Here, the synthesis of holey carbonylated (C-ny) graphene derivative and its application for gas sensing is demonstrated. The carbonylation of graphene oxide leads to the 3-fold increase in the ...concentration of carbonyl groups’ up to 9 at.% with a substantial elimination of other oxygen functionalities. Such a chemical modification is accompanied by the perforation of the graphene layer with the appearance of matrices of nanoscale holes, leading to corrugation of the layer and its sectioning into localized domains of the π-conjugated network. Combined with the predominant presence of carbonyls, granting the specificity in gas molecules adsorption, these features result in the enhanced gas sensing properties of C-ny graphene at room temperature with a selective response to NH3. Opposite chemiresistive response towards ammonia when compared to other analytes, such as ethanol, acetone, CO2, is demonstrated for the C-ny graphene layer both in humid and dry air background. Moreover, a selective discrimination of all of the studied analytes is further approached by employing a vector signal generated by C-ny multielectrode chip. Comparing the experimental results with the calculations performed in framework of density functional theory, we clarify the effect of partial charge transfer caused by water and ammonia adsorption on the chemiresistive response.
Display omitted
•GO can be converted to the carbonylated graphene containing up to 9 at.% of carbonyls.•Carbonylation leads to holey and corrugated structure of graphene layer.•Holey-matrixed structure and carbonyls enhance graphene gas sensing properties.•Carbonylated graphene exhibits an exceptional selectivity regarding the NH3 detection.
Display omitted
•5–500kW AC plasma torches for plasma chemical technologies are developed.•Air plasma gasification of coal, wood and RDF gives 43–55% of H2+CO in product gas.•Steam in the mix with ...other gases is using as plasma forming media in plasma torch.•Conversion is ∼99%, selectivity is ∼98%, during steam-CO2 plasma reforming of CH4.
The usage of plasma as a gasifying agent is efficient in waste to energy (WTE) gasification technologies. Over 20years the IEE RAS conducted researches in the field of Electrophysics, studied the properties of electrical discharges in gases and liquids in a wide range of pressures. AC plasma torches with long life time (thousands of hours) working on air, mixtures of steam, air, CO2 and CH4 have been developed. The power of these devices varies widely from 5 to 500kW and the thermal efficiency is 90–95%. Experimental results of wood, coal and refuse derived fuel (RDF) air plasma gasification are presented. The content of H2+CO is 43–55%vol., lower heating value (LHV) of product gas up to 6.61MJ/m3 when the specific energy consumption is 1.4–2.5MJ/kg of raw material. Methane reforming with usage of multi-gas plasma torch allows production of synthesis gas with H2 and CO selectivity up to 98%, methane conversion ∼99% and yield of soot is no more than 125mg/Nm3.
Specific features of using luminescent sensors with transducers based on a sensitive layer containing quantum dots immobilized in polymer matrixes of some fluorinated copolymers are described. ...Features of the formation of an analytical signal in time are studied. It is found that, in the analysis of some iodinated organic compounds, damped fluctuations of the luminescence intensity of the sensitive layer around a steady-state value can occur. Modern ideas of nonlinear and wave diffusion in polymer layers are attracted to explain the observed effects. Study of the kinetics of sorption by an independent method confirmed the fluctuations of sorption near its equilibrium value. The results obtained were used for the development of luminescent sensors based on quantum dots.
Recent results in magnonics - a topical and rapidly developing branch of spintronics and magnetoelectronics - are presented. The paper describes measurement techniques and theoretical approaches used ...to explore physical processes associated with the spin-wave propagation in complex nano- and micro-dimensional magnetic structures. The results of the application of magnetic structures in signal processing and transmission systems are discussed. In particular, results on spin wave propagation in distributed magnetic periodic structures, lumped systems, coupled waveguide structures, and controllable magnonic structures are considered. Specific examples of circuitry based on magnonic structures are discussed, and possibilities for further developing this circuitry are explored.
•Dynamics of the size-dependent FG Timoshenko beams with the von Kármán nonlinearity are studied.•The reference line simplifying the governing equations is introduced.•The results are validated ...through Lyapunov and wavelet spectra.•Influence of size and material grading coefficients on vibration characteristics is given.•Transition from regular to chaotic beam vibrations coincides with the Ruelle-Takens-Newhouse scenario.
Chaotic dynamics of microbeams made of functionally graded materials (FGMs) is investigated in this paper based on the modified couple stress theory and von Kármán geometric nonlinearity. We assume that the beam properties are graded along the thickness direction. The influence of size-dependent and functionally graded coefficients on the vibration characteristics, scenarios of transition from regular to chaotic vibrations as well as a series of static problems with an emphasis put on the load-deflection behavior are studied. Our theoretical/numerical analysis is supported by methods of nonlinear dynamics and the qualitative theory of differential equations supplemented by Fourier and wavelet spectra, phase portraits, and Lyapunov exponents spectra estimated by different algorithms, including Wolf’s, Rosenstein’s, Kantz’s, and neural networks. We have also detected and numerically validated a general scenario governing transition into chaotic vibrations, which follows the classical Ruelle-Takens-Newhouse scenario for the considered values of the size-dependent and grading parameters.
•Non-linear size dependent Sheremetev-Pelekh beams governing PDEs are derived.•Reliability and validity of the governing PDEs is studied regarding statics and dynamics.•Symmetric and non-symmetric ...frequency spectra distributions are detected and discussed.•The Pomeau-Mannevile route to chaos is illustrated in our infinite dimensional system.
In this work, a size-dependent model of a Sheremetev-Pelekh-Reddy-Levinson micro-beam is proposed and validated using the couple stress theory, taking into account large deformations. The applied Hamilton's principle yields the governing PDEs and boundary conditions. A comparison of statics and dynamics of beams with and without size-dependent components is carried out. It is shown that the proposed model results in significant, both qualitative and quantitative, changes in the nature of beam deformations, in comparison to the so far employed standard models. A novel scenario of transition from regular to chaotic vibrations of the size-dependent Sheremetev-Pelekh model, following the Pomeau-Manneville route to chaos, is also detected and illustrated, among others.
The current state of knowledge of the D-region ion photochemistry is reviewed. Equations determining production rates of electrons and positive ions by photoionization of atmospheric neutral species ...are presented and briefly discussed. Considerable attention is given to the progress in the chemistry of O
+
(
4
S), O
+
(
2
D), O
+
(
2
P), N
+
, N
2
+
, O
2
+
, NO
+
, N
4
+
, O
4
+
, NO
+
(N
2
), NO
+
(CO
2
), NO
+
(CO
2
)
2
, NO
+
(H
2
O)
n
for
n
= 1–3, NO
+
(H
2
O)(N
2
), NO
+
(H
2
O)
2
(N
2
), NO
+
(H
2
O)(CO
2
), NO
+
(H
2
O)
2
(CO
2
), O
2
+
(H
2
O), H
3
O
+
(OH), H
+
(H
2
O)
n
for
n
= 1–8, O
−
, O
2
−
, O
3
−
, O
4
−
, OH
−
, CO
3
−
, CO
4
−
, NO
2
−
, NO
3
−
, ONOO
−
, Cl
−
, Cl
−
(H
2
O), Cl
−
(CO
2
), HCO
3
−
, CO
3
−
(H
2
O), CO
3
−
(H
2
O)
2
, NO
3
−
(H
2
O), NO
3
−
(H
2
O)
2
, OH
−
(H
2
O), and OH
−
(H
2
O)
2
ions. The analysis of the D-region rocket ion mass spectrometer measurements shows that, among these ions, O
2
+
, NO
+
, NO
+
(H
2
O), and H
+
(H
2
O)
n
for
n
= 1–7 can make the main contribution to the total positive ion number density, and O
−
, O
2
−
, Cl
−
, OH
−
(H
2
O), CO
3
−
, HCO
3
−
, NO
3
−
, ONOO
−
, CO
4
−
, NO
3
−
(H
2
O), NO
3
−
(H
2
O)
2
, and
35
Cl
−
(CO
2
) ions can be responsible for the main contribution to the total negative ion number density. Photodetachment of electrons from O
−
, Cl
−
, O
2
−
, O
3
−
, OH
−
, NO
2
−
, and NO
3
−
, dissociative electron photodetachment of O
4
−
and OH
−
(H
2
O), and photodissociation of O
3
−
, O
4
−
, CO
3
−
, CO
4
−
, ONOO
−
, HCO
3
−
, CO
3
−
(H
2
O), NO
3
−
(H
2
O), O
2
+
(H
2
O), O
4
+
, N
4
+
, NO
+
(H
2
O), NO
+
(H
2
O)
2
, H
+
(H
2
O)
n
for
n
= 2–4, NO
+
(N
2
), and NO
+
(CO
2
) are studied, and the photodetachment and photodissociation rate coefficients are calculated using the current state of knowledge on the cross sections of these processes and fluxes of solar radiation.
The Maxwell–Stefan diffusion equations for multicomponent neutral gas mixtures with thermodiffusion ratios and diffusion correction factors in the Chapman–Cowling third-order approximation are ...derived. These thermodiffusion ratios and diffusion correction factors are presented explicitly as functions of masses, number densities, thermal conductivities, and the Chapman–Cowling collision integrals of the neutral species under consideration. Applications to the multicomponent mixture of atmospheric neutral gases O, N
2
, O
2
, He, H, Ar, H
2
, N, and NO are considered, and recommendations are given for using the results of this paper in studies of the Earth's atmosphere.
The spatial spin modulated structure (SSMS) of the cycloid type present in bulk BiFeO3 prevents the linear magnetoelectric effect. One way to influence this structure is to reduce the crystal size to ...the nanoscale. Various opinions are circulating in the literature about the effect of nanocrystal size on SSMS, and to investigate this issue, we used a number of methods, with zero-field NMR (ZF NMR) spectroscopy at the forefront. ZF NMR spectroscopy enables the direct observation of the distribution profile of local fields on iron atoms and defines the SSMS presence and its properties. We also examined the synthesized samples using XRD, TEM, and magnetometry. We conclude that SSMS persists as the nanocrystal size decreases to the cycloid period and less, becoming more harmonic. This is accompanied by the change of the anisotropy type from an “easy axis” to an “easy plane”. Magnetic measurements show a significant increase in the saturation magnetization, remanent magnetization, coercivity, and exchange bias of nanocrystals with sizes close to the cycloid period, which is probably associated with incomplete spin compensation in the case of an incomplete cycloid period. Despite the fact that SSMS is retained in the samples with decreased size, the magnetic properties experience a sharp increase up to applicable values.
PDF
