Impurity-Free Graphite Heater Material for Stable Joule Heating
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Solution Overview
Problem
Graphite materials used in heaters face challenges with varying specific resistance at different temperatures, leading to inefficiencies in Joule heat generation and durability issues due to unbalanced resistance values at room and high temperatures, and the introduction of metallic impurities from existing solutions.
Innovation Solution
A graphite material with specific resistance characteristics optimized for both room and high temperatures, achieved through controlled crystal size and graphitization degree, using a mixture of coke and graphite powders with a binder, processed to maintain a balanced specific resistance ratio and density, without metallic impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the specific resistance at room temperature is high, then the specific resistance at high temperatures is reduced greatly, but the resistance balance between room and high temperatures becomes poor
Solution Approach 1:
The invention changes the specific resistance parameters of graphite material by controlling crystal particle size (5-50 μm) and graphitization degree (0.45-0.65), achieving a balanced resistance ratio where the specific resistance at 1600°C is 0.85-1.05 times that at 25°C, resolving the contradiction between room temperature resistance and high temperature resistance balance
2Reliability
If metallic elements are added to suppress resistance change rate, then the resistance stability improves, but metallic impurities are introduced which are not preferable in semiconductor manufacturing
Solution Approach 1:
The invention extracts and eliminates metallic elements from the graphite material composition entirely, achieving resistance stability through non-metallic means by controlling crystal structure parameters (particle size 5-50 μm, graphitization degree 0.45-0.65) rather than through metallic additives, thus preventing metallic impurity contamination in semiconductor manufacturing
Solution Approach 2:
The invention uses a composite approach by combining graphite powder and coke powder in specific ratios (graphite powder 30-70 wt%, coke powder 70-30 wt%) to achieve desired resistance characteristics without metallic elements, creating a impurity-free composite graphite material
3Productivity
If the design cross section of the heater is reduced to compensate for low room temperature resistance, then the material efficiency improves, but the durability becomes inferior
Solution Approach 1:
The invention changes the physical parameters of graphite material (crystal particle size to 5-50 μm, graphitization degree to 0.45-0.65) to achieve optimal resistance balance, allowing the heater to maintain necessary heat generation with adequate cross-section while improving durability through balanced thermal and electrical properties
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 graphite material maintains stable Joule heat generation up to 1600°C with efficient heating efficiency and controlled resistance, enhancing the durability and performance of heating devices while avoiding metallic impurities.
Implementation Method 1
a method utilizing Joule heat generation from the main body
Data Source
AI summary
Provided is a metallic impurity-free graphite material utilizing Joule heat generation with well-balanced resistances at room temperature and at high temperatures. The graphite material has a specific resistance at 25°C (ρ25) of 10.0 µΩ·m or more and 12.0 µΩ·m or less; a specific resistance at 1600°C (ρ1600) of 9.5 µΩ·m or more and 11.0 µΩ·m or less; a ratio (ρ1600/ρ25) of specific resistance at 1600°C to that at 25°C of 0.85 or more and 1.00 or less; a temperature at which the minimum specific resistance (ρmin) appears of 500°C or higher and 800°C or lower; a ratio (ρmin/ρ25) of the minimum specific resistance to the specific resistance at 25°C of 0.70 or more and 0.80 or less; and a bulk density of 1.69 g/cm3 or more and 1.80 g/cm3 or less.