Thermal conductivity and thermoelectric properties in 3D macroscopic pure carbon nanotube materials

Sintered carbon nanotube (CNT) blocks and porous CNT sponges were prepared, and their thermoelectric properties were measured. The maximum dimensionless thermoelectric figure-of-merit, ZT, at room temperature of the sintered single-walled carbon nanotube (SWCNT) block is 9.34 × 10−5, which is twice higher than that of the sintered multi-walled carbon nanotube (MWCNT) block in this work and also higher than that of other sintered MWCNT blocks reported previously. In addition, the porous MWCNT sponge showed an ultra-low thermal conductivity of 0.021 W/(m K) and significantly enhanced ZT value of 5.72 × 10−4 at room temperature and 1 atm. This ZT value is higher than that of other 3D macroscopic pure CNT materials reported. The pronounced enhancement of the ZT in the porous MWCNT sponge is attributed to the ultra-low density, ultra-high porosity, and interconnected structure of the material, which lead to a fairly low thermal conductivity and better Seebeck coefficient. The finding of this work provides an understanding for exploring potential enhancement mechanisms and improving the thermoelectric properties of CNT-based thermoelectric composites.

Developing 3D-Printable Cathode Electrode for Monolithically Printed Microbial Fuel Cells (MFCs)

Microbial Fuel Cells (MFCs) employ microbial electroactive species to convert chemical energy stored in organic matter, into electricity. The properties of MFCs have made the technology attractive for bioenergy production. However, a challenge to the mass production of MFCs is the time-consuming assembly process, which could perhaps be overcome using additive manufacturing (AM) processes. AM or 3D-printing has played an increasingly important role in advancing MFC technology, by substituting essential structural components with 3D-printed parts. This was precisely the line of work in the EVOBLISS project, which investigated materials that can be extruded from the EVOBOT platform for a monolithically printed MFC. The development of such inexpensive, eco-friendly, printable electrode material is described below. The electrode in examination (PTFE_FREE_AC), is a cathode made of alginate and activated carbon, and was tested against an off-the-shelf sintered carbon (AC_BLOCK) and a widely used activated carbon electrode (PTFE_AC). The results showed that the MFCs using PTFE_FREE_AC cathodes performed better compared to the PTFE_AC or AC_BLOCK, producing maximum power levels of 286 μW, 98 μW and 85 μW, respectively. In conclusion, this experiment demonstrated the development of an air-dried, extrudable (3D-printed) electrode material successfully incorporated in an MFC system and acting as a cathode electrode.

Influence of Carburizing Time of Iron Powder Samples on the Carbon Content after Gas-Carburizing - Sintering Process

The paper presents experimental results of the influence of carburizing time of iron powder samples on the carbon content in the sample’s depth by layers, subjected to a GCS (Gas-Carburizing Sintering) method. Sintered steel elaboration by GCS method consist of enriching the Fe powder with carbon in gas medium in a single thermal cycle including the carburising operation followed by sintering, thereby achieving the sintered carbon steel. Numerical simulations were made using Abaqus/CAE software for mass diffusion analysis in order to find the appropriate diffusion coefficient value.