Intermetallics – advanced cathode materials in the electrolytic production of hydrogen

The intermetallics, Ti–Pt, Nb-Pd (80%Nb), Pd-Ta, Nb-Pd (65% Nb), Zr-Pt, Hf2Fe and PtMo3, of transition metals have been investigated as cathode materials for the electrolytic hydrogen evolution in an attempt to increase the electrolytic process efficiency. These materials were compared with conventional cathode, Ni. An significant upgrade of the electrolytic efficiency using intermetallics was achived. The effects of those cathode materials on the process efficiency were discussed in the context of transition metal features that issue from their d-electronic configuration.Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200

Mössbauer spectroscopic analysis of (Nd,Pr,Dy)2(Fe,Co,Ga)14B/α-Fe permanent magnetic nanocomposites

In this paper, it is reported the structural and magnetic properties of Nd13.7Pr0.7Dy0.2Fe73.1Co6.3Ga0.4B5.6 and Nd7.7Pr0.7Dy0.2Fe79.1Co6.3Ga0.4B5.6 magnetic nanocomposites, synthesized by melt-spinning and annealing methods. The Nd-Fe-B ribbons are melt-spun at v=30 m/s in high vacuum and annealed at 715oC for 4 min. in argon. Furthermore, X-ray diffraction and transmission 57Fe Mössbauer spectra at RT are used to investigate the effects of substituent elements: Dy, Pr, Co, Ga on the hard magnetic properties and microstructure of both nanocomposites. Analysis of Mössbauer spectra for Nd13.7Pr0.7Dy0.2Fe73.1Co6.3Ga0.4B5.6 is done in terms of ten Zeeman sextets, one paramagnetic doublet related to Nd1.1Fe4B4 phase and two hyperfine magnetic fields distributions extracted from spectrum. Similar result of analysis of the second nanocomposite is obtained with eleven sextets, one doublet and one distribution. One sextet corresponds to α-Fe phase, while we have identified six iron sextets corresponding to the six distinct iron sites in the Nd2Fe14B structure: 16k1, 16k2, 8j1, 8j2, 4c and 4e. The three remaining sextets belong to Fe3B structure with three inequivalent Fe sites: FeI(8g), FeII(8g) and FeIII(8g). The eleventh sextet of Nd7.7Pr0.7Dy0.2Fe79.1Co6.3Ga0.4B5.6 belongs to FeB. All relevant parameters for both nanocomposites: magnetic hyperfine field, isomer shift and quadrupole splitting are determined for each of these sites. To highlight the thermally induced structural transformations, the quenched samples have been analysed by differential scanning calorimetry and thermo-magnetic measurements. The magnetic properties, measured at RT on the quenched and annealed ribbons, revealed the relationship between the alloy chemical composition and processing.RoPM AM 2017 : 5th International Conference on Powder Metallurgy & Advanced Materials, 17-20th September 2017, Cluj Napoca, Romani

A Three - Detector High Resolution TDPAC Spectrometer

An advanced fast-slow coincidence scintillation spectrometer for the Timx Differential Perturbed y-y Angular Correlation (TDPAC) experiments is presented. It consists of three detectors with BaF2 scintillators and was developed in the Group for Hyperfine Interactions in the Institute for Nuclear Sciences in Vinca. The spectrometer is characterized with high detection efficiency, excellent time resolution, high counting rate performance and is operating in the temperature range 78-1300 K

Hyperfine interactions at 181Ta solute in ferromagnetic Hf-Ni alloys with low concentration of Hf atoms

We have measured hyperfine interactions of 181Ta probe in the polycrystalline 0.2at.%Hf-Ni, 2at.%Hf-Ni and 5at.%Hf-Ni alloys, by the time differential perturbed angular correlation (TDPAC) method at room temperature (RT). The hyperfine magnetic field (Hhf) in 0.2at.%Hf-Ni alloy at the 181Ta probe is 8.66(1)T, where the small atomic concentrations of Hf atoms mainly substitute on Ni host lattice sites. Three hyperfine interactions were detected in two other alloys. In the 2at.%Hf-Ni alloy, we found existence of Larmor precession frequency ωL (1)=536(2)Mrad/s at the 181Ta probe surrounded by Ni atoms and the second electric quadrupole interaction (EQI) ωQ (2)=2.20(2)Mrad/s at the 181Ta probe in new formed HfNi5 intermetallic phase. The third EQI ωQ (3)=137.4(1)Mrad/s corresponds to the small amount of monoclinic HfO2 phase contamination at T<900K. In the 5at%Hf-Ni alloy, magnetic dipole interaction (MDI) at the 181Ta probe is ωL (1)=536(6)Mrad/s, while the second EQI at the site of the same probe in HfNi5 is ωQ (2)=2.24(2)Mrad/s. The presence of ωQ (3)=128(1)Mrad/s at the 181Ta probe originating from HfO2 contamination is in good accordance with earlier published results for this phase.52. konferencija ETRAN-a : Jun 8-12, Palić, 2008

Hyperfine interactions at 181Ta solute in ferromagnetic Hf-Ni alloys with low concentration of Hf atoms

We have measured hyperfine interactions of 181Ta probe in the polycrystalline 0.2at.%Hf-Ni, 2at.%Hf-Ni and 5at.%Hf-Ni alloys, by the time differential perturbed angular correlation (TDPAC) method at room temperature (RT). The hyperfine magnetic field (Hhf) in 0.2at.%Hf-Ni alloy at the 181Ta probe is 8.66(1)T, where the small atomic concentrations of Hf atoms mainly substitute on Ni host lattice sites. Three hyperfine interactions were detected in two other alloys. In the 2at.%Hf-Ni alloy, we found existence of Larmor precession frequency ωL (1)=536(2)Mrad/s at the 181Ta probe surrounded by Ni atoms and the second electric quadrupole interaction (EQI) ωQ (2)=2.20(2)Mrad/s at the 181Ta probe in new formed HfNi5 intermetallic phase. The third EQI ωQ (3)=137.4(1)Mrad/s corresponds to the small amount of monoclinic HfO2 phase contamination at T<900K. In the 5at%Hf-Ni alloy, magnetic dipole interaction (MDI) at the 181Ta probe is ωL (1)=536(6)Mrad/s, while the second EQI at the site of the same probe in HfNi5 is ωQ (2)=2.24(2)Mrad/s. The presence of ωQ (3)=128(1)Mrad/s at the 181Ta probe originating from HfO2 contamination is in good accordance with earlier published results for this phase.52. konferencija ETRAN-a : Jun 8-12, Palić, 2008

Perturbed Angular Correlation Investigation of the Electric Field Gradient At Ta-181 Probe in the Hf2ni7 Compound

The perturbed angular correlation method was employed to study the temperature dependence of electric field gradients at the Ta-181 probe in the polycrystalline Hf2Ni7 compound. The temperature evolution of the sample content was measured using high-temperature X-ray diffraction. To check the magnetic order of the sample, magnetization measurements and additional perturbed angular correlation measurements with externally applied magnetic field were performed. All obtained spectra showed no evidence of magnetic order of the Hf2Ni7 phase. Within the experimental resolution of the apparatus, the measured electric field gradients at Ta-181 probe for the two inequivalent Hf-181/Ta-181 sites in the Hf2Ni7 compound appeared as one in the range of 78-944 K. A single quadrupole interaction implies that the electric field gradients at the two Hf sites must be quite similar. At 293 K, the measured quadrupole interaction parameters are v(Q) = 433(1) MHz and eta = 0.300(4). An increase of the quadrupole frequency and a gradual rising of the asymmetry parameter were observed with increasing temperature. The high-temperature X-ray diffraction indicated a build up of HfO2 above 693 K

Mineral Characterization of Soil Type Ranker Formed on Serpentines Occurring in Southern Belgrade Environs Bubanj Potok

The paper addresses the issue of health risk associated with the presence of chrysotile in the soil type ranker formed on massive serpentines occurring in the area of Bubanj Potok, a settlement located in the southern Belgrade environs, Serbia. Characterization of the ranker soil was conducted by scanning electron microscopy, X-ray diffraction, micro-Raman spectroscopy and transmission Fe-57 Mossbauer spectroscopy. Scanning electron microscopy figures showed regular shaped smectite (montmorillonite) particles, aggregates of chlorite, and elongated sheets of serpentines minerals antigorite. X-ray diffraction analysis confirmed the presence of detrital mineral quartz polymorph as well as minor amounts of other mineral species. Micro-Raman spectroscopy identified the presence of dominant minerals, such as montmorillonite, kaolinite, muscovite, gypsum, calcite, albite, amphiboles (hornblende/kaersutite) and orthoclase. Important polymorph silica modifications of quartz, olivine (forsterite), pyroxene (enstatite/ferrosilite, diopside/hedenbergite), and serpentine (antigorite/lizardite/chrysotile) were identified

Investigation of hydrogen absorption kinetics on intermetallic compounds Hf2Ni, Hf2Co and Hf2Fe

Polycrystalline intermetallics Hf2Ni, Hf2Co and Hf2Fe are investigated as the hydrogen absorbers in the temperature range 348 to 823 K, under the constant hydrogen pressure of 1 bar. The absorption process was carried out in typical volumetric apparatus and H/M mole ratios together with rate constants and activation energies for hydrogen absorption reaction were determined. Achieved hydrogen absorption capacities at 573 K are: 0.60, 0.90 and 1.48 and rate constants at 573 K are: 0.38×10-3, 0.55×10-3 and 4.72×10-3 s-1 for Hf2Ni, Hf2Co and Hf2Fe respectively. Determined activation energies are: for Hf2Ni, 38.44 kJ/mol, for Hf2Co, 19.62 kJ/mol and 2.74 kJ/mol for Hf2Fe. From the obtained experimental results, it was concluded that Hf2Fe has the best hydrogen absorption ability among the examined intermetallics

Ab-initio Study of the Site Preference of Cd Impurity in Hf-Ag and Zr-Ag Compounds

Conference on Computational Physics : September 5-8, Brussels, Belgium, 2007

Učinak Ga-As lasera na Streptococcus mutans i temperaturne promjene na koži i sluznici

Effects of the Ga-As soft laser on clinically oral-isolated Streptococcus mutans and on temperature changes of the finger pad and ear lobe skin and tongue mucosa were studied. Bacterial suspensions of S. mutans were placed on solid blood agar plates. The center of the plates was subjected to 3-min laser treatment every 24 h during a six-day period. Then the bacteria from the target area were maintained on a new plate and examined for survived bacteria. The use of the laser on the agar plate surface produced no bacterial or bacteriostatic effect. Additionally, temperature changes of the ear lobe skin and finger pad skin and tongue mucosa during and after laser treatment were not significantly different from the control values.U radu je ispitivan in vitro antibakterijski učinak Ga-As niskoenergetskog lasera na oralni Streptococcus mutans. Bakterije nasađene na ploče krvnog agara obasjavane su tri minute svakih 24 sata kroz šest dana. Nakon toga, bakterije s ciljanih mjesta presađene su na nove ploče. Osim toga, na pet ispitanika ispitivan je i temperaturni učinak lasera na kožu ušne resice, jagodice prsta i sluznicu vrha jezika. U in vitro uvjetima nije zabilježen baktericidni niti bakteriostatski učinak lasera. Temperaturne promjene na koži i sluznici jezika, tijekom i nakon zračenja, nisu bile statistički vjerodostojno različite od kontrolnih vrijednosti