Refining of corrosive insulating oils by selective liquid-liquid extraction process

In recent years copper sulphide formation in transformer windings has been recognized as one significant risk factor for operation of power transformers, due to number of failures which have occurred as a consequence of copper sulphide formation. Since sulphur compounds present in the insulating oil are recognized as the cause for copper sulphide formation, and in order to lower the risk of transformers failures, one of the possible solutions is removal corrosive sulphur from the oil, i.e. corrosive oils refining. In this paper the results obtained using selective liquid-liquid extraction process to remove the potentially corrosive and corrosive sulfur compounds from the oil are presented. Liquid -liquid extraction processes were widely used in petroleum industry in virgin base oil refining and waste oil re-refining to decrease aromatic content of the vacuum gas oil fractions and/or to remove other impurities from selected refinery streams. Selective liquid-liquid extraction (SLLE) process was developed and optimized for corrosive sulfur compounds extraction in insulating oils. Besides extraction of potentially corrosive sulfur species this process is highly efficient in used and waste oil re-refining. Amounts of co-solvent used in SLLE were finely tuned to increase selectivity for extraction of sulfur compounds in balance with application oil properties (electrical properties and oxidation stability). Solvent mass ratios were balanced according to polarity figures and surface tension properties. Other important process parameters: operating temperatures, number of cycles, solvents dosages were all optimized to achieve highest performance characteristics. Optimization of the process parameters in terms of extraction yield was performed in order to balance the oxidation stability of re-refined oils

Surface modification of the titanium implant using TEA CO2 laser pulses in controllable gas atmospheres - Comparative study

Interaction of a TEA CO2 laser, operating at 10.6 mu m wavelength and pulse duration of 100 ns (FWHM), with a titanium implant in various gas atmospheres was studied. The Ti implant surface modification was typically studied at the moderate laser beam energy density/fluence of 28 J/cm(2) in the surrounding of air, N-2, O-2 or He. The energy absorbed from the TEA CO2 laser beam is partially converted to thermal energy, which generates a series of effects, such as melting, vaporization of the molten material, shock waves, etc. The following titanium implant surface changes and phenomena were observed, depending on the gas used: (i) creation of cone-like surface structures in the atmospheres of air, N-2 and O-2, and dominant micro-holes/pores in He ambient; (ii) hydrodynamic features, most prominent in air; (iii) formation of titanium nitride and titanium oxide layers, and (iv) occurrence of plasma in front of the implant. It can be concluded from this study that the reported laser fluence and gas ambiences can effectively be applied for enhancing the titanium implant roughness and creation of titanium oxides and nitrides on the strictly localized surface area. The appearance of plasma in front of the implants indicates relatively high temperatures created above the surface. This offers a sterilizing effect, facilitating contaminant-free conditions. (C) 2011 Elsevier B.V. All rights reserved

Methods of purification and characterization of carbon nanotubes

In an attempt to purify MWNT in mild conditions, we have applied two different methods of purification. The first method of purifying the material was a combination of relatively often used methods, such as etching and acid treatment, and the second method was a relatively new one, using an organic polymer PmPV. Sample purity was obtained with SEM and ESR techniques

Methods of purification and characterization of carbon nanotubes

In an attempt to purify MWNT in mild conditions, we have applied two different methods of purification. The first method of purifying the material was a combination of relatively often used methods, such as etching and acid treatment, and the second method was a relatively new one, using an organic polymer PmPV. Sample purity was obtained with SEM and ESR techniques

Surface nanopatterning of Al/Ti multilayer thin films and Al single layer by a low-fluence UV femtosecond laser beam

The effects of UV femtosecond laser beam with 76 MHz repetition rate on two types of thin films on Si substrate - the Al single layer thin film, and the multilayered thin film consisted of five Al/Ti bilayers (total thickness 130 nm) - were studied. The surface modification of the target was done by low fluences and different irradiation times, not exceeding similar to 300s. Nanopatterns in the form of femtosecond-laser induced periodic surface structures (fs-LIPSS) with periodicity of LT 315 nm and height of 45 nm were registered upon irradiation of the thin films. It was shown that: (i) the fs-LIPSS evolve from ruffles similar to high spatial frequency LIPSS (HSFL) into a low spatial frequency LIPSS (LSFL) if a certain threshold of the fluence is met, (ii) the number of LSFL increases with the exposition time and (iii) the LSFL remain stable even after long exposure times. We achieved high-quality highly-controllable fabrication of periodic structures on the surface of nanosized multilayer films with high-repetition-rate low-fluence femtosecond laser pulses. Compared to the Al single layer, the presence of the Ti underlayer in the Al/Ti multilayer thin film enabled more efficient heat transmittance through the Al/Ti interface away from the interaction zone which caused the reduction of the ablation effects leading to the formation of more regular LIPSS. The different outcomes of interactions with multi and single layer thin films lead to the conclusion that the behavior of the LIPSS is due to thin film structure. (C) 2014 Elsevier B.V. All rights reserved