Sorption-atomic-absorption determination of platinum,palladium, and rhodium in dead autocatalysts

The conditions for determination and group concentration of platinum metals (PMs) in the presence of matrix components using new S,N-containing complex-forming sorbents in solutions obtained after decomposition of decontaminated autocatalysts are proposed. The technique of atomic-absorption determination of PMs from a solution (n × 10⁻⁴−n × 10⁻²; s _r = 0.15–0.07) and a solid phase (n × 10⁻⁵−n × 10⁻⁴; s _r = 0.20–0.12) is developed.     

Chemical preparation of samples of dead automobile catalyzers for subsequent determination of platinum, palladium, and rhodium using atomic emission spectrometry with inductively coupled plasma

Systematic studies of different methods for decomposition of samples of dead automobile catalyzers (ACs) on a ceramic base using mixtures of mineral acids and high-temperature alloying with the aim of subsequent determination of platinum, palladium, and rhodium using atomic emission spectrometry with inductively coupled plasma are presented. The behavior of matrix components of dead ACs under the conditions of sample decomposition is investigated. The effect of the results of determining platinum group metals is studied. The relative standard deviation of the results of the analysis performed according to the developed techniques is 11-9% at platinum, palladium, and rhodium concentrations ranging from 0.01 to 0.3%.     

Determination of platinum, palladium, and rhodium in automotive catalysts using high-energy secondary target X-ray fluorescence spectrometry

A fast and direct determination procedure for precious metals in spent automotive catalyst was developed using the novel high-energy polarized-beam XRF. A sample preparation method working directly on the ground material was optimized. The material was pressed as a pellet using wax as a binder; no internal standard was added. The standards for this application were available spent automotive catalyst, previously analyzed by ICP-OES to verify their concentration, prepared in the same way as the unknown samples. The investigated concentration ranged from nearly 0 to approximately 2700 ppm for Pt, to 500 ppm for Rh, and to 7500 ppm for Pd. The repeatability of the XRF measurement appeared to be better than 0.5%, while the precision of the whole method was approximately 1%. The accuracy of the XRF method was verified with the well-established (but very time-consuming) ICP-OES method; a good agreement (no difference when using the 95% confidence interval) was found for the results. When using an irradiation time of 500 s for the CsI secondary target and the Zr secondary target, the detection limits for Pt, Pd, and Rh were found to be better than 5 ppm.     

甲酸辅助溶出车用陶瓷催化剂中铂钯铑元素方法研究

试验采用甲酸对车用陶瓷催化剂进行预处理,再按照优化后的HJ 509——2009标准方法进行酸溶,采用电感耦合等离子体质谱法测定催化剂样品中铂、钯、铑的含量。结果显示:采用3 mL甲酸对催化剂样品预处理后蒸干,加入4 mL盐酸、3 mL硝酸、3 mL氢氟酸,在180℃下微波消解0.5 h,再经过赶酸、回流得到的铂、钯、铑的回收率均在95%~106%范围内。该方法可以改善HJ 509——2009标准方法对部分样品的不适用,可以满足目前车用陶瓷催化剂的检测要求。     

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

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

Thermal expansion of rhodium,iridium, and palladium at low temperatures

Coefficients (α) of linear thermal expansion of Rh, Ir, and Pd are reported to be respectively 8.45, 6.65, and 11.78×10^?6 ° K^?1 at 238°K, and 3.50, 3.43, and 6.21×10^?6 °K^?1 at 75°K. At temperatures below 10°K, α may be represented by $$\begin{gathered} 10^{10} \alpha = 20{\rm T} + 0.052{\rm T}^3 (Rh) \hfill \\ 10^{10} \alpha = 9{\rm T} + 0.070{\rm T}^3 (Ir) \hfill \\ 10^{10} \alpha = 40.5{\rm T} + 0.435{\rm T}^3 (Pd) \hfill \\ \end{gathered} $$ TheT andT ³terms are identifiable with electron and lattice vibrational components, respectively. Corresponding Grüneisen parameters are γ (electron)≈2.8, 2.7, and 2.22 for Rh, Ir, and Pd, and γ ₀ (lattice)≈2.0, 2.3, and 2.25.     

Determination of platinum and palladium in dead catalysts using inductively coupled plasma atomic emission spectrometry after sample digestion by high-temperature fusion

A technique for the determination of platinum and palladium in dead catalysts using ICP-AES after sample digestion by high-temperature fusion with potassium pyrosulfate is described. The technique is universal; it offers the possibility to analyze various brands of catalysts and their mixtures at a content of platinum and palladium of 0.1% to whole units of percent in a short time. The accuracy of results of determination of platinum and palladium is confirmed by comparison with the data of interlaboratory control. The relative standard deviation in the developed technique is 4–2.5% for the content of platinum and palladium of 0.1 to 0.5% and 2–1% for higher concentrations of these elements.     

Hydriding characteristics of palladium and platinum alloyed FeTi

Effect of alloying on the hydriding characteristics of FeTi with noble metals such as platinum and palladium (5% by weight) has been investigated. It is observed that palladium has a favourable effect with respect to easy activation, decreased hysteresis and lower plateau pressures for hydrogen absorption and desorption process. For Pd/FeTi, a saturation composition of Pd/FeTiH_1.85 having the -phase, has been obtained. Unlike this, for Pt/FeTi, the total hydrogen absorption is decreased significantly and a saturation composition of Pt/FeTiH_1.5 having only ₂ phase, is observed.     

Direct determination of oxalic acid by a bare platinum electrode contrasting a platinum nanoparticles-modified glassy carbon electrode

A bare platinum disk electrode without further decoration was directly used to determine oxalic acid (OA), showing good linear ranges of 0.57–104.01 μM and 104.01–228.75 μM with a low detection limit of 0.38 μM (S/N = 3). In contrast, platinum nanoparticles (PtNPs) dispersed on a glassy carbon electrode were successfully achieved by an one-step electrochemical deposition method, possessing relatively wider linear detection ranges of 1.14–342.80 μM and 342.80–548.92 μM for OA with a lower detection limit of 0.28 μM (S/N = 3). Both the proposed electrochemical sensors exhibit great reproducibility, stability and selectivity. In particular, they have been applied to the determination of OA in real spinach samples, showing excellent analytical performance.     

Synthesis of solvent-stabilized colloidal nanoparticles of platinum, rhodium, and ruthenium by microwave-polyol process

Solvent-stabilized Pt, Rh, and Ru colloidal nanoparticles were synthesized by a microwave-polyol process. They were characterized by TEM and XPS, XRD, and UV-vis examination. These colloids have small particle sizes with narrow size distribution, and they were stable in glycol upon storage under ambient condition for months. Separation and XPS characterization of the intermediate colloids demonstrated the two-step mechanism for the formation of solvent-stabilized metal colloids via hydrolysis.     

Atomic displacements in palladium/ platinum solid solutions

X-ray measurements reveal that Pd/Pt solid-solution alloys have higher Debye temperatures and lower root-mean-square dynamic displacements than the average for the pure metals. The root-mean-square static displacements are quantitatively interpreted in terms of a shortening of the Pd/Pt interatomic distance and the asymmetry of unlike neighbours about an average atom.     

Finding new phases for precipitate-hardening in platinum and palladium alloys

Precipitate hardening (via ordered phases rather than phase separation) of platinum and palladium can be effective even with a small volume-fraction of the ordered phase [M. Carelse, C.I. Lang, Scripta Materialia 54 (7) (2006) 1311]. The approach is particularly well suited to jewelry alloys which must be 95 wt.% pure and where ordered phases of 7:1 or 8:1 stoichiometries can be formed. We examined eight systems where this approach may lead to new applications: Pt-Al, Pd-Al, Pd-Cu, Pd-Mg, Pd-Nb, Pt-Mo, Pt-V, and Pd-V. In each system, using first-principles-based cluster expansion modeling, we have identified high stoichiometric-ratio phases that are stable. Furthermore, using Monte Carlo simulations, we have estimated the order-disorder transition temperatures to identify experimentally feasible phases. In three cases, the computational results are verified by experiment, suggesting that the remaining predictions are likely to be useful as well.     

制造铂铑热电偶微细丝的关键问题

总结、归纳了影响铂铑热电偶细丝生产的主要问题，指出影响铂铑热电偶细丝生产的主要问题，有以下3个方面：细丝断丝现象、平直度与抗拉强度、细丝表面质量。分析了各个问题产生的原因，提出了相应的解决问题的办法。     

Quantitative elemental analysis for rhodium and palladium in minerals by time-of-flight resonance ionization mass spectrometry

Results are presented for the trace analysis of Pd and Rh by time-of-flight-resonance ionization mass spectrometry (TOF-RIMS). The spectrometer, developed at the Advanced Mineral Technology Laboratory (Ontario, Canada), is based on a commercial laser-induced mass analyzer with upgrades that include independent laser ablation and ionization sources and pulsed ion optics to minimize noise caused by primary ion formation. The schemes presented for Rh and particularly for Pd detection are simpler than others reported in the literature. The experimental laser fluences were found to be in reasonable agreement with theoretical estimates. The TOF-RIMS measurements were quantified on the basis of calibration curves derived using reference samples covering 3 orders of magnitude in concentration. Minimum detection limits of ~15 parts per billion were found for both metals, with a precision of ~ +/-15%. Samples from sulfide, iron oxide, and silicate minerals were also examined. The results are in excellent agreement with those obtained using dynamics secondary ion mass spectrometry.     

Age-hardening reactions and microstructures of a dental gold alloy with palladium and platinum

The age-hardening reactions and microstructures of a dental casting gold alloy with some palladium and platinum were investigated by means of hardness tests, X-ray diffractometry, electrical resistivity measurements, and scanning and transmission electron microscopy. Ageing reactions during isothermal annealing were completed by two stages. The first stage corresponded to the formation of a metastable CuAu I phase within grains, and the second stage to a cellular reaction at grain boundaries. The former contributed to the hardening and the latter to the softening. An activation energy of 128 kJ mol^–1 for hardening was obtained. Two types of cell growth were observed and could be distinguished in terms of the homologous temperature.