本文選題：釹鐵硼永磁 + La\Ce取代��； 參考：《華南理工大學(xué)》2016年博士論文

【摘要】：永磁材料作為一些裝置中必不可少的組成部分,已經(jīng)在揚(yáng)聲器、硬盤和風(fēng)力發(fā)電等領(lǐng)域得到了廣泛的應(yīng)用。迄今為止,NdFe B永磁仍然是性能最好的室溫永磁材料。但是,NdFeB永磁高溫性能較低,昂貴的稀土元素Nd、Pr、Dy等導(dǎo)致磁體的成本增加。因此,本論文瞄準(zhǔn)于開發(fā)高性能低成本的釹鐵硼永磁材料,主要研究了廉價(jià)的La和Ce元素單獨(dú)和復(fù)合取代稀土元素Nd熔體快淬單相和納米復(fù)合(Nd_(1-x)Mx)yFe94-yB6(M=La,Ce,LaCe;x=0-0.7;y=10,12)磁體以及[Dy_(1-x)(La_0.5Ce_0.5)_x]10Fe84B6磁體的磁性能、微觀組織、特征溫度、矯頑力機(jī)制和交換耦合效應(yīng)的影響。同時(shí)研究了Co替代Fe對(duì)[(NdDy)(La/Ce)]FeB合金室溫磁性能和熱穩(wěn)定性的影響。論文還探討了磁性能變化的物理機(jī)制。首先分析了不同La部分替代Nd的NdFeB合金室溫磁性能。研究發(fā)現(xiàn),10%La取代Nd和5%La取代Nd有利于提高納米復(fù)合磁體和單相磁體的磁性能。其中前者的磁性能可達(dá)到:剩磁106 emu/g、最大磁能積138 kJ/m~3、矯頑力465 kA/m,后者可達(dá)到:剩磁104 emu/g、最大磁能積(BH)max=151 kJ/m~3和矯頑力721 kA/m。并且發(fā)現(xiàn)La取代也降低了磁體的居里溫度和自旋重取向溫度。對(duì)于部分Ce取代的NdFeB合金,研究表明,隨著Ce替代Nd量的增加,納米晶單相和納米復(fù)合合金的剩磁、磁能積和矯頑力下降。但是,20%Ce取代納米復(fù)合磁體的矯頑力發(fā)生了反常的增加,導(dǎo)致磁性能有一定程度的改善,磁性能達(dá)到:剩磁99 emu/g、最大磁能積103 kJ/m~3和矯頑力392 kA/m。對(duì)于單相合金,Ce取代磁體的磁性能隨著取代量增加逐漸降低的主要原因是Ce2Fe14B相的各向異性場(chǎng)低于Nd2Fe14B相在La_0.5Ce_0.5復(fù)合取代Nd的納米復(fù)合磁體中,也可以獲得較好的磁性能。x=0.1磁體的磁性能為剩磁114 emu/g、最大磁能積147 kJ/m~3和矯頑力471 kA/m。其中10%La或者La_0.5Ce_0.5取代Nd磁體的矯頑力表現(xiàn)出反常的增加。對(duì)比La_0.75Ce0.25和La0.25Ce_0.75替代的NdFe B合金,Ce替代導(dǎo)致更嚴(yán)重的磁性能下降,La更有益于合金的磁性能。作為對(duì)比,也研究了La_0.5Ce_0.5取代Dy元素的快淬[Dy_(1-x)(La_0.5Ce_0.5)_x]10Fe84B6合金。結(jié)果表明,30%La_0.5Ce_0.5取代Dy的磁體獲得了最佳的磁性能:Hcj=714 kA/m,(BH)max=43kJ/m~3。此外,研究還發(fā)現(xiàn),La_0.5Ce_0.5取代Nd和Dy磁體的高溫性能和矯頑力機(jī)制都有所不同。其中La_0.5Ce_0.5取代Nd的磁體的矯頑力機(jī)制更偏向于釘扎機(jī)制,而La_0.5Ce_0.5取代Dy的磁體更偏向于形核機(jī)制。通過對(duì)不同取代(La、Ce或者LaCe)磁體磁性能隨溫度的變化研究發(fā)現(xiàn),磁體的居里溫度TC和自旋重取向溫度TSR都有所降低。納米晶合金的TSR低于常規(guī)的微米晶合金。TEM結(jié)果顯示了La_0.5Ce_0.5混合取代磁體的晶粒細(xì)小,分布均勻,這也是它剩磁增強(qiáng)的原因。研究了磁體的Henkel曲線,回復(fù)曲線和磁導(dǎo)率以分析磁體的交換耦合作用。結(jié)果顯示,10%La取代Nd的納米復(fù)合磁體和5%La取代Nd的單相磁體的納米晶間的交換耦合作用也有所增加。最后,研究了Co取代Fe元素對(duì)富Nd和單相的磁體中磁體磁性能的影響。研究發(fā)現(xiàn),磁體的剩磁、矯頑力和飽和磁能積都隨著Co含量的上升而降低;但Co替代導(dǎo)致居里溫度增加,從而改善La、Ce替代合金的熱穩(wěn)定性。采用La_0.5Ce_0.5取代Nd和Dy的磁體在300-400 K范圍內(nèi)具有較低的矯頑力溫度系數(shù)和剩磁溫度系數(shù)。本論文研究表明,在快淬釹鐵硼磁體中,采用低成本的La或Ce元素部分取代Nd元素,通過成分優(yōu)化,可以在降低納米晶釹鐵硼永磁成本的基礎(chǔ)上,可以保持較好的磁性能。Co替代Fe可以進(jìn)一步改善這類磁體的高溫性能。
[Abstract]:As an essential component of some devices, permanent magnetic materials have been widely used in the fields of loudspeaker, hard disk and wind power generation. So far, NdFe B permanent magnet is still the best room temperature permanent magnetic material. However, the high temperature performance of NdFeB permanent magnet is low, and the cost of the precious rare earth elements Nd, Pr, Dy and so on leads to the increase of the cost of the magnets. Therefore, this paper is aimed at developing high performance and low cost Nd-Fe-B permanent magnetic materials, mainly studying the magnetic properties of the cheap La and Ce elements Nd melt fast quenching single phase and nanocomposite (Nd_ (1-x) Mx) yFe94-yB6 (M=La, Ce, LaCe; x=0-0.7, y=10,12) magnets and the magnetic properties of the magnets. The influence of microstructure, characteristic temperature, coercive force mechanism and exchange coupling effect on the magnetic properties and thermal stability of the Fe (NdDy) (La/Ce)]FeB alloy at room temperature was studied. The physical mechanism of the change of magnetic energy was also discussed. The magnetic properties of the NdFeB alloy at room temperature of the different La part of the substitute Nd were analyzed. Replacing Nd with Nd and 5%La helps to improve the magnetic properties of nanocomposite magnets and monophasic magnets. The magnetic properties of the former can be achieved: the magnetic energy of the former is 106 emu/g, the maximum magnetic energy product is 138 kJ/m~3, the coercive force is 465 kA/m, the latter can be reached: the remnant magnetic 104 emu/g, the maximum magnetic energy product (BH) max=151 kJ/m~ 3, and the coercive force 721 kA/m. and found La substitution also reduces the magnet. The Curie temperature and the spin reorientation temperature. For some Ce substituted NdFeB alloys, the study shows that the remanence, the magnetic energy product and the coercive force of the nanocrystalline and nanocomposite alloys decrease with the increase of the Ce substitution of Nd. However, the coercivity of the 20%Ce substituted nanocomposite magnets has been abnormal increasing, resulting in a certain degree of magnetic energy. The magnetic energy is improved: the magnetic properties of the remanence are 99 emu/g, the maximum magnetic energy product 103 kJ/m~3 and the coercive force 392 kA/m. for the single-phase alloy. The main reason for the gradual decrease of the magnetic properties of the Ce substituted magnets is that the anisotropy field of the Ce2Fe14B phase is lower than that of the Nd2Fe14B phase in the nanocomposite magnets of the La_0.5Ce_0.5 composite replacement Nd. The magnetic energy of the good magnetic energy.X=0.1 magnet is 114 emu/g, the maximum magnetic energy product 147 kJ/m~3 and the coercive force 471 kA/m. in which the coercive force of the 10%La or La_0.5Ce_0.5 substitution of the Nd magnet shows an abnormal increase. The magnetic properties of the alloy. As a contrast, the fast quenched [Dy_ (1-x) (La_0.5Ce_0.5) _x]10Fe84B6 alloy with La_0.5Ce_0.5 replacing the Dy element is also studied. The results show that the magnets with 30%La_0.5Ce_0.5 replace Dy have the best magnetic properties: Hcj=714 kA/m, (BH) max=43kJ/m~3.. The coercivity mechanism of the magnets with La_0.5Ce_0.5 instead of Nd is more biased towards the pinning mechanism, and the magnets with La_0.5Ce_0.5 instead of the Dy are more biased towards the nucleation mechanism. The magnetic properties of the magnets with different substitutions (La, Ce or LaCe) have been found by the change of the magnetic properties with the temperature, and the temperature TC of the magnets and the spin reorientation temperature TSR are found. The TSR of nanocrystalline alloy is lower than the conventional Microcrystalline Alloy.TEM results. The results show that the grain size and distribution of the La_0.5Ce_0.5 mixed magnets are fine and uniform. This is also the reason for its remanence enhancement. The Henkel curve, recovery curve and permeability of the magnets are studied to analyze the exchange coupling effect of the magnets. The results show that 10%La is a substitute for Nd. The interaction between nanocomposite magnets and the nanocrystals of single phase magnets with 5%La instead of Nd has also increased. Finally, the effect of Co substitutions on the magnetic properties of the magnets in Nd rich and single-phase magnets is studied. The study shows that the remanence of the magnets, coercive force and the saturated magnetic energy of the magnets are all decreased with the increase of the Co content; but the substitution of Co causes the substitution of the Co. Curie temperature increases, thus improving the thermal stability of La, Ce substitute alloy. The magnets with La_0.5Ce_0.5 to replace Nd and Dy have lower coercive force temperature coefficient and remanence temperature coefficient in the range of 300-400 K. On the basis of reducing the cost of nanocrystalline NdFeB permanent magnet, it is possible to maintain a better magnetic energy.Co instead of Fe to further improve the high temperature properties of these magnets.
【學(xué)位授予單位】：華南理工大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：TM273
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本文編號(hào)：1939468