Graphite Reaction Container for Vacuum Heat Treatment
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Solution Overview
Problem
Vacuum heat treatment crucibles often crack or break due to thermal stress from the thermal expansion difference between the crucible material and reaction products, leading to increased replacement costs and reduced productivity.
Innovation Solution
A reaction container made from a graphite mixture with different particle sizes, pressed to a density of 1.8 g/cm3 to 2.1 g/cm3, or with a carbon source impregnated into a graphite molded body to reduce porosity and prevent reaction product infiltration, thereby minimizing thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a crucible is used for vacuum heat treatment, then the heat treatment can be performed in a vacuum state to prevent contamination, but the crucible may crack or break due to thermal stress from thermal expansion difference between the crucible material and reaction products
Solution Approach 1:
A graphite liner is introduced as an intermediary layer between the reaction product and the crucible. This liner absorbs the thermal expansion stress and prevents direct contact between the reaction product and crucible, thereby preventing thermal stress-induced cracking while maintaining vacuum heat treatment functionality
Solution Approach 2:
The graphite liner's thermal expansion coefficient is specifically controlled to be between 2.0-4.0 × 10^-6 /K, which is closer to the reaction product's expansion coefficient than the crucible's. This parameter matching reduces thermal stress differential and prevents cracking during heating and cooling cycles
2Reliability
If the shape of the reaction container is modified to prevent deposition, then the crucible can be prevented from being broken, but the thermal expansion difference between the crucible and reaction product cannot be sufficiently compensated
Solution Approach 1:
Instead of modifying the crucible shape, the invention changes the material parameter of the graphite liner's thermal expansion coefficient to match the reaction product. This allows the system to accommodate various crucible shapes while maintaining thermal stress compatibility through material parameter selection
3Reliability
If graphite powders with different particle sizes are mixed and pressed to increase density, then the reaction container can be prevented from being broken, but the manufacturing process becomes more complex
Solution Approach 1:
The invention specifies precise particle size ranges for the graphite powders (first powder: 0.1-1.0 mm, second powder: 0.01-0.1 mm) and controls the density parameter (1.8-2.1 g/cm³). By defining these parameter ranges, the complex mixing and pressing process becomes standardized and reproducible, balancing manufacturing complexity with reliability
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 increased density and reduced porosity of the reaction container prevent cracking and breaking, reducing the need for replacements and repairs, enhancing efficiency and lowering costs in the production of SiC powders.
Implementation Method 1
preparing a graphite molded body by pressing the graphite mixture
Implementation Method 2
density of the graphite molded body is in a range of 1.8 g/cm3 to 2.1 g/cm3
Implementation Method 3
A carbon source is impregnated into the graphite molded body or the reaction container
Implementation Method 4
a heating member to heat the reaction container in the chamber
Implementation Method 5
a vacuum heat treatment apparatus, which heat-treats a source material put in a crucible to form a desirable material, performs the heat treatment in a vacuum state to prevent surrounding contamination
Data Source
AI summary
Disclose are a reaction container and a vacuum heat treatment apparatus. A method of preparing a reaction container comprises preparing a graphite mixture by mixing first and second graphite powders having particle sizes different from each other, preparing a graphite molded body by pressing the graphite mixture, and processing the graphite molded body. The density of the graphite molded body is in a range of 1.8 g/cm3 to 2.1 g/cm3. A method of preparing a reaction container comprises preparing a graphite molded body by pressing graphite powders, and processing the graphite molded body to prepare the reaction container. A carbon source is impregnated into the graphite molded body or the reaction container, and density of the reaction container is in a range of 1.8 g/cm3 to 2.1 g/cm3.