Multilayer integrated porous membranes are obtained in a monolithic frame containing two types of porous silicon: macroporous silicon with pore diameters up to 10 μm and channel silicon with channel ...diameters from 100 to 300 nm. A laboratory technology is proposed for preparing macroporous/channel silicon two-layer structures with the use of high-resistance
n
-Si substrates (1 Ω cm). The pore-formation mechanism and its effect on the morphology of porous layers for electrolytes using formic acid and ammonium hydroxide are discussed.
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The structure of individual multi-wall carbon nanotubes exposed to irradiation by a argon ions and electron flux, as well as subsequent heat processing in an inert medium has been studied using ...transmission electron microscopy and x-ray photoelectron spectroscopy. It has been shown that irradiation with argon ions and electrons leads to the formation of defects in the structure of carbon nanotubes, changes in the interlayer distance in the walls of nanotubes, and the fixing of functional oxygen-containing groups on their surface. Annealing of pre-irradiated nanotubes in an inert atmosphere causes a partial restoration of the multi-wall carbon nanotube structure. At the same time, in the case of irradiation with argon ions, the nanotube structure is being recovered and the oxygen concentration decreases. In the case of electron irradiation after annealing, extended multi-vacancy defects occur, on which functional groups containing a double chemical bond of carbon and oxygen (C=O) are formed. Using calculations carried out within the framework of density functional theory, the coupling energy values and optimized geometry for various configurations of vacancy clusters in the graphene plane have been obtained.
Experimental study of electronic structure of the initial multi-walled carbon nanotubes (MWCNTs) as well as the exposed to annealing and irradiation N-MWCNTs, was carried out by XPS and NEXAFS ...methods. Based on the obtained photoelectron valence band spectra and C K-edge absorption spectra, a theoretical description of the density of electronic states (DOS) near the Fermi level was proposed to explain the dependence of the DOS and the band gap on temperature, concentration of doping atoms and various atomic configurations formed in a system during synthesis, subsequent ion-beam and heat treatment of MWCNTs.
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Multiscale structure of two Co
x
Al
y
O
z
cermets was examined by a combination of XRD, SEM coupled with EDX, NMR (
59
Co;
27
Al), and textural measurements. A strong CoAlO/CoAl cermet monolith ...prepared by mechanical alloying of Co and Al powders followed by hydrothermal treatment and calcination in air comprised two parts: the metal core consisting of Co and a Co–Al alloy, and the outer oxide matrix including a mixture of Co
x
Al
3–
x
O
4
spinel and cobalt oxides. The two parts were separated by the alumina interface protecting the metal core against the oxidation. Al
2
O
3
/CoAlO/CoAl cermet prepared by mixing the Co–Al mechanically alloyed product and pure aluminum hydroxide with subsequent hydrothermal treatment and calcination in air consisted of three main parts: (i) large cobalt-free porous alumina (ii) surrounded by Co
x
Al
3–
x
O
4
spinel oxides, and (iii) the inner core containing pure Co metal particles covered with the Co–Al alloy. A random distribution of metal particles in the oxide matrix provided an enhanced microwave absorption. A developed porosity ensured a high activity of the catalyst prepared from the porous cermet in the hexane dehydrogenation under microwave heating.
With the use of X-ray photoelectron spectroscopy (XPS) there have been investigated the changes of the chemical state of nitrogen atoms in the structure of nitrogen-doped multiwalled carbon nanotubes ...(CNx-MWCNTs) resulting from the impact of pulsed ion beam at various parameters of the beam (energy density, number of pulses). It has been established that irradiation with the pulsed ion beam leads to a reduction of the total amount of nitrogen in CNx nanotubes. It has been shown that a single pulse irradiation of ion beam at the energy densities of 0.5, 1, 1.5J/cm2 leads to restructuring of the nitrogen from pyridinic and pyrrolic configuration to graphitic state. Complete removal of nitrogen (pyridinic, pyrrolic, graphitic) embedded in the structure of the walls of CNx nanotubes occurs at ten pulses and 1.5J/cm2.
It has been shown that solketal can be synthesized from glycerol and acetone irradiation in the presence of montmorillonite (MM) modified with an aqueous solution of 0.25 mol/L of HCl (0.25M HCl/MM). ...The reaction has been studied in a methanol solution at an acetone/glycerol molar ratio of 2.45–7.53, a catalyst concentration of 1.2–2.8 wt % (based on glycerol weight), and 30–56°C. It has been shown that solketal is the major product with a selectivity of 96.1–99.2%. The maximum solketal yield of 91.3% with a 98.6% selectivity is obtained within 15 min of reaction at an acetone/glycerol molar ratio of 7.53, a catalyst loading of 2.3 wt % (based on glycerol weight), and 56°C. The catalytic properties of 0.25M HCl/MM in the reaction under microwave and thermal heating conditions have been compared. It has been shown that the solketal yield in the reaction under MW irradiation is 2 times higher than that in the process with thermal heating.
Using the methods of X-ray photoelectron (XPS) and X-ray absorption near edge structure (XANES) spectroscopies with synchrotron radiation, data on changes in the electronic structure and chemical ...composition of nitrogen-containing multiwalled carbon nanotubes (N-MWCNTs) upon their exposure to the radiation of argon ions with an energy of 5 keV are obtained. It is found that the exposure leads to an increase in the degree of defectiveness of the N-MWCNTs structure and to the carbon oxidation with formation of various oxygen-containing groups (C–OH, C=O/COOH, C–O–C/O–C–O, and CO
3
). The presence of carbon–oxygen bonds on the surface of carbon nanotubes is associated with the formation of radiation defects. It is shown that an increase in the fraction of nitrogen atoms present in the substituting configuration in the N-MWCNTs wall structure due to the irradiation does not give rise to an increase in the density of the occupied states near the Fermi level against the background of an increase in the degree of structure defectiveness, carbon oxidation, and a decrease in the total nitrogen concentration. The obtained results show that the irradiation of N-MWCNTs with argon ions allows one to successfully functionalize their surface.
In order to evaluate the efficiency of the catalytic aquathermolysis process, physical modeling was carried out on bituminous sediments of Paleocene–Miocene carbonate rocks, characterized by the ...presence of open and closed fractures. In this context, three filtration experiments were performed on an unextracted reservoir model with extra-viscous oil (EVO). Prior to the experiments, the mineral composition of the rock was determined by X-ray diffraction analysis (XRD) and the content of organic matter and coking products was determined before and after the experiment by thermogravimetric analysis (TGA) as well as the group composition of oil (SARA) before and after the experiment by nuclear magnetic resonance (NMR), gas composition at the fluid separation line, and oil displacement coefficient (ODC). The results of the conducted experiments show that the efficiency of displacement of extraviscous oil could be significantly increased by the use of a solvent and the combined use of a solvent and a catalyst (+9.3% and +17.1% of the oil displacement coefficient, respectively), which is associated with the processes of oil refining.
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