BCMaterials Fortnightly Seminar #75 Alberto Maceiras - Anabel Pérez

ALBERTO MACEIRAS

(BCMATERIALS)

Magnetic cellulose nanocrystal nanocomposites for the development of green functional materials

A novel magnetic cellulosic material composed of cellulose nanocrystals (CNC) and cobalt ferrite (CoFe2O4) magnetic nanoparticles was developed through evaporation induced self-assembly (EISA). Cobalt ferrite nanoparticles demonstrated very good dispersibility on the structure of the cellulose nanocrystal template. The introduction glucose into CNC network allows the development of homogeneous crack-free CNC-based films and does not modifies neither the morphology nor the optical properties. In contrast, the introduction of CoFe2O4 nanoparticles within the layered structure of CNC film produces a marked decrease in the amount of the transmitted UV and visible light to yield films whose optical transparency is about ~2 %. 20 wt. % of CoFe2O4 nanoparticles inside the CNC matrix induced a maximum magnetization value of 13 emu.g-1, increased the real part of the dielectric permittivity from 10 (pure CNC film) to 12 and improved the thermostability of the nanocomposite, as evidenced from the increase of the onset temperature from 160 ºC to 220 ºC. Those features obtained in a non-petroleum-based composite provide insight into the development of the next generation of functional materials from biological and natural origin.

ANABEL PÉREZ

(BCMATERIALS)

Correlation between structure and mechanical properties in multicomponent single crystals based Ni-Mn-Ga alloys

The development of new high temperature ferromagnetic shape memory alloys, HTSMAs, has attracted considerable interest due to the evolution of actual requirements for modern applications. Ni-Mn-Ga alloys have been extensively studied as SMAs, since they exhibit the largest MSM effect, about 10% for modulated martensite and 12% for non-modulated. However, many efforts are still devoted to the improve of the mechanical properties, the reduction of the twinning stress for the non-modulated martensite, or the increase of operating temperature range. Our previous studies focused on the simultaneous addition of Fe, Co and Cu in the Ni45Co5Mn25-xFexGa20Cu5 system have shown an increase of TM > 100ºC and TC > 150ºC with promising properties as MSM materials for the samples Fe4 and Fe5. In the current work, these two alloys were selected for single crystal growth with the aim of analyze the correlation between the structure and the mechanical properties; and evaluate their workability as HTFSMAs.