Microwave Absorption Properties of BaFe12O19-TiO2 Composite Coated with Conducting Polymer

This study investigates microwave absorption properties of Ba-hexaferrite (BaFe₁₂O₁₉) and titanium dioxide (TiO₂) particles coated with conducting polymer (PANI) and BaFe₁₂O₁₉-TiO₂ mixture in the frequency range of 8–18 GHz. Samples having different magnetic to dielectric mass ratios and various thicknesses from 1.5 to 4 mm have been prepared to investigate effect of magnetic and dielectric fillers together with influence of conducting polymer layer on microwave absorption properties of BaFe₁₂O₁₉-TiO₂ composite. Structural, magnetic, and microwave absorption properties of composites have been investigated using X-ray diffraction, scanning electron microscopy and near field microwave measurements using vector network analyzer. Microwave measurements revealed that composites with PANI coating have much higher absorption values which are independent of an absorber thickness. Among PANI coated absorbers, sample having magnetic to dielectric mass ratio of 2 showed better microwave properties in 8–18 GHz range.     

多孔SiO2与TiO2复合纳米材料的制备及光催化性能

在溶胶水热法所合成的锐钛矿相TiO₂纳米晶基础上,利用模板剂调制的SiO₂溶胶进一步合成了多孔SiO₂与TiO₂复合纳米粒子,重点研究了复合SiO₂对纳米锐钛矿相TiO₂热稳定性及光催化活性的影响.结果表明,复合SiO₂提高了纳米锐钛矿相TiO₂的热稳定性,经过900℃热处理后的TiO₂仍然具有以锐钛矿相为主的相组成.在光催化降解罗丹明B实验过程中,经过高温热处理的复合纳米材料表现出优于Degussa P25 TiO₂的活性,这主要与其锐钛矿相结晶度提高和具有较大比表面积等有关.     

Zn-Ti取代的BaFe12O19铁氧体

采用标准陶瓷工艺,并进行湿压磁场成型和氧气氛烧结制备了高取向度、低介电损耗的各向异性Ｂａ（ＺｎＴｉ）ｘＦｅ１２－２ｘＯ１９多晶六角铁氧体,随着ｘ值增大,磁化强度减小,居里温度下降,磁晶各向异性常数减小。结果可以通过假设Ｚｎ＾２＋取代了四面体４ｆ１次点阵位和六面体２ｂ次点阵位上的ＦｅＴ＾３＋;Ｔｉ＾４＋取代了自旋向上的八面体１２ｋ,２ａ次点阵位上的Ｆｅ６３＋来解释。     

自蔓延高温合成钡铁氧体的研究

介绍了自蔓延高温合成技术合成BaFe12O19的过程，研究了热处理对产品性能的影响。用VSM对产物的磁性能进行了测量，用XRD对产物的物相进行了分析，用SEM对产物形貌和组织进行了观察。结果表明，采用自蔓延（SHS）高温合成的BaFe12O19具有良好的磁性能。     

The Influence of Powder Ferritization Technology on the Degree of Magnetic Texture in Plates of BaFe12O19 and SrFe12O19 Hexaferrites

Technical Physics Letters - We have studied the influence of a technology used for ferritization of the powders of barium and strontium hexaferrites on the degree of magnetic texture in pressed...     

自蔓延高温合成钡铁氧体的研究

介绍了自蔓延高温合成技术合成BaFe12O19的过程,研究了热处理对产品性能的影响.用VSM对产物的磁性能进行了测量,用XRD对产物的物相进行了分析,用SEM对产物形貌和组织进行了观察.结果表明,采用自蔓延(SHS)高温合成的BaFe12O19具有良好的磁性能.     

Molten salt synthesis of anisotropic BaFe12O19 powders

The formation mechanism, morphology, and magnetic properties of anisotropic BaFe₁₂O₁₉ powders prepared by the 0.8 Na₂SO₄-0.2 K₂SO₄ molten salt synthesis have been investigated. The reaction can be completed at temperatures lower than 845 °C which is the melting point of the 0.8 Na₂SO₄-0.2 K₂SO₄ salt mixture, due to the presence of the low melting phase related to the formation of BaSO₄ and Na₆CO₃(SO₄)₂. Even at temperatures lower than 845 °C, with the aid of the low melting phase, the morphology of ferrites was thin platelets. Magnetic properties such as coercivity, saturation magnetization, and remanent force are comparable to those found in other processing techniques. The orientation degree of the sintered body was very high due to anisotropic morphology; thus powders from molten salt synthesis are suitable for grain oriented ceramics.     

Thermal Treatment Influence on the Magnetic Properties and Degree of Orientation of BaFe12O19 Films

The process of preparation of oriented BaFe₁₂O₁₉ films with deposition of BaFe₁₂O₁₉ nanoparticles from 1-butanol suspension in a magnetic field was studied. The structural, microstructural, and magnetic properties were investigated by X-ray diffraction, scanning electronic microscopy, and magnetic measurements and the annealing conditions influence on the films?? orientations and microstructures was explored. The best BaFe₁₂O₁₉ film properties, saturation magnetization of 49?emu?g^?1, high values of coercive field (4.4?kOe), and squareness ratio of 0.92, were obtained on well-crystallized oriented BaFe₁₂O₁₉ films annealed at 1050?°C for 30?h.     

Mn掺杂锶铁氧体SrFe12O19电子结构及磁性的第一性原理研究

为了揭示掺杂离子对具有磁铅石构型的锶铁氧体材料磁性能的影响, 本研究探讨了锶铁氧体及其锰掺杂体系的稳定构型及其磁结构。研究结果表明, 锶铁氧体为亚铁磁性, 与前期的研究结果相吻合。通过比较GGA和GGA+U计算方法, 发现U值的选取对体系的电子结构和原子磁矩有显著影响。当U值为3.7 eV时, 体系由金属性转变为自旋向上带隙为1.71 eV的半导体。原胞总磁矩为40 μ_B。对于Mn替换掺杂的SrFe_12-xMn_xO₁₉体系, 通过不同占据位能量比较, 当单个Mn原子替换(x=0.5)时, Mn离子优先占据Fe (12k)位置; 而当两个Mn原子替换Fe原子(x=1.0)时, 两个Mn分别占据Fe (12k)和Fe (2a)位置。Mn掺杂对锶铁氧体的结构影响较小, 但对于体系的总磁矩和电子结构有较明显的影响。在Mn含量x=0.5和x=1.0时, 自旋向上带隙值分别降低到0.85和0.59 eV, 原胞的总磁矩为39和38 μ_B。本研究可为实验研究提供理论指导。     

The Influences of Nb2O5, MnO2, CuO and B2O3 Addition on the Magnetic Properties of BaFe12O19 Magnets

In the present study, we have investigated the influence of different types of doping elements on magnetic properties of M-type BaFe₁₂O₁₉ samples. It was observed that Nb₂O₅ addition increases the coercive field, the remanence magnetization (M _r), and saturation magnetization (M _s) values by about 27 %, 47 %, and 53 %, respectively. In the same manner, MnO₂ also improves the magnetic parameters significantly. The M _r and M _s values show increments up to 40 % in magnitude. On the other hand, the best magnetic properties were achieved by the addition of CuO to the B₂O₃ doped BaFe₁₂O₁₉. These materials have M _r and M _s values up to ～34 emu/g and ～62 emu/g, respectively.     

Preparation and photocatalytic characteristics of core-shell structure TiO2/BaFe12O19 nanoparticles

A core-shell structure TiO₂/BaFe₁₂O₁₉ composite nanoparticles that can photodegrade organic pollutants in the dispersion system effectively and can be recycled easily by a magnetic field is reported in this paper. The obtained samples were characterized by energy dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The TiO₂/BaFe₁₂O₁₉ magnetic photocatalyst is composed of two parts: (1) TiO₂ shell used for photocatalysis and (2) BaFe₁₂O₁₉ core for separation by the magnetic field. The photocatalytic activity of the as-prepared magnetic photocatalyst increased with increasing the thickness of TiO₂ coating layer. On the other hand, the saturation magnetizations of titania-coated BaFe₁₂O₁₉ nanoparticles decreased with increasing thickness of the titania coating, while the coercivity does not show any change after coating.     

碳化硅表面钡铁氧体薄膜制备与吸波性能

采用柠檬酸盐溶胶-凝胶法在碳化硅表面形成钡铁氧体薄膜.XRD表明生成的铁氧体为六角磁铅型晶体BaFe12O19.测定了材料在0.1～6.0 GHz内的介电常数与磁导率.与单纯钡铁氧体比较,碳化硅表面沉积钡铁氧体薄层后复合相吸波频段宽化,吸波能力增强.     

Enhancement of hard magnetic properties of BaFe12O19 nanoparticles

Barium hexaferrite nano particles are prepared through glycine assisted sol–gel auto combustion method with a minimal glycine to nitrate ratio and the pH values of 4, 6 and 9. X-ray diffraction patterns reveal the formation of hexagonal magneto-plumbite structure of BaFe₁₂O₁₉ with a weak intensity of secondary phase in the case of pH 4 and pH 6 samples. Interestingly disappearance of secondary phase at pH 9 sample is noticeable feature. Scanning electron microscope micrographs of the samples show the formation of characteristic hexagonal shape of barium hexaferrite. Constituent elements and chemical composition are analyzed using energy dispersive X-ray spectrum. Fourier Transform Infra Red and Raman spectra show the different metal–oxygen stretching vibration modes corresponding to octahedral, tetrahedral and trigonal bipyramidal sites of BaFe₁₂O₁₉. Magnetization studies show increase in saturation magnetization, squareness ratio, coercivity values on increasing the pH of the solution. 10 % enhancement of Curie temperature is observed (T_c = 495 °C of pH 9 sample) in comparison to its bulk counterpart T_c = 450 °C reported earlier. Enhancement of magnetic properties is achieved by optimizing pH and suitable choice of post annealing temperature during synthesis of nanoparticles of barium hexaferrite.     

Ag2O modified magnetic BaFe12O19/C3N4 photocatalysts with enhanced antibiotic removal: Photocatalytic mechanism and toxicity evaluation

Novel Ag₂O-BaFe₁₂O₁₉/C₃N₄ composites were prepared via a grind, solvothermal and deposition–precipitation methods. The physicochemical properties of the samples were tested by FT-IR, XRD, SEM, TEM, XPS, DRS, ESR, VSM, photocurrent test, and electrochemical impedance spectra test, respectively. The characterization manifested that Ag₂O was firmly anchored to the BaFe₁₂O₁₉/C₃N₄ to form heterogeneous hybrid. Most importantly, the formation of Ag₂O-BaFe₁₂O₁₉/C₃N₄ effectively promoted the charge transfer, eventually enhancing the photocatalytic performance. Meanwhile, the activity of the photocatalysts were assessed by photocatalytic removal of tetracycline (TC) under visible light irradiation. The results showed that Ag₂O-BaFe₁₂O₁₉/C₃N₄ photocatalyst has better photocatalytic activities than the pure component. The degradation rate reaches 80 % after 15 min, which is nearly 1.56 times higher than that of pure g-C₃N₄. The effects of Ag₂O content, photocatalyst dosage, pH value on TC degradation performances were studied in detail, respectively. The experimental results verified that pH value exhibited significant effects on TC degradation. The TC degradation rate was highest only when the initial solution pH = 7. This indicates that the photocatalyst also has high activity in neutral environment, and no additional pH adjustment is required. The results of plant growth test (mung bean seeds) showed that the degradation intermediates showed lower toxicity. Based on experiments and characterization, the possible carrier migration and photocatalytic degradation mechanism were proposed.     

The effect of Na2O addition on the magnetic properties of BaFe12O19 ferrites

The effect of Na₂O addition on the magnetic properties of isotropic BaFe₁₂O₁₉ ferrites from hot-rolled mill scale was investigated. Na₂O was added up to 0.2s%. The values of coercivity and energy product maximum are significantly increased, notably (BH)_max from 0.8 to 0.9× 10⁶ OeG, and those of intrinsic coercivity rise drastically from 2500 to 4000 0e when Na₂O up to 0.15% is added after calcination. On the other hand, the magnetic properties of the ferrites gradually deteriorate and the values of intrinsic coercivity vary very little when Na₂O up to 0.2% is added prior to calcination. The densification of ferrites is slightly decreased in the presence of the Na₂O, regardless of the time at which it is added.     

WO_3-TiO_2纳米材料的制备及其光催化性能

采用溶胶-凝胶法制备WO3-TiO2纳米复合材料,并用透射电镜和X射线衍射对所制备材料进行表征和分析。以WO3-TiO2纳米材料为光催化剂对甲基橙进行光催化降解处理,研究WO3的掺杂量、煅烧温度、光照时间等因素对甲基橙降解率的影响。结果表明:在紫外灯照射下,使用w(WO3)=3%、550℃下煅烧得到的WO3-TiO2纳米复合粉体0.02 g,甲基橙溶液20 mL(ρ=5 mg/L,pH=4),光催化3 h后,甲基橙降解率达到94.93%。     

BaFe12O19/SiO2-B2O3微晶玻璃陶瓷的制备和微波性能

采用柠檬酸sol-gel工艺合成了BaFe12O19/SiO2-B2O3微晶玻璃陶瓷，研究了SiO2-B2O3玻璃的含量，Ba/Fe原子比和热处理温度对体系析出晶相的影响，以及介电常数和磁异率在1MHz-6GHz频率范围的变化规律，结果表明，休系中SiO2-B2O3玻璃的含量和Ba/Fe比越高，BaF312O19相的析出越困难，前驱体合适的热处理温度为1000℃，介电常数和磁导率基本上随测试频率的增而加下降；介电损耗的最大值为0．43，磁损耗较小。     

Effect of Cr substitution on microwave absorption of BaFe12O19

The chromium substituted barium hexaferrites were prepared by self-propagating combustion method. The crystalline structure, complex permittivity, complex permeability, and hyperfine parameters of BaFe_12−xCr_xO₁₉ (x varies from 0.2 to 1.0 in a step of 0.2) were measured with X-ray diffraction, vector network analyzer and Mössbauer spectroscopy. At 850 °C, only a part of Cr³⁺ ions are permitted to enter the lattice of barium ferrite. With further calcination at 1000 °C, all Cr³⁺ ions enter the lattice. After substitution, the complex permittivity is increased. The Cr³⁺ ions substitute for the Fe³⁺ ions on the 2a site, and simultaneously lead to a quadrupole splitting on the 4f₁ site. These changes decrease the anisotropy field, which are accordant with the spectra of μ″. In the crystalline cells of the substituted barium ferrites, some Fe²⁺ ions are formed. It results in a bigger dielectric loss.     

The Effect of Condensation on the Morphology and Magnetic Properties of Modified Barium Hexaferrite (BaFe12O19)

Nano-Micro Letters - We present a comparison for the effect of condensation on the morphology and magnetic properties of oleic acid modified BaFe12O19 nanoparticles. Two different samples of...