For the first time, it was demonstrated that the catalytic properties of semiconductors can be activated using an external electric field only. More particularly, the TiO2 and Fe2O3 were found to ...produce noticeable amounts of carbon monoxide from carbon dioxide – water vapor gas mixture under the electric field with the strength in the 104 V/cm range. The reported process, i.e. the activation of semiconductors using the electric field is more efficient than the utilization of UV–vis radiation in terms of energy efficiency and amount of products formed.
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•Catalytic properties of semiconductors was activated using the external electric field only.•Wet CO2 was converted into CO over TiO2 and Fe2O3 in the presence of field in the 104 V/cm range.•The activity of investigated semiconductors depended on both surface and electronical properties.
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Integrated field-emission devices and integrated circuits (ICs) based on them are a promising direction in microelectronics, which is associated with the use of low-voltage and stable field ...emitters based on nanomaterials, such as carbon nanotubes (CNTs). The planar design of the field-emission device makes it possible to form CNTs at the end of a thin catalyst film 1–50 nm thick. The paper presents the results of the implementation of an integrated technology for manufacturing planar field-emission diodes with a CNT cathode formed at the end of a thin conducting film. The CNTs are grown by chemical-vapor deposition. A thin film of initially amorphous Co–Nb–N–(O) alloy is used as the growth catalyst. A feature of the technology is the crystallization of Co–Nb–N–(O) alloy during heating in the process of chemical-vapor deposition. As a result, Co nanoparticles are formed on the alloy surface, which catalyze the growth of CNTs. It is shown that this specific feature makes it possible to form CNTs locally, only in open areas of the Co–Nb–N–(O) alloy, for example, at the ends of a thin film. The choice of the Co–Nb–N–(O) alloy is substantiated. The stages of formation of planar field-emission diodes on a silicon substrate are described using standard manufacturing processes. The results of measuring the
I
–
V
characteristics of devices are presented. It is shown that the type of
I
–
V
characteristics is determined by the field emission characteristic of CNTs. The developed technological method for the local synthesis of CNTs at the ends of topologically formed regions of a thin Co–Nb–N–(O) alloy film can be incorporated into an integrated technology for the formation of planar field-emission devices.
For the solution of the problem of energy storage, new and more efficient functional electrode materials for electrochemical devices such as supercapacitors and their formation technologies are being ...developed. In particular, using the method of electrolyte-free electrophoretic codeposition, a composite material of carbon nanotubes (CNTs)/RuO
2
·
x
H
2
O with high specific capacitance and power values can be obtained. In this study, the optimal composition of a 50-mL suspension for electrophoretic deposition (EPD) is determined by sedimentation analysis. It is demonstrated that in the course of the iodoform reaction with acetone, I
2
(20 mg) ensures the saturation of particle surfaces with protons and their deposition on the cathode, thus replacing the electrolytes that introduce impurities into the final coating. It is established that the presence of a dispersing agent (5 mg of hydroxypropyl cellulose) is required in the suspension to maintain stability. The possibility of removing hydroxypropyl cellulose during annealing in air at a temperature of about 260°C is studied and confirmed by the methods of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Composite material, processed in this way and obtained from a suspension containing double-walled CNTs and RuO
2
·
x
H
2
O, equal to 2 and 10 mg, respectively, has a capacity of 21.5 and 8.6 mF/cm
2
at cyclic sweep rates of 10 and 100 mV/s, respectively. It is established that elevated temperatures and prolonged heat treatment lead to a deterioration in the electrochemical characteristics due to the degradation of RuO
2
·
x
H
2
O and the CNTs.
Abstract
This work shows the possibility of forming a planar diode structure based on carbon nanotubes formed on a catalytic alloy film Co-Nb-N-(O). The paper presents a technological route for the ...formation of a planar diode structure Si/SiO
2
/Si
3
N
4
/Co-Nb-N-(O)/SiO
2
and studies the emission characteristics. The current-voltage characteristic of the obtained diode structure in the Fowler-Nordheim coordinates is close to linear in the range from 15 to 22 V, which confirms the phenomenon of electron emission.
Abstract
This work demonstrates the possibility of using a combination of zinc oxide nanorods with silver nanoparticles as a self-cleaning SERS substrate. In addition to Raman scattering enhancement ...such structures demonstrate the self-cleaning effect during UV treatment. The ZnO nanorods (NRs) array was synthesized on a ZnO seed layer by the hydrothermal method. The Ag nanoparticles (NPs) array was formed by vacuum thermal evaporation over the ZnO NRs. Rhodamine-B 230 μM solution has been detected using the formed SERS-substrates without additional mathematical processing of the Raman spectra. Subsequent UV radiation treatment showed a 3-fold decrease in the intensity of the spectral peaks of the analyte.
Currently, there is a growing demand for miniaturized power supplies, including planar supercapacitors, whose principle of operation is based on fast redox reactions. This circumstance stimulates ...investigations of composite structures made of high-surface-area carbon-based materials and transition-metal compounds. In this paper, we report the results of studying coatings based on few-layer graphite nanoflakes FLGN/Ni(OH)
2
and their oxidized form OFLGN/Ni(OH)
2
, obtained by repeated electrophoretic deposition. These coatings are used in prototype parallel-plate (3D) and planar supercapacitors. A processing route using a 450-nm laser for pattern scribing is developed for the latter. It is shown that, by regulating the nickel-ion-source proportion in the suspension from 0.04 to 0.64 g/L, one can control the physical properties of the composite at the deposition stage. The composite’s physical properties are studied by cyclic voltammetry, scanning microscopy, and elemental analysis. The peak capacity values are obtained for samples with the minimum concentration (0.04 g/L); they turn out to be 1.51 and 1.31 F/g for the FLGN-containing samples and 1.86 and 1.29 F/g for the OFLGN-containing samples of bulk and planar supercapacitors, respectively.
In this paper, a method of fabrication of an Al-Ni powder energetic material with a 90-100 nm particles is proposed and experimental results of a study of its properties are presented. High values of ...specific energy and the rate of its release make it possible to use this material as an heat release element in thermoelectric power generation devices. It has been demonstrated experimentally that it is possible to maintain a voltage value higher than 1 V for 45 seconds as a result of combustion of a 3 gram Al-Ni sample that using a simple DC-DC converter will allow charging supercapacitors or accumulators.
Energy sources that can operate at extreme ambient temperatures and high humidity, as well as in an airless space, are one of the promising areas for research in electronics. The possibility of ...creating an autonomous thermoelectric generator with a fuel element based on nanosized powder Al–Ni–Fe3O4 energy materials is considered. Using bomb calorimetry and high-speed video filming, the influence of the composition of the energetic material on the thermal effect of the reaction and the nature of combustion has been investigated. Variants of designs of autonomous thermoelectric generators were proposed and experimental studies of their output characteristics were carried out using various fuel elements. Evaluation of the efficiency of the device was carried out and a working prototype was created.
Metallic nanoparticles are promising objects of study, since their properties greatly differ from the properties of bulk material. In analyzing nanoparticles, it is important to investigate their ...size, stability, structural features, and spatial arrangement. In this study, initial and annealed silver nanoparticles from ∼2 to 10 nm in size formed on a carbon substrate by vacuum thermal evaporation are investigated by high resolution transmission electron microscopy and their shape and structure are classified. The examined nanoparticle types include faceted ellipsoid ones with a polycrystalline structure, coarse ones with a single-crystal structure and twins, icosahedral and decahedral ones with multiple twinning, and fine single-crystal nanoparticles smaller than 3.5 nm. It is established that, after annealing, the total number of nanoparticles decreases by a factor of ~1.3, the number of fine nanoparticles almost halves, and the fraction of nanoparticles with icosahedral and decahedral cross sections increases by a factor of ~1.5. It is shown that nanoparticles smaller than 5 nm become unstable already after a few seconds of exposure to high-energy electrons. For fine single-crystal nanoparticles smaller than 3.5 nm, the average crystal-lattice parameter is found by precise determination of the centers of atomic columns in their images and calculation of the local distances between atoms located in the mutually perpendicular (200) and (022) planes. It is shown that, in such nanoparticles both before and after annealing, there are no noticeable crystal-structure distortions and their lattice parameter is similar to the value characteristic of bulk silver.
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