High-Temperature Self-Lubricating Metal Nitride-Based Nanostructure Composite Films

The film technology is one of the most efficient methods of modifying the surface properties of materials. The focus of recent attention in the solid lubricating materials is on the hard transition metal nitride films’ excellent high-temperature tribological properties applied in powertrains and cutting tools. This chapter reviewed the formation mechanism of Magnéli phases and the influence of Magnéli phases on the high-temperature tribological properties of hard transition metal nitride films synthesized using magnetron sputtering. The self-lubricating behavior and wear mechanism of the Magnéli phases are discussed from the point of view of crystallography. Some methods to enhance the wear resistance property of the metal nitride film are also discussed

Rethinking Mutual Information for Language Conditioned Skill Discovery on Imitation Learning

Language-conditioned robot behavior plays a vital role in executing complex tasks by associating human commands or instructions with perception and actions. The ability to compose long-horizon tasks based on unconstrained language instructions necessitates the acquisition of a diverse set of general-purpose skills. However, acquiring inherent primitive skills in a coupled and long-horizon environment without external rewards or human supervision presents significant challenges. In this paper, we evaluate the relationship between skills and language instructions from a mathematical perspective, employing two forms of mutual information within the framework of language-conditioned policy learning. To maximize the mutual information between language and skills in an unsupervised manner, we propose an end-to-end imitation learning approach known as Language Conditioned Skill Discovery (LCSD). Specifically, we utilize vector quantization to learn discrete latent skills and leverage skill sequences of trajectories to reconstruct high-level semantic instructions. Through extensive experiments on language-conditioned robotic navigation and manipulation tasks, encompassing BabyAI, LORel, and CALVIN, we demonstrate the superiority of our method over prior works. Our approach exhibits enhanced generalization capabilities towards unseen tasks, improved skill interpretability, and notably higher rates of task completion success.Comment: 16 page

Microstructure and Mechanical Properties of Magnetron Sputtering TiN-Ni Nanocrystalline Composite Films

In this paper, TiN-Ni nanostructured composite films with different Ni contents are prepared using the magnetron sputtering method. The composition, microstructure, and mechanical properties of composite films are analyzed using an X-ray energy spectrometer (EDS), a scanning electron microscope (SEM), X-ray diffraction technology (XRD), a transmission electron microscope (TEM), and nanoindentation. All the films grow in a columnar crystal structure. There are only TiN diffraction peaks in the XRD spectrum, and no diffraction peaks of Ni and its compounds are observed. The addition of the Ni element disrupts the integrity of TiN lattice growth, resulting in a decrease in the grain size from 60 nm in TiN to 25 nm at 20.6% Ni. The film with a Ni content of 12.4 at.% forms a nanocomposite structure in which the nanocrystalline TiN phase (nc-TiN) is surrounded by the amorphous Ni (a-Ni) phase. The formation of nc-TiN/a-Ni nanocomposite structures relies on the good wettability of Ni on TiN ceramics. The hardness and elastic modulus of the film gradually decrease with the increase in Ni content, but the toughness is improved. The hardness and elastic modulus decrease from 19.9 GPa and 239.5 GPa for TiN film to 15.4 GPa and 223 GPa at 20.6 at.% Ni film, respectively, while the fracture toughness increases from 1.5 MPa m1/2 to 2.0 MPa m1/2. The soft and ductile Ni phase enriched at the TiN grain boundaries hinders the propagation of cracks in the TiN phase, resulting in a significant increase in the film’s toughness. The research results of this paper provide support for the design of TiN-Ni films with high strength and toughness and the understanding of the formation mechanism of nanocomposite structures.info:eu-repo/semantics/publishedVersio

Enhancement on the hardness and oxidation resistance property of TiN/Ag composite films for high temperature applications by addition of Si

Titanium 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.info:eu-repo/semantics/publishedVersio

Tribological performance under different environments of Ti—C—N composite films for marine wear-resistant parts

The need for reducing the wear in mechanical parts used in the industry makes self-lubricant films one of the sustainable solutions to achieve long-term protection under different environmental conditions. The purpose of this work is to study the influence of C additions on the tribological behavior of a magnetron-sputtered TiN film in air, water, and seawater. The results show that the addition of C into the TiN binary film induced a new amorphous phase, and the films exhibited a dual phase of fcc (face-centered cubic)-TiN and amorphous carbon. The antifriction and wear-resistance properties were enhanced in air and water by adding 19.1at% C. However, a further increase in the C concentration improved anti-frictional properties but also led to higher wear rates. Although the amorphous phase induced microbatteries and accelerated the corrosion of TiN phases in seawater, the negative abrasion state was detected for all Ti–C–N films due to the adhesion of the tribocorrosion debris on the wear track.info:eu-repo/semantics/publishedVersio

Insights into the oxidation resistance mechanism and tribological behaviors of multilayered TiSiN/CrVxN hard coatings

In 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.info:eu-repo/semantics/publishedVersio

Multilayer Mo2N-Ag/SiNx films for demanding applications: Morphology, structure and temperature-cycling tribological properties

Nowadays 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.Supported by the National Natural Science Foundation of China, China (51801081, 52071159, 52171071, 52172090); Portugal National Funds through FCT project, Portugal (2021.04115); Outstanding University Young Teachers of ‘‘Qing Lan Project” of Jiangsu Province, China; Excellent Talents of ‘‘Shenlan Project” of Jiangsu University of Science and Technology, China; China Merchants Marine Scientific Research and Innovation Fund, China. Filipe Fernandes acknowledges the funding received in the aim of the projects: MCTool21 - ref. ‘‘POCI-01-0247- FEDER-045940”, CEMMPRE – ref. ‘‘UIDB/00285/2020” and SMARTLUB – ref. ‘‘POCI- 01-0145-FEDER-031807”.info:eu-repo/semantics/publishedVersio

Epigenomic analysis reveals prevalent contribution of transposable elements to cis-regulatory elements, tissue-specific expression, and alternative promoters in zebrafish

Transposable elements (TEs) encode regulatory elements that impact gene expression in multiple species, yet a comprehensive analysis of zebrafish TEs in the context of gene regulation is lacking. Here, we systematically investigate the epigenomic and transcriptomic landscape of TEs across 11 adult zebrafish tissues using multidimensional sequencing data. We find that TEs contribute substantially to a diverse array of regulatory elements in the zebrafish genome and that 37% of TEs are positioned in active regulatory states in adult zebrafish tissues. We identify TE subfamilies enriched in highly specific regulatory elements among different tissues. We use transcript assembly to discover TE-derived transcriptional units expressed across tissues. Finally, we show that novel TE-derived promoters can initiate tissue-specific transcription of alternate gene isoforms. This work provides a comprehensive profile of TE activity across normal zebrafish tissues, shedding light on mechanisms underlying the regulation of gene expression in this widely used model organism

LiFS: Low human-effort, device-free localization with fine-grained subcarrier information

Device-free localization of people and objects indoors not equipped with radios is playing a critical role in many emerging applications. This paper presents an accurate model-based device-free localization system LiFS, implemented on cheap commercial off-the-shelf (COTS) Wi-Fi devices. Unlike previous COTS device-based work, LiFS is able to localize a target accurately without offline training. The basic idea is simple: channel state information (CSI) is sensitive to a target's location and by modelling the CSI measurements of multiple wireless links as a set of power fading based equations, the target location can be determined. However, due to rich multipath propagation indoors, the received signal strength (RSS) or even the fine-grained CSI can not be easily modelled. We observe that even in a rich multipath environment, not all subcarriers are affected equally by multipath reflections. Our pre-processing scheme tries to identify the subcarriers not affected by multipath. Thus, CSIs on the "clean" subcarriers can be utilized for accurate localization. We design, implement and evaluate LiFS with extensive experiments in three different environments. Without knowing the majority transceivers' locations, LiFS achieves a median accuracy of 0.5 m and 1.1 m in line-of-sight (LoS) and non-line-of-sight (NLoS) scenarios respectively, outperforming the state-of-the-art systems. Besides single target localization, LiFS is able to differentiate two sparsely-located targets and localize each of them at a high accuracy