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1
Wrackmeyer, Bernd, und Elena V. Klimkina. „Spin-Spin Coupling Constants 1J(27Al,13C) and 1J(13C,11B) in Comparable Organoaluminum and -boron Compounds. NMR Spectroscopy of Lithium Tetra(tert-butyl)alanate“. Zeitschrift für Naturforschung B 63, Nr. 8 (01.08.2008): 923–28. http://dx.doi.org/10.1515/znb-2008-0801.
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The 13C, 27Al and 11B NMR spectra of tri(tert-butyl)alane, AlBut3, and of the corresponding borane, BBut3, respectively, were examined in order to determine the magnitude of the coupling constants 1J(27Al,13C) = 94±5 Hz and 1J(13C,11B) = 52±2 Hz by measurement of the line widths of the 13C NMR signals and of the relaxation rates of the quadrupolar 27Al and 11B nuclei. This is the first example of 1J(27Al,13C) determined for a monomeric trialkylalane. In addition, the coupling constants were calculated by DFT methods (B3LYP) using the 6-311+G(d,p) basis set. The 1H, 13C and 27Al NMR spectra of lithium tetra(tert-butyl)alanate, Li[AlBut4], were measured under various conditions. Ion-pair separation in THF revealed the expected patterns for 27Al-13C spin-spin coupling across one and two bonds as well as for the three-bond 27Al-1H spin-spin coupling.
2
Wong, Alan, Mark E. Smith, Victor Terskikh und Gang Wu. „Obtaining accurate chemical shifts for all magnetic nuclei (1H, 13C, 17O, and 27Al) in tris(2,4-pentanedionato-O,O′)aluminium(III) — A solid-state NMR case study“. Canadian Journal of Chemistry 89, Nr. 9 (September 2011): 1087–94. http://dx.doi.org/10.1139/v11-046.
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We report a complete set of high-resolution solid-state NMR spectra for all magnetic nuclei (1H, 13C, 17O, and 27Al) in the α-form of tris(2,4-pentanedionato-O,O′)aluminium(III), α-Al(acac)3. These high-resolution NMR spectra were obtained by using a host of solid-state NMR techniques: standard cross-polarization under the magic-angle spinning (CPMAS) method for 13C, 1-D homonuclear decoupling using the windowed DUMBO sequence for 1H, double-rotation (DOR) for 17O and 27Al, and multiple-quantum MAS for 27Al. Some experiments were performed at multiple magnetic fields. We show that the isotropic chemical shifts obtained for 1H, 13C, 17O, and 27Al nuclei in α-Al(acac)3 are highly resolved and accurate, regardless of the nature of the targeted nuclear spins (i.e., spin-1/2 or quadrupolar) and, as such, can be treated equally in comparison with computational chemical shifts obtained from a gauge-including projector-augmented wave (GIPAW) plane-wave pseudopotential DFT method.
3
Uddin, Md Shuza, K. A. Rafee, S. M. Hossain, R. Khan und S. M. Qaim. „Integral measurement of spectrum-averaged cross sections of a few threshold reactions induced by fast neutrons of a TRIGA reactor: comparison with integrated data from excitation functions given in various data libraries“. Radiochimica Acta 108, Nr. 7 (28.07.2020): 511–16. http://dx.doi.org/10.1515/ract-2019-3212.
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AbstractIntegral cross sections of the reactions 24Mg(n,p)24Na, 27Al(n,p)27Mg, 27Al(n,α)24Na, 58Ni(n,d + np)57Co and 60Ni(n,p)60Co were measured for the first time using the fast neutron spectrum of a TRIGA reactor extending from 0.5 to 20 MeV. The values obtained in this work were comparable with the recommended values for a pure 235U prompt fission spectrum. The measured integral value was utilized for integral test of excitation function of each reaction given in some data libraries, namely ENDF/B-VIII.0, TENDL-2017, IRDFF-1.05 and ROSFOND-2010. The integral measurements are generally consistent with the integrated values within 5 %, except for a few cases, e. g. the reaction 60Ni(n,p)60Co, where the data libraries appear to need improvement.
4
Kalamara, A., M. Serris, A. Spiliotis, D. Sigalos, N. Patronis, M. Kokkoris, M. Diakaki, M. Axiotis, A. Lagoyannis und R. Vlastou. „Activation cross section of the (n,2n) reaction on Hf isotopes“. HNPS Proceedings 23 (08.03.2019): 47. http://dx.doi.org/10.12681/hnps.1906.
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Cross sections of the 174Hf(n,2n)173Hf and 176Hf(n,2n)175Hf reactions have been experimentally determined relative to the 27Al(n,α)24Na reference reaction at incident neutron energies of 15.3 and 17.1 MeV by means of the activation technique. The irradiations were carried out at the 5 MV tandem T11/25 Accelerator Laboratory of NCSR "Demokritos" with monoenergetic neutron beams provided via the 3H(d,n)4He reaction, using a new Ti-tritiated target of 373 GBq activity. In the determination of the 176Hf(n,2n)175Hf reaction cross section the contamination of the 174Hf(n,γ)175Hf and 177Hf(n,3n)175Hf reactions has been taken into account. Moreover, the neutron beam energy has been studied by means of Monte Carlo simulation codes and the neutron flux has been determined via the 27Al(n,α)24Na reference reaction.
5
Boughriet, Abdel, Oscar Allahdin, Nicole Poumaye, Gildas Doyemet, Grégory Tricot, Bertrand Revel, Baghdad Ouddane und Michel Wartel. „Alkali-Activated Brick Aggregates as Industrial Valorized Wastes: Synthesis and Properties“. Ceramics 6, Nr. 3 (14.08.2023): 1765–87. http://dx.doi.org/10.3390/ceramics6030108.
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In recent works, many industrial by-products were employed as solid precursors for the synthesis of alkali-activated binders and as alternatives to Portland cement for the immobilization of hazardous, toxic and nuclear wastes. Among industrial wastes, alkali-activated brick was found to be an interesting porous composite for removing very toxic heavy metals (Pb2+, Cd2+, Co2+) and radio-nuclides (Sr2+, Cs+, Rb+) from aqueous solutions. The starting material is very attractive due to the presence of metakaolinite as a geo-polymer precursor and silica for increasing material permeability and facilitating water filtration. The alkaline reaction gave rise to geo-polymerization followed by partial zeolitization. Elemental surface micro-analysis was performed by Scanning Electron Microscopy (SEM) equipped with an Energy-Dispersive X-ray Spectrometer (EDS). The formation of crystalline phases was corroborated by X-ray diffraction (XRD) analysis. Information about 29Si, 27Al and 1H nuclei environments in crystallized and amorphous aluminosilicates was obtained by 29Si, 27Al and 1H MAS NMR. 27Al–1H dipolar-mediated correlations were investigated by employing dipolar hetero-nuclear multiple quantum coherence (D-HMQC) NMR, highlighting Al–O–H bonds in bridging hydroxyl groups (Si–OH–Al) that are at the origin of adsorptive properties. Aqueous structural stability and cationic immobilization characteristics before and after material calcination were investigated from acid-leaching experiments.
6
Рыжков, В. А., und М. В. Журавлев. „Определение стехиометрии покрытий AlN радиоактивацией сгустками коллективно ускоренных дейтронов“. Письма в журнал технической физики 49, Nr. 13 (2023): 39. http://dx.doi.org/10.21883/pjtf.2023.13.55736.19515.
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The use of deuteron bunches collectively accelerated in a Luce diode to an average energy of 1200±200 keV and a number of 1013 per shot is shown for the radioactive determination of the stoichiometry of AlN coatings with a known thickness. In each shot, the deuteron energy was determined by measuring the drift velocity of the virtual cathode collectively accelerating deuteron bunches, and the coating stoichiometry was determined with an accuracy of no worse than ±5% from the ratio of the activities of the 28Al/15O radionuclides induced in the nuclear reactions 27Al(d,p)28Al and 14N( d,n)15O, respectively.
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Noli, F., und P. Misaelides. „Application of Nuclear Techniques to the Investigation of the Oxidation Behavior of Ion-Implanted Steels“. HNPS Proceedings 7 (05.12.2019): 222. http://dx.doi.org/10.12681/hnps.2422.
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The oxidation behavior of ion-implanted steel samples in air, using Nuclear Reaction Analysis (NRA) and Rutherford Backscattering Spectroscopy (RBS) techniques. Austenitic stainless steel AISI 321 (Fe/Crl8/Ni8/Mn2/Ti) samples implanted with magnesium-, aluminum- and zirconium-ions (implantation energy 40 keV, dose: 1-1017 to 2-1017 ions/cm2) were oxidized in air in the temperature region 450-650 °C for several periods of time. The above implants were selected on the basis of the affinity to oxygen, as well as their ability to form protective oxides as MgO, AI2O3, Zr02 in order to improve the oxidation resistance of steel. The determination of the oxygen concentration and depth-profiles was performed by means of the 160(d, p)170 nuclear reaction. Rutherford Backscattering Spectroscopy was applied to investigate the near-surface layers and to determine the depth profiles of the implanted ions. The determination of the aluminum concentration and the depth distribution of the Al-ions was performed using the resonance at 992 keV of the 27Al(p, 7)28Si nuclear reaction whereas the concentration and the depth distribution of the Mg-ions by the means of the 24Mg(o;, p)27Al reaction. The excitation function of the 24Mg(a:, p)27Al nuclear reaction was studied in the energy region 4600-5000 keV and absolute cross section data allowing the determination of the Mg-profile were determined for this purpose.
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Ryzhkov, V. A., I. N. Pyatkov, E. V. Kibler, M. V. Zhuravlev und G. E. Remnev. „Comparison of collective accelaration of protons and deuterons in Luce diode with a polyethylene anode“. Izvestiya vysshikh uchebnykh zavedenii. Fizika 64, Nr. 1 (2021): 130–33. http://dx.doi.org/10.17223/00213411/64/1/130.
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Collective acceleration of protons and deuterons is compared in the same geometry of a Luce diode with a polyethylene anode at an accelerating diode voltage of 250 kV, current and pulse duration of relativistic electrons up to 30 kA and 90 ns, respectively. The accelerated ions were intercepted by B4C, BN, and AlN plates, in which analytical radionuclides were produced according to nuclear reactions 10B( p , α)7Be, 12C( p, γ)13N, 10B( d , n )11C, 12C( d , n )13N, 14N( d , n )15O and 27Al( d , p )28Al. The ion energy was determined according to the ratios of activity of the analytical radionuclides, while the number of accelerated ions was calculated from the number of induced nuclei of the radionuclides. It was found that the velocities of the main group of protons and deuterons were the same within the measurement error, and the average number of ions accelerated in one pulse was, on average, 3 times higher when protons were accelerated.
9
Kovalchuk, V. I. „Inclusive reactions of stripping and fragmentation involving light cluster nuclei at intermediate energies“. Nuclear Physics and Atomic Energy 23, Nr. 1 (25.03.2022): 20–25. http://dx.doi.org/10.15407/jnpae2022.01.020.
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In the framework of eiconal approximation and the double folding model, a formalism for calculating inclusive spectra of particles from stripping and fragmentation reactions involving light cluster nuclei is proposed. The cross-section of the 12C(3He, d)13N reaction at an incident particle energy of 81.4 MeV and the proton spectra from the deuteron fragmentation reaction with 56 MeV energies by 12C and 27Al nuclei are described. The calculated values satisfactorily fit the corresponding experimental data.
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Madej, Dominika. „Strontium Retention of Calcium Zirconium Aluminate Cement Paste Studied by NMR, XRD and SEM-EDS“. Materials 13, Nr. 10 (21.05.2020): 2366. http://dx.doi.org/10.3390/ma13102366.
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This work concerns the hydration mechanism of calcium zirconium aluminate as a ternary compound appearing in the CaO-Al2O3-ZrO2 diagram besides the calcium aluminates commonly used as the main constitutes of calcium aluminate cements (CACs). Moreover, a state-of-the-art approach towards significant changes in hydraulic properties was implemented for the first time in this work, where the effect of structural modification on the hydration behavior of calcium zirconium aluminate was proved by XRD, 27Al MAS NMR and SEM-EDS. The substitution of Sr2+ for Ca2+ in the Ca7ZrAl6O18 lattice decreases the reactivity of Sr-substituted Ca7ZrAl6O18 in the presence of water. Since the original cement grains remain unhydrated up to 3 h (Ca7ZrAl6O18) or 72 h (Sr1.25Ca5.75ZrAl6O18) of curing period in the hardened cement paste structures, strontium can be considered as an inhibition agent for cement hydration. The complete conversion from anhydrous 27AlIV to hydrated 27AlVI species was achieved during the first 24 h (Ca7ZrAl6O18) or 7 d(Sr1.25Ca5.75ZrAl6O18) of hydration. Simultaneously, the chemical shift in the range of octahedral aluminum from ca. 4 ppm to ca. 6 ppm was attributed to the transformation of the hexagonal calcium aluminate hydrates and Sr-rich (Sr,C)3AH6 hydrate into the cubic phase Ca-rich (Sr,C)3AH6 or pure C3AH6 in the hardened Sr-doped cement paste at the age of 7 d. The same 27Al NMR chemical shift was detected at the age of 24 h for the reference hardened undoped Ca7ZrAl6O18 cement paste.
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Kalamara, A., M. Serris, M. Anastasiou, M. Diakaki, M. Kokkoris, N. Patronis, V. Paneta, M. Axiotis, A. Lagoyannis und R. Vlastou. „Activation cross section for the (n,2n) reaction on 197Au“. HNPS Proceedings 22 (08.03.2019): 51. http://dx.doi.org/10.12681/hnps.1930.
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The cross section of the reaction channels 197Au(n,2n)196Aug+m1 and 197Au(n,2n)196Aum2 has been experimentally determined at 15.3 MeV, relative to the 27Al(n,α)24Na reference reaction, using the activation technique. The irradiation was carried out at the 5 MV tandem T11/25 Accelerator Laboratory of NCSR "Demokritos" with monoenergetic neutron beam provided by means of the 3H(d,n)4He reaction, using a new Ti-tritiated target of 373 GBq activity. The induced γ- ray activity was measured with a high resolution HPGe detector.
12
Wrackmeyer, Bernd, Elena V. Klimkina und Wolfgang Milius. „1,3,2-Diazaalumina-[3]ferrocenophanes with Alkyn-1-yl Substituents at Aluminum“. Zeitschrift für Naturforschung B 62, Nr. 10 (01.10.2007): 1259–66. http://dx.doi.org/10.1515/znb-2007-1005.
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The 1,3,2-diazaalumina-[3]ferrocenophane-ethyl(dimethyl)amine adduct 2, containing an Al-H function, reacts with terminal alkynes R-C≡C-H [R = nBu (a), tBu (b), Ph (c), SiMe3 (d)] by elimination of H2 to the amine adducts 4a - d containing an Al-C≡C-R function. Addition of pyridine leads to the corresponding pyridine adducts 5a - d, of which the molecular structure of 5d could be determined by single crystal X-ray diffraction. The formation of 4 is accompanied by side reactions such as trimerization of the alkynes to the 1,3,5-trisubstituted benzene derivatives 6a, c, and some polymerization of the alkynes. The solution-state structures of 4 and 5 were confirmed by multinuclear magnetic resonance spectroscopy (1H, 13C, 27Al, 29Si NMR). Structural features and molecular dynamics were investigated by appropriate 1H/1H NOE and magnetization transfer experiments, and particular attention was paid to the correct assignment of 13C(Al-C≡C-R) NMR signals.
13
Galanopoulos, S., M. Serris, G. Perdikakis, M. Kokkoris, C. T. Papadopoulos, R. Vlastou, A. Lagoyannis et al. „Cross Section Measurements on Isotopes of Ge and Hf Using the Activation Technique“. HNPS Proceedings 14 (05.12.2019): 167. http://dx.doi.org/10.12681/hnps.2267.
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Cross section measurements of neutron induced reactions on isotopes of Ge and Hf have been determined at energies 8.8, 9.6, 10.6, 11.1, 11.4 MeV using the activation technique. Neutrons produced by the 2H(d,n)3He reaction were used to irradiate pellets of natural Ge and Hf02- The neutron flux at the target position was determined using the 27Al(n,a)24Na, 93Nb(n,2n)92mNb and 197Au(n,2n)196Au reference reactions. HPGe detectors of relative efficiency εΓ=80% and 55% were used to determine the decay of the produced unstable nuclei. The cross section values were compared with those taken from the literature.
14
Chasapoglou, Sotirios, Michael Axiotis, George Gkatis, Sotirios Harissopulos, Michael Kokkoris, Anastasios Lagoyannis, Claudia Lederer-Woods et al. „Cross Section Measurements of (n,x) Reactions at 17.9 MeV Using Highly Enriched Ge Isotopes“. HNPS Advances in Nuclear Physics 28 (17.10.2022): 135–41. http://dx.doi.org/10.12681/hnps.3621.
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Τhe 70Ge(n,2n)69Ge, 72Ge(n,a)69mZn, 72Ge(n,p)72Ga and 73Ge(n,p)73Ga reactions have been measured by means of the activation technique at neutron energy 17.9 MeV. The quasimonoenergetic neutron beam was produced via the 2H(d,n)3He reaction at the 5.5 MV Tandem Van de Graaff accelerator of NCSR “Demokritos.” Isotopically highly enriched targets of 70Ge, 72Ge and 73Ge, provided by the nTOF collaboration at CERN, have been used, thus allowing accurate cross section measurements since no corrections are needed to compensate for the parasitic reactions from neighboring isotopes that exist in the case of using natural Ge target. The cross section has been deduced with respect to the 27Al(n,α)24Na reference reaction.
15
Chasapoglou, S., R. Vlastou, M. Kokkoris, M. Diakaki, V. Michalopoulou, G. Gkatis, A. Stamatopoulos et al. „Cross Section Measurements of (n,x) Reactions at 17.9 and 18.9 MeV Using Highly Enriched Ge Isotopes“. EPJ Web of Conferences 284 (2023): 01003. http://dx.doi.org/10.1051/epjconf/202328401003.
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Nine neutron induced reactions on Ge isotopes (70Ge(n,2n)69Ge, 76Ge(n,2n)75Ge, 73Ge(n,p)73Ga, 72Ge(n,p)72Ga, 73Ge(n,d/np)72Ga, 74Ge(n,d/np)73Ga, 74Ge(n,α)71mZn, 72Ge(n,α)69mZn, 73Ge(n,nα)69mZn) have been measured in this work at energies 16.4-18.9 MeV. For these reactions, most of the experimental datasets in literature were obtained with a natGe target. However, the residual nucleus produced by some reaction channels can also be produced from neighboring isotopes, acting as a contamination for the measured reactions. This contribution must be subtracted, based on theoretical calculations, bearing their own uncertainties. The use of enriched targets however, does not suffer from such contaminations, leading to accurate experimental results. In this scope, five highly isotopically enriched Ge samples have been used in this work. The quasi-monoenergetic neutron beams were produced via the 3H(d,n)4He reaction at the 5.5 MV Tandem Van de Graaff accelerator of N.C.S.R. ‘Demokritos’. The cross section of these nine reactions were measured using the activation method, with respect to the 27Al(n,α)24Na reference reaction.
16
Vlastou, R., D. Sigalas, A. Kalamara, M. Kokkoris, M. Anastasiou, M. Diakaki, M. Axiotis und A. Lagoyannis. „Neutron Beam Characterization at the Athens Tandem Accelerator NCSR “Demokritos”“. HNPS Proceedings 23 (08.03.2019): 34. http://dx.doi.org/10.12681/hnps.1904.
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A new Ti-tritiated target of 373 GBq activity has been installed at the 5.5MV tandem T11/25 Accelerator of NCSR "Demokritos", to produce neutrons in the energy range ~15-21 MeV by means of the 3H(d,n)4He reaction. The flux variation of the neutron beam is monitored with a BF3 detector, while the absolute flux is obtained with respect to reference reactions, such as the 27Al(n,a) reference reaction. In absence of time-of-flight capabilities, the energy spectrum of the neutron beam has been investigated by means of Monte Carlo simulations as well as by the Multiple Foil Activation Analysis technique, using reactions with different energy thresholds. The experimental results have been compared with the simulated ones in order to validate the simulations
17
Patronis, N., A. Kalamara, S. Harissopulos, M. Kokkoris, A. Lagoyannis und R. Vlastou. „Study of the 193Ir(n,2n)192Ir Reaction Cross Section“. HNPS Proceedings 24 (01.04.2019): 29. http://dx.doi.org/10.12681/hnps.1840.
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The 193Ir(n,2n)192Ir reaction cross section was measured relative to the 27Al(n,a)24Na and 197Au(n,2n)196Au reactions by means of the activation technique at two neutron beam energies: 10.0 and 10.5 MeV. The neutron beam was produced via the 2H(d,n)3Ηe reaction. The deuteron beam was provided by the 5.5 MV Tandem Van de Graaff accelerator of the N.C.S.R. “Demokritos”. After the irradiations the induced activity of the samples was measured through a 56% relative efficiency HPGe detector. The total reaction cross section for the population of the ground state (4+) and the first isomeric state (1-) was determined. The adopted method for the correction concerning the population of the product nucleus 192Ir through the 191Ir(n,γ)192Ir reaction is also presented.
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Vlastou, R., A. Kalamara, M. Kokkoris, M. Serris, N. Patronis, M. Diakaki, A. Spiliotis et al. „Investigation of (n,2n) reactions using the high energy neutron facility at NCSR “Demokritos”“. HNPS Proceedings 24 (01.04.2019): 117. http://dx.doi.org/10.12681/hnps.1853.
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In the high energy neutron facility at the 5.5MV tandem T11/25 Accelerator of NCSR "Demokritos", the neutron beam is produced by means of the 3H(d,n)4He reaction in the energy range ~15-21 MeV and at a flux of the order of 105 -106 n/cm2s. The beam has been characterized by means of the NeuSDesc and MCNP5 Monte Carlo simulations along with the multiple foil activation technique at various neutron energies. The neutron flux has been deduced using reference reactions, such as the 27Al(n,α) reaction, while the flux variation of the neutron beam was monitored by using a BF3 detector. After the characterization, the neutron beam has been used for (n,2n) reaction cross section measurements on Hf, Au and Ir isotopes via the activation technique. The irradiations were carried out at 15.3 and 17.1 MeV.
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Diakaki, Μ., R. Vlastou, S. Patas, S. Chasapoglou, M. Kokkoris, G. Alamanos, C. Frantzis, M. Axiotis, S. Harissopulos und A. Lagoyannis. „Activation Cross Section Measurement of the (n,2n) Reaction on 203Tl“. EPJ Web of Conferences 284 (2023): 01044. http://dx.doi.org/10.1051/epjconf/202328401044.
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The aim of the present work was to study the cross-section of the (n,2n) reaction on 203Tl, by irradiating a natural TlCl pellet target with monoenergetic neutron beams at 16.4, 18.9 and 19.3 MeV. The cross section of the 203Tl(n,2n)202Tl reaction was measured via the activation method, with respect to the 197Au(n,2n)196Au and 27Al(n,α)24Na reference reactions. At the same time, the 203Tl(n,3n)201Tl was also measured at 18.9 and 19.3 MeV. The monoenergetic neutron beams were generated at the 5.5 MV Tandem accelerator of NCSR “Demokritos”, using the 3H(d,n)4He reaction. In addition, theoretical calculations with the EMPIRE code have been performed, in order to find a suitable model for the description of the experimental data of the present work along with the data from literature.
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Vlastou, R., C. T. Papadopoulos, G. Perdikakis, M. Kokkoris, S. Kossionides, D. Karamanis und P. A. Assimakopoulos. „The Neutron Facility at NCSR "Demokritos"- Implementation in the Case of the 232Th(n,2n) and 241Am(n,2n) Reactions“. HNPS Proceedings 13 (20.02.2020): 136. http://dx.doi.org/10.12681/hnps.2963.
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In the 5.5 MV tandem T11/25 Accelerator Laboratory of NCSR "Demokritos" monoenergetic neutron beams can be produced in the energy ranges 120-650 keV, 4-11.5 MeV and 16-20.5 MeV by using the 7Li(p,n), 2H(d,n) and 3H(d,n) reactions, respectively. The corresponding beam energies and ions delivered by the accelerator, are 1.92-2.37 MeV protons, 0.8-9.6 MeV deuterons and 0.8-3.7 MeV deuterons, for the three reactions, respectively. Experimental results for neutron energies from threshold up to 11.5 MeV and at 17.1 MeV will be given for the 232Th(n,2n)231Th reaction, while for the 241 Am(n,2n)240 Am reaction, preliminary cross section data at 10.4, 10.6 and 17.1 MeV will be discussed. In the framework of the CERN n-TOF collaboration, the cross section of these reactions have been measured relative to the 197Au(n,2n)196Au, 27Al(n,a)24Na and 93Nb(n,2n) reaction cross sections, by using the activation method. In addition to the experimental work, theoretical Statistical model calculations are being carried out using the computer code STAPRE/F. The results are compared to the experimental data.
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Chasapoglou, Sotirios, Roza Vlastou, Michael Kokkoris, Maria Diakaki, Veatriki Michalopoulou, Athanasios Stamatopoulos, Michael Axiotis et al. „Cross Section Measurements of (n,x) Reactions In the Energy Range Between 16.4 and 18.9 MeV Using Highly Enriched Ge Isotopes“. HNPS Advances in Nuclear Physics 29 (05.05.2023): 20–26. http://dx.doi.org/10.12681/hnpsanp.5156.
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In this work, the cross sections of the neutron induced reactions 70Ge(n,2n)69Ge, 76Ge(n,2n)75Ge, 73Ge(n,p)73Ga, 72Ge(n,p)72Ga, 73Ge(n,d/np)72Ga, 74Ge(n,d/np)73Ga, 74Ge(n,α)71mZn, 72Ge(n,α)69mZn, 73Ge(n,nα)69mZn have been measured in the energy range between 16.4 and 18.9 MeV via the activation technique with respect to the 27Al(n,α)24Na reference reaction. Most of the existing experimental datasets found in literature for these reactions, were obtained with the use of a natGe target. In this case however, the residual nucleus produced from some reaction channels, could also be produced from neutron induced reactions in neighboring isotopes that exist in the natGe in their natural abundance, acting as a contamination to the measured yield of the reaction of interest. This parasitic contribution should then be subtracted, based on theoretical calculations that bear their own uncertainties. Isotopically enriched targets on the other hand, do not suffer from such contaminations, leading to more accurate experimental cross section results. In this work, five highly enriched targets have been used that helped in the determination of accurate cross section data, especially in the case of the73Ge(n,d/np)72Ga, 74Ge(n,d/np)73Ga and 73Ge(n,nα)69mZn challenging reactions, that will be presented in detail in this manuscript. The experiments were carried out at the 5.5 MV Tandem Van de Graaff accelerator of N.C.S.R. “Demokritos”, implementing the 3H(d,n)4He reaction for the production of the quasi-monoenergetic neutron beams.
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Perdikakis, G., und Et al. „Measurement of the 241Am(n,2n) Reaction Cross Section, by the Activation Method“. HNPS Proceedings 13 (20.02.2020): 144. http://dx.doi.org/10.12681/hnps.2964.
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The measurement of the cross section of the reaction 241Am(n,2n)240Am, has been performed, for the first time at neutron energies of 8.8, 9.6, 10.6 and 11.4 MeV, by the activation method. The monoenergetic neutron beam was produced at the 5.5MV TANDEM accelerator of NCSR "Demokritos", using the H{d,n) He reaction. During the 5-day long irradiation, the neutron flux was monitored by a BF3, counter. The neutron yield as well as the beam current, were recorded in 100 sec intervals by two multiscaling units. The radioactive target consisted of a 37GBq 241Am source enclosed in a Pb container. A natural Au foil, 27Al foil and a 93Nb foil were used as reference materials for the neutron flux determination. The activity of the irradiated targets, was measured off-line by a 56% relative efficiency, HPGe detector. The first preliminary results are presented and compared with evaluated libraries and existing data.
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Kalamara, A., R. Vlastou, M. Diakaki, M. Kokkoris, M. Anastasiou, V. Paneta, M. Axiotis, A. Lagoyannis und N. G. Nicolis. „Measurement of the 241Am(n,2n)240Am cross section at 17.5 MeV“. HNPS Proceedings 21 (08.03.2019): 160. http://dx.doi.org/10.12681/hnps.2024.
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The 241Am(n,2n)240Am reaction cross section has been measured at neutron beam energy 17.5 MeV, relative to the 27Al(n,α)24Na, 197Au(n,2n)196Au and 93Nb(n,2n)92mNb reference reaction cross sections, using the activation technique. The irradiation was carried out at the Van der Graaff 5.5 MV Tandem accelerator laboratory of NCSR “Demokritos” with monoenergetic neutron beam provided by means of the 3H(d,n)4He reaction, implementing a new Ti-tritiated target. The high purity Am target has been constructed at IRMM, Geel, Belgium and consisted of 40 mg 241Am in the form of AmO2 pressed into pellet with Al2O3 and encapsulated into Al container. Due to this high radioactivity (5 GBq), the Am target was enclosed in a Pb container for safety reasons. After the end of the irradiation, the activity induced by the neutron beam at the target and reference foils, was measured off-line by two 100%, a 50% and a 16% relative efficiency, HPGe detectors.
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Patas, Stavros, Sotiris Chasapoglou, Michalis Axiotis, Maria Diakaki, George Gkatis, Sotirios Harissopulos, Michael Kokkoris, Anastasios Lagoyannis, Eleni Tsivouraki und Roza Vlastou. „Activation Cross Section Measurement of the (n,2n) Reaction on 203Tl at 16.4 MeV, 18.9 MeV and Theoretical Calculations via the EMPIRE code“. HNPS Advances in Nuclear Physics 29 (05.05.2023): 162–66. http://dx.doi.org/10.12681/hnpsanp.5154.
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The aim of the present work was to study the cross-section of the (n,2n) and (n,3n) reactions on 203Tl, by irradiating a natural TlCl pellet target with monoenergetic neutron beams at 16.4, and 18.9 MeV. The cross section measurements were carried out using the activation method, with respect to the 197Au(n,2n)196Au and 27Al(n,α)24Na reference reactions. The monoenergetic neutron beams were generated in the 5.5 MV Tandem accelerator of NCSR “Demokritos”, using the 3H(d,n)4He reaction. Monte Carlo simulations have been performed to take into account the gamma-ray self-absorption results as well as the estimation of the neutron flux through the reference foils. Theoretical calculations with the code EMPIRE have also been performed, using the same parameterization implemented in the theoretical study of Ir and Au nuclei in an attempt to find a suitable model for the description of all the experimental results in this mass region.
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Patas, Stavros. „Activation Cross Section Measurement of the (n,2n) Reaction on 203Tl“. HNPS Advances in Nuclear Physics 28 (17.10.2022): 242–46. http://dx.doi.org/10.12681/hnps.3713.
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The aim of the present work was to study the cross-section of the (n,2n) reaction on 203Tl, by irradiating a natural TlCl pellet target with monoenergetic neutron beam at 18.9 MeV. The cross section of the 203Tl(n,2n)202Tl reaction, was measured implementing the activation method, with respect to the 197Au(n,2n)196Au and 27Al(n,α)24Na reference reactions. The monoenergetic neutron beam was produced in the 5.5 MV Tandem accelerator of NCSR Demokritos, using the 3H(d,n)4He reaction. After the irradiation, the induced activity of the samples was measured with a HPGe detector, which was properly shielded with lead blocks to reduce the contribution of natural radioactivity. Monte Carlo simulations implementing the MCNP code have been performed to take into account the gamma-ray self-absorption results as well as the estimation of the neutron flux through the reference foils. Finally, a comparison of theoretical calculations with the code EMPIRE and experimental data was carried out, with the aim of finding a suitable model for the description of the reaction cross section under study.
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Vlastou, R., A. Kalamara, G. Gkatis, A. Stamatopoulos, M. Kokkoris, S. Chasapoglou, M. Axiotis und A. Lagoyannis. „Isomeric cross section study of neutron induced reactions on Ge isotopes“. EPJ Web of Conferences 239 (2020): 01028. http://dx.doi.org/10.1051/epjconf/202023901028.
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Cross sections for the 70,76Ge(n,2n), 72,73Ge(n,p) and 72,74Ge(n, α) reactions have been measured at the 5.5 MV tandem T11/25 Accelerator Laboratory of NCSR Demokritos, using the activation technique. Neutron beams have been produced in the ~16-20 MeV energy region, by means of the 3H(d,n)4He reaction. The maximum flux has been determined to be of the order of 105 n/cm2 s, while the flux variation of the neutron beam was monitored by using a BF3 detector. The cross section has been deduced with respect to the 27Al(n, α)24Na and 93Nb(n,2n)92mNb reference reactions. The contaminations from reactions induced on neighboring Ge isotopes and leading to the same residual nucleus, have been taken into account. After the end of the irradiations, the activity induced by the neutron beams at the targets and reference foils, has been measured by HPGe detectors. Statistical model calculations using the EMPIRE code were performed on the data measured in this work as well as on data reported in literature.
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Haque, M. M., M. T. Islam, M. A. Hafiz, R. U. Miah und M. S. Uddin. „14.8 MeV Neutron Activation Cross Section Measurements for Ge Isotopes“. Journal of Scientific Research 1, Nr. 2 (09.04.2009): 173–81. http://dx.doi.org/10.3329/jsr.v1i2.1532.
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The cross sections of Ge isotopes were measured with the activation method at 14.8 MeV neutron energy. The quasi-monoenergetic neutron beams were produced via the 3H(d,n)4He reaction at the 150 kV J-25 neutron generator of INST, AERE. The characteristics γ-lines of the product nuclei were measured with a closed end coaxial 17.5 cm2 high purity germanium (HPGe) detector gamma ray spectroscopy. The cross sections were determined with reference to the known 27Al(n,α)24Na reaction. Cross section data are presented for 72Ge(n,p)72Ga, 74Ge(n,α)71mZn and 76Ge(n,2n)75m+gGe reactions. The cross section values obtained for the above reactions were 24.78±1.75 mb, 1.69±0.11 mb and 860±50 mb, respectively. The results obtained were compared with the values reported in literature as well as theoretical calculation performed by the statistical code SINCROS-II. The experimental data were found fairly in good agreement with the calculated and literature data. Keywords: Activation cross section; Neutron induced reaction; Gamma-ray spectroscopy; 14.8 MeV. © 2009 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. DOI: 10.3329/jsr.v1i2.1532
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Krupinski, Katrin, Erica Brendler, Robert Gericke, Jörg Wagler und Edwin Kroke. „A new aspect of the “pseudo water” concept of bis(trimethylsilyl)carbodiimide – “pseudohydrates” of aluminum“. Zeitschrift für Naturforschung B 73, Nr. 11 (27.11.2018): 911–18. http://dx.doi.org/10.1515/znb-2018-0137.
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AbstractBis(trimethylsilyl)carbodiimide (BTSC), so-called “pseudo water” because of some analogies such as similar (group)electronegativities of Me3Si– vs. H– and –N=C=N– vs. –O–, may form two different kinds of “pseudo hydrates” of metals (M), i.e. M–N(SiMe3)=C=N(SiMe3) and M–N≡C–N(SiMe3)2, derived from its carbodiimide and cyanamide isomeric forms, respectively. With anhydrous AlCl3 in Me3SiCl solution BTSC was shown to be capable of forming both kinds of solvates, i.e. Cl3Al–N(SiMe3)–C≡N(SiMe3) (1) and ((Cl3Al)(Me3Si)NCN)3–Al–(N≡C–N(SiMe3)2)3 (2). Both compounds were isolated as crystalline solids, which undergo condensation reactions upon storage. By single-crystal X-ray diffraction analysis the constitution of 1 was confirmed unambiguously, and quantum chemical calculations (B3LYP/6-311++g(d,p)) confirmed that compound 1 is 6 kcal mol−1 more stable than its hypothetical N,N-bis(trimethylsilyl)cyanamide isomer Cl3Al–N≡C–N(SiMe3)2. Compound 1 represents the first crystallographically confirmed disilylcarbodiimide complex of a metal salt. The molecules of compound 2 are heavily disordered in the solid state (positional disorder of N≡C–N(SiMe3)2 vs. N≡C–N(SiMe3)(AlCl3) and positional disorder of SiMe3 vs. AlCl3 groups in the latter). Therefore, the identity of 2 was additionally confirmed by 13C, 15N, 27Al and 29Si CP/MAS NMR spectroscopy.
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Müller, Gerhard, und Joachim Lachmann. „Vier- und fünffach koordinierte Organometall-Phosphankomplexe von Aluminium, Gallium, Indium und Thallium / Four- and Five-Coordinate Organometal Phosphine Complexes of Aluminum, Gallium, Indium, and Thallium“. Zeitschrift für Naturforschung B 48, Nr. 11 (01.11.1993): 1544–54. http://dx.doi.org/10.1515/znb-1993-1112.
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The organometal phosphine complexes ML3 (L = [o-(Ph2PCH2)C6H4]-; M = Al3+, Ga3+, In3a+) are obtained from MC13 and the lithiated ligand in diethyl ether. Tl[o-(Ph2PCH2)C6H4]3 is prepared from T1C1 by a disproportionation reaction. M1 species could not be detected with L as ligand. Al[o-(Ph2PCH2)C6H4]3 is the first triorganoaluminum bis(phosphine) adduct where C3P2 pentacoordination at aluminum has been definitely proven for both the solution (δ(27Al) =131 ppm, w1/2 = 12 kHz) and the solid state (d(Al–P) = 2.676(3)/2.782(2) A). The trigonal-bipyramidal coordination geometry (C3P2) at Al is achieved by two of the anionic phosphines acting as chelating ligands, spanning equatorial (C atoms) and axial sites (P atoms), while the third phosphine is only carbon-bonded. Like AlL3, the heavier congeners ML3 (M = Ga, In, Tl) are stereochemically nonrigid molecules in solution. Surprisingly, in the solid state only InL3 resembles the aluminum complex (C3P2 penta-coordination) while GaL3 and T1L3 contain four-coordinate metal centers (C3P). This may be rationalized by the noticeably less polar Ga–P bonds as compared to Al–P and In–P bonds, while in T1L3 the span of the ligand is not sufficient to allow for chelating coordination at a five- (or six-)coordinate Tl center.
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Gómez, Jennifer S., Andrew G. M. Rankin, Julien Trébosc, Frédérique Pourpoint, Yu Tsutsumi, Hiroki Nagashima, Olivier Lafon und Jean-Paul Amoureux. „Improved NMR transfer of magnetization from protons to half-integer spin quadrupolar nuclei at moderate and high magic-angle spinning frequencies“. Magnetic Resonance 2, Nr. 1 (17.06.2021): 447–64. http://dx.doi.org/10.5194/mr-2-447-2021.
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Abstract. Half-integer spin quadrupolar nuclei are the only magnetic isotopes for the majority of the chemical elements. Therefore, the transfer of polarization from protons to these isotopes under magic-angle spinning (MAS) can provide precious insights into the interatomic proximities in hydrogen-containing solids, including organic, hybrid, nanostructured and biological solids. This transfer has recently been combined with dynamic nuclear polarization (DNP) in order to enhance the NMR signal of half-integer quadrupolar isotopes. However, the cross-polarization transfer lacks robustness in the case of quadrupolar nuclei, and we have recently introduced as an alternative technique a D-RINEPT (through-space refocused insensitive nuclei enhancement by polarization transfer) scheme combining a heteronuclear dipolar recoupling built from adiabatic pulses and a continuous-wave decoupling. This technique has been demonstrated at 9.4 T with moderate MAS frequencies, νR≈10–15 kHz, in order to transfer the DNP-enhanced 1H polarization to quadrupolar nuclei. Nevertheless, polarization transfers from protons to quadrupolar nuclei are also required at higher MAS frequencies in order to improve the 1H resolution. We investigate here how this transfer can be achieved at νR≈20 and 60 kHz. We demonstrate that the D-RINEPT sequence using adiabatic pulses still produces efficient and robust transfers but requires large radio-frequency (rf) fields, which may not be compatible with the specifications of most MAS probes. As an alternative, we introduce robust and efficient variants of the D-RINEPT and PRESTO (phase-shifted recoupling effects a smooth transfer of order) sequences using symmetry-based recoupling schemes built from single and composite π pulses. Their performances are compared using the average Hamiltonian theory and experiments at B0=18.8 T on γ-alumina and isopropylamine-templated microporous aluminophosphate (AlPO4-14), featuring low and significant 1H–1H dipolar interactions, respectively. These experiments demonstrate that the 1H magnetization can be efficiently transferred to 27Al nuclei using D-RINEPT with SR412(270090180) recoupling and using PRESTO with R2227(1800) or R1676(270090180) schemes at νR=20 or 62.5 kHz, respectively. The D-RINEPT and PRESTO recoupling schemes complement each other since the latter is affected by dipolar truncation, whereas the former is not. We also analyze the losses during these recoupling schemes, and we show how these magnetization transfers can be used at νR=62.5 kHz to acquire in 72 min 2D HETCOR (heteronuclear correlation) spectra between 1H and quadrupolar nuclei, with a non-uniform sampling (NUS).
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Pluangklang, Chutima, und Kunwadee Rangsriwatananon. „Facile Method by Bentonite Treated with Heat and Acid to Enhance Pesticide Adsorption“. Applied Sciences 11, Nr. 11 (01.06.2021): 5147. http://dx.doi.org/10.3390/app11115147.
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In this work, simple conditions were applied to modify bentonite for the removal of pesticides from aqueous solution. Bentonite was modified in a single step as BA0.5 (with HCl 0.5 M) and BC500 (calcined at 500 °C) and combined steps with different sequences (BA0.5C500 and BC500A0.5). These adsorbents were characterised by XRD, XRF, FT-IR, 27Al MAS NMR, BET, NH3-TPD, TGA, HPLC, particle size analysis and zeta potential. Single-component adsorption with atrazine, diuron, 2,4-D and paraquat was used in aqueous solution at various pesticide concentrations, contact times and pH levels. It was found that the sequence of the treatment significantly affected atrazine adsorption. BC500A0.5 exhibited the highest efficiency for atrazine adsorption in a broad pH range of 3.0–9.0. Its adsorption at pH 6.0 was about 12 times greater than that of other adsorbents with an initial atrazine concentration of 50 mg L−1, which indicates BC500A0.5 specifically for the adsorption of atrazine. In addition, for the simultaneous adsorption of all four pesticides, BC500A0.5 was found to remove the maximum total amount of the pesticides, indicating that it could be used as a good multifunctional adsorbent. All modified bentonites showed similar diuron adsorption better than that of unmodified bentonite. The greatest adsorption of 2,4-D prefers BA0.5C500, occurring at pH 2–4. In the case of paraquat adsorption, all adsorbents are good at absorbing paraquat, but bentonite had the highest rate of paraquat removal, whereas BA0.5C500 was found to have the lowest, and the adsorption increased with increasing pH. Furthermore, the adsorption process on the adsorbents fits well with the Langmuir isotherm and pseudo-second-order kinetics models, as the thermodynamic parameters showed a spontaneous and endothermic process.
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Frank, Walter, Björn Gelhausen, Guido J. Reiß und Risto Salzer. „Untersuchungen an Systemen des Typs PCl3/MCl3/Aren (M = Al, Ga), I. Reaktionen mit Monohalogenbenzolen; Multikern-NMR-spektroskopische Charakterisierung von Aryldichlorhydrogenphosphoniumsalzen; Struktur des para-Fluorphenyldichlorphosphonium-tetrachloroaluminats“. Zeitschrift für Naturforschung B 53, Nr. 10 (01.10.1998): 1149–68. http://dx.doi.org/10.1515/znb-1998-1025.
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AbstractThe reactions of the monohalobenzenes with AlCl3 (GaCl3) and PCl3 have been monitored by 31P NMR spectroscopy. Primary product of the reaction with fluorobenzene and AlCl3 is the thermolabile para-fluorophenyldichlorophosphonium tetrachloroaluminate, which was characterized by 1H, 13C, 19F, 27Al and 31P NMR spectroscopy as well as by a crystal structure analysis (space group P21/c, a = 7.0720(10), b = 12.659(3), c = 15.413(3) Å, ß = 90.93(3)°, Z = 4, T = -110 °C). For the phosphonium ion we found a very good agreement of the experimental structural parameters and those obtained by ab initio quantum chemical calculations at the B3LYP 6-31++G(d,p) level of theory. Both, the experimentally determined and the calculated structure show a significant chinoid distortion of the para-disubstituted benzene ring. From the primary product the reaction proceeds to give exclusively para-fluorophenyl-(phenyl)dichlorophosphonium tetrachloroaluminate. With GaCl3 and fluorobenzene analogous tetrachlorogallates were observed, however, some by-products were recognized: para-ftuorophenylchlorofluorophosphonium and para-fluorophenyldifluorophosphonium tetrachlorogallate at the beginning of the reaction, bis(para-fluorophenyl)chlorophosphonium tetrachlorogallate at a later stage of the reaction. The reaction of chlorobenzene with PCl3 and AlCl3 yields analogous products as compared to the reaction with fluorobenzene. However, appreciable amounts of ortho- and some meta-chlorophenyldichlorophosphonium tetrachloroaluminate are by-products. If GaCl3 is used instead of AlCl3, numerous by-products and reaction intermediates are detectable. The major one is para-chlorophenyldihydrogenchlorophosphonium tetrachlorogallate. No principal differences were observed, when AlCl3 and GaCl3, respectively, reacted with bromobenzene and PCl3 giving phenylbromodichlorophosphonium and para-bromophenylbromodichlorophosphonium salts as well as some amounts of the ortho- and meta-bromophenyl derivatives. With iodobenzene the corresponding reactions exclusively give phenyldichloroiodophosphonium tetrachloroaluminate and -gallate, respectively.
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Luo, Junhua, Li Jiang, Juncheng Liang, Fei Tuo, Long He und Liang Zhou. „Cross-section measurements of (n, 2n) and (n, p) reactions on 124,126,128,130,131,132Xe in the 14 MeV region and theoretical calculations of their excitation functions *“. Chinese Physics C 46, Nr. 4 (01.04.2022): 044001. http://dx.doi.org/10.1088/1674-1137/ac3fa4.
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Abstract The reaction cross-sections of 124Xe(n, 2n)123Xe, 126Xe(n, 2n)125Xe, 128Xe(n, 2n)127Xe, 130Xe(n, 2n)129mXe, 132Xe(n, 2n)131mXe, 130Xe(n, p)130I, 131Xe(n, p)131I, and 132Xe(n, p)132I were measured at the 13.5, 13.8, 14.1, 14.4, and 14.8 MeV neutron energies. The monoenergetic neutrons were generated via the 3H(d,n)4He reaction at the China Academy of Engineering Physics using the K-400 Neutron Generator with a solid 3H-Ti target. A high-purity germanium detector was employed to measure the activities of the product. The reactions 93Nb(n, 2n)92mNb and 27Al(n, α)24Na were adopted for neutron flux calibration. The cross sections of the (n, 2n) and (n, p) reactions of the xenon isotopes were obtained within the 13–15 MeV neutron energy range. These cross-sections were then compared with the IAEA-exchange format (EXFOR) database-derived experimental data, together with the evaluation results of the CENDL-3, ENDF/B-VIII.0, JENDL-4.0, RUSFOND, and JEFF-3.3 data libraries, as well as the theoretical excitation function obtained using the TALYS-1.95 code. The cross-sections of the reactions (except for the 124Xe(n, 2n)123Xe and 132Xe(n, p)132I) at 13.5, 13.8, and 14.1 MeV are reported for the first time in this study. The obtained results are beneficial in providing better cross-section constraints for the reactions in the 13–15 MeV region, thus improving the quality of the corresponding database. Meanwhile, these data can also be used for the verification of relevant nuclear reaction model parameters.
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Bellisario, Valeria, Giulia Squillacioti, Marco Panizzolo, Federica Ghelli, Giuseppe Mariella, Irina Guseva Canu, Enrico Bergamaschi und Roberto Bono. „143 Urinary Metals Exposure and Oxidative Stress Biomarkers in Nanotechnology Workers: Results from the Nanoexplore Project“. Annals of Work Exposures and Health 67, Supplement_1 (01.05.2023): i72—i73. http://dx.doi.org/10.1093/annweh/wxac087.175.
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Abstract Exposure to metal oxides nanomaterials (NMs) might trigger adverse health effects. NMs can generate Oxidative Stress (OS), causing redox effects detectable in urine through suitable biomarkers. We evaluated the cross-sectional association of urinary OS biomarkers with urinary metal concentrations, using data collected in the multicenter international study NanoExplore. One hundred forty-one workers were recruited at three R&D and four industrial facilities employing NMs in different processes (paints/coating[PC];construction chemicals[CC]). Only 129 workers had complete data and, based on the personal work-shift exposure to NMs, they were classified as unexposed workers (n=41), workers with negligible/low exposure (n=37), and with moderate/high exposure (n=51). OS biomarkers (IsoP,MDA,TAP) and metals (27Al,47Ti,52Cr,118Sn) were quantified in urine samples collected before and after exposure monitoring campaign (2-4 work-shifts). Between-group comparisons were performed with non-parametric tests according to the data distribution. Highly exposed workers had significantly higher pro-oxidant (IsoP and MDA,p<0.005) and antioxidant (TAP,p<0.05) biomarkers concentrations. 47Ti,118Sn and 29Si were significantly higher in CC workers (p<0.005). IsoP and TAP were positively associated with 29Si (both p<0.001), 47Ti (p=0.036,p=0.003), 52Cr (p=0.048,p=0.003) and 118Sn (p=0.047,p=0.022). The ongoing analyses will assess the potential mediation role of OS and metal biomarkers. Occupational exposure to NMs can represent an underestimated hazard for people handling NMs products, increasing OS and potentially beginning pathological processes. Although the health significance of such findings needs to be further elucidated, the assessment of metals in urine may represent a useful tool for estimating the body burden of NMs long-term exposure.
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Cherniak, Daniele J., und E. Bruce Watson. „Al and Si diffusion in rutile“. American Mineralogist 104, Nr. 11 (01.11.2019): 1638–49. http://dx.doi.org/10.2138/am-2019-7030.
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Abstract Diffusion of Al and Si has been measured in synthetic and natural rutile under anhydrous conditions. Experiments used Al2O3 or Al2O3-TiO2 powder mixtures for Al diffusant sources, and SiO2-TiO2 powder mixtures or quartz-rutile diffusion couples for Si. Experiments were run in air in crimped Pt capsules, or in sealed silica glass ampoules with solid buffers (to buffer at NNO or IW). Al profiles were measured with Nuclear Reaction Analysis (NRA) using the reaction 27Al(p,γ)28Si. Rutherford Backscattering spectrometry (RBS) was used to measure Si diffusion profiles, with RBS also used in measurements of Al to complement NRA profiles. We determine the following Arrhenius relations from these measurements: For Al diffusion parallel to c, for experiments buffered at NNO, over the temperature range 1100–1400 °C: D Al = 1.21 × 10 − 2 exp ( − 531 ± 27 kJ/ mol − 1 / RT ) m 2 s − 1 . For Si diffusion parallel to c, for both unbuffered and NNO-buffered experiments, over the temperature range 1100–1450 °C: D Si = 8.53 × 10 − 13 exp ( − 254 ± 31 kJ/ mol − 1 / RT ) m 2 s − 1 . Diffusion normal to (100) is similar to diffusion normal to (001) for both Al and Si, indicating little diffusional anisotropy for these elements. Diffusivities measured for synthetic and natural rutile are in good agreement, indicating that these diffusion parameters can be applied in evaluating diffusivities in rutile in natural systems Diffusivities of Al and Si for experiments buffered at IW are faster (by a half to three-quarters of a log unit) than those buffered at NNO. Si and Al are among the slowest-diffusing species in rutile measured thus far. Diffusivities of Al and Si are significantly slower than the diffusion of Pb and slower than the diffusion of tetravalent Zr and Hf and pentavalent Nb and Ta. These data indicate that Al compositional information will be strongly retained in rutile, providing evidence for the robustness of the recently developed Al in rutile thermobarometer. For example, at 900 °C, Al compositional information would be preserved over ~3 Gyr in the center of 250 μm radius rutile grains, but Zr compositional information would be preserved for only about 300 000 yr at this temperature. Al-in-rutile compositions will also be much better preserved during subsolidus thermal events subsequent to crystallization than those for Ti-in-quartz and Zr-in-titanite crystallization thermometers.
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Srivastava, Vishal, C. Bhattacharya, T. K. Rana, S. Manna, S. Kundu, S. Bhattacharya, K. Banerjee et al. „Study of 26Mg through 1p pick-up reaction 27Al(d,3He)“. International Journal of Modern Physics E 26, Nr. 10 (Oktober 2017): 1750064. http://dx.doi.org/10.1142/s0218301317500641.
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The reaction [Formula: see text]Al([Formula: see text],3He) at 25 MeV beam energy has been utilized to study the states in even–even nucleus [Formula: see text]Mg. The spectroscopic factors have been extracted for the states of [Formula: see text]Mg up to 7.50[Formula: see text]MeV excitation energy using local, zero-range distorted wave Born approximation. The extracted spectroscopic factors have been compared with the previously reported values. The present results were also compared with the predictions from a theoretical shell model and rotational model.
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Qiu, Jiang-Zhen, Long-Fei Wang und Jiuxing Jiang. „SYSU-6, A New 2-D Aluminophosphate Zeolite Layer Precursor“. Molecules 24, Nr. 16 (16.08.2019): 2972. http://dx.doi.org/10.3390/molecules24162972.
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Two-dimensional aluminophosphate is an important precursor of phosphate-based zeolites; a new Sun Yat-sen University No. 6 (SYSU-6) with |Hada|2[Al2(HPO4)(PO4)2] has been synthesized in the hydrothermal synthesis with organic structure-directing agent (OSDA) of N,N,3,5-tetramethyladamantan-1-amine. In this paper, SYSU-6 is characterized by single-crystal/powder X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis, transmission electron microscopy, infrared and UV Raman spectroscopy, solid-state 27Al, 31P and 13C magic angle spinning (MAS) NMR spectra, and elemental analysis. The single-crystal X-ray diffraction structure indicates that SYSU-6 crystallized in the space group P21/n, with a = 8.4119(3), b = 36.9876(12), c = 12.5674(3), α = 90°, β = 108.6770(10)°, γ = 90°, V = 3704.3(2) Å3, Z = 4, R = 5.12%, for 8515 observed data (I > 2σ(I)). The structure has a new 4,12-ring layer framework topology linked by alternating AlO4 and PO4 tetrahedra. The organic molecules reside between the layers and are hydrogen-bonded to the inorganic framework. The new type of layer provides a greater opportunity to construct zeolite with novel topology.
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Riesgo-Gonzalez, Victor, David S. Hall, Katharina Marker, Dominic S. Wright und Clare P. Grey. „The Effect of Annealing on the Structure, Composition and Electrochemistry of NMC811 Coated with Al2O3 Using an Alkoxide Precursor“. ECS Meeting Abstracts MA2022-01, Nr. 2 (07.07.2022): 295. http://dx.doi.org/10.1149/ma2022-012295mtgabs.
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Increasing capacities and lowering costs of the cathode material is a key challenge in lithium ion-battery research. Towards this end, nickel-rich layered oxides of the formula Li[NixMnyCoy]O2 (NMC) with x ≥ 0.8 were developed. Compared to previously used cathodes such as LiCoO2 , nickel-rich NMCs reach lower costs by replacing most of the cobalt with nickel and they enable higher discharge capacities.1 Despite the presence of small amounts of cobalt and manganese as dopants to improve stability and rate-capability, these materials still show fast capacity fade during electrochemical cycling which cannot be overcome by modifying the ratio of their elements.2 New strategies to mitigate this degradation are therefore urgently needed for the use of these materials in practical applications such as electric vehicles.3 Most of the degradation that occurs in nickel-rich NMCs upon cycling starts at the cathode-electrolyte interface via surface reactions,oxygen evolution followed by rock-salt formationand transition metal dissolution.4–6 One way to slow down or stop these processes is by changing the nature of this interface through coatings. Although there is a large number of studies showing the benefits of using them, knowledge on the design of coatings with specific properties is still lacking.7,8 In this work, we develop a new solution-based deposition method for the synthesis of aluminium oxide coatings onto LiNi0.8Mn0.1Co0.1O2 (NMC811) secondary particles (Figure 1) and study the effect of annealing on their structure and electrochemical lifetime as new-generation cathode for lithium-ion batteries. Using energy dispersive X-ray spectroscopy (EDS) and X-ray fluorescence spectroscopy (XRF) we quantify the amount and distribution of aluminium oxide on the cathode particles. By using solid-state nuclear magnetic resonance (SS-NMR) and X-ray photoelectron spectroscopy (XPS), we track changes in the coating phase and composition as a function of annealing temperature. 27Al NMR spectroscopy provides direct evidence of the diffusion of the coating into the bulk of the particles leading to surface-layer doping. Finally, we evaluate the electrochemical performance of the coated materials in half cells using long-term galvanostatic cycling. This work provides insight on the effects of surface coating and doping on battery degradation and shows how, by carefully selecting synthetic conditions, coatings of cathode particles with tailored properties can be prepared. (1) Myung, S.-T.; Maglia, F.; Park, K.-J.; Yoon, C. S.; Lamp, P.; Kim, S.-J.; Sun, Y.-K. Nickel-Rich Layered Cathode Materials for Automotive Lithium-Ion Batteries: Achievements and Perspectives. ACS Energy Letters 2017, 2 (1), 196–223. https://doi.org/10.1021/acsenergylett.6b00594. (2) Noh, H.-J.; Youn, S.; Yoon, C. S.; Sun, Y.-K. Comparison of the Structural and Electrochemical Properties of Layered Li[NixCoyMnz]O2 (x = 1/3, 0.5, 0.6, 0.7, 0.8 and 0.85) Cathode Material for Lithium-Ion Batteries. Journal of Power Sources 2013, 233, 121–130. https://doi.org/10.1016/j.jpowsour.2013.01.063. (3) Kim, J.; Lee, H.; Cha, H.; Yoon, M.; Park, M.; Cho, J. Prospect and Reality of Ni-Rich Cathode for Commercialization. Advanced Energy Materials 2018, 8 (6), 1702028. https://doi.org/10.1002/aenm.201702028. (4) Rinkel, B. L. D.; Hall, D. S.; Temprano, I.; Grey, C. P. Electrolyte Oxidation Pathways in Lithium-Ion Batteries. J. Am. Chem. Soc. 2020, 142 (35), 15058–15074. https://doi.org/10.1021/jacs.0c06363. (5) Wandt, J.; Freiberg, A.; Thomas, R.; Gorlin, Y.; Siebel, A.; Jung, R.; Gasteiger, H. A.; Tromp, M. Transition Metal Dissolution and Deposition in Li-Ion Batteries Investigated by Operando X-Ray Absorption Spectroscopy. J. Mater. Chem. A 2016, 4 (47), 18300–18305. https://doi.org/10.1039/C6TA08865A. (6) Xu, C.; Märker, K.; Lee, J.; Mahadevegowda, A.; Reeves, P. J.; Day, S. J.; Groh, M. F.; Emge, S. P.; Ducati, C.; Layla Mehdi, B.; Tang, C. C.; Grey, C. P. Bulk Fatigue Induced by Surface Reconstruction in Layered Ni-Rich Cathodes for Li-Ion Batteries. Nat. Mater. 2020. https://doi.org/10.1038/s41563-020-0767-8. (7) Shi, Y.; Zhang, M.; Qian, D.; Meng, Y. S. Ultrathin Al2O3 Coatings for Improved Cycling Performance and Thermal Stability of LiNi0.5Co0.2Mn0.3O2 Cathode Material. Electrochimica Acta 2016, 203, 154–161. https://doi.org/10.1016/j.electacta.2016.03.185. (8) Neudeck, S.; Strauss, F.; Garcia, G.; Wolf, H.; Janek, J.; Hartmann, P.; Brezesinski, T. Room Temperature, Liquid-Phase Al2O3 Surface Coating Approach for Ni-Rich Layered Oxide Cathode Material. Chemical Communications 2019, 55 (15), 2174–2177. https://doi.org/10.1039/C8CC09618J. Figure 1
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Uddin, M. Shuza, M. Shamsuzzoha Basunia und Syed M. Qaim. „Excitation functions of some deuteron-induced nuclear reactions on Al“. Radiochimica Acta, 29.07.2021. http://dx.doi.org/10.1515/ract-2021-1065.
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Abstract Excitation functions of the reactions 27Al(d,αp)24Na, 27Al(d,2p)27Mg and 27Al(d,p)28Al were measured by the activation technique up to deuteron energies of 37 MeV. The available experimental databases of the reaction products 27Mg and 28Al were extended and compared with the nuclear model calculations based on the code TALYS-1.8. Our measured data are reproduced well by the model calculations after adjustment of a few free input parameters. The cross-section ratio of the (d,αp) to (d,2p) process as a function of projectile energy was deduced from the measured data, and the result is interpreted in terms of competition between a proton and an α-particle emission.
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KILIÇ, Ali İhsan. „NUCLEAR ASYMPTOTIC NORMALIZATION COEFFICIENT FOR 27Al →26Mg+p REACTION“. Eskişehir Teknik Üniversitesi Bilim ve Teknoloji Dergisi B - Teorik Bilimler, 30.05.2023. http://dx.doi.org/10.20290/estubtdb.1269417.
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The 26Mg(p,ɣ)27Al reaction is important in nuclear astrophysics as it play a crucial role in understanding the nucleosynthesis processes in red giants and Wolf-Rayet stars. The 26Mg(p,ɣ)27Al reaction is responsible for the production of 27Al in these stars, while the 26Mg(3He,d)27Al reaction provides information on the asymptotic normalization coefficient for the ground state of 27Al.The asymptotic normalization coefficient (ANC) method is an indirect method that provides information on the normalization of the overlap functions for a given reaction. This information is crucial for nuclear astrophysics as it allows for the calculation of the direct component of the reaction rate at astrophysical relevant energies.In this work, the angular distribution of the 26Mg(3He,d)27Al reaction have been analyzed using separate sets of optical potentials via the Distorted Wave Born Approximation which allows for a better understanding of the reaction mechanism and the determination of the ANC. Consequently,thecross section and Astrophysical S factor for 27Al→26Mg + p have been calculated for the direct capture
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Salimi, M., O. Kakuee, S. F. Masoudi, H. Rafi-kheiri, E. Briand, J. J. Ganem und I. Vickridge. „Determination and benchmarking of 27Al(d,α) and 27Al(d,p) reaction cross sections for energies and angles relevant to NRA“. Scientific Reports 11, Nr. 1 (10.09.2021). http://dx.doi.org/10.1038/s41598-021-97372-7.
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AbstractThe cross-sections of deuteron-induced nuclear reactions suitable for ion beam analysis, measured in different laboratories, are often significantly different. In the present work, differential cross-sections of 27Al(d,p) and 27Al(d,α) reactions were measured, and the cross sections benchmarked with thick target spectra obtained from pure aluminium for the first time in two independent laboratories. The 27Al(d,p) and (d,α) differential cross-sections were measured between 1.4 and 2 MeV at scattering angles of 165°, 150°, and 135° in the VDGT laboratory in Tehran (Iran), and the same measurements for detector angle of 150° were repeated from scratch, including target making, with independent equipment on the SAFIR platform at INSP in Paris (France). The results of these two measurements at 150° are in good agreement, and for the first time a fitted function is proposed to describe the Al-cross sections for which no suitable theoretical expression exists. The obtained differential cross-sections were validated through benchmarking, by fitting with SIMNRA deuteron-induced particle spectra obtained from a high purity bulk Al target at both labs for deuteron incident energies between 1.6 and 2 MeV. The thick target spectra are well-reproduced. The evaluated and benchmarked cross sections have been uploaded to the ion beam analysis nuclear data library database (www-nds.iaea.org/ibandl/).
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Lotay, G., P. J. Woods, M. Moukaddam, M. Aliotta, G. Christian, B. Davids, T. Davinson et al. „High-resolution radioactive beam study of the $$^{26}\hbox {Al}(d,p$$) reaction and measurements of single-particle spectroscopic factors“. European Physical Journal A 56, Nr. 1 (Januar 2020). http://dx.doi.org/10.1140/epja/s10050-019-00008-8.
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AbstractWe present a detailed comparison of shell model calculations with inverse kinematic transfer reaction data, obtained using a radioactive beam. Experimentally extracted spectroscopic factors from the $$^{26}\hbox {Al}(d,p)^{27}\hbox {Al}$$26Al(d,p)27Al reaction for both even and odd parity states are found to be exceptionally well reproduced by the shell model and a high level of consistency is observed between bound isobaric analog states in $$^{27}\hbox {Al}$$27Al and $$^{27}\hbox {Si}$$27Si, populated via (d, p) and (d, n) transfer, respectively. Furthermore, an evaluation of key resonances in the astrophysical $$^{26}\hbox {Al}(p,\gamma )^{27}\hbox {Si}$$26Al(p,γ)27Si reaction indicates that shell model calculations provide relatively accurate predictions for the existence of strong resonances and mirror nucleus comparisons appear to hold exceptionally well for proton-unbound levels. Consequently, we expect that the utilization of both techniques will likely be a very effective tool in the investigation of stellar processes outside the current reach of experiment.
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López-Ortega, A., J. M. Domínguez, A. Rojas-Hremández, A. Benitez-Patricio und M. Salmón. „Synthesis and Characterization of Ln/Al Pillared Clays“. MRS Proceedings 431 (1996). http://dx.doi.org/10.1557/proc-431-51.
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AbstractLa3+ −Al3+ and Ce3+ −A13+ pillar precursors were synthesized and intercalated in swelling montmorillonite type clays. 27Al-NMR and 139La-NMR spectra do not confirm chemical interaction between Al and La ions in solution, but after pillaring and calcination (400°C) d-spacings in the range 18.5 Å−20.5 Å indicate indeed a strong interaction between the Al-La species. Also, Ce4+ (Sulfate) cations do interact with Al3+ in the pillar-precursor-solution, into the pH interval 2.78≤p.H ≤3.99.
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Arango-Daza, Juan Camilo, Jose R. Cabrero-Antonino und Rosa Adam. „A General and Highly Versatile Heterogeneous Pd‐Catalyzed Oxidative Aminocarbonylation of Alkynes with Aromatic and Aliphatic Amines“. ChemSusChem, 02.05.2024. http://dx.doi.org/10.1002/cssc.202400331.
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An efficient heterogeneous catalytic system for the oxidative aminocarbonylation of alkynes and amines in the presence of CO/O2 to afford substituted propiolamides has been developed. The active nanocatalyst, [Pd/Mg3Al‐LDH]‐300(D), is composed by Pd nanoaggregates (2‐3 nm average particle size) stabilized over a partially dehydrated [Mg3Al‐LDH] matrix. The methodology has resulted widely applicable, being the first catalytic system, either homogeneous or heterogeneous, able to activate not only aliphatic amines but also poorly‐nucleophilic aromatic amines. In fact, >60 substituted propiolamides have been synthesized in good to excellent isolated yields through this methodology, being 27 novel compounds. An important characterization effort (XRD, 27Al MAS NMR, TGA, TPD‐CO2, BET area, XPS, HAADF‐HRSTEM and HRTEM) and optimization of the synthesis conditions of the optimal catalyst has been performed. This study, together with a series of kinetic and mechanistic essays, indicates that the optimal catalyst is composed by Pd(0) species stabilized in a partially dehydrated/dehydroxylated LDH material with a Mg/Al molar ratio of 3 and a small crystallite size. All the experimental data indicates that the in situ formation of [PdI2] active species in the material surface together with the presence of a matrix with the optimal acid/base properties are key aspects of this process.
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Karamanis, D., S. Andriamonje, P. A. Assimakopoulos, G. Doukellis, D. A. Karademos, A. Karydas, M. Kokkoris et al. „Statistical model calculations of the 232Th(n,2n) reaction“. HNPS Proceedings 11 (05.12.2019). http://dx.doi.org/10.12681/hnps.2214.
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On the context of the Cern n_TOF collaboration the 232Th(n,2n)231Th reaction cross section has been measured relative to the 56Fe(n,p)56Mn and 27Al(n,a)24Na reaction cross sections by the activation method for neutron energies up to 11 MeV. The neutrons were produced via the 2H(d,n) reaction using a deuterium filled gas-cell, at the 5.5MV TANDEM Accelerator of NCSR "Demokritos". In addition to the experimental work, theoretical Statistical model calculations have been performed using the computer code STAPRE/F. The code STAPRE is designed to calculate energy averaged cross sections for particle induced nuclear reactions with several emitted particles and gamma rays under the assumption of sequential evaporation. For the first evaporation step preequilibrium emission is taken into account while population of states resulting from the first equilibrium evaporation step is calculated using the Hauser-Feschbach theory. Fission process competition is also taken into account in the evaporation steps. Sensitive parameters for the calculation, like level density parameters, have been adopted after fitting experimental data for the competing (n,f) reaction. The results are being compared to the experimental data.
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Winter, Edda, Philipp Seipel, Tatiana Zinkevich, Sylvio Indris, Bambar Davaasuren, Frank Tietz und Michael Vogel. „Nuclear magnetic resonance (NMR) studies of sintering effects on the lithium ion dynamics in Li1.5Al0.5Ti1.5(PO4)3“. Zeitschrift für Physikalische Chemie, 11.10.2021. http://dx.doi.org/10.1515/zpch-2021-3109.
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Abstract Various nuclear magnetic resonance (NMR) methods are combined to study the structure and dynamics of Li1.5Al0.5Ti1.5(PO4)3 (LATP) samples, which were obtained from sintering at various temperatures between 650 and 900 °C. 6Li, 27Al, and 31P magic angle spinning (MAS) NMR spectra show that LATP crystallites are better defined for higher calcination temperatures. Analysis of 7Li spin-lattice relaxation and line-shape changes indicates the existence of two species of lithium ions with clearly distinguishable jump dynamics, which can be attributed to crystalline and amorphous sample regions, respectively. An increase of the sintering temperature leads to higher fractions of the fast lithium species with respect to the slow one, but hardly affects the jump dynamics in either of the phases. Specifically, the fast and slow lithium ions show jumps in the nanoseconds regime near 300 and 700 K, respectively. The activation energy of the hopping motion in the LATP crystallites amounts to ca. 0.26 eV. 7Li field-gradient diffusometry reveals that the long-range ion migration is limited by the sample regions featuring slow transport. The high spatial resolution available from the high static field gradients of our setup allows the observation of the lithium ion diffusion inside the small (<100 nm) LATP crystallites, yielding a high self-diffusion coefficient of D = 2 × 10−12 m2/s at room temperature.
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He, Long, Junhua Luo und Li Jiang. „New cross-section measurements of the (n,2n), (n,p) and (n,α) reactions on bromine in the 14 MeV region with detailed uncertainty quantification“. Chinese Physics C, 08.12.2022. http://dx.doi.org/10.1088/1674-1137/aca9bf.
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Abstract Measurement of the cross-sections of 79Br(n,2n)78Br, 81Br(n,p)81mSe, 81Br(n,α)78As, and 79Br(n,α)76As reactions was carried out at specific neutron energies precisely 13.5±0.2, 14.1±0.2, 14.4±0.2, and 14.8±0.2 MeV relative to the standard 93Nb(n,2n)92mNb and 27Al(n,α)24Na reference reactions using offline γ-ray spectrometry and neutron activation. The monoenergetic neutrons were generated at the China Academy of Engineering Physics, via a 3H(d,n)4He reaction using a K-400 Neutron Generator equipped with a solid 3H-Ti based target. The activity of reaction produce was obtained utilizing a high-purity germanium detector. The cross-sections of the (n,2n), (n,p), and (n,α) reactions on the bromine isotopes were conducted in the 13–15 MeV neutron energy range. The covariance analysis approach was employed for a thorough inspection of any uncertainties within the measured cross-section data. Discussion and comparison of the observed outcome were carried out with previously published data, in particular with the results of the JENDL-4.0, JEFF-3.3, TENDL-2019, and ENDF/B-VIII.0 data libraries, along with the theoretical excitation function curve derived by employed the TALYS-1.95 program. Improved cross-section restrictions for the investigated processes in the 13–15 MeV neutron energy range will be furnished by the current findings, which will help to raise the caliber of the associated databases. Furthermore, the parameters of the pertinent nuclear reaction models can be verified using this data.