Esta Abelev - Academia.edu (original) (raw)

Papers by Esta Abelev

In the present work we studied the anodic behavior of polycrystalline copper (Cu 99.995 wt%) in s... more In the present work we studied the anodic behavior of polycrystalline copper (Cu 99.995 wt%) in sodium hydroxide solutions at potential range below the Cu 2 O formation potential (depending on sodium hydroxide concentration), as well as the effect of various additives to the alkaline solutions on copper anodic characteristics. Peaks of anodic current appeared in a wide potential range below the reversible potential for Cu 2 O formation. The width of this potential range strongly depended on the solution alkalinity. An increase in NaOH concentration (from 0.0075 to 8.0 M) resulted in a shift of the anodic current onset to negative values, from −1.12 to −1.4 V vs. SCE and significant increase of anodic current, up to values above 10 −3 A/cm 2 . A pronounced increase of anodic current was detected for NaOH concentrations above 1.0 M. It is suggested that anodic current at potentials below the Cu 2 O formation potential is preferably associated with Cu dissolution, forming both soluble complex-ions, Cu(OH) n 1-n (n > 1), and poorly soluble CuOH. Poorly soluble CuOH precipitates over the Cu surface, suppressing Cu dissolution.

This work presents the novel nature of 2,4-hexadienoic acid potassium salt (potassium sorbate (KC... more This work presents the novel nature of 2,4-hexadienoic acid potassium salt (potassium sorbate (KCH 3 CH CHCH CHCO 2 )) as an effective copper aqueous corrosion inhibitor. The influence of pH and potassium sorbate concentration on copper corrosion in aerated sulfate and chloride solutions is reported. Degree of copper protection was found to increase with an increase in potassium sorbate concentration; an optimum concentration of this inhibitor in sulfate solutions was found to be 10 g/L. Copper is highly resistant to corrosion attacks by chloride ions in the presence of potassium sorbate. X-ray photoelectron spectroscopy (XPS) studies suggest that copper protection is achieved via the formation of a mixed layer of cuprous oxide, cupric hydroxide and copper(II)-sorbate at the metal surface.

Copper depassivation and repassivation characteristics in potassium sorbate solutions, subsequent... more Copper depassivation and repassivation characteristics in potassium sorbate solutions, subsequent to mechanical abrading are reported. The identification of copper repassivation kinetics obtained subsequent to mechanical damage of copper protective films formed in sorbate based solutions is discussed. The repassivation rate of copper in sorbate based solutions was measured by means of a slurryjet system capable of measuring single particle impingments on microelectrodes. Copper repassivation rates measured by this slurryjet system in sulfate solutions containing 10 g L −1 potassium sorbate were found to be in the range of 0.5-1.5 ms. An increase in the potassium sorbate concentration leads to a decrease in copper repassivation time at potentials ranging from 200 to 600 mV Ag/AgCl . The impingement angle between the copper surface and a single abrasive particle has no impact on copper repassivation time nor peak current (I max ) values. XPS studies revealed that copper passivation in potassium based solution was due to the formation of a thin film which is constituted of: Cu 2 O, Cu(OH) 2 and Cu(II)-sorbate, while copper(II)sorbate is mainly present at the top levels of the passive film. It is therefore recommended that the use of potassium sorbate as a passivating component in conjunction with the addition of strong oxidizing agents in chemical mechanical planarization (CMP) slurry design should be considered.

Ras Labs produces electroactive polymer (EAP)-based materials and actuators that bend, swell, rip... more Ras Labs produces electroactive polymer (EAP)-based materials and actuators that bend, swell, ripple and now contract (new development) with low electric input. This is an important attribute because of the ability of contraction to produce life-like motion. The mechanism of contraction is not well understood. Radionuclide-labeled experiments were conducted to follow the movement of electrolytes and water in these EAPs when activated. Extreme temperature experiments were performed on the contractile EAPs with very favorable results. One of the biggest challenges in developing these actuators, however, is the electrode-EAP interface because of the pronounced movement of the EAP. Plasma treatments of metallic electrodes were investigated in order to improve the attachment of the embedded electrodes to the EAP material. Surface analysis, adhesive testing and mechanical testing were performed to test metal surfaces and metal-polymer interfaces. Nitrogen plasma treatment of titanium produced a strong metal-polymer interface; however, oxygen plasma treatment of both stainless steel and titanium produced even stronger metal-polymer interfaces. Plasma treatment of the electrodes allows for the embedded electrodes and the EAP material of the actuator to work and move as a unit, with no detachment, by significantly improving the metal-polymer interface.

The electrochemical behavior of copper was studied in Na 2 SO 4 solutions (pH 4), containing pero... more The electrochemical behavior of copper was studied in Na 2 SO 4 solutions (pH 4), containing peroxide, benzotriasol (BTA) and glycine. The effect of BTA was initially evaluated in sulfate solution without peroxide and it was established that once BTA is present, copper undergoes a strong passivation process in a potential range below 0.2 V (SCE). At potentials above 0.2 V the protective layer of BTA is destroyed and copper suffers from localized corrosion attacks. Positive potentiodynamic sweep of the potential resulted in increase of anodic currents at potentials above 0.2 V and hysteresis appearance resulting in the formation of wide and deep pits on the surface of the copper substrate. The addition of H 2 O 2 to BTA containing solutions resulted in a rapid increase of OCP to values significantly higher than 0.2 V, leading to initiation of copper localized corrosion processes.

Accumulation and dissipation of charges (charging/discharging) in dielectric materials are vital ... more Accumulation and dissipation of charges (charging/discharging) in dielectric materials are vital processes for design and function of various devices and sensors . Charge accumulation in a dielectric layer occurs via various trapping mechanism(s) and is normally probed by electrical current-voltage and/or currentcapacitance measurements . Photoemission, utilizing UV, Xrays and lasers has also been employed for probing very fast (<10 À9 s) charging dynamics . Core-level X-ray photoemission, XPS, is especially attractive since additional chemical information can also be derived from the line positions of the corresponding peaks. However, the measured line positions are severely affected by local potentials developed due to the uncompensated charges resulting from photoelectron emission, especially for nonconducting samples or regions (layers or domains) within such samples . Over the last 3-4 decades, very successful methods of charge compensation in photoelectron spectroscopy have been developed using low energy electrons, ions and/or photons .

This paper presents the results of an experimental study of the initial cell spreading and adhesi... more This paper presents the results of an experimental study of the initial cell spreading and adhesion on longitudinally-and transversally-oriented micro-grooves produced by the laser irradiation of laser grooved Ti-6Al-4V surfaces. The initial spreading and orientations of human osteosarcoma (HOS) cells were observed and quantified after 15-min, 1-hour, 4-hour and 24-hour cell culture periods. Immuno-fluorescence staining of adhesion proteins (actin and vinculin) was then used to study the spreading and adhesion of HOS cells in 1 hour and 4 hour culture experiments. The initial cell adhesion was also quantified using enzymatic detachment tests. The results showed that cell spreading and adhesion were enhanced by longitudinally-and transversally-oriented micro-grooves. The effects, which increase with time, were not remarkable after 1 hour, but obvious after 4 hours. Contact guidance was found to promote cell adhesion due to the increase in interactions between the focal adhesions and the patterned extra-cellular matrix (ECM) proteins on the laser micro-grooved surfaces.

In this short communication we provide a glimpse into the unexpected, intriguing nature of 2,4-he... more In this short communication we provide a glimpse into the unexpected, intriguing nature of 2,4-hexadienoic acid potassium salt ͕potassium sorbate ͓K͑CH 3 CHvCHCHvCHCO 2 ͔͖͒, namely, its high superiority over other corrosion inhibitors to protect metals and alloys ͑copper, carbon steel, aluminum, and stainless steel͒ from surface degradation processes in a wide range of potentials in the presence of corrosive environments.

In the present work we report on carbonate-based solutions, which can provide copper passivity in... more In the present work we report on carbonate-based solutions, which can provide copper passivity in a wide potential range with the capability for producing protective characteristics similar to Al and W. This report focuses mainly on the identification of copper passivity parameters, such as potential range, anodic current limits, current characteristics, and rates of passivation and repassivation subsequent to mechanical damage of copper passivity in carbonate-based solutions. Copper is fully passivated in sulfate solutions containing potassium carbonate. The observed passivity is more pronounced in solutions containing higher carbonate content. On the contrary, increasing the sulfate concentration has the opposite effect on copper passivity than carbonate does. Friction of the passive film by repeated surface abrading resulted in a rapid repassivation of the mechanically activated surface sites. Thus, the use of a carbonate anion as a passivating component in a future chemical mechanical planarization ͑CMP͒ slurry design should be considered.

The effect of H 2 S at ppm level concentrations on iron corrosion in 3 wt% NaCl solutions saturat... more The effect of H 2 S at ppm level concentrations on iron corrosion in 3 wt% NaCl solutions saturated with CO 2 in the temperature range of 25-85°C is examined using electrochemical and surface science techniques. Small H 2 S concentrations (5 ppm) have an inhibiting effect on corrosion in the presence of CO 2 at temperatures from 25 to 55°C. At 85°C, however, 50 ppm H 2 S is needed to provide significant corrosion inhibition. At higher H 2 S concentrations, the corrosion rate increases rapidly, while still remaining below the rate for the H 2 S-free solution. Characterization of the iron surfaces after corrosion was carried out using X-ray photoelectron spectroscopy and X-ray diffraction. A sulfur peak (S2p) is observed at a binding energy of 161.8 eV in all cases, attributable to disulfide ðS 2À 2 Þ formation. Corrosion protection in the temperature range 25-55°C can be attributed to Fe(II) bonded to S and O. At 85°C, protection of the iron surface is most likely due to FeS 2 formation. Morphological changes on the iron surface after exposure to H 2 S containing solutions were observed by SEM. A thin protective film was seen after exposure to solutions containing 5 ppm H 2 S at 25°C, while at 85°C, with the addition of 50 ppm H 2 S to CO 2 -saturated brine solution, a dense protective film was formed on the iron surface.

The present work reports on carbonate-based solutions, which can provide copper passivity in a wi... more The present work reports on carbonate-based solutions, which can provide copper passivity in a wide potential range. This report focuses mainly on the identification of copper repassivation features obtained subsequent to mechanical damage of copper passive films in carbonate-based solutions. The repassivation rate of copper in carbonate-based solutions was measured with the use of a slurryjet system. The measured repassivation rate of copper in a slurryjet system utilizing a carbonate-based solution was found to be in the range of 1-2 ms. An increase in the concentration of carbonate ions leads to a decrease of the copper repassivation time at potentials ranging from 200 to 600 mV Ag/AgCl . The impingement angle between the copper surface and the single abrasive particle has an insignificant impact on the repassivation time and characteristics. It is therefore recommended that the use of carbonate anions as a passivating component in a future chemical mechanical planarization slurry design should be considered.

Etch-stop method for reliably fabricating sharp yet mechanically stable scanning tunneling micros... more Etch-stop method for reliably fabricating sharp yet mechanically stable scanning tunneling microscope tips