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 border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<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 BH 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 BH 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 &#181;m diamond polishing suspension</td>
		</tr>
		<tr>
			<td>MetaDi Supreme 3um diamond suspension</td>
			<td>Buehler</td>
			<td>406631128</td>
			<td>3 &#181;m diamond polishing suspension</td>
		</tr>
		<tr>
			<td>MetaDi Supreme 1um diamond suspension</td>
			<td>Buehler</td>
			<td>406630032</td>
			<td>1 &#181;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 &#181;m diamond polishing</td>
		</tr>
		<tr>
			<td>TriDent polishing cloth</td>
			<td>Buehler</td>
			<td>407522</td>
			<td>For 3 &#181;m diamond polishing</td>
		</tr>
		<tr>
			<td>ChemoMet polishing cloth</td>
			<td>Buehler</td>
			<td>407922</td>
			<td>For 1 &#181;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>BH analyzer</td>
			<td>University of Manchester</td>
			<td>Not applicable</td>
			<td>An in-house system for BH 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.remotexs.ntu.edu.sg/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.remotexs.ntu.edu.sg/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.remotexs.ntu.edu.sg/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.remotexs.ntu.edu.sg/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.remotexs.ntu.edu.sg/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.remotexs.ntu.edu.sg/files/ftp_upload/56376/56376fig6v2large.jpg">请单击此处查看此图的较大版本.</a>

Watch this Scientific Journal Video about Optimized Setup and Protocol for Magnetic Domain Imaging with In Situ Hysteresis Measurement at JoVE.com

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 ...

optimized-setup-protocol-for-magnetic-domain-imaging-with-situ

Nanyang Technological University

Research

JoVE Journal

Bioengineering

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

High-resolution Fiber-optic Microendoscopy for in situ Cellular Imaging

Many biological and clinical studies require the longitudinal study and analysis of morphology and function with cellular level resolution. Traditionally, multiple experiments are run in parallel, with individual samples removed from the study at sequential time points for evaluation by light microscopy. Several intravital techniques have been developed, with confocal, multiphoton, and second harmonic microscopy all demonstrating their ability to be used for imaging in situ 1. With these systems, however, the required infrastructure is complex and expensive, involving scanning laser systems and complex light sources. Here we present a protocol for the design and assembly of a high-resolution microendoscope which can be built in a day using off-the-shelf components for under US$5,000. The platform offers flexibility in terms of image resolution, field-of-view, and operating wavelength, and we describe how these parameters can be easily modified to meet the specific needs of the end user.
We and others have explored the use of the high-resolution microendoscope (HRME) in in vitro cell culture 2-5, in excised 6 and living animal tissues 2,5, and in human tissues in vivo 2,7. Users have reported the use of several different fluorescent contrast agents, including proflavine 2-4, benzoporphyrin-derivative monoacid ring A (BPD-MA) 5, and fluoroscein 6,7, all of which have received full, or investigational approval from the FDA for use in human subjects. High-resolution microendoscopy, in the form described here, may appeal to a wide range of researchers working in the basic and clinical sciences. The technique offers an effective and economical approach which complements traditional benchtop microscopy, by enabling the user to perform high-resolution, longitudinal imaging in situ.

High-resolution Fiber-optic Microendoscopy for in situ Cellular Imaging

In many biological and clinical situations it is advantageous to study cellular processes as they evolve in their native microenvironment. Here we describe the assembly and use of a low-cost fiber-optic microscope which can provide real time imaging in cell culture, animal studies, and clinical patient studies.

高分辨率光纤内窥镜为原位细胞成像

Many biological and clinical studies require the longitudinal study and analysis of morphology and function with cellular level resolution.  ...

科研

生物工程

Protocol for Relative Hydrodynamic Assessment of Tri-leaflet Polymer Valves

Limitations of currently available prosthetic valves, xenografts, and homografts have prompted a recent resurgence of developments in the area of tri-leaflet polymer valve prostheses. However, identification of a protocol for initial assessment of polymer valve hydrodynamic functionality is paramount during the early stages of the design process. Traditional in vitro pulse duplicator systems are not configured to accommodate flexible tri-leaflet materials; in addition, assessment of polymer valve functionality needs to be made in a relative context to native and prosthetic heart valves under identical test conditions so that variability in measurements from different instruments can be avoided. Accordingly, we conducted hydrodynamic assessment of i) native (n = 4, mean diameter, D = 20 mm), ii) bi-leaflet mechanical (n= 2, D = 23 mm) and iii) polymer valves (n = 5, D = 22 mm) via the use of a commercially available pulse duplicator system (ViVitro Labs Inc, Victoria, BC) that was modified to accommodate tri-leaflet valve geometries. Tri-leaflet silicone valves developed at the University of Florida comprised the polymer valve group. A mixture in the ratio of 35:65 glycerin to water was used to mimic blood physical properties. Instantaneous flow rate was measured at the interface of the left ventricle and aortic units while pressure was recorded at the ventricular and aortic positions. Bi-leaflet and native valve data from the literature was used to validate flow and pressure readings. The following hydrodynamic metrics were reported: forward flow pressure drop, aortic root mean square forward flow rate, aortic closing, leakage&#160;and regurgitant volume, transaortic closing, leakage, and total energy losses. Representative results indicated that hydrodynamic metrics from the three valve groups could be successfully obtained by incorporating a custom-built assembly into a commercially available pulse duplicator system and subsequently, objectively compared to provide insights on functional aspects of polymer valve design.

There has been renewed interest in developing polymer valves. Here, the objectives are to demonstrate the feasibility of modifying a commercial pulse duplicator to accommodate tri-leaflet geometries and to define a protocol to present polymer valve hydrodynamic data in comparison to native and prosthetic valve data collected under near-identical conditions.

协议相对液力评估的三单张聚合物阀

Limitations of currently available prosthetic valves, xenografts, and homografts have prompted a recent resurgence of developments in the area of ...

Magnetic Tweezers for the Measurement of Twist and Torque

Single-molecule techniques make it possible to investigate the behavior of individual biological molecules in solution in real time. These techniques include so-called force spectroscopy approaches such as atomic force microscopy, optical tweezers, flow stretching, and magnetic tweezers. Amongst these approaches, magnetic tweezers have distinguished themselves by their ability to apply torque while maintaining a constant stretching force. Here, it is illustrated how such a &#8220;conventional&#8221; magnetic tweezers experimental configuration can, through a straightforward modification of its field configuration to minimize the magnitude of the transverse field, be adapted to measure the degree of twist in a biological molecule. The resulting configuration is termed the freely-orbiting magnetic tweezers. Additionally, it is shown how further modification of the field configuration can yield a transverse field with a magnitude intermediate between that of the &#8220;conventional&#8221; magnetic tweezers and the freely-orbiting magnetic tweezers, which makes it possible to directly measure the torque stored in a biological molecule. This configuration is termed the magnetic torque tweezers. The accompanying video explains in detail how the conversion of conventional magnetic tweezers into freely-orbiting magnetic tweezers and magnetic torque tweezers can be accomplished, and demonstrates the use of these techniques. These adaptations maintain all the strengths of conventional magnetic tweezers while greatly expanding the versatility of this powerful instrument.

Magnetic tweezers, a powerful single-molecule manipulation technique, can be adapted for the direct measurements of the twist (using a configuration called freely-orbiting magnetic tweezers) and torque (using a configuration termed magnetic torque tweezers) in biological macromolecules. Guidelines for performing such measurements are given, including applications to the study of DNA and associated nucleo-protein filaments.

磁性镊子的扭曲和扭矩的测量

Single-molecule techniques make it possible to investigate the behavior of individual biological molecules in solution in real time. These techniques ...

Protocol for Biofilm Streamer Formation in a Microfluidic Device with Micro-pillars

Several bacterial species possess the ability to attach to surfaces and colonize them in the form of thin films called biofilms. Biofilms that grow in porous media are relevant to several industrial and environmental processes such as wastewater treatment and CO2 sequestration. We used Pseudomonas fluorescens, a Gram-negative aerobic bacterium, to investigate biofilm formation in a microfluidic device that mimics porous media. The microfluidic device consists of an array of micro-posts, which were fabricated using soft-lithography. Subsequently, biofilm formation in these devices with flow was investigated and we demonstrate the formation of filamentous biofilms known as streamers in our device. The detailed protocols for fabrication and assembly of microfluidic device are provided here along with the bacterial culture protocols. Detailed procedures for experimentation with the microfluidic device are also presented along with representative results.

Protocols for the study of biofilm formation in a microfluidic device that mimics porous media are discussed. The microfluidic device consists of an array of micro-pillars and biofilm formation by Pseudomonas fluorescens in this device is investigated.

协议生物膜形成的流光在微流体器件与微柱

Several bacterial species possess the ability to attach to surfaces and colonize them in the form of thin films called biofilms. Biofilms that grow in ...

Rapid Scan Electron Paramagnetic Resonance Opens New Avenues for Imaging Physiologically Important Parameters In Vivo

We demonstrate a superior method of 2D spectral-spatial imaging of stable radical reporter molecules at 250 MHz using rapid-scan electron-paramagnetic-resonance (RS-EPR), which can provide quantitative information under in vivo conditions on oxygen concentration, pH, redox status and concentration of signaling molecules (i.e., OH&#8226;, NO&#8226;). The RS-EPR technique has a higher sensitivity, improved spatial resolution (1 mm), and shorter acquisition time in comparison to the standard continuous wave (CW) technique. A variety of phantom configurations have been tested, with spatial resolution varying from 1 to 6 mm, and spectral width of the reporter molecules ranging from 16 &#181;T (160 mG) to 5 mT (50 G). A cross-loop bimodal resonator decouples excitation and detection, reducing the noise, while the rapid scan effect allows more power to be input to the spin system before saturation, increasing the EPR signal. This leads to a substantially higher signal-to-noise ratio than in conventional CW EPR experiments.

Rapid Scan Electron Paramagnetic Resonance Opens New Avenues for Imaging Physiologically Important Parameters In Vivo

A new electron paramagnetic resonance (EPR) method, rapid scan EPR (RS-EPR), is demonstrated for 2D spectral spatial imaging which is superior to the traditional continuous wave (CW) technique and opens new venues for in vivo imaging. Results are demonstrated at 250 MHz, but the technique is applicable at any frequency.

快速扫描电子顺磁共振打开新的途径成像生理重要参数<em&gt;在体内</em

We demonstrate a superior method of 2D spectral-spatial imaging of stable radical reporter molecules at 250 MHz using rapid-scan ...

Polyelectrolyte Complex for Heparin Binding Domain Osteogenic Growth Factor Delivery

During reconstructive bone surgeries, supraphysiological amounts of growth factors are empirically loaded onto scaffolds to promote successful bone fusion. Large doses of highly potent biological agents are required due to growth factor instability as a result of rapid enzymatic degradation as well as carrier inefficiencies in localizing sufficient amounts of growth factor at implant sites. Hence, strategies that prolong the stability of growth factors such as BMP-2/NELL-1, and control their release could actually lower their efficacious dose and thus reduce the need for larger doses during future bone regeneration surgeries. This in turn will reduce side effects and growth factor costs. Self-assembled PECs have been fabricated to provide better control of BMP-2/NELL-1 delivery via heparin binding and further potentiate growth factor bioactivity by enhancing in vivo stability. Here we illustrate the simplicity of PEC fabrication which aids in the delivery of a variety of growth factors during reconstructive bone surgeries.

Self-assembled polyelectrolyte complexes (PEC) fabricated from heparin and protamine were deposited on alginate beads to entrap and regulate the release of osteogenic growth factors. This delivery strategy enables a 20-fold reduction of BMP-2 dose in spinal fusion applications. This article illustrates the benefits and fabrication of PECs.

聚电解质复合物肝素结合域成骨生长因子交货

During reconstructive bone surgeries, supraphysiological amounts of growth factors are empirically loaded onto scaffolds to promote successful bone ...

Magnetic Levitation Coupled with Portable Imaging and Analysis for Disease Diagnostics

Currently, many clinical diagnostic procedures are complex, costly, inefficient, and inaccessible to a large population in the world. The requirements for specialized equipment and trained personnel require that many diagnostic tests be performed at remote, centralized clinical laboratories. Magnetic levitation is a simple yet powerful technique and can be applied to levitate cells, which are suspended in a paramagnetic solution and placed in a magnetic field, at a position determined by equilibrium between a magnetic force and a buoyancy force. Here, we present a versatile platform technology designed for point-of-care diagnostics which uses magnetic levitation coupled to microscopic imaging and automated analysis to determine the density distribution of a patient's cells as a useful diagnostic indicator. We present two platforms operating on this principle: (i) a smartphone-compatible version of the technology, where the built-in smartphone camera is used to image cells in the magnetic field and a smartphone application processes the images and to measures the density distribution of the cells and (ii) a self-contained version where a camera board is used to capture images and an embedded processing unit with attached thin-film-transistor (TFT) screen measures and displays the results. Demonstrated applications include: (i) measuring the altered distribution of a cell population with a disease phenotype compared to a healthy phenotype, which is applied to sickle cell disease diagnosis, and (ii) separation of different cell types based on their characteristic densities, which is applied to separate white blood cells from red blood cells for white blood cell cytometry. These applications, as well as future extensions of the essential density-based measurements enabled by this portable, user-friendly platform technology, will significantly enhance disease diagnostic capabilities at the point of care.

We present a magnetic levitation technique coupled with automated imaging and analysis in both a smartphone-compatible device and a device with embedded imaging and processing. This is applied to measure the density distribution of cells with two demonstrated biomedical applications: sickle cell disease diagnosis and separating white and red blood cells.

磁悬浮加上便携式成像与分析诊断疾病

Currently, many clinical diagnostic procedures are complex, costly, inefficient, and inaccessible to a large population in the world. The requirements for ...

Protocol for MicroRNA Transfer into Adult Bone Marrow-derived Hematopoietic Stem Cells to Enable Cell Engineering Combined with Magnetic Targeting

While CD133+ hematopoietic stem cells (SCs) have been proven to provide high potential in the field of regenerative medicine, their low retention rates after injection into injured tissues as well as the observed massive cell death rates lead to very restricted therapeutic effects. To overcome these limitations, we sought to establish a non-viral based protocol for suitable cell engineering prior to their administration. The modification of human CD133+ expressing SCs using microRNA (miR) loaded magnetic polyplexes was addressed with respect to uptake efficiency and safety as well as the targeting potential of the cells. Relying on our protocol, we can achieve high miR uptake rates of 80&#8211;90% while the CD133+ stem cell properties remain unaffected. Moreover, these modified cells offer the option of magnetic targeting. We describe here a safe and highly efficient procedure for the modification of CD133+ SCs. We expect this approach to provide a standard technology for optimization of therapeutic stem cell effects and for monitoring of the administered cell product via magnetic resonance imaging (MRI).

This protocol illustrates a safe and efficient procedure to modify CD133+ hematopoietic stem cells. The presented non-viral, magnetic polyplex-based approach may provide a basis for the optimization of therapeutic stem cell effects as well as for monitoring the administered cell product via magnetic resonance imaging.

MicroRNA 移植成人骨髓造血干细胞促进细胞工程与磁性靶向结合的协议

While CD133+ hematopoietic stem cells (SCs) have been proven to provide high potential in the field of regenerative medicine, their low retention rates ...

Measuring the Spin-Lattice Relaxation Magnetic Field Dependence of Hyperpolarized [1-13C]pyruvate

The fundamental limit to in vivo imaging applications of hyperpolarized 13C-enriched compounds is their finite spin-lattice relaxation times. Various factors affect the relaxation rates, such as buffer composition, solution pH, temperature, and magnetic field. In this last regard, the spin-lattice relaxation time can be measured at clinical field strengths, but at lower fields, where these compounds are dispensed from the polarizer and transported to the MRI, the relaxation is even faster and difficult to measure. To have a better understanding of the amount of magnetization lost during transport, we used fast field-cycling relaxometry, with magnetic resonance detection of 13C nuclei at ~0.75 T, to measure the nuclear magnetic resonance dispersion of the spin-lattice relaxation time of hyperpolarized [1-13C]pyruvate. Dissolution dynamic nuclear polarization was used to produce hyperpolarized samples of pyruvate at a concentration of 80 mmol/L and physiological pH (~7.8). These solutions were rapidly transferred to a fast field-cycling relaxometer so that relaxation of the sample magnetization could be measured as a function of time using a calibrated small flip angle (3&#176;-5&#176;). To map the T1 dispersion of the C-1 of pyruvate, we recorded data for different relaxation fields ranging between 0.237 mT and 0.705 T. With this information, we determined an empirical equation to estimate the spin-lattice relaxation of the hyperpolarized substrate within the mentioned range of magnetic fields. These results can be used to predict the amount of magnetization lost during transport and to improve experimental designs to minimize signal loss.

Measuring the Spin-Lattice Relaxation Magnetic Field Dependence of Hyperpolarized [1-13C]pyruvate

We present a protocol to measure the magnetic field dependence of the spin-lattice relaxation time of 13C-enriched compounds, hyperpolarized by means of dynamic nuclear polarization, using fast field-cycled relaxometry. Specifically, we have demonstrated this with [1-13C]pyruvate, but the protocol could be extended to other hyperpolarized substrates.

测量超极化 [1-13C]硫化的旋转-莱迪兹松弛磁场依赖性

The fundamental limit to in vivo imaging applications of hyperpolarized 13C-enriched compounds is their finite spin-lattice relaxation times. Various ...

Lipidico Injection Protocol for Serial Crystallography Measurements at the Australian Synchrotron

A facility for performing serial crystallography measurements has been developed at the Australian synchrotron. This facility incorporates a purpose built high viscous injector, Lipidico, as part of the macromolecular crystallography (MX2) beamline to measure large numbers of small crystals at room temperature. The goal of this technique is to enable crystals to be grown/transferred to&#160;glass syringes to be used directly in the injector for serial crystallography data collection. The advantages of this injector include the ability to respond rapidly&#160;to changes in the flow rate without interruption of the stream. Several limitations for this high viscosity injector (HVI) exist which include a restriction on the allowed sample viscosities to &#62;10 Pa.s. Stream stability can also potentially be an issue depending on the specific properties of the sample. A detailed protocol for how to set up samples and operate the injector for serial crystallography measurements at the Australian synchrotron is presented here. The method demonstrates preparation of the sample, including the transfer of lysozyme crystals into a high viscous media (silicone grease), and the operation of the injector for data collection at MX2.

The goal of this protocol is to demonstrate how to prepare serial crystallography samples for data collection on a high viscous injector, Lipidico, recently commissioned at the Australian synchrotron.

澳大利亚同步加速器串行晶体测量的利皮迪科注射协议

A facility for performing serial crystallography measurements has been developed at the Australian synchrotron. This facility incorporates a purpose built ...