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magment

Magment

Stan Zurek, Magment , Encyclopedia-Magnetica.com, {accessed 2019-03-19}

Magment (Magnetic cement) - a trade name used by the company Magment UG for a type of composite magnetic material comprising magnetic particles embedded in cement (concrete) or asphalt.1)2) There is a wider class of materials which can be categorised as magnetisable concrete.

Toroidal core made from Magment MC40 Copyright © Encyclopedia Magnetica

Internal structure and composition

Scrap ferrite transformers can be used a magnetic filler in magment scrap_ferrite_transformers_magment.jpg Copyright © Encyclopedia Magnetica

Magment is a composite material comprising two main fractions of magnetic particles. The larger fragments can be up to around 8 mm (like “gravel”) and the smaller around 2 mm (like “sand”). 3)4)

The magnetisable particles comprise up to 95% of weight, and provide appropriate magnetic properties. The cement (or asphalt) is a bonding agent.

The magnetic particles can be used from scrapped electronic parts, for example ferrite cores rejected during production or sorted electronic waste5). Ferrite material is especially useful because it provides: reasonable permeability, high corrosion resistance (it is already a form of oxide), high electrical resistivity, low hysteresis loss, good stability of properties versus time, and it is fairly inexpensive to obtain or produce various particle sizes.6)

According to the manufacturer, a suitable typical composition of the magnetic particles would be as follows:7)

Construction of magnetic components

Complex geometry like pot core can be made easily with magment pot_core_magment_magnetica.jpg Copyright © Encyclopedia Magnetica

The material is available from the manufacturer in a form of dry aggregate, pre-mixed with the specific ratio of magnetic particles and cement (similar to ready mixed concrete). Water must be added with a required ratio and mixed for instance in an ordinary cement mixer. The available processing time is around 30 min (before setting).8)

Steel mould tool for toroidal cores Copyright © Encyclopedia Magnetica

The inductive component is made first by designing the magnetic circuit. The windings (primary, secondary, etc.) can be wound first and placed in the appropriate form (mould) for casting. The wet concrete can the poured around the windings.

Sufficient density and quality of such magnetic concrete can be achieved without additional pressure or vibration.

The mould can be taken off after typically less than 1 hour and the concrete is strong enough to be walked on after 6 hours. Full strength is achieved after similar time as for ordinary concrete (28 days).9)

Applications

Inductor made with magment magment_inductor.jpg Copyright © Encyclopedia Magnetica

According to the manufacturer, magment can be used for many applications, for example:

Tests up to 30 kW stationary systems were demonstrated for wireless car charging.10)

Almost unlimited magnetic component size can be produced with the concrete-like processing.

Magment can be also used for making low-maintenance, hard-wearing surfaces (anti-vandalism).

Technical specification

Technical specification of Magment MC4011)
parameter conditions value
initial permeability at 25°C typically 40 ±10% (up to 70)
Curie temperature > 210°C
resistivity DC 20 Ω·m
density 3750 kg/m³
relative core loss 50 kHz, 100 mT 300 kW/m³
specific heat 700 J/(kg·K)
thermal conductivity 3 W/(m·K)
Young's modulus 25 000 MPa
compressive strength 20 MPa
tensile strength 2 MPa
B-H curve of Magment MC40 Copyright © Encyclopedia Magnetica
Specific core loss of Magment MC40 Copyright © Encyclopedia Magnetica
DC bias strength for Magment MC40 Copyright © Encyclopedia Magnetica
Inductance vs. DC bias for a typical 55 μH magment inductor Copyright © Encyclopedia Magnetica
Stored energy for 55 μH magment inductor Copyright © Encyclopedia Magnetica

Patents and awards

Silver Award certificate magment_silver_award_2016.jpg Copyright © Encyclopedia Magnetica

There are several patents related to the magnetic cement technology, for example:

In 2016 the company Magment UG won Silver Technology Award for “Magnetizable Concretes'' at the Materialica trade show.

Similarity to powder cores

Magment is a composite material, with certain amount of non-magnetic filling between the magnetic particles. Therefore, from a macroscopic viewpoint it behaves similarly to so called powder cores, whose permeability is a function of ratio of the magnetic content to the overall volume.

Effective magnetic permeability of such structure is significantly lower than that of the input magnetic material, because of the air gap between the particles.

The distributed air gap is capable of storing considerable amount of energy, which is why such materials are especially useful for power chokes and inductors typically used in high-power switch-mode converters and power supplies.

Because of the energy storage capability such materials are less useful for transformers. However, for devices with large physical dimensions such materials can still provide much better performance than the alternative solution - which would be normally some non-magnetic structure (like an ordinary concrete).

Therefore, with appropriate design magnetic shielding can be also achieved with such materials.

See also

* http://magment.de - official website

References

magment.txt · Last modified: 2017/03/09 14:01 by Stan Zurek

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