A master thesis from Aalborg University
Modifikation af metaloverflader ved brug af en polystyren skabelon: elektrisk potentiale kontrolleret partikel aflejring
[Modification of Metal Surfaces Using a Polystyrene Template: Electric Potential Controlled Particle Deposition]
Author(s)
Term
4. term
Education
Publication year
2008
Submitted on
2008-06-03
Pages
0 pages
Abstract
It was attempted to modify Cu, Al, and Cr surfaces by the use of a polystyrene template. The aim of the modification was a rough surface with a high water contact angle (CA). It was attempted to create the polystyrene (PS) template by a combination of a thin liquid film deposition (TLFD) technique and an electric potential. The TLFD technique was applied to utilize lateral capillary forces. The electric potential was applied because it, in literature, had been observed to enhance the lateral capillary forces. It was desired to achieve a template of closed-packed (CP) particles in mono-layer with a hexagonal lattice on the metal surfaces, to obtain the smallest solid fraction possible. Scanning electron microscopy and contact angle measurements were used to analyse the samples. Furthermore, dynamic light scattering was used to analyse the particles. The characterization of the metal surfaces showed large crystals on the Al surface. Therefore, Al was not used for further experiments. Cr had a porous surface and a CA of 95 +/- 12 degrees. Cu had a planar surface and a CA of 84 +/- 7 degrees. From experiments using the TLFD technique and glass slides, a PS concentration of 24 g/L and the withdrawal rates of 3 x 10^(-2) and 1 x 10^(-1) mm/s were found to be optimal for further investigations. The metal surfaces responded differently to the TLFD technique than the glass slides. This seemed to be caused by different surface structures and wettabilities of the surfaces. With the TLFD technique multi-layers were formed on the metal surfaces. Therefore, a positively charged potential was applied on the surface. Cr was not conductive, thus, the effect of the potential could only be considered from the Cu samples. The potential resulted in particles being repelled from the surface, and a thinner film was achieved. The effect was distinct when applying a potential of 300 mV. CP particle mono-layer with a hexagonal lattice were observed in some areas of the surfaces. It was attempted to remove the particles from gold coated samples. Heating of the sample for 2 hours at 550 degrees celcius resulted in crystals of several micrometers on the surface. Furthermore, the particles seemed to have shrunk, but had not been removed. The particles had also not been removed by the wash with toluene for 43 hours, but the sonication of samples in toluene for 5 minutes seemed to be the most effective method.
Det blev forsøgt at modificere Cu, Al og Cr overflader ved brug af en polystyren (PS) skabelon. Målet var, at opnå en ru overflade med en stor kontaktvinkel (CA) med vand. PS skabelonen var forsøgt dannet ved en kombination af en thin liquid film deposition (TLFD) teknik og et elektrisk potentiale. TLFD teknikken blev anvendt for at udnytte lateral kapillære krafter. Det elektriske potentiale blev påført, fordi det i litteraturen blev observeret, at det kunne forstærke de lateral kapillære krafter. Det var ønsket at opnå en skabelon af tæt-pakkede (CP) partikler i et monolag med et hexagonalt mønster på metaloverfladerne. Scanning elektron mikroskopi og kontakt vinkel målinger blev brugt til analyse af prøverne. Karakteriseringen af metaloverfladerne viste store krystaller på Al overfladen. Derfor blev Al ikke brugt til nogen videre forsøg. Cr havde en porøs overflade og en CA på 95 +/- 12 grader. Cu havde en plan overflade og en CA på 84 +/- 7 grader. Udfra forsøg med TLFD teknikken og glasoverflader blev en PS koncentration på 24 g/L og trækhastighederne på 3 x 10^(-2) og 1 x 10^(-1) mm/s fundet til at være optimale. Metaloverfladerne reagerede anderledes på TLFD teknikken end glasoverfladerne. Dette syntes at skyldes, at overfladerne havde forskellige overflade-strukturer og spændinger. Med TLFD teknikken blev der dannet multilag på metalover- fladerne, og derfor blev der tilført et positivt potentiale til over- fladerne. Cr ledte ikke strømmen, og derfor kunne effekten af potentialet kun vurderes ud fra Cu prøverne. Potentialet resulterede i at partikler blev frastødt, og en tyndere film blev opnået. Effekten var tydeligst ved et potentiale på 300 mV. CP partikelmonolag med et hexagonalt mønster blev observeret i nogle områder på nogle af prøverne. Det blev forsøgt at fjerne partiklerne fra guldbelagte prøver. Opvarmning til 550 grader celsius i 2 timer resulterede i dannelse af krystaller på overfladen. Desuden syntes partiklerne at have skrumpet, men var ikke fjernet. Partiklerne blev heller ikke fjernet ved vask med toluen i 43 timer, men påvirkningen af ultralyd i toluen syntes at være mest effektiv.
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