基于机械球磨法的茂金属PE/石墨/碳纳米管导电复合材料的制备及性能研究

以茂金属PE为基体,以石墨和碳纳米管为导电填料,采用机械球磨法,制备茂金属PE/石墨/碳纳米管导电复合材料,考察球磨时间、球磨温度、球磨转速和石墨含量等对复合材料导电性的影响。结果表明,在球磨时间60 min,球磨温度50℃,球磨转速150 r/min、导电填料15%石墨、5%碳纳米管的条件下,复合材料的电阻率降到1.36Ω·cm,可作为一种电磁屏蔽材料应用于电子元器件表面。     

PLA/木薯厌氧渣复合材料的制备工艺

以木薯厌氧渣为填料,聚乳酸(PLA)为基体,采用模压成型制备了PLA/木薯厌氧渣复合材料,探究了木薯渣填充量、偶联剂添加量、机械球磨时间、温度、转速及模压温度、压力、时间等因素对复合材料力学性能的影响。结果表明,偶联剂占木薯渣质量的2%,木薯渣填充量为10%,球磨时间为30 min,球磨温度为60℃,球磨转速为300 r/min,模压时间为6 min,模压温度为190℃,模压压力为10 MPa时,复合材料的弯曲强度为63.108 MPa,拉伸强度为44.155 MPa,力学性能较好。以PLA与木薯厌氧渣为主要原料制备复合材料,既能有效降低复合材料的生产成本又能使复合材料保持较好的力学性能,避免了废弃木薯渣对环境的污染,且为实现生物质资源的高值化利用提供理论依据。     

mPE/PE-LD/CB导电复合材料的制备与性能研究

采用在流变仪混炼器中密炼共混的方法制备了茂金属聚乙烯/低密度聚乙烯/炭黑（mPE/PE-LD/CB）导电复合材料,研究了共混温度、转速等工艺因素对mPE/PE-LD/CB复合材料流变性能的影响;并用差示扫描量热仪、扫描电子显微镜对复合材料的结晶性和微观形貌进行分析,同时测试了复合材料的表面电阻、体积电阻和力学性能。结果表明,最佳工艺条件为转速30 r/min、温度180 ℃、共混时间10 min;随着mPE含量的增加,复合材料的结晶度提高、导电性增大,力学性能提高。     

超高分子量聚乙烯/石墨包覆纳米铜复合导电材料研究

在NaBH4/EDA体系中还原CuCl2石墨层间化合物合成了石墨包覆纳米铜复合填料(GECNP).以GECNP为导电填料,采用球磨共混-热压成型工艺制备了超高分子量聚乙烯(UHMWPE)基复合材料.UHMWPE/GECNP复合材料的X射线衍射(XRD)分析表明:在制备过程中无新相生成;扫描电镜(SEM)观察发现:其微观结构均匀,GECNP以纳米片状分散于基体中,构成导电网络;有关导电性的研究表明:复合材料导电机制符合聚合物基复合材料的导电渗滤理论,渗滤阈值为8.766%,低于常规碳系填料.当GECNP体积浓度为12.8%时,体系电导率最高,为7.55S/cm,高于石墨纳米片填料.     

PE/多层石墨导热复合材料的制备与性能

PE、GPE为基材,多层石墨、石墨为填料,采用机械混炼法制备高导热塑料复合材料。SEM分析表明PE/多层石墨比GPE/多层石墨复合材料的插层效果更好。研究填料对复合材料的热导率和热稳定性的影响。结果表明:导热复合材料的热导率随填料填充量的增大而增大,多层石墨的填充量达到100%时,热导率为4.15 W.m-1.k-1。并且在相同填充量下PE/多层石墨较之GPE/多层石墨、PE/石墨、GPE/石墨的导热率更高。TGA分析表明:填充多层石墨、石墨的导热塑料复合材料热稳定性高于未填充的PE。经研究提出,形状比(径厚比)大和导热率高的导热填料更易形成导热网链;为了不影响导热填料的分散性,可先使基体材料与填料先混合均匀再增加其韧性、黏度等。     

镀镍石墨/硅橡胶导电复合材料的性能研究

以镀镍石墨为导电填料制备镀镍石墨/甲基乙烯基硅橡胶(MVQ)导电复合材料,并对其性能进行研究.结果表明,采用密炼工艺、硫化温度为110℃、偶联剂A-151和硫化剂双24用量分别为6和8份时,所制备的镀镍石墨/MVQ复合材料的导电性能和拉伸性能较好.     

转速对PP-g-MA改性石墨烯/TPU/PP复合材料力学和电学性能的影响

以热塑性聚氨酯(TPU)和聚丙烯(PP)为基体,石墨烯为导电填料,聚丙烯接枝马来酸酐(PP-g-MA)为界面增容剂,制备了石墨烯/TPU/PP/PP-g-MA导电复合材料。研究了螺杆转速对复合材料力学性能和电学性能的影响以及石墨烯在复合材料中的选择性分布状态。结果表明,随着螺杆转速从10 r/min提高到50 r/min,复合材料的拉伸强度提高了103.62%,断裂伸长率提高了161.47%,电导率提高了155.49%,体系中石墨烯选择性分布在TPU中,石墨烯/TPU在基体中则形成了共连续的导电网络。     

挤出牵引速度对聚乙烯/金属锡导电复合材料性能的影响

采用高温挤出热拉伸-低温注射成型的加工工艺,制备了聚乙烯/金属锡（PE/Sn）导电复合材料,研究了挤出造粒时不同切粒机转速（即热牵引速度）和Sn用量对其微观结构、导电性能及力学性能的影响。结果表明,当切粒机的转速由常规的35 r/min提高到50 r/min时,Sn在PE基体中成纤更细更长,PE/Sn复合材料导电所需的Sn的最低含量由常规时的9.2 %（质量分数,下同）降低到6.2 %,即导电逾渗值降低,且复合材料的力学性能略有上升。     

碳材料/橡胶导电复合材料的研究进展

介绍导电橡胶复合材料的渗流理论和量子隧穿效应两种导电机理。综述炭黑、石墨、碳纤维、碳纳米管、石墨烯等碳材料与橡胶制备的导电复合材料的国内外研究进展。碳纳米管和石墨烯等新型碳材料可赋予橡胶复合材料更优异的物理性能和导电、导热性能,为橡胶的功能化和多元化开拓了新的领域。多种碳材料并用可以降低填料添加量、提高导电橡胶电导率,是导电橡胶复合材料的发展趋势。     

导电填料/高密度聚乙烯(HDPE)导电复合材料的研究进展

综述了以炭黑、石墨、多壁碳纳米管为填料,以高密度聚乙烯为基体制备的复合材料电性能的研究进展。分析了不同填料对导电高分子材料的PTC、NTC效应等电性能的影响。     

Wet Milling of Fe/Al/Al2O3 and Fe2O3/Al/Al2O3 Powder Mixtures

Wet milling of Al₂O₃-aluminide alloy (3A) precursor powders in acetone has been investigated by milling Fe/Al/Al₂O₃ and Fe₂O₃/Al/Al₂O₃ powder mixtures. The influence of the milling process on the physical and chemical properties of the milled powders has been studied. Particle refinement and homogenization were found not to play a dominant role, whereas plastic deformation of the metal particles leads to the formation of dislocations and a highly disarranged polycrystalline structure. Although no chemical reactions among the powder components in Fe₂O₃/Al/Al₂O₃ powder mixtures were observed, the formation of a nanocrystalline, ordered intermetallic FeAl phase in Fe/Al/Al₂O₃ powder mixtures caused by mechanical alloying was detected. Chemical reactions of Fe and Al particle surfaces with the atmosphere and the milling media lead to the formation of highly porous hydroxides on the particle surfaces. Hence the specific surface area of the powders increases, while the powder density decreases during milling. The fraction of Fe oxidized during milling was determined to be 0.13. The fraction of Al oxidized during milling strongly depends on the metal content of the powder mixture. It ranges between 0.4 and 0.8.     

Preparation and properties of poly(Nε,Nε-dicarboxymethyl-l-lysine)

A new ampholytic homopolypeptide, $\text{poly}\text{(N}{}^{\mathrm{\epsilon }}\text{,N}{}^{\mathrm{\epsilon }}\text{-}\text{dicarboxy-methyl-}\text{l}\text{-lysine}\text{)}$, which has one tertiary amino and two carboxyl groups in the side chain has been derived from a hydrochloride salt of poly(L-lysine). The polymer in aqueous solution seems to be in the coil form with locally extended structure (LES) at neutral pH. In both the acidic and alkaline regions, the molar ellipticity of the polymer changes as a result of change in net charge on the side chain. The conformational changes may be from the coil with LES to other coiled forms. 5–7 M NaClO₄ and 80% aqueous methanol induce the α-helix in the polymer at neutral pH. Divalent cations, Cu²⁺ and Ca²⁺, do not induce any remarkably ordered structures such as α-helix or β-structure in the polymer in aqueous solution at any pH. Ultraviolet absorption studies show an absorption peak of the polymer-Cu²⁺ complex near 240 nm. Dependence of the peak intensity on pH at various q values ($\text{q =}\text{[}\text{Cu}{}^{\mathrm{2+}}\text{]}\text{[}\text{residue}\text{]}$) indicates the two steps of the complex formation. At q less than 0.64, the formation is described only with the first step. An average coordination number for Cu²⁺ at the first step was calculated to be about 2 by the method of Mandel and Leyte. The association constant of Cu²⁺ with the residue at the step was determined from the absorption data to be far smaller than that for the Cu²⁺-EDTA complex. The second step of the formation occurs in the case of large q but the absorption data for the second step cannot be obtained exactly due to precipitation.     

Sintering of Si3N4-Y2O3-Al2O3

Sintering kinetics of the system Si₃N4-Y2O₃-Al₂O3 were determined from measurements of the linear shrinkage of pressed disks sintered isothermally at 1500° to 1700°C. Amorphous and crystalline Si₃N₄ were studied with additions of 4 to 17 wt% Y₂O₃ and 4 wt% A1₂O₃. Sintering occurs by a liquid-phase mechanism in which the kinetics exhibit the three stages predicted by Kingery's model. However, the rates during the second stage of the process are higher for all compositions than predicted by the model. X-ray data show the presence of several transient phases which, with sufficient heating, disappear leaving mixtures of β ' -Si₃N₄ and glass or β '-Si₃N₄, α '-Si₃N₄, and glass. The compositions and amounts of the residual glassy phases are estimated.     

Participation of lewis base on vinyl chloride polymerization with Al(C2H5)3CCl4 catalyst system

The polymerization of vinyl chloride has been investigated using an $\text{Al}\text{(}\text{C}{}_2\text{H}{}_5\text{)}{}_3\text{CCl}{}_4$ catalyst system in the presence of various Lewis bases. Effective Lewis bases are γ-butyrolactone, diglyme and diethylenetriamine which are multidentate. The rate of polymerization is dependent not only on the basicity of the Lewis base used but also on a coordination number of one. The latter is the predominant factor. For the effect of polymeric amines, a tentative hypothesis is discussed.     

Ag2O-Doped Bi2Sr2Ca1Cu2Ox Superconductors Prepared via Melt-Quenching

Ag₂O-doped superconducting Bi₂Sr₂Ca₁Cu₂O _x ceramics were prepared by a melt-quenching–reheating method. It is found that the Ag₂O-doped, as-cast specimens exhibit superconductivity ( T _c= around 80 K) by heat treatment at temperatures around 800°C even in an evacuated and sealed silica glass tube, while the undoped specimens do not and vaporize by the corresponding heat treatment. Conversion of the Ag₂O-doped, as-cast specimens into superconducting ceramics when heated in an evacuated vessel is explained in terms of the oxygen donor of Ag₂O in the specimen. This finding enables us to fabricate a desired shape of superconducting Bi₂Sr₂Ca₁Cu₂O _x ceramics sealed in metals or glasses. The addition of Ag₂O to Bi₂Sr₂Ca₁Cu₂O _x melt, however, had deleterious influences on the superconducting properties ( T _c and J _c) of the resultant ceramics when obtained by heat treatment in air.     

Synthesis and Characterization of Ti0.33Ta0.33Nb0.33C and Ti0.33Ta0.33Nb0.33CxN1-x Whiskers

Ta_0.33Ti_0.33Nb_0.33C and Ta_0.33Ti_0.33Nb_0.33C _x N_{1− x} whiskers were synthesized via a carbothermal vapor-liquid-solid growth mechanism in the temperature range 900°-1450°C in Ar or N₂. The optimum temperature was 1250°C. Whiskers were obtained in a yield of 70-90 vol%. The whiskers were 0.5–1 µm in diameter and 10–30 µm in length. The starting materials that produced the highest whisker yield were: TiO₂, Ta₂O₅, Nb₂O₅, C, Ni, and NaCl. C was added to reduce the oxides, and Ni to catalyze whisker growth. NaCl was used as a source of Cl for vapor-phase transportation of Ta and Nb oxochlorides and Ti chlorides to the catalyst. The catalyst metal was recycled several times during the synthesis and was transported as NiCl₂( g ) according to thermodynamic calculations. The rate of formation and the chemical composition of the whiskers depended on the synthesis temperature, the choice of catalyst, and the atmosphere. At low temperatures, the whiskers were enriched in Nb and Ta, whereas the Ti content increased with increased synthesis temperature.