(SiC)p表面低成本化学改性的研究

为解决裸(SiC)P在应用中存在的不足,提出(SiC)P表面低成本化学改性的思路.采用简单的化学镀技术,改进氧化、亲水、敏化和活化的前处理工艺,对(SiC)P进行表面化学改性.确定了最佳的试验工艺,获得了镀层连续、无光滑(SiC)P裸露的较高质量的碳化硅复合粉体[简写为(Ni/SiC)P],通过SEM、EDS、XRD、TEM等测试,结果表明:改性后的(Ni/SiC)P较改性前的(SiC)P导电性有所提高,形貌、组成发生改变.同时分析了热处理对(Ni/SiC)P的影响,结果表明:随着温度的升高,(Ni/SiC)P表面改性层中的镍由非晶态转化为晶态.     

Ni/ZrO_2复合材料力学及介电性能研究

采用热压烧结方法,以氧化钇部分稳定氧化锆(Y-PSZ)粉体及不同粒径的金属Ni为原料,制备了Ni/ZrO2复合材料,研究了其力学和介电性能,探讨了烧结过程中Ni形貌的变化对复合材料介电性能的影响.结果表明,随不同粒径Ni粉的掺入,复合材料的抗弯强度减小,且较大粒径的Ni使材料抗弯强度减小更快.随Ni含量增加,复合材料断裂韧性增强.复合材料的介电常数和损耗与Ni粉含量和粒径有关.Ni含量相同时,较大粒径Ni粉的掺入使复合材料具有较高的介电常数和损耗,这是由于在烧结过程中Ni粉形貌发生变化引起的.     

热压烧结SiC/CCTO陶瓷电容器的工艺和性能

首先采用固相法合成CaCu_3Ti_4O_(12)(CCTO)粉体,与SiC粉体均匀混合后,采用真空热压制备了SiC/CCTO复合陶瓷电容器.采用DSC-TG技术分析了SiC/CCTO复合粉体的热行为,采用XRD、SEM等手段对样品进行表征,研究了SiC/CCTO复合陶瓷电容器的介电性能,并对其介电机理进行了探讨.结果发现,在950 ℃和 30 MPa的热压条件下制备出的 SiC/CCTO复合陶瓷电容器具有最高的介电常数ε_r≈3×10~8(1 kHz),分析认为其介电机理属于阻挡层机制,载流子在SiC与CCTO界面处聚积,形成空间电荷极化.     

泡沫铝基多孔金属复合材料吸波性能

采用雷达截面法研究表面涂覆吸波涂料的泡沫铝复合材料的吸波性能,讨论电磁波频率和吸波涂料种类对材料吸波性能的影响。结果表明,材料的吸波性能随频率的增加而增加;表面涂覆磁介质型吸波涂料的泡沫铝复合材料的吸波性能较佳,在12.0-18.0 GHz频段内样品CFe的吸波性能最好,而在26.5-40.0 GHz频段内样品CNi′的吸波性能最好。     

钴-铁沉积碳化硅颗粒及其吸波性能

目的提高碳化硅微粒的微波吸收性能。方法利用改进的化学镀法,以硫酸钴和硫酸亚铁为主盐,次亚磷酸钠为还原剂,施镀温度为50℃,使用机械搅拌和超声分散相结合的方法,在预处理后的微米碳化硅颗粒表面沉积钴铁合金。通过X射线衍射仪(XRD)、X射线能谱仪(EDS)和扫描电子显微镜(SEM)分别对化学镀前后材料的结晶状态、组成成分和形貌特征进行了表征;利用矢量网络分析仪对化学镀前后材料在2~18 GHz频率范围内的电磁性能进行了测试,并通过计算得到了材料微波反射率损耗。结果钴铁合金呈微球状均匀沉积在碳化硅表面,有效地改善了碳化硅材料的电磁性能和微波吸收性能。碳化硅的介电常数虚部存在界面极化和缺陷极化两个弛豫峰(9.1、13.8 GHz),而沉积钴铁合金后,碳化硅材料Co-Fe/SiC增加了两个弛豫峰:介电弛豫峰(11.7 GHz)和磁弛豫峰(12.6 GHz)。正是由于Co-Fe合金对微波信号的介电弛豫和磁弛豫,有效提升了材料的吸波性能。当吸波层厚度为2.4 mm时,反射率在10 dB以上的吸收带宽达到3.8 GHz,20 dB带宽可以达到1.5 GHz。当吸波层厚度为2.3 mm时,频率为12.7 GHz时达到最大吸收峰值–43 dB。结论在碳化硅材料表面沉积钴铁合金是一种有效改进材料微波吸收性能的方法,且该材料是一种高效、宽频的微波吸收材料。     

一种具有宽频吸波性能的环氧树脂基夹层复合板设计与制备

本文设计和制备了一种在C波段上具有宽频吸波性能的夹层复合材料,并用同轴电缆法和矢量网络分析仪分析了复合材料板的电磁参数和反射率。复合材料板厚度5mm,板表层与底层为玻璃纤维/环氧树脂复合材料,以“Fe50Ni50粉体/丁基橡胶纳米复合材料”为中间夹层。采用液相还原法制备了粒径约为100nm的球形Fe50Ni50粉末,采用二步共混法制备了Fe50Ni50 /IIR复合材料。研究表明, Fe50Ni50粉体/IIR纳米复合材料在2~18GHz频带上以磁损耗为主。表层与夹层的匹配是获得宽频吸波特性的关键,可以通过调整表层与夹层的厚度获得良好的吸波性能。当复合材料板厚度为5mm、夹层厚度为2mm时,板的R≤-10dB的吸波频带为5.6GHz~7.6GHz和16.8GHz~18GHz,吸波带宽达到3.2GHz,该材料在C波段吸波带宽达到2GHz,取得了突破。     

MWCNTs/TiO2复合粉体的制备及空间吸波模型研究

本文通过球磨法将MWCNTs和TiO2进行混合得出复合粉体,并用XRD、SEM、网络矢量分析仪对复合粉体进行表征,利用数值模型进行理论计算分析其空间吸波特性。研究结果表明加入无水乙醇湿混合的MWCNTs/TiO2复合粉体中的MWCNTs分散性较好;湿混合的MWCNTs/TiO2复合粉体在2～18GHz频段的波阻抗匹配特性和空间吸波能力更佳,为复合吸波材料的实际应用提供了理论参考。     

石墨烯/SnO2纳米纤维复合材料的制备及吸波性能的研究

采用静电纺丝、超声混合和热处理等方法制备石墨烯/SnO_2纳米纤维复合材料,然后使用X射线衍射(XRD)、电子显微镜(SEM/TEM)和矢量网络分析仪(VNA)等设备对其微观结构和吸波性能进行表征。结果表明:当厚度为3.0mm时,石墨烯/SnO_2纳米复合纤维材料在11.7GHz频率下的反射损耗(RL)可以达到极值-48.1dB,且低于-10dB的频宽可以达到6.1GHz。由于RL值低于-10dB,表示超过90%的入射电磁波可以被吸收,故石墨烯/SnO_2纳米纤维复合材料具有较好的吸波性能。     

MWCNTs/TiO_2复合粉体的制备及空间吸波模型研究（英文）

通过球磨法将MWCNTs和TiO_2进行混合得出复合粉体,并用XRD、SEM、网络矢量分析仪对复合粉体进行表征,利用数值模型进行理论计算分析其空间吸波特性。结果表明,加入无水乙醇湿混合的MWCNTs/TiO_2复合粉体中的MWCNTs分散性较好;湿混合的MWCNTs/TiO_2复合粉体在2～18 GHz频段的波阻抗匹配特性和空间吸波能力更佳,为复合吸波材料的实际应用提供了理论参考。     

BaFe_(12)O_(19)/BaTiO_3复合材料的制备及微波性能

采用溶胶凝胶法制备了钛酸钡(BaTiO_3, BTO)和钡铁氧体(BaFe_(12)O_(19), BFO)复合粉体.研究了该粉体的结晶情况、相结构、形貌及吸波性能.XRD结果表明,复合粉体的相结构与BFO粉体的相结构接近,但与BTO含量和烧结温度密切相关.SEM结果表明,复合粉体由微米晶粒和纳米晶粒组成,随着烧结温度的升高颗粒尺寸增大.吸波性能测试表明,粉体在500 MHz～18 GHz频率范围有多个吸收峰,BTO的加入明显改善了材料的吸波性能.     

热解碳涂层对Al_2O_3纤维编织体介电及吸波性能的影响(英文)

采用化学气相沉积法在Al2O3纤维编织体上沉积热解碳涂层,利用SEM及激光拉曼光谱表征沉积与未沉积热解碳界面层的纤维编织体,并研究热解碳沉积时间对纤维电导率及编织体X波段介电吸波性能的影响。结果表明:纤维电导率及编织体复介电常数随着热解碳沉积时间的延长而增大。电子松弛极化引起复介电常数实部的增大,电导损耗引起虚部的增大。热解碳涂层可以改善Al2O3纤维编织体的吸波性能,对于沉积60min热解碳涂层的编织体,反射率在9.5GHz附近达到-40.4dB,吸波频带接近4GHz.     

玻璃包覆FeSiBNbCu非晶丝的微波吸收性能(英文)

制备以石蜡为基体并具有玻璃包覆Fe73.5Si13.5B9Nb3Cu1非晶丝不同填充比的同轴介电样品,在相对较高的微波吸收频段(2~18 GHz)下研究短丝填充比(质量分数3%~9%)和样品厚度(1~7 mm)对同轴介电样品的微波吸收性能的影响规律。采用X射线衍射谱(XRD)、差示扫描量热分析(DSC)、扫描电子显微分析(SEM)和矢量网格分析仪(SNA)表征材料的微结构并评价其吸波性能。结果表明,不同填充比的同轴介电样品的复磁导率和复介电常数存在重要的频率范围(6~18 GHz)。模拟结果显示,具有3 mm厚度和7%填充比的样品具有较好的微波吸收性能,其反射率在14 GHz时达到峰值-34 dB。这对于开发具有更宽微波吸收范围应用的微丝介电材料是十分有益的。     

Effect of Critical Plasma Spray Parameters on Microstructure and Microwave Absorption Property of Ti<Subscript>3</Subscript>SiC<Subscript>2</Subscript>/Cordierite Coatings

Ti₃SiC₂/cordierite coatings with different critical plasma spray parameters (CPSP) were fabricated via atmospheric plasma spraying method. The microstructure and phase constitution of the as-sprayed Ti₃SiC₂/cordierite coatings were characterized. The effects of CPSP conditions on the electromagnetic shielding, and dielectric and microwave absorption properties of coatings in the frequency of 8.2-12.4 GHz were also measured and investigated. The results showed that both real and imaginary part of the complex permittivity decrease with increasing CPSP values, which can be ascribed to the decomposition of some Ti₃SiC₂ into TiC. The calculated reflection loss of the as-sprayed Ti₃SiC₂/cordierite coatings with different CPSP conditions and thicknesses indicates that coatings with CPSP 0.3, 0.35, and 0.425 exhibit excellent microwave absorption property in the thickness of 1.5 mm. In order to broaden the bandwidth of the coatings, a double-layer coating system was designed. The calculated reflection loss results show that when the thickness of matching layer is 0.3 mm and the thickness of absorbing layer is 1.5 mm, the double-layer coating system shows a proper microwave absorption property with a minimum absorption value of ?17.37 dB at 9.67 GHz and a absorption bandwidth (RL less than ?5 dB) of 4.16 GHz in the investigated frequency.     

Preparation and microwave absorption properties of Ni(Co/Zn/Cu)Fe_2O_4/SiC@SiO_2 composites

Ni(Co/Zn/Cu)Fe_2O_4/SiC@SiO_2, a microwave absorber, was prepared by the sol-gel method. The phase structure and the morphology of the microwave absorbers were characterized by X-Ray Diffraction(XRD) and scanning electron microscopy(SEM), respectively. Laser sizer(LS) and X-ray photoelectron spectroscopy(XPS) analysis show the core-shell structure of SiC@SiO_2. Coaxial method was used to measure the microwave absorption properties of the prepared composites in the frequency range of 2-18 GHz. When 70 wt% SiC is wrapped by 30 wt% SiO_2,and 50 wt% NiFe_2O_4 is added into 50 wt% SiC@SiO_2, the as-prepared powders are found to have advanced microwave absorption properties with a minimum reflection loss(RL) of -32.26 dB at about 6.08 GHz, and the available bandwidth is approximately 2.1 GHz when the RL is below -10 dB.     

Nd元素对Ce2Co17为基体的合金吸波性能的影响

目前,具有高效、宽、薄等特点的微波吸收材料已经引起了研究人员的广泛关注。在此文中,采用真空电弧熔炼和高能球磨法制备片状NdxCe2-xCo17合金粉末并且通过相关设备研究Nd含量和匹配厚度对相组成、形貌、电磁参数和微波吸收性能的影响。结果显示,Nd0.3Ce1.7Co17粉末的最大反射率可以达到-32.36dB,同时有效带宽能扩大4倍。此外,调整Nd含量能成功优化Ce2Co17合金粉末的微波吸收性能。随着Nd含量的增加,吸收峰有向低频段移动的趋势,并且当厚度为1.8mm时,Nd0.3Ce1.7Co17 粉末在7.28 GHz处,最大反射率可以达到-30.53 dB并且有效带宽为2.24 GHz,这些表明Nd-Ce-Co合金可以用作在C波段具有低厚度、宽频和高效等特点的理想吸收材料。     

Full X-Ku band microwave absorption by Fe(Mn)/Mn7C3/C core/shell/shell structured nanocapsules

New type of Fe(Mn)/Mn₇C₃/graphite nanocapsules was prepared by a modified arc discharge technique in ethanol vapor, with Fe(Mn) solid solution nanoparticles as the core, Mn₇C₃ as the inner shell, and graphite as the outer shell. The Cole-Cole semicircle approach was adopted to explain the ternary dielectric resonance, due to a cooperative consequence of the core/shell/shell interfaces and the dielectric Mn₇C₃ and C shells. A remarkable increase in the anisotropy energy led to a shift in the natural resonance frequency to 6.6 GHz. Dielectric losses come from the ternary dielectric resonance while magnetic losses were from the magnetic natural resonance. An optimal reflection loss (RL) of −142.1 dB was observed at 12 GHz for 5.0 mm thickness layer. RL exceeding −10 dB was obtained at 6.6-18 GHz for 1.4 mm thickness, covering the whole X band (8-12 GHz), Ku band (12-18 GHz), and some of C band (6.6-8.0 GHz). RL exceeding −20 dB was found at 6-10.6 GHz for 2.2 mm thickness.     

CoNi/g-C3N4/GQDs纳米胶囊的宽频电磁波吸收调制

通过两步法制备了CoNi/g-C₃N₄/GQDs三元复合纳米胶囊,利用XRD、SEM、FT-IR对其物相组成和微观形貌进行了详细表征,并对材料在1~18 GHz的微波电磁参数和吸波性能进行了测试和分析。结果表明,类海胆状的CoNi颗粒可以保证其复磁导率在较高水平,同时g-C₃N₄和GQDs在CoNi核心表面的复合可以通过界面偶极和本征偶极的互补性调控,调制微波介电特性和损耗。在L-Ku频段范围内,CoNi/g-C₃N₄/GQDs三元纳米胶囊通过介电调制的方式,极大地改善了电磁阻抗,获得了宽频吸收效果和吸波性能增强,在f=12.94 GHz和d=2.4 mm时,复合材料的反射损耗(RL)最小值达到-33.45 dB,当材料厚度为2.6 mm时,有效吸收频宽(RL<-10 dB)达到3.5 GHz。     

Synthesis of Flowerlike MoS2/CoNi Composites for Enhancing Electromagnetic Wave Absorption

The hierarchical MoS₂/CoNi composites were successfully synthesized by a two-step hydrothermal method. The large surface area of the MoS₂ enhances the dispersivity of the CoNi nanoparticles and the formation of abundant MoS₂/CoNi interfaces, which make an important contribution to the dielectric loss, and the introduction of the CoNi improves impedance matching and introduces magnetic loss, which can improve the absorption performance to electromagnetic waves. Through the calculation of the electromagnetic parameters, the minimum reflection loss (RL) value of the MoS₂/CoNi composites achieves -41.44 dB at 13.53 GHz under a thickness of 2.0 mm and the corresponding effective absorption bandwidth (RL below -10 dB) is 5.6 GHz. The MoS₂/CoNi composite has the potential to be applied to microwave absorption due to its strong absorption and wide bandwidth.