Environmental Engineering Reference
In-Depth Information
memory) materials were performed in 1980s, mostly on Cu-based and Ni
Ti alloys
-
[ 100
103 ]. They measured up to 12 K of adiabatic temperature changes for the
-
Ni
Ni alloy
[ 101 ]. However, their research was not focused on the application of these materials
in a cooling or heat pumping device, but rather on an analysis of different loading
conditions and the origin of these thermal effects. The
Ti alloy [ 102 ] and Cu
Zn
Sn [ 100 ] and up to 15 K for the Cu
Al
-
-
-
-
-
rst EsCE proposed for
cooling applications was published in 1992 by Nikitin et al. [ 104 ] in a polycrys-
talline Fe 49 Rh 51 alloy. They measured a negative adiabatic temperature change of
5.2 K under
the stress removal and indirectly estimated 8.7 K using the
Clausius
Clapeyron relation.
Between 2008 and 2014, the group at the University of Barcelona published
three papers on the EsCE of single-crystalline Cu 68 Zn 16 Al 16 , where they measured
a negative adiabatic temperature change of about 6 K in the temperature range
between 200 and 350 K [ 105 ], estimated it to 15 K using the Clausius
-
Clapeyron
relation [ 106 ], as well as analysing the homogeneity of the EsCE distribution along
the sample [ 107 ]. In 2012, Cui et al. [ 108 ] presented the EsCE on polycrystalline
Ni
-
Ti wires. They measured a positive adiabatic temperature change of 25.5 K
during the mechanical loading and a negative one of 17 K during the unloading.
Furthermore, Ossmar et al. [ 109 ] measured 16 K of negative adiabatic temperature
change under stress removal (unloading) on Ni 50.4 Ti 49.6 thin
-
lms. Bechtold et al.
[ 110 ] analysed the EsCE and the functional stability of the Ti 54.9 Ni 32.5 Cu 12.6 thin
lm and compared it with the Ni 50.4 Ti 49.6 alloy. It was shown that adding Cu to the
Ni
Ti alloy strongly increases the stability of the superelastic behaviour with no
training effect during the initial cycles, but it also reduces the EsCE (negative
adiabatic change of 6 K).
It should be noted that all the above-presented elastocaloric materials exhibit the
-
rst-order phase transition, which is related to the hysteresis behaviour and irrev-
ersibilities (the difference between the positive adiabatic temperature change and
the negative one). However, Xiao et al. [ 111 ] showed the EsCE of the single-
crystalline Fe 68.8 Pd 31.2 with the second-order, continuous structural phase transition
and near-zero hysteresis. They measured an adiabatic temperature change of about
2.5 K, but a near-zero hysteresis can be its great advantage. Furthermore, Guyomar
et al. [ 112 ] analysed the EsCE of the shape-memory polymer natural rubber and
measured an adiabatic temperature change of 10 K. The details about some of the
most interesting elastocaloric materials and the related EsCE are collected in
Table 10.13 . It should be noted that in recent years a lot of work was performed on
the thermal effects associated with the superelastic (elastocaloric) behaviour, where
they mostly studied the impact of the strain rate on the temperature changes of the
material; however, in most cases on the virgin samples (with not fully repeatable
behaviour) as well as not adiabatically (with lower strain-rates), e.g., [ 113 , 114 ].
Therefore, these studies as well as the earlier similar studies [ 100
-
103 ] are not
presented in Table 10.13 .
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