Cyclosilicate Glass-Ceramic Sealing with Tailored Thermal Expansion
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Solution Overview
Problem
Current sealing materials and coatings for metals and ceramics lack high thermal stability, mechanical strength, and tailored thermal expansion coefficients, limiting their effectiveness in high-temperature applications and complex geometries.
Innovation Solution
Development of highly crystallized, frit-sintered glass-ceramics with cyclosilicate crystal structures, specifically composed of silicon dioxide and oxides of calcium, barium, and strontium, which can be sintered at 900°-950° C to achieve high crystallinity, low residual glass, and tailored thermal expansion coefficients, suitable for metal-to-metal, metal-to-ceramic, and ceramic-to-ceramic sealing, as well as high-performance coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional sealing materials are used, then ease of manufacture is maintained, but thermal stability and mechanical strength are insufficient for high-temperature applications
Solution Approach 1:
The patent modifies the chemical composition parameters by incorporating specific cyclosilicate crystal structures with tailored thermal expansion coefficients (85-115×10^-7/°C) and controlling the ratio of network formers (SiO2, B2O3) to modifiers (CaO, SrO, BaO, Al2O3). This compositional parameter optimization enables high thermal stability while maintaining manufacturability through controlled sintering at 900-950°C
Solution Approach 2:
The invention creates a composite glass-ceramic material combining amorphous glass matrix with crystalline cyclosilicate phases (wollastonite, diopside, åkermanite). This composite structure integrates the thermal stability of crystals with the sealing capability of glass, achieving both high temperature resistance and ease of manufacture through frit-sintering processes
2Strength
If high crystallinity is achieved through extended sintering, then mechanical strength improves, but production time and energy consumption increase
Solution Approach 1:
The patent incorporates nucleating agents (TiO2, ZrO2, P2O5) in the initial glass composition that pre-establish crystallization sites. During sintering at 900-950°C, these pre-positioned nucleation sites rapidly trigger crystal formation, achieving high crystallinity (greater than 50%) in just 1-2 hours without requiring extended processing times
Solution Approach 2:
The invention optimizes the sintering temperature parameter to a specific range (900-950°C) that balances crystal growth rate with energy efficiency. This temperature window provides sufficient thermal energy for rapid crystallization and high mechanical strength while minimizing energy consumption and production time compared to conventional higher temperature sintering
3Reliability
If residual glass content is reduced to improve sealing performance, then cation migration decreases, but sintering becomes more difficult and porosity increases
Solution Approach 1:
The patent adjusts the chemical composition parameters by incorporating specific amounts of glass-forming oxides (SiO2: 40-70 wt%, B2O3: 10-30 wt%) and fluxes (CaO, SrO, BaO: 10-30 wt%) that control the viscosity-temperature relationship. This compositional optimization enables the glass matrix to sinter effectively at lower temperatures (900-950°C) while maintaining low residual glass content (10-30 wt%) and achieving dense, pore-free microstructures with superior sealing performance
Solution Approach 2:
The invention creates a composite microstructure where crystalline phases (providing structural integrity and low porosity) coexist with a controlled amount of glassy matrix (providing sealing capability). This composite architecture achieves reliable sealing performance with minimal continuous glass paths while maintaining ease of manufacture through the glass-ceramic sintering process that naturally densifies the material without requiring excessive glass content
4Reliability
If thermal expansion coefficient is tailored to match substrates, then sealing reliability improves, but composition control becomes more complex
Solution Approach 1:
The patent utilizes the thermal expansion coefficient as a controllable compositional parameter by adjusting the ratios of network modifiers (CaO, SrO, BaO) and network formers (SiO2, B2O3). By varying these oxide ratios within specified ranges, the thermal expansion coefficient can be precisely tuned to match different substrates (metals, ceramics, glass) while maintaining a relatively simple base composition, thus achieving reliable seals without excessive compositional complexity
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 glass-ceramic materials exhibit high thermal stability, zero or near-zero porosity, and tailored thermal expansion coefficients, making them suitable for high-temperature applications with minimal residual glass, ensuring no continuous glass path and reduced cation migration, thus providing superior sealing and coating performance.
Implementation Method 1
Glass-ceramics are polycrystalline materials formed by controlled crystallization of a precursor glass article. A glass-ceramic may be prepared by exposing a glass monolith to a thermal treatment for conversion to a crystalline state.
Implementation Method 2
The glass composition, particle size, and processing conditions are chosen such that the glass softens prior to crystallization and undergoes viscous sintering to maximum density just before the crystallization process is completed.
Implementation Method 3
The glass-ceramic materials of the invention can be used as sealing agents and as high performance coating for metals, metal alloys and ceramics... an expansion coefficient (range: 25-700° C.) greater than 90×10−7/° C.
Data Source
AI summary
The invention is directed to highly crystalline, frit-sintered glass-ceramic compositions having a coefficient of thermal expansion in the range of 85-115×10−7° C. The primary crystal phases of the glass-ceramics of the invention possess a cyclosilicate structure. The glass-ceramic of the invention are useful as metal-to-metal, metal-to-ceramic and ceramic-to-ceramic sealing agents, and also as high-performance coating for metals and ceramics.