Electron-Stimulated Desorption of Sodium and Potassium Atoms from Oxidized Tungsten

Technical Physics - We have analyzed electron-stimulated desorption (ESD) of neutral sodium and potassium atoms on oxidized tungsten. We propose a model describing ESD of atoms from the oxidized...     

Electron-Stimulated Desorption of Cesium Atoms from Graphene to Iridium Intercalated and not Intercalated with Cesium

Physics of the Solid State - The processes of electron-stimulated desorption of neutral cesium atoms from graphene to iridium are studied in the cases in which the graphene layer is or is not...     

Kinetics of the Atomic Structure of Palladium Nanoparticles during the Desorption of Hydrogen According to X-Ray Diffraction

The process of desorption of hydrogen from small palladium nanoparticles is monitored by time-resolved synchrotron X-ray diffraction. Changes in the diffraction patterns corresponding to the transition from the palladium β-phase to the α-phase are detected with an accuracy of 0.3 s. The model of the continuous change in the size of the β-phase region can be excluded, since the Rietveld analysis does not reveal a broadening of the diffraction peaks corresponding to the palladium lattice during desorption. The theoretical simulation shows the presence of a surface/core interface with different average cell parameters. However, the near-surface layers of the nanoparticle make a lower contribution to the observed diffraction reflections because of a lower crystallinity. The cell parameter in the nanoparticle core depends on the hydrogen concentration both in the core itself and in the shell due to the presence of stresses at the interface.

     

Peaks of Hydrogen Thermal Desorption: Simulation and Interpretation

Technical Physics - Different models of hydrogen thermal desorption peaks have been analyzed. The model of volume-averaged concentration dynamics with a continuum parameter makes it possible to...     

Photoelectron Spectroscopy of Nickel, Palladium, and Platinum Oxide Anions

The 364-nm negative ion photoelectron spectra of XO and OXO molecules (X=Ni, Pd, and Pt) are reported. The spectra yield the electron affinities (EAs): EA(NiO)=1.455±0.005 eV; EA(PdO)=1.672±0.005 eV; EA(PtO)=2.172±0.005 eV; EA(ONiO)=3.043±0.005 eV; EA(OPdO)=3.086±0.005 eV; EA(OPtO)=2.677±0.005 eV. In addition, for the diatomics, transitions from the anion X?²Π_3/2 and X?′²Π_1/2 states into neutral X?³Σ⁻, ³Π, and for NiO and PdO, ¹Π, are assigned. Several states have been reassigned from those in the existing literature. Anion ²Π_3/2-²Π_1/2 spin-orbit splittings are measured, as are neutral ³Π₂-³Π₁ spin-orbit splittings: the XO ³Π ₂-³Π₁ splittings increase from 405±30 cm⁻¹ (NiO) to 805±30 cm⁻¹ (PdO) to 3580±40 cm⁻¹ (PtO). A bond length shortening of 0.03±0.01 Å is measured upon electron detachment from NiO⁻, resulting in an anion bond length of 1.66±0.01 Å. The bond length does not change upon electron detachment from PdO⁻ using 3.4-eV photons. The Pt-O bond length decreases by 0.035±0.010 Å in the ³Π₁←²Π_3/2 transition. The spectrum of OPtO displays a significantly more extended vibrational progression than those of ONiO or OPdO, and the O-Pt bond length is found to decrease by 0.07±0.01 Å upon electron detachment. The spectra support the view that the Ni-O bond is largely ionic, the Pd-O bond is somewhat less so, and the Pt-O bond displays a substantial covalent character.     

Optical and Structural Properties of Palladium Nanofilms in Hydrogen Atmosphere

Optics and Spectroscopy - The crystal structure and optical properties of Pd thin films (thickness 10–130 nm) obtained by thermal deposition in vacuum are studied. It is shown that the Pd...     

Monte Carlo Simulation of Hydrogen Absorption in Palladium and Palladium-Silver Alloy

Russian Physics Journal - The paper presents Monte Carlo simulation of the hydrogen absorption in palladium and palladium-silver alloy of the composition PdxAg1–x (x = 0.7–0.9) at...     

Thermal Desorption Study of the Trapping and Retention of Hydrogen Isotopes upon Irradiation of Oxidized Metal Surfaces with Hydrogen Plasma

Patterns of hydrogen isotope trapping and retention are investigated by applying hydrogen ion radiation to nickel samples free of oxidation, tungsten samples with oxide layer on their surfaces, and tungsten samples with aluminum coating with oxide layer. It is found that hydrogen isotope desorption upon hydrogen ion plasma irradiation occurs in samples of tungsten and tungsten with aluminum coating, but not in nickel samples. It is concluded that hydrogen isotope transport through the tungsten–aluminum interface is initiated when one surface of a samples is irradiated with hydrogen plasma ions.     

Tracer Study on Catalytic Hydrogen Exchange Reactions over Nickel Catalyst

In heterogeneous catalysis it is important to know the reactivity of C-H bond in the hydrocarbon molecules. Experiments have been performed to obtain information about the exchange reaction of adsorbed hydrogen with methane and ethylene. In order to reduce the probability of forming products which contain more than one tritium atom, hydrogen labelled with H³ with low activity has been used.     

Spectra Studies of Complexes Between Palladium (II), Nickel (II) and Amino Acids

The complexes of Ni (His) 2·H2O, Ni (Gly) 2·2H2O, Pd (His)Cl2·H2O and Pd(Gly) 2·2H2O were synthesized. And the IR, electronic absorption and photoacoustic spectra of these complexes were measured in solid state. The nature of the metal-carboxylate coordinate bond were deduced from the variation in the carboxyl stretching frequencies. And the d-d transition absorptions of these complexes were interpreted quantitatively with the 3d scaling radial theory. Therefore, the structural characterizations were also discussed with their spectral behaviors.     

Infrared and Raman Spectra of Sulfur-Nitride Complexes of Nickel(II) and Palladium(II)

Abstract

The infrared and Raman spectra of trans-Ni(S₂N₂CH₃)₂ and Pd(S₃N)₂ were measured from 4000-200 cm^?1. The absorption bands were assigned by comparison to the sulfur nitride complexes of nickel(II), palladium(II) and platinum(II). Normal coordinate analyses on these complexes were carried on these data using molecular parameters taken from X-ray data. To aid in band assignments, isotope shift data on trans-⁶²Ni(S₂N₂CH₃)₂ have also been carried out.     

金属钯表面吸附氢同位素的量子力学计算

基于原子分子反应静力学和群论,应用密度泛函方法B3P86,对H(D,T)用基集合6311G,对Pd用基集合SDD,优化后进行势能面扫描,得到各分子的微观性质,包括构形、多重性、能量、电子状态、键角、平衡键长、谐振频率、谐性力常数和离解能,得到H2(D2,T2)和PdH(PdD,PdT)的电子状态分别为1Σ+g(D∞v)和2Σ+(C∞v),离解能分别为4.5918和2.6268eV.并进一步计算得到反应过程的△Hf°、△Sf°、△Gf°和平衡压力,并导出他们与温度的函数关系,计算结果与实验数据相近.     

Modification of the Atomic and Electronic Structures of Palladium as a Result of Hydrogen Dissolution

Physics of the Solid State - The features of changes in the atomic and electronic structures of palladium as a result of hydrogen dissolution are studied from the first principles. The binding...     

Adsorption,Desorption, Dissoziation und Rekombination von SO2 an einer Palladium(111)-Oberfläche

Adsorption, Desorption, Dissociation and Recombination of SO₂ on a Palladium (111) Surface The adsorption, desorption as well as decomposition- and recombination-reactions of SO₂ on Pd(1 1 1) were studied for temperatures T = 160-1200 K using LEED, AES, thermal desorption-mass-spectrometry and molecular beam techniques. At 160 K SO₂ adsorption with an initial sticking coefficient s₀ = 1 is molecular and non-ordered; it is characterized by a precursor state and leads to a saturation coverage Θ ≈ 0,3. Heating up the adlayer SO₂ is the only desorption product, namely directly from (SO₂)_ad in the α-peak (T_max = 240 K) and as the product of recombination of (SO)_ad and O_ad in the β-peak (T_max = 330-370 K). A great part of the oxygen originating from SO₂-dissociation is incorporated into the subsurface region, resulting in an atomic S-adlayer with Θ_S = 1/7 which exhibits a (\documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt 7 {\rm x}\sqrt 7 $\end{document}) R ± 19,1°-superstructure. This structure is also observed, if a 320 K-SO₂-exposure induced (2 × 2)-SO saturation layer with Θ_SO = 0,5 is heated up or if SO, is exposed at T > 500 K, where it corresponds to Θ_S, values of 3/7 and 2/7, respectively. Furthermore the poisoning effect of adsorbed sulfur on the dissociative O₂,-adsorption and the oxidation of sulfur by heating up an O? S-coadsorption layer were studied. As a result the following kinetic parameters (activation energies and frequency factors) were determined: .     

Reactivation of Promoted Nickel Catalysts for Deuterium Exchange between Hydrogen and Water in the Vapour Phase

Binary promoted nickel – chromium oxide and ternary promoted nickel – chromium oxide – aluminium oxide mixed catalysts were prepared for use in the present study. The catalysts were prepared by co-precipitation of the corresponding metal nitrates as carbonates followed by calcination in nitrogen atmosphere at 350 °C and reduction in hydrogen atmosphere at 320 °C. To prevent spontaneous oxidation of the catalysts, bidistilled water was added followed by heating of the catalyst mixtures at about 110 °C in hydrogen atmosphere for few hours. Deactivation of catalysts was studied by measurements of the variation of their activities with the time of contact of the reacting gas mixtures with the catalyst surface in the reaction chamber. It was found that while the catalytic activity of ternary catalysts for the isotopic exchange of deuterium between hydrogen and water vapour was higher than that of the binary one, the loss in activity of the former teas faster than the latter. Reactivation of the catalysts were carried out at different temperatures between 110–160°C in hydrogen atmosphere. Catalytic activity measurements indicated that higher temperatures are better for the reactivation process.     

Nickel/Chromium oxide/Zirconium oxide Catalysts for Hydrogen/Deuterium Isotopic Exchange

Catalysts composed of nickel and promoted with different metal oxides proved to be suitable for H/D isotropic exchange between hydrogen and water vapour. They loss their activity due to water condensation on their surfaces. Several nickel/chromium oxide/zirconium oxide catalysts of different composition were prepared by the coprecipitation technique. The liquid phase activity of these catalysts were followed using the hydrogen peroxide decomposition on their surfaces at different temperatures. The surface characteristics of the examined catalysts were followed by applying the BET method. The results were discussed and lead to the required catalyst composition which resists the water condensation on its surface during operation and has relatively high activity in the vapour phase H/D isotopic exchange reaction between hydrogen and water.