Abstract: In the article results of research of underwater concretes are resulted. Influences on concrete structures under water are revealed. The formulation of the optimal concrete mixtures, capable of providing the necessary physical, mechanical and operational characteristics for operation in salt and fresh water after hardening is given.
Abstract: During research were developed ideas about the formation of C6A4MS phase in the aluminate clinker. The influence of the mineral and chemical composition of the raw mixture on the formation of C6A4MS was studied. Schemes of phase transformations providing synthesis of C6A4MS are proposed in this paper. Within research also have been studied the processes of hydration and hardening of aluminate phases. It was found that C6A4MS exhibits high hydraulic activity. Preference is given for the content of C6A4MS in aluminate clinkers obtained using technogenic materials.
Abstract: The method of thermal depolymerization of polylactide wastes and products from it has been studied. At a temperature of 200-250 °C and a pressure of 5-10 mbar the maximum yield of crude lactide and pure lactide is 40 and 5.5 % by weight accordingly. The addition of catalysts (Zn, ZnO, SnO, C16H30O4Sn, Sb2O3) in an amount from 0.5 to 2.0 % by weight make it possible to intensify the process and increase the monomer yield by 3-10 times. The maximum amount of lactide (~60 wt %) is achieved by using of tin octoate (1.5 % wt) as the catalyst. The findings product is a mixture that consist of D-, L-lactide (~80 wt %) and m-lactide (~4 wt %) isomers, lactic acid (~2 wt %), oligomer of lactic acid (~14 wt %), water (<1 wt %), and has a melting point 92-96 °C.
Abstract: The paper studies the efficiency of plasma-assisted synthesis of bottom ash-based microspheres in the light of the liquid phase formation. The studies also include the assessment of morphology of obtained microspheres. It is shown that microspheres with high sphericity can be obtained with thermal plasma treatment. During thermal plasma treatment, the amount of silicon and aluminum relatively grows due to the decrease in the amount of calcium, titanium, magnesium, potassium, and natrium. The high content of silica and alumina in obtained microspheres indicates to their high thermal, chemical, and mechanical resistance.
Abstract: The effect of Nb content on microstructure, mechanical properties and phase formation in annealed and quenched binary Ti-Nb alloys were investigated using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analysis. The content of Nb varied in the range 0-37 mass % leading to significant changes in the microstructure. The annealed and furnace-cooled binary Ti-Nb samples exhibited HCP martensitic α` phase at a Nb content below 14 mass % and stable BCC β phase at higher contents of Nb. The structure of the quenched samples changed with increase of Nb content in the following order: coarse primary martensite → fine acicular (α`+α``) martensite → single β phase structure. The mechanical properties of alloys strongly depended on the Nb content and type of the dominating phase.
Abstract: Investigations of microarc calcium phosphate (CaP) boehmite-containing biocoatings on the pure titanium (Ti) alloy were presented. There were discovered relationships of coating properties (morphology, elemental and phase composition, zeta-potential, wettability) on the boehmite deposition parameters. A variation of the modification parameters of boehmite nanoparticles deposition allowed producing hydrophilic boehmite-containing CaP coatings with the roughness of 2.2-3.1 μm and nanoscale morphology. The influence of boehmite nanoparticles on the surface zeta-potential of the coating was found.
Abstract: In this study, relationship between corrosion resistance and crystallographic texture of α-titanium alloys has been investigated. Samples of α-titanium with different crystallographic texture were obtained by using non-vacuum electron beam cladding as well as cold rolling with a deformation ratios ε ~ 30% and ε ~ 60%. Obtained results show that the crystallographic texture of the surface of titanium influences the corrosion properties and biological compatibility the highest of corrosion resistance corresponds to alloys with a basal surface texture ((0001), (0002)).
Abstract: This work is devoted to investigation of the structure of Ti-TiAl3 composites reinforced by TiB2 or TiC hard particles and obtained by spark plasma sintering of elemental foils and ceramic powders. Sintering was carried out at the temperature of 830 oC under the pressure of 40 MPa during 10 minutes. Microstructure of the composites obtained was represented by alternated layers of titanium and intermetallic compound TiAl3. Also, it was found that at the Ti-TiAl3 interfaces thin intermediate layers were formed. Quantitative elemental analysis of these layers showed that Ti3Al, TiAl, and TiAl2 compounds, as well as Ti (Al) solid solution could be formed in these zones. Diffraction analysis did not reveal any transformations of initial reinforcing phases after sintering. Interlayers with titanium diboride had the average microhardness level of 3988 HV, and the average microhardness level of interlayers with TiC was 1610 HV.
Abstract: Hypereutectic silumin is aluminum-silicon alloy. It is widely used as the material for producing pistons and sliding bearings. The samples were obtained in Belorussian State University and in the Physical-Technical Institute of the National Academy of Sciences. The percentage of silicon is 18-20 wt.%. The structure has a large number of pores and cracks. The size of pores is 100 μm. The method of modification have been carried out in two steps. The first step is ion-plasma deposition ZrTiCu coating. The second step is melting the coating into the substrate. After modification microhardness is 3.2 GPa, wear resistance is 1.8 times less than in the untreated samples. The crystallites size is 0,2-0,4 μm. Thus, this method allows to obtain alloys in the near-surface layer, grinding the structure and increasing mechanical characteristics.