Tag Archives: Magnets

Phase Change Material with Magnets and Rubber

A research team from the University of Massachusetts is creating a phase change material made of magnets and rubber. They specifically place the magnets for predictable properties. Embedding magnets within the elastic material and coding their poles with different colors allows the team to orient the magnets in different directions. This changes the response of the material so that it can both absorb and release energy.

The magnets and rubber combination can not only drive high-power motion but can also quickly dampen impact-loading events. The material has several promising applications. It boosts the performance of robots, and improves helmets and other protective equipment, enabling them to dissipate energy quickly. The team uses laser cutters to make snug receptacles in the rubber for placing the 3 mm wide magnets, which are commonly available in stores.

Stretching the material causes a phase change, a physical property. By stretching it far enough, it is possible to reach a phase transition, where the material releases substantial potential energy. The team claims that the energy released can power a vehicle.

According to the researchers, the phase transition can store additional energy beyond that going into it mechanically. Therefore, a drone can easily recover this additional energy that the material releases. The excess energy gives the drone an extra boost.

The magnets assist in the phase shift, and this substantially amplifies the quantity of energy the material is releasing or absorbing. The team has discovered a way to use the magnets to fine-tune this phase shift.

The elastic properties of the rubber and the geometry of the holes determine the specific placement of the magnets. The team can tailor the specific response by controlling the elastic properties of the rubber strip, the hole geometry, the magnetic strength, and their placement positions. They claim the phase shift is both predictable and repeatable. They claim they can control the performance of the metamaterial, such as absorbing the energy caused by a large impact or releasing huge amounts of energy for an explosive movement. The team claims this metamaterial has helped them understand high-speed, high-acceleration movements.

The team has taken inspiration from similar fast-moving organisms in nature. This includes the trap-jaw ant and the mantis shrimp. Nature combines several fields to influence the way animals to store energy, including mechanically, chemically, or elastically.

To understand the concept that nature uses, the team combined magnetic fields with elastic forces. They combined them in synthetic materials for use in drones or robots. They claim they can tune the material to be efficient in the use of energy, such as for jumping robots that can transverse various obstacles.

Stretching the metamaterial makes it act just as a regular rubber band or a regular spring would. However, stretching it to a large extent makes the material go through a phase change, allowing it to store more energy than what it is receiving from the stretching. Releasing the material causes it to release the stored energy. A drone can use this extra energy for a boost.

A New Magnet for Electric Cars

The advent of electric cars is spawning innovations in almost every technology field including batteries, motors, wires, PCBs, electronics, and many more. Electric cars require powerful and efficient motors, and for that, magnets used in the motors must be stronger than usual.

Toyota Motor Corporation has developed a new magnet for electric motors, and they have reduced by 50% the use of critical rare-earth elements they were using so far. As the number of electric cars is set to increase rapidly in the future, Toyota is expecting this heat-resistant magnet, which uses less neodymium, will find increasing use in the electrified vehicles.

Neodymium, terbium, and dysprosium are rare-earth elements that industries popularly use when manufacturing strong magnets. Although the magnets made from these elements can operate in high-temperature conditions, they are expensive. Toyota has replaced a proportion of the neodymium in these magnets with lanthanum and cerium, as these are low-cost rare earth elements.

Manufacturers of magnets use neodymium as it provides their products with high heat resistance and coercivity—the ability to maintain magnetism at high temperatures. However, simply using less neodymium and using lanthanum and cerium instead would cause the motor to underperform. Therefore, Toyota had to adopt newer technologies to overcome the deterioration in motor performance. The result was a successful magnet with half the amount of neodymium, but equivalent levels of heat resistance and coercivity.

Toyota expects this new magnet to maintain a balance between the supply and demand of resources especially that of the valuable rare earth elements, while being useful in the expanding world of electric automobiles and robotics. Toyota is continuing in its efforts to enhance the performance further, and evaluate the use of the magnet in a greater number of products. They are also aiming to accelerate the development of technologies for mass-producing the magnets, so that different products can adopt them easily, including robots and vehicles.

Use of rare earth elements in magnets enables them to maintain magnetism even at high temperatures. For this, they require about 30% of the elements in the magnets to be of the rare earth types.

Adding neodymium in magnets makes them more powerful, but automotive applications require them to operate at high temperatures. Although adding terbium and dysprosium improves the high-temperature coercivity, it also makes the magnets more expensive. Toyota’s efforts at creating cheaper magnets with reduced use of neodymium have finally paid off.

Although at present, the production volumes of neodymium are adequate there are concerns that as the development of electrified vehicles picks up, the demand will outstrip supply. This is may become a bigger concern as electrified vehicles include hybrid electric as well as battery powered electric vehicles of all types are likely to become more popular in the future.

Toshiba uses three new technologies in their magnets to help maintain coercivity at high temperatures, even with reduced neodymium. For this, they had to refine the grains in the magnet, use two-layers of high-performance grain surfaces, and use an alloy with a specific ratio of lanthanum and cerium.