Silicon Carbide Cladding Brazing Filler for Dense Hermetic Joints
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Solution Overview
Problem
Existing silicon carbide joining methods in nuclear applications face challenges such as poor hermeticity, high joining pressure, and insufficient hydrothermal corrosion and radiation resistance, particularly in precursor joining methods, which result in volume shrinkage and pore formation.
Innovation Solution
A brazing filler material composed of polycarbosilane and glass powder, with specific mass ratios and heat treatment processes, is used to form a dense interlayer between a cladding tube and end plug, enhancing hermeticity and structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If precursor joining method is used, then hydrothermal corrosion resistance and radiation resistance are improved, but volume shrinkage and pore formation occur resulting in poor hermeticity
Solution Approach 1:
The patent uses a composite filler material consisting of polycarbosilane precursor and glass powder in specific ratios (95:5, 90:10, or 85:15 by weight). This composite approach combines the advantages of precursor materials (good corrosion and radiation resistance) with glass powder (ability to fill voids and improve density), resolving the contradiction between achieving good environmental resistance and maintaining hermeticity.
Solution Approach 2:
The patent optimizes multiple parameters including the precursor-to-glass powder ratio, glass powder particle size (1-10 μm), and heat treatment conditions (temperature and time). By carefully controlling these parameters, the method achieves complete consumption of the precursor during reaction, eliminating volume shrinkage and pore formation while maintaining good environmental resistance.
2Manufacturing precision
If interlayer thickness is increased to improve hermeticity, then assembly difficulty increases
Solution Approach 1:
The patent optimizes the interlayer thickness to a specific range of 2-10 μm. This parameter optimization achieves a balance where the interlayer is thick enough to provide good hermeticity and filling of voids, yet thin enough to avoid excessive assembly difficulty. The controlled thickness ensures complete reaction of the precursor without creating handling problems.
3Manufacturing precision
If glass-ceramic joining method is used, then sealing performance and heat resistance are improved, but radiation resistance and hydrothermal corrosion resistance deteriorate
Solution Approach 1:
The patent creates a composite filler system where polycarbosilane precursor reacts to form SiO2 and other phases that provide excellent radiation and corrosion resistance, while glass powder provides the sealing and filling function. This composite approach achieves both good hermeticity and environmental resistance, overcoming the limitations of pure glass-ceramic methods.
Solution Approach 2:
The filler material exhibits different functional zones: the glass powder components provide sealing and void-filling properties, while the precursor-derived components (SiO2, mullite, etc.) provide radiation and corrosion resistance. This local differentiation of material properties within the interlayer resolves the contradiction between sealing performance and environmental resistance.
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 achieves high joining strength, hermeticity, and improved resistance to hydrothermal corrosion and radiation, ensuring the safety and reliability of nuclear reactor claddings.
Implementation Method 1
a large amount of gas will be released during the precursor pyrolysis process, which causes a volume shrinkage and the formation of pores
Implementation Method 2
a large amount of gas will be released during the precursor pyrolysis process
Implementation Method 3
the brazing filler material includes the following raw materials: precursor, glass powder and organic solvent; the mass ratio of the precursor to the glass powder is 90-98 : 2-10
Data Source
AI summary
Disclosed are a solder for connection and a preparation method therefor and a method for connecting a silicon carbide cladding. The solder for connection comprises the following raw materials: a precursor, a glass powder and an organic solvent, wherein the mass ratio of the precursor to the glass powder is 90-98: 2-10. The solder for connection of the present invention is used for connecting a silicon carbide cladding. A glass additive phase formed by the glass powder has good wettability to silicon carbide and a high connection strength. The proportion of the glass powder is adjustable, so that the coefficient of thermal expansion of the glass additive phase is adjustable, and the stress of a joint after connection is controllable. A thick compact connection layer can be realized, facilitating engineering assembly and realizing better air tightness.