Motion of an oil-water interface induced by the formation of surfactant aggregates is reported. An oil-water system that generates surfactant aggregates at the oil-water interface is constructed with biomimetic motivation. We applied a system composed of ionic surfactant, co-surfactant and water, which is known to generate lamellar structure with low surfactant ratio (~ a few wt.%). In our system, a cationic surfactant is dissolved in water, whereas co-surfactant is dissolved in hydrocarbon solvent. Setting the oil and the water in contact with each other, the aggregates were formed at the oil-water interface. Accompanied with the generation of surfactant aggregates, the oil-water interface showed extension and retraction of circular extrude within a quasi 2-dimensional cell. Furthermore, the aggregates formed pillar-like structure due to the interfacial motion. By in situ measurement with small angle X-ray scattering and small angle neutron scattering, we revealed the aggregates have the lamellar structure where their interlayer distance was 28 nm to 30 nm. The internal structure of the aggregate pillar is also revealed. SANS measurement further revealed that the aggregates do not contain large amount of the organic solvent.
We have been developing a 3He neutron spin filter (NSF) for efficient utilization of pulsed neutrons, since it can polarize neutrons effectively in a wide energy range. In order to apply the 3He-NSF to experiments at an intense pulsed neutron experimental facility such as the J-PARC, it is important to make the system stable and easy to setup and operate, because the system is located inside a radiation shield for high energy gamma ray and neutrons. In this study, we have developed compact laser optics with a volume holographic grating (VHG) element for a spin-exchange optical pumping (SEOP) system, and composed an in-situ SEOP 3He-NSF. Current status in the development and application of the in-situ SEOP 3He-NSF at J-PARC is reported.
Surfactant bilayers experience thickness fluctuations even when the bilayer is swollen by small amount of solvent. Neutron scattering experiments reveal the characteristic features of the fluctuations. Neutron spin echo (NSE) in particular gives information about time scales of the motion and the fluctuation amplitude. Calculations using a simple computer model suggest that the static parameters, such as fluctuation amplitude, are measurable from small-angle scattering (SAS) data. Combination of SAS, NSE, and computer model provides essential knowledge on the bilayer dynamics. Calculations based on deformation free energy model of elastic membranes prove the feasibility of the scattering experiments and the computer model.
Antiferromagnetic phase in the highly H-doped LaFeAsO has been investigated by neutron powder diffraction at J-PARC MLF. The characteristic antiferromagnetic structure, the structural phase transition immediately above TN, and the established phase diagram are discussed. Measurements with multiprobe of muon, neutron, and synchrotron X-ray promoted present study.
For (7Li2S)x(P2S5)100–x glasses (x = 50, 60, and 70) and 7Li7P3S11 metastable crystal, time-of-flight neutron diffraction and synchrotron X-ray diffraction experiments were performed, and three-dimensional structures and conduction pathways of lithium ions were studied using the reverse Monte Carlo (RMC) modeling and the bond valence sum (BVS) approach. The conduction pathways of the lithium ions could be classified into two types: lithium “stable” and “metastable” regions, respectively. Moreover, it was found that there is a significant relationship between the activation energy of the electrical conduction and the topology of the conduction pathways of the lithium ions.
Prompt gamma-ray analysis (PGA) can be used for various research fields because the analytical method has many advantages, for example high accuracy, non-destructive measurement without chemical separation, and so on. Here I briefly review the principle and application of PGA. In chapter 5, I present a development of automatic measurement system of PGA at JRR-3M. Up to fourteen samples can be automatically measured by the system.
The small and wide angle neutron scattering instrument (TAIKAN) is designed to cover the wide q range of 0.0005<q<20Å-1 using neutrons with the wavelength range of 0.5<λ<7.8Å and five detector banks which are small-, middle-, high-, ultra-small-angle, and backward detector banks. In this paper, the status of detector installation and data reduction method are presented. In addition, the instrument performance on the wide q-range measurement with high q-resolution is discussed with experimental results of two standard samples, a glassy carbon and a silver behenate.
Neutron reflectometry is one of the powerful tools to investigate surface and interfacial structures of materials in the spatial range from nm to sub-μm. Because hydrogen and deuterium atoms have different scattering length for neutrons, this method can distinguish deuterated materials from normal ones in the mixture of soft-condensed matters, such as polymer blends, bio-mimic membranes, and so on. Also, neutrons have magnetic moment. This enables us to observe magnetic structures in magnetic thin layers which are widely utilized in the field of spintronics. In J-PARC MLF, horizontal and vertical type reflectometers are available. A horizontal type reflectometer SOFIA at BL16 is equipped with two downward neutron beam lines with different angles, 2.22 and 5.71 degrees to the horizontal for investigation of free interfaces. A vertical type reflectometer SHARAKU at BL17 is equipped with a convertible polarized / unpolarized neutron beam line and sample environments including magnets and refrigerators. In this paper, we provide a brief introduction and specifications of these reflectometers, together with some examples taken with them.