Mechanical activation of pre-alloyed NiTi2 and elemental Ni for the synthesis of NiTi alloys

ABSTRACT: This work reports on an efficient powder metallurgy method for the synthesis of NiTi alloys, involving mechanical activation of pre-alloyed NiTi2 and elemental Ni powders (NiTi2-Ni) followed by a press-and-sinter step. The idea is to take advantage of the brittle nature of NiTi2 to promote a better efficiency of the mechanical activation process. The conventional mechanical activation route using elemental Ti and Ni powders (Ti-Ni) was also used for comparative purposes. Starting with (NiTi2-Ni) powder mixtures resulted in the formation of a predominant amorphous structure after mechanical activation at 300 rpm for 2 h. A sintered specimen consisting mainly of NiTi phase was obtained after vacuum sintering at 1050 degrees C for 0.5 h. The produced NiTi phase exhibited the martensitic transformation behavior. Using elemental Ti powders instead of pre-alloyed NiTi2 powders, the structural homogenization of the synthesized NiTi alloys was delayed. Performing the mechanical activation at 300 rpm for the (Ti-Ni) powder mixtures gave rise to the formation of composite particles consisting in dense areas of alternate fine layers of Ni and Ti. However, no significant structural modification was observed even after 16 h of mechanical activation. Only after vacuum sintering at 1050 degrees C for 6 h, the NiTi phase was observed to be the predominant phase. The higher reactivity of the mechanically activated (NiTi2-Ni) powder particles can explain the different sintering behavior of those powders compared with the mechanically activated (Ti-Ni) powders. It is demonstrated that this innovative approach allows an effective time reduction in the mechanical activation and of the vacuum sintering step.info:eu-repo/semantics/publishedVersio

Exploring fabrication methods to highly sensitive and selective InP nanowire biosensors

FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFabrication methodologies for integration of nano-objects into microscale devices is still an active area of research. Here we analyze possible methods of incorporation of semiconductor nanowires into lithographically-defined electrode pads. Mechanically-146114FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ2015/16611-4Sem informação552491/2008-0479486/2012-3441799/2016-74. International Conference on Metamaterials and Nanophotonics15 a 19 de Julho de 2019Saint Petersburg, RussiaINSCIENCE; Bruker Nano Surfaces; ITMO UniversityITMO UniversityThe Brazilian authors acknowledge access to electron microscopy (LME) facilities at the National Nanotechnology Laboratory (LNNano, Brazil) and clean room facilities at both Semiconductor Component Center (CCSNano, UNICAMP) and Device Research Laborator

Electric current driven formation of micro-and nano-sized beads in thin Cr films

Nano films of chromium with thicknesses from 20 to 200 nm were deposited on silicon substrates and were treated by electric current induced by AFM tip in ambient atmosphere. The melting on the nanoscale, electric current induced migration of the material and chemical reaction of oxidization of chromium were revealed in melting craters around the point of application of the current by optical and electronic scanning microscopy, AFM, and Raman spectroscopy. The flow of the material induced by electric current is accompanied by formation and motion of the matrix of the spherical nanoparticles (beads) in the crater of melt on its periphery. The reaction of chromium oxidation and surface tension of the melted material on the silicon substrate are expected to be responsible for the matrix of nano beads formation under comparatively small currents. Raman spectroscopy confirms that in the vicinity of the periphery of the melted craters around AFM tip application, the beads of oxide phase Cr2O5 are present

Non-enzymatic electrochemical sensor based on ZnO nanoparticles/porous graphene for the detection of hypoxanthine in pork meat

In this study, we developed a pioneering non-enzymatic electrochemical sensor utilizing a flexible porous graphene electrode modified with ZnO nanoparticles (ZnO/fPGE sensor) to assess hypoxanthine (HXA) content in pork at post-mortem time. The ZnO/fPGE sensor was synthesized via hydrothermal method and direct laser writing with a CO2 laser on a polyimide film at ambient conditions. Its characterization was analyzed by Raman, Fourier-transform infrared spectroscopy, field-emission scanning microscopy, energy-dispersive x-ray spectroscopy, and cyclic voltammetric techniques. Linear response, the limit of detection, and sensitivity to the HXA were enhanced with the values of the range from 1.5 to 150, 0.14 µM, and 6.6 µA μM−1 cm−2, respectively. Effective resistance to common physiological interferences (such as uric acid, ascorbic acid, dopamine, glucose, and xanthine) was indicated, and additionally, the determination of HXA concentration in real samples with good selectivity is attributed to the synergistic effects between ZnO nanoparticles and fPGE. Therefore, the ZnO/fPGE has provided a favorable electrical environment for developing high-performance electrochemical biosensors to determine hypoxanthine in pork meat