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      20 March 2017, Volume 45 Issue 3 Previous Issue    Next Issue
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    GRAPHENE COLUMN
    Mechanical Properties of Graphene Reinforced Nickel-based P/M Superalloy
    Chuan-bo JI, Xiao-feng WANG, Jin-wen ZOU, Jie YANG
    2017, 45 (3): 1-6.   DOI: 10.11868/j.issn.1001-4381.2016.000600
    Abstract ( 1613 ( PDF (19919KB)( 341 Citation

    The graphene nanosheets were dispersed in the superalloy powder by using the wet mixing method, and then the nickel based FGH96 P/M superalloy was prepared with hot isostatic pressing (HIP)+hot extrusion (HEX)+hot isothermal forging (HIF)+heat treating (HT) processes. The results show that the graphene well disperses in the superalloy powder and keeps its original form during the following hot processing. After 0.1%(mass fraction) graphene is added, the average room temperature tensile strength and yield strength increase by 58MPa and 43MPa respectively, and the ductility increases from 21.0% to 37.3%; the tensile strength and yield strength at 650℃ increase by 58MPa and 28MPa, and the ductility increases from 18.5% to 26.5%. The mechanism of strengthening and toughening reinforcement was also analyzed based on graphene reinforced FGH96 superalloy.

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    Effect of Graphene Oxide on Anti-aging Property of Nitrile Butadiene Rubber
    Lin ZHANG, Duo-li CHEN, Min-hao ZHU, Zhen-bing CAI, Jin-fang PENG
    2017, 45 (3): 7-12.   DOI: 10.11868/j.issn.1001-4381.2015.001240
    Abstract ( 850 ( PDF (7686KB)( 178 Citation

    The blends with higher damping performance was prepared based on nitrile butadiene rubber (NBR) with addition of graphene oxide (GO) and modified graphene oxide (MGO) prepared by improved Hammer method. Meanwhile, the damping property and the anti-aging property of the blends were investigated by DMA, AFM, SEM and so forth. The results show that after the addition of the GO and MGO, the tangent of loss angle (tanδ) increases and also the anti-aging property is improved. When adding less amount of GO in the matrix, the anti-aging property is better; when adding MGO in the matrix, the amount of addition is not obviously related with the anti-aging property of the blends. The dispersion of GO and MGO has positive correlation with its anti-aging property. By microscopic analysis, the main reason for the decrease of anti-aging property of the blends is the agglomeration of the GO. The interface effect formed by the addition of MGO and GO is the main reason for its high damping property and anti-aging property.

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    Compatibilization of Graphene Oxide on Polypropylene/Polyamide 6 of Two Components
    Cong HE, Bao-li OU, Zheng-feng LI
    2017, 45 (3): 13-16.   DOI: 10.11868/j.issn.1001-4381.2015.001137
    Abstract ( 788 ( PDF (6179KB)( 155 Citation

    The graphene oxide were firstly prepared by a modified Hummers method, and then blended with polypropylene (PP)/polyamide 6(PA6) blends. The compatibilizations of the graphene oxide on the PP/PA6 blends were investigated by means of scanning electron microscopy (SEM). SEM observation shows the domain size of the dispersed PA6 phase significantly decreases with the addition of graphene oxide. Due to the chemical reaction of graphene oxide with amino group of PA6, a stronger interfacial adhesion between graphene oxide, PP and PA6 is obtained, which is confirmed by mechanical analysis. The improved mechanical properties and decreased dispersed PA6 domain indicate the graphene oxide plays the role of coupling species between the two polymers. Therefore, a clear compatibilization effect is induced by graphene oxide in the immiscible PP/PA6 blends.

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    Research Progress in Graphene/Rubber Conducting Nanocomposites
    Hui-min DONG, Huang-hai QIAN, Li-jun CHENG, Zheng-tao SU, Jia LIU, Wen-zhi WANG, Wei-qi MU
    2017, 45 (3): 17-27.   DOI: 10.11868/j.issn.1001-4381.2016.001332
    Abstract ( 1228 ( PDF (13091KB)( 630 Citation

    The conductive mechanism of graphene/rubber nanocomposites was introduced.Advances in the synthesis and properties of graphene and its derivatives, modifications of graphene, along with its hybrid fillers, as well as fabrication of related rubber conducting nanocomposites were reviewed.Many factors affecting the electrical properties, such as fabrication method, vulcanization, temperature, pressure, frequency and media etc. were also summarized.It was pointed out that the further research should be focused on multi-component graphene/rubber nanocomposites and its double percolation phenomenon.

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    Research Progress on Preparation of Graphene by Supercritical Fluid Exfoliation
    Sheng-fei HU, Wen-min WEI, Qing-ting LIU, Rong ZHANG
    2017, 45 (3): 28-34.   DOI: 10.11868/j.issn.1001-4381.2015.001011
    Abstract ( 1028 ( PDF (3120KB)( 389 Citation

    As a new type of two-dimensional carbonaceous material, graphene has excellent physical properties and great application potential. The key problem to realize graphene industrialization is to find a large-scale preparing method of graphene with high quality and low cost. In this paper, the advantages and disadvantages of preparation methods for graphene were first reviewed, and then the mechanism, research status and characterization methods of supercritical fluids exfoliated method were introduced in details. And the features of supercritical fluids exfoliated method with the assistance of ultrasonication and pyrene-polymers were summarized. The advantages of supercritical fluids exfoliated method are simple equipment, processing conditions easy to achieve and products with high quality, and a new way of thinking for the industrial production of graphene is provided.

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    RESEARCH ARTICLE
    Preparation and Characterization of Modified Montmorillonite/Paraffin Phase Change Microcapsules for Energy Storage
    Sen LIN, Shi-yong SUN, Xiang ZOU, Peng-yun GUO
    2017, 45 (3): 35-40.   DOI: 10.11868/j.issn.1001-4381.2016.001030
    Abstract ( 804 ( PDF (5094KB)( 239 Citation

    The phase change microcapsules of modified montmorillonite/paraffin were prepared by Pickering emulsion method. Analytic techniques of optical microscopy, scanning electron microscopy (SEM), infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and thermogravimetry (TG) were utilized for characterizing chemical structure, morphology and thermal properties. Results show that modified montmorillonite as a new type wall material has excellent performance for protecting core material of paraffin. FTIR spectra of phase change of modified montmorillonite/paraffin microcapsules shows that their characteristic peaks match with corresponding peaks of pure paraffin and modified montmorillonite. DSC results indicate that modified montmorillonite/paraffin microcapsules have similar solid-liquid phase change temperature with pure paraffin. The phase transition enthalpy values of microcapsules with paraffin contents varying from 55% to 80% are 110.5-147.2J/g, indicating that microcapsules have excellent thermal storage performance and the phase change properties can be adjusted by changing contents of paraffin. TG results confirm that modified montmorillonite/paraffin microcapsules have outstanding thermal stability. The presented study indicates that modified montmorillonite is a suitable wall material for preparing paraffin microcapsule. Modified montmorillonite/paraffin microcapsules have advantages of low cost and high performance with a great application potential in the field of thermal storage.

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    Creep Behavior of a 4.5%Re/3.0%Ru Containing Single Crystal Nickel-based Superalloy at Elevated Temperature
    De-long SHU, Su-gui TIAN, Jing WU, Bao-shuai ZHANG, Shuang LIANG
    2017, 45 (3): 41-46.   DOI: 10.11868/j.issn.1001-4381.2015.001144
    Abstract ( 754 ( PDF (5223KB)( 128 Citation

    The creep behavior of a containing 4.5%Re/3.0%Ru single crystal nickel-based superalloy at elevated temperatures was investigated by means of creep properties measurement and microstructure observations to specimens in different creep stages by SEM and TEM. Results show that the alloy exhibits good creep resistance at high temperature, and the creep life of the alloy at 1040℃/160MPa reaches 725h. During creep at high temperature, the γ' phase in alloy transforms into the N-type rafted structure along the direction vertical to the stress axis, the deformation mechanism of alloy during steady state creep is dislocations slipping in γ matrix and climbing over the rafted γ' phase. In the latter period of creep, the deformation mechanism of alloy is dislocations slipping and shearing into the rafted γ' phase. The alternate slipping of dislocations results in the twist of the rafted γ' phase to promote the initiation and propagation of the cracks along the interfaces of γ/γ' phases up to creep fracture, which is thought to be the fracture mechanism of alloy during creep at high temperature.

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    Mechanical Behavior of DP980 High Strength Steel Under Dynamic Tensile Tests
    Wen-yang TIAN, Fen LIU, Chun-hua WEI, Wei-sheng XIA, Yun-zhen YANG
    2017, 45 (3): 47-53.   DOI: 10.11868/j.issn.1001-4381.2015.000731
    Abstract ( 932 ( PDF (30106KB)( 146 Citation

    The mechanical behavior and fracture modes of DP980 high strength steels were studied by comparing the results of dynamic tensile tests at strain rates from 10-3s-1 to 103s-1. The results show that the strength of DP980 steel remains almost unchanged and the plasticity decreases by 7.5% as the strain rate increasing from quasi-static (10-3s-1) to 100s-1. When the strain rate increases from 100s-1 to 103s-1, the strength keeps increasing, while the plasticity increases by 14% at the strain rate ranging from 100s-1 to 102s-1, but then follows by a decrease of 24.7% in the range of 102s-1 to 103s-1. The strain rate sensitivity coefficient m increases with the increasing of the strain rate. During the plastic deformation, the multiplication reinforcement of dislocation and the motion resistance due to the acceleration of dislocation in ferrite matrix are the main reasons for the strength enhancement. The plastic deformation concentrates in the ferrite, and the microvoids and cracks propagate along the martensite-ferrite interface. In the thickness direction of specimen, the macrographs of fracture are "V" shape cups when strain rate is lower than 101s-1, but the pure sheer shape with 45° to the tensile direction when strain rate is over 101s-1.

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    Impulse Pressuring Diffusion Bonding of TiC Cermet to Stainless Steel Using Ti/Nb Interlayer
    Jia LI, Guang-min SHENG, Li HUANG
    2017, 45 (3): 54-59.   DOI: 10.11868/j.issn.1001-4381.2015.000177
    Abstract ( 653 ( PDF (14364KB)( 124 Citation

    Impulse pressuring diffusion bonding (IPDB) and constant pressuring diffusion bonding (CPDB) of TiC cermet to 304 stainless steel (304SS) using Ti/Nb interlayer was carried out at 890℃ under a impulse pressuring of 2-10MPa and a constant pressuring of 10MPa within a duration of only 4-12min, and a robust metallurgical bonding was achieved. Microstructure characterization and shear performance of the IPDB and CPDB joints were analyzed by SEM, EDS, XRD and shearing test. The results show that the interface phases in those two kinds of joints are similar, which are mainly σ phase, (β-Ti, Nb) and α+β-Ti solid solution. When the joint is bonded for 10min, shear strength of TiC/304SS CPDB joints is 55.6MPa, while the shear strength of IPDB joints reaches 110MPa. The fracture of CPDB joints is TiC cermet fracture, while that of IPDB joints is mixed fracture by alternated between TiC cermet and reaction layer.

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    Research on Weld Seam Models for Hydro-forming of Ellipsoidal Shell
    Wei-wei ZHANG, Bu-gang TENG
    2017, 45 (3): 60-65.   DOI: 10.11868/j.issn.1001-4381.2015.000098
    Abstract ( 622 ( PDF (3196KB)( 102 Citation

    In order to study the effect of weld seam models on hydro-forming of ellipsoidal shell, three kinds of models, i.e., comprehensive model rough model and no weld seam model were built and the influence was discussed on variation of axis length. An experiment for hydro-forming of ellipsoidal shell with initial axis length ratio 1.8 was first carried out, and the axis length varying with the increasing of internal pressure was obtained. Simulation on three kinds of finite element model was conducted, and the effect of weld seam models on the simulation accuracy was deeply discussed by a comparison of axis length variation between simulation and experiment. It is shown that little difference happens among the three kinds of weld seam models at the early stage of deformation, and the axis length deviation is less than 4%. However, there is worse simulation accuracy for the no weld seam model at the middle and late stage of deformation, and the axis length deviation is up to 15%. While both the comprehensive model and the rough model can successfully predict the axis length variation with the deviation no more than 5%. Finally, the rough model is selected on the basis of better simulation accuracy and simple weld seam model.

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    TIG Wire and Arc Additive Manufacturing of 5A06 Aluminum Alloy
    Dan HUANG, Zhi-hua ZHU, Hai-bin GENG, Jiang-tao XIONG, Jing-long LI, Fu-sheng ZHANG
    2017, 45 (3): 66-72.   DOI: 10.11868/j.issn.1001-4381.2015.000552
    Abstract ( 1546 ( PDF (26548KB)( 545 Citation

    Wire and arc additive manufacturing (WAAM) was investigated by tungsten inert gas arc welding method (TIG), in which φ1.2mm filler wire of aluminum alloy 5A06(Al-6Mg-Mn-Si) was selected as deposition metal. The prototyping process was conducted by a TIG power source (working in AC mode) manipulated by a four-axis linkage CNC machine. Backplate preheating temperature and arc current on deposited morphologies of single layer and multi-layer were researched. The microstructure was observed and the sample tensile strength was tested. For single layer, a criterion that describes the correlation between backplate preheating temperature and arc peak current, of which both contribute to the smoothening of the deposited layer. The results show that the layer height drops sharply from the first layer of 3.4mm and keeps at 1.7mm after the 8th layer. Fine dendrite grain and equiaxed grain are found inside a layer and coarsest columnar dendrite structure at layer boundary zone; whereas the microstructure of top region of the deposited sample changes from fine dendrite grain to equiaxed grain that turns to be the finest structure. Mechanical property of the deposited sample is isotropic, in which the tensile strength is approximately 295MPa with the elongation around 36%.

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    Tribological Behavior of Multi-layered WC-Co/MoS2-Ni Self-lubricating Coating Fabricated by Detonation Gun Spraying
    Tie-gang WANG, Bai-song LI, Bing YAN, Qi-xiang FAN, Yan-mei LIU, Jun GONG, Chao SUN
    2017, 45 (3): 73-79.   DOI: 10.11868/j.issn.1001-4381.2016.000002
    Abstract ( 713 ( PDF (13930KB)( 139 Citation

    The multilayered composite WC-Co/MoS2-Ni self-lubricating coatings were prepared by detonation gun spraying technology. The coating microstructure, element distribution, adhesive strength, and tribological properties were studied systematically. The results show that a little of MoS2 is oxidized and decomposed into gas of SO2 during the high-temperature spraying process. The SO2 left in the coating and can form into the micro porosities. The friction coefficient of the WC-Co coating first increases rapidly in the initial running-in phase, and then gradually increases slightly after entering into the steady-state phase; whereas the friction coefficient of multilayer composite coating steps in the steady-state phase soon and starts to decline gradually when the top WC-Co coating became perforated. By comparison, the coating cohesion declines slightly after adding the self-lubricating layer MoS2-Ni, but the friction coefficient decreases by about 40%, and the wear resistance is also improved slightly.

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    Influence of Y2O3 Content on Microstructure and Properties of Laser Alloying WC/Ni Metal Ceramic on 38CrMoAl Steel
    Li-ying HAN, Cun-shan WANG, Qiao FENG
    2017, 45 (3): 80-87.   DOI: 10.11868/j.issn.1001-4381.2015.000926
    Abstract ( 601 ( PDF (25615KB)( 133 Citation

    WC/Ni reinforced layers with different Y2O3 contents were fabricated on the surface of 38CrMoAl steel by laser alloying. The influence of Y2O3 content on the phase composition, microstructure, microhardness and tribological performance of the alloying layers were investigated via X-ray diffraction, scanning electron microscopy, electron microprobe, Vickers hardness tester and friction wear testing machine. The results show that the alloying layers with different Y2O3 contents all consist of γ-(Fe, Ni), martensite matrix, M3C, and WC phases. Nano-WC particles are mainly distributed between the dendrites in the top of the alloying layers, while the micro-scale WC particles with epitaxial growth layers are observed in the bottom of alloying layers. With the increase of Y2O3 content, the solidified microstructure with hypoeutectic morphology gradually refines, the number of the γ-(Fe, Ni) and M3C increases, and the number of martensite matrix decreases slightly. When Y2O3content (mass fraction, the same below) is more than 1.0%, the solidified microstructure slightly coarsens. With the increase of Y2O3 content, the hardness of the alloying layers increases first and then decreases; the friction coefficient and the wear mass loss exhibit the opposite trend. When the Y2O3 content is 1.0%, the hardness of the alloying layer is the highest, which is 2.4 times of hardness of matrix; the friction coefficient and the wear mass loss are the lowest, which are 17% and 8.9% of the matrix respectively.

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    Effect of SiC Content on Microstructure and Wear Resistance of Laser Cladding SiC/Ni60A Composite Coating
    Long-zhi ZHAO, Wu LIU, De-jia LIU, Ming-juan ZHAO, Jian ZHANG
    2017, 45 (3): 88-94.   DOI: 10.11868/j.issn.1001-4381.2015.001454
    Abstract ( 686 ( PDF (17827KB)( 140 Citation

    The SiC reinforced Ni60A alloy laser cladding coating on the 45 steel substrate was fabricated with the LDM2500-60 semiconductor laser equipment. The effect of SiC content on microstructure, dilution rate, wear resistance, friction coefficient and microhardness was investigated systematically.The results show that with the increase of SiC content, the microstructure of upper coating is refined obviously, the dilution rate, wear resistance, friction coefficient and microhardness increase firstly and then decrease; when the mass fraction of SiC is 20%, the wear resistance of the cladding coating is the best one, in which the wear loss of coating is only 0.0012g and is 1/36.3 of the matrix; the minimum friction coefficient is 0.464, the friction process is the most stable; the highest microhardness of the cladding coating is 1039.9HV0.2, which is 3.5 times of the substrate; but when the mass fraction of SiC is 25%, the microhardness and wear resistance of coating decrease.

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    Effect of Adding Elements on Microstructure of Mg-3Si Alloy
    Bin CUI, Liu YANG, Yun-lai DENG, Jun TAN, Qian ZHANG, Ting WANG
    2017, 45 (3): 95-101.   DOI: 10.11868/j.issn.1001-4381.2015.000136
    Abstract ( 627 ( PDF (16736KB)( 120 Citation

    The microstructure of alloy Mg-3Si (mass fraction/%, same as below) after successive additions with different elements of Zn, Nd, Gd and Y was observed and the microstructure evolution was investigated by scanning electron microscopy and X-ray diffraction. The results show the primary Mg2Si particles co-exist with eutectic Mg2Si particles in binary alloy Mg-Si. With minor addition of Zn element, only primary Mg2Si can be found in ternary Mg-3Si-3Zn system while eutectic Mg2Si particles disappear. In quaternary alloy Mg-2.0Nd-3.0Zn-3.0Si, the addition of Nd element can effectively refine the primary Mg2Si particles and form some Mg41Nd5 particles. After continuous adding of Gd and Y elements into quaternary system, Gd5Si3 and YSi particles increase significantly in the alloy Mg-8.0Gd-4.0Y-2.0Nd-3.0Zn-3.0Si, while volume fraction of primary Mg2Si decrease significantly. Thermo-Calc calculation predicts that the Gibbs free energy for primary particles Gd5Si3, YSi is lower, and therefore Gd, Y atom and Si are more likely to form compounds. In Mg-8Gd-4Y-2Nd-3Zn-3Si alloy, room temperature Gibbs free energy for primary particles Mg2Si, Gd5Si3, YSi is-9.56×104, -8.72×104, -2.83×104J/mol, respectively, and the mass fraction of these particles is 8.07%, 5.27%, 1.40% respectively.

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    Hot Compressive Deformation and Processing Maps of ZK60 and ZK60-1.0Er Magnesium Alloy
    Zhong-jun WANG, Xue-dan FU, Jing ZHU, Le ZHOU, Hong-bin WANG
    2017, 45 (3): 102-111.   DOI: 10.11868/j.issn.1001-4381.2016.000505
    Abstract ( 729 ( PDF (4676KB)( 138 Citation

    The hot compressive deformation behavior of ZK60 and ZK60-1.0Er magnesium alloy occurring homogenization was investigated by Gleeble-1500D thermal simulator, analyzing the characteristics of the flow stress changes of the two kinds of magnesium alloys at the temperature 160-420℃, the strain rate 0.0001-1.0s-1. The experimental results show that the two kinds of magnesium alloys are deformation temperature and strain rate sensitive materials, with the decrease of deformation temperature and the increase of strain rate, the flow stress increases; meanwhile, flow stress value tends to be constant after flow stress reaches peak value. Rare earth Er reduces the average deformation activation energy from 183kJ/mol to 153kJ/mol, and the stress index n value is improved from 6 to 8; dynamical recrystallization critical stress σc value decreases, with the increase of deformation temperature and the decrease of strain rate, and at 420℃/1.0s-1, rare earth Er reduces the critical stress σc value of occurring dynamic recrystallization from 76MPa to 50MPa. According to the obtained processing map by material dynamic model, combining with microstructure observations, rare earth Er reduces instability areas of ZK60 magnesium alloy, and increases power dissipation efficiency value ηmax from 35% to 45% at safety zone, promotes dynamic recrystallization grain nucleation, but inhibits recrystallization grain growth.

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    Effect of Heating Rate on Grain Structure and Superplasticity of 7B04 Aluminum Alloy Sheets
    Min CHEN, Ling-ying YE, Da-xiang SUN, Tao YANG, Guo-wei WANG, Xin-ming ZHANG
    2017, 45 (3): 112-118.   DOI: 10.11868/j.issn.1001-4381.2015.000850
    Abstract ( 727 ( PDF (9998KB)( 153 Citation

    Fine-grained 7B04 aluminum alloy sheets were manufactured through thermo-mechanical treatment. The effects of anneal heating rate on grain structure and superplasticity were investigated using electron back scattering diffraction (EBSD) and high temperature tensile test. The results show that at the heating rate of 5.0×10-3K/s, the average grain sizes along the rolling direction (RD) and normal direction (ND) are 28.2μm and 13.9μm respectively, the nucleation rate is 1/1000. With the increase of heating rate, the average grain size decreases, and the nucleation rate increases. When the heating rate increases to 30.0K/s, the average grain sizes along the RD and ND decrease respectively to 9.9μm and 5.1μm, and the nucleation rate increases to 1/80. Besides, with the increase of heating rate, the elongation of sheets also increases. The elongation of the specimens increases from 100% to 730% under the deforming condition of 773K/8×10-4s-1.

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    REVIEW
    Progress of Diamond-like Carbon Films
    Qing-yun CHEN, Kai-min SHI, Min-hua SU, Hui-yi LYU, Yu LUO, Chen ZENG
    2017, 45 (3): 119-128.   DOI: 10.11868/j.issn.1001-4381.2015.000229
    Abstract ( 926 ( PDF (2975KB)( 400 Citation

    Diamond-like carbon (DLC) films had many unique and outstanding properties such as high thermal conductivity, high hardness, excellent chemical inertness, low friction coefficients and wear coefficients. The properties and combinations were very promising for heat sink, micro-electromechanical devices, radiation hardening, biomedical devices, automotive industry and other technical applications, more research and a lot of attention were attracted in recent years. The research progress of diamond-like films and the nucleation mechanism of film were summarized, and application prospect of DLC films were demonstrated. The aim of this paper is to provide insights on the research trend of DLC films and the industry applications.

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