A critical review of diamond like carbon coating for wear resistance applications

In recent years innovation in carbon based materials have encouraged both researchers as well as industrialists to develop materials/composites with improved tribological properties. Researchers have been fascinated to develop diamond like carbon (DLC) or carbon nanotubes (CNTs) reinforced coatings to their good corrosion resistance, excellent wear resistance, good adhesion strength, and self -lubricious nature. The present review article is mainly focused on various techniques employed in order to process DLC/CNTs coatings as well as provide a summary of DLC/CNTs deposition on different substrates. The present study includes major types, properties and tribological behavior of carbon based materials and mechanisms involved in coating deposition. The study also discusses that deposition of DLC/CNTs coatings on the substrate materials enhances the wear, corrosion and mechanical properties of the substrate.     

Effect of ZrO2 nanoparticles addition to PEO coatings on Ti–6Al–4V substrate: Microstructural analysis,corrosion behavior and antibacterial effect of coatings in Hank's physiological solution

In this study, plasma electrolyte oxidation (PEO) method was employed to modify the surface of Ti–6Al–4V. Effects of different concentrations of ZrO₂ nanoparticles (0, 1, 3 and 5 g/l) into a phosphate-based electrolyte on the morphology, wettability, antibacterial and corrosion behaviors of coatings were investigated. Microstructural analyses of coatings were evaluated using scanning electron microscopy with an energy dispersive spectrometer. Also, X-ray diffraction, contact angle instrument and profilometry were respectively used to perform phase analysis, wettability, and surface roughness of the coatings. The antibacterial test was conducted with spot inoculation method on four pathogenic bacteria. Polarization and impedance spectroscopy measurements were performed in Hank's solution to investigate the corrosion behavior of coatings. The results revealed that PEO coatings without nanoparticles and by increasing the concentration of the ZrO₂ nanoparticles up to 3 g/l in the electrolyte led to a significant improvement in the antibacterial activities of gram-negative bacteria (P. aeruginosa and E. Coli). In the case of gram-positive bacteria, the PEO coated samples demonstrated improved antibacterial effects but addition of ZrO₂ nanoparticles in the PEO coatings resulted in deterioration of antibacterial effect. The sample coated with 3 g/l ZrO₂ nanoparticles showed the peak corrosion resistance compared to its counterparts.     

Alloying behavior and novel properties of CoCrFeNiMn high-entropy alloy fabricated by mechanical alloying and spark plasma sintering

An equiatomic CoCrFeNiMn high-entropy alloy was synthesized by mechanical alloying (MA) and spark plasma sintering (SPS). During MA, a solid solution with refined microstructure of 10 nm which consists of a FCC phase and a BCC phase was formed. After SPS consolidation, only one FCC phase can be detected in the HEA bulks. The as-sintered bulks exhibit high compressive strength of 1987 MPa. An interesting magnetic transition associated with the structure coarsening and phase transformation was observed during SPS process.     

Fabrication of cylindrical SiCf/Si/SiC-based composite by electrophoretic deposition and liquid silicon infiltration

Cylindrical SiC-based composites composed of inner Si/SiC reticulated foam and outer Si-infiltrated SiC fiber-reinforced SiC (SiC_f/Si/SiC) skin were fabricated by the electrophoretic deposition of matrix particles into SiC fabrics followed by Si-infiltration for high temperature heat exchanger applications. An electrophoretic deposition combined with ultrasonication was used to fabricate a tubular SiC_f/SiC skin layer, which infiltrated SiC and carbon particles effectively into the voids of SiC fabrics by minimizing the surface sealing effect. After liquid silicon infiltration at 1550 °C, the composite revealed a density of 2.75 g/cm³ along with a well-joined interface between the inside Si/SiC foam and outer SiC_f/Si/SiC skin layer. The results also showed that the skin layer, which was composed of 81.4 wt% β-SiC, 17.2 wt% Si and 1.4 wt% SiO₂, exhibited a gastight dense microstructure and the flexural strength of 192.3 MPa.     

三氯化铝/盐酸三甲胺离子液体中电沉积制备AI-Ni合金镀层

目的 研究离子液体中Ni2+浓度对Al-Ni合金镀层结构和成分的影响,同时考察电流密度对镀层表面形貌和织构的影响.方法 采用脉冲电流法,在含有不同浓度氯化镍的无水三氯化铝/盐酸三甲胺离子液体中,于不同电流密度下电沉积制备Al-Ni合金镀层.利用扫描电子显微镜、X射线衍射技术和能谱分析仪探究离子液体中Ni2+的浓度对Al-Ni合金镀层结构和成分的影响,考察电流密度对镀层表面形貌和织构的影响.结果 随着离子液体中Ni2+浓度的增加,镀层中镍的含量增多,表面胞状颗粒逐渐变小,表面趋于均匀,当Ni2+的浓度为0.2 mol/L时,形成铝镍金属间化合物.另外,随着电流密度的增加,镀层表面形貌由针状晶体变为棒状颗粒,并且颗粒逐渐增大.结论 离子液体中Ni2+的浓度和电流密度对Al-Ni合金镀层表面形貌、结构和成分有一定的影响.当溶液中Ni2+的浓度为0.2 mol/L、电流密度为6 mA/cm2时,电沉积4 h可制备得到厚度为10μm、由3μm大小晶粒组成、含有铝镍金属间化合物的合金镀层.     

Synergism of molecular weight,crystallization and morphology of poly(3-butylthiophene) for photovoltaic applications

A serial of poly(3-butylthiophene) (P3BTs) with molecular weights (MWs) ranged from 7 kDa to 50 kDa is synthesized and characterized. The DSC studies show that the thermal property and crystallinity of P3BT increase with MWs within the range from 7 kDa to 25 kDa, then decrease with further higher MW. The characteristic morphologies of incontinuous crystalline nanofibrils, interconnected nanofibrillar networks, and relative large clusters associate to low, medium and high MW P3BTs, respectively, demonstrate the strong correlation between MW, crystallinity and morphology of P3BT. It is found that the P3BT could be re-considered as the promising candidate for applications in organic optoelectronics if synergism of the crystallinity and morphology could be precisely controlled via tuning molecular weight. The polymer solar cells (PSCs) device based on P3BT with medium MW achieves an attractive power conversion efficiency of 3.5%, which is, to the best of our knowledge, the record for P3BT/PC₆₁BM PSCs and comparable to the well-studied P3HT devices.     

High vacuum tribological performance of DLC-based solid–liquid lubricating coatings: Influence of atomic oxygen and ultraviolet irradiation

In this paper, the composition, structure, morphology and high vacuum tribological properties of three DLC-based solid–liquid lubricating coatings were investigated after atomic oxygen (AO) and ultraviolet (UV) irradiations. The research results showed that AO and UV irradiations induced the structural changes, including oxidation, bond breaking and crosslinking reactions of the DLC film and liquid lubricants, and the destruction of AO irradiation was much stronger than that of UV irradiation. After irradiations, the friction coefficient of the DLC-based solid–liquid lubricating coatings was lower than that before irradiation (except for AO irradiation), but the wear rates were larger due to irradiation destruction.     

Tribological properties of Ni-based self-lubricating composites with addition of silver and molybdenum disulfide

Tribological properties of Ni-based composites containing silver and molybdenum disulfide were studied from room temperature to 700 °C. The composites were prepared by powder metallurgy technique and the phase composition and microstructure were addressed according to the characterization by SEM and XRD. The results show that the composites were composed of Ni, Cr₂O₃, Ag and Cr_xS_y phases after sintering. The best tribological properties were obtained when the silver and molybdenum disulfide contents were 20 wt% and 8.5 wt%, respectively. The tribo-chemical reaction occurred between Ag and Mo oxide during the rubbing process, which led to the formation of silver molybdate lubricating film. The improved tribological properties were attributed to the formation of silver molybdate lubricating tribolayers.     

Mechanical properties and dry-sliding tribological behavior of partially twinned Fe70Ni30 alloy

The mechanical properties and wear behavior of an Fe₇₀Ni₃₀ alloy with twinned martensite structure obtained by deep cryogenic treatment at ?196°c (DCT) were evaluated in comparison with that of coarse-grained (CG) Fe₇₀Ni₃₀ alloy (single austenite phase). The results showed that after the introduction of martensite with nano-scale twins, the Vickers hardness of Fe₇₀Ni₃₀ increased from 145 to 248 Hv. The friction coefficient of both samples was almost the same, and it decreased with increasing applied load and increased with increasing sliding speed. The XPS results indicated that oxide protecting film was formed on the worn surface, which may dominate the friction coefficient. The wear rate for both samples increased with increasing applied load and decreased slightly with increasing sliding speed. The wear resistance of DCT-Fe₇₀Ni₃₀ alloy was obviously enhanced. The wear mechanisms were investigated by SEM accordingly.     

Synthesis and fluorescent properties of Eu and Tb complexes with a series of new diamide ligands

A series of new diamide ligands were introduced into the complexes of Eu(NO₃)₃ and Tb(NO₃)₃ so as to improve the fluorescent properties. The fluorescent properties of the resulting complexes were investigated. It was found that the complexes subject to the excitation of UV light showed characteristic emission of europium and terbium ions, in particular, the Tb complexes had very much intense fluorescence.