Magneto-Optical Effects in Colloidal Solutions of Barium Hexaferrite

Hydrothermal synthesis was used to obtain lamellar magnetic particles of barium hexaferrite, and colloidal solutions were prepared on their basis. Magneto-optical effects in colloid solutions of barium hexaferrite were examined. It was found that the aqueous colloidal solution of coarse planar particles of barium hexaferrite is a magneto-optical medium that is nearly two orders of magnitude more effective than the colloid formed from isometric cobalt ferrite particles. It was shown that measuring the frequency dependence of the magneto-optical effects and approximating the experimental data with the Debye function makes it possible to find the frequency f₀ characteristic of the given colloid and to calculate the characteristic size of particles (or aggregates) creating the optical anisotropy in the colloid under the action of a magnetic field. A dichroism is observed in the aqueous colloid formed by coarse planar barium hexaferrite particles. This phenomenon is due to the change in the light scattering on coarse particles upon their orientation by a magnetic field.     

磁性TiO2/CoFe2O4纳米复合光催化材料的制备

以磁性CoFe2O4为核,采用改进的溶胶-凝胶法,制备了磁性TiO2/CoFe2O4纳米复合光催化材料.利用VSM(振动样品磁强计)技术对其磁性能进行了研究,结果表明:由该法所得的TiO2/CoFe2O4纳米复合光催化材料的饱和磁化强度虽稍弱于纯CoFe2O4纳米材料,但其矫顽力则优于CoFe2O4.TEM、XRD、UV-Vis等的结果表明,该纳米复合材料中的TiO2为锐钛矿结构;与TiO2相比,纳米复合材料对光的吸收拓展到了整个紫外-可见区,且吸收强度大大增强.对染料废水光催化降解的模拟研究表明,该复合材料在紫外光下,6 h可以使亚甲基蓝染料溶液的脱色率达95%,且重复使用3次时染料溶液的脱色率仍能保持在90%,明显优于纯TiO2.     

A new three-dimensional cobalt phosphate: Co5(OH2)4(HPO4)2(PO4)2

A three-dimensional (3D) cobalt phosphate: Co₅(OH₂)₄(HPO₄)₂(PO₄)₂ (1), has been synthesized by hydrothermal reaction and characterized by single-crystal X-ray diffraction, thermogravimetric analysis, and magnetic techniques. The title compound is a template free cobalt phosphate. Compound 1 exhibits a complex net architecture based on edge- and corner-sharing of CoO₆ and PO₄ polyhedra. The magnetic susceptibility measurements indicated that the title compound obeys Curie-Weiss behavior down to a temperature of 17 K at which an antiferromagnetic phase transition occurs.     

Thermosensitive and control release behavior of poly(N-isopropylacrylamide-co-acrylic acid)/nano-Fe3O4 magnetic composite latex particle that is synthesized by a novel method

In this study, a novel method was used to synthesize the poly(N-isopropylacrylamide-co-acrylic acid)/Fe₃O₄ (poly(NIPAAm-AA)/Fe₃O₄) magnetic composite latex. The crosslinked poly(NIPAAm-AA) polymer latex particles were first synthesized by the method of soapless emulsion polymerization, then Fe²⁺ and Fe³⁺ ions were introduced to bond with the -COOH groups of AA segments in poly(NIPAAm-AA) polymer latex particles. Further by a reaction with NH₄OH, Fe₃O₄ nanoparticles were generated in situ. The concentrations of acrylic acid (AA), crosslinking agent (N,N′-methylene bisacrylamide (MBA)), and Fe₃O₄ nanoparticles were important factors to influence the morphology and lower critical solution temperature (LCST) of poly(NIPAAm-AA)/Fe₃O₄ magnetic composite latex particles. The poly(NIPAAm-AA)/Fe₃O₄ latex particles were used as a thermosensitive drug carrier to load caffeine. The control release of caffeine was studies. Morphology-based schematic models were proposed to explain the control release behavior of the composite particles with different compositions. Moreover, the protein (albumin, acetylated from bovine serum (BSA)) was bound on the surface of poly(NIPAAm-AA)/Fe₃O₄ composite latex particles. The effects of AA, crosslinking agent and Fe₃O₄ contents on the amount of BSA binding were investigated at different temperatures and pH values. The composition-morphology-BSA conjugation relationship was established.     

Preparation of uniform rhodamine B-doped SiO2/TiO2 composite microspheres

Uniform rhodamine B (RB)-doped SiO₂/TiO₂ composite microspheres with catalytic and fluorescent properties were prepared by an easy and economical method in this paper. The composite microspheres were built up with well-dispersed silica particles as the cores, RB as both the doped agent and stabilizer, and the TiO₂ shells were obtained through the hydrolysis of TiCl₄ in water bath. The morphology and structure of the particles were characterized by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). The characterization results indicate that composite particles are all in spherical shape and have a narrow size distribution. The composite particles calcined above 500 °C reveal clear crystalline reflection peaks of the rutile TiO₂ which exhibits well catalytic property. The photocatalytic experiment was carried out in order to examine the catalytic property of composite microspheres. The fluorescent property of particles was also investigated. Dye-leakage test indicates that RB molecules entrapped in the composite particles by this method are stable inside the particles.     

掺La3+纳米钴铁氧体的制备、表征、磁性及其Peg-20000复合物的导电性研究

纳米铁氧体材料的许多电磁性质和光学性质已经有了一些研究[1]。为了改善其性能,有研究者将稀土Ce3 掺入铁氧体材料进行改性,发现其磁导率有明显改变[2]。纳米CoFe2O4因为具有较高的矫顽力、适中的饱和磁化强度、适中的机械强度和化学性质稳定而作为硬磁材料[3]。有研究表明,在CoFe2O4体系中掺入过渡金属离子可以改变其磁性[4],加入稀土Yb3 ,La3 可以使晶格发生畸变,增强磁光效应[5]。因此,本工作研究CoFe2O4体系中掺入La3 引起磁性的变化。磁性纳米粒子掺杂到导电聚合物中可制备高性能吸波材料[6]。因为单一的铁氧体在吸波过程中虽无…     

Structural and magnetic properties of CoxZn1−xFe2O4 nanocrystals synthesized by microwave method

Microwave assisted combustion method was used to produce nanocrystalline cobalt doped zinc ferrite, Co_xZn_1−xFe₂O₄, from stoichiometric mixture of (Co(NO₃)₂·6H₂O), (Fe(NO₃)₃·9H₂O), (Zn(NO₃)₂·6H₂O), and urea (CO(NH₂)₂) as a fuel. The structural, morphological and magnetic properties of the products were determined by X-ray powder diffractometry (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) respectively. The average crystallite sizes obtained from XRD were between 35 and 39 nm. Magnetization measurements indicate that samples with less Co content have superparamagnetic behavior at room temperature. When the Co substitution increases the saturation magnetization due to the magnetic character of the Co cations substituting the non-magnetic Zn and coercivity also increase due to anisotropic nature of cobalt. The Co_xZn_1−xFe₂O₄ nanocrystals exhibit typical features of an assembly of magnetic particles with a distribution of blocking temperatures and indicate the spin-glass behavior.     

Magnetic resonance study of (GdxY1−x)Co2 compounds

The results of magnetic resonance studies on ferrimagnetic (Gd_xY_1?x)Co₂ compounds, both below and above the Curie points, are presented. The ferrimagnetic resonance measurements show that the effective g values can be described by using the Wangsness relation. The spectroscopic splitting factors of cobalt atoms are not composition dependent. In the paramagnetic range the thermal variation of the linewidth is not linear and the g values are a function of temperature. This behavior is analyzed in correlation with the magnetic data.     

TiO2纳米管阵列负载不同形貌Cu2O薄膜的制备及光电性能研究

本论文采用阳极氧化法在金属钛基底上制备高度有序的TiO2纳米管阵列薄膜,然后采用脉冲电流法在TiO2纳米管阵列上沉积Cu2O,从而制备出Cu2O-TiO2纳米管阵列异质结复合薄膜。借助X射线衍射仪(XRD),场发射扫描电子显微镜(FESEM)和透射电子显微镜(TEM)等表征手段,详细探讨了Cu2O沉积过程中电解液的不同扰动方式(静止、磁力搅拌和超声搅拌)对复合薄膜物相和形貌的影响。实验结果表明电解液的扰动方式会影响Cu2O沉积过程中的离子扩散和微区化学环境,从而影响Cu2O的形貌。通过漫反射紫外-可见吸收光谱(UV-Vis)和光电流性能测试可知所制备的负载Cu2O型TiO2纳米管阵列薄膜具有显著的可见光响应效应。     

Synthesis and characterization of poly(3-thiophenyl acetic acid) (P3TAA)-BaFe12O19 nanocomposite

We have presented a method for the fabrication of poly(3-thiophenyl acetic acid) (P3TAA)-BaFe₁₂O₁₉ nanocomposites by the in situ polymerization of P3TAA in the presence of synthesized BaFe₁₂O₁₉ nanoparticles. The nanoparticles and the nanocomposite were analyzed by XRD, FTIR, TGA, TEM, VSM and conductivity techniques for structural and physicochemical characteristics. Crystallographic analysis revealed the phase as hexaferrite and X-ray line profile fitting yielded a crystallite size of 32 nm. The particles, observed by TEM, exhibit irregular shapes and sizes between 100 and 500 nm, revealing polycrystalline character when compared with the crystallite size from XRD. FTIR and TGA analysis results show that P3TAA is conjugated to the particle surface via a carboxylate group and that the composite has a polymer content of ∼10%. Magnetic hysteresis curves do not saturate at high fields, which is a characteristic feature of fine particle systems with grain sizes smaller than 1 μm. Conductivity measurements showed a semiconductor character of the nanocomposite.     

Isothermal gravimetry and magnetic properties of CoOMoO3γAl2O3 catalysts

Isothermal gravimetry and magnetic susceptibility of MoO₃, MoAl₂O₃, CoAl₂O₃ and CoMoAl₂O₃ with/without Na⁺ ions have been studied in order to investigate the reducibility of the systems in H₂ H₂—hydrocarbons and H₂—hydro-carbon—thiophene. These studies have evidenced the formation of metallic cobalt during reduction of cobalt—moly catalysts containing Na⁺ ions in the Al₂O₃ support. This metallic cobalt accelerates the reduction of supported MoO₃. However, in the absence of sodium, cobalt exerts an inhibitory influence on the reduction of MoAl₂O₃. The inhibition is caused mainly due to retention of the water evolved during the process by well-dispersed Co²⁺ ions which are incapable of undergoing reduction. The presence of sulfur also kelps in suppressing the reduction to cobalt metal.     

一锅法制备Co3O4/g-C3N4复合光催化剂及其光催化性能

以三聚氰胺和六水合氯化钴为原料,一锅法制备Co_3O_4负载的多孔石墨相氮化碳(Co_3O_4/g-C_3N_4)复合光催化材料。采用X射线衍射(XRD)、傅里叶变换红外(FT-IR)光谱、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、紫外-可见漫反射光谱(UV-Vis DRS)、光致发光光谱(PL)等手段对其结构和光学特性进行表征。以盐酸四环素(TC)为目标污染物,评价了不同负载量Co_3O_4/g-C_3N_4复合光催化剂的可见光催化性能。结果表明,所制备的Co_3O_4/g-C_3N_4复合光催化剂为多孔结构,其比表面积较大,并在可见光区域具有显著的吸收。利用原位生成的Co_3O_4纳米粒子在氮化碳表面形成异质结构,可有效转移光生载流子,降低光生电子-空穴的再结合率,从而提高光催化活性。并且存在最佳Co_3O_4复合量,当六水合氯化钴加入量为三聚氰胺的8%(w/w)时,所制备的复合光催化剂CoCN-8具有最佳的光催化性能。在可见光的照射下,60 min内可降解85%的TC,而同样条件下,纯g-C_3N_4仅降解23%的TC。     

Preparation and characterization of NiFe bimetallic micro-particles and its composite with silica shell

Magnetic NiFe particles were synthesized through hydrothermal method using hydrazine as reductant. Composite particles with core-shell structure were further achieved by depositing silicon dioxide generated via carbonation decomposition of sodium silicate solution on the surface of magnetic cores. Characterized by XRD, the Ni₉Fe particles are of fcc-type structure, and the structure of magnetic cores in composite particles was maintained despite being covered by SiO₂ shell. The existence of SiO₂ shells in the composite particles were demonstrated by SEM, EDS and IR. The results from TG and VSM indicated that the shell structure affected the physiochemical properties. The composite particles exhibited remarkable resistance to oxidation in comparison with Ni₉Fe particles due to being protected by SiO₂ shell. Meanwhile, both of them are soft magnetic materials, but Ms, Mr and Hc in Ni₉[email protected]₂ particle decreased compared with magnetic NiFe particles. The formation mechanisms of Ni₉Fe micro-particles and composite Ni₉Fe particles were discussed.     

Magnetic and electronic structure of TlCo2S2

An extensive investigation of the ferromagnetic compound TlCo₂S₂ has resulted in new information on the electronic and magnetic structure. Electronic structure calculations showed that magnetic ordering is energetically favorable with a clear driving force for ferromagnetic coupling within the cobalt layers. TlCo₂S₂ is metallic and the conductivity is due to holes in the valence band. XPS single crystal measurements did not show evidence of mixed oxidation states of cobalt. Neutron powder diffraction resulted in a ferromagnetic structure with the magnetic moment in the ab-plane. The derived magnetic moment of the cobalt atom is at 10 K and is in very good agreement with the value, at 10 K, inferred from the magnetic hysteresis curve.     

钛铁矿制备二氧化钛-四氧化三铁复合材料及其光催化应用

TiO_2因具有多种优异的特性被广泛应用在半导体光催化领域,但是纳米结构的TiO_2颗粒细微,在进行光催化反应之后,难以回收再利用。本文以廉价钛铁矿为原料制备光催化剂TiO_2,同时利用副产物铁合成Fe_3O_4,并采用简单温和的浸渍法制备Fe_3O_4/TiO_2磁性复合材料。通过XRD、FT-IR、SEM、EDS等手段对材料形态结构进行表征分析,并以光降解有机污染物若丹明B为探针反应,考察其光催化性能。结果表明,质量比为1∶10的Fe_3O_4/TiO_2复合材料结构稳定、分散均匀,具有最优的光催化活性(波长356nm下反应3h,若丹明B降解率达到64.0%),并表现出良好的重复性。同时,动力学结果显示降解符合一级反应动力学。     

复合软模板法可控制备红毛丹状AlOOH/Al2O3纳米材料

以Al(NO₃)₃为铝源,尿素为均相沉淀剂, 在聚乙二醇400(PEG4000)-DL-天冬氨酸形成的复合软模板体系中, 通过简单的常压回流方式成功合成出形貌和尺寸较为均一的红毛丹状γ-AlOOH纳米结构, 继而考察了反应物和添加剂用量对前驱体形貌和尺寸的影响, 并对γ-AlOOH纳米结构可能的形成机理进行了探讨. 实验结果表明, 所合成的红毛丹状γ-AlOOH具有球中球的核壳结构, 统计得内球直径约为400 nm, 外壳外径约为600 nm, 密集状态的壳层厚度约为15 nm, 毛刺状凸出物长度可达60 nm以上. 前驱体样品经600℃煅烧5 h后即转变为具有良好形貌继承性的γ-Al₂O₃, Brunauer-Emmett-Teller (BET) N₂-吸附实验表明其比表面积高达299.97 m²·g^-1.     

Exchange‐Coupled fct‐FePd/α‐Fe Nanocomposite Magnets Converted from Pd/Fe3O4 Core/Shell Nanoparticles

We report the controlled synthesis of exchange‐coupled face‐centered tetragonal (fct) FePd/α‐Fe nanocomposite magnets with variable Fe concentration. The composite was converted from Pd/Fe₃O₄ core/shell nanoparticles through a high‐temperature annealing process in a reducing atmosphere. The shell thickness of core/shell Pd/Fe₃O₄ nanoparticles could be readily tuned, and subsequently the concentration of Fe in nanocomposite magnets was controlled. Upon annealing reduction, the hard magnetic fct‐FePd phase was formed by the interdiffusion between reduced α‐Fe and face‐centered cubic (fcc) Pd, whereas the excessive α‐Fe remained around the fct‐FePd grains, realizing exchange coupling between the soft magnetic α‐Fe and hard magnetic fct‐FePd phases. Magnetic measurements showed variation in the magnetic properties of the nanocomposite magnets with different compositions, indicating distinct exchange coupling at the interfaces. The coercivity of the exchange‐coupled nanocomposites could be tuned from 0.7 to 2.8 kOe and the saturation magnetization could be controlled from 93 to 160 emu g^?1. This work provides a bottom‐up approach using exchange‐coupled nanocomposites for engineering advanced permanent magnets with controllable magnetic properties.     

晶种和磁场诱导联合法制备一维Fe3O4粒子

本文采用晶种和磁场诱导结合的方法制备出了一维Fe3O4纳米粒子,研究了晶种粒径大小、磁场强度、晶种添加量以及晶种分步次数对Fe3O4产品形貌的影响。结果表明,磁场强度增加,棒形颗粒数目增加;晶种分步次数增加,棒形粒子轴比增加;采用三次晶种可以得到轴比为9.0的棒形颗粒;少量的晶种有利于得到轴比一致、形貌均匀的棒形颗粒;大尺寸的晶种有利于得到链形颗粒。同时从颗粒间的相互作用能分析了磁场强度和晶种大小对形貌的影响。     

Effect of support and cobalt precursors on the activity of Co/AlPO4 catalysts in Fischer–Tropsch synthesis

Cobalt supported on amorphous aluminum phosphate (Co/AlPO₄) catalysts were prepared by the impregnation method using three different cobalt precursors such as cobalt nitrate, acetate and chloride to elucidate the activity of Fischer–Tropsch synthesis. The use of AlPO₄ as a support for cobalt-based catalysts exhibits better catalytic performance during FTS reaction than the corresponding Co/Al₂O₃ catalyst. TPR results also suggest that the reducibility of the catalysts varies with the nature of cobalt precursors employed during the impregnation on AlPO₄ support. The Co/AlPO₄ catalyst prepared from cobalt nitrate shows higher CO conversion and C₈+ selectivity than the others due to the facile formation of homogeneous cobalt particles with proper electronic characters and high reducibility. Interestingly, all Co/AlPO₄ showed a growth of filamentous carbon initiated from the large mobile cobalt particles during the reaction. The differences in catalytic properties of Co/AlPO₄ are mainly attributed to the cobalt particle size, reducibility with different electronic states of metallic cobalt, pore diameter of AlPO₄ and formation of filamentous carbon.     

叶酸对磁性Fe_3O_4纳米粒子的表面修饰

以FeCl3·6H2O作为单一铁源,1,6-己二胺作为胺化试剂,利用无模板的溶剂热方法制备了胺基功能化的磁性Fe3O4纳米粒子,并利用其键合叶酸分子,制备出表面修饰了叶酸的磁性Fe3O4复合纳米粒子。利用傅里叶变换红外光谱仪、X-射线衍射仪、透射电镜、差热-热重分析仪和振动样品磁强计对所得纳米粒子的形貌、粒径、化学组成和磁性能进行了表征。结果表明,叶酸分子通过化学键牢固键合在磁性纳米Fe3O4粒子表面,叶酸修饰的复合纳米粒子仍然具有良好的磁性能。