The changes in work function of group Ib and VIII metals on xenon adsorption,determined by field electron and photoelectron emission

The surface potentials of xenon on Ni, Pd, Pt, Rh, Ir, Ru, Fe, Cu, Ag and Au films have been determined by photoelectron emission as a function of the temperature of previous annealing. On Pd, Ir, Rh, Ru and Ag films, vapour- quenched at 78 K, the surface potential does not change significantly up to an annealing temperature of 400 K, but on Au and Ni it decreases with annealing. From measurements with a field emission microscope equipped with a probe-hole assembly it is found that the xenon surface potential is face specific. On Ir the largest surface potentials are found on the (111) and (100) tip regions. The variation with annealing temperature of the surface potential on a polycrystalline film may be attributed to the change in the contribution of the various crystal faces on the film surface.     

Synthesis, characterization, and electrochemical properties of mono-, di-, and trinuclear transition Metal [60]fullerene complexes containing diphosphine cis-Ph2PCH=CHPPh2 ligand

New transition metal fullerene complexes containing cis-Ph2PCH=CHPPh2 (dppet) ligand have been investigated. The mononuclear complexes (etau2-C60)M(cis-dppet) (1, 2; M = Pd, Pt) were prepared by reaction of C60 with M(dba)2 (dba = dibenzylideneacetone) followed by treatment with cis-dppet, while the in situ prepared 1 and 2 reacted with M1(PPh3)4 to afford dinuclear complexes (eta2 : eta2-C60)M(cis-dppet)M1 (PPh3)2 (3-6; M, M1 = Pd, Pt). Similarly, trinuclear complexes (eta2 : eta2-C60) M(cis-dppet)M1 (dppr) (7-10; M, M1 = Pd, Pt; dppr = (eta5-Ph2PC5H4)2Ru) could be synthesized by reaction of the in situ prepared 3-6 with dppr. 1-10 were characterized by elemental analysis and spectroscopy. Cyclic voltammetric studies on 2 (M = Pt), 3 (M = Pd, M1 = Pd) and 9 (M = Pt, M1 = Pd) provided further evidence for the eta2-coordination of C60 to one metal fragment or two metal fragments in these complexes.     

Low blank isotope ratio measurements of rhenium, osmium, and platinum using tantalum filaments with negative thermal ionization mass spectrometry

Platinum is most commonly used as a filament for Re and Os isotopic measurements, but it contains impurities of Re and Os. Tantalum is low in platinum group elements (PGE) and in Re, but it is not used for negative thermal ionization mass spectrometry because of high electron emission and high reactivity with O(2). High thermal electron emission from Ta distorts the preoptimized ion source optics. In addition, Ta consumes O(2), leaving little for samples, but O(2) is essential for isotopic ratio measurements of PGE and Re as they are measured as negatively charged oxides, such as OsO(3)(-) and PtO(2)(-). These problems are solved by prebaking a filament to remove tantalum oxides before sample loading, keeping relatively high filament temperatures and high O(2) pressures (P(O)((2))) during the sample run, and lowering the potential difference between the filament and the draw-out plate. At P(O)((2)) of ～1 × 10(-)(5) Torr in the source, strong (>10 V) stable (>6 h) peaks of ReO(4)(-), OsO(3)(-), and PtO(2)(-) are obtained at 750 °C for Re, 850 °C for Pt, and over 900 °C for Os. Accurate isotopic ratio measurements of Re, Os, and Pt at picogram levels are possible using Ta filaments.     

Determination of 18 siderophile elements including all platinum group elements in chondritic metals and iron meteorites by instrumental neutron activation

An instrumental neutron activation method is developed to analyze chondritic metals and iron meteorites. By changing irradiation and decay times, and selecting suitable γ-ray and X-ray photopeaks, not only all platinum group elements (Ru, Rh, Pd, Os, Ir, Pt) but also other siderophilic elements (Fe, Co, Ni, Cu, Ga, Ge, As, Mo, Sb, W, Re, Au) can be nondestructively determined in the meteoritic metal samples. To obtain analytical data as accurate as possible, interfering reactions and neutron flux gradients during irradiation are considered. Siderophile elemental abundances measured for the Odessa iron meteorite are highly consistent with the literature values. Rh abundances for bulk H, L, LL, EH, and EL chondrites, which had been scarcely reported in the literature, are derived from Rh/Ni abundance ratios in the metal separates of the corresponding chondritic groups.     

Epitaxially grown model catalyst particles of platinum, rhodium, iridium, palladium and rhenium studied by electron microscopy

In order to obtain oriented thin film model catalysts, small particles of Pt, Rh, Ir, Pd and Re (2–20 nm in size) were grown by high vacuum evaporation on NaCl cleavage faces or on in situ deposited NaCl films at 523–673 K. The particles were covered with a supporting film of Al₂O₃ or carbon and removed from the substrate. High resolution electron microscopy, selected area electron diffraction and weak-beam dark-field imaging were applied to determine the particular morphology, microstructure and orientation of the observed particles. Special attention was paid to Rh particles which appear in a variety of shapes. Pt, Ir and Pd model catalysts consist mainly of (001) oriented half octahedra which may exhibit truncations at the corners or on the top. This was also the dominant shape of Rh particles but in addition half tetrahedra in (011) epitaxy and multiply-twinned particles like decahedra in (001), (011) and (111) orientation were evident. These habits provide a definite “initial state” for study of the changes in structure and morphology of the particles during activating heat treatments necessary to induce catalytic activity of the Al₂O₃ supported metal films. Although Re films consisted of irregularly shaped particles, electron diffraction revealed a partial epitaxial alignment of both c.p.h. and f.c.c. Re.     

Phosphorescent Pt(II) and Pd(II) Complexes for Efficient,High‐Color‐Quality,and Stable OLEDs

Phosphorescent organic light‐emitting diodes (OLEDs) are leading candidates for next‐generation displays and solid‐state lighting technologies. Much of the academic and commercial pursuits in phosphorescent OLEDs have been dominated by Ir(III) complexes. Over the past decade recent developments have enabled square planar Pt(II) and Pd(II) complexes to meet or exceed the performance of Ir complexes in many aspects. In particular, the development of N‐heterocyclic carbene‐based emitters and tetradentate cyclometalated Pt and Pd complexes have significantly improved the emission efficiency and reduced their radiative lifetimes making them competitive with the best reported Ir complexes. Furthermore, their unique and diverse molecular design possibilities have enabled exciting photophysical attributes including narrower emission spectra, excimer ‐based white emission, and thermally activated delayed fluorescence. These developments have enabled the fabrication of efficient and “pure” blue OLEDs, single‐doped white devices with EQEs of over 25% and high CRI, and device operational lifetimes which show early promise that square planar metal complexes can be stable enough for commercialization. These accomplishments have brought Pt complexes to the forefront of academic research. The molecular design strategies, photophysical characteristics, and device performance resulting from the major advancements in emissive Pt and Pd square planar complexes are discussed.     

A comparative study of catalytic partial oxidation of methane over CeO2 supported metallic catalysts

In the present study, the catalytic partial oxidation of methane (CPOM) over various active metals supported on CeO2 (M/CeO2, M = Ir, Ni, Pd, Pt, Rh and Ru) has been investigated. The catalysts were characterized by X-ray diffraction (XRD), BET surface area, H2-temperature programmed reduction (H2-TPR), CO chemisorption and transmission electron microscope (TEM) analysis. Ir/CeO2 catalysts showed higher BET surface area, higher metal dispersion, small active metal nano-particles (approximately 3 nm) than compared to other M/CeO2 catalysts. The catalytic tests were carried out in a fixed R(mix) ratio of 2 (CH4/O2) in a fixed-bed reactor, operating isothermally at atmospheric pressure. From time-on-stream analysis at 700 degrees C for 12 h, a high and stable catalytic activity has been observed for Ir/CeO2 catalysts. TEM analysis of the spent catalysts showed that the decrease in the catalytic activity of Ni/CeO2 and Pd/CeO2 catalysts is due to carbon formation whereas no carbon formation has been observed for Ir/CeO2 catalysts.     

Growth Mechanism of Metal Clusters on a Graphene/Ru(0001) Template

Using first‐principles calculations combined with scanning tunneling microscopy experiments, we investigated the adsorption configurations, electronic structures and the corresponding growth mechanism of several transition metal (TM) atoms (Pt, Ru, Ir, Ti, Pd, Au, Ag, and Cu) on a graphene/Ru(0001) moiré template (G/Ru(0001)) at low coverage. We find that Pt, Ru, Ir, and Ti selectively adsorb on the fcc region of G/Ru(0001) and form ordered dispersed metal nanoclusters. This behavior is due to the unoccupied d orbital of the TM atoms and the strong sp³ hybridization of carbon atoms in the fcc region of G/Ru(0001). Pd, Au, Ag, and Cu form nonselective structures because of the fully occupied d orbital. This mechanism can be extended to metals on a graphene/Rh(111) template. By using Pt as an example, we provide a layer by layer growth path for Pt nanoclusters in the fcc region of the G/Ru(0001). The simulations of growth mechanism agree well with the experimental observations. Moreover, they also provide guidance for the selection of suitable metal atoms to form ordered dispersed metal nanoclusters on similar templates.     

In-situ X-ray Diffraction study of Metal Induced Crystallization of amorphous silicon

By covering amorphous silicon (a-Si) with a thin metal film, it is possible to lower the crystallization temperature of the a-Si (typically around 800 °C when using ramp anneals) to levels which can be used in a manufacturing process. This phenomenon of Metal Induced Crystallization (MIC) has been reported previously for Ni, Au and Al. In this work, in-situ X-ray Diffraction was used to study the MIC process for 20 different metals (Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Al). The 7 metals which lower the crystallization temperature the most are Ni, Pt, Pd, Cu, Au, Al and Ag. The crystallization kinetics were studied in detail for these 7 materials. In order to explain the MIC process, two models where used depending on the interaction of the metal with Si (eutectic or compound forming).     

Crystal structure and superconductivity of new ternary MTGe germanides (M = Ti,Zr,Hf and T = Ru,Os,Rh,Ir)

ZrIrGe and HfIrGe crystallize in the TiNiSi-type structure and exhibit a superconducting transition at 2.75K and 4.98K respectively. TiIrGe and HfRhGe have two allotropic varieties and their superconducting properties are strongly influenced by their crystal structure. On the other hand no superconducting transition has been observed above 1.6K for TiTGe (T = Ru,Os,Rh), ZrTGe (T = Ru,Os) and HfTGe (T = Ru,Os) which adopt either the ordered Fe₂P-type or the TiFeSi-type superstructure. This investigation shows clearly that the TiNiSi-type structure favors occurence of superconductivity in ternary germanides as previously found for ternary silicides.     

铂、钯材料ICP分析方法的研究

由于铂、钯材料被广泛应用于多种精密行业,其材料含量也越来越受到重视,目前采用的方法不是操作复杂就是范围太窄而不符合日常检测要求,因此急需建立一种简捷快速的、适用于铂、钯材料含量为95．0％-99．99％的化学分析方法。该文用电感耦合等离子发射光谱分析,测定铂、钯材料中铂（钯）、铑、铱、钌、金、银、铜、铁、镍、铝、铅、锰、铬、镁、锡、硅、锌及铋等杂质元素的方法,达到了检出限低、重复性好、回收率在88．3％-100％的检测目标。     

Adsorption of platinum (IV), palladium (II) and gold (III) from aqueous solutions onto L-lysine modified crosslinked chitosan resin

Crosslinked chitosan resin chemically modified with L-lysine has been used to investigate the adsorption of Pt(IV), Pd(II) and Au(III) from aqueous solutions. Batch adsorption studies were carried out with various parameters, such as initial metal ion concentration, contact time, pH and temperature. The maximum adsorption capacity was found at pH 1.0 for Pt(IV), at pH 2.0 for Au(III) and Pd(II). Langmuir and Freundlich isotherm models were applied to analyze the experimental data. The best interpretation for the experimental data was given by the Langmuir isotherm and the maximum adsorption capacity was found to be 129.26 mg/g for Pt(IV), 109.47 mg/g for Pd(II) and 70.34 mg/g for Au(III). The kinetic data was tested using pseudo-first-order and pseudo-second-order kinetic models. Kinetic data correlated well with the pseudo-second-order kinetic model, indicating that the chemical sorption was the rate-limiting step. Thermodynamic parameters like Gibbs free energy (DeltaG degrees), enthalpy (DeltaH degrees) and entropy (DeltaS degrees) were evaluated by applying the Van't Hoff equation. The thermodynamic study indicated that the adsorption process is spontaneous and exothermic in nature. The desorption studies were carried out using various reagents. The maximum percent desorption of precious metal ions were obtained when the reagent 0.7 M thiourea-2 M HCl was used.     

Giant Switchable Rashba Effect in Oxide Heterostructures

One of the most fundamental phenomena and a reminder of the electron's relativistic nature is the Rashba spin splitting for broken inversion symmetries in two‐dimensional condensed matter systems. Typically, this splitting is a tiny relativistic correction. By coupling ferroelectric BaTiO₃ and a 5d (or 4d) transition metal oxide with a large spin‐orbit coupling, Ba(Os,Ir,Ru)O₃, it is shown that giant Rashba spin splittings are indeed possible and even controllable by an external electric field. Based on density functional theory and a microscopic tight binding understanding, it is concluded that the electric field is amplified and stored as a ferroelectric Ti‐O distortion which, through the network of oxygen octahedra, induces a large (Os,Ir,Ru)‐O distortion. The BaTiO₃/Ba(Os,Ru,Ir)O₃ heterostructure is hence the ideal test station for switching and studying the Rashba effect and allows applications at room temperature.     

The search for novel superhard and incompressible materials on the basis of higher borides of <Emphasis Type="Italic">s</Emphasis>, <Emphasis Type="Italic">p</Emphasis>, <Emphasis Type="Italic">d</Emphasis> metals

The state of the art in the search for novel superhard and (or) incompressible materials on the basis of higher borides of s, p, d metals has been briefly reviewed. The information has been considered about experimental and theoretical studies of the following groups of borides: diborides of 4d, 5d heavy metals (Tc, Ru, Rh, Re, Os, and Ir), hexagonal tetraborides with the WB₄-type structure, and AMB₁₄ borides (where A, M are s, p metals) as well as of a number of related systems.     

Producing the MP2O7 (M = Nb, Ta, Re, Mo, W) diphosphates at high pressures and catalytic activity of the Pt(Pd)/MP2O7 systems in the reaction of hydrogen oxidation

The MP₂O₇ (M = W, Mo, Nb, Ta, Re) diphosphates have been synthesized under thermobaric conditions as initial matrices for the Pt(Pd)/MP₂O₇ hydrogen-oxygen catalytic systems.     

Separation of thorium and uranium from silicate rock samples using two commercial extraction chromatographic resins

A new chemical separation technique to isolate Th and U from silicate rocks was established by using two kinds of commercial extraction chromatographic resins. In the first column procedure, with U/TEVA·spec resin, almost all elements except Th and U were eluted by 4 M HNO(3). Th was then separated by using 5 M HCl, and U was finally isolated by successive addition of 0.1 M HNO(3). A significant amount of Zr still remained in the Th fraction, which was then further purified in the second column stage using TEVA·spec resin. In the second procedure, Zr was eluted first by using 2 M HNO(3), and then Th was collected by 0.1 M HNO(3). Both the Th and U fractions obtained by these procedures were sufficiently pure for thermal ionization mass spectrometric (TIMS) analysis. Recovery yields of Th and U exceeded 90%, and total blanks were <19 pg for Th and <10 pg for U. Our method has advantages over previous methods in terms of matrix effects, tailing problems, and degree of isolation. Since Th and U are effectively separated without suffering any matrix interference from coexisting cations and anions, this technique can be used not only for the analysis of igneous rock samples but also for the analysis of soils, marine sediments, carbonates, phosphates and seawater, groundwater, and surface water.     

La liaison metal-metal dans les clusters M12O36: I - Preparation et etude structurale des phases La4M6O19 (M = Ru,Os)

La₄Ru₆O₁₉ and La₄Os₆O₁₉ are prepared for the first time by the oxidation of stoechiometric mixtures of (La₂O₃ + RuO₂) and (La₂O₃ + Os) with excess KC10₃. The crystal structure of both compounds are solved by conventional Fourier and least-squares methods to R = 0.022 and R = 0.024, respectively, using automated four-circle diffractometer data. Both are isostructural with La₄Re₆O₁₉. M-M distances (2.488 Å for M = Ru and 2.499 Å for M = Os) show evidence of strong metal-metal interaction. Comparison of data for M = Ru, Os or Re reveals the evolution of some interatomic distances with Z.     

CoSb_2结构5d过渡金属二氮化物力学性质的第一性原理研究

基于密度泛函理论平面波赝势的第一性原理方法,对具有CoSb2结构5d过渡金属二氮化物TMN2(TM=Hf、Ta、w、Re、Os、Ir、Pt、Au)的晶格常数、电子结构和力学性能进行了计算.计算结果表明,对于该结构的二氮化物,除AuN2外,均同时满足热力学和机械稳定性标准;其中OsN2具有最高的体弹性模量和剪切模量分别为418和257GPa;态密度分析表明,过渡金属原子的5d轨道与氮原子的2p轨道之间发生了强烈的杂化现象,二者之间形成了较强共价键.     

Interdiffusion study in the Pd–Pt system

Interdiffusion, intrinsic, tracer and impurity diffusion coefficients are calculated in the Pd–Pt system. Interdiffusion coefficients are more or less insensitive to composition change. Activation energy varies in the range of 324–353 kJ/mol. Impurity diffusion coefficients calculated in this study and available tracer diffusion coefficients in pure elements indicate that Pd has higher diffusion rate compared to Pt in pure Pd, whereas, both the elements have similar diffusion rates in Pt. Kirkendall marker experiments indicate that Pd has much higher diffusion rate in Pd3.5at.%Pt compared to Pt.     

Reduction of oxide layer on various metal surfaces by atomic hydrogen treatment

The reduction of various metallic oxides was examined. Atomic hydrogen generated on a heated tungsten catalyzer was used for reduction. It was found that Cu, Ru, Nb, Mo, Rh, Pd, Ir and Pt oxides can be reduced by irradiation with atomic hydrogen. The activation energy for oxide removal was examined and it was found that the values were very small, 10^− 2 to 10^− 4 eV.