Nickel-graphite composites of variable architecture by graphitization-accompanied spark plasma sintering and hot pressing and their response to phase separation

We report the formation and phase separation response of nickel-graphite composites with variable-architecture phases by graphitization-accompanied consolidation via Spark Plasma Sintering and hot pressing. It was shown that the application of pressure during consolidation is crucial for the occurrence of graphitization and formation of 3D graphite structures. We evaluated the suitability of the synthesized composites as precursors for making porous structures. Nickel behaved as a space holder with the particle size and spatial distribution changing during consolidation with the temperature and determining the structure of porous graphite formed by phase separation by dissolution in HCl. The response of the consolidated Ni-Cgr to separation of carbon by its burnout in air was studied. The result of the carbon removal was either the formation of a dense and continuous NiO film on the surface of the compacts or oxidation through the compact thickness. The choice between these two options depended on the density of the compacts and on the presence of carbon dissolved in nickel. It was found that during the burnout of graphite from Ni-Cgr composites, sintering, rather than formation of pores, dominated

Control of particle size via chemical composition: Structural and magnetic characterization of Ni–Co alloy nanoparticles encapsulated in lamellar mixed oxides

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Production of Z⁰ bosons in elastic and quasi-elastic <i>ep</i> collisions at HERA

The production of Z&lt;sup&gt;0&lt;/sup&gt; bosons in the reaction ep→eZ&lt;sup&gt;0&lt;/sup&gt;p&lt;sup&gt;(⁎)&lt;/sup&gt;, where p&lt;sup&gt;(⁎)&lt;/sup&gt; stands for a proton or a low-mass nucleon resonance, has been studied in &lt;i&gt;ep&lt;/i&gt; collisions at HERA using the ZEUS detector. The analysis is based on a data sample collected between 1996 and 2007, amounting to 496 pb&lt;sup&gt;−1&lt;/sup&gt; of integrated luminosity. The Z&lt;sup&gt;0&lt;/sup&gt; was measured in the hadronic decay mode. The elasticity of the events was ensured by a cut on ηmax&lt;3.0, where η&lt;sub&gt;max&lt;/sub&gt; is the maximum pseudorapidity of energy deposits in the calorimeter defined with respect to the proton beam direction. A signal was observed at the Z&lt;sup&gt;0&lt;/sup&gt; mass. The cross section of the reaction ep→ eZ&lt;sup&gt;0&lt;/sup&gt;p&lt;sup&gt;(⁎)&lt;/sup&gt; was measured to be σ(ep→ eZ&lt;sup&gt;0&lt;/sup&gt;p&lt;sup&gt;(⁎)&lt;/sup&gt;)=0.13±0.06(stat.)±0.01(syst.) pb, in agreement with the Standard Model prediction of 0.16 pb. This is the first measurement of Z&lt;sup&gt;0&lt;/sup&gt; production in &lt;i&gt;ep&lt;/i&gt; collisions

Inclusive dijet cross sections in neutral current deep inelastic scattering at HERA

Single- and double-differential inclusive dijet cross sections in neutral current deep inelastic ep scattering have been measured with the ZEUS detector using an integrated luminosity of 374 pb(-1). The measurement was performed at large values of the photon virtuality, Q (2), between 125 and 20 000 GeV2. The jets were reconstructed with the k (T) cluster algorithm in the Breit reference frame and selected by requiring their transverse energies in the Breit frame, E-jet (T,B), to be larger than 8 GeV. In addition, the invariant mass of the dijet system, M-jj,M- was required to be greater than 20 GeV. The cross sections are described by the predictions of next-to-leading-order QCD

Measurement of the t dependence in exclusive photoproduction of Υ\Upsilon(1S) mesons at HERA

The exclusive photoproduction reaction gamma p -> Upsilon(1S) p has been studied with the ZEUS detector in ep collisions at HERA using an integrated luminosity of 468 pb^-1. The measurement covers the kinematic range 60<W<220 GeV and Q^2<1 GeV^2, where W is the photon-proton centre-of-mass energy and Q^2 is the photon virtuality. The exponential slope, b, of the t dependence of the cross section, where t is the squared four-momentum transfer at the proton vertex, has been measured, yielding b = 4.3 +2.0 -1.3 (stat.) +0.5 -0.6 (syst.) GeV^-2. This constitutes the first measurement of the t dependence of the gamma p -> Upsilon(1S) p cross section.Comment: 15 pages, 4 figures; http://dx.doi.org/10.1016/j.physletb.2012.01.00

Measurement of the Energy Dependence of the Total Photon-Proton Cross Section at HERA

The energy dependence of the photon-proton total cross section, σtotγp, was determined from e+p scattering data collected with the ZEUS detector at HERA at three values of the center-of-mass energy, W, of the γp system in the range 19

Measurement of Isolated Photons Accompanied by Jets in Deep Inelasic epep Scattering

The production of isolated high-energy photons accompanied by jets has been measured in deep inelastic ep scattering with the ZEUS detector at HERA, using an integrated luminosity of 326 pb^{-1}. Measurements were made for exchanged photon virtualities, Q^2, in the range 10 to 350 GeV^2. The photons were measured in the transverse-energy and pseudorapidity ranges 4 < ET^gamma < 15 GeV and -0.7 < eta^gamma < 0.9, and the jets were measured in the transverse-energy and pseudorapidity ranges 2.5 < ET^jet <35 GeV and -1.5 < eta^jet < 1.8. Differential cross sections are presented as functions of these quantities. Perturbative QCD predictions give a reasonable description of the shape of the measured cross sections over most of the kinematic range, but the absolute normalisation is typically in disagreement by 20-30%.Comment: 17 pages, 4 figures. Minor changes in published versio

Inclusive-Jet Photoproduction at HERA and Determination of αs\alpha_{s}

Inclusive-jet cross sections have been measured in the reaction ep->e+jet+X for photon virtuality Q2 < 1 GeV2 and gamma-p centre-of-mass energies in the region 142 < W(gamma-p) < 293 GeV with the ZEUS detector at HERA using an integrated luminosity of 300 pb-1. Jets were identified using the kT, anti-kT or SIScone jet algorithms in the laboratory frame. Single-differential cross sections are presented as functions of the jet transverse energy, ETjet, and pseudorapidity, etajet, for jets with ETjet > 17 GeV and -1 < etajet < 2.5. In addition, measurements of double-differential inclusive-jet cross sections are presented as functions of ETjet in different regions of etajet. Next-to-leading-order QCD calculations give a good description of the measurements, except for jets with low ETjet and high etajet. The influence of non-perturbative effects not related to hadronisation was studied. Measurements of the ratios of cross sections using different jet algorithms are also presented; the measured ratios are well described by calculations including up to O(alphas2) terms. Values of alphas(Mz) were extracted from the measurements and the energy-scale dependence of the coupling was determined. The value of alphas(Mz) extracted from the measurements based on the kT jet algorithm is alphas(Mz) = 0.1206 +0.0023 -0.0022 (exp.) +0.0042 -0.0035 (th.); the results from the anti-kT and SIScone algorithms are compatible with this value and have a similar precision.Comment: 53 pages, 17 figure