NH4+ directed assembly of zinc oxide micro-tubes from nanoflakes

A simple precipitation process followed with the heat treatment was developed to synthesize ZnO micro-tubes by self-assembly of nanoflakes composed of nanoparticles. The resulting ZnO micro-tubes demonstrated excellent photocatalytic performance in degrading methylene blue (MB) under UV illumination. It was found that NH4+ ion played a critical role in directing the assembly of the nanoflakes to form the micro-tube structure. A critical reaction ratio existed at or above which the ZnO micro-tubes could be obtained. For the mixtures of solutions of (NH4)2CO3 and zinc salt, the ratio () was 2:1

Piezoelectric Actuation Of Crack Growth Along Polymer/Metal Interfaces In Adhesive Bonds

A new experimental technique for determining mechanical properties of the polymer/metal interface was developed by replacing the conventional mechanical testing machine with a piezoelectric actuator. The actuator was made from a thin ferroelectric ceramic beam attached to a bilayer polymer/metal composite specimen. The trilayer specimen was loaded by applying ac electric fields on the piezoelectric actuator to drive crack growth along the polymer/metal interface. Using this technique, fatigue crack growth behavior of epoxy/ aluminum interface was studied as a function of electric field, crack length and cyclic frequency. The crack growth rate was found to depend on the magnitude of the applied electric field and decrease with testing frequency

In situ Transmission Electron Microscopy Studies of Electric-field-induced Phenomena in Ferroelectrics

High electric fields were delivered to specimens during imaging in the transmission electron microscopy (TEM) chamber to reveal details of electric field-induced phenomena in ferroelectric oxides. These include the polarization switching in nanometer-sized ferroelectric domains and the grain boundary cavitation in a commercial lead zirconate titanate (PZT) polycrystalline ceramic, the domain wall fracture in a Pb(Mg1/3Nb2/3)O3–PbTiO3 single crystal, and the transformation of incommensurate modulations in Pb0.99Nb0.02[(Zr1−xSnx)1−yTiy]0.98O3 (PZST100x/100y/2) polycrystalline ceramics. In the PZT ceramic, a cavitation process was uncovered for the electric field-induced intergranular fracture. In the ferroelectric single crystal, a preexisting crack was observed to deflect and to follow a 90° domain wall, indicating the presence of severe incompatible piezoelectric strains at thedomain wall. In the antiferroelectric PZST ceramics, the electric field-induced antiferroelectric-to-ferroelectric phase transformation was accompanied with the disappearance of incommensurate modulations.This article is from Journal of Materials Research 20 (2005): 1641–1653, doi:10.1557/JMR.2005.0213. Posted with permission.</p

Oxide film microstructure: the link between surface preparation processes and strength/durability of adhesively bonded aluminum. Final report

Strength and durability of adhesive bonding of aluminum alloys structures are intrinsically determined by the surface microstructures and interfacial failure micromechanisms. The current project presents a multidisciplinary approach to addressing critical issues controlling the strength and durability of adhesive bonds of aluminum alloys. Three main thrust areas have been pursued: surface treatment technology development to achieve desirable surface microstructures; relationship between surface structure and properties of adhesive bonds; and failure mechanisms of adhesively bonded components

As(III) and As(V) Adsorption by Hydrous Zirconium Oxide Nanoparticles Synthesized by a Hydrothermal Process Followed with Heat Treatment

Hydrous zirconium oxide (ZrO₂·<i>x</i>H₂O) were synthesized by a low-cost hydrothermal process followed with heat treatment. ZrO₂·<i>x</i>H₂O nanoparticles ranged from 6 nm to 10 nm and formed highly porous aggregates, resulting in a large surface area of 161.8 m² g^–1. The batch tests on the laboratory water samples demonstrated a very high degree of As(III) and As(V) removal by ZrO₂·<i>x</i>H₂O nanoparticles. The adsorption mechanism study demonstrated that both arsenic species form inner-sphere surface complexes on the surface of ZrO₂·<i>x</i>H₂O nanoparticles. Higher arsenic removal effect of these ZrO₂·<i>x</i>H₂O nanoparticles were demonstrated, compared with commercially available Al₂O₃ and TiO₂ nanoparticles. Ionic strength and competing ion effects on the arsenic adsorption of these ZrO₂·<i>x</i>H₂O nanoparticles were also studied. Testing with natural lake water confirmed the effectiveness of ZrO₂·<i>x</i>H₂O nanoparticles in removing arsenic species from natural water, and the immobilization of ZrO₂•xH₂O nanoparticles on glass fiber cloth minimized the dispersion of nanoparticles into the treated body of water. The high adsorption capacity of ZrO₂·<i>x</i>H₂O nanoparticles is shown to result from the strong inner-sphere surface complexing promoted by the high surface area, large pore volume, and surface hydroxyl groups of zirconium oxide nanoparticles