用人工神经网络研究合金元素对NdFeB永磁体磁性能的影响

为了系统研究合金元素对Nd-Fe-Co-Zr-B系永磁合金磁性能的影响，采用均匀设计方法设计了Nd、Co、Zr和B的4因素6水平U18（6^4）试验方案，根据试验结果，建立了合金成分与磁性能之间的人工神经网络（ANN）预测模型。利用该预测模型获得的成分-性能的二维曲线、三维曲面及等高线图，研究了单个合金元素以及多元素间的交互作用对NdFeB磁体磁性能的影响规律。结果表明：预测结果与实测结果吻合良好，预测精度高；Nd、Zr为提高矫顽力Hcj而降低剩磁Br的元素；Co、B则对提高Br有利而对提高Hcj不利；合金元素对Hcj与Br的影响呈相反的趋势；元素间交互作用对磁性能影响显著。     

晶粒取向与烧结NdFeB磁体的磁性能

研究了烧结ＮｄＦｅＢ磁体的硬磁性能与晶粒取向程度的关系，结果表明：随着晶粒取向程度的增强，磁体的剩余磁极化强度Ｊｒ单调上升、内禀矫顽力ｊＨｃ单调下降，磁感矫顽力ＢＨｃ先上升，达到一极大值后下降，从而导致了最大磁能积（ＢＨ）ｍａｘ的饱和行为。应用矫顽力的发动场理论很好地解释了这一实验现象。     

NdFeB纳米复合永磁薄膜的研究进展

就近几年来复合永磁薄膜的发展状况,对薄膜的制备技术、交换耦合作用以及提高磁性能的方法做了简要的评述.     

快淬Nd9Fe85-x MnxB6(x=0、0.5、1)磁性能研究

应用DTA，XRD，Moessbauer谱和VSM对快淬Nd9Fe85-xMnxB6(x=0、0.5、1）纳米复合材料磁性能进行了研究，发现少量Mn的掺杂能够显著促进快淬样品的晶化并提高快淬样品的永磁性能，在合适的热处理条件下，得到的最佳矫顽力和剩磁化分别从339．5kA/m和0．70提高到398．1kA/m和0．72，最大磁能积（BH）max从83．6kJ/m^3提高到87．5kj/m^3，而剩磁没有明显的下降，TMA显示Mn掺杂降低Nd2Fe14B相的居里温度并提高α-Fe相的居里温度，认为永磁性能的提高是由于Mn进入两相的晶格。     

纳米晶复合Nd10Fe76B10Nb4-xZrx（x=0～4）永磁合金的磁性能研究

采用熔体快淬法制备了成分为Nd10Fe76B10Nb4-xZrx(x=0～4)的合金条带,退火处理后得到了纳米晶复合永磁合金。利用振动样品磁强计(VSM)分析了该合金体系的退磁曲线、磁交互作用曲线(δM-H曲线)、磁化率χ随外加磁场变化曲线,研究了其磁性能及软、硬磁性相间的交换耦合作用的变化。结果表明,添加适量的Zr元素可细化晶粒,从而有效地增强合金中软、硬磁性相间的交换耦合作用,进而提高合金的综合磁性能。当Zr含量为2%(原子分数)时,制得的合金具有最佳的综合磁性能:jHc=1059.16kA/m,Br=1.08T,(BH)max=185.72kJ/m3。     

纯石墨粉对NdFeB烧结磁体的显微组织和磁性能的影响

主要研究了在烧结ＮｄＦｅＢ磁体的晶界添加Ｃ对显微组织和磁性能的影响。实验表明，随Ｃ添加量的增大，晶粒先粗化再细化，矫顽力呈先下降后上升再下降的趋势当Ｃ一达到０．４％ｗｔ时，晶界变得零乱而不规整。Ｘ射线衍射分析表明此时磁体内生成了Ｎｄ２Ｆｅ１７Ｃ相，矫顽力和晶粒尺寸的变化均与Ｎｄ２Ｆｅ１７Ｃ的生成有关。     

纳米晶复合Pr2Fe14B/α-Fe合金薄带的磁性

研究了双相纳米晶复合Ｐｒ２Ｆｅ１４Ｂ／α－Ｆｅ永磁合金薄带的剩磁增强效应与α－Ｆｅ体积分类、合金晶粒平均尺寸ｄ、辊速υ以及薄带厚度之间的关系，讨论了起始磁化过程，Ｈｃｉ与Ｈｅｘｔ关系以及形核场与交换耦合钉扎场的物理模型和磁硬化机理。     

晶化热处理条件对Nd2(FeCo)14B/α-Fe纳米复合材料磁性能的影响

用熔体快淬和晶化处理的方法制备了Nd2(FeCo)14B／α-Fe纳米复合材料。研究了晶化热处理温度和时间对材料磁性能的影响。结果表明Nd2Fe35.5Co2B4.5纳米复合材料的磁性能随热处理条件而变化．较高温度短时间比较低温度长时间热处理样品的磁性能稍好一些，并对其机理进行了研究。     

NdFeB纳米晶双相复合永磁材料研究进展

NdFeB纳米晶双相复合永磁材料，由于其潜在的优异磁性能和商业价值，成为当今材料领域研究的热点。本文就近年来NdFeB纳米晶双相复合永磁材料的发展状况，从该类合金的交换耦合作用、分类以及提高磁性能的方法三个方面为重点，作简要的评述。     

不同表面处理工艺对快淬NdFeB永磁粉抗氧化性和磁性能影响

本文对快淬ＮｄＦｅＢ永磁粉分别采用化学镀镍,重铬酸盐钝化处理,重铬酸盐钝化还原处理以及硅烷偶联处理的重铬酸盐钝化－还原／硅烷复合处理等工艺进行了表面包覆,研究了表面包覆处理前后的快淬ＮｄＦｅＢ磁粉的抗氧化特性,并初步比较了包覆处理前后的快府ＮｄＦｅＢ磁粉制成粘结ＮｄＦｅＢ磁体的磁性能,结果表明上述工艺方法的均能改善ＮｄＦｅＢ磁粉的抗氧化性,其中以重铬酸盐钝化－还原／硅烷偶联处理形成的包覆层的抗氧化     

Magnetic properties of Cu substituted Co-ferrite

Copper substituted Co-Cu ferrites Co_1 − xCu_xFe₂O₄ (0 ≤ x≤0.5) have been studied with Mössbauer spectroscopy, x-ray diffraction, and vibrating sample magnetometer (VSM). The Co-Cu ferrite toroidal core samples were sintered at 860-940 °C for 2 h and the initial permeability, quality factor, density and shrinkage were also measured. The crystal structure was found to be an inverse cubic spinel with the lattice constant a₀ = 8.390 Å and a₀ = 8.386 Å for Co-ferrite and Cu²⁺ substituted Co-ferrite, respectively, by Rietveld profile analysis using the FULLPROF program. Hyperfine field was decreased with increasing Cu²⁺ concentration. The saturation magnetization (Ms) of the Co-Cu ferrite annealed at 900 °C decreased drastically and the coercivity, Hc, dropped dramatically from about 1419 to 455 Oe as copper concentration x decreased from 0.0 to 0.5. This shows that Ms, Hc can be controlled using Cu content, and initial permeability and quality factor Q is nearly constant in Cu²⁺ substituted Co-ferrite. The toroidal core data showed that the density and shrinkage of Co_1 − xCu_xFe₂O₄ (0≤x ≤ 0.5) ferrites increased with increasing quantity of Cu ions.     

Magnetic properties,microstructures and domain structures of arc-plasma sprayed Nd-Fe-B permanent magnet

Thin Nd-Fe-B films prepared by arc-plasma spraying at different substrate temperatures were investigated for their magnetic and structural properties. The isotropic magnets with the best magnetic properties (_M H _c=1.2 MA m^–1, _o M _r=0.6 T, (BH)_max=64 kJ m^–3), were obtained after plasma spraying the Nd-Fe-B powders on water-cooled copper substrates and subsequently annealing the films for 0.5 h at 750 °C. The optimum magnetic properties of the anisotropic Nd-Fe-B films, i.e. _M H _c=1.2 MA^–1, _o M _r=0.9 T and (BH)_max=180 kJ m^–3, were obtained in films sprayed on to heated to 600 °C substrates. The magnetic properties of the sprayed films were strongly influenced by the microstructure. The domain structure of these films is also presented.     

Magnetic properties of Re-substituted Ni–Mn ferrite nanocrystallites

The effect of Fe³⁺ ions substitutions by rare-earth ions on magnetic properties of nanocrystalline Ni–Mn ferrite prepared by emulsion method was investigated. X-ray diffraction pattern indicated the presence of cubic structure of spinel ferrite. The crystallite sizes increased with an increase in the heat treatment temperatures, while it decreased for the substitution of rare-earth ions. The magnetic properties were changed with types of rare-earth ions and heat treatment temperatures. Room temperature Mössbauer spectra can differentiate between superparamagnetism and ferrimagnetism in nature.     

Magnetic and dielectric properties of cadmium substituted nickel cobalt nanoferrites

Nano particles of Cd_XNi_(0.5?X)Co_0.5Fe₂O₄ (x = 0.0, 0.1, 0.2 and 0.3) were prepared by coprecipitation method. The lattice constant and distribution of cation in A-site and B-site have been deduced through X-ray diffraction (XRD) data analysis. The lattice constant (?) was found to increase with increase in Cd²⁺ concentration in the spinel structure of Ni–Co ferrites. The saturation magnetization was found to decrease with increase in Cd concentration for all the samples. It is observed that the Curie temperature (T_c) is higher than in bulk counterpart. The dielectric constant increases with increase in Cd concentration. This increase in dielectric constant is attributed to the formation of Fe³⁺ ion in the octahedral site which increases the hopping between Fe³⁺ and Fe²⁺.     

高性能各向同性及各向异性Nd-Fe-B/Fe复合磁体的制备

采用将Nd-Fe-B磁粉与Fe粉混合的方法,并结合真空感应热压烧结技术制得高性能的各向同性及各向异性复合磁体。研究了Fe粉含量对热压磁体磁性能的影响,以及温度和压力对磁体致密度和磁性能的影响。结果表明,适量的Fe粉添加(3%,质量分数)可提高热压磁体磁性能;升高温度或提高压力均可大幅提高磁体致密度,但过高的烧结温度使晶粒快速长大,恶化磁体磁性能,而温度过低磁体难易全致密化。在最佳热压温度及压力下制备的热压磁体具有最佳的磁性能:Br=0.852T,Hcj=798kA/m,(BH)m=131.5kJ/m3,磁体密度达7.72g/cm3;热变形后,最大磁能积达331kJ/m3。     

Magnetic and electrical properties of lanthanum substituted yttrium iron garnets

Polycrystalline yttrium lanthanum iron garnets (Y₃La _x Fe_5-x O₁₂) with varying La substitution (0 ≤ x ≤ 0.5) have been prepared in the pellet form, and studied by X-ray diffraction, magnetization, a.c. susceptibility and electrical resistivity measurements. The lattice constants are determined and the applicability of Vegard’s law has been tested. The saturation magnetization (4 πM _S) decreases very slowly almost linearly with increasing x from x = 0.0–0.5 indicating minimal reduction in ferrimagnetism and least magnetic loss. Variation of saturation magnetic moment per formula unit at 300 K with x can be explained satisfactorily assuming the collinear spin-ordering model. The Curie temperature (T _c) reduces very slowly with increasing x, which is consistent with the observed decrease in 4 πM _S with x. The activation energy (E) decreases very slowly with increasing x for x > 0.1.     

Magnetic and optical properties of Mn doped ZnO nanocrystalline films

We have investigated the properties of Mn-doped ZnO nanocrystalline film growing on zinc foil by the hydrothermal method. X-ray photoelectron spectroscopy shows that the manganese ions exist as Mn2+ in the film. From UV-vis spectra, we observe a red shift in wavelength of absorption and greater reflectivity due to the Mn ion incorporation in ZnO lattices. The photoluminescence spectrum of the Mn-doped ZnO film shows two strong new blue peaks centered at 424 nm and 443 nm, besides the UV emission peak owing to the band gap of ZnO semiconductor. The magnetic property of the Mn-doped ZnO exhibits a room temperature ferromagnetic characteristic with a saturation magnetization (Ms) of 0.3902 x 10(-3) emu/cm3 and a coercive field of 47 Oe. We suggest that the blue emission of the Mn-doped ZnO film corresponds to the electron transition from the level of interstitial Zn and Mn to the valence band. The defects brought about by Mn ion incorporation are the main cause of the room temperature ferromagnetic property.     

钕铁硼永磁材料电镀Ni-P非晶态镀层

研究了钕铁硼永磁材料电沉积Ni-P合金非晶态镀层的镀液组成、工艺参数和工艺流程,分析了影响镀层性能的影响因素,包括电流密度、温度、镀液pH值及亚磷酸的含量等。测定了镀层与基体的结合强度;用中性盐雾试验评定了镀层的耐蚀性。结果表明,Ni-P非晶态镀层导磁率高,矫顽力低,化学稳定性好,耐蚀性优异,是钕铁硼永磁材料的一种理想保护镀层。     

Magnetic properties of polycrystalline gadolinium calcium vanadium and indium substituted YIG

The gadolinium garnet system {GdzY3-2x-zCa2x} [Fe2-yIny] (Fe3-xVx)O12was investigated as a function of x, y, and z for0 leq x leq 0.6, 0 leq y leq 1.0, and0 leq z leq 2.4. The relationships between their compositions and magnetic properties were clarified. It was shown that some combinations of components in this system displayed improvements with respect to temperature stability (alpha = 0.05%/°C-20 sim 60 degC) and ferromagnetic resonance linewidth (ΔH = 20 ∼ 30 Oe) as compared with conventional garnets.     

Nd－Fe－B永磁材料镀镍

针对Ｎｄ－Ｆｅ－Ｂ永磁材料组成元素钕（Ｎｄ）的氧化还原电势较负（－２．４４Ｖ）的特点，通过探索性试验，详细研试了Ｎｄ－Ｆｅ－Ｂ合金产品除油、出光和浸镀工艺的效果和工艺参数。结果表明，按照确定的工艺规范进行施镀，显著地提高了镀镍层与基体之间的结合强度，改善了镀镍层的质量。