Showing papers by "Lakshman Neelakantan published in 2010"
TL;DR: In this article, X-ray photoelectron spectroscopy was carried out to characterize the chemical nature of the electropolished surface of NiTi and its mechanism for NiTi shape memory alloy in methanolic sulfuric acid.
Abstract: Electropolishing and its mechanism for NiTi shape memory alloy in methanolic sulfuric acid have been investigated recently. In the current study, X-ray photoelectron spectroscopy was carried out to characterize the chemical nature of the electropolished surface. The electropolished surface is covered by a thin layer of TiO 2 . For an electropolished specimen, the Ni:Ti ratio at surface (∼1 nm) was 0.31, whereas for a mechanically polished specimen the ratio was 0.70. The second aspect of this work is the attempt to characterize the salt film formed during electropolishing. The characterization of salt-film showed sulfide and sulfate compounds of Ni and/or Ti. The crystallographic and topographical changes caused due to thermally induced phase transformation on an electropolished NiTi was followed by in situ XRD and AFM. AFM studies revealed significant changes in the surface features due to phase transformation. The surface roughness value increased by a factor of 2.
13 citations
TL;DR: An in situ tensile rig is proposed, which allows performing electrochemical (repassivation) experiments during dynamic mechanical testing of wires during dynamic Mechanical Testing of wires, and preliminary results on the repassivation behavior of Al wire are reported.
Abstract: An in situ tensile rig is proposed, which allows performing electrochemical (repassivation) experiments during dynamic mechanical testing of wires. Utilizing the basic components of a conventional tensile tester, a custom-made minitensile rig was designed and fabricated. The maximal force that can be measured by the force sensor is 80 N, with a sensitivity of 0.5 mV/V. The maximum travel range of the crosshead induced by the motor is 10 mm with a minimum step size of 0.5 nm. The functionality of the tensile test rig was validated by investigating Cu and shape memory NiTi wires. Wires of lengths between 40 and 50 mm with varying gauge lengths can be tested. An interface between wire and electrochemical setup (noncontact) with a smart arrangement of electrodes facilitated the electrochemical measurements during tensile loading. Preliminary results on the repassivation behavior of Al wire are reported.
9 citations