【作者】 王进；

【导师】 曾德长；

【作者基本信息】 华南理工大学 ， 材料加工工程， 2016， 博士

【摘要】 在全球气候变暖,能源日益短缺的今天,节能降耗已经成为一个全球性的重要研究课题。我国政府近年来也制定了多项政策来促进和鼓励节能技术的发展与推广。在电力电子应用中,软磁材料被广泛应用于制造各种能量转化的关键部件。因此,在电力电子应用领域中,具有低损耗和高饱和磁感应强度的软磁材料具有很大的应用价值。无论在高频领域的应用还是低频领域的应用都有巨大的应用前景。高性能软磁材料的应用不仅可以提高能量转化效率,减小设备体积,而且还可以在节约能源的同时降低资源的消耗。随着材料科学的发展,复合结构型的材料在应用方面体现出了越来越多的优势。复合结构型材料可以通过其多相比例的改变、相内及相间组织形貌的多样性来获得适用于不同场合的应用性能。在软磁材料中非晶/纳米晶软磁合金及磁粉芯便属于复合结构型的材料,近年来在研究者的不懈努力下,这两类软磁材料性能的可调性与应用的稳定性方面都取得了长足的发展。非晶/纳米晶软磁材料受到广泛关注的原因,一是由于其价格低廉,二是由于其具有十分优异的磁性能。非晶/纳米晶软磁材料是目前得到世界上众多科研工作者公认的综合性能最好的软磁材料,其具有高磁导率、高饱和磁通密度、低铁损、低矫顽力和良好的频率特性等优点。在众多领域,特别是各种电子电气元器件中,这类非晶/纳米晶软磁材料已经用于替代铁基非晶材料和钴基非晶材料。但是由于这类非晶/纳米晶软磁材料的研究较晚,对它的研究时间相对于其它传统的软磁材料而言相对较少,仍需要大量的时间和研究工作来进一步明确非晶/纳米晶软磁材料性能并对其制备工艺和配方进行不断的优化。磁粉芯不同于铁基非晶/纳米晶合金,它是一种由软磁粉末经过绝缘包覆后,通过粉末冶金方法制备的复合软磁材料。磁粉芯具有高频低损耗、高饱和磁通密度、温度稳定性好、磁导率随频率变化小、磁导率的恒定区域广且磁导率可通过绝缘介质和软磁粉末的比例来对应用性能进行调节等优点。被广泛应用于开关电器、扼流线圈、高精度设备仪器和电压器中。但是磁粉芯的磁性能受到粉末的粒度、成型压强以及绝缘粘结剂种类和绝缘粘结剂含量等因素的影响,同时与热处理温度也有着密切的联系,完善的制备工艺和详细的制备方法已经成为磁粉芯制备的关键技术和核心问题。本文从铁基非晶/纳米晶合金和磁粉芯入手对复合结构型软磁材料的制备及性能行了系统的研究。首先对铁基非晶/纳米晶合金复合结构型软磁材料进行了系统的研究。首先,我们添加了2at%的稀土元素到fe82.65cu1.35si2b14合金,添加稀土元素对合金的淬态结构、热稳定性、晶化行为以及磁性能有显著的影响。稀土元素y、gd、tb、dy的添加显著地提高了合金的非晶形成能力,同时也有效的提升了合金的热稳定性,对于合金的一次晶化温度提升至少55°c。稀土元素y、gd、tb、dy的添加改变了合金的晶化行为,得到了稳定的fe3b亚稳相。由于gd、tb、dy原子与fe原子间的反铁磁耦合,会显著降低合金的非晶基底的居里温度(tc)及合金的磁矩。y元素的添加有利于提升合金的软磁应用。450°c热处理60分钟后fe80.65cu1.35si2b14y2合金的饱和磁通密度(bs)和矫顽力(hc)分别为1.80t和6.5a/m。为了考察高温环境下的纳米晶软磁合金应用,我们针对于典型的hitperm型fe44co44zr7b4cu1合金进行了研究。我们在fe44co44zr7b4cu1合金中添加2at%的y、si、al、nb、ti这5种合金元素元素,并研究了这些合金元素的添加对合金淬态结构、热稳定性、晶化行为以及软磁性能的影响。结果表明,合金元素的添加依然使(fe44co44zr7b4cu1)98m2合金淬态保持非晶态结构,但对合金的热稳定性却有明显的影响。在众多的元素添加中,si元素和nb元素对二次晶化温度的提升最为显著,将合金的二次晶化温度提升至710°c,且使得合金在较宽的温度范围(500°c~650°c)内热处理1小时后能保持稳定的结构。si元素的添加不仅可以有效提高合金的软磁应用,并可以相对地降低合金的成本。在550°c的温度下热处理300个小时后的(fe44co44zr7b4cu1)98si2合金相比于550°c下热处理1个小时的样品,合金中的晶粒并没有发生明显的长大现象,约为15nm。而两者之间的矫顽力却有着较大的差距,热处理1个小时的样品矫顽力为50a/m,热处理300个小时的样品矫顽力为200a/m。通过能谱分析发现,合金中的si原子以及cu原子随着热处理时间的增加发生了偏聚现象,这可能是导致合金长时间热处理后矫顽力提升的原因。作为另一类复合结构型软磁材料——磁粉芯,本文也对其进行了系统的研究。本文对fe-si-b非晶粉芯和fe-si-al粉芯的制备工艺和软磁性能都进行了详细的研究,并得到一套较为完善的制备工艺。首先,通过对fe-si-b非晶粉芯制备工艺中的成型压强、绝缘粘结剂含量和绝缘粘结剂中不同种无机物添加的改变,来考察了fe-si-b非晶粉芯的表现性能,并对fe-si-b非晶粉芯的制备工艺进行优化。结果表明,随着成型压强的增大,fe-si-b非晶粉芯的磁导率(μe)提高同时损耗(P)降低。随着绝缘粘结剂含量的增加,Fe-Si-B非晶粉芯的磁导率和损耗皆降低。在含有相同绝缘粘结剂含量的情况下,相对于单独添加高岭土或Al2O3,高岭土和Al2O3的复合添加会获得最好的交流应用性能。通过调节成型压强、绝缘粘结剂含量和成分,可以有效的改变Fe-Si-B非晶粉芯的性能。在1600Mpa成型压强下压制成型,绝缘粘结剂含量为7wt%,成分包含有机硅树脂、高岭土及Al2O3所制得的Fe-Si-B非晶粉芯,经过400°C的热处理后,磁导率为28,在Bm为50mT时100kHz频率下损耗仅为44.3W/kg。通过之前研究Fe-Si-B非晶粉芯所得的结果,我们在Fe-Si-Al粉芯的研究中,选定成型压强为1600MPa。在对Fe-Si-Al粉芯的表现性能的研究中发现,粉芯制备工艺中绝缘粘结剂的含量、绝缘粘结剂成分及粉末粒度分布的改变对磁性能有明显地影响。结果表明,随着绝缘粘结剂含量的增加,Fe-Si-Al粉芯的磁导率损耗皆会降低。绝缘粘结剂含量相同时,高岭土和Al2O3的添加会提高Fe-Si-Al粉芯的交流应用性能。在粉末未经分筛时,最高磁导率Fe-Si-Al粉芯配方为1wt%的绝缘粘结剂添加,绝缘粘结剂成分为有机硅树脂、高岭土及Al2O3。其磁导率为60,在Bm为50mT时100kHz下损耗为25.2W/kg。最低损耗Fe-Si-Al粉芯配方为7wt%的绝缘粘结剂添加,绝缘粘结剂成分为有机硅树脂、高岭土及Al2O3。其磁导率为45,在Bm为50mT时100kHz下损耗为18.7W/kg。将原始粉末分筛过后,选用粒度越大的粉末制得的磁粉芯磁导率越高,但同时损耗也会增加。选用粒度<50μm的磁粉,绝缘粘结剂含量7wt%,绝缘粘结剂成分为有机硅树脂、高岭土及Al2O3制作的粉芯在Bm为50mT时100kHz下损耗最低,损耗值为14.0W/kg,同时磁导率也最低,磁导率值为40。更多还原

【Abstract】 With the increasingly serious of global warming and energy shortage, energy consumption has become a major global research. In recent years, our government has also developed a number of policies to promote and encourage the development and promotion of energy-saving technologies. Soft magnetic materials are widely used in the manufacture of various key components of energy conversion in power and electronics applications. Therefore, high saturation magnetic flux density and low-loss soft magnetic materials have great value both in the high frequency or low frequency applications in the field of power and electronics. The application of high-performance soft magnetic materials can not only improve the energy conversion efficiency and reduce the volume of equipment, but also reduce the consumption of resources at the same time.With the development of materials science, composite structural materials reflect more and more advantages in practical applications. The composite structural materials can be suitable for the application under different situations through the changes of multi-phase ratio and the diversity of morphology. The amorphous/ nanocrystalline soft magnetic alloys and magnetic powder cores are typical composite structural materials in soft magnetic materials. In recent years, these two types of soft magnetic materials have made great progresses in performance adjustability and application stability with the tireless efforts of researchers.The amorphous/nanocrystalline soft magnetic materials attracted much attention with its excellent magnetic properties and low prices. Such a soft magnetic material having the advantages of high permeability and saturation flux density, low coercivity and loss, good frequency characteristics, etc. It is recognized as the world’s best overall performance of soft magnetic material. The cobalt-based amorphous and iron-based amorphous has been replaced by the amorphous/nanocrystalline soft magnetic materials in many areas for a variety of electrical and electronic components in the present situation. However, the research period of the amorphous /nanocrystalline soft magnetic materials is relatively short compared to other other conventional soft magnetic materials. A lot of work still needed to further clarify the optimization of technology and formulations of the amorphous/nanocrystalline soft magnetic materials.Unlike the amorphous/nanocrystalline soft magnetic alloys, magnetic powder core is a kind of soft magnetic composite which produced by powder metallurgy process with soft magnetic powders after insulating coating. The magnetic powder cores have advantages of low-loss under high-frequency applications, good thermal stability, small permeability changes in frequency altering, high saturation flux density and wide permeability constant region. The permeability of magnetic powder core can be modified through the proportion of the insulating medium and soft magnetic powder to adjust the performance of the various applications also. And it is widely used in electrical switches, choke coils, high-precision instruments and equipment voltage vessels. However, the performance of the magnetic powder cores is affected by powder particle size, molding pressure and the type and content of insulating binder. The heat treatment temperature also played an important role. The improved preparation process and detailed preparation method are the key technology and core issues for the preparation of magnetic powder cores.In this paper, a systematic study on the preparation and properties of the composite structural soft magnetic materials was started with the amorphous/ nanocrystalline soft magnetic alloys. RE element(Y, Gd, Tb and Dy) substitutions(2at%) of Fe have dramatic effects on the microstructure, thermal stability, crystallization behavior and magnetic properties of the melt spun Fe82.65Cu1.35Si2B14 alloys. In detail, RE additions significantly improve the amorphous forming ability and thermal stability of the alloys. The primary crystallization temperatures are increased for at least 55°C. RE additions also change the crystallization behavior by the precipitation of a steady metastable Fe3 B phase. For Fe80.65Cu1.35Si2B14Gd2 alloy, the Fe3 B phase can be stably exist even the temperature rise up to 600°C. The Curie temperature(Tc) and magnetic moment for Gd, Tb, Dy doped alloys are significantly lower than Y doped and without doping alloys may due to the RE-Fe antiferromagnetic coupling in amorphous matrix. The addition of Y is found to be beneficial for the soft magnetic application of the alloy. The saturation flux density and coercivity for Fe80.65Cu1.35Si2B14Y2 alloy after 60 min annealing under 450°C are 1.80 T and 6.5A/m, respectively.In order to examine the application of nanocrystalline soft magnetic alloy under high temperature environment, typical HITPERM type Fe44Co44Zr7B4Cu1 alloy was targeted studied. Five kinds of alloying elements, Y, Si, Al, Nb and Ti, were added into Fe44Co44Zr7B4Cu1 alloy with atomic percentage of 2%. The effects of the element additions on the microstructure, thermal stability, crystallization behavior and magnetic properties were systematically investigated. The results show that the as-quenched state of(Fe44Co44Zr7B4Cu1)98M2 alloys remain amorphous with the addition of the alloying elements, but the thermal stability of the alloy there are significantly changed. Among the addition elements, Si and Nb increased the secondary crystallization temperature of the alloys most significantly. The secondary crystallization temperature was increased up to 710°C, the alloys can maintain a stable structure after 1 hour heat treatment in a wide temperature range from 500°C to 650°C. The addition of Si not only efficiently increased the soft magnetic applications of the alloy, but also reduced the cost. There is no obvious growth of the grains in(Fe44Co44Zr7B4Cu1)98Si2 alloys after 300 hours annealing under 550°C compared to 1 hour annealing sample. The grain size is ~15nm. But the coercivity of the two sample are much different. The coercivity of 1 hour annealed sample is 50A/m, while the 300 hours annealed sample is 200A/m. Through the Energy Dispersive Spectrometer(EDS) analysis, it was found that the segregation of Si and Cu atoms occurs with the increasing time of heat treatment which lead to the increasing of coercivity.The magnetic powder cores, as another type of composite structural soft magnetic materials, have been systematically investigated also. In this paper, the preparation process and soft magnetic properties of Fe-Si-B amorphous powder cores and Fe-Si-Al powder cores are detailed studied, and an improved preparation technology was obtained.In order to optimize the performance properties and the preparation process of Fe-Si-B amorphous powder cores, the properties of Fe-Si-B powder cores are investigated with altering the molding pressure, insulating binder content and types of inorganic additives in insulating binder. The results show that with the increasing of molding pressure, the permeability(μe) of powder cores increased while the loss(P) reduced. With the increasing of the insulating binder content, the μe and P are both reduced. In the case of the same insulating binder content, the powder cores with complex addition of Kaolin and α-Al2O3 obtained the best alternating current(AC) application performance compare to the simple Kaolin and α-Al2O3 addition. The performance of the Fe-Si-B amorphous powder cores can be effectively changed by altering the molding pressure, the insulating binder content and composition. The Fe-Si-B amorphous powder core manufactured with a molding pressure of 1600 MPa, insulating binder content of 7wt%, insulating binder composition containing silicone resin, Kaolin and α-Al2O3 and annealed under 400°C, the μe and P(at 100 kHz, Bm=50mT) are 28 and 44.3W/kg, respectively.With the prior studies of Fe-Si-B amorphous powder cores, we selected the molding pressure of 1600 MPa in the followed studies of Fe-Si-Al powder cores. It was found that the insulating binder content, insulating binder composition and particle size distribution of the magnetic powders in the preparation process can significantly influence the performance FeSi-Al powder cores. The results show that with the increasing of the insulating binder content, the μe and P of Fe-Si-Al powder cores are both reduced. In the case of the same insulating binder content, inorganic additives of Kaolin and α-Al2O3 added in the insulating binder can effectively improve the application performance of powder cores. In the condition of using magnetic powders without sieving,the core manufactured with insulating binder content of 7wt% and insulating binder composition containing silicone resin, Kaolin and α-Al2O3 obtained the highest μe of 60, while the P is 25.2W/kg(at 100 kHz, Bm=50mT). And the core manufactured with insulating binder content of 7wt% and insulating binder composition containing silicone resin, Kaolin and α-Al2O3 obtained lowest P of 18.7W/kg(at 100 kHz, Bm=50mT), while the μe is 45. With the sieving of original magnetic powders, the larger particle size of the magnetic powder was used, the higher of μe and P were obtained. The Fe-Si-Al powder core manufactured with particle size less than 50μm, insulating binder content of 7wt%, insulating binder composition containing silicone resin, Kaolin and α-Al2O3 obtained lowest P and μe are 14.0W/kg(at 100 kHz, Bm=50mT) and 40, respectively.更多还原