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This study investigated the impact of BaO/Al2O3 molar ratio on the electrical conductivity and Al coordination state of CaO–MgO–SiO2–Al2O3–BaO slag using four-electrode technique and 27Al MAS-NMR spectroscopy, respectively. With an increasing BaO/Al2O3 molar ratio from 0.14 to 0.36, BaO preferentially participated in charge compensation of Al3+, which facilitated the transition from AlO5 and AlO6 structures to AlO4 structure and increased the stability of AlO4 tetrahedra, thus enhancing the slag's polymerization and reducing its electrical conductivity. However, once the compensation achieved equilibrium, remaining BaO was involved in depolymerizing the tetrahedral structure and promoting the formation of AlO5 and AlO6 structures. Consequently, the decreased degree of polymerization and increased concentration of free ions together led to an increase in electrical conductivity. However, the increased migration resistance due to the large radius of Ba2+ ion is responsible for the electrical conductivity minimum near the molar ratio of 0.43. [ABSTRACT FROM AUTHOR]

Currently, the common way for structural investigation is to confirm the amorphous state of the quenched slag by XRD prior to Raman analysis. However, if the slag precipitates a few nanocrystals during quenching, XRD may not recognize them, but the slag structure has been changed. Therefore, this paper proposes to combine TEM with XRD and Raman for analyzing the slag structure and to verify it with blast furnace slag obtained by different quenching methods. The results show that the XRD curves of the slags obtained by quenching in water or on a stainless steel plate show amorphous states, but the deconvolution results of Raman spectra are significantly different. The TEM analysis finds a few crystals in the slag obtained by the latter, which is responsible for the structural differences. Therefore, it is necessary to confirm the amorphous state of the slag by both XRD and TEM before studying the structure. [ABSTRACT FROM AUTHOR]

Sulfide capacity is one of the essential properties of molten slag, which determines the sulfur content in the hot metal during the smelting process. In the present study, an artificial neural network model was developed to predict the sulfide capacity of molten slag over a wide range of components and temperature. A CaO–SiO2–MgO–Al2O3–FeO–TiO2–MnO slag database for sulfide capacity covering most of the previous confident literature was constructed. The influence of activation function, optimization algorithm, and various hidden layers on the performance of the models on sulfide capacity were studied using ten-fold cross-validation. The developed model shows excellent prediction performance, which is capable of accurately predicting complex slag systems, especially TiO2-bearing slag systems. The accuracy and nonlinear prediction ability of the model are verified by experiments, and the iso-sulfide capacity diagrams of CaO–SiO2–Al2O3, CaO–SiO2–TiO2–8 wt pct MgO–14 wt pct Al2O3, and CaO–SiO2–30 pct wt pct TiO2–MgO–14 wt pct Al2O3 slag systems at 1773 K were established with the model. [ABSTRACT FROM AUTHOR]

During sinter pot tests, Ni-containing sinter indices are greatly improved by the appropriate proportioning of different types of limonitic nickel laterite and application of sintering strengthening technology. After optimization, tumble index and productivity of Ni-containing sinter are increased by 27.17% and 20.62%, respectively, and solid fuel rate is reduced by 27.63% compared with the base case. In addition, the metallurgical performance is overall better with higher RI, similar RDI and narrower softening and melting drop intervals. The appropriate proportioning of different types of limonitic nickel laterite and the application of multi-force field strengthening technology contribute to the reduction of (MgO + Al2O3)/SiO2 mass ratio, further densification of sinter layer and extension of holding time of high temperature during sintering. Compared with the base case, sinter porosity is reduced from 48.92% to 20.18% and SFCA amount is increased from 8.78% to 27.12%. Much better quality Ni-containing sinter is consequently obtained. [ABSTRACT FROM AUTHOR]

High-purity Na8Ti5O14 was synthesized using Na2CO3 and TiO2 as the starting materials by a solid-phase reaction. Heat capacity of Na8Ti5O14 was measured by PPMS at low temperatures and MHTC 96 line at high temperatures. The changes in enthalpy at 298.15 K were Δ 0 298.15 K H m = 95.43 kJ mol−1, and standard molar entropy was S m θ = 569.35 J\,mol−1\,K−1, respectively. The changes in enthalpy ( Δ 298.15 T m H m ), entropy ( Δ 298.15 T m S m ), and Gibbs energy ( Δ 298.15 T m G m ) from (298.15 to 1303) K were calculated using heat capacity functions. [ABSTRACT FROM AUTHOR]

The pyrolysis behavior of FeS in the blast furnace process is of vital importance to control the gaseous sulfide species and emissions of the blast furnace gas and the sulfur content in the molten iron. This work presents an experimental study on the pyrolysis behavior of FeS under CO-H2 atmosphere from 200 °C to 900 °C by thermal-gravimetric and mass spectrometry (TG-MS). Besides, thermodynamic theoretical calculations were conducted to further understand the pyrolysis process. The results showed that only trace amounts of FeS was reduced to elemental Fe in any CO-H2 atmospheres studied. H2S and COS were the main gaseous sulfides generated by the pyrolysis reactions of FeS in CO-H2 atmosphere. Increasing the proportion of H2 in the reducing atmosphere reduced the pyrolysis reaction temperature of FeS, which was beneficial to the decomposition of total sulfides and promoted the conversion of sulfides to H2S. On the other hand, CO promoted the conversion of sulfides to COS. The appearance order of the gas product as increasing the temperature under the strong reducing atmosphere (CO-H2) was by H2S → COS → CS2 → S2 → S. [ABSTRACT FROM AUTHOR]

Knowledge of the equilibrium phase relationship in the V2O5–Na2O system is critical and essential for the sodium salts roasting process of slag-bearing vanadium, and those fundamental studies can be used to accelerate industrial optimization and update the process. Therefore, phase equilibrium and quenching and thermal analysis experiments on the V2O5–Na2O binary system were carried out in the present work under pO2 of 10−3.5 atm. The V2O5–Na2O system has 7 primary phase fields including two simple oxides (V2O5 and Na2O), and 5 binary compounds (Na2V12O31, Na10V24O65, NaVO3, Na4V2O7, and Na3VO4). The existence of Na2V12O31 and Na10V24O65 was experimentally confirmed and then characterized by EPMA, no extensive compounds or solid solutions were detected in the present study. The liquidus lines were experimentally determined in most of the primary phase fields in the temperature range from 500 °C to 800 °C. The temperatures and components of some invariant reactions, including Liq → V2O5 + Na2V12O31 (640 °C, 53 mol pct Na2O), Liq → Na10V24O65 + NaVO3 (504 °C, 40.2 mol pct Na2O), Liq → NaVO3 + Na4V2O7 (540 °C, 59.0 mol pct Na2O), and a new peritectic reaction at 570 °C with 32 mol pct Na2O were rechecked, and Liq + Na2V12O31 → Na10V24O65 was also reconstructed. The large amount of new phase equilibrium data proposed in this work will serve as reliable input for future thermodynamic reassessments of the V2O5–Na2O system within the CALPHAD framework to extensively improve the current V2O5-based thermodynamic databases. [ABSTRACT FROM AUTHOR]

To estimate accurately the coalbed methane content, a pressurized sampling method with the aid of frozen sealing is proposed. In addition, the influences of adsorption gas pressure, freezing temperature, soaking time in drilling fluid, drilling fluid type, and exposure time in the atmosphere on the gas loss rate and the gas desorption characteristics of frozen samples were evaluated. Under low gas pressure, the gas in adsorption and free state in the coal sample can be trapped completely by the freezing sampling method. However, an appropriate freezing temperature is necessary to limit gas loss caused by frost cracks. The addition of polymers to the drilling fluid can enhance gas solubility and improve the gas trap capacity of the freezing sampling method. Although the freezing method can seal the gas perfectly in a coal sample, gas loss caused by gas diffusion through the frozen body is still difficult to avoid. Therefore, reducing the sampling time can limit effectively the gas loss rate. The freezing sampling method was confirmed to be an efficient method for obtaining gas-containing geological samples in an in situ state. The gas loss characteristics of coalbed coal sampled using the freezing method can provide theoretical support for reducing and estimating gas loss during the freezing sampling process. [ABSTRACT FROM AUTHOR]

The interaction between V2O5 and ammonia is of great significance in both the selective catalytic reduction denitrification and the preparation of VN-based materials. In this study, the adsorption of NHx (x = 0–3) and H on V2O5 (001) surface is investigated by density functional theory. The binding of NHx and H at different sites on V2O5 (001) surface is revealed, and the reaction mechanism is discussed. The results show that Vb site had a strong ability to capture NH3, but the main site involved in the reaction was the Va site. NH2, NH and N were more easily adsorbed at the O sites than V sites with the decomposition of H atom from NH3. In the deoxygenation reaction of V2O5, O(1) on the surface of V2O5 (001) is the easiest to remove. The deoxygenation reactions are determined as H deoxygenation to form H2O and N deoxygenation to form NO. [ABSTRACT FROM AUTHOR]

Several industrial processes, such as those in metallurgical, chemical, ceramic, and cement industries, often involve solid–solid reactions. The solid reactions at high temperatures are often limited or controlled by solid diffusion, and some models have been suggested to describe the reaction behaviors. A model considering the particle shape, surface area, particle size distribution, and diffusion rate of reactants was established to develop a quantitative representation of the solid–solid reaction of powders in a binary reactant system. In this model, the interface of particles was divided into reaction and nonreaction surfaces, and the particle shape was divided into first- and second-level shapes. The area of the reaction interface was calculated, and the concentration distribution of the reactants was numerically expressed. The simulated kinetics curves of fractional conversion α with time for different average particle sizes and diffusion coefficients were shown to be useful for evaluating the kinetics of solid–solid reactions. The simulated kinetics curves and experimental data from the references were compared, and a good accuracy was achieved. [ABSTRACT FROM AUTHOR]

To increase the utilization of V-Ti-Magnetite ore in the burden of a blast furnace, we investigated replacing CaO with MgO. The high fraction of TiO2-bearing raw materials leads to a super-high TiO2 content in the blast furnace slag, typically above 30 wt pct, which affects normal blast furnace operation. The present study focuses on the sulfide capacity of slag containing a super-high TiO2 content. The effects of TiO2 content and the ratio of MgO to CaO (M/C) on the sulfide capacity of slag were examined using a gas-slag equilibrium method. In the CaO-SiO2-TiO2-MgO-Al2O3 slag system, as the content of TiO2 in the slag increased from 20 to 34 wt pct, the sulfide capacity decreased from 6.25 × 10−5 to 2.86 × 10−5. Above 30 wt pct TiO2, the influence of TiO2 content on the sulfide capacity became negligible. Increasing the (M/C) ratio induced a non-monotonic trend in the sulfide capacity, which first increased and then decreased. Thermodynamic and structural analyses were employed to characterize the experimental results. Thermodynamically, decreasing the CaO activity reduced the free oxygen in the slag with increasing TiO2 content. Furthermore, an increase of titanium suboxide slowed the reduction of the sulfide capacity. Mass substitution mainly influenced the availability of free oxygen in the slag, and then the sulfide stability and oxygen concentration worked together, resulting in a non-monotonic sulfide capacity when MgO was substituted for CaO. In addition, the sulfide capacity was dependent on the effect of both the quaternary molar basicity and the binary molar basicity. Finally, the structural analysis revealed that for a super-high TiO2 content in the slag, both the structure of Ti and the depolymerization reaction of Ti had an extremely important effect on desulfurization. [ABSTRACT FROM AUTHOR]

The solid-state reaction and diffusion behaviors of CaFe2O4 and TiO2 were investigated using a diffusion couple method at 1373 K to 1473 K under air atmosphere, and an in situ XRD method was used to analyze the solid-state reaction process. The reactions between calcium ferrite and TiO2 in the solid state are displacement reactions that produce perovskite and Fe2O3. The diffusion interface was divided into three layers based on phase analysis: layer I was composed of CaTiO3; layer II was composed of Fe2O3, CaTiO3, CaFe2O4, and Ca2Fe2O5; and layer III was composed of CaTiO3, Fe2O3, CaFe2O3, and CaFe4O7. The interface was formed in three stages. In stage I, CaTiO3 formed at the interface. In stage II, the gradual thickening of layers I and II was accompanied by the growth of the amount of CaTiO3 phase. In stage III, CF decomposed into CF2, and layer III formed. Micropores were formed in layer II due to the Kirkendall effect, and the diffusion rate of Ca2+ in CaFe2O4 was greater than that in CaTiO3. The squared thickness of layer I was found to depend linearly on time, and the expression for predicting the thickness of layer I was proposed: Δ x = (1.1731 × 10 - 18 T 2 - 3.0206 × 10 - 15 T + 1.9652 × 10 - 12) 1 2 · t 1 2 [ABSTRACT FROM AUTHOR]

As the titanium industry rapidly develops, low-grade ilmenite resources are drawing global attention. The direct use of low-grade ilmenite can result in low production efficiency and heavy pollution. In addition, the production of high-titanium slag via electric furnace melting consumes significant energy and possesses low production efficiency. Therefore, a novel process with low energy consumption is necessary for producing ultra-grade slag (UGS) for chlorination. For low-grade ilmenite, semi-molten reduction and magnetic separation were suggested in this study. The effects of carbon content, reduction time, and Na2CO3 addition on the reduction and separation behavior were studied. The results showed that the addition of Na2CO3 favored the formation of a semi-molten state, which was more conducive for the diffusion, aggregation, and growth of the metal phase. In this regard, excess carbon was not helpful, and it weakened the growth of the metal phase. Wet grinding and magnetic separation were used for beneficiation of the reduced sample for efficiently separating the slag iron and preventing the formation of agglomerates between slag and metal. For the sample with a carbon dosage of 13 pct, Na2CO3 dosage of 8 pct, reduction temperature of 1673 K (1400 °C), and 90 minutes holding time, high-titanium slag with a TiO2 grade of 81.63 pct and iron content of 4.53 pct was produced, with the TiO2 recovery rate of 93.43 pct and the yields of 55.37 pct. High-titanium slag can be used as a high-quality raw material to produce UGS for chlorination by leaching. [ABSTRACT FROM AUTHOR]

TiO2-FeO-Ti2O3 slag system is the dominant system for industrial high-titania slag production. In the present work, viscosities of TiO2-FeO and TiO2-FeO-Ti2O3 systems were experimentally determined using the concentric rotating cylinder method under argon atmosphere. A viscosity model suitable for the TiO2-FeO-Ti2O3 slag system was then established based on the modification of the Vogel-Fulcher-Tammann (VFT) equation. The experimental results indicate that completely melted high-titania slags exhibit very low viscosity of around 0.8 dPa s with negligible dependence on temperature and compositions. However, it increases dramatically with decreasing temperature slightly below the critical temperature. Besides, the increase in FeO content was found to remarkably lower the critical temperature, while the addition of Ti2O3 increases it. The developed model can predict the viscosities of the TiO2-FeO-Ti2O3 and TiO2-FeO systems over wide ranges of compositions and temperatures within experimental uncertainties. The average relative error for the present model calculation is < 18.82 pct, which is better than the previously developed models for silicate slags reported in the literature. An iso-viscosity distribution diagram was made for the TiO2-FeO-Ti2O3 slag system, which can serve as a roadmap for the Ilmenite smelting reduction process as well as the high titania slags tapping process. [ABSTRACT FROM AUTHOR]

A new approach is proposed to improve the strength of the vanadium titanium magnetite (VTM) sinter by adding preformed calcium ferrite (CF) to partially substitute the CaO. The effects of the sintering temperature, oxygen partial pressure (pO2), heating time, and substitution ratio of preformed CF on the mineralogy of the VTM sinter are examined through tablet sintering. The results indicate that sintering temperature significantly affects the matrix structure and pore morphology by influencing solid–liquid assimilation and bubble coalescence. With an increase in pO2, the generation of calcium ferrites and hematite is favored, and the matrix transforms into a melting corrosion structure. Heating time mainly affects the pore shape. The addition of preformed CF to VTM sintering can not only inhibit the generation of perovskite and promote the formation of calcium ferrites but also increase the quantity of melts and promote solid–liquid assimilation. [ABSTRACT FROM AUTHOR]

To elucidate the effects of FeS on the carbothermic reduction of ilmenite, a series of tests were conducted using non-isothermal thermogravimetric analysis at heating rates of 10°C/min, 15°C/min, 20°C/min, and 25°C/min. The Malek method was used to analyze the reduction mechanism and obtain a kinetic model, and the Starink method was used to calculate the apparent activation energy. The morphology of the reduction products was examined by scanning electron microscopy. A complementary series of isothermal carbothermic reductions tests was also performed in a vertical tube furnace to study the effect of FeS on the metallization of Fe and TiO2 grade in the slag phases. The results show that the carbothermic reduction of the ilmenite concentrate in the presence of FeS proceeds in four stages. FeS showed a negative effect to the carbothermic reduction of ilmenite as its addition of 2.5 wt.% increased the apparent activation energy from 486 kJ mol−1 to 565 kJ mol−1 and decreased metallization by 11.1% and TiO2 grade in the slag phases by 7.2%. [ABSTRACT FROM AUTHOR]

To increase the utilization fraction of V-Ti-Magnetite ore in the burden of the blast furnace over 80 pct, the technology of "replacing CaO with MgO" was discussed. The high content of TiO2-bearing raw materials leads to a super high TiO2 content in the blast furnace slag, which affects the normal operation of the blast furnace ironmaking process. The physicochemical properties of TiO2-bearing blast furnace slag such as viscosity are fundamentally determined by the high temperature and structure of the slag. In this study, Raman spectroscopy focusing on the effect of TiO2 and MgO/CaO ratio on the structure of super high TiO2-bearing blast furnace slag was performed. The results indicate that most of the Ti4+ ions are in the tetrahedron unit, and a few of Ti4+ ions are in the octahedron unit with a coordination number of six; this is confirmed by the presence an emission spectrum related to Ti-O stretching vibrations at wavenumbers less than 700 cm−1. The mole fraction of the band below 700 cm−1, which is related to the coupling of Al-O stretch vibration and the Ti-O stretch vibrations of Ti4+ in sixfold coordination, increased from 0.14 to 0.19 as the TiO2 content in CaO-SiO2-TiO2-MgO-Al2O3 slag increased from 20 to 34 mass pct. The (Q3)2/(Q2) ratio that is proposed as an index for the degree of polymerization (DOP) of melts decreased from 5.72 × 10−3 to 1.0 × 10−3 as the TiO2 content increased. Increasing the MgO/CaO ratio caused a slight decrease in the fraction of the bands below 700 cm−1 and resulted in the decrease of the (Q3)2/(Q2) ratio; thus, the DOP of the melts increased with increasing MgO/CaO ratio. The quantitative relationship, ln(η) = 0.91 + 0.11·ln((Q3)2/(Q2)), between the high-temperature structure information and the viscosity of TiO2-bearing blast furnace slag was established. [ABSTRACT FROM AUTHOR]

To increase the utilization fraction of vanadium titano-magnetite in the blast furnace burden to > 80 pct, a new slag zone with high MgO was found. The effect of the TiO2 content and MgO/CaO mass ratio on the viscosity and liquidus temperature of the high TiO2-bearing blast furnace slag was investigated in the present work. The results indicated that at a fixed CaO/SiO2 ratio of 1.1, the viscosity decreases with increasing TiO2 content at a range of 20 to 34 mass pct. Conversely, increasing the MgO/CaO ratio from 0.32 to 0.65 causes a slight increase in the slag viscosity. The activation energy may show a concomitant variation corresponding to the viscosity of slag. The liquidus temperature first increases and then slightly decreases with TiO2 content. However, the liquidus temperature first decreases and then increases with the MgO/CaO ratio, similar to the variation of the thermodynamic calculation using FactSage software. Various viscosity models were employed to predict the viscosity, and Yan's model was found to be the most reliable in predicting the viscosity in the present study. In addition, the iso-viscosity distribution diagram was obtained using Yan's model calculation. It may have potential for application in the blast furnace ironmaking process with super-high (> 80 pct) vanadium titano-magnetite. A suitable slag composition was found to satisfy the smelting process in a blast furnace with super-high TiO2 content at low temperature by using more MgO and less CaO content. [ABSTRACT FROM AUTHOR]

The electric conductivity of high-titania slag of TiO2-Ti2O3-FeO-CaO-SiO2-Al2O3-MgO slag system was measured by means of four-electrode alternating current (AC) impedance method. The results show that high-titania slag exhibits a good electric conductivity, around 45 to 141 S cm−1 with slight dependence on the temperature, which is of several orders of magnitude higher than that of the silicate slags. Further, electric conductivity of high-titania slag decreased with the increasing FeO content, whereas, the increasing Ti3+/Ti4+ and TiO2 contents caused a significant increase in the electric conductivity. Based on the experimental results and the calculated results, the conductive mechanism of high-titania slag was discussed in detail. It can be concluded that the high-titania slag exhibits a characteristic of electronic–ionic mixed conductivity, but the effect of electronic conduction dominates above the liquidus temperature; however, with the decreasing temperature, the electronic conductivity was gradually weakened. The mechanism was postulated to be a random walk of electrons between tetravalent titanium and trivalent titanium dispersed in the melt. [ABSTRACT FROM AUTHOR]

A novel method of smelting a mixture of two types of laterite ore (saprolitic and limonitic) to prepare ferronickel has been investigated. Thermodynamic analysis revealed that the melting temperature of the slag phase dropped below 1400°C with increasing FeO content, which can be regulated by adjusting the ratio of limonite and the carbon content. The experimental results also proved that the melting degree of the reduced pellets increased with increasing limonitic laterite ratio and that the reduction as well as magnetic separation was enhanced when the reduction was carried out in the presence of limonitic laterite ore. A ferronickel product with 8.08 wt.% Ni, 80.09 wt.% Fe, and 3.75 wt.% C was prepared by heating the mixture to 1380°C in the presence of 6 wt.% carbon content and 5 wt.% limonitic laterite ore, followed by magnetic separation. The Ni and Fe recoveries were 89.26% and 81.64 wt.%, respectively. [ABSTRACT FROM AUTHOR]

Oxygen potential of TiO2-FeO-Ti2O3 ternary slags was determined by the electromotive force (EMF) method based on the solid electrolyte oxygen sensor at 2003 K (1730 °C). The effect of FeO content and Ti3+/Ti4+ mass ratio on the oxygen potential of the high-titania slag was also studied. At a fixed Ti3+/Ti4+ mass ratio of 3.11, the oxygen potential increased with increasing FeO content. Increase of Ti3+/Ti4+ mass ratio from 2.29 to 3.60 caused a significant decrease in the oxygen potential of the slag. Comparing measured oxygen potential with the calculated values indicated that the oxygen potential of the slag might be determined by FeO/Fe equilibrium reaction rather than TiO2/Ti2O3 reaction. In addition, the experimentally measured oxygen potential values were modeled by multiple linear regression analysis, and a semi-empirical mathematical correlation was established between the oxygen potential and slag compositions. The iso-oxygen potential distribution diagram based on the mathematical model was obtained for the high-titania slag. [ABSTRACT FROM AUTHOR]

The electrical conductivity of the CaO-SiO2-Al2O3-MgO-TiO2 slag was determined using the four-electrode method. The effect of the Al2O3 and Al2O3/SiO2 mass ratio on the electrical conductivity was studied. At a fixed CaO/SiO2 ratio of 1.20, the electrical conductivity decreases with increasing Al2O3 from 16 mass pct to 24 mass pct because of the increased polymerization of aluminosilicate structures and the reduced amount of conductive ions. However, it increases with Al2O3 of more than 24 mass pct because of the difference in the stable energy between [AlO4]5− and [SiO4]4−. Increasing the Al2O3/SiO2 ratio from 0.47 to 0.79 causes the electrical conductivity to increase and has an opposite effect when the ratio is greater than 0.79. Furthermore, Raman spectroscopy of the quenched slags was analyzed to understand the structural role of Al2O3 and Al2O3/SiO2 mass ratio in the network. The Raman spectroscopy results indirectly supported the variations of electrical conductivity with the composition of the slags. [ABSTRACT FROM AUTHOR]

A structure-based viscosity model has been developed for the CaO-MgO-FeO-SiO2-Al2O3 system and its subsystems. A critical analysis of the experimental data for iron oxide aluminosilicate systems has been conducted and used in the optimization of a model, which provides a link between the viscosity and the structures of the melts. The structural characteristics of aluminosilicate melt can be described by four types of oxygen: bridging oxygen Oi0, non-bridging oxygen Oj-, free oxygen O2−, and excess bridging oxygen O*. The present model is capable of predicting the viscosities in the CaO-MgO-FeO-SiO2-Al2O3 system and its subsystems over wide ranges of composition and temperature above the liquidus within experimental uncertainties, and the average of relative errors for this model was found to be 19.94 pct. This model includes FeO-SiO2, CaO-SiO2-FeO, Al2O3-SiO2-FeO, MgO-SiO2-FeO, CaO-SiO2-MgO-FeO, CaO-SiO2-Al2O3-FeO, and CaO-MgO-SiO2-Al2O3-FeO. It was found that the effects of different metal cations on the viscosity can be determined, and the ability to reduce viscosity in the silicate melts follows the order: FeO > CaO > MgO. In the present model, the predicted viscosity decreased when CaO was initially initial added to the Al2O3-MgO-FeO-SiO2 system at a fixed SiO2 content because Ca2+ has the highest priority for charge compensation and FeO is the strongest modifier for this slag. [ABSTRACT FROM AUTHOR]

Random value impulse noise of images has many sources, such as image sensor, electronic components, etc. How to removal of noise and restore degraded image is always an interesting problem. The decision based algorithms as efficient methods to suppress noise have been extensively studied for a long time. In this type of algorithms, the first step is to classify the corrupted pixels from the surroundings, but it is not an easy thing since each image is different. The efficiency of the classification has great influence on the overall performances of the algorithms. A difference based median filter which can efficiently locate the random value impulse noise is proposed in this paper. Based on this filter, a new algorithm for removal of impulse noise in images is designed. A comparison of the performances is made among several existing algorithms in term of Image Enhancement Factor, Peak Signal-to-Noise Ratio and Structure Similarity Index. Finally, the proposed method is used for underwater image processing to suppress the random value impulse noise modified by Histogram Equalization operation. Visual and quantitative results indicate that the proposed method outperforms most of algorithms for removal of impulse noise in literatures. [ABSTRACT FROM AUTHOR]

Ultrasonic vibration was applied to the solidification process of calcium ferrite (CF) to modify the grain size and improve the homogeneity of the solidified microstructure. The effects of ultrasound on microstructure, density, compressive strength, and reducibility were studied. The acoustic pressure decreased and then increased along the axis symmetry due to the attenuation of acoustic pressure and reflection of ultrasonic waves in the melt under a fixed power. When the ultrasonic power was increased, the general acoustic pressure increased, which was beneficial to the avoidance of macropores and to improvement of the microstructure. Coarse acicular CF grains were significantly refined; the grain size decreased from 1967 to 442 μm when the ultrasonic power was increased from 0 to 300 W. The density of the samples increased from 4370 to 4680 kg/m3 due to cavitation and acoustic streaming effects. Ultrasonic vibration greatly improved the ultimate compressive strength of CF; the values were 41.8 ± 2.1 to 67.3 ± 3.4 MPa for ultrasonic powers of 100 to 300 W, respectively. Without ultrasonic treatment, it was only 37.4 ± 1.9 MPa. Ultrasonic vibration also influenced the reduction time of CF due to the composition segregation in the slag during solidification. [ABSTRACT FROM AUTHOR]

The wetting behaviors of a TiO2 substrate by calcium ferrite (CF) series slags were investigated using an improved sessile drop method at 1523 K (1250 °C). The initial contact angles were in the range 35 to 50 deg, the final equilibrium apparent contact angles were < 20 deg, and the spreading durations were in the range 75 to 180 seconds. The CF-TiO2 system showed reactive wetting, which was categorized into four dynamic stages. Stage I: physical spreading, stage II: slow linear spreading, stage III: fast linear spreading, and stage IV: equilibrium. Interfacial reactions yielded CaTiO3 during reactive spreading, thereby transitioning TiO2 wetting into CaTiO3 wetting and then forming Fe2TiO5 and FeTiO3 owing to the excess Fe2O3 and FeO that had accumulated in the interfacial zone. Although stage III spreading was faster than stage II spreading, adding MgO to the slag slowed stage III spreading. The interfacial microstructure of the residual slag was roughly divided into three layers owing to the different densities of the slag and solid products. The top layer was composed of CaTiO3 and Fe2O3, the middle one was composed of CaTiO3 and Fe2TiO5, and the bottom one was composed of Fe2TiO5 and FeTiO3. Adding TiO2 to the slag produced a dense CaTiO3-containing interfacial layer, resulting in CF being detected in the residual slag. [ABSTRACT FROM AUTHOR]

Calcium ferrite (CF) is a very important binder phase in iron ore sintering processes. To improve the microstructure of CF, power ultrasound was introduced during its solidification process, and the effect of immersion depth of ultrasonic probe (IDUP) on the properties of CF was investigated in detail. The results indicated that the microstructure of CF was greatly refined; the grain size decreased from 2864 μm without ultrasonic vibration to 841 μm with ultrasonic vibration at an immersion depth of 30 mm. Without ultrasonic vibration, the density and compressive strength of CF slag were 3904 kg/m3 and 38.3 MPa, respectively. When the IDUP was increased from 10 to 30 mm, the density and compressive strength of CF increased from 4049 to 4452 kg/m3 and 52.5 to 87.3 MPa, respectively. Further, the reducibility of CF was examined. The reduction time, at the same reduction rate, decreased from 347 minutes without ultrasonic vibration to 200 minutes with ultrasonic vibration at an IDUP of 30 mm. The rate-limiting step was obviously improved, which may be attributable to the grain refinement of CF and composition segregation in the slag. In general, the properties of CF were greatly improved due to the cavitation and acoustic streaming of ultrasonic waves. [ABSTRACT FROM AUTHOR]

The present study demonstrates the dependence of viscosity on chemical composition and temperature of high-titania slag, a very important raw material for producing titanium dioxide. The results indicated that completely molten high-titania slag exhibits a viscosity of less than 1 dPa s with negligible dependence on temperature. However, it increases dramatically with decreasing temperature slightly below the critical temperature, i.e., the solidus temperature of the slag. Above the critical temperature, the slag samples displayed the same order of viscosity at 0.6 dPa s, regardless of their compositional variation. However, the FeO, CaO, and MgO were confirmed to decrease viscosity, while SiO2 and Ti2O3 increase it. The apparent activation energy for viscosity-temperature relation and liquidus temperature based on experiments and thermodynamic calculations are also presented. Conclusively, the critical temperatures of the slags are on average 15 K below their corresponding calculated liquidus temperatures. The increase in FeO content was found to considerably lower the critical temperature, while the increase in both Ti2O3 and TiO2 contents increases it. The main phases of the slag in solid state, as indicated by X-ray diffraction, are (Fe, Mg)xTiyO5 (x + y = 3, pseudobrookite) and rutile. [ABSTRACT FROM AUTHOR]

Molybdenum hemicarbide (Mo2C) can be widely used in the fields of steel, metal ceramics, and catalyst of hydrogen-involved reactions. This work reported a new and simple method for preparing molybdenum hemicarbide by reducing and carbonizing MoO2 with methanol, and both thermodynamic and experimental studies were carried out. Based on the results, the reduction and carbonization routes are obtained: MoO2 was reduced and carburized directly to Mo2C in one step at lower temperatures, and first reduced to metallic Mo and then carburized to Mo2C at higher temperatures. The reduction mechanisms at low and high temperatures were proposed as well: The pseudomorphic transformation mechanism dominated the reaction at low temperatures, but at high temperatures, the reaction obeyed the chemical vapor transport mechanism. [ABSTRACT FROM AUTHOR]

Calcium ferrite (CF) is a significant intermediate adhesive phase in high-basicity sinters. The wettability between calcium ferrite (CF) and gangue plays an important role in the assimilation process. The wettability of CF-based slags, in which a constant amount (2 mass pct.) of Al2O3, MgO, SiO2, and TiO2 was added, on solid SiO2 (cristobalite) substrates at 1523 K (1250 °C) was investigated. The interfacial microstructure and spreading mechanisms were discussed for each sample. All the tested slag samples exhibited good wettability on the SiO2 substrate. The initial apparent contact angles were in the range of 20 to 50 deg, while the final apparent contact angles were ~ 5 deg. The wetting process could be divided into three stages on the basis of the change in diameter, namely the “linear spreading” stage, “spreading rate reduction” stage, and “wetting equilibrium” stage. It was found that the CF-SiO2 wetting system exhibits dissolutive wetting and the dissolution of SiO2 into slag influences its spreading process. The spreading rate increases with a decrease in the ratio of viscosity to interfacial tension, which is a result of the addition of Al2O3, MgO, SiO2, and TiO2. After cooling, a deep corrosion pit was formed in the substrate and a diffusion layer was generated in front of the residual slag zone; further, some SiO2 and Fe2O3 solid solutions precipitated in the slag. [ABSTRACT FROM AUTHOR]

The effects of the Al2O3 concentration and Al2O3/SiO2 ratio on the density and surface tension of molten aluminosilicate CaO-SiO2-Al2O3-9 mass pct MgO-1 mass pct TiO2 slag were investigated at temperatures from 1723 K to 1823 K (1450 °C to 1550 °C) using the Archimedean method and the maximum bubble pressure (MBP) technique, respectively. The mechanism of the changes in density and surface tension with composition was analyzed from the viewpoint of the degree of polymerization in the structure and the types of oxygen species in the melts. At a fixed CaO/SiO2 ratio of 1.20, the density decreased with increasing Al2O3 content up to 25 mass pct, subsequently increasing. Increasing the Al2O3/SiO2 ratio from 0.47 to 0.92 caused an increase in the density at a fixed CaO content, and the density decreased slightly when the Al2O3/SiO2 ratio was greater than 0.92. Based on the structural information, the density decreased when the Al2O3 content enhanced the network structure and increased when the (Q2 + Q3)/(Q0 + Q1) ratio and structural complexity decreased. The surface tension increased with increasing Al2O3 content and Al2O3/SiO2 ratio. On the one hand, the surface-active component of SiO2 decreased; on the other hand, the concentration of [AlO4]5− tetrahedra and metal cations that act as charge compensators increased at the melt surface. A model based on the anionic and cationic radii and the Butler equation was employed to predict the surface tension, and an iso-surface tension diagram was obtained at 1773 K (1500 °C). [ABSTRACT FROM AUTHOR]