TY - THES

T1 - Dynamic wetting phenomena of CaO-SiO2-Al2O3-Li2O slag on magnesia

AU - Ijaz, Muhammad Usama

N1 - no embargo

PY - 2024

Y1 - 2024

N2 - This thesis aims to investigate the wetting behavior of CaO-SiO2-Al2O3-Li2O slags on magnesia refractory, studying the impact of slag compositions and temperatures on the wetting behavior. The study focuses on the influence of Li2O on wetting behavior of the slag. In the initial phase, slag samples were prepared in the laboratory with varying Li2O content while keeping the basicity and alumina content fixed. The powders of the slag components were mixed using a Turbula mixer. For pre-melting of the samples, a vertical tube furnace at elevated temperatures was used. Simultaneously, substrates were prepared by cutting and polishing magnesia chromite refractory materials. The viscosities of the slags as a function of lithium oxide content and temperature were calculated using the FactSage 8.2 viscosity module. Additionally, the melting temperatures of the slag systems were determined through thermodynamic simulations of FactSage 8.2. A further comparative study between the melting temperatures obtained from thermodynamic simulations and derived from the drop profiles of the slags was carried out. To conduct in-situ measurements of contact angle, smaller slag pieces were precisely deposited on the substrate through the sessile drop method. The experiment was carried out using a Thermo-Optical Dynamic Wetting Apparatus (TODWA). A high-speed camera for the recording and analysis of drop profiles was attached. The experiments involved heating the samples to a temperature of 1350°C. The spreading of the slags was observed and recorded for analysis of melting temperature, and wetting behavior of slags at higher temperatures. Subsequently, high-speed camera images were subjected to detailed analysis using the image processing software SCA-20, to accurately measure contact angles. The increasing of lithium oxide content enhanced the wettability of the slags. Across all slag systems, a consistent wetting phenomenon was observed as characterized by higher contact angles at lower temperatures, followed by drastic spreading at higher temperatures. Also, higher Li2O content marked notable change in contact angle and slag spreading at lower temperatures. Slag A (0% Li2O) initiated spreading at 1235°C, while Slag B (2% Li2O) exhibited spreading at an even lower temperature of 1180°C. Further increases in Li2O content resulted in even earlier slag spreading, e.g. Slag F (10% Li2O) showed spreading at approximately 1100°C. Following in-situ TODWA analysis, the slag samples were prepared for subsequent microstructural and compositional analysis. Detailed analysis was carried out using scanning electron microscopy (SEM) and compositional analysis using an EDS detector. Increasing lithium oxide content enhanced the wettability of the slags. Deposition of slag A (0% Li2O) on the refractory resulted in an intermediate layer of 405 µm thickness, while the deposition of slag B (2% Li2O) resulted in a layer of just 120 µm. As lithium oxide content increased further, the thickness of the intermediate layer showed a consistent decrease. An increase in lithium oxide content also intensified slag penetration into the refractory and the dissolution of refractory components along its grain boundaries.

AB - This thesis aims to investigate the wetting behavior of CaO-SiO2-Al2O3-Li2O slags on magnesia refractory, studying the impact of slag compositions and temperatures on the wetting behavior. The study focuses on the influence of Li2O on wetting behavior of the slag. In the initial phase, slag samples were prepared in the laboratory with varying Li2O content while keeping the basicity and alumina content fixed. The powders of the slag components were mixed using a Turbula mixer. For pre-melting of the samples, a vertical tube furnace at elevated temperatures was used. Simultaneously, substrates were prepared by cutting and polishing magnesia chromite refractory materials. The viscosities of the slags as a function of lithium oxide content and temperature were calculated using the FactSage 8.2 viscosity module. Additionally, the melting temperatures of the slag systems were determined through thermodynamic simulations of FactSage 8.2. A further comparative study between the melting temperatures obtained from thermodynamic simulations and derived from the drop profiles of the slags was carried out. To conduct in-situ measurements of contact angle, smaller slag pieces were precisely deposited on the substrate through the sessile drop method. The experiment was carried out using a Thermo-Optical Dynamic Wetting Apparatus (TODWA). A high-speed camera for the recording and analysis of drop profiles was attached. The experiments involved heating the samples to a temperature of 1350°C. The spreading of the slags was observed and recorded for analysis of melting temperature, and wetting behavior of slags at higher temperatures. Subsequently, high-speed camera images were subjected to detailed analysis using the image processing software SCA-20, to accurately measure contact angles. The increasing of lithium oxide content enhanced the wettability of the slags. Across all slag systems, a consistent wetting phenomenon was observed as characterized by higher contact angles at lower temperatures, followed by drastic spreading at higher temperatures. Also, higher Li2O content marked notable change in contact angle and slag spreading at lower temperatures. Slag A (0% Li2O) initiated spreading at 1235°C, while Slag B (2% Li2O) exhibited spreading at an even lower temperature of 1180°C. Further increases in Li2O content resulted in even earlier slag spreading, e.g. Slag F (10% Li2O) showed spreading at approximately 1100°C. Following in-situ TODWA analysis, the slag samples were prepared for subsequent microstructural and compositional analysis. Detailed analysis was carried out using scanning electron microscopy (SEM) and compositional analysis using an EDS detector. Increasing lithium oxide content enhanced the wettability of the slags. Deposition of slag A (0% Li2O) on the refractory resulted in an intermediate layer of 405 µm thickness, while the deposition of slag B (2% Li2O) resulted in a layer of just 120 µm. As lithium oxide content increased further, the thickness of the intermediate layer showed a consistent decrease. An increase in lithium oxide content also intensified slag penetration into the refractory and the dissolution of refractory components along its grain boundaries.

KW - Schlacken

KW - Basizität

KW - Benetzbarkeit

KW - (BSE)Rückgestreutes Elektron

KW - (EDS)Energiedispersive Röntgenspektroskopie

KW - (FTIR)Fourier-Transformations-Infrarot

KW - (LIBs)Lithium-Ionen-Batterien

KW - (SEM)Rasterelektronenmikroskop

KW - (TODWA)Thermo-optisches dynamisches Benetzungsgerät

KW - (θ)Kontaktwinkel

KW - (θa)Fortschreitender Kontaktwinkel

KW - (θr)Zurückweichender Kontaktwinkel

KW - (ρ)Dichte

KW - (g)Erdbeschleunigung

KW - (H)Kontaktwinkel-Hysterese

KW - (pO2)Partialdruck von Sauerstoff

KW - (σ)Oberflächenfreie Energie

KW - (σsv)Oberflächenfreie Energie des Festkörpers

KW - (σlv)Oberflächenfreie Energie der Flüssigkeit

KW - (σsl)Oberflächenfreie Energie der Fest-Flüssigkeits-Grenzfläche

KW - (Wsl)Arbeit der Adhäsion

KW - Slags

KW - Basicity

KW - Wettability

KW - (BSE)Back Scattered Electron

KW - (EDS)Energy Dispersive X-ray Spectroscopy

KW - (FTIR)Fourier Transform Infrared

KW - (LIBs)Lithium-Ion Batteries

KW - (SEM)Scanning Electron Microscope

KW - (TODWA)Thermo-Optical Dynamic Wetting Apparatus

KW - (θ)Contact Angle

KW - (θa)Advancing Contact Angle

KW - (θr)Receding Contact Angle

KW - (ρ)Density

KW - (g)Gravitational acceleration

KW - (H)Contact Angle Hysteresis

KW - (pO2)Partial pressure of Oxygen

KW - (σ)Surface Free Energy

KW - (σsv)Surface Free Energy of solid

KW - (σlv)Surface Free Energy of liquid

KW - (σsl)Surface free Energy of Solid-Liquid Interface

KW - (Wsl)Work of Adhesion

M3 - Master's Thesis

ER -