Jarmo Laakso

The effects of supercritical carbon dioxide treatment on the morphology and electrochemical performance of LiFePO4 cathode materials

As cathode materials, LiFePO4 particles have been investigated after a supercritical carbon dioxide (scCO2) treatment. We first produced LiFePO4 through a hydrothermal method. Then, scCO2 was introduced to change the morphology of the particles. Three effects have been found after the scCO2 treatment; the breakup of the aggregated LiFePO4 platelets into separate plates, the purification of LiFePO4, and the formation of porous LiFePO4. Electrochemical measurements showed that the performance of LiFePO4 greatly improved after the scCO2 treatment. Finally, a theoretical model was used to explain the mechanism of the morphology change.

Bacterial growth on a superhydrophobic surface containing silver nanoparticles

The antibacterial effect of silver can be exploited in the food and beverage industry and medicinal applications to reduce biofouling of surfaces. Very small amount of silver ions are enough to destructively affect the metabolism of bacteria. Moreover, superhydrophobic properties could reduce bacterial adhesion to the surface. In this study we fabricated superhydrophobic surfaces that contained nanosized silver particles. The superhydrophobic surfaces were manufactured onto stainless steel as combination of ceramic nanotopography and hydrophobication by fluorosilane. Silver nanoparticles were precipitated onto the surface by a chemical method. The dissolution of silver from the surface was tested in an aqueous environment under pH values of 1, 3, 5, 7, 9, 11 and 13. The pH value was adjusted with nitric acid and ammonia. It was found that dissolution rate of silver increased as the pH of the solution altered from the pH of de-ionized water to lower and higher pH values but dissolution occurred also in de-ionized water. The antimicrobial potential of this coating was investigated using bacterial strains isolated from the brewery equipment surfaces. The results showed that the number of bacteria adhering onto steel surface was significantly reduced (88%) on the superhydrophobic silver containing coating.