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Thick InAlN layers (In-molar fraction >0.37) on GaN buffer layers were prepared using a close-coupled showerhead metalorganic chemical vapor deposition (MOCVD) reactor. This work provides a discussion of the dependence of reactor parameters (pressure, ammonia flow and temperature) and unintentional Ga-incorporation on structural, optical and chemical properties of those layers down to the nanoscale. Rutherford back-scattering spectrometry, Auger electron spectroscopy, and transmission electron microscopy with the energy dispersive X-ray analysis were used for in-depth chemical analysis of layers. A diminishing Ga-auto-incorporation in thick InAlN layer creates a chemically graded InAl(Ga)N interlayer that assists in releasing of interfacial strain and paves the way toward In-rich InAlN layer. The rate of unintentional Ga-auto-incorporation in InAlN layers increases with decreasing of growth temperature, and increasing of reactor pressure and ammonia flow during growth. Raman and photoluminescence spectroscopy were used to get the crystal structural fingerprint influenced by Ga-incorporation. We suggested that Ga could incorporate at nitrogen vacancies at high reactor pressures (≥200 mbar). Screw dislocations and/or N-vacancies in InAl(Ga)N layers may be energetically favorable sites for In-incorporation and lead to compositional fluctuation and local In-rich InAl(Ga)N phase.

Microporous carbon fibers prepared by controlled carbonization of cellulose proved promising carrier of nano- and microparticles of solid active substances. The average pore size of the carbon fibers ranges from 0.5 to 0.6 nm and, therefore, molecules of many low- molecular substances are excluded. Consequently, the nano- and microparticles formed by precipitation of a solution in the presence of fibers are deposited exclusively on their outer surface. In this way, composite materials with favorable macro-structure can be created because large surface of appropriate active substance remains easily accessible for the desired action. Technical problems connected with the direct application of nano- and microparticles are avoided. The practical advantages of the microporous carbon fibers prepared from cellulose comprise feasibility of their preparation, as well as general availability and low price of the raw material. Moreover, compared to particulate carriers with identical diameter, fibrous carriers exhibit reduced resistance against flow of liquids and gases. The pertinence of carriers based on the microporous carbon fibers prepared from delignified cellulose has been tested with the deposition of nano- and microparticles of hydrated ferric hydroxide, Fe(OH)3·(H2O)n. Compared with particulate ferric hydroxide, the resulting heterogeneous composite showed increased efficiency in adsorptive removal of harmful arsenic from water.

A joint investigation of n-undecane (n-UND) in the bulk and confined states in irregular silica gel (SG) matrices differing in their surface composition via two extrinsic probes using positron annihilation lifetime spectroscopy (PALS) and electron spin resonance (ESR) as well as DSC technique is presented. Ortho-positronium (o-Ps) exhibits a pronounced change in the annihilation behavior as detected by the o-Ps lifetime,τ3, as a function of temperature due to the enhanced amorphization of the n-UND after confinement with respect to the bulk solid n-UND. In addition, with an exception of the low-T region it exhibits rather small alterations in the confined state in the unmodified (virgin) SG100A-SIL compared to modified (silanized) SG100A - C4. On the other side, the stable free radical of nitroxide type 2,2,6,6-tetramethylpiperidinyl-1-oxy(TEMPO) shows the essential differences in the spectral properties with temperature not only in the confined n-UND with respect to the bulk sample, but especially in the confined state in the modified SG-C4 matrix compared to the unmodified SG100A-SIL one. These differences are attributed to the presence and absence of the preferential interaction of the polar spin probe TEMPO with the polar surface of the virgin SG matrix or the apolar surface of the silanized SG100A-C4 one, respectively. The coinciding relationships between the characteristic PALS and ESR temperatures reflecting the changes in annihilation and rotation dynamics of the respective extrinsic probes are related to the dynamic and phase transitions as found by wide-T DSC.

Undoped and BaZrO3 nanopowder-doped MgB2/Nb/Cu single filament wires were prepared by modified internal magnesium diffusion (IMD) process using 0, 2 and 5 wt% BaZrO3 addition in amorphous B powder. Superconducting MgB2 phase was formed during heat treatment at temperatures from 650 to 670 °C. The wire microstructure was analysed using XRD, SEM, TEM and EDS to study BaZrO3 dopant interaction with Mg and B precursors during the heat treatment and effect of dopant on MgB2 superconductor. The BaZrO3 nanopowder decomposed and its products reacted with Mg and B producing relatively large BaB6 grains and nanograins of ZrB2 and MgO phases which were not detected by conventional XRD measurements due to their low grain size. Measured MgB2 lattice parameters varied with the dopant addition and heat treatment temperature. Different possible origins of MgB2 lattice deformation were discussed, and it was shown that Zr substitution in MgB2 lattice could not cause this deformation.

The biosorbent used in this study was prepared from wood-decay fungus Fomes fomentarius. The chemical modification of biosorbent with potassium–copper hexacyanoferrate (KCuHCF) for cesium sorption in aqueous solutions studies was used. It was found that the biosorbent has a high 137Cs absorbability in the wide range of pH, even in the solutions with high ionic strength. The developed method for 137Cs determination by using modified bio-sorbent was applied to various types of water delivered by the Water Research Institute in Bratislava. 137Cs was measured on HPGe detector and 137Cs activity was less than the minimum detectable activity (5mBq L−1). The tested modified bio-sorbent is suitable for pre-concentration of 137Cs from water.

The presented work describes an effective method for 226Ra determination using laboratory- prepared MnO2-SiO2 composite resin. Samples were traced with 133Ba for radium radiochemical recoveries monitoring which were in the range of (77 – 100%). MnO2- SiO2 composite resin was used to collect for 226Ra from water samples (pH = 6.5–7.0). Radium was eluted from the column with 50 mL of 4 mol L−1 HNO3 at a flow rate of 1.5 mL min−1. Alpha-spectrometric counting of Ba(Ra)SO4 microprecipitate was used for 226Ra determination. The new developed method was used to the 226Ra determination in samples of natural mineral, mountain spring, drinking and natural healing waters from Slovakia and Czech Republic.

The well-known method of planar flow casting has been used for preparation single- and tri-layered ribbons of the same composition to attain ribbon thickness significantly different. The aim was to suppress potentially undesired surface effects of chemical or topological differences between ribbon surfaces/volume. The prepared ribbons’ composition was Co47Fe21Mo6.5B21Si4.5 and the samples were investigated for structural, chemical and magnetic properties in amorphous (as-cast) and crystalline state. The average thickness was ∼55 µm for the trilayer and ∼14.5 µm for the monolayer, thus the thickness ratio was somewhat more than 3:1. The composition chosen targeted low saturation magnetostriction and nanocrystallization improved soft magnetic properties more namely for trilayer. The reduction of large surface/volume ratio, that enables shrinking surfaces to squeeze efficiently the small volume of single ribbon, proved effective indeed.

Local atomic structure of liquid and amorphous Al80 − xTxSi20 (where T = Fe, Co, Ni and x = 10, 15) alloys has been studied by X-ray diffraction (XRD) and molecular dynamics simulations. Chemical short-range order in the liquid and amorphous alloys has been found to be similar to that in the corresponding crystalline counterparts. Formation and evolution of crystalline phases during heat-treatment of the as-quenched ternary alloys up to liquid state were shown using in-situ XRD. Analysis of the morphology of the as-quenched and annealed Al-T-Si ribbons has been performed by transmission electron microscopy.

The aim of this study is to characterize adsorbed liquid in montmorillonite structure for different levels of adsorption by both thermoanalytical and microstructural methods. Montmorillonite of Ca type is used for the analysis. Water desorption process occurring typically between 50 and 180 °C is analysed in details by thermogravimetric analysis. Thermal response of adsorbed water for the selected steps of desorption process is studied by differential scanning calorimetry. Corresponding characterization of free volume is performed by positron annihilation lifetime spectroscopy. An attempt to determine a correlation of characterization method results is provided.

Surface nanomachining based on single-point diamond turning is a viable technology for the preparation of high-quality surfaces. It found its first extensive use in infrared optics, but it is also attractive for X-ray optics. The challenge is that the X-rays used in laboratories have wavelengths 4 orders of magnitude shorter than infrared radiation. Though recent studies have shown promising results, periodic surface ripples as a footprint of the regular cutting tool scanning proved to be an unavoidable feature, producing unwanted effects in reciprocal space. Hence, the presented paper addresses the problem of finishing Ge monocrystalline X-ray surfaces while keeping all benefits of nanomachining. To do so, chemomechanical polishing, Ar+ ion beam bombardment, and UV laser irradiation were tested separately. Chemomechanical polishing proved to be rather time consuming, whereas ion beam bombardment was not sufficient to suppress the ripples even at the highest available energies. In contrast, UV laser irradiation turned out to be a suitable and time-efficient finishing tool to fully suppress the ripples while keeping the local rms surface roughness around 1 nm.

Combination of mechanical alloying and friction stir processing was used for the fabrication of Al/(Al13Fe4 + Al2O3) nano-composites. Pre-milled hematite + Al powder mixture was introduced into the stir zone generated on 1050 aluminum alloy sheet by friction stir processing. Uniform and active milled powder mixture reacted with plasticized aluminum to produced Al13Fe4 + Al2O3 particles. Al13Fe4 intermetallic showed elliptical shape with a typical size of ~ 100 nm, while nano-sized Al2O3 exhibited irregular floc-shaped particles that formed clusters with the remnant of iron oxide particles in the fine recrystallized aluminum matrix. As the milling time (1-3 h) of the introduced powder mixture increased, the volume fraction of Al13Fe4 + Al2O3 particles increased in the fabricated composite. The hardness and ultimate tensile strength of the fabricated nano-composites varied from 54.5 to 75 HV and 139 to 159 MPa, respectively; these are much higher than those of the friction stir processed base alloy (33 HV and 97 UTS). The highest hardness and strength were achieved for the nano-composite fabricated using the 3-h milled powder mixture; hard nano-sized reaction products and fine recrystallized grains of Al matrix had major and minor roles on enhancing these properties, respectively.

Alloys of composition (Fe-Co)83(Sn-P)5B12 have been prepared by planar flow casting method in air with substitution Co = 0; 5; 10 at. % for Fe and substitution P = 2 at. % for Sn. All as-cast ribbons were amorphous and submitted to chemical and thermal analyses, scanning and transmission electron microscopy and magnetic measurements. Hysteresis loops of strips after nanocrystallization at 380 and 400 °C for 30 min changed their shape – the saturation magnetization increased for Co containing alloys Js = 1.74–1.80 T. The off-axis component of magnetic anisotropy decreased significantly due to the annealing. Coercivity in this case considerably increased due to the growth of grain size and crystalline volume fraction. The samples annealed at 350 °C disclosed a relaxed state with changes in microstructure and achieved very good soft-magnetic properties namely for P substituted alloys.

Si-poor Fe 74 Nb 3 Cu 1 Si 8 B 14− x P x , ( x =0, 3) nanocrystalline ribbon-form alloys often form surfaces, which exert in-plane force on underlying ribbon interior when nanocrystallized in even modest presence of oxygen. Mostly unwanted hard-ribbon-axis magnetic anisotropy is standard result. Essential sources of the surface-caused stress have been sought and influence of P instead of B substitution on this effect was studied too. Preferred surface crystallization (PSC) was found to be the major reason. However P substitution suppresses PSC and promotes Fe-oxide formation, which eases the stress, softens the surfaces and provides different annealing evolution of surface properties.

This work investigates the free-volume properties of the dimethyl sulfoxide (DMSO)–water mixtures by positron annihilation lifetime spectroscopy over a wide temperature range of 20–320 K. The processes of melting and solidification of the water, DMSO and the DMSO–water mixtures at 1.8, 2.0 and 10% vol. DMSO respectively were studied. It was found that the recrystallization during heating of the water–DMSO cryoprotective mixtures above 160 K at low DMSO concentrations is affected by the amount of DMSO in the mixture. The amount of amorphous phase formed during cooling influences the hysteresis between cooling and heating cycles which could be crucial for cell survival. Experiments also show the time dependence of crystallization which indicates that rapid heating can suppress this secondary crystallization which is undesirable during the cell thawing process. Similar concentrations of DMSO (1.8% and 2% vol. DMSO in water) where a 2% vol. DMSO mixture secures cell survival but 1.8 vol% does not, showed differences in structural and dynamic properties that are key factors in cell survival. These results were supported by differential scanning calorimetry and low frequency dielectric spectroscopy measurements. The obtained data are in strong agreement with the observed cryoprotective efficacy of the DMSO–water mixtures on living cells.

The properties of Fe-Co-Sn / P-B ribbons prepared by planar flow casting of the melt were investigated by various methods in as-cast and nanocrystallized state. To examine the influence of surfaces on ribbon’s magnetic properties was the major aim. As the surfaces and the ribbon interior possess slightly different properties, mutual macroscopic force is generated and it can affect the magnetic properties. The ribbon with P 2 at % and P-free one was annealed at two different temperatures to achieve partially nanocrystalline structure. P-free ribbon shows tilted hysteresis loop after annealing, what indicates a possible surface squeeze effect. The increase of coercivity after higher temperature annealing at 380 °C is due to the formation of a bcc-Fe phase with a larger grain size and higher crystallinity contents. Oxides, mainly Fe2O3 have been confirmed on surfaces of both the lower temperature (350 °C) annealed ribbons. P substitution appears to reduce the mutual force by impeding the formation of crystalline phase during 350 °C annealing.

The aim of the work is to study interface formation between Al2O3 particles and Al(Ca) matrix in dependence of Ca content. Aluminium matrix composites (AMC) subjected to investigation were prepared by gas pressure assisted infiltration of alumina beds with aluminium-calcium alloys. It is shown that alumina particles in the AMC are covered with a monocalcium aluminates layer whose coherence increases with increasing amounts of Ca in the aluminium-calcium alloys. Moreover, Al4Ca intermetallic phases are formed with increasing Ca content and interconnect alumina particles. XRD confirms the presence of both CaAl2O4 and CaAl4O7 ternary phases. However, HRTEM analysis confirmed CaAl2O4 with a rather complex structure containing a high density of stacking faults. It appeared that annealing at 735 °C does improve consistency of interface for Al 2 wt.%Ca/Al2O3 AMC, but do not affect the thickness of the interface in dependence on annealing time. Keywords: Al2O3 particles, AlCa alloy, Gas pressure infiltration, Interface, Aluminium matrix composites

Readers should note that there is a phrase missing in the Acknowledgment Section of this article as published