Plasma assisted deposition of Au/SiO2 multi-layers as surface plasmon resonance-based red colored coatings

In this work, the expanding thermal plasma chemical vapor deposition in combination with radio frequency magnetron sputtering is used to deposit dielectric/metal multi-layers with controlled size and density of nanoparticles. The multi-layer structure serves the purpose of increasing the nanoparticle number density, without changing the metal particle size, shape and the interparticle distance. The possibility of independently tuning and, therefore, controlling the nanoparticle size and number density allows developing surface plasmon resonance-based deep-colored coatings. The influence of the number of layers, metal surface area coverage, and thickness of the dielectric layer on the multi-layer nanostructure and on the developed color is presented here in detail. The nanoparticle size and distribution have been measured by transmission electron microscopy. Rutherford back-scattering and infra-red transmission spectroscopy have been used to determine the metal surface coverage and the film chemistry, respectively. Optical properties of the nano-composite layers have been investigated by UV-VIS spectroscopy and exhibit an increase in amplitude of the plasmon absorption spectra at a fixed plasmon resonance frequency with an increase in the number of layers

In-situ STEM imaging of growth and phase change of individual CuAlX precipitates in Al alloy

Age-hardening in Al alloys has been used for over a century to improve its mechanical properties. However, the lack of direct observation limits our understanding of the dynamic nature of the evolution of nanoprecipitates during age-hardening. Using in-situ (scanning) transmission electron microscopy (S/TEM) while heating an Al-Cu alloy, we were able to follow the growth of individual nanoprecipitates at atomic scale. The heat treatments carried out at 140, 160, 180 and 200 °C reveal a temperature dependence on the kinetics of precipitation and three kinds of interactions of nano-precipitates. These are precipitate-matrix, precipitate-dislocation, and precipitate-precipitate interactions. The diffusion of Cu and Al during these interactions, results in diffusion-controlled individual precipitate growth, an accelerated growth when interactions with dislocations occur and a size dependent precipitate-precipitate interaction: growth and shrinkage. Precipitates can grow and shrink at opposite ends at the same time resulting in an effective displacement. Furthermore, the evolution of the crystal structure within an individual nanoprecipiate, specifically the mechanism of formation of the strengthening phase, θ′, during heat-treatment is elucidated by following the same precipitate through its intermediate stages for the first time using in-situ S/TEM studies

Effects of Cu on the microstructural and mechanical properties of sputter deposited Ni-Ti thin films

The microstructure of sputter deposited Ti-rich Ni-Ti thin films doped with Cu in the range 0–20.4 at.% and annealed for 1 h at 500 and 600 °C has been investigated and correlated with the mechanical properties of the films measured by depth-sensing nanoindentation. X-ray diffraction analysis showed the microstructural evolution of Ni-Ti thin films when doped with Cu and annealed at different temperatures. Heat treatments promoted the nucleation and growth of Ti2Ni precipitates in Ti-rich Ni-Ti thin films, which affected the stability of austenitic and martensitic phases at ambient temperature. Doping with Cu caused the formation of Ti(Ni, Cu)2 plate precipitates, which became more finely and densely dispersed in the grains with increasing Cu content. TEM analysis showed a columnar grain morphology extended through the whole films thickness, while with increasing Cu content a noticeable lateral grain refinement was induced by segregation of a (Ni, Cu)-rich phase to grain boundaries. The nano-hardness increased almost linearly with increasing Cu content owing to this grain refinement, though differences between samples annealed at different temperatures were found which could be related to the evolution of Ti(Ni, Cu)2 plate precipitates with annealing temperature and Cu content. The Young's modulus exhibited a similar dependence on Cu content as nano-hardness, though no significant differences were observed with increasing annealing temperatures

De struktuur van korrelgrenzen in geordende legeringen

Mechanical Maritime and Materials Engineerin

TEM DETERMINATION OF INCOHERENT TWIN-BOUNDARY STRUCTURE IN L12 ORDERED ALLOYS

The structure of incoherent Σ=3 twin boundaries in the L12 ordered alloy Cu3Au is investigated employing TEM. The boundary planes are found to vary about ten degrees from a {112} plane. Employing the TEM method of α-fringes common diffraction vectors are used for determining the rigid-body translation between the two crystals at the boundary. No dilatation has been found at a (754) incoherent twin boundary within experimental error. Four grain boundary areas having different translations that preserve the density in the boundary are demonstrated, separated from each other by an antiphase boundary on one side of the boundary plane

THE INTERACTION OF DISLOCATIONS AND A COHERENT TWIN BOUNDARY IN ORDERED Cu3AU AS STUDIED BY IN-SITU DEFORMATION IN A TEM

In order to investigate the microstructural behaviour of grain boundaries in L12-ordered Cu3Au during plastic deformation, in-situ deformation experiments were performed in a transmission electron microscope. The dislocation structure at a coherent twin boundary (CTB) before and after straining the specimen using a single-tilt straining holder is analysed in a double-tilt holder. During the in-situ deformation specific slip systems were active in both crystals from which dislocation transmission across the CTB was expected. However, the majority of the moving superdislocations are absorbed into the boundary, and change the boundary structure locally from a symmetrical structure into an asymmetrical one and vice versa. The implication is that grain-boundary fracture might occur if larger strains are applied to the specimen for which experimental evidence is given

Selective photoetching and transmission electron microscopy studies of defects in heteroepitaxial GaN

Contains fulltext : 112559.pdf (publisher's version ) (Open Access

Structure and morphology of epitaxial PbZrO3 films grown by metalorganic chemical vapor deposition

Contains fulltext : 112549.pdf (publisher's version ) (Open Access

In situ TEM observations on the structural evolution of a nanocrystalline W-Ti alloy at elevated temperatures

The thermal stability and nanoscale structural evolution at elevated temperatures of a sputter deposited W-Ti alloy thin film were studied by a combination of ex situ and in situ techniques. XRD, FIB, SEM-EDX and STEM-EDX were used to characterise the film annealed ex situ in vacuum at 1373 K for 48 h. In situ TEM heating experiments were conducted at various temperatures up to 923 K to capture transitional phenomena occurring in the alloy upon heating and cooling. At a microscopic level, the alloy annealed at 1373 K for 48 h transformed from a single-phase β-(WTi) solid solution into a two-phase alloy consisting of Ti-rich grains in equilibrium with Ti-depleted β-(WTi) solid solution grains. In situ TEM observations revealed initial Ti segregations along columnar grain boundaries at T ∼ 423–573 K, followed by Ti-rich clusters formation in the grains interior at T ∼ 573–773 K. The microstructure observed at 923 K remained stable upon cooling to room temperature and consisted of Ti-rich segregations along the columnar grain boundaries and of alternate Ti-rich and Ti-depleted nanoscale domains in the grains interior, which formed a stable dual-phase nanocrystalline structure.</p