Crystalline cellulose nanofibers are obtained from the bark of Cereus Forbesii, a cactus native to the arid areas of South America. The obtaining of cellulose nanofibers was carried out in several steps: pretreatment of the raw material, elimination of hemicellulose and lignin to obtain cellulose, and an acid hydrolysis of cellulose to obtain crystalline cellulose nanofibers. The cellulose nanofibers obtained have a crystallinity index of 82% and a nanofiber diameter of 18 nm. An average crystallite size of 6 nm was calculated for the crystalline domains that form cellulose nanofibers. The high crystallinity of the obtained cellulose nanofibers makes the sample very homogeneous and decomposes in a relatively narrow temperature range (between 290°C and 375°C). The complete degradation of crystalline cellulose polymer chains takes place between 375°C and 600°C. The morphological and structural studies are carried out by scanning electron microscopy of field emission, infrared spectrometry with Fourier transform, and powder X-ray diffraction. The thermal stability of the samples is determined by thermogravimetric analysis.

A straightforward method for the synthesis of CoFe _2.7 /CoFe ₂ O ₄ core/shell nanowires is described. The proposed method starts with a conventional pulsed electrodeposition procedure on alumina nanoporous template. The obtained CoFe _2.7 nanowires are released from the template and allowed to oxidize at room conditions over several weeks. The effects of partial oxidation on the structural and magnetic properties were studied by x-ray spectrometry, magnetometry, and scanning and transmission electron microscopy. The results indicate that the final nanowires are composed of 5 nm iron-cobalt alloy nanoparticles. Releasing the nanowires at room conditions promoted surface oxidation of the nanoparticles and created a CoFe ₂ O ₄ shell spinel-like structure. The shell avoids internal oxidation and promotes the formation of bi-magnetic soft/hard magnetic core/shell nanowires. The magnetic properties of both the initial single-phase CoFe _2.7 nanowires and the final core/shell nanowires, reveal that the changes in the properties from the array are due to the oxidation more than effects associated with released processes (disorder and agglomeration).