P. V. Kharitonskii

The effect of the conditions of formation on ferromagnetic properties of iron-containing oxide coatings on titanium

Oxide coatings formed on titanium by plasma-electrolytic oxidation in a Na3PO4 + Na2B4O7 + Na2WO4 + Fe2(C2O4)3 electrolyte-suspension at different current densities and different durations of treatment are shown to have ferromagnetic properties. The coercive force of the specimens reaches maximum values of 124 and 380 Oe at 300 and 10 K, respectively, when the thickness of coatings is about 3–5 mm. Crystallites with a mean size of ∼50 nm are found to be present in pores of the coatings. Based on the experimental data, combined with the results of theoretical modeling carried out previously, crystallites are concluded to be iron particles surrounded with a shell composed of oxides and/or hydroxides. The existence of crystallites and their spatial sizes determine the ferromagnetic properties of the coatings.

Magnetic properties of plasma-electrolytic iron-containing oxide coatings on aluminum alloy

Applications of the plasma-electrolytic oxidation technique for the formation of magnetically active oxide coatings on aluminum and titanium are reviewed. Specimens of aluminum-, iron-, and tungsten-containing oxide layers on aluminum substrates with ferro- and ferrimagnetic properties are experimentally produced and studied, as well as specimens that can be remagnetized at certain external magnetic field intensities and specimens the magnetization of which is opposite to the external field. The existence of nano- and microscale crystallites, in which aluminum and metals from the electrolyte are accumulated, are found in pores of the coatings. The crystallites supposedly determine the magnetic properties of the specimens. A correlation between the Fe/Σ(W, Al) atomic ratio in crystallites and the magnetic properties of the systems studied is discovered.

Oxide layers with ferro- and ferrimagnetic characteristics formed on aluminum via plasma electrolytic oxidation

Abstract(Fe+Co)-containing oxide coatings are formed on aluminum alloy. It is established that at a temperature of ∼2 K, the coatings manifest ferromagnetic properties. The coatings, formed within 5 min, are characterized by an anomalously high coercive force Hc = 1300 Oe. At room temperature (300 K), they manifest ferromagnetic properties, whereas in external fields of ∼30 kOe they tend to transition into the antiferromagnetic state. It is concluded that magnetism is in this case due to the presence in the coating’s pores of crystallites ∼50–100 nm in size that consist predominantly of reduced iron, cobalt, and aluminum.

The Investigation of Superparamagnetic Colloidal Particles FemOn-SiO2

Colloidal particles based on iron oxides and silica were obtained by sol-gel method. Hysteresis curves at various temperatures were built by MPMS SQUID VSM. Theoretically calculated values of samples remanent magnetization were compared to experimental data. Despite of the average particles size about 10 nm sample has remanent magnetic moment. The phenomena may be explained on the basis of magnetostatic interaction between particles. The magnetic state of analyzed samples can be conditional on the presence of several phases with very different magnetic properties or the size effect.

Influence of Magnetostatic Interactions on Magnetization Process of Iron-Containing Coatings, Produced Using the Plasma Electrolytic Oxidation Method

In this paper we research the process of magnetization of iron-containing coatings obtained on aluminum and titanium plasma electrolytic oxidation. It is shown that the formation of a remnant magnetic moment mainly determined by the magnetostatic interaction particles (phases). This interaction leads to a decrease of the blocking volume of particles (phases). Thus, a large number of superparamagnetic particles (phases) obtain stable magnetic moments and are involved in creating of the remnant magnetization of the sample.

The thermal effect on magnetic properties of iron-containing coatings formed on titanium by plasma-electrolytic oxidation

The effect of annealing in air at Tan temperature up to 800°C on the magnetic characteristics, elemental and phase composition, and surface morphology of iron-containing oxide coatings on titanium is studied. Annealing at Tan ≤ 500°C does not seem to affect the composition and morphology of coatings. The coercive force (Hc) of specimens equals 70 Oe at room temperature and 256 Oe at 2 K. Upon annealing at 700 or 800°C, the Hc value decreases to 13 Oe. The change in the magnetic characteristics correlates with the crystallization of a number of iron and titanium phosphates, the redistribution of elements in the coatings and pores, and the surface formation of microcrystals and whiskers.

Magnetic Properties of Plasma Electrolytic Iron-Containing Oxide Coatings on Aluminum and Simulation of Demagnetizing Process

Magnetic properties of iron-containing coatings obtained on aluminum by plasma electrolytic oxidation were analyzed in this paper. Theoretical curves of demagnetization of these objects are obtained. It is shown that the magnetic states of the analyzed samples can be caused by the presence of several phases with very different magnetic properties.

Magnetic characteristics of iron-modified oxide layers on titanium

Iron-modified TiO2 coatings on titanium exhibiting ferromagnetic properties are formed by combining plasma electrolytic oxidation (PEO) and impregnation with subsequent annealing. It is found that iron is contained in the composition of dispersed particles with sizes of 1–10 μm distributed over the surface of the coatings. It is shown that the coercive force of the coating on titanium samples is 20–70 Oe. The composition, structure, and magnetic properties of the samples with coatings prepared via direct PEO and by combining PEO and impregnation are compared. It is concluded that impregnation and annealing procedures can be used to impart ferromagnetic properties to PEO coatings with different compositions, e.g., protective coatings and coatings applied in catalysis or medicine.

Application of Plasma Electrolytic Oxidation for the Formation of Magnetoactive Oxide Layes

Using plasma electrolytic oxidation technique we obtained ferromagnetic coatings on titanium and alluminium. The measured coercive force, ~ 100 Oe at room temperature, is closer to the values corresponding to magnetically hard materials. The coatings are of interest as protective electromagnetic screens. The coatings were studied by XRD, XPS, XSA and SEM. There are crystallites of ~50 nm in size containing reduced and oxidized iron in the pores of the coatings. We consider that magnetic properties of the coatings are related with these crystallites.

Correlation of the Microrelief of the Surface of Structure and Magnetic Properties of Oxidic Coverings on the Titan

The technique of system parametrization of a microrelief of surfaces plasma electrolytic oxidation coverings on the titan is offered. Correlation of topology of surfaces of oxidic coverings with their thickness and magnetic properties is established.