Introduction
Among all kinds of materials discovered by material scientists, none has as significant an enabling effect on our daily lives as permanent magnets. They are inconspicuous but oh so vital in the functioning of hundreds of technologies across basic consumer electronics up to industrial equipment. But what are these permanent magnets really, and how do they form? Please welcome the practical and virtual guide to the fascinating life of our permanent magnet from its creation till the present day.
What are permanent magnets?
Permanent magnetic are materials that continuously exhibit a magnetic field on their own without the application of any power. Unlike temporary magnets that become demagnetized once the magnetizing force is withdrawn, the setup used in this experiment survives numerous measures of permanent magnets that keep their attractive force for a rather long time. This unique feature makes them very useful in many applications in different fields of endeavor.
Brief history of magnetism
Magnetism has existed for thousands of years – the first people observed natural magnetic material, lodestone. Many ancient Greek, Chinese, and Middle Eastern cultures were intrigued by the rocks that draw iron. Nonetheless, the long story of magnet and magnetic materials did not commence until the nineteenth century and then attempts were made to understand magnetism and create the first artificial permanent magnetic bodies.
The Birth of a Permanent Magnet
If we are to understand and fully realize the permanent magnet's life story, that is an excellent place to start. The birth of a permanent magnet can be a natural phenomenon or a result of man-made effort, but the basic principles of any physical and chemical science are followed in its creation.
Natural formation
Permanent magnets occur naturally in geological processes, and it takes millions of years for the phenomenon to occur. The best-known universally acknowledged ferrimagnetic mineral is magnetite, available in numerous rock structures. Magnetism is produced by the spinning molten core of the Earth and surrounding material; this force causes specified classes of iron-bearing stones in the Earth's crust to become charged. As time passes, the minerals change shape in the magnetic domains, thus becoming naturally induced permanent magnets.
Manufacturing process
Although permanent magnets naturally occur, most of the magnets used today are man-made via carefully designed methods. Now, let us discuss the main activities of making permanent magnets come to life.
Raw materials
It starts with the choice of suitable materials for the transformation process in the enterprise. Permanent magnets of various kinds are made of different chemical elements with multiple compositions. For instance, ferrite magnets are produced by coercive and antiferromagnetic material, iron oxide with additives of barium or strontium, and neodymium magnets created by Neodymium, iron, and boron. The type of material used defines the characteristics of the magnet and how it will perform in its intended setting.
Aligning magnetic domains
After preparing the raw materials the manners in which the domains of the material are aligned becomes vital. Magnetic domains are arbitrary areas in the mass of the material where numerous groups of atoms exhibit aligned magnetic moments in the same axis. Consequently, in its unaligned state, these domains randomly lay in all directions and thus the overall magnetic field is null.
To achieve this, manufacturers apply several methods to align these domains in a way that forms a permanent magnet. One standard method is to place the material in a condition where it can be shaped easily, for instance, by heating it to a specific temperature and then exposing it to a strong external magnetic field. When the material cools down or polymerizes, the oriented domains are then 'frozen' permanently, giving the desired magnetic structure.
Magnetization techniques
The fifth step of creating a permanent magnet is called magnetization. This involves taking the aligned material through an even stronger magnetic field normally provided by electromagnets. This high field strength leads to the improved orientation of the magnetic domains to one another to produce the maximum magnetization and direction of the magnet.
The method for putting the magnetic domains in a desired orientation will vary based on the properties that one wants to achieve for the final magnet. For example, specific uses need the forces acting over the volume to be homogenous; in other cases, it may be advantageous to have specific shapes of field.
Types of Permanent Magnets
With the improvement of technology, there are many different types of permanent magnets in the world that are used in different fields. Both types have different properties and characteristics that qualify them for particular uses. So, let's take a closer look at the most widely used types of permanent magnets in the present-day world.
Ferrite magnets
Ferrite magnets, commonly referred to as ceramic magnets, are among the most common forms of permanent magnets. They are formed with iron oxide combined with barium or strontium carbonate. Ferrite magnets are cheap, highly resistant to corrosion, and can readily withstand high and low temperatures. Their magnetic strength is not as high as some other types; they are cheap and durable and find usefulness in AC motors, speakers, magnetic sorting machines, and many more.
Alnico magnets
Alnico magnets are named after the base composition of aluminum, which is mixed with nickel and cobalt and mainly contains Iron. As stated, these magnets are among the first high-performance permanent magnets that were invented at the beginning of the twentieth century. The quality of Alnico magnets is that they have great properties in terms of temperature and can retain magnetism up to high temperatures. It is applied in sensors, pickups of guitars, specific electrical motors, etc.
Samarium-cobalt magnets
SmCo magnets are rare earth magnets with high magnetic properties now in use. These materials are characterized with high magnetic properties and good thermal and chemical stability. Permanent magnets used in SmCo can operate at high temperatures, up to 300 ° C, so they are applicable for aerospace applications, military, and industrial. However, owing to the high cost of cobalt, the batteries are expensive and thus not commonly used.
Neodymium magnets
NdFeB or neodymium magnets are the most powerful permanent magnets that exist in the market at present. NdFeB magnets are made from Neodymium, Iron, and Boron elements and give the highest field strength for the given size of the magnet. This continues to provide a higher strength-to-weight ratio, which has transformed many industries, including miniaturization of electronic electric motors. Neodymium magnets are used in the manufacturing of hard disk drives in computers, wind power turbines, MRI invents, and many more.
Properties and Characteristics
Before analyzing some scenarios of the use and advertisement of permanent magnets, we need to understand the properties and characteristics of the magnets. They dictate the overall performance of a magnet in this or that application and or operating conditions.
Magnetic field strength
The strength of a magnetic field, expressed in Tesla(T) or Gauss (G), tells us how strong a magnet is. This property is essential in establishing the nature of the magnet's interaction with other magnetic substances. For example, neodymium magnets can generate a field of up to 1.4 tesla, while ferrite materials can only generate up to 0.4 tesla.
Coercivity
Coercivity is the degree to which a magnet material is resistant to demagnetization. It denotes the level at which the strength of the magnetic field is necessary to demagnetize the magnet. Permanent magnets with high coercive force, such as neodymium and samarium cobalt magnets, can withstand more demagnetization from external magnetic fields or mechanical shock loads.
Temperature sensitivity
Temperature is one factor among several that can have a significant impact on the behavior and properties of permanent magnets; a temperature change can significantly affect how well permanent magnets perform. The coercive force also varies with the type of magnet and is always coupled with an operational temperature range. Out of this range, the magnet may 'lose' its magnetic pull for a temporary period or may even fail to regain it back at all. For instance, neodymium magnets change their properties when exposed to high temperatures; above 80°C, the magnets will lose their magnetic properties, while samarium cobalt magnets have much higher operating temperatures and do not demagnetize easily.
Corrosion resistance
The coils based on the magnets should have high or some amount of corrosion proof, this is again required for the magnets that are used in tough or outdoor conditions. Magnets made of ferrite are especially good at this job, as they are able to resist corrosive attack or oxidation. However, neodymium magnets are comparatively more sensitive to corrosion and usually, need a protective layer to protect them in severe operating environments.
Applications in Various Industries
The use of permanent magnets in the design of many products has been possible due to their unique characteristics. Starting with essential household appliances and ending with scientific equipment, those remarkable components are indispensable nowadays. It is necessary to look at the most critical areas of application of permanent magnets in different industries.
Electronics and technology
In the area of electronics, it is tough to find electronic devices that do not use permanent magnets. They are used in the construction of speakers and headphones, which work together with electromagnets for the generation of sound. There is always the use of powerful neodymium magnets in the hard drives of computers to read data from magnetic disks and write data to these disks. It ranges from holding the cases of smartphones and tablets to putting the gadgets to sleep modes using small magnets.
Automotive sector
The automotive industry has adopted the use of permanent magnets in automobiles for enhanced performance and efficiency. Electric and hybrid vehicles employ permanent magnet motion power vehicle engines due to the dense power they deliver. They are also used in the sensors in every modern car, for instance, checking on the speed of the wheels or the performance of the engine. Traditional internal combustion engines, too, get some or the other use of magnets in alternators and starter motors.
Medical field
Permanent magnets have revolutionized medical imaging and treatment technologies. Magnetic Resonance Imaging (MRI) machines use mighty magnets to generate detailed images of the human body. Smaller magnets are used in various medical devices, such as hearing aids and pacemakers. In dentistry, magnets are employed in prosthodontics and orthodontics to secure dentures and assist with tooth movement.
Renewable energy
The renewable energy sector, particularly wind power, has seen significant advancements thanks to permanent magnets. Wind turbine generators often use neodymium magnets to convert mechanical energy into electricity more efficiently than traditional induction generators. This has allowed for the development of more giant, more powerful wind turbines capable of generating substantial amounts of clean energy.
Aerospace industry
In aerospace applications, where weight and performance are critical factors, permanent magnets play a vital role. They are used in various aircraft systems, including flight controls, fuel pumps, and cabin pressurization. Satellites and spacecraft also rely on magnets for attitude control, power generation, and scientific instruments.
The Environmental Impact of Permanent Magnets
While permanent magnets contribute significantly to technological advancements and energy efficiency, their production and disposal can have environmental implications. As we continue to rely on these powerful components, it's crucial to consider their full lifecycle impact and work towards more sustainable practices.
Mining and extraction
The production of permanent magnets, especially rare-earth magnets like neodymium, begins with the mining and extraction of raw materials. This process can have significant environmental consequences, including habitat disruption, soil erosion, and potential water pollution. The extraction of rare earth elements, in particular, has been associated with environmental concerns due to the use of harsh chemicals and the generation of toxic waste.
Manufacturing processes
The manufacturing of permanent magnets involves energy-intensive processes, including melting, casting, and sintering at high temperatures. These processes contribute to carbon emissions and energy consumption. Additionally, the use of various chemicals in the production process can lead to air and water pollution if not properly managed.
Recycling and sustainability efforts
As awareness of the environmental impact of permanent magnets grows, there is an increasing focus on recycling and sustainable production methods. Recycling permanent magnets can help reduce the need for new raw material extraction and minimize waste. However, the recycling process for rare-earth magnets is complex and still in its early stages of development.
Efforts are underway to develop more environmentally friendly manufacturing processes and to find alternative materials that can provide similar magnetic properties with less environmental impact. Some researchers are exploring ways to create strong magnets using more abundant elements, potentially reducing the reliance on rare earth minerals.
Conclusion
Permanent magnets, born from nature and refined by human ingenuity, have evolved into indispensable components in various applications. From raw materials to powering electric vehicles, medical breakthroughs, and renewable energy solutions, they demonstrate the potential of materials science. As technology and sustainability continue to advance, the evolution of permanent magnets will play a crucial role in shaping our future.
Permanent magnets, a silent workhorse of the modern age, are being researched for new materials, improved manufacturing processes, and innovative applications. Their life story, from creation to application, promises exciting developments and possibilities for generations to come, showcasing the profound impact of scientific principles on our lives and the world around us.