New conductive materials for tissue engineering are needed for the development of regenerative strategies for nervous, muscular, and heart tissues. Polycaprolactone (PCL) is used to obtain biocompatible and biodegradable nanofiber scaffolds by electrospinning. MXenes, a large class of biocompatible 2D nanomaterials, can make polymer scaffolds conductive and hydrophilic. However, an understanding of how their physical properties affect potential biomedical applications is still lacking. We immobilized Ti 3 C 2 T x MXene in several layers on the electrospun PCL membranes and used positron annihilation analysis combined with other techniques to elucidate the defect structure and porosity of nanofiber scaffolds. The polymer base was characterized by the presence of nanopores. The MXene surface layers had abundant vacancies at temperatures of 305− 355 K, and a voltage resonance at 8 × 10 4 Hz with the relaxation time of 6.5 × 10 6 s was found in the 20−355 K temperature interval. The appearance of a long-lived component of the positron lifetime was observed, which was dependent on the annealing temperature. The study of conductivity of the composite scaffolds in a wide temperature range, including its inductive and capacity components, showed the possibility of the use of MXene-coated PCL membranes as conductive biomaterials. The electronic structure of MXene and the defects formed in its layers were correlated with the biological properties of the scaffolds in vitro and in bacterial adhesion tests. Double and triple MXene coatings formed an appropriate environment for cell attachment and proliferation with mild antibacterial effects. A combination of structural, chemical, electrical, and biological properties of the PCL−MXene composite demonstrated its advantage over the existing conductive scaffolds for tissue engineering.
The paper presents frequency f and temperature T p dependences of phase shift angle H, admittance r and capacitance C p for the as-deposited and annealed (CoFeZr) x (CaF 2 ) (100Àx) nanocomposite films deposited by ion-beam sputtering of a compound target in a mixed argon-oxygen gas atmosphere in vacuum chamber. The studied films presented metallic FeCoZr ''cores'' covered with FeCo-based oxide ''shells'' embedded into oxygen-free dielectric matrix (fluorite). It was found for the metallic phase content within the range of 52.2 at.% 6 x 6 84.3 at.% in low-f region that H values were negative, while in the high-f region we observed the H < 0 o . It was obtained that the f-dependences of capacitance module displayed minimum at the corresponding frequency when the H(f) crossed its zero line H = 0 o . It was also observed that the r(T p ) dependence displayed the occurrence of two minima that were related to the values of H 1 = 90°(the first minimum) and of H 2 = À90°(the second one). Some possible reasons of such behavior of (CoFeZr) x (CaF 2 ) (100Àx) nanocomposite films are discussed.
The paper presents results of testing electric properties (resistance, capacity and phase angle in an equivalent parallel circuit) of ferromagnetic alloy-dielectric nanocomposites (FeCoZr) x (PZT) (100Àx) produced by ion-beam sputtering in vacuum conditions. The measurements have been performed using alternating current within the frequency range of 50 Hze1 MHz for measuring temperatures ranging from 77 K to 373 K. In nanocomposites (CoFeZr) x (PZT) (100Àx) , produced by ion beam sputtering using a beam of combined argon and oxygen ions, for x approaching the percolation threshold, frequency dependences of the phase angle 4 that resemble those occurring in RLC parallel circuits have been observed. In the low frequency area, the phase angle of 90 4 < 0 occurs. It corresponds to the capacitive type of conduction. In the high frequency area, the inductive type of conduction with 0 4 90 occurs. At the resonance frequency f 0 , characterized by the phase angle of 4 ¼ 0 , the capacity value reaches its strong local minimum. A theoretical basis for a model of the AC hopping conduction for metal-dielectric nanocomposites has been developed and on that basis frequency dependences of the phase angle, resistance and capacitive current density components have been analyzed. The obtained theoretical and experimental results have been compared.
This paper presents the investigations of electrical properties and eect of annealing on conductivity of (CoFeZr)x(CaF2)100−x nanocomposites produced by ion-beam sputtering in the Ar and O2 ambient. Investigations into conductivity of (CoFeZr)x(CaF2)100−x nanocomposites depending on the measuring temperature and the annealing temperature have been performed. The application of a combined argonoxygen beam brings about lowering of the potential barrier on the surface of nanoparticles. In the course of annealing the additional oxidation occurs. First it proceeds on the surface and then all through the metallic-phase particles.
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