For the first time in the world, a group of young scientists from NUST MISIS have managed to synthesize a unique MAX phase with the inclusion of elements atypical for this class of substances — vanadium and iron. The innovative composition will provide the MAX phase with additional magnetic properties. The resulting hybrid material will be used in cutting-edge spintronics and micro-electronics.
MAX phase is a new, predicted, and experimentally studied artificial class of heat-resistant materials (they have been around since 2013). They possess an unusual combination of chemical, physical, electrical, and mechanical properties, as well as a special layered structure and a unique combination of the most popular properties of metal and ceramics. They can be described by the general formula Mn+1AXn, where M is a transition metal, A is an element of the IIIA or IVA subgroups of the periodic table, and X is carbon or nitrogen.
The specific set of properties these materials have is due to the unique atomic-layered structure of their crystal lattice. MAX phases have amazing properties that combine the advantages of metals and ceramics: they demonstrate so-called elastic stiffness, chemical resistance, thermal & electrical conductivity, low specific gravity, a high elasticity modulus, a low coefficient of thermal expansion, high heat resistance, and flame resistance.
Better yet, these materials are relatively soft and most of them are easy to handle, while still maintaining resistance to thermal shock and damage. Some are even resistant to fatigue failure and oxidation. At room temperature, they can be compressed to 1hPa and are able to fully recover from the removal of a load, scattering about 25% of the mechanical energy on the principal of the card deck’s compression. At higher temperatures, these materials typically shift from brittle to plastic in terms of behavior.
The study of MAX phases is just getting started, and there isn’t yet a full understanding of the general magnetic characteristics of these atomic-layered materials. However, scientists know that the magnetic properties of the materials are reported by late transition metals. The synthesis of MAX-phases with the inclusion of these elements is an especially difficult task however, as these elements are not composed of structurally similar materials.
“Our research team has managed to obtain magnetic MAX-phase with iron, which is a late
d-element,for the first time in the world. At the same time, the iron solubility was 10%, before it was indicated in [published] literature that the possibility of dissolving it was only 03.-0.5%, which was within the experimental accuracy and didn’t inspire confidence. We have found the synthesis parameters which allow us to get stable magnetic MAX phases. Obtaining MAX phases with the inclusion of iron in their structure has become possible due to multiple attempts of synthesizing the material at various temperatures and time parameters of plasma-spark sintering, the simultaneous study of phase composition, structure, & the determination of the solubility limit, a detailed analysis of the experiment results, and the detection of the kinetics of the processes of sintering in complex carbide systems”, — noted Anna Poznyak, head of the project and researcher at the NUST MISIS Department of Functional Nanosystems and High-Temperature Materials.
The potential fields of application for magnetic MAX phases currently range from magnetic cooling to the latest spin-electronic devices and instruments.
The properties of these unique materials allow researchers to develop fundamentally new areas of use, for example, in technologies that include high-performance engines or damage-resistant thermal systems that increase fatigue resistance and stiffness retention in high temperatures. They can be used for the production of especially rigid and heat-resistant refractories, high-temperature heating elements (furnace spirals), and coatings for biocidal radiation-resistant electrical contacts, devices, and mechanisms in the nuclear industry.