Barocaloric material
From Wikipedia, the free encyclopedia
Barocaloric materials are characterized by strong, reversible thermic responses to changes in pressure. Many involve solid-to-solid phase changes from disordered to ordered and rigid under increased pressure, releasing heat. Barocaloric solids undergo solid-to-solid phase change.[1] One barocaloric material processes heat without a phase change: natural rubber.[2]
Barocaloric effects can be achieved at pressures above 200 MPa for intermetallics or about 100 MPa in plastic crystals. However, NH4I changes phase at pressures of 80 MPa.[3] The hybrid organic–inorganic layered perovskite (CH3–(CH2)n−1–NH3)2MnCl4 (n = 9,10), shows reversible barocaloric entropy change of ΔSr ~ 218, 230 J kg−1 K−1 at 0.08 GPa at 294-311.5 K (transition temperature).[4]
Barocaloric materials are one of several classes of materials that undergo caloric phase transitions. The others are magnetocaloric, electrocaloric, and elastocaloric. Magnetocaloric effects typically require field strengths larger than 2 T, while electrocaloric materials require field strengths in the kV to MV/m range. Elastocaloric materials may require force levels as large as 700 MPa.
