173114-3
Wang et al.
Appl. Phys. Lett. 88, 173114 ͑2006͒
tation. According to the report of Lai et al.,17 we can obtain
the expression for the heat of fusion ⌬Hf in terms of the
diameter of nanowire D, as shown in the following equation:
The financial support from the National Natural Science
Foundation of China ͑Nos. 19974052, 50172048, 10374090,
and 10274085͒, Ministry of Science and Technology of
China ͑No. 2005CB623603͒, Hundred Talent Program of
Chinese Academy of Sciences, and Talent Foundation of An-
hui Province ͑2002Z020͒ are gratefully acknowledged.
⌬Hf = ⌬H0͑1 − 2t0/D͒2,
͑2͒
where ⌬H0 is the heat of fusion for bulk materials, and t0 is
the given critical thickness of liquid overlayer covering the
cylindrical core at the melting temperature Tm. It can be seen
from the Eq. ͑2͒ that with the increase of diameter D the
value of t0/D obviously decreases, which results in the ob-
vious increase of the heat of fusion ⌬Hf. Therefore, accord-
ing to Eq. ͑1͒, the relation between Tm͑D͒ and 1/D should be
curvilinear, and this is in agreement with the result of Fig.
3͑b͒.
Moreover, if we linearly extrapolate the melting tem-
perature from the small diameter to the bulk Zn, it is about
414.3 °C ͓as line b shown in Fig. 3͑b͔͒ lower than the ex-
perimental value of 419.58 °C.24 There are two reports that
give similar results. The first one is the MD simulation in the
heating process of titanium nanowires by Wang et al.10 The
extrapolated bulk melting temperature of 1542 K is also re-
markably lower than the experimental value of 1943 K for
bulk titanium. The second one is also the MD simulation on
the Ni nanowires by Wen et al.25 All these studies have got-
ten significantly lower melting temperature of the bulk when
linearly extrapolating from the nanowires studies. However,
if we extrapolate the curve from the large diameter to the
bulk Zn, we will find that the melting point is near the ex-
periment value for the bulk ͓as curve a shown in Fig. 3͑b͔͒,
which means that the ⌬Hf change with the diameters should
be considered.
In summary, we have prepared Zn nanowire arrays using
a direct current electrodeposition in the holes of PAAM tem-
plates with different diameters. Using the differential scan-
ning calorimetry, the melting behavior of Zn nanowires has
been investigated. The melting temperature of Zn nanowires
has been found depending on the sizes of nanowires and
being curvilinear with the reciprocal of the diameter of the
nanowires due to the heat of fusion change with the change
of the diameter. Therefore, after understanding the nature and
the trend of the melting point change, it is possible to tune
the melting point of nanomaterials by simply controlling the
size of nanomaterials.
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