ABSTRACT A flame-emission spectrometer was built to determine the elemental composition of powdered minerals that are important in copper smelting processes. The feedstock, consisting of milled concentrate, was fed into an oxyacetylene flame without sample preparation. The elemental composition (Cu, Fe, S, Si, and Zn) was determined by applying an artificial neural network (ANN) to a set of emission spectra obtained from Cu and Fe pure elemental powders, five pure mineral powders of known composition and 30 binary mixtures of these mineral samples. The ANN model was able to accurately predict the Cu and Fe content of these mineral powders within better than 2% of the value obtained from ICP-OES. The analysis was repeated on 12 industrial samples with well-known compositions. Spectra from these samples were analyzed both in isolation of the reference minerals and together with the reference minerals, giving similar results.

A corrosion study examined stainless steel (SS) S31600/SS316 after exposure to the liquid metal galinstan and gases, including nitrogen, n-pentane, isobutane, and R245fa, at 150 °C under dynamic conditions for 3.5, 9.5, and 20.5 days. Ampules partly filled with galinstan and the gas were continuously stirred to create regions of gas-only, gas–liquid, and liquid-only exposure. Posttest examinations used a variety of qualitative and quantitative methods (visual observation, scanning electron microscopy with energy dispersive X-ray spectroscopy, surface profilometry, and chemical analysis) to evaluate coupons and galinstan samples for evidence of corrosion. In the gas-exposed region, no corrosion was detected in any coupon. In the liquid region, galinstan constituents were found to be localized to grain boundaries for nitrogen and isobutane coupons but dispersed on n-pentane coupons; a gallium oxide layer was found on R245fa coupons. In the liquid–gas interface region, severe corrosion was found on the n-pentane 20.5-day and the isobutane 9.5- and 20.5-day coupons; fine scattered corrosion on the R245fa 9.5-day coupon but not on the 20.5-day coupon was observed. Profilometry results indicated the least roughness change for coupons in n-pentane, a higher change in nitrogen, then in isobutane, and the highest in R245fa. In the presence of refrigerants and under dynamic conditions, intergranular attack on SS may be enhanced by chemical reactions combined with microsegregation of galinstan or gallium oxide elements on SS grain boundaries. Further work is required to confidently identify and explain this corrosion mechanism.

Commercial bulk hydrogen is mainly produced in petrochemical steam reforming furnaces inside centrifugally cast Nb-modified HP austenitic stainless steels tubes, which operate at temperatures above 900 °C. In-service aging causes well known microstructural modifications such as the transformation of primary niobium carbides, NbC, into the G-phase (Ni16Nb6Si7). Unexpected operational problems, such as reduced feedstock flow may, in a few minutes, cause severe overheating. These short-time temperature surges, can lead tubes to premature failure often through the formation of large longitudinal cracks. Little is known about the integrity of the tubes that undergo a temperature surge without cracking. Thus, understanding the microstructural changes brought upon by these events becomes extremely important when assessing the reuse of these tubes. In the present work, by means of optical microscopy, scanning electron microscopy and transmission electron microscopy with energy dispersive X-ray spectroscopy, two Nb and NbTi-modified HP steels tubes, which cracked due to high temperature surges, were analyzed. Results show that insitu dissolution of the G-phase in the thermally affected regions causes this phase to be replaced by fine NbC or (NbTi)C precipitates. These microstructural transformations suffered by the tubes during the short-time overheating and cooling cycles are thus presented and discussed in terms of their practical consequences.

Cu-Ni-Fe alloys are promising inert anodes for green Al production but their corrosion resistance must be improved. Here, protective (Co,Ni)O coatings are deposited by high velocity oxygen fuel (HVOF) process on Cu-Ni-Fe alloys. The influence of the coating and substrate compositions on their behavior is studied at 1000 °C under argon and air. On Cu-rich alloy, CoxNi1−xO coatings with higher nickel content slow down oxygen diffusion to the substrate, as well as copper diffusion to the sample surface. On Ni-rich alloy, the formation of a NiFe2O4 scale is observed, whose thickness decreases as the Ni content of the CoxNi1−xO coatings increases.

AbstractTitanium diboride (TiB2) is considered as a promising cathode material for Al production. However, the manufacture of TiB2 cathodes is facing numerous challenges. In this study, electrodeposition of TiB2 on graphite was performed in molten fluoride (FLiNaK) electrolyte at 600°C by using a periodically interrupted current technique for various electrodeposition times (from 10 to 75 minutes) and at two different current densities (−0.12 and −0.5 A/cm2). It is shown that the TiB2 coating morphology/microstructure strongly depends on the applied current density. Denser coatings were obtained at jon = −0.12 A/cm2 with a growth rate of ca. 0.7 µm/min. The thicker films display a preferential crystallographic orientation along the [110] plan. At jon = −0.5 A/cm2, TiB2 coatings are deposited at a growth rate of ca. 6 µm/min with no crystallographic texture. They present a porous and stratified morphology with numerous transversal macrocracks. All TiB2 coatings show excellent wettability for molten Al as confirmed by sessile drop experiments. However, significant molten Al infiltration occurs in the TiB2 coatings, which accumulates at the coating/graphite interface, inducing the coating delamination.

ABSTRACT Blue Sky Uranium Corporation’s Amarillo Grande Project in Rio Negro Province, Argentina, features the Ivana near-surface uranium deposit, which has significant vanadium credits. This article begins by reviewing the project location and the specific qualities of the Ivana deposit that led to decisions on the Ivana mining and mineral processing methods. The bulk of the article describes the thought process that resulted in the innovative and unique conceptual milling process for uranium and vanadium recovery. The deposit mineralogy is described in detail. The milling process begins with attrition scrubbing of the mined material to reject coarser barren material and increase mill feed grade by four times. Alkaline carbonate leaching is followed by pressure filtration. The pregnant leach solution is concentrated with concomitant reagent and water recovery using membrane filtration. Activated carbon columns remove the organic impurities from the concentrated leach solution, which then feeds the unique solvent extraction circuit. The solvent extraction process separates uranium and vanadium. Uranium is precipitated as uranium peroxide, which is calcined to U3O8. Vanadium is precipitated as ammonium vanadate, which is calcined to V2O5. The process releases no liquid effluents to the environment.