Author’s Accepted Manuscript Silver-coated glass fabric composites prepared by electroless plating Yu Tai, Chunju Xu, Huiyu Chen
PII: DOI: Reference:
S0167-577X(16)30885-0 http://dx.doi.org/10.1016/j.matlet.2016.05.118 MLBLUE20929
To appear in: Materials Letters Received date: 29 April 2016 Revised date: 20 May 2016 Accepted date: 25 May 2016 Cite this article as: Yu Tai, Chunju Xu and Huiyu Chen, Silver-coated glass fabric composites prepared by electroless plating, Materials Letters, http://dx.doi.org/10.1016/j.matlet.2016.05.118 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Silver-coated glass fabric composites prepared by electroless plating Yu Tai, Chunju Xu*, Huiyu Chen* School of Materials Science and Engineering, North University of China, Taiyuan 030051, China *
Corresponding authors. Tel. /Fax: +86-351-3559669,
E-mail: [email protected]
(C. Xu), [email protected]
Abstract: Silver-coated glass fabrics have been successfully obtained by a facile and versatile electroless plating method, and the silver layers on the surface of glass fabrics were compact and uniform. The purity and quality of these silver coatings were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. It was found that the quality of the coating layer was influenced by the dosage of reducing agent and reaction time. The composites possessed an excellent conductivity, and the optimal volume resistivity could reach 6.54×10-4 Ω·cm. It was expected that such conductive composites have extensive application in shielding materials. Graphical abstract
Glass fabrics/silver core-shell composites were successfully prepared via an electroless plating route at 30 oC in an alkaline bath, and the optimal volume resistivity of such composites with compact silver layers could reach 6.54×10-4 Ω·cm. 1
Keywords: Composite materials; Electrical properties; Glass fabrics; Electroless plating. 1. Introduction During recent years, smart functional textiles with metallic layers on their surfaces have attracted a great deal of attention due to their novel properties such as good electrical conductivity, light weight, flexibility, and so on [1-5]. These composites can be used in electromagnetic interference (EMI) shielding, electronic sensors, and smart clothing. In addition, silver-coated fibers also possess antibacterial functions besides EMI [6, 7]. Goli et al reported a simple method to impart antibacterial properties on the surface of polypropylene (PP) fibers by attaching silver nanoparticles (Ag NPs), and the result showed that Ag NPs-coated PP fibers have excellent antibacterial activity with 100% removal efficiency . Many methods have been developed to prepare metallic coatings on the surface of substrates, such as sputter, spinning, and electroless depositioin [9-11]. Among these techniques, electroless plating is a promising method for the surface modification, because it can deposit continuous and uniform coatings on conductive or nonconductive substrates. In our previous work, we have successfully deposited silver or copper layers on different fibers by electroless plating [12-15]. In addition, Park et al. prepared optically tunable nano-structured Ag films on glass substrate for enhanced Raman scattering (SERS) activities by electroless-plating method. The result indicated that the obtained Ag films exhibit very even SERS activity over an area up to hundreds thousand square-micrometers, and the enhancement factor estimated using benzenethiol as a prototype adsorbate reaches ～2×105 . Jang and Ryu fabricated conductive paper with a level of electrical conductivity and great physical strength by addition of a small amount of Ag-plated carbon fiber to the pulp . Lee et al prepared nickel-coated polyester textiles via an electroless 2
plating method and further fabricated full-cells in the forms of clothes and watchstraps, which exhibited comparable electrochemical performance to those of conventional metal foil-based cells even under severe folding−unfolding motions simulating actual wearing conditions. Furthermore, the wearable textile battery was integrated with flexible and lightweight solar cells on the battery pouch to enable convenient solar-charging capabilities . Kwak et al prepared Ag-coated cotton fabric with excellent antibacterial and conductive properties through a facile thermal reduction process at a low temperature . We previously fabricated conductive glass [email protected]
composites, and the optimal volume resistivity of such composites with compact nickel layers could reach 6.25×10-3 Ω·cm . In this work, uniform silver coatings were successfully obtained on the surface of glass fabrics via an electroless deposition approach. The quality of the coatings was closely related to the dosage of reducing agent and reaction time, respectively. Such composites with compact silver layers show excellent conductivity with volume resistivity of 6.54×10-4 Ω·cm
2. Experimental procedure Materials and method: All chemical reagents were in analytical grade and used without further purification. The plain white glass fabrics (density of 140 g/m2 and thickness of 0.15 mm) were used as substrate. The glass fabric samples were cut into 4 cm×5 cm, weighed, and then pretreated. The pretreatment process was carried out by cleaning, etching, sensitization, and activation. Then the treated glass fabrics were finally immersed in an electroless silver plating bath. The silver plating bath was a mixture of solution A and solution B. Solution A consisted of 0.8 g of C6H12O6, 0.08 g of C4H6O6, and 2.0 mL of C2H5OH in 20 mL of deionized water. Solution B, namely, Ag(NH3)2+ solution, contained 0.8 g of AgNO3, 0.3 g of NaOH and 2.0 mL of NH3·H2O 3
in 20 mL of deionized water. Then the Ag(NH3)2+ solution was dropwise added into solution A, and the reaction bath temperature was maintained at 30 oC with water bath shaker. After reaction of 40 min, the product was collected, rinsed, and dried. Characterizations: The surface morphology and microstructure analysis of the silver-coated glass fabrics were invested by a JEOL JSM-6510 scanning electron microscope (SEM), and X-ray diffraction (XRD) spectrometer (Bruker D8 focus) with Cu Kα radiation (λ=0.15406 nm), respectively. The volume resistivity was measured by a SB 120 four-point-probe instrument.
3. Results and discussion Fig. 1a showed the XRD pattern of silver-coated glass fabrics. Five diffraction peaks were observed at 38.1, 44.3, 64.4, 77.4, and 81.5 correspond to (111), (200), (220), (311) and (222) planes of face-centered cubic silver, respectively, and the result was in good agreement with reported data (JCPDS No. 04-0783). No peaks of oxide or other impurities were detected, indicating that the glass fabrics were successfully deposited with a pure silver layer. Fig. 1b shows the SEM image of the obtained silver-coated glass fabrics, from which it can be seen that the silver layer was compact and continuous, and some small particles coexisted on the surface of fabrics. No peeled coating was found, indicating that the adherence between glass fabrics and silver coatings was very strong. Fig. 2 showed the SEM images of the silver-coated glass fabrics prepared with different dosage of reducing agent. The silver coatings were not perfect when only small amount of reducing agent was used (Fig. 2a and b), and some broken positions were clearly seen. The surface of glass fabrics was almost coated with silver particles when the reducing agent was increased to 0.6 g (Fig. 2c). Perfect silver layers could be obtained when the amount of glucose was further increased to 4
0.8 g or above, at this stage, the coatings was continuous and compact (Fig. 1b and 2d). More silver particles existed on the surface of coatings as the concentration of glucose was higher, because the reduction of Ag+ to metallic Ag was fast enough. The initially formed silver nuclei would grow in the solution instead of deposition on the surface as compact coatings, and finally the suspended silver particles were attached on the glass fabrics as silver clusters. The reduction process could be expressed as the following equation (1) and (2). The silver ions were unstable in the alkaline solution and were easily formed Ag2O. Silver ions could not be completely reduced to metallic silver if the dosage of reducing reagent was too low. With the concentration of glucose increasing, the partially formed Ag2O could be reduced to Ag finally. Ag+ + C6H12O6 + OH- → Ag + RCOO- + H2O
Ag2O + C6H12O6 → CH2OH-(CHOH)4-COOH + Ag
Fig.3 shows the SEM images of samples obtained with different deposition time. In the initial 20 min, the amount of silver on the surface of glass fabrics was increased obviously with reaction proceeding (Fig. 3a and b). As the plating time was extended to 30 min, almost all the surface of glass fabrics was coated with Ag except some minute broken positions (Fig. 3c). In addition, the thickness of metal layer was increased as well. Continuous coating layers on the surface of glass fabrics could be obtained when the electroless plating time was further prolonged to 40 min or more (Fig. 3d). Simultaneously, more silver clusters on the surface of coating layers existed once the plating time was extended longer. As time increased, the isolated silver particles in the solution would be deposited to the surface of coatings. Surely the attachment between the attached particles and coating was not strong. The plot of volume resistivity of Ag-coated glass fabrics prepared with different electroless 5
plating time was shown in Fig. 4. The sample obtained with reaction time of 40 min possessed the minimum volume resistivity of 6.54 × 10-4 Ω·cm. If the reaction time was too short, the silver coatings had some broken positions and the conductivity was relatively poor. With reaction proceeding, the silver layer would be turned from isolated metal to dense coating, so the conductive path would be formed on the surface of glass fabrics and the volume resistivity decreased. However, larger silver clusters were produced if the reaction proceeds too long, and the silver clusters were separated by empty dielectric gaps which weakened electrical transport through the coating . Therefore, the volume resistivity would increase again.
4. Conclusions In summary, silver-coated glass fabrics were successfully prepared at 30 oC via an electroless plating method. Glucose was used as an environmental-friendly reducing agent. The silver coatings with pure composition on the surface of glass fabrics could be tuned from incompact to perfect. The quality of silver layer was closely related to the dosage of reducing agent and reaction time. Composites with compact and continuous silver coatings on the surface of glass fabrics possess excellent conductivity, and such conductive composites can be used as shielding materials, electronic sensors, and etc. The current method is simple, low cost, and environmental-friendly, and can be extended to fabricate other metallic coatings on various substrates.
Acknowledgments This work was supported by Research Fund for the Doctoral Program of Higher Education of China (20121420120006), Shanxi Province Science Foundation for Youths (2014021016-1), Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi, and Scientific Research Foundation for the Returned Overseas Chinese Scholars, Ministry of 6
Education of China.
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Figure captions Fig.1. (a) XRD pattern and (b) SEM image of the sample obtained in the typical synthesis. Fig.2. SEM images of samples obtained with glucose of (a) 0.2, (b) 0.4, (c) 0.6, and (d) 1.2 g. Fig.3. SEM images of the composites prepared with reaction time of (a) 10, (b) 20, (c) 30, and (d) 60 min.
Fig.4. The relationship between the volume resistivity and plating time.
Volume resistivity /×10 cm
1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 10
30 50 9 40 Reaction time / min
Figure 4 Highlights
Silver-coated glass fabrics were prepared via electroless plating
Glucose was used as green reducing agent
The silver layer is compact, uniform, and continuous
The composites possessed an excellent conductivity of 6.5410-4 cm