Inorganic Materials: Applied Research最新文献

The chemical stability of Nd_0.33Zr₂(PO₄)₃ fine-grained ceramics, which can be used for immobilization of rare earth elements (REE) that are part of high-level waste was studied. Single-phase Nd_0.33Zr₂(PO₄)₃ submicron powders with the structure of the mineral kosnarite were prepared by colloid-chemical synthesis. Powders were prepared by successive annealing at 600, 800, and 900°C for 6 h at each stage. Nd_0.33Zr₂(PO₄)₃ ceramic was Nd_0.33Zr₂(PO₄)₃ ceramics was produced using spark plasma sintering method (SPS). The relative density of the ceramic was 89.9%; the average grain size was 5–20 μm. The chemical stability of the ceramic in the static mode at 90°C in distilled water and mineral water, as well as in acidic media (0.1 M HCl) and alkaline media (0.01 M NaOH), was studied. The ceramics have high hydrolytic stability. The influence of the contact medium on the rate and mechanism of Nd leaching from the surface of Nd_0.33Zr₂(PO₄)₃ fine-grained ceramic samples was studied. The de Groot-van der Sloot model was used to analyze the resulting leaching rate R_i against time t of experiment. Nd leaching occurs by dissociation of Nd from the ceramic surface in acidic medium, diffusion from the inner layers in alkaline medium and mineral water, and dissolution of the ceramic surface layer in distilled water.

In this work, the following are investigated: structure, phase composition and mechanical properties under static tension of titanium alloys Ti–(36–40)Zr–9Ta (at %) for medical use after hot rolling and quenching. After rolling, the alloys consist of α'- and β-phases. The results of the research show that the hardening of alloys leads to the almost complete dissolution of the β-phase and the release of α'- and α"-phases. Investigations of mechanical properties of alloys Ti–(36–40)Zr–9Ta (at %) show that, in terms of tensile strength, the studied alloys Ti–36Zr–9Ta, Ti–38Zr–9Ta, and Ti–40Zr–9Ta are similar to the VT6 alloy widely used for implants (σ = 835–1100 MPa), and, in terms of plasticity (δ = 15–21%) and low value of Young’s modulus (E = 53–73 GPa), significantly exceeds it.

The processes in polymer films based on polypropylene containing fluorinated additives during modification of films in corona discharge plasma are studied. The chemical composition, relief, adhesion and deformation properties of the film surface before and after modification in plasma were studied using the methods of X-ray photoelectron spectroscopy and atomic force microscopy. It has been established that in films under the influence of corona discharge plasma migration of the fluoropolymer additive to the surface occurs. In this case, the chemical composition and structure of the film changes, and local structures containing oxygen, fluorine and carbon atoms are formed on the surface. Local structures have an electrical resistance that is different from the electrical resistance of the surface of the original film. Plasma modification leads to an improvement in the elastic and adhesive properties of the polypropylene film surface.

The main goal of the article is to familiarize specialists working in the field of medical devices (MDs) with existing approaches to the study of their biocompatibility, set out in the standards of the GOST (State Standard) ISO 10993 series. The concept of the GOST (State Standard) ISO 10993 series of standards lies in establishing the biological safety and functional effectiveness of MDs in the terms of biological risk, as necessary and sufficient conditions for biocompatibility of MDs in clinical application. The main attention in the general scheme of assessing the biological safety of MD is paid to the program of toxicological studies (tests), consisting of a set of methods that take into account the category, purpose, and duration of MD functioning.

An experimental evaluation of the decrease in actual physical and mechanical characteristics of low pressure polyethylene (HDPE) pipes depending on the duration and conditions of their operation has been conducted. To assess the impact of operational factors on the pipe characteristics, the following parameters were determined: tensile elongation and tensile strength, thermal stability (induction period of oxidation (IPO) of the material), and degree of crystallinity. It was found that, after prolonged operation of HDPE pipes compared to the initial normative values, the most significantly affected parameters are the tensile elongation and the induction period of oxidation. Moreover, the changes in tensile elongation and IPO parameters have a similar nature in terms of the loss of properties, indicating a correlation between them. The most sensitive indicators for predicting the service life of HDPE pipes are the tensile elongation and the induction period of oxidation. On the basis of the data obtained, it seems promising to monitor the IPO value when determining the technical condition of polyethylene pipes. A calculated forecast of the service life of polyethylene pipes based on reaching their ultimate state has been performed.

High-density polyethylene (HDPE)/Fe₃O₄ composites with Fe₃O₄ nanofiller contents of ω = 1, 3, and 5 vol % have been obtained by hot pressing of a homogeneous mixture of HDPE and a synthesized Fe₃O₄ nanopowder. The structure and thermal properties of the HDPE/Fe₃O₄ nanocomposites have been studied; it has been found that, with an increase in the Fe₃O₄ nanoparticle concentration in the polymer matrix, the morphology of the supramolecular structure of the HDPE matrix drastically changes. It has been established that, with an increase in the nanofiller concentration, the mobility of macromolecular chains in the matrix and the crystalline lamellae thickness decrease. Nanoparticles disrupt the regularity of lamellae in the crystalline phase of the polymer matrix and prevent the formation and growth of new crystalline domains in the amorphous region.

The paper presents a method of microwave influence on ferrocene C₁₀H₁₀Fe and graphite to obtain multilayer carbon nanotubes (MWCNTs)—designed to improve the electrical and thermophysical properties of Organosilicon elastomer (Silagerm 8020). Diagnostics and characterization of the synthesized MWCNTs were carried out by energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. According to SEM data, it follows that the morphology of the synthesized MWCNTs has the form of filamentous formations intertwined in bundles with a diameter of individual MWCNTs from 40 to 60 nm and a length up to several microns. At the same time, the surface of most of the MWCNTs is covered with a continuous layer of iron (Fe). The EDX method also confirmed the Fe and oxygen content on the surface of the MWCNTs. The XRD method identified the presence of Fe in combination with carbon in the form of Fe₃C iron carbide and pure Fe iron at 44.7°. The compound Fe₃C is also referred to the active phase of Fe allowing the synthesis of MWCNTs. By increasing the concentration of MWCNTs in the elastomer, an increase in thermal conductivity with percolation transition was achieved at a concentration of 8% MWCNTs. The maximum thermal conductivity of the nanomodified elastomer was 0.48 W/(m °C), which corresponded to the mass concentration of MWCNTs equal to 8 wt %. At the same time, the electrical conductivity of the composite, when the MWCNT concentration was changed from 1 to 8%, increased in the range from 4 × 10^–5 to 2.4 S cm^–1 and is also due to the percolation of MWCNTs in the elastomer matrix.

The surface properties and chemical structure of nanosized coatings deposited on the surface of polyethylene terephthalate track-etched membranes by magnetron sputtering of ultrahigh molecular weight polyethylene and polytetrafluoroethylene in a vacuum have been studied. Application of coatings leads to hydrophobization of surface of the original membranes, the degree of which depends on the type of polymer used for sputtering and the coating thickness. The use of this modification method causes smoothing of structural inhomogeneities of the surface layer of membranes, which is explained by the deposition of coatings in the pore channels at a certain depth from the inlet and the overlap of pores on the surface of modified membranes. In addition, the deposition of coatings on the surface of track-etched membranes leads to a change in the shape of pores. The pore diameter decreases significantly on the modified side and remains unchanged on the untreated side of the membrane, while the membrane pores acquire an asymmetrical (conical) shape. The study of chemical structure of coatings using X-ray photoelectron spectroscopy showed that they contain oxygen-containing functional groups owing to oxidation of the polymer matrix. The developed composite membranes can be used in membrane distillation processes for seawater desalination.

Optimization of the process of mineralization of polycaprolactone fibers with vaterite microparticles by varying the concentrations of the working solutions of salts, calcium chloride and sodium carbonate, is proposed. The optimum parameters of mineralization of polycaprolactone fibers with calcium carbonate particles in the vaterite polymorphic modification are found. The effect of the concentrations of the working solutions of the salts and time of ultrasonic treatment on the monodispersity of CaCO₃ microparticles present in the composition of the synthesized coating is studied. The concentrations of the working solutions of the salts are varied from 0.25 to 1 mol and the time of US treatment is varied from 30 to 90 s. The obtained tissue-engineered scaffolds can find application in regenerative medicine and for local and prolonged release of drugs. For their successful use for medical purposes, special requirements must be met, namely, the minimum possible polydispersity and the existence of calcium carbonate microparticles in the vaterite polymorphic modification.

Abstract—The effect of the anionic composition of zinc salts upon interaction with tin(IV) chloride on the production of zinc orthostannate by the sol-gel method under the influence of microwave radiation is studied. It is determined that the temperature at which the synthesis of zinc orthostannate begins depends on the type of zinc-containing salt used and is 800°C for zinc sulfate and zinc acetate and 900°C for zinc nitrate. It is revealed that, when using zinc chloride, the formation of tetra-ammine zinc chloride occurs, which decomposes during roasting and does not allow synthesizing the target product. When synthesizing complex oxides from simple ones, the difference in the diffusion coefficients of Zn²⁺ and Sn⁴⁺ cations leads not only to the Kirkendall and Frenkel effects but also to a deviation from stoichiometry (γ nonstoichiometry). From a mixture of simple oxides of stoichiometric composition, a solid solution of zinc oxide is formed in the stoichiometric compound 2ZnO·SnO₂ and a phase consisting of tin oxide or enriched in it.