时间：2014年7月12日（周六）上午9：30-10：30
地点：工学部新九教环境工程系会议室
Electroplatingof Binary Alloys: Control over Composition and Structure
Giovanni Zangari
Department of Materials Science and Engineering
University of Virginia, Charlottesville VA22904-4745 USA
Electroplating is a powerful yet simple technology
for the production of metallic coatings. Alloy electroplating is of particular
interest since the ability to plate new alloys may enhance properties and even
enable novel functions, in micro- as well as macro-scale applications.
Unfortunately, process control is much more difficult with alloys, as
exemplified by the limited set of alloys currently used in production
environments.
A thermodynamic approach to alloy electroplating,
which uses the enthalpy of formation to control composition and structure, can
provide insight into the mechanisms of structure formation and microstructure
control in alloys, suggesting innovative ways to develop alloy plating
processes or improve existing ones. In alloy electrodeposition the Nernst
equation becomes
, where the activityai(alloy)of the elementiin the alloy may be described for
example by a regular solution approximation. For alloys forming solid solutions
this results in a positive shift of the deposition potential ofi, facilitating co-deposition and
enabling composition control at low deposition rates. Examples of this
behavior, including Au-Cu and Fe-Pt alloys, will be presented, and the effect
of complexation will be discussed.
On the other hand, when solid solutions are
thermodynamically unstable, the alloying behavior cannot be described by the
above approach but instead depends strongly on atomistic interactions, kinetic
processes at the growing interface, or the double layer structure, as will be shown
for Au-Ni, Ag-Cu and Ag-Ni alloys. In these cases, phase separation at the
nanoscale can be tuned by the deposition kinetics.
ShortBio
GiovanniZangari is currently a professor of materials science at the University of
Virginia. He received his MS in Nuclear Engineering from Politecnico di Milano
and his PhD in Metallurgical Engineering from the Politecnico di Torino. Before
coming to Virginia, he was a post-doc at Carnegie Mellon University and an
assistant, then associate professor at the U. of Alabama, Tuscaloosa. His
research activities lie at the intersection of materials science and
electrochemistry; in particular, his group is focused on developing the
fundamental science and processing knowledge to tailor materials for
micro/nano-electronics, magnetics, and most recently energy conversion
applications. Current interests encompass the fundamentals of alloy
electrodeposition, the synthesis of semiconductor materials for energy
applications, the tailoring of electron transport properties in dielectric
oxides, and the design of novel magnetic storage devices. Prof. Zangari has
published more than 150 articles and has co-authored a book on
electrodeposition science and technology. He is a Fellow of the Electrochemical
Society, the current Chair of the Electrodeposition Division of ECS, and a
vice-chair of Division 5 of ISE.
