hydrophilic and oleophilic areas are distinguishable; however, macroscopically, the TiO 2 surface exhibits high amphiphilicity. ExperimentalTiO 2 thin films of 0.3 mm thickness were prepared from anatase sol (Ishihara Ltd., Japan) by a spray coating method on various solid substrates. The samples were then annealed at 773 K to eliminate organic compounds that were mixed in the sol. The contact angle measurements were performed using a commercial contact angle meter (FACE, Japan), giving the experimental error ±1. FTIR reflection absorption spectra were recorded on a Bio-rad FTS-40A spectrophotometer. The spectra were taken at 4 cm ±1 resolution with a DTGS detector.Friction force microscopy (FFM) investigations were conducted using a commercial system (Seiko Instruments Inc., SPA 300) with a 20 mm scanner. A triangular-shaped Si 3 N 4 cantilever with a torsion spring constant of 100 Nm ±1 was used for FFM imaging . The typical force between the tip and the sample was 10 ±9 N. Since the tip of the Si 3 N 4 cantilever is hydrophilic, the interaction between the tip and a hydrophilic surface shows higher friction (bright); in contrast, the friction force between the tip and a hydrophobic surface is lower (dark). The contrast between hydrophilic and hydrophobic regions could be clearly seen when the humidity was controlled to be higher than 75 %. Topographic images were also acquired using the same system.All the experiments were conducted under ambient conditions.

The use of Al2O3 polycrystalline fibers and whiskers as strengtheners in high‐temperature composites is of great interest owing to their high elastic modulus and their thermal and chemical stability. The authors describe in this communication a novel type of crystalline α‐Al2O3 fiber. These new fibers—termed ribbons by the authors—have a high specific surface area, which, together with their optical properties and low cost, makes them suitable for use as protective films in composites and as crystalline surfaces for other α‐Al2O3 fiber production methods.

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α‐alumina (α‐Al2O3, corundum) fibers exhibit high thermal and chemical stability, as well as good mechanical properties, even at high temperatures. Such characteristics make them good candidates for use in composites. Nevertheless, very few methods of producing α‐Al2O3 fibers are available. In the present work, we describe a method that uses aluminum pieces deposited on SiO2 powder, in an argon atmosphere, at temperatures in the range 1300°–1600°C. The α‐Al2O3 fibers are obtained via vapor‐liquid‐solid deposition. The novel addition of nickel and cobalt (or their oxides) allows the use of temperatures >1500°C, resulting in improved fiber production. We demonstrate that the metals do not contaminate the fibers produced in this way. Finally, we also estimate the tensile strength of the Al2O3 fibers produced through this method.

An Al-Mg-Si alloy matrix composite reinforced with 10% volume of alumina whiskers (Al 2 O 3 w) has been processed by powder metallurgy and investigated. The Al 2 O 3 w were produced as single crystal c-axis alpha alumina fibres at pre-pilot scale via Vapour Liquid Solid (VLS) deposition in a cold-wall airtight furnace with alumina linings. As far as we know, this is the first report of the utilization of whiskers of Al 2 O 3 as reinforcing elements for Al alloys. Tensile tests have been performed on the composite at room and high temperature. Results show that the AA6061 alloy reinforced with the as-produced Al 2 O 3 whiskers has remarkably high mechanical properties at room temperature. This is attributed to the high quality of the Al 2 O 3 single crystals and to the strong bonding attained between them and the 6061 alloy matrix.