Ps. I can't rely on Wikipedia for it. I really would appreciate if those materials are procurable in India.
Dear Russel Rasheed, carbon fiber Show a negative co-efficient of Expansion.
Due to special configuration of chemical bonds, some (mainly, nonorganic) compounds demonstrates abnomal (negative) values of thermal expansion coefficient α.
There are graphite of hexagonal structure and minerals (metal oxides, including complex oxides) such as SiO2 (α = -4,2*10-6 K-1), LiAlSiO4 (α = -4,0*10-6 K-1), PbTiO3 (α = -3,5*10-6 K-1), TaOVO4 (α = -4,4*10-6 K-1), Sc2W3O12 (α = -2,2*10-6 K-1), LuW3O12 (α = -6,8*10-6 K-1), ZrW2O8 (α = -8,7*10-6 K-1), as well as AlPO4 (α = -11,7*10-6 K-1).
All the best
All the above examples belong to highly oriented one or two dimensional structures where the our-of plane vibration or deformation causes a shrinking structure resulting in apparent coefficient of expansion - at least in certain directions. Otherwise, because of the non-symmetric nature of bond potential the COE is always positive.
Dear Georgy:
That's not exactly right: even some non-oriented polymers like Aromatic polyimides - (see for example my publications in Eur.Polym.Journal) have CTE around ) or even below 0 - due to straight chain structure
Best Regards, Leonid
Cubic Zirconium Tungstate (ZrW2O8). AM2O8 family of materials (where A = Zr or Hf, M = Mo or W) and ZrV2O7. A2(MO4)3 also is an example of controllable negative thermal expansion.
Ordinary ice shows NTE in its hexagonal and cubic phases at very low temperatures. In its liquid form, pure water also displays negative thermal expansivity below 3.984 °C.Rubber elasticity shows NTE at normal temperatures
As Mr. G Sankaranarayanan mentioned, H2O ice Ih does exhibit a negative coefficient of thermal expansion (NCTE) along both the a- and c-axes below about 75 K (see Rottger et al.). For a detailed review paper on NCTE materials see Negative Thermal Expansion: A Review by Miller et al. Both articles are attached. I hope these help!
Article Lattice constants and thermal expansion of H2O and D2O Ice I...
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