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Novel magnesium matrix composites reinforced with carbon nanotubes have been processed by powder metallurgy. Blends of metal powders and multi-wall carbon nanotubes were compacted by uniaxial hot pressing followed by hot isostatic pressing. A uniform dispersion of nanotubes in the metal matrix was obtained. A coating method of nanotubes is described, which is promising to improve the matrixreinforcement bonding strength. R54 E. Carreño-Morelli et al.: Carbon nanotube/magnesium composites

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A device has been designed and built for unidirectional infiltration of ceramic preforms with a molten metal. It allows production of Al or Mg alloys reinforced with short or continuous ceramic fibres. The apparatus has been tested for different alloys and preforms by varying the process parameters (infiltration pressure, fibre content, melt superheat, preform preheat and solidification speed). As an example, full infiltration of Al 2 O 3-SAFFIL chopped preforms with an Al-4wt.%Cu-1wt.%Mg-0.5wt.%Ag alloy has been achieved under controlled conditions by using a gas pressure between 1 and 3 MPa. The resulting metal matrix composite has been characterised by microscopical observations and mechanical tests. Measurements of Young's modulus, density, microhardness and mechanical loss show that the optimal process conditions for Al-4wt.%Cu-1wt.%Mg-0.5wt.%Ag-SAFFIL composites are a temperature of 750°C for both preform and melt and the maximum infiltration pressure of 3 MPa. Preliminary tests have shown that the gas pressure infiltration apparatus is also suitable to produce continuous fibre reinforced and hybrid metal matrix composites.

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Transversely varying thickness modes in trapped energy resonators with shallow and beveled contours Development and performance of a semiautomated 200 MHz surface acoustic wave resonator arraybased sensor test apparatus Rev.Since surface transverse wave resonators are becoming increasingly used in high-frequency electrical component applications, there is a pressing need for reliable simulation tools in this field. We develop analytical techniques for prediction of the resonant peaks of practical devices and apply them to the results of experiments in this laboratory and in others. The devices investigated are three-grating structures composed of three arrays of metal strips or grooves on quartz substrates, which support a shear horizontal surface wave polarization. The outer gratings act as mirrors for the cavity resonance. The influence of the main design parameters on the resonator response is studied.

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