Teixeira, S. S., M. P. F. Graça, J. Lucas, M. A. Valente, P. I. P. Soares, M. C. Lança, T. Vieira, J. C. Silva, J. P. Borges, L. - I. Jinga, G. Socol, C. Mello Salgueiro, J. Nunes, and L. C. Costa,
"Nanostructured LiFe5O8 by a Biogenic Method for Applications from Electronics to Medicine",
Nanomaterials, vol. 11, no. 1: MDPI AG, pp. 193, jan, 2021.
AbstractThe physical properties of the cubic and ferrimagnetic spinel ferrite LiFe5O8 has made it an attractive material for electronic and medical applications. In this work, LiFe5O8 nanosized crystallites were synthesized by a novel and eco-friendly sol-gel process, by using powder coconut water as a mediated reaction medium. The dried powders were heat-treated (HT) at temperatures between 400 and 1000 °C, and their structure, morphology, electrical and magnetic characteristics, cytotoxicity, and magnetic hyperthermia assays were performed. The heat treatment of the LiFe5O8 powder tunes the crystallite sizes between 50 nm and 200 nm. When increasing the temperature of the HT, secondary phases start to form. The dielectric analysis revealed, at 300 K and 10 kHz, an increase of $ε$′ (≈10 up to ≈14) with a tan$δ$ almost constant (≈0.3) with the increase of the HT temperature. The cytotoxicity results reveal, for concentrations below 2.5 mg/mL, that all samples have a non-cytotoxicity property. The sample heat-treated at 1000 °C, which revealed hysteresis and magnetic saturation of 73 emu g−1 at 300 K, showed a heating profile adequate for magnetic hyperthermia applications, showing the potential for biomedical applications.
RM, N., N. ER, L. MC, and M. - M. JN,
"New Experimental Facts Concerning the Thermally Stimulated Discharge Current in Dielectric Materials",
Advanced Materials Forum Iv, vol. 587-588, no. 587-588, pp. 328-332, Jan, 2008.
Abstractn/a
Neagu, R. M., E. R. Neagu, M. C. Lanca, and J. N. Marat-Mendes,
"New Experimental Facts Concerning the Thermally Stimulated Discharge Current in Dielectric Materials",
Advanced Materials Forum Iv, vol. 587-588, pp. 328-332, 2008.
AbstractThe thermally stimulated discharge current (TSDC.) method is a very sensitive and a very selective technique to analyze dipole disorientation and the movement of de-trapped space charge (SC). We have proposed a variant of the TSDC method, namely the final thermally stimulated discharge current (FTSDC) technique. flee experimental conditions can be selected so that the FTSDC is mainly determined by the SC de-trapping. The temperatures of the maximum intensity of the fractional polarization peaks obtained at low temperature, in the range of the local (secondary) relaxation, are in general about 10 to 20 K above the poling temperature. Measurements of the FTSDC in a wide temperature range demonstrate the existence of an apparent peak at a temperature T-ma shifted with about 10 to 30 K above the charging temperature T-c. The shift of T-ma with respect to T-c depends on the experimental conditions. The peak width at the half maximum intensity decreases as T-c increases and the thermal apparent activation energy increases. The variations are not monotonous revealing the temperature range where the molecular motion is stronger and consequently the charge trapping and de-trapping processes are affected. Our results demonstrate that there is a strong similarity between the elementary peaks obtained by the two methods, and the current is mainly determined by SC de-trapping. Even the best elementary peaks are not fitted very well by the analytical equation, indicating that the hypothesis behind this equation have to be reconsidered.
Neagu, R. M., E. R. Neagu, C. M. Lanca, and J. N. Marat-Mendes,
"New Experimental Facts Concerning the Thermally Stimulated Discharge Current in Dielectric Materials",
Advanced Materials Forum Iv, vol. 587-588, pp. 328-332, 2008.
AbstractThe thermally stimulated discharge current (TSDC.) method is a very sensitive and a very selective technique to analyze dipole disorientation and the movement of de-trapped space charge (SC). We have proposed a variant of the TSDC method, namely the final thermally stimulated discharge current (FTSDC) technique. flee experimental conditions can be selected so that the FTSDC is mainly determined by the SC de-trapping. The temperatures of the maximum intensity of the fractional polarization peaks obtained at low temperature, in the range of the local (secondary) relaxation, are in general about 10 to 20 K above the poling temperature. Measurements of the FTSDC in a wide temperature range demonstrate the existence of an apparent peak at a temperature T-ma shifted with about 10 to 30 K above the charging temperature T-c. The shift of T-ma with respect to T-c depends on the experimental conditions. The peak width at the half maximum intensity decreases as T-c increases and the thermal apparent activation energy increases. The variations are not monotonous revealing the temperature range where the molecular motion is stronger and consequently the charge trapping and de-trapping processes are affected. Our results demonstrate that there is a strong similarity between the elementary peaks obtained by the two methods, and the current is mainly determined by SC de-trapping. Even the best elementary peaks are not fitted very well by the analytical equation, indicating that the hypothesis behind this equation have to be reconsidered.
Neagu, R. M., E. R. Neagu, C. M. Lanca, J. N. Marat-Mendes, A. T. Marques, A. F. Silva, A. P. M. Baptista, C. Sa, F. J. L. A. Alves, L. F. Malheiros, and M. Vieira,
"New Experimental Facts Concerning the Thermally Stimulated Discharge Current in Dielectric Materials",
Advanced Materials Forum Iv, vol. 587-588, pp. 328-332, 2008.
Abstractn/a