Abstract
The work is devoted to the study of the porous structure formation of anodic alumina films at the initial stage of aluminium anodizing. SEM images of the surface morphology of the oxalic ...acid anodic films were analyzed. It was shown that at the initial stage, both major and minor pores are formed, the diameter ratio of which is about 1.16 and does not depend on the anodizing voltage. The results obtained indicate that the minor pores in the anodic films are located inside hexagonal cells composed of the major pores.
A single-stage centrifugation method is used for the precipitation and crystallization of a solution of a hybrid halide perovskite compound of the CH
3
NH
3
PbI
3
composition. The perovskite films ...are annealed in the temperature range of 80–140°C, during which the excess of the
N
-methylpyrrolidone solvent was removed by evaporation. The X-ray phase analysis of the synthesized perovskite layer is carried out. The morphology of the surface of the layers after crystallization and the transmission spectra in the optical range are studied. The experiments and research results showed that the optimal temperature regime for the formation and crystallization of lead triiodide methylammonium perovskite films is 100–110°C. The perovskite layers obtained in these processing regimes have a surface morphology with a uniform granular crystal structure and are highly uniform. Moreover, in solar cells based on perovskite-like CH
3
NH
3
PbI
3
structures with an annealing temperature of 100–110°C, the short-circuit currents reached 16.0 mA/cm
2
. At the same time, at annealing temperatures of perovskite layers above 120°С, the maximum value of the short-circuit currents did not exceed 14.0 mA/cm
2
.
The paper presents the results of thermal studies for a sample of aluminum with nanoporous alumina using thermal imaging measurements. As a heating element, a carbon thread based on a viscose ...technical thread was used. On the base of results, it was established that local heating of the sample surface by the contact method using a linear heat source can be used in thermometry to determine the thermal conductivity of solid multicomponent dielectric materials.
Introduction.
For controlled thermal management of power electronics devices, an important task is to increase the efficiency of heat removal from active components.
Aim.
To introduce a new approach ...to placing a linear contact-type heat source on the surface of thin samples in order to study the features of propagation of heat fluxes in oxide substrates from materials with different thermal conductivities.
Methods and materials.
The paper presents the results of studies of the propagation of heat fluxes in oxide substrates with different thermal conductivity (glassceramic and aluminum oxide ceramic - polycor). To generate the heat flux, a linear heat source was used, for which an electrically conductive carbon fiber was applied.
Results.
Thermograms and temperature distribution profiles were obtained at different periods of heating time on the surface of the substrate with a heating element and on its reverse side. It was shown that the placement of the linear heat source, implemented using an electrically conductive carbon filament, on the surface of the studied samples and time monitoring of thermograms from two opposite surfaces of the samples allowed to obtain data for evaluating the thermal properties of oxide substrates. The distribution of the heat flux in a homogeneous material near the generation point had the form of a cone of a heat pipe with a base on the surface with a heat source. The thermal cone for an aluminum oxide ceramic substrate had a larger angle of inclination than that in the case of glassceramic.
Conclusion.
The results obtained allowed to propose a method for reduction of thermal resistance of a heatconducting substrate by creating conditions for increasing the area of heat-conducting section.
The results of research on anodizing thin aluminum films 100 nm thick on SiO
2
–Si plates at 30 V in a 0.3 M aqueous solution of oxalic acid are presented. The effect of the electrolyte temperature ...on the morphology of porous anodic aluminum oxide (PAAO) films is studied. The pore diameter and interpore distance are determined by the computer analysis of the SEM images of the morphology of the anode films using the ImageJ software. The data obtained show that the pore diameter does not depend on the temperature of the electrolyte and the time of the process, but is determined only by the anodizing voltage. In the electrolyte temperature range of 5 to 40°C, the pore diameter of the PAAO films is 20 ± 0.5 nm, and the interpore distance is 77.7 nm. The research results indicate that a change in the temperature of the electrolyte, in contrast to the anodizing voltage, affects only the growth rate of the anode film, and not its porous morphology.
Nucleophilic cyclopropanation of arylideneimidazolones possessing a peripheral chiral center and the subsequent fractional crystallization of diastereomers allows access to the compounds with an ...enantiomerically uniform configuration of the spirocyclic donoracceptor cyclopropane fragment. They were used to study the mechanism of the cycloaddition reaction with aldehydes; it was demonstrated that stereochemical information from the cyclopropane fragment is lost during the reaction.
Biochemistry of bioluminescence of the marine parchment tubeworm
has been in research focus for over a century; however, the results obtained by various groups contradict each other. Here, we report ...the isolation and structural elucidation of three compounds from
algae, which demonstrate bioluminescence activity with
luciferase in the presence of Fe
ions. These compounds are derivatives of polyunsaturated fatty acid peroxides. We have also obtained their structural analogues and demonstrated their activity in the bioluminescence reaction, thus confirming the broad substrate specificity of the luciferase.
The paper presents the results of studies of heat fluxes in a printed circuit board made of aluminum with nanoporous anodic alumina, generated by linear heat source. It is established that in this ...case the shape of the cone of the heat pipe with the beginning from a point heating source on the surface was characterized by expansion towards the back side of the aluminum base. This effect leads to a decrease in the thermal resistance of the printed circuit board.
The paper presents methods for improving the quality of SEM images of the surface of nanoporous anodic aluminum oxide. The algorithm of the pore size determination using ImageJ software was ...described. The proposed algorithm is based on the analysis of large data arrays taken from the limited surface areas. The distribution of pore diameter depending on their quantity is presented. The parameters of surface morphology of nanoporous anodic alumina films obtained in the present study agree with literature data.
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