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 activitya_i(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.