Plasma-Formed SiC Particles for Improved Flowability
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Solution Overview
Problem
Existing methods for producing SiC particles result in highly irregular, high aspect ratio particles with sharp edges, leading to issues such as nozzle clogging, poor flowability, high porosity in coatings, and adverse effects on processing and performance due to ultrafine particles.
Innovation Solution
A method involving plasma pyrolysis of a polymeric ceramic precursor to produce amorphous SiC particles, which are less irregular, have lower aspect ratios, and exhibit improved processability, using a plasma spray torch to inject droplets into a plasma jet for pyrolysis and quenching in a water bath.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods (Acheson process, electrothermal fluidized bed, or polymer pyrolysis followed by milling) are used to produce SiC particles, then SiC material can be obtained, but the particles become highly irregular with high aspect ratios and sharp edges, leading to poor flowability and nozzle clogging
Solution Approach 1:
The invention changes the fundamental processing parameters by using plasma spray deposition instead of conventional heating and mechanical milling. This transforms the particle formation process from a high-temperature thermal process followed by mechanical size reduction to a controlled plasma-based deposition process that directly forms particles with desired morphology, achieving both manufacturing precision and flowability
Solution Approach 2:
The invention replaces the mechanical milling process with a plasma-based deposition process. Instead of mechanically crushing and milling SiC material to achieve desired particle sizes (which creates irregular shapes and sharp edges), the plasma spray process directly forms particles with controlled morphology through vapor deposition, eliminating the mechanical size reduction step that causes poor flowability
2Length of moving object
If conventional milling processes are used to reduce particle size, then desired particle size can be achieved, but particles become highly irregular with high aspect ratios, causing packing difficulties and high porosity in coatings
Solution Approach 1:
The invention replaces mechanical size reduction with plasma-based vapor deposition. Instead of using ball mills or crushers that fracture particles into irregular shapes with high aspect ratios, the plasma spray process deposits SiC from the vapor phase, forming particles with controlled, regular shapes and appropriate size distribution, thereby achieving both desired particle size and shape regularity
Solution Approach 2:
The invention utilizes phase transitions (solid to vapor to solid) in the plasma spray process. SiC material is vaporized in the plasma jet and then deposits as particles upon cooling, allowing direct formation of particles with controlled morphology and size without mechanical size reduction, thus achieving both particle size control and shape regularity
3Area of stationary object
If ultrafine particles are present in SiC powders, then high surface area can be achieved, but viscosity of slurries is significantly raised and oxidation susceptibility increases due to high surface to volume ratio
Solution Approach 1:
The invention changes the particle size distribution parameters by controlling the plasma spray process to produce particles with optimized size ranges. Instead of generating ultrafine particles with high surface area that are prone to oxidation, the process produces particles with controlled size distribution that maintains adequate surface area for coating performance while minimizing oxidation susceptibility through reduced surface-to-volume ratio
Solution Approach 2:
The invention utilizes the inert plasma environment during particle formation to prevent oxidation. The plasma spray process occurs in a controlled atmosphere that protects the freshly formed particles from oxidation, especially important for preventing oxidation of high-surface-area particles, thereby reducing oxidation susceptibility while maintaining beneficial surface area characteristics
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 SiC particles with reduced crystallinity, lower aspect ratios, and fewer sharp edges, enhancing flowability and reducing oxidation susceptibility, thereby improving coating application and performance.
Implementation Method 1
the atomized droplets of polymeric ceramic precursor are heated to a temperature of 1000°C to 1400°C... During the pyrolysis, in one example of the present disclosure, using the plasma jet, the atomized droplets of polymeric ceramic precursor are heated
Implementation Method 2
a plasma jet generated by a plasma spray torch, wherein the droplets undergo pyrolysis in the plasma jet
Implementation Method 3
the plasma jet is generated by passing a flow plasma generating gas though an electrical arc
Implementation Method 4
amorphous particles of SiC... the resultant material is then crushed and milled... amorphous SiC particles formed by the plasma spray pyrolysis
Data Source
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AI summary
The preparation of amorphous SiC particles (45) is disclosed wherein a polymeric ceramic precursor is subjected to plasma spraying. The polymeric ceramic precursor, for example, in the form of atomized droplets, is injected into a plasma jet (40) and subject to pyrolysis. The amorphous SiC particles (45) can be used in the preparation of environmental barrier coatings (EBCs) for protection of ceramic matrix materials (CMCs). For example, a bond coat containing the amorphous SiC particles (45) can be applied to a CMC substrate by slurry processing.