Chemically Strengthened Ceramic Spacers for Vacuum Insulated Panels
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Solution Overview
Problem
Metal spacers in vacuum insulated panels face limitations such as low compressive stress, thermal mismatch with glass substrates, and increased thermal conductivity, leading to issues like micro-cracking, hertzian cracks, and higher u-factors, which affect insulation performance and aesthetics.
Innovation Solution
The use of ceramic spacers, chemically strengthened via ion exchange processes, with compressive and tensile stress regions, to provide improved compressive strength, thermal expansion matching, and reduced thermal conductivity, while maintaining transparency and aesthetic appeal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal spacers are used in vacuum insulated panels, then the spacers provide structural support and maintain vacuum gap, but the metal spacers cause thermal conductivity increase and thermal mismatch with glass substrates leading to micro-cracking and hertzian cracks
Solution Approach 1:
The patent changes the material parameters of the spacers by using chemically strengthened glass with modified compositional parameters (adding Al2O3, B2O3, SiO2) to achieve both high compressive strength (≥400 MPa) and low thermal conductivity, eliminating the thermal bridge effect caused by metal spacers while maintaining structural support capability
Solution Approach 2:
The patent employs composite material design by creating a chemically strengthened glass spacer system with multiple oxide components (alumina, boron oxide, silica) that combine to provide both mechanical strength and thermal insulation properties, resolving the contradiction between strength and thermal conductivity
2Strength
If metal spacers are used in vacuum insulated panels, then the spacers provide structural support, but the CTE mismatch between metal and glass substrates causes pillar movement and micro-cracking under thermal loading
Solution Approach 1:
The patent modifies the thermal expansion parameters by selecting glass composition with Al2O3 content of 5-30 wt% and B2O3 content of 10-40 wt%, which adjusts the CTE of spacers to be within 20% of the glass substrate CTE, preventing thermal mismatch stresses that cause micro-cracking while maintaining structural support
Solution Approach 2:
The patent applies homogeneity principle by ensuring the spacer material (chemically strengthened glass) has matched thermal and mechanical properties with the glass substrates, creating a homogeneous system that expands and contracts uniformly under thermal loading, eliminating relative movement and interface cracking
3Loss of energy
If larger spacer separations are used to reduce thermal conduction, then the insulation performance improves, but the vacuum stress loading cannot be supported with conventional metal spacers
Solution Approach 1:
The patent applies preliminary action by pre-strengthening the glass spacers through chemical strengthening processes (ion exchange) before installation, creating compressive stress fields within the spacer material that enable them to support vacuum loads at larger separations (≥40 mm) without deformation, thus allowing greater spacing for reduced thermal conduction
4Ease of manufacture
If metal spacers are used, then the spacers can be shaped and installed easily, but they create visible elements that negatively impact aesthetics and increase u-factor
Solution Approach 1:
The patent changes the optical parameters of the spacers by using transparent glass material with visible light transmission properties matched to the surrounding glass, making the spacers visually imperceptible while maintaining their structural function, thereby improving aesthetics and reducing the effective u-factor by eliminating visible thermal bridges
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 ceramic spacers enhance the insulation performance by allowing larger spacer separations, reducing heat transfer, minimizing glass defects, and improving the u-factor, while maintaining a visually appealing appearance.
Implementation Method 1
chemically strengthened via ion exchange processes
Implementation Method 2
Providing a vacuum in the space between the substrates reduces conduction and convection heat transport
Implementation Method 3
reduces conduction and convection heat transport, and thus provides insulating properties
Implementation Method 4
reducing radiative energy with a low-emissivity (low-E) coating provided on one of the substrates
Data Source
AI summary
A vacuum insulating panel includes first and second substrates (e.g., glass substrates), a hermetic edge seal, a pump-out port, and spacers sandwiched between at least the two substrates. The gap between the substrates may be at a pressure less than atmospheric pressure to provide insulating properties. The vacuum insulating panel may include ceramic (e.g., aluminosilicate glass) spacers, which may be chemically strengthened.