Superhydrophobic Zr-based metallic glass surface with
high adhesive force
Ning Li,1,a) Ting Xia,1 Liping Heng,2 and Lin Liu1,a)
1
School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074,
People’s Republic of China
Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People’s
2
Republic of China
Supplementary Material for surface energy difference between two BMGs
To reveal the possible mechanism that responsible for the different water contact angles
between the Zr- and the Pd-based MG, the essential CAs of the two MGs’ surface (polished to
mirror surface with roughness about 9 nm, as described in figure 5a) are measured by
deionized water. Figure 5 (b) presents a hydrophobic Pd-based MG surface with CA of about
98.8±0.8°, while the Zr-based MG surface with a relatively small CA of about 82.5±0.9°, as
described in figure 5 (c), shows a hydrophilicity. To further analyze this difference, CAs are
measured by methylene iodide and the surface free energies (SFEs) of the two MGs are
calculated according to the following eqution:31, 32
1/ 2
1  c os  2sd   ld

1/ 2
/l 

 2  
p
s
1/ 2 p
l
/l

1/ 2
(3)
where  is the contact angle,  l is the SFE of the liquid used in the measurements, the
superscripts d and p refer to the dispersion force and hydrogen bonding (one of polar
terms) components,  s is the SFE of the solid MG sample, which can be calculated as:
a)
Authors to whom correspondence should be addressed. Electronic address: hslining@mail.hust.edu.cn (Ning Li)
and lliu2000@mail.hust.edu.cn (Lin Liu).
1
 s   sd   sp
(4)
The properties of the both deionized water and methylene iodide can be obtained from Ref.
31. According to equation (3), surface free energies of both MGs are calculated and the results
are listed in Table II. The dispersion forces (  sd ) of two MGs are almost identical, while the
polar term (corresponding to hydrogen bonding,  sp ) of the Zr-based MG (3.5±0.4) is much
larger that of the Pd-based MG (0.19±0.07), indicating that there is a more tendency of the
Zr-based MG surface to interact with surrounding small molecules33, what is the main reason
for the hydrophilic Zr-based MG surface with a higher surface free energy by comparing with
the Pd-based MG surface.
(a)
Pd40Cu30Ni10P20
Zr35Ti30Be26.75Cu8.25
98.8±0.8°
(b)
82.5±0.9°
(c)
FIG. 5. The 3D profile of the smooth BMG surface (a); the essential contact angles on
the Pd- (b) and the Zr-based (c) MG surfaces.
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Table II Surface free energy (SFE) of both Zr- and Pd-based MGs.
Contact angle (º)
Surface free energy (mJ/m2)
Deionized
water
Methylene
iodide
 sd
 sp
s
Pd40Cu30Ni10P20
98.8±0.8
54.5±0.9
34.6±0.3
0.19±0.07
34.7±0.4
Zr35Ti30Be26.75Cu8.25
82.5±0.9
44.3±0.5
34.0±0.5
3.5±0.4
37.5±0.3
 sd , Dispersion force component of the surface free energy.
 sp , Hydrogen bonding (one of polar terms) component of the surface free energy.
 s , Surface free energy of the solid MG.
3