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SUMMARY:Atom dynamics and Neutron Vibrational Spectroscopy NiNbZr Glassy M
 embranes
DTSTART:20170616T140000
DTEND:20170616T150000
DTSTAMP:20260410T232732Z
UID:1553341d57fc292c3c2744b96f9db41a83cc9d0ae0d382c4e5045a69
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Dhanesh Chandra \n\nUniversity of Nevada\, Reno \nCryst
 alline Pd/Pd-Ag membranes are generally used in hydrogen separation from C
 O2 and other gases in power generation applications. Inexpensive amorphous
  Ni-based alloys are being developed as an alternative to expensive Pd all
 oys. Amorphous membrane ribbons of (Ni0.60Nb0.40)100-xZrx fabricated by me
 lt-spinning method exhibit high permeabilities of hydrogen between 200-400
 oC [1-4]. Atom probe tomography (APT) revealed Nb-rich and Zr-rich cluster
 s embedded in a Ni-rich matrix whose compositions that deviated from the n
 ominal overall composition of the membrane. Fukuhara et al. [5] reported i
 cosahedral cluster arrangement of Ni-Nb-Zr atoms\; we also found clusters 
 based on APT and neutron SANS data\, which can be interpreted as icosahedr
 al arrangement. Neutron vibrational spectroscopy of these alloy yielded po
 ssible positions of hydrogen. Atom dynamic studies by X-ray photon correla
 tion spectroscopy (XPCS) revealed a dramatic reversible acceleration of th
 e atomic motion under hydrogen atmosphere at low temperatures\; these effe
 cts are observed by standard thermodynamic/kinetic measurements. Dynamic m
 echanical analyses (DMA) indicated amorphous to amorphous phase transition
 s well below the recrystallization temperature\, as well as the change ela
 stic modulus as a function of temperature. Devitrification kinetics of the
 se amorphous ribbons by using the John-Mehl-Avrami method showed Avrami ex
 ponents ranging from 1.92 to 2.47 indicating diffusion controlled 3-D grow
 th mechanism. In an attempt to develop new alloys we show liquidus profile
 s for the ternary system using CALPHAD methodology. Hydrogen permeation\, 
 atom probe tomography\, small angle neutron scattering\, neutron vibration
 al spectroscopy\, dynamic mechanical analyses\, XPCS and devitrification k
 inetic aspects of these membranes will be presented.\n(This research is su
 pported by US DOE-NNSA grant\, DE-NA0002004 and DOE-NETL FE0000998).\n \n
 References:\n\n	S. Sarker\, D. Chandra et al\, Applied Physics A\, A 122\,
  168 (2016).\n	M.D. Dolan\, N.C. Dave\, A.Y. Ilyushechkin\, L.D. Morpeth\,
  K.G. McLennan\, J. Membr. Sci. 285 (2006) 30\n	S.M Kim\, D. Chandra et al
 \, Journal of Non-Crystalline Solids\, 358 (2012) 1165–1170.\n	S. Paglie
 ri\, N. Pal\, D. Chandra\, Journal of Membrane Science\, 378 (2011) 42-50.
 \n	M. Fukuhara\, N. H. Oji\, A. Inoue\, S. Emura\, JALCOM\,497 (2010) 182
 –187\n
LOCATION:Emosson
STATUS:CONFIRMED
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