| 1. |
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| 2. |
- Laarz, Eric, et al.
(författare)
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Colloidal processing of Al2O3-based composites reinforced with TiN and TiC particulates, whiskers and nanoparticles
- 2001
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Ingår i: Journal of the European Ceramic Society. - 0955-2219 .- 1873-619X. ; 21:8, s. 1027-1035
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Tidskriftsartikel (refereegranskat)abstract
- A colloidal processing route has been developed for the preparation of dense and homogeneous Al2O3–TiN/TiC composites. The dispersion and rheological properties of mixtures of TiN or TiC particulates and Al2O3 particles were investigated using electrokinetics and steady-shear rheology. We found that well-dispersed aqueous suspensions with low viscosity could be prepared by adding a poly(acrylic acid) dispersant and controlling pH in the alkaline range. This processing scheme was also suitable for preparation of whisker and nanoparticle composite suspensions. The alumina-based composite suspensions with a secondary-phase concentration of 25 vol.% were freeze-granulated and hot-pressed, and the resulting bodies were fully densified with well-dispersed secondary phases. Homogeneous Al2O3–TiN nanoparticle composites could only be prepared with additions of up to 5 vol.% nanoparticles; higher additions resulted in agglomeration and subsequent grain growth of the nanoparticles.
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| 3. |
- Wojas, Natalia
(författare)
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The dynamic surface nature of calcite and its role in determining the adsorptive stability toward hydrophobizing carboxylic fatty acids
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Calcium carbonate has attracted a lot of interest over the centuries. Nowadays, mainly as mineral pigment and filler, it has a wide use in technological applications ranging from paper, construction, polymers, and environmental solutions to consumer goods. Amongst these uses, the filler pigment is required to display either hydrophilicity (for applications in aqueous colloidal systems, including, for example, in paper and emulsion paints), or, in contrast, oleophilicity (for applications in contact with oil-based systems, such as plastics and volatile solvent-containing sealants). To achieve oleophilicity, and resulting hydrophobicity, the filler is surface treated, typically using carboxylic fatty acids. In this thesis, effects of humidity and fatty carboxylic acids vapor on CaCO3 surface wettability and nanomechanical properties were studied, with the aim to gain knowledge on layer packing density and order, as well as resistance to water exposure and mechanical wear. A better understanding of the dynamic nature of the calcite surface presented in this work allows the industry to increase sustainable control over materials production and storage. First, a setup combining an atomic force microscope (AFM) with a humidifier was used to map nanomechanical properties of growing surface domains (hydrated form of CaCO3) formed by ion dissolution, diffusion, and redeposition, a process that is not reversible upon drying. Secondly, AFM and contact angle goniometer measurements showed that the stability of the calcite surface improves with increasing carboxylic acid chain length (C2 to C18). Meanwhile, X-ray photoelectron spectroscopy and vibrational sum frequency spectroscopy techniques demonstrated that a coherent layer with maximum packing density of carboxylate and carboxylic acid species was achieved with the use of stearic acid (C18) with high enough vapor pressure and exposure time. The AFM images successfully visualized that a complete C18 monolayer is capable of countering nano-wear of the calcite surface despite the humidity (under the range of loads investigated in this work) and the layer has self-healing properties, while calcite displayed high abrasive wear. Further, when calcite coated by a highly packed monolayer of C18 was covered with a water droplet, a large contact angle hysteresis resulted in a coffee ring effect (CRE). That is leading to formation of hillocks at the contact line consisting of dissolved fatty carboxylic acid and possibly calcium bicarbonate Ca(HCO3)2 molecules transported from the bare calcite region that also is created next to the droplet edge. Interestingly, C18 coated calcite remained considerably more stable in the case where a water droplet saturated with octanoic acid was used instead of water; thus, it was concluded that the CRE can be contained via reduction of the liquid surface tension and contact angle hysteresis.
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| 4. |
- Hedlund, Artur, et al.
(författare)
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Microstructures of cellulose coagulated in water and alcohols from 1-ethyl-3-methylimidazolium acetate : contrasting coagulation mechanisms
- 2019
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 26:3, s. 1545-1563
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Tidskriftsartikel (refereegranskat)abstract
- Abstract: Coagulation of cellulose solutions is a process whereby many useful materials with variable microstructures and properties can be produced. This study investigates the complexity of the phase separation that generates the structural heterogeneity of such materials. The ionic liquid, 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]), and a co-solvent, dimethylsulfoxide (DMSO), are used to dissolve microcrystalline cellulose in concentrations from 5 to 25 wt%. The solutions are coagulated in water or 2-propanol (2PrOH). The coagulated material is then washed and solvent exchanged (water → 2PrOH → butanone → cyclohexane) in order to preserve the generated microstructures upon subsequent drying before analysis. Sweep electron microscopy images of 50 k magnification reveal open-pore fibrillar structures. The crystalline constituents of those fibrils are estimated using wide-angle X-ray spectroscopy and specific surface area data. It is found that the crystalline order or crystallite size is reduced by an increase in cellulose concentration, by the use of the co-solvent DMSO, or by the use of 2PrOH instead of water as the coagulant. Because previous theories cannot explain these trends, an alternative explanation is presented here focused on solid–liquid versus liquid–liquid phase separations. Graphical abstract: [Figure not available: see fulltext.].
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| 5. |
- Heydari, Golrokh, 1982-, et al.
(författare)
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Temperature-Dependent Deicing Properties of ElectrostaticallyAnchored Branched Brush Layers of Poly(ethylene oxide)
- 2016
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 32:17, s. 4194-4202
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Tidskriftsartikel (refereegranskat)abstract
- The hydration water of hydrophilic polymersfreezes at subzero temperatures. The adsorption of suchpolymers will result in a hydrophilic surface layer that stronglybinds water. Provided this interfacial hydration water remainsliquidlike at subzero temperatures, its presence could possiblyreduce ice adhesion, in particular, if the liquidlike layer isthicker than or comparable to the surface roughness. Toexplore this idea, a diblock copolymer, having one branchedbottle-brush block of poly(ethylene oxide) and one linear cationic block, was electrostatically anchored on flat silica surfaces. Theshear ice adhesion strength on such polymer-coated surfaces was investigated down to −25 °C using a homebuilt device. Inaddition, the temperature dependence of the ice adhesion on surfaces coated with only the cationic block, only the branchedbottle-brush block, and with linear poly(ethylene oxide) was investigated. Significant ice adhesion reduction, in particular, attemperatures above −15 °C, was observed on silica surfaces coated with the electrostatically anchored diblock copolymer.Differential scanning calorimetry measurements on bulk polymer solutions demonstrate different thermal transitions of waterinteracting with branched and linear poly(ethylene oxide) (with hydration water melting points of about −18 and −10 °C,respectively). This difference is consistent with the low shear ice adhesion strength measured on surfaces carrying branchedbottle-brush structured poly(ethylene oxide) at −10 °C, whereas no significant adhesion reduction was obtained with linearpoly(ethylene oxide) at this temperature. We propose a lubrication effect of the hydration water bound to the branched bottlebrushstructured poly(ethylene oxide), which, in the bulk, does not freeze until −18 °C.
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| 6. |
- Karlsson, Mikael, 1978, et al.
(författare)
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Characterisation of silicon, zirconium and aluminium coated titanium dioxide pigments recovered from paint waste
- 2019
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Ingår i: Dyes and Pigments. - : Elsevier BV. - 0143-7208 .- 1873-3743. ; 162, s. 145-152
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Tidskriftsartikel (refereegranskat)abstract
- © 2018 Elsevier Ltd Titanium dioxide (TiO2) is the major white pigment used by the paint industry. However, the production of TiO2is associated with a high carbon footprint. An alternative source of pigment could be created by developing a method to recover it from waste paint. In this paper two rutile pigments with different surface treatments were recovered from paint by a thermal recycling process. The pigments were analysed using powder x-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), surface area measurements (BET), laser diffraction for particle size analysis and zeta potential measurements before and after the recycling process. It was concluded that the rutile cores of both pigments were intact and there were no major changes in particle size distribution or surface charge for either pigment induced by the recycling process. However, XPS and zeta potential measurements showed that the surface coating of the pigments can be more or less degraded depending on the chemical nature, which might imply the need for further re-coating after-treatment. Another option would be to find another application for the pigment where the quality and function of the coating is of less importance.
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| 7. |
- Li, Jing, et al.
(författare)
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Towards the mechanism of electrochemical activity and self-healing of 1 wt% PTSA doped polyaniline in alkyd composite polymer coating : Combined AFM-based studies
- 2016
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Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 6:23, s. 19111-19127
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Tidskriftsartikel (refereegranskat)abstract
- A composite solvent-borne alkyd coating with 1 wt% p-toluene sulfonic acid (PTSA) doped polyaniline (PANI) was prepared. The mechanisms of electrochemical activity and self-healing properties of the composite coating were investigated by in situ atomic force microscopy (AFM), intermodulation AFM (ImAFM), electrochemical controlled (EC)-AFM combined with cyclic voltammetry (CV), Kelvin force microscopy (KFM), and Fourier transform infrared spectroscopy (FTIR), as well as open-circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) methods. The ImAFM demonstrates the multiphase structure of the composite coating and a high compatibility between the doped PANI and alkyd matrix. The CV and EC-AFM results reveal a high electrochemical activity of the doped PANI in the composite coating as well as reversible redox reactions between the emeraldine salt (ES) and leuco emeraldine base (LB) forms. The Volta potential mapping of KFM demonstrates a strong self-healing ability of the doped PANI in air conditions. The good electrochemical connection between the fine network of PANI in the composite coating and metal surface underneath enable the occurrence of reversible redox reaction between the ES/LB forms of doped PANI and a concomitant release of dopant anions both in air and in 3 wt% NaCl solution as demonstrated by OCP and EIS results. These therefore lead to the strong passivation and self-healing effect of the composite coated on the carbon steel surface.
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| 8. |
- Pradhan, Sulena, et al.
(författare)
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Effect of sonication on particle dispersion, administered dose and metal release of non-functionalized, non-inert metal nanoparticles
- 2016
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Ingår i: Journal of nanoparticle research. - : Springer. - 1388-0764 .- 1572-896X. ; 18:9
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we elucidate the effect of different sonication techniques to efficiently prepare particle dispersions from selected non-functionalized NPs (Cu, Al, Mn, ZnO), and corresponding consequences on the particle dose, surface charge and release of metals. Probe sonication was shown to be the preferred method for dispersing non-inert, non-functionalized metal NPs (Cu, Mn, Al). However, rapid sedimentation during sonication resulted in differences between the real and the administered doses in the order of 30–80 % when sonicating in 1 and 2.56 g/L NP stock solutions. After sonication, extensive agglomeration of the metal NPs resulted in rapid sedimentation of all particles. DLVO calculations supported these findings, showing the strong van der Waals forces of the metal NPs to result in significant NP agglomeration. Metal release from the metal NPs was slightly increased by increased sonication. The addition of a stabilizing agent (bovine serum albumin) had an accelerating effect on the release of metals in sonicated solutions. For Cu and Mn NPs, the extent of particle dissolution increased from <1.6 to ~5 % after sonication for 15 min. A prolonged sonication time (3–15 min) had negligible effects on the zeta potential of the studied NPs. In all, it is shown that it is of utmost importance to carefully investigate how sonication influences the physico-chemical properties of dispersed metal NPs. This should be considered in nanotoxicology investigations of metal NPs. Graphical Abstract: [Figure not available: see fulltext.]
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| 9. |
- Andersson Trojer, Markus, et al.
(författare)
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Elastic strain-hardening and shear-thickening exhibited by thermoreversible physical hydrogels based on poly(alkylene oxide)-grafted hyaluronic acid or carboxymethylcellulose
- 2020
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 22:26, s. 14579-14590
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Tidskriftsartikel (refereegranskat)abstract
- The formation of strongly elastic physical gels based on poly(alkylene oxide)-grafted hyaluronan or carboxymethylcellulose, exhibiting both shear-thickening and strain-hardening have been studied using rheometry and explained using a slightly different interpretation of the transient network theory. The graft copolymers were prepared by a quantitative coupling reaction. Their aqueous solutions displayed a thermoreversible continuous transition from Newtonian fluid to viscoelastic solid which could be controlled by the reaction conditions. The evolution of all material properties of the gel could be categorized into two distinct temperature regimes with a fast evolution at low temperatures followed by a slow evolution at high temperatures. The activation energy of the zero shear viscosity and the relaxation time of the graft inside the interconnecting microdomains were almost identical to each other in both temperature regimes. This suggests that the number of microdomains remained approximately constant whereas the aggregation number inside the microdomains increased according to the binodal curve of the thermosensitive graft.
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| 10. |
- Bergenstråhle, Malin, 1977-, et al.
(författare)
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Dynamics of Cellulose-Water Interfaces : NMR Spin-Lattice Relaxation Times Calculated from Atomistic Computer Simulations
- 2008
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Ingår i: Journal of Physical Chemistry B. - Washington : ACS Publications. - 1520-6106 .- 1520-5207. ; 112:9, s. 2590-2595
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Tidskriftsartikel (refereegranskat)abstract
- Solid-state nuclear magnetic resonance (CP/MAS 13C NMR) spectroscopy has often been used to study cellulose structure, but some features of the cellulose NMR spectrum are not yet fully understood. One such feature is a doublet around 84 ppm, a signal that has been proposed to originate from C4 atoms at cellulose fibril surfaces. The two peaks yield different T1, differing by approximately a factor of 2 at 75 MHz. In this study, we calculate T1 from C4-H4 vector dynamics obtained from molecular dynamics computer simulations of cellulose Iβ-water interfacial systems. Calculated and experimentally obtained T1 values for C4 atoms in surface chains fell within the same order of magnitude, 3-20 s. This means that the applied force field reproduces relevant surface dynamics for the cellulose-water interface sufficiently well. Furthermore, a difference in T1 of about a factor of 2 in the range of Larmor frequencies 25-150 MHz was found for C4 atoms in chains located on top of two different crystallographic planes, namely, (110) and (10). A previously proposed explanation that the C4 peak doublet could derive from surfaces parallel to different crystallographic planes is herewith strengthened by computationally obtained evidence. Another suggested basis for this difference is that the doublet originates from C4 atoms located in surface anhydro-glucose units with hydroxymethyl groups pointing either inward or outward. This was also tested within this study but was found to yield no difference in calculated T1.
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