低温固相反应法制备的NiFe2O4纳米颗粒的结构与磁性

采用低温固相反应法制备了晶粒尺寸在8—47nm之间的NiFe₂O₄纳米颗粒系列样品，用X射线衍射仪(XRD)、高分辨中子粉末衍射谱仪、振动样品磁强计和超导量子干涉仪等对样品的晶体结构、宏观磁性和纳米颗粒的表面各向异性进行了分析研究.XRD和中子衍射测量结果显示纳米颗粒的晶格常数略高于块体材料，样品的氧参量表明纳米颗粒的晶格畸变程度没有块体材料严重.相对块体材料，纳米颗粒具有较小的磁化强度、较大的矫顽力和各向异性能密度.纳米颗粒从多畴转变为单畴的临界尺寸约为40nm，超顺磁性临界尺寸约为16nm.     

室温固相反应制备Keggin结构K3PW12O40·10H2O纳米粒子

采用室温固相反应制备Keggin结构钨磷酸钾纳米粒子,并通过元素分析、红外光谱、X射线衍射、电镜等进行了表征.     

CoFe2O4纳米颗粒的结构、磁性以及离子迁移

聚乙烯醇(PVA)溶胶凝胶法制备出CoFe2O4纳米微粉,用X 射线衍射研究了铁氧体纳米颗粒的结构.测量了CoFe2O4纳米颗粒80-873 K的变温穆斯堡尔谱,发现纳米颗粒的磁转变温度范围为793-813 K,比块体材料的磁性转变温度要低.CoFe2O4纳米颗粒的德拜温度θA=674 K,θB=243 K,比块体材料要小.CoFe2O4纳米颗粒超精细场Hf随温度的变化符合T3/2+T5/2定理.当温度较高时,平均同质异能移IS随温度的升高而减小,并呈线性关系.     

固相反应法制备Co掺杂ZnO的磁性和光学性能研究

研究了以固相反应法制备Co掺杂ZnO粉体的磁性和光学性能，测试结果表明对于均匀掺杂的Zn_0.95Co_0.05O粉体，Co²⁺随机取代Zn²⁺的位置进入ZnO晶格.Co²⁺之间的3d自旋电子耦合交换作用使得近邻的Co²⁺自旋反平行，Zn_0.95Co_0.05O粉体在3—300K表现为顺磁性，而非铁磁性. 关键词： ZnO 固相反应 稀磁半导体 顺磁性     

室温固相反应制备AgX纳米粉末

首次利用ＡｇＮＯ３与ＫＸ（Ｘ为Ｃｌ＾－,Ｂｒ＾－,Ｉ＾－）的室温固相反应成功地年鉴轩出纳米ＡｇＸ粉末。并结合ＸＲＤ,ＴＥＭ,ＴＧ／ＤＴＡ测试对其结构和性能进行了表征。发现固相反应制得的超细ＡｇＸ与水相法制得的相应常粒ＡｇＸ颜色有所不同。     

退火Ge/Fe多层膜的固相反应与磁性

研究并发现在退火Ge/Fe多层膜中表面的晶化和生成化合物的温度均高于内部,并仔细探讨了Raman谱的反常,研究了在退火过程中物相变化与磁性的关系. 关键词：     

NiFe2O4纳米粉末的制备及磁性研究

以硝酸铁、硝酸镍以及柠檬酸为原料,采用凝胶-热分解法制备了N iFe2O4纳米粉末。利用X射线衍射确定了粉体的相结构、比表面积和晶格常数,扫描电子显微镜(SEM)观察了颗粒的形貌,振动样品磁强计(VSM)测量样品的磁性能。结果表明:所制备的样品均为尖晶石结构,颗粒粒径为36nm~68nm,且颗粒的粒径随着热处理温度的升高而增大,样品的比饱和磁化强度最大可达54.63 emu/g。同时,文章也对反应的动力学原理进行了研究,得出N iFe2O4纳米颗粒形成的活化能为15.8kJ/mol。     

固相反应法制备的CoxZn1-xO磁性能的研究

采用固相反应烧结法制备了Co掺杂ZnO的粉末和压片样品. XRD衍射表明样品中Co²⁺离子取代Zn²⁺离子进入了ZnO晶格中. 在室温下样品均表现为顺磁性, 利用密度泛函理论(DFT+U)方法计算得到的Co₂Zn₁₄O₁₆体系反铁磁基态更稳定, 并通过Co, O原子电子迁移变化, 表明了CoZnO体系中磁性机理更倾向于Co²⁺—O^2-—Co²⁺成键的间接交换作用模型. 改进了安德森模型中的直接交换积分J_pd公式. 提出两个可能的途径来实现具有本征铁磁性氧化物半导体.     

磁性纳米颗粒Fe3O4固定化纤维素酶的光谱学研究

以氨水作沉淀剂,用共沉淀法制备了磁性纳米颗粒Fe3O4,并以此为载体,通过碳化二亚胺的活化作用将纤维素酶固定化,通过傅里叶红外和重复多次催化实验证实纤维素酶在磁性纳米颗粒上的固定,透射电镜表征了固定化酶微粒的形貌.用DNS分光光度法测定固定化纤维素酶的活性,研究表明磁性固定化酶的催化作用的最适温度为60℃和pH值为3.94～5.50.结果表明,磁性固定化纤维素酶具有比自由酶更好的热稳定性,贮存稳定性和更广泛的pH值适用范围,为纤维素的转化和利用效率的提高提供了理论基础.     

室温固相反应制备纳米四水磷酸锌的热化学研究

以Na3PO4·12H2O和ZnSO4·7H2O为原料,采用室温固相反应制备纳米四水磷酸锌,用微量热法研究该反应的反应焓和四水磷酸锌的标准摩尔生成焓.根据Hess定律,设计了一个新的热化学循环:以4mol/LHCl溶液为量热溶剂,用RD496微热量计于298.15K测定了反应物与产物在量热溶剂中的溶解焓分别为(-47.180±0.084)和(-7.617±0.096)kJ/mol,同时测定两种溶液的紫外光谱、折光率和电导率.两种溶液的紫外吸收曲线重叠,稀释500倍后的电导率值分别是2180、2181μS/cm,折光率值分别是1.3679、1.3678.计算出该固相反应的反应焓为-39.530kJ/mol,同时得到纳米四水磷酸锌的标准摩尔生成焓,推荐其值为-4354.004kJ/mol.     

Tuneable magnetic properties of hydrothermally synthesised core/shell CoFe2O4/NiFe2O4 and NiFe2O4/CoFe2O4 nanoparticles

The aim of this study was to prepare a novel targeting nano drug delivery system of 2-methoxyestradiol (2-ME) based on the folic acid-modified bovine serum albumin, in order to improve the clinical application disadvantages and antitumor effect of 2-ME. In this study, 2-methoxyestradiol-loaded albumin nanoparticles (2-ME-BSANPs) were prepared by desolvation method, and then the activated folic acid was conjugated to 2-ME-BSANPs by covalent attachment (2-ME-FA-BSANPs). The size and zeta potential of 2-ME-FA-BSANPs were about 208.8 ± 5.1 nm and ?32.70 ± 1.01 mV, respectively. 2-ME loading efficiency and loading amount of the nanoparticles were 80.49 ± 3.80 and 10.25 ± 1.59 %, respectively. SEM images indicated that 2-ME-FA-BSANPs were of a round shape, similar uniform size, and smooth surface. Studies on drug release indicated that 2-ME-FA-BSANPs had the properties of sustained and controlled release, which provided them with the ability to fight continually against cancer cells. Internalization analysis demonstrated that 2-ME-FA-BSANPs-targeting drug delivery system could get efficiently transferred into the cells through the folic acid-mediated endocytosis, leading to higher apoptosis and affording higher antitumor efficacy against SMMC-7721 cells in vitro compared with 2-ME alone. Furthermore, the cell-cycle arrest of 2-ME-FA-BSANPs on the SMMC-7721 cells occurred at G2/M phase, and 2-ME-FA-BSANPs did not change the inhibition of the tumor mechanisms of 2-ME. Based on these results, it was concluded that albumin nanoparticles could be the promising nano carrier for 2-ME, and 2-ME-FA-BSANPs-targeting drug delivery system may be promising candidate for providing high treatment efficacy with minimal side effects in future cancer therapy.     

Size-dependent magnetic properties of CoFe2O4 nanoparticles prepared in polyol

Highly crystalline CoFe(2)O(4) nanoparticles with different diameters ranging from 2.4 to 6.1 nm have been synthesized by forced hydrolysis in polyol. The size can be controlled through adjusting the nominal water/metal molar ratio. X-ray diffraction, transmission electron microscopy, x-ray absorption spectroscopy and (57)Fe M?ssbauer spectrometry were employed to investigate the structure and the microstructure of the particles produced. Magnetic measurements performed on these particles show that they are superparamagnetic with a size-dependent blocking temperature. At 5 K, high saturation magnetization (~85 emu g(-1)) approaching that of the bulk was found for the larger particles, whereas a very large coercivity (14.5 kOe) is observed for the 3.5 nm sized particles.     

The study of transition on NiFe2O4 nanoparticles prepared by co-precipitation/calcination

In this study, the NiFe₂O₄ nanoparticles have been prepared by co-precipitation and calcination process. Using a vibrating sample magnetometer (VSM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive spectrometer of X-ray (EDX), and X-ray photoelectron spectroscopy (XPS), the samples obtained by co-precipitation and then by further calcination have been analyzed. The experimental results show that the precursor synthesized by co-precipitation is the composite of both amorphous FeOOH and Ni(OH)₂, but has no amorphous NiFe₂O₄. The results of both EDX and XPS revealed that the FeOOH species is wrapped up by Ni(OH)₂ species. In the calcination process, the amorphous composite is dehydrated and transformed gradually into crystalline NiFe₂O₄ nanoparticles, with the metal ions diffusing. The reaction is different from the one used to prepare other ferrite (e.g., CoFe₂O₄, MnFe₂O₄, Fe₃O₄, etc.) nanoparticles directly by co-precipitation. With increasing calcination temperature, the NiFe₂O₄ grains grow and the magnetization is enhanced.     

Magnetic properties of ZnFe2O4 nanoparticles produced by a low-temperature solid-state reaction method

ZnFe₂O₄ nanoparticles with average grain size ranging from 40 to 60 nm behaving superparamagnetic at room temperature have been produced using a low-temperature solid-state reaction (LTSSR) method without ball-milling process. Abnormal magnetic properties such as S-shape hysteresis loops and non-zero magnetic moments were observed. ZnFe₂O₄ nanoparticles were also synthesized using a NaOH coprecipitation method and a PVA sol-gel method to study the relationship between the preparation processes and the magnetic properties. Spin-glass behavior was observed in the low temperature solid-state reaction produced Zn ferrite in the zero-field cooled (ZFC) measurement. Our work proves that the various preparation methods will to some extent determine the properties of magnetic nanoparticles.     

NiFe2O4纳米线阵列的制备与磁性

在氧化铝模板的纳米孔洞中, 用电化学的方法沉积铁镍合金纳米线,经过550℃30h氧化处理, 成功制备出 NiFe2O4纳米线阵列. 分别用扫描电子显微镜 (SEM) 、透射电子显微镜 (TEM) 、x射线衍射仪 (XRD) 和振动样品磁场计 (VSM) 对样品的形貌、晶体结构和磁学性质进行了表征测试. SEM和TEM观察结果显示氧化铝模板的孔洞分布均匀,孔心距约为110nm; 纳米线的直径约为70nm. XRD显示纳米线阵列的物相结构为NiFe2O4; VSM测试结果表明,NiFe2O4纳米线阵列膜的易磁化方向垂直于膜面. 当垂直磁化时磁滞回线的矩形比约为0.5,矫顽力为41×103A/m,比氧化处理前的铁镍合金纳米线阵列都有显著提高.     

热分解法制备MnFe2O4纳米粒子及其超顺磁性

采用热分解法制备了单相的锰铁氧纳米颗粒,X射线衍射以及透射电镜测量显示其颗粒大小约为20 nm.磁滞回线测量显示室温超顺磁性.零场和非零场磁测量显示制备的MnFe2O4纳米粒子平均截止温度为84.3 K,样品中最大颗粒的截止温度为230 K,且平均截止温度与外场H2/3存在线性关系.     

Magnetic properties and microwave absorption in Ni-Zn and Mn-Zn ferrite nanoparticles synthesized by low-temperature solid-state reaction

In this work, Mn_0.7Zn_0.3Fe₂O₄ and Ni_0.7Zn_0.3Fe₂O₄ nanoparticles with super-paramagnetic properties and size distribution from 10 to 52 nm were investigated. These particles were produced by a low-temperature solid-state reaction method without the ball-milling process. The size and morphology of the nanocrystallites were determined by X-ray diffraction, transmission electron microscopy and scanning tunneling microscopy methods. Magnetic measurements such as alternating gradient field magnetometers were used to justify the super-paramagnetic properties of these nanoparticles. Their microwave absorption in the range of 8-18 GHz was studied by a vector network analyzer. Responses of the device under tests were studied. Also, the percentage of the resin, the size and thickness of the mount were determined. The band width of 2.3 GHz was obtained with reflection-loss/written-loss of −16 dB around 10.4 GHz.