Publications

A mathematical model for the electroless deposition of copper on a planar electrode is presented and used to make time-dependent predictions on the various quantities in the system. The model takes into account mass transport by diffusion and migration, Butler-Volmer kinetics at the electrode surface, and mixed potential theory. A finite difference approach is used to solve the equations, and the resultant model is used to predict the concentration profiles, potential response, and plating rate as a function of time and concentration of various reactive components. © 1999 The Electrochemical Society. S0013-4651(98)02-031-X. All rights reserved.

Zinc-nickel-phosphorus alloys were electrodeposited from acid sulfate baths at various current densities and phosphorus levels and were characterized for their corrosion resistance. The corrosion and sacrificial protection abilities of the zinc-nickel and zinc-nickel-phosphorus alloys were tested by chronopotentiometric and linear polarization techniques. Galvanostatic stripping technique was used to determine the qualitative composition of these alloys; the surface morphology and relative composition of the alloys were studied using scanning electron microscopy and energy dispersive X-ray diffraction studies.

A mathematical model that includes an anode (carbon) decomposition reaction has been used to predict the temperature of a lithium-ion cell during medium- and high-rate discharge conditions. This work describes how various design parameters and the activation energy for the decomposition reaction of the anode (carbon) affect the predicted temperature of a LixC6/LiyNiO2 cell. The predicted results show that the particle size in the negative electrode (assumed here to be petroleum coke) is an important parameter for predicting the temperature of the cell. (C) 1999 The Electrochemical Society. S0013-4651(98)05-051-4. All rights reserved.

A complex impedance model for spherical particles was used to determine the lithium ion diffusion coefficient in graphite as a function of the state of charge (SOC) and temperature. The values obtained range from of 1.12 × 10 -10 to 6.51 × 10 -10 cm 2 /s at 25°C for 0 and 30% SOC, respectively, and for 0% SOC, the value at 55°C was 1.35 × 10 -10 cm 2 /s. The conventional potentiostatic intermittent titration technique (PITT) and Warburg impedance approaches were also evaluated, and the advantages and disadvantages of these techniques were exposed. © 1999 The Electrochemical Society. S0013-4651(98)02-032-1. All rights reserved.

Quaternary spinels doped with chemically modified chromium oxide (mCrO2.65) LiCryMn2 - yO4 with y = 0.02, 0.05 and 0.1 completely stabilize the spinel structure. Cyclic voltammograms of pure spinel exhibit high irreversibility compared with that obtained initially. The spinel doped with chemically modified chrome oxide mCrO2.65 causes the peak separation to decrease contributing to the electrochemical reversibility of the doped cathode material. Negligible shift of the peak potentials was observed for these cathodes. Chromium dopant enhances the mass transfer of Li+ in the active material. The Li+ diffusion coefficient in LiCr0.1Mn1.9O4 estimated from an analysis of the Warburg impedance is two order of magnitude higher than that in pure spinel. © 1998 Elsevier Science S.A. All rights reserved.

With the aggressive growth of the lithium-ion battery market, several companies have recently offered their version of the lithium-ion battery for consumer purchase. This paper describes the physical design, rate, cycle-lifetime, and self-discharge performance of cells from Sony, Matsushita, A&T, Moli, and Sanyo lithium-ion batteries. The study used a total of 85 lithium-ion cells from these manufacturers. All cells performed as indicated by manufacturers specifications and the performance and design differences are discussed. The design differences include discussion of gas chromatography-mass spectroscopy (GC-MS) analysis of the electrolytes, a differential scanning calorimetry (DSC) analysis of separators, the activation of a positive temperature coefficient (PTC), and a comparison of the basic physical parameters of each cell. Performance characterization shows an excellent high discharge rate performance of the A&T and Matsushita cells, an excellent cycle-lifetime performance for Sony cells, and negligible effects of self-discharge. © 1998 Elsevier Science S.A.

Hydrogen permeation and corrosion inhibition characteristics of several organic compounds were studied on a type 1010 (UNS G10100) steel membrane in 0.5 M hydrochloric acid (HCl). Tafel extrapolation and linear polarization methods were used to estimate the corrosion rate, while the Devanathan-Stachurski technique was used to determine the hydrogen permeation rate. A simple corrosion model was used to correlate inhibitor concentration to its inhibiting efficiency. Maximum corrosion reduction and hydrogen permeation inhibiting efficiencies were measured as 82% and 98%, respectively.

The inhibition of hydrogen permeation by zinc-nickel electrodeposited alloy was investigated using the Devanathan-Stachurski permeation technique. The hydrogen evolution and hydrogen permeation rates for the zinc-nickel alloy electrodeposits on iron are compared with the rates for bare iron, zinc electroplated on iron, and nickel electroplated on iron. Hydrogen evolution rates and hydrogen permeation rates were followed as functions of time at different applied potentials. The hydrogen permeation inhibition for thin zinc-nickel electroplates (20 s at 10 mA cm-2 and 10 s at 20 mA cm-2) averaged 80% and intermediate to that of nickel and zinc. This inhibition was considered to be mostly due to kinetic effects. Zinc-nickel electroplated for 20 and 40 min. at 10 mA cm-2 inhibited the hydrogen permeation greater than 95% as compared to bare iron. This inhibition was due to both kinetics and the barrier effect caused by the diffusion resistance of the membrane.

Integral diffusion coefficients were measured for potassium hydroxide over a concentration range of 0.1 M to 11 M at 1, 10, and 25 °C using the simplified diaphragm cell procedure of Mills, Woolf, and Watts. Differential diffusion coefficients were calculated using the iterative regression method of Stokes over the same concentration and temperature range. An empirical correlation relating the differential diffusion coefficients as a function of temperature and concentration was made with a standard error of 8 × 10-7 Cm2·S-1 and an average deviation of 5 × 10-7 cm2·s-1.