Papers by Keyword: Small-Angle Neutron Scattering

Abstract: Nanosteels are used in automotive applications to accomplish resource-efficiency while providing high-tech properties. Quantitative data and further understanding on the precipitation kinetics in Nanosteels can contribute to fulfil this goal. Small-Angle Neutron Scattering measurements are performed on a Fe-C-Mn-V steel, previously heat-treated in a dilatometer at 650°C for several holding times from seconds to 10 hours. The evolution of the precipitate volume fraction, size distribution and number density is calculated by fitting the experimental Small-Angle Neutron Scattering curves. The effect of phase transformation on precipitation kinetics is also discussed. Complementary Transmission Electron Microscopy, Scanning Electron Microscopy and Inductively Coupled Plasma Optical Emission Spectroscopy measurements are performed to support the Small-Angle Neutron Scattering data analysis.

Abstract: New La0.54Ho0.11Sr0.35Mn1-xCuxO3 manganites were obtained by sol-gel method using oxides and acetates and sintered finally in air at 12000 C for 15 h. The samples were studied by X-ray diffraction, magnetic and electric methods. Space group, lattice constants, average size of the crystalline blocks and positions of cations/anions in the unit cell, were determined using the FullProf code. The samples contain only a perovskite phase with an orthorhombic structure (Pnma space group). Small-angle neutron scattering (SANS) measurements were performed on the SANS-1 setup at the FRG-1 reactor of the GKSS Research Centre (Geesthacht, Germany). The sizes of magnetic clusters have been determined at room temperature.

Abstract: The microstructure of ferrofluids (magnetite/oleic acid/benzene) with an excess of free oleic acid is investigated by small-angle neutron scattering (SANS). For such excess higher than 25 vol. % a sharp break in the stability of ferrofluids occurs followed by coagulation and precipitation. Below this value the influence of the surfactant excess on the stability of ferrofluids is insignificant; neither particle aggregation nor surfactant agglomeration is observed. The interaction of free acid molecules in the ferrofluids is compared with that in pure benzene solutions. A significant increase in the attraction is observed for acid molecules in the ferrofluids, which is related to the loss of magnetic fluids stability at high excess of acid.

Abstract: Contrast variation method in small-angle neutron scattering (non-polarized neutrons) is applied to magnetic fluids (MFs) with magnetite dispersed in benzene and coated with myristic or oleic acid in zero external magnetic field. The basic functions approach for polydisperse superparamagnetic systems is used to get structure parameters of particles in MFs.

Abstract: This paper presents a physically based precipitation model which aims at describing precipitation kinetics when it occurs exclusively on dislocations. We present specific nucleation, growth and coarsening equations, which are integrated in a set of differential equations. This model is successfully applied to the case of precipitation of NbC in a ferritic steel, whose kinetics has been determined by small-angle neutron scattering.