Nov. 15, 23
Spark Plasma Sintering (SPS) is a sintering technique that uses uniaxial forces and pulsed DC currents to solidify powders at high rates at low atmospheric pressure. This direct heating allows the application of very high heating and cooling rates, allowing the inherent properties of the nano-powders to be maintained in their fully dense products.
HAOYUE is a professional manufacturer of sintering furnaces and atmosphere furnaces and this article will introduce you to some of the materials suitable for SPS. We concentrate here on some relevant applications, mainly hard materials.
One of the most immediate applications for SPS is the sintering of high melting point materials such as titanium nitride. The bulk form of this ceramic has received little attention due to the poor sintering properties and inherent brittleness. Studies have shown that pure titanium nitride can be sintered to high densities by using very high pressures on the order of 1-5 GPa.
Similarly, transition metal carbide nitrides are becoming increasingly important materials because of their excellent properties in the fields of superhardness, tribology, superconductivity, and electrical and thermal conductivity. Titanium carbide nitride is the most widely used material because it is the main component of commercial cermets. Because of the high temperatures required to sinter this material, SPS has become a useful technique and has been used to densify titanium carbide powders at relatively low temperatures.
Powder Metallgury S3 Spark Plasma Sintering System
As in the previous case, grain growth is an important issue in determining the mechanical properties of transparent ceramics. Fine-grained transparent Al2O3 ceramics have recently attracted a lot of attention due to their excellent mechanical and optical properties. Conventional sintering requires very high temperatures and long holding times, which can lead to insufficient mechanical properties. Recently it has been shown that one can sinter normal grade commercial powders to transparency by discharge plasma sintering. This effect is only effective under SPS vacuum conditions.
As a difficult to sinter ceramic, tetragonal zirconia polycrystalline (TZP) samples are usually opaque even after sintering at high temperatures. While porosity can be controlled by sintering conditions, it is still important that it keeps grain size as small as possible. Scientists believe that high pressure discharge plasma sintering (HP-SPS) is an extremely simple and effective way to obtain high IR transparent tetragonal ZrO2 compared to the pre-sintering plus HIP method.
Conventional sintering techniques (e.g., hot isostatic pressing) require processing the material at temperatures high enough to exceed the dissociation temperature of the radioisotope oxide, which leads to the formation of partially non-metallic ceramic regions. Studies have shown that SPS is also capable of densifying materials at lower temperatures and in less time than conventional processes. Spark plasma sintering minimizes grain growth and is therefore well suited for materials requiring top mechanical properties.
Materials with extremely low coefficient of thermal expansion (CTE) are of interest for many different applications, from cookware to aerospace applications. It is known that sintering these materials to obtain dense ceramic bodies is complex due to their narrow sintering temperature range and tendency to form glassy phases. As a result, the resulting ceramic materials usually have low mechanical properties and Young's modulus through conventional pressureless natural sintering methods.
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