Salt-induced square prism Pd microtubes and their ethanol electrocatalysis properties

International Nuclear Information System (INIS)

Jiang, Kunpeng; Ma, Shenghua; Wang, Yinan; Zhang, Ying; Han, Xiaojun

2017-01-01

Highlights: • A simple method is established to fabricate square prism Pd microtubes. • The novel square prism Pd microtubes are based on a salt-induced aggregation event. • The surface of the square prism tubes convert from cataphracted nanosheets to spheres after calcinations treatment. • The square prism pure Pd tubes show excellent electro catalytic activity towards ethanol oxidation. - Abstract: The synthesis of square prism tubes are always challenging due to their thermo and dynamical instability. We demonstrated a simple method using Pd"2"+ doped PoPD oligomers as building blocks to assemble into 1D square prism metal-organic microtubes, which consists of cataphracted nanosheets on the surfaces. After high temperature treatment, the microtubes became square prism Pd tubes with a cross section size of 3 μm. The pure Pd microtubes showed excellent catalyzing activity towards the electro oxidation of ethanol. Their electrochemically active surface area is 48.2 m"2 g"−"1, which indicates the square prism Pd tubes have great potential in the field of fuel cell.

Salt-induced square prism Pd microtubes and their ethanol electrocatalysis properties

Energy Technology Data Exchange (ETDEWEB)

Jiang, Kunpeng; Ma, Shenghua; Wang, Yinan; Zhang, Ying; Han, Xiaojun, E-mail: hanxiaojun@hit.edu.cn

2017-05-01

Highlights: • A simple method is established to fabricate square prism Pd microtubes. • The novel square prism Pd microtubes are based on a salt-induced aggregation event. • The surface of the square prism tubes convert from cataphracted nanosheets to spheres after calcinations treatment. • The square prism pure Pd tubes show excellent electro catalytic activity towards ethanol oxidation. - Abstract: The synthesis of square prism tubes are always challenging due to their thermo and dynamical instability. We demonstrated a simple method using Pd{sup 2+} doped PoPD oligomers as building blocks to assemble into 1D square prism metal-organic microtubes, which consists of cataphracted nanosheets on the surfaces. After high temperature treatment, the microtubes became square prism Pd tubes with a cross section size of 3 μm. The pure Pd microtubes showed excellent catalyzing activity towards the electro oxidation of ethanol. Their electrochemically active surface area is 48.2 m{sup 2} g{sup −1}, which indicates the square prism Pd tubes have great potential in the field of fuel cell.

Effects of metal composition and ratio on peptide-templated multimetallic PdPt nanomaterials

International Nuclear Information System (INIS)

Merrill, Nicholas A.; Nitka, Tadeusz T.; McKee, Erik M.; Merino, Kyle C.; Drummy, Lawrence F.

2017-01-01

It can be difficult to simultaneously control the size, composition, and morphology of metal nanomaterials under benign aqueous conditions. For this, bioinspired approaches have become increasingly popular due to their ability to stabilize a wide array of metal catalysts under ambient conditions. In this regard, we used the R5 peptide as a three-dimensional template for formation of PdPt bimetallic nanomaterials. Monometallic Pd and Pt nanomaterials have been shown to be highly reactive toward a variety of catalytic processes, but by forming bimetallic species, increased catalytic activity may be realized. The optimal metal-to-metal ratio was determined by varying the Pd:Pt ratio to obtain the largest increase in catalytic activity. To better understand the morphology and the local atomic structure of the materials, the bimetallic PdPt nanomaterials were extensively studied by transmission electron microscopy, extended X-ray absorption fine structure spectroscopy, X-ray photoelectron spectroscopy, and pair distribution function analysis. The resulting PdPt materials were determined to form multicomponent nanostructures where the Pt component demonstrated varying degrees of oxidation based upon the Pd:Pt ratio. To test the catalytic reactivity of the materials, olefin hydrogenation was conducted, which indicated a slight catalytic enhancement for the multicomponent materials. Finally, these results suggest a strong correlation between the metal ratio and the stabilizing biotemplate in controlling the final materials morphology, composition, and the interactions between the two metal species.

Effects of Metal Composition and Ratio on Peptide-Templated Multimetallic PdPt Nanomaterials

Energy Technology Data Exchange (ETDEWEB)

Merrill, Nicholas A.; Nitka, Tadeusz T.; McKee, Erik M.; Merino, Kyle C.; Drummy, Lawrence F.; Lee, Sungsik; Reinhart, Benjamin; Ren, Yang; Munro, Catherine J.; Pylypenko, Svitlana; Frenkel, Anatoly I.; Bedford, Nicholas M.; Knecht, Marc R.

2017-02-22

It can be difficult to simultaneously control the size, composition, and morphology of metal nanomaterials under benign aqueous conditions. For this, bio-inspired approaches have become increasing popular due to their ability to stabilize a wide array of metal catalysts under ambient conditions. In this regard, we used the R5 peptide as a 3D template for the formation of PdPt bimetallic nanomaterials. Monometallic Pd and Pt nanomaterials have been shown to be highly reactive towards a variety of catalytic processes, but by forming bimetallic species, increased catalytic activity may be realized. The optimal metal-to-metal ratio was determined by varying the Pd:Pt ratio to obtain the largest increase in catalytic activity. To better understand the morphology and the local atomic structure of the materials, the bimetallic PdPt nanomaterials were extensively studied using transmission electron microscopy, extended X-ray absorption fine structure spectroscopy, X-ray photoelectron spectroscopy, and pair distribution function analysis. The resulting PdPt materials were determined to form multicomponent nanostructures where the Pt component demonstrated varying degrees of oxidation based upon the Pd:Pt ratio. To test the catalytic reactivity of the materials, olefin hydrogenation was conducted which indicated a slight catalytic enhancement for the multicomponent materials. These results suggest a strong correlation between the metal ratio and the stabilizing biotemplate in controlling the final materials morphology, composition, and the interactions between the two metal species.

Structure and Mobility of Metal Clusters in MOFs: Au, Pd, and AuPd Clusters in MOF-74

DEFF Research Database (Denmark)

Vilhelmsen, Lasse; Walton, Krista S.; Sholl, David S.

2012-01-01

is just as important for nanocluster adsorption as open Zn or Mg metal sites. Using the large number of clusters generated by the GA, we developed a systematic method for predicting the mobility of adsorbed clusters. Through the investigation of diffusion paths a relationship between the cluster......Understanding the adsorption and mobility of metal–organic framework (MOF)-supported metal nanoclusters is critical to the development of these catalytic materials. We present the first theoretical investigation of Au-, Pd-, and AuPd-supported clusters in a MOF, namely MOF-74. We combine density...... functional theory (DFT) calculations with a genetic algorithm (GA) to reliably predict the structure of the adsorbed clusters. This approach allows comparison of hundreds of adsorbed configurations for each cluster. From the investigation of Au8, Pd8, and Au4Pd4 we find that the organic part of the MOF...

Synthesis of Pd and Rh metal nanoparticles in the interlayer space of organically modified montmorillonite

International Nuclear Information System (INIS)

Patel, Hasmukh A.; Bajaj, Hari C.; Jasra, Raksh Vir

2008-01-01

This study reports the synthesis of palladium and rhodium metal nanoparticles supported on montmorillonite (MMT) and partially organically modified MMT (POMM) using tetraamine palladium and hexaamine rhodium complex as precursor for palladium and rhodium respectively. The synthesized nanoparticles were characterized by powder X-ray diffraction PXRD and TEM. The PXRD study shows characteristic crystallographic planes for Pd and Rh metal and confirm the formation of metal nanoparticles in MMT and POMM. The TEM images reveal the effect of organic modification of MMT on decreasing particle size of Pd and Rh metal. The Pd and Rh metal nanoparticles are agglomerated in pristine MMT while nanoparticles are well dispersed in POMM. ICP-AES analysis was carried out to estimate quantitative amount of Pd and Rh metal in MMT and POMM

A fast response hydrogen sensor with Pd metallic grating onto a fiber's end-face

Science.gov (United States)

Yan, Haitao; Zhao, Xiaoyan; Zhang, Chao; Li, Qiu-Ze; Cao, Jingxiao; Han, Dao-Fu; Hao, Hui; Wang, Ming

2016-01-01

We demonstrated an integrated hydrogen sensor with Pd metallic grating fabricated on a fiber end-face. The grating consists of three thin metal layers in stacks, Au, WO3 and Pd. The WO3 is used as a waveguide layer between the Pd and Au layer. The Pd layer is etched by using a focused ion beam (FIB) method, forming a Pd metallic grating with period of 450 nm. The sensor is experimentally exposed to hydrogen gas environment. Changing the concentration from 0% to 4% which is the low explosive limit (LEL), the resonant wavelength measured from the reflection experienced 28.10 nm spectral changes in the visible range. The results demonstrated that the sensor is sensitive for hydrogen detection and it has fast response and low temperature effect.

Development of an inter-atomic potential for the Pd-H binary system.

Energy Technology Data Exchange (ETDEWEB)

Zimmerman, Jonathan A.; Hoyt, Jeffrey John (McMaster University, Hamilton, Ontario, Canada); Leonard, Francois Leonard; Griffin, Joshua D.; Zhou, Xiao Wang

2007-09-01

Ongoing research at Sandia National Laboratories has been in the area of developing models and simulation methods that can be used to uncover and illuminate the material defects created during He bubble growth in aging bulk metal tritides. Previous efforts have used molecular dynamics calculations to examine the physical mechanisms by which growing He bubbles in a Pd metal lattice create material defects. However, these efforts focused only on the growth of He bubbles in pure Pd and not on bubble growth in the material of interest, palladium tritide (PdT), or its non-radioactive isotope palladium hydride (PdH). The reason for this is that existing inter-atomic potentials do not adequately describe the thermodynamics of the Pd-H system, which includes a miscibility gap that leads to phase separation of the dilute (alpha) and concentrated (beta) alloys of H in Pd at room temperature. This document will report the results of research to either find or develop inter-atomic potentials for the Pd-H and Pd-T systems, including our efforts to use experimental data and density functional theory calculations to create an inter-atomic potential for this unique metal alloy system.

Electronic Structure of the fcc Transition Metals Ir, Rh, Pt, and Pd

DEFF Research Database (Denmark)

Andersen, O. Krogh

1970-01-01

We give a complete description of a relativistic augmented-plane-wave calculation of the band structures of the paramagnetic fcc transition metals Ir, Rh, Pt, and Pd. The width and position of the d band decrease in the sequence Ir, Pt, Rh, Pd; and N(EF)=13.8,23.2,18.7, and 32.7 (states/atom)/Ry,......We give a complete description of a relativistic augmented-plane-wave calculation of the band structures of the paramagnetic fcc transition metals Ir, Rh, Pt, and Pd. The width and position of the d band decrease in the sequence Ir, Pt, Rh, Pd; and N(EF)=13.8,23.2,18.7, and 32.7 (states....../atom)/Ry, respectively. Spin-orbit coupling is important for all four metals and the coupling parameter varies by 30% over the d bandwidth. Detailed comparisons with de Haas—van Alphen Fermi-surface dimensions have previously been presented and the agreement was very good. Comparison with measured electronic specific...

Creep mechanisms and constitutive relations in pure metals

International Nuclear Information System (INIS)

Nix, W.D.

1979-01-01

The mechanisms of creep of pure metals is briefly reviewed and divided into two parts: steady state flow mechanisms, and non-steady state flow mechanisms and constitutive relations. Creep by diffusional flow is now reasonably well understood, with theory and experiment in good agreement. The closely related phenomenon of Harper--Dorn creep can also be understood in terms of diffusion between dislocations. Power law creep involves the climb of edge disloctions controlled by lattice self diffusion. Theoretical treatments of this process invariably give a power law exponent of 3. This natural creep law is compared with the data for FCC and BCC metals. It is suggested that diffusion controlled climb is the controlling process in BCC metals at very high temperatures. Stacking fault energy effects may preclude the possibility that creep is controlled entirely by lattice self diffusion in some FCC metals. The subject of power law breakdown is presented as a natural consequence of the transition to low temperature flow phenomena. The role of core diffusion in this transition is briefly discussed. The mechanisms are presented by which pure metals creep at elevated temperatures. While most of this review deals with the mechanisms of steady state flow, some discussion is devoted to creep flow under non-steady state conditions. This topic is discussed in connection with the development of constitutive equations for describing plastic flow in metals

Molecular Dynamics Simulation of Solidification of Pd-Ni Clusters with Different Nickel Content

Directory of Open Access Journals (Sweden)

Chen Gang

2014-01-01

Full Text Available Molecular dynamics simulation has been performed for investigating the glass transition of Pd-Ni alloy nanoparticles in the solidification process. The results showed that the Pd-Ni nanoparticles with composition far from pure metal should form amorphous structure more easily, which is in accordance with the results of the thermodynamic calculation. There are some regular and distorted fivefold symmetry in the amorphous Pd-Ni alloy nanoparticles. The nanoclusters with bigger difference value between formation enthalpies of solutions and glasses will transform to glass more easily than the other Pd-Ni alloy nanoclusters.

Design of Pd-Based Bimetallic Catalysts for ORR: A DFT Calculation Study

Directory of Open Access Journals (Sweden)

Lihui Ou

2015-01-01

Full Text Available Developing Pd-lean catalysts for oxygen reduction reaction (ORR is the key for large-scale application of proton exchange membrane fuel cells (PEMFCs. In the present paper, we have proposed a multiple-descriptor strategy for designing efficient and durable ORR Pd-based alloy catalysts. We demonstrated that an ideal Pd-based bimetallic alloy catalyst for ORR should possess simultaneously negative alloy formation energy, negative surface segregation energy of Pd, and a lower oxygen binding ability than pure Pt. By performing detailed DFT calculations on the thermodynamics, surface chemistry and electronic properties of Pd-M alloys, Pd-V, Pd-Fe, Pd-Zn, Pd-Nb, and Pd-Ta, are identified theoretically to have stable Pd segregated surface and improved ORR activity. Factors affecting these properties are analyzed. The alloy formation energy of Pd with transition metals M can be mainly determined by their electron interaction. This may be the origin of the negative alloy formation energy for Pd-M alloys. The surface segregation energy of Pd is primarily determined by the surface energy and the atomic radius of M. The metals M which have smaller atomic radius and higher surface energy would tend to favor the surface segregation of Pd in corresponding Pd-M alloys.

Hydrogen storage in Pd nanocrystals covered with a metal-organic framework

Science.gov (United States)

Li, Guangqin; Kobayashi, Hirokazu; Taylor, Jared M.; Ikeda, Ryuichi; Kubota, Yoshiki; Kato, Kenichi; Takata, Masaki; Yamamoto, Tomokazu; Toh, Shoichi; Matsumura, Syo; Kitagawa, Hiroshi

2014-08-01

Hydrogen is an essential component in many industrial processes. As a result of the recent increase in the development of shale gas, steam reforming of shale gas has received considerable attention as a major source of H2, and the more efficient use of hydrogen is strongly demanded. Palladium is well known as a hydrogen-storage metal and an effective catalyst for reactions related to hydrogen in a variety of industrial processes. Here, we present remarkably enhanced capacity and speed of hydrogen storage in Pd nanocrystals covered with the metal-organic framework (MOF) HKUST-1 (copper(II) 1,3,5-benzenetricarboxylate). The Pd nanocrystals covered with the MOF have twice the storage capacity of the bare Pd nanocrystals. The significantly enhanced hydrogen storage capacity was confirmed by hydrogen pressure-composition isotherms and solid-state deuterium nuclear magnetic resonance measurements. The speed of hydrogen absorption in the Pd nanocrystals is also enhanced by the MOF coating.

Polydopamine-mediated surface-functionalization of graphene oxide for heavy metal ions removal

International Nuclear Information System (INIS)

Dong, Zhihui; Zhang, Feng; Wang, Dong; Liu, Xia; Jin, Jian

2015-01-01

By utilizing polydopamine (PD) nano-thick interlayer as mediator, polyethylenimine (PEI) brushes with abundant amine groups were grafted onto the surface of PD coated graphene oxide (GO) uniformly via a Michael-Addition reaction and produced a PEI–PD/GO composite nanosheets. The PEI–PD/GO composite exhibited an improved performance for adsorption of heavy metal ions as compared to PEI-coated GO and pure GO. The adsorption capacities for Cu 2+ , Cd 2+ , Pb 2+ , Hg 2+ are up to 87, 106, 197, and 110 mg/g, respectively. To further make the GO based composite operable, PEI–PD/RGO aerogel was prepared through hydrothermal and achieved a high surface area up to 373 m 2 /g. Although the adsorption capacity of PEI–PD/RGO aerogel for heavy metal ions decreases a little as compared to PEI–PD/GO composite dispersion (38, 32, 95, 113 mg/g corresponding to Cu 2+ , Cd 2+ , Pb 2+ , and Hg 2+ , respectively), it could be recycled several times in a simple way by releasing adsorbed metal ions, indicating its potential application for cleaning wastewater. - Graphical abstract: Polyethylenimine (PEI) brushes were grafted onto the surface of graphene oxide (GO) uniformly via a Michael-Addition reaction between the PEI and polydopamine interlayer coated on GO surface. The PEI–PD/GO composite exhibited an improved performance for adsorption of heavy metal ions compared to PEI-coated GO and pure GO. - Highlights: • We prepared polyethylenimine grafted polydopamine-mediated graphene oxide composites. • Introduction of PD layer increases metal ions adsorption capacity. • PEI–PD/RGO aerogel exhibited a superior adsorption performance. • PEI–PD/RGO aerogel can be recycled several times in a simple way

Electronic structure of transition metal dichalcogenides PdTe2 and Cu0.05PdTe2 superconductors obtained by angle-resolved photoemission spectroscopy

International Nuclear Information System (INIS)

Liu Yan; Zhao Jian-Zhou; Yu Li; Hu Cheng; Liu De-Fa; Peng Ying-Ying; Xie Zhuo-Jin; He Jun-Feng; Chen Chao-Yu; Feng Ya; Yi He-Mian; Liu Xu; Zhao Lin; He Shao-Long; Liu Guo-Dong; Dong Xiao-Li; Zhang Jun; Lin Cheng-Tian; Chen Chuang-Tian; Xu Zu-Yan

2015-01-01

The layered transition metal chalcogenides have been a fertile land in solid state physics for many decades. Various MX 2 -type transition metal dichalcogenides, such as WTe 2 , IrTe 2 , and MoS 2 , have triggered great attention recently, either for the discovery of novel phenomena or some extreme or exotic physical properties, or for their potential applications. PdTe 2 is a superconductor in the class of transition metal dichalcogenides, and superconductivity is enhanced in its Cu-intercalated form, Cu 0.05 PdTe 2 . It is important to study the electronic structures of PdTe 2 and its intercalated form in order to explore for new phenomena and physical properties and understand the related superconductivity enhancement mechanism. Here we report systematic high resolution angle-resolved photoemission (ARPES) studies on PdTe 2 and Cu 0.05 PdTe 2 single crystals, combined with the band structure calculations. We present in detail for the first time the complex multi-band Fermi surface topology and densely-arranged band structure of these compounds. By carefully examining the electronic structures of the two systems, we find that Cu-intercalation in PdTe 2 results in electron-doping, which causes the band structure to shift downwards by nearly 16 meV in Cu 0.05 PdTe 2 . Our results lay a foundation for further exploration and investigation on PdTe 2 and related superconductors. (rapid communication)

PdRu/C catalysts for ethanol oxidation in anion-exchange membrane direct ethanol fuel cells

Science.gov (United States)

Ma, Liang; He, Hui; Hsu, Andrew; Chen, Rongrong

2013-11-01

Carbon supported PdRu catalysts with various Pd:Ru atomic ratios were synthesized by impregnation method, and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), electrochemical half-cell tests, and the anion-exchange membrane direct ethanol fuel cell (AEM-DEFC) tests. XRD results suggest that the PdRu metal exists on carbon support in an alloy form. TEM study shows that the bimetallic PdRu/C catalysts have slightly smaller average particle size than the single metal Pd/C catalyst. Lower onset potential and peak potential and much higher steady state current for ethanol oxidation in alkaline media were observed on the bimetallic catalysts (PdxRuy/C) than on the Pd/C, while the activity for ethanol oxidation on the pure Ru/C was not noticeable. By using Pd/C anode catalysts and MnO2 cathode catalysts, AEM-DEFCs free from the expensive Pt catalyst were assembled. The AEM DEFC using the bimetallic Pd3Ru/C anode catalyst showed a peak power density as high as 176 mW cm-2 at 80 °C, about 1.8 times higher than that using the single metal Pd/C catalyst. The role of Ru for enhancing the EOR activity of Pd/C catalysts is discussed.

Synthesis of PdO/MCM-41 nanocomposites using trans-[PdCl2(PEt3)2] as the source of metal

International Nuclear Information System (INIS)

Hernandez-Pineda, Jessica; Rio, Jose Manuel del; Carreto, Enrique; Terres, Eduardo; Montoya, J. Asencion; Zuniga-Gonzalez, Maria de Jesus; Morgado, Jorge

2009-01-01

Three PdO/MCM-41 nanocomposites containing PdO species that are dispersed on an MCM-41 support have been prepared using trans-[PdCl 2 (PEt 3 ) 2 ] as the source of metal. Thermal gravimetric analysis of the decomposition of this complex in air reveals a remarkable mass loss of all nonmetallic elements centered at 300 deg. C. The materials were characterized with X-ray powder diffraction (XRPD), nitrogen sorption and TEM, which showed that the PdO nanoparticles were present inside the pores of MCM-41. XRPD analysis confirms formation of PdO (palladinite) nanocrystals, as the sole crystalline phase present in the nanocomposites.

Pure Electric and Pure Magnetic Resonances in Near-Infrared Metal Double-Triangle Metamaterial Arrays

International Nuclear Information System (INIS)

Cao Zhi-Shen; Pan Jian; Chen Zhuo; Zhan Peng; Min Nai-Ben; Wang Zhen-Lin

2011-01-01

We experimentally and numerically investigate the optical properties of metamaterial arrays composed of double partially-overlapped metallic nanotriangles fabricated by an angle-resolved nanosphere lithography. We demonstrate that each double-triangle can be viewed as an artificial magnetic element analogous to the conventional metal split-ring-resonator. It is shown that under normal-incidence conditions, individual double-triangle can exhibit a strong local magnetic resonance, but the collective response of the metamaterial arrays is purely electric because magnetic resonances of the two double-triangles in a unit cell having opposite openings are out of phase. For oblique incidences the metamaterial arrays are shown to support a pure magnetic response at the same frequency band. Therefore, switchable electric and magnetic resonances are achieved in double-triangle arrays. Moreover, both the electric and magnetic resonances are shown to allow for a tunability over a large spectral range down to near-infrared. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Surface noble metal modified PdM/C (M = Ru, Pt, Au) as anode catalysts for direct ethanol fuel cells

International Nuclear Information System (INIS)

Mao, Han; Huang, Tao; Yu, Aishui

2016-01-01

In this article, we studied the surface noble metal modification on Pd nanoparticles, other than the homogeneous or core-shell structure. The surface modification will lead to the uneven constitution within the nanoparticles and thus more obvious optimization effect toward the catalyst brought by the lattice deformation. The surface of the as-prepared Pd nanoparticles was modified with Ru, Pt or Au by a moderate and green approach, respectively. XPS results confirm the interactive electron effects between Pd and the modified noble metal. Electrochemical measurements show that the surface noble metal modified catalysts not only show higher catalytic activity, but also better stability and durability. The PdM/C catalysts all exhibit good dispersion and very little agglomeration after long-term potential cycles toward ethanol oxidation. With only 10% metallic atomic ratio of Au, PdAu/C catalyst shows extraordinary catalytic activity and stability, the peak current reaches 1700 mA mg"−"1 Pd, about 2.5 times that of Pd/C. Moreover, the PdAu/C maintains 40% of the catalytic activity after 4500 potential cycles. - Highlights: • Pd-based catalysts with complicated exposed facets. • Much enhanced electrocatalytic activity and stability with about 10% noble metal M (M = Ru, Pt, Au) on Pd nanoparticles. • The outstanding electrocatalytic performance of PdAu/C towards ethanol oxidation after the Au modification.

Surface noble metal modified PdM/C (M = Ru, Pt, Au) as anode catalysts for direct ethanol fuel cells

Energy Technology Data Exchange (ETDEWEB)

Mao, Han; Huang, Tao, E-mail: huangt@fudan.edu.cn; Yu, Aishui, E-mail: asyu@fudan.edu.cn

2016-08-15

In this article, we studied the surface noble metal modification on Pd nanoparticles, other than the homogeneous or core-shell structure. The surface modification will lead to the uneven constitution within the nanoparticles and thus more obvious optimization effect toward the catalyst brought by the lattice deformation. The surface of the as-prepared Pd nanoparticles was modified with Ru, Pt or Au by a moderate and green approach, respectively. XPS results confirm the interactive electron effects between Pd and the modified noble metal. Electrochemical measurements show that the surface noble metal modified catalysts not only show higher catalytic activity, but also better stability and durability. The PdM/C catalysts all exhibit good dispersion and very little agglomeration after long-term potential cycles toward ethanol oxidation. With only 10% metallic atomic ratio of Au, PdAu/C catalyst shows extraordinary catalytic activity and stability, the peak current reaches 1700 mA mg{sup −1} Pd, about 2.5 times that of Pd/C. Moreover, the PdAu/C maintains 40% of the catalytic activity after 4500 potential cycles. - Highlights: • Pd-based catalysts with complicated exposed facets. • Much enhanced electrocatalytic activity and stability with about 10% noble metal M (M = Ru, Pt, Au) on Pd nanoparticles. • The outstanding electrocatalytic performance of PdAu/C towards ethanol oxidation after the Au modification.

MIS gas sensors based on porous silicon with Pd and WO{sub 3}/Pd electrodes

Energy Technology Data Exchange (ETDEWEB)

Solntsev, V.S. [Institute of Semiconductor Physics, National Academy of Science of Ukraine, 03028, Kiev (Ukraine); Gorbanyuk, T.I., E-mail: tatyanagor@mail.r [Institute of Semiconductor Physics, National Academy of Science of Ukraine, 03028, Kiev (Ukraine); Litovchenko, V.G.; Evtukh, A.A. [Institute of Semiconductor Physics, National Academy of Science of Ukraine, 03028, Kiev (Ukraine)

2009-09-30

Pd and WO{sub 3}/Pd gate metal-oxide-semiconductor (MIS) gas sensitive structures based on porous silicon layers are studied by the high frequency C(V) method. The chemical compositions of composite WO{sub 3}/Pd electrodes are characterized by secondary-ion mass spectrometry (SIMS). The atomic force microscopy (AFM) was used for morphologic studies of WO{sub 3}/Pd films. As shown in the experiments, WO{sub 3}/Pd structures are more sensitive and selective to the adsorption of hydrogen sulphide compared to Pd gate. The analyses of kinetic characteristics allow us to determine the response and characteristic times for these structures. The response time of MIS-structures with thin composite WO{sub 3}/Pd electrodes (the thickness of Pd is about 50 nm with WO{sub 3} clusters on its surface) is slower compared to the structures with Pd electrodes. Slower sensor responses of WO{sub 3}-based gas sensors may be associated with different mechanism of gas sensitivity of given structures. The enhanced sensitivity and selectivity to H{sub 2}S action of WO{sub 3}/Pd MIS-structures can also be explained by the chemical reaction that occurs at the catalytic active surface of gate electrodes. The possible mechanisms of enhanced sensitivity and selectivity to H{sub 2}S adsorption of MIS gas sensors with WO{sub 3}/Pd composite gate electrodes compared to pure Pd have been analyzed.

Density functional theory based study of chlorine doped WS2-metal interface

International Nuclear Information System (INIS)

Chanana, Anuja; Mahapatra, Santanu

2016-01-01

Investigation of a transition metal dichalcogenide (TMD)-metal interface is essential for the effective functioning of monolayer TMD based field effect transistors. In this work, we employ the Density Functional Theory calculations to analyze the modulation of the electronic structure of monolayer WS 2 with chlorine doping and the relative changes in the contact properties when interfaced with gold and palladium. We initially examine the atomic and electronic structures of pure and doped monolayer WS 2 supercell and explore the formation of midgap states with band splitting near the conduction band edge. Further, we analyze the contact nature of the pure supercell with Au and Pd. We find that while Au is physiosorbed and forms n-type contact, Pd is chemisorped and forms p-type contact with a higher valence electron density. Next, we study the interface formed between the Cl-doped supercell and metals and observe a reduction in the Schottky barrier height (SBH) in comparison to the pure supercell. This reduction found is higher for Pd in comparison to Au, which is further validated by examining the charge transfer occurring at the interface. Our study confirms that Cl doping is an efficient mechanism to reduce the n-SBH for both Au and Pd, which form different types of contact with WS 2 .

Fatigue and corrosion of a Pd-based bulk metallic glass in various environments

Energy Technology Data Exchange (ETDEWEB)

Watanabe, L.Y. [East Los Angeles College, Monterey Park, CA 91754 (United States); Roberts, S.N. [Keck Laboratory of Materials Science, California Institute of Technology, Pasadena, CA 91125 (United States); Baca, N. [Department of Chemistry and Biochemistry, California State University Northridge, Northridge, CA 91330 (United States); Wiest, A. [Naval Surface Warfare Center, Norco, CA (United States); Garrett, S.J. [Department of Chemistry and Biochemistry, California State University Northridge, Northridge, CA 91330 (United States); Conner, R.D., E-mail: rdconner@csun.edu [Department of Manufacturing Systems Engineering and Management, California State University Northridge, 18111 Nordhoff St., Mail Code 8295, Northridge, CA 91330 (United States)

2013-10-15

Bulk metallic glasses (BMGs) possess attractive properties for biomedical applications, including high strength, hardness and corrosion resistance, and low elastic modulus. In this study, we conduct rotating beam fatigue tests on Pd{sub 43}Ni{sub 10}Cu{sub 27}P{sub 20} bulk metallic glass in air and Eagle's medium (EM) and measure the corrosive resistance of the alloy by submersion in acidic and basic electrolytes. Fatigue results are compared to those of commonly used biometals in EM. Rotating beam fatigue tests conducted in air and in Eagle's medium show no deterioration in fatigue properties in this potentially corrosive environment out to 10{sup 7} cycles. A specimen size effect is revealed when comparing fatigue results to those of a similar alloy of larger minimum dimensions. Corrosion tests show that the alloy is not affected by highly basic (NaOH) or saline (NaCl) solutions, nor in EM, and is affected by chlorinated acidic solutions (HCl) to a lesser extent than other commonly used biometals. Corrosion in HCl initiates with selective leaching of late transition metals, followed by dissolution of Pd. - Highlights: • Fatigue limit of 600 MPa with no deterioration when exposed to Eagle's medium. • Fatigue shows sample size effect. • Pd-based BMG is unaffected by saline or strong basic solutions. • Pd-based BMG is substantially more resistant to chlorinated acids than CoCrMo, 316 L Stainless, or Ti6Al4V alloys. • Corrosion shows selective leaching of late transition metals, followed by Pd and P.

Formation of hydroxyapatite on Ti-coated Ti-Zr-Cu-Pd bulk metallic glass

International Nuclear Information System (INIS)

Qin, F.X.; Wang, X.M.; Wada, T.; Xie, G.Q.; Asami, K.; Inoue, A.

2009-01-01

In this research, Ti coating was conducted on Ti 40 Zr 10 Cu 36 Pd 14 bulk metallic glass (BMG) in order to increase the formation rate of hydroxyapatite layer. The formation behavior of bone-like hydroxyapatite on Ti-coated and uncoated Ti 40 Zr 10 Cu 36 Pd 14 bulk metallic glasses (BMGs) was studied. The surface morphology of Ti-coated and uncoated Ti 40 Zr 10 Cu 36 Pd 14 BMG was investigated by scanning electron microscopy and energy dispersive X-ray spectroscopy. The results revealed that the alkali pretreatment in 5 M NaOH solution at 60degC for 24 h had a beneficial effect on the formation of porous sodium titanate on Ti-coated Ti 40 Zr 10 Cu 36 Pd 14 BMG. A bone-like hydroxyapatite layer was able to form on the alkali-treated Ti-coated Ti 40 Zr 10 Cu 36 Pd 14 BMG after a short-time immersion in simulated body fluid (SBF). On the contrary, hydroxyapatite formation was not observed on the uncoated Ti 40 Zr 10 Cu 36 Pd 14 BMG after the same chemical treatments. (author)

Solvent and stabilizer free growth of Ag and Pd nanoparticles using metallic salts/cyclotriphosphazenes mixtures

Energy Technology Data Exchange (ETDEWEB)

Díaz Valenzuela, C. [Departamento de Química, Facultad de Química, Universidad de Chile, La Palmeras 3425, Nuñoa, Casilla 653, Santiago de Chile (Chile); Valenzuela, M.L., E-mail: mlvalenzuela@unab.cl [Universidad Andres Bello, Departamento de Ciencias Química, Facultad de Ciencias Exactas, Av. Republica 275, Santiago (Chile); Caceres, S.; Diaz, R. [Departamento de Química, Facultad de Química, Universidad de Chile, La Palmeras 3425, Nuñoa, Casilla 653, Santiago de Chile (Chile); O' Dwyer, C. [Applied Nanoscience Group, Department of Chemistry, University College Cork, Cork (Ireland); Micro and Nanoelectronics Centre, Tyndall National Institute, Lee Maltings, Cork (Ireland)

2013-12-16

Cyclotriphosphazene is used as a sacrificial solid-state template to synthesize a range of Ag and Pd nanoparticles with diverse geometries by thermal treatment using MLn/N{sub 3}P{sub 3}(O{sub 2}C{sub 12}H{sub 8}){sub 3} mixtures. The Pd and Ag nanoparticles are synthesized by solid-state pyrolysis of AgPPh{sub 3}[CF{sub 3}SO{sub 3}]/N{sub 3}P{sub 3}(O{sub 2}C{sub 12}H{sub 8}){sub 3} and PdCl{sub 2}/N{sub 3}P{sub 3}(O{sub 2}C{sub 12}H{sub 8}){sub 3} mixtures with molar relationships of 1:1, 1:5 and 1:10 respectively, in air and at 800 °C. The morphology of the as-prepared nanoparticles is found to depend on the molar ratio of the precursor mixture, the preparation method and of the nature of the metal. Ag and Pd, microcrystals were thermally grown on Si from the respective 1:1 precursors while that metal foams were grown from 1:5 ratios precursors on SiO{sub 2} wafers. High resolution transmission electron microscopy investigations reveal in most cases small crystals of Pd. HRSTEM measurements indicate that the formation of the Pd and Ag nanoparticles occurs through a phase demixing and dewetting mechanism. This approach has potential to be a useful and facile method to prepare metallic nanoparticles without requiring solutions or surfactants for application in electronic, catalytic and sensor materials and devices. - Highlights: • Pyrolysis MLn/N{sub 3}P{sub 3}(O{sub 2}C{sub 12}H{sub 8}){sub 3} mixtures under air, give Pd and Ag nanoparticles. • AgPPh{sub 3}[CF{sub 3}SO{sub 3}] and PdCl{sub 2} in molar ratios 1:1 and 1:5 were used. • Metal foams were obtained from 1:5 ratios when deposited on SiO{sub 2.} • Using crucible supporting in 1:1 metal/trimer <2 nm Pd nanoparticles were obtained. • The probable mechanism involves a dewetting, nucleation and ripening crystallization.

Study of the interface stability of the metal (Mo, Ni, Pd/HfO2/AlN/InGaAs MOS devices

Directory of Open Access Journals (Sweden)

Huy Binh Do

2017-08-01

Full Text Available The degeneration of the metal/HfO2 interfaces for Mo, Ni, and Pd gate metals was studied in this paper. An unstable PdOx interfacial layer formed at the Pd/HfO2 interface, inducing the oxygen segregation for the Pd/HfO2/InGaAs metal oxide capacitor (MOSCAP. The low dissociation energy for the Pd-O bond was the reason for oxygen segregation. The PdOx layer contains O2− and OH− ions which are mobile during thermal annealing and electrical stress test. The phenomenon was not observed for the (Mo, Ni/HfO2/InGaAs MOSCAPs. The results provide the guidance for choosing the proper metal electrode for the InGaAs based MOSFET.

Titania Supported Pt and Pt/Pd Nano-particle Catalysts for the Oxidation of Sulfur Dioxide

DEFF Research Database (Denmark)

Koutsopoulos, Sotiris; Johannessen, Tue; Eriksen, Kim Michael

2006-01-01

Several types of titania (anatase) were used as supports for pure platinum and Pt–Pd bimetallic alloy catalysts. The preparation methods, normal wet impregnation technique and flame aerosol synthesis, obtained metal loadings of 2% by weight. The prepared catalysts were tested for SO2 oxidation...... activity at atmospheric pressure in the temperature range 250–600 °C. The SO2 to SO3 conversion efficiency of the Pt–Pd alloy was significantly higher than that of the individual metals. The effects of the preparation method and the titania type used on the properties and activity of the resulting catalyst...

Density functional theory based study of chlorine doped WS{sub 2}-metal interface

Energy Technology Data Exchange (ETDEWEB)

Chanana, Anuja; Mahapatra, Santanu, E-mail: santanu@dese.iisc.ernet.in [NanoScale Device Research Laboratory, Department of Electronic Systems Engineering, Indian Institute of Science, Bengaluru, Karnataka 560012 (India)

2016-03-07

Investigation of a transition metal dichalcogenide (TMD)-metal interface is essential for the effective functioning of monolayer TMD based field effect transistors. In this work, we employ the Density Functional Theory calculations to analyze the modulation of the electronic structure of monolayer WS{sub 2} with chlorine doping and the relative changes in the contact properties when interfaced with gold and palladium. We initially examine the atomic and electronic structures of pure and doped monolayer WS{sub 2} supercell and explore the formation of midgap states with band splitting near the conduction band edge. Further, we analyze the contact nature of the pure supercell with Au and Pd. We find that while Au is physiosorbed and forms n-type contact, Pd is chemisorped and forms p-type contact with a higher valence electron density. Next, we study the interface formed between the Cl-doped supercell and metals and observe a reduction in the Schottky barrier height (SBH) in comparison to the pure supercell. This reduction found is higher for Pd in comparison to Au, which is further validated by examining the charge transfer occurring at the interface. Our study confirms that Cl doping is an efficient mechanism to reduce the n-SBH for both Au and Pd, which form different types of contact with WS{sub 2}.

Steady-State Spectroscopic Analysis of Proton-Dependent Electron Transfer on Pyrazine-Appended Metal Dithiolenes [Ni(pdt)2], [Pd(pdt)2], and [Pt(pdt)2] (pdt = 2,3-Pyrazinedithiol).

Science.gov (United States)

Kennedy, Steven R; Kozar, Morgan N; Yennawar, Hemant P; Lear, Benjamin J

2016-09-06

We report the structural, electronic, and acid/base properties of a series of ML2 metal dithiolene complexes, where M = Ni, Pd, Pt and L = 2,3-pyrazinedithiol. These complexes are non-innocent and possess strong electronic coupling between ligands across the metal center. The electronic coupling can be readily quantified in the monoanionic mixed valence state using Marcus-Hush theory. Analysis of the intervalence charge transfer (IVCT) band reveals that that electronic coupling in the mixed valence state is 5800, 4500, and 5700 cm(-1) for the Ni, Pd, and Pt complexes, respectively. We then focus on their response to acid titration in the mixed valence state, which generates the asymmetrically protonated mixed valence mixed protonated state. For all three complexes, protonation results in severe attenuation of the electronic coupling, as measured by the IVCT band. We find nearly 5-fold decreases in electronic coupling for both Ni and Pt, while, for the Pd complex, the electronic coupling is reduced to the point that the IVCT band is no longer observable. We ascribe the reduction in electronic coupling to charge pinning induced by asymmetric protonation. The more severe reduction in coupling for the Pd complex is a result of greater energetic mismatch between ligand and metal orbitals, reflected in the smaller electronic coupling for the pure mixed valence state. This work demonstrates that the bridging metal center can be used to tune the electronic coupling in both the mixed valence and mixed valence mixed protonated states, as well as the magnitude of change of the electronic coupling that accompanies changes in protonation state.

Ion beam mixing in Ag-Pd alloys

International Nuclear Information System (INIS)

Klatt, J.L.; Averback, R.S.; Peak, D.

1989-01-01

Ion beam mixing during 750 keV Kr + irradiation at 80 K was measured on a series of Ag-Pd alloys using Au marker atoms. The mixing in pure Ag was the greatest and it decreased monotonically with increasing Pd content, being a factor of 10 higher in pure Ag than in pure Pd. This large difference in mixing cannot be explained by the difference in cohesion energy between Ag and Pd in the thermodynamic model of ion beam mixing proposed by Johnson et al. [W. L. Johnson, Y. T. Cheng, M. Van Rossum, and M-A. Nicolet, Nucl. Instrum. Methods B 7/8, 657 (1985)]. An alternative model based on local melting in the cascade is shown to account for the ion beam mixing results in Ag and Pd

First principles investigation of the activity of thin film Pt, Pd and Au surface alloys for oxygen reduction

DEFF Research Database (Denmark)

Tripkovic, Vladimir; Hansen, Heine Anton; Rossmeisl, Jan

2015-01-01

Further advances in fuel cell technologies are hampered by kinetic limitations associated with the sluggish cathodic oxygen reduction reaction. We have investigated a range of different formulations of binary and ternary Pt, Pd and Au thin films as electrocatalysts for oxygen reduction. The most...... active binary thin films are near-surface alloys of Pt with subsurface Pd and certain PdAu and PtAu thin films with surface and/or subsurface Au. The most active ternary thin films are with pure metal Pt or Pd skins with some degree of Au in the surface and/or subsurface layer and the near-surface alloys...

Matemathical description of solidification cooling curves of pure metals

Directory of Open Access Journals (Sweden)

Arno Müller

1998-10-01

Full Text Available The introduction of an "incubation time" to the Schwarz classical mathematical description of metals solidification, resulted in a new model called Modified Schwarz Model. By doing so it was possible to identify and quantify the "delay time" that separates the two heat waves traveling independently in a casting during the solidification: the Supercooled / Superheated Liquid and the Solid / Liquid. The thermal shock produced in the initial stage of the undercooling generation process, can be used as an important parameter in the forecasting of the solidification's behavior of pure metals and alloys, when changing mold's materials, pouring and ambient temperatures. The hypercooling proneness degree of metals and alloys, can also be calculated.

Ru-assisted synthesis of Pd/Ru nanodendrites with high activity for ethanol electrooxidation

Science.gov (United States)

Zhang, Ke; Bin, Duan; Yang, Beibei; Wang, Caiqin; Ren, Fangfang; Du, Yukou

2015-07-01

Due to the specific physical and chemical properties of a highly branched noble metal, the controllable synthesis has attracted much attention. This article reports the synthesis of Pd/Ru nanodendrites by a facile method using an oil bath in the presence of polyvinyl pyrrolidone, potassium bromide and ascorbic acid. The morphology, structure, and composition of the as-prepared catalysts were characterized by means of X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. In the electrochemical measurement, the as-prepared Pd7/Ru1 bimetallic nanodendrites provide a large electrochemically active surface area and exhibit high peak current density in the forward scan toward ethanol electrooxidation, which is nearly four times higher than those of a pure Pd catalyst. The as-prepared Pd7/Ru1 catalysts also exhibit significantly enhanced cycling stability toward ethanol oxidation in alkaline medium, which are mainly ascribed to the synergetic effect between Pd and Ru. This indicates that the Pd7/Ru1 catalysts should have great potential applications in direct ethanol fuel cells.Due to the specific physical and chemical properties of a highly branched noble metal, the controllable synthesis has attracted much attention. This article reports the synthesis of Pd/Ru nanodendrites by a facile method using an oil bath in the presence of polyvinyl pyrrolidone, potassium bromide and ascorbic acid. The morphology, structure, and composition of the as-prepared catalysts were characterized by means of X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. In the electrochemical measurement, the as-prepared Pd7/Ru1 bimetallic nanodendrites provide a large electrochemically active surface area and exhibit high peak current density in the forward scan toward ethanol electrooxidation, which is nearly four times higher than those of a pure Pd catalyst. The as-prepared Pd7/Ru1 catalysts also exhibit significantly

Electrical conductivity dependence of thin metallic films of Au and Pd as a top electrode in capacitor applications

International Nuclear Information System (INIS)

Nazarpour, S.; Langenberg, E.; Jambois, O.; Ferrater, C.; Garcia-Cuenca, M.V.; Polo, M.C.; Varela, M.

2009-01-01

Electrical conductivity dependence of thin metallic films of Au and Pd over the different perovskites was investigated. It is found from electrical properties that crystallographic growth orientation of Au and Pd thin layers attained from X-ray diffraction results indicate the slop of current (I)-voltage (V) plots. Besides, surface morphology and topography was considered using Field Emission Scanning Electron Microscopy and Atomic Force Microscopy, respectively. Obtained results showed the Stranski-Krastanov growth of the Pd and Au. Indeed, diminishing of the root-mean-square roughness of Pd/BiMnO 3 /SrTiO 3 following by Au deposition should be concerned due to growth of Au onto the crack-like parts of the substrate. These crack-like parts appeared due to parasitic phases of the Bi-Mn-O system mainly Mn 3 O 4 (l 0 l) and Mn 3 O 4 (0 0 4 l). The different response in the electrical properties of heterostructures suggests that electrical conductance of the Au and Pd thin metallic films have the crystallographic orientation dependence. Furthermore, polycrystallinity of the thin metallic films are desired in electrode applications due to increase the conductivity of the metallic layers.

Microstructural study of metal-metal composites elaborated by interdiffusion between pure nickel and devitrified Fe-Ni-Mo-B glasses

International Nuclear Information System (INIS)

Ratovondrahona, E.; Bouquet, G.; Portier, R.

1993-01-01

It is well known that amorphous metallic alloys are able to give rise to microcrystallized structures when submitted to the effect of temperature, i.e. when devitrification takes place. These microstructures are particularly interesting for various applications. Materials produced from devitrified amorphous phase generally exhibit good mechanical properties, but are accompanied by some brittleness. In order to avoid this disadvantage, the authors tried to elaborate a composite material resulting from diffusion heat treatments carried out on alternate stackings of amorphous alloys and pure metal sheets. The idea is that by choosing discerning metallic glass and an appropriate diffusion heat treatment temperature, it might be possible to obtain mechanically hard phases, such as metallic borides, and disperse these compounds in the pure metallic matrix to be reinforced. Here, the authors only present the microstructural results of this study, although some preliminary mechanical tests have been preformed

Pure high dose metal ion implantation using the plasma immersion technique

International Nuclear Information System (INIS)

Zhang, T.; Tang, B.Y.; Zeng, Z.M.; Kwok, T.K.; Chu, P.K.; Monteiro, O.R.; Brown, I.G.

1999-01-01

High energy implantation of metal ions can be carried out using conventional ion implantation with a mass-selected ion beam in scanned-spot mode by employing a broad-beam approach such as with a vacuum arc ion source, or by utilizing plasma immersion ion implantation with a metal plasma. For many high dose applications, the use of plasma immersion techniques offers a high-rate process, but the formation of a surface film along with the subsurface implanted layer is sometimes a severe or even fatal detriment. We describe here an operating mode of the metal plasma immersion approach by which pure implantation can be obtained. We have demonstrated the technique by carrying out Ti and Ta implantations at energies of about 80 and 120 keV for Ti and Ta, respectively, and doses on the order of 1x10 17 ions/cm 2 . Our experiments show that virtually pure implantation without simultaneous surface deposition can be accomplished. Using proper synchronization of the metal arc and sample voltage pulse, the applied dose that deposits as a film versus the part that is energetically implanted (the deposition-to-implantation ratio) can be precisely controlled.copyright 1999 American Institute of Physics

Pd surface functionalization of 3D electroformed Ni and Ni-Mo alloy metallic nanofoams for hydrogen production

Science.gov (United States)

Petica, A.; Brincoveanu, O.; Golgovici, F.; Manea, A. C.; Enachescu, M.; Anicai, L.

2018-03-01

The paper presents some experimental results regarding the functionalization of 3D electroformed Ni and Ni-Mo alloy nanofoams with Pd nanoclusters, as potential cathodic materials suitable for HER during seawater electrolysis. The electrodeposition from aqueous electrolytes containing NiCl2 and NH4Cl has been applied to prepare the 3D Ni nanofoams. Ni-Mo alloys have been electrodeposited involving aqueous ammonium citrate type electrolytes. Pd surface functionalization has been performed using both electroless and electrochemical procedures. Pd content varied in the range of 0.5 – 8 wt.%, depending on the applied procedure and the operation conditions. The use of a porous structure associated with alloying element (i.e. Mo) and Pd surface functionalization facilitated enhanced performances from HER view point in seawater electrolyte (lower Tafel slopes). The determined Tafel slope values ranged from 123 to 105 mV.dec-1, suggesting the Volmer step as rate determining step. The improvement of the HER catalytic activity may be ascribed to a synergistic effect between the high real active area of the 3D electroformed metallic substrate, Ni alloying with a left transition metal and surface modification using Pd noble metal.

Magnetic domains and frustration in metallic CePdAl

Energy Technology Data Exchange (ETDEWEB)

Lucas, Stefan; Huesges, Zita; Huang, Chien-Lung; Stockert, Oliver [Max Planck Institute CPfS, Dresden (Germany); Fritsch, Veronika; Sakai, Akito [EP 6, Electronic Correlations and Magnetism, University of Augsburg (Germany); Grube, Kai; Taubenheim, Christian; Loehneysen, Hilbert von [Karlsruhe Institute of Technology (Germany)

2016-07-01

Magnetic frustration is an exciting topic in condensed matter physics, since it can lead to new ground states of materials, e.g. a spin liquid or spin glass state. Effects of magnetic frustration have been investigated intensively for insulating materials. However, the existence of magnetic frustration in metallic systems is still under debate. CePdAl is a metallic Kondo system, where geometric magnetic frustration arises from the formation of Ce ions on a distorted Kagome lattice. Neutron scattering experiments revealed, that only two thirds of the magnetic Ce moments order antiferromagnetically below T{sub N}=2.7 K, whereas the other third remains mainly disordered. Thermodynamic as well as neutron scattering measurements are presented to verify the existence of partial magnetic frustration in CePdAl. Recently neutron diffraction experiments under magnetic fields applied along two orthogonal directions in the magnetically hard basal plane were performed. They show opposite effects on the magnetic intensity of a selected magnetic domain depending on the field direction with respect to the propagation vector. If this is only an effect of different domain population or also due to a change in magnetic frustration shall be discussed.

Improved ethanol electrooxidation performance by shortening Pd-Ni active site distance in Pd-Ni-P nanocatalysts

Science.gov (United States)

Chen, Lin; Lu, Lilin; Zhu, Hengli; Chen, Yueguang; Huang, Yu; Li, Yadong; Wang, Leyu

2017-01-01

Incorporating oxophilic metals into noble metal-based catalysts represents an emerging strategy to improve the catalytic performance of electrocatalysts in fuel cells. However, effects of the distance between the noble metal and oxophilic metal active sites on the catalytic performance have rarely been investigated. Herein, we report on ultrasmall (~5 nm) Pd-Ni-P ternary nanoparticles for ethanol electrooxidation. The activity is improved up to 4.95 A per mgPd, which is 6.88 times higher than commercial Pd/C (0.72 A per mgPd), by shortening the distance between Pd and Ni active sites, achieved through shape transformation from Pd/Ni-P heterodimers into Pd-Ni-P nanoparticles and tuning the Ni/Pd atomic ratio to 1:1. Density functional theory calculations reveal that the improved activity and stability stems from the promoted production of free OH radicals (on Ni active sites) which facilitate the oxidative removal of carbonaceous poison and combination with CH3CO radicals on adjacent Pd active sites.

Electronic structure of Pd42.5Ni7.5Cu30P20, an excellent bulk metallic glass former: Comparison to the Pd40Ni40P20 reference glass

International Nuclear Information System (INIS)

Hosokawa, S.; Sato, H.; Happo, N.; Mimura, K.; Tezuka, Y.; Ichitsubo, T.; Matsubara, E.; Nishiyama, N.

2007-01-01

In-house photoemission and inverse-photoemission spectra (PES and IPES) were measured on Pd 42.5 Ni 7.5 Cu 30 P 20 and Pd 40 Ni 40 P 20 bulk metallic glasses in order to clarify the origin of excellent glass-forming ability from the viewpoint of electronic structure. Minima are observed for both the metallic glasses at a slightly higher energy than the Fermi level. Incident photon-energy dependent PES spectra were obtained using synchrotron radiation and the Pd 4d partial density of states (DOS) was estimated from the PES data. Soft X-ray emission spectra were also measured near the Ni and Cu 2p 3/2 absorption edges to evaluate, respectively, the Ni and Cu 3d partial DOS in the valence band. The Pd 4d and the Ni and Cu 3d partials in the conduction band were obtained from X-ray absorption spectra around the Pd 3p 3/2 and Ni and Cu 2p 3/2 absorption edges, respectively. It was found that the Pd 4d partial DOS near the Fermi energy largely decreases and becomes localized by replacing the Ni atoms with the Cu atoms, which may be closely related to the excellent glass-forming ability of the Pd 42.5 Ni 7.5 Cu 30 P 20 bulk metallic glass due to a selective formation of Pd-P covalent bonds

Preparation and characterization of metallic supported thin Pd-Ag membranes for hydrogen separation

OpenAIRE

Fernandez, Ekain; Medrano, Jose Antonio; Melendez, Jon; Parco, Maria; Viviente, J.L.; van Sint Annaland, Martin; Gallucci, Fausto; Pacheco Tanaka, David A.

2015-01-01

This paper reports the preparation and characterization of thin-film (4-5 µm thick) Pd-Ag metallic supported membranes for high temperature applications. Various thin film membranes have been prepared by depositing a ceramic interdiffusion barrier layer prior to the simultaneous Pd-Ag electroless plating deposition. Two deposition techniques for ceramic layers (made of zirconia and alumina) have been evaluated: atmospheric plasma spraying and dip coating of a powder suspension. Initially, the...

Metallization of Kevlar fibers with gold.

Science.gov (United States)

Little, Brian K; Li, Yunfeng; Cammarata, V; Broughton, R; Mills, G

2011-06-01

Electrochemical gold plating processes were examined for the metallization of Kevlar yarn. Conventional Sn(2+)/Pd(2+) surface activation coupled with electroless Ni deposition rendered the fibers conductive enough to serve as cathodes for electrochemical plating. The resulting coatings were quantified gravimetrically and characterized via adhesion tests together with XRD, SEM, TEM; the coatings effect on fiber strength was also probed. XRD data showed that metallic Pd formed during surface activation whereas amorphous phases and trace amounts of pure Ni metal were plated via the electroless process. Electrodeposition in a thiosulfate bath was the most efficient Au coating process as compared with the analogous electroless procedure, and with electroplating using a commercial cyanide method. Strongly adhering coatings resulted upon metallization with three consecutive electrodepositions, which produced conductive fibers able to sustain power outputs in the range of 1 W. On the other hand, metallization affected the tensile strength of the fiber and defects present in the metal deposits make questionable the effectiveness of the coatings as protective barriers. © 2011 American Chemical Society

Spin pumping damping and magnetic proximity effect in Pd and Pt spin-sink layers

Science.gov (United States)

Caminale, M.; Ghosh, A.; Auffret, S.; Ebels, U.; Ollefs, K.; Wilhelm, F.; Rogalev, A.; Bailey, W. E.

2016-07-01

We investigated the spin pumping damping contributed by paramagnetic layers (Pd, Pt) in both direct and indirect contact with ferromagnetic Ni81Fe19 films. We find a nearly linear dependence of the interface-related Gilbert damping enhancement Δ α on the heavy-metal spin-sink layer thicknesses tN in direct-contact Ni81Fe19 /(Pd, Pt) junctions, whereas an exponential dependence is observed when Ni81Fe19 and (Pd, Pt) are separated by 3 nm Cu. We attribute the quasilinear thickness dependence to the presence of induced moments in Pt, Pd near the interface with Ni81Fe19 , quantified using x-ray magnetic circular dichroism measurements. Our results show that the scattering of pure spin current is configuration-dependent in these systems and cannot be described by a single characteristic length.

Damage induced by swift heavy ions in a pure metallic target: iron. Experimental results and numerical simulation

International Nuclear Information System (INIS)

Legrand, P.

1993-01-01

The damage induced when a high energy deposition occurs in the electronic system of a pure metal (Ag, Co, Fe, Ni, Pd, Pt, Ti, W, Zr) has been investigated using two methods: low temperature swift heavy ion (O, Ar, Kr, Xe, Pb, u) irradiations and computer simulations by molecular dynamics. Irradiations reveal that up to now, it is only in iron, titanium, cobalt and zirconium targets that high levels of energy deposition in electronic excitations lead to a new mechanism of defect creation in addition to the effects of elastic collisions. This mechanism might be the Coulomb explosion: the incident ion creates in its wake a cylinder of highly ionized matter; Coulomb repulsions of short duration in metallic targets could then set a great number of neighbouring atoms into motion and lead to permanent atomic displacements. Using molecular dynamics, we confirm that atomic displacements can indeed occur when neighbouring perturbated atoms receive even a very small amount of kinetic energy (≤ 1 eV). This happens only if the repulsive movements are collective and coherent. Defect creation and annealing of preexisting defects which occur in iron at different energy deposition levels are successfully simulated. An original empirical N-body potential, allowing a realistic description of the bulk properties of the body centered cubic iron, is used. (author). refs., figs., tabs

On the Feasibility of Very-Low-Density Pure Metal Foams as Bright High-Energy X-ray Sources

Science.gov (United States)

Colvin, Jeffrey; Felter, Thomas

2003-10-01

We have used the Busquet approximation (M. Busquet, Phys. Fluids B 5(11), 4191 (1993)) to explore calculationally what the possible x-ray conversion efficiencies into the K-band would be from irradiating very-low-density pure metal foams with tens of kilojoules of 1/3-micron laser light. We will discuss the advantages of pure metal foams as bright high-energy x-ray sources, and some results of this calculational study. We will also present our ideas for how to fabricate pure metal foams with densities of a few milligrams per cubic centimeter. This work was performed under the auspices of the US Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

Metal release behavior of surface oxidized stainless steels into flowing high temperature pure water

International Nuclear Information System (INIS)

Fujiwara, Kazuo; Tomari, Haruo; Nakayama, Takenori; Shimogori, Kazutoshi; Ishigure, Kenkichi; Matsuura, Chihiro; Fujita, Norihiko; Ono, Shoichi.

1987-01-01

In order to clarify the effect of oxidation treatment of Type 304 SS on the inhibition of metal release into high temperature pure water, metal release rate of individual alloying element into flowing deionized water containing 50 ppb dissolved oxygen was measured as the function of exposure time on representative specimens oxidized in air and steam. The behavior of metal release was also discussed in relation to the structure of surface films. Among the alloying elements the amount of Fe ion, Cr ion and Fe crud in high temperature pure water tended to saturate with the exposure time and that of Ni ion and Co ion tended to increase monotonously with the exposure time for all specimens tested. And the treatment of steam-oxidation was the most effective to decrease the metal release of alloying elements and the treatment by air-oxidation also decreased the metal release. These tendencies were confirmed to correlate well with the structure of the surface films as it was in the results in the static autoclave test. (author)

Heterogeneous nanocomposites composed of silver sulfide and hollow structured Pd nanoparticles with enhanced catalytic activity toward formic acid oxidation

International Nuclear Information System (INIS)

Chen, Dong; Cui, Penglei; Liu, Hui; Yang, Jun

2015-01-01

Highlights: • Core–shell Ag-Ag/Pd nanoparticles with an Ag core and an Ag/Pd alloy shell are prepared via galvanic replacement reaction. • Heterogeneous Ag2S-hollow Pd nanocomposites are fabricated by converting the Ag component into Ag2S using element sulfur. • The heterogeneous Ag2S-hollow Pd nanocomposites display enhanced activity for formic acid oxidation due to electronic coupling effect. • The methodology may find applications to produce the semiconductor-metal nanocomposites with interesting architectures and tailored functionalities. - Abstract: Nanocomposites consisting semiconductor and noble metal domains are of great interest for their synergistic effect-based enhanced properties in a given application. Herein, we demonstrate a facile approach for the synthesis of heterogeneous nanocomposites consisting of silver sulfide (Ag 2 S) and hollow structured Pd nanoparticles (hPd). It begins with the preparation of core–shell nanoparticles with an Ag core and an alloy Ag/Pd shell in an organic solvent via galvanic replacement reaction (GRR) between Ag seed particles pre-synthesized and Pd 2+ ion precursors. The Ag component is then removed from the core and shell regions of core–shell Ag-Ag/Pd nanoparticles, and converted into Ag 2 S by elemental sulfur (S). The Ag 2 S forms the semiconductor domain in the nanocomposite and shares the solid-state interface with the resultant hollow structured Pd nanoparticle. As demonstrated, the Ag 2 S-hPd nanocomposites exhibit superior catalytic activity and durability for formic acid oxidation, compared to the pure Pd nanoparticles prepared by oleylamine reduction of Pd ion precursors and commercial Pd/C catalyst, due to the electronic coupling between semiconductor and noble metal domains in the nanocomposites. In addition, the structural transformation from core–shell to heterogeneous nanocomposites may provide new opportunities to design and fabricate hybrid nanostructures with interesting

Adsorption of HCN molecules on Ni, Pd and Pt-doped (7, 0) boron nitride nanotube: a DFT study

Science.gov (United States)

Habibi-Yangjeh, Aziz; Basharnavaz, Hadi

2018-05-01

We studied affinity of pure and Ni, Pd and Pt-doped (7, 0) boron nitride nanotubes (BNNTs) to toxic HCN molecules using density functional theory calculations. The results indicated that the pure (7, 0) BNNTs can weakly adsorb HCN molecules with adsorption energy of -0.2474 eV. Upon adsorption of HCN molecules on this nanotube, the band gap energy was decreased from 3.320 to 2.960 eV. The more negative adsorption energy between these transition metal-doped (7, 0) BNNTs and HCN molecules indicated that doping of (7, 0) BNNTs with Ni, Pd and Pt elements can significantly improve the affinity of BNNTs toward this gas. Additionally, it was found that the interaction energy between HCN molecules and Pt-doped BNNTs is more negative than those of the Ni and Pd-doped BNNTs. These observations suggested that the Pt-doped (7, 0) BNNTs are strongly sensitive to HCN molecules and therefore it may be used in gas sensor devices for detecting this toxic gas.

Transformation of Sodium Bicarbonate and CO2 into Sodium Formate over NiPd Nanoparticle Catalyst

Science.gov (United States)

Wang, Mengnan; Zhang, Jiaguang; Yan, Ning

2013-09-01

The present research systematically investigated, for the first time, the transformation of sodium bicarbonate and CO2 into sodium formate over a series of Ni based metal nanoparticles (NPs). Ni NPs and eight NiM (M stands for a second metal) NPs were prepared by a facile wet chemical process and then their catalytic performance were evaluated in sodium bicarbonate hydrogenation. Bimetallic NiPd NPs with a composition of 7:3 were found to be superior for this reaction, which are more active than both pure Ni and Pd NPs. Hot filtration experiment suggested the NPs to be the truly catalytic active species and kinetic analysis indicated the reaction mechanism to be different than most homogeneous catalysts. The enhanced activity of the bimetallic nanoparticles may be attributed to their smaller size and improved stability.

Solubility and diffusion of hydrogen in pure metals and alloys

International Nuclear Information System (INIS)

Wipf, H.

2001-01-01

Basic facts are presented of the absorption of hydrogen gas by metals and the diffusion of hydrogen in metals. Specifically considered are crystalline metals without defects and lattice disorder (pure metals), low hydrogen concentrations and the possibility of high hydrogen gas pressures. The first introductory topic is a short presentation of typical phase diagrams of metal hydrogen systems. Then, hydrogen absorption is discussed and shown to be decisively determined by the enthalpy of solution, in particular by its sign which specifies whether absorption is exothermic or endothermic. The formation of high-pressure hydrogen gas bubbles in a metal, which can lead to blistering, is addressed. It is demonstrated that bubble formation will, under realistic conditions, only occur in strongly endothermically hydrogen absorbing metals. The chief aspects of hydrogen diffusion in metals are discussed, especially the large size of the diffusion coefficient and its dependence on lattice structure. It is shown that forces can act on hydrogen in metals, causing a directed hydrogen flux. Such forces arise, for instance, in the presence of stress and temperature gradients and can result in local hydrogen accumulation with potential material failure effects. The final aspect discussed is hydrogen permeation, where the absorption behavior of the hydrogen is found to be in general more decisive on the permeation rate than the value of the diffusion coefficient. (orig.)

First principles investigation of the activity of thin film Pt, Pd and Au surface alloys for oxygen reduction

DEFF Research Database (Denmark)

Tripkovic, Vladimir; Hansen, Heine Anton; Rossmeisl, Jan

2015-01-01

driving force for surface segregation, diffusion to defects or surface self-assembling. On the basis of stability and activity analysis we conclude that the near surface alloy of Pd in Pt and some PdAu binary and PtPdAu ternary thin films with a controlled amount of Au are the best catalysts for oxygen......Further advances in fuel cell technologies are hampered by kinetic limitations associated with the sluggish cathodic oxygen reduction reaction. We have investigated a range of different formulations of binary and ternary Pt, Pd and Au thin films as electrocatalysts for oxygen reduction. The most...... active binary thin films are near-surface alloys of Pt with subsurface Pd and certain PdAu and PtAu thin films with surface and/or subsurface Au. The most active ternary thin films are with pure metal Pt or Pd skins with some degree of Au in the surface and/or subsurface layer and the near-surface alloys...

Effect of an in-plane ligand on the electronic structures of bromo-bridged nano-wire Ni-Pd mixed-metal complexes, [Ni(1-x)Pd(x)(bn)2Br]Br2 (bn = 2S,3S-diaminobutane).

Science.gov (United States)

Sasaki, Mari; Wu, Hashen; Kawakami, Daisuke; Takaishi, Shinya; Kajiwara, Takashi; Miyasaka, Hitoshi; Breedlove, Brian K; Yamashita, Masahiro; Kishida, Hideo; Matsuzaki, Hiroyuki; Okamoto, Hiroshi; Tanaka, Hisaaki; Kuroda, Shinichi

2009-08-03

Single crystals of quasi-one-dimensional bromo-bridged Ni-Pd mixed-metal complexes with 2S,3S-diaminobutane (bn) as an in-plane ligand, [Ni(1-x)Pd(x)(bn)(2)Br]Br(2), were obtained by using an electrochemical oxidation method involving mixed methanol/2-propanol (1:1) solutions containing different ratios of [Ni(II)(bn)(2)]Br(2) and [Pd(II)(bn)(2)]Br(2). To investigate the competition between the electron-correlation of the Ni(III) states, or Mott-Hubbard states (MH), and the electron-phonon interaction of the Pd(II)-Pd(IV) mixed valence states, or charge-density-wave states (CDW), in the Ni-Pd mixed-metal compounds, X-ray structure analyses, X-ray oscillation photograph, and Raman, IR, ESR, and single-crystal reflectance spectra were analyzed. In addition, the local electronic structures of Ni-Pd mixed-metal single crystals were directly investigated by using scanning tunneling microscopy (STM) at room temperature and ambient pressure. The oxidation states of [Ni(1-x)Pd(x)(bn)(2)Br]Br(2) changed from a M(II)-M(IV) mixed valence state to a M(III) MH state at a critical mixing ratio (x(c)) of approximately 0.8, which is lower than that of [Ni(1-x)Pd(x)(chxn)(2)Br]Br(2) (chxn = 1R,2R-diaminocyclohexane) (x(c) approximately 0.9) reported previously. The lower value of x(c) for [Ni(1-x)Pd(x)(bn)(2)Br]Br(2) can be explained by the difference in their CDW dimensionalities because the three-dimensional CDW ordering in [Pd(bn)(2)Br]Br(2) observed by using X-ray diffuse scattering stabilizes the Pd(II)-Pd(IV) mixed valence state more than two-dimensional CDW ordering in [Pd(chxn)(2)Br]Br(2) does, which has been reported previously.

First principles calculations and experimental insight into methane steam reforming over transition metal catalysts

DEFF Research Database (Denmark)

Jones, Glenn; Jakobsen, Jon Geest; Shim, Signe Sarah

2008-01-01

This paper presents a detailed analysis of the steam reforming process front first-principles calculations, supported by insight from experimental investigations. In the present work we employ recently recognised scaling relationships for adsorption energies of simple molecules adsorbed at pure...... metal Surfaces to develop an overview of the steam reforming process catalyzed by a range of transition metal surfaces. By combining scaling relationships with thermodynamic and kinetic analysis, we show that it is possible to determine the reactivity trends of the pure metals for methane steam...... in situ TEM measurements under a hydrogen atmosphere. The overall agreement between theory and experiment (at 773 K, 1 bar pressure and 10% conversion) is found to be excellent with Ru and Rh being the most active pure transition metals for methane steam reforming, while Ni, Ir, Pt, and Pd...

A theoretical study on pure bending of hexagonal close-packed metal sheet

Science.gov (United States)

Mehrabi, Hamed; Yang, Chunhui

2018-05-01

Hexagonal close-packed (HCP) metals have quite different mechanical behaviours in comparison to conventional cubic metals such as steels and aluminum alloys [1, 2]. They exhibit a significant tension-compression asymmetry in initial yielding and subsequent plastic hardening. The reason for this unique behaviour can be attributed to their limited symmetric crystal structure, which leads to twining deformation [3-5]. This unique behaviour strongly influences sheet metal forming of such metals, especially for roll forming, in which the bending is dominant. Hence, it is crucial to represent constitutive relations of HCP metals for accurate estimation of bending moment-curvature behaviours. In this paper, an analytical model for asymmetric elastoplastic pure bending with an application of Cazacu-Barlat asymmetric yield function [6] is presented. This yield function considers the asymmetrical tension-compression behaviour of HCP metals by using second and third invariants of the stress deviator tensor and a specified constant, which can be expressed in terms of uniaxial yield stresses in tension and compression. As a case study, the analytical model is applied to predict the moment-curvature behaviours of AZ31B magnesium alloy sheets under uniaxial loading condition. Furthermore, the analytical model is implemented as a user-defined material through the UMAT interface in Abaqus [7, 8] for conducting pure bending simulations. The results show that the analytical model can reasonably capture the asymmetric tension-compression behaviour of the magnesium alloy. The predicted moment-curvature behaviour has good agreement with the experimental results. Furthermore, numerical results show a better accuracy by the application of the Cazacu-Barlat yield function than those using the von-Mises yield function, which are more conservative than analytical results.

Crystallization of Pd40CU30Ni10P20 bulk metallic glass with and without pressure

DEFF Research Database (Denmark)

Yang, B.; Jiang, Jianzhong; Zhuang, Yanxin

2007-01-01

The glass-transition behavior of Pd40Cu30Ni10P20 bulk metallic glass was investigated by differential scanning calorimetry (DSC) and X-ray powder diffraction (XRD). The effect of pressure on the crystallization behavior of Pd40Cu30Ni10P20 bulk glass was studied by in situ high-pressure and high...

Transformation of Sodium Bicarbonate and CO2 into Sodium Formate over NiPd Nanoparticle Catalyst

Directory of Open Access Journals (Sweden)

Mengnan eWang

2013-09-01

Full Text Available The present research systematically investigated, for the first time, the transformation of sodium bicarbonate and CO2 into sodium formate over a series of Ni based metal nanoparticles (NPs. Ni NPs and eight NiM (M stands for a second metal NPs were prepared by a facile wet chemical process and then their catalytic performance were evaluated in sodium bicarbonate hydrogenation. Bimetallic NiPd NPs with a composition of 7:3 were found to be superior for this reaction, which are more active than both pure Ni and Pd NPs. Hot filtration experiment suggested the NPs to be the truly catalytic active species and kinetic analysis indicated the reaction mechanism to be different than most homogeneous catalysts. The enhanced activity of the bimetallic nanoparticles may be attributed to their smaller size and improved stability.

Effect Of Natural Convection On Directional Solidification Of Pure Metal

Directory of Open Access Journals (Sweden)

Skrzypczak T.

2015-06-01

Full Text Available The paper is focused on the modeling of the directional solidification process of pure metal. During the process the solidification front is sharp in the shape of the surface separating liquid from solid in three dimensional space or a curve in 2D. The position and shape of the solid-liquid interface change according to time. The local velocity of the interface depends on the values of heat fluxes on the solid and liquid sides. Sharp interface solidification belongs to the phase transition problems which occur due to temperature changes, pressure, etc. Transition from one state to another is discontinuous from the mathematical point of view. Such process can be identified during water freezing, evaporation, melting and solidification of metals and alloys, etc.

Enhancing the biofuel upgrade performance for Pd nanoparticles via increasing the support hydrophilicity of metal-organic frameworks.

Science.gov (United States)

Sun, Qi; Chen, Meng; Aguila, Briana; Nguyen, Nicholas; Ma, Shengqian

2017-09-08

In this work, the influence of the hydrophilic/hydrophobic nature of metal-organic framework (MOF) materials on the catalytic performance of supported Pd nanoparticles for biofuel upgrade was studied. We show that the introduction of hydrophilic groups on a MOF can greatly enhance the performance of the resultant catalyst. Specifically, Pd nanoparticles supported on MIL-101-SO 3 Na with superhydrophilicity (Pd/MIL-101-SO 3 Na) far outperforms pristine MIL-101 and the benchmark catalyst Pd/C in the hydrodeoxygenation reaction of vanillin, a model component of pyrolysis oil derived from the lignin fraction. This is attributed to a favorable mode of adsorption of the highly water soluble reactants on the more hydrophilic support in the vicinity of the catalytically active Pd nanoparticles, thereby promoting their transformation.

Disruption, segregation, and passivation for Pd and noble-metal overlayers on YBa2Cu3O/sub 6.9/

International Nuclear Information System (INIS)

Wagener, T.J.; Gao, Y.; Vitomirov, I.M.; Aldao, C.M.; Joyce, J.J.; Capasso, C.; Weaver, J.H.; Capone II, D.W.

1988-01-01

We have investigated interfaces formed when Pd and the noble metals Cu, Ag, and Au are deposited onto polycrystalline samples of YBa 2 Cu 3 O/sub 6.9/ fractured in ultrahigh vacuum. Synchrotron-radiation photoemission results show that Cu and Pd overlayers leach oxygen from the underlying YBa 2 Cu 3 O/sub 6.9/ substrate, disrupt the superconductor, and destroy electronic states near the Fermi level. Interface reactions become kinetically limited at room temperature after the deposition of ∼4 A of Cu or Pd, significantly sooner than for the reactive metals Fe, Al, Ti, and In. The presence of Ba near the surface after the deposition of more than 100 A of Cu and Pd reflects substrate disruption and subsequent surface segregation. In contrast, overlayers of Ag and Au do not disrupt the superconductor substrate, no segregation is observed, but the overlayers are nonuniform and the quality of passivation is in question for coverages <100 A

High-temperature stability of Au/Pd/Cu and Au/Pd(P)/Cu surface finishes

Science.gov (United States)

Ho, C. E.; Hsieh, W. Z.; Lee, P. T.; Huang, Y. H.; Kuo, T. T.

2018-03-01

Thermal reliability of Au/Pd/Cu and Au/Pd(4-6 wt.% P)/Cu trilayers in the isothermal annealing at 180 °C were investigated by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and transmission electron microscopy (TEM). The pure Pd film possessed a nanocrystalline structure with numerous grain boundaries, thereby facilitating the interdiffusion between Au and Cu. Out-diffusion of Cu through Pd and Au grain boundaries yielded a significant amount of Cu oxides (CuO and Cu2O) over the Au surface and gave rise to void formation in the Cu film. By contrast, the Pd(P) film was amorphous and served as a good diffusion barrier against Cu diffusion. The results of this study indicated that amorphous Pd(P) possessed better oxidation resistance and thermal reliability than crystalline Pd.

Hydrazine reduction of metal ions to porous submicro-structures of Ag, Pd, Cu, Ni, and Bi

Energy Technology Data Exchange (ETDEWEB)

Wang Yue; Shi Yongfang; Chen Yubiao [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Wu Liming, E-mail: liming_wu@fjirsm.ac.cn [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China)

2012-07-15

Porous submicro-structures of Ag, Pd, Cu, Ni, and Bi with high surface area have been prepared by the reduction of hydrazine in glycerol-ethanol solution at room temperature or 120-180 Degree-Sign C. Phase purity, morphology, and specific surface area have been characterized. The reactions probably undergo three different mechanisms: simple reduction for Ag and Pd, coordination-then-reduction for Cu and Ni, and hydrolysis-then-reduction for Bi. The reductant hydrazine also plays an important role to the formation of the porous submicro-structure. The reaction temperature influences the size of the constituent particles and the overall architecture of the submicro-structure so as to influence the surface area value. The as-prepared porous metals have shown the second largest surface area ever reported, which are smaller than those made by the reduction of NaBH{sub 4}, but larger than those made by hard or soft template methods. - Graphical abstract: Porous submicro-structures of Ag, Pd, Cu, Ni, and Bi with high surface area have been prepared by the reduction of hydrazine in the glycerol-ethanol solution at room temperature or 120-180 Degree-Sign C. The reactions undergo different mechanisms: simple reduction for Ag and Pd, coordination-then-reduction for Cu and Ni, and hydrolysis-then-reduction for Bi. Highlights: Black-Right-Pointing-Pointer Syntheses of porous Ag, Pd, Cu, Ni, and Bi with high surface area. Black-Right-Pointing-Pointer Ag and Pd undergo simple reduction. Black-Right-Pointing-Pointer Cu and Ni undergo coordination-then-reduction. Black-Right-Pointing-Pointer Bi undergoes hydrolysis-then-reduction. Black-Right-Pointing-Pointer The as-prepared metals have shown the second largest surface area ever reported.

Separation and Recovery of Precious Metals from Leach Liquors of Spent Electronic Wastes by Solvent Extraction

Energy Technology Data Exchange (ETDEWEB)

Nguyen, Thi Hong; Wang, Lingyun; Lee, Man Seung [Mokpo National University, Mokpo (Korea, Republic of)

2017-04-15

Solvent extraction was employed to recover precious metals (Au (III), Pd (II) and Pt (IV)) from the leach solution of spent electronic wastes containing Cu (II), Cr (III) and Fe (III). First, pure Fe (III) and Au (III) were recovered by simultaneous extraction with Cyanex 923 followed by selective stripping with HCl and Na{sub 2}S{sub 2}O{sub 3}. Second, Pt (IV), Pd (II) and Cu (II) were extracted by Alamine 336 from the raffinate. After the removal of Cu (II) by stripping with weak HCl, Pd (II) and Pt (IV) were separately stripped by controlling the concentration of thiourea in the mixture with HCl. A process flow sheet for the separation of precious metals was proposed.

Fast microwave-assisted solvothermal synthesis of metal nanoparticles (Pd, Ni, Sn) supported on sulfonated MWCNTs: Pd-based bimetallic catalysts for ethanol oxidation in alkaline medium

CSIR Research Space (South Africa)

Ramulifho, T

2012-01-01

Full Text Available The preparation of metal nanoparticles (Pd, Ni, Sn) supported on sulfonated multi-walled carbon nanotubes (SF-MWCNTs) using a very rapid microwave-assisted solvothermal strategy has been described. Electrocatalytic behaviour of the SF...

Molecular dynamics simulation study of thermodynamic and mechanical properties of the Cu-Pd random alloy

International Nuclear Information System (INIS)

Davoodi, J.; Ahmadi, M.; Rafii-Tabar, H.

2010-01-01

Molecular dynamics (MD) simulations have been performed to investigate the thermodynamic and mechanical properties of Cu-x% Pd (at%) random alloy, as well as those of the Cu 3 Pd and CuPd 3 ordered alloys, in the temperature range from 200 K up to the melting point. The quantum Sutton-Chen (Q-SC) many-body interatomic potentials have been used to describe the energetics of the Cu and Pd pure metals, and a standard mixing rule has been employed to obtain the potential parameters for the mixed (alloy) states. We have computed the variation of the melting temperature with the concentration of Pd. Furthermore, the variation of the cohesive energy, the order parameter, the thermal expansion coefficient, the density, the isobaric heat capacity, the bulk modulus, and the elastic stiffness constants were also calculated at different temperatures and concentrations for these materials. The computed variations of the thermodynamic and mechanical properties with temperature are fitted to a polynomial function. Our computed results show good agreement with other computational simulations, as well as with the experimental results where they have been available.

Thermophysical properties of 22 pure metals in the solid and liquid state - The pulse-heating data collection

Science.gov (United States)

Hüpf, T.; Cagran, C.; Pottlacher, G.

2011-05-01

The workgroup of subsecond thermophysics in Graz has a long tradition in performing fast pulseheating experiments on metals and alloys. Thereby, wire-shaped specimens are rapidly heated (108 K/s) by a large current-pulse (104 A). This method provides thermophysical properties like volume-expansion, enthalpy and electrical resistivity up to the end of the liquid phase. Today, no more experiments on pure metals are to be expected, because almost all elements, which are suitable for pulse-heating so far, have been investigated. The requirements for pulse-heating are: a melting point which is high enough to enable pyrometric temperature measurements and the availability of wire-shaped specimens. These elements are: Co, Cu, Au, Hf, In, Ir, Fe, Pb, Mo, Ni, Nb, Pd, Pt, Re, Rh, Ag, Ta, Ti, W, V, Zn, and Zr. Hence, it is the correct time to present the results in a collected form. We provide data for the above mentioned quantities together with basic information on each material. The uniqueness of this compilation is the high temperature range covered and the homogeneity of the measurement conditions (the same method, the same laboratory, etc.). The latter makes it a good starting point for comparative analyses (e.g. a comparison of all 22 enthalpy traces is in first approximation conform with the rule of Dulong-Petit which states heat capacity - the slope of enthalpy traces - as a function of the number of atoms). The data is useful for input parameters in numerical simulations and it is a major purpose of our ongoing research to provide data for simulations of casting processes for the metal working industry. This work demonstrates some examples of how a data compilation like this can be utilized. Additionally, the latest completive measurement results on Ag, Ni, Ti, and Zr are described.

Facile conversion of bulk metal surface to metal oxide single-crystalline nanostructures by microwave irradiation: Formation of pure or Cr-doped hematite nanostructure arrays

International Nuclear Information System (INIS)

Cho, Seungho; Jeong, Haeyoon; Lee, Kun-Hong

2010-01-01

We report a method for converting the surfaces of bulk metal substrates (pure iron or stainless steel) to metal oxide (hematite or Cr-doped hematite) nanostructures using microwave irradiation. When microwave radiation (2.45 GHz, single-mode) was applied to a metal substrate under the flow of a gas mixture containing O 2 and Ar, metal oxide nanostructures formed and entirely covered the substrate. The nanostructures were single crystalline, and the atomic ratios of the substrate metals were preserved in the nanostructures. When a pure iron sheet was used as a substrate, hematite nanowires (1000 W microwave radiation) or nanosheets (1800 W microwave radiation) formed on the surface of the substrate. When a SUS410 sheet was used as a substrate, slightly curved rod-like nanostructures were synthesized. The oxidation states of Fe and Cr in these nanorods were Fe 3+ and Cr 3+ . Quantitative analyses revealed an average Fe/Cr atomic ratio of 9.2, nearly identical to the ratio of the metals in the SUS410 substrate.

Pressure effect on crystallization temperature in Zr70Pd30 metallic glass

DEFF Research Database (Denmark)

Jiang, Jianzhong; Jeppesen, S; Saida, J.

2004-01-01

The pressure effect on amorphous-to-quasicrystalline-to-intermetallic phase transformations in a Zr70Pd30 metallic glass has been investigated by in situ x-ray diffraction measurements using synchrotron radiation. It is found that the glass crystallizes in two steps: (1) amorphous...... temperature for the formation of quasicrystals has been further discussed with the nucleation theory. ©2004 American Institute of Physics....

Atomistic modeling of an impurity element and a metal-impurity system: pure P and Fe-P system

International Nuclear Information System (INIS)

Ko, Won-Seok; Lee, Byeong-Joo; Kim, Nack J

2012-01-01

An interatomic potential for pure phosphorus, an element that has van der Waals, covalent and metallic bonding character, simultaneously, has been developed for the purpose of application to metal-phosphorus systems. As a simplification, the van der Waals interaction, which is less important in metal-phosphorus systems, was omitted in the parameterization process and potential formulation. On the basis of the second-nearest-neighbor modified embedded-atom method (2NN MEAM) interatomic potential formalism applicable to both covalent and metallic materials, a potential that can describe various fundamental physical properties of a wide range of allotropic or transformed crystalline structures of pure phosphorus could be developed. The potential was then extended to the Fe-P binary system describing various physical properties of intermetallic compounds, bcc and liquid alloys, and also the segregation tendency of phosphorus on grain boundaries of bcc iron, in good agreement with experimental information. The suitability of the present potential and the parameterization process for atomic scale investigations about the effects of various non-metallic impurity elements on metal properties is demonstrated. (paper)

Promotion of Phenol Photodecomposition over TiO2 Using Au, Pd, and AuPd Nanoparticles

DEFF Research Database (Denmark)

Su, Ren; Tiruvalam, Ramchandra; He, Qian

2012-01-01

Noble metal nanoparticles (Au, Pd, AuPd alloys) with a narrow size distribution supported on nanocrystalline TiO2 (M/TiO2) have been synthesized via a sol-immobilization route. The effect of metal identity and size on the photocatalytic performance of M/TiO2 has been systematically investigated u...

Vibration-accelerated activation of flow units in a Pd-based bulk metallic glass

Energy Technology Data Exchange (ETDEWEB)

Li, Ning, E-mail: hslining@mail.hust.edu.cn [School of Materials Science and Engineering, and State Key Laboratory of Material Processing and Die & Mould Technology, Huazhong University of Science and Technology, Wuhan 430074 (China); Liu, Ze [Department of Engineering Mechanics, School of Civil Engineering, Wuhan University, Wuhan 430072 (China); Wang, Xinyun [School of Materials Science and Engineering, and State Key Laboratory of Material Processing and Die & Mould Technology, Huazhong University of Science and Technology, Wuhan 430074 (China); Zhang, Meng [Institute of Advanced Wear & Corrosion Resistant and Functional Materials, Jinan University, Guangzhou 510632 (China)

2017-04-24

Controlled activation of flow units and in-situ characterization of mechanical properties in metallic glasses are facing challenges thus far. Here, vibrational loading is introduced through nanoscale dynamic mechanical analysis technique to probe vibration-accelerated atomic level flow that plays a crucial role in the mechanical behavior of metallic glasses. The intriguing finding is that high vibrational frequency induces deep indentation depth, prominent pop-in events on load–depth curves and low storage modulus, exhibiting a vibration-facilitated activation of flow units in Pd{sub 40}Cu{sub 30}Ni{sub 10}P{sub 20} metallic glass. Theoretical analysis revealed that vibration-moderated activation time-scale accelerate the activation of flow units and responsible for the above scenario.

Glycerol electro-oxidation in alkaline medium using Pd/C and PdSn/C electrocatalysts prepared by electron beam irradiation

International Nuclear Information System (INIS)

Geraldes, Adriana Napoleao; Silva, Dionisio Fortunato da; Pino, Eddy Segura; Spinace, Estevan Vitorio; Oliveira Neto, Almir; Linardi, Marcelo; Santos, Mauro Coelhos dos

2013-01-01

Carbon-supported metal nanoparticles were prepared for fuel cell applications by radiation-induced reduction of metal ions precursors. Pd/C and PdSn/C electrocatalysts (Pd:Sn atomic ratio 90:10), prepared by using electron beam irradiation, were tested for glycerol electro-oxidation in single alkaline direct glycerol fuel cell (ADGFC). EDX analysis showed that the Pd:Sn atomic ratio is very similar to the nominal one. X-ray diffractograms of PdSn/C electrocatalyst showed the presence of Pd (fcc) phase. Cyclic voltammetry (CV) indicated that Pd/C and PdSn/C electrocatalysts have good activity for glycerol electro-oxidation, at room temperature. Experiments with single ADGFC were carried out from 60 to 90 deg C, using Pd/C and PdSn/C electrocatalysts and glycerol 2.0 mol.L -1 , as fuel. The best performance was obtained at 85 deg C, for both electrocatalysts. The Pd/C and PdSn/C electrocatalysts showed similar performance (34 mW cm -2 ), at 85 deg C. (author)

Ag Isotopic Evolution of the Mantle During Accretion: New Constraints from Pd and Ag Metal-Silicate Partitioning

Science.gov (United States)

Righter, K.; Schonbachler, M.

2018-01-01

Decay of (sup 107) Pd to (sup 107) Ag has a half-life of 6.5 times 10 (sup 6) mega-annums. Because these elements are siderophile but also volatile, they offer potential constraints on the timing of core formation as well as volatile addition. Initial modelling has shown that the Ag isotopic composition of the bulk silicate Earth (BSE) can be explained if accretion occurs with late volatile addition. These arguments were tested for sensitivity for pre-cursor Pd/Ag contents, and for a fixed Pd/Ag ratio of the BSE of 0.1. New Ag and Pd partitioning data has allowed a better understanding of the partitioning behavior of Pd and Ag during core formation. The effects of S, C and Si, and the effect of high temperature and pressure has been evaluated. We can now calculate D(Ag) and D(Pd) over the wide range of PT conditions and variable metallic liquid compositions that are known during accretion. We then use this new partitioning information to revisit the Ag isotopic composition of the BSE during accretion.

Synthesis and characterisation of YbPdSb

Energy Technology Data Exchange (ETDEWEB)

Haines, Charles R.S.; Brown, Philip A.C.; Grosche, Friedrich M. [Department of Physics, Cavendish Laboratory, University of Cambridge (United Kingdom)

2016-07-01

The intermetallic compound YbPdSb can form in two structures: the low temperature (LT) half-Heusler phase, in which the Yb atoms form a frustrated fcc structure, and the high temperature (HT) Pnma modification. We have prepared phase pure samples of both structures and report resistivity, magnetisation and heat capacity measurements on both. The LT phase is a Kondo lattice system showing large-moment Curie-Weiss paramagnet behaviour without any phase transition anomalies down to the lowest temperatures measured. The resistivity is rather insensitive to temperature from room temperature down to ∝50 K where it decreases steeply with further cooling. By contrast, in the HT phase the magnetic susceptibility displays weak temperature dependence and the resistivity falls with decreasing temperature in the way expected of a weakly correlated metal. These findings suggest that in contrast to the electronic state in the LT structure, the 4f-shell of Yb is completely filled in the HT structure of YbPdSb, presenting an interesting opportunity to study the interplay between lattice and electronic structure within the same compound.

Thermophysical properties of 22 pure metals in the solid and liquid state – The pulse-heating data collection

Directory of Open Access Journals (Sweden)

Pottlacher G.

2011-05-01

Full Text Available The workgroup of subsecond thermophysics in Graz has a long tradition in performing fast pulseheating experiments on metals and alloys. Thereby, wire-shaped specimens are rapidly heated (108 K/s by a large current-pulse (104 A. This method provides thermophysical properties like volume-expansion, enthalpy and electrical resistivity up to the end of the liquid phase. Today, no more experiments on pure metals are to be expected, because almost all elements, which are suitable for pulse-heating so far, have been investigated. The requirements for pulse-heating are: a melting point which is high enough to enable pyrometric temperature measurements and the availability of wire-shaped specimens. These elements are: Co, Cu, Au, Hf, In, Ir, Fe, Pb, Mo, Ni, Nb, Pd, Pt, Re, Rh, Ag, Ta, Ti, W, V, Zn, and Zr. Hence, it is the correct time to present the results in a collected form. We provide data for the above mentioned quantities together with basic information on each material. The uniqueness of this compilation is the high temperature range covered and the homogeneity of the measurement conditions (the same method, the same laboratory, etc.. The latter makes it a good starting point for comparative analyses (e.g. a comparison of all 22 enthalpy traces is in first approximation conform with the rule of Dulong-Petit which states heat capacity – the slope of enthalpy traces – as a function of the number of atoms. The data is useful for input parameters in numerical simulations and it is a major purpose of our ongoing research to provide data for simulations of casting processes for the metal working industry. This work demonstrates some examples of how a data compilation like this can be utilized. Additionally, the latest completive measurement results on Ag, Ni, Ti, and Zr are described.

Nanoalloying and phase transformations during thermal treatment of physical mixtures of Pd and Cu nanoparticles

Directory of Open Access Journals (Sweden)

Vineetha Mukundan

2014-03-01

Full Text Available Nanoscale alloying and phase transformations in physical mixtures of Pd and Cu ultrafine nanoparticles are investigated in real time with in situ synchrotron-based x-ray diffraction complemented by ex situ high-resolution transmission electron microscopy. The combination of metal–support interaction and reactive/non-reactive environment was found to determine the thermal evolution and ultimate structure of this binary system. At 300 °C, the nanoparticles supported on silica and carbon black intermix to form a chemically ordered CsCl-type (B2 alloy phase. The B2 phase transforms into a disordered fcc alloy at higher temperature (> 450 °C. The alloy nanoparticles supported on silica and carbon black are homogeneous in volume, but evidence was found of Pd surface enrichment. In sharp contrast, when supported on alumina, the two metals segregated at 300 °C to produce almost pure fcc Cu and Pd phases. Upon further annealing of the mixture on alumina above 600 °C, the two metals interdiffused, forming two distinct disordered alloys of compositions 30% and 90% Pd. The annealing atmosphere also plays a major role in the structural evolution of these bimetallic nanoparticles. The nanoparticles annealed in forming gas are larger than the nanoparticles annealing in helium due to reduction of the surface oxides that promotes coalescence and sintering.

Molecular dynamics simulation study of thermodynamic and mechanical properties of the Cu-Pd random alloy

Energy Technology Data Exchange (ETDEWEB)

Davoodi, J., E-mail: jdavoodi@znu.ac.ir [Departmant of Physics, University of Zanjan, P.O. Box 45371-38111, Zanjan (Iran, Islamic Republic of); Ahmadi, M. [Departmant of Physics, University of Zanjan, P.O. Box 45371-38111, Zanjan (Iran, Islamic Republic of); Rafii-Tabar, H. [Department of Medical Physics and Biomedical Engineering and Research Center for Medical Nanotechnology and Tissue Engineering, Shahid Beheshti University of Medical Sciences, Evin, Tehran (Iran, Islamic Republic of); Computational Physical Sciences Research Laboratory, Department of Nano-Science, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of)

2010-06-25

Molecular dynamics (MD) simulations have been performed to investigate the thermodynamic and mechanical properties of Cu-x% Pd (at%) random alloy, as well as those of the Cu{sub 3}Pd and CuPd{sub 3} ordered alloys, in the temperature range from 200 K up to the melting point. The quantum Sutton-Chen (Q-SC) many-body interatomic potentials have been used to describe the energetics of the Cu and Pd pure metals, and a standard mixing rule has been employed to obtain the potential parameters for the mixed (alloy) states. We have computed the variation of the melting temperature with the concentration of Pd. Furthermore, the variation of the cohesive energy, the order parameter, the thermal expansion coefficient, the density, the isobaric heat capacity, the bulk modulus, and the elastic stiffness constants were also calculated at different temperatures and concentrations for these materials. The computed variations of the thermodynamic and mechanical properties with temperature are fitted to a polynomial function. Our computed results show good agreement with other computational simulations, as well as with the experimental results where they have been available.

Lipid solubility of the platinum group metals Pt, Pd and Rh in dependence on the presence of complexing agents

International Nuclear Information System (INIS)

Zimmermann, Sonja; Menzel, Christoph M.; Stueben, Doris; Taraschewski, Horst; Sures, Bernd

2003-01-01

All complexing agents had a significant influence on octanol solubility of PGM. - Investigations on the bioaccumulation of the platinum group metals (PGM) Pt, Pd and Rh in aquatic organisms are of growing interest in environmental research due to the increasing emission of these metals by motor vehicles with catalytic converters. Until now, nothing is known about the possible influence of complexing agents on the bioaccumulation capacity of these precious metals. According to the partition coefficient between 1-octanol and water (P OW ) as a measure of bioaccumulation, in this study a simple shaking method was performed in order to investigate the effects of different complexing agents (L-methionine, thio urea, EDTA, humic substances, bile compounds) on the octanol solubility of the PGM. The results demonstrated a significant influence of all agents used. L-Methionine and thio urea decreased the lipid solubility. In contrast, the presence of EDTA, humic substances and especially bile caused a higher transfer of metals in the octanol phase. For most complexing agents tested, the transfer of Pd to the lipid phase was significantly higher compared with Rh and Pt, except for bile acid where the highest octanol solubility was found for Pt. Recent experimental results on PGM accumulation in zebra mussels confirm a high bioaccumulation of Pd which could be predicted from the lipid solubility

Lipid solubility of the platinum group metals Pt, Pd and Rh in dependence on the presence of complexing agents

Energy Technology Data Exchange (ETDEWEB)

Zimmermann, Sonja; Menzel, Christoph M.; Stueben, Doris; Taraschewski, Horst; Sures, Bernd

2003-07-01

All complexing agents had a significant influence on octanol solubility of PGM. - Investigations on the bioaccumulation of the platinum group metals (PGM) Pt, Pd and Rh in aquatic organisms are of growing interest in environmental research due to the increasing emission of these metals by motor vehicles with catalytic converters. Until now, nothing is known about the possible influence of complexing agents on the bioaccumulation capacity of these precious metals. According to the partition coefficient between 1-octanol and water (P{sub OW}) as a measure of bioaccumulation, in this study a simple shaking method was performed in order to investigate the effects of different complexing agents (L-methionine, thio urea, EDTA, humic substances, bile compounds) on the octanol solubility of the PGM. The results demonstrated a significant influence of all agents used. L-Methionine and thio urea decreased the lipid solubility. In contrast, the presence of EDTA, humic substances and especially bile caused a higher transfer of metals in the octanol phase. For most complexing agents tested, the transfer of Pd to the lipid phase was significantly higher compared with Rh and Pt, except for bile acid where the highest octanol solubility was found for Pt. Recent experimental results on PGM accumulation in zebra mussels confirm a high bioaccumulation of Pd which could be predicted from the lipid solubility.

Effects of composition and microstructure of Pd-Cu-Si metallic glassy alloy thin films on hydrogen absorbing properties

International Nuclear Information System (INIS)

Kajita, Susumu; Kohara, Shinji; Onodera, Yohei; Fukunaga, Toshiharu; Matsubara, Eiichiro

2011-01-01

Thin films of Pd-Cu-Si metallic glassy alloys for a hydrogen sensor were fabricated by a sputtering method. In order to find out the effect of the composition and the microstructure of them on the hydrogen absorbing property (the H 2 response), the structural parameters based on the short-range order (SRO) were measured. Additionally, the change of the structural parameters with hydrogen absorption was measured, and the correlations of the change with the H 2 response and the hydrogen induced linear expansion coefficient (LEC) were examined. The H 2 response decreased with increases in Si content and the structural parameters. These results can be explained by the positive effects of Si content and the structural parameters on the formation of a trigonal prism which is a structural unit of Pd-based amorphous alloys, and by the negative effect of the trigonal prism on absorbing hydrogen. From the observation of the elongation of the Pd-Pd atomic distance with absorbing hydrogen, H atoms are supposed to occupy the space between Pd atoms. The amount of the change in the Pd-Pd atomic distance showed the positive correlations with the H 2 response and the LEC. (author)

Magnetism in ordered metallic perovskite compound GdPd3BxC1-x

International Nuclear Information System (INIS)

Pandey, Abhishek; Mazumdar, Chandan; Ranganathan, R.; Dattagupta, S.

2009-01-01

We report results of dc-magnetization, ac-susceptibility and magnetoresistance measurements on crystalline metallic-perovskite compounds GdPd 3 B x C 1-x (x=0.25, 0.50, 0.75 and 1.00) and the parent cubic compound GdPd 3 . The interest in these materials stems from the observation of negative temperature coefficient of resistance and negative thermal expansion in some of the members of this series. In the present study, we show that by substitution of non-magnetic elements, boron and carbon, the nature of the magnetic interaction can be varied from dominating ferromagnetic to antiferromagnetic and finally to a canted magnetic structure without altering the crystal symmetry of the compounds. The variation of magnetic interaction by modifying the lattice parameter resembles Ruderman-Kittel-Kasuya-Yosida (RKKY) oscillations.

Promotion Effect of Alkali Metal Hydroxides on Polymer-Stabilized Pd Nanoparticles for Selective Hydrogenation of C–C Triple Bonds in Alkynols

OpenAIRE

Nikoshvili, Linda Zh.; Bykov, Alexey V.; Khudyakova, Tatiana E.; Lagrange, Thomas; Héroguel, Florent; Luterbacher, Jeremy S.; Matveeva, Valentina G.; Sulman, Esther M.; Dyson, Paul J.; Kiwi-Minsker, Lioubov

2017-01-01

Postimpregnation of Pd nanoparticles (NPs) stabilized within hyper-cross-linked polystyrene with sodium or potassium hydroxides of optimal concentration was found to significantly increase the catalytic activity for the partial hydrogenation of the C–C triple bond in 2-methyl-3-butyn-2-ol at ambient hydrogen pressure. The alkali metal hydroxide accelerates the transformation of the residual Pd(II) salt into Pd(0) NPs and diminishes the reaction induction period. In addition, the selectivity t...

Synthesis, characterization and photocatalytic activity of noble metal-modified TiO2 nanosheets with exposed {0 0 1} facets

International Nuclear Information System (INIS)

Diak, Magdalena; Grabowska, Ewelina; Zaleska, Adriana

2015-01-01

Graphical abstract: - Highlights: • TiO 2 nanosheets with exposed {0 0 1} facets were prepared by hydrothermal method. • Pd and Ag NPs-loaded enhanced the photocatalytic activity under visible irradiation. • Photodeposition is an effective method to obtain noble metal NPs on TiO 2 surface. - Abstract: Pt, Pd, Ag and Au nanoparticles were photodeposited on the {0 0 1} crystal facets of the TiO 2 anatase nanosheets. Morphological and surface characterization of the samples as well as photocatalytic activity were studied. The influence of metal precursor concentration used during photodeposition (0.05−0.5%) on size of formed metal nanoparticles together with UV and vis-mediated activity of Pt, Pd, Ag or Au−TiO 2 was investigated. Generally, samples obtained by photodeposition of noble metal nanoparticles using their 0.2% precursor solutions revealed highest activity in phenol degradation reaction under visible light (λ > 420 nm). The photoactivity of the as-prepared samples with respect to the modified metal species was ordered Ag≅Pd > Au > Pt. TEM analysis showed that photodeposited metal nanoparticles appeared only on {0 0 1} facets of TiO 2 . The average degradation rate of phenol in the presence of Pd and Ag−TiO 2 was 0.5 μmol dm −3 min −1 after 60 min of irradiation under visible light, and was five times higher than that of pure TiO 2 nanosheets

Difference in metallic wear distribution released from commercially pure titanium compared with stainless steel plates.

Science.gov (United States)

Krischak, G D; Gebhard, F; Mohr, W; Krivan, V; Ignatius, A; Beck, A; Wachter, N J; Reuter, P; Arand, M; Kinzl, L; Claes, L E

2004-03-01

Stainless steel and commercially pure titanium are widely used materials in orthopedic implants. However, it is still being controversially discussed whether there are significant differences in tissue reaction and metallic release, which should result in a recommendation for preferred use in clinical practice. A comparative study was performed using 14 stainless steel and 8 commercially pure titanium plates retrieved after a 12-month implantation period. To avoid contamination of the tissue with the elements under investigation, surgical instruments made of zirconium dioxide were used. The tissue samples were analyzed histologically and by inductively coupled plasma atomic emission spectrometry (ICP-AES) for accumulation of the metals Fe, Cr, Mo, Ni, and Ti in the local tissues. Implant corrosion was determined by the use of scanning electron microscopy (SEM). With grades 2 or higher in 9 implants, steel plates revealed a higher extent of corrosion in the SEM compared with titanium, where only one implant showed corrosion grade 2. Metal uptake of all measured ions (Fe, Cr, Mo, Ni) was significantly increased after stainless steel implantation, whereas titanium revealed only high concentrations for Ti. For the two implant materials, a different distribution of the accumulated metals was found by histological examination. Whereas specimens after steel implantation revealed a diffuse siderosis of connective tissue cells, those after titanium exhibited occasionally a focal siderosis due to implantation-associated bleeding. Neither titanium- nor stainless steel-loaded tissues revealed any signs of foreign-body reaction. We conclude from the increased release of toxic, allergic, and potentially carcinogenic ions adjacent to stainless steel that commercially pure Ti should be treated as the preferred material for osteosyntheses if a removal of the implant is not intended. However, neither material provoked a foreign-body reaction in the local tissues, thus cpTi cannot be

A first-principles study on the interaction of biogas with noble metal (Rh, Pt, Pd) decorated nitrogen doped graphene as a gas sensor: A DFT study

Science.gov (United States)

Zhao, Chunjiang; Wu, Huarui

2018-03-01

Density functional theory calculations are carried out to investigate the adsorption characteristics of methane (CH4), carbon dioxide (CO2), hydrogen (H2), hydrogen sulfide (H2S), nitrogen (N2), and oxygen (O2) on the surface of pyridine-like nitrogen doped graphene (PNG) as well as noble metal (Rh, Pt, Pd) decorated PNG to elaborate their potentials as gas sensors. The adsorption intensities of biogas on noble metal (Rh, Pt, Pd) decorated PNG are in the order of O2> H2S> N2> CH4> CO2> H2, which are corresponded to the order of their sensitivity on surface. Compared with biogas adsorption on pristine PNG, there exist higher adsorption ability, higher charge transfer and higher orbital hybridization upon adsorption on noble metal (Rh, Pt, Pd) decorated PNG. Consequently, the noble metal (Rh, Pt, Pd) decorated PNG can transform the existence of CH4, CO2, H2, H2S, N2, and O2 molecules into electrical signal and they could potentially be used as ideal sensors for detection of biogas in ambient situation.

Raman spectroscopy of DNA-metal complexes. I. Interactions and conformational effects of the divalent cations: Mg, Ca, Sr, Ba, Mn, Co, Ni, Cu, Pd, and Cd

OpenAIRE

Duguid, J.; Bloomfield, V.A.; Benevides, J.; Thomas Jr, G.J.

1993-01-01

Interactions of divalent metal cations (Mg2+, Ca2+, Ba2+, Sr2+, Mn2+, Co2+, Ni2+, Cu2+, Pd2+, and Cd2+) with DNA have been investigated by laser Raman spectroscopy. Both genomic calf-thymus DNA (> 23 kilobase pairs) and mononucleosomal fragments (160 base pairs) were employed as targets of metal interaction in solutions containing 5 weight-% DNA and metal:phosphate molar ratios of 0.6:1. Raman difference spectra reveal that transition metal cations (Mn2+, Co2+, Ni2+, Cu2+, Pd2+, and Cd2+) ind...

The mechanism of transition-metal (Cu or Pd)-catalyzed synthesis of benzimidazoles from amidines: theoretical investigation.

Science.gov (United States)

Li, Juan; Gu, Honghong; Wu, Caihong; Du, Lijuan

2014-11-28

In this study, the Cu(OAc)2- and [PdCl2(PhCN)2]-catalyzed syntheses of benzimidazoles from amidines were theoretically investigated using density functional theory calculations. For the Cu-catalyzed system, our calculations supported a four-step-pathway involving C-H activation of an arene with Cu(II) via concerted metalation-deprotonation (CMD), followed by oxidation of the Cu(II) intermediate and deprotonation of the imino group by Cu(III), and finally reductive elimination from Cu(III). In our calculations, the barriers for the CMD step and the oxidation step are the same. The results are different from the ones reported by Fu et al. in which the whole reaction mechanism includes three steps and the CMD step is rate determining. On the basis of the calculation results for the [PdCl2(PhCN)2]-catalyzed system, C-H bond breaking by CMD occurs first, followed by the rate-determining C-N bond formation and N-H deprotonation. Pd(III) species is not involved in the [PdCl2(PhCN)2]-catalyzed syntheses of benzimidazoles from amidines.

Phase transformation induced by swift heavy ion irradiation of pure metals

International Nuclear Information System (INIS)

Dammak, H.; Dunlop, A.; Lesueur, D.

1996-01-01

It is now unambiguously established that high electronic energy deposition (HEED), obtained by swift heavy ion irradiation, plays an important role in the damage processes of pure metallic targets: (i) annealing of the defects created by elastic collisions in Fe, Nb, Ni and Pt, and (ii) creation of additional defects in Co, Fe, Ti and Zr. For Ti, we have recently evidenced by transmission electron microscopy observations that the damage creation by HEED is very important and leads to a phase transformation. Titanium evolves from the equilibrium hcp alpha-phase to the high pressure omega-phase. We studied the influence of three parameters on this phase transformation: ion fluence, electronic stopping power and irradiation temperature. The study of Ti and the results concerning other metals (Fe, Zr, etc.) and the semi-metal Bi allow us to propose criteria to predict in which metals HEED could induce damage: those which undergo a phase transformation under high pressure. As a matter of fact, beryllium is strongly damaged when submitted to HEED and seems to behave very similarly to titanium. The fact that such phase changes from a crystalline form to another form were only observed in those metals in which high pressure phases exist in the pressure-temperature diagram, strongly supports the Coulomb explosion model in which the generation of (i) a shock wave and (ii) collective atomic movements are invoked to account for the observed damage creation. (orig.)

Review of Supported Pd-Based Membranes Preparation by Electroless Plating for Ultra-Pure Hydrogen Production.

Science.gov (United States)

Alique, David; Martinez-Diaz, David; Sanz, Raul; Calles, Jose A

2018-01-23

In the last years, hydrogen has been considered as a promising energy vector for the oncoming modification of the current energy sector, mainly based on fossil fuels. Hydrogen can be produced from water with no significant pollutant emissions but in the nearest future its production from different hydrocarbon raw materials by thermochemical processes seems to be more feasible. In any case, a mixture of gaseous compounds containing hydrogen is produced, so a further purification step is needed to purify the hydrogen up to required levels accordingly to the final application, i.e., PEM fuel cells. In this mean, membrane technology is one of the available separation options, providing an efficient solution at reasonable cost. Particularly, dense palladium-based membranes have been proposed as an ideal chance in hydrogen purification due to the nearly complete hydrogen selectivity (ideally 100%), high thermal stability and mechanical resistance. Moreover, these membranes can be used in a membrane reactor, offering the possibility to combine both the chemical reaction for hydrogen production and the purification step in a unique device. There are many papers in the literature regarding the preparation of Pd-based membranes, trying to improve the properties of these materials in terms of permeability, thermal and mechanical resistance, poisoning and cost-efficiency. In this review, the most relevant advances in the preparation of supported Pd-based membranes for hydrogen production in recent years are presented. The work is mainly focused in the incorporation of the hydrogen selective layer (palladium or palladium-based alloy) by the electroless plating, since it is one of the most promising alternatives for a real industrial application of these membranes. The information is organized in different sections including: (i) a general introduction; (ii) raw commercial and modified membrane supports; (iii) metal deposition insights by electroless-plating; (iv) trends in

Metal modified tungsten carbide (WC) for catalytic and electrocatalytic applications

Science.gov (United States)

Mellinger, Zachary J.

One of the major challenges in the commercialization of proton exchange membrane fuel cells (PEMFC) is the cost, and low CO tolerance of the anode electrocatalyst material. The anode typically requires a high loading of precious metal electrocatalyst (Pt or Pt--Ru) to obtain a useful amount of electrical energy from the electrooxidation of methanol (CH3OH) or ethanol (C2H5OH). The complete electro--oxidation of methanol or ethanol on these catalysts produces strongly adsorbed CO on the surface, which reduces the activity of the Pt or Pt--Ru catalysts. Another major disadvantage of these electrocatalyst components is the scarcity and consequently high price of both Pt and Ru. Tungsten monocarbide (WC) has shown similar catalytic properties to Pt, leading to the utilization of WC and metal modified WC as replacements to Pt and Pt--Ru. In this thesis we investigated WC and Pt--modified WC as a potentially more CO--tolerant electrocatalysts as compared to pure Pt. These catalysts would reduce or remove the high loading of Pt used industrially. The binding energy of CO, estimated using temperature programmed desorption, is weaker on WC and Pt/WC than on Pt, suggesting that it should be easier to oxidize CO on WC and Pt/WC. This hypothesis was verified using cyclic voltammetry to compare the electro--oxidation of CO on WC, Pt/WC, and Pt supported on carbon substrates, which showed a lower voltage for the onset of oxidation of CO on WC and Pt/WC than on Pt. After observing these improved properties on the Pt/WC catalysts, we decided to expand our studies to investigate Pd--modified WC as Pd is less expensive than Pt and has shown more ideal properties for alcohol electrocatalysis in alkaline media. Pd/WC showed a lower binding energy of CO than both its parent metal Pd as well as Pt. Then, density functional theory (DFT) calculations were performed to determine how the presence of Pd affected the bonding of methanol and ethanol on the WC surface. The DFT studies showed

Monometallic Pd and Pt and Bimetallic Pd-Pt/Al2O3-TiO2 for the HDS of DBT: Effect of the Pd and Pt Incorporation Method

Directory of Open Access Journals (Sweden)

Reynaldo Martínez Guerrero

2014-01-01

Full Text Available The effect of the preparation method of monometallic Pd and Pt and bimetallic Pd-Pt/Al2O3-TiO2 catalysts on the hydrodesulfurization (HDS of dibenzothiophene (DBT was investigated in this study. The synthesis was accomplished using three methods: (A impregnation, (B metal organic chemical vapor deposition (MOCVD, and (C impregnation-MOCVD. The bimetallic Pd-Pt catalyst prepared by the impregnation-MOCVD method was most active for the HDS of DBT compared to those prepared by the single impregnation or MOCVD method due to the synergetic effect between both noble metals. The greater selectivity toward biphenyl indicated that this bimetallic Pd-Pt catalyst preferentially removes sulfur via the direct desulfurization mechanism. However, the bimetallic Pd-Pt catalyst prepared using the single MOCVD method did not produce any cyclohexylbenzene, which is most likely associated with the hydrogenation/dehydrogenation sites.

Geochemical behaviour of palladium in soils and Pd/PdO model substances in the presence of the organic complexing agents L-methionine and citric acid.

Science.gov (United States)

Zereini, Fathi; Wiseman, Clare L S; Vang, My; Albers, Peter; Schneider, Wolfgang; Schindl, Roland; Leopold, Kerstin

2016-01-01

Risk assessments of platinum group metal (PGE) emissions, notably those of platinum (Pt), palladium (Pd) and rhodium (Rh), have been mostly based on data regarding the metallic forms used in vehicular exhaust converters, known to be virtually biologically inert and immobile. To adequately assess the potential impacts of PGE, however, data on the chemical behaviour of these metals under ambient conditions post-emission is needed. Complexing agents with a high affinity for metals in the environment are hypothesized to contribute to an increased bioaccessibility of PGE. The purpose of this study is to examine the modulating effects of the organic complexing agents, L-methionine and citric acid, on the geochemical behavior of Pd in soils and model substances (Pd black and PdO). Batch experimental tests were conducted with soils and model substances to examine the impacts of the concentration of complexing agents, pH and length of extraction period on Pd solubility and its chemical transformation. Particle surface chemistry was examined using X-ray photoelectron spectroscopy (XPS) on samples treated with solutions under various conditions, including low and high O2 levels. Pd was observed to be more soluble in the presence of organic complexing agents, compared to Pt and Rh. Pd in soils was more readily solubilized with organic complexing agents compared to the model substances. After 7 days of extraction, L-methionine (0.1 M) treated soil and Pd black samples, for instance, had mean soluble Pd fractions of 12.4 ± 5.9% and 0.554 ± 0.024%, respectively. Surface chemistry analyses (XPS) confirmed the oxidation of metallic Pd surfaces when treated with organic complexing agents. The type of organic complexing agent used for experimental purposes was observed to be the most important factor influencing solubility, followed by solution pH and time of extraction. The results demonstrate that metallic Pd can be transformed into more bioaccessible species in the presence of

Geometric, stability, and electronic properties of gold-doped Pd clusters (Pd{sub n}Au, n = 3~20)

Energy Technology Data Exchange (ETDEWEB)

Huan, Hao; Chen, Yan; Wang, Tao; Ye, Xiang, E-mail: yexiang@shnu.edu.cn [Shanghai Normal University, Department of Physics (China); Gu, Xiao, E-mail: gx@cqu.edu.cn [Chongqing University, Department of Applied Physics (China)

2016-11-15

The structure, stability, and electronic properties of Pd{sub n}Au (n = 3~20) clusters are studied by density functional theory. The results show that the clusters studied here prefer three-dimensional structures even with very small atom number. It is found that the binding energies of Pd{sub n}Au clusters are higher than the corresponding pure Pd{sub n} clusters with the same atom number. Most Pd{sub n}Au clusters studied here are magnetic with magnetic moments ranging from 1.0 to 7.0 μ{sub B.} The dissociation energies of Pd atoms are lower than the doped gold atom, that is the doped Au atom will increase the mother clusters stability and activity.

μ+ studies of dilute PdFe alloys

International Nuclear Information System (INIS)

Nagamine, K.; Nishida, N.; Yamazaki, T.; British Columbia Univ., Vancouver

1976-08-01

In order to investigate the ordering mechanism among giant moments around Fe impurities in Pd, μ + was used to probe the conduction electron polarization in PdFe alloys above and below the critical concentration of 0.1 at. % with reference to pure Pd. Below the ordering temperatures the broadening of the μ + field for 0.015 at. % Fe is substantially larger than that for 0.28 at. % Fe, when normalized to the bulk magnetization. The results can be explained in terms of an RKKY spin oscillation in the region outside the giant moment. (author)

The influence of surface oxygen and hydroxyl groups on the dehydrogenation of ethylene, acetic acid and hydrogenated vinyl acetate on pure Pd(1 0 0): A DFT study

Energy Technology Data Exchange (ETDEWEB)

Huang, Yanping [Key Laboratory for Green Chemical Technology of Ministry of Education, R& D Center for Petrochemical Technology, Tianjin University, Tianjin (China); Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072 (China); Dong, Xiuqin [Key Laboratory for Green Chemical Technology of Ministry of Education, R& D Center for Petrochemical Technology, Tianjin University, Tianjin (China); Yu, Yingzhe, E-mail: yzhyu@tju.edu.cn [Key Laboratory for Green Chemical Technology of Ministry of Education, R& D Center for Petrochemical Technology, Tianjin University, Tianjin (China); Zhang, Minhua, E-mail: mhzhangtj@163.com [Key Laboratory for Green Chemical Technology of Ministry of Education, R& D Center for Petrochemical Technology, Tianjin University, Tianjin (China)

2016-12-01

Highlights: • All dehydrogenation reactions in vinyl acetate synthesis on Pd(1 0 0) were studied. • The energy barriers of the transition state of the three reactions were calculated. • The influence of surface Os and OHs on all dehydrogenation actions was discussed. - Abstract: On the basis of a Langmuir–Hinshelwood-type mechanism, the dehydrogenation of ethylene, acetic acid and hydrogenated vinyl acetate (VAH) on pure Pd(1 0 0) with surface oxygen atoms (Os) and hydroxyl groups (OHs) was studied with density functional theory (DFT) method. Our calculation results show that both Os and OHs can consistently reduce the activation energies of dehydrogenation of ethylene, acetic acid and VAH to some degree with only one exception that OHs somehow increase the activation energy of VAH. Based on Langmuir–Hinshelwood mechanism, the three dehydrogenation reactions in presence of surface Os and OHs are almost consistently favored, compared with the corresponding processes on clean Pd(1 0 0) surfaces, and thus a Langmuir–Hinshelwood-type mechanism may not be excluded beforehand when investigating the microscopic performance of the oxygen-assisted vinyl acetate synthesis on Pd(1 0 0) catalysts.

The sticking probability for H-2 in presence of CO on some transition metals at a hydrogen pressure of 1 bar

DEFF Research Database (Denmark)

Johansson, Martin; Lytken, Ole; Chorkendorff, Ib

2008-01-01

The sticking probability for H-2 on Ni, Co, Cu, Rh, Ru, Pd, it and Pt metal films supported on graphite has been investigated in a gas mixture consisting of 10 ppm carbon monoxide in hydrogen at a total pressure of 1 bar in the temperature range 40-200 degrees C. Carbon monoxide inhibits the stic......The sticking probability for H-2 on Ni, Co, Cu, Rh, Ru, Pd, it and Pt metal films supported on graphite has been investigated in a gas mixture consisting of 10 ppm carbon monoxide in hydrogen at a total pressure of 1 bar in the temperature range 40-200 degrees C. Carbon monoxide inhibits...... the sticking probability significantly for all the metals, even at 200 degrees C. In the presence of 10 ppm CO, the sticking probability increases in the order It, Pt, Ni, Co, Pd, Rh, Ru, whereas for Cu, it is below the detection limit of the measurement, even in pure H2. The sticking probability for H2...

Characterization for solidification and phase transformations of pure-titanium steel weld metal with time-resolved X-ray diffraction system

International Nuclear Information System (INIS)

Terasaki, Hidenori; Komizo, Yu-ichi; Nishino, Fumihiro; Ikeda, Masahiko

2007-01-01

Understanding and controlling solidification and phase transformation process of weld metal is essential for forming the microstructure with superior mechanical property. Recent evolution of analysis technique makes for solidification and phase transformation process to be in-situ analyzed, in direct and reciprocal lattice space. In the present work, unidirectional-solidification and phase transformation in the weld metal of commercial pure-titanium in Gas Tungsten Arc welding was in-situ observed by using Time-Resolved X-Ray Diffraction system with two-dimensional pixel detector. An undulator beam was used as a probe. Larger diffraction area could be detected in the time-resolution of 0.05 seconds, in unidirectional solidification and subsequent phase transformation process of pure-titanium weld metal. Furthermore, the microstructure formation during β-α phase transformation was in situ observed with High temperature Laser Scanning Confocal Microscopy. The crystal configurations in unidirectional solidification of weld metal and rapid change of phase ratio in reconstructive phase transformation were clearly analyzed. (author)

Fuel cells based on the use of Pd foils

Energy Technology Data Exchange (ETDEWEB)

Cabot, P. L.; Guezala, E. [Laboratori de Ciencia i Tecnologia Electroquimica de Materials, Barcelona (Spain); Casado, J. [Departamento de Investigacion, Carburos Metalicos, Barcelona (Spain)

1999-10-01

Fuel cells with hydrogen diffusion lead anodes are of particular interest because the ability of lead to filter hydrogen with 100 per cent selectively, thus making it possible to take impure hydrogen from industrial flue gases and use it as feedstock to produce clean energy. In this investigation an alkaline fuel cell with a Pd-based hydrogen diffusion anode combined with a carbon-PFTE oxygen diffusion cathode was built up and tested at low temperatures. The fuel cell was operated by feeding pure hydrogen and pure oxygen at atmospheric pressures and closing the circuit by means of different external loads. Quasi-stationary currents were obtained for each load when the Pd foils were assembled using elastic joints to allow the anode creasing. Experiments with different sections indicated that the anode was the limiting electrode. Results showed that the slowest reactions in the overall anodic process depend on the anode preparation. When Pd black was present only at the Pd/electrolyte interface, the slowest reaction occurred on the gas/Pd interface. For anodes with Pd black on both sides of the foil, the maximum anode power densities were 11 and 18 mW cm{sup 2} at 25 and 50 degrees C, respectively; the corresponding anode current densities were 30 and 65 mA cm{sup 2}. Significant improvements in the anode current and power densities were achieved via surface modification by cathodically charging Pd pieces with atomic hydrogen, and Pd foils with electrodeposited Pd+Pt blacks, obtaining roughly double the power and current density. 31 refs., 9 figs.

Nanostructured Ti-Zr-Pd-Si-(Nb) bulk metallic composites: Novel biocompatible materials with superior mechanical strength and elastic recovery.

Science.gov (United States)

Hynowska, A; Blanquer, A; Pellicer, E; Fornell, J; Suriñach, S; Baró, M D; Gebert, A; Calin, M; Eckert, J; Nogués, C; Ibáñez, E; Barrios, L; Sort, J

2015-11-01

The microstructure, mechanical behaviour, and biocompatibility (cell culture, morphology, and cell adhesion) of nanostructured Ti45 Zr15 Pd35- x Si5 Nbx with x = 0, 5 (at. %) alloys, synthesized by arc melting and subsequent Cu mould suction casting, in the form of rods with 3 mm in diameter, are investigated. Both Ti-Zr-Pd-Si-(Nb) materials show a multi-phase (composite-like) microstructure. The main phase is cubic β-Ti phase (Im3m) but hexagonal α-Ti (P63/mmc), cubic TiPd (Pm3m), cubic PdZr (Fm3m), and hexagonal (Ti, Zr)5 Si3 (P63/mmc) phases are also present. Nanoindentation experiments show that the Ti45 Zr15 Pd30 Si5 Nb5 sample exhibits lower Young's modulus than Ti45 Zr15 Pd35 Si5 . Conversely, Ti45 Zr15 Pd35 Si5 is mechanically harder. Actually, both alloys exhibit larger values of hardness when compared with commercial Ti-40Nb, (HTi-Zr-Pd-Si ≈ 14 GPa, HTi-Zr-Pd-Si-Nb ≈ 10 GPa and HTi-40Nb ≈ 2.7 GPa). Concerning the biological behaviour, preliminary results of cell viability performed on several Ti-Zr-Pd-Si-(Nb) discs indicate that the number of live cells is superior to 94% in both cases. The studied Ti-Zr-Pd-Si-(Nb) bulk metallic system is thus interesting for biomedical applications because of the outstanding mechanical properties (relatively low Young's modulus combined with large hardness), together with the excellent biocompatibility. © 2014 Wiley Periodicals, Inc.

Evidence of polymorphous amorphous-to-quasicrystalline phase transformation in Zr66.7Pd33.3 metallic glass

DEFF Research Database (Denmark)

Jiang, Jianzhong; Saksl, K.; Saida, J.

2002-01-01

The amorphous-to-quasicrystalline phase transformation and the pressure effect on the transformation in a Zr66.7Pd33.3 metallic glass have been investigated by in situ x-ray diffraction measurements using synchrotron radiation. It is found that the transformation is a polymorphous reaction...

The magnetic properties of Ce/Pd surface alloys investigated using DFT

KAUST Repository

Shuttleworth, I.G.

2014-06-01

The surface alloys that form between Ce and Pd(1 1 1), Pd(1 0 0) and both unreconstructed and missing-row type Pd(1 1 0) at low Ce coverage ( θCe=19ML) have shown permanent magnetism that is mediated in part by an RKKY-like delocalized Ce 6s-Pd 5s interaction. The Pd 4d states are significantly affected by alloying and their behavior cannot be explained by a purely spin-dependent Hamiltonian. Experimental observations of changes to the Pd 4d states are explained and the implications of Ce/Pd magnetism in reforming catalysis are discussed. © 2014 Elsevier B.V. All rights reserved.

The magnetic properties of Ce/Pd surface alloys investigated using DFT

KAUST Repository

Shuttleworth, I.G.

2014-01-01

The surface alloys that form between Ce and Pd(1 1 1), Pd(1 0 0) and both unreconstructed and missing-row type Pd(1 1 0) at low Ce coverage ( θCe=19ML) have shown permanent magnetism that is mediated in part by an RKKY-like delocalized Ce 6s-Pd 5s interaction. The Pd 4d states are significantly affected by alloying and their behavior cannot be explained by a purely spin-dependent Hamiltonian. Experimental observations of changes to the Pd 4d states are explained and the implications of Ce/Pd magnetism in reforming catalysis are discussed. © 2014 Elsevier B.V. All rights reserved.

Theoretical studies of the work functions of Pd-based bimetallic surfaces

International Nuclear Information System (INIS)

Ding, Zhao-Bin; Wu, Feng; Wang, Yue-Chao; Jiang, Hong

2015-01-01

Work functions of Pd-based bimetallic surfaces, including mainly M/Pd(111), Pd/M, and Pd/M/Pd(111) (M = 4d transition metals, Cu, Au, and Pt), are studied using density functional theory. We find that the work function of these bimetallic surfaces is significantly different from that of parent metals. Careful analysis based on Bader charges and electron density difference indicates that the variation of the work function in bimetallic surfaces can be mainly attributed to two factors: (1) charge transfer between the two different metals as a result of their different intrinsic electronegativity, and (2) the charge redistribution induced by chemical bonding between the top two layers. The first factor can be related to the contact potential, i.e., the work function difference between two metals in direct contact, and the second factor can be well characterized by the change in the charge spilling out into vacuum. We also find that the variation in the work functions of Pd/M/Pd(111) surfaces correlates very well with the variation of the d-band center of the surface Pd atom. The findings in this work can be used to provide general guidelines to design new bimetallic surfaces with desired electronic properties

Efficient Catalytic Reduction of Hexavalent Chromium With Pd-decorated Carbon Nanotubes

Energy Technology Data Exchange (ETDEWEB)

Kim, Ji Dang; Choi, Hyun Chul [Chonnam National University, Gwangju (Korea, Republic of)

2016-05-15

Heavy metal pollution is currently a serious environmental issue. Chromium (Cr) and chromium compounds are commonly found in wastewater discharged by various industries such as wood preservation, leather tanning, electroplating, metal finishing, and the production of chemicals. Pd nanoparticles can easily be introduced into CNTs by performing DCC-activated amidation. Our TEM and XRD results indicate that well-dispersed metallic Pd nanoparticles are anchored on the surface of the amidated CNTs. The XPS results suggest that the Pd content of the sample is approximately 9.8 atomic %. In comparison with the commercial Pd catalyst, the prepared Pd-CNTs were demonstrated to exhibit good catalytic activity in the reduction of 4-NP by NaBH4. Moreover, the Pd-CNT catalyst can easily be separated by performing a simple filtration and reused over at least 10 cycles. This Pd-CNT catalyst is therefore believed to have significant potential for use as a reusable catalyst in the reduction of Cr(Vi)

Formation of Mixed-Ligand Complexes of Pd2+ with Nucleoside 5'-Monophosphates and Some Metal-Ion-Binding Nucleoside Surrogates

Directory of Open Access Journals (Sweden)

Oleg Golubev

2014-10-01

Full Text Available Formation of mixed-ligand Pd2+ complexes between canonical nucleoside 5'-monophosphates and five metal-ion-binding nucleoside analogs has been studied by 1H-NMR spectroscopy to test the ability of these nucleoside surrogates to discriminate between unmodified nucleobases by Pd2+-mediated base pairing. The nucleoside analogs studied included 2,6-bis(3,5-dimethylpyrazol-1-yl-, 2,6-bis(1-methylhydrazinyl- and 6-(3,5-dimethylpyrazol-1-yl-substituted 9-(β-d-ribofuranosylpurines 1–3, and 2,4-bis(3,5-dimethylpyrazol-1-yl- and 2,4-bis(1-methylhydrazinyl-substituted 5-(β-d-ribofuranosyl-pyrimidines 4–5. Among these, the purine derivatives 1-3 bound Pd2+ much more tightly than the pyrimidine derivatives 4, 5 despite apparently similar structures of the potential coordination sites. Compounds 1 and 2 formed markedly stable mixed-ligand Pd2+ complexes with UMP and GMP, UMP binding favored by 1 and GMP by 2. With 3, formation of mixed-ligand complexes was retarded by binding of two molecules of 3 to Pd2+.

Alloying behaviour of electroplated Ag film with its underlying Pd/Ti film stack for low resistivity interconnect metallization

International Nuclear Information System (INIS)

Ezawa, Hirokazu; Miyata, Masahiro; Tatsumi, Kohei

2014-01-01

Highlights: • Alloying behavior of Ag/Pd/Ti film stack was studied by annealing at 400-800 °C. • The Ag film resistivity decreased with increasing annealing temperature. • Formation of the Pd-Ti intermetallics was found to be dominant over Ag-Pd alloying. • The excess Ti was consumed to form Ti oxides, which inhibited Ti alloying with Ag. -- Abstract: In this paper, viability of electroplated Ag film into device application was studied. Alloying behavior of the Ag film with its underlying Pd(50 nm)/Ti(100 nm) film stack was investigated with respect to heat treatment at different temperatures from 400 °C to 800 °C in an argon ambient. After annealing at 400 °C, the electrical resistivity of the Ag film increased due to Pd alloying with Ag. Formation of Pd–Ti intermetallic phases became dominant over Ag–Pd alloying with increasing annealing temperature, leading to the resistivity decrease of the Ag film. The resistivity of the 800 °C annealed Ag film approached that of its as-plated Ag film. The excess Ti atoms which were not consumed to form the intermetallic phases with the Pd atoms migrated to the Ag film surface to form Ti oxides along the Ag grain boundaries on the topmost film surface. The Ag/Pd/Ti film stack has been confirmed to maintain the resistivity of the Ag film at as-plated low levels after high temperature annealing. This paper also discusses process integration issues to enable the Ag metallization process for future scaled and three dimensionally chip stacked devices

Multiphase layered oxide growth on pure metals. I. General formulation

International Nuclear Information System (INIS)

Fromhold, A.T. Jr.

1982-01-01

A general formulation for the simultaneous growth of any number of layered planar oxide phases on a pure metal under diffusion-controlled conditions has been developed. Four individual situations have been developed in detail, namely, situations in which the predominant mode of ion transport is by cation interstitials, cation vacancies, anion interstitials, or anion vacancies. The generalized formulation enables the determination of quasi-steady-state growth kinetics following step function changes in the experimental conditions such as ambient oxygen pressure or temperature. Numerical evaluation of the coupled growth equations for the individual phases is required to deduce the general predictions of the theory. In the limit of two-layer growth by cation interstitial diffusion, the present formulation reproduces the earlier results of Fromhold and Sato

TVA - Thermionic Vacuum Arc - A new type of discharge generating pure metal vapor plasma

International Nuclear Information System (INIS)

Musa, G.; Popescu, A.; Mustata, I.; Borcoman, I.; Cretu, M.; Leu, G.F.; Salambas, A.; Ehrich, H.; Schumann, I.

1996-01-01

In this paper it is presented a new type of discharge in vacuum conditions generating pure metal vapor plasma with energetic metal ions content. The peculiarities of this heated cathode discharge are described and the dependence of the measured ion energy of the working parameters are established. The ion energy value can be easily and smoothly changed. A nearly linear dependence between energy of ions and arc voltage drop has been observed. The ion energy can be increased by the increase of the interelectrode distance, decrease of cathode temperature, change of the relative position of the electrodes and by the decrease of the arc discharge current. A special configuration with cylindrical geometry has been used to develop a small size and compact metal vapour plasma gun. Due to the mentioned peculiarities, this discharge offers new openings for important applications. (author)

Synergetic effects in CO adsorption on Cu-Pd(111) alloys

DEFF Research Database (Denmark)

Lopez, Nuria; Nørskov, Jens Kehlet

2001-01-01

We present density functional calculations for the interaction of CO on different Cu-Pd(111) bulk and surface alloys. The modification of the adsorption properties with respect to hose of the adsorption on pure Cu(111) and Pd(111) is described in terms of changes in the adsorption sites...... and the change of the electronic structure occurring upon alloying. The presence of cooperative, synergetic. effects is found to be important specially for Cu-rich bulk alloys. In this case. a larger adsorption energy is found for the inactive component than for the pure inactive system. This activation induces...

Pd/PdO functionalization of SnO{sub 2} nanowires and ZnO nanotetrapods

Energy Technology Data Exchange (ETDEWEB)

De Zorzi, C.; Rossetto, G. [ICIS-CNR, Padova (Italy); Calestani, D.; Zha, M.Z.; Zappettini, A.; Lazzarini, L.; Villani, M.; Zanotti, L. [IMEM-CNR, Parma (Italy); El Habra, N. [ICIS-CNR, Padova (Italy); Dipt. Scienze Chimiche, Universita di Padova (Italy)

2011-08-15

Tin oxide (SnO{sub 2}) and zinc oxide (ZnO) nanostructures are widely studied because of their peculiar physical and chemical properties and the large number of possible application fields. Surface functionalization of these materials is a very important topic because it is a powerful tool for modifying or tuning their properties, in order to better match the device requests. For example, palladium/palladium oxide (Pd/PdO) nanoparticles are often used to enhance selectivity of chemoresistive gas sensing properties of metal-oxide nanostructures. SnO{sub 2} nanowires and ZnO nanotetrapods have been grown on large areas by a combination of metal evaporation and controlled oxidation, while a MOCVD (Metal Organic Chemical Vapor Deposition) process has been chosen in order to deposit Pd/PdO nanoparticles on the surface of the obtained oxide nanostructures. Samples morphology, structure and composition have been studied by means of SEM and TEM microscopy, EDS microanalysis and X-Ray diffraction. The different results, obtained as a function of the synthesis and annealing parameters, are discussed focusing the attention to the experimental conditions that allowed the authors to obtain an optimal ''spotted'' coverage of oxide nanostructures, which is often required for gas sensing application. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Highly active Pd-In/mesoporous alumina catalyst for nitrate reduction.

Science.gov (United States)

Gao, Zhenwei; Zhang, Yonggang; Li, Deyi; Werth, Charles J; Zhang, Yalei; Zhou, Xuefei

2015-04-09

The catalytic reduction of nitrate is a promising technology for groundwater purification because it transforms nitrate into nitrogen and water. Recent studies have mainly focused on new catalysts with higher activities for the reduction of nitrate. Consequently, metal nanoparticles supported on mesoporous metal oxides have become a major research direction. However, the complex surface chemistry and porous structures of mesoporous metal oxides lead to a non-uniform distribution of metal nanoparticles, thereby resulting in a low catalytic efficiency. In this paper, a method for synthesizing the sustainable nitrate reduction catalyst Pd-In/Al2O3 with a dimensional structure is introduced. The TEM results indicated that Pd and In nanoparticles could efficiently disperse into the mesopores of the alumina. At room temperature in CO2-buffered water and under continuous H2 as the electron donor, the synthesized material (4.9 wt% Pd) was the most active at a Pd-In ratio of 4, with a first-order rate constant (k(obs) = 0.241 L min(-1) g(cata)(-1)) that was 1.3× higher than that of conventional Pd-In/Al2O3 (5 wt% Pd; 0.19 L min(-1) g(cata)(-1)). The Pd-In/mesoporous alumina is a promising catalyst for improving the catalytic reduction of nitrate. Copyright © 2015 Elsevier B.V. All rights reserved.

Equation of state for thermodynamic properties of pure and mixtures liquid alkali metals

International Nuclear Information System (INIS)

Mousazadeh, M.H.; Faramarzi, E.; Maleki, Z.

2010-01-01

We developed an equation of state based on statistical-mechanical perturbation theory for pure and mixtures alkali metals. Thermodynamic properties were calculated by the equation of state, based on the perturbed-chain statistical associating fluid theory (PC-SAFT). The model uses two parameters for a monatomic system, segment size, σ, and segment energy, ε. In this work, we calculate the saturation and compressed liquid density, heat capacity at constant pressure and constant volume, isobaric expansion coefficient, for which accurate experimental data exist in the literatures. Results on the density of binary and ternary alkali metal alloys of Cs-K, Na-K, Na-K-Cs, at temperatures from the freezing point up to several hundred degrees above the boiling point are presented. The calculated results are in good agreement with experimental data.

STRUCTURAL INTERACTIONS OF HYDROGEN WITH BULK AMORPHOUS MICROSTRUCTURES IN METALLIC SYSTEMS UNDERSTANDING THE ROLE OF PARTIAL CRYSTALLINITY ON PERMEATION AND EMBRITTLEMENT

Energy Technology Data Exchange (ETDEWEB)

Brinkman, Kyle; Fox, Elise; Korinko, Paul; Adams, Thad

2010-05-10

The development of metallic glasses in bulk form has led to a resurgence of interest into the utilization of these materials for a variety of applications. A potentially exciting application for these bulk metallic glass (BMG) materials is their use as composite membranes to replace high cost Pd/Pd-alloy membranes for enhanced gas separation processes. One of the major drawbacks to the industrial use of Pd/Pd-alloy membranes is that during cycling above and below a critical temperature an irreversible change takes place in the palladium lattice structure which can result in significant damage to the membrane. Furthermore, the cost associated with Pd-based membranes is a potential detractor for their continued use and BMG alloys offer a potentially attractive alternative. Several BMG alloys have been shown to possess high permeation rates, comparable to those measured for pure Pd metal. In addition, high strength and toughness when either in-situ or ex-situ second phase dispersoids are present. Both of these properties, high permeation and high strength/toughness, potentially make these materials attractive for gas separation membranes that could resist hydrogen 'embrittlement'. However, a fundamental understanding of the relationship between partially crystalline 'structure'/devitrification and permeation/embrittlement in these BMG materials is required in order to determine the operating window for separation membranes and provide additional input to the material synthesis community for improved alloy design. This project aims to fill the knowledge gap regarding the impact of crystallization on the permeation properties of metallic glass materials. The objectives of this study are to (i) determine the crystallization behavior in different gas environments of Fe and Zr based commercially available bulk metallic glass and (ii) quantify the effects of partial crystallinity on the hydrogen permeation properties of these metallic glass membranes.

Application of vacuum metallurgy to separate pure metal from mixed metallic particles of crushed waste printed circuit board scraps.

Science.gov (United States)

Zhan, Lu; Xu, Zhenming

2008-10-15

The principle of separating pure metal from mixed metallic particles (MMPs) byvacuum metallurgy is that the vapor pressures of various metals at the same temperature are different As a result, the metal with high vapor pressure and low boiling point can be separated from the mixed metals through distillation or sublimation, and then it can be recycled through condensation under a certain condition. The vacuum metallurgy separation (VMS) of MMPs of crushed waste printed circuit boards (WPCBs) has been studied in this paper. Theoretical analyses show that the MMPs (copper, zinc, bismuth, lead, and indium, for example) can be separated by vacuum metallurgy. The copper particles (0.15-0.20 mm) and zinc particles (<0.30 mm) were chosen to simulate the MMPs of crushed WPCBs. Experimental results show that the separated efficiency of zinc in the copper-rich particles achieves 96.19 wt % when the vacuum pressure is 0.01-0.10 Pa, the heating temperature is 1123 K, and the heating time is 105 min. Under this operation condition, the separated efficiency of zinc in the copper-rich particles from crushed WPCBs achieves 97.00 wt % and the copper purity increases from 90.68 to 99.84 wt %.

The Simple, Effective Synthesis of Highly Dispersed Pd/C and CoPd/C Heterogeneous Catalysts via Charge-Enhanced Dry Impregnation

Directory of Open Access Journals (Sweden)

Lawrence D’Souza

2016-05-01

Full Text Available Pd/C and CoPd/C heterogeneous catalysts have been synthesized by adopting Charge Enhanced Dry Impregnation (CEDI. The particles size distribution, their high metal surface-to-bulk ratios, and synthesis feasibility are unmatchable to any known noble metal bimetallic heterogeneous catalyst preparation techniques. Next generation Fuel Cells and Fischer-Tropsch catalytic processes economy will be benefited from the proposed methodology.

FY 1999 project on the development of new industry support type international standards. Standards development of chemical analysis and non-destructive inspection methods for pure titanium metals; 1999 nendo shinki sangyo shiengata kokusai hyojun kaihatsu jigyo seika hokokusho. Junchitan no shiken hyoka hoho no hyojunka

Energy Technology Data Exchange (ETDEWEB)

NONE

2000-03-01

To propose it to ISOTC79 and ISOTC135, study was conducted for standardization of chemical analysis method and non-destructive inspection method for industrial use pure titanium. As the chemical analysis method, the inductively coupled plasma atomic emission spectrometry which has good detection limit was developed, and at the same time, the standardization of spark and/or glow discharged atomic emission spectrometry was developed. As the non-destructive inspection method, developmental study on the following was carried out: surface defect inspection method of pure titanium metals by laser scanning inspection system or CCD camera; internal defect inspection of pure titanium sheet and coil by plate wave ultrasonic inspection method; internal defect inspection of pure titanium bar by eddy current method; inspection of very small leakage of pressurized fluid through defects in pure titanium pipe and tube by pressure differential testing method. As a result of the study, standards of system performance and tolerance were determined in analysis of Pd, Si, Al, Cu, Mo, Zr, Nb, Ta and Y. Further, analytical conditions and application ranges of the spark discharged atomic emission spectrometry were made definite in terms of 19 elements including Mn, Fe, Ni, Cr, Sn, Pb, Si, Al, V, Cu, Mo, Zr, Nb, Ta, Co, B, Y, C and W. (NEDO)

Metal-semiconductor transition at a comparable resistivity level and positive magnetoresistance in Mn3Mn1-x Pd x N thin films

Science.gov (United States)

Xu, T.; Ji, G. P.; Cao, Z. X.; Ji, A. L.

2018-02-01

Thin films of antiperovskite Mn3Mn1-x Pd x N with x up to 0.36 were grown by reactive magnetron co-sputtering method. All the deposits exhibit a [1 0 0] preferential orientation, with the lattice constant slightly enlarged in samples with ever more Pd atoms partially substituting the MnI atoms in Mn3MnN matrix. The replacement of MnI atoms in antiperovskite structure by Pd atoms, besides reducing the saturation magnetization, also invokes a metal-semiconductor transition which occurs remarkably at a comparable resistivity level. Moreover, a positive magnetoresistance was observed in samples of a high Pd content. These tunable electrical and magnetic properties of ternary antiperovskite compounds might promise some ingenious applications in electronic industry.

Investigating unexpected magnetism of mesoporous silica-supported Pd and PdO nanoparticles

KAUST Repository

Song, Hyon Min

2015-01-13

The synthesis and magnetic behavior of matrix-supported Pd and PdO nanoparticles (NPs) are described. Mesoporous silica with hexagonal columnal packing is selected as a template, and the impregnation method with thermal annealing is used to obtain supported Pd and PdO NPs. The heating rate and the annealing conditions determine the particle size and the phase of the NPs, with a fast heating rate of 30 °C/min producing the largest supported Pd NPs. Unusual magnetic behaviors are observed. (1) Contrary to the general belief that smaller Pd NPs or cluster size particles have higher magnetization, matrix-supported Pd NPs in this study maintain the highest magnetization with room temperature ferromagnetism when the size is the largest. (2) Twin boundaries along with stacking faults are more pronounced in these large Pd NPs and are believed to be the reason for this high magnetization. Similarly, supported PdO NPs were prepared under air conditions with different heating rates. Their phase is tetragonal (P42/mmc) with cell parameters of a = 3.050 Å and c = 5.344 Å, which are slightly larger than in the bulk phase (a = 3.03 Å, c = 5.33 Å). Faster heating rate of 30 °C/min also produces larger particles and larger magnetic hysteresis loop, although magnetization is smaller and few twin boundaries are observed compared to the supported metallic Pd NPs.

Studies of valence of selected rare earth silicides determined using Si K and Pd/Rh L{sub 2,3} XANES and LAPW numerical studies

Energy Technology Data Exchange (ETDEWEB)

Zajdel, P., E-mail: pawel.zajdel@us.edu.pl [Institute of Physics, University of Silesia, ul. Uniwersytecka 4, 40-007 Katowice (Poland); Kisiel, A., E-mail: andrzej.kisiel@uj.edu.pl [M. Smoluchowski Institute of Physics, Jagiellonian University, ul. Lojasiewicza 11, 30-348 Kraków (Poland); Szytuła, A., E-mail: andrzej.szytula@uj.edu.pl [M. Smoluchowski Institute of Physics, Jagiellonian University, ul. Lojasiewicza 11, 30-348 Kraków (Poland); Goraus, J., E-mail: jerzy.goraus@us.edu.pl [Institute of Physics, University of Silesia, ul. Uniwersytecka 4, 40-007 Katowice (Poland); Balerna, A., E-mail: antonella.balerna@lnf.infn.it [Laboratori Nazionali di Frascati, INFN, Lab DAPHINE-Light, Via E. Fermi 40, I-00044 Frascati (Italy); Banaś, A., E-mail: slsba@nus.edu.sg [Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603 (Singapore); Starowicz, P., E-mail: pawel.starowicz@uj.edu.pl [M. Smoluchowski Institute of Physics, Jagiellonian University, ul. Lojasiewicza 11, 30-348 Kraków (Poland); Konior, J., E-mail: jerzy.konior@uj.edu.pl [M. Smoluchowski Institute of Physics, Jagiellonian University, ul. Lojasiewicza 11, 30-348 Kraków (Poland); Cinque, G., E-mail: gianfelice.cinque@diamond.ac.uk [Diamond Light Source, Harwell Campus, OX11 0DE Chilton-Didcot (United Kingdom); Grilli, A., E-mail: antonio.grilli@lnf.infn.it [Laboratori Nazionali di Frascati, INFN, Lab DAPHINE-Light, Via E. Fermi 40, I-00044 Frascati (Italy)

2015-12-01

Highlights: • The Si K and Pd L{sub 3} edges of R{sub 2}PdSi{sub 3} (R = Ce, Nd, Tb, Dy, Ho, Er) and HoRh{sub 2−x}Pd{sub x}Si{sub 2} are reported. • The R–Si bonds possess polar and 4d5s bands of Pd and Rh metallic characters. • There is no indication of Ce having a different valence than the other rare earths. • The positions and features of the calculated edges exhibit a fair agreement up to ≈10 eV. • The supercell used for Ho{sub 2}PdSi{sub 3} is good enough to reproduce the Si K edge. - Abstract: We report on the investigation of Si and Pd/Rh chemical environments using X-ray Absorption Near Edge Spectroscopy in two different families of rare earth silicides R{sub 2}PdSi{sub 3} (R = Ce, Nd, Tb, Dy, Ho, Er) and HoRh{sub 2−x}Pd{sub x}Si{sub 2} (x = 0, 0.5, 0.75, 1.0, 1.5, 1.8, 2.0). The Si K, Pd L{sub 3} and Rh L{sub 3} absorption edges were recorded in order to follow their changes upon the variation of 4f and 4d5s electron numbers. In both cases it was found that the Si K edge was shifted ≈0.5 eV toward lower energies, relative to pure silicon. In the first family, the shift decreases with increasing number of f-electrons, while the Si K edge remains constant upon rhodium–palladium substitution. In all cases the Pd L{sub 3} edge was shifted to higher energies relative to metallic Pd. No visible change in the Pd L{sub 3} position was observed either with a varying 4f electron count or upon Pd/Rh substitution. Also, the Rh L{sub 3} edge did not change. For two selected members, Ho{sub 2}PdSi{sub 3} and HoPd{sub 2}Si{sub 2}, the Wien2K’09 (LDA + U) package was used to calculate the electronic structure and the absorption edges. Si K edges were reproduced well for both compounds, while Pd L{sub 3} only exhibited a fair agreement for the second compound. This discrepancy between the Pd L{sub 3} theory and experiment for the Ho{sub 2}PdSi{sub 3} sample can be attributed to the specific ordered superstructure used in the numerical calculations

The effect of noble metal additives on the optimum operating temperature of SnO2 gas sensors

Science.gov (United States)

Mohammad-Yousefi, S.; Rahbarpour, S.; Ghafoorifard, H.

2017-12-01

The effect of Pd and Au additives on gas sensing properties of SnO2 was investigated. SnO2 pallets were fabricated and sintered at 900 °C for 90 minutes. Several nanometer layers of Pd and Au were deposited on separate SnO2 pallets and were intentionally dispersed into the SnO2 pallets by long heat treatment (400 °C for 1 Day). All metal loaded samples showed significant enhancement in response level and optimum operating temperature compare to pure SnO2 gas sensors. The amount of enhancement was strongly dependent on the material and the thickness of deposited metal layer. Studying butanol response showed that increasing the thickness of metal causes the response level to increase. Further thickness increase caused contrary effect and decreased the performance of sensors. Best results were achieved at 10 nm-thick Au and 7 nm-thick Pd. Generally, Pd-SnO2 samples demonstrated better performance than Au-SnO2 ones, however, Au-SnO2 samples were proved to be good candidate to sense reducing gases with lower hydrogen atoms in their formula. Given experimental results were also good evidence of chemical activity of gold and simply confirms the relation between chemical activity and gold particle size. Results were qualitatively described by gas diffusion theory and surface reactions take place on metal particles.The first section in your paper

Session 6: Catalytic hydro-dehalogenation of halon 1211 (CBrClF{sub 2}) over carbon supported Pd-Fe, Pd-Co and Pd-Ni bimetallic catalysts

Energy Technology Data Exchange (ETDEWEB)

Hai, Yu; Kennedy, E.M.; Md Azhar, Uddin; Dlugogorski, B.Z. [Newcastle Univ., Process Safety and Environment Protection Group, School of Engineering, Callaghan, NSW (Australia)

2004-07-01

In the current study, we present the result of our investigation on the hydro-dehalogenation of halon 1211 with hydrogen over carbon supported Pd-Fe, Pd-Co and Pd-Ni bimetallic catalysts. In addition to dissociatively adsorbing hydrogen, Fe, Co and Ni themselves can facilitate cleavage of C-halogen bonds. The effect of the interaction of a second metal (Fe, Co and Ni) with Pd on the conversion of halon 1211 and selectivity to CH{sub 2}F{sub 2} for the catalytic hydro-dehalogenation of halon 1211 is discussed. Activated carbon is chosen as support in order to minimize the interaction of support with the metals. The obtained experimental results show that the introduction of Fe, Co and Ni to Pd catalysts has a significant influence on the catalytic hydro-dehalogenation of halon 1211, especially with respect to the selectivity to CH{sub 2}F{sub 2}. The presence of Fe increases the amount of halon 1211 adsorbed on the surface of catalysts and enhances the cleavage of C-halogen bonds in halon 1211, resulting in a higher halon 1211 conversion level and selectivity to hydrocarbons. Higher selectivity to CHBrF{sub 2} is ascribed to the secondary reaction: CF{sub 2} + HBr {yields} CHBrF{sub 2}. (authors)

Refining of crude uranium by solvent extraction for production of nuclear pure uranium metal

International Nuclear Information System (INIS)

Gupta, S.K.; Manna, S.; Singha, M.; Hareendran, K.N.; Chowdhury, S.; Satpati, S.K.; Kumar, K.

2007-01-01

Uranium is the primary fuel material for any nuclear fission energy program. Natural uranium contains only 0.712% of 235 U as fissile constituent. This low concentration of fissile isotope in natural uranium calls for a very high level of purity, especially with respect to neutron poisons like B, Cd, Gd etc. before it can be used as nuclear fuel. Solvent extraction is a widely used technique by which crude uranium is purified for reactor use. Uranium metal plant (UMP), BARC, Trombay is engaged in refining of uranium concentrate for production of nuclear pure uranium metal for fabrication of fuel for research reactors. This paper reviews some of the fundamental aspects of this refining process with some special references to UMP, BARC. (author)

Density functional calculations on 13-atom Pd12M (M = Sc—Ni) bimetallic clusters

International Nuclear Information System (INIS)

Tang Chun-Mei; Chen Sheng-Wei; Zhu Wei-Hua; Tao Cheng-Jun; Zhang Ai-Mei; Gong Jiang-Feng; Zou Hua; Liu Ming-Yi; Zhu Feng

2012-01-01

The geometric structures, electronic and magnetic properties of the 3d transition metal doped clusters Pd 12 M (M = Sc—Ni) are studied using the semi-core pseudopots density functional theory. The groundstate geometric structure of the Pd 12 M cluster is probably of pseudoicosahedron. The I h -Pd 12 M cluster has the most thermodynamic stability in five different symmetric isomers. The energy gap shows that Pd 12 M cluster is partly metallic. Both the absolutely predominant metal bond and very weak covalent bond might exist in the Pd 12 M cluster. The magnetic moment of Pd 12 M varies from 0 to 5 μ B , implying that it has a potential application in new nanomaterials with tunable magnetic properties

Determination of the impurities in some pure metals, alloys, ores, plants, and coating materials with emission spectrography

Energy Technology Data Exchange (ETDEWEB)

Chao, C N; Lee, S L; Tsai, H T

1976-07-01

There are many methods in the instrumental analysis. Among them, the emission spectrographic methods are developed and compiled in analyzing diverse samples. Semi-quantitative method is used widely in general samples, such as alloys, ores, sands, plants, coating materials--etc. However, in quantitative analysis, determination of the metallic impurities contents in the pure metals depends upon the matrix effect. It is necessary to convert to the form identically for unknown and standard alike. Though the technique may be different, all of these methods are easily prepared and applied on new materials.

Creep in commercially pure metals

International Nuclear Information System (INIS)

Nabarro, F.R.N.

2006-01-01

The creep of commercially pure polycrystalline metals under constant stress has four stages: a virtually instantaneous extension, decelerating Andrade β creep, almost steady-state Andrade κ creep, and an acceleration towards failure. Little is known about the first stage, and the fourth stage has been extensively reviewed elsewhere. The limited experimental evidence on the physical mechanism of the second stage is reviewed and a critical discussion is given of various theories of this stage. The dependence of strain rate on stress in the third, steady-state, period seems to fall into two regimes, a power law with an exponent of about 4-5, and a rather closely exponential law. The limits of the parameters within which a simple theory of the exponential dependence can be expected to be valid are discussed, and found to be compatible with experiments. Theories of the power-law dependence are discussed, and, appear to be unconvincing. The theoretical models do not relate closely to the metallographic and other physical observations. In view of the weakness of theory, experiments which may indicate the physical processes dominant in steady-state creep are reviewed. It is usually not clear whether they pertain to the power-law or the exponential regime. While the theories all assume that most of the deformation occurs homogeneously within the grains, most experimental observations point strongly to a large deformation at or close to the grain boundaries. However, a detailed study of dislocation processes in a single grain of polycrystalline foil strained in the electron microscope shows that most of the observed strain can be accounted for by the motion of single dislocations through the subgrain structure. There is no clear reconciliation of these two sets of observations. Grain-boundary sliding cannot occur without intragranular deformation. One or other process may dominate the overall deformation; the geometrically dominant process may not be the rate

Magnetism and transport studies in off-stoichiometric metallic perovskite compounds GdPd{sub 3}B{sub x} (x=0.25, 0.50 and 0.75)

Energy Technology Data Exchange (ETDEWEB)

Pandey, Abhishek, E-mail: abhishek.phy@gmail.co [S. N. Bose National Centre for Basic Sciences, Block-JD, Sector-III, Salt Lake, Kolkata 700098 (India); Experimental Condensed Matter Physics Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India); Mazumdar, Chandan, E-mail: chandan.mazumdar@saha.ac.i [Experimental Condensed Matter Physics Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India); Ranganathan, R. [Experimental Condensed Matter Physics Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India)

2010-12-15

We report the magnetic and transport properties of the off-stoichiometric metallic perovskite like compounds GdPd{sub 3}B{sub x} (x=0.25, 0.50 and 0.75). Our results show that doping with boron in the lattice of parent binary-compound GdPd{sub 3} leads to lattice expansion. Which in turn manifests in contrasting magnetic and transport behaviors of the doped compounds in comparison with the undoped GdPd{sub 3}. An attempt has been made to compare and correlate the results of magnetic and transport measurements of GdPd{sub 3}B{sub x} with that of stoichiometric compositions GdPd{sub 3}B{sub x}C{sub 1-x}. The comparative study of GdPd{sub 3}B{sub x} and GdPd{sub 3}B{sub x}C{sub 1-x} confirms that there is a strong correlations between the structural, magnetic and transport properties of these compounds.

Temperature dependent current transport of Pd/ZnO nanowire Schottky diodes

Science.gov (United States)

Gayen, R. N.; Bhattacharyya, S. R.; Jana, P.

2014-09-01

Zinc oxide (ZnO) nanowire based Schottky barrier diodes are fabricated by depositing Pd metal contact on top of vertically well-aligned ZnO nanowire arrays. A vertical array of ZnO nanowires on indium tin oxide (ITO) coated glass substrates is synthesized by hybrid wet chemical route. Scanning electron microscopy (SEM), x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) measurement confirm the formation of stoichiometric well-aligned hexagonal (h-ZnO) nanowire arrays with wurtzite structure. Temperature dependent current-voltage (I-V) measurements on palladium-ZnO (Pd/ZnO) nanowire Schottky junctions in the temperature range 303-383 K exhibit excellent rectifying character. From these nonlinear I-V plots, different electrical parameters of diode-like reverse saturation current, barrier height and ideality factor are determined as a function of temperature assuming pure thermionic emission model. The ideality factor is found to decrease while the barrier height increases with the increase in temperature. The series resistance values calculated from Cheung’s functions also show temperature dependency. Such behavior can be attributed to the presence of defects that traps carriers, and barrier height inhomogeneity at the interface of the barrier junction. After barrier height inhomogeneity correction, considering a Gaussian distributed barrier height fluctuation across the Pd/ZnO interface, the estimated values of mean barrier height and modified Richardson constant are more closely matched to the theoretically predicted value for Pd/ZnO Schottky barrier diodes. The variation of density of interface states as a function of interface state energy is also calculated.

Regional cerebral blood flow in pure dysarthria. A 3D-SSP study

International Nuclear Information System (INIS)

Okamoto, Kensho; Kamogawa, Kenji; Okuda, Bungo; Kawabata, Keita; Tachibana, Hisao

2007-01-01

Pure dysarthria from brain infarction is a rare condition, and its pathophysiology remains unclear. To clarify the underlying mechanism of pure dysarthria, we investigated the lesion sites and regional cerebral blood flow in patients with pure dysarthria. We examined 18 consecutive patients with pure dysarthria (9 men and 9 women; mean age, 71 years) who underwent MRI and cerebral blood flow studies. To visualize the regional cerebral blood flow, we generated Z score images using the three-dimensional stereotactic surface projection (3D-SSP) method with single-photon emission computed tomography (SPECT) and N-isopropyl-p [ 123 I]iodoamphetamine. Data on the brain surface perfusion extracted by the 3D-SSP analysis were compared between the pure dysarthria (PD) patients and 9 control subjects. MRI revealed multiple lacunar infarctions involving the internal capsule and/or corona radiata in 11 patients, left internal capsule-corona radiata infarction in 4 patients, and pontine infarction in 3 patients. SPECT with 3D-SSP demonstrated bilateral frontal cortical hypoperfusion in all patients, particularly in the anterior opercular region. Based on intergroup comparisons, the PD group exhibited pronounced cortical hypoperfusion in the opercular and medial frontal regions, left more than right. In conclusion, pure dysarthria is considered to originate from frontal cortical hypoperfusion, mainly in the anterior opercular and medial frontal regions, which is probably due to interruption of the corticosubcortical neural networks relevant to speech expression and articulation. In addition, it is suggested that left hemispheric lesions may make a greater contribution to the development of pure dysarthria than do right ones. (author)

Facile preparation of ZIF-8@Pd-CSS sandwich-type microspheres via in situ growth of ZIF-8 shells over Pd-loaded colloidal carbon spheres with aggregation-resistant and leach-proof properties for the Pd nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Zhang, Tong; Lin, Lu [State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian, 116024 (China); Zhang, Xiongfu, E-mail: xfzhang@dlut.edu.cn [State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian, 116024 (China); Liu, Haiou; Yan, Xinjuan [State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian, 116024 (China); Liu, Zhang; Yeung, King Lun [Department of Chemical and Biomolecular Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR (China)

2015-10-01

Graphical abstract: - Highlights: • Uniform-sized colloidal carbon spheres were synthesized from low-cost glucose. • Pd nanoparticles were loaded onto the carbon spheres via self-reduction method. • A layer of ZIF-8 shell was in situ grown over the Pd-loaded carbon spheres. • The ZIF-8@Pd-CCS showed leach-proof and aggregation-resistant properties of Pd. - Abstract: Aiming to enhance the stability of noble metal nanoparticles that are anchored on the surface of colloidal carbon spheres (CCSs), we designed and prepared a new kind of sandwich-structured ZIF-8@Pd-CCS microsphere. Typically, uniform CCSs were first synthesized by the aromatization and carbonization of glucose under hydrothermal conditions. Subsequently, noble metal nanoparticles, herein Pd nanoparticles, were attached to the surface of CCSs via self-reduction route, followed by in situ assembly of a thin layer of ZIF-8 over the Pd nanoparticles to form the sandwich-type ZIF-8@Pd-CCS microspheres. X-ray diffraction (XRD) patterns and Fourier transform infrared spectroscopy (FTIR) spectra confirmed the presence of crystalline ZIF-8, while TEM analysis revealed that the ZIF-8 shells were closely bound to the Pd-loaded CCSs. The shell thickness could be tuned by varying the ZIF-8 assembly cycles. Further, liquid-phase hydrogenation of 1-hexene as the probe reaction was carried out over the ZIF-8@Pd-CCS microspheres and results showed that the prepared microspheres exhibited excellent agglomeration-resistant and leach-proof properties for the Pd nanoparticles, thus leading to the good reusability of the ZIF-8@Pd-CCS microspheres.

The influence of local volume forces on surface relaxation of pure metals and alloys: Applications to Ni, Al, Ni3Al

International Nuclear Information System (INIS)

Savino, E.J.; Farkas, D.

1987-11-01

We present an analysis of the relative influence of the interatomic potential, lattice structure and defect symmetry on the calculated and measured distortion for the free surfaces of alloys and pure metals. In particular, the effect of using local ''volume'' dependent interactions is studied, as opposed to simple pair interatomic forces. The dependence of the relaxation on the lattice structure is examined by comparing pure metals with ordered alloys. A Green function method for surface relaxation is presented and used for the above analysis as well as for studying the influence of different surface symmetries. Examples based on computer simulation of Ni, Al and Ni 3 Al for some surface orientations are presented. (author). 33 refs, 4 figs

Seed-mediated co-reduction in a large lattice mismatch system: synthesis of Pd-Cu nanostructures.

Science.gov (United States)

Kunz, Meredith R; McClain, Sophia M; Chen, Dennis P; Koczkur, Kallum M; Weiner, Rebecca G; Skrabalak, Sara E

2017-06-08

Metal nanoparticles (NPs) are of interest for applications in catalysis, electronics, chemical sensing, and more. Their utility is dictated by their composition and physical parameters such as particle size, particle shape, and overall architecture (e.g., hollow vs. solid). Interestingly, the addition of a second metal to create bimetallic NPs adds multifunctionality, with new emergent properties common. However, synthesizing structurally defined bimetallic NPs remains a great challenge. One synthetic pathway to architecturally controlled bimetallic NPs is seed-mediated co-reduction (SMCR) in which two metal precursors are simultaneously co-reduced to deposit metal onto shape-controlled metal seeds, which direct the overgrowth. Previously demonstrated in a Au-Pd system, here SMCR is applied to a system with a larger lattice mismatch between the depositing metals: Pd and Cu (7% mismatch for Pd-Cu vs. 4% for Au-Pd). Through manipulation of precursor reduction kinetics, the morphology and bimetallic distribution of the resultant NPs can be tuned to achieve eight-branched Pd-Cu heterostructures with Cu localized at the tips of the Pd nanocubes as well as branched Pd-Cu alloyed nanostructures and polyhedra. Significantly, the symmetry of the seeds can be transferred to the final nanostructures. This study expands our understanding of SMCR as a route to structurally defined bimetallic nanostructures and the synthesis of multicomponent nanomaterials more generally.

Composite metal-hydrogen electrodes for metal-hydrogen batteries. Final report, October 1, 1993 - April 15, 1997

International Nuclear Information System (INIS)

Ruckman, M.W.; Strongin, M.; Weismann, H.

1997-04-01

The purpose of this project is to develop and conduct a feasibility study of metallic thin films (multilayered and alloy composition) produced by advanced sputtering techniques for use as anodes in Ni-metal hydrogen batteries that would be deposited as distinct anode, electrolyte and cathode layers in thin film devices. The materials could also be incorporated in secondary consumer batteries (i.e. type AF(4/3 or 4/5)) which use electrodes in the form of tapes. The project was based on pioneering studies of hydrogen uptake by ultra-thin Pd-capped Nb films, these studies suggested that materials with metal-hydrogen ratios exceeding those of commercially available metal hydride materials and fast hydrogen charging and discharging kinetics could be produced. The project initially concentrated on gas phase and electrochemical studies of Pd-capped niobium films in laboratory-scale NiMH cells. This extended the pioneering work to the wet electrochemical environment of NiMH batteries and exploited advanced synchrotron radiation techniques not available during the earlier work to conduct in-situ studies of such materials during hydrogen charging and discharging. Although batteries with fast charging kinetics and hydrogen-metal ratios approaching unity could be fabricated, it was found that oxidation, cracking and corrosion in aqueous solutions made pure Nb films and multilayers poor candidates for battery application. The project emphasis shifted to alloy films based on known elemental materials used for NiMH batteries. Although commercial NiMH anode materials contain many metals, it was found that 0.24 μm thick sputtered Zr-Ni films cycled at least 50 times with charging efficiencies exceeding 95% and [H]/[M] ratios of 0.7-1.0. Multilayered or thicker Zr-Ni films could be candidates for a thin film NiMH battery that may have practical applications as an integrated power source for modern electronic devices

Measurement of benzenethiol adsorption to nanostructured Pt, Pd, and PtPd films using Raman spectroelectrochemistry.

Science.gov (United States)

Pomfret, Michael B; Pietron, Jeremy J; Owrutsky, Jeffrey C

2010-05-04

Raman spectroscopy and electrochemical methods were used to study the behavior of the model adsorbate benzenethiol (BT) on nanostructured Pt, Pd, and PtPd electrodes as a function of applied potential. Benzenethiol adsorbs out of ethanolic solutions as the corresponding thiolate, and voltammetric stripping data reveal that BT is oxidatively removed from all of the nanostructured metals upon repeated oxidative and reductive cycling. Oxidative stripping potentials for BT increase in the order Pt oxidizing potentials via cleavage of the Pt-S bond. In contrast, on nanoscale Pd and PtPd, BT is irreversibly lost due to cleavage of BT C-S bonds at oxidizing potentials, which leaves adsorbed sulfur oxides on Pd and PtPd films and effects the desulfurization of BT. While Pd and PtPd films are less sulfur-resistant than Pt films, palladium oxides, which form at higher potentials than Pt oxides, oxidatively desulfurize BT. In situ spectroelectrochemical Raman spectroscopy provides real-time, chemically specific information that complements the cyclic voltammetric data. The combination of these techniques affords a powerful and convenient method for guiding the development of sulfur-tolerant PEMFC catalysts.

Preparation technology of 103Pd-110Agm composite alloy membranes

International Nuclear Information System (INIS)

Liu Zhuo; Chen Daming; Jin Xiaohai; Li Zhongyong; Guo Feihu; Qin Hongbin

2012-01-01

The preparation of 103 Pd- 110 Ag m alloy membranes was the basis for the production of 103 Pd- 125 I composite sources. Taking 103 Pd and 110 Ag m as trace elements, the method of non-electrolytical plating was chosen to prepare the alloy membrane. A γ-detector and electron microscope (SEM) were used for quantitative and qualitative analysis, respectively. The pre-treatment of the support before the preparation of Palladium-silver composite membranes was discussed in detail. It was found that when the concentration of PdCl 2 was between 0.5 and 2.0 mmol/L the result was good. The effects of various factors were investigated, including the proportion of Pd and Ag, the concentrations of the total metal, ammonium hydroxide hydrazine and ethylenediaminetetraacetic acid, temperature, the time, and the rotation speed. By improving the reaction conditions the alloy membrane with metallic luster was obtained. Besides, the presence of Pd and Ag was observed in the alloy membranes by qualitative analysis. (authors)

Magnetism in ordered metallic perovskite compound GdPd{sub 3}B{sub x}C{sub 1-x}

Energy Technology Data Exchange (ETDEWEB)

Pandey, Abhishek [S.N. Bose National Centre for Basic Sciences, Block-JD, Sector-III, Salt Lake, Kolkata 700098 (India); Experimental Condensed Matter Physics Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India)], E-mail: abhishek.phy@gmail.com; Mazumdar, Chandan [Experimental Condensed Matter Physics Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India)], E-mail: chandan.mazumdar@saha.ac.in; Ranganathan, R. [Experimental Condensed Matter Physics Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India); Dattagupta, S. [Indian Institute of Science Education and Research, Block-HC, Sector-III, Salt Lake, Kolkata 700106 (India)

2009-08-15

We report results of dc-magnetization, ac-susceptibility and magnetoresistance measurements on crystalline metallic-perovskite compounds GdPd{sub 3}B{sub x}C{sub 1-x} (x=0.25, 0.50, 0.75 and 1.00) and the parent cubic compound GdPd{sub 3}. The interest in these materials stems from the observation of negative temperature coefficient of resistance and negative thermal expansion in some of the members of this series. In the present study, we show that by substitution of non-magnetic elements, boron and carbon, the nature of the magnetic interaction can be varied from dominating ferromagnetic to antiferromagnetic and finally to a canted magnetic structure without altering the crystal symmetry of the compounds. The variation of magnetic interaction by modifying the lattice parameter resembles Ruderman-Kittel-Kasuya-Yosida (RKKY) oscillations.

Synthesis and Characterization of a Triphos Ligand Derivative and the Corresponding Pd ^II Complexes: Triphos Ligand Derivative and Corresponding Pd ^II Complexes

Energy Technology Data Exchange (ETDEWEB)

Miller, Deanna L.; Boro, Brian J.; Grubel, Katarzyna; Helm, Monte L.; Appel, Aaron M.

2015-11-16

The synthesis of the new bis(2-(diphenylphosphino)ethyl)methylhydroxyphosphine tridentate phosphine ligand, LCH2OH/Ph, is reported. The ligand reacts with [Pd(Cl)2(PhCN)2 to form [Pd(LCH2OH/Ph)Cl]Cl. Exchange of the chloride ions for triflate (OTf–) using AgOTf yielded pure [Pd(LCH2OH/Ph)OTf]OTf. In addition to spectral characterization the free ligand, LCH2OH/Ph, and Pd(II) complex, [Pd(LCH2OH/Ph)OTf]OTf, are structurally characterized. This research was supported by the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Biosciences, and Geosciences. Pacific Northwest National Laboratory is a multiprogram national laboratory operated by Battelle for DOE.

Boosting catalytic activity of metal nanoparticles for 4-nitrophenol reduction: Modification of metal naoparticles with poly(diallyldimethylammonium chloride)

Energy Technology Data Exchange (ETDEWEB)

You, Jyun-Guo; Shanmugam, Chandirasekar [Department of Chemistry, National Sun Yat-sen University, Taiwan (China); Liu, Yao-Wen; Yu, Cheng-Ju [Department of Applied Physics and Chemistry, University of Taipei, Taiwan (China); Tseng, Wei-Lung, E-mail: tsengwl@mail.nsysu.edu.tw [Department of Chemistry, National Sun Yat-sen University, Taiwan (China); School of Pharmacy, College of Pharmacy, Kaohsiung Medical University, Taiwan (China); Center for Nanoscience and Nanotechnology, National Sun Yat-sen University, Taiwan (China)

2017-02-15

Highlights: • The choice of capping ligand determines catalytic activity of metal nanocatalysts. • PDDA-capped metal nanoparticles electrostatically interact with 4-NP and BH4{sup −}. • PDDA-capped metal nanoparticles have good recyclability and large scalability. • PDDA-capped Pd nanoparticles show the highest rate constant and activity parameter. - Abstract: Most of the previously reported studies have focused on the change in the size, morphology, and composition of metal nanocatalysts for improving their catalytic activity. Herein, we report poly(diallyldimethylammonium chloride) [PDDA]-stabilized nanoparticles (NPs) of platinum (Pt) and palladium (Pd) as highly active and efficient catalysts for hydrogenation of 4-nitrophenol (4-NP) in the presence of NaBH4. PDDA-stabilized Pt and Pd NPs possessed similar particle size and same facet with citrate-capped Pt and Pd NPs, making this study to investigate the inter-relationship between catalytic activity and surface ligand without the consideration of the effects of particle size and facet. Compared to citrate-capped Pt and Pd NPs, PDDA-stabilized Pt and Pd NPs exhibited excellent pH and salt stability. PDDA could serve as an electron acceptor for metal NPs to produce the net positive charges on the metal surface, which provide strong electrostatic attraction with negatively charged nitrophenolate and borohydride ions. The activity parameter and rate constant of PDDA-stabilized metal NPs were higher than those of citrate-capped metal NPs. Compared to the previously reported Pd nanomaterials for the catalysis of NaBH4-mediated reduction of 4-NP, PDDA-stabilized Pd NPs exhibited the extremely high activity parameter (195 s{sup −1} g{sup −1}) and provided excellent scalability and reusability.

ALTERNATIVE MATERIALS TO PD MEMBRANES FOR HYDROGEN PURIFICATION

Energy Technology Data Exchange (ETDEWEB)

Korinko, P; T. Adams

2008-09-12

Development of advanced hydrogen separation membranes in support of hydrogen production processes such as coal gasification and as front end gas purifiers for fuel cell based system is paramount to the successful implementation of a national hydrogen economy. Current generation metallic hydrogen separation membranes are based on Pd-alloys. Although the technology has proven successful, at issue is the high cost of palladium. Evaluation of non-noble metal based dense metallic separation membranes is currently receiving national and international attention. The focal point of the reported work was to evaluate two different classes of materials for potential replacement of conventional Pd-alloy purification/diffuser membranes. Crystalline V-Ni-Ti and Amorphous Fe- and Co-based metallic glass alloys have been evaluated using gaseous hydrogen permeation testing techniques.

ZnCr2S4: Highly effective photocatalyst converting nitrate into N2 without over-reduction under both UV and pure visible light.

Science.gov (United States)

Yue, Mufei; Wang, Rong; Cheng, Nana; Cong, Rihong; Gao, Wenliang; Yang, Tao

2016-08-03

We propose several superiorities of applying some particular metal sulfides to the photocatalytic nitrate reduction in aqueous solution, including the high density of photogenerated excitons, high N2 selectivity (without over-reduction to ammonia). Indeed, ZnCr2S4 behaved as a highly efficient photocatalyst, and with the assistance of 1 wt% cocatalysts (RuOx, Ag, Au, Pd, or Pt), the efficiency was greatly improved. The simultaneous loading of Pt and Pd led to a synergistic effect. It offered the highest nitrate conversion rate of ~45 mg N/h together with the N2 selectivity of ~89%. Such a high activity remained steady after 5 cycles. The optimal apparent quantum yield at 380 nm was 15.46%. More importantly, with the assistance of the surface plasma resonance effect of Au, the visible light activity achieved 1.352 mg N/h under full arc Xe-lamp, and 0.452 mg N/h under pure visible light (λ > 400 nm). Comparing to the previous achievements in photocatalytic nitrate removal, our work on ZnCr2S4 eliminates the over-reduction problem, and possesses an extremely high and steady activity under UV-light, as well as a decent conversion rate under pure visible light.

ZnCr2S4: Highly effective photocatalyst converting nitrate into N2 without over-reduction under both UV and pure visible light

Science.gov (United States)

Yue, Mufei; Wang, Rong; Cheng, Nana; Cong, Rihong; Gao, Wenliang; Yang, Tao

2016-08-01

We propose several superiorities of applying some particular metal sulfides to the photocatalytic nitrate reduction in aqueous solution, including the high density of photogenerated excitons, high N2 selectivity (without over-reduction to ammonia). Indeed, ZnCr2S4 behaved as a highly efficient photocatalyst, and with the assistance of 1 wt% cocatalysts (RuOx, Ag, Au, Pd, or Pt), the efficiency was greatly improved. The simultaneous loading of Pt and Pd led to a synergistic effect. It offered the highest nitrate conversion rate of ~45 mg N/h together with the N2 selectivity of ~89%. Such a high activity remained steady after 5 cycles. The optimal apparent quantum yield at 380 nm was 15.46%. More importantly, with the assistance of the surface plasma resonance effect of Au, the visible light activity achieved 1.352 mg N/h under full arc Xe-lamp, and 0.452 mg N/h under pure visible light (λ > 400 nm). Comparing to the previous achievements in photocatalytic nitrate removal, our work on ZnCr2S4 eliminates the over-reduction problem, and possesses an extremely high and steady activity under UV-light, as well as a decent conversion rate under pure visible light.

Development of casting investment preventing blackening of noble metal alloys part 1. Application of developed investment for Ag-Pd-Cu-Au alloy.

Science.gov (United States)

Kakuta, Kiyoshi; Nakai, Akira; Goto, Shin-ichi; Wakamatsu, Yasushi; Yara, Atushi; Miyagawa, Yukio; Ogura, Hideo

2003-03-01

The objective of this study is to develop a casting investment that prevents the blackening of the cast surface of noble metal alloys. The experimental investments were prepared using a gypsum-bonded investment in which the metallic powders such as boron (B), silicon (Si), aluminum (Al) and titanium (Ti) were added as oxidizing agents. An Ag-Pd-Cu-Au alloy was cast into the mold made of the prepared investment. The effect of the addition of each metal powder was evaluated from the color difference between the as-cast surface and the polished surface of the cast specimen. The color of the as-cast surface approached that of the polished surface with increasing B and Al content. A lower mean value in the color difference was obtained at 0.25-1.00 mass% B content. B and Al are useful as an additive in a gypsum-bonded investment to prevent the blackening of an Ag-Pd-Cu-Au alloy. The effects of Si and Ti powder addition could not be found.

Inert anode containing base metal and noble metal useful for the electrolytic production of aluminum

Science.gov (United States)

Ray, Siba P.; Liu, Xinghua

2000-01-01

An inert anode for production of metals such as aluminum is disclosed. The inert anode comprises a base metal selected from Cu and Ag, and at least one noble metal selected from Ag, Pd, Pt, Au, Rh, Ru, Ir and Os. The inert anode may optionally be formed of sintered particles having interior portions containing more base metal than noble metal and exterior portions containing more noble metal than base metal. In a preferred embodiment, the base metal comprises Cu, and the noble metal comprises Ag, Pd or a combination thereof.

Inhibitory effect of Ti-Ag alloy on artificial biofilm formation.

Science.gov (United States)

Nakajo, Kazuko; Takahashi, Masatoshi; Kikuchi, Masafumi; Takada, Yukyo; Okuno, Osamu; Sasaki, Keiichi; Takahashi, Nobuhiro

2014-01-01

Titanium-silver (Ti-Ag) alloy has been improved for machinability and mechanical properties, but its anti-biofilm properties have not been elucidated yet. Thus, this study aimed to evaluate the effects of Ti-Ag alloy on biofilm formation and bacterial viability in comparison with pure Ti, pure Ag and silver-palladium (Ag-Pd) alloy. Biofilm formation on the metal plates was evaluated by growing Streptococcus mutans and Streptococcus sobrinus in the presence of metal plates. Bactericidal activity was evaluated using a film contact method. There were no significant differences in biofilm formation between pure Ti, pure Ag and Ag-Pd alloy, while biofilm amounts on Ti-20% Ag and Ti-25% Ag alloys were significantly lower (p<0.05). In addition, Ti-Ag alloys and pure Ti were not bactericidal, although pure Ag and Ag-Pd alloy killed bacteria. These results suggest that Ti-20% Ag and Ti-25% Ag alloys are suitable for dental material that suppresses biofilm formation without disturbing healthy oral microflora.

Oxidation-induced spin reorientation in Co adatoms and CoPd dimers on Ni/Cu(100)

Science.gov (United States)

Chen, K.; Beeck, T.; Fiedler, S.; Baev, I.; Wurth, W.; Martins, M.

2016-04-01

Ultrasmall magnetic clusters and adatoms are of strong current interest because of their possible use in future technological applications. Here, we demonstrate that the magnetic coupling between the adsorbates and the substrate can be significantly changed through oxidation. The magnetic properties of Co adatoms and CoPd dimers deposited on a remanently magnetized Ni/Cu(100) substrate have been investigated by x-ray absorption and x-ray magnetic circular dichroism spectroscopy at the Co L2 ,3 edges. Using spectral differences, pure and oxidized components are distinguished, and their respective magnetic moments are determined. The Co adatoms and the CoPd dimers are coupled ferromagnetically to the substrate, while their oxides, Co-O and CoPd-O, are coupled antiferromagnetically to the substrate. Along with the spin reorientation from the pure to the oxidized state, the magnetic moment of the adatom is highly reduced from Co to Co-O. In contrast, the magnetic moment of the dimer is of similar order for CoPd and CoPd-O.

Metastable Transition Metal Alloys Produced by Rapid Quenching: Structure and Properties.

Science.gov (United States)

1984-01-01

cobalt or nickel continuous ribbons 1 . 2 mm wide and about fromthe angaeseiro, coalt r nikel 30 jum thick. Differential scanning calori- groups or B metal... wire , obtained from the International Nb1Pd,:’o NbPds 70 "藿 (MoPtaI- NbPt, I structure Nickel Co., and palladium powder (-325 mesh) ob- tained from...This is consistent with the work of Black S(k) denote that of a 99.999+% pure lead wire using the integral et l.i who predict that the tunneling-level

Electric-field effects on magnetic anisotropy in Pd/Fe/Pd(0 0 1) surface

International Nuclear Information System (INIS)

Haraguchi, Shinya; Tsujikawa, Masahito; Gotou, Junpei; Oda, Tatsuki

2011-01-01

Electric-field (EF) effects have been studied on magnetic anisotropy in the metallic surfaces Pt/Fe/Pt(0 0 1) and Pd/Fe/Pd(0 0 1) by means of the first-principles electronic structure calculation which employs the generalized gradient approximation. The variation of anisotropy energy with respect to the EF is found to be opposite to each other. The modulus rate of the variation is larger by a few factors in the Pt substrate than in the Pd one. These results agree qualitatively well with the available experimental data. The electronic structures are presented and the origins in EF effects are discussed along a line of the second perturbative fashion.

Size and alloying induced shift in core and valence bands of Pd-Ag and Pd-Cu nanoparticles

International Nuclear Information System (INIS)

Sengar, Saurabh K.; Mehta, B. R.; Govind

2014-01-01

In this report, X-ray photoelectron spectroscopy studies have been carried out on Pd, Ag, Cu, Pd-Ag, and Pd-Cu nanoparticles having identical sizes corresponding to mobility equivalent diameters of 60, 40, and 20 nm. The nanoparticles were prepared by the gas phase synthesis method. The effect of size on valence and core levels in metal and alloy nanoparticles has been studied by comparing the values to those with the 60 nm nanoparticles. The effect of alloying has been investigated by comparing the valence and core level binding energies of Pd-Cu and Pd-Ag alloy nanoparticles with the corresponding values for Pd, Ag, and Cu nanoparticles of identical sizes. These effects have been explained in terms of size induced lattice contractions, alloying induced charge transfer, and hybridization effects. The observation of alloying and size induced binding energy shifts in bimetallic nanoparticles is important from the point of view of hydrogen reactivity

RuPd, RuCo, PdCo and RuPdCo materials as candidates for cathode catalyzers in PEM fuel cells; Materiales RuPd, RuCo, PdCo y RuPdCo como candidatos a catalizadores catodicos en celdas de combustible tipo PEM

Energy Technology Data Exchange (ETDEWEB)

Leyva Noyola, Fatima; Solorza Feria, Omar [Centro de Investigacion y Estudios Superiores del IPN, Mexico, D.F. (Mexico)]. E-mail: fleyva@cinvestav.mx

2009-09-15

This work reports on the catalytic activity of RuPd, RuCo, PdCo and RuPdCo material for oxygen reduction reaction (ORR). These materials were synthesized using chemical reduction with NaBH{sub 4} as a reducing agent in THF, in ambient temperature and pressure conditions. The evaluation of the catalytic activity was done using cyclic voltamperometry (CV) and rotary disc electrode (RDE) in H{sub 2}SO{sub 4} 0.5 M. The kinetic results showed that the electrochemical reaction involves 4 electrons and the transfer of the first electron is the determinant stage. The values of {alpha}, i0 and the Tafel slope were very similar for the four materials studied, around 0.4, 5x10{sup -6} mA cm{sup -2} and 60 mV dec-1, respectively. Although these values are less than those reported for nanostructured platinum, they are better than those reported for other materials such as pure Pd, which enables them to be considered as cathode catalysts for a proton exchange membrane fuel cell. [Spanish] En este trabajo se reporta la actividad catalitica de los materiales RuPd, RuCo, PdCo y RuPdCo para la reaccion de reduccion de oxigeno (RRO). Estos materiales fueron sintetizados por el metodo de reduccion quimica, usando NaBH{sub 4} como agente reductor en THF, en condiciones de temperatura y presion ambiental. La evaluacion de la actividad catalitica fue realizada usando Voltamperometria Ciclica (VC) y Electrodo Disco Rotatorio (EDR) en H{sub 2}SO{sub 4} 0.5 M. Los resultados cineticos mostraron que la reaccion electroquimica procede por la via de 4 electrones y la etapa determinante es la transferencia del primer electron. Los valores de {alpha}, i0 y pendiente de Tafel fueron muy similares para los 4 materiales estudiados, siendo estos de alrededor de 0.4, 5x10{sup -6} mA cm{sup -2} y 60 mV dec{sup -1}, respectivamente. Sin embargo, aun cuando estos valores son menores que los reportados para platino nanoestructurado, son mejores que los reportados para otros materiales como el Pd puro

Sum-frequency generation spectroscopy on metals, oxides, and oxide-supported metal particles; Summenfrequenzerzeugungsspektroskopie an Metallen, Oxiden und oxidgetraegerten Metallpartikeln

Energy Technology Data Exchange (ETDEWEB)

Aumer, Andreas

2010-06-21

This thesis focuses on 4 different model systems of surface science. The experimental techniques used for the measurements include sum frequency generation (SFG), thermal desorption spectroscopy (TDS), low energy electron diffraction (LEED), Auger electron spectroscopy (AES), infrared adsorption spectrosocopy (IRAS) and scanning tunneling microscopy (STM). By using SFG, measurements could be performed up to a pressure of 50 mbar. The systems under investigation were: CO on Pt(111), water on Ag(001) and on MgO/Ag(001), CO on Au/MgO/Ag(001), and CO on Au-Pd/MgO/Ag(001). The system of CO on Pt(111) exhibits a two peak-pattern under certain pressure and temperature conditions which has not been studied so far. Various experiments helped to elucidate the origin of this distinct behaviour. The measurements of water on Ag(001) and MgO/Ag(001) show that on MgO, water first adsorbs as a monolayer with a following multilayer, whereas on Ag(001) it adsorbs as a multilayer from the beginning. The monolayer can be studied below the multilayer and some resonances can be identified. For the case of Au/MgO/Ag(001), STM shows that the growth mode of Au depends on the thickness of the supporting MgO film, which can not be seen with spectroscopic methods. For mixed Au-Pd particles on MgO/Ag(001) a clear difference in the adsorption behaviour between pure metal particles and mixed particles can be seen, which is explained by an interaction between these metals. Annealing the mixed particles to 600 K leads to a segregation of the metals, where the Au atoms diffuse to the shell and the Pd atoms make up the core. The results of all these measurements are discussed in the light of recent publications. (orig.)

Switchable CO2 electroreduction via engineering active phases of Pd nanoparticles

Institute of Scientific and Technical Information of China (English)

Dunfeng Gao; Fan Yang; Shu Miao; Jianguo Wang; Guoxiong Wang; Xinhe Bao; Hu Zhou; Fan Cai; Dongniu Wang; Yongfeng Hu; Bei Jiang; Wen-Bin Cai; Xiaoqi Chen; Rui Si

2017-01-01

Active-phase engineering is regularly utilized to tune the selectivity of metal nanoparticles (NPs) in heterogeneous catalysis.However,the lack of understanding of the active phase in electrocatalysis has hampered the development of efficient catalysts for CO2 electroreduction.Herein,we report the systematic engineering of active phases of Pd NPs,which are exploited to select reaction pathways for CO2 electroreduction.In situ X-ray absorption spectroscopy,in situ attenuated total reflection-infrared spectroscopy,and density functional theory calculations suggest that the formation of a hydrogen-adsorbed Pd surface on a mixture of the α-and β-phases of a palladium-hydride core (α+β PdHx@PdHx) above-0.2 V (vs.a reversible hydrogen electrode) facilitates formate production via the HCOO* intermediate,whereas the formation of a metallic Pd surface on the β-phase Pd hydride core (β PdHx@Pd) below-0.5 V promotes CO production via the COOH* intermediate.The main product,which is either formate or CO,can be selectively produced with high Faradaic efficiencies (＞90％) and mass activities in the potential window of 0.05 to-0.9 V with scalable application demonstration.

Activation of charcoal made from japanese cypress as oxygen electrode in fuel cell by deposition of Pd-metal/Heteropolyacids of the micropores; Kinzokuparajiumu-heteroporisan no bunsan tanzi niyoru hinoki mokutan no nenryo denchisansokyoku to shiteno kinouka

Energy Technology Data Exchange (ETDEWEB)

Yumine, Takuya.; Kominami, Hiroshi.; Kera, Yoshiya. [Kinki University, osaka (Japan); Abe, Ikuo. [Osaka Municipal Technology Research Institute, Osaka (Japan)

1998-12-31

Pd- and Pt-metal were observed by TEM to be highly disperdsed on charcoal prepared from Japanese Cypress [Hinoki] at 900degreeC (Pd, Pt/H2). Nafion-sheet was hot-pressed with Pd/H2 and Pt/H2 disc-pellets placed in the other sides to make a fuel cell-electrode unit. The 1-V curve in the H{sub 2}-O{sub 2} fuel were measured : The voltage certainly grew with increase in the amount of Pd-metal (1{yields}13wt%) and with a mixing of [Nafion] powder (11wt%). The discharge character was greatly improved with the addition of heteropolyacid (H{sub 3}PMo{sub 11}VO{sub 42};PVMo{sub 11}). When a charcoal prepared from Hinoki at 2400degreeC (HG) was used, the inner resistivity was about 10-times lower than the case of H2 used, although the dispersed states of Pd-metal became considerably poor on HG rather than H2. The actuvuty also increased further with the addition of Nafion and PVMo{sub 11}. (author)

Oxygen reduction reaction (orr) on bimetallic AuPt and AuPd(1 0 0)-electrodes: Effects of the heteroatomic junction on the reaction paths

Science.gov (United States)

Schulte, E.; Belletti, G.; Arce, M.; Quaino, P.

2018-05-01

The seek for materials to enhance the oxygen reduction reaction (orr) rate is a highly relevant topic due to its implication in fuel cell devices. Herein, the orr on bimetallic electrocatalysts based on Au-M (M = Pt, Pd) has been studied computationally, by performing density functional theory calculations. Bimetallic (1 0 0) electrode surfaces with two different Au:M ratios were proposed, and two possible pathways, associative and dissociative, were considered for the orr. Changes in the electronic properties of these materials with respect to the pure metals were acknowledged to gain understanding in the overall reactivity trend. The effect of the bimetallic junction on the stability of the intermediates O2 and OOH was also evaluated by means of geometrical and energetic parameters; being the intermediates preferably adsorbed on Pt/Pd atoms, but presenting in some cases higher adsorption energies compared with bare metals. Finally, the kinetics of the Osbnd O bond breaking in O2∗ and OOH∗ adsorbed intermediates in the bimetallic materials and the influence of the Au-M junction were studied by means of the nudge elastic-band method. A barrierless process for the scission of O2∗ was found in Au-M for the higher M ratios. Surprisingly, for Au-M with lower M ratios, the barriers were much lower than for pure Au surfaces, suggesting a highly reactive surface towards the orr. The Osbnd O scission of the OOH∗ was found to be a barrierless process in Ausbnd Pt systems and nearly barrierless in all Ausbnd Pd systems, implying that the reduction ofO2 in these systems proceeds via the full reduction of O2 to H2O , avoiding H2O2 formation.

Variables process effect in the pure ferritic metal contribution deposited with an tubular metal-cored E111T5-K3 wire

International Nuclear Information System (INIS)

Svoboda, Hernan G; Ramini de Rissone, N.M; Surian, E; De Vedia, L

2004-01-01

The welding deposit performed with an ANSI-AWS E111T5-K3 type from the system C-Mn-Ni-Mo metal coring tubular welding, with a low slag generation was studied. Different operatives configurations with two thermal contribution levels (1 kJ and 1.5 kJ) and two types of protector gases (CO 2 and Ar-20%CO 2 ) at two welding position (under hand and ascendant vertical) were analyzed. The resulting pure contributor metal from the different process configurations was chemical, mechanically and structural characterized and the effect of the different process conditions was evaluated. The microstructure is fundamentally composed by FS(NA) and AF. For similar values of hardness and strength, good values of tenacity were observed and they show little variation with the process variables studied (AG)

Metadislocation reactions and metadislocation networks in the complex metallic alloy ξ'-Al-Pd-Mn

International Nuclear Information System (INIS)

Heggen, Marc; Feuerbacher, Michael

2005-01-01

Metadislocations are novel structural defects firstly observed in the complex metallic alloy ξ'-Al-Pd-Mn. We present a transmission electron microscopy study on metadislocation reactions and networks. It is shown that metadislocations can dissociate into partials, which leads to a decrease of the elastic line energy. Connected groups of metadislocations can assume large and complex network structures with large total Burgers vectors. However, the local elastic strain at the individual metadislocation cores as well as the fault-plane energies remain small. By this mechanism, effective large Burgers vectors, contributing massively to plastic strain, can be distributed over a large portion of the material

Influence of metal coating methods on the activity of bimetal-containing zeolite catalysts of Co, Pd-ZSM-5 in carbon monoxide oxidation

Science.gov (United States)

Oleksenko, L. P.; Lutsenko, L. V.; Yatsimirskii, V. K.

2011-07-01

It has been established that catalytic activity in the CO oxidation of bimetal-containing zeolite Co,Pd-systems based on ZSM-5 and obtained via ion exchange and impregnation at different orders of the introduction of metal cations is higher than that of monometal-containing systems Co-ZSM-5 and Pd—ZSM-5. Through TPD of NH3, it was determined that coordination-unsaturated bicationic associates are formed in Co,Pd/ZSM-5 zeolites obtained by ion exchange. It was found that the activity of bimetal-containing systems depends on the relation of the active components.

Study on growth of highly pure uranium compounds

International Nuclear Information System (INIS)

Shikama, Tatsuo; Ochiai, Akira; Suzuki, Kenji.

1992-01-01

We developed the systems for growing highly pure uranium compounds to study their intrinsic physical properties. Uranium metal was zone refined under low contamination conditions as far as possible. Chemical analysis of the purified uranium was performed using the inductive coupled plasma emission spectrometry (ICP). The problem that emission spectra of the uranium conceal those of analyzed impurities was settled by extraction of the uranium using tri-n-butyl-phosphate (TBP). The result shows that some metallic impurities such as Pb, Mn, Cu etc. evaporated by the r.f. heating and other usual metallic impurities moved to the end of rod with molten zone. Therefore, we conclude that the zone refining technique is much effective to the removal of metallic impurities and we obtained highly purified uranium metal of 99.99 % up with regard to metallic impurities. Using the purified uranium, we attempted to grow a highly pure uranium-titanium single crystals. (author)

Hydrogen Production on Ag-Pd/TiO2 Bimetallic Catalysts: Is there a Combined Effect of Surface Plasmon Resonance with Schottky Mechanism on the Photo-Catalytic Activity?

KAUST Repository

Nadeem, Muhammad A.; Al-Oufi, Maher; Wahab, Ahmed K.; Anjum, Dalaver H.; Idriss, Hicham

2017-01-01

Despite many observations that plasmonics can enhance photocatalytic reactions, their relative role in the overall reaction rate is not thoroughly investigated. Here we report that silver nanoparticles contribution in the reaction rate by its plasmonic effect is negligible when compared to that of Pd (Schottky effect). To conduct the study a series of Ag−Pd/TiO2 catalysts have been prepared, characterized and tested for H2 production from water in the presence of an organic sacrificial agent. Pd was chosen as a standard high work function metal needed for the Schottky junction to pump away electrons from the conduction band of the semiconductor and Ag (whose work function is ca. 1 eV lower than that of Pd) for its high plasmonic resonance response at the edge of the bandgap of TiO2. While H2 production rates showed linear dependency on plasmonic response of Ag in the Pd−Ag series, the system performed less than that of pure Pd. In other words, the plasmonic contribution of Ag in the Ag−Pd/TiO2 catalyst for hydrogen production, while confirmed using different excitation energies, is small. Therefore, the “possible” synergistic effect of plasmonic (in the case of Ag) and Schottky-mechanism (in the case of Pd) is minor when compared to that of Schottky-effect alone.

Hydrogen Production on Ag-Pd/TiO2 Bimetallic Catalysts: Is there a Combined Effect of Surface Plasmon Resonance with Schottky Mechanism on the Photo-Catalytic Activity?

KAUST Repository

Nadeem, Muhammad A.

2017-03-28

Despite many observations that plasmonics can enhance photocatalytic reactions, their relative role in the overall reaction rate is not thoroughly investigated. Here we report that silver nanoparticles contribution in the reaction rate by its plasmonic effect is negligible when compared to that of Pd (Schottky effect). To conduct the study a series of Ag−Pd/TiO2 catalysts have been prepared, characterized and tested for H2 production from water in the presence of an organic sacrificial agent. Pd was chosen as a standard high work function metal needed for the Schottky junction to pump away electrons from the conduction band of the semiconductor and Ag (whose work function is ca. 1 eV lower than that of Pd) for its high plasmonic resonance response at the edge of the bandgap of TiO2. While H2 production rates showed linear dependency on plasmonic response of Ag in the Pd−Ag series, the system performed less than that of pure Pd. In other words, the plasmonic contribution of Ag in the Ag−Pd/TiO2 catalyst for hydrogen production, while confirmed using different excitation energies, is small. Therefore, the “possible” synergistic effect of plasmonic (in the case of Ag) and Schottky-mechanism (in the case of Pd) is minor when compared to that of Schottky-effect alone.

Effects of Cu over Pd based catalysts supported on silica or niobia

Directory of Open Access Journals (Sweden)

Roma M.N.S.C.

2000-01-01

Full Text Available Palladium and palladium-copper catalysts supported on silica and niobia were characterized by H2 chemisorption and H2-O2 titration. Systems over silica were also analyzed by transmission electron microscopy and EXAFS. The metallic dispersion decreased from 20% to 7% when the content of Pd was increased from 0.5wt.-% to 3wt.-% in monometallic catalysts. The addition of 3 wt.-% Cu to obtain Pd-Cu catalysts caused a remarkable capacity loss of hydrogen chemisorption. TPR analysis suggested an interaction between the two metals and EXAFS characterization of the catalyst supported on silica confirmed the formation of Pd-Cu alloy. Pd/Nb2O5 catalysts showed turnover numbers higher than those obtained with the Pd/SiO2 systems in the cyclohexane dehydrogenation. However, the bimetallic catalysts showed very low turnover numbers.

Ethanol electrooxidation on Pt/C and Pd/C catalysts promoted with oxide

Energy Technology Data Exchange (ETDEWEB)

Xu, Changwei [Department of Chemistry and Institute of Nanochemistry, Jinan University, Guangzhou 510632 (China); State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Shen, Pei kang [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Liu, Yingliang [Department of Chemistry and Institute of Nanochemistry, Jinan University, Guangzhou 510632 (China)

2007-02-10

This research aims to investigate Pd-based catalysts as a replacement for Pt-based catalysts for ethanol electrooxidation in alkaline media. The results show that Pd/C has a higher catalytic activity and better steady-state behaviour for ethanol oxidation than that of Pt/C. The effect of the addition of CeO{sub 2} and NiO to the Pt/C and Pd/C electrocatalysts on ethanol oxidation is also studied in alkaline media. The electrocatalysts with a weight ratio of noble metal (Pt, Pd) to CeO{sub 2} of 2:1 and a noble metal to NiO ration 6:1 show the highest catalytic activity for ethanol oxidation. The oxide promoted Pt/C and Pd/C electrocatalysts show a higher activity than the commercial E-TEK PtRu/C electrocatalyst for ethanol oxidation in alkaline media. (author)

Amorphous Pd-assisted H 2 detection of ZnO nanorod gas sensor with enhanced sensitivity and stability

KAUST Repository

Kim, Hyeonghun

2018-02-05

For monitoring H2 concentrations in air, diverse resistive gas sensors have been demonstrated. In particular, Pd-decorated metal oxides have shown remarkable selectivity and sensing response for H2 detection. In this work, H2 sensing behavior of amorphous Pd layer covering ZnO nanorods (am-Pd/ZnO NRs) is investigated. This is the first report on the enhanced gas sensing performance attained by using an amorphous metal layer. The amorphous Pd layer is generated by reduction reaction with a strong reducing agent (NaBH4), and it covers the ZnO nanorods completely with a thickness of 2 ∼ 5 nm. For comparison, crystalline Pd nanoparticles-decorated ZnO nanorods (c-Pd/ZnO NRs) are produced using a milder reducing agent like hydrazine. Comparing the c-Pd/ZnO NRs sensor and other previously reported hydrogen sensors based on the crystalline Pd and metal oxides, the am-Pd/ZnO NRs sensor exhibits a remarkable sensing response (12,400% at 2% H2). The enhancement is attributed to complete cover of the amorphous Pd layer on the ZnO NRs, inducing larger interfaces between the Pd and ZnO. In addition, the amorphous Pd layer prevents surface contamination of the ZnO NRs. Therefore, the am-Pd/ZnO NRs sensor maintains initial sensing performance even after 5 months.

Amorphous Pd-assisted H 2 detection of ZnO nanorod gas sensor with enhanced sensitivity and stability

KAUST Repository

Kim, Hyeonghun; Pak, Yusin; Jeong, Yeonggyo; Kim, Woochul; Kim, Jeongnam; Jung, Gun Young

2018-01-01

For monitoring H2 concentrations in air, diverse resistive gas sensors have been demonstrated. In particular, Pd-decorated metal oxides have shown remarkable selectivity and sensing response for H2 detection. In this work, H2 sensing behavior of amorphous Pd layer covering ZnO nanorods (am-Pd/ZnO NRs) is investigated. This is the first report on the enhanced gas sensing performance attained by using an amorphous metal layer. The amorphous Pd layer is generated by reduction reaction with a strong reducing agent (NaBH4), and it covers the ZnO nanorods completely with a thickness of 2 ∼ 5 nm. For comparison, crystalline Pd nanoparticles-decorated ZnO nanorods (c-Pd/ZnO NRs) are produced using a milder reducing agent like hydrazine. Comparing the c-Pd/ZnO NRs sensor and other previously reported hydrogen sensors based on the crystalline Pd and metal oxides, the am-Pd/ZnO NRs sensor exhibits a remarkable sensing response (12,400% at 2% H2). The enhancement is attributed to complete cover of the amorphous Pd layer on the ZnO NRs, inducing larger interfaces between the Pd and ZnO. In addition, the amorphous Pd layer prevents surface contamination of the ZnO NRs. Therefore, the am-Pd/ZnO NRs sensor maintains initial sensing performance even after 5 months.

Critical current of pure SNS junctions

International Nuclear Information System (INIS)

Golub, A.A.; Bezzub, O.P.

1982-01-01

Boundary conditions at the superconductor-normal metal interface are determined, taking into account the differences in the effective masses and the density of states of the metals constituting the transition and assumed to be pure. The potential barrier of the interface is chosen to be zero. The critical current of the junction is calculated [ru

Understanding the Room Temperature Ferromagnetism in GaN Nanowires with Pd Doping

International Nuclear Information System (INIS)

Manna, S; De, S K

2011-01-01

We report the first synthesis and characterization of 4d transition metal palladium-doped GaN nanowires (NWs). Room temperature ferromagnetism has been observed in high quality Vapor Liquid Solid (VLS) epitaxy grown undoped n-type GaN nanowires. It was proposed that this type of magnetism is due to defects which are not observed in Bulk GaN because of large formation energy of defects in bulk GaN. Here we have successfully doped 4d transition metal Pd in GaN NWs. We find fairly strong and long-range ferromagnetic coupling between Pd substituted for Ga in GaN . The results suggest that 4d metals such as Pd may also be considered as candidates for ferromagnetic dopants in semiconductors.

Biosorpsi Tanaman Puring (Codiaeum variegatum Terhadap Emisi Timbal (Pb Pada Kendaraan Bermotor

Directory of Open Access Journals (Sweden)

Nur Amalia P

2014-07-01

Full Text Available Enhancement the motorized vehicle number will be potential for air pollution in the big cities. One of the pollutant which is resulted from burning process fuel is timbale (Pb metal. Alternative effort that is used to decrease the higher timbale (Pb metal pollutantmaterial is with manner biosorption use puring plant (codiaeumvariegatum.The aim of this research is to know the puring plantability in absorbs Pb metal. The treatment methodis used to sprinkling plant and without sprinkling and than directly exposure to plant with period 3,6 and 9 days. The result of research  that puring leaves ability can absorb Pb concentration metal between (1 until 1,5 ppm or 0,304 mg/Kg at nine days of period exposure, it order can be considered as biosorption agent Pb metal pollution.

Sensitive triplet exciton detection in polyfluorene using Pd-coordinated porphyrin

NARCIS (Netherlands)

Mikhnenko, O.V.; Blom, P.W.M.; Loi, M.A.

2011-01-01

We developed a sensitive spectroscopic method to probe triplet concentration in thin films of polyfluorene (PF) at room temperature. The energy of photoexcited triplet excitons is transferred to the guest metal-organic complex, meso-tetratolylporphyrin-Pd (PdTPP), and detected as phosphorescent

The interaction of deuterium with AgPd/Pd(111) surface alloys

Energy Technology Data Exchange (ETDEWEB)

Diemant, Thomas; Martin, Jan; Behm, R. Juergen [Institute of Surface Chemistry and Catalysis, Ulm University (Germany)

2016-07-01

AgPd/Pd(111) surface alloys, which consist of a reactive and an inert metal, represent an ideal test case for the study of ensemble effects on bimetallic surfaces. In the present contribution, we have studied their deuterium adsorption properties by temperature-programmed desorption (TPD) measurements. The structural properties (surface contents and atom distribution) were determined already earlier by high-resolution scanning tunnelling microscopy (STM), which enables us to correlate the structural properties of these surface alloys to their adsorption behaviour. Most prominently, a steady decrease of the adsorbate coverage with increasing Ag content is observed. The results will be compared to findings on the interaction of CO with these surface alloys.

Ab initio calculations of non-stoichiometric copper nitride, pure and with palladium

International Nuclear Information System (INIS)

Moreno-Armenta, Maria G.; Soto, Gerardo; Takeuchi, Noboru

2011-01-01

Research highlights: → The most stable arrangement corresponds to the Cu 3 N-anti ReO 3 structure. → Formation energy of Cu 32 Vac 0 N 8 and Cu 24 Pd 8 Vac 0 N 8 are very similar. → The biggest volume in the compound is Cu 31 Pd 1 Vac 0 N 8/ . → Small amount introduction of extra metal atoms in copper nitride is possible. - Abstract: We present first principles calculations of copper nitride by using periodic density functional theory within a plane-wave ultrasoft pseudopotential scheme. The insertions of extra Cu and/or Pd atoms in the empty sites, vacancy reorganization, and substitution of Cu by Pd atoms were studied. We have used an equivalent reduced-symmetry 2 x 2 x 2 Cu 3 N-like cubic super-cell. Small Cu and/or Pd concentrations and vacancy rearrangements in the copper sub-lattice were conveniently calculated in these low-symmetry cells. We cover probable situations like: the occupation of the initially empty copper sites by (1) copper atoms, and by (2) palladium; (3) the relocation of vacancies in the copper sub-lattice; and (4) the substitution of small quantities of copper by palladium atoms in the copper sub-lattice. The equilibrium volumes and energies after relaxing the atomic positions are compared to those of intrinsic copper nitride. We found that the most stable arrangement corresponds to the ideal stoichiometric Cu 3 N. We also found that any deviation from this ideal configuration shift the semiconductor state to a metallic or semi-metallic one.

Metal Nanoparticles Covered with a Metal-Organic Framework: From One-Pot Synthetic Methods to Synergistic Energy Storage and Conversion Functions.

Science.gov (United States)

Kobayashi, Hirokazu; Mitsuka, Yuko; Kitagawa, Hiroshi

2016-08-01

Hybrid materials composed of metal nanoparticles and metal-organic frameworks (MOFs) have attracted much attention in many applications, such as enhanced gas storage and catalytic, magnetic, and optical properties, because of the synergetic effects between the metal nanoparticles and MOFs. In this Forum Article, we describe our recent progress on novel synthetic methods to produce metal nanoparticles covered with a MOF (metal@MOF). We first present Pd@copper(II) 1,3,5-benzenetricarboxylate (HKUST-1) as a novel hydrogen-storage material. The HKUST-1 coating on Pd nanocrystals results in a remarkably enhanced hydrogen-storage capacity and speed in the Pd nanocrystals, originating from charge transfer from Pd nanocrystals to HKUST-1. Another material, Pd-Au@Zn(MeIM)2 (ZIF-8, where HMeIM = 2-methylimidazole), exhibits much different catalytic activity for alcohol oxidation compared with Pd-Au nanoparticles, indicating a design guideline for the development of composite catalysts with high selectivity. A composite material composed of Cu nanoparticles and Cr3F(H2O)2O{C6H3(CO2)3}2 (MIL-100-Cr) demonstrates higher catalytic activity for CO2 reduction into methanol than Cu/γ-Al2O3. We also present novel one-pot synthetic methods to produce composite materials including Pd/ZIF-8 and Ni@Ni2(dhtp) (MOF-74, where H4dhtp = 2,5-dihydroxyterephthalic acid).

Capability of defective graphene-supported Pd{sub 13} and Ag{sub 13} particles for mercury adsorption

Energy Technology Data Exchange (ETDEWEB)

Meeprasert, Jittima; Junkaew, Anchalee; Rungnim, Chompoonut; Kunaseth, Manaschai [National Nanotechnology Center, NSTDA, 111 Thailand Science Park, Klong Luang, Pathum Thani 12120 Thailand (Thailand); Kungwan, Nawee [Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Promarak, Vinich [School of Molecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology, Wangchan, Rayong 21210 (Thailand); Namuangruk, Supawadee, E-mail: supawadee@nanotec.or.th [National Nanotechnology Center, NSTDA, 111 Thailand Science Park, Klong Luang, Pathum Thani 12120 Thailand (Thailand)

2016-02-28

Graphical abstract: Defective graphene (DG) supported Ag{sub 13} and Pd{sub 13} nanoparticles acts as sorbents for elementary mercury (Hg{sup 0}) adsorption. Hg is inert to DG surface, but it moderately adsorbs on deposited Ag{sub 13}-DG and strongly adsorbs on deposited Pd{sub 13}-DG. - Highlights: • Pd{sub 13}-DG composite has highest stability. • Pd{sub 13}-DG composite is the most reactive sorbent for Hg{sup 0} adsorption. • Hg{sup 0} adsorption abilities of Pd-DG composites are relatively higher than those of Ag-DG composites. • The d-band center of deposited metal is an adsorption descriptor of composite models. - Abstract: Reactivity of single-vacancy defective graphene (DG) and DG-supported Pd{sub n} and Ag{sub n} (n = 1, 13) for mercury (Hg{sup 0}) adsorption has been studied using density functional theory calculation. The results show that Pd{sub n} binds defective site of DG much stronger than the Ag{sub n}, while metal nanocluster binds DG stronger than single metal atom. Metal clustering affects the adsorption ability of Pd composite while that of Ag is comparatively less. The binding strength of −8.49 eV was found for Pd{sub 13} binding on DG surface, indicating its high stability. Analyses of structure, energy, partial density of states, and d-band center (ε{sub d}) revealed that the adsorbed metal atom or cluster enhances the reactivity of DG toward Hg adsorption. In addition, the Hg adsorption ability of M{sub n}-DG composite is found to be related to the ε{sub d} of the deposited M{sub n}, in which the closer ε{sub d} of M{sub n} to the Fermi level correspond to the higher adsorption strength of Hg on M{sub n}-DG composite. The order of Hg adsorption strength on M{sub n}-DG composite are as follows: Pd{sub 13} (−1.68 eV) >> Ag{sub 13} (−0.67 eV) ∼ Ag{sub 1} (−0.69 eV) > Pd{sub 1} (−0.62 eV). Pd{sub 13}-DG composite is therefore more efficient sorbent for Hg{sup 0} removal in terms of high stability and high adsorption

Parkinson Disease Protein DJ-1 Binds Metals and Protects against Metal-induced Cytotoxicity*

Science.gov (United States)

Björkblom, Benny; Adilbayeva, Altynai; Maple-Grødem, Jodi; Piston, Dominik; Ökvist, Mats; Xu, Xiang Ming; Brede, Cato; Larsen, Jan Petter; Møller, Simon Geir

2013-01-01

The progressive loss of motor control due to reduction of dopamine-producing neurons in the substantia nigra pars compacta and decreased striatal dopamine levels are the classically described features of Parkinson disease (PD). Neuronal damage also progresses to other regions of the brain, and additional non-motor dysfunctions are common. Accumulation of environmental toxins, such as pesticides and metals, are suggested risk factors for the development of typical late onset PD, although genetic factors seem to be substantial in early onset cases. Mutations of DJ-1 are known to cause a form of recessive early onset Parkinson disease, highlighting an important functional role for DJ-1 in early disease prevention. This study identifies human DJ-1 as a metal-binding protein able to evidently bind copper as well as toxic mercury ions in vitro. The study further characterizes the cytoprotective function of DJ-1 and PD-mutated variants of DJ-1 with respect to induced metal cytotoxicity. The results show that expression of DJ-1 enhances the cells' protective mechanisms against induced metal toxicity and that this protection is lost for DJ-1 PD mutations A104T and D149A. The study also shows that oxidation site-mutated DJ-1 C106A retains its ability to protect cells. We also show that concomitant addition of dopamine exposure sensitizes cells to metal-induced cytotoxicity. We also confirm that redox-active dopamine adducts enhance metal-catalyzed oxidation of intracellular proteins in vivo by use of live cell imaging of redox-sensitive S3roGFP. The study indicates that even a small genetic alteration can sensitize cells to metal-induced cell death, a finding that may revive the interest in exogenous factors in the etiology of PD. PMID:23792957

Superconductivity in Pd-Intercalated Ternary Rare-Earth Polychalcogenide NdSeTe_2

International Nuclear Information System (INIS)

Wang Pei-Pei; Xue Mian-Qi; Long Yu-Jia; Zhao Ling-Xiao; Cai Yao; Yang Huai-Xin; Li Jian-Qi; Ren Zhi-An; Chen Gen-Fu

2015-01-01

We synthesize a set of Pd-doped polycrystalline samples Pd_xNdSeTe_2 and measure their physical properties. Compared with pure NdSeTe_2, the charge density wave (CDW) order is continuously suppressed with the Pd-intercalation. Bulk superconductivity first appears at x = 0.06 with T_c nearly 2.5K, coexisting with a CDW transition at 176K. Further Pd-doping enhances T_c, until it reaches the maximum value 2.84K at x=0.1, meanwhile the CDW transition vanishes. The upper critical field for the optimal doping sample Pd_0_._1NdSeTe_2 is determined from the R-H measurement, which is estimated to be 0.6 T. These results provide another kind of ideal compound for studying the interplay between CDW and superconductivity systematically. (paper)

Highly selective and reversible chemosensor for Pd(2+) detected by fluorescence, colorimetry, and test paper.

Science.gov (United States)

Wang, Mian; Liu, Xiaomei; Lu, Huizhe; Wang, Hongmei; Qin, Zhaohai

2015-01-21

A "turn-on" fluorescent and colorimetric chemosensor (RBS) for Pd(2+) has been designed and synthesized through introduction of sulfur as a ligand atom to Rhodamine B. RBS exhibits high selectivity (freedom from the interference of Hg(2+ )in particular) and sensitivity toward Pd(2+) with a detection limit as low as 2.4 nM. RBS is also a reversible sensor, and it can be made into test paper to detect Pd(2+) in pure water. Compared to the chemosensors that introduced phosphorus to Rhodamine to detect Pd(2+), RBS can be synthesized more simply and economically.

Ultra-low Pt decorated PdFe Alloy Nanoparticles for Formic Acid Electro-oxidation

International Nuclear Information System (INIS)

Zhou, Yawei; Du, Chunyu; Han, Guokang; Gao, Yunzhi; Yin, Geping

2016-01-01

Highlights: • A cost-efficient way is used to prepare transition-noble metal alloy nanoparticles. • The Pd 50 Fe 50 /C catalyst shows excellent activity for formic acid oxidation (FAO). • Much activity enhancement of FAO is acquired by ultra-low Pt decorated Pd 50 Fe 50 . • A synergistic mechanism between Pt clusters and PdFe is proposed during the FAO. - Abstract: Palladium (Pd), has demonstrated promising electro-catalytic activity for formic acid oxidation, but suffers from extremely low abundance. Recently alloying with a transition metal has been considered as an effective approach to reducing the loading of Pd and enhancing the activity of Pd-based catalysts simultaneously. Herein, carbon supported PdFe nanoparticles (NPs) are synthesized at room temperature by using sodium borohydride as reducing agent and potassium ferrocyanide as Fe precursor. The Pd 50 Fe 50 alloy sample annealed at 900 °C for 1 h shows the best catalytic activity among Pd x Fe 1-x (x = 0.2, 0.4, 0.5, 0.6, and 0.8) towards formic acid oxidation. To further improve both catalytic activity and stability, the ultra-low Pt (0.09 wt %) decorated Pd 50 Fe 50 NPs (PtPd/PdFe) are prepared via the galvanic replacement reaction. Compared with Pd 50 Fe 50 /C, the PtPd/PdFe/C Exhibits 1.52 times higher catalytic activity and lower onset potential (−0.12 V). The significant enhancements of formic acid oxidation can be attributed to the accelerated dehydrogenation reaction of formic acid by Pt atomic clusters. Moreover, the PtPd/PdFe/C also demonstrates better tolerance to poisons during formic acid oxidation.

Perpendicular magnetic anisotropy in granular multilayers of CoPd alloyed nanoparticles

Science.gov (United States)

Vivas, L. G.; Rubín, J.; Figueroa, A. I.; Bartolomé, F.; García, L. M.; Deranlot, C.; Petroff, F.; Ruiz, L.; González-Calbet, J. M.; Pascarelli, S.; Brookes, N. B.; Wilhelm, F.; Chorro, M.; Rogalev, A.; Bartolomé, J.

2016-05-01

Co-Pd multilayers obtained by Pd capping of pre-deposited Co nanoparticles on amorphous alumina are systematically studied by means of high-resolution transmission electron microscopy, x-ray diffraction, extended x-ray absorption fine structure, SQUID-based magnetometry, and x-ray magnetic circular dichroism. The films are formed by CoPd alloyed nanoparticles self-organized across the layers, with the interspace between the nanoparticles filled by the non-alloyed Pd metal. The nanoparticles show atomic arrangements compatible with short-range chemical order of L 10 strucure type. The collective magnetic behavior is that of ferromagnetically coupled particles with perpendicular magnetic anisotropy, irrespective of the amount of deposited Pd. For increasing temperature three magnetic phases are identified: hard ferromagnetic with strong coercive field, soft-ferromagnetic as in an amorphous asperomagnet, and superparamagnetic. Increasing the amount of Pd in the system leads to both magnetic hardness increment and higher transition temperatures. Magnetic total moments of 1.77(4) μB and 0.45(4) μB are found at Co and Pd sites, respectively, where the orbital moment of Co, 0.40(2) μB, is high, while that of Pd is negligible. The effective magnetic anisotropy is the largest in the capping metal series (Pd, Pt, W, Cu, Ag, Au), which is attributed to the interparticle interaction between de nanoparticles, in addition to the intraparticle anisotropy arising from hybridization between the 3 d -4 d bands associated to the Co and Pd chemical arrangement in a L 10 structure type.

Nanoporous, Metal Carbide, Surface Diffusion Membranes for High Temperature Hydrogen Separations

Energy Technology Data Exchange (ETDEWEB)

Way, J. Douglas [Colorado School of Mines, Golden, CO (United States). Dept. of Chemical and Biological Engineering; Wolden, Colin A. [Colorado School of Mines, Golden, CO (United States)

2013-09-30

Colorado School of Mines (CSM) developed high temperature, hydrogen permeable membranes that contain no platinum group metals with the goal of separating hydrogen from gas mixtures representative of gasification of carbon feedstocks such as coal or biomass in order to meet DOE NETL 2015 hydrogen membrane performance targets. We employed a dual synthesis strategy centered on transition metal carbides. In the first approach, novel, high temperature, surface diffusion membranes based on nanoporous Mo₂C were fabricated on ceramic supports. These were produced in a two step process that consisted of molybdenum oxide deposition followed by thermal carburization. Our best Mo₂C surface diffusion membrane achieved a pure hydrogen flux of 367 SCFH/ft² at a feed pressure of only 20 psig. The highest H₂/N₂ selectivity obtained with this approach was 4.9. A transport model using “dusty gas” theory was derived to describe the hydrogen transport in the Mo₂C coated, surface diffusion membranes. The second class of membranes developed were dense metal foils of BCC metals such as vanadium coated with thin (< 60 nm) Mo₂C catalyst layers. We have fabricated a Mo₂C/V composite membrane that in pure gas testing delivered a H₂ flux of 238 SCFH/ft² at 600 °C and 100 psig, with no detectable He permeance. This exceeds the 2010 DOE Target flux. This flux is 2.8 times that of pure Pd at the same membrane thickness and test conditions and over 79% of the 2015 flux target. In mixed gas testing we achieved a permeate purity of ≥99.99%, satisfying the permeate purity milestone, but the hydrogen permeance was low, ~0.2 SCFH/ft².psi. However, during testing of a Mo₂C coated Pd alloy membrane with DOE 1 feed gas mixture a hydrogen permeance of >2 SCFH/ft².psi was obtained which was stable during the entire test, meeting the permeance associated with

PREPARATION, CHARACTERIZATIONS AND MODIFICATION OF Ni-Pd/NATURAL ZEOLITE CATALYSTS

Directory of Open Access Journals (Sweden)

Wega Trisunaryanti

2010-06-01

Full Text Available Preparation, and modification of Ni-Pd/natural zeolite as well as their characterizations had been carried out. The aim of this research for the fututure is to prepare the best characters catalyst for the conversion of waste plastics fraction to gasoline fraction (C5-C12 hydrocarbons. The preparation of catalysts was performed by reacting a natural zeolite with the precursor of Ni(NO32. 9H2O and PdCl2 in an ammonia solution (25%. The modifications were performed by varying the rasio of Ni/Pd loaded to the zeolite, whereas the Pd was previously loaded and total metal content was 1 wt.% based on the zeolite. The characterization of catalysts included determination of acidity gravimetrically by adsorption of ammonia or pyridine vapour  base method, metal content by Atomic Adsorption Spectrophotometer (AAS and X-ray Fluoresence (XRF and crystallinity by X-ray Diffraction (XRD. The treatment of catalysts using Etilene Diamine Tetra Acetic acid  (EDTA was performed to study the metal distribution on the outer or inner surface of the zeolite. The characterization results showed that the loading of metals to the zeolite increased its acidity and decreased its spesific surface area, however, did not defect its crystallnity.  The metals loaded on the zeolite were distributed inside the pore and at outer surface of the zeolite. For all catalyst samples, the acidities determined using ammonia were higher than those of pyridine, and the acidities determined before the EDTA treatment was lower than those after the treatment.  Metal contents of the zeolite before the EDTA treatment were higher than those after the treatment. The EDTA treatment enhanced the crystallinity of the sampel. The relationship between the metal rasio towards the acidity of the catalyst samples were in variation. Catalyst samples produced in this research have good characters, thus promisingly can be used for conversion process of waste plastics to gasoline fraction.    Keywords

PdNi- and Pd-coated electrodes prepared by electrodeposition from ionic liquid for nonenzymatic electrochemical determination of ethanol and glucose in alkaline media.

Science.gov (United States)

Huang, Hsin-Yi; Chen, Po-Yu

2010-12-15

Nonenzymatic electrochemical determination of ethanol and glucose was respectively achieved using PdNi- and Pd-coated electrodes prepared by electrodeposition from the novel metal-free ionic liquid (IL); N-butyl-N-methylpyrrolidinium dicyanamide (BMP-DCA). BMP-DCA provided an excellent environment and wide cathodic limit for electrodeposition of metals and alloys because many metal chlorides could dissolve in this IL where the reduction potentials of Pd(II) and Ni(II) indeed overlapped, leading to the convenience of potentiostatic codeposition. In aqueous solutions, the reduction potentials of Pd(II) and Ni(II) are considerably separated. The bimetallic PdNi coatings with atomic ratios of ∼ 80/20 showed the highest current for ethanol oxidation reaction (EOR). Ethanol was detected by either cyclic voltammetry (CV) or hydrodynamic amperometry (HA). Using CV, the dependence of EOR peak current on concentration was linear from 4.92 to 962 μM with a detection limit of 2.26 μM (σ=3), and a linearity was observed from 4.92 to 988 μM using HA (detection limit 0.83 μM (σ=3)). The Pd-coated electrodes prepared by electrodeposition from BMP-DCA showed electrocatalytic activity to glucose oxidation and CV, HA, and square-wave voltammetry (SWV) were employed to determine glucose. SWV showed the best sensitivity and linearity was observed from 2.86 μM to 107 μM, and from 2.99 mM to 10.88 mM with detection limits of 0.78 μM and 25.9 μM (σ=3), respectively. For glucose detection, the interference produced from ascorbic acid, uric acid, and acetaminophen was significantly suppressed, compared with a regular Pt disk electrode. Copyright © 2010 Elsevier B.V. All rights reserved.

An unsaturated metal site-promoted approach to construct strongly coupled noble metal/HNb3O8 nanosheets for efficient thermo/photo-catalytic reduction.

Science.gov (United States)

Shen, Lijuan; Xia, Yuzhou; Lin, Sen; Liang, Shijing; Wu, Ling

2017-10-05

Creating two-dimensional (2D) crystal-metal heterostructures with an ultrathin thickness has spurred increasing research endeavors in catalysis because of its fascinating opportunities in tuning the electronic state at the surface and enhancing the chemical reactivity. Here we report a novel and facile Nb 4+ -assisted strategy for the in situ growth of highly dispersed Pd nanoparticles (NPs) on monolayer HNb 3 O 8 nanosheets (HNb 3 O 8 NS) constituting a 2D Pd/HNb 3 O 8 NS heterostructure composite without using extra reducing agents and stabilizing agents. The Pd NP formation is directed via a redox reaction between an oxidative Pd salt precursor (H 2 PdCl 4 ) and reductive unsaturated surface metal (Nb 4+ ) sites induced by light irradiation on monolayer HNb 3 O 8 NS. The periodic arrangement of metal Nb nodes on HNb 3 O 8 NS leads to a homogeneous distribution of Pd NPs. Density functional theory (DFT) calculations reveal that the direct redox reaction between the Nb 4+ and Pd 2+ ions leads to a strong chemical interaction between the formed Pd metal NPs and the monolayer HNb 3 O 8 support. Consequently, the as-obtained Pd/HNb 3 O 8 composite serves as a highly efficient bifunctional catalyst in both heterogeneous thermocatalytic and photocatalytic selective reduction of aromatic nitro compounds in water under ambient conditions. The achieved high activity originates from the unique 2D nanosheet configuration and in situ Pd incorporation, which leads to a large active surface area, strong metal-support interaction and enhanced charge transport capability. Moreover, this facile Nb 4+ -assisted synthetic route has demonstrated to be general, which can be applied to load other metals such as Au and Pt on monolayer HNb 3 O 8 NS. It is anticipated that this work can extend the facile preparation of noble metal/nanosheet 2D heterostructures, as well as promote the simultaneous capture of duple renewable thermal and photon energy sources to drive an energy efficient

SIMS as a new methodology to depth profile helium in as-implanted and annealed pure bcc metals?

Energy Technology Data Exchange (ETDEWEB)

Gorondy-Novak, S. [CEA, DEN, Service de Recherches de Métallurgie Physique, Université Paris-Saclay, F-91191 Gif-sur-Yvette (France); Jomard, F. [Groupe d' Etude de la Matière Condensée, CNRS, UVSQ, 45 avenue des Etats-Unis, 78035 Versailles cedex (France); Prima, F. [PSL Research University, Chimie ParisTech – CNRS, Institut de Recherche de Chimie Paris, 75005 Paris (France); Lefaix-Jeuland, H., E-mail: helene.lefaix@cea.fr [CEA, DEN, Service de Recherches de Métallurgie Physique, Université Paris-Saclay, F-91191 Gif-sur-Yvette (France)

2017-05-01

Reliable He profiles are highly desirable for better understanding helium behavior in materials for future nuclear applications. Recently, Secondary Ions Mass Spectrometry (SIMS) allowed the characterization of helium distribution in as-implanted metallic systems. The Cs{sup +} primary ion beam coupled with CsHe{sup +} molecular detector appeared to be a promising technique which overcomes the very high He ionization potential. In this study, {sup 4}He depth profiles in pure body centered cubic (bcc) metals (V, Fe, Ta, Nb and Mo) as-implanted and annealed, were obtained by SIMS. All as-implanted samples exhibited a projected range of around 200 nm, in agreement with SRIM theoretical calculations. After annealing treatment, SIMS measurements evidenced the evolution of helium depth profile with temperature. The latter SIMS results were compared to the helium bubble distribution obtained by Transmission Electron Microscopy (TEM). This study confirmed the great potential of this experimental procedure as a He-depth profiling technique in bcc metals. Indeed, the methodology described in this work could be extended to other materials including metallic and non-metallic compounds. Nevertheless, the quantification of helium concentration after annealing treatment by SIMS remains uncertain probably due to the non-uniform ionization efficiency in samples containing large bubbles.

Influence of strain and metal thickness on metal-MoS₂ contacts.

Science.gov (United States)

Saidi, Wissam A

2014-09-07

MoS2 and other transition metal dichalcogenides are considered as potential materials in many applications including future electronics. A prerequisite for these applications is to understand the nature of the MoS2 contact with different metals. We use semi-local density functional theory in conjunction with dispersion corrections to study the heterostructures composed of Pd and Pt monolayers with (111) orientation grown pseudomorphically on MoS2(001). The interface properties are mapped as a function of the number of deposited overlayers, as well as a function of tensile and compressive strains. Although we show that the dependence of the contacts on strain can be fully explained using the d-band model, we find that their evolution with the number of deposited metal layers is markedly different between Pd and Pt, and at variance with the d-band model. Specifically, the Pt/MoS2 heterostructures show an anomalous large stability with the deposition of two metal monolayers for all investigated strains, while Pd/MoS2 exhibits a similar behavior only for compressive strains. It is shown that the results can be rationalized by accounting for second-nearest-neighbor effect that couples MoS2 with the subsurface metal layers. The underpinnings of this behavior are attributed to the larger polarizability and cohesive energy of Pt compared to Pd, that leads to a larger charge-response in the subsurface layers.

CO oxidation on PdO surfaces

DEFF Research Database (Denmark)

Hirvi, Janne T.; Kinnunen, Toni-Jani J.; Suvanto, Mika

2010-01-01

Density functional calculations were performed in order to investigate CO oxidation on two of the most stable bulk PdO surfaces. The most stable PdO(100) surface, with oxygen excess, is inert against CO adsorption, whereas strong adsorption on the stoichiometric PdO(101) surface leads to favorable...... oxidation via the Langmuir–Hinshelwood mechanism. The reaction with a surface oxygen atom has an activation energy of 0.66 eV, which is comparable to the lowest activation energies observed on metallic surfaces. However, the reaction rate may be limited by the coverage of molecular oxygen. Actually...... adsorption, following the Eley–Rideal mechanism and taking advantage of the reaction tunnel provided by the adjacent palladium atom, has an activation energy of only 0.24 eV. The reaction mechanism and activation energy for the palladium activated CO oxidation on the most stable PdO(100)–O surface...

Efficient Pd@MIL-101(Cr) hetero-catalysts for 2-butyne-1,4-diol hydrogenation exhibiting high selectivity

KAUST Repository

Yin, Dongdong; Li, Chuang; Ren, Hangxing; Shekhah, Osama; Liu, Jinxuan; Liang, Changhai

2017-01-01

Pd@MIL-101(Cr) hetero-catalysts have been successfully prepared using the metal-organic chemical vapour deposition (MOCVD) approach, by choosing [Pd(η-CH)(η-CH)] as a volatile precursor, and the hydrothermally stable metal-organic framework, MIL-101

Measurement of barrier height of Pd on diamond (100) surface by X-ray photoelectron spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Li, F.N. [Institute of Wide Band Gap Semiconductors, Xi' an Jiaotong University, Xi' an 710049 (China); Nation Key Laboratory of ASIC, HSRI, Shijiazhuang 050051 (China); Liu, J.W. [International Center for Young Scientists, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 3050044 (Japan); Zhang, J.W.; Wang, X.L.; Wang, W.; Liu, Z.C. [Institute of Wide Band Gap Semiconductors, Xi' an Jiaotong University, Xi' an 710049 (China); Wang, H.X., E-mail: hxwangcn@mail.xjtu.edu.cn [Institute of Wide Band Gap Semiconductors, Xi' an Jiaotong University, Xi' an 710049 (China)

2016-05-01

Highlights: • Metal-semiconductor contacts of Pd/hydrogen-terminated diamond and Pd/oxygen-terminated diamond have been investigated by XPS measurements. • The barrier height for Pd/hydrogen-terminated diamond (ohmic contact) has been measured to be −0.27 eV. • The barrier height for Pd/oxygen-terminated diamond (Schottky contact) has been measured to be 1.73 eV. - Abstract: Barrier height (Φ{sub BH}) values for Pd/hydrogen-terminated diamond (H-diamond) and Pd/oxygen-terminated diamond (O-diamond) have been investigated by X-ray photoelectron spectroscopy technique. H-diamond and O-diamond have been formed on the same diamond (100) layer grown by microwave plasma-enhanced chemical vapor deposition,on which Pd layers have been evaporated. The Φ{sub BH} values for Pd/H-diamond and Pd/O-diamond are determined to be −0.27 eV and 1.73 eV, respectively. It indicates that Pd is a suitable metal for ohmic and Schottky contacts on H-diamond and O-diamond, respectively. The experimental Φ{sub BH} values are in good agreement with the theoretical calculation results.

Efficient Pd@MIL-101(Cr) hetero-catalysts for 2-butyne-1,4-diol hydrogenation exhibiting high selectivity

KAUST Repository

Yin, Dongdong

2017-01-05

Pd@MIL-101(Cr) hetero-catalysts have been successfully prepared using the metal-organic chemical vapour deposition (MOCVD) approach, by choosing [Pd(η-CH)(η-CH)] as a volatile precursor, and the hydrothermally stable metal-organic framework, MIL-101(Cr) as a support. The prepared Pd@MIL-101(Cr) hetero-catalysts characterized with various analytical techniques, exhibited highly monodispersed immobilized Pd nanoparticles in the MIL-101(Cr) cavities, while retaining the pristine crystallinity and porosity. The intact hybrid Pd@MIL-101(Cr) has been demonstrated to be an efficient catalyst for 2-butyne-1,4-diol hydrogenation with excellent activity, stability and selectivity (2-butene-1,4-diol (>94%)).

High stability and high activity Pd/ITO-CNTs electrocatalyst for direct formic acid fuel cell

International Nuclear Information System (INIS)

Qu, Wei-Li; Gu, Da-Ming; Wang, Zhen-Bo; Zhang, Jing-Jia

2014-01-01

Graphical abstract: The addition of ITO in Pd/CNTs catalyst significantly improves the activity and stability of catalyst for formic acid electrooxidation due to excellent stability and high electrical conductivity of ITO, and metal-support interaction between Pd nanoparticles and ITO. - Highlights: • Pd catalyst with ITO and CNTs as a mixture support for DFAFC was first prepared by microwave-assisted polyol process. • The activity and stability of Pd/ITO-CNTs catalyst is significantly higher than those of Pd/CNTs. • When ITO content is 50% of ITO/CNTs support mass, Pd/ITO-CNTs exhibits the best performance. - Abstract: Indium tin oxide (ITO) and carbon nanotube hybrid has been explored as a support for Pd catalyst. Pd/ITO-CNTs catalysts with different ITO contents were prepared by the microwave-assisted polyol process. The as-prepared Pd/ITO-CNTs catalysts were characterized by X-ray diffraction (XRD), energy dispersive analysis of X-ray (EDAX), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), and electrochemical measurements in this work. The TEM results show that Pd particle size distribution in the Pd/ITO-CNTs catalyst is more uniform than that in Pd/CNTs, indicating that the ITO can promote the dispersion of Pd nanoparticles. It is found that there is metal-support interaction between Pd nanoparticles and ITO in the Pd/ITO-CNTs catalyst through XPS test. The results of electrochemical tests prove that the Pd/ITO-CNTs catalysts exhibit higher electro-catalytic activity and stability than Pd/CNTs toward formic acid electrooxidation. When the ITO content is 50% of ITO-CNTs support mass, the Pd/ITO-CNTs catalyst has the best catalytic performance for formic acid electrooxidation. The peak current density of formic acid electrooxidation on the Pd/ITO-CNTs50% electrode is 1.53 times as high as that on Pd/CNTs, 2.31 times higher than that on Pd/ITO. The results of aging

Effect of noble metal doping on the structural properties of lanthanum cobaltite

International Nuclear Information System (INIS)

Dharmadhikari, Dipti V.; Athawal, Anjali A.

2016-01-01

Pristine and Noble metal (Ag and Pd) doped lanthanum cobaltite samples have been synthesised by Hydrothermal method. Lanthanum in the A-Site and Co at B-site of Lanthanum cobaltite (LaCoO 3 ) perovskites were partially doped by silver and palladium (4%). Crystal structure analysis revealed that the hydrothermal synthesis led to the formation of pure nanocrystalline perovskite structure. Morphological analysis of the samples shows that the noble metal doping affects the morphology of the samples. Pristine sample shows spherical to oval shaped particles while the doping results in the formation of irregular shaped, spherical and rod shaped particles. Silver doping results in the agglomeration of particles. The particles were observed to be fused with each other to form rod shaped structures in case of palladium doped samples. (author)

Biocompatibility study on Ni-free Ti-based and Zr-based bulk metallic glasses

Energy Technology Data Exchange (ETDEWEB)

Li, T.H. [Institute of Material Science and Engineering, National Central University, Taoyuan, Taiwan (China); Wong, P.C. [Department of Biomedical Engineering, National Yang-Ming University, Taipei, Taiwan (China); Chang, S.F. [Department of Mechanical Engineering, National Central University, Taoyuan, Taiwan (China); Tsai, P.H. [Institute of Material Science and Engineering, National Central University, Taoyuan, Taiwan (China); Jang, J.S.C., E-mail: jscjang@ncu.edu.tw [Institute of Material Science and Engineering, National Central University, Taoyuan, Taiwan (China); Department of Mechanical Engineering, National Central University, Taoyuan, Taiwan (China); Huang, J.C. [Department of Materials and Optoelectronic Science, National Sun Yat-Sen University, Kaohsiung, Taiwan (China)

2017-06-01

Safety and reliability are crucial issues for medical instruments and implants. In the past few decays, bulk metallic glasses (BMGs) have drawn attentions due to their superior mechanical properties, good corrosion resistance, antibacterial and good biocompatibility. However, most Zr-based and Ti-based BMGs contain Ni as an important element which is prone to human allergy problem. In this study, the Ni-free Ti-based and Zr-based BMGs, Ti{sub 40}Zr{sub 10}Cu{sub 36}Pd{sub 14}, and Zr{sub 48}Cu{sub 36}Al{sub 8}Ag{sub 8}, were selected for systematical evaluation of their biocompatibility. Several biocompatibility tests, co-cultural with L929 murine fibroblast cell line, were carried out on these two BMGs, as well as the comparison samples of Ti6Al4V and pure Cu. The results in terms of cellular adhesion, cytotoxicity, and metallic ion release affection reveal that the Ti{sub 40}Zr{sub 10}Cu{sub 36}Pd{sub 14} BMG and Ti6Al4V exhibit the optimum biocompatibility; cells still being attached on the petri dish with good adhesion and exhibiting the spindle shape after direct contact test. Furthermore, the Ti{sub 40}Zr{sub 10}Cu{sub 36}Pd{sub 14} BMG showed very low Cu ion release level, in agreement with the MTT results. Based on the current findings, it is believed that Ni-free Ti-based BMG can act as an ideal candidate for medical implant. - Highlight: • Ni-free bulk metallic glass is promising material for medical implants. • Ni-free Ti-based BMG presents similar cellular adhesion as Ti6Al4V. • Ni-free Ti-based BMG shows less cytotoxicity, and metallic ion release than Ti6Al4V.

Effect of barrier height on friction behavior of the semiconductors silicon and gallium arsenide in contact with pure metals

Science.gov (United States)

Mishina, H.; Buckley, D. H.

1984-01-01

Friction experiments were conducted for the semiconductors silicon and gallium arsenide in contact with pure metals. Polycrystalline titanium, tantalum, nickel, palladium, and platinum were made to contact a single crystal silicon (111) surface. Indium, nickel, copper, and silver were made to contact a single crystal gallium arsenide (100) surface. Sliding was conducted both in room air and in a vacuum of 10 to the minus 9th power torr. The friction of semiconductors in contact with metals depended on a Schottky barrier height formed at the metal semiconductor interface. Metals with a higher barrier height on semiconductors gave lower friction. The effect of the barrier height on friction behavior for argon sputtered cleaned surfaces in vacuum was more specific than that for the surfaces containing films in room air. With a silicon surface sliding on titanium, many silicon particles back transferred. In contrast, a large quantity of indium transferred to the gallium arsenide surface.

The hydrogen interaction in an FCC FePd alloy with a vacancy

Energy Technology Data Exchange (ETDEWEB)

Ardenghi, S [Instituto de AstronomIa y Fisica del Espacio (IAFE), CC 67-Suc 28 (C1428ZAA) Ciudad Autonoma de Buenos Aires (Argentina); Gonzalez, E; Jasen, P; Juan, A [Departamento de Fisica, Universidad Nacional del Sur, Av. Alem 1253 BahIa Blanca (8000) (Argentina)], E-mail: cajuan@uns.edu.ar

2009-04-15

The absorption of hydrogen in the ordered face-centered cubic FePd alloy is investigated using a density functional calculation method. Changes in the electronic structure and bonding after introducing an Fe or Pd vacancy are analysed. H locates close to a tetrahedral site and the H-metal bond is achieved at the expense of the interfacial Fe-Pd bond.

Synthesis and characterization of bulky mesoporous silica Pd-MCM-41

International Nuclear Information System (INIS)

Nagata, Hidezumi; Nakahira, Atsushi; Hirao, Norie; Baba, Yuji; Onoki, Takamasa; Yamasaki, Yuki

2008-01-01

Bulky palladium catalyst supported on mesoporous silica MCM-41 (Pd-MCM-41) was successfully synthesized by hydrothermal hot-pressing method. In this study, the structure of the palladium species in Pd-MCM-41 bulk before and after heat-treatment process was revealed by X-ray diffraction (XRD), X-ray absorption near edge structure (XANES) and transmission electron microscopy (TEM). Also, the microstructure and mesoporous property of Pd-MCM-41 bulk was discussed. As a result, it was revealed that these dense Pd-MCM-41 bulks possessed a high surface area of over 1000 m 2 /g and the structure of palladium of Pd-MCM-41 bulk is almost equal to palladium (0) metal. (author)

Ab initio modeling of plasticity in HCP metals: pure zirconium and titanium and effect of oxygen

International Nuclear Information System (INIS)

Chaari, Nermine

2015-01-01

We performed atomistic simulations to determine screw dislocations properties in pure zirconium and titanium and to explain the hardening effect attributed to oxygen alloying in both hexagonal close-packed transition metals. We used two energetic models: ab initio calculations based on the density functional theory and calculations with an empirical potential. The complete energetic profile of the screw dislocation when gliding in the different slip planes is obtained in pure Zr. Our calculations reveal the existence of a metastable configuration of the screw dislocation partially spread in the first order pyramidal plane. This configuration is responsible for the cross slip of screw dislocations from prismatic planes, the easiest glide planes, to pyramidal or basal planes. This energy profile is affected by oxygen addition. Ab initio calculations reveal two main effects: oxygen enhances pyramidal cross slip by modifying the dislocation core structure, and pins the dislocation in its metastable sessile configuration. The same modeling approach is applied to titanium. In pure Ti, the same configurations of the screw dislocation in Zr are obtained, but with different energy levels. This leads to a different gliding mechanism. The same way as in Zr, oxygen enhances pyramidal glide in Ti by modifying the dislocation core structure. Besides, oxygen atom lowers the energy of the metastable configuration but not enough to pin the dislocation in this sessile configuration. (author) [fr

The Electrochemical Atomic Layer Deposition of Pt and Pd nanoparticles on Ni foam for the electrooxidation of alcohols

CSIR Research Space (South Africa)

Modibedi, RM

2012-10-01

Full Text Available Electrodeposition of Pt and Pd metal by surface limited redox replacement reactions was performed using the electrochemical atomic layer deposition. Carbon paper and Ni foam were used as substrates for metal deposition. Supported Pt and Pd...

Nitrite reduction mechanism on a Pd surface.

Science.gov (United States)

Shin, Hyeyoung; Jung, Sungyoon; Bae, Sungjun; Lee, Woojin; Kim, Hyungjun

2014-11-04

Nitrate (NO3-) is one of the most harmful contaminants in the groundwater, and it causes various health problems. Bimetallic catalysts, usually palladium (Pd) coupled with secondary metallic catalyst, are found to properly treat nitrate-containing wastewaters; however, the selectivity toward N2 production over ammonia (NH3) production still requires further improvement. Because the N2 selectivity is determined at the nitrite (NO2-) reduction step on the Pd surface, which occurs after NO3- is decomposed into NO2- on the secondary metallic catalyst, we here performed density functional theory (DFT) calculations and experiments to investigate the NO2- reduction pathway on the Pd surface activated by hydrogen. Based on extensive DFT calculations on the relative energetics among ∼100 possible intermediates, we found that NO2- is easily reduced to NO* on the Pd surface, followed by either sequential hydrogenation steps to yield NH3 or a decomposition step to N* and O* (an adsorbate on Pd is denoted using an asterisk). Based on the calculated high migration barrier of N*, we further discussed that the direct combination of two N* to yield N2 is kinetically less favorable than the combination of a highly mobile H* with N* to yield NH3. Instead, the reduction of NO2- in the vicinity of the N* can yield N2O* that can be preferentially transformed into N2 via diverse reaction pathways. Our DFT results suggest that enhancing the likelihood of N* encountering NO2- in the solution phase before combination with surface H* is important for maximizing the N2 selectivity. This is further supported by our experiments on NO2- reduction by Pd/TiO2, showing that both a decreased H2 flow rate and an increased NO2- concentration increased the N2 selectivity (78.6-93.6% and 57.8-90.9%, respectively).

Application of a parallel genetic algorithm to the global optimization of medium-sized Au-Pd sub-nanometre clusters

Science.gov (United States)

Hussein, Heider A.; Demiroglu, Ilker; Johnston, Roy L.

2018-02-01

To contribute to the discussion of the high activity and reactivity of Au-Pd system, we have adopted the BPGA-DFT approach to study the structural and energetic properties of medium-sized Au-Pd sub-nanometre clusters with 11-18 atoms. We have examined the structural behaviour and stability as a function of cluster size and composition. The study suggests 2D-3D crossover points for pure Au clusters at 14 and 16 atoms, whereas pure Pd clusters are all found to be 3D. For Au-Pd nanoalloys, the role of cluster size and the influence of doping were found to be extensive and non-monotonic in altering cluster structures. Various stability criteria (e.g. binding energies, second differences in energy, and mixing energies) are used to evaluate the energetics, structures, and tendency of segregation in sub-nanometre Au-Pd clusters. HOMO-LUMO gaps were calculated to give additional information on cluster stability and a systematic homotop search was used to evaluate the energies of the generated global minima of mono-substituted clusters and the preferred doping sites, as well as confirming the validity of the BPGA-DFT approach.

Surfactant-controlled synthesis of Pd/Ce0.6Zr0.4O2 catalyst for NO reduction by CO with excess oxygen

International Nuclear Information System (INIS)

Chen, L.F.; Gonzalez, G.; Wang, J.A.; Norena, L.E.; Toledo, A.; Castillo, S.; Moran-Pineda, M.

2005-01-01

For the first time, this work reports a surfactant-controlled synthetic method to obtain a nanophase of mesoporous ceria-zirconia solid solution containing cationic defects in the crystalline structure. The incorporation of a cationic surfactant (myristyltrimethylammonium bromide) into the ceria-zirconia solid network not only controlled the pore diameter distribution but also induced creation of the lattice defect. Ceria-zirconia solid solution showed crystal microstrain and structural distortion that varied with the calcination temperature. Compared to pure ceria, the addition of zirconium to the ceria promoted the bulk oxygen reducibility and enhanced the thermal stability of the solid. Hydrogen could be stored into or released from the PdO/Ce 0.6 Zr 0.4 O 2 catalyst during the TPR procedure, which is associated to the formation/decomposition of a PdH x phase, due to the hydrogen dissociation catalyzed by metallic Pd. At cool start of reaction, NO reduction by CO with excess oxygen over the Pd/Ce 0.6 Zr 0.4 O 2 catalyst showed selectivity around 100% to N 2 . A competition between NO reduction by CO and CO oxidation by O 2 was observed: at reaction temperatures below 200 deg. C, NO inhibited CO oxidation activity; however, at reaction temperatures above 200 deg. C, high activity of CO oxidation resulted in an inhibition effect on NO reduction

Pd Nanoparticles and MOFs Synergistically Hybridized Halloysite Nanotubes for Hydrogen Storage.

Science.gov (United States)

Jin, Jiao; Ouyang, Jing; Yang, Huaming

2017-12-01

Natural halloysite nanotubes (HNTs) were hybridized with metal-organic frameworks (MOFs) to prepare novel composites. MOFs were transformed into carbon by carbonization calcination, and palladium (Pd) nanoparticles were introduced to build an emerging ternary compound system for hydrogen adsorption. The hydrogen adsorption capacities of HNT-MOF composites were 0.23 and 0.24 wt%, while those of carbonized products were 0.24 and 0.27 wt% at 25 °C and 2.65 MPa, respectively. Al-based samples showed higher hydrogen adsorption capacities than Zn-based samples on account of different selectivity between metal and hydrogen and approximate porous characteristics. More pore structures are generated by the carbonization reaction from metal-organic frameworks into carbon; high specific surface area, uniform pore size, and large pore volume benefited the hydrogen adsorption ability of composites. Moreover, it was also possible to promote hydrogen adsorption capacity by incorporating Pd. The hydrogen adsorption capacity of ternary compound, Pd-C-H3-MOFs(Al), reached 0.32 wt% at 25 °C and 2.65 MPa. Dissociation was assumed to take place on the Pd particles, then atomic and molecule hydrogen spilled over to the structure of carboxylated HNTs, MOFs, and the carbon products for enhancing the hydrogen adsorption capacity.

Pd Nanoparticles and MOFs Synergistically Hybridized Halloysite Nanotubes for Hydrogen Storage

Science.gov (United States)

Jin, Jiao; Ouyang, Jing; Yang, Huaming

2017-03-01

Natural halloysite nanotubes (HNTs) were hybridized with metal-organic frameworks (MOFs) to prepare novel composites. MOFs were transformed into carbon by carbonization calcination, and palladium (Pd) nanoparticles were introduced to build an emerging ternary compound system for hydrogen adsorption. The hydrogen adsorption capacities of HNT-MOF composites were 0.23 and 0.24 wt%, while those of carbonized products were 0.24 and 0.27 wt% at 25 °C and 2.65 MPa, respectively. Al-based samples showed higher hydrogen adsorption capacities than Zn-based samples on account of different selectivity between metal and hydrogen and approximate porous characteristics. More pore structures are generated by the carbonization reaction from metal-organic frameworks into carbon; high specific surface area, uniform pore size, and large pore volume benefited the hydrogen adsorption ability of composites. Moreover, it was also possible to promote hydrogen adsorption capacity by incorporating Pd. The hydrogen adsorption capacity of ternary compound, Pd-C-H3-MOFs(Al), reached 0.32 wt% at 25 °C and 2.65 MPa. Dissociation was assumed to take place on the Pd particles, then atomic and molecule hydrogen spilled over to the structure of carboxylated HNTs, MOFs, and the carbon products for enhancing the hydrogen adsorption capacity.

Ion beam induced effects on the ferromagnetism in Pd nanoparticles

International Nuclear Information System (INIS)

Kulriya, P. K.; Mehta, B. R.; Agarwal, D. C.; Agarwal, Kanika; Kumar, Praveen; Shivaprasad, S. M.; Avasthi, D. K.

2012-01-01

Present study demonstrates the role of metal-insulator interface and ion irradiation induced defects on the ferromagnetic properties of the non-magnetic materials. Magnetic properties of the Pd nanoparticles(NPs) embedded in the a-silica matrix synthesized using atom beam sputtering technique, were determined using SQUID magnetometry measurements which showed that ferromagnetic response of Pd increased by 3.5 times on swift heavy ion(SHI) irradiation. The ferromagnetic behavior of the as-deposited Pd NPs is due to strain induced by the surrounding matrix and modification in the electronic structure at the Pd-silica interface as revealed by insitu XRD and XPS investigations, respectively. The defects created by the SHI bombardment are responsible for enhancement of the magnetization in the Pd NPs.

O{sub 2} adsorption and dissociation on the Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and 13) tri-metallic nanoparticles: A DFT study

Energy Technology Data Exchange (ETDEWEB)

Li, Sha; Yang, Yongpeng; Huang, Shiping, E-mail: huangsp@mail.buct.edu.cn

2017-07-15

Highlights: • O{sub 2} adsorption and dissociation on Pd{sub 13-n}Ni{sub n}@Pt{sub 42} NPs are performed by DFT. • Adsorption energies of O{sub 2} and O are strongly affected by the coordination number. • Adsorption energy and d-band center displays the opposite change tendency. • Ni{sub 13}@Pt{sub 42} is the most active catalyst among Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and 13) NPs. - Abstract: Density functional theory calculations are performed to investigate O{sub 2} adsorption and dissociation on the icosahedral Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and 13) tri-metallic nanoparticles. The parallel adsorption of O{sub 2} on Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and 13) is stronger than the vertical adsorption. The adsorption of O{sub 2} on the bridge site (B1) is favorable in the Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and 13) nanoparticles, while the adsorption of O atom on the hollow site (H1) is preferred. The adsorption energies of O{sub 2} and O are strongly affected by the coordination number. Low coordination site shows strong adsorption of O{sub 2} and O on the Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and 13) nanoparticles. The adsorption energies of O{sub 2} and O atoms are found to be correlated well with the d-band center of surface Pt. For the Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and13) nanoparticles catalysts, the ORR activity follows the order of Ni{sub 13}@Pt{sub 42} > Pd{sub 13}@Pt{sub 42} > Pd{sub 12}Ni{sub 1}@Pt{sub 42} > Pd{sub 1}Ni{sub 12}@Pt{sub 42}, illustrating that the Ni{sub 13}@Pt{sub 42} is the strongest ORR activity among the Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and13) nanoparticles catalysts. Our results have important significance to understand the mechanism of O{sub 2} dissociation on the Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and 13) tri-metallic nanoparticles.

Influence of strain and metal thickness on metal-MoS{sub 2} contacts

Energy Technology Data Exchange (ETDEWEB)

Saidi, Wissam A., E-mail: alsaidi@pitt.edu [Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania 15261 (United States)

2014-09-07

MoS{sub 2} and other transition metal dichalcogenides are considered as potential materials in many applications including future electronics. A prerequisite for these applications is to understand the nature of the MoS{sub 2} contact with different metals. We use semi-local density functional theory in conjunction with dispersion corrections to study the heterostructures composed of Pd and Pt monolayers with (111) orientation grown pseudomorphically on MoS{sub 2}(001). The interface properties are mapped as a function of the number of deposited overlayers, as well as a function of tensile and compressive strains. Although we show that the dependence of the contacts on strain can be fully explained using the d-band model, we find that their evolution with the number of deposited metal layers is markedly different between Pd and Pt, and at variance with the d-band model. Specifically, the Pt/MoS{sub 2} heterostructures show an anomalous large stability with the deposition of two metal monolayers for all investigated strains, while Pd/MoS{sub 2} exhibits a similar behavior only for compressive strains. It is shown that the results can be rationalized by accounting for second-nearest-neighbor effect that couples MoS{sub 2} with the subsurface metal layers. The underpinnings of this behavior are attributed to the larger polarizability and cohesive energy of Pt compared to Pd, that leads to a larger charge-response in the subsurface layers.

Part II: Oxidative Thermal Aging of Pd/Al2O3 and Pd/CexOy-ZrO2 in Automotive Three Way Catalysts: The Effects of Fuel Shutoff and Attempted Fuel Rich Regeneration

Directory of Open Access Journals (Sweden)

Qinghe Zheng

2015-10-01

Full Text Available The Pd component in the automotive three way catalyst (TWC experiences deactivation during fuel shutoff, a process employed by automobile companies for enhancing fuel economy when the vehicle is coasting downhill. The process exposes the TWC to a severe oxidative aging environment with the flow of hot (800 °C–1050 °C air. Simulated fuel shutoff aging at 1050 °C leads to Pd metal sintering, the main cause of irreversible deactivation of 3% Pd/Al2O3 and 3% Pd/CexOy-ZrO2 (CZO as model catalysts. The effect on the Rh component was presented in our companion paper Part I. Moderate support sintering and Pd-CexOy interactions were also experienced upon aging, but had a minimal effect on the catalyst activity losses. Cooling in air, following aging, was not able to reverse the metallic Pd sintering by re-dispersing to PdO. Unlike the aged Rh-TWCs (Part I, reduction via in situ steam reforming (SR of exhaust HCs was not effective in reversing the deactivation of aged Pd/Al2O3, but did show a slight recovery of the Pd activity when CZO was the carrier. The Pd+/Pd0 and Ce3+/Ce4+ couples in Pd/CZO are reported to promote the catalytic SR by improving the redox efficiency during the regeneration, while no such promoting effect was observed for Pd/Al2O3. A suggestion is made for improving the catalyst performance.

Atomic resolution structural insights into PdPt nanoparticle–carbon interactions for the design of highly active and stable electrocatalysts

International Nuclear Information System (INIS)

Slanac, Daniel A.; Li Lin; Mayoral, Alvaro; Yacaman, Miguel José; Manthiram, Arumugam; Stevenson, Keith J.; Johnston, Keith P.

2012-01-01

Graphical abstract: - Abstract: Interfacial interactions between sub-4 nm metal alloy nanoparticles and carbon supports, although not well understood at the atomic level, may be expected to have a profound influence on catalytic properties. Pd 3 Pt 2 alloy particles comprised of a disordered surface layer over a corrugated crystalline core are shown to exhibit strong interfacial interactions with a ∼20–50 nm spherical carbon support, as characterized by probe aberration corrected scanning transmission electron microscopy (pcSTEM). The disordered shells were formed from defects introduced by Pd during arrested growth synthesis of the alloy nanoparticles. The chemical and morphological changes in the catalyst, before and after cyclic stability testing (1000 cycles, 0.5–1.2 V), were probed with cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and pcSTEM. The strong metal–support interaction, along with the uniform alloy structure raised the mass activity by a factor of 1.8 versus pure Pt. The metal–support interactions also mitigated nanoparticle coalescence, dissolution, and ripening, resulting in only a 20% loss in mass activity (versus 60% for pure Pt on carbon) after the cyclic stability test. The design of alloy structure, guided by insight from atomic scale pcSTEM, for enhanced catalytic activity and stability, resulting from strong wetting with a deformable disordered shell, has the potential to be a general paradigm for improving catalytic performance.

Facile synthesis of Pt–Pd bimetallic nanoparticles by plasma discharge in liquid and their electrocatalytic activity toward methanol oxidation in alkaline media

Energy Technology Data Exchange (ETDEWEB)

Kim, Sung-Min; Lee, Yu-Jin [Center for Surface Technology and Applications, Korea Aerospace University, Gyeonggi-do, 412-791 (Korea, Republic of); Department of Materials Engineering, Korea Aerospace University, Gyeonggi-do, 412-791 (Korea, Republic of); Kim, Jung-Wan [Center for Surface Technology and Applications, Korea Aerospace University, Gyeonggi-do, 412-791 (Korea, Republic of); Division of Bioengineering, InCheon National University, Incheon, 406-772 (Korea, Republic of); Lee, Sang-Yul, E-mail: sylee@kau.ac.kr [Center for Surface Technology and Applications, Korea Aerospace University, Gyeonggi-do, 412-791 (Korea, Republic of); Department of Materials Engineering, Korea Aerospace University, Gyeonggi-do, 412-791 (Korea, Republic of)

2014-12-01

The Pt–Pd bimetallic nanoparticles for direct methanol fuel cell applications were successfully prepared by plasma discharge in aqueous solution. The obtained nanoparticles were characterized by energy dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, and transmission electron microscopy. During plasma discharge, the nanoparticles were produced from the erosion of electrodes. It was noted that the erosion amount of anode electrodes was much greater than that of cathode electrodes so that the composition of Pt–Pd bimetallic nanoparticles could be changed with different power types and electrode configurations. Diffraction patterns fitted from Gaussian devolution indicated that the crystalline phase of Pt{sub 40}Pd{sub 60} products was composed of pure Pt, pure Pd and Pt–Pd alloy phases. The morphology of synthesized nanoparticles showed that nanowires connected with quasi-spherical nanoparticles with 2–3 nm in diameter were observed and large spherical particles with > 50 nm in diameter were also detected intermittently. The cyclic voltammetric measurement and continuous potential scan demonstrated that Pt{sub 40}Pd{sub 60} had much higher catalytic activity and better resistance to CO poisoning than Pt{sub 94}Pd{sub 6} and Pt{sub 1}Pd{sub 99} for methanol oxidation. These results indicate that the Pt{sub 40}Pd{sub 60} could be an excellent candidate for the direct methanol fuel cell applications.

XRD and HREM studies of nanocrystalline Cu and Pd

International Nuclear Information System (INIS)

Nieman, G.W.; Weertmen, J.R.; Siegel, R.W.

1991-01-01

Consolidated powders of nanocrystalline Cu and Pd have been studied by x-ray diffraction (XRD) and high resolution electron microscopy (HREM) as part of an investigation of the mechanical behavior of nanocrystalline pure metals. XRD line broadening measurements were made to estimate rain size, qualitative grain size distribution and average long range strains in a number of samples. Mean grain sized range from 4-60 nm and have qualitatively narrow grain size distributions. Long range lattice strains are of the order of 0.2-3% in consolidated samples. These strains apparently persist and even increase in Cu samples after annealing at 0.35 Tm (498K) for 2h, accompanied by an apparent increase in grain size of ≥2x. Grain size, grain size distribution width and internal strains vary somewhat among samples produced under apparently identical processing conditions. HREM studies show that twins, stacking faults and low-index facets are abundant in as-consolidated nanocrystalline Cu samples. In this paper methodology, results and analysis of XRD and HREM experiments are presented

Environmental tests of metallization systems for terrestrial photovoltaic cells

Science.gov (United States)

Alexander, P., Jr.

1985-01-01

Seven different solar cell metallization systems were subjected to temperature cycling tests and humidity tests. Temperature cycling excursions were -50 deg C to 150 deg C per cycle. Humidity conditions were 70 deg C at 98% relative humidity. The seven metallization systems were: Ti/Ag, Ti/Pd/Ag, Ti/Pd/Cu, Ni/Cu, Pd/Ni/Solder, Cr/Pd/Ag, and thick film Ag. All metallization systems showed a slight to moderate decrease in cell efficiencies after subjection to 1000 temperature cycles. Six of the seven metallization systems also evidenced slight increases in cell efficiencies after moderate numbers of cycles, generally less than 100 cycles. The copper based systems showed the largest decrease in cell efficiencies after temperature cycling. All metallization systems showed moderate to large decreases in cell efficiencies after 123 days of humidity exposure. The copper based systems again showed the largest decrease in cell efficiencies after humidity exposure. Graphs of the environmental exposures versus cell efficiencies are presented for each metallization system, as well as environmental exposures versus fill factors or series resistance.

Effect of Ni and noble metals (Ru, Pd and Pt) on performance of bifunctional MoP/SiO2 for hydroconversion of methyl laurate

Science.gov (United States)

Nie, Ziyang; Zhang, Zhena; Chen, Jixiang

2017-10-01

SiO2 supported bifunctional MoP catalysts modified with different metal promoters (Ni, Ru, Pd, Pt), where Mo/Ni and Mo/M(M = Ru, Pd and Pt) atomic ratios was respectively 10 and 40, were prepared by TPR method from the phosphate precursors. It was found that the introduction of metal promoters facilitated the reduction of phosphate precursor and enhanced the dispersion of MoP. However, the MoP catalyst acidity was scarcely influenced by the small amount of metal promoters. In the hydroconversion of methyl laurate, the promoters enhanced the MoP catalyst activity for conversion of methyl laurate and hydrogenation of alkenes (intermediate), but reduced isomerization ability. Among the promoters, Ru was an optimum to decrease selectivity to alkenes while maintain high selectivity to iso-alkanes, and Mo40RuP showed better stability than MoP. At 380 °C and 3.0 MPa, the conversion of methyl laurate, the total selectivity to C11 and C12 hydrocarbons and the selectivity to iso-alkanes maintained at 100%, ∼94% and ∼30% on Mo40RuP during 102 h, respectively. The good stability of Mo40RuP is ascribed to that the presence of Ru prevented the sintering of MoP particles and suppressed carbon deposition.

Study of Pd-Sn/Al{sub 2}O{sub 3} catalysts prepared by an oxide colloidal route; Etude de catalyseurs Pd-Sn/Al{sub 2}O{sub 3} prepares par voie colloidale oxyde

Energy Technology Data Exchange (ETDEWEB)

Verdier, St.

2001-09-01

The oxide colloidal route, developed in the laboratory for mono-metallic catalysts, consists in preparing a metallic oxide hydro-sol which leads to the supported catalyst after deposition onto a support and an activation stage. In this work, this method has been adapted to the preparation of alumina supported bimetallic Pd-Sn catalysts to determine its interest for the control of the properties of the bimetallic phase (size, composition and structure). In the preliminary study concerning tin oxide sols, SnO{sub 2} (size=2,3 nm) and Sn{sub 6}O{sub 4}(OH){sub 4} (size = 25 nm) nano-particles were synthesized by neutralization respectively for tin(IV) and tin(H). The control through the pH of the aggregation of the PdO and SnO{sub 2} particles revealed that increasing oxide solubility promotes integral re-dispersion of the oxide particles. To synthesize oxide bimetallic sols, three strategies were defined. Copolymerization (formation of a mixed oxide nano-sol by cross condensation of both metals) does not lead to a mixed oxide Pd-Sn phase. Surface precipitation (neutralization of the second metal in the presence of the first oxide sol) yields nano-particles of both oxides in close interaction. Adsorption (adsorption of the second metal onto the first oxide sol) significantly occurs when contacting tin with a basic PdO sol (hydrolytic adsorption). The characterization and the assessment of the catalytic properties (selective hydrogenation of buta-1,3-diene) of the catalysts prepared by deposition of oxide bimetallic sols showed that the oxide colloidal route allows the control of the properties of the supported bimetallic phase. Moreover, our results display that both Pd-Sn alloy formation and,aggregation of the metallic particles contribute to increase the selectivity for this reaction. (author)

Investigations of Pd-Cu electrocatalyst for oxygen reduction reaction in acidic media with RDE method

Energy Technology Data Exchange (ETDEWEB)

Fouda-Onana, F.; Bah, S.; Savadogo, O. [Ecole Polytechnique de Montreal, Montreal, PQ (Canada). Laboratoire de nouveaux materiaux pour l' energie et l' electrochimie

2008-07-01

The kinetics of the oxygen reduction reaction (ORR) has been studied extensively with different platinum bi-metallic alloys such as Pt-Fe, Pt-Ni, Pt-Co. However, palladium-based bi-metallic alloys are being considered as a substitute for platinum in electrocatalysts. This paper reported on a study that investigated the ORR on bi-metallic Pd-Cu electrocatalyst. Different contents in Cu were analyzed and an optimal Cu composition leading to the highest ORR activity was found. A mechanism of the ORR kinetics for this catalyst was introduced based on the value of the Tafel slope. A smooth increase in surface area up to 50 per cent Cu was observed to a constant value of 23 cm{sup 2}. Such behaviour was due to the high dispersion of Pd as Cu increased and segregated. A volcano-shape was found between the kinetic current, activation energy and the Cu composition. The maximum exchange current density and the lowest activation energy were found for Pd50Cu50, which corresponded to the highest surface area. All Pd-Cu alloys presented a higher kinetic current than Pd alone. 3 refs., 1 tab., 3 figs.

Ex situ generation of stoichiometric HCN and its application in the Pd-catalysed cyanation of aryl bromides: evidence for a transmetallation step between two oxidative addition Pd-complexes.

Science.gov (United States)

Kristensen, Steffan K; Eikeland, Espen Z; Taarning, Esben; Lindhardt, Anders T; Skrydstrup, Troels

2017-12-01

A protocol for the Pd-catalysed cyanation of aryl bromides using near stoichiometric and gaseous hydrogen cyanide is reported for the first time. A two-chamber reactor was adopted for the safe liberation of ex situ generated HCN in a closed environment, which proved highly efficient in the Ni-catalysed hydrocyanation as the test reaction. Subsequently, this setup was exploited for converting a range of aryl and heteroaryl bromides (28 examples) directly into the corresponding benzonitriles in high yields, without the need for cyanide salts. Cyanation was achieved employing the Pd(0) precatalyst, P( t Bu) 3 -Pd-G3 and a weak base, potassium acetate, in a dioxane-water solvent mixture. The methodology was also suitable for the synthesis of 13 C-labelled benzonitriles with ex situ generated 13 C-hydrogen cyanide. Stoichiometric studies with the metal complexes were undertaken to delineate the mechanism for this catalytic transformation. Treatment of Pd(P( t Bu) 3 ) 2 with H 13 CN in THF provided two Pd-hydride complexes, (P( t Bu) 3 ) 2 Pd(H)( 13 CN), and [(P( t Bu) 3 )Pd(H)] 2 Pd( 13 CN) 4 , both of which were isolated and characterised by NMR spectroscopy and X-ray crystal structure analysis. When the same reaction was performed in a THF : water mixture in the presence of KOAc, only (P( t Bu) 3 ) 2 Pd(H)( 13 CN) was formed. Subjection of this cyano hydride metal complex with the oxidative addition complex (P( t Bu) 3 )Pd(Ph)(Br) in a 1 : 1 ratio in THF led to a transmetallation step with the formation of (P( t Bu) 3 ) 2 Pd(H)(Br) and 13 C-benzonitrile from a reductive elimination step. These experiments suggest the possibility of a catalytic cycle involving initially the formation of two Pd(ii)-species from the oxidative addition of L n Pd(0) into HCN and an aryl bromide followed by a transmetallation step to L n Pd(Ar)(CN) and L n Pd(H)(Br), which both reductively eliminate, the latter in the presence of KOAc, to generate the benzonitrile and L n Pd(0).

Diatomite-supported Pd-M (M=Cu, Co, Ni) bimetal nanocatalysts for selective hydrogenation of long-chain aliphatic esters.

Science.gov (United States)

Huang, Changliang; Zhang, Hongye; Zhao, Yanfei; Chen, Sha; Liu, Zhimin

2012-11-15

Diatomite supported Pd-M (M=Cu, Co, Ni) bimetal nanocatalysts with various metal compositions were prepared and characterized by means of X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. It was demonstrated that the metal nanoparticles were uniformly distributed on the support, and their size was centered around 8 nm with a relatively narrow size distribution. The catalysts were used to catalyze hydrogenation of long-chain aliphatic esters, including methyl palmitate, methyl stearate, and methyl laurate. It was indicated that the all diatomite-supported Pd-based bimetal catalysts were active to the selective hydrogenation of long-chain esters to corresponding alcohols at 270°C, originated from the synergistic effect between the metal particles and the diatomite support. For the selective hydrogenation of methyl palmitate, Pd-Cu/diatomite with metal loading of 1% and Pd/Cu=3 displayed the highest performance, giving a 1-hexadecanol yield of 82.9% at the substrate conversion of 98.8%. Copyright © 2012 Elsevier Inc. All rights reserved.

The effect of microemulsion composition on the morphology of Pd nanoparticles deposited at the surface of TiO2 and photoactivity of Pd-TiO2

Science.gov (United States)

Długokęcka, Marta; Łuczak, Justyna; Polkowska, Żaneta; Zaleska-Medynska, Adriana

2017-05-01

A series of microemulsion (ME) system, constituted by different water to surfactant molar ratios (Wo) and oil to surfactant mass ratios (S), have been applied for Pd-TiO2 preparation. The effect of ME properties on the morphology of Pd nanoparticles formed at TiO2 surface and an effect of Pd size and distribution on the surface and photocatalytic properties of Pd-TiO2 were investigated. Microemulsion systems were characterized by means of viscosity, density, dynamic light scattering as well as surface tension measurements to find a correlation between the conditions of Pd nanoparticles formation, their morphology and photocatalyst features. The photocatalysts were characterized by transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), UV-vis diffuse-reflectance spectroscopy (DRS), BET surface area and elemental analysis. The photocatalytic properties of Pd-modified TiO2 particles were studied in a model reaction of phenol photodegradation under Vis irradiation, as well as active species involved in the photocatalytic reaction were determined. Microemulsion composition was found to be a crucial parameter in determining the features of the TiO2-based photocatalysts covered by metallic nanoparticles. The highest photocatalytic activity under Vis radiation was observed for the Pd-TiO2 sample (average diameter 2.4 nm) obtained using 0.1 mol% Pd in the ME system containing 1.5 wt% of water and 82.8 wt% of cyclohexane with average droplet size of 2.83 ± 0.18 nm. In this regard, synthesis of such metal-semiconductor composites through the microemulsion route should always be preceded by investigation of ME properties in order to the eliminate the inhibitory effect of ME internal structure.

Effective-medium calculations for hydrogen in Ni, Pd, and Pt

DEFF Research Database (Denmark)

Christensen, Ole Bøssing; Stoltze, Per; Jacobsen, Karsten Wedel

1990-01-01

The effective-medium theory is applied to a study of the energetics of the hydrides of Ni, Pd, and Pt, stressing the properties of PdHθ for 0≤θ≤1. The calculated heat of solution and the heat of hydride formation for the three systems agree very well with experiment. We determine the favored...... structure for PdHθ by calculating the total energy and lattice expansion of different configurations. Vibrational frequencies and diffusion barriers of H in Pd are also treated. A simple and transparent physical picture of the hydrogen-metal interaction is developed. From the calculated energetics we make...... a model calculation of the phase diagram of hydrogen in palladium in qualitative agreement with experiment. On this basis we propose a new explanation of the peculiarities of the Pd-H system....

The role of tin-promoted Pd/MWNTs via the management of carbonaceous species in selective hydrogenation of high concentration acetylene

International Nuclear Information System (INIS)

Esmaeili, Elaheh; Mortazavi, Yadollah; Khodadadi, Abbas Ali; Rashidi, Ali Morad; Rashidzadeh, Mehdi

2012-01-01

Highlights: ► Synthesis of highly active tin-promoted catalysts by polyol method for selective hydrogenation of high concentration of acetylene. ► A positive change in the catalytic activities of tin-promoted catalysts results from distinct geometric and electronic effects. ► Change in the coverage of acetylenic overlayers for different temperature regions corresponds to the change of the number of isolated adsorption sites. ► The isolated adsorption sites are responsible for the enhancement of selectivity to ethylene with increased temperatures, via the management of the carbonaceous species over the catalyst surface. - Abstract: In the present study, Pd/MWNTs are synthesized using polyol process and modified by tin as a promoter for selective hydrogenation of high concentrated acetylene feedstock. Polyol method results in highly dispersed nanoparticles with a depletion of particle size for tin-promoted Pd catalysts as characterized by TEM. Tin promoter plays a considerable role in hydrogenation of pure acetylene stream. This is attributed to formation of Pd 2 Sn structural phase, confirmed by XRD and TPR techniques, composed mainly of intermetallic species. Catalytic behavior of tin-promoted Pd catalysts is affected by geometric and electronic factors which are more pronounced in the case of Sn/Pd = 0.25. A discontinuity in Arrhenius plots for the Sn-promoted catalysts is appeared, which seems to be due to a kinetic factor as a result of change in acetylene coverage on Pd metallic ensembles at low and high temperature ranges. Higher selectivity of the catalysts to ethylene is attributed to the presence of more isolated adsorption sites on the catalyst surface originated from both intermetallic compounds confirmed by XPS and the ones formed via the carbonaceous species upon the acetylene hydrogenation reaction.

Isotopically pure single crystal epitaxial diamond films and their preparation

International Nuclear Information System (INIS)

Banholzer, W.F.; Anthony, T.R.; Williams, D.M.

1992-01-01

The present invention is directed to the production of single crystal diamond consisting of isotopically pure carbon-12 or carbon-13. In the present invention, isotopically pure single crystal diamond is grown on a single crystal substrate directly from isotopically pure carbon-12 or carbon-13. One method for forming isotopically pure single crystal diamond comprises the steps of placing in a reaction chamber a single substrate heated to an elevated diamond forming temperature. Another method for forming isotopically pure single crystal diamond comprises diffusing isotopically pure carbon-12 or carbon-13 through a metallic catalyst under high pressure to a region containing a single crystal substrate to form an isotopically pure single crystal diamond layer on said single crystal substrate

Bimetallic Au-decorated Pd catalyst for the liquid phase hydrodechlorination of 2,4-dichlorophenol

International Nuclear Information System (INIS)

Zhou, Juan; Chen, Huan; Chen, Quanyuan; Huang, Zhaolu

2016-01-01

Graphical abstract: 2,4-Dichlorophenol can be converted to phenol via the catalytic HDC method over Pd-Au/CNTs and the catalytic activity first increased and then decreased with Au content. - Highlights: • Bimetallic catalysts had smaller metal particles and larger number of exposed active site than the monometallic catalysts. • The cationization of Pd particles increased with Au content in the bimetallic catalysts. • The bimetallic catalysts exhibited higher catalytic activities for HDC of 2,4-DCP than the monometallic counterparts. • The concerted pathway for HDC of 2,4-DCP was more predominant with increasing Au content in the bimetallic catalyst. - Abstract: Monometallic and bimetallic Pd-Au catalysts supported on multi-walled carbon nanotubes (CNTs) with varied Au cooperation amounts were prepared using the complexing-reduction method in the presence of tetrahydrofuran (THF). The liquid phase catalytic hydrodechlorination (HDC) of 2,4-dichlorophenol (2,4-DCP) was investigated over these bimetallic catalysts. The catalysts were characterized by N 2 adsorption-desorption isotherms, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and H 2 chemisorption. Characterization results showed that the co-reduction of Pd and Au mainly formed alloy-like structure. The bimetallic catalysts had smaller metal particles and larger numbers of exposed active site than that of monometallic catalysts. In addition, compared with Pd(1.7)/CNTs and Au(0.4)/CNTs, the binding energies of Pd 3d 5/2 shifted to higher positions while that of Au 4f 7/2 had negative shifts in the Pd-Au bimetallic catalysts, which can be ascribed to the electrons transferred from metal Pd to Au and the cationization of Pd particles was enhanced. Accordingly, the bimetallic Pd-Au particles with different Au contents in the catalysts exhibited varied synergistic effects for the catalytic HDC of 2,4-DCP, with Pd(1.8)Au(0.4)/CNTs having the highest catalytic activity

More active and sulfur resistant bimetallic Pd-Ni catalysts

Energy Technology Data Exchange (ETDEWEB)

Betti, Carolina; Carrara, Nicolás; Badano, Juan; Lederhos, Cecilia; Vera, Carlos; Quiroga, Mónica, E-mail: mquiroga@fiq.unl.edu.ar [Instituto de Investigaciones en Catálisis y Petroquímica, INCAPE (FIQ-UNL, CONICET), Santa Fe (Argentina)

2018-02-15

The influence of the kind of metal precursor and the sequence of impregnation on the properties of Pd-Ni catalysts was evaluated during the test reaction of selective hydrogenation of styrene to ethylbenzene by means of physicochemical characterization. The focus was put on the final hydrogenating activity and the resistance to deactivation by sulfide compounds (thiophene). The used techniques of characterization were ICP, XPS, XDR, TPR, CO chemisorption and TEM. XPS results indicated the presence of different Pd species: Pd{sup δ-}, Pd{sup 0} and Pd{sup δ+}. In the case of the Ni containing catalysts, Ni{sup 0} and NiO species were also detected. These palladium and nickel species would be responsible of the variation of activity and sulfur resistance of the catalysts. NiClPd catalysts had a higher resistance to deactivation by sulfur poisoning. This was associated to a higher concentration of Pd{sup η+}Cl{sub x}O{sub y} species that would prevent the adsorption of thiophene by both steric and electronic effects. It could also be due to the lower concentration of Pd{sup 0} and Ni{sup 0} on these catalysts, as compared to those shown by the PdNiCl catalysts. Both the Pd{sup 0} and Ni{sup 0} species are more prone to poisoning because of their higher electronic availability. (author)

Size effects of nano-spaced basal stacking faults on the strength and deformation mechanisms of nanocrystalline pure hcp metals

Science.gov (United States)

Wang, Wen; Jiang, Ping; Yuan, Fuping; Wu, Xiaolei

2018-05-01

The size effects of nano-spaced basal stacking faults (SFs) on the tensile strength and deformation mechanisms of nanocrystalline pure cobalt and magnesium have been investigated by a series of large-scale 2D columnar and 3D molecular dynamics simulations. Unlike the strengthening effect of basal SFs on Mg alloys, the nano-spaced basal SFs are observed to have no strengthening effect on the nanocrystalline pure cobalt and magnesium from MD simulations. These observations could be attributed to the following two reasons: (i) Lots of new basal SFs are formed before (for cobalt) or simultaneously with (for magnesium) the other deformation mechanisms (i.e. the formation of twins and the edge dislocations) during the tensile deformation; (ii) In hcp alloys, the segregation of alloy elements and impurities at typical interfaces, such as SFs, can stablilise them for enhancing the interactions with dislocation and thus elevating the strength. Without such segregation in pure hcp metals, the edge dislocations can cut through the basal SFs although the interactions between the dislocations and the pre-existing SFs/newly formed SFs are observed. The nano-spaced basal SFs are also found to have no restriction effect on the formation of deformation twins.

Microwave-induced direct spin-flip transitions in mesoscopic Pd/Co heterojunctions

Science.gov (United States)

Pietsch, Torsten; Egle, Stefan; Keller, Martin; Fridtjof-Pernau, Hans; Strigl, Florian; Scheer, Elke

2016-09-01

We experimentally investigate the effect of resonant microwave absorption on the magneto-conductance of tunable Co/Pd point contacts. At the interface a non-equilibrium spin accumulation is created via microwave absorption and can be probed via point contact spectroscopy. We interpret the results as a signature of direct spin-flip excitations in Zeeman-split spin-subbands within the Pd normal metal part of the junction. The inverse effect, which is associated with the emission of a microwave photon in a ferromagnet/normal metal point contact, can also be detected via its unique signature in transport spectroscopy.

Microwave-induced direct spin-flip transitions in mesoscopic Pd/Co heterojunctions

International Nuclear Information System (INIS)

Pietsch, Torsten; Egle, Stefan; Keller, Martin; Fridtjof-Pernau, Hans; Strigl, Florian; Scheer, Elke

2016-01-01

We experimentally investigate the effect of resonant microwave absorption on the magneto-conductance of tunable Co/Pd point contacts. At the interface a non-equilibrium spin accumulation is created via microwave absorption and can be probed via point contact spectroscopy. We interpret the results as a signature of direct spin-flip excitations in Zeeman-split spin-subbands within the Pd normal metal part of the junction. The inverse effect, which is associated with the emission of a microwave photon in a ferromagnet/normal metal point contact, can also be detected via its unique signature in transport spectroscopy. (paper)

Preliminary study on metallic inclusion in nuclear fuel

International Nuclear Information System (INIS)

Fukuzawa, Takashi; Tanaka, Masahiro; Tanabe, Tetsuo; Imoto, Shosuke

1984-01-01

In recent postirradiation tests, metallic fission products such as Mo, Ru, Rh and Pd are known to precipitate as metallic inclusions in the fuel. These inclusions remain as insoluble residues and provide various problems in different fields of the reprocessing. In this report are presented preliminary results of the study on the ternary phase diagram of Mo-Ru-Pd system and on their properties in nitric acid or various oxidative environments. It is concluded that (1) most of metallic inclusions which are insoluble in nitric acid show epsilon phase, Ru base hcp alloy, in which a large amount of Mo and Pd are soluble, (2) Pd, however, seems to deposit separately in the fuel pin because of its high vapor pressure, (3) Mo fraction in the inclusion would be highly dependent on oxygen potential in the fuel pin. (author)

Thermodynamic assessment of the palladium-tellurium (Pd-Te) system

International Nuclear Information System (INIS)

Gosse, S.; Gueneau, C.

2011-01-01

Among the fission products formed in nuclear fuels, the platinum-group metal palladium and the chalcogen element tellurium exhibit strong interaction. It is therefore of interest to be able to predict the chemical equilibria involving the Pd and Te fission products. A thermodynamic assessment is carried out using the Calphad (Calculation of Phase Diagram) method to investigate the behaviour of Pd-Te alloy system in nuclear fuels under irradiation and under waste disposal conditions. The Pd-Te binary description was optimized using experimental data found in literature including thermodynamic properties and phase diagram data. To validate the calculated phase diagram and thermodynamic properties, the results are compared with data from the literature. Both calculated and experimental phase diagrams and thermodynamic properties are in good agreement in the whole Pd-Te composition range. (authors)

Systematic Identification of Promoters for Methane Oxidation Catalysts Using Size- and Composition-Controlled Pd-Based Bimetallic Nanocrystals.

Science.gov (United States)

Willis, Joshua J; Goodman, Emmett D; Wu, Liheng; Riscoe, Andrew R; Martins, Pedro; Tassone, Christopher J; Cargnello, Matteo

2017-08-30

Promoters enhance the performance of catalytic active phases by increasing rates, stability, and/or selectivity. The process of identifying promoters is in most cases empirical and relies on testing a broad range of catalysts prepared with the random deposition of active and promoter phases, typically with no fine control over their localization. This issue is particularly relevant in supported bimetallic systems, where two metals are codeposited onto high-surface area materials. We here report the use of colloidal bimetallic nanocrystals to produce catalysts where the active and promoter phases are colocalized to a fine extent. This strategy enables a systematic approach to study the promotional effects of several transition metals on palladium catalysts for methane oxidation. In order to achieve these goals, we demonstrate a single synthetic protocol to obtain uniform palladium-based bimetallic nanocrystals (PdM, M = V, Mn, Fe, Co, Ni, Zn, Sn, and potentially extendable to other metal combinations) with a wide variety of compositions and sizes based on high-temperature thermal decomposition of readily available precursors. Once the nanocrystals are supported onto oxide materials, thermal treatments in air cause segregation of the base metal oxide phase in close proximity to the Pd phase. We demonstrate that some metals (Fe, Co, and Sn) inhibit the sintering of the active Pd metal phase, while others (Ni and Zn) increase its intrinsic activity compared to a monometallic Pd catalyst. This procedure can be generalized to systematically investigate the promotional effects of metal and metal oxide phases for a variety of active metal-promoter combinations and catalytic reactions.

Comparative in vitro biocompatibility of nickel-titanium, pure nickel, pure titanium, and stainless steel: genotoxicity and atomic absorption evaluation.

Science.gov (United States)

Assad, M; Lemieux, N; Rivard, C H; Yahia, L H

1999-01-01

The genotoxicity level of nickel-titanium (NiTi) was compared to that of its pure constituents, pure nickel (Ni) and pure titanium (Ti) powders, and also to 316L stainless steel (316L SS) as clinical reference material. In order to do so, a dynamic in vitro semiphysiological extraction was performed with all metals using agitation and ISO requirements. Peripheral blood lymphocytes were then cultured in the presence of all material extracts, and their comparative genotoxicity levels were assessed using electron microscopy-in situ end-labeling (EM-ISEL) coupled to immunogold staining. Cellular chromatin exposition to pure Ni and 316L SS demonstrated a significantly stronger gold binding than exposition to NiTi, pure Ti, or the untreated control. In parallel, graphite furnace atomic absorption spectrophotometry (AAS) was also performed on all extraction media. The release of Ni atoms took the following decreasing distribution for the different resulting semiphysiological solutions: pure Ni, 316L SS, NiTi, Ti, and controls. Ti elements were detected after elution of pure titanium only. Both pure titanium and nickel-titanium specimens obtained a relative in vitro biocompatibility. Therefore, this quantitative in vitro study provides optimistic results for the eventual use of nickel-titanium alloys as surgical implant materials.

Study of Pd-Au/MWCNTs formic acid electrooxidation catalysts

Energy Technology Data Exchange (ETDEWEB)

Mikolajczuk, Anna; Borodzinski, Andrzej; Kedzierzawski, Piotr; Lesiak, Beata [Institute of Physical Chemistry, Polish Academy of Sciences, ul. Kasprzaka 44/52, 01-224 Warszawa (Poland); Stobinski, Leszek [Institute of Physical Chemistry, Polish Academy of Sciences, ul. Kasprzaka 44/52, 01-224 Warszawa (Poland); Faculty of Materials Science and Engineering, Warsaw University of Technology, ul. Woloska 141, 02-507 Warsaw (Poland); Koever, Laszlo; Toth, Jozsef [Institute of Nuclear Research, Hungarian Academy of Sciences (ATOMKI), P. O. Box 51, 4001 Debrecen (Hungary); Lin, Hong-Ming [Department of Materials Engineering, Tatung University, 40, Chungshan N. Rd., 3rd Sec, 104, Taipei (China)

2010-12-15

The Pd-Au multiwall carbon nanotubes (MWCNTs) supported catalyst exhibits higher power density in direct formic acid fuel cell (DFAFC) than similar Pd/MWCNTs catalyst. The Pd-Au/MWCNTs catalyst also exhibits higher activity and is more stable in electrooxidation reaction of formic acid during cyclic voltammetry (CV) measurements. After preparation by polyol method, the catalyst was subjected to two type of treatments: (I) annealing at 250 C in 100% of Ar, (II) reducing in 5% of H{sub 2} in Ar atmosphere at 200 C. It was observed that the catalyst after treatment I was completely inactive, whereas after treatment II exhibited high activity. In order to explain this effect the catalysts were characterized by electron spectroscopy methods. The higher initial catalytic activity of Pd-Au/MWCNTs catalyst than Pd/MWCNTs catalyst in reaction of formic acid electrooxidation was attributed to electronic effect of gold in Pd-Au solution, and larger content of small Au nanoparticles of 1 nm size. The catalytic inactivity of Pd-Au/MWCNTs catalysts annealed in argon is attributed to carbon amorphous overlayer covering of Pd oxide shell on the metallic nanoparticles. (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Structural behavior of Pd40Cu30Ni10P20 bulk metallic glass below and above the glass transition

DEFF Research Database (Denmark)

Mattern, N.; Hermann, H.; Roth, S.

2003-01-01

The thermal behavior of the structure of Pd40Cu30Ni10P20 bulk metallic glass has been investigated in situ through the glass transition by means of high-temperature x-ray synchrotron diffraction. The dependence of the x-ray structure factor S(q) of the Pd40Cu30Ni10P20 glass on temperature follows...... the Debye theory up to the glass transition with a Debye temperature theta=296 K. Above the glass transition temperature T-g, the temperature dependence of S(q) is altered, pointing to a continuous development of structural changes in the liquid with temperature. The atomic pair correlation functions g......(r) indicate changes in short-range-order parameters of the first and the second neighborhood with temperature. The temperature dependence of structural parameters is different in glass and in supercooled liquid, with a continuous behavior through the glass transition. The nearest-neighbor distance decreases...

Chirality in distorted square planar Pd(O,N)2 compounds.

Science.gov (United States)

Brunner, Henri; Bodensteiner, Michael; Tsuno, Takashi

2013-10-01

Salicylidenimine palladium(II) complexes trans-Pd(O,N)2 adopt step and bowl arrangements. A stereochemical analysis subdivides 52 compounds into 41 step and 11 bowl types. Step complexes with chiral N-substituents and all the bowl complexes induce chiral distortions in the square planar system, resulting in Δ/Λ configuration of the Pd(O,N)2 unit. In complexes with enantiomerically pure N-substituents ligand chirality entails a specific square chirality and only one diastereomer assembles in the lattice. Dimeric Pd(O,N)2 complexes with bridging N-substituents in trans-arrangement are inherently chiral. For dimers different chirality patterns for the Pd(O,N)2 square are observed. The crystals contain racemates of enantiomers. In complex two independent molecules form a tight pair. The (RC) configuration of the ligand induces the same Δ chirality in the Pd(O,N)2 units of both molecules with varying square chirality due to the different crystallographic location of the independent molecules. In complexes and atrop isomerism induces specific configurations in the Pd(O,N)2 bowl systems. The square chirality is largest for complex [(Diop)Rh(PPh3 )Cl)], a catalyst for enantioselective hydrogenation. In the lattice of two diastereomers with the same (RC ,RC) configuration in the ligand Diop but opposite Δ and Λ square configurations co-crystallize, a rare phenomenon in stereochemistry. © 2013 Wiley Periodicals, Inc.

The effect of CNTs on structures and catalytic properties of AuPd clusters for H2O2 synthesis.

Science.gov (United States)

Yang, Hua-feng; Xie, Peng-yang; Yu, Hui-you; Li, Xiao-nian; Wang, Jian-guo

2012-12-28

The structures and catalytic properties of AuPd clusters supported on carbon nanotubes (CNTs) for H(2)O(2) synthesis have been investigated by means of density functional theory calculations. Firstly, the structures of AuPd clusters are strongly influenced by CNTs, in which the bottom layers are mainly composed of Pd and the top layers are a mix of Au and Pd due to the stronger binding of Pd than Au on CNTs. Especially, it is found that O(2) adsorption on the Pd/CNTs interfacial sites is much weaker than that on the only Pd sites, which is in contrast to transition metal oxide (for example TiO(2), Al(2)O(3), CeO(2)) supported metal clusters. Furthermore, Pd ensembles on the interfacial sites have far superior catalytic properties for H(2)O(2) formation than those away from CNT supports due to the changes in electronic structures caused by the CNTs. Therefore, our study provides a physical insight into the enhanced role of carbon supports in H(2)O(2) synthesis over supported AuPd catalysts.

Use of Pd-Pt loaded graphene aerogel on nickel foam in direct ethanol fuel cell

Science.gov (United States)

Tsang, Chi Him A.; Leung, D. Y. C.

2018-01-01

A size customized binder-free bimetallic Pd-Pt loaded graphene aerogel deposited on nickel foam plate (Pd-Pt/GA/NFP) was prepared and used as an electrode for an alkaline direct ethanol fuel cell (DEFC) under room temperature. The effect of fuel concentration and metal composition on the output power density of the DEFC was systematically investigated. Under the optimum fuel concentration, the cell could achieve a value of 3.6 mW cm-2 at room temperature for the graphene electrode with Pd/Pt ratio approaching 1:1. Such results demonstrated the possibility of producing a size customized metal loaded GA/NFP electrode for fuel cell with high performance.

Hydrothermal Method Using DMF as a Reducing Agent for the Fabrication of PdAg Nanochain Catalysts towards Ethanol Electrooxidation

Directory of Open Access Journals (Sweden)

Yue Feng

2016-07-01

Full Text Available In this article, we developed a facile one-step hydrothermal method using dimethyl formamide (DMF as a reducing agent for the fabrication of PdAg catalyst. The scanning electron microscope (SEM and transmission electron microscopy (TEM images have shown that the as-synthesized PdAg catalyst had a nanochain structure. The energy-dispersive X-ray analyzer (EDX spectrum presented the actual molar ratio of Pd and Ag in the PdAg alloy. Traditional electrochemical measurements, such as cyclic voltammetry (CV, chronoamperometry (CA and electrochemical impedance spectrometry (EIS, were performed using a CHI 760D electrochemical analyzer to characterize the electrochemical properties of the as-synthesized catalyst. The results have shown that the PdAg catalyst with a nanochain structure displays higher catalytic activity and stability than pure Pd and commercial Pd/C catalysts.

Catalytic reduction of 4-nitrophenol over Ni-Pd nanodimers supported on nitrogen-doped reduced graphene oxide

Energy Technology Data Exchange (ETDEWEB)

Liu, Lijun, E-mail: liulj@wtu.edu.cn [College of Chemistry and Chemical Engineering, Wuhan Textile University, Wuhan 430073, People' s Republic of China (China); Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Chen, Ruifen; Liu, Weikai [College of Chemistry and Chemical Engineering, Wuhan Textile University, Wuhan 430073, People' s Republic of China (China); Wu, Jiamin [Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Gao, Di, E-mail: gaod@pitt.edu [Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States)

2016-12-15

Catalytic reduction of toxic 4-nitrophenol to 4-aminophenol over magnetically recoverable nanocatalysts has attracted much attention. Herein, we report a Ni-Pd/NrGO catalyst through the growth of Ni-Pd nanodimers (NDs) on nitrogen-doped reduced graphene oxide (NrGO). The Ni-Pd NDs show a heterogeneous nanostructure with Ni and Pd subparts contacting with each other, remarkably different from the frequently-observed core/shell nanoparticles (NPs) or nanoalloy. The formation of Ni-Pd NDs follows an initial deposition of Pd NPs on the graphene and in-situ catalytic generation of Ni subparts over the newly-generated Pd NPs. The resulting Ni-Pd/NrGO exhibits a superior catalytic activity towards the reduction of 4-nitrophenol at room temperature with a high rate constant (3400 s{sup -1} g{sup -1}) and a low activated energy (29.1 kJ mol{sup -1}) as compared to unsupported Ni-Pd NDs and supported monometallic catalysts. The conversion rate of 4-NP is calculated to be 99.5% and the percent yield (%) of 4-AP is as high as 99.1%. A synergistic catalysis mechanism is rationally proposed, which is ascribed to the electronic modification of Ni-Pd metals due to the strong metal/support interaction (SMSI) effect as well as the electron transfer between Ni and Pd. The hybrid catalyst shows soft ferromagnetic properties and can be magnetically separated and recycled without obvious loss of activity.

Metal adsorption on monolayer blue phosphorene: A first principles study

Science.gov (United States)

Khan, Imran; Son, Jicheol; Hong, Jisang

2018-01-01

We investigated the electronic structure, adsorption energies, magnetic properties, dipole moment and work function of metal adatoms (Mg, Cr, Mo, Pd, Pt, and Au) adsorption on a blue phosphorene monolayer. For Mg, Pt and Au metals, the most stable state was found in hollow site while for Cr, Mo and Pd metals we found an adsorption in valley site. We suggest that the Pd and Pt atoms prefer 2D growth mode while the Mg, Cr, Mo and Au atoms prefer 3D island growth mode on monolayer phosphorene. The electronic band structures and magnetic properties were dependent on the doping site and dopant materials. For instance, the semiconducting features were preserved in Mg, Pd, Pt, and Au doped systems. However, the Cr and Mo doped systems displayed half-metallic band structures. The total magnetic moment of 4.05, 2.0 and 0.77 μB /impurity atom were obtained in Cr, Mo and Au doped systems whereas the Mg, Pd and Pt doped systems remained nonmagnetic. We also investigated the magnetic interaction between two transition metal impurities. We observed ferromagnetic coupling between two transition metal impurities in Cr and Mo doped systems while the Au doped system displayed almost degenerated magnetic state. For Mg, Cr, and Mo adsorptions, we found relatively large values of dipole moments compared to those in the Pd, Pt and Au adsorptions. This resulted in a significant suppression of the work function in Mg, Cr and Mo adsorptions. Overall, adsorption can tune the physical and magnetic properties of phosphorene monolayer.

Bioinspired metal-cell wall-metal sandwich structure on an individual bacterial cell scaffold.

Science.gov (United States)

Zhang, Xiaoliang; Yu, Mei; Liu, Jianhua; Li, Songmei

2012-08-25

Pd nanoparticles were introduced to individual Bacillus cells and dispersedly anchored on both the inside and outside of the cell walls. The anchored nanoparticles served as "seeds" to drive the formation of double metallic layers forming a metal-cell wall-metal sandwich structure at the single-cell level.

Antiferromagnetic Mott insulating state in the single-component molecular material Pd(tmdt)2

Science.gov (United States)

Takagi, Rina; Sari, Dita Puspita; Mohd-Tajudin, Saidah Sakinah; Ashi, Retno; Watanabe, Isao; Ishibashi, Shoji; Miyagawa, Kazuya; Ogura, Satomi; Zhou, Biao; Kobayashi, Akiko; Kanoda, Kazushi

2017-12-01

A family of compounds built by a single molecular species, M (tmdt) 2, with a metal ion, M , and organic ligands, tmdt, affords diverse electronic phases due to M -dependent interplays between d electrons in M , and π electrons in tmdt. We investigated the spin state in Pd (tmdt) 2 , a π -electron system without a d -electron contribution, through 1H nuclear magnetic resonance (NMR) and muon-spin resonance experiments. The temperature profiles of the NMR linewidth, relaxation rate, and asymmetry parameter in muon decay show an inhomogeneous antiferromagnetic order with moments distributed around ˜0.1 μB that onsets at above 100 K. This result provides an example of the antiferromagnetic order in a pure π -electron system in M (tmdt) 2, and it demonstrates that correlation among the π electrons is so strong as to give the Néel temperature over 100 K. The small and inhomogeneous moments are understandable as the crucial disorder effect in correlated electrons situated near the Mott transition.

High activity of novel Pd/TiO2 nanotube catalysts for methanol electro-oxidation

International Nuclear Information System (INIS)

Wang Mei; Guo Daojun; Li Hulin

2005-01-01

Electro-oxidation of methanol in sulfuric acid solution was studied using palladium well-dispersed on titanium nanotubes, in relation to methanol oxidation processes in the direct oxidation methanol fuel cell. Pd dispersed on titania nanotubes, which leads to high surface area substrates, showed excellent catalytic activities compared to those of pure Pd and Pd-TiO 2 nanoparticles. TEM results show a narrow distribution of TiO 2 nanoparticles whose particle size is about 10nm, and uniform nano-sized TiO 2 nanotubes with 10nm in diameters are seen from HRTEM . A homogeneous structure in the composite nanomaterials is indicated by XRD analysis. The composite electrode activities were measured by cyclic voltammetry (CV) and at 25 deg. C it was found that 3wt% Pd in titania nanotubes had the best activity for methanol oxidation

A DFT study and micro-kinetic analysis of acetylene selective hydrogenation on Pd-doped Cu(111) surfaces

International Nuclear Information System (INIS)

Ma, Ling-Ling; Lv, Cun-Qin; Wang, Gui-Chang

2017-01-01

Semi-hydrogenation of acetylene in a hydrogen-rich stream is an industrially important process. Inspired by the recent experiments that Cu(111) surface doped by a small number of Pd atoms can exhibit excellent catalytic performance toward the dissociation of H_2 molecule as well as the high selective hydrogenation of acetylene as compared with pure Cu and Pd metal alone at low-temperature, here we performed systematic first-principles calculations to investigate the corresponding reaction mechanism related to the acetylene hydrogenation processes on single atom alloys (SAAs) and monolayer Pd/Cu(111) (i.e.,1.00 ML Pd/Cu(111)) model catalysts in detail, and to explore the possible factors controlling the high selectivity on SAAs. Our results clearly demonstrate that the SAA catalyst has higher selectivity for the ethylene formation than that of 1.00 ML Pd/Cu(111), and lower activity for the acetylene conversion compared with that of 1.00 ML Pd/Cu(111). The relatively high selectivity on SAA is mainly due to the facile desorption of ethylene and moderate activity in the dissociation of molecular H_2. The main factor which lowers the selectivity towards the ethylene formation on 1.00 ML Pd/Cu(111) is that this system has a higher capacity to promote the breaking of C−H/C−C bonds, which leads to the formation of carbonaceous deposits and polymers such as benzene, and thus reduces the selectivity for the ethylene formation. Meanwhile, it was found that the desorption energy of ethylene on these two surfaces was smaller than the energy barrier of further hydrogenation, which results in the absence of ethane on these two systems. Micro-kinetic model analysis provides a further valuable insight into the evidence for the key factors controlling the catalytic activity and selectivity towards the selective hydrogenation of acetylene. Our findings may help people to design a highly selective hydrogenation catalyst by controlling the balance between the H_2 dissociation and

A DFT study and micro-kinetic analysis of acetylene selective hydrogenation on Pd-doped Cu(111) surfaces

Science.gov (United States)

Ma, Ling-Ling; Lv, Cun-Qin; Wang, Gui-Chang

2017-07-01

Semi-hydrogenation of acetylene in a hydrogen-rich stream is an industrially important process. Inspired by the recent experiments that Cu(111) surface doped by a small number of Pd atoms can exhibit excellent catalytic performance toward the dissociation of H2 molecule as well as the high selective hydrogenation of acetylene as compared with pure Cu and Pd metal alone at low-temperature, here we performed systematic first-principles calculations to investigate the corresponding reaction mechanism related to the acetylene hydrogenation processes on single atom alloys (SAAs) and monolayer Pd/Cu(111) (i.e.,1.00 ML Pd/Cu(111)) model catalysts in detail, and to explore the possible factors controlling the high selectivity on SAAs. Our results clearly demonstrate that the SAA catalyst has higher selectivity for the ethylene formation than that of 1.00 ML Pd/Cu(111), and lower activity for the acetylene conversion compared with that of 1.00 ML Pd/Cu(111). The relatively high selectivity on SAA is mainly due to the facile desorption of ethylene and moderate activity in the dissociation of molecular H2. The main factor which lowers the selectivity towards the ethylene formation on 1.00 ML Pd/Cu(111) is that this system has a higher capacity to promote the breaking of Csbnd H/Csbnd C bonds, which leads to the formation of carbonaceous deposits and polymers such as benzene, and thus reduces the selectivity for the ethylene formation. Meanwhile, it was found that the desorption energy of ethylene on these two surfaces was smaller than the energy barrier of further hydrogenation, which results in the absence of ethane on these two systems. Micro-kinetic model analysis provides a further valuable insight into the evidence for the key factors controlling the catalytic activity and selectivity towards the selective hydrogenation of acetylene. Our findings may help people to design a highly selective hydrogenation catalyst by controlling the balance between the H2 dissociation and

Bimetallic Au-decorated Pd catalyst for the liquid phase hydrodechlorination of 2,4-dichlorophenol

Energy Technology Data Exchange (ETDEWEB)

Zhou, Juan [School of the Environment, Donghua University, Shanghai 201620 (China); Chen, Huan, E-mail: hchen404@njust.edu.cn [Key Laboratory of Jiangsu Province for Chemical Pollution Control and Resources Reuse, School of Environmental & Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Chen, Quanyuan; Huang, Zhaolu [School of the Environment, Donghua University, Shanghai 201620 (China)

2016-11-30

Graphical abstract: 2,4-Dichlorophenol can be converted to phenol via the catalytic HDC method over Pd-Au/CNTs and the catalytic activity first increased and then decreased with Au content. - Highlights: • Bimetallic catalysts had smaller metal particles and larger number of exposed active site than the monometallic catalysts. • The cationization of Pd particles increased with Au content in the bimetallic catalysts. • The bimetallic catalysts exhibited higher catalytic activities for HDC of 2,4-DCP than the monometallic counterparts. • The concerted pathway for HDC of 2,4-DCP was more predominant with increasing Au content in the bimetallic catalyst. - Abstract: Monometallic and bimetallic Pd-Au catalysts supported on multi-walled carbon nanotubes (CNTs) with varied Au cooperation amounts were prepared using the complexing-reduction method in the presence of tetrahydrofuran (THF). The liquid phase catalytic hydrodechlorination (HDC) of 2,4-dichlorophenol (2,4-DCP) was investigated over these bimetallic catalysts. The catalysts were characterized by N{sub 2} adsorption-desorption isotherms, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and H{sub 2} chemisorption. Characterization results showed that the co-reduction of Pd and Au mainly formed alloy-like structure. The bimetallic catalysts had smaller metal particles and larger numbers of exposed active site than that of monometallic catalysts. In addition, compared with Pd(1.7)/CNTs and Au(0.4)/CNTs, the binding energies of Pd 3d{sub 5/2} shifted to higher positions while that of Au 4f{sub 7/2} had negative shifts in the Pd-Au bimetallic catalysts, which can be ascribed to the electrons transferred from metal Pd to Au and the cationization of Pd particles was enhanced. Accordingly, the bimetallic Pd-Au particles with different Au contents in the catalysts exhibited varied synergistic effects for the catalytic HDC of 2,4-DCP, with Pd(1.8)Au(0.4)/CNTs having the highest

Effectiveness of using pure copper and silver coupon corrosivity monitoring (CCM) metal strips to measure the severity levels of air pollutants in indoor and outdoor atmospheres

CSIR Research Space (South Africa)

Foax, LJ

2008-10-01

Full Text Available Severity levels of air pollutants rich in oxides, chlorides and sulphides were successfully measured in indoor and outdoor atmospheres using pure copper and silver coupon corrosivity monitoring (CCM) metal strips when the maximum exposure periods...

LaFePdO3 perovskite automotive catalyst having a self-regenerative function

International Nuclear Information System (INIS)

Tanaka, Hirohisa; Tan, Isao; Uenishi, Mari; Taniguchi, Masashi; Kimura, Mareo; Nishihata, Yasuo; Mizuki, Jun'ichiro

2006-01-01

An automotive gasoline engine is operated close to the stoichiometric air-to-fuel ratio to convert the pollutant emissions simultaneously, accompanying with redox (reduction and oxidation) fluctuations in exhaust-gas composition through adjusting the air-to-fuel ratio. An innovative LaFe 0.95 Pd 0.05 O 3 perovskite catalyst, named 'the intelligent catalyst', has been developed, and which has a new self-regenerative function of the precious metal in the inherent fluctuations of automotive exhaust-gas. The LaFe 0.95 Pd 0.05 O 3 perovskite catalyst, La located at the A-site, was prepared by the alkoxide method. Pd located at the B-site of the perovskite lattice in the oxidative atmosphere, and segregated out to form small metallic particles in the reductive atmosphere. The catalyst retained a predominantly perovskite structure throughout a redox cycle of the exhaust-gas, while the local structure around Pd could be changed in a completely reversible manner. The agglomeration and growth of Pd particles is suppressed, even under the severe environment, as a result of the movement between inside and outside the perovskite lattice. It is revealed that the self-regenerative function of Pd occurs even at 200 deg. C, unexpectedly low temperature, in the LaFe 0.95 Pd 0.05 O 3 catalyst. Since the high catalytic activity is maintained, the great reduction of Pd loading has been achieved. The intelligent catalyst is expected as a new application of the rare earth, and then the technology is expected in the same way in the global standard of the catalyst designing

Structure determination of chitosan-stabilized Pt and Pd based bimetallic nanoparticles by X-ray photoelectron spectroscopy and transmission electron microscopy

International Nuclear Information System (INIS)

Wu, Lihua; Shafii, Salimah; Nordin, Mohd Ridzuan; Liew, Kong Yong; Li, Jinlin

2012-01-01

Chitosan (CTS)-stabilized bimetallic nanoparticles were prepared at room temperature (rt.) in aqueous solution. Palladium (Pd) and platinum (Pt) were selected as the first metals while iron (Fe) and nickel (Ni) functioned as the second metals. In order to obtain the noble metal core-transition metal shell structures, bimetallic nanoparticles were prepared in a two-step process: the preparation of mono noble metallic (Pd or Pt) nanoparticles and the deposition of transition metals (Fe or Ni) on the surface of the monometallic nanoparticles. The structures of the nanoparticles were studied using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The XPS results show that Pd and Pt exist mainly in zero valences. The presence of Fe and Ni in the bimetallic nanoparticles affects the binding energy of Pd and Pt. Moreover, the studies of O 1s spectra indicate the presence of Fe or Ni shells. The analyses of TEM micrographs give the particle size and size distributions while the high-resolution TEM (HRTEM) micrographs show the existence of noble metal core lattices. The results confirm the formation of noble metal core-transition metal shell structures. -- Highlights: ► Chitosan-stabilized bimetallic nanoparticles were prepared at room temperature in aqueous solution. ► The presence of Fe or Ni shells was proven by XPS study. ► The existence of noble metal cores covered by amorphous shells was indicated by TEM study. ► The formation of noble metal core-transition metal shell structures was confirmed.

Syngas upgrading in a membrane reactor with thin Pd-alloy supported membrane

NARCIS (Netherlands)

Brunetti, A.; Caravella, A.; Fernandez Gesalaga, E.; Pacheco Tanaka, D. A.; Gallucci, F.; Drioli, E.; Curcio, E.; Viviente, J. L.; Barbieri, G.

2015-01-01

In hydrogen production, the syngas streams produced by reformers and/or coal gasification plants contain a large amount of H2 and CO in need of upgrading. To this purpose, reactors using Pd-based membranes have been widely studied as they allow separation and recovery of a pure hydrogen stream.

The effect of microemulsion composition on the morphology of Pd nanoparticles deposited at the surface of TiO{sub 2} and photoactivity of Pd-TiO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Długokęcka, Marta [Faculty of Chemistry, Gdańsk University of Technology, ul. G. Narutowicza 11/12, 80-233 Gdansk (Poland); Łuczak, Justyna, E-mail: justyna.luczak@pg.gda.pl [Faculty of Chemistry, Gdańsk University of Technology, ul. G. Narutowicza 11/12, 80-233 Gdansk (Poland); Polkowska, Żaneta [Faculty of Chemistry, Gdańsk University of Technology, ul. G. Narutowicza 11/12, 80-233 Gdansk (Poland); Zaleska-Medynska, Adriana, E-mail: adriana.zaleska@ug.edu.pl [Faculty of Chemistry, Gdańsk University of Technology, ul. G. Narutowicza 11/12, 80-233 Gdansk (Poland); Faculty of Chemistry, University of Gdansk, ul. Wita Stwosza 63, 80-308 Gdansk (Poland)

2017-05-31

Highlights: • Pd was deposited on TiO{sub 2} surface via microemulsion route (water-to-cyclohexane system). • Reaction parameters influencing the size distribution of Pd nanoparticles was investigated. • Photocatalytic activity was maximized at average droplet size of 2.83 ± 0.18 nm. • Superoxide radical was the dominant oxidizing species in the phenol degradation. - Abstract: A series of microemulsion (ME) system, constituted by different water to surfactant molar ratios (W{sub o}) and oil to surfactant mass ratios (S), have been applied for Pd-TiO{sub 2} preparation. The effect of ME properties on the morphology of Pd nanoparticles formed at TiO{sub 2} surface and an effect of Pd size and distribution on the surface and photocatalytic properties of Pd-TiO{sub 2} were investigated. Microemulsion systems were characterized by means of viscosity, density, dynamic light scattering as well as surface tension measurements to find a correlation between the conditions of Pd nanoparticles formation, their morphology and photocatalyst features. The photocatalysts were characterized by transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), UV–vis diffuse-reflectance spectroscopy (DRS), BET surface area and elemental analysis. The photocatalytic properties of Pd-modified TiO{sub 2} particles were studied in a model reaction of phenol photodegradation under Vis irradiation, as well as active species involved in the photocatalytic reaction were determined. Microemulsion composition was found to be a crucial parameter in determining the features of the TiO{sub 2}-based photocatalysts covered by metallic nanoparticles. The highest photocatalytic activity under Vis radiation was observed for the Pd-TiO{sub 2} sample (average diameter 2.4 nm) obtained using 0.1 mol% Pd in the ME system containing 1.5 wt% of water and 82.8 wt% of cyclohexane with average droplet size of 2.83 ± 0.18 nm. In this regard, synthesis of such metal-semiconductor composites

Enhancing the production of hydrogen via water-gas shift reaction using Pd-based membrane reactors

Energy Technology Data Exchange (ETDEWEB)

Mendes, Diogo; Chibante, Vania; Mendes, Adelio; Madeira, Luis M. [LEPAE, Chemical Engineering Department, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto (Portugal); Zheng, Ju-Meng [Dutch Separation Technology Institute (DSTI), 3800 AE Amersfoort (Netherlands); Tosti, Silvano; Borgognoni, Fabio [ENEA, Unita Tecnica Fusione, C.R. ENEA Frascati, Via E. Fermi 45, Frascati (RM) I-00044 (Italy)

2010-11-15

In this work, it is described an experimental study regarding the performance of a Pd-Ag membrane reactor recently proposed and suitable for the production of ultra-pure hydrogen. A dense metallic permeator tube was assembled by an innovative annealing and diffusion welding technique from a commercial flat sheet membrane of Pd-Ag. A ''finger-like'' configuration of the self-supported membrane has been designed and used as a packed-bed membrane reactor (MR) for producing ultra-pure hydrogen via water-gas shift reaction (WGS). A CuO/ZnO/Al{sub 2}O{sub 3} catalyst, from REB Research and Consulting, was used for packing the WGS membrane reactor. The performance of the reactor was evaluated in terms of CO conversion and H{sub 2} recovery in a wide range of conditions: temperature from 200 C to 300 C, feed pressure from 1.0 bar to 4.0 bar, vacuum and sweep-gas modes and with a simulated reformate feed (4.70% CO, 34.78% H{sub 2}O, 28.70% H{sub 2}, 10.16% CO{sub 2} balanced in N{sub 2}). Also, the effect of the reactants feed composition was investigated and discussed. CO conversions remained in most conditions above the thermodynamic equilibrium based on feed conditions. In particular, it is worth mentioning that around 100% of CO conversion and almost complete H{sub 2} recovery was achieved when operating the MR at 300 C with a GSHV = 1200 L{sub N} kg{sub cat}{sup -1} h{sup -1}, P{sub feed} = 4 bar, P{sub perm} = 3 bar and using 1000 mL{sub N} min{sup -1} of sweep-gas. (author)

Methanol and ethanol electrooxidation on Pt and Pd supported on carbon microspheres in alkaline media

Energy Technology Data Exchange (ETDEWEB)

Xu, Changwei; Cheng, Liqiang; Liu, Yingliang [Department of Chemistry and Institute of Nanochemistry, Jinan University, Guangzhou 510632 (China); Shen, Peikang [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China)

2007-05-15

Noble metal (Pt, Pd) electrocatalysts supported on carbon microspheres (CMS) are used for methanol and ethanol oxidation in alkaline media. The results show that noble metal electrocatalysts supported on carbon microspheres give better performance than that supported on carbon black. It is well known that palladium is not a good electrocatalyst for methanol oxidation, but it shows excellently higher activity and better steady-state electrolysis than Pt for ethanol electrooxidation in alkaline media. The results show a synergistic effect by the interaction between Pd and carbon microspheres. The Pd supported on carbon microspheres in this paper possesses excellent electrocatalytic properties and may be of great potential in direct ethanol fuel cells. (author)

Hybrid NiCoOx adjacent to Pd nanoparticles as a synergistic electrocatalyst for ethanol oxidation

Science.gov (United States)

Wang, Wei; Yang, Yan; Liu, Yanqin; Zhang, Zhe; Dong, Wenkui; Lei, Ziqiang

2015-01-01

To improve the electrocatalytic activity of Pd for ethanol oxidation, hybrid NiCoOx adjacent to Pd catalyst (Pd-NiCoOx/C) is successfully synthesized. Physical characterization shows NiCoOx is closely adjacent to Pd nanoparticles in Pd-NiCoOx/C catalyst, which leads to Strong Metal-Support Interactions (SMSI) between the NiCoOx and Pd nanoparticles, in favor of the electrocatalytic properties. The Pd-NiCoOx/C catalyst is estimated to own larger electrochemically active surface area than Pd/C and Pd-NiO/C catalysts. Moreover, compared to Pd/C catalyst, the onset potential of Pd-NiCoOx/C catalyst is negative 40 mV for ethanol oxidation. Noticeably, the current density of Pd-NiCoOx/C catalyst is 2.05 and 1.43 times higher contrasted to Pd/C and Pd-NiO/C catalysts accordingly. Importantly, the Pd-NiCoOx/C catalyst exhibits better stability during ethanol oxidation, which is a promising electrocatalyst for application in direct alkaline alcohol fuel cells.

Au@Pd core-shell nanobricks with concave structures and their catalysis of ethanol oxidation.

Science.gov (United States)

Wang, Wenjin; Zhang, Jie; Yang, Shengchun; Ding, Bingjun; Song, Xiaoping

2013-10-01

Au@Pd core-shell nanobricks (CNBs) with concave surfaces and Pd shells with a thickness of approximately 5 nm were synthesized by co-reduction of HAuCl4 and H2 PdCl4 in the presence of Au seeds and Ag ions. These as-synthesized concave CNBs exhibit significantly enhanced catalytic activity for the electrooxidation of ethanol in alkaline media compared to the commercially-used Pd black. The improved performance of the Au@Pd CNBs can be attributed to the exposed stepped surfaces, high-index facets, and the synergistic effects of the core and shell metals. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The crystal structures of jaguéite, Cu₂Pd₃Se₄, and chrisstanleyite, Ag₂Pd₃Se₄

DEFF Research Database (Denmark)

Topa, Dan; Makovicky, Emil; Balic Zunic, Tonci

2006-01-01

equipped with a CCD area-detector. The crystal structure of chrisstanleyite, ideally Ag2Pd3Se4, monoclinic a 5.676(2), b 10.342(4), c 6.341(2) Å, ß 114.996(4)º, space group P21/c, has been solved by direct methods and refi ned to an R1 index of 8.3% for 1203 unique refl ections measured with MoK X......The crystal structure of jaguéite, ideally Cu2Pd3Se4, monoclinic, a 5.672(5), b 9.909(9), c 6.264(6) Å, ß 115.40(2)º, space group P21/c, has been solved by direct methods and refi ned to an R1 index of 5.52% for 956 unique refl ections measured with MoK X-radiation on a P-4 Bruker diffractometer......(Ag)-Pd2 system of metal-metal bonds, help to stabilize the open-work structure composed of PdSe4 squares....

Arsenic Removal from Aqueous Solution Using Pure and Metal-Doped Titania Nanoparticles Coated on Glass Beads: Adsorption and Column Studies

Directory of Open Access Journals (Sweden)

M. Ihsan Danish

2013-01-01

Full Text Available Nanosized metal oxide, Titania, provides high surface area and specific affinity for the adsorption of heavy metals, including arsenic (As, which is posing a great threat to the world population due to its carcinogenic nature. In this study, As(III adsorption was studied on pure and metal- (Ag- and Fe- doped Titania nanoparticles. The nanoparticles were synthesized by liquid impregnation method with some modifications, with crystallite size in the range of 30 to 40 nm. Band gap analysis, using Kubelka-Munk function showed a shift of absorption band from UV to visible region for the metal-doped Titania. Effect of operational parameters like dose of nanoparticles, initial As(III concentration, and pH was evaluated at 25°C. The data obtained gave a good fit with Langmuir and Freundlich isotherms and the adsorption was found to conform to pseudo-second-order kinetics. In batch studies, over 90% of arsenic removal was observed for both types of metal-doped Titania nanoparticles from a solution containing up to 2 ppm of the heavy metal. Fixed bed columns of nanoparticles, coated on glass beads, were used for As(III removal under different operating conditions. Thomas and Yoon-Nelson models were applied to predict the breakthrough curves and to find the characteristic column parameters useful for process design. The columns were regenerated using 10% NaOH solution.

Spin-independent transparency of pure spin current at normal/ferromagnetic metal interface

Science.gov (United States)

Hao, Runrun; Zhong, Hai; Kang, Yun; Tian, Yufei; Yan, Shishen; Liu, Guolei; Han, Guangbing; Yu, Shuyun; Mei, Liangmo; Kang, Shishou

2018-03-01

The spin transparency at the normal/ferromagnetic metal (NM/FM) interface was studied in Pt/YIG/Cu/FM multilayers. The spin current generated by the spin Hall effect (SHE) in Pt flows into Cu/FM due to magnetic insulator YIG blocking charge current and transmitting spin current via the magnon current. Therefore, the nonlocal voltage induced by an inverse spin Hall effect (ISHE) in FM can be detected. With the magnetization of FM parallel or antiparallel to the spin polarization of pure spin currents ({{\\boldsymbol{σ }}}sc}), the spin-independent nonlocal voltage is induced. This indicates that the spin transparency at the Cu/FM interface is spin-independent, which demonstrates that the influence of spin-dependent electrochemical potential due to spin accumulation on the interfacial spin transparency is negligible. Furthermore, a larger spin Hall angle of Fe20Ni80 (Py) than that of Ni is obtained from the nonlocal voltage measurements. Project supported by the National Basic Research Program of China (Grant No. 2015CB921502), the National Natural Science Foundation of China (Grant Nos. 11474184 and 11627805), the 111 Project, China (Grant No. B13029), and the Fundamental Research Funds of Shandong University, China.

Selective recovery of Pd(II) from extremely acidic solution using ion-imprinted chitosan fiber: Adsorption performance and mechanisms

Energy Technology Data Exchange (ETDEWEB)

Lin, Shuo [School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Wei, Wei [School of Chemical Engineering, Chonbuk National University, Jeonbuk 561-756 (Korea, Republic of); Wu, Xiaohui; Zhou, Tao [School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Mao, Juan, E-mail: monicamao45@hust.edu.cn [School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Yun, Yeoung-Sang, E-mail: ysyun@jbnu.ac.kr [School of Chemical Engineering, Chonbuk National University, Jeonbuk 561-756 (Korea, Republic of)

2015-12-15

Highlights: • An acid-resisting chitosan fiber was prepared by ion-imprinting technique. • Pd(II) and ECH were as template and two-step crosslinking agent, respectively. • IIF showed a good adsorption and selectivity performance on Pd(II) solutions. • Selectivity was due to the electrostatic attraction between −NH{sub 3}{sup +} and [PdCl{sub 4}]{sup 2−}. • Stable sorption/desorption performance shows a potential in further application. - Abstract: A novel, selective and acid-resisting chitosan fiber adsorbent was prepared by the ion-imprinting technique using Pd(II) and epichlorohydrin as the template and two-step crosslinking agent, respectively. The resulting ion-imprinted chitosan fibers (IIF) were used to selectively adsorb Pd(II) under extremely acidic synthetic metal solutions. The adsorption and selectivity performances of IIF including kinetics, isotherms, pH effects, and regeneration were investigated. Pd(II) rapidly adsorbed on the IIF within 100 min, achieving the adsorption equilibrium. The isotherm results showed that the maximum Pd(II) uptake on the IIF was maintained as 324.6–326.4 mg g{sup −1} in solutions containing single and multiple metals, whereas the Pd(II) uptake on non-imprinted fibers (NIF) decreased from 313.7 to 235.3 mg g{sup −1} in solution containing multiple metals. Higher selectivity coefficients values were obtained from the adsorption on the IIF, indicating a better Pd(II) selectivity. The amine group, supposedly the predominant adsorption site for Pd(II), was confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The pH value played a significant role on the mechanism of the selective adsorption in the extremely acidic conditions. Furthermore, the stabilized performance for three cycles of sorption/desorption shows a potential for further large-scale applications.

Selective recovery of Pd(II) from extremely acidic solution using ion-imprinted chitosan fiber: Adsorption performance and mechanisms

International Nuclear Information System (INIS)

Lin, Shuo; Wei, Wei; Wu, Xiaohui; Zhou, Tao; Mao, Juan; Yun, Yeoung-Sang

2015-01-01

Highlights: • An acid-resisting chitosan fiber was prepared by ion-imprinting technique. • Pd(II) and ECH were as template and two-step crosslinking agent, respectively. • IIF showed a good adsorption and selectivity performance on Pd(II) solutions. • Selectivity was due to the electrostatic attraction between −NH_3"+ and [PdCl_4]"2"−. • Stable sorption/desorption performance shows a potential in further application. - Abstract: A novel, selective and acid-resisting chitosan fiber adsorbent was prepared by the ion-imprinting technique using Pd(II) and epichlorohydrin as the template and two-step crosslinking agent, respectively. The resulting ion-imprinted chitosan fibers (IIF) were used to selectively adsorb Pd(II) under extremely acidic synthetic metal solutions. The adsorption and selectivity performances of IIF including kinetics, isotherms, pH effects, and regeneration were investigated. Pd(II) rapidly adsorbed on the IIF within 100 min, achieving the adsorption equilibrium. The isotherm results showed that the maximum Pd(II) uptake on the IIF was maintained as 324.6–326.4 mg g"−"1 in solutions containing single and multiple metals, whereas the Pd(II) uptake on non-imprinted fibers (NIF) decreased from 313.7 to 235.3 mg g"−"1 in solution containing multiple metals. Higher selectivity coefficients values were obtained from the adsorption on the IIF, indicating a better Pd(II) selectivity. The amine group, supposedly the predominant adsorption site for Pd(II), was confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The pH value played a significant role on the mechanism of the selective adsorption in the extremely acidic conditions. Furthermore, the stabilized performance for three cycles of sorption/desorption shows a potential for further large-scale applications.

An investigation of the mimetic enzyme activity of two-dimensional Pd-based nanostructures

Science.gov (United States)

Wei, Jingping; Chen, Xiaolan; Shi, Saige; Mo, Shiguang; Zheng, Nanfeng

2015-11-01

In this work, we investigated the mimetic enzyme activity of two-dimensional (2D) Pd-based nanostructures (e.g. Pd nanosheets, Pd@Au and Pd@Pt nanoplates) and found that they possess intrinsic peroxidase-, oxidase- and catalase-like activities. These nanostructures were able to activate hydrogen peroxide or dissolved oxygen for catalyzing the oxidation of organic substrates, and decompose hydrogen peroxide to generate oxygen. More systematic investigations revealed that the peroxidase-like activities of these Pd-based nanomaterials were highly structure- and composition-dependent. Among them, Pd@Pt nanoplates displayed the highest peroxidase-like activity. Based on these findings, Pd-based nanostructures were applied for the colorimetric detection of H2O2 and glucose, and also the electro-catalytic reduction of H2O2. This work offers a promising prospect for the application of 2D noble metal nanostructures in biocatalysis.In this work, we investigated the mimetic enzyme activity of two-dimensional (2D) Pd-based nanostructures (e.g. Pd nanosheets, Pd@Au and Pd@Pt nanoplates) and found that they possess intrinsic peroxidase-, oxidase- and catalase-like activities. These nanostructures were able to activate hydrogen peroxide or dissolved oxygen for catalyzing the oxidation of organic substrates, and decompose hydrogen peroxide to generate oxygen. More systematic investigations revealed that the peroxidase-like activities of these Pd-based nanomaterials were highly structure- and composition-dependent. Among them, Pd@Pt nanoplates displayed the highest peroxidase-like activity. Based on these findings, Pd-based nanostructures were applied for the colorimetric detection of H2O2 and glucose, and also the electro-catalytic reduction of H2O2. This work offers a promising prospect for the application of 2D noble metal nanostructures in biocatalysis. Electronic supplementary information (ESI) available: TEM images, EDX and dispersion stability of Pd-based nanomaterials

Optical characterization of broad plasmon resonances of Pd/Pt nanoparticles

Science.gov (United States)

Valizade-Shahmirzadi, N.; Pakizeh, T.

2018-04-01

In this paper, optical properties of nanoparticles (nanodisks and nanospheres) composed of photofunctional metals like palladium (Pd) and platinum (Pt) over a large dimension range are investigated using the electromagnetic simulation and quasi-static theory. These characteristics are compared with their counterparts in plasmonic gold (Au) nanoparticles. Pd/Pt-nanodisks with larger dimension have higher absorption and lower scattering efficiencies than Au-nanodisks that accompany with lower extinction efficiencies and broader resonances. Although an increment in the dimension (diameter and height) of Au/Pd/Pt-nanoparticles decreases the absorption-to-scattering ratios, these ratios are less sensitive to the height size in Au-nanodisks, which causes their LSPR spectra become much broader. It is noteworthy that the LSPR quality factor of Pd nanoparticles is improved by considering the radiative damping and depolarization in quasi-static method unlike the Au nanoparticles. The importance of the highly absorptive Pd/Pt nanoparticles can be traced in the photo-functionalized and energy applications.

Pd-Ag membrane reactor for steam reforming reactions: a comparison between different fuels

NARCIS (Netherlands)

Gallucci, F.; Basile, A.

2008-01-01

The simulation of a dense Pd-based membrane reactor for carrying out the methane, the methanol and the ethanol steam reforming (SR) reactions for pure hydrogen production is performed. The same simulation is also performed in a traditional reactor. This modelling work shows that the use of membrane

Sensorial status in patients with pure accomodative esotropia.

Science.gov (United States)

Castro-Vite, O I; Vargas-Ortega, A J; Aguilar-Ruiz, A; Murillo-Correa, C E

2016-12-01

To evaluate the sensorial status in patients with pure accommodative esotropia. Ambispective study, patients with pure accommodative esotropia that were found in orthotropy when using its correction glasses were included. 67 patients were included, mean age was 3.68±1.28 years, the near and far ocular deviation was 19±8.8 PD and 18.71±10.61 PD respectively. The visual acuity in the right eye was 0.183 ±0.11 logMAR, in the left eye was 0.188±0.12 logMAR. The average spherical equivalent was +5.50 diopters, for the right eye was +5.46 ±1.61 diopters and for the left eye +5.71 v±1.6 diopters. The average AC/A ratio was 5.19±0.92 Δ/1. 90% of the patients had a grade of near stereopsis: 42% had stereopsis equal or better to 70 arc seconds and 81% had stereopsis equal or better to 400 arc seconds, having an average of 205 arc seconds. 85% of the patients had some grade of far stereopsis: 16% had stereopsis equal or better to 70 arc seconds and 66% had a stereopsis equal or better to 400 arc seconds, having an average of 334.9 arc seconds. There was not statistically significant correlation between the grade of deviation and the stereopsis when using its correction. This study has detected that the sensorial status is compromised even with adequate and appropriate treatment, nevertheless, there is a low frequency of amblyopia. Copyright © 2016 Sociedad Española de Oftalmología. Publicado por Elsevier España, S.L.U. All rights reserved.

Pd supported on carbon containing nickel, nitrogen and sulfur for ethanol electrooxidation.

Science.gov (United States)

Yang, Zi-Rui; Wang, Shang-Qing; Wang, Jing; Zhou, Ai-Ju; Xu, Chang-Wei

2017-11-13

Carbon material containing nickel, nitrogen and sulfur (Ni-NSC) has been synthesized using metal-organic frameworks (MOFs) as precursor by annealing treatment with a size from 200 to 300 nm. Pd nanoparticles supported on the Ni-NSC (Pd/Ni-NSC) are used as electrocatalysts for ethanol oxidation in alkaline media. Due to the synergistic effect between Pd and Ni, S, N, free OH radicals can form on the surface of Ni, N and S atoms at lower potentials, which react with CH 3 CO intermediate species on the Pd surface to produce CH 3 COO - and release the active sites. On the other hand, the stronger binding force between Pd and co-doped N and S is responsible for enhancing dispersion and preventing agglomeration of the Pd nanoparticles. The Pd(20 wt%)/Ni-NSC shows better electrochemical performance of ethanol oxidation than the traditional commercial Pd(20 wt%)/C catalyst. Onset potential on the Pd(20 wt%)/Ni-NSC electrode is 36 mV more negative compared with that on the commercial Pd(20 wt%)/C electrode. The Pd(20 wt%)/Ni-NSC in this paper demonstrates to have excellent electrocatalytic properties and is considered as a promising catalyst in alkaline direct ethanol fuel cells.

Texture-dependent twin formation in nanocrystalline thin Pd films

International Nuclear Information System (INIS)

Wang, B.; Idrissi, H.; Shi, H.; Colla, M.S.; Michotte, S.; Raskin, J.P.; Pardoen, T.; Schryvers, D.

2012-01-01

Nanocrystalline Pd films were produced by electron-beam evaporation and sputter deposition. The electron-beam-evaporated films reveal randomly oriented nanograins with a relatively high density of growth twins, unexpected in view of the high stacking fault energy of Pd. In contrast, sputter-deposited films show a clear 〈1 1 1〉 crystallographic textured nanostructure without twins. These results provide insightful information to guide the generation of microstructures with enhanced strength/ductility balance in high stacking fault energy nanocrystalline metallic thin films.

Carbon supported Pd-Co-Mo alloy as an alternative to Pt for oxygen reduction in direct ethanol fuel cells

Energy Technology Data Exchange (ETDEWEB)

Rao, Ch. Venkateswara [National Centre for Catalysis Research, Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036, TN (India); Viswanathan, B., E-mail: bvnathan@acer.iitm.ernet.i [National Centre for Catalysis Research, Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036, TN (India)

2010-03-01

Carbon black (CDX975) supported Pd and Pd-Co-Mo alloy nanoparticles are prepared by the reduction of metal precursors with hydrazine in reverse microemulsion of water/Triton-X-100/propanol-2/cyclohexane. The as-synthesized Pd-Co-Mo/CDX975 is heat treated at 973, 1073 and 1173 K to promote alloy formation. The prepared materials are characterized by powder XRD and EDX. Face-centred cubic structure of Pd is evident from XRD. The chemical composition of the respective elements in the catalysts is evaluated from the EDX analysis and observed that it is in good agreement with initial metal precursor concentrations. Oxygen reduction measurements performed by linear sweep voltammetry indicate the good catalytic activity of Pd-Co-Mo alloys compared to Pd. This is due to the suppression of (hydr)oxy species on Pd surface by the presence of alloying elements, Co and Mo. Among the investigated catalysts, heat-treated Pd-Co-Mo/CDX975 at 973 K exhibited good ORR activity compared to the catalysts heat treated at 1073 and 1173 K. This is due to the small crystallite size and high surface area. Rotating disk electrode (RDE) measurements indicated the comparable ORR activity of heat-treated Pd-Co-Mo/CDX975 at 973 K with that of commercial Pt/C. Kinetic analysis reveals that the ORR on Pd-Co-Mo/CDX975 follows the four-electron pathway leading to water. Moreover, Pd-Co-Mo/CDX975 exhibited substantially higher ethanol tolerance during the ORR than Pt/C. Good dispersion of metallic nanoparticles on the carbon support is observed from HRTEM images. Single-cell direct ethanol fuel cell tests indicated the comparable performance of Pd-Co-Mo/CDX975 with that of commercial Pt/C. Stability under DEFC operating conditions for 50 h indicated the good stability of Pd-Co-Mo/CDX975 compared with that of Pt/C.

Fusion of 110Pd with 110Pd

International Nuclear Information System (INIS)

Morawek, W.

1991-07-01

In the framework of this thesis the excitation functions of the systems 110 Pd + 110 Pd and 110 Pd + 104 Ru could be measured. The evaporation-residual-nucleus cross sections is deviating from lighter systems dominated by channels, which arise from evaporation of α particles. In the reaction 110 Pd + 110 Pd no xn channels were observed. In comparison to other reactions qualitatively a strong fusion hindrance of this system is shown. (orig./HSI) [de

Surfactant-controlled synthesis of Pd/Ce{sub 0.6}Zr{sub 0.4}O{sub 2} catalyst for NO reduction by CO with excess oxygen

Energy Technology Data Exchange (ETDEWEB)

Chen, L.F. [Laboratorio de Catalisis y Materiales, SEPI-ESIQIE, Instituto Politecnico Nacional, Av. Politecnico S/N, Col. Zacatenco, 07738 Mexico D.F. (Mexico); Departamento de Ingenieria Quimica, Universidad Autonoma Metropolitana-A, Av. San Pablo 180, Col. Reynosa-Tamaulipas, 02200 Mexico D.F. (Mexico); Gonzalez, G. [Laboratorio de Catalisis y Materiales, SEPI-ESIQIE, Instituto Politecnico Nacional, Av. Politecnico S/N, Col. Zacatenco, 07738 Mexico D.F. (Mexico); Wang, J.A. [Laboratorio de Catalisis y Materiales, SEPI-ESIQIE, Instituto Politecnico Nacional, Av. Politecnico S/N, Col. Zacatenco, 07738 Mexico D.F. (Mexico)]. E-mail: jwang@ipn.mx; Norena, L.E. [Departamento de Ingenieria Quimica, Universidad Autonoma Metropolitana-A, Av. San Pablo 180, Col. Reynosa-Tamaulipas, 02200 Mexico D.F. (Mexico); Toledo, A. [Grupo de Molecular Ingenieria, Instituto Mexicano del Petroleo, Eje Lazaro Cardenas 152, 07730 Mexico D.F. (Mexico); Castillo, S. [Grupo de Molecular Ingenieria, Instituto Mexicano del Petroleo, Eje Lazaro Cardenas 152, 07730 Mexico D.F. (Mexico); Moran-Pineda, M. [Grupo de Molecular Ingenieria, Instituto Mexicano del Petroleo, Eje Lazaro Cardenas 152, 07730 Mexico D.F. (Mexico)

2005-04-30

For the first time, this work reports a surfactant-controlled synthetic method to obtain a nanophase of mesoporous ceria-zirconia solid solution containing cationic defects in the crystalline structure. The incorporation of a cationic surfactant (myristyltrimethylammonium bromide) into the ceria-zirconia solid network not only controlled the pore diameter distribution but also induced creation of the lattice defect. Ceria-zirconia solid solution showed crystal microstrain and structural distortion that varied with the calcination temperature. Compared to pure ceria, the addition of zirconium to the ceria promoted the bulk oxygen reducibility and enhanced the thermal stability of the solid. Hydrogen could be stored into or released from the PdO/Ce{sub 0.6}Zr{sub 0.4}O{sub 2} catalyst during the TPR procedure, which is associated to the formation/decomposition of a PdH{sub x} phase, due to the hydrogen dissociation catalyzed by metallic Pd. At cool start of reaction, NO reduction by CO with excess oxygen over the Pd/Ce{sub 0.6}Zr{sub 0.4}O{sub 2} catalyst showed selectivity around 100% to N{sub 2}. A competition between NO reduction by CO and CO oxidation by O{sub 2} was observed: at reaction temperatures below 200 deg. C, NO inhibited CO oxidation activity; however, at reaction temperatures above 200 deg. C, high activity of CO oxidation resulted in an inhibition effect on NO reduction.

Exchange-Dominated Pure Spin Current Transport in Alq3 Molecules.

Science.gov (United States)

Jiang, S W; Liu, S; Wang, P; Luan, Z Z; Tao, X D; Ding, H F; Wu, D

2015-08-21

We address the controversy over the spin transport mechanism in Alq3 utilizing spin pumping in the Y3Fe5O12/Alq3/Pd system. An unusual angular dependence of the inverse spin Hall effect is found. It, however, disappears when the microwave magnetic field is fully in the sample plane, excluding the presence of the Hanle effect. Together with the quantitative temperature-dependent measurements, these results provide compelling evidence that the pure spin current transport in Alq3 is dominated by the exchange-mediated mechanism.

The electrochemical atomic layer deposition of Pt and Pd nanoparticles on Ni foam for the electro oxidation of alcohols

CSIR Research Space (South Africa)

Modibedi, RM

2013-01-01

Full Text Available procedure The chemicals used in the preparation were Platinum solution (1mM H2PtCl6 pH = 1, SA Precious Metals), Pd solution (1mM PdCl2 pH = 1, SA Precious Metals), (copper sulphate solution (1mM CuSO4.5H2O pH = 1, Merck) were prepared in perchloric...

Ultra-pure soft water ameliorates atopic skin disease by preventing metallic soap deposition in NC/Tnd mice and reduces skin dryness in humans.

Science.gov (United States)

Tanaka, Akane; Matsuda, Akira; Jung, Kyungsook; Jang, Hyosun; Ahn, Ginnae; Ishizaka, Saori; Amagai, Yosuke; Oida, Kumiko; Arkwright, Peter D; Matsuda, Hiroshi

2015-09-01

Mineral ions in tap water react with fatty acids in soap, leading to the formation of insoluble precipitate (metallic soap) on skin during washing. We hypothesised that metallic soap might negatively alter skin conditions. Application of metallic soap onto the skin of NC/Tnd mice with allergic dermatitis further induced inflammation with elevation of plasma immunoglobulin E and proinflammatory cytokine expression. Pruritus and dryness were ameliorated when the back of mice was washed with soap in Ca2+- and Mg2+-free ultra-pure soft water (UPSW). Washing in UPSW, but not tap water, also protected the skin of healthy volunteers from the soap deposition. Furthermore, 4 weeks of showering with UPSW reduced dryness and pruritus of human subjects with dry skin. Washing with UPSW may be therapeutically beneficial in patients with skin troubles.

TiO2 Nanorods Decorated with Pd Nanoparticles for Enhanced Liquefied Petroleum Gas Sensing Performance.

Science.gov (United States)

Dhawale, Dattatray S; Gujar, Tanaji P; Lokhande, Chandrakant D

2017-08-15

Development of highly sensitive and selective semiconductor-based metal oxide sensor devices to detect toxic, explosive, flammable, and pollutant gases is still a challenging research topic. In the present work, we systematically enhanced the liquefied petroleum gas (LPG) sensing performance of chemical bath deposited TiO 2 nanorods by decorating Pd nanoparticle catalyst. Surface morphology with elemental mapping, crystal structure, composition and oxidation states, and surface area measurements of pristine TiO 2 and Pd:TiO 2 nanorods was examined by high resolution transmission electron microscopy with energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and nitrogen adsorption-desorption characterization techniques. LPG sensing performance of pristine TiO 2 and Pd:TiO 2 nanorods was investigated in different LPG concentration and operating temperature ranges. The LPG response of 21% for pristine TiO 2 nanorods is enhanced to 49% after Pd catalyst decoration with reasonably fast response and recovery times. Further, the sensor exhibited long-term stability, which could be due to the strong metal support (Pd:TiO 2 ) interaction and catalytic properties offered by the Pd nanoparticle catalyst. The work described herein demonstrates a general and scalable approach that provides a promising route for rational design of variety of sensor devices for LPG detection.

A Comprehensive Study on the Electronic State of Hydrogen in α-Phase PdH(D)x-Does a Chemical Bond Between Pd and H(D) Exist?

Science.gov (United States)

Dekura, Shun; Kobayashi, Hirokazu; Ikeda, Ryuichi; Maesato, Mitsuhiko; Yoshino, Haruka; Ohba, Masaaki; Ishimoto, Takayoshi; Kawaguchi, Shogo; Kubota, Yoshiki; Yoshioka, Satoru; Matsumura, Syo; Sugiyama, Takeharu; Kitagawa, Hiroshi

2018-06-12

The palladium(Pd)-hydrogen(H) system is one of the most famous hydrogen storage systems. Although there has been much research on β-phase PdH(D)x, we comprehensively investigated the nature of the interaction between Pd and H(D) in α-phase PdH(D)x (x H(D) chemical bond for the first time, by various in situ experimental techniques and first-principles theoretical calculations. The lattice expansion by H(D) dissolution in the α-phase lattice suggests the existence of interaction between Pd and H(D). The decrease of magnetic susceptibility and the increase of electrical resistivity indicate that the electronic states are changed by the H(D) dissolution in the α phase. In situ solid-state 1H and 2H NMR results and first-principles theoretical calculations revealed that a Pd-H(D) chemical bond exists in the α phase, but the bonding character of the Pd-H(D) chemical bond in the α phase is quite different from that in the β phase; the nature of the Pd-H(D) chemical bond in the α phase is a localized covalent bond whereas that in the β phase is a metallic bond. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Oxidation behaviour of metallic glass foams

Energy Technology Data Exchange (ETDEWEB)

Barnard, B.R. [Department of Materials Science and Engineering, 434 Dougherty Hall, University of Tennessee, Knoxville, TN 37996-2200 (United States)], E-mail: bbarnard@utk.edu; Liaw, P.K. [Department of Materials Science and Engineering, 434 Dougherty Hall, University of Tennessee, Knoxville, TN 37996-2200 (United States); Demetriou, M.D.; Johnson, W.L. [Department of Materials Science, Keck Laboratory, California Institute of Technology, Pasadena, CA 91125 (United States)

2008-08-15

In this study, the effects of porosity on the oxidation behaviour of bulk-metallic glasses were investigated. Porous Pd- and Fe-based bulk-metallic glass (BMG) foams and Metglas ribbons were studied. Oxidizing experiments were conducted at 70 deg. C, and around 80 deg. C below glass-transition temperatures, (T{sub g}s). Scanning-electron microscopy/energy-dispersive spectroscopy (SEM/EDS) studies revealed little evidence of oxidation at 70 deg. C. Specimens exhibited greater oxidation at T{sub g} - 80 deg. C. Oxides were copper-based for Pd-based foams, Fe-, Cr-, and Mo-based for Fe-based foams, and Co-based with borosilicates likely for the Metglas. Pd-based foams demonstrated the best oxidation resistance, followed by Metglas ribbons, followed by Fe-based foams.

Ultrahigh vacuum dc magnetron sputter-deposition of epitaxial Pd(111)/Al2O3(0001) thin films.

Science.gov (United States)

Aleman, Angel; Li, Chao; Zaid, Hicham; Kindlund, Hanna; Fankhauser, Joshua; Prikhodko, Sergey V; Goorsky, Mark S; Kodambaka, Suneel

2018-05-01

Pd(111) thin films, ∼245 nm thick, are deposited on Al 2 O 3 (0001) substrates at ≈0.5 T m , where T m is the Pd melting point, by ultrahigh vacuum dc magnetron sputtering of Pd target in pure Ar discharges. Auger electron spectra and low-energy electron diffraction patterns acquired in situ from the as-deposited samples reveal that the surfaces are compositionally pure 111-oriented Pd. Double-axis x-ray diffraction (XRD) ω-2θ scans show only the set of Pd 111 peaks from the film. In triple-axis high-resolution XRD, the full width at half maximum intensity Γ ω of the Pd 111 ω-rocking curve is 630 arc sec. XRD 111 pole figure obtained from the sample revealed six peaks 60°-apart at a tilt angles corresponding to Pd 111 reflections. XRD ϕ scans show six 60°-rotated 111 peaks of Pd at the same ϕ angles for 11[Formula: see text]3 of Al 2 O 3 based on which the epitaxial crystallographic relationships between the film and the substrate are determined as [Formula: see text]ǁ[Formula: see text] with two in-plane orientations of [Formula: see text]ǁ[Formula: see text] and [Formula: see text]ǁ[Formula: see text]. Using triple axis symmetric and asymmetric reciprocal space maps, interplanar spacings of out-of-plane (111) and in-plane (11[Formula: see text]) are found to be 0.2242 ± 0.0003 and 0.1591 ± 0.0003 nm, respectively. These values are 0.18% lower than 0.2246 nm for (111) and the same, within the measurement uncertainties, as 0.1588 nm for (11[Formula: see text]) calculated from the bulk Pd lattice parameter, suggesting a small out-of-plane compressive strain and an in-plane tensile strain related to the thermal strain upon cooling the sample from the deposition temperature to room temperature. High-resolution cross-sectional transmission electron microscopy coupled with energy dispersive x-ray spectra obtained from the Pd(111)/Al 2 O 3 (0001) samples indicate that the Pd-Al 2 O 3 interfaces are essentially atomically abrupt and

Functionalised metal-organic frameworks : A novel approach to stabilising single metal atoms

NARCIS (Netherlands)

Szilagyi, P.A.; Rogers, D. M.; Zaiser, I.; Callini, E; Turner, Stuart; Borgschulte, A; Züttel, A.; Geerlings, J.J.C.; Hirscher, M; Dam, B.

2017-01-01

We have investigated the potential of metal-organic frameworks for immobilising single atoms of transition metals using a model system of Pd supported on NH₂-MIL-101(Cr). Our transmission electron microscopy and in situ Raman spectroscopy results give evidence for the first time that

Catalytic reduction of nitrate and nitrite ions by hydrogen : investigation of the reaction mechanism over Pd and Pd-Cu catalysts

NARCIS (Netherlands)

Ilinitch, OM; Nosova, LV; Gorodetskii, VV; Ivanov, VP; Trukhan, SN; Gribov, EN; Bogdanov, SV; Cuperus, FP

2000-01-01

The catalytic behavior of mono- and bimetallic catalysts with Pd and/or Cu supported over gamma-Al2O3 in the reduction of aqueous nitrate and nitrite ions by hydrogen was investigated. The composition of the supported metal catalysts was analysed using secondary ion mass spectroscopy (SIMS) and

Noble-Metal Chalcogenide Nanotubes

Directory of Open Access Journals (Sweden)

Nourdine Zibouche

2014-10-01

Full Text Available We explore the stability and the electronic properties of hypothetical noble-metal chalcogenide nanotubes PtS2, PtSe2, PdS2 and PdSe2 by means of density functional theory calculations. Our findings show that the strain energy decreases inverse quadratically with the tube diameter, as is typical for other nanotubes. Moreover, the strain energy is independent of the tube chirality and converges towards the same value for large diameters. The band-structure calculations show that all noble-metal chalcogenide nanotubes are indirect band gap semiconductors. The corresponding band gaps increase with the nanotube diameter rapidly approaching the respective pristine 2D monolayer limit.

Charge-exchange neutral hydrogen measurements in TFTR using Pd-MOS microsensors

International Nuclear Information System (INIS)

Bastasz, R.; Kilpatrick, S.J.; Ruzic, D.N.

1991-06-01

An array of Pd-metal-oxide semiconductor (Pd-MOS) diodes has been used to monitor the fluence and energy of charge-exchange neutral hydrogen isotopes striking the wall of the Tokamak Fusion Test Reactor (TFTR). The array was positioned 4 cm behind the graphite-tiled wall at the toroidal midplane and exposed to several hundred plasma discharges. Hydrogen isotopes striking the Pd-MOS diodes were detected by measuring the leakage current, which is affected by the presence of these species at the Pd/SiO 2 interface. It was found that the midplane flux strongly increased for neutral-beam heated plasmas and correlated with co-injected neutral beam power. The majority of the neutral flux was <50 eV in energy but its energy distribution extended to above 500 eV. 20 refs., 4 figs

Radiation effects on metals, alloys and cement

International Nuclear Information System (INIS)

Lucki, G.; Sciani, V.

1988-12-01

High - energy particle irradiation of materials brings as a consequence changes in their atomic structures that alter the electrical, magnetic and mechanical properties which are the most important characteristics for practical applications of metals and alloys. A review is made on experimental results of in-pile (IEA-RI reactor) and CV-28 cyclotron irradiated materials. Resistivity measurements on CuPd and FeNi alloys showed different behaviour during fast neutron irradiation. While CuPd had almost coincidental relaxation curves, FeNi presented a distinguishable short and long-range ordering with the critical order-disorder temperature at 515 0 C. Vacancy supersaturation curves of FeNiSi (49-49-2 at %), FeNiCr (49-95-49, 95-0,1 at. %), FeNiMo (50-50 at.% + 50 ppm) and pure FeNi (50-50 at.%), determined by means of the Magnetic After Effect are presented as an effective pre-selection method of nuclear materials before the destructive stage of void formation and swelling. A displacement of damage peak from 480 to 500 and 570 0 C was detected on pure AISI 321 stainless steel and with 0,05 wt.% and 0,10 wt.% of Nb additions by means of resistivity and micro-hardness. Ultrasound techniques applied to fast neutron irradiated portland cement paste (fluence 7,2 x 10 18 n/cm 2 ) showed a 24% decrease in its dynamic elasticity modulus. Helium diffusion on Au, Ag and Al foils irradiated in cyclotron was studied, suggesting a vacancy mechanism for single He atom diffusion. Embrittlement by Alpha particle implantation in cyclotron to simulate in-pile (n,α) reaction-was measured by high temperature creep on AISI 316 stainles steel. (author) [pt

Hydrogen-Induced Buckling of Pd Films Deposited on Various Substrates

KAUST Repository

Vlček, Marián

2015-07-01

A Pd-H system is a model system suitable for studying interactions of hydrogen with metals. In the present work, we studied hydrogen-induced buckling of thin Pd films deposited on various substrates with different bonding strengths (sapphire, glimmer) and also the effect of deposition temperature. Lattice expansion and phase transitions were investigated by X-ray diffraction of synchrotron radiation. The influence of the substrate and microstructure of the film on the buckling process and phase transformation to palladium hydride are discussed.

Hydrogen-Induced Buckling of Pd Films Deposited on Various Substrates

KAUST Repository

Vlček, Mariá n; Luká č, František; Vlach, Martin; Prochá zka, Ivan; Wagner, Stefan; Uchida, Helmut; Pundt, Astrid; Gemma, Ryota; Čí žek, Jakub

2015-01-01

A Pd-H system is a model system suitable for studying interactions of hydrogen with metals. In the present work, we studied hydrogen-induced buckling of thin Pd films deposited on various substrates with different bonding strengths (sapphire, glimmer) and also the effect of deposition temperature. Lattice expansion and phase transitions were investigated by X-ray diffraction of synchrotron radiation. The influence of the substrate and microstructure of the film on the buckling process and phase transformation to palladium hydride are discussed.

Liquid phase catalytic hydrodebromination of tetrabromobisphenol A on supported Pd catalysts

International Nuclear Information System (INIS)

Wu, Ke; Zheng, Mengjia; Han, Yuxiang; Xu, Zhaoyi; Zheng, Shourong

2016-01-01

Highlights: • Pd catalysts supported on TiO_2, CeO_2, Al_2O_3 and SiO_2 were prepared. • Deposition-precipitation method resulted in positively charged smaller Pd particle. • Complete debromination of tetrabromobisphenol A could be achieved on Pd/TiO_2. • Pd/TiO_2 prepared by the deposition-precipitation method was more active. - Abstract: Tetrabromobisphenol A (TBBPA) is a widely used brominated flame retardant and reductive debromination is an effective method for the abatement of TBBPA pollution. In this study, Pd catalysts supported on TiO_2, CeO_2, Al_2O_3 and SiO_2 were prepared by the impregnation (the resulting catalyst denoted as im-Pd/support), deposition-precipitation (the resulting catalyst denoted as dp-Pd/support), and photo-deposition (the resulting catalyst denoted as pd-Pd/support) methods. The catalysts were characterized by N_2 adsorption-desorption isotherm, X-ray diffraction, transmission electron microscopy, measurement of zeta potential, CO chemisorption, and X-ray photoelectron spectroscopy. The results showed that at an identical Pd loading amount (2.0 wt.%) Pd particle size in dp-Pd/TiO_2 was much smaller than those in im-Pd/TiO_2 and pd-Pd/TiO_2. Pd particle size of the dp-Pd/TiO_2 catalyst increased with Pd loading amount. Additionally, Pd particles in the dp-Pd/TiO_2 catalysts were positively charged due to the strong metal-support interaction, whereas the cationization effect was gradually attenuated with the increase of Pd loading amount. For the liquid phase catalytic hydrodebromination (HDB) of TBBPA, tri-bromobisphenol A (tri-BBPA), di-bromobisphenol A (di-BBPA), and mono-bromobisphenol A (mono-BBPA) were identified as the intermediate products, indicative of a stepwise debromination process. The catalytic HDB of TBBPA followed the Langmuir-Hinshelwood model, reflecting an adsorption enhanced catalysis mechanism. At an identical Pd loading amount, the Pd catalyst supported on TiO_2 exhibited a much higher catalytic activity

Transformation of Unsaturated Fatty Acids/Esters to Corresponding Keto Fatty Acids/Esters by Aerobic Oxidation with Pd(II)/Lewis Acid Catalyst.

Science.gov (United States)

Senan, Ahmed M; Zhang, Sicheng; Zeng, Miao; Chen, Zhuqi; Yin, Guochuan

2017-08-16

Utilization of renewable biomass to partly replace the fossil resources in industrial applications has attracted attention due to the limited fossil feedstock with the increased environmental concerns. This work introduced a modified Wacker-type oxidation for transformation of unsaturated fatty acids/esters to the corresponding keto fatty acids/esters, in which Cu 2+ cation was replaced with common nonredox metal ions, that is, a novel Pd(II)/Lewis acid (LA) catalyst. It was found that adding nonredox metal ions can effectively promote Pd(II)-catalyzed oxidation of unsaturated fatty acids/esters to the corresponding keto fatty acids/esters, even much better than Cu 2+ , and the promotional effect is highly dependent on the Lewis acidity of added nonredox metal ions. The improved catalytic efficiency is attributed to the formation of heterobimetallic Pd(II)/LA species, and the oxidation mechanism of this Pd(II)/LA catalyst is also briefly discussed.

3D-macroporous chitosan-based scaffolds with in situ formed Pd and Pt nanoparticles for nitrophenol reduction.

Science.gov (United States)

Berillo, Dmitriy; Cundy, Andrew

2018-07-15

3D-macroporous chitosan-based scaffolds (cryogels) were produced via growth of metal-polymer coordinated complexes and electrostatic interactions between oppositely charged groups of chitosan and metal ions under subzero temperatures. A mechanism of reduction of noble metal complexes inside the cryogel walls by glutaraldehyde is proposed, which produces discrete and dispersed noble metal nanoparticles. 3D-macroporous scaffolds prepared under different conditions were characterised using TGA, FTIR, nitrogen adsorption, SEM, EDX and TEM, and the distribution of platinum nanoparticles (PtNPs) and palladium nanoparticles (PdNPs) in the material assessed. The catalytic activity of the in situ synthesised PdNPs, at 2.6, 12.5 and 21.0 μg total mass, respectively, was studied utilising a model system of 4-nitrophenol reduction. The kinetics of the reaction under different conditions (temperature, concentration of catalyst) were examined, and a decrease of catalytic activity was not observed over 17 treatment cycles. Increasing the temperature of the catalytic reaction from 10 to 22 and 35 °C by PdNPs supported within the cryogel increased the kinetic rate by 44 and 126%, respectively. Turnover number and turnover frequency of the PdNPs catalysts at room temperature were in the range 0.20-0.53 h -1 . The conversion degree of 4-nitrophenol at room temperature reached 98.9% (21.0 μg PdNPs). Significantly less mass of palladium nanoparticles (by 30-40 times) was needed compared to published data to obtain comparable rates of reduction of 4-nitrophenol. Copyright © 2018 Elsevier Ltd. All rights reserved.

Carbon Supported Oxide-Rich Pd-Cu Bimetallic Electrocatalysts for Ethanol Electrooxidation in Alkaline Media Enhanced by Cu/CuOx

Directory of Open Access Journals (Sweden)

Zengfeng Guo

2016-04-01

Full Text Available Different proportions of oxide-rich PdCu/C nanoparticle catalysts were prepared by the NaBH4 reduction method, and their compositions were tuned by the molar ratios of the metal precursors. Among them, oxide-rich Pd0.9Cu0.1/C (Pd:Cu = 9:1, metal atomic ratio exhibits the highest electrocatalytic activity for ethanol oxidation reaction (EOR in alkaline media. X-ray photoelectron spectroscopy (XPS and high resolution transmission electron microscopy (HRTEM confirmed the existence of both Cu and CuOx in the as-prepared Pd0.9Cu0.1/C. About 74% of the Cu atoms are in their oxide form (CuO or Cu2O. Besides the synergistic effect of Cu, CuOx existed in the Pd-Cu bimetallic nanoparticles works as a promoter for the EOR. The decreased Pd 3d electron density disclosed by XPS is ascribed to the formation of CuOx and the spill-over of oxygen-containing species from CuOx to Pd. The low Pd 3d electron density will decrease the adsorption of CH3COads intermediates. As a result, the electrocatalytic activity is enhanced. The onset potential of oxide-rich Pd0.9Cu0.1/C is negative shifted 150 mV compared to Pd/C. The oxide-rich Pd0.9Cu0.1/C also exhibited high stability, which indicated that it is a candidate for the anode of direct ethanol fuel cells (DEFCs.

H{sub 2} dissociation on γ-Al{sub 2}O{sub 3} supported Cu/Pd atoms: A DFT investigation

Energy Technology Data Exchange (ETDEWEB)

Wang, Hongtao [College of Environmental Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Key Laboratory of Coal Science and Technology of Shanxi Province and Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Chen, Lijuan [Key Laboratory of Coal Science and Technology of Shanxi Province and Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Lv, Yongkang, E-mail: lykang@tyut.edu.cn [Key Laboratory of Coal Science and Technology of Shanxi Province and Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Ren, Ruipeng, E-mail: s2003wht@126.com [Key Laboratory of Coal Science and Technology of Shanxi Province and Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China)

2014-01-30

The density functional theory (DFT) was applied to investigate the promotion effects of single Cu and Pd atoms deposition on γ-Al{sub 2}O{sub 3} surface for the adsorption and dissociation of H{sub 2} molecule, which is of importance for many catalysis reactions. Due to its strong Lewis acidity, the tri-coordinated surface Al site was identified to be the most preferable site for both Cu and Pd location. The inner surface electrons rearrangement from O to Al of alumina was found to be a key factor to stabilize the Cu/Pd adsorption configurations, rather than the total electrons transfer between Cu/Pd and the surface. It was found that the supported Cu and Pd atoms are more active for H{sub 2} dissociation than the clean γ-Al{sub 2}O{sub 3} surface. The supported Pd is more active than Cu for H{sub 2} dissociation. In addition, the metal–support interaction of the γ-Al{sub 2}O{sub 3} supported Cu/Pd atoms are more favored than the metal–metal interaction of the metal clusters for the H{sub 2} dissociated adsorption.

Isolation of high purity americium metal via distillation

Science.gov (United States)

Squires, Leah N.; King, James A.; Fielding, Randall S.; Lessing, Paul

2018-03-01

Pure americium metal is a crucial component for the fabrication of transmutation fuels. Unfortunately, americium in pure metal form is not available; however, a number of mixed metals and mixed oxides that include americium are available. In this manuscript a method is described to obtain high purity americium metal from a mixture of americium and neptunium metals with lead impurity via distillation.

A DFT study and micro-kinetic analysis of acetylene selective hydrogenation on Pd-doped Cu(111) surfaces

Energy Technology Data Exchange (ETDEWEB)

Ma, Ling-Ling [Department of Chemistry, Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education) and Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin 300071 (China); Lv, Cun-Qin, E-mail: lcq173@126.com [College of Chemistry and Environmental Engineering, Shanxi Datong University, Datong 037009, Shanxi Province (China); Wang, Gui-Chang, E-mail: wangguichang@nankai.edu.cn [Department of Chemistry, Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education) and Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin 300071 (China)

2017-07-15

Semi-hydrogenation of acetylene in a hydrogen-rich stream is an industrially important process. Inspired by the recent experiments that Cu(111) surface doped by a small number of Pd atoms can exhibit excellent catalytic performance toward the dissociation of H{sub 2} molecule as well as the high selective hydrogenation of acetylene as compared with pure Cu and Pd metal alone at low-temperature, here we performed systematic first-principles calculations to investigate the corresponding reaction mechanism related to the acetylene hydrogenation processes on single atom alloys (SAAs) and monolayer Pd/Cu(111) (i.e.,1.00 ML Pd/Cu(111)) model catalysts in detail, and to explore the possible factors controlling the high selectivity on SAAs. Our results clearly demonstrate that the SAA catalyst has higher selectivity for the ethylene formation than that of 1.00 ML Pd/Cu(111), and lower activity for the acetylene conversion compared with that of 1.00 ML Pd/Cu(111). The relatively high selectivity on SAA is mainly due to the facile desorption of ethylene and moderate activity in the dissociation of molecular H{sub 2}. The main factor which lowers the selectivity towards the ethylene formation on 1.00 ML Pd/Cu(111) is that this system has a higher capacity to promote the breaking of C−H/C−C bonds, which leads to the formation of carbonaceous deposits and polymers such as benzene, and thus reduces the selectivity for the ethylene formation. Meanwhile, it was found that the desorption energy of ethylene on these two surfaces was smaller than the energy barrier of further hydrogenation, which results in the absence of ethane on these two systems. Micro-kinetic model analysis provides a further valuable insight into the evidence for the key factors controlling the catalytic activity and selectivity towards the selective hydrogenation of acetylene. Our findings may help people to design a highly selective hydrogenation catalyst by controlling the balance between the H{sub 2

A simple approach to uniform PdAg alloy membranes: Comparative study of conventional and silver concentration-controlled co-plating

KAUST Repository

Zeng, Gaofeng

2014-03-01

An Ag-controlled co-plating method was developed for the preparation of palladium/silver alloy membranes on porous tubular alumina supports. By controlling the feed rate of Ag to the Pd bath, the concentration of the silver in the plating bath was restricted during the course of plating. As a result, preferential deposition of silver at the beginning was suppressed and uniform dispersion of silver inside the membrane with silver composition in the desired range was achieved. Ultrathin (∼2.5 μm) PdAg alloy membranes with uniform silver composition of ∼25% were successfully obtained. The membrane showed a hydrogen permeance of 0.88 mol m-2 s-1 and pure-gas H2/N2 selectivity of 2140 at 823 K with ΔP = 100 kPa. Only one hydride phase existed in the studied temperature range from 373 to 823 K with ΔPH=100kPa. Direct comparisons with the conventional simply-mixed co-plating method showed that membranes made by the novel Ag-controlled co-plating method had much more uniform silver distribution, smoother surface, denser membrane structure, higher utilization rate of metal sources, and shorter alloying time. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

A simple approach to uniform PdAg alloy membranes: Comparative study of conventional and silver concentration-controlled co-plating

KAUST Repository

Zeng, Gaofeng; Shi, Lei; Liu, Yunyang; Zhang, Yanfeng; Sun, Yuhan

2014-01-01

An Ag-controlled co-plating method was developed for the preparation of palladium/silver alloy membranes on porous tubular alumina supports. By controlling the feed rate of Ag to the Pd bath, the concentration of the silver in the plating bath was restricted during the course of plating. As a result, preferential deposition of silver at the beginning was suppressed and uniform dispersion of silver inside the membrane with silver composition in the desired range was achieved. Ultrathin (∼2.5 μm) PdAg alloy membranes with uniform silver composition of ∼25% were successfully obtained. The membrane showed a hydrogen permeance of 0.88 mol m-2 s-1 and pure-gas H2/N2 selectivity of 2140 at 823 K with ΔP = 100 kPa. Only one hydride phase existed in the studied temperature range from 373 to 823 K with ΔPH=100kPa. Direct comparisons with the conventional simply-mixed co-plating method showed that membranes made by the novel Ag-controlled co-plating method had much more uniform silver distribution, smoother surface, denser membrane structure, higher utilization rate of metal sources, and shorter alloying time. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Removal of platinum group metals contained in molten glass using copper

International Nuclear Information System (INIS)

Uruga, Kazuyoshi; Sawada, Kayo; Arita, Yuji; Enokida, Youichi; Yamamoto, Ichiro

2007-01-01

Removal of platinum group metals (PGMs) such as Pd, Ru, and RuO 2 from molten glass by using various amounts of liquid Cu was done as a basic study on a new vitrification process for a high-level radio-active waste. We prepared two types of borosilicate glasses containing PGMs and Cu, respectively. These glasses were mixed together and heated at 1,473 K for 4h in Ar atmosphere. More than 95% of Pd were removed as a spherical metal button composed of Pd-Cu alloy when Cu was added in an amount 0.5 times the weight of Pd. Nearly 95% of Ru was also removed as a spherical button with 2.5-5 times as much Cu addition as Ru in weight. Ruthenium oxide was reduced to metallic Ru by a reaction with Cu in the molten glass. The removal fraction was increased by increasing the amount of Cu and reached 63% when Cu addition was 7.5 times as much as RuO 2 in weight. By addition of Si as a reducing agent, nearly 90% of Pd and Ru were removed with Cu and Si metal composites even under O 2 :Ar=20:80 (v/v) condition. (author)

An oxygen-vacancy-rich Z-scheme g-C3N4/Pd/TiO2 heterostructure for enhanced visible light photocatalytic performance

Science.gov (United States)

Guo, Yanru; Xiao, Limin; Zhang, Min; Li, Qiuye; Yang, Jianjun

2018-05-01

An oxygen-vacancy-rich Z-scheme g-C3N4/Pd/TiO2 ternary nanocomposite was fabricated using nanotubular titanic acid as precursors via a simple photo-deposition of Pd nanoparticles and calcination process. The prepared nanocomposites were investigated by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and UV-visible diffuse reflectance spectroscopy, respectively. For g-C3N4/TiO2 binary nanocomposites, at the optimal content of g-C3N4 (2%), the apparent photocatalytic activity of 2%g-C3N4/TiO2 was 9 times higher than that of pure TiO2 under visible-light illumination. After deposition of Pd (1 wt%) at the contact interface between g-C3N4 and TiO2, the 2%g-C3N4/Pd/TiO2 ternary nanocomposites demonstrated the highest visible-light-driven photocatalytic activity for the degradation of gaseous propylene, which was 16- and 2-fold higher activities than pure TiO2 and 2%g-C3N4/TiO2, respectively. The mechanism for the enhanced photocatalytic performance of the g-C3N4/Pd/TiO2 photo-catalyst is proposed to be based on the efficient separation of photo-generated electron-hole pairs through Z-scheme system, in which uniform dispersity of Pd nanoparticles at contact interface between g-C3N4 and TiO2 and oxygen vacancies promote charge separation.

Ag/Pd core-shell nanoparticles by a successive method: Pulsed laser ablation of Ag in water and reduction reaction of PdCl{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Mottaghi, N. [Department of Physics, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Ranjbar, M., E-mail: ranjbar@cc.iut.ac.ir [Department of Physics, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Farrokhpour, H. [Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Khoshouei, M. [Max Planck Institute of Biochemistry, Department of Molecular Structural Biology, Am Klopferspitz 18, Martinsried 82152 (Germany); Khoshouei, A.; Kameli, P.; Salamati, H. [Department of Physics, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Tabrizchi, M. [Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Jalilian-Nosrati, M. [Physics department, Central Azad University, Tehran 14676-86831 (Iran, Islamic Republic of)

2014-02-15

In this study Ag/Pd nanoparticles (NPs) have been fabricated by a successive method; first, colloids of Ag nanoparticles (NPs) have been prepared in water by pulsed laser ablation in liquid (PLAL) method. Then PdCl{sub 2} solution (up to 0.2 g/l) were added to the as-prepared or aged colloidal Ag NPs. Characterizations were done using UV–vis spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmissions electron microscopy (TEM) techniques. Spectroscopy data showed that surface plasmon resonance (SPR) peaks of as-prepared Ag NPs at about λ = 400 nm were completely extinguished after addition of PdCl{sub 2} solution while this effect was not observed when aged Ag NPs are used. XRD and XPS results revealed that by addition of the PdCl{sub 2} solution into the as-prepared Ag NPs, metallic palladium, and silver chloride composition products are generated. TEM images revealed that as a result of this reaction, single and core-shell nanoparticles are obtained and their average sizes are 2.4 nm (Ag) and 3.2 nm (Ag/Pd). The calculated d-spacing values form XRD data with observations on high magnification TEM images were able to explain the chemical nature of different parts of Ag/Pd NPs.

Density functional theory study of elemental mercury adsorption on boron doped graphene surface decorated by transition metals

Energy Technology Data Exchange (ETDEWEB)

Jungsuttiwong, Siriporn, E-mail: siriporn.j@ubu.ac.th [Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani 34190 (Thailand); Wongnongwa, Yutthana [Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani 34190 (Thailand); Namuangruk, Supawadee [National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), Klong Luang, Pathum Thani 12120 (Thailand); Kungwan, Nawee [Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Promarak, Vinich [Department of Material Science and Engineering, School of Molecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology, Rayong 21210 (Thailand); Kunaseth, Manaschai, E-mail: manaschai@nanotec.or.th [National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), Klong Luang, Pathum Thani 12120 (Thailand)

2016-01-30

Graphical abstract: Decoration of Pd{sub 4}-A (square planar) on B-doped graphene significantly promotes Hg{sup 0} adsorption, a single site of Pd{sub 4} cluster on BDG could strongly adsorb up to six Hg atoms. - Highlights: • Transition metal atom and cluster binds strongly on B-doped graphene surface. • Decoration of transition metal on B-doped graphene significantly promotes Hg{sup 0} adsorption. • Adsorption strength of Hg{sup 0} atom on metal decorated B-doped graphene: Pd > Pt > Ru > W > Cu. • One site decorated Pd4 cluster adsorbed Hg{sup 0} strongly up to six atoms.

Mood Expression in Real-Time Computer Generated Music using Pure Data

DEFF Research Database (Denmark)

Scirea, Marco; Nelson, Mark; Cheong, Yun-Gyung

2014-01-01

This paper presents an empirical study that investigated if procedurally generated music based on a set of musical features can elicit a target mood in the music listener. Drawn from the two-dimensional affect model proposed by Russell, the musical features that we have chosen to express moods...... are intensity, timbre, rhythm, and dissonances. The eight types of mood investigated in this study are being bored, content, happy, miserable, tired, fearful, peaceful, and alarmed. We created 8 short music clips using PD (Pure Data) programming language, each of them represents a particular mood. We carried...

Recovery and utilization of valuable metals from spent nuclear fuel. 3: Mutual separation of valuable metals

International Nuclear Information System (INIS)

Kirishima, K.; Shibayama, H.; Nakahira, H.; Shimauchi, H.; Myochin, M.; Wada, Y.; Kawase, K.; Kishimoto, Y.

1993-01-01

In the project ''Recovery and Utilization of Valuable Metals from Spent Fuel,'' mutual separation process of valuable metals recovered from spent fuel has been studied by using the simulated solution contained Pb, Ru, Rh, Pd and Mo. Pd was separated successfully by DHS (di-hexyl sulfide) solvent extraction method, while Pb was recovered selectively from the raffinate by neutralization precipitation of other elements. On the other hand, Rh was roughly separated by washing the precipitate with alkaline solution, so that Rh was refined by chelate resin CS-346. Outline of the mutual separation process flow sheet has been established of the combination of these techniques. The experimental results and the process flow sheet of mutual separation of valuable metals are presented in this paper

Adsorption of guaiacol on Fe (110) and Pd (111) from first principles

Science.gov (United States)

Hensley, Alyssa J. R.; Wang, Yong; McEwen, Jean-Sabin

2016-06-01

The catalytic properties of surfaces are highly dependent upon the effect said surfaces have on the geometric and electronic structure of adsorbed reactants, products, and intermediates. It is therefore crucial to have a surface-level understanding of the adsorption of the key species in a reaction in order to design active and selective catalysts. Here, we study the adsorption of guaiacol on Fe (110) and Pd (111) using dispersion-corrected density functional theory calculations as both of these metals are of interest as hydrodeoxygenation catalysts for the conversion of bio-oils to useable biofuels. Both vertical (via the oxygen functional groups) and horizontal (via the aromatic ring) adsorption configurations were examined and the resulting adsorption and molecular distortion energies showed that the vertical sites were only physisorbed while the horizontal sites were chemisorbed on both metal surfaces. A comparison of guaiacol's horizontal adsorption on Fe (110) and Pd (111) showed that guaiacol had a stronger adsorption on Pd (111) while the Fe (110) surface distorted the Csbnd O bonds to a greater degree. Electronic analyses on the horizontal systems showed that the greater adsorption strength for guaiacol on Pd (111) was likely due to the greater charge transfer between the aromatic ring and the surface Pd atoms. Additionally, the greater distortion of the Csbnd O bonds in adsorbed guaiacol on Fe (110) is likely due to the greater degree of interaction between the oxygen and surface Fe atoms. Overall, our results show that the Fe (110) surface has a greater degree of interaction with the functional groups and the Pd (111) surface has a greater degree of interaction with the aromatic ring.

Liquid phase catalytic hydrodebromination of tetrabromobisphenol A on supported Pd catalysts

Energy Technology Data Exchange (ETDEWEB)

Wu, Ke [State Key Laboratory of Pollution Control and Resource Reuse, Jiangsu Key Laboratory of Vehicle Emissions Control, School of the Environment, Nanjing University, Nanjing 210023 (China); Zheng, Mengjia [Kuang Yaming Honors School, Nanjing University, Nanjing 210023 (China); Han, Yuxiang [State Key Laboratory of Pollution Control and Resource Reuse, Jiangsu Key Laboratory of Vehicle Emissions Control, School of the Environment, Nanjing University, Nanjing 210023 (China); Xu, Zhaoyi, E-mail: zhaoyixu@nju.edu.cn [State Key Laboratory of Pollution Control and Resource Reuse, Jiangsu Key Laboratory of Vehicle Emissions Control, School of the Environment, Nanjing University, Nanjing 210023 (China); Zheng, Shourong [State Key Laboratory of Pollution Control and Resource Reuse, Jiangsu Key Laboratory of Vehicle Emissions Control, School of the Environment, Nanjing University, Nanjing 210023 (China)

2016-07-15

Highlights: • Pd catalysts supported on TiO{sub 2}, CeO{sub 2}, Al{sub 2}O{sub 3} and SiO{sub 2} were prepared. • Deposition-precipitation method resulted in positively charged smaller Pd particle. • Complete debromination of tetrabromobisphenol A could be achieved on Pd/TiO{sub 2}. • Pd/TiO{sub 2} prepared by the deposition-precipitation method was more active. - Abstract: Tetrabromobisphenol A (TBBPA) is a widely used brominated flame retardant and reductive debromination is an effective method for the abatement of TBBPA pollution. In this study, Pd catalysts supported on TiO{sub 2}, CeO{sub 2}, Al{sub 2}O{sub 3} and SiO{sub 2} were prepared by the impregnation (the resulting catalyst denoted as im-Pd/support), deposition-precipitation (the resulting catalyst denoted as dp-Pd/support), and photo-deposition (the resulting catalyst denoted as pd-Pd/support) methods. The catalysts were characterized by N{sub 2} adsorption-desorption isotherm, X-ray diffraction, transmission electron microscopy, measurement of zeta potential, CO chemisorption, and X-ray photoelectron spectroscopy. The results showed that at an identical Pd loading amount (2.0 wt.%) Pd particle size in dp-Pd/TiO{sub 2} was much smaller than those in im-Pd/TiO{sub 2} and pd-Pd/TiO{sub 2}. Pd particle size of the dp-Pd/TiO{sub 2} catalyst increased with Pd loading amount. Additionally, Pd particles in the dp-Pd/TiO{sub 2} catalysts were positively charged due to the strong metal-support interaction, whereas the cationization effect was gradually attenuated with the increase of Pd loading amount. For the liquid phase catalytic hydrodebromination (HDB) of TBBPA, tri-bromobisphenol A (tri-BBPA), di-bromobisphenol A (di-BBPA), and mono-bromobisphenol A (mono-BBPA) were identified as the intermediate products, indicative of a stepwise debromination process. The catalytic HDB of TBBPA followed the Langmuir-Hinshelwood model, reflecting an adsorption enhanced catalysis mechanism. At an identical Pd

CO-induced Pd segregation and the effect of subsurface Pd on CO adsorption on CuPd surfaces

International Nuclear Information System (INIS)

Padama, A A B; Villaos, R A B; Albia, J R; Diño, W A; Nakanishi, H; Kasai, H

2017-01-01

We report results of our study on the adsorption of CO on CuPd surfaces with bulk stoichiometric and nonstoichiometric layers using density functional theory (DFT). We found that the presence of Pd atoms in the subsurface layer promotes the adsorption of CO. We also observed CO-induced Pd segregation on the CuPd surface and we attribute this to the strong CO–Pd interaction. Lastly, we showed that the adsorption of CO promotes Pd–Pd interaction as compared to the pristine surface which promotes strong Cu–Pd interaction. These results indicate that CO adsorption on CuPd surfaces can be tuned by taking advantage of the CO-induced segregation and by considering the role of subsurface Pd atoms. (paper)

Basal cell carcinoma: PD-L1/PD-1 checkpoint expression and tumor regression after PD-1 blockade.

Science.gov (United States)

Lipson, Evan J; Lilo, Mohammed T; Ogurtsova, Aleksandra; Esandrio, Jessica; Xu, Haiying; Brothers, Patricia; Schollenberger, Megan; Sharfman, William H; Taube, Janis M

2017-01-01

Monoclonal antibodies that block immune regulatory proteins such as programmed death-1 (PD-1) have demonstrated remarkable efficacy in controlling the growth of multiple tumor types. Unresectable or metastatic basal cell carcinoma, however, has largely gone untested. Because PD-Ligand-1 (PD-L1) expression in other tumor types has been associated with response to anti-PD-1, we investigated the expression of PD-L1 and its association with PD-1 expression in the basal cell carcinoma tumor microenvironment. Among 40 basal cell carcinoma specimens, 9/40 (22%) demonstrated PD-L1 expression on tumor cells, and 33/40 (82%) demonstrated PD-L1 expression on tumor-infiltrating lymphocytes and associated macrophages. PD-L1 was observed in close geographic association to PD-1+ tumor infiltrating lymphocytes. Additionally, we present, here, the first report of an objective anti-tumor response to pembrolizumab (anti-PD-1) in a patient with metastatic PD-L1 (+) basal cell carcinoma, whose disease had previously progressed through hedgehog pathway-directed therapy. The patient remains in a partial response 14 months after initiation of therapy. Taken together, our findings provide a rationale for testing anti-PD-1 therapy in patients with advanced basal cell carcinoma, either as initial treatment or after acquired resistance to hedgehog pathway inhibition.

The Sticking Probability for Hydrogen on Ni, Pd, and Pt at a Hydrogen pressure of 1 bar

DEFF Research Database (Denmark)

Johansson, Martin; Lytken, Ole; Chorkendorff, Ib

2007-01-01

A technique for measurements of the sticking probability of hydrogen on metal surfaces at high (ambient) pressure is described. As an example, measurements for Ni, Pd and Pt at a hydrogen pressure of 1 bar and temperatures between 40 and 200 degrees C are presented. The sticking probabilities are......, Pt. The transition between beta- and alpha-phase in the H-Pd system has a significant effect on the activity for Pd....

A three-dimensional hierarchical nanoporous PdCu alloy for enhanced electrocatalysis and biosensing

Energy Technology Data Exchange (ETDEWEB)

Liu Aihua [Laboratory for Nanobioelectronics and Biosensors, Qingdao Institute of Bioenergy and Bioprocess Technology, and Key Laboratory for Biofuels, Chinese Academy of Sciences, Qingdao 266101 (China); Geng Haoran [School of Chemistry and Chemical Engineering, University of Jinan, Jinan 250022 (China); Xu Caixia, E-mail: chm_xucx@ujn.edu.cn [School of Chemistry and Chemical Engineering, University of Jinan, Jinan 250022 (China); Qiu Huajun, E-mail: qiuhuajun@gmail.com [Laboratory for Nanobioelectronics and Biosensors, Qingdao Institute of Bioenergy and Bioprocess Technology, and Key Laboratory for Biofuels, Chinese Academy of Sciences, Qingdao 266101 (China)

2011-10-10

Highlights: {yields} Nanotubular mesoporous PdCu (NM-PdCu) alloy is facilely fabricated via one-step metal replacement reaction between nanoporous Cu and H{sub 2}PdCl{sub 4}. {yields} The NM-PdCu exhibits remarkably improved structure stability and electrocatalytic activity towards formic acid and hydrogen peroxide oxidation compared with NP-Pd. {yields} When coupled with GOx, the GOx/NM-PdCu electrode can be used for sensitive detection of glucose over a wide concentration range. - Abstract: Nanoporous copper (NPC) obtained by dealloying CuAl alloy is used as both three-dimensional template and reducing agent for the fabrication of nanoporous PdCu alloy with hollow ligaments by a simple galvanic replacement reaction with H{sub 2}PdCl{sub 4} aqueous solution. Electron microscopy and X-ray diffraction characterizations demonstrate that after the replacement reaction, the ligaments become hollow tubular structure and the ligament shell is also comprised of small pores and nanoparticles with a typical size of {approx}4 nm (third order porosity). The as-prepared nanotubular mesoporous PdCu alloy (NM-PdCu) structure exhibits remarkably improved electrocatalytic activity towards the oxidation of formic acid and H{sub 2}O{sub 2} compared with nanoporous Pd (NP-Pd), and can be used for sensitive electrochemical sensing applications. After coupled with glucose oxidase (GOx), the enzyme modified NM-PdCu electrode can sensitively detect glucose over a wide linear range (0.5-20 mM).

A three-dimensional hierarchical nanoporous PdCu alloy for enhanced electrocatalysis and biosensing

International Nuclear Information System (INIS)

Liu Aihua; Geng Haoran; Xu Caixia; Qiu Huajun

2011-01-01

Highlights: → Nanotubular mesoporous PdCu (NM-PdCu) alloy is facilely fabricated via one-step metal replacement reaction between nanoporous Cu and H 2 PdCl 4 . → The NM-PdCu exhibits remarkably improved structure stability and electrocatalytic activity towards formic acid and hydrogen peroxide oxidation compared with NP-Pd. → When coupled with GOx, the GOx/NM-PdCu electrode can be used for sensitive detection of glucose over a wide concentration range. - Abstract: Nanoporous copper (NPC) obtained by dealloying CuAl alloy is used as both three-dimensional template and reducing agent for the fabrication of nanoporous PdCu alloy with hollow ligaments by a simple galvanic replacement reaction with H 2 PdCl 4 aqueous solution. Electron microscopy and X-ray diffraction characterizations demonstrate that after the replacement reaction, the ligaments become hollow tubular structure and the ligament shell is also comprised of small pores and nanoparticles with a typical size of ∼4 nm (third order porosity). The as-prepared nanotubular mesoporous PdCu alloy (NM-PdCu) structure exhibits remarkably improved electrocatalytic activity towards the oxidation of formic acid and H 2 O 2 compared with nanoporous Pd (NP-Pd), and can be used for sensitive electrochemical sensing applications. After coupled with glucose oxidase (GOx), the enzyme modified NM-PdCu electrode can sensitively detect glucose over a wide linear range (0.5-20 mM).

Influence of zeolite structure on the activity and durability of Co-Pd-zeolite catalysts in the reduction of NOx with methane

International Nuclear Information System (INIS)

Pieterse, J.A.Z.; Van den Brink, R.W.; Booneveld, S.; De Bruijn, F.A.

2003-01-01

Selective catalytic reduction of NO with CH 4 was studied over ZSM-5, MOR, FER and BEA zeolite-based cobalt (Co) and palladium (Pd) catalysts in the presence of oxygen and water. As compared to other catalytic systems reported in literature for CH 4 -SCR in the presence of water, zeolite supported Co-Pd combination catalysts are very active and selective. The most active catalysts, based on MOR and ZSM-5, are characterised by well-dispersed Pd ions in the zeolite that activate methane. Wet ion exchange is a good method to achieve high dispersion of Pd provided that it is carried out in a competitive manner. The presence of cobalt (Co 3 O 4 , Co-oxo ions) boosts SCR activity by oxidising NO to NO 2 . The activity of the zeolite-based Co-Pd combination catalysts decreases with prolonged times on stream. The severity of the deactivation was found to be different for different zeolite topologies. The characterisation and evaluation of freshly calcined catalysts and spent catalysts show two things that occur during reaction: (1) zeolite solvated metal cations disappear in favour of (inactive) metal oxides and presumably larger metal entities, i.e. loss of dispersion; (2) loss of crystallinity affiliated with steam-dealumination and the concomitant formation of extra-framework aluminium (EFAL) in the presence of water. Both phenomena strongly depend on the (reaction) temperature. The deactivation of Co-Pd-zeolite resembles the deactivation of Pd-zeolite. Hence, future research could encompass the stabilisation of Pd (cations) in the zeolite pores by exploring additives other than cobalt. For this, detailed understanding on the siting of Pd in zeolites is important

Reductive dechlorination of {gamma}-hexachlorocyclohexane using Fe-Pd bimetallic nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Nagpal, Varima; Bokare, Alok D. [Center for Nanobioscience, Agharkar Research Institute, G.G. Agarkar Road, Pune 411004, Maharashtra (India); Chikate, Rajeev C. [Department of Chemistry, MES Abasaheb Garware College, Karve Road, Pune 411004 (India); Rode, Chandrashekhar V. [Chemical Engineering and Process Development Division, National Chemical Laboratory, Pune 411008 (India); Paknikar, Kishore M., E-mail: paknikar@vsnl.com [Center for Nanobioscience, Agharkar Research Institute, G.G. Agarkar Road, Pune 411004, Maharashtra (India)

2010-03-15

Nanoscale Fe-Pd bimetallic particles were synthesized and used for degradation of lindane ({gamma}-hexachlorocyclohexane) in aqueous solution. Batch studies showed that 5 mg/L of lindane was completely dechlorinated within 5 min at a catalyst loading of 0.5 g/L and the degradation process followed first-order kinetics. GC-MS analysis in corroboration with GC-ECD results showed the presence of cyclohexane as the final degradation product. The proposed mechanism for the reductive dechlorination of lindane involves Fe corrosion-induced hydrogen atom transfer from the Pd surface. The enhanced degradation efficiency of Fe-Pd nanoparticles is attributed to: (1) high specific surface area of the nanoscale metal particles (60 m{sup 2}/g), manyfold greater that of commercial grade micro- or milli-scale iron particles ({approx}1.6 m{sup 2}/g); and, (2) increased catalytic reactivity due to the presence of Pd on the surface. Recycling and column studies showed that these nanoparticles exhibit efficient and sustained catalytic activity.

Mapping metals in Parkinson's and normal brain using rapid-scanning x-ray fluorescence

International Nuclear Information System (INIS)

Popescu, Bogdan F Gh; George, Martin J; McCrea, Richard P E; Devon, Richard M; George, Graham N; Hanson, Akela D; Chapman, L Dean; Nichol, Helen; Bergmann, Uwe; Garachtchenko, Alex V; Luening, Katharina; Kelly, Michael E; Harder, Sheri M; Pickering, Ingrid J

2009-01-01

Rapid-scanning x-ray fluorescence (RS-XRF) is a synchrotron technology that maps multiple metals in tissues by employing unique hardware and software to increase scanning speed. RS-XRF was validated by mapping and quantifying iron, zinc and copper in brain slices from Parkinson's disease (PD) and unaffected subjects. Regions and structures in the brain were readily identified by their metal complement and each metal had a unique distribution. Many zinc-rich brain regions were low in iron and vice versa. The location and amount of iron in brain regions known to be affected in PD agreed with analyses using other methods. Sample preparation is simple and standard formalin-fixed autopsy slices are suitable. RS-XRF can simultaneously and non-destructively map and quantify multiple metals and holds great promise to reveal metal pathologies associated with PD and other neurodegenerative diseases as well as diseases of metal metabolism.

Revival of pure titanium for dynamically loaded porous implants using additive manufacturing.

Science.gov (United States)

Wauthle, Ruben; Ahmadi, Seyed Mohammad; Amin Yavari, Saber; Mulier, Michiel; Zadpoor, Amir Abbas; Weinans, Harrie; Van Humbeeck, Jan; Kruth, Jean-Pierre; Schrooten, Jan

2015-09-01

Additive manufacturing techniques are getting more and more established as reliable methods for producing porous metal implants thanks to the almost full geometrical and mechanical control of the designed porous biomaterial. Today, Ti6Al4V ELI is still the most widely used material for porous implants, and none or little interest goes to pure titanium for use in orthopedic or load-bearing implants. Given the special mechanical behavior of cellular structures and the material properties inherent to the additive manufacturing of metals, the aim of this study is to investigate the properties of selective laser melted pure unalloyed titanium porous structures. Therefore, the static and dynamic compressive properties of pure titanium structures are determined and compared to previously reported results for identical structures made from Ti6Al4V ELI and tantalum. The results show that porous Ti6Al4V ELI still remains the strongest material for statically loaded applications, whereas pure titanium has a mechanical behavior similar to tantalum and is the material of choice for cyclically loaded porous implants. These findings are considered to be important for future implant developments since it announces a potential revival of the use of pure titanium for additively manufactured porous implants. Copyright © 2015 Elsevier B.V. All rights reserved.

Microstructure evolution of an Al-Pd-Co alloy

Czech Academy of Sciences Publication Activity Database

Kahalová, Ĺ.; Kusý, M.; Buršík, Jiří; Svoboda, Milan; Illeková, E.; Švec, P.; Dolinšek, J.; Janovec, J.

2008-01-01

Roč. 46, č. 4 (2008), s. 221-227 ISSN 0023-432X R&D Projects: GA ČR(CZ) GA106/07/1259 Institutional research plan: CEZ:AV0Z20410507 Keywords : complex metallic alloys * Al-Pd-Co system * differential thermal analysis Subject RIV: JG - Metallurgy Impact factor: 1.345, year: 2007

Extraction behaviour and mechanism of Pt(iv) and Pd(ii) by liquid-liquid extraction with an ionic liquid [HBBIm]Br.

Science.gov (United States)

Liu, Wenhui; Wang, Qi; Zheng, Yan; Wang, Shubin; Yan, Yan; Yang, Yanzhao

2017-06-06

In this study, a method of one-step separation and recycling of high purity Pd(ii) and Pt(iv) using an ionic liquid, 1-butyl-3-benzimidazolium bromate ([HBBIm]Br), was investigated. The effects of [HBBIm]Br concentration, initial metal concentration, and loading capacity of [HBBIm]Br were examined in detail. It was observed that [HBBIm]Br was a very effective extractant for selectively extracting Pd(ii) and precipitating Pt(iv). Through selectively extracting Pd(ii) and precipitating Pt(iv), each metal with high purity was separately obtained from mixed Pd(ii) and Pt(iv) multi-metal solution. The method of one-step separation of Pd(ii) and Pt(iv) is simple and convenient. The anion exchange mechanism between [HBBIm]Br and Pt(iv) was proven through Job's method and FTIR and 1 H NMR spectroscopies. The coordination mechanism between [HBBIm]Br and Pd(ii) was demonstrated via single X-ray diffraction and was found to be robust and distinct, as supported by the ab initio quantum-chemical studies. The crystals of the [PdBr 2 ·2BBIm] complex were formed first. Moreover, the influence of the concentrations of hydrochloric acid, sodium chloride, and sodium nitrate on the precipitation of Pt(iv) and extraction of Pd(ii) was studied herein. It was found that only the concentration of H + could inhibit the separation of Pt(iv) because H + could attract the anion PtCl 6 2- ; thus, the exchange (anion exchange mechanism) between the anions PtCl 6 2- and Br - was prevented. However, both the concentration of H + and Cl - can obviously inhibit the extraction of Pd(ii) because H + and Cl - are the reaction products and increasing their concentration can inhibit the progress of the reaction (coordination mechanism).

Charge transfer, lattice distortion, and quantum confinement effects in Pd, Cu, and Pd-Cu nanoparticles; size and alloying induced modifications in binding energy

International Nuclear Information System (INIS)

Sengar, Saurabh K.; Mehta, B. R.; Gupta, Govind

2011-01-01

In this letter, effect of size and alloying on the core and valence band shifts of Pd, Cu, and Pd-Cu alloy nanoparticles has been studied. It has been shown that the sign and magnitude of the binding energy shifts is determined by the contributions of different effects; with quantum confinement and lattice distortion effects overlapping for size induced shifts in case of core levels and lattice distortion and charge transfer effects overlapping for alloying induced shifts at smaller sizes. These results are important for understanding gas molecule-solid surface interaction in metal and alloy nanoparticles in terms of valance band positions.

Magnetic-property changes in epitaxial metal-film sandwiches

International Nuclear Information System (INIS)

Brodsky, M.B.

1982-08-01

Epitaxial metal-film sandwiches (EMFS) containing Pd or Cr, have been prepared between single-crystal Ag or Au. The modified Pd/Cr show major changes in physical properties. Pd has a stretched lattice parameter in Au-Pd-Au, which combines with a tetragonal distortion to cause exchange enhancements up to 28,000 and spin-fluctuation temperatures of 1 to 10 K. In Au-Cr-Au, Cr takes up the fcc structure, leading to superconductivity due to a high N(E/sub F/). These results are contrasted to data for Ag-Pd-Ag and Ag-Cr-Ag EMFS

Molecular mechanism of PD-1/PD-L1 blockade via anti-PD-L1 antibodies atezolizumab and durvalumab.

Science.gov (United States)

Lee, Hyun Tae; Lee, Ju Yeon; Lim, Heejin; Lee, Sang Hyung; Moon, Yu Jeong; Pyo, Hyo Jeong; Ryu, Seong Eon; Shin, Woori; Heo, Yong-Seok

2017-07-17

In 2016 and 2017, monoclonal antibodies targeting PD-L1, including atezolizumab, durvalumab, and avelumab, were approved by the FDA for the treatment of multiple advanced cancers. And many other anti-PD-L1 antibodies are under clinical trials. Recently, the crystal structures of PD-L1 in complex with BMS-936559 and avelumab have been determined, revealing details of the antigen-antibody interactions. However, it is still unknown how atezolizumab and durvalumab specifically recognize PD-L1, although this is important for investigating novel binding sites on PD-L1 targeted by other therapeutic antibodies for the design and improvement of anti-PD-L1 agents. Here, we report the crystal structures of PD-L1 in complex with atezolizumab and durvalumab to elucidate the precise epitopes involved and the structural basis for PD-1/PD-L1 blockade by these antibodies. A comprehensive comparison of PD-L1 interactions with anti-PD-L1 antibodies provides a better understanding of the mechanism of PD-L1 blockade as well as new insights into the rational design of improved anti-PD-L1 therapeutics.

A general approach to mesoporous metal oxide microspheres loaded with noble metal nanoparticles

KAUST Repository

Jin, Zhao; Xiao, Manda; Bao, Zhihong; Wang, Peng; Wang, Jianfang

2012-01-01

Catalytic microspheres: A general approach is demonstrated for the facile preparation of mesoporous metal oxide microspheres loaded with noble metal nanoparticles (see TEM image in the picture). Among 18 oxide/noble metal catalysts, TiO 2/0.1 mol Pd microspheres showed the highest turnover frequency in NaBH 4 reduction of 4-nitrophenol (see picture). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A general approach to mesoporous metal oxide microspheres loaded with noble metal nanoparticles

KAUST Repository

Jin, Zhao

2012-04-26

Catalytic microspheres: A general approach is demonstrated for the facile preparation of mesoporous metal oxide microspheres loaded with noble metal nanoparticles (see TEM image in the picture). Among 18 oxide/noble metal catalysts, TiO 2/0.1 mol Pd microspheres showed the highest turnover frequency in NaBH 4 reduction of 4-nitrophenol (see picture). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and characterization of carbon supported PdNi nanocatalysts for electroreduction of oxygen

Energy Technology Data Exchange (ETDEWEB)

Khan, Muhammad Sufaid; Milian, Rosendo Parra, E-mail: sufaidkhan1984@gmail.com [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Araraquara, SP (Brazil). Instituto de Química; Gallo, Irã Borges Coutinho; Villullas, Hebe Mercedes [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Sao Paulo, SP (Brazil). Instituto de Química

2016-07-01

Full text: In this work, PdNi nanoparticles were prepared by a modified polyol method [1] with different Pd:Ni nominal ratios (80:20, 70:30 and 50:50, in atoms) and then supported on carbon (Vulcan XC-72). The structural properties of all materials were characterized by X-ray diffraction (XRD). Data show the formation PdNi alloys, as indicated by the decreased of the Pd lattice parameter compared Pd/C. The Pd 4d band electronic occupancy was assessed by X-ray Absorption Spectroscopy measurements that were carried out around the Pd L3 edge. Results evidenced that the presence of Ni decreases the electronic vacancy of the Pd 4d band. The electrocatalytic activity for the oxygen reduction reaction (ORR) was studied using the rotating disk electrode technique in O{sub 2}-saturated H{sub 2}SO{sub 4} and NaOH solutions. Overall, all PdNi materials presented better catalytic performance for the ORR than pure Pd, in both acidic and alkaline media. The production of H{sub 2}O{sub 2} was quantified using the rotating ring-disk technique, which allowed detecting this reaction intermediate by oxidizing it at the ring electrode. In all cases, data indicate low production of H{sub 2}O{sub 2}, which suggests that the ORR occurs mainly through the 4 electron mechanism on all catalysts studied in this work. Additionally, all prepared materials were submitted to stability tests by continuous potential cycling up to 1.0 V (vs. RHE). These studies evidenced that stability of Pd against dissolution is affected by the presence of Ni, with significant improvement for the PdNi alloys containing 20 and 30% Ni. Acknowledgments. Thanks are due to FAPESP (2014/12255-6) and CNPq (407143/2013-0) for financial support, and to the Brazilian Synchrotron Light Laboratory (LNLS) for the XAS experiments. References [1] S. Sun, C.B. Murray, D. Weller, L. Folks, A. Moser. Science 287, 1989 (2000). (author)

Hysteresis-free nanoplasmonic pd-au alloy hydrogen sensors

DEFF Research Database (Denmark)

Wadell, Carl; Nugroho, Ferry Anggoro Ardy; Lidström, Emil

2015-01-01

hydrogen sensors. By increasing the amount of Au in the alloy nanoparticles up to 25 atom %, we are able to suppress the hysteresis between hydrogen absorption and desorption, thereby increasing the sensor accuracy to below 5% throughout the investigated 1 mbar to 1 bar hydrogen pressure range. Furthermore......, we observe an 8-fold absolute sensitivity enhancement at low hydrogen pressures compared to sensors made of pure Pd, and an improved sensor response time to below one second within the 0-40 mbar pressure range, that is, below the flammability limit, by engineering the nanoparticle size....

Schottky Barrier Height of Pd/MoS2 Contact by Large Area Photoemission Spectroscopy.

Science.gov (United States)

Dong, Hong; Gong, Cheng; Addou, Rafik; McDonnell, Stephen; Azcatl, Angelica; Qin, Xiaoye; Wang, Weichao; Wang, Weihua; Hinkle, Christopher L; Wallace, Robert M

2017-11-08

MoS 2 , as a model transition metal dichalcogenide, is viewed as a potential channel material in future nanoelectronic and optoelectronic devices. Minimizing the contact resistance of the metal/MoS 2 junction is critical to realizing the potential of MoS 2 -based devices. In this work, the Schottky barrier height (SBH) and the band structure of high work function Pd metal on MoS 2 have been studied by in situ X-ray photoelectron spectroscopy (XPS). The analytical spot diameter of the XPS spectrometer is about 400 μm, and the XPS signal is proportional to the detection area, so the influence of defect-mediated parallel conduction paths on the SBH does not affect the measurement. The charge redistribution by Pd on MoS 2 is detected by XPS characterization, which gives insight into metal contact physics to MoS 2 and suggests that interface engineering is necessary to lower the contact resistance for the future generation electronic applications.

Indolenine meso-substituted dibenzotetraaza[14]annulene and its coordination chemistry toward the transition metal ions Mn(III), Fe(III), Co(II), Ni(II), Cu(II), and Pd(II).

Science.gov (United States)

Khaledi, Hamid; Olmstead, Marilyn M; Ali, Hapipah Mohd; Thomas, Noel F

2013-02-18

A new dibenzotetraaza[14]annulene bearing two 3,3-dimethylindolenine fragments at the meso positions (LH(2)), has been synthesized through a nontemplate method. X-ray crystallography shows that the whole molecule is planar. The basicity of the indolenine ring permits the macrocycle to be protonated external to the core and form LH(4)(2+)·2Cl(-). Yet another structural modification having strong C-H···π interactions was found in the chloroform solvate of LH(2). The latter two modifications are accompanied by a degree of nonplanar distortion. The antiaromatic core of the macrocycle can accommodate a number of metal ions, Mn(III), Fe(III), Co(II), Ni(II) and Cu(II), to form complexes of [Mn(L)Br], [Mn(L)Cl], [Fe(LH(2))Cl(2)](+)·Cl(-), [Co(L)], [Ni(L)], and [Cu(L)]. In addition, the reaction of LH(2) with the larger Pd(II) ion leads to the formation of [Pd(2)(LH(2))(2)(OAc)(4)] wherein the macrocycle acts as a semiflexible ditopic ligand to coordinate pairs of metal ions via its indolenine N atoms into dinuclear metallocycles. The compounds LH(2), [Co(L)], and [Ni(L)] are isostructural and feature close π-stacking as well as linear chain arrangements in the case of the metal complexes. Variable temperature magnetic susceptibility measurements showed thermally induced paramagnetism in [Ni(L)].

Shape-controlled synthesis of Pd polyhedron supported on polyethyleneimine-reduced graphene oxide for enhancing the efficiency of hydrogen evolution reaction

Science.gov (United States)

Li, Jing; Zhou, Panpan; Li, Feng; Ma, Jianxin; Liu, Yang; Zhang, Xueyao; Huo, Hongfei; Jin, Jun; Ma, Jiantai

2016-01-01

The catalytic activity of noble-metal nanoparticles (NPs) often has closely connection with their sizes and geometric shape. In the work, polyhedral NPs of palladium (Pd) with controlled sizes, shapes, and different proportions of {100} to {111} facets on the surface were prepared by a seed-mediated approach. Electrochemical experiment demonstrates that the catalytic performance of the Pd nanocubes (NCs) enclosed by {100} facets is more active than Pd octahedrons enclosed by {111} facets for the hydrogen evolution reaction (HER), which is consistent with density functional theory (DFT) calculation results. Meanwhile, with the assistance of a polyethyleneimine-reduced graphene oxide (PEI-rGO) support, the examined Pd cube/PEI-rGO50:1 (10 wt. %) electrocatalyst presents outstanding HER activity comparable with that of commercial Pt/C catalyst. This correlation between the HER catalytic activity and surface structure will contribute to the reasonable design of Pd catalysts for HER with high efficiency and low metal loading.

Facile synthesis of PdAgTe nanowires with superior electrocatalytic activity

Science.gov (United States)

Hong, Wei; Wang, Jin; Wang, Erkang

2014-12-01

In this work, ultrathin Te nanowires (NWs) with high-aspect-ratio are prepared by a simple hydrothermal method. By using Te NWs as the sacrificial template, we demonstrate a facile and efficient method for the synthesis of PdAgTe NWs with high-quality through the partly galvanic replacement between Te NWs and the corresponding noble metal salts precursors in an aqueous solution. The compositions of PdAgTe NWs can be tuned by simply altering the concentration of the precursors. After cyclic voltammetry treatment, multi-component PdAgTe NW with a highly active and stable surface can be obtained. The structure and composition of the as-prepared nanomaterials are analyzed by transmission electron microscope, X-ray diffraction, energy dispersive X-ray spectroscopy, inductively coupled plasma-mass spectroscopy and X-ray photoelectron spectroscopy. Electrochemical catalytic measurement results prove that the as synthesized PdAgTe NWs present superior catalytic activity toward ethanol electrooxidation in alkaline solution than the commercial Pd/C catalyst, which making them can be used as effective catalysts for the direct ethanol fuel cells.

Oxidation behaviour of noble-metal inclusions in used UO2 nuclear fuel

International Nuclear Information System (INIS)

McEachern, R.

1997-07-01

The literature on the chemistry of the noble-metal (Mo-Rh-Ru-Pd-Tc) inclusions found in used nuclear fuel has been reviewed. The Mo-Ru-Pd phase diagram is reasonably well understood, and the pseudoternary Mo-(Tc+Ru)-Rh+Pd) system can be used to qualitatively understand the phase chemistry of the noble-metal inclusions. The kinetics of the oxidation reaction are not particularly well understood, but they are of limited applicability to understanding the properties of used fuel. In contrast, it is important to determine the thermodynamic activity of molybdenum in noble-metal inclusions, so that analysis of their molybdenum content can be used as a probe of the local oxygen potential of the used fuel. (author)

Purification of uranium metal

International Nuclear Information System (INIS)

Suzuki, Kenji; Shikama, Tatsuo; Ochiai, Akira.

1993-01-01

We developed the system for purifying uranium metal and its metallic compounds and for growing highly pure uranium compounds to study their intrinsic physical properties. Uranium metal was zone refined under low contamination conditions as far as possible. The degree of the purity of uranium metal was examined by the conventional electrical resistivity measurement and by the chemical analysis using the inductive coupled plasma emission spectrometry (ICP). The results show that some metallic impurities evaporated by the r.f. heating and other usual metallic impurities moved to the end of a rod with a molten zone. Therefore, we conclude that the zone refining technique is much effective to the removal of metallic impurities and we obtained high purified uranium metal of 99.99% up with regarding to metallic impurities. The maximum residual resistivity ratio, the r.r.r., so far obtained was about 17-20. Using the purified uranium, we are attempting to grow a highly pure uranium-titanium single crystals. (author)

Interfacial properties of stanene-metal contacts

Science.gov (United States)

Guo, Ying; Pan, Feng; Ye, Meng; Wang, Yangyang; Pan, Yuanyuan; Zhang, Xiuying; Li, Jingzhen; Zhang, Han; Lu, Jing

2016-09-01

Recently, two-dimensional buckled honeycomb stanene has been manufactured by molecular beam epitaxy growth. Free-standing stanene is predicted to have a sizable opened band gap of 100 meV at the Dirac point due to spin-orbit coupling (SOC), resulting in many fascinating properties such as quantum spin Hall effect, quantum anomalous Hall effect, and quantum valley Hall effect. In the first time, we systematically study the interfacial properties of stanene-metal interfaces (metals = Ag, Au, Cu, Al, Pd, Pt, Ir, and Ni) by using ab initio electronic structure calculations considering the SOC effects. The honeycomb structure of stanene is preserved on the metal supports, but the buckling height is changed. The buckling of stanene on the Au, Al, Ag, and Cu metal supports is higher than that of free-standing stanene. By contrast, a planar graphene-like structure is stabilized for stanene on the Ir, Pd, Pt, and Ni metal supports. The band structure of stanene is destroyed on all the metal supports, accompanied by a metallization of stanene because the covalent bonds between stanene and the metal supports are formed and the structure of stanene is distorted. Besides, no tunneling barrier exists between stanene and the metal supports. Therefore, stanene and the eight metals form a good vertical Ohmic contact.

Heterocycles by Transition Metals Catalyzed Intramolecular Cyclization of Acetylene Compounds

International Nuclear Information System (INIS)

Vizer, S.A.; Yerzhanov, K.B.; Dedeshko, E.C.

2003-01-01

Review shows the new strategies in the synthesis of heterocycles, having nitrogen, oxygen and sulfur atoms, via transition metals catalyzed intramolecular cyclization of acetylenic compounds on the data published at the last 30 years, Unsaturated heterocyclic compounds (pyrroles and pyrroline, furans, dihydro furans and benzofurans, indoles and iso-indoles, isoquinolines and isoquinolinones, aurones, iso coumarins and oxazolinone, lactams and lactones with various substitutes in heterocycles) are formed by transition metals, those salts [PdCl 2 , Pd(OAc) 2 , HgCl 2 , Hg(OAc) 2 , Hg(OCOCF 3 ) 2 , AuCl 3 ·2H 2 O, NaAuCl 4 ·2H 2 O, CuI, CuCl], oxides (HgO) and complexes [Pd(OAc) 2 (PPh 3 )2, Pd(PPh 3 ) 4 , PdCl 2 (MeCN) 2 , Pd(OAc ) 2 /TPPTS] catalyzed intramolecular cyclization of acetylenic amines, amides, ethers, alcohols, acids, ketones and βdiketones. More complex hetero polycyclic systems typical for natural alkaloids can to obtain similar. Proposed mechanisms of pyrroles, isoquinolines, iso indoles and indoles, benzofurans and iso coumarins, thiazolopyrimidinones formation are considered. (author)

Copper corrosion in pure oxygen-free water

International Nuclear Information System (INIS)

Moeller, K.

1995-12-01

The study was initiated following reports on corrosion of Copper in water in absence of Oxygen. Quartz glass tubes containing pure water and Copper plates were sealed in two different ways, using Palladium or Platinum foils, respectively. Tests were also performed with Copper wires. The insulated systems contained Oxygen initially. The Oxygen was dissolved in the water, and in the air column between the water surface and the Palladium/Platinum foils. The tubes were kept in a hot cabinet at 50 C for a total of two years. The exposed plates were analyzed in different ways, e g using reflectance FTIR. The amounts of oxide formed were also weighed. The following conclusions could be drawn: No difference in color was observed for the Pd and Pt seals except in one case for the Copper wire, where only a slight difference was noticed. No significant difference in oxidation between the plates with Pd or Pt seals in quartz glass tubes. No oxide growth was observed during the last year. The corrosion rate at 50 C is below 2.3 micrograms Copper/cm 2 /year. A certain imbalance was noted between the amounts of oxides formed, and expected amount estimated from the original amount of oxygen in the system. A significant amount of water has 'disappeared' from the tubes. 17 refs, 10 figs, 3 tabs

Thermal Analysis of Pure Uranium Metal, UMo and UMoSi Alloys Using a Differential Thermal Analyzer

International Nuclear Information System (INIS)

Yanlinastuti; Sutri Indaryati; Rahmiati

2010-01-01

Thermal analysis of pure uranium metal, U-7%Mo and U-7%Mo-1%Si alloys have been done using a Differential Thermal Analyzer (DTA). The experiments are conducted in order to measure the thermal stability, thermochemical properties of elevated temperature and enthalpy of the specimens. From the analysis results it is showed that uranium metal will transform from α to β phases at temperature of 667.16°C and enthalpy of 2.3034 cal/g and from β to γ phases at temperature of 773.05 °C and enthalpy of 2.8725 cal/g and start melting at temperature of 1125.26 °C and enthalpy of 2.1316 cal/g. The U-7%Mo shows its thermal stability up to temperature of 650 °C and its thermal changes at temperature of 673.75 °C indicated by the formation of an endothermic peak and enthalpy of 0.0257 cal/g. The U-7%Mo-1%Si alloys shows its thermal stability up to temperature of 550 °C and its thermal changes at temperature of 574.18 °C indicated by the formation of an endothermic peak and enthalpy of 0.613 cal/g. From the three specimens it is showed that they have a good thermal stability at temperature up to 550 °C. (author)

Noble metal alloys for metal-ceramic restorations.

Science.gov (United States)

Anusavice, K J

1985-10-01

A review of the comparative characteristics and properties of noble metal alloys used for metal-ceramic restorations has been presented. Selection of an alloy for one's practice should be based on long-term clinical data, physical properties, esthetic potential, and laboratory data on metal-ceramic bond strength and thermal compatibility with commercial dental porcelains. Although gold-based alloys, such as the Au-Pt-Pd, Au-Pd-Ag, and Au-Pd classes, may appear to be costly compared with the palladium-based alloys, they have clearly established their clinical integrity and acceptability over an extended period of time. Other than the relatively low sag resistance of the high gold-low silver content alloys and the potential thermal incompatibility with some commercial porcelain products, few clinical failures have been observed. The palladium-based alloys are less costly than the gold-based alloys. Palladium-silver alloys require extra precautions to minimize porcelain discoloration. Palladium-copper and palladium-cobalt alloys may also cause porcelain discoloration, as copper and cobalt are used as colorants in glasses. The palladium-cobalt alloys are least susceptible to high-temperature creep compared with all classes of noble metals. Nevertheless, insufficient clinical data exist to advocate the general use of the palladium-copper and palladium-cobalt alloys at the present time. One should base the selection and use of these alloys in part on their ability to meet the requirements of the ADA Acceptance Program. A list of acceptable or provisionally acceptable alloys is available from the American Dental Association and is published annually in the Journal of the American Dental Association. Dentists have the legal and ethical responsibility for selection of alloys used for cast restorations. This responsibility should not be delegated to the dental laboratory technician. It is advisable to discuss the criteria for selection of an alloy with the technician and the

Positron prevacancy effects in pure annealed metals

International Nuclear Information System (INIS)

Smedskjaer, L.C.

1981-06-01

The low-temperature prevacancy effects sometimes observed with positrons in well-annealed high-purity metals are discussed. It is shown that these effects are not experimental artifacts, but are due to trapping of the positrons. It is suggested that dislocations are responsible for these trapping effects. 46 references, 5 figures

A thermodynamic description of the system Pd-Rh-H-D-T

Energy Technology Data Exchange (ETDEWEB)

Joubert, J.-M., E-mail: jean-marc.joubert@icmpe.cnrs.fr [Chimie Metallurgique des Terres Rares, Institut de Chimie et des Materiaux Paris-Est, CNRS, Universite Paris-Est, UMR 7182, 2-8 Rue Henri Dunant, F-94320 Thiais (France); Thiebaut, S. [CEA/DAM/Valduc, F-21120 Is sur Tille (France)

2011-02-15

The quinary system D-H-Pd-Rh-T has been described thermodynamically by the CALPHAD approach. Previous descriptions of the binary subsystems have been used. To model the high pressure data an equation of state for the gases D{sub 2} and T{sub 2} compatible with the CALPHAD approach has been obtained similar to that previously used for H{sub 2}. A complete literature search has been undertaken for the three ternary systems H-Pd-Rh, D-Pd-Rh and Pd-Rh-T and the most significant experimental data have been selected for a thermodynamic assessment of these systems. In order to complement the available data, pressure-composition curves have been measured at different temperatures for the two last systems in the present work. Calculations and optimization of the system under para-equilibrium conditions, i.e. in pseudo-binary systems (Pd,Rh)-H, (Pd,Rh)-D or (Pd,Rh)-T, have been achieved using a pseudo-atom describing the Pd-Rh solid solution. This special method allows the presence of a miscibility gap in the binary metallic system to be dealt with. We show that a simple combination of the binary systems alone is unable to properly describe these ternary systems and that ternary interaction parameters have to be introduced. The binary and ternary systems may then be combined to perform calculations in the quinary D-H-Pd-Rh-T system. It is believed that extrapolation in systems containing different isotopes are fairly accurate provided that the so-called Toop model is used.

Anti-tumor immunotherapy by blockade of the PD-1/PD-L1 pathway with recombinant human PD-1-IgV.

Science.gov (United States)

Zhang, C; Wu, S; Xue, X; Li, M; Qin, X; Li, W; Han, W; Zhang, Y

2008-01-01

Blockade of the programmed death-1 (PD-1)/PD-ligand 1 (PD-L1) pathway can delay tumor growth and prolong the survival of tumor-bearing mice. The extracellular immunoglobulin (Ig) V domain of PD-1 is important for the interaction between PD-1 and PD-L1, suggesting that PD-1-IgV may be a potential target for anti-tumor immunotherapy. The extracellular sequence of human PD-1-IgV (hPD-1-IgV) was expressed in Escherichia coli and purified. The anti-tumor effect of hPD-1-IgV on tumor-bearing mice was tested. hPD-1-IgV recombinant protein could bind PD-L1 at molecular and cellular levels and enhance Cytotoxic T Lymphocyte (CTL) activity and anti-tumor effect on tumor-bearing mice in vivo. The percentage of CD4(+)CD25(+) T cells in tumor-bearing mice was decreased compared with control mice after administration of the recombinant protein. Our results suggest that inhibition of the interaction between PD-1 and PD-L1 by hPD-1-IgV may be a promising strategy for specific tumor immunotherapy.

Electro-deposition of Pd on Carbon paper and Ni foam via surface limited redox-replacement reaction for oxygen reduction reaction

International Nuclear Information System (INIS)

Modibedi, Remegia M.; Mathe, Mkhulu K.; Motsoeneng, Rapelang G.; Khotseng, Lindiwe E.; Ozoemena, Kenneth I.; Louw, Eldah K.

2014-01-01

Pd nanostructured catalysts were electrodeposited by surface-limited redox replacement reactions using the electrochemical atomic layer deposition technique. Carbon paper and Ni foam were used as substrates for the electrodeposition of the metal. Supported nanostructured Pd electrodes were characterized using electrochemical methods and scanning electron microscopy. Carbon paper and Ni foam produced good quality deposits with some agglomeration on Ni foam. The EDX profiles confirmed the presence of Pd particles. Cyclic voltammograms of the electrodeposited Pd on substrates showed features characteristic of polycrystalline Pd electrodes. In the acidic electrolyte a very weak oxygen reduction reaction (ORR) activity was observed on Pd/Carbon paper electrode when compared to Pd/Ni foam electrode. The Pd/Ni foam electrode showed improved ORR activity in alkaline medium

Biomolecule-coated metal nanoparticles on titanium.

Science.gov (United States)

Christensen, Stephen L; Chatt, Amares; Zhang, Peng

2012-02-07

Immobilizations of nanoparticles and biomolecules on biocompatible substrates such as titanium are two promising approaches to bringing new functionalities to Ti-based biomaterials. Herein, we used a variety of X-ray spectroscopic techniques to study and better understand metal-thiolate interactions in biofunctionalized metal nanoparticle systems supported on Ti substrates. Using a facile one-step procedure, a series of Au nanoparticle samples with varied biomolecule coatings ((2-mercatopropionyl)glycine (MPG) and bovine serum albumin (BSA)) and biomolecule concentrations are prepared. Ag and Pd systems are also studied to observe change with varying metal composition. The structure and properties of these biomolecule-coated nanoparticles are investigated with scanning electron microscopy (SEM) and element-specific X-ray techniques, including extended X-ray absorption fine structure (Au L(3)-edge), X-ray absorption near-edge structure (Au L(3), Ag L(3), Pd L(3), and S K-edge), and X-ray photoelectron spectroscopy (Au 4f, Ag 3d, Pd 3d, and S 2p core level). It was found that, by comparison of SEM and X-ray spectroscopy results, the coating of metal nanoparticles with varying model biomolecule systems can have a significant effect on both surface coverage and organization. This work offers a facile chemical method for bio- and nanofunctionalization of Ti substrates as well as provides a physical picture of the structure and bonding of biocoated metal nanoparticles, which may lead to useful applications in orthopedics and biomedicine.

Catalytic activity of bimetal-containing Co,Pd systems in the oxidation of carbon monoxide

Science.gov (United States)

Oleksenko, L. P.; Lutsenko, L. V.

2013-02-01

The catalytic activity of low-percentage Co,Pd systems on ZSM-5, ERI, SiO2, and Al2O3 supports in the oxidation of CO was studied. The activity of bimetal-containing catalysts was shown to depend on the nature of the catalyst and the amount and ratio of their active components. According to the results of thermoprogrammed reduction with H2 (H2 TPR) and X-ray photoelectron spectroscopy (XPS) data, the metals are distributed as isolated cations or Coδ+-O-Pdδ+ clusters with cobalt and palladium cations surrounded by off-lattice oxygen in Co,Pd systems. The 0.8% Co,0.5% Pd-ZSM-5 bimetal catalysts were found to be more active due to the presence of clusters.

PdCu alloy nanoparticle-decorated copper nanotubes as enhanced electrocatalysts: DFT prediction validated by experiment

Science.gov (United States)

Wu, Dengfeng; Xu, Haoxiang; Cao, Dapeng; Fisher, Adrian; Gao, Yi; Cheng, Daojian

2016-12-01

In order to combine the advantages of both 0D and 1D nanostructured materials into a single catalyst, density functional theory (DFT) calculations have been used to study the PdCu alloy NP-decorated Cu nanotubes (PdCu@CuNTs). These present a significant improvement of the electrocatalytic activity of formic acid oxidation (FAO). Motivated by our theoretical work, we adopted the seed-mediated growth method to successfully synthesize the nanostructured PdCu@CuNTs. The new catalysts triple the catalytic activity for FAO, compared with commercial Pd/C. In summary, our work provides a new strategy for the DFT prediction and experimental synthesis of novel metal NP-decorated 1D nanostructures as electrocatalysts for fuel cells.

Stabilization of Palladium Nanoparticles on Nanodiamond-Graphene Core-Shell Supports for CO Oxidation.

Science.gov (United States)

Zhang, Liyun; Liu, Hongyang; Huang, Xing; Sun, Xueping; Jiang, Zheng; Schlögl, Robert; Su, Dangsheng

2015-12-21

Nanodiamond-graphene core-shell materials have several unique properties compared with purely sp(2) -bonded nanocarbons and perform remarkably well as metal-free catalysts. In this work, we report that palladium nanoparticles supported on nanodiamond-graphene core-shell materials (Pd/ND@G) exhibit superior catalytic activity in CO oxidation compared to Pd NPs supported on an sp(2) -bonded onion-like carbon (Pd/OLC) material. Characterization revealed that the Pd NPs in Pd/ND@G have a special morphology with reduced crystallinity and are more stable towards sintering at high temperature than the Pd NPs in Pd/OLC. The electronic structure of Pd is changed in Pd/ND@G, resulting in weak CO chemisorption on the Pd NPs. Our work indicates that strong metal-support interactions can be achieved on a non-reducible support, as exemplified for nanocarbon, by carefully tuning the surface structure of the support, thus providing a good example for designing a high-performance nanostructured catalyst. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structural stability of Pd40Cu30Ni10P20 metallic glass in supercooled liquid region

International Nuclear Information System (INIS)

Jiang, J.Z.; Saksl, K.

2004-01-01

Phase separation of bulk and ribbon Pd 40 Cu 30 Ni 10 P 20 glasses, annealed in the supercooled liquid region at ambient pressure and high pressures, has been studied by means of differential scanning calorimetry (DSC) and X-ray diffraction techniques. DSC measurements show only one glass transition event in all annealed samples, indicating that no phase separation occurs in the alloy annealed in the supercooled liquid region. Phase analyses reveal at least six crystalline phases in the crystallized sample: monoclinic, tetragonal Cu 3 Pd-like, rhombohedral, fcc-Ni 2 Pd 2 P, fcc-(Ni, Pd) solid solution, and body-centered tetragonal (bct) Ni 3 P-like phases. Annealing treatments under external pressures in the vicinity of the glass transition temperature neither induce phase separation nor alter the glass transition temperature of the Pd 40 Cu 30 Ni 10 P 20 bulk glass

Effect of different surface treatments and retainer designs on the retention of posterior Pd-Ag porcelain-fused-to-metal resin-bonded fixed partial dentures.

Science.gov (United States)

Chen, Xiwen; Zhang, Yixin; Zhou, Jinru; Chen, Chenfeng; Zhu, Zhimin; Li, Lei

2018-02-01

The aim of this study was to investigate the adhesive property of palladium-silver alloy (Pd-Ag) and the simulated clinical performance of Pd-Ag porcelain-fused-to-metal (PFM), resin-bonded, fixed partial dentures (RBFPDs). A total of 40 Pd-Ag discs (diameter=5 mm) were prepared and divided into the following four groups (n=10): a) No sandblasting, used as a control; and b, 50 µm; c, 110 µm; and d, 250 µm aluminum oxide (Al 2 O 3 ) particles, respectively. Another 50 discs were pre-sandblasted and divided into five groups (n=10) subjected to different treatments: e) Sandblasting, used as a control; f) silane; g) alloy primer; h) silica coating + silane and i) silica coating + alloy primer. All 90 discs were bonded to enamel with Panavia F 2.0 and then subjected to shear bond strength (SBS) testing. The fracture surfaces were examined by scanning electron microscopy. Next, 40 missing maxillary second premolar models were restored with one of the four following RBFPD designs (n=10): I) A premolar occlusal bar combined with molar double rests (MDR); II) both occlusal bars with a wing (OBB); III) a premolar occlusal bar combined with a molar dental band (MDB); and IV) two single rests adjacent to the edentulous space with a wing (SRB) used as a control. All specimens were aged with thermal cycling and mechanical loading. Subsequently, they were loaded until broken. The data were analyzed by one-way analysis of variance. Al 2 O 3 (250 µm) abrasion provided the highest SBS (P<0.05). The alloy primer and silica + silane exhibited increased SBS. Furthermore, fracture analysis revealed that the failure mode varied among the different treatments. Whereas MDB exhibited the highest retention (P<0.05), that of OBB was greater than that of MDR (P<0.05), and the control exhibited the lowest retention. Abrasion with Al 2 O 3 (250 µm) effectively increased the adhesive property of Pd-Ag. Additionally, treatment with the alloy primer and silica coating + silane was able to

New experimental set-up and procedure for analyzing the dynamics of permeation of H2(g) across Pd-based metallic membranes

International Nuclear Information System (INIS)

Decaux, C.; Millet, P.; Decaux, C.

2006-01-01

. Impedances of the sorbing (permeating) membrane materials are then calculated using the theory of linear and time-invariant systems, by numerically Fourier-transforming the discretely sampled pressure signals. Using appropriate initial and boundary conditions, it is shown that the rate constants of the two major steps of the sorption (permeation) mechanisms can be separately accessed, i.e. surface resistances related to hydrogen dissociation (upstream side) and recombination (downstream side) processes, and bulk diffusion impedance. This experimental equipment and this treatment procedure therefore provide a new tool for analyzing the dynamics of hydrogen permeation across metallic membranes. This tool can be used for diagnosis purposes and for optimizing the structure and composition of permeation membranes. Results obtained with Pd and Pd 77 Ag 23 foils are presented and discussed. (authors)

Effect of the strong metal-support interaction on hydrogen sorption kinetics of Pd-capped switchable mirrors

NARCIS (Netherlands)

Borgschulte, A.; Westerwaal, R.J.; Rector, J.H.; Dam, B.; Griessen, R.P.; Schoenes, J.

2004-01-01

The morphology and electronic structure of Pd clusters grown on oxidized yttrium surfaces are investigated by scanning tunneling microscopy and ultraviolet photoelectron spectroscopy. The hydrogen sorption mediated by the Pd clusters is determined from the optically monitored switching kinetics of

Dissolving, trapping and detrapping mechanisms of hydrogen in bcc and fcc transition metals

Directory of Open Access Journals (Sweden)

Yu-Wei You

2013-01-01

Full Text Available First-principles calculations are performed to investigate the dissolving, trapping and detrapping of H in six bcc (V, Nb, Ta, Cr, Mo, W and six fcc (Ni, Pd, Pt, Cu, Ag, Au metals. We find that the zero-point vibrations do not change the site-preference order of H at interstitial sites in these metals except Pt. One vacancy could trap a maximum of 4 H atoms in Au and Pt, 6 H atoms in V, Nb, Ta, Cr, Ni, Pd, Cu and Ag, and 12 H atoms in Mo and W. The zero-point vibrations never change the maximum number of H atoms trapped in a single vacancy in these metals. By calculating the formation energy of vacancy-H (Vac-Hn complex, the superabundant vacancy in V, Nb, Ta, Pd and Ni is demonstrated to be much more easily formed than in the other metals, which has been found in many metals including Pd, Ni and Nb experimentally. Besides, we find that it is most energetically favorable to form Vac-H1 complex in Pt, Cu, Ag and Au, Vac-H4 in Cr, Mo and W, and Vac-H6 in V, Nb, Ta, Pd and Ni. At last, we examine the detrapping behaviors of H atoms in a single vacancy and find that with the heating rate of 10 K/min a vacancy could accommodate 4, 5 and 6 H atoms in Cr, Mo and W at room temperature, respectively. The detrapping temperatures of all H atoms in a single vacancy in V, Nb, Ta, Ni, Pd, Cu and Ag are below room temperature.

Determination of redox reaction rates and orders by in situ liquid cell electron microscopy of Pd and Au solution growth.

Science.gov (United States)

Sutter, Eli A; Sutter, Peter W

2014-12-03

In-situ liquid cell transmission and scanning transmission electron microscopy (TEM/STEM) experiments are important, as they provide direct insight into processes in liquids, such as solution growth of nanoparticles, among others. In liquid cell TEM/STEM redox reaction experiments, the hydrated electrons e(-)aq created by the electron beam are responsible for the reduction of metal-ion complexes. Here we investigate the rate equation of redox reactions involving reduction by e(-)aq generated by the electron beam during in situ liquid TEM/STEM. Specifically we consider the growth of Pd on Au seeds in aqueous solutions containing Pd-chloro complexes. From the quantification of the rate of Pd deposition at different electron beam currents and as a function of distance from a stationary, nanometer-sized exciting beam, we determine that the reaction is first order with respect to the concentration of hydrated electrons, [e(-)aq]. By comparing Pd- and Au-deposition, we further demonstrate that measurements of the local deposition rate on nanoparticles in the solution via real-time imaging can be used to measure not only [e(-)aq] but also the rate of reduction of a metal-ion complex to zerovalent metal atoms in solution.

Photoelectrocatalytic Glucose Oxidation to Promote Hydrogen Production over Periodically Ordered TiO2 Nanotube Arrays Assembled of Pd Quantum Dots

International Nuclear Information System (INIS)

Zhang, Yajun; Zhao, Guohua; Shi, Huijie; Zhang, Ya-nan; Huang, Wenna; Huang, Xiaofeng; Wu, Zhongyi

2015-01-01

Highlights: • Solar-driven PEC glucose oxidation to promote hydrogen production was presented. • The excellent PEC activity of Pd QDs@TNTAs was investigated. • The rate of hydrogen production from glucose was about 15 times than water. • A low-cost and efficient method in renewables-to-hydrogen conversion was put forward. - Abstract: The development of highly efficient and low-cost approaches for catalytic hydrogen production from renewable energy is of tremendous importance for a truly sustainable hydrogen-based energy carrier in future life. Herein, the probability of utilizing solar light to product hydrogen from biomass derivative, glucose, was systematically demonstrated by using the periodically ordered TiO 2 nanotube arrays (TNTAs) assembled of Palladium quantum dots (Pd QDs), i.e. Pd QDs@ TNTAs as photoanode. The results showed that remarkably increased photocurrent density was obtained in the glucose solution compared to the pure KOH electrolyte over as-prepared photoelectrode, which indicated that the glucose could be faster oxidized than water oxidation, and thus could promote the hydrogen production on Pt cathode. The yield of hydrogen production from glucose oxidation reached as high as 164.8 μmol cm −1 over Pd QDs@TNTAs photoanode and Pt cathode system (denoted as Pd QDs@TNTAs/Pt) under the solar light irradiation for 6 h, which was about 15 times higher than that from pure water splitting. The superior hydrogen production performance could be attributed to the less endergonic process of the glucose oxidation than water, as well as the efficient synergistic photoelectrocatalytic (PEC) glucose oxidation over Pd QDs@TNTAs photoanode which possesses excellent photoelectrochemical performance and structure characteristics. Moreover, a probable mechanism for the PEC hydrogen production from biomass derivatives oxidation was proposed and discussed

Ultrasound-induced crystallization around the glass transition temperature for Pd40Ni40P20 metallic glass

International Nuclear Information System (INIS)

Ichitsubo, Tetsu; Matsubara, Eiichiro; Kai, Satoshi; Hirao, Masahiko

2004-01-01

We have found that crystallization of a Pd 40 Ni 40 P 20 bulk metallic glass is accelerated in the vicinity of the glass transition temperature T g when it is subjected to sub/low-MHz frequency ultrasonic vibration. Resonance frequencies and internal frictions have been measured with the electromagnetic acoustic resonance (EMAR) technique. In the initial heating process of an as-cast glassy sample, the resonance frequencies jump up just above T g under ultrasonic excitation, which is attributed to nano-crystallization that is confirmed by the X-ray diffraction profile. However, such a notable change is not observed without ultrasonic vibration. The irregular Λ-shaped internal-friction peaks are also observed prior to the abrupt crystallization. This rapid crystallization is considered to be caused by a stochastic resonance, in which the jump frequency of atoms matches the frequency of the interatomic-potential change by the ultrasonic vibration

Electrochemical chiral recognition by microparticle coatings of Pd complexes with bridging cyclometalated phosphines

Energy Technology Data Exchange (ETDEWEB)

Domenech, Antonio [Departament de Quimica Analitica, Facultat de Quimica, Universitat de Valencia, Dr. Moliner 50, 46100 Burjassot, Valencia (Spain)], E-mail: antonio.domenech@uv.es; Koshevoy, Igor O.; Penno, Dirk; Ubeda, Maria Angeles [Departament de Quimica Inorganica, Facultat de Quimica, Universitat de Valencia, Dr. Moliner 50, 46100 Burjassot, Valencia (Spain)

2008-03-10

The palladium(II) dinuclear complex with bridging cyclometalated phosphines, {l_brace}Pd{sub 2}[{mu}-(C{sub 6}H{sub 4})PPh{sub 2}]{sub 2}({mu}-O{sub 2}CCH{sub 3}){sub 2}{r_brace} (Pd{sub 2}L{sub 2}), having a paddlewheel structure, is reversibly oxidized in CH{sub 2}Cl{sub 2} to a dinuclear palladium(III) analogue via two successive one-electron steps. Solid state voltammetry of Pd{sub 2}L{sub 2} in contact with aqueous electrolytes produce as one-electron oxidation with two competing mechanisms involving anion intercalation/anion binding between/to metal centres, chloride ions acting as inhibitors for the first pathway. R- and S-Pd{sub 2}L{sub 2} produces a significant stereoselective electrocatalytic activity with respect to the oxidation of L- and D-glutamic acid in alkaline media.

Raman spectroscopy of DNA-metal complexes. I. Interactions and conformational effects of the divalent cations: Mg, Ca, Sr, Ba, Mn, Co, Ni, Cu, Pd, and Cd.

Science.gov (United States)

Duguid, J; Bloomfield, V A; Benevides, J; Thomas, G J

1993-11-01

Interactions of divalent metal cations (Mg2+, Ca2+, Ba2+, Sr2+, Mn2+, Co2+, Ni2+, Cu2+, Pd2+, and Cd2+) with DNA have been investigated by laser Raman spectroscopy. Both genomic calf-thymus DNA (> 23 kilobase pairs) and mononucleosomal fragments (160 base pairs) were employed as targets of metal interaction in solutions containing 5 weight-% DNA and metal:phosphate molar ratios of 0.6:1. Raman difference spectra reveal that transition metal cations (Mn2+, Co2+, Ni2+, Cu2+, Pd2+, and Cd2+) induce the greatest structural changes in B-DNA. The Raman (vibrational) band differences are extensive and indicate partial disordering of the B-form backbone, reduction in base stacking, reduction in base pairing, and specific metal interaction with acceptor sites on the purine (N7) and pyrimidine (N3) rings. Many of the observed spectral changes parallel those accompanying thermal denaturation of B-DNA and suggest that the metals link the bases of denatured DNA. While exocyclic carbonyls of dT, dG, and dC may stabilize metal ligation, correlation plots show that perturbations of the carbonyls are mainly a consequence of metal-induced denaturation of the double helix. Transition metal interactions with the DNA phosphates are weak in comparison to interactions with the bases, except in the case of Cu2+, which strongly perturbs both base and phosphate group vibrations. On the other hand, the Raman signature of B-DNA is largely unperturbed by Mg2+, Ca2+, Sr2+, and Ba2+, suggesting much weaker interactions of the alkaline earth metals with both base and phosphate sites. A notable exception is a moderate perturbation by alkaline earths of purine N7 sites in 160-base pair DNA, with Ca2+ causing the greatest effect. Correlation plots demonstrate a strong interrelationship between perturbations of Raman bands assigned to ring vibrations of the bases and those of bands assigned to exocyclic carbonyls and backbone phosphodiester groups. However, strong correlations do not occur between

Pure and multi metal oxide nanoparticles: synthesis, antibacterial and cytotoxic properties.

Science.gov (United States)

Stankic, Slavica; Suman, Sneha; Haque, Francia; Vidic, Jasmina

2016-10-24

Th antibacterial activity of metal oxide nanoparticles has received marked global attention as they can be specifically synthesized to exhibit significant toxicity to bacteria. The importance of their application as antibacterial agents is evident keeping in mind the limited range and effectiveness of antibiotics, on one hand, and the plethora of metal oxides, on the other, along with the propensity of nanoparticles to induce resistance being much lower than that of antibiotics. Effective inhibition against a wide range of bacteria is well known for several nano oxides consisting of one metal (Fe 3 O 4 , TiO 2 , CuO, ZnO), whereas, research in the field of multi-metal oxides still demands extensive exploration. This is understandable given that the relationship between physicochemical properties and biological activity seems to be complex and difficult to generalize even for metal oxide nanoparticles consisting of only one metal component. Also, despite the broad scope that metal oxide nanoparticles have as antibacterial agents, there arise problems in practical applications taking into account the cytotoxic effects. In this respect, the consideration of polymetallic oxides for biological applications becomes even greater since these can provide synergetic effects and unify the best physicochemical properties of their components. For instance, strong antibacterial efficiency specific of one metal oxide can be complemented by non-cytotoxicity of another. This review presents the main methods and technological advances in fabrication of nanostructured metal oxides with a particular emphasis to multi-metal oxide nanoparticles, their antibacterial effects and cytotoxicity.

Pure and multi metal oxide nanoparticles: synthesis, antibacterial and cytotoxic properties

Directory of Open Access Journals (Sweden)

Slavica Stankic

2016-10-01

Full Text Available Abstract Th antibacterial activity of metal oxide nanoparticles has received marked global attention as they can be specifically synthesized to exhibit significant toxicity to bacteria. The importance of their application as antibacterial agents is evident keeping in mind the limited range and effectiveness of antibiotics, on one hand, and the plethora of metal oxides, on the other, along with the propensity of nanoparticles to induce resistance being much lower than that of antibiotics. Effective inhibition against a wide range of bacteria is well known for several nano oxides consisting of one metal (Fe3O4, TiO2, CuO, ZnO, whereas, research in the field of multi-metal oxides still demands extensive exploration. This is understandable given that the relationship between physicochemical properties and biological activity seems to be complex and difficult to generalize even for metal oxide nanoparticles consisting of only one metal component. Also, despite the broad scope that metal oxide nanoparticles have as antibacterial agents, there arise problems in practical applications taking into account the cytotoxic effects. In this respect, the consideration of polymetallic oxides for biological applications becomes even greater since these can provide synergetic effects and unify the best physicochemical properties of their components. For instance, strong antibacterial efficiency specific of one metal oxide can be complemented by non-cytotoxicity of another. This review presents the main methods and technological advances in fabrication of nanostructured metal oxides with a particular emphasis to multi-metal oxide nanoparticles, their antibacterial effects and cytotoxicity.

Catalyst activity or stability: the dilemma in Pd-catalyzed polyketone synthesis.

Science.gov (United States)

Amoroso, Francesco; Zangrando, Ennio; Carfagna, Carla; Müller, Christian; Vogt, Dieter; Hagar, Mohamed; Ragaini, Fabio; Milani, Barbara

2013-10-28

A series of Pd-complexes containing nonsymmetrical bis(aryl-imino)acenaphthene (Ar-BIAN) ligands, characterized by substituents on the meta positions of the aryl rings, have been synthesized, characterized and applied in CO/vinyl arene copolymerization reactions. Crystal structures of two neutral Pd-complexes have been solved allowing comparison of the bonding properties of the ligand. Kinetic and mechanistic investigations on these complexes have been performed. The kinetic investigations indicate that in general ligands with electron-withdrawing substituents give more active, but less stable, catalytic systems, although steric effects also play a role. The good performance observed with nonsymmetrical ligands is at least in part due to a compromise between catalyst activity and lifetime, leading to a higher overall productivity with respect to catalysts based on their symmetrical counterparts. Additionally, careful analysis of the reaction profiles provided information on the catalyst deactivation pathway. The latter begins with the reduction of a Pd(II) Ar-BIAN complex to the corresponding Pd(0) species, a reaction that can be reverted by the action of benzoquinone. Then the ligand is lost, a process that appears to be facilitated by the contemporary coordination of an olefin or a CO molecule. The so formed Pd(0) complex immediately reacts with another molecule of the initial Pd(II) complex to give a Pd(I) dimeric species that irreversibly evolves to metallic palladium. Mechanistic investigations performed on the complex with a nonsymmetrical Ar-BIAN probe evidence that the detected intermediates are characterized by the Pd-C bond trans to the Pd-N bond of the aryl ring bearing electron-withdrawing substituents. In addition, the intermediate resulting from the insertion of 4-methylstyrene into the Pd-acyl bond is a five-member palladacycle and not the open-chain η(3)-allylic species observed for complexes with Ar-BIANs substituted in ortho position.

Catalytic transformations of fatty acids derivatives for food, oleochemicals and fuels over carbon supported platinum group metals

Energy Technology Data Exchange (ETDEWEB)

Simakova, I.

2010-07-01

The main focus of the research is in the development of an alternative harmless Pd-based hydrogenation technology compared to the traditional one based on Ni. Pd counterparts could be recycled, is more active and resistant to acids and form less trans isomers. In order to be economically viable and competitive this technology has to be based on the best catalyst that means an optimized combination of high activity, high life-time and high selectivity. Therefore, the engineering aspects were closely taken into account and much effort was directed into the design of Pd on a mesoporous carbon support as well as in establishing the correlation between catalyst characteristics and its activity in the C=C hydrogenation and isomerization. Detailed characterization (TEM, XRD, XPS, TPR, CO TPD, physisorption and CO chemisorption) of the tested catalysts was carried out. In addition, the influence of temperature, hydrogen pressure, catalytic concentration on the fatty-acid and isomeric composition of hydrogenated oils were determined in the absence of mass transfer limitations. Deoxygenation by full decarboxylation of -COOH function of fatty acid is the best way to make green diesel because paraffins are produced and utilization of expensive hydrogen is not required. Deoxygenation was systematically investigated over Pd/C (Sibunit) using saturated fatty acids C16 - C20 and C22, as feeds, producing one less carbon containing, diesel-like hydrocarbons. The same decarboxylation rates were obtained for pure saturated fatty acids. Comparison of deoxygenation rate for stearic, oleic or linoleic acids as a feedstock at 300 deg C under 1 vol% hydrogen over mesoporous Pd/C (Sibunit) catalyst revealed that catalyst activity and selectivity increased with less unsaturated feedstock. The main products in the case of stearic acid were desired C17 hydrocarbons, whereas the amounts of C17 aromatic compounds increased in case of oleic and linoleic acids. Catalyst deactivation was relatively

High spin-polarization in ultrathin Co2MnSi/CoPd multilayers

International Nuclear Information System (INIS)

Galanakis, I.

2015-01-01

Half-metallic Co 2 MnSi finds a broad spectrum of applications in spintronic devices either in the form of thin films or as spacer in multilayers. Using state-of-the-art ab-initio electronic structure calculations we exploit the electronic and magnetic properties of ultrathin Co 2 MnSi/CoPd multilayers. We show that these heterostructures combine high values of spin-polarization at the Co 2 MnSi spacer with the perpendicular magnetic anisotropy of binary compounds such as CoPd. Thus they could find application in spintronic/magnetoelectronic devices. - Highlights: • Ab-initio study of ultrathin Co 2 MnSi/CoPd multilayers. • Large values of spin-polarization at the Fermi are retained. • Route for novel spintronic/magnetoelectronic devices

Synthesis and Characterization of Electrodeposited C-PANI-Pd-Ni Composite Electrocatalyst for Methanol Oxidation

Directory of Open Access Journals (Sweden)

S. S. Mahapatra

2014-01-01

Full Text Available Electropolymerization of aniline at the graphite electrodes was achieved by potentiodynamic method. Electrodeposition of Pd (C-PANI-Pd and Ni (C-PANI-Ni and codeposition of Pd-Ni (C-PANI-Pd-Ni microparticles into the polyaniline (PANI film coated graphite (C-PANI were carried out under galvanostatic control. The morphology and composition of the composite electrodes were obtained using scanning electron microscopy (SEM and energy dispersive X-ray analysis (EDX techniques. The electrochemical behavior and electrocatalytic activity of the electrode were characterized using cyclic voltammetry (CV, electrochemical impedance spectroscopy (EIS, and chronoamperometric (CA methods in acidic medium. The C-PANI-Pd-Ni electrode showed an improved catalytic performance towards methanol oxidation in terms of lower onset potential, higher anodic oxidation current, greater stability, lower activation energy, and lower charge transfer resistance. The enhanced electrocatalytic activity might be due to the greater permeability of C-PANI films for methanol molecules, better dispersion of Pd-Ni microparticles into the polymer matrixes, and the synergistic effects between the dispersed metal particles and their matrixes.

Exfoliated Pd/HNb{sub 3}O{sub 8} nanosheet as highly efficient bifunctional catalyst for one-pot cascade reaction

Energy Technology Data Exchange (ETDEWEB)

Lee, Nahaeng; Chung, Young-Min, E-mail: ymchung@kunsan.ac.kr

2016-05-01

Graphical abstract: - Highlights: • Ultrathin and highly acidic HNb{sub 3}O{sub 8} nanosheet was prepared by exfoliation of layered niobium oxide. • Pd/HNb{sub 3}O{sub 8} nanosheet showed excellent catalytic performance for one-pot cascade reaction. • The reaction performance of Pd/HNb{sub 3}O{sub 8} nanosheet is 7.1 and 1.2 times higher than that of layered Pd/KNb{sub 3}O{sub 8} or Pd/HNb{sub 3}O{sub 8}, respectively. • Significant promoting effect of support acidity on the reaction performance was observed. - Abstract: Ultrathin two-dimensional metal oxide nanosheets have drawn attention as potential solid acid catalysts owing to their strong acidity, attributed to the bridged OH groups formed on the nanosheets. In this study, a new class of bifunctional acid–metal catalyst was realized by the deposition of Pd on layered niobium oxide (KNb{sub 3}O{sub 8} and HNb{sub 3}O{sub 8}) or its exfoliated nanosheet (Pd/HNb{sub 3}O{sub 8}-NS) and applied to one-pot cascade deacetalization and hydrogenation. It was found that the acid strength of the support exerted a large influence not only on the promotion of the first deacetalization step, but also on the acceleration of the subsequent hydrogenation step. Comparative experiments using a series of Pd/HZSM-5 catalysts with different acidities reconfirmed the crucial role of acid strength on hydrogenation. However, the superior catalytic activity of Pd/HNb{sub 3}O{sub 8}-NS for hydrogenation compared to that of Pd/HZSM-5 of similar acidity suggests a more efficient ensemble effect of the strong acid sites with the nearby metal sites on the nanosheet surface. Among the catalysts used, Pd/HNb{sub 3}O{sub 8}-NS showed the best catalytic performance for one-pot cascade reaction affording the desired product (benzyl alcohol) in approximately 92% yield, which was 7.1 and 1.2 times higher than that of layered Pd/KNb{sub 3}O{sub 8} or Pd/HNb{sub 3}O{sub 8}, respectively. The excellent catalytic performance of Pd/HNb{sub 3

Density functional investigation of mercury and arsenic adsorption on nitrogen doped graphene decorated with palladium clusters: A promising heavy metal sensing material in farmland

International Nuclear Information System (INIS)

Zhao, Chunjiang; Wu, Huarui

2017-01-01

Highlights: • PNG can be acted as micro-sensor for monitoring heavy metal in agriculture. • The most favorable adsorption site of Pd atom or cluster on PNG is the vacancy site. • The Pd atom or cluster enhance the reactivity of PNG toward Hg and AsH_3 adsorption. • The efficiency of a sorbent can be tuned by tailoring the ε_d of adsorbed metals. - Abstract: Density functional theory calculations are carried out to study the adsorption of mercury and arsenic on Pd_n (n = 1–6) supported on pyridine-like nitrogen doped graphene (PNG). Owing to the promising sensitivity in trace amounts of atoms or molecules, PNG can be acted as micro-sensor for sensing heavy metals in agriculture soils. Through the analyses of structural and electronic properties of pristine PNG and Pd atom decorated PNG, we find that the most favorable adsorption site for Pd atom is the vacancy site. The analyses of structural and electronic properties reveal that the Pd atom or clusters can enhance the reactivity for Hg and AsH_3 adsorption on PNG. The adsorption ability of Hg on Pd_n decorated PNG is found to be related to the d-band center (ε_d) of the Pd_n, in which the closer ε_d of Pd_n to the Fermi level, the higher adsorption strength for Hg on Pd_n decorated PNG. Moreover, the charge transfer between Pd_n and arsenic may constitute arsenic adsorption on Pd_n decorated PNG. Further design of highly efficient carbon based sorbents for heavy metals removal should be focused on tailoring ε_d of adsorbed metals.

Water growth on metals and oxides: binding, dissociation and role of hydroxyl groups

Energy Technology Data Exchange (ETDEWEB)

Salmeron, M.; Bluhm, H.; Tatarkhanov, M.; Ketteler, G.; Shimizu, T.K.; Mugarza, A.; Deng, Xingyi; Herranz, T.; Yamamoto, S.; Nilsson, A.

2008-09-01

The authors discuss the role of the presence of dangling H bonds from water or from surface hydroxyl species on the wetting behavior of surfaces. Using Scanning Tunneling and Atomic Force Microscopies, and Photoelectron Spectroscopy, they have examined a variety of surfaces, including mica, oxides, and pure metals. They find that in all cases, the availability of free, dangling H-bonds at the surface is crucial for the subsequent growth of wetting water films. In the case of mica electrostatic forces and H-bonding to surface O atoms determine the water orientation in the first layer and also in subsequent layers with a strong influence in its wetting characteristics. In the case of oxides like TiO{sub 2}, Cu{sub 2}O, SiO{sub 2} and Al{sub 2}O{sub 3}, surface hydroxyls form readily on defects upon exposure to water vapor and help nucleate the subsequent growth of molecular water films. On pure metals, such as Pt, Pd, and Ru, the structure of the first water layer and whether or not it exhibits dangling H bonds is again crucial. Dangling H-bonds are provided by molecules with their plane oriented vertically, or by OH groups formed by the partial dissociation of water. By tying the two II atoms of the water molecules into strong H-bonds with pre-adsorbed O on Ru can also quench the wettability of the surface.

Photoelectron diffraction study of Rh nanoparticles growth on Fe3O4/Pd(111) ultrathin film

International Nuclear Information System (INIS)

Abreu, G. J. P.; Pancotti, A; Lima, L. H. de; Landers, R.; Siervo, A. de

2013-01-01

Metallic nanoparticles (NPs) supported on oxides thin films are commonly used as model catalysts for studies of heterogeneous catalysis. Several 4d and 5d metal NPs (for example, Pd, Pt and Au) grown on alumina, ceria and titania have shown strong metal support interaction (SMSI), for instance the encapsulation of the NPs by the oxide. The SMSI plays an important role in catalysis and is very dependent on the support oxide used. The present work investigates the growth mechanism and atomic structure of Rh NPs supported on epitaxial magnetite Fe 3 O 4 (111) ultrathin films prepared on Pd(111) using the Molecular Beam Epitaxy (MBE) technique. The iron oxide and the Rh NPs were characterized using X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction and photoelectron diffraction (PED). The combined XPS and PED results indicate that Rh NPs are metallic, cover approximately 20 % of the iron oxide surface and show height distribution ranging 3–5 ML (monolayers) with essentially a bulk fcc structure.

Pure spin current manipulation in antiferromagnetically exchange coupled heterostructures

Science.gov (United States)

Avilés-Félix, L.; Butera, A.; González-Chávez, D. E.; Sommer, R. L.; Gómez, J. E.

2018-03-01

We present a model to describe the spin currents generated by ferromagnet/spacer/ferromagnet exchange coupled trilayer systems and heavy metal layers with strong spin-orbit coupling. By exploiting the magnitude of the exchange coupling (oscillatory RKKY-like coupling) and the spin-flop transition in the magnetization process, it has been possible to produce spin currents polarized in arbitrary directions. The spin-flop transition of the trilayer system originates pure spin currents whose polarization vector depends on the exchange field and the magnetization equilibrium angles. We also discuss a protocol to control the polarization sign of the pure spin current injected into the metallic layer by changing the initial conditions of magnetization of the ferromagnetic layers previously to the spin pumping and inverse spin Hall effect experiments. The small differences in the ferromagnetic layers lead to a change in the magnetization vector rotation that permits the control of the sign of the induced voltage components due to the inverse spin Hall effect. Our results can lead to important advances in hybrid spintronic devices with new functionalities, particularly, the ability to control microscopic parameters such as the polarization direction and the sign of the pure spin current through the variation of macroscopic parameters, such as the external magnetic field or the thickness of the spacer in antiferromagnetic exchange coupled systems.

Improvement on the electrical characteristics of Pd/HfO{sub 2}/6H-SiC MIS capacitors using post deposition annealing and post metallization annealing

Energy Technology Data Exchange (ETDEWEB)

Esakky, Papanasam, E-mail: papanasamte@gmail.com; Kailath, Binsu J

2017-08-15

Highlights: • Post deposition annealing (PDA) and post metallization annealing (PMA) on the electrical characteristics of Pd/HfO{sub 2}/6H-SiC MIS capacitors. • Post deposition N{sub 2}O plasma annealing inhibits crystallization of HfO{sub 2} during high temperature annealing. • Plasma annealing followed by RTA in N{sub 2} results in formation of hafnium silicate at the HfO{sub 2}-SiC interface. • PDA reduces interface state density (D{sub it}) and gate leakage current density (J{sub g}) by order. • PMA in forming gas for 40 min results in better passivation and reduces D{sub it} by two orders and J{sub g} by thrice. - Abstract: HfO{sub 2} as a gate dielectric enables high electric field operation of SiC MIS structure and as gas sensor HfO{sub 2}/SiC capacitors offer higher sensitivity than SiO{sub 2}/SiC capacitors. The issue of higher density of oxygen vacancies and associated higher leakage current necessitates better passivation of HfO{sub 2}/SiC interface. Effect of post deposition annealing in N{sub 2}O plasma and post metallization annealing in forming gas on the structural and electrical characteristics of Pd/HfO{sub 2}/SiC MIS capacitors are reported in this work. N{sub 2}O plasma annealing suppresses crystallization during high temperature annealing thereby improving the thermal stability and plasma annealing followed by rapid thermal annealing in N{sub 2} result in formation of Hf silicate at the HfO{sub 2}/SiC interface resulting in order of magnitude lower density of interface states and gate leakage current. Post metallization annealing in forming gas for 40 min reduces interface state density by two orders while gate leakage current density is reduced by thrice. Post deposition annealing in N{sub 2}O plasma and post metallization annealing in forming gas are observed to be effective passivation techniques improving the electrical characteristics of HfO{sub 2}/SiC capacitors.

Recovery and use of fission product noble metals

International Nuclear Information System (INIS)

Jensen, G.A.; Rohmann, C.A.; Perrigo, L.D.

1980-06-01

Noble metals in fission products are of strategic value. Market prices for noble metals are rising more rapidly than recovery costs. A promising concept has been developed for recovery of noble metals from fission product waste. Although the assessment was made only for the three noble metal fission products (Rh, Pd, Ru), there are other fission products and actinides which have potential value

Expression of PD-1 and PD-L1 in poorly differentiated neuroendocrine carcinomas of the digestive system: a potential target for anti-PD-1/PD-L1 therapy.

Science.gov (United States)

Roberts, Jordan A; Gonzalez, Raul S; Das, Satya; Berlin, Jordan; Shi, Chanjuan

2017-12-01

Poorly differentiated neuroendocrine carcinoma of the digestive system has a dismal prognosis with limited treatment options. This study aimed to investigate expression of the PD-1/PD-L1 pathway in these tumors. Thirty-seven patients with a poorly differentiated neuroendocrine carcinoma of the digestive system were identified. Their electronic medical records, pathology reports, and pathology slides were reviewed for demographics, clinical history, and pathologic features. Tumor sections were immunohistochemically labeled for PD-1 and PD-L1, and expression of PD-1 and PD-L1 on tumor and tumor-associated immune cells was analyzed and compared between small cell and large cell neuroendocrine carcinomas. The mean age of patients was 61 years old with 18 men and 19 women. The colorectum (n=20) was the most common primary site; other primary sites included the pancreaticobiliary system, esophagus, stomach, duodenum, and ampulla. Expression of PD-1 was detected on tumor cells (n=6, 16%) as well as on tumor-associated immune cells (n=23, 63%). The 6 cases with PD-1 expression on tumor cells also had the expression on immune cells. Expression of PD-L1 was visualized on tumor cells in 5 cases (14%) and on tumor-associated immune cells in 10 cases (27%). There was no difference in PD-1 and PD-L1 expression between small cell and large cell neuroendocrine carcinomas. In conclusion, PD-1/PD-L1 expression is a frequent occurrence in poorly differentiated neuroendocrine carcinomas of the digestive system. Checkpoint blockade targeting the PD-1/PD-L1 pathway may have a potential role in treating patients with this disease. Copyright © 2017 Elsevier Inc. All rights reserved.

Surface structure and reaction property of CuCl2-PdCl2 bimetallic catalyst in methanol oxycarbonylation: A DFT approach

International Nuclear Information System (INIS)

Meng, Qingsen; Wang, Shengping; Shen, Yongli; Yan, Bing; Wu, Yuanxin; Ma, Xinbin

2014-01-01

Surface structure of CuCl 2 -PdCl 2 bimetallic catalyst (Wacker-type catalyst) was built employing density functional theory (DFT) calculations, and the reaction mechanism of methanol oxycarbonylation over the CuCl 2 -PdCl 2 surfaces was also investigated. On the CuCl 2 -PdCl 2 surface, the active site for methanol oxidation was confirmed as Cu-Cl-Cu (Pd). Comparing with pure CuCl 2 surface, the introduction of Pd atom causes the electron repopulation on the surface and lowers the energy barrier for methanol oxidation, but the number of the active site decreases with the increasing of Pd doping volume. Agreed with previous experimental results, the Pd site is most favorable for the CO insertion, indicated by the lowest activation barrier for the formation of COOCH 3 on Pd atom. The lowest energy barrier for the formation of DMC appears when COOCH 3 species adsorbed on Pd atom and methoxyl adsorbed on Cu atoms, which is 0.42 eV. Finally, the reconstruction of the unsaturated surface is a spontaneous and exothermic process. Comparing with other surfaces, the rate-limiting step, methanol oxidation, on CuCl 2 -PdCl 2 surface with Pd/Cu = 1:17 has the lowest energy barrier, which is agreed with the experimental observation that PdCl 2 -CuCl 2 catalyst with Pd/Cu = 1:20 has the favorable activity. The adsorbed methoxyl will further lower the activation barrier of methanol oxidation, which is agreed with experimental observation that the Wacker-type catalysts have an induction period in the methanol oxidative carbonylation system.

Crystallization of Zr₂Pd_xCu_1-x and Zr₂Ni_xCu_1-x Metallic Glass

Energy Technology Data Exchange (ETDEWEB)

Xu, Min [Iowa State Univ., Ames, IA (United States)

2008-01-01

One interesting aspect of rretallic glasses is the numerous instances of the deviation of the phase selection from the amorphous state to thermodynamically stable phases during the crystallization process. Their devitrification pathways allow us to study the relationship between the original amorphous structure and their crystalline counter parts. Among the various factors of phase selections, size and electronic effects have been most extensively studied. Elucidating the phase selection process of a glassy alloy will be helpful to fill in the puzzle of the changes from disordered to ordered structures. In this thesis, Two model Zr₂Pd_xCu_1-x and Zr₂Ni_xCu_1-x (x = 0, 0.25, 0.5, 0.75 and 1) glassy systems were investigated since: (1) All of the samples can be made into a homogenous metallic glass; (2) The atomic radii differ from Pd to Cu is by 11%, while Ni has nearly the identical atomic size compare to Cu. Moreover, Pd and Ni differ by only one valence electron from Cu. Thus, these systems are ideal to test the idea of the effects of electronic structure and size factors; (3) The small number of components in these pseudo binary systems readily lend themselves to theoretical modeling. Using high temperature X-ray diffraction (HTXRD) and thermal analysis, topological, size, electronic, bond and chemical distribution factors on crystallization selections in Zr₂Pd_xCu_1-x and Zr₂Ni_xCu_1-x metallic glass have been explored. All Zr₂Pd_xCu_1-x compositions share the same Cu11b phase with different pathways of meta-stable, icosahedral quasicrystalline phase (i-phase), and C16 phase formations. The quasicrystal phase formation is topologically related to the increasing icosahedral short range order (SRO) with Pd content in Zr₂Pd_xCu_1-x system. Meta-stable C16 phase is competitive with

The role of Pd in the transport of Ag in SiC

International Nuclear Information System (INIS)

Olivier, E.J.; Neethling, J.H.

2013-01-01

This paper presents results in support of a newly proposed transport mechanism to account for the release of Ag from intact TRISO particles during HTR reactor operation. The study reveals that the migration of Ag in polycrystalline SiC can occur in association with Pd, a relatively high yield metallic fission product. The migration takes place primarily along grain boundary routes, seen in the form of distinct Pd, Ag and Si containing nodules. Pd is known to rapidly migrate to the SiC and iPyC interface within TRISO particles during operation. It has been shown to chemically corrode the SiC to form palladium silicides. These palladium silicides are found present along SiC grain boundaries in nodule like form. It is suggested that Ag penetrates these nodules together with the palladium silicide, to form a Pd, Ag and Si solution capable of migrating along SiC grain boundaries over time.

The role of Pd in the transport of Ag in SiC

Energy Technology Data Exchange (ETDEWEB)

Olivier, E.J., E-mail: jolivier@nmmu.ac.za [Centre for High Resolution Transmission Electron Microscopy, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Neethling, J.H. [Centre for High Resolution Transmission Electron Microscopy, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa)

2013-01-15

This paper presents results in support of a newly proposed transport mechanism to account for the release of Ag from intact TRISO particles during HTR reactor operation. The study reveals that the migration of Ag in polycrystalline SiC can occur in association with Pd, a relatively high yield metallic fission product. The migration takes place primarily along grain boundary routes, seen in the form of distinct Pd, Ag and Si containing nodules. Pd is known to rapidly migrate to the SiC and iPyC interface within TRISO particles during operation. It has been shown to chemically corrode the SiC to form palladium silicides. These palladium silicides are found present along SiC grain boundaries in nodule like form. It is suggested that Ag penetrates these nodules together with the palladium silicide, to form a Pd, Ag and Si solution capable of migrating along SiC grain boundaries over time.

Growth and Magnetotransport Properties of Dirac Semimetal Candidate Cu3PdN

Science.gov (United States)

Quintela, C. X.; Campbell, N.; Harris, D. T.; Shao, D. F.; Xie, L.; Pan, X. Q.; Tsymbal, E. Y.; Rzchowski, M. S.; Eom, C. B.

Since the discovery of three-dimensional Dirac semimetals (DSM) Cd3As2 and Na3Bi, many efforts have been made to identify new DSM materials. Recently, nitride antiperovskite Cu3PdN has been proposed by two different groups as a new DSM candidate. However, until now, the experimental realization of bulk Cu3PdN and the study of its electronic properties has been hindered due to the difficulty of synthesizing bulk single crystals of this material. Here, we report the first growth and magnetotransport characterization of epitaxial Cu3PdN thin films on (001) SrTiO3 substrates. Magnetotransport measurements reveal p-type metallic conduction with very low temperature coefficient of the resistance and small non-linear magnetoresistance at low temperatures. The successful growth of Cu3PdN thin films opens the path to investigating the unknown electronic properties of this material, and provides a template for further research on other antiperovskite DSM candidates such as Cu3ZnN.

Heavy metal and proximate composition associated with the ...

African Journals Online (AJOL)

User

2014-05-08

May 8, 2014 ... Levels of Cu, Mn, Pd and Zn in mushroom samples analysed were ... metal concentration in soil and fungal factors such as species ..... Levels of trace elements in the fruiting bodies ... Toxicity of non-radioactive heavy metals.

Microstructure and corrosion of Pd-modified Ti alloys produced by powder metallurgy

International Nuclear Information System (INIS)

Ashworth, M.A.; Davenport, A.J.; Ward, R.M.; Hamilton, H.G.C.

2010-01-01

A method for the fabrication of titanium alloy parts with enhanced corrosion resistance by a powder metallurgy route is presented in this paper. Commercial purity titanium powders modified with Pd have been hot isostatically pressed (HIPped) and the microstructure and distribution of the noble metal characterised by optical and scanning electron microscopy. The electrochemistry of the HIPped alloy has been assessed and the effect of powder size fraction evaluated. Results show that the phase composition and electrochemistry of the HIPped Pd-modified alloy is equivalent to that of wrought grade 7 Ti.

High spin-polarization in ultrathin Co2MnSi/CoPd multilayers

Science.gov (United States)

Galanakis, I.

2015-03-01

Half-metallic Co2MnSi finds a broad spectrum of applications in spintronic devices either in the form of thin films or as spacer in multilayers. Using state-of-the-art ab-initio electronic structure calculations we exploit the electronic and magnetic properties of ultrathin Co2MnSi/CoPd multilayers. We show that these heterostructures combine high values of spin-polarization at the Co2MnSi spacer with the perpendicular magnetic anisotropy of binary compounds such as CoPd. Thus they could find application in spintronic/magnetoelectronic devices.

Nanoindentation study on the characteristic of shear transformation zone in a Pd-based bulk metallic glass during serrated flow

Science.gov (United States)

Liao, G. K.; Long, Z. L.; Zhao, M. S. Z.; Peng, L.; Chai, W.; Ping, Z. H.

2018-04-01

This paper presents the research on the evolution of shear transformation zone (STZ) in a Pd-based bulk metallic glass (BMG) during serrated flow under nanoindentation. A novel method of estimating the STZ volume through statistical analysis of the serrated flow behavior was proposed for the first time. Based on the proposed method, the STZ volume of the studied BMG at various peak loads have been systematically investigated. The results indicate that the measured STZ volumes are in good agreement with that documented in literature, and the STZ size exhibits an increasing trend during indentation. Moreover, the correlation between the serrated flow dynamics and the STZ activation has also been evaluated. It is found that the STZ activation can promote the formation of self-organized critical (SOC) state during serrated flow.

Superconducting thin films of As-free pnictide LaPd{sub 1-x}Sb{sub 2} grown by reactive molecular beam epitaxy

Energy Technology Data Exchange (ETDEWEB)

Retzlaff, Reiner; Buckow, Alexander; Kurian, Jose; Alff, Lambert [Institute of Materials Science, Technische Universitaet Darmstadt, Petersenstr. 23, 64287 Darmstadt (Germany)

2013-07-01

We use reactive molecular beam epitaxy as synthesis technique for the search of arsenic free pnictide superconductors. Epitaxial thin films of LaPd{sub 1-x}Sb{sub 2} were grown on (100) MgO substrates from elemental sources by simultaneous evaporation of high purity La, Pd and Sb metals by e-gun. LaPd{sub 1-x}Sb{sub 2} belongs to a novel class of pnictide superconductors with a peculiar pnictide square net layer. Previously, we have reported epitaxial growth of isostructural Bi based compounds. The substitution of Bi by Sb leads to thin films with metallic behavior and room temperature resistivity of about 85 μΩ cm. The highest observed transition temperature T{sub c} inLaPd{sub 1-x}Sb{sub 2} is 3.1 K and does not depend on x. We discuss strategies to increase T{sub c} in this pnictide subfamily.

Ion-beam-mixing in metal-metal systems and metal-silicon systems

International Nuclear Information System (INIS)

Hung, L.

1984-01-01

The influence of energetic ion bombardment on the composition and structure of thin film materials and utilization of ion-beam-mixing techniques to modify interfacial reactions are reported in this thesis. The phase formation in metals by using ion mixing techniques has been studied. Upon ion irradiation of Al/Pt, Al/Pd and Al/Ni thin films, only the simplest intermetallic compounds of PdAl and NiAl were formed in crystalline structure, while the amorphous phase has been observed over a large range of composition. Ion mixing of Au/Cu bilayers resulted in the formation of substitutional solid solutions with no trace of ordered compounds. The formation of the ordered compound CuAu was achieved either by irradiation of bilayers with Ar ions at elevated substrate temperature or by irradiation of the mixed layers with He ions at relatively low temperature. In the Au/Al system several crystal compounds existed in the as-deposited samples. These phases remained crystalline or transformed into other equilibrium compounds upon ion irradiation. The results suggest that the phase formation by ion mixing is dependent on the high quench rate in the collision cascade region and the atomic mobility at the irradiation temperature. The argument can be applied to silicide forming systems. With near-noble metals, the mixed atoms are mobile and form metallurgically distinct phases. With refractory metals, amorphous phases are formed due to lack of atomic mobility

Differention of parkinson's disease, multiple system atrophy and pure autonomic failure using I-123 MIBG myocardial scintigraphy

International Nuclear Information System (INIS)

Zhang, Z.; Religiosol, D.; Machac, J.; Nahm, K.F.; Kaufmann, H.C.; Yahr, M.D.

2004-01-01

Purpose: Clinical differentiation of Parkinson's disease (PD), multiple system atrophy (MSA), and pure autonomic failure (PAF) may be difficult. 123I MIBG studies have shown significantly reduced cardiac uptake in patient with PD but not in MSA suggesting that postganglionic neurons are only affected in PD. No systematic study using 123I MIBG in patients with PAF has been reported. The Objective of this study is to investigate whether MSA, PD, and PAF can be differentiated by 1231 MIBG myocardial scintigraphy. Methods: 1231 MIBG was synthesized using Cu(I) assisted kit method (labeling efficiency 99.84±0.47%, n = 17). Five patients with a clinical diagnosis of MSA (age 63±11), 4 with PD (62±10), 4 with PAF (60±7), and 3 normal controls (50±19) were referred to NM blinded to the categories of the patients. SPECT and planar chest imaging was taken 15 min (early) and 4 hours (delayed) postinjection of 200-351 MBq 123I MIBG using a Picker triple head SPECT camera. Regions of interest were placed over the heart (H) and mediastinum (M); the average count ratios (H/M) were calculated. Each subject had a separate 201Tl perfusion imaging to exclude significant myocardial perfusion defects. Results: As shown in the Table, the H/M ratio in patients with MSA was significantly lower than that in normal subjects (P = 0.027) in early imaging, but not in the delayed imaging. Both H/M ratios in PD and PAF were significantly lower than that in MSA in early (P = 0.006, P = 0.008) and delayed (P< 0.0001, P < 0.00001) imaging. Only delayed uptake ratio showed significant difference (P = 0.013) between PD and PAF. Conclusions: 123I MIBG cardiac uptake in delayed imaging was significantly reduced in patients with PD and PAF while it was normal in MSA. Significant cardiac uptake difference was also found between PD and PAF. 123I MIBG myocardial scintigraphy appears to provide helpful information in the differential diagnosis of these disorders. (authors)

Enhanced photocatalytic degradation of methylene blue on carbon nanotube-TiO{sub 2}-Pd composites

Energy Technology Data Exchange (ETDEWEB)

Kim, Eun Hye; Choi, Hyun Chul [Dept. of Chemistry, Chonnam National University, Gwangju (Korea, Republic of)

2016-11-15

Semiconductor-based photocatalysis is recognized as a promising technique for addressing energy and environmental issues. Among various semiconductors, the use of titanium dioxide (TiO-2) as a photocatalyst in solar energy conversion and pollutant degradation has been widely investigated because of its high efficiency, photostability, and low toxicity. However, its practical application is restricted by the intrinsic wide band gap of TiO-2 and the rapid recombination of photogenerated electron–hole pairs. Therefore, several remedial methods have been proposed, such as the doping of TiO{sub 2} with metallic or non-metallic elements, increasing its surface area, sensitization with dyes, and the generation of defect structures. We have successfully prepared CNT–TiO{sub 2}–Pd composites with a simple two-step sol–gel method. We characterized the composites with TEM and XRD, and demonstrated that anatase TiO{sub 2} and metallic Pd nanoparticles were deposited onto the surfaces of the CNTs. The average particle size of these nanoparticles was approximately 3.4 nm. The prepared catalyst was found to exhibit a higher activity in MB photodegradation than the reference systems. The synergy of the combination of CNTs and Pd nanoparticles with TiO{sub 2} provides superior MB degradation. More comprehensive studies of the mechanism for this synergy between the metal nanoparticles and TiO{sub 2} that enhances the photocatalytic activity of CNT–TiO{sub 2} are underway in our laboratory.

Metallic double shell hollow nanocages: the challenges of their synthetic techniques.

Science.gov (United States)

Mahmoud, M A; El-Sayed, M A

2012-03-06

Hollow metallic nanoparticles have been attracting the attention of many researchers in the past five years due to their new properties and potential applications. The unique structure of the hollow nanoparticles; presence of two surfaces (internal and external), and the presence of both cavities and pores in the wall surfaces of these nanoparticles are responsible for their unique properties and applications. Here the galvanic replacement technique is used to prepare nanocages made of gold, platinum, and palladium. In addition, hollow double shell nanoparticles are made of two metal shells like Au-Pt, Pt-Au, Au-Pd, Pd-Au, Pd-Pt, and Pt-Pd. Silver nanocubes are used as templates during the synthesis of hollow nanoparticles with single metal shell or double shell nanocages. Most of the problems that could affect the synthesis of solid Silver nanocubes used as template as well as the double shell nanocages and their possible solutions are discussed in a detail. The sizes and shapes of the single-shell and double-shell nanocages were characterized by a regular and high-resolution TEM. A SEM mapping technique is also used to image the surface atoms for the double shell hollow nanoparticles in order to determine the thickness of the two metal shells. In addition, optical studies are used to monitor the effect of the dielectric properties of the other metals on the plasmonic properties of the gold nanoshell in these mixed nanoparticles.

Preparation of carbon-free TEM microgrids by metal sputtering

International Nuclear Information System (INIS)

Janbroers, S.; Kruijff, T.R. de; Xu, Q.; Kooyman, P.J.; Zandbergen, H.W.

2009-01-01

A new method for preparing carbon-free, temperature-stable Transmission Electron Microscope (TEM) grids is presented. An 80% Au/20% Pd metal film is deposited onto a 'holey' microgrid carbon supported on standard mixed-mesh Au TEM grids. Subsequently, the carbon film is selectively removed using plasma cleaning. In this way, an all-metal TEM film is made containing the 'same' microgrid as the original carbon film. Although electron transparency of the foil is reduced significantly, the open areas for TEM inspection of material over these areas are maintained. The metal foil can be prepared with various thicknesses and ensures good electrical conductivity. The new Au/Pd grids are stable to at least 775 K under vacuum conditions.

Preparation of carbon-free TEM microgrids by metal sputtering.

Science.gov (United States)

Janbroers, S; de Kruijff, T R; Xu, Q; Kooyman, P J; Zandbergen, H W

2009-08-01

A new method for preparing carbon-free, temperature-stable Transmission Electron Microscope (TEM) grids is presented. An 80% Au/20% Pd metal film is deposited onto a 'holey' microgrid carbon supported on standard mixed-mesh Au TEM grids. Subsequently, the carbon film is selectively removed using plasma cleaning. In this way, an all-metal TEM film is made containing the 'same' microgrid as the original carbon film. Although electron transparency of the foil is reduced significantly, the open areas for TEM inspection of material over these areas are maintained. The metal foil can be prepared with various thicknesses and ensures good electrical conductivity. The new Au/Pd grids are stable to at least 775K under vacuum conditions.

Toxicity of platinum, palladium and rhodium to Daphnia magna in single and binary metal exposure experiments.

Science.gov (United States)

Zimmermann, Sonja; Wolff, Carolina; Sures, Bernd

2017-05-01

Mainly due to automobile traffic, but also due to other sources, the platinum group elements (PGE) platinum (Pt), palladium (Pd) and rhodium (Rh) are introduced into aquatic biotopes where they accumulate in sediments of lakes and rivers. However, the toxicity of these noble metals to aquatic organisms is not well understood and especially toxicity studies under standardized condition are lacking. Thus, the toxicity of Pt, Pd and Rh to Daphnia magna was tested in single metal exposure experiments according to OECD guideline 202. Immobility and lethality was recorded after 24 h and 48 h of exposure and EC 50 and LC 50 , respectively, were determined. As the nominal exposure concentration of Pd differed significantly from the quantified concentration, the control of the real exposure concentration by chemical analysis is mandatory, especially for Pd. The toxicity decreased in the order Pd > Pt ≫ Rh with e.g. LC 50 (48 h) values of 14 μg/L for Pd, 157 μg/L for Pt and 56,800 μg/L for Rh. The exposure period had a clear effect on the toxicity of Pt, Pd and Rh. For Pt and Rh the endpoint immobility was more sensitive than the endpoint lethality whereas Pd toxicity was similar for both endpoints. The Hill slopes, which are a measure for the steepness of the concentration-response curves, showed no significant discrepancies between the different metals. The binary metal exposure to Pt and Pd revealed a more-than-additive, i.e. a synergistic toxicity using the toxic unit approach. The present study is a start to understand the toxicity of interacting PGE. The modes of action behind the synergistic effect are unclear. Copyright © 2017 Elsevier Ltd. All rights reserved.

Mechanism of NO Photocatalytic Oxidationon g-C3N4 Was Changed by Pd-QDs Modification

Directory of Open Access Journals (Sweden)

Yuhan Li

2015-12-01

Full Text Available Quantum dot (QD sensitization can increase the light absorption and electronic transmission of photocatalysts. However, limited studies have been conducted on the photocatalytic activity of photocatalysts after modification by noble metal QDs. In this study, we developed a simple method for fabricating Pd-QD-modified g-C3N4. Results showed that the modification of Pd-QDs can improve the NO photocatalytic oxidation activity of g-C3N4. Moreover, Pd-QD modification changed the NO oxidation mechanism from the synergistic action of h+ and O2− to the single action of ·OH. We found that the main reason for the mechanism change was that Pd-QD modification changed the molecular oxygen activation pathway from single-electron reduction to two-electron reduction. This study can not only develop a novel strategy for modifying Pd-QDs on the surface of photocatalysts, but also provides insight into the relationship between Pd-QD modification and the NO photocatalytic oxidation activity of semiconductor photocatalysts.

Centrifugal Deposited Au-Pd Core-Shell Nanoparticle Film for Room-Temperature Optical Detection of Hydrogen Gas.

Science.gov (United States)

Song, Han; Luo, Zhijie; Liu, Mingyao; Zhang, Gang; Peng, Wang; Wang, Boyi; Zhu, Yong

2018-05-06

In the present work, centrifugal deposited Au-Pd core-shell nanoparticle (NP) film was proposed for the room-temperature optical detection of hydrogen gas. The size dimension of 44, 48, 54, and 62 nm Au-Pd core-shell nanocubes with 40 nm Au core were synthesized following a solution-based seed-mediated growth method. Compared to a pure Pd NP, this core-shell structure with an inert Au core could decrease the H diffusion length in the Pd shell. Through a modified centrifugal deposition process, continues film samples with different core-shell NPs were deposited on 10 mm diameter quartz substrates. Under various hydrogen concentration conditions, the optical response properties of these samples were characterized by an intensity-based optical fiber bundle sensor. Experimental results show that the continues film that was composed of 62 nm Au-Pd core-shell NPs has achieved a stable and repeatable reflectance response with low zero drift in the range of 4 to 0.1% hydrogen after a stress relaxation mechanism at first few loading/unloading cycles. Because of the short H diffusion length due to the thinner Pd shell, the film sample composed of 44 nm Au-Pd NPs has achieved a dramatically decreased response/recovery time to 4 s/30 s. The experiments present the promising prospect of this simple method to fabricate optical hydrogen sensors with controllable high sensitivity and response rate at low cost.

Preparation and characterization of Pd{sub x}Ag{sub y}/C electrocatalysts for ethanol electrooxidation reaction in alkaline media