Magnets and The Materials of Which They are Made
So Many Different Shapes Too!
Magnets are metals or rocks that generate a magnetic field around themselves. This invisible field attracts other magnets as well as some materials.
Magnets are an integral part of modern life. They're used in refrigerators, magnetic toys, and medical processes alike.
Alnico
Alnico magnets are a widely-used permanent magnet material in industrial applications due to their superior temperature stability and corrosion resistance. Not only that, but these magnets boast high magnetic force, which can be further strengthened through alloying with copper or titanium for increased strength. Furthermore, alnico magnets are much less expensive than rare earth or ceramic magnets due to their superior price-to-performance ratio.
Alnico magnets come in different shapes and sizes. These magnets may be constructed out of aluminum, nickel, or cobalt from round to square, rectangular, or hexagonal.
Magnets are typically ground to exact specifications and tested for performance and quality control, guaranteeing they perform as designed and manufactured correctly. The manufacturer can also determine if additional corrosion protection or painting is needed on the magnets to maximize lifespan.
Magnets may be coated for identification and aesthetic appeal. They may also be protected with zinc or nickel coatings to increase their durability in harsh environments.
These alnico magnets are created through the heat treatment process known as sintering, which involves heating and pressure to consolidate loose pulverized material into a solid mass. Once formed, they can be cast, molded, or machined into the desired shape and configuration.
This production method is ideal for small Alnico magnets, as it easily mixes and combines aluminum, iron, nickel, and cobalt. Furthermore, this is an efficient method since there's no need for coating after production.
Another method for manufacturing Alnico magnets is casting, which uses a mixture of aluminum, nickel, and cobalt to produce magnets with greater strength than those created through sintering. However, this process requires more effort when making large or complex shapes since the molten mixture must be cast into a mold.
Alnico magnets, referred to as "Mishima's magnets," were first developed in the 1920s by Tokushichi Mishima and quickly gained notoriety for their superior energy product, coercivity, and coercivity enhancement compared to steel magnets at that time. At their peak performance, these early Alnico alloys boasted energy products of 1 MGOe (12 kJ/m3) and coercive forces of 400 Oe (32 kA/m).
Ceramic
Ceramic magnets are one of the most cost-effective and versatile on the market, known for their robust and durable qualities. These magnets can be used in various applications, from refrigerators to DIY projects and beyond.
Magnets come in different shapes, such as discs, rings, blocks, and cylinders. They are primarily composed of iron oxide and strontium carbonate; their charcoal gray color makes them highly durable and resistant to damage or breakage.
Magnets are typically manufactured using powder technology techniques, which involve mixing two materials and heating them to temperatures of 1800-2000 degrees Fahrenheit. At this high temperature, the compounds undergo chemical conversion to form ferrite. Wet milling then reduces this ferrite material to a very fine particle size using the magnetite material.
After this step, the material is dried and formed into different shapes by either dry pressing or die injection. Once heated to approximately 2,000deg F (2,000deg C), this step is known as sintering. It is similar to the kilning process in ceramic pottery production.
This process can take up to 36 hours. Once complete, the ceramic magnets are dense and ready for grinding to customer specifications. This expensive and time-consuming step can be accomplished using diamond-coated machining tools.
Sintering can be used on both permanent and soft ceramic magnets. While not as strong as permanent-type ceramic magnets, soft magnets retain their magnetic properties for extended periods - often used in choke coils or intermediate transformers.
Magnets, in particular, may be more sensitive to heat and vulnerable to demagnetization if exposed to extreme temperatures. This poses a significant concern in specific applications, such as microwave communication.
Magnets, in general, are more vulnerable to corrosion than other types of magnets and must be operated under certain conditions to maintain their strength. For instance, heating an interest past its maximum operating temperature (Tmax) will eventually result in demagnetization, which cannot be recovered once cooled.
Neodymium
Neodymium (Nd), atomic number 60, is a soft silvery-white metal that tarnishes quickly when exposed to air. It must be stored under an inert atmosphere or sealed inside a plastic container to avoid this problem. Nd is essential in neodymium, iron, and boron alloys used for permanent magnets.
In 1885, Austrian chemist Carl Auer von Welsbach discovered diatomite from a mixture of rare-earth oxides called didymium. It can be found in significant amounts in monazite sand, bastnasite ores, and some igneous rocks.
Neptune, in addition to its strong magnetic properties, is essential for other purposes. For example, it's used in high-quality products like microphones, professional loudspeakers, in-ear headphones, and computer hard disks; plus, it's employed in MRI scanners for producing accurate images of human bodies without using radiation.
Due to its magnetic properties, neodymium magnets can be formed into various shapes, such as blocks, rings, arcs, discs, and spheres. They are permanently bonded to a piece of material like hard plastic before being heat-treated for strength and longevity.
Some neodymium magnets are bonded to other materials, such as copper and nickel, for applications where their range of uses would otherwise be limited. Furthermore, this produces smaller sizes than possible if molded from the pure metal.
Neodymium magnets have been developed that work at higher temperatures, such as those found in wind turbines. However, since their ferromagnetic properties start to fade at 80/176 oC/oF, you must select the correct grade of neodymium magnet for your application.
Nd3+ ions are another vital use of neodymium in colored glass production, giving it a reddish-purple or violet hue commonly found in color televisions, fluorescent lamps, and energy-saving lamps. Furthermore, Nd3+ ions help remove yellow sodium glare caused by flames in welding equipment.
Rare Earth
Neodymium magnets, or NdFeB or Neo magnets, are the most prevalent type of rare earth permanent magnet. These robust materials find applications in everything from electric vehicles to medical equipment.
At some point in the manufacturing process, Neodymium atoms are coated with iron oxide to enhance their magnetic properties and strengthen them against corrosion. Once they have been shaped, a magnetic field is applied to align their molecules.
Neodymium magnets possess anisotropy, or the property of aligning unpaired electrons in one direction, giving them higher magnetic energy than ferrite magnets due to their unusual ability to reorient their magnetization during production.
NdFeB magnets boast a high resistance to demagnetization, meaning they will remain magnetized even when exposed to other magnets or dropped. This property makes them ideal for applications involving prolonged use in extreme temperatures or corrosive environments.
Neodymium magnets are widely used in industrial applications due to their superior strength. Furthermore, neodymium magnets find applications in medical devices like magnetic resonance imaging and magnetic therapy.
They come in various shapes, such as discs, rings, and blocks. They're commonly used for sticking into drilled holes on metal surfaces or other uses like magnetic bearings.
Other popular shapes of rare earth magnets include rods, bars, and horseshoes. These magnets can be employed in meters as well as other high-temperature applications.
Another popular shape of neodymium magnets is ring-shaped magnets, which have a round shape with an indent in the center and can be attached to metal surfaces. These magnets can be positioned along a surface and mated to another magnet for precise alignment in applications whose strengths match.
Samarium cobalt is a widely-used rare earth magnet used in various applications. Although not as strong as neodymium magnets, they boast excellent corrosion resistance and the capacity to work over a more comprehensive temperature range - making them an excellent alternative to Alnico magnets when exposed to extreme temperatures such as those experienced in marine or automotive settings.