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Abstract In this work, the tribological properties of three different high-performance polymers have been investigated at different temperature regimes. In addition, wear behaviour of PEEK composites (reinforced with different TiO 2 content) has also been studied and compared at different temperatures. SEM cross-sectional analysis of the transfer film layers (TFLs) on steel counterparts was carried out to understand the formation of TFLs. Further, the thickness and distribution of TFLs were measured using nanoindentation as well as possible structural changes of the materials by Fourier transformed infrared (FTIR) technique. Based on experimental investigation, it was concluded that the development of transfer film and wear performance of polymeric materials, can be greatly affected by materials' brittle-ductile transition behaviour, depending on the temperature tested. Highlights • Among presently investigated materials, PEEK/PEEK composites showed more effectiveness to develop resilient TFLs. • PBI shows better wear behaviour at room temperature, though their high temperature wear resistance is not that promising. • In general, higher the combination of hardness, rigidity and ductile of materials, better is the wear resistance. [ABSTRACT FROM AUTHOR]

A functionally graded NbC – high chromium white cast iron composite was successfully fabricated by centrifugal casting for high wear applications. The migration of primary NbC particles to the outer periphery, as predicted by Stokes' law, resulted in an extremely hard outer layer at the surface of a softer bulk material. Microstructural characterisation showed that both the volume fraction and the morphology of the carbides varies along the thickness of the specimen. At the outer surface, the NbC was present as primary carbides while Chinese-script NbC was found in the bulk of the material. Hardness, sliding wear and three-point bending tests confirmed that the outer layer was harder and more wear resistant than the rest of the material, which was correspondingly tougher. The study of the fracture surface of the specimens showed that there is a strong bond between NbC and the matrix such that delamination between the reinforcements and the matrix did not occur during fracture. If Chinese-script NbC can be reduced or prevented in the bulk material, further improvements to toughness could be achieved. [ABSTRACT FROM AUTHOR]

The sliding behavior of two titanium alloys processed by laser powder bed fusion, with and without heat treatment, was investigated alongside two as-received conventionally-processed versions of these alloys. These samples presented a wide range of microstructures often encountered in Ti alloys. Oxidative, abrasive and adhesive wear always occurred when sliding against steel. However, wear rates were similar regardless of the friction and hardness if material removal mainly occurred through abrasion and/or adhesion. Martensitic phases decomposed during sliding while nano-crystalline grains enhanced oxidative wear which reduced friction. With a stable nanocrystalline microstructure that confers ultrahigh hardness, wear rate and friction can be substantially reduced by promoting oxidative over abrasive or adhesive wear. • Dry sliding of two conventionally- and LPBF-processed Ti alloys was investigated. • A nano-crystalline microstructure enhances oxide formation which reduces friction. • α′ or α″ is unstable in the presence of frictional heat and oxygen diffusion. • A stable ultrahard nanocrystalline microstructure can reduce both wear and friction. • This microstructure promotes oxidative wear and minimizes adhesion/abrasion. [ABSTRACT FROM AUTHOR]

[Display omitted] • GUP suppressed the activation of multiple inflammasomes. • GUP inhibits inflammasome activation by preventing ASC oligomerization. • GUP inhibits neutrophil release in the LPS-induced acute lung injury model. • GUP may be a candidate drug for the treatment of inflammasome-mediated diseases. Glycyrrhiza uralensis polysaccharides (GUP) has biological activities such as immune regulation, anti-tumor, and liver protection, and has good development prospects in the fields of medicines and health products, but its specific mechanism of action is not yet clear. In our study, we confirmed that GUP can effectively inhibit the activation of the NLRP3 inflammasome. Mechanistically, GUP blocked the activation of the inflammasome by significantly inhibiting the oligomerization and speckle aggregation of the apoptosis-related protein ASC. In addition, GUP effectively ameliorated LPS-induced acute lung injury in mice. Our findings indicate that the Traditional Chinese Medicine (TCM) GUP has broad-spectrum anti-inflammatory effects and is a potential drug candidate for the treatment of inflammasome-related diseases. [ABSTRACT FROM AUTHOR]

AISI 440 stainless steels reinforced with various volume fractions of niobium carbide (NbC) particles of up to 25 vol% were fabricated in-situ using an argon arc furnace and then heat-treated to produce a martensitic matrix. Optical and scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and electron back-scatter diffraction (EBSD) techniques were used to analyze the microstructure, phases and composition of these composites. Interestingly, it was found that Chinese-script NbC could nucleate on existing primary NbC particles creating NbC clusters with complex microstructures. Additionally, hardness tests were used to evaluate viability in mining and mineral processing applications. The increase in NbC content resulted in an overall increase in the hardness of the composites while causing a marginal decrease in the amount of Cr in solid solution with the matrix, which could be a concern for corrosion resistance. The latter was due to the fact that the NbC lattice could dissolve a minor amount of Cr. Thermodynamic simulations also attributed this to a slight increase in M 7 C 3 precipitation. Nonetheless, these novel composites show great promise for applications in wear and corrosive environments. [ABSTRACT FROM AUTHOR]

[Display omitted] • Powder-fed laser-based directed energy deposition of Beta-C was successful. • Due to a high dislocation density, the Beta-C alloy had a fast-ageing response. • Higher strength was achieved compared to conventionally-processed aged Beta-C. • The ageing response was further accelerated by carbon additions. • With added carbon, the alloy was harder, less ductile but strength was unchanged. This work investigates the viability of fabricating Ti-3Al-8V-6Cr-4Mo-4Zr (Beta-CTM) using laser-based and powder-fed directed energy deposition. To determine an appropriate ageing strategy, heat treatments were conducted at 440 °C and 480 °C over different periods of time and their effectiveness were determined through hardness testing. After identifying an optimal ageing treatment, tensile properties were investigated on the samples in the as-built and aged conditions. The microstructure, hardness and tensile properties of the as-built sample was found to resemble that of a conventionally-manufactured and solution-treated alloy. However, as compared to conventionally-manufactured Ti-3Al-8V-6Cr-4Mo-4Zr subjected to the same ageing temperature, the ageing process was much quicker with the DED-processed alloy because of its high dislocation density. Furthermore, the latter can also achieve much higher strength while also having comparable ductility. To achieve a similar ageing response and tensile behavior, conventionally-manufactured Ti-3Al-8V-6Cr-4Mo-4Zr would require cold-working prior to ageing. Carbon additions were also investigated to further accelerate the ageing response and to refine the β grain size. While the ageing response was much quicker and a much harder alloy can be produced, the carbon amount added was insufficient for β grain refinement, which resulted in reduced ductility without a change in strength. [ABSTRACT FROM AUTHOR]

Room temperature cyclic compressive testing of high purity fine (FG) and coarse (CG) grained Ti 2 AlC were carried out in combination with Resonant Ultrasound Spectroscopy (RUS) tests and post mortem Electron-backscatter Diffraction (EBSD). The results show that the room temperature mechanical response of Ti 2 AlC can be divided in four stress regions with distinct underlying mechanisms: (a) Region I (FG: 0 to ≈ 175 MPa; CG: 0 to ≈ 100 MPa) characterized by a linear elastic behavior; (b) Region II (FG: from ≈175 to ≈ 350 MPa; CG from ≈100 to ≈ 200 MPa) in which stress strain hysteric behavior due to reversible dislocation flow in the soft grains; (c) Region III (FG: from ≈350 to ≈ 1100 MPa; CG from ≈200 to ≈650 MPa) accumulation of dislocation walls (DWs) results in cyclic hardening and contribute to larger hysteretic loops and thus a larger energy dissipation per loading cycle than in Region II; (d) Region IV (FG: from ≈1100 MPa to failure, CG from ≈600 MPa to failure) characterized by the occurrence of microcracking that, in addition to the other aforementioned deformation mechanisms, contributes to the energy dissipated in each loading cycle. [ABSTRACT FROM AUTHOR]

Background: Extracellular signal-regulated protein kinase (ERK) is known to be involved in pro-inflammatory and chemotactic events in response to injury. The aim of this study is to elucidate whether ERK plays any role in 17β-estradiol (E2)-mediated attenuation of lung injury and pro-inflammatory mediators after trauma-hemorrhage. Methods: Male Sprague-Dawley rats underwent trauma-hemorrhage (mean blood pressure ∼40 mm Hg for 90 min) followed by fluid resuscitation. At the onset of resuscitation, rats were treated with vehicle (cyclodextrin), E2 (1 mg/kg body weight [BW]), or the ERK inhibitor PD98059 (2 mg/kg BW). At 2 h after sham operation or trauma-hemorrhage, various parameters were measured. Results: Trauma-hemorrhage led to a significant increase in lung ERK phosphorylation, which was associated with increased lung myeloperoxidase activity, wet-to-dry weight ratio, interleukin (IL)-6, tumor necrosis factor (TNF)-α, intercellular adhesion molecule (ICAM)-1, cytokine-induced neutrophil chemoattractant (CINC)-1, and macrophage inflammatory protein-2 levels. Circulatory IL-6, TNF-α, and lactate levels were also increased after trauma-hemorrhage compared with shams. Administration of E2 or ERK inhibitor PD98059 after trauma-hemorrhage attenuated the trauma-hemorrhage–induced increase in lung injury markers, ERK phosphorylation and cytokines/chemokines, ICAM-1 production, as well as circulatory cytokines and lactate levels. Conclusion: These results collectively suggest that the salutary effects of E2 on the lung after trauma-hemorrhage are mediated via an ERK pathway and subsequent downregulation of pro-inflammatory mediator production. [Copyright &y& Elsevier]

In this study, the tribological properties of an AlSi10Mg alloy that was fabricated using laser powder bed fusion, an additive manufacturing technique, was investigated in both the as-built (but stress-relieved) and T6-treated condition. The stress-relieved condition consists of elongated Al grains and a dendritically-arranged nano-crystalline Si-phase. T6 treatment, a conventional heat treatment for cast AlSi10Mg alloys, caused this Si phase to dissolve, re-precipitate and coarsen, which resulted in a loss of hardness, toughness and strength. Dry sliding wear tests were conducted against both a bearing stainless steel and a much harder SiC, and with the sliding direction either perpendicular or parallel to the building direction. In almost all conditions it was found that the T6 treatment either had no statistically significant effect on the wear rate or was detrimental. • In the stress-relieved condition, the wear performance is isotropic. • Wear anisotropy occurred in the T6 condition. • The wear rate against steel is more severe than against SiC. • Frictional response is not necessarily indicative of wear performance. • T6 treatment is generally not recommended for sliding wear performance. [ABSTRACT FROM AUTHOR]

In this present work, the sliding wear behaviour of hybrid polymer nanocomposites was investigated under different loading conditions and against different counterface roughness. Two different polymers matrices, epoxy and polyamide 66, with classic micro-sized short carbon fiber and graphite flakes as tribo-fillers were investigated with and without TiO 2 reinforcing nanoparticles. It was found that the synergistic effect between nanoparticles and micro-sized fillers on friction and wear performance depended on the tribological system involved. In particular, for epoxy-based composites, the incorporation of TiO 2 nanoparticles was only beneficial against a sufficiently rough disc but detrimental otherwise. Whilst for polyamide nanocomposites, the combination of nanoparticles and other fillers resulted in low friction and wear against both rough and smooth disks, particularly at higher applied contact pressures. When the cross-sections of the transfer films were analysed using a high-resolution SEM, it was found that TiO 2 nanoparticles are only beneficial if they can blend with other wear debris to form a TiO 2 -enriched transfer film. The strengthened film provides the support required for other dislodged TiO 2 nanoparticles to achieve the rolling effect, thus reducing friction and wear. In contrast, if TiO 2 cannot effectively blend into the transfer film, TiO 2 nanoparticles act as an abrasive that readily abrades away the comparatively softer film, thus exposing the polymer to fresh asperities on the steel counterface, a detrimental outcome to both friction and wear. Hence, to design high wear resistant composite materials, it is important to understanding the interactions between different tribo-fillers for particular circumstances or contact conditions. • Polyamide and epoxy composites with and without TiO 2 nanoparticles were studied. • Depending on the tribological system, the TiO 2 may or may not be beneficial. • Improved friction and wear are due to TiO 2 -enriched transfer film formation. • TiO 2 -enriched transfer films promote the rolling effect. • TiO 2 acts as an abrasive instead if TiO 2 -enriched transfer films do not form. [ABSTRACT FROM AUTHOR]

A two-body wear test experiment was performed on human enamel, in simulated chewing motion, against non-veneered zirconia ceramic. Aim-1 was to ascertain the effect of zirconia roughness on enamel wear. Aim-2 was to ascertain the relative enamel wear between enamel-zirconia wear pair and enamel-enamel control pair. Six molar and premolar human enamel cusps per group were used for a dental wear test against laboratory polished (LP) zirconia and laboratory polished and clinically adjusted (LP + CA) zirconia. Enamel antagonists were tested against incisor teeth as a control group to demonstrate laboratory enamel wear. Two-body wear tests were conducted in a dual-axis biomimetic dental wear simulator. 49N loading force was used for 120,000 cycles with 1 mm lateral movement of the test specimen at 1.6Hz frequency, under constant ambient temperature water flow. Surface roughness before testing was determined using 3D profilometry. Loss of enamel height and volume i.e. vertical wear and volumetric wear respectively, were measured by superimposition of before and after testing scans by 3D laser scanning. Scanning electron microscopy was used for surface morphology assessment. One-way ANOVA and Post Hoc Multiple Comparisons with Bonferroni corrections were used at the 5% significance level to determine whether surface finish affected volumetric and vertical enamel loss. The relationship between volumetric and vertical loss of enamel was assessed using Pearson's correlation test. No significant difference was found between LP and LP + CA zirconia in vertical and volumetric enamel wear results. Control enamel had significantly higher vertical and volumetric enamel wear than LP and LP + CA zirconia. Pearson correlation revealed a strong relationship between vertical wear and volumetric wear of enamel. Within the constraints of the test method in this experiment, zirconia irrespective of surface preparation, was found to cause less vertical and volumetric enamel wear compared to control enamel. No statistically significant difference was seen between LP zirconia and LP + CA zirconia. Image 1 [ABSTRACT FROM AUTHOR]

Post heat treatment is essential for additively manufactured alloys to eliminate residual stress and in some cases further improve mechanical performance. This study systematically investigated the hardening response of a Ti-6Al-2Sn-4Zr-6Mo alloy processed by laser powder bed fusion (LPBF) to a one-step heat treatment. The results revealed significant hardening at both 500 °C and 650 °C. Most notably, an ultra-high peak-hardness of 563VHN was achieved within 5 mins of heat treatment at 650 °C due to a unique martensite-decomposed α+β microstructure consisting of alternating long β laths that are ∼5 nm thick and α laths that are ∼35 nm thick, and within the α laths are also short β laths that are ∼2 nm thick with an ∼11 nm inter-spacing. The influence of both types of β laths on the α lath thickness was established and related to the ultra-high hardness observed, which provides new insight for the design of new metastable LPBF-processed Ti alloys. [Display omitted] [ABSTRACT FROM AUTHOR]

Highlights • The as-built material is strongly anisotropic and process parameters dependent. • T6 heat-treated material can be considered as a reference for this type of manufacturing process. • The influence of defect size on the fatigue limit is analyzed by the Kitagawa-type diagrams. • ALM material (HT and not HT) is less sensitive to defect than conventional cast alloys. Abstract This work shows the impact of microstructure and defect on the fatigue life of an AlSi10Mg manufactured by Additive Layer Manufacturing (ALM). Samples were manufactured via a laser powder-bed process: two configurations (0° and 90°) are considered in order to evaluate the impact of the building direction on fatigue properties. 3D X-Ray tomography was used to characterize the defect population. The microstructure was characterized by considering four parameters: melt-pools, crystallographic grains, dendritic structure and precipitates. The fatigue properties were determined by establishing S-N curves for machined samples, with and without T6 heat-treatment, at R = −1 under tensile loading. The size of the defect responsible for the fatigue failure was determined in each sample so as to establish a relationship between the fatigue limit and the defect size using Kitagawa-type diagrams. In order to study a broader range of defect size, artificial defects were introduced using electro-discharge machining. The following observations are made: (i) after heat-treatment, the boundaries of melt-pools and the dendritic structure are not visible. Si is organized into pure precipitates homogeneously distributed over space and intermetallic Fe based compounds are observed in the form of needles; (ii) The impact of building direction on fatigue life is seen only after T6 heat treatment; (iii) An improvement of the fatigue resistance is observed after T6, in spite of the presence of intermetallic needles; (iv) The fatigue limit is controlled by the defect size both before and after T6 heat treatment, and it seems that the influence of T6 decreases as the defect size increases. [ABSTRACT FROM AUTHOR]

In recent years, we have found that the dysregulation of the cyclic-GMP-AMP synthase (cGAS)‒stimulator of interferon genes (STING) pathway leads to the development of immune and inflammatory diseases, therefore, finding compounds that can specifically regulate this pathway is essential for effective regulation of the immune pathway for addressing inflammatory diseases. Licorice flavonoids (LFs), are active ingredients extracted from the Chinese herb licorice, which has been reported to have strong anti-inflammatory activity in previous studies. Here, we report that LFs inhibit the activation of the cGAS-STING pathway evidenced by the inhibition of the expression of type I interferons and related downstream genes such as interferon-stimulated gene 15 (ISG15) and C-X-C motif chemokine ligand 10 (CXCL10), as well as inflammatory cytokines such as interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). Notably, LFs markedly improve the LPS-induced acute lung injury by inhibiting the excessive activation of cGAS-STING signaling pathway. Mechanistically, LFs treatment leads to the blocking of 2′3′-cyclic GMP-AMP (cGAMP) synthesis resulting in an inhibition of the activation of the cGAS-STING pathway. Our results indicate that LFs is a specific inhibitor of the cGAS-STING pathway, which is suggested to be a potential candidate for the treatment of cGAS-STING pathway-mediated inflammatory diseases. [Display omitted] • Licorice flavonoids in licorice can specifically inhibit the cGAS-STING signaling pathway. • Licorice flavonoids inhibit the cGAS-STING pathway by reducing the synthesis of 2′3′-cGAMP. • Licorice flavonoids have ameliorative effects on acute lung injury in mice. [ABSTRACT FROM AUTHOR]