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  • 1. Acciaro, Roberta
    et al.
    Aulin, Christian
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Lindström, Tom
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Varga, Imre
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Investigation of the formation, structure and release characteristics of self-assembled composite films of cellulose nanofibrils and temperature responsive microgels2011Ingår i: Soft Matter, ISSN 1744-683X, Vol. 7, nr 4, s. 1369-1377Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The possibility of forming self-organized films using charge-stabilized dispersions of cellulose I nanofibrils and microgel beads of poly-(N-isopropylacrylamide-co-acrylic acid) copolymer is presented. The build-up behavior and the properties of the layer-by-layer (LbL)-constructed films were studied using quartz crystal microbalance with dissipation (QCM-D) and ellipsometry. The morphology of the formed films was also characterized using atomic force microscopy (AFM) imaging. The applied methods clearly demonstrated the successful LbL-assembly of the monodisperse microgels and nanofibrils. The in situ QCM-D measurements also revealed that contrary to the polyelectrolyte bound microgel particles, the nanofibrils-bound gel beads preserve their highly swollen state and do not suffer a partial collapse due to the lack of interdigitation of the oppositely charged components. To probe the accessibility of the gel beads in the formed films, the room temperature (similar to 25 degrees C) loading and release of a fluorescent dye (FITC) was also investigated. The incorporation of the cellulose nanofibrils into the multilayer resulted in an open structure that was found easily penetrable for the dye molecules even at constant room temperature, which is in sharp contrast with previously reported systems based on synthetic polyelectrolytes. The amount of dye released from the multilayer films could be fine-tuned with the number of bilayers. Finally, the thermoresponsivity of the films was also shown by triggering the burst release of the loaded dye when the film was collapsed.

  • 2. Afonso, Damien
    et al.
    Valetti, Sabrina
    Fraix, Aurore
    Bascetta, Claudia
    Petralia, Salvatore
    Conoci, Sabrina
    Feiler, Adam
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Sortino, Salvatore
    Multivalent mesoporous silica nanoparticles photo-delivering nitric oxide with carbon dots as fluorescence reporters2017Ingår i: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 9, nr 36, s. 13404-13408Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Amino-terminated mesoporous silica nanoparticles embedding carbon dots (MSCD) formed by calcination were functionalized with a nitric oxide (NO) photodonor (1) to give a robust MSCD-1 conjugate. The intense fluorescence of MSCDs was strongly quenched in MSCD-1 by effective energy transfer. Visible light excitation of MSCD-1 liberates NO, suppresses the energy transfer mechanism and leads to concomitant fluorescence restoration of the MSCD scaffold, which acts as an optical reporter for the released NO. The MSCD-1 hybrid is also able to encapsulate the highly hydrophobic photosensitizer temoporfin, preserving the fluorescence reporting function.

  • 3. Alberius, Peter Carl Anders
    et al.
    Corkery, Robert W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. KTH, Skolan för kemivetenskap (CHE), Kemi, Fysikalisk kemi.
    Spray-drying process for the manufacture of dye-loaded particles.2007Patent (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    According to a first aspect of the invention, a process is provided for the prepn. of amorphous particles comprising a homogeneous distribution of one or more dyes encapsulated by an amorphous, siliceous encapsulating agent, the process comprising: (a) providing a precursor of the encapsulating agent in liq. form; (b) providing the one or more dyes in liq. form; (c) mixing the liq. forms; (d) spraying the mixt. to form droplets comprising the one or more dyes and encapsulating agent; and (e) heating the droplets to form the particles comprising the one or more dyes encapsulated by the siliceous encapsulating agent; wherein at least one of the liq. forms provided is aq. and the or each aq. liq. form is acidic. According to a second aspect of the invention, encapsulated dyes made by the process of the first aspect of the invention are provided. [on SciFinder(R)]

  • 4.
    Alexander, Shovsky
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Polyelectrolyte complexes of bottle brush copolymers: Solution and adsorption properties2011Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The aim of this thesis work was to systematically investigate the physico-chemical properties of polyelectrolyte complexes (PECs) formed by bottle brush and linear polyelectrolytes in solution and at solid / liquid interfaces. Electrostatic self-assembly of oppositely charged macromolecules in aqueous solution is a versatile strategy to construction of functional nanostructures with easily controlled properties. Bottle brush architecture, introduced into the PEC, generates a number of distinctive properties of the complexes, related to a broad range of application, such as colloidal stability and protein repellency to name a few. To utilize these materials in a wide range of applications e.g. drug delivery, the understanding of the effects of polymer architecture and solution parameters on the properties of bottle brush PECs is of paramount importance. This thesis constitutes a systematic investigation of PECs formed by a series of cationic bottle-brush polyelectrolytes and a series of anionic linear polyelectrolytes in aqueous solution. The focus of the first part of the thesis was primarily on formation and characterization of PECs in solution, whereas the adsorption properties and adsorption kinetics of bottle-brush polyelectrolytes and their complexes was investigated in the second part of the thesis work. In particular, effects of the side-chain density of the bottlebrush polyelectrolyte, concentration, mixing ratio and molecular weigh of the linearpolyelectrolyte on formation, solution properties, stability and adsorption of PECs were addressed.

    The pronounced effect of the side-chain density of the bottle-brush polyelectrolyte on the properties of stoichiometric and nonstoichiometric PECs was demonstrated. Formation of PECs by bottle-brush copolymers with high density of side-chains results in small, watersoluble, molecular complexes having nonspherical shape, independent of concentration. Whereas formation of PEC-aggregates was revealed by bottle-brush polyelectrolytes with low side chain density, the level of aggregation in these complexes is controlled by polyelectrolyte concentration. The structure of the PECs formed with low molecular weight polyanions is consistent with the picture that several small linear polyelectrolyte molecules associate with the large bottle-brush. In contrast, when complexation occurs between polyanions of high molecular weigh and the bottle-brush polymers considerably larger PECs are formed, consistent with several bottle-brush polymers associating with one high molecular weight polyanion.

    Ladda ner fulltext (pdf)
    FULLTEXT01
  • 5.
    Alipour, Yousef
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Furnace Wall Corrosion in a Wood-fired Boiler2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Förnybara träbaserade bränslen har ökat i användning under de senaste decennierna, eftersom det är koldioxidneutrala. Emellertid är träbaserade bränslen, och i synnerhet använt trä (även känt som återvunnet trä, returträ eller träavfall), mer korrosivt än skogsbränsle, på grund av högre halter klor och tungmetaller. Dessa ökar korrosionsproblemen på eldstadsväggarna, särskilt på platser där syrehalten är låg.

    Korrosionsmekanismer undersöks vanligtvis på överhettare dvs. på områden där materialets temperatur och syrenivån är högre än vid eldstadsväggarna. Färre arbeten har utförts på eldstadskorrosion i returträ pannor, vilket är motiveringen till detta projekt. Normalt sätt så görs endast i laboratorietester där resultaten är lättare att tolka. I kraftverk är tolkningen mer komplicerad. Undersökningar av korrosionsprocesser försvåras av flera faktorer såsom panndesign, förbränningsegenskaper, rökgassammansättning, beläggningskemi och så vidare. Därför bör laboratorietester kompletteras med fältförsök. Detta doktorandprojekt kan således bidra till att fylla denna brist.

    Eldstadsväggarna är uppbyggda av flera rör som svetsas samman och de består vanligtvis av 16Mo3 stål. Rören kan vara belagda eller obelagda. Tester har därför genomförts på 16Mo3 samt på höglegerade material vilka är lämpliga som skyddande beläggningar.

    Olika typer av prov som exponerats i förbränningspannor av returträ analyserades med olika tekniker såsom SEM (svepelektronmikroskopi), EDS (energidispersiv spektroskopi), WDS (våglängd dispersiv spektroskopi), FIB (fokuserad jonstråle) LOM (ljusoptisk mikroskopi), XRD (röntgendiffraktion), och GD-OES (glimurladdning med optisk emissionsspektroskopi). Miljön samt korrosionsprocesser har modellerats termodynamiskt med mjukvaran TC (Termo-Calc®).

    Resultaten visade att 16Mo3 i eldstadsväggen angrips av väteklorid, vilket leder till bildning av järnklorid och en samtidig oxidation av järnkloriden. Järnkloridskiktet verkade nå ett stationärt tillstånd vad avser tjocklek.

    Sex veckors prov visade att A 625 (nickelkromlegering) och Kanthal APMT (järnkromaluminiumlegering) hade den lägsta korrosionshastigheten (ca 25-30% av korrosionshastigheten för 16Mo3), följt av 310S (rostfritt stål). Vi har funnit att de olika legeringarna angrips genom olika mekanismer, även om de var exponerade i pannan samtidigt på samma plats. Den dominerande korrosionsmekanismen för legeringen A 625 verkar i huvudsak bero på kalium och bly, medan bly inte attackerar Kanthal APMT. Kalium angriper aluminiumoxidskiktet på Kanthal APMT, vilket leder till bildning av icke-skyddande aluminat medan klor i sin tur attackerar basmaterialet. Resultaten visar att rostfritt stål attackeras genom klor-inducerad korrosion samt kalium och bly i kombination.

    Reducering av temperaturen kan minska korrosionshastigheten hos 16Mo3. Men denna lägre korrosionshastighet motsvarar ett lågt slutligt ångtryck hos kraftverket, vilket inte är fördelaktigt för elverkningsgraden.

    De kortare exponeringarna visade att samtidig förbränning av avloppsslam med returträ kan leda till minskad avsättning av kalium och klor i form av alkaliklorider på eldstadsväggarna. Detta ledde till korrosionsminskning av alla studerade material. Dessa alkaliklorider skulle kunna reagera med aluminiumsilikaterna från slammet och omvandlas till alkalisilikater. Detta verkar minska den alkali-inducerade korrosionen på A 625, APMT och 310S. Den aluminiumoxid som bildades på APMT och det kromoxidskikt som bildades på A 625 upprätthölls med tillsats av slam.

    Ladda ner fulltext (pdf)
    Thesis
  • 6.
    Alipour, Yousef
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    High temperature corrosion in a biomass-fired power boiler: Reducing furnace wall corrosion in a waste wood-fired power plant with advanced steam data2013Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The use of waste (or recycled) wood as a fuel in heat and power stations is becoming more widespread in Sweden (and Europe), because it is CO2 neutral with a lower cost than forest fuel. However, it is a heterogeneous fuel with a high amount of chlorine, alkali and heavy metals which causes more corrosion than fossil fuels or forest fuel.

    A part of the boiler which is subjected to a high corrosion risk is the furnace wall (or waterwall) which is formed of tubes welded together. Waterwalls are made of ferritic low-alloyed steels, due to their low price, low stress corrosion cracking risk, high heat transfer properties and low thermal expansion. However, ferritic low alloy steels corrode quickly when burning waste wood in a low NOx environment (i.e. an environment with low oxygen levels to limit the formation of NOx). Apart from pure oxidation two important forms of corrosion mechanisms are thought to occur in waste environments: chlorine corrosion and alkali corrosion.

    Although there is a great interest from plant owners to reduce the costs associated with furnace wall corrosion very little has been reported on wall corrosion in biomass boilers. Also corrosion mechanisms on furnace walls are usually investigated in laboratories, where interpretation of the results is easier. In power plants the interpretation is more complicated. Difficulties in the study of corrosion mechanisms are caused by several factors such as deposit composition, flue gas flow, boiler design, combustion characteristics and flue gas composition. Therefore, the corrosion varies from plant to plant and the laboratory experiments should be complemented with field tests. The present project may thus contribute to fill the power plant corrosion research gap.

    In this work, different kinds of samples (wall deposits, test panel tubes and corrosion probes) from Vattenfall’s Heat and Power plant in Nyköping were analysed. Coated and uncoated samples with different alloys and different times of exposure were studied by scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDX), X-ray diffraction (XRD) and light optical microscopy (LOM). The corrosive environment was also simulated by Thermo-Calc software.

    The results showed that a nickel alloy coating can dramatically reduce the corrosion rate. The corrosion rate of the low alloy steel tubes, steel 16Mo3, was linear and the oxide scale non-protective, but the corrosion rate of the nickel-based alloy was probably parabolic and the oxide much more protective. The nickel alloy and stainless steels showed good corrosion protection behavior in the boiler. This indicates that stainless steels could be a good (and less expensive) alternative to nickel-based alloys for protecting furnace walls.

    The nickel alloy coated tubes (and probe samples) were attacked by a potassium-lead combination leading to the formation of non-protective potassium lead chromate. The low alloy steel tubes corroded by chloride attack. Stainless steels were attacked by a combination of chlorides and potassium-lead.

    The Thermo-Calc modelling showed chlorine gas exists at extremely low levels (less than 0.1 ppm) at the tube surface; instead the hydrated form is thermodynamically favoured, i.e. gaseous hydrogen chloride. Consequently chlorine can attack low alloy steels by gaseous hydrogen chloride rather than chlorine gas as previously proposed. This is a smaller molecule than chlorine which could easily diffuse through a defect oxide of the type formed on the steel.

    Ladda ner fulltext (pdf)
    Licentiate thesis
    Ladda ner (pdf)
    Abstract-sammanfattning
  • 7.
    Alipour, Yousef
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Reducing furnace wall corrosion by coating the furnace tubes in a waste wood fired boiler plant2012Konferensbidrag (Refereegranskat)
  • 8.
    Alipour, Yousef
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Davis, C.
    Szakalos, Peter
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Henderson, Pamela
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. Vattenfall Res & Dev AB, Sweden.
    Corrosion of the low alloy steel 16Mo3 in the furnace region of used-wood fired boilersManuskript (preprint) (Övrigt vetenskapligt)
  • 9.
    Alipour, Yousef
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Henderson, P.
    Vattenfall, Sweden.
    Corrosion of furnace wall materials in waste-wood fired power plant2015Ingår i: Corrosion Engineering, Science and Technology, ISSN 1478-422X, E-ISSN 1743-2782, Vol. 50, nr 5, s. 355-363Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Corrosion tests were performed with four different materials exposed at the furnace wall in a power boiler burning recycled wood, with the aim of evaluating coatings to reduce the corrosion. The nickel base Alloy 625 and the iron-chromium-aluminium alloy Kanthal APMT had the lowest corrosion rates followed by the stainless steel 310S. The low alloy steel 16Mo3, from which the walls are constructed, had the highest rate. Different corrosion mechanisms were found to occur according to the alloy type. Thermodynamic modelling showed that chlorine gas exists at extremely low levels under the prevailing conditions and the hydrated form is thermodynamically favoured.

  • 10.
    Alipour, Yousef
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Henderson, Pamela
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Initial Corrosion of Waterwalls Materials in a Waste Wood Fired Power PlantManuskript (preprint) (Övrigt vetenskapligt)
  • 11.
    Alipour, Yousef
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Henderson, Pamela
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    The effect of co-firing of sewage sludge with waste wood on furnace wall corrosion2014Ingår i: International Symposium On High-Temperature Oxidation And Corrosion Hakodate, Hokkaido Japan, 2014, 23-27 June, 2014Konferensbidrag (Refereegranskat)
  • 12.
    Alipour, Yousef
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Henderson, Pamela
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. Vattenfall Res & Dev AB, Sweden.
    Szakalos, Peter
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Effect of temperature on corrosion of furnace walls in a waste wood fired boiler2015Ingår i: Materials at High Temperature, ISSN 0960-3409, E-ISSN 1878-6413, Vol. 32, nr 1-2, s. 188-196Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    One way of reducing the furnace wall corrosion is to lower the temperature of the wall by reducing the boiler pressure. To test this, four coupons of 16Mo3 were exposed in the furnace wall of a waste wood fired boiler for 1075 h. The temperatures of the samples were individually controlled in the range 280-410 degrees C. The corrosion rates and corrosion mechanism were investigated. The deposits were analysed by XRD and SEM/EDS. The corrosion fronts were studied by focused ion beam milling (FIB)/EDS. The environment was modelled by Thermo-Calc. The amount of potassium and chlorine in the deposit decreased with decreasing temperature. The FIB sections showed a distinctive iron chloride layer at the corrosion front, with an outer layer of iron oxide. The corrosion rate decreased with decreasing metal temperature, but the boiler pressure needs to be reduced to a low level to achieve this, which is not beneficial for the electrical efficiency and therefore not a viable way of reducing corrosion.

  • 13.
    Alipour, Yousef
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Henderson, Pamela
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Szakalos, Peter
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    The effect of a nickel alloy coating on the corrosion of furnace wall tubes in a waste wood fired power plant2014Ingår i: Materials and corrosion - Werkstoffe und Korrosion, ISSN 0947-5117, E-ISSN 1521-4176, Vol. 65, nr 2, s. 217-225Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The use of waste wood as a fuel in power plants is becoming more widespread in Europe, because it is a renewable energy source with a lower cost than forest fuel. However it is more corrosive than coal and corrosion problems have arisen in the furnace wall area of a low NOx heat and power boiler. The furnace walls are made of a low alloy steel which has been coated in some parts with a nickel alloy to reduce corrosion. In this work, furnace tubes coated with a nickel alloy were compared to the uncoated tubes of the low alloy steel 16Mo3 after 3 years of exposure in the boiler. The nickel alloy coating and uncoated material were also compared with more controlled testing on a corrosion probe lasting for about 6 weeks. The corrosion rates were measured and the samples were chemically analysed by SEM/EDS/WDS and XRD methods. The corrosive environment was also modelled with Thermo-Calc software. The corrosion rates measured from the probe and tube samples of 16Mo3 agreed well with each other, implying linear corrosion rates. The results also showed that the use of nickel alloy coatings changes the corrosion mechanism, which leads to a dramatic reduction in the corrosion rate. The results are discussed in terms of the corrosion mechanisms and thermodynamic stability of the corrosion products.

  • 14.
    Alipour, Yousef
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Talus, A.
    Henderson, Pamela
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. Vattenfall AB, Stockholm 169 92, Sweden.
    Norling, R.
    The effect of co-firing sewage sludge with used wood on the corrosion of an FeCrAl alloy and a nickel-based alloy in the furnace region2015Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 138, s. 805-813Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of digested sewage sludge as a fuel additive to reduce corrosion of furnace walls has been studied. The nickel base alloy Alloy 625 and the iron-chromium-aluminium alloy Kanthal APMT™ were exposed for 14.25. h at the furnace wall in a power boiler burning 100% used (also known as waste or recycled) wood. The test was then repeated with the addition of sewage sludge to the waste wood. The samples were chemically analysed and thermodynamically modelled and the corrosion mechanisms were investigated. The results showed that the co-firing of sewage sludge with recycled wood leads to a reduction in the corrosion. Attack by a potassium-lead combination appeared to be the main corrosion mechanism in Alloy 625 during waste wood combustion, while attack by alkali chloride was found to be dominant in APMT alloy.

  • 15.
    Alipour, Yousef
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Viklund, Peter
    Henderson, Pamela
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    The analysis of furnace wall deposits in a low-NOx waste wood-fired bubbling fluidised bed boiler2012Ingår i: VGB PowerTech Journal, ISSN 1435-3199, Vol. 92, nr 12, s. 96-100Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    Increasing use is being made of biomass as fuel for electricity production as the price of natural wood continues to rise. Therefore, more use is being made of waste wood (recycled wood). However, waste wood contains more chlorine, zinc and lead, which are believed to increase corrosion rates. Corrosion problems have occurred on the furnace walls of a fluidised bed boiler firing 100 % waste wood under low-NOx conditions. The deposits have been collected and analysed in order to understand the impact of the fuel.

    Ladda ner fulltext (pdf)
    fulltext
  • 16.
    Alvarez-Asencio, Ruben
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Thormann, Esben
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Note: Determination of torsional spring constant of atomic force microscopy cantilevers: Combining normal spring constant and classical beam theory (vol 84, 096102, 2013)2014Ingår i: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 85, nr 7, artikel-id 079901Artikel i tidskrift (Refereegranskat)
  • 17.
    Alvarez-Asencio, Rubén
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Bettini, Eleonora
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Pan, Jinshan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Leygraf, Christofer
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Nanotribology and Microstructure of a CoCrMo Alloy: A TribologicalProperties Mapping StudyManuskript (preprint) (Övrigt vetenskapligt)
  • 18.
    Alvarez-Asencio, Rubén
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Pan, Jinshan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Thormann, Esben
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Tribological Properties Mapping: Local Variation in Friction Coefficient and Adhesion2013Ingår i: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 50, nr 3, s. 387-395Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Tribological properties mapping is a new technique that extracts friction coefficient and adhesion maps obtained from lateral atomic force microscope (LAFM) images. By imaging the surface systematically as a function of load, a series of images can be tiled, and pixelwise fitted to a modified Amontons' Law to obtain friction coefficient and adhesion maps. This removes the ambiguity of friction contrast in LAFM imaging which can be a function of the load used for imaging. In ambient laboratory, air and tetradecane, a sample of Vancron(A (R))40, commercial powder metallurgical tool alloy containing nitrogen, have been scanned using a standard silicon cantilever in order to obtain tribological data. The tribological properties mapping provides unique information regarding the heterogeneous alloy microstructure as well as shedding light on the tribological behavior of the alloy.

  • 19.
    Alvarez-Asencio, Rubén
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Sabibi, Majid
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Pan, Jinshan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Ejnermark, Sebastian
    Ekman, Lars
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Role of Microstructure on Pitting  Corrosion Initiation of an Experimental Tool Alloy: A Peak Force QNM Atomic Force Micrscopy StudyManuskript (preprint) (Övrigt vetenskapligt)
  • 20.
    Alvarez-Asencio, Rubén
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Thormann, Esben
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. Chemistry, Materials and Surfaces, SP Technical Research Institute of Sweden.
    Note: Determination of torsional spring constant of atomic force microscopy cantilevers: Combining normal spring constant and classical beam theory2013Ingår i: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 84, nr 9, s. 096102-096102-3Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A technique has been developed for the calculation of torsional spring constants for AFM cantilevers based on the combination of the normal spring constant and plate/beam theory. It is easy to apply and allow the determination of torsional constants for stiff cantilevers where the thermal power spectrum is difficult to obtain due to the high resonance frequency and low signal/noise ratio. The applicability is shown to be general and this simple approach can thus be used to obtain torsional constants for any beam shaped cantilever.

  • 21.
    Alvarez-Asencio, Rubén
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Wallqvist, Viveca
    Kjellin, Mikael
    Leungo, Gustavo
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Nordgren, Niklas
    Nanomechanical Properties of Human Skin Studies by AFM and a Novel Hair IndenterManuskript (preprint) (Övrigt vetenskapligt)
  • 22.
    An, Junxue
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dèdinaitè, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Winnik, Francoise M.
    Qiu, Xing-Ping
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Temperature-Dependent Adsorption and Adsorption Hysteresis of a Thermoresponsive Diblock Copolymer2014Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, nr 15, s. 4333-4341Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A nonionic-cationic diblock copolymer, poly(2-isopropyl-2-oxazoline)(60)-b-poly((3-acrylamidopropyl)- trimethylammonium chloride)(17), (PIPOZ(60)-b-PAMPTMA(17)), was utilized to electrostatically tether temperature-responsive PIPOZ chains to silica surfaces by physisorption. The effects of polymer concentration, pH, and temperature on adsorption were investigated using quartz crystal microbalance with dissipation monitoring and ellipsometry. The combination of these two techniques allows thorough characterization of the adsorbed layer in terms of surface excess, thickness, and water content. The high affinity of the cationic PAMPTMA(17) block to the negatively charged silica surface gives rise to a high affinity adsorption isotherm, leading to (nearly) irreversible adsorption with respect to dilution. An increase in solution pH lowers the affinity of PIPOZ to silica but enhances the adsorption of the cationic block due to increasing silica surface charge density, which leads to higher adsorption of the cationic diblock copolymer. Higher surface excess is also achieved at higher temperatures due to the worsening of the solvent quality of water for the PIPOZ block. Interestingly, a large hysteresis in adsorbed mass and other layer properties was observed when the temperature was cycled from 25 to 45 degrees C and then back to 25 degrees C. Possible causes for this temperature hysteresis are discussed.

  • 23.
    An, Junxue
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Nilsson, Anki
    Holgersson, Jan
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Comparison of a Brush-with-Anchor and a Train-of-Brushes Mucin on Poly(methyl methacrylate) Surfaces: Adsorption, Surface Forces, and Friction2014Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 15, nr 4, s. 1515-1525Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Interfacial properties of two types of mucins have been investigated at the aqueous solution/poly(methyl methacrylate) (PMMA) interface. One is commercially available bovine submaxillary mucin, BSM, which consists of alternating glycosylated and nonglycosylated regions. The other one is a recombinant mucin-type fusion protein, PSGL-1/mIgG(2b), consisting of a glycosylated mucin part fused to the Fc part of an immunoglobulin. PSGL-1/mIgG(2b) is mainly expressed as a (timer upon production. A quartz crystal microbalance with dissipation was used to study the adsorption of the mucins to PMMA surfaces. The mass of the adsorbed mucin layers, including the adsorbed mucin and water trapped in the layer, was found to be significantly higher for PSGL-1/mIgG(2b) than for BSM. Atomic force microscopy with colloidal probe was employed to study interactions and frictional forces between mucin-coated PMMA surfaces. Purely repulsive forces of steric origin were Observed between PSGL-1/mIgG(2b) mucin layers, whereas a small adhesion was detected between BSM layers and attributed to bridging. Both mucin layers reduced the friction force between PMMA surfaces in aqueous solution. The reduction was, however, significantly more pronounced for PSGL-1/mIgG(2b). The effective friction coefficient between PSGL-1/mIgG(2b)-coated PMMA surfaces is as low as 0.02 at low loads, increasing to 0.24 at the highest load explored, 50 nN. In contrast, a friction coefficient of around 0.7 was obtained between BSM-coated PMMA surfaces. The large differences in interfacial properties for the two mucins are discussed in relation to their structural differences.

  • 24.
    An, Junxue
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Jin, Chunsheng
    Dedinaite, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Technical Research Institute of Sweden.
    Holgersson, Jan
    Karlsson, Niclas G.
    Claesson, Per Martin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Technical Research Institute of Sweden.
    Influence of Glycosylation on Interfacial Properties of Recombinant Mucins: Adsorption, Surface Forces, and Friction2017Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 33, nr 18, s. 4386-4395Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Interfacial properties of two brush-with-anchor mucins, C-P55 and C-PSLex, have been investigated at the aqueous solution/poly(methyl methacrylate) (PMMA) interface. Both are recombinant mucin-type fusion proteins, produced by fusing the glycosylated mucin part of P-selectin glycoprotein ligand-1 (PSLG-1) to the Fc part of a mouse immunoglobulin in two different cells. They are mainly expressed as dimers upon production. Analysis of the O-glycans shows that the C-PSLex mucin has the longer and more branched side chains, but C-P55 has slightly higher sialic acid content. The adsorption of the mucins to PMMA surfaces was studied by quartz crystal microbalance with dissipation. The sensed mass, including the adsorbed mucin and water trapped in the layer, was found to be similar for these two mucin layers. Atomic force microscopy with colloidal probe was employed to study surface and friction forces between mucin-coated PMMA surfaces. Purely repulsive forces of steric origin were observed between mucin layers on compression, whereas a small adhesion was detected between both mucin layers on decompression. This was attributed to chain entanglement. The friction force between C-PSLex-coated PMMA is lower than that between C-P55-coated PMMA. at low loads, but vice versa at high loads. We discuss our results in terms of the differences in the glycosylation composition of these two mucins.

  • 25.
    An, Junxue
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Jin, Chunsheng
    Dėdinaitė, Andra
    Holgerssond, Jan
    Karlssonb, Niclas G.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Influence of Glycosylation on Interfacial Properties of Recombinant Mucins: Adsorption, Surface Forces and FrictionManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Interfacial properties of two brush-with-anchor mucins, C-P55 and C-PSLex, have been investigated at the aqueous solution/poly(methylmethacrylate) (PMMA) interface. Both are recombinant mucin-type fusion proteins, produced by fusing the glycosylated mucin part of P-selectin glycoprotein ligand-1 (PSLG-1) to the Fc part of a mouse immunoglobulin in two different cells. They are mainly expressed as dimers upon production. Analysis of the O-glycans shows that the C-PSLex mucin has the longer and more branched side chains, but C-P55 has slightly higher sialic acid content. The adsorption of the mucins to PMMA surfaces was studied by quartz crystal microbalance with dissipation. The sensed mass, including the adsorbed mucin and water trapped in the layer, was found to be similar for these two mucin layers. Atomic force microscopy with colloidal probe was employed to study surface and friction forces between mucin-coated PMMA surfaces. Purely repulsive forces of steric origin were observed between mucin layers on compression, whereas a small adhesion was detected between both mucin layers on decompression. This was attributed to chain entanglement. The friction force between C-PSLex-coated PMMA is lower than that between C-P55-coated PMMA at low loads, but vice versa at high loads. We discuss our results in terms of the differences in the glycosylation composition of these two mucins.

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  • 26.
    An, Junxue
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Liu, Xiaoyan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Technical Research Institute of Sweden.
    Korchagina, Evgeniya
    Winnik, Francoise M.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Technical Research Institute of Sweden.
    Effect of solvent quality and chain density on normal and frictional forces between electrostatically anchored thermoresponsive diblock copolymer layers2017Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 487, s. 88-96Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Equilibration in adsorbing polymer systems can be very slow, leading to different physical properties at a given condition depending on the pathway that was used to reach this state. Here we explore this phenomenon using a diblock copolymer consisting of a cationic anchor block and a thermoresponsive block of poly(2-isopropyl-2-oxazoline), PIPOZ. We find that at a given temperature different polymer chain densities at the silica surface are achieved depending on the previous temperature history. We explore how this affects surface and friction forces between such layers using the atomic force microscope colloidal probe technique. The surface forces are purely repulsive at temperatures <40 degrees C. A local force minimum at short separation develops at 40 degrees C and a strong attraction due to capillary condensation of a polymer-rich phase is observed close to the bulk phase separation temperature. The friction forces decrease in the cooling stage due to rehydration of the PIPOZ chain. A consequence of the adsorption hysteresis is that the friction forces measured at 25 degrees C are significantly lower after exposure to a temperature of 40 degrees C than prior to heating, which is due to higher polymer chain density on the surface after heating.

  • 27.
    An, Junxue
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Liu, Xiaoyan
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Linse, Per
    Dedinaite, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi. SP Technical Research Institute of Sweden, Sweden .
    Winnik, Francoise M.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Tethered Poly(2-isopropyl-2-oxazoline) Chains: Temperature Effects on Layer Structure and Interactions Probed by AFM Experiments and Modeling2015Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, nr 10, s. 3039-3048Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thermoresponsive polymer layers on silica surfaces have been obtained by utilizing electrostatically driven adsorption of a cationic-nonionic diblock copolymer. The cationic block provides strong anchoring to the surface for the nonionic block of poly(2-isopropyl-2-oxazoline), referred to as PIPOZ. The PIPOZ chain interacts favorably with water at low temperatures, but above 46 degrees C aqueous solutions of PIPOZ phase separate as water becomes a poor solvent for the polymer. We explore how a change in solvent condition affects interactions between such adsorbed layers and report temperature effects on both normal forces and friction forces. To gain further insight, we utilize self-consistent lattice mean-field theory to follow how changes in temperature affect the polymer segment density distributions and to calculate surface force curves. We find that with worsening of the solvent condition an attraction develops between the adsorbed PIPOZ layers, and this observation is in good agreement with predictions of the mean-field theory. The modeling also demonstrates that the segment density profile and the degree of chain interpenetration under a given load between two PIPOZ-coated surfaces rise significantly with increasing temperature.

  • 28.
    An, Junxue
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Zander, Thomas
    Liu, Xiaoyan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Linse, Per
    Dédinaité, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Technical Research Institute of Sweden.
    Winnik, Francoise M.
    Qiu, Xing-Ping
    Claesson, Per Martin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Technical Research Institute of Sweden.
    Tethered Poly(2-Isopropyl-2-Oxazoline) Chai: Temperature Effects of Layer Structure and Interactions Probed by AFM Experiments and ModelingManuskript (preprint) (Övrigt vetenskapligt)
  • 29.
    Anantha, Krishnan Hariramabadran
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Örnek, Cem
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Ejnermark, S.
    Medvedeva, A.
    Sjöström, J.
    Pan, Jinshan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    In situ AFM study of localized corrosion processes of tempered AISI 420 martensitic stainless steel: Effect of secondary hardening2017Ingår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 164, nr 13, s. C810-C818Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of secondary hardening of tempered AISI 420 martensitic stainless steel on the corrosion behavior in aqueous 0.01 M NaCl has been studied, in-situ, using atomic force microscopy (AFM) to monitor real-time localized corrosion processes. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy, and X-ray diffraction analyses confirmed the presence of undissolved and secondary carbides (Cr23C6, Cr7C3, Cr3C2, Cr3C, Cr2C, and CrC) as well as retained austenite, all finely dispersed in the tempered martensitic matrix. Electrochemical measurements, consisted of monitoring of the open-circuit potential vs. time and cyclic polarization in 0.01 M NaCl solution, were performed to evaluate the passivity and its breakdown, and it was seen that initiation sites for localized corrosion were predominantly peripheral sites of carbides. In-situ AFM measurements revealed that there was a sequence for localized corrosion in which the neighboring matrix next to secondary carbides dissolved first, followed by corrosive attack on regions adjacent to undissolved carbides. Tempering at 500◦C reduced the corrosion resistance and the ability to passivate in comparison to tempering at 250◦C.

  • 30.
    Anantha, Krishnan Hariramabadran
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Örnek, Cem
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Ejnermark, Sebastian
    Medvedeva, Anna
    Sjöström, Johnny
    Pan, Jinshan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Correlative Microstructure Analysis and In Situ Corrosion Study of AISI 420 Martensitic Stainless Steel for Plastic Molding Applications2017Ingår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 164, nr 4, s. C85-C93Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, the corrosion behavior of tempered AISI 420 martensitic stainless steel (MSS) was studied by in-situ atomic force microscopy (AFM) in 0.1M NaCl and correlated with the microstructure. Thermocalc simulation, dilatometry, and X-ray diffraction (XRD) were performed to investigate phase transformation which showed the formation of M3C, M7C3, and M23C6 type of carbides and also retained austenite. Optical microscopy, scanning electron microscopy (SEM), and AFM characterization revealed undissolved carbides and tempering carbides in the martensitic matrix. Volta potential mapping measured by scanning Kelvin probe force microscopy (SKPFM) indicated higher electrochemical (practical) nobility of the carbides with respect to the martensitic matrix whereas regions adjacent to carbides showed lower nobilities due to chromium depletion. Open circuit potential and cyclic potentiodynamic polarization measurements showed metastable corrosion activities associated with a weak passive behavior and a risk for localized corrosion along certain carbide boundaries. In-situ AFM measurements revealed selective dissolution of certain carbide interphases and martensitic inter-lath regions indicating higher propensity to localized corrosion.

  • 31.
    Andrén, Oliver
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Ingverud, Tobias
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Hult, Daniel
    Håkansson, Joakim
    Caous, Josefin
    Zhang, Yuning
    Anderson, Therese
    Pedersen, Emma
    Björn, Camilla
    Löwenhielm, Peter
    Malkoch, Michael
    Linear-Dendritic Polyesters as Antimicrobial HydrogelsManuskript (preprint) (Övrigt vetenskapligt)
  • 32.
    Anghel, Clara
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Hultquist, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Limbäck, Magnus
    Influence of Pt, Fe/Ni/Cr–containing intermetallics and deuterium on the oxidation of Zr-based materials2005Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 340, nr 2-3, s. 271-283Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An in situ gas phase analysis technique and the 18O-SIMS technique are used to evaluate the transport of oxygen and hydrogen in oxidation of Zr-based materials. At 400 °C, it is found that oxygen dissociation efficiency decreases in the order: Pt > Zr2Fe > Zr2Ni > ZrCr2 Zircaloy-2. Two Zr-plates partly coated with 200 Å porous Pt, with and respectively without D in the substrate, were oxidized in two stages at 400 °C. SIMS depth profiles in the Pt area show that an enhanced oxidation takes place mainly by inward oxygen transport. A minimum in the oxide thickness was found near the Pt area on both Zr plates. Two Ar-filled Zircaloy-2 tubes with ZrSn liner were exposed at 370 °C to 22 mbar water, filled in from one side. Our experimental results suggest that a proper choice of the SPP composition and size distribution can lead to reduced hydrogen uptake during oxidation of Zr-based materials in water.

  • 33. Antikhovich, I. V.
    et al.
    Kharitonov, Dima S.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. Belarusian State Technological University, Belarus.
    Chernik, A. A.
    Dobryden, Illia B.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Corrosion Resistance of Nickel Coatings Deposited from Low-Temperature Nickel-Plating Electrolytes2017Ingår i: Russian journal of applied chemistry, ISSN 1070-4272, E-ISSN 1608-3296, Vol. 90, nr 4, s. 566-573Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The corrosion resistance of nickel coatings on a copper substrate, plated from low-temperature electrolytes based on acetates, tartrates, and isobutyrates, was studied by the methods of electrochemical impedance spectroscopy (EIS) and polarization curves. The tests were performed in a 0.3% NaCl solution. The nickel coatings exhibit high chemical activity, dissolving in the NaCl solution. The electrochemical step is the limiting step of the corrosion process.

  • 34. Arvidsson, M.
    et al.
    Ringstad, L.
    Skedung, L.
    Duvefelt, Kenneth
    KTH, Skolan för industriell teknik och management (ITM).
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Feeling fine - the effect of topography and friction on perceived roughness and slipperiness2017Ingår i: Biotribology, ISSN 2352-5738, Vol. 11, s. 92-101Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    (1) Background. To design materials with specific haptic qualities, it is important to understand both the contribution of physical attributes from the surfaces of the materials and the perceptions that are involved in the haptic interaction. (2) Methods. A series of 16 wrinkled surfaces consisting of two similar materials of different elastic modulus and 8 different wrinkle wavelengths were characterized in terms of surface roughness and tactile friction coefficient. Sixteen participants scaled the perceived Roughness and Slipperiness of the surfaces using free magnitude estimation. Friction experiments were performed both by participants and by a trained experimenter with higher control. (3) Results and discussion. The trends in friction properties were similar for the group of participants performing the friction measurements in an uncontrolled way and the experiments performed under well-defined conditions, showing that the latter type of measurements represent the general friction properties well. The results point to slipperiness as the key perception dimension for textures below 100 μm and roughness above 100 μm. Furthermore, it is apparent that roughness and slipperiness perception of these types of structures are not independent. The friction is related to contact area between finger and material. Somewhat surprising was that the material with the higher elastic modulus was perceived as more slippery. A concluding finding was that the flat (high friction) reference surfaces were scaled as rough, supporting the theory that perceived roughness itself is a multidimensional construct with both surface roughness and friction components.

  • 35. Arvidsson, Martin
    et al.
    Ringstad, Lovisa
    Skedung, Lisa
    Duvefelt, Kenneth
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Rutland, Mark W
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Feeling fine – the effect of topography and friction on perceived roughness and slipperiness2016Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    To be able to design materials with specific haptic qualities, it is important to understand not only the contribution of physical attributes from the surfaces of the materials, but also the perceptions that are involved in the haptic interaction with the materials. A series of 16 wrinkled surfaces with two different materials (Young’s modulus of 1,600 and 20,000 psi, respectively) and 8 different wrinkle wavelengths (30‑120 µm, and two unwrinkled reference surfaces) were thus characterized in terms of surface roughness and finger friction coefficient. Sixteen participants scaled the perceived Roughness and Slipperiness of the surfaces using the method of free magnitude estimation. Five of the sixteen participants conducted friction measurements during their perceived slipperiness session, and an experimenter conducted friction measurements in a separate experiment with higher experimental control. The trends in friction properties were similar for the group of participants performing the friction measurements in an uncontrolled way and the experiments performed under well-defined conditions, showing that the latter type of measurements represent the general friction properties well. The results point to slipperiness as the key perception dimension for textures below 100 µm and roughness above 100 µm. In the interval between 30 and 50 µm it is hard to discriminate between the wavelengths, these surfaces also exhibit the highest slipper­iness and the lowest roughness. Furthermore, it is apparent that roughness and slipperiness perception of these types of structures are not indepen­dent; which is also supported by an increased friction between 80‑100 µm that corresponds well with both a change in slipperiness and in roughness. The increased friction in this specific wavelength region is related to an increased contact area between finger and material. Somewhat surprising was the fact that the material with the higher Young’s modulus was perceived as more slippery, especially for the smaller wavelengths, this is also the range where it was difficult to differentiate between the wave­lengths. A concluding finding was that the flat (high friction) references surfaces were scaled as rough, supporting the theory that perceived roughness itself is a multidimensional construct with both surface rough­ness and friction components.

  • 36.
    Arvidsson, Martin
    et al.
    Department of Psychology, Stockholm University.
    Skedung, Lisa
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Aikala, Maiju
    Oy Keskuslaboratorio - Centrallaboratorium Ab.
    Danerlöv, Katrin
    YKI Institute for Surface Chemistry.
    Kettle, John
    Oy Keskuslaboratorio - Centrallaboratorium Ab.
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Berglund, Birgitta
    Department of Psychology, Stockholm University.
    Haptic perception of fine surface texture: Psychophysical interpretation of the multidimensional spaceManuskript (preprint) (Övrigt vetenskapligt)
  • 37.
    Asencio, Rubén Alvarez
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Cranston, Emily D.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Atkin, Rob
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Ionic Liquid Nanotribology: Stiction Suppression and Surface Induced Shear Thinning2012Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, nr 26, s. 9967-9976Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The friction and adhesion between pairs of materials (silica, alumina, and polytetrafluoroethylene) have been studied and interpreted in terms of the long-ranged interactions present. In ambient laboratory air, the interactions are dominated by van der Waals attraction and strong adhesion leading to significant frictional forces. In the presence of the ionic liquid (IL) ethylammonium nitrate (EAN) the van der Waals interaction is suppressed and the attractive/adhesive interactions which lead to "stiction" are removed, resulting in an at least a 10-fold reduction in the friction force at large applied loads. The friction coefficient for each system was determined; coefficients obtained in air were significantly larger than those obtained in the presence of EAN (which ranged between 0.1 and 0.25), and variation in the friction coefficients between systems was correlated with changes in surface roughness. As the viscosity of ILs can be relatively high, which has implications for the lubricating properties, the hydrodynamic forces between the surfaces have therefore also been studied. The linear increase in repulsive force with speed, expected from hydrodynamic interactions, is clearly observed, and these forces further inhibit the potential for stiction. Remarkably, the viscosity extracted from the data is dramatically reduced compared to the bulk value, indicative of a surface ordering effect which significantly reduces viscous losses.

  • 38. Atkin, Rob
    et al.
    Li, Hua
    Sweeney, James
    Elbourne, Aaron
    Webber, Grant
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Warr, Gregory Goodman
    Effect of surface nanostructure and ion structure on the nanotribology of the graphite: Ionic liquid interface2014Ingår i: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 248Artikel i tidskrift (Övrigt vetenskapligt)
  • 39.
    Aulin, Christian
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Varga, Imre
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Claesson, Per
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Lindström, Tom
    STFI-Packforsk AB.
    Buildup of Polyelectrolyte Multilayers of Polyethyleneimine and Microfibrillated Cellulose Studied by in situ Dual Polarization Interferometry and Quartz Crystal Microbalance with Dissipation2008Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, nr 6, s. 2509-2518Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Polyethyleneimine (PEI) and Microfibrillated cellulose (MFC) have been used to buildup polyelectrolyte multilayers (PEM) on silicone oxide and silicone oxynitride surfaces at different pH values and with different electrolyte and polyelectrolyte/colloid concns. of the components.  Consecutive adsorption on these surfaces was studied by in situ dual-polarization interferometry (DPI) and quartz crystal microbalance measurements.  The adsorption data obtained from both the techniques showed a steady buildup of multilayers.  High pH and electrolyte concn. of the PEI soln. was found to be beneficial for achieving a high adsorbed amt. of PEI, and hence of MFC, during the buildup of the multilayer.  On the other hand, an increase in the electrolyte concn. of the MFC dispersion was found to inhibit the adsorption of MFC onto PEI.  The adsorbed amt. of MFC was independent of the bulk MFC concn. in the investigated concn. range (15-250 mg/L).  At. force microscopy measurements were used to image a MFC-treated silicone oxynitride chip from DPI measurements.  The surface was found to be almost fully covered by randomly oriented microfibrils after the adsorption of only one bilayer of PEI/MFC.  The surface roughness expressed as the rms-roughness over 1 μm2 was calcd. to be 4.6 nm (1 bilayer).  The adsorbed amt. of PEI and MFC and the amt. of water entrapped by the individual layers in the multilayer structures were estd. by combining results from the two anal. techniques using the de Feijter formula.  These results indicate a total water content of ca. 41% in the PEM.

  • 40.
    Badal Tejedor, Maria
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. RISE.
    Interfacial and material aspects of powders with relevance to pharmaceutical tableting performance2017Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Tablets are the most common forms of drug administration. They are convenient to administer and easy to manufacture. However, problems associated with the adhesion of the powders to the tableting tools are common. This phenomenon is known as sticking and even though it has been well documented and studied, it remains poorly understood. The many factors that contribute to good performance of the powders make the sticking problem difficult to solve.

    The goal of this study is to establish a relationship between the properties measured at the nanoscale to the overall tablet mechanical properties, tablet performance and powder pre-processing induced modifications. By using atomic force microscopy (AFM) we aim to develop an analytical method to characterize the mechanical and adhesive properties of the pharmaceutical powders at the nanoscale. Other methodologies such as scanning electron microscopy (SEM), thermal analyses (DSC, TGA) and tablet strength test were also used. The materials used in this study are commonly used excipients, a sticky drug and magnesium stearate (MgSt). Two different approaches offered by AFM were employed: sharp tip imaging and colloidal probe force measurements. Nano-mechanical properties of the materials were evaluated with a sharp tip cantilever showing that higher adhesion correlates with higher tablet cohesion and that both are significantly affected by the presence of MgSt. AFM characterization of the particle surface mechanical properties at the nanoscale was also used to detect the crystallinity and amorphicity levels of the materials. New approaches to presenting such data considering the particle heterogeneity and to track the dynamics of surface recrystallization are revealed. Adhesive interactions between a steel sphere and sticky and non-sticky powders were performed with the colloidal probe technique. Sticky materials presented a higher adhesion against the steel surface, and reveal the mechanism of stickiness.

    This work thus contributes to the provision of predictability of the performance of formulations at an early stage of the development process.

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  • 41.
    Badal Tejedor, Maria
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP, Technical Research Institute of Sweden, Box 5607, SE-114 86 Stockholm, Swede.
    Nordgren, N.
    Schuleit, M.
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP, Technical Research Institute of Sweden, Box 5607, SE-114 86 Stockholm, Swede.
    Millqvist-Fureby, A.
    Tablet mechanics depend on nano and micro scale adhesion, lubrication and structure2015Ingår i: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 486, nr 1-2, s. 315-323Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Tablets are the most convenient form for drug administration. However, despite the ease of manufacturing problems such as powder adhesion occur during the production process. This study presents surface and structural characterization of tablets formulated with commonly used excipients (microcrystalline cellulose (MCC), lactose, mannitol, magnesium (Mg) stearate) pressed under different compaction conditions. Tablet surface analyses were performed with scanning electron microscopy (SEM), profilometry and atomic force microscopy (AFM). The mechanical properties of the tablets were evaluated with a tablet hardness test. Local adhesion detected by AFM decreased when Mg stearate was present in the formulation. Moreover, the tablet strength of plastically deformable excipients such as MCC was significantly decreased after addition of Mg stearate. Combined these facts indicate that Mg stearate affects the particle-particle bonding and thus elastic recovery. The MCC excipient also displayed the highest hardness which is characteristic for a highly cohesive material. This is discussed in the view of the relatively high adhesion found between MCC and a hydrophilic probe at the nanoscale using AFM. In contrast, the tablet strength of brittle materials like lactose and mannitol is unaffected by Mg stearate. Thus fracture occurs within the excipient particles and not at particle boundaries, creating new surfaces not previously exposed to Mg stearate. Such uncoated surfaces may well promote adhesive interactions with tools during manufacture.

  • 42.
    Badal Tejedor, Maria
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. RISE Research Institutes of Sweden, Sweden.
    Nordgren, Niklas
    Schuleit, Michael
    Millqvist-Fureby, Anna
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    AFM Colloidal Probe Measurements Implicate Capillary Condensation in Punch-Particle Surface Interactions during Tableting2017Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 33, nr 46, s. 13180-13188Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Adhesion of the powders to the punches is a common issue during tableting. This phenomenon is known as sticking and affects the quality of the manufactured tablets. Defective tablets increase the cost of the manufacturing process. Thus, the ability to predict the tableting performance of the formulation blend before the process is scaled-up is important. The adhesive propensity of the powder to the tableting tools is mostly governed by the surface surface adhesive interactions. Atomic force microscopy (AFM) colloidal probe is a surface characterization technique that allows the measurement of the adhesive interactions between two materials of interest. In this study, AFM steel colloidal probe measurements were performed on ibuprofen, MCC (microcrystalline cellulose), alpha-lactose monohydrate, and spray-dried lactose particles as an approach to modeling the punch particle surface interactions during tableting. The excipients (lactose and MCC) showed constant, small, attractive, and adhesive forces toward the steel surface after a repeated number of contacts. In comparison, ibuprofen displayed a much larger attractive and adhesive interaction increasing over time both in magnitude and in jump-in/jump-out separation distance. The type of interaction acting on the excipient steel interface can be related to a van der Waals force, which is relatively weak and short-ranged. By contrast, the ibuprofen steel interaction is described by a capillary force profile. Even though ibuprofen is not highly hydrophilic, the relatively smooth surfaces of the crystals allow "contact flooding" upon contact with the steel probe. Capillary forces increase because of the "harvesting" of moisture due to the fast condensation kinetics leaving a residual condensate that contributes to increase the interaction force after each consecutive contact. Local asperity contacts on the more hydrophilic surface of the excipients prevent the flooding of the contact zone, and there is no such adhesive effect under the same ambient conditions. The markedly different behavior detected by force measurements clearly shows the sticky and nonsticky propensity of the materials and allows a mechanistic description.

  • 43. Bain, C. D.
    et al.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Langevin, D.
    Meszaros, R.
    Nylander, T.
    Stubenrauch, C.
    Titmuss, S.
    von Klitzing, R.
    Complexes of surfactants with oppositely charged polymers at surfaces and in bulk2010Ingår i: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 155, nr 1-2, s. 32-49Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Addition of surfactants to aqueous solutions of polyelectrolytes carrying an opposite charge causes the spontaneous formation of complexes in the bulk phase in certain concentration ranges. Under some conditions, compact monodisperse multichain complexes are obtained in the bulk. The size of these complexes depends on the mixing procedure and it can be varied in a controlled way from nanometers up to micrometers. The complexes exhibit microstructures analoguous to those of the precipitates formed at higher concentrations. In other cases, however, the bulk complexes are large, soft and polydisperse. In most cases, the dispersions are only kinetically stable and exhibit pronounced non-equilibrium features. Association at air-water interfaces readily occurs, even at very small concentrations. When the surfactant concentration is small, the surface complexes are usually made of a surfactant monolayer to which the polymer binds and adsorbs in a flat-like configuration. However, under some conditions, thicker layers can be found, with bulk complexes sticking to the surface. The association at solid-water interfaces is more complex and depends on the specific interactions between surfactants, polymers and the surface. However, the behaviour can be understood if distinctions between hydrophilic surfaces and hydrophobic surfaces are made. Note that the behaviour at air-water interfaces is closer to that of hydrophobic than that of hydrophilic solid surfaces. The relation between bulk and surface complexation will be discussed in this review. The emphasis will be given to the results obtained by the teams of the EC-funded Marie Curie RTN "SOCON".

  • 44.
    Banerjee, Indradumna
    et al.
    KTH, Skolan för bioteknologi (BIO), Proteomik och nanobioteknologi.
    Salih, Tagrid
    KTH, Skolan för bioteknologi (BIO), Proteomik och nanobioteknologi.
    Ramachandraiah, Harisha
    KTH, Skolan för bioteknologi (BIO), Proteomik och nanobioteknologi.
    Erlandsson, J.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Petterson, T.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Silva, AC
    Karlsson, M
    Russom, Aman
    KTH, Skolan för bioteknologi (BIO), Proteomik och nanobioteknologi.
    LDH based neonatal diagnostics on a low-cost slipdisc based sample preparation platform.2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    INTRODUCTION

    Slipdisc is developed as a sample preparation platform based on slipchip technology [1], using a handwinded clockwork mechanism allowing sample processing from one spot to another with defined precision without the need for sophisticated tools or alignment (Fig.1). An ordinary smartphone or camera can be used to image and analyse the results making it an ideal tool for resource limited settings. Here, we demonstrate a bioassay for detecting LDH (Fig.2), a crucial enzyme found in all living cells which leaks out when the cellular membrane is damaged. This makes LDH a biomarker for several medical conditions in newborns, such as Ozkiraz-13, necrotizing enterocolitis (NEC), and Asphyxia.

    EXPERIMENTAL

    For assembling the slipdisc optically transparent, robust and disposable CD like polycarbonate discs were used with superhydrophobic coating on all except the embedded microfluidic channels. For the LDH assay, heparinized plasma samples were spiked with 7 different concentrations of the LDH enzyme (Lee Biosolutions, USA). These concentrations ranged from clinically normal to abnormal concentrations and used to construct a standard curve for LDH enzyme.

    RESULTS AND DISCUSSION

    The ability of the SlipDisc to quantify LDH enzyme levels from plasma samples was evaluated (Fig.3). Using 7 different concentrations, a standard curve with clinically relevant LDH concentrations was obtained (Fig4). Image and data analyses, including linear regression and Pearson’s correlation, were completed using Image processing tool in Matlab.

    CONCLUSION

    We demonstrate a low-cost neonatal diagnostics platform for the detection of LDH from plasma using a novel SlipDisc platform. The SlipDisc can further be modified to separate plasma from whole blood samples in order to fully integrate the assay. Its simple operation and smartphone based detection capabilities make it an ideal device for point-of-care neonatal diagnostics.

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  • 45. Bartenstein, J. E.
    et al.
    Liu, Xiaoyan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Lange, K.
    Claesson, Per Martin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Briscoe, W. H.
    Polymersomes at the solid-liquid interface: Dynamic morphological transformation and lubrication2018Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 512, s. 260-271Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Polymersomes are hollow spheres self-assembled from amphiphilic block copolymers of certain molecular architecture. Whilst they have been widely studied for biomedical applications, relatively few studies have reported their interfacial properties. In particular, lubrication by polymersomes has not been previously reported. Here, interfacial properties of polymersomes self-assembled from poly(butadiene)-poly(ethylene oxide) (PBD-PEO; molecular weight 10,400 g mol−1) have been studied at both hydrophilic and hydrophobic surfaces. Their morphology at silica and mica surfaces was imaged with quantitative nanomechanical property mapping atomic force microscopy (QNM AFM), and friction and surface forces they mediate under confinement between two surfaces were studied using colloidal probe AFM (CP-AFM). We find that the polymersomes remained intact but adopted flattened conformation once adsorbed to mica, with a relatively low coverage. However, on silica these polymersomes were unstable, rupturing to form donut shaped residues or patchy bilayers. On a silica surface hydrophobized with a 19 nm polystyrene (PS) film, the polymer vesicles formed a more stable layer with a higher surface coverage as compared to the hydrophilic surface, and the interfacial structure also evolved over time. Moreover, friction was greatly reduced on hydrophobized silica surfaces in the presence of polymersomes, suggesting their potential as effective aqueous lubricants.

  • 46.
    Benselfelt, Tobias
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Cranston, Emily D.
    Department of Chemical Engineering, McMaster University.
    Ondaral, Sedat
    Department of Pulp and Paper Technology, Karadeniz Technical University.
    Johansson, Erik
    Cellutech AB.
    Brumer, Harry
    The Michael Smith Laboratories and the Department of Chemistry, The University of British Columbia.
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Adsorption of Xyloglucan onto Cellulose Surfaces of Different Morphologies: An Entropy-Driven Process2016Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 17, nr 9, s. 2801-2811Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The temperature-dependence of xyloglucan (XG) adsorption onto smooth cellulose model films regenerated from N-methylmorpholine N-oxide (NMMO) was investigated using surface plasmon resonance spectroscopy, and it was found that the adsorbed amount increased with increasing temperature. This implies that the adsorption of XG to NMMO-regenerated cellulose is endothermic and supports the hypothesis that the adsorption of XG onto cellulose is an entropy-driven process. We suggest that XG adsorption is mainly driven by the release of water molecules from the highly hydrated cellulose surfaces and from the XG molecules, rather than through hydrogen bonding and van der Waals forces as previously suggested. To test this hypothesis, the adsorption of XG onto cellulose was studied using cellulose films with different morphologies prepared from cellulose nanocrystals (CNC), semicrystalline NMMO-regenerated cellulose, and amorphous cellulose regenerated from lithium chloride/dimethylacetamide. The total amount of high molecular weight xyloglucan (XGHMW) adsorbed was studied by quartz crystal microbalance and reflectometry measurements, and it was found that the adsorption was greatest on the amorphous cellulose followed by the CNC and NMMO-regenerated cellulose films. There was a significant correlation between the cellulose dry film thickness and the adsorbed XG amount, indicating that XG penetrated into the films. There was also a correlation between the swelling of the films and the adsorbed amounts and conformation of XG, which further strengthened the conclusion that the water content and the subsequent release of the water upon adsorption are important components of the adsorption process.

  • 47.
    Bergström, L. Magnus
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Explaining the growth behavior of surfactant micelles2015Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 440, s. 109-118Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The growth behavior of surfactant micelles has been investigated from a theoretical point of view. It is demonstrated that predictions deduced from the spherocylindrical micelle model, which considers micelles that are only able to grow in the length direction, are inconsistent with experimental measurements. Accordingly, the rise in aggregation numbers above a certain concentration, roughly corresponding to the second critical micelle concentration, appears to be much stronger than predicted by the spherocylindrical micelle model. On the other hand, predictions deduced from the general micelle model, which considers micelles that are able to grow with respect to both width and length, show excellent agreement with experimental observations. The latter theory is based on bending elasticity and it is demonstrated that the associated three parameters spontaneous curvature, bending rigidity and saddle-splay constant may all be determined for a micellar system from experimental measurements of the aggregation number as a function of surfactant concentration. The three parameters turn out to influence the appearance of a micellar growth curve rather differently. In accordance, the location of the second cmc is mainly determined by the saddle-splay constant and the bending rigidity. The shape of the growth curve, when going from the region of weakly growing micelles at low surfactant concentrations to strongly growing micelles above the second cmc, is mainly influenced by the bending rigidity.

  • 48.
    Bergström, L. Magnus
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Aratono, Makoto
    Synergistic effects in mixtures of two identically charged ionic surfactants with different critical micelle concentrations2011Ingår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 7, nr 19, s. 8870-8879Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Expressions for the critical micelle concentration (cmc) and activity coefficients as functions of surfactant composition in mixtures of two identically charged monovalent ionic surfactants are derived from the nonlinear Poisson-Boltzmann (PB) theory. For the special case of no added salt, the simple expression cmc(alpha) = xcmc(1)(alpha) + (1 - x)cmc(2)(alpha) is deduced, where the exponential parameter alpha > 1 depends on the number of ionic species in a surfactant molecule as well as the curvature of the self-assembled interface. Theoretical predictions are compared with cmc values obtained with some different experimental techniques for mixtures of the two cationic surfactants didodecyldimethylammonium bromide (DDAB) and dodecyltrimethylammonium bromide (DTAB) in water and in the absence of added salt. It is demonstrated that the PB theory generates significantly better agreement with experimental data than predicted by ideal behaviour or the regular mixture theory. We find that maximum synergistic effects occur at a DDAB mole fraction in solution y = 0.005. According to the PB theory, this very low value of y corresponds to a mole fraction of DDAB in the self-assembled interfacial aggregates equal to x = 0.995. Moreover, our calculations of the surfactant composition in the self-assembled interfacial aggregates above cmc demonstrate that the transition from small micelles to large bilayer aggregates is found to consistently occur at a mole fraction of DDAB equal to about x = 0.41-0.42, irrespective of the surfactant molar ratio in solution. Experimental observations strongly support the fact that concentrations of free surfactant, as well as the surfactant composition in the self-assembled interfacial aggregates, may be accurately calculated from the non-linear Poison-Boltzmann theory. On the other hand, a micelle-to-bilayer transition induced by changes in surfactant mole fraction in the self-assembled interfacial aggregates is consistent with neither ideal surfactant behaviour nor synergistic behaviour according to the regular mixture theory.

  • 49.
    Bergström, L. Magnus
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Garamus, Vasil M.
    Geometrical Shape of Micelles Formed by Cationic Dimeric Surfactants Determined with Small-Angle Neutron Scattering2012Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, nr 25, s. 9311-9321Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of spacer group on the geometrical shape of micelles formed by quaternary-bis dimeric (Gemini) surfactants C12H25N(CH3)(2)(CH2)(5)N(CH3)(2)C12H25 (12-s-12) has been investigated with small-angle neutron scattering (SANS). Dimeric surfactants with a short spacer unit (12-3-12 and 124-12) are observed to form elongated general ellipsoidal micelles with half axes a < b < c, whereas SANS data demonstrate that 12-s-12 surfactants with 6 <= s <= 12 form rather small spheroidal micelles rather than strictly spherical micelles. By means of comparing our present SANS results with previously determined growth rates using time-resolved fluorescence quenching, we are able to conclude that micelles formed by 12-6-12, 12-8-12, 12-10-12, and 12-12-12 are shaped as oblate rather than prolate spheroids. As a result, our present investigation suggests a never before reported structural behavior of Gemini surfactant micelles, according to which micelles transform from elongated ellipsoids to nonelongated oblate spheroids as the length of the spacer group is increased. The aggregation number of oblate micelles is observed to monotonously decrease with an increasing length of the surfactant spacer group, mainly as a result of a decreasing minor half axis (a), whereas the major half axis (b) is rather constant with respect to s. We argue that geometrically heterogeneous elongated micelles are formed by dimeric surfactants with a short spacer group mainly as a result of the surface charges becoming less uniformly distributed over the micelle interface. As the length of the spacer group increases, the distance between intramolecular charges become approximately equal to the average distance between charges on the micelle interface, and as a result, rather small oblate spheroidal micelles with a more uniform distribution of surface charges are formed by dimeric 12-s-12 surfactants with 6 <= s <= 12.

  • 50.
    Bergström, L. Magnus
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Skoglund, Sara
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Danerlöv, Katrin
    Garamus, Vasil M.
    Pedersen, Jan Skov
    The growth of micelles, and the transition to bilayers, in mixtures of a single-chain and a double-chain cationic surfactant investigated with small-angle neutron scattering2011Ingår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 7, nr 22, s. 10935-10944Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Self-assembly in aqueous mixtures of a single-chain (DTAB) and a double-chain cationic surfactant (DDAB) has been investigated with small-angle neutron scattering (SANS). Small oblate spheroidal micelles formed by DTAB grow with respect to width and length to form mixed ellipsoidal tablet-shaped micelles as an increasing fraction of DDAB is admixed into the micelles. The growth behaviour of the micelles is rationalized from the general micelle model in terms of three bending elasticity constants spontaneous curvature (H(0)), bending rigidity (k(c)) and saddle-splay constant ((k(c)) over bar kc). It is found that micelles grow with respect to width, mainly as a result of decreasing k(c)H(0), and in the length direction as a result of decreasing k(c). The micelles are still rather small, i.e. about 140 angstrom in length, as an abrupt transition to large bilayer aggregates is observed. The micelle-to-bilayer transition is induced by changes in aggregate composition and is observed to occur at a mole fraction of DDAB equal to about x = 0.48 in D(2)O, which is a significantly higher value than previously observed for the same system in H(2)O (x = 0.41). An abrupt micelle-to-bilayer transition is in agreement with predictions from the general micelle model, according to which an abrupt transition from micelles to bilayers is expected to occur at xi H(0) = 1/4, where x is the thickness of the self-assembled interface, and we may conclude that H(0)(D(2)O) > H(0)(H(2)O) for the system DDAB/DTAB in absence of added salt. Samples with bilayers are found to be composed of bilayer disks coexisting with vesicles. Disks are found to always predominate over vesicles with mass fractions about 70-90% disks and 10-30% vesicles. Micelles, disks and vesicles are observed to coexist in a few samples close to the micelle-to-bilayer transition.

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