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Attapulgite is one kind of phyllosilicate minerals of abundant reserves and rather low costs, and the unique structure of attapulgite have attracted wide attention from fields of photocatalysis and dye adsorption etc. In the present work, exfoliated attapulgite nanofibers were incorporated into polyetheretherketone (PEEK) and PEEK filled with short carbon fibers (CF), respectively. Role of attapulgite in tribo-performance of the PEEK-based materials was explored. Our results demonstrate that addition of attapulgite into pure PEEK reduces substantially wear of the polymeric matrix. More interestingly, adding low-loading attapulgite nanofibers into CF-reinforcing PEEK lowers greatly the friction and wear. The hybrid nanocomposites developed in the present work is very promising for applications under harsh sliding conditions. Thorough characterizations of the worn surfaces reveal that physio-chemical products of attapulgite nanofibers exert an important influence on growth of a resilient tribofilm. [Display omitted] • Attapulgite nanofibers were incorporated into PEEK and CF-reinforcing PEEK. • Attapulgite nanofibers improves substantially wear resistance of PEEK. • PEEK filled with attapulgite/CF combination exhibits ultra-high tribo-performance. • Physio-chemical products of attapulgite is important for tribofilm growth. [ABSTRACT FROM AUTHOR]

Tribological behaviors of carbon fibers (CF) reinforced poly-ether-ether-ketone (PEEK) composites are investigated at low speeds ranging from 0.01 to 0.2 m/s under pressures varying from 1 to 30 MPa. Nano-Bi 2 O 3 , nano-SiO 2 and conventional solid lubricants (graphite and polytetrafluoroethylene) are further added into CF-reinforced PEEK, respectively. It is demonstrated that a small load and relatively high speed are favorable for the wear-reduction role of nano-Bi 2 O 3 , while the positive role of nano-SiO 2 is pronounced at a high load and speed. Friction and wear-reduction roles of the solid lubricants are the most significant at low load and low speed. It turns out that functionalities of the fillers are closely associated with their roles in tribofilm growth governed by complex physical and chemical actions. • Tribological mechanisms of PEEK composites at relatively low speeds were studied. • Nano-Bi 2 O 3 reduces wear of CF/PEEK at speeds higher than 0.05 m/s under 1 MPa. • Nano-SiO 2 enhances wear resistance of CF/PEEK at a high load and 0.1 m/s. • Graphite/PTFE plays an excellent lubrication role at the low speed range studied. • Tribological performance of the materials is closely related to tribofilm growth. [ABSTRACT FROM AUTHOR]

Multi-walled carbon nanotubes (MWCNTs), and MWCNTs/zirconia nanoparticles (nano-ZrO 2) hybrids were compounded into a formulated non-asbestos brake material of phenolic binder, respectively. It is demonstrated that even low-loading above nanofillers switching virtually the original brake material to an extremely wear-resistant self-lubricating material. More interestingly, the addition of MWCNTs/nano-ZrO 2 hybrids leads to formation of a double-deck tribofilm yielding extraordinarily low friction and wear. First-principles calculations demonstrate that O atoms from air ambience break carbon-carbon backbones of CNTs, facilitating them to convert into graphitic nanograins. Our work provides direct evidence that graphitic nanograins and nano-ZrO 2 are digested within the beneath layer of the tribofilm, whilst chelation of polymer chains radicals with nano-ZrO 2 expedites formation of a carbon-based lubricous top layer. The present work puts forward a new strategy for endowing numerous mechanical motion systems with a robust self-lubrication characteristic via tuning tribofilms' nanostructures. Growth of a double-deck tribofilm yielding ultra-low friction and wear. Image 1 [ABSTRACT FROM AUTHOR]

Tribological behaviors of polyphenylenesulphide (PPS) filled with hydrolysable nanoparticles, i.e. hexagonal boron nitride (BN), beta silicon nitride (Si 3 N 4 ) or beta silicon carbide (SiC) nanoparticles, are investigated when sliding in sea water against a stainless steel. It is demonstrated that the addition of BN or SiC nanoparticles enhances significantly the tribological performance of PPS. In particular, SiC nanoparticles enhance the wear resistance of PPS by up to 100 times. Our work provides evidence that a robust tribofilm containing hydrolysis products of SiC, i.e. silica gel, protect the steel from wear and corrosion. Si 3 N 4 nanoparticles play a positive role only if hydrolysis reaction occurs. This work paves the way for regulating interface structures and properties of polymer-metal pairs lubricated with sea water. [ABSTRACT FROM AUTHOR]

Tribological behaviors of polytetrafluoroethylene (PTFE) reinforced with carbon fibers (CF), aramid fibers (AF) and hybrid "CF + AF" were comparatively investigated. It is demonstrated that the hybrid composites reinforced with "CF + AF" exhibit greatly enhanced wear resistance, when compared to the composites reinforced only with CF or AF. Adding only 0.3 vol% silica (SiO 2) nanoparticles into the hybrid composites further reduces wear rate by up to 47.3%. Mechanochemistry of PTFE molecules and nanostructures of the tribofilms were comprehensively explored. Our work provides direct evidence that SiO 2 nanoparticles released from the composites are compacted into the tribofilms, while the reinforcement types exert an important influence on mechanochemistry of PTFE molecules. This work puts forward new strategies for developing highly wear-resistant PTFE composites via regulating tribo-physical and -chemical actions. • Reinforcement types play a key role in mechanochemistry of PTFE molecules. • Mechanochemistry of PTFE molecules and nanostructures of the tribofilms were explored. • Our work provides evidence that nano-SiO 2 released from PTFE composite is compacted into tribofilms. • Compaction of nano-SiO 2 into the tribofilm significantly enhances its robustness. [ABSTRACT FROM AUTHOR]