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Title: Characterization and corrosion behaviour of CoNi alloys obtained by mechanical alloying

CoNi alloys including Co{sub 30}Ni{sub 70}, Co{sub 50}Ni{sub 50} and Co{sub 70}Ni{sub 30} were prepared via mechanical alloying using Co and Ni powders. The crystallinity and short-range order were studied using X-ray diffraction and X-ray absorption spectroscopy. The results show that the milling process increases the number of vacancies, especially around the Co atoms, while the milling time decreases the crystalline size and enhances the crystallinity. X-ray photoelectron spectroscopy was used to characterise the chemical composition of the samples surface. The magnetic properties were analysed using zero-field cooling, field cooling and a magnetic hysteresis loops. The magnetic saturation moment is approximately 1.05 μ{sub B}/atom; this value decreases with the mechanical alloying time, and it is proportional to the cobalt concentration. The polarization and impedance curves in different media (NaCl, H{sub 2}SO{sub 4} and NaOH) showed similar corrosion resistance values. The corrosion resistance increased in the order NaCl, H{sub 2}SO{sub 4} and NaOH. A good passivation layer was formed in NaOH due to the cobalt and nickel oxides on the particle surfaces. - Highlights: • Ni{sub x}Co{sub 100-x} alloys were synthesized by mechanical alloying • Milling time decrease size and enhances crystallinity. • Oxygen is not present in a significant percentagemore » in bulk but is detected on the surface. • Magnetic saturation moment is 1.05 mB/atom and decrease with mechanical allowing time • Corrosion resistance is higher in NaOH than in NaCl or HCl solutions.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [1] ;  [3]
  1. Instituto Politécnico Nacional, ESIQIE, Departamento de Ingeniería en Metalurgia y Materiales, México, D. F. (Mexico)
  2. (Spain)
  3. Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química-Física Aplicada, 28049 Madrid (Spain)
  4. Instituto de Ciencia de Materiales de Madrid, ICMM-CSIC, Cantoblanco, 28049 Madrid (Spain)
  5. Spline Spanish CRG Beamline at the European Synchrotron Radiation Facilities, ESRF, BP 220-38043, Grenoble Cedex (France)
Publication Date:
OSTI Identifier:
22340381
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Characterization; Journal Volume: 93; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABSORPTION; ABSORPTION SPECTROSCOPY; CARBONATES; COBALT ALLOYS; CORROSION; CORROSION RESISTANCE; FINE STRUCTURE; HYSTERESIS; MAGNETIC PROPERTIES; NICKEL OXIDES; OXYGEN; PARTICLES; POLARIZATION; SODIUM CHLORIDES; SODIUM HYDROXIDES; X RADIATION; X-RAY DIFFRACTION; X-RAY PHOTOELECTRON SPECTROSCOPY; X-RAY SPECTROSCOPY