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Highly active Keggin-type silicotungstic acid (SiW12) with oxygen vacancy (Ov) defects was encapsulated into the magnetic floral N-doped carbon microspheres (γ-Fe2O3@NC-300) through the facile one-step air pyrolysis of the precursor comprising core–shell Fe3O4@polydopamine (Fe3O4@PDA) and SiW12 to prepare γ-Fe2O3@NC@SiW12-300. The fabricated catalysts were systematically characterized and subsequently employed for the oxidation desulfurization (ODS) of the model fuel. The magnetic floral γ-Fe2O3@NC@SiW12-300 catalyst exhibited nearly perfect catalytic activity, which under mild conditions could remove 100% amount of 4000 ppm DBT in model fuel within 20 min (0.03 g catalysts and n(H2O2)/n(S) of 2). The catalyst activity is mainly attributed to the high activity SiW12 with the Ov defect and its outstanding dispersibility in γ-Fe2O3@NC, along with the high number of exposed active sites. A selected catalyst, γ-Fe2O3@NC@SiW12-300, showed a noticeable turnover frequency (TOF) (110.07 h−1) and lower activation energy (38.79 kJ mol−1) in oxidative desulfurization (ODS) with good recyclability. HO˙ radical was found to be the active species involved in ODS as confirmed by the EPR and scavenger experiments. Additionally, the fabricated catalyst can be conveniently separated and recycled within an externally applied magnetic field. [ABSTRACT FROM AUTHOR]

In this study, the synthesis of Co/Al hydrotalcite (layered double hydroxides: LDHs) using insoluble Al[(OH).sub.3] by a hydrothermal method is described. The syntheses were conducted under various conditions. The as-prepared Co/Al-C[O.sub.3.sup.2-]-LDH was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The tribological properties of the products were evaluated in base oil using four-ball and Plint friction testers. The LDH thus synthesized displays perfect hexagonal platelike morphology having a disk diameter in the range of 0.2-1.5 µm with a thickness of 40 nm. The addition of the product Co/Al-C[O.sub.3.sup.2-]-LDH, as an additive to the base oil, significantly reduces the friction coefficient (22.3%) and wear (26.1%) compared to base oil alone. The morphology and chemistry of the worn surface were characterized by SEM, atomic force microscopy (AFM), and X-ray absorption near-edge structure (XANES) spectroscopy. The results show that the structural distortion of LDH induced by mechanochemical processes during friction consumes the friction force between the rubbed surfaces, and as a result, the friction and the wear is reduced. Thus, our results show that the LDH sheets absorbed on the worn surface can prevent direct contact between the friction pairs (surfaces) and decreases the roughness of the worn surface. Key words: Co/Al hydrotalcites, antifriction, tribochemistry, X-ray absorption near-edge structure (XANES). La presente etude decrit la synthese d'hydrotalcite de Co/Al (hydroxydes doubles lamellaires ou HDL) a l'aide d'Al[(OH).sub.3] insoluble par methode hydrothermale. Les syntheses ont ete realisees dans diverses conditions. Les Co/Al-C[O.sub.3.sup.2-]-HDL ainsi prepares ont ete caracterises par diffractometrie de rayons X (DRX) et microscopie electronique a balayage (MEB). Les proprietes tribologiques des produits ont ete etudiees dans de l'huile de base a l'aide de bancs d'essai de frottement a quatre billes et de tribometres Plint. Les HDL ainsi synthetises presentent une morphologie hexagonale parfaite en plaque dont le diametre de disque est compris entre 0,2 et 1,5 µm et l'epaisseur egale a 40 nm. L'ajout du produit Co/Al-C[O.sub.3.sup.2-]-HDL, comme additif a l'huile de base, reduit considerablement le coefficient de frottement (22,3%) et l'usure (26,1%), par rapport a l'huile de base seule. La morphologie et la chimie de la surface usee ont ete caracterisees par MEB, microscopie a force atomique (MFA) et spectroscopie de structure pres du front d'absorption de rayons X. Les resultats montrent que la distorsion structurale des HDL provoquee par les processus mecanochimiques ayant lieu lors des frottements reduit la force de frottement presente entre les surfaces enduites, ce qui entraine une diminution du frottement et de l'usure. Nos resultats demontrent ainsi que les feuilles d'HDL absorbees sur la surface usee peuvent empecher les paires de frottement (surface) d'etre en contact et reduisent la rugosite de la surface usee. [Traduit par la Redaction] Mots-cles: hydrotalcites de Co/Al, antifriction, tribochimie, spectroscopie de structure pres du front d'absorption de rayons X., Introduction Layered double hydroxides (LDHs) are a class of layered anionic clays having the general formula of [[M.sub.(1-x).sup.2+][M.sub.x.sup.3+][(OH).sub.2]][([A.sup.n-]).sub.x/n] x z[H.sub.2]O, where [M.sup.2+] (Mg, Mn, Fe, Co, Ni, Cu, Zn, etc.) [...]

The roles of various fillers, i.e. short carbon fibers (SCF), graphite, hexagonal structured tungsten disulfide (WS 2 ) and aluminium nitride (AlN) nanoparticles, on the tribologial performance of polyphenylene sulphid (PPS) were explored with low-sulfur diesel as lubricant. It was demonstrated that the nanoparticles, especially AlN, remarkably improved the tribologial performance of PPS composites under diesel lubrication conditions. Moreover, presence of only very limited quantity of diesel results in the best tribological performance. It was manifested that the tribological performance was closely dependent on the tribofilm formed on steel counterface. Tribo-chemical reactions of PPS with both the steel counterpart and AlN nanoparticles were identified, as deemed important for generation of a robust tribofilm. [ABSTRACT FROM AUTHOR]

Abstract: La(OH)3 nanoparticles and serpentine/La(OH)3 composite particles were synthesized via sol–gel method. The phase compositions, micro-morphology of the synthesized particles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The tribological properties of different samples were tested and compared by the MM-10W Multi-functional friction abrasion tester and MHK-500 Ring-block wear testing machine. The TEM figure indicates that La(OH)3 nanoparticles are granular, the average size of the particles is 50nm. The SEM figure of the composite particles illustrates that La(OH)3 particles uniformly coat on the surface of serpentine particles. The results of the friction tests indicate that serpentine, La(OH)3 and serpentine/La(OH)3 composite particles all exhibit friction-reducing and anti-wear properties compared to the base oil. The oil containing the composite particles have the best friction-reducing, anti-wear and self-repairing properties. The friction coefficients are reduced by 24.63% and the diameters of friction spots are reduced by 41.88% compared to the base oil. The energy spectrum of tribosurface gives evidence of that the contact area of rubbing pair was repaired by composite particles during friction tests. [Copyright &y& Elsevier]

Highlights: [•] The use of magnesite to prepare Mg–Al–CO3 LDH is novel. [•] The LDH used as lubricant additive were few reported. [•] LDH possesses an excellent property on reducing friction and wear of friction pair. [Copyright &y& Elsevier]

Highly active Keggin-type silicotungstic acid (SiW 12 ) with oxygen vacancy (O v ) defects was encapsulated into the magnetic floral N-doped carbon microspheres (γ-Fe 2 O 3 @NC-300) through the facile one-step air pyrolysis of the precursor comprising core-shell Fe 3 O 4 @polydopamine (Fe 3 O 4 @PDA) and SiW 12 to prepare γ-Fe 2 O 3 @NC@SiW 12 -300. The fabricated catalysts were systematically characterized and subsequently employed for the oxidation desulfurization (ODS) of the model fuel. The magnetic floral γ-Fe 2 O 3 @NC@SiW 12 -300 catalyst exhibited nearly perfect catalytic activity, which under mild conditions could remove 100% amount of 4000 ppm DBT in model fuel within 20 min (0.03 g catalysts and n (H 2 O 2 )/ n (S) of 2). The catalyst activity is mainly attributed to the high activity SiW 12 with the O v defect and its outstanding dispersibility in γ-Fe 2 O 3 @NC, along with the high number of exposed active sites. A selected catalyst, γ-Fe 2 O 3 @NC@SiW 12 -300, showed a noticeable turnover frequency (TOF) (110.07 h -1 ) and lower activation energy (38.79 kJ mol -1 ) in oxidative desulfurization (ODS) with good recyclability. HO˙ radical was found to be the active species involved in ODS as confirmed by the EPR and scavenger experiments. Additionally, the fabricated catalyst can be conveniently separated and recycled within an externally applied magnetic field.

Corrosion and wear products of metallic implants can lead to severe adverse tissue reactions. However, there is an absence of effective means to reduce the tribocorrosion of metal. The main purpose of this study is to reveal a mechanism of engineering a barrier layer on metal surfaces via adding functional particles into the polymer counterpart. B 4 C and BN particles were compounded into a polyetheretherketone (PEEK) matrix and their tribological performance of PEEK-based composites sliding against stainless steel was compared in simulated body fluid. Results demonstrate that the addition of B 4 C reduces significantly friction and wear. In particular, the addition of only 1 vol% B 4 C reduces wear of PEEK by up to 94.8%, and tribocorrosion of steel is also obviously mitigated. It is discovered that hydrolysis of B 4 C particles triggered by friction and deposition of Ca 2+ and phosphate ions dominate formation of the barrier layer at the friction interface. The barrier layer endows the PEEK-metal sliding pair simultaneously enhanced anti-wear and anti-corrosion performance., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)