Porous-Dense Powder Structure Using a Sacrificial Composite
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Solution Overview
Problem
Current methods for creating objects from powders often result in fully dense parts but lack the ability to form objects with controlled porous structures integrated with fully dense parts, which are essential for applications like bipolar plates in hydrogen electrolyzers and fuel cells.
Innovation Solution
A method involving a composite with a sacrificial material and a powder, where the composite is densified and bonded in a single process to form an intermediate object, and the sacrificial material is subsequently removed, allowing for the creation of objects with both porous and dense parts integrated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If cold isostatic pressing is used to form a green object, then the object can be handled and takes the desired shape, but the object remains porous and requires additional sintering steps
Solution Approach 1:
The object is divided into two distinct regions: a porous structure region and a fully dense region. This segmentation allows each region to have different density characteristics suitable for its specific function, resolving the contradiction between handling capability and density control by providing both porous and dense areas within the same object.
Solution Approach 2:
Different regions of the object are given different local qualities - the porous region provides flexibility and handling ease, while the fully dense region provides structural integrity and precision. This local differentiation resolves the contradiction by allowing each region to optimize for its specific requirement.
2Productivity
If hot isostatic pressing is used to consolidate powder, then the object is formed as a fully dense object in a single step, but the process requires complex equipment and high pressure
Solution Approach 1:
The consolidation process is segmented into two stages: first forming a green object with cold isostatic pressing, then selectively sintering only the dense region. This segmentation allows the use of simpler equipment for each stage rather than requiring complex hot isostatic pressing equipment for the entire object.
Solution Approach 2:
Instead of applying full hot isostatic pressing to the entire object, the invention applies sintering only to the specific region where full density is required. This partial action reduces equipment complexity and processing requirements while still achieving the desired fully dense region.
3Productivity
If field assisted sintering technology is used, then the object is formed as a fully dense object with shorter processing time, but only uniaxial compaction is possible
Solution Approach 1:
The compaction process is segmented into two stages: first uniaxial compaction to form a green body, then isostatic pressing to achieve uniform density distribution. This segmentation allows the combination of both compaction methods, achieving both speed and versatility.
Solution Approach 2:
Uniaxial compaction is performed as a preliminary action to form the green body with basic shape, followed by isostatic pressing to achieve uniform density. This preliminary action allows the subsequent sintering to be more effective and efficient.
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 composite objects with controlled porous structures and fully dense parts, enhancing their structural integrity and performance in applications such as bipolar plates, while reducing production complexity and cost.
Implementation Method 1
This involves using a mould, often made from a flexible material such as rubber, in which the powder is placed and then the mould is pressed (typically by pressing the mould isostatically under a fluid) at ambient temperature to cause the powder to be compacted to form the green object
Implementation Method 2
The green object is placed in, for example, a furnace, and the heat causes the compacted material of the green object to densify under diffusion bonding and pore closure mechanisms to become a fully dense or solid object
Implementation Method 3
The canister is then removed from the object through mechanical and/or chemical processes such as leaching
Data Source
AI summary
A method for creating an object by consolidating a powder includes providing a composite including a first material arrange to form a porous structure and a second, sacrificial, material surrounding the first material. The composite may be surrounded with a powder and an intermediate objecting may be formed having a dense part bonded to the composite by densifying and bonding the powder to the composite in a single process. The second material may be removed from the intermediate object to from the object, which may include the porous structure and the dense part bonded to the porous structure.