配电网半绝缘电磁式PT加装消谐器后损坏原因分析研究

研究了铁磁谐振机理和特点,得出了铁磁谐振简化等效电路和PT承受电压计算方法,分析了半绝缘PT加装一次消谐器后的损坏原因,提出了改进措施。     

铁磁构件内外表面裂纹低频漏磁检测技术研究

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。     

Enhancement in magnetic,piezoelectric and ferroelectric properties on substitution of titanium by iron in barium calcium titanate ceramics

Lead free polycrystalline ceramics with compositional formula Ba_0.90Ca_0.10Ti_1–3x/4Fe_xO₃ (BCT), (x=0.000, 0.005, 0.010, 0.015 and 0.020) were prepared by the solid state reaction method. The effect of substitution of Fe³⁺ ion at Ti-site on the ferroelectric and piezoelectric properties of BCT ceramics was studied. Remanant polarisation (P_r) and saturation polarisation (P_s) show an increasing trend while the reverse trend was observed for coercive field (E_c) with Fe³⁺ substitution. The values of the piezoelectric charge coefficient (d₃₃) and piezoelectric coupling coefficient (k_p) was found to increase with increase in Fe content. Ceramic sample with x=0.02 was found to have a maximum value of d₃₃ (130 pC/N) and k_p (29%). The prepared ceramic samples show magnetic properties as confirmed by recorded MH loops. On substitution of Fe³⁺ ions, the ferroelectric BCT ceramics show clear transformation of the diamagnetic nature of BCT ceramics to weak ferromagnetism.     

Synthesis of double perovskite La2MnNiO6 nanoparticles as highly efficient oxygen evolution electro-catalysts

Double perovskite La₂MnNiO₆ nanoparticles (approximately 30 nm in diameter) were synthesized using a modified sol-gel method followed by a firing process and used as promising electrode materials for oxygen evolution reactions (OERs). The phase purity of the nanoparticles was verified using X-ray diffraction and Raman spectroscopy measurements. La₂MnNiO₆ nanoparticles crystallize in a monoclinic structure (P2₁/n space group) with refined lattice parameters of a = 5.461(5) Å, b = 5.512(3) Å, c = 7.760(5) Å, and β = 90.10(2)°. The elemental composition, particle size, size distribution, and surface area of the La₂MnNiO₆ nanoparticles were also investigated. La₂MnNiO₆ nanoparticles are ferromagnetic in nature and exhibit hysteresis with a saturation magnetization value of approximately 9 emu/g. La₂MnNiO₆ nanoparticles exhibit highly efficient electro-catalytic activity for OERs with a low onset over-potential (approximately 65 mV) and low Tafel slope values (120 mV/dec) in alkaline media. The over-potential of La₂MnNiO₆ nanoparticles at a current density of 10 mA/cm² is in good agreement with the reported over-potential (ƞ₁₀) of double perovskites, commercial Pt/C and IrO₂ electro-catalysts for promoting OERs.     

Impact of rare earth europium (RE-Eu3+) ions substitution on microstructural,optical and magnetic properties of CoFe2−xEuxO4 nanosystems

In this study, pure cobalt ferrite (CoFe₂O₄) nanoparticles and europium doped CoFe₂O₄ (CoFe_2−xEu_xO₄; x = 0.1, 0.2, 0.3) nanoparticles were synthesized by the precipitation and hydrothermal approach. The impact of replacing trivalent iron (Fe³⁺) ions by trivalent rare earth europium (RE-Eu³⁺) ions on the microstructure, optical and magnetic properties of the produced CoFe₂O₄ nanoparticles was studied. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectra exposed the consistency of a single cubic phase with the evidence of Eu₂O₃ phases for x ≥ 0.2. FTIR transmittance spectra showed that, the all investigated samples have three characteristic metal-oxygen bond vibrations corresponding to octahedral B-site (υ₁ and υ₂) and tetrahedral A-site (υ₃) around 415 cm⁻¹, 470 cm⁻¹ and 600 cm⁻¹ respectively. XRD and energy dispersive X-ray spectroscopy studies affirmed the integration of RE-Eu³⁺ ions within CoFe₂O₄ host lattice and decrease of average crystals size from 13.7 nm to 4.7 nm. Transmission electron microscopy (TEM) analysis showed the crucial role played by RE-Eu³⁺ added to CoFe₂O₄ in reducing the particle size below 5 nm in agreement with XRD analysis. High resolution-TEM (HR-TEM) analysis showed that the as-synthesized spinel ferrite, i.e., CoFe_2−xEu_xO₄, nanoparticles are single-crystalline with no visible defects. In addition, the HR-TEM results showed that pure and doped CoFe₂O₄ have well-resolved lattice fringes and their interplanar spacings matches that obtained by XRD analysis. Magnetic properties investigated by the vibrating sample magnetometer technique illustrated transformation of magnetic state from ferromagnetic to superparamagnetic at 300 K resulting in introducing RE-Eu³⁺ in CoFe₂O₄ lattice. At low temperature (~5 K) the magnetic order was ferromagnetic for both pure and doped CoFe₂O₄ samples. Substitution of Fe³⁺ ions in CoFe₂O₄ nanoparticles with RE-Eu³⁺ ions optimizes the sample nanocrystals size, cation distribution and magnetic properties for many applications.     

非晶玻璃包裹细丝的制备与铁磁共振性能的应用

非晶玻璃包裹细丝不仅具有电、磁、强度和塑性等方面的显著特点,而且具有突出的自然铁磁共振性能,作为吸波材料具有潜在的应用价值.阐述了玻璃包裹熔融纺丝法制备非晶玻璃包裹细丝的基本原理和实验参数,介绍了细丝产生铁磁共振性能的基本原理,及在吸波材料方面的应用.     

Effects of ferromagnetic components on energetic ion confinement in ITER

By using a fully three dimensional magnetic field orbit-following Monte-Carlo code, the energetic ion confinement was investigated for the current conceptual design of the ferromagnetic components in ITER which will be employed for reducing the toroidal magnetic field (TF) ripple. The ferromagnetic insert is effective in the reference standard scenario with Q = 10 (Scenario No. 2) and steady state scenario with Q = 5 (Scenario No. 4) to improve the energetic ion confinement. Over-compensation appears at half of the full toroidal magnetic field and its effect becomes stronger when the quantity of the ferromagnetic insert is increased in order to more reduce the TF ripple at the full toroidal magnetic field. Though the current design is acceptable, whether to increase the ferromagnetic insert to achieve lower TF ripple amplitude at the full field operation depends on how prospected are possibilities of lower field operations. Planned test blanket modules do not induce large loss (<1%) at the full field in Scenario No. 4. At the half field, however, the loss reaches ∼10% for the alpha particles due to localized large TF ripple.     

Microstructure and martensitic transformation of Ni–Fe–Ga–Si ferromagnetic shape memory alloys

The effects of the fourth element Si on the martensitic transformation and magnetic properties of Ni–Fe–Ga magnetic shape memory alloys were investigated. A complete thermoelastic martensitic transformation in Ni–Fe–Ga–Si alloys was observed in the temperature range of 218–285 K. The martensitic transformation temperatures of Ni–Fe–Ga alloys are obviously decreased by the substitution of Si for Ga element, that is, the substitution of 1 at.% Si for Ga leads to a decrease of martensitic transformation temperature of about 39.6 K. Moreover, the substitution of Si for Ga leads to a decrease of the saturation magnetic field and the magnetic anisotropy constant K₁ obviously.     

金属磁记忆法诊断的理论基础——铁磁性材料的弹—塑性应变磁化

电磁感应定律证明,铁磁性材料在地球磁场中的自发磁化来源于定向应力作用下材料本身的应变和交变应力作用下材料的非对称弹－塑性应变。某种铁磁性材料的自发磁化过程可由该材料的磁化和退磁曲线来估计,由此推得的磁弹性现象图与实验结果相一致。     

换热管漏磁检测磁化结构有限元分析

针对铁磁性换热管特点,以漏磁检测原理为基础,利用有限元分析软件,建立换热管漏磁检测磁化结构三维模型。研究换热管漏磁检测磁化结构中磁芯几何参数(磁芯内径d和中间磁芯长度l)改变时,换热管内表面圆柱形缺陷产生的漏磁场分布情况,得到磁感应强度轴向分量与径向分量随磁芯几何参数改变时的变化规律。