Manganese dioxide nanomaterials have wide applications in many areas from catalysis and Li−ion batteries to gas sensing. Understanding the crystallization pathways, morphologies, and formation of defects in their structure is particularly important but still a challenging issue. Herein, we employed an arsenal of X-ray diffraction (XRD), scanning electron microscopy (SEM), neutron diffraction, positron annihilation spectroscopies, and ab initio calculations to investigate the evolution of the morphology and structure of α-MnO 2 nanomaterials prepared via reduction of KMnO 4 solution with C 2 H 5 OH prior to being annealed in air at 200−600 °C. We explored a novel evolution that α-MnO 2 nucleation can be formed even at room temperature and gradually developed to α-MnO 2 nanorods at above 500 °C. We also found the existence of H + or K + ions in the [1 × 1] tunnels of α-MnO 2 and observed the simultaneous presence of Mn and O vacancies in α-MnO 2 crystals at low temperatures. Increasing the temperature removed these O vacancies, leaving only the Mn vacancies in the samples.

Investigation of BIPO decay to measure the purity of 208Tl and 214Bi in the ββ source foils plays an important role in SuperNEMO international colaboration project. In this article, we report the successful results in the measurement of both long and short life of BiPo events with FADC 500Mhz. Especially, a very low of BiPo events from Yunohara powder is correctly detected and measured.

The structure of poly (styrenesulfonic acid)- grafted poly(ethylene-co- tetrafluoroethylene) polymer electrolyte membrane (ETFE-PEM) was investigated by comparison with those of precursor original ETFE film and styrene-grafted films (grafted-ETFE) using positron annihilation lifetime spectroscopy (PALS) and small angle Xray scattering (SAXS). PALS of these samples indicated that there were two lifetime components, which were assigned to the annihilation of ortho- Positronium (o-Ps). The two types of o-Ps relate to the free volume at sub nanoscale locating in the crystalline and amorphous phases. SAXS profiles of these samples indicated the presence of lamellar stacks andlamellar grains. Sizes of lamellar stacks and lamellar grains varied significantly during the graftingprocess, whereas only change a little bit at sulfonation process and at wet state. A compination of PALS and SAXS allowed us to investigate the structures of ETFEPEMs with scale ranging from several Ångströms to micrometer.

The variation of lamellar structures of poly(styrenesulfonic acid)-grafted poly (ethylene-co-tetrafluoroethylene) proton exchange membranes dependence on preparation procedures and grafting degree (GD) was investigated by small angle X-ray scattering. The detail structures of lamellar including lamellar period L, thickness of lamellar crystal Lc, thickness of lamellar amorphous La, and linear crystallinity Lc/L were examined by a 1D correlation function. The lamellar structures were recognized at the grafting step and did not change under the sulfonation process. With GD  79 %, Lc significantly decreased (corresponding to the increase of La) and then retained in the GDs of 79-117 %. Note that the retained values of Lc, La, and linear crystallinity in the GDs of 79-117 % are the origin of high conductivity and mechanical strength of membranes under severe operation conditions for fuel cell applications.