The combustion synthesis (CS) is an autogenous and strongly exothermic chemical reaction in a powdered mixture of a strong reducer and oxidizer. Such processes, due to short duration and fast quench, can be a source of novel nanomaterials. Here we present (i) the CS synthesis of SiC nanowires (SiCNWs) and (ii) the magnesiothermic reduction of the asbestos waste. The resulting raw and purified products were analyzed with different chemical and physicochemical techniques (XRD, SEM, TGA and Raman spectroscopy) to verify its composition and morphology.
Materials Science. Non-Equilibrium Phase Transformations.
Vol. 6 (2020), Issue 1
Table of Contents
The proposed review looks at some aspects concerning ferroelectrics that are characterized by high dielectric constant at/ or near Curie temperature. Particular attention haс been paid to the doping of BaTiO3 with rare earth elements because they prove to be very promising for the production of supercapacitors. It is pointed out that the preparation of ceramic materials with high dielectric permittivity by sol-gel method is of huge interest due to the numerous advantages inhered to this technology.
The microscopic and macroscopic views of copper electrodeposits obtained on plastically deformed copper substrates of different deformation degrees have been investigated. Experiments have been performed under galvanostatic conditions. There appear, depending upon the degree of reduction realized during substrate rolling, three types of deposit: epitaxial, homogenous and texture. Epitaxial growth is observed on unreformed substrate and on the substrates with lesser deformation degree (up to 60 %). With the increase of the substrate reduction degree, heterogeneous type of the deposit appeared and the phenomenon of twinning was stated. On very much deformed substrates, as well as in presence of organic additives, field oriented texture type of the deposit is obtained. On very deformed substrates macroscopic uneven deposits appeared, with the linear structure which follows the direction of substrate rolling. Possible explanations of this phenomenon are given.
Enhancement of corrosion resistance of steel, coated with various coatings on the base of SiO2, TiO2, ZrO2 and CeO2pg(s) 15-16
Different corrosion-resistant coatings based on various SiO2, TiO2, ZrO2 and CeO2oxides have been applied to various steels by the sol-gel method and spray pyrolysis. The obtained experimental coatings were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and weight loss measurements in 3.5% NaCl medium. TiO2 / SiO2 and CeO2/SiO2 coatings treated at lower temperatures (500oC) have been shown to exhibit higher corrosion resistance than ZrO2/SiO2 samples. Increasing the treatment temperature decreases the protective properties of the invesitgated coatings. The enhanced protective properties of TiO2/SiO2 are probably due to their low crystallized fine grained structure and relatively dense surface without visible cracks.
This paper analyses the oxidation resistance of ductile irons containing 2.11, 3, 4.28, 4.49 and 4.81 wt.% Si that were held at 850 °C for 32 hours. A scale was formed on all the samples and their weight increased. The scale thickness and increase in weight were decreased with increase of the silicon content, especially when the silicon content > 4 wt.%. The compactness of the scale on the sample surface is significantly higher at higher silicon contents. The results obtained indicate that the resistance of ductile iron to high-temperature oxidation increases with increasing silicon content.
Compression was carried out of modified copper powder workpieces at a pre-determined value of the pressure. High temperature sintering of the workpieces in a neutral medium at a temperature of 1,000°C was performed. A high density metal-ceramic composite material was obtained. Its structure and physico-chemical parameters were determined. Lead-free prototypes were created, corresponding to the weight and dimensions of the reference standard lead passive elements for high energy impact.
A methodology for analyzing and evaluating macroscopic level of first-order phase transition in 3D printer technology is proposed. A classic Stefan-Schwarz task was used. A 3D mathematical model of the Stefan-Schwarz problem is made. The finite element method for numerical solution is applied.
A numerical experiment was evaluated. A geometric drop (flow) model in 3D printer technology is proposed. The idea of filling a “flow” drop by smaller droplets than a “flow” has been investigated numerically. The temperature field at filling in the flow as hereditary was investigated.