Effects of Nanofilled Particle Forms and Dispersion Modes on Properties of Carbon-Based Energy Storage Composites

How to improve the thermal conductivity of phase change materials (PCMs) is always the key to thermal control technology. At present, the thermal conductivity of PCMs has two ways to improve: one is to fill the matrix with high thermal conductivity and the other is to fill nanoparticles. After combining the two methods, the choice of filled nano-SiO2, carbon nanotubes (CNTs), or graphene (GNPs) has different effects on the performance of carbon-based energy storage composites. Filling paraffin with foamed carbon increased the thermal conductivity of pure paraffin from 0.25 W/(m·K) to 8.3083 W/(m·K), an increase of 33.2 times. When the nanoparticle mass fraction is 5%, the enthalpy of GNP composites is 10 J·g-1 less than that of SiO2 composites. Under the same mass fraction, compared with the thermal conductivity enhancement effect of SiO2 composites, the thermal conductivity increase effects of CNTs and GNP composites are 6.7 and 15.8 times the thermal conductivity increase of SiO2 composites, respectively. The comparison of theoretical and experimental values shows that different nanoparticle forms and dispersion modes have different effects on the performance of carbon-based energy storage composites, among which GNPs have the greatest improvement in the thermal conductivity of carbon-based composites.

Ba substitution for enhancement of the thermoelectric properties of LaCoO3 ceramics (0⩽x⩽0.75)

In the present work, dense perovskite ceramics were successfully prepared from a series of La1–xBaxCoO3 solid solutions in the range of substitution 0 ⩽ x ⩽ 0.75 using solid state reaction and conventional sintering. Structural properties of La1–xBaxCoO3 were systematically investigated and thermoelectric properties were measured in the temperature range of 330–1000 K. The results show that the thermoelectric properties of Ba-substituted LaCoO3 depend on x. Indeed, at 330 K, electrical conductivity presents an optimum value for x = 0.25 with a value of σmax ≈ 2.2×105 S·m−1 whereas the Seebeck coefficient decreases when x and/or the temperature increases. The Ba-substituted LaCoO3 samples exhibit p-type semiconducting behaviour. The best power factor value found is 3.4×10−4 W·m−1·K−2 at 330 K for x = 0.075, which is 10% higher than the optimum value measured in La1–xSrxCoO3 for x = 0.05. The thermal diffusivity and thermal conductivity increase with increasing temperature and Ba concentration. La1–xBaxCoO3 shows a maximum figure of merit (ZT = 0.048) for x = 0.05 at 330 K, 25% higher than the best value in La1−xSrxCoO3 compounds.

Structural and chemical comparison between moderately oxygenated and edge oxygenated graphene: mechanical, electrical and thermal performance of the epoxy nanocomposites

Two different graphitic powders, namely: moderately-oxidized graphene oxide (mGO) synthesized via a chromium-based technique and a commercial edge-oxidized graphene oxide (eGO), were characterized and incorporated into an epoxy resin, suitable for wind turbine blade structural components. Raman spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis revealed low oxygen content, but divergent structural characteristics for both powders confirming the increased basal-plane functionality of mGO compared to the peripherally decorated eGO. It is also shown that the eGO, displays carbon-based impurities. The inclusion of mGO, into the epoxy resulted in an initial glass transition temperature (Tg) increase (~ 5 °C at 4.4 vol.% mGO) but thereafter Tg decreased sharply. On the contrary, the inclusion of eGO resulted only in a progressive Tg increase. Introduction of just 1 vol.% of eGO deteriorated the tensile strength (~ 15% reduction) of the epoxy, while the strength of the mGO-filled samples was retained. Inclusion of mGO results in a percolation threshold (increase from 4.6 × 10−16 to 6 × 10−9 S/cm) at 0.53 vol.%; in contrast, at the same filler content, the eGO-filled systems are characterized by drastically lower conductivity values (3.4 × 10−16 S/cm). Nevertheless, further analysis indicates similar intrinsic conductivity (~ 10−6 S/cm) for the two fillers. Finally, the maximum achieved thermal conductivity increase with mGO was 200% (at 9.13 vol.%) compared with the unfilled epoxy, while the respective increase with eGO was 150% (at 18 vol.%).

Thermal Properties of Soil Samples from Coastal Sand Landform in Ilaje Local Government Area of Ondo State, Nigeria

This study examines the thermal conductivity of some selected soil samples from coastal sandlandform inIlaje local government area of Ondo State, Nigeria. The soil samples were sieved into different particle sizes; 300 , 425 , 600 , 850 , and 1180  with appropriate mesh and moulded in form of a Lee’s disc. The thermal conductivity of the samples was determined using parallel plate method. The value of the thermal conductivity increase as the moisture content increaseand decrease with increase in particle sizes for the soil samples. The values of the thermal conductivity obtained  rangedbetween 0.3444  and1.8894 . It was noted that the conductivity of the landforms conforms to the range of conductivities of soil required for some specific crops such as maize, cowpea, pineapple, okro and root crops. The results in the research would be useful to soil/building and soil scientists as well as modern mechanized farmers in determined  appropriate land forms for agricultural and structural purposes.

Experimental Characterization of the Vertical and Lateral Heat Transfer in 3D-SIC Packages

In this paper, we present the experimental characterization of 3D packages using a dedicated stackable test chip. An advanced CMOS test chip with programmable power distribution has been designed, fabricated, stacked and packaged in molded and bare die 3D packages. The packages have been experimentally characterized in test sockets with and without cooling, and soldered to the PCB. Using uniform and localized hot spot power distribution, the thermal self-heating and thermal coupling resistance and the lateral spreading in the 3D packages have been studied. Furthermore, the measurements have been used to characterize the thermal properties of the epoxy mold compound and the die-die interface and to calibrate a thermal model for the calculation of equivalent properties of underfilled μbump arrays. This model has been applied to study the trade-off between the stand-off height reduction and the underfill thermal conductivity increase in order to reduce the inter die thermal resistance.

Study on Thermal Conductivities of Composite Adsorbents for Adsorption Refrigeration

Twenty-four Cacl2/ENG molded composite adsorbents specimen were successfully prepared by aqueous solution and squeezing method. The thermal conductivities of the samples were tested by nanoflash LFA447. The experiment results show that: the thermal conductivity perpendicular to the direction of compression is over 1.2 times higher than that parallel to the direction of compression, which prove that the thermal conductivity is anisotropic. Within a certain range, the thermal conductivity is enhanced with increasing density and decreasing mass ratio. Under mass ratio is 2:1 and density rise from 600 kg/m3 to 700 kg/m3, thermal conductivity increase fastest. Density and mass ratio has coupling effect on the thermal conductivity of Cacl2/ENG molded composite adsorbents.

Microstructure and Thermoelectric Properties of B4C+TiB2 Composite by Hot Pressed Sintering

TiB2 doped B4C composite whichTiB2 contents were 12.4% and 25.4% have been fabricated by the combination of the ball milling process and hot pressing technology. The phase analysis and microstructure of the composite materials are investigated through X-ray diffraction and scan electron microscope, respectively. In addition, thermoelectric properties of the composite materials are studied. The results show that the microcracks are easy to form in the interface between B4C and TiB2. It is also found that, the electrical and thermal conductivity increase wi2. Edit Paperth the increase of TiB2 doping, while the Seebeck coefficient decreases with the increase of TiB2 doping. The thermoelectric figure of merit of the B4C+25.4%TiB2 composite material is 50% higher than that of B4C at 573K, while the ZT of B4C+25.4% TiB2 composite material is lower than that of B4C at 873K.