The sintered magnet concept was developed in 1957 by Professor Peter Eisenman and was first used in the construction of photovoltaic panels in Germany and the United States. The sintered magnet concept is based on the natural chemical reaction that forms a compound when combining an element with a non-magnetical nucleus. With sintered technology, the properties of the low-diy center material are changed significantly by the temperature-dependent change in processing temperature which produced a peak in the thermal conductivity at 880 C with a subsequent cooling down in thermal conductivity of below 810 C resulting in a sintered powder with higher thermal conductivity. The new sintered material also exhibits high compressive strength at room temperature.
The use of this sintered ndfeb coating was first used to coat steel foils with the intention of improving strength and fatigue life. The coating was found to have superior wear resistance, with the reduction of both heat and mechanical stresses for applications requiring high compressive loads. It was later discovered that the combined effect of the two properties led to the improvement in the electrical output of the metal foils, with the ability to generate a large current capacity per unit area of the coating. The ability to increase the compressive force as required for load bearing, coupled with the increase in the size of the metal plates would enable the development of much larger structures with much higher tensile strengths than could previously be achieved. Other industries soon applied the concept to coatings other metals with similar results.
The application of this unique sintered coating is also useful in the manufacturing industry where the application and function of permanent magnets are critical to the performance of many processes. In addition to the benefits already described, the sintered coating also provides additional strength and durability compared to standard non-magnetic cladding. The use of sintered materials offers a number of advantages over other manufacturing methods. For example, sintered foils do not need the use of any flux. Furthermore, they can offer a 50% improvement in the level of conductivity compared to non-magnetized foil laminates. This means that using sintered materials in place of foil laminates in high load applications such as vibratory strain relief grinders and vibratory sander will enable these machines to operate at optimum efficiencies for significantly longer periods of time.
Due to the unique electrical and magnetic properties of sintered materials, the sintered metal component in these applications has the ability to support a much larger current capacity than non-sintered components. In particular, sintered metal foils with a thickness of about 0.15 to offer a positive current capability which enables these machines to run continuously at high levels of load. In addition, because the current carrying capacity of sintered sheets is much higher, these components offer the unique ability to handle higher poundage and thicker gauge materials.
The application of sintered components requires a different type of coating to achieve the beneficial mechanical properties. A two-part application process known as ndfeb magnets and grain-metal electroplating can be used. In the ndfeb magnets process, the flat magnet form of a sheet metal is coated with an abrasive material which leaves a grainy finish on the flat magnet sheet. The sintered metal material may also contain dyes which are coated on both the flat magnet sheet and the flat metal surface. The grains in the ndfeb magnets can be any size, but typically they are a quarter to half a millimeter in width.
While the process described above is considered relatively low maintenance, it is important to note that mechanical oils and dust must be removed from the sintered metal components after use. If these components are not properly maintained, there is a possibility that the mechanical oils or other treatments will dry out and fail prematurely. Spark plasma sintering is also considered low maintenance, but because sintered metals must have sufficient surface area to accept the sintered compound, it is necessary to apply the sintered compound over a long period of time. If the sintered metal components are exposed to moisture, cracks can develop.
These two technologies provide an alternate method to achieve high induced friction and increased strength with the same mechanical properties. Unlike sintered materials, microstructure in heat treatment allows for a significant increase in the formation of large molecular bridges and nanometer sized grains. This additional layer provides a much higher level of tensile strength than any other known technology. Heat treatment is also capable of providing a significant increase in the generation of high levels of mechanical energy.
Microstructure-based engineered magnets may provide a practical alternative to the current sintered nd-fe-b magnetic alignment factor products on the market. Because the particles in the engineered magnet material are so small, the mechanical properties are greatly improved. The particles formed are much larger, which allows the engineered particles to form hollow metal shells with nearly micron sized grains. These hollows are then filled with sintered nd-Fe-b metal, which greatly improves both the tensile strength and mechanical properties.