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Formation and alteration of the stratiform copper deposits
Published in Adam Piestrzyński, Mineral Deposits at the Beginning of the 21st Century, 2001
The principal alterations of sulfide ores in a zone of the secondary sulfide enrichment are connected with reactions of copper reduction and iron replacement by copper. In a result, the primary minerals (pyrite, chalcopyrite, bornite) are replaced by covellite, digenite and djurleite. The sequence of replacement, such as: pyrite – chalcopyrite – bornite – covellite – digenite – djurleite – native copper, takes place under conditions of impeded water-exchange. Thus, parageneses and zonation like such a primary oneself appear. The secondary sulfide enrichment zone of the Bankroft deposit can serve as an example.
MIC Detection and Assessment
Published in Torben Lund Skovhus, Dennis Enning, Jason S. Lee, Microbiologically Influenced Corrosion in the Upstream Oil and Gas Industry, 2017
Mohita Sharma, Gerrit Voordouw
New techniques allow the study of metal binding to microorganisms and related biomolecules using a small sample size (Beech et al. 1999). These have indicated a correlation between the corrosion products and the associated microbial action contributing to microbially influenced pitting corrosion (Table 9.1). These include the microbial deposition of Fe oxides and Mn oxides and hydroxides by manganese and iron-oxidizing bacteria that leads to tubercle formation (Dickinson and Lewandowski 1996). Predominance of iron-reducing bacteria (IRB) will increase the fraction of Fe2+ in theoxide layer. IOB, on the other hand, oxidize Fe2+ to Fe3+, forming an insoluble Fe2O3 layer that may protect the metal surface from corrosion depending on how intact this layer is (Papavinasam 2013). The presence of magnetite, mackinawite, and greigite among the corrosion products indicates the participation of SRB in corrosion. Corrosion tubercles with siderite and iron sulfide were found to be associated with a MIC failure site of a gas transmission pipeline, which had disbonded tape coating (Jack et al. 1995). Enning et al. (2012) found the deposition of siderite and amorphous iron sulfide and coprecipitated minerals like calcite in the corrosion crust of experimental and field samples incubated with marine SRB where metallic iron was provided as the sole electron donor for sulfate reduction. Sherar et al. (2011) reported that corrosion product morphology (in the form of nonstoichiometric tetragonal mackinawite, stoichiometric hexagonal troilite, or cubic ferrous sulfide) on the surface of the metal is dependent on the pH, nutrients, and the concentration of sulfide formed (Sherar et al. 2011). They also found mackinawite to be the dominant iron phase formed in both biotic (SRB consortium) and abiotic conditions. Chalcocite, covellite, djurleite, and copper sulfides could also be formed by SRB during corrosion of copper and its alloys (Beech and Gaylarde 1999 and references therein).
Deposition of stoichiometry – tailored amorphous Cu-S thin films by MOCVD technique
Published in Phase Transitions, 2023
Bolutife Olofinjana, Tobiloba Grace Fabunmi, Frank Ochuko Efe, Oladepo Fasakin, Adebowale Clement Adebisi, Marcus Adebola Eleruja, Olumide Oluwole Akinwunmi, Ezekiel Oladele Bolarinwa Ajayi
Over the years, copper sulphide has gained much interest due to its versatility and potential applications in optoelectronics and solid-state devices such as solar cells, electrochemical sensors, supercapacitors, gas sensors cathode materials in lithium rechargeable batteries, thin film coating for windows filters, among others [1]. This is a result of their tunable semiconductive and metallic characteristics based on their composition [2]. Copper sulphide belongs to a group of chemical compounds with the general molecular formula CuxSy, which can be both synthetic and natural (minerals) materials. Copper sulphide has varieties of stable phase compositions at room temperature among which are, covellite (CuS), anilite (Cu1.75S), digenite (Cu1.8S), djurleite (Cu1.95S), and chalcocite (Cu2S). They have properties in between the most prominent minerals of Cu2S (chalcocite) and CuS (covellite). They are known to have direct band gap energy between 2.4 and 3.8 eV; and absorption coefficients of around 104 cm−1 [3]. The room temperature electrical resistivity is of the order of 10−3–105 Ωm [4,5], which shows the tunable nature of copper sulphide as a result of their stoichiometry. The presence of different phases also has a great influence on electrical properties [6]. The I-V characteristics can be linear showing ohmic behavior [7] in some cases, and diode characteristics in both forward and reverse bias, in others [8].
An Analysis of Copper Concentrate from a Kupferschiefer-type Ore from Legnica-Glogow Copper Basin (SW Poland)
Published in Mineral Processing and Extractive Metallurgy Review, 2021
In Table A3 the mineral composition of the investigated concentrate is presented. The content of all sulfide minerals is about 33%. The sample contains copper sulfide minerals as chalcopyrite, bornite, chalcocite with digenite/djurleite and covellite. Moreover, among the sulfide minerals, the concentrate contains relatively high contents of pyrite with marcasite, galena and sphalerite. Assuming that the content of all sulfides is 100%, the content of non-copper-bearing sulfides in the concentrate is about 30%. The main gangue minerals occurring in the concentrate are clay minerals with micas, calcium and magnesium carbonates and quartz with a content about 46%. The presence of quite high contents of gangues and non-copper-bearing sulfides, equal to 67%, is one of the main reasons for the dilution of the concentrate, which significantly lowers the copper grade in the concentrate.
Magnetic phase transitions around room temperature in Cu
Published in Phase Transitions, 2019
Annette Setzer, Pablo D. Esquinazi, Lukas Botsch, Oliver Baehre, Eti Teblum, Anat Itzhak, Olga Girshevitz, Gilbert Daniel Nessim
The phase diagram of CuS with is rich in different phases around room temperature. Nine regions with six phases or mixtures of some of those phases were reported in the literature in the temperature region 260 K 380 K [1]. These phases were found to be anilite, covellite, djurleite, low-digenite, high-digenite and high-chalcocite. Their real structure at a given temperature, the position of the Cu and S atoms in the unit cell and the unit cell itself in each of those structures have been subject of a number of studies. The metastability of some of the found structures, the influence of the degree of atomic ‘disorder’ and nonstoichiometric samples prevented a complete clarification of several details of this rich phase diagram.