Zdeněk Jansa

Naturally occurring asbestos (NOA) represents an environmental issue that cannot be addressed solely through mineralogical identification. Reliable assessment requires the integration of morphological, chemical, and crystallographic information together with geological, environmental, and health-related considerations. This study revisits analytical observations obtained from soil and sediment samples collected in the Pilsen Region, Czech Republic, and uses them as a case study to demonstrate the multidisciplinary nature of NOA identification and assessment. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were used as complementary techniques to characterize fibrous particles and asbestos-related mineral phases. XRD identified crystalline phases corresponding to chrysotile, anthophyllite, and actinolite, whereas SEM observations revealed fibrous morphologies and dimensional analysis of selected particles from Series 1 demonstrated dimensions corresponding to commonly applied criteria for respirable mineral fibres. Particular attention is given to the fact that crystallographic phase identification alone is insufficient to demonstrate an asbestiform habit and that robust interpretation therefore requires correlation between morphology, elemental composition, and mineral structure. The study further highlights methodological difficulties associated with heterogeneous soil and sediment matrices, sample preparation, and the absence of harmonized procedures for naturally occurring asbestos in soils and sediments. Rather than presenting asbestos occurrence in the investigated area as an entirely new finding, the work demonstrates how existing analytical evidence can be integrated into a broader framework linking geology, materials characterization, environmental monitoring, public health, and regulatory practice. The Pilsen Region thus serves as a model case illustrating the need for coordinated multidisciplinary approaches to NOA assessment.

Hot isostatic pressing (HIP) is commonly applied to reduce porosity in additively manufactured components; however, its influence on crystallographic defects, residual stresses, and grainboundary evolution in laser directed energy deposited (L-DED) AISI 316L stainless steel remains insufficiently described. This study combines X-ray diffraction (XRD), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and energy-dispersive spectroscopy (EDS) to evaluate the multiscale structural changes induced by HIP at 1150 °C and 100 MPa. The phase constitution, crystallite size, lattice microstrain, apparent residual stresses, grain morphology, grain-boundary character, and oxide inclusions were compared among the initial powder, as-built L-DED material, and HIP-treated specimens in the build and transverse directions. XRD showed that processing preserved the FCC austenitic solid solution while substantially modifying its defect state. For the (111) reflection, the apparent crystallite size increased from approximately 25-26 nm in the as-built condition to 138-159 nm after HIP, accompanied by pronounced peak narrowing, reduced lattice microstrain, and redistribution of the hkl-dependent residual stresses. SEM and EBSD revealed dissolution of the cellular/dendritic substructure, recrystallization, grain coarsening, and a marked decrease in low-angle grain boundaries. The fraction of Σ3 boundaries increased from approximately 28-30% in the as-built specimens to about 66% after HIP, while the fraction of grains with GOS ≤ 2° approached 99%. These results demonstrate that HIP affects L-DED 316L beyond densification by promoting defect annihilation, grain-boundary migration, recrystallization, and stress redistribution across crystallite and grain length scales.

Ti-Nb-Zr-Ag medium entropy alloy (MEA) thin films were designed using empirical high-entropy alloy (HEA) design parameters as chemically complex coating for potential biomaterial applications and deposited on Si substrates at room temperature by combined RF/DC magnetron co-sputtering. The structural role of Ag was evaluated by comparison with an Ag-free Ti-Nb-Zr reference film, both in the as-deposited state and after stepwise annealing up to 1100 °C. Systematic Ag-content screening on carbon-coated TEM grids showed that Ag promoted nanoscale phase separation, Ag nanoparticle formation, and increased crystallinity already during the early stages of film growth. Based on this screening, a film containing approximately 13 at.% Ag was selected for detailed structural and chemical analysis. In the as-deposited state, the Ag-containing film exhibited an amorphous-nanocrystalline structure, with nanoscale crystalline domains within the columnar film matrix and dispersed Ag nanoparticles, whereas the Ag-free reference film remained predominantly amorphous. The crystalline domains were structurally related predominantly to a bcc β-(Nb,Zr)-type phase. After annealing, the Ag-free reference film transformed into a porous granular microstructure dominated by chemically simpler oxide phases, while the Ti-Nb-Zr-Ag film retained a more compact morphology and developed chemically complex tetragonal ZrO2-type regions incorporating Ti, Nb, Zr, and Ag. X-ray photoelectron spectroscopy further showed that Ag remained in a metallic state after annealing and that the Ag-containing film exhibited less pronounced oxidation of Ti and Zr. These findings identify Ag as an active structural and chemical modifier in Ti-Nb-Zr-Ag MEA thin films, affecting nanoscale phase separation, crystallization, oxidation response, and morphological integrity during high-temperature annealing.

Improving the performance of metallic implants increasingly relies on the development of multifunctional surface modifications that combine structural stability, bioactivity, and prevention of bacterial colonization. Medium-entropy alloys (MEAs) represent a promising approach for such coatings, as their chemical complexity allows the formation of structurally stable matrices with tunable properties. In this study, Ti-Nb-Zr and Ti-Nb-Zr-Ag thin films were deposited by magnetron sputtering and subjected to annealing at temperatures of up to 1100 °C to evaluate the influence of Ag, added for its antibacterial potential, on structural evolution. The as-deposited Ag-free film was fully amorphous, whereas the Ag-containing film exhibited a predominantly amorphous matrix with finely dispersed crystalline nanoparticles, indicating that Ag promoted early-stage crystallization. Both films displayed a fine columnar morphology (column diameter ~15 nm) with dome-like protrusions, a hierarchical surface structure favorable for protein adhesion. Upon annealing, the Ag-free film recrystallized into a granular, loosely packed morphology, while the Ag-containing film retained a compact structure, demonstrating the stabilizing role of Ag. These findings underscore the potential of Ag-containing amorphous MEAs for forming multifunctional coatings with enhanced thermal stability, antibacterial functionality, and biointerface-relevant surface features for advanced biomedical applications.

Lifted Kramers spin degeneracy (LKSD) has been among the central topics of condensed-matter physics since the dawn of the band theory of solids^1,2. It underpins established practical applications as well as current frontier research, ranging from magnetic-memory technology^3–7 to topological quantum matter^8–14. Traditionally, LKSD has been considered to originate from two possible internal symmetry-breaking mechanisms. The first refers to time-reversal symmetry breaking by magnetization of ferromagnets and tends to be strong because of the non-relativistic exchange origin¹⁵. The second applies to crystals with broken inversion symmetry and tends to be comparatively weaker, as it originates from the relativistic spin–orbit coupling (SOC)^16–19. A recent theory work based on spin-symmetry classification has identified an unconventional magnetic phase, dubbed altermagnetic^20,21, that allows for LKSD without net magnetization and inversion-symmetry breaking. Here we provide the confirmation using photoemission spectroscopy and ab initio calculations. We identify two distinct unconventional mechanisms of LKSD generated by the altermagnetic phase of centrosymmetric MnTe with vanishing net magnetization^20–23. Our observation of the altermagnetic LKSD can have broad consequences in magnetism. It motivates exploration and exploitation of the unconventional nature of this magnetic phase in an extended family of materials, ranging from insulators and semiconductors to metals and superconductors^20,21, that have been either identified recently or perceived for many decades as conventional antiferromagnets^21,24,25.

The paper presents the possibilities of heat treatment of low-density structural steels usable for springs. Heats have been prepared with chemical compositions 0.7 wt% C and 1 wt% C, as well as 7 wt% Al and 5 wt% Al. Samples were prepared from ingots weighing approximately 50 kg. These ingots were homogenised, then forged, and hot rolled. Primary transformation temperatures and specific gravity values were determined for these alloys. For low-density steels, there usually needs to be a solution to achieve the required ductility values. At cooling rates of 50 °C/s and 100 °C/s, the kappa phase is not present. A SEM analysed the fracture surfaces for the presence of transit carbides during tempering. The martensite start temperatures ranged from 55–131 °C, depending on the chemical composition. The densities of the measured alloys were 7.08 g/cm³ and 7.18 g/cm³, respectively. Therefore, heat treatment variation was carried out to achieve a tensile strength of over 2500 MPa, with ductility of almost 4%. Hardnesses above 60 HRC were achieved for 1 wt% C heats using the appropriate heat treatment.

The present work aimed to study the properties of medium-carbon steel during tempering treatment and to present the strength increase of medium-carbon spring steels by strain-assisted tempering (SAT). The effect of double-step tempering and double-step tempering with rotary swaging, also known as SAT, on the mechanical properties and microstructure was investigated. The main goal was to achieve a further enhancement of the strength of medium-carbon steels using SAT treatment. The microstructure consists of tempered martensite with transition carbides in both cases. The yield strength of the DT sample is 1656 MPa, while that of the SAT sample is about 400 MPa higher. On the contrary, plastic properties such as the elongation and reduction in area have lower values after SAT processing, about 3% and 7%, respectively, compared to the DT treatment. Grain boundary strengthening from low-angle grain boundaries can be attributed to the increase in strength. Based on X-ray diffraction analysis, a lower dislocation strengthening contribution was determined for the SAT sample compared to the double-step tempered sample.