Mariusz Andrzejczuk

Microstructure of Haynes ® 282 ® Superalloy after Vacuum Induction Melting and Investment Casting of Thin-Walled Components

The aim of this work was to characterize the microstructure of the as-cast Haynes® 282® alloy. Observations and analyses were carried out using techniques such as X-ray diffraction (XRD), light microscopy (LM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray spectroscopy (EDS), wave length dispersive X-ray spectroscopy (WDS), auger electron spectroscopy (AES) and electron energy-loss spectrometry (EELS). The phases identified in the as-cast alloy include: γ (gamma matrix), γʹ (matrix strengthening phase), (TiMoCr)C (primary carbide), TiN (primary nitride), σ (sigma-TCP phase), (TiMo)2SC (carbosulphide) and a lamellar constituent consisting of molybdenum and chromium rich secondary carbide phase together with γ phase. Within the dendrites the γʹ appears mostly in the form of spherical, nanometric precipitates (74 nm), while coarser (113 nm) cubic γʹ precipitates are present in the interdendritic areas. Volume fraction content of the γʹ precipitates in the dendrites and interdendritic areas are 9.6% and 8.5%, respectively. Primary nitrides metallic nitrides (MN), are homogeneously dispersed in the as-cast microstructure, while primary carbides metallic carbides (MC), preferentially precipitate in interdendritic areas. Such preference is also observed in the case of globular σ phase. Lamellar constituents characterized as secondary carbides/γ phases were together with (TiMo)2SC phase always observed adjacent to σ phase precipitates. Crystallographic relations were established in-between the MC, σ, secondary carbides and γ/γʹ matrix.

Biomimetic and Electrodeposited Calcium-Phosphates Coatings on Ti - Formation, Surface Characterization, Biological Response

© 2012 Pisarek et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Biomimetic and Electrodeposited Calcium-Phosphates Coatings on Ti – Formation, Surface Characterization, Biological Response

Kinetics of anatase phase formation in TiO2 films during atomic layer deposition and post-deposition annealing

Anatase phase formation in TiO2 films obtained by atomic layer deposition (ALD) is investigated. At growth temperature close to 200 °C, the anatase phase of TiO2 originates from crystalline seeds formed in an amorphous layer. These seeds, formed in the initial stages of a film growth, allow an expansion of the anatase phase in the amorphous parts and their transformation. This expansion occurs either during a further growth process or during a post-deposition annealing at relatively low temperatures (160–220 °C). The process of a lateral expansion of the anatase phase within the amorphous one was found to be thermally activated with an activation energy of 1.5 eV.

Microstructure investigations of dental composite samples prepared by focused ion beam technique

In this study, microstructures of dental composites were observed using high resolution scanning transmission electron microscopy (HR STEM). Samples for these observations were prepared by focused ion beam system. Two kinds of dental composites were investigated: (1) polymer‐ceramic composite containing nano‐sized ceramic fillers and (2) ceramic‐polymer composite based on the nano‐structured yttrium stabilized zirconia. The first composite is a popular material for dental fillings whereas the second is used for the fabrication of fixed partial dentures. The results are discussed in terms of the evaluation of fabrication process of the composites.

Massive Ag migration through metal/ceramic nano-multilayers: an interplay between temperature, stress-relaxation and oxygen-enhanced mass transport

The phase stability and microstructural evolution of nano-multilayer (NML) coatings during thermal treatments have attracted increasing attention in several technological fields, such as plasmonics, optics and joining. In the present study, the microstructural evolution of (Ag/AlN)5nm/10nm NML coating upon heating in air and under vacuum was investigated by a combinatorial approach using SEM, TEM, XPS and XRD (both in the laboratory and at the synchrotron facility). Fast heating of the Ag/AlN NML in air up to 420 °C leads to an extensive migration of nano-confined Ag to the NML surface at temperatures as low as 200 °C, much below the Ag bulk melting point. Remarkably, the migration of Ag towards the surface is negligible for a similar heat treatment under vacuum, as well as for a thick Ag layer (i.e. in the absence of a nano-confinement of Ag). Outward migration of Ag is driven by the reduction of internal interfaces (i.e. nanograin- and phase-boundaries) in combination with the relaxation of thermally induced compressive stresses. The enhanced mobility of Ag in an O-rich atmosphere is attributed to the reduction of the activation energies for vacancy formation in the confined Ag nanolayers, as induced by the chemical interaction of inwardly diffusing O with Ag along Ag/AlN interfaces. The combined effects of nano-confinement, thermal stresses and an O-rich atmosphere in the Ag/AlN NML may be exploited for novel low-temperature joining applications.

Morphology of TiO2 nanotubes revealed through electron tomography

In this work, scanning-transmission electron microscopy (STEM) tomography was successfully applied to characterize the three-dimensional structure of titanium oxide nanotubes prepared by the electrochemical anodization of the Ti substrate. The results provided detailed information about the morphology of nanotubes as well as insight into their growth. The segmentation of reconstructed images made it possible to estimate the surface area and volume of the nanotubes. The highest specific surface area was obtained for the lowest anodization voltage of 10V, and corresponds closely to that obtained using the porosimetry technique.

Electrochemical properties of lithium–titanium oxide, modified with Ag–Cu particles, as a negative electrode for lithium-ion batteries

Composites of Li4Ti5O12 with Ag–Cu particles were successfully synthesized by solid-state reaction followed by thermal decomposition of the metal substrates. The presence of metallic particles was confirmed by X-ray diffraction, scanning transmission electron microscopy and X-ray photoelectron spectroscopy. Galvanostatic charge–discharge tests showed improved specific capacity and capacity retention of Li4Ti5O12/Ag–Cu composites at a 10C current rate, while cyclic voltammetry and electrochemical impedance spectroscopy revealed changes in Li+ ion chemical diffusion coefficient values and charge-transfer resistance with increasing amount of Ag–Cu in prepared powders. The synthesis and structural, morphological and electrochemical evaluation of Li4Ti5O12/Ag–Cu powders, carried out in this work, were also presented here for the first time.

WxC-β-SiC Nanocomposite Catalysts Used in Aqueous Phase Hydrogenation of Furfural

This study investigates the effects of the addition of tungsten on the structure, phase composition, textural properties and activities of β-SiC-based catalysts in the aqueous phase hydrogenation of furfural. Carbothermal reduction of SiO2 in the presence of WO3 at 1550 °C in argon resulted in the formation of WxC-β-SiC nanocomposite powders with significant variations in particle morphology and content of WxC-tipped β-SiC nano-whiskers, as revealed by TEM and SEM-EDS. The specific surface area (SSA) of the nanocomposite strongly depended on the amount of tungsten and had a notable impact on its catalytic properties for the production of furfuryl alcohol (FA) and tetrahydrofurfuryl alcohol (THFA). Nanocomposite WxC-β-SiC catalysts with 10 wt % W in the starting mixture had the highest SSA and the smallest WxC crystallites. Some 10 wt % W nanocomposite catalysts demonstrated up to 90% yield of THFA, in particular in the reduction of furfural derived from biomass, although the reproducible performance of such catalysts has yet to be achieved.

Hybrid disordered blends formed from fullerene porous layers and zinc oxide grown by atomic layer deposition

Thermally evaporated fullerene C60 porous films served as templates for a hybrid (molecular-inorganic) disordered blend formation. C60 films were covered with zinc oxide (ZnO) grown by atomic layer deposition. ZnO filled every pore in the C60 layer which led to the formation of C60–ZnO films with separate and distinguishable phases of C60 and ZnO constituents. Morphological, structural, optical, and electrical properties of the so-obtained films were investigated. Deposition of ZnO polycrystalline films on C60 porous layers resulted in the formation of ZnO with additional structural defects, compared to the films grown on planar substrates, which affected the electrical transport in the ZnO–C60 layers.

Fabrication of corrugated Ge-doped silica fibers

We present a method of fabricating Ge-doped SiO2 fibers with corrugations around their full circumference for a desired length in the longitudinal direction. The procedure comprises three steps: hydrogenation of Ge-doped SiO2 fibers to increase photosensitivity, recording of Bragg gratings with ultraviolet light to achieve modulation of refractive index, and chemical etching. Finite-length, radially corrugated fibers may be used as couplers. Corrugated tapered fibers are used as high energy throughput probes in scanning near-field optical microscopy.