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The preparation of high-efficiency, stable, and low-cost graphene coating on the stainless steel substrate was highly anticipated but remained a challenge. Here, the graphene-CrC nanocomposite coatings were prepared on the 304 stainless steel ball (SS) by using the simple mechanical ball milling, which is in a gradient structure of graphene-CrC towards outside (G/SS). Notably, the graphene coatings could be strongly bonded on the SS surface by C-Cr bonding, which could provide excellent durability. Corrosion analysis revealed that graphene-CrC coatings would remarkably enhance the anticorrosion property of SS at the range of 293–328 K. The corrosion rates of the G/SS were merely 0.0336 × 10−4 mm day−1, which was significantly slower than that of the SS (1.58 × 10−4 mm day−1) at the room temperature. The double-layered coating could slow down the wear rate from 14.1 × 10−6 mm3 N−1 m−1 to 4.82 × 10−6 mm3 N−1 m−1. The present work could light on a straightforward strategy for the development of graphene coatings on metal substrate.

The preparation of low-cost, high-efficiency and stable oxygen reduction reaction (ORR) catalysts is highly anticipated but remains a challenge. Herein, a novel strategy of CaCl2 solution inducing gelatin crosslinking and acting as aligned pore template was put forward for preparation of Fe-N doped aligned hierarchical porous carbon. Furthermore, the microtopography and length of aligned pore can be controlled by adding NaCl solution. The prepared catalyst exhibited short-range aligned honeycomb hierarchical porous structure with large specific surface area and highly homogeneous distribution of Fe-Nx active sites (Fe-NHHPC-900). Notably, in addition to excellent durability in the alkaline electrolyte, Fe-NHHPC-900 possessed excellent ORR performance with positive half-wave potential of 0.86 V, superior to commercial Pt/C catalysts. As electrode materials of supercapacitors, Fe-NHHPC-900 also displayed a high specific capacitance, excellent rate performance and excellent stability. This work also proved that the unique aligned porous structure can effectively optimize catalyst activity and improve supercapacitor performance.

A simple route was developed to prepare graphene coating on mild steel balls (MS) by mechanical ball-milling. In order to facilitate the interface reaction, we introduce the Cr layer onto the MS surface (Cr/MS) through vacuum deposition. The graphene coatings were prepared by ball-milling on a buffer Cr/MS double-layered structure. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) results indicated the graphene coatings were strongly bonded to the substrate with the help of Cr23C6. Raman mapping and STEM results showed that the graphene coating was continuous and homogeneous. The corrosion rate of graphene covered MS was only 0.016 mm year−1, which was much less than that of MS (1.02 mm year−1). The graphene coating can significantly improve the wear resistance, the coefficient of friction decreased from 0.225 to 0.18. The present study shed light on a promising strategy for the development of graphene coatings on MS.

A simple method similar to frying was used to pyrolysis of renewable biomass carbon milk powder in NaCl/Na2CO3 molten salt at 700 °C under the air atmosphere to prepare nitrogen-doped hierarchical porous carbon. This preparation method displayed a simple preparation process with the low requirements for equipment and low-cost raw materials. The prepared optimal nitrogen-doped porous carbon material exhibited a hierarchical porous with macropores, mesopores, and micropores and had a high specific surface area of 1095 m2 g−1. As supercapacitors electrodes, The prepared optimal sample displayed a high specific capacitance of 391.5 F g−1 at 0.5 A g−1 and an excellent rate performance. It also exhibited excellent cycle stability (only loss of 4.4% capacitance) at 4 A g−1 over 5000 cycles. Moreover, In a symmetrical two-electrode system of 1 M Na2SO4, the assembled supercapacitor displayed a high energy density of 33.0 Wh kg−1 at 0.25 A g−1, maintained a high energy density of 22.3 Wh kg−1 at 20 A g−1 and exhibited excellent stability at 5 A g−1 over 5000 cycles. The assembled symmetrical PVA/Na2SO4 solid supercapacitor can successfully light up the light emitting diode (LED). This work provided a sample and low consumption way to prepare N doped hierarchical porous carbon electrode material for high performance supercapacitors.

Corrosion protection of metals is an active research area due to its importance for commercial applications. However, conventional coating exhibits limited durability, thermal stability and conductivity and is thus not suitable. Although graphene has shown the potential for corrosion protection, it is difficult to directly grow high-quality graphene on commercial steels. Herein, a simple ball-milling method is used to prepare graphene coating on stainless steel balls (SS) for corrosion protection, in which the SS are uniformly encapsulated with graphene coatings by in situ mechanical peeling of graphite crystals. The graphene coating is strongly bonded to the SS via Cr C bonding, which provides a base for long-lasting corrosion protection. Corrosion analysis reveals that the corrosion rate of the graphene covered SS was reduced up to twenty times lower than that of the bare SS. Furthermore, in situ exfoliated graphene coating can significantly improve the wear resistance, which the wear rate decreased from 6.45 × 10 −13 to 4.31 × 10 −13 m 2 N −1 . The present study can also provide a straightforward approach towards preparing graphene coatings on metal substrate.

A simple route was developed to prepare graphene coating on mild steel (MS) balls by mechanical ball-milling. In order to facilitate the interface reaction, we introduced Ti layer onto the MS surface (Ti/MS) through vacuum deposition. The graphene coatings were prepared by ball-milling on a buffer Ti/MS double-layered structure, and were strongly bonded to the substrate via TiC. The corrosion rate of graphene-covered MS was only 8.2 nm day−1, which was much less than that of the bare MS (794.5 nm day−1). The corrosion resistance was up to 38676 Ω cm2, which was almost two orders of magnitude higher than that of the bare MS (369 Ω cm2). Moreover, the graphene coating demonstrated stable and long-term anticorrosive performance after 30 days immersion. The present study lights on expanding the applications of graphene coatings to a wider range.

At present, the application of doped graphene have been widely studied in supercapacitor, but the preparation of co-doped graphene electrode materials for high rate performance supercapacitor is still a challenge. In this work, we reported an effective method to prepare S/N co-doped graphene (SNG-H) through a self-generated high gas pressure by heating graphene with (NH4)2SO4 and melamine in a sealed vacuum copper tube under 600 °C. During heating treatment, the self-generated high gas pressure was formed by pyrolysis of the precursors in a sealed space. The X-ray photoelectron spectroscopy result showed that N and S atomic percentage of SNG-H were 6.22 at% and 2.82 at% which higher than that doped method using inert gas. This result indicated that the self-generated high gas pressure by pyrolysis of the precursors in a sealed space promoted the incorporation of heteroatoms into the lattice of graphene. Meanwhile, this method avoided the resources consumption of using inert gas (N2 and Ar) and effectively reduced gas pollution emissions. As the supercapacitor electrode material, the specific capacitance of SNG-H electrode material reached 264.3 F g−1 at 0.5 A g−1 and showed excellent rate capability at 200 mV s−1 in a three-electrode system. SNG-H also exhibited high capacitance performance, excellent rate capability (82% capacitance retention from 1 to 20 A g−1) and excellent cycling stability (95%) after 5000 cycles at 5 A g−1 in a symmetric two-electrode system. SNG-H was prepared through a self-generated high gas pressure in a sealed vacuum copper tube under 600 °C. This method improved the content of doped heteroatoms in SNG-H and enhanced the supercapacitor rate performance of SNG-H as an electrode material.

Three dimensional graphene/phenolic resin (3DGP) composites were synthesized via in-situ polymerization in graphene hydrogels (GHs). The water in the GH was perfectly replaced with resole resin due to the infiltration of resole resin into the GH and the evaporation of water from the GH by heating in the appropriate temperature. The 3DGP composite was obtained successfully by in-situ polymerization. The prepared composite can retain the complete 3D network structure to achieve good dispersion of graphene sheets forming 3D conducting network in polymer. The mechanical and electrical properties were measured, and the results showed that the composite possessed good electrical conductivity and compressive property. The compressive strength of 3DGP composite (441.11 MPa) increased by 14.24% compared with that of pure phenolic resin. In addition, the electrical conductivity of 3DGP composite reached 2.73 S/cm with a graphene loading of 2.15 wt% due to the 3D interconnected structure.

Homogeneous Ti/Al 2 O 3 composites with different volume percentages of Ta 2 O 5 addition were prepared at different temperatures via hot pressing sintering. Laminated Ti/Al 2 O 3 composites with different volume percentages of Ta 2 O 5 added were prepared. The effects of Ta 2 O 5 on the composition, microstructure, mechanical properties and elements diffusion of the composites were characterized and investigated. Ta 2 O 5 inhibited the production of TiAl and Ti 3 Al by forming solid solution with Ti or new reaction product of Al. This solid solution melted and filled the void of Al 2 O 3 phase to increase the density of Ti/Al 2 O 3 composites at high temperature. Mechanical properties had also been improved by this phenomenon. Because Al element couldn’t diffuse in Ta or react with it, Al couldn’t diffuse through the Ta-enriched area at the interface of Ti and Al 2 O 3 .

A novel core@shell structured nanocomposite particles with carbon as soft shell and nanoAl2O3 as hard core were prepared by electrostatic self-assembly, and the subsequent hydrothermal and high temperature treatment. By adjusting concentration of nanoAl2O3, the average size of the composite particles vary from 750 nm to 150 nm, the corresponding to the thickness of the carbon shell in the range of 355–55 nm. On the basic of the TEM and Raman results, the shell materials were composed of the amorphous carbon. As confirmed by XPS, the Al2O3 @C composite particles had a stable structure, owing to the formation of the interfacial bonding between carbon shell and nanoAl2O3 after the carbonization process. Moreover, the nanoAl2O3 @carbon composite abrasive could lead to a decrease in the surface damage and roughness of the sapphire wafer compared with the nanoalumina abrasive, owing to the elastic effect coming from the amorphous carbon shell.

Graphene has been successfully fabricated by a novel method, using graphite powder and NMP (N-Methyl Pyrrolidone) as the raw materials based on the principles of liquidoid exfoliation and mechanical milling. SEM, TEM and Raman spectrum were utilized to characterize the morphology of the homemade graphene, illustrating the few defects and rare layers were endowed in this study. Afterwards, the homemade and commercial graphene were doped into Al 2 O 3 powder with the mass ratio of 0%, 1%, 2%, and 3% to reinforce the mechanical properties of the matrix. The composites were processed at 1600 °C, pressure of 30 MPa and soaking time of 1 h by vacuum hot pressing. The test results illustrated the bending strength and fracture toughness tended to be intensive at first and subdued afterwards, achieving the optimal performance of 625.4±18.2 MPa and 6.07±0.22 MPa m 1/2 at 2 wt% prepared graphene additive, and the commercial grapheme owned the best heighten effect in 3 wt% graphene/Al 2 O 3 composites. Compared to the blank Al 2 O 3 sintered samples, the graphene/Al 2 O 3 specimens (both prepared and commercial additive) behaved evident increase in mechanical properties, even upon 30% enhanced in fracture toughness and bending strength generally by the prepared grapheme. Moreover, the prepared graphene had better improvement effect than commercial graphene in enhancing mechanical properties of Al 2 O 3 ceramic.

Ti/Al 2 O 3 composites with different volume percentages of Pr 6 O 11 added (0–12.0 vol.%) were prepared by pressureless sintering at 1600 °C for 1.5 h. The influences of Pr 6 O 11 on the composition, microstructure and mechanical properties of the composites were characterized and investigated. The results showed that Pr 6 O 11 could promote the sintering of the composites by generating some new interfacial reaction products, such as AlTiO 2 , Pr 2 Ti 2 O 7 and PrAlO 3 . Pr 6 O 11 could also inhibit the production of TiAl and Ti 3 Al by the same mechanism. Additionally, Pr 6 O 11 changed hexagonal alumina to tetragonal alumina. The latter could improve the mechanical properties of the composites by the effects of crack deflection and particle pullout when it was present in proper amounts. Composites showed satisfactory comprehensive properties when the content of Pr 6 O 11 was no more than 3.0 vol.%.

Highly active and stable of carbon supported nickel molybdenum alloy and molybdenum carbide hybrid electrocatalyst (NiMo-Mo 2 C/C) has been developed for hydrogen evolution reaction (HER) in an acidic solution. The NiMo-Mo 2 C/C electrocatalyst was synthesized by a two-step microwave-assisted deposition/carbonthermal reduction method. Compared with commercial Mo 2 C, it is found that NiMo-Mo 2 C/C showed much better electrocatalytic activity for HER with a small onset overpotential of 90 mV (j = 1 mA cm −2 ) and Tafel slope of 73 mV dec −1 as well as good stability in acidic solution. Such enhanced catalytic activities may originate from its anchored structure and electrochemical performance of NiMo and Mo 2 C.

Ti/Al2O3 composites with Pr6O11 addition varied from 0 vol% to 2.5 vol% were prepared by vacuum hot pressing sintering at 1420 °C under the pressure of 30 MPa for 1.5 h. The microstructure and the mechanical properties of the as-sintered Ti/Al2O3 composites were investigated. The results showed that there were some new phases, determined as AlTiO2, Pr2Ti2O7 and PrAlO3, instead of intermetallic compounds at the interface and grain boundary of Ti and Al2O3. And when the addition of Pr6O11 reached 2.0 vol%, satisfactory mechanical properties of the composite were achieved. The enhancement mechanism of mechanical properties could be contributed to the elimination of intermetallic compounds and the “pinning effect” caused by the small pinning particles, confirmed as Pr2Ti2O7, generated at the grain boundaries. For these reasons, the grain boundaries cohesion of Ti phase and Al2O3 phase were strengthened. When fracture behavior occurred, the fracture mode of Ti/Al2O3 composites with Pr6O11 additions was both intergranular fracture and transgranular fracture.

A novel in situ templates etching method is used to prepare three-dimensional (3D) interconnected Fe-N doped hierarchical porous carbon materials. Citric acid serves as a carbon source and etchant. Fe2O3 nanoparticles not only provide the iron source by in situ etching but also act as templates to construct the hierarchical porous structure. The prepared optimal sample displays a high specific surface area of 1643.6 m2 g−1 with an interconnected abundant hierarchical porous structure and homogeneous distribution of Fe and N elements in the carbon. The optimized sample displays excellent catalytic oxygen reduction reaction (ORR) performance with a positive half-wave potential (0.85 V), efficient four-electron reaction and excellent durability, which are superior to those of Pt/C (20 wt%) catalyst. Meanwhile, due to the unique interconnected hierarchical porous structure, it also exhibits a high specific capacitance of 378.6 F g−1 at 0.5 A g−1 and an excellent rate capability of 276.6 F g−1 at 20 A g−1 as supercapacitors electrode materials in 6 M KOH. This work provides a simple design for the preparation of 3 D interconnected Fe-N doped hierarchical porous carbon electrode materials that display potential applications in ORR catalysts and supercapacitors.

Chemometric tools equipped with a Plackett-Burman (P-B) design, a central composite design (CCD) and a desirability profile were employed to optimise the QuEChERS (quick, easy, cheap, effective, rugged and safe) method for the quantification of thiacloprid, spirotetramat and spirotetramat's four metabolites in pepper. The average recoveries were in the range of 71.6-119.5%, with relative standard deviations ⩽ 12.1%. The limit of quantification for the method was less than 0.01 mg/kg. The method was applied to field samples to evaluate the residual characteristics of thiacloprid and spirotetramat. The data showed that the first+first-order model is a better fit than the first order model for the dissipation of thiacloprid and spirotetramat in pepper. The half-lives of thiacloprid and spirotetramat in pepper are 0.81 and 1.21 days, respectively. The final residues were between 0.016 mg/kg and 0.13 mg/kg for thiacloprid and 0.08 mg/kg and 0.12 mg/kg for spirotetramat.