Co-reporter:Xiaowei Li, Peng Guo, Lili Sun, Xiao Zuo, Dong Zhang, Peiling Ke, Aiying Wang
Carbon 2017 Volume 111() pp:467-475
Publication Date(Web):January 2017
DOI:10.1016/j.carbon.2016.10.033
Amorphous carbon (a-C) films co-doped by two metals exhibit a desirable combination of mechanical and tribological properties for wider applications. Nevertheless, the structural evolution of metal co-doped a-C films from the atomic and electronic scales is a critical pre-requisite to illustrate the intrinsic mechanism of residual stress reduction. Herein, we first fabricated the Ti/Al co-doped a-C films with different concentrations by a hybrid ion beam system. When the co-doped Ti/Al concentrations were
Co-reporter:Shucan Zhang, Zhenyu Wang, Peng Guo, Peiling Ke, Magnus Odén, Aiying Wang
Surface and Coatings Technology 2017 Volume 322(Volume 322) pp:
Publication Date(Web):15 August 2017
DOI:10.1016/j.surfcoat.2017.05.030
•CrB2 coatings were fabricated by DC magnetron sputtering.•Increasing deposition temperature promoted (001) preferred orientation of CrB2.•(001) orientation and structural densification resulted in hardness of 50.7 ± 2 GPa.The influence of deposition temperature in the range of 100 °C to 400 °C on the microstructure and mechanical properties of CrB2 coatings by DC magnetron sputtering was studied. The coating texture changed from random mixed orientation with (101) and (001) planes to the preferred (001) orientation when increasing the deposition temperature. Moreover, the microstructure coating evolved from an underdense structure to a bulky columnar structure (~ 50 nm), and finally to a dense nanoscale columnar structure (~ 7 nm). This structural densification was mainly attributed to the enhanced atomic surface diffusion with increasing deposition temperature. It resulted in promotion of the (001) preferred orientation and greatly enhanced the mechanical properties. Specifically, when the deposition temperature was 300 °C, the CrB2 coatings exhibited the highest toughness while superhardness (51 ± 2 GPa) was achieved for coating grown at 400 °C.
Co-reporter:Sheng Cai;Peng Guo;Jingzhou Liu;Dong Zhang;Peiling Ke
Tribology Letters 2017 Volume 65( Issue 3) pp:79
Publication Date(Web):13 May 2017
DOI:10.1007/s11249-017-0862-4
Tribological properties of MoS2/C coatings with different carbon contents (44.7–84.3 at.%) deposited by magnetron sputtering were systematically investigated under atmospheric environment. During tribological tests, the coating with the least MoS2 content exhibited the lowest friction coefficient and wear rate, while coating with the most MoS2 showed the worst performance. To understand friction and wear mechanism, multiple analytical tools such as SEM, EDS, Raman, XPS and TEM were applied to investigate the composition and structure. TEM and SEM characteristics proved that the tribofilm with multilayered structure was formed on the tribopair. The C-rich layer adhered to the tribopair and the top layer was well-ordered MoS2 tribofilm, and the dominated amorphous MoS2 was found between the two layers. It suggested that the shear plane was mainly made of well-ordered MoS2 transfer film, while carbon improved the mechanical properties of the coatings, served as a lubricant and also inhibited the oxidation of MoS2.
Co-reporter:Peng Guo, Xiaowei Li, Lili Sun, Rende Chen, Peiling Ke, Aiying Wang
Thin Solid Films 2017 Volume 640(Volume 640) pp:
Publication Date(Web):31 October 2017
DOI:10.1016/j.tsf.2017.09.001
•Cu-containing diamond-like carbon films were deposited by a hybrid ion beam system.•Nanoscale Cu particles began to evolve in the Cu concentration range of 2.6–7.0 at.%.•The incorporation of Cu atoms greatly reduced the residual stress of the pure carbon film.•The antibonding between Cu and C accounted for the reduction of residual stressCu incorporated diamond-like carbon (Cu-DLC) films were deposited on Si/glass substrate by a hybrid ion beam deposition system, which consists of a direct current (DC) magnetron sputtering of Cu target and a linear ion source. The Cu concentration (from 0.1 to 39.7 at.%) in the Cu-DLC films was controlled by varying the sputtering current. The dependence of residual stress, microstructure and atomic bond structure upon Cu concentration was investigated systematically. Results indicated that the nanoscale Cu particles began to evolve from the carbon matrix in the Cu concentration range of 2.6–7.0 at.%. The residual stress of the Cu-DLC films (less than 0.60 GPa) showed a significant reduction compared with that of the pure carbon film (2.0 GPa). Theoretical calculations revealed that the formation of antibonding between Cu and C and the relaxation of distorted bond angles and bond length accounted for the significant reduction of residual stress caused by Cu incorporation.
Co-reporter:Ting Guo, Cuicui Kong, Xiaowei Li, Peng Guo, Zhenyu Wang, Aiying Wang
Applied Surface Science 2017 Volume 410(Volume 410) pp:
Publication Date(Web):15 July 2017
DOI:10.1016/j.apsusc.2017.02.254
•Ti/Al co-doped diamond-like carbon films were fabricated by a hybrid ion beam method.•Process parameters affected the structure and chemical state of co-doped Ti and Al.•The relation between microstructure and properties was investigated systematically.•The guidance to tailor the Ti/Al-DLC films with high performance was provided.Co-doping two metal elements into diamond-like carbon (DLC) films can reach the desirable combined properties, but the preparation and commercialized application of metal co-doped DLC films with well-defined structural properties are currently hindered by the non-comprehensive understanding of structural evolutions under different process parameters. Here, we fabricated the Ti/Al-DLC films using a unique hybrid ion beam system which enabled the independent control of metal content and carbon structure. The evolutions of microstructure, residual compressive stress and mechanical properties induced by the different process parameters including sputtering currents, C2H2 or CH4 source gases and bias voltages were investigated systematically in order to perform in-depth analysis on the relation between the structure and properties in Ti/Al-DLC films. Results revealed that the variations of process parameters seriously affected the concentration and chemical bond state of co-doped Ti/Al atoms in amorphous carbon matrix or incident energies of C ions, which brought the complicated effect on amorphous carbon structures, accounting for the change of residual compressive stress, hardness and toughness. The present results provide the guidance for suitable, effective parameters selection to tailor the Ti/Al-DLC films with high performance for further applications.Download high-res image (268KB)Download full-size image
Co-reporter:Zhenyu Wang, Xiaowei Li, Jie Zhou, Pei Liu, Qing Huang, Peiling Ke, Aiying Wang
Journal of Alloys and Compounds 2016 Volume 661() pp:476-482
Publication Date(Web):15 March 2016
DOI:10.1016/j.jallcom.2015.11.170
•The nanocomposite V–Al–C coatings were deposited.•Structure evolution of V–Al–C coatings upon annealing temperature was studied.•The pure V2AlC MAX phase was obtained after annealing beyond 700 °C.•The correlation between the structure and mechanical properties was established.•Toughness and tribological properties were optimized with structure evolution.V2AlC belongs to a family of ternary nano-laminate alloys known as the MAX phases, which exhibit a unique combination of metallic and ceramic properties. In this work V–Al–C coatings with deposited (V,Al)2C nano-crystallines and amorphous phase were magnetron sputtered from V2AlC compound target. The subsequent vacuum annealing for 1 h was carried out at 600 °C, 700 °C and 800 °C, respectively. The crystallization of V2AlC MAX phase was detected by annealing at 600 °C. Meanwhile, a small amount of amorphous carbon phase appeared. Further increasing annealing temperature to 700 °C led to a complete transformation from amorphous V–Al–C phase to V2AlC phase, as well as a significant increase in the amorphous carbon content. It was noticed that the crystallinity of V2AlC phase was significantly enhanced and amorphous carbon was almost disappeared after annealing at 800 °C. The coating toughness became better with the increase in the content of V2AlC MAX phase. The optimized mechanical and tribological properties of the annealed V–Al–C coatings were further discussed in terms of the microstructure evolution.
Co-reporter:Lili Sun, Peng Guo, Peiling Ke, Xiaowei Li, Aiying Wang
Diamond and Related Materials 2016 Volume 68() pp:1-9
Publication Date(Web):September 2016
DOI:10.1016/j.diamond.2016.05.006
•Cu and Cr co-doped diamond-like carbon films were firstly fabricated.•Good hydrophobicity and superior mechanical performance were obtained.•The mechanism of hydrophobicity relied on graphitization and copper oxidation.•Surface topographical microstructure could also promote the hydrophobicity of film.By choosing carbide-forming element Cr and non-carbide-forming element Cu as co-doped metal elements, we firstly fabricated Cu and Cr co-doped diamond-like carbon (Cu/Cr-DLC) films using a facile hybrid ion beam deposition system. The effect of Cu/Cr co-doping on wettability and mechanical properties of DLC films were focused. The resultant Cu/Cr-DLC films were shown to afford good hydrophobicity and superior mechanical performance. In particular, the film with Cu11.88%Cr6.57% (at.%) exhibited a relatively high water contact angle of 103.6°, lower residual stress of 0.89 GPa and high hardness of 13.44 GPa. The combined structural analysis demonstrated that the synergistic Cu/Cr co-doping resulted in the critical and significant relaxation of distorted CC bond length, which ultimately caused the reduction in residual stress. Due to the formation of hard Cr carbide nano-particles in amorphous carbon matrix, the films maintained the high value of hardness. In addition, noted that the interesting wetting variety from hydrophilic to hydrophobic state was attributed to the enhanced surface graphitization and emergence of copper oxidation phases, and the film topographical microstructure could also promote the hydrophobicity of film when the maximum height of roughness was in a certain range. These results provide an expected robust synthesis method to make DLC film a promising protective coating for long lasting hydrophobic application and related harsh fields.
Co-reporter:Xiaowei Li, Dong Zhang, Kwang-Ryeol Lee, Aiying Wang
Thin Solid Films 2016 Volume 607() pp:67-72
Publication Date(Web):31 May 2016
DOI:10.1016/j.tsf.2016.04.004
•The bond characteristics as 3d electrons changed from bonding, nonbonding to antibonding.•The TM–C bond was a mixture of covalent and ionic characters.•Reduced strength and directionality of TM–C bond led to small distortion energy change.•The weak TM–C bond accounted for the reduced compressive stress caused by TM.First-principles calculation was performed to investigate the effect of metal doping on the structural characteristics of amorphous carbon system, and the 3d transition metals (TM) were particularly selected as representative case. Results showed that the total energy in TM–C systems caused by distorting the bond angles was reduced distinctly for comparison with that in C–C system. Further electronic structure revealed that as the 3d electrons of doped TM increased, the bond characteristic of highest occupied molecular orbital changed from bonding (Sc, Ti) to nonbonding (V, Cr, Mn, Fe) and finally to antibonding (Co, Ni, Cu) between the TM and C atoms. Meanwhile, the TM–C bond presented a mixture of the covalent and ionic characters. The decrease of strength and directionality of TM–C bonds resulted in the total energy change upon bond angle distortion, which demonstrated that the bond characteristics played an important role in reducing residual stress of TM-doped amorphous carbon systems.
Co-reporter:Zhenyu Wang, Xiaowei Li, Xin Wang, Sheng Cai, Peiling Ke, Aiying Wang
Surface and Coatings Technology 2016 Volume 304() pp:553-559
Publication Date(Web):25 October 2016
DOI:10.1016/j.surfcoat.2016.07.061
•The hard yet tough V-Al-C-N nanocomposite coating was successfully prepared.•The correlation between the structure and mechanical properties was established.•The high H/E ratio of 0.11 and elastic recovery of 69% were obtained.•The nanocomposite V-Al-C-N coatings exhibited a low wear rate (< 1.5 × 10− 16 m3/Nm).•The Magnéli phase of V2O5 was formed during friction stage.Hard coatings have been widely used in industrial applications as wear-resistant coatings, but are prone to failure due to the high intrinsic brittleness. In order to improve toughness without significantly sacrificing hardness, here we designed the V-Al-C-N nanocomposite coatings, and the microstructures consisting of V-based nanocrystalline hard phases and sp2-riched amorphous carbon soft phases were successfully manipulated by sputtering V2AlC target under various N2 flow rates. Results indicated that the coating hardness was almost independent on the N2 flow rate and maintained around ~ 30 GPa as changing N2 flow rate from 5 to 20 sccm, while the toughness was significantly improved, and the high H/E ratio of 0.11 and elastic recovery of 69% could be obtained, respectively. In addition, the V-Al-C-N nanocomposite coatings showed low wear rate (< 1.5 × 10− 16 m3/Nm) under a normal load of 10 N. The hard yet tough characteristic and high wear resistance for the deposited coatings were attributed to the special nanocomposite microstructures as well as the synergistic lubricant effect derived from both sp2-riched amorphous carbon and V2O5 Magnéli phases formed during friction stage.
Co-reporter:Xiaowei Li, Peng Guo, Lili Sun, Aiying Wang, and Peiling Ke
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 50) pp:27878
Publication Date(Web):November 27, 2015
DOI:10.1021/acsami.5b09774
Amorphous carbon films (a-C) codoped by two metal elements exhibit the desirable combination of tribological and mechanical properties for widely potential applications, but are also prone to catastrophic failure due to the inevitable residual compressive stress. Thus far, the residual stress reduction mechanism remains unclear due to the insufficient understanding of the structure from the atomic and electronic scale. In this paper, using ab initio calculations, we first designed a novel Cu/Cr codoped a-C film and demonstrated that compared with pure and Cu/Cr monodoped cases, the residual stress in Cu/Cr codoped a-C films could be reduced by 93.6% remarkably. Atomic bond structure analysis revealed that the addition of Cu and Cr impurities in amorphous carbon structure resulted in the critical and significant relaxation of distorted C–C bond lengths. On the other hand, electronic structure calculation indicated a weak bonding interaction between the Cr and C atoms, while the antibonding interaction was observed for the Cu–C bonds, which would play a pivot site for the release of strain energy. Those interactions combined with the structural evolution could account for the drastic residual stress reduction caused by Cu/Cr codoping. Our results provide the theoretical guidance and desirable strategy to design and fabricate a new nanocomposite a-C films with combined properties for renewed applications.Keywords: ab initio calculation; amorphous carbon; bond structure; codoping; residual stress
Co-reporter:Kai Zhou, Peiling Ke, Xiaowei Li, Yousheng Zou, Aiying Wang
Applied Surface Science 2015 Volume 329() pp:281-286
Publication Date(Web):28 February 2015
DOI:10.1016/j.apsusc.2014.12.162
Highlights
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N-DLC film electrode was synthesized by glow discharge PECVD using a hybrid ion beam system.
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N-DLC film electrode showed a wide potential window over 4.0 V and a nearly reversible electrode reaction.
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The electrochemical properties of electrode were dominated by the atomic bonds in N-DLC films.
Co-reporter:Zhenyu Wang, Dong Zhang, Peiling Ke, Xincai Liu, Aiying Wang
Journal of Materials Science & Technology 2015 Volume 31(Issue 1) pp:37-42
Publication Date(Web):January 2015
DOI:10.1016/j.jmst.2014.06.002
TiN coatings were deposited using a hybrid home-made high power impulse magnetron sputtering (HIPIMS) technique at room temperature. The effects of substrate negative bias voltage on the deposition rate, composition, crystal structure, surface morphology, microstructure and mechanical properties were investigated. The results revealed that with the increase in bias voltage from −50 to −400 V, TiN coatings exhibited a trend of densification and the crystal structure gradually evolved from (111) orientation to (200) orientation. The growth rate decreased from about 12.2 nm to 7.8 nm per minute with the coating densification. When the bias voltage was −300 V, the minimum surface roughness value of 10.1 nm was obtained, and the hardness and Young's modulus of TiN coatings reached the maximum value of 17.4 GPa and 263.8 GPa, respectively. Meanwhile, the highest adhesion of 59 N was obtained between coating and substrate.
Co-reporter:Zongjian Feng, Peiling Ke, Aiying Wang
Journal of Materials Science & Technology 2015 Volume 31(Issue 12) pp:1193-1197
Publication Date(Web):December 2015
DOI:10.1016/j.jmst.2015.10.014
Due to the excellent corrosion resistance and high irradiation damage resistance, Ti2AlC MAX phase is considered as a candidate for applications as corrosion resistant and irradiation resistant protective coating. MAX phase coatings can be fabricated through firstly depositing a coating containing the three elements M, A, and X close to stoichiometry of the MAX phases using physical vapor deposition, followed by heat treatment in vacuum. In this work, Ti–Al–C coating was prepared on austenitic stainless steels by reactive DC magnetron sputtering with a compound Ti50Al50 target, and CH4 used as the reactive gas. It was found that the as-deposited coating is mainly composed of Ti3AlC antiperovskite phase with supersaturated solid solution of Al. Additionally, the ratio of Ti/Al remained the same as that of the target composition. Nevertheless, a thicker thermally grown Ti2AlC MAX phase coating was obtained after being annealed at 800 °C in vacuum for 1 h. Meanwhile, the ratio of Ti/Al became close to stoichiometry of Ti2AlC MAX phases. It can be understood that owing to the higher activity of Al, it diffused quickly into the substrate during annealing, and then more stable Ti2AlC MAX phases transformed from the Ti3AlC antiperovskite phase.
Co-reporter:Wei Yang, Yongchun Guo, Dapeng Xu, Jinhua Li, Ping Wang, Peiling Ke, Aiying Wang
Surface and Coatings Technology 2015 Volume 261() pp:398-403
Publication Date(Web):15 January 2015
DOI:10.1016/j.surfcoat.2014.10.044
•(Cr:N)-DLC film with CrN and CrC crystalline phases was deposited on 316L stainless steel.•(Cr:N)-DLC film showed low sp3/sp2 ratio, high micro-hardness and improved binding strength.•(Cr:N)-DLC film showed an excellent tribological property compared with Cr-DLC film.In this paper, diamond-like carbon (DLC) films doped with CrN nano-crystalline were prepared on 316L stainless steel using a hybrid beam deposition system (including a linear ion source (LIS) and a DC magnetron sputtering of Cr target). The microstructure and composition of the films were studied using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Mechanical and tribological properties were investigated using nano-indentation and tribological tester. The results showed that an N doping could significantly influence the microstructure and properties of the as-deposited films. On one hand, the N atoms doped in the film tended to form Cr–N, –CN–H and C–N bonding, which would enhance the binding strength. On the other hand, the formation of CrN/CrC nano-crystalline due to N doping dispersed in the amorphous DLC matrix could play an important role and increase its hardness. In addition, the (Cr:N)-DLC showed low friction coefficient and wear rate compared with the Cr-DLC film.
Co-reporter:Xiaowei Li
The Journal of Physical Chemistry C 2015 Volume 119(Issue 11) pp:6086-6093
Publication Date(Web):March 2, 2015
DOI:10.1021/acs.jpcc.5b00058
Ab initio molecular dynamics simulation based on density functional theory was performed to investigate (Ti, Cr, or W)-incorporated diamond-like carbon (DLC) films. The structure models were generated from liquid quench containing 64 atoms. The dependence of the residual compressive stress, bulk modulus and tetra-coordinated C content on the Ti, Cr, and W concentrations in the range of 1.56 to 7.81 atom % was studied. The present simulation results reveal that the residual stress strongly depends on the incorporated Ti, Cr, and W atoms. With the incorporation of Ti at 1.56 atom %, Cr at 4.69 atom %, and W at 3.13 atom % to DLC films, the compressive stress was reduced by 46.9%, 81.4%, and 82.5%, respectively, without obvious deterioration of the mechanical properties. However, at higher Ti, Cr, and W concentrations, the compressive stress increased for each case, which was consistent with the experimental results. Structural analysis using both the bond angle and bond length distributions indicates that the small amount of Ti or W incorporation efficiently relaxes both the highly distorted bond angles and bond lengths, whereas the Cr incorporation only relaxes the distorted bond lengths, which decreases the residual compressive stress and provides theoretical explanations for the experiments.
Co-reporter:Xiaowei Li, Peiling Ke, Aiying Wang
Thin Solid Films 2015 Volume 584() pp:204-207
Publication Date(Web):1 June 2015
DOI:10.1016/j.tsf.2014.11.072
•The dependence of structure and properties on Ti concentration was investigated.•Residual compressive stress can be reduced seriously by Ti incorporation.•There is no obvious degradation of mechanical properties due to the Ti incorporation.•The stress reduction attributed to the relaxation of highly distorted bond structure.Structural properties of Ti-doped diamond-like carbon (DLC) films as a function of Ti concentrations (1.56–7.81 at.%) were investigated by ab initio molecular dynamics simulation to clarify the stress reduction mechanism. Results showed that with introducing Ti into DLC films, the residual compressive stress decreased firstly and then increased, which was consistent with the previous experimental results. Structural analysis revealed that the addition of Ti efficiently relaxed both the highly distorted bond angles and bond lengths, which led to the reduction of residual stress; the increase of residual stress at the high Ti concentration was attributed to the existence of distorted Ti–C structures and the increased fraction of distorted CC bond lengths.
Co-reporter:Peng Guo, Lili Sun, Xiaowei Li, Sheng Xu, Peiling Ke, Aiying Wang
Thin Solid Films 2015 Volume 584() pp:289-293
Publication Date(Web):1 June 2015
DOI:10.1016/j.tsf.2015.01.018
Co-reporter:Zongjian Feng, Peiling Ke, Qing Huang, Aiying Wang
Surface and Coatings Technology 2015 Volume 272() pp:380-386
Publication Date(Web):25 June 2015
DOI:10.1016/j.surfcoat.2015.03.037
•The oxidation of Ti2AlC coating at 750 °C in air and pure water vapor was studied.•Ti2AlC coating improves the oxidation resistance of the substrate alloy.•The scale formed on Ti2AlC coating exhibits a four-layered microstructure in air.•No distinct oxide scale formed on the Ti2AlC coating in pure water vapor.The scale behavior of Ti2AlC coating at 750 °C in air and pure water vapor was investigated. A four-layered scale, a thick TiO2 and Al2O3 mix oxide outer layer, followed by a thin α-(Al, Cr)2O3 sublayer, a thick Fe2O3 and TiO2 mix oxide mid-layer and a thin Al2O3-rich oxide inner layer in sequence, developed on the Ti2AlC coatings in air. Whereas internal oxidation occurred, no distinct oxide scale formed on the Ti2AlC coating in the case of the oxidation in pure water vapor. The Ti2AlC coating improved the oxidation resistance of 316LSS in air, especially in wet air.
Co-reporter:Yousheng Zou, Linlin He, Kang Dou, Shalong Wang, Peiling Ke and Aiying Wang
RSC Advances 2014 vol. 4(Issue 102) pp:58349-58356
Publication Date(Web):30 Oct 2014
DOI:10.1039/C4RA10266E
Boron doped microcrystalline diamond (BDMD) films with different boron concentrations were deposited on Si (100) by microwave plasma chemical vapor deposition in a gas mixture of CH4/H2/TMB. The influence of boron concentration on the surface morphology, microstructure, and electrochemical properties of BDMD film electrodes was studied. It was found that boron dopants play an important role in the structural quality and electrochemical properties of BDMD film electrodes. The increase of doped boron concentration results in the reduction of diamond grain size and the domination of two peaks located at approximately 500 and 1220 cm−1 in the Raman spectra. Marked differences are observed for BDMD film electrodes with various boron concentrations in impedance characteristics. The electron transfer reaction on BDMD film electrodes becomes faster and reversibility is improved with the increase of boron concentration. Meanwhile, the electrochemical reactions on the BDMD film electrodes become a diffusion controlled process. The non-enzymatic glucose sensors based on as-prepared BDMD film electrodes were developed. The glucose oxidation peak position and current density are dependent on the B/C ratio for the BDMD film electrodes. The results show that appropriate boron doping concentration can improve the conductivity and electrocatalytic activity of BDMD film electrodes. The BDMD film electrode with B/C ratio of 10000 ppm exhibits the highest sensitivity of 96.88 μA mM−1 cm−2, lowest detection limit of 0.018 mM and widest linear range of 0.1 to 5 mM. The developed non-enzymatic glucose sensors based on as-prepared BDMD film electrodes demonstrate selective detection of glucose in alkaline solution containing interfering species of ascorbic acid and uric acid.
Co-reporter:Xiaowei Li, Peiling Ke, Kwang-Ryeol Lee, Aiying Wang
Thin Solid Films 2014 Volume 552() pp:136-140
Publication Date(Web):3 February 2014
DOI:10.1016/j.tsf.2013.12.012
•The dependence of films properties on different incident angles was investigated.•The change of incident angles reduced the stress without obvious damage of density.•The stress reduction attributed to the relaxation of highly distorted bond length.The influence of incident angles of energetic carbon atoms (0–60°) on the structure and properties of diamond-like carbon (DLC) films was investigated by the molecular dynamics simulation using a Tersoff interatomic potential. The present simulation revealed that as the incident angles increased from 0 to 60°, the surface roughness of DLC films increased and the more porous structure was generated. Along the growth direction of DLC films, the whole system could be divided into four regions including substrate region, transition region, stable region and surface region except the case at the incident angle of 60°. When the incident angle was 45°, the residual stress was significantly reduced by 12% with little deterioration of mechanical behavior. The further structure analysis using both the bond angles and bond length distributions indicated that the compressive stress reduction mainly resulted from the relaxation of highly distorted C–C bond length.
Co-reporter:Xiaowei Li, Peiling Ke, He Zheng, Aiying Wang
Applied Surface Science 2013 Volume 273() pp:670-675
Publication Date(Web):15 May 2013
DOI:10.1016/j.apsusc.2013.02.108
Abstract
Structural properties and growth evolution of diamond-like carbon (DLC) films with different incident energies were investigated systematically by the molecular dynamics simulation using a Tersoff interatomic potential for carbon-carbon interaction. The results revealed that the density, sp3 fraction and residual compressive stress as a function of incident energy increased firstly and then decreased; when the incident energy was 70 eV/atom, the density could reach to 3.0 g/cm3 with the maximal compressive stress of 15.5 GPa. Structure analysis indicated that the deviation of both bond angles and lengths from the equilibrium position led to the generation of a large residual stress, while the high compressive stress mainly attributed to the decrease of both bond angles and lengths among carbon atoms. The growth of DLC films underwent a formation process of “Line-Net” structure accompanied with the interaction of many atomic motion mechanisms, and the “Point” stage was only found for DLC films with low incident energy.
Co-reporter:Wei Dai, Peiling Ke, Aiying Wang
Surface and Coatings Technology 2013 Volume 229() pp:217-221
Publication Date(Web):25 August 2013
DOI:10.1016/j.surfcoat.2012.03.076
Co-reporter:Xiao-Wei Li, Min-Woong Joe, Ai-Ying Wang, Kwang-Ryeol Lee
Surface and Coatings Technology 2013 Volume 228(Supplement 1) pp:S190-S193
Publication Date(Web):15 August 2013
DOI:10.1016/j.surfcoat.2012.06.031
The residual stress and atomic bond structure of Si-incorporated diamond-like carbon films were investigated by the molecular dynamics simulation using Tersoff interatomic potential. The effect of Si incorporation into amorphous carbon matrix was analyzed for the various Si concentrations ranging from 0 to 2.1 at.%. The present simulation revealed that the incorporation of a small amount of Si significantly reduced the residual compressive stress: when the Si content was 0.54 at.%, the minimal compressive stress of 1.4 GPa was observed. Structural analysis using the radial distribution function and the bond angle distribution indicated that the compressive stress reduction resulted from the relaxation of highly distorted bond angles less than 109.5°.Highlights► The residual compressive stress can be reduced seriously by Si incorporation. ► There is no large degradation of number density due to the Si incorporation. ► The stress reduction attributes to the relaxation of distorted bond angles below 109.5°.
Co-reporter:Xiaopeng Qin, Peiling Ke, Aiying Wang, Kwang Ho Kim
Surface and Coatings Technology 2013 Volume 228() pp:275-281
Publication Date(Web):15 August 2013
DOI:10.1016/j.surfcoat.2013.04.040
•MoS2-Ti composite coatings were deposited by a novel hybrid HIPIMS system.•Doping Ti enabled MoS2 coatings to grow into a dense amorphous structure.•Ti reacting with O to form titanium oxides inhibited the oxidation of MoS2.•Doped Ti improved the tribological behavior of pure MoS2 coating in ambient air.•The mechanism was discussed in terms of higher coating hardness and adhesion.The MoS2-Ti composite coatings were deposited by a hybrid high power impulse magnetron sputtering (HIPIMS) source of Ti combined with a direct current magnetron sputtering (DC-MS) source of MoS2. The composition, microstructure, mechanical and tribological behaviors of the MoS2-Ti composite coatings were investigated using the various analytical techniques (XPS, SEM, XRD, TEM, nano-indentation, scratch and ball-on-disk test). The results showed that doping Ti using HIPIMS technique enabled MoS2 coatings to grow in the form of a dense amorphous structure. The crystallization degree of the MoS2-Ti composite coatings decreased with the increase of doped titanium content. Ti reacting with O to form titanium oxides in the surface inhibited the oxidation of MoS2. The hardness and adhesion of the composite coatings reached its maximum within a certain range of Ti content. Doped Ti improved the tribological properties of pure MoS2 coatings in the atmospheric environment. The coefficient of friction (COF) decreased with the increase of Ti content. The lowest average COF at 0.04 and the wear rate at 10− 7 mm3 N− 1 m− 1 were achieved at the optimum of Ti content at 13.5 at.%. The improved tribological property was discussed in terms of the obtained higher hardness and better adhesion of the composite coatings combined with inhibition of MoS2 oxidation.
Co-reporter:Wei Yang, Bailing Jiang, Aiying Wang, Huiying Shi
Journal of Materials Science & Technology 2012 Volume 28(Issue 8) pp:707-712
Publication Date(Web):August 2012
DOI:10.1016/S1005-0302(12)60119-4
Co-reporter:Xiaowei Li, Aiying Wang, Kwang-Ryeol Lee
Thin Solid Films 2012 Volume 520(Issue 19) pp:6064-6067
Publication Date(Web):31 July 2012
DOI:10.1016/j.tsf.2012.05.010
The interaction between impurity atom (Si, Ge, and Sn) and carbon atom in diamond-like carbon (DLC) system was investigated by the first principles simulation method based on the density functional theory. The tetrahedral configuration was selected as the calculation model for simplicity. When the bond angle varied in a range of 90°–130° from the equivalent state of 109.471°, the distortion energy and the electronic structures including charge density of the highest occupied molecular orbital (HOMO) and partial density of state (PDOS) in the different systems were calculated. The results showed that the addition of Si, Ge and Sn atom into amorphous carbon matrix significantly decreased the distortion energy of the system as the bond angles deviated from the equilibrium one. Further studies of the HOMO and PDOS indicated that the weak covalent bond between Si(Ge, Sn) and C atoms was formed with the decreased strength and directionality, which were influenced by the electronegative difference. These results implied that the electron transfer behavior at the junction of carbon nano-devices could be tailored by the impurity element, and the compressive stress in DLC films could be reduced by the incorporation of Si, Ge and Sn because of the formation of weaker covalent bonds.Highlights►Distortion energy after bond angle distortion was decreased comparing with CC unit. ►The weak covalent bond was formed between impurity atoms and corner carbon atoms. ►Observed electron transfer behavior affected the strength and directionality of bond. ►Reduction of strength and directionality of bond contributed to small energy change.
Co-reporter:Wei Dai, Peiling Ke, Myoung-Woon Moon, Kwang-Ryeol Lee, Aiying Wang
Thin Solid Films 2012 Volume 520(Issue 19) pp:6057-6063
Publication Date(Web):31 July 2012
DOI:10.1016/j.tsf.2012.04.016
Diamond-like carbon (DLC) films with various titanium contents were investigated using a hybrid ion beam system comprising an anode-layer linear ion beam source and a DC magnetron sputtering unit. The film composition and microstructure were characterized carefully by X-ray photoelectron spectroscopy, transmission electron microscopy and Raman spectroscopy, revealing that the doped Ti atoms had high solubility in the DLC films. The maximum solubility was found to lie between about 7 and 13 at.%. When the Ti content was lower than this solubility, the doped Ti atoms dissolved in the DLC matrix and the films exhibited the typical features of the amorphous DLC structure and displayed low compressive stresses, friction coefficients and wear rates. However, as the doped content exceeded the solubility, Ti atoms bonded with C atoms, resulting in the formation of carbide nano-particles embedded in the DLC matrix. Although the emergence of the carbide nano-particles promoted graphitizing due to a catalysis effect, the film hardness was enhanced to a great extent. On the other hand, the hard carbides particles caused abrasive wear behavior, inducing a high friction coefficient and wear rate.Highlights► Ti doped DLC films (Ti ~ 24 at.% )were deposited by a hybrid ion beam system. ► Solubility of the Ti atoms in the DLC films was found around 7 ~ 13 at .%. ► Microstructure evolution from DLC to nanocomposite played key role in film behaviors.
Co-reporter:Wei Dai, Aiying Wang
Journal of Alloys and Compounds 2011 Volume 509(Issue 13) pp:4626-4631
Publication Date(Web):31 March 2011
DOI:10.1016/j.jallcom.2011.01.132
Metal incorporation is one of the most effective methods for relaxing internal stress in diamond-like carbon (DLC) films. It was reported that the chemical state of the incorporated metal atoms has a significant influence on the film internal stress. The doped atoms embedding in the DLC matrix without bonding with C atoms can reduce the structure disorder of the DLC films through bond angle distortion and thus relax the internal stress of the films. In present paper, Al atoms, which are inert to carbon, were incorporated into the DLC films deposited by a hybrid ion beams system comprising an anode-layer ion source and a magnetron sputtering unit. The film composition, microstructure and atomic bond structure were characterized using X-ray photoelectron spectroscopy, transmission electron microscopy and Raman spectroscopy. The internal stress, mechanical properties and tribogoical behavior were studied as a function of Al concentration using a stress-tester, nanoindentation and ball-on-disc tribo-tester, respectively. The results indicated that the incorporated Al atoms were dissolved in the DLC matrix without bonding with C atoms and the films exhibited the feature of amorphous carbon. The structure disorder of the films tended to decrease with Al atoms incorporation. This resulted in the distinct reduction of the internal stress in the films. All Al-DLC films exhibited a lower friction coefficient compared with pure DLC film. The formation of the transfer layer and the graphitization induced by friction were expected to contribute to the excellent friction performance.Research highlights► Weak carbide former, Al element, was incorporated into DLC films using a hybrid ion beams system comprising an anode-layer ion source and a magnetron sputtering unit. ► The structure disorder of the films tended to decrease with Al atoms doping, which resulted in the distinct reduction of the film internal stress and hardness, but the internal stress dropped faster than the hardness. ► The DLC films with low internal stress and high hardness can be acquired by Al incorporation.
Co-reporter:Wei Dai, Aiying Wang
Surface and Coatings Technology 2011 205(8–9) pp: 2882-2886
Publication Date(Web):
DOI:10.1016/j.surfcoat.2010.10.057
Co-reporter:Wei Dai, Peiling Ke, Aiying Wang
Vacuum 2011 Volume 85(Issue 8) pp:792-797
Publication Date(Web):1 February 2011
DOI:10.1016/j.vacuum.2010.11.013
Cr-containing diamond-like carbon (Cr-DLC) films was deposited on silicon wafers by a hybrid beams system, which consists of a DC magnetron sputtering and a linear ion source. The chromium content in the films was adjusted by varying the fraction of Ar in the Ar and CH4 gas mixture. The composition, microstructure, surface morphology, mechanical properties and tribological behavior of the films were investigated by XPS, TEM, AFM, SEM, nano-indentation and tribological tester as a function of Cr content. It is shown that, as the Cr content increased from 1.49 to 40.11 at.%, the Cr-DLC films transfer from amorphous DLC with dispersed metallic-like Cr to composite DLC with carbide phases embedding in the DLC matrix, and the film surface morphology also evolve from flat surface into rough surface with larger hillocks. The amorphous Cr-DLC films exhibit a low friction coefficient and wear rate as pure DLC, while the composite Cr-DLC films show a higher friction coefficient and wear rate, although they possess a relatively high hardness.Research highlights► The Cr-DLC films with various Cr contents were deposited by the hybrid beams hybrid beam source. ► The Cr-DLC films transfer from amorphous DLC with dispersed metallic-like Cr to composite DLC with carbide phases embedding in the DLC matrix, as the Cr content increased. ► The amorphous Cr-DLC films exhibit a low friction coefficient and wear rate as pure DLC, while the composite Cr-DLC films show a higher friction coefficient and wear rate.
Co-reporter:Wei Dai, Guosong Wu, Aiying Wang
Applied Surface Science 2010 Volume 257(Issue 1) pp:244-248
Publication Date(Web):15 October 2010
DOI:10.1016/j.apsusc.2010.06.076
Abstract
Cr-containing hydrogenated amorphous carbon (Cr–C:H) films were deposited on silicon substrates using a DC reactive magnetron sputtering with Cr target in an Ar and C2H2 gas mixture. The composition, bond structure, mechanical hardness and elastic recovery of the films were characterized using energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and nano-indentation. The film tribological behavior was also studied by a ball-on-disc tribo-tester. The results showed that the films deposited at low C2H2 flow rate (<10 sccm) presented a feature of composite Cr–C:H structure, which consisted of hard brittle chromium carbide phases and amorphous hydrocarbon phase, and thus led to the observed low elastic recovery and poor wear resistance of the films. However, the film deposited at high C2H2 flow rate (40 sccm) was found to present a typical feature of polymer-like a-C:H structure containing a large amount of sp3 C–H bonds. As a result, the film revealed a high elastic recovery, and thus exhibited an excellent wear resistance.
Co-reporter:Wei Dai, Guosong Wu, Aiying Wang
Diamond and Related Materials 2010 Volume 19(Issue 10) pp:1307-1315
Publication Date(Web):October 2010
DOI:10.1016/j.diamond.2010.06.018
Cr-incorporated diamond-like carbon (Cr-DLC) films were deposited on AZ31 magnesium alloy as protective coatings by a hybrid beams deposition system, which consists of a DC magnetron sputtering of Cr target (99.99%) and a linear ion source (LIS) supplied with CH4 precursor gas. The Cr concentration (from 2.34 to 31.5 at.%) in the films was controlled by varying the flow ratio of Ar/CH4. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to investigate the microstructure and composition of Cr-DLC films systematically. An electrochemical system and a ball-on-disk tribotester were applied to test the corrosion and tribological properties of the film on the AZ31 substrate, respectively. At low Cr doping (2.34 at.%), the film mainly exhibited the feature of amorphous carbon, while at high doping (31.5 at.%), chromium carbide crystalline phase occurred in the amorphous carbon matrix of the film. In this study, all the prepared Cr-DLC films showed higher adhesion to AZ31 than the DLC film. Especially for the film with low Cr doping (2.34 at.%), it owned the lowest internal stress and the highest adhesion to substrate among all the films. Furthermore, this film could also improve the wear resistance of magnesium alloy effectively. But, none of the films could improve the corrosion resistance of the magnesium alloy in 3.5 wt.% NaCl solution due to the existence of through-thickness defects in the films.Research Highlights► In the present paper, the Cr-DLC films were successfully deposited on magnesium alloy (AZ31), where the incorporated Cr concentration could be well controlled by varying the Ar/C2H2 flow ratio. The deposited Cr-DLC films showed a very good adhesive strength to the soft AZ31 substrate compared with the pure DLC film. Specifically, the most important results obtained here is that the Cr-DLC film with low Cr doping could significantly improve the wear resistance of the magnesium alloy, even it did slight contribution to the improvement of corrosion resistance of AZ31 alloy. ► The works described in this paper is considered as one of the pioneer studies in the research of Cr-DLC coatings used to modify the surface properties of magnesium alloys, as the reviewer’s comment.
Co-reporter:Guosong Wu, Wei Dai, He Zheng, Aiying Wang
Surface and Coatings Technology 2010 205(7) pp: 2067-2073
Publication Date(Web):
DOI:10.1016/j.surfcoat.2010.08.103
Co-reporter:Guosong Wu, Lili Sun, Wei Dai, Lixin Song, Aiying Wang
Surface and Coatings Technology 2010 204(14) pp: 2193-2196
Publication Date(Web):
DOI:10.1016/j.surfcoat.2009.12.009
Co-reporter:Wei Dai, He Zheng, Guosong Wu, Aiying Wang
Vacuum 2010 Volume 85(Issue 2) pp:231-235
Publication Date(Web):20 August 2010
DOI:10.1016/j.vacuum.2010.06.001
Cr-containing diamond-like carbon films were deposited on silicon wafers by a combined linear ion beam and DC magnetron sputtering. The influence of the bias voltage on the growth rate, atomic bond structure, surface topography and mechanical properties of the films were investigated by SEM, XPS, Raman spectroscopy, AFM, and nano-indentation. It was shown that the chromium concentration of the films increased with negative bias voltage and that a carbide phase was detected in the as-deposited films. The surface topography of the films evolved from a rough surface with larger hillocks reducing to form a smoother flat surface as the bias voltage increased from 0 to −200 V. The highest hardness and elastic modulus were obtained at a bias voltage of about −50 V, while the maximum sp3 bonding fraction was acquired at −100 V. It was suggested that the mechanical properties of the films not only depended on the sp3 bonding fraction in the films but also correlated with the influence of Cr doping and ion bombardment.
Co-reporter:Lili Sun, Peng Guo, Xiaowei Li, Aiying Wang
Diamond and Related Materials (March 2017) Volume 73() pp:
Publication Date(Web):March 2017
DOI:10.1016/j.diamond.2016.10.022
•A wettability mechanism for W-DLC and Cu-DLC is proposed.•The mechanism relies on the bond characteristic between metal and C atoms.•Results offered a facile strategy to design DLC films with wettability properties.By specifically selecting the carbide-forming metal (W) and non-carbide-forming metal (Cu) as the doped metal, we fabricated the W and Cu doped diamond-like carbon (W-DLC and Cu-DLC) films by hybrid ion beam system, respectively. And a comparative study on structure and wetting properties of W-DLC and Cu-DLC films was focused. For Cu-DLC films, the wettability transformation from hydrophilicity (76.56°) to hydrophobicity (105.6°) was observed. While in case of W-DLC films, the wettability of films maintained the hydrophilicity (73.6 ± 3.93°) within the presented W concentration. Based on the surface energy calculation and electronic structure analysis from first-principles calculations, we firstly gained insight into the wettability behavior of W-DLC and Cu-DLC films in terms of the bond characteristics formed between doped metal and C atoms. Results showed that the anti-bonding characteristic between Cu and C atoms reduced the polar components of surface energy and dangling bonds, contributing to the improvement of hydrophobic property, while the non-bonding characteristic for WC bond resulted in the appearance of dipoles, leading to the hydrophilic character. It was in particularly concluded that the different bond characteristic between metal and C atoms played a key role in the wettability of metal doped DLC films. The obtained results offer a facile strategy to design DLC films with tailored wettability properties for the promising hydrophobic applications.
Co-reporter:Wei Yang, Peiling Ke, Yong Fang, He Zheng, Aiying Wang
Applied Surface Science (1 April 2013) Volume 270() pp:
Publication Date(Web):1 April 2013
DOI:10.1016/j.apsusc.2013.01.073
Ti and N co-doped diamond-like carbon ((Ti:N)-DLC) film was deposited on the MAO coated substrate using a hybrid beam deposition system, which consists of a DC magnetron sputtering of Ti target and a linear ion source (LIS) with C2H2 and N2 precursor gas. The microstructure and properties of the duplex (Ti:N)-DLC/MAO coating were investigated. Results indicate that the (Ti:N)-DLC top film with TiN crystalline phase was formed. Ti and N co-doping resulted in the increasing ID/IG ratio. The significant improvement in the wear and corrosion resistance of duplex (Ti:N)-DLC/MAO coating was mainly attributed to the increased binding strength, lubrication characteristics and chemical inertness of (Ti:N)-DLC top film. The superior low-friction and anti-corrosion properties of duplex (Ti:N)-DLC/MAO coating make it a good candidate as protective coating on magnesium alloy.Highlights► The duplex (Ti:N)-DLC coating with TiN crystalline phase on the MAO coating was deposited on AZ80 Mg alloy. ► The binding strength of duplex (Ti:N)-DLC/MAO coating was improved significantly. ► The duplex (Ti:N)-DLC/MAO coatings showed excellent tribological and corrosive properties.
