Synergistic effect of polyindole decoration on bismuth neodymium ferrite powder for achieving wideband microwave absorber

Recently, composite materials with outstanding absorption properties, like extraordinary absorbing capability, light weight, and thin in size, are required to solve the challenges of electromagnetic pollution. In addition, most of the work is based on the optimization of absorber material structure, and microstructure. In the current work, we improved the reflection loss feature of Bi_0.5Nd_0.5FeO₃ nanopowders via decoration with polyindole polymer by tuning the filler loading of the nanocomposite in the matrix. XRD, UV–Vis, XPS, and FESEM were used to determine the physicochemical features of the as-prepared nanocomposite. The minimum RL was lowered further with the increasing filler loading at 25 wt%. The lower RL of ?22 dB was noticed for 2.2 mm thickness at 11.5 GHz. The maximum value of the SE_R for a 25 wt% sample was 5.5, whereas 19 dB and 24.5 dB values were recorded for SE_A and SET, respectively. The resonance peak above 11.5 GHz demonstrated the better outcome of the absorber at high frequency. Good impedance matching characteristics, conductive features, dielectrics, and magnetic losses were all credited with the excellent reflection loss and electromagnetic interference shielding efficiency. The as-prepared nanocomposite materials that have been proven are interesting prospects for electromagnetic reflection loss and interference shielding that is lightweight, flexible, and extremely effective.     

Targeted design of polyaniline-graphene oxide,barium-strontium titanate,hard-soft ferrite,and polyester multi-phase nanocomposite for highly efficient microwave absorption

The current paper focuses on synthesizing a high-efficiency microwave absorber via incorporating the nanofillers of graphene oxide-polyaniline (GO-PANI), barium-strontium titanate (BST), and soft-hard ferrite within the polyester matrix. The nanocomposite magnets of (Ba_0.5Sr_0.5Fe₁₂O₁₉)_1-x hard/(CoFe₂O₄)_x soft (x = 0.2, 0.5, and 0.8) were prepared using sol-gel auto-combustion method. The GO-PANI and BST were successfully synthesized by in situ polymerization and improved polymerization, respectively. The phase structure, chemical structure, morphology, and microwave absorption properties of the synthesized nanocomposites were characterized by X-ray diffractometer (XRD), Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscope (SEM), vector network analyzer (VNA) techniques, respectively. The results showed that the synergistic effects of the combination of dielectric (BST), conductive (GO-PANI), and magnetic materials (hard-soft ferrites) provided the reflection loss values of less than ?20 dB (>99% absorption) in the X-band region. The minimum reflection loss of ?35 dB (>99.99% absorption) was obtained by the optimal formulation including (Ba_0.5Sr_0.5Fe₁₂O₁₉)_0.2 (CoFe₂O₄)_0.8, and the weight ratio of 1: 2 for both BST/soft-hard ferrite and hard-soft ferrite + BST/GO-PANI with the thickness of 1 mm. According to the results, the thickness factor plays a key role in improving the impedance matching. Consequently, the proposed nanocomposite can be employed as a novel kind of microwave absorbers with good impendence matching and high absorption.     

Magnetic and electric properties of BFO–NFO nanocomposites

Multiferroic nanocomposites of (1−x)BiFeO₃–xNiFe₂O₄ for x=0.2, 0.4, and 0.6 were prepared by a sol gel technique. The synthesized nanocomposites were characterized by X-ray diffraction (XRD). XRD confirmed, they being nanocomposites having desired phase with crystallite size ranging from 14.0 nm to 3.6 nm. The morphological analysis was done with the help of Transmission electron microscopy (TEM), which revealed the particle size to be in the range of 10–7 nm. Polarization–electric field (P–E) loop tracer was used to determine the ferroelectric properties of the nanocomposites. The dielectric constant at room temperature was analyzed upto 1 MHz frequency and was found to increase with increasing concentration. In order to investigate the magnetic behavior, a superconducting quantum interference device (SQUID) was used. The nanocomposites were analyzed by increasing the magnetic field up to 25 kOe and the magnetization was found to increase from 6 emu/g for x=0.2–10 emu/g for x=0.6, which was found to be optimum for the technological applications. The appropriate combination of two phases gave rise to higher magnetization.     

低温自反应淬熄法制备微纳米钡铁氧体空心复相陶瓷微珠吸波剂

以Fe(NO3)3-Ba(NO3)2-CO(NH2)2-酚醛树脂-硅烷偶联剂KH550为反应体系,采用低温自反应淬熄法结合热处理工艺,制备了微/纳米钡铁氧体空心复相陶瓷微珠。通过扫描电子显微镜、X射线衍射仪、透射电子显微镜、热分析及高速摄影技术测定了热处理前后微纳米钡铁氧体空心复相陶瓷微珠的形貌、结构及组成,并研究了其形成机理。结果表明:热处理前空心复相陶瓷微珠粒径为0.59至27.1μm,主要为非晶态;热处理后复相陶瓷微珠由六角晶型的Ba3Fe32O51、BaFe12O19和Ba5Fe14O26组成,且表现出片晶与固溶体相互交叉的现象。特殊的试验条件使得团聚粉粒子在火焰场中飞行过程中在受热蓄能阶段、热释放阶段、后燃烧阶段与快速凝固阶段都具有不同的反应机理,从而使得尺寸细化,具有较微米级微珠不同的本征参数。     

尖晶石型铁氧体Cu_xZn_(1-x)Fe_2O_4(x=0~0.5)的制备及光催化性能的研究

采用溶胶-凝胶法制备了尖晶石型铁氧体Cu x Zn1-x Fe2O4。利用XRD,SEM对纳米颗粒的结构、形貌进行了表征。结果表明,所合成的样品为尖晶石型铁氧体,形貌呈规则颗粒,随着Cu掺杂量的增加可使样品粒径减小。通过对甲基橙的降解情况对其光催化活性进行了研究。结果表明,经过Cu2+掺杂可加快甲基橙降解速率,少量掺杂的Cu x Zn1-x Fe2O4样品,光催化活性可以提高。     

磺酸磁性石墨烯固体酸的制备、表征及初步应用研究

以氧化石墨烯,Co（NO3）2·6H2O和Fe（NO3）3·9H2O为离子源利用水热法一步制备磁性石墨烯（Co Fe2O4-h GO）,用磺酸重氮盐将其重氮化制得磺酸磁性石墨烯固体酸,采用FT-IR、XRD、VSM和酸碱反滴定法测对其进行了表征。结果表明,链接石墨烯的Co Fe2O4为单相立方尖晶石结构,平均粒径为27 nm,饱和比磁化强度MS为29.7 A·m2/kg,其表面酸量为2.7 mmol/g。用乙酸与正己醇的酯化反应初步评估其催化性能：在90℃,乙酸与正丁醇摩尔比为1∶1,催化剂用量为3wt%,反应时间为4 h的条件下,乙酸转化率为59.1%。     

含钴废水处理方法及其研究进展

介绍了目前国内外含钴废水的主要处理方法,包括氢氧化物沉淀法、硫化物沉淀法、铁氧体沉淀法、吸附法、离子交换树脂法、溶剂萃取法、膜分离法、生物法等,分析了每种方法的优、缺点及其应用情况,指出多种处理技术的组合工艺将是含钴废水处理的新方向。     

共沉淀法制备的锰锌铁氧体材料的磁性能分析

采用化学共沉淀法,通过加入分散剂,制备了团聚程度低、结晶度完好、具有较好磁性能、不同组成的锰锌铁氧体粉末晶体.对样品进行热处理后,分别测定了烧结温度对其XRD晶相、饱和磁化强度、磁滞回线的影响以及组成变化对其饱和磁化强度、磁滞回线的影响.结果表明:烧结温度升高有利于形成尖晶石型的锰锌铁氧体,提高其磁性能;原料中ZnO,MnO,Fe2O3的摩尔比为22.32∶27.18∶50.5时,锰锌铁氧体的磁性能最佳.     

改性BaFe2O4载氧体生物质化学链气化特性

以溶胶凝胶法制备了BaFe₂O₄载氧体以及Ni、Ce、K修饰的BaFe₂O₄载氧体,筛选出最佳载氧体为10%(质量)K修饰的BaFe₂O₄载氧体(10K-BF),探究了不同反应条件对其性能的影响,通过H₂-TPR、XRD、SEM、BET对载氧体表征。实验结果表明,Ni、Ce、K的添加均提高了载氧体的合成气产率,10K-BF载氧体在水蒸气与生物质质量比(S/B)等于3,过氧系数α=0.20,反应温度800℃时,气化效果最好,合成气产率1.864 m³/(kg Biomass),氢气产率1.038 m³/(kg Biomass),碳转化率90.49%,积炭率1.33%,10次循环后仍有较高的气体产率及碳转化率。H₂-TPR表明10K-BF载氧体在300℃开始释氧,在生物质热解的初始阶段即可参与反应,有利于焦油的裂解;XRD表明10K-BF载氧体再生后可以恢复部分尖晶石结构。     

Interface-layer-assisted reliable ferroelectricity in BiFeO3 thin films by chemical solution deposition

BiFeO₃ thin films, specifically those fabricated by chemical solution deposition, suffer from severe leakage that hinder the acquirements of their intrinsic high polarizations and are thus normally not considered for use in practical electronics. The controlled fabrication of thin films with reduced leakage is of vital importance. In the present work, BiFeO₃ films (with thicknesses below ~300 nm), assisted by an interfacial amorphous layer, were fabricated by chemical solution deposition on Pt/Ti/SiO₂/Si substrates. This facile method facilitates the growth of the mentioned amorphous layer, and the ferroelectric properties of the obtained films were greatly enhanced. The conducting mechanisms of both types of thin films were systematically investigated to understand the impact of the designed interface. The results not only advance the potential use of BiFeO₃ thin films in electromechanical devices but also promote chemical solution deposition as a promising methodology for the fabrication of high-quality ferroelectric films with compressed leakage.