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磁性测量法检测氧化铁磁性纳米颗粒在单畴团簇中的不可逆热核反应
Detection of irreversible fusion of iron oxide magnetic nanoparticle into single-domain clusters by magnetic measurements |
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| 课程网址: |
http://videolectures.net/slonano07_jagodic_dif/
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| 主讲教师: |
Marko Jagodič
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| 开课单位: |
数学物理力学研究所
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| 开课时间: |
2008-02-12
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| 课程语种: |
英语
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| 中文简介: |
铁磁流体是磁性纳米颗粒在合适的载液中的胶体稳定的悬浮液。由于其独特的性质，如磁粘效应和广泛的可能的医学和技术应用，它们是一个深入研究的主题。铁磁流体的聚集程度是决定这种铁磁流体在应用中的适用性的关键性质之一。为了合成具有令人满意和可控的聚集性质的铁磁流体，理解聚集体形成的机理并具有确定聚集程度的方法是至关重要的。我们制备了由分散在n癸烷中的平均尺寸为11nm的磁赤铁矿纳米颗粒组成的铁磁流体。通过在基础介质中共沉淀Fe 2和Fe 3离子来制备纳米颗粒。通过油酸涂层实现纳米颗粒在癸烷中的分散。制备具有两种不同浓度（浓缩和稀释）的铁磁流体。零场干燥和现场干燥的铁磁流体的TEM图像表明，如果铁磁流体暴露于外部磁场，则将单个纳米颗粒熔合成少数纳米颗粒的簇。由于与单个粒子相比簇的尺寸更大，因此簇之间存在更强的相互作用，因此它们很容易组合成聚集体。因此，颗粒融合成簇可能是聚集体形成过程中的重要机制。在我们的工作中，我们试图通过磁测量检测单个粒子不可逆地融合成簇。由于簇是单畴粒子，表现为超自旋，簇检测的问题减少到确定平均磁粒尺寸的已知问题。在商用SQUID磁力计（Quantum Design MPMS XL 5）上进行零场冷却/场冷磁化（ZFC / FC），AC磁化率和M（H）测量。我们表明，用于检测稀释的以及浓缩的铁磁流体中的单域簇的最明显的方法是通过M（H）磁性测量来确定粒度。
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| 课程简介: |
Ferrofluids are colloidally stable suspensions of magnetic nanoparticles in a suitable carrier liquid. Because of their unique properties, such as magnetoviscous effect and a wide spectrum of possible medical and technical applications, they are a subject of intense research. The extent of aggregation of a ferrofluid is one of its key properties determining the suitability of such a ferrofluid for applications. In order to synthesize ferrofluids with satisfactory and controllable aggregation properties it is crucial to understand the mechanism of aggregate formation and to have a method for determining the extent of aggregation. We prepared a ferrofluid composed of maghemite nanoparticles of the average size of 11 nm dispersed in n-decane. The nanoparticles were prepared by coprecipitation of Fe2+ and Fe3+ ions in basic medium. Dispersion of nanoparticles in decane was achieved by oleic acid coating. Ferrofluids with two different concentration (concentrated and diluted) were prepared. TEM images of zero-field dried and field dried ferrofluids suggest that fusion of single nanoparticles into clusters of few nanoparticles takes place if the ferrofluid is exposed to an external magnetic field. Because of the bigger size of the clusters in comparison to single particles there is a stronger interaction between the clusters so they easily combine into aggregates. The fusion of particles into clusters could be thus an important mechanism in the process of aggregate formation. In our work we tried to detect the irreversible fusion of single particles into clusters by magnetic measurements. As the clusters are single-domain particles behaving as super-spins the problem of cluster detection reduces to the known problem of determining the average magnetic particle size. Zero-field-cooled/field-cooled magnetization (ZFC/FC), AC susceptibility and M(H) measurements were carried out on a commercial SQUID-based magnetometer (Quantum Design MPMS XL-5). We show that the most evident method for detecting single-domain clusters in diluted as well as in concentrated ferrofluids is determining the particle size from M(H) magnetic measurement.
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| 关 键 词: |
铁磁流体; 聚集程度; 磁粘效应
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| 课程来源: |
视频讲座网
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| 最后编审: |
2019-09-21：cwx
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| 阅读次数: |
51
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