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The epoxy molding compound (EMC) with thermal conductive pathways was developed by structure designing. Three kinds of EMCs with different thermal conductivities were used in this investigation, specifically epoxy filled with Si 3 N 4 , filled with hybrid Si 3 N 4 /SiO 2 , and filled with SiO 2 . Improved thermal conductivity was achieved by constructing thermal conductive pathways using high thermal conductivity EMC (Si 3 N 4 ) in low thermal conductivity EMC (SiO 2 ). The morphology and microstructure of the top of EMC indicate that continuous network is formed by the filler which anticipates heat conductivity. The highest thermal conductivity of the EMC was 2.5 W/m K, reached when the volume fraction of EMC (Si 3 N 4 ) is 80% (to compare with hybrid Si 3 N 4 /SiO 2 filled-EMC, the content of total fillers in the EMC was kept at 60 vol %). For a given volume fraction of EMC (Si 3 N 4 ) in the EMC system, thermal conductivity values increase according to the order EMC (Si 3 N 4 ) particles filled-EMC, hybrid Si 3 N 4 /SiO 2 filled-EMC, and EMC(SiO 2 ) particles filled-EMC. The coefficient of thermal expansion (CTE) decreases with increasing Si 3 N 4 content in the whole filler. The values of CTE ranged between 23 Â 10 À6 and 30 Â 10 À6 K À1. The investigated EMC samples have a flexural strength of about 36-39 MPa. The dielectric constant increases with Si 3 N 4 content but generally remains at a low level (<6, at 1 MHz). The average electrical volume resistivity of the EMC samples are higher than 1.4 Â 10 10 X m, the average electrical surface resistivity of the EMC samples are higher than 6.7 Â 10 14 X.

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A finite element method was developed to predict the effective thermal conductivity of particle filled epoxy composites. Three-dimensional models, which considered the effect of filler geometry, filler aspect ratio, conductivity ratio of filler to matrix, and interfacial layer were used to simulate the microstructure of epoxy composites for various filler volume fractions up to 30%. The calculated thermal conductivities were compared with results from existing theoretical models and experiments. Numerical estimation of ellipsoids-in-cube model accurately predicted thermal conductivity of epoxy composites with alumina filler particles. The number of length division during mesh process and particle numbers used in the finite element analysis affect the accuracy of calculated results. At a given value of filler content, the numerical results indicated a ratio of conductivity of filler to matrix for achieving the maximum thermal conductivity.

Yttria-stabilized zirconia (YSZ) based potentiometric gas sensors have been widely utilized for detecting NO x (NO and NO 2 ). Nevertheless, it is still remains challenging issue for YSZ-based sensors to sense total NO x due to the opposite response signals to NO and NO 2 . Herein, we report an efficient strategy to sense total NO x at high temperature (above 300 °C) by designing a dual functional sensing electrode (SE); namely, the SE will simultaneously convert NO (in NO x mixture) to NO 2 and electrocatalyze all of the obtained NO 2 to generate the response signal of total NO x . In comparison with those previously reported total NO x sensors, the proposed total NO x sensor will be featured with a simplified sensor configuration and desirable long-term stability. To confirm the practicability of the proposed strategy, the NO conversion rate of several metal oxides and their composites have been measured and it turns out that the Co 3 O 4 /NiO shows relatively high NO conversion rate. Further study indicates a YSZ-based sensor consisting of (Co 3 O 4 + 20 wt % NiO)-SE and Mn-based RE demonstrates satisfactory performance in detecting total NO x . For instance, analogous response magnitude to NO and NO 2 as well as the mixture of NO/NO 2 (within 35 ppm) is witnessed for the sensor; particularly, the sensor gives acceptable stability and response/recovery rate at the operating temperature of 500 °C within the examined period. In summary, the use of dual functional SE (e.g., Co 3 O 4 /NiO composite SE) indeed addressed those issues of concern in monitoring the level of total NO x and has provided a promising alternative way for designing future high-performance total NO x sensor.