| 1. |
- Andersson, Gabriella, et al.
(författare)
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Structure of Fe-Co/Pt(001) superlattices : a realization of tetragonal Fe-Co alloys
- 2007
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 19:1, s. 016008-
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Tidskriftsartikel (refereegranskat)abstract
- The structural properties of a tetragonally distorted Fe1-xCox alloy, in the form of Fe1-xCox/Pt(001) superlattices with x = 0.64, have been investigated experimentally. The study follows recent theoretical predictions on the enhanced uniaxial magnetocrystalline anisotropy of such alloys with specific combinations of chemical composition and tetragonal distortion. The ratio between out-of-plane and in-plane lattice parameters in the Fe0.36Co0.64 layers, c/a, was found to vary between 1.18 and 1.31, depending on the thickness ratio between the alloy and the spacer. This covered the range of interest c/a = 1.20-1.25 in the previous calculations and should be compared to c/a = 1 in the original bcc alloy lattice. Simulations of x-ray diffraction patterns as well as density functional calculations support the derivation of the Fe0.36Co0.64 lattice parameters.
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| 2. |
- Bergstrom, Jens, et al.
(författare)
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Very High Cycle Fatigue of Two Ductile Iron Grades
- 2016
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 87:5, s. 614-621
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Tidskriftsartikel (refereegranskat)abstract
- Two ductile iron grades, EN-GJS-600-3 a ferritic-pearlitic grade, and EN-GJS-600-10 a silicon strengthened ferritic nodular iron grade, are studied in the very high cycle fatigue range using a 20kHz ultrasonic test equipment. Fatigue strengths and SN-curves are achieved, and fracture surfaces and microstructures are investigated. The ferritic grade with higher ductility displays a lower fatigue strength at 10(8) load cycles than the ferritic-pearlitic grade, 142 and 167MPa, respectively. Examination of fracture surfaces shows that fatigue failures are controlled by micropores in both of the ductile iron grades, while the graphite nodule distributions do not seem to influence the difference in fatigue strengths. Prediction of the fatigue strengths, using a model for ductile iron proposed by Endo and Yanase, indicates a large potential for improvement in particular for the ferritic grade.
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| 4. |
- Boström, Tobias, et al.
(författare)
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ERDA of Ni-Al2O3/SiO2 solar thermal selective absorbers
- 2008
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 92:10, s. 1177-1182
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Tidskriftsartikel (refereegranskat)abstract
- Thin film materials for the use in solar thermal absorbers have been investigated using time-of-flight energy elastic recoil detection analysis (ERDA). The ERDA measurements proved to be very efficient in detecting the elemental depth composition of a selective solar absorber. The three-layer absorber is composed of an 80% nickel-20% alumina film at the base, a 40% nickel-60% alumina layer in the middle and finally an AR film of silica or hybrid-silica film at the top. The difference between solution volume percent and actual volume percent could be investigated when studying individual nickel-alumina films with varying ratios coated on glass substrates. The result showed that there was a maximum difference of 3% between the calculated solution volume percent and the actual volume percentages in the solid films. The ERDA measurements also indicate that about 15% of the nickel found in the nickel-alumina composite films is bound in the form of NiO.
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| 5. |
- Boström, T, et al.
(författare)
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Structure and morphology of nickel-alumina/silica solar thermal selective absorbers
- 2011
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Ingår i: Journal of Non-Crystalline Solids. - : Elsevier BV. - 0022-3093 .- 1873-4812. ; 357:5, s. 1370-1375
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Tidskriftsartikel (refereegranskat)abstract
- Nickel-alumina/silica thin film materials for the use in solar thermal absorbers have been investigated using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Elastic Recoil Detection Analysis (ERDA). The TEM images revealed that all layers have a very small thickness variation and that the layers are completely homogenous. High resolution images showed 5-10 nm (poly) crystalline nickel nano-particles. ERDA showed that both the silica and alumina compositions contain more oxygen than 2:1 and 3:2 respectively. SEM showed the surface morphology and characteristics of the top silica anti-reflection layer. Hybrid-silica has showed to generate a smoother surface with less cracking compared to pure silica. The final curing temperature revealed to be of importance for the formation of cracks and the surface morphology.
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| 6. |
- Brohede, Ulrika, et al.
(författare)
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Percolative drug diffusion from cylindrical matrix systems with unsealed boundaries
- 2007
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Ingår i: Journal of Pharmaceutical Sciences. - : Elsevier BV. - 0022-3549 .- 1520-6017. ; 96:11, s. 3087-3099
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Tidskriftsartikel (refereegranskat)abstract
- Release of NaCl in both the axial and radial directions from cylindrical ethyl cellulose tablets were investigated by the alternating ionic current method. The pore structure of the investigated binary mixtures was examined by mercury porosimetry and scanning electron microscopy, and the nm range fractal surface dimension of tablet pore walls was extracted from krypton gas adsorption isotherms. The drug release was shown to consist of two overlapping processes of which the first was ascribed to dissolution of NaCl close to the tablet boundary followed by subsequent diffusion through a thin ethyl cellulose layer and a second from which a porosity percolation threshold of 0.22 could be extracted. As well, a cross-over to effective-medium behaviour at a porosity of 0.44 was observed. The presented findings showed that drug release from matrix tablets with unsealed tablet walls substantially differs from earlier investigated release processes for which the drug has only been allowed to escape through one of the flat tablet surfaces. Thus, the present study brings forward knowledge important for the tailoring of controlled drug delivery vehicles with optimum release patterns.
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| 15. |
- Högström, Herman, et al.
(författare)
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Optical Excitation of Surface Phonon Polaritons in Silicon Carbide by a Hole Array Fabricated by a Focused Ion Beam
- 2007
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Ingår i: Optical materials (Amsterdam). - : Elsevier BV. - 0925-3467 .- 1873-1252. ; 30:2, s. 328-333
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Tidskriftsartikel (refereegranskat)abstract
- Silicon carbide (SiC) is a polar material with a lattice resonance in the thermal infrared causing a wavelength interval with a negative dielectric function. Within this interval SiC can support surface waves. To excite surface waves, i.e., surface phonon polaritons (SPP), the sample has to be structured with a periodic micro-pattern. The possibilities of using a focused ion beam (FIB) for microfabrication of periodic microstructures in silicon carbide (SiC) is investigated. We present optimized parameters for the microfabrication of SiC with a FIB, as well as calculated and experimental optical results confirming the sensitive optical properties of the material required for the surface excitation are not destroyed by the preparation process.
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| 17. |
- Nilsson, Martin, et al.
(författare)
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Mesopore structure of microcrystalline cellulose tablets characterized by nitrogen adsorption and SEM : The influence on water-induced ionic conduction
- 2006
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 110:32, s. 15776-15781
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Tidskriftsartikel (refereegranskat)abstract
- Tablets of microcrystalline cellulose were formed at different compaction pressures and physical properties, such as pore size distribution, surface area, and pore surface fractality, were extracted from N-2 adsorption isotherms. These properties were compared to previously published data on the water-induced ionic conductivity of the tablets. The conduction process was shown to follow a percolation model with a percolation exponent of 2 and a porosity percolation threshold of similar to 0.1. The critical pore diameter for facilitated charge transport was shown to be in the 5-20 nm range. When the network of pores with a diameter in this interval is reduced to the point where it no longer forms a continuous passageway throughout the compact, the conduction process is dominated by charge transport on the surfaces of individual microfibrils mainly situated in the bulk of fibril aggregates. A fractal analysis of nitrogen adsorption isotherms showed that the dominant interface forces during adsorption is attributed to surface tensions between the gas and the adsorbed liquid phase. The extracted fractal dimension of the analyzed pore surfaces remained unaffected by the densification process at low compaction pressures (< similar to 200 MPa). At increased densification, however, pore-surface structures smaller than similar to 100 nm become smoother as the fractal dimension decreases from similar to 2.5 at high porosities to similar to 2.3 for the densest tablets under study.
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| 20. |
- Strömberg, Mattias, et al.
(författare)
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Aging phenomena in ferrofluids suitable for magnetic biosensor applications
- 2007
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 101:2, s. 023911-
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Tidskriftsartikel (refereegranskat)abstract
- Agingphenomena were investigated in three different ferrofluids containing submicron sizedmagnetic beads consisting of a cluster of iron oxide nanoparticlesembedded in a dextrane matrix with primary amine groups onthe surface (one fresh sample and one sample aged duringthree months) and with a plain surface (only dextrane onthe surface, aged for three months), suitable for magnetic biosensorapplications. The main characterization technique used was measurement of thefrequency dependent complex magnetization using a superconducting quantum interference device.The experimental factors considered were the effect of ultrasonication, temperature,dc bias magnetic field, and addition of sodium dodecyl sulphatesurfactant. The stability against aging was found to depend stronglyon the bead surface, and the reproducibility of a refreshingprocedure involving addition of surfactant in combination with ultrasonication wasshown to be low. Aggregation was shown to be stronglyaffected by the presence of even a small bias magneticfield. Applying a dc bias field caused the formation ofmore or less stable chainlike aggregates with various lengths.
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| 21. |
- Surpi, Alessandro, et al.
(författare)
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Focused ion beam fabrication procedures of x-ray micro Fresnel zone plates
- 2007
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Ingår i: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 17:3, s. 617-622
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Tidskriftsartikel (refereegranskat)abstract
- In this paper the use of focused ion beam (FIB) mask-less lithography is presented as a novel and simple way to fabricate x-ray Fresnel zone plates (FZPs), and a prototype of a FIB-made 100 nm resolution FZP with 38 zones is described. Considerations for future developments—the maximum aspect ratio achievable by FIB lithography in nickel, a way to produce zones with a parabolic transverse profile, as theoretically required for the highest efficiency in focusing—are also reported.
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| 25. |
- Valizadeh, Sima, 1959-
(författare)
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Electrodeposition of Ag/Co and Au/Co compositionally modulated thin films and nanowire arrays
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the past decade, electrochemical synthesis of metallic nanowires within the pores of porous membranes have attracted considerable attention because of their special optical, electronic, and magnetic properties as well as potential for nanotechnological applications. The concept of using membranes as a template for fabrication of metallic nanowires by electrodeposition is considered as an alternative solution to overcome the difficulty of fabricating fibrils with very small diameters by lithographic methods. In this thesis, electrodeposition processes based on a single electrolyte were developed in order to produce compositionally modulated Ag/Co and Au/Co systems for one-dimensional nanowires and 2-dimensional thin films. The methods developed are based on pulse-plating in which two metals are deposited from a single solution bath using either potentiostatic or galvanostatic control and a pulsed deposition technique. Here, the nobler element is kept at much lower concentration than the less noble element so that the rate of reduction of the nobler element becomes diffusion limited. The chemical response of multilayered nanowire is evaluated by cyclic voltammetry and interpreted in comparison with electrochemical behaviour of recessed disk microelectrode. The electrochemical deposition of 8 nm Ag/15 nm Co as well as 4 nm Au/12 nm Co multilayers based on the new technique called nanomaterial membrane-based synthesis have been performed. As a working electrode, ion track etched polycarbonate membranes were employed. The morphology of the deposited films as well as deposited so called "Nanodes" have been investigated by transmission electron microscopy, x-ray diffraction, scanning electron microscopy, atomic force microscopy and energy-dispersive x-ray spectroscopy. Magnetic measurements with the external field parallel and perpendicular to the film plane on Ag/Co and Au/Co multilayered nanowire arrays have been investigated. In case of Co nanowires, difference of saturation fields between the parallel and perpendicular orientation fields corresponds well to the expected demagnetisation field value due to the shape anisotropy in case of an infinite thin Co cylinder. The evidence of magnetic anisotropy was observed on Au/Co multilayered nanowires.
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