1,721,146 research outputs found
Slag-Metal Separation in Mn Ferroalloy Production
No full textThe separation of slag and metal in the ferroalloy production process is an important issue that has an impact on both the ecological and environmental considerations of the entire production process. The extensive mixing of metal and slag during the tapping into ladles leads to the formation of a considerable amount of metal droplets in slag due to interfacial interaction and turbulence of the molten flow from the tap-hole. The entrainment of metal droplets into the slag phase causes ferroalloy losses with the slag, creating additional difficulties in the removal of metal from the slag. It is known that the separation of metal and slag is strongly influenced by interfacial phenomena and for this reason they were studied in this thesis, and the influence of interfacial tension and surface tension were also discussed for ferroalloy-slag systems.
The main goal of this research work was to understand interfacial phenomena between ferroalloy and slag. This has been achieved by developing a methodology for investigating the interfacial interaction in ferroalloy-slag systems, modelling the separation of molten slag and metal in OpenFOAM, and assessing operational parameters and physical properties affecting the formation of metal-slag emulsion and metal droplets in slag. The microstructure of slag and metal phases under different conditions has also been extensively addressed.
This thesis demonstrates a novel methodology for estimating the interfacial tension between metal and slag which combines experiments in the sessile drop furnace and multiphase modelling in OpenFOAM. It was concluded that the interfacial interaction can be significantly altered by surface-active elements such as sulfur in ferroalloy-slag systems, as well as by changing the composition of the slag, which causes to the transfer of species or elements across the interface, creating interfacial instability and reducing the interfacial tension. As a consequence, the significant instability of the interface leads to higher losses of metal with the slag
Electrode paste behaviour in Søderberg electrodes in ferroalloys production
No full textThe main goal of this work has been to study the melting behavior of electrode paste used in Søderberg electrodes in ferroalloy production. It has been done by first measuring temperatures in an industrial electrode and identifying the temperature profiles the electrode paste goes through before baking. In the second part flow of electrode paste has been studied in a parallel plate viscometer.
Long thermocouples were used to measure the temperature in steel cylinders following the electrode casing, from a couple of meters above the molten paste level down to below the contact clamp tip. The temperature measurements show that the molten paste has a temperature of 80° C, and that temperatures of up to 280° C are reached above the contact clamp. The high temperatures above the contact clamp are caused by induced currents from the current tubes coming close to the electrode casing before entering the contact clamps.
A COMSOL model was used to model the effect of increased heating above the contact clamps, where after the model was compared to the experimental temperature measurements done. The model shows that by reducing the induced heating from the current tubes, the temperatures can be significantly lowered in the area above the contact clamps. Installing copper shields or increased flow of electrode air can be used to reduce the heating from induced currents in casing.
The flow measurements in the parallel plate viscometer showed that electrode paste is a non- Newtonian liquid with shear thinning characteristics in the temperature range 20-80° C. The electrode paste starts to flow at temperatures 25° C below the softening point of the binder. The electrode pastes tested in this work reach half the original height at around 75° C.
The viscosities measured in the parallel plate viscometer are apparent viscosities as many of the assumption in the underlaying equations are not followed in the measurement set-up used. Among other things the shear rate varies during measurements and is not even throughout the sample. Thus, apparent viscosity found in this work is only applicable under the same conditions as the experiments done, but can be used, with awareness of the measurement limitations, in industrial electrodes as measurement conditions are close to what is observed in industrial electrodes.
A mix of coal-tar pitch and fines were found to behave non-Newtonian liquid behavior above 30 % addition of anthracite fines. Increased fines content increases the viscosity of the mix and at 73% fines content the system is “locked” and does not flow.
The influence of coarse particles on electrode paste flow has also been studied in the parallel plate viscometer, where increased coarse content was found to increases apparent viscosity. Apparent viscosity of electrode pastes with more than 60 % coarse particles are heavily influenced by particle-particle interactions, as apparent viscosity does not increase much with more addition of coarse material. Paste with 70 % coarse particles have very little flow up to temperatures of 120 °C
Reduction of MnO and SiO2 from Assmang and Comilog based Slags
No full textSilicomanganese(SiMn) and ferromanganese (FeMn) represent essential ingredients for the steel producing industries due to enhancing effects on steel quality. While extensive efforts have been made in investigating the kinetics of ferromanganese production, kinetic information on the silicomanganese process is rather scarce.
The goal of this work was to investigate how different raw materials/charge compositions affect the reduction rate of MnO and SiO2 in SiMn production. The experimental work was carried out in a thermogravimetric furnace in CO-gas at ambient pressure with coke as reducing agent. Investigated charge compositions contained ore (Comilog or Assmang) and HC FeMn slag in a 1:1 ratio, quartz and coke. Melting behaviour was investigated for the mentioned Comilog charge at temperatures 1200-1400°C and compared to charge based on Comilog and quartz at corresponding temperatures. Both mixing and layering of raw materials in crucible were evaluated.
The slag formation temperature was determined to be in the range of 1250-1300°C for all investigated charges. All materials had formed a slag phase at 1250°C when materials were prepared by mixing in the crucible, whereas the quartz particles remained undissolved until 1300°C when prepared by layering.
Assmang and Comilog in combination with HC FeMn slag and quartz show highly similar reduction behaviour, however the rapid reduction stage was initiated at a lower temperature for Assmang, i.e 1535°C vs 1545°C for Comilog.
Charges based on Comilog ore, HC FeMn slag and quartz start to reduce at approximately 50°C lower temperature compared to charges based on Comilog, quartz and coke (and limestone), in spite of lower sulphur content, lower basicity and lower driving force.
There was no observed correlation between the total basicity/viscosity and the reduction rate. However, it was shown that the rate constant increases with the sulphur content.
Foaming was observed at 1550°C for Assmang charges, whereas the first occurrence was at approximately 1560°C for Comilog. It was concluded that the foaming phenomena is a result of initiation of the rapid reduction stage
Electrical Resistivity in Carbon Materials Converting to SiC
No full textMålet med dette arbeidet har vært å undersøke hvordan ledningsevnen i karbonmaterialer endres som følge av interaksjon med SiO gass ved høye temperaturer. Dette har blitt gjort som et ledd i å øke forståelsen av hvordan den elektriske ledningsevnen til karbon- og delvis omdannede materialer påvirker strømbanene i silisiumsovnen. Fordelingen av strøm i ovnens indre sone er avgjørende for å oppnå tilstrekkelig høy temperatur, og dermed også en optimal produksjonsprosess. Flere studier som omhandler karbonmaterialer brukt i produksjon av silisium er blitt tilgjengelig de siste par årene, men verken utstyr for å måle eller målinger gjort i karbonmaterialer som reagerer med SiO gass er tidligere rapportert. Målene som ønskes oppnådd er blitt undersøkt ved
• Utvikling av utstyr og måling av elektrisk resistivitet i karbonmaterialer som reagerer
med SiO gass ved en oppholdstemperatur på 1635 °C.
• Måling av elektrisk resistivitet i motsvarende ureagerte karbonmaterialer av trekull, samt varmebehandlet char og kull som funksjon av tid og temperatur.
Utstyret som ordinært benyttes til måling av resistivitet i karbonmaterialer er blitt modifisert ved å inkludere en enhet som produserer SiO gass. Både Si+SiO2 partikler og pellets av SiO2+SiC er blitt benyttet som reaktanter for produksjon av SiO gass ved oppvarming til mellom 1800 °C og 1870 °C. Trekull og varmebehandlet char ble delvis omdannet til SiC ved reaksjon med SiO gass, samt dannelse av et horisontalt lag av kondensat. Begrenset omdannelse til SiC ble påvist ved kartlegging av elementer i varmebehandlet char, mens en tilnærmet fullstendig omdannelse av trekull ble observert i materialet under laget av kondensat.
Når måltemperaturen ble oppnådd, var begrensede mengder SiC og kondensat dannet og den elektriske resistiviteten var lav. Med økende tid og SiO trykk reagerte karbonpartikler til SiC, samt at det ble dannet et lag av kondensat. Den elektriske resistiviteten økte svakt fra 10.9 mΩm til 13.7 mΩm i HT char, noe som sammenfaller med begrenset mengde reagert materiale. I de to målingene av trekull ble en større økning funnet, opp fra 17.9 mΩm og 12.5 mΩm til 200 mΩm og 150 mΩm. Da kondensat fra SiO gass inneholder SiO2 som er kjent som en god elektrisk isolator, er dannelsen av kondensat derfor antatt å overskygge effekten av SiC dannelse.
Den elektriske resistiviteten til trekull og varmebehandlet kull ble ved 1640 °C målt til henholdsvis 10.3 ± 0.3 mΩm og 7.0 ± 0.5 mΩm. Sammen med varmebehandlet char målt til 9.1 ± 0.2 mΩm ved 1610 °C i et forarbeid til dette prosjektet [1], er forskjellen mellom materialene ved temperaturer over 1100 °C signifikant. I tillegg, undersøkelser av holdetid ved høy temperatur viste ingen endring i resistivitet som funksjon av holdetid i verken trekull eller HT kull
Phases and Zones in the Silicon Process
Full text linkDifferent zones and materials formed during the production of silicon in a silicon furnace has been examined in this thesis. Samples from two industrial scale silicon furnaces have been have been studied. The excavations were of Wacker furnace 4 and Wacker furnace 1.
Wacker furnace 4 was excavated in August 2015 and samples retrieved are studied to gain a broader understanding of the zones observed by visual inspection of the furnace. Samples were collected from different zones in the furnace.
Wacker furnace 1 was excavated in April 2016. Samples studied were retrieved from areas close to the electrode, from the top of it to the bottom. The main focus was to see how charge materials change along the electrode when moving down in the furnace.
Fissured SiO2 phase is found in samples collected from both Wacker furnace 4 and Wacker furnace 1. They are discussed to be unreacted quartz, condensate or quartz transformed to amorphous phase with some cristobalite. They are concluded to be condensate or transformed quartz, as they are found in high temperatures areas, were softened and melted quartz is assumed to be more smooth.
In Wacker furnace 4, both green and brown condensate is found. It is discussed if the green and brown condensate origins from the same area, where some proba- bly has been moved due to the excavation method. Foamed slag is found near the loose charge and in the middle zone. SiC crust is found on the side of the elec- trode, and in the lower and upper part of the furnace. SiC crust is found in both electrode track zone and middle zone. A SiC/slag-mixture is found at the bottom of the furnace. The slag is mainly gehlenite and anorthrite. It has low viscosity.
In Wacker furnace 1, unreacted charge was found in the pre-reaction area. Un- reacted charge was found down to 1.2 m down in the furnace from the electrode holder. Half converted and fully converted coal to SiC was found 1.5 m from the electrode holder. Condensate with Si in a SiO2-matrix was found 2 m from the electrode holder. Both condensate and SiC crust was found at the bottom of the electrode and in the electrode track zone between electrode 1 and 3. There is found more product of Si underneath the electrode than in the electrode track zone between electrode 1 and 3. This indicates a Si pool.
The materials that make up the zones are different between furnace 4 and 1. This is due to operational history.
The characterization of samples from both furnaces by LOM, EDS, BSD and EPMA are coherent with the first impression and guesstimated characterization of the samples by visual inspection during the excavation.
LOM is a good way to get a preliminary impression of what the sample consists of and how a sample will look in the SEM and EPMA. SEM and EDS is good enough methods for qualitative characterization of phases in a Si furnace. The EDS analysis will be wrong, but consistent for phases of Si and SiC. The problem of carbon coating, making both Si and SiC contain carbon, is solved since the phases will be differed by the amount of carbon found.
Slag samples are hard to analyze and to obtain good qualitative characterization with SEM and EDS. The slag analysis is better by the use of EPMA, but an ap- proximately characterization can be done with the SEM and EDS.
To determine if SiO2 phase found is from condensation or if it is transformed quartz, is hard to do by SEM and EPMA. XRD is proposed as a method for characterization
Interaction of Eutectic Fe-Si-B Alloy with Graphite Crucibles
Full text linkThe work in this thesis was performed as a part of the AMADEUS project. The goal was to experimentally investigate the interaction between eutectic Fe-Si-B alloy and dense graphite crucibles, and the results will be compared to previous work performed by the author (2017) on eutectic Si-B alloy. The results will be used to ultimately decide if eutectic Fe-Si-B alloy in graphite crucibles is suitable for application in latent heat thermal energy storage (LHTES) systems. The experiments were performed on eutectic Fe-Si-B alloy with a composition of 64 wt.% Fe,26 wt.% Si, and 9 wt.% B, contained in dense graphite crucibles. The experimental work wasconducted in a resistance heated furnace in 5N Ar (g) atmosphere, in which three different typesof experiments were performed:
The samples were subjected to 20 °C above the melting temperature for 1 h, before one or two temperature cycles between Tm ± 20 °C were initiated.
The samples were subjected to 1550 °C for 1 h, before one or two temperature cycles between Tm ± 20 °C were initiated.
The samples were subjected to 1550 °C for 1 h, before one temperature cycle between Tm ± 100 °C was initiated.
The characterisation of the samples was mainly performed by light optical microscopy (LOM), scanning electron microscopy (SEM), and electron probe micro-analyser (EPMA). Wetting tests of Fe-Si-B alloy on graphite and alumina were also performed.
It was found that very little silicon had penetrated into the crucible to form SiC, while significant penetration was observed in the previous work performed by the author. This indicates that eutectic Fe-Si-B has a lower degrading effect on the crucible compared to eutectic Si-B alloy, which is desirable for the intended application.
No continuous SiC barrier layer was observed in any of the samples containing Fe-Si-B alloy. Some single SiC and B4C particles were observed along the edges of the alloy, in addition to a eutectic B(4+delta)C phase in several areas of the alloy. The total amount of carbon present in the eutectic Fe-Si-B alloy still appeared to be lower compared to eutectic Si-B alloy, and it can thus be assumed that the Fe-Si-B alloy will remain more stable with time compared to the Si-Balloy.
The wettability of the Fe-Si-B alloy on graphite was found to be high, with a measured contact angle of approx. 30°. High wettability might result in more penetration of silicon in the crucible, and consequently faster degradation of the crucible. However, since very little penetration of silicon was observed in the crucible, the high wettability will most likely not be a challenge in the intended application.
The wettability of the Fe-Si-B alloy on alumina was found to be low, with measured contact angles of approx. 120°. This, in addition to low reactivity between the materials, indicates that alumina might be a possible alternative crucible material for eutectic Fe-Si-B alloy in the intended application.
Unlike the Si-B alloy, the volume of the Fe-Si-B alloy was found to be shrinking during solidification. This is a desirable material property for the intended application due to previous challenges caused by volume expansion during solidification of the alloy.
Five different phases were identified by EPMA analysis. This includes FeB and Si4BFe4 as matrices, SiB6 and Si2B5Fe2 as eutectic phases, and SiC particles located at the edge of the samples. It is uncertain if the two three-component phases, Si4BFe4 and Si2B5Fe2, were metastable or if they were stable due to carbon saturation of the system. Two modifications of boron carbide were found, namely B4C and B(4+delta)C. B4C was formed as particles in the same areas as SiC, while B(4+delta)C appeared to be a eutectic phase. The B(4+delta)C was found to contain more boron compared to B4C, in addition to slightly more aluminium impurities.
The fusion enthalpy of Fe-Si-B with 64 wt.% Fe, 26 wt.% Si, and 9 wt.% B was calculated in FactSage to be 3.67 kJ/cm3. This is slightly lower than for eutectic Si-B, which has a fusion enthalpy of 4.42 kJ/cm3, but still sufficiently high for the intended application. The samples in the wetting tests showed signs of melting in the range between 1200-1250 °C, and the slight deviation from the theoretical melting temperature is considered to be due to carbon saturation.
The obtained composition of the master alloy was confirmed to be close to the ideal compositionby ICP-MS analysis. Other than the alloying elements, only very small concentrations of Al and Mn were detected. The results obtained in this work are thus considered to be representative for eutectic Fe-Si-B alloy with a composition of 64 wt.% Fe, 26 wt.%Si, and 9 wt.% B.
The overall results indicate that eutectic Fe-Si-B alloy with the composition of 64 wt.% Fe, 26 wt.% Si, and 9 wt.% B is highly suitable for the application as phase change material in latent heat thermal energy storage (LHTES) systems. The results also indicate that alumina might be a possible alternative crucible material for the intended application
Production of Silicomanganese from Comilog Ore - Reduction Behavior
No full textThe reduction behavior of silicomanganese (SiMn) charges based on Comilog ore was investigated. The charges were heated up to to different temperatures by using a thermogravimetric graphite tube furnace. The weight loss during heating was measured and compared with slag and metal compositions for each sample for investigating the reduction for the charges. The aim was to investigate the reduction rates for silicon and manganese in SiMn production, and to find out if limestone added as a flux has positive impact on the degree of reduction for silicon and manganese.
For investigating the slag and metal compositions for the samples it was used SEM (EDS) and EPMA.
It was found that the slag in SiMn charges will foam at high temperature when heating rate of 4.5 °C/minute. The temperature for this foaming was 1600 °C for SiMn charge with limestone and 1650 °C for charge without limestone.
The MnO reduction will start at 1400 °C in SiMn charges, and the reduction of silica will start occur at 1550 °C in SiMn charges. These temperatures was found to be the same for SiMn charges both with and without limestone.
The SiMn charges was found to have a liquid slag phase at 1250 °C according to the binary phase diagram for MnO-SiO2.
SiMn charge with limestone added as a flux had higher degree of reduction of both manganese and silicon than SiMn charge without limestone
Wetting properties and interactions of SiO2-CaO-Al2O3 slags on SiC
No full textFuktingsegenskapene til slagg på SiC har blitt undersøkt i en fuktingsovn. Seks sammensetninger av slag ble testen på tre forskjellige SiC materialle. Alle slaggene ble funnet til å reagere med SiC, og det var foreslått at de mest sannsynlige reaksjonene var mellom og SiC eller mellom og SiC. Dette var videre støttet opp under av SEM EDS analysen, men ingen klare svar var funnet. Reaksjonene gjorde det vanskelig og fastslå ordentlige kontakt vinkler, men slaggene virket å fukte SiC nøytralt godt. To av substratene var porøse som førte til at slaggene penetrerte og fløt gjennom de, som gjorde det enda vanskligere å finne ordentlige kontakt vinkler
Interaction of SiO-gas and Charcoal and the Formation of SiC and Si
No full textFor å nå eit høgt utbytte i produksjonen av silisium, er det viktig å fange stigande SiO-gass ved reaksjon med karbonhaldig materialar for å danne SiC. Den påfølgjande reaksjonen mellom SiC og SiO-gass er kjend for å produsere elementær Si. Til trass for fleire studiar om anvendelegheita av trekol i silisiumsomner er kunnskapen innanfor dette feltet manglande. Nyare studiar indikerer mot en lågare temperatur for silisiumsproduksjon i SiC enn tidlegare tenkt mogleg. Målet med denne avhandlinga vil vere å utforske interaksjonen mellom SiO-gass og trekol og formasjonen av SiC. Vidare vil den lågare temperaturen for silisiumsproduksjon i SiC bli granska.
For å oppnå dette, vart ein omn med varmeelement av grafitt brukt for å varme opp grafittdiglar med SiO2/Si og trekol separert med ein gass-gjennomtrengeleg disk. Temperaturar vart valt både over og under den teoretiske minste temperaturen for Si-produksjon og eksakte temperaturar vart målt inne i ladninga av trekol.
Vist i denne oppgåva, er formasjonen av SiC og elementær Si frå trekol. Ein lineær samanheng vart funnet mellom endring i massen til trekolet når samanlikna med temperatur. Vidare viser studien ein signifikant vekst av både ein- og fleirkrystallar på både partikkeloverflater og innsida av porer. Dei ulike krystallmorfologiane, saman med resultat frå XRD-analyse, bekrefter 3C beta-SiC og indikerar til 4H alpha-SiC. Strukturelle endringar vart observert når trekol blir konvertert til SiC og krystallvekst inne i porer er tenkt til å forklare dette. Det ble òg funne elementær Si ved 1781.8 °C, ein temperatur som er under teoretisk minimum for Si-produksjon.To achieve a high yield in the silicon production process, the capture of ascending SiO-gas by reaction with carbonaceous materials to form SiC is of great importance. The following reaction between SiC and SiO-gas is known to produce elemental Si. Although several studies on the use of charcoal in silicon furnaces exist, the knowledge within this field is lacking. Newer studies indicate a lower temperature of Si formation in SiC than previously thought possible. The goal of this thesis will be to investigate the interaction of SiO-gas and charcoal and the formation of SiC. Furthermore, the lower temperature of elemental Si formation in SiC will be investigated.
To accomplish this, a graphite resistance-heating furnace was used to heat up graphite crucibles containing SiO2/Si and charcoal separated by a gas-permeable disc. Temperatures were chosen both above and below the theoretic minimum temperature of Si production and exact temperatures were measured inside the charcoal charge.
Shown in this thesis, is the formation of SiC and elemental Si from charcoal. A linear mass change of the charcoal charge was found to occur when compared with temperature. Furthermore, this study shows a significant growth of mono- and poly-crystals both on the particle surface and inside pores. The various morphologies of these crystals, combined with XRD results, confirm 3C beta-SiC and indicate to 4H alpha-SiC. Structural changes in charcoal were observed as it converts to SiC and crystal growth inside pores is believed to have caused this. Finally, elemental Si was found to have been formed at 1781.8 °C, which is below the theoretic minimum temperature of Si formation
Interaction of Eutectic Fe-Si-B Alloy with Graphite Crucibles
No full textThe work in this thesis was performed as a part of the AMADEUS project. The goal was to experimentally investigate the interaction between eutectic Fe-Si-B alloy and dense graphite crucibles, and the results will be compared to previous work performed by the author (2017) on eutectic Si-B alloy. The results will be used to ultimately decide if eutectic Fe-Si-B alloy in graphite crucibles is suitable for application in latent heat thermal energy storage (LHTES) systems. The experiments were performed on eutectic Fe-Si-B alloy with a composition of 64 wt.% Fe,26 wt.% Si, and 9 wt.% B, contained in dense graphite crucibles. The experimental work wasconducted in a resistance heated furnace in 5N Ar (g) atmosphere, in which three different typesof experiments were performed:
The samples were subjected to 20 °C above the melting temperature for 1 h, before one or two temperature cycles between Tm ± 20 °C were initiated.
The samples were subjected to 1550 °C for 1 h, before one or two temperature cycles between Tm ± 20 °C were initiated.
The samples were subjected to 1550 °C for 1 h, before one temperature cycle between Tm ± 100 °C was initiated.
The characterisation of the samples was mainly performed by light optical microscopy (LOM), scanning electron microscopy (SEM), and electron probe micro-analyser (EPMA). Wetting tests of Fe-Si-B alloy on graphite and alumina were also performed.
It was found that very little silicon had penetrated into the crucible to form SiC, while significant penetration was observed in the previous work performed by the author. This indicates that eutectic Fe-Si-B has a lower degrading effect on the crucible compared to eutectic Si-B alloy, which is desirable for the intended application.
No continuous SiC barrier layer was observed in any of the samples containing Fe-Si-B alloy. Some single SiC and B4C particles were observed along the edges of the alloy, in addition to a eutectic B(4+delta)C phase in several areas of the alloy. The total amount of carbon present in the eutectic Fe-Si-B alloy still appeared to be lower compared to eutectic Si-B alloy, and it can thus be assumed that the Fe-Si-B alloy will remain more stable with time compared to the Si-Balloy.
The wettability of the Fe-Si-B alloy on graphite was found to be high, with a measured contact angle of approx. 30°. High wettability might result in more penetration of silicon in the crucible, and consequently faster degradation of the crucible. However, since very little penetration of silicon was observed in the crucible, the high wettability will most likely not be a challenge in the intended application.
The wettability of the Fe-Si-B alloy on alumina was found to be low, with measured contact angles of approx. 120°. This, in addition to low reactivity between the materials, indicates that alumina might be a possible alternative crucible material for eutectic Fe-Si-B alloy in the intended application.
Unlike the Si-B alloy, the volume of the Fe-Si-B alloy was found to be shrinking during solidification. This is a desirable material property for the intended application due to previous challenges caused by volume expansion during solidification of the alloy.
Five different phases were identified by EPMA analysis. This includes FeB and Si4BFe4 as matrices, SiB6 and Si2B5Fe2 as eutectic phases, and SiC particles located at the edge of the samples. It is uncertain if the two three-component phases, Si4BFe4 and Si2B5Fe2, were metastable or if they were stable due to carbon saturation of the system. Two modifications of boron carbide were found, namely B4C and B(4+delta)C. B4C was formed as particles in the same areas as SiC, while B(4+delta)C appeared to be a eutectic phase. The B(4+delta)C was found to contain more boron compared to B4C, in addition to slightly more aluminium impurities.
The fusion enthalpy of Fe-Si-B with 64 wt.% Fe, 26 wt.% Si, and 9 wt.% B was calculated in FactSage to be 3.67 kJ/cm3. This is slightly lower than for eutectic Si-B, which has a fusion enthalpy of 4.42 kJ/cm3, but still sufficiently high for the intended application. The samples in the wetting tests showed signs of melting in the range between 1200-1250 °C, and the slight deviation from the theoretical melting temperature is considered to be due to carbon saturation.
The obtained composition of the master alloy was confirmed to be close to the ideal compositionby ICP-MS analysis. Other than the alloying elements, only very small concentrations of Al and Mn were detected. The results obtained in this work are thus considered to be representative for eutectic Fe-Si-B alloy with a composition of 64 wt.% Fe, 26 wt.%Si, and 9 wt.% B.
The overall results indicate that eutectic Fe-Si-B alloy with the composition of 64 wt.% Fe, 26 wt.% Si, and 9 wt.% B is highly suitable for the application as phase change material in latent heat thermal energy storage (LHTES) systems. The results also indicate that alumina might be a possible alternative crucible material for the intended application
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