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Effects of processing parameters on the corrosion properties of dissimilar friction stir welds of aluminium and copper

  • Authors: Akinlabi, Esther Titilayo , Anthony, Andrews , Akinlabi, Stephen A.
  • Date: 2013
  • Subjects: Aluminium alloy , Copper , Corrosion , Friction stir welding
  • Type: Article
  • Identifier: uj:5019 , http://hdl.handle.net/10210/13159
  • Description: The influence of friction stir welding processing parameters on dissimilar joints conducted between aluminium alloy (AA5754) and commercially pure copper (C11000) was studied. The welds were produced by varying the rotational speed from 600 to 1200 r/min and the feed rate from 50 to 300 mm/min. The resulting microstructure and the corrosion properties of the welds produced were studied. It was found that the joint interfacial regions of the welds were characterized by interlayers of aluminium and copper. The corrosion tests revealed that the corrosion resistance of the welds was improved as the rotational speed was increased. The corrosion rates of the welds compared to the base metals were improved compared with Cu and decreased slightly compared with the aluminium alloy. The lowest corrosion rate was obtained at welds produced at rotational speed of 950 r/min and feed rate of 300 mm/min which corresponds to a weld produced at a low heat input.
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Microstructural characterizations of dissimilar friction stir welds

  • Authors: Akinlabi, Esther Titilayo , Reddy, Randall D. , Akinlabi, Stephen A.
  • Date: 2012
  • Subjects: Friction stir welding , Scanning Electron Microscopy , Aluminum alloys , Copper
  • Type: Article
  • Identifier: uj:5332 , ISSN 2070-3740 , http://hdl.handle.net/10210/8871
  • Description: This paper reports the microstructural characteristics of dissimilar friction stir welds between 5754 aluminium alloy and C11000 copper. Dissimilar Friction Stir Welds of 5754 aluminium and C11000 copper were produced by varying the rotational speeds between 600 and 1200 rpm and the feed rate between 50 and 300 mm/min. The welds were characterized through Scanning Electron Microscopy (SEM). The SEM analysis revealed the levels of metallurgical bonding achieved at the joint interfaces of the welds produced and it can be established that better metallurgical bonding and good mixing of both materials joined were achieved in welds produced at lower feed rates of 50 mm/min and 150 mm/min while defect population was found to be common in the welds produced at high feed rate of 300 mm/min.
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Non-destructive testing of dissimilar friction stir welds

  • Authors: Akinlabi, Esther Titilayo , Levy, Adrian C. S. , Akinlabi, Stephen A.
  • Date: 2012
  • Subjects: Friction stir welding , Non-destructive testing , Aluminum alloys , Copper
  • Type: Article
  • Identifier: uj:5333 , ISSN 2078-0966 , http://hdl.handle.net/10210/8876
  • Description: friction stir welds between 5754 aluminium alloy and C11000 copper. The Friction stir welds of 5754 aluminium alloy and C11000 copper were produced at different tool rotational speeds and feed rates. The tool rotational speed was varied between 600 and 1200 rpm while the feed rate was varied between 50 and 300 mm/min. The visual inspection and the x-ray radiographic testing techniques were employed to conduct the tests; these tests were conducted on the welds to ascertain the joint integrity before characterization to have an idea of the quality of the welds. No visual defects were observed on all the welds considered but the x-ray radiography technique revealed the presence of wormhole defects and discontinuities in some of the welds. It was found that the welds produced at 950 rpm with varied feed rates were the best quality welds produced and this was substantiated with the microstructural evaluation of the joint interface. It was found that these welds have good mixing and metallurgical bonding at the interfaces.
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Friction stir welding of aluminium and copper : fracture surface characterizations

  • Authors: Akinlabi, Esther Titilayo , Akinlabi, Stephen A.
  • Date: 2014
  • Subjects: Aluminium , Copper , Fracture surfaces , Friction stir welding
  • Type: Article
  • Identifier: uj:4745 , ISSN 2078-0966 , http://hdl.handle.net/10210/11731
  • Description: Butt welds of aluminium alloy and copper alloy were produced by Friction Stir Welding by varying the feed rate and keeping all other parameters constant. The final weld matrix was composed of welds produced by a constant rotational speed of 600 rpm and the feed rate varied between 50 and 300mm/min. The microstructure and fracture surfaces of the joint interfaces were investigated. The results revealed that the joint interface was characterised with mixed layers of both materials joined. The strongest weld was produced at the highest feed rate employed at 300 mm/min. The fracture surfaces were characterised with thin layers of intermetallic compounds and can be considered fit for practical applications.
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Pyrazole and pyrazolyl copper and zinc complexes in ring opening polymerization of ε-caprolactone and D,L-lactide

  • Authors: Appavoo, Divambal
  • Date: 2012-06-07
  • Subjects: Pyrazoles , Copper , Zinc , Polymerization , Caprolactones , Lactides
  • Type: Thesis
  • Identifier: uj:8668 , http://hdl.handle.net/10210/5023
  • Description: M.Sc. , Six pyrazole and pyrazolyl compounds, 3,5-dimethylpyrazole (L1), 3,5-diphenylpyrazole (L2), 3,5-di-tert-butylpyrazole (L3), bis(3,5-dimethylpyrazol-1-yl)methane (L4), bis(3,5-diphenylpyrazol-1-yl)methane (L5) and bis(1,2-bis{(3,5-dimethylpyrazol-1-yl)methyl}benzene (L6), were reacted with Zn(II) and Cu(II) benzoates to form pyrazole and pyrazolyl metal benzoates. The complexes are [Zn(C6H5COO)2(L1)2] (1), [Zn(3,5-NO2-C6H3COO)2(L1)2] (2), [Zn(4-OH-C6H4COO)2(L1)2] (3), [Zn(2-Cl-C6H4COO)2(L1)2] (4), [Zn(C6H5COO)2(L2)2] (5), [Zn(3,5-NO2-C6H3COO)2(L2)2] (6), [Zn(4-OH-C6H4COO)2(L2)2] (7), [Zn(2-Cl-C6H4COO)2(L2)2] (8), [Zn(3,5-NO2-C6H3COO)2L4] (9), [Zn(4-OH-C6H4COO)2L6] (10), [Zn2(C6H5COO)4L6]n (11), [Zn(3,5-NO2-C6H3COO)2L6] (12), [Zn(2-Cl-C6H4COO)2L6] (13), [Cu(C6H5COO)2(L1)2] (14), [Cu(3,5-NO2-C6H3COO)2(L1)2] (15), [Cu(4-OH-C6H4COO)2(L1)2] (16), [Cu(2-Cl-C6H4COO)2(L1)2] (17), [Cu(C6H5COO)2(C6H5COOH)]2 (18), [Cu(2-Cl-C6H4COO)2(L3)2] (19), [Cu(C6H5COO)2L4] (20), [Cu(2-Cl-C6H4COO)2L4] (21), [Cu(C6H5COO)2DMSO]2 (22), [Cu(C6H5COO)2L6]2 (23), [Cu(2-Cl-C6H4COO)2L6]2n (24), [Cu(4-OH-C6H4COO)2L6]2(25) and [Cu(3,5-NO2-C6H3COO)2L6]n (26). The molecular structures of the Zn(II) and Cu(II) complexes 6, 9, 11, 14, 17-19, 22-26 were determined by X-ray diffraction studies that revealed four types of geometries adopted by these complexes: (i) 4-coordinate tetrahedral (6, 9, 14), (ii) 6-coordinate octahedral (17), (iii) paddle wheel (18, 19, 22, 23, 25) and (iv) polymeric structures (11, 24, 26). Catalysis studies performed with selected complexes (1-4, 9-17, 23-26) revealed that they initiate the ring opening polymerization (ROP) of ε-caprolactone (ε-CL) and D,L-lactide at elevated temperatures, and under solvent-free conditions and in toluene respectively. Polycaprolactone (PCL) and poly(D,L-lactide) (PLA) produced were of moderate molecular weights (858-4 757 Da for PCL and 602-3 185 Da for PLA) and polydispersity indices (1.36-2.16 for PCL and 1.42-2.35 for PLA). End group of the iv polymers, determined by MALDI-TOF MS, were benzoates, hydroxyl, methoxy groups and cyclic. From the 13C{1H} NMR spectra of polymers synthesized, the stereochemistry of PLA was predominantly isotactic.
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Adsorption of arsenic on lanthanum and cerium nanoparticles adsorbents during hydrometallurgical extraction of copper

  • Authors: Bamidele, Emmanuel Anuoluwa
  • Date: 2019
  • Subjects: Lanthanum , Copper , Cerium , Nanoparticles , Extraction (Chemistry) , Arsenic - Absorption and adsorption
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/413042 , uj:34782
  • Description: M.Tech. (Extraction Metallurgy) , Abstract: Various activities of mining, mineral processing and extraction releases arsenic into the environment. The reported presence of high concentration of arsenic in lakes surrounding a selected silver, cobalt and copper mines has gained serious attention of the scientific community. This research encompasses the characterization of a low-grade copper oxide ore using atomic absorption spectrometer, x-ray fluorescence (XRF), x-ray diffractometer (XRD), SEM-EDS and Induced Coupled Plasma Mass Spectroscopy (ICP-MS). Leaching and adsorption of the copper ore sample was carried out using sulphuric acid of varying molarity -3M, 2M, 1.5M, 1M and 0.5M – and two Lanthanum and Cerium nanoparticles adsorbents were prepared for the adsorption of arsenic from the ore sample during the hydrometallurgical extraction of copper -leaching- process. This study revealed that there is a direct relationship between the concentration of acid and arsenic dissolution. The %As adsorption on Lanthanum nanoparticles adsorbent is lower at higher acid molarity and higher at lower sulphuric acid molarity. While in the case of Cerium adsorbent, there is a deviation. The Cerium ions were able to actively react with arsenic at higher acid molarity hence causing higher adsorption at higher molarity of acid than lower molar mass. Arsenate removal efficiency increases sharply with increasing adsorbent dosage, though there were some anomalies which were observed to be because of competing ions on the adsorption. The increase in temperature was found to reduce the adsorption efficiency of both the Cerium and Lanthanum nanoparticles adsorbents. The effect of acid molarity, adsorbent dosage and temperature were also studied on copper and iron dissolution in the extraction process. Low copper dissolution rate was achieved due to the activation of active binding sites by the Cerium and Lanthanum adsorbents which might have attracted some copper ions. The copper dissolution rate obtained when Cerium impregnated adsorbent was used gave better copper recovery than when Lanthanum adsorbents were applied. The values of RL obtained for each of the adsorption carried out shows that the nature of Langmuir model is unfavourable for Lanthanum nanoparticles, but the linear value obtained for RL in the case of Cerium nanoparticles makes it fit into the model. It is important to note that Cerium nanoparticles adsorbent performs better with increasing acid molarity while Lanthanum nanoparticles adsorbent performs better with increasing adsorbent dosage. Considering the findings obtained from studying different parameters such as acid molarity, temperature and adsorbent dosage, it can be concluded that Cerium nano adsorbent is a better adsorbent than Lanthanum nano adsorbent.
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Influence of tool rotational speed on microstructure and joint strength of friction stir spot welded pure copper

Sulphur formation in a medium temperature leach and a potential means to mitigate sulphur ball formation using lignosulphonate

  • Authors: Dube, Prosper
  • Date: 2020
  • Subjects: Nonferrous metals , Copper
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/481833 , uj:43672
  • Description: M.Tech. (Extraction Metallurgy) , Abstract: Copper Pressure Leach residue (CPL) contain unleached copper and at times significant amounts of sulphur. The issue of elemental sulphur formation may be handled using additives or surfactants, which act as dispersants of molten sulphur. This dispersion allows the transfer of dissolved oxygen (or ferric as an oxidant) to the sulphide surface where the reaction can occur. Test work was carried out in an autoclave on CPL residues at different conditions, seeking to identify the conditions which lead to the formation of elemental sulphur. An operating window was to be established that would significantly reduce the chances of formation of elemental sulphur balls. It was found that the use of lignosulphonate as a dispersant may mitigate the effects of sulphur ball formation during process excursions. While investigating sulphur ball formation, copper extraction efficiency was also tracked. This aided in establishing an ideal operating window. The pressure leaching behaviour of copper leach residue was studied under different operating conditions in a temperature range of between 120oC to 155oC to map the formation of sulphur balls. Varying acid dosages from low acid (5 g/L) to intermediate acid (30 g/L) to high acid (40 g/L) were investigated. The effect of varying oxygen partial pressure in the autoclave between 4 and to 6 bar was also investigated. The production of sulphur balls was observed under the following conditions - high acid and low oxygen partial pressure test work, high acid and low temperature test work and low temperature test work. Experiments where sulphur balls were found to be present, were repeated using surfactants. In this study, lignosulphonates were used and were found to be effective dispersing agents. A minimum dosage of 1 g/L lignosulphonate was found to mitigate the formation of elemental sulphur as its introduction managed to reduce the tendency to form elemental sulphur in the autoclave. The effect of lignosulphonate addition on copper recoveries saw a good association on test work number CPL_12 and test work number CPL_12B, Non-lignosulphonate testwork produced 85% copper recovery and the lignosulphonate testwork on CPL_12 with 2 g/L showed an increase to 94% and CPL_12B with 1 g/L showing a copper recovery of 97%. The high acid test work showed an increase in...
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Effect of powder density variation on premixed Ti-6Al-4V and Cu composites during laser metal deposition

Effect of plunge depth on weld integrity of friction stir welds of dissimilar aluminium and copper

Characterisation of tool geometries for friction stir lap welds of aluminium and copper

  • Authors: Ewuola, Oluwatoyin Olabisi
  • Date: 2015
  • Subjects: Friction stir welding , Dissimilar welding , Welded joints - Cracking , Aluminum , Copper
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://ujcontent.uj.ac.za8080/10210/370322 , http://hdl.handle.net/10210/212826 , uj:21032
  • Description: Abstract: The patenting of the Friction Stir Welding (FSW) process in 1991 opened up a process that was known within a relatively small circle of researchers to the entire research community. As a ground-breaking process in the field of joining, FSW offered a chance for the types of joining that had been fraught with lots of difficulties using the prevalent traditional means of joining. Dissimilar metal joining had been plagued with more challenges compared to similar metal joining due to issues related to differences in thermal expansion and conductivity, wettability, melting properties, microstructural properties and other material properties. Fusion welding of some dissimilar materials such as Aluminium and titanium; Aluminium and Steel had been nearly impossible; the few welds that were successful resulted in defects (like wormhole, lack of penetration, porosity, cracks) and welding imperfections. Hence, the advent of FSW, a solid state welding technique, provided a way out of the many difficulties that arise in the joining of dissimilar metals. Aluminium and copper are also two of such dissimilar metals whose material properties make them useful for a wide range of applications. However, due to the wide differences in their material properties, both metals had been difficult to join using the fusion welding technology. Recently, lots of successes have been achieved in the joining of both dissimilar metals using FSW and a lot of these are recorded in the open literature. Nonetheless, most of the successes recorded in the FSW of aluminium and copper have been in the butt weld configuration. Literatures abound on the FSW of aluminium and copper in butt configuration, while there are... , M.Phil. (Mechanical Engineering)
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Laboratory evaluation of the flotation response of a copper cobalt oxide ore to gasoil-rinkalore mixtures

  • Authors: Kime, M. B. , Ntambwe, J. , Mwamba, J.
  • Date: 2015
  • Subjects: Cobalt , Copper , Froth flotation , Rinkalore
  • Type: Article
  • Identifier: uj:5141 , http://hdl.handle.net/10210/14119
  • Description: Froth flotation remains to date as one of the most used metallurgical processes for concentrating metal-bearing minerals in ores. Oxide ores are relatively less amenable to froth flotation and require a judicious choice of reagents for the recovery of metals to be optimised. Laboratory batch flotation tests were conducted to determine the effect of two types of gasoil-rinkalore mixtures on the flotation response of a copper cobalt oxide ore sample. The head assay conducted on the initial ore sample showed that it contained about 2.90% of Cu, 0.12% of Co. Upon the flotation test work, the results obtained indicated that the concentrate obtained with use of the mixture gasoil-rinkalore RX yielded 8.24% Cu and 0.22% Co concentrate grades with recoveries of 76.0% Cu and 78.0% Co respectively. But, the concentrate obtained by use of the mixture gazoil-rinkalore RX3 yielded relatively bad results with 5.92% Cu and 0.18% Cu concentrate grades with recoveries of 70.3% Cu and 65.3% Co respectively.
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Friction stir spot welding between copper and aluminium : microstructural evolution

  • Authors: Mubiayi, Mukuna P. , Akinlabi, Esther Titilayo
  • Date: 2015-03-18
  • Subjects: Aluminum , Copper , Friction stir spot welding , Energy dispersive spectroscopy mapping
  • Type: Article
  • Identifier: uj:5129 , ISBN 9789881925398 , http://hdl.handle.net/10210/14092
  • Description: Friction Stir Spot Welding (FSSW) process was employed to produce lap spot welds of C11000 copper and aluminium alloy AA1060. The microstructures of the spot welds produced at different processing parameters were analyzed. Copper rings with different lengths were observed in all the spot welds. An Energy Dispersive Spectroscopy (EDS) mapping of a region of the keyhole and the Copper rings was conducted, results showed the presence of Copper particles in the Aluminium matrix and almost no Aluminium particles are found in the Copper rings. Furthermore, the distribution of the fine Copper fragments and particles in the zone close to the Aluminium parent material of some of the produced spot welds were seen in the Scanning Electron Microscopy (SEM) images.
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Characterization of the intermetallic compounds in aluminium and copper friction stir spot welds

Microstructure and electrical resistivity properties of copper and aluminium friction stir spot welds

Effect of process parameters on tensile strength and morphology of friction stir spot welds of aluminium and copper

Friction stir welding of dissimilar materials between aluminium alloys and copper - an overview

  • Authors: Mubiayi., Mukuna P.
  • Date: 2013
  • Subjects: Aluminium , Copper , Friction stir welding
  • Type: Article
  • Identifier: http://ujcontent.uj.ac.za8080/10210/390844 , uj:4847 , ISBN 978-988-19252-9-9 , http://hdl.handle.net/10210/12514
  • Description: Friction Stir Welding (FSW) is a solid state welding process used for welding similar and dissimilar materials. The process is widely used because it produces sound welds and does not have common problems such as solidification and liquefaction cracking associated with the fusion welding techniques. The FSW of Aluminium and its alloys has been commercialised; and recent interest is focused on joining dissimilar materials. However, in order to commercialise the process, research studies are required to characterise and establish process windows. In particular, FSW has inspired researchers to attempt joining dissimilar materials such as aluminium to copper which differ in properties and sound welds with none or limited intermetallic compounds has been produced. In this paper, we review the current research state of FSW between aluminium and copper with a focus on the resulting weld microstructure, mechanical testing and the tools employed to produce the welds and also an insight into future research in this field of study.
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Parametric effects on leaching behavior of nickel-copper matte in ammonia

Synthesis of conjugated polymer encapsulated nanoparticles and their applications to electrochemical sensing

  • Authors: Myeni, Nosipho
  • Date: 2019
  • Subjects: Electrochemical sensors , Copper , Nanoparticles
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/474172 , uj:42731
  • Description: Abstract: The merging of biotechnology and nanotechnology has led to intense research on nanomaterials for the development of high performance electrochemical sensors for the detection of chemical and biological analytes. Nanomaterials, particularly metal-polymer nanocomposite exhibit interesting physical, chemical and electronic properties, highly dependent on their controllable size and shape, which are distinct from their corresponding bulk state. Metal-polymer composites integrated as electrode materials play a vital role in the fabrication of the electrochemical sensor. The integration of the metal nanoparticles into the polymer matrix, combines the synergetic effect of the interface of the nanoparticles and the polymer, increasing the electro-chemically active surface area, leading to enhanced electron transfer which intensely improves the sensing performance including; sensitivity, selectivity and stability... , M.Sc. (Chemistry)
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Kinetic and catalytic evaluation of γ-Al2O3 supported Cu and Au nanoparticles on various reactions and determination of their surface area and sizes through quantitative ligand adsorption

  • Authors: Ndolomingo, Matumuene Joe
  • Date: 2016
  • Subjects: Heterogeneous catalysis , Thin films, Multilayered , Nanochemistry , Gold , Copper
  • Language: English
  • Type: Doctoral (Thesis)
  • Identifier: http://hdl.handle.net/10210/233948 , uj:23898
  • Description: Ph.D. (Chemistry) , Abstract: Catalysis has increasingly become a crucial enabling technology permitting the functionalization and utilization of a myriad of raw materials. Within this thesis we report on the kinetic analysis and catalytic activity of γ-Al2O3 supported copper and gold nanoparticles on the rate of oxidation of various reactions under mild conditions. The organothiol adsorption-based technique, using the Langmuir approach for the determination of specific surface area of these supported copper and gold nanoparticles is also reported. Alumina, γ-Al2O3 and the mixed oxide Li2O/γ-Al2O3 were used as supports for the copper and gold particles. The synthesis of copper and gold nanoparticles is simply carried out via homogeneous deposition precipitation using CO(NH2)2 as precipitating agent, and thereafter reduced using NaBH4 resulting in the formation of small particles with a fairly narrow size distribution. Cationic imidazolium ionic liquids, 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) were used as stabilizers for copper and gold nanoparticles. These catalysts were evaluated in the oxidation of methylene blue, morin and benzyl alcohol. The effects of Li2O as additive, and that of ionic liquids as stabilizers were investigated. A fair agreement was found between particle sizes obtained from ligand adsorption and TEM methods. The particle sizes of both methods deviate in the order of 3–13% for γ-Al2O3-containing copper catalysts, and 0-15% for gold-based catalyst. Copper and gold-based catalysts were revealed to be very active in the investigated reactions, especially when Li2O is used as additive, and imidazolium ionic liquids as stabilizing agents. The kinetic data obtained could be modeled in terms of the Langmuir–Hinshelwood model; that is both reactants are assumed to be adsorbed on the surface of the nanoparticles. The apparent reaction rate could therefore be related to the surface S of the nanoparticles, to the kinetics constant k, related to the rate determining steps, and to the adsorption constant of the reactants. Atomic absorption spectroscopy (AAS), X-ray diffraction spectrometry (XRD), N2-physisorption Brunauer–Emmet–Teller (BET), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and temperature programmed reduction (TPR) are used for the full characterization of the catalysts. The ligand adsorption was followed by ultraviolet-visible spectroscopy (UV-vis), while the oxidation reactions were followed by UV-vis, gas chromatography (GC-FID), and gas chromatography–mass spectrometry (GC-MS).
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