19 research outputs found
Flux dependent MeV self-ion- induced effects on Au nanostructures: Dramatic mass transport and nano-silicide formation
We report a direct observation of dramatic mass transport due to 1.5 MeV Au2+
ion impact on isolated Au nanostructures of an average size 7.6 nm and a height
6.9 nm that are deposited on Si (111) substrate under high flux (3.2x10^10 to
6.3x10^12 ions cm-2 s-1) conditions. The mass transport from nanostructures
found to extend up to a distance of about 60 nm into the substrate, much beyond
their size. This forward mass transport is compared with the recoil
implantation profiles using SRIM simulation. The observed anomalies with theory
and simulations are discussed. At a given energy, the incident flux plays a
major role in mass transport and its re-distribution. The mass transport is
explained on the basis of thermal effects and creation of rapid diffusion paths
at nano-scale regime during the course of ion irradiation. The unusual mass
transport is found to be associated with the formation of gold silicide
nanoalloys at sub-surfaces. The complexity of the ion-nanostructure interaction
process has been discussed with a direct observation of melting (in the form of
spherical fragments on the surface) phenomena. The transmission electron
microscopy, scanning transmission electron microscopy and Rutherford
backscattering spectroscopy methods have been used.Comment: 16 pages, 6 Figure
Proton and Ammonia Intercalation into Layered Iron Chalcogenides
Structurally related to the iron-based superconductors, two new intercalated iron chalcogenides (H0.5NH3)Fe2Ch2 where Ch = S, Se have been prepared. By topochemical conversion, the protons were exchanged by lithium to form (Li0.5NH3)Fe2Ch2. Hydrogen bonding plays a significant role in the guest-host interactions of these intercalated phases
Melting point of dried gold nanoparticles prepared with ultrasonic spray pyrolysis and lyophilisation
A coupled process of ultrasonic spray pyrolysis and lyophilisation was used for the synthesis of dried gold nanoparticles. Two methods were applied for determining their melting temperature: uniaxial microcompression and differential scanning calorimetry (DSC) analysis. Uniaxial microcompression resulted in sintering of the dried gold nanoparticles at room temperature with an activation energy of 26–32.5 J/g, which made it impossible to evaluate their melting point. Using DSC, the melting point of the dried gold nanoparticles was measured to be around 1064.3°C, which is close to pure gold. The reason for the absence of a melting point depression in dried gold nanoparticles was their exothermic sintering between 712 and 908.1°C