
The patent extracts and removes harmful chemicals (hydrofluoric acid and chlorine) from the purification process entirely, replacing them with a vacuum-based physical purification method that achieves high graphite purity without corrosive or toxic substances
Solution Approach 2:
The patent creates a vacuum environment (inert atmosphere with pressure less than 5 Torr) in the heating furnace to prevent oxidation and contamination of graphite during high-temperature heating, enabling purification without reactive chemicals
2Manufacturing precision
If hydrofluoric acid method or chlorination roasting method is used to purify graphite, then graphite purity can be improved, but environmental protection issues arise due to strong corrosivity and toxicity
Solution Approach 1:
The patent converts the harmful effect of metal impurities in graphite into a beneficial purification process by heating graphite to high temperatures in a vacuum environment, causing metal impurities to volatilize or carbonize and separate from the graphite matrix without using toxic chemicals
Solution Approach 2:
The patent uses a vacuum environment (pressure less than 5 Torr) as an inert atmosphere to prevent oxidation and contamination during heating, enabling environmentally friendly purification that eliminates harmful chemical byproducts
3Manufacturing precision
If high temperature heating is applied to volatilize or carbonize metal impurities, then graphite purity is improved, but energy consumption increases
Solution Approach 1:
The patent utilizes phase transitions of metal impurities (melting, volatilization, or carbonization) at high temperatures to separate them from graphite. By controlling the vacuum environment and heating temperature, impurities transition to gas phase or react with carbon, achieving purification while managing energy consumption efficiently
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method reduces production costs and environmental impact while achieving graphite and silicon carbide purities greater than 99.99%, preventing impurity escape and defects during crystal growth, thereby enhancing the quality of silicon carbide crystals.
Implementation Method 1
heating the graphite crucible, by a heater disposed in the heating furnace, to control a temperature of the graphite crucible to be at least higher than melting point temperatures of some of metal impurities in the graphite material, and maintaining the temperature of the graphite crucible for a preset time, so that the some of metal impurities in the graphite material are volatilized or carbonized
Implementation Method 2
the some of metal impurities in the graphite material are volatilized or carbonized
Implementation Method 3
after vacuuming the heating furnace, filling the heating furnace with a protective atmosphere, and controlling a pressure in the heating furnace to be less than 5 Torr
Implementation Method 4
maintaining the pressure of the graphite crucible and the temperature of the graphite crucible for a preset time, so that a silicon carbide crystal grows from the seed
Data Source
AI summary
Disclosed is a method for purifying a graphite material, which includes the following steps of: after placing the graphite material in a graphite crucible, placing the graphite crucible into a heating furnace; after vacuuming the heating furnace, filling the heating furnace with a protective atmosphere, and controlling a pressure in the heating furnace to be less than 5 Torr; and heating the graphite crucible, by a heater disposed in the heating furnace, to control a temperature of the graphite crucible to be at least higher than melting point temperatures of some metal impurities in the graphite material for a preset time period, so that the some metal impurities in the graphite material are volatilized or carbonized, and the graphite crucible is purified. Therefore, while the graphite material is purified under a condition with high vacuum, high temperature and low pressure, the graphite crucible is also purified.