0.8ZnFe2O4-0.2MnFe2O4纳米颗粒磁化性质的实验研究

对采用化学共沉淀法制备的ZnFe2O4,MnFe2O4以及两者混合的3种纳米颗粒体系的磁化性质进行了实验研究.在室温下测量了它们的磁化曲线,结果表明ZnFe2O4颗粒是顺磁性的,MnFe2O4及0.8Zn Fe2O40.2MnFe2O4混合颗粒呈超顺磁性.MnFe2O4颗粒的实验曲线和无相互作用的Langevin理论曲线间有较大偏差.混合颗粒体系的磁化强度不等于单独两种颗粒的磁化强度的简单相加.应用偶极子相互作用和颗粒团聚效应解释了MnFe2O4颗粒和混合颗粒体系的磁化性质.     

自形成MnFe2O4磁性液体的磁性研究

采用共沉淀法制备MnFe2O4磁性纳米微粒,并配制自形成磁性液体．测量了微粒粒径,以及MnFe2O4磁性纳米微粒、自形成磁性液体的磁性．磁性液体呈现出微粒所具有的矫顽力,其比饱和磁化强度与剩余磁化强度之比都是3：1的关系．在高场下的磁化性质随声。变化．通过分析得出自形成MnFe2O4磁性液体的磁性除与微粒磁性、微粒体积分数Фv 以及基液磁性有关外,还受微粒表面非磁性层的影响．     

自形成MnFe2O4磁性液体的磁性研究

采用共沉淀法制备MnFe2O4磁性纳米微粒,并配制自形成磁性液体.测量了微粒粒径,以及MnFe2O4磁性纳米微粒、自形成磁性液体的磁性.磁性液体呈现出微粒所具有的矫顽力,其比饱和磁化强度与剩余磁化强度之比都是3∶1的关系.在高场下的磁化性质随v变化.通过分析得出自形成MnFe2O4磁性液体的磁性除与微粒磁性、微粒体积分数v以及基液磁性有关外,还受微粒表面非磁性层的影响.     

ZnFe2O4基磁凝胶的制备及磁性

用自形成法制备ZnFe2O4磁凝胶,并进一步研究包裹ZnFe2O4的γ-Fe2O3磁凝胶的制备,用振动样品磁强计(VSM)对ZnFe2O4和包裹ZnFe2O4的γ-Fe2O3磁性微粒及配制的胶体处在溶胶和凝胶的磁性测量.结果表明ZnFe2O4磁性微粒和胶体呈顺磁性,而包裹ZnFe2O4的γ-Fe2O3磁性微粒和胶体呈亚铁磁性.ZnFe2O4凝胶较其溶胶易磁化,而ZnFe2O4/γ-Fe2O3凝胶较其溶胶难磁化.从微观机制上解释了产生这些磁性差异的原因.

Abstract：

ZnFe2O4 magnetic gel is prepared by the self-formed method, and the preparation of γ-Fe2O3 coated with ZnFe2O4 is studied. The magnetization of ZnFe2O4 and γ-Fe2O3 nanoparticles coated with ZnFe2O4 and their gels and sols are measured by a vibrating sample magnetometer(VSM). The results show that the ZnFe2O4 powder and its colloid are paramagnetic, while the γ-Fe2O3 magnetic particles coated with ZnFe2O4 and colloid show ferrimagnetism. ZnFe2O4 gel is easier to be magnetized than sol. However, ZnFe2O4/γ-Fe2O3 gel is harder magnetized than sol. The reason for the difference in magnetization is interpreted microscopically.     

二元CoFe2O4-p-MgFe2O4磁性液体的制备及磁化特性研究

采用化学共沉淀法制备了CoFe2O4强磁性纳米微粒和p-MgFe2O4(Mg(OH)2与Fe(OH)3的混合物)弱磁性纳米微粒.并按体积比为1:1将CoFe2O4磁性液体、p-MgFe2O4顺磁磁性液体混合,得到二元CoFe2O4-p-Mg-Fe2O4磁性液体.实验结果表明混合磁性液体的磁化强度不能简单等于两种单一磁性液体磁化强度的叠加.在CoFe2O4磁性液体中,其磁性微粒在无场时会自发组装形成对磁化强度无贡献的闭合环状团聚体结构.二元磁性液体磁化时,这种CoFe2O4微粒环可能部分破裂.根据偶极子相互作用能判断CoFe2O4体系与p-MgFe2O4体系无相互作用,因此可根据单元磁性液体的磁化性质为基础来分析二元磁性液体的磁化性质.

Abstract：

Strong magnetic CoFe2O4 nanoparticles and weak magnetic p-MgFe2O4 (mixture of hydroxide Mg(OH)2 and Fe(OH)3) nanoparticles are produced by the chemical co-precipitation technology. Binary ferrofluids of CoFe2O4-p-MgFe2O4 are obtained by mixing CoFe2O4 ferrofluids and p-MgFe2O4 paramagnetic fluids in a ratio of 1: 1 (v/v). The experimental results indicate that the magnetization of the binary ferrofluid is not simple summation of the two single magnetic fluids. Without external magnetic field,some particles can self-assemble into aggregates of closed ring-like structures, which make no contribution to the magnetization for the CoFe2O4 ferofluid. In the magnetization process of the binary ferrofluid, the closed ring-like structure can partially break. Based on the interaction between two dipoles, it can be judged that there is no magnetic interaction between the CoFe2O4 magnetic system and the p-MgFe2O4 magnetic system. Therefore, the magnetization behavior of the binary ferrofluids can be analyzed based on the single magnetic fluids.     

CuFe2O4纳米微粒及其自形成磁性液体的磁性研究

对用共沉淀法制备的CuFe2O4磁性纳米微粒及其合成的自形成磁性液体在室温下进行磁性测量.其结果表明CuFe2O4微粒的饱和磁化强度较小,粉末与自形成磁性液体均呈超顺磁性-无剩磁、无矫顽力.用Langevin理论对测得的磁性进行了对比分析,从微粒间的相互作用解释了粉末和磁性液体的实测磁化曲线与Langevin理论的不同偏离现象.     

CuFe2O4纳米微粒及其自形成磁性液体的磁性研究

对用其沉淀法制备的CuFe2O4磁性纳米微粒及其合成的自形成磁性液体在室温下进行磁性测量.其结果表明CuFe2O4微粒的饱和磁化强度较小,粉末与自形成磁性液体均呈超顺磁性-无剩磁、无矫顽力.用Langevin理论对测得的磁性进行了对比分析,从微粒间的相互作用解释了粉末和磁性液体的实测磁化曲线与Langevin理论的不同偏离现象.     

自形成MnFe2O4磁性液体的制备和磁性

用化学共沉淀法制备MnFe2O4纳米微粒,并且采用自形成法制备了粒子型磁性液体.在这种磁性液体中,通过适当的酸蚀,Mn2+和Fe3+离子从MnFe2O4纳米微粒溶解并吸附在磁性微粒表面以阻止微粒团聚.微粒和磁性液体都呈磁滞回线.这种磁化性质可能来源于在高场下产生的不可逆团聚.

Abstract：

MnFe2O4 nanoparticles are prepared by chemical coprecipitation method. Based on the MnFe2O4 nanoparticles, a self-formed ionic ferrofluid is synthesized. In the ferrofluid, Mn2+ and Fe3+ ions dissolved from the MnFe2O4 nanoparticles via suitable acid attack are adsorbed on the surface of the magnetic particles, thus preventing the particles from aggregating. The average thickness of ionized layers of the ferrofluid particles is about 1 to 2 nm.Both the particles and the ferrofluids have hysteresis behavior. The behavior may result from irreversible aggregation induced under high magnetic field.     

由Ni2O3/Fe2O3复合纳米微粒构成的离子型磁性液体的磁化性质研究

采用Massart法合成了Ni2O3/Fe2O3复合微粒磁性液体,并用振动样品磁强计(VSM)对磁性微粒及其磁性液体的磁化性质进行了测量.用Langevin理论进行了磁性液体磁化曲线的拟合.实验结果表明,磁性液体的实际测量的比饱和磁化强度小于理论值,并且磁性液体的初始磁化率大于Langevin理论曲线的初始磁化率.用零场下磁性液体中的微粒自组装结构对实验现象进行了解释.     

由Ni_2O_3/Fe_2O_3复合纳米微粒构成的离子型磁性液体的磁化性质研究

采用Massart法合成了Ni2O3/Fe2O3复合微粒磁性液体,并用振动样品磁强计(VSM)对磁性微粒及其磁性液体的磁化性质进行了测量.用Langevin理论进行了磁性液体磁化曲线的拟合.实验结果表明,磁性液体的实际测量的比饱和磁化强度小于理论值,并且磁性液体的初始磁化率大于Langevin理论曲线的初始磁化率.用零场下磁性液体中的微粒自组装结构对实验现象进行了解释.     

超声辅助磁性纳米四氧化三铁催化过氧化氢降解亚甲蓝染料的研

建立了一种基于超声辅助磁性四氧化三铁纳米微粒催化过氧化氢降解亚甲蓝染料的方法,研究了四氧化三铁纳米微粒浓度、过氧化氢浓度、pH值、反应时间、超声时间和温度等对催化降解反应的影响.结果表明,当四氧化三铁纳米粒子浓度为600mg/L,过氧化氢浓度为0.32mol/L,pH值为5,超声时间为3min,温度为30℃,反应时间为2h时,模拟染料废水中亚甲蓝的去除率最高可达到95%.     

Multiferroic BaTiO3-CoFe2O4 Nanostructures

We report on the coupling between ferroelectric and magnetic order parameters in a nanostructured BaTiO3-CoFe2O4 ferroelectromagnet. This facilitates the interconversion of energies stored in electric and magnetic fields and plays an important role in many devices, including transducers, field sensors, etc. Such nanostructures were deposited on single-crystal SrTiO3 (001) substrates by pulsed laser deposition from a single Ba-Ti-Co-Fe-oxide target. The films are epitaxial in-plane as well as out-of-plane with self-assembled hexagonal arrays of CoFe2O4 nanopillars embedded in a BaTiO3 matrix. The CoFe2O4 nanopillars have uniform size and average spacing of 20 to 30 nanometers. Temperature-dependent magnetic measurements illustrate the coupling between the two order parameters, which is manifested as a change in magnetization at the ferroelectric Curie temperature. Thermodynamic analyses show that the magnetoelectric coupling in such a nanostructure can be understood on the basis of the strong elastic interactions between the two phases.     

氯化锰和钼酸对盐渍地棉花幼苗生长耐盐性影响的研究

为了开发利用盐渍土地,给棉花的抗盐栽培提供理论依据。试验研究氯化锰(MnCl2.4H2O)和钼酸(H2MoO4.H2O)浸种对盐渍地棉花幼苗生长耐盐性的影响。通过对幼苗长度、根系活力、幼苗叶片叶绿素含量、过氧化物酶(POD)活性的测定,结果显示:氯化锰和钼酸混合液对棉花幼苗的耐盐性有显著影响,其中以1 000mg/L的MnCl2.4H2O+200 mg/L的H2MoO4.H2O混合液,效果最佳。     

Chemico-Viscous Remanent Magnetization in the Fe3O4-yFe2O3 System

The chemical remanent magnetization (CRM) acquired when single-domain size magnetite (Fe(3)0(4)) oxidizes to maghemite (gammaFe(2)O(3)) in a 50-microtesla field at a series of 13 temperatures from 1000 to 6560C is of similar intensity to viscous remanent magnetization (VRM) acquired under the same field and temperature conditions by unoxidized magnetite. The remanences of the oxidized and unoxidized phases also have similar resistances to demagnetization. These similarities imply that the remanence of the oxidized material is a chemico-viscous remanent magnetization (CVRM) having some of the characteristics of both classic growth CRM and thermally activated VRM. At low temperatures in partially oxidized grains, VRM of the magnetite core and growth CRM of the maghemite surface layer contribute about equally to CVRM. Near the Curie point, intensity of CVRM increases to a Hopkinson-type peak. High-temperature CVRM is more resistant to demagnetization than the thermoremanent magnetization (TRM) produced from cooling through the Curie point.     

Orbital ordering transition in La4Ru2O10

We report experimental evidence for a full orbital ordering transition in the two-dimensional lanthanum ruthenate La4Ru2O10. The observable consequences of this orbital ordering include the loss of the Ru local moment, a structural distortion which partitions Ru-O bonds into axially oriented short and long sets, a sharp jump in electrical resistivity, and the opening of a spin gap that is visible in neutron scattering experiments. This is a rare example of a discrete orbital ordering transition in a 4d transition metal oxide and demonstrates that orbital effects can have an influence on the properties of layered ruthenates, a family of compounds that notably includes the p-wave superconductor Sr2RuO4 and the field-tuned quantum critical metamagnet Sr3Ru2O7.