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首页> 外文期刊>RSC Advances >Stable room temperature magnetic ordering and excellent catalytic activity of mechanically activated high surface area nanosized Ni0.45Zn0.55Fe2O4
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Stable room temperature magnetic ordering and excellent catalytic activity of mechanically activated high surface area nanosized Ni0.45Zn0.55Fe2O4

机译：机械活化的高表面积纳米Ni0.45Zn0.55Fe2O4的稳定室温磁序和出色的催化活性

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Herein we report the structural, microstructural, dc magnetic and hyperfine properties along with catalytic activity of mechanosynthesized nanosized Ni(0.45)Zn(0.5)5Fe(2)O(4) (similar to 12 nm). The Rietveld refinement of the powder X-ray diffraction data, high resolution transmission electron microscopy and the infield Mossbauer study suggest that the sample is nanosized pure single phase cubic spinel of Rd (3) over barM symmetry with good crystallinity and it possesses equilibrium cation distribution ((Fe0.453+Zn0.552+)(A)[Fe1.553+Ni0.452+](B)O-4). The sample exhibits ferrimagnetic ordering with high saturation magnetization (M-SAT = 53, 72 and 76 emu g(-1) at 300, 100 and 10 K, respectively), coercivity (H-C = 280, 1200 and 2800 Oe at 300, 100 and 10 K, respectively), collective magnetic excitations, spin canting and memory effect in dc magnetization. The infield Mossbauer study suggests that the interior region of the particles is perfectly ferrimagnetic in nature, while the spins at the surface region are ferrimagnetically coupled but noncollinearly aligned. Despite its nanometric size, the sample does not show superparamagnetic behavior but rather retains stable magnetic order at room temperature due to enhancement of stress and surface anisotropy energy caused by high energy ball milling. We have shown that the presence of collective magnetic state along with surface spin disorder are the underlying reason for having slow dynamics and memory effect in the sample. Further, the BET (Brunauer-Emmett-Teller) surface area and the pore volume of the sample are 233 m(2) g(-1) and 0.475 cm(3) g(-1), respectively. The temperature programmed desorption (TPD) of ammonia suggests that the surface of this porous material is highly acidic (1.516 mmol g(-1)). Because of its high surface acidity and BET surface area the material acts as an efficient heterogeneous catalyst in the one pot synthesis of 3,4-dihydropyrimidine-2(1H)-ones (DHPMs) by Biginelli condensation reaction. This sample can be used in magnetic data storage devices, coding, storing and retrieving of binary numbers through magnetic field change and also as a very efficient heterogeneous, magnetically separable and recyclable catalyst.
机译：在这里，我们报告的结构，微观结构，直流磁和超精细性能，以及机械合成的纳米Ni（0.45）Zn（0.5）5Fe（2）O（4）（类似于12 nm）的催化活性。粉末X射线衍射数据的Rietveld精修，高分辨率透射电子显微镜和野外Mossbauer研究表明，该样品是bar（M）对称的Rd（3）纳米级纯单相立方晶尖晶石，具有良好的结晶度，并且具有平衡的阳离子分布（（Fe0.453 + Zn0.552 +）（A）[Fe1.553 + Ni0.452 +]（B）O-4）。样品表现出高饱和磁化强度的亚铁磁排序（分别在300、100和10 K时M-SAT = 53、72和76 emu g（-1）），矫顽力（在300、100时HC = 280、1200和2800 Oe和10 K）分别表示直流磁化中的集体磁激励，自旋倾斜和记忆效应。内场Mossbauer的研究表明，粒子的内部区域本质上是完美的亚铁磁性，而表面区域的自旋是亚铁磁性耦合的，但不是共线排列的。尽管具有纳米级尺寸，但由于高能球磨引起的应力和表面各向异性能的增强，样品在室温下并未表现出超顺磁性，而是保持稳定的磁序。我们已经表明，集体磁性态的存在以及表面自旋失调是样品中动力学和记忆效应缓慢的根本原因。此外，样品的BET（Brunauer-Emmett-Teller）表面积和孔体积分别为233 m（2）g（-1）和0.475 cm（3）g（-1）。氨的程序升温脱附（TPD）表明该多孔材料的表面呈高酸性（1.516 mmol g（-1））。由于其较高的表面酸度和BET表面积，该材料在通过Biginelli缩合反应一锅合成3,4-二氢嘧啶-2（1H）-酮（DHPM）时，可作为高效的多相催化剂。该样品可用于磁性数据存储设备，通过磁场变化对二进制数进行编码，存储和检索，还可以用作非常有效的异质，可磁分离和可循环利用的催化剂。

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