Science | Chiu Tang

Prof Chiu Tang
High Resolution Powder Diffraction

Chiu Tang Chiu Tang is the Principal Beamline Scientist for BL-I11, the High Resolution Powder Diffraction Beamline. He has specific experience in synchrotron instrumentation and the development of sample environments. His main research activities are the structural and mechanical properties of materials using synchrotron powder diffraction and laboratory techniques, including the studies of structural changes in applied materials and minerals at non-ambient conditions.

Email: Chiu Tang
Tel: +44 (0) 1235 778407
Beamline I11: High Resolution Powder Diffraction

Key Research Areas

Structural properties of materials, Structure determination, Phase identification, Microstructures of materials, Structural transitions/transformations

Current Research Interests

One of my research interests is in the calcium carbonate which is common substance found in rocks (limestone, chalk, marble, etc), shells of marine organisms, corals and snails. CaCO3 exists in several polymorphic forms: the anhydrous calcite, aragonite and vaterite and hydrated phases ikaite and monohydrocalcite. To study these carbonates are fundamental to understanding cycling of CO2 in the Earth over geologic time. For example, the formation of monoclinic CaCO3.6H2O (ikaite) at low temperatures (≤ 273K) has prompted the use of this phase as a palaeo-indicator of global climate change. Upon warming of ikaite (280-340 K), calcium carbonate pseudo-morphs (glendonites, vaterite) are formed. These mineral formations are widespread in the geologic record, and indicate either periods of glaciation or polar latitude. Establishing the physical chemistry of CaCO3.6H2O decomposition is important for understanding the CaCO3 - H2O system, and for predicting the effects of climate change on these phases.

Chiu Tang diagram

SEM pictures: dehydrated ikaite crystallites (main feature) and vaterite crystalline domains (inset)

Recently, my research team have grown crystals of CaCO3 polymorphs. Some of these were used to study the thermal transformation of aragonite to calcite using Raman spectroscopy, high temperature synchrotron powder diffraction and scanning electron microscopy (SEM). The results were compared with those obtained from biogenic aragonite (mussel nacre). Anomalous thermal behaviour in the form of plateau regions in the lattice parameter expansion of both the progenitor aragonite and transformed calcite phases was observed.

 

Lattice cell volume expansion per formula unit of aragonite and calcite as a function of temperature

Selected Publications

  1. “The ikaite-to-vaterite transformation: new evidence from diffraction and imaging” C.C. Tang, S.P. Thompson, J.E. Parker, A.R. Lennie, F. Azough & K. Kato, J. Applied Cryst. (2009), 42, 225-233.
  2. “A study of the aragonite-calcite transformation using Raman spectroscopy, synchrotron powder diffraction and scanning electron microscopy” J.E. Parker, S.P. Thompson, A.R. Lennie, J. Potter & C.C. Tang Cryst, Eng. Comm. (2010), 12, 1590–1599.
  3. “High-throughput powder diffraction on beamline I11 at Diamond” J.E. Parker, S.P. Thompson, T.M. Cobb, F. Yuan, J. Potter, A.R. Lennie, S. Alexander, C.J. Tighe, J.A. Darr, J.C. Cockcroft & C.C. Tang J. Applied Cryst. (2011), 44, 102-110.
  4. “Fast X-ray powder diffraction on I11 at Diamond” S.P. Thompson, J.E. Parker, J. Marchal, J. Potter, A. Birt, F. Yuan, R.D. Fearn, A.R. Lennie, S.R. Street & C.C. Tang J. Synchrotron Rad. (2011) – in press