Glass-Modified Oxidation Coating for Hydrolysis-Prone Composites
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Solution Overview
Problem
Oxidation protection systems for carbon-carbon composite structures face hydrolytic instability due to the formation of water-soluble diboron trioxide at high temperatures, leading to material loss and degradation.
Innovation Solution
A method involving the application of boron and silicon slurries, each comprising specific glass compounds, modifiers, and carriers, followed by heating, to form a boron-glass and silicon-glass layer on the composite structure, which includes pretreatment with aluminum oxide or monoaluminium phosphate to enhance stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If layers of boron carbide and silicon carbide are used for oxidation protection, then oxidation resistance is improved, but hydrolytic stability deteriorates due to formation of water-soluble diboron trioxide
Solution Approach 1:
The patent introduces glass modifiers (metal oxides such as Al2O3, SiO2, B2O3, MgO, CaO, SrO, BaO, PbO, ZnO, TiO2, ZrO2, HfO2) as intermediary substances that react with diboron trioxide to form stable glass phases. These modifiers act as mediators between the boron carbide layer and water, preventing direct hydrolysis while maintaining oxidation protection functionality.
Solution Approach 2:
The patent creates a composite glass system combining multiple oxides (B2O3, SiO2, and various metal oxides) to form a multi-phase glass structure. This composite approach leverages the synergistic effects of different oxides: B2O3 provides low melting point and glass formation, SiO2 provides structural framework and water resistance, while metal oxides provide stability and react with diboron trioxide to form stable compounds.
2Stability of the object's composition
If glass modifiers are added to the slurry composition, then hydrolytic stability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent combines multiple glass modifiers and glass formers into a single integrated glass system within the slurry. Rather than applying separate coatings for each component, all modifiers (Al2O3, SiO2, B2O3, MgO, CaO, etc.) are merged into one slurry composition that forms a unified glass phase during heating, simplifying the manufacturing process while achieving complex functionality.
Solution Approach 2:
The patent optimizes the weight percentages of various components in the slurry to achieve desired properties. By carefully controlling parameters such as B2O3 (10-40 wt%), SiO2 (30-60 wt%), and metal oxide (5-20 wt%) content, the system achieves hydrolytic stability without requiring excessive complexity in composition or processing.
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 solution significantly reduces material loss and increases the water stability of the oxidation protection system, providing effective protection against oxidation at high temperatures.
Implementation Method 1
glass modifiers, which may react with diboron trioxide to form stable glass phases
Implementation Method 2
heating the carbon-carbon composite structure
Data Source
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AI summary
Systems and methods for forming an oxidation protection system on a composite structure are provided. In various embodiments, the oxidation protection system comprises a boron-glass layer formed on the composite substrate and a silicon-glass layer formed over the boron-glass layer. Each of the boron-glass layer and the silicon-glass layer include a glass former and a glass modifier.