FeO Content Research Articles

A study on microwave absorption properties of polyaniline/nitrile rubber/graphene/Fe3O4 composites with a thickness of 0.7 mm and high flexibility

AbstractThe genotoxic effect of microwave radiation on humans is one of the leading causes of some diseases like cancer. Despite many reported materials for microwave absorption, there is still a demand for a super‐thin and flexible microwave absorber. In the present work, we synthesized Fe3O4/graphene/polyaniline/nitrile butadiene rubber composites with a thickness of 0.7 mm using a melt mixing method. Then, we comprehensively studied the electromagnetic and microwave absorption properties of the composites from 8 to 12 GHz. The composite with 38 wt% Fe3O4 and 6 wt% graphene exhibited the highest microwave absorption of more than 8 dB in the entire range of 8–12 GHz, with a minimum reflection loss of −14 dB at 10.3 GHz. By increasing the weight content of Fe3O4 and graphene, the imaginary part of dielectric permeability and magnetic permeability initially went up and then declined, resulting in poor impedance matching. Hence, we precisely controlled the weight content of the fillers to reach the highest impedance matching and attenuation constant. Consequently, this work opened up a unique way for developing super‐thin, lightweight, flexible microwave‐absorbing materials.

Application of MLR, BP and PCA-BP Neural Network for Predicting FeO in Bottom-Blowing O2-CaO Converter

In order to accurately predict the FeO content of slag in the bottom-blowing O2-CaO process of the dephosphorization converter, multiple linear regression model, backpropagation (BP) neural network model and principal component analysis–backpropagation (PCA-BP) combined with neural network model were established to predict the FeO content of slag. It was found that the PCA-BP combined neural network model has the highest prediction accuracy by using principal component analysis to reduce the dimension of influencing factors of FeO content in slag and eliminate the correlation between input variables. The average absolute error is 1.178%, which is 0.78% lower than that of multiple linear regression model and 0.453% lower than that of multiple linear regression model. When the prediction error range is 3.0%, the prediction hit rate of the model is 96%, and when the prediction error range is 2.0%, the prediction hit rate of the model is 78%. The prediction model has important reference value for actual production.

Solubility and Activity of Iron Oxide in Solid Solutions between Ca<sub>2</sub>SiO<sub>4</sub> and Ca<sub>3</sub>P<sub>2</sub>O<sub>8</sub> at 1573 K

Towards better understanding of fundamental dephosphorization slags of the FeO-CaO-SiO2-P2O5 quaternary system, this study aimed at clarifying the thermochemical properties of iron oxide in Ca2SiO4-Ca3P2O8 solid solutions. The solubility and activity of FeO in the solid solutions coexisting with CaSiO3 at 1573 K were determined by SEM-EDX analysis and a gas equilibrium method, respectively. Based on the present experimental results, the phase relationships could be explained that the solid solution of high FeO solubility coexists with CaSiO3 and liquid slag of low FeO content, while the solid solution of low FeO solubility coexists with CaO and liquid slag of high FeO content.

Effects of sludge on the ash fusion behaviors of high ash-fusion-temperature coal and its ash viscosity predication

The co-gasification of sludge and coal is a promising way to regulate coal ash fusion characteristics and recover energy from sludge simultaneously. In this paper, the ash fusion behaviors of high ash-fusion-temperature (AFT) Datong coal, textile dyeing sludge (TDS), their mixtures, and the corresponding AFT modification mechanisms on laboratory scale were investigated by an AFT tester, X-ray diffractometer, Raman spectrometer, and FactSage software. The AFTs of Datong coal mixtures decreased slowly when TDS share was in the range of 0–6%, quickly (6–9%), and then nearly stable (>9%) because of its corresponding increasing basic oxide values (the total content of SO3, CaO, MgO, Fe2O3, Na2O, and K2O). The generations of low melting-point minerals of hercynite and anorthite with TDS additions resulted in the AFT decrease. The decreasing intensity of Si–O–Si peak and the increasing ratio bond of bridging oxygen and non-bridging oxygen led to the AFT decrease. Both the decreases in the temperature at which all minerals change into liquid-phase and the continuously increasing liquid-phase content (at the same relative high temperature) in Datong coal mixed ashes with increasing TDS mass ratio were contributed to the variations of AFT. The viscosity-temperature characteristics variation was also predicted using FactSage calculation. The 9.0–12.0% mass ratio of TDS might be suitable for Datong coal entrained-flow bed gasification.

Dry Magnetic Separation of Ash from a Coal Power Station

The purpose was to expand the applicaation area of dry ash in power plants. It was shown that using ash with a low content of Fe2O3 (~7%) allows to obtain a high-iron concentrate with a Fe2O3 content of 70%. The Fe2O3 extraction from ash is dependent on the magnetic induction and fractional ash composition. The conclusion was made about the possibility of using the obtained magnetite concentrate in ferrous metallurgy in the manufacture of basic iron and steel.

Geochronology, geochemistry, and mineral chemistry of the Lingshan-Huangshan complex, South China: Insights into Nb and Ta enrichment

The Huangshan Nb-Ta deposit, located at the northern segment of the Qin-Hang metallogenic belt of South China, is closely associated with the Lingshan-Huangshan complex. As a large Nb-Ta deposit, with the Nb-Ta mineralization hosted by the late two phases of the Lingshan-Huangshan complex, the factors that led to Nb and Ta enrichment in the Huangshan deposit remain unclear. Therefore, we conducted a comprehensive investigation of petrography, geochronology, whole-rock geochemistry, and mineral compositions (zircon and mica) of the Lingshan-Huangshan complex. The Lingshan-Huangshan complex comprises the Lingshan coarse-grained porphyritic amphibole-biotite granite, the Huangshan coarse-grained biotite granite, the fine-grained albite-biotite granite, and the pegmatite from the center outwards. Zircon U-Pb dating shows that the different phases within this complex formed at 133.4–132.7 Ma. They are characterized by high SiO2 (66.46–79.11 wt%), total alkali (7.38–10.39 wt%) contents, moderate A/CNK values (average of 1.01), and high Ga/Al and Zr + Nb + Ce + Y values, presenting geochemical affinities to A-type granites. Combined with the pre-existing Nd-Hf isotopic data, they originated from the Proterozoic crust of South China with some input of juvenile crustal or mantle-derived materials. The whole-rock Al2O3, TiO2, and Fe2O3 contents and Nb/Ta and Zr/Hf ratios decrease with increasing SiO2 contents from the Huangshan coarse-grained biotite granite, the fine-grained albite-biotite granite to the pegmatite. These variations, together with the increasing Hf and Th + U + Y in zircon and increasing Rb, Nb, and Ta in mica, indicate that these phases (especially the late two) underwent highly fractional crystallization. The Lingshan coarse-grained porphyritic amphibole-biotite granite shares part of the whole-rock geochemical variations with the other phases, but its Nb/Ta ratios varied discordantly, which may be attributed to the solidified residual crystal-rich mush. The increasing F and Li in micas from the early to late phases of the Lingshan-Huangshan complex reflect enrichment of F and Li content during the magmatic evolution process, which is conducive to enhancing the solubilities of Nb and Ta in the melt. Accordingly, we suggest that the Nb-Ta enrichment in the Huangshan deposit is closely associated with highly fractionated magma and elevated volatile elements F and Li in melts.

Petrogenesis of the Alubaogeshan granite in the Maodeng Mo-Bi-Sn-Cu deposit, southern Great Xing’an Range, NE China: Constraints from apatite, plagioclase, magnetite and ilmenite geochemistry

The Maodeng deposit, located in Xilinhot, Inner Mongolia, is a typical Mo-Bi-Sn-Cu deposit in the southern segment of the Great Xing’an Range. It is genetically related to the Alubaogeshan granitic complex, which is composed of porphyritic monzogranite (G1), granite porphyry (G2), and alkali feldspar granite (G3). However, the comparison of physical–chemical condition and magmatic evolution of different lithofacies has not been conducted. We present in-situ major-trace elements and Sm-Nd isotopes of apatite, in-situ major-trace elements of plagioclase, as well as in-situ major elements of magnetite and ilmenite from the G1 and G2, with the goal of discussing magma genesis and its constraints on mineralization. The apatites from the two granites are characterized by relative enrichment in F and light rare earth elements (LREEs) but depletion in Cl, S, and heavy rare earth elements (HREEs), as well as obviously negative Eu, Sr, Nb, Ba, Zr, and Hf and positive Y anomalies, indicating that the two granites have similar sources and experienced significant crystallization differentiation. When compared to G1, apatites from G2 exhibit more significant Eu, Sr, and Y anomalies, as well as lower (La/Sm)N and (La/Yb)N ratios, likely due to intensive crystallization of plagioclase and exsolution of Cl-bearing magmatic fluids. The presence of core-rim zoning patterns with BSE-bright and BSE-grey domains in some G2 apatite crystals indicates extensive hydrothermal alteration. The plagioclases within G1 belong to andesine–oligoclase series corresponding to magmatic water contents of 1.4 to 1.9 wt%, and those in G2 belong to oligoclase–albite series with calculated magmatic water contents of 2.1 to 2.2 wt%. The plagioclase crystals from G1 are characterized by prominently positive Eu and moderately positive Sr and Ba anomalies, with crystals from G2 showing strongly negative Eu, Ba and Sr anomalies, indicating more significant fractionating plagioclase and apatite in G2 than G1. The magnetite compositions are distinguished by high FeO, TiO2, and MnO contents. Ilmenite usually cuts and dissolves magnetite, and contains a lot of FeO, TiO2, MnO, and Nb2O3. The magnetite and ilmenite from the two granites have a coherent negative correlation between Ti and Fe3+ but a consistent positive correlation between Ti and Fe2+, implying that they crystallized from a homologous silicate magma. During the crystallization of apatites, magmatic oxygen fugacities of the two granites were slightly above the ΔNNO buffer line. However, these were near the FMQ buffer line when the magnetite and ilmenite were in equilibrium at temperatures ranging from 561 to 666 °C, indicating a decreasing trend in oxygen fugacity during magma evolution. The apatites of both G1 and G2 have high εNd(t) values (+0.59 to + 1.94 and − 2.13 to + 0.42, respectively), and young two-stage Nd model ages (tDM2 = 775–884 Ma and 897–1106 Ma, respectively), suggesting the predominant origin of these rocks by the partial melting of a juvenile mafic lower crust and “old” pre-existing crustal components, having a substantial proportion of continental crust for G2. The decline in oxygen fugacity, enrichment of F element, highly crystallization differentiation, intense melt/fluid interaction, and the strong hydrothermal alteration for the ore-related granite could contribute to the formation of the Maodeng deposit.

Iron Loss During Continental Weathering in the Early Carboniferous Period Recorded by Karst Bauxites

AbstractSignificant iron (Fe) loss can occur during continental weathering and efflux to the ocean via runoff, historically affecting global Fe cycling and marine ecosystems. Here, we report extremely low Fe content in early Carboniferous (ca. 340 Ma) bauxites in southwestern China. These bauxites were formed by redeposition of terrestrial soils along the paleo‐continental margin of the western South China Plate in warm climates. The bauxites contain high δ56Fe (−0.17‰ to +1.15‰) values with a negative correlation between Fe2O3 and δ56Fe, indicating that a substantial amount of Fe(III) was reduced to isotopically light dissolved Fe(II) and effuxed to the ocean via reductive dissolution under anoxic conditions. The low Corg content and low FeHR/FeT, Mo/Al, U/Al, and V/Al ratios of bauxite suggest that this reduction process occurred during the pedogenic (continental weathering) rather than the depositional/diagenetic stage of karst bauxite formation. Most of the dissolved Fe(II) were rapidly re‐oxidized to Fe(III) and transported toward the paleo‐continental margin forming iron ores with δ56Fe values around zero (−0.13‰ to +0.16‰). The negative correlation between Al2O3 and Fe2O3 contents in global karst bauxites suggests common Fe loss processes during continental weathering in geological periods favoring karst bauxite formation, such as during the Carboniferous, Permian, and Cretaceous periods and the Cenozoic era. Karst bauxite may thus provide a record of Fe loss during continental weathering and act as an indicator of enhanced Fe flux to oceans.

The release analysis of As and Cr metals in lead-zinc smelting slag: Mineralogical analysis, bioavailability and leachability analysis

Mining and smelting are the main sources of soil heavy metal pollution. Leaching and release of heavy metals in soils has been extensively studied. However, there are few researches on the release behavior of heavy metals from the Angle of mineralogy of smelting slag. This study focuses on the pollution of arsenic and chromium by traditional pyrometallurgical lead-zinc smelting slag in southwest China. Based on the mineralogy of smelting slag, the release behavior of heavy metals in smelting slag was studied. As and Cr deposit minerals were identified by MLA analysis, and the weathering degree and bioavailability of As and Cr deposit minerals were analyzed. The results showed that the weathering degree of slag was positively correlated with the bioavailability of heavy metals. The leaching experiment results showed that the higher pH was beneficial to the release of As and Cr. It was found that the chemical forms of As and Cr changed from relatively stable forms to easily released forms (As5+ to As3+ and Cr3+ to Cr6+) by characterizing the metallurgical slag during leaching. In the transformation process, the S in the pyrite as the enclosing layer is eventually oxidized to SO42-, which will accelerate the dissolution of the enclosing mineral. SO42- will occupy the adsorption site of As on the mineral surface, thus reducing the adsorption amount of As on the mineral surface. Fe is finally oxidized to Fe2O3, and the increase of Fe2O3 content in the waste residue will produce strong adsorption effect on Cr6+ and slow down the release of Cr6+. The results show that the release of As and Cr is controlled by the pyrite coating.

Composition optimization and high-temperature characteristics of fluorine-free CaO-SiO2-FeO-B2O3-MnO dephosphorization slag

ABSTRACT The effect of the proportion of each component on the viscosity and melting temperature of fluorine-free CaO-SiO2-FeO-B2O3-MnO dephosphorization slag (DS) was simulated by FactSage software. A reasonable composition control interval and molten pool temperature were obtained. The orthogonal experiment led to the optimal ratio of the dephosphorization agent, which was further verified by laboratory dephosphorization experiments. The experimental results showed that with the increase in FeO, B2O3, and MnO content, the melting temperature and viscosity of DS decreased. With the increase in basicity, the melting temperature increased but the viscosity decreased. B2O3 had the greatest effect on melting temperature, while FeO had the greatest effect on viscosity. At 1400°C, the optimum ratio of DS is 9 wt% B2O3, 10 wt% MnO, 45 wt% FeO, and the basicity is 4.0. The dephosphorization experiment carried at the optimum ratio resulted in the maximum dephosphorization degree of 93%.

Viscosity Variations and Tribological Performances of Oleylamine-Modified Fe3O4 Nanoparticles as Mineral Oil Additives

In order to improve the flowabilities and anti-friction and anti-wear properties of lubricants, the viscosity variations and tribological performances of oleylamine-modified Fe3O4 nanoparticles as mineral oil additives were systematically investigated via rotational parallel plate rheometer, ball–disc reciprocating tribometer, non-contact three-dimensional surface profiler, scanning electron microscope, energy dispersive X-ray spectrometer and X-ray photoelectron spectroscopy. Spherical monodisperse Fe3O4 nanoparticles were synthesized and dispersed into mineral oils to obtain lubricants with mass fractions of 1%, 3%, 5%, 8%, 10% and 20%, respectively. These lubricants have excellent stabilities within 12 months. Interestingly, the dynamic viscosity and kinematic viscosity of the lubricants first decrease and then increase with the increase in Fe3O4 content, and the lubricants’ viscosity is at a minimum when the mass concentration is 5%. The tensile curves also show that with the mass fraction increase, the lubricants’ tackiness and adhesion have the same change law, and both reach the lowest point when the mass concentration is 5%. Meanwhile, Fe3O4 nanoparticles can improve the tribological properties of the base oils. It is worth noting that the maximum reduction in the wear volume at 25 °C is up to 93.8% compared with base oils when the additive concentration of the Fe3O4 nanoparticles is 5 wt%.

Effect of the Carbon Mixing Ratio on Mineral Evolution and Gasification Dephosphorization during the Pre-reduction Sintering Process of Bayan Obo Iron Ore Concentrate

The pre-reduction sintering process is an effective measure to fundamentally solve the detrimental circulating accumulation of phosphorus in iron- and steel-making procedures. The effect of the carbon mixing ratio on the mineral evolution, gasification dephosphorization and pre-reduction degree of sintering products was primarily investigated based on the phosphorus occurrence status in Bayan Obo iron ore concentrate. The obtained results indicated that iron oxide was dominantly transformed from magnetite into wüstite, and metallic iron was basically not detected. Regarding silicate slag, the precipitated dendritic phase accounted for a higher content of FeO and MgO and a lower content of Na2O + K2O and SiO2 over the vitreous matrix phase. Moreover, as the carbon mixing ratio was increased from 5 to 25 wt%, the gasification dephosphorization and pre-reduction degree first increased from 11.3% and 30.7%, respectively, to 70.0% and 67.4%, respectively, due to the enhanced reducing atmosphere and then decreased to 45.0% and 59.0%, respectively, led by the increased content of liquid slag and the reduced permeability of the burden layer. Both maximum values were obtained at a 20 wt% carbon mixing ratio. Furthermore, the pre-reduction sintering products as raw materials for blast furnaces could not only largely reduce the phosphorus content in hot metal but could also dramatically decrease coke usage and carbon dioxide emissions, which could be highly beneficial to realize carbon peaking and carbon neutrality.

Spatial prediction and influencing factors identification of potential toxic element contamination in soil of different karst landform regions using integration model

The prediction of contamination distribution of potentially toxic elements (PTEs) in soils of Guangxi province, China and the identification of their controlling factors pose great challenges due to diverse bedrock types, intense leaching and weathering, and discontinuous terrain distributions. Herein, we integrated the random forest (RF) and empirical Bayesian kriging (EBK) to interpret and predict complex PTEs contamination distribution from three different karst landform regions (fenglin, fengcong, isolated peak plain) in Guangxi province. The modeling results are compared with the commonly used ordinary kriging and regression-kriging. In this study, our developed RF-EBK model combines the advantages of the RF and EBK model to promote the prediction accurately and efficiently. In this study, it was shown that the integration RF-EBK model exhibited desirable for Cd and As concentrations, with R2 of 0.89 and 0.83, respectively. The average RMSE and MAE of integration RF-EBK model decreased by 39% and 44%, respectively, relative to the regression-kriging with the second highest accuracy. Furthermore, the modeling results showed that approximately 41.96% and 18.96% of total area was classified as Cd and As polluted and above regions (Igeo >0) in Guangxi province, respectively. Higher Cd concentration was observed in the soil of fenglin and fengcong regions than that in isolated peak plain region due to the secondary enrichment and parent rock inheritance, while the As concentration exhibited no significant difference among the three regions. The modeling results indicated that the elevated Cd concentration might be associated with soil CaO concentration and alkaline soil environment, whereas As concentration tended to be increased with the elevating Fe2O3 concentrations in weakly acidic soil environment. This result confirmed the applicability and effectiveness of integration model in predicting complex spatial patterns of soil PTEs and identifying their controlling factors.

Enhancing flame retardancy of polyphenylene sulfide nanocomposite fibers by the synergistic effect of catalytic crosslinking and physical barrier

AbstractProtective clothing with fascinating flame‐retardant features is urgently needed to reduce the large amount of smoke and heat released from combustion during fire protection. In this study, polyphenylene sulfide (PPS) nanocomposite resin with efficient flame retardancy is obtained by mixing a low content of graphene and Fe2O3via a twin screw extruder. Followed by, the PPS/G/Fe2O3fibers are fabricated via melting spinning. The PPS/G/Fe2O3nanocomposite resin with 0.3 wt% of graphene and 1.0 wt% of Fe2O3performs the best during the flame retardant tests, giving a shorter self‐extinguishing time, lower peak heat release rate (22.3 kW/m2), total heat release (11.3 MJ/m2) and total smoke production (1.32 m2) than others. The pyrolysis analysis indicates that a large number of products with fused rings are formed in the residual char layer, which effectively inhibit the release of heat and smoke and thus improve the flame retardancy of PPS nanocomposite resin. In addition, the flame retardant textile weaved with PPS/G/Fe2O3fibers gives a high‐limiting oxygen index (40.1%), zero after‐flame time, no droppings and small damaged length (114 mm in warp and 98 mm in weft direction) during the standard flame retardancy tests provided by a third‐party independent inspection organization. The fabrication of PPS fibers with effective and enhanced synergistic flame retardancy through melting spinning is facile and scalable, providing a promising strategy for advanced protective clothing.

Geochemical characteristics of spherules from the Pivdenna kimberlite pipe, East Azov region (Ukraine): implications for their sources and origin

The composition of spherules and particles of native metals from the Pivdenna kimberlite pipe, Ukraine, was studied using the SEM/EDS method. Three varieties of spherules have been distinguished: titanium-manganese-iron-silicate (TMIS) spherules, Ca-rich silicate spherules, and magnetite-wustite-iron (MW-I) spherules. TMIS spherules are composed of homogeneous glass, some having a native iron core. Large TMIS spherules may contain a crystalline phase with needle-like armalcolite. Ca-rich silicate spherules can be subdivided into two subtypes: calcium-silicate (CS) spherules where SiO2 and CaO are the dominant constituents, and calcium-iron-silicate (CIS) spherules with significant FeO content. CS spherules may contain a core consisting of native phases (Fe, Fe-Si, and Mn-Si-Fe). Native metal particles are represented by native Cu and native Zn. The spherule varieties from the Pivdenna pipe are similar to those from other kimberlite pipes in the world. We infer that the formation of spherules occurred in gas-melt streams, separately from the kimberlites, and propose a model for the formation of the most common variety of spherules (TMIS and MW-I varieties) in the region of the core-mantle boundary (CMB). First, a melt of the Fe-Ti-Mn-Si-O system was formed in ultra-low-velocity zones (ULVZ) as a result of thermochemical reactions (reduction) between the molten core and solid oxide-silicate rocks. The melt then migrates to shallower levels, where a decrease in temperature initiates oxidation with the formation of SiO2-TiO2-FeO-MnO-Fe0 melt, i.e. parent melt of TMIS and MW-I spherules. We interpret the formation of native metals in kimberlites as a result of the decomposition of nitrides, which came from the Earth’s core via intratelluric flows

Geochemistry and Geometrical Features of the Upper Cretaceous Vitulano Para-Autochthonous Karst Bauxites (Campania Region, Southern Italy): Constraints on Genesis and Deposition

In the Vitulano area, Upper Cretaceous bauxite bodies fill small depressions and karst cavities within Cretaceous shallow-water limestones. These bauxites were studied to understand the processes that led to their formation. Geochemical, mineralogical, and petrographic analyses were carried out on the bauxite samples, together with image analysis providing geometric parameters. The texture of Vitulano bauxite consists of ooids and sub-circular aggregates dispersed in a predominantly Ca-rich matrix. Ooids are generally formed by a single large core, often surrounded by an alternation of different aggregates of boehmite and Al-hematite reflecting different climate periods. The composition is dominated by the major elements Al2O3 and CaO with lower concentrations of Fe2O3 and SiO2. Boehmite, calcite, hematite, and anatase are the main mineralogical phases identified. Image analysis provided values of fractal dimension D that gives information on carbonate platform exposure times since it is linked to long-lasting sub-aerial events and diffusion-limited cluster aggregation processes. The tectonic evolution of the area played an important role in the genesis of the Vitulano bauxites since it favored the erosion, transport, and re-deposition of pre-existing bauxite material from the surrounding Campania bauxites. Based on this hypothesis, Vitulano bauxites are defined and classified as para-autochthonous, and this was supported by Eu/Eu* vs. Sm/Nd and Eu/Eu* vs. TiO2 Al2O3 indices displaying a similarity between Vitulano and the other Campania bauxites.

Heterogeneous data-driven measurement method for FeO content of sinter based on deep learning and tensor decomposition

FeO content is an important index reflecting the reducibility and drum strength of sinter, which is of great significance to the subsequent iron-making process. However, due to the time delay of chemical analysis method, FeO content cannot be obtained in real-time, which promotes the research on online measurement methods. Based on deep learning and information fusion, this paper proposes an intelligent heterogeneous data-driven method to accurately measure the level of FeO content in real time. Firstly, in view of the interference information such as background and furnace contour, the region proposal network is adopted to detect the burning ore region in the cross-section image of sintering machine. Secondly, a split attention-based deep convolutional neural network is constructed to extract deep image features. In particular, a fuzzy labeling strategy is proposed aiming at the problem of dividing images at the junction of different levels. In the end, the image features and the sintering process variables are fused through a bilinear model, and tensor decomposition is introduced to obtain the final fusion feature. Experimental results on actual industrial data demonstrate the effectiveness of the proposed method for measuring the level of FeO content, achieving an excellent accuracy of 98.35%.

Optimal Alkalinity Model of Ladle Furnace Slag for Bearing Steel Production Based on Ion–Molecule Coexistence Theory

The fatigue life of bearing steel is closely related to the total oxygen content (T(O)) of the liquid steel. In order to stably and effectively control the T(O) during the ladle furnace (LF) refining process, we established a calculation model of optimal alkalinity for the refining slag CaO–SiO2–Al2O3–MgO–FeO–CaF2 at 1853 K based on ion–molecule coexistence theory (IMCT). Here, the influencing factors are discussed. The results show that the maximum value of NFeO occurred when the optimal alkalinity was around five at varied FeO contents, and that the optimal alkalinity basically remained the same with changes in FeO content. With the increase of MgO content, the optimal alkalinity decreased. However, the change in the value of NFeO against the higher alkalinity was not obvious at a given MgO content. The effect of Al2O3 content on the optimal alkalinity was opposite to that of MgO. With the increasing Al2O3 content, the optimal alkalinity obviously increased, while the maximum value of NFeO occurred when the Al2O3 content varied from 35 wt% to 45 wt% at higher alkalinity. The higher w(CaO)/w(Al2O3) mass ratio had a distinct effect on the value of NFeO against alkalinity, while the effect of alkalinity on the value of NFeO was not obvious at a fixed CaF2 level. This optimal alkalinity model based on IMCT can provide a certain guiding role in the process of refining slag composition optimization and is conducive to effectively controlling total oxygen content in the refining process.

Anatomy of rocky planets formed by rapid pebble accretion

We present a series of papers dedicated to modelling the accretion and differentiation of rocky planets that form by pebble accretion within the lifetime of the protoplanetary disc. In this first paper, we focus on how the accreted ice determines the distribution of iron between the mantle (oxidized FeO and FeO1.5) and the core (metallic Fe and FeS). We find that an initial primitive composition of ice-rich material leads, upon heating by the decay of26Al, to extensive water flow and the formation of clay minerals inside planetesimals. Metallic iron dissolves in liquid water and precipitates as oxidized magnetite Fe3O4. Further heating by26Al destabilizes the clay at a temperature of around 900 K. The released supercritical water ejects the entire water content from the planetesimal. Upon reaching the silicate melting temperature of 1700 K, planetesimals further differentiate into a core (made mainly of iron sulfide FeS) and a mantle with a high fraction of oxidized iron. We propose that the asteroid Vesta’s significant FeO fraction in the mantle is a testimony of its original ice content. We consider Vesta to be a surviving member of the population of protoplanets from which Mars, Earth, and Venus grew by pebble accretion. We show that the increase in the core mass fraction and decrease in FeO contents with increasing planetary mass (in the sequence Vesta – Mars – Earth) is naturally explained by the growth of terrestrial planets outside of the water ice line through accretion of pebbles containing iron that was dominantly in metallic form with an intrinsically low oxidation degree.

Water-Rock Interactions in the Metamorphic Complex of Geothermal Field: Case Study in Wahlua Complex, Buru Island

In Indonesia, surface thermal manifestation is commonly found in a volcanic geological setting. However, hot springs and alteration minerals in study area occur on metamorphic rock. In order to study its correlation with the emergence of the thermal fluid, the objective of this study is to characterize each metamorphic zone based on rock chemistry and the appearance of index minerals. Consequently, the correlation with thermal fluid chemistry can be observed. Data for this study are surface rock samples and thermal manifestation data. Metamorphic zones were determined by integrating geomorphology, petrography, and X-Ray Fluorescence (XRF) analyses. Three metamorphic zones were identified, namely, Garnet Zone, Biotite Zone, and Chlorite Zone. Garnet Zone is characterized by high concentrations of CaO and Al2O3 due to the presence of garnet. The abundance of biotite and muscovite in Biotite Zone may contribute to the highest concentration of K2O than the other two zones. Meanwhile, Chlorite Zone is characterized by the concentrations of SiO2, Fe2O3, and MgO. However, the composition of MgO might be influenced by mineral-fluid reaction. There are two clusters of thermal manifestation, which are western and eastern cluster manifestations. Western cluster manifestations are in the Biotite Zone. Meanwhile, the eastern cluster manifestation is in the Chlorite Zone. However, both clusters’ fluid chemistry shows significant differences in some elements such as SiO2, Na, K, Fe, and Mg concentration. It might suggest that the enrichment and depletion of these constituents in thermal fluid might correlate with each metamorphic zone’s characteristics. An inconsistent pattern between thermal fluid composition and rock chemistry was found in Mg concentration. It is most likely that the Mg concentration was influenced by groundwater dilution rather than the mineral-fluid interaction. The study concludes that the appearance of index minerals shows consistencies with composition variation of some elements in the manifestation fluid, such as SiO2, Na, K, and Fe.