镀银空心玻璃微珠柔性导电膜的研制

采用化学镀方法在空心玻璃微珠表面包覆金属银,获得镀银空心玻璃微珠(Ag@HGMs)复合粒子。利用扫描电子显微镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)、透射电子显微镜(TEM)和半导体粉末电阻率仪对Ag@HGMs复合粒子的微观形貌、尺寸、结构、组分和导电性进行表征。结果显示,最佳工艺条件下所得Ag@HGMs粉末的体积电阻率为2.85×10^-4Ω·cm,表面镀银层致密、完整。将Ag@HGMs粉末作为导电填料,以液体硅橡胶为柔性基体,制备了具有三明治结构的柔性导电膜,Ag@HGMs复合粒子夹在两层硅胶中间。当导电填料的质量分数为4.76%时,膜的体积电阻率为2.33×10^-3Ω·cm。在反复拉伸、折叠后,Ag@HGMs复合粒子依然粘合在导电网络中,且其表面镀银层未脱落,膜的导电性变化微小。     

多巴胺改性空心玻璃微珠表面化学镀银工艺

先采用多巴胺溶液活化空心玻璃微珠(HGM),再化学镀银。研究了硝酸银质量浓度、葡萄糖质量浓度和装载量对银利用率和镀银HGM导电性的影响。采用扫描电镜(SEM)和能谱仪(EDS)分析了镀银HGM的形貌和表面成分。结果表明,经多巴胺活化后,HGM表面成功附着了一层聚多巴胺膜。当硝酸银质量浓度为15 g/L、葡萄糖质量浓度为30 g/L和装载量为4 g/L时,镀液中的银利用率达71.5%,镀银HGM的导电性良好(体积电阻率为34 mΩ·cm),表面银层均匀、致密。     

表面活性剂对空心玻璃微珠化学镀银影响的研究

采用不同的表面活性剂对化学镀液进行分散、润湿,用AgNO3活化剂代替传统的PdC12进行化学镀银包覆空心玻璃微珠,并对所得银包粉体进行粒径分析、煅烧。研究了表面活性剂对化学镀银的影响。结果显示:包覆均匀的颗粒煅烧效果好,而且用PVP作为表面活性剂化学镀银能得到低于4×10-3Ω·cm的体积电阻的导电填料。     

酸性化学镀法制备泡沫铝用Ni/TiH2包覆粉末发泡剂的工艺及性能研究

酸性条件下,对常用发泡剂TiH2粉末的表面进行均匀、质量比可控的Ni层包覆,提高其释氢温度并延缓释氢速率。结果表明,以硫酸镍为主盐,NaH2PO2.H2O为还原剂,制备Ni/TiH2复合粉体的最佳工艺条件为:硫酸镍质量浓度30 g/L,NaH2PO2.H2O质量浓度30 g/L,pH值4.5～4.8,缓冲剂浓度为20 g/L,稳定剂浓度为0.8 mg/L,络合剂A浓度为8 mL/L,络合剂B浓度为18 g/L,温度为80℃。Ni含量为30%Ni/TiH2复合粉体镀镍后,开始释氢温度比镀镍前提高300℃,同时释氢速率也得到明显减缓。     

Cu/Ag复合电磁屏蔽涂料的研究

为提高铜系电磁屏蔽涂料的抗氧化性与电磁屏蔽效能 ,本文采用化学镀法在铜粉体上沉积金属银层 ,获得了具有更为优良导电性的Cu/Ag复合电磁屏蔽涂层 ,表面电阻率由铜系涂层的 0 0 5Ω·cm下降到 0 0 0 2 5Ω·cm。优良的电导率使得涂层具有很好的电磁屏蔽性能 ,Cu/Ag复合涂层的电磁屏蔽效能在 10 0KHz～ 1 5GHz频段范围内达到 - 80dB左右。研究还表明镀银工艺中化学镀的时间对粉体的电导率有重要影响。     

镀银玻璃微珠/硅橡胶导电复合材料导电性能的影响因素

研究镀银玻璃微珠的用量、粒径、表面改性工艺以及导电硅橡胶硫化程度等对镀银玻璃微珠/硅橡胶复合材料导电性能的影响.结果表明,镀银玻璃微珠的粒径越大,复合材料的导电性能越好;湿法预处理和原位改性-分散工艺制得复合材料的导电性能和导电稳定性优于直接干混工艺;导电硅橡胶硫化程度的提高有利于提高材料的导电性能;Payne效应的大小与导电硅橡胶的体积电阻率有很强的相关性.     

Ni/GFF/EP导电复合电磁屏蔽材料的制备及性能

采用化学镀法在玻璃纤维织物(GFF)上制备出镀镍玻璃纤维织物(Ni/GFF),将Ni/GFF作为导电填料与环氧树脂(EP)复合,制备了镀镍玻璃纤维织物/环氧树脂复合材料(Ni/GFF/EP)。对还原剂浓度、主盐液浓度、氨水浓度、化学镀反应时间等工艺参数对Ni/GFF导电性的影响进行研究,优化了化学镀工艺。研究了GFF镀镍改性对复合材料力学性能的影响以及Ni/GFF复合环氧树脂前后的屏蔽效能。结果表明,Ni/GFF/EP复合材料的体积电阻率为5.06×10~(-3)Ω·cm,弯曲强度为230 MPa,冲击强度为11.56 kJ·m~(-2),屏蔽效能为67 dB~77 dB。     

镀银玻璃微珠填充导电硅橡胶的研制

研究了镀银玻璃微珠的用量、硅烷偶联剂的种类及用量等对硅橡胶硫化胶导电性能和力学性能等方面的影响。结果表明,采用乙烯基三过氧叔丁基硅烷（VTPS）对镀银玻璃微珠表面进行预处理，可以改善胶料的混炼工艺,也可以提高硫化胶的力学性能、导电性能和导电稳定性能；添加180份VTPS处理的镀银玻璃微珠，导电硅橡胶体积电阻率小于0．01Ω．cm。     

还原剂和氢氧化钠对涤纶纤维化学镀银的影响

通过化学镀银制得导电涤纶纤维。研究了粗化液的NaOH含量和温度对纤维表面形貌和断裂强度的影响,并分析了化学镀银液中还原剂种类和NaOH含量对纤维增重率和表面电阻率的影响。涤纶纤维的最优粗化工艺条件为:NaOH 200 g/L,温度65°C,时间30 min,磁力搅拌。化学镀银的最优工艺条件为:葡萄糖8 g/L,50%(体积分数)甲醛4 g/L,NaOH 2.4 g/L,室温,时间30 min。在最优工艺下,纤维增重率达12.91%,银层光滑、致密,表面电阻率为2.45Ω/cm。     

高导电镀银粒子/硅橡胶复合材料的制备研究

以自制玻璃微珠/银复合粒子作为导电填料、硅橡胶作为基胶,制备出具有高导电性能的硅橡胶复合材料,研究了导电复合粒子的添加量对橡胶复合材料物理性能和导电性能的影响。结果表明:自制玻璃微珠/银复合粒子的体积电阻率为3.14×10-4Ω.cm,导电性能优良;随着复合粒子添加量的增加,硅橡胶复合材料的导电性能和邵尔A硬度增加,但其它力学性能却呈下降趋势。当复合粒子的添加量为300phr时,硅橡胶复合材料的体积电阻率达到0.009Ω.cm,表现出优良的导电性能。     

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.     

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.     

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.     

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.