BaWO4:Ce Single Crystals Codoped with Na Ions

Single crystals of BaWO4, BaWO4:0.5at.%Ce; BaWO4:1at.%Ce; BaWO4:0.5at.%Ce,1at.%Na; and BaWO4:1at.%Ce,2at.%Na were grown from an inductively heated iridium crucible by the Czochralski method on a Malvern MSR4 puller. They were investigated using Electron Paramagnetic Resonance (EPR) spectroscopy at helium temperatures. One isolated center of high (D2d or S4) symmetry was found and two or more other centers of lower symmetry were identified, depending on crystal doping. From the fitting using the EPR-NMR program, the following parameters of g-matrix for the high symmetry center were found: gx = 1.505, gy = 1.505, and gz = 2.731. The linewidth vs. temperature revealed an increasing exponential tendency with increasing temperature. It showed one phonon at the lower temperatures and a Raman + Orbach effect at the higher temperatures. Radioluminescence and pulse height spectra showed rather poor scintillation properties, without any contribution from cerium emission

Spontaneous charging affects the motion of sliding drops

Water drops moving on surfaces are not only an everyday phenomenon seen on windows but also form an essential part of many industrial processes. Previous understanding is that drop motion is dictated by viscous dissipation and activated dynamics at the contact line. Here we demonstrate that these two effects cannot fully explain the complex paths of sliding or impacting drops. To accurately determine the forces experienced by moving drops, we imaged their trajectory when sliding down a tilted surface, and applied the relevant equations of motion. We found that drop motion on low-permittivity substrates is substantially influenced by electrostatic forces. Our findings confirm that electrostatics must be taken into consideration for the description of the motion of water, aqueous electrolytes and ethylene glycol on hydrophobic surfaces. Our results are relevant for improving the control of drop motion in many applications, including printing, microfluidics, water management and triboelectric nanogenerators

Work time analysis of drivers in the aspect of road traffic safety

W artykule omówiono problemy związane z czasem pracy kierowców transportu drogowego oraz ich wpływ na bezpieczeństwo w ruchu drogowym. Analizę czasu pracy kierowcy przeprowadzono na przykładzie dwóch firm transportowych działających na Sądecczyźnie. Analizie poddano czas pracy kierowców i ich odpoczynek w okresie dziennym, tygodniowym i dwutygodniowym. Wyniki analizy przedstawiono w formie tabelarycznej oraz graficznej.The author of the article discusses problems related to the work time of road transport drivers and their impact on safety in road traffic. Analysis of drivers’ work time was in two transport companies operating in the Sącz area. Work time of drivers was subjected to analysis, along with their rest in daily, weekly and bi-weekly periods. The results of the analysis are presented in a graphic and tabular form

Temperature dependence of the EPR spectra of the nanocrystalline TiN and TiC dispersed in a carbon matrix

Two powder samples: nanocrystalline titanium carbide (TiC) and titanium nitride (TiN) dispersed in a carbon matrix were synthesized by a nonhydrolytic sol-gel process. Both samples were characterized by the X-ray diffraction and transmission electron microscopy. The transmission electron microscopy examination of the TiC and TiN nanoparticles showed that their average crystalline size was about 20 urn. The temperature dependence of the EPR spectra for both samples was measured in 10 K to 200 K temperature range. A similar very narrow (about 0.2 mT) EPR line centered at g approximate to 2 (at room temperature) was recorded in both samples. The EPR line observed in both samples is arising from electron conductivity centers dispersed in the carbon matrix and it was fitted by Dysonian line shape. The temperature dependence of the EPR spectrum showed different behavior of these two samples. It is suggested that in the sample TiC/C multiwall carbon nanotubes are formed while in the sample TiN/C the graphite structure dominates

Temperature Dependence of the EPR Spectra of the Nanocrystalline TiN and TiC Dispersed in a Carbon Matrix

Two powder samples: nanocrystalline titanium carbide (TiC) and titanium nitride (TiN) dispersed in a carbon matrix were synthesized by a nonhydrolytic sol-gel process. Both samples were characterized by the X-ray diffraction and transmission electron microscopy. The transmission electron microscopy examination of the TiC and TiN nanoparticles showed that their average crystalline size was about 20 nm. The temperature dependence of the EPR spectra for both samples was measured in 10 K to 200 K temperature range. A similar very narrow (about 0.2 mT) EPR line centered at g≈2 (at room temperature) was recorded in both samples. The EPR line observed in both samples is arising from electron conductivity centers dispersed in the carbon matrix and it was fitted by Dysonian line shape. The temperature dependence of the EPR spectrum showed different behavior of these two samples. It is suggested that in the sample TiC/C multiwall carbon nanotubes are formed while in the sample TiN/C the graphite structure dominates

Magnetic Study of Nanocrystalline TiB₂, TiC, B₄C Powders Doped to AISI 316L Austenitic Steel

The investigations into ferromagnetic resonance and magnetic susceptibility of nanocrystalline TiB₂, TiC, and B₄C powders (Ti-B-C system) doped to AISI 316L austenitic steel with different amounts (3 vol.%, 5 vol.% and 7 vol.%) have been carried out. The ferromagnetic resonance spectra were recorded in the temperature range from helium up to room temperature. The three tested composite samples contain a number of magnetic phases in different proportions. They reveal a structure originating from several different complex magnetic centers. The composites revealed such magnetic phenomena as paramagnetism, (anti)ferromagnetism, and superparamagnetism. Magnetic susceptibility investigations supported the ferromagnetic resonance studies and their analysis. Magnetic properties of the TiB₂, TiC, B₄C powders doped to AISI steel may play important role in further possible applications of these composite systems

Paramagnetic centers in nanocrystalline TiC/C system

Electron paramagnetic resonance is applied to study the defect centers in nanocrystalline titanium carbide dispersed in carbon matrix (TiCx/C) synthesized by the non-hydrolytic sol-gel process. The presence of Ti3+ paramagnetic centers is identified below 120 K along with a minor contribution from localized defect spins coupled with the conduction electron system in the carbon matrix. The temperature dependence of the resonance intensity of the latter signal indicates weak antiferromagnetic interactions. The presence of paramagnetic centers connected with trivalent titanium is suggested to be the result of chemical disorder, which can be further related to the observed anomalous behavior of conductivity, hardness, and corrosion resistance of nanocrystalline TiCx/C. © 2007 Elsevier B.V. All rights reserved

Ageing effect in nanocrystalline TiCx/C studied by EPR

TiC/C nanocrystalline material: titanium carbide TiC dispersed in a carbon matrix has been prepared by a nonhydrolytic sol-gel process. Temperature dependence of the electron paramagnetic resonance (EPR) spectra of this material has been studied in the 3.5-120 K range. Two very different EPR lines have been recorded in fresh sample at temperatures below 120 K arising from the Ti(III) complex (broad and asymmetric line) and conduction electrons (very narrow line). In the same aged sample (1 year old) the magnetic anisotropy of Ti(III) line has increased while a narrow line attributed to conduction electrons has vanished. The existence of the paramagnetic centers connected with trivalent titanium ions could the result of disordering processes. The increase of anisotropy in Ti(III) line could be connected with the oxidation processes. The temperature dependence of the integrated intensity of the broad line revealed the presence of titanium antiferromagnetic dimers. The disappearance of a narrow EPR line suggests that the oxidation process (ageing effect) could influence also the electrical properties of titanium carbide. © 2008 Elsevier B.V. All rights reserved