The proper selection of electrical contact materials is one of the critical steps in designing a metal contact microelectromechanical system ͑MEMS͒ switch. Ideally, the contact should have both very low contact resistance and high wear resistance. Unfortunately this combination cannot be easily achieved with the contact materials currently used in macroswitches because the available contact force in microswitches is generally insufficient ͑less than 1 mN͒ to break through nonconductive surface layers. As a step in the materials selection process, three noble metals, platinum ͑Pt͒, rhodium ͑Rh͒, ruthenium ͑Ru͒, and their alloys with gold ͑Au͒ were deposited as thin films on silicon ͑Si͒ substrates. The contact resistances of these materials and their evolution with cycling were measured using a specially developed scanning probe microscope test station. These results were then compared to measurements of material hardness and resistivity. The initial contact resistances of the noble metals alloyed with Au are roughly proportional to their resistivities. Measurements of contact resistance during cycling of different metal films were made under a contact force of 200-250 N in a room air environment. It was found that the contact resistance increases with cycling for alloy films with a low concentration of gold due to the buildup of contamination on the contact. However, for alloy films with a high gold content, the contact resistance increase due to contamination is insignificant up to 10 8 cycles. These observations suggest that Rh, Ru, and Pt and their gold alloys of low gold content are prone to contamination failure as contact materials in MEMS switches.

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Carbon nanofibre (CNF) reinforced epoxy composites were characterized using nanoindentation, Atomic Force Microscopy (AFM) and Ultrasonic Force Microscopy (UFM). These tests were supplemented with ultrasonic wave propagation and three-point bend test methods. CNFs were functionalised with oxygen to improve dispersion and adhesion in the epoxy matrix. The CNF/epoxy composites showed an improvement in modulus and hardness compared to those of neat epoxy resin. The improvement was dependent on the functionalisation treatment time; however, the increase was of a different magnitude when measured by three methods: nanoindentation, wave propagation method and three-point bend (TPB) test. Thus, the indention test technique is capable of providing mechanical properties from a limited size and/or quantity of nanocomposites, which is generally the case during the initial material development stage. Further, the AFM-UFM was able to characterize the dispersion behavior of CNFs in nanocomposites, which is an important factor to improve the mechanical properties of nanocomposites. However, UFM provided much clearer information about dispersion than AFM. Finally, AFM-UFM appears to be a promising technique for observing nanocomposites at nanoscale and it has potential for the mapping of the local surface stiffness at nanoscale.

Two-step sintering route was applied for the densification SiC by promoting the role of liquid phase. The specimen contained 8 vol% of liquid phase composed of Al2O3 and Y2O3. The heating schedule consisted with initial rapid heating to 2000°C and immediate quenching to 1700 or 1750°C. By heating at elevated temperature, even distribution of the liquid phase was intended. The heat treatment at reduced temperature was to suppress the evaporative loss of the liquid and to secure the time for densification. The two-step sintering effectively suppressed loss of mass and coarsening. The resultant SiC was thus dense and was composed of fine grains exhibiting hardness of 2321 kgf/mm2.