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超低损耗FeSiAl磁粉芯的制备与性能

蹇汉杰, 鲍康馨, 孙旗, 王力, 盛汝昌, 赵利明, 冒爱琴, 郑翠红

蹇汉杰, 鲍康馨, 孙旗, 等. 超低损耗FeSiAl磁粉芯的制备与性能[J]. 复合材料学报, 2024, 42(0): 1-9.
引用本文: 蹇汉杰, 鲍康馨, 孙旗, 等. 超低损耗FeSiAl磁粉芯的制备与性能[J]. 复合材料学报, 2024, 42(0): 1-9.
JIAN Hanjie, BAO Kangxin, SUN Qi, et al. Preparation and performance of ultra-low core loss FeSiAl soft magnetic composites[J]. Acta Materiae Compositae Sinica.
Citation: JIAN Hanjie, BAO Kangxin, SUN Qi, et al. Preparation and performance of ultra-low core loss FeSiAl soft magnetic composites[J]. Acta Materiae Compositae Sinica.

超低损耗FeSiAl磁粉芯的制备与性能

基金项目: 安徽省科技厅重点研发项目(202104a05020031)
详细信息
    通讯作者:

    郑翠红,硕士,教授,硕士生导师,主要研究方向为无机非金属材料 E-mail: zhch@ahut.edu.cn

  • 中图分类号: TM271; TB332

Preparation and performance of ultra-low core loss FeSiAl soft magnetic composites

Funds: Key R&D Project of Anhui Provincial Department of Science and Technology (202104a05020031)
  • 摘要: 目前家电、汽车和手机等产品的电子元器件日益呈现小型化、智能化的发展趋势,因此,降低磁粉芯(SMCs)在高频、大功率下应用时的功率损耗是适应其发展的必要措施。将气雾化Fe-9.6 wt%Si-5.4 wt%Al(FeSiAl)磁粉进行磷化绝缘处理,经预热处理、成型和退火热处理,得到了超低损耗FeSiAl复合磁粉芯(SMCs)。分析结果表明,磷化后的FeSiAl磁粉经热处理后,颗粒表面包覆的磷酸盐转变为硅酸盐,且磁粉中晶粒长大,磁粉的矫顽力降低;制得的磁粉芯功率损耗也明显降低,这主要归因于磁滞损耗的显著降低;当磷酸使用量为0.5 wt%时,50 kHz下功率损耗由79.44 mW·cm−3降低至58.56 mW·cm−3

     

    Abstract: Currently, electronic components applied in household electric appliances, cars and mobile phones are increasingly presenting a trend of miniaturization and intelligence. Thus, it is urgent to reduce the core loss of soft magnetic composites (SMCs) apply at high frequency and high power. In this work, gas atomized Fe-9.6wt%Si-5.4wt%Al (FeSiAl) magnetic powder was firstly subjected to a phosphating process for electrical insulation, then the phosphated FeSiAl magnetic powder was heated, formed, and annealed, resulting in FeSiAl SMCs. Analytical results show that the particle surface of the phosphated FeSiAl magnetic powder was transformed from phosphate to silicate after heat treatment, accompanied by an increase in its crystalline size and a decrease in its coercivity. Core loss of the obtained SMCs also decreases apparently, due to the significant decrease in their hysteresis loss. Moreover, when the amount of the phosphoric acid used reaches 0.5 wt%, the core loss decreases from 79.44 mW·cm−3 to 58.56 mW·cm−3 at 50 kHz.

     

  • FeSiAl金属磁粉芯具有优良的频率稳定性、功率损耗低、价格低等优点,广泛应用于开关电源、滤波电感器和脉冲变压器[1-4]。随着电器小型化、智能化的发展,磁粉芯需要具有更低的功率损耗。在生产磁粉芯过程中,磁粉绝缘包覆工艺、热处理等因素直接影响磁粉芯功率损耗[5]。磁粉的绝缘包覆包括有机包覆、无机包覆和有机-无机复合包覆等[6],业界广泛采用磷酸有机溶液(丙酮、乙醇等)作为磷化液对磁粉进行包覆处理,即通过化学反应在磁粉表面形成一层绝缘磷化膜。但磷酸在有机溶液中与磁粉反应不完全,后续生产中残留磷酸有腐蚀磁粉的风险,造成功率损耗升高[7];另外有机物用量大、易挥发、污染较为严重。

    因此本文尝试采用气雾化FeSiAl磁粉为原料,以水为溶剂的磷化方案,结合热处理的方式,以进一步降低FeSiAl磁粉芯的功率损耗,提高磁粉芯的磁性能。

    实验所用气雾化FeSiAl磁粉(颗粒粒径<74 μm)为马鞍山新康达磁业股份有限公司提供,浓磷酸(浓度>85 wt%)购自山东满堂红新材料有限公司,硬脂酸锌(颗粒粒径<13 μm)购自灵寿县中石恒达矿产品加工厂,硅树脂购自山东大易化工有限公司。磷酸加入量分别为磁粉质量的0.1 wt%、0.2 wt%、0.3 wt%、0.4 wt%、0.5 wt%;与磁粉混合均匀后加热机械搅拌至干燥;在680℃、N2气氛下热处理1 h,再分别添加磁粉质量0.5 wt%硅树脂粘结剂和0.3 wt%硬脂酸锌脱模剂;在2090 MPa下将磁粉压制成环形试样(外径26.92 mm、内径 14.73 mm、高度 11.10 mm)。压制成型的试样在680℃、N2气氛下退火1 h,得到复合磁粉芯样品,实验流程如图1所示。按照磷酸含量从小到大,将磷化后磁粉未预热处理的样品编号为0.1 wt%HP/FeSiAl、0.2 wt%HP/FeSiAl、0.3 wt%HP/FeSiAl、0.4 wt%HP/FeSiAl、0.5 wt%HP/ FeSiAl;同理磷化经预热处理后的样品编号为0.1~ 0.5 wt%HPT/FeSiAl。

    图  1  实验流程示意图
    Figure  1.  Diagram of experimental proces

    采用带有能谱仪(EDS)的JSM-7800型号扫描电子显微镜(SEM)观察样品的微观形貌;用Microtest63770 LCR计测量磁粉芯在1~1000 kHz下的有效磁导率(μe)。用ST2643型超高阻、微电流测试仪测量磁粉芯体电阻率(ρv)。用SY8216 B-H功率分析仪测量了磁粉芯100 mT、10~150 kHz的功率损耗(Pcv);用日本理学Ultima IV 型号X射线衍射(XRD)对样品进行物相分析。用Micro Sense公司生产的EZ7型振动样品磁强计(VSM)测量样品的饱和磁化强度(Ms)和矫顽力(Hc)。用日本岛津公司生产的IRAffinity型傅里叶变换红外光谱仪(FTIR)测试了磁粉的红外吸收光谱。用赛默飞世尔科技公司生产的EscaLab 250 Xi型X射线光电子能谱仪(XPS)测试了磁粉的表面元素价态。

    磁粉在磷化后及磷化预热处理后颗粒形貌分别如图2(a)、(b)所示。图2(a)中大颗粒和小颗粒分散,有少量团聚现象;而图2(b)中小颗粒和大颗粒相结合,少量小颗粒分散在大颗粒周围;这是因为磷化后磁粉颗粒团聚,但结合容易脱落,经过预热处理增强了颗粒之间的结合,导致小颗粒聚集在大颗粒上。图2(c)为磷化后磁粉颗粒形貌及其表面元素分布图。磁粉颗粒表面除了Fe、Si、Al外,O、P元素分布均匀。

    图  2  (a)磷化后及 (b)预热处理磁粉颗粒SEM图像;(c)磷化后颗粒EDS元素分布图;磁粉XRD分析图谱
    Figure  2.  SEM images of (a)phosphated and (b)heated powders, (c)EDS results of phosphated powders

    图3 (a)、(b)分别为磁粉芯的密度)和有效磁导率(μe)与磷酸含量的关系图。由图3(a)知,在磷酸加入量为0.1~0.5 wt%范围内,HP/FeSiAl磁粉芯ρ值无明显变化;HPT/FeSiAl磁粉芯ρ值在相同磷酸加入量时小于前者,且随磷酸加入量增加而减小,从5.89 g·cm−3减小到5.83 g·cm−3。从图2(a)、(b) 中可知,预热处理后小颗粒磁粉聚集在大颗粒磁粉上,在后续压制成型过程中小颗粒不能更好的滑动并填充到大颗粒之间的气隙中,导致其密度的降低;随磷酸加入量的增加,预热处理后的磁粉颗粒聚集现象更加明显,进一步降低了磁粉芯密度。HP/FeSiAl和HPT/FeSiAl磁粉芯μe和其ρ值趋势一致。磁粉芯主要由磁性物质、绝缘物质和气隙组成,磁粉芯ρ降低,则同体积下磁性物质含量降低导致其μe下降[8, 9],0.5 wt%HPT/FeSiAl相较0.1 wt%HPT/FeSiAl 磁粉芯μe从74.52下降到52.10。在相同磷酸加入量时,经过预热处理后的磁粉芯具有更低的ρμe

    图  3  磷酸含量对磁粉芯(SMCs) (a)密度、(b)有效磁导率的影响
    Figure  3.  Effects of the proportion of H3PO4 on the SMCs (a)ρ, (b)μe

    图4为磁粉芯样品在10~150 kHz间功率损耗(Pcv)随频率(f )变化关系,由图4可知,随着磷酸加入量的增加,HP/FeSiAl和HPT/FeSiAl磁粉芯Pcv均呈现下降趋势;且在相同磷酸加入量时HPT/FeSiAl磁粉芯Pcv更低,0.5 wt%HP/FeSiAl、0.5 wt%HPT/FeSiAl磁粉芯Pcv分别为79.44 mW·cm−3和58.56 mW·cm−3

    图  4  磁粉芯的功率损耗随频率变化图
    Figure  4.  Pcv of SMCs varies with frequency

    磁粉芯的Pcv分为三个部分,分别为涡流损耗(Pe)、磁滞损耗(Ph)、剩余损耗(Pr)[10-12]。涡流损耗是在磁芯线圈中加上交流电压时因磁芯材料存在电阻,线圈中激励电流流过时产生的损耗;磁芯电阻率越大则磁粉颗粒间产生的涡流效应越小,相应地磁芯的涡流损耗减小[13]。当磁芯的外加磁场去除时磁芯中的一部分磁畴随之发生转动恢复

    原来的方向,然而另一部分磁畴需要克服畴壁的摩擦发生刚性转动而保持磁化方向,这部分克服摩擦消耗掉的能量即为磁滞损耗[14]。剩余损耗是由于磁化弛豫效应或磁性滞后效应引起的损耗。剩余损耗占比很小可忽略不计[15],因此对功率损耗进行损耗分离可只考虑涡流损耗与磁滞损耗两部分。公式如下所示:

    Pcv=Pe+Ph+Pr (1)

    涡流损耗Pe包括颗粒间(Ptere)和颗粒内部的涡流损耗(Ptrae),分别表示为如下公式:

    Ptere=CtereB2mf2 (2)
    Ptrae=CtraeB2mf2 (3)

    其中CtereCtrae分别为颗粒间和颗粒内的涡流系数,Bm为最大磁通密度,f为频率。

    磁滞损耗Ph与准静态磁滞回线的面积和频率f成正比,可以表示为:

    Ph=ChBmf (4)

    其中Ch为磁滞系数。

    忽略Pr后,将各组样品100 mT、10~150 kHz下Pcv进行损耗分离,拟合得到如图5所示结果,其中0.5 wt%HP/FeSiAl和0.5 wt%HPT /FeSiAl磁粉芯损耗分离拟合结果和电阻率(ρv)见表1。由图5(a)、(b),同系列之间的Pe差别不明显,预热处理后Pe略有下降;由图5(c)、(d)可知,两种处理方式得到的磁粉芯Ph随着磷酸加入量增加而显著下降,因此Ph的降低是导致磁粉芯Pcv下降的主要原因。磷酸加入量相同时经预热处理后磁粉芯的Ph更低,由表1,0.5 wt%HP/FeSiAl样品Ph为35.03 mW·cm−3,0.5 wt%HPT/FeSiAl样品为16.17 mW·cm−3

    图  5  样品的涡流损耗和磁滞损耗随频率变化关系图
    Figure  5.  Pe and Ph of SMCs varies with frequency
    表  1  磁粉芯的电阻率、功率损耗、涡流损耗和磁滞损耗
    Table  1.  Comparison of electrical resistivity, core loss, eddy current loss and hysteresis loss of SMCs
    SampleCore loss/(mW·cm−3)Eddy current coefficientEddy current loss/(mW·cm−3)Hysteresis coefficientHysteresis loss/(mW·cm−3)Electrical resistivity/(Ω·cm)
    0.5 wt%HP/FeSiAl79.441.74×10−643.537.01×10−335.0325.23×106
    0.5 wt%HPT/FeSiAl58.561.63×10−640.733.23×10−316.172.48×106
    Notes: Bm—Maximum magnetic induction intensity=100 mT; f—Frequency=50 kHz
    下载: 导出CSV 
    | 显示表格

    图6是将 FeSiAl原料与经过680℃、N2热处的FeSiAl磁粉进行XRD分析的结果;经过680℃、N2热处理的FeSiAl磁粉在(220)晶面的衍射峰向小角度偏移,这是因为晶胞参数增大;根据高斯函数拟合并使用Debye-Scherrer公式可得到磁粉的平均晶粒尺寸。预热处理后FeSiAl磁粉晶粒平均尺寸由未预热处理的32.66 nm增大到40.85 nm。根据报道[16, 17]磷化后的磁粉经过高温热处理可使颗粒中晶界减少,晶粒尺寸增大,从而削弱了对磁畴壁的钉扎效应,使其矫顽力(Hc)减小。因此经预热处理后磁粉芯Ph减小可能是由其晶粒平均尺寸增大导致。

    图  6  FeSiAl磁粉的XRD 图谱
    Figure  6.  XRD pattern of FeSiAl magnetic powder

    使用Micro Sense公司生产的EZ7型振动样品磁强计对0.1 wt%HP/FeSiAl、0.3 wt%HP/FeSiAl、0.5 wt%HP/FeSiAl、0.1 wt%HPT/FeSiAl、0.3 wt% HPT/FeSiAl、0.5 wt%HPT/FeSiAl磁粉样品进行了磁滞回线的分析,得到图7中的磁滞回线。上述磁粉饱和磁化强度(Ms)在113.16 emu·g−1 ~120.07 emu·g−1之间;两种处理方式得到的磁粉Ms均随磷酸加入量增加而降低;预热处理后Ms更低,但降低幅度较小。图7中磁粉的Hc图5Ph变化趋势一致。Hc越大意味着磁畴壁转动需要克服的摩擦力越大,转动时损耗的能量就更大,在外加磁场循环过程中对应的Ph升高[3, 21]

    图  7  磁粉芯样品磁滞回线
    Figure  7.  Hysteresis loops of SMCs

    本文与此前报道的FeSiAl基磁粉芯及马鞍山新康达磁业有限公司提供的商用FeSiAl磁粉芯Pcvμe进行对比,结果如表2,可得本实验制备的磁粉芯具有超低的Pcv,完全满足商用标准。

    表  2  本文与此前报道磁粉芯性能对比
    Table  2.  Comparison of previously reported SMCs properties and this work
    Sample Core loss/(mW·cm−3) Permeability Refs
    f=50 kHz f=100 kHz
    0.5 wt%HPT/FeSiAl 58.56 190.1 52.1 (f=100 kHz) This work
    SiO2@FeSiAl 77.6 216.53 57(f=1 MHz) [18]
    MoS2/FeSiAl 181 454 90.6(f=1 MHz) [19]
    2.25 wt%WS2/FeSiAl 171 431 62~64(f=50 kHz) [20]
    Commercially SMCs <120 60(f=100 kHz) NCD Co., Ltd.
    Notes:Bm—Maximum magnetic induction intensity=100 mT; f—Frequency; SiO2@FeSiAl—SiO2 coated spherical-FeSiAl SMC;MoS2/FeSiAl and 2.25 wt%—WS2/FeSiAl MoS2 and 2.25 wt%WS2 coated FeSiAl SMCs respectively;Commercially SMCs—Atomized FeSiAl SMCs produced by Ma’anshan New Conda Magnetic Industrial Co., Ltd.
    下载: 导出CSV 
    | 显示表格

    将未经处理、磷化后和磷化后经预热处理的FeSiAl磁粉分别进行XPS测试,得到了样品的Fe2p、Si2p和Al2p图谱。如图8-10所示。图8(a)中Fe2p特征峰可被分解为位于706.7 eV、710.57 eV、712.65 eV的三个峰,分别对应于金属Fe、Fe2+和Fe3+。根据金属Fe的特征峰所占面积比例计算出其含量占比为13.99%;Fe主要以氧化物的形式存在于颗粒表面,这是在其生产过程中被高温蒸汽氧化所致[22];Fe2+和Fe3+的占比分别是40.35%、45.66%。除Si0与Al0外,在Si2p与Al2p的图谱中分别观察到了Si4+ (101.69 eV)、Al3+(74.04 eV)特征峰的存在。综上结果,在FeSiAl磁粉颗粒表面主要由FeO、Fe2O3、SiO2、Al2O3等氧化物组成,另有少量单质Fe、Si和Al。

    图  8  FeSiAl粉的XPS分析图谱
    Figure  8.  XPS spectra of FeSiAl powder
    图  10  磷化后及预热处理FeSiAl粉 (a)XRD图谱(b)FTIR光谱
    Figure  10.  (a) XRD pattern (b) FTIR spectrum of FeSiAl powder after phosphating and heating
    图  9  磷化后磁粉XPS分析图谱
    Figure  9.  XPS spectra of phosphated FeSiAl powder

    将FeSiAl粉磷化后进行XPS分析,结果如图9。Fe2p图谱中Fe2p3/2 (713.59 eV)特征峰对应为Fe3+;观察到磁粉表面Fe、Fe2+的特征峰消失,磷酸将Fe与FeO氧化,反应产物主要是FePO4[23, 24]。Al2p图谱中只剩下Al3+的特征峰,这对应磷化反应生成的铝磷酸盐,事实上磷化层中铝磷酸盐含量更大[25]。为了进一步了解磷化层中的化学组成,另制备了5 wt%磷酸磷化FeSiAl磁粉并进行XRD和FTIR测试得到如图10图谱,由图10(a)可知即使提高磷酸加入量,检测到的AlPO4衍射峰也十分微弱。在图10(b)磷化后的FeSiAl磁粉FTIR光谱中检测到位于1084 cm−1、558 cm−1、509 cm−1的三个峰是属于PO43-的特征振动峰[26]。综上磁粉表面主要由AlPO4、FePO4、SiO2等物质组成。在磷化处理过程中磁粉表面发生的主要反应如下:

    2FeO+2H3PO4=2FePO4+2H2O+H2 (5)
    2Fe+2H3PO4=2FePO4+3H2 (6)
    Fe2O3+2H3PO4=2FePO4+H2O (7)
    Al2O3+2H3PO4=2AlPO4+H2O (8)

    图11为磷化后经过预热处理磁粉的XPS分析图谱。由图可知,Fe2p的谱图中出现了Fe2+与少量Fe0特征峰,而Fe3+特征峰消失。根据报道[27, 28],结合图10(b)中Si2p (102.52 eV)峰的位置,由于高温磷化层中的物质发生了转化:即FePO4分解产生Fe2O3与P2O5,内部Fe被氧化为FeO后,再与Fe2O3、SiO2反应生成Fe2SiO4和金属Fe,AlPO4分解成为Al2O3和P2O5图10(a)中经过预热处理的磁粉中出现了Fe2SiO4的衍射峰,Fe2SiO4是Fe 占中心的八面体结构,在图10(b)中观察到位于1070 cm−1和642.8 cm−1处的吸收峰分别来自SiO4四面体的Si-O键不对称伸缩振动峰和FeO6 八面体的Fe-O键不对称伸缩振动峰[29, 30]。在图10(b)中位于1119 cm−1和923 cm−1的吸收峰分别是来自P2O5的P=O和O—P—O键的不对称伸缩振动峰[25, 31]。预热处理过程中反应如下:

    2FePO4=Fe2O3+P2O5 (9)
    2Fe+O2=2FeO (10)
    Fe2O3+FeO+SiO2=Fe2SiO4+Fe (11)
    2AlPO4=Al2O3+P2O5 (12)
    图  11  磷化预热处理后磁粉的 XPS分析图谱
    Figure  11.  XPS spectra of heated FeSiAl powder after phosphating

    综合XPS和FTIR的分析结果,图12展示了磁粉在磷化及预热处理过程中磁粉表面的可能反应过程。预热处理后,磁粉内晶界减少,且表面反应产生的Fe使磁粉芯电阻率(ρv)降低,表1中0.5 wt%HP/ FeSiAl样品ρv为25.23×106 Ω·cm,0.5 wt%HPT/ FeSiAl样品降低至2.48×106 Ω·cm。磁粉芯的颗粒内涡流损耗Ptrae分为经典涡流损耗和异常涡流损耗[32],经典涡流损耗是由颗粒内均匀流动的涡流产生,异常涡流损耗为磁畴壁的运动而在磁畴周围产生的微观涡流损耗。根据报道[32, 33]磁粉芯经过预热处理后高电阻率的晶界减少会导致经典涡流损耗上升,但经典涡流损耗占比极小;而占比较大的异常涡流损耗在预热处理后降低;因此导致了0.5 wt%HPT/FeSiAl相较0.5 wt%HP /FeSiAl磁粉芯Pe略微下降。

    图  12  磷化及预热处理过程磁粉表面反应示意图
    Figure  12.  Diagram about reactions of phosphating and heating process on the surface of FeSiAl powder

    (1)使用磷酸水溶液作为磷化剂,复合磁粉芯Pcv随着磷酸使用量的增加而减小,磷酸含量从0.1 wt%增加到0.5 wt%时,磁粉芯功率损耗从127.80 mW·cm−3下降到79.44 mW·cm−3 (50 kHz、100 mT);由于非磁性物质的增加,磁粉芯μe也降低。

    (2)磷化磁粉经过预热处理后,磁粉晶粒长大,晶界减少,复合磁粉芯的磁滞损耗大幅降低,当磷酸用量为0.5 wt%时,磁粉芯Pcv从79.44 mW·cm−3降低至58.56 mW·cm−3 (50 kHz、100 mT)。

    (3)磷化后的FeSiAl磁粉颗粒表面磷化层主要有AlPO4、FePO4等物质构成;经过预热处理的磁粉磷化层发生变化,表面主要物质可能为Al2O3、Fe2SiO4、P2O5与单质铁等;由于晶界减少和单质铁的生成,预热处理后复合磁粉芯电阻率有所下降,但仍保持较高水平。

  • 图  1   实验流程示意图

    Figure  1.   Diagram of experimental proces

    图  2   (a)磷化后及 (b)预热处理磁粉颗粒SEM图像;(c)磷化后颗粒EDS元素分布图;磁粉XRD分析图谱

    Figure  2.   SEM images of (a)phosphated and (b)heated powders, (c)EDS results of phosphated powders

    图  3   磷酸含量对磁粉芯(SMCs) (a)密度、(b)有效磁导率的影响

    Figure  3.   Effects of the proportion of H3PO4 on the SMCs (a)ρ, (b)μe

    图  4   磁粉芯的功率损耗随频率变化图

    Figure  4.   Pcv of SMCs varies with frequency

    图  5   样品的涡流损耗和磁滞损耗随频率变化关系图

    Figure  5.   Pe and Ph of SMCs varies with frequency

    图  6   FeSiAl磁粉的XRD 图谱

    Figure  6.   XRD pattern of FeSiAl magnetic powder

    图  7   磁粉芯样品磁滞回线

    Figure  7.   Hysteresis loops of SMCs

    图  8   FeSiAl粉的XPS分析图谱

    Figure  8.   XPS spectra of FeSiAl powder

    图  10   磷化后及预热处理FeSiAl粉 (a)XRD图谱(b)FTIR光谱

    Figure  10.   (a) XRD pattern (b) FTIR spectrum of FeSiAl powder after phosphating and heating

    图  9   磷化后磁粉XPS分析图谱

    Figure  9.   XPS spectra of phosphated FeSiAl powder

    图  11   磷化预热处理后磁粉的 XPS分析图谱

    Figure  11.   XPS spectra of heated FeSiAl powder after phosphating

    图  12   磷化及预热处理过程磁粉表面反应示意图

    Figure  12.   Diagram about reactions of phosphating and heating process on the surface of FeSiAl powder

    表  1   磁粉芯的电阻率、功率损耗、涡流损耗和磁滞损耗

    Table  1   Comparison of electrical resistivity, core loss, eddy current loss and hysteresis loss of SMCs

    SampleCore loss/(mW·cm−3)Eddy current coefficientEddy current loss/(mW·cm−3)Hysteresis coefficientHysteresis loss/(mW·cm−3)Electrical resistivity/(Ω·cm)
    0.5 wt%HP/FeSiAl79.441.74×10−643.537.01×10−335.0325.23×106
    0.5 wt%HPT/FeSiAl58.561.63×10−640.733.23×10−316.172.48×106
    Notes: Bm—Maximum magnetic induction intensity=100 mT; f—Frequency=50 kHz
    下载: 导出CSV

    表  2   本文与此前报道磁粉芯性能对比

    Table  2   Comparison of previously reported SMCs properties and this work

    Sample Core loss/(mW·cm−3) Permeability Refs
    f=50 kHz f=100 kHz
    0.5 wt%HPT/FeSiAl 58.56 190.1 52.1 (f=100 kHz) This work
    SiO2@FeSiAl 77.6 216.53 57(f=1 MHz) [18]
    MoS2/FeSiAl 181 454 90.6(f=1 MHz) [19]
    2.25 wt%WS2/FeSiAl 171 431 62~64(f=50 kHz) [20]
    Commercially SMCs <120 60(f=100 kHz) NCD Co., Ltd.
    Notes:Bm—Maximum magnetic induction intensity=100 mT; f—Frequency; SiO2@FeSiAl—SiO2 coated spherical-FeSiAl SMC;MoS2/FeSiAl and 2.25 wt%—WS2/FeSiAl MoS2 and 2.25 wt%WS2 coated FeSiAl SMCs respectively;Commercially SMCs—Atomized FeSiAl SMCs produced by Ma’anshan New Conda Magnetic Industrial Co., Ltd.
    下载: 导出CSV
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  • 目的 

    目前家电、汽车和手机等产品的电子元器件日益呈现小型化、智能化的发展趋势。因此,降低磁粉芯在高频、大功率下应用时的功率损耗是适应其发展的必要措施。行业内广泛采用磷酸有机溶液作为包覆磁粉的方案降低磁粉芯功率损耗,但残存磷酸有恶化磁粉芯磁性能风险,另外有机溶剂用量大、挥发性强且污染较为严重。因此本文采用磷酸水溶液磷化磁粉的方法来获得绝缘层(磷化层),结合热处理的方式去除多余磷酸并进一步降低磁粉芯功率损耗。

    方法 

    称取适量的Fe-9.6 wt%Si-5.4 wt%Al(FeSiAl)磁粉,分别按FeSiAl磁粉重量的0.1 wt%、0.2wt%、0.2wt%、0.4 wt%和0.5 wt%称取磷酸,将称取的磷酸分别溶于10 mL水中,再将FeSiAl磁粉加入到配制得磷酸水溶液中,混合搅拌、加热至干燥,制得5种磷化磁粉样品。磷化包覆的磁粉经过680 ℃、N气氛预热处理1h后添加0.5 wt%硅树脂粘结剂、0.3 wt%硬脂酸锌脱模剂并混合均匀;在2090 MPa下将磁粉压制成环形试样(外径26.92 mm、内径 14.73 mm、高度 11.10 mm)。最后,压制成型的试样在680℃、N气氛下退火1h,得到了超低损耗FeSiAl复合磁粉芯(SMCs)。另设置未经预热处理的磁粉芯作为对照组,按照磷酸加入量从小到大编号为0.1~0.5wt%HP/FeSiAl,同理预热处理样品编号为0.1~0.5wt%HPT/FeSiAl。

    结果 

    ①在磷酸的水溶液中气雾化FeSiAl磁粉可成功在表面生成绝缘层,结合XRD、XPS和FTIR分析结果表明:绝缘层主要由磷酸盐组成,经过预热处理后绝缘层以AlO、FeSiO、PO为主。②0.5wt%HPT/FeSiAl相较于0.5wt%HP/FeSiAl磁粉芯密度更低,这是热处理后的磁粉颗粒相结合,压制过程中小颗粒不易滑动填充至气隙中导致。0.5wt%HPT/FeSiAl磁粉芯中气隙的增多使磁粉芯中磁性物质占比降低;对比0.5wt%HP/FeSiAl磁粉芯有效磁导率74.52下降到52.10(100 kHz),另外功率损耗从79.44mW·cm降低至58.56mW·cm(50 mT、100 kHz)。③通过对HPT/FeSiAl和HP/FeSiAl磁粉芯的功率损耗分离并拟合发现预热处理后磁粉芯磁滞损耗降低幅度与功率损耗接近,涡流损耗略有降低。④使用高斯函数拟合XRD分析图谱并根据Debye-Scherrer公式得到磁粉的平均晶粒尺寸,计算结果表明预热处理后的磁粉晶粒尺寸长大,此前报道显示高温热处理的磁粉晶粒尺寸明显增大,晶界减少,从而削弱了对磁畴壁的钉扎效应,磁滞损耗降低。⑤0.5wt% HPT/FeSiAl相较于0.5wt%HP/FeSiAl磁粉芯电阻率由25.23×10 Ω·cm降低至2.48×10 Ω·cm,预热处理过程中产生的单质Fe加之颗粒内晶界减少导致电阻率降低,但电阻率仍保持了较高水平。磁粉芯经过热处理后高电阻率的晶界减少会导致经典涡流损耗上升,但经典涡流损耗占比极小;而占比较大的异常涡流损耗在热处理后降低;因此导致了磁粉芯略微下降。

    结论 

    磷酸水溶液磷化FeSiAl磁粉并结合预热处理的方式可获得超低损耗HPT/FeSiAl复合磁粉芯。经预热处理,磁粉表面剩余酸性物质被去除,磁粉芯有效磁导率降低,适用于较低磁导率应用场景;功率损耗显著降低,完全满足商业气雾化FeSiAl磁粉芯标准。

  • 金属磁粉芯,因其具有高饱和磁通密度和有效磁导率而广泛应用于电工领域。当今社会家电、汽车、手机等工业品电子元器件的发展呈现出小型化、智能化的趋势,因此减少磁粉芯在高频、大功率应用下的功率损耗是适应电子元器件发展的必要措施。作为磁粉芯生产过程中重要步骤之一,磷化处理过程通常在有机溶剂中进行,有机溶剂易挥发、污染较大,且磷化后残留的酸性物质有腐蚀磁粉的风险。

    本文通过对气雾化FeSiAl磁粉进行磷化处理,再对其进行热处理,去除多余酸性物质,制备了具有超低损耗的FeSiAl复合金属磁粉芯(soft magnetic composites, 简写SMCs)。较低含量的磷酸可在FeSiAl磁粉表面形成一层薄而均匀的绝缘层,经过预热处理后,磁粉表面磷酸盐转变为硅酸盐,磁粉颗粒内晶体长大,晶界减少,磁畴壁转动克服能量减少,磁粉矫顽力降低;得到的磁粉芯功率损耗急剧降低,主要归因于磁滞损耗明显降低损;当磷酸加入量为0.5 wt%时,制备的磁粉芯体电阻率为2.48×106 Ω·cm,功率损耗仅为58.56mW·cm-3

    磁粉芯的功率损耗随频率变化图

    磷化及预热处理过程磁粉表面反应示意图

图(12)  /  表(2)
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出版历程
  • 收稿日期:  2024-06-24
  • 修回日期:  2024-07-29
  • 录用日期:  2024-07-30
  • 网络出版日期:  2024-08-18

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