这项工作是在 EPSRC 赠款 EP/K027956/2 的资助下进行的。本文后面的所有基础数据都可以从相应的作者访问。

1. 在原位进行域成像的样本的准备 BH 测量 <ol> <li> 机器两个 U 形零件 (a 和 B) 从感兴趣的钢, 如 图 1 所示, 由电火花加工。注意两个部分之间的差异, 即 1 mm 较粗的水平部分和 1 mm 的倒角, 是为了确保在样品 (a 部分) 安装和研磨后的已知和所需厚度 (1.5 mm) (见 图 1 有关维度和过程 2.1-2.4 的详细信息) </li>
</ol> 2。金相试样的制备 <ol> <li> 热压缩安装部件 a, 最好使用生成透明装入的化合物. 
	注意: 使用正确的化合物量, 以避免在压缩安装过程中损坏样品。安装的最终厚度应大于样品高度的 5-10 毫米。值得注意的是, 有可能是由压缩安装引起的残余应力, 这可能会导致对域结构的一些影响。
	<ol> <li> 将部件 A 与两条腿正面朝上, 放入压缩安装机的模具中. </li>
		<li> 在模具中加入约20毫升甲基丙烯酸甲酯复合粉末. </li>
		<li> 使用以下参数启动安装周期: 加热时间-4.5 分钟, 冷却时间-4 分钟, 压力-290 Bar 和温度-180 和 #176; C. </li>
		<li> 在循环完成后取出装载, 并检查厚度。它应该介于 20-25 mm 之间. </li>
	</ol> </li> <li> 在研磨机上使用320粒度的碳化硅纸对装入样品的两条腿进行研磨, 直到表面露出腿底. 
	注: 建议自动磨削, 以确保安装后的两个平面平行研磨. </li>
	<li> 研磨安装的另一侧, 并经常检查直到 U 形试样表面的平坦部分显示, 研磨直到矩形表面显露出来. </li>
	<li> 使用卡尺测量显示样品的长度, 并继续仔细研磨并频繁测量。显露的样品长度将最初增加与研磨 (典型地少许超过23毫米, 当最初的长方形形状被显露)。一旦长度达到25.05 和 #177, 停止研磨; 0.05 毫米。此时, 抛光试样的尺寸将与传感器零件 ( 图 1 中的 B 部分) 相同, 即 25 mm 长度和 1.5 mm 厚度。这个过程与样品的被设计的斜切一起 (部分 a 图 1 ), 给已知和需要的样品厚度, 在大约十微米的容忍之内, 在研磨以后. </li>
	<li> 根据标准的软钢金相试样制备程序对样品进行抛光 14 . 
	警告: 不要 re-grind 样本, 因为这会改变样本厚度, 从而导致不准确的 BH 测量. </li>
	<li> 使用合适的试剂 (例如, 纯铁或低碳钢的 2% nital) 用棉签蚀刻抛光样品, 直到抛光表面变成哑光. </li>
	<li> 在光学显微镜下检查样品。有效的蚀刻将清楚地揭示样品的显微组织. </li>
	<li> 再次使用1和 #181; m 金刚石抛光剂, 直到蚀刻表面层完全除去。如果不确定, 请在显微镜下检查. </li>
	<li> 重复步骤 2.6-2.8, 4-6 次。这将删除任何工作硬化表面层. </li>
	<li> 用氧化铝悬浮液完成抛光2分钟. 
	注意: 在这里可以暂停实验. </li>
</ol> 3。磁通密度的制备 (B) 测量线圈 <ol> <li> 使传感器使用部件 B, 如 图 1 所示。
	<ol> <li> 在 B 部分的 U 形 ( 即 最长边) 的底部环绕一层双面磁带。
		<li> 使用0.20 毫米直径的漆包线铜线, 在 B 部分的最长一侧环绕一层, 50 匝圈, 在线圈的每一端留出大约100毫米的导线. </li>
		<li> 用800砂砾砂纸从导线的每一端的最后 20 mm 中取下搪瓷. </li>
	</ol> </li> <li> 检查线圈和样品之间的电气短路。
	<ol> <li> 用万用表将其设置为测试连续性。触摸一个探头到 B 部分, 另一根导线一端. 
		注: 线圈与样品之间不应有连续性, 如果线圈与样品之间有连续性, 导线就会短路至样品, 线圈应拆卸并重新. </li>
	</ol> </li> </ol> 4。设置域成像平台 <ol> <li> 安装/修复在 图 2 中显示的测试平台上的示例。
	<ol> <li> 将前面板显示在 图 2 (a) 上的平面上, 并将装入的样本放入前板的孔中. </li>
		<li> 应用热熔胶枪周围的安装样品, 以保持它到位. </li>
		<li> 将 B 部分通过励磁线圈插入样品夹的底部; 样品应从样品架顶部凸出约1毫米. </li>
		<li> 将后板固定在样品架背面, 并松弛地拧紧底部螺母, 确保霍尔传感器与样品通过目视检查对齐. </li>
		<li> 将励磁电流应用于激磁线圈, 形成电磁铁, 便于装配和对准. </li>
		<li> 将部件 a 的顶部与 B 部分的底部对齐, 如图 2 , 在上述电磁铁的磁力帮助下 (最大力感在完美对准的情况下), 以及通过目视检查, 如果样品装载是透明的。在 BH 回路测量的精度方面, a 和 B 部分的精确耦合是非常重要的。有关详细说明, 请参阅讨论. </li>
		<li> 将顶部板螺栓固定在样品架上. </li>
		<li> 拧紧底部螺母以在 a 部分和 B 部分之间施加压力。值得注意的是, 紧可能会引起材料内部的压力, 从而引起对畴结构的应力效应。测试平台现在应该类似于 图 2b . </li>
	</ol> </li> <li> 将该示例用于在视觉领域中始终保持良好的聚焦。如果使用了50倍或更高的物镜, 并且在应用铁液之前必须进行, 则强烈推荐此步骤. 
	<ol> <li> 在一个干净的玻璃幻灯片上放入一块樱桃大小的模型粘土. </li>
		<li> 将测试平台放置在建模粘土的顶部, 并将样品与钻机大致居中对齐. </li>
		<li> 在样品表面顶部放置三张镜片组织, 以进行保护. </li>
		<li> 水平整个测试平台使用水准机为显微镜与样品近似地与新闻中心一致. </li>
	</ol> </li> </ol> 5。磁畴成像 <ol> <li> 稀释油基铁液。
	<ol> <li> 使用吸管绘制1毫升的油性铁液, 并将其添加到5毫升的小瓶中. </li>
		<li> 加入0.5 毫升的原溶剂 (碳氢化合物油) 的铁液进入小瓶. </li>
		<li> 抖动十年代. </li>
	</ol >> </li> <li> 铁液在样品上的应用. 
	<ol> <li> 使用吸管绘制单滴 (约0.25 毫升) 的铁液, 并应用于样品表面. </li>
		<li> 在样品上放一个干净的显微镜幻灯片, 然后慢慢地滑动样品表面的玻璃滑动, 形成一个薄而均匀的层。一个好的光洁度应该是半透明的琥珀色. </li>
	</ol> </li> <li> 静态域成像 <ol> 在铁液干涸之前观察光显微镜下的域模式。使用充足的照明和小孔径 (通过调整光圈膜片) 的最佳对比度. 
		注意: 避免将铁液暴露在强光下, 因为这可能会使铁液干燥. </li>
		<li> 用丙酮擦拭或冲洗, 在域成像后去除铁液. </li>
		<li> 在实验后彻底清洗样品表面并干燥样品. </li>
	</ol> </li> <li> 动态域成像 <ol> 将高速摄像机连接到显微镜. <li>
		<li> 将磁场应用于样品, 使 DWs 移动。本试验台可用于在与样品表面平行的情况下应用多达 4 kA/米的电场。垂直场可以使用与其轴线垂直于表面的线圈来应用. </li>
		<li> 将示例安全地修复到测试平台。应用热熔体周围的样品使用胶枪如有必要。固化后的胶水可以很容易地在实验后被去除. 
		注: 步骤 5.1-5.2 也适用于此处. </li>
	</ol> </li> </ol> 6 #160; 原位 BH 测量和域成像 <ol> <li> 连接 原位 域成像系统, 如 图 3 中所示. 
	<ol> <li> 将传感器励磁线圈连接到 BH 分析器的电源输出。我们使用了曼彻斯特大学开发的 in-house BH 分析器。在我们以前的出版物 15 中可以找到详细的说明. </li>
		<li> 将霍尔传感器连接到 BH 分析器的 输入通道 。
		<li> 连接传感器 b 线圈到 BH 分析器的 b 输入通道。
		<li> 将 BH 分析器的 H 和 B 输出连接到两个模拟输入通道 (称为 "da 方框以后"), 分别确保将两个输入设置为地面源 (GS). </li>
		<li> 将高速相机中的同步连接到 DA 框之外的同步. </li>
		<li> 将高速摄像机的触发器连接到 DA 框的触发器. </li>
	</ol> </li> <li> 在 BH 分析器软件中输入测试参数。样本的横截面积应在 m 2 中输入;在这种情况下, 6 x 10 - 6 m 2 . </li>
	<li> 根据 DA 软件的指令设置数据同步参数. 
	<ol> <li> 将同步出率 (2000/秒) 设置为高速相机的帧速率 (500 帧/秒) 乘以每个帧的数据点数 (每帧 4). </li>
		<li> 将 pre-trigger 长度 (百分比) 设置为与照相机相同. </li>
	</ol> </li> <li> 设置准备录制的高速摄像机。即, 摄像头将开始等待触发. </li>
	<li> 打开 bh 分析器并应用1赫兹励磁正弦电流来测量主回路; 将显示 bh 循环的图像. </li>
	<li> 检查已测量的 BH 循环在强制字段、剩磁、磁饱和度等方面大致是预期的。如果不是, 则应检查 a 部分和 B 部分之间的机械耦合. </li>
	<li> 通过从 BH 分析器发送触发信号或单击 DA 软件界面上的触发器按钮, 可以触发照相机. </li>
	<li> 停止在 DA 软件中至少一个 BH 循环周期后记录数据和视频. </li>
	<li> 关闭 BH 分析器 
	注意: 不要让电流通过样品长时间运行, 特别是当直流电 (DC) 被使用时, 因为电流会使样品升温并迅速干燥铁液. </li>
	<li> 清除示例并刷新以供将来分析. </li>
</ol>

<ol>
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作者没有什么可透露的。

金相试样的制备是苦法对畴型质量的关键。初始粗磨所产生的地下损伤可以掩盖实际的畴结构。这些人工作用通常导致 DWs 和许多次要的领域特征的差对比由于损伤和有时一个迷宫象样式。非晶表面层可能由于严重的表面损伤而形成, 这将给一个不具代表性的域结构。因此, 重要的是要小心磨削金相样品的领域成像, 以尽量减少地下损害的第一位。额外的程序, 如建议的蚀刻抛光周期, 这篇论文或长期化学机械抛光通常是必要的, 以消除其余损坏的表面层。你需要格外小心的样品准备的原位 BH测量过度研磨或磨将改变试样厚度;需要精确的厚度知识来确定正确的b值, 因为 a 部分的通量密度是通过测量 b 部分的通量密度来推断的。软件输出的b值与所提供的横截面面积成正比, 因此, 10% 的厚度错误将导致b值中的大约10% 错误。然而关系是非线性的, 因此一个简单的定标在测量以后不是可能的。过地上的样品仍然可以用于域成像, 但应该注意的是, 测量的bh循环将不会定量地代表正在检查的样本部分的真实bh曲线。H度量值仍应近似地代表实际值, 而B数值由于减小的厚度和平坦部分的截面面积而减小。在 overgrinding 的情况下, 你可以采取的样品从装载测量的厚度后, 所有的域成像完成后, 然后缩放原位测量 B 值 (为传感器) 的因素等于设计/最终厚度近似于实际的B值 (对于示例), 仅作为补救措施。
铁液的活性对动态域成像尤为重要。如果 DW 运动的程度低于预期, 则应使用 DC 应用领域来检查熟悉样品的铁液性能。如果问题仍然存在, 铁液需要更换。新鲜的铁液是最活跃的, 它在贮存过程中沉淀。建议在每次试验中用原溶剂稀释少量的新鲜铁液。关于铁液的活动或反应时间的数据 (对正在检查的样品的畴结构的变化) 是不可用的, 而后者据信是在微秒的范围内根据供应商 (雷内 V, 2016)。在本研究中, 磁场用于动态域成像的频率为1赫兹, 也是主要BH回路测量的最佳频率。在较高磁化频率下, 铁液的性能尚待评估。
虽然苦涩方法是方便和敏感的它的决议是相对地低 (大约1µm) 11。这限制了静态域模式的方法在显示 DWs 分离的钢的应用; 2 µm但是, 在应用领域的作用下, 随着域大小的增加, 动态域成像仍有价值。目前的测试钻机只能应用一个与样品表面平行的现场原位 BH测量。为了研究晶粒取向钢的晶体结构或 DW 运动过程的影响, 需要考虑试样取样阶段的纹理或晶粒方向, 以确保选择合适的样品取向。
原位 BH回路测量的意义是双重的。首先, 它能够对 DW 的运动过程进行定量的解释, 就应用领域和磁性特性而言。其次, 它有助于在BH回路行为、磁性特性和钢的显微结构之间建立一个基本的联系, 并最终帮助解释 EM 传感器的微结构评估信号。将 DW 的运动过程和/或畴结构与复杂的显微组织, 特别是晶粒的晶体取向联系起来, 具有很大的挑战性和意义。今后, 将对样品进行电子回散衍射 (EBSD) 分析, 并将其映射到静态和动态域模式。结果将有助于解释不同的类型的领域模式观察到的各种谷物和不同领域的墙运动过程中与谷物方向有关的应用领域的方向。
当正确实现时, 此方法产生的BH循环应接近于使用闭合磁路环形试样产生的, 作为 a 和 B 组成一个闭合磁路。然而, 如果两个部分都没有完美地装配在一起, 将会引入一个空气间隙, 将会产生失真。这种失真将显示为BH循环剪切;一个众所周知的效果, 其特点是增加最大的H, 减少磁剩磁和循环出现更多的 ' 对角线 '。建议使用bh循环测量系统在安装前先使用部件 a 来获取一个bh循环, 以便与测试期间所获得的环路进行比较, 从而可以对磁耦合进行评估并优化重复性。
我们选择了 a 和 B 部分的尺寸, 考虑了以下因素和要求。部分 a 和 B 部分的差异原因已在步骤2.1 中说明。步骤2中描述的安装过程主要规定了用于这些测试的样本的水平长度 (25 mm, 请参见图 1)。一个大的抛光表面积, 由水平长度和深度 (4 mm,图 1) 决定, 有利于光学显微镜以及样品的制备。样品的厚度应为从所检查材料中产生足够刚性样品所需的最低限度;1.5 毫米在这种情况下。在选择厚度时, 也应考虑加工的实用性和成本。试样的横向横截面越小, 所给电流的励磁线圈产生的通量密度就越大。更高的电流导致更多的热量产生和铁液迅速干燥。励磁线圈的大数轮是可取的。两条腿的长度 (15 mm,图 1) 决定了钻机的高度。后者必须小于样品阶段和显微镜物镜之间的最大间距。最大通量密度和应用领域是最佳的由用户决定和是应用具体的。从观察中可以清楚地看出, 当bh循环接近饱和度时 ( bh循环会显示一个非常小的 dB/dH), 但是这段曲线从非常低的应用领域延伸到非常高的应用领域, 并且可能需要值接近100 kA/米之前的材料可以真正说是磁性饱和。从我们的经验的最大应用领域 2 kA/米 (适用于纯铁或软钢, 如所有的钢在这本佩普研究r)-10 kA/米 (对于硬钢, 如马氏体钢) 应磁化的样本超过 ' 膝盖 ' 的主要BH循环, 在此期间, 最重要的领域墙壁运动预计会发生。
总之, 目前的系统的域成像与原位 bh的测量证明是工作, 将 DW 的运动过程直接连接到钢的BH环。这一方法预计将成为一个有用的工具, 以基础研究的微观结构-磁性性能关系的钢, 结合进一步的显微组织表征。

各种电磁传感器已经开发或商业化, 用于评估和监测在工业加工、热处理或服务曝光时铁素体钢的显微组织、机械性能或蠕变损伤1 ,2。这些传感器以非破坏性的和不接触的方式运作, 其原理是铁素体钢的微观结构变化改变了它们的电学和磁性特性。为了从微观结构上解释 em 信号, 必须将 em 信号与它们的因果磁特性联系起来, 然后再将它们与材料的显微结构相结合。多频 em 传感器的互感器和 em 特性 (例如相对渗透率和电导率) 的各种 em 传感器信号之间的关系在电磁学研究中得到了很好的建立, 具有分析已报告几种典型传感器几何图形3的关系。然而, EM 或磁性属性 (如初始渗透率、矫顽力) 和特定微结构之间的关系仍然或多或少是经验性的、定性的, 或者在许多情况下是不可用的, 特别是当有超过一种类型的微结构特征, 影响磁性行为4。
铁磁性材料包含磁畴, 由磁矩组成, 由畴壁 (DWs) 隔开。随着磁场的应用, 域将重新通过 DW 运动、域核化和生长以及/或域旋转。关于领域理论的更多细节可以在别处找到5。如沉淀物或晶界等微观结构特征可以与这些过程相互作用, 从而影响铁磁性材料的磁性特性4,6,7,8.在应用磁场时, 钢的不同显微组织特征及其磁性能会影响到畴结构和 DW 运动过程。在不同的应用领域和频率下, 需要研究磁畴结构和 DWs 与显微组织特征之间的相互作用, 以建立一个基本的联系钢.
磁滞环或BH环路可以描述材料的基本磁性特性, 如矫顽力、剩磁、微分和增量磁导率等。BH回路分析已成为一种有用的无损检测技术, 用于评价铁素体钢的显微组织和力学性能9,10。BH循环是在所检查的材料 (B) 与外加磁场 (H) 之间的磁通密度的图形。当一个磁场是由一个具有时变电流的励磁线圈在样品中诱发的, B是用第二个线圈来检测的, 而H是用磁场传感器测量的 (通常是霍尔传感器) 放置在靠近样品表面的位置。对材料的BH特性的最精确的测量可以使用封闭的磁路进行, 如由环形样品所提供的, 但其他方法, 如使用单独的励磁核心可以产生令人满意的结果。在磁测量过程中, 能够对 DW 运动过程进行原位观测, 并直接将其与磁性能和微观结构联系起来, 具有重要的科学意义和实用价值。同时, 在不影响另一方的情况下, 进行领域观测或磁性测量是非常具有挑战性的。
在各种领域成像技术中, 苦法, 即利用细磁性粒子来揭示磁性 DWs, 具有明显的优势, 包括易于设置和高灵敏度11。由于使用的介质,例如铁液, 需要大量的经验和时间来获得高质量的模式和一致的结果使用苦味的方法。标准金相试样的制备, 预期和优化光学显微镜 (OM) 和扫描电子显微镜 (SEM), 通常产生不满意的苦味模式, 许多钢, 因为苦味的方法是不太宽容的残余地下损伤和伴生的人为作用比 OM 和 SEM。由于铁液的使用不当, 可能会产生人工效应。本文详细介绍了其他样品的制备方法, 比较了标准的金相组织, 铁液的制备和应用, 用光学显微镜对畴结构的观测, 以及原位磁测量.
许多研究的领域结构的观测单晶 (如硅铁12) 或晶粒取向的硅电工钢已报告13。在这些材料中, 只涉及少量的显微结构特征 (即晶粒/晶体方向和晶界), 而畴构造相对粗糙 (域宽度为 0.1 mm12)。本文对多晶铁素体钢 (包括低碳钢 (0.17% C) 的域模式进行了观察和报道。低碳钢有更细粒度 (大约25µm 平均在等效圆直径) 和更细的领域结构 (与领域宽度在千分尺的顺序) 比电工钢, 因此显示复杂的相互作用各种显微结构特征和 DW 运动过程。
本文提出了一种用原位 BH (磁滞) 测量的方法进行动态域成像的新型定制钻机。报道的方法利用了传统苦味法的方便性和高灵敏度, 使原位BH 测量不中断或干扰畴壁运动过程。这有助于建立一个直接和定量的联系之间的领域壁运动过程-微观结构特征相互作用的铁素体钢与他们的BH循环。这一方法可望成为一个有用的工具, 为基础研究钢的微观结构-磁性能关系, 并帮助解释电磁传感器信号的无损评估钢组织。

<table><tbody><tr><td>EMG 911 ferro-fluid</td><td>Ferrotec</td><td>89U1000000</td><td>Oil based Ferro-fluid for domain imaging</td></tr><tr><td>Solvent for EMG 900 series ferro-fluid</td><td>Ferrotec</td><td>89Z5000000</td><td>Original solvent for the EMG 900 series ferro-fluid for diluting the original ferro-fluid</td></tr><tr><td>AxioScope polarised light microscope</td><td>Zeiss</td><td>430035-9270-000</td><td></td></tr><tr><td>S-Mize High Speed Camera</td><td>AOS Technologies AG</td><td>160021-10</td><td>High speed camera that can be connected to the microscope for recording videos</td></tr><tr><td>Midas DA Software</td><td>Xcitex, Inc</td><td></td><td>Synchronize the high-speed video with the &lt;em&gt;BH&lt;/em&gt; data</td></tr><tr><td>MiDas DA Module BNC Breakout Box</td><td>Xcitex, Inc</td><td>185124H-01L</td><td>The hardware for data synchronizing the video and &lt;em&gt;BH&lt;/em&gt; data</td></tr><tr><td>TransOptic mounting compounds</td><td>Buehler</td><td>20-3400-08</td><td>Transparent thermoplastic acrylic mounting material</td></tr><tr><td>MetaDi Supreme 9um diamond suspension</td><td>Buehler</td><td>406633128</td><td>9 &amp;micro;m diamond polishing suspension</td></tr><tr><td>MetaDi Supreme 3um diamond suspension</td><td>Buehler</td><td>406631128</td><td>3 &amp;micro;m diamond polishing suspension</td></tr><tr><td>MetaDi Supreme 1um diamond suspension</td><td>Buehler</td><td>406630032</td><td>1 &amp;micro;m diamond polishing suspension</td></tr><tr><td>MasterPrep polishing suspension</td><td>Buehler</td><td>406377032</td><td>Alumina polishing suspension</td></tr><tr><td>UltraPad polishing cloth</td><td>Buehler</td><td>407122</td><td>For 9 &amp;micro;m diamond polishing</td></tr><tr><td>TriDent polishing cloth</td><td>Buehler</td><td>407522</td><td>For 3 &amp;micro;m diamond polishing</td></tr><tr><td>ChemoMet polishing cloth</td><td>Buehler</td><td>407922</td><td>For 1 &amp;micro;m diamond polishing</td></tr><tr><td>MicroCloth polishing cloth</td><td>Buehler</td><td>407222</td><td>Final polishing using the alumina polishing suspension</td></tr><tr><td>Nital 2%</td><td>VWR International</td><td>DIUKNI4307A</td><td>For etching</td></tr><tr><td>&lt;em&gt;BH&lt;/em&gt; analyzer</td><td>University of Manchester</td><td>Not applicable</td><td>An in-house system for &lt;em&gt;BH&lt;/em&gt; analysis</td></tr></tbody></table>

optimized setup and protocol for magnetic domain imaging with in situ hysteresis measurement

本文阐述了用苦味法获取最佳域模式所需的样品制备协议, 重点介绍了与标准金相试样制备方法相比的额外步骤。本文提出了一种新的动态领域成像的定制钻机,原位 bh (磁滞) 测量, 并详细阐述了传感器的准备和钻机的使用, 以确保准确的bh测量的协议。还介绍了静态和普通动态域成像 (不需要原位 BH测量) 的协议。报道的方法利用了传统苦味法的方便性和高灵敏度, 使原位 BH测量不中断或干扰畴壁运动过程。这有助于建立一个直接和定量的联系之间的领域壁运动 processes–microstructural 特征相互作用的铁素体钢与他们的BH循环。该方法可望成为对钢中 microstructure–magnetic 性质关系的基础研究的有用工具, 并有助于解释电磁传感器信号对钢结构的无损评价。

图 4显示了两个高质量的静态域模式的示例, 它们分别用于工业级纯铁和低碳钢的无外加磁场。人们可以在材料和不同类型的模式中清楚地看到 DWs, 包括例如平行 (或180°) 和90° DWs 在不同的谷物中的包。由于研磨质量好, 由于磨削造成的地下损伤, 没有任何迹象显示区域模式的随机失真;结果表明与显微组织有很强的联系。例如, 180 ° DW 间距 (通常约10µm 用于纯铁和低碳钢的约5µm) 随着晶粒尺寸的增加 (大约200µm 用于纯铁和25µm 的低碳钢平均当量圆直径) 和域模式 a取决于晶粒的晶体取向。应该注意的是, 在苦味模式中观察到的 dw 厚度并不反映真正的布洛克 dw 厚度, 估计为纯铁5约为 30 nm。模式质量的高度均匀性表明, 铁液的应用是最佳的。
图 5说明了由于表面准备不佳而导致的结果不理想的几个示例,图 5和 5b, 或者如果您在动态映像过程中无法安全地修复该示例, 或者对示例进行了级别测试。注意即使是非常小的偏移运动是明显的显微镜下。视频将在应用字段的作用下脱离焦点, 与示例表面垂直, 如图 5c 所示;或者在应用的并联交流电场的情况下, 样品将在应用领域的频率上横向摆动。
图 6显示了从 DW 移动过程视频中提取的一系列域图像, 在原位测量的BH循环的不同点上。视频清晰地显示了 DW 移动进程和BH循环中的位置之间的强链接。例如, 180 ° DWs 过渡到90°的区域 A 发生在 BH 回路的 "膝部" 附近, 即在磁化过程中的点1和50之间;在退磁过程中, 点225和250之间的进程反转, 这表明了向应用领域方向旋转的域。有趣的是, 大多数的180° DWs 在底部系列的图像没有明显移动。原因不明。一种可能性可能是应用的领域方向, 碰巧是近似地垂直于领域方向, 因此不可能导致180° DWs 移动或转动领域与领域方向一致。然而, 区域 B 中标记的段在磁化和退磁期间分别向左和向右凸出, 而在 C 区则只略微向左凸出。这些现象似乎表明, 可能有地下粒子或夹杂物扰乱了本地域的方向, 使组件与应用领域平行, 因此在其作用下移动。这也表明磁化不完全饱和。还需要进一步分析晶粒和任何地下颗粒的晶体取向的畴方向和显微结构特征。
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56376/56376fig1.jpg"> 
图 1: 传感器和试样部件的图纸原位域成像 (单位: mm)<a href="//ecsource.jove.com/files/ftp_upload/56376/56376fig1large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56376/56376fig2.jpg"> 
图 2:原位域成像钻机4的示意图组装图。 (a)在组装前分离部件(b)完成程序集.<a href="//ecsource.jove.com/files/ftp_upload/56376/56376fig2large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/56376/56376fig3v3.jpg"> 
图 3:原位域成像系统的组件和连接示意图.<a href="//ecsource.jove.com/files/ftp_upload/56376/56376fig3v3large.jpg">请单击此处查看此图的较大版本.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/56376/56376fig4v2.jpg"> 
图 4: 纯铁和 0.2% 碳钢的静态域模式.<a href="//ecsource.jove.com/files/ftp_upload/56376/56376fig4v2large.jpg">请单击此处查看此图的较大版本.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/56376/56376fig5v2.jpg"> 
图 5: 由于未能正确遵守协议而导致的不满意的域模式的示例.(a)无序域模式 (与图 3中相同的低碳钢样本) 缺乏与微观结构的联系, 原因是样品表面制备较差;(b) 由于铁液在铸低碳钢试样上的应用不佳而造成反差差的模糊模式;(c)域模式在纯铁样品的垂直场的作用下脱离焦点<a href="//ecsource.jove.com/files/ftp_upload/56376/56376fig5v2large.jpg">请单击此处查看此图的较大版本.</a>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/56376/56376fig6v2.jpg"> 
图 6: 从域壁移动过程视频中提取的一系列域图像, 该帧对应于在原位测量BH循环中的一系列点, 其中有标记的感兴趣区域显示域旋转, 可能与铸低碳钢试样的显微结构特征的相互作用.<a href="//ecsource.jove.com/files/ftp_upload/56376/56376fig6v2large.jpg">请单击此处查看此图的较大版本.</a>

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Optimized Setup and Protocol for Magnetic Domain Imaging with In Situ Hysteresis Measurement

用原位滞后测量进行磁畴成像的优化设置和协议

本文详细介绍了用原位 bh测量的动态域成像的测试平台的采样和传感器的准备程序和协议, 以达到最佳的域模式质量和准确的bh测量.

This paper elaborates the sample preparation protocols required to obtain optimal domain patterns using the Bitter method, focusing on the extra steps ...

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Optimized Setup and Protocol for Magnetic Domain Imaging with In Situ Hysteresis Measurement

9.3K 次观看.  University of Warwick. 本文详细介绍了用原位 bh测量的动态域成像的测试平台的采样和传感器的准备程序和协议, 以达到最佳的域模式质量和准确的bh测量.

视频: Optimized Setup and Protocol for Magnetic Domain Imaging with In Situ Hysteresis Measurement

Frequency Mixing Magnetic Detection Scanner for Imaging Magnetic Particles in Planar Samples

The setup of a planar Frequency Mixing Magnetic Detection (p-FMMD) scanner for performing Magnetic Particles Imaging (MPI) of flat samples is presented. It consists of two magnetic measurement heads on both sides of the sample mounted on the legs of a u-shaped support. The sample is locally exposed to a magnetic excitation field consisting of two distinct frequencies, a stronger component at about 77 kHz and a weaker field at 61 Hz. The nonlinear magnetization characteristics of superparamagnetic particles give rise to the generation of intermodulation products. A selected sum-frequency component of the high and low frequency magnetic field incident on the magnetically nonlinear particles is recorded by a demodulation electronics. In contrast to a conventional MPI scanner, p-FMMD does not require the application of a strong magnetic field to the whole sample because mixing of the two frequencies occurs locally. Thus, the lateral dimensions of the sample are just limited by the scanning range and the supports. However, the sample height determines the spatial resolution. In the current setup it is limited to 2 mm. As examples, we present two 20 mm &#215; 25 mm p-FMMD images acquired from samples with 1 &#181;m diameter maghemite particles in silanol matrix and with 50 nm magnetite particles in aminosilane matrix. The results show that the novel MPI scanner can be applied for analysis of thin biological samples and for medical diagnostic purposes.

A scanner for imaging magnetic particles in planar samples was developed using the planar frequency mixing magnetic detection technique. The magnetic intermodulation product response from the nonlinear nonhysteretic magnetization of the particles is recorded upon a two-frequency excitation. It can be used to take 2D images of thin biological samples.

混频磁探测仪在平面样品成像磁性微粒

The setup of a planar Frequency Mixing Magnetic Detection (p-FMMD) scanner for performing Magnetic Particles Imaging (MPI) of flat samples is presented. ...

科研

工程学

Remote Magnetic Actuation of Micrometric Probes for in situ 3D Mapping of Bacterial Biofilm Physical Properties

Bacterial adhesion and growth on interfaces lead to the formation of three-dimensional heterogeneous structures so-called biofilms. The cells dwelling in these structures are held together by physical interactions mediated by a network of extracellular polymeric substances. Bacterial biofilms impact many human activities and the understanding of their properties is crucial for a better control of their development &#8212; maintenance or eradication &#8212; depending on their adverse or beneficial outcome. This paper describes a novel methodology aiming to measure in situ the local physical properties of the biofilm that had been, until now, examined only from a macroscopic and homogeneous material perspective. The experiment described here&#160;involves introducing magnetic particles into a growing biofilm to seed local probes that can be remotely actuated without disturbing the structural properties of the biofilm. Dedicated magnetic tweezers were developed to exert a defined force on each particle embedded in the biofilm. The setup is mounted on the stage of a microscope to enable the&#160;recording of time-lapse images of the particle-pulling period. The particle trajectories are then extracted from the pulling sequence and the local viscoelastic parameters are derived from each particle displacement curve, thereby providing the 3D-spatial distribution of the parameters. Gaining insights into the biofilm mechanical profile is essential from an engineer&#39;s point of view for biofilm control purposes but also from a fundamental perspective to clarify the relationship between the architectural properties and the specific biology of these structures.

Remote Magnetic Actuation of Micrometric Probes for in situ 3D Mapping of Bacterial Biofilm Physical Properties

This paper shows an original methodology based on the remote actuation of magnetic particles seeded in a bacterial biofilm and the development of dedicated magnetic tweezers to measure in situ the local mechanical properties of the complex living material built by micro-organisms at interfaces.

测微探针进行远程磁驱动<em&gt;原位</em&gt; 3D细菌生物膜物理性质的映射

Bacterial adhesion and growth on interfaces lead to the formation of three-dimensional heterogeneous structures so-called biofilms. The cells dwelling in ...

生物工程

Monitoring Dendritic Cell Migration using 19F / 1H Magnetic Resonance Imaging

Continuous advancements in noninvasive imaging modalities such as magnetic resonance imaging (MRI) have greatly improved our ability to study physiological or pathological processes in living organisms. MRI is also proving to be a valuable tool for capturing transplanted cells in vivo. Initial cell labeling strategies for MRI made use of contrast agents that influence the MR relaxation times (T1, T2, T2*) and lead to an enhancement (T1) or depletion (T2*) of signal where labeled cells are present. T2* enhancement agents such as ultrasmall iron oxide agents (USPIO) have been employed to study cell migration and some have also been approved by the FDA for clinical application. A drawback of T2* agents is the difficulty to distinguish the signal extinction created by the labeled cells from other artifacts such as blood clots, micro bleeds or air bubbles. In this article, we describe an emerging technique for tracking cells in vivo that is based on labeling the cells with fluorine (19F)-rich particles. These particles are prepared by emulsifying perfluorocarbon (PFC) compounds and then used to label cells, which subsequently can be imaged by 19F MRI. Important advantages of PFCs for cell tracking in vivo include (i) the absence of carbon-bound 19F in vivo, which then yields background-free images and complete cell selectivityand(ii) the possibility to quantify the cell signal by 19F MR spectroscopy.

Monitoring Dendritic Cell Migration using 19F / 1H Magnetic Resonance Imaging

Tracking of cells using MRI has gained remarkable attention in the past years. This protocol describes the labeling of dendritic cells with fluorine (19F)-rich particles, the in vivo application of these cells, and monitoring the extent of their migration to the draining lymph node with 19F/1H MRI and 19F MRS.

监测树突状细胞迁移<sup&gt; 19</sup&gt; F /<sup&gt; 1</sup&gt; H磁共振成像

Continuous  advancements in noninvasive imaging modalities such as magnetic resonance  imaging (MRI) have greatly improved our ability to study ...

免疫与感染

Spectral and Angle-Resolved Magneto-Optical Characterization of Photonic Nanostructures

Photonic crystals are periodic nanostructures that can support a variety of confined electromagnetic modes. Such confined modes are usually accompanied by local enhancement of electric field intensity that strengthens light-matter interactions, enabling applications such as surface-enhanced Raman scattering (SERS) and surface plasmon enhanced sensing. In the presence of magneto-optically active materials, the local field enhancement gives rise to anomalous magneto-optical activity. Typically, the confined modes of a given photonic crystal depend strongly on the wavelength and incidence angle of the incident electromagnetic radiation. Thus, spectral and angular-resolved measurements are needed to fully identify them as well as to establish their relationship with the magneto-optical activity of the crystal. In this article, we describe how to use a Fourier-plane (back focal plane) microscope to characterize magneto-optically active samples. As a model system, here we use a plasmonic grating built out of magneto-optically active Au/Co/Au multilayer. In the experiments, we apply a magnetic field on the grating in situ and measure its reciprocal space response, obtaining the magneto-optical response of the grating over a range of wavelengths and incident angles. This information enables us to build a complete map of the plasmonic band structure of the grating and the angle and wavelength dependent magneto-optical activity. These two images allow us to pinpoint the effect that the plasmon resonances have on the magneto-optical response of the grating. The relatively small magnitude of magneto-optical effects requires a careful treatment of the acquired optical signals. To this end, an image processing protocol for obtaining magneto-optical response from the acquired raw data is laid out.

Photonic band structure enables understanding how confined electromagnetic modes propagate within a photonic crystal. In photonic crystals that incorporate magnetic elements, such confined and resonant optical modes are accompanied by enhanced and modified magneto-optical activity. We describe a measurement procedure to extract the magneto-optical band structure by Fourier space microscopy.

光子纳米结构的光谱和角度解析磁-光学特性

Photonic crystals are periodic nanostructures that can support a variety of confined electromagnetic modes. Such confined modes are usually accompanied by ...

Magnetic Field Mapping using Off-Axis Electron Holography in the Transmission Electron Microscope

Off-axis electron holography is a powerful technique that involves the formation of an interference pattern in a transmission electron microscope (TEM) by overlapping two parts of an electron wave, one of which has passed through a region of interest on a specimen and the other is a reference wave. The resulting off-axis electron hologram can be analyzed digitally to recover the phase difference between the two parts of the electron wave, which can then be interpreted to provide quantitative information about local variations in electrostatic potential and magnetic induction within and around the specimen. Off-axis electron holograms can be recorded while a specimen is subjected to external stimuli such as elevated or reduced temperature, voltage, or light. The protocol that is presented here describes the practical steps that are required to record, analyze, and interpret off-axis electron holograms, with a primary focus on the measurement of magnetic fields within and around nanoscale materials and devices. Presented here are the steps involved in the recording, analysis, and processing of off-axis electron holograms, as well as the reconstruction and interpretation of phase images and visualization of the results. Also discussed are the need for optimization of the specimen geometry, the electron optical configuration of the microscope, and the electron hologram acquisition parameters, as well as the need for the use of information from multiple holograms to extract the desired magnetic contributions from the recorded signal. The steps are illustrated through a study of specimens of B20-type FeGe, which contain magnetic skyrmions and were prepared with focused ion beams (FIBs). Prospects for the future development of the technique are discussed.

Guidelines are presented for recording and interpreting off-axis electron holograms to provide quantitative images of magnetic fields in nanoscale materials and devices in the transmission electron microscope.

Off-axis electron holography is a powerful technique that involves the formation of an interference pattern in a transmission electron microscope (TEM) by ...

Optimizing Magnetic Force Microscopy Resolution and Sensitivity to Visualize Nanoscale Magnetic Domains

Magnetic force microscopy (MFM) enables mapping local magnetic fields across a sample surface with nanoscale resolution. To perform MFM, an atomic force microscopy (AFM) probe whose tip has been magnetized vertically (i.e., perpendicular to the probe cantilever) is oscillated at a fixed height above the sample surface. The resultant shifts in the oscillation phase or frequency, which are proportional to the magnitude and sign of the vertical magnetic force gradient at each pixel location, are then tracked and mapped. Although the spatial resolution and sensitivity of the technique increases with decreasing lift height above the surface, this seemingly straightforward path to improved MFM images is complicated by considerations such as minimizing topographical artifacts due to shorter range van der Waals forces, increasing the oscillation amplitude to further improve sensitivity, and the presence of surface contaminants (in particular water due to humidity under ambient conditions). In addition, due to the orientation of the probe's magnetic dipole moment, MFM is intrinsically more sensitive to samples with an out-of-plane magnetization vector. Here, high-resolution topographical and magnetic phase images of single and bicomponent nanomagnet artificial spin-ice (ASI) arrays obtained in an inert (argon) atmosphere glovebox with &lt;0.1 ppm O2 and H2O are reported. Optimization of lift height and drive amplitude for high resolution and sensitivity while simultaneously avoiding the introduction of topographical artifacts is discussed, and detection of the stray magnetic fields emanating from either end of the nanoscale bar magnets (~250 nm long and &lt;100 nm wide) aligned in the plane of the ASI sample surface is shown. Likewise, using the example of a Ni-Mn-Ga magnetic shape memory alloy (MSMA), MFM is demonstrated in an inert atmosphere with magnetic phase sensitivity capable of resolving a series of adjacent magnetic domains each ~200 nm wide.

Magnetic force microscopy (MFM) employs a vertically magnetized atomic force microscopy probe to measure sample topography and local magnetic field strength with nanoscale resolution. Optimizing MFM spatial resolution and sensitivity requires balancing decreasing lift height against increasing drive (oscillation) amplitude, and benefits from operating in an inert atmosphere glovebox.

优化磁力显微镜分辨率和灵敏度，以可视化纳米级磁畴

Magnetic force microscopy (MFM) enables mapping local magnetic fields across a sample surface with nanoscale resolution. To perform MFM, an atomic force ...

Quantitative Magnetic Resonance Imaging of Skeletal Muscle Disease

Quantitative magnetic resonance imaging (qMRI) describes the development and use of MRI to quantify physical, chemical, and/or biological properties of living systems. Neuromuscular diseases often exhibit a temporally varying, spatially heterogeneous, and multi-faceted pathology. The goal of this protocol is to characterize this pathology using qMRI methods. The MRI acquisition protocol begins with localizer images (used to locate the position of the body and tissue of interest within the MRI system), quality control measurements of relevant magnetic field distributions, and structural imaging for general anatomical characterization. The qMRI portion of the protocol includes measurements of the longitudinal and transverse relaxation time constants (T1 and T2, respectively). Also acquired are diffusion-tensor MRI data, in which water diffusivity is measured and used to infer pathological processes such as edema. Quantitative magnetization transfer imaging is used to characterize the relative tissue content of macromolecular and free water protons. Lastly, fat-water MRI methods are used to characterize fibro-adipose tissue replacement of muscle. In addition to describing the data acquisition and analysis procedures, this paper also discusses the potential problems associated with these methods, the analysis and interpretation of the data, MRI safety, and strategies for artifact reduction and protocol optimization.

Neuromuscular diseases often exhibit a temporally varying, spatially heterogeneous, and multi-faceted pathology. The goal of this protocol is to characterize this pathology using non-invasive magnetic resonance imaging methods.

骨骼肌疾病的定量磁共振成像

Quantitative magnetic resonance imaging (qMRI) describes the development and use of MRI to quantify physical, chemical, and/or biological properties of ...

医学

High-Speed Magnetic Tweezers for Nanomechanical Measurements on Force-Sensitive Elements

Single-molecule magnetic tweezers (MTs) have served as powerful tools to forcefully interrogate biomolecules, such as nucleic acids and proteins, and are therefore poised to be useful in the field of mechanobiology. Since the method commonly relies on image-based tracking of magnetic beads, the speed limit in recording and analyzing images, as well as the thermal fluctuations of the beads, has long hampered its application in observing small and fast structural changes in target molecules. This article describes detailed methods for the construction and operation of a high-resolution MT setup that can resolve nanoscale, millisecond dynamics of biomolecules and their complexes. As application examples, experiments with DNA hairpins and SNARE complexes (membrane-fusion machinery) are demonstrated, focusing on how their transient states and transitions can be detected in the presence of piconewton-scale forces. We expect that high-speed MTs will continue to enable high-precision nanomechanical measurements on molecules that sense, transmit, and generate forces in cells, and thereby deepen our molecular-level understanding of mechanobiology.

Here, we describe a high-speed magnetic tweezer setup that performs nanomechanical measurements on force-sensitive biomolecules at the maximum rate of 1.2 kHz. We introduce its application to DNA hairpins and SNARE complexes as model systems, but it will be also applicable to other molecules involved in mechanobiological events.

高速磁镊，用于力敏元件的纳米力学测量

Single-molecule magnetic tweezers (MTs) have served as powerful tools to forcefully interrogate biomolecules, such as nucleic acids and proteins, and are ...

生物化学

Fabrication of Magnetic Platforms for Micron-Scale Organization of Interconnected Neurons

The ability to direct neurons into organized neural networks has great implications for regenerative medicine, tissue engineering, and bio-interfacing. Many studies have aimed at directing neurons using chemical and topographical cues. However, reports of organizational control on a micron-scale over large areas are scarce. Here, an effective method has been described for placing neurons in preset sites and guiding neuronal outgrowth with micron-scale resolution, using magnetic platforms embedded with micro-patterned, magnetic elements. It has been demonstrated that loading neurons with magnetic nanoparticles (MNPs) converts them into sensitive magnetic units that can be influenced by magnetic gradients. Following this approach, a unique magnetic platform has been fabricated on which PC12 cells, a common neuron-like model, were plated and loaded with superparamagnetic nanoparticles. Thin films of ferromagnetic (FM) multilayers with stable perpendicular magnetization were deposited to provide effective attraction forces toward the magnetic patterns. These MNP-loaded PC12 cells, plated and differentiated atop the magnetic platforms, were preferentially attached to the magnetic patterns, and the neurite outgrowth was well aligned with the pattern shape, forming oriented networks. Quantitative characterization methods of the magnetic properties, cellular MNP uptake, cell viability, and statistical analysis of the results are presented. This approach enables the control of neural network formation and improves neuron-to-electrode interface through the manipulation of magnetic forces, which can be an effective tool for in vitro studies of networks and may offer novel therapeutic biointerfacing directions.

This work presents a bottom-up approach to the engineering of local magnetic forces for control of neuronal organization. Neuron-like cells loaded with magnetic nanoparticles (MNPs) are plated atop and controlled by a micro-patterned platform with perpendicular magnetization. Also described are magnetic characterization, MNP cellular uptake, cell viability, and statistical analysis.

为互连神经元微缩组织制造磁平台

The ability to direct neurons into organized neural networks has great implications for regenerative medicine, tissue engineering, and bio-interfacing. ...

获得高质量的超极化氙 129 磁共振图像

Troubleshooting and Quality Assurance in Hyperpolarized Xenon Magnetic Resonance Imaging: Tools for High-Quality Image Acquisition

Hyperpolarized (HP) xenon magnetic resonance imaging (129Xe MRI) is a recently federal drug administration (FDA)-approved imaging modality that produces high-resolution images of an inhaled breath of xenon gas for investigation of lung function. However, implementing 129Xe MRI is uniquely challenging as it requires specialized hardware and equipment for hyperpolarization, procurement of xenon imaging coils and coil software, development and compilation of multinuclear MR imaging sequences, and reconstruction/analysis of acquired data. Without proper expertise, these tasks can be daunting, and failure to acquire high-quality images can be&#160;frustrating, and expensive. Here, we present some quality control (QC) protocols, troubleshooting practices, and helpful tools for129Xe MRI sites, which may aid in the acquisition of optimized, high-quality data and accurate results. The discussion will begin with an overview of the process for implementing HP 129Xe MRI, including requirements for a hyperpolarizer lab, the combination of 129Xe MRI coil hardware/software, data acquisition and sequence considerations, data structures, k-space and image properties, and measured signal and noise characteristics. Within each of these necessary steps lies opportunities for errors, challenges, and unfavorable occurrences leading to poor image quality or failed imaging, and this presentation aims to address some of the more commonly encountered issues. In particular, identification and characterization of anomalous noise patterns in acquired data are necessary to avoid image artifacts and low-quality images; examples will be given, and mitigation strategies will be discussed. We aim to make the 129Xe MRI implementation process easier for new sites while providing some guidelines and strategies for real-time troubleshooting.

作者聚焦：使用超极化氙 129 MRI 研究肺部疾病 

Here, we present a protocol for obtaining high-quality hyperpolarized xenon-129 magnetic resonance images, covering hardware, software, data acquisition, sequence selection, data management, k-space utilization, and noise analysis.

超极化氙磁共振成像的故障排除和质量保证：用于高质量图像采集的工具

Hyperpolarized (HP) xenon magnetic resonance imaging (129Xe MRI) is a recently federal drug administration (FDA)-approved imaging modality that produces ...

用原位滞后测量进行磁畴成像的优化设置和协议

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