Qiaoxin Zhang

Bioinspired multifunctional hetero-hierarchical micro/nanostructure tetragonal array with self-cleaning, anticorrosion, and concentrators for the SERS detection.

Heterohierarchical micro/nanostructure tetragonal array consisted of engineering materials of microprotrusion-like Cu and secondary nanostructured dendrite Ag have been fabricated via a primary cell-induced deposition and a facile galvanic displacement reaction combined with photolithography technique on Cu foil. Confined by the circle microwell tetragonal array of the photoresist template, regular microprotrusion-like Cu with the tunable size of diameter can be easily deposited on the surface of Cu foil. Then, the secondary dendritic Ag nanostructures in situ grow on the surface of microprotrusion via a galvanic displacement reaction, leading to the formation of heterohierarchical micro/nanostructure tetragonal array, which is similar to the surface microstructure of the lotus leaf. Inspired by this novel surface structure of imitating lotus leaf, its wettability has been systematically investigated. The results indicate that the fabricated heterohierarchical micro/nanostructure regular array after the surface fluoration presents a remarkable superhydrophobic performance. Initiated from its superhydrophobicity, an excellent self-cleaning property has also been demonstrated. In addition, the durability of the superhydrophobic surfaces is examined in the wide pH range of corrosive liquids. Notably, the fabricated superhydrophobic surface can be potentially used as concentrators, which presents a great perspective in the field of analysis through employing the SERS detection as an example.

Sliding Speed and Load Dependence of Tribological Properties of Ti3SiC2/TiAl Composite

The tribological properties of Ti3SiC2/TiAl composite (TTC) slid against a GCr15 steel counterface were investigated at sliding speeds in the range of 0.2–0.8 ms−1 and loads that ranged from 2 to 8 N. The results showed that the tribological properties of TTC strongly depended on the covering percentage of tribofilm on the TTC worn surface, which varied with changes in sliding speed and load. The tribofilm mainly consisted of Al-Ti-Si oxides, which provided a self-antifriction action that resulted in a reduction in the friction coefficient and an increase in the wear rate.

Tribological behavior of TiAl matrix self-lubricating composites reinforced by multilayer graphene

The tribological performance of multilayer graphene-reinforced TiAl matrix self-lubricating composites (GTMSC) is significantly influenced by elastic and plastic deformation during sliding wear. The primary purpose of this study is to investigate the dry tribological behaviors of GTMSC at different applied loads. The sliding tribology tests are carried out at 4, 8, 12 and 16 N, respectively. The friction coefficients and wear rates are analyzed under the condition of elastic or plastic deformation. The elastic or plastic deformation is determined by comparing the yield stress with the von Mises stress obtained by the numerical simulation method. The results show that GTMSC exhibits different tribological behaviors under the condition of elastic or plastic deformation. It is found that GTMSC shows excellent tribological performances at 12 N for the elastic deformation, resulting in the formation of anti-friction films. Nevertheless, GTMSC exhibits poor tribological behaviors at 16 N due to the plastic deformation, leading to the destruction of anti-friction films and the formation of cracks.

Effect of graphene nanoplate addition on the tribological performance of Ni3Al matrix composites

The main objective of this work has been the characterization of wear behavior of the graphene nanoplates (GNPs) in Ni3Al matrix composites (NMC). The friction and wear behaviors of NMC with the addition of 1 wt.% GNPs against Si3N4 ball are tested under different loads using a constant speed of 0.2 m/s. Tribological test results have revealed that small amounts of GNPs are able to drastically improve the antifriction and antiwear properties of NMC. A possible explanation for these results is that, the GNPs not only provide an enhanced effect for NMC to produce better wear resistance, but also form a local protective layer on the contact surfaces to reduce the friction. The investigation shows that GNPs hold great potential applications as an effective solid lubricant for Ni3Al matrix composites and possibly other alloys.

Tribological Behavior of NiAl–1.5 wt% Graphene Composite Under Different Velocities

The progress in aerospace field requires a new NiAl matrix composite that can stand against wear and decrease the energy dissipation through decreasing friction. In this study, the tribological behavior of NiAl–1.5 wt% graphene composite is investigated at room temperature under a constant load of 12 N and different sliding velocities. The results show that the friction coefficient and wear rate increase with increasing sliding velocity from 0.2 to 0.4 m/s due to the adhesion between the sliding bodies and tearing of the graphene layer. The friction coefficient and wear rate tend to decrease at a sliding velocity of 0.6 m/s as a result of severe plastic deformation and grain refinement of the worn surface. However, at 0.8 m/s the friction coefficient reaches a minimum value and the wear rate increases and changes the wear mechanism to fatigue wear. It can be concluded that various wear mechanisms lead to different tribological performance of NiAl–1.5 wt% graphene composite.

Tribological properties of TiAl matrix self-lubricating composites incorporated with tungsten disulfide and zinc oxide

To better understand the temperature-adjusted action of tungsten disulfide (WS2) and zinc oxide (ZnO) in self-lubricating composites, dry sliding tribological properties of TiAl matrix self-lubricating composites (TMSC) containing WS2, ZnO and WS2–ZnO against Si3N4 counterface are comparatively investigated from 25 to 800 °C. Tribological results suggest that TMSC containing WS2–ZnO exhibit the lowest friction coefficients and wear rates than TMSC containing only WS2 or ZnO over the wide temperature range, confirming the self-adjusted action of WS2–ZnO as the temperature changes. Specifically, WS2 is beneficial to the improvements of tribological properties within 200 °C, WS2 and ZnWO4 for 400 °C, ZnWO4 and ZnO for 600 °C and ZnO for 800 °C.

Wear and Friction of TiAl Matrix Self-Lubricating Composites against Si3N4 in Air at Room and Elevated Temperatures

More durable, low-friction bearing materials over a wide temperature range are needed for turbine components and other high-temperature bearing applications. The current study reported the tribological properties of TiAl matrix self-lubricating composites (TMC) containing MoS2 (a low-temperature lubricant, below 500°C), hBN (a medium-temperature lubricant, below 600°C), and Ti3SiC2 (a high-temperature lubricant, above 600°C) designated as MhT against an Si3N4 counterface at temperatures ranging from 25 to 800°C in air. The load was 10 N and the sliding speed was 0.2 m/s for all tests. Tribological studies indicated that TMC containing MhT showed a lower friction coefficient and wear rate in comparison to TiAl-based alloy at all test temperatures, which was attributed to the excellent synergetic lubricating effect of MoS2, hBN, and Ti3SiC2. TMC containing 5 wt% MhT exhibited the best tribological properties over a wide temperature range.

Formation of Friction Layers in Graphene-Reinforced TiAl Matrix Self-Lubricating Composites

The friction layer structure has been proved to be formed during severe plastic deformation and markedly improves the tribological properties of material. The dry friction and wear performance of graphene-reinforced TiAl matrix self-lubricating composites (GTMSC) at different sliding velocities are systematically researched. GTMSC show the best tribological properties and special friction layer structure containing a wear-induced layer and a grain refinement layer with a nanocrystalline (NC) structure under surface after sliding at a sliding speed of 1.1 m/s. Nanoindentation results show that the grain refinement layer has a higher hardness and elastic modulus than the wear-induced layer. This special microstructure of friction layers beneath the surface after sliding leads to a low coefficient of friction and high wear resistance of GTMSC. Moreover, it is deduced that the appearance of an NC structure results in hardening of the material. The formation mechanisms of friction layers are researched in detail. It can be concluded that the formation of a wear-induced layer results from frictional heat and fracture of the counterpart. The formation of a grain refinement layer is due to severe plastic deformation and dynamic recrystallization. Severe plastic deformation results in the formation of an NC structure and dynamic recrystallization leads to grain refinement.

Low-cost and large-scale fabrication of a superhydrophobic 5052 aluminum alloy surface with enhanced corrosion resistance

Superhydrophobic 5052 aluminum alloy substrates with excellent corrosion resistance have been fabricated by a simple and low-cost method of acid treatment and modification of fluoroalkyl-silane combined with surface passivation. Via an etching process with hydrochloric acid, hierarchical convex–concave micro/nano-structures have been formed on 5052 aluminum alloy surfaces. Then they were covered with a flocculent layer after passivation with potassium permanganate. The wettability and corrosion resistance of the as-prepared substrates have been systematically investigated. The results indicate that aluminum alloy substrates with an etching time of 5 min and passivation time of 180 min exhibit good superhydrophobicity with a water contact angle of 153 ± 0.7°. In addition, corrosion resistance was also explored by potentiodynamic polarization curves and electrochemical impedance spectroscopy. Clearly, the corrosion resistance of the as-prepared aluminum alloy substrates has been greatly enhanced, which will be positive to extend further the applications of Al alloys in engineering fields, such as shipbuilding and oceanographic engineering.

Friction and Wear Properties of TiAl-Ti3SiC2-MoS2 Composites Prepared by Spark Plasma Sintering

TiAl matrix self-lubricating composites (TMC) with various weight percentages of Ti3SiC2 and MoS2 lubricants were prepared by spark plasma sintering (SPS). The dry sliding tribological behaviors of TMC against an Si3N4 ceramic ball at room temperature were investigated through the determination of friction coefficients and wear rates and the analysis of the morphologies and compositions of wear debris, worn surfaces of TMC, and the Si3N4 ceramic ball. The results indicated that TMC with 10 wt% (Ti3SiC2-MoS2) lubricants had good tribological properties due to the unique stratification subsurface microstructure of the worn surface. The friction coefficient was about 0.57, and the wear rate was 4.22 × 10−4 mm3 (Nm)−1. The main wear mechanisms of TMC with 10 wt% (Ti3SiC2-MoS2) lubricants were abrasive wear, oxidation wear, and delamination of the friction layer. However, the main wear mechanisms of TMC without Ti3SiC2 and MoS2 lubricants were abrasive wear and oxidation wear. The continuous friction layer was not formed on the worn surfaces. The self-lubricating friction layer on the frictional surface, different phase compositions and hardness, as well as density of TMC contributed to the change in the friction coefficient and wear rate.