Low CTE Adhesive Bonding for Space Mirrors
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Solution Overview
Problem
Existing adhesives for lightweight mirrors in space-based imaging applications face challenges such as limited CTE matching capability, short working life, incompatibility with porous 3D printed cores, high viscosity, and high cure temperatures, which restrict their use with materials like Zerodur®, Clearceram™, and cordierite.
Innovation Solution
Development of adhesive formulations with low CTE (<0.5 ppm/°C) and low cure temperatures (100 to 400°C) that enable bonding between low CTE materials, such as Zerodur®, Clearceram™, and cordierite, while providing strong bond strength (3000-6000 psi) and resistance to moisture absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If existing adhesives are used for bonding lightweight mirror components, then bonding capability is achieved, but the adhesive has high viscosity which makes it difficult to dispense through small extrusion nozzles
Solution Approach 1:
The patent modifies the physical and chemical parameters of the adhesive formulation, specifically reducing viscosity by adjusting composition (e.g., using lower viscosity resins, modifying particle size distribution, adding flow modifiers) to enable dispensing through small nozzles while maintaining bonding performance
2Adaptability or versatility
If existing adhesives are used for bonding lightweight mirror components, then bonding capability is achieved, but the adhesive has high cure temperature which excludes use with desirable core materials like Zerodur and Clearceram
Solution Approach 1:
The patent changes the chemical composition and curing mechanism of the adhesive to achieve low-temperature curing (e.g., using room temperature curing resins, UV-curing systems, or modified epoxy systems) that is compatible with temperature-sensitive materials like Zerodur and Clearceram while maintaining bond strength
3Manufacturing precision
If existing adhesives are used for bonding lightweight mirror components, then bonding capability is achieved, but the adhesive has high CTE and high moisture absorption which make them unsuitable for high precision applications
Solution Approach 1:
The patent modifies the adhesive formulation to achieve low CTE by selecting base materials and fillers with matching thermal expansion coefficients, and reduces moisture absorption through hydrophobic additives, proper curing, and barrier formulations, thereby ensuring dimensional stability and precision for space-based imaging applications
4Adaptability or versatility
If existing adhesives are used for bonding lightweight mirror components, then bonding capability is achieved, but the adhesive has limited CTE matching capability which can only be used with very limited types of materials
Solution Approach 1:
The patent develops composite adhesive formulations incorporating multiple fillers (e.g., silica, alumina, titania) with different CTE values to create a tunable adhesive that can match the thermal expansion of various core materials including metals, ceramics, and composites, thereby expanding material compatibility
Solution Approach 2:
The patent adjusts the adhesive formulation parameters including base resin type, filler composition, filler loading, and particle size distribution to optimize CTE matching for different substrate materials while maintaining other critical properties like strength and flexibility
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 new adhesive formulations allow for the efficient bonding of lightweight mirror components with low CTE materials, overcoming previous limitations in terms of temperature compatibility and bond strength, thereby enhancing the precision and reliability of space-based imaging mirrors.
Implementation Method 1
bonding the faceplate to the core structure is achieved through the use of first adhesive formulations that include: (1) fused silica particles having diameters that range between 1 to 60 micrometers... (2) an activator including 25 to 50 weight % sodium silicate, 25 to 50 weight % sodium hydroxide... These first adhesive formulations advantageously have a low curing temperature in the range of 100 to 250° C.
Implementation Method 2
bonding the faceplate to the core structure is achieved through the use of second adhesive formulations that include: (1) a binder comprising 40 to 60 weight % monoaluminum phosphate and 40 to 60 weight % water... (2) a composition that includes a first set of particles having a coefficient of thermal expansion equal to or less than 0.05 ppm/° C.... These second adhesive formulations advantageously have a low curing temperature in the range of 100 to 400° C.
Data Source
AI summary
Methods of forming a mirror by bonding a faceplate to a core structure using adhesive formulations that include fused silica particles having diameters that range between 1 to 60 micrometers with an average diameter of the silica particles being between 8 to 10 micrometers. The adhesive formulation further includes an activator including 25 to 50 weight % sodium silicate, 25 to 50 weight % sodium hydroxide and a liquid. The fused silica particles constitute 70 to 80 weight % of the adhesive formulation and the activator constitute 20 to 30 weight % of the adhesive formulation.