Melt Separation Research Articles

Direct analyses of fluorine in aqueous fluids extracted from 1-GPa experiments

Fluorine has been proposed as a useful geochemical tracer for tracking the transport of volatile elements in subduction zones as it is the last volatile element to be exsolved during magma ascent and crystallization. Accurate determination of the concentration of fluorine in geological fluids under high P-T conditions would greatly further the understanding of its geochemical behavior during aqueous transport and magma genesis in arcs. Mass balance is the most widely used method for calculating fluid compositions in hydrothermal experiments. However, the method is inaccurate when phase compositions and/or proportions have large uncertainties. In the current study, we present an alternative method based on the direct measurement of the concentration of F in fluids by extracting the enclosed liquid within experimental samples, and by performing high-pressure liquid chromatography (HPLC) analysis. We then compared the results of the direct analysis with those obtained by mass-balance calculations. Our experimental data demonstrated that direct analysis yielded more accurate concentration values than mass-balance calculation. The direct method is a useful alternative, when i) the phase assemblage is complex, ii) the total F content or the fluid proportion is low, or iii) when there is significant presence of hydrous melts. Caution should be exercised when applying direct analysis to samples that contained insoluble quench phases and/or were low in fluid. Direct HPLC analysis, combined with an improved extraction method that ensures the separation of quench phase, minerals and melts, could be of great utility for studying water-rock reactions.

Effect of Melt Conditioning on Removal of Fe from Secondary Al-Si Alloys Containing Mg, Mn, and Cr

Primary intermetallic sludge formation in hypoeutectic secondary Al7.1Si(1.5-xM)FexMM alloys was investigated in view of potential Fe removal by separation of sludge and Al melt. M is Mg, Mn, and Cr, with Mg as typical alloying element and Mn and Cr as additions to modify the sludge. Differential thermal analysis was used to determine the onset temperatures of sludge formation and solidification of the (Al)-solid solution. These temperatures were compared with results from the semi-empirical sludge factor approach and thermodynamic calculations. The chosen conditioning temperature of 620 °C is slightly above the onset temperature of solidification of the (Al)-solid solution in all alloys. At 620 °C, sludge did not form in alloys with xMg ≥ 0.6 at. pct. In all other alloys, sludge has formed. In the ternary Al7.1Si1.5Fe alloy and the alloy with xMg = 0.3 at. pct, the hexagonal αh phase is responsible for binding Fe, whereas Mg remains in the melt. The cubic αc phase binds Fe from the melt of Mn- and Cr-containing alloys. The (Al,Si)2Cr and Al13Cr4Si4 phases additionally bind Cr. The potential separation of the sludge from the residual melt leads to relative Fe removal up to 67 pct and relative transition-metal removal up to 65 and 83 pct.

Message in a bottle: Spontaneous phase separation of hydrous Vesuvius melt even at low decompression rates

Violent explosive volcanic eruptions are destructive and threaten millions of people and infrastructure. Ejected ash, pumice and gases are end-products of volcanic factories sourced deep within magma chambers and conduits. The different production stages are not directly observable. However, experimental simulation reveals different stages of dynamic volcanic processes. The starting point of explosive volcanic eruptions is determined by the phase separation of an H2O fluid from a supersaturated hydrous silicate melt. The number of formed H2O fluid vesicles per unit volume of silicate melt (VND) is a basic property that controls the efficiency of fluid-melt separation, ascent velocity and finally explosive volcanism. We performed decompression experiments at superliquidus temperatures to simulate phase separation of a single phase hydrous silicate melt during ascent with AD79 Vesuvius white pumice composition using decompression rates of 0.024–1.7 MPa⋅s−1. The white pumice buried Herculaneum and Pompeii and is representative of other catastrophic phonolitic and trachytic explosive eruptions like the violent 39 ka Campi Flegrei and the 1815 AD Tambora eruption. Here we report a high log⁡VND of 5.2 (in mm−3) that is independent from decompression rate within the investigated range. Even at a decompression rate of 0.024 MPa⋅s−1 the formation of a high VND inevitably causes rapid degassing due to short H2O diffusion distances from the melt into fluid vesicles. A decompression rate meter based on nucleation theory, which is commonly used to estimate magma ascent velocity during volcanic eruptions using VND of volcanic ejecta, cannot be adapted to explain our experimentally determined decompression rate independent VND. Alternatively, decompression induced H2O–silicate melt phase separation may be described by diffusion controlled spinodal decomposition where maximum supersaturation is reached. This process occurs spontaneously and free of activation energy if hydrous melt is driven into thermodynamic instability where the second derivative of free energy of mixing to the H2O content is ≤0. However, the decompression rate independent VND has profound consequences for the dynamics of natural polyphase hydrous magma phase separation. Even at low ascent rates spontaneous hydrous melt phase separation facilitates rapid density decrease accompanied by sudden increase of magma buoyancy triggering explosive eruptions.

Fluid–Silicate Separation of an Ultrabasic Melt into High-Potassium and Low-Potassium Fractions: Evidence from Picrites of the Late Cretaceous Ultrabasic Volcanic Complex, Eastern Kamchatka

The mineral and chemical compositions of the layered subvolcanic ultrabasic rocks formed through fluid–silicate (liquid) separation of the ultrabasic magma into high-potassium and low-potassium fractions are characterized by the example of the layered picritic sill from the Late Cretaceous ultrabasic volcanic complex of Eastern Kamchatka. It is determined that the main potassium concentrator in the picrites from the high-potassium layers is a residual volcanic glass containing up to 8–9 wt % K2O, which is unique for ultrabasic melts.

CALCULATION OF THE EQUIVALENT ELECTRICAL PARAMETERS OF THE INDUCTOR OF INDUCTION CHANNEL FURNACE WITH DEFECTS IN ITS LINING

Aim. The aim of the paper is to determine a quantitative relationship between measured impedance of the inductor and the electrical characteristics of the separated melt circuit parts for the determination of the place of a liquid metal leakage and for the improvement in such way the diagnostic system of lining state of induction channel furnaces. Technique. The study was performed on the basis of the concepts of theoretical electrical engineering, mathematical physics, and mathematical modeling. Results. Using two equivalent electrical circuits of the inductor the analytical expressions and graphical dependencies, which determine a quantitative relationship between the parameters of the separated parts of a liquid-metal circuit and the impedance of the whole inductor measured in practice, for the presence of different lining defects, were found. The method for calculating the increments of equivalent electrical parameters of the inductor as a function of increments of the parameters of the secondary liquid-metal circuit was proposed. Scientific novelty. It is proved that for small changes (less than 10 %) of the parameters of the liquid-metal circuit, it is expedient to use a linear relationship between its increments and to create the sensitivity matrix, which clearly shows the presence of a strong or weak interrelation between the disturbed values of the parameters of the secondary circuit and the inductor. Practical significance. The use of this technique allows to develop the database for various types of lining defects for a given furnace and on its basis to predict the places of a melt leakage and the state of furnace lining owing to periodical measurements of the inductor parameters.

Phosphorus migration mechanism between iron and high phosphorus gangue phase at high temperatures

The phosphorus migration mechanism during melting separation of non-carbon-reduced high phosphorus iron ore was investigated. Firstly, the equilibrium compositions of hydrogen-reduced high phosphorus iron ore at different temperatures were simulated by the use of equilibrium composition module of HSC Chemistry software. Then, thermodynamic calculation was verified by the real heat treatment of simulated hydrogen-reduced high phosphorus iron ore with several pure reagents including self-made pure fluorapatite. The iron particles in the simulated samples gathered and grew up during heat treatment. Meanwhile, the hypoeutectic structure of Fe–P with grid shape of high phosphorus phase and circular shape of low phosphorus phase emerged within those iron particles. With the penetration of phosphorus from the periphery into the iron particles, the grid structure became denser and denser. It proves that the elemental phosphorus can be reduced from the gangue phase by metallic iron without solid carbon at high temperatures.

The birth, growth and ageing of the Kaapvaal subcratonic mantle

The Kaapvaal craton and its underlying mantle is probably one of the best studied Archean entity in the world. Despite that, discussion is still vivid on important aspects. A major debate over the last few decades is the depth of melting that generated the mantle nuclei of cratons. Our new evaluation of melting parameters in peridotite residues shows that the Cr2O3/Al2O3 ratio is the most useful pressure sensitive melting barometer. It irrevocably constrains the pressure of melting (melt separation) to less than 2 GPa with olivine (ol), orthopyroxene (opx) and spinel (sp) as residual phases. Garnet (grt) grows at increasing pressure during lithosphere thickening and subduction via the reaction opx + sp → grt + ol. The time of partial melting is constrained by Re-depletion model ages (TRD) mainly to the Archean (Pearson and Wittig 2008). However, only 3% of the ages are older than 3.1 Ga while crustal ages lie mainly between 3.1 to 2.8 Ga for the W- and 3.7 to 2.8 Ga for the E-block. Many TRD-ages are probably falsified by metasomatism and the main partial melting period was older than 3.1 Ga. Also, Nd- and Hf- model ages of peridotitic lithologies from the W-block are 3.2 to 3.6 Ga old. The corresponding very negative eNd (−40) and eHf values (−65) signal the presence of subducted crustal components in these old mantle portions. Subducted components diversify the mantle in its chemistry and thermal structure. Adjustment towards a stable configuration occurs by fluid transfer, metasomatism, partial melting and heat transfer. Ages of metasomatism from the Lu-Hf isotope system are 3.2 Ga (Lace), 2.9 Ga (Roberts Victor) and 2.62 Ga (Finsch) coinciding with the collision of cratonic blocks, the growth of diamonds, metamorphism of eclogites and of Ventersdoorp magmatism. The cratonic lithosphere was stabilized thermally by the end of the Archean and cooled since then with a rate of 0.07 °C/Ma.

Magmatic sulfide immiscibility at an active magmatic-hydrothermal system: The case of La Fossa (Vulcano, Italy)

Magmatic sulfide minerals preserved in fresh volcanic rocks can be used to trace sulfur and chalcophile element evolution in magmatic systems and to constrain the potential magmatic contribution to ore-forming fluids. In this work, we present a petrographic and microanalytical study of magmatic sulfides in the products of La Fossa (Vulcano, southern Italy), an active arc-related volcano currently with a shallow acidic hydrothermal system, and discuss the results with petrological data obtained from melt inclusions. While the sulfur-rich basalts feeding the plumbing system were oxidized and sulfide-undersaturated, as common in arc-basalts, a major event of sulfide melt separation from the silicate melt occurred at the trachytic stage, in the shallow reservoir (minimum depth based on H2O content of melt inclusions is 1200–2200 m), promoted by the lowering of fO2. Sulfide immiscibility was unrelated to magnetite fractionation and was encountered after a notable sulfur loss at the transition from mafic to intermediate magma composition. The late sulfide saturation implies that the silicate melt became enriched in Cu with differentiation. This is indicated by the relatively high Cu concentration in the analyzed sulfide blebs, comparable to the composition of sulfides found in other active arc volcanoes as well as in magmatic systems associated with porphyry copper mineralization. The newly reported occurrence of sulfide immiscibility in the La Fossa shallow reservoir has implications for the evolution of sulfur in the plumbing system and for the contribution of magmatic sulfur and metals to surface fumaroles, as well as to the deep hydrothermal fluids during non-eruptive periods. The results indicate that La Fossa volcano is a possible active analogue of mineralizing magmatic-hydrothermal systems.

Integrating field, textural, and geochemical monitoring to track eruption triggers and dynamics: a case study from Piton de la Fournaise

Abstract. The 2014 eruption at Piton de la Fournaise (PdF), La Réunion, which occurred after 41 months of quiescence, began with surprisingly little precursory activity and was one of the smallest so far observed at PdF in terms of duration (less than 2 days) and volume (less than 0.4 × 106 m3). The pyroclastic material was composed of golden basaltic pumice along with fluidal, spiny iridescent and spiny opaque basaltic scoria. Density analyses performed on 200 lapilli reveal that while the spiny opaque clasts are the densest (1600 kg m−3) and most crystalline (55 vol. %), the golden pumices are the least dense (400 kg m−3) and crystalline (8 vol. %). The connectivity data indicate that the fluidal and golden (Hawaiian-like) clasts have more isolated vesicles (up to 40 vol. %) than the spiny (Strombolian-like) clasts (0–5 vol. %). These textural variations are linked to primary pre-eruptive magma storage conditions. The golden and fluidal fragments track the hotter portion of the melt, in contrast to the spiny fragments and lava that mirror the cooler portion of the shallow reservoir. Exponential decay of the magma ascent and output rates through time revealed depressurization of the source during which a stratified storage system was progressively tapped. Increasing syn-eruptive degassing and melt–gas decoupling led to a decrease in the explosive intensity from early fountaining to Strombolian activity. The geochemical results confirm the absence of new input of hot magma into the 2014 reservoir and confirm the emission of a single shallow, differentiated magma source, possibly related to residual magma from the November 2009 eruption. Fast volatile exsolution and crystal–melt separation (second boiling) were triggered by deep pre-eruptive magma transfer and stress field change. Our study highlights the possibility that shallow magma pockets can be quickly reactivated by deep processes without mass or energy (heat) transfer and produce hazardous eruptions with only short-term elusive precursors.

Immiscible hydrous Fe\u2013Ca\u2013P melt and the origin of iron oxide-apatite ore deposits

The origin of iron oxide-apatite deposits is controversial. Silicate liquid immiscibility and separation of an iron-rich melt has been invoked, but Fe–Ca–P-rich and Si-poor melts similar in composition to the ore have never been observed in natural or synthetic magmatic systems. Here we report experiments on intermediate magmas that develop liquid immiscibility at 100 MPa, 1000–1040 °C, and oxygen fugacity conditions (fO2) of ∆FMQ = 0.5–3.3 (FMQ = fayalite-magnetite-quartz equilibrium). Some of the immiscible melts are highly enriched in iron and phosphorous ± calcium, and strongly depleted in silicon (<5 wt.% SiO2). These Si-poor melts are in equilibrium with a rhyolitic conjugate and are produced under oxidized conditions (~FMQ + 3.3), high water activity (aH2O ≥ 0.7), and in fluorine-bearing systems (1 wt.%). Our results show that increasing aH2O and fO2 enlarges the two-liquid field thus allowing the Fe–Ca–P melt to separate easily from host silicic magma and produce iron oxide-apatite ores.

The role of carbonate-fluoride melt immiscibility in shallow REE deposit evolution

The Lugiin Gol nepheline syenite intrusion, Mongolia, hosts a range of carbonatite dikes mineralized in rare-earth elements (REE). Both carbonatites and nepheline syenite-fluorite-calcite veinlets are host to a previously unreported macroscale texture involving pseudo-graphic intergrowths of fluorite and calcite. The inclusions within calcite occur as either pure fluorite, with associated REE minerals within the surrounding calcite, or as mixed calcite-fluorite inclusions, with associated zirconosilicate minerals. Consideration of the nature of the texture, and the proportions of fluorite and calcite present (∼29 and 71 mol%, respectively), indicates that these textures most likely formed either through the immiscible separation of carbonate and fluoride melts, or from cotectic crystallization of a carbonate-fluoride melt. Laser ablation ICP-MS analyses show the pure fluorite inclusions to be depleted in REE relative to the calcite. A model is proposed, in which a carbonate-fluoride melt phase enriched in Zr and the REE, separated from a phonolitic melt, and then either unmixed or underwent cotectic crystallization to generate an REE-rich carbonate melt and an REE-poor fluoride phase. The separation of the fluoride phase (either solid or melt) may have contributed to the enrichment of the carbonate melt in REE, and ultimately its saturation with REE minerals. Previous data have suggested that carbonate melts separated from silicate melts are relatively depleted in the REE, and thus melt immiscibility cannot result in the formation of REE-enriched carbonatites. The observations presented here provide a mechanism by which this could occur, as under either model the textures imply initial separation of a mixed carbonate-fluoride melt from a silicate magma. The separation of an REE-enriched carbonate-fluoride melt from phonolitic magma is a hitherto unrecognized mechanism for REE-enrichment in carbonatites, and may play an important role in the formation of shallow magmatic REE deposits.

Magmatic evolution and controls on rare metal-enrichment of the Strange Lake A-type peralkaline granitic pluton, Québec-Labrador

Although it is well known that A-type granites are enriched in the rare earth elements (REE) and other high field strength elements (HFSE), the magmatic processes that concentrate these elements are still poorly understood. The 1.24 Ga Strange Lake pluton in northern Québec-Labrador provides an extraordinary example of hyper-enrichment in the REE, Zr, and Nb in a peralkaline A-type granite. The pluton consists of two hypersolvus granite units (southern and northern) and a transsolvus granite, all of which contain perthitic alkali feldspar as the earliest major mineral; the transsolvus granite also contains separate albite and microcline crystals. Arfvedsonite, a sodic amphibole, occurs exclusively as phenocrysts in the transsolvus granite, whereas in the hypersolvus granite it is present as a late, interstitial phase. The primary HFSE minerals are zircon, monazite-(Ce), gagarinite-(Ce) and the pyrochlore group minerals.Magma evolution was monitored by the alumina content in the bulk rock, which decreases from the southern to the northern hypersolvus granite and is lowest in the transsolvus granite. Alkalinity indices and bulk Si, Fe, Rb, REE, Zr, Nb concentrations show the opposite trend. Alkali feldspar compositions mirror the trend shown by the bulk rock, i.e., decreasing Al contents are accompanied by increasing Si, Fe3+, REE, Zr and Nb contents.The major driving forces for the evolution of the hypersolvus magma prior to emplacement were the early separation of a fluoride melt from the silicate melt and the crystallization of alkali feldspar and HFSE-rich phases (zircon, monazite-(Ce), pyrochlore group). An alkali feldspar-rich crystal-mush containing LREE-fluoride melt droplets was emplaced as the least evolved southern hypersolvus granite. Massive fractionation of alkali feldspar led to a sharp increase in ƒH2O and F− activity in the magma chamber that triggered the crystallization of arfvedsonite and was followed by emplacement of the northern hypersolvus granite, which contained a higher proportion of LREE-fluoride melt droplets. Further evolution in the magma chamber led to a transition from a miaskitic to an agpaitic composition. The transsolvus granite was intruded in the form of a low viscosity crystal mush of alkali feldspar, quartz, arfvedsonite (after appreciable crystallization of arfvedsonite) and LREE-fluoride melt droplets. Upon emplacement, arfvedsonite (and gagarinite-(Ce)) crystals segregated as cumulates in response to a combination of flow differentiation and gravity settling. The immiscible fluoride melt accumulated in a volatile-rich residual silicate magma, which migrated to the top of the pluton where it formed the F-REE-rich cores of highly mineralized pegmatites.

Reduction and melting separation mechanism of boron-bearing iron concentrate/coal composite pellet

Realizing the boron and iron separation through selective reduction and melting separation of boron-bearing iron concentrate is of great significance for the utilization of crude ludwigite. The reduction and melting separation mechanism of boron-bearing iron concentrate/coal composite pellet was systematically investigated. The reduction and melting separation test of small size pellet was performed to reveal the evolution of slag and iron in the melting separation process. The isothermal reduction experiment showed the relationship between reduction stage and melting separation stage, and the step reduction and melting separation was perfectly achieved. Coal particles existed through the reduction and melting separation process and finally formed brown residue around the separated product. The pellet could not realize melting separation when the B2O3 content in the concentrate was lower than 6.00 wt%.

Liquid-liquid phase separation and solidification behavior of Al55Bi36Cu9 monotectic alloy with different cooling rates

Abstract The cooling rate has a significant effect on the solidification behavior and microstructure of monotectic alloy. In this study, different cooling rate was designed through casting in the copper mold with different bore diameters. The effects of different cooling rate on the solidification behavior of Al55Bi36Cu9 (at.%) immiscible alloy have been investigated. The liquid-liquid phase separation of Al55Bi36Cu9 immiscible alloy melt was investigated by resistivity test. The solidification microstructure and phase analysis of Al55Bi36Cu9 immiscible alloy were performed by the SEM and XRD, respectively. The results showed that the liquid-liquid phase separation occurred in the solidification of Al55Bi36Cu9 monotectic melt from 917 °C to 653 °C. The monotectic temperature, liquid phase separation temperature and immiscibility zone of Al55Bi36Cu9 monotectic alloy was lower than those of Al-Bi binary monotectic alloy. The solidification morphology of Al55Bi36Cu9 monotectic alloy was very sensitive to the cooling rate. The Al/Bi core-shell structure formed when Al55Bi36Cu9 melt was cast in the copper mold with a 8 mm bore diameter.

On Thermocapillary Mechanism of Spatial Separation of Metal Melts

Theoretical research has been devoted to the study of binary metal melts behavior in a thin capillary. Earlier it has been found experimentally that unusually significant and quick redistribution of melts components takes place along capillary after the cooling. Numerical simulation of concentration-induced convection has been carried out to explain these experimental data. Two-component melt of both liquid metals filling vertical thin capillary with non-uniform temperature distribution on the boundaries is considered. It is assumed that the condition of absolute non-wetting is valid on the sidewalls. Because of this effect there is a free surface on vertical boundaries, where thermocapillary force is appeared due to the external longitudinal temperature gradient. It makes to move liquid elements at a big distance, compared with axial size of capillary. Effects of adsorption-desorption on the surface, thermal and concentration-capillary forces, convective motion in a volume and diffusion generate the large-scale circulation. This process includes the admixture carrying-out on the surface in the more hot higher part of the channel, its following transfer down along the boundary due to the thermocapillary force and its return in the volume over the desorption in the lower part of capillary. Intensity of motion and processes of adsorption-desorption on the free boundary have the decisive influence upon the formation of concentration fields and speed of components redistribution. Thus, one of the possible mechanisms of longitudinal division on components of liquid binary mixtures in thin channels has been demonstrated.

Formation of Metallic Phase on Reducing-Gas Injection in Multicomponent Oxide Melt. Part 3. Separation of Ferronickel and Oxide Melt

Using the equations of physicochemical hydrodynamics and experimental results regarding the surface and interphase properties of metallic and oxide melts, the conditions in which metallic phase is formed in the bubbling of carbon monoxide through molten oxidized nickel ore are described. The critical dimensions of the gas bubble (Rb.cr) and the metal droplet (rd.cr) moving in oxide melt without change in size are determined in the range 1550–1750°C. It is found that Rb.cr increases slightly from 6.35 × 10–2 m at 1550°C to 6.58 × 10–2 m at 1750°C. With change in the droplet composition and the temperature, rd.cr varies from 2.1 × 10–3 to 2.9 × 10–3 m. The dimensions of the metal droplet formed at a single bubble during the reduction of nickel and iron from oxide melt are determined. As the content of nickel and iron oxides in the melt decreases with increase in the overall CO consumption, the nickel content in the ferronickel droplets falls from 89 to 18%, while the droplet diameter decreases from 1.4 × 10–3 to 8.0 × 10–4 m. The droplet mass falls correspondingly from 9.4 × 10–5 to 1.6 × 10–5 kg. The conditions in which the bubble–droplet system rises through the melt are determined. Over the whole range of temperature and Ni content, the bubble–droplet system begins to rise through the oxide melt when rd/Rb is less than 0.68–0.78. To assess the stability of the bubble–droplet system, with the given bubble and droplet dimensions, the parameters determining their joint motion are calculated. It is found that breakaway of the metal droplet from the bubble is not possible in pyrometallurgical systems. The formation of metal phase as a result of the bubbling of carbon monoxide through the oxide melt is described. In this process, the interaction of the oxide melt with the gas is accompanied by the formation of metal droplets, which become attached to the surface of gas bubbles and move to the surface of the oxide melt. Metal with 80–90% Ni is formed at first. With decrease in the nickel content in the oxide melt, its content in the metal declines to 20%. At the surface of the oxide melt, the metal droplets coalesce. When their diameter is greater than 5 × 10–3 m, they break away from the surface and fall to the bottom. If the falling drop collides with ascending bubble–droplet systems, they may coalesce with it or flow around it. On coalescence, the small droplets will be assimilated and rise to the surface. The breakaway force of the droplet from the bubble significantly exceeds the gravitational force on the droplet. Therefore, the bubble–droplet system is stable for all the size ratios considered.

Effects of Pre‐Reduction Degree of Ironsand on Slag Properties in Melting Separation Process

Ironsand is a kind of titanomagnetite ore and has been maturely used through direct reduction (DR) and melting separation (MS) processes. As an intermediate parameter, pre‐reduction degree (PRD) can be controlled in the upstream DR, and has a considerable influence on metal/slag separation in subsequent MS. Thus, the effects of PRD on the properties of melting separation slag from pre‐reduced ironsand are studied in order to ensure the melting separation sufficient at the condition of slag with high titanium oxide content. The softening, melting, and flowing temperatures of slag show different variation trends along with PRD changing, and the slag at 90% PRD has the narrowest softening‐flowing temperature interval. The viscosity of slag of 90% PRD also shows the proper smelting characteristic. Moreover, Raman spectra results indicate the increase PRD reduces the depolymerized product Si–O–M (metal), which is mainly caused by the decreasing of network‐modifier FeO. Polymerization degree ψ ((Q3 + Q2)/(Q1 + Q0)) illustrates the high PRD is consistent with the complicated silicon network structures, especially when PRD is larger than 90%.

Volume and Surface Properties of a Bismuth-Containing Separating Nickel Melt

The influence of a bismuth impurity on the properties of solid and liquid alloys in the concentration range that obeys Henry’s law is considered. The structural and physicochemical properties, specifically, the density and the surface tension, of real melts are studied on relatively pure metals. The changes in the properties of the melts are estimated from changes in the temperature dependences of the density and the surface tension upon heating and cooling and in the concentration dependences of these parameters at a constant temperature. These dependences exhibit a correlation between the volume and surface properties of the melts: the density and the surface tension increase or decrease simultaneously. The introduction of bismuth in the nickel melt is accompanied by the appearance of a relatively strong compression effect (i.e., a decrease in the melt volume). At a certain bismuth content in the melt, the compression effect weakens because of the appearance of an excess phase or its associates and melt separation.

Natural convection characterization during melting of phase change materials: Development of a simplified front tracking method

This study presents the development of a front tracking method for melting of phase change materials (PCMs) inside horizontal shell and tube heat exchangers. Two numerical models, i.e. pure conduction (PC) model as well as combined conduction and natural convection (CCNC) model, are used to develop the method. Governing equations are numerically solved by ANSYS Fluent v17.2. The PC model benefits from simplicity but its prediction is far from reality, whereas CCNC model’s prediction is more realistic but its modeling is complicated. Generally, during the melting process, the upper half of the system is affected by the upward buoyancy-driven melted PCM motion. To consider this phenomenon, the front tracking method assumes that the upper and lower halves of the system have two separate melting fronts. Therefore, it is assumed that the natural convection contributes only to the upper half until the upper half liquid fraction value reaches unity. Meanwhile, the lower half melting front is assumed to be the same as that of the PC model. Once the upper half is totally melted, the method attributes the rest of the natural convection to the lower half of the system. Using three different PCMs and three different geometries, two correlations have been developed for each half based on two dimensionless numbers; i.e. the shell-to-tube radius ratio and PC model liquid fraction. The method is then verified using another PCM, which has not been included during the correlation development stage to guarantee the methods validity. These correlations provide results within ±15% discrepancy range.

Supergravity separation for recovering Pb and Sn from electronic waste

Abstract Electronic waste (e-waste) contains plenty of toxic substances as well as valuable metals (e.g. Pb and Sn). The storage of e-waste presents a long-term environmental issue but also an opportunity to recover valuable metals. Supergravity as a novel technology was used to separate and recover Pb-Sn alloy from e-waste in this study. Based on the different melting points of various metals, it can separate Pb and Sn from e-waste by melt separation in a supergravity field produced by a centrifugal apparatus. Several parameters affecting the recovery of Pb and Sn were investigated. Under optimal conditions including a gravity coefficient of 1000, centrifugal time of 5 min, and temperature of 410 °C, the recovery values of Pb and Sn were 54.41% and 41.94%, respectively. The (Pb + Sn)% of Pb-Sn alloy was 94.84 wt.% and the mass ratio of Pb/Sn was 0.66. This Pb-Sn alloy was suitable as raw materials for industrial applications. Some solid solutions were formed with Sn may be the main reason for the low recovery of Sn.