SiC Composite Film Boiling with Chlorine-Free Polymer Precursors

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Solution Overview

Problem

Existing methods for producing silicon-carbide-based composites, such as CVI, FB, PIP, and MI, face issues like low growth rates, corrosion, high operational costs, and inefficiencies, making them unsuitable for industrial-scale production due to challenges with raw materials like MTS and SMP-10.

Innovation Solution

A film boiling method using a chlorine-free organosilicon polymer, specifically liquid polysilanes, is employed to produce silicon-carbide-based composites, offering a more efficient and cost-effective process by reducing hydrochloric acid gas generation and enabling continuous processing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If MTS is used as raw material gas for CVI method, then SiC matrix layer can be formed by thermal decomposition, but the growth rate of SiC is low and formation takes a long time

Engineering Contradiction:

Improvequality of SiC matrix layerVSAvoidgrowth rate of SiC

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent changes the chemical parameters of the raw material from MTS (methyltrichlorosilane) to TMS (tetramethylsilane), altering the molecular structure to eliminate chlorine content. This parameter change enables faster SiC formation kinetics while maintaining matrix layer quality, resolving the contradiction between reliability and productivity.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If MTS is used as raw material, then SiC can be infiltrated between fibers, but hydrogen chloride (HCl) is generated causing equipment corrosion and requiring frequent neutralization processing

Engineering Contradiction:

Improveinfiltration qualityVSAvoidhydrogen chloride generation

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent extracts the harmful chlorine element from the raw material molecule by selecting TMS instead of MTS. This extraction eliminates HCl generation during decomposition, removing the harmful factor while preserving the beneficial infiltration capability of the SiC matrix formation process.

Inventive Principle:

Principle #2Taking out (Extraction)

3Ease of manufacture

If film boiling method with MTS is used, then cost is reduced, but hydrochloric acid gas remains in processing liquid requiring frequent renewal

Engineering Contradiction:

Improvemanufacturing costVSAvoidprocessing liquid renewal frequency

Core Design Contradiction:

Ease of manufactureVSLoss of substance

Solution Approach 1:

By extracting chlorine from the raw material system (using TMS instead of MTS), the patent eliminates hydrochloric acid gas generation. This allows the processing liquid to be reused without frequent renewal, reducing substance loss while maintaining cost effectiveness.

Inventive Principle:

Principle #2Taking out (Extraction)

4Productivity

If MI method is used, then production time is short and process is convenient, but reaction between metal Si and carbon fibers cannot be suppressed

Engineering Contradiction:

Improveproduction speedVSAvoidfiber strength

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent employs a disposable organic solvent carrier system in the film boiling process that delivers Si source efficiently and rapidly. This approach achieves fast production like MI method while the solvent system prevents harmful reactions between metal Si and fibers, protecting fiber strength without requiring expensive pre-treatment.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 method allows for the production of silicon-carbide composites with improved efficiency and reduced costs, enabling higher carbon content and enhanced oxidation resistance through decarbonization processing, making it suitable for industrial applications.

Implementation Method 1

a film boiling method is carried out using an organosilicon polymer having a chlorine-free polysilane skeleton and/or a chlorine-free polycarbosilane skeleton

Methodology Applied

Scientific EffectFilm boiling: Boiling

Implementation Method 2

forming a SiC matrix layer by thermal decomposition of methyltrichlorosilane

Methodology Applied

Scientific EffectThermal decomposition: Pyrolysis

Implementation Method 3

vapor-phase impregnation (deposition) is carried out, SiC can be infiltrated between the fibers of the preform for forming

Methodology Applied

Scientific EffectVapor-phase infiltration (deposition): Physical Vapour Deposition

Data Source

PatentUS11148978B2Method for producing silicon-carbide-based composite

Publication Date: 2021.10.19 IHI AEROSPACE CO LTD

AI summary

A method for producing a silicon-carbide-based composite. In the production of a silicon-carbide-based composite comprising a carbon-fiber-reinforced/silicon carbide composite (a C/SiC composite) or a silicon-carbide-fiber-reinforced/silicon carbide composite (a SiC/SiC composite), a film boiling method is carried out, using an organosilicon polymer having a chlorine-free polysilane skeleton and/or a chlorine-free polycarbosilane skeleton. The organosilicon polymer is in a liquid form at room temperature. The molar ratio of Si and C in the matrix of the C/SiC composite or the SiC/SiC composite is Si:C=1:1.08 to 1:1.43.