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[Display omitted] Nickel-based materials have been extensively deemed as promising anodes for sodium-ion batteries (SIBs) owing to their superior capacity. Unfortunately, the rational design of electrodes as well as long-term cycling performance remains a thorny challenge due to the huge irreversible volume change during the charge/discharge process. Herein, the heterostructured ultrafine nickel sulfide/nickel phosphide (NiS/Ni 2 P) nanoparticles closely attached to the interconnected porous carbon sheets (NiS/Ni 2 P@C) are designed by facile hydrothermal and annealing methods. The NiS/Ni 2 P heterostructure promotes ion/electron transport, thus accelerating the electrochemical reaction kinetics benefited from the built-in electric field effect. Moreover, the interconnected porous carbon sheets offer rapid electron migration and excellent electronic conductivity, while releasing the volume variance during Na+ intercalation and deintercalation, guaranteeing superior structural stability. As expected, the NiS/Ni 2 P@C electrode exhibits a high reversible specific capacity of 344 mAh g−1 at 0.1 A g−1 and great rate stability. Significantly, the implementation of NiS/Ni 2 P@C//Na 3 (VPO 4) 2 F 3 SIB full cell configuration exhibits relatively satisfactory cycle performance, which suggests its widely practical application. This research will develop an effective method for constructing heterostructured hybrids for electrochemical energy storage. [ABSTRACT FROM AUTHOR]

[Display omitted] • Low power density laser treatment causes oxidation and amorphization of UHMWPE. • High power density laser treatment results in carbonization of UHMWPE. • Laser-induced carbonization can improve the tribological properties of UHMWPE. The influencing mechanism of laser treatment on the tribological behavior of ultrahigh molecular weight polyethylene (UHMWPE) in a seawater environment was studied. The relation between the surface chemical composition and morphology of UHMWPE under different laser processing parameters and tribological properties in seawater environment was obtained. Oxidation and amorphization occurred when UHMWPE was laser-treated at relatively low-power densities (1.92 × 105 and 3.94 × 105 W/cm2), causing the slightly increase in wear rate of UHMWPE. Carbonization occurred after relatively high-power densities laser treatment (6.01 × 105, 8.12 × 105 and 1.00 × 106 W/cm2), causing significantly increase in wear resistance and decrease in friction coefficient. The laser-induced carbonization products were mainly composed of amorphous and graphitic carbon, which served as a solid lubricant during friction, thereby significantly improving the tribological properties of UHMWPE in the seawater environment. A method of laser-induced carbonization was proposed to improve the tribological properties of polymer materials in a seawater environment. Controlling the degrees of surface oxidation and carbonization of UHMWPE effectively regulated its tribological properties in seawater environments. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to investigate the thermal oxidation characteristics of the unsaturated bonds (C=C) of trimethylolpropane trioleate (TMPTO) and to reveal the high temperature oxidation decay mechanism of unsaturated esters and the nature of the anti-oxidation properties of the additives. Design/methodology/approach: Using a DXR laser microscopic Raman spectrometer and Linkam FTIR600 temperature control platform, the isothermal oxidation experiments of TMPTO with or without 1.0 wt. % of different antioxidants were performed. Findings: The results indicated that the Raman peaks of =C-H, C=C and -CH2- weaken gradually with prolonged oxidation time, and the corresponding Raman intensities drop rapidly at higher temperatures. The aromatic amine antioxidant can decrease the attenuation of peak intensity, as it significantly reduces the rate constant of C=C thermal oxidation. The hindered phenolic antioxidant has a protective effect during the early stages of oxidation (induction period), but it may accelerate the oxidation of C=C afterwards. Originality/value: Research on the structure changes of synthetic esters during oxidation by Raman spectroscopy will be of great importance in promoting the use of Raman spectroscopy to analyze the oxidation of lubricants. [ABSTRACT FROM AUTHOR]

The friction of PEEK under artificial seawater lubrication was reduced after laser treatment. The reduction in friction for the laser treated PEEK under low power density was mainly due to the adsorption of water molecules and cations on the surface of PEEK. For the PEEK treated with high laser power density, solid lubrication due to surface carbonization was the main reason for the reduction of friction and wear. [Display omitted] • Low power density laser treatment reduces friction due to the adsorption of water molecules and cations on PEEK surface. • High power density laser treatment significantly improves friction and wear of PEEK due to carbonization of PEEK surface. The effect of laser treatment on the tribological performance of PEEK under seawater lubrication was studied. The surface morphology and wettability of the laser treated PEEK were analyzed. The relationship between the surface chemical composition and the tribological performance of the laser treated PEEK was discussed. Results show that oxidation occurred during laser treatment with relatively low laser power density, there was no obvious change in surface roughness. Carbonization occurred for the treatment with high laser power density, surface roughness increased significantly, made the surface more hydrophobic. The friction of PEEK under artificial seawater lubrication was reduced after laser treatment. The reduction in friction for the laser treated PEEK under low power density was mainly due to the adsorption of water molecules and cations on the surface of PEEK. For the PEEK treated with high laser power density, solid lubrication due to surface carbonization was the main reason for the reduction of friction and wear. [ABSTRACT FROM AUTHOR]

Effects of thermal aging on the blend phase morphology of polyimide/ultrahigh molecular weight polyethylene (PI/UHMWPE) blend composites were studied by using Raman Mapping. Friction and wear tests were conducted to study the influence of thermal aging on the tribological properties of the blend composites. The results indicate that the phase morphology of PI/UHMWPE blend composites could be controlled by thermal aging. At relatively low thermal aging temperatures (100 °C, 120 °C), the blend with high PI/UHMWPE ratio tended to form continuous layered structures. As a consequence, the tribological performance was significantly improved. While for the blend with low PI/UHMWPE ratio, the improvement of tribological performance was not significant. For the blends thermal aged at relatively high temperature (150 °C), the tribological performance was poor due to significant phase separation that occurred after thermal aging. • Thermal oxidation resistance of UHMWPE could be significantly improved by blending PI to the UHMWPE matrix. • The phase morphology of PI/UHMWPE blend composites could be controlled by thermal aging. • The wear resistance of PI/UHMWPE blend was improved after thermal aging at the temperature below melting point. [ABSTRACT FROM AUTHOR]

1) A triboelectric series of polymers based on the measurement of triboelectrification with a conductive solution (3.5 wt% NaCl solution) was established, which can be used to rank the triboelectric properties of polymers rubbing with NaCl solution. In the triboelectric series, carbon chain polymers generally demonstrate more significant triboelectric performance than the heterocatenary polymers. In addition, the fluoropolymers show more significant triboelectric performance than other carbon chain polymers. 2) Electron transfer is the main mechanism of triboelectric charge transfer between polymers and aqueous solutions, and ion transfer and liquid molecular transfer are less significant than electron transfer. [Display omitted] • A triboelectric series of polymers based on the measurement of triboelectrification with a conductive solution (3.5 wt% NaCl solution) was established. • Mechanisms of the effects of the electronegativity of the functional groups, EDL, and wettability on the triboelectrification properties were analyzed. • Electron transfer is the main mechanism of triboelectric charge transfer between polymers and aqueous solutions. • A term called triboelectronegativity was proposed, which refers to the triboelectric properties of polymers rubbing with NaCl solution. Triboelectrification between polymers and aqueous solutions has received much attention in energy harvesting, self-powerful sensing, and other fields. However, the triboelectric series between commonly used polymers and aqueous solutions have not been systematically measured and studied. Based on the established solid–liquid triboelectric charge measurement method, we quantitatively measured the charge density caused by the triboelectric charge transfer among 14 common polymers and established a triboelectric series of polymers rubbing with sodium chloride solution. The influence mechanisms of the electronegativity of the functional groups, structures of the electric double layer, and wettability on the triboelectrification between polymer and aqueous solution were discussed in detail. And it was found that electron transfer is the main mechanism of triboelectric charge transfer between polymers and aqueous solutions. This work provides a new perspective for the quantitative study of polymer triboelectric series, helps to deeply understand the nature of the triboelectrification phenomenon of polymers, and may serve as guidance for designing and preparing new polymer materials with excellent triboelectric properties. [ABSTRACT FROM AUTHOR]

Polyimide/ultrahigh molecular weight polyethylene (PI/UHMWPE) blends with different mass ratio were produced. A ratio-image method was adopted by plotting the ratio of Raman peak intensity of a typical band of PI with that of UHMWPE as a function of position, Raman Mapping images with a relatively high accuracy and enhanced visualization were obtained. Two-phase distribution morphologies of the blends were studied using Raman Mapping. Effects of blend phase morphology and phase distribution on the tribological properties of blend composites were investigated. The results indicated that both the phase structures and their distribution are obviously different for the PI/UHMWPE blends with different mass ratios, which significantly influence the tribological properties of the blends. PI phase disperses in an island form in the UHMWPE matrix phase when the mass ratio of PI/UHMWPE is relatively small (10/90). The scattered PI dispersed phase effectively reduces the friction coefficient of the blend and improves the wear resistance. For the PI/UHMWPE blend composite with the mass ratio of 30/70, layered PI phase forms and distributes in the UHMWPE matrix phase, improving bearing capacity and wear resistance of the blends. Large continuous area structure and phase separation occurs in the blend when the mass ratio of PI/UHMWPE increases to 50/50, resulting in a significant reduction in the wear resistance of the blend composite. Image 1 • A ratio-image method was adopted by plotting the ratio of Raman peak intensity of a typical band of PI with that of UHMWPE as a function of position. • Different phase morphologies and their distribution are formed for the PI/UHMWPE blends with different mass ratios. • PI/UHMWPE blend with island or layered morphology of PI improves the tribological properties of UHMWPE. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to investigate the thermal oxidation behavior of trimethylolpropane trioleate (TMPTO) base oil when exposed to Fe surfaces. Design/methodology/approach: Samples of TMPTO bulk oil were placed in Fe vessels and heated in an oven to accelerate the oxidation at different time intervals, while others were placed in glass vessels and used as experimental controls. Subsequently, the physicochemical properties of the oxidized TMPTOs, including the kinematic viscosity and acid value, were measured and a structural analysis was conducted using the Raman and Fourier transform infrared (FTIR) techniques. Findings: The results demonstrate that the TMPTO bulk oil exhibited an exponential increase in the kinematic viscosity along with the increasing acid value over the oxidation time. The Fe surface significantly increased the kinematic viscosity of TMPTO, while only mildly impacting its acid value compared with the experimental controls. The structural analysis results of the TMPTO suggest that the C = C and = C-H bonds were the vulnerable sites. Furthermore, the results suggest that the Fe surface evidently accelerates the chemical reactions of the C = C and the = C-H bonds, and less alcohols and more carbonyl products were identified in the oil samples that were heated in the Fe vessels. Originality/value: The results demonstrate that the Fe surfaces affected the oxidation behavior of the TMPTO base oil, and an interaction mechanism between the Fe and the TMPTO is developed. [ABSTRACT FROM AUTHOR]

Objective: As disc fragment completely loses contact with the parent disc and can migrate in all directions of the epidural space, making it appear similar to schwannoma, it is fairly difficult to make a definitive diagnosis for mimicking tumor discs. The aim of this research is to differentially diagnose mimicking tumor discs and schwannomas using coronal magnetic resonance imaging (MRI) of three‐dimensional fast‐field echo with water‐selective excitation (CMRI). Methods: Among 76 patients (38 men and 38 women; mean age, 52.88 ± 15.80 [range, 18–78 years]) who were retrospectively examined in this study, 38 were primarily diagnosed with schwannomas and pathologically diagnosed with mimicking tumor discs after surgery, and 38 were primarily diagnosed with neurogenic tumors and pathologically diagnosed with schwannomas after surgery. Open surgery was performed in all the patients between March 2016 and April 2020. The preliminary diagnosis of all patients was considered an intraspinal tumor based on conventional two‐dimensional MRI sequences. After open surgery, the final diagnosis was confirmed to mimic a tumor disc or schwannoma based on postoperative pathology reports. The sensitivity, specificity, and reliability of CMRI and conventional MRI for identifying mimicking tumor discs and schwannomas were compared. Chi‐square and McNemar tests were used for statistical analyses. Results: Symptoms were considerably relieved in all the patients after surgery. Seven patients had grade 1 extensor digitorum longus, triceps surae, or quadriceps femoris muscle strength prior to surgery. No nerve root injury was observed in any of the patients. CMRI showed significantly higher sensitivity (94.74%) and specificity (94.74%) than conventional MRI (71.05% and 92.11%, respectively; p = 0.012 < 0.05, and p = 1 > 0.05, respectively) for differential identification between mimicking tumor discs and schwannomas. Moreover, CMRI showed a higher reliability (kappa value = 0.787) than conventional MRI (kappa value = 0.374). Conclusions: CMRI is a better non‐invasive technology for the identification of intraspinal lesions, especially for differentiating between mimicking tumor discs and schwannomas. [ABSTRACT FROM AUTHOR]

This study aims to investigate a novel high‐efficient antioxidant for synthetic ester oils. An ester‐bridged antioxidant, phloroglucinol tris (3‐[3,5‐di‐tert‐butyl‐4‐hydroxyphenyl]) propionate (PTP), was successfully synthesised in high yield under relatively mild reaction conditions. Thermal stability and oxidation resistance of diisooctyl adipate (DOA) ester oil were determined and compared to the typical commercial phenol antioxidants, including its tribological properties. The results indicate that the prepared PTP antioxidant exhibits considerably higher thermal stability than commercial antioxidants, and it also improves the oxidation resistance of the synthetic ester oil more effectively. Moreover, the addition of PTP antioxidant enhanced the wear protection of DOA ester oil without deteriorating its lubricating performance. The ester‐bridged antioxidant can be used as a multifunctional additive, which not only exerts excellent thermal stability and oxidation resistance, but can also act as an efficient anti‐wear agent in synthetic ester oils. [ABSTRACT FROM AUTHOR]

In this work, the causes of failure of electroplating silver coatings on aero-engine nuts were explored. And the microhardness of low temperature pulsed DC magnetron sputtering silver coatings was increased by 25%, and the bonding force was increased by about 1.2 times. At high temperature, the friction coefficients of magnetron sputtering silver coatings was about 20% lower than that of electroplating silver coatings, and the wear volume was about 90% lower than that of it at maximum. The wear mechanism of magnetron sputtering silver coatings was mainly abrasive wear, while that of electroplating silver coatings was mainly adhesive wear. Besides, the results of molecular dynamics showed that silver coatings would move and aggregate in layers during the friction. • Adhesive wear and abrasive wear cause failure of silver coatings on aero-engine nuts. • Low hardness, poor bonding, and thickness uniformity are defect of silver coatings. • Magnetron sputtering silver coatings better perform at high temperature. • Silver coatings transfers and aggregates during friction. [ABSTRACT FROM AUTHOR]

Herein, the internal lubrication of polyether ether ketone (PEEK) with added whiskered carbon nanotubes (Wh-CNTs) was investigated under point-contact dry sliding conditions with various loads and velocities. The wear rate of the composite was reduced by 86.99% at a maximum Hertzian contact pressure of 344.69 MPa, which was attributed to the addition of additives with excellent mechanical properties and high-temperature stability. Wh-CNTs could be uniformly distributed in the PEEK to form a three-dimensional (3D) network structure with load-bearing capacity, thus the load could be effectively borne to prevent crack propagation on the PEEK surface. Besides, the filler was induced to form a micron-sized 3D spherical structure with a ball bearing effect, which promotes lubrication more effectively than the fragment structure. [ABSTRACT FROM AUTHOR]

[Display omitted] • HPN exhibits superior friction-reducing and anti-wear behaviors as additive. • HPN can adsorb and deposit at the friction interface due to the P-O-Ti bonds. • The tribofilm containing HPN can protect titanium alloy from severe wear. • The repulsive force between HPN and oil molecules is the key to friction reduction. In this work, a self-assembled hybrid phosphate nanoflower (HPN) containing Ba 3 (PO 4) 2 and NaBaPO 4 was synthesized via BaCO 3 primary crystals inducement. A ball-on-disc reciprocating tribometer was used to explore the tribological behavior of HPN as an additive for polyalphaolefin 8 (PAO8) on titanium alloy. Compared with the neat PAO8, after being lubricated with PAO8 containing HPN, the friction coefficient and wear rate decreased by 74.98% and 99.89%, respectively. The tribofilm at the friction interface was characterized and conformed by SEM, EDS, XPS, and cross-sectional TEM. As an additive to PAO8, HPN can participate in the formation of tribofilm and exhibit superior friction-reducing and anti-wear properties for titanium alloy. It was demonstrated that due to the P-O-Ti bonds, HPN can easily adsorb and deposit at the friction interface to form a tribofilm against wear. Besides, the simulation experiments showed that the repulsive force at the solid-liquid interface between HPN and oil molecules is the key to friction reduction and lubrication, and the comparative tribological experiments of different types of base oils were performed to verify the results of molecular dynamics. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to study the thermal oxidation performance of antioxidant additives in ester base oils deeply. Design/methodology/approach: ReaxFF molecular dynamics was used to simulate the thermal oxidation process of butyl octyl diphenylamine and octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propanoate as two antioxidant additives act on the Trimethylolpropane trioleate (TMPTO) base oil. Meanwhile, combining with the infrared spectroscopy characterization results of the thermal oxidation test, this paper provides theoretical support for the development of high-performance synthetic lubricants and their antioxidant additives. Findings: The results show that butyl octyldiphenylamine easily removes the hydrogen atom on the secondary amine, which promotes the formation of more long carbon chain diene radicals or polyene hydroperoxides from TMPTO. Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propanoate could easily decompose into octadecyl hydroperoxide and 2,6-di-tert-butyl 4-propionylphenol, which could convert into 2-tert-butyl-4-peroxyethyl-6-hydroperoxy-tert-butylphenol in the middle of the thermal oxidation reaction, prompting TMPTO to form more short-chain alkenyl and olefin hydroperoxide or other oxide. Originality/value: The main change characteristics of base oil molecules are the first thermal decomposition to form oleic acid groups and ethane cyclopropane methyl oleate. Under the action of butyl octyldiphenylamine and octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propanoate, the deep oxidation and decomposition reaction are slowed down. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2020-0037/ [ABSTRACT FROM AUTHOR]

PI/UHMWPE blends are going to be used as the bush material of sliding bearings under high speed dry condition in one project. Prior to the fabrication of these bearings, the tribological properties PI/UHMWPE blends with various component ratio under the specific service condition was investigated by using a pin-on-disk tribometer. The results revealed that the compression modulus of PI/UHMWPE blends increases with the increase in PI content. Furthermore, the coefficient of friction and wear rate decrease firstly and then increase slightly with the increase in PI content, both of which reach the minimum value when PI content is 70%. The analyses of transfer membrane indicate that both of UHMWPE and PI can transfer to the metal counterface, while the increase of PI content is more conducive to the increase of transfer membrane. • The coefficient of friction and wear rate of PI/UHMWPE blends decrease firstly and then increases slightly with the increase in PI content, both of which reach the minimum value when PI content is 70%. • The analyses of transfer membrane indicate that both UHMWPE and PI can transfer to the metal counterface, while the increase of PI content is more conducive to the increase of transfer membrane. [ABSTRACT FROM AUTHOR]

The oxidation behavior of the synthetic ester oils di‐isooctyl adipate (DOA) and tri‐isodecyl trimellitate (TDTM) was investigated by analysing the oxidation induction time and oxidation onset temperature via pressure differential scanning calorimetry tests, and the variation in viscosity after oven accelerated oxidation tests. Moreover, theoretical calculations of the fractional free volumes and oxygen diffusion coefficients of DOA and TDTM were performed, and atomistic‐scale insights into the oxidative mechanisms of both oils were proposed based on reactive molecular dynamic (RMD) simulations. Better oxidation resistance for TDTM was confirmed with experimental observations. RMD results indicated that the C―O bonds of the alcohol chain and ester group of DOA were susceptible to oxidation. However, only the dissociation of the C―O bond of the alcohol chain initiated the oxidation of TDTM. Additionally, more degradation fragments for DOA were identified, along with the formation of a polymerized product, while no large molecules formed for TDTM. [ABSTRACT FROM AUTHOR]

Polymeric materials have a short history of employment as tribological materials in liquid-propellant rocket engines, but they hold promise for the future. Even those polymer materials served already in rocket engines are based on inaccurate or unsubstantiated data. For these reasons, aging tests of polyformaldehyde (POM) and ultra-high molecular weight polyethylene (UHMWPE) in rocket-grade hydrogen peroxide solution were carried out, and then tribological experiments were conducted in this work. The objective is to provide a sound foundation of further selecting or developing polymeric materials for tribological application in rocket-grade hydrogen peroxide environment. The micrographs of polymer specimen with various aging time indicate that POM has poorer aging resistance in hydrogen peroxide solution than UHMWPE. A new absorption peak assigned to hydroxyl group appears on FTIR spectra of POM after aging test due to the oxidation by hydrogen peroxide solution. It is deduced from thermoanalysis that the amorphous regions is the main area influenced by hydrogen peroxide solution. Results of tribological experiments display that the friction coefficients of both POM and UHMWPE decrease with the increase in aging time from 0 to 240 h. However, the wear rates of POM and UHMWPE present different trends with the increase of aging time; the wear rate of POM decreases, whereas the wear rate of UHMWPE increases. [ABSTRACT FROM AUTHOR]

Abstract: As oxidation stability of engine oil was hard to evaluate in field, this paper tried to propose a field test method to determine the oxidation onset temperature (OOT) of gasoline engine oil. A theoretical model of grey average value of oil spot image and OOT was established by using spot test method, image processing, and Pressure Differential Scanning Calorimetery method. The oil sample unknown OOT was taken to spot test and image processing in field to obtain the grey average value. The OOT can be calculated by bringing the grey average value to the established theoretical model. This approach was successfully used for OOT determination of 4 different kinds of engine oils with good accuracy and precision. The absolute error of mineral oils was less than 4.52°C, and synthetic oils were less than 1.2°C. This convenient, low‐cost, and reliable method can achieve OOT of engine oil in field determination and provide reference for engine oil drain interval evaluation. [ABSTRACT FROM AUTHOR]

A method is reported for the determination of diphenylamine and butylated hydroxytoluene in mineral and synthetic oil. The procedure used differential pulse voltammetry with a glassy carbon electrode. This method was then used for determining these antioxidants in supporting electrolyte consisting of dilute sulfuric acid and sodium dodecyl sulfonate in ethanol. Anodic peaks were obtained for both analytes. Oxidation peaks at 250 mV were observed from a mixture of butylated hydroxytoluene and dinonyl diphenylamine, allowing their simultaneous determination. This approach was successfully used for the determination of dinonyl diphenylamine and butylated hydroxytoluene in fortified mineral and synthetic oils with good accuracy and precision. [ABSTRACT FROM AUTHOR]