The Study on the Conductivity Performance and Shielding Effectiveness of Electro-magnetic Radiation of Polyethylene Film with Different Content of Carbon Black Particles

With the help of the testing apparatus made by ourselves for shielding electromagnetic radiation, the electric conductivity and shielding effectiveness of electromagnetic radiation of polyethylene film contained different content of carbon particles was systematically studied in this paper. The results indicate that the electric conductivity and shielding effectiveness of electromagnetic radiation of polyethylene /carbon film have closely relations with content of carbon black particles, which exists a critical content value as 14%～30% and its properties will have a tremendous change.

Calculation of photon shielding properties for some neutron shielding materials

The objective of the present study is to calculate photon shielding parameters for seven polyethylene-based neutron shielding materials. The parameters include the effective atomic number(Z_(eff)), the effective electron density(N_(eff)) for photon interaction and photon energy absorption,and gamma-ray kerma coefficient(kc). The calculations of Z_(eff)are presented as a single-valued and are energy dependent. While Z_(eff)values were calculated via simplistic powerlaw method, the energy-dependent Z_(eff)for photon interaction(Z_(PI-eff)) and photon energy absorption(Z_(PEA-eff)) are obtained via the direct method for energy ranges of 1 keV–100 GeV and 1 keV–20 Me V, respectively. The kccoefficients are calculated by summing the contributions of the major partial photon interactions for energy range of 1 keV–100 MeV. In most cases, data are presented relative to pure polyethylene to allow direct comparison over a range of energy. The results show that combination of polyethylene with other elements such as lithium and aluminum leads to neutron shielding material with more ability to absorb neutron and crays. Also, the kerma coefficient first increases with Z of the additive element at low photon energies and then converges with pure polyethylene at energies greater than 100 keV.

Correlation between Electrical Conductivity and Microwave Shielding Effectiveness of Natural Rubber Based Composites, Containing Different Hybrid Fillers Obtained by Impregnation Technology

The paper presents the synthesis and characterization of carbon black/silicone dioxide hybrid fillers obtained by an impregnation technology. The electromagnetic interference shielding effectiveness of the composites filled with carbon black/silicone dioxide hybrid fillers was measured in wide frequency range of 1 - 12 GHz. The dc and ac electrical conductivity of composites also have been investigated. The relationship between electrical (dc and ac) conductivity and shielding effectiveness was analyzed. A positive correlation was found between the absorptive shielding effectiveness and ac conductivity for composites comprising conductive carbon black/silica filler, when the filler loading is above the percolation threshold.

Microwave Absorption and Shielding Property of Composites with FeSiAl and Carbonous Materials as Filler

Silicone rubber composites filled with FeSiAI alloys and multi-walled carbon nanotubes （MWCNT）/graphite have been prepared for the first time by a coating process. The complex permittivity and permeability of the composites were measured with a vector network analyzer in a 1-4 GHz frequency range, and the DC electric conductivity was measured by a standard four-point contact method. These parameters were then used to calculate the reflection loss （RL） and shielding effectiveness （SE） of the composites. The results showed that the added MWCNT increased the permittivity and permeability of composites in the L-band, while the added graphite increased only the permittivity. The variation lies in the interactions between two carbonous absorbents. Addition of 1 wt% MWCNT enhanced the RL in the L-band （minimum -5.7 dB at 1 ram, -7.3 dB at 1.5 ram）, while the addition of graphite did not. Addition of MWCNT as well as graphite reinforced the shielding property of the composites （maximum SE 13.3 dB at 1 ram, 18.3 dB at 1.5 ram） owing to the increase of conductivity. The addition of these carbonous materials could hold the promise of enforcing the absorption and shielding property of the absorbers.

Basic solutions of multiple parallel symmetric mode-III cracks in functionally graded piezoelectric/piezomagnetic material plane

The Schmidt method is adopted to investigate the fracture problem of multiple parallel symmetric and permeable finite length mode-III cracks in a functionally graded piezoelectric/piezomagnetic material plane. This problem is formulated into dual integral equations, in which the unknown variables are the displacement jumps across the crack surfaces. In order to obtain the dual integral equations, the displacement jumps across the crack surfaces are directly expanded as a series of Jacobi polynomials. The results show that the stress, the electric displacement, and the magnetic flux intensity factors of cracks depend on the crack length, the functionally graded parameter, and the distance among the multiple parallel cracks. The crack shielding effect is also obviously presented in a functionally graded piezoelectric/piezomagnetic material plane with mul- tiple parallel symmetric mode-III cracks.

Analysis of Mode-Ⅰ Crack Tip Shielding by Microcracking in Brittle Materials

The stress shielding effect of profuse microcracks at the tip of a macroscopic stationary mode Ⅰ crack is studied. The analysis method adopted combines the micromechanical approach with the effective elastic medium approach. The anisotropic constitutive relation of the effective elastic medium is based on the DMG damage model developed by the authors for microcrack weakened brittle materials undergoing damage in form of elastic modulus degradation as a result of stable microcrack growth. The stress and strain fields at the crack tip and the condition of path independence of J integral in the damage zone are discussed under some reasonable approximations. A modified J integral method is thereby proposed to calculate the ratio of near tip to remote stress intensity factors and compared with the conventional method of J conservation.

碳化硼/铅/聚乙烯复合材料的热稳定性及屏蔽性能

制备了质量分数3%、4%、5%及6%碳化硼以和不同厚度的碳化硼/铅/聚乙烯复合材料,并对碳化硼/铅/聚乙烯复合材料的热稳定性和屏蔽性能进行了研究。经测试可知:当不同试样处于同一厚度时,添加质量分数6%碳化硼复合材料的高温基础性能较好;热重测试表明,该试样的质量损失较低,有效保持了其基础性能。同时,添加质量分数为6%碳化硼的复合材料的应用效果最佳,具有较好的粒子屏蔽性能。该结果为碳化硼/铅/聚乙烯复合材料的制备和性能评估提供了可靠的依据。

乙烯基非交联电缆屏蔽料性能与分散剂含量关系研究

非交联绝缘材料具有优异的电气机械性能,同时生产能耗少、可回收利用,成为目前电缆绝缘料的研究热点,但与之匹配的非交联半导电屏蔽料的研究还鲜有报道。导电炭黑的分散性对屏蔽料的性能影响重大。文中选用线性低密度聚乙烯(LLDPE)为基体树脂,白油为分散剂,采用熔融共混法制备了非交联电缆屏蔽料。研究了白油含量对屏蔽料中炭黑分散、结晶性能、体积电阻率和机械性能的影响。结果表明添加白油会促进炭黑的分散,但白油含量过大会降低屏蔽料的结晶度,增加其体积电阻率并降低拉伸强度和断裂伸长率。当白油含量为2 wt%时,屏蔽料体积电阻率最小,力学性能最佳。该研究为非交联半导电屏蔽料在乙烯基非交联电缆的应用研究提供了参考。

高压电缆半导电屏蔽材料双逾渗网络对电阻率稳定性的影响

半导电屏蔽材料是制造高压电缆的关键组分,但仍存在电阻率高及其稳定性差难题。基于此,该文提出构筑双逾渗网络结构思路,选择乙烯-丙烯酸丁酯共聚物(ethylene-butyl acrylate copolymer,EBA)和低密度聚乙烯(low density polyethylene,LDPE)作为基体、导电炭黑(conductive carbon black,CB)作为导电填料制备半导电屏蔽材料,系统研究半导电屏蔽材料结构演变规律,评价半导电屏蔽材料结晶行为、电学性能、力学性能、表面光洁度等关键性能。实验结果表明:EBA与LDPE质量比为6:4时,半导电屏蔽材料内部形成双逾渗导电网络结构,相比于常规分布结构,其23和90℃的体积电阻率分别降低46.7%和74.4%,对应的正温度系数(positive temperature coefficient,PTC)降低52.1%,表明具有良好的电阻率稳定性。此外,该半导电屏蔽材料还具有优异的力学性能和表面光洁度。该结果可为高压电缆半导电屏蔽材料开发提供一定理论基础与数据支撑。

空间辐射屏蔽材料研究进展

银河宇宙射线、太阳宇宙射线、辐射带等辐射环境会对元器件、航天员等产生各种空间辐射效应,威胁航天器的正常工作以及航天员的生命健康。材料屏蔽是目前最有效的辐射防护措施之一,对保障航天任务的顺利进行有着重要的作用。本文针对元器件、航天员以及飞行器平台防护3类典型对象,梳理不同场景下空间辐射屏蔽材料研究进展,并对金属复合材料、聚合物材料等空间辐射屏蔽材料的发展方向进行探讨。

超高分子量聚乙烯纤维表面金属化改性及应用

超高分子量聚乙烯(ultra-high molecular weight polyethylene,UHMWPE)纤维及织物因表面呈化学惰性且高度结晶,导致其与复合材料基体之间的界面结合力弱,影响复合材料性能.为增强纤维表面活性,通过无电沉积金属铜的方法实现UHMWPE纤维表面金属化改性,制备UHMWPE-Cu复合纤维,分别考察金属镀层对UHMWPE纤维的形貌、晶体结构、表面粗糙度和电导率等性能的影响,并研究UHMWPE-Cu复合纤维与聚氨酯树脂基体之间的界面黏接性能和抗穿刺性能.结果表明,无电沉积金属化赋予了纤维良好的导电性能,电导率可达660.79 S/cm.同时,金属化增加了纤维的表面活性,提高了纤维与树脂基体之间的界面黏接性能.UHMWPE纤维可增强聚氨酯复合材料的剥离强度,相对于未改性纤维样品提高了108%.此外,UHMWPE纤维的金属化也显著提高了其复合材料的抗穿刺性能,与未改性样品相比,改性的样品抗穿刺性能提升了35%.金属化还大幅度提高了复合材料的电磁屏蔽性能,电磁屏性能可达53 dB,远优于屏蔽应用的合格电磁干扰强度值(20 dB).UHMWPE纤维表面金属化在电磁屏蔽上具有广阔的应用前景.

盾构穿越岩溶复合地层注浆充填技术研究

针对盾构穿越岩溶复合地层处治难题,结合南京市和燕路过江通道江南幕府山段工程建设实践,对盾构穿越岩溶复合地层工况中复合地层特征及治理技术进行研究,研发了适用于岩溶复合地层治理区域的新型注浆充填材料,形成固体废弃物注浆材料工业制备工艺;设计了基于时空效应的注浆治理方法,形成了深部地层长距离控域注浆治理关键技术;基于关联度判别准则的注浆效果评价可拓理论模型,对注浆治理效果进行科学检验与评价,形成了盾构穿越岩溶复合地层协同控灾关键技术。最终形成盾构穿越岩溶复合地层治理体系,具有显著的技术经济效益。

PP/PC光扩散材料的制备及其抗紫外性能优化

采用实验室自制的密炼机制备了聚丙烯(PP)/聚碳酸酯(PC)共混材料,通过形貌分析、流变测试、拉伸试验、缺口冲击强度测试、光学测试等对复合材料的微观形貌、流变性能、力学性能和光学性能进行了表征,并研究了2-(2’-羟基-5’-甲基苯基)苯并三唑(UV-P)填充PP/PC复合材料的抗紫外性能。结果表明,在透光性和雾度的耦合性能方面,PC相含量存在一个阈值;在抗紫外性能方面,UV-P的添加量存在一个阈值。当PC含量为3%(质量分数,下同)时,所制备的共混物的拉伸强度为30.40 MPa,抗冲击强度在44.85 J/m;在添加0.1份UV-P之后,紫外光区域的平均透过率为1.04%,此时的透光率为83.39%,雾度为93.65%,制备的复合材料具有良好的散射效果,且对紫外光线有强烈的吸收作用。

边界形变互耦混响室屏蔽效能测试技术研究

为了解决混响室环境下屏蔽效能测试存在的系统结构复杂和测试结果误差大等问题,使用边界形变代替机械搅拌、互耦混响室代替嵌套混响室、柔性屏蔽布代替金属壳体等方法,提出了一种基于边界形变技术的互耦混响室屏蔽效能测试方法,简化了测试装置,增加了使用频率带宽。通过对混响室内部功率密度归一化处理,提出了混响室条件下屏蔽效能定义新方法,修正了测试装置、受试材料加载等对混响室内电场分布的影响,提高了测试的准确性。试验研究了研制的边界形变互耦混响室屏蔽效能测试系统的有效性,并探索了接收天线位置及指向对复合材料屏蔽效能测试结果的影响规律。研究发现研制的屏蔽效能测试系统动态范围为60~90 dB,内部电场标准偏差均小于3 dB,可以用于屏蔽效能测试;受试复合材料在1~10 GHz频率范围内屏蔽效能均值在28~34 dB之间波动,5组测试数据的最大标准偏差为1.96 dB,变异系数小于8.05%,测试结果重复性好。

PE基屏蔽材料阻燃性能及力学性能研究

采用3种无卤无硫绿色阻燃剂,制备了聚乙烯(PE)基屏蔽材料,研究了阻燃剂种类和用量对PE基屏蔽材料阻燃性能的影响,通过均匀试验设计方法确立了最佳阻燃剂配方,研究了屏蔽功能材料种类和用量对PE基屏蔽材料极限氧指数和力学性能的影响。结果表明:3种阻燃剂中,膨胀型无卤阻燃剂对PE基屏蔽材料极限氧指数的提升作用最大;增加屏蔽功能材料用量有利于阻燃层的形成和稳定,进而改善PE基屏蔽材料的阻燃性能,提升其力学性能。

微观结构视角下的Ti_(3)C_(2)T_(x) MXene基电磁波复合屏蔽/吸收材料研究及进展

电子设备的迅速发展和广泛使用产生了大量电磁波,不仅影响其他电子设备的正常运行,还对人类健康造成危害。高性能电磁干扰屏蔽(EMI)和电磁波吸收(EMA)材料对控制电磁污染、保护人体和其他系统在民用或军事应用中至关重要。作为一种新型的二维材料,MXenes因具有特殊的层状结构、高比表面积、丰富的天然缺陷和特殊的金属特征,近年来在电磁屏蔽和微波吸收领域引起了广泛关注。主要介绍了Ti_(3)C_(2)T_(x) MXene的合成方法和特点,并总结了近年来它在电磁屏蔽和微波吸收性能方面的最新研究和应用。主要创新点在于重点介绍Ti_(3)C_(2)T_(x) MXene的合成工艺、结构设计以及引入不同材料形成不同复合材料对其电磁性能的影响。

飞机雷电耦合机理及屏蔽性能影响因素分析

复合材料飞机的雷电间接效应防护是现代飞机亟需解决的难点问题之一。通过建立等效电路研究雷电对飞机的不同电磁耦合机理,分析复合材料飞机在蒙皮敷设金属网的屏蔽性能及影响因素,并通过对比实际情况,验证所提金属网体积计算方法的有效性。理论分析与仿真计算结果表明,在蒙皮表面敷设金属网可为复合材料飞机提供有效雷电防护,且金属网参数对屏蔽性能影响较大。此外,提出的金属网体积及感应电流计算方法,可为复合材料飞机雷电间接效应屏蔽性能的进一步优化提供参考。

PE/CNT复合材料对空间质子的屏蔽效能仿真分析

随着遥感卫星对观测精度需求的增长,国内外积极探索新型高效质子防护材料。为研究聚乙烯掺杂碳纳米管屏蔽质子效能,本文利用Geant4软件开展质子屏蔽仿真,探究碳纳米管掺杂浓度、管壁直径、排布方式和管壁层数对复合材料质子屏蔽效能的影响规律,并与纯聚乙烯进行对比分析。结果表明,质子屏蔽效能对掺杂浓度、管壁直径和排布方式较敏感,受管壁层数影响相对较小;在高掺杂浓度、大管壁直径和规则排布的情况下,复合材料表现出更优异的质子屏蔽效能;相同质量厚度下,碳纳米管掺杂浓度为10%和20%的复合材料质子屏蔽后的电离剂量分别比纯聚乙烯最大降低了7.40%和12.83%。本文研究结果为辐射防护材料设计提供了数据支撑。

ZnO/Fe_(3)O_(4)复合涂层织物的制备及电磁屏蔽性能研究

采用平纹纯棉织物为基布,聚氨酯为粘结剂,通过涂覆的方法制备ZnO/Fe_(3)O_(4)复合涂层织物。研究不同涂料种类对涂层织物电磁屏蔽性能的影响,分别使用X射线衍射仪、扫描电子显微镜和矢量网络分析仪对样品的物相结构、微观形貌和屏蔽性能进行了测试。结果表明由于介电损耗和磁损耗的协同效应,ZnO/Fe_(3)O_(4)复合涂层织物在X波段(8.2~12.4 GHz)内显示出较好的电磁屏蔽性能,屏蔽效能SE最高可达10.98 dB,最佳SSE/t值为256.5 dBcm^(3)/g。

中子和伽马射线综合屏蔽材料研究进展

核屏蔽设计的主要任务是屏蔽中子和γ射线,因此,兼具中子和γ射线综合屏蔽性能的屏蔽材料无疑是核屏蔽设计时的最佳选择。本文主要针对中子和γ射线综合屏蔽材料的种类、基质材料和性能进行了分析和综述,探讨了现有中子和γ射线综合屏蔽材料存在的主要问题,认为屏蔽材料的屏蔽性能与其他性能(如力学性能、耐热性等)之间的矛盾是屏蔽材料需要解决的关键问题。最后,展望了未来中子和γ射线综合屏蔽材料的研究方向,指出结构功能一体化屏蔽材料的研究应用是未来一大发展趋势。