Category Archives: General

Square Wave Pulsating Overpotential Treatment of Chromic Acid Solution


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Systematic investigation of square wave pulsating overpotential (SWPO) treatment of a chromic acid solution is presented. Some preliminary potentiodynamic scans, potentiostatic deposits, potential steps and capacitance vs. potential curves were measured in order to establish the practical range of the SWPO signal parameters. The results show that properly adjusting the electrochemical parameters of the cyclic alternating potential perturbation it is possible to obtain cracked or crack free metallic chromium or chromium oxide/hydroxide mixed coatings. The different deposit morphologies were characterized through scanning electron microscopy and their chemical composition and micro hardness was measured. Some insight into the possible mechanisms of coating growth under this potential cycling treatment is given.

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Overview of the UK Surface engineering sector


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Surface engineering is a sub-discipline of materials science and covers a multitude of processes such as electroplating, anodising, electro-polishing, heat treatment processes, physical vapour deposition and the like. The term surface engineering was promoted by, amongst others, Professor Tom Bell of the University of Birmingham defining it as “the design of surface and substrate together as a functionally graded system to give a cost-effective performance enhancement of which neither is capable on its own”. Imagine a world without cars, aeroplanes, trains, computers, mobile phones, medical implants, buildings, electronics, in fact virtually no manufactured products – that’s a world without surface engineering. Thus, the application of surface engineering is vital to the success of almost every commercial and industrial product: from aero engines to aeroplanes, from iPods to surgical implants and from razor blades to racing cars.

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Adsorption and Corrosion Inhibition Characteristics of Some Thiophene-3-Carbohydrazide Derivatives on Low Carbon Steel in Hydrochloric Acid Solutions


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Fig. 7: Molecular orbital plots of organic compounds

New compounds of corrosion inhibitors namely amino-N’-(3-(hydroxyimino)butan-2-ylidene)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbohydrazide (1), amino-N’-(thiophen-2-ylmethylene)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbohydrazide (2) and amino-N’-(1-(pyridin-2-yl)ethylidene)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbohydrazide (3) were synthesized and its inhibiting action on the corrosion of carbon steel in 1 M hydrochloric acid at 25ºC was investigated by various corrosion monitoring techniques. A Potentiodynamic polarization, AC impedance and electrochemical frequency modulation methods have been used. Potentiodynamic polarization studies showed that these derivatives were mixed type inhibitors. The effect of temperature on the corrosion behavior of carbon steel in 1 M HCl with the addition of these compounds were studied in the temperatures 25 and 45ºC. The adsorption of these inhibitors on carbon steel surface from hydrochloric acid obeyed the Langmuir adsorption isotherm. Quantum chemical method is used to explore the relationship between the inhibitors molecular properties and their inhibition efficiency.

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Sodium-bismuth-lead low temperature liquid metal battery


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Fig. 3: Image of a Na negative electrode after three charge-discharge cycles

The development of a low temperature liquid metal battery based on ionic liquids namely, sodium-bis(trifluoromethylsulfonyl)imide (Na[TFSI]) in tetraethylammonium-bis(trifluoromethylsulfonyl) imide ([TEA][TFSI]) will be discussed. Such a battery should be easily accessible for fluid flow measurements which is still a challenge with the conventional high temperature systems. Cells comprising a Na negative electrode, 20 mole% Na[TFSI] in [TEA][TFSI] ionic liquid electrolyte and a Pb-Bi eutectic positive electrode were constructed and operated at 160 °C. Galvanostatic cycling experiments were conducted at low C rates (C/26) for 13 h corresponding to 50% depth of discharge. A discharge capacity of 565 mAh/g was found. Furthermore electrochemical impedance spectroscopy was used to characterize the aging of the cells.

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An improved analytical method for reducing edge built up and estimation of thickness in selective plating using variable perimeter-to-area ratio window test mask


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In this paper, we attempt to present a new approach and analytical relation between perimeter-to-area ratio (P/A) and the plated thickness using Variable Area Window (VAW) test mask for improved thickness estimation. Although, the approach is illustrated using selective plating of gold films by varying two dimensional patterned windows on metallised silicon surface as an example, yet the method can be applied to other cases also. The method includes selective electroplating of gold in rectangular and circular windows wherein P/A of patterned shapes (squares, rectangles and circles) has been varied from 0.001 cm-1 to 0.4 cm-1 i.e. a factor of 400, a range normally used for practical modern MEMS devices. Experiments show that in general the thickness increases with increasing P/A because of current crowding. However, in contrast to using current density for control of this current crowding as reported in literature, we report that by careful design of mask pattern and improved material parameters, one can control and even achieve a slope reversal in the plot of thickness vs. P/A. The increase in thickness as measured by slope of linear fit is about 3 µm/(P/A in µm-1) for sharp edges compared to about 0.8 µm/(P/A in µm-1) for curved edges within the experimental errors. The general applicability of these relations to practical cases is confirmed by analysing the previously reported trends of data from the literature on Ni films using similar patterned shapes.

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