Stability of nanomaterials during their life cycle is a crucial problem of modern nanoscience. In order to understand the processes, which are going in the nanostructures, the comprehensive study of ...the influence of media with different acidity on the nickel nanotubes morphology and structure was carried out. On the base of the analysis of nanotubes characteristics, sequential evolution of degradation stages involving the surface passivation, formation of point defects, pitting and destruction of nanotubes walls was determined. The results are of importance for the wide range of potential nickel nanostructures applications, which are associated with their using in real-life conditions. To improve Ni nanostructures stability, the possible ways of surface protections from the aggressive environment effect and the routes of nanostructures covering with gold, organosilicon compounds and polymer coatings were considered. Demonstrated approaches for nanostructures covering provide an opportunity of surface functionalization for attaching of different molecules. It is useful for targeted delivery of drugs and genes, biodetection, bioseparation and catalysis application.
•The influence of media with different pH (1...7) on nanotubes was studied.•Nanotubes morphology and structure after interaction were analyzed.•Ni nanotubes degradation mechanism was described.•Degradation scheme: passivation → formation of point defects → pitting → destruction.•Ways of surface protection with gold, organosilicon and polymer coatings were shown.
Digital rock physics is used for the investigation of oil and gas reservoirs. It involves various mathematical simulations on a digital representation of a rock sample, which is usually obtained with ...imaging techniques. Focused ion beam scanning electron microscopy (FIB-SEM) tomography provides high-resolution images of sequential layers of a sample, and segmentation of these images is a key stage in the construction of 3D digital rock. Conventional segmentation methods are not applicable for FIB-SEM images due to specific artifacts such as the pore-back effect. We propose a new segmentation algorithm that relies on the marker-controlled watershed, variance filter and morphological operations. The results are validated with the use of manually labelled ground truth data. Furthermore, we develop a new metric for evaluation of segmentation quality. This metric is based on analysis of segmented regions and, in the case of porous media, provides more reliable evaluation than pixel-wise measures.
Due to the Ni nanotubes’ shape anisotropy, low specific density, large specific surface, and uniform magnetic field, they have been offered as carriers for targeted delivery of drug or protein and ...the process of their formation from synthesis stage to the stage of surface modification and protein attaching has been demonstrated. Some steps to hasten their biomedical application have been applied. First, to have full control over the carrier dimensions and structure parameters, electrodeposition method in pores of polyethylene terephthalate template has been applied. Second, to understand the scope of Ni nanostructures application, their degradation in media with different acidity has been studied. Third, to improve the biocompatibility and to make payloads attachment possible, nanotubes surface modification with organosilicon compound has been carried out. At last, the scheme of protein attaching to the nanostructure surface has been developed and the binding process was demonstrated as an example of the bovine serum albumin.
Within the approach based on chemical modification of domain boundaries of polycrystalline graphene, a transistor channel is proposed for enhanced current modulation,
I
on
/
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off
ratio, in the 3 to ...5 order of magnitude. We observed that two types of samples functionalized by
N
-methylpirrolidone (NMP) and weakly fluorinated graphene are able to demonstrate high current modulation. Experimentally,
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on
/
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~ 10
3
was found for NMP functionalized graphene and
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on
/
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off
~ 10
4
–10
5
for weakly fluorinated graphene. Modeling of these two systems allows us to clarify the mechanism of carrier transport in the multi-barrier films of functionalized graphene films. It is shown that remarkable value for
I
on
/
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off
as about 10
6
can be observed for the films comprising graphene regions (graphene quantum dots, GQDs) with size of ~ 30–300 nm and ~ 75–100 nm fluorinated graphene barriers. Relatively high values of
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on
/
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off
~ 10
3
–10
5
are also predicted for large graphene areas separated with thin (100 nm) barriers for the weakly fluorinated graphene samples. Our study paves a way towards controllable 2D transistors.
Metal foams, which are similar to other types of foam materials, are composed of solid material with a significant proportion of the volume consisting of pores. Although metal foams retain some of ...the properties of the original material, they also possess several advantageous characteristics such as low density and thermal conductivity, high specific stiffness, and porosity. As a result, metal foams are becoming increasingly popular for applications such as heat exchangers, soundproofing devices, and gas–liquid filters. Additive manufacturing has the potential to expand the production capabilities of foams by reducing materials consumption and the creation of complex geometry. This work demonstrates the possibility of direct 3D printing of metal foams made of titanium, aluminum, and aluminum-bronze using direct energy deposition and special parameters of the printing process. This method is superior to traditional methods in terms of cost and the absence of additional stages of preparation and post-processing. The open porosity of the foam can be easily changed by varying the laser power. The laser power in the range of 10 to 180 W along with rapid prototyping makes it possible to obtain metal foams of complex geometry with a high degree of open porosity (up to 50% for titanium and up to 30% for aluminum alloys), not inferior in quality to foams obtained by conventional methods. Moreover, by changing the printing modes, it is possible to adjust the structure of foam from uniform to columnar, increasing the thermal conductivity and insulating properties of the samples.
The 10 m
muon hodoscope made of drift tubes with length of 3.7 m and diameter of 52 mm is under development and construction at the NRC Kurchatov Institute—IHEP. In total, 768 drift tubes are grouped ...into six identical multilayers, each consisting of two tube layers with parallelly placed tubes. The orientation of tubes in adjacent multilayers is orthogonal; thus, the hodoscope has six
and six
layers of tubes. The mechanical structure, on-chamber electronics, and data acquisition system are described. Expected technical characteristics and some test results are presented.
The proppant is a granular material with a typical size of 0.2 to 1.2 mm. It is used to prevent the closure of fractures in the reservoir created by hydraulic fracturing procedure, which is actively ...used in the oil and gas industry. Some types of proppant are manufactured from porous technical ceramics. Presence of internal voids can dramatically decrease the proppant grain mechanical strength and consequently proppant pack conductivity under natural stress. For a detailed study of proppant particles' internal porosity structure and its relation to the pack's strength, we applied X-ray microtomography (microCT), which allows to observe this structure non-destructively. In the work, we presented our approaches for digital analysis of reconstructed 3D microCT images for studying the internal voids and the homogeneity of their distribution inside the proppant. We used an automatic thresholding for primary segmentation of pores and particles. We apply 3D marker-controlled watershed to separate individual proppant particles. We propose features for characterization of radial and layered porosity distribution for each particle and homogeneity evaluation. The correctness of our method was tested on synthetic models. Current results indicate probable dependence of proppant strength properties on its internal porosity, but not on the homogeneity of porosity distribution.
Modern electronic systems and equipment used in aerospace and nuclear technology, as well as many scientific and medical devices, are used under the influence of a wide range of ionizing radiation ...(electrons, protons, heavy charged particles etc.). Protons or heavy charged particles exposure can lead to failures in the operation of spacecrafts electronic devices, which is associated with the radiation effects occurrence in an integrated circuits. One of the most effective ways to solve this problem is protection by radiation shields. Linear and mass paths of protons and Ar+ ions in Al, Al2O3, Bi, and W77, 7Cu22, 3 composite shields were calculated using a SRIM software package. It is shown that the protection efficiency against high-energy ions by materials with large atomic charge values (Z) is higher from the position of linear ranges of particles, and lower from the position of mass ranges than materials with low Z values. The dependence of the threshold energy on the serial number of particles for Al, Bi and W77, 7Cu22, 3 composite shields is determined. The effect of the sequence in the arrangement and layer thicknesses in the Bi/Al/Al2O3 multilayered structures on the protection efficiency against high-energy ions was studied.
The SPASCHARM experiment is aimed at a systematic study of the nucleon spin structure and the spin dependence of the strong interaction of antimatter and matter with matter at energies up to 45 GeV. ...As part of the first stage of the experiment, the study of the spin properties of hadrons will take place in a beam of negatively charged hadrons on existing beamline 14 at the operating SPASCHARM setup at the U70 facility. At the second stage, the production of polarized beams of protons and antiprotons is envisaged in beamline 24A of the U-70 accelerator facility. A polarized antiproton beam will certainly become a unique beam in the world. It is planned to measure single-spin asymmetries in dozens of reactions, both on hydrogen and on various nuclei. At the SPASCHARM facility, it is also possible to measure the transverse polarization of hyperons and elements of the spin density matrix of vector mesons. The spin structure of the nucleon will be investigated in the study of quarkonium production to determine the contribution of gluons to the proton spin. The presence of two types of polarized beams and eight types of nonpolarized beams (π
±
,
K
±
,
p
,
,
d
,
C
), in combination with a polarized target, expands the range of studies of polarization phenomena and enhances the uniqueness of the project.
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