Mechanical and magnetic properties of composites based on biogenic hydroxyapatite modified by magnetite (1; 5; 25 and 50 wt

A magnetocaloric effect (MCE) due to adiabatic change of temperature was directly measured in an Fe47.1Mn26.1Ga26.8 alloy undergoing martensitic transformation. Its values in the high-temperature region were positive, while in the temperature range below temperatures of martensitic transformation, the adiabatic change of temperature in the magnetic field was negative. The x-ray diffraction analysis revealed the presence of a Heusler L21 (B2) phase and a γ-phase in the Fe47.1Mn26.1Ga26.8 alloy above temperature of martensitic transformation. The features of field-dependent magnetization and temperature variation in MCE indicate the occurrence of ferromagnetic-to-antiferromagnetic transition in the γ-phase, which is responsible for the observed inverse magnetocaloric effect.

Static and dynamical magnetic properties of the amorphous and crystalline A2-type ordered Heusler Fe2CrGa-alloy films are investigated and compared with the properties of the bulk A2-type ordered Fe2CrGa alloy.Unlike literature results for bulk Fe2CrGa alloy, a complete structural disorder in amorphous state gives rise to a drastic decrease of alloy saturation magnetization.Annealing of amorphous films at Tann = 740 K leads to their crystallization with the formation of the disordered A2-type structure and the magnetic properties of such crystalline films close to those of bulk alloy.Ferromagnetic resonance (FMR) investigations show that both amorphous and crystalline Fe2CrGa-alloy films are microscopically inhomogeneous in both magnetic and structural aspects.Based on the FMR spectra analysis, it can be concluded that, in crystalline Fe2CrGa-alloy films, there are regions with order close to the crystallographic L21 and Hg2CuTi types.These results perfectly correlate with first-principal calculations of the magnetic properties of Fe2CrGa alloy.As shown, the Slater-Pauling rule is not applicable for full Heusler alloys with inverse crystalline Hg2CuTi-type structure.

Ультразвуковим обробленням в кульовому млині (УЗКМ) крупнозернистих порошкових сумішей алюмінію, заліза, кобальту, міді, ніклю та хрому одержано високодисперсні порошки (ВДП) багатокомпонентних стопів системи AlCoCrCuFeNi та досліджено вплив міді на їх фазовий склад та магнетні властивості.Методами рентґеноструктурної аналізи та магнетометрії показано, що всі ВДП, одержані УЗКМ, знаходяться в високоентропійному стані та містять в собі два твердих розчини -ОЦК і ГЦК.При цьому кількість ОЦК-фази і величина питомої намагнетованости насичення в ВДП зменшуються зі збільшенням вмісту міді в вихідних КЗПС.Показано також, що феромагнетизм одержаних ВДП обумовлений головним чином присутністю

By electric spark dispersion were produced for the first time ultrafine powders (up to 5 mu m) of high-entropy alloy (HEA) FeNiCoCrCu in various liquid media (ethanol, propanol, and water), and their effect on the phase composition and the ratio of the volume fractions of gamma(1) and gamma(2) phases was determined in comparison with this ratio in the original ingot. According to the analysis of the structure parameters and characteristics of the hyperfine magnetic interaction, as shown, the obtained powders inherit the phase composition of the cast alloy, but the formation of the b.c.c. phase, as well as simple and complex oxides after dispersion in ethanol and water, and dispersion in propanol also causes a change in the ratio gamma(1) i gamma(2) phases and the appearance of special carbides. The results are the basis for the development of a new method for obtaining highly dispersed and nanosized HEA powders.

Ультразвуковим обробленням у кульовому млині (УЗКМ) крупнозернистих порошкових сумішей (КЗПС) алюмінію, заліза, кобальту, міді, нікелю та хрому вперше одержано високодисперсні порошки високоентропійних стопів системи AlCoCrCuFeNi та досліджено вплив вмісту алюмінію і хрому на їхній фазовий склад та магнетні властивості

For the first time, ultrafine powders (UFP) of high-entropy alloys (HEA) of the AlCoCrCuFeNi system are produced by ultrasonic milling of the coarsegrained powder mixture of aluminium, iron, cobalt, copper, nickel and chromium in a ball mill. X-ray analysis, Mossbauer spectroscopy and magnetic measurements shows that the phase composition and magnetic properties of UFP are affected by the aluminium and chromium contents. These investigations have shown that all UFPs produced by ultrasonic milling are in highentropy state and contain two solid solutions with f.c.c. and b.c.c. lattices. Both the quantity of b.c.c. phase and magnitude of specific saturation magnetization of UFPs depend on the aluminium and chromium contents in the original powder mixture. Ferromagnetism of the obtained UFPs is shown to be mainly due to the presence of b.c.c. phase.

In the present work magnetite nanopowders were synthesized by chemical precipitation using FeCl 3 ·6H 2 O and FeCl 2 ·4H 2 O (80 °C, maintaining 5 min–1 h) and decomposition of FeC 2 O 4 (470 °C, in hydrocarbon and nitrogen media maintaining 2 h) and investigated by X-ray diffraction analysis, IR spectroscopy and Scanning electron microscopy. Specific surface area and magnetic properties (specific saturation magnetization and coercive force) were also evaluated. It was shown that the time of synthesis did not influence on the phase composition and nanopowder with specific surface area equal to 141 m 2 /g could be prepared using chemical precipitation method for 5 min. Thermal decomposition method was found to allow obtaining of nanopowders with the higher degree crystallinity. It was established that increasing time of chemical precipitation causes decreasing the specific saturation magnetization from to 62 down to 53.5 emu/g and coercive force from 18.1 down to 3.0 Oe. Thermal decomposition method significantly improve magnetic properties and allow to obtain magnetite nanopowder with the specific saturation magnetization 135 emu/g.

Magnetite powder (FeO·Fe2O3 or Fe3O4) is obtained by the chemical precipitation method, using FeCl3·6H2O and FeCl2·4H2O as a starting materials in the presence of hydrazine N2H4 at a temperature of 80 °C. X-ray diffraction analysis, infrared spectroscopy, and scanning electron microscopy are used for the study of the phase composition and morphology of the synthesized powder. Its specific surface area and magnetic properties such as, in particular, the specific saturation magnetization, coercive force and residual induction are investigated. It is established that the composition of the synthesized powder is represented by magnetite as the main phase with a small admixture of hematite. It is shown that the particles of the obtained magnetite have sizes of 33-84 nm and tend to the agglomeration. The prepared powder has superparamagnetic properties (specific magnetization — 35 A · m2/kg, coercive force — 0.24 kA/m, residual induction — 0.009 T) and is promising for the biocomposite creation.

Інститут загальної та неорганічної хімії ім.В. І. Вернадського НАН України,

The conditions and technique for obtaining single-mode size distributions of spark-erosive aluminum particles are given. The statistical parameters of the size distributions of spark-erosive aluminum particles and caverns on the surface of its granules, obtained at a submilisecond duration of discharge pulses were calculated. A comparative analysis of the volumes of metal of erosion caverns and particles is carried out. The agreement of the diameter distributions of spark-erosive particles and caverns obtained in practice with the following theoretical distributions of a continuous random variable: Gauss, Weibull, the integral of the Rosin-Rammler function, and also log-normal distribution is verified. In this case, the parameters of theoretical distributions were calculated both by the statistical parameters of the distributions obtained in practice, and by the criterion of the smallest value of the average module of the relative deviation of the theoretical and practical distributions. It has been shown that for the values of the parameters of theoretical distributions that correspond to the statistical parameters of practical distributions, the distribution of erosive particles by diameters is in the best agreement with the Gauss distribution, and the caverns – with the distribution of integral of the Rosin-Rammler function. References 27, figures 2, tables 3.

Technological processes for the synthesis of composite systems based on bovine (rather than synthetic) hydroxyapatite are rarely described. That's why the influence of the heat treatment medium on the properties of the composite system bovine hydroxyapatite/magnetite (BHA/Fe3O4) obtained using physico-mechanical and chemical methods were investigated. It was established that the most efficient medium for heat treatment of studied materials is vacuum. Due to XRD analysis data allow us to assert that the most perfect lattice is formed with the use of the chemical method for production and heat treatment in a vacuum (crystallinity 86%), and the least perfect one is formed by the mechanical method for production and heat treatment in a nitrogen medium (71%). The method for adding magnetite has only a minor effect. Investigated conditions of heat treatment of composite systems BHA/Fe3O4 promoted obtaining optimal magnetic properties and stable behavior in experiments in vitro.

Плазмоэрозионный метод получения наноразмерных частиц ме

A comparative analysis of the magnetic, size and deformation effects of martensitic transformation in aged Cu–Al–Mn alloys with a minimum width of the temperature hysteresis was performed. According to the experimental studies of the behavior of alloys during martensitic transformations, the changes in temperature dependences of thermal expansion, magnetic susceptibility and electrical resistance, depending on preliminary thermomagnetic treatment of alloys, were found. The thermomagnetic treatment contributes to a change in the magnitude of volume effect of martensitic transformation. Using magnetic analysis, the state and distribution of precipitated particles, affecting both the magnetic characteristics and the volume effects of martensitic transformation in the alloys, were determined.

A simple and cheap spark erosion method was used to produce Cu/Cu2O core-shell nanoparticles. Morphological and structural studies of the obtained material showed that it consists of Cu and Cu/Cu2O core-shell nanoparticles with sizes about 9-25 and 30-50 nm, respectively. The latter demonstrate ferromagnetic properties (specific saturation magnetization is 0.27 A.m(2)/kg) without additional heat treatment in oxidizing environment. The causes of the ferromagnetic properties of the material obtained are analyzed.

В роботі досліджено влив термомеханічного оброблення полікристалічного стопу Fe–Ni–Co–Ti на його магнетну поведінку. Об’єктом дослідження обрано феромагнетний стоп, який було піддано попередньому термомеханічному обробленню. Характеристичні температури мартенситного та магнетного перетворень визначено на основі температурних залежностей низькопольової магнетної сприйнятливости, електроопору та намагнетованости. За даними поведінки польових залежностей намагнетованости виявлено, що відносне збільшення намагнетованости аустенітної фази на 30% досягається в результаті додаткової дії пластичної деформації матеріялу при одновісному розтягу по відношенню до вихідного стану. Зміна магнетних характеристик стопу, залежно від обраного попереднього термомеханічного оброблення, пов’язана зі зменшенням об’ємної долі феромагнетної фази при старінні й утворенням системи мікронеоднорідностей у матеріялі, що приводить до виникнення додаткової наведеної магнетної анізотропії як при обраному обробленні, так і, особливо, в процесі деформування.

Методами рентґеноструктурної аналізи, електронної мікроскопії та магнетометрії досліджено структуру, фазовий склад, дисперсність і магнетні властивості високодисперсних порошків стопів міді з залізом і кобальтом, одержаних методою електроіскряного оброблення у дистильованій воді, етиловому спирті та гасі.Показано, що у процесі електроіскряного оброблення в порошках формуються пересичені тверді розчини між міддю, залізом і кобальтом та їхні оксиди CoO, Cu 2 O, FeO й карбіди Co 3 C, Fe 2 C, Fe 3 C, кількість яких істотно залежить від типу робочої рідини.Крім того, показано, що електроіскряне оброблення приводить до значного подрібнення структури; при цьому форма частинок порошків близька до сферичної, а їхні розміри знаходяться в інтервалі від 0,1 до 10 мкм.Концентрація металів у твердих розчинах після електроіскряного оброблення набагато (на 2-3 порядки) перевищує рівноважні значення концентрації для цих систем у масивних зразках.