Platinum Metals Rev., 1999, 43, (1), 41
ABSTRACTS: January 1999
of current literature on the platinum metals and their alloys
Mechanism of Platinum-Enhanced Oxidation of Silicon at Low Temperatures
h. kobayashi, t. yuasa, k. yamanaka, k. yoneda and y. todokoro, J. Chem. Phys ., 1998, 109, (12), 4997–5001.
Pt-enhanced oxidation of Si below 300°C was studied using a Pt layer deposited on 1 nm thick Si oxide-covered Si. The Si oxide layer grew between the Pt layer and the Si substrate on low temperature heat treatment, but where Pt was directly deposited on the Si substrate Si oxide formed, mainly on the Pt layer. Oxidation is enhanced by applying a positive bias voltage to the Si substrate during heat treatment. O ions are the moving species in the oxide layer. The reaction at the interface is the rate-determining step.
Transformations in Undercooled Molten Pd40.5Ni40.5P19
c. w. yuen and h. w. kui, J. Mater. Res ., 1998, 13, (11), 3034–3042
Liquid phase separation by nucleation and growth (LNG) occurred in undercooled molted Pd40.5, Ni40.5P19 for undercooling ΔT ≤ 60 K (ΔT = T 1 – T 3 where T1 is the liquidus and T is the kinetic crystallisation temperature). Liquid state spinodal decomposition (LSD) occurred for ΔT ≥ 100. The transition regime from LNG to LSD occurs for 60 ≤ ΔT ≤ 100 K. LSD is an important factor in glass-forming in metallic alloys.
Surface Composition of Ru Containing Duplex Stainless Steel after Passivation in Non-Oxidizing Media
g. myburg, k. varga, w. o. barnard, p. baradlai, l. tomcsÁnyi, j. h. potgieter, c. w. louw and m. j. van staden, Appl. Surf. Sci ., 1998, 136, (1/2), 29–35
The passive layers which form spontaneously on duplex stainless steels (DSSs) and 0.3% Ru duplex stainless steel (DSS:Ru) in HCl and H2SO4 were studied. Cr concentrations were ∼3% higher in the passive layers of both, but Ni concentrations were lower. Mo enrichment was only observed for DSS:Ru pas-sivated in HCl. The passive layer on DSS:Ru contained more Cr2O3 than Cr(OH)3 and more Fe2+ than Fe3+, compared to DSS.
The Shape Memory Effect in Equiatomic TaRu and NbRu Alloys
r. w. fonda, h. n. jones and r. a. vandermeer, Scr. Mater ., 1998, 39, (8), 1031–1037
Shape memory (SM) alloys based on Nb50Ru50 (1) and Ta50Ru50 (2), have SM transition temperatures > 1000°C. The SM effect is due to the high temperature, tetragonal-to-cubic (β to β′) phase transition at 885°C for (1) and 1120°C for (2), and occurs at Ru contents of ∼ 40–55%.
Time-Reversal Symmetry-Breaking Superconductivity in Sr2RuO4
g. m. luke, y. fudamoto, k. m. kojima, m. i. larkin, j. merrin, b. nachumi, y. j. uemura, y. maeno, z. q. mao, y. mori, h. nakamura and m. sigrist, Nature, 1998, 394, (6693), 558–561
Muon spin-relaxation measurements are reported on the superconductor Sr2RuO4. These show the spontaneous appearance of an internal magnetic field below the transition temperature. The superconducting state is characterised by the breaking of time-reversal symmetry which, with other symmetry considerations, suggests that superconductivity in Sr2RuO4 is of ‘p -wave’ (odd-parity) type, analogous to superfluid 3He.
Pt11-Directed Self-Assembly of a Dinuclear Cyclophane Containing Two Fullerenes
t. habicher, j.-f. nierengarten, v. gramlich and f. diederich, Angew. Chem. Int. Ed ., 1998, 37, (13/14), 1916–1919
Self-assembly of two C60 hexakis-adducts, each with a di(4-pyridyl)methano addend, and two Pt” centres yielded the fullerene-containing rigid dinuclear cyclophane (1), a new class of supramolecular multìfullerene arrays. X-ray crystallography of (1) showed a perfectly planar parallelogram formed by four vertex atoms of the cyclophane at the cost of substantial angle strain. Larger complex fullerene arrays should be possible.
Synthesis and Characterization of New Rh(III) Compounds with the K4CdCl6 Structure-Type: Sr3M RhO6 (M = Y, Sc, In)
r. c. layland, s. l. kirkland, p. nÚÑez and h.-c. zur loye, J. Solid State Chem ., 1998, 139, (2), 416–421.
Sr3MRhO6 (M = Y, Sc, In) compounds were syn-thesised and structurally characterised by Rietveld refinement of powder XRD data in the space group R3c; Z = 6. The compounds, which are isostructural with K4CdCl6, have a structure of infinite one-dimensional chains of alternating face-shared RhO6 octahedra and M O6, trigonal prisms. The Sr cations are located in a distorted square antiprismatic position.
Ruthenium Carbonyl Clusters in Faujasite Cages: Synthesis and Characterization
g.-c. shen, a. m. liu and m. ichikawa, Inorg. Chem ., 1998, 37, (21), 5497–5506
[Ru3(CO)12] clusters in faujasite, Na56Y, cages are activated at 298–363 K in H2 giving intrafaujasite anchoring of [H4Ru4(CO)12]. RuIII(NH3)6 in Na56X in CO/H2 activated slowly at 298–363 K, via conversion of intermediates [Ru(NH3)5(CO)]2+ and Ru1(CO)3 to [Ru6(CO)18]2-. The Na+ α-cage cations and faujasite topology are significant in the anchoring mechanism.
Relay of Positive Holes from Photoirradiated Pt-Loaded TiO2 Particles in an Aqueous Phase to t -butylhydroquinone in an Oil Phase
t. ohno, k- nakabeya, k. fujihara and m. matsumura, J. Photochem. Photobiol., A: Chem ., 1998, 117, (2), 143–147
Evolution of H2 and oxidation of I ions proceeded concurrently on photoirradiated Pt-loaded TiO2 particles suspended in aqueous Kl-containing solution. The photochemical reaction is stopped by the back reaction, when I3- ions, which are preferentially reduced over H2 evolution, reach a certain level. Addition of t -butylhydroquinone/t -butylquinone dissolved in an oil phase, produced a redox reaction where the I3 ions oxidise the f-butylhydroquinone. The product concentration in the aqueous phase can thus be kept low.
Chemiluminescence and Catalysis of the Decomposition of Dimethyldioxirane Adsorbed from the Gas Phase on Silipore Containing a tris(bipyridyl)ruthenium Complex Ru(bpy)3Cl2 and 9, 10-diphenylanthracene
d. v. kazakov, a. i. voloshin, n. n. kabal’nova, s. l. khursan, v. v. shereshovets and v. p. kazakov, Izv. RAN, Ser. Khim ., 1998, (8), 1516–1521
The kinetics of the decomposition of dimethyldioxirane (DMD) adsorbed from the gas phase on a silipore surface was studied in the presence of chemi-luminescent (CL) activators, such as Ru(bpy)3Cl2 (1) and 9, 10-diphenylanthracene. The CL yield of the DMD decomposition was estimated at 4 × 10-9 Einstein mol-1 and the chemiexcitation yield of methylacetate was estimated at 4 × 10-4.
Intrazeolitic Photoreactions of Ru(bpy)33+ with Methyl Viologen
s. k. das and p. k. dutta, Langmuir, 1998, 14, (18), 5121–5126
The reaction of Ru(bpy)33+-zeolite Y with H2O to give Ru(bpy)32+ was greatly accelerated (hours) by visible light, compared to the dark (days), even though intermediate species were similar. The promotion of reactivity by light is attributed to the nature of the visible charge-transfer bands. Reactivity is enhanced when ion-exchanged methyl viologen is in nearby supercages and there is spectral evidence of pyridone production.
Multistep Photocatalytic Reduction of Dioxygen by Immobilized [Ru(bpy)3]2+ in Nafion and Cellulose Matrices and Macrocyclic Cobalt(III) Complexes
j. premkumar and r. ramaraj, J. Chem. Soc., Dalton Trans ., 1998, (21), 3667–3672
The multistep one-electron photocatalytic reduction of O2 to H2O2 was performed using systems of [Ru(bpy)3]2+ (1) incorporated into membranes of Nafion and cellulose, and macrocyclic Co(III) complexes, as the catalyst. The electron transfer process took place efficiently in the membrane rather than in homogeneous solution.
Efficient Light-to-Electrical Energy Conversion with Dithiocarbamate-Ruthenium Polypyridyl Sensitizers
r. argazzi, c. a. bignozzi, g. m. hasselmann and g. j. meyer, Inorg. Chem ., 1998, 37, (18), 4533–4537
Ru(dcbH)(dcbH2)(L) sensitisers, where L is diefhyldithiocarbamate, dibenzyldithiocarbamate or pyrrolidinedithiocarbamate, dcbH is 4-(COOH)-4′-(COO)-2, 2′-bipyridine, and dcbH1 is 4, 4′-(COOH)2-2, 2′-bipyridine, were anchored to nanocrystalline TiO2 films for light to electrical energy conversion in regenerative photoelectrochemical cells. The sensitisers have intense MLCT bands centred at ∼ 380 and 535 nm that sensitise TiO2 over a broad spectral range. Interfacial electron transfer processes are quantified.
Effects of RuO2 on Activity for Water Decomposition of a RuO2/Na2Ti3O7 Photocatalyst with a Zigzag Layer Structure
s. ogura, m. kohno, k. sato and y. inoue, J. Mater. Chem ., 1998, 8, (11), 2335–2337
Na2Ti3O7 (1), having a zigzag layer structure containing highly dispersed RuO2, decomposes H2O to H2 and O2 upon UV irradiation. Photocatalyst (1) was impregnated with RuCl3 aqueous solution or Ru3(CO)12 dissolved in tetrahydrofuran. The Ru loading was 0.7 wt.%. The ability to form O surface radicals upon UV irradiation may be correlated with the photocatalytic activity in this layered titanate.
New DNA-Binding Ruthenium (II) Complexes as Photoreagents for Mononucleotides and DNA
c. moucheron and a. kirsch-de mesmaeker, J. Phys. Org. Chem ., 1998, 11, (8/9), 577–583
The spectroscopic properties of two photoprobes for DNA, Ru(phen)2 (PHEHAT)2+ (1) and Ru(TAP)2- (PHEHAT)2+ (2) (phen = 1, 10-phenanthroline, TAP = 1, 4, 5, 8-tetraazaphenanthrene, PHEHAT = 1, 10-phenanthrolino [5, 6-b ] -1, 4, 5, 8, 9, 12-hexaazatriphenylene) were studied and compared with complexes containing either an extended planar ligand or π -acceptor ligands. Complex (1) luminesces upon intercalation between DNA and base pairs while the luminescence of (2) was quenched by binding to DNA.
ELECTRODEPOSITION AND SURFACE COATINGS
Preparation of Hydrophobic Platinum Electrodes by Composite-Plating
y. ono, t. kamata, s.-h. kim, m. yasuda, a. yoshiyama, t. nonaka and y. nishiki, Denki Kagaku, 1998, 66, (7), 720–726
Hydrophobic Pt electrodes were prepared by composite-plating Pt with PTFE fine particles on Pt substrate in an amidosulfuric acid-dinitrodiammine Pt complex bath, containing a cationic surfactant under ultrasonic irradiation. Optimised electrodes had contact angles with water > 150°, and were stable in strongly acidic, neutral and alkaline solutions, after anodic and cathodic polarisation at 200 mA cm-2, for 10 h.
Electrodeposited Platinum Microparticles in a Sulfonate-Polyaniline Film for the Electrosorption of Methanol and Sorbitol
c.-h. yang and t.-c. wen, Electrochim. Acta, 1998, 44, (2–3), 207–218
Studies of Pt microparticles electrodeposited into a 2, 5-diaminobenzenesulfonic acid-modified polyani-line (SPANI) film on IrO2 electrodes showed that under constant deposition potential the microparticles were dispersed in the SPANI in a three-dimensional array. This procedure yielded spherical catalyst particles. For catalyst loadings of ∼ 7 mg cm-2 deposited at -200 mV, the electrosorption coverages of sorbitol are greater than those of MeOH by ∼ 15%.
Formation of Catalytic Pd on ZnO Thin Films for Electroless Metal Deposition
r. d. sun, d. a. tryk, k. hashimoto and a. fujishima, J. Electrochem. Soc ., 1998, 145, (10), 3378–3382
The formation of highly dispersed Pd species on ZnO thin films as a catalyst for electroless metal deposition was studied. A yellow-brown Pd species, identified as hydrolytic Pd(OH)2, was efficiently adsorbed onto the ZnO surface which had been made highly porous by partial dissolution in acidic PdCl2. In the subsequent electroless metal deposition step, Pd(OH)2 was first reduced to Pd(0) by a reductant, such as HCHO, contained in the deposition bath. Pd particles can thus act as highly active catalytic nuclei for several types of electroless metal depositions.
Pulsed Electrodeposition Synthesis and Hydrogen Absorption Properties of Nanostructured Palladium-Iron Alloy Films
k. j. bryden and j. y. ying, J. Electrochem. Soc, 1998, 145, (10), 3339–3346
Nanostructural pure Pd and Pd-Fe alloy films for H2 separation and membrane reactions were prepared by pulsed electrodeposition. Crack-free films were prepared using short pulse duration, long times between pulses and a plating temperature of 60°C. Films containing > 20 at.% Fe were stable against grain growth to 400°C without any α→β phase transition. The Pd-Fe nanoalloys had very fast H2 absorption kinetics at room temperature, without activation.
APPARATUS AND TECHNIQUE
Photoelectrochemical Fabrication of Submicrometer Platinum Pattern on Titanium Dioxide Single Crystal Surface
h. ishii, s. juodkazis, s. matsuo and h. misawa, Chem. Lett. Jpn ., 1998, (7), 655–656
Submicrometer patterning of TiO2-rutile single crystal surfaces by Pt was achieved using photocatalytic reduction of PtCl42- to Pt in an aqueous solution of H2PtCl6. Pt patterns, ∼ 700 nm wide, were fabricated along the focal point traces of a 380 nm wavelength laser beam (power 158 μW) on me rutile substrates. The stage velocity was 0.43 μm s-1. Using this technique, fabrication of well defined Pt patterns, formed of Pt islands 50∼200 nm in size, is possible.
A Novel Ni-Ru-P Amorphous Alloy Composite Membrane and Its Performance Study
g. wu, b. liu and j.-f. deng, Chem. Lett. Jpn ., 1998, (9), 889–890
A Ni-Ru-P amorphous alloy composite membrane supported on ceramic tube was prepared by electroless plating, first by high temperature activation of the outer surface with a paste containing PdCl2 then by plating in a solution containing NiCl2+6H2O, NaH2PO2, RuCl3, Na3C6H5O7.2H2O, NH4Cl and triethenolamine. The Ni88.6Ru0.2P11.2 amorphous membrane had better permselectivity for H2 than porous and Ni-P membranes. The Ni-Ru-P membrane reactor itself had a promoting effect on EtOH dehydrogenation.
Determination of Sulfite in Sugar and Sulfur Dioxide in Air by Chemiluminescence Using the Ru(bipy)32+-KBrO3 System
f. wu, z. he, h. meng and y. zeng, Analyst, 1998, 123, (10), 2109–2112
Sulfite in sugar and SO2 in air were determined by a chemiluminescence (CL) method using Ru(bipy)32+-SO32--KBrO3 (bipy = 2, 2′-bipyridyl) and triethanolamine as SO2 absorbent material. The sulfite concentration was proportional to the CL intensity in the range 2.5 × 10-8 − 9.5 × 10-5 1-1. The limit of detection was 3.8 × 10-9 mol 1-1 and the relative standard deviation was 4.6% for 5 × 10-1 mol 1-1 sulfite solution.
Light Emitting Electrochemical Devices from Sequentially Adsorbed Multilayers of a Polymeric Ruthenium(II) Complex and Various Polyanions
a. wu, j. lee and m. f. rubner, Thin Solid Films, 1998, 327–329, 663–667
Solid-state light-emitting electrochemical devices were made from sequentially adsorbed multilayers, 7–59Å thick per bilayer, of a positively charged polyester containing Ru(bpy)32+ polyester and polyanions. Devices fabricated with polyanions containing weakly acidic carboxylic acid groups displayed symmetric behaviour but more diode-like behaviour was observed where the polyanions contained the strongly acidic sulfonic acid group. The best devices had an external quantum efficiency of 3.2% (photons/electron) and a maximum light output of ∼ 1350 nW with poly(acrylic acid) as the polyanion.
Oxidative Conversion of Methane to CO and H2 over Pt or Pd Containing Alkaline and Rare Earth Oxide Catalysts
v. r. choudhary, b. prabhakar, a. m. rajput and a. s. mamman, Fuel, 1998, 77, (13), 1477–1481
The activity and selectivity of Pt and Pd (1.0 wt.%) catalysts containing MgO, CaO and rare earth oxides, were studied in the oxidative conversion of CH4 to CO and H2 at 700 and 800°C for low contact times. Pt/Gd2O3 and Pd/Sm2O3 performed best, with high selectivity for CO but low selectivity for H2 due to the reverse H2O gas shift reaction.
Ultrasonic Irradiation as Activity and Selectivity Improving Factor in the Hydrogenation of Cinnamaldehyde over Pt/SiO2 Catalysts
g. szÖllÖsi, b. tÖrÖk, g. szakonyi, i. kun and m. bartÓk, Appl. Catal. A: Gen ., 1998, 172, (2), 225–232
The effect of ultrasound on the Pt catalysed hydrogenation of cinnamaldehyde was studied in the liquid phase over Pt/SiO2, Pt/Al2O3, Pt/C and EuroPt-1 catalysts at 333 K and under 1 atm H2. Over the Pt/SiO, catalyst, sonochemical pretreatment greatly improved the chemoselectivity of the formation of cinnamyl alcohol (80%), with the reaction rate increasing twofold. The beneficial effect of the ultrasound is explained by assuming the formation of effective metal-support active centres, which provide stronger acceptor sites for C=O adsorption.
Water-Promoted Ammonia Oxidation by a Platinum Amine Complex in Zeolite HZSM-5 Catalyst
a. c. m. van den broek, j. van grondelle and r. a. van santen, Catal. Lett ., 1998, 55, (1–4), 79–82
[Pt(NH3)4]HZSM-5 was found to be an active catalyst for NH3 oxidation at low temperature (473 K) and becomes even more active in the presence of H2O. The reaction was carried out both with a reaction mixture containing H2O and one which was dry. The selectivity to N2 was increased in the presence of H2O and it appears that H2O enhances the reaction rate for N2 production.
Two Reaction Paths at Different Temperatures in the Reduction of Nitrogen Monoxide with Hydrogen over Supported Palladium Catalysts
a. ueda, t. nakao, m. azuma and t. kobayashi, Chem . Lett. Jpn ., 1998, (7), 595–596
Two conversion maxima at 373 and 573 K, were discovered in NO reduction with H2 over Pd catalysts supported on metal oxides, when O2 is present in the stream of reactants. This is due to a switch in the reaction path, as the temperature is raised, between the direct reduction of NO by H2 and the reduction by H2 of in situ generated NO2. Among the Pd catalysts studied, Pd/TiO2 showed the highest conversion of NO.
Polymer-Supported Palladium-Nickel Bimetallic Catalyst for the Regioselective Hydroesterification of Styrene
b.-s. wan, s.-j. liao, y. xu and d.-r. yu, J. Mol. Catal., A: Chem ., 1998, 136, (3), 263–268
The polymer-supported PVP-PdCl2-4NiCl2-PPh3 bimetallic system [PVP = poly(N -vinyl-2-pyrrolidone)] gave 100% conversion and 99% selectivity to the branched ester in styrene hydroesterification at 80°C and 2.1 MPa CO pressure in 10 h. The remarkable selectivity and activity were caused by a strong synergic effect of PdCl2-NiCl2 and a polymer protection effect. The catalytically active species are nm sized particles with Pd(0) species.
Orthopalladated Triaryl Phosphite Complexes as Highly Active Catalysts in Biaryl Coupling Reactions
d. a. albisson, r. b. bedford, s. e. lawrence and p.n.scully, Chem. Commun ., 1998, (19), 2095–2096
Orthopalladation of tris(2, 4-di-tert -butylphenyl) phosphite produced a dimeric Pd complex which is a very active catalyst in biaryl coupling reactions. For the coupling of aryl halides (4-bromoacetophenone as substrate) with phenylboronic acid (Suzuki reaction) high turnover numbers (TONs) of 1, 000, 000 [mol product (mol Pd) 1] and turnover frequencies of ∼ 900, 000 [mol product (mol Pd)-1h-1] were obtained in toluene at 110°C, while when aryl bromides (4-bromoacetophenone) reacted with aryltin reagents (Stille reaction) TONs of ≤ 830, 000 were obtained.
A Highly Selective Water-Soluble Dicationic Palladium Catalyst for the Biphasic Hydroxycarbonylation of Alkenes
m. schreuder goedheijt, j. n. h. reek, p. c. j. kamer and p. w. n. m. van leeuwen, Chem. Commun ., 1998, (22), 2431–2432
The biphasic Pd-catalysed formation of carboxylic acids from alkenes and CO in the presence of a water-soluble bidentate diphosphine catalyst with a xan-thene-type backbone and a Bronsted acid cocatalyst is described. The dicationic Pd/Xantphos-s/TsOH system was very effective and 100% selective in the hydroxycarbonylation of alkenes. Under optimised conditions, metallic Pd formation was not observed and initial turnover frequencies dropped only slightly within hours, showing the high stability of the system.
A Water-Soluble Rhodium Complex as a Catalyst Precursor for the Hydroformylation of Olefins
s. u. son, j. w. han and y. k. chung, J. Mol. Catal., A: Chem ., 1998, 135, (1), 35–39
A H2O-soluble cationic (sugar-substituted arene) rhodium complex was prepared by the reaction of [Rh(COD)Cl2] with AgBF2 and then with phenyl-β-D-glucopyranoside. The Rh complex displays exceptionally high regioselectivity and high conversion to branched-chain aldehydes in the hydroformylation of styrene derivatives.
Rhodium-Catalyzed Hydrocarbonylation of Acetic Acid into Higher Acids
p. serp, l. chateau, r. feurer, a. kiennemann and p. kalck, J. Mol. Catal, A: Chem ., 1998, 136, (3), 269–278
The hydrocarbonylation of acetic acid into higher homologues catalysed by Rh/iodide systems was studied at 20 MPa and 220°C. The [RhI2(CO)2] homogeneous precursor had mean turnover frequencies of 67 h 1 and selectivity ≤ 80% in propionic acid; while for heterogeneous catalysis, Rh/activated C was efficient for the conversion of acetic acid into propionic acid (80% selectivity) in a fixed bed reactor.
Ruthenium Catalyzed Asymmetric Transfer Hydrogenation of β-Ketoesters
k. everaere, j.-f. carpentier, a. mortreux and m.bulliard, Tetrahedron: Asymmetry, 1998, 9, (17), 2971–2974
Chemiselective transfer hydrogenation of β-ketoesters to the corresponding alcohols is achieved in the presence of catalytic combinations of [RuCl2(η6-arene)]2 and ephedrine or diamino-type chiral ligands. Activities up to 190 h-1 were achieved at 20°C and moderate to good enantiomeric excesses of 36–94% were obtained. The results showed the dramatic effect of the arene ligand both on the enantioselectivity and the activity of the catalyst.
Calixarene-Core Multifunctional Initiators for the Ruthenium-Mediated Living Radical Polymerization of Methacrylates
j. ueda, m. kamigaito and m. sawamoto, Macromolecules, 1998, 31, (20), 6762–6768
Calixarene-core initiators with four, six and eight dichloroacetate units initiate living radical polymerisation of methyl methacrylate (MMA) catalysed by RuCl2(PPh3)3 in the presence of Al(OiPr), in toluene at 80°C to give tetra-, hexa-, and octa-armed star polymers of controlled lengths, respectively. The polymers that were produced had controlled molecular weights and narrow molecular weight distributions. Octa-armed star polymers with block copolymers of MMA and n-butyl methacrylate as arm chains were also prepared by sequential block copolymerisation initiated by the calixarene-core initiators.
Pt Inclusion Compounds as Oxygen Reduction Catalysts in Polymer-Electrolyte Fuel Cells
g. faubert, d. guay and j. p. dodelet, J. Electrochem. Soc, 1998, 145, (9), 2985–2992
Pt-based catalysts for the cathodes of PEFCs were prepared from the intercalation of PtClx, in high specific area graphite or C black. When the intercalated Pt was reduced by K-naphthalene complex, metallic Pt inclusions were obtained in HS300 or Vulcan. The Pt-inclusion catalysts performed best after a conditioning period of 48 h at 0.5 V vs. RHE. In the high-current region, Pt inclusions in graphite or C black performed better than commercial catalyst with higher Pt loadings. Thus higher current densities can be achieved or the Pt loadings can be lowered.
Fabrication and Testing of a H2-O2 Fuel Cell Using MoxRuySez
t. romero, r. rivera, o. solorza and p. j. sebastian, Int. J. Hydrogen Energy, 1998, 23, (11), 1041–1044
MoxRuySez electrocatalyst (1) for O2 reduction in a fuel cell was synthesised and characterised. A H2-O2 fuel cell was constructed, using H2SO4 as the electrolyte, and (1) supported on C as cathode and Pt/C as anode. The cell was tested at room temperature and atmospheric pressure. The H2-O2 cell was ∼32% efficient with no degradation in the output with time.
ELECTRICAL AND ELECTRONIC ENGINEERING
Preparation of High Quality RuO2 Electrodes for High Dielectric Thin Films by Low Pressure Metal Organic Chemical Vapor Deposition
j. m. lee, j. c. shin, c. s. hwang, h. j. kim and c.-g. suk, J. Vac. Sci. Technol. A, 1998, 16, (5), 2768–2771
Pure, conducting and crack-free RuO2 thin films with electrical resistivity of 45–60 μΩ cm were deposited on a Si substrate at 250–450°C by low pressure MOCVD using Ru(C11H19O2)3 as a precursor. At the lower deposition temperature, with small O additions, smoother and denser RuO2 thin films were deposited. These films had better step coverage needed for high dielectric electrodes in ULSI DRAM.
Role of Yttria-Stabilized Zirconia Produced by Ion-Beam-Assisted Deposition on the Properties of RuO2 on SiO2/Si
q. x. jia, p. arendt, j. r. groves, y. fan, j. m. roper and s. r. foltyn, J. Mater. Res ., 1998, 13, (9), 2461–2464
Highly conductive biaxially textured RuO2 thin films were deposited on SiO2 substrates by pulsed laser deposition, using yttria-stabilised ZrO2 (YSZ) prepared by ion-beam-assisted-deposition (IBAD) as a template. The biaxially oriented RuO2 had a room-temperature resistivity of 37μΩ cm and residual resistivity ratio > 2. Ba0.5Se0.5TiO3 thin films deposited on RuO2/IBAD-YSZ/SiO2/Si had a pure (111) orientation normal to the substrate surface and a dielectric constant above 360 at 100 kHz.
Ferroelectric Properties of SrRuO3/(Ba,Sr)TiO3/SrRuO3 Epitaxial Capacitor
t. kawakubo, s. komatsu, k. abe, k. sano, n. yanase and n.fukushima, Jpn. J. Appl. Phys ., 1998, 37, (9B), 5108–5111
The ferroelectric properties of SrRuO3/(Bax,Sr1-x TiO3/SrRuO3 (x = 0–1) all-perovskite heteroepitaxial capacitors were studied on SrTiO3 substrates. A peak relative dielectric constant of 870 and maximum remanent polarisation of 58 μC cm-2 were obtained, dependent on the Ba content at a dielectric film thickness of 20 nm. These are the highest storage capacitors and the thinnest ferroelectric capacitors reported so far. Deep submicron ferroelectric and dielectric memory applications are discussed.
Preparation and Characterization of RuO2 Thin Films
y. s. huang and p. c. liao, Solar Energy Mater. Solar Cells, 1998, 55, (1–2), 179–197
RuO2 thin films prepared by MOCVD and reactive sputtering under various conditions are reported. The films were specular, crack-free and adhered well to the substrate. Films deposited at substrate temperature > 100°C had metallic character. The grain-boundary scattering model fits well for films of grain size ∼ 12–50 nm. With MOCVD a nearly strain-free, high-quality RuO2 thin film can be deposited on Si substrate.