La-Ca-Co-Zn 掺杂M型锶铁氧体的相变过程和磁性能研究

采用陶瓷法制备La-Ca-Co-Zn 掺杂的M型锶铁氧体Sr0.3La0.3Ca0.4Fe10.625Co0.225Zn0.1O19。使用高温X射线衍射仪、振动样品磁强计、热分析、和扫描电子显微镜等对Sr0.3La0.3Ca0.4Fe10.625Co0.225Zn0.1O19 在25°C 到1450°C的相变过程进行了分析,并且讨论了其磁性能。实验结果表明：La-Ca-Co-Zn 掺杂的M型六方铁氧体的形成主要分为两个部分,在大概700℃左右,SrCO3 和Fe2O3先反应生成中间相Sr3Fe2O7-d,然后Sr3Fe2O7-d再和剩下的Fe2O3反应生成M相,并且Sr3Fe2O7-d中的Fe离子化合价与温度有关;随着温度升高,La3+, Ca2+, Co2+ 和 Zn2+开始逐渐溶入中间相或者随后生成的M相中,且在M相中分布均匀;和高温射线衍射仪检测结果不同的是在700℃左右退火时,得到了钙钛矿相;在1200℃烧结,可以得到单一程度很高的M相,但有少量的第二相存在,第二相的存在有利于提高烧结致密度;当烧结温度为1380℃时,铁氧体开始分解;Sr0.3La0.3Ca0.4Fe10.625Co0.225Zn0.1O19 铁氧体粉末退磁曲线的矩形度要低于SrFeO12的退磁曲线矩形度。     

溶胶-凝胶法制备SmZn掺杂纳米钡铁氧体磁性能

以柠檬酸为络合剂,利用溶胶-凝胶自蔓延燃烧法制备Sm及SmZn掺杂的M型纳米钡铁氧体(Ba1-xSmxFe12O19及Ba1-xSmxFe12-xZnxO19,x=0～0.6)粉末样品,进而利用X射线衍射仪对所制钡铁氧体样品的结构进行表征、分析。结果显示,钡铁氧体的物相组成与掺杂含量关系密切:当掺杂量x超过0.2时,在制备的样品中会出现α-Fe2O3及SmFeO3等杂相,对样品的磁性能产生不利的影响。由于受到超精细场、磁稀释及自旋倾斜的影响,掺杂Sm3+后,钡铁氧体的饱和磁化强度(Ms)先增大后减小,而矫顽力(Hc)则随着掺杂含量的增加而增大。掺杂Zn2+后,磁性能的研究结论显示Zn2+替代4f2晶位的Fe3+,使制备的钡铁氧体的Ms有所升高,而Hc下降。     

溶胶-凝胶法制备La0.8Sr0.2CoO3纳米材料

以La(NO3)3·6H2O、Sr(NO3)2、Co(NO3)2·6H2O为原料,用EDTA络合溶胶-凝胶法制备La0.8Sr0.2CoO3凝胶,在700℃、800℃、900℃煅烧,制得La0.8Sr0.2CoO3粉体.用DTA、FT-IR、XRD、SEM等手段对制备过程、热分解机理及粉体的性能进行了研究.在700℃焙烧2 h得到La0.8Sr0.2CoO3纯相纳米粉,颗粒呈球形.选取700℃焙烧2 h的La0.8Sr0.2CoO3粉体制成管状传感器,进行NO2敏感性能测试,探讨了相同NO2浓度下,传感器敏感信号与温度的关系.结果表明:纳米La0.8Sr0.2CoO3粉体在450℃时对NO2的敏感信号最大,输出的电动势信号与NO2浓度之间呈线性关系.     

稀土掺杂镍基铁氧体的制备和性能

在同等条件下,通过溶胶-凝胶法,制备了四种稀土离子掺杂的镍基复合铁氧体NiAyFe2-yO4(A为Ce,Nd,La或Y,y=0.1)。对粉末的结构和磁性能进行表征,结果表明:四种离子掺杂后,均能形成在室温条件下具有超顺磁性的镍基铁氧体粉末,Y3+掺杂可以形成纯净的镍基铁氧体。对粉末的电磁性能进行表征,结果表明:掺杂后,铁氧体的复介电常数实部ε’和虚部ε″在2～18 GHz增大,尤以La3+掺杂的效果最为明显;与未掺杂的样品相比,四种离子掺杂的样品复磁导率实部μ’和虚部μ″均减小,在2～18 GHz,四种样品的复磁导率实部μ’先急剧减小,后逐渐增大;掺杂离子的半径和掺杂量对电磁参数的改变起主要作用。     

La0.6Sr0.4Co0.8Fe0.2O3-δ超细粉体的溶胶凝胶-自燃烧法制备及其性能表征

采用溶胶凝胶-自燃烧法合成La0.6Sr0.4Co0.8Fe0.2O3-δ(LSCF)复合氧化物粉体,用XRD、TG-DTA、TEM等对产物形成过程及微观结构进行了表征.结果表明,溶胶凝胶-自燃烧法一步合成了粒径为30～70nm的具有钙钛矿结构的La0.6Sr0.4Co0.8Fe0.2O3-δ超细粉体,粉体具有较高烧结活性,1100℃下烧结2 h相对密度达到95%.利用热膨胀仪测量发现样品从室温到1000℃的平均膨胀系数为19.3×10-6/K;直流四探针法电导测试表明,样品在200～600℃温度范围内电导率随温度的升高而升高,由580 S·cm-1升至最大值1000 S·cm-1,在600℃后样品的电导率随着温度的升高缓慢降低,样品的电导率在200～800℃温度范围内均高于580 S·cm-,能很好地满足中低温SOFC的使用要求.     

离子取代镍基铁氧体的性能及吸波涂层优化设计

在同等实验条件下,以镍铁氧体为基体,通过溶胶-凝胶法,制备二元镍基复合铁氧体Ni0.5A0.5Fe2O4(A=Zn,Co,Mn,Cu)。用X射线衍射仪、扫描电子显微镜、振动样品磁强计和矢量网络分析仪对粉末的结构及电磁性能进行表征并对其吸波性能进行优化设计。结果表明:4种离子取代后均能形成在室温条件下具有超顺磁性的纯净镍基铁氧体粉末。离子取代使铁氧体样品的复介电常数实部ε′增大,虚部ε″在2~6 GHz和13~18 GHz变小,在6~13 GHz增大。Zn2+、Mn2+、Cu2+3种离子取代样品与未进行离子取代的NiFe2O4相比,其复磁导率实部μ′变化不大,而Co2+离子取代样品的μ′整体要大于其他几种离子取代样品及未取代样品的μ′;在2~11 GHz进行Zn2+、Co2+、Mn2+3种离子取代样品的虚部μ″变大,且以Ni0.5Zn0.5Fe2O4的最大,Cu2+取代样品的虚部μ″与未取代样品的虚部μ″相比变化不大。利用传输线理论优化设计时发现,Co2+取代后的复合铁氧体没有匹配点,Zn2+取代后的复合铁氧体匹配效果最好,在最佳匹配厚度为5.63 mm时,其最小反射率峰值为-36.26 dB,小于-10 dB的频宽可达4.7 GHz。     

微波辅助溶胶凝胶法合成La0.8Sr0.2Co0.5Fe0.5O3阴极材料及性能研究

使用一种新的理想方法--微波辅助溶胶凝胶法,在35 min内快速制备了钙钛矿结构的La0.8Sr0.2Co0.5Fe0.5O3(LSCF)纳米材料;以8%Y2O3稳定化的ZrO2(YSZ)为电解质,La0.8Sr0.2Co0.5Fe0.5O3为阴极,铂电极为阳极,制备了LSCF/YSZ/Pt固体氧化物电池.采用X射线粉末衍射(XRD)、傅里叶红外光谱(FT-IR)、扫描电子显微镜(SEM)、BET和电化学阻抗谱(EIS)等技术研究了La0.8Sr0.2Co0.5Fe0.5O3材料的成相过程、粉晶结构、电极/电解质微观相貌和电池电化学性能.结果发现经过1 min的微波辐射,凝胶开始分解,3 min后有钙钛矿相生成,到35 min时形成了完整的钙钛矿晶相,相应粉体的粒径和比表面积分别为22.7 nm和38.9 m2/g;在1094 K,0 mV偏置电压下电极/电解质界面电阻为0.775 Ω·cm2,活化能为2.34 eV.研究发现,偏置电压越大则活化能越低.     

Co_(0.8)Zn_(0.2)Fe_2O_4及其磁电复合薄膜的制备与表征

采用溶胶-凝胶法制备Zn2+取代钴铁氧体Co0.8Zn0.2Fe2O4及Co0.8Zn0.2Fe2O4/(Ba0.85Ca0.15)(Zr0.1Ti0.9)O3磁电复合薄膜(CZFO/BCZT)。利用X射线衍射仪(XRD)、场发射扫描电子显微镜(FE-SEM),拉曼光谱仪及振动样品磁强计(VSM)等对样品进行表征。研究表明,沉积在Pt(111)/Ti/SiO2/Si衬底上的CZFO薄膜为多晶结构,无明显择优取向,处于压应变状态。磁场平行于CZFO薄膜表面的饱和磁化强度和矫顽力分别为405emu/cm3和780×79.577A/m,其矫顽力高于CZFO粉体样品。制备的磁电复合薄膜结晶质量良好,多层纳米结构清晰完整。     

RE(Nd,Tb)FeCoB合金体系的微波吸收特性研究（英文）

采用熔炼、高能球磨、微氧化热处理工艺,制备RE(Nd,Tb)FeCoB粉体,借助X射线衍射仪和网络矢量分析仪等,研究不同B含量的NdFeCo粉体组织结构和微波吸收特性,以及用重稀土Tb取代NdFeCoB合金中的Nd后粉体的组织结构和微波吸收特性。结果发现:在Nd10.53Fe77.84Co11.63合金中加入B元素后会析出Nd2Fe14B相,而且,粉体中α-Fe相的相对含量随着B元素含量的增加而增加;用重稀土Tb取代NdFeCoB合金中的Nd后粉体主要由α-Fe、Tb2Fe14B、Tb2Fe17以及少量的Tb2O3相组成;(Nd10.53Fe77.84Co11.63)97B3粉体具有最低的吸收峰频率,其反射率最小值和吸收峰频率分别为–9.5 dB和4.5 GHz;用重稀土Tb取代(Nd10.53Fe77.84Co11.63)97B3合金中的Nd后,粉体的吸收峰频率升高到6.3 GHz,但反射率最小值降低到–11 dB。     

Microwave Properties of RE(Nd, Tb)FeCoB Alloy System

采用熔炼、高能球磨、微氧化热处理工艺,制备RE(Nd,Tb)FeCoB粉体,借助X射线衍射仪和网络矢量分析仪等,研究不同B含量的NdFeCo粉体组织结构和微波吸收特性,以及用重稀土Tb取代NdFeCoB合金中的Nd后粉体的组织结构和微波吸收特性。结果发现:在Nd10.53Fe77.84Co11.63合金中加入B元素后会析出Nd2Fe14B相,而且,粉体中α-Fe相的相对含量随着B元素含量的增加而增加;用重稀土Tb取代NdFeCoB合金中的Nd后粉体主要由α-Fe、Tb2Fe14B、Tb2Fe17以及少量的Tb2O3相组成;(Nd10.53Fe77.84Co11.63)97B3粉体具有最低的吸收峰频率,其反射率最小值和吸收峰频率分别为–9.5 dB和4.5 GHz;用重稀土Tb取代(Nd10.53Fe77.84Co11.63)97B3合金中的Nd后,粉体的吸收峰频率升高到6.3 GHz,但反射率最小值降低到–11 dB。     

Electrochemical properties of La0.8Sr0.2FeO3-δbased composite cathode for intermediate temperature SOFC

La0.8Sr0.2FeO3-δ is a new kind of cathode material for intermediate SOFC, but its electrochemical activity is relative poor for the lanthanum gallate based solid oxide fuel cell. In this paper, a novel composite cathode of La0.8Sr0.2FeO3-δ/La0.9 Sr0.1Ga0.8Mg0.2O3-δ was prepared on the LSGM electrolyte substrate by screen-printing method. The results of cathodic polarization measurements show that the overpotential decreases significantly when the composite cathode is used instead of the La0.8Sr0.2FeO3-δ single layer cathode. The cathodic overpotential of the composite La0.8Sr0.2FeO3-δ/La0.9Sr0.1Ga0.8 Mg0.2O3-δ cathode is 150 mV at the current density of 0.2 A·m-2 at 800 ℃, while the cathodic overpotential of the La0.8 Sr0.2 FeO3-δ single layer cathode is higher thaN260 mV at the same condition. The electrochemical impedance spectroscopy was employed to investigate the polarization resistance of the cathode. The polarization resistance of the composite cathode is 1.20 Ω·m2 in open circuit condition, while the value of the single La0.8 Sr0.2 FeO3-δ cathode is 1.235 Ω·m2.     

Inductive heat property of Fe3O4 nanoparticles in AC magnetic field for local hyperthermia

Magnetite (Fe3O4) nanoparticles with different magnetic properties were prepared by coprecipitation of Fe3+ and Fe2+ with aqueous NaOH solution.The inductive heat properties of Fe3O4 nanoparticles in an alternating current (AC) magnetic field were investigated for local hyperthermia. The maximum saunder the optimum conditions of Fe3+:Fe2+ molar ratio at 1.8:1. The Ms of Fe3O4 nanoparticles decreased as the Fe3+ /Fe2+ molar ratio increased. But the coercivity Hc increases with the increasing of Fe3+ /Fe2+ molar ratio. Exposed in the AC magnetic field for 29 min, the temperatures of physiological saline suspension containing Fe3O4 nanoparticles were 42-97.5 ℃.The inductive heat property of Fe3O4 nanoparticles in AC magnetic field decreases as Hc increases, but increases with the increasing of Ms. The Fe3O4 nanoparticles would be useful as good thermoseeds for localized hyperthermia treatment of cancers.     

(Fe_(1-x)Co_x)_(80)Zr_(10)B_(10)(x=0,0.1,0.2,0.3)合金的热性能、结构和磁性能研究

采用单辊快淬法制备(Fe1-x Cox)80Zr10B10(x=0,0.1,0.2,0.3)非晶合金,并对4种合金在不同温度下进行等温热处理。利用差热分析仪(DTA),X射线衍射仪(XRD),透射电镜(TEM)和振动样品磁强计(VSM)等测试手段对样品的热性能、微观结构及磁性能进行研究。结果表明,未添加Co元素的Fe80Zr10B10合金的热稳定性明显高于添加Co元素的合金,而(Fe1-x Cox)80Zr10B10(x=0.1,0.2,0.3)合金的热稳定性相差不大。Fe80Zr10B10和Fe72Co8Zr10B10合金的晶化过程相似;Fe64Co16Zr10B10和Fe56Co24Zr10B10合金的晶化过程相似。4种合金的矫顽力(Hc)呈现先上升后下降的趋势,在873 K达到最大值。     

Suppressed Antiferromagnetism and Superconductivity in As-deficient Iron-based Superconductor of SrFe_(1.8)Co_(0.2)As_x

Iron-based superconductors namely Sr(Fe1.8Co0.2)As1.8 (FeAs1.8) and Sr(Fe1.8Co0.2)As1.85 (FeAs1.85) with As deficiency are prepared by solid-state reaction. X-ray diffraction reveals that the polycrystalline phase forms in the studied samples, identical to typical SrFe2As2 (122) matrix. Resistive and magnetic measurements show that the superconducting transition temperatures (Tc) are about 19 K for both FeAs1.8 and FeAs1.85. Compared with the performances of typical iron-based 122 superconductors arising fr...     

Preparation and electrochemical characteristics of CO3（PO4）2-coated LiNi0.8Co0.2O2 by solid-state reaction at room temperature

LiNi0.8Co0.2O2 particles were modified by Co3（PO4）2 coating. The effects of the Co3（PO4）2 coating on the structure and electrochemical properties of the LiNi0.8Co0.2O2 cathode material were investigated. The Co3（PO4）2 coating forms a thin layer on the surface of the LiNi0.8Co0.2O2 material and a solid solution by interacting with the LiNi0.8Co0.2O2 core material during calcination at 700℃ for 4 h. Charge-discharge experiment results show that the Co3（PO4）2 coating improves the cycling stability of the LiNi0.8Co0.2O2 cathode material. The capacity retention of the pristine LiNi0.8Co0.2O2 cathode after 50 cycles is 83.6%, whereas it is 91.7% in the case of the LiNi0.8Co0.2O2 cathode coated with 1 wt.% Co3（PO4）2. Storage tests of the 4.35 V charged electrode at 60℃ after a month show that the Co3（POg）2-coated sample exhibits good storage properties compared with the pristine sample.     

Ba2+替代对Sr4Al14O25:Eu2+, Dy3+结构和发光性能的影响

采用高温固相反应按化学式Sr4-xBaxAl14O25: Eu2+, Dy3+(x＝0, 0.8, 1.6, 2.4, 3.2, 4) 配比原料,合成长余辉发光材料。X射线衍射分析表明,当x＝0.8时,产物物相为单斜结构SrAl2O4和磁铅矿结构SrAl12O19共存;当x>1.6时,产物主相转变为BaAl2O4六角结构。对所得样品采用360 nm光照,发射光谱表明,样品发光是以Eu2+为发光中心,由Eu2+电子4f65d-4f7跃迁所致,并且随着Ba掺入量的增加,样品发射光谱峰位产生移动,这是由于Sr2+取代产物中Ba2+位置后,导致晶格收缩,影响Eu2+的5d能级劈裂,从而影响电子4f65d-4f7跃迁。余辉光谱显示x>1.6时,产物的余辉发光是以BaAl2O4基质中Eu2+为发光中心。余辉衰减检测和热释光谱分析发现不同掺Ba量的样品余辉衰减快慢不同,是由于其中存在的陷阱能级深度不同,且陷阱能级越深,其余辉时间越长     

Structure and magnetic properties of mechanically alloyed Tb0.2Pr0.8(Fe0.4Co0.6)1.93 and magnetostriction of its epoxy composite

The C15 Laves phase with composition Tb0.2Pr0.8(Fe0.4Co0.6)1.93 was synthesized by mechanical alloying (MA) and subsequent annealing process. The structure and magnetic properties of Tb0.2Pr0.8(Fe0.4Co0.6)1.93 were investigated by means of X-ray diffraction (XRD), a vibrating sample magnetometer, and a standard strain technique. The effect of annealing on the structure and magnetic properties was studied. The analysis of XRD shows that the high Pr-content Tb0.2Pr0.8(Fe0.4Co0.6)1.93 alloy with the single phase of MgCu2-type structure can be success-fully synthesized by MA method. The sample annealed at 450℃ is fotmd to have a coercivity of 196 kA/m at room temperature. An ep-oxy/Tb0.2Pr0.8(Fe0.4Co0.6)1.93 composite was produced by a cold isostatic pressing technique. A large magnetostriction of 400 ppm, at an ap-plied magnetic field of 800 kA/m, was found for the composite. The epoxy-bonded Tb0.2Pr0.8(Fe0.4Co0.6)1.93 composite combines a high mag-netostriction with a significant coereivity, which is a promising magnetostrictive material.     

质子转移对低热法制备SrFe12O19结构和性能的影响

以Fe(NO3)3·9H2O、Sr(NO3)2和C6O7H8为原料,NH3为质子转移剂,在不同pH值条件下,进行低热固相反应,制备出系列前驱体,经900℃灼烧后得到相应产物。采用XRD、SEM和VSM对产物进行表征。结果表明,合成出的产物为平均粒径约100 nm的SrFe12O19纳米粉体。并发现随着pH值从6增加到11,合成产物的XRD衍射峰出现峰值先变大后变小现象;3种晶格参数(a,c,Vcell)出现先减小,后增大规律,而结晶度Xc则先变大,后变小。在pH=10时,所对应的晶格参数均发生最大拐点变化,因此产物的磁性能表现最佳(Ms=51.4 A·m2/kg、Mr=29.5 A·m2/kg、Hc=71.2 A/m),表明磁性粒子表面在此条件下磁交换作用最强。