| 1. |
- Bidulsky, Robert, et al.
(författare)
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Interparticle Neck Connections in Innovative Insulated Iron Powder Compounds
- 2015
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Ingår i: Acta Physica Polonica A. - 0587-4246 .- 1898-794X. ; 128:4, s. 647-650
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Tidskriftsartikel (refereegranskat)abstract
- Goal of the present paper is the analysis of the interparticle neck connections in a system made of insulated iron powder compounds with different additions of an Al-Mg-Si-Cu alloy (0.25, 0.5 and 0.75 wt%). The introduction of the aluminium alloy powder has been made in order to improve the mechanical properties, evaluated as thetransverse rupture strength, without decreasing the agnetic properties (evaluated in terms of iron loss and coercivity force). The fracture analysis of investigated systems puts into evidence the breaking of interparticle neck connections. Heat treatment (at the temperature of 500C) contributes to the early stages of interparticle neck developments. The chosen aluminium alloy presents a sort of pre-sintering behaviour at 500C, with the possibility of mass-transport processes around the insulated iron powder compounds. The air heat treatment applied aims at providing an increase in the mechanical behaviour of the material, with a final good rigidity after the cooling process. Fracture surfaces and transverse rupture strength values show that, at 500 MPa, the strength and the area related to the inter-particle necks can be correlated to the occasional broken insulated point-to-point surfacesthat hinder the development of inter-particles necks.
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| 2. |
- Gutfreund, Philipp, et al.
(författare)
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Depletion at solid/liquid interfaces : Flowing hexadecane on functionalized surfaces
- 2011
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 134:6, s. 064711-
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Tidskriftsartikel (refereegranskat)abstract
- We present a neutron reflectivity study on interfaces in contact with flowing hexadecane, which is known to exhibit surface slip on functionalized solid surfaces. The single crystalline silicon substrates were either chemically cleaned Si(100) or Si(100) coated by octadecyl-trichlorosilane (OTS), which resulted in different interfacial energies. The liquid was sheared in situ and changes in reflectivity profiles were compared to the static case. For the OTS surface, the temperature dependence was also recorded. For both types of interfaces, density depletion of the liquid at the interface was observed. In the case of the bare Si substrate, shear load altered the structure of the depletion layer, whereas for the OTS covered surface no effect of shear was observed. Possible links between the depletion layer and surface slip are discussed. The results show that, in contrast to water, for hexadecane the enhancement of the depletion layer with temperature and interfacial energy reduces the amount of slip. Thus a density depletion cannot be the origin of surface slip in this system.
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| 3. |
- Gutfreund, Philipp, et al.
(författare)
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The Search for Nanobubbles by Using Specular and Off-Specular Neutron Reflectometry
- 2016
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 32:35, s. 9091-9096
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Tidskriftsartikel (refereegranskat)abstract
- We apply specular and off-specular neutron reflection at the hydrophobic silicon/water interface to check for evidence of nanoscopic air bubbles whose presence is claimed after an ad hoc procedure of solvent exchange. Nanobubbles and/or a depletion layer at the hydrophobic/water interface have long been discussed and generated a plethora of controversial scientific results. By combining neutron reflectometry (NR), off-specular reflectometry (OSS), and grazing incidence small angle neutron scattering (GISANS), we studied the interface between hydrophobized silicon and heavy water before and after saturation with nitrogen gas. Our specular reflectometry results can be interpreted by assuming a submolecular sized depletion layer and the off-specular measurements show no change with nitrogen super saturated water. This picture is consistent with the assumption that, following the solvent exchange, no additional nanobubbles are introduced at significant concentrations (if present at all). Furthermore, we discuss the results in terms of the maximum surface coverage of nanobubbles that could be present on the hydrophobic surface compatibly with the sensitivity limit of these techniques.
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