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Electrical lifetime of alumina-mesogenic epoxy composite sheet is improved by the addition of mica without reducing thermal conductivity. We developed an electrical tree progression simulation to optimize the composition ratio of four species of fillers (mica and three types of alumina fillers). This simulation is based on the electric field analysis with the use of a two-dimensional finite-difference method. The simulation revealed that the electrical lifetime of the composite sheet increases depending on the amount of mica filler although it is saturated at 1.3 vol. %. The calculated electrical lifetime of the sheet with mica filler is 1.5–2.0 times longer than that of the sheet without mica. This result agrees with the experimental at high applied voltage of 7 kVrms. A low mica ratio is suitable in the view of the thermal conductivity of the composite sheet because thermal conductivity of mica filler is much lower than that of alumina filler. The effective amount of mica filler was determined at 1.3 vol. % to possess high thermal conductivity and long electrical lifetime. As a result, a composite sheet with thermal conductivity of 8.7 W m−1 K−1 and the electrical lifetime 13 times longer than the sheet without mica at 4 kVrms was obtained. [ABSTRACT FROM AUTHOR]

Examines the performance of niobium aluminum alloy superconductors fabricated by Transformation-heat base up-quenching (TRUQ). Principles for TRUQ; Critical current density; Ohmic heating; Thermal conduction.

Examines the field performance of a high-resolution nuclear magnetic resonance superconducting magnet. Persistent-mode operation of the magnet; Field decay; Field homogeneity.

Examines the persistent-mode operation of a high temperature superconducting magnet cooled by a cryocooler. Thermal conductance; Decay behaviors; Temperature increase of the magnet due to persistent current switch.

The effect of organic–inorganic interfaces on the thermal conductivity of composite materials was studied by evaluating thermal conductive resistance at the organic–inorganic interfaces experimentally. Polymer layers were sandwiched between thin ceramic plates to produce multilayer stacked samples. Through the comparison between the thermal conductivities of the multilayer stacked materials and those of single component materials for both polymers and ceramics, the thermal resistance at the interface between a polymer and a ceramic plate was evaluated. The results suggest that the contribution of thermal resistance becomes significant for actual composite materials because of the increase in the number of interfaces. The results also demonstrate that organic modifications of an inorganic surface could effectively reduce interfacial thermal resistance. The control of interfaces seems to be effective for improving the thermal conduction property of composite materials. [ABSTRACT FROM AUTHOR]