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Implant materials with micro/nanostructures bear a closer resemblance with the features of natural bone, which influences the wettability, bone differentiation, and vascularization of materials. However, it is still technically challenging to design the inner wall and surface micro/nanostructures on macroporous bioceramics due to their brittleness. In this work, micro/nanostructured composites with Si3N4 whiskers as a framework, and the (inner) surface covered with SiC nanowires were prepared, denoted as SiC‐nw@Si3N4‐w bioceramics. The synthesis, adopting the green chemistry concept, was utilized from environmental products (carbon evaporated in the furnace at high temperature) and reaction impurities (carbon obtained by polymer pyrolysis and silicon obtained by Si3N4 decomposition) to synthesize SiC nanowires via a vapor‐solid growth mechanism. The prepared SiC‐nw@Si3N4‐w bioceramics have potential applications in bone repair due to their cell adhesion and proliferation. [ABSTRACT FROM AUTHOR]

The poor dispersion of multiwalled carbon nanotubes (MWCNTs) and weak interfacial adhesion of fabric and resin matrix seriously affect the tribological performance of fabric‐reinforcement resin composites. Tannic acid (TA), a plant‐derived compound, which is similar to mussel‐inspired polydopamine, can adhere to various substrates under a weak basic buffer solution. Therefore, in this work, TA‐modified MWCNTs were incorporated into TA functionalized fabric composite to improve the tribological performance of the fabric composite. The results indicate that the MWCNTs and fabric were successfully modified with TA. The wear tests revealed that the TA‐MWCNTs reinforcement TA‐fabric resin composites exhibited the best tribological performance, in which the friction coefficient and volume wear rate decreased by 16.9% and 40%, respectively, compared with pristine fabric composite. The favorable interfacial bonding between fabric and resin is beneficial to the friction force transfer to the load‐bearing fabric, decreasing the stress focus and thus reducing the damage to composite materials. Meanwhile, the good dispersion of MWCNTs contributes to the excellent lubrication performance. This simple and eco‐friendly method of treating fillers with TA provides a new approach to achieve high‐performance tribological materials. [ABSTRACT FROM AUTHOR]

A CoCrFeNi-Ag-Mo self-lubricating composite was fabricated by spark plasma sintering. The effect of Ag and Mo addition on the microstructure, mechanical and tribological properties of CoCrFeNi high entropy alloy (HEA) was systematically investigated. Ag addition led to the formation of Ag-rich phase in CoCrFeNi HEA matrix. With the addition of Mo, part of Ag-rich phases were distributed inside the Mo-rich phase. There were clear diffusion regions between Mo and HEA matrix, residual Mo phases and dispersed Ag-rich phases in Mo-rich phases. The hardness and strength were decreased with the addition of Ag and increased with the addition of Ag and Mo. The ultimate plasticity strain of CoCrFeNi-Ag-Mo composite exceeded 45%. The coupling addition of Ag and Mo effectively improved the tribological properties from room temperature to 800 °C. This phenomenon could be ascribed to the low hardness and yield strength of CoCrFeNi-Ag composite, as well as the thermo-softening due to the friction-induced heat and high experimental temperature. At room temperature, Ag-rich phases acted as a lubricant, and Mo-rich phases improved the anti-wear property. At 400 °C, tiny Ag particles were uniformly distributed on the worn surface, which played roles in friction-reducing. At 800 °C, the Ag2MoO4 layers in-situ formed by tribo-chemistry reactions offered good lubricating and anti-wear functions. [ABSTRACT FROM AUTHOR]

This study employs first‐principles calculations to investigate the structural stability, electronic properties, and elastic properties of Co‐, Ni‐, Cu‐, and Mo‐doped β‐Si3N4. After optimizing the structure of each doped system, it can be determined that all systems are stable structures, as evidenced by the binding energy and forming energy. Then, the electronic properties of the doped systems are analyzed using the energy band and density of states. The findings reveal that the introduction of Co, Ni, and, Cu, reduces the energy bandgap compared to pure Si3N4. More notably, the doping of Mo eliminates the bandgap and results in strong metallicity in the doped systems. Moreover, all doped systems display magnetic moments. Finally, the investigation of elastic properties shows that all doped structures are ductile. The doping of Co, Ni, Cu, and Mo metals improves the toughness of Si3N4. In addition, the doping change of Co is the most obvious. These findings provide a theoretical foundation for future research on the preparation of ductile Si3N4 ceramics. [ABSTRACT FROM AUTHOR]

β-Si3N4 whiskers were synthesized by using a moderately low-temperature heat-treatment process, with the aid of a low weight fraction of multiple aids (Y2O3-MgO). The synthesis conditions and aspect ratio of the whiskers were adjusted by changing the MgO content in the composite additive system, heat treatment temperature and holding time. The phase composition and morphology of the whiskers were analyzed by XRD and SEM, respectively. The phase transformation could be completed at 1700°C by introducing only 0.5 wt% MgO. The heat-treated temperature was successfully further reduced to 1650°C by extending the holding time to 5 h. The introduction of MgO can make the whiskers form rapidly at a lower temperature. By introducing a small amount of MgO and appropriately extending the holding time at a lower treatment temperature has been proved to be an effective method to obtain β-Si3N4 whiskers with higher aspect ratio under mild conditions. [ABSTRACT FROM AUTHOR]

In the vicinity of the top dead center of a diesel engine, the piston rings operate in a low-speed, high-load, and high-temperature environment, which is detrimental to the formation of an effective lubrication oil film. Consequently, it presents significant challenges for predicting the tribological characteristics of the piston ring-cylinder liner friction (PRCL) assembly. This study explores the micro-friction behavior of PRCL assemblies near the top dead center in engines using the molecular dynamics approach. The tribological characteristics of the PRCL, especially the microscopic wear mechanisms, were analyzed under various operating conditions such as ring sliding speed, ring back load, operating temperature, and lubricant supply amount. The liner surface morphology, liner wear, and lubricant film distribution were used to evaluate the tribological characteristics. It was determined that the lubricant supply amount has the most significant impact on the micro-friction behavior of the PRCL assembly. [ABSTRACT FROM AUTHOR]

We report on a patient with severe ulcerative pyoderma gangrenosum that was recalcitrant to systemic corticosteroid, tumour necrosis factor antagonist and ciclosporin treatment and finally controlled when spesolimab was added to the treatment regimen. [ABSTRACT FROM AUTHOR]

CsPbX3 inorganic perovskites have gained widespread attention due to the excellent stability and interesting properties. This article focuses on the exciton properties of CsPbBr3 with different layer numbers. The electronic and optical properties are also investigated. The distribution of excitons (electrons and holes) is closely related to the density of states near the bottom of the conduction band and the top of valence band. Based on potential analysis, it is found that the excitons are affected by the bromine atoms. With increasing thickness, the bandgap decreases and the absorption spectrum that appears obviously in the bandgap moves to lower energy, the maximum binding energy of bright excitons becomes smaller, and the corresponding Bohr radius becomes larger. These results provide a theoretical basis for the theoretical and experimental studies of CsPbBr3 and provide some guidance for the design of optoelectronic devices. [ABSTRACT FROM AUTHOR]

The development of HfC-SiC has been challenging due to difficulties in achieving sintering and satisfactory mechanical properties. However, this study aims to overcome these limitations by incorporating WC as an additive. SPS was employed to process HfC-SiC and HfC-SiC doped with 5 vol.% WC. The resulting samples were then evaluated for their oxygen content, relative density, Vickers hardness, bending strength, indentation fracture toughness, and microstructure. The Vickers hardness (20.50 ± 0.20 GPa), flexural strength (600.19 ± 84.00 MPa), and indentation fracture toughness (5.76 ± 0.54 MPa·m1/2) of HfC-30 vol.% SiC-5 vol.% WC ceramics are higher than HfC-30 vol.% SiC ceramics. Doping 5 vol.% WC in HfC-30 vol.% SiC not only reduces the oxygen content of samples but also produces the (Hf,W)C solid solution and refines the microstructures, which are the main reasons for the higher mechanical properties of HfC-30 vol.% SiC-5 vol.% WC ceramics. In summary, this study successfully addresses the challenges associated with HfC-SiC by incorporating WC as an additive, leading to improved mechanical properties and microstructures. [ABSTRACT FROM AUTHOR]

Ni-WC composite coatings on 35CrMoV alloy surface were successfully prepared by mechanical vibration field-assisted laser cladding technology. Optical microscopy (OM) and scanning electron microscopy (SEM) were used to study the microstructure of the composite coatings without vibration and at different vibration frequencies; the phase composition of the cladding layer was studied by X-ray diffraction (XRD); and an energy dispersive spectrometer (EDS) was used for elemental plane scanning analysis. The grain growth trend under different convection directions was simulated. The wear resistance and mechanical properties of the composite coating were analyzed by friction and wear testing machine, three-dimensional surface profiler, and microhardness tester. The vibration field generated by the self-improved shaking table device is used to assist laser cladding. The effect of mechanical vibration on the quality of the cladding layer was studied. The results show that compared with the coating without mechanical vibration, an appropriate increase in vibration frequency contributes to the refinement of the grains. The original coarse dendrite structure becomes a fine needle-like structure, and the fine grain size gradually decreases. The application of vibration can improve the effect of grain refinement. The vibration makes the grain size distribution more uniform and the microhardness fluctuation of the cladding layer decreases. The experimental results show that mechanical vibration can improve the microstructure uniformity of the coating by selecting suitable vibration parameters. The average friction coefficient and wear width are reduced, and the microhardness is also increased. [ABSTRACT FROM AUTHOR]

The Cs2SnX4 (X = Cl, Br, and I) halide perovskites are currently emerging as a new family of 2D materials and promising candidates for photovoltaic and optoelectronic devices. Herein, the structural, electronic, and optical properties of the Cs2SnX4 multilayers (Ms) with 1–3 layers are investigated by density functional theory (DFT). The structural properties show that the bond length variation of Cs2SnX4 is closely related to surface effects. The Cs2SnCl4 Ms have the lowest formation energies and the best stability, and the formation energies decrease and the stability improves when the number of layers increases. The electronic properties show that the direct‐bandgap semiconductor Cs2SnX4 Ms bandgap values (Cl: 1.513–1.188–0.932, Br: 1.342–1.015–0.862, I: 1.198–0.903–0.729) decrease with the change from 1 to 3 layers and from Cl to I. The p orbitals of X atoms and 5p orbitals of Sn atoms are mainly involved in conduction. The optical properties indicate that Cs2SnX4 Ms achieve coverage and adjustability in the near‐infrared and visible‐light ranges. The calculations provide a fundamental theoretical basis for the research and application of Cs2SnX4. [ABSTRACT FROM AUTHOR]

The overlaps between segmental vitiligo (SV) and nonsegmental vitiligo (NSV) suggest the underlying features of SV, which may be helpful for treating SV. In this study, 379 vitiligo patients were recruited and divided into SV (33.2%), mild‐to‐moderate NSV (M‐NSV, affected body affected area [BSA] ≤10%, 34.0%), and severe NSV (S‐NSV, affected BSA >10%, 32.7%) groups. Demographics and clinical data were collected through in‐person interviews. The disease activity, progression, and prognosis were assessed through 6 months' follow‐up. Serum cytokines profile and tissue‐infiltrating immune cells were measured by ELISA assay and immunofluorescence, respectively. The SV exhibited lower rates of autoimmune comorbidities and recurrence than the S‐NSV, but performed similar to the M‐NSV. Moreover, the disease activity, progression, serum cytokines profile, and tissue‐infiltrating Th/c1 cells in the active SV and M‐NSV were comparable, but differed significantly from those of the active S‐NSV. The clinical and immunological similarities between SV and M‐NSV presented a deeper autoimmune understanding of SV. Additionally, a classification of active vitiligo according to disease extent may be more clinically meaningful than subtypes for guiding immunomodulatory treatment. [ABSTRACT FROM AUTHOR]

Si3N4 as a structural ceramic is desirable for applications in spacecraft, transportation, and energy, but its poor high‐temperature properties still do not satisfy the actual requirements. Here, a TiC0.3N0.7 reinforced Si3N4 ceramic is successfully designed and fabricated via the high‐temperature nitridation of TiCx. It is found that TiC0.3N0.7 grains with the size of 1‐2 μm are uniformly dispersed in the Si3N4 matrix and show a firm bond with substrate. Compared with pure Si3N4, the doping of harder TiCN phase can effectively improve ceramic's hardness and fracture toughness at a certain temperature. Importantly, the ceramic material displays extraordinary wear resistance across a wide temperature range (eg, the wear rate of TiC0.3N0.7 containing Si3N4 over 63 times and 178 times better than pure Si3N4 at 600 and 900°C, respectively). More broadly, a correlation between wear mechanism and temperature is established, and the result shows that the mechanical strength and tribochemical oxidation as two key factors determine the wear behavior of the material. These results developed here can provide a springboard for preparation and optimization of multiphase ceramics that serve under high‐temperature conditions. [ABSTRACT FROM AUTHOR]

Abstract: Si3N4/Ag composites were firstly prepared through SPS technology, using Si3N4 and AgNO3 as raw materials. Utilizing the coordination bonding of Ag+ ions with nitrogen atoms of Si3N4, in situ generated Ag particles about 1 μm were tightly anchored on Si3N4 surface, thereby preventing the outflow of silver during sintering process. Meanwhile, smaller silver particles about 20 nm were located at the grain boundaries of Si3N4, which effectively improved the mechanical and tribological properties of Si3N4‐based composites. Finally, the Si3N4/Ag composites reinforced by Ag particles showed a friction coefficient of 0.48 ± 0.01, wear rate of 1.79 × 10−6 mm3 N−1 m−1 and fracture toughness of 7.05 ± 0.2 MPa m1/2, respectively. [ABSTRACT FROM AUTHOR]

In this article, the dry-sliding tribological behaviors of TiAl-based composites reinforced with 20 and 40 vol% in situ synthesized TiB produced by a hot-press sintering process were investigated from room temperature (RT) to 800 °C. The results show that the high-temperature wear resistance of the TiAl alloy is improved by adding the TiB particles under all the testing temperatures, and the more the TiB reinforcement, the better the wear resistance is. This improvement is more significant at 600 °C and above, especially for the composite with 40 vol% TiB, whose wear rate is 4-10 times lower than TiAl at 600 and 800 °C. Accordingly, the wear mechanisms transfer from abrasion wear at low and moderate temperature (RT, 200 and 400 °C) to oxidation wear at high temperature (600 and 800 °C). In addition to the brittle-to-ductile transition of the materials and oxide layer formation, the phase transition of AlO and TiO may be partly responsible for the promising wear resistance at high temperatures. [ABSTRACT FROM AUTHOR]

In this article, the tribological behaviors of tin-based Babbitt alloy ZChSnSb 8–8 sliding against AISI 302 stainless steel lubricated by seawater were investigated. The results indicated that the friction coefficient decreases with increasing load and sliding speed, and the wear rate increases slightly with load but decreases with sliding speed. The low friction coefficient and wear rate are attributed to the unique “concrete structure” and seawater. As a lubrication medium, seawater has lubricating, cooling, and corrosive effects on the sliding couple. [ABSTRACT FROM PUBLISHER]

In this paper, the tribological behavior of nanoeutectic Fe1.87C0.13 alloy and its coarse-grained-eutectic counterpart under air and vacuum was investigated. The results showed that the wear rate of both alloys was lower in air than in vacuum, and their friction coefficient was related to applied load and testing atmosphere. The nanoeutectic Fe1.87C0.13 alloy exhibited lower wear rate than the coarse grained counterpart in both environments. The wear rate of both alloys increased but the friction coefficient decreased with increasing applied load under both air and vacuum. The dominant wear mechanisms were adhesion wear in vacuum but oxidation wear along with slight delamination in air. [ABSTRACT FROM AUTHOR]

This article presents a new solution for the lubrication and wear problem of TiAl alloy in vacuum by coating Ti3AlC2 layer. Ti3AlC2 coating and Ti‐46Al‐2Cr‐2Nb alloy substrate are simultaneously consolidated by hot‐pressed approach. The coating demonstrates superior self‐lubricity, CoF of 0.2 and negligible wear, in the vacuum of 2.0 × 104 Pa. A transition layer is formed in the interface, resulting in very strong coating adhesion. [ABSTRACT FROM AUTHOR]

In this paper, Cu/AlMgB composites with by weight percent, 5, 10 and 20 % of the AlMgB (referred to CA-5, CA-10 and CA-20) were fabricated by hot-press sintering method. The mechanical and dry-sliding tribological properties of the three composites were investigated. The results indicated that the densities of the Cu/AlMgB composites were lower than copper, whereas the hardness higher. The friction and wear behaviors of the composites were strongly dependent on the AlMgB content. The friction coefficient was in the range of 0.73-1.0 for CA-5, but it was always steady at about 0.2 for CA-10 and CA-20. Accordingly, the increase in the AlMgB concentration can improve the wear resistance of the composites. [ABSTRACT FROM AUTHOR]

The microstructure, mechanical and dry-sliding tribological properties of TiAl-based composites with 20 and 40 vol% in situ formed TiAlC, produced by hot press sintering process, are investigated. The microstructural characterization reveals that TiAlC phase is in the form of spherical particles and large blocks, and the quantity of the blocks increases with TiAlC content. This difference in the morphology and distribution of the TiAlC phase leads to the discrepancy of the wear resistance of the composites. In contrast to the Ti-46Al-2Cr-2Nb intermetallics, the dry-sliding wear resistance of the TiAl/TiAlC composites first declines slightly and then enhances with the TiAlC content. Furthermore, the TiAl/40 % TiAlC composite shows low wear rate at higher sliding speed. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the effect of counterface of AISI 52100 steel and ceramics of SiC, AlO, and SiN on the tribological behavior of TiAlC at ambient. The results showed that the tribological properties of TiAlC are strongly dependent on the counterfaces. Under present test conditions, the tribocouple of TiAlC/SiC exhibits lower coefficient of friction (CoF) 0.40, TiAlC/AISI 52100 steel shows a rising CoF from 0.1 to 0.63, both TiAlC/SiN and TiAlC/AlO tribopartners exhibit higher CoF of 1.22 in average. The TiAlC exhibits the lowest wear rate sliding against AISI 52100 steel, the wear rate of TiAlC sliding against AlO, SiN, and SiC are higher and comparable. The morphologies of the worn surfaces of the TiAlC are observed by scanning electron microscopy, and the element states are analyzed by X-ray photoelectron spectroscopy. The wear mechanisms are discussed. [ABSTRACT FROM AUTHOR]

In this paper, we reported the tribological behavior of TiAlC disk sliding against SiC ball from room temperature (RT) to 1,000 °C. The tribological properties are highly dependent of testing temperature. At RT, the coefficient of friction (CoF) is as low as 0.34 in the steady state, but the wear rate is relative high (4.26 × 10 mm/Nm). At 200 and 400 °C, the CoF is as high as 1.21, and the wear rates are very high, about on the order of 10 mm/Nm. From 600 to 1,000 °C, however, TiAlC exhibits quite low wear rate on the order of 10 mm/Nm and relative moderate CoF, 0.60-0.80. The compacted continuous oxide layer at 600 °C and above might be responsible for the outstanding wear resistance. [ABSTRACT FROM AUTHOR]

It is a challenge to design self-lubricating materials that exhibit and maintain reduced friction coefficient as well as high strength over a wide range of temperatures. A high-temperature self-lubricating nickel-alloy-based composite was created using the hot pressing technique. The composite exhibited high relative density, and simultaneously superior lubricating properties, average friction coefficient below 0.25 from room temperature to 800 °C, and high strength, 470 MPa of tensile strength and 1500 MPa of compressive strength. The composite was very promising in high-temperature tribology. [ABSTRACT FROM AUTHOR]

Ga‐based liquid metal (GLM) can be used as a current‐carrying lubricant, due to its combination of excellent electrical conductivity and good lubricity. However, the influence of electric field parameters on the lubrication mechanism of GLM is still unclear. This paper attempts to investigate the influence of current magnitude, voltage magnitude, current direction, and load on the lubrication behaviors of GLM at atmosphere and room temperature (≈26 °C). It is found that the interface action mechanism induced by an electric field is mainly reflected in four aspects, namely, Joule heating effect, electric field force, electrochemical effect, and electromigration effect. These interfacial physical and chemical effects are governed by the current magnitude, voltage magnitude, current direction, and load, bringing about distinct frictional products and thereby influencing the lubrication behaviors. Briefly, FeGa3 can only be formed when the current reaches 6 A and the load is above 40 N, and it has obvious friction‐reducing properties, but increases the wear due to its low content. When the frictional product is just the Ga‐rich film, the increase of oxidation degree is detrimental to the wear resistance. [ABSTRACT FROM AUTHOR]

In this work, a novel Cu/AlMgB14 composite was prepared by hot-press sintering, and its tribological responses to the AlMgB14 content and sintering temperature under deionized water and liquid paraffin media were investigated. As the results show, the wear resistance of pure copper is greatly enhanced by adding AlMgB14 in both media. Besides, the Cu/AlMgB14 composites sintered at lower sintering temperature show better lubricating irrespective of the AlMgB14 content due to the porosity of the specimens, while those sintered at higher temperature show gradually improved wear resistance with the AlMgB14 content increasing due to the growingly improved hardness. In addition, in liquid paraffin, a lower COF and a comparable wear rate to that in deionized medium are obtained due to the hydrophobic and lipophilicity of the composites. [ABSTRACT FROM AUTHOR]