Some observations describing the electrochemical surface annealing of austenitic stainless steel

Cold-worked austenitic stainless steels have been subject to a pulsed electrochemical treatment in fairly concentrated aqueous solutions of sodium nitrite. The electrochemical reactions that occur transform the strain-induced martensite phase, originally formed by the cold work, back to the austenite phase. However, unlike the conventional thermal annealing process, electrochemically induced surface annealing also hardens the surface of the alloy. Because the process causes transformation of the surface martensite, we term it "electrochemical surface annealing", despite the fact that it results in an increase in surface hardness.

Parasitic feedthrough cancellation techniques for enhanced electrical characterization of electrostatic microresonators

Capacitive parasitic feedthrough is an impediment that is inherent to all electrically interfaced micron scale resonant devices, resulting in increased challenges to their integration in more complex circuits, particularly as devices are scaled to operate at higher frequencies for RF applications. In this paper, a technique to cancel the undesirable effects of capacitive feedthrough that was previously proposed is here developed for an on-chip implementation. The method reported in this paper benefits from the simplicity of its implementation, and its effectiveness is demonstrated in this paper. This technique is demonstrated for two disk-plate resonators that have been excited in the wine glass mode at 5.4 MHz, though applicable to almost any electrically interfaced resonator. Measurements of the electrical transmission from these resonators show that the magnitude of the frequency response of the system is enhanced by up to 19 dB, while the phase is found to shift through a full 180° about the resonant frequency. This method is proposed as a useful addition to other techniques for enhancing the measured response of electrostatic micromechanical resonators. © 2009 Elsevier B.V. All rights reserved.

Electrochemical Impedance Spectroscopy Of Peo Coating On Aluminum Alloy In Nacl Solution

Various Plasma Electrolytic Oxidation (PEO) ceramic coatings were prepared on LY12 aluminum alloy by adjusting the concentration of sodium silicate solution. Optical microscope (OM), XRD and EIS were used to study their morphology, composition and anti corrosion behavior in NaCl solution. Increasing concentration of sodium silicate leads to the increase of the total coating thickness while too high and too low concentration lead to the decrease of inner dense layer. The main composition of PEO coatings prepared in 20, 40 and above 60g/L concentration solution are correspondingly alumina, alumina with mullite, and amorphous phase. The corrosion resistance is determined by the inner dense layer. Increasing the thickness of inner dense layer can improve the anti-corrosion performance. PEO coating's corrosion resistance in acidic, alkaline and neutral NaCl solution is proved and the corrosion mechanism involved is also discussed.

Numerical verification for instrumented spherical indentation techniques in determining the plastic properties of materials

 Instrumented indentation tests have been widely adopted for elastic modulus determination. Recently, a number of indentation-based methods for plastic properties characterization have been proposed, and rigorous verification is absolutely necessary for their wide application. In view of the advantages of spherical indentation compared with conical indentation in determining plastic proper-ties, this study mainly concerns verification of spherical indentation methods. Five convenient and simple models were selected for this purpose, and numerical experiments for a wide range of materials are carried out to identify their accuracy and sensitivity characteristics. The verification results show that four of these five methods can give relatively accurate and stable results within a certain material domain, which is defined as their validity range and has been summarized for each method.

Adsorption of human serum albumin onto gold: a combined electrochemical and ellipsometric study

Human serum albumin adsorption onto gold surfaces was investigated by electrochemical and ellipsometric methods. Albumin adsorption onto gold was confirmed by the change of the open circuit potential of gold and by the ellipsometric parameter variation during albumin immobilization. In both experiments the parameters reached stable values within 10-15 min. The albumin adsorption layer thickness measured with the ellipsometer was about 1.5 nm. The adsorption of albumin Under applied potential was also investigated and it was found that both positive and negative applied potential promote albumin adsorption. Changes in the optical parameters of bare gold and albumin adsorbed onto gold surface under applied potential were investigated with in Situ ellipsometry. The similarity and reversibility of the optical changes showed that adsorbed albumin was stable on the gold surface Under the applied potential range (-200-600 mV). The cyclic voltammograms of K3Fe(CN)(6) on the modified gold surface showed that albumin Could partly block the oxidation and reduction reaction. (C) 2004 Elsevier Inc. All rights reserved.