Brno University of Technology

A piezoactive nanofiber composite PVDF film with TiO2 nanoparticles included in it was synthesized by electrospinning. The composition, morphology and structure of the films were investigated. The high efficiency of films in the processes of piezophotocatalytic decomposition of organic dye in water is shown.

Nanomaterials with high specific surface area and high absorption capacity are attracting increased interest aimed at imparting the desired magnetic properties. This work is devoted to the study of the effect of heat treatment in a hydrogen atmosphere on the microstructure, adsorption and magnetic properties of heterogeneous FePt/h-BN nanomaterials. Obtained via the polyol process, FePt nanoparticles (NPs) had a size < 2 nm and were uniformly distributed over the surface of hexagonal boron nitride (h-BN) nanosheets. The temperature-activated fcc→fct phase transformation in ultrafine FePt NPs has been well documented. FePt NPs act as active centers dissociating H2 molecules and transfer adsorbed hydrogen atoms to the h-BN. Density functional theory (DFT) calculations also indicate that the h-BN substrate can absorb hydrogen adsorbed on the FePt NPs. This hydrogen circulation in the FePt/h-BN system promoted the fcc→fct phase transformation and allowed to control the magnetic properties. FePt/h-BN nanomaterials also exhibited a high adsorption capacity with respect to various organic dyes.

ZrO 2 and Ag doped ZrO 2 powders were prepared from mixtures of ZrO 2 and AgNO 3 commercial powders (99:1 and 95:5 wt %) by pulsed electron beam evaporation (PEBE) in vacuum. Samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), textural and magnetic analysis, photocatalytic test, photoluminescence spectroscopy (PL) and cell cytology (Vero and Hela). XRD analysis confirmed the presence of monoclinic ZrO 2 phase and cubic Ag phase in the final product. НRTEM pictures showed a large range of particle sizes approximately from 10 to 500 nm; the spherical silver nanoparticles (NPles) (10 nm) were observed on the ZrO 2 particle surfaces. Ferromagnetic contribution in pure ZrO 2 powder was 0,002 emu/g, and in Ag doped ZrO 2 powders it reached 0,016 emu/g. It was found that Ag doped ZrO 2 powders showed increased photocatalytic activity in methyl orange (MO) compared with pure ZrO 2 NPles. The produced powders can be used to kill Hela cancer cells, as low (

Magnonics is a field of science that addresses the physical properties of spin waves and utilizes them for data processing. Scalability down to atomic dimensions, operations in the GHz-to-THz frequency range, utilization of nonlinear and nonreciprocal phenomena, and compatibility with CMOS are just a few of many advantages offered by magnons. Although magnonics is still primarily positioned in the academic domain, the scientific and technological challenges of the field are being extensively investigated, and many proof-of-concept prototypes have already been realized in laboratories. This roadmap is a product of the collective work of many authors that covers versatile spin-wave computing approaches, conceptual building blocks, and underlying physical phenomena. In particular, the roadmap discusses the computation operations with Boolean digital data, unconventional approaches like neuromorphic computing, and the progress towards magnon-based quantum computing. The article is organized as a collection of sub-sections grouped into seven large thematic sections. Each sub-section is prepared by one or a group of authors and concludes with a brief description of the current challenges and the outlook of the further development of the research directions.

AbstractAdrenal glands are the major organs releasing catecholamines and regulating our stress response. The mechanisms balancing generation of adrenergic chromaffin cells and protecting against neuroblastoma tumors are still enigmatic. Here we revealed that serotonin (5HT) controls the numbers of chromaffin cells by acting upon their immediate progenitor “bridge” cells via 5-hydroxytryptamine receptor 3A (HTR3A), and the aggressive HTR3Ahigh human neuroblastoma cell lines reduce proliferation in response to HTR3A-specific agonists. In embryos (in vivo), the physiological increase of 5HT caused a prolongation of the cell cycle in “bridge” progenitors leading to a smaller chromaffin population and changing the balance of hormones and behavioral patterns in adulthood. These behavioral effects and smaller adrenals were mirrored in the progeny of pregnant female mice subjected to experimental stress, suggesting a maternal-fetal link that controls developmental adaptations. Finally, these results corresponded to a size-distribution of adrenals found in wild rodents with different coping strategies.

COOH plasma polymer layers deposited onto polycaprolactone (PCL) nanofibers by plasma polymerization of CO2 and C2H4 in the Ar atmosphere were obtained and tested for diabetic wound healing. Simply by changing the deposition time, very different morphologies of coated PCL nanofibers were achieved. In vivo tests revealed that by applying modified nanofibers for 10 days, wound healing accelerated by 32.1%. Compared to a controlled wound characterized by an acute inflammatory process, wounds covered with nanofibers with platelet-rich plasma demonstrated complete healing with a high percentage of collagen fibers on Day 19.

A new piezophotocatalytically active membrane based on polyvinylidene fluoride (PVDF) nanofibers with α-Fe 2 O 3 nanoparticles incorporated into them has been synthesized by electrospinning. The composition, morphology and structure of α-Fe 2 O 3 containing PVDF nanofibers mats were investigated by SEM, XRD, Raman, FTIR, XPS and DSC. Studies have shown that the inclusion of α-Fe 2 O 3 nanoparticles promotes additional crystallization and self-polarization of PVDF into an electroactive β-phase. With the help of XPS, the mechanism of interfacial ion-dipole electrostatic interaction, leading to self-polishing and crystallization of the structure, is shown. Using measurements of VB XPS, UPS and the frequency dependence of the dielectric constant, the role of polarization effects on the formation of long-lived metastable energy states in the electronic structure of PVDF near the Fermi level is shown. Piezocatalytic and piezophotocatalytic activity was assessed by the decomposition of Methylene Blue (MB) under the influence of ultrasound and UV-Vis radiation. The efficiency of piezocatalysis and piezophotocatalysis was 60.4% and 99.5%, respectively. With the help of experiments on the capture of active redox forms, it was found that ∙OH radicals are the main component of the MB degradation. Two different mechanisms of generating ∙OH radicals for piezocatalysis and piezophotocatalysis have been reasonably proposed. The stability of the catalyst was shown after five successive cycles of piezophotocatalysis. • The interfacial interaction α-Fe 2 O 3 and dipoles in PVDF provide self-poling and crystallization of α to β phase. • Piezophototronic effect in α-Fe 2 O 3 -PVDF greatly improves the catalytic properties. • The catalytic activity of α-Fe 2 O 3 -PVDF films can be enhanced by ultrasound and flowing-water • The output voltage piezoresponse of α-Fe 2 O 3 -PVDF based PENG are influenced by bending and ultrasound stress. • A higher piezoelectric potential is more favorable for photocatalytic activity.

Knowledge of the spin-wave dispersion relation is a prerequisite for the explanation of many magnonic phenomena as well as for the practical design of magnonic devices. Spin-wave dispersion measurement by established optical techniques such as Brillouin light scattering or the magneto-optical Kerr effect at ultralow temperatures is often forbiddingly complicated. By contrast, microwave spectroscopy can be used at all temperatures but it usually lacks spatial and wave-number resolution. Here we develop a variable-gap-propagating-spin-wave-spectroscopy (VGPSWS) method for the deduction of the dispersion relation of spin waves in a wide frequency and wave-number range. The method is based on the phase-resolved analysis of the spin-wave transmission between two antennas with variable spacing, in conjunction with theoretical data treatment. We validate the method for in-plane magnetized $\mathrm{Co}$-$\mathrm{Fe}$-$\mathrm{B}$ and yttrium iron garnet thin films in $\mathbf{k}\ensuremath{\perp}\mathbf{B}$ and $\mathbf{k}\ensuremath{\parallel}\mathbf{B}$ geometries by deducing the full set of material and spin-wave parameters, including spin-wave dispersion, hybridization of the fundamental mode with the higher-order perpendicular standing spin-wave modes, and surface spin pinning. The compatibility of microwaves with low temperatures makes this approach attractive for cryogenic magnonics at the nanoscale.

Complicated geometry in combination with surface treatment strongly deteriorates fatigue resistance of metallic dental implants. Mechanical properties of pure Ti grade 2, usually used for dental implant production, were shown to be significantly improved due to intensive grain refinement via Conform SPD. The increase of the tensile strength properties was accompanied by a significant increase in the fatigue resistance and fatigue endurance limit. However, the SLA treatment usually used for the implants' surface roughening, resulted in the fatigue properties and endurance limit decrease, while this effect was more pronounced for the ultrafine-grained comparing to the coarse-grained material when tested under tensile-tensile loading mode. The testing of the implants is usually provided under the bending mode. Even though different testing condition for the conventional specimens tests and implants testing was adopted, a numerical study revealed their comparable fatigue properties. The fatigue limit determined for the implants was 105% higher than the one for coarse-grained and only by 4 % lower than the one for ultrafine-grained Ti grade 2. Based on the obtained results, conventional specimens testing can be used for the prediction of the fatigue limit of the implants.

AbstractFerromagnetic topological insulators exhibit the quantum anomalous Hall effect, which is potentially useful for high‐precision metrology, edge channel spintronics, and topological qubits.  The stable 2+ state of Mn enables intrinsic magnetic topological insulators. MnBi2Te4 is, however, antiferromagnetic with 25 K Néel temperature and is strongly n‐doped. In this work, p‐type MnSb2Te4, previously considered topologically trivial, is shown to be a ferromagnetic topological insulator for a few percent Mn excess. i) Ferromagnetic hysteresis with record Curie temperature of 45–50 K, ii) out‐of‐plane magnetic anisotropy, iii) a 2D Dirac cone with the Dirac point close to the Fermi level, iv) out‐of‐plane spin polarization as revealed by photoelectron spectroscopy, and v) a magnetically induced bandgap closing at the Curie temperature, demonstrated by scanning tunneling spectroscopy (STS), are shown. Moreover, a critical exponent of the magnetization β ≈ 1 is found, indicating the vicinity of a quantum critical point. Ab initio calculations reveal that Mn–Sb site exchange provides the ferromagnetic interlayer coupling and the slight excess of Mn nearly doubles the Curie temperature. Remaining deviations from the ferromagnetic order open the inverted bulk bandgap and render MnSb2Te4 a robust topological insulator and new benchmark for magnetic topological insulators.

The method of inclusion of various additives into a polymer depends highly on the material in question and the desired effect. In the case of this paper, nitride salts were introduced into polyvinylidene fluoride fibers prepared by electrospinning. The resulting changes in the structural, chemical and electrical properties of the samples were observed and compared using SEM-EDX, DSC, XPS, FTIR, Raman spectroscopy and electrical measurements. The observed results displayed a grouping of parameters by electronegativity and possibly the molecular mass of the additive salts. We virtually demonstrated elimination of the presence of the γ-phase by addition of Mg(NO3)2, Ca(NO3)2, and Zn(NO3)2 salts. The trend of electrical properties to follow the electronegativity of the nitrate salt cation is demonstrated. The performed measurements of nitrate salt inclusions into PVDF offer a new insight into effects of previously unstudied structures of PVDF composites, opening new potential possibilities of crystalline phase control of the composite and use in further research and component design.

In this study, ZrO2 coatings with different thicknesses were grown by the electron beam evaporation technique. The crystalline structure was studied by XRD analysis which suggested the tetragonal and monoclinic phases for ZrO2 coatings. Additionally, the film thickness slightly enhanced the crystallinity. The surface morphology and fractal features were analyzed using Scanning Electron Microscopy (SEM). The surface statistical parameters and the fractal geometry were employed to analyze the impact of the coating thickness and homogeneity on the morphology of the films. The statistical processing and fractal dimension revealed variations in the morphology parameters due to the electron beam evaporation method applied for different thicknesses of samples. Based on these results, it can be concluded that the surface microtexture and fractal dimension area correlated with the thickness and homogeneity of the crystalline structure.

The pure-phase BiFeO3 was obtained in one stage by solution combustion synthesis. The influence of the heat treatment process on the phase composition, magnetic, and optical properties was studied. The calcination of the powder led to a decrease in the fraction of the impurity phase from 7 to 1% and an increase in the crystallite size. X-ray diffraction revealed the formation of a pure phase upon heat treatment at 600 °C. The band gap of the samples increases from 1.91 to 2.06 eV with an increase in the crystallite size. M–H loops measured at room temperature showed a strong ferromagnetic character. For the initial powder, Ms was ~ 1.9 emu/g. The dependence of the magnetic properties on the crystallite size has been established.

Metasurfaces are ultrathin nanostructured surfaces that can allow arbitrary manipulation of light. Implementing dynamic tunability into their design could allow the optical functions of metasurface...

Modern material science often makes use of polyvinylidene fluoride thin films because of various properties, like a high thermal and chemical stability, or a ferroelectric, pyroelectric and piezoelectric activity. Fibers of this polymer material are, on the other hand, much less explored due to various issues presented by the fibrous form. By introducing carbon nanotubes via electrospinning, it is possible to affect the chemical and electrical properties of the resulting composite. In the case of this paper, the focus was on the further improvement of interesting polyvinylidene fluoride properties by incorporating carbon nanotubes, such as changing the concentration of crystalline phases and the resulting increase of the dielectric constant and conductivity. These changes in properties have been explored by several methods that focused on a structural, chemical and electrical point of view. The resulting obtained data have been documented to create a basis for further research and to increase the overall understanding of the properties and usability of polyvinylidene fluoride fiber composites.