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Abstract During the fabrication of functional high-endothermic-enthalpy graphite/SiO 2 composite coating, the oxidation and vaporization of raw materials have become serious issues in hyperthermal preparation environment. In this study, these issues were addressed through densification and modification of the feedstock powder. Then, the corresponding coating was prepared by optimized plasma-spraying parameters. By investigating the modified feedstock powder and the resulting splats and coatings by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy, we realized an optimized composite feedstock powder preparation process and an ideal coating structure. The compactness of the powder reached its optimum after treating at 1400 °C for 2 h. After heat treatment densification and Ni shell covering processes, the modified powder exhibited good oxidation resistance, vaporization resistance, and spreading performance during plasma spraying. Thus, a pure and dense composite coating was prepared. Positive laser resistance performance was observed during the initial laser ablation test, which proved that this modified graphite/SiO 2 coating has good application potential in the laser protection field. Moreover, this study provides an experimental basis and a feasible method for difficult-to-spray composite coatings' preparation, such as graphite/SiO 2 composite. [ABSTRACT FROM AUTHOR]

Graphite and SiO 2 composite was prepared by hot-pressing at 1300 °C for 3 h under a uniaxial load of 20 MPa. The ablation behavior of graphite and SiO 2 composite by high-intensity continuous laser was investigated. The X-ray diffraction, scanning electron microscopy, 3D-super-depth-digital microscopy, Raman spectroscopy and reflectivity were used to characterize the sample. The results show that under low laser power (500 W/cm 2 ), and no obvious damage appears, while just the irradiation area changes from grey to white and the reflectivity increases. With the laser power increasing, some heat-absorbing chemical reactions between graphite and SiO 2 occurred on the surface, and SiC was produced, which can increase the energy consumption of the surface and thus reduce the absorbed laser energy of the interior. Moreover, at the center of irradiation area, the formation of columnar structure graphite is beneficial to obstruct laser energy conduction from surface to interior material. [ABSTRACT FROM AUTHOR]

• The Cu matrix composites were prepared by traditional flake powder metallurgy method. • Different fillers GF/rGO/Gr were used for making different composites. • The mechanical and thermal properties are increased significantly. • rGO works better than compared to other two fillers. Nowadays copper matrix composites are of keen interest due to their increasing demand in thermal packaging systems and the electronic industry. In this study, Cu matrix composites are fabricated by using different fillers (graphite, reduced graphene oxide and graphene) by adopting the simple flake powder metallurgy method. SEM and XRD were done to study the microstructure analysis and diffraction pattern of powders and composites. Hardness and thermal conductivity of different Cu matrix composites were measured to see the effect of different fillers. It is found that the reduced graphene oxide gave better results compared to graphite and graphene when used as filler with Cu matrix. The Cu-rGO composites have excellent hardness and thermal conductivity values compared with Cu-GF and Cu-Gr composites as well as from pure Cu. [ABSTRACT FROM AUTHOR]

Abstract Graphene and its derivatives have a high value of thermal conductivity and good mechanical properties. Rare studies focused on the anisotropic thermal conductivity, while anisotropic thermal conductivity and hardness of reduced graphene oxide/metal are still far behind the expected values. In this work, different mesh sizes of graphite and graphene oxide were used for making copper-graphite and copper-reduced graphene oxide composites with the powder metallurgy technique. Raman, XRD, XPS and SEM were performed to evaluate the disorder, phase analysis, surface morphology and microstructure evolution of the composites as well as synthesized graphene oxide. Anisotropic thermal conductivity and Vickers hardness of the composites were characterized to check the effects of different mesh size on copper-graphite and copper-reduced graphene oxide composite. Results show that anisotropic thermal conductivity in-plane and through-plane ratio (1.68) and hardness (71.2 HV) which is 80% and 61% greater than pure copper were attained at only 1 wt% graphene oxide mesh size 3500 μm copper-reduced graphene oxide composite. Moreover, graphite and graphene oxide mesh size (3500 μm) gave good results compared with mesh sizes 500 μm and 1000 μm. The good anisotropic thermal conductivity and high hardness suggest that it may be ideal materials as heat sinks in thermal packaging. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract Composite coatings consisting of flake graphite and SiO 2 fillers in a hyperbranched polycarbosilane (HBPCS) matrix were designed and prepared to meet the requirements of laser protection. The laser ablation behavior of the composite coatings were investigated. Control experiments were designed to study the performance of SiO 2 during laser irradiation. The results show that the introduction of SiO 2 changes the anti-laser protective mechanism and can improve the anti-laser property of the coating. High power laser irradiation results in pyrolysis of HBPCS and the formation of SiC particles. Chemical reactions between SiO 2 , graphite, and SiC play an important role in consuming energy, and provide an excellent cooling effect to the substrate, leading to decreased temperature. SiC particles formed on the surface of the laser ablation area act as a shield to prevent the laser from irradiating deeper layers of the coating. Due to the cooling effect and thermal stability of SiC, the proposed coating shows a good anti-laser property. [ABSTRACT FROM AUTHOR]

In this paper, copper-graphite composites were prepared through powder metallurgy technique (hot press sintering) in order to figure out the impact of graphite by varying concentrations and mesh sizes. SEM and XRD were performed to analyze the microstructure and phase analysis. Hardness and thermal conductivity of the composites were measured to check the effect of graphite concentrations and varying mesh size on copper-graphite composites. At low concentration 3 wt% graphite, the hardness values were significantly increased and excellent result was obtained at 3500 μm mesh size (65 HV), while for copper the value was 40 H V. The best thermal conductivity horizontal to vertical ratio difference (2.71) was obtained at 5 wt% 3500 μm mesh size much higher than pure copper (0.93). • Cu-GF composites were successfully fabricated through powder metallurgy route. • Effect of mesh sizes and different concentration of GF is observed on Cu-GF composites. • The hardness of Cu-GF composites improve with the addition of GF. • The anisotropic TC ratio also improves with the addition of GF. [ABSTRACT FROM AUTHOR]

In this study, the effect of novel metal tantalum was investigated on the properties of copper-graphite composites. The complete mechanical behavior of copper-tantalum-graphite hybrid composites was examined. The addition of tantalum increased the compressive, tensile and bending strength of composites as well as the hardness and thermal conductivity. The compression, tensile, bending and hardness values for Cu–Ta-GF (0.5) composites are 20.7%, 138%, 69% and 93% higher than pure Cu and these are also far better than Cu-GF composites. The excellent mechanical and thermal properties with good relation of strength-ductility ratio open up a new window to use these materials as heat sinks in thermal packaging system. • The Cu-GF-Ta hybrid composites were fabricated successfully. • Effect of Tantalum metal was checked on Cu-GF composites. • Remarkable mechanical properties were noticed with the addition of Ta alloying element. • The interface bonding was almost improved significantly. [ABSTRACT FROM AUTHOR]