Seven different types of nanocrystals were used as additives in aluminosilicate bricks to determine if this is a valid method of decreasing the thermal diffusivity of the bricks for use as plant coating in the iron and steel industries. Each type of nanocrystal was added in concentration percentages of 0.5, 1, and 2 wt. % to determine the effect of concentration on thermal transport and physical properties. It was found that all of the samples at 2 wt. % showed improved mechanical compression resistance. Bricks containing nano-aluminium hydroxide at 2 wt. % filler concentration were found to have the lowest thermal diffusivity of all the samples at 0.585 ± 0. 003 mm2/s, indicating that of the samples tested, these bricks would be the most thermally insulating. Bricks containing nano-calcium carbonate at 2 wt. % filler concentration were found to have the greatest resistance to mechanical compression breaking where a pressure of 103.0 ± 0.1 MPa was reached.
Using the Transient Plane Source, TPS technique, the authors investigated the thermal properties of a series of yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBCs). The YSZ coatings had varying amounts of impurities (Zr, Y, Si, Al oxides) and the amount of impurity affected the post-spray properties of the coating. TBCs are exposed to high temperatures during their regular operation, which can lead to the degeneration of the coating if the impurity content is high enough. The thermal conductivity of the sprays were measured before exposure to heat and then after exposure to high temperatures ( > 1000°C). After exposure to heat, the thermal conductivity of all the coatings increased by roughly 50%, which is undesirable because TBCs protect components of a machine that aren’t supposed to be exposed to heat. A higher impurity content led to a higher thermal conductivity value after exposure to heat.
Thermal barrier coatings (TBC) are plasma sprayed onto gas turbine parts in order to improve combustion efficiency and component life time. Two TBC are looked at in this report: yttria partially stabilized zirconia (YPSZ) and dysprosia partially stabilized zirconia (DyPSZ). Both the TPS and laser flash techniques were used to measure the thermal conductivity of the coatings and the results were compared. In addition the effect of barrier microstructure on thermal conductivity was investigated.
Yttria-stabilized zirconia (YSZ) powders containing varying amounts of SiO2 and Al2O3 impurities were plasma sprayed onto metallic substrates and subsequently investigated. The authors were interested in how the impurities affected sintering rates, thermal conductivity, linear contraction, and pore size and architecture among other things. The YSZ coatings were heat treated at 1400°C for 10 hours and then analyzed for the properties mentioned above. A machine was used to measure the thermal conductivity of the coatings.
In this paper, a thermally conductive insulated inorganic nanolayer of AlO(OH) was coated onto the surface of multi-walled carbon nanotubes (MWCNTs) to create a novel thermally conductive material. The coating of MWCNTs with this inorganic layer can effectively avoid the formation of electrically conductive networks in the Pi matrix and provides excellent thermal (conductivity) properties.
