MgO Content Research Articles

Isothermal reduction and nitridation kinetics of ilmenite concentrate in ammonia gas

Low-temperature chlorination is considered a suitable process for ilmenite containing high contents of MgO and CaO. However, reduction carbonization or nitridation is essential to convert titanium oxide to carbide or nitride, which can be enriched by magnetic separation. In this paper, the isothermal reduction–nitridation kinetics of Panzhihua ilmenite concentrate in an ammonia atmosphere was investigated. Both model–free and model–fitting methods were used to compare the isothermal kinetics. The reaction process can be divided into two successive stages: the reduction reaction and the nitridation reaction. The average apparent activation energy for the reduction reaction was 139.63 kJ/mol, obtained by the model–free method. The reduction process can also be subdivided into two stages by the model–fitting method. The chemical reaction (G(α) = 1–(1–α)1/3 = kt) and three–dimensional diffusion (G(α) = [1–(1–α)1/3]2 = kt) were identified as the mechanism function for the reduction process. The activation energies of these two stages were 121.73 kJ/mol and 141.40 kJ/mol, respectively. The function G(α) = 1–(1–α)1/3 = kt, which also corresponds to the chemical reaction mechanism (R3), exhibited the best fit for the nitridation stage. The corresponding activation energy was 32.10 kJ/mol. Metallic iron and Ti3O5 were formed in the reduction stage, while Ti3O5 was then transformed to Ti(N,O) in the nitridation stage.

Evaluation of Structural Stability, Mechanical Properties, and Corrosion Resistance of Magnesia Partially Stabilized Zirconia (Mg-PSZ).

Nano Zirconia (ZrO2) has been used in dental implants due to having excellent mechanical properties and biocompatibility that match the requirements for the purpose. Zirconia undergoes phase transformation during heating: monoclinic (room temperature to 1170 °C), tetragonal (1170 °C to 2370 °C), and cubic (>2370 °C). Most useful mechanical properties can be obtained when zirconia is in a multiphase form or in partially stabilized zirconia (PSZ), which is achieved by adding small amounts of a metal oxide dopant, such as MgO (magnesia). This study aimed to synthesize nano Mg-PSZ from a local resource found in West Kalimantan, Indonesia, and examine its structural stability, biochemical stability, and mechanical properties. Nano Mg-PSZ was prepared from a zircon local to Indonesia, from West Kalimantan Province, MgSO4∙7H2O, and polyethylene glycol (PEG)-6000 was used as a template. The obtained t-ZrO2 after calcination at 800 °C was shown to be stable at room temperature. The highest percentage of the t-ZrO2 phase was obtained at Zr0.95Mg0.05O2 with a variation of 99.5%. The hardness of Mg-PSZ increased from 554 MPa for ZrO2 without MgO doping to 5266 MPa for ZrO2 with a doping of 10% MgO. An in vitro biodegradation test showed that the greater the concentration of MgO in doping the ZrO2, the greater the degradation resistance of Mg-PSZ in simulated body fluid (SBF) solution.

Geochemistry and Mineralogy of Peridotites and Chromitites from Zhaheba Ophiolite Complex, Eastern Junggar, NW China: Implications for the Tectonic Environment and Genesis

The Zhaheba ophiolite is an ocean relic of the Zhaheba-Aermantai oceanic slab, a branch of the early Paleozoic Paleo-Asian Ocean. The peridotites consist mainly of harzburgite, lherzolite and minor dunite, chromitite. This study describes the whole-rock geochemistry and mineral chemistry of the Zhaheba peridotite and chromitite for the purpose of constraining their tectonic environment and genesis. The major oxides and the trace element concentrations of the peridotites are comparable with abyssal peridotite, but fall outside the field of SSZ (suprasubduction zone) peridotite and the fore-arc peridotite. The massive chromites belong to the high-Cr group, with an average Cr# (Cr/(Cr + Al)) atomic ratio) value of chromian spinel of 0.77, whereas the average Mg# value is 0.60. The disseminated chromites give a lower concentration of Cr2O3 (38.96–42.15 wt.%, average 40.35 wt.%) and lower Cr# values (0.50–0.56, average 0.53), but slightly higher contents of MgO (13.23 wt.%) and Mg# (0.61) than the massive chromites. In the diagrams of Cr#-Mg#, NiO-Cr# and TiO2-Cr#, the massive chromites fall in the field of boninite, and the disseminated chromite in the peridotite plot fall in the field of abyssal peridotite and mid-oceanic ridge basalt (MORB). The massive chromitites, with high-Cr, display a boninite affinity, whereas the disseminated chromite plot in the high-Al and abyssal peridotite type field may be generated by the extension of the Zhaheba ocean in the MOR environment then experienced deep subduction and exhumation. The calculated degrees of partial melting for the massive chromites are 21%−22%, and for the disseminated chromites in peridotites the degrees are 17%−18%. The calculated values of fO2 for the massive chromites range from −1.44 to +0.20, and the values for the disseminated chromites range from −0.32 to +0.18. The inferred parental melt composition for massive chromitite falls in the field of boninite in an arc setting, whereas the disseminated chromite in peridotites are in the field of a MORB setting. This indicates that the parental magmas of the former were more refractory than the latter. A two-stage evolution model for the chromites was proposed, in which disseminated chromites were first formed in an MOR environment and then modified by later-stage melts and fluids, and formed massive chromites were formed in an SSZ setting during intra-oceanic subduction.

Correlation of MgO loading to spinel inversion, octahedral site occupancy, site generation and performance of bimetal Co–Ni catalyst for dry reforming of CH4

The influence of MgO content on the structural characteristics and performance of bimetallic Co–Ni catalyst was investigated for CO2 reforming of CH4. Three different catalysts with the same amount of active metals (Co and Ni) but different Mg loading in the Mg–Al support were prepared by co-precipitation method. The catalysts were subjected to different characterization techniques to obtain information about their bulk, structural, textural properties, site formation and performance for DRM. Results showed there was reduction in the surface area (N2 adsorption), a change from a single bulk phase spinel to dual-phase (XRD), and an increase in the degree of spinel inversion (Al-NMR) from 0.29 to 0.57, as the MgO loading changed from 25% to 65% in the support. There was also improved support basicity (CO2-TPD), metal support interaction changed (STEM EDX), the ease of metal reduction and site formation (Ni/Co K-edge XANES) became better as the MgO loading increased. Improved MgO loading facilitated the formation of inverse spinel and MgO - Ni/Co solid phase, which enhanced better reactants conversion and faster conversion of deposited carbon from the catalysts surface during DRM.

Zirconium/hafnium fractionation and rare earth element systematics in sub-cratonic garnet pyroxenites, Norway

Ten previously studied garnet pyroxenites and one eclogite from orogenic peridotites in the Western Gneiss Region of Norway were analysed for whole-rock major and trace and mineral trace elements to characterise the evolutionary stages of the East Greenland sub-cratonic mantle. A continuous range of whole-rock MgO contents (17–30 wt.%) correlates inversely with hbox {Na}_2hbox {O}, hbox {Al}_2hbox {O}_3, and CaO contents. In contrast, rare earth element (REE) compositions allow the samples to be devided into two types. Type I samples have relatively flat primitive mantle (PM) normalised REE patterns (0.4-6.8 times PM values) with minor fractionation of middle–heavy REEs. Type II samples are simlar to type I samples but have higher light REE contents (6.1–57 times PM values) that reflect metasomatic enrichment. Whole-rock Zr contents (1–27,upmu hbox {g},hbox {g}^{-1}) and Zr/Hf ratios (17–39) are positively correlated. Type I samples have low Zr/Hf ratios that mostly differ from type II samples, indicating that metasomatism modified the initially sub-chondritic Zr/Hf ratios. Garnet Zr–Zr/Hf–Y–Ti systematics suggest that metasomatic enrichment transformed the type I samples into type II samples, consistent with processes observed in other cratonic areas (e.g., the northern East European Platform and the Kaapvaal Craton). The formation of type I pyroxenite in dunite from a melt at sim 100,text {km} depth implies the sub-chondritic Zr/Hf ratios were inherited from that melt. Such melts are thought to form by melting of garnet-bearing, melt-depleted mantle, which is consistent with models for recycling of Archaean palaeo-oceanic crust throughout the mantle prior to the formation of the sub-cratonic lithosphere beneath East Greenland.

Experimental study on flow properties of blast furnace slag with different alumina contents based on the image measurement method

This paper established a novel visualization method for measuring blast furnace slag(BFS) flow properties and investigated the effect of alumina content on the CaO–SiO2–Al2O3–MgO BFS system. The outcomes indicate that elevating Al2O3 concentration in the BFS mixture from 14% to 26% results in a rise of critical flow temperature Tc from 1332.5 °C to 1384.1 °C, leading to a deterioration of BFS flow properties. However, the critical flow velocity Vc of BFS rises from 1.82 mm/min to 2.91 mm/min, representing a 60% increment. BFS with high Al2O3 content was found to be more likely to form high melting point crystals, such as gehlenite, with better crystallization, which is one of the main reasons for the deterioration of BFS flow properties. Fourier Transform Infrared Spectrometer (FTIR) and Raman spectra analysis indicate that the proportional content of simple silicate structures denoted as QSi0([SiO4]4−),QSi1([Si2O7]6−) decreased with increasing Al2O3 content, while those of complex silicate structures, QSi2([Si3O10]8−),QSi3([Si3O9]6−) increased. Furthermore, the Si–O–Al structural unit concentration progressively increased, indicating that the escalation in bridging oxygen within the BFS system raised the polymerization degree of the BFS, leading to a more complex aluminosilicate structure. Notably, the [AlO4]5- tetrahedra content within the BFS has reached saturation at roughly 21%. Further increases in Al2O3 content induced an excess of [AlO6]9−octahedra formation, which generally acts as a network modifier to lower the polymerization degree of the BFS system. However, this effect was not noticeable in this study, which may be attributable to the low basicity (CaO/SiO2 = 0.99) and MgO content (MgO/Al2O3 = 0.21–0.34) of the BFS samples in this study.

The Effects of MgO and Al2O3 Content in Sinter on the Softening-Melting Properties of Mixed Ferrous Burden.

The softening-melting properties of mixed ferrous burden made from high-basicity sinter with increased MgO and Al2O3 content and acid pellets was investigated for optimization. The influences of MgO and Al2O3 are discussed with the aid of phase analysis. The results showed that, with decreasing MgO mass%/Al2O3 mass% in mixed burden, all the softening-melting characteristic temperatures decreased, which can be attributed to the low melting temperature and viscosity of the slag caused by MgO and Al2O3. The permeability of the melting zone deteriorated again when MgO mass%/Al2O3 mass% decreased to a certain content. The softening interval widened slightly at first and then narrowed, while the melting interval first increased slightly and then increased greatly later. It can be deduced that the softening properties were improved, but the melting properties were worsened. Under comprehensive consideration of its softening-melting properties, permeability, iron ore reduction and the thermal state of the blast furnace hearth, the optimal softening-melting properties of a mixed ferrous burden with MgO mass%/Al2O3 mass% of 0.82 is optimal.

Geochemistry and petrogenesis of late Neoproterozoic Nuweibi and Atawi rare metals bearing granites, central Eastern Desert, Egypt

Nuweibi albite granite (NAG) and Atawi two feldspar granites (AG) are silica rich, highly evolved intrusions and rare metals-bearing in the Central Eastern Desert of Egypt exhibiting different stages of magmatic-late magmatic evolution. Both are evolved from low-P2O5 metaluminous to peraluminous granitic magma resulting from partial melting of crustal source. The chemical features of both of NAG and AG as Na2O + K2O, FeOt/MgO, Ga, Nb and Ta high concentrations are compatible with an anorogenic within plate tectonic setting. However, NAG have higher concentration of Al2O3, Na2O, MnO, Ga, Rb, Hf and Ta and lower concentrations of SiO2, TiO2, Fe2O3t, MgO, CaO, K2O, P2O5, Ba, Zr, Y, Sn, W, F and REEs. NAG shows obvious enrichment of heavy rare earth elements (HREEs) relative to light rare earth elements (LREEs), negative Eu anomaly and tetrad effect. On the other hand, AG has higher concentration of REEs and its pattern is slightly enriched in LREEs relative to HREEs with negative Eu anomaly. For NAG, the fluid-mobilization of REEs and other trace elements is supported by very low ratios of Eu/Eu* (0.17–0.3), (La/Yb)n (0.06–0.4), Nb/Ta (0.44–1.09), Zr/Hf (1.84–2.61), K/Rb (66.8–109.9) and Y/Ho ratios (2.9–6.3) together with high Sr/Eu (160–440). On the other hand, AG represents moderately fractionated granitic melt in regard to chondrites still showing chondritic or almost chondritic Nb/Ta (5.5–15.9), Zr/Hf (14.8–28.6), Y/Ho (26.2–45), K/Rb (99.24–346.28) and Sr/Eu (56.6–520) ratios indicating the lower effect of late magmatic fluid-rock interaction compared to NAG. Fluid phase enriched in alkalis from a nearly solidified granite causes local albitization in Atawi and Nuweibi areas where Nuweibi granite is more albitized. Moreover, greisenization (decomposition of feldspar and Fe-mica) is also more common in NAG.

Cretaceous Nb-enriched basalts in the western Gan-Hang belt, South China: A response to slab window opening during the Paleo-Pacific ridge subduction

The role of recycled slab-mantle interaction in the formation of mantle-derived rocks during the Paleo-Pacific subduction remains to be tested. In this study Nb-enriched basalts (NEBs) are identified in Shanggao, western part of the Gan-Hang belt, South China. These volcanic rocks have 40Ar/39Ar ages of ∼90 Ma. They are tholeiitic to calc-alkaline in composition and have low SiO2 (50.1–53.4 wt%), high MgO (5.86–7.10 wt%), and Nb (10.7–14.3 ppm) contents. These NEBs have high Nb/La (0.91–0.99) and Nb/U (14.8–21.0) ratios and chondrite-normalized patterns with slightly enriched light rare earth elements (LREEs) ((La/Yb)N = 5.32–6.52). Their primitive mantle-normalized patterns are similar to E-MORB-like characteristics. These features indicate that these NEBs were derived from a mixed source between the asthenospheric mantle and slab-derived adakitic components in the garnet stability field. Their Sr-Nd-Pb-Hf isotopic compositions also reflect the contribution of the subducted oceanic crust including minor sediments in the source. These NEBs are spatially associated with adakitic rocks, A-type granites, and related mineral deposits in the Gan-Hang belt, clearly supporting a tectonic model in which the Cretaceous ridge subduction and slab window opening occurred during the enhanced slab rollback of the Paleo-Pacific plate. The melting of residual eclogites caused by episodic upwelling of the asthenospheric mantle can account for the formation of the NEBs in a back­arc extensional setting.

Structural effects observed in rods fabricated from magnesium powder and multi-walled carbon nanotubes using different parameters of forward-backward rotating die extrusion (KOBO)

In this study the effects induced by 0.5 vol% of multiwalled carbon nanotubes (MWCNTs) in magnesium based rods, obtained by cold and hot forward-backward rotating die extrusion method (KOBO) were presented. A composite billets were fabricated from powder, sonically mixed prior to hot pressing under vacuum, and then extruded. Prior the extrusion process the billets were either at room temperature or heated up to 150 °C. The macrostructure and microstructure of rods surface, cross and longitudinal sections were characterized by LM, SEM with EDS and XRD methods. Moreover, the tensile strength, hardness and open porosity were determined for Mg/MWCNTs composites and reference rods of pure magnesium processed by KOBO. Presented studies allow to recognize the phenomena occurring in extruded rods, as well the role of initial billets heating and extrusion rate. After hot KOBO in all rod volume the nanotubes formed an elongated skeleton with some submicro or nanosized MgO content. But when the cold KOBO and higher extrusion rate were applied, two types of microstructure were detected in the rod, and the rod consisted of Mg-MWCNTs/MgO core well connected with surrounding free of skeleton α-Mg layer doped with single MWCNTs and nanosized MgO. That phenomena was not earlier reported in literature. Moreover, the Rietveld XRD examinations revealed a spectacular refinement of metal matrix crystallites in dynamic recrystallization, and this effect occurred due to MWCNTs presence. The MWCNTs application caused the rods properties increase. However, greater mechanical properties and lower porosity were obtained by extrusion of the heated up to 150 °C billet.

Genesis and depositional environment of the Carboniferous Baishanquan iron deposit in Eastern Tianshan, Northwestern China

Submarine volcanic-hosted iron deposits are the most important iron deposit in Northwestern China. However, their origin remains controversial. Here, we present detailed studies of the petrology, geochronology, geochemistry and FeSi isotopes of iron ores from Baishanquan deposit in Eastern Tianshan, Northwestern China. Similar to Precambrian banded iron formations (BIFs), the Baishanquan deposit is hosted in a volcanic-sedimentary succession, the iron ores are characterized by banding with alternate iron-rich and silica-rich layers, and the mineral assemblage is dominant by magnetite, quartz and Fe-silicates. The iron ores show distinct light rare earth elements (REE) depletion [(La/Yb)PAAS = 0.24–0.47], no significant Eu anomalies (Eu/Eu⁎ = 0.88–1.16), relatively high Y/Ho ratios (30–34), and δ30Si values in quartz from the iron ores ranging from −0.80 to 1.67‰. These data indicate mixed seawater and low-temperature submarine hydrothermal source for both the iron and silica. The absence of negative Ce anomalies suggests that the depositional environment was characterized by low oxygen conditions similar to modern oxygen minimum zones. Positive δ56Fe values in most magnetite (−0.45 to +1.02‰) suggest partial Fe(II) oxidation of the iron ores. Interestingly, the iron ores also contain relatively high Al2O3, CaO, MgO, and Zr concentrations, indicating that the sedimentary basin was subject to periodic clastic input. Indeed, zircon LA-ICP-MS UPb dating of interlayered dacite indicates that the Baishanquan volcanic-sedimentary rocks and associated iron ores were deposited at 327.3 ± 2.8 Ma (N = 25, MSWD = 0.52). This is significant because the appearance of these iron deposit provides direct evidence that marine ferruginous conditions – at least locally - may have still been present at Carboniferous period.

Influence of catalyst composition on NOx storage and reduction characteristics of Ag catalyst supported on MgO-doped alumina

A novel material (Ag/MgO-Al2O3) for storage of NOx under cold-start conditions and its reduction in the high-temperature stabilized phase is synthesized, and the influence of MgO and Ag loading on its NOx removal performance is investigated. A high MgO loading increases the NOx storage capacity but also decreases the stability of adsorbed NOx. Moreover, it decreases the adsorption rate at early times since NOx spillover is inhibited. The catalysts with the lowest Ag and MgO loading exhibit the highest NO oxidation activity. The amount of NOx storage increases with a decrease in Ag loading and is attributed to enhanced spillover of NOx to the support. Increasing the Ag and MgO content leads to an enhanced NH3 and C3H6 oxidation activity, which is explained by the presence of Ag metallic clusters. Further, the NH3-SCR and C3H6-SCR activity decrease with Ag and MgO loading. Thus, the catalyst composition can be tuned to obtain the desired activity for various oxidation and reduction reactions.

Petrogenesis of high-alumina basalts: Implications for magmatic processes associated with the opening of the South China Sea

Results of International Ocean Discovery Program (IODP) Expeditions on the northern continental margin of the South China Sea (SCS) have nullified the early notion that the SCS is a magma-poor margin. However, there are continuing debates on how the rapid transition from continent to ocean is supported by geochemical and petrologic data, and whether such a process was related to plate subduction or mantle plume activities. Here we present the results of bulk-rock and plagioclase phenocryst geochemistry of the basalts generated during the early spreading stage (initial and steady ocean stages) of SCS basin extension, which were drilled at IODP Sites U1500 and U1503, respectively. We combined these findings with published data from the late spreading stage of the SCS basin, which provides an excellent opportunity to examine the magmatic processes associated with the evolution of the SCS basin. Our results revealed that the SCS basalts generally exhibit higher Al contents than global Mid-Ocean Ridge Basalts, particularly at lower MgO contents, which is similar to the characteristics of modern arc basalts. Nevertheless, their origins are site-specific and complex. For instance, some of the Site U1503 basalts originated through fractional crystallization of water-rich parental magmas with the lowest degree of melting, while the basalts from the other sites, including Site U1500, were primarily generated by the accumulation of plagioclase. More specifically, the water-rich magmas from Site U1503 displayed strong subduction signals in terms of trace elements, and their correlations with Al2O3 content suggest that they are the product of partial melting of the mantle wedge, closely related to the northward subduction of proto-SCS. This subduction had a significant effect on triggering the opening of the SCS, rather than a mantle plume. Moreover, the Site U1500 basalts exhibit a significant increase in plagioclase An values with the increase of host magma Al contents, indicating that the plagioclase floatation mechanism cannot account for the origin of their plagioclase accumulation. Therefore, we propose that the high abundance of plagioclase in Site U1500 basalts requires rapid ascent of magma, supporting a rapid rifting and strong magmatism during the initial opening of the SCS.

Low-temperature calcination composite binder from dolomite and its application to facing board materials

The article presents the research to obtain low-temperature calcination binder from dolomitic limestone with a MgO content of less than 20%. The initial dolomite material was calcinated at the following temperature range from 700 to 800 ℃ and firing time 25–45 min. The result of the selection of the optimal firing conditions is semi-calcination product caustic dolomite with a minimum content of residual Mg(CO3)2 and free CaO with bending strength 10–11 MPa. Physical-mechanical characteristics and mineral composition of samples were determined by the use of differential thermal analysis and infrared spectroscopy studies. Preliminary experimental samples of facing composite board materials were prepared and the main physico-chemical parameters were determined: bending strength 4–7.6 MPa, density 800–1400 kg/m3 and water absorption 10–25%. A three-dimensional model for the production of glass dolomite slabs has been developed.

In-situ hydrothermally derived highly responsive MgO doped mesoporous KIT-6 based novel humidity sensor

ABSTRACT Herein in this work, the synthesis as well as study of Magnesium-oxide loaded mesoporous silica KIT-6 (a 3D material, first synthesised by Ryoo’s research group in 2003 material, in Korean Institute of Technology) for sensing at room temperature was done by employing KIT-6 as a hard template. The unique arrangement mesoporous KIT-6 having Ia3d symmetry along with a three-dimensional cubic arrangement of pore provides more tunnels for transportation of charge carriers. Water molecules are more effectively adsorbable due to KIT-6’s extremely porous structure, and the mesoporous framework’s broad, uniform pore channels make it simple for charged ions to flow freely. Despite these qualities, undoped KIT-6 does not exhibit a superior relative humidity (RH) sensitivity in humid environments hence metallic nanoparticles (MgO/KIT-6) have been used to improve the sensing capabilities of RH sensors. In the current work, we offer a straightforward, easy-to-follow hydrothermal synthesis method for producing effective humidity sensing materials made of MgO-loaded KIT-6. Different MgO concentrations (1, 5 and 10 wt%) were added to KIT-6 in order to employ it as a humidity sensor material to effectively monitor and regulate humidity levels. Here at MgO/KIT-6 presents swift humidity response and recovery time along with it change in ≥3 orders of magnitude in resistance were observed over as compared to pure KIT-6 in the 11%–98% RH range at room temperature. The structural insights were examined using X-ray diffraction (XRD), Fourier transform infrared, High-resolution transmission electron microscopy , Field emission scanning electron microscopy with energy dispersive x-ray (EDX) microanalysis and textural properties of the synthesised mesoporous KIT-6 silica and MgO/KIT-6 (X) nanocomposites were examined in depth with the N2 adsorption-desorption isotherm from which it was analysed that as the amount of MgO is incremented, the surface area gets decreased. Among all the tested samples of different weight%, optimal results obtained for 5 weight% MgO-loaded KIT-6 [abbreviated as MgO/KIT-6(5)] exhibits impressive humidity sensing responsiveness, little hysteresis, short response as well as recovery time (31 s/35 s), consistent linearity, extremely high accuracy over a varied working temperature range, repeatability and great stability in the 11–98% RH range. The investigation of humidity sensing properties of MgO/KIT-6 hybrid nanocomposite justifies that this material is good candidates to be used as a innovative high performance humidity sensor.

Phase Equilibrium studies in the system “FeO”–SiO2–Al2O3–CaO–MgO at 1200 °C and Po2 10-8atm

Iron oxides and silica are the major components of copper smelting slag. The oxides of aluminum, calcium and magnesium are also present in the slag that is introduced through copper concentrate, flux and refractories. Liquidus temperatures of the copper smelting slags are usually controlled by Fe/SiO2. The concentrations of Al2O3, CaO and MgO, and FeO/Fe2O3 in the slag can also affect the liquidus temperatures where FeO/Fe2O3 is a function of oxygen partial pressure. High temperature equilibration under controlled oxygen partial pressure followed by quenching and electron probe microanalysis were used to determine the compositions of the liquid and solid phases at 1200 °C and Po2 10-8 atm. The experimental results are presented in the forms of pseudo-ternary sections “FeO”-CaO-SiO2 at fixed 2, 4 and 6 wt pct MgO, and 2 + 2, 4 + 4 and 6 + 6 wt pct MgO + Al2O3. Spinel and tridymite are the major primary phases in the composition range investigated. In addition, CaSiO3, pyroxene, olivine, and melilite are also present. The isotherms in the spinel and tridymite primary phase fields move towards higher SiO2 concentration directions with increasing CaO, Al2O3, and MgO concentrations. The experimentally determined results are compared with the FactSage calculations.

The phase evolution of resin‐bonded Al2O3‐Al refractory containing magnesia under N2‐blowing

AbstractPhenolic resin‐bonded Al2O3‐Al‐MgO refractories were prepared from sintered alumina and aluminum as raw materials, adding 3 wt%, 9 wt% and 15 wt% high‐purity magnesia. The green samples were treated at 200°C and heated at 1300°C and 1600°C in a nitrogen atmosphere. The results showed that the phases after heating at 1300°C were α‐Al2O3, spinel solid solution (MgAlON), Al4O4C, Al4C3 and unreacted aluminum. The phases after heating at 1600°C were α‐Al2O3, spinel solid solution (MgAlON), Al4O4C, Al4C3, (Al2OC)x(AlN)1‐x solid solution, Al8O3N6, and unreacted aluminum, with a tendency to shift from Al‐O‐C to MgAlON with increasing MgO content. MgAlON was obtained by in situ synthesis of MgO, Al2O3, Al, and N2 at 1300°C. With sufficient magnesia, the stability of Al4O4C and Al4C3 decreases at 1600°C, and AlON is formed with better stability and can be solubilized into MgAlON. That is, when magnesia was added to the phenolic resin‐bound Al2O3‐Al composite under a nitrogen atmosphere, more stabilized MgAlON was formed.

Effect of MgO on corrosion mechanism under LF refining slag for MgAlON–MgO composites synthesized from spent MgO–C brick: Wetting behaviour, reaction process and infiltration mechanism

The Ladle Furnace (LF) refining slag resistance of MgAlON–MgO composites synthesized from spent MgO–C brick was investigated using the sessile drop technique, manifesting that MgAlON with slag corrosion thickness of 780 µm exhibits the best slag resistance than other composites. MgAlON–MgO composites react with the slag to generate calcium aluminate, spinel, and TiN. Furthermore, MgAlON–MgO composites with different MgO content show different corrosion process. The corrosion process of MgAlON and MgAlON–4.2 wt%MgO proceeds with wetting, reaction, and infiltration processes, while that of MgAlON–10.5 wt%MgO and MgAlON–15.7 wt%MgO only proceeds with wetting and infiltration processes. Compared with MgAlON–10.5 wt%MgO and MgAlON–15.7 wt%MgO, MgAlON and MgAlON–4.2 wt%MgO show low contact angle, presenting good slag wettability. Nevertheless, the viscosity of molten slag decreases with increasing MgO content, and MgAlON–MgO composites with high MgO content (MgAlON–10.5 wt%MgO and MgAlON–15.7 wt%MgO) show high porosity, thus aggravating the infiltration of molten slag. Compared with the wetting behaviour between molten slag and MgAlON–MgO composites, the infiltration of slag plays a decisive role in the slag corrosion process. Therefore, MgAlON and MgAlON–4.2 wt%MgO exhibit better slag resistance, showing the potential application in the ladle furnace.

Characteristics of clamshell flour Donax sp from Sapola sub-village of Seram Island

Clam meat is consumed by the people of Sapola sub-village on Seram Island, and the shells are processed into flour by roasting and soaking in a husk ash solution. This traditional method, with its simple and inexpensive equipment, causes pollution. Another method of producing shell flour that uses NaOH as a solvent has resulted in shell flour with high mineral content. The objective of this study was to compare the physical and chemical properties of Donax sp shell flour using the traditional method and the chemical method with NaOH solution. Laboratory analysis was used as the research method in this study. The process included examinations on shape, size, color, and yield of the shell flour, as well as the water content and mineral content of CaCO3, MgO, SiO2, and sulphur. The results revealed differences in the physical properties and mineral content of clam shell flour when using traditional and chemical methods. Donax sp shell flour obtained by soaking purplish-white NaOH, powder form size 18 mesh size, CaCO3 content of 96.60%, MgO 0.03%, SiO2 0.33%, Sulphur 0.02%, water 0.27%, yield 41.67%, while clam shell flour obtained by burning silver white, powder form size 18, CaCO3 content of 85.92%, MgO 0.06%, SiO2 0.33%, Sulphur 0.01%

Effect of additives in increasing ash fusion temperature during co-firing of coal and palm oil waste biomass

Biomass has the potential to cause slagging and fouling during combustion due to its high potassium and high chlorine contents, as well as its low ash melting temperature. This study aims to identify suitable additives for co-firing of coal with palm oil waste. Magnesium, aluminosilicate, aluminum, silicate, calcium, and potassium-based additives were tested at a dosage of 6 wt%. The results indicate that magnesium-based additives significantly increase MgO content, while aluminum-based additives considerably decrease the SiO2/Al2O3 ratio. Both of these effects contribute to an increase in the ash fusion temperature (AFT) of the four samples, with an average percentage increase in the ash fusibility index (AFI) above 25 %. Additionally, additives like CaHPO4, CaO, kaolin, and K2CO3 consistently raise the AFT, although the average percentage increase in AFI is lower than 25 %. However, further investigation is required to determine optimal dosage of additives and address other issues, such as corrosion tendency.