Enhanced Mechanical and Electrochemical Performances of Silica

Research Article Cite This: ACS Appl. Mater. Interfaces 2019, 11, 24308−24317

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Enhanced Mechanical and Electrochemical Performances of SilicaBased Coatings Obtained by Electrophoretic Deposition Qi Zeng,*,†,‡,§ Wenlu Wan,§ and Liqiong Chen§ Shenzhen Institutes of Advanced Technology and ‡Key Laboratory of Health Informatics, Chinese Academy of Sciences, Shenzhen 518055, China § Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China

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ABSTRACT: To solve the existing problems of silicon dioxide (SiO2) coating fabricated by the sol−gel method, such as complicated process, long production cycle, uncontrollable quality, etc., an improved electrophoretic deposition (EPD) combined with the sintering process was proposed to prepare SiO2 coating on a dark nickel (Ni)-coated Q235 steel substrate. Silica sol was prepared by basic catalysis, containing silica of ∼130 g L−1 with viscosities below 4 mPa s. Silica sol powder was characterized by the differential thermal analysis, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. EPD was applied to prepare SiO2 coating on the Ni adhesive layer, followed by the sintering process to improve the compactness. In addition, the effects of EPD and sintering parameters were also evaluated. Potentiodynamic polarization and electrochemical impedance spectra were utilized to assess the corrosion behavior of the coating. The results showed that the EPD coating demonstrated excellent wear resistance when deposited at 15 V for 40 s and sintered at 400 °C for 45 min, exhibiting ∼6 μm thickness and a compact morphology. It also showed superior corrosion resistance with icorr of 1.02 × 10−7 A cm−2, which was 2 orders of magnitude lower than that of dip-coating. Combining the EPD and sintering processes could shorten the fabrication period of SiO2 inorganic coating and also improve the mechanical and corrosion properties, providing guidance for inorganic ceramic fabrication and showing potential for practical applications. KEYWORDS: silica sol, electrophoretic deposition (EPD), sintering, corrosion, wear resistance

1. INTRODUCTION Inorganic films have the advantages of stable chemical properties,1 good thermal stability,2 high intensity,3 high aging resistance,4 easy regeneration,5 etc., which have become an important research direction in the field of film technology and have been widely used in various industries. Inorganic materials like ceramics usually have higher hardness and tensile strength than other materials since their molecular structure is composed of ionic and covalent bondings, which make dislocation motion difficult. In recent years, increasing research interest has been given to SiO2 ceramic coating because of its good wear resistance, thermal insulation, high hardness, strong corrosion resistance, and good dielectric properties.6 However, the general characteristics such as adhesion strength, morphology, uniformity, and thickness of SiO2 coatings significantly depend on the applied film technology. Many researchers have contributed to the fabrication of these ceramic materials. The plasma-enhanced chemical vapor deposition technique can deposit ultrathin films with a thickness of several hundred nanometers at lower temperatures.7,8 The compact films adhere tightly to various substrates with low porosity; nevertheless, it is unsuitable for low dielectric or thermal insulation materials.9 Electrochemical corrosion-thermal oxidation is a common method for preparing porous SiO2 insulating films.10 Kan et al.11 fabricated a thick SiO2 coating with a porosity of 55−75% from macroporous Si © 2019 American Chemical Society

(macro-PS) by electrochemical etching from p-type Si, followed by wet oxidation at 1050 °C; however, the temperature was too high and the fabrication process was relatively complex to be controlled effectively. Sol−gel science is an amalgamation of solution and gelation with a simple process, which has been demonstrated to be a well-characterized method and widely applied to produce a great variety of porous materials.12−15 The best and oldest commercial method to produce homogeneous sol−gel coatings is the dipping process, but serious border effects often occur and the maximum thickness attainable is undesirable, which is governed by the concentration of sols and withdrawal rates.13,16 As an improvement, electrophoretic deposition (EPD) is widely applied for ceramic suspensions, which has attracted increasing interest in the development of advanced materials and contributed to obtain higher thickness from silica sol with enhanced corrosion resistance.17−19 It mainly contains two processes, that is, (a) direction migration of suspended and charged colloidal particles/molecules in dispersed media under an applied electric field, and (b) particle/molecule deposition on the surface of an oppositely charged electrode to form uniform and compact coatings.20 In general, solid particles Received: April 30, 2019 Accepted: June 18, 2019 Published: June 18, 2019 24308

DOI: 10.1021/acsami.9b07585 ACS Appl. Mater. Interfaces 2019, 11, 24308−24317

Research Article

ACS Applied Materials & Interfaces

storage in a closed environment for more than 5 months. The final concentration of silica was ∼130 g L−1, with viscosities below 4 mPa s. 2.2. Electrophoretic Deposition (EPD). Q235 steel substrates with a size of 50 mm × 30 mm × 1 mm were used to prepare dipping and EPD coatings. The ground and polished steel substrates were cleaned with an alkaline solution (Na2CO3/Na3PO4/NaOH/Na2SiO3) for more than 15 min and subsequently washed with deionized water at 60 and 25 °C. Finally, 0.5 M H2SO4 was used to activate the substrate. Prior to EPD, the substrate surfaces were electrodeposited with a dark Ni thin film as the adhesive layer in the Ni electrolyte (1 M Ni2SO4·6H2O, 0.1 M NiCl2·6H2O, additive ∼0.6 M) at 0.45 A under 60 °C for 30 min. EPD coatings were deposited in the potentiostatic condition using the silica sol above; the Q235 steel and graphite were used as the working electrode and the counter electrode, respectively. The EPD setup and the corresponding schematic diagram of electrophoretic migration are shown in Figure 1a and b respectively.

having particle sizes 3 mm. 2.3.2. XRD Analysis. The phases formed in the synthesized silica sol powder and the coatings developed at the optimized condition were recorded and analyzed by an X-ray diffractometer (XRD, Rigaku DMAX/2400, Japan) with a step size of 0.0167° at a scan rate of 5° min−1 with Cu Kα radiation (λ = 0.154056 nm). The XRD measurements were performed with an acceleration voltage at 40 kV and 40 mA current to record data in a range of 2θ of 10−90°.14,41 2.3.3. FT-IR Spectra Analysis. Fourier transform infrared spectroscopy (FT-IR) in the range of 400−4000 cm−1 using an AVATAR370 spectrophotometer (Nicolet) was performed to identify the molecular structure of compounds, with a 0.1 wt % potassium bromide (KBr) pellet technique.14,42 2.3.4. Tribology. The frictional coefficient (FC) of the samples was measured using a wear testing machine (PMJ-II) fabricated according to the standard ISO 8251. The outer edge of the friction wheel was bonded with 320 mesh sandpaper. The specimens were mounted onto a reciprocating table with a traveling distance of 30 mm for 400 cycles and a load of 500 g. Finally, the wear resistance (WR) of the coating was evaluated by the quality change of the as-fabricated samples before (M1) and after (M2) friction, as shown in the following equation

WR (number of cycles/mg) =

400 400 = ΔM M1 − M 2

Therefore, spherical SiO2 colloidal particles could be obtained by dissolving silicon in an alkaline condition, which was stable with better performances. The schematic diagram of the colloidal structure of silica sol is shown in Figure 2a. Figure 2b shows the differential thermal analysis (DTA) of the silica sol powder. Water usually existed in three forms in silica sol, “free water” disappeared entirely before heating to 110 °C, “absorbed water” was lost when heated to 140−220 °C, and “structural water” did not vanish until 400−700 °C.44 It could be seen from Figure 2 that the silica sol powder had a heat-absorption valley at ∼100 °C and disappeared at ∼140 °C, indicating that the evaporation of the solvent and water in the gel pores mainly occurred in this range, as well as the dehydration and polycondensation of silicon hydroxyl groups (Si−OH). In addition, there appeared a wide exothermic peak at ∼370 °C. The inset shows that the spherical particles in the silica sol powder distributed uniformly with less than 100 nm in diameter, and the particles were less agglomerated. Figure 3 represents the characteristic functional groups of the unsintered and sintered silica sol powders. The bands at ∼469 and ∼797 cm−1 and the strong and wide absorption band at ∼1100 cm−1 were attributed to bending, rocking, and antisymmetric stretching vibrations of the Si−O−Si group, respectively. The band at ∼1640 cm−1 was attributed to the H−

(6)

2.3.5. Morphology. A scanning electron microscope (SEM, Zeiss SIGMA 300, Germany) was used to analyze the surface morphology and microstructure of the as-fabricated samples, and the energydispersive spectrometer (EDS) was used to analyze the elements. 2.3.6. Electrochemical Analysis. The electrochemical characteristics of all samples were assessed by a range of electrochemical methods. A PARSTAT2273 electrochemical workstation with a conventional 24310


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under the condition of deposition for 40 s and sintering at 400 °C for 45 min. As observed, the adhesive strength decreased gradually with the increasing deposition potential (Figure 5a). The edge effect during the EPD process would be more serious with a higher potential, resulting in the silica particles accumulating densely on the edge. Thus, the coating could crack and fall off easily after being dried and sintered. Significantly, the increasing potential would increase the content of nanoparticles in coatings, which would improve the hardness and reduce the porosity to some degree as shown in Figure 5b,c. Incorporation of SiO2 nanoparticles (NPs) into the Ni-coated steel substrate endued desirable porosity and hardness. Meanwhile, higher hardness leads to better scratch resistance.49 However, the content of SiO2 NPs exceeded the intercalating ability of metal substrates when the EPD potential reached over 15 V, therefore leading to the decreased hardness and increased porosity of SiO2 coating. Moreover, the higher potential over 15 V increased the oxygen (O2) evolution during the EPD process, and a portion of the gas failed to escape in time due to the hindrance of the EPD layer at a high deposition rate, thus forming the pores in the coating. It could be seen from Figure 5d that the impedance of the coating obtained at 10 V was the lowest, presenting the worst corrosion resistance, since the thin film could not inhibit the infiltration of chloride ions (Cl−) effectively under this condition. Although it also had good corrosion resistance at 20 V, the edge effect at high potential was not conducive to the adhesion of the coating, accelerating the infiltration of Cl− and further reducing corrosion resistance. However, the radius of the impedance spectrum was the largest at 15 V, exhibiting the highest impedance and the best corrosion resistance in the NaCl solution. Figure 5e represents the microscope images of EPD samples at different potentials. The coating obtained at low potential was thin, and the deposition amount would increase with the potential. It could be found that a large number of particles adhered to the surface of the substrate at 20 V since the high potential increased the thickness of the coating with the deposition amount, resulting in the aggregation of the silica sol. Therefore, the silica sol would be deposited on the substrate in a nonuniformly granular form. However, the coating was much denser and smoother at 15 V. 3.2.2. Effect of EPD Time on Steel Substrates. Figure 6 shows the effect of EPD time on coating properties under the condition of deposition at 15 V and sintering at 400 °C for 45 min. As shown in Figure 6a,b, the adhesive strength and hardness of the coating decreased distinctly when the EPD time reached over 40 s, mainly owing to the O2 produced by electrolysis during the EPD process, leading to the cracking, inhomogeneity, poor adhesion, and even peeling-off of the coating. Figure 6c shows that it had relatively high porosity when the EPD time was less than 40 s, whereas it tended to be stable with continuous deposition. Since some nanoparticles on the surface of the substrate could not be fully embedded in the surface of the Ni layer at the initial stage, they easily detached from the surface and formed pores after an ultrasonic bath. The EPD coating gradually becomes thicker along with the deposition, and the exfoliation of nonembedded nanoparticles does not result in the formation of pores connecting the coating to the substrate, thus decreasing the porosity significantly. It could be seen from Figure 6d that the silica coating obtained at 15 V for 40 s presented the best corrosion resistance; the edge effect would reduce the uniformity of the coating as well as adhesion after a longer EPD time. As

Figure 3. FT-IR spectra for (a) unsintered and (b) sintered SiO2 powders from silica sol.

O−H deformation bond, demonstrating the incorporation of water in the SiO2 network. The band at ∼973 cm−1 showed the presence of the Si−OH stretching bond, which was responsible for silica immersion. It disappeared after being sintered at 400 °C (Figure 3b), indicating that the Si−O−Si bond would be completely synthesized from Si−OH during the high-temperature sintering process. In addition, the bands at ∼2849 and ∼2920 cm−1 also disappeared after being sintered, which was mainly due to the removal of organics. A small band at 3459− 3630 cm−1 was attributed to stretching vibrations of OH− groups on the silica surface, which could be due to the formation of silica sol and the absorption of water molecules from atmospheric air because of its hygroscopic nature.45,46 Figure 4 shows the XRD patterns of silica sol powder unsintered and sintered at different temperatures. The XRD

Figure 4. XRD patterns of silica sol powder. Unsintered (a) and sintered at 400 °C (b), 500 °C (c), and 800 °C (d).

patterns showed a characteristic huge amorphous hump at ∼23° and confirmed with JCPDS file no. (79-1711).47 The effect of sintering temperature on grain growth resembled that of earlier studies.48 It also showed that the crystallization would be more obvious at higher temperatures. 3.2. Characterization of EPD Coatings. Ni composite coating with doped particles was introduced to provide good adhesion for steel substrates and SiO2 coating. On the other hand, the EPD coating could address the defects of Ni composite coating, such as porosity and corrosion resistance, to achieve desirable ceramic coating. The electrode reaction varied with the EPD potential, time, and other factors, which were investigated systematically. Adhesive strength, hardness, porosity, and impedance properties of EPD coatings were also studied in detail. 3.2.1. Effect of EPD Potential on Steel Substrates. Figure 5 shows the effect of the EPD potential on coating properties 24311


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Figure 5. Effect of the EPD potential on (a) adhesive strength, (b) hardness, (c) porosity, and (d) corrosion resistance of silica coating. Representative microscopic images at different EPD potentials are displayed in panel (e).

at 15 V for 40 s and sintered at different temperatures for 45 min. It could be seen that the impedance curves of three sintered samples were significantly higher than that of the unsintered one, indicating the shrinkage of pores in the sintered coating. The impedance curve of sintered specimens at 400 °C was obviously higher than those of the other ones, demonstrating that the EPD coating had the highest impedance with the best compactness after being sintered under this condition. It inhibited the infiltration of Cl− to a certain extent, and a better barrier layer was formed to protect the substrate from corrosion effectively. However, lower or higher temperature was not conducive to the compactness of the EPD coating, leading to larger porosity. In addition, the sintering time was also critical. The impedance curves of the samples sintered for 45 and 60 min were both higher than that for 30 min (Figure 7e), indicating that the EPD coating after a period of time delayed the corrosion rate, thereby improving the corrosion resistance of the substrate. However, the radius of the impedance spectrum under the condition of 45 min was the largest, showing excellent corrosion performance. The sintering process could not only enhance the compactness of the coating but also improve the adhesion and hardness, resulting in better corrosion resistance. In the circuit, Rs represents the solution impedance, Rct represents charge-transfer impedance of the electric double layer (EDL), and Rf is the faradaic impedance of the coating. The constant phase elements (CPEs) are introduced to replace

observed in Figure 6e, the coating surface obtained at other EPD times was worse than that at 40 s. The deposition amount of the coating increased with time and finally tended to be stable since the deposition process was a balanced process of deposition and shedding. As the EPD continued, the silica sol particles covered the surface of the anode and the relevant deposition current decreased. The EPD process reached equilibrium with the maximum deposition amount until 40 s. After that, the equilibrium would be broken. 3.2.3. Effect of Sintering Treatment on Steel Substrates. The structure of the coating porosity before and after sintering can be expressed as shown in Figure 7a,b. There exist mainly two kinds of pores, that is, opening holes and closed ones. The opening holes can be caused by the deficiency of the substrate and affect the corrosion resistance of the EPD coating, whereas the closed holes mostly affect its thickness and stress.40 As observed in Figure 7b, the coating becomes denser with lower porosity. To evaluate potential damages to the substrate by the sintering process applied to the coating, the EIS test was performed on specimens with silica coating undergoing different sintering temperatures and times. Besides, the impedance results could be well-fitted by the equivalent circuit model, as shown in Figure 7c. The sintering treatment applied to the EPD coating might affect the protective properties of the coating, promoting the coating to be more compact and stable. Figure 7d shows the Nyquist plots of EPD coatings deposited 24312


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Figure 6. Effect of EPD time on (a) adhesive strength, (b) hardness, (c) porosity, and (d) corrosion resistance of silica coating. Representative microscopic images for different EPD time are displayed in panel (e).

which has been described in detail in the literature (−1 < n < 1).52,53 The dispersive exponent n can be caused by a series of factors, such as the distribution of reaction rates and nonuniform current distribution. After the sintering process, the impedance of EPD coating Rf increased from 17.76 to 769 kΩ cm2, suggesting the increasing corrosion resistance. Such a high increment was attributed to the sintering process, which improved the compactness and uniformity of the coating. The active area of the coupled dissolution reaction decreased, making it difficult for the corrosive ions to reach the surface of the substrate. Consequently, the corrosion of the working electrode slowed down significantly. Besides, Rct of the EPD coating increased from 22.11 to 1973 Ω cm2, reflecting that the rate of charge-transfer reactions in the coating reduced dramatically. 3.3. Mechanical and Corrosion Behaviors of Coatings for EPD and Dipping. The tribological performance of the samples was measured on a wear testing machine, as shown in Figure 8a. The Ni-coated steel substrate was worn out and fell off quickly at 200 s with a high friction coefficient (FC) of 0.6. However, the dip-coating sample exhibited improved tribological performance with a much lower FC ∼ 0.42 and a much longer antiwear life (400 s). This may be ascribed to the dipcoated silica sol thin film that improved its hardness and abrasive resistance to some extent. However, the EPD sample was equipped with better hardness, exhibiting the lowest FC of 0.3 and maintaining the longest antiwear life (600 s) with nearly intact coating, which confirmed that the EPD coating

Figure 7. (a, b) Schematic diagram of the porosities of unsintered and sintered coating. (c) Equivalent circuits used for fitting the corresponding EIS system. (d, e) Nyquist plots of EPD coatings under different sintered temperatures and sintered times, respectively.

the capacitors, relating the roughness and nonuniform distribution of the electric field on the electrode surface.50,51 Impedance of CPE can be mathematically expressed by the following equation50 1 ZCPE = Y0(jw)n (9) 24313


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Figure 8. (a) Variation of the friction coefficient with time of the as-prepared samples at an applied load of 500 g. (b) Comparison of the as-prepared samples on hardness, immersion time until corrosion occurred in 3.5% NaCl solution, and wear resistance. (c, d) Corresponding potentiodynamic polarization curves and Nyquist plot.

had excellent tribological property and the EPD process could greatly decrease and stabilize the FC. Figure 8b shows that the EPD coating demonstrated the best wear resistance with 14.2 ± 0.3 mg mass loss. Moreover, the sintering process increased its hardness up to 122.3 ± 2.5 N mm−2 with enhanced mechanical properties by densifying the coating. It also exhibited enhanced salt-water corrosion resistance in 3.5% NaCl solution, with the longest immersion time for 304.7 ± 5.5 h until corrosion occurred. As shown in Figure 8c, the potentiodynamic polarization curves of Ni coating, dip-coating, and EPD coating had similar shapes in the given solution. It could be found that Ni coating presented the lowest Ecorr of −0.327 V, which increased to −0.263 and −0.219 V after being modified with dip-coating and EPD coating, respectively, indicating a corresponding decreasing corrosion tendency. Furthermore, the icorr of Ni coating was ∼1.04 × 10−3 A cm−2, which decreased to 1.72 × 10−5 and 1.02 × 10−7 A cm−2 when modified with dip-coating and EPD coating, respectively. The decrement of 2 orders of magnitude indicated superior corrosion resistance of Q235 steel modified with SiO2/Ni coating. The pronounced improvement above was due to the densification of the EPD coating after being sintered. On the other hand, the radius of the impedance spectrum of the EPD coating was the largest (Figure 8d), showing that the EPD coating-modified Q235 steel had the highest impedance among those three coatings. It could effectively slow down the electron transfer and inhibit the infiltration of the corrosive medium into the substrate, further improving the corrosion resistance. 3.4. Morphology. Figure 9 shows the morphologies and microstructures of different coatings on the dark Ni-modified Q235 steel substrate. It could be seen from Figure 9a that the coating obtained by the dipping process was loose and porous. Although it was improved after being sintered, there still existed large holes, as shown in Figure 9b, which was not good for improving corrosion resistance. During drying, the coating

Figure 9. (a, b) SEM images of unsintered and sintered dip-coating, respectively; (c, d) corresponding cross-section morphology and EDS spectra of dip-coating. (e, f) SEM images of unsintered and sintered EPD coating, respectively; (g, h) corresponding cross-section morphology and EDS spectra of EPD coating.

became brittle when stress concentrating on structural defects could not be released. Moreover, the surface tension of the liquid in the gel hole would further produce a great capillary 24314


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ACS Applied Materials & Interfaces contraction force at the gas−liquid interface during drying, resulting in the collapse of the gel network structure, destruction of the nanoporous structure, and even cracking and peeling-off.54,55 Figure 9c presents the cross-section morphology of dip-coating with ∼3 μm thickness, and the Ni content was more than 75% and Si was only 5.59%, as shown in the EDS diagram (Figure 9d). However, the EPD coating was much more compact with less holes after being sintered, demonstrating much better quality than that of dip-coating shown in Figure 9e−g. It appeared to have a much thicker coating of ∼6 μm, which was beneficial for mechanical and corrosion resistance. The EDS diagram in Figure 9h shows that the contents of Ni and Si were 10.95 and 37.47%, respectively, indicating good compactness of the EPD coating after being sintered, therefore contributing to better corrosion resistance. 3.5. IR and XRD Analysis of Coatings. The IR spectra of silica sol powder, dip-coating, and EPD coating are shown in Figure 10. An absorption peak that appeared at 1600−1650

Figure 11. XRD spectra of (a) silica sol powder, (b) dip-coating, and (c) EPD coating.

4. CONCLUSIONS Combing EPD and sintering process was proposed to prepare SiO2 coating on a dark Ni-coated Q235 steel substrate to solve the existing problems of ceramic films fabricated by the conventional sol−gel method. The EPD coating after sintering demonstrated excellent wear resistance with 14.2 ± 0.3 mg mass loss and increased hardness up to 122.3 ± 2.5 N mm−2, under the condition of deposition for 40 s at 15 V and sintering at 400 °C for 45 min. It also showed ∼6 μm thickness and a compact morphology. Excellent corrosion resistance was also observed, with the Rf and Rct increasing up to 769 kΩ cm2 and 1973 Ω cm2, respectively. The corresponding icorr was reduced down to 1.02 × 10−7 A cm−2. Moreover, it exhibited enhanced salt-water corrosion resistance in a 3.5% NaCl solution, with the longest immersion time of 304.7 ± 5.5 h until corrosion occurred. In summary, this two-step method could shorten the fabrication period of SiO2 inorganic coating to achieve thicker and denser ceramic coatings equipped with desirable and controllable properties, showing the potential for use in anticorrosion applications. We anticipate that this method can be used in broader applications for high-performance inorganic ceramic materials or the barrier layer as well as electret.

Figure 10. IR spectra of (a) silica sol powder, (b) dip-coating, and (c) EPD coating.

cm−1, as shown in Figure 10a,c, was the H−O−H stretching vibration characteristic of water, whereas no peak existed in this range in Figure 10b. The EPD coating was much thicker than that of dip-coating; therefore, the crystal water or absorbed water in the pores of the coating did not evaporate completely during the high-temperature sintering process. The peak at 3662 cm−1 shown in Figure 10c was attributed to H−OH stretching vibration and hydrogen bonding between hydroxyl groups. In addition, the Si−O bond was undamaged. It could be seen from Figure 10b,c that the peaks at 800 cm−1 and around 460 cm−1 were O−Si−O symmetrical and asymmetric stretching vibration, respectively, and the peak at 1000−1120 cm−1 was the asymmetric stretching vibration of Si−O−Si in different chemical environments. Figure 11 shows the XRD spectra of silica sol powder, dipcoating, and EPD coating. As observed, there existed an amorphous diffraction peak of SiO2 around the 24° region. Ni and Fe peaks also appeared on the spectra since Ni was applied as the adhesive layer and the EPD coating was not very thick, leading to the exposure of Fe and Ni elements during the XRD test. On the other hand, as an active metal in the substrate, Fe electrolysis occurred inevitably during the anodic EPD process, also resulting in the inclusion of Ni and Fe in the coating. Moreover, higher sintering temperature contributed to crystallization. As shown in Figure 11b, the peak of the dipcoating around 50° was much higher than that of EPD because of the loose and porous coating, as shown in Figure 9b.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]; [email protected]. Tel: +86 755 8658 5206. ORCID

Qi Zeng: 0000-0003-1448-4061 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This research was financially supported by Shenzhen Science and Technology Research Program (JCYJ20170818154035069, JCYJ20170818160050656) and Key Laboratory of Health Informatics Program of Chinese Academy of Sciences (2011DP173015).

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NOTE ADDED AFTER ASAP PUBLICATION This paper was published on the Web on June 28, 2019, with the incorrect affiliation designation for author Liqiong Chen. The corrected version was reposted on July 10, 2019.

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Enhanced Mechanical and Electrochemical Performances of Silica

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