High Ductility Ti and NiTi Foams via Gelcasting
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Solution Overview
Problem
Current methods for producing titanium (Ti) and NiTi foams result in brittle materials due to high contamination with elements like N, O, C, and H, leading to insufficient ductility and fatigue properties, making them unsuitable for high-quality bone replacements.
Innovation Solution
A method involving gelcasting of a Ti, Ti-alloy, or NiTi powder suspension with specific particle size and purity, followed by slow calcination and sintering under controlled conditions to achieve high ductility, with a minimum of 10% plastic deformation without rupture, and a sintering process that includes heating to 1200-1500°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If polyurethane replica technique is used to manufacture Ti foams, then porous structure with desired morphology is achieved, but high contamination with N, O, C, H occurs resulting in embrittlement and low ductility (about 3% strain)
Solution Approach 1:
The invention changes the manufacturing parameters by switching from polyurethane replica technique to gelcasting procedure, and implements specific calcination parameters (slow heating rate of 20°C/hour to 400-600°C) to control contamination levels and achieve high ductility while maintaining desired porous structure
Solution Approach 2:
The invention uses inert atmosphere during calcination and sintering processes to prevent oxidation and contamination of the Ti powder, thereby maintaining low contamination levels (C < 0.03 wt%, O < 0.8 wt%, N < 0.5 wt%) and achieving high ductility without compromising the porous structure morphology
2Reliability
If gelcasting procedure is used to manufacture Ti foams, then low contamination with N, O, C is achieved resulting in high ductility, but the process complexity and manufacturing steps increase
Solution Approach 1:
The invention segments the manufacturing process into distinct steps: powder preparation with specific purity requirements, gelcasting forming, slow calcination (400-600°C at 20°C/hour), and sintering (1200-1500°C). This segmentation allows control of each parameter to achieve high ductility while managing process complexity
Solution Approach 2:
The invention performs preliminary purification of Ti powder before gelcasting to ensure contamination levels are below specified thresholds (C < 0.03 wt%, O < 0.8 wt%, N < 0.5 wt%), and implements preliminary slow calcination step to remove organic residues without causing embrittlement, thereby ensuring high ductility is achieved from the start
3Reliability
If Ti powder with particle size less than 100 μm is used, then high ductility and low contamination are achieved, but the powder handling and suspension preparation become more difficult
Solution Approach 1:
The invention optimizes the powder particle size parameter to be less than 100 μm but not too fine (avoiding sub-10 μm particles that are excessively pyrophoric), and adjusts the powder composition parameters (C < 0.03 wt%, O < 0.8 wt%, N < 0.5 wt%) to balance handling ease with achieving high ductility in the final foam product
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 highly porous Ti, Ti-alloy, or NiTi foams with greater than 70% porosity and a theoretical density less than 30%, enabling deformation of over 10% in compression, essential for load-bearing implants with improved mechanical properties.
Implementation Method 1
Bring said powder suspension into a desired form by gelcasting to form a green artefact
Implementation Method 2
A calcination step wherein said green artefact is calcined
Implementation Method 3
Sintering said artefact
Data Source
AI summary
A method for manufacturing a high ductility Ti-, Ti-alloy or NiTi-foam, meaning a compression strain higher than 10%, includes: preparing a powder suspension of a Ti-, NiTi- or Ti-alloy powder, bringing the said powder suspension into a desired form by gelcasting to form a green artifact. The method also includes a calcination step wherein the green artifact is calcined, and sintering the artifact. The calcination step includes a slow heating step wherein said green artifact is heated at a rate lower or equal to 20° C./hour to a temperature between 400° C. and 600° C. and the Ti-, NiTi- or Ti-alloy powder has a particle size less than 100 μm. A high ductility Ti-, Ti-alloy or NiTi foam, with a compression higher than 10%, with a theoretical density less than 30%, pore size (cell size) between 50 to 1000 μm can be obtained with such a method.