Effects of pH and citric acid contents on characteristics of ester-derived BaFe12O19 powder

The single domain size of BaFe₁₂O₁₉ powder with crystallite sizes less than 200 nm was produced using a citric acid precursor method. Fe³⁺ and Ba²⁺, in a molar ratio of 12, were chelated by COOH⁻ in an aqueous solution. After ethylene glycol additions, esterification, dehydration, and calcination led to the formation of ester-derived BaFe₁₂O₁₉ powder. High pH and/or high citric acid contents in the starting solution are required to complete chelate metallic ions in the solution and to form pure barium ferrite powder at 1073 K. Pure single magnetic domain BaFe₁₂O₁₉ particles of M(30 kOe)≈54 emu/g, M_r≈28 emu/g, and H_c≈3.7 kOe were produced using [citric acid]/[metallic ions]=1.5 and pH7.     

Direct measurement of the magnetocaloric effect in La0.67Ca0.33MnO3

Polycrystalline perovskite La_0.67Ca_0.33MnO₃ was synthesized by a sol–gel method. Its adiabatic temperature change ΔT_ad induced by a magnetic field change was measured directly. At 268 K, near its Curie temperature T_C, ΔT_ad of La_0.67Ca_0.33MnO₃ induced by a magnetic field change of 2.02 T reaches 2.4 K. The latent heat Q and magnetic entropy change −ΔS_M induced by a magnetic field change were calculated from the temperature dependence of ΔT_ad and zero-field heat capacity C_p. The maximum values of Q and −ΔS_M in La_0.67Ca_0.33MnO₃ induced by a magnetic field change of 2.02 T are 1.85 J g⁻¹ and 6.9 J kg⁻¹ K⁻¹, respectively. The former is larger than the phase transition latent heat of heating or cooling, which is about 1.70 J g⁻¹.     

Influence of chemistry and hot rolling conditions on high permeability non-grain oriented silicon steel

This paper discusses the influence of chemical composition on the final electromagnetic properties in higher permeability material. Furthermore, the effect of the hot rolling practice and the end of austenite transformation temperature range on the hot band microstructure is described. The magnetic polarization J₅₀₀₀ better than 1.7 T, using hot rolling conditions 40 mm transfer bar thickness, finish mill entry temperature 1000 °C, and finishing temperature 800–840 °C and after decarburization heat treatment and grain growth treatment, was obtained.     

Topological order in the phase diagram for high-temperature superconductors with point defects

Applying a Lindemann like criterion obtained previously by Kierfeld et al. [J. Kierfeld, T. Nattermann, T. Hwa, Phys. Rev. B 55 (1997) 626], we estimate the magnetic field and temperature for a high-T_c superconductor, at which a topologically ordered vortex glass phase becomes unstable with respect to a disorder-induced formation of dislocations. The employed criterion is shown to be equivalent to a conventional phenomenological Lindemann criterion including the values for the numerical factors, i.e., for the Lindemann number. The positional correlation length of the topologically ordered vortex glass is calculated.     

Strukturelle Charakterisierung der Dicyanamid-Komplexe von Kupfer(II), Nickel(II) bzw. Kobalt(II) mit Aminopyridinen

Summary New dicyanamide complexes of the typeM[N(CN)₂]₂ L ₂ (M=Cu or Ni;L=2-, 3-, 4-aminopyridine, 2-amino-5-nitropyridine) and Co[N(CN)₂]₂ (2-amino-5-nitropyridine)₂ were prepared and studied by spectroscopic methods as well as by room-temperature magnetic moments. The results show that the Cu(II) complexes have elongated pseudooctahedral structures while the Ni(II) and Co(II) complexes are octahedral. In most cases the N(CN)₂ groups are in bridging function and through their cyanide nitrogens, or-more rarely-amide and cyanide nitrogens connect the basic structure units into polymeric conglomerates. In the Cu(II) systems exchange coupling is seen from the _eff value or ESR spectrum.

Professor Viktor Gutmann zum 70. Geburtstag gewidmet     

Synthesis and crystal structure of a new one-dimensional system with end-to-end single dicyanamide bridges between nickel(II) centres

The complex [Ni(tn)₂{N(CN)₂}]ClO₄ (tn=trimethylenediamine) has been synthesized and the structure has been determined. The complex forms a one-dimensional chain structure via the bidentate bridging ligand dicyanamide. A two-dimensional networks is formed via interchain hydrogen bond interactions.     

Fe3O4/葡聚糖/抗体磁性纳米生物探针的制备和层析检测

在免疫检测中 ,经常利用一些具有特殊物理化学性质的标记物对抗体 (或抗原 )进行偶联标记 ,在抗体与抗原识别后 ,通过对标记物的定性和定量检测而达到对抗原 (或抗体 )检测的目的 .传统的免疫标记物包括放射性同位素 [1] 、酶 [2 ] 、胶体金 [3] 和有机荧光染料分子 [4 ] 等 .近年来 ,随着纳米技术的发展 ,半导体荧光纳米晶 [5,6 ] 和磁性纳米晶 [7] 在免疫检测方面受到了广泛关注 .磁性纳米晶性能稳定 ,较易制备 ,可与多种分子复合使粒子表面功能化 ,并且由于磁纳米晶具有超顺磁性 ,为样品的分离、富集和提纯提供了很大方便 .这些优点使它…     

Recyclable,non-leaching antimicrobial magnetic nanoparticles

Recyclable antimicrobial magnetic nanoparticles, Fe₃O₄@P(St-co-AcQAC), were prepared through surfactantfree seeded emulsion polymerization involving a polymerizable, hydrophobic quaternary ammonium compound (QAC). These antimicrobial magnetic nanoparticles demonstrated excellent antimicrobial activities against both Grampositive and Gram-negative bacteria, and can be reused for multiple times.     

磁性微珠的制备及其在生物样品分离富集中的应用

磁性微珠作为一种新型的功能材料,广泛应用于磁性材料、生物医学、细胞学、生物工程及分离工程等诸多领域,并显示出强大的生命力。本文对磁性微珠的结构、性质、制备方法及其在生物样品的分离富集等方面的应用,进行了总结和评述,引用文献62篇。     

化学发光磁酶免疫法检测O157∶H7大肠埃希菌

O157∶H7大肠埃希菌是一种致病力非常强的微生物.近年来,陆续有其引起食物中毒事件的报道.1996年日本发生O157∶H7大肠埃希菌食物中毒的爆发流行,感染病例逾万人,死亡9例.2001年我国江苏及安徽等地也发生了肠出血性O157∶H7大肠埃希菌所引发的感染性腹泻事件.目前O157∶H7大肠埃希菌实验室常规检测方法为分离培养计数法,此法费时费力,需要几天的时间才能得到检测结果[1,2],缺乏应对突发事件的能力,因此亟需开发快速检测技术.近年来,多种微生物快速检测技术如ELISA法[3]、热解质谱测定法[4]、多聚酶链反应[5]、荧光成像技术[6]、生物发…