The Study of Enhanced Mechanical Properties for Cu/Gr/2024Al Composite

2024Al alloy powder as matrix material with nanocopper-modified graphene as reinforcement was studied to explore the effects of graphene on the tissue, hardness, friction performance of the composite. The Cu/Gr/2024Al composites were prepared via three-dimensional mixed powder and vacuum hot press sintering. The results found that the nanocopper-modified graphene could be uniformly distributed in the aluminum alloy matrix, and formed a good binding interface with the matrix material. When the graphene content was 0.75 wt.% and 1.0wt%, the impact yield strength and the hardness reached the maximum of 434.8 MPa and 118.4 HV5, which were 27.24% and 43.11% higher than that of 2024Al respectively. Furthermore, with the increase of nanocopper-modified graphene content, the corrosion resistance of composite materials in 3.5%Cl-concentration solution was improved.

Flexible Diodes/Transistors Based on Tunable p-n-Type Semiconductivity in Graphene/Mn-Co-Ni-O Nanocomposites

We report a novel Mn-Co-Ni-O (MCN) nanocomposite in which the p-type semiconductivity of Mn-Co-Ni-O can be manipulated by addition of graphene. With an increase of graphene content, the semiconductivity of the nanocomposite can be tuned from p-type through electrically neutral to n-type. The very low effective mass of electrons in graphene facilitates electron tunneling into the MCN, neutralizing holes in the MCN nanoparticles. XPS analysis shows that the multivalent manganese ions in the MCN nanoparticles are chemically reduced by the graphene electrons to lower-valent states. Unlike traditional semiconductor devices, electrons are excited from the filled graphite band into the empty band at the Dirac points from where they move freely in the graphene and tunnel into the MCN. The new composite film demonstrates inherent flexibility, high mobility, short carrier lifetime, and high carrier concentration. This work is useful not only in manufacturing flexible transistors, FETs, and thermosensitive and thermoelectric devices with unique properties but also in providing a new method for future development of 2D-based semiconductors.

Gr/Cu Composites: Microstructure and Properties

Graphene(Gr) reinforced copper matrix composites(Gr/Cu) were prepared by powder metallurgy process, and the effects of graphene content on microstructure and properties of the composites were investigated. The microstructure, density, hardness and electrical conductivity of the composites were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), density measurement, hardness tester and conductivity meter. The results show that the interface bonding of the composite is good, there is no crack and no obvious interface reaction; there are a lot of dislocations and twins in Cu matrix. With the increase of graphene content, the density, heat capacity and thermal conductivity of the composites decrease, but the hardness increases first and then decreases.

Effect of Graphene Content on the Micromorphology, Microhardness and Micro Frictional Resistance of Co-Ni-Graphene Composite Coating

In order to obtain the alloy composite material with high hardness, good anti-friction property and low friction coefficient, the electrodeposition technology was used to prepare nanocrystalline Co-Ni-graphene composite coating on the surface of low carbon steel by means of ultrasonic dispersion combined with mechanical agitation. The influence of graphene content in electrolyte on composite coating was studied. The surface microstructure, composition, phase structure, micro-hardness and micro-wear properties of composite coating were measured by scanning electron microscopy, energy spectrometer, X-ray diffractometer, micro-hardness tester and UNMT-1 comprehensive mechanical testing system for micro-nanometer materials. The results show that with the increase of the content of graphene in the electrolyte the graphene particles were embedded in the alloy coating, which changes the crystal structure of the alloy coating and improves the microhardness and micro friction resistance of the coating. When the content of graphene in the electrolyte was 0.9g/L the microstructure of the composite coating was fine and uniform, the highest microhardness value was 678 HV, the minimum average friction coefficient was 0.15, and the composite coating had good wear resistance.

Microstructure and Thermodynamic Analysis of Graphene-Reinforced Coating Surface

The microstructure of coatings with different graphene content and the hardness of cladding layer under different distance between coil and samples were investigated. The results showed that with the increase of graphene, the mean particle size of the powder did not get significantly coarser. The defects and oxides were appeared in the cladding layer and graphene diffused into the substrate. Distance between induction coil and sample has great impact on the hardness of coating, the higher hardness was measured in the distance between 6-8cm. The thermodynamic analysis of coating nucleation was carried out.

Modification of Graphene and Friction and Wear Property of its Epoxy Resin Matrix Composites

The graphene was modified by silane coupling agent KH560, the epoxy resin was reinforced by the modified graphene (KH-graphene) to produce KH-graphene/epoxy resin composites, and the effect of KH-graphene content and load on the friction and wear property of the composites was studied. The results showed that the KH560 was successfully grafted to the surface of graphene; The KH-graphene decreased the mass loss and friction coefficient of the epoxy resin, and with increasing the KHgraphene content, the mass loss and friction coefficient of KH-graphene/epoxy resin composites both showed a decreasing trend, and when the load was 150N, KH-graphene content was 0.5%, the mass loss and friction coefficient of composites were reduced by 44.9% and 17.4%; With increasing the load, the mass loss and friction coefficient of KH-graphene/epoxy resin composites also showed a decreasing trend; The wear form was mainly fatigue wear under the low load, and KH-graphene could inhibit the generation and expansion of micro-cracks; After the load increased, the wear form was mainly abrasive wear; After the graphene added, the wear scar of the worn surface of composites was relatively reduced.

The influence of two types of functional particles on the electromagnetic properties and mechanical properties of double-layer coated basalt fiber fabrics

The double-layer coated basalt fiber fabric was prepared using polyurethane as the matrix and adopting a coating technology on the basalt fiber fabric. Firstly, the influence of two types of functional particles, graphite and graphene, on the dielectric properties (the real and imaginary parts and the loss tangent value), shielding effectiveness and mechanical properties of the double-layer coated basalt fiber fabric was analyzed. Then, the double-layer coated basalt fiber fabric of two types of structures, graphite/fabric/graphite and graphene/fabric/graphite, were prepared. Secondly, the influence of the contents of graphite and graphene on the electromagnetic properties and mechanical properties of the double-layer coated basalt fiber fabric using the method of controlling variables was studied. The results showed that the polarizing ability, the loss ability, the attenuating ability and the shielding ability of the double-layer coated basalt fiber fabric for the graphene coating were all superior to those of the graphite coating. Within the range of 0–1100 MHz, when the graphite content was 20%, the polarizing ability, the loss ability and the attenuating ability of the double-layer fabric were the strongest. When the graphene content was 20%, the polarizing ability to electromagnetic waves of the double-layer fabric was the strongest; when the graphene content was 15%, both the loss ability and attenuating ability to electromagnetic waves of the double-layer fabric were the strongest; and when the graphene content was 5%, the shielding ability to electromagnetic waves of the double-layer fabric was the strongest. When the graphite content was 20% and the graphene content was 10%, the displacement was within the range of 0–4.7 mm, and the load was 3411.1 N.

Microstructure and Fracture Mechanism Investigation of Porous Silicon Nitride–Zirconia–Graphene Composite Using Multi-Scale and In-Situ Microscopy

Silicon nitride–zirconia–graphene composites with high graphene content (5 wt.% and 30 wt.%) were sintered by gas pressure sintering (GPS). The effect of the multilayer graphene (MLG) content on microstructure and fracture mechanism is investigated by multi-scale and in-situ microscopy. Multi-scale microscopy confirms that the phases disperse evenly in the microstructure without obvious agglomeration. The MLG flakes well dispersed between ceramic matrix grains slow down the phase transformation from α to β-Si3N4, subsequent needle-like growth of β-Si3N4 rods and the densification due to the reduction in sintering additives particularly in the case with 30 wt.% MLG. The size distribution of Si3N4 phase shifts towards a larger size range with the increase in graphene content from 5 to 30 wt.%, while a higher graphene content (30 wt.%) hinders the growth of the ZrO2 phase. The composite with 30 wt.% MLG has a porosity of 47%, the one with 5 wt.% exhibits a porosity of approximately 30%. Both Si3N4/MLG composites show potential resistance to contact or indentation damage. Crack initiation and propagation, densification of the porous microstructure, and shift of ceramic phases are observed using in-situ transmission electron microscopy. The crack propagates through the ceramic/MLG interface and through both the ceramic and the non-ceramic components in the composite with low graphene content. However, the crack prefers to bypass ceramic phases in the composite with 30 wt.% MLG.