No abstract

In this study, the effects of Ultrasonic Nano-crystal Surface Modification (UNSM) on residual stresses, microstructure changes and mechanical properties of austenitic stainless steel 304 were investigated. The dynamic impacts induced by UNSM leads to surface nanocrystallization, martensite formation, and the generation of high magnitude of surface compressive residual stresses (-1400 MPa) and hardening. Highly dense deformation twins were generated in material subsurface to a depth of 100 µm. These deformation twins significantly improve material work-hardening capacity by acting both as dislocation blockers and dislocation emission sources. Furthermore, the gradually changing martensite volume fraction ensures strong interfacial strength between the ductile interior and the two nanocrystalline surface layers and thus prevents early necking. The microstructure with two strong surface layers and a compliant interior embedded with dense nanoscale deformation

No abstract

Optical properties of colloidal plasmonic titanium nitride nanoparticles are examined with an eye on their photothermal and photocatalytic applications via transmission electron microscopy and optical transmittance measurements. Single crystal titanium nitride cubic nanoparticles with an average size of 50 nm, which was found to be the optimum size for cellular uptake with gold nanoparticles [1], exhibit plasmon resonance in the biological transparency window and demonstrate a high absorption efficiency. A self-passivating native oxide at the surface of the nanoparticles provides an additional degree of freedom for surface functionalization. The titanium oxide shell surrounding the plasmonic core can create new opportunities for photocatalytic applications. an excitement to develop technologies for a broad range of applications. The wide range of carrier concentrations available from several material classes spans the electromagnetic spectrum from the ultra-violet through the midinfrared [2]. Additionally, the broad variety of materials studied in the field provide extra degrees of freedom to solve technological challenges thanks to the unique properties such as tunability, process compatibility, chemical stability, etc [3]. KeywordsTransition metal nitrides, especially titanium nitride (TiN), have been studied for the last three decades due to the unique combination of their material properties [4]. Metallic behavior of TiN combined with its hardness and chemical stability has attracted attention in microelectronics research [5]. Adjustable optical properties and stoichiometry of TiN thin films were examined in the 1990s [6]. The optical characterization of TiN thin films was extensively performed later with the increasing interest in the field of plasmonics [7][8][9][10]. Improved properties with epitaxial TiN thin films have recently been demonstrated with a hyperbolic metamaterial and a plasmonic waveguide [11,12]. As a refractory plasmonic material, TiN holds the potential to solve critical issues associated with the softness and low melting points of plasmonic metals such as gold and silver [13,14]. In contrast to thin films, TiN nanoparticles have not been extensively studied until recently. Localized surface plasmons (LSPs) in TiN nanoparticles were first theoretically analyzed by Quinten [15], while their first experimental demonstration was performed by Reinholdt et al. [16] In their work, cubic nanoparticles smaller than 10 nm with a broad size dispersion were fabricated through laser ablation, and plasmon resonance peaks centered around 730 nm wavelength were reported. Reinholdt et al. proposed the use of TiN nanoparticles as inorganic, stable color pigments. We have previously shown that TiN nanoparticles provide field enhancement comparable to that achievable with Au, with a broader peak spectrally positioned in the biological transparency window [17]. In a more recent study, we experimentally analyzed the absorption efficiencies of lithographically fabricated TiN and Au nanoparticles an...

No abstract

No abstract

Rhenium nanocrystalline particles (Re NPs), of 2 nm size, were prepared from NH4ReO4 under mild conditions in neat alcohol. The unsupported Re NPs convert secondary and benzylic alcohols to ketones and aldehydes, respectively, through catalytic acceptorless dehydrogenation (AD). The oxidant- and acceptor-free neat dehydrogenation of alcohols to obtain dihydrogen gas is a green and atom-economical process for making carbonyl compounds. Secondary aliphatic alcohols give quantitative conversion and yield. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Re K-edge X-ray absorption near-edge structure (XANES), and X-ray absorption fine structure (EXAFS) data confirmed the characterization of the Re NPs as metallic rhenium with surface oxidation to rhenium(IV) oxide (ReO2). Isotope labeling experiments revealed a novel γ-CH activation mechanism for AD of alcohols.

No abstract