In this study, wide-angle X-ray diffraction, X-ray absorption spectroscopy, and transmission electron microscopy were employed to address the crystalline structure and morphology of ...poly(p-xylylene)–PbS nanocomposite thin films prepared by vapor deposition polymerization as well as their evolution upon thermal annealing. It was found that as-synthesized samples with different PbS contents demonstrate similar diffraction patterns that cannot be fully ascribed to a decrease in crystallite size, indicating distorted crystal structure of PbS nanoparticles compared to the bulk PbS. X-ray absorption spectroscopy reveals wide distribution of Pb–S bond lengths with a minimum value of 2.67 Å, which can be attributed to the presence of molecular (PbS) n clusters in the studied films. It was shown that thermal annealing can be used to control the size of PbS nanoparticles and, as a consequence, optical properties of the composite films. The UV–vis absorption spectra demonstrate pronounced red shift of the absorption edge correlated with the growth of PbS nanoparticles upon annealing. Comprehensive analysis of several theoretical models describing the effect of nanoparticles size on optical band gap of the composite material has been performed and compared with the experimental data.
The effect of the structure of novel synthesized macromonomers of methoxy oligo(ethylene glycol)-
block
-oligo(propylene glycol) methacrylates on their manifestation of amphiphilic properties in ...water and a water–hexane mixture is studied. The effect of the length of the hydrophilic and hydrophobic blocks of the macromonomers on the surface or interfacial tension and partition between the phases in water and a water–hexane mixture on the position of the macromonomers in the two-dimensional amphiphilicity diagram of organic substances is shown.
Composite hydrogels in the poly-N-vinylpyrrolidone – RE(NO3)3 × xH2O system with RE = La, Gd, Yb were prepared in various forms (native, native dried in the air, dried in air and ground into powder). ...They were studied by methods of wide- and small-angle X-ray scattering, differential scanning calorimetry, scanning electron microscopy, and electron microprobe analysis. The composition of native PVP and PVP with powdered RE(NO3)3 × xH2O includes 4 types of structural water, which content depends on the RE type. The PVP/La(NO3)3 × 6H2O surface includes “flower-like structures” consisting of whisker fragments up to 15–20 μm in size. The size of structural inhomogeneities of air-dried and then swollen in water hydrogels decreases with decreasing RE radii as well as the degree of the swelling. The antimicrobial activity (AMA) in the dark relative to Staphylococcus aureus, Escherichia coli, and Candida albicans is characteristic of all the samples. The AMA of RE(NO3)3 × xH2O (RE = La, Gd, Yb) is more effective by as compared with PVP/RE(NO3)3 × xH2O besides PVP/La(NO3)3 × 6H2O. This can be explained by different composition of particles with lanthanum on the surface of hydrogels as compared with La(NO3)3 × 6H2O. The relationship of AMA with the size of structural inhomogeneities in hydrogels, surface morphology, water content, and the role of microorganisms is not ruled out.
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•Poly-N-vinylpyrrolidone-based hydrogels with rare earth nitrates were prepared.•The type of rare earth affects the content of structural water in the hydrogels.•All composite hydrogels possess antimicrobial activity in the dark.•The hydrogels microstructure depends on the type of rare earth.
We present an improved measurement of the carbon-nitrogen-oxygen (CNO) solar neutrino interaction rate at Earth obtained with the complete Borexino Phase-III dataset. The measured rate, ...R_{CNO}=6.7_{-0.8}^{+2.0} counts/(day×100 tonnes), allows us to exclude the absence of the CNO signal with about 7σ C.L. The correspondent CNO neutrino flux is 6.6_{-0.9}^{+2.0}×10^{8} cm^{-2} s^{-1}, taking into account the neutrino flavor conversion. We use the new CNO measurement to evaluate the C and N abundances in the Sun with respect to the H abundance for the first time with solar neutrinos. Our result of N_{CN}=(5.78_{-1.00}^{+1.86})×10^{-4} displays a ∼2σ tension with the "low-metallicity" spectroscopic photospheric measurements. Furthermore, our result used together with the ^{7}Be and ^{8}B solar neutrino fluxes, also measured by Borexino, permits us to disfavor at 3.1σ C.L. the "low-metallicity" standard solar model B16-AGSS09met as an alternative to the "high-metallicity" standard solar model B16-GS98.
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•Zwitterionic and anionic surfactants demonstrate the formation of giant linear long-lived WLMs at low concentrations.•Such micron length WLMs form a three-dimensional elastic ...gel-like structure also called temporally persistent network.•At heating the long linear “unbreakable” WLMs transform into short linear “unbreakable” WLMs.•At increasing surfactant concentration, the long-lived linear micelles transform into fast-breaking branched micelles.•The viscosity and terminal relaxation time drop crucially due to the branched micelles formation.
Rheometry, small-angle neutron scattering, and cryo-transmission electron microscopy were combined to investigate the structure and properties of mixed wormlike micelles (WLMs) of zwitterionic (oleylamidopropyl dimethyl betaine) and anionic (sodium dodecylsulfate) surfactants. This system demonstrates the formation of giant linear long-lived WLMs, which even at extremely low surfactant concentration reach a sufficient length to entangle with each other and form a three-dimensional temporally persistent network. Stability of these micelles can be due to electrostatic attraction between the headgroups of the anionic and zwitterionic surfactants and favorable volume/length hydrophobic ratio in the surfactant mixture. Heating of these systems leads to the transition of temporally persistent network with predominantly elastic properties into transient network exhibiting viscoelasticity, which is due to the shortening of long-lived WLMs. At increasing surfactant concentration, the long-lived linear micelles transform into fast-breaking branched micelles, which is due to the screening of electrostatic interactions by salt released from the dissociated surfactant molecules. The transition results in the drop of viscosity and approaches the system to the behavior of Maxwell fluid with a single relaxation time. The observed structural transitions strongly affecting the rheological properties can be exploited in various applications of zwitterionic surfactants.
The possibilities of low-voltage scanning electron microscopy for visualization of specific features of the microstructure in internal layers of multilayer polymer films are demonstrated by the ...example of “chitosan–polyelectrolyte complex–alginic acid” composite. The process of electron beam interaction with a sample at low electron energies is considered. The key parameters of low-voltage electron microscopy, which make it possible to increase the resolution of SEM images of polymer systems, are discussed.
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•Combined vacuum electrospark deposition and pulsed arc evaporation technology.•Double-layer NiAlCrCoHf coating for protection of LBPF Ni superalloy.•Electrospark treatment ...effectively removes surface defects and smooths surface.•Epitaxial oriented crystallization in electrospark layers.•Dense Al2O3 oxide layer formed on coatings protects against oxidation at 1000 °C.
The combined vacuum technology involving electrospark deposition (ESD) and pulsed arc evaporation (PAE) is used to deposit a double-layer NiAlCrCoHf coating onto a substrate manufactured by a laser powder bed fusion (LPBF) of heat-resistant EP741 nickel superalloy. Thickness of the ESD and PAE layers are 35 and 4 µm, respectively. The energy parameters of ESD ensuring the predominantly epitaxial oriented crystallization of the melt at each successive event of discharge transfer are identified. The top layer of the PAE coating is characterized by a hardness of more than 13 GPa due to a combination of the lamellar and columnar nanostructure. Heating to a temperature of 700 °C causes precipitation of strengthening CrCoNi and Ni2AlHf phases in coating layers. The single-layer ESD coating and the double-layer PAE/ESD coating efficiently protect EP741 nickel alloy against oxidation at 1000 °C. A barrier oxide layer based on Al2O3 with a thickness of <1 µm is formed on the coatings.
Electrorheological fluids based on polydimethylsiloxane filled with halloysite nanotubes were studied. The filler structure was characterized by TEM, SEM, and X-ray diffraction. When an electric ...field is applied to suspensions, their rheological behavior changes - the contribution of the elastic component becomes significant and samples behave like a solid body. The effect of the electric field and filler concentration on the electrorheological behavior was investigated. The influence of water content on the filler structure, as well as on electrorheological and electrophysical properties of suspensions, was considered. Electrorheological fluids filled by halloysite with small water content exhibit slightly higher rheological characteristics under an electric field than dried ones. This study shows the prospects of using halloysite nanotubes as a dispersed phase for electrorheological fluids.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
In the 1st part of this article, hardmetal deformation processes caused by bending loads were examined in-situ by transmission electron microscopy. The major objective of this work is to examine ...hardmetal deformation processes in special thin hardmetal samples as a result of applying tensile loads in-situ directly in a transmission electron microscope with the aid of the push-to-pull method. Applying tensile loads to the samples results in the plastic deformation of the Co-based binder phase leading to the formation of different crystal lattice defects in the binder. Force-time and displacement-time curves recorded when loading the samples and maintaining the loads provide evidence for continuous processes of the formation and movement of crystal lattice defects, presumably dislocations, in the WC phase and Co-based binder leading to a high rate of the binder plastic deformation. After increasing the tensile loads up to a certain level leading to the severe plastic deformation of the binder phase, the samples suddenly fail as a result of the crack initiation and propagation at WC-Co interfaces. Presence of cobalt on the WC surface after the cracking suggests that the cracks propagate through the binder region adjacent to the interface rather than through the interface itself.
•The deformation behavior of hardmetal under tensile loads was investigated using in situ TEM techniques.•Applying tensile loads to the samples is found to result in the plastic deformation of the Co-based binder.•Crack propagation path lies in Co-based binder in the area, adjacent to the WC-Co interface.
Zr-Mo-Si-B coatings were successfully deposited using non-reactive magnetron sputtering of ceramic ZrMoSiB target. Structural investigations have been carried out using X-ray diffraction analysis, ...high-resolution transmission and scanning electron microscopy, glow-discharge optical-emission, and energy-dispersive spectroscopy. The coatings were subjected to the indentation using nanohardness-tester and picoindenter module placed in the column of transmission electron microscope. The obtained results show that the coatings consist of hcp-ZrB2 phase with needle crystallites 5-10 nm in diameter elongated in the direction of growth. The coatings demonstrated relatively high mechanical properties and recordable elastic recovery up to 84%. Results of indentation tests exhibited the close results.
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