Two ChE PhD graduate students from the Podlaha Group received prestigious travel awards from The Electrochemical Society to attend their annual meeting in New Orleans May 28-June 2 . Xiaohua Geng...
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- Metal alloy nanotubes – Electrodeposition into nanoporous templates is today dominated by research of nanowires, central for the next generation of sensing materials in diverse areas such as magnetic sensing for computers, detection of DNA in biosensors, identifying cracks in space and aircraft, and readers of magnetic inks and magnetic cards. The tunability of ferromagnetic materials is possible by controlling the composition as a homogeneous alloy or artificially layered structure with paramagnetic spacers on the nanoscale. In our earlier work, we showed that alloy nanotubes of CoNiCu and Cu can be deposited into nanoporous templates by manipulating the current efficiency through the selection of a dilute electrolyte. More recently, we have reported that nanotubes with modulated composition exhibit giant magnetoresistance (GMR), a large (> 1%) change in the deposit resistance with an applied magnetic field (Figure 1). It is the first demonstration of a metallic nanotube with GMR properties.
- Micropillars – Compositionally modulated ferro/para-magnetic materials having layer sizes in the nanometer regime exhibit GMR, but can also impart other unique properities. An alternative multilayered architecture is micro-size pillars. These materials have potential for tailoring properties of microdevices. Figure 2 shows a SEM micrograph of an array of square 180 x 180 um CoCu/Cu multilayer microposts, 500 um tall. The layer sizes depicted in the figure are roughly 150 nm, far too large for property enhancement, but are used to verify the electrodeposition pulse technique. Reducing the layers to the nanometer range (9 nm) resulted in a room temperature GMR. The main challenge in electrodeposition of such tall structures is the control of the composition and layer size along the length of the microstructure, compounded by the fact that the boundary layer is dynamic. Other systems of interest are layered Invar (FeNi) with Cu to minimize and tailor the coefficient of thermal expansion (CTE) and NiFeW/Cu for a combination of lower CTE and hardness.
- Multilayers as a precursor for nanomolds – Multilayer films are not only of interest for their magnetic, thermal or mechanical properties, but could also be explored as an alternative nanomold – a low cost choice to conventional electron beam and focused ion beam pattern generators. Figure 3 shows a typical nanoscale multilayer system with a subsequent preferential etching step to create the mold. Preliminary work has shown that it is possible to etch layers in the submicron range. A current research goal is to create features 10s of nanometers for use as a mold in the fabrication of molecular electronics, nanostructured sub-wavelength optics and nanochannels for DNA detection. Key factors that dictate the preparation of discrete features include: selectivity of the etchant, and a priori compositional uniformity of the electrodeposited layers.
- Metal Matrix Nanocomposites – Composite materials, consisting of a nanometric particle embedded into a metal matrix yield materials with tailored properties depending on the particle type. For example, alumina particles included into a Ni or Cu matrix enhances the material’s hardness and tribological properties over that of the parent metal. In addition, the use of particles in the nano-regime is critical to fabricate composite materials that have promise as components of micro-size devices (i.e. heating elements for micro-reactors). A plethora of research has demonstrated different combinations of particle-metal systems as thin films, but few focus on how the particle interacts with the reducing ions and far fewer demonstrate the ability to control the composition in microstructures. We have shown that alumina particles can in some cases enhance or inhibit the metal reduction reaction, though future research is needed to understand the controlling features and limits of these changes.
- Alloy Modeling – Many electrodeposited nanostructures of interest are comprised of alloy systems that have coupled kinetic rates, thus it is not straight forward to predict the resulting alloy composition. Anomalous codeposition often refers to the inhibition of a metal reaction rate due to the presence of a less noble codepositing element. A case in point, is electrodeposited NiFe (permalloy composition) formerly of interest as a material for ferromagnetic read heads. In contrast, induced codeposition is classically described by the Mo or W refractory elements codeposited with the more noble Ni, Fe or Co. Interestingly, without the iron-group elements in the electrolyte it is today not possible to reduce molybdate or tungstate ions from an aqueous solution. Results in our lab have showed that both inhibition and enhancement features of the iron-group elements can occur in a single electrolyte. A steady-state model with Langmuir-type kinetics and a boundary layer approach captures some of the behavior of the experimental data. Recent work in our lab has also suggested that rare earth elements codeposited with Fe or Co exhibit induced and anomalous codeposition behavior, prompting the question as to the generality of the existing model.
- B.S. (Chemical Engineering) University of Connecticut, 1986
- Ph.D. (Chemical Engineering) Columbia University, 1992
- Postdoctoral Fellowship (Materials Science) Ecole Polytechnique de Lausanne, Switzerland, 1993-1998
- X. Geng and E. J. Podlaha, Nano Letters, accepted November 16, 2016 DOI: 10.1021/acs.nanolett.6b03065 (in press, but currently available on-line: http://pubs.acs.org/doi/abs/10.1021/acs.nanolett.6b03065)
- E. Vernickaite, U. Bubniene, H. Cesiulis, A. Ramanavicius, and E. J. Podlaha “A hybrid approach to fabricated nanowire-nanoparticle composites of a Co-W alloy and Au nanoparticles Journal of The Electrochemical Society, 163 (7) D344-D348 (2016).
- A. Kola and E. J. Podlaha, “Ag-W Electrodeposits with High W Content from Thiourea-Citrate Electrolytes,” Journal of Electroanalytical Chemistry, 761, 125–130 (2016).
- S. Sun and E.J. Podlaha, “Examination of Ni-W Induced Codeposition by Intensity Modulated Photocurrent Spectroscopy (IMPS),” Journal of The Electrochemical Society, 161 (6) D362-D366 (2014). doi:10.1149/2.097406jes
- S. Sun, T. Bairchanya and E.J. Podlaha, “Induced Codeposition Behavior of Electrodeposited NiMoW Alloys,” Journal of The Electrochemical Society, 160 (10) D434-D440 (2013). doi:10.1149/2.014310jes
- Hana Kim, M. Murphy and E.J. Podlaha, “Electrodeposition of High Aspect Ratio Super Invar Microstructures,” Journal of The Electrochemical Society, 159 (9): D549-D554 (2012). doi:10.1149/2.002209jes
- S. Sun and E.J. Podlaha, “Electrodeposition of Mo-rich, MoNi Alloys from an Aqueous Electrolyte,” Journal of The Electrochemical Society, 159 (2): D1-D6 (2012). doi:10.1149/2.091202jes
- M. Esteves, P. T. A. Sumodjo, E. J. Podlaha, “Electrodeposition of CoNiMo thin films using glycine as additive: anomalous and induced codeposition,” Electrochimica Acta, 56 (25): 9082-9087 (2011).
- D. Pinisetty, D. Davis, E. J. Podlaha-Murphy, M. C. Murphy, A. B. Karki, D. P. Young and R. V. Devireddy, “Characterization of Electrodeposited Bismuth-Tellurium Nanowires and Nanotubes,” Acta Materialia, 59 (6): 2455-2461 (2011).
- S. Lucatero and E. J. Podlaha, “Influence of Citric and Ascorbic Acid on Electrodeposited Au/FeAu Multilayered Nanowires,” Journal of The Electrochemical Society, 157 (6): D370-D375 (2010).
- M. Gupta and E.J. Podlaha, “Electrodeposition of CuNiW Alloys: thin films, nanostructured multilayers and nanowires” Journal of Applied Electrochemistry, 40 1429-1439 (2010).
- D. Davis, M. Zamanpour, M. Moldovan, D. Young and E. J. Podlaha, “Electrodeposited, GMR CoNiFeCu Nanowires and Nanotubes from Electrolytes Maintained at Different Temperatures,” Journal of The Electrochemical Society, 157 D317-D322 (2010).
- Jessy Elhajj, Miriam Ismail, Julio Warzywoda Albert Sacco Jr., Richard Kurtz and Elizabeth J. Podlaha, “Electrochemical Fabrication of TiO2-Au Nanocomposites,” Journal of Electrochemical Society, 157 (1): D5-D9 (2010).
- S. Lucatero, W. H. Fowle and E. J. Podlaha, “Electrodeposited Au/FeAu Nanowires with Controlled Porosity,” Electrochemical and Solid State Letters, 12 (12): D96-D100 (2009).
- Henrikas Cesiulis, Xiagong Xie and Elizabeth Podlaha-Murphy,” Electrodeposition of Co-W Alloys with P and Ni,” Materials Science (Medžiagotyra), 15 (2): 1392-1320 (2009).
- V. Kublanovsky, O. Bersirova, Iu. Iapontseva, H. Cesiulis, E. Podlaha-Murphy, “Cobalt-Molybdenum-Phosphorous Alloys: Electrodeposition and Corrosion Properties,” Protection of Metals and Physical Chemistry of Surfaces (Fizikokhimiya Poverkhnosti i Zashchita Materialov), 45 (5): 534-540 (2009).
- Frank Nelson Crespilho, P.T. A. Sumodjo, M.C. Esteves, E. J. Podlaha, V. Zucolotto, “Development of Highly Selective Enzymatic Devices based on Deposition of Permselective Membranes on Aligned Nanowires,” Journal of Physical Chemistry C, 113 (15): 6037-6041 (2009).
- E. J. Podlaha, "Selective Electrodeposition of Nanoparticulates into Metal Matrices," Nano Letters, 1 (8): 413-416 (2001).
Joined the Chemical Engineering Department in Spring 2007.
Electrodeposited nanostructured materials define a variety of systems, such as compositionally modulated multilayers with nano-sized layers, nanowires and metal matrix nanocomposites, of interest for a wide range of applications. A common challenge to each electrodeposited system is the control of composition and the great versatility in the resulting properties. Below are few examples of electrodeposited nanostructured materials that we have recently studied:
Research & Scholarship Interests
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College Research Initiatives
ChE Professor Elizabeth Podlaha-Murphy's research was featured in Nano Letters for her article on "Coupled, Simultaneous Displacement and Dealloying Reactions into Fe-Ni-Co Nanowires for Thinning Nanowire Segments".
ChE Professor Elizabeth Podlaha-Murphy was awarded a patent for “Photocatalyst with enhanced stability for hydrogen production and oxidative reactions”