ABSTRACTS: October 1983
ABSTRACTS: October 1983
of current literature on the platinum metals and their alloys
The Constitution of Ternary Systems: 4th, 5th and 6th Group Transition Metals—Rhenium or Platinum Metals Carbon—Part 2
h. holleck, Metall, 1983, 37, (7), 703–708
Phase diagrams of ternary carbides of Ti, Zr, Hf, V, Nb and Ta with Pt, Pd, Os, Ir, are constructed at temperatures 1300°C, 1500°C, 2000°C; comparisons with ternary Cr, Mo and W carbides are made.
Electrical Properties of Narrow Gap Semiconductor PtSb2
a. dargys and j. kundrotas, J. Phys. Chem. Solids, 1983, 44, (13), 261–267
Results of measurements of conductivity, Hall and Seebeck coefficients on Te doped n-type crystals of PtSb2 are presented. The Hall coefficient and Seebeck coefficients undergo sign inversion twice, below and above room temperature. Below 200K PtSb2 can be described by a simple conduction and valence band model. The energy gap, electron conductivity mass, acoustic phonon limited electron mobility and mobility ratio are determined. At higher temperatures a more complicated valence band model is needed to account for the results.
Superconductivity and Critical Field Strengths of Palladium-Boron-Hydrogen Alloys
h. brodowsky and j. fleischhauer, Z. Naturforsch., A, 1983, 38, (6), 676–679
Transition temperature and critical field strengths have been observed on superconducting Pd-B-H alloys with different B: H ratios. Homogeneous samples, prepared by equilibrium methods, exhibit superconductivity above 3K for B contents less than x = 0.07 (x = mole B : mole Pd). Pd-B alloys need less H for reaching a fixed transition temperature than B free alloys. Critical field strengths for Tc = oK increase linearly with increasing B content.
Adsorption of Aliphatic Hydrocarbons C6 on Pd-Ru Alloy
v. g. dobrokhotov, e. a. shalvashvili, l. f. pavlova and v. m. gryaznov, Izv. Akad. Nauk SSSR, Ser. Khim., 1983, (7), 1478–1482
Studies of the reversible adsorption of hexane, hexene-1 and hexadiene-1,5 on Pd-6wt.% Ru alloys were made by chromatography at 275−360K. H2 was found to affect adsorption of n-hexane on the alloys. The increase of partial pressure of H2 decreased the adsorption in the α -phase in the alloy-hydrogen system and increased it in the β -phase. Adsorption and catalytic surface centres are very different.
How Epitaxial are Pd2Si-Si Interfaces?
z. liliental, r. w. carpenter and r. tuenge, Thin Solid Films, 1983, 104, (1/2), 17–29
Pd2Si layers produced by evaporation or sputtering onto Si substrates were studied by spectroscopy. The Si/Pd2Si interfaces produced by evaporation were polycrystalline and rougher than those produced by sputtering. Electrical measurements of the ideality factor for Schottky barriers made from these materials produced higher values for the rougher evaporation formed interfaces, consistent with interface-roughness-induced scattering.
Hydrogen Effects in Metal Catalysts
z. paal and p. g. menon, Catal. Rev., Sci. Eng., 1983, 25, (2), 229–324
A comprehensive review is given of effects of H2 on physical and chemical properties and catalytic activity and selectivity of platinum group metal and gold catalysts. (203 Refs).
Cross Section for Photoelectron Capture by in AgBr
r. j. deri and j. p. spoonhower, Appl. Phys. Lett., 1983, 43, (1), 65–67
The lifetime of photogenerated electrons in AgBr crystals doped with Ir3+ ions was determined from photoconductivity measurements. The lifetime was short at room temperature, 13–150ps for crystals with 89–4ppm of dopant. This material may be of interest in studying picosecond phenomena in semiconductors. A cross section of 26±5Å2 was deduced for photoelectron capture by centres.
The Effect of High Pressure on Formation of Intermediate Phases in the System Os-Sn
n. v. kalyaeva and s. v. popova, Izv. Akad. Nauk SSSR, Neorg. Mater., 1983, 19, (7), 1106–1109
Studies of the effect of high pressure on the formation of intermediate phases in Os-Sn were made on alloys prepared from powder mixtures of Os and Sn containing 25−75 at.%Sn. The results showed the formation of intermediate phase Os3Sn7 at 7.7 MPa pressure and at 900–1600K.
Oxygen-Spinels in Ruthenium and Iridium
b. krutzsch and s. kemmler-sack, Mater. Res. Bull., 1983, 18, (6), 647–652
In the systems Co-Ru-O and Co-Ir-O cubic spinel type phases of composition Co3−xRuxO4(0.4 ≤ x ≤ 1) and Co2.5Ir0.5O4 have been synthesised. The Co can be partially substituted by Fe and Mn (Co2.3−yMyRu0.7O4, o ≤ y ∼ 0.7, M = Mn, Fe) or Cu. A transition from low to high concentration of free electrons can be detected by vibrational spectroscopy.
A Study by Electrochemically Modulated Infrared Reflectance Spectroscopy of the Electrosorption of Formic Acid at a Platinum Electrode
b. beden, a. bewick and c. lamy, J. Electroanal. Chem., Interfacial Electrochem., 1983, 148, (1), 147–160
This work is a first attempt to compare the qualitative results given by EMIRS which is a new spectroscopic technique useful for the “in situ” identification of adsorbed species at the electrode/electrolyte interface, to the quantitative determination of the adsorbed layer, as obtained by conventional electrochemistry. It is shown that so-called CO species detected by EMIRS during the chemisorption of formic acid on a Pt electrode, are the dominant species over a large potentional range.
Anodic Characteristics of Amorphous Ternary Palladium-Phosphorus Alloys Containing Ruthenium, Rhodium, Iridium or Platinum in a Hot Concentrated Sodium Chloride Solution
m. hara, r. hashimoto and t. masumoto, J. Appl. Electrochem., 1983, 13, (3), 295–306
Amorphous ternary Pd-based alloys containing platinum group metals as an additional element were prepared by rapid quenching from the molten state and their anodic characteristics were studied in NaCl solution of pH 4 and 80°C. The alloys containing sufficient amounts of Rh, Pt or Ir were passivated by anodic polarisation and their corrosion rates at high current densities in the Cl− evolution region were extremely low. The amorphous Pd41Ir40P19 alloy had the desired stable, high electrocatalytic activity for Cl− evolution and high overvoltage for O2 evolution.
Study of the Kinetic and Reduction Mechanism of OsO4 by NaBH4 in Alkali Solution
v. s. khain and a. a. volkov, Kinet. Katal., 1983, 24, (3), 525–530
A study of the reaction kinetics of OsO4 with NaBH4 showed that the process goes through various stages forming Os(VII), Os(VI) and Os(IV). The Os(VI) to Os(IV) reduction stage was the limiting one. A possible mechanism of the process and optimum conditions for obtaining OsO2 are suggested.
Oxidative Electropolymerisation of Polypyridyl Complexes of Ruthenium
c. d. ellis, l. d. margerum, r. w. murray and t. j. meyer, Inorg. Chem., 1983, 22, (9), 1283–1291
Polypyridyl complexes of Ru, containing aromatic amine groups, such as [(bpy)Ru(4-pyNH2)2]2+(bpy = 2,21-bipyridine, 4-pyNH2 = 4-aminopyridine), undergo electrochemically induced oxidative polymerisation. The resulting polymers form fairly stable electrochemically active films on the oxidising electrode, which can be Pt, SnO2 or vitreous C.
Electrocatalytic Oxidation of Chloride to Chlorine Based on Polypyridine Complexes of Ruthenium
c. d. ellis, j. a. gilbert, w. r. murphy and t. j. meyer, J. Am. Chem. Soc., 1983, 105, (14), 4842–4843
Spectrometric studies of the chemical and electrochemical oxidation of either or the one-electron oxidised form of the dimer, in the presence of chloride showed the generation of Cl2 gas. During electrolysis at a “coarse” (12 holes/linear in.) reticulated vitreous C electrode potentiostated at + 1.20V in ∼ 30ml of a 0.05MHCl solution containing 1.35 × 10−5 mol of (II), a yield of 1.04 × 10−4 mol of Cl2 in 132 min was observed.
Hydrogen Production with Visible Light by Using Dye-Sensitized TiO2 Powder
k. hashimoto, t. kawai and t. sakata, Nouv. J. Chim., 1983, 7, (4), 249–253
H2 was produced from H2O by exciting various organic dyes on Pt/TiO2 or TiO2 with visible light in the presence of a reducing agent. The quantum efficiency of H2 production was estimated to be in the order of 10−1 for with EDTA as reducing agent. It is postulated that H2 is produced by the reduction of H2O through a dye-sensitised process.
Efficient Hydrogen Production from Water by Visible Light Excitation of Fluorescein-Type Dyes in the Presence of a Redox Catalyst and a Reducing Agent
k. hashimoto, t. kawai and t. sakata, Chem. Lett., 1983, (5), 709–712
A H2 production system for visible light without an electron relay, efficient in the high pH region has been constructed with some fluorescein derivatives in the presence of a redox catalyst and a sacrificial reducing agent. The photogalvanic cell was <semiconductor or Pt (light | dibromofluorescein, TEOA | Pt(dark)>; the open voltage was ∼800 mV.
Design, Preparation and Characterization of RuO2/TiO2 Colloidal Catalytic Surfaces Active in Photooxidation of Water
g. blondeel, a. harriman, g. porter, d. urwin and j. kiwi, J. Phys. Chem., 1983, 87, (14), 2629–2636
The preparation and optimisation of RuO2xH2O catalyst obtained by hydrolysis of RuCl3 on TiO2 power are described. The catalyst is active in dark and light-induced sacrificial systems mediating O2 evolution in solution. The effects of pH, temperature, concentration and other experimental variables affecting the preparation of the catalyst are described. By electron microscopy it is shown that the active catalytic species consists of islands of RuO2.xH2O, present as agglomerates of 10–20nm interspersed with TiO2 particles of 200nm diameter.
Visible Light-Induced Formation of Hydrogen and Thiosulfate from Aqueous Sulfide/Sulfite Solutions in CdS Suspensions
d. h. m. w. thewissen, a. h. a. tinnemans, m. eeuwhorst-reinten, k. timmer and a. mackor, Nouv. J. Chim., 1983, 7, (3), 191–194
Cleavage of H2S into H2 and S occurs in aqueous suspensions of CdS loaded with RuO2upon illumination with visible light. The influence of various anions on this process is presented. Addition of sulphate makes the process very efficient. A 4-fold increase in H2 production is observed.
Metal Cluster Photocatalysis: Photoinduced Hydrogenation of Ethylene by the Tetraruthenium Cluster Complex H4Ru4(CO)12
y. doi, s. tamura and k. koshizuka, J. Mol. Catal., 1983, 19, (2), 213–222
Near-u.v. irradiation of the H4Ru4(CO)12 complex in heptane solution induces the catalytic hydrogenation of C2H4 in the presence of H2 at 35°C. The mechanism most consistent with the experimental facts involves photodissociation of CO from the catalyst precursor H4Ru4(CO)12 as the first step in the catalytic cycle. The properties of photogenerated catalytic species are compared with those of the active species in thermal catalysis by H4Ru4(CO)12.
ELECTRODEPOSITION AND SURFACE COATINGS
Adhesion and Hardness of Platinum Coatings Electrodeposited from Molten Salts
r. p. walters, m. j. lynch and d. r. flinn, Plat. Surf. Finish., 1983, 70, (5), 91–95
By using a direct-pull solder method, the adhesion of Pt coatings to TZM (0.41% Ti, 0.10% Zr, balance Mo) and Fe10Cr substrates was determined. The average fracture value was 331 MPa with fracture occurring in the substrate or in some combination of the substrate, coating or solder, but not at the deposit/substrate interface, indicating that the true adhesion of the coatings is greater than the measured fracture values. Cross sectional hardness values were dependent on the average grain width, with hardness 50–120HK25 at 35 and 8μ m from the interface.
Studies of Electrodeposition of Thick Films of Bright Palladium Layers
p. a. iuzikis and s. i. knotianovich, Zh. Prik. Khim. (Leningrad), 1983, 56, (4), 777–781
Studies of the effect of various additions on the kinetics of the Pd electrodeposition process from ammonium chloride electrolyte showed that adding saccharine and highly sulphurated castor oil to the Pd electrolyte resulted in a greatly increased cathodic polarisation. This allowed the production of low porosity, fine-grained bright layers up to 30μ m.
LABORATORY APPARATUS AND TECHNIQUE
Digital Carbon Monoxide Detector/II/
j. p. dauchot, a. hecq and m. t. grognia, Electrocomponent Sci. Technol., 1983, 10, (2 + 3), 151–156
The switch off concentration phenomena in CO oxidation on Pt and the parallel steep variation of resistance or surface potential of thin Pt films have been used to develop a C detector. Coating the Pt film with an increasing thickness of PTFE makes this switch off point move to increasing CO concentrations, therefore a series of electrical elements, Pt thin film resistances, Pt MOS diodes or Pt gas MOS transistors covered by calibrated thicknesses of PTFE can switch off at well determined CO concentrations and form the basis of a digital detector.
Pd/a-Si : H Metal-Insulator-Semiconductor Barrier Diode for Hydrogen Detection
a. d’amico, g. fortunato, g. petrocco and c. coluzza, Appl. Phys. Lett., 1983, 421, (11), 964–965
Hydrogenated amorphous Si produced by the glow-discharge technique was used to construct very low cost, high quality MIS structures using Pd as catalytic metal for H2 detection. With this device, H2 concentrations in H2-N2 mixture as low as 100ppm were detected. There is an indication that the ultimate limit is much lower.
Pt/Al2O3-Cl in Pure Hydrocarbon Reforming
j. n. beltramini, e. e. martinell, e. j. churin, n. s. figoli and j. m. parera, Appl. Catal., 1983, 7, (1), 43–55
The deactivating effects of different paraffins, naphthenes and aromatics were studied during their reforming over a Pt/Al2O3 catalyst. The coke formation was found to be directly related to the structure of hydrocarbons or to those of their principal products. The five carbon atom ring was the most important coke precursor for naphthenes. The deactivation effect of coke not only depends on its amount but its effects in different ways on the metallic and the acidic functions of the catalyst.
Reversible Isothermal Sorption of Hydrogen by Tungsten Trioxide in Presence of Platinum
a. r. berzins and p. a. sermon, Nature, 1983, 303, (5917), 506–508
The absorption of gaseous H2 by 3% Pt/WO3 which forms non-stoichiometric bronze HxWO3, (0 < x < 0.5) is almost entirely reversible at 273–423K, with molecular H2 being desorbed with decreasing pressure (0–140kPa). Desorption is preferred to reduction-dehydration.
Ion-Exchange of Amminated Palladium and Platinum in Synthetic Sodium Zeolites
p. fletcher and r. p. townsend, Zeolites, 1983, 3, (2), 129–133
The ion-exchange characteristics of amminated Pt(II) and Pd(II) ions in the synthetic zeolites Na-X, Na-Y and Na mordenite were measured. Equilibrium studies were conducted at 25°C. Highly selective isotherms, exhibiting partial exchange, were observed in all cases. For both the [Pt(NH3)4]2+ and the [Pd(NH3)4]2+ ions, the selectivity sequence was observed to be MOR > Y > X. The results are compared with other recent work on ion-exchange in zeolites with amminated transition on noble ions.
Promotion with Adatoms and Microdeposits of Catalysts Used in Electrochemical Energetics Systems
yu. b. vassiliev, J. Res. Inst. Catal., Hokkaido Univ., 1983, 30, (2), 89–106
Studies of the influence of various adatoms and microdeposits of Pt, Pd, Ir, Rh, Ru on relatively inert supports (Ti, glass C, pyrographite, Au, Nb, etc.) show that the catalytic effect depends primarily on the mechanism of the electrochemical reaction. The adatom can act either as promoter or poison. With decreasing cluster size on the support, the specific catalytic activity of a single atom in a cluster can both increase (Pt, Ir, Rh on glass carbon and Ti) and decrease (Pd on glass carbon) or remain unaffected (Pd on Nb).
Hydrogenation of Styrene on Pd/γ -Al2O3 and Pd-Mn/γ -Al2O3 Catalysts
i. sandelescu, x. yandong and v. pirvelescu, Rev. Chim. (Bucharest), 1983, 34, (4), 311–313
Studies of chromatographic pulse catalytic hydrogenation of styrene over Pd/γ -Al2O3 and Pd-Mn/γ -Al2O3 catalysts showed that an irreversible reaction of styrene to ethylbenzene which occurred on Pd/γ -Al2O3 was controlled by the Pd concentration. A mechanism of a styrene → ethylbenzene ⇌ ethylcyclohexane reaction on the Pd-Mn/γ -Al2O3 catalyst was explained. In both cases, the selectivity of the reaction depended on the transition metal components in the catalyst composition.
On the Selectivity of Palladium Catalysts in Synthesis Gas Reactions
j. m. driessen, e. k. poels, j. p. hindermann and v. ponec, J. Catal., 1983, 82, (1), 26–34
Reactions of CO/H2 mixtures were studied on a series of 2wt.% Pd/SiO2 with and without Mg and La promoting additives. The studied promoters affected the activity of the catalysts increasing the selectivity for “oxygenates” and suppressing the selectivity for CH4. Promoters also create a new type of ionic adsorption centre for CO and NO adsorption. It is concluded that Pd “ions” are the centres for activation of CO toward methanol whereas Pd metal supplies hydrogen atoms for hydrogenation.
Palladium-Tungsten Catalysts for Automotive Exhaust Treatment
k. m. adams and h. s. gandhi, Ind. Eng. Chem., Prod. Res. Dev., 1983, 22, (2), 207–212
The modification of Pd catalysts with non-noble metal oxides resulted in desirable catalytic activities for Pd-WO3/γ -Al2O3. The data showed that the Pd-WO3 catalyst oxidises saturated hydrocarbons with higher conversions than Pt when the synthetic exhaust is reducing. It also selectively reduces NO to N2, although with lower conversions than Rh.
Fischer-Tropsch Product Distribution for Rh/TiO2
a. takeuchi, j. r. katzer and g. c. a. schuit, J. Catal., 1983, 82, (2), 477–478
Studies were made of the total product distribution from CO hydrogenation catalysed by 3.0 wt.%Rh/TiO2 catalyst at 423K; the catalyst (0.10g) was prereduced at 475K. The large deficit in C2 hydrocarbons is due to the formation of ethanol. This suggests that a common intermediate may be involved in the formation of hydrocarbons and alcohols from CO + H2 catalysed by Rh/TiO2.
Fischer-Tropsch Synthesis of Hydrocarbons on V2O3–Supported Ruthenium Catalysts
e. kikuchi, h. nomura, m. matsumoto and y. morita, Appl. Catal., 1983, 7, (1), 1–9
Hydrogenation of CO was studied on Ru catalysts supported on various transition metal oxides. Ru/V2O3 catalysts showed significantly high turnover frequency based on H2 chemisorption. Product distribution shifted to heavier molecular weight hydrocarbons and a relatively high unsaturate: saturate ratio.
Enhancement of the Methanol Formation from CO and H2 over Supported Ruthenium Catalysts by the H2-H2O Treatment
y. kobori, h. yamasaki, s. naito, t. onishi and k. tamaru, Chem. Lett., 1983, (4), 553–556
Supported Ru catalysts, which were treated by H2-H2O mixture at elevated temperatures, could synthesise methanol with drastically enhanced production from CO and H2, and with 50% selectivity.
Direct Oxidative Transformation of Aldehydes to Amides by Palladium Catalysis
y. tamaru, y. yamada and z.-i. yoshida, Synthesis, 1983, (6), 474–476
The Pd catalysed oxidative transformation of aldehydes to the corresponding morpholine amides, using an oxidation system, Pd(OAc)2/ArBr/K2CO3, is reported. Aromatic and aliphatic were effectively converted, though cinnamaldehyde was not.
Rhodium-Catalysed Low Pressure Hydroformylation of Higher α -Olefins: New, Thermally Stable Rhodium Catalysts by Reaction of RhH(CO)(Ph3)3 with Phosphinous Acids
m. matsumoto and m. tamura, J. Mol. Catal., 1983, 19, (3), 365–367
Rh-catalysed, low pressure hydroformylation of 1-dodecene was restudied in dodecylbenzene solution in the presence of a large excess of PPh3. The formation of a new Rh complex, Rh2(CO)2(PPh3)2(R2PO)2 which is probably produced by reaction of RhH(CO)(PPh3)3 with the phosphinous acid, improves the thermal stability of the Rh complex in the solution.
Highly Reactive Rh(I) Hydrido Compounds
t. okano and t. yoshida, J. Synth. Org. Chem., Jpn., 1983, 41, (4), 359–364
Three types of Rh(1) hydridotrialkylphosphine complexes, trans -RhH(N2)L2 (L=P(t-Bu)3, PPh(t-Bu)2, PCy3, P(i-Pr)3), Rh2H2(μ -N2)L4 (L = PCy3, P(i-Pr)3) and RhHLn (n = 3, L = P(i-Pr)3, PEt3; n = 4, L = PEt3) were prepared by reducing RhCl3.3H2O with Na/Hg in THF. They proved to be extremely strong nucleophiles and were efficient catalysts for hydrogenation of nitriles, ketones and alkynes, and the H-D exchange reaction of H2 and H-C (sp2, sp3) bond with D2O through activation of H2 and H2O, respectively. They also catalysed the hydrogenation of carbonyl and nitro compounds with H2O-CO and the hydroformylation of olefins with formaldehyde.
Hydrogenation of Carbon Monoxide by Ruthenium Complexes with Iodide Promoters: Catalytic and Mechanistic Investigations
b. d. dombek, J. Organomet. Chem., 1983, 250, (1), 467–487
CO and H2 are converted into organic products, including methanol, ethylene glycol and ethanol, by halide-promoted Ru catalysts in organic solvents. Iodide salts are exceptionally good promoters for this system. Two Ru complexes, and are present during catalysis and essential for optimum activity.
ELECTRICAL AND ELECTRONIC ENGINEERING
Pile Up of Implanted Phosphorus during Palladium Silicide Formation and the Characteristics of Schottky Barrier Diodes
a. kikuchi, J. Appl. Phys., 1983, 54, (7), 3998–4000
Schottky barrier diodes, produced from Pd2Si or Al-Si were fabricated on Si surfaces, whose impurity concentrations were controlled by P ion implantations. The forward voltages of Schottky barrier diodes made from Pd2Si show a much greater lowering than those made from Al-Si for implanted doses of 5 × 1013/cm2 and higher. Spreading resistance measurements show that the implanted P atoms are piled up at the Pd2Si/Si interface during Pd2Si formation, this reduces the effective barrier height.