Polymer-Derived Ceramic Fibers With Improved Spinnability
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Solution Overview
Problem
Current ceramic fibers, particularly SiC fibers, are costly and limited in availability, while existing SiCN fibers lack spinnability, making them unsuitable for large-scale production and high-temperature applications.
Innovation Solution
A method is developed to produce silicon oxycarbide (SiOC) and silicon carbonitride (SiOCN) fibers using a hybrid precursor mixture of siloxane or silazane with spinning reagents like polyacrylic acid (PAA) or polyvinylpyrrolidone (PVP) through processes such as wet spinning, melt spinning, or electrospinning, followed by crosslinking and pyrolysis to enhance spinnability and achieve uniform fibers with controlled morphology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SiC fibers are produced using conventional methods, then high mechanical strength and thermal stability are achieved, but the cost is high and availability is limited
Solution Approach 1:
The invention changes the chemical composition parameters of the precursor polymer by incorporating nitrogen-containing groups (silazane units) into the polysiloxane structure. This compositional modification enables the production of SiOCN fibers with properties comparable to or exceeding traditional SiC fibers, while using more abundant and cost-effective raw materials
Solution Approach 2:
The invention creates a composite precursor system combining siloxane and silazane units in a single polymer chain. This composite structure allows simultaneous formation of Si-O-C-N ceramic network during pyrolysis, producing fibers with enhanced mechanical strength and thermal stability while reducing production cost compared to conventional SiC fiber routes
2Ease of manufacture
If SiCN fibers are produced to reduce cost, then cost-effectiveness is improved, but spinnability is lost making them unsuitable for large-scale production
Solution Approach 1:
The invention introduces nitrogen-containing silazane units at specific locations within the polysiloxane chain rather than uniformly throughout. This localized modification maintains the bulk polymer's spinnability while providing localized sites for forming the desired SiOCN ceramic structure during pyrolysis
Solution Approach 2:
The invention carefully adjusts the molar ratio of siloxane to silazane units in the precursor polymer to optimize both spinnability and final fiber properties. By controlling this compositional parameter, the polymer maintains appropriate viscosity and processability for spinning while ensuring sufficient nitrogen content for forming the cost-effective SiOCN ceramic structure
3Manufacturing precision
If hybrid precursor mixture with spinning reagents is used to improve spinnability, then uniform fibers with controlled morphology are achieved, but process complexity increases
Solution Approach 1:
The invention combines the precursor polymer synthesis and fiber spinning steps into a single integrated process. The siloxane-silazane copolymer is synthesized with inherent spinnability, eliminating the need for separate solution preparation, solvent removal, and crosslinking steps required by conventional wet-spinning methods
Solution Approach 2:
The invention extracts and eliminates the need for external spinning reagents and solvents by designing a self-spinnable precursor polymer. The copolymer's inherent chain flexibility and intermolecular interactions provide sufficient viscosity control and fiber-forming capability without requiring additional additives or complex spinning baths
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 ceramic fibers with improved spinnability, thermal stability up to 1000°C, and controlled composition, offering a cost-effective alternative to existing fibers with enhanced mechanical and thermal properties suitable for aerospace applications.
Implementation Method 1
The preceramic polymer fibers are crosslinked to form crosslinked preceramic polymer fibers
Implementation Method 2
The preceramic polymer fibers are pyrolyzed to form the ceramic fiber materials
Data Source
AI summary
Ceramic matrix composite (CMC) materials are a desired solution for lightweight and high temperature applications. CMC materials can be reinforced with polymer-derived ceramic (PDC) fibers, which advantageously possess intrinsic thermal stability and high mechanical strength. Carbon-rich SiOC and SiOCN fibers were synthesized via hand-drawing and electrospinning polymer pyrolysis of a hybrid precursor materials with the aid of a spinning reagent. The prepared fibers are crosslinked and pyrolyzed for polymer-to-ceramic conversion.