Multi walled carbon nanotubes (MWCNTs) and carbonized resorcinol-formaldehyde (RF) resin were used to create a conducting aerogel with a high electrical conductivity and Seebeck coefficient but a low thermal conductivity. The addition of the MWCNTs caused the figure of merit (ZT) for the aerogel to increase by two orders of magnitude. The researchers determined that it was possibly to control the electrical conductivity, thermal conductivity, and Seebeck coefficient independently of ...
A variety of tannin-formaldehyde aerogels were produced in order to examine the effects of pH and dilution during their manufacture. The authors produced a phase diagram that could describe them. Extensive physical property characterization was performed on the sample aerogels, including porosity, thermal conductivity, volume shrinkage, BET surface area and microscopic texture. Conditions under which the highest surface area and pore volumes were produced were identified. The TPS instrument was ...
Ultralow density silica aerogels were formulated by sol-gel process using tetramethyl orthosilicate as the precursor. A supercritical drying step was performed using acetonitrile solvent extraction. These aerogels were found to have a high specific surface area (~812m2/g) and they were found to be excellent thermal insulators with thermal conductivities ranging from 0.024 to 0.043 W/m K at temperatures up to 400oC....
This paper proposes conducting carbon aerogels, composed of graphene and multi-walled carbon nanotubes, as an option for a thermoelectric material. The researchers found that this combination of materials increased the electrical conductivity and the Seebeck coefficient due to bridging effects, and decreased the thermal conductivity through high porosity and a uniquely structured 3-D skeleton. Atomic force microscopy and X-ray diffraction were used to quantify the physical structure of the aerogels. ...
This article investigates how the thermal conductivity of a resorcinol-formaldehyde aerogels varies with increasing resorcinol (R) to water (W) ratios. The thermal conductivity was measured using a transient plane source (TPS) method. As the R:W increases so does the thermal conductivity, this is because there is more conductive solids present to transfer more energy....