of current literature on the platinum metals and their alloys · abstracts of current literature on...

ABSTRACTS of current literature on the platinum metals and their alloys PROPERTIES Scanning Tunneling Microscopy of the Annealing of a Thin Platinum Film on Highly Oriented Pyrolytic Graphite X. CHuAN ZHOU and E. GULARI, Acta ctyst., 1991,

Scanning tunneling microscopy was used to study morphological changes in a thin Pt film deposited on highly oriented pyrolytic graphite (HOPG) during annealing. In air the film could be imaged with a vertical resolution of 0.5A and a lateral resolution of 20A. After annealing below 573 K surface morphology changed only slightly; at 573-873 K the originally uniformly distributed “rolling hills” of Pt coagulated into larger lumps. Above 873 K Pt crystal facets started to form on the surface. At 1123 Kmuch of the surface turned into well defined F’t crystal facets. Above 1123 K the Pt f h started to crack and formed scattered crystals on the HOFG surface. The crystabed Pt was preferentially oriented with the (1 11) plane parallel to the substrate graphite (0001) basal plane, indicating epitaxy of the Pt overlayer with the graphite substrate underneath.

Kinetic Studies of the Chemical Vapor Deposition of Platinum

S. ROY and P. A. YOUNG, Chem Muter., 1991, 3, (2),

The chemical vapour deposition (CVD) of Pt was monitored by FTIR and UV spectroscopies using cis-[PtMe,(MeNC),l as precursor in order to ex- amine the effects of H, and UV irradiation, which can enhance CVD. Pt deposition in a 2 cm pathlength UV cell under UV irradiation at <300 MI occurred on a pyrex target. Irradiation at longer wavelengths gave negligible deposition. The effect of H, in a 10 cm pathlength pyrex cell was to accelerate the reaction.

Hydrogen, Hydrogen SuKde and Hydrocarbon Coadsorption on Pt( l l1) and Pt(l10): Selective Formation of

A47, (l), 17-21

B. MXON, P. R. NORTON, E. C. OU, R. J. PUDDEPHATT,

222-224

Alkylthiols D. VASSILAKIS, C.-M. PRADIER, Y. BERTHIER and J. OUDAR, Appl. surf. Sci., 1991, 47, (3), 273-280 The simultaneous adsorption of diolefme, H, and H, S on Pt single a y s t a l s forms mercaptan and alkanes. The nature, amount and temperature of desorption of these p d u c t s depend on the size and configuration of the diolefme and on the structure of the surface. Mechanisms are proposed to explain the observed surface reactions. Some compounds are selectively produced when H, S reacts firstly with the diolefme; this occurs with C,H, on (111) and (110) orientations, and with C,H, on Pt(ll0).

Magneto-Optical Kerr Effect and Perpen- dicular Magnetic Anisotropy of Evaporated and Sputtered Co/Pt Multilayer Structures

McDANIEL and H. Do, 3. Appl. Phys., 1991, 69, (7),

Thin and ultrathin Co/Pt multilayered structures were prepared on glass substrates by electron-beam evaporation at room temperature and by sputtering at various substrate temperatures and sputtering pressures. Perpendicular magnetic anisotropy was found in samples with Co/Pt bilayer thicknesses near 3 &lo A and total thicknesses of the layer stack of (300 A. The effects of sputtering parameters, such as pressure and substrate temperature, on the magneto-optical Kerr effect were studied.

Perpendicular Magnetic Anisotropy in PtlFe Multilayers

and M. HASHIMOTO, 3. Appl. Phys., 1991, 69, (S),

Perpendicular magnetic anisotropy and related magnetic properties in Pt/Fe multilayers were investigated. Pt/Fe com sitionally modulated f h s (CMFs) with - an 18w”pt layer and Fe layer <5A become perpendicularly magnetised films. Surface magnetic anisotropy (KJ was 0.46 erg/cmz and volume anisotropy (K.,) was - -2 x 10’ erg/cm3 at room temperature. The K, is almost equivalent to that of Pt/Co CMFs and increases with decreasing temperature. The absolute value of K., is much larger than that of the Pt/Co s stem. The effective

changes from positive to negative at T - 200 K with decreasing temperature.

Permanent Magnetic Properties in Fe-Pt- Nb System Alloys

P. HE, W. A. MCCAHAN, J. A. WOOLLAM, F. SEQUEDA, T.

402 1-428

T. KATAYAMA, Y. SUZUKI, Y. MSHIEURA, T. SUGMOTO

Part IIB, 5658-5660

magnetic anisotropy of IFe(4.7 x )/Pt(18.5A)Im CMF

K. WATANABE, 3. 3m. h t . Met., 1990, 54, (11), 1284- 1290 Magnetic properties and temperature dependence of Fe-Pt-Nb ternary alloys were investigated by various techniques. Permanent magnetic properties were obtained by water-quenching from the 7-phase region and tempering at -850-900 K in the phase region. A Fe-39.5 at.%Pt-0.75 at.%Nb alloy exhibits the maximum energy product of 167 kJ/m3, with a residual flux density of 1.05 T and a coercivity of 398 kA/m. These properties are superior to those of basic binary Fe-Pt. The Fe-Pt-Nb composition range is wider than that of Fe-Pt, so the heat-treatments can be easily controlled, and the reproducibility of the magnetic properties can be improved. Fe-38Pt-1Nb has excellent rectangular hysteresis loops at 400 and 290 K with stable thermal properties.

Platinum Metals Rev., 1991, 35, (3), 152-165 152

Amorphous Phase Formation in an As- Deposited Platinum-GaAs Interface D.-H. KO and R. SINCLAIR, Appl. Phys. Lett., 1991,58,

A thin amorphous intermixed layer at the Pt-GaAs interface in as-deposited Pt/GaAs and Si/Pt/GaAs samples has been investigated by various techniques. The intermixed layer forms below the native oxide of the GaAs substrate and consists of the elements: Pt, Ga and As. It is suggested that this layer forms during the deposition process of the Pt.

High Temperature Reactions between Sic and Platinum T. C. CHOU, 3. Muter. sci., 1991, 26, (5 ) , 1412-1420 Solid state reactions between Sic and Pt were performed at 900-11OO0C. In the reaction zones, alternating layers of Pt, Si and C, and Pt,Si and C were formed at 900 and looO°C, respectively. Both the Pt,Si and R,Si phases were stable at respective temperatures, but annealings at ll0OoC produced alternating layers of mixed Pt silicides and C. The formation of Pt silicides gave rise to interfacial melting between Sic and Pt and Sic decomposed into C and Si at all the temperatures. The Si reacted with Pt and formed Pt silicides, while the carbon formed clusters and was unrective.

Solid State Reactions of Sic with Co, Ni, and Pt T. c . CHOU, A. JOSHI and J. W A D S W O R ~ , 7. Muter. Res., 1991, 6, (4), 796-809 Solid state reactions between Sic ceramics and Pt, Ni and Co were studied at 800-1200OC for various times under He or vacuum. The WSiC reactions at 900, 1000 and ll0OoC were very similar to each other; interfacial melting was observed and Pt,Si, Pt,Si and a mixture of Pt silicides, respectively, were formed upon annealing. C precipitation behaviour, annealing conditions, diffusion phenomena and major reaction products for diffusion couples are given. A CPFZ(C precipitation free zone) was generated in Ni/SiC and &/Sic but not in Pt/SiC. While a CPZ(carbon precipitated zone) was formed in all the systems, both M-CPZ(modulated) and R-CPZ(random) were noted in the Pt and Ni systems, but only a R-CPZ in the Co system.

Magnetic-Field-Induced Strong Diamagnetic Transition in the Quasi-One- Dimensional Halogen-Bridged Platinum Complex [Pt(en) I[Pt(en) 212 I(Cl0,) (Where en Represents Ethylenediamine) M. HARuKI and P. WACHTER, Phys. Rev. B, 1991,43,

DC magnetisation measurements on the quasi-one- dimensional halogen-bridged Pt title complex show a magnetic-field induced strong diamagnetic transition at fields above 20 kOe. The diamagnetic signals are as large as 3.5-72% of complete diamagnetism and show large fluctuations. The transition temperature to pararnagnetkm is at - 180 K.

(17), 1851-1853

(7), 6273-6276

Interfacial Reactions between Palladium Thin Films and InP D. G . IVEY, L. ZHANG and P. JIAN, 3. Mazer. sci., Muter. Elecnm, 1991, 2 , (l), 21-27 The reaction between a thin layer of Pd( = 100 nm) and an InP substrate was studied at annealing temperatures of 250-45OOC for up to 30 s, which are typical annealing conditions encountered during contact fabrication. Pd reacted readily with InP forming an amorphous ternary phase which later transformed to crystalline Pd,InP on annealing. Pd,InP had an ordered cubic structure, and mkrotwins, 2-3 atomic layers thick, were identified in the ternary phase and these formed along the (110) and (1 10) planes.

Comparative Study on Phase Formation in AI-Pd Thin Film by Ion Beam Mixing and Thermal Annealing - R. Y. LEE, J. H. PARK and c. N. WHANG, 3. Muter. sci., 1991, 26, (3), 721-725 Ion beam mixing and/or thermal annealing were con- ducted to study the phase formation and dissociation in Al-Pd thin films prepared by sequential evaporation. The intermetallic compounds formed by ion mixing with Ar+ were found to be Al3PdZ and AlPd at a dose of 1.5 x 10l6 Ar+/cm2. Thermal annealing after t h i s radiation gave two new phases of All Pd and Al,Pd, in addition to AllPd2 and AlPd. For an as- annealed sample without Ar+ bombardment, the observed phases are Al, Pd, Al Pd 2 and AlPd.

Retardation of Grain Boundary Reactions in Ag-Pd-Cu AUoys by Additions of Small Amounts of Other Elements I. KAWASHIMA, Y. ARAI<I and H. OHNO, 3. Muter. Sci.,

The grain boundary reactions in Ag-ZS%Pd-lO%Cu (mass%) with 1% of Al, Co, Sn, G or In were studied. Addition of Sn and G retarded grain boundary reactions. Grain interior reactions were ac- celerated with Q, Sn and In additions, with G being the most effective. The activation energies for the grain interior and grain boundary reactions were 192-1% and 144-208 kJ/mol, respectively. Addi- tions retarded the growth but not the nucleation at the grain boundary.

Mechanical-Strain-Induced Influences on Hydrogen Diffkion within Pd,,Ag2, AUoy Membranes x. Q. TONG and P. A. LEWIS, 3. Less-Common Met.,

Sudden changes in H z gas pressure on the upstream side of tubular membranes of Pd7,AgZl and Pd,, Pt ,, alloys are known to produce complementary changes of H pressure an the downstream side; this has been attributed to “elastic dynamic” or “mechanically induced memory” effects. Further experiments show that such effects could be associated with combina- tions of Gorsky effect and self-strain-induced diffusion-elastic effect migrations of H interstitials in the walls of the membranes.

1991, 26, (4), 1113-1118

1991, 169, (l), 157-165

Platinum Metals Rev . , 1991, 35, (3) 153

Hydrogen Permeable Palladium-Silver Alloy Membrane Supported on Porous Ceramics S. UEMNA, T. MATSUDA and E. KIKUCHI, J . Membrane Sci., 1991, 56, (3), 315-325 The H permeability and selectivity of a composite membrane consisting of misable Pd-Ag alloy film supported on the outer surface of a porous alumina cylinder were investigated. The membrane had much higher flux than commercially obtained Pd-based membranes for H separation. The high H flux was due to the thinness of the f h and its high H solubility. H embrittlement was suppressed by alloying the thin Pd film with Ag, and 100% H selectivity was retained even at relatively low temperatures.

On the Origin of a Lattice Expansion in Palladium and Pd-Au Vapour Deposits on Variaus Substrates c. KUHRT and R. ANTON, Thin Solid Films, 1991, 198,

Vapour deposits of'Pd and Pd-Au alloy particles and films were produced under UHV or in high vacuum, with and without the admission of H,O, on amorphous fdms of C and SiO, and single crystal surfaces of NaCl and KBr. In all cases lattice expansions of up to 2.6% were measured, depending on the condition of degassing of the substrate and on the residual gas composition during deposition, especially with respect to water vapour. Lattice expansion correlated with the presence of H on or in the substrate materials, as detected by SIMS.

Mechanical Behavior of Nanocrystalline Cu and Pd

Muter. Res., 1991, 6, (3, 1012-1027 Bulk mechanical properties of nanocrystalline Pd and Cu samples, consolidated from powders prepared by inert gas condensation, were measured. Average grain sizes were 3-50 nm and mean lattice strains ranged from 0.02-3%. Densities rang from 97-72% of that of a coarse-grained standard. Microhardness exceeds that of annealed, coarse-grained samples by a factor of 2-5, despite indications that sample porosity reduces hardness values below the ultimate value. Uniaxial tensile strength is also high.

The Palladium-Rich P&Ho(Er) Systems Y. SAKAMOTO, K. TAKA0 and Y. NAGAOKA, J. Muter.

Pd-Ho and Pd-Er alloys containing 10-21.0 at.% Ho(Er) prepared by arc-melting in Ar and heat treated to - 1193 K for 10 min followed by quenching in iced H,O were studied by various metallographic, spectroscopic and electrical resistance measurements. It is concluded that the magnitude of the order-disorder transition temperature, T,, for the reaction a-Pd + L1,-type Pd,RE (or W,RE where RE is Ce, Sm or Eu)=Pd,RE of the Pd-RE alloys is due to the magnitude of the metallic radius of the rare-earth metals.

(1-2), 301-315

G . W. NIEMAN, J. R. WEERTMAN and R. W. SIEGEL, J.

S C ~ . , Lett., 1991, 10, (6), 341-344

A Contribution to Coupled Reduction of Rare Earth Oxides with Pd and H,

and R. FERRO, z. Metallkd., 1991, 82, (3), 169-173 Stoichiometry and structural types of Pd-rare earth alloys are presented. Results from reacting Gd,O,- Pd mixtures with H , are reported. For alloys containing up to 20 at.% Gd the reduction was nearly complete and Pd-rich Gd-Pd alloys were obtained. For Pd solid solutions containing up to - 12 at.% Gd nearly single-phase samples of composition close to the nominal ones were obtained. For 10-22 at.% Gd when two solid phases, Pd and GdP,, are stable at temperatures over 537OC, twephase alloys not too far from the nominal ones of eutectic appearance were obtained.

Kinetic and Thermodynamic Investiga- tion of Hydrogen Absorption by Ternary LaNi Al and LaNi A1-Pd Alloys M. v. SUSIC and Y. M. SOLONIN, Int. J. Hydrogen

Differential scanning calorimetry and X-ray analysis of H, absorption by ternary LaNi,Al and a LaNi,Al- Pd alloy containing 4 % Pd showed that in a flowing H, atmosphere H absorption by the fmt alloy took place exothermally at about 150 and 45OOC. The alloys containing Pd behaved similarly with absorption facilitated by the presence of Pd, and the formation of a new phase with a phase transition at 150°C was observed.

Mechanical Alloying of the Pd-Si System. Investigation of the Early and Late Mill- ing Stages

V. CONTARDI, R. MARAZZA, G. RAMBALDI, G. ZANICCHI

Emrgt, 1991, 16, (4), 271-276

M. MAGINI, N . BASILI, N . BURGIO, G . ENNAS, S. MARTELLI, F. PADELLA, E. PARADISO and P . SUSINI, Muter. Sci. Eng., 1991, A134, 1406-1409 Four Pd-Si compositions: Pd,.,Si, Pd,Si, Pd,Si and Pd , Si, have been processed by mechanical alloying. After the early milling stages, consisting of very fine fragmentation of the Si particles into a Pd matrix, the Pd Si, Pd, Si and Pd, Si can nucleate intermetallic Pd , Si, depending on the milling conditions and/or the milling apparatus. Further milling seems to pro- mote amorphisation, probably starting from the previously formed Pd , Si compound.

Standard Molar Enthalpies of Formation of Me,Ge, (Me Zr, Nb, Mo), MeGe (Me

Ru, Rh, Pd) and PdlGe by High- Temperature Calorimetry W.-G. JUNG and 0. J . KLEPPA, J. Less-Common Met.,

The standard enthalpies of formation of the above 4d transition-metal germanides were determined using a high-temperature calorimeter at 1473+2 K. Liquid (Ni + Ge) alloys were used as solvents in the solute- solvent drop experiments, and values were obtained for Zr,Ge, and I%,&,. Values of -56.9e1.4 kJ/mol for RUG, - 113.8k2.1 kJ/mol for RhGe and -92.921.5 kJ/mol for PdGe were obtained.

1991, 169, (l), 93-103

Platinum Metals Rev. , 1991, 35, (3) 154

Hydrazine Decomposition on a Clean Rhodium Surface: A Temperature Pro- grammed Reaction Spectroscopy Study J. PRASAD and J. L. GLAND, hngmuir, 1991, 7, (4), 722-726 The adsorption, desorption and decomposition of N,H, on a Rh foil surface was studied as a function of its coverage by temperature programmed reaction spectroscopy. The gas-phase products observed depend markedly on the initial hydrazine coverage. At low coverage only H, and N2 desorb from the surface, but at near monolayer Coverage H,, NH,, N, and diimide are observed. Simultanmus desorption of N2 and NH, at 220 K for high coverages suggests the direct decomposition of hydrazine N,H,- N, +H(ad) and N,H,+H(ad)-NH,. Diimide formation was observed over a wide range of N,H, coverages above 220K

Dissociation of Nitric Oxide and Reaction with Hydrogen on Rh(l11) and Various Stepped Rh(ll1) Surfaces

Surf. Sci., 1991, 246, (1-3), 135-140 The reaction between NO and H, was studied on Rh(ll1) and stepped surfaces: Rh(331), Rh(211) and Rh(321) by scanning field emission probe-hole microscopy. Reaction start-up temperature strongly depends on NO coverage, and is sensitive to surface structure. At low NO coverage the reaction starts by 240 K on Rh(321), and at a much higher temperature on Rh(211) and Rh(ll1). On Rh(321) characteristic features of both (100) and (1 11) steps are observed.

Infrared Spectroscopy at High Pressure. Interaction of N 2 with Rh/Al,O, at Am- bient Temperature

WORLEY, 3. Am. Chem. Soc., 1991, 113, (8),

A new high-pressure infrared cell reactor capable of variable temperature operation was used to study the interaction of N, with Rh/Al, 0, catalyst fdms in the pressure regime 1 x to 9000 Tom at 298 K. The results were in good agreements with those previously obtained for similar catalysts at low temperatures and pressures. Infrared bands for chemisorbed and physisorbed N, species were detected and assigned.

Solidifcation of Copper-Rhodium Alloy Single Crptal~

R. M. WOLF, J. W. BAKKER and B. E. NIEUWENHUYS,

J. P. WEY, H. D. BURKElT, W. C. NEELY and S. D.

2919-2922

M. P. DELPLANCKE, M. JARDINIER-OFFERGELD and F. BOUILLON, Mater. Chem. Phys., 1991, 27, (3), 225 -2 33 The preparation of Cu-Rh alloy single crystals by the vertical Bridgman method is described. Dendritic structures are formed during the solidification process of 1.5, 4, 8.75 and 15 at.%Rh alloys. Various methods are used to characterise the solute distribution. Formation conditions and the thermal stability of the structures are also discussed.

Ditrusion of Ir-Dimers on Ir(l10) Sur- faces by Atomic-Exchange and Atomic- Hopping Mechanisms T. T. TSONG and c.-L. CHEN, Surf. Sci., 1991, 246,

On the Ir(ll0) surface, single Ir adatoms and Ir- dimers can diffuse along, as well as across, the 1101 surface channels. The across-channel diffusion most probably occurs by an atomicexchange mechanism. The visited-site-lattice for Ir and Ir, is the (1 x 1) net of the substrate lattice. Atomic jumps are concluded to extend only to the nearest-neighbour sites. For single Ir-adatoms, a s i o n across the channels is easier than along the channels. For Ir-dimers the along-channel diffusion is easier. The energies needed for single Ir-atoms and I r - h e r s to hop along the channel and to displace across the channel by atomic exchanges are derived. The binding energy of the dimer is 1. 10+0. 11 eV.

Structure and Magnetic Properties of FeRuGaSi Multilayer Thin Film

(1-3), 13-24

T. M. JAGIELINSKI, A. M. ZELTSER and C. F. BRUCKER, J. Appl. Phys., 1991, 69, (8), Part IIB, 5628-5630 The structure and magnetic properties of FeRuCaSi thin films used in VHF (150 MHz) recording heads have been studied. The best soft magnetic properties of coercivity (0.2-0.3 Oe), permeability (2000 at 1 MHz and 400-500 at 150 MHz), and magnetostric- tion (<W6), were obtained after annealing at 450-50O0C. This magnetic behaviour is attributed to the phase transformations and the increase in the grain size of the films occurring during annealing.

Phase Equilibria in the RuO -Bi 0 Xu0 System

Len., 1991, 10, (2), 69-70 Studies of interactions between CuO and the conductive phases RuOz or Bi,Ru,O, in thick-fdm resistors have been performed and the ternary phase diagram of the Ru0,-Bi,O,-CuO system is presented. The phase equilibria indicate reactions between the conductive Bi,Ru,O, phase in thick-fh resistor material and the CuO, which was added as a temperature coefficient of resistivity modifier, with CuO being incorporated into the pyochlore crystal structure, resulting in the Bi, - ,C~Ru,O, solid solution. When RuO, was the conductive compo- nent, CuO did not react with it.

Growth and Characterization of RuSe, Single Crystals

Mazer. Res. E d . , 1991, 126, (l), 11-17 Single crystals of RuSe,, up to 10 x 8 x 6 mm’, were grown by an oscillating chemical vapour transport method using ICI, as the transport agent. Optimum conditions for the growth of large single crystals are given. Crystal stoichiomeuy is discussed, and electrical resistivity and Hall effect measurement indicate n-type semiconducting properties.

S. BERNlK, M. HROVAT and D. KOLAR, J. Mater. sci.,

J.4. SHEU, Y.-S.SHIH, S.4. LIN and Y . 4 . HUANG,


CHEMICAL COMPOUNDS Crystal Growth and Properties of R2Ba2CuPt08 (R = Ho, Er, Y), R2 Ba Cu, PtO ,,, and Ba, CuPt O9

and T. FUKUDA, 3. Cyst. Growth, 1991, 109, (1-4),

Three new Pt complex oxides have been identified as products of the CuO-flux growth of R-Ba-Cu-0 (R = Ho, Er, Y) superconducting oxides in Pt crucibles. These oxides are formed under normal atmospheric conditions and a growth mechanism for the compounds involving incorporation of Pt from the crucible is proposed. The crystal structure of R,Ba,CuPtO, has been determined. The T-1” temperature dependence of the conductivity is explained by a -Cu~+-O~--Pt‘+-O~- conduction chain model. The magnetic susceptibility measurements reveal an antiferromagnetic interaction of spins Ho”, El’+, and Cuz+.

High-Nuclearity Platinum-Osmium Alloy Cluster Complexes. Synthesis and Structural Characterizations of Pt 0 s 6 - (CO) 2 2 (COD) and Pt, a 6 (CO) 21 (COD) 2

R. D. ADAMS, J.C. LII and w. wu, Inorg. Chem., 1991,

The fmt example of a possible series of new high- nuclearity Pt-0s carbonyl cluster complexes having structures based upon alternating layers of Pt and 0 s are reported. The clusters were formed when Pt,0s3(CO),,,(COD),, where COD is 1,s-cyclo- octadiene, was refluxed under N, for 30 min.

The Synthesis of Os3Pt Clusters. X-ray Crystal Structure of Os,Pt(CO) I I (PPh3)2 D. H. FARRAR, R. R. GUKATHASAN and J. A. L~NNISS, Inorg. Chim. Acra, 1991, 179, (2), 271-274 The reaction of 0s,(CO),,(NCMe) (1) with sources of PtL, gave new clusters 0s,Pt(CO),,L, as major products, where L is PPh, or PBu,Ph. Each 0s-Pt edge was bridged by a carbonyl ligand, while the re- maining nine carbonyl ligands were terminally bound to 0s atoms. The minor products from the reaction of (1) and PtL, were phosphine-substituted derivatives of Os,(CO),, and the raft clusters 0s,(CO),, -,(NCMe), with n = 1, 2. Crystal structures of the products are given.

Syntheses and Crystal Structures of [Pd9As8 (PPh,) D. FENSKE and c. PERSAU, z. Anorg. Allg. Chem., 1991, 593, (2), 61-68 A new cluster [Pd,As,(PPh,),l which was prepared by reaction of [PdCI,@Ph,),l with As(SiMe,), was characterised by X-ray crystal structure analysis. The cluster molecule has four [Pd,(PPh,),l units bridged by As, units with a further Pd atom being located in the centre of the cluster. The reaction of [PdCl,(PPh,),l with Sb(SiMe,), yielded [Pd,Sb,(PPh,),l which has a b.c.c. Pd,-cluster.

Y. SAITO, T. SHISHIDO, N. TOYOTA, K. UKEI, T. SASAKI

426-43 1

30, (lo), 2257-2258

and [I’d9 Sb 6(PPh3)

Structural, Magnetic, and Charge Transport Properties of Bis[(5,10,15,20- Tetrameth ylporph yrinato)Palladium(II)l Perrhenate, [Pd(tmp)l [ReO, 1 E. M. MCGHEE, B. M. HOFFMAN and J . A. IBERS, Znorg. Chem., 1991, 30, (9), 2162-2165 Electrochemical oxidation was used to produce the new molecular conductor [Pd(tmp)l ,[ReO, 1, which is composed of partially oxidised Pd(tmp) cations stacked metal-over-metal and surrounded by chains of ReO, anions. Single crystal room temperature conductivity along the needle axis averages 30/Q cm, and can be fitted to an expression that describes a semiconductor with temperature-dependent carrier mobility, and is comparable with that of the best Pt- spine conductors, despite the interplanar separation being -3.38 hi, compared to that for Pt-Pt of 2.95 hi. This conductor is isostructural with [Ni(tmp)l ,[ReO,l and LCu(tmp)l ,[ReO,I.

Ring Migration Reactions of (C5Mes)Rh(PMe3)H2. Evidence for q 3 Slippage and Metal-to-Ring Hydride Migration w. D. JONES, v. L. KUYKENDALL and A. D. SELMECZY, Orgamtallics, 1991, 10, ( 3 , 1577-1586 The reactions of (C,Me,)Rh(PR,)H, (PR, =PMe,, PMe,Ph, PMePh,, PPh,) with D, gas occurred quickly at 25OC, leading to the stepwise exchange of H for D. Kinetic studies showed a second-order reaction mechanism involving Rh and D. (C,Me,)Rh(PMe,)H, also reacted with PMe, at 4OoC to yield C,Me,H and HRh(PMe,), in a reaction displaying bimolecular kinetics. Isotope effect studies showed no rate difference with the dideuteride Rh complex.

Synthesis and Reactivity of Rhodium(I) Complexes of the Type Rh(G

E. KwASKOWSKA-CHEC and A. M. TRZECIAK, Transinim Met. Chem., 1991, 16, (2), 212-214 The carbonyl ligands in the Rh’ complexes Rh(L-L)(CO), (L-L is anthranilate (AA) or N-phenylanthranilate (FA) ions) were replaced by P(OPh), to form the mono- or disubstituted products. Under Ar at [P(OPh),lfiRhl)4 the ortho-metdated Rh’ complex Rh[P(OPh) I - [P(OC,H,)(OPh),l was formed. The Rh(AA)(CO), complex was used as a catalyst precursor in hydroformylation of olefms.

Reaction of Ru(q-RC5 H4)C1(PPh3)2 with Carbon Dieulfide

Coord. Chem., 1991, 22, (4), 255-258 The reaction ofCS, with Ru(q-C,H,)Cl(PPh,), produced [Ru(q-C,H,)(CS,)(PPh,),l+ by two different routes. Results suggest that the formation of the CS, derivatives is related to the partial dissociation of the Ru-CI bond, which increases with the basicity of the phosphine attached to the metal.

L)(CO)[P(OPh) 3 1 and Rh(GL)[P(OPh) 3 1 2

A. GUTIERREZ-ALONSO and L. BALLESTER REVENTOS, 3.

Platinum Metah Rev., 1991, 35, (3) 156

ELECTROC HEMISTRY Electrocatalytic Properties of Ultrafine Platinum Particles for Oxidation of Methanol and Formic Acid in Aqueous Solutions

and Y. TAKASU, Electrochim. Acta, 1991, 36, (5/6),

The effect of size of ultrafime Pt particles prepared by vacuum evaporation onto a glassy C rod, on the electrochemical oxidation of MeOH and HCOOH acid was examined by cyclic voltamwtry. The specific activity for the oxidation of MeOH decreased by decreasing the Pt particle size, whereas that of the HCOOH acid increased as the particle size decreased.

XPS Analysis of Amorphous Ni-Nb-Sn-Pt Alloy Catalysts for Electro-Oxidation of Formaldehyde

Sci. Eng., 1991, A134, 1070-1073 Amorphous Ni-40Nb-xSn-(3-x)F't alloy ribbons were prepared and used for the electrmxidation of HCHO after surface activation by HF. Maximum activity was observed at - 0.4 at.%Sn. X P S revealed that the surface layer was rich in Pt and deficient in Ni, but that the surface concentration decreased continuously with increasing Sn content.

Electrochemical Properties of Ultra-Fine Palladium Particles for Adsorption and Absorption of Hydrogen in an Aqueous HClO, Solution

K. YAHIKOZAWA, Y. FUJII, Y. MATSUDA, K. NISHIMURA

973-978

A. KAWASHIMA, K. ASAMI and K. HASHIMOTO, Maoter.

N. TATEISHI, K. YAHIKOZAWA, K. NISHIMURA, M. SUZUKI, Y. IWANAGA, M. WATANABE, E. ENAMI, Y.

(7), 1235-1240 MATSUDA and Y. T ~ U , Electrochim. Acta, 1991,36,

Ultra-fine Pd particles were prepared by vacuum evaporation onto a plane of glassy C (GC) rod. Their diameters were estimated to be 2-10 nm by SEM. Properties of Pd/GC electrodes in H adsorption and absorption were characterised by cyclic voltammetry. Adsorption strength of H species on the Pd particles of Pd/GC did not depend on the particle size, whereas amounts of the adsorbed H species and the absorbed ones into the Pd particles were dependent.

Electrochemical Hydrogen lnsertion into Palladium and Palladium-Nickel Thin Films

tmchim. Acta, 1991, 36, (7), 1203-1208 A generator-detector mode with the rotating ring- disk electrode was used to determine the difference between Pd and Pt electrode behaviour and the origin of the larger overpotentials at Pd-H evolving cathodes. The use of thin f h (1-10 pm) Pd disk electrodes has allowed full H or D charging of the metal phase in short times. This electrode system enables measurements of the H uptake in PdH, f h s to be made, with PdH,.,, being the maximum.

J. M. ROSAMILIA, J. A. ABYS and B. MILLER, Elec-

The Role of the Electrolyte Anion in Anodic Dissolution of the Pd(100) Surface T. SOLOMUN, J. Electroanal. Chem. InteflaCial Elec- tmchem., 1991, 302, (1 and 2), 31-46 Electrodissolution of Pd during its electro-oxidation in H,SO, was studied by XPS, LEED, cyclic voltammetry and IR spectroscopy. At the beginning of the surface electro-oxidation reaction Pd species, showing a rather large shift of the (34 core levels (2.5 eV towards the high binding-energy site), were elec- trogenerated at the surface in H,SO,, but not in HCIO, electrolyte. Their concentration was directly related to the anion surface concentration. A surface complex of the type PdO(HS0,) acted as a precursor in the formation of highly soluble PdSO, . Adsorption Properties of an Iridium Oxide Electrode: A Thermodynamic Approach 0. A. PETRII and A. VITIN'SH, Elektdhimiya, 1991, 27, (4), 461-476 Adsorption properties of electrodes made of thermally prepared IrOx, deposited on Ti layers were studied by potentiometric titration during isoelectric conditions in 0.1 M KNO, . A strong dependence of the acid-oxidation properties of the IrO,/Ti electrode on the stoichiometry of the active oxidation surface, characterised by the value of the e lec tde potential at the determined pH of the solution, was observed.

Characterization of DSA-Type Oxygen Evolving Electrodes. Choice of Base Metal

HINDEN, T h e m h i m . Acta, 1991, 176, 31-47 The effect of the base metals: Ti, Ta, Zr, Nb and some of their alloys, on the performance of Ir02- Ta 0 coated DSA-type 0 -evolving electrodes was investigated. The thermal behaviour and 0 affinity sequence of the metals in relation to the electrode preparation procedure were determined ther- mogravimetrically . The chemical and electrochemical stability of the base metal was directly related, through the wear mechanism, to the savice life of the electrode, measured in 30% Hz SO, at 8OoC and 750 mA/crnZ. Ta-based electrodes have the longest ser- vice life of 1700 h, compared to 120 h for Ti-based electrodes.

Morphological and Microstructural Study of the TinrO, -Ta 0 Electrode: Effect of the Preparation Temperature

Electrochim. Acta, 1991, 36, (5/6), 991-998 Morphological and structural examinations of dimen- sionally stable electrode coatings (Ir02-Taz0,) (70:30 mol %) show that at moderate fumg tempexatures, - 55OOC, separation of phases occurs with the formation of agglomerates of I r 0 2 crystals and amorphous Ta,O,. At -750OC both crystalline IrO, and Ta,O, are present.

G. P. VERCESI, J. ROLEWIW, C. COMNINELLIS and J.

G. P . VERCESI, J.-Y. W I N and C. COMNINELLIS,

Platinum Metals Rev., 1991, 35, (3) 157

Reaction between [(TPP)Ru(CO)l'- and Methyl Iodide. Evidence for Formation of a Ruthenium(I1) Carbonyl Methylated Tetraphenylchlorin Derivative

WISH, Inorg. Chem., 1991, 30, (8), 1957-1960 This study provides the first example for elec- trogeneration of a methylated chlorin. The reaction between [(TPP)Ru(CO)l'-, where TPP is the dia- nion of tetraphenylporphyrin, and CH,I differs from that of reduced Co, Fe, and Rh porphyrins because a stable o-bonded CHI derivative is not formed.

Y. J. DENG, X. H. MU, P. TAGLIATESTA and K. M.

PHOTOCONVERSION Photocatalytic Dehydrogenation of Pen- tane in the Presence of RhCl(CO)(PR,), (R = CH,, iso-C,H, and n-C,H9)

CHIKOVA, E. A. GRIGORYAN, A. 0. BORISOV and v. D. MAKHAEV, Kinet. Katal., 1991, 32, (2), 473-477 Studies of the effect of the nature of phosphine ligands on the activity and selectivity of the process during dehydrogenation of p t a n e solutions in the presence of RhCI(CO)(PR,), (R = CHI, iso-C,H, and n-C, H,) were performed in the IR spectra region on >270nm light exposure.

Tris(2,2 '-bipyridine) Ruthenium(I1) Complex by Viologens m Anionic Micellar and Polyelectrolyte Solutions: Variation with Alkyl Chain of Viologens J. w. PARK, M. Y. SUK and B.-T. AHN, Bull. Korean Chem. Soc., 1990, 11, (6), 552-557 Luminescence quenching reactions of photoexcited tris(2,2 '-bipyridine) Ru(I1) complex cation, Ru(bpy) + , by dialkylviologens were studied in Na dodecyl sulphate (SDS), poly(styrenesu1phonate) (PSS) and poly(vinylsu1phonate) (WS) solutions. The relative quenching rate varies widely with the microheterogeneous media used. The highest quenching rate was observed for methyldodecylviologen in homogeneous aqueous medium, dibenzylviologen in SDS and PVS and dimethylviologen in PSS.

Preparation and Photochemical Charac- teristics of the Copolymer Pendant Tris(2,2 '-bipyridine)Ruthenium-Mercury [Ru(bpy), ,+.Hg2C16 Complex R. RAMARAJ, A. K I M and M. KANEKO, J. Photochem. Photobwl. A: Chem., 1991, 56, (2-3), 287-293 The title Ru-Hg copolymer pendant complex was prepared and characterised by IR, visible absorption and emission spectroscopies and emission decay measurements. The solubility and excited state lifetime both in DMF solution and the film state were quite different from those of the low molecular Ru- Hg complex reported before. The emission from the excited ply-Ru-Hg was much longer than that from the poly-Ru in DMF solution.

N. K. KHANNANOV, E. A. KOCHETKOVA, G. N. MEN-

Luminescence Quenching of

APPARATUS AND TECHNIQUE Preparation of an Oxygen Sensor Com- posed of Tightly Stacked Membranel- ElectrodelElectrolyte K. KATAKURA, A. NOMA, z. OGUMI and z. TAKEHARA, Denki Kugaku, 1991, 58, (12), 1184-1189 An amperometric 0 sensor operating at room temperature was constructed using a porous Pt cathode on Nafion and perfluoropolymer as the 0 transport limiting membrane, which was directly bound on the cathode by plasma polymerisation. The 0 reduction current increased with increasing 0 concentration, from 0 to 30 ppm. A microsized 0 sensor can be prepared in principle.

Kinetics of Oxygen Interaction with PtKeO, Sensors: Application of a New Pressure Modulation Spectroscopy A. DUBBE, H. D. WIEMHOFER, K. D. SCHIERBAUM and w. G ~ P E L , Sens. Actuators B, 1991,4, (1 & 2), 23-28 A new method for characterisation of the dynamic response of the electrode potential upon sinusoidal 0, partial-pressure variations, and its powerful application was demonstrated in a study of the kinetics of different Pt electrodes on GO-doped GO, elec- trolytes. Surface diffusion effects play a major part in the overall kinetics of the 0, response of their microstructures. Gradients of the 0 , surface concentration were analysed in an independent spectroscopic study on CeO, samples with Pt contacts.

A Laser Power Detector Built Up by Ap- plication of Thick-Film Technology J. NICOLICS and w. S M ~ A N A , Sens. Actuators A , 1991,

A structure for a laser power detector using thick-film technology was developed. The incident laser radiation caused a heat flow in a metal plate where the resultant temperature differences, detected by thick- fdm Pt sensor elements, acted as a measure of the laser power. The sensitivity of the sensor was calculated and experimentally determined. The in- dicated laser power was independent of the radial in- tensity distribution of the laser beam.

Schottky-Barrier and Conductivity Gas Sensors Based upon PdISnO, and PtiTiO, K. D. SCHIERBAUM, u. K. KIRNER, J . F. GEIGER and w . &PEL, Sens. Actuators B, 1991, 4, (1& 2), 87-94 Electronic conductivity, mixed conductivity and Schottky-barrier sensors based on SnO, and TiO, modified by Pt and Pd metals can be used to detect CO, CH,, H , and 0, gases. Sensor response signals result from changes in surface and bulk conduc- tivities or in Schottky-barrier heights, which are measured using different geometric arrangements of Pt or Pd metal contacts. Studies showed that reliable sensor properties can only be achieved either by forming stable metal/oxide interfaces or by adjusting a stable dopant distribution.

25, (1-3), 235-239


HETEROGENEOUS CATALYSIS Hydrogenation of Olefms on Platinum c.-M. PRADIER and Y. BERTHIER, 3. Catal., 1991,129,

The hydrogenation of buta-1,3-diene and isoprene was studied on three Pt planes. The reaction for buta- diene was structure sensitive, with an increase in the turnover frequency by a factor of 5 from the denser to the rougher planes: Pt(111)<Pt(100)<Pt(110). There is a remarkable correlation between variations of the reaction orders and changes in the selectivity. The surface works as a bi-functional catalyst: hydrogenation and exchange seem not to occur upon the same kind of sites. The catalytic surfaces works with a HC layer present, not identical on the three studied surfaces.

Hydrocracking and Isomerization of n- Octane and 2,2 ,.l-Trimethylpentane over a Platinum/Alumina-Pillared Clay c . DOBLIN, J . F. MATHEWS and T. w. TURNEY, Appl.

The hydrocracking and isomerisation of n-octane and 2,2,4trimethylpentane (TMP) over an AlzO,- pillared clay (A-PILC), containing 0.16% Pt were studied in a microreactor at atmospheric pressure, at 175-325OC and weight hourly space velocity of 0.48-7.5h. The Pt/A-PILC catalyst underwent an initial stabilisation period of -30 h, resulting in changes in the physical structure of the catalyst. The catalyst showed ideal hydrocracking behaviour for nC, giving high isomerisation yields, with a maximum isomer yield of 64% at 80% conversion. For hydrocracking 2,2,4-TMP, the major reaction was A type &scission giving a product with >96% isobutane at all conversions.

Platinum-Tin Complexing and Its Ap- plication to Catalysis

Catalysts for the dehydrogenation of long chain alkanes were prepared by impregnating a y-Al,O, support with a [PtCl,(SncI,),l2 - complex using H,PtCl, and SnCl, solutions in an acidic medium. The catalytic performance of the catalyst prepared by the complex method was remarkably improved compared to the Pt-Sn dehydrogenation catalyst prepared by non-complex methods.

Infrared Study of CO Adsorption on Pt- Rh/A12 0 Catalysts

Faraday Trans., 1991, 87, (9), 1479-1483 Studies of CO adsorption on Pt/Al,O,, Rh/Al,O, and Pt-Rh/Al,O,, at 303-573 K were performed by FTIR spectroxopy. Catalysts containing Rh were precalcined at either 673 K or 873 K before reduction in H, and exposure to CO. The intensities of IR bands due to gem-dicarbonyl and linear carbonyl species were a function of both the precalcination temperature and the temperature of contact with CO.

(2), 356-367

Catal., 1991, 70, (2), 197-212

L. Y. JIN, Apfd. catd., 1991, 72, (I), 33-38

J. A. ANDERSON and C. H. ROCHESTER, J. Chem. SOC.,

Improved Higher Alcohols Selectivity in Syngas Reaction (CO + H2) over Platinum Deposited on Rare Earth Ox- ides of the Fluorite Structure J. EL FALLAH, F. LE NORMAND, s. BOUJANA and A. KIENNEMANN, Eur. 3. Solid Stnte Inorg. Chem., 1991,

The effect of rare earth oxide as support on the reactivity of Pt in syngas conversions was tested. A chain growth process, giving up to C, alcohols is observed on Pt deposited on rare earth oxides of the fluorite type(CeO,,Pr,O,,,Tb,O,).Thisremarkableselec- tivity is explained by the creation of anionic vacancies at the interface of the metallic particle and the support, similar to that previously reported for Pd. On such catalytic sites both the dissociation of the CO molecule and the chain growth process occurs. F'raseodymia gives the most effective support for improved higher alcohol formation.

Hydrogenation of Acetylene over Various Group ,VnI Metals: Effect of Particle Size and Carbonaceous Deposits A. J. DEN HARTOG, M. DENG, F. JONGERIUS and v.

Supported Pt, Pd, Rh and Ir catalysts were studied for the hydrogenation of CzH2 and the effect of the particle size on this reaction was established. Rh and Ir show effects that can most probably be explained by the influence of the particle size on the intermediate of direct hydrogenation to C,H, while for Pt and Pd the effect of deposition of carbonaceous layers prevails.

Gas-Phase Hydrogenation of Styrenes by Transfer over Pd/AlPO, Catalysts

MARINAS and M. E. SEMPERE, React. Kinet. catal. Lett., 1991, 43, (11, 1-6 The hydrogenation of styrene and a-methylstyrene over Pd/AlPO,, using cyclohexene as donor is reported. The catalysts were activated in the pulse reactor and retained H, which was subsequently used to reduce the olefm. The amount of ethylbenzene produced from the styrene can be ac- counted for by H transferred by cyclohexene and H stored over the catalyst surface during treatment with cyclohexene, intended to reduce the impregnating metal salt.

Kinetics of Liquid-Phase Hydrogenation of Hexene-1 on Palladium Sulphide Catalyst L. v. SHALIMOVA, A. D. BERENTS, s. v. wwv and 0. v. CHEBAEVA, Kinet. Katal., 1991, 32, (I), 55-59 Studies of the kinetic dependence of hexene-1 hydrogenation in benzene solution in the liquid phase in a flow system over a Pd sulphide/Al,O, catalyst were performed at 50-150°C and HI pressure of 5 MPa. Intermediate adsorption stages were calculated and an equation for the rate of change of the concentrations of basic components was obtained.

28, Suppl., 433-436

PoNEc, J. Mol. Catal., 1990, 60, (l), 99-108

M. A. ARAhiENDfA, V. BORAU, C. JIMkNEZ, 1. M.


A New Palladium-Catalyzed Coupling Reaction of Vinyl and Allylic Triflates with Pyrimidine Nucleoeides

Vinyl trifluoromethane sulphonates (triflates) form Pd intermediates which react with pyrimidine nucleosides to yield C-5 alkyl substituted nucleosides, after hydrogenation of the vinyk coupling products with H, and Pd/C in MeOH under mild conditions. The reaction is a general one since mono-, disubstituted and cyclic vinylic triflates give high yields of the corresponding C-5 alkyl-substituted nucleoside.

Oxidation State of the Surface of Palladium in the Catalytic Combustion of Hydrogen M. G. JONES, T. G. NEVELL, R. J. EWEN and c. L. HONEYBOURNE, Appl. Catal., 1991, 70, (2), 277-286 The activity of supported Pd catalysts for the oxidation of H, was studied at 80-500°C using a microcalorimetric technique and XPS. The reaction involved a surface layer of 0, , and was inhibited by adsorbed H,O. Palladium(I1) oxide was formed on the surface of metallic Pd under 0, at 45OOC. Heating in H, at 25OOC reduced this surface layer and produced deactivated catalyst but the activity was subsequently restored by exposure to 0,.

Methylcyclopentane Conversion Catalysis by Zeolite Encaged Palladium Clusters and Palladium-Proton Adducts

M. E. HASAN, Can. 3. Chem., 1991,69, (2), 198-200

X. BAI and W. M. H. SACHTLER, 3. Caul., 1991, 129, (l), 121-129 The conversion of methylcyclopentane (MCP) was studied over the prototype catalysts HY, Pd/HY, PdNaHY and proton-free Pd/NaY. Ring opening of MCP to hexane isomers was catalysed by Pd, clusters, but ring enlargement (RE) of MCP to cyclohexane and benzene required metal sites and protons. The RE of MCP was catalysed by the “electrondeficient” [Pd,HI + adducts more effec- tively than by separate metal and acid sites. The catalysts containing Pd and protons in the same zeolite cavity, were dramatically more active for RE than a mixture of HY and proton-free PdNaY.

Direct and Indirect Promotion of PdN and CaZ + Ions x. BAI, z. ZHANG and w. M. H. SACHTLER, Appl. Catal., 1991, 72, (l), 165-178 Studies of Pd in Nay or Cay zeolites tested as catalysts for HC conversion reactions showed that the pre-exchanged Caz + cations in Y zeolite increase the concentration of [Pd,HI+ adducts and subsequently improve the rate and stability of the catalyst for ring enlargement, while decreasing the ring opening rate of methylcyclopentane. The results suggest a direct interaction of the charge compensating ions (Ca’ + or Na+) with Pd particles and an indirect effect viz. by affecting the concentration of electron-deficient Pd- proton-adducts.

Liquid-Phase Oxidation of Propylene on Supported Palladium Mono- and Bimetallic Catalysts in Acetic Acid

A. I. BORONIN and E. M. MOROZ, Kinet. Katal., 1991,

Studies of the oxidation of propylene and propylene glycol and their acetates in acetic acid solutions, in HNO, were performed in the presence of heterogeneous Pd, Pd-Pt and Pd-Rh catalysts deposited on C, SO, and TiO, supports. The Pd-Pt catalysts were found to be most resistant to deactivation in the presence of reactive S. One of the reasons for deactivation of the catalysts was the formation of cyanide metal complexes on the support surfaces.

Effect of Promoters on the Catalytic Ac- tivity of Rh,(CO),2/TiOz for CO Hydrogenation Y. CHEN, J. DU, Y. CHEN and z. DU, 3. Fuel Chem. Technol., 1991, 19, (l), 1-7 The activities for CO hydrogenation in a continuous flow microreactor of promoted Rh catalysts were in the order Rh, N-TiO, >Rh, /Ti0 , >Rh, /Mg-TiO, . On the Rh,N-TiO, catalyst CO was completely converted to CH, at 200OC, while for CO hydrogenation at various H,:CO ratios on Rh,/Mg-TiO,, CO, was always present in the product. Catalyst dispersions were determined by H,-0, titrations. A high H:M ratio occurred for Rh,(CO),,N,O,-TiO,, which was caused by the low temperature reduction of V,O, catalysed by metallic Rh. The H:Rh ratio was in the same order as their activities. Only a twin CO band without linear or bridged CO was found during temperature programmed adsorption and desorption of co. HCN Synthesis from NH, and CH, on Rh and Ir M. P. s u k ~ z and D. G. L~FFLER, React. Kinet. catal. Lett., 1991, 43, (l), 195-199 The synthesis of hydrocyanic acid from CH, and NH, on Rh and Ir wires was studied at temperatures between 1200 and 1500 K, at a pressure of one atmosphere. Activation energies and pre-exponential factors are reported.

The Effect of CeO Support upon Activity and Selectivity of Ru and Co Fischer Tropsch Catalysts

M. WINTERBOTTOM, Eur. J. solid state Inorg. Chem., 1991, 28, (2), 453-456 5% Ru and Co catalysts supported on G O , were prepared by impregnation and characterised by TPR. Their catalytic activities and selectivities were tested in H, and CO reactions and compared with a Ru/SiO, catalyst in the range 1-9 atm and 260OC. RdSiO, and Co/SiO, catalysts gave CH, only at 1 atm and 70% CH, at 9 atm, while Ru/GO, and Co/CeO, gave significantly smaller quantities (20-80%) of CH, over the same pressure range.

A. V. KARANDIN, E. V. GUSEVSXAYA, V. A. LIKHOLOBOV,

32, (2), 367-374

A. F. Y. AL-SHAMhtARY, I. T. CAGA, A. Y. TATA and J.

Platinum MetaE Rev., 1991, 35, (3) 160

HOMOGENEOUS CATALYSIS Substitution of Halogen in Vinylbromide and Reduction of Vinylhalogenides to Ethylene in the Syetem PtO-NaI- HClO4-H 2 0 S. A. MITCHENKO, V. V. ZAMASHCHIKOV and A. A. SHUBIN, Kinet. Katal., 1991, 32, (2), 343-345 Studies of the kinetics of the NaI (2.5 M)- HClO4(O-2.5 M)-H20 system at 8OoC catalysed by Pt(I1) (0.004-0.06 M) showed the substitution of B by iodine in vinylbromide (RBr). When tHCl0,I > 0, parallel substitution of RBr occurred by reduction to ethylene, and in acid solutions the formed vinyliodide also reacted with Pt(II) yielding ethylene. A phase mechanism is provided which includes oxidative addition of vinylhalogenide to Pt(I1) with the intermediate formation of a-vinyl Pt(IV) complexes.

’ H-NMR-Study of Deuterium Exchange in Styrene under the Conditions of Hydrocarboxylation Catalysed by Palladium Complexes YU. G. NOSKOV, N. A. NOVIKOV, M. I. TEREKHOVA and E. s. PETROV, Kinet. Katal., 1991, 32, (2), 331-335 A study of the hydrocarboxylation of styrene catalysed by PdCI,(Ph,P), at 1 10°C and CO pressure of 2.0 MPa by the deuterium exchange method showed that terminal protons of unreacted substrate were noticeably substituted by D, but that proton exchange in the a-position of phenyl groups was not observed. When the pressure was decreased and SnCl, was added, proton exchange occurred in both C atoms of the vinyl styrene group.

Homogeneous Catalytic Hydrogenation of Alkenes by Zero-Valent Palladium Complexes of cis-Fiued Dinitrogen Ligands R. VAN ASSELT and C. J. ELSEVIER, 3. MOl. Catd., 1991, 65, (3), L13-Ll9 Zero-valent Pd complexes (DIAN)Pd(olefm) containing a cis-fmed dinitrogen ligand (DIAN) (N,N’-diaryl-diiminmenaphthene) are active as catalysts in the homogeneous hydrogenation of various unsaturated substrates. The title hydrogenation can be performed under mild conditions (THF, 2OoC and 1-1.5 bar of H, pressure). This results in complete conversion of various substituted alkenes to the corresponding alkanes.

Palladium-Catalyzed Coupling Reactione of Trifluoroacetimidoyl Iodides with Olefins and 1-Alkynes K. ~ A M A and H. WATANABE, Tmahedtim Lett.,

Pd-catalysed coupling of trifluoroacetimidoyl iodides with olefins and also 1-alkpes produced vifluoromethylated a, &unsaturated imines which were transformed into N heterocycles bearing CF , - group. N-aryl vifluoroacetimidoyl iodides underwent smooth palladation with Pd , (dba) , .CHU 3 .

1991, 32, (ll), 1459-1462

Palladium Catalysed Tandem Cyclieation- Anion Capture Processes Initiated by Alkyl- and ?r-Allyl-Palladium Species R. GRIGG, s. SUKIRTHALINGAM and v. SRIDHARAN, Tetrahedron Len., 1991, 32, (22), 2545-2548 Palladium catalysed tandem cyclisation-anion capture processes initiated by oxidative addition of benzylic or allylic halides or acetates to Pd(0) occurred regio- and stereo-specifically in good yield. The benzylic halide reacted with Na tetraphenylborate in the presence of Pd(0) to yield 69 % of the organic species. Examples of “anion” capture involving formate (H-), and organo- Sn, -Zn and -B species are described.

Palladium-Catalyzed @-Vinylation of Vinyl Acetate with En01 Triflates. An Entry to 1 -Acetoxy-1 , 3-Dienes P. G. CIATTINI, E. MORERA and G. ORTAR, Tetrahedron

Reaction of enol viflates with vinyl acetate in the presence of Pd(0Ac) , catalyst produced 1-acetoxy-1, 3-dienes as the major products in 40-79% isolated yields. Formation of the 8-vinylated product was si@icantly favoured. The results showed that steric effects prevail over electronic factors in these organo- Pd reactions, in contrast to the corresponding reactions with enol ethers where electronic factors predominate.

Synthesie of Carboxylic and Phosphonic a-Amino Acids Using Palladium Allylic Alkylation

Lett., 1991, 32, (12), 1579-1582

J. P. GENET, S. JUGE, I. BESNIER, J. UZIEL, D. FERROUD, N. KARDOS, S. ACHI, J. RUIZ-MONIES and S.

78 1-786 THoRIMBERT, Bull. sot. Chim. Fr., 1990, 12, (6),

Schiff bases derived h m glycine and alanine esters were alkylated in the presence of Pd catalysts under neutral or basic conditions using dylic carbonates, esters or halides. Asymmetric Pd allylic alkylation of the benzophenone imine glycine methyl ester using Pd(OAc), + (+)DIOP was achieved with up to 70% ee. After hydrolysis, several functionalised a- aminoacids-enzyme inhibitors-were obtained.

Cationic PaUadium(II)-Diphosphine Com- plexes as Catalysts for the Carbonylation of Alkenes to Ketones

Chem. Soc., Chem. Commun., 1991, (6), 421-423 Cationic Pd complexes of the type [(dppp)Pd (solvent),ltXI,, where X = a non or weakly co-ordinating anion and dppp = 1,3-bis(diphenylphosphino)propane, are active catalysts for the carbonylation to ketones, for the selective formation of E-1,5-diphenylpent-l-en-3-one from styrene. In the presence of water and depending on the acidity conditions dimerisation to the much less catalytically active [(dppp)Pd(p-OH),Pd(dppp)IX, takes place, the structure of which has been determined by X-ray crystallography.

C. PISANO, G. CONSIGLIO, A. SIRONf and M. MORET, 3.


New Highly Water-Soluble Surfactants Stabilize Colloidal Rhodium(0) Suspen- sions Useful in Biphasic Catalysis

Catal., 1991, 65, (3), L35-L40 New highly water-soluble uisulphonated surfactants C H ,, and C ,H efficiently stabilise suspensions of colloidal (20-301) ~ ( 0 ) particles. These novel protective-colloid agents provide the means to per- form catalytic hydrogenations of alkenes without cosolvents in real biphasic liquid-liquid conditions, and to recycle the aqueous colloidal suspensions after decantation.

Selective Catalytic Reduction of Aromatic Nitro Compounds Using CO and Water with Highly Active Rhodium-Phosphine Chelate Complexes

Caul., 1991, 65, (3), L5-L7 The reduction of aromatic nitro compounds, such as nitrobenzene, nitroanilines, chloronitrobenzenes, etc., was found to proceed at significant rates with remarkably high nitro-group selectivities under extremely mild reaction conditions of room temperature, and atmospheric CO pressure, using Rh phosphine chelate complexes. The reduction was complete in the case of pnitroaniline. 1-Nitro- anthraquinone was also converted to l-amino- anthraquinone with extremely high selectivity.

Homogeneous Catalytic Asymmetric Hydrogenolysis of Sodium Epoxysuc- ciuate: the First Example of Asymmetric Hydrogenolysis of an Epoxide A. s. c. CHAN and J. P. COLEMAN, 3. Chem. SOC.,

The fmt example of the asymmetric catalytic hydrogenolysis of an epoxide, Na epoxysuccinate, is discussed in which the chiral product is formed via a critical bond-brraking process using Rh catalysts containing chiral phosphine ligands. The enantioselec- tivity of the catalyst system was found to be independent of the H, pressure, and the reaction rate is faster under higher H, pressure, while the enan- Uoselectivity is lower at higher reaction temperatures.

Regioselective Rhodium-Catalysed Hydroformylation of Olefins: Efficient Synthesis of Ethyl 2-Formylpropanoate from Ethyl Acrylate D. NEIESECKER and R. &u, N m J . Chem., 1991, 15,

Ethyl acrylate hydroformylation was performed using in situ generated catalysts from tRh(CO),ClI, and a phosphole or phosphanorbornadiene at 40°C and 20 bar syngas pressure and was compared to the Rh/1,4bis(diphenylphosphino)butane system. The hydroformylation of ethyl acrylate was brought about under mild reaction conditions by a Rh- monophosphane system. The phosphanorborna- dienes were superior ligands for this reaction.

C. LARPENT, F. BRISE-LE ME" and H. PATIN, 3. MOl.

K. NOMURA, M. ISHINO and M. M A M A , 3. MOl.

Chem. C a m n . , 1991, (9, 535-536

(4), 279-281

Rhodium(III) Biphasic and Phase- Transfer-Catalyzed Hydrogenolysis of Chloroarenes under Exceptionally Mild Conditions v. v. GRUSHIN and H. ALPER, & g a m u ~ ~ i c s , 1991,

The Rh(II1) complexes L,Rh(H)Cl, tL = tricyclohexylphosphine or triisopropylphosphinel were excellent catalysts for the hydrogenolysis of chloroarenes. The reaction proceeded under biphasic (40% NaOH, PhCH,) conditions, or giving higher product yields, under phase-transfer conditions, using benzyltriethylammonium chloride as the quater- nary ammonium salt. The reaction occurred under mild conditions.

Catalytic Tail-to-Tail Dimerization of Methyl Acrylate Using Rh(IIQ Catalysts M. BROOKHART and s. SABO-ETIENNE, 3. Am. Chem.

Cp*(P(OMe),)Rh(C,H,)(H)+(l) (where Cp* is C,Me,) catalysed ethylene dimerisation and further treatment of (1) with methyl acrylate (MA) resulted in initial formation of Cp*(P(OMe),)Rh(CH,CH,- CO,Me)+ followed by slow tail-to-tail dimerisation of MA. A much more reactive catalyst was prepared when Cp*(C, H,)RhCH, CH, CH, -pH+ (2) was used in which P(OMe), was replaced by a labile ethylene ligand. A long-lived catalyst system could be generated by adding neat MA to (2) under 1 atm of H, . Total turnover numbers of up to 1.3 x 10' were achieved with > 99% conversion of MA.

Rhodium(II) Perfluorobutyrate Catalyzed Hydrosilylation of 1-Alkynes. Trans Ad- dition and Rearrangement to AUylsilanes

CLAYTON and J. LIN, organometa&cs, 1991, 10, (5 ) ,

Hydrosilylation of 1-alkynes catalysed by Rh(I1) periluorobutyrate or chloroplatinic acid formed either allylsilaws or vinylsilanes in moderate to high isolated yields, dependent on the mode of addition of reactants. The duality of these transformations depended on co-ordination of the organosilane or akyne with the transition-metal catalyst.

Hydrosilylation of Phenylacetylene via an Oe(SiEt , ) (q2 -H2) Intermediate Catalyzed by OsHCl(C0) (FPr ,)

Organometallics, 1991, 10, (2), 462-466 The five-co-ordinated hydrido carbonyl complex OsHCI(CO)(F'Pr,), catalysed the addition of triethylsilane to phenylacetylene. Trans- and cis- F'hHC=CH(SiEt,) were selectively obtained in high yields depending on the reaction conditions. Although the +yl compound Os((El- HC=CHPh)Cl(CO) (P'Pr,), was the main species under hydrosilylation conditions, the d o n proceeded via the silyl eydrogen intermediate

10, (5 ) , 1620-1622

SOC., 1991, 113, (7), 2777-2779

M. P. DOYLE, K. G. HIGH, C. L. NESLONEY, T. W.

1225-1226

M. A. ESTERIELAS, L. A. OR0 and C. VALERO,

Os(SEt3)CI (11 '-Hd(co)(PPr3) 2.


Ruthenium-Catalysed Aerobic Oxidation of Alcohols via Multistep Electron Transfer

3. Chem. Soc., Chem. Commun., 1991, (7), 473-475 The aerobic oxidation of primary alcohols occurs under mild conditions at 2OoC in air via a triple catalytic system of RuCl(0Ac) (PPh,) ,-hydro- quinone-Co(salophen) (PPh,) [H,salophen = N, N'-bis(salicylidene)-o-phenylenediaminel. The present multistep electron transfer system leads to a very mild aerobic process which can be run under a reduced partial pressure of O,(air).

Formaldehyde and Formates as Sources of Synthesis Gas via Ruthenium- Catalyzed Decomposition Reactions

Mol. Catal., 1991, 64, (3), 337-347 Paraformaldehyde can be decomposed into mostly CO and H, with a Ru phosphine catalytic system, and with the s a m catalyst HCOOH is fully decarbox- ylated into CO, and H,. The best chemical systems for the generation of CO/H2 mixtures are aqueous methyl formate solutions. Ru , (CO) I I - tricyclohexylphosphine decarbonylated methyl formate, and simultaneously catalysed the water gas shift reaction. The catalytic species is [HRu , (CO) ,I I - formed by the reaction of Ru , (CO) with phosphine and water. The present precess can be applied to hydrogenation and to hydrocarbonylation reactions.

Selective Reduction of Dimethyl Oxalate by Ruthenium Carbonyl Carboxylates in Homogeneous Phase. Part IS'

PIACENTI, 3. Mol. Catal., 1991, 64, (3), 257-267 Ethylene glycol can be selectively obtained from dhethyl oxalate by hydrogenation in homogeneous phase in the presence of Ru,(CO),(CH,COO),- (PPr,),. In order to avoid decomposing the substrate the hydrogenation must be performed at 120°C to completely convert the oxalic diester and then at 18OOC to hydrogenate the intermediate methyl glycolate.

Catalytic Carbonylation of Acetone Oxime at Bisoximatodiruthenium Complexes: A Simple Access to Anhydrous Acetonine. Isolation and Molecular Structure of [Ru~(CO),(M~~CNO)~(M~~CNOH)I M. LANGE", n. SMIECKLI-EVANS and G. sfh- FINK, Hdv. Chim. A m , 1991, 74, (3), 549-553 Acetone oxime reacted with CO in the presence of catalytic amounts of [Ru,(CO),(Me,CNO),- (Me,CNOH),l (1) to yield 2,3,4,5,-tetrahydro- 2,2,4,4,6-pentamethylpyrimidine (acetonine), CO , and NH , . The reaction may proceed via carbonylation of Me,C=NOH to the unstable intermediate Me, C = N - OCHO which undergoes decarboxylation to give the corresponding imine Me,C=NH.

J.-E.BdiCKVALL, R. L. CHOWDHURY and U. KARLSON,

G. JENNER, E. M. NAHME and S. LIB-KONRATH, 3.

U. MATl'EOLI, G. MENCHI, M. BIANCHI and P.

Ruthenium Complex-Catalysed Highly Selective Codimerisation of Acetylenes and Alkenes T.-A. MITSUDO, s.-w. ZHANG, M. NAGAO and T. WATANABE, 3. Chem. SOC., Chem. Conmnm., 1991,

2,CDienes were prepared in high yields with high regioselectivity by the codimerisation of acetylenes and alkenes in the presence of a catalytic amount of Ru(cod)(cot), where cod is cycloocta-1,5-diene and cot is cycloocta-1,3,5-triene, at 80OC. The best yield was obtained in pyridine, while in triethylamine, toluene and tri-n-butylamine as solvents, the yields were low.

Reactivity and Catalytic Activity of [RuBr2(Me2SO),l

Chim. Acza, 1991, 179, (l), 17-23 [RuBr,(Me,SO),l was used as precursor for the synthesis of many Ru(1I) complexes containing bromide ion and other ligands. The complexes synthesised were of the types: [RuBr,L,l (L=PPh,; L, =phen or bpy), [RuBr,(Me,SO),L,l (L=py, hPh3; L z =phen, bpy or o-phenylenediamine), etc. [RuBr , (Me SO) , 1 was used as a catalyst for the oxidation of PPh, by 0,.

(8), 598-599

B. C. PAUL, U. C. S A R h U and R. K. PODDAR, h r g .

FUEL CELLS A Methanol Fuel Cell Having a Molybdenum-Modified Platinum-SPE Membrane Electrode H. NAKAJIMA,~. Chem. Technol. Bwtechnol., 1991,50,

Studies of the modiflition of a methanol fuel cell made of a Pt-solid polymer electrolyte composite (Pt- SPE) with Mo showed that adsorption of Mo species on Pt enhances catalytic activity for MeOH oxidation both at F't and Pt-SPE electrodes. The treatment with Mo increased the cell voltage by 100-200 mV at a current density lower than 2 mA per apparent unit area. MeOH permeated through the SPE membrane and reduced stability of the fuel cell.

(4), 555-561

CORROSION PROTECTION Alloys Cathodically Modified with Noble Metals J. H. POTGIETER, 3. Appl. Electmchem., 1991,21, (6), 47 1-482 Cathodic alloying platinum group metal additives to Cr greatly increases the corrosion resistance of Cr in non-oxidising acid environments. The corrosion resistance of Fe-Cr stainless steels was significantly increased by addition of <0.5% of platinum group metals. When Mo and platinum p u p metals occurred together in the alloy, a synergistic beneficial effect was exerted on the corrosion mistance. AUoyiug of stainless steels with Pd leads to a significant increase in the corrosion resistance of the steels.


CHEMICAL TECHNOLOGY ELECTRICAL AND ELECTRONIC ENGINEERING New Methods of Uranium0 Production

Using a Pt-Loaded . Gas-Diffusion Electrode M. SHIBATA and N. FURWA, 3. Appl. Electrochem.,

A local-cell mode and a fuel-cell mode are proposed as new methods for the production of uranous nitrate. In the local-cell mode the cell consists of a Pt loaded gas diffusion electrode and a system of circulation for uranyl nitrate solution and H gas, although H gas is required instead of the power source. H gas is the more economical method if it is easily obtained. In the fuel-cell mode the reduction can take place at a Pt gauze cathode in the catholyte, above the gas diffusion electrode. Uranyl ions are spontaneously reduced to 250-300 gldm' U(1V) using these methods and electrical energy is obtained by the fuel-cell mode.

Water Gas Shift Reaction Assisted by a Palladium Membrane Reactor

Eng. Chem. Res., 1991, 30, (3), 585-589 The water gas shift reaction was operated at 673 K in a double tubular type membrane reactor, the inner tube of which was Pd membrane of thickness 20 pm, supported on a porous glass cylinder. The membrane reactor gave higher levels of CO conversion beyond the equilibrium attainable in a closed system, resulting from a shift of thermodynamic equilibrium toward the product side, caused by the selective and rapid removal of H from the reaction system. The amount of steam needed to achieve reasonable levels of conversion could be reduced, and from computer simulation, the high reaction efficiency attained by this membrane reactor is credited to the thinness of the Pd fdm.

1991, 21, (3), 226-230

S. UEMIYA, N. SATO, H. ANDO and E. KIKUCHI, Id.

GLASS TECHNOLOGY Heterogeneous Platinum Nucleation and Crystallization of a Heavy-Metal Fluoride Glass

Am. Ceram. Soc., 1991, 74, (4), 788-796 The effect of controlled heterogeneous nucleation by Pt on the crystallisation of a ZrF,-BaF,-LaF,-AlF,- NaF glass was studied, using various levels of Pt doping introduced into the glass by a combination of PtCl, doping and melting-atmosphere variation. The effect of doping levels and melting conditions on the incorporation of Pt and the subsequent nucleation of crystals was studied by optical microscopy, SEM, DSC and XRD. Increased Pt in the glass increased the number of nucleation sites for the growth of p- ZrF,-BaF, crystals. The crystallisation of this glass changed from surface controlled to bulk controlled with an increased number of nuclei. An accurate ap- proximation of the number of nuclei in the glass was also found.

J. M. JEWELL, J. JAGANATHAN and I. D. AGGARWAL, 7.

Conduction Mechanism in PtSi/Si Schottky Diodes M. WITTMER, Phys. Rev. B, 1991, 43, (5), 4385-4395 The conduction mechanism in PtSi/Si Schottky diodes was studied over temperatures 80-300 K. Above 100 K the forward current-voltage (IN) characteristic of the diodes is highly ideal and obeys the thermionic-emission theory, including image- force lowering of the barrier. Some diodes show a deviation from this behaviour, due to carrier recom- bination in the depletion region. Carrier recombina- tion is also responsible for the soft behaviour of the reverse I N characteristic. The temperature dependence of the barrier height and the bias- independent position of the quasi-Fermi-level at the interface are associated with a high density of interface states. The activation energy for current transport at low temperatures suggests that these states are due to substitutional Pt atoms on the Si.

The Effect of Sintering Temperature on the Barrier Height of pType PtSi Schottky Diodes V. W. L. CHIN, S. M. NEWBERY, J. W. V. STOREY and U. THEDEN, AUt. 3. Phys., 1991, 44, (I), 67-72 The effect of sintering temperature on the barrier height of p-type <100> PtSi Schottky diodes was studied by various means. The diodes sintered in a furnace under foaming gas at 35OOC for 40 min had a barrier height of 0.235 eV, which is lower than diodes sintered at 475OC for an additional 20 minutes (0.290 eV). For IR detection a low barrier height and high IR responsivity are necessary. Thus sintering by the first method is preferable, giving a cutoff wavelength of 5.3 pm at a reverse bias of 2 V, and a Schottky emission coefficient of -0.5 eV-".

Ultraviolet, Visible, and Infrared Response of PtSi Schottky-Barrier Detec- tors Operated in the Front-Illuminated Mode C. K. CHEN, B. NECHAY and B.-Y. TSAUR, IEEE Trans. Electron Devices, 1991, 38, (9, 1094-1103 The quantum efficiency of PtSi Schottky barrier detectors was measured as a function of wavelength, from 0.23-7 pm. For front-illuminated PtSilp-Si devices at low temperatures, quantum efficiencies of 40-70% are obtained for the UV and visible regions with little loss of the IR photoresponse that is obtained for operation in the conventional back- illumination mode. At room temperatures for front- illumination the quantum efficiencies are - the same in the UV and visible regions, but the IR response decreases abruptly beyond the Si absorption edge. Calculated quantum efficiencies in the UV and visible regions agree well with measured efficiencies. The temporal response of front-illuminated PtSilp-Si was fast enough for operation at video frame rates.

Platinum Metak Rev., 1991, 35, (3) 164

Wear Reliabiliiy of Gold-Flashed Palladium vs. Hard Gold on a High-speed Digital Connector System

Plat. Surf. Finish., 1991, 78, (3), 5743 The wear characteristics of Au-flashed Pd and hard Au terminals in high-speed digital connector systems were evaluatedafter 60, 125, 250, 375, 500 and 1000 insertion and withdrawal cycles for thicknesses in the range 1.25 to 2.5 pm. Contact areas and wear tracks were examined by various techniques. The location, size, shape and depth of wear tracks were quan- titatively examined and compared.

Thermal Stability of Pd-In Ohmic Con- tacts to n-GaAs Formed by Scanned Elec- tron Beam and Rapid Thermal Annealing

Lett., 1991, 27, (2), 149-151 Thermally stable and low resistance Pd-In ohmic contacts to n-GaAs were formed using scanned electron beam (SEB) and rapid thermal annealing (RTA). A specific contact resistance e, of - Q cm2 was obtained using both techniques with the SEB annealed contacts exhibiting a superior surface morphology. High temperature ageing of the contacts showed that the SEB annealed contacts were more stable than RTA contacts, as displayed by an increase in their respective e, values, a factor of - 5 for SEB annealed contacts, against an increase by a factor of -8 for RTA contacts after 25 h of ageing.

Thermally Stable and Nonspiking Pd/Sb(Mn) Ohmic Contact to p-GaAs

E. J. KUDRAK, J. A. ABYS, I . KADIJA and J. J . MAISANO,

K. PRASAD, L. FARAONE aiid A. G. NASSIBIAN, Electron.

C. C. HAN, X. Z. WANG, S. S. LAU, R. M. POTEMSKI, M. A. TISCHLER and T. F. KUECH, Appl. PbS. Lett., 1991, 58, (15), 1617-1619 A thermally stable, nonspiking Pd/Sb(Mn) ohmic contact to p-GaAs was developed based on the solid- phase regrowth mechanism. The contact metallisa- tion consisted of a layered structure of Pd(250 i)/Sb(100 A)/Mn(lO A)/Pd(250 A)/p-GaAs. Rapid thermal annealing of the contact at 50OOC for 10 s yielded contact resistivities of - 2 x 10W6 cm’ and 4 x lo-’ Q cm’ on substrates doped to 2.5 x IO1*/cm3 and 4 x 1019/cm3, respectively.

Temperature Cycling Effec9s between Sn/Pb Solder and Thick Film Pd/Ag Con- ductor Metallization B.-S. ~ I O U , K. c. LIU, J.-G. DUH and P. s. PALANISAMY, IEEE Trans. Components, Hybrids, Manuf Technol., 1991, 14, (l), 233-237 Thermal cycling effects on the solder joint between thick f im mixed Pd/Ag conductor and Sn/Pb solder are investigated. Microstructural evolution of the interfacial morphology, elemental and phase distribution are probed by electron microscopy and XRD. Microstructural analysis reveals the formation of intermetallic compounds: Pd Sn, Pd, Sn, Pd Sn ,, PdSn, Pd,Pb, Ag,Snand Ag,Sn after thermal cycles from -55 to +125OC.

Contact Resistance Characteristics of Noble Metal Alloys for Connector Contacts s. UMEMURA, K . 4 . YASUDA and T. AOKI, IEEE Trans. Componenrs, Hybrids, Manuf Technol.. 1991,14, ( I ) ,

Contact resistance characteristics, corrosion characteristics and the degradation mechanism for Pd, Ag, Au and Ni containing binary and ternary alloys were investigated to find useful lower cost noble metal alloy for connector contacts. The test conductor contacts are clad inlays mated with each other, clad inlays mated with hard gold plating and clad inlays with hard gold flash mated with inlays of the same material. Air mixed with SO,, NO,, Cl, or H,S were the test gases. The following alloys are listed in order of increasing contact resistance: Au- Ag, Ag-Pd, Au-Ag-Pd, Au-Pd and Pd-Ni. The domi- nant corrosion products causing an increase in contact resistance were the chlorides in Pd alloys.

A Study of the Discharge Phenomena of Rhodium-Plated Contact Reed Switches T. KOBAYASHI, K. HINOHARA and C. KAWAKITA, IEEE Trans. Componenrs, Hybrids, Manuf Technol., 1991, 14, (l), 20-22 The discharge phenomena of high breakdown voltage reed switches, such as the pressurised reed switch and vacuum reed switch, and the discharge phenomena of general purpose reed switches, with respect to their basic mechanism and reactions were studied. Rh- plated reed switches with contacts treated with high temperature 0 for surface deactivation were used in the study. lXe contacts were analysed after discharge, and it was found that the N cation and 0 anion serve as carriers in the discharge for the pressurised reed switch and general purpose reed switch, and a nitride is formed on the cathode and oxidation increases on the anode. In the vacuum reed switch, the 0 anion triggers the discharge as a carrier, and oxidation increases on the anode.

181-186

MEDICAL USES Screening of a Stable Cholesterol Ox- idase for the Fabrication of Microbiosen- sor of Cholesterol by the Embodiment of Cholesterol Oxidase and a Platinized Platinum Electrode

IKARIYAMA, Denki Kagaku, 1990, 58, (12),

Microbiosensors for cholesterol of diameter 100 pm were fabricated by direct imbilisation of cholesterol oxidases from different sources on a platinised Pt electrode. The response current of the cholesterol senwr decreased gradually at +0.6 V (vs. Ag/AgCl), however, reproducible, stable responses were obtained at +0.5 V. The response of the microbiosensor for cholesterol determination was very rapid, the response time being 20 s. This sensor detects cholesterol contents of 1.3-52 pM.

S. YAMAUCHI, M. YAOITA, R. NAGAI, Y. YOSHIDA and Y.

1 103- 1106


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