Cobalt Substrate Research Articles

Emission Mössbauer study of the interface between a cobalt substrate and a polyimide coating

The emission Mossbauer technique is used to study the chemical structure of the interphase formed between a cobalt substrate and a polyimide coating. The results are interpreted to indicate that the coating is bonded to the cobalt substrate by means of carboxylate bonds with Co2+ ions in the oxide film at the interface.

Behaviour of cobalt infiltration and abnormal grain growth during sintering of diamond on cobalt substrate

The infiltration behaviour of molten cobalt into a diamond powder compact was examined when the latter was placed on a cobalt disc and held at high pressure of 5.8 GPa and high temperature of 1350 to 1500° C. The larger the grain size of the starting diamond powder and the higher the holding temperature, the more easily cobalt infiltrated into the diamond compact. The infiltration is considered to occur because of the negative pressure in the voids formed between diamond grains. Although diamond powder was consolidated in this process of cobalt infiltration, abnormal grain growth was also observed in the boundary between cobalt and diamond compact because of the dissolution and precipitation process of the compact into molten cobalt.

Emission Mössbauer Study of the Interface Between a Cobalt Substrate and a Polyimide Coating

The emission Mössbauer technique is used to study the chemical structure of the interphase formed between a cobalt substrate and a polyimide coating. The results are interpreted to indicate that the coating is bonded to the cobalt substrate by means of carboxylate bonds with Co2+ ions in the oxide film at the interface.

Study of the cobalt diffusion in CVD-layers by scanning Auger microscopy (SAM)

Multilayers of TiC/Al2O3/TiC were deposited by CVD (Chemical Vapor Deposition) on pure cobalt, cemented carbides (WC-Co) and Al2O3 substrates. By a low angle cut produced with a ball cratering technique, depth profile measurements were determined by SAM.

Oxidation by cobalt(III) acetate. Part 9. Effect of substituents on the oxidative cleavage of glycols in acetic acid

The kinetics of oxidative cleavage of glycols by cobalt(III) acetate in acetic acid have been studied. The substrates examined include cis- and trans-cyclopentane- and cyclohexane-1,2-diols and their mono- and di-methyl derivatives. The rates were first-order in both cobalt(III) acetate and substrate in all cases. In the oxidation of five-membered ring diols, cis-diols were generally oxidized faster than the trans-isomers. Complex results were obtained in the case of six-membered ring diols. Thermodynamic parameters were calculated for all the substrates. A mechanism involving a bidentate complex of cobalt(III) acetate dimer and the glycol is suggested, except for the case of trans-cyclopentane-1,2- diols, for which a monodentate intermediate is proposed.

Mechanism of the bromate ion oxidation of the cobalt(II) complex of trans-cyclohexane-1,2-diamine-NNN′N′-tetra-acetic acid

Kinetics of the oxidation of [Co(cdta)]2–(H4cdta =trans-cyclohexane-l,2-diamine-NNN′N′-tetra-acetic acid) by bromate ion have been studied in the ranges of [H+]= 1 × 10–2– 1 × 10–3 mol dm–3 and [BrO3–]= 5 × 10–2– 37.5 × 10–2 mol dm–3 at 60 °C with I=1.0 mol dm–3(KNO3). The second-order rate constant k in the rate law d[Co(cdta)–]/dt=k[Co(cdta)2–][BrO3–] is dependent on [H+] : k=a[H+]2/(b+[H+]). A reasonably good fit of the data to this equation is obtained with a=(13.1 ± 1.2)× 10–2 dm6 mol–2 s–1 and b=(5.31 ± 0.2)× 10–3 mol dm–3. A possible mechanism has been deduced. This involves an inner-sphere electron transfer path in which a binuclear species containing the cobalt(II) substrate and BrO2+ is formed in the slow step.

Oxidation by cobalt(III) acetate. Part 4. Kinetics and mechanism of the oxidation of glycols in acetic acid

The oxidative cleavage of 1,2-glycols by cobalt(III) acetate in acetic acid was studied kinetically in order to clarify the reaction mechanism. The rates were first-order in both cobalt(III) acetate and substrate for the oxidation of all the diols used. cis-Cyclopentane-1,2-diol and decalin-9,10-diol were more rapidly oxidized than the corresponding trans-isomers, respectively, whereas cis-cyclohexane-1,2-diol was more slowly oxidized than the trans-isomer. The oxidation of trans-2-methoxycyclohexanol was much slower than that of the corresponding diol. The mechanism involving the formation of a bidentate complex between cobalt(III) acetate dimer and glycol is discussed.

Influence of amines on the catalytic asymmetric hydrogenation of benzil in the system Co(dmgH)2·2H2O+amine+quinine kinetics of the reaction and further refinement of details of asymmetric induction

It has been found that the hydrogenation kinetics of PhCOCOPh is first order in the cobalt complex and substrate. It has also been observed that the optical yield of the asymmetric hydrogenation of benzil depends on the pKa of amines. Mechanism involving complexation of benzil by amines (in solution) is postulated

Interaction of cis-(amine)-bis-(ethylene diamine) cobalt(III) salicylates with Fe(III), Al(III) and Cu(II): Stability constants of [(NH 3)(en) 2CoCO 2C 6H 3( X)OM] ( n+1)+ species

The cis-(amine)-bis-(ethylene diamine) cobalt(III) salicylates, [(NH 3)(en) 2CoCO 2C 6H 3( X)OH] 2+ ( X = H, 5-Br, 5-SO 3 −, 5-NO 2 and 3-NO 2), have been synthesised. The association equilibria involving the deprotonated form of these complexes and Fe(III), Al(III) and Cu(II) have been studied spectrophotometrically in aqueous medium. The p K OH of the salicylate complexes and the stability constants of the binuclear species. [(NH 3)-(en) 2CoCO 2C 6H 3( X)OM] ( n+1)+ , are reported at 29·5(±0·2)°C and μ = 1·0 M (adjusted with NaClO 4). For a given cobalt(III) substrate, the stability constants of the binuclear species ( K ML ) decrease in the sequence: Fe(III)>Al Al(III)>Cu(II). Both p K OH and log K ML values decrease in the sequence: H > 5-Br > 5-SO 3 − > 5-NO 2 > 3-NO 2. Log K ML vs p K OH plots are linear with slopes close to unity for all the three metal ions. The metal ions in their binuclear complexes are presumed to be chelated by the phenate oxygen and the carboxyl group bound to the Co(III) centre.

Acid hydrolysis of carboxylatopentaamminecobalt(III) complexes Kinetics and mechanism of aquation of malonato, succinato, o-phthalato and o-methoxy benzoato pentaamminecobalt(III) complexes

The kinetics of aquation of malonato, succinato, o-phthalato and o-methoxybenzoato pentaamminecobalt(III) complexes have been studied in aqueoys acidic media adjusted to 0·3 M ionic strength. At [H +] = 0·005 − 0·3 M and 55 − 70°C, the observed pseudofirst-order rate constants are described by the relationship: k obs = k 1 + k 2 [H +] where k 1 and k 2 stand for the rate constants of spontaneous and acid catalysed equation of (NH 3) 5CoCO 2(CH 2) n CO 2H 2+ ( n = 1,2), (NH 3) 5CoCO 2C 6H 4CO 2H 2+ and (NH 3) 5CoCO 2C 6H 4OCH 3 2+ species respectively. The rate and the activation parameters for the k 1 and k 2 paths have been determined. The results indicate that the unbound carboxyl group does not exert a specific catalytic effect on the spontaneous and acid catalysed paths of aquation of the cobalt(III) substrates derived from the dicarboxylic acids. CoO bond fission appears to be rate limiting in both k 1 and k 2 paths of all complexes. The possibility of CO bond breaking, however, can not be ruled out in the k 2 path of the o-phthalato complex.

Metal ion catalysed acid hydrolysis of acidopentaammine cobalt(III) complexes: Kinetics and mechanism of Al(III), Ga(III) and In(III) catalysed hydrolysis of malonatopentaamminecobalt(III) complex

Al(III), Ga(III) and In(III) have been found to catalyse the aquation reaction of the malonatopentaamminecobalt(III) complex. The catalytic activities of these metal ions have been ascribed to the formation of the reactive species, (NH 3) 5CoCO 2CH 2CO 2M 4+. At 60°C and 0·3M ionic strength (adjusted with NaClO 4), the equilibrium constant ( K′ 2) of the reaction, ( NH 3) 5 CoCO 2 CH 2 H 2+ + M 3− ⇌ ( NH 3) 3 CoCO 2 CH 2 CO 2 M 4− + H 4− and the rate constant ( k 3) of aquation of the binuclear species, ( NH 3) 5 CoCO 2 CH 2 CO 2 M 4+ + H 2 O → ( NH 3) 5 CoOCH 2 3+ + CH 2( CO 2) 2 M 4− are found to be 0·334(±0·036), 1·01(±0·07) × 10 −5 sec −1 for Al(III); 0·55(±0·02), 1·01(±0·10) × 10 −5 sec −1 for Ga(III); and 0·178(±0·086), 0·635(±0·157) × 10 −5 sec −1 for In(III) respectively. The species, [(NH 3) 5CoCO 2CH 2CO 2Ga 2OH] 6+, has also been found to be involved as the catalytically active labile intermediate in the Ga(III) ion catalysed aquation of the cobalt(III) substrate. The activation parameters for the metal ion catalysed path of aquation of the malonato complex have been determined. CoO bond fission is tentatively suggested to be the rate determining step in the k 3 path.

Direct observation of the dibromide radical anion oxidation of tris(bipyridyl)ruthenium(II). Evidence for a triplet-to-triplet energy transfer mechanism in the photosensitized redox decomposition of cobalt(III) substrates

Direct observation of the dibromide radical anion oxidation of tris(bipyridyl)ruthenium(II). Evidence for a triplet-to-triplet energy transfer mechanism in the photosensitized redox decomposition of cobalt(III) substrates

The magnetic properties of Co-Ni-Fe films

H_{k} , \deltaH_{k} ,\alpha_{90} and H c have been measured for vapor-deposited nonmagnetostrictive Co-Ni-Fe films, 1500 A thick. All parameters except H c have been measured using the transverse-biased permeability apparatus. H k increases linearly with cobalt melt content up to 15-percent cobalt, \deltaH_{k} and H c increase with increasing cobalt and substrate temperature. α 90 decreases in the region 0-15-percent cobalt and then increases with increased cobalt melt content and substrate temperature. The coefficient of magnetoelastic composition sensitivity S is the slope of the curve η versus the ratio of nickel to iron in the melt for a constant cobalt percentage about the point \eta = 0 . The value of S increases rapidly with substrate temperature to a maximum near 300°C if the cobalt percentage is small. For larger amounts of cobalt S is reduced and is more independent of temperature. It is proposed that the volume fraction and the mobility of the grain boundaries in the film structure are primarily responsible for S .