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In the present investigation, steel plates were joined at different tool traversing speed by friction stir welding keeping other parameters same. Microstructural char- acterization was carried out with optical and scanning electron microscopes. At weld nugget pearlite and bainite were present within ferrite matrix. Thermo-me- chanically and heat affected zones microstructure consisted of pearlite and ferrite. Second phase area fraction and matrix grain size at different regions were varied depending on welding parameters. Weld nugget exhibited substantial improvement in microhardness with respect to base metal. In this respect heat affected zone re- vealed minimum microhardness and was below base metal value. Tensile tests were carried out on standard and miniature specimens in scanning electron micro- scope. Highest joint efficiency to the tune of ~82 % and ~120 % of that of base metal obtained for standard and miniature specimens, respectively machined from weld fabricated at lowest welding speed. With increment in welding speed assem- bly strength was reduced for both types of specimens. Standard specimens failed from heat affected zone and miniature specimens failed through centre of weld nugget. Apart from matrix grain size and second phase area fraction, precipitation of microalloyed carbide / carbonitride was responsible for altering the joint strength.

Since the world economy has been confronted with an increasing risk of supply shortages of critical raw materials (CRMs), there has been a major interest in identifying alternative secondary sources of CRMs. Bauxite residues from alumina production are available at a multi-million tonnes scale worldwide. So far, attempts have been made to find alternative re-use applications for bauxite residues, for instance in cement / pig iron production. However, bauxite residues also constitute an untapped secondary source of CRMs. Depending on their geological origin and processing protocol, bauxite residues can contain considerable amounts of valuable elements. The obvious primary consideration for CRM recovery from such residues is the economic value of the materials contained. However, there are further benefits from re-use of bauxite residues in general, and from CRM recovery in particular. These go beyond monetary values (e.g. reduced investment / operational costs resulting from savings in disposal). For instance, benefits for the environment and health can be achieved by abatement of tailing storage as well as by reduction of emissions from conventional primary mining. Whereas certain tools (e.g. life-cycle analysis) can be used to quantify the latter, other benefits (in particular sustained social and technological development) are harder to quantify. This review evaluates strategies of bauxite residue re-use / recycling and identifies associated benefits beyond elemental recovery. Furthermore, methodologies to translate risks and benefits into quantifiable data are discussed. Ultimately, such quantitative data are a prerequisite for facilitating decision-making regarding bauxite residue re-use / recycling and a stepping stone towards developing a zero-waste alumina production process. © 2018 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The development of a hybrid system, capable of storing energy, and with the additional benefit of Cu extraction is discussed in this work. A fixed bed flow cell (FBFC) was used in which a composite negative electrode containing CuFeS2 (80 wt. %) and carbon black (20 wt. %) in graphite felt was separated from a positive (graphite felt) electrode by proton exchange membrane. The anolyte (0.2M H2SO4) and catholyte (0.5M Fe2+ in 0.2M H2SO4 with or without 0.1M Cu2+ addition) were circulated in the cell. With the addition of Cu2+ in the catholyte, the electrochemical activity of the Fe2+/Fe3+ redox couple over graphite felt was significantly improved. Ultimately, in the CuFeS2||Fe2+/Cu2+ (CFeCu) FBFC system the specific capacity increased continuously to 26.4 mAh-g-1 in 500 galvanostatic charge/discharge (GCD) cycles, compared to the CuFeS2||Fe2+ (CFe) system (13.9 mAh-g-1). Interestingly, the specific discharge energy gradually increased to 3.6 Wh-kg-1 in 500 GCD cycles for the CFeCu system compared to 3.29 Wh-kg-1 for the CFe system in 150 cycles. In addition to the energy storage, 10.75 % Cu was also extracted from the mineral, which is an important feature of CFeCu system as it would allow for Cu extraction and recovery through hydrometallurgical methods.

Cutter consumption and parameters such as cutter ring wear has a great relevance in the overall excavation time and cost in hard rock tunnel boring machines (TBMs), especially in hard rock conditions. Cutter wear involves a complex tribological system that interacts also with the geologicy of the rock mass. Understanding the processes and failure mechanisms during cutter wear (e.g. modes of contact, wear, load effects) and assessing the influence of temperature on cutter ring wear processes enables new knowledge to be applied to get better cutter consumption predictions and future improvements in cutter ring development. In addition, it might be used to evaluate the suitability of the new rock abrasivity test method (Rolling Indentation Abrasion Test, RIAT) for assessing cutter ring wear. © 2018. This is the authors’ accepted and refereed manuscript to the article.

Das Atmospharenpartikel-Kinetikmodell ist ein hilfreiches Werkzeug, um die Partikelkinetik in Abhangigkeit der Verweilzeit zu bestimmen. Dieses Modell ermoglicht die Quantifizierung verschiedenster Einflussparameter in einer RecoDust-Pilotanlage zur pyrometallurgischen Aufbereitung von zinkhaltigen Stauben. Dabei sind die wichtigsten Parameter die Temperatur, Gaszusammensetzung und -geschwindigkeit, Partikelgrose sowie die Partikeleingangstemperatur. Die Grose des gewahlten Betrachtungsraumes orientiert sich an der Grose des vorhandenen Reaktors. Die Fluidphase wird als Euler-Phase betrachtet und die Partikel uber einen Lagrange-Ansatz modelliert. Als Ergebnis wird die Anderung der Zusammensetzung in Abhangigkeit von der Reaktionsgeschwindigkeit in dem Partikel fur gegebene Parameter erhalten.

Argon oxygen decarburization (AOD) slag represents more than 50 wt% of the slag from stainless steel production. Although some applications are available, e.g. as aggregates for road constructions or fertilizers, they are characterized by low economic value and limited applicability. In order to increase the economic value of AOD slag, alternative applications have been proposed, e.g. as partial or full replacement for Ordinary Portland Cement (OPC). The work presented here investigates whether the adaptation of the AOD slag chemistry within a high temperature process leads to an improvement of its hydraulic properties and thereby can demonstrate its potential to be converted into a hydraulic binder suitable for OPC replacement. For this purpose, three synthetic AOD slags with basicities (CaO/SiO2) of 2.0, 2.2, and 2.4 were synthesized, and the effect of the CaO/SiO2 ratio on the material stability, the amount of tricalcium silicate formed, and their hydraulic properties investigated. X-Ray diffraction, scanning electron microscope (SEM), and isothermal calorimetry analysis were used to characterize the microstructure and the hydraulic activity. The results show that the proposed method is indeed a promising way to stabilize a stainless steel AOD slag and convert it into a hydraulic binder. This article is protected by copyright. All rights reserved.