Aerogel Aging via Dielectric Heating
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Solution Overview
Problem
Traditional methods for producing aerogels are time-consuming, particularly due to the lengthy aging stage, which is crucial for achieving satisfactory mechanical and thermal performance, and existing solutions do not adequately address this issue.
Innovation Solution
The process employs dielectric heating, such as microwave or high-frequency electromagnetic irradiation, to significantly reduce the aging time while maintaining the necessary mechanical and insulating properties of aerogels, allowing for the production of aerogels in both granular and composite forms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional drying methods (subcritical or supercritical) are used, then aerogels can be obtained with satisfactory mechanical and thermal performance, but the production time is excessively long (minimum 8 hours for lyogel formation plus drying time)
Solution Approach 1:
The invention changes the physical state parameter of the solvent from liquid to supercritical fluid, and uses electromagnetic field heating to change the temperature parameter rapidly. This allows the drying process to proceed much faster while maintaining the aerogel's structural integrity and performance characteristics through controlled supercritical conditions.
Solution Approach 2:
The invention utilizes the phase transition of the solvent from liquid to supercritical fluid state, and employs electromagnetic heating to facilitate this transition rapidly. The supercritical drying process enables fast solvent removal while preserving the aerogel's porous structure, thus achieving both high productivity and reliable mechanical/thermal performance.
2Productivity
If aging time is reduced to increase productivity, then production time decreases, but mechanical and thermal performance becomes insufficient
Solution Approach 1:
The invention applies electromagnetic field heating to rapidly change the temperature parameter during the aging process, enabling sufficient physicochemical modifications and syneresis mechanisms to occur in much shorter time. This parameter change allows reduced aging time while maintaining satisfactory mechanical and thermal performance.
Solution Approach 2:
The invention replaces traditional thermal conduction heating with electromagnetic field heating (microwave or high frequency). This substitution enables rapid and uniform heating throughout the gel structure, accelerating the aging process and syneresis mechanisms without compromising the final material properties, thus achieving both reduced time and maintained performance.
3Loss of time
If electromagnetic heating (microwave or high frequency) is applied during aging, then aging time is significantly reduced, but energy consumption increases
Solution Approach 1:
The invention employs continuous electromagnetic field heating throughout the aging process, maintaining constant energy input to sustain rapid heating and accelerate syneresis mechanisms continuously. This continuous action enables significant time reduction despite high energy consumption, as the process cannot be interrupted without resetting the rapid heating cycle.
Solution Approach 2:
The invention utilizes electromagnetic heating to rapidly induce and maintain supercritical fluid conditions during drying. The energy consumption is justified by the extremely rapid phase transitions and solvent removal achieved, which would take much longer with traditional heating methods. The supercritical state enables fast drying while preserving aerogel structure.
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
This approach allows for the rapid production of aerogels with thermal conductivity values less than 25 mW/m.K and appropriate mechanical properties, comparable to those produced by traditional methods, without the need for extended reaction times.
Implementation Method 1
heating the reaction medium by the application of an electromagnetic field
Implementation Method 2
heating the reaction medium by the application of microwave irradiation
Data Source
Figure 1
AI summary
The present invention relates to a process for producing aerogels, comprising the following successive steps: a) formation or casting of a sol in a reactor, optionally in the presence of a reinforcing material and/or an additive, b) complete gelling of the sol into a lyogel; c) optionally hydrophobization of the lyogel resulting in a hydrophobized lyogel; d) drying of the optionally hydrophobized lyogel so as to obtain an aerogel; said process being characterized in that the complete gelling step b) comprises dielectric heating by microwave or high-frequency electromagnetic irradiation, inducing an increase in temperature so as to reach a set temperature for complete gelling Tb in a range of from 100°C to 200°C, preferably from 100°C to 150°C, the temperature Tb being maintained in this range for a period of time U sufficient to attain complete gelling of the lyogel, and more particularly the end of syneresis of the lyogel.