Active Brazing Ceramic Collars for Sodium Thermal Battery Seals
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Solution Overview
Problem
The existing metallization and thermal compression bonding processes for bonding Ni rings to alpha-alumina collars in sodium-based thermal batteries are time-consuming, expensive, and difficult to scale, with insufficient bond strength and high residual stresses due to thermal expansion mismatch, limiting the cost-effectiveness and performance of sodium metal halide batteries.
Innovation Solution
Active brazing is used to join Ni rings and alpha-alumina collars using a braze alloy composition with high resistance to sodium and halide corrosion, reducing the number of process steps and eliminating the need for metallization and thermal compression bonding, while achieving bond strengths comparable to conventional methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metallization and thermal compression bonding processes are used to bond Ni rings to alpha-alumina collars, then bond strength is achieved, but manufacturing time and cost increase significantly
Solution Approach 1:
The invention changes the bonding parameters by using active brazing alloy composition with specific chemical composition (containing reactive elements like Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, In, Ga, Ge, Al, Si, B, P) that enables bonding at lower temperatures and in shorter times compared to conventional metallization and thermal compression bonding processes, while maintaining adequate bond strength
Solution Approach 2:
The invention extracts and eliminates the metallization step from the conventional two-step process (metallization + thermal compression bonding), using only the active brazing process to achieve both metallization and bonding functions in a single step, thereby reducing manufacturing time and complexity
2Strength
If metallization and thermal compression bonding processes are used to bond Ni rings to alpha-alumina collars, then bond strength is achieved, but manufacturing cost increases
Solution Approach 1:
The invention merges the metallization and bonding functions into a single active brazing process, eliminating the need for separate metallization step and reducing the number of process steps from two to one, thereby simplifying manufacturing and reducing cost
Solution Approach 2:
The invention uses active brazing alloy with specific composition parameters that enable cost-effective manufacturing by reducing process complexity and eliminating expensive metallization materials and equipment while maintaining adequate bond strength for battery application
3Strength
If conventional bonding processes are used, then adequate bond strength is achieved, but residual stresses increase due to thermal expansion mismatch
Solution Approach 1:
The invention changes the bonding temperature parameter to be lower than conventional thermal compression bonding, and uses active brazing alloy composition that accommodates thermal expansion mismatch between Ni rings and alpha-alumina collars, thereby reducing residual stresses while maintaining bond strength
Solution Approach 2:
The active brazing alloy acts as a composite material with specific composition (containing reactive elements combined with base metals) that provides both bonding function and stress accommodation, creating a transition layer that reduces thermal expansion mismatch between dissimilar materials
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
Active brazing results in reliable, long-lasting bonds with reduced manufacturing costs and time, and minimal residual stresses, enhancing the performance and cost-effectiveness of sodium-based thermal batteries by providing sufficient bond strength and hermetic seals.
Implementation Method 1
active brazing is used to join Ni rings and alpha-alumina collars using a braze alloy composition with high resistance to sodium and halide corrosion
Implementation Method 2
deforming a portion of the second portion of the outer metal ring into the first inwardly extending recess of the first outwardly facing sealing surface of the ceramic collar by active brazing
Data Source
AI summary
The present application provides for ceramic collars and metal rings for active brazing in sodium-based thermal batteries. The ceramic collar may be an alpha-alumina collar configured for active brazing, and thereby sealing, to outer and inner Ni rings for use in NaMx cells. The portions of the alpha-alumina collar active brazed to the outer and inner Ni rings may be outwardly facing and include inwardly extending recesses. The portions of the outer and inner Ni rings active brazed to the outwardly facing portions of the collar may be inwardly facing. The alpha-alumina collar may include a greater coefficient of thermal expansion than each of the outer and inner Ni rings, and the alpha-alumina collar and outer and inner Ni rings may be configured such that a portion of the outer and inner Ni rings is deformed into the inwardly extending recesses of the alpha-alumina collar after active brazing thereof.