•The recent progress in magnetocaloric effect (MCE) studies.•Interactions between magnetic and structural subsystems in FeRh alloys.•Novel medical applications of MCE (local hyperthermia and drug ...delivering).•Advances in locomotion methods of robots in the gastrointestinal tract.•Minimal-invasive methods that are based on the use of magnetic fields.
We analyze the applications of the magnetocaloric effect (MCE) achieved with advanced magnetic materials and technologies. New results such as the use of MCE-based composite material for ‘smart’ coating of implants, which allows for a controlled release of drugs over time. The material is comprised of two layers: the one manifesting a large MCE and the other made of a temperature-responsive polymer containing the drug. The latter is released by the polymer if the temperature induced by magnetic field (due to MCE) is changed. The polymer undergoes sharp phase transition in response to the slight temperature drop of ∼1–3 °C (down to 34–36 °C in the body). Local cooling is achieved with FeRh alloy, one of the most perspective MCE materials with the first order phase transition. It is critically important to take into account several peculiarities of phase transition and MCE behavior in these series of alloys. Recent studies on high-purity samples showed an ‘irreversible’ effect of MCE indicating that the temperature of FeRh does not return to its initial value after the full cycle of the magnetic field during dynamic MCE measurements. A theoretical explanation based on ab initio calculations has been provided. Magnetic hyperthermia in oncology is rapidly developing therapeutic modality. Recent experiments have shown that Mn-Zn ferrite emerges as a cost-effective material for this method compared with currently used magnetite nanoparticles. We present our achievements on magnetically guided capsule endoscopy. The advances in magnetically guided capsule endoscopy are also discussed. We provide the experimental setup for the computer-controlled system of magnetic field sources that create necessary forces to control the position of the capsule in five degrees of freedom in a given area. The system has the feedback on the position and is designed to monitor the endoscopic capsule during gastrointestinal tract examination.
•Anomalies of magnetothermal properties in REMs condition their unique properties.•A study of Tb and Ho using a series of different experimental methods.•New magnetic phases may exist with sufficient ...purity and perfection of the crystals.•The experimental results are compared with the theoretically predicted phases.
The trend in modern experimental physics of magnetic phenomena is the increasing complexity of experimental methods, or a combination of methods to study even well studied “classical” magnetic materials. The development of related sciences (materials science, chemistry, nanotechnology), as well as the emergence of modern highly informative laboratory and research complexes allows simultaneous analysis of both bulk and local magnetic properties on the same samples. At the same time, the samples are subject to increased requirements in terms of chemical purity and degree of structural perfection. The combination of these factors leads to the discovery of new properties of well-known magnetic materials. This is particularly noticeable in the case of heavy rare earth metals, where a high degree of purity and absence of impurities can lead to the appearance of new magnetic phases and phase transitions. It is important to note that the complexity of the experimental detection of some non-collinear magnetic phases causes the need for theoretical analysis and mathematical modelling of the fundamental possibility of the existence of a type of magnetic ordering in rare-earth metals in order to exclude the experimental error. In this paper we present the modeling of the experimental results of high purity single-crystalline samples of Tb and Ho 5,6 trying to find theoretical and phenomenological patters which explain the existence of certain magnetic phases in the series of heavy lanthanides.
•Poor reproducibility an bulk FeRh alloys produced by arc melting.•Fe100−xRhx alloys with x = 50, 50.5 and 51 prepared by induction melting.•Comparison of the magnetocaloric responses and phase ...transition features.•Induction melting is advantageous to prepare FeRh binary alloys.•Fe content influences the reproducibility of the phase transition features•Further studies about the impact of synthesis parameters are necessary.
Magnetoelastic transitions (METs) in bulk in nearly equiatomic Fe-Rh alloys produced by arc melting may show poor reproducibility related to insufficient chemical homogeneity and presence of impurity phases in variable concentrations. To better understand the synthesis conditions that reliably yield bulk FeRh materials with reproducible MET characteristics, Fe100-xRhx alloys with x = 50, 50.5 and 51 at. % were prepared by induction melting and thermal annealing under identical conditions. The fabricated samples were cut into several slices, followed by characterization of METs in each of the slices using isothermal and isofield magnetization measurements, differential scanning calorimetry, and direct measurements of the magnetocaloric effect. All of the slices exhibit METs between the AFM and FM states, but the transitions are abrupt with nearly the same change of magnetization, ΔM, when x = 50.5 and 51, whereas for the x = 50 alloy the transition spreads over a wide temperature interval and ΔM may fluctuate by as much as 10 % from one specimen to another. A comparison of the magnetocaloric responses of x = 50 and 51 materials is presented. The clearly different effect of the magnetic field on the transition in both directions leads to significant differences in the reversibility and maximum values of the magnetic field-induced entropy and adiabatic temperature changes, as well as average hysteresis losses. In terms of reproducibility, our results suggest that induction melting is a more appropriate technique to prepare these binary alloys.
—The present work surveys literature data related to the study of iron–rhodium-based (Fe–Rh) alloys. The crystal, magnetic, and electronic properties of the FeRh alloy and FeRh-based materials in the ...form of both bulk, thin-film, and nano-structured objects are considered. Peculiarities of the first-order antiferromagnet–ferromagnet transition are analyzed, and various explanations of its nature are discussed. Different approaches to the preparation of the iron–rhodium-based alloys are reported; an analysis of the effect of heat treatment conditions on the properties of the material and their reproducibility in measuring the magnetocaloric properties is performed. Causes for the record values of the magnetocaloric effect (MCE) observed for the material are shown, and prospects of the application of this alloy in magnetic refrigeration technology, medicine, electronics, and magnetic data recording technology are discussed.
•Two bulk Fe49Rh51 samples produced by two different temperature regimes.•Rapidly quenched (FQ) in iced-water and slow cooled (SC) with rate of 2 K/min.•The effects of cooling rate on the phase ...transition in Fe49Rh51 were studied.•The temperature of the AFM-FM transition was similar for FQ and SC samples.•Difference in ΔSM(T) curves and magnetization change: sharper changes for FQ sample.•Difference on hysteresis losses values is shown.
We have investigated the effects of quenching rate on the thermal dependence of the magnetic entropy change ΔSM(T) and the magnetic field induced hysteresis loss through the antiferromagnetic (AFM) ↔ ferromagnetic (FM) transformation in bulk Fe49Rh51. Two nearly identical square-prism-shaped samples were subjected to two different temperature cooling regimes; one was rapidly quenched (FQ) in iced-water and another slow cooled (SC) to room temperature at a cooling rate of 2 K/min. The temperature of the AFM ↔ FM transition is similar for both samples, but the FQ sample shows much sharper temperature- and magnetic field-induced magnetization change; in addition, the total magnetization change is 14% larger. In FQ material, the magnetocaloric effect, i.e., ΔSM(T) quickly approaches saturation above 1 T and shows a large peak value at 2 T (13.9 versus 8.9 Jkg−1 K−1 in SC material), but a larger average hysteresis loss FWHM in the temperature range coinciding with of the full-width at half-maximum of the ΔSM(T) curve.
Vaccination against COVID-19 is the most effective method of controlling the spread of SARS-CoV-2 and reducing mortality from this disease. The development of vaccines with high protective activity ...against a wide range of SARS-CoV-2 antigenic variants remains relevant. In this regard, evaluation of the effectiveness of physical methods of virus inactivation, such as ultraviolet irradiation (UV) of the virus stock, remains relevant. This study demonstrates that the UV treatment of SARS-CoV-2 completely inactivates its infectivity while preserving its morphology, antigenic properties, and ability to induce the production of virus-neutralizing antibodies in mice through immunization. Thus, the UV inactivation of SARS-CoV-2 makes it possible to obtain viral material similar in its antigenic and immunogenic properties to the native antigen, which can be used both for the development of diagnostic test systems and for the development of an inactivated vaccine against COVID-19.
Abstract
Effect of strain rate, quantity of plastic deformation and temperature of material on characteristics of material at electromagnetic forming is considered. It is shown that strength ...characteristics increase with growth of strain rate, and the plasticity increases with an increase in the value of plastic deformation and temperature. The variant of writing of the constitutive equation considering these changes is offered, and its use in calculations can significantly increase efficiency of calculations of operations of electromagnetic forming.
Abstract
Calculation results of different wave tasks are analyzed. It is shown that deformation heating of material is intensive near the boundary surface and quickly decreases during insignificant ...removal from it. The conclusion is drawn that for obtaining exact solutions of wave tasks in nonisothermal statement it is necessary to consider redistribution of temperature in materials because of the heat transfer and its influence on the intense deformed condition of materials of different designs. Calculation results are given. The sensitivity of the decision to change of specific heat capacity and the thermal diffusivity entering wave equation of heat conductivity is noted.
Nowadays, one of the most important global goals in medicine is to find ways to control cancer. Magnetic fluid hyperthermia is a promising method for cancer treatment due to its localized influence ...and low damage to healthy tissue. Ferrite nanoparticles are widely used in this cancer modality because of their low Curie temperature, biocompatibility, and production simplicity. In this work, (Mn
(1−
x
)
Zn
x
)Fe
2
O
4
sol was obtained by hydrothermal synthesis from chlorides of zinc, manganese, and iron (III) at 180 °C for
x
= 0.1 and
x
= 0.2. The results of dynamic light scattering analysis have shown that the average hydrodynamic diameter of nanoparticles in the sol is about 70 nm. According to scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM), the powdered nanoparticles are spherical with a high degree of crystallinity. X-ray powder diffraction analysis (XRD) has confirmed single-phase formation in samples. The magnetic properties measured have indicated that the nanoparticles have reached temperatures close to the range required for deactivation of cancer cells under the influence of a variable magnetic field.
Highlights
Manganese–zinc ferrite sol was synthesized by the hydrothermal method.
Manganese–zinc ferrite nanoparticles were characterized by structural, morphological, and optical studies.
Magnetic properties of manganese–zinc ferrite sol indicated that the nanoparticles obtained have relatively low saturation temperatures.
Manganese–zinc ferrite nanoparticles are prospective agents for cancer treatment applications.