查找使用阿拉丁产品的科研文献

Effect of Semi-Conductive Layer Modified by Magnetic Particle SrFe12O19 on Charge Injection Characteristics of HVDC Cable

Yanhui Wei,Mingyue Liu,Jiaxing Wang,Guochang Li,Chuncheng Hao,Qingquan Lei

For high voltage direct current (HVDC) cable, a semi-conductive layer lies between the conductor and the insulation layer; as the charge migrates the path from the conductor to the insulation material, it will affect space charge injection. In this work, the research idea of changing the injection path of moving charges within semi-conductive layer by magnetic particles was proposed. Semi-conductive composites with different SrFe12O19contents of 1 wt.%, 5 wt.%, 10 wt.%, 20 wt.%, and 30 wt.% were prepared, and the amount of injected charges in the insulation sample was characterized by space charge distribution, polarization current, and thermally-stimulated depolarization current. The experimental results show that a small amount of SrFe12O19can significantly reduce charge injection in the insulation sample, owing to the deflection of the charge migration path, and only part of the electrons can enter the insulation sample. When the content is 5 wt.%, the insulation sample has the smallest charge amount, 0.89 × 10−7C, decreasing by 37%, and the steady-state current is 6.01 × 10−10A, decreasing by 22%. When SrFe12O19content exceeds 10 wt.%, the charge suppression effect is not obvious and even leads to the increase of charge amount in the insulation sample, owing to the secondary injection of charges. Most moving charges will deflect towards the horizontal direction and cannot direct access to the insulation sample, resulting in a large number of charges accumulation in the semi-conductive layer. These charges will seriously enhance the interface electric field near the insulation sample, leading to the secondary injection of charges, which are easier to inject into the insulation sample.Keywords:HVDC cable;semi-conductive composites;SrFe12O19;space charge accumulation

Correlation of the heat treatment feature and magnetic properties of the SrFe12O19@ZnFe2O4 core-shell nanofibers

Jianfeng Dai,Xinchao Wen,Wei Feng,Chen Cheng,Danqiang Huang

Nanocomposite SrFe 12 O 19 @ZnFe 2 O 4 with core-shell structure has been synthesized in one step via coaxial electrospinning followed by heat treatment in air. The samples comprise two phases, the structure change from fiber coated particles to core-shell fibers, and finally form a scattered sheet structure. The inner diameter of the nanofiber with core-shell structure is 100 nm and the outer diameter is 170 nm, two-phase coupling interface is obvious, and the length of the nanofiber can reach 1.8 μm. The magnetic properties of the composites show a decreasing trend after upward, reaching the highest Ms (43 emu/g) and Hc(4524 Oe) at 900 °C, which is better than for other materials with various morphologies such as sheet and particle. The hysteresis loop at 900 °C shows a single-phase-like magnetic characteristic, indicating the existence of effective exchange coupling. This study provides a basis for the preparation of hard-soft nanocomposite ferrite fibers with controlled core-shell structure, excellent exchange coupling and outstanding magnetic properties .

Effect of SiO2 in situ cross-linked CS/PVA on SrFe12O19 scaffolds prepared by 3D gel printing for targeting

Jing Duan,Huiping Shao,Jialei Wu,Hongyuan Liu,Siqi Wang,Tao Lin

The design of magnetic composite scaffolds with superior properties has the potential to construct a targeted delivery platform with hyperthermia. In this study, strontium hexaferrite (SrFe 12 O 19 , SrM) magnetic nanoparticles (MNPs) were obtained by the chemical precipitation method. Non-toxic cross-linked biogels were prepared for adhesive ceramic scaffolds, and chitosan/polyvinylalcohol (CS/PVA)-bonded SrM magnetic nanoscaffolds were successfully prepared by 3D gel printing (3DGP) method. The effects of PVA physical cross-linking and in situ formed SiO 2 on the properties of CS-bonded scaffolds were evaluated, and the compressive strengths were increased from 6.13 ± 2.45 MPa to 8.80 ± 2.02 MPa and 17.18 ± 2.15 MPa, respectively. The results showed that the saturation magnetization of SiO 2 /CS/PVA/SrM composite scaffolds was 59.96 emu/g. In vitro immersion experiments showed that the degradation rates of SiO 2 /CS/PVA/SrM scaffolds were 4.90% after 28 days, and the in situ SiO 2 improved the deposition of calcium salts on the scaffolds. The experiments showed that the SrM magnetic scaffolds could not only concentrate magnetic fields to improve the efficiency of targeting deposition but also achieve a weak targeting process without external magnetic field assistance. In vitro cell proliferation test showed that MC3T3-E1 cells had good adhesion and proliferation on the surface of SiO 2 /CS/PVA/SrM scaffolds, which indicated that the scaffolds may be used for bone repairing.

Magnetic Properties and Exchange Coupling Effects of SrFe12O19@MFe2O4 (M = Co, Ni, Zn) as Hard-Soft Magnetic Ferrite Core–Shell Nanofibers

Huang Danqiang,Wen Xinchao,Dai Jianfeng,Wang Qing,Liu Hui,Li Zengpeng

In this study, SrFe 12 O 19 @MFe 2 O 4 (M = Co, Ni, Zn) core–shell nanofibers were fabricated by coaxial electrostatic spinning. The composites obtained at an annealing temperature of 900 °C are composed of SrFe 12 O 19 in pure phase and MFe 2 O 4 (M = Co, Ni, Zn) in different spinels. X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), and transmission electron microscope (TEM) were used to describe the structure and morphology of nanofibers. Magnetic Property Measurement Systems (MPMS) are used to characterize the magnetic properties of nanofibers. Sr@Ni and Sr@Zn fibers all exhibit a unique core–shell structure, while Sr@Co fibers are connected by a lamellar structure. The single-phase hysteresis lines for each composite indicate the presence of exchange coupling effects between the hard/soft magnetic composite phases. The magnetic properties of the composites change as the soft magnetic material in the shell layer changes. Sr@Co has the highest M s (69.43 emu/g) and M r (33.82 emu/g), whereas Sr@Zn has the highest H c (2927 Oe). The switching plant curves indicate that the best exchange coupling of the three groups of samples is for Sr@Co. The magnetic properties of the composites are explained in terms of the nanofiber diameter, the exchange coupling between the two phases, and the nature of the soft magnetic phase itself. It is shown that the exchange coupling of composites is closely related to the type of composite.

Composite xNiFe2O4/(1-x)SrFe12O19 oxygen carriers for chemical looping reforming of bioethanol coupled with water splitting to coproduce syngas and hydrogen

Mingxuan Zhong,Chenxuanzi Wang,Jiajun Xu,Yongcheng Cai,Bo Xiao,Tingting Xu,Xun Wang

Sr–Fe oxides are suitable oxygen carriers (OCs) with excellent cyclic stability. However, the moderate redox activity causes a deficiency in H 2 yield in chemical looping reforming coupled with water splitting (CLR-WS) process. Herein, we designed and prepared the composite xNiFe 2 O 4 /(1-x)SrFe 12 O 19 OCs by ball milling method, which exhibited both high redox activity and high cyclic stability during reactions. A series of characterizations showed that the introduction of NiFe 2 O 4 promoted the oxygen vacancy formation and the release of lattice oxygen, facilitating the reforming of bioethanol in fuel reactor (FR). During CLR-WS process, a high carbon conversion of 79.20 % and a H 2 yield of 13.23 mmol/g OC were achieved by 3Ni7Sr OC at 800 °C, outperforming that of the conventional SrFe 12 O 19 OC. Moreover, the severe carbon deposition and sintering issues inherent to NiFe 2 O 4 were avoided due to the presence of Sr. All Sr-containing composite OCs showed H 2 purity exceeding 99.26 % and excellent cycling stability with no apparent activation of oxygen transport capacity over 3000 min redox reactions.

Unlocking Synergistic Photo-Fenton Catalysis with Magnetic SrFe12O19/g-C3N4 Heterojunction for Sustainable Oxytetracycline Degradation: Mechanisms and Applications

Song Cui,Yaocong Liu,Xiaolong Dong,Xiaohu Fan

The widespread contamination of aquatic environments by tetracycline antibiotics (TCs) poses a substantial threat to public health and ecosystem stability. Although photo-Fenton processes have demonstrated remarkable efficacy in degrading TCs, their practical application is limited by challenges associated with catalyst recyclability. This study reports the development of a novel magnetic recoverable SrFe12O19/g-C3N4heterostructure photocatalyst synthesized via a facile one-step co-calcination method using industrial-grade precursors. Comprehensive characterization revealed that nitrogen defects and the formation of heterojunction structures significantly suppress electron (e−)–hole (h+) pair recombination, thereby markedly enhancing catalytic activity. The optimized 7-SFO/CN composite removes over 90% of oxytetracycline (OTC) within 60 min, achieving degradation rate constants of 0.0393 min−1, which are 9.1 times higher than those of SrFe12O19(0.0043 min−1) and 4.2 times higher than those of g-C3N4(0.0094 min−1). The effectively separated e−play three critical roles: (i) directly activating H2O2to generate ·OH radicals, (ii) promoting the redox cycling of Fe2+/Fe3+ions, and (iii) reducing dissolved oxygen to form ·O2−species. Concurrently, h+directly oxidize OTC molecules through surface-mediated reactions. Furthermore, the 7-SFO/CN composite exhibits exceptional operational stability and applicability, offering a transformative approach for scalable photocatalytic water treatment systems. This work provides an effective strategy for designing efficient and recoverable photocatalysts for environmental remediation.

Fabrication of magnetic dual Z-scheme heterojunction materials for efficient photocatalytic performance: The study of ternary novel MIL-88A(Fe)/BiOBr/SrFe12O19 nanocomposite

Jiabao Gu,Qianwen Li,Xuanyu Long,Xiaohan Zhou,Nan Liu,Zequan Li

In this study, we synthesized the MBSr (MIL-88A(Fe)/BiOBr/SrFe 12 O 19 ) dual Z-scheme heterojunction via an accessible hydrothermal method and investigated the photocatalytic performance of MBSr composites for Rhodamine B (RhB) and Methylene blue (MB). The MBSr-1% photocatalyst exhibited excellent photocatalytic performance, resulting the degradation rate of RhB reached approximately 96.2% within 60 min, which was higher than that of M88 (34%), BiOBr (89%) and M88/BiOBr-7% (93.7%) composites. And the MBSr-1% could eliminate 90.1% of MB within 90 min, which displayed the best photodegradation efficiency of prepared photocatalysts. The enhanced photocatalytic performance can be ascribed to the formation of dual Z-scheme heterojunction, which enhanced visible-light absorption and facilitated the transfer of photoinduced carriers. The MBSr-1% was proved to have excellent stability and reusability after six-recycling run. Furthermore, the major reactive species were h + , •O 2 − and •OH by radical trapping experiments. Finally, a possible photocatalytic pathway and mechanism of MBSr photocatalysts was proposed.

Improved magnetic properties of self-composite SrFe12O19 powder prepared by Fe3O4 nanoparticles

Ruoshui Liu,Di'an Wu,Xiang Yu,Ningfang Zhou,Dan Liu,Lichen Wang,Zhiyi Xu,Huayang Gong,Tongyun Zhao,Jirong Sun,Fengxia Hu,Baogen Shen

Sintered polycrystalline strontium hexaferrite, which is one of the most widely used permanent magnetic materials, has been applied in many areas such as electrical and mechanical transductor devices. Improving the coercivity ( H cJ ) of M-type strontium hexaferrite with a nominal composition SrFe 12 O 19 (SrM) plays an essential role to adapt to many modern applications, but is limited by the process and purity of raw materials. In this work, we prepared SrM powders with different iron resources, sintering temperatures, and Fe/Sr atom ratios. It was found that using Fe 3 O 4 nanoparticles with a Fe/Sr atom ratio of 12 at 1100 °C performed the self-composites with 70% nano-size and 30% micro-size, which had the best performance. The coercivity reaches 348.9 kA/m, which is improved compared to pure SrM obtained by other iron resources in the solid-state method. This process shows a unique formation mechanism and the resulting self-composite microstructure eventually causes enhancement in the properties, which provides a new way for high-performance hexaferrites.

Preparation and magnetic properties of Sm and Co/Zn/Ca co-doped SrFe12O19 hexaferrite

Siyuan Wang,Wei Cai,Dongsheng Shi,Jingwu Zheng,Liang Qiao,Haibo Chen,Naoki Wakiya,Naonori Sakamoto,Takahiko Kawaguchi,Shenglei Che

High-performance SrFe 12 O 19 meets the current demands for lightweight and high-efficiency devices. In this study, Sm‒(Co/Zn/Ca) co-doped spherical SrFe 12 O 19 powders were synthesized via ultrasonic spray pyrolysis. This approach overcomes the limitation of single Sm doping in M-type strontium ferrite, which enhances coercivity but decreases saturation magnetization. The effects of co-doping on the structural and magnetic properties of the material were systematically investigated using X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, Brunauer–Emmett–Teller, Mössbauer spectroscopy, and both room-temperature and low-temperature vibrating sample magnetometry (VSM). Among all the synthesized samples, SrSm 0.20 Zn 0.05 Fe 11.75 O 19 exhibited the highest saturation magnetization ( M s = 78.983 emu/g) while maintaining a coercivity of 7.097 kOe. Compared to SrSm 0.20 Fe 11.80 O 19 , Sm‒Zn co-doping resulted in a 20.12% increase in M s with only a 0.42% reduction in H cj . The results indicate that Zn 2+ preferentially substitutes Fe 3+ at the 4f 2 spin-down sites, reducing the contribution of reverse magnetic moments and thereby enhancing M s . Additionally, as a non-magnetic ion, Zn 2+ does not disrupt Fe‒O‒Fe super-exchange interactions, leading to a minimal reduction in H cj . In contrast, Ca 2+ tends to occupy the 12k and 2a spin-up sites, which reduces spin-up magnetic moments, negatively affecting M s enhancement. Moreover, Co 2+ , being a magnetic ion, disturbs Fe‒O‒Fe super-exchange interactions when incorporated into the SrFe 12 O 19 lattice, leading to a more significant decrease in coercivity. The magneton number ( n B ) calculated from low-temperature VSM confirmed the magnetic moment enhancement effect in the co-doped system, while Mössbauer spectroscopy provided further insights into the hyperfine interactions. This study demonstrates that the Sm‒(Co/Zn/Ca) co-doping strategy effectively balances M s and H cj , significantly improving the magnetic performance of SrFe 12 O 19 . Furthermore, ultrasonic spray pyrolysis proves to be a scalable and cost-effective synthesis method, showing great potential for the large-scale production of high-performance ferrite powders. These findings provide a theoretical foundation for optimizing SrFe 12 O 19 magnetic properties and offer new perspectives for its application in permanent magnet technology.

Tailoring magnetic properties of SrFe12O19 ferrites through Dy–Ni Co-substitution: A comprehensive study

Ruo-Ding Mao,Xing Zhang,Yi-Lei Li,Mu Lan,Wen-Ning Ren,Sheng-Jiang Huang,Xin Chang,Bing-Jie Wang,Yan Jiao,Le-Zhong Li,Xiao-Hui Wu

A solid-phase synthesis method was utilized to create a range of ferrite samples, specifically Sr 1- x Dy x Fe 12- x Ni x O 19 , where x values varied (0, 0.01, 0.02, 0.03, and 0.05). Through X-ray diffraction (XRD) analysis, it was found that up to x  ≤ 0.03, the XRD pattern showed no discernible impurity phases. However, at x  = 0.05, an observable impurity peak attributed to α-Fe 2 O 3 emerged. Room temperature hysteresis loop measurements revealed consistent hard magnetic behavior across all samples. Notably, changes in coercive force directly correlated with magnetocrystalline anisotropy. As substitution increased, the initial saturation magnetization ( M S ) of 59.68 emu/g (at x  = 0.00) moderately reduced to 57.79 emu/g (at x  = 0.05), representing a modest decline of 3.17 %. A clear trend was observed: decreasing grain size led to diminishing dielectric constants. Moreover, a strong link between the Nyquist diagram's semicircle diameter and sample resistivity was evident, showing distinctive metal-semiconductor behavior. These findings shed light on the structural and magnetic characteristics of Dy and Ni co-substituted SrFe 12 O 19 ferrites, suggesting potential for enhanced performance in advanced magnetic and electronic devices. This study significantly contributes to the field of ferrite materials, deepening our insights and paving the way for innovative applications in diverse technological domains.

Effect of SrFe12O19 Orientation in the Inner Semiconductive Layer on Charge Accumulation Characteristics of HVDC Cable

Yanhui Wei,Mingyue Liu,Zhaochen Wang,Xuejing Li,Guochang Li,Chuncheng Hao,Qingquan Lei