Microstructure and tribological behavior of WS2-Ag composite films deposited by RF magnetron sputtering

WS₂-Ag composite films were deposited on medium carbon steel substrate by RF magnetron sputtering method. The morphology and microstructure of the composite films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The tribological behavior was investigated using a ball-on-disk tribometer in vacuum and in humid air. In the range of Ag content of the film from 4.2 at.% to 40.4 at.%, Ag phase dispersed in amorphous WS₂ matrix, and it changed from amorphous to crystalline structure with the increase of Ag content. The friction coefficients of composite films in humid air were lower and more stable than those of pure WS₂ film, and the environmental sensitivity of tribological behavior decreased obviously with the addition of Ag in the films. At the content of 16.2 at.% Ag, the composite film was dense and adherent, and exhibited excellent tribological performance both in vacuum and in humid air.     

Tribological properties of lubricating oil with micro/nano-scale WS2 particles

The tribological properties of lubricating oil containing micro/nano-scale WS₂ (90 nm, 2 µm) and ionic liquid [C₇H₁₁F₃N₂O₃S] are evaluated using a four-ball friction tester. Results show that the addition of micro/nano-scale WS₂ can improve the tribological properties of the base oil; moreover, adding the ionic liquid as a solvent may lead to a better mixing of the micro/nano-scale WS₂ and base oil and promote the dispersion of WS₂ in the sample oil. The base oil with 90 nm nano-WS₂ and ionic liquid presents the best anti-friction and anti-wear properties at 1 wt.% content. The surface analysis of wear scars reveals that ploughing is the main cause of wear in the three bottom balls. Furthermore, the wear furrows of nano-WS₂ as lubricating additive are uniform and symmetrical and can homogenously appear on the friction area. This work proves that the micro/nano-scale WS₂ plays an important role in improving the performance of tribological properties of lubricating oil.     

Synthesis of a fullerene/expanded graphite composite and its lubricating properties

A fullerene/expanded graphite composite, in which fullerene crystals were incorporated into the expanded graphite interspaces, was prepared by chemical and thermal treatments and its lubricating properties in commercial grease were investigated. Expanded graphite, which was synthesized from graphite by oxidizing by KMnO₄ in 98% H₂SO₄ containing NaNO₃ and by heating at 400 °C for 3 min, and fullerene were placed in a stainless steel tube, and were heated in a furnace under vacuum at 600 °C for 2 weeks. The fullerene/expanded graphite composite obtained was characterized by X-ray diffraction analysis (XRD), Fourier transform infrared (FT-IR) spectroscopy, and scanning electron microscopy (SEM). XRD and FT-IR analyses showed that crystalline fullerene was present in the material and SEM images confirmed that it existed in the expanded graphite interspaces. The composite was blended with a commercial grease, and its lubricating properties were investigated using a four-ball lubricant tester. These properties were evaluated by measuring the wear scar diameter and wear volume loss of the test ball. The combination of composite and grease provided a better lubricating performance than that of pure graphite and grease.     

等离子体电解氧化法制备多孔TiO2/V2O5复合物膜层及其增强光催化产氢活性

较差的光催化产氢效率极大地阻碍了TiO₂光催化剂的工业化应用。为此,本文在含有NH₄VO₃的磷酸盐溶液中,采用等离子体电解氧化(PEO)法制备了多孔TiO₂/V₂O₅复合膜光催化剂,通过扫描电子显微镜(SEM)、能谱仪(EDS)、X射线衍射(XRD)、X射线光电子谱(XPS)和紫外可见漫反射光谱(UV-Vis DRS)对其组成、结构及光吸收性质进行了表征,并采用气相色谱评价了薄膜催化剂的光催化产氢性能,研究了电解液中NH₄VO₃含量对膜的结构、组成和光催化产氢性能的影响。结果表明:复合膜催化剂主要由锐钛矿和金红石型TiO₂组成,具有微孔结构,V₂O₅主要以无定形形式存在于膜中,与TiO₂有很强的相互作用,影响TiO₂的晶面间距。研究发现,元素V抑制了TiO₂的结晶和金红石型TiO₂的形成,扩大了薄膜的光学吸收范围。针对Na₂S+ Na₂SO₃溶液中的光催化产氢性能的研究显示,在质量浓度为1 g/L NH₄VO₃的电解液中制备的TiO₂/V₂O₅薄膜的光催化活性最高,优于近年来报道的其他光催化剂。光催化重复实验表明,该复合膜催化剂具有较高的稳定性和较为恒定的光催化活性。     

Effects of aging treatment on microstructure and tribological properties of nickel-based high-temperature self-lubrication wear resistant composite coatings by laser cladding

The NiCr/Cr₃C₂–WS₂ high-temperature self-lubrication wear resistant composite coatings were fabricated on substrate of a hot-rolled AISI304 austenitic stainless steel by laser cladding. The high-temperature phase stability of the composite coatings was evaluated by aging at 600 °C for 10 h, 30 h, 50 h, and the microstructures of the as-laser clad and aged coatings were examined by means of XRD, SEM, EDS, respectively. The sliding wear resistance of the as-laser clad and aged coatings was evaluated at 600 °C. The results show that NiCr/Cr₃C₂–WS₂ composite coating has excellent high-temperature phase stability, the γ-(Fe,Ni)/Cr₇C₃ eutectic phases, Cr₇C₃ and (Cr,W)C hard phases, CrS/WS₂ mixed solid lubricant phases all existed in the as-laser clad and aged coatings. The volume fraction of eutectic phases decreased gradually with the increasing of aged time due to their dissolution. The microhardness of the aged coating decreased slightly after aging the coating 50 h at 600 °C due to the dissolution of the eutectic phases and notable breaking or granulation of the Cr₇C₃ hard phase, but the tribological properties were not significantly affected by aging treatment.     

Tribological properties of Ti2N-Wx% coatings deposited by magnetron sputtering

Ti₂N-W_x% coatings with different tungsten contents were deposited using unbalanced magnetron sputtering technology. The microstructures and mechanical properties of Ti₂N-W_x% coatings have been characterized by SEM, X-ray diffraction (XRD), nanoindentation and adhesion techniques. The tribological performance of the coatings was investigated using an oscillating friction and wear tester under dry conditions. Indexable inserts with Ti₂N-W_x% coatings were applied to turning AISI 1045 steel material by a lathe. Micron-drills with Ti₂N-W_x% coatings were adopted in the ultra-high speed (10⁵ rpm) Printed Circuit Board (PCB) through-hole drilling test. Experimental results indicate that the coating microstructure, mechanical properties and wear resistance vary according to the tungsten content. Ti₂N-W_14% coated inserts showed the best wear resistance in 1045 steel turning and PCB through-hole drilling tests. The service life of a Ti₂N-W_14% coated tool is five times greater than that of an uncoated tool in PCB through-hole drilling test.     

Residual stress of graded-index-like films deposited by radio frequency ion-beam sputtering

In this study, Ta₂O₅-SiO₂ composite films with various proportions of Ta₂O₅ were prepared by radio frequency ion-beam sputtering deposition. The residual stress of each composite film was analyzed. The residual stresses of different graded-index-like layers made of composite films were studied. The results show that the residual stress of a single layered composite film was lower than that of pure SiO₂ or a pure Ta₂O₅ film. Furthermore, when the composite film was made graded-index-like, the residual stress was reduced.     

Properties of nanocomposite film combining hard TiN matrix with embedded fullerene-like WS2 nanoclusters

We have developed hard self-lubricant coatings combining a hard matrix (TiN) and a self-lubricant phase in the form of inorganic-like WS₂ fullerene. The nanoparticles were injected from the preparation chamber directly to the sample surface during reactive sputtering from a Ti target in Ar/N₂ atmosphere. The injection of the particles led to the local oxidation of the matrix due to the flow of residual oxygen from the preparation chamber; therefore, the final composite was TiN/Ti-O-WS₂. The observation of the composite film by scanning and transmission electron microscopies showed the incorporation of the WS₂ nanoparticles; however, their bonding with the matrix was weak. The analysis of the wear tracks did not show any presence of WS₂ in the contact.     

Multiferroic properties of BiFeO3/Bi4Ti3O12 double-layered thin films fabricated by chemical solution deposition

Multiferroic BiFeO₃/Bi₄Ti₃O₁₂ (BFO/BTO) double-layered film was fabricated on a Pt(111)/Ti/SiO₂/Si(100) substrate by a chemical solution deposition method. The effect of an interfacial BTO layer on electrical and magnetic properties of BFO was investigated by comparing those of pure BFO and BTO films prepared by the same condition. The X-ray diffraction result showed that no additional phase was formed in the double-layered film, except BFO and BTO phases. The remnant polarization (2P_r) of the double-layered film capacitor was 100 μC/cm² at 250 kV/cm, which is much larger than that of the pure BFO film capacitor. The magnetization-magnetic field hysteresis loop revealed weak ferromagnetic response with remnant magnetization (2M_r) of 0.4 kA/m. The values of dielectric constant and dielectric loss of the double-layered film capacitor were 240 and 0.03 at 100 kHz, respectively. Leakage current density measured from the double-layered film capacitor was 6.1 × 10^− 7 A/cm² at 50 kV/cm, which is lower than the pure BFO and BTO film capacitors.     

Dispersion effect and auto-reconditioning performance of nanometer WS<Subscript>2</Subscript> particles in green lubricant

This paper reported on dispersion effect and dispersing techniques of nanometer WS₂ particles in the green lubricant concocted by us. And it also researched on auto-reconditioning performance of nanometer WS₂ particles to the abrasive surfaces of steel ball from four-ball tribology test and piston ring from engine lubrication test. The treated and untreated nanometer WS₂ particles were analysed by infrared spectrum. And the elementary component and interior elementary distribution of abrasive surface repaired by nanometer WS₂ particles were analysed by multifunction electron spectrometer. The results showed that the combinative method of ultrasonic dispersion, mechanical agitation and surface modification could improve the dispersion uniformity and stability of nanometer WS₂ particles in the green lubricant effectively. And the optimal ratio of the mass between surface modifier and nanometer WS₂ particles was 1: 2.5, the optimal treating time was 5 h. And IR analysis indicated that surface modifier could react with hydroxide radicals on surfaces of WS₂ particles and modify the surfaces, and the long lipophilic groups on surfaces of nanometer WS₂ particles could stretch in oil adequately and form steric hindrance layers between particles which prevented particles from conglomerating and depositing. In addition, tribological tests and surface analysis indicated that there were WS₂ adsorption film and reaction film on abrasive surfaces during the tribological tests, which could fill and level up the furrows on abrasive surfaces. As a result, the abrasive surfaces were repaired effectively by nanometer WS₂ particles.     

Preparation and photoelectrochemical performance of TiO2/HS-CH2-COOH/Cu3Se2 composite film

In this paper, the TiO₂/HS-CH₂-COOH/Cu₃Se₂ composite film photoanodes were fabricated on conducting glass plates. Cu₃Se₂ nanoparticles were used as the sensitizer and the bi-functional modifier HS-CH₂-COOH was used at the interface between Cu₃Se₂ and TiO₂ films to improve the properties of the film photoanode. The characterization results show that the sol-gel prepared anatase TiO₂ film has a compact and uniform surface, while the tetragonal Cu₃Se₂ film has a coarse surface which is made up of uniform elongated particles. The photoelectrochemical experimental results indicate that the TiO₂/HS-CH₂-COOH/Cu₃Se₂ composite film photoanodes have a good photovoltaic property.     

In-situ energy-dispersive X-ray diffraction of metal sulfide assisted crystallization of strongly (001) textured photoactive tungsten disulfide thin films

Highly (001) textured tungsten disulphide (WS₂) thin films were grown by rapid metal (Ni, Pd) sulfide assisted crystallization of amorphous reactively sputtered sulfur-rich tungsten sulfide (WS_3 + x) and by metal sulfide assisted sulfurization of tungsten metal films. The rapid crystallization was monitored by real-time in-situ energy dispersive X-ray diffraction (EDXRD). Provided that a thin nickel or palladium film was deposited prior to the deposition of WS_3 + x or W, the films crystallized very fast (about 20 nm/s) at temperatures above the metal sulfide eutectic temperature. After crystallization, isolated MeS_x crystallites are located on the surface of the WS₂ layer, which was proved by scanning electron microscopy. The metal sulfide assisted crystallized WS₂ layers exhibit a pronounced (001) orientation with large crystallites up to 2 µm. The in-situ EDXRD analysis revealed distinct differences of the two crystallization routes from tungsten and from amorphous, sulfur-rich WS_3 + x precursors, respectively. The crystallized WS₂ films showed photoactivity. Combined with the high absorption coefficient of 10⁵ cm^− 1 and a indirect band gap of 1.8 eV these properties make such films suitable for absorber layers in thin film solar cells.     

A study of the erosion-corrosion behavior of nano-Cr2O3 particles reinforced Ni-based composite alloying layer in aqueous slurry environment

To investigate the role of nano-Cr₂O₃ particles on the erosion-corrosion behavior of composite alloying layer, a nano-Cr₂O₃ particles reinforced Ni-based composite alloying layer was fabricated onto AISI 316L stainless steel (SS) via a duplex surface treatment, consisting of Ni/nano-Cr₂O₃ predeposited by electric brush plating, and subsequent Ni-Cr-Mo-Cu multi-element surface alloying by a double glow process. The microstructure and composition of composite alloying layer were characterized by means of X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). The results indicated that the added nano-Cr₂O₃ particles were homogeneously distributed in the alloying layer and didn’t decompose or react with surrounding metal matrix under alloying temperature (1000 °C) condition. A series of electrochemical techniques, including potentiodynamic polarization, open circuit potential (OCP), current response and electrochemical impedance spectroscopy (EIS), was employed to evaluate the corrosion properties of nano-Cr₂O₃ particles reinforced composite alloying layer under various hydrodynamic conditions. Erosion-corrosion tests were conducted in 3.5% NaCl solution plus sand particles with varying concentration (50-150 g/L) at different rotation speeds (600-1100 rpm). To estimate the influence of the nature of different nano-particles on the erosion-corrosion property of composite alloying layer, nano-SiO₂ particles reinforced Ni-based composite alloying layer, single alloying layer and 316L SS was selected as the reference materials for all the corrosion and erosion-corrosion tests.     

Enhanced giant magnetoimpedance effect in FINEMET/TiO2 composite ribbons

In order to study the influence of semiconductors on the magnetic properties and giant magnetoimpedance effect of FINEMET ribbon, titanium dioxide coating layer with different thickness was sputtered onto the free surface of the FINEMET ribbon by RF magnetron sputtering to prepare the FINEMET/TiO₂ composite ribbons. The morphology, magnetic properties, and giant magnetoimpedance of the FINEMET/TiO₂ composite ribbons were analyzed. The results show that the GMI ratio of composite ribbons first increases and then decreases with the increase of TiO₂ layer thickness (0?~?150 nm). When the thickness of TiO₂ thin film is 100 nm, the GMI ratio reaches the maximum 57.3%, which indicates that a certain thickness of TiO₂ thin film can significantly improve the GMI effect. The result can be explained by the combined result of electromagnetic interaction and stress between TiO₂ thin film and the FINEMET ribbon.

     

The preparation and mechanical properties of novel PVA/SiO2 film

The aim of this work is the evaluation of the mechanical properties of composite PVA/SiO₂. A powder impregnation process with integrated inline continuous plasma of SiO₂ was used to produce PVA/SiO₂ composite. PVA/SiO₂ composite was processed into test laminates by compression mounding and the interface-dominated composite properties were studied. When compared to PVA, the mechanical properties of PVA/SiO₂ were significantly increased, such as tensile strength, tensile modulus and elongation at break, and the damping capacity of PVA/SiO₂ film increased with increasing ratio of SiO₂.     

Preparation and investigation of PVDF/PMMA/TiO2 composite film

Polyvinylidene fluoride (PVDF)/Polymethylmethacrylate (PMMA)/Titanium dioxide (TiO₂) composite, and its films was prepared and studied in detail. The structure, morphology, crystalline behavior, thermal, and mechanical properties of PVDF/PMMA/TiO₂ film were investigated through FT-IR/ATR, SEM, XRD, DSC, TGA, and Py-GC/MS, respectively. The results showed that the blended material and its film have favorable thermal and mechanical properties. The TiO₂ particles finely dispersed in the composite featured by crystalline regions of PVDF and homogeneous amorphous regions consisted of PVDF and PMMA, resulting in an advantageous properties and improvement of tensile strength and elongation at break of the PVDF/PMMA film. However, the TiO₂ can greatly narrow the thermally stable margin of PVDF in PVDF/PMMA/TiO₂ composite for at least 100 °C with catalysis decomposition effect.     

Compressive properties and cracking behaviour of 3D interpenetrating hierarchical Al2O3p/steel composite

A hierarchical-architectured Al₂O₃/40Cr steel composite was fabricated by squeeze casting. In the composite, the Al₂O₃ particulate-reinforced 40Cr steel matrix composite and pure 40Cr steel formed a 3D interpenetrating composite. The uniaxial compressive properties as well as the cracking behaviour, the strengthening and toughening mechanisms of the composite were investigated and discussed. The compressive strength, fracture strain, and elasticity modulus of the architectured composite are 903.5?MPa, 18.8%, and 197?GPa, which are 1.5, 4.0, and 1.7 times the values of the uniformly Al₂O₃p-reinforced composite, respectively. Special origination and propagation ways of the cracks in the composites were observed with a 3D X-ray microscope, and the contributions of 3D framework structure on the strengthening and toughening of the composite were confirmed.     

Fabrication of porous TiO2 film via hydrothermal method and its photocatalytic performances

Porous anatase (TiO₂) films were fabricated onto stainless steel substrates with Ti(OC₄H₉)₄ as a precursor via hydrothermal process. The crystallization and porous structure of TiO₂ film were dependent on the time and temperature of the hydrothermal reaction. A TiO₂ film with orderly porous structure and high crystallization was obtained upon treatment at 150 °C for 2 h. The grain size of TiO₂ is ca. 6 nm, and pore diameter is ca. 10 nm. Diffusion of Fe into the porous TiO₂ film occurred; Fe also diffused onto the surface of the film with the extension of hydrothermal reaction time or increase of the reaction temperature. The diffusion reaction has a large effect on the formation of porous TiO₂ film as well as its interface texture. However, it does not change the crystal phase of the TiO₂. The resultant TiO₂ film showed high photocatalytic activity towards degradation of gaseous formaldehyde.     

Structure and tribological property of MoSx-CrTiAlN film by unbalanced magnetron sputtering

MoS_x-CrTiAlN film was deposited on Mg alloy substrates using unbalanced magnetron sputtering. First of all, the CrTiAlN layer was synthesized in a gas mixture of Ar + N₂, and then the MoS_x layer on CrTiAlN were deposited by a single MoS_x target. The composition, structure and tribological property of MoS_x-CrTiAlN film were characterized by X-ray photoelectron spectrometry, X-ray diffraction, transmission electron microscopy and ball-on-disc tester. The experimental results show that crystallography structure of CrTiAlN layer is FCC whilst the MoS_x layer has a mixed microstructure with hexagonal and amorphous state. The coefficient of friction of MoS_x-CrTiAlN film is a function of load and shows a steady decreasing with the increasing in applied load.     

聚乳酸/纳米SiO2复合纤维的制备及力学性能

首先用硅烷偶联剂(GPS)对纳米SiO2进行接枝改性,利用粒径分析仪、FTIR和沉降实验对改性前后纳米SiO2的粒径大小、结构和溶剂稳定性的变化进行了表征;然后将改性前后的纳米SiO2分别与聚乳酸(PLA)在双螺杆挤出机中熔融混合,利用牵伸卷绕装置制备了PLA/SiO2和PLA/M-SiO2(改性后SiO2)复合纤维。利用视频显微镜和单纱强力仪研究了不同纳米SiO2含量对PLA/SiO2和PLA/M-SiO2复合纤维结构形貌和力学性能的影响,以及不同牵伸倍数对PLA/M-SiO2复合纤维结构形貌和力学性能的影响。结果表明M-SiO2粒径明显减小,且硅烷偶联剂结构中的有机官能团与SiO2表面硅羟基发生反应,减少了其表面Si-OH的量,使得M-SiO2表现出良好的溶剂稳定性和分散性;PLA/M-SiO2复合纤维的力学性能较PLA/SiO2复合纤维得到了明显的改善;当改性纳米SiO2含量为1%时复合纤维强度最好;当牵伸倍数为3时复合纤维强度最好。