Solvent extraction is one of the effective methods for extracting copper and nickel from aqueous solution of pregnant liquid solution. This research is mainly based on direct solvent extraction method. The effect of extraction of D2EHPA on extraction of copper and nickel ions in synthetic solution has been investigated. In this study, by changing the levels of parameters such as speed and time of mixing, concentration of extractor, acidity (pH) and temperature were determined to extract copper and nickel from synthetic solution. It should be noted that, in this synthetic solution, the amount of copper was 770 ppm, nickel 3200 ppm, iron 800 ppm, and 200 ppm. The results of the experiments showed that the best and highest extraction of copper and nickel ions at 5 min, speed of 700 rpm, temperature= 45 ° C, extractor concentration= 30% and ratio A / O = 3 at pH = 6.
We have investigated the precipitation phenomena which occur at high aging temperatures in an Al-Mg alloy with high Mg concentration by means of Vickers hardness (HV) testing, differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and analytical scanning transmission electron microscopy (STEM-EDX). It was found that the hardness and heat changes are closely correlated, and that the size of the exothermic heat peak depends on the quantity of β'- phase formed during isothermal aging prior to the DSC measurements. This implies that the formation of β'-phase precipitates is mainly responsible for the increase in hardness. Our TEM observations showed that β'-phase precipitates are plate-like in morphology and form on matrix {100}planes, whilst stable β-phase precipitates are granular in shape. In-situ TEM using a heating holder revealed that β-phase precipitates grew by consumption of β'-phase platelets. Element-maps obtained by STEM-EDX indicated that the composition of β'-phase platelets was approximately Al-33at%Mg.
It has studied the influence of different artificial ageing parameters on Vicker’s hardness characteristics and friction stir processing on surface modification of scandium inoculated Al-Zn-Mg alloys. The aluminium alloys were solution treated at 465°C for one hour, quenched in water and artificial ageing at 120°C, 140°C, and 180°C at different time of ageing upto twenty hours. Further, friction stir processing healed the casting porosity and refine cast microstructures. These microstructural changes led to a significant improvement in both strength and ductility the aluminium alloys (7xxx series). Generally, high tool rotation rate is beneficial to break coarse second-phase particles, heal the casting porosity, homogenize and consequently increase strength. Therefore, friction stir processing is adopted to modify the microstructure of cast aluminium alloys to refine grain and enhance mechanical properties.
Safety is paramount importance along with enhancing fuel efficiency of the transport car over the last three decades. Advanced high strength steels play a pivotal role towards achieving the desired structural characteristics of the motor vehicles. Many structural components have been replaced by advanced high strength steels like IF steel, Bake hardening steel, HSLA steel, Micro alloyed steel, Dual Phase steel, Ferrite Bainite steel, Martensitic steel, Hot formed steel, TRIP steel, TWIP steel etc. along with austenitic and ferrite grade stainless steels due to its superior strength and ductility. In the current context it has been attempted to see the causes behind the development of those mentioned steels from conventional to third generation as well the strengthening mechanisms employed towards the development of advanced high strength structural steels. It has been observed from literature study that substantial development have been progressed from metallurgical point of view in this matter over the last decade.
Influence of carbon content substrates and different coating thickness Aluminium Chromium Nitride (AlCrN) coatings was investigated and reported in the studies. Low carbon steel (EN353) and high carbon steel (EN31) rectangular blocks were used as substrates. AlCrN coatings with two different thickness was deposited on these substrates using Balzers rapid coating system machine. The morphology, crystal structure, mechanical and tribological properties (surface hardness, wear resistance and coefficient of friction (COF)) of the coatings were examined using SEM, Optical Microscope, AFM analysis, Micro-Hardness tests, Scratch Tester TR-101 and Pin on Disc testing tribometer at atmospheric conditions. It was shown that surface morphology of D C Arc deposited AlCrN coatings is affected by the substrates properties (carbon content). The increase in the carbon contents of the substrates resulted in the increase of adhesion force between the substrates and coatings. It was also found that, AlCrN/EN31 steel with smooth roughness has the higher wear resistance than AlCrN/EN353 steel substrate.
This article presents the microstructural and thermomechanical study of the Bassar remetlted steel obtained from melting Bassar as-smelted steel. Bassar as-smelted Steel is steel made by direct reduction of Bandjeli iron ore in a natural draught furnace. Bandjeli village is located in the Bassar Region in the Republic of Togo (West Africa). The Bassar remelted steel was obtained by melting at 1370°C of Bassar as-smelted Steel in a high frequency furnace to eliminate inclusions and pores contained in the Bassar as-smelted Steel. The microstructural and mechanical analyses show that the Bassar remelted steel is homogeneous and contains no defects compared to as-smelted steel. The microstructure of the remelted Steel is formed of ferritic grain whose average size is more than 0.5 mm. Some precipitates are observed in grain and grain boundaries. Heat treatment shows that the average grain size increases as the annealing temperature increases. For the sample annealed at 600°C for one hour, its tensile strength is 338 MPa and the strain rate is 20%. The mechanical properties of the Bassar remelted steel decrease after annealed at 800°C and 950°C for one hour.
The study “the effect of holding time on the hardness of mild steel case hardened with carburizing material energized by cow-bone” has been x-rayed. The mild steel specimens used for the study were carburized in the furnace at 900C at various holding times of 2 hrs, 4 hrs, 6 hrs, and 8 hrs, using 65% charcoal / 35% cow-bone as carburizing material. Hardness values were obtained using Vickers Micro-hardness Tester Machine, from the hardness values, hardness profiles were plotted. The result of the study clearly showed that the hardness of the carburized steel increased with increase in holding time. The hardness profile results were higher for higher holding time (surface hardness: 830 Hv for 2 hrs, 850 Hv for 4 hrs, 900 Hv for 6 hrs and 1000 Hv for 8 hrs) and also the plot of the profile for 8 hrs holding time was higher than that of 6 hrs, and that of 6 hrs was higher than that of 4 hrs, and in that order. This clearly showed that holding time has effect on the hardness of case hardened steel.
The Equal Channel Angular Extrusion (ECAE) process is a promising technique for imparting large plastic deformation to materials without a resultant decrease in cross-sectional area. The die consists of two channels of equal cross section intersecting at an angle of 110°C. The work piece is placed in one channel and extruded into the other using a punch. In the present study, Influence of equal channel angular extrusion on room temperature, the mechanical properties of Aluminum Alloy AA 6351 alloy was investigated. The results show that, the mechanical properties of Aluminum AA 6351alloy, such as yield strength, ultimate tensile strength and elongation, can be improved heavily by equal channel angular extrusion. Processing routes, processing temperature and extrusion passes have important influence on room temperature mechanical properties of processed Aluminum AA 6351alloy by equal channel angular extrusion. The mechanical properties such as yield strength and ultimate tensile strength can be enhanced when Aluminum AA 6351 alloy was processed by equal channel angular extrusion for single pass at route A at 303 K.
Iron oxide in samples of clay containing 8.15% iron oxide was leached in aqueous oxalic acid and hydrochloric acid solutions. Leaching experiments were conducted in the temperature range of 40–80°C for times up to 90 minutes in 0.2 M to 2 M acid solutions. The mixed kinetic mechanism seemed to be the most appropriate model to fit the kinetic data of leaching in oxalic acid while product layer diffusion controlled reaction model seemed to be the most appropriate one for leaching in hydrochloric acid. The Arrhenius activation energy for leaching in oxalic acid was found to be 41.035 kJ/mole while that for hydrochloric acid was 50.82 kJ/mole.
Oven-dewatering of Otamiri clay designated for production of porcelain was carried out over a time and temperature range: 30-130 mins. and 80-110°C respectively, following a well strategize step-wise preparation of the clay in as-mine condition. Multi-factorial analysis of periodic water loss during the drying process was also carried out using a derived empirical model. Water loss at 100°C by evaporation through a rectangular surface was found to be least compared to other drying temperatures considered irrespective of the drying time. This was basically due to the fall-back of condensed part of the water leaving the drying clay as steam, since steam can re-convert to water without any change in temperature. Evaluations from generated results indicate that the evaporation rates of the Otamiri clay and the standard error incurred in predicting water loss for each value of the drying times considered, as obtained from experiment, derived model and regression model were 0.0770, 0.0733 and 0.0733g min-1 as well as 0.8051, 2.1 x 10-4 and 3.45 x 10-5 % respectively. The maximum deviation of the model-predicted water loss (from experimental results) was less than 20%, implying a model confidence level above 80%.
Galena particles (concentrate) were analyzed by sedimentation method using conventional technique, appropriate apparatus and reagents. A critical evaluation of the relationship between effective particle depth and a consortium of factorials; settling time and particle diameter was carried out using a derived model which is two-factorial-quadratic in nature. Results of the sedimentation analysis show increased effective depth reached by the particles as a result of decrease in the descending particle diameter, and increased settling time. The validity of derived model; β = 2 x 10-5 γ2 - 5 x 10-4 γ – 1.5 x 10-3 α + 0.2176 is rooted on the core expression β - 1.5 x 10-3 = 2 x 10-5 γ2 - 5 x 10-4 γ + 0.2176 where both sides of the expression are correspondingly approximately equal to 0.2. The model validity was verified through comparative evaluation of the settling rates from experimental and model-predicted results. These settling rates are 0.002 and 0.0025 m/mins. respectively which are in proximate agreement. The standard error incurred in predicting the effective particle depth for each value of settling time & particle diameter considered as evaluated from experiment and derived model are 0.0018 and 0.0027 & 0.0005 and 0.0024 respectively. Maximum deviation of model-predicted results from experiment was less than 3%, implying a confidence applicability level of about 97%.
Evolution of the microstructure and mechanical properties of the hypereutectic Al-16.5mass%Si-3.77mass%Cu alloy by treatment in the liquid state by magnetohydrodynamic (MHD) and hydrodynamic (HD) methods, followed by processing in the solid state by equal channel angular pressing (ECAP) method and thermal treatment has been investigated. This alloy has in initial state a very low value of plasticity at room temperature. Optical microscopy technique was employed in order to determine the evolution of the microstructure after different operating conditions of ECAP and thermal treatments. It was demonstrated that it is possible to significantly improve mechanical properties of this alloy by means of combining a low number of ECAP passes after an adequate combination of MHD+HD processing and thermal treatments.
Manganese and zinc contained in the electrolyte paste of spent zinc-carbon dry cell batteries were leached in sulfuric acid in presence of hydrogen peroxide as a reducing agent. Kinetic parameters were established from the time versus extent of dissolution curves using temperature as variable and keeping the other parameters fixed. Three reactions models (i) Liquid film diffusion controlled, (ii) Diffusion controlled through the product layer and (iii) Chemical reaction controlled were considered for the selection of the appropriate reaction model for the dissolution of manganese and zinc. The kinetic data of leaching for both manganese and zinc were found to follow the chemical reaction controlled process, i..e., where, τ = time for complete disappearance of particles and X = fraction of reacted particles. Activation energy of manganese and zinc were found to be 46.27 KJ/mol and 52.39 KJ/mol respectively; which again justified the appropriateness of the model. At a leaching temperature of 60°C, the extent of dissolution, under the conditions investigated, reached up to 81% for manganese within 21 minutes of leaching and 75% for zinc within 30 minutes of leaching.
In this work, TiAlN and AlCrN coatings were deposited on ASTM-SA213-T-11 boiler steel using Balzer’s rapid coating system (RCS) machine (make Oerlikon Balzers, Swiss) under a reactive nitrogen atmosphere. The corrosion resistance of the substrate, TiAlN-coated and AlCrN-coated samples in a 5 wt% NaCl solution was evaluated and compared by salt fog (spray) test for 24 hrs, 48 hrs and 72 hrs. The weight loss per unit area increases with the duration of the test. The samples were monitored and analyzed by using Weight loss measurement, XRD and SEM/EDAX techniques. The weight loss per unit area in case of nanosructured thin TiAlN coating is less than as compared to the nanostructured AlCrN coating and uncoated boiler steel in all test conditions.
Effects of strain rates on tensile properties and fracture behavior of Al-6Si-0.5Mg alloy containing 0.5 – 4 wt% Cu were studied. The solution treated alloys, containing different amounts of Cu, were aged isochronally for 1 hour at temperatures up to 300°C. Tensile strengths were found to increase with ageing temperature, the maximum being attained at peak aged condition (1 hr at 225°C). Addition of Cu resulted in an increase in tensile strength and 2 wt% Cu addition showed the maximum strength. Evaluation of tensile properties at three different strain rates (10-4, 10-3 and 10-2 s-1) showed that strain rates affected the tensile properties significantly. At higher strain rates the strength was better but ductility was poor.
This paper assesses the reliability level of Pb-Sb-Cu alloy electrical resistance dependence on its melting temperature and copper input concentration. The alloy was cast by pouring a stirred mixture of heated Pb-Sb alloy and powdered copper into a sand mould and then furnace cooled. Results of electrical test carried out indicate that the electrical resistance of the Pb-Sb-Cu alloy decreases with increase in the melting temperature of the Pb-Sb-Cu alloy. This invariably implied decrease in the electrical resistivity of the alloy. Increased copper addition (0.99-8.26 wt%) to the base alloy (Pb-Sb) also correspondingly decreased the electrical resistance. The experimental results were complement by results generated using a derived model. The validity of the two-factorial derived model expressed as: ξ = - 0.1248ɤ - 0.0398ϑ + 66.615 was rooted on the expression ξ - 66.615 = - 0.1248ɤ - 0.0398ϑ where both sides of the expression are correspondingly approximately equal. Statistical analysis of the experiment, derived model & regression model-predicted results shows that the standard errors incurred in predicting the Pb-Sb-Cu alloy electrical resistance for each value of the melting temperature and copper input were 0.1247, 0.1722 & 3.517 x 10-5 % and 0.4276, 0.1797 & 0.3593 % respectively. Evaluations indicate that Pb-Sb-Cu alloy electrical resistance per unit rise in the melting temperature and copper mass-input as obtained from experiment, derived model & regression model-predicted results were 0.2507, 0.2309 & 0.2496 Ω /°C and 0.094, 0.0866 & 0.0936 Ω / g respectively. Deviational analysis indicated that the maximum deviation of derived model-predicted electrical resistance from the experimental results was less than 3%. This translated into over 97% operational confidence and reliability level for the derived model and over 0.97 reliability coefficient for the Pb-Sb-Cu alloy electrical resistance dependence on the alloy melting temperature and copper input concentration.
The paper describes the method for modeling of nanostructure polymerizable multicomponent oxide melts, which can be used for systems of type Me2O-SiO2 (Me = monovalent cation), with the results of a molecular dynamics simulation as input. The models of the short-range and medium-range orders taking into account dual behavior of monovalent alkali metal cations able to form stable groups with oxygen atoms are built. The melt structure is described with help of heterogeneous descriptors which are constructed using the polymer models and molecular dynamics results. The model is a heterogeneous graph which is built with gradually increasing of mapping levels (from selection heterogeneous graph vertices associated with individual particles, to forming connected components of vertices corresponding polyanionic complexes and rings in the melt. Quantitative calculations of the structure associated characteristics are carried out using the distribution function of graph vertices. We have modeled nanostructure and studied polymerization processes in the system SiO2-Na2O in the range of five compositions by the above method. In particular, we calculated the radial and angular distribution, the distribution of the coordination numbers, the bond lengths, the mole portions of different types of oxygen atoms, the complex anions in the model system taking into account sodium ions, the proportion of flat rings in polyanionic complexes, as well as the average connection factor. The obtained results give a satisfactory agreement with the characteristics in the range having experimental data. A number of results the structure modeling has a scientific novelty and practical significance.
This paper showcases the reliability level associating welding voltage dependence of heat affected zone (HAZ) hardness of aluminium, cast iron and mild steel weldments cooled in groundnut oil. These materials were welded using shielded metal arc technique and the HAZ hardness of the various groundnut oil cooled weldments determined. Three models were derived and used as tools for the empirical analysis of the influence of welding voltage on the HAZ hardness of the weldments. The results of the analysis show that the HAZ hardness of weldments is significantly and reliably affected by the operational welding voltage. Results evaluations largely show that on welding aluminium, cast iron and mild steel, and similarly cooling their respective weldments in groundnut oil, an empirical was used to predict aluminium weldment HAZ hardness as equivalent of HAZ hardness interaction between cast iron and mild steel. Aluminium weldment HAZ hardness was evaluated as a product of a multiplication operation between the general voltage product rule (GVPR) ((βa βm + βa βc)/ βc βm)0.2396 and the ratio; HAZ hardness product of cast iron and mild steel/ HAZ hardness sum of cast iron and mild steel ( ŋ ɤ /( ŋ + ɤ )). Predicted values of the HAZ hardness of cast iron and mild steel were comparatively analyzed and also found very reliably dependent on the GVPR which is a collective function of their respective welding voltage. The validity of the model was rooted on the core model expression; (βa /βc + βa/βm ) = (ζ /ɤ + ζ / ŋ)4.1737 where both sides of the expression were correspondingly equal. Computational analysis of generated results shows that aluminium, cast iron & mild steel weldment HAZ hardness per unit welding voltage as evaluated from experiment and derived model were 1.4714, 4.1818 & 2.3318 (VHN)V-1 and 1.4714, 4.1821 & 2.3319 (VHN)V-1 respectively. Deviational analysis indicates that the maximum deviation of model-predicted HAZ hardness from the experimental results is less than 0.006%. This translates into over 99.99% operational confidence and reliability level for the derived models and over 0.9999 reliability coefficient for the welding voltage dependence of HAZ hardness.
