Colossal and reversible barocaloric effect in liquid-solid-transition materials n-alkanes

Abstract

Emerging caloric cooling technology provides a green alternative to conventional vapor-compression technology which brings about serious environmental problems. However, the reported caloric materials are much inferior to their traditional counterparts in cooling capability. Here we report the barocaloric (BC) effect associated with the liquid-solid-transition (L-S-T) in n-alkanes. A low-pressure of ~50 MPa reversibly triggers an entropy change of ~700 J kg−1 K−1, comparable to those of the commercial refrigerants in vapor-based compression systems. The Raman study and theoretical calculations reveal that applying pressure to the liquid state suppresses the twisting and random thermal motions of molecular chains, resulting in a lower configurational entropy. When the pressure is strong enough to drive the L-S-T, the configurational entropy will be fully suppressed and induce the colossal BC effect. This work could open a new avenue for exploring the colossal BC effect by evoking L-S-T materials.

Room‐Temperature Colossal Elastocaloric Effects in Three‐Dimensional Graphene Architectures: An Atomistic Study

“…Moreover, our systems exhibit a larger mechanocaloric strength than most reported mC materials over a wide range of |ΔT|, and they are only second to recently reported n-alkanes. [104] As for the isothermal entropy changes, our results lie at a middle level compared to recently reported colossal BC materials with ΔS > 300 J kg −1 K −1 such as plastic crystals [24] NPG, PG, and n-alkanes. [104] As has been reported by Varshney et al, [48] the pillared graphene architecture also features a high thermal conductivity of ≈25 W m −1 K −1 , along both the in-plane and out-of-plane directions, while previously reported mC materials possess thermal conductivity typically below ≈10 Wm −1 K −1 .…”

“…[104] As for the isothermal entropy changes, our results lie at a middle level compared to recently reported colossal BC materials with ΔS > 300 J kg −1 K −1 such as plastic crystals [24] NPG, PG, and n-alkanes. [104] As has been reported by Varshney et al, [48] the pillared graphene architecture also features a high thermal conductivity of ≈25 W m −1 K −1 , along both the in-plane and out-of-plane directions, while previously reported mC materials possess thermal conductivity typically below ≈10 Wm −1 K −1 . Ni 1−x Fe x S [105] offers a high thermal conductivity of ≈11.5 Wm −1 K −1 within the mC family, less than one-half of our value.…”

“…Moreover, our systems exhibit a larger mechanocaloric strength than most reported mC materials over a wide range of |Δ T |, and they are only second to recently reported n‐alkanes. [ 104 ] As for the isothermal entropy changes, our results lie at a middle level compared to recently reported colossal BC materials with Δ S > 300 J kg −1 K −1 such as plastic crystals [ 24 ] NPG, PG, and n‐alkanes. [ 104 ]…”

“…Figure 6 provides the values of adiabatic temperature changes, isothermal entropy changes, and mechanocaloric strength for our systems ( [5,10] and [5,12]) at room temperature, which are compared with other leading experimental mechanocaloric materials including eC [64,65,67,70,[85][86][87][88][89][90][91][92][93][94][95] and BC [7,11,17,18,[21][22][23][24]37,40,[96][97][98][99][100][101][102][103][104] materials. In practice, |ΔT| and |ΔS| associated with caloric materials are measured with direct, quasi-direct, or indirect methods.…”

On the colossal barocaloric effect in higher n-alkanes

“…At the time of review of the manuscript, Lin et al 48 published a paper also focused on the analysis of the colossal BC effect in alkanes. Despite using different alkanes in their study (only C16 and C18) and a completely different experimental and computational approach, the main conclusions are equivalent and the presented results and discussion are complementary to each other.…”