Elementary steps and mechanism of electrodeposition of Al from complex hydride ions in tetrahydrofuran baths

Electrocrystallization of Al cannot be achieved from aqueous media, but is possible from low melting-point organic salts, and from aromatic and etheric solutions. In the present paper studies are reported on the kinetics and mechanisms of electrodeposition of Al from plating baths of varying ratios of AlCl₃ and LiAlH₄ dissolved in tetrahydrofuran (THF). A complementary paper, which follows, deals with the topic of nucleation and growth processes involved in Al phase electrocrystallization and provides experimental results on that process. Steady-state cathodic and anodic Tafel polarization relations are determined, complemented by ac impedance studies. Back-reaction corrected Tafel plots enable anodic and cathodic transfer coefficients (α) to be evaluated together with corresponding stoichiometric numbers (ν). Critical evaluation both of the present α and ν results, and previous α values in the literature, enables a mechanism of elementary steps in Al deposition from the hydrido-chloride baths to be proposed.     

Profile evolution of edge parameters during L/H and H/L mode transitions on compass-D

On COMPASS-D the profile evolution of electron density, electron temperature, perpendicular electric field, poloidal impurity velocity, and neutral density at the outboard mid-plane has been investigated during ohmic single null diverted (SND) discharges undergoing an L/H, H/L, and another L/H transition. This was achieved using a novel combined diagnostic consisting of thermal helium beam and Doppler spectrometry, sharing the same lines of sight. To generate the transitions first an ELM-free H-mode phase was produced by terminating the gas fuelling. Within this H-mode a stepped gas puff was applied triggering an intermediate L-mode phase followed by a second ELM-free phase. It was found that on COMPASS-D the L/H transition is not preceded by a change in velocity or electric field shear. The maximum electric field shear of ∇ ▽E _ψ ≈2×10³kV/m² develops after the L/H transition around the 95% flux surface. Although the neutral density at the separatrix is of the ordern _D ≈ 10¹⁷m⁻³ no indication of a local influence could be concluded. However, a correlation between the decay of the shear and the gas puff was observed. Presented at the Workshop on Role of Electric Fields in Plasma Confinement and Exhaust, Budapest, 18–19 June 2000. This work was jointly funded by the UK Department of Trade and Industry and EURATOM. The author H. Meyer is funded by a Marie Curie Research Training Grant.     

Excimer laser machining of microvias in glass substrates for the manufacture of high density interconnects

Machining of microvias in 100?C50???m thick CMZ glass using an excimer laser (248?nm) was investigated. The effect of various laser process parameters: pulse energy, repetition rate, irradiation time were studied to optimise the microvia drilling process and a process window was identified. Through-hole drilling of 100???m diameter (entry hole) microvias was achieved at a fluence (energy density) as low as 2.3?J/cm² with an irradiation time of 30?C40?s at a repetition rate of 20?Hz, giving a taper angle between 22?C24^° relative to the vertical. However, by increasing the fluence to 4.5?J/cm², this reduced the machining time to 5?C10?s and taper angle to 14^°, giving an exit hole diameter of around 45?C50???m. With 50???m thick glass, it was possible to machine through-hole microvias with smaller entry hole diameters down to 40???m. Machined microvias were characterised to investigate debris, recast layer and microcrack formation. Debris and recast layer around the machined features was minimised by using a protective photoresist layer coating on the glass and through appropriate operating parameter selection. Microcracks along the sidewalls of the microvias could not be avoided, but their severity depended on the laser machining parameters used.     

Studies on the Preparation of 2-Indolyl Triflates and Related Compounds

Upon treatment with trifluoromethanesulfonic acid anhydride (triflic anhydride), oxindole (4) is converted into 1-(trifluoromethanesulfonyl)indol-2-y1 trifluoromethanesulfonate (10) in 70% yield. Some attempted reactions of 1-(trifluoromethanesulfonyl)indole (13), conveniently prepared by treating indole (12) with n-butyllithium and triflic anhydride, are described.     

Development of inositol-based antagonists for the D-myo-inositol 1,4,5-trisphosphate receptor

The syntheses of four D-myo-inositol 1,4,5-trisphosphate (InsP(3)) derivatives, incorporating phosphate bioisosteres at the 5-position, are reported. The methyl phosphate ester and sulfate derivatives retain InsP(3) receptor (InsP(3)R) agonist activity; the compounds that possess a methylphosphonate or a carboxymethyl moiety are InsP(3)R antagonists.