My friend and colleague Rex Harris, who has died aged 82, was known for his research on permanent magnetic materials, being among the first to recognise the value of hydrogen in materials processing. He was an activist scientist concerned to reduce global heating.

Born near Newport, Monmouthshire, he was the son of Emily Prosser, a domestic servant, later recognised for her work for charity and the Women’s Institute, and Frederick Harris, who had been a miner but, sponsored by the NUM, went on to become a road engineer.

Rex went to Larkfield grammar school in Chepstow, then studied metallurgy at the University of Birmingham, where he remained for the rest of his working life.

He met Vera Hipkiss, a student nurse, at a university party in 1963 and married her two years later. Graduating in 1960, he took a PhD in 1964, and subsequently became professor of metallurgy (1988) and department head (1996-2001). He held visiting professorships at IFW Dresden and the Jožef Stefan Institute (Slovenia).

His research focused on the alloying behaviour of rare earth elements and the interaction of hydrogen with metals – key aspects of today’s green energy and transport revolutions. In the 1970s he toured the Birmingham campus on a hydrogen moped. More recently, his hydrogen-powered canal boat showcased sustainable electrical transport. He once said he wished he was “20 years younger, as all my professional life I’ve been waiting for the hydrogen bus”.

He is best known for his work on permanent magnetic materials, and published more than 500 papers on the subject. In the 80s Rex and colleagues developed a method to reduce magnetic alloys of neodymium, iron and boron (NdFeB) into fine powders using hydrogen in a process known as hydrogen decrepitation. This process was subsequently commercialised worldwide for NdFeB magnet production.

Recently, an adaptation of the process has enabled recycling of NdFeB magnets recovered from scrap, using 80% less energy to create magnets when compared with virgin sources, and avoiding all effluent issues.

In 1994 Rex was elected a fellow of the Royal Academy of Engineering. His brother Jack had been made a fellow of the Royal Academy in 1987 and they became the only two brothers to have received this honour.

Rex had deep commitments to teaching, research, friends and family. Many of his 150 research students occupy prominent positions in magnet development organisations worldwide. True to his working-class roots he championed human rights, remaining a lifelong Labour party supporter. His Welsh heritage gave him a love of folk music and singing, and he was a deft performer on the harmonica, which was always present in his top jacket pocket.

Vera died in 2021 after a short illness. Rex is survived by their daughter, Margaret, and two sons, David and Christopher.