聚苯胺/涤纶织物化学镀镍-铁合金及其电磁屏蔽性能

以聚苯胺/涤纶为柔性基材,通过化学镀Ni–Fe合金制备了对电磁波具有高吸收低反射的Ni–Fe/PANI/PET复合织物。研究了预镀镍时间、化学镀Ni–Fe合金时间及其镀液中Ni²⁺与Fe²⁺的质量浓度比对Ni–Fe/PANI/PET复合织物电导率、电磁屏蔽性能和微观结构的影响。结果表明：先预镀镍40 min,再在Ni²⁺与Fe²⁺的质量浓度比为4∶1、总质量浓度为10 g/L的条件下化学镀Ni–Fe合金40 min,所得复合织物的电导率最高为103 S/cm,力学性能良好。此外,Ni–Fe/PANI/PET复合织物在0.03～3 000 MHz波段表现出高吸收低反射的电磁屏蔽性能。     

涤纶基铜层表面化学镀镍–磷合金工艺

以涤纶织物为基材,对其化学镀铜后再化学镀镍–磷合金镀层。探讨了化学镀Ni–P合金工艺各因素对镀金属织物导电性和增重率的影响,通过正交试验优化了化学镀Ni–P合金工艺,并对镀Cu/Ni–P合金织物的结合牢度、耐蚀性和电磁屏蔽效能进行了表征。结果表明,涤纶基铜层表面化学镀Ni–P合金镀层的最优配方和工艺为:NiS O4·6H2O 26 g/L,Na H2PO2·H2O 24 g/L,Na3C6H5O730 g/L,Na2B4O7·10H2O 6 g/L,温度80°C,p H 11,时间25 min。最优工艺下制备的镀铜/镍–磷织物的结合强度高,耐腐蚀性和电磁屏蔽性能良好。     

玻璃纤维/环氧树脂复合材料表面金属化工艺研究

提出一种在玻璃纤维/环氧树脂复合材料表面化学镀镍的简化工艺,首先在复合材料表面引入含有镀镍短纤维的过渡层,复合材料与过渡层共固化成型。通过机械粗化、酸化、化学镀工艺成功地在玻璃纤维/环氧树脂复合材料表面沉积一层连续致密的Ni-P镀层。采用超景深显微镜观察化学镀后镀层的表面形貌,并采用SEM对镀层截面特征进行观测。系统地研究了化学镀时间、装载量对镀层表面形貌、镀层厚度与镀层沉积速度的影响规律,并测量了复合材料/镍镀层界面结合强度。试验结果表明,当化学镀时间为8 h、装载量为1.25 dm2/L时,镀层厚度能达到38.96μm,镀层结合强度达到8.45 MPa。     

RTM制备玻璃纤维增强环氧树脂复合材料的力学性能分析

以环氧树脂为基体,短切玻璃纤维和玻璃纤维布为增强材料,通过RTM工艺制备了玻璃纤维增强环氧树脂(GF/EP)复合材料,并研究了RTM工艺制备玻璃纤维布增强环氧树脂(L-GF/EP)和短切玻璃纤维增强环氧树脂(S-GF/EP)复合材料的拉伸和弯曲性能,分析了开孔对两种复合材料拉伸性能的影响。结果表明:在拉伸过程中,开孔试样因孔边产生的应力集中,导致其拉伸强度与无孔试样相比下降了30%左右;玻纤铺层类型的不同对复合材料的力学性能具有显著影响;L-GF/EP复合材料内部结构完整,在载荷作用下,复合材料的弯曲断裂呈现一定的假塑性断裂模式,达到弯曲极限挠度值后,出现一定程度的回弹现象,其力学性能优于S-GF/EP复合材料。     

PA66化学镀Ag、Ni电磁屏蔽材料的制备及性能研究

以PA66(尼龙66)织物为基材,通过预处理后化学镀Ag、Ni的方法制备表面均匀、质量轻、耐蚀性好、屏蔽效能高的复合电磁屏蔽材料。研究了PA66表面化学镀Ag、Ni、Ni-Ag和Ag-Ni,分别用SEM分析了制备材料的表面形貌,用综合物性测量仪测试了磁滞回线(VSM),用法兰同轴测试仪测试了屏蔽效能(EMSE),用电化学工作站测试了材料耐腐蚀性能(Tafel),结果显示PA66-Ag/Ni具有最好的耐蚀效果,该复合电磁屏蔽织物面密度只有66g/m~2,而屏蔽性能最高可达71dB,在同类型低密度电磁屏蔽材料中具有优异的性能。     

镀覆工艺对镀镍铝粉/硅橡胶复合材料电磁屏蔽性能的影响

采用不同镀覆工艺(置换法、还原法和先置换后还原法)制备镀镍铝粉,研究镀覆工艺对镀镍铝粉/甲基乙烯基硅橡胶(MVQ)复合材料电磁屏蔽性能的影响。结果表明:采用置换法制备的镀镍铝粉镍镀层厚度较小;采用还原法制备的镀镍铝粉镀层结合强度较低;采用先置换后还原法制备的镀镍铝粉镀层厚度较大,镀层结合强度较高;采用先置换后还原法制备的镀镍铝粉/MVQ复合材料电磁屏蔽性能优异,在30～3 000 MHz频段内,其电磁屏蔽效能在55～95 dB之间。     

轻质环氧树脂/镀镍碳纤维/乙炔炭黑复合导电泡沫的制备与性能

通过环氧树脂(EP)泡沫泡孔壁和泡孔框架中均匀分布的镀镍碳纤维(NCCF)和乙炔炭黑(ACET)构建有效的导电网络,成功制备了逾渗值仅为0.81%(体积分数)的EP/NCCF/ACET复合导电泡沫。采用化学镀的方法制备得到了NCCF,将NCCF和ACET分散在EP中,作为不同维度的导电填料,两者在基体中具有协同效应,利用化学发泡法制备了轻质的EP/NCCF/ACET复合导电泡沫。通过扫描电子显微镜及电性能、电磁屏蔽性能、力学性能等测试对EP复合导电泡沫进行表征。结果表明,NCCF和ACET在EP泡沫基体中均匀分散,NCCF在泡孔框架中相互搭接,ACET在NCCF间起到桥接作用,两者共同作用形成连续的导电网络。两种填料协同作用能显著提高材料的电性能和电磁屏蔽性能,电导率最高可以达到13.14 S/m,平均屏蔽效能可达到20.7 d B。同时,在一定含量范围内,NCCF的加入能够提升泡沫材料的拉伸性能。     

多层纤维增强环氧树脂复合材料结构设计与电磁屏蔽效能预测模型

构建渐进导电网络结构是一种降低导电材料电磁波反射率的有效策略。利用芳纶纤维(AF)、还原氧化石墨烯负载芳纶纤维(rGO@AF)与碳纤维(CF),制备多层纤维增强环氧树脂复合材料(AF/rGO@AF/CF/EP),研究CF/EP和AF/rGO@AF/CF/EP的电磁屏蔽性能。通过单层纤维的电磁参数和电导率预测,得到多层纤维增强环氧树脂复合材料电磁屏蔽效能的简化模型。结果表明：单层CF/EP的反射损耗效能(SER)为12.3 dB,总电磁屏蔽效能(SE_T)为40.2 dB,与之相比,AF/rGO@AF/CF/EP的SER降至9.6 dB,SE_T提高至43.6 dB,说明梯度导电网络结构在保证材料屏蔽效能的同时降低复合材料的反射损耗。利用简化模型得到AF/rGO@AF/CF/EP的电磁屏蔽效能为42.6 dB,表明该模型准确预测多层结构复合材料的电磁屏蔽性能。     

化学镀在电磁屏蔽织物制备中的应用

介绍了电磁屏蔽材料的屏蔽原理、化学镀的原理及其在电磁屏蔽织物中的应用;重点慨述了镀银、镀铜、镀镍以及镀铜/镍、镀镍/铜/镍、镀铜/镍/银等主要化学镀电磁屏蔽织物及制备方法;提出开发具有环保的化学镀方法、多层镀及复合镀织物将是化学镀电磁屏蔽织物的发展方向.     

玻璃纤维增强环氧树脂复合材料的力学性能研究

本文以环氧树脂为基体,经改性过的短切玻璃纤维为增强材料,制备了玻璃纤维增强环氧树脂(GF/EP)复合材料。探究了玻璃纤维与环氧树脂配比、固化条件对GF/EP复合材料力学性能的影响。结果表明:当玻纤用量为20%、固化温度为120℃、固化时间为3.0 h时制备的GF/EP复合材料拉伸强度约为38.52 MPa、冲击强度约为6.46k J/m2;GF/EP复合材料经60℃、5%的食盐水浸泡48 h后力学性能下降,SEM显示纤维与树脂的粘结界面经腐蚀后被破坏。     

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.     

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.     

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.     

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.