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Titanium has emerged as one of the most tissue-compatible metallic materials. The high degree of biocompatibility is intimately connected with the oxide that forms on the metal surface. In the present work a broad characterization has been made of titanium samples pretreated both by presently used clinical procedures (mechanical machining, ultrasonic cleaning and autoclaving) and by alternative preparation procedures such as electropolishing and anodic oxidation. The former samples are found to have a surface oxide of TiO2 which is 30–50 Å thick, with some trace element contamination and a relatively large carbon content (30–50 % of a monoatomic layer). The anodically oxidized samples also consist of TiO2 with an oxide thickness range of 50–2000 Å, but the morphology and crystallinity of the anodic oxides are found to depend on thickness and preparation conditions.The main methods of investigation used in the present study were ESCA, SIMS and transmission electron microscopy.

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The atomic and electronic structures of kappa‐Al2O3 are determined using theoretical first‐principles techniques based on density‐functional theory (DFT), plane waves, and pseudopotentials. The obtained structure is confirmed by analysis of powder X‐ray diffraction data. The structure is orthorhombic with oxygen ions in close‐packed ABAC stacking and aluminum ions occupying both tetrahedral (1/4) and octahedral (3/4) interstitial sites. A growth model for chemical vapor deposition of kappa‐Al2O3 is proposed based on the atomic structure. Calculated electronic structure and charge density yield a band gap of 5.3 eV and a high ionic character of the bonds. The study shows the applicability of DFT‐based methods to complex and metastable materials.

Six Ti(C,N)-TiN-WC-Co cermet materials originating from the same powder mixture but sintered to different stages of the sintering cycle have been studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDX), electron energy-loss spectroscopy (EELS), and energy-filtered transmission electron microscopy (EFTEM). At 1350 ЊC, the binder phase exists both as solid and as liquid phase. The cobalt is nanocrystalline before melting, probably due to deformation during milling. A tungsten-rich inner rim starts to form and is very inhomogeneously distributed on the Ti(C,N) cores, indicating that it is difficult to nucleate the inner rim. The outer rim mainly forms at the sintering temperature and accounts for grain growth during the holding time. There are no major variations in metal content of the carbonitride phases in the materials sintered to 1350 ЊC or higher, although the N/(CϩN) atomic ratio changes somewhat. Close to the core-rim boundary of the materials sintered at 1430 ЊC, there is often an enrichment of nitrogen in the core that is believed to be the result of nitrogen diffusion from the tungsten-rich rim to the titanium-rich core during cooling.

The microstructure of anodic oxide films grown on Ti-6A1-4V in H 2 SO 4 was investigated by SEM, TEM, STEM, EDX, and AES, as a complement to a recent surface spectroscopic investigation of the same oxides by XPS, AES, and SIMS. The anodic oxide films are heterogeneous and the texture reflects the duplex microstructure (a and /3 phases) of the underlying metal. Porous oxide regions are observed with different appearances on a-phase and mixed-phase regions. The oxide films are essentially amorphous in the investigated thickness range 60-300 nm (in contrast to as-grown anodic films on pure Ti), but crystallize to the anatase structure upon annealing. Considerable lateral variation of the V content in the oxide is observed, reflecting the corresponding variation in the underlying metal. The results are compared with a previous, similar investigation of anodic oxides on pure Ti.

Using submerged jet electropolishing, extremely thin (less than 10 nm), continuous, thermal oxide "windows" have been prepared on polycrystalline titanium (Ti). The preparation technique is described in detail. It has allowed a systematic investigation of the structure of thermal surface oxide layers on Ti in the thickness range 6-40 nm, corresponding to oxidation temperatures 100-450 degrees C. Auger electron spectroscopy was used for oxide characterization and for depth profiling to determine oxide thickness. The thinnest oxides, less than 10 nm, are amorphous, morphologically homogeneous, and with essentially no contrast in the transmission electron microscopy (TEM) pictures. As the oxide thickness is increased up to 40 nm, a texture corresponding to the grain structure of the oxidized metal becomes gradually more visible. At the same time the oxide becomes increasingly more crystalline. The results are compared with previously published corresponding results for thicker anodic oxides on Ti.

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