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The effect of applied load on the tribological behaviors of single DLC coating and DLC/Cr 3 C 2 –NiCr duplex coating was explored in the paper experimentally, and the role of cermet interlayer on the duplex coating tribological behavior was analyzed from the perspective of carbonaceous transfer film formation. Results proved that the duplex coating wear rate under 20 N was the lowest, about 1/6 of that of the single coating. The existence of Cr 3 C 2 –NiCr interlayer can prevent the top DLC film from being damaged in high load friction, reduce the fluctuation and vibration of the friction interface, and help the friction-induced graphitized carbonaceous transfer film to maintain on the friction counterpart, thus realizing the low-friction of the duplex coating. Furthermore, the critical conditions under which the friction-induced carbonaceous transfer film of a single coating maintains on the friction counterpart are explored by designed experiments. Results show that the carbonaceous transfer film derived from the single coating can only maintain on the friction counterpart under conditions of low load, low sliding frequency, and high humidity, which indirectly confirms the excellent tribological performance of the duplex coating. [ABSTRACT FROM AUTHOR]

In this study, experimental analysis and finite element modeling (FEM) were employed to investigate the microstructure and mechanical properties of duplex coatings composed of a Cr 3 C 2 –NiCr interlayer and a top AlCrN film in comparison with these of a single AlCrN film. Results showed a significant improvement in the adhesive strength, load-bearing capacity, H/E, and H3/E2 ratios, and hardness of the AlCrN/Cr 3 C 2 –NiCr duplex coatings compared to the single AlCrN film, especially the wear resistance that increased by nearly eight times under heavy loads. Moreover, FEM analysis revealed that the duplex design reduced the stress concentration area on the surface of AlCrN film and kept it far away from the contact interface during load-bearing. [ABSTRACT FROM AUTHOR]

WC/a-C nano-multilayers with different modulation ratio (WC:a-C) ranging from 1:10 to 1.5:1 were deposited by fixing a-C individual layer thickness and tailoring WC individual layer thickness. The effect of modulation ratio on mechanical and tribological performance of WC/a-C nano-multilayers were investigated. Superior mechanical and tribological properties were simultaneously achieved at modulation ratio of 1:1.2. In addition to the improvement of mechanical properties, the improved tribological properties should also be attributed to the friction-induced formation of a WO 3 -rich transfer film under an appropriate WC individual layer thickness, which combing the graphitized worn film surface constructed an intrinsically weak-interacting sliding interface (WO 3 /C interface). Also, graphitized carbon is an essential coadjutant for the formation of WO 3 -rich transfer film. [ABSTRACT FROM AUTHOR]

Effects of carbide content on the mechanical and tribological properties of DLC/Cr 3 C 2 –NiCr duplex coatings were systematically investigated. Results revealed that cermet coating with high carbide content provided strong support for the top DLC film by bearing most of the contact stress, thus improving its hardness, load-bearing capacity, and adhesion strength. The increased carbide content increased the contact and shear stresses on duplex coating during the friction process, intensifying the graphitization of the top DLC film but inhibiting the formation of a graphitized transfer film on the counterpart, thus slightly increasing its friction coefficient. However, the predominant wear mechanism changed from high-efficiency abrasive wear to low-efficiency adhesive wear for low to high carbide content, superior wear resistance was thereby achieved. [Display omitted] • Effects of carbide content on mechanical and tribological properties of duplex coatings was systematically studied. • Contact stress distribution in duplex coatings during the load-bearing process was clarified by FEM analysis. • Tribological mechanisms were revealed from many aspects of energy description, phase transition and contact mechanics. [ABSTRACT FROM AUTHOR]

A novel nanomultilayered architecture was developed through magnetron sputtering to simultaneously achieve excellent mechanical and tribological properties in TiB 2 /a-C film. Structural optimization was conducted by adjusting the modulation period from 1 to 10.5 nm. Film hardness and toughness were significantly improved and reached the optimal value at Λ = 6.6 nm. Combination of a sufficient number of heterointerfaces and appropriate individual layer thickness played a key role in hardening and toughening. The internal stress increased linearly with the increase in modulation period, which may be related to the reduction in the number of interfaces. Furthermore, a low friction coefficient of about 0.1 was achieved in the steady state at Λ ≤ 6.6 nm due to the formation of a uniform and compact transfer film on the worn ball surface. The improved mechanical performance and the presence of an effective transfer film resulted in an outstanding anti-wear performance at Λ = 6.6 nm. [ABSTRACT FROM AUTHOR]

[Display omitted] • Friction-induced reconstruction behavior of sliding interface and low friction mechanism of WC/a-C films are studied. • Moisture and oxygen are two essential factors for the formation of a WO 3 -rich transfer film. • Intrinsically weak interaction of the WO 3 /C interface is the origin of low friction. Tungsten carbide reinforced amorphous carbon (WC/a-C) films exhibit significantly lower coefficient of friction (COF) than typical a-C films in the atmospheric environment; thus, they are promising candidates for use as solid lubricants. However, the low friction mechanism of WC/a-C films remains poorly understood. Here, we revealed that the friction-induced formation of WO 3 -rich transfer film changed the real sliding interface between the initial friction pair materials into an interface between a WO 3 -rich transfer film and carbon-rich worn film surface (WO 3 /C interface). First-principles calculations indicated that the WO 3 /C interface showed weaker interactions than the C/C interface of the a-C film under the same conditions, particularly when the dangling carbon bonds at the sliding interface were not completely passivated. This resulted in a reduced COF of the WO 3 /C interface. Thus, friction-induced reconstruction of the sliding interface to an intrinsically weak-interacting interface is proposed as a new path to further improve the tribological performance of a-C-based films. [ABSTRACT FROM AUTHOR]

Nanocomposite WC/a-C coatings with variable contents of tungsten carbide (WC 1− x ) and amorphous carbon (a-C) were successfully fabricated using a magnetron sputtering process. The microstructure, mechanical properties and tribological behaviors of the as-fabricated coatings were investigated and compared. The results showed that the “superlattice coating” feature of an alternating multilayer structure with a-C and WC 1− x nanocrystallites layers on the nanoscale was formed. These multilayer superlattice structures led to diminished residual stress and improved the strength of the adhesion to the substrate. The WC/a-C coating with W 5.43 at.% exhibited low friction coefficients of 0.05 at 25 °C and 0.28 at 200 °C. This significant improvement in the tribological performances of the WC/a-C coating was mainly attributed to the superior “superlattice” microstructure and the formation of a continuously compacted tribofilms, which was rich in graphitized carbon at 25 °C and dominated by the friction triggered WO 3 at 200 °C. Moreover, the WC/a-C coating with W 5.43 at.% achieved optimal anti-wear properties at 25 °C due to the synergistic combination of the enhancement effects of the WC 1− x nanoparticles and the partition effect from the transfer film that restricted direct contact of the steel ball with the coating and thus prevented further intense wear. The accelerated wear of the WC/a-C coating with the increase of the WC phase content at 200 °C might be due to the combination of oxidation wear and abrasive wear that originated from the WC 1− x phase. [ABSTRACT FROM AUTHOR]

Titanium alloys are characterized by poor tribological performance, and their conventional use has been restricted to non-tribological applications. Surface films and surface texturing are effective methods to improve the tribological properties of sliding surfaces. In this study, the patterns of micro-dimples with different densities and diamond-like carbon (DLC) films were fabricated on the surface of titanium alloy by laser surface texturing and magnetron sputtering, respectively. The effects of dimple densities and DLC phase transformation on the tribological behavior of the titanium alloy under dry friction and liquid lubrication conditions were investigated. The results showed that DLC film with appropriate dimple area density (44%) are effective in enhancing reducing-friction property of titanium alloy substrate because of the entrapment of wear particles in the dimples and dimple-induced graphitization during sliding motions, while the 24% textured specimen exhibited outstanding wear resistance. [ABSTRACT FROM AUTHOR]

Abstract: Different sizes of ZnWO4 photocatalysts were synthesized by a hydrothermal method. The as-prepared sample shows highly efficient photocatalytic activity for the degradation of RhB under UV irradiation, which significantly vary with the increase of the hydrothermal temperatures. Surface photovoltage spectrum (SPS), field-induced surface photovoltage spectrum (FI-SPS) and surface photovoltage transient (TPV) techniques are used to investigate the detailed photoinduced charge transfer behavior. Results indicate that the ZnWO4 synthesized at 413K possess the largest BET surface area and the abundant donor surface states which are assumed to inhibit the recombination of the photogenerated electron–hole pairs, and thus a significant enhancement in the reaction rate is observed. [Copyright &y& Elsevier]

• The introduction of Cr 3 C 2 -NiCr interlayer significantly extends the life of the CrN film at 550 °C. • The duplex coating exhibits superior high temperature oxidation resistance. • Top CrN film effectively improves hot corrosion resistance of Cr 3 C 2 -NiCr coating. • Chlorine-induced corrosion in uncovered holes is the main reason of top CrN film failure. In this study, an optimized duplex coating, consisting of a thick Cr 3 C 2 -NiCr interlayer and a top CrN film, were designed and deposited by HVOF and PVD. And then hot corrosion behaviors were systematically investigated, and corresponding corrosion mechanisms are discussed in detailed. Results showed that the thickness of the oxide scale of duplex coating is approximately one-tenth that of the Cr 3 C 2 -NiCr coating. Due to the formation of Cr 2 O 3 oxide film, the CrN/Cr 3 C 2 -NiCr duplex coating exhibits superior hot corrosion resistance. However, chlorine-induced corrosion in uncovered holes is the main cause of local failure of duplex coating. [ABSTRACT FROM AUTHOR]

• Textured DLC films were in-situ deposited by masking substrate with metallic meshes. • Covered region became concave part while exposed region became protruding part. • In-situ surface texturing improved film hardness, elastic modulus and lipophilicity. • DLC-T52% reached the lowest COF and wear rate under dry and lubricated conditions. Surface texturing is emerging as one of the viable means that can be applied to improve the tribological properties of diamond like carbon (DLC) films. In this study, textured DLC films were in-situ fabricated by masking the substrate with metallic meshes during the deposition process. The tribological behaviors of the textured DLC films with micro-dimples densities of 39%, 52% and 58% were studied and compared with that of the un-textured DLC films under dry friction and liquid lubrication conditions. The results showed that the textured DLC films with micro-dimples density of 52% exhibited the lowest average coefficient of friction (COF) and wear rate both under dry friction and liquid lubrication conditions. The improved tribological performance of the textured DLC films with optimum micro-dimples density (52%) under dry friction could be attributed to the friction-induced graphitization of the textured layer and entrapment of wear debris in the micro-dimples. Under liquid lubrication condition, the micro-dimples played the double role of wear debris and lubricating oil reservoirs, then the graphitized textured layer on the worn surface combined with the liquid lubrication film formed a solid-liquid duplex lubricating, thus achieving significantly lower friction and wear. [ABSTRACT FROM AUTHOR]

Abstract: Nanosized TiO2 photocatalysts of anatase, rutile and mixed-phase were synthesized through hydrolysis method. The influence of the interface junction between anatase and rutile TiO2 on the photo-generated charge carriers properties were studied by Kelvin probe (KP), surface photovoltage (SPV) and transient photovoltage (TPV) techniques. The KP results revealed that the difference of the surface work function between anatase and rutile might cause the formation of built-in field at the interface in mixed-phase TiO2. The role of the interface junction was further testified through the characteristics of photo-generated charge carriers by SPV and TPV. [Copyright &y& Elsevier]

A Ti 40 Zr 25 Ni 3 Cu 12 Be 20 bulk metallic glass (BMG) is treated by laser shock peening (LSP) with 1, 2 and 30 times, and then the phase structure, thermal, mechanical and tribocorrosion behaviors of the Ti-based BMG after LSP processing were studied in detail. The results demonstrate that although LSP did not significantly alter the phase structure of the Ti-based BMG, it facilitated rejuvenation and induced residual compressive stress within the BMG, thereby introducing internal structural heterogeneity. This heterogeneity promoted the generation of a substantial amount of free volume in the LSP-processed BMG specimens, leading to a marked improvement in plasticity and resistance to crack propagation. Consequently, the LSP-1 specimen exhibited higher surface microhardness (7.1 GPa) and plasticity, making it both plastic and tough and mitigating fatigue peeling wear caused by brittleness during reciprocating sliding wear. The average tribocorrosion volume loss rate of the LSP-1 specimen decreased by approximately 11 % to 5.73 × 10−4 mm3 N−1 m−1 (400 mV). However, excessive LSP resulted in elevated surface roughness (552.9 nm) and rejuvenation (ΔH relax = 3.68 J g−1), rendering the surface of LSP-2 specimens more susceptible to pitting and significantly reducing their tribocorrosion resistance. • Ti 40 Zr 25 Ni 3 Cu 12 Be 20 bulk metallic glass is treated by laser shock peening. • Rejuvenation and residual compressive stress are introduced on BMG. • The nanohardness and plasticity of BMG was promoted by laser shock peening. • The tribocorrosion resistance of Ti-based BMG can be optimized by LSP. [ABSTRACT FROM AUTHOR]

• A series of solvent additives 1,8-diiodooctane (DIO), 1-chloronaphthalene (CN), 1-phenylnaphthalene (PN), 1-methylnaphthalene (MN) were used to effectively control the morphology and transport properties of a kind of pristine perylene diimide dimer (Bis-PDI-T-EG) films. • The PCE of PerSCs based on the 1-methylnaphthalene doped Bis-PDI-T-EG electron transport layer increase by 18% compared to the reference device without solvent additives. It could be further improved by adding 0.05 wt% graphene together with 0.05 v/v% 1-methylnaphthalene, and the hysteresis effect was reduced. Perylene diimide derivatives (PDIs) are a kind of very promising non-fullerene electron transport material for organic-inorganic perovskite solar cells (PerSCs), owing to their excellent photoelectric properties and low-cost synthesis. However, their tendency to form aggregates strongly influences the film morphology and transport properties. Herein, we provided a simple way to tune the morphology and transport properties of PDIs by solvent additive engineering. A series of solvent additives (1,8-diiodooctane, 1-chloronaphthalene, 1-phenylnaphthalene, 1-methylnaphthalene) was investigated for their role in the morphology and transport property of PDI dimer (Bis-PDI-T-EG) film as well as on the photovoltaic performance of PerSCs. Among these four solvent additives, 1-methylnaphthalene (MN) was found one of the best additive that possesses good adjusting ability to control both morphological and electrical properties of Bis-PDI-T-EG film. The fabricated PerSCs with optimized Bis-PDI-T-EG + 0.05 v/v% MN electron transport layer (ETL) displayed the best power conversion efficiency (PCE) of 14.96%. The performance of PerSCs was further improved by adding 0.05 wt% graphene together with 0.05 v/v% MN, and the maximum PCE of 15.11% was achieved. [ABSTRACT FROM AUTHOR]

The pure MoS 2 coating always performs high friction coefficient and short service life when used in high humidity or after long-time storage in humid atmospheric environment. In this study, the MoS 2 /Pb-Ti composite and MoS 2 /Pb-Ti multilayer coatings are deposited to improve the corrosion resistance in 3.5 wt% NaCl solution and tribological performance in high humidity condition. The electrochemical impedance spectra and salt spray test shown that the MoS 2 /Pb-Ti composite and multilayer coatings can inhibit the permeation of oxygen and other corrosive elements, thus resulting a high corrosion resistance. Furthermore, compared with pure MoS 2 coating, the tribological performance of the MoS 2 /Pb-Ti composite and multilayer coatings is also improved significantly owing to the high mechanical properties and compact structure. Moreover, the heterogenous interfaces in MoS 2 /Pb-Ti multilayer coating play an important role to improve the corrosion resistance and tribological performance of coatings. Overall, the dual-doping and multilayer construction are promising approaches to design the MoS 2 coatings as the environmentally adaptive lubricants. [ABSTRACT FROM AUTHOR]

Boron carbide doped DLC coating can combine the property superiority of these two materials to create high-performance carbon-based coating, while the final property of the composite coating is strongly dependent on the proportion of coating components. The aim of this study was to investigate the effect of boron carbide content on the mechanical and tribological properties of the magnetron sputtered B 4 C/a-C coatings, as well as the relevant low friction mechanism. It was found that both the carbon matrix and introduced boron carbide were amorphous and the composite coating exhibited typical columnar structure. Appropriate doping of boron carbide significantly enhanced coating hardness, toughness as well as the adhesion strength and carrying ability, and all of them reached the optimal value when the B concentration was 2.92 at.%. It was also found that the B 4 C/a-C coating with B 2.92 at.% exhibited the lowest steady friction coefficient about 0.05 and highest wear resistance at 20% RH. None of boric acid was formed on the sliding interface under the tested humidity range. Thus, the improved tribological properties were mainly attributed to the enhanced mechanical properties and friction-induced formation of an intact graphitized carbon transfer layer on the counterpart under specific humidity condition. [ABSTRACT FROM AUTHOR]

A ternary Ti-25Al-17 Nb coating (89.5 vol. % O phase and 4.3 vol. % α 2 phase) was fabricated from the pre-alloyed powder by in-situ laser synthesis. The powder was laser scanned to form α 2 phase at high temperature and subsequently precipitated primary Ti 2 AlNb phase (O phase) in an acicular structure; while the secondary fine acicular O phase was squeezed due to the expansion of α 2 phase with induced some edge dislocations and mixed dislocations. The dense and hard Al 2 O 3 film gradually replaced the loose and porous TiO 2 oxide film as an oxygen diffusion barrier, thereby reducing the possibility of brittle oxide formation and significantly increasing the wear resistance and oxidation resistance, results in an excellent wear resistance at 800 ℃. [Display omitted] • Ti2AlNb-based alloy coating with 89.5 % O-phase was synthesized by laser in-situ cladding on Ti-6Al-4V. • TEM indicates that O phase precipitates from α2 phase and satisfies (001)O//(0001)α2 orientation. • EBSD indicates that secondary O phase grains was restrained and distributed in the deformed region. • O-based coating exhibits good wear resistance at 800 °C profit from dense and hard Al2O3 film. [ABSTRACT FROM AUTHOR]

The Fe-based amorphous amorphous coating with a thickness of 150 μm was prepared by detonation spraying. Under a constant strain rate (0.01 s−1 and 0.50 s−1) and a holding time of 50 s, the Fe-based amorphous coatings were subjected to room temperature nanoindentation creep tests with the penetration depth varying from 50 nm to 500 nm, then the depth-dependent creep deformation mechanism of Fe-based amorphous coating during nanoindentation tests were investigated in detail. The results show that the creep responses of coating obviously depend on the indentation penetration depth (h p) and the indentation load rate, i.e., the creep displacement of coating increases with the increase of h p and loading strain rate. This is mainly due to the rapid increase in the shear transition zone volume of the coating as the h p increases, making it easier for the shear band to be excited to nucleate, and results in an obvious creep deformation. Moreover, at high strain rates, the initiation rate of the free volume in the amorphous coating far exceeds its annihilation rate, resulting in a large amount of excess free volume in the amorphous coating, which makes it easier to excite multiple shear bands in the amorphous coating and cause creep plastic deformation. • Fe-based amorphous coatings were deposited by detonation spraying. • The amorphous coating displays a very significant indentation size effect. • Lager shear transition zone volume induces the multiple initiations of shear bands. • Free volume is more likely to accumulate and promote creep at high strain rates. [ABSTRACT FROM AUTHOR]

Abstract: The magnetic mixed hemimicelles solid-phase extraction (MMHSPE), based on the adsorption of cation surfactant octadecyltrimethylammonium bromide (OTMABr) onto magnetite nanoparticles (Fe3O4 NPs) to form mixed hemimicelles, was proposed for the preconcentration of several sulfonamides (SAs) compounds including sulfamethoxazole (SMX), sulfamethoxydiazine (SMD), sulfadimethoxine (SDM) and sulfaquinoxaline (SQX) from environmental water samples. This method avoided the time-consuming column-passing process of loading large volume samples in traditional SPE through the rapid isolation of OTMABr-coated Fe3O4 NPs with an adscititious magnet. Mixed hemimicelles formed on the surface of Fe3O4 NPs by OTMABr showed great adsorptive tendency towards analytes. The OTMABr-coated Fe3O4 NPs adsorbents were easy to be prepared, low cost and environmentally friendly. A comprehensive study on the adsorption conditions such as the amount of the surfactant, the solution pH, the desorption condition and the maximum extraction sample volume were optimized. A concentration factor of 1000 was achieved by the extraction of 500mL of environmental water samples using MMHSPE. Detection limits obtained for SMX, SMD, SDM and SQX were 0.026, 0.024, 0.033 and 0.030μgL−1, respectively. Good recoveries (70–102%) with low relative standard deviations (1–6%) were achieved in analyzing spiked water samples. Low concentration of SQX was found in hospital primary and final sewage effluent sample. [Copyright &y& Elsevier]