Karel Jurek

Microanalysis of Glass Containing Alkali Ions

Abstract. The common problems connected with alkali ion migration during EPMA were studied on glasses containing nearly all possible alkali ions (Na, K, Rb, Cs). Binary silica glasses were prepared by melting from a very pure batch in Pt crucible. The glasses were carefully polished using alcohol to prevent surface corrosion by water and they were stored in vacuum. The specimens were coated with carbon layers approximately 30-nm thick and exposed to a 50- keV electron beam of 100 μm diameter. It was found that all alkali ions migrate under the electron beam, but the rate of the migration depends on the current density. The decay curves (characteristic X-ray intensity versus time) are similar in shape in all cases. The decay curve shows two transport regimes, the first being linear-like, the second being the exponential-like. The first transport regime busts into the rapid alkali migration after a time known as the incubation period. The period is in general longer for the larger-alkali ions size. It was found that even large rubidium and caesium ions migrate inside the glass with the same mechanism as sodium and potassium ions. While for K, Rb, and Cs ions the incubation periods were observed under the suitable experimental conditions, binary glass containing Na exhibits no observable incubation period. Except for the binary Na2O + SiO2 glass, the suitable experimental conditions for reliable quantitative EPMA can be found.

A domain study of magnetization processes in a stress-annealed metallic glass ribbon for fluxgate sensors

Abstract The magnetization processes in a metallic glass ribbon at different places with different magnetization curves have been studied together with the magnetic domain structure observed by the scanning electron microscopy technique. In a hysteresis-free region the domain walls are fixed as expected, but regions with hysteric behaviour reveal reproducible as well as non-reproducible types of domain wall movements.

Chromium-doped DLC for implants prepared by laser-magnetron deposition.

Diamond-like carbon (DLC) thin films are frequently used for coating of implants. The problem of DLC layers lies in bad layer adhesion to metal implants. Chromium is used as a dopant for improvement of adhesion of DLC films. DLC and Cr-DLC layers were deposited on silicon, Ti6Al4V and CoCrMo substrates by a hybrid technology using combination of pulsed laser deposition (PLD) and magnetron sputtering. The topology of layers was studied using SEM, AFM and mechanical profilometer. Carbon and chromium content and concentration of trivalent and toxic hexavalent chromium bonds were determined by XPS and WDS. It follows from the scratch tests that Cr doping improved adhesion of DLC layers. Ethylene glycol, diiodomethane and deionized water were used to measure the contact angles. The surface free energy (SFE) was calculated. The antibacterial properties were studied using Pseudomonas aeruginosa and Staphylococcus aureus bacteria. The influence of SFE, hydrophobicity and surface roughness on antibacterial ability of doped layers is discussed.

Mixed alkali effect in glass irradiated by 50 keV electron beam

Abstract A series of three sodium–potassium-silicate glasses with different alkali contents were prepared. The glasses were exposed to a 50 keV electron bombardment of defocused beams of various current densities. Decay curves (alkali X-ray intensity versus time) have been measured and analysed to obtain incubation periods and maximum transport rates. Obtained data have been compared with those known for binary alkali-silicate glass. The results confirm the influence of the mixed alkali effect on the transport behaviour of alkali ions under the electron bombardment.

Structure determination of KLaS2, KPrS2, KEuS2, KGdS2, KLuS2, KYS2, RbYS2, NaLaS2 and crystal-chemical analysis of the group 1 and thallium(I) rare-earth sulfide series.

One of the purposes of this work is to provide a crystallographic review of group 1 and thallium rare-earth ternary sulfides M(+)Ln(3+)S2. We have therefore determined crystal structures of KLaS2, KPrS2, KEuS2, KGdS2, KLuS2, KYS2, RbYS2, which belong to the α-NaFeO2 structural family (R3m), as well as NaLaS2, which is derived from the disordered NaCl structural type (Fm3m). The determined structures were compared with known members of the group 1 as well as thallium(I) rare-earth sulfides by the standard tools of crystal-chemical analysis such as comparison of bond-valences, analysis of interatomic distances and comparison of the unit-cell parameters. The results indicate why the cubic structural type is limited to Li(+) and Na(+) members of the series only. The analysis has also revealed frequent problems in the reported crystal structures, especially in the determination of the K(+) compounds, probably due to severe absorption and different accuracy and sensitivity of various instruments. Intense diffuse scattering has been discovered in NaLaS2, which will be the subject of further investigation. The newly determined as well as already known structures are summarized, together with critical comments about possible errors in the previous structure determinations.

Investigation of the atmospheric RF torch-barrier plasma jet for deposition of CeOx thin films

Abstract An atmospheric pressure RF torch-barrier discharge system with flowing plasma jet channel was studied as a tool for coatings of aluminum substrates by CeO x thin films. Cerium precursors were supplied to the plasma jet in the form of aerosol of the water solution of cerium salts. CeO x thin films were obtained on the Al substrate at certain deposition conditions. Properties of deposited CeO x films were studied by electron microprobe system. Surface of the films was analyzed by XPS method. ‘In situ’ emission spectroscopy of active plasma jet channel was performed in order to obtain more parameters about atmospheric plasma jet channel.

Optical properties of laser-prepared Er- and Er,Yb-doped LiNbO3 waveguiding layers

Doped LiNbO3 films were prepared from Er- and Er,Yb-doped monocrystalline targets using laser ablation. SiO2/Si was used as a substrate. Polycrystalline films were synthesized at substrate temperatures of 650–800 ° C. The influence of the deposition conditions on the film crystallinity, surface morphology, dopant concentration, optical properties (using the m-line technique and spectroscopic ellipsometry), and luminescence was studied. The films were luminescent at 1530 nm and were waveguiding.

Properties of thin N-type Yb0.14Co4Sb12 and P-type Ce0.09Fe0.67Co3.33Sb12 skutterudite layers prepared by laser ablation

The properties of thin thermoelectric layers (about 60 nm in thickness) prepared by pulsed laser deposition are presented. Hot pressed targets were made from “middle” temperature range thermoelectric bulk materials with the potential high figure of merit ZT. P-type and N-type layers were prepared from Yb0.19Co4Sb12 and Ce0.1Fe0.7Co3.3Sb12 targets, respectively. The thin films were deposited on quartz glass substrates using KrF excimer laser. The individual layers were prepared by applying different laser beam energy densities (2 or 3 J cm−2) at several substrate temperatures (200, 250, or 300 °C). Crystallinity and composition of the layers were examined by x-ray diffraction and wavelength dispersive analysis, respectively. Homogeneity of Yb across a surface of the Yb filled film was explored by secondary ion mass spectrometry. The thermoelectric properties, the Seebeck coefficient, the electrical resistivity, and the power factor, for the best prepared P and N layer are presented in the temperature range...

Doped biocompatible layers prepared by laser

The contribution deals with KrF laser synthesis and study of doped biocompatible materials with focus on diamond-like carbon (DLC) and hydroxyapatite (HA). Overview of materials used for dopation is given. Experimental results of study of HA layers doped with silver are presented. Films properties were characterized using profilometer, SEM, WDX, XRD and optical transmission. Content of silver in layers moved from 0.06 to 13.7 at %. The antibacterial properties of HA, silver and doped HA layers were studied in vivo using Escherichia coli cells.

Potassium Migration in Silica Glass During Electron Beam Irradiation

Potassium glass was irradiated by 10, 30 and 50 keVelectron beams of various diameters and the time decay of potassium x-radiation was measured. These measurements were complemented by SEM observation of the etched cross sections of exposed areas and potassium depth concentration profiles in order to observe structural changes in the glass. Whilst the temperature increase remained low, the length of the incubation period was inversely proportional to the specimen current density and a possible explanation of this phenomenon was suggested.