Papers by Keyword: Pd

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Authors: Ke Jing Yang, Yulia Ivanisenko, J. Markmann, Hans Jorg Fecht
Abstract: In situ tensile tests were conducted on ultra fine grained (UFG) pure Pd and Pd-x% Ag (x=20, 60) alloys of different stacking fault energies (SFEs) with the aim to study the general features of the deformation process of UFG materials as well as the peculiarities brought by the alloying. Grey scale correlation analysis (GSCA) was used to determine the true strain as well as the surface flow within the gauge length. It was shown that the largest values of strength and uniform elongation were obtained in Pd-20% Ag alloy. The GSCA revealed different macroscopic flow processes in this sample as compared with pure Pd and Pd-60% Ag alloy. In particular, pure Pd and Pd-60% Ag alloy demonstrated rapid localization of plastic flow in the neck area, whereas Pd-20% Ag samples showed a large contribution of homogenous deformation even after neck formation. It has been proposed that larger strain hardening capacity of Pd-20% Ag alloy is related to its lower SFE as compared with that of pure Pd: the lower is the SFE, the more difficult is the cross slip and climb of split dislocations, which leads to enhanced dislocation storage and, ultimately, to increased strain hardening. At the same time, further decrease of SFE in Pd-60% Ag sample leads to development of deformation twinning and consequent reduction of strain hardening. The dimpled structure of fracture surfaces in the samples will also be discussed in relationship to these findings.
Authors: Zhi Yuan Zhang, Fu Shen Zhang
Abstract: In the present study, a green process for cuprous chloride synthesis from waste printed circuit boards (PCBs) was developed. High value-added cuprous chloride (98.7% purity) was obtained by treating metallic particles of waste PCBs with solution of cupric sulfate and sodium chloride. Typical noble metal (Pd) was dissolved by forming a stable chloride complex during the synthesis process as Cu2+ played the role of oxidant or concentrated in the residue. Under the optimum condition (VNaCl/mCuSO4 ratio = 6, [C/[Cu2+] mole ratio = 1.05, treatment time = 30 min, operation temperature = 60 °C), yield of cuprous chloride was 74.0% and approximately 98.5% of the copper could be recovered. It is believed that the process proposed is effective and practical for Cu recovery from waste PCBs.
Authors: Wei Jie Lu, D.T. Shi, T.R. Crenshaw, A. Burger, W.E. Collins
Authors: Dao Hua Sun, Peng Yao Li, Xue Liang Li
Abstract: We report the facile synthesis of triangular Pd nanoplates using aqueous extract of Syzygium Samarangense leaf. The morphology and structure of the obtained Pd nanoplates were characterized by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy analysis. FTIR spectra indicated that C=C, COH, and OCOH were mainly responsible for the formation of the Pd nanoplates.
Authors: You Ming Cao
Abstract: Pd catalyst is very active in Suzuki reaction. As a heterogeneous catalyst, SWNTs/Pd shows highly catalytic ability with Suzuki reaction. We will demonstrate the effect of catalyst’s amount, the reaction time and temperature on Suzuki reaction in this work. In comparison, a control experiment used commercial Pd/C as catalyst in Suzuki reaction has been done. An optimum reaction condition of about reacting 60 min at 50°C with 5% (mass%) catalyst is confirmed finally, and a better catalytic ability of SWNTs/Pd than commercial Pd/C is also observed.
Authors: Samantha Zimnik, Christian Piochacz, Sebastian Vohburger, Christoph Hugenschmidt
Abstract: We report on time-dependent Positron annihilation induced Auger Electron Spectroscopy (PAES) study on 0.5 monolayers (ML) Ni on polycrystalline Pd accompanied by complementary X-ray induced Photoelectron Spectroscopy (XPS). The normalized PAES spectra showed a significant decrease in the Ni intensity and an increase in the Pd intensity as a function of time. To rule out varying influence on the elements e.g. from surface contaminates due to the residual gas, a time-dependent XPS analysis was performed on pure Ni and Pd as well as to analyze the main contaminants C and O. The O fraction was found to be constant within the measurement time and the time constants for C significantly differ from those of Ni and Pd in the PAES data. Consequently, it was concluded that the PAES data show a superposition of C contamination and structural changes at the surface of Ni/Pd.
Authors: Yulia Ivanisenko, Hans Jörg Fecht
Abstract: Instrumented high pressure torsion, i.e. mechanical test in a torsion mode under high pressure, allows interesting possibility of materials testing, because materials mechanical response can be studied in a practically unlimited shear strain range. We have studied microstructures formed in initially coarse crystalline and nanocrystalline (nc) Pd and its alloys after instrumented HPT up to shear strain 300, and revealed signatures of similar processes occurring in all these materials. In particular, we found traces of cooperative grain boundary sliding in the form of aligned in parallel segments of boundaries of several grains with straightened triple points. Fracture surfaces contained shear bands. Texture measurements revealed lower dislocation activity in nanocrystalline state as compared with coarse crystalline one. Therefore we argue that cooperative grain boundary sliding is an important deformation mechanism at large strain which develops in both ultrafine grained (ufg) and nanocrystalline materials. In nc and ufg materials planes of cooperative grain boundary sliding act as precursors of shear bands and shear occurs along planes formed by numerous grain boundaries.
Authors: Ichiro Yamanaka, Yuta Nabae
Abstract: Steady generation of electricity (360 mW cm-2 at 1173 K) with dry methane fuel was successfully performed in solid oxide fuel cells (SOFC) by Pd-Ni bimetallic catalyst on porous composite anode prepared from La0.8Sr0.2CrO3 (LSCr) and Ce0.8Sm0.2O1.9 (SDC) (50:50 wt%). The amounts of carbon deposition were quite small under the open and closed circuit conditions. Synergy of Pd and Ni electrocatalysts was observed on the LSCr-SDC anode for the oxidation of dry methane. A small amount of carbon deposition over the anode during the open circuit conditions could be easily and quickly removed by gasification with steam. Data of detailed kinetic studies and electrochemical analysis strongly suggest that (i) methane decompose to hydrogen and carbon over the Pd-Ni catalyst, (ii) hydrogen is electrochemically oxidized with O2- to water, and (iii) carbon is quickly reformed with water to hydrogen and carbon oxides.
Authors: A.S. Al–Fatesh, A.H Fakeeha, A.E. Abasaeed
Abstract: The catalytic reforming of methane with carbon dioxide using Pd promoter on 1% Ni/20%TiO2-P25+80%α-Al2O3 was investigated. An experimental study was carried out using the catalyst prepared by impregnation method. The catalysts were dried at 120°C and calcined at 900°C. The reforming reactions were carried out using CO2/CH4/N2 feed ratio of 5/5/1, F/W=44 ml/min.gcat and reaction temperature of 700°C. The effect of nominal load of Pd ranging from 0.0 to 0.48 was studied by evaluating catalyst activity, stability, coke and (H2/CO) ratio. The prepared catalysts were tested in micro reactor at atmospheric pressure. The effluents were analyzed using an online gas chromatography equipped with a thermal conductivity detector. EDS and TGA for the fresh and spent catalysts were evaluated. Results indicate that the addition of small amounts of Pd is preferable in terms of activity and carbon deposition than higher Pd loading. For instance, 0.01%Pd gives a conversion of 78.4 for CH4 and 4.9% deactivation factor. While, 0.48%Pd gives a conversion of 75.6 for CH4 and 29.9% deactivation factor. Thus higher loading of Pd causes the catalyst to show poor performance with lower conversion and higher carbon formations. It can be concluded that Pd promoter has an optimal concentration with respect to the active metal of the catalyst beyond which the performance deteriorates.
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