Values For Pd Research Articles

Using Enrichment Factor Approach for Source Identification of Potentially Toxic Heavy Metals along Benin-Ore-Sagamu Expressway in Nigeria

The variation in heavy metal concentration in different environment is dependent on the emission source. Source identification of heavy metal plays an important role in providing solution to its contamination in the atmosphere. Hence, the objective of this paper is to engage enrichment factor (EF) approach to evaluate the source identification of potentially toxic heavy metals along the Benin-Ore-Sagamu Expressway in Nigeria in four sampling locations (A, B, C and D) that are denoted with high traffic congestion. The source identification of Cu, Zn, Mn, Ni, Pd, Cd, Cr and Pb contamination in the study area were determined using appropriate standard methods. The EF values indicated for Cu ranged from (2.3-5.9), Zn (0.48-0.86), Mn (0.29-0.49), Ni (1.27-4.03), Pd (37012.18-59922.57), Cd (1909.11-2844.81), Cr (4.56-7.76) and Pb (0.77-4.64). The results suggest crustal source enrichment for Zn and Mn while Cu, Ni, Cr and Pb were enriched moderately. However, the EF values for Pd and Cd were found to be greater than 50, indicating extremely severe enrichment. The findings of this study provide evidence of anthropogenic impact on heavy metals pollution in the study area that is attributed to the intense vehicular traffic.

A new synergistic hydrocolloid with superior rheology: Locust bean /xanthan gum binary solution powdered by different drying methods

In the current study, a novel gum powder containing locust bean and xanthan gums was prepared by three different drying methods of their synergistic aqueous solutions: direct cabinet drying (CD), drying after alcohol precipitation (PD), and direct freeze drying (FD). The purpose of this process is to develop ready-to-use synergistic gum powders with improved rheological properties by modifying intermolecular interactions. Significant improvements in viscosity, consistency efficiency and pseudoplastic character were observed for PD, followed by CD and FD, as well as the higher values of G′ and G″ values of PD, indicating a stronger entanglement network development between the macromolecules for PD. PD exhibited better elasticity and shear resistance compared to FD and CD in the strain sweep test. In Lissajous curves, straight line shapes were found for synergistic solutions at low strain, which continued for increasing strain values for PD and CD. However, the pronounced viscous behavior was found for FD at 500% strain. Compared to CD and FD, PD exhibited a more desirable thixotropic character. A lower zeta potential was observed in the production of synergistic gums using the PD process. Gel strength was found to be higher for PD. Therefore, PD was a more effective method to produce a ready-to-use synergistic powder with better viscoelastic properties and a more stable solution.

Gas-sensing properties and first-principles comparative study of metal (Pd, Pt)-decorated MoSe2 hierarchical nanoflowers for efficient SO2 detection at room temperature

The online detection and control of concentration for agricultural greenhouse gas SO2 is an important technology to ensure normal agricultural production. This paper reports on a facile hydrothermal method to synthesis Pd-decorated and Pt-decorated MoSe2 nanomaterials, i.e. multistage flower-like structures with attached nanometallic particles and nanosheets hierarchical structures. The Pd/MoSe2 and Pt/MoSe2 hierarchical materials were characterized for the nanostructure, microscopic morphology and elemental compositions. The gas-sensing properties results show that the Pd/MoSe2 and Pt/MoSe2 nanofilm sensors have good sensitivity, stability and response rate to SO2 gas. The response values for the metal Pd and Pt decorated samples to 20 ppm SO2 were 2.04 and 3.42 times higher than those for the intrinsic MoSe2 samples at room temperature. The hierarchical flower-like structure proved to be beneficial in providing more adsorption drop points. In addition, based on the first-principles, the geometrical parameters and electronic properties of the metal-decorated modified structures were calculated to comparatively investigate the enhanced sensing mechanism of SO2 by nanoflower materials. The Pt-MoSe2 nanofilm sensor achieves a high sensitivity detection with a response value of 2.89 for low concentration (1 ppm) of SO2, which is confirming the promotion of charge transfer by metal decorating. This study suggests that Pd-MoSe2 and Pt-MoSe2 hierarchical structures may be recommended for the detection of the agricultural greenhouse gas SO2.

Применение meta-GGA функционала scan к расчету поверхностных свойств Pd и IR

The results of first-principles calculations of the structural and surface characteristics of palladium and iridium using the VASP software package with the Meta-GGA SCAN functional are presented. The calculations of the lattice constant values for bulk metals Pd and Ir for various PBE and SCAN functionals showed the best convergence and agreement with the experimental values when using the SCAN functional. The values of the surface energy and the work function of an electron from the surface of a Pd and Ir plate with a thickness of 1 to 10 monolayers were calculated taking into account relaxation for various orientations of the surface face (100), (110), (111). Smaller error and better agreement with experimental values was obtained using the SCAN functionality, especially for palladium. The values obtained for different orientations of the surface face satisfy the relation: σ110 > σ100 > σ111. The most close-packed face has the lowest surface energy.

Crystal synthesis and Debye temperature determination of PdSb2: Usefulness of single crystal precise structure analysis

Single crystals of pyrite-type PdSb2 were grown by sealing a stoichiometric proportion of the elements in an evacuated silica glass tube and heating the tube in a furnace at 930 K for 20 days. The crystal structure of PdSb2 [space groupPa3¯, a = 6.4659(2) Å, u = 0.37331(3), Z = 4] was refined to R1 = 0.0171 for 374 unique reflections obtained by single-crystal X-ray diffraction experiments. The lattice constant, a, and anion-anion distance of 2.8677(3) Å are slightly different from the previously reported values. The single crystal diffraction method has excellent advantages such that the Debye temperature can be determined for each crystallographically independent site. The obtained ΘD values for Pd and Sb in PdSb2 are 258 K and 214 K, respectively. Characteristically, the Debye temperatures, ΘD, of both atoms in PdSb2 were found to be very low among the pyrite-type transition metal pnictides and chalcogenides. Certain regularities between the cation–anion bonding distances and Debye temperatures were found in pyrite-type compounds. The vibration of anion contributes to the highest energy part of the normal mode of thermal vibration, when the cation–anion bonding distances in pyrite-type compounds are shorter than 2.6 Å.

Extraction of rhenium(VII) and palladium(II) from nitric acid solution using N-cyclohexyl-2-pyrrolidone as an extractant

ABSTRACT Extraction behavior of Pd(II) and Re(VII) from HNO3 aqueous solutions (0.1–5.0 M, M = mol∙dm−3) to CH2Cl2 containing N-cycrohexyl-2-pyrrolidone (NCP, 0.1–2.0 M) as an extractant has been examined. As a result, it was found that distribution ratios (D) of Pd(II) and Re(VII) under [HNO3] = 3.0 M increase with increasing [NCP] from 0.1 to 2.0 M and that plots of log D vs. log[NCP] show linear relationships with slopes of approximately 2. It was also found that the D values for Pd(II) increase with increasing [HNO3] up to 3.0 M and decrease in the higher [HNO3] region (<5.0 M) and those of Re(VII) increase with an increase in [HNO3] up to 1.0 M and decrease with a further increase in [HNO3] (<5 M). From these results, it was suggested that the extraction reactions of Pd(II) and Re(VII) take place with two NCP molecules and compete with the extraction of HNO3. Moreover, it was clarified that IR spectra (1550–1700 cm−1) of CH2Cl2 solutions containing extracted Pd(II) and Re(VII) species are consistent with that of trans-Pd(NO3)2(NCP)2 and similar to that of HReO4(NCP)2, respectively. From these results, it is proposed that Pd(II) and Re(VII) species in HNO3 aqueous solutions are extracted to CH2Cl2 phase containing NCP as Pd(NO3)2(NCP)2 and HReO4(NCP)2.

Energy Levels, Wavelengths, Probabilities, and Oscillator Strengths of Transition for Ge-Like Pd, Ag, and Cd Ions

High-accuracy calculations of energy levels, wavelengths, probabilities, and oscillator strengths of transition of resonance lines for Ge-like Pd, Ag, and Cd ions have been performed. For the accurate treatment of relativity, the contributions of Breit interactions and quantum electrodynamics correction were considered. The calculated values of energy levels and wavelengths, including core–valence corrections, are found to be in excellent agreement with other theoretical and experimental values for Ge-like Pd, Ag, and Cd ions. The number of energy levels and wavelengths we considered is larger than that of any other theoretical calculations. The transition probabilities are also given where no other theoretical results and experimental values are available.

Enhanced performance of supported Pd-Pt bimetallic catalysts prepared by modified electroless deposition for butane dehydrogenation

The alumina supported Pd-Pt based bimetallic catalysts were prepared by modified electroless deposition and evaluated for butane dehydrogenation. The bimetallic Pd-Pt catalysts exhibited superior performance compared to that of monometallic catalysts. The superior performance may be attributed to strong synergistic interaction between metals, stronger metal-support interaction and lower acidity. The higher activity of alloyed Pd-Pt metal resulted in higher conversion for bimetallic catalysts. The lower acidity resulted in higher butene selectivity and stability for bimetallic catalysts by minimizing cracking and secondary reactions. The co-deposited catalyst with more uniform distribution of Pd and Pt metals showed better performance than bimetallic catalysts prepared by sequential deposition. Co-deposited Pd-Pt/Al catalyst showed the highest butane conversion (50 %), butene yield (42 %) and stability. The reported yield is much higher than many reported values for Pt or Pd based catalysts. The co-deposited Pd-Pt/Al catalyst also exhibited better dehydrogenation performance in comparison to corresponding co-impregnated bimetallic catalyst.

Characterization of Pd and Pd@Au core-shell nanoparticles using atom probe tomography and field evaporation simulation

We report on atom probe tomography analyses of Pd and Pd@Au nanoparticles embedded in a Ni matrix and the effects of local evaporation field variations on the atom probe data. In order to assess the integrity of the reconstructed atom maps, we performed numerical simulations of the field evaporation processes and compared the simulated datasets with experimentally acquired data. The distortions seen in the atom maps for both Pd and Pd@Au nanoparticles could be mostly ascribed to local variations in chemical composition and elemental evaporation fields. The evaporation field values for Pd and Ni, taken from the image hump model and assumed in the simulations, yielded a good agreement between experimental and simulation results. In contrast, the evaporation field for Au, as predicted from the image hump model, appeared to be substantially overestimated and resulted in a large discrepancy between experiments and simulations.

Determination of palladium in soil samples by slotted quartz tube-flame atomic absorption spectrophotometry after vortex-assisted ligandless preconcentration with magnetic nanoparticle-based dispersive solid-phase microextraction.

In this study, a rapid and effective dispersive solid-phase microextraction (d-SPME) method was developed to preconcentrate Pd from aqueous extract of soil samples by slotted quartz tube-flame atomic absorption spectrometry (SQT-FAAS). The unique properties of magnetic nanoparticles (MNPs) were used to directly isolate Pd from the sample solutions without the need for complexation. Significant parameters of the extraction method such as magnetic nanoparticle type and amount, pH and amount of buffer solution, amount of eluent, and mixing type and period were optimized together with other instrumental parameters to boost the absorbance signal of Pd. An SQT was fitted onto the burner head to boost the interaction between Pd atoms and hollow cathode lamp radiation to enhance absorbance signals. The limit of detection (LOD) and limit of quantification (LOQ) values for Pd determined (d-SPME-MNP-SQT-FAAS) were 6.4 and 21.4ng/mL, respectively. The percentage relative standard deviation of the developed method was calculated as 6.6%. The method was applied to soil samples taken from the campus area and spiked recovery experiments were performed to evaluate the method's accuracy/applicability. Satisfactory percent recovery results (90-101%) were obtained for different spiked concentrations and this proved the accuracy/applicability of the method.

Barrier heights of Au, Pt, Pd, Ir, Cu on nitrogen terminated (1 0 0) diamond determined by X-ray photoelectron spectroscopy

In this work, we used X-ray photoelectron spectroscopy to measure barrier height values for different metals (Au, Pt, Pd, Ir, Cu) on nitrogen terminated (1 0 0) diamond. Three types of diamond surface (hydrogen-, oxygen-, fluorine-terminated diamond surface) were used as the initial surfaces. Then, nitrogen terminated diamond surface was formed by reactive ion etching on the initial diamond surfaces for comparison. Thin films of Au, Pt, Pd, Ir and Cu were evaporated by electron beam to form metal/N-diamond contacts, respectively. The barrier height values for Au, Pt, Pd, Ir and Cu on nitrogen terminated (1 0 0) diamond contacts were determined to be 2.37 eV, 2.14 eV, 1.78 eV, 2.20 eV and 1.84 eV, respectively.

Saturation of superstorms and finite compressibility of the magnetosphere: Results of the magnetogram inversion technique and global PPMLR‐MHD model

AbstractWe report on novel features of the saturation process of the polar cap magnetic flux and Poynting flux into the magnetosphere from the solar wind during three superstorms. In addition to the well‐known effect of the interplanetary electric (Esw) and southward magnetic (interplanetary magnetic field (IMF) Bz) fields, we found that the saturation depends also on the solar wind ram pressure Pd. By means of the magnetogram inversion technique and a global MHD numerical model Piecewise Parabolic Method with a Lagrangian Remap, we explore the dependence of the magnetopause standoff distance on ram pressure and the southward IMF. Unlike earlier studies, in the considered superstorms both Pd and Bz achieve extreme values. As a result, we show that the compression rate of the dayside magnetosphere decreases with increasing Pd and the southward Bz, approaching very small values for extreme Pd ≥ 15 nPa and Bz ≤ −40 nT. This dependence suggests that finite compressibility of the magnetosphere controls saturation of superstorms.

Effect of improved TLD dosimetry on the determination of dose rate constants for (125)I and (103)Pd brachytherapy seeds.

To more accurately account for the relative intrinsic energy dependence and relative absorbed-dose energy dependence of TLDs when used to measure dose rate constants (DRCs) for (125)I and (103)Pd brachytherapy seeds, to thereby establish revised "measured values" for all seeds and compare the revised values with Monte Carlo and consensus values. The relative absorbed-dose energy dependence, f(rel), for TLDs and the phantom correction, Pphant, are calculated for (125)I and (103)Pd seeds using the EGSnrc BrachyDose and DOSXYZnrc codes. The original energy dependence and phantom corrections applied to DRC measurements are replaced by calculated (f(rel))(-1) and Pphant values for 24 different seed models. By comparing the modified measured DRCs to the MC values, an appropriate relative intrinsic energy dependence, kbq (rel), is determined. The new Pphant values and relative absorbed-dose sensitivities, SAD (rel), calculated as the product of (f(rel))(-1) and (kbq (rel))(-1), are used to individually revise the measured DRCs for comparison with Monte Carlo calculated values and TG-43U1 or TG-43U1S1 consensus values. In general, f(rel) is sensitive to the energy spectra and models of the brachytherapy seeds. Values may vary up to 8.4% among (125)I and (103)Pd seed models and common TLD shapes. Pphant values depend primarily on the isotope used. Deduced (kbq (rel))(-1) values are 1.074 ± 0.015 and 1.084 ± 0.026 for (125)I and (103)Pd seeds, respectively. For (1 mm)(3) chips, this implies an overall absorbed-dose sensitivity relative to (60)Co or 6 MV calibrations of 1.51 ± 1% and 1.47 ± 2% for (125)I and (103)Pd seeds, respectively, as opposed to the widely used value of 1.41. Values of Pphant calculated here have much lower statistical uncertainties than literature values, but systematic uncertainties from density and composition uncertainties are significant. Using these revised values with the literature's DRC measurements, the average discrepancies between revised measured values and Monte Carlo values are 1.2% and 0.2% for (125)I and (103)Pd seeds, respectively, compared to average discrepancies for the original measured values of 4.8%. On average, the revised measured values are 4.3% and 5.9% lower than the original measured values for (103)Pd and (125)I seeds, respectively. The average of revised DRCs and Monte Carlo values is 3.8% and 2.8% lower for (125)I and (103)Pd seeds, respectively, than the consensus values in TG-43U1 or TG-43U1S1. This work shows that f(rel) is TLD shape and seed model dependent suggesting a need to update the generalized energy response dependence, i.e., relative absorbed-dose sensitivity, measured 25 years ago and applied often to DRC measurements of (125)I and (103)Pd brachytherapy seeds. The intrinsic energy dependence for LiF TLDs deduced here is consistent with previous dosimetry studies and emphasizes the need to revise the DRC consensus values reported by TG-43U1 or TG-43U1S1.

Atomic Structure of Cr2O3/Ag(111) and Pd/Cr2O3/Ag(111) Surfaces: A Photoelectron Diffraction Investigation

A detailed investigation concerning the atomic structure of Cr2O3 and Pd/Cr2O3 ultrathin films deposited on a Ag(111) single crystal is presented. The films were prepared by MBE (molecular beam epitaxy) and characterized in situ by LEED (low energy electron diffraction), XPS (X-ray photoelectron spectroscopy), and XPD (X-ray photoelectron diffraction). Evidences of rotated domains and an oxygen-terminated Cr2O3/Ag(111) surface were observed, along with significant contractions of the oxide’s outermost interlayer distances. The deposition of Pd atoms on the Cr2O3 surface formed a four-monolayer film, fcc packed and oriented in the [111] direction, which presented changes in monolayer spacing and lateral atomic distance compared to the expected values for bulk Pd. The observed surface structure may shed light on new physical properties such as the induced magnetic ordering in Pd atoms.

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

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.

Adsorption Behaviors of Platinum Group Metals in Simulated High Level Liquid Waste Using Macroporous (MOTDGA-TOA)/SiO2-P Silica-based Absorbent

As fundamental research for separation of platinum group metals (PGMs) from high level liquid waste (HLLW) by macroporous silica-based adsorbent, (MOTDGA-TOA)/SiO2-P adsorbent was prepared by impregnation of N,N′-dimethyl-N,N′-di-n-octyl-thiodiglycolamide (MOTDGA) and Tri-n-octylamine (TOA) into silica/polymer composite support (SiO2-P). The adsorption behavior of Ru(III), Rh(III), and Pd(II) in simulated HLLW onto the adsorbent were investigated by the batch method to obtain their corresponding equilibrium and kinetic data. The adsorbent showed strong adsorption for Pd(II) and the adsorption reached equilibrium within 2 hr. High distribution coefficient (Kd) values for Pd(II) were obtained in 0.1–1 M HNO3 concentration. In addition, the use of both MOTDGA and TOA improved adsorption of Ru(III) and Rh(III) better than individual use of them. Especially, the Kd value for Ru(III) towards (MOTDGA-TOA)/SiO2-P adsorbent was three times larger than that in the adsorption using only with MOTDGA or TOA as extractant. The adsorptions of Ru(III), Rh(III), and Pd(II) followed the Langmuir adsorption model, and were found to be controlled by the chemisorption mechanism.

Separation Factors for Hydrogen Isotopes in Palladium Hydride

This investigation examines how equilibrium pressures of single isotope metal–hydrogen systems can be used to determine the separation behavior of hydrogen isotopes in a mixed-isotope metal hydrogen system. The separation factor for a hydrogen–deuterium system, αHD, describes the equilibrium hydrogen isotope partition between the solid and gaseous phases. Very few values of αHD are reported for metals other than palladium, and the values for Pd are scattered with the origin of the scatter not fully understood. Wicke and Nernst and Trentin et al. have proposed models that relate αHD to the ratio of single isotope equilibrium pressures and the isotopic composition of the solid. The approaches of these models and the resulting equations appear to differ; however, as will be shown here, they are identical. It also will be shown that Raoult’s law, employed by both models, is not needed. This puts the model derivation on a firmer theoretical basis. New measurements of αHD values are determined over a large temperature range and D/H ratio in β-phase Pd hydride, and they are compared with the model predictions, validating the model. Since experimental values for αHD are often not available for other systems, while single isotope equilibrium pressures are available, the model provides a valuable tool for predicting separation factors. Moreover, the model can also be used to estimate separation factors involving the third hydrogen isotope, tritium.

Sorption Behavior of Nickel and Palladium in the Presence of NH3(aq)/NH4+

ABSTRACTIt is necessary to assess the impact of nitrate salts and their reduction products (e.g. NH3(aq)/NH4+) contained in low-level radioactive waste generated from nuclear reprocessing process for the safety assessment of geological disposal of the waste. In the present study, sorption behavior of Ni and Pd on pumice tuff was investigated in the presence of NH3(aq)/NH4+. Under various NH3(aq)/NH4+ concentration, pH and ionic strength conditions, distribution coefficient (Kd) of Ni and Pd on pumice tuff was determined by a batch experiment. For Ni system, the Kd values showed no significant dependence on initial NH4+ concentration ([NH4+]ini &lt; 1 M) in neutral pH region, which agreed with the prediction from thermodynamic data. For Pd system, the Kd values decreased with an increase of [NH4+]ini, suggesting the formation of stable ammine complexes (Pd(NH3)m2+ (m: 1 – 4)). The obtained Kd values for Ni and Pd were analyzed using a surface complexation model. By taking complexes predicted by thermodynamic data into account, sorption behavior of Ni and Pd in the presence of NH3(aq)/NH4+ were well explained.

Relaxation Behavior of Ca-Based Bulk Metallic Glasses

The relaxation behavior of Ca60Mg20Zn20, Ca60Mg20Cu20, Ca65Mg15Zn20, Ca50Mg20Cu30, and Ca55Mg18Zn11Cu16 bulk metallic glasses was determined in the glass transition region using differential scanning calorimetry (DSC) with heating rates from 1 to 160 K/min. The activation enthalpy of structural relaxation and the fragility index m were found to be smaller in the glassy state (onset of the glass transition) than in the supercooled liquid state (end of glass transition). The Ca-based glass-forming liquids showed strong behavior of the relaxation time, with the fragility indexes m in the range of 33 to 40. The strong liquid behavior implies sluggish kinetics of crystallization in the supercooled liquid region and explains the very good glass-forming ability (GFA) of these alloys. The critical cooling rate for amorphization Rc of the Ca-based bulk metallic glasses was estimated to be in the range of 0.3 to 10 K/s, which is similar to Rc values for the best Pd- and Zr-based metallic glass-forming alloys discovered so far.

Grain- and phase-boundary stress effects in nanocrystalline materials

Based on the principal of virtual work, we derive an equation that describes the balance between volume and interface stresses in a particulate two-phase nanocomposite belonging to the class of random heterogeneous materials. Extracting absolute values of interface stress requires precise measurement of residual-strain-free lattice parameters and determination of interface area as well as volume fractions of phases. We find a value of 3.5±0.2Nm-1 for the isotropic phase-boundary stress of the Ag/Ni interface and a value of 0.67±0.1Nm-1 for the grain-boundary stress of Ag. If we compare this value with literature values for Gd, Pd and Fe, it appears that grain-boundary stress linearly correlates with the melting temperature of those elements.