溶胶-凝胶自燃烧法合成镍铜锌纳米晶铁氧体及其吸波性能的研究

利用溶胶-凝胶自燃烧法合成了Ni0.25Cu0.25Zn0.5Fe2-xCexO4纳米晶铁氧体.借助DTA和XRD技术,对干凝胶的热分解过程、合成纳米晶的成分及其吸波性能进行了研究.结果表明,由金属硝酸盐和柠檬酸形成的干凝胶具有自燃烧的特性.通过自燃烧反应可以直接获得镍锌铜铁氧体粉末,经900℃热处理后可以转变成单一的尖晶石相,吸波性能测试发现,Ni0.25Cu0.25Zn0.5Fe2-xCexO4的吸波性能在8.2GHz～12.5GHz范围内随x的变化而不同,当x=0.07时,吸波性能最好,最高吸收峰值达到29.634dB.     

Ni0．5Zn0．5La0．05Fe1.95O4铁氧体的制备与吸波性能研究

采用高分子凝胶法制备了Ni0．5Zn0．5La0．05Fe1.95O4铁氧体。当煅烧温度为600℃时,立方晶系尖晶石结构的Ni0．5Zn0．5La0．05Fe1.95O4相初步形成。掺杂稀土La后,Ni0．5Zn0．5La0．05Fe1.95O4铁氧体的吸波性能显著提高,吸收峰向高频移动,其电磁波反射率小于～10dB的频宽可达2．7GHz,最小反射率为-15．6dB。     

共沉淀法制备的BaNiZn0.5Co0.5Cex Fe16-x O27纳米铁氧体微波吸收特性研究

采用共沉淀法制备了BaNiZn0.5 Co0.5 Cex Fe16-x O27(x=0,0.01,0.03,0.05)纳米铁氧体粉末,就铈元素的含量对该铁氧体微波性能的影响进行了对比研究,用AV3618型微波矢量网络分析仪测试了样品在8.2GHz～12.5GHz范围内的微波吸收特性.实验发现,稀土元素铈的含量影响材料的吸波性能,当x=0.03时,BaNiZn0.5Co0.5CexFe16-xO27铁氧体的吸波性能最佳.对于BaNiZn0.5Co0.5Ce0.03Fe15.97O27铁氧体吸波材料,当涂层厚度为1mm时,在11.8GHz频率处,最大吸收衰减量达14.8dB,9dB以上带宽大于2GHz,其复介电常数ε"最大值为1.83,复磁导率μ"最大值为0.95,添加铈是提高该铁氧体吸波材料性能的一种途径.     

掺杂Sm~(3+)的Ni-Zn铁氧体微观组织和磁性能研究

研究了掺杂Sm3+的Ni-Zn铁氧体微观组织和磁性能。随着Sm3+含量的增加,第二相的晶粒尺寸明显增加,并且抑制基体晶粒的长大,使得基体晶粒细化。Ni0.4Zn0.6Fe1.97Sm0.03O4试样在1150℃到1300℃的温度下烧结,粒度都明显增加。在1250℃烧结的材料密度为5.23 g/cm3,并且初始磁导率达到424,因此在1250℃烧结的试样有较好的综合性能,而且损耗较小。     

化学共沉淀法制备的BaNiZnCexFe16-xO27超微粉末的微波吸收特性

采用化学共沉淀法制备了BaNiZnCexFe16-xO27铁氧体吸波材料,就铈元素的含量对钡镍锌铁氧体吸波性能的影响进行了对比研究.实验发现在涂层厚度为1mm,测试频段为8.2GHz～12.5GHz频率范围内,当x=0.03时,该铁氧体材料的微波吸收特性最佳,在11.6GHz处,最大吸收值达13.6dB,10 dB以上带宽大于1.4GHz,其复介电常数ε″最大值为1.3,复磁导率μ″最大值为0.78,添加铈是提高钡镍锌铁氧体吸波材料性能的一种有效途径.     

机械合金化MlNi_(3.55)Co_(0.75)Mn_(0.4)Al_(0.3)/Mg复合储氢合金的相结构和电化学性能

采用机械合金化法制备了MlNi3.55Co0.75Mn0.4Al0.3+x%Mg(Ml=富镧混合稀土;x=3,5,7,10)复合储氢合金。利用X射线衍射和电化学测试方法对MlNi3.55Co0.75Mn0.4Al0.3铸态合金和MlNi3.55Co0.75Mn0.4Al0.3/Mg复合合金的相结构和电化学性能进行了研究。X射线衍射结果发现,MlNi3.55Co0.75Mn0.4Al0.3合金由单一的La Ni5相组成。而MlNi3.55Co0.75Mn0.4Al0.3/Mg复合合金由La Ni5主相和小量的(La,Mg)2Ni3相组成,且合金中(La,Mg)2Ni3相的含量随镁含量x的增大而增多。此外,当复合合金中镁含量较多(x=10)时,复合合金有非晶化的趋势。电化学性能测试结果发现,当添加镁含量较少(x≤7)时,合金的最大放电容量、放电性能以及循环稳定性都好于MlNi3.55Co0.75Mn0.4Al0.3合金的相应性能,其中x=5时,合金的综合电化学性能最佳。合金电化学性能的改善得益于合金中形成恰当比例的La Ni5和(La,Mg)2Ni3相。     

MnO_2掺杂对NiZn铁氧体磁性能的影响

采用传统陶瓷工艺制备了MnO2掺杂Ni0.88Zn0.12Fe1.98O4铁氧体材料。实验发现,较高的烧结温度有助于NiZn铁氧体磁导率的提高,但过高和过低烧结温度都不利于材料品质因数的提高,从降低损耗的角度考虑,最佳烧结温度为1220℃。当NiZn铁氧体中MnO2掺杂量为1.5%时,铁氧体晶粒生长均匀,平均晶粒尺寸适中,能获得最高的品质因数,过低或过高的掺杂量都不利于损耗的降低。铁氧体饱和磁感应强度随MnO2掺杂量的增多先上升,后下降,但总体的变化程度都不大。而矫顽力则随掺杂量的增多持续下降。相关的影响机制在文中作了详细的讨论。     

WC-8(Fe, Co, Ni)RE合金性能研究

用不同比例的Fe和Ni部分代替WC-8Co合金中的粘结剂Co，再添加微量的碳粉和稀土氧化物Y2O3制得WC-8(Fe，Co，Ni)RE硬质合金，测试了其物理机械性能，研究了粘结剂各种成分及烧结温度、烧结气氛对硬质合金性能的影响。在一定的烧结工艺下，以Fe和Ni部分代替Co所制得的WC-8(Fe，Co，Ni)RE硬质合金，其性能可以达到甚至超过YG8的标准，同时对影响WC-8(Fe，Co，Ni)RE硬质合金性能的一些因素进行了讨论。     

磁性Fe、Co、Ni纳米粒子的吸波性能研究

利用直流电弧等离子法在101.32 kPa(760 Torr)(H2+Ar)混合气氛下制备了Fe、Co、Ni纳米粒子,通过XRD、TEM、VSM及TC-436(LECO LTD.)N/O分析仪对纳米粒子进行了形貌和成分的表征,并通过矢量网络分析仪,利用同轴方法对粒子复合材料进行了电磁参数的测定。结果证明:在2~8 GHz频率范围内,Fe、Ni、Co纳米粒子/固体石蜡复合材料的复介电常数虚部ε″在3~4 GHz7、~10 GHz、14~16 GHz频段均出现峰值,Fe、Ni纳米粒子/固体石蜡复合材料复磁导率的虚部μ″吸收峰值分别在11~13 GHz、4~6 GHz频段处,Co纳米粒子/固体石蜡复合材料复磁导率的虚部μ″吸收峰值并没有出现。利用实验所得到的数据模拟了Fe、Ni、Co纳米粒子/固体石蜡复合材料不同厚度的电磁损耗能力,当涂层厚度为2 mm时,Fe纳米粒子/固体石蜡复合材料在8 GHz频率范围达到30 dB的吸收值。在2~18 GHz频率范围内,当涂层厚度为4 mm和5 mm时,Ni纳米粒子/固体石蜡复合材料出现了两个吸收峰,其值均大于10 dB。因此,通过Fe、Co、Ni纳米粒子的复合吸波材料可以展宽吸收电磁波的频段。     

石墨烯复合及Y替代La对AB_5型储氢合金电化学性能的影响

用熔炼法制备储氢合金La Ni_(3.55)Mn_(0.4)Al_(0.3)Co_(0.75)及Y掺杂储氢合金La0. 9Y0. 1Ni3. 55Mn0. 4Al0. 3Co0. 75,并用球磨法将La0. 9Y0. 1Ni3. 55Mn0. 4Al0. 3Co0. 75与石墨烯复合制得复合储氢材料。各样品的电化学性能测量发现,用Y部分替代La可以提高储氢合金La Ni_(3.55)Mn_(0.4)Al_(0.3)Co_(0.75)的最大放电容量、循环稳定性和高倍率放电特性。复合石墨烯后样品La0. 9Y0. 1Ni3. 55Mn0. 4Al0. 3Co0. 75-石墨烯的电化学性能进一步提升,其最大放电容量达到290 m Ah/g,60次循环后电极的容量保持率为85. 7%,样品的高倍率放电性能表现出色,放电电流在900 m A/g时容量保持率为80. 4%是La Ni_(3.55)Mn_(0.4)Al_(0.3)Co_(0.75)样品的1. 5倍。     

Microwave absorbing properties of NdFeCo magnetic powder

NdFeCo magnetic powder was prepared by the process of smelting,high-energy ball milling and oxidation heat treating.The effects of oxidation heat treatment and Co content on phase composition and microwave absorbing properties of NdFeCo magnetic powder were investigated by an X-ray diffractometer(XRD)and vector network analyzer.The minimum reflectivity of Nd23.25Fe36.75Co40 powder before oxidation heat treatment was-6.2 dB,and that of oxidized powder decreased to-14.0 dB.The microwave absorbing properties of NdFeCo magnetic powder could be improved effectively by oxidation heat treatment.With the increase of Co content,the Fe2O3 reduced and the Nd2O3 increased;Fe3Co7 phase appeared when the content of Co increased to 40%(mass ratio);the absorption peak was found to move towards lower frequency region first,and then it moved towards a higher frequency region.Nd23.25Fe66.75Co10 powder had better comprehensive properties in absorbing microwave in the frequency band of 3-13 GHz.The value of minimum reflectivity and absorption peak frequency,when the coating thickness(d)was 1.8 mm,were-19.7 dB and 4.8 GHz,respectively.     

氧化石墨烯修饰FeSiCr纳米复合材料的微波吸收性能

采用等离子体电弧蒸发和表面改性技术制备氧化石墨烯（GO）修饰FeSiCr纳米复合材料（FeSiCr/GO），并对其微波吸收性能进行研究。拉曼光谱结果显示氧化石墨烯与FeSiCr纳米颗粒成功复合。通过TEM对FeSiCr/GO微观形貌进行表征，观察到少量絮状氧化石墨烯点缀于FeSiCr纳米颗粒表面，并且FeSiCr纳米颗粒分布在层状氧化石墨烯周围，形成氧化石墨烯修饰FeSiCr纳米复合材料。通过引入氧化石墨烯，可增加材料的电导率和界面极化能力，使FeSiCr/GO的微波吸收性能显著提升。模拟计算结果显示，在4.3 GHz处，FeSiCr/GO最小反射损耗（RL_min）可达－69.1 dB，调整涂层厚度在1.1~5.0 mm之间变化，其有效吸收频带（RL≤－10 dB）范围为2.6~18 GHz。微波吸收性能的改善可归因于阻抗匹配优化和微波损耗能力增强。      

Electromagnetic and microwave absorption properties of Er-Ho-Fe alloys

The Er_xHo_(2-x)Fe_(17)(x = 0.0, 0.1,0.2, 0.3, 0.4) powders were prepared by arc melting and high energy ball milling method. The influence of the Er substitution on phase structure, morphology, saturation magnetization,electromagnetic parameters was investigated by X-ray diffraction(XRD),scanning electron microscopy(SEM), vibrating sample magnetometer(VSM) and vector network analyzer(VNA),respectively. The results show that the saturation magnetization increases and the average particle size increases with the increase of Er content. The minimum absorption peak frequency shifts towards a lower frequency region with the increase of Er content. The Er_(0.3)Ho_(1.7)Fe_(17) powder can achieve the minimum RL of-24.07 dB at 6.96 GHz with a thickness of 2.0 mm and the minimum RL is less than-20 dB at the thickness range from 2.0 to 3.0 mm. The minimum RL of Er_(0.3)Ho_(1.7)Fe_(17) is-37.26 dB at5.68 GHz and the frequency bandwidth of R-10 dB reaches about 1.2 GHz with a thickness of 2.4 mm.And the microwave absorbing properties of the composite with different weight ratios of Er_(0.3)Ho_(1.7)Fe_(17)/graphene were researched. The microwave absorbing peaks of the composite shift to lower frequency with the increase of graphene content. The values of the minimum RL of Er_(0.3)Ho_(1.7)Fe_(17)/graphene are close to-10 dB with absorbing coating thicknesses increased.     

Co掺杂对RGO/Fe3O4复合材料组织结构和吸波性能的影响

研究了Co掺杂对还原氧化石墨烯(RGO)/Fe₃O₄复合材料结构、形貌和吸波性能的影响规律.采用一步水热法分别制备RGO/Fe₃O₄和Co掺杂的RGO/Fe₃O₄复合材料,通过扫描电子显微镜、X射线衍射仪和X射线光电子能谱分析Co掺杂对复合材料的微观形貌、相组成及表面元素价态的影响;利用矢量网络分析仪测定两种复合材料在2~18 GHz频率范围内的相对复介电常数和复磁导率,模拟计算了Co掺杂对RGO/Fe₃O₄复合吸波性能的影响规律.结果表明:部分Co参与了水热反应生成了CoCO₃、Co₃O₄和Co₂O₃,还有部分Co以单质形式存在,其通过正负电荷吸引机制,影响Fe3+在氧化石墨烯(GO)表面的配位,使得负载在还原氧化石墨烯(RGO)表面的Fe₃O₄纳米颗粒部分迁移至RGO片层间;Co掺杂改善了复合材料的导电能力和磁损耗能力,使复合材料的吸波能力显著增强.反射率模拟结果表明:掺杂后与掺杂前相比,当匹配厚度d=2.00 mm时,最大反射损耗提高3.44 dB,有效吸收频带拓宽2.88 GHz;当匹配厚度d=2.50 mm时,最大反射损耗提高8.45 dB,有效吸收频带拓宽2.73 GHz.Co掺杂对RGO/Fe₃O₄复合材料的结构和形貌有显著影响,并有效改善复合材料的吸波性能.      

Research on microwave electromagnetic properties of Tb-Fe-Cr alloy

The Tb-Fe-Cr alloy powders were prepared by the arc melting method and high energy ball milling.The phase structure and themicrostructure of the alloys powders were analyzed by X-ray diffraction(XRD) and scanning electron microscopy(SEM),and then their microwave absorbing properties were analyzed by Vector network analyzer.The results showed that the absorption peak values of Tb9Fe88Cr3alloy with a material thickness of 2.0 mm were lower than-16.5 dB when ball milling time was from 50 to 60 h,and the wide frequency ofreflectivity under-10 dB were all more than 4 GHz.When the ball milling time was 50 h,the alloy powders had better electromagnetic properties.The absorption peak value of alloy reached-25.8 dB,and the wide frequency of reflectivity under-10 dB reached 4.8 GHz.When theball milling time was more than 70 h,the alloy powders would become thinner,leading to worse electromagnetic properties of the alloy,theabsorption peak shifted towards low frequency under the same material thickness.The TbxFe97-xCr3(x=7,9,11,13,15 mol.%) alloy dealtwith 60 h ball milling time had better wide-frequency characteristic under 1.8 mm of material thickness.The absorption peak shifted towardshigher frequency region from lower frequency region with increased atom percent of Tb in the alloy,and the inflexion point appeared whenx=13.At low frequency,the microwave absorbing properties of Tb11Fe86Cr3 alloy was better than those of the others.The absorption peakvalue of Tb15Fe82Cr3 alloy was-24 dB,and the wide frequency of reflectivity under-10 dB was 4.5 GHz.     

中空SiC球形纳米颗粒的合成及吸波性能

特殊结构和组成是决定电磁波吸收性能的关键因素.采用自组装技术合成碳包覆二氧化硅(SiO2@C)的球形纳米颗粒,经高温热处理后制备出中空SiC球形纳米颗粒.通过扫描电镜(SEM)和X射线衍射仪(XRD)对样品进行微观形貌分析和物相分析,采用矢量网络分析仪对样品的电磁参数进行测试,借助SiC的介电损耗以及其特殊的微观结构对...     

FeSiAlCr合金/W型六角晶系Ba铁氧体复合粉体的制备及微波特性

以雾化Fe85Si2Al6Cr7粉和溶胶凝胶法制备的W型六角晶系Ba1Co0.9Zn1.1Fe16O27铁氧体粉末为原料,通过高能球磨复合改性得到FeSiAlCr合金/W型六角晶系Ba铁氧体复合粉体。采用X射线衍射仪(XRD)和扫描电镜(SEM)对该粉体的微结构和形貌进行分析和观察,利用微波矢量网络分析仪系统测定粉体试样在2~18 GHz频段内的复介电常数和复磁导率以及吸波涂层试样板的吸波性能,研究该复合粉体的微波电磁特性和电磁损耗性能。结果表明,FeSiAlCr合金/W型六角晶系Ba铁氧体复合粉体颗粒保持W型铁氧体的六角片状晶粒形貌和微结构;其ε′、ε″、μ′和μ″均高于W型铁氧体而低于Fe合金的对应值;FeSiAlCr合金含量与复合材料的磁损耗和介电损耗的相对强弱密切相关,Fe合金含量适中的复合材料,其吸波涂层厚度为2 mm时,在2~18 GHz全频段的吸波性能高于20 dB,峰值点达50 dB。     

退火处理对FeCo纳米粒子吸波性能的影响

用KBH4作为还原剂,采用化学还原法制备FeCo纳米粒子,然后在400~600℃下退火。利用X射线衍射仪、扫描电镜、X射线光电子能谱仪和振动样品磁强计对FeCo纳米粒子进行表征,用网络矢量分析仪测定其电磁参数,并分析FeCo的吸波性能,研究退火温度对FeCo纳米粒子吸波性能的影响。结果表明,化学还原法制备的FeCo纳米粒子,在厚度为5 mm时对频率为2.24 GHz电磁波的反射损耗最大,为-14.9 dB,损耗机制以介电损耗为主。随退火温度从400℃升高到600℃,FeCo纳米粒子的介电损耗逐渐减小而磁损耗逐渐增大,在400℃退火后的FeCo粒子具有最优的电磁匹配特性和最高的反射损耗,在厚度为3.55 mm时对4.48 GHz电磁波的反射损耗为-49.14 dB。     

FeNiCrAl0.4Cux高熵合金实现对C-Ku波段电磁波的有效吸收

对吸波材料的研究，本质就是通过调整材料的成分、结构等来调控其复介电常数和复磁导率，使电磁波尽可能多地进入吸波材料内部，以增强材料对电磁波的吸收能力。采用高能球磨法制备了具有软磁性能的 FeNiCrAl0.4 Cux（x = 0.2，0.4，0.6，0.8，1.0；摩尔比）高熵合金吸波材料，球磨后的粉末呈不规则的片状结构。实验结果表明，通过调节Cu元素的含量可以提高粉末颗粒的长径比和形状相关各向异性，促进表面极化，从而改善粉末的复介电常数和复磁导率，进一步增强电磁损耗能力。随着Cu元素摩尔比从0.2增加到1.0，粉末的阻抗匹配逐渐提高，衰减系数和反射损耗也逐渐增强，当x = 1.0时合金粉末拥有最高的衰减系数和最低的反射损耗-23.74 dB，厚度为2.0 mm。值得注意的是，通过调节材料的厚度， FeNiCrAl0.4Cux的有效吸波带宽（反射损耗＜-10 dB）几乎可以覆盖整个C—Ku （4~18 GHz）波段。本研究对实现高熵合金吸波材料宽频吸收具有重要意义。     

Magnetic and microwave absorbing properties of Ce-Co-based alloy powders driven with lanthanum content

The composites of Ce-Co-based alloys doped with La content were fabricated via a vacuum arc melting method.The influences of La addition on microstructure,electromagnetic parameters,magnetic property and microwave absorbing property were measured by the corresponding equipment.The morphology characteristics manifest that all samples display sheet structure,and the average particle size of alloy powders increases with increasing La content The saturation magnetization(M_S) decreases with increasing La addition as a whole.The minimum reflection loss(RL) of La_(0.4)Ce_(1.6)Co_(17) alloy powder about-42.29 dB can be obtained about-42.29 dB at 7.84 GHz with the matching thickness of 1.8 mm,and the corresponding effective bandwidth can achieve about 2.24 GHz.In addition,the minimum RL frequency moves towards a lower frequency region as the La content increases.The minimum RL of La_(0.3)Ce_(1.7)Co_(17)alloy powder is less than-20 dB ranging from 1.2 to 2.4 mm in the whole 4-16 GHz.The maximum bandwidth can reach about 4.88 GHz at the given thickness of 1.2 mm.In general,these all indicate that the La addition is beneficial to improving the microwave absorbing performance in both effective bandwidth and absorption intensity.