Platinum Metals Rev., 1985, 29, (4), 185
ABSTRACTS: October 1985
Of Current Literature On The Platinum Metals And Their Alloys
A Scanning Auger Microscopy Study of the Influence of Platinum on the High-Temperature Oxidation of a Nickel-Silicon-Magnesium Alloy
g. r. johnston, j. l. cocking and w. c. johnson, Oxid. Met., 1985, 23, (5/6), 237–249.
The oxide scale on Ni-4.4Si-0.1Mg alloy samples heated in air at 1100°C were analysed by high resolution scanning Auger microscopy. Concentration profiles through the oxide were taken. The presence of Pt, either in contact with the alloy or in the hot zone of the furnace increased the oxidation rate by an order of magnitude in comparison with the Pt-free rate. In the absence of Pt the multi-layered oxide scale was an outer layer of Mg-doped Ni oxide, overlying a silicate layer (Mg,Ni)2SiO4, on top of a thin interfacial layer of SiO2. With Pt present the concentration of Mg in the oxide scale was below the detection limit.
Compositional Variations in the Near Surface Layers, an Atom-Probe Study of Cosegregation of Sulfur in Pt-Rh and Pt-Ir Alloys
m. ahmad and t. t. tsong, J. Chem. Phys., 1985, 83, (1), 388–396
Equilibrium composition depth profiles with true single atomic layer depth resolution were obtained for the (001) plane of a Pt-Ir and five Pt-Rh alloys using the atom-probe field ion microscope. Pt segregates to the top two layers in Pt-Ir, and Rh segregates to the top layer in Pt-Rh alloys after annealing for 5 minutes at 700°C. An S overlayer segregates to the surface of these alloys, even though the bulk impurity content < 100ppm. The coverage of S overlayers for Pt-Rh alloys varies between 0.22 and 0.52 of a monolayer, and increases with increasing surface Rh.
Ion-Induced Phase Formation in Metal-Silicon Systems
l. s. hung and j. w. mayer, Thin Solid Films, 1985, 123, (2), 135–144
4He ion backscattering techniques and TEM were used to investigate the interaction of ion beams with thin film structures in a number of silicide forming systems. The mixed layer was an equilibrium compound for Pd and Pt metals and an amorphous phase for refractory metals. For Pd, the Pd2Si phase grew with ion dose and remained crystalline up to high dose. Pd-Si and Pt-Si were the only systems where silicides formed and remained crystalline during ion irradiation at room temperature. Differences at liquid N2 temperatures with doses were observed.
Study on the Electrical Conductivity of Pt/ZnO Catalysts
h. zu-pei, g. xiu-ying and l. wen-zhao, J. Catal. (Dalian, China), 1985, 6, (1), 87–90
An in situ examination of the electrical conductivity of Pt/ZnO catalysts during or after H treatment at room temperature and ⩾300°C has been performed. The electrical conductivity increased instantaneously by six orders of magnitude when Pt/ZnO catalyst pellets were exposed to H at room temperature. But it returned to its original value if the pellet was purged with N2 or evacuated at room temperature to remove H2.
Perpendicular Magnetic Anisotropy in Pd/Co Thin Film Layered Structures
p. f. carcia, a. d. meinhaldt and a. suna, Appl. Phys. Lett., 1985, 47, (2), 178–180
Magnetic studies have been made of thin film periodic Pd/Co layered structures with ultrathin Co (4−13Å). Films with Co of thicknesses <8Å were easy to magnetise along a direction normal to the film surface. The best films had saturation magnetisation of ∼500emu/cm3 and a coercivity of 550 Oe, and could be used for vertical magnetic recording.
The Mg-Pd (Magnesium-Palladium) System
a. a. nayeb-hashemi and j. b. clark, Bull. Alloy Phase Diagrams, 1985, 6, (2), 164–167
An assessed Mg-Pd phase diagram from 0−1600°C based on several cited references is reported. A discussion of intermediate phases, crystal structure data and lattice parameter data is also presented.
The H2-O2 Reaction on Palladium Studied over a Large Pressure Range: Independence of the Microscopic Sticking Coefficients on Surface Condition
h. m. dannetun, d. sÖderberg, i. lundstrÖm and l. h. g. petersson, Surf. Sci., 1985, 152/153, (1), 559–568
The H2-O2 reaction was studied on the Pd gate of a Pd-MOS structure over a large pressure range. By measuring shifts in the C vs. V curve the changes in free H atom concentrations can be monitored. These results and others indicate a critical ratio of 0.4 where the surface turns from being O dominated to being H dominated. The critical ratio is independent of the absolute pressures and of surface conditions and shows no temperature dependence from 50−200°C. This implies H and O have similar sticking coefficients at the Pd surface. This device can be used as an H sensor in a catalytic reaction over a large pressure range.
XPS Studies on the Surface of Amorphous Pd80Si20 Alloys
y. takagi, c.-h. hwang, h. sekizawa and k. kawamura, Jpn. J. Appl. Phys., 1985, 24, (4), 390–396
The depth profiles of the chemical states and composition of Pd and Si near the surface region of amorphous Pd80Si20 alloys have been studied by XPS. The depth profile can be divided into three characteristic regions: bulk, transient and skin. On passing through the transient region from the bulk to the skin, the amount of SiO2 increases while that of Pd decreases. In the skin, amorphous SiO coexists with metallic Pd. The chemical state of Si in this region depends on the preparation conditions.
Hydrogen Adsorption States at the External and Internal Palladium Surfaces of a Palladium-Silicon Dioxide-Silicon Structure
l.-g. petersson, h. m. dannetun, j. fogelberg and i. lundstrÖm, J. Appl. Phys., 1985, 58, (1), 404–413
The H2 adsorption states at the external and internal Pd surfaces of a H sensitive Pd-SiO2-Si (Pd-MOS) structure have been studied in high and ultra high vacuum. The steady state response of the Pd-MOS shows a logarithmic dependence on H2 pressure. The heat of adsorption of the internal surface is coverage dependent. There are always H adsorption states available at the internal surface, independent of the applied pressure, which explains how the Pd-MOS structure acts as an H sensor over wide pressures.
Electrical Conductivity of (Bi,Pb)2MO4 (M=Pd,Pt) Linear Chain Compounds
n. bettahar, p. conflant, j. c. boivin, f. abraham and d. thomas, J. Phys. Chem. Solids, 1985, 46, (3), 297–299
Partial oxidation of Pd in Bi2PdO4 was achieved by substituting Pb2+ for Bi3+ up to Bi1.91Pb0.09PdO4. Partial oxidation is necessary to stabilise the isostructural Pt compound Bi1−xPbxPtO4 in the range 0.33 ⩽ x ⩽ 0.52. Pt compounds had relatively high conductivities (σ ≃ 10/Ω cm) and low activation energies (≃ 0.02eV) with small variations in x. Pd compounds had lower conductivities which increased linearly with mean oxidation degree.
Oxygen Potential and the Chemical State of the Fission Products Ruthenium, Rhodium and Palladium in Irradiated Oxide Fuels
m. s. chandrasekhariah, J. Nucl. Mater., 1985, 130, 366–374
Thermodynamic properties of intermetallic compounds of the type M3U and M3Pu where M = Pd, Rh or Ru are examined. These intermetallics have unusual thermodynamic stability. The presence of these intermetallics in nuclear fuel urania-plutonia is unexplained. The critical O potential of the oxide fuel matrix for their formation is suggested.
Redox, Ligand-Exchange, Oligomerization, and Hydrosilation Chemistry of trans-Dichloro(ethylene) (phenazine) platinum
a. r. siedle, k. r. mann, d. a. bohling, g. filipovich, p. e. toren, f. j. palensky, r. a. newmark, r. w. duerst, w. l. stebbings, h. e. mishmash and k. melancon, Inorg. Chem., 1985, 24, (14), 2216–2223
A series of compounds of the type trans-(amine)PtCl2(C2H4) (where amine = phenazine, quinoxaline, pyrazine, phenazine N-oxide, 2,6-dimethylpyrazine, tetramethylpyrazine, acridine) was prepared by displacement of chloride from PtCl3(C2H4).− (phenazine)PtCl2(C2H4) is an effective hydrosilation catalyst and is the source of a series of novel bimetallic Pt-phenazine complexes and of polymetallic reduction products which are accessible by a number of routes.
η 3-Allylpalladium Compounds
p. w. jolly, Angew. Chem., Int. Ed. Engl., 1985, 24, (4), 283–295
An in-depth study of the chemistry of the Pd-C bond is presented concentrating on η 3-allylpalladium complexes. Their preparations, structures and reactions are examined. These complexes are frequently involved as intermediates in the Pd catalysed transformations of dienes. (76 Refs.)
A Novel Giant Palladium Cluster
m. n. vargaftik, v. p. zagorodnikov, i. p. stolyarov, i. i. moiseev, v. a. likholobov, d. i. kochubey, a. l. chuvilin, v. i. zaikovsky, k. i. zamaraev and g. i. timofeeva, J. Chem. Soc., Chem. Commun., 1985, (14), 937–939
Various analytical techniques have been used to examine a new catalytically active cluster prepared by reduction of Pd(OAc)2 by H2 in the presence of L = 1,10-phenanthroline, or 2,21-bipyridine, followed by O2 treatment. The cluster produced contains a closely packed metal nucleus (570±30Pd atoms), bearing 60±3 co-ordinated L and 180±10 OAc− in the outer sphere of the cluster. It is soluble in H2O and polar organic solvents, and catalytically active in the oxidative acetoxylation of ethylene by O2 to form vinyl acetate.
Synthesis of Novel Chiral Ruthenium Complexes of 2,21-Bis (diphenylphosphino)-1,11-binaphthyl and Their Use as Asymmetric Catalysts
t. ikariya, y. ishii, h. kawano, t. arai, m. saburi, s. yoshikawa and s. akutagawa, J. Chem. Soc., Chem. Commun., 1985, (13), 922–924
Reactions of [RuCl2(COD)]n, (COD = cyclo-octa-1,5-diene) with the chiral bidentate phosphine ligands give new chiral Ru(II) complexes Ru2Cl4(BINAP)2(NEt3) and Ru2Cl4(p-tolyl-BINAP)2(NEt3). These act as excellent catalysts.
The Au/GaPc-Cl/Ferri, Ferrocyanide/GaPc-Cl/Pt Photoelectrochemical Cell
w. j. buttner, p. c. rieke and n. r. armstrong, J. Am. Chem. Soc., 1985, 107, (12), 3738–3739
A photoelectrochemical cell has been constructed based upon vacuum-deposited (chlorogallium phthalocyanine, GaPc-Cl) thin films in contact with a Au/GaPc-Cl anode and a Pt/GaPc-Cl cathode, and a ferri/ferrocyanide redox electrolyte which acts as contacting phase between photoanode and photocathode. The work function difference between the two metals gives the driving force for the photoelectrochemical response. The resulting cell gave a photopotential response ∼20% of the theoretical maximum dictated by the sum of the apparent band gaps.
Energy- and Electron-Transfer Processes for the Lowest Triplet Excited State of Tetrakis(diphosphito)diplatinate(II)
j. r. peterson and k. kalyanasundaram, J. Phys. Chem., 1985, 89, (12), 2486–2492
Efficient transfer of excitation energy from was found to occur to various acceptors including naphthalene and . Efficient formation of redox products occurs both in reductive and oxidative quenching. Intense room temperature phosphorescence, high solubility in aqueous and non-aqueous media and long triplet lifetimes make useful as an energy sensitiser.
Hydrogen Photoproduction in a Continuous Flow System with u.v.-Light and Aqueous Suspensions of RuOx/Pt/TiO2
r. simarro, s. cervera-march and s. esplugas, Int. J. Hydrogen Energy, 1985, 10, (4), 221–226
H2 generation rates of up to 110μ mol/h have been obtained in a continuous gas flow apparatus for the liquid phase photolysis of water using neutral aqueous suspensions of RuOx/Pt/TiO2.
Radiation Reduced Ir Sols: A Study of Their Catalytic Efficiency for Reduction of H2O to H2 by MV+• Compared with Pt Catalysts
m.-o. delcourt and n. keghouche, Nouv. J. Chim., 1985, 9, (4), 235–240
Ir colloids were prepared and used as catalysts to convert H2O to H2 via electron transfer from MV+•. Kinetic parameters using pulse radiolysis indicated that a fast process involves the fresh metal particles, while a slow one corresponds to a H-covered surface state. H2 production with Pt or Ir was investigated and a catalytic mechanism is proposed. The Pt and Ir metal surfaces are almost totally covered by adsorbed H atoms, the desorption of which controls the overall process. H2 desorption competes with MV2+ hydrogenation, the latter being favoured at high metal concentrations.
An Iridium-Bipyridine Complex as a Photosensitizer for the Bromide Oxidation to Bromine by Oxygen
a. slama-schwok, s. gershuni, j. rabani, h. cohen and d. meyerstein, J. Phys. Chem., 1985, 89, (12), 2460–2464
An Ir(III)-bipyridine complex, [Ir(C3-N1-bpy)(bpy)2]2+, was used as a photosensitiser in aqueous bromide solutions. Steady-state photolysis of oxygenated solutions by near-u.v. and visible light produces equal concentrations of and H2O2. The quantum yield of equivalents depends on pH, illumination dose and bromide concentration.
Hydrogen from Hydrogen Sulfide Cleavage. Improved Efficiencies via Modification of Semiconductor Particulates
m. barben, e. pelizzetti, g. borgarello, n. serpone, m. grÄtzel, l. balducci and m. visca, Int. J. Hydrogen Energy, 1985, 10, (4), 249–253
Visible light irradiation of CdS dispersions containing H2S in alkaline aqueous media gives efficient H2 evolution; however, an improvement is observed when the CdS particles are loaded with RuO2. A combination of TiO2 and CdS both loaded with RuO2 gives increased efficiency. The H2 evolution rate depends on the preparation conditions of CdS and TiO2. For the best catalyst combination and under direct sunlight irradiation the overall conversion efficiency of solar energy is 2%.
The Effect of the Substitution of Ru for Ti on the Electro- and Photoelectrochemical Properties of TiO2 Crystals
c. gutiÉrrez and p. salvador, J. Electroanal. Chem. Interfacial Electrochem., 1985, 187, (1), 139–150
The photoelectrochemical behaviour of a Ru doped TiO2 crystal electrode of composition Ti0.97Ru0.03O2 in contact with aqueous electrolyte was investigated. The substitution of Ru4+ for Ti4+ in the TiO2 has two main effects, namely sensitisation to visible light and reduction of the overpotential for O2 evolution.
ELECTRODEPOSITION AND SURFACE COATINGS
Experience with Platinum Aluminide Coatings in Land-Based Gas Turbines
r. bauer, k. schneider and h. w. grÜnling, High Temp. Technol., 1985, 3, (2), 59–64
Two Pt aluminide coatings were applied by a two-stage process to industrial gas turbines. Hot-corrosion crucible tests with salt mixtures to simulate actual blade deposits were then performed. Significant improvement to resistance against hot corrosion at intermediate temperatures 750−850°C and against high temperature oxidising conditions of ∼950°C were found. Coating life exceeded that of conventional NiCrSi coatings.
Electroplated Palladium-Silver (60/40wt%) Alloy as a Contact Material
f. i. nobel, IEEE Trans. Components, Hybrids Manuf. Technol., 1985, CHMT-8, (1), 163–172
The use of electroplated 60Pd-40Ag in electronic and electrical applications is discussed. The properties of the deposits, including wearability, contact resistance, hardness and density of deposits, corrosion resistance, corrosion and preparations before use are examined. Comparisons with 80:20 Pd-Ni, Ag, Pd and hard Au are made. It is concluded the Pd-Ag electrodeposit is comparable to hard Au.
LABORATORY APPARATUS AND TECHNIQUE
New High Temperature Palladium Detectors for Oxygen Determination. Part I. Principles and General Signal Formula of a Semi-Continuous Detector
e. kozlowski, m. bownik and t. gÓrecki, Fresenius’ Z. Anal. Chem., 1985, 320, (7), 757–761
A new high temperature O2 detector which operates in repeatable cycles is described. The detector has a 1.5g thin Pd foil bed in a stainless steel chamber in which, during the first part of the cycle, H2 is made to dissolve. In the second part the sample gas flows through the bed. An instantaneous temperature rise due to the heat evolved in the reaction of the O2 contained in the sample gas with H2 dissolved in the bed gives a measure of the O2 content. An equation for the output signal has been theoretically derived and experimentally confirmed in the range 205−450°C.
On the Chemical Oscillations in Differential Reactors: A Case Study of Ammonia Oxidation on Platinum
p. nowobilski and c. g. takoudis, Chem. Eng. Commun., 1985, 33, (1–4), 211–217
A review of the theories of the isothermal reaction mechanisms of NH3 oxidation on a heterogeneous Pt catalyst is presented. It is shown that even in a differential catalytic reactor with conversions much less than 5%, the changes of the bulk concentrations of the reacting species may drastically affect the dynamic behaviour of the reaction system; it is suggested that they may drive the oscillations.
Free Radical Formation in the Catalytic Oxidation of NH3 over a Polycrystalline Pt Surface at High Temperatures
g. s. selwyn and m. c. lin, Langmuir, 1985, 1, (2), 212–219
The catalytic oxidation of NH3 over a polycrystalline Pt surface at 800−1400K was investigated. Free radicals and transient species produced included NH, NH2, OH, HNO, NO2 and diatomic NH and OH. NH produced was diminished drastically by O2 and yielded a desorption energy of 66kcal/mol.
Mathematical Modeling of Catalytic Converter Lightoff. Part II: Model Verification by Engine-Dynamometer Experiments; Part III: Predictions of Vehicle Exhaust Emissions and Parametric Analysis
s. h. oh and j. c. cavendish, AIChE J., 1985, 31, (6), 935–942; 943–949
A transient mathematical model was developed to describe the behaviour of packed-bed catalytic converters during warmup. The predictions of the model agree very well with the results of enginedynamometer experiments for three Pt/Al2O3 catalysts of widely different properties. Two catalysts were surface impregnated with 0.09wt.% and 0.56wt.%Pt and one was subsurface-impregnated. The model was also used to simulate the performance of a packed-bed converter during the cold-start period of vehicle emission tests. Effects of poisons on catalysts, and converter designs are examined.
Production of Hydroxylamine from Nitrogen Oxide: A Short Review
g. r. tauszik and p. crocetta, Appl. Catal., 1985, 17, (1), 1–21
The industrial production of hydroxylamine by hydrogenation of NO in dilute H2SO4 using a Pt/C catalyst was studied. Various aspects of this process, including catalyst composition, reaction kinetics and mechanisms, role of mass transport phenomena and the electrochemical reduction of NO, are discussed. It is concluded that more experimental work is needed to clarify the reaction mechanism and that attention to catalyst poisoning is needed. (40 Refs.)
Dynamic Behavior of Automotive Catalysts. III. Transient Enhancement of Water-Gas Shift over Rhodium
r. k. herz and j. a. sell, J. Catal., 1985, 94, (1), 166–174
The responses of catalysts Rh/Pt/Ce/Al2O3, Pt/Ce/Al2O3 and Pt/Rh/Al2O3 were examined for the water-gas shift reaction in engine exhaust gases. A transient reduction in CO emission was observed over all three catalysts when they were stabilised under rich exhaust and then given a is exposure to lean exhaust. Explanations of part of the responses were made, but lean-to-rich step response experiments gave evidence for the water-gas shift reaction.
Characteristics and Surface Morphology Change of Modified PtRh10 Gauze of HCN Synthesis
t. baczyńska, m. seweryniak and j. wrzyszcz, React. Kinet. Catal. Lett., 1985, 17, (1), 21–25
The modification of Pt-Rh10 gauze catalysts, used for HCN synthesis, by coating their surfaces with a thin film of Pt-Rh/Al2O3 is reported. Comparisons in activity, selectivity and morphological changes in the catalyst surface for standard gauzes and those covered with a thin film are reported.
The Deuterium-Exchange Reaction between Water and Hydrogen with the Thin-Film Hydrophobic Catalyst
h. yamashita, m. mizomoto and s. matsuda, Nippon Kagaku Kaishi, 1985, (4), 669–673
The D2 exchange reaction between H2O and H2 with a hydrophobic Pt/porous PTFE catalyst as support was studied. Catalyst reactivity was measured in a trickle bed reactor at atmospheric pressure and temperature 20−70°C. Pt particles on thin film PTFE work efficiently as catalysts because the reactants were easily diffused to the active sites. The isotopic exchange rate with the thin film catalyst increased with the increase in the liquid : gas ratio and with the rise of the reaction temperature.
Colloidal Noble Metal Catalysts Supported on Ion-Exchange Resins
y. nakao and k. kaeriyama, Kobunshi Ronbunshu, 1985, 42, (4), 223–229
Hydrosols of Pt, Rh, Pd and Ru were prepared from aqueous solutions of the corresponding noble metal salts by NaBH4 reduction. Anion exchange resins adsorbed the colloidal particle to give noble metal catalysts for hydrogenation, while for cation exchange resins only a H-form resin adsorbed colloidal Rh and Ru to give supported catalysts. Electron micrographs indicate that Rh on the cation exchange resins has more “coagulated” states than on the anion exchange resins. Two mechanisms for the adsorption are presented. Catalytic activity is higher for cation exchange resin.
Some Catalytic Properties of Palladium and Rhodium Supported Catalysts
g. a. del angel, b. coq, g. ferrat, f. figueras and s. fuentes, Surf. Sci., 1985, 156, (2), 943–951
Some reactions involving C-H, C-C, C-Cl and C-O bonds were investigated on Rh and Pd supported catalysts in relation to the metallic structure. Generally there is a structure insensitivity for Pd, but not for Rh. For Rh, small particles are more active than large particles when SiO2 is the support.
Synthesis Gas Conversion Utilizing Mixed Catalyst Composed of CO Reducing Catalyst and Solid Acid. IV. Selective Synthesis of C2, C3, and C4 Paraffins from Synthesis Gas
k. fujimoto, h. saima and h. tominaga, J. Catal., 1985, 94, (1), 16–23
Synthesis gas could be converted selectively to C2-C4 paraffins with hybrid catalysts of Pd/SiO2 (methanol synthesis catalyst) and Y-type zeolite. Best conditions were 300−350°C and 1.0−5.1 MPa. A hybrid catalyst containing a steam-treated high SiO2 Y-zeolite gave C2-C4 paraffins with a selectivity >85%, with almost no aromatic hydrocarbons and coke with CH4 selectivity of 2% or less, while CH3OH conversion on the zeolite gave aromatic hydrocarbons and coke with selectivities of 30% and 11%, respectively.
g. p. royer, w.-s. chow and k. s. hatton, J. Mol. Catal., 1985, 31, (1), 1–13
The preparation and evaluation of Pd catalysts made from polyethylenimine(PEI)/SiO2 composites are discussed. PEI was adsorbed on either porous SiO2 beads or SiO2 gel. After crosslinking, the material was loaded with base to increase surface area and availability of the polymer. Pd/PEI/SiO2 beads are used effectively in suspension with HCOOH acid as the H donor; deprotonation of carbobenzoxy-Glycine-O-t-butyl is very rapid compared to Pd/C.
Preparations of TiO2-Attached Rh Catalysts and Their Catalysis
y. iwasawa and h. sato, Chem. Lett. Jpn., 1985, (4), 507–510
The preparation of new TiO2-attached Rh catalysts is described. The catalysts were prepared by the reaction between Rh(η 3-C3H5)3 and surface OH groups on TiO2 followed by chemical treatment with H2. The catalysts had higher activities for ethane hydrogenolysis and ethene hydrogenation than a conventional impregnated Rh catalyst. The most active catalyst was the mononuclear Rh hydride species. The surface structures of these catalysts have no analogues with homogeneous and conventional heterogeneous catalysts, and may be typical examples of a new class of catalysts.
Preparation and Catalytic Activity for Ammonia Synthesis of Several Ruthenium Supported Catalysts
p. ramirez de la piscina, n. hous and j. e. sueiras, Z. Anorg. Allg. Chem., 1985, 522, 235–240
Supported Ru catalysts were prepared from RuCl3.3H2O and K4[Ru(CN)6].3H2O solutions, upon several acid/base pretreated γ -Al2O3 samples, using water and acetone as solvents. An increasing Ru content of the catalysts with increasing acid site content of the support is observed, when K4[Ru(CN)6].3H2O is used as a precursor. Catalysts prepared from K4[Ru(CN)6].3H2O were about 10 fold more active than those prepared from RuCl3.3H2O. The more active catalyst was sensitive to acid pretreatment of γ -Al2O3, while those prepared from RuCl3.3H2O were not.
Carbonylative Cross-Coupling Reaction of Aryl Iodides with Alkylaluminums by Palladium Complex Catalysis
y. wakita, t. yasunaga and m. kojima, J. Organomet. Chem., 1985, 288, (3), 261–268
Secondary and/or tertiary alcohols and unsymmetrical ketones have been obtained in moderate to good yields by Pd catalysed carbonylative coupling of aryl iodides with alkylaluminium compounds under very mild conditions. The type of reaction product depended on the kind of Al reagent used.
Homogeneous Catalytic Hydrogenation of Soybean Oil : Palladium Acetylacetonate
s. koritala, J. Am. Oil Chem. Soc., 1985, 62, (3), 517–520
Soybean oil was hydrogenated with Pd acetylacetonate at 60−170°C, 150psi H2 pressure and 1−60ppm Pd. The best linolenate selectivity was found at 80−120°C. At 120°C Pd acetylacetonate hydrogenated faster than the Pd/C catalyst. Trans isomerisation with the homogeneous catalyst was much higher than with Pd/C.
Homogeneous Catalysis of the Water Gas Shift Reaction by (Polypyridine) Rhodium Complexes
d. mahajan, c. creutz and n. sutin, Inorg. Chem., 1985, 24, (13), 2063–2067
Homogeneous catalysis in the water gas shift reaction under mild conditions (<100°C and 1atm CO) was achieved with several (polypyridine)Rh(I) complexes as catalyst precursors in alcohol-water mixtures. Complex was the most active catalyst precursor (∼3 turnovers/h at 90°C).
Rhodium Complexes as Catalysts for Hydrosilylation Crosslinking of Silicone Rubber
m. heidingsfeldovÁ, J. Appl. Polym. Sci., 1985, 30, (5), 1837–1846
The vulcanisation of a Si rubber compound, based on polysiloxane-containing vinyl and Si-H groups catalysed by [RhCl(CO)2]2, [RhCl(C2H4)2]2, [RhCl(1,5-COD)]2, [RhCl(NBD)]2, RhCl[P(C6H5)3]3, and Rh(acac)3 (1,5-COD = 1,5-cyclooctadiene, NBD = nornbornadiene, acac = acetylacetonate) was studied. Effect of solvent, the cross-linking density of the rubber, sol content, vulcanisation times and catalysts were examined.
Electrode Designs and Concepts for Bipolar Alkaline Fuel Cells
k. kordesch, j. gsellmann and r. d. findlay, Int. J. Hydrogen Energy, 1985, 10, (5), 317–324
The construction and production of mass produced alkaline fuel cells are described. The multiple layer electrodes used in alkaline electrolytes, and alkaline and acidic electrolytes are discussed. All use Pt/C with various amounts of Pt in their construction.
A Chemically Regenerative Redox Fuel Cell. II
j. t. kummer and d.-g. oei, J. Appl. Electrochem., 1985, 15, (4), 619–629
Redox fuel cells with V2+/V3+ and Mo3+/Mo4+ redox couples as the anolyte and a catalyst system for VO2+ oxidation were examined. Highly acidic (∼3M H2SO4) molybdate solutions were readily reduced by H2 using Pt or Pd as catalyst.
ELECTRICAL AND ELECTRONIC ENGINEERING
Tungsten-Platinum Alloy Schottky Barriers on n-Type GaAs
t. okumura and k. n. tu, Appl. Phys. Lett., 1985, 47, (1), 42–44
Alloys of W and Pt were studied as Schottky contact materials in n-type GaAs. Schottky barrier heights for W50Pt50 and W80Pt20 were measured, and were found to be 0.90±0.02eV by C-V and photoresponse techniques, and did not change with annealing at 350°C for 20h. However the value from the I-V technique changed from ∼0.6 to 0.7 eV upon annealing. W50Pt50 was the more stable on GaAs.
Platinum Intermetallic Resistors for GaAs-Based Circuits
s. tiwari and w. h. price, Electron. Lett., 1985, 21, (10), 429–430
A simple technique for making GaAs/Pt intermetallic resistors of sheet resistance ∼25Ω /□ is described. The resistors were made by reacting a 300Å Pt film with GaAs and then sintering. X-ray diffraction identified PtGa and PtAs2 in all samples, and PtGa2 in samples annealed at 450°C. The TCR was ∼9.2 × 10−4/°C at 25°C, and the resistors were stable up to current densities of 105A/cm2.
Properties of Electroplated Noble Metal Layers as Contact Materials for Switching Contacts
h. grossmann, m. huck, g. schaudt and f. j. wagner, Metall, 1985, 39, (7), 619–623
Various electrodeposits of 5μ m and 10μ m thicknesses on non-precious metals were tested on a model device as materials in switching contacts in relays and keys. The resistance of the electroplated contact layers was related to their hardness. Electrodeposits were tested at various electric load conditions: 28−550mA DC at 12V and 24V. For loads of 12V/12mA and on a layer thickness of 5μ m the following number of operations were possible: AuCo 5 × 104, AuPd6Cu2 5 × 106, Pd, PdNi20 ∼ 107, Rh> 107.
Electron Emission and Surface Composition of Osmium and Osmium-Tungsten Coated Dispenser Cathodes
d. brion, j.-c. tonnerre and a. shroff, Appl. Surf. Sci., 1985, 20, (4), 429–456
The surface composition of impregnated cathodes with coatings of pure Os 50−30,000Å thick or mixed Os-W coatings (10−70% Os) were measured by AES, during activation and short duration ageing at 1000°CB (degrees Celsius brightness). During activation of cathodes with pure Os coatings (>3000Å) the W diffuses into the Os until saturation of the θ phase occurs throughout the coating depth. Electron emission from cathodes coated with pure Os is three times greater than that of “type S” cathodes, whatever the coating thickness. Electron emission from mixed-coated cathodes is slightly less than that of pure Os.