γ-Fe 2 O 3 /SiO 2 core-shell nanoparticles with different shell thicknesses were prepared to elucidate the condition for superspin-glass (SSG) dynamics. As the shell thickness decreases, the contribution of interparticle dipolar interaction becomes apparent in the magnetic dynamics of nanoparticle assembly. The frequency dependence of peaks in ac-magnetic susceptibility in samples with strong interactions slows down, which is characterized as the emergence of a spin-glasslike phase. Aging in magnetization relaxation is found in a strongly interacting sample with an interparticle distance of L 14 nm but is scarce in a sample with L = 18 nm. Scaling analysis reveals an increase in superparamagnetic properties with an increase in L. Therefore the critical interparticle distance necessary for SSG transition is 15-18 nm with 11-nm γ-Fe 2 O 3 nanoparticles. This corresponds to the ratio of interparticle-interaction energy to the magnetic-anisotropy energy E dip /E a of 6-12%.

The energy-resolved neutron imaging system, RADEN, has been installed at the pulsed neutron source in the Materials and Life Science Experimental Facility of the Japan Proton Accelerator Research Complex. In addition to conventional neutron radiography and tomography, RADEN, the world’s first imaging beam-line at a pulsed neutron source, provides three main options for new, quantitative neutron imaging techniques: Bragg-edge imaging to visualize the spatial distribution of crystallographic information, resonance absorption imaging for elemental composition and temperature information, and polarized neutron imaging for magnetic field information. This paper describes the results of characterization studies of the neutronic performance and installed devices at RADEN and shows the results of several demonstration studies for pulsed neutron imaging.

To achieve high-performance proton-exchange membranes (PEMs), understanding of the polymer structure/ property relationship is crucial. In particular, the structure of water clusters (number, size, interdomain distance, interconnectivity, etc.) and hydrophobic domains dominates important membrane properties, such as proton conductivity and mechanical strength, which can be adjusted by the monomer sequence in the polymer chains. In the present paper, we have prepared three sulfonated polyphenylene-based copolymers (SPP-MP, SPP-BP, and SPP-QP) whose main chain components were the same but their sequence differed by the use of different hydrophobic monomers (monophenylene, -MP; biphenylene, -BP; and quinquephenylene, -QP, respectively). Careful investigation of the proton nuclear magnetic resonance ( 1 H NMR) spectra suggested that the randomness of the hydrophilic component (sulfophenylene unit) was dominated by the hydrophobic component: 51% for -MP, 32% for -BP, and 19% for -QP, respectively. Transmission electron microscopy (TEM) observation of the three polyphenylene ionomer membranes revealed that the lower randomness of the hydrophilic component caused a larger hydrophilic domain size in their phase-separated morphology under dry conditions. Small-angle X-ray scattering (SAXS) measurements suggested that SPP-QP, with the lowest randomness of the hydrophilic component, possessed the most pronounced periodic structure under humidified conditions. The connectivity of water clusters, estimated by the small-angle neutron scattering (SANS) measurements, was in the order SPP-QP > SPP-MP > SPP-BP with a minor humidity dependence. The proton conductivity and elongation at break increased with increasing connectivity of the water clusters or decreasing randomness of the hydrophilic component. These results suggest that the sequence of the hydrophobic component strongly affected the hydrophilic component, and accordingly, the membrane morphology and properties.

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