Expanded Graphite Sheet Purification for High-Purity Applications
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Solution Overview
Problem
Conventional expanded graphite sheets contain high levels of impurities, such as Si and sulfur compounds, which contaminate the environment and degrade product quality when used in manufacturing processes like silicon single crystal production, leading to yield deterioration.
Innovation Solution
A high-purity expanded graphite sheet is produced by heat-treating the material under specific conditions to evaporate and volatilize impurities, achieving impurity levels below detection limits, and then using halogenated organic gases to enhance purity, followed by desulfurization with hydrogen gas, resulting in a sheet suitable for use in high-purity applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional expanded graphite sheets are used in high-purity manufacturing processes, then the basic functional requirements are met, but impurities contaminate the environment and degrade product quality
Solution Approach 1:
The patent applies preliminary action by performing multiple purification treatments during the manufacturing process before the product is put into service. The expanded graphite undergoes oxidation treatment, washing, drying, and heat treatment to remove impurities such as Si, Fe, Al, and sulfur compounds before packaging and shipping, ensuring low impurity content at the time of use.
Solution Approach 2:
The patent applies parameter changes by controlling the oxidation treatment parameters (using specific acid concentrations and temperatures), heat treatment parameters (temperature and duration), and washing parameters to achieve the desired impurity levels. By optimizing these parameters, the patent reduces sulfur content to 15 ppm or less and total impurity content to 20 ppm or less.
2Manufacturing precision
If the expanded graphite sheet is manufactured with extremely low impurity content, then product quality is maintained, but the manufacturing process becomes more complex
Solution Approach 1:
The patent merges multiple purification operations into a integrated manufacturing process. The oxidation treatment, washing, drying, and heat treatment steps are combined in a sequential process flow, where each step contributes to impurity removal. This integration achieves high purification effectiveness while managing process complexity through systematic organization of operations.
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
The method effectively prevents impurity-related degradation and yield deterioration in products by ensuring the expanded graphite sheet has impurities at levels below detection limits, even after packaging and shipping, maintaining high product quality and yield.
Implementation Method 1
heat-treating the material under specific conditions to evaporate and volatilize impurities
Implementation Method 2
using halogenated organic gases to enhance purity
Implementation Method 3
desulfurization with hydrogen gas
Data Source
AI summary
An object is to provide an expanded graphite sheet at the use stage that can prevent can prevent degradation in product quality and deterioration in product yield by inhibiting the expanded graphite sheet from containing impurities even when the expanded graphite sheet is actually used.An expanded graphite sheet at the use stage in a condition in which the expanded graphite sheet is packed with a packing material and thereafter removed from the packing material, characterized in that all of the amounts of Al, B, Be, Ca, Cu, Fe, Li, Mg, Ni, S, Ti, V, and Zn as determined by an ICP emission spectroscopy method, the amounts of K and Na as determined by an atomic absorption spectrometry method, and the amount of Si as determined by an absorption spectrophotometry method are at a level less than the detection limit.