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The composite material made of biodegradable chitosan as a matrix and spinel CoFe2O4, exhibiting the ferrimagnetic properties, was proposed to be suitable for application in modern transducers, for instance in a loudspeaker without a permanent magnet. The spinel was obtained by high-energy ball milling followed by annealing. The composites were prepared by the solvent casting method. The dielectric studies using broadband impedance spectrometer and the applied methodology of subtracting the conductivity term from the dielectric absorption spectra pointed to the presence of two low-frequency relaxations in chitosan as well as in the composites: α - related to the glass transition (310-350 K), and σ - related to the migration of protons (350-420 K). In the high frequency range, the secondary β-relaxation, related to side group motions by means of the glucosidic linkage, was observed in the temperature range 300-350 K. However, for the composite samples, additionally, the process associated with the migration of oxygen vacations in the spinel grains was detected within the temperature range 350-380 K. One can notice a significant decrease in the activation energy of all processes with increasing contents of spinels in the chitosan matrix. [ABSTRACT FROM AUTHOR]

The process of magnetic relaxation was studied in bismuth ferrite BiFeO3multiferroic micro-cubes obtained by means of microwave assisted Pechini process. Two different mechanisms of relaxation were found. The first one is a rapid magnetic relaxation driven by the domain reorientations and/or pinning and motion of domain walls. This mechanism is also responsible for the irreversible properties at low temperatures. The power-law decay of the magnetic moment confirms that this relaxation takes place in the system of weakly interacting ferromagnetic or superferromagnetic domains. The second mechanism is a long-term weak magnetic relaxation due to spin glass-phase. [ABSTRACT FROM AUTHOR]

The development of tissue scaffolds able to provide proper and accelerated regeneration of tissue is a main task of tissue engineering. We developed a nanocomposite gel that may be used as an injectable therapeutic scaffold. The nanocomposite gel is based on biocompatible gelling agents with embedded nanoparticles (iron oxide, silver, and hydroxyapatite) providing therapeutic properties. We have investigated the microstructure of the nanocomposite gel exposed to different substrates (porous materials and biological tissue). Here we show that the nanocomposite gel has the ability to self-reassemble mimicking the substrate morphology: exposition on porous mineral substrate caused reassembling of nanocomposite gel into 10× smaller scale structure; exposition to a section of humerus cortical bone decreased the microstructure scale more than twice (to ≤3 μm). The reassembling happens through a transitional layer which exists near the phase separation boundary. Our results impact the knowledge of gels explaining their abundance in biological organisms from the microstructural point of view. The results of our biological experiments showed that the nanocomposite gel may find diverse applications in the biomedical field.