含碳纳米管微波吸收材料的制备及其微波吸收性能研究

用竖式炉流动法,以二茂铁为催化剂,噻吩为助催化剂,苯为碳源通过催化裂解反应制备了碳纳米管,碳纳米管的外径为20-50nm,内径10-30nm,长度50-1000μm.分别以碳纳米管、羰基铁粉、碳纳米管与羰基铁粉的混合物为吸收剂制备了微波吸收材料,研究了上述三种微波吸收材料在2-18GHz的吸波性能,与纯碳纳米管和纯羰基铁粉微波吸收材料相比, 碳纳米管与羰基铁粉复合微波吸收材料在2-18GHz的吸收峰明显向低频移动.在含碳纳米管的微波吸收材料中,碳纳米管作为偶极子在交变电场的作用下,产生极化电流,电磁波的能量转换为其他形式的能量,瑞利散射效应和界面极化也是含碳纳米管微波吸收材料的主要吸波机理.     

碳纳米管复合材料表面化学镀Ni-P合金

用化学镀的方法在多壁碳纳米管表面沉积Ni-P合金,制备了碳纳米管复合材料,并对制备的复合材料进行透射电子显微镜(TEM)和X射线衍射(XRD)表征.通过XRD分析表明,沉积在碳纳米管表面的Ni-P合金是非晶态的.TEM观察复合碳纳米管发现,在其表面沉积有分散均匀的纳米级金属颗粒,Ni-P合金呈球形,粒径大小约为20～30 nm.磁性测试结果为:其矫顽力是412.0 Oe,剩磁比为0.23.     

石墨烯/碳纳米管复合材料的微波吸收性能研究

石墨烯和碳纳米管都是新型纳米尺寸碳材料,具有极大的比表面积、良好的导电性以及优秀的机械性能等特性。通过微波膨化法在石墨烯(寡层石墨)表面空隙结构内生长了碳纳米管,制备出石墨烯/碳纳米管复合材料,碳纳米管不仅可以发挥连接石墨烯层片结构的作用,还可以与石墨烯共同发挥协同吸波效应;同时生长碳纳米管所添加的催化剂在微波状态下分解为纳米磁性颗粒,提高整体复合材料的吸波性能。通过采用SEM、EDX、XRD等对材料的形貌、化学成分进行表征,并用矢量网络分析仪测试了材料在2~18GHz频带内的复介电常数和复磁导率,利用计算机模拟出不同厚度的微波衰减性能。结果表明,材料的电磁损耗机制由电介质损耗、磁损耗共同构成,微波吸收峰随着材料厚度的增加向低频移动,当厚度为2.5mm时,在14.4GHz时最大损耗值为-28dB,并且在频带12.4~17.7GHz的范围内达到-10dB的吸收。     

多壁碳纳米管/环氧树脂复合材料的吸波性能

本文将高温碱处理多壁碳纳米管分散到环氧树脂中制成多壁碳纳米管/环氧树脂吸波复合材料,并研究了该复合材料的微波吸收性能。改变碳纳米管高温碱处理的浓度可以使复合材料的最大吸收峰向高频方向移动,与此同时,吸收峰强度和吸波频宽也有所提高,这对于调整雷达吸波材料的吸波频段、吸波强度和吸波频宽有着十分重要的意义。测试结果还表明,这种新型吸波复合材料的体积电阻率在106~107Ω.cm数量级,具有良好的抗静电的能力。     

镀Al空心玻璃微球FeCo合金/环氧树脂复合材料的吸波性能

利用磁控溅射法对空心玻璃微球表面镀Al。研究了由镀Al空心玻璃微球FeCo合金/环氧树脂制成的复合材料在2~18GHz频段范围内的电磁特性, 利用模型计算了所制备样品的微波反射率。结果表明, 在镀Al空心玻璃微球和FeCo合金粉末总体积分数一定的条件下, 随着镀Al空心玻璃微球与FeCo 合金体积比的增加, 复合材料介电常数实部ε′减小, 虚部ε″ 变化不明显; 磁导率的实部μ′ 和虚部μ″ 均减小; 反射率峰值向高频方向移动。 当 镀Al空心玻璃微球与FeCo合金体积比2∶1时, 涂层厚度为2mm, 吸收峰值达到-29.69dB, 其面密度仅为3.71kg/m2, 吸收率小于-10dB的带宽达到2.4GHz。由此可见, 通过改变镀Al空心玻璃微球与FeCo合金的体积比, 可以调节电磁参数, 提高材料的吸波性能。      

镀镍碳纳米管／PPESK复合材料的制备及微波吸收性能

采用化学镀工艺在多壁碳纳米管表面包覆镍-磷合金,并将其与杂萘联苯聚醚砜酮(PPESK)混合制备吸波复合材料。通过扫描电镜、能量散射光谱对镀镍碳管的形貌和成分进行分析,反射率测试系统对复合材料在8 GHz~18 GHz频段的微波吸收特性进行表征。结果表明,在镀镍过程中使用超声振荡有利于得到均匀的镀层。当吸波样品平均厚度为0.97 mm,碳管含量为5 phr时,镀镍碳管/PPESK复合材料的最大吸收峰在10.9 GHz(RL=-27.5 dB),RL<-10 dB的频宽为4.0 GHz。随着填料含量增加,吸收峰往低频方向移动。     

碳纳米管/三元乙丙橡胶复合材料吸波性能的研究

考察了碳纳米管的介电常数,磁导率以及碳纳米管/三元乙丙橡胶复合材料的电磁吸波性能.研究结果表明,碳纳米管介电常数值远大于磁导率值,且电损耗远大于磁损耗,说明碳纳米管是一种电损耗型吸波介质.通过弓形法测定了碳纳米管/三元乙丙橡胶复合材料在2～18GHz范围内的电磁波吸收性能,结果表明,复合材料在5～18GHz范围内具有较好的微波吸收性能.     

镍钴合金包覆碳纳米管复合材料

采用化学镀法制备了表面镀镍钴的多壁碳纳米管,得到一维纳米复合材料.采用透射电镜、X射线衍射及振动样品磁强计等对镀镍钴碳纳米管的形貌、微结构与磁性能进行了表征,还采用网络矢量分析仪对该复合材料在2～18GHz频段内的电磁参数进行了研究并作了对微波反射率的数值拟合.结果表明:可以通过在碳纳米管表面镀上磁性金属层来调节材料的综合吸波性能,在镍钴比例为6:4的时候,其吸收峰最强,达到-18dB.     

Ni-P化学镀制备钡铁氧体基红外-微波一体化隐身材料

为使钡铁氧体粉末具有红外隐身性能,采用化学镀工艺在钡铁氧体表面镀Ni-P合金,系统研究了化学镀制备工艺对钡铁氧体复合粒子红外发射率的影响.得出了镀Ni-P合金的最佳工艺条件为:硫酸镍30g/L,次亚磷酸钠20g/L,柠檬酸钠70g/L,硫酸铵50g/L,反应温度85℃,pH值为10.0.借助于XRD、SEM等分析测试手段对样品的晶体结构、粒径及表面形貌进行了表征,利用FT-IR的漫反射系统以及矢量网络分析仪对材料的红外发射率和微波吸收性能进行了测试,结果表明:钡铁氧体表面包覆了完整的Ni-P合金镀层;钡铁氧体复合粒子在8～14μm的红外发射率最低降至0.5910,在2～18GHz频段内最大反射率为-24.3dB,大于-10dB的吸收频带宽约2.8GHz,具有良好的红外和微波隐身性能;钡铁氧体复合粒子有望实现红外-微波一体化隐身.     

镀镍碳纳米管的微波吸收性能研究

用竖式炉流动法制备了碳纳米管,碳纳米管的外径40nm～70nm,内径7nm～10nm,长度50μm～1000μm,呈直线型,用化学镀法在碳纳米管表面镀上了一层均匀的金属镍。碳纳米管吸波涂层在厚度为0.97mm时,在8GHz～18GHz,最大吸收峰在11.4GHz(R=-22.89dB),R<-10dB的频宽为3.0Hz,R<-5dB的频宽为4.7GHz。镀镍碳纳米管吸波涂层在相同厚度下,最大吸收峰在14GHz(R=-11.85dB),R<-10dB的频宽为2.23Hz,R<-5dB的频宽为4.6GHz。碳纳米管表面镀镍后虽然吸收峰值变小,但吸收峰有宽化的趋势,这种趋势对提高材料的吸波性能是有利的。碳纳米管作为偶极子在电磁场的作用下,会产生耗散电流,在周围基体作用下,耗散电流被衰减,从而雷达波能量被转换为其它形式的能量。     

碳化硅颗粒填充的碳纳米管/环氧树脂复合材料的吸波性能

以碳纳米管、碳化硅颗粒为原料制备环氧树脂复合吸波材料,并对其吸波性能进行测试,研究了碳纳米管、碳化硅颗粒含量与复合材料吸波性能的关系.结果表明碳纳米管、碳化硅颗粒的含量对复合材料的吸波性能有较大影响.随碳纳米管含量的增加,碳纳米管/环氧树脂复合材料的吸波性能先提高后降低,碳纳米管含量存在最佳值(12%,质量分数).将碳...     

The impact of fluorinated MWCNT additives on the enhanced dynamic mechanical properties of e-beam-cured epoxy

Multi-walled carbon nanotubes were embedded into e-beam-cured epoxy resin to improve the mechanical properties of epoxy resin. The surfaces of these carbon nanotubes were modified using a fluorination treatment to improve their dispersion and adhesion in epoxy resin. The dynamic mechanical properties of epoxy/carbon nanotube composites were investigated at various heating rates and frequencies. As an effect of fluorination treatment, the semi-ionic bond of C–F on the surface of multi-walled carbon nanotubes played an important role in the improved dispersion and adhesion of carbon nanotubes into the epoxy resin. The storage modulus and loss modulus of the composites increased with higher applied frequency. The activation energy of the composites was increased by the effects of a higher heating rate due to the slow heat transfer in the epoxy/carbon nanotube composites. Eventually, the dynamic mechanical properties of the investigated epoxy were significantly improved by the carbon nanotubes dispersed therein via the fluorination treatment.     

复合材料中碳纤维的铺设方式对吸波性能的影响

实验采用东华大学自制的碳纤维作为吸波剂，在基体环氧树脂中平行排列，制备出了吸波复合材料。采用矢量网络分析仪在2~18GHz波段，对复合材料的吸波性能进行测试。结果表明：复合材料的吸波性能不仅与碳纤维含量有关，还与碳纤维在基体中的排列方式有关，当碳纤维含量为3．2％（质量分数）时，吸波复合材料最大反射衰减为-18．64dB，反射率〈-10dB的频率带宽为2．6GHz，同时采用电磁理论对材料的吸收机理进行了探讨。     

Single-walled carbon nanotube incorporated novel three phase carbon/epoxy composite with enhanced properties

In the present work, single-walled carbon nanotubes were dispersed within the matrix of carbon fabric reinforced epoxy composites in order to develop novel three phase carbon/epoxy/single-walled carbon nanotube composites. A combination of ultrasonication and high speed mechanical stirring at 2000 rpm was used to uniformly disperse carbon nanotubes in the epoxy resin. The state of carbon nanotube dispersion in the epoxy resin and within the nanocomposites was characterized with the help of optical microscopy and atomic force microscopy. Pure carbon/epoxy and three phase composites were characterized for mechanical properties (tensile and compressive) as well as for thermal and electrical conductivity. Fracture surfaces of composites after tensile test were also studied in order to investigate the effect of dispersed carbon nanotubes on the failure behavior of composites. Dispersion of only 0.1 wt% nanotubes in the matrix led to improvements of 95% in Young's modulus, 31% in tensile strength, 76% in compressive modulus and 41% in compressive strength of carbon/epoxy composites. In addition to that, electrical and thermal conductivity also improved significantly with addition of carbon nanotubes.     

快速固化碳纳米管/苎麻纤维/环氧树脂复合材料层板的制备与性能

针对植物纤维/树脂基复合材料高性能化问题,本研究以羟基化碳纳米管/无水乙醇分散液预先浸渍苎麻纤维织物,得到了碳纳米管分散均匀的碳纳米管/苎麻纤维多尺度复合织物,并进一步以快速固化环氧树脂为基体,采用真空辅助树脂灌注成型工艺(VARI)制备了碳纳米管改性的苎麻纤维/环氧树脂基复合材料层板(PRFC)。研究结果表明,相比未采用碳纳米管改性的苎麻纤维/环氧树脂复合材料(RFC),PRFC的弯曲强度提高14.7%,冲击强度提高20.9%。相比碳纳米管预先分散于环氧树脂基体中制备的碳纳米管改性苎麻纤维/环氧树脂复合材料(MRFC),PRFC的力学性能提高更显著。同时,PRFC的吸湿性能比MRFC和RFC的明显降低。     

Dispersion and reinforcing mechanism of carbon nanotubes in epoxy nanocomposites

Carbon nanotube based epoxy composites have been fabricated at room temperature and refrigeration process using sonication principle. Flexural moduli, electrical conductivity, glass transition temperature of epoxy resin as well as nanocomposite samples have been determined. Distribution behaviour of carbon nanotubes in the epoxy matrix was examined through scanning electron microscopy. Composite samples showed better properties than resin samples due to strengthening effect of the filled nanotubes. Refrigerated nanocomposites obtained increasing mechanical property because of better dispersion due to low temperature settlement of polymers. Improvement of electrical conductivity was due to the fact that aggregated phases form a conductive three-dimensional network throughout the whole sample. The increasing glass transition temperature was indicative of restricting movement of polymer chains that ascribe strong interaction presented between carbon nanotubes and epoxy chains that was again supplemented by Raman study and SEM.     

镀镍炭毡复合材料的微波吸收特性

用玻璃纤维、镀镍炭毡和高导电性镀镍炭纤维与环氧树脂复合制备了三层结构复合材料证明了镀镍碳毡的吸波性能与镍含量有关；在适当的设计条件下，辅之以少量的炭黑、铁氧体添加剂，可获得较为理想的微波吸收特性