Supercapacitors are energy storage devices that can cleanly and efficiently meet the growing energy demand. The presentwork describes the synthesis of nanoparticles of cobalt ferrite (CoFe2O4) by the combustion method and their use with activated carbon (AC) to manufacture supercapacitors. In order to study the influence of composition on the electrochemical properties, supercapacitors with three different compositions were produced: Fe90 (90% CoFe2O4 and 10% AC), Fe50 (50% CoFe2O4 and 50% AC) and Fe10 (10% CoFe2O4 and 90% AC). Microstructural and morphological analyses were performed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electronmicroscopy (TEM), and Raman spectroscopy. Cyclic voltam-metry (CV), galvanostatic charge-discharge (GCD), floating and electrochemical impedance spectroscopy (EIS) tests were performed. XRD, SEM, TEM and Raman results showed that the combustion method was effective for the production of CoFe2O4 nanoparticles. SEM and Raman spectroscopy results showed that the AC has a porous structure and low crystallinity. According to CV, GCD and floating tests, all three supercapacitors presented excellent electrochemical stability. The Fe50 composition yielded the lowest equivalent series resistance, while the Fe10 composition yielded the highest capacitance. The results show that the combination of AC with CoFe2O4 is promising for the use in supercapacitors.

For the first time, alumina functionally graded materials (FGMs) with additions of niobium oxide, lithium fluoride and zirconia were produced by spark plasma sintering (SPS) and their sintering behaviour and dynamic properties were studied aiming to evaluate possibility of their use as ballistic shielding. Six groups of alumina samples with different layer compositions were produced by SPS at 1400 ?C/5min. The samples were characterized by dilatometry, scanning electron microscopy (SEM) and Hopkinson split bar method. The composition with the zirconia addition exhibited lower shrinkage rates at higher temperatures than the groups without zirconia, which promoted small sample shrinkage, resulting in lower density and higher porosity. The dynamic test showed that the alumina FGMs with layer containing LiF had the highest strain and strain rate values, exhibiting that the presence of continuous gradients in the composition positively affects the ceramic properties. Densification, layer change and cracks propagating through the material layers were also analysed by SEM analyses.