Corrosion of diffusion zinc coatings in sodium chloride solutions

Diffusion galvanizing is widely used in the pipe industry for coating the threaded surface of pipe couplings, protecting water and gas pipelines, and other metal products. Diffusion coatings have a number of advantages over other types of zinc coatings. In this work, electrochemical and gravimetric methods are used to study the corrosion behavior of diffusion zinc coatings in sodium chloride solutions. The corrosion rate depends non-linearly on the thickness of the coating. At the initial stages, the corrosion rate of coatings depends on the structure of the phases on the surface, and with an increase in the holding time, the corrosion rate depends to a greater extent on the properties of the products formed during the corrosion process. Films of corrosion products of diffusion zinc coatings consist of zinc oxide/hydroxide and basic zinc salts, while the composition of the film changes with increasing coating thickness

Magnetic and structural properties of barium hexaferrite BaFe12O19 from various growth techniques

Barium hexaferrite powder samples with grains in the m-range were obtained from solid-state sintering, and crystals with sizes up to 5 mm grown from PbO, Na2CO3, and BaB2O4 fluxes, respectively. Carbonate and borate fluxes provide the largest and structurally best crystals at significantly lower growth temperatures of 1533 K compared to flux-free synthesis (1623 K). The maximum synthesis temperature can be further reduced by the application of PbO-containing fluxes (down to 1223 K upon use of 80 at % PbO), however, Pb-substituted crystals Ba1-xPbxFe12O19 with Pb contents in the range of 0.23(2) x 0.80(2) form, depending on growth temperature and flux PbO content. The degree of Pb-substitution has only a minor influence on unit cell and magnetic parameters, although the values for Curie temperature, saturation magnetization, as well as the coercivity of these samples are significantly reduced in comparison with those from samples obtained from the other fluxes. Due to the lowest level of impurities, the samples from carbonate flux show superior quality compared to materials obtained using other methods

Molecular structure of chemically carbonized poly (vinylidene fluoride) films (IR-spectroscopy data)

The relevance of the research is caused by the importance of elaboration and improvement of the carbon-based nanomaterials synthesis technique. Synthesis of a chain-like carbon and study of its properties are of fundamental interest for experimental check of compliance of numerous models of one-dimensional structures to a real physical object. Chemical treatment of poly (vinylidene fluoride) in a liquid dehydrofluorinating medium allows obtaining a carbon/rich layer on the polymer surface containing chains of various lengths in which carbon atoms are connected to each other with either double bonds or alternating single and triple ones. Theoretical calculations predict a semiconductor-type conductivity of the material, which makes it interesting for use in the field of micro- and nanoelectronics. The main aim is to reveal changes in the molecular composition of polyvinylidene fluoride as a result of chemical dehydrofluorination and subsequent storage at normal and reduced air pressure. Object of the research is a chemically dehydrofluorinated poly (vinylidene fluoride) film. Method of research is infrared spectroscopy. Results. During chemical dehydrofluorination of poly (vinylidene fluoride) the fluorine-substituted polyene fragments, as well as conjugated double and triple carbon-carbon bonds are formed. Hydroxyl groups, contained in water, in the components of dehydrofluorinating mixture and in the atmospheric air, attach to the carbon chains thus preventing conjugated carbon-carbon bonds generation. Drying of the samples, dehydrofluorinated in a liquid medium, under reduced pressure promotes the formation of longer chain fragments, in which the carbon atoms are interconnected by multiple bonds. The observed increase in triple carbon-carbon bonds IR absorption band at 2050-2100 cm-1most obviously shows occurrence of the carbine-like atomic arrangement of polyyne type

Flux Single Crystal Growth of BaFe12−xTixO19 with Titanium Gradient

Titanium substituted barium hexaferrite BaFe12−xTixO19 single crystal was grown by the top seeded solution growth method from flux on the seed with controlled cooling below 1175 °C. Titanium substitution level gradient in the single crystal in the vertical and horizontal directions was studied. Two planes were cut and polished. A justification for the linear gradient of Ti substitution in a BaFe12−xTixO19 single crystal is proposed; substitution levels in the center and periphery were determined. It was shown that upon growth by the top seeded solution growth method, crystals with a linear Ti substitution level gradient from x = 0.73 to x = 0.77 for a distance of 11 mm along pulling direction were obtained. The study led to the conclusion about the relationship of the gradient and changes in the composition of the nutrient solution

Molecular structure of chemically carbonized poly (vinylidene fluoride) films (IR-spectroscopy data)

Актуальность исследования обусловлена важностью разработки и совершенствования методов синтеза наноматериалов на основе углерода. Синтез и исследование свойств цепочечного углерода представляет фундаментальный интерес для экспериментальной проверки соответствия многочисленных моделей одномерных структур реальному физическому объекту. Химическая обработка поливинилиденфторида в жидкой дегидрофторирующей среде позволяет получить на поверхности полимера обогащённый углеродом слой. В нём имеются цепи различной протяжённости, состоящие из атомов углерода, связанных либо двойными, либо чередованием одинарных и тройных связей. Теоретические расчеты предсказывают полупроводниковый тип проводимости такого материала, что делает его интересным для использования в области микро- и наноэлектроники. Цель исследования: выявить изменения молекулярного состава поливинилиденфторида в результате химического дегидрофторированияи и последующего хранения при обычном и пониженном давлении воздуха. Объект: химически дегидрофторированная пленка поливинилиденфторида. Методы: инфракрасная спектроскопия. Результаты. При химическом дегидрофторировании поливинилиденфторида происходит формирование фторзамещённых полиеновых фрагментов, а также сопряженных двойных и тройных углерод-углеродных связей. Присоединение к углеродной цепи гидроксильных групп, содержащихся в воде, компонентах дегидрофторирующей смеси и атмосферном воздухе, препятствует образованию сопряженных углерод/углеродных связей. Сушка при пониженном давлении образцов, дегидрофторированных в жидкой среде, способствует образованию более протяжённых фрагментов цепей, в которых атомы углерода соединены между собой кратными связями. Наблюдаемый при этом рост ИК поглощения тройных углерод/углеродных связей в области 2050-2100 см{-1} наиболее очевидно демонстрирует возникновение карбиноподобного атомного упорядочения полиинового типа.The relevance of the research is caused by the importance of elaboration and improvement of the carbon-based nanomaterials synthesis technique. Synthesis of a chain-like carbon and study of its properties are of fundamental interest for experimental check of compliance of numerous models of one-dimensional structures to a real physical object. Chemical treatment of poly (vinylidene fluoride) in a liquid dehydrofluorinating medium allows obtaining a carbon/rich layer on the polymer surface containing chains of various lengths in which carbon atoms are connected to each other with either double bonds or alternating single and triple ones. Theoretical calculations predict a semiconductor-type conductivity of the material, which makes it interesting for use in the field of micro- and nanoelectronics. The main aim is to reveal changes in the molecular composition of polyvinylidene fluoride as a result of chemical dehydrofluorination and subsequent storage at normal and reduced air pressure. Object of the research is a chemically dehydrofluorinated poly (vinylidene fluoride) film. Method of research is infrared spectroscopy. Results. During chemical dehydrofluorination of poly (vinylidene fluoride) the fluorine-substituted polyene fragments, as well as conjugated double and triple carbon-carbon bonds are formed. Hydroxyl groups, contained in water, in the components of dehydrofluorinating mixture and in the atmospheric air, attach to the carbon chains thus preventing conjugated carbon-carbon bonds generation. Drying of the samples, dehydrofluorinated in a liquid medium, under reduced pressure promotes the formation of longer chain fragments, in which the carbon atoms are interconnected by multiple bonds. The observed increase in triple carbon-carbon bonds IR absorption band at 2050-2100 cm-1most obviously shows occurrence of the carbine-like atomic arrangement of polyyne type

Extremely Polysubstituted Magnetic Material Based on Magnetoplumbite with a Hexagonal Structure: Synthesis, Structure, Properties, Prospects

Crystalline high-entropy single-phase products with a magnetoplumbite structure with grains in the μm range were obtained using solid-state sintering. The synthesis temperature was up to 1400 °C. The morphology, chemical composition, crystal structure, magnetic, and electrodynamic properties were studied and compared with pure barium hexaferrite BaFe12O19 matrix. The polysubstituted high-entropy single-phase product contains five doping elements at a high concentration level. According to the EDX data, the new compound has a formula of Ba(Fe6Ga1.25In1.17Ti1.21Cr1.22Co1.15)O19. The calculated cell parameter values were a = 5.9253(5) Å, c = 23.5257(22) Å, and V = 715.32(9) Å3. The increase in the unit cell for the substituted sample was expected due to the different ionic radius of Ti/In/Ga/Cr/Co compared with Fe3+. The electrodynamic measurements were performed. The dielectric and magnetic permeabilities were stable in the frequency range from 2 to 12 GHz. In this frequency range, the dielectric and magnetic losses were −0.2/0.2. Due to these electrodynamic parameters, this material can be used in the design of microwave strip devices

Polysubstituted High-Entropy [LaNd](Cr0.2Mn0.2Fe0.2Co0.2Ni0.2)O3 Perovskites: Correlation of the Electrical and Magnetic Properties

La-, Nd- and La/Nd-based polysubstituted high-entropy oxides (HEOs) were produced by solid-state reactions. Composition of the B-site was fixed for all samples (Cr0.2Mn0.2Fe0.2Co0.2Ni0.2) with varying of A-site cation (La, Nd and La0.5Nd0.5). Nominal chemical composition of the HEOs correlates well with initial calculated stoichiometry. All produced samples are single phase with perovskite-like structure. Average particle size is critically dependent on chemical composition. Minimal average particle size (~400 nm) was observed for the La-based sample and maximal average particle size (5.8 μm) was observed for the Nd-based sample. The values of the configurational entropy of mixing for each sample were calculated. Electrical properties were investigated in the wide range of temperatures (150–450 K) and frequencies (10−1–107 Hz). Results are discussed in terms of the variable range hopping and the small polaron hopping mechanisms. Magnetic properties were analyzed from the temperature and field dependences of the specific magnetization. The frustrated state of the spin subsystem was observed, and it can be a result of the increasing entropy state. From the Zero-Field-Cooling and Field-Cooling regimes (ZFC-FC) curves, we determine the <S> average and Smax maximum size of a ferromagnetic nanocluster in a paramagnetic matrix. The <S> average size of a ferromagnetic cluster is ~100 nm (La-CMFCNO) and ~60 nm (LN-CMFCNO). The Smax maximum size is ~210 nm (La-CMFCNO) and ~205 nm (LN-CMFCNO). For Nd-CMFCNO, spin glass state (ferromagnetic cluster lower than 30 nm) was observed due to f-d exchange at low temperatures

Preparation, phase stability, and magnetization behavior of high entropy hexaferrites

Summary: The polycrystalline SrFe12O19 samples deeply substituted up to at.67% by Al3+, Ga3+, In3+, Co3+, and Cr3+ cations with a high configurational mixing entropy were prepared by solid-phase synthesis. Phase purity and unit cell parameters were obtained from XRD and analyzed versus the average ionic radius of the iron sublattice. The crystallite size varied around ∼4.5 μm. A comprehensive study of the magnetization was realized in various fields and temperatures. The saturation magnetization was calculated using the Law of Approach to Saturation. The accompanying magnetic parameters were determined. The magnetic crystallographic anisotropy coefficient and the anisotropy field were calculated. All investigated magnetization curves turned out to be nonmonotonic. The magnetic ordering and freezing temperatures were extracted from the ZFC and FC curves. The average size of magnetic clusters varied around ∼350 nm. The high values of the configurational mixing entropy and the phenomenon of magnetic dilution were taken into account

A-Site Cation Size Effect on Structure and Magnetic Properties of Sm(Eu,Gd)Cr_0.2Mn_0.2Fe_0.2Co_0.2Ni_0.2O₃ High-Entropy Solid Solutions

Three high-entropy Sm(Eu,Gd)Cr0.2Mn0.2Fe0.2Co0.2Ni0.2O3 perovskite solid solutions were synthesized using the usual ceramic technology. The XRD investigation at room temperature established a single-phase perovskite product. The Rietveld refinement with the FullProf computer program in the frame of the orthorhombic Pnma (No 62) space group was realized. Along with a decrease in the V unit cell volume from ~224.33 Å3 for the Sm-based sample down to ~221.52 Å3 for the Gd-based sample, an opposite tendency was observed for the unit cell parameters as the ordinal number of the rare-earth cation increased. The average grain size was in the range of 5–8 μm. Field magnetization was measured up to 30 kOe at 50 K and 300 K. The law of approach to saturation was used to determine the Ms spontaneous magnetization that nonlinearly increased from ~1.89 emu/g (Sm) up to ~17.49 emu/g (Gd) and from ~0.59 emu/g (Sm) up to ~3.16 emu/g (Gd) at 50 K and 300 K, respectively. The Mr residual magnetization and Hc coercive force were also determined, while the SQR loop squareness, k magnetic crystallographic anisotropy coefficient, and Ha anisotropy field were calculated. Temperature magnetization was measured in a field of 30 kOe. ZFC and FC magnetization curves were fixed in a field of 100 Oe. It was discovered that the Tmo magnetic ordering temperature downward-curve decreased from ~137.98 K (Sm) down to ~133.99 K (Gd). The spin glass state with ferromagnetic nanoinclusions for all the samples was observed. The average and Dmax maximum diameter of ferromagnetic nanoinclusions were calculated and they were in the range of 40–50 nm and 160–180 nm, respectively. The mechanism of magnetic state formation is discussed in terms of the effects of the A-site cation size and B-site poly-substitution on the indirect superexchange interactions