Effect of Annealing on the Magnetic Properties of FeCoNiCuNbSiB Soft Magnetic Alloys

A series of nanocrystalline soft magnetic alloys with nominal compositions of Fe66.8-xCo10NixCu0.8Nb2.9Si11.5B8 (x = 1–15 at%) were developed and studied. Effects of annealing on the soft magnetic properties, crystallization behavior, and domain structure were investigated. The alloys with higher Ni content were prone to exhibit stronger magnetic anisotropy. The Fe66.8Co10Ni10Cu0.8Nb2.9Si11.5B8 alloy exhibited excellent soft magnetic properties, including the low permeability of 2000, low coercivity of about 0.6 A/m, and low remanence of 2.4 mT, together with a temperature gap of 128 K between two crystallization onset temperatures. It has been found that the Ni content and the annealing process possess significant effects on the soft magnetic property of the nanocrystalline alloys. It shows that the developed Fe66.8Co10Ni10Cu0.8Nb2.9Si11.5B8 nanocrystalline alloy exhibits great potentials for applying in the field of common mode chokes or current transformers, due to its ability to resist the direct current.

Effect of Substituting Hf for Zr on Fe-Co-M-Nb-B (M = Zr, Hf) Amorphous Alloys with High Saturation Magnetization

The soft magnetic amorphous ribbons of (FexCo1−x)85M9Nb1B5 (M = Zr or Hf, x = 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9) were investigated in this study. Replacing Zr by Hf turned out to increase saturation magnetization and, at the same time, reduce the coercivity, both of which serve together in enhancing the soft magnetic performance of the alloys. Moreover, the optimum ratio of Fe/Co was determined after the survey on different alloys with varying Fe/Co ratio resulting in the maximum saturation magnetization while keeping the coercivity low. After optimization, the highest saturation magnetization of 1.62 T was achieved with coercity of 11 A/m. While substitution of Hf for Zr slightly reduced the crystallization onset temperature of the amorphous structure, the thermal stability of the soft magnetic amorphous alloys was not significantly affected by the Zr/Hf replacement.

The effect of nitrogen (III) oxide on direct synthesis of concentrated nitric acid

The effect of nitrogen (III) oxide on the process of dinitrogen tetroxide separation in a dephlegmator during preparation of a "crude mixture" (HNO3–N2O4–N2O3–NO2–NO–H2O) in the production of concentrated nitric acid by direct synthesis was studied in this work. The dependence of crystallization onset on the composition of the N2O4–N2O3 mixture and temperature was determined. The refrigerant capable of maintaining the optimal temperature of the N2O4 extraction was suggested. The absence of nitrogen (III) oxide and nitrogen (I) oxide in the autoclave acid was confirmed.

Photocatalytic Activity of Nanocoatings Based on Mixed Oxide V-TiO2 Nanoparticles with Controlled Composition and Size

V-TiO2 photocatalyst with 0 ≤ V ≤ 20 mol% was prepared via the sol–gel method based on mixed oxide titanium–vanadium nanoparticles with size and composition control. The mixed oxide vanadium–titanium oxo-alkoxy nanonoparticles were generated in a chemical micromixing reactor, coated on glass beads via liquid colloid deposition method and underwent to an appropriate thermal treatment forming crystallized nanocoatings. X-ray diffraction, Raman, thermogravimetric and differential thermal analyses confirmed anatase crystalline structure at vanadium content ≤ 10 mol%, with the cell parameters identical to those of pure TiO2. At a higher vanadium content of ~20 mol%, the material segregation began and orthorhombic phase of V2O5 appeared. The crystallization onset temperature of V-TiO2 smoothly changed with an increase in vanadium content. The best photocatalytic performance towards methylene blue decomposition in aqueous solutions under UVA and visible light illuminations was observed in V-TiO2 nanocoatings with, respectively, 2 mol% and 10 mol% vanadium.

Chemical Composition and Low-Temperature Fluidity Properties of Jet Fuels

The physicochemical properties of petroleum-derived jet fuels mainly depend on their chemical composition, which can vary from sample to sample as a result of the diversity of the crude diet processed by the refinery. Jet fuels are exposed to very low temperatures both at altitude and on the ground in places subject to extreme climates and must be able to maintain their fluidity at these low temperatures otherwise the flow of fuel to turbine engines will be reduced or even stopped. In this work, an experimental evaluation of the effect of chemical composition on low-temperature fluidity properties of jet fuels (freezing point, crystallization onset temperature and viscosity at −20 °C) was carried out. Initially, a methodology based on gas chromatography coupled to mass spectrometry (GC–MS) was adapted to determine the composition of 70 samples of Jet A1 and Jet A fuels. This methodology allowed quantifying the content, in weight percentage, of five main families of hydrocarbons: paraffinic, naphthenic, aromatic, naphthalene derivatives, and tetralin- and indane-derived compounds. Fuel components were also grouped into 11 classes depending on structural characteristics and the number of carbon atoms in the compound. The latter compositional approach allowed obtaining more precise model regressions for predicting the composition–property dependence and identifying individual components or hydrocarbon classes contributing to increased or decreased property values.

Crystallization temperatures of complex ferroalloys

Thermo-gravimetric method was used to determine the temperature of crystallization onset of alloys of the Fe – Ni – Cr – C – Si system depending on concentration of chromium and nickel. It was shown that complex ferroalloys containing 0.2 – 21.0 % Ni (at Cr = 25 – 28 %); 0.5 – 45.0 % Cr (at Ni = 10 – 11 %); 2.0 % C and 0.3 % Si, iron, and impurities belong to the category of low-melting alloys and have rational values (1320 – 1400 °C) of crystallization temperatures in terms of their use for steel processing in the ladle. An increase of the chromium content to more than 45 % in these alloys is accompanied by an intense increase of their temperatures of the crystallization onset.

Initial Growth and Crystallization Onset of Plasma Enhanced-Atomic Layer Deposited ZnO

Direct plasma enhanced-atomic layer deposition (PE-ALD) is adopted for the growth of ZnO on c-Si with native oxide at room temperature. The initial stages of growth both in terms of thickness evolution and crystallization onset are followed ex-situ by a combination of spectroscopic ellipsometry and X-ray based techniques (diffraction, reflectivity, and fluorescence). Differently from the growth mode usually reported for thermal ALD ZnO (i.e., substrate-inhibited island growth), the effect of plasma surface activation resulted in a substrate-enhanced island growth. A transient region of accelerated island formation was found within the first 2 nm of deposition, resulting in the growth of amorphous ZnO as witnessed with grazing incidence X-ray diffraction. After the islands coalesced and a continuous layer formed, the first crystallites were found to grow, starting the layer-by-layer growth mode. High-temperature ALD ZnO layers were also investigated in terms of crystallization onset, showing that layers are amorphous up to a thickness of 3 nm, irrespective of the deposition temperature and growth orientation.

Microwave-assisted Synthesis of 1-(perfluorohexyl)-3-methylimidazolium iodide

ABSTRACTA perfluorinated ionic liquid, 1-(perfluorohexyl)-3-methylimidazolium iodide, was synthesized via microwave reaction and compared to a non-fluorinated analog. Typically, the synthesis of fluorinated ionic liquids involves long reaction times and multiple steps. We have demonstrated a shortened synthesis and a more straightforward procedure, by using a microwave reactor for the microwave-assisted synthesis of 1-(perfluorohexyl)-3-methylimidazolium iodide. The addition of fluorinated alkyl chains on imidazolium ionic liquid cations increases the molecular free volume of the ionic liquid which is beneficial for increasing CO2 physisorption. Computational and experimental data shows an increased CO2 solubility and capacity for fluorinated ionic liquids. The perfluoroalkyl functionalized ionic liquid is characterized using 1H and 19F NMR spectroscopy, FTIR spectroscopy, and DSC. By DSC, a crystallization onset is near -31 °C and while the onset of the melting point between -30 and -17 °C.

Physicochemical properties of ternary Fe-Si-Nb and Fe-Al-Nb metallic systems

The Russian Federation has a sufficient number of promising deposits of niobium raw materials which can satisfy the niobium and tantalum demands of Russian metallurgical enterprises for many decades. Ferroalloy technologists are faced with the difficult tasks of developing from various types of ore raw materials not only effective processes for its processing but also new acceptable rational compositions of niobium-containing ferroalloys. The chemical composition of niobium ferroalloy should, on the one hand, correspond to the product obtained by benefication (concentrate) and, on the other hand, satisfy the requirements of steelmakers for ferroalloys intended for microalloying niobium steel. To develop rational compositions of new niobium-containing ferroalloys in this work the physicochemical characteristics (which include crystallization temperature and density) of alloys containing 10-50% Nb, 10-40% Si, and 5-30% Al were studied. Two-component Fe-Nb metal alloys have a rational crystallization onset temperature (<1400 °С) only when the niobium content is not more than 10%. To achieve rational crystallization onset temperatures it is necessary to use complex alloys with silicon and aluminum. Studies have shown that a decrease in the crystallization onset temperature of complex niobium alloys occurs when the niobium content decreases with an increase in the concentration of silicon or aluminum. Three-component alloys Fe-Si-Nb and Fe-Al-Nb with a content of 15-20% Nb, 32-40 Si% or 12-30% Al belong to the category of low-melting ferroalloys. To achieve rational density values light metals such as silicon or aluminum must be introduced into a two-component system. The studied three-component alloys with a content of 25-40% Si or 15-30% Al have rational density values both from the point of view of their production and application to the processing of steel melt. The best physicochemical characteristics providing high service properties are possessed by complex niobium (15-20% Nb) FeNbSi alloys with 32-40% Si and FeNbAl with 15-30% Al which are recommended for widespread use in ladle microalloying of steels.