Microcapsule Shell Integrity at 600°C via Composite Coating
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Solution Overview
Problem
High-temperature phase change materials, such as molten salts with melting points between 200° C. and 600° C., are difficult to encapsulate effectively, as existing methods fail to provide thermally stable microcapsule shells that maintain integrity at elevated temperatures.
Innovation Solution
A method involving the application of a coating layer with an inorganic binder, a high molecular weight organic film former, and an inorganic filler, optionally with a sacrificial layer, to create microcapsules that remain intact at high temperatures, using a process that includes heating to remove the film former and sacrificial layer, resulting in a thermally stable microcapsule shell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing encapsulation methods are used for high-temperature phase change materials, then the encapsulation process is simple, but the microcapsule shells fail to maintain integrity at elevated temperatures
Solution Approach 1:
The patent employs a composite coating structure consisting of an inorganic binder matrix embedded with inorganic filler particles. This composite material provides thermally stable microcapsule shells that maintain integrity at temperatures up to 600°C. The inorganic filler reinforces the binder matrix, creating a robust shell structure resistant to thermal degradation and rupture.
Solution Approach 2:
The patent utilizes phase change of the binder material during processing. The binder is applied in a molten or viscous state to ensure complete coating coverage, then heated to remove organic film formers and cure the inorganic binder, transforming it into a thermally stable solid matrix that forms the final durable shell structure.
2Reliability
If a thick coating layer is applied to protect the phase change material, then thermal stability is improved, but the coating material requirements become more stringent
Solution Approach 1:
The patent applies different functional components at different locations within the coating structure. The inorganic binder provides the continuous matrix phase for structural integrity, while inorganic filler particles are distributed throughout to provide localized reinforcement and thermal stability. This spatial distribution of properties allows the coating to achieve high thermal stability without requiring excessive thickness.
3Duration of action of stationary object
If the coating is heated to remove organic film formers, then long-term thermal stability is achieved, but the organic binder is degraded
Solution Approach 1:
The patent deliberately removes organic film formers through controlled heating after the coating is applied and the inorganic binder is set. This extraction of organic components eliminates materials that would degrade at high temperatures, leaving behind a purely inorganic shell structure that is thermally stable for long-term use in high-temperature applications.
Solution Approach 2:
The organic film formers serve as temporary, sacrificial components during the coating application and initial curing process. They perform their function of enabling coating formation and then are intentionally removed through heating, as they are not intended to remain in the final product that will experience high temperatures.
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 produces microcapsules that remain thermally stable up to 600° C., with less than 5% rupture, enabling their use in thermal energy storage systems and other high-temperature applications.
Implementation Method 1
The microcapsule shells remain intact or thermally stable (i.e., they do not crack or break apart) at elevated temperatures of up to 600° C.
Implementation Method 2
Heating then results in removal of the sacrificial layer and at least a portion of the film former of both the inner and outer coatings.
Implementation Method 3
Phase change materials (PCM) are substances with a relatively high heat-of-fusion or latent-heat capable of storing and releasing relatively large amounts of energy when they melt or solidify.
Implementation Method 4
Phase change materials (PCM) are substances with a relatively high heat-of-fusion or latent-heat capable of storing and releasing relatively large amounts of energy when they melt or solidify.
Data Source
AI summary
The present disclosure relates to a method of encapsulating microcapsules containing relatively high temperature phase change materials and the microcapsules so produced. The microcapsules are coated with an inorganic binder, film former and an inorganic filler. The microcapsules may include a sacrificial layer that is disposed between the particle and the coating. The microcapsules may also include an inner coating layer, sacrificial layer and outer coating layer. The microcapsules are particularly useful for thermal energy storage in connection with, e.g., heat collected from concentrating solar collectors.