Events
High Throughput Nanoceramics Synthesis and Discovery; Clean, Fast and Controllable Methods
| Date: | Wednesday 1 November 2006 16:00 - 17:00 |
| Location: | Eng 139 |
Asbtract:
Novel supercritical (sc-) fluid based routes to ceramic nanoparticles are described (using a novel continuous sc-water system). The sc-water flow system produces highly crystalline doped nano-powders in a single step that possess very high surface areas (typically >150m2g-1). Due to the effect of both pressure and temperature during syntheses, the method also enables manufacture of nano-materials that are difficult or impossible to make using more conventional techniques. The precise control of conditions in the flow system allows us to influence product characteristics (e.g. size, shape, composition). This process has been used for the manufacture of nano-bioceramics, nanoparticles for solid oxide fuel cells, battery materials, doped titanias (dielectrics and photocatalysts) and printable ceramic inks. Dr Darr will also provide brief details of the new £1.1 million three year EPSRC "High Throughput Nano-Materials Discovery" project [EPSRC reference EP/D038499/1]. This research will encompass aspects of nano-materials synthesis, automation, high-pressure engineering, and process control, reaction chemistry, parallel photocatalyst screening (hydrogen production from water), analytical science and intelligent computing.
Background on supercritical water:
In the manufacture of doped or heterometallic nano-materials, hydrothermal treatments can offer relatively low temperature (compared to sintering) and clean processing routes. Superheated water is of interest for a number of applications (e.g. destruction of toxins) as it retains some useful properties at near-critical or at supercritical conditions (critical parameters are Tc=378°C; Pc=22O Bar). The vast majority of hydrothermal syntheses tend to be conducted in batch reactions, which take up to a few days. The QMUL group have pioneered continuous hydrothermal flow systems for the manufacture of crystalline nanomaterials in suspensions. The basic process involves mixing a flow of superheated or supercritical water with a flowing aqueous solution of metal salts to give rapid precipitation and growth of well-defined nano-particles. The composition of the nano-materials is controlled by the ratio of metal salts in the feed and the presence of auxiliary pH or redox modifiers. The method can sometimes produce nano-particles with compositions that cannot readily be made using more conventional methods.
