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We present thermal conductivity measurements of micromachined 500 nm thick silicon-nitride ͑Si-N͒ beams suspended between two SiN islands, in the temperature range from 77 to 325 K. The measured thermal conductivity, k, of SiN at high temperatures is in good agreement with previously measured values for SiN grown by low-pressure chemical vapor deposition, but behaves much differently as temperature is lowered, showing a dependence more similar to polycrystalline materials. Preliminary structural characterization by x-ray diffraction suggests that the material is likely nano-or polycrystalline. The micromachined suspended platform structure is designed to allow highly accurate measurements of the thermal conductivity of deposited metallic, semiconducting, or insulating thin films. As a demonstration, we present measurements of a 200 nm thick sputtered molybdenum film. In the entire temperature range the measured thermal conductivity matches the prediction of the Wiedemann-Franz thermal conductivity determined from measured electrical conductivity.

We present measurements of thermopower (Seebeck coefficient) and electrical resistivity of a wide selection of polycrystalline ferromagnetic films with thicknesses ranging from 60 − 167 nm. For comparison, a copper film of similar thickness was measured with the same techniques. Both the thermal and electrical measurements, made as a function of temperature from 77 − 325 Kelvin, are made using a micro-machined thermal isolation platform consisting of a suspended, patterned silicon-nitride membrane. We observe a strong correlation between the resistivity of the films and the thermopower. Films with higher resistivity and residual resistivity ratios, indicating a higher concentration of static defects such as impurities or grain boundaries, with rare exception show thermopower of the same sign, but with absolute magnitude reduced from the thermopower of the corresponding bulk material. In addition, iron films exhibit the pronounced low-temperature peak in thermopower associated with magnon drag, with a magnitude similar to that seen in bulk iron alloys. These results provide important groundwork for ongoing studies of related thermoelectric effects in nanomagnetic systems, such as the spin Seebeck effect.

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Composite materials are widely used in aeronautical, marine and automotive industries, because of their excellent mechanical properties, low density and ease of manufacture .However, composite laminates are susceptible to delaminations, which may not be visible externally, but can substantially affect the performance of the structure. Vibration testing, in particular delamination detection, in the composite structures is an active research area. ' D Alembert principle is used to determine the theoretical natural frequency of laminated orthotropic composite plate. The present free vibration experimental study of simply supported square laminated plates is based on the comparison between natural frequencies of healthy and delaminated composite plates. The test square plates made of hand lay up 8 layers E-glass woven fibre and epoxy resin are used here. The present paper discusses the observations made on the measured natural frequencies of vibration testing from both the healthy and the delaminated square simply supported plates. The possibility of the delamination detection by vibration testing is also introduced. The effects of delamination area on the natural frequencies of the plate are presented. The delamination in composite laminates has considerable effect on the natural frequencies of the plate.