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Queen Mary University of LondonQueen Mary University of London
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School of Engineering and Materials Science
Research Student Awards

PhD Thesis: Discovery of New Functional Oxides by Thick Film Combinatorial Methods

Author: ZHANG, Yong

Year: 2008

Supervisor(s): Shoufeng Yang

Thick film combinatorial libraries for searching new functional oxide materials were created using the London University Search Instrument (LUSI), a combinatorial robot based on an aspirating-dispensing printer work station. The work presented in this thesis describes the process of sample preparation, including (i) ceramic ink preparation, which involves assessment of Vibro and Dyno milling, selection of dispersant (sedimentation tests/SEM), formulation of inks (selection of solvent and binder/volume fraction). The problem of particle segregation during drying of mixture inks was prohibited by adding thixotropic agents. The shapes of dried droplet residues were studied and several methods of controlling were suggested. Also, ceramic well-plates were produced using the morphogenic effects of droplet drying. (ii) substrate preparation, which involves platinum coating (sputtering/electroless), SEM and conductivity characterisation, surface hydrophobisation of substrates and investigation on sample retention on substrates. A remounting route to produce permanent libraries was developed. (iii) Library synthesis, which involves printer calibration, establishment of printing protocol, printing trials, libraries planning and sample sintering. The problem of using carbonates and zinc during sintering were explored. (iv) library management, which requires a sample labelling system and a database for managing sample data (composition, powder, ink, firing condition, substrate etc.). The work successfully solved the major problems affecting thick film combinatorial methods and developed an integrated process for producing large batch of combinational libraries, paving way to map composition-structure- property relationships in large regions of compositional space for materials science.