High Voltage Engineering,Part 1: Polymer Matrix Composites,Vol 44,No. 01
Polyethylene (PE) is a kind of essential insulation materials, but the low thermal conductivity limits its further application. Dispersing high-thermal-conductive inorganic particles into PE resin can improve the entire thermal conductivity effectively, which also has influences on its arc resistance and dielectric properties. Consequently, we chose boron nitride (BN) microparticles and micro-/nano-hybrid particles as fillers to prepare two categories of PE/BN composites with different filler loadings. In addition to measuring thermal conductivity of various samples, the effect of thermal conductivity on arc resistance was analyzed through high-voltage arc-tracking test. Evaluations were also conducted with relative permittivity and AC breakdown strength measurements of various samples. The results show that the thermal conductivity improves with the increasing BN filler loading from 0 to 40%, and the arc resistance of composites is enhanced simultaneously. However, the relative permittivity increases significantly and the AC breakdown strength drops remarkably with a relatively high filler loading (over 20%). Moreover, at the same filler loading, adding BN micro/nano-hybrid particles into PE is more favorable for increasing thermal conductivity, enhancing arc resistance and keeping satisfied dielectric properties.
Journal of Inorganic Materials,Part 1: Polymer Matrix Composites,Vol 34,No. 02
A new silver nanoparticles loaded graphene oxide (AgNPs@GO) was obtained through the ultrasonic assisted liquid phase method. In AgNPs@GO, silver nanoparticles (AgNPs) were mainly anchored at the oxygen containing groups and defects of graphene oxide (GO) sheets with part of GO sheets reduced and some Ag (0) atoms oxidized to Ag
+ ions. AgNPs@GO exhibited significantly stronger ability for inhibiting
Pseudomonas aeruginosa than AgNPs and GO. Therefore, AgNPs@GO was further introduced to polyethylene (PE) matrix as an additive to prepare a new composite material 0.48wt%-AgNPs@GO/PE. Compare with bare PE and AgNPs doped PE composites, 0.48wt%-AgNPs@GO/PE not only had a better antibacterial ability and stronger water vapor barrier property, but also had better dissolution resistance properties (dissolved out less nonvolatile substances) than PE in water and ethanol solution.
Proceedings of the CSEE,Part 1: Polymer Matrix Composites,Vol 36,No. 03
The development of HVDC transmission technology in China puts forward higher requests to the insulating properties of dielectric materials. Polymer nanodielectric materials have drawn extensive attention for their excellent properties, and the interface has become a hot topic. The interface is the nanoscale transition region between nano-filler and polymer matrix, and due to its special formation mechanism, the interface has different properties from the polymer matrix and nano-filler. Meanwhile, because the interface plays a leading role in the composite materials, its microstructure and properties will directly influence the macroscopic properties of the nanocomposite. This paper reviewed the introduced formation mechanism, structure and model of the interface, discussed its influence on aggregation structure of polymer and the trap theory and analyzed the mechanism of interface in the electrical properties of nanocomposites. Finally the study on local dielectric properties of the interface by using electrostatic force microscopy (EFM) was discussed.
Transactions of the Chinese Society of Agricultural Engineering,Part 1: Polymer Matrix Composites,Vol 31,No. 04
In this study, cellulose nano-fibril (CNF)/nano-silicon dioxide composites were prepared by mimicking the fast paper-making method. Mechanical property, thermal degradation and moisture adsorption of the composites were stuthed. The results revealed that tensile strength and modulus decreased as the loading of nano-silicon dioxide increased. The measured density value of CNF was 1,305.04 kg/cm
3 while the density of CNF with 20% nano-silicon was only 1 132.9 kg/cm
3. Tensile strength of CNF was 120.98 MPa and modulus was 6.41 GPa. As the loading of nano-silicon dioxide increased, the tensile strength and modulus decreased sharply. When the content of nano-silicon dioxide reached 20%, the tensile of nano-composite was 49.41 MPa and the modulus was 2.96 GPa. The thermal stability of nano-composite was improved after adding nano-silicon dioxide. The onset cellulose decomposition temperature was around 27°C and weight loss in this period was around 4%. Although the onset decomposition temperature of nanocomposites did not increase, the lower weight loss indicated less initial decompositions in this stage. In addition, as the content of silica became higher, the char residue increased. The amount of dry plain CNF was 23%, noticeably smaller than that of corresponding CNF/nano-silicon dioxide samples, which ranged from 30% and 65%. Degradation models including the Kissinger, modified Coats-Redfern and Flynn-Wall-Ozawa (F-W-O) methods were utilized to calculate the activation energy. The Kissinger method led to an apparent activation energy ranging from 150 to 225 for all films. NFC with inorganic silica normally showed a higher activation energy than the control, and high clay content also resulted in high activation energy. Results from the modified Coats-Redfern and F-W-O methods were similar (activation energy ranged from 180 to 220) to the observations. Nano-silicon dioxide provides barrier to the oxygen, which leads to an improvement in flame retardant property. Limiting oxygen index of the tested CNF was 21.8, which is similar to normal paper but lower than CNF with nano-silicon dioxide. Limiting oxygen index of the CNF with 20% nano-silicon dioxide was 24.20%. The CNF/nano-silica dioxide composites were placed in a container with relative humidity 95% for 24 hours and moisture content of composites increased along with time. Among all composites, CNF/nano-silicon dioxide showed higher moisture sensitivity than plaint CNF. The higher the nano-silica dioxide content was, the more moisture was absorbed. The final moisture content (FMC) of CNF was around 20% while the FMC of CNF with 20%nano-silica dioxide was around 26%. Contact angle was used to determine surface wettability of these nanocomposites. The contact angle of plain CNF was 55.9°. As the nano-silicon dioxide content increased, the contact angle of nanocomposites decreased. When the loading of nano-silicon dioxide was lower than 10%, the contact angle of nanocomposite was similar with CNF. However, as the loading of nano-silicon dioxide increased to 15%, the contact angle of the nanocomposite was only 45.4°. When the content of nano-silicon dioxide was 20%, the contact angle decreased to 40.4°. In conclusion, mechanic and water adsorption properties of cellulose nano-fibril were affected by the added nano-silicon dioxide amount, but the thermal property of the cellulose nano-fibril/ nano-silicon dioxide was stable.
High Voltage Engineering,Part 1: Polymer Matrix Composites,Vol 44,No. 05
As a main insulating material in the DC cable attachment, silicon rubber has the problem of space charge accumulation. It is important to study the trap characteristics of silicone rubber nanocomposites for the suppression of space charge accumulation in polymer materials. Consequently, using methyl vinyl silicone rubber as base rubber, we prepared silicone rubber samples, which were doped with different contents (5%, 10% and 20%) of SiO
2. The fracture surface of samples was observed by scanning electron microscope. Under the charge and discharge conditions of positive and negative corona, the potential decay characteristics of the sample were measured by an electrostatic probe. In order to obtain the hole-type trap characteristics and electron-type trap characteristics of samples, we adopted the two-trap-level model and the isothermal surface potential decay model. The results show that the hole-type traps in pure silicone rubber are mostly shallow traps, while most electron-type traps are deep traps. When the content of doped nano SiO
2 particles is 5%, the hole-type trap depth and trap density of the composite are more than those of pure silicone rubber. At the same time, the hole-type traps and electron-type traps are dominated by deep traps. When the content of nano SiO
2 particles in composite increases to 10% and 20%, the hole-type and electron-type deep traps densities decrease significantly, and the surface potential is rapidly attenuated by a large number of shallow traps in the material. The results can provide some reference values for the modification of silicone rubber materials in DC cable accessories.
Journal of Inorganic Materials,Part 1: Polymer Matrix Composites,Vol 30,No. 06
The graphene coated glass fiber composites were obtained from the electrostatic adsorption of graphene oxide on bovine serum albumin (BSA) modified the glass fibers, and the subsequent reduction of graphene oxide coated glass fibers by hydroiodic acid at low temperature of 40 °C. The phase structure and functional groups of graphene oxide were studied by XRD and FT-IR, respectively. SEM images showed that the graphene wrapped effect was improved with pH decreasing, when pH of graphene oxide dispersion was less than 6. Zeta potential of graphene oxide and BSA molecule were tested by Particle size/Zeta potential instrument, which showed that the isoelectric points of graphene oxide and BSA were smaller than 3 and 5.3, respectively. Conductivity of graphene wrapped glass fiber composites reached 4.5 S/m, and conductive glass fibers maintained original conductivity after different levels of bending. Moreover, due to the reduction of graphene, the conductivity increased slightly after the heat-treatment above 100 °C. These results prove that the conductive glass fibers can be used at high temperature.
Journal of Inorganic Materials,Part 1: Polymer Matrix Composites,Vol 34,No. 07
Polyaniline–carbon pillared graphene composite (PGR) was successfully prepared by vacuum extraction induced self-assembly and pyrolysis method. The effects of the mass ratio of aniline monomer (AN) to graphene oxide (GO) on the structure and electrochemical properties of PGR were investigated by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and electrochemical characterization. The results showed that the polyaniline–carbon pillars were uniformly distributed between the graphene (GR) layers to form a three-dimensional conductive network with expanded interlayer space and nitrogen doping, which effectively improved the structural stability and electrochemical performance of GR. The as-prepared PGR with the mass ratio of AN to GO at 1:1 exhibits a high reversible capacity of 653 mAh/g at a current density of 100 mA/g and an excellent rate capability of 343 mAh/g at a current density of 1 A/g, both of which are much higher than those of the GR electrode (101 mAh/g).
Journal of Aeronautical Materials,Part 1: Polymer Matrix Composites,Vol 36,No. 08
Conductive composites based on epoxy (bisphenol A, E-54) filled with graphene nanoplatelets (GNPs, KNG-CZ030) and cured in the presence of 2-ethyl-4-methy imidazole (2,4-EMI) were prepared by solution blending assisted with ultrasonic dispersion. Nonconductive inorganic fillers (NaCl or TiO
2) were added as a second filler to study their effects on dispersal uniformity of GNPs and electrical properties of composite. It is found that by adding NaCl and TiO
2, the dispersal uniformity of GNPs is improved and the conductivity of composite is increased with reduced room temperature volume resistivity. When the room temperature volume resistivity of NaCl/GNPs/E-54 and TiO
2/GNPs/E-54 composites is 10
6 Ω·m, their mass fractions are 0.75% and 0.72% respectively, which are lower than 0.97%, the mass fraction of GNPs/E-54 composite without adding inorganic particles.
Iron Steel Vanadium Titanium,Part 1: Polymer Matrix Composites,Vol 37,No. 09
Terahertz is the last researched band of the electromagnetic waves, which will play an important role in the field of stealth and anti-stealth research in the future. TiO
2, Fe-TiO
2 and BaTiO
3 nanoparticle samples were prepared by sol-gel method, which were doped into short carbon fiber/epoxy resin composites. Absorption properties of Ti-doped short carbon fiber/epoxy resin composites were investigated and mathematical model was established by using XRD and THz-TDS. The results show that the mixed nanoparticles have optimum absorption properties at 1.12 THz, with 78.1 of absorption index.
Journal of Aeronautical Materials,Part 1: Polymer Matrix Composites,Vol 37,No. 10
The optimum hybrid ratio range of carbon/basalt hybrid fiber reinforced resin composites was studied. Hybrid fiber composites with nine different hybrid ratios were prepared before tensile test. According to the structural features of plain weave, the performance parameters of unit cell were calculated. Finite element model was established by using SHELL181 in ANSYS. The simulated values of the sample stiffness in the model were approximately similar to the experimental ones. The stress nephogram shows that there is a critical hybrid ratio which divides the failure mechanism of HFRP into single failure state and multiple failure states. The tensile modulus, strength and limit tensile strain of HFRP with 45% resin are simulated by finite element method. The result shows that the tensile modulus of HFRP with 60% hybrid ratio increases by 93.4% compared with basalt fiber reinforced polymer (BFRP), and the limit tensile strain increases by 11.3% compared with carbon fiber reinforced polymer (CFRP).
Journal of Aeronautical Materials,Part 1: Polymer Matrix Composites,Vol 39,No. 11
Graphene oxide (GO) modified epoxy resin (GH81) was prepared by mechanical grinding, and the dispersion of GO in the epoxy resin (H81) was analyzed by optical microscope, while the melting performances and curing behaviors of H81 and GH81 were researched through rheometer and differential scanning calorimeter respectively. The results show that GO is uniformly dispersed into the matrix resin, and the addition of GO hardly affects the melt viscosity and curing condition of the matrix resin at all. In addition, the 0° tensile strength, bending strength and compression strength of GH81 based carbon fiber reinforced polymetric composite (GH81-300) are 2 270 MPa, 2 239 MPa and 1 529 MPa respectively, which are increased by 6.4%, 7.2% and 7.1% respectively, as compared with those of composite without GO.
Iron Steel Vanadium Titanium,Part 1: Polymer Matrix Composites,Vol 37,No. 12
Composite material (TiO
2/BFSF) of TiO
2 loaded on blast furnace slag fibre (BFSF) was prepared by impregnation-depositing process using BFSF as the carrier. The crystal form, grain size, specific surface area of TiO
2 and microstructure of the composite TiO
2/BFSF were characterized by XRD, particle size analyzer and Zeta potential meter, N
2 adsorption and desorption instrument, SEM and EDS, respectively. The photocatalysis performances of TiO
2/BFSF were evaluated by degradation of methylene blue (MB) simulating dyeing waste water. The results show that with 3 times of impregnation-depositing in 20 g/L TiO
2 suspension system, TiO
2 can be uniformly coated on the BFSF and 94. 8% MB can be degraded by composite TiO
2/BFSF under the ultraviolet light irradiation for 180 min. After 4 times of recycle, the degradation rate of MB is still maintained at 65%.
Journal of Inorganic Materials,Part 1: Polymer Matrix Composites,Vol 30,No. 13
To broaden the bandwidth of focused transducer with suppressing the multi-mode coupling phenomenon, and improving the electro-acoustic conversion efficiency, we used 1-3 piezoelectric composites as the ultrasonic emission material to replace Pb-based lanthanum doped zirconate titanates ceramic. A new type of lens-focused transducer was designed and produced based on 1-3 piezoelectric composites. Through the comparative study of frequency characteristic, it is proved that the lens-focused transducer with 1-3 piezoelectric composites can not only increase the bandwidth of the transducer which is 3.13 times that of the one based on Pb-based lanthanum doped zirconate titanates, but also suppress the radial vibration obviously to obtain a single pure vibration mode. Besides, the electro-acoustic conversion efficiency of the former lens-focused transducer is 1.88 times that of the latter. These results provide a theoretical and experimental foundation for the realization of ultrasonic transducer of high efficiency on reliability and stability.
Earthquake Engineering and Engineering Dynamics,Part 1: Polymer Matrix Composites,Vol 38,No. 14
The finite element model for the buried pipe made with four composite layers (0/90/0/90) connected by socket and spigot joint was established to study its seismic behavior. The mechanic property of the joint was calculated and the corresponding parameters for the equivalent springs in three directions were obtained. Under varied earthquake intensities, the distribution of the pipe displacement, the effective stress in four composite layers and the seismic behavior of the joint were studied. Results indicate that: the axial stress in 0 degree layers was 75% larger than that in 90 degree layers; the relative displacement and resisting force in the equivalent springs located at joint E increased with the increasing earthquake intensity; the axial relative displacement at joint E was kept within the allowable value under the action of 0.2 g, 0.4 g, 0.6 g seismic excitation and works in normal state under all three seismic intensities.
Journal of Inorganic Materials,Part 1: Polymer Matrix Composites,Vol 34,No. 15
The Co
3O
4@activated carbon fibers (ACF) composites were prepared through a facile hydrothermal method followed by calcination process, involving the growth of Co
3O
4 nanowires on ACF surface. Co(NO
3)
2·6H
2O was used as Co source, urea and NH
4F as additives. The structures and morphologies of Co
3O
4@ACF composites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), N
2 adsorption/desorption measures and thermogravimetric analysis (TGA). The electrochemical properties of Co
3O
4@ACF composites were investigated by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS). The results showed that the Co
3O
4 nanowire arrays uniformly grew on the surface of ACF along the vertical direction, forming abundant mesoporous structures. The Co
3O
4@ACF composites with various Co
3O
4 fractions could be obtained by adding different amounts of Co(NO
3)
2·6H
2O. Furthermore, the Co
3O
4@ACF composite with 47 wt% Co
3O
4 fraction exhibited a high specific capacitance of 566.9 F/g at a current density of 1 A/g, which was almost twice as high as that of pure Co
3O
4. Even at 15 A/g, the composite still delivered a specific capacitance of 393.3 F/g, showing good rate capability. The specific capacitance of the composite could retain 84.2% of initial value after 5 000 charging/discharging cycles, which indicates its superior cycling stability.
High Voltage Engineering,Part 1: Polymer Matrix Composites,Vol 45,No. 16
Converter transformer bushing is an insulation weak link of the converter transformer. Especially, the radial temperature difference generated by the core of the bushing will cause the electric field to be distorted, easily leading to insulation fault during operation. In view of this, we studied the radial electric field distribution of a ±600 kV ultra-high-voltage converter transformer bushing under different working conditions, and applied an insulating epoxy resin with nonlinear conductivity to suppress the radial electric field distortion of the bushing. The research results show that the electric field distribution of the bushing core at the flange is distorted by radial temperature differences with the increase in the bushing load, and the distortion field strength near the flange is as high as 12 kV/mm under full load. At the same time, the decrease in field strength of the bushing core near the guide rod increases the electrical strength of the end SF
6 gas by nearly three times, which is highly likely to cause gas discharge. After the replacement by insulating epoxy resin with nonlinear conductivity, the electric field distortion of the bushing core at the flange is greatly reduced, and the insulation load of SF
6 gas and transformer oil at the end of the bushing is also effectively alleviated. The epoxy core loss in nonlinear bushing increases during its operation. However, compared with the current heating in the conductor, the loss increase can be ignored. The simulation results prove the feasibility of the insulating epoxy resin with nonlinear conductivity to suppress the electric field distortion of bushing core and reduce the probability of failure.
