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在静电复印、磁共振成像、铁磁流体、数据存储和磁性墨水中的磁性应用的令人感兴趣的候选者。 初步结果表明，与现有材料相比，有三个潜在的优势：1）碳涂层可防止氧化，2）该工艺可能比其他制备10-100 nm尺寸范围内纳米颗粒的方法更有效，3）具有大磁晶各向异性的合金纳米颗粒显示出室温磁稳定性。 该研究将探索对这些纳米粒子的技术应用至关重要的科学问题。 一个推力领域包括实验，以了解碳涂层的形成，并将反应参数和颗粒形态相关联。 这些知识用于优化生长过程和扩大生产，这两者对于商业化至关重要。 第二个重点领域是磁性表征。 精细颗粒磁体的理论模型用于设计具有数据存储所需的室温磁滞的纳米颗粒。在碳区域中生成后，用DC和AC磁力仪、热磁分析、穆斯堡尔谱、零场NMR和磁性圆二色性研究了纳米颗粒的磁性行为。 将结果与不同应用的技术基准进行比较，以确定哪些可能性是有希望的。合金纳米晶体的新的实验数据进行了比较细颗粒磁性预测，以扩大在单畴磁体的磁滞和开关速率的基本理解。

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.