The increasing awareness of sustainability motivates the development of building materials from renewable resources. The requirements of wood-based products with improved durability, for example, an enhanced liquid repellence, is still a challenge. The aim of this thesis is to develop and study concepts to functionalize wood surfaces to obtain superhydrophobicity or superamphiphobicity, i.e. extreme liquid repellence of both water and oils. Birch and acetylated birch veneer samples were surface-modified by hydrophobized silicone nanofilaments. Specifically, birch samples surface-modified by fluorinated silicone nanofilaments (F-SMB) showed superamphiphobicity, which repelled water, ethylene glycol and hexadecane with static contact angles greater than 150° and roll-off angles lower than 10°. Birch and acetylated birch samples surface-modified by non-fluorinated silicone nanofilaments (SMB and SMAB) showed superhydrophobicity with static contact angles greater than 160° towards water, even for samples prepared using the shortest silicone nanofilaments reaction time of 1 h. In liquid uptake measurements submerging the F-SMB in water, ethylene glycol and hexadecane, a superamphiphobic plastron effect was observed which indicates that the wood surface was in Cassie-Baxter state. The plastron reduced the liquid uptake rate and extent depending on the interactions (diffusion and solubility) between the liquid and the silicone nanofilaments. The F-SMB showed good self-cleaning properties towards water and hexadecane. In multicycle Wilhelmy plate measurements, the SMB showed a lower water uptake than that of the acetylated samples, while the SMAB showed the lowest water uptake, i.e. a pronounced increased water resistance, due to a combined effect of acetylation and surface modification. In addition, the SMB exhibited more color change than the SMAB, which was caused by the release of hydrochloric acid during the surface modification process. / Den ökande medvetenheten kring hållbarsamhällsutvecklingmotiverarutveckling avbyggmaterial från förnybara resurser. Kraven på träbaserade produkter med förbättrad beständighet, exempelvisennödvändig vätskeavvisandeförmåga, är fortfarande en utmaning.Syftet med dennaavhandling äratt utveckla och studera koncept för attfunktionalisera träytorför att uppnåsuperhydrofobicitet ochsuperamfifobicitet, dvs en extrem vätskerepellerande egenskap för både vatten och oljor.Björk-och acetyleradebjörkfanérproverytmodifierades med hydrofobiserad silikon-nanofilament. Specifikt visade björk ytmodifierademedfluorerade silikon-nanofilament (F-SMB) superamfifobicitet, som repelleradevatten, etylenglykol och hexadekan med kontaktvinklar större än 150° och avrullningsvinklar lägre än 10°. Björk-och acetyleradebjörkproverytmodifierademedicke-fluorerade silikon-nanofilament (SMB och SMAB) visade superhydrofobicitet med kontaktvinklar större än 160° förvatten, även förprover framställda medkortast reaktionstid på 1 timme.Vid vätskeupptagningsmätningargenom att sänka F-SMB i vatten, etylenglykol och hexadekanobserverades en plastroneffekt som indikerade att träytan var i Cassie-Baxter-tillstånd. Plastronen minskade F-SMB vätskeupptagningshastighet och -nivåberoende på växelverkan(diffusion och löslighet) mellan vätskan och silikon-nanofilament. F-SMB uppvisadegoda självrengörande egenskaper förvatten och hexadekan.Vidmulticykel Wilhelmy-mätningarvisade SMB ett lägre vattenupptag än det acetylerade träet, medan SMAB visade denlägsta vattenupptagningen,det vill säga en mycketmärkbar ökad vattenavvisning, tack vareav en kombinerad effekt av acetylering och ytmodifiering. Dessutom uppvisade SMB en störrefärgförändring än SMAB, orsakad av frisättningen av saltsyra under ytmodifieringsprocessen. / <p>QC 20201113</p>

In this thesis I investigate characteristics of turbulent flow in a channel where one of the walls has riblets, superhydrophobic microribs, or a hybrid surface with traditional riblets built on a superhydrophobic microrib surface. PIV measurements are used to find the velocity profile, the turbulent statistics, and shear stress profile in the rectangular channel with one wall having a structured test surface. Both riblets and superhydrophobic surfaces can each provide a reduction in the wall shear stress in a turbulent channel flow. Characterizing the features of the flow using particle image velocimetry (PIV) is the focus of this research. Superhydrophobicity results from the combination of a hydrophobic coating applied to a surface with microrib structures, resulting in a very low surface energy, such that the fluid does not penetrate in between the structures. The micro-rib structures are aligned in the streamwise flow direction. The riblets are larger than the micro-rib structure by an order of magnitude and protrude into the flow. All the test surfaces were produced on silicon wafers using photolithographic techniques. Pressure in the channel is maintained below the Laplace pressure for all testing, creating sustainable air pockets between the microribs. Velocity profiles, turbulent statistics, shear stress profiles, and friction factors are presented. Measurements were acquired for Reynolds numbers ranging from 4.5x10^3 to 2.0x10^4. Modest drag reductions were observed for the riblet surfaces. Substantial drag increase occurred over the superhydrophobic surfaces. The hybrid surfaces showed the greatest drag reduction. Turbulence production was strongly reduced during riblet and hybrid tests.