Abstract: We report the microstructural and magnetic properties
of Ni50Mn39Sn11 and Ni50Mn36Sn14 ribbon Heusler alloys.
Experimental results were obtained by differential scanning
calorymetry, X-ray diffraction and vibrating sample magnetometry
techniques. The Ni-Mn-Sn system undergoes a martensitic structural
transformation in a wide temperature range. For example, for
Ni50Mn39Sn11 the start and finish temperatures of the martensitic and
austenite phase transformation for ribbon alloy were Ms=336K,
Mf=328K, As=335K and Af=343K whereas no structural
transformation is observed for Ni50Mn36Sn14 alloys. Magnetic
measurements show the typical ferromagnetic behavior with Curie
temperature 207 K at low applied field of 50 Oe. The complex
behavior exhibited by these Heusler alloys should be ascribed to the
strong coupling between magnetism and structure, being their
magnetic behavior determined by the distance between Mn atoms.
Abstract: A novel physico-chemical route to produce few layer graphene nanoribbons with atomically smooth edges is reported, via acid treatment (H2SO4:HNO3) followed by characteristic thermal shock processes involving extremely cold substances. Samples were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy. This method demonstrates the importance of having the nanotubes open ended for an efficient uniform unzipping along the nanotube axis. The average dimensions of these nanoribbons are approximately ca. 210 nm wide and consist of few layers, as observed by transmission electron microscopy. The produced nanoribbons exhibit different chiralities, as observed by high resolution transmission electron microscopy. This method is able to provide graphene nanoribbons with atomically smooth edges which could be used in various applications including sensors, gas adsorption materials, composite fillers, among others.