水泥基复合材料的吸波性能

对普通硅酸盐水泥与吸波材料制成的复合材料的吸波性能进行了研究。为军事掩体、军用机场及其它固定军用目标干扰雷达探测找到了一种合适的方法,也为大型建筑物的电磁波防护提供了一种新途径。研究了羰基铁粉、氧化镍和纳米氧化钛3种吸波材料与水泥制成的复合材料的吸波性能,并分析了纳米氧化钛的用量、分散方式及试样厚度对电磁波反射衰减的关系。结果表明：在8～18GHz频率范围内。纳米氧化钛与水泥制成的复合材料的反射率均小于-7dB,在16．24GHz时其反射率达-16．34dB,反射率小于-10dB的带宽达4．5GHz。     

La0．8Ba0．2Mn1-yCuyO3的微波吸收性能

用溶胶-凝胶法制备了La0．8Ba0．2Mn1-yCuyO3系列微粉,测量了部分样品在2～18GHz范围的复介电常数和复磁导率并根据测量数据计算出材料的微波反射率,结果表明La0．8Ba0．2Mn1-yCuyO3系列具有较好的微波吸收性能,当y为0．13时,1．8mm厚时的最大吸收峰值达到28dB,10dB以上的吸收带宽达到3．1GHz;当y为0．17时,1．8mm厚时的最大吸收峰值达到29db,10dB122＆的吸收带宽达到2．5GHz。电磁频谱分析表明La0．8Ba0．2Mn1-yCuyO3以介电损耗为主,同时具有一定的磁损耗。     

钡铁氧体粉末表面化学镀Ni-Co-P涂层的制备及吸波性能(英文)

为了提高钡铁氧体(BaFe12O19)对电磁波的吸收能力,采用化学镀方法在钡铁氧体表面镀Ni-Co-P金属合金涂层,制得了复合粉末材料.利用扫描电子显微镜、能量散射谱和X射线衍射仪分别对镀膜前后的钡铁氧体粉末的微观形貌和结构进行了表征,用矢量网络分析仪测试了镀膜前后钡铁氧体粉末与石蜡混合样品的电磁损耗和微波吸收性能.结果表明:经过活化后的钡铁氧体粉末表面沉积了均匀、致密的Ni-Co-P合金涂层,改性后的钡铁氧体粉末吸波性能显著提高,在2～18GHz频段内,最大反射率为27-2dB,大于-10dB的吸收频带宽约3.6GHz(8.0～11.6GHz).     

微波辐射二氧化碳法制备烟秆基颗粒活性炭

研究了以烟秆废弃物为原料，木焦油为主的复合黏结剂，采用微波辐射二氧化碳法制备颗粒活性炭的可行性．系统探索了微波功率，活化时间以及二氧化碳流量对颗粒活性炭吸附性能和产率的影响，得到了微波辐射二氧化碳法制备颗粒活性炭的最佳工艺条件：微波功率700W，活化时间70min，二氧化碳流量0．15L／min．用此工艺条件制得的颗粒活性炭，碘吸附值为960．30mg／g，亚甲基蓝吸附值13mL／0．1g，产率为43．37％．同时，测定了该颗粒活性炭氮气吸附，通过BET法计算了活性炭的比表面积，并通过DFT表征了活性炭的孔径结果．结果表明，该活性炭为微孔型，BET比表面积为986．65m^2／g，总孔容为0．5152mL／g．     

微波辐射甘蔗渣制造活性炭的试验研究

以ZnCl2为活化剂，采用微波辐射甘蔗渣制备活性炭，研究了微波功率、活化时间、ZnCl2用量与甘蔗渣质量比、干燥功率对活性炭性能的影响。试验的最佳反应条件：ZnCl2与甘蔗渣质量比为2．5：1．0、炭化及活化微波有效功率为35W／g（甘蔗渣，干重）、炭化及活化时间为25min、干燥有效功率为12W／g（活性炭，干重）。在上述条件下制得的活性炭的比表面积为1250m^2／g以上。     

水蒸气活化法制备椰壳活性炭的孔结构特征

以农林废弃物椰壳在600℃炭化2h后的炭化料为原料,以水蒸气为活化剂,研究了活化温度、活化时间、水蒸气用量对活性炭的比表面积、微孔容积和收率等的影响。结果表明：椰壳炭化料的比表面积仅为185m^2／g,且以中孔为主。在活化过程中,通过提高活化温度和水蒸气用量缩短了活化时间,扩宽了孔径;当水蒸气用量和活化温度较为适宜时,延长活化时间,有利于微孔的形成。活性炭的比表面积、总孔容积、微孔容积可达：1465m^2／g,0．9703cm^3/g,0．7519cm^2／g。并通过非定域密度函数理论（NLDFT）对活性炭的孔径分布进行了表征。     

Fe3O4／聚苯胺纳米复合材料的吸波性能研究

以磺基水杨酸（SSA）为乳化剂和掺杂剂,过硫酸铵（APS）为氧化剂,采用乳液聚合的方法合成了导电聚苯胺（PANI）包覆磁性四氧化三铁（Fe3O4）的纳米核-壳复合材料,并对纳米Fe3O4及复合材料进行了XRD、SEM、FT—IR表征。研究了Fe3O4／PANI纳米材料在2～18GHz范围的微波电磁特性与吸波性能,结果表明：复合材料密度为0．12g／cm^3时,其平均衰减为-5dB,最大衰减为-12dB,衰减为-5dB时的频宽可达6GHz。     

多壁碳纳米管/聚苯硫醚管复合材料的电磁性能

采用熔融共混法制备了多壁碳纳米管/聚苯硫醚复合材料,研究了在0.5~18 GHz频段,不同碳纳米管含量对复合材料电磁性能的影响。结果表明,介电常数实部与虚部随着碳纳米管含量的增加而增大, 介电常数实部在测量范围内随频率的增加而减小, 具有明显的频响特性;复合材料的磁导率随多壁碳纳米管含量的增加变化不明显, 呈弱磁性;通过对复合材料反射衰减的计算发现,当吸收层匹配厚度为2 mm 时,复合材料在0.5~18 GHz频段具有较好的微波吸收性能;当碳纳米管含量为7 %（质量分数,下同）时,反射衰减最大达- 31.5 dB ,反射衰减小于- 10 dB的频宽为2.2 GHz。     

导电聚苯胺的合成及电磁学性能、吸波性能研究

分别采用溶液聚合、乳液聚合、正相和反相微乳液聚合法合成了不同掺杂、不同电导率(电导率范围10^-5-10S／cm)的聚苯胺，测试了导电聚苯胺的电磁学参数和吸波性能。结果证明：制得的聚苯胺在2～12GHz范围内有较好的吸波性能，在2．12GHz范围内，雷达波反射率绝对值大于10dB的频宽范围大于7．5GHz，最大吸收率达到30dB。     

聚烯烃纳米级催化剂载体及其纳米复合材料

采用纳米级柱撑插层载体制备烯烃聚合催化剂。载体比表面积为721．23m^2／g，孔体积为0．4536cm^3／g，孔径在4～40nm间分布。所得催化剂比表面积为140．47～300m^2／g，孔体积为0.1519～0．2057cm^3/g及较宽孔径分布1～40nm。对催化剂进行常压聚合考核及其影响因素研究，每克催化剂的活性为20～100g／h,适于烯烃聚合。X射线表征表明其纳米颗粒结构的形成。     

Morphology and microwave absorption of carbon nanotube/bismaleimide foams

Proper dispersion should be guaranteed when using carbon nanotubes (CNTs) as effective absorbents. Physical dispersion methods, such as mechanical mixing, ball milling, and calendering process (three‐roll milling), were adopted to disperse CNTs in the bismaleimide matrix to foam. The effects of the dispersion methods on viscosity, bubble morphology, and microwave‐absorbing properties at 12–18 GHz were studied. The results indicated that, three‐roll milling can more efficiently separate individual CNTs from the agglomerates compared with the other two methods. This method exhibited the highest viscosity, the most irregular cell shape, and the best microwave‐absorbing property. The effects of CNT concentration and foam thickness on the microwave‐absorbing properties were also studied. The reflectivity decreased and the position of the reflectivity peak moved to a lower value with increase in CNT concentration and foam thickness. The foam with 30 mm thickness achieved a reflection loss below ?8 dB over 3.0 GHz in the range of 13.5–16.5 GHz. The minimum value is ?14.2 dB at 14.6 GHz. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40233.     

High electromagnetic wave absorbing performance of activated hollow carbon fibers decorated with CNTs and Ni nanoparticles

Activated hollow carbon fibers (ACHFs) decorated with carbon nanotubes (CNTs) and nickel nanoparticles (CNTs–Ni–ACHFs) were prepared by thermal reduction and chemical vapor deposition technique. Microwave reflection loss, permittivity and permeability of CNTs–Ni–ACHFs composites as novel electromagnetic wave absorbents were studied in the frequency range of 2–18 GHz. It was demonstrated that CNTs–Ni–ACHFs absorbents possessed the best microwave absorbing performances whose minimum reflection loss was −43.457 dB at 13.10 GHz with a thickness of 2.0 mm, which is much better than those of Ni–ACHFs and ACHFs samples. The dielectric polarizations and magnetic loss derived from the effect of the porous structures, Ni nanoparticles, and defects in the CNTs–Ni–ACHFs composites are playing an important role for the excellent microwave absorbing performances.     

聚氨酯泡沫夹层复合材料的制备及其吸波性能研究

根据电磁波阻抗匹配原理,制备了聚氨酯泡沫夹层结构复合吸波材料,研究了不同结构组成对材料吸波性能的影响。实验结果表明:当匹配层中加入质量分数15%的二氧化锰,聚氨酯泡沫夹芯层中加入质量分数5%的二氧化锰和10%的石墨和反射层中加入质量分数35%的石墨时,测试频段为8～18 GHz,聚氨酯泡沫夹层结构复合材料的最大吸收峰为12.9 GHz(R=-35.7 dB),R-10 dB的频宽为1.5 GHz。     

轻薄炭黑涂层的制备及其微波吸收性能研究

利用混合强酸对炭黑(CB)进行氧化处理,并以有机硅树脂为基体制备了CB涂层。通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)、矢量网络分析(VNA)等方法对制备的4种不同填充量的涂层样品进行微观结构和电磁性能表征。微观结构分析表明：CB颗粒尺寸为纳米级,直径大小约为60 nm,氧化处理后的表面形态呈“褶皱”状;制备的CB涂层表面平整、厚度均匀,密度仅为1.1 g/cm3,兼具轻质柔性的特征。微波反射率测试结果显示,在8～18 GHz范围内,涂层样品均表现出了优异的微波吸收性能。当填充量为3.7%时,厚度仅为1.6 mm的涂层有效吸波频宽达到5.13 GHz,吸波强度为-26.5 dB;当填充量为2.3%时,厚度为1.9 mm的涂层有效吸波频宽达到最大值(5.44 GHz),覆盖整个Ku波段,厚度为2.5 mm的涂层有效吸波频宽为4.44 GHz,覆盖整个X波段。     

夹芯型吸波结构耐老化性能研究

选取紫外辐照、湿热及盐雾等典型海洋环境因素,对设计的夹芯型吸波结构开展加速老化实验,对比考核夹芯型吸波结构与吸波贴片的耐老化性能。结果表明:紫外老化15 d后,夹芯型吸波结构面层Q-GFRP的介电常数降幅最大,导致其有效带宽向高频方向削减达0.41 GHz;盐雾老化30 d后,吸波贴片的氧化锈蚀最严重,致使其吸收峰值和有效带宽较老化前分别下降达-6.59 d B,削减达2.40 GHz;得益于Q-GFRP的保护,夹芯型吸波结构的耐老化性能明显优于吸波贴片,且经加速老化处理后,仍可满足水面舰艇在X波段、Ku波段的雷达隐身需求。     

Ecofriendly and cost-effective composites of titanium slag and carbonyl iron for lightweight and tunable microwave absorption

For obtaining the ecofriendly microwave absorbing composites, flake carbonyl iron was mixed to the flotation carbon waste of titanium slag by ball-milling processes. The composites of 4 h ball-milling present excellent microwave absorbing performance of minimum reflected loss (RL) of ?54.9 dB at 7.8 GHz with thickness of 2.6 mm. The same composites provide the performance of RL < ?10 dB with the thickness from 1.2 mm to 5 mm at corresponding matching frequency from 3.3 GHz to 18 GHz. It means that the absorbing peak can be tunable at the wide frequency range with only adjusting the thickness. The strong absorbing intensity and wide tunable frequency range are attributed to the proper impedance matching of dielectric property from flotation carbon waste of titanium slag and magnetic property from carbonyl iron. Also, this work provides a research approach for handling industrial waste which contains carbon.     

壳核结构SiC/C纤维的制备与吸波性能的研究

采用活性碳纤维转换法制备了壳核结构SiC/C纤维,采用拉曼光谱、SEM、XRD以及热重分析等测试方法对比研究了生成SiC的厚度对壳核结构SiC/C纤维样品的热重及吸波性能的影响。结果表明:包裹SiC壳层后样品吸波性能得到提高,样品厚度为3.0 mm时,保温4 h样品的最小反射损耗在8.24 GHz处达到-17.22 dB,低于-10 dB(90%的电磁波被吸收)的频宽在2.0 mm处达到4.8 GHz(11.12~15.92 GHz);保温3 h样品的最小反射损耗在8.23 GHz处达到-14.45 dB,低于-10 dB(90%的电磁波被吸收)的频宽在2.0 mm处达到4.56 GHz(10.88~15.44 GHz);且随着SiC含量的升高,试样微波吸收性能有所增强;制备的壳核结构SiC/C纤维样品起始氧化温度提高了150 ℃以上,并且最终残余质量在50%左右,即包裹SiC纤维后样品的抗氧化能力大大提高。     

RAM-相变微胶囊红外微波隐身复合材料

采用种子微悬浮聚合法,以月桂酸为相变芯材,苯乙烯-二乙烯基苯共聚物为壁材,分别掺杂纳米Fe_3O_4和还原氧化石墨烯(RGO)两种雷达吸波材料(RAM),制备了具有红外微波兼容隐身功能的微胶囊材料(RAM-MCPCM)。采用差示扫描量热仪(DSC)、扫描电子显微镜(SEM)、振动样品磁强计(VSM)和矢量网络分析仪等对材料性能进行了表征。结果表明:RAM-MCPCM微观形貌呈表面微凸球状,仍然具有较高相变潜热;涂层厚度为0.5 mm时,Fe_3O_4-MCPCM[w(Fe_3O_4)=8%]/环氧涂层在5.25 GHz时反射率达到最小值-0.54 d B,RGO-MCPCM[w(RGO)=4%]/环氧涂层在8.8 GHz时反射率达到最小值-1.21 d B,两种涂层在环境温度升高时都具有一定控温作用,具备红外微波兼容隐身性能。     

Microwave absorbing properties of a radar absorbing structure composed of carbon nanotube papers/glass fabric composites

In this study, carbon nanotube papers were employed in fabricating thin and broadband radar absorbing structures (RAS). Different concentrations of the CNT papers have been made by using a vacuum filtration method, with 20 × 20 cm in size and 21-27 μm in thickness. An epoxy resin was added into the CNT paper and then cured to become a composite with 1-5 wt.% of CNTs and 83-309 μm in thickness. The complex permittivity and permeability (ε′, ε″, μ′, μ″) of the CNT paper composites were measured using the transmission/reflection method in the frequency range of 2-18 GHz. The results reveal that the real (ε′) and imaginary (ε″) parts of the complex permittivity are increased with the CNT concentration. The ε′ of 5 wt.% CNT sample reaches 323 at 2 GHz and then decreases to 49.0 at 18 GHz. The ε″ reaches 321 at 2 GHz and decreases to 26.0 at 18 GHz. The CNT paper composite combined with a glass fabric composite used for a dielectric spacer is fabricated for an innovative RAS and the reflection loss is measured using the arch method in a microwave anechoic chamber. The results show that the 5 wt.% CNT paper composite/glass fabric composite absorbers attain maximum reflection loss of −13.3 dB at 12.0 GHz, −13.8 dB  at 10.0 GHz, and −16.0 dB at 7.5 GHz for spacer thickness of 1.5, 2.0, and 3.0 mm, respectively.     

Synthesis and microwave absorbing characteristics of flake‐like polypyrrole filled composites in X‐band

Polypyrrole (PPy)/montmorillonite (MMT) nanocompounds were prepared by in situ chemical oxidative polymerization of pyrrole in the presence of MMT. The results indicate PPy is intercalated into MMT interlayers and the morphology of obtained PPy in nanocompounds is changed to flake‐like rather than granular particles as pristine PPy. The resultant PPy/MMT nanocompounds and pristine PPy were used as microwave absorbing filler separately to prepare microwave absorbing PPy/MMT and PPy epoxy composites. The results indicate PPy/MMT epoxy composites exhibit much better microwave absorbing properties than those filled by pristine PPy. The maximum reflection loss of 20 wt% PPy/MMT filled composite is −32.63 dB at 10.55 GHz with a matching thickness of 2.8 mm, and the effective absorption bandwidth with the reflection loss below −10 dB is from 8.6 GHz to 12.4 GHz, which almost covers the whole X‐band. We postulated that the morphology change of PPy in PPy/MMT and its better dispersion may be responsible for the enhancement of microwave absorption. POLYM. COMPOS., 37:532–538, 2016. © 2014 Society of Plastics Engineers