Metal hydride composites
Project lead
Dr Ashleigh Cousins, ashleigh.cousins@csiro.au
Lead researchers
Dr Alex Ilyushechkin
Dr Liang Liu
Dr Xin Yu
Dr Wendy Tian
Dr Cherry Chen
Dr Shiqin Yan
Dr Daniel Liang
Challenge
Metal Hydrides (MH) are formed when metals or inter-metallic alloys react with H2. These reactions can be reversible, allowing the alloys to be used for hydrogen compression and storage applications.
One of the challenges however is that the metal alloys break down into a fine powder with hydrogen cycling. This lowers the thermal conductivity of the system, resulting in poor heat transfer. This in turn increases the charging and discharging time for MH vessels, which is often limited by heat flow. The powder formed consists of very small particles (sizes in the range of a few microns). In metal hydride systems this requires filters to be installed to stop migration of the particles and potential clogging of valves and other downstream equipment.
What we are doing
One method to improve the performance of MH vessels is to house the hydride in composite structures. These structures can potentially accommodate the volume expansion resulting from H2 sorption and improve heat transfer by adding additives with a high thermal conductivity. They can also bind the particles, removing issues relating to particle migration from reaction vessels.
This project explored three potential avenues for improving the performance of MH vessels at low cost:
• Adapting CSIRO’s carbon fibre monolith work [Mineral Resources]
• Compacts with expanded natural graphite [Energy]
• Compacts with thermal conductivity enhancers and polymers [Manufacturing]
Outcomes to date
- A hydrogen cycling rig was constructed as part of this project to analyse the sample’s integrity with cycling. It has the ability to cycle H2 at pressures up to 50 bar through samples and monitor their H2 uptake, also providing some data on H2 capacity, stability and sorption-desorption kinetics. Experiments lasting up to 1200 cycles were completed.
- The addition of thermal conductivity enhancers and binders did not reduce the H2 capacity of the alloys.
- Thermal conductivities up to 12 W/mK were achieved while maintaining a high proportion of alloy in the composite (above 85 wt%)
- All composite structures showed some level of structural degradation with cycling. However, there are some sample compositions that provide the ability to maintain their structure after 1200 H2 cycles.
Lessons learned
- Thermal conductivity can be significantly enhanced with even a small addition of enhancer. For example, adding 5 wt% Expanded Natural Graphite (ENG) was able to increase conductivity from around 0.1 W/mK for loose alloy powder to 4 W/mK for the compact.
- Thermal conductivity, while a useful screening method, should not be used in isolation when evaluating performance. Parameters such as H2 permeability should also be assessed.
Project finish date
December 2023
Relevant project publications
Liu, L., Ilyushechkin, A., Liang, D., Cousins, A., Tian, W., Chen, C., Yin, J., Schoeman, L., 2023, Metal hydride composite structures for improved heat transfer and stability for hydrogen storage and compression applications, Inorganics 11, 181, https://doi.org/10.3390/inorganics11050181
Conference presentations
17th International Symposium of Metal-Hydrogen systems, Perth, 31 Oct – 4 Nov 2022.
Presenter: Alex Ilyushechkin
Title: Metal Hydride-carbon composite structures for improved heat transfer
Australian Hydrogen Research Community conference, Canberra, 8-10 Feb 2023.
Presenter: Wendy Tian
Title: Hydrogen storage and transportation using metal hydride/polymer composite
NZ Hydrogen Research Symposium, Wellington, 31 Jan – 2 Feb 2024
Presenter: Ashleigh Cousins
Title: Metal hydride systems for hydrogen compression
HyResearch record
H2ES FSP Metal hydride composites – HyResearch: Australian Hydrogen R&D Portal (csiro.au)