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11.
《Ceramics International》2023,49(16):26411-26419
Double substitution of strontium hexaferrite by calcium and aluminum leads to a tremendous rise of hard magnetic properties, such as coercivity and natural ferromagnetic resonance frequency (NFMR). However, the properties are also inextricably linked to the material microstructure (especially, particle size), to the solid solution inhomogeneity as well as aluminum ions distribution among iron sites in crystal structure. In this work, we obtained M-type hexaferrite particles Sr1-x/12Cax/12Fe12-xAlxO19 (x = 4–6) via a facile citrate-nitrate auto-combustion method and studied the influence of the annealing temperature in a broad range on the microstructure, features of crystal structure and hard magnetic properties. At low annealing temperatures (900–1000°С) hexaferrite nanoparticles with 90% of nominal Al content and a wide chemical distribution are formed. Next, with an increase in the annealing temperature the distribution significantly narrows, chemical composition becomes close to the nominal one and particles size transfer firstly to submicron, then to micron range. The aluminum distribution over iron sites is independent distinctly on the annealing temperature. For all the compositions single domain particles with the maximum coercivity values between 22.8 and 36 kOe are obtained at 1200 °C. At 900–1000 °C the samples demonstrate coercivities up to 25 kOe, while above 1300 °C, the crystallites begin to pass into a polydomain state with a reduced coercivity. The hexaferrites with narrow chemical distribution reveal resonance absorption in sub-terahertz band. The highest NFMR frequency of 270 GHz was observed for x = 5.5 sample annealed at 1400 °C. 相似文献
12.
《Ceramics International》2023,49(20):32377-32387
Herein, we report the wet-chemical synthesis of a ferromagnetic nickel-doped ZnO (Zn1-xNixO) nanocatalyst as a novel and visible-light-driven photocatalyst. Through X-ray diffraction, UV/Vis absorption, electronic studies, and current-voltage experiments, the effect of the ferromagnetic nickel dopant on the structural, optical, morphological, and electrical properties of the synthesized Zn1-xNixO nanocatalyst was studied. The Ni-doping introduced the structural variation in the Zn1-xNixO nanocatalyst, exhibiting a visible light-triggered optical band gap of 2.96 eV and an excellent current conductivity of 6.3 × 10−4 Sm−1. Moreover, the synthesis of the Zn1-xNixO catalyst at the nanoscale enhanced its surface energy, showing a robust affinity to stick with the dye and pathogenic microbes. The synergistic effects of all the mentioned features enable our Zn1-xNixO nanocatalyst to efficiently generate and transport reactive oxygen species (ROS) under visible light illumination. Regarding antibacterial action, the as-synthesized Zn1-xNixO nanocatalyst showed 1.7% higher activity against E. coli than that of the drug Ciprofloxacin. In addition, doped nanocatalysts mineralize almost 97% of the Allura red dye in just 80 min with a constant rate value of 0.036 min−1. The impedance study and post-application XRD proposed that our Zn1-xNixO nanocatalyst has good conductivity and structural stability. Applications studies show the unusual photocatalytic activity of as-synthesized Zn1-xNixO nanocatalysts, which makes it a suitable candidate for industrial discharge treatment applications at the expense of solar light. 相似文献
13.
《Ceramics International》2022,48(9):12209-12216
We report the structural, magnetic, electrical and broadband microwave absorption in La0.7Na0.3MnO3 sample synthesized by microwave (MW) irradiation (Na0.3LMO_MW) and compare them to the sample synthesized by solid-state (SS) reaction method (Na0.3LMO_SS). Single phase Na0.3LMO_MW was synthesized at 800 °C in 30 min, whereas, Na0.3LMO_SS sample was obtained by sintering at 1200 °C for 48 h. Although both these samples show ferromagnetic transition at TC ~324.8 K, the MW-synthesized sample shows distinct physical properties: broad ferromagnetic transition, smaller saturation magnetization, a large difference between the magnetic ordering and metal-insulator transition temperatures, a large high-field magnetoresistance, a table top-like magnetocaloric effect, and a large low-field microwave absorption compared to the solid state synthesized sample. These differences are suggested to arise from magnetic heterogeneity induced by smaller grain size and surface spin disorder in the MW synthesized La0.7Na0.3MnO3. 相似文献
14.
《Ceramics International》2022,48(22):32827-32836
To investigate the crystal structure, electrical properties, and magnetic properties of Ca–Sn co-doped Y3-xCaxFe5-xSnxO12 (x = 0.00–0.25 in steps of 0.05), solid-state reaction experiments, first principles calculations, and complex crystal bonding theoretical calculations were performed. The relative permittivity (εr) is strongly correlated with the average bond ionicity when Ca2+ is added. Furthermore, appropriate Sn4+ substitution significantly lowers the dielectric loss (tanδε) associated with the lattice energy. The right amount of Ca–Sn co-doping can change the saturation magnetization (4πMS) and improve the microscopic morphology of YIG, lowering the ferromagnetic resonance linewidth (ΔH) of YIG. The optimized microwave dielectric and magnetic properties are as follows: εr = 14.7, tanδε = 4.15 × 10?4, 4πMS = 1680 G, and ΔH = 53 Oe for Y2.8Ca0.2Fe4.8Sn0.2O12 sintered for 6 h at 1425 °C. Based on this material, a simple 3D model of a strip-line circulator with an insertion loss of less than 0.3 dB at each port and isolation greater than 20 dB in the 10–12 GHz range was developed, indicating the potential of the material for microwave high-frequency components such as circulators. 相似文献
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介绍磁粉检验用B型和E型标准试块的设计、结构、研制、试验和应用。结果表明,两种标准试块都达到了国外同类标准试块的先进水平。 相似文献
18.
针对承压设备中铁磁性构件内外壁损伤检测问题,发展了一种低频漏磁检测技术。对低频漏磁信号进行分析处理,提取出的低频漏磁信号的幅值和相位信息,用于铁磁构件内外表面损伤检测与定量评价。通过数值仿真和检测实验,研究了裂纹深度和位置(上表面或下表面)的裂纹对漏磁场特征参数空间分布的影响。结果表明,漏磁信号的幅值特征参数和相位特征参数均可用于铁磁性构件上下表面一定深度范围内裂纹检测及定量表征,但两个参数对不同位置及深度范围内裂纹检测的敏感性不同。当裂纹位于试件上表面时,幅值特征参数对裂纹深度变化更敏感;而当裂纹位于试件下表面时,相位特征参数对裂纹深度变化的敏感性更高。本文研究工作为承压设备中铁磁性构件内外壁损伤检测做了有益探索。 相似文献
19.
铁磁性物体在地磁场中的自发运动磁化 总被引:3,自引:0,他引:3
依据法拉第电磁感应定律和铁磁性物质在磁化一退磁过程中的能量差异,阐明了铁磁性物体在地磁场中的摆动、振动和周期性往复平动都会引起该物体的自发磁化。虽然每次磁化一退磁过程之后物体上的剩磁增量非常微小,但随着循环次数的增加该物体最终必然被强烈地自发磁化。从而推知:地磁场的矢量特性和纬度效应对金属磁记忆检测与诊断技术适用性和可靠性的影响都不大。 相似文献
20.
Xiao Xu Makoto Nagasako Wataru Ito Rie Y. Umetsu Takeshi Kanomata Ryosuke Kainuma 《Acta Materialia》2013,61(18):6712-6723
We present the magnetic properties and the magnetic phase diagram of Ni50Mn50?xGax ferromagnetic shape memory alloys across a wide concentration range. Martensitic transformation, intermediate transformation, B2–L21 order–disorder transformation, Néel and Curie temperatures are determined for the prepared samples. The martensitic transformation temperature decreases with increasing Ga concentration and bends two times when crossing the Curie temperature and the intermediate-phase transformation temperature. Spontaneous magnetization and its composition dependence were also investigated. Composition dependence of the transformation temperatures and the spontaneous magnetization in the martensite phase of Ni50Mn50?xGax are compared with those of Ni50Mn50?xInx and Ni50Mn50?xSnx, revealing a similarity in the NiMn-based alloy systems. 相似文献