The Antifouling and Drag-Reduction Performance of Alumina Reinforced Polydimethylsiloxane Coatings Containing Phenylmethylsilicone Oil

Fouling-release coatings reinforced with micro-alumina and nano-alumina were prepared based on polydimethylsiloxane (PDMS) containing phenylmethylsilicone oil. The surface properties, mechanical properties, leaching behavior of silicone oil, anti-fouling and drag-reduction performance of the coating were studied. The results show that the addition of alumina can significantly improve the tensile strength, elastic modulus and Shore’s hardness of the coating. The adhesion experiments of marine bacteria and Navicula Tenera show that the addition of alumina can reduce the antifouling performance of the coating, which is related to the stripping mode of fouling organisms. The fouling organisms leave the coating surface by shearing, and the energy required for shearing is proportional to the elastic modulus of the coating. At 800–1400 rpm, the addition of alumina will reduce the drag reduction performance of the coating, which is related to the drag reduction mechanism of PDMS. PDMS counteracts part of the resistance by surface deformation. The larger the elastic modulus is, the more difficult the surface deformation is. The experiment of silicone oil leaching shows that the increase of alumina addition amount and the decrease of particle size will inhibit the leaching of silicone oil.

Microstructure and electrical conductivity of 3Y-TZ/Al2O3 composites

Various amounts of Al2O3 (0.25, 0.5 and 1.0mol%) were added to tetragonal polycrystalline material (3YTZP), prepared using the hydrothermal crystallization method. The effects of the added amount as well as the sintering temperature on the microstructure and electrical properties of the 3Y-TZP/Al2O3 composites were investigated. The alumina addition was found to affect the microstructure of the 3Y-TZP samples obtained after sintering at 1400 or 1500?C only to a slight extent. The lowest values of the blocking factor, which represents the contribution of grain boundary resistivity to the total resistivity of a polycrystal, were observed for the 3Y-TZP with Al2O3 additions of 0.25 or 0.5mol% at measurement temperatures of 550 and 600 ?C. The study proves that the 3Y-TZP/Al2O3 should be taken into consideration as solid electrolyte in the intermediatetemperature solid oxide fuel cells.

Effect study of an amount of active alumina addition on the properties of alumina refractories with a complex additive of chromium oxide and zirconium dioxide

An effect of active alumina amount introduced into a batch (7.5 - 22.0 %) on the properties of alumina samples containing a complex additive of chromium oxide (10 %) and zirconium dioxide (3 %) was studied. The optimal amount of introduced active alumina (12.5 %) was established, which ensures the production of samples fired at a temperature of 1580 ºС, with the lowest open porosity (18.2 %), the highest apparent density (3.25 g/cm3) and the highest cold crushing strength (117 N/mm2), refractoriness under a load of 0.2 N/mm2 > 1700 ºС, thermal shock resistance (in the mode of 1300 ºС — water) not less than 7 thermal cycles.The results of carried out studies were used in the development of production technology of domestic refractory products based on fused corundum, α-form alumina, active alumina, containing the complex addition of chromium oxide and zirconium dioxide, by semi-dry pressing method. These refractory products characterized by high properties and intended for service at a temperature of 1850 ºС in the combustion chamber of carbon black production reactors.The use of these refractories in the lining of above mentioned high-temperature industrial units will allow to increase a duration of their operation due to an increase in the refractory durability in service, as well as to save material and energy resources associated with a relining of the reactors.