Research 

 

Our lab is part of the Clean Technologies Research Institute (CTRI) at Dalhousie University. For more details about CTRI, see here.

 

Overall Aims of Our Research Program

  • to use a chemical approach to understand the underlying physical principles relating structure to properties of materials;

  • to contribute to the advancement of understanding of thermal properties of materials;

  • to contribute to basic understanding of materials, with an eye to applications such as phase change materials for energy storage and thermal regulation, thermoelectrics, materials with zero thermal expansion for reduced thermal stress, and thermochromic materials for thermally erasable toner. 

 

Selected Current/Recent Research

Our publications are listed here.

 

Phase Change Materials:

Thermal Energy Storage and Temperature Regulation

  • Transitions of phase-change materials (PCMs) can be used for heat storage;
  • PCMs store more energy stored per unit volume or unit mass than materials that store thermal energy just by heat capacity (sensible heat);
  • Our goals are to develop materials that store energy very efficiently, with regard to robust properties after thermal cycling, and form-stable PCMs with enhanced thermal conductivity. 
Dodecanoic acid as a promising phase-change material for thermal energy storage. L. Desgrosseilliers, C. A. Whitman, D. Groulx  and M. A. White, Appl. Thermal Eng. (2013).
Characterization of Thermal Performance of a Solid-Solid Phase Change Material, Di-n-Hexylammonium Bromide, for Potential Integration in Building Materials. C. A. Whitman, M.B. Johnson and M.A. White. Thermochimica Acta 531, 54-59 (2012).

See also: Edible Oils as Practical Phase Change Materials for Thermal Energy Storage. S. Kahwaji and M. A. White. Appl. Sci.  19, 1627:1-17 (2019).  Open Access

 

Heat Transport in Nanostructured Materials

  • Properties of materials change as they get very small;

  • Heat conduction is changed by interfaces and boundaries separated by less than the phonon mean free path;

  • Thermal conductivity is reduced so Fourier’s Law no longer applies;

  • Nanostructuring is a potentially useful mechanism to reduce thermal conductivity;

  • Our goal is to understand the thermal conductivity of materials with micro- to nanoscale level structure, including carbon nanotube materials, carbon nanotube/polymer composites and complex, natural and synthetic nanostructures, such as ivory, nacre and synthetic nacre.

Elephant Ivory: a Low Thermal Conductivity, High Strength Nanocomposite. M.B. Jakubinek, C. Samarasekera and M.A. White, Journal of Materials Research, 21, 287-292 (2006).

 		  
 
 

Relationship Between Thermal Conductivity and Structure of Nacre from Haliotis fulgens. L. P. Tremblay, M.B. Johnson, U. Werner-Zwanziger and M.A. White, Journal of Materials Research26, 1216-1224 (2011).

 

Thermal conductivity of tunable lamellar Al2O3/PMMA hybrid composites. R. Chen, M.B. Johnson, K.P. Plucknett and M.A. White. J. Mater. Res. 27, 1869-1876 (2012).

 		  
  Physical properties of sheet drawn from arrays of multiwalled carbon nanotubes. J.-H. Pöhls, M.B. Johnson, M.A. White, R. Malik, B. Ruff, C. Jayasinghe, M.J. Schulz and V. Shanov. Carbon 50, 4175-4183 (2012).  See also Jakubinek et al., Carbon 50, 244-248 (2012), and Carbon 48, 3947-3952 (2010).    
 

Controlled Thermal Expansion

  • Most materials expand when heated, but some, such as ZrW2O8, contract when heated!
  • Controlled thermal expansion can reduce the thermal stress experienced by a material when it is exposed to a large temperature gradient;
  • Our goals are to develop materials with low overall thermal expansion, by preparation of solid solutions of positive and negative thermal expansion materials, and by manipulating mechanical properties to make composites with reduced thermal stress;
  • We also investigate the role of structure on thermal conductivity of framework materials with low positive (or negative) thermal expansion.
 

The Effect of Microstructure on Thermal Expansion Coefficients in Powder-Processed Al2Mo3O12. L. P. Prisco, C.P. Romao, F. Rizzo, M.A. White and B. A. Marinkovic, J. Mater. Sci. (2013).

 

Near-Zero Thermal Expansion in In(HfMg)0.5Mo3O12. K.J. Miller, C. P. Romao, M. Bieringer, B. A. Marinkovic, L.Prisco and M. A. White, J. Amer. Ceram. Soc. (2013).

 

Negative Thermal Expansion Materials: Thermal Properties and Implications for Composite Materials. M. B. Jakubinek, C. A. Whitman and M. A. White, Journal of Thermal Analysis and Calorimetry 99(1), 165-172 (2010).

Thermoelectric Materials

  • Thermoelectrics convert waste energy to power, but are not yet highly efficient;
  • Efficiency can be increased by lowering thermal conductivity;
  • Our goal is to understand mechanisms to reduce thermal conductivity, such as scattering of heat-carrying acoustic phonons by guests rattling in cage structures.

X-ray Absorption Studies of Local Structure and Electronic Properties of NaxSi136 (0<x<24) Clathrates. A.D. Ritchie, M.A. MacDonald, P. Zhang, M.A. White, M. Beekman, J. Gryko and G. Nolas, Phys.Rev.B, 82, 155207:1-9 (2010).
Thermal and lattice dynamical properties of Na8Si46 clathrate. L. Qiu, M.A.White, Z. Li, J.S. Tse, C.I. Ratcliffe, C.A. Tulk, J. Dong and O.F. Sankey, Phys. Rev. B 64, 24303:1-6 (2001).

Thermochromic Materials

  • Materials that change colour with temperature are thermochromic;
  • We concentrate on three-component organic systems in which one component melts, and other two undergo interactions that change the colour;
  • Our aim is to understand the role of packing interactions between components, and how this affects colour density and staying power.

New Insights Concerning the Mechanism of Reversible Thermochromic Mixtures. H. Tang, D. C. MacLaren and M.A. White, Can. J. Chem.88, 1063-1070 (2010).

 

 

Current or Recent Research Collaborations

D. L. Bryce, University of Ottawa: NMR Crystallography;

U. Werner-Zwanziger, Dalhousie University: NMR Studies of Materials;

A. Windle, University of Cambridge: Carbon Nanotube Materials;

J. Zwanziger, Dalhousie University: Negative Thermal Expansion Materials;

M. Bieringer, University of Manitoba: Thermal Expansion; 

D. Groulx, Dalhousie, Mechanical Engineering: Heat Storage Materials;

J. Majzlan, Friedrich‑Schiller University, Germany: Mineral Thermodynamics;

B. Marinkovic, Pont.Univ.Católica do Rio de Janeiro, Brazil: Negative Thermal Expansion Materials;

G. Nolas, University of South Florida, USA: Thermoelectric Materials;

B. Simard, Steacie Institute for Molecular Sciences, NRC, Ottawa: Carbon Nanotube Composites;

V. Shanov, University of Cincinnati, USA: Carbon Nanotube Materials;

A. Wilkinson, Georgia Tech, USA: Negative Thermal Expansion Materials