| 1. |
- Bielecki, Johan, 1982, et al.
(författare)
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Structural and magnetic properties of isovalently substituted multiferroic BiFeO3 : Insights from Raman spectroscopy
- 2012
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 86:184422
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Tidskriftsartikel (refereegranskat)abstract
- Raman spectra, supplemented by powder x-ray diffraction and magnetization data of isovalently A- and B-site substituted BiFeO3 in the Bi1−xLaxFeO3 (0≤x≤1), Bi1−xTbxFeO3 (0≤x≤0.2), and Bi0.9Sm0.1Fe1−xMnxO3 (0≤x≤0.3) series, are presented. A good agreement between the structural transitions observed by x-ray diffraction and the vibrational modes observed in the Raman spectra is found over the whole substitutional ranges, and in particular we find spectroscopic signatures of a PbZrO3-type structure for Bi0.8La0.2FeO3. Mode assignments in the substituted materials are made based on Raman spectra of the end-members BiFeO3 and LaFeO3. Moreover, by comparing spectra from all samples with R3c structure, the phonon assignment in BiFeO3 is revisited. A close connection between the degree of octahedral tilt and the Raman shift of the A1 oxygen a−a−a− tilt mode is established. An explanation for the strong second-order scattering observed in Bi1−xLaxFeO3 and Bi1−xTbxFeO3 is suggested, including the assignment of the previously mysterious BiFeO3 mode at 620 cm−1. Finally, the magnetization data indicates a transition from a cycloidal modulated state towards a canted antiferromagnet with increasing A-site substitution, while Bi0.9Sm0.1Fe1−xMnxO3 with x=0 and 0.15 exhibit an anomalous closing of the hysteresis loop at low temperatures. For low A-site substitution levels (x≤0.1) the decreasing Raman intensity of the Fe derived modes correlates with the partial destruction of the spin cycloid as the substitution level increases.
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| 2. |
- Cai, Shengzhen, et al.
(författare)
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Curing of wood treated with vinyl acetate-epoxidized linseed oil copolymer (VAc-ELO)
- 2016
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Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 70, s. 305-312
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Tidskriftsartikel (refereegranskat)abstract
- Scots pine sapwood was treated with a new formulation consisting of vinyl acetate (VAc) and epoxidized linseed oil (ELO) catalyzed by potassium persulfate to impart protection to wood. The effects of various curing temperatures, durations, and solution uptakes on dimensional stability (DS) and leachability were studied. The new formulation provided good anti-swelling efficiency (ASE) ranging from 35% to 47% with negligible leaching of the treating agent after four cycles of water soaking and oven drying (2%-2.5%). The extent of polymerization in wood was observed by FTIR-attenuated total reflectance (FTIR-ATR) by evaluation of the areas below typical IR bands as a function of curing temperature and time. Linear relationships were found with high R-2 values. The FTIR data of extracted samples were interpreted that chemical reactions took place between the resulting copolymer and wood components.
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| 3. |
- Cai, Shengzhen, et al.
(författare)
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Mechanical properties and decay resistance of Scots pine (Pinus sylvestris L.) sapwood modified by vinyl acetate-epoxidized linseed oil copolymer
- 2016
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Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 70, s. 885-894
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Tidskriftsartikel (refereegranskat)abstract
- Equilibrium moisture content (EMC), mechanical properties, and durability of Scots pine (Pinus sylvestris L.) sapwood modified by vinyl acetate epoxidized linseed oil (WVA-ELO) have been studied. Microscopic observations revealed that the impregnated copolymer is mainly in cell walls, rays, resin canals, and a small fraction in the cell lumens. Under the same climate conditioning, the EMC of the treated wood was in the range of 6.0%-8.2%, which was significantly lower than that of untreated wood (about 12%). Mechanical tests performed on paired samples (control and treated) showed a slight reduction on the mechanical properties of WVA-ELO. The decay resistance against basidiomycete fungi of WVA-ELO was significantly improved as demonstrated by laboratory tests. It was found that 8% weight percentage gain (WPG) was sufficient to ensure decay resistance against the test fungi with <5% mass loss (ML), which led to durability class (DC) of 2.
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| 4. |
- Cai, Shengzhen, et al.
(författare)
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Properties of epoxidised linseed oil-furfuryl alcohol and vinyl acetate-furfuryl alcohol treated wood
- 2014
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Furfurylation process is a well-studied wood modification method. Properties such as dimensional stability, decay resistance, moisture uptake and weathering have been reported to be greatly improved after treatment. However, the main remaining challenge for this process lies in the negative impact on the mechanical properties, especially the hardness which increased significantly. This has a direct impact on the structural applications of the material. In this context, new formulations consisting of combinations of furfural alcohol (FA) mixed with epoxidised linseed oil (ELO) or vinyl acetate (VA) were prepared and impregnated into Scots pine sapwood and cured without any additional crosslinking agents. Maleic anhydride was used as catalyst for polymerisation. The impact of the treatments has been studied concerning the mechanical properties, dimensional stability and durability. The average WPGs obtained after impregnation with VA-FA and ELO-FA treatments were 37.4% and 59.7% for samples intended for dimensional stability and 40.5% and 26.4% for samples intended for mechanical tests. With the achieved WPGs, the dimensional stability was significantly improved reaching an ASE of 63.3% and 43.1% for VA-FA-treated and ELO-FA-treated samples respectively. Mass loss caused by basidiomycetes fungi was in the range between 2 to 4% for both treatments, while the untreated samples lost more than 30%. MOE was almost not affected by the treatments, while impact bending strength increased by 26% after the ELO-FA treatment and decreased by 30% after the VA-FA treatment. Brinell hardness increased only by 21% for ELO-FA treatment and 64% for VA-FA treatment. These results showed that the combination of ELO with FA could result in durable timber without significant negative effect on the mechanical properties. Moreover, no darkening of the ELO-FA samples was observed.
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| 5. |
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| 6. |
- Cai, Shengzhen
(författare)
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Scots pine (Pinus sylvestris L.) sapwood modification by vinyl acetate-epoxidized plant oil copolymer : precursor syntheses, characterization, modified wood properties and durability
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A new bio-based formulation consisting of plant oil and vinyl acetate was developed for wood modification aiming at improving some of the material’s properties. In–situ epoxidation of linseed oil (LO) and soybean oil (SO) was carried out at different times with purpose of preparing epoxidized oils with various epoxy content. For comparison, commercially available epoxidized linseed oil (ELO®) and epoxidized soybean oil (ESO®) were also included in the study. The epoxidized oils were subsequently reacted with vinyl acetate (VAc) to investigate the effect of epoxidation degree on the copolymerization reaction between epoxidized oils and VAc. Results showed that a copolymer can be formed between VAc and epoxidized LO with high epoxy content, while no reaction occurred between VAc and SO or its epoxidized derivatives. As the most reactive monomer among studied oils, the epoxidized LO with highest epoxy content (i.e. ELO®) was selected for further investigation to determine the optimal conditions for its copolymerization reaction with VAc. The effect of feed ratio, reaction temperature, reaction time and catalyst amount on the efficiency of the copolymerization reaction was evaluated by measuring the yields of formed copolymer under different conditions. DSC and NMR were used to confirm the formation of copolymer and reveal the chemical structure of the obtained copolymer. The optimized formulation was further impregnated into wood and subsequently cured, and the progress of curing process monitored using ATR–FTIR spectroscopy. It was found that an increase of curing temperature or duration resulted in improved wood dimensional stability, while weight percentage gain (WPG) was not significantly affected. In addition, insignificant correlation between WPG and anti–swelling efficiency (ASE) was found for the VAc–ELO® treated wood. From energy saving and economical point of view, 168 h of curing duration at 90°C is sufficient to achieve a satisfying dimensional stability. Moreover, the VAc–ELO® treated wood showed great leaching resistance to water. By using light– and scanning electron microscopy, it was found that the copolymer formed inside wood was mainly located in rays, resin canals and occasionally in the cell lumina. Like most wood treatments, the mechanical properties of VAc–ELO® treated wood samples were slightly decreased compared to untreated wood, especially MOR, compression parallel to the grain (∥) and hardness perpendicular to the grain (⊥). The difference between control and treated samples gradually increase as a result of increasing WPG. Durability tests showed that 8% WPG was enough to ensure decay resistance against the tested fungi (improved up to durability class 2), and thus can be used to protect wood used in above ground applications.
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| 7. |
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| 8. |
- Jebrane, Mohamed, et al.
(författare)
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Synthesis and characterization of new vinyl acetate grafting onto epoxidized linseed oil in aqueous media
- 2015
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 132:24
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Tidskriftsartikel (refereegranskat)abstract
- Modified poly (vinyl acetate) copolymers with epoxidized linseed oil (ELO) as co-monomer have been prepared. The polymerization was performed in aqueous medium without any additional protective colloid in the presence of sodium persulfate as catalyst. The effect of vinyl acetate (VAc)/ELO feed ratio, reaction temperature, reaction time, and catalyst amount has been studied. FTIR spectroscopy showed that the reaction between ELO and VAc resulted in slight decrease and shift in ELO characteristic bands of oxirane groups; and new bands were detected in the copolymer spectra attributed to PVAc and ELO functional groups. Moreover, new signals attributable to the copolymer were observed in the H-1 NMR spectra ( 4.07 and 1.62 ppm) and in the C-13 NMR spectra ( 15.29 and 31.0 ppm). Analysis by differential scanning calorimetry (DSC) showed a single T-g for the copolymerization product of VAc and ELO and two T-g for the PVAc/ELO blend, indicating the chemical reaction between VAc and ELO.
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| 9. |
- Jebrane, Mohamed, et al.
(författare)
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The reactivity of linseed and soybean oil with different epoxidation degree towards vinyl acetate and impact of the resulting copolymer on the wood durability
- 2017
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Ingår i: eXPRESS Polymer Letters. - : Department of Polymer Engineering, Scientific Society of Mechanical Engineering. - 1788-618X. ; 11, s. 383-395
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Tidskriftsartikel (refereegranskat)abstract
- Linseed (LO) and soybean oil (SO) were in-situ epoxidized with peracetic acid to produce different degree of epoxidized LO and epoxidized SO. For comparison purpose, commercial epoxidized linseed oil (ELO (R)) and epoxidized soybean oil (ESO (R)) were also included in the study. The effect of epoxidation degree on the copolymerization reaction between epoxidized oils and vinyl acetate (VAc) was investigated. Results showed that a copolymer can be formed between VAc and epoxidized LO with high epoxy content, while no reaction occurred between VAc and SO or its epoxidized derivatives. As the most reactive monomer among the studied oils, the epoxidized LO with highest epoxy content (i.e. ELO (R)) was mixed with VAc and then impregnated into the wood using three different ELO (R) /VAc formulations either as solution or as emulsions. After curing, the impact of the resulting copolymer issued from the three tested formulations on the wood durability was evaluated. Results showed that the formulation comprising VAc, ELO (R), H2O, K2S2O8 and alkaline emulsifier (Formulation 3) can significantly improve wood's durability against white rot- (Trametes versicolor) and brown rot fungi (Postia placenta and Coniophora puteana). Treated wood of 8% weight percentage gain (WPG) was sufficient to ensure decay resistance against the test fungi with less than 5% mass loss.
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| 10. |
- Knee, Christopher, 1973, et al.
(författare)
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High Pressure Crystal and Magnetic Phase Transitions in Multiferroic Bi0.9La0.1FeO3
- 2014
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 1520-5002 .- 0897-4756. ; 26:2, s. 1180-1186
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Tidskriftsartikel (refereegranskat)abstract
- The crystal and magnetic structures of multiferroic Bi0.9La0.1FeO3 have been studied using high resolution neutron powder diffraction in the pressure range 0-8 GPa. Two structural phase transitions are observed. The first, at similar to 1 GPa, transforms the polar R3c structure to an antipolar PbZrO3-like root 2a(p) x 2 root 2a(p) x 2a(p) perovskite superstructure; the second, at similar to 5 GPa, results in a smaller, root 2a(p) x root 2a(p) x 2a(p) unit cell and a structure described with Ibmm (nonstandard setting of Imma) symmetry, in which the a(-)a(-)b(0) octahedral tilt system is retained and the antipolar cation displacements lost. Accompanying the changes in the nuclear structure, the antiferromagnetic spin structure evolves from a cycloid, with a modulation length, lambda approximate to 770 angstrom, to collinear arrangements with the moments aligned along the b-axis (Pbam) and the a-axis (Ibmm) of the orthorhombic unit cells. In comparison with BiFeO3 the transition from a rhombohedral to an orthorhombic structure is suppressed by similar to 3 GPa, reflecting the dilution of the stereochemically active bismuth lone pair by lanthanum. A correlation between the cell contraction of Bi1-xLaxFeO3 (0.0
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