Percorrer por autor "Luan, Jing"
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- Deciphering the mechanical strengthening mechanism: Soft metal doping in ceramic matrices: A case study of TiN-Ag filmsPublication . Luan, Jing; Kong, Fanlin; Xu, Junhua; Fernandes, Filipe; Evaristo, Manuel; Dong, Songtao; Cavaleiro, Albano; Ju, Hongbo; Fernandes, FilipeSoft metals have been widely added into ceramic-based films for fully meeting the demanding requirements of green tribological applications. However, the resulting considerable increase of the mechanical strength by adding a soft metal below 5 at.%, which reversed the rule-of-mixture, was still not fully revealed. In this paper, a case study of TiN-Ag films was carried out to investigate the strengthening mechanism induced by adding soft metal in TiN-Ag composite/multilayered films deposited by magnetron sputtering. The results showed that dual-phases of fcc-TiN and fcc-Ag co-existed in the composite films with the Ag particles embedded in the matrix. In some areas of the Ag particles, with a size below 4 nm, epitaxial growth with the TiN template was detected, which obliged the lattice to be distorted and shrunken. Consequently, both hardness and elastic modulus were enhanced from 21 and 236 GPa, for the reference TiN film, to 26 and 323 GPa for the TiN-Ag composite film with 2.4 at.% Ag. The possibility of having the epitaxial growth of Ag within TiN were also confirmed by designing a TiN/Ag multilayered film with an Ag layer thickness of ∼3 nm.
- Design and magnetron sputtering of nanomultilayered W2N/Ag-SiNx films: Microstructural insights and optimized self-lubricant properties from room temperature to 500 ◦CPublication . Luan, Jing; Kong, Fanlin; Evaristo, Manuel; Fernandes, Filipe; Zhou, Yazhou; Cavaleiro, Albano; Ju, Hongbo; Fernandes, FilipeNovel multilayered films were engineered by integrating W2N and Ag-SiNx layers in a multilayer structure to obtain improved hardness and tribological properties. The films were fabricated by alternating magnetron sputtering, depositing 40 nm layers of W2N with varying thickness of Ag-SiNx layers varying in thickness from 4 to 20 nm. The effect of the increase thickness of the Ag-SiNx layers in the films microstructure and tribological properties were accessed. Tribological experiments were conducted at room temperature (RT), 500 °C, and RT-500 °C cycling conditions. The results revealed the production of a multilayered structure comprising single fcc-W2N layers interspersed with dual-phase layers consisting of fcc-Ag and amorphous SiNx phases. Tribological results indicated an improvement in the tribological performance with increase thickness of the Ag-SiNx layer up to 12 nm. The tribo-synergistic/combined action of both W2N and Ag-SiNx layers, along with the presence of layered lubricant tribo-phases of WO3 and Ag2WO4, showcased the pivot role in reducing friction and enhancing wear resistance. The optimized multilayered film, featuring a 12 nm Ag-SiNx layer, demonstrated exceptional tribological properties under temperature-cycling from RT to 500 °C.
- Design of DC semi-industrial magnetron-sputtered W-Ti-N/Ag composite films: Insights into the microstructure and mechanical propertiesPublication . Fernandes, Filipe; Luan, Jing; Wang, Yiping; Dong, Songtao; Evaristo, Manuel; Cavaleiro, Albano; Ju, HongboA semi-industrial magnetron sputtering system was employed to deposit a series of W-Ti-N/Ag composite films with varying Ag content, aiming to provide practical parameters for industrial-scale PVD applications. The films were deposited by DC sputtering a W + 30 wt%Ti alloy target and an Ag target in an Ar and N2 atmosphere. The results indicated that the composite films, regardless of Ag content, exhibited a face-centered cubic (fcc) structure and consisted of a three-phase mixture of W2N, TiN and Ag. The Ag particles were embedded within the crystalline grains of solid solution of (WTi)2N and (TiW)N, resulting in grain refinement and increased interface density in the films. The predominant cross-section fracture of the Ag-alloyed was identified as transgranular. Both hardness and elastic modulus of the composite films gradually decreased with the Ag content due to the soft nature of the Ag phase.
- Enhancement on the hardness and oxidation resistance property of TiN/Ag composite films for high temperature applications by addition of SiPublication . Ju, Hongbo; Xu, Luyao; Luan, Jing; Geng, Yaoxiang; Xu, Junhua; Yu, Lihua; Yang, Junfeng; Fernandes, FilipeTitanium nitride and silver (TiN/Ag) composite films exhibited the excellent self-lubricating properties in a wide temperature range due to the formation of the Ag rich tribolayer in the contact. However, Ag addition usually reduces the hardness and oxidation resistance properties of the films. In this paper, TiN/Ag/Si3N4 composite films were deposited using RF magnetron co-sputtering system to improve the mechanical and oxidation resistance properties of the TiN/Ag film. XRD and TEM analysis revealed that three-phases could be identified on the TiN/Ag/Si3N4 films: face-centered cubic (fcc) TiN, fcc-Ag and amorphous Si3N4 phases. The hardness of the TiN/ Ag film increased from ~16 GPa to ~24 GPa for TiN/Ag/Si3N4 with 15.3 at.% of Si due to the formation of the nanocomposite structure. The addition of Si allowed a significant improvement on the oxidation resistance temperature, and effectively avoiding of Ag diffusion, and thereby contributing the stability of the hardness of the film after annealing treatment.
- Exploring tribological characteristics of ZrN-MoSN composite films fabricated via RF magnetron sputtering: Insights from microstructure and performance analysisPublication . Luan, Jing; Lu, Hongying; Xu, Junhua; Fernandes, Filipe; Fernandes, Filipe; Evaristo, Manuel; Ma, Bingyang; Xie, Fuxiang; Cavaleiro, Albano; Ju, HongboAchieving the stringent demands of sustainable tribological industrial applications poses a significant challenge, particular in optimizing the self-lubricant performance of nitride-based films. This paper tackled this challenge by designing and depositing a series of ZrN-MoSN composite films with varying (Mo + S)/Zr ratios, employing RF magnetron sputtering, aimed to enhance the tribological properties through utilizing the high loading capacity of the ZrN matrix and the exceptional self-lubricating attributes of Mo-S-N additives. After conducting thorough investigations on the microstructure, and tribological properties, the results revealed that the dense columnar structured ZrN-MoSN composite films displayed a polycrystalline composition comprising fcc-ZrN and hcp-MoS2 phases, intertwined with amorphous phases of Mo(SN)x and MoS2(N2). (Mo + S)/Zr ratios below 1.08 exhibited a minor impact on the room temperature (RT) tribological properties, while higher ratios led to degradation on RT average friction coefficient (COF) and wear rate (WR). However, the synergistic effect of ZrN matrix and the tribo-phases of layered MoO3 and hard ZrO2 contributed to the significant enhanced 500 °C tribological properties, particularly with an optimized (Mo + S)/Zr ratio of 0.43.
- Insights into the oxidation resistance mechanism and tribological behaviors of multilayered TiSiN/CrVxN hard coatingsPublication . Ju, Hongbo; Athmani, Moussa; Luan, Jing; AL-Rjoub, Abbas; Cavaleiro, Albano; Yaqub, Talha Bin; Chala, Abdelouahad; Ferreira, Fabio; Fernandes, FilipeIn the last decades, vanadium alloyed coatings have been introduced as potential candidates for self-lubrication due to their perfect tribological properties. In this work, the influence of V incorporation on the wear performance and oxidation resistance of TiSiN/CrN film coatings deposited by direct current (DC) reactive magnetron sputtering is investigated. The results show that vanadium incorporation significantly decreases the oxidation resistance of the coatings. In general, two layers are formed during the oxidation process: i) Ti(V)O2 on top, followed by a protective layer, which is subdivided into two layers, Cr2O3 and Si–O. ii) The diffusion of V controls the oxidation of V-containing coatings. The addition of vanadium improves the wear resistance of coatings, and the wear rate decreases with increasing V content in the coatings; however, the friction coefficient is independent of the chemical composition of the coatings. The wear of the V-containing coatings is driven by polishing wear.
- Microstructure, Mechanical, and Tribological Properties of Mo2N/Ag-SiNx Nanomultilayers with Varying Modulation PeriodsPublication . Fernandes, Filipe; Luan, Jing; Wang, Lei; Dong, Songtao; Ferreira, Fábio; Mo, Changpan; Cavaleiro, Albano; Ju, Hongbo; Kiryukhantsev-Korneev, PhilippThe multilayered Mo2N/Ag-SiNx self-lubricant films were designed and deposited using a DC (Direct Current) magnetron sputtering system under mixed gas atmosphere of N2 and Ar. The modulation ratio (thickness ratio of Mo2N to Ag-SiNx) was fixed at 2:1, while the modulation periods (thickness of Mo2N and its adjacent Ag-SiNx layer) were set at 20, 40, and 60 nm. The results indicated that all multilayer films, regardless of modulation period, exhibited a combination of face-centered cubic (fcc) and amorphous phases. Specifically, fcc-Mo2N was detected in the Mo2N layers, while fcc-Ag and amorphous SiNx co-existed in the Ag-SiNx layers. The multilayered architecture induced residual stress and interface strengthening, resulting in hardness values exceeding 21 GPa for all films. Compared to Mo2N and Ag-SiNx monolayer films, the multilayer structure significantly enhanced tribological properties at room temperature, particularly in terms of wear resistance. The Mo2N/Ag-SiNx multilayer films exhibit ~25% lower friction than Ag-SiNx, ~3% lower than Mo2N, and achieve remarkable wear rate reductions of ~71% and ~85% compared to Ag-SiNx and Mo2N, respectively, demonstrating superior tribological performance. The synergistic effects of both modulation layers and relative high hardness were key factors contributing to the enhanced tribological behavior.
- Multilayer Mo2N-Ag/SiNx films for demanding applications: Morphology, structure and temperature-cycling tribological propertiesPublication . Ju, Hongbo; Zhou, Rui; Luan, Jing; Yu, Lihua; Xu, Junhua; Zuo, Bin; Yang, Junfeng; Geng, Yaoxiang; Zhao, Lijun; Fernandes, FilipeNowadays there is the need to avoid the excessive consumption of liquid lubricant oils, as they are harmful to the environment and hard to disposal. Self-lubricant films have been seen as the sustainable solution to achieve a long-term lubrication under high temperature-cycling conditions. In this manuscript, multilayer Mo2N-Ag/SiNx films with a fixed modulation ratio (thickness of Mo2N-Ag to SiNx) of 3:1, with changing modulation period (Λ, thickness of Mo2N-Ag and SiNx) from 8 to 200 nm were produced to achieve an effective balance between the lubricious phase diffusion control and the adequate formation of the low friction tribo-layers. Results showed that a dual-phase of fcc-Mo2N and fcc-Ag co-existed in Mo2N-Ag layers, while the SiNx layer exhibited an amorphous character. Both room temperature (RT) lubricant and wear-resistance properties of the films were improved by increasing Λ from 8 to 64 nm, while a further increase of Λ degraded the wear-resistance properties. The multilayer film at Λ = 64 nm exhibited an excellent RT-500 °C temperature-cycling tribological properties. Mechanical properties and the synergistic effect of both modulation layers were the cause for the improvement of the tribological properties.
- Mutual promotion on the mechanical and tribological properties of the nacre-like self-lubricant film designed for demanding green tribological applicationsPublication . Hongbo, Ju; Luan, Jing; Wang, Yiping; Bondarev, Andrey; Evaristo, Manuel; Geng, Yaoxiang; Xu, Junhua; Cavaleiro, Albano; Fernandes, Filipe; Fernandes, FilipeThe inverse relationship between the tribological and mechanical properties of environmentally friendly self-lubricant films, induced by the addition of soft lubricant agents that can diffuse quickly at elevated temperatures, has hindered the widespread use of these materials in industrial applications. This paper took this challenge to break through the above established relationship by developing novel nacre-like multilayered Mo2N–SiNx/Ag–SiNx self-lubricant films via an radio frequency (RF) magnetron sputtering system for real applications where harsh conditions at elevated temperatures exist. The multilayered films, deposited by alternating deposition of Mo2N–SiNx and Ag–SiNx modulation layers, exhibited three phases of face-centered cubic (fcc) Mo2N, fcc Ag and SiNx, where SiNx encapsulated the nano-crystalline Mo2N and Ag phases in each layer to successfully induce a “brick and mortar” nacre-like microstructure (in the area without the coherent structure). The epitaxy growth of the Ag–SiNx layers with thickness below 6 nm on the Mo2N template resulted in an extraordinary increase in both the hardness and elastic modulus, which was able to prevent severe degradation of the mechanical properties caused by the addition of Ag. The room-temperature anti-friction property could be enhanced by increasing the Ag–SiNx layer thickness due to the excellent lubricant nature of Ag, which acts in synergy with Mo2N, while the wear rate below 4×10−8 mm3/(N·mm) was due to the high mechanical strength. The tribological properties at 600 °C also benefited from the interlocked multilayered architecture, which allowed an extreme low friction coefficient of ~0.12 and a negligible wear rate (WR). This behavior was attributed to the synergism between the lubricant action of Ag and Mo2N and the tribo-phase transformation from Ag2Mo4O13 to Ag2MoO4.
- Mutually enhanced mechanical and tribological properties in magnetron sputtered Mo2N/Ag-SiNx self-lubricating multilayered films via epitaxial growth designPublication . Fernandes, Filipe; Luan, Jing; Wang, Lei; Dong, Songtao; Choukourov, Andrei; Yang, Junfeng; Kalin, Mitjan; Cavaleiro, Albano; Ju, Hongbo; Vincenzini, P.Achieving simultaneous enhancement of both mechanical and self-lubricating properties by incorporating soft lubricants into nitride films has been a longstanding challenge in the development of solid lubricant materials. This paper introduced a novel approach to overcome this challenge by developing coherent-structured Mo2N/Ag-SiNx multilayered films using radio frequency (RF) magnetron sputtering. The multilayer films were designed with a fixed modulation period of 30 nm, while the modulation ratio (γ) was varied from 1:9 to 1:1. The Mo2N layers exhibited a single fcc-Mo2N phase, while the Ag-SiNx layers formed a dual-phase structure comprising fcc-Ag nanoparticles embedded in an amorphous SiNx matrix. At a modulation ratio of 1:9, the Ag-SiNx layer epitaxially grew on the Mo2N template, resulting in a coherent structure. This coherent structure significantly enhanced both the hardness and elastic modulus, reaching approximately 36 GPa and 230 GPa, respectively. The improved wear resistance at room temperature can be attributed to the coherent strengthening effect, which not only elevated the film's hardness but also eliminated sharp interfaces between modulation layers, thereby reducing crack initiation sites. In temperature-cycling tribo-testing from room temperature to 600 °C, the film with a γ of 1:9 maintained a stable coefficient of friction around 0.2, except during the initial room temperature, where it was 0.4. The wear rate could not be accurately calculated due to the adhered tribolayer on the top of the wear track following the initial tribo-test at 600 °C. The excellent tribological properties across temperature cycles were attributed to the synergistic lubricant characteristics of both layers and the formation of self-lubricating tribo-phases. The optimized Mo2N/Ag-SiNx multilayered films provide an effective balance of lubrication and mechanical stability under extreme conditions, making them highly promising for high-performance engineering applications.