CoFe2O4/TiO2纳米复合薄膜的制备与磁性

以钛酸丁酯和金属盐酸盐为原料,采用溶胶-凝胶工艺制备了磁性CoFe2O4/TiO2复合薄膜.通过综合热分析(DSC)、X射线衍射仪(XRD)、扫描电镜(SEM)、原子力显微镜(AFM)、偏光显微镜(PLM)观测了复合薄膜的相结构和表面形貌,探讨了薄膜的合成机理,采用振动样品磁场计测量样品的磁性.研究发现,溶胶-凝胶法制得的复合薄膜中,随着热处理温度的升高,两相组分晶体各自析出长大,CoFe2O4均匀地分布在TiO2网状基体中.样品经800℃退火后得到了平整的CoFe2O4/TiO2磁性复合薄膜,晶粒平均粒径大约为19nm.随着热处理温度的升高,复合薄膜的磁性增强.     

CoFe2O4铁氧体纳米颗粒的结构与磁性

用聚乙烯醇(PVA)溶胶-凝胶法制备出CoFe2O4纳米微粉,用X射线衍射(XRD)研究了Co铁氧体纳米颗粒的结构,用振动样品磁强计(VSM)测量了宏观磁性随焙烧温度的变化。随焙烧温度的升高,矫顽力下降,而饱和磁化强度升高。323~873K的变温穆斯堡尔谱测量发现纳米颗粒的磁转变温度TC在793~813K之间,比块体材料的磁转变温度要低。     

Effect of CoFe2O4 content on the dielectric and magnetoelectric properties in Pb(ZrTi)O3/CoFe2O4 composite

Ferroelectric Pb(Zr_0.53Zr_0.47)O₃ (PZT) and ferromagnetic CoFe₂O₄ (CFO) composite ceramics, [(1???x)PZT???xCFO for x?=?10, 20, 30, 40 and 50 wt.%], were prepared by a conventional solid-state reaction method. X-ray diffraction studies revealed that only PZT and CFO phases were present in the composite samples and no other phase was detected. The 0.9PZT-0.1CFO composite ceramic displayed better piezoelectric properties. The piezoelectric resonance frequency increased with the CFO content, but the resonance peak attenuated rapidly and disappeared when the CFO content equaled to 0.5. The permittivity peak temperature was the same as that of pure PZT ceramics. 0.9PZT-0.1CFO composite also had the highest magnetoelectric (ME) coupling coefficient among the studied PZT-CFO composite ceramics. The ME coefficient linearly increased with ac frequency up to 100 kHz.     

模板法合成的CoFe2O4纳米管的结构与磁性

利用阳极氧化铝(AAO)模板,用化学方法合成了三种不同孔径的CoFe2O4(CFO)纳米管.X射线衍射(XRD)分析表明,纳米管由无择尤取向、立方尖晶石结构的多晶CoFe2O4构成;透射电镜(TEM)观察显示,随着纳米管直径的增大,管壁厚度和CoFe2O4颗粒直径随之增大;进一步的磁性测量表明,纳米管阵列的矫顽力、磁滞回线的矩形比也随着纳米管直径的增大而增大.     

Co0.7Fe0.3/CoFe2O4纳米复合材料的水热法一步合成与磁性

采用水热法一步合成了Co0.7Fe0.3/CoFe2O4纳米复合材料。利用粉末X射线衍射(XRD)、透射电子显微镜(TEM)观察了纳米复合材料的结构及形貌。室温穆斯堡尔谱(MS)明显地由对应于尖晶石型钴铁氧体(CoFe2O4)和体心立方钴铁合金(Co0.7Fe0.3)的两组六线谱叠加而成。在室温下,利用振动样品磁强计(VSM)测量材料的磁滞回线,表明Co0.7Fe0.3/CoFe2O4纳米复合材料具有较高的比饱和磁化强度(Ms=84.82A·m2/kg)和矫顽力(μ0Hc=0.15T)。     

电化学法制备的CoFe2O4薄膜

首先在硫酸盐溶液中由电镀法制备CoFe2合金薄膜,然后采用阳极氧化法在碱性溶液中氧化CoFe2合金薄膜制备CoFe2O4薄膜,再在空气气氛中、600℃退火3h.用原子分光光度计(AAS)法测量合金中Co2 、Fe2 的含量.由质量法测定铁钴合金薄膜的厚度,研究了电镀CoFe2合金薄膜的工艺条件(电压、时间、温度)对CoFe2薄膜厚度的影响.分别用X射线衍射仪(XRD)、扫描电子显微镜(AFM)和振动样品磁强计(VSM)观测薄膜的相成分、表面形貌和磁性能.结果表明,制备的CoFe2O4薄膜具有尖晶石结构,退火促进了CoFe2O4薄膜的结晶,降低了饱和磁化强度,但增大了矫顽力.     

磁场退火对CoFe2O4微粒形貌及磁性能的影响

采用化学共沉淀法合成材料,分别在0.1T和0.5T的磁场下800℃退火制备了CoFe2O4颗粒样品,系统研究了磁场退火对样品形貌和磁性能的影响.X射线衍射(XRD)谱和扫描电子显微镜(SEM)分析结果表明,磁场退火后样品结晶度变好,因磁场诱导而生成较圆润的圆形颗粒.磁测量结果表明,磁场下退火制备的样品反位缺陷减少,从而...     

Mg2+-Zr4+复合取代对CoFe2O4磁致伸缩材料性能的影响

为了实现钴铁氧体在低磁场下有较高的应变灵敏度,采用Mg2+-Zr4+协同取代的方式,通过固相合成法制备了CoFe2O4磁致伸缩材料,并研究了Mg2+-Zr4+复合取代对材料的微观结构、饱和磁化强度、磁致伸缩性能及应变灵敏度的影响.结果表明,在1300℃烧结的样品均为纯净的尖晶石相,并且随着Zr4+离子取代量的增加,材料的饱和磁化强度与磁晶各向异性常数呈现增大趋势,磁致伸缩系数减小,应变灵敏度先增大后减小.在Mg2+取代量为0.05、Zr4+取代量为0.02时,低磁场域下CoFe2O4磁致伸缩材料的应变灵敏度达到最高值,为4.3×10–9 A/m,可应用于磁传感器等领域.     

添加CoFe_2O_4和CaB_2Si_(0.67)O_(5.34)助溶剂对永磁铁氧体磁性能的影响

通过常规陶瓷工艺,结合离子取代,以CaB_2Si_(0.67)O_(5.34)作为助溶剂,添加Co Fe_2O_4铁氧体制备了Ca_(0.218)Sr_(0.43)La_(0.432)Fe_(12)O_(19+δ)永磁铁氧体材料。实验结果显示,在成分相同的情况下,与传统的离子取代相比,以Co Fe2O4的形式添加,更能有效发挥Co2+改善永磁铁氧体磁性能的潜力,所获材料的Br可以提高4%,同时其Hcj可以提高3%。当Co Fe2O4的添加量为7.8wt%时,在空气中1190~1200℃下保温2h烧结,材料的显微结构、密度得到了显著改善,磁性能Hcb为331k A/m,Hcj为416k A/m时,Br可以达到0.458T。     

Magnetic and dielectric properties of a double-percolating Ni0.3Zn0.7Fe1.95O4-Ni-polymer composite

A novel three-phase, double-percolating composite with a ferromagnetic phase (NiZn ferrite) and metallic inclusion (nickel) embedded in the polyvinylidene fluoride matrix is prepared by a simple hot-molding method. The large ferrite particles in the composite not only act as magnetic phase, endowing the composite with high initial permeability, but also present as a high-volume fraction discrete (nonpercolating) phase, confining polymer and metallic particles into a continuous double-percolating structure of low volume fractions. The increase in the content of the magnetic nickel particles compensates the decrease in the content of the NiZn ferrite, hence a stable initial permeability with an enhanced dielectric constant has been observed. The dielectric losses of the composites were reduced compared with the previous works.     

CoFe2O4涂层对Co基非晶薄带GMI效应的影响

通过磁控溅射法在Co基非晶薄带(Co66Fe4NiSi15B14)上制备CoFe2O4涂层(镀膜),在75kHz～2.5MHz频率范围内观察其巨磁阻抗效应(GMI)随外加磁场的变化。实验结果显示,在Co基非晶薄带上涂覆CoFe2O4薄膜,可以提高薄带的GMI效应,并且在频率为1.2MHz时,具有CoFe2O4涂层的非晶薄带巨磁阻抗比较无涂层薄带提高了近30%。研究发现,当趋肤效应显著时材料表面粗糙度对GMI效应有较大影响。通过在Co基非晶薄带表面镀膜的方式降低样品表面粗糙度,减小表面退磁场的影响,从而提高了材料的GMI效应。     

Structural and Multiferroic Properties of Bi3.4La0.6Ti3O12/CoFe2O4 Composite Thin Films

Bi_3.4La_0.6Ti₃O₁₂ and CoFe₂O₄ were synthesized by chemical solution route, and Bi_3.4La_0.6Ti₃O₁₂/CoFe₂O₄ multilayers were deposited by spin coating on Pt substrate. X-ray diffraction of multilayer structures reveals composite-like polycrystalline film. Leakage current is less than 10^?5 A at electric field < 90 KV/cm and follows the Ohmic behavior. Dielectric response shows relaxation and the loss (tan δ) is below 3% at 10⁶ Hz. Room temperature ferrroelectric polarization (P_r) = 20.2 μC/cm² and ferromagnetic memory (M_r) = 46.5 emu/cm³ has been obtained. Co-existence of FE and FM response can be attributed to stress and different permeability and permittivity involved in multilayer structures.     

高矫顽力CoFe2O4薄膜的研究进展及矫顽力机理分析

矫顽力是钴铁氧体薄膜作为高密度磁记录以及磁光记录介质的重要指标.本文综述了激光脉冲沉积法和磁控溅射法制备的高矫顽力(大于400kA/m)钴铁氧体薄膜材料的国内外研究进展,并对其高矫顽力的产生机理进行了分析.     

层状结构LiMn0.5Ni0.5O2材料的合成及性能

廉价正极材料的研究开发及应用是目前锂离子电池进一步发展和推广应用的关键.采用高温固相合成LiMn0.5Ni0.5O2材料,用XRD对合成材料结构进行表征,并用恒电流法进行电化学性能测试,在此基础上对材料进行Al掺杂改性.实验结果表明,合成材料经微量掺杂后具有较好的电化学循环性能,可作为锂离子电池的替代正极材料。     

Fe_3O_4/C纳米材料的简易制备及其电化学性能

以三氯化铁FeCl_3·6H_2O、尿素CO(NH_2)_2和葡萄糖为原料采用一步水热法制备出前驱体,经过热处理后制备出了Fe_3O_4/C纳米材料。当热处理温度为500℃时前驱体分解为Fe_3O_4/C材料,热处理温度升高到600℃时产物中有FeO和单质Fe出现。所制备的Fe_3O_4/C纳米材料的电化学性能优于商品化纳米Fe_3O_4,600℃下热处理产物循环稳定性最好,在0.2 C的电流密度下循环100次后可逆比容量为648 mAh/g,这可能是由于原位生成的单质铁增加了电极颗粒之间的导电性。     

草酸铜掺杂DMcT/PAn复合材料电化学性能

掺杂草酸铜之后,DMcT/PAn复合材料的氧化还原峰电位差和电化学阻抗大大减少,氧化还原峰电流增加,首次放电(40 mA/g)比容量由186 mAh/g增加到298 mAh/g,经50次循环后,容量衰减率由68.8%减少到37.3%.研究结果表明:掺杂草酸铜加快了DMcT/PAn复合材料的氧化还原反应,提高了复合材料的放电比容量,改善了循环性能.     

Preparation, characterization and photocatalytic performance of Co/Ni Co-doped TiO2 nanopowders

Co/Ni co-doped TiO₂ nanopowders (dopant amount varying from 0 to 0.75 mol.% Co/0.75 mol.% Ni) were prepared by sol-gel method. The nanopowders were characterized by means of X-ray diffraction and transmission electron microscopy, respectively. The results showed that the structure of all the powders was anatase and that the particle size of the powders was in the range of 40–50 nm. The photocatalytic performances of the nanopowders were studied by examining the degradation of methyl orange. The results showed that the dopant amount was a key factor affecting photocatalytic performance. 0.05 mol.% Co/0.05 mol.% Ni co-doped TiO₂ nanopowders had the best photocatalytic performance, and the photocatalytic performance of which was also better than that of 0.1 mol.% Co- or 0.1 mol.% Ni-doped TiO₂ nanopowders.     

Structure and properties of PP/TiO2 based polymer nanocomposites

ABSTRACT

The transient pulse testing is used in bridgewire-charges to measure the electrothermal performance non-destructively rather than by the conventional inspection. The conventional inspection has the disadvantage of destruction with a number of products tested, while the transient pulse testing can give a dynamic electrothermal curve at a user's command. In addition, the transient pulse testing can be used to measure a passel of products one by one rather than by a statistical spot check. Unfortunately, a statistic spot check cannot provide the firing reliability of products efficiently. The other way round, the transient pulse testing may put an end to the possibility of loss for users absolutely. The reason that the transient pulse testing is not devastating for products is that these mixtures of a product have a required thermal stability, and then are simultaneously able to be responded reliably by a very small pulse current. We have determined that these red matches based on Si/Pb₃O₄/DDNP mixtures electrothermal responsibility curves. Firing performance, measurements of the transient pulse testing, and electrothermal parameters are presented in this paper.     

Ti/SnO_2+Sb_2O_4+GF/MnO_x电极的制备及性能研究

采用热分解和电沉积相结合方法制备了Ti/Sn O2+Sb2O4+CF/Mn Ox电极,利用SEM、XRD和XPS方法对其进行了表征。应用快速电极寿命法测试了该电极在60℃,1.0 mol/L H2SO4溶液中的预期使用寿命,用循环伏安法考察了该电极的电催化性能,结果表明该电极寿命较长并且电催化性能优于传统锰电极,是一种性能优良的电催化剂。     

Photoresponse and electrical properties of Al/nanostructure NiFe2O4/p-Si/Al photodiode

The electrical characterization of Al/NiFe₂O₄/p-Si/Al photodiode was investigated by current–voltage and capacitance-voltage characteristics. The barrier height and ideality factor magnitudes of the Al/NiFe₂O₄/p-Si/Al diode were found to be 0.82 and 5.2 eV, respectively. The optical properties of the NiFe₂O₄ film have been investigated and the optical band gap was found to be 2.66 eV. The photoresponse results indicate that the diode exhibits a photodiode behavior, and the photocurrent of the diode increases by increasing illumination intensity. The density of interface states of the diode was determined by conductance method. The obtained results show that the series resistance of the diode is decreased with increasing frequency. The obtained results indicate that NiFe₂O₄ spine oxide material can be used in diode applications.