Solubility Of Pd Research Articles

Evaluation of Thermodynamic Model of Pd(II) Complex Formation with Isosaccharinic Acid

Palladium-107 is one of the selected radionuclides in the safety assessment of geological disposal of radioactive waste. Although isosaccharinic acid (ISA) forms strong complexes with many elements and enhances element solubility, the thermodynamic evaluation of the complex of Pd with ISA has not been conducted. In this study, the solubility of Pd(OH)2 at pH 8.5–12.5 in the presence of ISA was investigated under inert gas (N2) atmosphere. Furthermore, the coordination state of aqueous Pd and ISA was investigated by X-ray absorption and Fourier transform infrared spectroscopy, respectively. According to experimental results, the number of OH ligands in the mixed complex depends on pH. The thermodynamic model and conditional equilibrium constants of the Pd-ISA complex were estimated by slope analyses of solubility experiments at different pH levels and ionic strengths based on the specific ion interaction theory. Hence, the impact of complexation with ISA on Pd(II) solubility under disposal conditions could be quantified using the proposed thermodynamic models in this study.

Dissolution behavior of palladium and rhodium in glass melts: Implications for the viscosity and electrical conductivity of high-temperature melts

This article investigated the solubility of platinum group metals (PGMs) in sodium borosilicate glass and its effect on the viscosity and electrical conductivity of melts. The role of PGMs in the viscosity and electrical conductivity of melts was examined using the rotating cylinder method and impedance spectroscopy, respectively. Moreover, XRD, XPS, and SEM were used to measure the phase compositions, valence states, and microstructures, respectively, of the glass samples with different PGMs contents. The results showed that the solubility of Pd and Rh in sodium borosilicate glass was estimated to be less than 110 ppm by weight. The higher concentrations of Pd and Rh resulted in Pd-rich and Rh-rich inclusions in the glass matrix, which eventually agglomerated to form metallic Pd, Rh and Rh2O3. The evolution of viscosity and electrical conductivity with different temperatures followed the Arrhenius equation with a fairly good linear relationship between ln η and ln κ.

Sulfide mineralization in Sikhuran ophiolite complex, Esfandagheh, Iran: Implications from trace element composition of silicate and sulfides

The Sikhuran ophiolite complex in Esfandagheh, Kerman province, is considered one of the important chromite mining areas in southern Iran. The complex is comprised of mainly tectonized harzburgite of residual upper mantle, depleted harzburgite, chromitite, dunite, and orthopyroxenite of the transition zone, as well as upper cumulates of ultramafic-mafic rocks. Sulfide disseminations, i.e., pentlandite, chalcopyrite, chalcocite, millerite, and heazlewoodite are hosted by dunite and chromitite in the upper part of the transition zone. The abundance of Base Metal Sulfides (BMS) as interstitials of olivine shows early stage sulfur saturation in Mg-rich magmas. Low Ni contents of ubiquitous olivine indicate that Ni in the primary silicate melt is preferentially concentrated in the sulfide liquid. The high activity of Ni in the melt is evidenced by the dominance of Ni-rich pentlandite and other Ni-bearing minerals from the Sikhuran ophiolite complex. Major and trace element compositions indicate that pentlandite is the main PGE-carrier with ƩPGE up to 44 ppm. Palladium, the most abundant PGE, is partitioned into pentlandite by diffusion of Monosulfide Solid Solution (MSS). The factors affecting this mechanism include the initial concentration of Pd, low compatibility of Pd compared to IPGEs, and decreasing solubility of Pd in MSS with decreasing temperature. Generally, although no detailed studies have been conducted on the occurrence of sulfide minerals in Iran; sulfide mineralization with coarse sulfide minerals in the Sikhuran can be a new perspective for mining companies and economic geologists.

Methane oxidation to methyl trifluoroacetate by simple anionic palladium catalyst: Comprehensive understanding of K2S2O8-based methane oxidation in CF3CO2H

The partial oxidation of methane to methyl trifluoroacetate (MeTFA) in trifluoroacetic acid (HTFA) is one of the most selective methane conversion reactions. We report that the simple anionic form of palladium, PdCl42- can effectively convert methane to MeTFA compared to neutral PdCl2 in the K2S2O8-HTFA oxidation system. The anionic catalyst form appears to increase the Pd solubility in the polar protic HTFA solvent, thereby facilitating transformation to PdTFA42- which is supposed to be the real catalytic species in this PdCl42- - catalyzed methane oxidation. It was found that not only methane oxidation but also solvent HTFA oxidation proceeded to a substantial degree, which limited the yield of MeTFA by consuming the oxidant, K2S2O8. Furthermore, for the first time, the role of trifluoroacetic anhydride (TFAA) was identified; it removes water produced by KHSO4 and HF, which are the reduced form of K2S2O8 and the oxidation byproduct of HTFA, respectively. The reaction equations for methane to MeTFA, and HTFA to CO2 in K2S2O8-HTFA system are suggested.

Biogeochemical Redox Processes Controlling the Element Cycling: Insights from Karst-Type Bauxite, Greece

The occurrence of very-high-grade bauxite ores of karst-type deposits resulting from Fe-leaching is of particular importance, because they are widespread in the Mediterranean metallogenetic province and result in the natural beneficiation of the ore quality. The present study focuses on mineral transformations and variations of major and trace elements, including platinum-group elements (PGE) and mineral chemistry along a bauxite profile from the Parnassos-Ghiona deposit, Greece underlying a fault. The most salient feature of the multicolor ores (grey–whitish, yellowish, deep red, deep grey to brown-red color, from top to bottom) is their association with fossilized and present-day microorganisms, which, by their reducing and/or oxidizing activity, catalyze redox reactions and provide nucleation sites for the precipitation of secondary minerals. Texture relationships between mineral and variations in the mineral chemistry, suggesting the sequence in their formation, indicate a multistage evolution. The recorded compositional variations show that the Al enrichment is accompanied by increase in the TOC, As, Pd and U, and chondrite-normalized REE patterns exhibit a similar trend and positive Ce anomalies. A lower (Pt + Pd) content and higher Pd/Pt ratio, ranging from 1.0 to 5.5 in the bauxite profile compared to those in Fe-Ni laterite deposits with the Pd/Pt ratio ranging from 0.1 to 0.68, reflect the higher solubility and mobility of Pd compared to that of Pt, and differences in their origin and genesis. A positive correlation between Pd and As and the elevated As content (up to 960 mg/kg) in multicolor ores compared to brown-red samples (average 10 mg/kg As) confirms their mobilization and redeposition.

Synthesis of Metastable Ternary Pd-W and Pd-Mo Transition Metal Carbide Nanomaterials.

Research and catalytic testing of platinum group transition metal carbides have been extremely limited due to a lack of reliable, simple synthetic approaches. Powder samples have been reported to phase separately above 1%, and only thin-film samples have been reported to have appreciable amounts of precious metal doping. Herein, we demonstrated, through the simple co-precipitation of Pd and W or Mo precursors and their subsequent annealing, the possibility to readily form ternary carbide powders. During the investigation of the Pd-W ternary system, we discovered a new hexagonal phase, (PdW)2C, which represents the first non-cubic Pd ternary carbide. Additionally, the solubility of Pd in the Pd-W-C and Pd-Mo-C systems was increased to 24 and 32%, respectively. As a potential application, these new materials show an enhanced activity for the methanol oxidation reaction (MOR) compared to industrial Pd/C.

The solubility of gold and palladium in magmatic brines: Implications for PGE enrichment in mafic-ultramafic and porphyry environments

We performed experiments to determine the solubility of Au and Pd in magmatic aqueous fluids as a function of oxygen fugacity (ƒO2), temperature (T), pH and total chloride concentration (Cltotal). Experiments were conducted at 800–1000 °C and 200 MPa in an externally-heated rapid-quench Molybdenum-Hafnium Carbide (MHC) cold-seal pressure vessel assembly. We employed a synthetic fluid inclusion (SFI) technique to entrap equilibrated, hydrothermal fluids in response to in situ fracturing of quartz cylinders at experimental run conditions. The solubility of Au and Pd both have positive relationships with ƒO2, temperature, acidity and chlorinity. Concentrated aqueous brines containing 63 wt.% NaCl can dissolve wt.% levels of Au (∼1.2 wt.%) and Pd (∼1.7 wt.%) at metal saturation in relatively oxidized conditions, 1.44 log units above the Ni-NiO oxygen buffer (NNO+1.44), and mildly acidic pH at 900 °C and 200 MPa. Thermodynamic modeling of experimental results suggests that Au is mainly transported as AuCl(aq) at high pH and low Cltotal conditions, whereas HAuCl2(aq) and potentially AuCl2(aq)− predominates at low pH and high Cltotal conditions. Results from thermodynamic modeling also suggest Pd is mobilized in significant contributions by both PdCl2(aq) and PdCl3(aq)− with the latter gaining predominance in response to increasing Cltotal. Calculated fluid/melt partition coefficients for Au and Pd in low-density, magmatic vapors at 1000 °C and 200 MPa suggest that Pd may experience fractionation from Au in porphyry Au-Cu (±Pd, Pt) systems due to the restricted compatibility of Pd in the fluid phase (requiring strongly acidic and substantially high ƒO2 conditions). Moreover, high-density, concentrated aqueous brines facilitate the compatibility of Pd in the fluid phase which may be important with respect to the formation of platinum-group element (PGE)-enriched horizons in layered mafic intrusions (e.g., J-M Reef, Stillwater Complex, U.S.A.). The potential for magmatic, near-neutral pH, high-salinity brines to dissolve significant amounts of Pd as Pd(II)-chloride complexes (∼400 to ∼900 µg/g) well below the NNO buffer suggests that such fluids may be responsible for late-stage hydrothermal remobilization of Pd within mafic-ultramafic igneous environments (e.g., Cu-Ni-PGE footwall deposits and low-sulfide PGE deposits in the Sudbury Igneous Complex, Canada).

Temperature Dependence of Hydrogen Solubility and Diffusivity in Hydrogen Permeable Membrane of Pd-Cu Alloy with B2-Type Crystal Structure

The temperature dependence of hydrogen solubility and diffusivity of Pd–53mol%Cu alloy membrane with the B2–type crystal structure has been investigated. The hydrogen permeation tests are performed using ultra–pure hydrogen (more than 9N) purified by a Pd–Ag alloy membrane to avoid any influences of impurities. It is found that the hydrogen permeability decreases significantly at low temperatures, especially near room temperature. The time dependence of hydrogen flux is monitored and found that the hydrogen flux decreases gradually during about 4 ~ 5 days after rapid cooling down to room temperature from 623 K.The results of the temperature dependence of the hydrogen permeability are analyzed in view of the consistent description of hydrogen permeation based on hydrogen chemical potential, where the hydrogen flux is proportional to the product of the mobility for hydrogen diffusion, B, and the PCT factor, fPCT. In this study, the pressure–composition–isotherms (PCT curves) for Pd–53Cu alloy with B2 structure are measured for the first time by the in–situ XRD–PCT method, and they are applied to estimate the PCT factors. Then, the temperature dependence of the PCT factor and the mobility for hydrogen diffusion is evaluated. It is revealed that the decrement in hydrogen permeability at low temperatures is mainly attributable to the decrement of the mobility for hydrogen diffusion.According to the positron annihilation experiments, the defects density is considered to be small in Pd–53Cu alloy with the B2 structure even at room temperature, suggesting that the excess Cu atoms in Pd–53Cu alloy occupy the positions of Pd sublattice, at which the Cu atoms form a local BCC–Cu unit. The diffusion of Cu atoms corresponds to the diffusion of BCC–Cu units in the B2 structure. Therefore the diffusion of Cu atoms and the configuration of BCC–Cu units in B2 structure could be a key to understand the gradual transition of hydrogen diffusivity at low temperatures.

Ion flotation of palladium by using cationic surfactants – Effects of chloride ions

Separation and recovery of platinum group metals (PGM) from dilute solutions have been examined using precipitation, ion exchange, and solvent extraction. Flotation separation of palladium (Pd) was investigated in the current study. Experimental results showed that Cl− forms complexes with Pd2+ ion and rendered Pd more soluble. Changes of speciation and solubility of Pd affected flotation separation significantly. Separation efficiency of Pd at pH 2.0 increased from 4.9%–79.4% as Cl− concentration increased from 1.4 × 10-3 to 0.1 M when using cetyltrimethylammonium bromide (CTAB) as the collector. Different collectors showed various removal efficiencies, and CTAB and 1-hexadecyltrimethylammonium chloride (HDTAC) resulted in effective separation of Pd among four cationic collectors used. Effects of collector dose on Pd removal efficiency were discussed as well. The electrostatic interaction between cationic collector and anionic Pd-Cl species (PdCl3− and/or PdCl42-) was the main mechanism for Pd flotation separation. It was demonstrated that flotation separation of Pd could be an effective technology for dilute systems.

Chronic toxicity of 50 metals to Ceriodaphnia dubia

Metals are essential elements for human life but may cause disorders when exposure is excessive. Previously, we reported on the acute toxicity of 50 metals; however, the chronic toxicity data of some metals are not available. Therefore, we conducted chronic toxicity tests to determine the effects of 50 metals on the water flea, Ceriodaphnia dubia. The IC20 of 20 metals (Be, Sc, Cr, Co, Ni, Cu, Zn, Y, Ru, Ag, Cd, In, Te, W, Os, Pt, Au, Hg, Tl and Pb) were <100 μg/L; nine metals (Al, V, As, Se, Zr, Nb, Rh, Sb and Bi) were 100 ≤ IC20 < 1000 μg/L; 16 metals (Li, Mg, K, Ti, Mn, Fe, Ga, Ge, Rb, Sr, Mo, Sn, Cs, Ba, Re and Ir) were 1000 ≤ IC20 ≤ 100 000 μg/L; and two metals (Na and Ca) were >100 000 μg/L. Three metals (Pd, Hf and Ta) did not show IC20 at the upper limit of respective aqueous solubility, and IC20 s were not obtained. The maximum test concentrations (almost aqueous solubility) of Pd, Hf and Ta were 83, 2400 and 5.3 μg/L, respectively. These data show the high correlation between our IC50 s for C. dubia and those for Dahpnia magna published previously. The IC50 s of 47 metals were not correlated with electronegativity, first ionization energy, atomic weight, atomic number, covalent radius, atomic radius or ionic radius.

Specific features of the formation, catalytic activity, and corrosion stability of PdCu electrolytic co-deposit

A mixed electrolytic deposit (ED) of PdCu (~20 at.% Cu) is synthesized from a solution of 1 mМ PdSO4 + 5 mМ CuSO4 + 0.5 M H2SO4 in the region of copper underpotential deposition (+400 mV vs. RHE). The incorporation of copper into the Pd deposit increases its true surface area (Strue) by a factor of ~20 and changes its hydrogen sorption characteristics. The ED PdCu demonstrates higher specific activity in FAOR as compared with individual Pd deposit (Еdep = 0.4 V). The specific solubility of Pd from ED PdCu is shown to be 2–3 times lower than the solubility of ED Pd; however, its total solubility from PdCu increases due to the strong increase in Strue.

Codeposition of Pd and Pb and electrocatalytic properties of their composite

A mixed electrolytic deposit (e.d.) PdPb with 33 ± 4 at.% Pb is obtained on the gold electrode from 5 mM PdCl2 + 0.7 mM Pb(ClO4)2 + 0.1 M HClO4 under potentiostatic conditions in the region of lead underpotential deposition (+100 mV vs. RHE). The deposit is characterized by SEM, EDX, XPS, CVA and ICP- AES methods before and after polarization measurements. The problem of thermodynamic instability of the deposit is discussed. It is shown that cycling of the potential of e.d. PdPb in the interval of 0.1–1.25 V results in preferential dissolution of Pb; however, no dense Pd shell is formed. The codeposition of Pb with Pd increases the degree of dispersion and the defectiveness of the deposit. The possible reasons for the lower specific activity of e.d. PdPb in formic acid oxidation reaction (FAOR) as compared with e.d. Pd are considered. The high solubility of Pd from e.d. PdPb as compared with e.d. Pd is observed. The latter effect cannot be explained by only the increased surface area of the Pd component; it is assumed that the defectiveness of the deposit structure is also responsible for this effect.

The solubility of palladium (Pd) in crude oil at 150, 200 and 250 °C and its application to ore genesis

Although most economic palladium deposits occur in mafic igneous rocks and are the products of magmatic processes, there are a number of polymetallic deposits hosted by organic-rich (bituminous) black shales in which the palladium reaches exploitable concentrations. Considering that palladium is rarely concentrated by hydrothermal processes, and as organic-rich black shales are the source beds for the production of hydrocarbons and bitumen commonly records the path taken by these hydrocarbons, it is reasonable to entertain the possibility that liquid hydrocarbons may act as an ore fluid for palladium. In order to test the potential of liquid hydrocarbons to act as ore fluids, Pd (0) metal wires were reacted with three crude oils, A, B and C (A being the lightest and C being the heaviest crude oil), at temperatures of 150, 200 and 250˚C. After reaction at 150˚C, the Pd concentrations in crude oils A, B and C were 60 ± 20 ppb, 19 ± 4ppb, and 128 ± 29 ppb, respectively. The corresponding concentrations at 200 ˚C, were 18 ± 6ppb, 17 ± 6ppb, and 50 ± 15 ppb, respectively, and at 250˚C, were 16 ± 2 ppb, 11 ± 1 ppb and 26 ± 2 ppb, respectively (n=3). The measured solubility of Pd was highest in the heaviest crude oil, C. All three oils reached their maximum Pd concentration at 150˚C, with Pd concentration decreasing progressively as temperature increased to 250˚C. To gain insights into the mechanism controlling the dissolution of Pd in crude oil, we analysed the reacted Pd wires using X-ray Photoelectron Spectroscopy (XPS). The XPS spectrum displays a well-defined thiol (R-SH) peak at a binding energy of 163eV, which indicates that Pd has an affinity for reduced organosulfur compounds. Moreover, Pd concentrations were observed to increase with the total thiol content of the oil, thereby corroborating the results of the XPS analyses. Our results clearly show that Pd solubility in crude oil is promoted by the presence of thiols. As thiol-rich hydrocarbons usually develop in deep, high temperature (100–140°C) carbonate sequences containing abundant sulfate mineralization, it is thought that the thiols are the products of thermochemical sulfate reduction (TSR) (Machel, 2001). We therefore propose that liquid hydrocarbons, which have interacted with sulfate at relatively high temperature, may serve as effective ore fluids for palladium.

Platinum-group minerals and Fe–Ni minerals in the Sartohay podiform chromitite (west Junggar, China): Implications for T–pH–fO2–fS2 conditions during hydrothermal alteration

Complex assemblages consisting of native iron + pentlandite, pentlandite + heazlewoodite + magnetite, heazlewoodite + magnetite + platinum-group minerals (PGM), and millerite ± heazlewoodite are associated with three types of altered chromites (partly altered chromite, double-rimmed chromite, and porous chromite) discovered in the Sartohay podiform chromitite hosted by the Sartohay ophiolitic mélange in west Junggar of China. We propose a two-stage genetic model to explain the chromite alteration processes based on detailed petrographic observations and thermodynamic calculations. Reactions between primary chromite and olivine formed porous Fe2+-rich chromite and chlorite patches under low-temperature, reducing conditions. Afterwards, oxidizing Fe3+- and CO2-rich fluids derived from host serpentinite were incorporated into the Fe2+-rich chromite, shifting its composition to heterogeneous Fe3+-rich chromite (ferrian chromite). Thermodynamic calculations suggest that the co-evolution of fO2 and fS2 played a crucial role in controlling the formation and/or transformation of the Fe–Ni minerals coevally with the sulfides, antimonides, and alloys of platinum-group elements (PGE). Pd and Pt precipitated as sulfides, while Ir precipitated as an alloy when log fS2 ranged from –16.0 to –14.2 within the heazlewoodite stability field. Compared with the host serpentinite, the fO2 in the Sb-bearing fluid equilibrated with chromitite was low enough to decrease the Pd solubility, leading to co-precipitation of Sb and Pd.

Cyclodextrin-Assisted Synthesis of Pd/Co/C Nanopolyhedra by ZIF-67 as a Highly Acid Tolerant Catalyst for Hexavalent Chromium Reduction.

The palladium/cobalt/carbon (Pd/Co/C) nanopolyhedra were synthesized by calcinating the precursor prepared by a cyclodextrin (CD) modified palladium acetylacetonate loaded on ZIF-67, hydroxypropyl-β-cyclodextrin (HP-β-CD)-[Pd(acac)2]/ZIF-67. On one hand, the HP-β-CD was used to increase the solubility of Pd(acac)2 by supramolecular interactions, and on the other hand, ZIF-67 was employed to provide the Co/C as the magnetic support. The Pd/Co/C nanopolyhedra obtained with the assistance of HP-β-CD have high activity and reusability for the reduction of the dichromate ion in the presence of formic acid without using any buffer solution, and no significant leaching of metallic Co of the catalyst was observed. This could be ascribed to the fact that the presence of HP-β-CD could lead to a more homogeneous distribution of metallic Pd in the Pd/Co/C nanopolyhedra, which could prevent the dissolution of metallic Co by formic acid.

Evaluation of palladium diffusion in Ti-Rich TiNi alloys

In order to study the diffusion kinetics of Pd into Ti-rich TiNi alloys, diffusion annealing treatments of palladium-coated Ti53Ni47 and Ti50.2Ni49.8 alloys were carried out at temperatures ranging from 700 to 1000 °C. Linear Arrhenius temperature dependencies with the pre-exponential factors of 2 ± 1.1 × 10−10 and 1.05 ± 1.5 × 10−8 m2 s−1 and the activation energies of −128 ± 4 and −153 ± 10 kJ mol−1 were obtained for Pd diffusivity into Ti53Ni47 and Ti50.2Ni49.8 alloys, respectively. The suggested mechanism for Pd diffusion in Ti53Ni47 was anti-site bridge mechanism. While the rapid diffusion of Pd in Ti50.2Ni49.8 was attributed to the high volume fraction of vacancies in Ni sub-lattice of TiNi lattice and Next Nearest jumps of Pd atoms into abundant Ni vacancies. The lower diffusivity of Pd in Ti53Ni47 was related to the dominant diffusion mechanisms in two systems and low solubility of Pd in Ti2Ni precipitates which located in grain boundaries, as well.The other part of the study was denoted to inter-diffusion studies in Ti53Ni47/Pd and Ti50.2Ni49.8/Pd diffusion couples, which confirmed the higher diffusivity of Pd in Ti50.2Ni49.8.

The solubility of Pd and Au in hydrous intermediate silicate melts: The effect of oxygen fugacity and the addition of Cl and S

The solubilities of Pd and Au in a hydrous trachyandesitic melt were experimentally determined at 1000 °C and 200 MPa at oxygen fugacity (ƒO2) from 0.45 log units below to 6.55 log units above the Ni-NiO buffer (NNO). The effect of adding metal-binding ligands (i.e. Cl and S) to the silicate melt was also studied. The solubility of Au increases from 0.15 ± 0.1 to 3.85 ± 1.48 ppm in Cl- and S-free melts with ƒO2 increasing from NNO−0.45 to NNO+6.55 with a slope that suggests that it is present in 1+ oxidation state over the entire studied ƒO2 range. On the other hand, Pd solubility, shows a more moderate increase with ƒO2, especially in the lower half of the studied range, increasing from 2.66 ± 0.25 ppm at NNO−0.45 to only 3.62 ± 0.38 ppm at NNO+1.72 in Cl- and S-free melts. Overall, the variation in Pd solubility as a function of ƒO2 indicates Pd being dissolved in the silicate melt in both zero and 1+ oxidation state, with the former being dominant below NNO+4.5. At NNO−0.45 to +3.48, the addition of 3170–4060 ppm Cl to the silicate melt increased the solubility of Au by an average factor of 1.5, in comparison to Cl-free melts. However, at NNO+6.55, Au solubility increased by a factor of 2.5. The addition of Cl had a negligible effect on the solubility of Pd except for a large increase (factor of 2.4) at NNO+6.55. At reducing conditions (NNO−0.45), the addition of 170 ppm S to the silicate melt increased the solubility of Au by a factor of ∼4 but did not change the solubility of Pd in comparison to S-free melts. The observation that Pd is dominantly present as Pd0 at NNO < +4.5 may explain the lack of complexation with potential reduced sulfur-bearing and chloride ligands. As one may expect similar behavior in fluids degassing from magmas at depth, the lack of oxidized Pd species could be an important factor behind the scarcity of economically viable Pd-rich magmatic-hydrothermal deposits observed in nature.

Experimental Investigation of the Isothermal Section in Fe-Gd-Pd Ternary System at 873 K

Isothermal section of Fe-Gd-Pd ternary system at 873 K has been established by means of x-ray diffraction (XRD), differential scanning calorimetry (DSC), and scanning electron microscope (SEM) with energy disperse x-ray spectroscopy (EDS) in backscattered electron imaging modes. The isothermal section consists of 14 single-phase regions, 25 two-phase regions, and 12 three-phase regions. At 873 K, no ternary compound was found and the binary inermetallic compounds Gd3Pd and Fe23Gd6 are not stable, whereas the compound Fe23Gd6 decomposes into compounds Fe17Gd2 and Fe3Gd. The XRD and the SEM/EDS analysis show that there is almost no solubility of Gd in the FePd and FePd3 phases, and the solubilities of Pd in Fe17Gd2, Fe3Gd and Fe2Gd and Fe in GdPd2, α-Gd3Pd4 and Gd3Pd2 are all less than 1 at.%. Meanwhile, the solubilities of Fe in GdPd3, α-GdPd and Gd7Pd3 are determined to be as high as 1.37, 5.31, and 4.18 at.% Fe, respectively.

High Efficiency Direct Ammonia Type Fuel Cells based on BaZr x Ce0.8-X Y0.2O3/Pd Oxide-Metal Junctions

Recently, ammonia has attracted a considerable interest as a prospective carbon-free fuel source for fuel cells due to the low cost, ease in liquefaction and transportation at ambient temperatures, and high volumetric energy density. The proton conducting ceramic fuel cells (PCFCs) using proton-conducting oxides, such as BaZr x Ce0.8-x Y0.2O3- d , as an electrolyte is promising as a direct ammonia type fuel cells. The water formation in PCFCs is mainly progressive at the cathode side, unlike solid oxide fuel cells (SOFCs), and therefore, the contamination of the ammonia fuels into the exhaust water is precluded, thereby eliminating re-purification of water exhaust and simplifying total systems. Hydrogen membrane fuel cell (HMFC), which was firstly proposed by Ito et al., consists of an ultrathin proton conducting ceramic electrolyte supported on a dense hydrogen permeable metal anode. The cell facilitates efficient power generation, giving 900 mW cm-2 at 400°C, since reduced electrolyte thickness can significantly decreases the ohmic loss at lower temperatures. This unique cell configuration could be advantageous for ammonia fuel cells because 1) the NO x formation at the anode is perfectly prevented because NH3 gases are isolated from the oxide electrolytes by Pd solid anode and 2) Pd is expected to capture efficiently the hydrogen gases produced by the pyrolysis of ammonia due to the large ahydrogen sorption ability. Herein, we demonstrated the high efficiency power generation of the direct ammonia type HMFC due to the hydrogen pumping effects realized by BaZr0.1Ce0.7Y0.2O3- d (BZCY) and Pd heterointerface. Ohmic characteristics of the heterojunctions, altogether with hydrogen solubility of Pd, can facilitate the hole proton exchange between Pd and BZCY regardless of the lowered hydrogen concnetartion in NH3-fed anodes. The cell gained the maximum power density of 0.52 W cm-2 at 600°C, which was much higher than the champion data of ammonia PCFCs.

Fabricating the AuPdPt Ternary Nanophase Diagram at 800 °C To Guide the Exploration of Optimal Catalyst for n-Hexane Oxidation

A good knowledge of nanophase diagrams is critical to understanding the performance of nanomaterials. Herein, we for the first time fabricate a AuPdPt ternary nanophase diagram at 800 °C by experimental means. The solid-state synthesis strategy enables a precise synthesis of AuPdPt trimetallic nanoparticles with a full range of compositions and desired size distributions. By studying the phase behavior of those TMNPs, we succeed in mapping out the boundary curve and tie lines. Interestingly, the AuPdPt nanophase boundary shifts obviously to the Au-rich region as compared to the case of the corresponding bulk diagram, likely due to the combination of size and composition effects. Besides, owing to the different solubility of Pd in Au-rich and Pt-rich matrix, some tie lines do not parallel the baseline. These observations greatly improve our basic understanding of nanophase diagrams and are expected to be valuable references for other systems. Moreover, the as-fabricated nanophase diagram is successfully ap...