Johnson Matthey Technology Review - Volume 69, Issue 2, 2025

The concept of a circular economy for rare earth elements (REEs) is being developed. The circular economy involves optimising the lifecycle of products to achieve sustainable and efficient consumption. REEs are considered critical elements of high economic value. Considering limited rare earth reserves, secondary source REEs are very important to sustainable use. Spent nickel-metal hydride (Ni-MH) batteries are electronic waste containing valuable REEs. Ni-MH batteries that have reached their age limit, if thrown away, will become hazardous waste. Recycling Ni-MH battery waste efficiently enables REEs to be recovered and reused. The REE recovery process has challenges that must be considered such as efficiency, low REE concentration, environmental concerns and scalability, thus requiring the development of new, efficient recovery methods and processes for REE. Currently the hydrometallurgical method is preferred for REE recovery from Ni-MH batteries because it has high yields, low energy requirements, ease of separation from base metals and low greenhouse gas emissions. One such REE recovery using hydrochloric acid on a pilot scale yielded 91.6% lanthanum.

Floating offshore wind (FOW) farms are key in meeting Europe’s renewable energy targets, harnessing wind energy from waters 60 m or deeper, where bottom-fixed farms are unfeasible. Additionally, floating structures allow for the installation of larger turbines than stationary farms, which in turn leads to a greater energy output. However, cable failures dramatically impact the energy transmission from the farms and cause most of the financial losses. Monitoring and maintenance tasks are challenging due to the harsh ocean conditions. The FLoating Offshore Wind turbine CAble Monitoring (FLOW-CAM) project, supported by European Union’s HORIZON 2020 programme, studies the structural health monitoring (SHM) of defects in the power cables of the FOW farms which encompass inspection and detection applications. An SHM system integrated with a remotely operated vehicle (ROV) was developed for underwater inspection and maintenance, supporting collection and presentation of essential data through an advanced interface. Part I details the technologies and methods used in this research.

Part II reports on a new structural health monitoring (SHM) system integrated with a remotely operated vehicle (ROV) developed for underwater inspection and maintenance, part of the FLoating Offshore Wind turbine CAble Monitoring (FLOW-CAM) project, supported by European Union’s HORIZON 2020 programme. Image data from underwater systems are analysed using computer vision techniques. Investigations into cable defect detection and the estimation of corrosion and remaining useful life (RUL) have been held to monitor cable health, achieving results close to reality. FLOW-CAM’s collective works establish a basis for advancing underwater inspection and maintenance, concentrating on the development of practical and effective tools and strategies to optimise the functionality and reliability of floating offshore wind (FOW) farms.

One of the key aspects in the field of nanotechnology is the production of consolidated nanomaterials, which have unique properties and can be used in various fields, such as electronics, medicine, energy and others. Severe plastic deformation (SPD) methods can provide formation of nanostructures in various materials. However, resulting grain size and nature of the emerging structure depend not only on the SPD method used, but also on the processing modes, phase composition and initial microstructure of the material. This review discusses various methods for producing consolidated nanomaterials based on SPD, such as: extrusion, pressure processing, rotation, thermomechanical processing, equal-channel angular pressing (ECAP), water impact processing, vibration processing, electron beam processing and magnetic processing. Their influence on the structure and properties of metallic materials, as well as some areas of the most effective application, have been studied. This article discusses ways to obtain the minimum grain size in various materials and considers data on the evolution of the microstructure during intense deformations.

Neodymium-iron-boron is a rare earth element (REE)-based permanent magnet material. Its main magnetic phase is Nd2Fe14B and it has minor phase neodymium-rich or α-iron. The neodymium-iron-boron permanent magnet has a remarkable maximum energy product ((BH)Max) reaching 474 kJ m⁻³ or nearly 60 mega-gauss-oersteds (MGOe), making neodymium-iron-boron magnets highly suitable for wide use in various technological applications. A commercial neodymium-iron-boron magnet contains 22–32 wt% of REEs such as neodymium, dysprosium, praseodymium and lanthanum. As a result of increasing demand for these materials, the availability of REE from natural resources are decreasing and several REEs such as neodymium, dysprosium and praseodymium are in the critical category. Recycling neodymium-iron-boron magnet waste to recover the REEs is one possible solution to provide raw materials for the permanent magnet industry while minimising electronic device waste. Pyrometallurgical and hydrometallurgical metal extraction processes are commonly used for REE recovery. These two methods are excellent for REE recovery and relatively easy to conduct, allowing pyrometallurgical and hydrometallurgical methods to be adopted on industrial scale to benefit the availability of raw materials for the neodymium-iron-boron magnet industry.