Projects supported by the Czech Science Foundation

The main topic of the grant project is the study of thin films of hybrid composites based on carbon allotropes (especially C60) and transition (and noble) metals, their preparation, modification and characterization, and also the study of their biological properties (i.e., biotolerance, adhesion of bone-type cells, their growth, differentiation, etc.). The purpose is to develop novel hybrid materials with well-defined structures and interesting properties attractive for applications (e.g., for tissue engineering). For fabrication of the composites, suitable deposition techniques will be used; for characterization of the films an arsenal of analytical methods will be at our disposal. The preliminary experiments demonstrated an interesting aspect of the project – the possibility of preparing composite materials with regular structures at a (sub-) micron scale level either created due to spontaneous self-organization (induced by a certain deposition kinetics), or because of coordinated phase separation initiated by thermal annealing or irradiation with energy ion beams. The specific goal of this project is to shed more light on the onset, mechanisms and kinetics of the above-mentioned phenomena.

The semiconductors based on ZnO doped by magnetic impurities belong to a new class of advanced materials, dilute magnetic semiconductors, which have recently received much experimental and theoretical attention as a suitable spin source for spintronic applications. Some of the highly doped wide band gap materials like (Zn,Mn)O reveal a ferromagnetic like behavior near and above room temperature, which is considered as a major criterium for spintronic applications. The present project focuses on material and technological aspects of transition metal (TM) and rare earth (RE) doped ZnO thin films fabricated by metalorganic chemical vapor deposition (MOCVD) technique. The TM and RE elements will be incorporated either by ion implantation followed by annealing or by in-situ MOCVD using MO precursors as TM sources. The corresponding bulk materials will be prepared by ceramic route or as single crystals. The sythetized materials will be chemically and structurally characterized and their magnetic and electric transport properties will be thoroughly examined. The thermodynamic and electronic structure calculations will be used as auxiliary tools to model the MOCVD process and to interpret the physical properties.

Nanostructures for optics and photonics will be deposited in crystals and amorphous materials using ion implantation, which offers a many possibilities of the functional devices preparation. We will focus on a more detailed study of single crystal materials and glasses implanted by metal and light ions. The combination of appropriate substrate and implanted ion enables us to prepare materials with the desired properties (optical, electrical). Our intention is to define relation between the nano-particles morphology and the optical properties (band gap, photoluminescence), structural changes and dopant positioning in the host matrix. Energetic ions modifying solid materials will be used for the fundamental study of stopping powers of ions in solid compounds and simultaneously will be provided validation of semi-empirical models used in simulation. The simulations and knowledge of empirical stopping powers are irreplaceable in nanostructure synthesis using ion implantation. Measurement of ion stopping in compounds will be realized using transmission and backscattering ion beam methods.

The research focused on graphene and other 2D materials is in the forefront of materials science. The proposed project addresses the investigation of graphene based materials (graphene and its composites with transition metal dichalcogenides) interaction with ion beams. The ion beam irradiation depending on the used ion beam parameters induces formation of defects, structural disorder and introduction of dopants. Only few works have been published on the proposed topic so far; however, most of the unusual properties of 2D materials like exotic  ferromagnetism, anomalously high electrical and thermal conductivity or electrocatalytic activity are associated with this phenomenon. The project will be focused on ion beam irradiation of various graphene forms, such as bulk powder, assembled papers and CVD deposited layers. In addition, the composites of graphene with transition metal dichalcogenides in the form of papers and CVD layers will be investigated.

Silicate glass is one of the most important and widely spread technical materials. It is frequently used in the applications where it is exposed to the particle radiations of different energies. Therefore, it is very important to study the changes in glass caused by the radiation both from technical applications point of view (changes in glass properties) as well as from point of view of glass science (changes in glass structure).The project will perform a systematic investigation of changes in glass structure and properties caused by electrons irradiation in different energy ranges from about 3 keV up to MeV's and by proton irradiation (MeV). The compositional changes and inhomogeneities on the micron scale will be characterized by EPMA. Evolution of structural changes will be studied by XPS, NMR, and Raman spectroscopy. Surface topographies will be characterized by AFM and SEM. Moreover, the molecular dynamics simulations will be used as a theoretical tool for the interpretation of the experimental findings. Chemical durability of glass irradiated with electrons/protons will be established and nanoindentation methods will be used for the characterization of mechanical properties. Expected results may enhance the applicability of glass and improve its limiting properties.

The interactions between metals and polymers will be studied using complementary analytical techniques on different metal-polymer and metal-polymer-metal systems. The research is of interest from the fundamental point of view and for broad practical utilization of metal coated polymers in analytical chemistry, electronics, food packaging etc. The specimens will be prepared by sputtering or vacuum deposition of 10-100 nm thick layers of different metals Au, Ag, Pd and Pt on various polymers PET, PMMA, PE and PTFE. The structure characterization will be provided using profilometer, TEM, AAS spectroscopy, RBS, ERD). The electrical resistance and magnetic properties will be measured. Nanointendenter device will be used for the determination of the layers adhesion. The layer morphology will be studied using AFM and SEM. Ion implantation and ion assisted mixing of metal particles and polymer structure will be used for composite preparation. For mobility and diffusion study of metals in polymer substrate RBS, XPS will be used.

The aim of the project is development of new advanced cast multiphase gamma based TiAl-8Nb-X alloys alloyed with the graded carbon content (0.2 to 1 at. %), produced so far only by powder metallurgy. Sufficient thermo-mechanical stability of these alloys will be guaranteed by the lamellar structure strengthened by favorable distributed precipitates obtained using an optimized complex heat treatment. The main pertinent applications of the alloys suggested are turbocharger rotor or gas turbine blade in automotive and power industry, respectively, in which a decisive degradation mechanism represents creep-fatigue interaction at higher temperatures. The structure of new-developed cast alloys and its thermo-mechanical stability will be studied both in virgin state after optimized heat treatment and after high temperature creep-fatigue tests. Neutron diffraction (in-situ and post-mortem studies), TEM (transmission electron microscopy) and other modern experimental techniques will be used for the structure analysis and the study of damage mechanisms.

Currently there is renewal of interest in actuation functionality using high temperature shape memory alloys with transformation temperatures above 100°C (HTSMA) driven by strong demand for reliable and powerful actuators to be used in engines and gas turbines, where it is preferable to adopt single piece compact adaptive actuator over more complex multicomponent assemblies. The aim of this project is to clarify the reasons for poor dimensional and functional stability and fatigue failure of NiTiX actuators. The research will be performed by combination earlier developed and used methods (thermomechanical fatigue testing, in-situ X-ray and neutron diraction, TEM and micromechanics modeling) . The research will be coordinated with worldwide academic and industrial partners currently developing HTSMA actuators. Approaches to modify the microstructure of NiTiX alloys so so they act as well performing HTSMA actuators for 100°C-300°C temperature range will be proposed (adjustment of composition, degree of cold work, heat treatment, texture, grain size, precipitation strengthening).

The aim of the submitted proposal is to get financial support for development of Monte Carlo methods for simulations of complex neutron optical systems, including their experimental validation and application to the research of dispersive multiple reflections of neutrons in elastically bent crystals. The new methods will be implemened in existing and well established software package RESTRAX, which has been developed at the NPI Řež. The results of experimental research of multiple Bragg reflections supported by Monte Carlo simulations will be employed in the development of high-resolution monochromators and analyzers. The ultimate goal of the proposed research is twofold: (a) Creation of an easy to use, validated and efficient software for modeling and optimization of neutron spectrometers employing advanced neutron optics elements and for data analysis; (b) Development and tests of dispersive multiple reflection monochromators suitable for ultra-high resolution measurements.

Complex investigations of point defects in ZnO are proposed in the present project. Positron annihilation spectroscopy (PAS) including also variable energy PAS using slow positron beam will be used as a principal technique for defect studies. State-of-art ab-initio theoretical calculations will be employed for interpretation of PAS data. Defects in ZnO single crystals will be compared with those in epitaxial and nanocrystalline ZnO thin films. Defects studies will be combined with electrical (temperature-dependent Hall effect, deep level transient spectroscopy) and optical (photoluminescence, optical transmission) measurements in order to find a link between predominant defect configurations and specific electrical and optical properties of ZnO samples. Moreover, in the present project we intend to investigate interaction of hydrogen and nitrogen with point defects in ZnO and influence hydrogen and nitrogen on electrical and optical properties. A new UHV chamber for on-line sputtering of ZnO films will be constructed and connected to slow positron beam. This novel setup enables to perform variable energy PAS investigations of thin ZnO films in-situ during film deposition. It gives us an exclusive possibility to investigate formation of defects and incorporation of impurities into ZnO lattice during film growth.