Heavy lifting

Scientists at The University of Nottingham have successfully levitated diamond and some of the heaviest elements, including lead and platinum.

Using liquid oxygen, the main component in many rocket fuels, to increase the buoyancy created by a specially designed superconducting magnet, they could now, in theory, levitate an object with a density 15 times larger than that of osmium, the heaviest metal known in nature.

The science behind the research could be used to develop a variety of potential applications, especially in the mining and pharmaceutical industries.

Writing in the New Journal of Physics, the team led by Professor Laurence Eaves and Professor Peter King, in the University’s School of Physics and Astronomy, describes how mixtures of oxygen and nitrogen in liquid and gaseous states provide sufficient buoyancy to levitate a wide range of objects, including diamonds, a £1 coin and heavy metals such as gold, silver, lead and platinum.

Some materials, called diamagnetic, tend to become magnetised in a direction opposite to the magnetic field being applied to them. Magnetic levitation occurs when the force on such an object is strong enough to balance the weight of the object itself. If the object is immersed in a fluid such as a gaseous oxygen, the levitation can be enhanced by the effect of buoyancy caused by the ‘magneto-Archimedes’ effect.

Liquid oxygen is highly combustible and potentially dangerous to work with. However, it makes it much easier to float dense objects using commercially available magnets because the inherent magnetism of each molecule of oxygen boosts the buoyancy effect. This allows the levitation of objects as heavy as gold with relatively low-power magnets.

Photo courtesy of the Institute of Physics

Professors Eaves and King and their co-workers have now investigated the use of a safer mixture of liquid nitrogen and oxygen, and found the optimum mixture for floating heavy objects in safety, making commercial applications of this technology possible. For example, in mining for precious stones such as diamonds, a method for accurately filtering the precious gems from the surrounding rock and soil would be desirable.

Professor King said: “You can use this technology to accurately sort minerals. Under vibration you throw crushed ore into the air and in the magnet the different components experience different effective gravity. They therefore tend to land at different times and after a short while the vibration sorts them into bands according to their density. The method can discriminate between components with very small differences in density enabling you to extract the precious parts you require.”

Their research lab at University Park is also the only facility in the UK specialising in zero-gravity experiments and is currently being used by various research groups, including one studying how plants germinate and grow in zero-gravity conditions, essential knowledge for long-haul space flights.