Hydroxyurea is associated with lower prevalence of albuminuria in adults with sickle cell disease

Albuminuria is an early manifestation of sickle cell nephropathy. Prior small case series suggests benefit of hydroxyurea in reducing albuminuria, with a similar trend noted in pediatric studies. We aimed to comprehensively evaluate hydroxyurea use and prevalence of albuminuria in adult sickle cell patients

Mechanistic differences in transgranular and intergranular cracking of austenitic stainless steels

Many alloys, notably the austenitic stainless steels, exhibit intergranular as well as transgranular stress corrosion cracking (SCC) in Cl- environments. The mechanism of cracking in both these modes and the conditions under which the transition from trans to intergranular cracking or vice versa occur are topics of much debate and research. Some recent work have suggested that the mechanism of trans and intergranular stress corrosion cracking are identical. In this study, by using the load pulsing technique, it has been determined that the velocity in intergranular SCC is about 2 to 3 times higher than transgranular SCC. Also, by studying the effect of temperature on the crack propagation rate the activation energy in both modes of cracking was found to be similar thereby suggesting that the rate limiting step in both types of cracking may be the same

The Ph Effect On Chemical Mechanical Planarization Of Copper

This study explores the effect of pH on the chemical mechanical polishing (CMP) characteristics of copper in H2O2 and KIO 3 based slurries under various dynamic and static conditions. High purity copper disc was used to study the dissolution and oxidation kinetics at various pH (2 to 10) with 5% H2O2 or 0.1M KIO 3. Electrochemical techniques were used to investigate the dissolution/passivation behavior of Cu. The affected surface layers of the statically etched Cu-disc were investigated using X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). In 5% H 2O2, the Cu removal rate decreases with an increase in pH and reaches minimum at pH 6, and then increases under alkaline conditions. XPS results indicate that the surface oxide formed at various pH values was responsible for this CMP trend. However, with 0.1M KIO3, the CMP removal rates were found to be lower at pH 2. The maximum was observed at pH 4, then the removal rate decreased with the increase of pH. The lower value of removal rate at pH2 was due to the fast interaction between Cu and KIO 3 and the precipitation of CuI on the pad, which makes the pad glassy, resulting in lowered removal rates. This was confirmed by XPS measurements. The decreased CMP removal rates when the pH is higher than 4 might be due to the weaker oxidation power of KIO3 with the increase of pH

Post-Exposure Evaluation Of Thermal Barrier Coatings By Electrochemical Impedance Spectroscopy

High temperature behavior of air plasma sprayed (APS) thermal barrier coatings (TBC) was investigated in this study by electrochemical impedance spectroscopy (EIS). Scanning electron microscope (SEM) was used to examine cross-sectional morphology of exposed TBC. It was found that characteristic EIS spectra were obtained effectively to differentiate variant post-exposed TBC such as isothermal oxidation and cyclic oxidation. In addition, the type and length of high temperature exposure were qualitatively discernible from the EIS data. A model of an EIS alternative current (AC) equivalent circuit was proposed quantitatively to relate the EIS parameters to the morphological properties of the exposed TBC and functional relationships have been established between them. From the results, EIS has been identified capable of monitoring the microstructure of post-exposed TBC and evaluating TBC damage. © 2001 Materials Research Society

Effect Of Hydrogen Peroxide On Oxidation Of Copper In Cmp Slurries Containing Glycine And Cu Sulfate

This study compares the oxidative dissolution, passivation, and polishing behavior of copper chemical mechanical polishing in the presence of hydrogen peroxide, glycine and copper sulfate. High purity discs were used to study the dissolution and oxidation kinetics under static and dynamic conditions at pH 4 with varying H2O2 concentrations. Changes in surface chemistry of the statically etched copper-disc were investigated using X-ray photoelectron spectroscopy (XPS). With the addition of glycine and copper sulfate to the slurry, the copper removal rates increased significantly and the maximum removal rate shifted to a H2O2 concentration of 3%. Electrochemical investigation indicates an enhanced dissolution of copper, which might be due to the strong catalytic activity of Cu(II)-glycine complexes in decomposing H2O2 to yield hydroxyl radicals. XPS results suggest that the passivation at higher H2O2 concentrations in the presence of glycine and copper sulfate is provided by the OH radicals adsorbed on Cu surface

The Role Of Chemical Constituents In Copper Cmp Slurries

Copper chemical mechanical planarization is one of the most critical techniques for damascenes interconnect processing. The demand for copper CMP slurries that can provide high polishing rates and fewer defects at low down force has increased with the integration of copper and low-k dielectrics. This requirement warrants copper CMP more to be a chemistry-driven process rather than a mechanically dominated one. The present investigation was focused on the understanding of the removal mechanism during copper CMP using hydrogen peroxide based slurries under the influence of various pH. Ethylenediamine (EDA) and glycine (Gly) were used as complexing agents, and 3-amino-triazol (ATA) was used as inhibitor, The electrochemical process involved in the oxidative dissolution of copper was investigated by potentiodynamic polarization studies. The affected surface layers of the statically etched Cu were investigated using X-ray photoelectron spectroscopy (XPS). Atomic force microscopy was employed to study the surface planarity after CMP process

Electrochemical Characterization Of Copper Chemical Mechanical Polishing

Chemical mechanical polishing (CMP) of copper was performed using H2O2 as oxidizer and alumina particles as abrasives. The interaction between the Cu surface and the slurry was investigated by potentiodynamic measurements taken during the polishing process as well as under static conditions. The Cu removal rate reached a maximum at 1% H2O2 concentration, and decreased with a further increase in H2O2 concentration. The static etch rate showed the same trend. Atomic force microscopic measurements were performed on both the etched surface and polished surface. It was shown that the surface roughness of the polished surface increased as the H2O2 concentration increased. This can be explained by changes in the structure of the passivating layer and the dominating role of the dynamic repassivation during polishing. © 2003 Elsevier B.V. All rights reserved

Xps And Electrochemical Studies On Tungsten-Oxidizer Interaction In Chemical Mechanical Polishing

Electrochemical interaction between the oxidizer and the metal is believed to play a key role in material removal in tungsten CMP. In this study, we use X-ray Photoelectron Spectroscopy (XPS) in conjunction with electrochemical measurements in both in-situ polishing conditions as well as in static solutions, to identify the passivation and dissolution modes of tungsten. Dissolution of tungsten oxides was found to be the primary non-mechanical tungsten removal mechanism in CMP. ©2000 Materials Research Society