Slags are molten oxides and are present in a number of the high temperature industrial processes, for example, smelting processes used to produce metals and coal gasification processes used to produce electricity. These complex liquid oxide phases play a key role in removing unwanted elements from the several hundred million tonnes of metal produced annually as well as in removing massive amounts of coal ashes during the gasification processes. Given the scale of the industry even small improvements to operating practice result in significant economic gains. Despite the relative maturity of the metallurgical and coal industries, problems of accurately predicting the physical and chemical properties of complex slags still remain. Understanding and controlling the behaviour of the slag phase is crucial to improving the technical and economic efficiencies of these operations. Viscosity is one of the most important properties of the slags. The aim of this project is to develop a general model of the viscosities of complex molten and multi-phase slag systems based on the fundamental chemical and structural properties of the melts. These fundamental properties will be derived from chemical thermodynamic models, which have recently been developed in collaboration by the research teams of The University of Queensland and The University of Montreal. The fundamental properties derived from the thermodynamic model will then be related to the viscosity of the homogeneous liquid slag. In addition, use of new thermodynamic models in conjunction with the FactSage computer database, will enable the viscosities of multi-phase systems of importance to industrial operations to be predicted. The viscosity modelling has the potential for widespread industrial applications. Summary of the work undertaken by PhD candidate: · • critical and broad review of scientific literature on the theory of liquid viscosity, experimental results and models of the silicate structure, experimental results and models of the viscosity of fully liquid as well as partly crystallised silicate melts (chapters 1-6);• modified Urbain viscosity model for fully liquid slags in the Alz03- CaO-'FeO'-SiOz system at metallic iron saturation (chapter7);• heterogeneous viscosity model (Roscoe's equation with newly optimised coefficients in conjunction with thennodynamic computer package FactSage©) for partly crystallised slags in the Ah03-CaO-'FeO'-Si02 system at metallic iron saturation (chapter 8);• application of the Vladimirov/Jak polymeric model to the description of the slag structure in the Al2)3- CaO-‘FeO”-SiO2 system at metallic iron saturation and estimation of the average size of the structural units of viscous flow in this system (chapter 9);• quasi-chemical viscosity model for fully liquid slags in the Ah03-CaO-'FeO'-Si02 system at metallic iron saturation (chapter 10);• development of the high temperature viscosity apparatus (chapter 11); applications of the modified Urbain viscosity model to various industrial processes (coal blending, slag deposit flow) (chapter 12).