ZnFe2O4纳米结构制备及其M(o)ssbauer谱分析

通过水解Zn/Fe3O4纳米粒子制备ZnFe2O4纳米结构,采用XRD和TEM检测产品的成分和形貌变化,验证反应过程方程的正确性.结果表明:当反应温度为260℃时,产品中含有ZnO纳米棒,随着反应温度升至300℃,ZnO纳米棒逐渐消失,得到纯度较高的ZnFe2O4纳米颗粒,粒度分布在20～30nm范围内.产品的M(o)...     

纳米ZnFe_2O_4的制备及其光催化降解苯酚的协同效应

在干法室温条件下,利用滚压振动磨将金属锌制备成粒度大约40nm的锌粉,用化学共沉淀法制备粒度为10nm左右的Fe3O4。利用Zn-Fe3O4水解系统制备纳米ZnFe2O4,当温度达到300℃后,XRD图上明显出现ZnFe2O4的各个衍射峰,由透射电子显微镜可知,300℃和320℃时得到的纳米粒子都在20nm左右。分别用电子衍射、高分辨电镜对两个样品进行了表征。在距离6cm的30W紫外灯照射下,光催化降解苯酚的实验表明光催化降解的效率顺序为:ZnFe2O4-ZnO-Fe2O3>ZnO-Fe2O3>ZnFe2O4>ZnO>Fe2O3。     

Fe_2O_3/ZnFe_2O_4纳米复合材料的制备及其光学特性

采用水热法制备了Fe2O3/ZnFe2O4纳米复合材料,使用XRD、TEM、SEM等测试手段对产物进行了表征,并采用紫外-可见分光光度计（UV-Vis）对产物的光学吸收特性进行了研究,结果表明,改变反应物的浓度和Zn掺杂比例可以分别得到Fe2O3/ZnFe2O4复合物和Zn掺杂Fe2O3。Fe2O3和ZnFe2O4的复合可以明显扩展Fe2O3在可见光波段的吸收范围,Zn掺杂Fe2O3样品的吸收可以达到红外波段。     

共沉淀法合成ZnFe_2O_4纳米颗粒及其电磁性能研究

采用共沉淀法制备出尖晶石型ZnFe2O4纳米颗粒,通过透射电子显微镜(TEM)、X射线衍射仪(XRD)、振动样品磁强计(VSM)和矢量网络分析仪分析样品的表面形貌、晶体结构、化学成分、磁化性能和电磁性能。研究结果表明,前驱体混合物的焙烧温度为500℃时得到ZnFe2O4纳米颗粒,尺寸在14~17nm范围内,粒度分布均匀,为单晶立方结构;当焙烧温度为500~800℃时,样品表现出亚铁磁性,随着焙烧温度升高,颗粒尺寸增大,离子的倒反系数减小,饱和磁化强度降低;所选样品在2~18GHz频率范围内多次出现损耗峰,介质在松弛极化和色散过程中,将电场能转化为热能而耗散掉,从而获得良好的电磁性能。所用方法工艺简单,设备成本低。     

双微乳液法制备纳米磁性Fe3O4粉体的研究

现代诊断学的发展使得纳米级超顺磁性的Fe3O4粒子在医学领域具有重要应用价值.本实验采用双微乳液法制备纳米磁性Fe3O4粉体.从反应物浓度、表面活性剂用量、油相用量及反应温度等方面讨论对产物粒径的影响,通过正交试验确定了制备纳米Fe3O4粉体的最佳工艺条件.对获得的粉体采用激光散射法粒度测试、XRD物相分析和粒径计算、原子力显微镜(AFM)和透射电子显微镜(TEM)形貌观察、振动样品磁强计磁性测定等进行表征,结果表明制备的Fe3O4粉体平均粒径约为24nm、粒度分布均匀、分布带较窄且产物纯度高;该粉体具有超顺磁性,饱和磁化强度在66A·m2/kg左右.     

共沉淀法制备纳米Fe3O4及其对橙黄Ⅱ的降解

通过共沉淀法制备Fe3O4纳米颗粒,采用X射线衍射(XRD)、扫描电子显微镜(SEM)和比表面孔隙分析(BET)对样品进行表征。以合成的纳米Fe3O4催化H2O2氧化降解橙黄Ⅱ,考察了共沉淀法制备过程中的Fe2+/Fe3+的摩尔比、反应温度、pH值、Fe离子浓度等因素对Fe3O4催化性能的影响。结果表明在Fe2+/Fe3+的摩尔比为3∶4、反应温度80℃、pH值为10、Fe离子浓度为0.1mol·L-1的条件下制备出的Fe3O4纳米颗粒催化活性最高,其粒径为20nm左右。并且未干燥的磁流体对橙黄Ⅱ的降解效率明显高于Fe3O4粉体。     

纳米CoFe_2O_4颗粒制备及性能研究

铁酸钴具有很多优良特性,应用广泛,其制备方法多为微乳液法,本文中用化学共沉淀法制备了纳米CoFe2O4颗粒。将Co2+和Fe3+的混合液加入沉淀剂溶液中,选用NaOH作为沉淀剂,探讨了温度、保温时间以及NaOH的加入方式对颗粒粒径的影响。用激光粒度分析仪、SEM、XRD、VSM测试了颗粒的大小、形貌、分散状况及饱和磁化强度。结果表明:在制备过程中,适当降低反应温度,缩短反应时间,快速加入NaOH可减小颗粒的粒径,且用此法制备出的CoFe2O4粉末饱和磁化强度为46.776A·m2/kg。     

超声波化学法制备纳米铁酸锌粉末的影响因素

超声辐射Fe(NO3)3·9H2O、不同锌盐和脲的混合水溶液得到前驱体,再经过高温焙烧得到纳米ZnFe2O4粉末.得到的纳米ZnFe2O4粉末用X射线衍射(XRD),傅立叶转换红外光谱(FT-IR)表征得到确认.系统研究了超声波化学法制备纳米铁酸锌粉末工艺中不同锌盐、超声波辐射时间、焙烧温度和焙烧时间等影响因素,结果表明:Fe(NO3)3·9H2O与Zn(NO3)2·6H2O为原料,超声波辐射为4h,焙烧温度为950q℃,焙烧时间为14h可制备结晶良好、分散性好、粒度小于100nm的尖晶石型铁酸锌粉末.     

纳米铁酸锌的制备与应用

以乙酰丙酮铁(Fe(acac)3)和一水合乙酰丙酮锌(Zn(acac)2.H2O)为主要原料,用均匀共沉淀法制备ZnFe2O4纳米晶粒。XRD表明,这是由细小的晶种组成的粒径在70-100nm的ZnFe2O4晶体颗粒。再利用甲基丙烯酸甲酯(MMA)分散乳液聚合,得到粒径在30-70nm具有核壳结构的纳米ZnFe2O4/PMMA复合粒子。     

NiFe2O4纳米粒子的水热合成及表征

以Ni(NO3)2·6H2O和Fe(NO3)3·9H2O为主要原料,在聚乙二醇(PEG)存在下,采用水热法制备了磁性NiFe2O4纳米粒子,用X射线衍射仪(XRD)、透射电子显微镜(TEM)和振动样品磁场计(VSM)等分析方法对样品进行了表征.结果表明:水热法合成的NiFe2O4纳米粒子为尖晶石结构,粒度分布均匀,为方形形貌,粒子直径范围在50～60nm;比饱和磁化强度为25.83emu/g,剩磁为6.167emu/g,矫顽力达85.87Oe.     

ZnFe2O4-Fe3O4 und yig als magnetische dielektrika

The magnetic and electric fields found in zinc ferrite and yttrium iron garnet have been studied with the aid of electron diffraction. In these magnetic dielectrics, the magnetic field strength in e.m.u. proved to be comparable with the electric one in e.s.u.; i.e., both the values were estimated to be about 100. The wavelength of microwave to be absorbed by the materials concerned was evaluated to be about 1 mm in terms of the LC model.     

Polymorphism of the Ag8S4O4 and Ag6S3O4 compounds

Experimental results of the reaction occurring between aqueous solutions of AgNO₃ and Na₂S₂O₃ were presented in this work. It has been demonstrated that these reagents form two phases to which the summary formulas: -Ag₈S₄O₄ and -Ag₆S₃O₄ were ascribed. The -Ag₈S₄O₄ phase crystallizes in a tetragonal system and has the following parameters of the unit cell: a = b = 0.72052 nm, c = 0.51140 nm, V = 0.26550 nm³, Z = 1, d_x = 6.60 g/cm³. At 223°C -Ag₈S₄O₄ undergoes an irreversible, endothermic polymorphic transition. The heat of this transition amounts 8.03 × 10^–3 J/mol. A high-temperature polymorphic form -Ag₈S₄O₄ melts at 400°C. The -Ag₆S₃O₄ phase crystallizes in a monoclinic system and has the following parameters of the unit cell:a = 2.09616 nm, b = 0.53118 nm, c = 1.49885 nm, = 102.78°, V = 1.62753 nm³, Z = 8, d_x = 6.59 g/cm³. -Ag₆S₃O₄ also undergoes an irreversible, endothermic polymorphic transition at 221°C. The heat of this transition amounts 7.65 × 10^–3 J/mol. A high-temperature form, -Ag₆S₃O₄, melts at 390°C.     

0.64BaTi4O9-0.36BaEu2Ti4O12/BaTi4O9纤维复合陶瓷的介电性研究

对0.64BaTi4O9-0.36BaEu2Ti4O12/BaTi4O9纤维复合陶瓷新材料的相组成、介电性能和样品表面原子的化学组成及Ti元素的价态变化进行了研究.研究结果表明该复合陶瓷新材料只由BaTi4O9和BaEu2Ti4O12两相组成.加入BaTi4O9纤维后,复合陶瓷材料中Ti3+离子和Ti2+离子的含量降低,氧元素的含量提高,并且BaTi4O9纤维对该材料体系的介质损耗有明显的改善作用,其中含10vol%BaTi4O9纤维的BET10试样的性能最佳,其εr=55,tgδ=3×10-4(在1MHz条件下).     

Magnetic Properties of Nanocrystalline CoFe2O4/ZnFe2O4 Bilayers

Nanocrystalline spinel CoFe₂O₄/ZnFe₂O₄ bilayers were deposited by the pulsed laser deposition technique on amorphous fused quartz substrate at different substrate temperatures ranging from room temperature to 750?°C. The magnetic properties of the bilayers and of the single layer films deposited in identical conditions were studied at 300?K and at 10?K. Magnetic properties of the bilayers, in general, were found to be in between the individual values of the single layers. Magnetic measurements at 10?K clearly showed a two stepped magnetic hysteresis loop corresponding to the switching of the magnetic moments of the soft ZnFe₂O₄ and the hard CoFe₂O₄ layers. A study was also carried out by changing the thickness of ZnFe₂O₄ layer in the bilayer. This study showed that the magnetic properties of the bilayers even at room temperature can be controlled to some extent by changing the thickness of the soft ZnFe₂O₄ layer while maintaining a low substrate temperature of 350?°C.     

X-ray diffraction study of the CuCr2O4-NiFe2O4 system

Phase relations in the Cu_1-xNi_xCr_2(1-x) solid-solution system, containing Jahn-Teller active cations, were studied by powder x-ray diffraction. The solid solutions with jc > 0.5 were found to have a cubic NiFe₂O₄ (Fd3m) structure. In the range 0.1 <x < 0.4, a cubic phase of approximate composition Cu_0.6Ni_0.4Cr_1.2Fe_0.8O₄ was shown to coexist with a tetragonal phase of composition Cu_0.9Cr_1.2Fe_0.2O₄. The results were interpreted under the assumption that the degree of inversion of the spinel phase varies significantly across the morphotropic region. The lattice parameters and degree of inversion of the solid solutions were determined as a function of composition. The distributions of the divalent and trivalent cations over tetrahedral and octahedral sites were tentatively assessed.     

Spinel Phase Relations in the Fe3O4–CuFe2O4 System

Phase equilibria involving spinel solid solutions, delafossite, and hematite in the Fe–Cu–O system are studied by emf measurements in solid-electrolyte galvanic cells. The results demonstrate that, above 1250 K, Fe₃O₄ and CuFe₂O₄ form a continuous series of solid solutions. At lower temperatures, the solid solution disproportionates with the formation of delafossite and Fe₂O₃, and two spinel solid solutions appear: one based on Fe₃O₄ and the other based on Cu₂FeO₄. The compositions of the spinel phases in equilibrium with delafossite and Fe₂O₃ are determined in the range 1100–1250 K.