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Platinum Metals Rev., 1989, 33, (1), 24

ABSTRACTS: January 1989

of current literature on the platinum metals and their alloys

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PROPERTIES

Catalytic Etching of Platinum Foils and Thin Films in Hydrogen-Oxygen Mixtures

v. w. dean, m. frenklach and j. phillips, J. Phys. Chem., 1988, 92, (20), 5731–5738

Catalytic etching of Pt thin films and foils during H2 oxidation was found to occur at surface temperature > 725K and with initial O:H ratio >2:1. Metal was transported away from the reaction focus and con-comitantly large Pt particles (1 μ m) were found downstream on top of the original structure. Catalytic etching is attributed to the interaction of homogeneously formed radicals, most likely HO2, with the Pt surface, and the subsequent evaporation of metastable Pt-containing species. A model is presented. Thermal etching (thermally accelerated movement toward equilibrium) occurred under all other conditions.

The Tunneling Action of Group VIII Metal Particles in Catalyzed Graphite Hydrogenation

p. j. goethel and r. t. yang, J. Catal., 1988, 114, (1), 46–52

A new catalytic action, termed tunneling, observed in catalysed graphite hydrogenation was studied for Pt, Ru and Ni using particle sizes below 1 μ m. For a particular size of particles the tunnel lengths were measured and the longest tunnel measured was used in the rate calculation. To within an experimental error of ±5%, all particles were found to tunnel at the same speed independent of the particle size. The rates of tunneling compared to the rates of monolayer channeling were based on per unit metal surface area. The tunneling rates were consistently higher by approximately one order of magnitude for all catalysts.

The Metal-Carbon Stretch in the Vibrational Spectrum of CO Adsorbed on Pt{111}

d. hoge, m. tÜshaus, e. schweizer and a. m. bradshaw, Chem. Phys. Lett., 1988, 151, (3), 230–235

The Pt-C stretching mode of the “on-top” species in the adsorption system Pt{111}-CO has been detected using Fourier transform i.r. reflecton-absorption spectroscopy and a Ge:Cu detector. Its band lies in the low frequency region and was previously undetectable. The frequency is 476±1 cm−1 at low coverages and 467±1 cm−1 at θ = 0.5. A band half-width of 4−6 cm−1 was observed and is comparable to that of internal C-O stretch, but with intensity ∼ 70 times weaker. The result is consistent with electron energy loss spectroscopic data.

Solid-State Amorphization in Al-Pt Thin Films

j. m. legresy, b. blanpain and j. w. mayer, J. Mater. Res., 1988, 3, (5), 884–889

The Al-Pt amorphous phases were formed by solid-state reaction either between polycrystalline Al and Pt layers or between binary Al-Pt amorphous and polycrystalline Al layers. In the first case, an amorphous phase is observed in as-deposited films that were not exposed to temperatures higher than ∼ 70°C. In the latter case, the transformation starts at ≤200°C and the complete amorphisation of the structure is obtained at 450°C.

Effect of Large Boron Additions to Magnetically Hard Fe-Pt Alloys

k. inomata, t. sawa and s. hashimoto, J. Appl. Phys., 1988, 64, (5), 2537–2540

Studies of the effect of B content on the magnetic properties of ternary (Fe0.6Pt0.4)100−x Bx and (Fe1−yPty)83B17 alloy ribbons showed that B changes the compositions of the ordered FePt(γ 1) phase, which coexists with Fe2 B at various alloy compositions so that the actual Pt content of γ 1 rises with increasing B content. The addition of B also increases the coercive force remarkably, especially at low Pt concentrations, and reduces the annealing time required for high coercivity. A coercive force of iHc = 5.6KOe was obtained for (Fe0.65Pt0.35)83B17.

AES and SIMS Surface Characterization of Pt-Ni Single-Crystal Alloys

m. abon, j. c. bertolini and h. montes, Appl. Surf. Sci., 1988, 32, (4), 343–351

The surface composition and the secondary ion mass spectrometry (SIMS) ionisation coefficient of (111) orientated Pt-Ni single-crystal alloys, Pt10Ni90, Pt50Ni50 and Pt78Ni22 in at.%, under steady-state ion sputtering, are compared to those properties of Ni(111) and Pt (111). Enhancement of Ni+ yield for Pt-rich alloys was observed, and is evidence for an electronic interaction between Ni and Pt in these alloys.

X-Ray Study of Short-Range Order in Ternary Pd-Au-Rh Solid Solutions

v. m. silonov, t. v. skorobogatova, a. a. katsnel’son and o. v. kris’ko, Fiz. Met. Metallov., 1988, 66, (4), 788–791

An X-ray study of localised short-range order in ternary Pd-Au-Rh solution was performed and the evaluation of its partial parameter is reported. Correlation of concentration dependance of microhardness, partial and general parameters of short-range order in ternary and binary Pd-Ag alloys is also given.

The Effect of the Heat Treatment of Pd Thin Film Alloy on the Hydrogenation of Olefins

j. tamaki, m. yamamura and t. imanaka, Bull. Chem. Soc. Jpn., 1988, 61, (5), 1725–1729

Studies of the Pd-(B,P) thin film alloys, prepared by RF sputtering, showed that before heat treatment selectivity for partial hydrogenation of olefins increased with increasing B or P concentrations in the films. After heat treatment selectivity was reduced over Pd films with a low B or P content but increased for high B or P content films. This high selectivity was due to small ensemble size, the low electron density of Pd, and Pd3B, Pd4.8P or Pd5P2 phase formation. Heat treatment affected the columnar structure of the film.

Hydrogen-Deuterium Reactions on Palladium-Iron Bilayers: A Permeation Investigation

d. k. kuhn and h. h. johnson, J. Appl. Phys., 1988, 64, (7), 3461–3467

The permeation of H, D and H-D through Fe coated with thin surface films of Pd was measured and experimental results for the individual and simultaneous permeation were presented. The results showed that besides the normal bulk isotope diffusivity dependence, an isotopic surface reaction occurs between H and D. A model was presented for the isotopes of H which allows for the competition for surface sites and the formation of HD gas.

Phase Equilibria in the Pd-Zr-Fe System

s. shebut, e. m. sololovskaya, i. g. sokolova and t. p. loboda, Vestn. Mosk. Univ., Ser. Khim., 1988, 29, (4), 412–414

Physico-chemical studies of interactions of Pd with Zr and Fe at 800°C showed that compositions of the cross-section specify the character of metal interactions in the boundary systems. The most important single phase region appeared to be ternary Pd-Fe based solid solution; Pd dissolved in itself up to 12at.%Fe, whereas dissolution of Pd in Fe did not exist. The α -solid solution was formed at 3.928±5 × 10−3Å in 90Pd–5Fe–5Zr and at 3.888±5 × 10−3 Å in 80Pd–15Fe–5Zr alloys. When Pd concentration increased to 48at.% in Pd-Fe based system, another phase corresponding to α -solid solution appeared.

The Composition, Structure and Electronic Properties of Thermally Prepared Iridium Dioxide Films

i. d. belova, t. v. varlamova, b. sh. galyamov, yu. e. roginskaya, r. r. shifrina, s. g. prutchenko, g. i. kaplan and m. a. sevostyanov, Mater. Chem. Phys., 1988, 20, (1), 39–64

It is reported that the composition of starting solutions affects the degree of crystallinity, crystallite size and orientation, composition of both crystalline and amorphous phases, surface area, and electrical properties of the thermally prepared Ir oxide films for use as electrode materials.

Soft Magnetic Properties of FeRuGaSi Alloy Films: SOFMAX®

k. hayashi, m. hayakawa, w. ishikawa, y. ochiai, y. iwasaki and k. aso, J. Appl. Phys., 1988, 64, (2), 772–779

The effect of introducing Ru into an Fe-Ga-Si alloy film of typical thickness 3μ m on properties such as saturation magnetic induction, film internal stress and wear resistivity has been investigated. High frequency permeability of the laminated structure film has also been studied. Adding 4−8at.% Ru upgrades the soft magnetic properties, the mechanical and other properties of the alloy simultaneously. Typical compositions Fe72Ru4Ga7Si17 and Fe68Ru8Ga7Si17 (at.%) were excellent soft magnetic materials.

Icosahedral Phase Formation in Rapidly Quenched Aluminium-Ruthenium Alloys

s. m. anlage, b. fultz and k. m. krishnan, J. Mater. Res., 1988, 3, (3), 421–425

Systematic rapid quenching studies on the icosahedral phase-forming system Al1−xRux for x<20 at.% were performed by electron microscopy and XRD to determine their composition, constituent phase and phase morphology. It is shown that the icosahedral phase must form directly from the liquid and, at these quench rates, is always found in the presence of second or third phases. The metastable phase diagram is found to be valid for rapid solidification of Al1−xRux at piston and anvil quench rates.

Compression of the Heavy-Fermion Compound URu2Si2 to 50GPa

h. luo, s. dabos, u. benedict and j. c. spirlet, J. Less-Common Met., 1988, 142, L23–L25

XRD studies of the heavy-fermion compound URu2Si2 in a diamond anvil cell were performed at room temperature and high pressure. Its tetragonal structure was stable through the pressure range up to 50GPa. The bulk modulus B0=247GPa and its pressure derivative were calculated by fitting the V(P) data to the Birch and Murnaghan equations. Its pressure behaviour was compared with that of other heavy-fermion systems.

CHEMICAL COMPOUNDS

Second Sphere Coordination Adducts of Phosphane-Transition Metal Complexes with β -Cyclodextrin and its Methylated Derivative

d. r. alston, a. m. z. slawin, j. f. stoddart, d. j. williams and r. zarzycki, Angew. Chem. Int. Ed. Engl., 1988, 27, (9), 1184–1185

X-ray analysis has been used to show that trans-[Pt(PMe3)Cl2(NH3)] inserts its hydrophobic PMe3 into the narrow opening of β -cyclodextrin, and does not bind to α -cyclodextrin. The results have implications for the design of drug delivery systems and H2O soluble catalysts.

Platinum Hydride Complexes A2PtH4 with A=Na, K, Rb or Cs

w. bronger, g. auffermann and p. mÜller, J. Less-Common Met., 1988, 142, 243–253

Studies were performed on Pt hydride complexes prepared by the reaction of binary alkali-metal hydrides with Pt sponge in H2. X-ray examination of powdered samples and neutron diffraction methods on the deuterated compounds revealed the crystal structure. The high temperature modifications crystallise in the K2PtCl6-type structure with H occupying two-thirds of the Cl positions. The tetragonal structures of the low temperature modifications were characterised by square planar [PtH4]2− groups.

Complex Formation in PdCl2-MgCl2 System

l. s. kravchuk, n. i. ivashchenko, p. p. mardilovich and m. v. zaretskii, Vest. Akad. Navuk BSSR, 1988, (3), 33–37

The u.v. spectroscopy of the complex formation in aqueous solutions of PdCl2-MgCl2 showed an interaction between these compounds yielding a number of variable composition complexes stable to hydrolysis at relatively high values of pH ∼ 4. The solid-state condensed phases obtained from Pd and Mg chlorides were found to decompose to corresponding metal oxides at much lower temperatures.

Ruthenium(IV)-Oxo Complexes: A Novel Hydrophobic Effect of Tertiary Phosphine Ligands on the Selective Oxidation of Alcohols

m. e. marmion and k. j. takeuchi, J. Chem. Soc., Dalton Trans., 1988, (9), 2385–2391

The second order rate constant for alcohol oxidation by [RuIVO(bipy)2(ER3)]2+ (bipy is 2,2′-bipyridine and ER3 is a tertiary phosphine or arsine ligand) in aqueous solution was found to be dependent on the hydrophobic nature of the target alcohol, and increased in the order: methanol<ethanol<propan-1-ol<2-methypropan-1-ol<butan-1-ol<3-methylbutan-1-ol<pentan-1-ol. The rate is also dependent on the nature of the phosphine ligand; with ER3=PPh3 the rate is 520 times greater than with ER3=PEt3. High primary isotope effects (kH/kD=10) were observed.

Ruthenium(III) Ion Complexes with Nucleic Acid Bases and Nucleosides

e. tselepi-kalouli and n. katsaros, J. Inorg. Biochem., 1988, 34, (1), 63–74

From i.r., diffuse reflectance spectra, conductivity and magnetochemical studies, the interaction of Ru3+ with ligands in complexes of the nucleic bases adenine, guanine, cytosine and the nucleoside adenosine with Ru trichloride, is suggested to be through the N of the purine or pyrimidine ring. Ru3+-thio-cytosine has metal-ligand interaction through S and the nucleoside complexes Ru3+-guanosine and Ru3+-inosine have metal ions bound to carbonyl O of the purine ring.

ELECTROCHEMISTRY

Oxygen Reduction at Nafion Film-Coated Platinum Electrodes: Transport and Kinetics

d. r. lawson, l. d. whiteley, c. r. martin, m. n. szentirmay and j. i. song, J. Electrochem. Soc., 1988, 135, (9), 2247–2253

Nafion (commercial perfluorosulphonate ionomer) coated Pt elecrodes have been prepared by high temperature film casting methods. Solution processed films showed much better adhesion characteristics and better physical and chemical properties than simple re-cast films. The results from diffusion solubility and kinetic studies with 0.7M H3PO4 as electrolyte are compared with data for bare Pt electrodes.

Methanol Oxidation Characteristics of Rare Earth Tungsten Bronze Electrodes Doped with Platinum

k.-i. machida, m. enyo, g.-y. adachi and j. shiokawa, J. Electrochem. Soc., 1988, 135, (8), 1955–1961

Studies of Pt doped rare earth W bronzes, Pt/Ln0.1WO3 (Ln is Y, La and lanthanides), showed a higher specific electrocatalytic activity and much lower heat of oxidation for the electro-oxidation of CH3OH at 288−323K, than ordinary Pt electrodes. Low rest potentials (0.3−0.39V) and high oxidation current densities (20−60 μ Acm−2) are reported for Pt doped electrodes. It was found that the electrocatalytic activity depended on the lattice constants of bronzes, as well as on the redox potential of the WO3/WO3 + couple (0.15−0.45V).

Effect of Deposition of Platinum Metals on the Dissolution Rates of Cobalt, Nickel and Chromium in Acid Solutions

l. v. gaisenko, a. i. marshakov and yu. n. mikhailovskii, Zashch. Met., 1988, 24, (5), 729–733

Effect of Pt and Rh deposition on the dissolution rates of Co(0.28cm2), Ni(1.13cm2) and Cr was studied on a disc electrode in 0.05−0.5M SO42− background solutions, in the presence of H2PtCl6 or RhCl3, and at pH 2.0−1.9. The addition of Pt and Rh inhibited the dissolution rate of Ni and Cr at constant potential but Co dissolution rate increased.

Reaction of Chloroplatinic Acids and Platinum Chloride with Isopropyl Alcohol

v. i. perevalova, n. b. shitova, l. ya. al’m and v. k. duplyakin, Zh. Obshch. Khim., 1988, 58, (8), 1694–1697

Studies of the reaction of H2PtCl6 and PtCl4 with isopropyl alcohol at room temperature showed the formation of a number of Pt(II) complexes of the type [(C3H6)PtCl3 −n(iso-C3H7OH)n]z (n=0−1, z=1−0). The increase of Cl content in Pt(IV) during transfer of PtCl4 to H2PtCl6 and also in reaction solution during reduction of H2PtCl6 in the presence of HCl, displaces the equilibrium compositon of Pt(II) complexes in favour of H2PtCl4 formation.

A Poly[tris (N-(bipyridylbutyl)pyrrole) ruthenium(II)]-RuO2 Catalytic Modified Electrode for Organic Oxidations

s. cosnier, a. deronzier and j.-c. moutet, Inorg. Chem., 1988, 27, (14), 2389–2390

The behaviour and catalytic properties of modified electrodes such as Pt/poly[RuL3]2+-RuO2, which denotes electrodes covered with a polypyrrole film bonded to a tris(bipyridyl)Ru(II) complex and containing dispersed RuO2 particles, have been studied and found to be useful for the electro-oxidation of benzyl alcohol to benzaldehyde in acetonitrile.

Interaction of Metallic Palladium with Platinum Chlorocomplex in Aqueous Solution

n. l. kovalenko, l. i. kochubeeva, n. v. grizan, v. g. chumakov and g. a. moiseeva, Zh. Neorg. Khim., 1988, 33, (9), 2328–2332

Studies of the interaction of Pd black with HCl solutions of K2PtCl4 and K2PtCl6 at 150−180°C showed that Pd reduces Pt(II) and Pt(IV) forming a number of solid Pt-Pd solutions with dependance on the molar ratio of Pd:Pt. During a partial reduction, disproportionation of Pt2+ was observed.

PHOTOCONVERSION

Laser-Driven Chemical Vapor Deposition of Platinum at Atmospheric Pressure and Room Temperature from Cp Pt(CH3)3

l. vogel koplitz, d. k. shuh, y.-j. chen, r. s. williams and j. i. zink, Appl. Phys. Lett., 1988, 53, (18), 1705–1707

Laser photolysis of Cp Pt(Me)3 (Cp=η 5-C5H5, Me=CH3) at room temperature and atmospheric pressure produces thin films and patterned structures of metal on solid substrates. The two different types of films obtained in the presence and absence of H, and the ability to prepattern the substrate in the absence of H and subsequently develop the shiny Pt deposit in the presence of H and additional Cp Pt(Me)3 support the hypothesis of both photochemical and thermal pathways.

Interfacial Photoreactions at the Photosynthetic Membrane Interface: An Upper Limit for the Number of Platinum Atoms Required to Form a Hydrogen-Evolving Platinum Metal Catalyst

e. greenbaum, J. Phys. Chem., 1988, 92, (16), 4571–4574

The hexachloroplatinate ion has been reduced to metallic Pt (requiring 4 reducing equivalents) by a new reaction at a photosynthetic membrane interface. Isolated spinach chloroplasts were illuminated with single-turnover, saturating flashes of light. Pt precipitated onto the membrane surface is photocatalytically active and produces H2.

Photocatalytic Hydrogen Generation from Water-Organic Solutions Using Polytungstates

m. i. rustamov, n. z. muradov, a. d. guseinova and yu. v. bazhutin, Int. J. Hydrogen Energy, 1988, 13, (19), 533–538

The addition of colloidal Pt greatly increased the rate of evolution of photochemically generated H2 from H2O-EtOH solutions using a polytungstate catalyst. The effects of amount of colloidal Pt, concentrations of reagents, temperature and pH, on the rate of H2 generation have been studied. At optimal conditions the ratio of amount of H2 evolved to initial amount of Pt exceeded 1000:1. The polytungstate is photo-reduced and stoichiometric amounts of H2 and acetaldehyde were formed.

Catalytic Fixation of Nitrogen by the Photocatalytic CdS/Pt/RuO2 Particulate System in the Presence of Aqueous [Ru(Hedta)N2] Complex

m. m. taqui khan, r. c. bhardwaj and c. bhardwaj, Angew. Chem. Int. Ed. Engl., 1988, 27, (7), 923–925

A truly catalytic fixation of N2 to NH3 by photochemical fixation was studied in aqueus solution at 30°C and 1 atm N2 in a semiconductor CdS/Pt/RuO2 particulate system excited by visible light (λ =505nm) and catalysed by [Ru(Hedta)N2] (Hedta is the trianion of ethylenediaminetetraacetic acid). NH3 yield was 6.8 mol per mol of catalyst per hour.

Photo-Induced Defect States in a Quasi One-Dimensional Mixed-Valence Platinum Complex

s. kurita, m. haruki and k. miyagawa, J. Phys. Soc. Jpn., 1988, 57, (5), 1789–1796

Studies of photo-induced absorption effects in [Pt(en)2][Pt(en)2Cl2](ClO4)4 single crystals (en is ethylenediamine) irradiated at 77K by the light within the charge-transfer absorption band (CT band) or higher, showed two absorption bands (A and B) below the CT band. The A and B bands were induced only by the light with E//chain and preferentially polarised for E//chain, showing that the photo-induced defect states were located on individual chains, and not associated with interchain defects.

Luminescence Decay Characteristics of Ru(bpy)32+ in Dilute Single Crystals and Polymer Hosts

e. krausz and g. moran, J. Lumin., 1988, 42, (1), 21–27

Luminescence decay characteristics for Ru(bpy)32+ doped in dilute single crystals and polymer hosts were measured at 1.5−77K using 1 ms square-pulse excitation from an acousto-optically modulated Ar+ laser. The temperature dependence of the decay times is consistent with luminescence from three states of equal degeneracy, separated by (8±0.5) and (60±5)cm−1, respectively.

Polyelectrolyte-Stabilized Metal Oxide Hydrosols as Catalysts for the Photo-oxidation of Water by Zinc Porphyrins

g. s. nahor, s. mosseri, p. neta and a. harriman, J. Phys. Chem., 1988, 92, (15), 4499–4504

Negatively charged Ir oxide and Ru dioxide colloids in neutral H2O have been stabilised with a surface layer of polyelectrolyte. Electrostatic forces between these colloids and H2O soluble Zn porphyrins of opposite electronic charges produced a high rate constant for interfacial electron transfer between the colloids and radical cations derived from Zn porphyrins. Oxidation of H2O to O2 was not observed.

Intramolecular Energy Transfer in the Covalently Linked Dimeric Complex [(bpy)2Ru(b-b)Ru(biq)2]4+

r. h. schmehl, r. a. auerbach and w. f. wacholtz, J. Phys. Chem., 1988, 92, (22), 6202–6206

The covalently linked dimer [(bpy)2Ru(bb)Ru(biq)2]4+ (bpy is bipyridine, b-b is 1,4-bis-[2-(4′-methyl-2,2′-bipyridyl-4-yl)ethyl]benzene, and biq is 2,2′-biquinoline) was prepared and its photophysical behaviour in room-temperature solutions and low temperature glasses was studied. Luminescence was observed from both Ru→bpy metal-to-ligand charge-transfer (MLCT) and Ru→biq MLCT states.

ELECTRODEPOSITION AND SURFACE COATINGS

Platinum Plating for Decorative and Functional Applications

m. pushpavanam and s. r. natarajan, Met. Finish., 1988, 86, (9), 25–27

Three plating electrolytes containing Pt as dinitrosulphato Pt complex, “p-salt” and hydroxyplatinate were studied in view of their decorative and functional applications. The electrolyte containing dinitrosulphato Pt complex was found to be most suitable for the studied applications and thicknesses of up to 10μ m could be obtained easily. The bath had very high stability and required little maintenance, by simple adjustment of pH and metal content. The bath could be used for plating on Ti.

A New Method for the Preparation of Platinum Electrodes with Single-Crystal (100) Surface

m. sumino and s. shibata, Denki Kagaku, 1988, 56, (4), 286–287

A thin polycrystalline Pt film has been electrodeposited from H2PtCl6 solution onto smooth polycrystalline Pt foils and then preferentially recrystallised to the (100) structure by heating for ∼ 2−4s at a temperature lower than the melting point of Pt bulk (∼ 1200−1400°C). The method described produces electrodes with well-defined single crystal (100) surface structures without the disadvantages of single crystal electrodes prepared from Pt beads.

APPARATUS AND TECHNIQUE

Hydrogen and Ammonia Response of Metal-Silicon Dioxide-Silicon Structures with Thin Platinum Gates

a. spetz, m. armgarth and i. lundstrÖm, J. Appl. Phys., 1988, 63, (3), 1274–1283

Studies of H2 and NH3 induced voltage shifts of the capacitance-voltage (C-V) curve of metal-oxidesemiconductor (MOS) structures with Pt gates showed the sensitivity of the devices to these gases. From the study of temperature (75−200°C), Pt-film thickness (3−70nm), ambient O2 concentration dependences of NH3 and H2 induced voltage shifts, models for gas detection mechanism are described. H atoms from H2 dissociation produced a dipole layer at the metal-oxide interface, while NH3 was detected by surface potential changes capacitively coupled to the semiconductor surface through voids in the catalytic Pt film.

Surface Control of Platinized Platinum as a Transducer Matrix for Micro-Enzyme Electrodes

y. ikariyama, s. yamauchi, t. yukiashi and h. ushioda, J. Electroanal. Chem., 1988, 251, (2), 267–274

The importance of anodic polarisation of a platinised surface for the microfabrication of enzyme electrodes is reported. A glucose oxidase-incorporated microplatinised electrode shows responses not only to glucose but also to other saccharides.

The Temperature Characteristics of an H2S-Sensitive Pd-Gate MOS Transistor

z. weixin and z. yibing, Sens. Actuators, 1988, 15, (1), 85–93

The effects of atmospheric H2S on the sensitivity, response speed and selectivity of a p-channel Pd-gate metal-oxide-semiconductor (MOS) transistor were studied at various temperatures. The device was highly sensitive to H2S even at room temperature, and its performance was improved at the optimum temperature of 150°C. At 200°C and with good ventilation in air, complete reversibility was obtained.

Use of Zirconium and Ruthenium Isotope Correlations in the Analysis of Spent Nuclear Fuels

w. smulek, r. k. al-dabbagh, k. goroncek and m. borkowski, J. Radioanal. Nucl. Chem., Artic., 1988, 121, (2), 385–393

Methods for the determination of Pu contribution to the total burnup of a spent nuclear fuel of low initial enrichment in 235U (3.6%) have been studied. The use of isotope ratios of stable Ru and Zr fission products 101Ru:104Ru, 93Zr:96Zr and 91Zr:96Zr is proposed and the method verified by determination of the total burnup of the fuel from the 137Cs and 148Nd monitors and subtraction from this value of the partial burnup due to 235U.

HETEROGENEOUS CATALYSIS

Hydrogenation of 1,3-Butadiene on Pt(111) Comparison with Results on Pt(110) and Pt(100)

c.-m. pradier, e. margot, y. berthier and j. oudar, Appl. Catal., 1988, 43, (1), 177–192

Hydrogenation of 1,3-butadiene adsorbed on Pt(111) at low pressure, p=10−7atm, was studied under quasiatmospheric pressure. A first saturation state was rapidly reached, equivalent to one butadiene molecule per 2–3 Pt atoms, with no reduction in catalytic activity. A mechanism is proposed which is not affected by controlled S adsorption (s=0.1). S slightly improved the selectivity toward butenes, but total poisoning occurred for S adsorption of s=0.5.

Stability of Bimetallic Reforming Catalysts

j. m. parera and j. n. beltramini, J. Catal., 1988, 112, (2), 357–365

The effect of coke deposition on catalytic activity, selectivity and stability of the catalysts Pt/Al2O3, Pt-Re/Al2O3 and Pt-Re-S/Al2O3 was studied in the reforming of n-hexane and methylcyclopentane. Coke deposited on Pt during the first few hours of the run produced deactivation. Coke deposited on the support later produced slight deactivation.

Interaction between Iridium and Platinum Precursors in the Preparation of Iridium-Platinum Catalysts

j. xue, y.-j. huang and j. a. schwarz, Appl. Catal., 1988, 42, (1), 61–76

Incipient wetness and wet impregnation methods have been used to prepare catalysts Pt/Al2O3, Ir/Al2O3 and Pt-Ir/Al2O3. On adsorption of catalytic precursors, the effect of metal concentration and pH of the impregnation solution during wet impregnation shows that at low weight loadings the amount of adsorbed metal in a bimetallic system can be predicted from the adsorption capacity of the metal when adsorbed alone.

Effect of HCl on Activity and Dispersion of Platinum and Palladium Deposited on Alumina

v. i. anan’in, n. ya. pryakhina, l. v. gerasimova, g. m. sen’kov and a. i. trokhimets, Vest. Akad. Navuk BSSR, Ser. Khim. Navuk, 1988, (3), 30–33

The effect of HCl on activity and dispersion of Pt/Al2O3 and Pd/Al2O3 catalysts was studied on Al2O3 samples impregnated with PdCl2 for 1 hour, with 0.1M HCl or with an aqueous solution of H2PtCl6, followed by drying in air at 283±10K and calcination in a muffle furnace for 3 hours at 773±20K. The interaction of impregnating solutions of the catalysts is considered. The results show that the support pretreatment with HCl in the gas phase increases the activity and dispersity of Pt and Pd supported catalysts.

Conversion of n-Pentane and Methylcyclopentane on Pt-Cr/Al2O3 and Pt-Sn/Al2O3 Catalysts

l. vlaev, l. damyanov, ch. bonev and a. palazov, Izv. Khim. (Sofia), 1988, 21, (2), 145–151

Supported Pt catalysts Pt-Cr/Al2O3 and Pt-Sn/Al2O3 prepared from Pt/Al2O3 catalysts either by deposition of the second metal from CrO2Cl2 or SnCl4 vapours, or by simple impregnation from aqueous solutions of H2CrO4 or SnCl2, were studied by i.r. spectroscopy during conversion of n-pentane and methylcyclopentane. The results showed increased selectivity in methylcyclopentane dehydroisomerisation and lower hydrocracking activity of bimetallic catalysts. It was also found that the nature of promoting agent, its deposition technique and its fixing on the surface of Pt/Al2O3 are all equally important in the determination of various formation mechanisms and stabilisation of bimetallic clusters.

Selectivity of Pt-Re-S/Al2O3-Cl Reforming Catalyst as a Function of Feed Composition

j. m. grau, r. j. verderone, c. l. pieck, e. l. jablonski and j. m. parera, Ind. Eng. Chem. Res., 1988, 27, (10), 1751–1754

The selectivity and deactivation by coke of Pt-Re-S/Al2O3-Cl catalysts with different chlorine content were studied during reforming of commercial naphtha cuts and cuts prepared by doping a typical naphtha for reforming with n-paraffins and isomer fractions, by chromatographic analysis. Gaseous effluents were analysed and compared with the cut composition. Cuts with a higher content of n-paraffins than isomers with the same number of C atoms produced higher aromatics formation.

Deactivation of Pt Catalysts by Oxygen. 1. Kinetics of the Catalyst Deactivation

p. j. m. dijkgraaf, m. j. m. rijk, j. meuldijk and k. van der wiele, J. Catal., 1988, 112, (2), 329–336

The effect of O2 pressure, reactant concentration, pH and temperature on the deactivation kinetics of a commercial Pt/C catalyst used in an aqueous slurry for the oxidation of D-gluconate to D-glucarate at 50°C has been studied. The deactivation is governed by O2 coverage of the Pt surface and occurs exponentially under steady state conditions.

Sintering of Silica-Supported Platinum Catalysts during Ethylene Oxidation

n. l. wu and j. phillips, J. Catal., 1988, 113, (1), 129–143

X-ray diffraction has been used to study sintering of Pt/SiO2 catalysts under C2H4 + O2 at 600°C, and has shown changes in Pt particle size distribution consistent with intraparticulate atomic transport. This behaviour differs markedly from that for Pt/SiO2 under nonreactive (O2, CO2, H2O, C2H4, N2) atmospheres, in which changes in particle size distribution are due to particle growth by coalescence.

H2 Evolution from Various Aqueous Solutions over Thermally Reduced TiO2 and Pt-TiO2 Powder

a. kudo, k. domen, k. -i. maruya and t. onishi, Bull. Chem. Soc. Jpn., 1988, 61, (5), 1535–1538

Reduction of H2O (or H+) to form H2 over reduced TiO2 and Pt/TiO2 has been studied in distilled H2O and aqueous solutions of HCl, H2SO4, HNO3, and NaOH. H2 evolved moderately in distilled H2O and NaOH solutions over reduced TiO2 powder, while reaction in aqueous HCl and H2SO4 was strongly suppressed due to H+ presence. H2 evolution over reduced Pt/TiO2 was rapid.

Metal-Support Effects on Acetone Hydrogenation over Platinum Catalysts

b. sen and m. a. vannice, J. Catal., 1988, 113, (1), 52–71

Turnover frequencies for acetone hydrogenation to isopropylalcohol over high-temperature reduced (HTR) Pt/TiO2 catalyst were found to be > 500 times higher than those of hydrogenation over Pt/SiO2 and Pt powder. Pt/TiO2 enhanced specific activity (per g Pt) 10 fold. The activation energies and pressure dependencies for all catalysts (Pt/η −Al2O3 and Pt/Au were also studied) are similar and the hydrogenation over Pt crystallite is structure insensitive. The results demonstrate a clear support effect previously observed only for CO hydrogenation.

PTFE Dispersed Hydrophobic Catalysts for Hydrogen-Water Isotope Exchange. I. Preparation and Characterization. II. Water Poisoning

a. d. belapurkar, n. m. gupta, r. m. iyer and k. v. s. ramarao, Appl. Catal., 1988, 43, (1), 1–13; 15–31

A 0.1 μ m uniform polytetrafluoroethene (PTFE) film has been deposited on different substrates and catalysts prepared by dispersing Pt metal over these substrates. These catalysts have longer life than uncoated catalysts when used for an isotopic H2-[2H] water exchange process for the production and detritiation of heavy water. In the second paper water induced catalytic poisoning has been studied by observation of 1H−2H exchange rates. The thin, porous, polymeric film minimises water condensation and lowers the substrate-water interaction.

Dehydrogenation of n-Hexane on Platinum Containing X-Zeolite Modified by the Transition Metals

t. i. gintovt, i. i. urbanovich and l. a. kupcha, Vest. Akad. Navuk BSSR, Ser. Khim. Navuk, 1988, (4), 29–33

Studies of the state of active components in bimetallic contacts and of catalytic properties of Pt/X-zeolite catalysts modified with Re, Mo and W were performed during aromatisation of n-hexane by spectroscopic and microscopic techniques. The modification of the Pt/X-zeolite catalysts by Re, Mo and W resulted in an increase in metal dispersity and catalytic activity.

Study of the Reaction of Complete Oxidation of Styrene on Palladium-Manganese Catalyst

s. a. marusyak, v. ya. vol’fson and v. m. vlasenko, Kinet. Katal., 1988, 29, (3), 591–595

Studies of the kinetic dependence of the reaction of a complete oxidation of styrene on its concentration, and changes during styrene chemisorption on the surface of 0.5wt.%Pd-Mg catalyst revealed the presence of critical reaction phenomena.

Effect of Dispersion of Supported Palladium on its Electronic and Catalytic Properties in the Hydrogenation of Vinylacetylene

yu. a. ryndin, l. v. nosova, a. i. boronin and a. l. chuvilin, Appl. Catal., 1988, 42, (1), 131–141

The effect of Pd particle size in the selective gasphase hydrogenation of vinylacetylene has been studied. The specific catalytic activity (turnover number TON) of SiO2 or γ -Al2O3 supported Pd was approximately constant over a particle size range of 40−180Å. When the Pd particle size was reduced from 40 to 10Å the TON fell by one order of magnitude and the binding energy of the Pd 3d5/2 level increased by 0.6eV.

Hydrogenation of Thiophene Catalysed by a Palladium Alizarin on γ -Al2O3 and Rhenium Sulphide

a. s. lobach, yu. m. shul’ga, k. kh. heinrich and m. wahren, Izv. Akad. Nauk SSSR, 1988, (8), 1722–1727

X-ray studies of the hydrogenation of thiophene to thiophane in various solutions in the presence of Pd catalysts prepared by the deposition of Pd metallo-complex compounds with alizarin c onto γ -Al2O3 supports (Pd(al-c)/Al2O3), were performed at 16MPa and 200−235°C. The results were compared with data previously obtained on Pd/C, Pd/Al2O3 and Re sulphide catalysts. Activity of the catalysts during their use in a number of methyl cyclohexane solutions decreased in the order: Pd/C > Pd/Al2O3 ≃ Pd(al-c)/Al2O3 > Re sulphide. The results show that the catalytic activity of the Pd catalyst depends on the supports.

Studies of Carbon Dioxide Hydrogenation over Supported Palladium Catalysts

x.-z. jiang, j.-b. bao, y. chen, j.-x. liu and s.-y. xu, J. Catal. (Dalian, China), 1988, 9, (2), 122–130

Three supported Pd catalysts, 5.1%Pd/La2O3, 4.2%Pd/SiO2 and 6.3%La-4.9%Pd/SiO2, were studied and characterised under atmospheric pressure and at 633−693K by various techniques. The difference in catalytic activity was attributed to the metal-support interaction and to the effect of the La promoter. Possible reactive intermediates for CH3OH synthesis by CO2 and CO hydrogenation were also studied.

Effect of NO on the CO-Induced Disruption of Rhodium Crystallites

f. solymosi, t. bÁnsÁgi and É. novÁk, J. Catal., 1988, 112, (1), 183–193

From i.r. spectroscopy studies it has been shown that addition of NO to CO accelerates oxidative disruption and hinders reductive agglomeration of Rh/Al2O3 catalysts. The acceleration of CO induced oxidative disintegration was shown by accelerated formation of gem-dicarbonyl, RhI(CO)2, from Rhx-CO species, even with NO : CO ratios of only 1 : 100. Reductive agglomeration of RhI sites was shown by the CO induced transformation of RhI(CO)2 to Rh-COx at 448K.

Promoting Effect of Lanthana in the Hydrogenation of Carbon Monoxide over Supported Rhodium Catalysts

r. kieffer, a. kiennemann, m. rodriguez, s. bernal and j. m. rodriguez-izquierdo, Appl. Catal., 1988, 42, (1), 77–89

Supported Rh catalysts Rh/La2O3, Rh/SiO2, Rh/Al2O3 and ternary phases Rh/La2O3/SiO2 containing 0.1−8.5% La2O3 showed high activity and selectivity towards C2-oxygenates for the CO + H2 reaction. The presence of 0.25% La2O3 in ternary catalysts clearly showed a promoting effect. Studies of characterisation and catalytic activity suggest that the covering of Rh particles by La2O3 is caused by the redissolution of La2O3 during the impregnation process.

Preparation and Characterization of a Novel Catalyst for the Hydrogenation of Dinitriles to Aminonitriles

f. mares, j. e. galle, s. e. diamond and f. j. regina, J. Catal., 1988, 112, (1), 145–156

Highly selective partial hydrogenation of aliphatic α,ω -dinitriles to ω -aminonitriles has been achieved using an efficient Rh/MgO catalyst. The selectivity was due to the high dispersion of the Rh (catalyst content 4−5%) which allows a strong interaction between active metal and adsorbed species with the support, and due also to the basic MgO support facilitating desorption of basic compounds. The preparation and the role of high surface area MgO support are reported, and catalyst preparation discussed.

Promoting Effects of Se on the Activity and Selectivity of Rh-ZrO2 Catalysts for Ethene Hydroformylation

y. izumi, k. asakura and y. iwasawa, J. Chem. Soc., Chem. Commun., 1988, (19), 1327–1328

Studies of Se-modified Rh/ZrO2 catalysts prepared by treatment of Rh/ZrO2 with Me2Se or by co-impregnation showed that Se had a marked promoting effect on the activity and selectivity of these catalysts for ethene hydroformylation, due to the preferable interaction of CO with Se2− on Rh, and the stabilisation of propanoyl intermediates by Se-Rh ensembles. Optimum Se : Rh ratios are reported.

Conversion of Syngas on Bimetallic Ruthenium Containing Catalysts

g. d. zakumbaeva, l. b. shapovalova, zh. t. omarov, e. n. litvyakov and a. sh. kuanyshev, Neftekhim., 1988, 28, (4), 507–512

The 5%Ru-Cu/Al2O3 catalysts with Ru:Cu ratios (at.%) of 1:0.18, 1:0.68, 1:1.59, 1:3.71 and 1:14.3 were studied in order to explain the effect of the structure of active centers on the direction of the catalytic conversion of syngas. The catalysts were prepared by saturation of Al2O3 by aqueous solution of RuOHCl3 and CuCl2.2H2O followed by a 3 hour reduction in H2 at 573−673K, washing and drying at 303−323K. In comparison to Ru/Al2O3, where the CO2 hydrogenation yielded methane only, on bimetallic Ru-Cu/Al2O3 catalysts the reaction yielded higher molecular hydrocarbons. The maximum yield of C2-Cn hydrocarbons occurred on Ru-Cu(1:0.18)/Al2O3 catalyst but decreased with an increase of Cu content.

Activated Hydrogen Chemisorption on Ru-Cu/SiO2 Bimetallic Substrates

t. okuhara, t. jin, y. zhou and j. m. white, J. Phys. Chem., 1988, 92, (14), 4141–4147

Temperature-programmed desorption (TPD) in UHV has been used to study H2 adsorption-desorption on Ru-Cu bimetallic particles supported on SiO2, and on Cu films deposited on Ru(0001). Enhanced high temperature H2 desorption arising from adsorption of H2 at elevated temperatures was observed for Ru-Cu/SiO2 but not for Ru/SiO2 or Cu/SiO2.

Preparation and Characterisation of ZrO2 Stabilized with Ru(IV) and La(III)

y.-c. long, z.-d. zhang, k. dwight and a. wold, Mater. Res. Bull., 1988, 23, (5), 631–636

In determining the stability of dispersed RuO2 on ZrO2, a solid solution of Ru(IV) oxide in ZrO2 was studied and showed increased stability toward H2 reduction from 90°C to over 200°C, compared with bulk RuO2. Further addition of 5mol% La(III) oxide increased the stability of dispersed Ru(IV) at up to 800°C.

Reduction of Carbon Monoxide and Dioxide by Metal Carbonyls on a Pyrolysed Polymeric Support

g. c. grunewald and r. s. drago, J. Chem. Soc., Chem. Commun., 1988, (17), 1206–1208

Pyrolysed polyacrylonitrile (PPAN) has been studied as a novel support for Ru3(CO)12 in the Fischer-Tropsch reaction and the methanation of CO2. The catalyst 2%Ru/PPAN showed improved selectivity to low molecular weight hydrocarbons and no products above C5, compared to 2%Ru/Al2O3. It is thought that activity could be improved with increased support surface area. Activities are comparable for methanation of CO2, with CH4 the only product if CO2 is not in great excess.

HOMOGENEOUS CATALYSIS

Synthesis and Catalytic Properties of Sulphoxide Bridge Platinum(II) Compounds

v. n. spevak, v. i. lobadyuk, a. e. trofimov, n. k. skvortsov, n. a. moldavskaya and v. o. reikhsfel’d, Zh. Obshch. Khim., 1988, 58, (8), 1689–1694

Bridge compounds of the type [Pt2(R2SO)2X4] where R2SO is dimethyl-, diethyl- or dipropylsulphoxide and X is chloride-, bromide- or iodide-ions, were prepared and their catalytic activities studied. The presence of trans-→cis isomerisation was observed in [Pt(DMSO)2Cl2] compounds (DMSO is dimethylsulphoxide). The Pt sulphoxide bridged complexes showed high catalytic activity in comparison to corresponding single nuclear complexes. Discrepancies and changes of reaction rates with temperature and the effect of acid ligands confirmed higher stability of Pt sulphoxide bridge complexes in comparison to analogue Pt olefin compounds.

Homogeneous and Supported Platinum Complex Catalysts with Nitrogen-Containing Ligands in Hydrogenation of Unsaturated Hydrocarbons

e. g. kliger, l. p. shuikina, o. p. parenago and v. m. frolov, Izv. Akad. Nauk SSSR, Ser. Khim., 1988, (10), 2420–2422

Studies of homogeneous and supported Pt complex catalysts incorporating higher aliphatic amine ligands during hydrogenation of unsaturated hydrocarbons showed the highest activity and reaction rate for the Pt system, H2PtCl6-(C8H17)3N−(i−C4H9)2AlH, at 20°C and under H2 pressure of 40kPa. The highest hydrogenation rate was observed with olefins containing a terminal double bond while the hydrogenation of cyclo- and α -olefins, and dienes with linear or cyclic structure proceeded in zero order, and of disubstituted olefins and acetylenes in first order.

Water-Soluble Dinuclear Rhodium Complexes as Catalytic Precursors for the Hydroformylation of Alkenes in a Two Phase System

p. kalck, p. escaffre, f. serein-spirau, a. thorez, b. besson, y. colleuille and r. perron, New J. Chem., 1988, 12, (6–7), 687–690

The catalyst precursors HRh(CO)(TPPTS)3 and Rh2(μ -SR)2(CO)2(TPPTS)2 where TPPTS is the water-soluble tris(m-sulphophenyl)phosphine ligand, exhibited high selectivity towards corresponding aldehydes for the low pressure hydroformylation of alkenes. The Rh2 complexes showed higher rates and higher selectivity to linear aldehydes (∼95%) than the mononuclear complexes. TPPTS maintained the complexes in the aqueous phase while the products were obtained in the organic phase, thus enabling complete catalyst recovery.

Very Efficient Reduction of NAD(P)+ with Formate Catalysed by Cationic Rhodium Complexes

r. ruppert, s. herrmann and e. steckhan, J. Chem. Soc., Chem. Commun., 1988, (17), 1150–1151

The first example of effective and selective reduction of NAD+ and NADP+ (nicotinamide cofactors used in enzyme-catalysed reactions) by Na formate catalysed by metal complexes such as RhIII (C5Me5)(bpy)2+ (bpy is bipyridyl) is reported. In contrast with enzymatic reduction, with this system the same reagent can reduce both NAD+ and NADP+, and at a rate independent of NADP+ concentrations. Only very mild conditions are needed.

Ruthenium Catalysed Oxidation of Alkanes with Alkylhydroperoxides

t.-c. lau, c.-m. che, w.-o. lee and c.-k. poon, J. Chem. Soc., Chem. Commun., 1988, 21, 1406–1407

The cis-[RuIII(L)2(OH2)2]2+ complexes (L=substituted 2,2′-bipyridines or 1,10-phenanthrolines) catalysed oxidation of saturated hydrocarbons to alcohols and ketones by t-butylhydroperoxide (TBHP). The catalysts were highly active for oxygenation of alkanes with TBHP and a turnover number of over 1000 can be readily achieved at room temperature. The low values of kinetic isotope effect (kH/kD=3.5 for cyclohexane) and tertiary to secondary C-H bond relative reactivities of about 6.5 for adamantane, are in a range expected for H atom abstraction by radical species.

Liquid-Phase Dehydrogenation of Methanol with Homogeneous Ruthenium Complex Catalysts

h. itagaki, s. shinoda and y. saito, Bull. Chem. Soc. Jpn., 1988, 61, (7), 2291–2294

The effects of the additives LiCl, Li acetate, acetic acid and ethyldiphenylphosphine on the initial rate of dehydrogenation of CH3OH, yielding HCHO and H2, using the catalyst Ru(OAc)Cl(PEtPh2)3 where OAc is an acetato ligand, have been studied under refluxing conditions. The catalyst was deactivated gradually by the displacement of the bidentate OAc with H and CO ligands during the reaction. A mechanism is proposed, involving these cis-disposed sites being used for splitting the C-H bonds.

Production of Ethanol from Synthesis Gas Using Promoted Homogeneous Bimetallic Ru-Co Catalysts

r. a. head and r. whyman, New J. Chem., 1988, 12, (6–7), 675–677

Studies of the effect of Co addition to a Ru catalyst system and the effect of different promoters and solvents were performed. The results showed that EtOH can be produced directly from synthesis gas using composite homogeneous bimetallic Ru-Co catalysts, together with alkali metal halide or quaternary ammonium halide promoters in polar aprotic solvent mixtures, with enhanced selectivity.

FUEL CELLS

Electrocatalysis by Ad-Atoms. Part XXIII. Design of Platinum Ad-Electrodes for Formic Acid Fuel Cells with Ad-Atoms of the IVth and the Vth Groups

w. watanabe, m. horiuchi and s. motoo, J. Electroanal. Chem., 1988, 250, (1), 117–125

It has been found that ad-atoms greatly enhance the activity of Pt electrocatalysts for formic acid oxidation. Optimum coverages with ad-atoms have been determined and activity enhancement by ad-atoms at these coverages found to increase in the orders Pb>Sn>Ge and Bi>Sb>As. The ad-atoms Pb, Bi and Sb showed a 3-fold enhancement of the activity of Pt. It was found that ad-electrodes with increased activity also had increased tolerance against poisoning.

Localization of Platinum in Low Catalyst Loading Electrodes to Attain High Power Densities in SPE Fuel Cells

e. a. ticianelli, c. r. derouin and s. srinivasan, J. Electroanal. Chem., 1988, 251, (2), 275–295

Three methods to obtain high power densities in solid polymer electrolyte (SPE) fuel cell systems have been studied, involving the variation of the wt.% of the Pt/C-supported electrocatalyst and the sputtering of Pt thin films onto the electrode. The optimum configuration obtained was 20wt.% Pt/C-supported electrocatalyst onto which was sputtered a 50nm Pt film. This showed twice the power density of conventional 10wt.% Pt/C electrodes. At 1 A/cm2 current density, cell potentials were 0.6V and 0.54V with H2/O2 and H2/air reactants, at 80°C and 3/5 atm pressure. Pt utilisation was 15−20%.

Stability and Activity of Platinum/Carbon Catalysts

a. honji, t. mori and y. hishinuma, Nippon Kagaku Kaishi, 1988, (8), 1391–1396

The stability and activity of Pt/C catalysts in H3PO4 fuel cells has been assessed with different types of C: Denka Black, Regal 660R and Vulcan XC-72R. Denka Black was shown to be the most stable for reaction with O2 and steam because graphite spacing is smaller and crystallite size larger than the other carbons. Pt/Denka Black showed higher activity for O2 reduction in 98 wt% H3PO4 at 190°C.

Enhancement in Methanol Oxidation by Molybdenum Modification of Pt-SPE Electrodes

j. wang, h. nakajima and h. kita, J. Electroanal. Chem., 1988, 250, (1), 213–217

Studies of Mo-modified Pt-SPE electrodes (SPE is solid polymer electrolyte) showed further enhancement for the oxidation of CH3OH compared with a corresponding metal electrode, especially at low polarisation (∼0.1V). At polarisations of ∼0.2−0.3V, catalytic activity was enhanced ∼102 times with temperature increase from 25 to 80°C.

Cathodic Reduction of Oxygen on Platinum Electrode of a Fuel Cell with Mixed Solution of Trifluoromethanesulfonic Acid and Phosphoric Acid

m. yamashita, j. tanaka and h. takemura, Nippon Kagaku Kaishi, 1988, (8), 1384–1390

The effect of adding CF3SO3H to 85% H3PO4 solution on O2 reduction on a rotating Pt disc electrode has been studied. Results from laser Raman studies of reaction products showed that CF3SO3H was nearly completely dissociated when in mol fraction, x<0.45. When x>0.45 some of the CF3SO3H remained undissociated despite H+ interactions with oxygen of P=O bond in molecular H3PO4. The addition of CF3SO3H enhanced O2 solubility and diffusion coefficient, and increased the exchange current density and the voltage of the fuel cell.

Study of Photo-Assisted Fuel Cell

h. harada, m. ohto and y. hayashi, Nippon Kagaku Kaishi, 1988, (8), 1229–1231

A methanol fuel cell combined with a photocatalytic Pt/TiO2 reaction apparatus is reported. This new type of cell was shown to work as a CH3OH fuel cell in the dark and as a H2−O2 fuel cell under illumination. Methanol was reformed into H2 by the photocatalytic reaction using Pt/TiO2, and evolved H2 was provided for the anode of the fuel cell. The performance of this cell under illumination was better than that of the CH3OH fuel cell.

Selective Synthesis of Acetaldehyde Using a Fuel Cell System in the Gas Phase

k. otsuka, y. shimizu and i. yamanaka, J. Chem. Soc., Chem. Commun., 1988, (18), 1272–1273

A Pd/H3PO4/Pd fuel cell has been used to produce CH3CHO by the partial oxidation of C2H4 at temperatures <395K. It was shown that Pd is a specific electrocatalyst. Selectivity for CH3CHO was > 97% and current efficiency was 100±5%. Unlike the Wacker process this method is simple and the gaseous reagents can be handled easily. Furthermore no corrosive aqueous PdCl2, CuCl2 and HCl solution was needed and the separation of the reactants reduced the danger of explosion.

Amorphous Alloy Catalysts for Electro-Oxidation of Methanol and Its Derivatives in a Sulphuric Acid Solution

a. kawashima, t. kanda and k. hashimoto, Mater. Sci. Eng., 1988, 99, 521–524

Amorphous Ni-Ti, Ni-Zr, Ni-Nb and Ni-Ta alloys containing a few wt.% of platinum group metals which were surface activated by immersion in HF solution showed high electrocatalytic activities for CH3OH, HCHO and HCO2 H oxidation in fuel cells, and high corrosion resistance in H2SO4. Partial substitution of Pt by Ru, Si, Ge, Sn, or Pb further enhanced activity. Surface activation was due to Pt, Ru and/or Sn enrichment of the surface layer as well as surface roughening.

CHEMICAL TECHNOLOGY

Catalytic Membrane for Simultaneous Chemical Reaction and Separation Applied to a Dehydrogenation Reaction

y.-m. sun and s.-j. khang, Ind. Eng. Chem. Res., 1988, 27, (7), 1136–1142

A reactor containing a tubular Pt-impregnated Vycor glass membrane has been used to catalytically dehydrogenate cyclohexane in the membrane itself, thus combining catalytic activity with separation selectivity. An improved equilibrium conversion compared to the equilibrium based on feed conditions, is reported. A mathematical model is used to show that the catalytic membrane reactor is a better converter with high space time operation than an inert membrane reactor which incorporates its catalyst in the feed-side chamber. However, with low space time operation the catalytic membrane reactor is less effective for this dehydrogenation.

ELECTRICAL AND ELECTRONIC ENGINEERING

Platinum Wire Wedge Bonding: A New IC and Microsensor Interconnect

j. v. mantese and w. v. alcini, J. Electron. Mater., 1988, 17, (4), 285–289

Ultrasonic ball or wedge bonding of Au or Al is the traditional method for making electrical interconnects between die and chip header for most integrated circuit (IC) and microsensor devices. This article describes a new method of making electrical connection between die and chip header. Interconnects were made by using a conventional wire bonder to ultrasonically wedge bond 0.032 mm diameter Pt wires to both Pt and Al thin films. Interconnects made by this method are very strong, as compared with Au wire bonds, with pull stengths of ∼13g. Electrical studies showed contact resistances of ≤0.05Ω. Annealing tests of the bonds made to thin metal films of Pt on Ti on sapphire showed no signs of electrical or mechanical degradation after anneals at 900°C for 1 hour in pure O2.

Dependence of PtSi Schottky Diode Electrical Behaviour on the Platinum Film Thickness and on the Annealing Process

f. la via, p. lanza, o. viscuso, g. ferla and e. rimini, Thin Solid Films, 1988, 161, (1–2), 13–20

From studies of current-voltage characteristics the current density in thin PtSi/Si<111 > Schottky diodes (30nm Pt film) was shown to be nearly an order of magnitude higher than that in thick diodes (60nm Pt film). In thin diodes current density also increased with increased perimeter to area ratio. The effect was caused by vertical diffusion of Pt deposited on the SiO2 region surrounding the contact area. The results have relevence for device fabrication with avoidance of additional processes, such as As ion implantation.

Barrier Effect of E-Beam Evaporated Tungsten Interlayer in Al/W/PtSi Metallization Layer

b.-s. chiou, h.-s. lo and p.-h. chang, J. Electron. Mater., 1988, 17, (5), 397–404

The reaction characteristic of Al/PtSi and the effectiveness of W diffusion barrier interlayer in the Al/W/PtSi metallisation system were studied and ideal I−V characteristic and low constant end resistance were obtained in PtSi/nSi and PtSi/n+Si contact systems. In the Pt/Si system, no PtSi was formed on annealing at 200°C for 30 min, while only PtSi was observed at > 350°C. A new phase, PtAl2, was observed after sintering at 350°C for 15 min. The W diffusion barrier layer was found to enhance the stability of Al/PtSi. The W layers of 500Å and 1000Å were effective up to 450°C annealing for 1 hour and 500°C for 4 hours, respectively.

Pt-Coated Substrate Effect on Oxide Superconductive Films in Low-Temperature Processing

s. hatta, h. higashino, k. hirochi, h. adachi and k. wasa, Appl. Phys. Lett., 1988, 53, (2), 148–150

Low-temperature film preparation techniques have been used to grow high Tc ErBaCuO superconducting films on Pt-coated substrates at 650°C. The films were produced easily and found to be of excellent quality, the Pt buffer layer improving the films superconductivity as well as its crystallinity.

Growth of α Rh2As on GaAs(001) in a Molecular-Beam Epitaxy System

a. guivarc’h, m. secouÉ, b. guenais, y. ballini, p. a. badoz and e. rosencher, J. Appl. Phys., 1988, 64, (2), 683–687

Thin films of α Rh2 As have been grown on GaAs(001) in a molecular-beam epitaxy system by co-deposition of Rh and As from separate sources. Various electrical measurements have shown that the charge carriers are exclusively holes with a concentration similar to that of the best silicides. α Rh2 As is a good metal with resistivity of 20 μ Ωcm, suitable for electronic applications. α Rh2As and GaAs have several features in common, namely symmetry, almost equivalent unit-cell constant and f.c.c. As sublattices. However, the epitaxial arrangement observed was not the expected unrotated relationship.

Study of Charge Compensation Mechanism in IrOx Electrochromic Reactions by In Situ Electrogravimetry

h. masuda, t. yoshino, k. arai and n. baba, Chem. Lett. Jpn., 1988, (8), 1337–1338

IrOx electrochromic films have been prepared by periodic reverse current electrodeposition from sulphatoiridate solutions, and the charge compensation mechanism in the colouring/ bleaching reactions studied by in situ electrogravimetry. A liquid phase quartz microbalance was used to measure weight change. The results indicate that the cations were ejected from the IrOx film to a bulk electrolyte.

Electrically Controllable Optical Attenuator with High Deposition Rate IrOx Film

t. yaji, t. katsube, m. hara and y. nakagawa, Appl. Surf. Sci., 1988, 33/44, 1244–1252

A new type of electrically controllable optical attenuator is reported, using a solid electrochromic (EC) device consisting of an “iridium tin oxide (ITO)/sputtered IrOx film (SIROF)/polystyrene sulphonic acid (PSSA)/WO3/ITO” structure. SIROF as the EC material gave uniform absorption change in a wide wavelength range (350-1500nm).

Electrical Properties of Conductive Materials Used in Thick-Film Resistors

a. dziedzic and l. golonka, J. Mater. Sci., 1988, 23, (9), 3151–3155

The resistance, temperature coefficient of resistance and temperature dependence of IrO2, RuO2 and Bi2Ru2O7 compounds screen printed on Al2O3 substrates and fired at 875°C have been studied between −196 and 850°C. RuO2 and IrO2 layers showed high sintering ratios and their resistance increased with temperature as in single crystals. Qualitive agreement of resistance temperature dependences of Bi2Ru2O7 films and polycrystalline Bi2Ru2O7, and a discrepancy with single crystal behaviour were observed, suggesting the dominant importance of grain surface and regions between the grains.

Electrophysical Properties and Phase State of Thick-Layer Resistors Based on Pb2Ru2O6, Modified by Titanium(IV) Oxide Compounds

n. s. lozinskii, a. i. gruba, m. a. shevtsova and v. i. volkov, Izv. Vyssh. Ucheb. Zaved., Khim. Khim. Tekhnol., 1988, 31, (8), 17–20

X-ray phase and electrophysical measurements of thick-layer resistors based on Pb2Ru2O6 modified by Ti(IV) oxide were carried out. The results showed that Ti modification decreases resistance and transfer temperature coefficient of resistance of the resistor in the region of negative values.

MEDICAL USES

Structure, Activity and Mode of Action of Antitumor Platinum Compounds

t. wenxia, q. yun and d. anbang, Pure & Appl. Chem., 1988, 60, (8), 1271–1278

The quantitative relationship between activity and structure of some 40 anti-tumour Pt complexes has been studied by CNDO/2-SCF method. A new complex [Pt(TMCPDA)(Cl-Ac)2] where TMCPDA is 1,2,2′-trimethyl-1,3-cyclopentanediamine, was designed, synthesised and screened and showed as high activity as cisplatin but with much lower toxicity. The mode of action of cisplatin with DNA has been studied by 13C NMR and CNDO/2.

Platinum(II) Binding to Metallothioneins

j. bongers, j. u. bell and d. e. richardson, J. Inorg. Biochem., 1988, 32, (1), 55–62

Equine renal metallothionein (MT) has been reacted with excess K2PtCl4 at pH2, resulting in a polymeric adduct containing 17±2mol Pt/mol MT. A monomeric adduct Pt7MT was obtained at neutral pH and was shown to have Pt2+ to cysteine thiolate co-ordination from a study of its rates of reaction with iodoacetic acid and 5,5′-dithiobis(2-nitrobenzoic acid). Adducts from the reaction of K2PtCl4 with apoMT chemically modified at the N-terminal methionine residue, Cd7MT and native MT are also reported. Implications for the metabolism of Pt anti-cancer drugs are discussed.

Bis(Platinum) Complexes Containing Two Platinum cis-Diammine Units. Synthesis and Initial DNA-Binding Studies

n. p. farrell, s. g. de almeida and k. a. skov, J. Am. Chem. Soc., 1988, 110, (15), 5018–5019

The synthesis and DNA binding of bis(Pt) complexes containing two units of the anti-tumour-active cis-diammine complex linked by variable-length hydrocarbon chains of the general formula [{cis-PtCl2(NH3)}2NH2(CH2)nNH2] is reported. A study of the inhibition of restriction endonuclease activity on linearised DNA revealed greater inhibition by these complexes (especially the n=4 derivative) compared to that of cisplatin, cis-[PtCl2(NH3)2]. These bis(Pt) complexes represent the first examples of Pt species with greater affinity for DNA than cisplatin.

Tarnish and Corrosion Behaviour of Palladium-Silver Alloys

l. a. o’brien and r. m. german, J. Mater. Sci., 1988, 23, (10), 3563–3571

Binary and commercial Pd-Ag dental alloys containing 50−75%Ag showed the greatest resistance to both tarnish and corrosion, probably due to saturation of the d-electron shell in this composition range. The commercial Pd-Ag alloys were more corrosion resistant but had lower tarnish resistance than the binary Pd-Ag alloys, due in part to the minor alloying with In or Zn. The addition of Cu increases the segregation of Ag which adversely affects both tarnish and corrosion resistance. In comparison with other noble metal dental alloys, the Pd-Ag alloys rank fairly high in both tarnish and corrosion resistance.

Spectroscopic Properties of Bioactive Complexes K2[RuH2OCl5]

i. e. chernikova, i. a. khartonik, d. n. kachurina and t. m. buslaeva, Dokl. Akad. Navuk BSSR, 1988, 32, (8), 696–698

Spectroscopic properties of the bioactive complex K2[Ru(H2O)Cl5] were studied by vibrational and other spectroscopic techniques. The vibrational spectra of the complexes were interpreted on the basis of a normal co-ordination analysis. The anti-tumour activity of this complex was also studied.

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