Preparation and mechanical properties of TLCP/UP/GF in-situ hybrid composites

One kind of novel reactive thermotropic liquid crystalline polymer-methacryloyl copolymer （LCMC） containing polyester mesogenic units was synthesized. Its structure, morphology and properties were investigated systemically by Ubbelohde viscometer, differential scanning calorimetry （DSC）, Fourier transform infrared spectroscopy （FTIR）, wide-angle X-ray diffractometry （WAXD） and polarizing optical microscopy （POM）. The results indicate that it is one kind of nematic thermotropic liquid crystal polymer （TLCP）. The impact strength, bending strength and the morphologies of impact fracture surface of LCMC, unsaturated polyester （UP） and glass fiber （GF） in-situ hybrid composites were studied by Izod impact tester, universal testing machine and scanning electron microscopy （SEM）, respectively. The results show that the impact and bending strength of composites containing LCMC are improved, especially the composites containing 5% LCMC increases most obviously. These results with SEM results reveal that LCMC plays an important role in the improvement of interfacial adhesive between matrix and fiber.     

Preparation and properties of nano-CeO2/Zn composites

The nano-composite powders of CeO2/Zn were prepared with high energy ball milling and the nano-composite materials of CeO2/Zn were fabricated with vacuum sintering powder metallurgy. Meanwhile, the composite and structure were analyzed by the means of XRD and FESEM. From the comparison of different nano-CeO2 contents composites, the best corrosion resistance and hardness, and the optimum content of nano-CeO2 were achieved. The result shows that corrosion resistance, hardness and uniformity of metal structure can be improved significantly with nano-CeO2; at the same time, the optimal corrosion resistance, hardness and microstructure are obtained when the mass fraction of nano-CeO2 is 1%.     

Preparation and microwave absorption properties of FeNi/graphite nanocomposites

FeNi/graphite nanocomposites were prepared by reducing FeCl3-NiCl2-GlCs in H2. The elemental composition, structure, magnetic and microwave absorption of FeNi/graphite nanocomposites were investigated using X-ray diffraction, energy dispersive spectra, hysteresis loop and electromagnetic parameter analysis. The results show that with the increase of the reduced temperature, the number and size of particles of FeNi increases, and the FeNi/graphite nanocomposites changes to soft magnetism. FeNi/graphite nanocomposites bear microwave absorption properties. With the increase of the thickness of the sample, the matching frequency tends to shift to the low frequency region, and theoretical reflection loss becomes less at the matching frequency. Microwave absorption property in the low frequency region of FeNi/graphite nanocomposites prepared at 600 ℃ （FeNi/C600） is the best. When the thickness is 2 ram, the maximum theoretical reflection loss of FeNi/C600 is -4.3 dB and the matching frequency is 3.5 GHz.     

Preparation and microwave dielectric properties of Csf/Si3N4 composites

The CJSi3N4 composites were prepared by hot-press sintering method using α-Si3N4 power, short carbon fibers and La2O3-Y2O3 sintering additives. The mechanical and microwave dielectric properties of CjSi3N4 composites were studied and discussed. The results show that the addition of the short carbon fibers can not destroy the relative density of the sintered samples, but it deteriorates the flexural strength of the sintered samples, so the flexural strength of the silicon nitride matrix is the highest among the samples. The real part （ε3 and the imaginary part （ε＇3 of the permittivity of CsfCSi3N4 composites greatly increase with increasing voltmae fraction of the short carbon fibers, achieve the maximum 73.1 and 101.5, respectively. A strong frequency dependence of the imaginary part （ε″） of the permittivity is observed.     

Mechanical and dielectric properties of Ni/Al2O3 composites

Ni/Al2O3 composites were prepared by hot pressing approach. The relationship between their microstructure, mechanical, dielectric and magnetic properties with Ni particle content was studied. By increasing the amount of metal in the composite, the relative density and the bending strength decrease gradually. The possible reason is that non-wetting between Ni and alumina in the preparation results in weak adhesion of the Ni/A; interface. For the composites, the maximum fracture toughness is 6.4 MPa. m^1/2, which is about 25% higher than that of pure alumina ceramic. The increase in toughness of the Ni/Al2O3 composites is due to the deformation of nickel particles. The complex dielectric constant measurements indicate that the real part and the imaginary part increase greatly with the Ni content in the frequency range of 8.2-12.4 GHz. The real part and the imaginary part of complex permeability of the composites also increase with increasing Ni content.     

Mechanical and electrical properties of carbon nanotube reinforced epoxide resin composites

Carbon nanotubes （CNTs）/epoxide resin composites were prepared, the mechanical and electrical properties of the composites were investigated. The effects of concentration and dispersion state of CNTs on the tensile strength, tensile modulus and electrical resistance of the composites were studied. The results indicate that the CNTs can be dispersed well in the epoxide resin matrix by ultrasonic method, and the mechanical and electrical properties of epoxide resin matrix can be improved significantly. The tensile tests show that the tensile strength and tensile modulus are higher than those of epoxide resin if the content of CNTs is less than 1.75% （mass fraction）. When the content of CNTs is 0.75%, the conditional best results are obtained, the tensile strength of the composite is the highest, increased by 18.3% and the tensile modulus is increased by 20.5% compared with the matrix. With the increase of CNTs, the electrical resistance of the composites decreases greatly, while the conductivity of the composite increases. The percolation threshold values of electrical characteristic transformation for this composite material were determined for the first time.     

Preparation and properties of scintillating glass doped with organic activators

A series of scintillating glasses were developed by doping organic activators into low melting temperature glasses according to different ratios. The fluorescence spectra and the transmission spectra of some scintillating glasses were explored and the actual concentration organic in scintillating glass was estimated. The results show that it is feasible to prepare the scintillating glass by doing organic scintillating activators into the low-melting glasses. There are two main reasons for the weak optical properties of the scintillation glasses： one is that the actual concentration of organic activators doped in the glasses is very low, and the other is the existence of lots of defects formed in the scintillating glasses due to the evaporation of organic activator, lowering the transmission of glasses. The fluorescence emission peaks of the glasses move to a longer wavelength compared with those in organic matrixes. To increase the light output of the glass, the optical transmittance of the glasses must be improved and the concentration of activators in the glasses must be increased.     

Preparation and dielectric properties of porous silicon nitride ceramics

Porous silicon nitride ceramics with difference volume fractions of porosity from 34.1% to 59.2% were produced by adding different amount of the pore-forming agent into initial silicon nitride powder. The microwave dielectric property of these ceramics at a frequency of 9.36 GHz was studied. The crystalline phases of the samples were determined by X-ray diffraction analysis. The influence of porosity on the dielectric properties was evaluated. The results show that α-Si3N4 crystalline phase exists in all the samples while the main crystalline phase of the samples is β-Si3N4, indicating that the αβ transformation happens during the preparation of samples and the transformation is incomplete. There is a dense matrix containing large pores and cavities with needle-shaped and flaky β-Si3N4 grains distributing. The dielectric constant of the ceramics reduces with the increase of porosity.     

导电陶瓷Ti3SiC2-Cu-C复合材料的制备与性能研究

用粉末冶金法制备了一定含量的镀铜和不镀铜Ti3SiC2-Cu-C复合材料,以及Cu-C复合材料,对它们的物理和力学性能进行了测试,并在滑动速度为10m/s,载荷为4.9N的干摩擦条件下进行了36h磨损试验,结果表明:镀铜Ti3SiC2-Cu-C复合材料的导电性、硬度、抗弯强度和耐磨性优于不镀铜Ti3SiC2-Cu-C复合材料和Cu-C复合材料。     

玻璃陶瓷复合材料的制备、微结构和性能

采用电子陶瓷工艺制备了一系列玻璃/锶长石陶瓷复合材料,并对复合材料进行X射线衍射分析、扫描电镜观察和性能测试。结果表明:复合材料的介电常数、热膨胀系数和显微硬度随着锶长石含量的增加而增加,而介电损耗随锶长石含量的增加而减小。锶长石含量大于50%(质量分数)的复合材料中α石英和方石英的析出增加了材料的热膨胀系数,但对材料的介电性能影响不大。所制备的复合材料具有低的介电常数(5.2~5.8)、低的介电损耗(0.10%~0.25%)、低的热膨胀系数(4.4×10-6~6.2×10-6℃-1)和低的烧结温度(≤900℃),有望用于电子封装领域。     

Preparation and mechanical properties of electrically conductive polypyrrole-poly(ethylene-co-vinyl acetate) composites

Electrically conductive polymer composite materials that possess good electrical and mechanical properties are prepared in two steps: first, a concentrated emulsion is generated by dispersing with stirring a toluene solution of pyrrole and a host polymer (poly(ethylene-co-vinyl acetate) or polyethylene) in a small amount of an aqueous solution of a surfactant (sodium dodecylsulfate); secondly, the oxidative polymerization of the monomer is carried out by introducing with stirring an aqueous solution of an oxidant (FeCl₃). After polymerization, flexible and stretchable conductive films can be obtained by hot-pressing the obtained composite powders. The conductivity of the composite exhibits a percolation threshold in the range 5–20 wt.% and reaches values as high as 5–7 S/cm. The mechanical properties of the composite films are determined by measuring the tensile strength as a function of elongation for various proportions of the conductive polymer in the composite and contents of vinyl acetate in the host polymer. Scanning electron microscopy (SEM) micrographs indicate that the hot-pressed materials possess a fluid-like morphology.     

Tailoring microstructure and mechanical properties of aluminum matrix composites reinforced with novel Al/CuFe multi-layered core-shell particles

Aluminum matrix composites (AMCs), reinforced with novel pre-synthesized Al/CuFe multi-layered core- shell particles, were fabricated by different consolidation techniques to investigate their effect on microstructure and mechanical properties. To synthesize multi-layered Al/CuFe core-shell particles, Cu and Fe layers were deposited on Al powder particles by galvanic replacement and electroless plating method, respectively. The core-shell powder and sintered compacts were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDX), pycnometer, microhardness and compression tests. The results revealed that a higher extent of interfacial reactions, due to the transformation of the deposited layer into intermetallic phases in spark plasma sintered composite, resulted in high relative density (99.26%), microhardness (165 HV_0.3) and strength (572 MPa). Further, the presence of un-transformed Cu in the shell structure of hot-pressed composite resulted in the highest fracture strain (20.4%). The obtained results provide stronger implications for tailoring the microstructure of AMCs through selecting appropriate sintering paths to control mechanical properties.     

石墨烯纳米片增强铝基复合材料的制备与性能

采用高能球磨、放电等离子烧结以及热挤压工艺制备含量为5.0％(体积分数)的石墨烯增强铝基复合材料.分别采用X射线光电子能谱、透射电镜及拉伸试验研究挤压态复合材料的显微组织与力学性能,发现5.0％(体积分数)的石墨烯分散在铝晶界上,并且未与铝基体发生界面反应.最终,挤压态复合材料的屈服强度和抗拉强度高达462 MPa和4...     

WS2增强CoCrTi复合材料的制备及高温摩擦学性能

采用热压烧结技术制备了CoCrTi-(2.5, 4.0, 6.0)WS₂复合材料,并优化了WS₂的含量。通过球-盘式高温摩擦试验机研究了复合材料在室温至1000 ℃范围内的摩擦学性能。使用X射线衍射仪和扫描电镜等分析了复合材料的显微组织和物相组成。结果表明:适量WS₂的添加显著提高了材料的硬度与摩擦学性能。3种复合材料的摩擦因数和磨损率均表现出大致相同的变化趋势:在室温至400 ℃的试验条件下,摩擦因数随温度的升高而降低,磨损率变化趋势则相反。在400 ℃到1000 ℃,摩擦因数随温度的升高小幅增大;磨损率随温度的升高先减小后增大最后减小,在800 ℃时达到最大值。在给定的试验条件下,WS₂含量为4.0wt%的复合材料具有最佳的高温摩擦学性能。在低温下试样表现出不同程度的磨粒磨损,在高温下的磨损机理为氧化磨损。     

Microstructures and mechanical properties of BP/7A04 Al matrix composites

The microstructures and interface structures of basalt particle reinforced 7A04 Al matrix composites (BP/7A04 Al) were analyzed by using OM, TEM, SEM and EDS, and the mechanical properties of 7A04 Al alloy were compared with those of BP/7A04 Al matrix composites. The results show that the basalt particles are dispersed in the Al matrix and form a strong bonding interface with the Al matrix. SiO₂ at the edge of the basalt particles is continuously replaced by Al₂O₃ formed in the reaction, forming a high-temperature reaction layer with a thickness of several tens of nanometers, and Al₂O₃ strengthens the bonding interface between basalt particles and Al matrix. The dispersed basalt particles promote the dislocation multiplication, vacancy formation and precipitation of the matrix, and the precipitated phases mainly consist of plate-like η (MgZn₂) phase and bright white band-shaped or ellipsoidal T (Al₂Mg₃Zn₃) phase. The bonding interface, high dislocation density and dispersion strengthening phase significantly improve the mechanical properties of the composites. The yield strength and ultimate tensile strength of BP/7A04 Al matrix composites are up to 665 and 699 MPa, which increase by 11.4% and 10.9% respectively compared with 7A04 Al alloy without basalt particles.     

Preparation by pulsed current electrochemical polymerisation and properties of ordered comb-shaped polyaniline/carbon fibres composites for flexible supercapacitor electrodes

ABSTRACT

Flexible polyaniline/carbon fibres (PANI/CFs) nanocomposites with comb-shaped polyaniline (PANI) nanorods were fabricated by using a one-step pulse current approach. The morphology, chemical structure, crystalline structure and electrochemical performances of well-controlled PANI/CFs composites were characterised and evaluated by FE-SEM, FT-IR, Raman spectra, XRD and electrochemical working station. The electrochemical performance of comb-shaped PANI/CFs nanocomposites as supercapacitor electrodes was obtained by controlling the polymerisation time and types of current. The optimised polyaniline/carbon fibres from preparation with pulse current for 7?min (PANI/CFs-PC-7) composite showed good electrochemical performance with maximum specific capacitance of 323?F?g^?1 of sample mass at a current density loading of 1?A?g^?1, together with better rate capability, bendability and good cycling stability, which are essential in high-performance supercapacitor electrodes. In addition, the highly efficient and convenient approach paves the way to large-scale commercial applications of the flexible ordered nanocomposites.