Hydrophobic Aerogels Gradient Core-Shell Structure
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Solution Overview
Problem
Existing aerogels based on SiO2 are brittle and have high carbon content, which affects their hydrophobicity, combustibility, and mechanical stability, limiting their application in thermal insulation and other fields.
Innovation Solution
Development of gels with primary particles composed of oxidic units and [RxSiO(4-x)/2] units, where the concentration of [RxSiO(4-x)/2] units changes from the inside to the outside, creating a gradient or core-shell structure that reduces direct oxidic particle contacts and increases hydrophobicity and mechanical strength while minimizing carbon content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If aerogels are made from pure SiO2 networks, then thermal insulation performance is improved, but mechanical brittleness increases and hydrophobicity decreases
Solution Approach 1:
The patent creates hybrid aerogels by combining SiO2 primary particles with organic-functionalized silane units ([RxSiO(4-x)/2] where R is an organic radical). This composite structure integrates the thermal insulation benefits of inorganic SiO2 networks with the mechanical flexibility and hydrophobicity of organic functional groups, resolving the contradiction between thermal performance and mechanical properties
Solution Approach 2:
The patent introduces a concentration gradient of organic-functionalized units within the aerogel structure, where the concentration of [RxSiO(4-x)/2] units varies from the interior to the exterior of primary particles. This local variation in composition allows different regions to fulfill different functions: the SiO2-rich core provides thermal insulation while the organic-functionalized shell provides mechanical flexibility and hydrophobicity
2Reliability
If surface modification with hydrophobic groups is performed to reduce water absorption, then hydrophobicity is improved, but carbon content increases leading to higher combustibility
Solution Approach 1:
The patent carefully controls the concentration and type of organic radicals (R groups) in the [RxSiO(4-x)/2] units to achieve the desired hydrophobicity while maintaining low carbon content. By optimizing parameters such as the degree of substitution (x) and the size of organic radicals, the patent finds a balance between hydrophobic performance and combustibility, using minimal carbon-containing groups to achieve sufficient water repellency without creating fuel for combustion
Solution Approach 2:
The patent uses small organic radical groups (such as methyl or ethyl groups) that replicate the essential hydrophobic function of larger hydrocarbon chains while containing significantly less carbon. These minimal carbon-containing units provide the necessary water repellency through their hydrophobic character without contributing substantial fuel load, thus copying the hydrophobic effect while minimizing combustibility
3Reliability
If post-silylation is performed to achieve permanent hydrophobicity, then hydrophobicity is improved, but manufacturing complexity increases
Solution Approach 1:
The patent incorporates organic-functionalized silane units ([RxSiO(4-x)/2]) directly into the aerogel network during the sol-gel formation process, rather than performing subsequent surface modification. This preliminary incorporation of hydrophobic units ensures permanent hydrophobicity is achieved as an intrinsic property of the aerogel structure, eliminating the need for separate post-silylation steps and reducing manufacturing complexity
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 resulting gels exhibit enhanced hydrophobicity, reduced combustibility, and improved mechanical stability, making them suitable for thermal insulation and other applications with low thermal conductivity and high flexibility.
Implementation Method 1
These are produced by formation of a network of SiO2 primary particles by means of a sol-gel process
Implementation Method 2
network formation occurs in aqueous solutions to give hydrogels
Implementation Method 3
linkage and sintering of the contact areas in a sol-gel process
Implementation Method 4
Permanent hydrophobicity is achieved by treatment of the surface of gel networks with hydrophobic groups, preferably by modification
Implementation Method 5
networks have the disadvantages which are generally known in the prior art for aerogels, namely that they are crumbly and brittle
Implementation Method 6
These lyogels can be converted into aerogels by removal of the solvent
Implementation Method 7
While the pores are filled with solvent in the case of a lyogel
Implementation Method 8
primary particles which are made up of oxidic units and [RxSiO(4-x)/2] units, wherein the primary particles have a change in the concentration of [RxSiO(4-x)/2] units from the inside to the outside
Implementation Method 9
Aerogels having high porosities (>60%) and a low density (2 gels, are built up of networks which are composed of primary particles
Implementation Method 10
The pores of the aerogel are accordingly filled with air
Data Source
AI summary
The problem addressed by the invention is that of producing aerogels which have as high and permanent a hydrophobicity as possible and which have a reduced combustibility, that is as low a carbon content as possible, and are simultaneously less rigid and brittle than known systems, i.e. which with reduced combustibility have a high flexibility and high stability at the same time, that is high mechanical load-bearing capacity. Said problem is solved in that the invention provides gels chosen from lyogel or aerogel, which are synthesised from oxide units and [RxSiO(4-x)/2] units, wherein the primary particles have a change of concentration in [RxSiO(4-x)/2] units from the inside to the outside, wherein x can be the same or different and is 1 or 2, and R can be the same or different and is hydrogen or an organic substituted or unsubstituted radical, and wherein the oxide units contain [SiO4/2] units, and a method for producing same. The gels provided can be used in cosmetic, medical or for chromatographic applications, and as a catalyst or catalyst support. If the gels are aerogels, same are preferably used for thermal and/or acoustic insulation.