Halloysite is a rare derivative of kaolin where the mineral occurs as nanotubes. It was named after Belgian geologist Juan Baptiste Julien d'Omalius d'Halloy in 1826. Halloysite tubes are formd by weathering of the plate-like kaolin particles that cause them to roll up while also leaching out impurities that result in high purity nanotubes. The size of the halloysite particles varies within 1-15 microns in length and 10-150 nm of inner diameter.
Typical kaolin plate-like structure Pure halloysite tubular structure
Halloysite has a wide variety of industrial uses beyond simple kaolin and commands a significant premium above the average kaolin price. It is short supply due to the exhaustion of existing global reserves and the closing of environmentally damaging mines in China.
Halloysite's main applications are in ceramics, where it is used in the manufacture of high-quality porcelain by adding whiteness, transparency and exceptional strength to the final fired product, and as a petroleum cracking catalyst.
High quality porcelain Petrochemical cracking catalyst
New research into the use of halloysite nanotubes for a number of high-tech industries is leading to the development of exciting new markets for the material. The nanotubes can be filled with many materials such as biocides, drugs, proteins and polyelectrolytes which leads to potential applications which include:
- contolled release of anticorrosion agents
- sustained release of herbicides, insecticides, fungicides and anti-microbials
- sustained release of drugs, food additives and fragrances
- templating synthesis of nano-structures
- uses as catalytic supports amd molecular sieves
- specific ion adsorption
- use as polymer fillers for performance improvement
- use in advanced ceramic materials such as biocompatible implants
High Purity Alumina Feedstock
The natural extreme high-purity of halloysite-kaolin compared with standard kaolin makes it a very attractive premium-quality feed material for the production of High Purity Alumina (HPA).
HPA is a high-value, high margin and in-demand product as it is a critical ingredient required for the production of synthetic sapphire. Synthetic sapphire is used in the manufacture of substrates for LED lights, semiconductor wafers used in the electronics industry, and scratch-resistant sapphire glass used for wristwatch faces, optical windows and smartphone components. There is no substitute for HPA in the manufacture of synthetic sapphire.
HPA LED globes
HPA is a recognised key ingredient for lithium-ion batteries. Higher battery energy density is driving demand for HPA use in battery separators leading to a forecast significant surge in HPA demand at a greater than 20% compound annual growth rate to 2025.
Battery storage Electric vehicles
HPA products are categorised on the basis of purity level with a resultant increasing market value, ie:
- 3N is 99.9% aluminium oxide (US$5,000 - US$15,000 per tonne)
- 4N is 99.99% aluminium oxide (US$15,000 - US$30,000 per tonne)
- 5N is 99.999% aluminium oxide (US$30,000 - US$50,000 per tonne)
HPA testwork on Andromeda Metals' Poochera halloysite-kaolin has confirmed that 4N purity is achievable with only a single purification stage which compares favourably to peer companies which require multiple purification stages to reach 4N purity.