Tribological properties of nano-graphite as an additive in mixed oil-based titanium complex grease

Nano-graphite was chosen as an additive to improve the tribological properties of titanium complex grease. The influence of the concentration of nano-graphite (N-G) with three average diameter sizes (2 μm, 3.5 μm, and 6 μm) on the tribological properties of titanium complex grease was researched. It was determined that the optimum concentration of the three types of N-G is 0.8 wt%, 1.0 wt%, and 1.2 wt%. Futhermore, the titanium complex grease modified with nano-graphite with a concentration of 0.8 wt% is the optimum grease. Subsequently, the influence of load on the tribological properties of grease containing the optimum concentration (N-G) was studied. Compared to the base grease, the optimum grease showed a lower average friction coefficient, smaller diameter and better tribological performance under the same experimental load. The influence of dispersion homogeneity of N-G on the tribological properties of titanium complex grease was also investigated. The base titanium complex grease and titanium complex grease modified with nano-graphite were synthesized in the laboratory and their tribological properties were evaluated via the four-ball test. The worn surface of their wears scar was observed using SEM and the states of the typical elements were analyzed via XPS. It was uncovered that nano-graphite can improve the tribological properties of titanium complex grease due to the physical friction reduction by nano-graphite due to its interlayer slide and the supplemental effect of the tribochemical reaction anti-wear film composed of TiO₂ and Fe₃C.

Increasing the size of nano-graphite led to an increase in the optimum additive concentration and decrease in the degree of improvement in the tribological properties of grease.     

Coordinating influence of multilayer graphene and spherical SnAgCu for improving tribological properties of a 20CrMnTi material

In order to increase the service life and operational reliability of a 20CrMnTi-steel-based gearing system, the friction and wear behavior of 20CrMnTi needs to be further improved. In this study, the sliding friction and wear properties of 20CrMnTi, 20CrMnTi-1.50 wt% graphene (20-Gr), 20CrMnTi-15.00 wt% SnAgCu (20-Sn), and 20CrMnTi-15.00 wt% SnAgCu-1.50 wt% graphene (20-Gr-Sn) were examined on a ball-on-disk tribometer. The friction and wear properties at 0–85 min of 20-Gr-Sn were significantly better compared to those of 20CrMnTi, 20-Gr, and 20-Sn. Metallic oxides appeared on the smooth wear scar of 20-Gr-Sn, which were tightly combined with the 20CrMnTi-based material. This caused a lubrication film with low hardness (approximately 1.25 GPa) to form on the grain-refined layer with high hardness (approximately 5.92 GPa). Graphene and SnAgCu in the lubrication film exhibited excellent coordinating lubrication to result in a low friction coefficient and lower wear rate. The obtained results can provide a good reference for increasing the service life of 20CrMnTi-steel-based gear systems.

In order to increase the service life and operational reliability of a 20CrMnTi-steel-based gearing system, the friction and wear behavior of 20CrMnTi needs to be further improved.     

Efficient tribological properties of azomethine-functionalized chitosan as a bio-lubricant additive in paraffin oil: experimental and theoretical analysis

A simple condensation of chitosan (from shrimp shells) and 4-hydroxybenzaldehyde was performed to yield bio-lubricant additive comprised of azomethine functional groups to be used with paraffin lube oil in industries. The synthesized Schiff base derivative of chitosan (SBC) additive was characterized using a CHN analyzer and FT-IR spectroscopy, and the thermal stability was explored using thermogravimetry. The rheological properties of SBC additives in paraffin oil were studied and are discussed herein. The tribological properties of SBC were tested in paraffin as the base oil employing a four-ball tester with different experimental conditions (viz. the concentration of the additive, applied load, speed and time duration), following ASTM D4172A standards. The optimum concentration of the additive in the base oil was found to be 150 ppm, exhibiting minimum coefficient of friction, but with higher concentrations of additive in base oils, the coefficient of friction increased. UV-Vis spectroscopy studies were also performed to confirm the formation of SBC and dispersion stability. The determined tribological parameters, such as the coefficient of friction, mean wear scar diameters and mean wear scar volumes, were found to significantly reduce the coefficient of friction of paraffin oil upon the addition of SBC. The state of steel balls upon exposure to various experimental conditions was analyzed and explained based on outcomes from FESEM, EDX, ferrography and AFM spectroscopy. The insights into interactions of the synthesized SBC with the metal surface were explored using ab initio density functional theory, Fukui indices, molecular dynamics simulation and radial distribution function.

Schiff base derivative of chitosan as biolubricant additive explored in paraffin lube oil.     

Tribological properties of synthetic base oil containing polyhedral oligomeric silsesquioxane grafted graphene oxide

The dispersion of graphene-based materials in lubricating oil is a prerequisite for improving its friction and wear performance. In this study, polyhedral oligomeric silsesquioxane (POSS) grafted graphene oxide (GO) was synthesized with an aim to improve the dispersibility of graphene in synthetic base oil. The composition and morphology of POSS-GO conjugates were characterized by FTIR, XPS, Raman spectroscopy, TEM and SPM. The tribological behavior of base oil with various concentrations of POSS-GO were examined using a UMT-3 friction and wear tester, and the worn surfaces were analyzed using Raman spectroscopy. It was found that concentrations of POSS-GO additives in the base oil is an important aspect for decreasing the friction and wear of the lubricated solid contacts. At lower and higher concentrations of POSS-GO, the lubricating effect is not effective or even worse. In contrast, at optimized concentration of POSS-GO, graphene sheets could form a boundary tribofilm between the contact, resulting in reduction of the friction coefficient and wear.

The dispersion of graphene-based materials in lubricating oil is a prerequisite for improving its friction and wear performance.     

Mechanical synthesis of chemically bonded phosphorus–graphene hybrid as high-temperature lubricating oil additive

Red phosphorus (P) was covalently attached to graphene nanosheets (Gr) using high-energy ball-milling under a nitrogen atmosphere. Benefiting from the formation of phosphate and P–O–C bonds on graphene surfaces, the resulting phosphorus–graphene (P–Gr) hybrids exhibited excellent dispersion stability in polyalkylene glycol (PAG) base oil compared with graphene. Moreover, tribological measurement indicated that addition of 1.0 wt% P–Gr into PAG resulted in significant reduction in friction coefficient (up to about 12%) and wear volume (up to about 98%) for steel/steel contact at 100 °C, which was likely due to the formation of a boundary lubrication film on the sliding surfaces during the friction and wear processes. XPS analysis demonstrated that the tribofilm is composed of FeO, Fe₃O₄, FeOOH, FePO₄, and the compounds containing C–O–C and P–O bonds.

Red phosphorus (P) was covalently attached to graphene nanosheets (Gr) using high-energy ball-milling under a nitrogen atmosphere.     

Graphene platelet reinforced copper composites for improved tribological and thermal properties

In this work, investigations were conducted to evaluate a type of graphene platelet–reinforced copper (GPL/Cu) composite for enhanced tribological and thermal properties. The pin-on-disc (steel) results show that the wear loss and the friction coefficient of the composites decrease by nearly 80% and 70%, respectively, in comparison with those of pure Cu. Thermal conductivity of the composites initially improves substantially by approximately 30% with a slight loading of 0.25 vol% GPLs and decreases gradually with a higher content of GPLs. Microstructural analysis reveals that the enhancement in the tribological property is attributed to both the self-lubricating property of GPLs and grain refinement while the improvement in the thermal property is closely associated with the uniform dispersion of GPLs.

The uniform dispersion and self-lubricating property of GPLs enhance both the tribological and thermal performances.     

2D graphene/FeOCl heterojunctions with enhanced tribology performance as a lubricant additive for liquid paraffin

The purpose of this study is to prepare graphene/FeOCl (G/FeOCl) heterojunctions via a microwave-pyrolysis approach and probe into the synergistic lubrication of G with FeOCl in liquid paraffin (LP). The morphology and chemical composition of specimens were analysed by utilizing scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS) techniques. The tribological property of G/FeOCl was determined, and the interaction between the G/FeOCl heterojunction and friction pair was carried out through simulation calculations. The results indicated that neither G nor FeOCl significantly improved the lubrication performance of LP. However, together with FeOCl, G as lubrication additives greatly improved the lubrication performance of LP. Under the load of 1.648 GPa, the mean friction coefficient and wear scar diameter of LP containing 0.20 wt% G/FeOCl were 66.1% and 44.7% inferior to those of pure LP, respectively. Scanning electron microscopy (SEM) and elemental mapping analyses of worn scars revealed the formation of G/FeOCl layer tribofilms that prevent direct contact between metals. In addition, the high interfacial energy between graphene and FeOCl calculated based on first-principles density functional theory (DFT) further confirmed that graphene and FeOCl simultaneously form friction films with wear resistance and wear reduction effect at the friction interface, which is consistent with the experimental results. This study, therefore, provides a pathway for low-friction lubricants by deploying G/FeOCl two-dimensional material systems.

Graphene/FeOCl (G/FeOCl) heterojunctions were prepared by microwave-pyrolysis, thoroughly characterised and used to probe the synergistic lubrication of G with FeOCl in liquid paraffin. We provide a pathway for low-friction lubricants by deploying G/FeOCl 2D materials.     

Covalent polymer functionalized graphene oxide/poly(ether ether ketone) composites for fused deposition modeling: improved mechanical and tribological performance

This paper presents a novel method using poly(aryl ether ketone) containing pendant carboxyl groups to covalently functionalize graphene oxide. The functionalized graphene oxide (LFG) was used to prepare poly(ether ether ketone) (PEEK) composites through melt blending. It is found that LFG has great interface adhesion to the PEEK matrix, and just a small amount of it can simultaneously improve the strength and toughness of the composites, while unmodified graphene oxide could enhance strength but cause toughness damage. The tensile and impact strength of composite with 0.1 wt% LFG are 5.7% and 20.5% higher than that of neat PEEK, respectively. In addition, 0.5 wt% LFG composite shows great friction and wear performance with friction coefficient and specific wear rate 27.3% and 18.3% lower than that of PEEK. Furthermore, the composites can be used as practical high-performance additive manufacturing materials because LFG is able to improve the mechanical performance of the fused deposition modeling (FDM) composite samples significantly.

A polymer “bridge” was designed to connect graphene oxide and poly(ether ether ketone), making stronger and tougher composites.     

Long-term stably dispersed functionalized graphene oxide as an oil additive

In oil lubrication systems, it is essential to continuously supply lubricant to the contact surface during practical applications. Herein, to realize its long-term stable dispersion in oil, graphene oxide was modified with polyisobutylene succinimide (PIBS, trade name T154), which is an effective dispersant for lubricating oils. Characterization of the T154-modified graphene oxide (GO-T154) by FTIR, XPS, and XRD revealed that the surface of the graphene platelets was covered by the T154 chains, and the dimensions of the graphene platelets had obviously decreased. The dispersion study demonstrated the long-term stability of a GO-T154/oil suspension, which could stand for more than a year without any significant precipitation. The lubricating property was greatly improved by the addition of GO-T154; more specifically, for the optimal performance, the friction coefficient decreased by 54%, and the wear rate decreased by 60%. Micro observation of the worn surfaces indicated that well-dispersed GO-T154 could enter the gap between the friction surfaces, forming a transfer film to separate the rubbing surface. With the long-term stability, high thermal stability and outstanding tribological properties of the suspension, GO-T154 promises to realize practical applications of graphene in lubricating oil.

T154 modified graphene oxide as an oil additive exhibited excellent tribological properties, long-term stable dispersity and high thermal properties.     

Enhancing the mechanical and tribological properties of epoxy composites via incorporation of reactive bio-based epoxy functionalized graphene oxide

The high rigidity and brittleness of traditional thermosetting resin based on bisphenol epoxy limits its many potential technical applications. Here, a novel tertiary amine containing cardanol-based epoxy resin (NC-514-DEA) was synthesized by reaction of diethanolamine (DEA) with cardanol epoxy resin (NC-514). Moreover, NC-514-DEA modified graphene oxide (GOND) was prepared and used as a reactive nano-reinforcing filler for epoxy composites. The results show that, compared with neat epoxy resin, the fracture toughness of the epoxy composite with 0.5 wt% GOND is increased by nearly 10%, and the friction coefficient is reduced from 0.567 to 0.408, demonstrating the best performance among specimens. The improved mechanical and wear resistance properties of prepared composites were attribute to the synergistic effect of NC-514-DEA and GO, which inhibited the generation and propagation of cracks by enhancing the interfacial interaction and distributing stress. In addition, the synthetic process of GOND is green, simple and efficient, providing a novel way for designing epoxy composite materials with many potential applications.

Superior mechanical and tribological properties of epoxy nanocomposites were obtained by introducing novel reactive bio-based epoxy-modified graphene oxide nanomaterials.     

Preparation of ultra-high mechanical strength wear-resistant carbon fiber textiles with a PVA/PEG coating

Polyvinyl alcohol (PVA) is an organic polymer that is non-toxic, harmless to the human body, and has good biocompatibility. Polyethylene glycol (PEG) is a polymer that has good lubricity and compatibility. The unique graphite structure of carbon fibers can promote the potential application of carbon–fiber composites in tribology. This study explores the relationship between two kinds of organic polymer compounds and carbon fiber cloth (CFC), specifically a PVA/PEG composite coating that is impregnated on the CFC surface. The CFC is synthesized by chemical cross-linking, and the CFC composites (PVA/PEG/CFC) were synthesized. The tribological properties of PVA/PEG/CFC were tested under different concentrations, loads, and velocities. The effects of the different lubricants, surface morphologies, and tensile strengths on the mechanical and tribological properties of PVA/PEG/CFC were studied. In comparison to the original CFC, the friction coefficient and wear morphology of the composite material were reduced and the friction coefficient trend was stable. The addition of PVA/PEG improved the surface lubrication performance of the composite material and reduced the average friction coefficient. In addition, under the different lubrication mechanisms, oil as a lubricant can significantly reduce the friction coefficient and surface wear. In summary, the biocompatible coating process that is proposed in this study can effectively improve the tribological properties of the surface of the CFC.

Polyvinyl alcohol (PVA) is an organic polymer that is non-toxic, harmless to the human body, and has good biocompatibility. Polyethylene glycol (PEG) is a polymer that has good lubricity and compatibility. As a new coating material, PVA/PEG has good mechanical properties.     

Influence of Mn on the iron-based friction material directly prepared by in situ carbothermic reaction from vanadium-bearing titanomagnetite concentrates

In this work, we prepared an iron-based frictional material from vanadium-bearing titanomagnetite concentrates by in situ carbothermic reaction with improved tribological properties. Effects of Mn content (1–4 wt%) on the microstructure and properties of iron-based friction material were investigated. The microstructure and properties of iron-based friction material with Mn are significantly improved. In particular, the friction coefficient decreases from 0.54 to 0.40–0.49 and the wear rate reduces from 1.899 × 10⁻⁷ cm³ J⁻¹ to 0.229 × 10⁻⁷ cm³ J⁻¹ – 1.309 × 10⁻⁷ cm³ J⁻¹. Appropriate Mn addition (1–3 wt%) contributes efficiently to the sintering densification and increasing laminated pearlites. Comparatively, the density, hardness and wear resistance are improved. The dominant wear mechanism changes from severe abrasive wear to mild abrasive wear and oxidative wear is also enhanced. However, when Mn content increases to 4 wt%, the microstructure, relative density, hardness and wear performance of iron-based friction material are deteriorated. Consequently, the optimal addition of Mn is 3 wt% in the iron-based friction material.

In this work, we prepared an iron-based frictional material from vanadium-bearing titanomagnetite concentrates by in situ carbothermic reaction with improved tribological properties.     

Facile fabrication of long-chain alkyl functionalized ultrafine reduced graphene oxide nanocomposites for enhanced tribological performance

Due to their ultrathin 2D laminated structure as well as excellent mechanical and thermal stabilities, ultrafine graphene-based nanoparticles exhibit fascinating advantages as highly-efficient lubricant additives. However, it remains a daunting challenge to achieve good and durable dispersion of these graphene-based nanoparticles in lubricating oils. Herein, we report a facile and efficient integration strategy involving particle size miniaturization, surface grafting with octadecyl alcohol (OA), and partial chemical reduction to prepare a novel long-chain alkyl functionalized ultrafine reduced graphene oxide (RGO-g-OA) with highly-dispersive capacity and superior tribological performance. The chemical composition and structural characteristics, microstructural morphology, and particle size distribution of RGO-g-OA were systematically investigated. Combining significantly improved lipophilicity derived from the long-chain alkyl grafting and partial chemical reduction with the small-size effect gave rise to outstanding long-term dispersion stability (as long as one month) of RGO-g-OA in the finished oil. Moreover, the friction coefficient and wear volume of finished oil with merely 0.005 wt% RGO-g-OA greatly reduced to 0.065 and 10 316 μm³, decreased by 9.7% and 44%, respectively, compared to those of pristine finished oil, demonstrating remarkable friction reduction and anti-wear performances. Consequently, owing to the characteristics of facile fabrication, durable dispersion stability, and superior tribological performance at an extremely low content, this novel nanoadditive shows a promising application potential in the tribology field.

Long-chain alkyl functionalized ultrafine reduced graphene oxide nanocomposites with outstanding dispersibility and enhanced lubricating performances.     

Dispersion stability and tribological properties of additives introduced by ultrasonic and microwave assisted ball milling in oil

Graphene and MoS₂ were modified by organic molecules to obtain modified reduced graphene oxide (MRGO) and modified molybdenum disulfide (MMD) powders. MRGO and MMD were uniformly dispersed in base oil (PAO6) by ultrasonic and microwave assisted ball milling (UMBM). This study tested the dispersion stability and tribological properties of additives in the oil, and analyzed the elements of the friction surface. Besides, the mechanism of anti-friction and anti-wear was discussed. The results show that the UMBM method is an effective way to introduce additives in lubricating oil. Compared with direct addition, it can effectively improve the dispersion stability of additives in the oil, so that additives can be better deposited and adsorbed on the friction surface in the friction process, and improve the tribological properties of lubricating oil.

Additives were uniformly dispersed in base oil by ultrasonic and microwave assisted ball milling.     

Synergistic effect of reduced graphene oxide/carbon nanotube hybrid papers on cross-plane thermal and mechanical properties

Graphene paper has attracted great attention as a heat dissipation material due to its excellent thermal conductivity and mechanical properties. However, the thermal conductivity of graphene paper in the normal direction is relatively poor. In this work, the cross-plane thermal conductivities (K_⊥) and mechanical properties of the reduced graphene oxide/carbon nanotube papers with different CNT loadings were studied systematically. It was found that the K_⊥ decreased from 0.0393 W m⁻¹ K⁻¹ for 0 wt% paper to 0.0250 W m⁻¹ K⁻¹ for 3 wt% paper, and then increased to 0.1199 W m⁻¹ K⁻¹ for 20 wt% paper. The papers demonstrated a maximum elastic modulus of 6.1 GPa with 10 wt% CNT loading. The CNTs acted as scaffolds to restrain the graphene sheets from corrugating and to reinforce the mechanical properties of the hybrid papers. The more CNTs that filled the gaps between graphene sheets, the greater the number of channels of the transmission of phonons and the looser the structure in the cross-plane direction. Further mechanism analysis revealed the synergistic effects of CNT loadings and graphene sheets on enhancing the thermal and mechanical performance of the papers.

The top-view SEM images for (a) rGO, (b) rGO/CNT-3%, (c) rGO/CNTs-20% and the corresponding schematic diagram of photon transmission with different spacer CNTs loadings (a-i, b-ii, c-iii).     

Friction and mechanical properties of amino-treated graphene-filled epoxy composites: modification conditions and filler content

It remains a challenge for graphene to reach its full potential as a lubricant and wear-resistant material in thermosetting resin composites. In this study, the mechanical properties and friction properties of amino-treated graphene-filled epoxy composites, which were influenced by the conditions for the modification of graphene and filler content, were investigated. The mechanical properties were measured by tensile examination and the tribological properties were determined using a ball-on-disk tribometer. The results showed that the composite filled with amino-treated graphene for a short reaction time exhibited the best tribological behavior, where the friction coefficient was 57.9% lower than that of the pure resin and the wear rate was 92.2% less than that of the neat resin. Simultaneously, this amino-treated graphene also resulted in enhanced mechanical properties and T_g in the nanocomposite, implying its good crosslinking network and strong interface strength. The wear track analysis demonstrated that the excellent wear resistance was induced by its improved toughness, which restrained the crack propagation of fatigue wear and decreased the size of debris, promoting the formation of a transfer film, and thus protecting the contact surface. The tribological properties also varied with the concentration of the nanofiller, which showed the best performance at 0.2 wt%. Through the optimization of the modification conditions and concentration, this work highlights a promising strategy for the application of graphene-related materials in the field of tribology.

The enhancement in resistance to the propagation of cracks in epoxy composites by adding GO-0.5 results in excellent wear resistance.     

Mechanical and tribological performance of a hybrid MMC coating deposited on Al–17Si piston alloy by laser composite surfacing technique

Laser composite surfacing (LCS) is a photon driven manufacturing technology that can be utilized for depositing hybrid metal matrix composite coatings (HMMC) on softer Ti/Al/Mg alloys to enhance their tribo-mechanical properties. LCS offers the advantages of higher directionality, localized microstructural refinement and higher metallurgical bonding between coating and substrate. The current research presents the tribo-mechanical evaluation and characterization of solid lubricant based Ni–WC coatings deposited by LCS on Al–Si piston alloy by varying the concentration of graphite between 5-to-15-weight percentage. The tribological behavior of LCS samples was investigated using a ball-on-plate tribometer. Results indicate that the surface hardness, wear rate and friction coefficient of the Al–Si hypereutectic piston alloy were improved after LCS of graphite based HMMC coatings. The maximum surface hardness of 781H_v was acquired for the Ni–WC coating containing 5 wt% graphite. The friction coefficient of Al–Si under dry sliding conditions was reduced from 0.47 to 0.21. The reduction in the friction coefficient was attributed to the formation of a shearable transfer layer, which prevented delamination and reduced adhesion, abrasion and fatigue cracking.

The addition of graphite as solid lubricant has significantly reduced the friction coefficient and wear of a Ni–WC composite coating.     

A study on the tribological property of MoS2/Ti–MoS2/Si multilayer nanocomposite coating deposited by magnetron sputtering

Pure MoS₂ coatings are easily affected by oxygen and water vapor to form MoO₃ and H₂SO₄ which cause a higher friction coefficient and shorter service life. In this work, five kinds of MoS₂/Ti–MoS₂/Si multilayer nanocomposite coatings have been deposited by using unbalanced magnetron sputtering with different modulation period ratios. The tribological tests and nano-indentation experiments have been carried out in order to study the tribological and mechanical properties of the multilayer nanocomposite coating. The results show that the hardness and internal stress of the multilayer nanocomposite coatings are superior to those of the pure MoS₂ coating. The polycrystalline columnar structures are effectively inhibited and the coating densification increases due to the multilayer nanostructure and the doped elements of Ti and Si. The nanocomposite coating with a modulation period ratio of 100 : 100 shows the lowest friction coefficient and wear rate. The multilayer nanocomposite coatings exhibit excellent tribological property under a heavy constant load. Interfaces in multilayer nanostructure coating is able to hinder the dislocations motion and the crack propagation. The doped elements of Ti and Si with nano-multilayer structure enhances the mechanical and tribological properties of MoS₂ coating. This study provides guidelines for optimizing the mechanical and tribological properties of MoS₂ coating.

Pure MoS₂ coatings are easily affected by oxygen and water vapor to form MoO₃ and H₂SO₄ which cause a higher friction coefficient and shorter service life.     

Interfacial modification of basalt fiber filling composites with graphene oxide and polydopamine for enhanced mechanical and tribological properties

Due to the chemical inertness of the basalt fiber (BF) surface, the weaker interfacial bonding between BF and polymer matrices will seriously affect the further application of basalt fiber enhanced composites. In this study, a continuous and compact graphene oxide (GO) layer was grafted onto the surface of basalt fiber (BF) using biomimetic polydopamine (PDA) as a bridge to improve the mechanical and tribological properties of polyamide 6. The impact and flexural strength of the PA6 composites filled by the GO grafting BF (GO–PDA–BF/PA6) indicated that the introduction of GO has made a larger improvement in interface bonding performance between BF and PA6 matrix. The friction and wear tests showed the wear rate of the GO–PDA–BF/PA6 composite decreased by 51% compared with BF/PA6 composites and it also showed the best wear resistance and load-carrying capacity under various applied loads and sliding speeds, explained by the improved interface bonding between GO–PDA–BF and PA6 matrix and the anti-wear protective transfer film formed by GO in the worn surface. This study provided a considerable flexibility strategy of tailoring the interfacial compatibility between reinforcement and matrix for effectively improving the comprehensive performance of composites.

Graphene oxide was grafted onto the surface of basalt fiber via polydopamine to enhance the interfacial adhesion of PA6 composites.     

Tribo-induced photoluminescent behavior of graphene and YSZ:Er/graphene composite films

In the present work, a novel method was developed to study the evolving surface state of graphene film as it is subject to friction, characterized by photoluminescence properties. We prepared the graphene film (GF) and YSZ:Er (Er³⁺-Y³⁺ co-doped ZrO₂)/graphene composite films (ZGCF). The Raman spectra and photoluminescence properties of the GF and ZGCF were characterized before and after the sliding friction. A remarkable phenomenon was observed that after friction the GF generated a more pronounced luminescence response than it had prior, apparently due to graphene quantum dots which were found in the wear debris of the GF. Furthermore, the introduction of graphene into YSZ:Er nanoparticles (NPs) resulted in an unmistakable red-shift on the main luminescence bands of ZGCF after the applied friction. This is explained by the formation of considerable graphene scrolls in the wear debris of ZGCF due to the interaction of the graphene and the YSZ:Er NPs. It can be concluded that changes to the configuration of graphene greatly influence the tribo-induced photoluminescence response. Our findings justify further investigation into the composition and morphology of worn surfaces in order to better understand how photoluminescence relates to frictional effects. In addition, this work proposes the in situ fabrication of graphene quantum dots and nanoscale scrolls as a new potential application of the tribo-induced photoluminescence study.

In the present work, a novel method was developed to study the evolving surface state of graphene film as it is subject to friction, characterized by photoluminescence properties.