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Subero J.,CVG Venalum | Subero J.,Antonio Jose de Sucre National Experimental Polytechnic University
TMS Light Metals | Year: 2013

This paper reports a study on the structure and porosity of calcined petroleum coke (CPC), the impact on mechanical properties of the corresponding baked anodes; and their behaviour in electrolytic reduction cells, especially the susceptibility towards thermal shock. This work was supported by characterization techniques used by CVG Venalum and PDVSA (Venezuela), such as mercury porosimetry, physisorption, and image analysis by optical microscopy (OM). The results indicated that good CPC quality is reflected by good mechanical anode properties as long as the anode manufacturing process is stable. The anode properties are related to the OTI (optical texture index). It is therefore possible to predict the anode behaviour from the CPC structure and porosity, take appropriate action, and decrease the net carbon consumption (NCC). Source

Gonzalez G.,Antonio Jose de Sucre National Experimental Polytechnic University | Pacheco A.,Antonio Jose de Sucre National Experimental Polytechnic University
Acta Microscopica | Year: 2010

Nowadays, Zinc Aluminum Alloys (ZA) are generally used for galvanization, in order to prevent the attack produced by corrosion. In this investigation, the microstructure of deposited layers of ZA on SAE 1020 steel is evaluated, as well as its behavior when submitted to tensile tests. For this purpose, several standardized test were carried out according to the norm COVENIN 299, after applying the covering layers of alloys; Zn-4%Al, Zn-%6Al and the Zn-10%Al by the method of hot immersion. After performing the tensile test, a metallographic examination was made, according to norm ASTM E-3. The measurement of the thickness of the layers and the counting of cracks was made by Optics Microscopy (OM). The microstructure analysis was made by Scanning Electronic Microscopy (SEM). The characterization of the microcomponents was made with the application of EDX. It can be concluded that the samples with better mechanical properties, were those covered with the alloy of Zn - 6%Al. The observed microstructure displayed Zn-Al-Fe precipitates in a rich Zinc matrix; they increase in quantity and size with the percentage of aluminum in the alloy. Source

Galatro D.,Antonio Jose de Sucre National Experimental Polytechnic University | Verruschi E.,Antonio Jose de Sucre National Experimental Polytechnic University
19th International Congress of Chemical and Process Engineering, CHISA 2010 and 7th European Congress of Chemical Engineering, ECCE-7 | Year: 2010

A simulation model of the ethylene oxide-ethylene glycol (EG) plant was developed using Pro II based on the production scheme of SD (Sci Design Licensor). The simulation was structured in two modules, i.e., ethylene oxide and ethylene glycol plant. The EG plant had multi-effect evaporation, reaction and separation train section. A subroutine was included for modeling the reactor of ethylene glycol production. The multi-effect evaporator was simulated using dynamic programming. This evaporation system is a key section in the optimization of the model (via case study and eventually using other strategies), to achieve optimal conditions for the next step separation of the methyl ethylene glycol, diethylene glycol, and triethylene glycol. This is an abstract of a paper presented at the 19th International Congress of Chemical and Process Engineering and 7th European Congress of Chemical Engineering (Prague, Czech Republic 8/28/2010-9/1/2010). Source

Gonzalez L.,Antonio Jose de Sucre National Experimental Polytechnic University | Gonzalez G.,Antonio Jose de Sucre National Experimental Polytechnic University
Acta Microscopica | Year: 2013

There is little information on the characteristics of the coatings obtained at different times of immersion in the processes of hot galvanized with zinc + aluminum alloys, the objective of this study was to evaluate by scanning electron microscopy the influence of immersion time on the thickness Zn-7Al coating hot-dip deposited on a steel SAE 1015. Were prepared by a total of 48 specimens of 50x25x3 mm plates, which were applied by a coating of 8 groups at different times of immersion in the metal bath (30 seconds and 5 minutes 1,2,3,4), method was used for the bulk density to verify the chemical composition of the alloy in the molten bath, and Scanning Electron Microscopy and EDS to know the elements present and the thickness of each zone of the coatings, as well as an adherence assay [4] and a thickness measurement by magnetic induction machine. Coating thicknesses were measured at 31.75 microns average for a time of 30 seconds, 36.14 microns for 1 minute, increased to 99.94 microns for the last time 5 minutes. We conclude that the grip each of the specimens subjected to coating with the Zn-7As not present any problems. A longer time of immersion of the workpiece in the molten bath greater the total thickness of the coating obtained. Source

Chicot D.,University of Lille Nord de France | Gil L.,Antonio Jose de Sucre National Experimental Polytechnic University | Silva K.,Central University of Venezuela | Roudet F.,University of Lille Nord de France | And 3 more authors.
Thin Solid Films | Year: 2010

A methodology for determining the thin film hardness from a microindentation loading curve is proposed. The loading curve is modelled to compute the dynamic Martens hardness using the indentation depth reached during the test. Moreover, the indentation size effect is taken into account by applying the strain gradient plasticity theory. Then, the dynamic Martens hardness and the hardness length-scale factor are used to express the applied load as a function of the indentation depth. The proposed model involves three parameters: (i) the dynamic Martens macro-hardness, equivalent to the hardness obtained for an infinite applied load, (ii) the hardness length-scale factor, which represents the material resistance to plastic deformation under indentation and (iii) a corrective load, considering the rounded tip effect of the indenter and the zero shift. The model is validated on a 316L stainless steel which subsequently is used as a substrate material for two different Diamond Like-Carbon thin films. The coated systems involved both a hydrogen-free mostly amorphous carbon-chromium (a-C) film of ∼ 2.6 μm in thickness and a hydrogenated, amorphous carbon (a-C:H) solid lubricant of ∼ 2 μm. © 2010 Elsevier B.V. Source

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