Synthesis Properties and Applications of Carbon-Coated Magnetic Nanoparticles

在碳弧中制备的金属和合金纳米晶体是静电复印、磁共振成像、铁磁流体、数据存储和磁性油墨等磁性应用的有趣候选者。初步结果表明，与现有材料相比，碳涂层具有三个潜在的优势：1)碳涂层可以防止氧化；2)该工艺可能比其他方法更有效地制备10-100 nm尺寸范围的纳米颗粒；3)具有大磁晶各向异性的合金纳米颗粒具有室温磁稳定性。这项研究将探索这些纳米颗粒技术应用的关键科学问题。一个重点领域包括实验，以了解碳涂层的形成，并将反应参数和颗粒形态联系起来。这些知识用于优化生长过程和扩大生产规模，这两者对于商业化都是必不可少的。第二个重点领域是磁性表征。利用细颗粒磁体的理论模型，设计了具有室温磁滞的纳米颗粒，以满足数据存储的需要。在碳槽中生成后，利用直流和交流磁强计、热磁分析、穆斯堡尔谱、零场核磁共振和磁圆二色性研究了纳米颗粒的磁性行为。将结果与不同应用程序的技术基准进行比较，以确定哪些可能性是有希望的。将合金纳米晶的新实验数据与细颗粒磁性预测进行比较，以扩展对单畴磁体中磁滞和开关率的基本理解。

9500313 Majetich Metal and alloy nanocrystals prepared in a carbon arc are interesting candidates for magnetic applications in xerography, magnetic resonance imaging, ferrofluids, data storage, and magnetic inks. Preliminary results demonstrate three potential advantages over existing materials: 1) the carbon coating prevents oxidation, 2) this process may be more efficient than other methods for preparing nanoparticles in the 10-100 nm size range, and 3) alloy nanoparticles with large magnetocrystalline anisotropy show room temperature magnetic stability. The research will explore scientific questions critical to the technical applications of these nanoparticles. One thrust area includes experiments to understand the formation of the carbon coating, and to correlate reaction parameters and particle morphology. This knowledge is used to optimize the growth process and to scale up production, both of which are essential for commercialization. The second thrust area focus as on magnetic characterization. Theoretical models of fine particle magnets are used to design nanoparticles with room temperature hysteresis required for data storage. After generation in the carbon are, the magnetic behavior of the nanoparticles are studied with DC and AC magnetometry, thermomagnetic analysis, Mossbauer spectroscopy, zero field NMR, and magnetic circular dichroism. The results are compared with technical benchmarks for the different applications to determine which possibilities are promising. New experimental data for alloy nanocrystals are compared with fine particle magnetism predictions to expand the fundamental understanding of hysteresis and switching rates in monodomain magnets.