Download - Zeolites and Negative Thermal Expansion
Zeolites and Negative Thermal ExpansionRachel Pallant, Josie Paton,
Alen Akhabaev, Ross Davies
Zeolites Microporous Minerals
› Microporous – Contains pores with diameters <2nm
› Mineral – Naturally occurring substance that is a stable solid rtp
206 structures identified Base SinO2n, other molecules can be
included
Negative Thermal Expansion
•Caused by decrease in bond angles•With no/little energy bond angle is 180°•Energy provided by heat overcomes electrostatic forces of electron groups mutually repelling•Molecule bends, Si-Si distance now smaller although bonds are longer
Zeolites chosen Control – MEP Positive thermal expansion – DON Negative thermal expansion – EDI, YUG Detail - STI
MEP (1104 atoms) Already proven to have negative
thermal expansion
DON (1152 atoms) Was modelled to have positive thermal
expansion
EDI (1872 atoms) Was modelled to have negative
thermal expansion
YUG (2160 atoms) Was modelled to have negative
thermal expansion
STI (2592 atoms) Showed an unusual shift
STI Detail (1728 atoms) Using smaller temperature steps still
just showed a sudden shift Only two of the side lengths changed,
not all three
STI Structure Animation Structure of STI at 90K
Thank You!