Bidirectional Freeze Casting Wedge Cooling Surface
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Solution Overview
Problem
Conventional techniques for fabricating large-scale porous aligned lamellar structures are limited by random ice crystal nucleation and growth, hindering the scale-up of layered structures for larger applications, despite the demand for more controlled and environmentally friendly methods.
Innovation Solution
A bidirectional freezing technique is employed, using a wedge-shaped cooling surface to generate both vertical and horizontal temperature gradients, allowing for the controlled nucleation and growth of ice crystals and the formation of large-size single-domain porous lamellar structures in ceramic, metallic, or polymeric materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional unidirectional freezing is used, then the process is simple and environmentally friendly, but random ice crystal nucleation results in multiple small-size domains with various orientations, preventing large-scale single-domain structure formation
Solution Approach 1:
The patent introduces a wedge-shaped element that creates asymmetric thermal fields, transforming the symmetric unidirectional temperature gradient into a bidirectional gradient. This asymmetry in the cooling surface geometry (with different slopes on either side) directs ice crystal nucleation and growth in a controlled manner, achieving large-scale single-domain structures while maintaining relative simplicity in the apparatus design.
2Length of stationary object
If conventional freeze casting is used, then the technique is applicable to various materials and environmentally friendly, but the scale-up fabrication of large-size aligned lamellar structures is severely hindered
Solution Approach 1:
The patent transitions from unidirectional freezing (one-dimensional temperature gradient) to bidirectional freezing by introducing a second dimension to the temperature gradient through the wedge-shaped cooling surface. This dimensional change enables simultaneous control of ice crystal growth in multiple directions, allowing the formation of large-size aligned lamellar structures with improved uniformity and orientation control.
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 enables the production of large-scale aligned lamellar structures comparable to natural nacre, providing a higher level of control over structural features and enabling the design of advanced bioinspired materials with improved mechanical properties.
Implementation Method 1
The cooling surface is cooled to cool the slurry at a specified cooling rate. Crystals comprising the liquid first nucleate at a first end of the wedge
Implementation Method 2
Crystals comprising the liquid first nucleate at a first end of the wedge, with the first end of the wedge comprising a thinnest region of the wedge
Implementation Method 3
This can be achieved through control of nucleation of crystals comprising a liquid (e.g., ice crystals) and growth of the crystals under a temperature gradient having a vertical component and a horizontal component generated by covering the cold finger with a wedge
Implementation Method 4
The cooling surface is in contact with the first substantially planar surface. The cooling surface is cooled to cool the slurry at a specified cooling rate
Data Source
AI summary
This disclosure provides systems, methods, and apparatus related to freeze casting. In one aspect, a method comprises providing an apparatus. The apparatus comprises a container and a cooling surface. A bottom of the container comprises a wedge. The wedge comprises a first substantially planar surface and a second substantially planar surface with an angle between the first and the second substantially planar surfaces. An interior bottom of the container comprises the second substantially planar surface. The cooling surface is in contact with the first substantially planar surface. A slurry is deposited on the second substantially planar surface, the slurry comprising a plurality of particles in a liquid. The cooling surface is cooled to cool the slurry at a specified cooling rate.