FeNi films of different thickness and FeNi/(Fe, Co)/FeNi trilayers were prepared by magnetron sputtering deposition onto glass substrates. The permalloy films had a columnar microstructure. The ...detailed analysis of the magnetic properties based on the magnetic and magneto-optical measurements showed that at thicknesses exceeding a certain critical thickness, hysteresis loops acquire a specific shape and the coercive force of the films increase sharply. The possibility of the estimation of the perpendicular magnetic anisotropy constant using the Murayama equation for the thickness dependence of saturation field was demonstrated. The results of studies of the structural and magnetic properties of FeNi films laminated by Fe and Co spacers with different thickness are presented.
Abstract
We report on the experimental and theoretical study of the near-field diffraction of optical vortices (OVs) at a two-dimensional diffraction grating. The Talbot effect for the optical ...vortices in the visible range is experimentally observed and the respective Talbot carpets for the optical vortices are experimentally obtained for the first time. It is shown that the spatial configuration of the light field behind the grating represents a complex three-dimensional lattice of beamlet-like optical vortices. A unit cell of the OV lattice is reconstructed using the experimental data and the spatial evolution of the beamlet intensity and phase singularities of the optical vortices is demonstrated. In addition, the
self-healing
effect for the optical vortices, which consists in flattening of the central dip in the annular intensity distribution, i.e., restoring the image of the object plane predicted earlier is observed. The calculated results agree well with the experimental ones. The results obtained can be used to create and optimize the 3D OV lattices for a wide range of application areas.
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•One-dimensional materials as supports for ammonia decomposition (AD) catalysts.•The coating of alumina nanofibers (ANF) by carbon increases TOF by 2 times.•The introduction of cesium ...to the carbon coated ANF increases TOF by 6 times.•The coating of ANF by carbon is very favorable for high activity of ruthenium in AD.
The study of ruthenium catalysts for ammonia decomposition on carbonized and noncarbonized Al2O3 nanofibers (ANF) showed that activity of the catalysts with carbonized supports (ANFC) was twofold higher as compared to noncarbonized ones. Thus, on Ru/ANFC and Ru-Cs/ANFC the release of hydrogen reached 8.7 and 18.3 mmol H2/(min·gcat), respectively, whereas on Ru/ANF and Ru-Cs/ANF, only 4.4 and 9.6 mmol H2/(min·gcat), respectively. According to TEM, Ru particles on ANFC have a greater size than on ANF but are distributed more uniformly. As shown by TEM, XRD and XPS data, ANFC and ANF fibers are strongly different.
Burning coal seams, characterized by massive carbon monoxide (CO) emissions, the presence of secondary sulfates, and high temperatures, represent suitable environments for thermophilic sulfate ...reduction. The diversity and activity of dissimilatory sulfate reducers in these environments remain unexplored. In this study, using metagenomic approaches,
in situ
activity measurements with a radioactive tracer, and cultivation we have shown that members of the genus
Desulfofundulus
are responsible for the extremely high sulfate reduction rate (SRR) in burning lignite seams in the Altai Mountains. The maximum SRR reached 564 ± 21.9 nmol S cm
−3
day
−1
at 60°C and was of the same order of magnitude for both thermophilic (60°C) and mesophilic (23°C) incubations. The
16S rRNA
profiles and the search for
dsr
gene sequences in the metagenome revealed members of the genus
Desulfofundulus
as the main sulfate reducers. The thermophilic
Desulfofundulus
sp. strain Al36 isolated in pure culture, did not grow at temperatures below 50°C, but produced spores that germinated into metabolically active cells at 20 and 15°C. Vegetative cells germinating from spores produced up to 0.738 ± 0.026 mM H
2
S at 20°C and up to 0.629 ± 0.007 mM H
2
S at 15°C when CO was used as the sole electron donor. The Al36 strain maintains significant production of H
2
S from sulfate over a wide temperature range from 15°C to 65°C, which is important in variable temperature biotopes such as lignite burning seams. Burning coal seams producing CO are ubiquitous throughout the world, and biogenic H
2
S may represent an overlooked significant flux to the atmosphere. The thermophilic spore outgrowth and their metabolic activity at temperatures below the growth minimum may be important for other spore-forming bacteria of environmental, industrial and clinical importance.
•Gas phase and surface reaction models are proposed to describe the growth of carbon nanotubes in PAA membranes.•A complimentary experimental study of CNT formation from ethanol precursor is ...performed.•A new method for characterizing carbon nanotubes geometry by SEM and TEM image processing is suggested.•The dependence of carbon growth rate on the temperature, pressure, argon and ethanol flow rate is investigated.•The predictions of developed models are in good agreement with the experimental data
Porous anodic alumina (PAA) membranes represent a widely used and extensively studied template for production of carbon nanotubes (CNT). The PAA–CNT membranes possess a number of unique properties, such as controllable nanotube geometry, size– and chemically–based selectivity as well as high water permeability. In this work, we first propose a combination of gas phase and surface reaction models to quantitatively describe the growth of carbon nanotubes in PAA membranes in a commercial CVD reactor. A complimentary experimental study of CNT formation from ethanol precursor with argon as a carrier gas is performed. A new method for characterizing carbon nanotubes geometry by SEM and TEM image processing of membrane cross–sections is proposed. The simulations show that the carbon growth rate (in nm/min) averaged over the membrane remains constant during the deposition process until the pore diameter becomes relatively small, and rapidly falls to zero after that. The carbon nanotube thickness near the membrane surface is slightly higher than that in the membrane center. The carbon growth rate increases with synthesis temperature and pressure, while it decreases with the argon flow rate. The dependence of carbon growth rate on the ethanol/water flow rate reaches maximum at some intermediate value. These results are supported by the experimental data obtained from SEM/TEM image processing. It is found that the SEM data provide overestimated values of nanotube diameter and thickness in comparison with the TEM data. The obtained results provide new insights into the CNT growth kinetics in nanoporous media, and develop quantitative guidelines for synthesis of CNT–PAA membranes with precisely controlled nanopore geometry. It also validates the combined homogenous / heterogeneous reaction model by comparison with carbon deposition kinetics on a nanometer scale.
The assessment of microbial contamination is an important aspect of ensuring human food safety. One of the modern methods for the evaluation of microbial contamination is the estimation of the amount ...of ATP using firefly luciferase. In this case, the choice of an effective composition of the extraction buffer is crucial. In this study, we examined the influence of silver and gold nanoparticles on the firefly bioluminescent system during the ATP extraction process. It was found that gold nanoparticles stabilized with benzalkonium chloride and Triton X-100 enhanced bioluminescent system signal intensity due to metal-enhanced bioluminescence. Moreover, silver and gold nanoparticles could be used as extracting agents. So, using gold nanoparticles stabilized with BAC and Triton X-100 as ATP extraction agents with further detection by a bioluminescent system makes it possible to develop an ATP biosensor with higher sensitivity.
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•Safe and sensitive bioluminescent method of microbial contamination assessment.•Explanation of MEB-effect in firefly bioluminescence.•Bioluminescent signal enhancement due to adding gold and silver nanoparticles.
We have studied, both experimentally and theoretically, the unusual temperature dependence of the phonon spectra in NdCoO
, SmCoO
and GdCoO
, where the Co
ion is in the low-spin (LS) ground state, ...and at the finite temperature, the high-spin (HS) term has a nonzero concentration nHS due to multiplicity fluctuations. We measured the absorption spectra in polycrystalline and nanostructured samples in the temperature range 3-550 K and found a quite strong breathing mode softening that cannot be explained by standard lattice anharmonicity. We showed that the anharmonicity in the electron-phonon interaction is responsible for this red shift proportional to the nHS concentration.
•Solid-state reaction in Ag/Al thin films has been investigated.•Phase sequence has been determined: Ag+Al→(Ag)+(Al)→ (Ag)+δ-Ag2Al→µ-Ag3Al.•Autocatalytic nature of intermetallic compound formation ...has been established.•Kinetic parameters of the µ-Ag3Al formation have been determined for the first time.
A solid-state reaction process in Ag/Al multilayer thin films has been investigated by the methods of in situ electron diffraction, simultaneous thermal analysis, transmission electron microscopy and X-ray diffraction with the aim of studying the phase formation kinetics of intermetallic compounds. The sequence of the phase transformations in the solid-state reaction has been established: Ag+Al→(Ag)+(Al)→(Ag)+δ-Ag2Al→μ-Ag3Al. The process of the solid-state interaction has been shown to consist of two steps; each of them is described by a kinetic model of the nth order reactions with autocatalysis. The kinetic parameters of the autocatalytic process of the phase formation for δ-Ag2Al and µ-Ag3Al, have been determined, in particular, their apparent activation energy: 126 kJ/mol and 106 kJ/mol, respectively.
The development of effective catalysts for the pyrolysis of light hydrocarbons with the production of carbon nanomaterials represents a relevant direction. In the present work, the influence of ...copper addition on performance of a self-dispersed Ni-catalyst and structural features of the obtained carbon nanofibers (CNFs) was studied. The precursors of Ni and Ni-Cu catalysts were prepared by activation of metal powders in a planetary mill. During contact with the C2H4/H2 reaction mixture, a rapid disintegration of the catalysts with the formation of active particles catalyzing the growth of CNFs has occurred. The kinetics of CNF accumulation during ethylene decomposition on Ni- and Ni-Cu catalysts was studied. The effect of temperature on catalytic performance was explored and it was shown that introduction of copper promotes 1.5–2-fold increase in CNFs yield in the range of 525–600 °C; the maximum CNFs yield (100 g/gcat and above, for 30-min reaction) is reached on Ni-Cu-catalyst at 575–600 °C. A comparative analysis of the morphology and structure of CNF was carried out using electron microscopy methods. The growth mechanism of carbon filaments in the shape of “railway crossties” on large nickel crystals (d > 250 nm) was proposed. It was found that the addition of copper leads to a decrease in the bulk density of the carbon product from 40–60 to 25–30 g/L (at T = 550–600 °C). According to the low-temperature nitrogen adsorption data, specific surface area (SSA) of CNF samples (at T < 600 °C) lies in the range of 110–140 m2/g, regardless of the catalyst composition; at T = 600 °C the introduction of copper contributed to an increase in the specific surface of CNF by 100 m2/g.
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