Objectives:

• To study diffusion reactions at planar aluminum-spinel (Al–MgAl2O4) interfaces.

• To investigate the effect of an external electric field on diffusion reactions at such interfaces.

Ion Exchange at Metal–Ceramic InterfacesIon Exchange at Metal–Ceramic InterfacesF. Ernst,F. Ernst,11 R. Raj R. Raj22

11Case Western Reserve University, Case Western Reserve University, 22University of Colorado at BoulderUniversity of Colorado at BoulderDMR-0208008DMR-0208008

Result:

Tempering aluminum–spinel interfaces in applied electric fields, we found credible evidence that diffusion reactions of magnesium, aluminum, and oxygen ions can be controlled by the strength and polarity of applied electric fields. Positive ions were more mobile than negative ions in a spinel under the influence of applied electric fields. Differences in mobility and valency of constituent ions suggest a correlation between interdiffusion and electrical fields, which is conceptually consistent with the electrostatic model of mechanical adhesion.

MgAl2O4Al film

Al

O

Mg

Mg-deficient reaction layer

Right: High-resolution TEM image revealing the interface structure of an as-grown Al–MgAl2O4.

Right: Composition profiles show the different response (diffusion) of ions across the interface when annealing in an external electric field.

Al film MgAl2O4

2 nm

Al3+

Mg2+

Ion Exchange at Metal–Ceramic InterfacesIon Exchange at Metal–Ceramic InterfacesF. Ernst,F. Ernst,11 R. Raj R. Raj22

11Case Western Reserve University, Case Western Reserve University, 22University of Colorado at BoulderUniversity of Colorado at BoulderDMR-0208008DMR-0208008

Education and OutreachEducation and Outreach• On January 14 and 21, 2005, the On January 14 and 21, 2005, the

team at Case invited students of the team at Case invited students of the Ruffing Montessori middle school in Ruffing Montessori middle school in Cleveland Heights for two lectures on Cleveland Heights for two lectures on "Materials and Microscopy" and a "Materials and Microscopy" and a hands-on demonstration of scanning hands-on demonstration of scanning electron microscopy and electron microscopy and transmission electron microscopy. (transmission electron microscopy. (http://www.ruffingeast.org/webpages/middle_school.htmhttp://www.ruffingeast.org/webpages/middle_school.htm ))

• Jeremy MarkJeremy Mark, an undergraduate , an undergraduate student performed his senior project student performed his senior project in relation to this project. in relation to this project.

• Gurpreet SinghGurpreet Singh, graduate student , graduate student at UCB, was trained in UHV at UCB, was trained in UHV techniques, thin-film preparation, techniques, thin-film preparation, and mechanical testing of thin films.and mechanical testing of thin films.

• Yeonseo YuYeonseo Yu, graduate student at , graduate student at Case completed his Ph.D. degree in Case completed his Ph.D. degree in August 2005. His Ph.D. thesis is August 2005. His Ph.D. thesis is based on the work on this project.based on the work on this project.

Broader ImpactsBroader Impacts• The latest results of this project are The latest results of this project are

going to be presented at the 2006 going to be presented at the 2006 TMS Annual Meeting & Exhibition.TMS Annual Meeting & Exhibition.

• A journal article about the effects of A journal article about the effects of annealing under applied electric annealing under applied electric fields is in preparation.fields is in preparation.