Micromechanics of Amorphous Metal/Polymer Hybrid Structures with 3D Cellular Architectures: Size Effects, Buckling Behavior, and Energy Absorption Capability.

By designing advantageous cellular geometries and combining the material size effects at the nanometer scale, lightweight hybrid microarchitectured materials with tailored structural properties are achieved. Prior studies reported the mechanical properties of high strength cellular ceramic composites, obtained by atomic layer deposition. However, few studies have examined the properties of similar structures with metal coatings. To determine the mechanical performance of polymer cellular structures reinforced with a metal coating, 3D laser lithography and electroless deposition of an amorphous layer of nickel-boron (NiB) is used for the first time to produce metal/polymer hybrid structures. In this work, the mechanical response of microarchitectured structures is investigated with an emphasis on the effects of the architecture and the amorphous NiB thickness on their deformation mechanisms and energy absorption capability. Microcompression experiments show an enhancement of the mechanical properties with the NiB thickness, suggesting that the deformation mechanism and the buckling behavior are controlled by the brittle-to-ductile transition in the NiB layer. In addition, the energy absorption properties demonstrate the possibility of tuning the energy absorption efficiency with adequate designs. These findings suggest that microarchitectured metal/polymer hybrid structures are effective in producing materials with unique property combinations.

Nonaqueous Sol-Gel Synthesis of Anatase Nanoparticles and Their Electrophoretic Deposition in Porous Alumina.

Titanium dioxide (TiO2) nanoparticles were synthesized by nonaqueous sol-gel route using titanium tetrachloride and benzyl alcohol as the solvent. The obtained 4 nm-sized anatase nanocrystals were readily dispersible in various polar solvents allowing for simple preparation of colloidal dispersions in water, isopropyl alcohol, dimethyl sulfoxide, and ethanol. Results showed that dispersed nanoparticles have acidic properties and exhibit positive zeta-potential which is suitable for their deposition by cathodic electrophoresis. Aluminum substrates were anodized in phosphoric acid in order to produce porous anodic oxide layers with pores ranging from 160 to 320 nm. The resulting nanopores were then filled with TiO2 nanoparticles by electrophoretic deposition. The influence of the solvent, the electric field, and the morphological characteristics of the alumina layer (i.e., barrier layer and porosity) were studied.

The electrodeposition of FeCrNi stainless steel: microstructural changes induced by anode reactions.

The FeCrNi alloy, whose composition is close to that of stainless steel 304, was prepared by electrodeposition and characterized. Nanocrystalline FeCrNi (nc-FeCrNi) was obtained by employing a double-compartment cell where the anode is separated from the cathode compartment, while amorphous FeCrNi (a-FeCrNi) was deposited in a conventional single electrochemical cell. The carbon content of nc-FeCrNi was found to be significantly lower than that of a-FeCrNi, suggesting that carbon inclusion is responsible for the change in the microstructure. The major source of carbon is associated with the reaction compounds at the anode electrode, presumably decomposed glycine. Crystal structure analysis by XRD and TEM revealed that the as-deposited nc-FeCrNi deposits consist of α-Fe which transforms to γ-Fe upon thermal annealing. Nanoindentation tests showed that nc-FeCrNi exhibits higher hardness than a-FeCrNi, which is consistent with the inverse Hall-Petch behavior.