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A multi-stimuli responsive, self-assembling, boronic acid dipeptide

Chemical Communications

Jones, Brad H.; Martinez, Alina M.; Wheeler, Jill S.; Mckenzie, Bonnie; Miller, Lance L.; Wheeler, David R.; Spoerke, Erik D.

Modification of the dipeptide of phenylalanine, FF, with a boronic acid (BA) functionality imparts unique aqueous self-assembly behavior that responds to multiple stimuli. Changes in pH and ionic strength are used to trigger hydrogelation via the formation of nanoribbon networks. Furthermore, we show for the first time that the binding of polyols to the BA functionality can modulate a peptide between its assembled and disassembled states.

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TYPE Journal Article YEAR 2015
DOIOSTIScopus

Room-temperature voltage tunable phonon thermal conductivity via reconfigurable interfaces in ferroelectric thin films

Nano Letters

Ihlefeld, Jon F.; Foley, Brian M.; Scrymgeour, David; Michael, Joseph R.; Mckenzie, Bonnie; Medlin, Douglas L.; Wallace, Margeaux; Trolier-Mckinstry, Susan; Hopkins, Patrick E.

Dynamic control of thermal transport in solid-state systems is a transformative capability with the promise to propel technologies including phononic logic, thermal management, and energy harvesting. A solid-state solution to rapidly manipulate phonons has escaped the scientific community. We demonstrate active and reversible tuning of thermal conductivity by manipulating the nanoscale ferroelastic domain structure of a Pb(Zr0.3Ti0.7)O3 film with applied electric fields. With subsecond response times, the room-temperature thermal conductivity was modulated by 11%.

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TYPE Journal Article YEAR 2015
DOIOSTIScopus

Deformation behavior of sub-micron and micron sized alumina particles in compression

Sarobol, Pylin; Chandross, Michael E.; Carroll, J.D.; Mook, William M.; Boyce, Brad L.; Kotula, Paul G.; Mckenzie, Bonnie; Bufford, Daniel C.; Hall, Aaron

The ability to integrate ceramics with other materials has been limited due to high temperature (>800°C) ceramic processing. Recently, researchers demonstrated a novel process, aerosol deposition (AD), to fabricate ceramic films at room temperature (RT). In this process, sub-micron sized ceramic particles are accelerated by pressurized gas, impacted on the substrate, plastically deformed, and form a dense film under vacuum. This AD process eliminates high temperature processing thereby enabling new coatings and device integration, in which ceramics can be deposited on metals, plastics, and glass. However, knowledge in fundamental mechanisms for ceramic particles to deform and form a dense ceramic film is still needed and is essential in advancing this novel RT technology. In this work, a combination of experimentation and atomistic simulation was used to determine the deformation behavior of sub-micron sized ceramic particles; this is the first fundamental step needed to explain coating formation in the AD process. High purity, single crystal, alpha alumina particles with nominal sizes of 0.3 µm and 3.0 µm were examined. Particle characterization, using transmission electron microscopy (TEM), showed that the 0.3 µm particles were relatively defect-free single crystals whereas 3.0 µm particles were highly defective single crystals or particles contained low angle grain boundaries. Sub-micron sized Al2O3 particles exhibited ductile failure in compression. In situ compression experiments showed 0.3µm particles deformed plastically, fractured, and became polycrystalline. Moreover, dislocation activity was observed within these particles during compression. These sub-micron sized Al2O3 particles exhibited large accumulated strain (2-3 times those of micron-sized particles) before first fracture. In agreement with the findings from experimentation, atomistic simulations of nano-Al2O3 particles showed dislocation slip and significant plastic deformation during compression. On the other hand, the micron sized Al2O3 particles exhibited brittle fracture in compression. In situ compression experiments showed 3µm Al2O3 particles fractured into pieces without observable plastic deformation in compression. Particle deformation behaviors will be used to inform Al2O3 coating deposition parameters and particle-particle bonding in the consolidated Al2O3 coatings.

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TYPE SAND Report YEAR 2014
DOIOSTI

Morphology and growth kinetics of straight and kinked Tin whiskers

Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science

Michael, Joseph R.; Grant, Richard P.; Mckenzie, Bonnie; Yelton, W.G.

Time-lapse SEM studies of Sn whiskers were conducted to estimate growth kinetics and document whisker morphologies. For straight whiskers, growth rates of 3 to 4 microns per day were measured at room temperature. Two types of kinked whiskers were observed. For Type A kinks, the original growth segment spatial orientation remains unchanged, there are no other changes in morphology or diameter, and growth continues. For Type B kinks, the spatial orientation of the original segment changes and it appears that the whisker bends over. Whiskers with Type B kinks show changes in morphology and diameter at the base, indicating grain boundary motion in the film, which eliminates the conditions suitable for long-term whisker growth. To estimate the errors in the whisker growth measurements, a technique is presented to correct for SEM projection effects. With this technique, the actual growth angles and lengths of a large number of whiskers were collected. It was found that most whiskers grow at moderate or shallow angles with respect to the surface; few straight whiskers grow nearly normal to the surface. In addition, there is no simple correlation between growth angles and lengths for whiskers observed over an approximate 2-year period. © 2012 The Minerals, Metals & Materials Society and ASM International (outside the USA).

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TYPE Journal Article YEAR 2013
OSTIScopus

Copper ionic liquids: Tunable ligand and anion chemistries to control electrochemistry and deposition morphology

Journal of Electroanalytical Chemistry

Pratt, Harry D.; Ingersoll, David; Hudak, Nicholas S.; Mckenzie, Bonnie

A multi-technique investigation was performed on three copper-based ionic liquids to elucidate the influence of coordinating ligands and charge-balancing anions on the electrochemical properties of the materials. Galvanostatic cycling of Cu(OHCH2CH2NH2)6(BF 4)2 (Cu1) in 1-butyl-3-methyl-imidazolium hexafluorophosphate gave partially reversible plating of copper that was consistent with cyclic voltammetry data (collected using an ionic liquid-based reference electrode verified with measurements of ferrocene, cobaltocene, and lithium). Scanning electron microscopy also showed pitting in the copper-coated surface of the electrode that was consistent with the stripping wave observed by cyclic voltammetry. Potentiostatic deposition in neat Cu1 showed significant dendrite formation. The substitution of the OHCH2CH 2NH2 ligands of Cu1 with stronger coordinating NH(CH 2CH2OH)2 in Cu(NH(CH2CH 2OH)2)6(BF4)2 (Cu2) resulted in the complete suppression of both copper stripping and dendrite formation. Substitution of the BF4- anions of Cu2 with CF3SO3- in Cu(NH(CH2CH2OH)2)6(CF 3SO3)2 (Cu3) shifted the copper deposition 0.1 V more negative and produced slightly larger spherical particles (1.5 μm versus 5 μm). The results suggested that while the anion composition influenced particle size, and the metal-ligand bond strength helped control particle morphology, both factors affected the electrochemical properties including the plating and stripping of copper. © 2013 Elsevier B.V. All rights reserved.

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TYPE Journal Article YEAR 2013
DOIOSTIScopus
Results 51–100 of 156
Results 51–100 of 156