There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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Dynamics and Modelling of Ocean Waves

In several series of lithium, sodium, and potassium borosilicate glasses whose compositions traverse known regions of liquid–liquid phase separation, we have applied triple-quantum magic-angle spinning (3QMAS) 11B and 17O NMR to obtain high-resolution information about short-range structure and connections among various network structural units, and their variation with composition and thermal history. Oxygen-17 3QMAS spectra reveal changes in connectivities between silicate and BO3 ([3]B) and BO4 ([4]B) units, by quantifying populations of bridging oxygens such as B–O–B, Si–O–B and Si–O–Si, and of non-bridging oxygens. [3]B–O–Si and [4]B–O–Si as well as [3]B–O–[3]B and [4]B–O–[3]B linkages can be distinguished. 11B MAS and 3QMAS at a magnetic field of 14.1 T allow proportions of several borate units to be determined, including [3]B in boroxol ring and non-ring sites and [4]B with 3 versus 4 Si neighbors. By combining the 11B and 17O NMR results, detailed information on Si/B mixing in sodium borosilicates can be derived, showing, for example, that [4]B and non-ring [3]B tend to mix with silicate units, while ring [3]B is mainly connected to borate groups. In a preliminary study of the effects of varying alkali cation, potassium-containing glasses are similar to those in the sodium borosilicate system, but a lithium borosilicate seems to exhibit considerably greater chemical heterogeneity. In annealing experiments that converted an optically clear to obviously phase-separated glasses, the ratio of [3]B to [4]B does not change significantly, but part of the non-ring [3]B converts to ring [3]B as the degree of unmixing increases.

Solid-State NMR Study of Metastable Immiscibility in Alkali Borosilicate Glasses

TiO2 additions up to 10 mass% behaved as a basic oxide and lowered the viscosity in the CaO–SiO2–17 mass% Al2O3–10 mass% MgO-based slags by depolymerizing the silicate network structure. Raman spectroscopy revealed the sum of NBO/Si 1 and 3 decreased while the sum of NBO/Si 2 and 4 increased with TiO2 content. Unlike the silicate structures, the aluminate structures seems to be relatively unaffected by TiO2 additions according to the FTIR results. 5 mass% TiO2 significantly decreased the viscosity compared to the TiO2 free slags, but beyond 5 mass% TiO2 meaningful changes in the viscosity was not observed. From the comparison of the viscosity at constant TiO2 of 5 and 10 mass% and varying CaO/SiO2 ratio, increasing the CaO/SiO2 ratio was more effective in decreasing the viscosity than TiO2 additions.

Effect of TiO2 on the Viscosity and Slag Structure in Blast Furnace Type Slags

This review focuses on elucidating the viscosity of ironmaking slags and the effect of various components in the multi-component calcium-silicate-based slag system on the viscosity. Using various widely used spectroscopic techniques including Fourier transform infrared (FTIR), Raman, X-ray photoelectron spectroscopy (XPS), and nuclear magnetic resonance (NMR), the viscous behavior and the slag structure of this system were correlated. In particular, the review begins with an introduction to the viscous behavior of binary silicate systems and an identification of the intricate details of the slag structure. Using the binary system as a basis, the compounded effect of typical ironmaking slag components such as Al2O3, MgO, alkali oxides, and TiO2 on the viscosity is introduced through expansion to a quinary slag system. Using a combination of the aforementioned spectroscopic methods, the meticulous details of the slag structure were ascertained, and the depolymerization or polymerization mechanisms of the silicate and alumino-silicate structures were subsequently identified. This review also compares well-known viscosity prediction models with experimentally measured values and identifies potential fields of research in the ironmaking industry associated with slag viscosities.

A Review of the Relationship between Viscosity and the Structure of Calcium‐Silicate‐Based Slags in Ironmaking

The effect of Al2O3 and CaO/SiO2 on the viscosity of the CaO-SiO2-10 mass pct MgO-Al2O3 slags was studied at fully liquid temperatures of 1773 K (1500 °C) and below. At fixed CaO/SiO2 between 0.8 and 1.3, higher Al2O3 content increased the slag viscosity due to the polymerization of the aluminate structures. At fixed Al2O3 of 15 and 20 mass pct, increasing the CaO/SiO2 from 0.8 to 1.3 resulted in lower viscosity due to the depolymerization of the aluminate structure.

Effect of Al2O3 and CaO/SiO2 on the Viscosity of Calcium-Silicate–Based Slags Containing 10 Mass Pct MgO

The effect of basicity on the mold fluxes crystallization was investigated in this article. The time-temperature-transformation (TTT) diagrams and continuous-cooling-transformation (CCT) diagrams of mold fluxes with different basicity were constructed by using single, hot thermocouple technology (SHTT). The results showed that with the increase of basicity, the incubation time of isothermal crystallization became shorter, the crystallization temperature was getting higher, and the critical cooling rate of continuous cooling crystallization became faster. The X-ray diffraction analysis suggested that calcium silicate (CaO·SiO2) was precipitated at the upper part of the TTT diagram and cuspidine (Ca4Si2O7F2) was formed at the lower part, when the basicity of mold fluxes was within 1.0 to 1.2. However, when basicity was 0.8, only the cuspidine phase was formed. A kinetic study of isothermal crystallization process indicated that the increase of the basicity tended to enhance the mold flux crystallization, and the crystallization activation energy became smaller. The crystallization mechanism of cupsidine was changing from one-dimensional growth to three-dimensional growth with a constant number of nuclei, when the basicity of mold fluxes varied from 0.8 to 1.2.

A Kinetic Study of the Effect of Basicity on the Mold Fluxes Crystallization

Iron ores consisting of significant TiO2 such as ilmenite are low cost ores, but due to the high TiO2 content its use may result in significant issues within the blast furnaces such as lower reduction degree,1–4) changes in the liquidus temperature in slag,5–7) lower residual removal by the slag,8–10) and viscosity changes within the bosch and hearth.11–15) However, potential benefits of TiO2 in the blast furnace slags have also been known by forming a protective layer of titanium carbo-nitride on the refractory brick and inhibiting the premature failure and erosion of the hearth.9,15–18) Ohno and Ross13) found TiO2 additions increase the slag viscosity in the CaO–SiO2–Al2O3–TiO2 slags under reducing atmospheres of C/CO equilibrium. Shankar et al.19) revealed the effect of TiO2 in the CaO–SiO2–MgO–Al2O3 slag system, where the viscosity decreased with TiO2 up to 2 mass%. Saito et al.14) found TiO2 lowered the viscosity in the CaO–SiO2–MgO–Al2O3 slag system at 10 mass% and 20 mass% TiO2. However, the viscosity data between 0 to 10 mass% TiO2 is still ill-defined. In this study, the influence of TiO2 from 0 to 10 mass% on the viscous behavior of CaO–SiO2–17 mass%Al2O3–10 mass%MgO slags have been investigated and correlated to the slag structure using XPS (X-Ray Photoelectron Spectroscopy).

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Influence of TiO2 on the Viscous Behavior of Calcium Silicate Melts Containing 17 mass% Al2O3 and 10 mass% MgO

With the development of advanced high strength steel (AHSS), a large amount of aluminum was added into steels. The reaction between aluminum in the molten steel and silica based mold flux in the continuous-casting process would tend to cause a series of problems and influence the quality of slabs. To solve the above problems caused by the slag–steel reaction, nonreactive lime-alumina-based mold flux system has been proposed. In this article, the effect of Li2O and Na2O on the crystallization behavior of the lime-alumina-silica-based mold flux has been studied by using the single hot thermocouple technology (SHTT) and double hot thermocouple technology (DHTT). The results indicated that Li2O and Na2O in the above mold flux system play different roles as they behaved in traditional lime-silica based mold flux, which would tend to inhibit general mold flux crystallization by lowering the initial crystallization temperature and increasing incubation time, especially in the high-temperature region. However, when their content exceeds a critical value, the crystallization process of mold fluxes in low temperature zone would be greatly accelerated by the new phase formation of LiAlO2 and Na
 x
 Al
 y
 Si
 z
 O4 crystals, respectively. The crystalline phases precipitated in all samples during the experiments are discussed in the article.

Effects of Li 2 O and Na 2 O on the Crystallization Behavior of Lime-Alumina-Based Mold Flux for Casting High-Al Steels

The effect of BaO and MgO content on the viscosity and structure of the CaO-Al2O3 based mold flux system has been studied in this article. The viscosity results suggested that the addition of BaO tends to increase the viscosity of flux system, due to the polymerization of the melts network structure that leads to the increase of the apparent activation energy for viscous flow. However, the addition of MgO tends to decrease the viscosity of the slag melt, in which the free O2– ions depolymerize the network structure leading to the reduction of melt flow resistance and apparent activation energy. The results of FTIR (Fourier transform infrared) and Raman for the molten structures showed that the released O2– ions by BaO and MgO, working as network breaker, can break Si O bonds for the [SiO4]4 −-tetrahedral structure units; leading to the reduction of the symmetric Q1([Si2O7]6 −) stretching vibrations and the increase of symmetric Q0([SiO4]4 −) stretching vibrations. While for [AlO4]5 −-tetrahedral structure units, they would be connected and the aluminate-silicate network structure become more complicated due to the strong charge compensation effect that BaO introduced. However, the major role that MgO played is to release O2– ions to depolymerize the complex network structure, due to its weak charge compensation effect.

Wanlin Wang

Papers

Effect of Al2O3 and CaO/SiO2 on the Viscosity of Calcium-Silicate–Based Slags Containing 10 Mass Pct MgO

A Kinetic Study of the Effect of Basicity on the Mold Fluxes Crystallization

Influence of TiO2 on the Viscous Behavior of Calcium Silicate Melts Containing 17 mass% Al2O3 and 10 mass% MgO

Effects of Li 2 O and Na 2 O on the Crystallization Behavior of Lime-Alumina-Based Mold Flux for Casting High-Al Steels

Effect of alkaline earth metal oxides on the viscosity and structure of the CaO-Al2O3 based mold flux for casting high-al steels