Physics

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Research Topic Summary.

Austenitic stainless steels, cobalt–chromium alloys, commercially pure titanium and its alloys have been widely used as biomaterials because of their very low cost as compared to other metallic materials, good corrosion resistant properties and adequate biocompatibility in the body environment. However, their low hardness level and poor tribological behavior in terms of wear resistance has been a major limitation to a wider application. In order to improve their surface hardness and tribological properties, it is generally admitted that the most convenient thermochemical processes that could be used are low temperature nitriding and/or carburizing. The origin of these improvements is that nitrogen or carbon diffusion process results in the formation of an expanded austenite layer without the formation of the undesirable stable nitride or carbide phases. Despite the numerous investigations, the structure and formation of expanded austenite phase have not yet been completely clarified. All existing models of nitrogen and carbon transport in austenite are limited to the continuum level and are not directly applicable to polycrystals, where lateral diffusion fluxes and grain-to-grain mechanical interaction cannot be excluded. Thus, the main question that will be addressed in the scope of this project, is the role of diffusion across grain boundaries on nitrogen and carbon transport in polycrystalline biomedical alloys. Next important aspect is related to the thermal stability of expanded austenite. Decomposition of expanded austenite, which is a thermally activated process, involves precipitation of chromium nitrides or chromium carbides. As a consequence, chromium is retracted from solid solution and the favorable corrosion properties of the biomedical alloys are lost. Therefore, the next issue that will be addressed within the framework of this project, is to analyze the mass transport processes and kinetics during annealing of the biomedical alloys.

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Research Topic Summary.

Graphene is a 2D nanocarbon material, carbon atomic hexagons monolayer. It is at the top of the significant interest due to the giant electron and hole mobility, charge carrier multiplication, flexibility, optical transparency, chemical inertness and other outstanding properties. One of the possible applications of the graphene is use of the graphene in Schottky contacts instead of the metal. Due to the very high mobilities the graphene can be used as a channel layer in field effect transistors and transistor based biosensors. Till now graphene was usually synthesized by chemical vapor deposition of the graphene on catalytic Cu, Ni, Co foils. Afterward, the long process of the graphene transfer onto the targeted semiconductor or dielectric substrates was used. It is a complex and time consuming procedure. Control of the graphene/semiconductor contact and graphene nanolayer properties are complicated in such a case. In present study graphene will be directly synthesized on the dielectric surface by plasma assisted processes. Effects of the graphene structure on characteristics of the sensors will be studied. The charge transfer and self-doping processes will be investigated. The relation between properties of the synthesized graphene layer and characteristics of the graphene-based sensors will be studied.

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Research Topic Summary.

Diamond-like carbon (DLC) film as an effective protective coating has been extensively studied for more than two decades, due to the outstanding properties such as low friction coefficient, high wear resistance or chemical inertness, biocompatibility and optical transparency. Doping metal elements (Zr or Cr) into diamond-like carbon (DLC) films can improve the mechanical and tribological properties, but the preparation and commercialized application of metal (Zr Cr) doped DLC films with well-defined structure and required mechanical and tribological properties are currently hindered by the non-comprehensive understanding of structural evolutions under different magnetron sputtering parameters, used metal types or concentration.

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Research Topic Summary.

The new millennium has begun to pay close attention to new materials. Many sensors, controlling devices that transform information and energy are already being successfully used. One class of such materials is inorganic complex metal oxides with so-called active dielectric properties. They are often referred to as "smart materials". It are substances which transform various physical effects (mechanical, thermal, radiative, light, electric or magnetic, etc.) into an electrical signal which can be recorded. In addition, these materials have the opposite effect - when exposed to an electric field, they change their state - ferroelectric, ferroelastic, electrostriction, pyroelectric, magnetoelectric, electro-optical, electrocaloric and other phenomena are observed. For a long time (about 20 years) in the world of science and technology, these materials have been emphasized as necessary for ferromagnetics or ferroelectrics. However, the first multiferroic material with ferroelectric and (albeit weak) ferromagnetic properties was synthesized in 2003, BiFeO3 (BFO). The combined effect of having both properties (ferroelectric and ferromagnetic at room temperature) was discovered only in 2014. Using ferromagnetic additional layers, a team of scientists from the United States developed a multilayer superlattice structure with magnetoelectric properties. These properties make it possible to look at these materials as a completely new type of memory cell, the magnetization (and direction) of which can only be changed by an electric field. Moreover, due to the residual magnetization effect, the storage of information in these memories will not require energy support. The proposed research on this topic will be carried out by synthesizing multiferroic magnetoelectric layers by reactive magnetron sputter deposition. Structures consisting of ferroelectric and ferromagnetic layers will be formed and the magnetoelectric effect will be investigated.

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Research Topic Summary.

In this work, the surface of metal oxide nanoparticles (ZnO, CuO) will be functionalized (with nanoparticles, graphene, maxene) in order to obtain room temperature light-activated sensors. Their physical properties, such as the change of the barrier layer due to exposure to light and surface adsorption, will be investigated. Semiconducting metal oxide nanowires are widely used in sensors due to their tunable electron transport properties and high surface-to-volume ratio. Nanowire sensors have previously been shown to have much higher stability compared to other nanoparticle counterparts. High sensitivity and stability can be obtained by integrating many nanowires, the diameter of the nanowire has a great influence on the performance of the sensor. However, metal oxide gas sensors require high operating temperatures (typically 300–500 °C), but their limited selectivity for similar gases limits their application in real-world situations. Light activation has been shown to be an alternative to heat activation, opening room temperature sensor measurement possibilities, but with lower sensitivity and selectivity compared to heating activation. ZnO nanowires are often used for chemiresistive sensing due to their many advantages, such as high sensing response and long-term stability. Among other structures, ZnO tetrapods (a structure composed of 4 connected nanowires) are also interesting for chemiresistive sensing and have been used in UV sensing and gas sensors. The high surface-to-volume ratio and porosity of ZnO nanostructures can contribute to the development of a room-temperature gas sensor. In our laboratory, a breakthrough in ZnO sensors was recently obtained, and a record level of sensitivity was demonstrated.

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Research Topic Summary.

Extensive research for new functional materials that increase the efficiency of fuel cells and lead to practical use of these materials is performed there. KOKE operating temperature, structural dimensions, and price can be reduced by applying the materials that are used for manufacturing electrolytes (ZrO2/Y2O3, CeO2/Gd2O3, etc.), and to reduce the thickness of electrolyte to 1-2 µm. The main goal of this work is to find new solutions to produce thin-film SOFC with a focus on the currently existing for the new architectures. This research will aim to select the best materials, synthesizing not in a group of analyzed lanthanum strontium gallium magnesium oxide (LSGM) La0.80Sr0.20Ga0.80Mg0.20O3-X and technologies and the influence of technological parameters on the formation of SOFC heterostructures, which will allow improving the efficiency of such fuel cells. The research objects of the work are: a) the influence of impurities on the properties of the layers; the influence of the composition and technological parameters on the ionic properties of the layers; b) the influence of charge carrier diffusion coefficient and their mobility on ionic properties. Thin ionic layers will be formed using physical vacuum technology. The survey aims to find out and control the physical, chemical, and other properties of thin layers and, based on research, to determine the practical application of such systems.

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Research Topic Summary.

The exploitation of renewable energy sources, such as solar energy, hydrogen gas, etc. allows reducing the emission of greenhouse gases. The efficiency of light conversion into energy in solar cells depends on the efficiency of absorbed radiation, which can be ensured by developing new semiconductor materials that absorb a wide spectrum, combining elements with different absorption into double or triple tandems, and improving the efficiency of light scattering and absorption by applying frameworks used in photonics and related technologies. Various kinds of nanostructures that are smaller than the wavelength of light and are ordered or in random arrangements can significantly increase the optical path of light in semiconductor materials, reflect unabsorbed radiation, resonantly absorb electromagnetic radiation, inject hot carriers into the semiconductor bandgap, thus utilizing a wider spectrum of impinging radiation. Another promising direction in the field of light loss mitigation and enhancement of efficiency is the development of photonic structures. They are characterized by selective interaction with radiation of the appropriate wavelength, which is obtained by selecting the geometry of nanostructures that ensures the desired optical properties. This work aims at the creation of photonic heterostructures, characterization of their interaction with light, and evaluation of potential applications for energy generation. The objectives of the work are devoted to simulating and experimentally originating light-absorbing heterojunctions of plasmonic and semiconductor materials exploiting self-assembly and thin film deposition methods. To characterize the charge transport phenomena occurring in these nanostructures using kinetic spectroscopy and photoelectrochemical measurements. To adapt heterostructures to renewable energy applications.