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Durable superhydrophobic wool fabrics coating with nanoscale Al2O3 layer by atomic layer deposition
Applied Surface Science 349 (2015) 876–879
Contents lists available at ScienceDirect
Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc
Short Communication Durable superhydrophobic wool fabrics coating with nanoscale Al2 O3 layer by atomic layer deposition
a r t i c l e
i n f o
Keywords: Atomic layer deposition Aluminum oxide Wool fabrics Superhydrophobic
a b s t r a c t To obtain superhydrophobic surface, aluminum oxide was deposited onto wool fabrics using atomic layer deposition (ALD) by exposing them to alternating pulses of trimethylaluminum and water at 80 ◦ C. Scanning electron microscope (SEM) and X-ray fluorescence (XRF) analysis showed that Al2 O3 layer and uniform Al2 O3 nanoparticle were formed around the surface of ALD coated wool fiber, which showed higher surface roughness than control wool fiber. The static water contact angles of ALD coated wool fabrics increased from 130◦ to around 160◦ , and had a higher durability than that of control wool fabric. The dynamic water contact angles of all samples were also tested. Furthermore, the common household liquids also existed as ball-like droplet on the ALD coated wool fabrics and as stain spot on the control wool fabrics after exposure for 1800 s. © 2015 Elsevier B.V. All rights reserved.
1. Introduction Wool fiber has been widely used for a long time in human history, as it has many advantages, such as good elasticity, softy, and warmth. However, wool products are easy to touch ash and fragile, which makes wool products are not easy to clean. The superhydrophobic surfaces with a static water contact angle lager than 150◦ have attracted abundant investigative efforts because of the selfcleaning and anti-snow sticking properties, which would increase the potential application value of materials. At present, a variety of techniques have been rapidly proposed for superhydrophobic materials. Shi et al. combine a layer-by-layer assembling technique with electrochemical deposition to prepare superhydrophobic coatings on gold threads [1]. Öner et al. fabricate ultrahydrophobic silicon surfaces by photolithography and hydrophobized using silanization reagents [2]. Manca et al. fabricate superhydrophobic and simultaneously antireflective surfaces by a double-layer coating comprising trimethylsiloxane (TMS) surface functionalized silica nanoparticles through a sol–gel process [3]. Yunying Wu et al. prepare transparent and ultra water-repellent thin films by microwave plasma chemical vapor deposition using as a raw material. In addition, polypropylene, Al2 O3 , SiO2 and their hybrids have been used to prepare superhydrophobic surfaces [4–8]. However, in many cases, the reported approaches are not appropriate for the natural fibers especially for protein fibers, as the treatment temperature was too high for protein fiber that it could cause a considerable thermal degradation resulting into the yellowing, fragile and non-bonded superhydrophobic layer of protein fibers. An alternative approach is to utilize the chemical reaction on the protein fabrics to form a uniform superhydrophobic layer at a relative low temperature. Hyde et al. increase the water contact angle from 0◦ to 127◦ using atomic layer deposition (ALD) of Al2 O3 on cotton at 100 ◦ C [9]. In view of the different structure http://dx.doi.org/10.1016/j.apsusc.2015.05.061 0169-4332/© 2015 Elsevier B.V. All rights reserved.
and chemical groups between cotton and wool fiber, the cotton is hydrophilic and the wool is hydrophobic, thus we considered using the atomic layer deposition transformed the hydrophobic surface of wool fiber to superhydrophobic. To the best of our knowledge, few studies report the superhydrophobic wool fabric obtained by using ALD technology. Most ALD processes contain two time-separated half-reactions. As the precursor and co-reactant species transported into reactor separately, two surface reactions occur and each of the surface reaction is self-limiting, then the two reactions proceed sequential, eventually deposit an atomic level control film [10]. The binary reaction for Al2 O3 ALD [11] is 2Al(CH3 )3 + 3H2 O → Al2 O3 + 3CH4 H = −376 kcal Because the formation of a strong Al O bond during Al2 O3 ALD, the surface reactions are very efficient and self-limiting, so that the Al2 O3 ALD can be deposited at relative low temperature available for wool fabrics. In this study, we deposited Al2 O3 onto wool fabrics by ALD at 80 ◦ C to offer a durably superhydrophobic wool fabric. The morphologies, chemical elements and superhydrophobic properties of samples were characterized.
2. Experimental 2.1. Materials Wool fabrics (twill-weave, 200 g/m2 ) were obtained from Yangzhou Jindi Wool Textile Co., Ltd. (Jiangsu, China). Trimethylaluminum (TMA) was purchased from Strem Chemicals, Inc. Deionized water (I degree, specific resistance is 10–16 M cm at 25 ◦ C) was produce by Molgeneral (Molecular, USA).
Short Communication / Applied Surface Science 349 (2015) 876–879
877
Fig. 1. The schematic process of Al2 O3 ALD on wool fibers.
2.2. Atomic layer deposition (ALD) process ALD of Al2 O3 was performed onto wool fabrics and silicon wafer, which was acted as a reference whether the ALD reactions happen on the surface through the color change. ALD experiment was carried out in a hot-wall closed chamber-type ALD reactor (Savannah system, Cambridge Nanotech. Inc., USA). The deposition of Al2 O3 used trimethylaluminum (TMA) and deionized water as the aluminum and oxygen source, respectively. Considering the high temperature has a significant damage on wool fiber, the ALD deposition temperature was set at 80 ◦ C. Prior to ALD processing, wool fabrics were placed in the ALD reactor and heated in vacuum (7.9E−1 Torr) to 80 ◦ C, kept at this temperature for 5 min. The temperature of the reactant lines for TMA and water was room temperature. To begin ALD, the reactor was cleaned by the nitrogen, and then two precursors were alternately introduced into the reactor separated by nitrogen purge step, which was critical to remove byproduct and remaining precursors. In the first half of the cycle, the wool fabric was exposed to water for 15 s followed by purging the nitrogen for 80 s. In the second half of the cycle, it was exposed to TMA for 15 s followed by purging the reactor with nitrogen for 150 s. During ALD processing, deposition cycle was 100 and pressure was maintained at 3.0 Torr. Pulse time for water and TMA were 0.015 and 0.2 s, respectively. The schematic process of Al2 O3 ALD on wool fibers is shown in Fig. 1. Moreover, ALD coated wool fabrics were heated in a muffle furnace up to 700 ◦ C for 1 h, and the residue is named ALD-residue. 2.3. Characterization Scanning electron microscopy (SEM): morphologies of wool fabrics, ALD coated wool fabrics and ALD-residue were examined on a scanning electron microscope (JSM-5610LV, JEOL Co. Ltd, Japan) at 15 kV after gold coating. X-ray fluorescence (XRF): the chemical elements of the wool fabrics were investigated by using the EAGLE III (EDAX Inc., USA) with the channel rage of 0–4000. The micro focus X-ray tube voltage was 38 kV and the diameter of X-ray focus point on sample was 100 m. Static water contact angles: the static water contact angles on the wool fabrics with and without ALD coating were measured using a JY-PHb contact angle goniometer (Chengde Yingchuang Co., Ltd, China). All reported contact angle values are obtained within 30 min after the dropping on the wool fabrics. Dynamic water contact angle: the dynamic water contact angle on the wool fabrics with and without ALD coating were carried out
under ambient conditions with a JY-PHb contact angle goniometer (Chengde Yingchuang Co., Ltd, China) by using the dynamic sessile drop technique. The volume of water droplet was 1 l. The advancing and receding contact angles ( A and R ) were calculated from the meniscus force when the liquid was inflated and sucked up from the sample surface, respectively. Optical photographs: the optical photographs of water, orange juice, milk, coffee, tea and coca cola droppings on the wool fabrics with and without ALD coating were measured by a digital camera (Canon, EOS 7D, Japan) after 30 min. 3. Results and discussion 3.1. Morphologies and chemical elements of wool fabrics Fig. 2 shows the SEM images and X-ray fluorescence (XRF) curves of control wool fabrics and ALD wool fabrics coated with 100 cycles of Al2 O3 at 80 ◦ C. From Fig. 2(a), the surface of control wool fiber was surrounded by cuticle layer which overlaps in one direction. Comparatively, Fig. 2(b) shows that nanoparticles could be seen clearly on the surface of wool fiber after ALD process. From XRF curves, Al was found on the surface of ALD coated wool fabrics. However, the intensity of S on the surface of ALD wool fabric was induced by 72.1% compared with that of control wool fabric. Fig. 3(c) shows the microphotograph of ALD-residue after ALD coated wool fabric was heated in a muffle furnace up to 700 ◦ C for 1 h. It could be seen clearly that ALD-residue has wool-like structure and its diameter decreased compared with that of ALD coated wool fiber. These suggested that a layer Al2 O3 was formed around the surface of ALD coated wool fabrics, and shrank after the heat treatment. Generally, the nano Al2 O3 particles on the surface of wool fiber were uniform due to a large amount of functional groups of wool fibers adsorbing water molecules, and most of them seem to be circles and their average diameter was between 100 and 200 nm. Atomic layer deposition can achieve very controlled uniform coatings on the surface of the substrate, especially when the substrate has enough functional groups under optimized condition. 3.2. Superhydrophobic of ALD coated wool fabrics Fig. 3 shows the static water contact angles and photos of the liquids on the control wool fabrics and ALD coated wool fabrics as a function of time. The static water contact angle of control wool fabrics was about 130◦ , which is also hydrophobic. Interestingly, the static water contact angle of ALD coated wool fabrics increased to around 160◦ , which suggested that ALD coated wool
878
Short Communication / Applied Surface Science 349 (2015) 876–879
Fig. 3. Static water contact angles and photos of the different kinds of liquids on the (a) control wool fabrics and (b) ALD coated wool fabrics as a function of time. Table 1 Static water contact angles and dynamic contact angles of control wool fabrics and ALD coated wool fabrics as a function of time.
Fig. 2. SEM images of (a) control wool fabrics, (b) ALD wool fabrics coated with 100 cycles of Al2 O3 at 80 ◦ C, and (c) ALD-residue; X-ray fluorescence (XRF) curves of (a) control wool fabrics, (b) ALD wool fabrics coated with 100 cycles of Al2 O3 at 80 ◦ C.
Samples
Static contact angle (deg)
Dynamic contact angle A (deg)
B (deg)
Control wool fabric (after 60 s) Control wool fabric (after 1800 s) ALD coated wool fabric (after 60 s) ALD coated wool fabric (after 1800 s)
130 ± 3
136 ± 2
124 ± 3
–
–
160 ± 2
169 ± 2
155 ± 3
160 ± 3
168 ± 2
153 ± 1
0
respectively. However, the dynamic contact angle of control wool fabrics could not be tested when the exposure time was over 1800 s. Conversely, the advancing contact angle and receding contact angle of ALD coated wool fabrics were about 169◦ and 155◦ , which also showed higher durability within 1800 s. Theoretically, the wettability of the surface is the combine impact of the surface roughness and chemical composition of the sample. The nano Al2 O3 particles increased the surface roughness of ALD coated wool fabrics as the similar surface of lotus leaf with superhydrophobic effect. When the droplet hangs on the embossments of the surface, the contact area between droplet and ALD coated wool fabrics was smaller than that between droplet and control wool fabrics. Furthermore, the common household liquids, such as water, orange juice, milk, coffee, tea and coca cola, exists as ball-like droplet on the ALD coated wool fabrics and as stain spot on the control wool fabric after exposure for 1800 s, which are shown in Fig. 3(a) and (b). 4. Conclusion
fabrics had a superhydrophobic surface. After exposure to atmosphere for 1800 s, the static water contact angle of control wool fabrics decreased to almost 0◦ , and that of ALD coated wool fabrics was still about 160◦ . The static water contact angles and dynamic contact angles of control wool fabrics and ALD coated wool fabrics as a function of time were summarized in Table 1. After exposure to atmosphere for 60 s, the advancing contact angle and receding contact angle of control wool fabrics were 136◦ and 124◦ ,
The results illustrated that the wool fabrics coated with Al2 O3 could be prepared through the ALD process and a layer of Al2 O3 and the nano Al2 O3 particles could be found on the surface of ALD wool fabrics. The ALD Al2 O3 coating on wool fabrics changed the surface roughness and surface energy, resulting into the increasing static water contact angle from 130◦ to 160◦ . The advancing contact angle and receding contact angle of ALD coated wool
Short Communication / Applied Surface Science 349 (2015) 876–879
fabrics were also increased to about 169◦ and 155◦ . Interestingly, the results showed that ALD coated wool fabrics could keep the superhydrophobic surface after exposure to atmosphere for 1800 s, indicating the higher durability of superhydrophobic of ALD coated wool fabrics than control wool fabrics. It was confirmed that ALD coating method could prepare superhydrophobic protein products applied in water-proof and self-cleaning fields. Acknowledgments We greatly acknowledge the support from the National Natural Science Foundation of China (Project No. 51203124, 51325306). The authors are grateful to Professor Yong Qin (Institute of Coal Chemistry, Chinese Academy of Sciences) for the help of ALD apparatus and his valuable advice. References [1] F. Shi, Z. Wang, X. Zhang, Combining a layer-by-layer assembling technique with electrochemical deposition of gold aggregates to mimic the legs of water striders, Adv. Mater. 17 (2005) 1005–1009. [2] D. Öner, T.J. McCarthy, Ultrahydrophobic surfaces. Effects of topography length scales on wettability, Langmuir 16 (2000) 7777–7782. [3] M. Manca, A. Cannavale, L.D. Marco, A.S. Aricò, R. Cingolani, G. Gigli, Durable superhydrophobic and antireflective surfaces by trimethylsilanized silica nanoparticles-based sol–gel processing, Langmuir 25 (2009) 6357. [4] H.Y. Erbil, A.L. Demirel, Y. Avcı, O. Mert, Transformation of a simple plastic into a superhydrophobic surface, Science 299 (2003) 1377–1380. [5] R. Jafari, R. Menini, M. Farzaneh, Superhydrophobic and icephobic surfaces prepared by RF-sputtered polytetrafluoroethylene coatings, Appl. Surf. Sci. 257 (2010) 1540–1543. [6] W.A. Daoud, J.H. Xin, X. Tao, Superhydrophobic silica nanocomposite coating by a low-temperature process, J. Am. Ceram. Soc. 87 (2004) 1782–1784. [7] J.T. Han, Y. Zheng, J.H. Cho, X. Xu, K. Cho, Stable superhydrophobic organicinorganic hybrid films by electrostatic self-assembly, J. Phys. Chem. B 109 (2005) 20773–20778. [8] S.G. Lee, D.S. Ham, D.Y. Lee, H. Bong, K. Cho, Transparent superhydrophobic/translucent superamphiphobic coatings based on silica–fluoropolymer hybrid nanoparticles, Langmuir 29 (2013) 15051–15057. [9] G.K. Hyde, K.J. Park, S.M. Stewart, J.P. Hinestroza, G.N. Parsons, Atomic layer deposition of conformal inorganic nanoscale coatings on three-dimensional
879
natural fiber systems: effect of surface topology on film growth characteristics, Langmuir 23 (2007) 9844–9849. [10] S.M. George, Atomic layer deposition: an overview, Chem. Rev. 110 (2009) 111–131. [11] S.M. George, A.W. Ott, J.W. Klaus, Surface chemistry for atomic layer growth, J. Phys. Chem. 100 (1996) 13121–13131.
Xingfang Xiao a,b Genyang Cao a,b Fengxiang Chen a,c Yunrong Tang a Xin Liu a,b,∗ Weilin Xu a,b,∗ a Key Laboratory of Green Processing and Functional Textiles of New Textile Materials, Ministry of Science and Technology, Wuhan Textile University, Wuhan 430200, PR China b College of Material Science and Engineering, Wuhan Institute of Technology, Wuhan 430205, PR China c Faculty of Materials Science and Engineering, Hubei University, Wuhan 430062, PR China ∗ Corresponding authors at: Key Laboratory of Green Processing and Functional Textiles of New Textile Materials, Ministry of Science and Technology, Wuhan Textile University, Wuhan 430200, PR China. Tel.: +86 02759367690; fax: +86 02759367690. E-mail addresses: xinliu [email protected] (X. Liu), [email protected] (W. Xu).
5 February 2015 2 May 2015 4 May 2015 Available online 18 May 2015
Contents lists available at ScienceDirect
Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc
Short Communication Durable superhydrophobic wool fabrics coating with nanoscale Al2 O3 layer by atomic layer deposition
a r t i c l e
i n f o
Keywords: Atomic layer deposition Aluminum oxide Wool fabrics Superhydrophobic
a b s t r a c t To obtain superhydrophobic surface, aluminum oxide was deposited onto wool fabrics using atomic layer deposition (ALD) by exposing them to alternating pulses of trimethylaluminum and water at 80 ◦ C. Scanning electron microscope (SEM) and X-ray fluorescence (XRF) analysis showed that Al2 O3 layer and uniform Al2 O3 nanoparticle were formed around the surface of ALD coated wool fiber, which showed higher surface roughness than control wool fiber. The static water contact angles of ALD coated wool fabrics increased from 130◦ to around 160◦ , and had a higher durability than that of control wool fabric. The dynamic water contact angles of all samples were also tested. Furthermore, the common household liquids also existed as ball-like droplet on the ALD coated wool fabrics and as stain spot on the control wool fabrics after exposure for 1800 s. © 2015 Elsevier B.V. All rights reserved.
1. Introduction Wool fiber has been widely used for a long time in human history, as it has many advantages, such as good elasticity, softy, and warmth. However, wool products are easy to touch ash and fragile, which makes wool products are not easy to clean. The superhydrophobic surfaces with a static water contact angle lager than 150◦ have attracted abundant investigative efforts because of the selfcleaning and anti-snow sticking properties, which would increase the potential application value of materials. At present, a variety of techniques have been rapidly proposed for superhydrophobic materials. Shi et al. combine a layer-by-layer assembling technique with electrochemical deposition to prepare superhydrophobic coatings on gold threads [1]. Öner et al. fabricate ultrahydrophobic silicon surfaces by photolithography and hydrophobized using silanization reagents [2]. Manca et al. fabricate superhydrophobic and simultaneously antireflective surfaces by a double-layer coating comprising trimethylsiloxane (TMS) surface functionalized silica nanoparticles through a sol–gel process [3]. Yunying Wu et al. prepare transparent and ultra water-repellent thin films by microwave plasma chemical vapor deposition using as a raw material. In addition, polypropylene, Al2 O3 , SiO2 and their hybrids have been used to prepare superhydrophobic surfaces [4–8]. However, in many cases, the reported approaches are not appropriate for the natural fibers especially for protein fibers, as the treatment temperature was too high for protein fiber that it could cause a considerable thermal degradation resulting into the yellowing, fragile and non-bonded superhydrophobic layer of protein fibers. An alternative approach is to utilize the chemical reaction on the protein fabrics to form a uniform superhydrophobic layer at a relative low temperature. Hyde et al. increase the water contact angle from 0◦ to 127◦ using atomic layer deposition (ALD) of Al2 O3 on cotton at 100 ◦ C [9]. In view of the different structure http://dx.doi.org/10.1016/j.apsusc.2015.05.061 0169-4332/© 2015 Elsevier B.V. All rights reserved.
and chemical groups between cotton and wool fiber, the cotton is hydrophilic and the wool is hydrophobic, thus we considered using the atomic layer deposition transformed the hydrophobic surface of wool fiber to superhydrophobic. To the best of our knowledge, few studies report the superhydrophobic wool fabric obtained by using ALD technology. Most ALD processes contain two time-separated half-reactions. As the precursor and co-reactant species transported into reactor separately, two surface reactions occur and each of the surface reaction is self-limiting, then the two reactions proceed sequential, eventually deposit an atomic level control film [10]. The binary reaction for Al2 O3 ALD [11] is 2Al(CH3 )3 + 3H2 O → Al2 O3 + 3CH4 H = −376 kcal Because the formation of a strong Al O bond during Al2 O3 ALD, the surface reactions are very efficient and self-limiting, so that the Al2 O3 ALD can be deposited at relative low temperature available for wool fabrics. In this study, we deposited Al2 O3 onto wool fabrics by ALD at 80 ◦ C to offer a durably superhydrophobic wool fabric. The morphologies, chemical elements and superhydrophobic properties of samples were characterized.
2. Experimental 2.1. Materials Wool fabrics (twill-weave, 200 g/m2 ) were obtained from Yangzhou Jindi Wool Textile Co., Ltd. (Jiangsu, China). Trimethylaluminum (TMA) was purchased from Strem Chemicals, Inc. Deionized water (I degree, specific resistance is 10–16 M cm at 25 ◦ C) was produce by Molgeneral (Molecular, USA).
Short Communication / Applied Surface Science 349 (2015) 876–879
877
Fig. 1. The schematic process of Al2 O3 ALD on wool fibers.
2.2. Atomic layer deposition (ALD) process ALD of Al2 O3 was performed onto wool fabrics and silicon wafer, which was acted as a reference whether the ALD reactions happen on the surface through the color change. ALD experiment was carried out in a hot-wall closed chamber-type ALD reactor (Savannah system, Cambridge Nanotech. Inc., USA). The deposition of Al2 O3 used trimethylaluminum (TMA) and deionized water as the aluminum and oxygen source, respectively. Considering the high temperature has a significant damage on wool fiber, the ALD deposition temperature was set at 80 ◦ C. Prior to ALD processing, wool fabrics were placed in the ALD reactor and heated in vacuum (7.9E−1 Torr) to 80 ◦ C, kept at this temperature for 5 min. The temperature of the reactant lines for TMA and water was room temperature. To begin ALD, the reactor was cleaned by the nitrogen, and then two precursors were alternately introduced into the reactor separated by nitrogen purge step, which was critical to remove byproduct and remaining precursors. In the first half of the cycle, the wool fabric was exposed to water for 15 s followed by purging the nitrogen for 80 s. In the second half of the cycle, it was exposed to TMA for 15 s followed by purging the reactor with nitrogen for 150 s. During ALD processing, deposition cycle was 100 and pressure was maintained at 3.0 Torr. Pulse time for water and TMA were 0.015 and 0.2 s, respectively. The schematic process of Al2 O3 ALD on wool fibers is shown in Fig. 1. Moreover, ALD coated wool fabrics were heated in a muffle furnace up to 700 ◦ C for 1 h, and the residue is named ALD-residue. 2.3. Characterization Scanning electron microscopy (SEM): morphologies of wool fabrics, ALD coated wool fabrics and ALD-residue were examined on a scanning electron microscope (JSM-5610LV, JEOL Co. Ltd, Japan) at 15 kV after gold coating. X-ray fluorescence (XRF): the chemical elements of the wool fabrics were investigated by using the EAGLE III (EDAX Inc., USA) with the channel rage of 0–4000. The micro focus X-ray tube voltage was 38 kV and the diameter of X-ray focus point on sample was 100 m. Static water contact angles: the static water contact angles on the wool fabrics with and without ALD coating were measured using a JY-PHb contact angle goniometer (Chengde Yingchuang Co., Ltd, China). All reported contact angle values are obtained within 30 min after the dropping on the wool fabrics. Dynamic water contact angle: the dynamic water contact angle on the wool fabrics with and without ALD coating were carried out
under ambient conditions with a JY-PHb contact angle goniometer (Chengde Yingchuang Co., Ltd, China) by using the dynamic sessile drop technique. The volume of water droplet was 1 l. The advancing and receding contact angles ( A and R ) were calculated from the meniscus force when the liquid was inflated and sucked up from the sample surface, respectively. Optical photographs: the optical photographs of water, orange juice, milk, coffee, tea and coca cola droppings on the wool fabrics with and without ALD coating were measured by a digital camera (Canon, EOS 7D, Japan) after 30 min. 3. Results and discussion 3.1. Morphologies and chemical elements of wool fabrics Fig. 2 shows the SEM images and X-ray fluorescence (XRF) curves of control wool fabrics and ALD wool fabrics coated with 100 cycles of Al2 O3 at 80 ◦ C. From Fig. 2(a), the surface of control wool fiber was surrounded by cuticle layer which overlaps in one direction. Comparatively, Fig. 2(b) shows that nanoparticles could be seen clearly on the surface of wool fiber after ALD process. From XRF curves, Al was found on the surface of ALD coated wool fabrics. However, the intensity of S on the surface of ALD wool fabric was induced by 72.1% compared with that of control wool fabric. Fig. 3(c) shows the microphotograph of ALD-residue after ALD coated wool fabric was heated in a muffle furnace up to 700 ◦ C for 1 h. It could be seen clearly that ALD-residue has wool-like structure and its diameter decreased compared with that of ALD coated wool fiber. These suggested that a layer Al2 O3 was formed around the surface of ALD coated wool fabrics, and shrank after the heat treatment. Generally, the nano Al2 O3 particles on the surface of wool fiber were uniform due to a large amount of functional groups of wool fibers adsorbing water molecules, and most of them seem to be circles and their average diameter was between 100 and 200 nm. Atomic layer deposition can achieve very controlled uniform coatings on the surface of the substrate, especially when the substrate has enough functional groups under optimized condition. 3.2. Superhydrophobic of ALD coated wool fabrics Fig. 3 shows the static water contact angles and photos of the liquids on the control wool fabrics and ALD coated wool fabrics as a function of time. The static water contact angle of control wool fabrics was about 130◦ , which is also hydrophobic. Interestingly, the static water contact angle of ALD coated wool fabrics increased to around 160◦ , which suggested that ALD coated wool
878
Short Communication / Applied Surface Science 349 (2015) 876–879
Fig. 3. Static water contact angles and photos of the different kinds of liquids on the (a) control wool fabrics and (b) ALD coated wool fabrics as a function of time. Table 1 Static water contact angles and dynamic contact angles of control wool fabrics and ALD coated wool fabrics as a function of time.
Fig. 2. SEM images of (a) control wool fabrics, (b) ALD wool fabrics coated with 100 cycles of Al2 O3 at 80 ◦ C, and (c) ALD-residue; X-ray fluorescence (XRF) curves of (a) control wool fabrics, (b) ALD wool fabrics coated with 100 cycles of Al2 O3 at 80 ◦ C.
Samples
Static contact angle (deg)
Dynamic contact angle A (deg)
B (deg)
Control wool fabric (after 60 s) Control wool fabric (after 1800 s) ALD coated wool fabric (after 60 s) ALD coated wool fabric (after 1800 s)
130 ± 3
136 ± 2
124 ± 3
–
–
160 ± 2
169 ± 2
155 ± 3
160 ± 3
168 ± 2
153 ± 1
0
respectively. However, the dynamic contact angle of control wool fabrics could not be tested when the exposure time was over 1800 s. Conversely, the advancing contact angle and receding contact angle of ALD coated wool fabrics were about 169◦ and 155◦ , which also showed higher durability within 1800 s. Theoretically, the wettability of the surface is the combine impact of the surface roughness and chemical composition of the sample. The nano Al2 O3 particles increased the surface roughness of ALD coated wool fabrics as the similar surface of lotus leaf with superhydrophobic effect. When the droplet hangs on the embossments of the surface, the contact area between droplet and ALD coated wool fabrics was smaller than that between droplet and control wool fabrics. Furthermore, the common household liquids, such as water, orange juice, milk, coffee, tea and coca cola, exists as ball-like droplet on the ALD coated wool fabrics and as stain spot on the control wool fabric after exposure for 1800 s, which are shown in Fig. 3(a) and (b). 4. Conclusion
fabrics had a superhydrophobic surface. After exposure to atmosphere for 1800 s, the static water contact angle of control wool fabrics decreased to almost 0◦ , and that of ALD coated wool fabrics was still about 160◦ . The static water contact angles and dynamic contact angles of control wool fabrics and ALD coated wool fabrics as a function of time were summarized in Table 1. After exposure to atmosphere for 60 s, the advancing contact angle and receding contact angle of control wool fabrics were 136◦ and 124◦ ,
The results illustrated that the wool fabrics coated with Al2 O3 could be prepared through the ALD process and a layer of Al2 O3 and the nano Al2 O3 particles could be found on the surface of ALD wool fabrics. The ALD Al2 O3 coating on wool fabrics changed the surface roughness and surface energy, resulting into the increasing static water contact angle from 130◦ to 160◦ . The advancing contact angle and receding contact angle of ALD coated wool
Short Communication / Applied Surface Science 349 (2015) 876–879
fabrics were also increased to about 169◦ and 155◦ . Interestingly, the results showed that ALD coated wool fabrics could keep the superhydrophobic surface after exposure to atmosphere for 1800 s, indicating the higher durability of superhydrophobic of ALD coated wool fabrics than control wool fabrics. It was confirmed that ALD coating method could prepare superhydrophobic protein products applied in water-proof and self-cleaning fields. Acknowledgments We greatly acknowledge the support from the National Natural Science Foundation of China (Project No. 51203124, 51325306). The authors are grateful to Professor Yong Qin (Institute of Coal Chemistry, Chinese Academy of Sciences) for the help of ALD apparatus and his valuable advice. References [1] F. Shi, Z. Wang, X. Zhang, Combining a layer-by-layer assembling technique with electrochemical deposition of gold aggregates to mimic the legs of water striders, Adv. Mater. 17 (2005) 1005–1009. [2] D. Öner, T.J. McCarthy, Ultrahydrophobic surfaces. Effects of topography length scales on wettability, Langmuir 16 (2000) 7777–7782. [3] M. Manca, A. Cannavale, L.D. Marco, A.S. Aricò, R. Cingolani, G. Gigli, Durable superhydrophobic and antireflective surfaces by trimethylsilanized silica nanoparticles-based sol–gel processing, Langmuir 25 (2009) 6357. [4] H.Y. Erbil, A.L. Demirel, Y. Avcı, O. Mert, Transformation of a simple plastic into a superhydrophobic surface, Science 299 (2003) 1377–1380. [5] R. Jafari, R. Menini, M. Farzaneh, Superhydrophobic and icephobic surfaces prepared by RF-sputtered polytetrafluoroethylene coatings, Appl. Surf. Sci. 257 (2010) 1540–1543. [6] W.A. Daoud, J.H. Xin, X. Tao, Superhydrophobic silica nanocomposite coating by a low-temperature process, J. Am. Ceram. Soc. 87 (2004) 1782–1784. [7] J.T. Han, Y. Zheng, J.H. Cho, X. Xu, K. Cho, Stable superhydrophobic organicinorganic hybrid films by electrostatic self-assembly, J. Phys. Chem. B 109 (2005) 20773–20778. [8] S.G. Lee, D.S. Ham, D.Y. Lee, H. Bong, K. Cho, Transparent superhydrophobic/translucent superamphiphobic coatings based on silica–fluoropolymer hybrid nanoparticles, Langmuir 29 (2013) 15051–15057. [9] G.K. Hyde, K.J. Park, S.M. Stewart, J.P. Hinestroza, G.N. Parsons, Atomic layer deposition of conformal inorganic nanoscale coatings on three-dimensional
879
natural fiber systems: effect of surface topology on film growth characteristics, Langmuir 23 (2007) 9844–9849. [10] S.M. George, Atomic layer deposition: an overview, Chem. Rev. 110 (2009) 111–131. [11] S.M. George, A.W. Ott, J.W. Klaus, Surface chemistry for atomic layer growth, J. Phys. Chem. 100 (1996) 13121–13131.
Xingfang Xiao a,b Genyang Cao a,b Fengxiang Chen a,c Yunrong Tang a Xin Liu a,b,∗ Weilin Xu a,b,∗ a Key Laboratory of Green Processing and Functional Textiles of New Textile Materials, Ministry of Science and Technology, Wuhan Textile University, Wuhan 430200, PR China b College of Material Science and Engineering, Wuhan Institute of Technology, Wuhan 430205, PR China c Faculty of Materials Science and Engineering, Hubei University, Wuhan 430062, PR China ∗ Corresponding authors at: Key Laboratory of Green Processing and Functional Textiles of New Textile Materials, Ministry of Science and Technology, Wuhan Textile University, Wuhan 430200, PR China. Tel.: +86 02759367690; fax: +86 02759367690. E-mail addresses: xinliu [email protected] (X. Liu), [email protected] (W. Xu).
5 February 2015 2 May 2015 4 May 2015 Available online 18 May 2015