Heyi Ge

Modified carbon fiber/magnetic graphene/epoxy composites with synergistic effect for electromagnetic interference shielding over broad frequency band

The study on electromagnetic interference (EMI) shielding materials is a long-standing project in civil and military areas. In this work, a novel kind of shielding material was fabricated and the shielding effectiveness (SE) over broad frequency was investigated. The epoxy (EP) resin was reinforced by reduced graphene oxide coated carbon fiber (rGO-CF, GCF) and Fe3O4 nanoparticles deposited rGO nanohybrids (magnetic graphene, MG). With only 0.5wt% of GCF and 9wt% of MG, the GCF/MG3/EP exhibited excellent SE (>30dB over 8.2-26.5GHz) and a maximum value of 51.1dB at 26.5GHz, which had a 31.7% increase than that of GCF/EP. The 3-aminopropyltriethoxysilane (APTES) modified MG (NMG) gained better dispersion in resin and could further increased absorbing property of composites. The synergistic effect between GCF and MG raised by 3D interpenetration structure of the ternary nanocomposite was favorable for high efficient shielding in wide frequency range. This composites show promise in lightweight and high-efficiency EMI shielding field.

Effects of ZrO2 Fiber on the Mechanical Properties of Nano-ZrO2/Al2O3 Ceramic Composite

The effects of nano-ZrO2, ZrO2 fiber and sintering additives on the mechanical properties of Al2O3 ceramic composite were investigated by means of orthogonal experimental design. Meanwhile, the effect of environmental temperature on flexural strength of Al2O3 ceramic composite was tested. XRD and SEM were used to analyze the microstructure. The results showed that the content of ZrO2 fiber had the greatest effect on flexural strength and fracture toughness, followed by the content of nano-ZrO2. Nano-ZrO2 made the crystalline grains of Al2O3 smaller. ZrO2 fiber pulled out from Al2O3 matrix could consume energy of crack and increase the flexual strength and toughness of ceramic composite.

Effects of fiber loading and chemical treatments on properties of sisal fiber-reinforced sheet molding compounds

In this study, the effects of fiber loading from 0 vol.% to 15 vol.% and the chemical treatments on the properties of the sisal fiber-reinforced sheet molding compounds were investigated. The chemical treatments were performed with alkali, γ-ammoniapropyl-triethoxy-silane (KH-550) and γ-methacryloxypropyl-trimethoxy-sliane (KH-570), respectively, to improve the interfacial adhesion between sisal fiber and the matrix (unsaturated polyester resin). The changes of surface morphology and sisal fiber functional groups were investigated by scanning electron microscopy and Fourier transform infrared spectroscopic analysis, respectively. Compared to the untreated sisal fiber-reinforced sheet molding compounds, the mechanical property of the treated sisal fiber-reinforced sheet molding compounds increased due to the interfacial enhancement between sisal fiber and the matrix, which could be observed through the scanning electron microscopy images of fracture surface. Moreover, the better interfacial adhesion was also assisted in water absorption resistance and the thermal stability of the treated sisal fiber-reinforced sheet molding compounds. In the chemical treatments, KH-570 treatment was proved to be an effective method to improve the interfacial adhesion between sisal fiber and the matrix.

Synthesis of polymeric emulsifier and its application in epoxy emulsion-type sizing agent for carbon fiber

A new kind of polymeric emulsifier was readily synthesized through one-pot three-stage processes. Fourier transform infrared spectroscope (FTIR) combined with conversion rate of epoxide groups tests was applied to characterize the chemical composition of the polymeric emulsifier. The emulsion sizing based on the self-made polymeric emulsifier was prepared through phase inversion emulsification method. The stability of the sizing agent was evaluated by centrifugal sedimentation and particle size investigations. The surface morphology of CF was observed by scanning electron microscope (SEM). The effects of the sizing agent on CF handleability were examined by abrasion resistance, hairiness amount and stiffness tests. The results indicated that after sizing, the CF obtained an appreciable enhancement in handleability. Finally, interlaminar shear strength (ILSS) of sized CF/epoxy resin composite increased by 55.39% compared with that of the desized one.

Preparation and Properties of Emulsion Type Sizing Agent for Carbon Fiber

The epoxy resin and polyalkylene glycol allyl glycidyl ether (AEPH) were used to prepare the emulsion type epoxy sizing agents for carbon fiber (CF) by phase inversion emulsification method. Effects of mass ratio of mixed emulsifiers and emulsifiers/resin (ωe/r) and shear rate on stability of emulsion were investigated by centrifugal sedimentation analysis. Scanning electron microscope (SEM) was used to analyze the surface morphology of carbon fiber. Results show that the optimal emulsion was obtained when mass ratio of polyoxyethylene octylphenol ether-10 (OP-10), polysorbate-80 (Tween-80) and sodium dodecyl benzene sulfonate (SDBS) was 65:25:10, ωe/r was 9% and shear rate was 9000 r/min. The centrifugal sedimentation mass fraction of emulsion is 10.1%. SEM micrograph shows that the sizing agent forms a smooth film covering the carbon fibers.

The Influence of Thermal Fatigue on the Properties of Glass Fiber/ Epoxy Composites

In this paper, glass fiber reinforced epoxy composites were prepared according to laminated plates design principles by using glass fiber/epoxy composite prepreg. The mechanical property of glass fiber/epoxy composite and water absorption have been investigated before and after thermal cycles. Thermal cycles were performed in the temperature range between −40°—80°. Through different thermal cycles (0, 60, 120, 180 cycles), it was found that the mechanical property of different ply of glass fiber/epoxy matrix composites was decreased and water absorption of composites were increased. Moreover, scanning electron microscopy (SEM) was used to characterize the fracture morphologies of glass fiber/epoxy composites before and after thermal cycles. SEM images showed that after 180 thermal cycles, the bonding effect of glass fiber and epoxy matrix interfacial layer became worse and pores increased, leading to the decrease in the mechanical properties and the increase in the water absorption.

Preparation of ZrO 2 Composite Ceramics with High Thermal Shock Resistance

The physical and mechanical properties of nanometer ZrO2-ZrO2 fiber composite ceramics were studied by introduction of ZrO2 fiber. ZrO2 composite ceramics at different sintering temperature was investigated by porosity and water absorption measurements, flexual strength and thermal shock resistance analysis. Results showed that ZrO2 composite ceramics containing 15 wt% ZrO2 fiber with sintering temperature of 1650°C exhibited good mechanical properties and thermal shock resistance. The porosity and the water absorption were 8.84% and 1.62%, respectively. The flexual strength was 975 MPa and the thermal shock times reached 31 times. Scanning electron microscope (SEM) was used to analyze the microstructure of ZrO2 composite ceramics.

Study on Epoxy Based Magnetorheological Elastomers

To improve the mechanical properties and the MR effect of MRE, we use flexible epoxy as the matrix of MRE. It shows that both the mechanical properties and the MR effect of epoxy based MRE improved. At room temperature the highest absolute modulus increase was 203 MPa when the intensity of magnetic field was 0.2T while the carbonyl iron content was 71.4%. Temperature influenced the MR effect. When at -40°C the maximum storage modulus increased more than 2356 MPa and changed with the temperature. Meanwhile, the morphology of the epoxy based MRE was studied by scanning electron microscopy (SEM).

Thermal Shock Resistance of ZrO2 Fiber/Al2O3 Ceramics

The physical and mechanical properties of alumina (Al2O3) ceramics by introduction of zirconia (ZrO2) fiber were studied. ZrO2/Al2O3 ceramics at different sintering temperature was investigated by porosity and water absorption measurements, flexual strength and thermal shock resistance analysis. Results showed that Al2O3 ceramics containing 15 wt% ZrO2 fiber with sintering temperature of 1650°C exhibited good mechanical properties and thermal shock resistance. The porosity and water absorption were 7.4% and 0.69%, respectively. The flexual strength was 613 MPa and the thermal shock times reached 29 times. Scanning electron microscope (SEM) was used to analyze the microstructure of Al2O3 ceramics.

Enhanced Electromagnetic Interference Shielding Performance of Sisal Fiber/Polypropylene Composites with RGO-Fe3O4 Nanohybrids Treatment

RGO (reduced graphene oxide)-Fe3O4 nanohybrids were successfully synthesized by a solvothermal reduction method. Fe3O4 nanoparticles, RGO and the nanohybrids were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy and vibrating sample magnetometer (VSM). The electromagnetic interference (EMI) shielding effectiveness (SE) of RGO-Fe3O4/SF/PP composite was much higher than that of Fe3O4/SF/PP composite at 8-12 GHz, which was attributed to synergistic effect between RGO and Fe3O4 nanoparticles. The EMI SE (%) improved with the increase of RGO-Fe3O4 content and the maximum value of 80.44% was obtained for the RGO-Fe3O4/SF/PP composite. Furthermore, the dominant shielding mechanism of RGO-Fe3O4/SF/PP was absorption.