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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on ErNp3 by Materials Project

Np3Er is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Np sites. In the first Np site, Np is bonded to eight Np and four equivalent Er atoms to form NpEr4Np8 cuboctahedra that share corners with twelve equivalent NpEr4Np8 cuboctahedra, edges with eight equivalent ErNp12 cuboctahedra, edges with sixteen NpEr4Np8 cuboctahedra, faces with four equivalent ErNp12 cuboctahedra, and faces with fourteen NpEr4Np8 cuboctahedra. All Np–Np bond lengths are 3.20 Å. All Np–Er bond lengths are 3.20 Å. In the second Np site, Np is bonded to eight equivalent Np and four equivalent Er atoms to form NpEr4Np8 cuboctahedra that share corners with four equivalent NpEr4Np8 cuboctahedra, corners with eight equivalent ErNp12 cuboctahedra, edges with twenty-four NpEr4Np8 cuboctahedra, faces with six equivalent ErNp12 cuboctahedra, and faces with twelve NpEr4Np8 cuboctahedra. All Np–Er bond lengths are 3.20 Å. Er is bonded to twelve Np atoms to form ErNp12 cuboctahedra that share corners with four equivalent ErNp12 cuboctahedra, corners with eight equivalent NpEr4Np8 cuboctahedra, edges with eight equivalent ErNp12 cuboctahedra, edges with sixteen equivalent NpEr4Np8 cuboctahedra, faces with four equivalent ErNp12 cuboctahedra, and faces with fourteen NpEr4Np8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on YNp3 by Materials Project

Np3Y is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Np sites. In the first Np site, Np is bonded to eight Np and four equivalent Y atoms to form NpY4Np8 cuboctahedra that share corners with twelve equivalent NpY4Np8 cuboctahedra, edges with eight equivalent YNp12 cuboctahedra, edges with sixteen NpY4Np8 cuboctahedra, faces with four equivalent YNp12 cuboctahedra, and faces with fourteen NpY4Np8 cuboctahedra. All Np–Np bond lengths are 3.25 Å. All Np–Y bond lengths are 3.25 Å. In the second Np site, Np is bonded to eight equivalent Np and four equivalent Y atoms to form NpY4Np8 cuboctahedra that share corners with four equivalent NpY4Np8 cuboctahedra, corners with eight equivalent YNp12 cuboctahedra, edges with twenty-four NpY4Np8 cuboctahedra, faces with six equivalent YNp12 cuboctahedra, and faces with twelve NpY4Np8 cuboctahedra. All Np–Y bond lengths are 3.25 Å. Y is bonded to twelve Np atoms to form YNp12 cuboctahedra that share corners with four equivalent YNp12 cuboctahedra, corners with eight equivalent NpY4Np8 cuboctahedra, edges with eight equivalent YNp12 cuboctahedra, edges with sixteen equivalent NpY4Np8 cuboctahedra, faces with four equivalent YNp12 cuboctahedra, and faces with fourteen NpY4Np8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HoNp3 by Materials Project

Np3Ho is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Np sites. In the first Np site, Np is bonded to eight Np and four equivalent Ho atoms to form NpHo4Np8 cuboctahedra that share corners with twelve equivalent NpHo4Np8 cuboctahedra, edges with eight equivalent HoNp12 cuboctahedra, edges with sixteen NpHo4Np8 cuboctahedra, faces with four equivalent HoNp12 cuboctahedra, and faces with fourteen NpHo4Np8 cuboctahedra. All Np–Np bond lengths are 3.23 Å. All Np–Ho bond lengths are 3.23 Å. In the second Np site, Np is bonded to eight equivalent Np and four equivalent Ho atoms to form NpHo4Np8 cuboctahedra that share corners with four equivalent NpHo4Np8 cuboctahedra, corners with eight equivalent HoNp12 cuboctahedra, edges with twenty-four NpHo4Np8 cuboctahedra, faces with six equivalent HoNp12 cuboctahedra, and faces with twelve NpHo4Np8 cuboctahedra. All Np–Ho bond lengths are 3.23 Å. Ho is bonded to twelve Np atoms to form HoNp12 cuboctahedra that share corners with four equivalent HoNp12 cuboctahedra, corners with eight equivalent NpHo4Np8 cuboctahedra, edges with eight equivalent HoNp12 cuboctahedra, edges with sixteen equivalent NpHo4Np8 cuboctahedra, faces with four equivalent HoNp12 cuboctahedra, and faces with fourteen NpHo4Np8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np3Hg by Materials Project

Np3Hg is Uranium Silicide-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Np sites. In the first Np site, Np is bonded to eight Np and four equivalent Hg atoms to form distorted NpNp8Hg4 cuboctahedra that share corners with twelve equivalent NpNp8Hg4 cuboctahedra, edges with eight equivalent NpNp8Hg4 cuboctahedra, edges with eight equivalent HgNp12 cuboctahedra, faces with four equivalent HgNp12 cuboctahedra, and faces with ten equivalent NpNp8Hg4 cuboctahedra. There are four shorter (3.21 Å) and four longer (3.27 Å) Np–Np bond lengths. All Np–Hg bond lengths are 3.27 Å. In the second Np site, Np is bonded in a distorted square co-planar geometry to eight equivalent Np and four equivalent Hg atoms. All Np–Hg bond lengths are 3.21 Å. Hg is bonded to twelve Np atoms to form HgNp12 cuboctahedra that share corners with four equivalent HgNp12 cuboctahedra, edges with eight equivalent HgNp12 cuboctahedra, edges with sixteen equivalent NpNp8Hg4 cuboctahedra, faces with four equivalent HgNp12 cuboctahedra, and faces with eight equivalent NpNp8Hg4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np3H by Materials Project

Np3H crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Np sites. In the first Np site, Np is bonded in a 10-coordinate geometry to six Np and four equivalent H atoms. There are three shorter (2.46 Å) and three longer (2.80 Å) Np–Np bond lengths. There are three shorter (2.80 Å) and one longer (2.92 Å) Np–H bond lengths. In the second Np site, Np is bonded in a trigonal planar geometry to six equivalent Np and three equivalent H atoms. All Np–H bond lengths are 2.17 Å. H is bonded in a distorted trigonal planar geometry to eleven Np atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ThNp3 by Materials Project

Np3Th is alpha La-derived structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Np sites. In the first Np site, Np is bonded to eight Np and four equivalent Th atoms to form NpTh4Np8 cuboctahedra that share corners with twelve equivalent NpTh4Np8 cuboctahedra, edges with eight equivalent ThNp12 cuboctahedra, edges with sixteen NpTh4Np8 cuboctahedra, faces with four equivalent ThNp12 cuboctahedra, and faces with fourteen NpTh4Np8 cuboctahedra. There are four shorter (3.21 Å) and four longer (3.25 Å) Np–Np bond lengths. All Np–Th bond lengths are 3.21 Å. In the second Np site, Np is bonded to eight equivalent Np and four equivalent Th atoms to form NpTh4Np8 cuboctahedra that share corners with four equivalent NpTh4Np8 cuboctahedra, corners with eight equivalent ThNp12 cuboctahedra, edges with twenty-four NpTh4Np8 cuboctahedra, faces with six equivalent ThNp12 cuboctahedra, and faces with twelve NpTh4Np8 cuboctahedra. All Np–Th bond lengths are 3.25 Å. Th is bonded to twelve Np atoms to form ThNp12 cuboctahedra that share corners with four equivalent ThNp12 cuboctahedra, corners with eight equivalent NpTh4Np8 cuboctahedra, edges with eight equivalent ThNp12 cuboctahedra, edges with sixteen equivalent NpTh4Np8 cuboctahedra, faces with four equivalent ThNp12 cuboctahedra, and faces with fourteen NpTh4Np8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np3Cd by Materials Project

Np3Cd is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Np sites. In the first Np site, Np is bonded to eight Np and four equivalent Cd atoms to form NpNp8Cd4 cuboctahedra that share corners with twelve equivalent NpNp8Cd4 cuboctahedra, edges with eight equivalent CdNp12 cuboctahedra, edges with sixteen NpNp8Cd4 cuboctahedra, faces with four equivalent CdNp12 cuboctahedra, and faces with fourteen NpNp8Cd4 cuboctahedra. There are four shorter (3.22 Å) and four longer (3.26 Å) Np–Np bond lengths. All Np–Cd bond lengths are 3.26 Å. In the second Np site, Np is bonded to eight equivalent Np and four equivalent Cd atoms to form distorted NpNp8Cd4 cuboctahedra that share corners with four equivalent NpNp8Cd4 cuboctahedra, corners with eight equivalent CdNp12 cuboctahedra, edges with twenty-four NpNp8Cd4 cuboctahedra, faces with six equivalent CdNp12 cuboctahedra, and faces with twelve NpNp8Cd4 cuboctahedra. All Np–Cd bond lengths are 3.22 Å. Cd is bonded to twelve Np atoms to form CdNp12 cuboctahedra that share corners with four equivalent CdNp12 cuboctahedra, corners with eight equivalent NpNp8Cd4 cuboctahedra, edges with eight equivalent CdNp12 cuboctahedra, edges with sixteen equivalent NpNp8Cd4 cuboctahedra, faces with four equivalent CdNp12 cuboctahedra, and faces with fourteen NpNp8Cd4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ZrNp3 by Materials Project

Np3Zr is alpha La-derived structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Np sites. In the first Np site, Np is bonded to eight Np and four equivalent Zr atoms to form NpZr4Np8 cuboctahedra that share corners with twelve equivalent NpZr4Np8 cuboctahedra, edges with eight equivalent ZrNp12 cuboctahedra, edges with sixteen NpZr4Np8 cuboctahedra, faces with four equivalent ZrNp12 cuboctahedra, and faces with fourteen NpZr4Np8 cuboctahedra. There are four shorter (3.06 Å) and four longer (3.19 Å) Np–Np bond lengths. All Np–Zr bond lengths are 3.19 Å. In the second Np site, Np is bonded to eight equivalent Np and four equivalent Zr atoms to form NpZr4Np8 cuboctahedra that share corners with four equivalent NpZr4Np8 cuboctahedra, corners with eight equivalent ZrNp12 cuboctahedra, edges with twenty-four NpZr4Np8 cuboctahedra, faces with six equivalent ZrNp12 cuboctahedra, and faces with twelve NpZr4Np8 cuboctahedra. All Np–Zr bond lengths are 3.06 Å. Zr is bonded to twelve Np atoms to form ZrNp12 cuboctahedra that share corners with four equivalent ZrNp12 cuboctahedra, corners with eight equivalent NpZr4Np8 cuboctahedra, edges with eight equivalent ZrNp12 cuboctahedra, edges with sixteen equivalent NpZr4Np8 cuboctahedra, faces with four equivalent ZrNp12 cuboctahedra, and faces with fourteen NpZr4Np8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2022

O 2 Oxidation and Sublimation Kinetics of Single Silicon Nanoparticles at 1200–2050 K: Variation of Reaction Rates, Evolution of Structural and Optical Properties, and the Active-to-Passive Transition

Sublimation and O 2 etching kinetics for a series of individual silicon (Si) nanoparticles (NPs) were studied for NP temperatures (T NP ) from 1200 to 2050 K, using a single NP mass spectrometry technique. Sublimation was significant for T NP > 1700 K, with rates reasonably well fit to Arrhenius kinetics, but evolving, particularly during initial heating. O 2 etching efficiencies varied from NP-to-NP and with changing T NP , but also evolved dramatically over time. For T NP ≤ 1500 K, NPs were observed to passivate after losing 30 to 50% of the initial NP mass. At higher T NP , etching efficiency decreased over time, but never passivated. Interestingly, bulk Si passivation has not been observed for the range of T NP and O 2 pressures used here, and a model was developed to test the effects of several NP-specific mechanistic parameters on both the initial and time-dependent etching behavior. As a result, the optical properties of the hot NPs were also found to evolve as the NPs etched, particularly during the initial fast mass loss, and correlations between emission intensities and etching kinetics were examined.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

Materials Data on Np3Be by Materials Project

BeNp3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Be is bonded in a distorted body-centered cubic geometry to fourteen Np atoms. There are eight shorter (2.73 Å) and six longer (3.15 Å) Be–Np bond lengths. There are two inequivalent Np sites. In the first Np site, Np is bonded in a distorted body-centered cubic geometry to four equivalent Be and four equivalent Np atoms. All Np–Np bond lengths are 2.73 Å. In the second Np site, Np is bonded in a 8-coordinate geometry to six equivalent Be and eight equivalent Np atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg3Np by Materials Project

Mg3Np is alpha bismuth trifluoride structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are three inequivalent Mg sites. In the first Mg site, Mg is bonded in a distorted body-centered cubic geometry to eight equivalent Mg and six Np atoms. All Mg–Mg bond lengths are 3.17 Å. There are two shorter (3.66 Å) and four longer (3.67 Å) Mg–Np bond lengths. In the second Mg site, Mg is bonded in a body-centered cubic geometry to four Mg and four Np atoms. Both Mg–Mg bond lengths are 3.17 Å. All Mg–Np bond lengths are 3.17 Å. In the third Mg site, Mg is bonded in a distorted body-centered cubic geometry to eight equivalent Mg and six Np atoms. There are two shorter (3.66 Å) and four longer (3.67 Å) Mg–Np bond lengths. There are two inequivalent Np sites. In the first Np site, Np is bonded in a distorted body-centered cubic geometry to fourteen Mg atoms. In the second Np site, Np is bonded in a distorted body-centered cubic geometry to fourteen Mg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Np3Se5 by Materials Project

Np3Se5 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Np+3.33+ sites. In the first Np+3.33+ site, Np+3.33+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of Np–Se bond distances ranging from 2.91–3.12 Å. In the second Np+3.33+ site, Np+3.33+ is bonded to seven Se2- atoms to form distorted edge-sharing NpSe7 pentagonal bipyramids. There are a spread of Np–Se bond distances ranging from 2.79–2.96 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to four Np+3.33+ atoms to form distorted SeNp4 trigonal pyramids that share corners with six SeNp5 square pyramids, corners with two equivalent SeNp5 trigonal bipyramids, corners with six equivalent SeNp4 trigonal pyramids, edges with three SeNp5 square pyramids, edges with two equivalent SeNp5 trigonal bipyramids, and an edgeedge with one SeNp4 trigonal pyramid. In the second Se2- site, Se2- is bonded to five Np+3.33+ atoms to form SeNp5 square pyramids that share corners with four equivalent SeNp5 square pyramids, corners with five equivalent SeNp5 trigonal bipyramids, corners with eight equivalent SeNp4 trigonal pyramids, edges with three SeNp5 square pyramids, edges with two equivalent SeNp5 trigonal bipyramids, edges with two equivalent SeNp4 trigonal pyramids, and a faceface with one SeNp5 square pyramid. In the third Se2- site, Se2- is bonded to five Np+3.33+ atoms to form distorted SeNp5 trigonal bipyramids that share corners with six SeNp5 square pyramids, corners with four equivalent SeNp5 trigonal bipyramids, corners with four equivalent SeNp4 trigonal pyramids, edges with six SeNp5 square pyramids, and edges with four equivalent SeNp4 trigonal pyramids. In the fourth Se2- site, Se2- is bonded to five Np+3.33+ atoms to form distorted SeNp5 square pyramids that share corners with eight SeNp5 square pyramids, a cornercorner with one SeNp5 trigonal bipyramid, corners with four equivalent SeNp4 trigonal pyramids, an edgeedge with one SeNp5 square pyramid, edges with four equivalent SeNp5 trigonal bipyramids, edges with four equivalent SeNp4 trigonal pyramids, and a faceface with one SeNp5 square pyramid.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaNp3 by Materials Project

NaNp3 is alpha bismuth trifluoride structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Na is bonded to twelve Np atoms to form NaNp12 cuboctahedra that share corners with four equivalent NaNp12 cuboctahedra, corners with eight equivalent NpNa4Np8 cuboctahedra, edges with eight equivalent NaNp12 cuboctahedra, edges with sixteen equivalent NpNa4Np8 cuboctahedra, faces with four equivalent NaNp12 cuboctahedra, and faces with fourteen NpNa4Np8 cuboctahedra. There are eight shorter (3.18 Å) and four longer (3.30 Å) Na–Np bond lengths. There are two inequivalent Np sites. In the first Np site, Np is bonded to four equivalent Na and eight Np atoms to form distorted NpNa4Np8 cuboctahedra that share corners with twelve equivalent NpNa4Np8 cuboctahedra, edges with eight equivalent NaNp12 cuboctahedra, edges with sixteen NpNa4Np8 cuboctahedra, faces with four equivalent NaNp12 cuboctahedra, and faces with fourteen NpNa4Np8 cuboctahedra. There are four shorter (3.18 Å) and four longer (3.30 Å) Np–Np bond lengths. In the second Np site, Np is bonded to four equivalent Na and eight equivalent Np atoms to form NpNa4Np8 cuboctahedra that share corners with four equivalent NpNa4Np8 cuboctahedra, corners with eight equivalent NaNp12 cuboctahedra, edges with twenty-four NpNa4Np8 cuboctahedra, faces with six equivalent NaNp12 cuboctahedra, and faces with twelve NpNa4Np8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NpPd3 by Materials Project

NpPd3 is Uranium Silicide-like structured and crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent Np sites. In the first Np site, Np is bonded to twelve Pd atoms to form NpPd12 cuboctahedra that share corners with six equivalent NpPd12 cuboctahedra, edges with twelve PdNp4Pd8 cuboctahedra, faces with six PdNp4Pd8 cuboctahedra, and faces with eight NpPd12 cuboctahedra. There are a spread of Np–Pd bond distances ranging from 2.92–2.99 Å. In the second Np site, Np is bonded to twelve Pd atoms to form NpPd12 cuboctahedra that share corners with twelve equivalent NpPd12 cuboctahedra, edges with twelve PdNp4Pd8 cuboctahedra, faces with six equivalent NpPd12 cuboctahedra, and faces with six PdNp4Pd8 cuboctahedra. There are a spread of Np–Pd bond distances ranging from 2.92–2.95 Å. There are four inequivalent Pd sites. In the first Pd site, Pd is bonded in a distorted square co-planar geometry to four Np and four Pd atoms. All Pd–Pd bond lengths are 2.93 Å. In the second Pd site, Pd is bonded in a distorted square co-planar geometry to four Np and four equivalent Pd atoms. All Pd–Pd bond lengths are 2.93 Å. In the third Pd site, Pd is bonded to four Np and eight Pd atoms to form distorted PdNp4Pd8 cuboctahedra that share corners with twelve equivalent PdNp4Pd8 cuboctahedra, edges with eight NpPd12 cuboctahedra, edges with eight equivalent PdNp4Pd8 cuboctahedra, faces with four NpPd12 cuboctahedra, and faces with four equivalent PdNp4Pd8 cuboctahedra. There are two shorter (2.83 Å) and two longer (3.03 Å) Pd–Pd bond lengths. In the fourth Pd site, Pd is bonded to four Np and eight Pd atoms to form distorted PdNp4Pd8 cuboctahedra that share corners with twelve equivalent PdNp4Pd8 cuboctahedra, edges with eight NpPd12 cuboctahedra, edges with eight PdNp4Pd8 cuboctahedra, faces with four NpPd12 cuboctahedra, and faces with four PdNp4Pd8 cuboctahedra. There are one shorter (2.83 Å) and one longer (3.01 Å) Pd–Pd bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Identification of 2,2-dinitropropanol, a Hydrolyzed Product of Aged Eutectic Bis(2,2-dinitropropyl) Acetal – Bis(2,2-dinitropropyl) Formal Mixture

Eutectic bis(2,2-dinitropropyl) acetal - bis(2,2-dinitropropyl) formal mixture, nitroplasticizer (herein called NP) has historically been produced by either the ter Meer or oxidative nitration synthesis process, wherein 2,2-dinitropropanol (DNPOH) is produced as an intermediate step in both processes. Therefore that DNPOH, could be present in NP either as a production or hydrolysis degradation product is worth investigation. Here, we synthesized DNPOH, validated the synthesis using NMR, and identified DNPOH in aged NP using liquid chromatography tandem time of flight – quadrupole mass spectrometry (LC-QTOF). Using these results, for the first time we positively identify that DNPOH is absent from NP after its production, but is present as a degradation product through hydrolysis from a thermo-chemical aging profile of NP. To hydrolyze NP, prerequisite is the presence of both water and acid. Despite the presence of water in NP, DNPOH is only generated in the late stage of the aging process, when acid concentration is sufficiently high. It has been previously shown both theoretically and experimentally that a primary step of NP degradation is HONO elimination followed by decomposition, wherein nitric acid, nitrous acid, and water are produced (NP→NP’+2HONO and 2HONO→NO+NO 2 +H 2 O). It is shown from this reaction series that water slows HONO decomposition and therefore in small quantities, 100 s of ppm, water actually stabilizes NP against hydrolysis by equilibrium and reducing acidity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Catalytic Transformation of Positional Nitrophenol Isomers on Highly Active Ag/Linde‐Type A4 Zeolite: A Comparative Analysis

Abstract The catalytic transformation of ortho‐( o‐ NP), meta‐( m‐ NP) and para‐nitrophenols ( p‐ NP) by Ag nanoparticles (Ag‐NPs) stabilised on zeolite A4 (ZA4) is presented for the first time. The catalysts are prepared by microwave‐assisted synthesis (Ag/ZA4‐MW) or ion exchange (Ag/ZA4‐IE). The results indicate that the nitrophenol reduction rate depends on the molecule structure and the presence of low‐coordinated metallic Ag‐NPs (∼2 nm and sub nanometric species). Meanwhile, the reactivity tendency depends on the synthesis methodology ( m‐ NP> p‐ NP> o‐ NP and o‐ NP> m‐ NP> p‐ NP for Ag/ZA4‐MW and Ag/ZA4‐IE, respectively). The turnover frequency (TOF) values estimated for nitrophenols reduction are superior for Ag/ZA4‐MW catalyst by several orders of magnitude compared with those obtained for Ag/ZA4‐IE catalyst. In addition, the catalyst exhibits remarkable catalytic stability for the reduction of p‐ NP even after the fifth consecutive catalytic run. The presently prepared catalysts are characterised by superior catalytic activity for the reduction of nitroaromatic compounds than similar Ag‐based materials reported in the literature.

Horta‐Fraijo, Patricia↗
DOE OSTI2022

Dinuclear Complexes of Uranyl, Neptunyl, and Plutonyl: Structures and Oxidation States Revealed by Experiment and Theory

Dinuclear perchlorate complexes of uranium, neptunium, and plutonium were characterized by reactivity and DFT, with results revealing structures containing pentavalent, hexavalent, and heptavalent actinyls, and actinyl-actinyl interactions (AAIs). Electrospray ionization produced native complexes [(AnO 2 ) 2 (ClO 4 ) 3 ] - for An:An = U:U, Np:Np, Pu:Pu, and Np:Pu, which are intuitively formulated as actinyl(V) perchlorates. However, DFT identified lower-energy structures [(AnO 2 )(AnO 3 )(ClO 4 ) 2 (ClO 3 )] - comprising a perchlorate fragmented to ClO 3 , actinyl(VI) cation An VI O 2 2+ , and neutral AnO 3 . For U:U and Np:Np, and Np in Np:Pu, the coordinated AnO 3 is calculated as actinyl(VI) with an equatorial oxo, [O yl =An VI =O yl ][=O eq ], whereas for Pu:Pu, it is plutonyl(V) oxyl, [O yl =Pu V =O yl ][-O eq • ]. The implied lower stability of Pu VI versus Np VI indicates weaker Pu=O eq versus Np=O eq bonding. Adsorption of O 2 by the U:U complex suggests oxidation of U V to U VI , corroborating the assignment of perchlorate [(An V O 2 ) 2 (ClO 4 ) 3 ] - . DFT predicts the O 2 adducts are [(An VI O 2 )(O 2 )(An VI O 2 )(ClO 4 ) 3 ] - with actinyls oxidized from +V to +VI by bridging peroxide, O 2 2- . In accordance with reactivity, O 2- addition is computed as substantially exothermic for U:U and least favorable for Pu:Pu. Collision-induced dissociation of native complexes eliminated ClO 2 to yield [(AnO 2 )(O) 2 (AnO 2 )(ClO 4 ) 2 ] - , in which fragmented O atoms bridge as oxyl O -• and oxo O 2- to yield uranyl(VI) and plutonyl(VI), or as oxos O 2- to yield neptunyl(VII), [O yl =Np VII =O yl ] 3+ .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Collective Nanoparticle Dynamics Associated with Bridging Network Formation in Model Polymer Nanocomposites

The addition of nanoparticles (NPs) to polymers is a powerful method to improve the mechanical and other properties of macromolecular materials. Such hybrid polymer–particle systems are also rich in fundamental soft matter physics. Among several factors contributing to mechanical reinforcement, a polymer-mediated NP network is considered to be the most important in polymer nanocomposites (PNCs). Here, we present an integrated experimental–theoretical study of the collective NP dynamics in model PNCs using X-ray photon correlation spectroscopy and microscopic statistical mechanics theory. Silica NPs dispersed in unentangled or entangled poly(2-vinylpyridine) matrices over a range of NP loadings are used. Static collective structure factors of the NP subsystems at temperatures above the bulk glass transition temperature reveal the formation of a network-like microstructure via polymer-mediated bridges at high NP loadings above the percolation threshold. The NP collective relaxation times are up to 3 orders of magnitude longer than the self-diffusion limit of isolated NPs and display a rich dependence with observation wavevector and NP loading. A mode-coupling theory dynamical analysis that incorporates the static polymer-mediated bridging structure and collective motions of NPs is performed. It captures well both the observed scattering wavevector and NP loading dependences of the collective NP dynamics in the unentangled polymer matrix, with modest quantitative deviations emerging for the entangled PNC samples. Here, we identify an unusual and weak temperature dependence of collective NP dynamics, in qualitative contrast with the mechanical response. Hence, the present study has revealed key aspects of the collective motions of NPs connected by polymer bridges in contact with a viscous adsorbing polymer medium and identifies some outstanding remaining challenges for the theoretical understanding of these complex soft materials.

36 MATERIALS SCIENCE↗