Co-reporter:Aimin Liang, Yuwen Li, Hongyu Liang, Liwei Ni, Junyan Zhang
Materials Letters 2017 Volume 189() pp:221-224
Publication Date(Web):15 February 2017
DOI:10.1016/j.matlet.2016.12.022
•A favorable chromium coating electrodeposited from Cr(III) electrolyte.•The coating reveals anti-wear performance similar to conventional hard chromium.•The developing direction on thick Cr coating from Cr(III) electrolyte was elucidated.Decades of application has proved that electrodeposited chromium (Cr) coating is a perfect coating material. Unfortunately, almost all of these excellent coatings for anti-wear, i.e., hard Cr coatings, are produced by traditional electrodepositing process based on highly toxic Cr(VI). In this research, we reported a promising Cr coating embedded with graphite nanocrystals, which was electrodeposited from a Cr(III) electrolyte and reveals favorable anti-wear performance similar to that of conventional hard Cr coating in a range of sliding velocities. In addition, the developing direction of researches on electrodepositing thick Cr coating from Cr(III) electrolyte was elucidated via comparative investigation of the friction and wear behaviors of three typical Cr coatings.
Co-reporter:Youxin DuanFuping Pan, Qiao Liu, Yan Zhou, Aimin Liang, Junyan Zhang
The Journal of Physical Chemistry C 2017 Volume 121(Issue 2) pp:
Publication Date(Web):January 4, 2017
DOI:10.1021/acs.jpcc.6b11056
Self-assemly of block copolymers (BCPs) and phenolic resin (PR) is an important method to prepare ordered mesoporous polymers (OMPs) and carbon materials (OMCs). In the process, phase separation of the BCP–PR composite is a critical step which is, however, time-consuming in aqueous solution. Here we report, for the first time, a new salt-induced phase separation strategy to achieve this goal. Triblock copolymer F127 and phenol-formaldehyde resin (PF) are used as the template and precursor, respectively, and sodium chloride (NaCl) is applied to induce the coagulation and phase separation of the F127–PF composite which is transformed to be OMC at high temperature. It is found that the maintenance of the ordered mesostructure is highly dependent on the pH of the F127–PF solution under NaCl interference. A hypothetical mechanism is proposed to explain the role of pH in the formation of ordered mesostructure when salt is introduced into the self-assembly system. The effects of pH, salt concentration, and varied salts on the structures and properties of the as-prepared OMCs are investigated in detail. The new salt-induced phase separation strategy can synthesize OMC facilely and can provide a new insight into understanding the process of preparing ordered mesoporous materials by self-assembly more deeply.
Co-reporter:Bin Zhang;Yong Xue;Li Qiang;Kaixong Gao;Qiao Liu;Baoping Yang
Applied Nanoscience 2017 Volume 7( Issue 8) pp:835-842
Publication Date(Web):30 October 2017
DOI:10.1007/s13204-017-0622-7
Friction properties of carbon nanotubes have been widely studied and reported, however, the friction properties of carbon nanotubes related on state of itself. It is showing superlubricity under nanoscale, but indicates high shear adhesion as aligned carbon nanotube film. However, friction properties under high load (which is commonly in industry) of carbon nanotube films are seldom reported. In this paper, carbon nanotube films, via mechanical rubbing method, were obtained and its tribology properties were investigated at high load of 5 to 15 N. Though different couple pairs were employed, the friction coefficients of carbon nanotube films are nearly the same. Compared with bare stainless steel, friction coefficients and wear rates under carbon nanotube films lubrication reduced to, at least, 1/5 and 1/(4.3–14.5), respectively. Friction test as well as structure study were carried out to reveal the mechanism of the significant reduction wear and friction on steel surface. One can conclude that sliding and densifying of carbon nanotubes at sliding interface contribute to the sufficient decrease of friction coefficients and wear rates.
Co-reporter:Yan Wang, Xiao Ling, Yongfu Wang, Jun Zhao, Junyan Zhang
Tribology International 2017 Volume 115(Volume 115) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.triboint.2017.06.033
•Fullerene-like hydrogenated carbon films were deposited on Si substrates, steel and Si3N4 balls.•Depositing the structural films on steel and Si3N4 counterbodies is an effective way to achieve lower friction in humid air.•The tribological difference can probably be explained by the changes of these films' structures and mechanical properties.Fullerene-like hydrogenated carbon (FL-C:H) films were prepared on Si substrates, steel and Si3N4 balls by plasma enhanced chemical vapor deposition with methane gas. The frictional behaviors of steel/FL-C:H, Si3N4/FL-C:H, F-steel/FL-C:H and F-Si3N4/FL-C:H couples were investigated and their worn surfaces were analyzed by scanning electron microscopy (SEM) and 3D surface profiles. The results showed that the F-steel/FL-C:H and F-Si3N4/FL-C:H couples had lower friction and wear than the steel/FL-C:H and Si3N4/FL-C:H ones, respectively. The tribological differences are due to the change of microstructures and accordingly mechanical properties for FL-C:H films on a Si substrate, steel and Si3N4 balls.
Co-reporter:Xingkai Zhang, Yan Zhou, Junyan Zhang
Progress in Natural Science: Materials International 2017 Volume 27, Issue 3(Volume 27, Issue 3) pp:
Publication Date(Web):1 June 2017
DOI:10.1016/j.pnsc.2017.04.016
A simple and feasible method was developed to fabricate in-situ reduced graphene oxide-polyvinyl alcohol composite (GO-PVA) coatings as protective layers on magnesium substrates. Polyvinyl alcohol was used as an in-situ reductant to transform GO into reduced GO. Contiguous and uniform GO-PVA coatings were prepared on magnesium substrates by dip-coating method, and were further thermally treated at 120 °C under ambient condition to obtain in-situ reduced GO-PVA coatings. Owing to the reducing effect of PVA, thermal treatment at low temperature led to effective in-situ reduction of GO as confirmed by XRD, Raman, FTIR and XPS tests. The corrosion current density of magnesium substrates in 3.5 wt% NaCl solution could be lowered to its 1/25 when using in-situ reduced GO-PVA coatings as protective layers.
Co-reporter:Xingkai Zhang, Yan Zhou, Bin Zhang, Junyan Zhang
Materials Letters 2017 Volume 197(Volume 197) pp:
Publication Date(Web):15 June 2017
DOI:10.1016/j.matlet.2017.03.119
•An improved galvanic replacement deposition method was developed.•Continuous and compact Pd coatings were prepared on copper by the above method.•The coupled Al foils donated electrons for the deposition of Pd instead of copper.•The annealed Pd coatings showed denser structure and better protective property.Although copper has a lower redox potential than palladium, it is hard to prepare compact and uniform palladium coatings on copper substrates via galvanic replacement reactions. In this work, an improved galvanic replacement method was developed to achieve facile synthesis of compact palladium coatings on copper substrates in the presence of coupled aluminum foils. The aluminum foils played an important role in donating electrons for palladium deposition instead of copper substrates. The SEM, EDS and XRD results revealed the deposited coatings showed homogeneous surface morphology and were composed of pure palladium. The obtained palladium coatings had good oxidation resistance, and could maintain the silver-white appearance after annealed at 200 °C for 10 min. The palladium coatings became denser owing to the sintering effect of thermal treatment, and therefore possessed lower corrosion current density in 3.5 wt% NaCl solution in the electrochemical experiments.
Co-reporter:Fuping Pan, Youxin Duan, Aimin Liang, Junyan Zhang, Ying Li
Electrochimica Acta 2017 Volume 238(Volume 238) pp:
Publication Date(Web):1 June 2017
DOI:10.1016/j.electacta.2017.04.044
Effective integration of hierarchically porous architecture and high-density distribution of dopant sites into carbon is essential to improve the activity of heteroatom-doped carbon for oxygen reduction reaction (ORR). Herein, we present a general sealed space-assisted approach to fabricate N,P-codoped porous carbon networks (NP-PCN) by calcination of a self-assembled mixture of C6H14N2O2, NH4H2PO4, and NaCl. The NaCl assemblies serve as a space-enclosed nanoreactor for the effective formation of hierarchical pores with high surface area and dense N,P-induced dopants by preventing the loss of N,P-containing gasses from the decomposition of precursors during annealing. The NP-PCN is applied as an ORR catalyst and exhibits excellent performance with a positive half-wave potential of 0.82 V vs. RHE, a low Tafel slope of 59 mV dec−1, high tolerance to methanol, and high durability in alkaline media, making NP-PCN a promising alternative to costly platinum for the ORR. The enhanced performance is attributed to the combination of hierarchical pores and optimized N,P codoping, which significantly enhances the available number of catalytic sites by exposing the N,P-induced dopants and facilitates mass transfer in the ORR process. This finding opens a new avenue for the design of advanced porous carbons to improve their electrocatalytic activity.Download high-res image (187KB)Download full-size image
Co-reporter:Yan Wang, Xiao Ling, Yongfu Wang, Junyan Zhang
Diamond and Related Materials 2017 Volume 79(Volume 79) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.diamond.2017.08.015
•Fullerene-like hydrogenated carbon film is deposited from CH4 and CF4/N2 gas.•N atoms promote the formation of more cross-linked FL structure.•F atoms destroy FL continuous network structure by terminating sp2 bond linking state.•The N-6 film exhibits 18.6 GPa hardness, 83% elasticity and a super-smooth surface.Richer fullerene-like (FL) structure interface layers with sp2‑carbon rich are observed in the sliding contacts of ultra-low friction fullerene-like hydrogenated carbon (FL-C:H) films, which can offer a new design possibility to further optimize these films' tribological performances by element doping such as hydrogen, fluorine and nitrogen. In this paper, we provide an understanding about the structure-performance relationship such as the effects of FL structures and incorporated elements such as fluorine and nitrogen. Meanwhile, the detailed structure, mechanical and frictional behaviors and surface properties of the doped films have been investigated. The results indicate that N atoms promote the formation of more cross-linked FL structure, while F atoms terminate sp2 bond linking state of curved graphitic similar to hydrogen, and thus destroy the FL continuous network structure. Moreover, the N-6 FL-C:H film exhibits higher hardness (~ 18.6 GPa), better elasticity recovery (~ 83%) and a very smooth morphology (rms ~ 0.242 nm), lower friction (0.017) and wear (1.25 × 10− 9 mm3/Nm).Download high-res image (211KB)Download full-size image
Co-reporter:Zhenbin Gong, Xiaolong Jia, Wei Ma, Bin Zhang, Junyan Zhang
Applied Surface Science 2017 Volume 413(Volume 413) pp:
Publication Date(Web):15 August 2017
DOI:10.1016/j.apsusc.2017.04.057
•Graphitic-like/MoS2 films with hierarchical structure were synthesized by PECVD plus magnetron sputtering under heating conditions.•Macro-scale superlubricity can be achieved by GL/MoS2-600 under higher normal load, high speed in the atmosphere.•The GL/MoS2 films could match the requirements of large scale, high bear-capacity and wear-resistance of actual working conditions.Friction and wear result in a great amount of energy loss and the invalidation of mechanical parts, thus it is necessary to minimize friction in practical application. In this study, the graphitic-like/MoS2 films with hierarchical structure were synthesized by the combination of pulse current plasma chemical-vapor deposition and medium frequency unbalanced magnetron sputtering in preheated environment. This hierarchical structure composite with multilayer nano sheets endows the films excellent tribological performance, which easily achieves macro superlubricity (friction coefficient ∼0.004) under humid air. Furthermore, it is expected that hierarchical structure of graphitic-like/MoS2 films could match the requirements of large scale, high bear-capacity and wear-resistance of actual working conditions, which could be widely used in the industrial production as a promising superlubricity material.
Co-reporter:Yongfu Wang, Yan Wang, Xingkai Zhang, Jing Shi, Kaixiong Gao, Bin Zhang, Junyan Zhang
Applied Surface Science 2017 Volume 420(Volume 420) pp:
Publication Date(Web):31 October 2017
DOI:10.1016/j.apsusc.2017.05.169
•The steel ball-film structure transformed from graphite-like to fullerene-like structure.•The Si substrate-film structure began in FL structure and kept it through the thickness.•The FL structural film friction couples could achieve ultra-low friction in open air.•The 3 h/Si-3 h/Fe ball couple exhibited super-low friction (0.009) and wear life (5.5 × 105 cycles).In this study, we prepared hydrogenated amorphous carbon films on steel balls and Si substrates (steel ball- and Si substrate-films) with different deposition time, and discussed their carbon nanostructural evolutions and tribological behaviors. The steel ball-film structure started to be graphite-like structure and then gradually transformed into fullerene-like (FL) structure. The Si substrate-film structure began in FL structure and kept it through the thickness. The difference may be result from the competition between high starting substrate temperature after additional nitriding applied on the steel balls (its supply power is higher than that in the film deposition), and relaxation of compressive stress from energized ion bombardment in film deposition process. The FL structural film friction couples could achieve ultra-low friction in open air. In particular, the Si substrate-film with 3 h, against the steel ball-film with 2 h and 3 h, exhibited super-low friction (∼0.009) and superlong wear life (∼5.5 × 105 cycles). Our result could widen the superlubricity scope from previously high load and velocity, to middle load and velocity.Download high-res image (257KB)Download full-size image
Co-reporter:Zhenbin Gong;Jing Shi;Wei Ma;Bin Zhang
RSC Advances (2011-Present) 2017 vol. 7(Issue 6) pp:3506-3506
Publication Date(Web):2017/01/04
DOI:10.1039/C6RA90137A
Correction for ‘Engineering-scale superlubricity of the fingerprint-like carbon films based on high power pulsed plasma enhanced chemical vapor deposition’ by Zhenbin Gong et al., RSC Adv., 2016, 6, 115092–115100.
Co-reporter:Fuping Pan;Aimin Liang;Youxin Duan;Qiao Liu;Ying Li
Journal of Materials Chemistry A 2017 vol. 5(Issue 25) pp:13104-13111
Publication Date(Web):2017/06/27
DOI:10.1039/C7TA03005C
Although mesopore designs are expected to play a key role in exploring electrocatalytic properties of carbons, facile preparation of mesoporous carbons (MPCs) with efficient dopants to enable high performance remains a great challenge. Herein, we for the first time introduce a self-growth-templating concept for the fabrication of three-dimensional (3D) N,P,Co-doped MPC frameworks, simply through pyrolysis of vitamin B12 in NaCl assembly-enclosed nanoreactors. The route realizes the controllable formation of mesoporous templates and elimination of the templates, as well as in situ doping of N, P, and Co into MPCs in a one-step enclosed-space-assisted pyrolysis process. The highly mesoporous architecture not only enhances mass transportation but also provides the 3D electrocatalytic surface to expose highly active N,P,Co-induced dopants. These features endow MPCs with excellent activity as bifunctional electrocatalysts in oxygen reduction (E1/2 of 0.85 V, JK of 51 mA cm−2 at −0.71 V and Tafel slope of 53 mV dec−1) and CO2 reduction reactions (overpotential of −0.19 V, maximum FE of 62% for CO and Tafel slope of 129 mV dec−1), coupled with high electrochemical stability in aqueous electrolytes. We expect that the self-constructing vision can afford useful insights to guide the development of other advanced mesoporous materials other than carbon for broad applications.
Co-reporter:Jing Shi;Yongfu Wang;Zhenbin Gong;Bin Zhang;Chengbing Wang
Advanced Materials Interfaces 2017 Volume 4(Issue 8) pp:
Publication Date(Web):2017/04/01
DOI:10.1002/admi.201601113
High performance solid lubricant materials with long wear life remain as one of the challenges in space technology. It is of great significance to lower the solid film's friction and wear and to prolong its service life in vacuum. Hydrogenated fullerene-like carbon film produced by dc-pulsed power source behaves ultralong wear life (≫1.8 × 105 cycles) and ultralow wear rate (2.2 × 10−8 mm3 Nm−1) as well as low friction (≈0.14) in high vacuum (2.3 × 10−4 Pa). To understand its long wear life reason, the interfacial structural evolution is investigated after steady state friction is achieved. By observing the interfacial nanostructure evolution, it is found that the friction and wear properties are related to the friction-induced phase transformation from fullerene like structure to nanocrystalline graphite and the deposition of tribofilm on Al2O3 counterface. And this process is analyzed by X-ray photoelectron spectroscopy, micro-Raman spectra and is observed through transmission electron microscopy. The results enrich hydrogenated fullerene-like carbon film friction mechanisms and expand its potential application in space.
Co-reporter:Jing Shi, Zhenbin Gong, Chengbing Wang, Bin Zhang, Junyan Zhang
Diamond and Related Materials 2017 Volume 77(Volume 77) pp:
Publication Date(Web):1 August 2017
DOI:10.1016/j.diamond.2017.06.005
•Tribological properties of a-C:H films in vacuum, air, dry nitrogen, argon and oxygen atmospheres were investigated.•Superlubricity was achieved for self-mated a-C:H film counterparts in dry nitrogen atmosphere.•Synergistic effect of electrostatic repulsion and tribofilm of a-C:H film friction was discussed to disclose the superlubricity mechanism.In this study, hydrogenated amorphous carbon (a-C:H) films prepared by plasma enhanced chemical vapor deposition had distinguishing tribology behaviors in dry nitrogen, oxygen, argon, humid air and vacuum. Both the friction and wear rates of a-C:H films sliding against Al2O3 in nitrogen and argon were lower than that in oxygen and humid air atmospheres. And superlubricity (0.009) was achieved in dry nitrogen atmosphere for self-mated a-C:H counterpart. From the viewpoint of various gas molecules' adsorption, the a-C:H films' friction behavior was investigated. Micro-Raman and scanning electron microscope (SEM) were employed to study the interfacial structural evolution and tribofilm distribution in different atmospheres. X-ray photoelectron spectroscopy (XPS) was used to reveal the relation between wear rate and tribo-oxidation reaction in various atmospheres. We confirmed that nitrogen molecule provided repulsion force at sliding interface and reduced friction of a-C:H film. Meantime, graphitic tribofilm also played a significant role. It was stated that electronic repulsion force aroused by adsorption was enough for ultra-low friction, while the presence of graphitic tribofilm had synergetic effect with it in achieving superlubricity. This study provided considerations and discussions about interfacial electronic character's effect on friction behaviors of carbon based film.Download high-res image (277KB)Download full-size image
Co-reporter:Guangqiao Liu, Yan Zhou, Bin Zhang, Kaixiong Gao, Li Qiang and Junyan Zhang
RSC Advances 2016 vol. 6(Issue 64) pp:59039-59044
Publication Date(Web):13 Jun 2016
DOI:10.1039/C6RA10961F
The fullerene-like (FL) nanostructure is extremely important for fullerene-like hydrogenated carbon (FL-C:H) films that exhibit excellent mechanical properties and ultralow friction in ambient air, but the details of the contributing nanostructures are not well understood. We have prepared FL-C:H films with different morphologies and contents of FL nanostructures through tailoring the pulse bias duty cycle, and have investigated the contribution of the FL nanostructures. It is found that the straighter graphitic nanostructures in FL-C:H films could form under a high pulse bias duty cycle, and the low pulse bias duty cycle could increase the five-membered ring fractions, which results in more curved FL nanostructures with a larger curvature radius. Further investigation proved that the FL nanostructures with the more curved morphology could increase the mechanical properties and improve the tribological performance of the FL-C:H films. This work established a convenient controlling method to prepare FL-C:H films with tailored structures and performance.
Co-reporter:Xingkai Zhang and Junyan Zhang
RSC Advances 2016 vol. 6(Issue 36) pp:30695-30698
Publication Date(Web):11 Mar 2016
DOI:10.1039/C6RA01435F
A facile electroless plating strategy to obtain nickel coatings on copper substrates was designed to simplify the plating baths and procedure. The plating baths contained only nickel sulfate and ammonia. The aluminium connected to the copper substrates served as the electron source for nickel deposition. The nickel coatings obtained via this approach were tested and proved to possess excellent anticorrosion behavior.
Co-reporter:Junmeng Guo, Yongfu Wang, Hongyu Liang, Aimin Liang, Junyan Zhang
Applied Surface Science 2016 Volume 364() pp:288-293
Publication Date(Web):28 February 2016
DOI:10.1016/j.apsusc.2015.12.090
Highlights
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We prepared hydrogenated carbon films with different content of the fullerene-like nanostructure.
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There is a linear relationship between the fullerene-like content and the mechanical properties, tribological behavior of as-deposited FL-C:H films.
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New fullerene-like nanostructure may serve as a self-lubrication without addition of any other lubricant during the friction process.
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New fullerene-like nanostructure may originate from the rapid annealing and stress relaxation during friction process.
Co-reporter:Xingkai Zhang, Yan Zhou, Aimin Liang, Bin Zhang, Junyan Zhang
Surface and Coatings Technology 2016 Volume 304() pp:519-524
Publication Date(Web):25 October 2016
DOI:10.1016/j.surfcoat.2016.07.071
•Electroless iron plating was achieved from the reducing agent-free bath.•The coupled aluminum could shift the potential of substrates negatively and serve as the electron source for iron deposition.•Fe-rGO coatings were obtained from the reducing agent-free bath adding GO.•Fe-rGO coatings had the smaller nodule size and denser structure, and therefore enhanced corrosion resistance.Inspired by its role in inducing electroless iron plating, aluminum was used to prepare iron coatings on copper substrates from the simple plating bath containing no reducing agents. The electrochemical investigation indicated that the coupled aluminum could shift the potential of copper substrates to an enough negative value to initiate iron plating in the alkaline plating bath and serve as the electron source for continuous deposition of iron. To improve the corrosion resistance of the iron coatings, graphene oxide (GO) was added in the former plating bath and the iron-reduced graphene oxide (Fe-rGO) composite coatings could be successfully obtained. Compared with the iron coatings, the Fe-rGO coatings exhibited smaller nodule size and denser structure as revealed by scanning electron microscope and X-ray diffraction results. Hence, Fe-rGO coatings demonstrated significant improvement in the corrosion resistance with increasing in open circuit potential (OCP) and reducing in corrosion current density.
Co-reporter:Dr. Fuping Pan;Youxin Duan;Dr. Xinkai Zhang; Junyan Zhang
ChemCatChem 2016 Volume 8( Issue 1) pp:163-170
Publication Date(Web):
DOI:10.1002/cctc.201500893
Abstract
The design and fabrication of oxygen reduction reaction (ORR) electrocatalysts with high performance at low cost remains a big challenge but is crucial for the commercialization of fuel cells. Here, we report a simple and economical method for the direct mass production of nitrogen/sulfur co-doped graphene (NS-G) by using cysteine as single precursor and self-assembled NaCl as a structure-directing template through the solid-phase pyrolysis method. The resultant NS-G possesses a high specific surface area of 435.13 m2 g−1, effective N (1.85 at %) and S (0.99 at %) dual doping and enhanced conductivity, which contribute largely to the exposure of highly active sites and to the promotion of electron transport in the ORR process. Accordingly, the NS-G exhibits excellent ORR performance with a positive half-wave potential of 0.768 V (versus reversible hydrogen electrode), four-electron pathway, low Tafel slope of 60 mV dec−1, and high stability in alkaline medium. These merits make NS-G a promising alternative to costly Pt for ORR.
Co-reporter:Hongyu Liang, Yongfeng Bu, Yutian Zhang, Junyan Zhang
Journal of Colloid and Interface Science 2015 Volume 444() pp:109-114
Publication Date(Web):15 April 2015
DOI:10.1016/j.jcis.2014.12.063
Graphene oxide (GO) was investigated as a low-cost and high-efficient scavenger for high-concentration formaldehyde in alkali media. It showed very high removal capacity, 411 mg of formaldehyde per milligram of GO, and strong resistant to temperature changes. Additionally, the used GO can be easily renewed by a simple electrochemical method. By analyzing the componential and electrochemical characterizations of GO before and after use, the results showed that the degradation mechanism of formaldehyde is a collaborative process of chemical oxidation and physical adsorption, and the former dominates the degradation process. With the aid of oxygen-containing groups in GO, most formaldehyde can be easily oxidized by GO in alkaline media (this is equivalent to GO was reduced by formaldehyde). On the other hand, the used GO (reduced GO, noted as rGO) exhibits more ideal electronic double-layer capacitor (EDLC) feature than GO, along with higher rate capacitance (up to 136 F g−1 at 50 A g−1). In short, GO is not only an efficient formaldehyde scavenger, but the used GO (rGO) can serve as promising electrical energy storage material. This study provides new insights for us to reutilize the discarded adsorbents generated from the environmental protection.
Co-reporter:Jia Wang, Zhongyue Cao, Fuping Pan, Fuguo Wang, Aimin Liang, Junyan Zhang
Applied Surface Science 2015 Volume 356() pp:695-700
Publication Date(Web):30 November 2015
DOI:10.1016/j.apsusc.2015.08.091
Highlights
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a-C:H films deposited by high frequency unipolar pulse PECVD.
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The film structures can be adjusted by bias voltage.
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More graphitic structures form at high bias voltage.
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The mechanical and tribological properties are improved by these structures.
Co-reporter:Li Qiang, Kaixiong Gao, Lifang Zhang, Jian Wang, Bin Zhang, Junyan Zhang
Applied Surface Science 2015 Volume 353() pp:522-529
Publication Date(Web):30 October 2015
DOI:10.1016/j.apsusc.2015.06.040
Highlights
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W and Ti atoms were introduced successfully into the film together by co-sputtering W/Ti twin-target.
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Introduction of W atom significantly enhanced the hardness and retained the low internal stress.
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The friction and wear resistance could be further improved significantly by W incorporating.
Co-reporter:Yongfu Wang, Junmeng Guo, Junyan Zhang and Yong Qin
RSC Advances 2015 vol. 5(Issue 129) pp:106476-106484
Publication Date(Web):01 Dec 2015
DOI:10.1039/C5RA20892K
Hitherto, among carbon-based thin films, fullerene-like hydrogenated carbon (FL-C:H) films exhibit unique ultralow friction and wear in open or humid air, but the mechanisms responsible for the friction regime are still not clear. Here, we provide definitive experimental evidences obtained from the wear tracks and debris of FL-C:H films, and show that FL-C:H films’ surface undergoes gradual transformation into a richer and more stable fullerene-like nanostructure, due to the increasing content of pentagonal and heptagonal carbon rings in addition to the six-membered graphene rings, as a result of thermal and strain effects from the repeated friction. The sliding-induced in situ promotion of the FL structures at frictional contact leads to ultralow friction and wear in open air. The results establish an excellent low friction and wear regime for the structural film, and develop the lubrication mechanisms of carbon-based films.
Co-reporter:Hongyu Liang, Yongfeng Bu, Yan Zhou, Yongfu Wang and Junyan Zhang
RSC Advances 2015 vol. 5(Issue 29) pp:22305-22309
Publication Date(Web):19 Feb 2015
DOI:10.1039/C5RA01400J
To meet the lubrication demands of future MEMS/NEMS, thickness-controllable carbon films have been successfully prepared directly on silicon substrates by carbonizing electrophoresis-deposited trichloroacetic acid (TCA) molecular films. Compared with easily worn-out TCA molecular films, the transformed carbon films exhibit ultra-low friction coefficients and wear rates, along with strong adhesion to silicon substrates. These results prove that the idea of transforming organic molecular films into carbon thin films is a unique and promising approach to fabricate thickness-controllable and wear-resistant carbon-based solid lubricants for MEMS/NEMS.
Co-reporter:Lifang Zhang, Fuguo Wang, Li Qiang, Kaixiong Gao, Bin Zhang and Junyan Zhang
RSC Advances 2015 vol. 5(Issue 13) pp:9635-9649
Publication Date(Web):23 Dec 2014
DOI:10.1039/C4RA14078H
Fluorine easily substitutes hydrogen in DLC films due to its monovalence and high electronegativity. The peculiarities of fluorine bestow low surface energy, low inner stress, good thermal stability, preeminent tribological properties and biocompatibility on fluorine-containing, diamond-like carbon (F-DLC) films. Although there are some reviews that introduce the important advances in DLC films, they are not particularly focused on the promising F-DLC films. In this review, we mainly concentrate on the mechanical and tribological properties of F-DLC films. The mechanical properties, including hardness, modulus, and inner stress, will be discussed thoroughly. More importantly, the eminent tribological properties of F-DLC films would be emphasized based on the surface passivation and repulsive forces induced by fluorine atoms from the surface chemical and micro-mechanical viewpoints. Finally, some existing challenges and promising breakthroughs about F-DLC films are also proposed. It is expected that these films would be produced on a large scale and applied extensively in industrial applications such as micro-electro-mechanical systems, ultra-large scale integrated circuits, thin film transistor liquid crystal displays and biomedical devices.
Co-reporter:Hongyu Liang, Yongfeng Bu, Jianning Ding and Junyan Zhang
RSC Advances 2015 vol. 5(Issue 50) pp:39884-39888
Publication Date(Web):16 Apr 2015
DOI:10.1039/C5RA03900B
This research presents a general electrophoretic deposition (EPD) method, which offers selective preparation of various heteroatom-containing (i.e., H, Cl, F, N, and S) carboxylic acid molecular (CAM) films directly on silicon wafers, as long as the precursors are water-soluble carboxylic acids. Among them, the as-prepared fluoro-carboxylic acid (trifluoroacetic acid) molecular film with controllable thickness exhibits a longer wear life than self-assembled monolayers (SAMs), along with very low friction coefficient and a superior tolerance to humidity. It may be a promising candidate to replace SAMs as a more wear-resistant solid lubricant in micro/nano electromechanical systems (MEMS/NEMS).
Co-reporter:Dr. Fuping Pan;Dr. Qiuping Zhao;Dr. Jia Wang; Junyan Zhang
ChemElectroChem 2015 Volume 2( Issue 12) pp:2032-2040
Publication Date(Web):
DOI:10.1002/celc.201500301
Abstract
Advanced Fe–N-doped graphene (FeNG) electrocatalysts are developed for the oxygen reduction reaction (ORR) by annealing a mixture of sustainable and low-cost corn starch, urea, and FeCl3. The Fe–N coordinations and Fe/Fe3C nanoparticles can be controllably achieved through space confinement and pyrolysis temperature-induced effects, respectively. Electrochemical tests show that, compared to the commercial Pt/C catalyst, the ORR half-wave potential of FeNG is 99 mV more positive in KOH and 34 mV more negative in H2SO4, with higher stabilities in both media. More importantly, the ORR mechanisms of FeNG are demonstrated to be diverse in both KOH and H2SO4, owing to the various catalytic centers. The obtained results indicate that the enhanced ORR activity in basic media can mainly be ascribed to quaternary N and Fe/Fe3C sites, whereas the ORR performance in acidic media originates primarily from Fe–NX complexes. The electrocatalytic origin of these species is governed, primarily, by their unique electronic structures and specific environments in different pH solutions.
Co-reporter:Xiaogang Fu, Jutao Jin, Yanru Liu, Zhiyang Wei, Fuping Pan, and Junyan Zhang
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 6) pp:3930
Publication Date(Web):March 5, 2014
DOI:10.1021/am405130w
The large-scale synthesis of nitrogen doped graphene (N-graphene) with high oxygen reduction reaction (ORR) performance has received a lot of attention recently. In this work, we have developed a facile and economical procedure for mass production of edge-nitrogen-rich graphene nanoplatelets (ENR-GNPs) by a combined process of ball milling of graphite powder (GP) in the presence of melamine and subsequent heat treatment. It is found that the ball milling process can not only crack and exfoliate pristine GP into edge-expanded nanoplatelets but also mechanically activate GP to generate appropriate locations for N-doping. Analysis results indicate that the doped N atoms mainly locate on the edge of the graphitic matrix, which contains ca. 3.1 at.% nitrogen content and can be well-dispersed in aqueous to form multilayer nanoplatelets. The as-prepared ENR-GNPs electrocatalyst exhibits highly electrocatalytic activity for ORR due to the synergetic effects of edge-N-doping and nanosized platelets. Besides, the stability and methanol tolerance of ENR-GNPs are superior to that of the commercial Pt/C catalyst, which makes the nanoplatelets a promising candidate for fuel cell cathode catalysts. The present approach opens up the possibility for simple and mass production of N-graphene based electrocatalysts in practice.Keywords: Ball milling; edge-nitrogen-rich graphene; electrocatalyst; fuel cell; oxygen reduction reaction;
Co-reporter:Yongfu Wang, Junmeng Guo, Kaixiong Gao, Bin Zhang, Aimin Liang, Junyan Zhang
Carbon 2014 Volume 77() pp:518-524
Publication Date(Web):October 2014
DOI:10.1016/j.carbon.2014.05.057
Fullerene-like hydrogenated carbon (FL-C:H) films that exhibit ultra-low friction and wear in humid conditions have been the subject of extensive researches, but the structure–performance relationship such as the evolution of FL structures under friction is not well understood. We have prepared FL-C:H films with different FL content, and have addressed a detailed investigation on the relationship. It is found that with the increase in FL content, the friction and wear of FL-C:H films can reach as low as 0.011 and 1.48 × 10−8 mm3/Nm, respectively. Examination of the corresponding wear tracks by Raman spectroscopy reveals that not graphitization but friction-induced promotion of FL structures causes the ultra-low friction and wear of FL-C:H films. We therefore claim that FL structures are in close positive relations with the excellent tribological performance of FL-C:H films.
Co-reporter:Li Chen, Baoping Yang and Junyan Zhang
RSC Advances 2014 vol. 4(Issue 10) pp:5213-5219
Publication Date(Web):11 Dec 2013
DOI:10.1039/C3RA45690K
A mixed film composed of crown-type molecule hexachlorotribenzotriquinacene (HCTQ) and 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane (TA), together with their single-component films, were formed on hydroxylated silicon substrates by self-assembly. The formation and surface properties of the films were characterized by means of ellipsometry, contact angle measurement, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectrometry, multi-functional X-ray photoelectron spectra (XPS), and atomic force microscopy (AFM). The nano- and micro-tribological behavior of the films was evaluated by AFM and ball-on-plate tribometer, respectively. The results show that the mixed film exhibits enhanced nano- and micro-tribological properties as compared to the single-component films. This is attributed to the synergic effect between the load-carrying capacity of the crown-type molecule and the friction-reducing contribution of the straight chain molecule. The multiple functional groups and rigid aromatic backbone in the crown-type molecule enhance the stability and the anti-wear property of the mixed film, while the flexible alkylsilane serves as lubricant for reducing the friction. In addition, the two-step assembly of the crown-type molecule and alkylsilane can form more densely packed and ordered mixed film, which is beneficial to improving the durability and anti-wear property.
Co-reporter:Jutao Jin, Fuping Pan, Luhua Jiang, Xiaogang Fu, Aiming Liang, Zhiyang Wei, Junyan Zhang, and Gongquan Sun
ACS Nano 2014 Volume 8(Issue 4) pp:3313
Publication Date(Web):March 6, 2014
DOI:10.1021/nn404927n
Two-dimensional materials based on ternary system of B, C and N are useful ranging from electric devices to catalysis. The bonding arrangement within these BCN nanosheets largely determines their electronic structure and thus chemical and (or) physical properties, yet it remains a challenge to manipulate their bond structures in a convenient and controlled manner. Recently, we developed a synthetic protocol for the synthesis of crumpled BCN nanosheets with tunable B and N bond structure using urea, boric acid and polyethylene glycol (PEG) as precursors. By carefully selecting the synthesis condition, we can tune the structure of BCN sheets from s-BCN with B and N bond together to h-BCN with B and N homogenously dispersed in BCN sheets. Detailed experiments suggest that the final bond structure of B and N in graphene depends on the preferentially doped N structure in BCN nanosheets. When N substituted the in-plane carbon atom with all its electrons configured into the π electron system of graphene, it facilitates the formation of h-BCN with B and N in separated state. On the contrary, when nitrogen substituted the edge-plane carbon with the nitrogen dopant surrounded with the lone electron pairs, it benefits for the formation of B–N structure. Specially, the compound riched with h-BCN shows excellent ORR performance in alkaline solution due to the synergistic effect between B and N, while s-BCN dominant BCN shows graphite-like activity for ORR, suggesting the intrinsic properties differences of BCN nanosheets with different dopants bond arrangement.Keywords: BCN sheet; catalyst-free; oxygen reduction reaction; tunable bond structure
Co-reporter:Qiao Liu, Youxin Duan, Qiuping Zhao, Fuping Pan, Bin Zhang, and Junyan Zhang
Langmuir 2014 Volume 30(Issue 27) pp:8238-8245
Publication Date(Web):2017-2-22
DOI:10.1021/la404995y
Graphene-like nitrogen-doped carbon nanosheets (NCN) have become a fascinating carbon-based material for advanced energy storage and conversion devices, but its easy, cheap, and environmentally friendly synthesis is still a grand challenge. Herein we directly synthesized porous NCN material via the facile pyrolysis of chitosan and urea without the requirement of any catalyst or post-treatment. As-prepared material exhibits a very large BET surface area of ∼1510 m2 g–1 and a high ratio of graphitic/pyridinic nitrogen structure (2.69 at. % graphitic N and 1.20 at. % pyridinic N). Moreover, compared to a commercial Pt/C catalyst, NCN displays excellent electrocatalytic activity, better long-term stability, and methanol tolerance ability toward the oxygen reduction reaction, indicating a promising metal-free alternative to Pt-based cathode catalysts in alkaline fuel cells. This scalable fabrication method supplies a low-cost, high-efficiency metal-free oxygen reduction electrocatalyst and also suggests an economic and sustainable route from biomass-based molecules to value-added nanocarbon materials.
Co-reporter:Jutao Jin, Xiaogang Fu, Qiao Liu and Junyan Zhang
Journal of Materials Chemistry A 2013 vol. 1(Issue 35) pp:10538-10545
Publication Date(Web):01 Jul 2013
DOI:10.1039/C3TA11144J
A novel hybrid, with g-C3N4 embedded CoO particles covalently supported on a two-dimensional graphene sheet, is synthesized by a facile and scalable method towards the oxygen reduction reaction (ORR) for fuel cells. The composite hybrid with a suitable loading of g-C3N4@cobalt oxide on graphene exhibits excellent electrocatalytic activity and a dominant four-electron oxygen reduction pathway in basic solution. The kinetic-limiting current density (Jk) is 16.78 mA cm−2 at −0.25 V, approaching that of 20% Pt–C (17.22 mA cm−2) at the same potential. The performance gap between the hybrid and 20% Pt–C in terms of the half-wave potential difference (ΔE½) is 25 mV in alkaline solution. Furthermore, the hybrid is robust and methanol tolerant, making it a good candidate as a cathodic electrocatalyst in fuel cells.
Co-reporter:Fuping Pan, Jutao Jin, Xiaogang Fu, Qiao Liu, and Junyan Zhang
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 21) pp:11108
Publication Date(Web):October 7, 2013
DOI:10.1021/am403340f
Designing and fabricating advanced oxygen reduction reaction (ORR) electrocatalysts is critical importance for the sake of promoting widespread application of fuel cells. In this work, we report that nitrogen-doped graphene (NG), synthesized via one-step pyrolysis of naturally available sugar in the presence of urea, can serve as metal-free ORR catalyst with excellent electrocatalytic activity, outstanding methanol crossover resistance as well as long-term operation stability in alkaline medium. The resultant NG1000 (annealed at 1000 °C) exhibits a high kinetic current density of 21.33 mA/cm2 at −0.25 V (vs Ag/AgCl) in O2-saturated 0.1 M KOH electrolyte, compared with 16.01 mA/cm2 at −0.25 V for commercial 20 wt % Pt/C catalyst. Notably, the NG1000 possesses comparable ORR half-wave potential to Pt/C. The effects of pyrolysis temperature on the physical prosperity and ORR performance of NG are also investigated. The obtained results demonstrate that high activation temperature (1000 °C) results in low nitrogen doping level, high graphitization degree, enhanced electrical conductivity, and high surface area and pore volume, which make a synergetic contribution to enhancing the ORR performance for NG.Keywords: metal-free catalysis; nitrogen-doped graphene; oxygen reduction reaction; pyrolysis synthesis;
Co-reporter:Qiao Liu, Jutao Jin, and Junyan Zhang
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 11) pp:5002
Publication Date(Web):May 11, 2013
DOI:10.1021/am4007897
Here, the hybrid of NiCo2S4 nanoparticles grown on graphene in situ is first described as an effective bifunctional nonprecious electrocatalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in the alkaline medium. NiCo2S4@N/S-rGO was synthesized by a one-pot solvothermal strategy using Co(OAc)2, Ni(OAc)2, thiourea, and graphene oxide as precursors and ethylene glycol as the dispersing agent; simultaneously, traces of nitrogen and sulfur were double-doped into the reduced graphene oxide (rGO) in the forms of pyrrolic-N, pyridinic-N, and thiophenic-S, which are often desirable for metal-free ORR catalysts. In comparison with commercial Pt/C catalyst, NiCo2S4@N/S-rGO shows less reduction activity, much better durability, and superior methanol tolerance toward ORR in 0.1 M KOH; it reveals higher activity toward OER in both KOH electrolyte and phosphate buffer at pH 7.0. NiCo2S4@graphene demonstrated excellent overall bicatalytic performance, and importantly, it suggests a novel kind of promising nonprecious bifunctional catalyst in the related renewable energy devices.Keywords: bifunctional catalyst; cobalt sulfide; doping effect; fuel cell; graphene; nonprecious electrocatalyst; oxygen evolution; oxygen reduction;
Co-reporter:Hongyu Liang, Yongfeng Bu, Junyan Zhang, Zhongyue Cao, and Aimin Liang
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 13) pp:6369
Publication Date(Web):June 20, 2013
DOI:10.1021/am401495y
As a layered material, graphene oxide (GO) film is a good candidate for improving friction and antiwear performance of silicon-based MEMS devices. Via a green electrophoretic deposition (EPD) approach, GO films with tunable thickness in nanoscale are fabricated onto silicon wafer in a water solution. The morphology, microstructure, and mechanical properties as well as the friction coefficient and wear resistance of the films were investigated. The results indicated that the friction coefficient of silicon wafer was reduced to 1/6 its value, and the wear volume was reduced to 1/24 when using GO film as solid lubricant. These distinguished tribology performances suggest that GO films are expected to be good solid lubricants for silicon-based MEMS/NEMS devices.Keywords: adhesion; electrophoretic deposition; friction; graphene oxide film; solid lubricant; wear;
Co-reporter:Kexing Niu, Baoping Yang, Jinfeng Cui, Jutao Jin, Xiaogang Fu, Qiuping Zhao, Junyan Zhang
Journal of Power Sources 2013 Volume 243() pp:65-71
Publication Date(Web):1 December 2013
DOI:10.1016/j.jpowsour.2013.06.007
•Polyethyleneimine (PEI) was used as nitrogen source in the catalyst synthesis for the first time.•Graphene-based Co/N/rGO(NH3) as high-performance cathode catalyst for oxygen reduction reaction in alkaline solution.•Graphene-based Co/N/rGO catalytic activity is better than the single N/rGO or heat-treatment in Ar one.•Similar catalytic activity as Pt/C towards ORR in alkaline solution.This study develops a promising catalyst for oxygen reduction reaction (ORR) via a simple two-step heat treatment of a mixture of cobalt(II) nitrate hexahydrate (Co(NO3)2·6H2O), polyethyleneimine (PEI), and graphene oxide (GO), firstly in argon atmosphere and then in ammonia atmosphere. X-ray photoemission spectroscopy (XPS) result reveals that the catalyst has pyridinic N-dominant (46% atomic concentration among all N components) on the surface. The kinetics measurement of the catalyst in 0.1 M KOH solution using a rotating disk electrode (RDE) reveals that the catalyst (Co/N/rGO(NH3)) has high activity. Furthermore, the number of electrons exchanged during the ORR with the catalyst is determined to be ∼3.9, suggesting that the ORR is dominated by a 4e− reduction of O2 to H2O. The catalyst has good stability, and its performance is superior to the commercial Pt/C(20%) catalyst in alkaline condition, making the material a promising substitute to noble metal ORR electrocatalyst on the cathode side of fuel cells.
Co-reporter:Xiaogang Fu, Jutao Jin, Yanru Liu, Qiao Liu, Kexing Niu, Junyan Zhang, Xiaoping Cao
Electrochemistry Communications 2013 Volume 28() pp:5-8
Publication Date(Web):March 2013
DOI:10.1016/j.elecom.2012.11.017
Graphene-xerogel-based Co–N cathode catalyst (Co–N-GX) for the oxygen reduction reaction (ORR) was prepared through a simple approach. The Co–N-GX shows a more positive onset potential, higher cathodic density for the ORR in alkaline media than graphene-sheet-based Co–N catalyst (Co–N-GS), highlighting the importance of high specific surface area for improving the ORR performance. The proposed approach makes the Co–N-GX catalyst a non-precious metal cathode catalyst for fuel cells.Highlights► Melamine promoted GO hydrogel was used to prepare high surface area graphene xerogel. ► The graphene-xerogel-based Co–N catalyst (Co–N-GX) shows excellent ORR activity. ► The high specific surface area plays a crucial role in ORR activity enhancement. ► The facile preparation and low-cost material have promising application in fuel cells.
Co-reporter:Qiao Liu and Junyan Zhang
CrystEngComm 2013 vol. 15(Issue 25) pp:5087-5092
Publication Date(Web):23 Apr 2013
DOI:10.1039/C3CE40251G
This work presents a facile and general solvothermal approach to prepare hierarchical cobalt sulfides (ComSn) microflowers, which are composed of curved nanosheets. The homogeneous phases of Co9S8, Co3S4 and Co1−xS could be obtained just by adjusting the molar ratio of cobalt acetate to thiourea. The structure and morphology of the as-prepared cobalt sulfides were investigated by powder X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy (TEM) and high-resolution TEM, X-ray photoelectron spectroscopy and N2-sorption measurements. The possible growth process was discussed on the basis of time-dependent experimental results. The ComSn materials exhibited great electrocatalytic activities towards both oxygen reduction and oxygen evolution reactions, making them a kind of promising electrode materials for fuel cells and batteries.
Co-reporter:Yongfu Wang, Bin Zhang, Zhenbin Gong, Kaixiong Gao, Yujing Ou, Junyan Zhang
Journal of Molecular Structure 2013 Volume 1052() pp:102-104
Publication Date(Web):25 November 2013
DOI:10.1016/j.molstruc.2013.08.021
•There is smaller friction coefficient in magnetized water than in water.•The stronger magnetic intensity, the lower the friction coefficient in magnetized water becomes.•Magnetic field weaken hydrogen bonding in water.The effect of a static magnetic field on hydrogen bonding of liquid water has been examined by frictional experiments in this paper. It was found that the friction coefficient was smaller in different intensity magnetized water than in water, and became larger with the increasing water temperature. According to the thermal motion of water molecule known to become stronger and thus hydrogen-bonding gets weaker when water temperature increases, a thermal dynamic effect analogous to the increase of temperature was assumed, and the frictional differences were probably because of the weak effect of the magnetic field on hydrogen bonding among water molecules.
Co-reporter:Li Qiang;Bin Zhang;Kaixiong Gao;Zhenbin Gong
Friction 2013 Volume 1( Issue 4) pp:350-358
Publication Date(Web):2013 December
DOI:10.1007/s40544-013-0031-1
Fluorine-incorporated hydrogenated fullerene-like nanostructure amorphous carbon films (F-FLC) were synthesized by employing the direct current plasma enhanced chemical vapor deposition (dc-PECVD) technique using a mixture of methane (CH4), tetra-fluoromethane (CF4), and hydrogen (H2) as the working gases. The effect of the fluorine content on the bonding structure, surface roughness, hydrophobic, mechanical, and tribological properties of the films was systematically investigated using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman analysis, atomic force microscope (AFM), contact angle goniometer, nano-indenter, and reciprocating ball-on-disc tester, respectively. The fluorine content in the films increased from 0 to 2.1 at.% as the CF4 gas flow ratio increased from 0 to 3 sccm, and incorporated fluorine atoms existed in the form of C-FX (X = 1, 2, 3) bonds in the film. The fullerene nanostructure embedded in the hydrogenated amorphous carbon films was confirmed by Raman analysis. The water contact angle was significantly increased because of fluorine doping, which indicates that the hydrophobicity of the carbon films could be adjusted to some extent by the fluorine doping. The hardness and elastic modulus of the films remained relatively high (22 GPa) as the fluorine content increased. Furthermore, the friction coefficient of the carbon films was significantly reduced and the wear resistance was enhanced by fluorine doping.
Co-reporter:Qiao Liu and Junyan Zhang
Langmuir 2013 Volume 29(Issue 11) pp:3821-3828
Publication Date(Web):February 20, 2013
DOI:10.1021/la400003h
Graphitic carbon nitride (g-C3N4) polymer was doped with cobalt species and supported on a similar sp2 structure graphene, to form a novel nitrogen–metal macrocyclic catalyst for the oxygen reduction reaction (ORR) in alkaline fuel cells. The structural characterizations confirmed the formation of Co–N bonds and the close electron coupling between Co-g-C3N4 and graphene sheets. The electrocatalytic measurements demonstrated Co-g-C3N4-catalyzed reduction of oxygen mainly in a four electron pathway. The improvement of ORR activity is closely related to the abundant accessible Co–Nx active sites and fast charge transfer at the interfaces of Co-g-C3N4/graphene. Also, Co-g-C3N4@graphene exhibited comparable ORR activity, better durability, and methanol tolerance ability in comparison to Pt/C, and bodes well for a promising non-noble cathode catalyst for the application of direct methanol fuel cells. The chemical doping strategy in this work would be helpful to improve other present catalysts for fuel cell applications.
Co-reporter:Aimin Liang, Liwei Ni, Qiao Liu, Junyan Zhang
Surface and Coatings Technology 2013 Volume 218() pp:23-29
Publication Date(Web):15 March 2013
DOI:10.1016/j.surfcoat.2012.12.021
Uniform and flat thick Cr coating (CR3 coating) was electrodeposited from a Cr(III) electrolyte containing chromium chloride and urea under the optimized process conditions. The microstructure of the coating and its tribological properties under various loads was examined. Furthermore, the performance comparison of the CR3 coating with the hard Cr coating (CR6 coating) fabricated by conventional Cr(VI) electrodepositing process, and the heat-treated thick Cr coating (CR3H coating) from the same Cr(III) electrolyte, was performed. The result shows that the main phase of the CR3 coating is amorphous, with the nanocrystals of body-centered cubic structure chromium (bcc Cr) and graphite embedded in it. The existence of the nanocrystals of bcc Cr and graphite in Cr coatings is probably the common feature of all amorphous Cr coatings from Cr(III) electrolytes. In the scope of the bearable load of the CR3 coating, its tribological properties were a little worse than those of the CR6 coating. After annealing at 180 °C for 2 h, the wear resistance of the coating was improved to a certain extent. We found the interfacial carbon film between the CR3 coating and steel substrate, which caused poor bonding and consequently insufficient load-bearing capability of the coating. There is a need to further improve the load-bearing capability and wear resistance of the CR3 coating. In view of the great environmental advantage of Cr(III) electrodeposition process and no difference of wear resistance in order of magnitude between the CR3 coating and CR6 coating, Cr(III) electrodeposition technology is still a developing direction with promising prospect.Highlights► Nanocrystals of bcc Cr and graphite are embedded in amorphous thick Cr coating. ► The wear resistance of thick Cr coating was systematically investigated. ► Interfacial carbon film weakened the bonding between thick Cr coating and substrate.
Co-reporter:Jutao Jin, Xiaogang Fu, Qiao Liu, Yanru Liu, Zhiyang Wei, Kexing Niu, and Junyan Zhang
ACS Nano 2013 Volume 7(Issue 6) pp:4764
Publication Date(Web):May 6, 2013
DOI:10.1021/nn3046709
Nitrogen-doped graphene sheets (NGS), synthesized by annealing graphite oxide (GO) with urea at 700–1050 °C, were studied as positive electrodes in a vanadium redox flow battery. The NGS, in particular annealed at 900 °C, exhibited excellent catalytic performance in terms of electron transfer (ET) resistance (4.74 ± 0.51 and 7.27 ± 0.42 Ω for the anodic process and cathodic process, respectively) and reversibility (ΔE = 100 mV, Ipa/Ipc = 1.38 at a scan rate of 50 mV s–1). Detailed research confirms that not the nitrogen doping level but the nitrogen type in the graphene sheets determines the catalytic activity. Among four types of nitrogen species doped into the graphene lattice including pyridinic-N, pyrrolic-N, quaternary nitrogen, and oxidic-N, quaternary nitrogen is verified as a catalytic active center for the [VO]2+/[VO2]+ couple reaction. A mechanism is proposed to explain the electrocatalytic performance of NGS for the [VO]2+/[VO2]+ couple reaction. The possible formation of a N–V transitional bonding state, which facilitates the ET between the outer electrode and reactant ions, is a key step for its high catalytic activity.Keywords: graphene sheets; nitrogen doping; redox flow battery; [VO]2+/[VO2]+ couple reaction
Co-reporter:Li Qiang, Bin Zhang, Yan Zhou, Junyan Zhang
Solid State Sciences 2013 20() pp: 17-22
Publication Date(Web):
DOI:10.1016/j.solidstatesciences.2013.03.003
Co-reporter:Jinfeng Cui, Li Qiang, Bin Zhang, Xiao Ling, Tao Yang, Junyan Zhang
Applied Surface Science 2012 Volume 258(Issue 12) pp:5025-5030
Publication Date(Web):1 April 2012
DOI:10.1016/j.apsusc.2012.01.072
Abstract
Ti-doped diamond-like carbon (DLC) films were deposited on Si substrates at room temperature by magnetron sputtering Ti twin-target in methane and argon mixture atmosphere. The DLC films with different Ti concentrations were fabricated by varying the gas flow ratio of Ar/CH4. X-ray photoelectron spectroscopy (XPS), Raman spectra were used to analyze the composition and the microstructure of the films. The internal stress was calculated by using the Stoney equation, where the curvature of the film/substrate was measured by BGS 6341 type film stress tester. The mechanical and tribological properties of the films were systematically studied by the nano-indentor and reciprocating ball-on-disc tester, respectively. The Ti atomic concentration in the films increased from 0.41% to 8.2% as the Ar/CH4 flow ratio increased from 60/190 to 140/110. The Ti atoms exist mainly in the form of metallic-like Ti rather than TiC when Ti concentration is 0.41%, confirmed by XPS analysis. As the Ti concentration rose to 6.7%, the Ti-DLC films transformed to composite DLC films with carbide phase embedded in the DLC matrix because of the formation of TiC. As a result, the hardness is decreased, while the stress is dramatically increased. The Ti-DLC films with 0.41% Ti doping showed a relatively high hardness (13.75 GPa), low stress (0.56 GPa), extremely low wear rate (∼10−10 mm3/Nm) and low friction coefficient (0.05).
Co-reporter:Aimin Liang, Junyan Zhang
Surface and Coatings Technology 2012 206(17) pp: 3614-3618
Publication Date(Web):
DOI:10.1016/j.surfcoat.2012.02.053
Co-reporter:Yijun Liu, Jia Luo, Bin Liu, Junyan Zhang
Applied Surface Science 2011 Volume 257(Issue 15) pp:6429-6434
Publication Date(Web):15 May 2011
DOI:10.1016/j.apsusc.2011.02.021
Abstract
The objective of the present study is to preliminarily explore the effect of surface chemistry modification of Ti6Al4V with a fluorine-contained copolymer thin film on the cellular behavior of osteoblasts. A fluorine-contained random copolymer thin film was fabricated on Ti6Al4V substrate, and then characterized by X-ray photoelectron spectroscopy (XPS), contact angle meter and surface profiler. The results showed that the surface modification of Ti6Al4V alloy could simultaneously transform the surface chemical constitution and reduce the surface energy evidently. However, the surface morphology and roughness of the Ti6Al4V substrate were hardly changed after the modification. By immersion process with simulated body fluid (SBF) and then by in vitro cytotoxicity test with MC3T3-E1 osteoblasts, the fluorine-contained copolymer thin film exhibited desirable stability and admirable cytocompatibility. In conclusion, the fluorine-contained copolymer thin film could be easily applied in modifying various solid surfaces, and the as-fabricated film also has potential applications in biomedical field.
Co-reporter:Z. Wang;C. B. Wang;B. Zhang;J. Y. Zhang
Tribology Letters 2011 Volume 41( Issue 3) pp:607-615
Publication Date(Web):2011 March
DOI:10.1007/s11249-010-9739-5
Friction and wear behaviors of hydrogenated fullerene-like (H-FLC) carbon films sliding against Si3N4 ceramic balls were performed at different contact loads from 1 to 20 N on a reciprocating sliding tribometer in air. It was found that the films exhibited non-Amontonian friction behaviors, the coefficient of friction (COF) decreased with normal contact load increasing: the COF was ~0.112 at 1 N contact load, and deceased to ultralow value (~0.009) at 20 N load. The main mechanism responsible for low friction and wear under varying contact pressure is governed by hydrogenated carbon transfer film that formed and resided at the sliding interfaces. In addition, the unique fullerene-like structures induce well elastic property of the H-FLC films (elastic recovery 78%), which benefits the high load tolerance and induces the low wear rate in air condition. For the film with an ultralow COF of 0.009 tested under 20 N load in air, time of flight secondary ion mass spectrometry (ToF-SIMS) signals collected inside and outside the wear tracks indicated the presence of C2H3− and C2H5− fragments after tribological tests on the H-FLC films surface. We think that the tribochemistry and elastic property of the H-FLC films is responsible for the observed friction behaviors, the high load tolerance, and chemical inertness of hydrogenated carbon-containing transfer films instead of the graphitization of transfer films is responsible for the steady-state low coefficients of friction, wear, and interfacial shear stress.
Co-reporter:Yuanlie Yu, Junyan Zhang
Electrochemistry Communications 2010 Volume 12(Issue 3) pp:390-393
Publication Date(Web):March 2010
DOI:10.1016/j.elecom.2010.01.001
Amorphous carbon nitride films with good photoluminescence could be ultrafastly fabricated by liquid-phase electrochemical decomposition of fullerene derivative, C60[(NH2)2CNCN]5. The structure of the as-prepared films, characterized by transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy, was consisted of sp2 hybrid C, sp3 hybrid C, C–N, CN and CN bands. Further study showed that the thickness of the films increased with the increase of the deposition time and the concentration of C60[(NH2)2CNCN]5. The optical tests indicated that the as-obtained films have distinct photoluminescence, no obvious decrease was observed more than one month later.
Co-reporter:Junyan Zhang, Yuanlie Yu, Deming Huang
Solid State Sciences 2010 Volume 12(Issue 7) pp:1183-1187
Publication Date(Web):July 2010
DOI:10.1016/j.solidstatesciences.2010.03.017
Multilayer graphene oxide nanosheets were fabricated using commercially available expanded graphite by simple ultrasonic treatment and then were incorporated into the amorphous carbon matrix as fillers by electrochemical deposition. The electrical conductivity of the films was strongly improved due to the contribution of the multilayer graphene oxide sheets. Moreover, the Young’s modulus, hardness and elastic recovery of the composite films were measured to be about 171.1 GPa, 10.1 GPa and 81.4%, respectively, compared to 137.4 GPa, 5.1 GPa and 44.3% of undoped a-C:H films prepared at the same conditions. Additionally, the friction coefficient was tested to be 0.15 (0.5 N, 2 Hz) and the antiwear life was prolonged to about 200 s while the undoped DLC films obtained at the same condition were easy to be frazzled.
Co-reporter:Zhenbin Gong, Jing Shi, Bin Zhang, Junyan Zhang
Carbon (May 2017) Volume 116() pp:
Publication Date(Web):May 2017
DOI:10.1016/j.carbon.2017.01.106
Amorphous carbon films are widely used as solid lubricant coating. However, the mechanism response for its superlow friction has not been well explored. The previous results indicated that graphitic tribofilms are formed at rubbing interfaces, which leading to decreasing of friction coefficient. But in some cases, the friction coefficients of graphite (0.1–0.6) are much high than the amorphous carbon films (0.05–0.01), where the graphitic theory is quite limited and the interpretation is poor. Using high resolution transmission electron microscopy and Raman spectra, we monitor the structure evolution of tribofilms and friction coefficient drop during running-in. We demonstrate that a kind of graphene nano scroll particle was developed in the tribofilms consisting of outer graphene shell and inner amorphous core. And the relationship between friction drop and graphene nano scroll evolution suggests that, incommensurate contact of such nano scrolls, may be the dominant dissipation modes for amorphous carbon.
Co-reporter:Wei Ma, Zhenbin Gong, Kaixiong Gao, Li Qiang, Junyan Zhang, Shurong Yu
Materials Letters (15 May 2017) Volume 195() pp:
Publication Date(Web):15 May 2017
DOI:10.1016/j.matlet.2017.02.135
•Carbon quantum dots (CQDs)/Ionic liquid (IL) nanoparticles were fabricated by simple modification.•IL-modified CQDs showed a super-low friction coefficient about 0.006 with the CQDs content of 3.6%.•The sphere-in-shell structure of IL/CQDs nanoparticles lead to the outstanding tribological performance.Carbon quantum dots (CQDs) and ionic liquid (IL) nanoparticles were fabricated by simple modification. The structures and properties of these particles were measured with HRTEM, FTIR, Raman Spectrometer and friction test. More importantly, IL-modified CQDs as lubricant material demonstrated excellent tribological performance and obtained a super-low friction coefficient about 0.006 and wear rate about 0.7 × 10−14 m3/Nm with the CQDs content of 3.6%. The results revealed that IL-modified CQDs might provide a new idea to investigate various lubricant materials to achieve super-low friction and could be intensively studied for other practical applications.
Co-reporter:Fuping Pan, Aimin Liang, Youxin Duan, Qiao Liu, Junyan Zhang and Ying Li
Journal of Materials Chemistry A 2017 - vol. 5(Issue 25) pp:NaN13111-13111
Publication Date(Web):2017/05/22
DOI:10.1039/C7TA03005C
Although mesopore designs are expected to play a key role in exploring electrocatalytic properties of carbons, facile preparation of mesoporous carbons (MPCs) with efficient dopants to enable high performance remains a great challenge. Herein, we for the first time introduce a self-growth-templating concept for the fabrication of three-dimensional (3D) N,P,Co-doped MPC frameworks, simply through pyrolysis of vitamin B12 in NaCl assembly-enclosed nanoreactors. The route realizes the controllable formation of mesoporous templates and elimination of the templates, as well as in situ doping of N, P, and Co into MPCs in a one-step enclosed-space-assisted pyrolysis process. The highly mesoporous architecture not only enhances mass transportation but also provides the 3D electrocatalytic surface to expose highly active N,P,Co-induced dopants. These features endow MPCs with excellent activity as bifunctional electrocatalysts in oxygen reduction (E1/2 of 0.85 V, JK of 51 mA cm−2 at −0.71 V and Tafel slope of 53 mV dec−1) and CO2 reduction reactions (overpotential of −0.19 V, maximum FE of 62% for CO and Tafel slope of 129 mV dec−1), coupled with high electrochemical stability in aqueous electrolytes. We expect that the self-constructing vision can afford useful insights to guide the development of other advanced mesoporous materials other than carbon for broad applications.
Co-reporter:Jutao Jin, Xiaogang Fu, Qiao Liu and Junyan Zhang
Journal of Materials Chemistry A 2013 - vol. 1(Issue 35) pp:NaN10545-10545
Publication Date(Web):2013/07/01
DOI:10.1039/C3TA11144J
A novel hybrid, with g-C3N4 embedded CoO particles covalently supported on a two-dimensional graphene sheet, is synthesized by a facile and scalable method towards the oxygen reduction reaction (ORR) for fuel cells. The composite hybrid with a suitable loading of g-C3N4@cobalt oxide on graphene exhibits excellent electrocatalytic activity and a dominant four-electron oxygen reduction pathway in basic solution. The kinetic-limiting current density (Jk) is 16.78 mA cm−2 at −0.25 V, approaching that of 20% Pt–C (17.22 mA cm−2) at the same potential. The performance gap between the hybrid and 20% Pt–C in terms of the half-wave potential difference (ΔE½) is 25 mV in alkaline solution. Furthermore, the hybrid is robust and methanol tolerant, making it a good candidate as a cathodic electrocatalyst in fuel cells.
