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High entropy silicide ceramics

2021-02-18

A High Entropy alloy (HEA) is an alloy containing five or more metallic elements, each with an atomic content of between 5% and 35%. It is also known as a multi-principal element alloy. Similar to high-entropy alloys, High Entropy Ceramics (HEC) are generally defined as ceramic materials with simple crystal structures (e.g., bore-centered cubic BCC, face-centered cubic FCC, and densely packed hexagonal HCP) consisting of five or more metallic elements and one nonmetallic element. The high entropy material contains a variety of randomly distributed elements, which makes it have a high entropy value. It has been pointed out that high entropy materials have excellent mechanical properties, thermophysical properties, radiation resistance and corrosion resistance.High entropy ceramic materials can be divided into high entropy oxide ceramics and high entropy non-oxide ceramics from the point of view of nonmetallic elements. In the high entropy non-oxide ceramics, high entropy borides, high entropy carbides and high entropy nitride compounds are mainly studied at present. In this work, a high entropy silicide synthesis is reported for the first time. Silicide ceramics have excellent high temperature oxidation resistance, electrical conductivity and thermal conductivity, etc., can be used as high temperature thermal protection materials, electrode materials, high temperature structural parts, high temperature heating elements, such as MoSi2, TSi2, NbSi2, HfSi2. Among them, MoSi2 is the most widely used, especially as a well-known high temperature heating element used in the air temperature can reach more than 1800 degrees Celsius.It is possible to further regulate the properties of silicide ceramics through high entropy, enrich the research content of high entropy ceramics, and promote the development and application of silicide materials has important significance. The high entropy silicide has a dense hexagonal crystal structure at room temperature, indicating that the Beta-MoSi2 phase, which is stable only at high temperature, can be stabilized to room temperature by high entropy. However, some zirconium elements combine with the oxygen impurity which is unavoidable in the material and form a small amount of zirconia heterophase, which provides research content for the subsequent composition design and process improvement. The hardness of the high entropy obtained silicide between the hardness of the one-component silicides, due to material hardness is influenced by many factors, such as porosity, grain size, impurity content and interface characteristics, only by the hardness of the existing test data can not simply is concluded that high entropy to improve silicide ceramic material hardness by conclusion, still need to combine the theoretical calculation and nano hardness measurement confirmed that further work is under way.

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