Monolithic SiC Flow Reactor Modules Without Porous Interfaces
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Solution Overview
Problem
The production of silicon carbide (SiC) fluidic modules with tortuous internal passages faces challenges due to the formation of porous interfaces and rough internal channel surfaces, leading to contamination and mechanical failures, especially when using sandwich assembly methods.
Innovation Solution
A method involving the use of a positive mold within silicon carbide powder, followed by pressing and sintering, to create a monolithic silicon carbide structure with low porosity and smooth internal passage surfaces, achieving surface roughness in the range of 0.1 to 80 μm Ra.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sandwich assembly approach is used to join fired slabs, then internal channels can be formed, but porous interfaces form at the joining layer causing contamination and mechanical failure
Solution Approach 1:
The internal channels are formed by placing a removable mandrel within a single green body before firing, rather than joining multiple fired slabs. This segmentation approach creates the channels in one monolithic structure, eliminating the need for joining layers and the associated porosity problems.
Solution Approach 2:
The mandrel is positioned within the green body before firing to define the internal channel geometry. This preliminary action allows the channel shape to be established during the forming stage, and the mandrel is subsequently removed after firing to create the final hollow channel structure without requiring post-firing joining operations.
2Ease of manufacture
If sandwich assembly approach is used to join fired slabs, then internal channels can be formed, but internal channel surfaces have undesirable roughness due to coarse ceramic grains
Solution Approach 1:
The channel structure is formed as an integral part of the monolithic body using a mandrel, rather than creating channels through joining operations. This allows the channel surface to be defined by the mandrel geometry and the fine structure of the green body, resulting in smoother surfaces without the grain roughness introduced by joining coarse-grained slabs.
Solution Approach 2:
The mandrel serves as a positive model that copies its smooth external geometry onto the internal channel surface. By forming the green body around the mandrel and then removing the mandrel after firing, the channel surface replicates the mandrel's smooth profile, achieving low roughness values without requiring post-processing of rough joined surfaces.
3Adaptability or versatility
If multiple layers of green-state SiC sheets are used to build up fluidic module slice-by-slice, then complex shapes can be formed, but small step-like structures form in curved profiles of internal passages
Solution Approach 1:
Instead of building up the structure layer-by-layer from the outside, the invention forms the green body as a continuous monolithic structure around a mandrel. The mandrel defines the internal passage geometry, and the green body material is compacted around it in one operation, eliminating the step-like structures that would result from layer-by-layer construction.
Solution Approach 2:
The mandrel is positioned and secured within the green body before compaction and firing. This preliminary placement ensures that the internal passage geometry is established in advance, allowing complex curved profiles to be formed continuously without the discrete layer boundaries that would create steps in slice-by-slice construction.
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 results in SiC fluidic modules with low open porosity and smooth internal surfaces, ensuring easy cleanability, reduced pressure drop, and improved mixing and heat exchange performance.
Implementation Method 1
pressing the volume of silicon carbide powder with the mold inside to form a pressed body
Implementation Method 2
heating the pressed body to remove the mold
Implementation Method 3
sintering the pressed body to form a monolithic silicon carbide structure or fluidic module
Data Source
AI summary
A module and a process for forming a monolithic substantially closed-porosity silicon carbide fluidic module having a tortuous fluid passage extending through the module, the tortuous fluid passage having an interior surface, the interior surface having a surface roughness in the range of from 0.1 to 10 μm Ra. The process includes positioning a positive fluid passage mold within a volume of silicon carbide powder, the powder coated with a binder; pressing the volume of silicon carbide powder with the mold inside to form a pressed body; heating the pressed body to remove the mold; and sintering the pressed body.