ABSTRACT
There is an urgent need for new, better instrumentation and techniques for detecting and characterizing special nuclear material (SNM), i.e., highly enriched uranium and plutonium. The development of improved instruments and techniques requires experiments performed with the SNM itself, which is of limited availability. This paper describes the findings of experiments performed at the National Criticality Experiments Research Center conducted using new instruments and techniques on unclassified, kg-quantity SNM objects. These experiments, performed in the framework of the Department of Energy, National Nuclear Security Administration Consortium for Monitoring, Technology, and Verification, focused on detecting, characterizing, and localizing SNM samples with masses ranging from 3.3 to 13.8 kg, including plutonium and highly enriched uranium using prototype detectors and techniques. The work demonstrates SNM detection and characterization using recently-developed prototype detection systems. Specifically, we present new results in passive detection and imaging of plutonium and uranium objects using gamma-ray and dual particle (fast neutron and gamma-ray) imaging. We also present a new analysis of the delayed neutron emissions during active interrogation of uranium using a neutron generator.
ABSTRACT
In the present investigation, we report the transformation of alpha-LiVOPO 4 to alpha-Li 3V 2(PO 4) 3, leading to an enhancement of capacity. The alpha-LiVOPO 4 sample was synthesized by a sol-gel method, followed by sintering at 550-650 degrees C in a flow of 5% H 2/Ar. The structural transformation of a triclinic alpha-LiVOPO 4 structure to a monoclinic alpha-Li 3V 2(PO 4) 3 structure was observed at higher sintering temperatures (700-800 degrees C in a flow of 5% H 2/Ar). The alpha-Li 3V 2(PO 4) 3 phase was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermal gravimetric analysis, and X-ray absorption near edge spectrum (XANES) techniques. The valence shift of vanadium ions from +4 to +3 states was observed using in situ XANES experiments at V K-edge. The structural transformation is ascertained by the shape changes in pre-edge and near edge area of X-ray absorption spectrum. It was observed that the capacity was enhanced from 140 mAh/g to 164 mAh/g via structural transformation process of LiVOPO 4 to Li 3V 2(PO 4) 3.
ABSTRACT
In this paper, we report the synthesis of carbon coated Li(Mn0.35Co 0.2Fe0.45)PO4 and discuss the effect of Co2P formation during the carbothermal reduction process, which enhances the electrochemical performance of cathode material for lithium ion batteries. It was observed that Co2P was favorably formed in 5% H2/Ar than in Ar atmosphere. The conductivity of Li(Mn0.35Co0.2Fe0.45)PO4/C sintered at 600-800 degrees C in 5% H2/Ar is increased as the temperature is increased. The O K-edge X-ray absorption near edge spectrum (XANES) demonstrates that content of hole carriers is increased in Li(Mn0.35Co0.2Fe0.45)PO4/C as the amount of Co2P increased. We also observed that the capacity of Li(Mn0.35Co0.2Fe0.45)PO4/C is increased with sintering temperature, and it exhibited a maximum capacity of 166 mAh/g at 700 degrees C. It was found that the enhancement in the discharge capacity of sintered Li(Mn0.35Co0.2Fe0.45)PO4/C was as a result of its higher electrical conductivity under 5% H2/Ar atmosphere as compared with Ar atmosphere.
ABSTRACT
A significant enhancement of zero resistance temperature [T(c(zero))] from 78 K for x = 0 to 92.5 K for x = 0.2 in the series (Hg(0.5)Pb(0.5))(Sr(2-x)Ba(x))(Ca(0.7)Y(0.3))Cu(2)O(7-delta) compounds has been found. On the basis of the O K-edge X-ray-absorption near-edge structure (XANES) spectra for the series of (Hg(0.5)Pb(0.5))(Sr(2-x)Ba(x))(Ca(0.7)Y(0.3))Cu(2)O(7-delta) samples with x = 0-0.5, the chemical substitution of Ba(2+) for Sr(2+) gives rise to a decrease in the O 2p hole concentration within the out-of-plane oxygen sites, while that within the in-plane CuO(2) layers remains almost unchanged for 0
ABSTRACT
An equation of the form K=C/[1 - (V/V max)]n relating the bulk modulus K to the relative volume V/V max of lung region during inflation-deflation maneuvers is proposed. It well represents the observed fact that the bulk modulus becomes infinitely large when the regional volume approaches its maximum capacity V max. The parameter C describes the bulk modulus at low regional volume whereas the parameter n quantifies the rate at which the bulk modulus changes during the inflation-deflation maneuvers. The mathematical expressions for the regional pressure, P, and volume V , are obtained by integrating the equation K=VdP/dV. They fit exceedingly well with the experimental data recorded during inflation-deflation tests of six excised canine lung lobes.
