Na2CO3作沉淀剂制备NiZnCu铁氧体粉末及其性能研究

采用化学共沉淀法制备NiZnCu铁氧体时,如果采用NaOH或者氨水作为沉淀剂,会造成Zn2+离子的大量损失.为此,本文选用Na2CO3为沉淀剂制备了名义配方为Ni0.4-xZn0.6CuxFe2O4(x=0,0.05,0.10,0.15,0.20)的铁氧体粉末,并对其结构和磁性能作了研究.实验发现,前驱体粉末在900℃...     

Al替代和烧结温度对NiZn铁氧体磁性能的影响

采用陶瓷工艺制备了Al替代的Ni0.5Zn0.5AlxFe2-xO4(x=0~0.10)铁氧体材料,用XRD、B-H分析仪和阻抗分析仪对其结构和磁性能进行了研究。实验发现,最佳烧结温度为1 250℃,过高和过低的烧结温度不利于降低磁芯损耗。当Al3+替代量x=0.06时,铁氧体能获得较好综合磁性能。     

Co2+对CoxFe3-xO4铁氧体结构与磁特性的影响

采用化学共沉法制备了纳米尺度的钴铁氧体CoxFe3-xO4（x=0．2～1．0）粉料,并在1260—1340℃温度下进行了退火处理,利用X射线衍射仪（XRD）、振动样品磁强计（VSM）对样品的结构和磁性进行了测量和分析。实验结果表明,当钴含量高（x≥0．7）时样品形成了单一的具有尖晶石结构的钴铁氧体,而钴含量x〈0．7时样品生成了尖晶石结构的钴铁氧体相和仪α-Fe2O3相CoxFe3-xO4的比饱和磁化强度σs随x的增加呈现出了先增后减的趋势,在x=0．8时出现峰值;x=0．5～0．8范围内,矫顽力日。随钴含量的增加有所下降,随后迅速增加,在x=1．0附近能同时得到较大的σs和Hc值。     

Fe3O4／Ag复合纳米材料的制备及SERS研究

采用乙酰丙酮铁作为有机前驱体盐,在二苄基醚溶液中,以油酸、油胺为表面活性剂,十六醇作为“分解促进剂”,分解前驱体乙酰丙酮铁,制备四氧化三铁纳米颗粒。以四氧化三铁纳米颗粒为“种子”,加入醋酸银,以油胺为还原剂,制备Fe3O4/Ag复合磁性纳米材料。利用透射电子显微镜对纳米材料的形貌进行了表征,通过紫外～可见吸收光谱和拉曼光谱仪对纳米材料的表面增强拉曼散射光谱进行表研究,采用铷硼磁铁对磁性纳米材料的磁性进行初步研究。实验结果表明：FelO2／Ag复合磁性纳米颗粒既具有磁性又具有贵金属光谱特性;相对Fe304而言,Fe3O4/Ag复合纳米粒子具有更好的s隙S增强效果。     

废旧锂离子电池溶胶-凝胶法制备CoFe_2O_4磁致伸缩材料的研究

以废旧锂离子电池为原料,采用溶胶-凝胶法制备具有磁致伸缩性能的钴铁氧体。探讨了前驱体的煅烧温度和煅烧时间对钴铁氧体的晶型结构、晶粒尺寸、形貌以及磁致伸缩性能的影响。通过TG技术辅助确定适宜的前驱体煅烧温度范围;利用XRD表征钴铁氧体晶型结构;使用磁致伸缩性能测量仪测试材料的磁致伸缩性能。研究表明,前驱体适宜的煅烧条件为煅烧温度800℃,煅烧时间3h;适宜条件下所得产品的密度比为82%,其最大磁致伸缩参数为-1.012×10-4。     

热处理工艺对尖晶石型Ni0.5Zn0.45Co0.05Fe2O4静磁性能的影响

利用溶胶凝胶法制备了尖晶石型 Ni0.5Zn0.45Co0.05Fe2O4 纳米颗粒,设置了3种热处理工艺,发现随着热处理温度的提高,热处理时间的延长,颗粒长大,静磁性能提高。当热处理温度为800℃,保温8h,材料具有比较好的静磁性能（Ms=30.241Oe,Hc=73.261 emg/g,μi=0.210）。另外,将前驱体在磁场条件下热处理,得到颗粒尺寸比同种热处理工艺未加磁场条件下的大,并且静磁性能有了比较大的提高,其比饱和磁化强度甚至比在更高热处理温度,更长热处理时间下制备的NiZnCo铁氧体大。     

镍锌钴铁氧体/碳纳米管复合吸波材料的制备及表征

采用沸腾回流法制备了Ni0.4Zn0.35Co0.25LaxFe2-xO4/碳纳米管(CNTs)复合吸波材料,考察了镧(La)的掺杂量对复合材料磁性及吸波性能的影响。研究表明:沸腾回流法制备的铁氧体为单相尖晶石结构,纳米铁氧体粒子成功包覆在碳纳米管上。La3+掺杂量x=0.07时,产物的矫顽力(Hc)最大,且吸波性能最佳。     

气泡液膜法制备Ni_(0.7)Zn_(0.3)Fe_2O_4铁氧体的前驱体纳米粒子

采用新颖的气泡液膜法,将Zn2+、Ni2+和Fe3+与OH-的共沉淀反应在气泡液膜中完成,制备了Ni0.7Zn0.3Fe2O4铁氧体前驱体纳米粒子,经元素分析、FT-IR、XRD和SEM等表征。实验结果表明,前驱体较精确地保持了原料溶液中Zn2+、Ni2+和Fe3+的配料摩尔比。前驱体分别经300、400、500、600、700或800℃烧结,制得Ni0.7Zn0.3Fe2O4铁氧体,用XRD和VSM表征。结果表明,在700℃烧结制得的Ni0.7Zn0.3Fe2O4铁氧体的粒径为26.92nm,磁饱和磁化强度sσ=64.22A.m2/kg,剩余磁化强度rσ=14.25A.m2/kg,内秉矫顽力jHc=16kA/m。将这种Ni-Zn铁氧体分散到合成油中,制成耐高温磁性液体。     

Co含量对Zn0.6CoxFe2.4-xO4结构与磁性的影响

采用溶胶-凝胶方法制备纳米尺度钴锌铁氧体Zn0.6CoxFe2.4-xO4(x=0～0.30)颗粒,利用X射线衍射仪(XRD)分析晶体结构和相变过程,利用振动样品磁强计(VSM)对其磁性进行测量和分析.实验结果表明,钴锌铁氧体Zn0.6Co0.15Fe2.25O4在800℃时生成单一尖晶石相锌钴铁氧体,在550～800℃温度区间出现R-Fe2O3过渡相.随钴含量的增加,Zn0.6CoxFe2.4-xO4的比饱和磁化强度先增后减,x=0.075～0.15比饱和磁化强度较高;Zn0.6CoxFe2.4-xO4在1300℃时x=0.075的矫顽力为47163.6A/m,x≥0.15时矫顽力在1200℃附近随温度缓慢上升,在1200～1300℃之间为平台状态,并且随钴含量的增加,矫顽力略有升高.在x=0.10附近,可同时获得较高的比饱和磁化强度和较高的矫顽力.     

含锰锌铁氧体磁性生物活性玻璃陶瓷制备工艺及其性能研究

在磷灰石/硅灰石生物活性玻璃陶瓷(A-WGC)中掺杂锰锌铁氧体, 制备出一种新型的磁性生物活性玻璃陶瓷, 并研究了不同制备工艺对其磁性和生物活性的影响. 结果表明, 使用不同掺杂工艺制备的材料的主晶相均为硅灰石、磷灰石、氟磷灰石和分子式为Zn_0.75Mn_0.75Fe _1.5O₄的锰锌铁氧体. 在充磁至7.96×10⁵A·m^-1时, 各材料的饱和磁化强度相差不大, 在5.4~5.9A·m²·kg^-1之间. 材料的生物活性与烧结前和锰锌铁氧体前驱体复合的A-WGC原料的反应活性有关, A-WGC原料的反应活性越低, 材料的生物活性越好. 比较各材料, 采用将A-WGC前驱体高温煅烧后再与锰锌铁氧体前驱体固相混合的工艺制备的材料具有良好的磁性和较高的生物活性.     

ZnxFe3—xO4的制备及性能

采用合适加剂在碱性溶液中制备了ＦｅＺｎ铁氧体，研究了其形成机理及磁性能，提出ＦｅＺｎ铁氧体的形成机理为：Ａｎ＾２＋＋２Ｆｅ＾３＋＋８０Ｈ＾－→ＺｎＦｅ２Ｏ４＋４Ｈ２Ｏ Ｆｅ＾２＋＋２Ｆｅ＾２＋＋８０Ｈ＾－→Ｆｅ３Ｏ４＋４Ｈ２Ｏ。     

Zn_xFe_（3－x）O_4的制备及性能

采用合适添加剂在碱性溶液中制备了ＦｅＺｎ铁氧体，研究了其形成机理及磁性能．提出ＦｅＺｎ铁氧体的形成机理为：     

La掺杂纳米晶Ni-Zn铁氧体的制备及电磁性能

采用高分子凝胶法制备了Ni0.5Zn0.5LaxFe2-xO4（x=0,0.02,0.05和0.08）纳米晶铁氧体.采用X射线衍射仪（XRD）、透射电镜（TEM）和HP8510网络分析仪分别对其结构、形貌和电磁性能进行了研究.结果表明,当x=0,0.02和0.05时,所得粉体为纯立方晶系尖晶石结构.Ni0.5Zn0.5Fe2O4粉体平均粒径为70nm.随着La离子掺杂量的增加,红外光谱中550cm-1处吸收峰向高波数移动,420cm-1处吸收峰向低波数移动.La离子的掺杂对Ni-Zn铁氧体的电磁性能有一定的影响.在X波段,与Ni0.5Zn0.5Fe2O4铁氧体相比,掺杂La的Ni-Zn铁氧体的tanδm值降低,tanδε值升高.Ni0.5Zn0.5La0.02Fe1.98O4铁氧体的tanδε平均值为0.616.     

Preparation and electromagnetic properties of zinc ferrite/expanded graphite composites

An effective process for the synthesis of nano spinel zinc ferrite/expanded graphite composites was developed in order to get an electromagnetic interference shielding material. Firstly, expandable graphite was prepared using sulfuric and nitric acid solutions. Then, the precursor of the composites was produced by chemical co-precipitation method, followed by heating treatment. The obtained composites were characterized by X-ray diffraction and scanning electron microscopy. The dielectric and magnetic properties were determined using vector network analyzer and vibrating sample magnetometry. The results showed that ferrite nanoparticles with the sizes of about 50–150 nm were uniformly dispersed on the surface and interspace of EG. The magnetic properties of the composites changed by adjusting the ferrite/EG ratio and the composites had high dielectric constant in the range of 2–18 GHz. These properties of the prepared composites suggest that they can be used as a promising electromagnetic interference shielding material.     

Synthesis and characterization of manganese ferrite nanostructure by co-precipitation,sol-gel,and hydrothermal methods

ABSTRACT

In this research work, manganese ferrite nanoparticles (MnFe₂O₄) were synthesized by three different methods including the co-precipitation, sol-gel, and hydrothermal route. Structure, size, morphology, and magnetic properties of nanostructures were determined and compared using X-ray diffraction, Fourier-transform infrared spectroscopy, field emission scanning electron microscopy analysis (FESEM), and the vibration sample magnetometer (VSM). X-ray diffraction analysis from Debye–Scherrer’s formula with the (2θ?=?35.08°) peak indicated that the mean size of the synthesized manganese ferrite nanocrystallites were obtained to be 36, 45, and 16?nm for co-precipitation, sol-gel, and hydrothermal, respectively. Also, the sample prepared by the hydrothermal method has the lowest crystal sizes, which it is approved by FESEM analysis. Field emission scanning electron microscopy analysis images confirmed the existence of three types of basic morphology of MnFe₂O₄ nanoparticles: spherical shape, multi-walled hollow nanosheets, and reticular structure. In addition, Based on VSM data magnetization saturation (M_s) was 41.89?emu/g for hydrothermal synthesized samples, 38.76?emu/g for co-precipitation samples, and 9.52?emu/g for sol-gel samples. These findings show that various methods of nanoparticle synthesis can lead to different particle sizes and magnetic properties.     

Spindly cobalt ferrite nanocrystals: preparation, characterization and magnetic properties

In this paper we describe the preparation of homogeneously needle-shaped cobalt ferrite (CoFe(2)O(4)) nanocrystals on a large scale through the smooth decomposition of urea and the resulting co-precipitation of Co(2+) and Fe(3+) in oleic acid micelles. Furthermore, we found that other ferrite nanocrystals with a needle-like shape, such as zinc ferrite (ZnFe(2)O(4)) and nickel ferrite (NiFe(2)O(4)), can be prepared by the same process. Needle-shaped CoFe(2)O(4) nanocrystals dispersed in an aqueous solution containing oleic acid exhibit excellent stability and the formed colloid does not produce any precipitations after two months, which is of prime importance if these materials are applied in magnetic fluids. X-ray diffraction (XRD) measurements were used to characterize the phase and component of the co-precipitation products, and demonstrate that they are spinel ferrite with a cubic symmetry. Transmission electron microscopy (TEM) observation showed that all the nanocrystals present a needle-like shape with a 22?nm short axis and an aspect ratio of around?6. Varying the concentration of oleic acid did not bring about any obvious influence on the size distribution and shapes of CoFe(2)O(4). The magnetic properties of the needle-shaped CoFe(2)O(4) nanocrystals were evaluated by using a vibrating sample magnetometer (VSM), electron paramagnetic resonance (EPR), and a M?ssbauer spectrometer, and the results all demonstrated that CoFe(2)O(4) nanocrystals were superparamagnetic at room temperature.     

Mn_(0.2)Zn_(0.8)Fe_(2-x)Ce_xO_4铁氧体纤维的制备、结构及其磁性能

以柠檬酸和金属盐为原料,采用有机凝胶-热分解法成功制备了Mn0.2Zn0.8Fe2-xCexO4(x=0~0.04)系列铁氧体纤维。通过XRD、SEM和VSM等技术对产物进行了表征,研究了Ce3+掺杂对Mn-Zn铁氧体纤维的结构,微观形貌及磁性能的影响。结果表明,所制得的纤维轴向较为均匀,长径比较大,直径在0.5~3.5μm之间,组成纤维的晶粒平均尺寸为11.6~12.8nm。Ce3+掺杂没有引起Mn0.2Zn0.8Fe2-xCexO4纤维结构的明显变化,仍为单一的立方尖晶石结构,但晶格常数和晶粒粒径随Ce3+掺入量的增加而略微增大。Ce3+掺杂使Mn-Zn铁氧体纤维的饱和磁化强度增大,矫顽力下降,软磁性能有所提高。     

Studies of the magnetic field intensity on the synthesis of chitosan-coated magnetite nanocomposites by co-precipitation method

Chitosan-coated magnetite nanocomposites (Fe₃O₄/CS) were prepared under different external magnetic field by co-precipitation method. The effects of the magnetic field intensity on phase composition, morphology and magnetic properties of the Fe₃O₄/CS nanocomposites were investigated by X-ray diffractometer (XRD), Fourier transform infrared analysis (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). The results showed that the intensity of the magnetic field in the co-precipitation reaction process did not result in the phase composition change of the magnetic chitosan but improved the crystallinity of magnetite. The morphology of Fe₃O₄/CS nanocomposites was greatly changed by the magnetic field. It was varied from random spherical particles to chain-like cluster structure and rod-like cluster structure with the magnetic field intensity increased in the synthetic process. The VSM results indicated that all the products had excellent superparamagnetic properties regardless of the presence or the absence of the magnetic field, and the saturation magnetization values of the Fe₃O₄/CS nanocomposites were significantly improved by the magnetic field.     

Effect of Substitutions of Zn for Mn on Size and Magnetic Properties of Mn–Zn Ferrite Nanoparticles

In this study Mn?CZn ferrite nanoparticles (Mn_(1?x)Zn _x Fe₂O₄, x=0, 0.3 and 0.5) were produced by a chemical co-precipitation method. The structure and size of the Mn?CZn ferrite nanoparticles were characterized using X-ray diffraction (XRD) and Transmission electron microscopy (TEM). Results show that the ferrite nanoparticles have the spinel structure. It was found that the size of Mn?CZn ferrite nanoparticles decreases by increasing of the Zn concentration. The magnetic properties of Mn?CZn ferrite nanoparticles were investigated with a vibrational sample magnetometer (VSM) and it was observed that Mn_0.7Zn_0.3Fe₂O₃ ferrite nanoparticles have the maximum saturation magnetization and that the initial susceptibility decreases with the increase in Zn concentration.     

Structural and electrical properties of Gd3+ ion substituted CoGdxFe(2-x)O4 nano-ferrites

Nano particles of CoGdxFe(2-x)O4, with x = 0.0, 0.1, 0.3, 0.5 have been prepared by chemical co-precipitation method. The as synthesized particles are annealed at 300 degrees C for two hours to improve crystallinity. The X-ray diffraction patterns reveal the single cobalt ferrite phase formation and the average crystallite size decreases to 7 nm in the Gd3+ ion doped sample (with x = 0.5) compared to 27 nm in case of un-doped cobalt ferrite sample. The electrical properties for the different compositions of Gd3+ ion substituted cobalt ferrite material were studied in the frequency range 100 Hz to 10 MHz at room temperature using WK impedance analyzer. It is found that the electrical conductivity of the samples increases with increasing Gd3+ ion concentration. The results of our investigations reveal a strong dependence of material properties on Gd3+ ion doping.