The authors gratefully acknowledge continued funding and support for the project from the Atomic Weapons Establishment, AWE Plc. (UK) and Imperial College London.

1.目标制造和组装<ol><li>机目标油缸从固体股票所需的尺寸。 </li><li>通过去除加工痕迹准备滚筒表面。均匀的漫反射面最好的PDV反思。了良好的结果得到具有光水磨与&gt; 1200砂砾。 </li><li>表征目标成分， 即测量以下： 筒的长度，直径和壁厚（在多个位置） 弹的长度，直径 顶弧的长度，直径 所有的上述质量</li><li>安装在气缸安装环和手臂PDV。 </li><li>安装PDV探针运动的坐骑和到PDV手臂。 </li><li>插入对象气缸中的拱形体，使得拱形体的后部是与缸的后部平齐（这应该在一个车间平面来完成）。这三个M3螺丝的设计保持了弧顶的地方，同时允许缸&#39;剥离AW在扩展时，AY“。 </li><li>放置在目标气缸中的安装硬件，以使圆筒的入口是与安装环的前端面齐平。固定在气缸内到位6 M4平头螺钉。 </li><li>沿气缸外壁的长度安装的加热/冷却装置和键热电偶。 </li><li>清洁FC / APC（套圈连接器，倾斜的身体接触）接口PDV探头纤维纤维清洁布的结束和检查用光纤镜。这一点很重要，以减少背反射。 </li><li>使用可见光（660纳米）3R类激光大致对齐的探针，使它们垂直于所述气缸（ 即 ，反射光的探头落回）。 </li><li>安装使用循环基本反射率电路。 1类1550纳米激光连接至输入端1，对PDV探头输入2和功率计输入3.对齐PDV探针反过来使得返回的功率被最大化。 </li></ol><ol><li>使用桶塞和深度千分尺校准目标环到筒的末端，以减少冲击倾斜。 </li><li>安装片段减灾系统和门保护。 </li><li>放置在枪管的目标对准塞。 </li><li>安装目标组件和对准塞。 </li><li>在筒的端部安装在触发化妆配对并连接到定时硬件和诊断。从测量与触发到弧顶弹丸撞击接触的距离。 </li><li>安装高速摄影的转向镜。 </li><li>对准反射镜，得到通过目标箱口的汽缸的正交视图，并锁定就位。 </li><li>对准高速摄像机和闪光灯的目标槽外。俯视枪管，放置高速摄像机和一个闪光灯在3点钟相对于汽缸。将相机IVV在9点钟和另一个闪光灯在12点。在此配置中，高速相机将前光裂纹跟踪和IVV将提供映衬图像的边缘检测。 </li><li>连接加热/冷却设备的目标和真空馈电得来。 </li><li>注意：用合适的眼镜和其他注意事项打开IV级激光器，示波器和PDV系统。 </li><li>检查的功率电平被发送到PDV探针。与PDV系统，通常使用约5毫瓦每个探针与每通道1毫瓦为参考。 </li><li>检查PDV探头对准功率计。一旦满意的取向使用红外卡以测量那里的PDV探针正在寻找的圆柱体表面上。 </li><li>打开的参照用激光，并检查由每个探针给出的差拍信号的质量。调整激光（S）以设置所需的零速度差频的波长（设置此约5千兆赫）。 </li><li>一旦满意的目标阿里gnment，触发位置，摄像头和反光镜调整，PDV探头对准和位置，并缓解框架关闭目标坦克。 </li><li>取下对准插头;安装弹丸。 </li><li>安装摄像头和照明（帧速率，曝光，定时），并进行测试成像。典型的帧速率大约250,000帧/秒，这两款相机，拥有约0.5微秒曝光。第一图像通常定时为与冲击的瞬间重合。 </li></ol> 3.准备射击<ol><li>安装臀位隔膜是适用于需要烧制压力。 </li><li>关闭臀位，并开始在目标坦克撤离。目标为在50毫托的区域的真空度。 </li><li>执行所有诊断的最终设置（示波器延迟，触发器，相机设置等 ）。集示波器为PDV在50微秒每格，每点25皮秒和20％的预触发，得到500微秒的窗口。触发邻scilloscopes和摄像头，使得零时间恰逢影响的时间。 </li><li>最终触发测试;检查计时是否准确。 </li><li>打开激光器;手臂相机。 </li><li>关闭室;确保激光和高压互锁是在正确的位置。 </li><li>使用LabVIEW软件要求开始加热/冷却。 </li><li>充电枪所需的点火压力。 </li><li>当在压力下，做最后的检查，所有诊断系统武装。 </li><li>隔离的加热或冷却装置。 </li><li>倒计时“3，2，1火”。 </li><li>发泄目标和捕获的坦克。 </li><li>保存所有示波器和相机数据。 </li></ol> 4.前次拍摄<ol><li>关闭激光器和等待枪充分均衡在大气中。 </li><li>打开目标槽，收集所有的金属碎片和整理出的Ti-6AL-4V。 </li></ol> 5.数据分析<ol><li>执行STFT分析的PDV OScilloscope数据，以减少速度历史敖每刀郎和12的分析。 </li><li>与软件，如提到的设备表的过程的高速成像数据。高速摄像机镜头将提供时间和破坏应变，使裂纹的形成和生长分析。的映衬图像从IVV提供清晰边缘检查气缸的充分变形轮廓。 </li><li>测量和称重回收的片段。选择与有趣的功能片段，如逮捕骨折并准备显微镜。 <ol><li>节，安装，和波兰的片段;然后分析在电子显微镜。电子背散射衍射提供的质地和微观结构沿着二次电子成像信息探测断裂面，并确定故障模式。 </li></ol></li></ol>

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The authors have nothing to disclose.

此方法使材料在拉伸加载的高速率调查在宽的温度范围内，从低温到〜1000 K，独特这种设计。然而，这增加了一定的挑战实验设置和执行。首先，以优化温度控制的拱形插入件需要由合适的材料加工。 4340钢用在这里，虽然任何高温高硬度钢应该足够了。同样，因为整个扩张驱动器现在从聚合物弹丸始发此需要从一个非脆性塑料制成，如机级聚碳酸酯在此工作。 具有插入件和...

材料的动态破坏是其整体机械性能的一个重要方面，并具有关联到众多行业，包括汽车，航空航天和军事仅举几。而在低应变速率失败通常是通过常规的拉伸试验，在其中一个细长的样品在从端部张力加载，在高应变率研究这样的形状/配置需要一个样品是非常小的，以便保持一个整个试验伪机械平衡。在一个单一的裂缝的外观，周围的材料会放宽，有效地阻止了任何相邻失效站点的发展。这限制了可以在任一项实验中同时观察到骨折的人数，并防止有关故障的统计数据来确定的重要信息。 扩缸测试是一种行之有效的技术特征以何种方式魔石LS失败，并在高速负荷片段。在测试中，取得所关心的材料的圆筒沿其内圆周被均匀地加载，发射穿过壁的应力波和使所述圆筒膨胀。不久，这样的径向波消散和周围的圆周均匀拉伸环向应力占主导地位。为应力和应变率是断裂和破碎行为是由材料的性质完全支配气缸周围一样。测试缓解了上述问题，因为一般大样本的圆周均匀应力1下促进多个故障点开始。 在开发这种实验技术的主要目的是使温度在不断扩大的圆筒的断裂和碎裂行为中的作用的研究。的样品温度的控制将允许调查如何动态拉伸强度，断裂机制，fragm该材料的entation行为受到影响。例如在金属，温度的升高可引起从脆性转变为韧性断裂，最终失败之前容纳更多的塑料的工作。有些材料如Ti-6AL-4V也能表现出绝热剪切本地化2。而样品变形，塑性工作产生热。如果软化作为该温度升高的结果的速率大于工作从变形硬化的速率，不稳定性可以形成，其中有大量的塑性变形在一个非常局部频带（绝热剪切带）发生。这种反应被促进在钛一6A1-4V由于其导热性差，并有可能限制其有效性的应用，如轻型装甲。 这种新的测试方法必须满足两个主要标准。首先，该方法必须产生10 4秒-1的量级的径向应变率，通常见于弹道和影响的事件，让比较以往的研究多采用传统的装载方案。其次，驱动机构需要由样品温度下不受影响，以确保实验之间的一致性。最初的汽缸膨胀机构使用的炸药，要么干脆直接填充样品缸3-5或使用中间驱动程序。在后一种情况下，一个缓冲器用于6，其中样品被放置在一个钢筒，在依次包含炸药。的明显限制是，作为样品气缸装有驱动器的材料（在炸药的形式）加热缸也将加热的电荷。虽然这可能不是直接引起的电荷开始许多类型的爆炸性的含有聚合物粘合剂材料，将来自样品气缸融出。同样地，当冷却时一些炸药变得非常敏感。这意味着，炸药驱动器不适合于温度研究。另一种方法使用洛伦兹力扩张-样品被放置在一个驱动线圈7，8的高电流注入该驱动线圈（通常重型铜丝），诱导样品中的相对电流。这些对立的电流有关联的磁场而相互采取行动，磁压力的内面驱动向外样本。再次，加热该材料将产生不利的样品内的铜驱动线圈的影响。自从20世纪70年代晚9气体枪已被用于气缸膨胀。在这些实验中使用的缸中的插入件的材料是一种聚合物，所述驱动未来既是弹丸的结果，并插入变形在冲击。此插入通常是橡胶或塑料10中，强度和延展性，其中将受到严重影响的温度。暖气会使插入太软了，散热会使其行为在脆性的方式，以便它失败过早。 实验几何由拱形体安装在目标气缸内，与位于大约沿着圆筒的长度中途尖端一个钢。单级光气枪然后用于向上发射的聚碳酸酯弹丸的凹面进入气缸的速度下，以1000米/秒-1。靶的轴线是圆筒小心地对准到气体枪管的轴线，以便于可重复和一致的负载。宝的影响和随后的流周围的伪刚性钢风帽lycarbonate弹，带动缸到从内壁扩张。小心使用拱形体插入件和弹丸的凹面的几何形状进行了优化的水力代码的计算机模拟，以产生气缸所需的扩张。使用4340合金钢为拱形体使实验与汽缸在温度作为其强度比聚碳酸酯弹丸在感兴趣的温度范围高得多，从而确保该驱动机构保持一致。 Ogives从加热和冷却实验只追回表现出最小的变形的影响的结果。 样品圆筒的加热和冷却是通过温度控制硬件安装完成到在拱形体插入件的后部的机加工凹槽。用于冷却样品到低温（〜100 K），在拱形体的凹部是密封的铝盖和液氮为flowed通过空腔。作为目标气缸具有与样品通过传导冷却的拱形体接触面积大。来加热对象气缸到温度接近1000 K，陶瓷和镍铬合金电阻加热器被放置在拱形凹槽。高电流电源提供高达1千瓦，加热顶弧和缸体。气缸和卵形被热从目标隔离在单级气 - 炮架通过使用MACOR陶瓷隔板。该坦克还适度真空（&lt;0.5托）下这有助于热操纵实验期间举行。 为了诊断气缸的碎裂过程中，实验设计包括变频PDV多个通道，以测量在沿着汽缸点的膨胀速度。 PDV是一个相对较新的11，基于光纤的干涉技术，该技术使得能在高动态事件表面速度的测定。在一个PDV测量，多普勒频移从感兴趣的移动表面用光纤探针是结合未移位的光，产生一个拍频成正比的移动表面的速度的反射光。从本质上讲，PDV系统是使用在近红外（1550纳米）的通信技术的进步，以在GHz范围记录的拍频快速迈克尔逊干涉仪。在当前研究中使用100毫米焦距PDV探针的安装系统可确保它们从滚筒的温度分离和提供更容易对齐。用100毫米焦距的探针的另一优点是，它们提供足够的光学访问启用高速摄影测量整个汽缸的膨胀轮廓。四个探针，AD的排列和位置，沿着汽缸示于图1的两个高速摄像机这里采用。高速摄像机幻影V16.10操作25万FPS和IVV超高速集成电路12/24幅相机，捕捉24幅图像。该IVV照相机背光，使得气缸被照亮的剪影使气缸的径向扩大的边缘被精确地跟踪。幽灵相机正面受光影像的失败并开始分段处理。高速摄影然后可以与测速相关，得到应变和应变率沿整个样本。高速成像也允许精确测量破坏应变及断裂模式沿表面。 实验方法在下面的协议部分中提供提供了一种控制在膨胀汽缸的实验中，通过该不同断裂机理可以被激活或抑制样品温度的手段。该技术会导致温度的动态负载情况下的作用，更全面的了解。

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	<tbody>
		<tr height="22">
			<td height="22" style="height:22px;width:268px;">Item</td>
			<td style="width:235px;">Company / Manufacturer</td>
			<td style="width:344px;">Part Number</td>
			<td style="width:307px;">Comments / Description</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">1550 nm CW Laser</td>
			<td style="width:235px;">NKT Photonics</td>
			<td style="width:344px;">Koheras Adjustik</td>
			<td style="width:307px;">x 2</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">1550 nm Power Amplifier</td>
			<td style="width:235px;">NKT Photonics</td>
			<td style="width:344px;">Koheras Boostik HPA</td>
			<td style="width:307px;"></td>
		</tr>
		<tr height="21">
			<td height="42" rowspan="2" style="height:42px;width:268px;">Delay Generators</td>
			<td style="width:235px;">Quantum Composers</td>
			<td style="width:344px;">9500+ Digital Delay Pulse Generator</td>
			<td style="width:307px;">8 output version</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:235px;">Stanford Research Systems</td>
			<td style="width:344px;">DG535 Digital Delay Generator</td>
			<td style="width:307px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">16 Channel Digitiser</td>
			<td style="width:235px;">Agilent Technologies</td>
			<td style="width:344px;">U1056B Chassis + 4 X U1063A Digitiser</td>
			<td style="width:307px;"></td>
		</tr>
		<tr height="21">
			<td height="42" rowspan="2" style="height:42px;width:268px;">High Bandwidth Oscilloscopes</td>
			<td style="width:235px;">Teledyne LeCroy</td>
			<td style="width:344px;">WaveMaster 816Zi-A</td>
			<td style="width:307px;">Expansion Velocity, Gen 3 PDV</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:235px;">Tektronix</td>
			<td style="width:344px;">DPO71604C</td>
			<td style="width:307px;">Projectile Velocity, Gen 1 PDV</td>
		</tr>
		<tr height="21">
			<td height="84" rowspan="4" style="height:84px;width:268px;">High Speed Imaging Systems</td>
			<td style="width:235px;">Vision Research</td>
			<td style="width:344px;">Phantom v16.10</td>
			<td style="width:307px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:235px;">Invisible Vision</td>
			<td style="width:344px;">IVV UHSi-24</td>
			<td style="width:307px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:235px;">Zeiss Optics</td>
			<td style="width:344px;">Planar T* 1,4/85</td>
			<td style="width:307px;">85mm Prime Lens</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:235px;">Nikon</td>
			<td style="width:344px;">AF-S Nikkor 70-200mm f/2.8 ED VR II</td>
			<td style="width:307px;">70-200mm Telephoto Lens</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Flash Lamp</td>
			<td style="width:235px;">Bowens</td>
			<td style="width:344px;">Gemini Pro 1500W</td>
			<td style="width:307px;">x 2</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">PDV Probe</td>
			<td style="width:235px;">Laser 2000</td>
			<td style="width:344px;">LPF-04-1550-9/125-S-21.5-100-4.5AS-60-3A-3-3</td>
			<td style="width:307px;">x 4 (Custom order)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:268px;">PDV System</td>
			<td style="width:235px;">Built in-house by the Institute of Shock Physics</td>
			<td style="width:344px;">Custom Build</td>
			<td style="width:307px;">3rd Generation (Upshifted) 8 Channel Portable PDV System</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Control Software</td>
			<td style="width:235px;">National Instruments</td>
			<td style="width:344px;">LabVIEW 2013</td>
			<td style="width:307px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Control Hardware for heating</td>
			<td style="width:235px;">National Instruments</td>
			<td style="width:344px;">NI-DAQ 6009 USB</td>
			<td style="width:307px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Heating Power Supply</td>
			<td style="width:235px;">BK Precision</td>
			<td style="width:344px;">BK1900</td>
			<td style="width:307px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Thermocouple Logger</td>
			<td style="width:235px;">Pico Technology</td>
			<td style="width:344px;">TC-08</td>
			<td style="width:307px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:268px;">100 mm Single Stage Light Gas Gun</td>
			<td style="width:235px;">Physics Applications, Inc. (PAI)</td>
			<td style="width:344px;">Custom Build</td>
			<td style="width:307px;">Capable of at least 1000 meters per second with ~ 2 kg projectile</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Image analysis software</td>
			<td style="width:235px;">National Institutes of Health</td>
			<td style="width:344px;">ImageJ</td>
			<td style="width:307px;">Open source, free</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Image analysis software</td>
			<td style="width:235px;">Mathworks</td>
			<td style="width:344px;">MATLAB r2014a</td>
			<td style="width:307px;">With image processing toolboxes</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Material sectioning saw</td>
			<td style="width:235px;">Struers</td>
			<td style="width:344px;">Accutom-50</td>
			<td style="width:307px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Electron Microscope</td>
			<td style="width:235px;">Zeiss</td>
			<td style="width:344px;">Auriga</td>
			<td style="width:307px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Electron Backscatter Diffraction</td>
			<td style="width:235px;">Bruker</td>
			<td style="width:344px;">e-Flash 1000</td>
			<td style="width:307px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">EBSD software</td>
			<td style="width:235px;">Bruker</td>
			<td style="width:344px;">eSprit</td>
			<td style="width:307px;"></td>
		</tr>
	</tbody>
</table>

a method for studying the temperature dependence of dynamic fracture and fragmentation

一体的动态断裂是晚期现象通常简化条件下，在其中将样品均匀的应力和应变速率下变形下研究。这可以通过均匀地装入一个圆筒的内表面来制造。由于轴对称，随着气缸膨​​胀壁被置于拉伸箍应力即围绕圆周均匀。虽然有多种技术来产生这种扩张例如爆炸物，电磁驱动器，和现有的气枪技术它们都限定在一个事实，即样品气缸必须在室温下进行。我们提出使用气体喷枪便于实验上从150 K至800ķ缸具有一致的，可重复加载的新方法。这些高度诊断实验用来检验温度对断裂机制负责故障，以及它们对碎片统计所得的影响的效果。实验几何形状采用了钢卵形位于靶圆筒内，与位于大约一半的小费。单级光气枪，然后用于启动聚碳酸酯弹丸进入气缸在1000米/秒-1。弹丸冲击和周围的刚性顶弧流，找到从内侧样品圆柱体。使用一个不变形的拱形插入件使我们能够安装温度控制硬件缸体的后部内。液氮（LN 2）用于冷却和电阻高电流负载进行加热。的换高档光子多普勒测速（PDV）的多个信道跟踪沿气缸使直接比较计算机模拟的膨胀速度，而高速成像用于测量断裂应变。将回收筒片段也受到光学和电子显微镜，以确定失效机理。

数据的质量将首先取决于实验定时。如果延迟从触发到影响都是正确的那么闪光灯会产生足够的光线在目标缸开始变形，使高速摄像机，以产生清晰的图像。在这种情况下，从取景相机的图像将有一个明确的映衬边缘可用于跟踪整个圆柱体的变形。软件如ImageJ的可用于提取线路输出对各帧数据，生成一个图像， 如图2。理想情况下，PDV就能追踪膨胀速度为〜100微秒，这将取决于圆筒的...

Watch this Scientific Journal Video about A Method for Studying the Temperature Dependence of Dynamic Fracture and Fragmentation at JoVE.com

A Method for Studying the Temperature Dependence of Dynamic Fracture and Fragmentation

Fracture and fragmentation are late stage phenomena in dynamic loading scenarios and are typically studied using explosives. We present a technique for driving expansion using a gas gun which uniquely enables control of both loading rate and sample temperature.

为研究动态断裂及破碎的温度敏感性的方法

The dynamic fracture of a body is a late-stage phenomenon typically studied under simplified conditions, in which a sample is deformed under uniform ...

a-method-for-studying-temperature-dependence-dynamic-fracture

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Unit 1

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Temperature and Heat

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8.5K 次观看.  Imperial College London. Fracture and fragmentation are late stage phenomena in dynamic loading scenarios and are typically studied using explosives. We present a technique for driving expansion using a gas gun which uniquely enables control of both loading rate and sample temperature.

视频: A Method for Studying the Temperature Dependence of Dynamic Fracture and Fragmentation

Real-Time DC-dynamic Biasing Method for Switching Time Improvement in Severely Underdamped Fringing-field Electrostatic MEMS Actuators

Mechanically underdamped electrostatic fringing-field MEMS actuators are well known for their fast switching operation in response to a unit step input bias voltage. However, the tradeoff for the improved switching performance is a relatively long settling time to reach each gap height in response to various applied voltages. Transient applied bias waveforms are employed to facilitate reduced switching times for electrostatic fringing-field MEMS actuators with high mechanical quality factors. Removing the underlying substrate of the fringing-field actuator creates the low mechanical damping environment necessary to effectively test the concept. The removal of the underlying substrate also a has substantial improvement on the reliability performance of the device in regards to failure due to stiction. Although DC-dynamic biasing is useful in improving settling time, the required slew rates for typical MEMS devices may place aggressive requirements on the charge pumps for fully-integrated on-chip designs. Additionally, there may be challenges integrating the substrate removal step into the back-end-of-line commercial CMOS processing steps. Experimental validation of fabricated actuators demonstrates an improvement of 50x in switching time when compared to conventional step biasing results. Compared to theoretical calculations, the experimental results are in good agreement.

The robust device design of fringing-field electrostatic MEMS actuators results in inherently low squeeze-film damping conditions and long settling times when performing switching operations using conventional step biasing. Real-time switching time improvement with DC-dynamic waveforms reduces the settling time of fringing-field MEMS actuators when transitioning between up-to-down and down-to-up states.

实时直流偏置的动态法切换时间改善严重欠阻尼边缘化场静电MEMS致动器

Mechanically underdamped electrostatic fringing-field MEMS actuators are well known for their fast switching operation in response to a unit step input ...

科研

工程学

Characterization of Full Set Material Constants and Their Temperature Dependence for Piezoelectric Materials Using Resonant Ultrasound Spectroscopy

During the operation of high power electromechanical devices, a temperature rise is unavoidable due to mechanical and electrical losses, causing the degradation of device performance. In order to evaluate such degradations using computer simulations, full matrix material properties at elevated temperatures are needed as inputs. It is extremely difficult to measure such data for ferroelectric materials due to their strong anisotropic nature and property variation among samples of different geometries. Because the degree of depolarization is boundary condition dependent, data obtained by the IEEE (Institute of Electrical and Electronics Engineers) impedance resonance technique, which requires several samples with drastically different geometries, usually lack self-consistency. The resonant ultrasound spectroscopy (RUS) technique allows the full set material constants to be measured using only one sample, which can eliminate errors caused by sample to sample variation. A detailed RUS procedure is demonstrated here using a lead zirconate titanate (PZT-4) piezoceramic sample. In the example, the complete set of material constants was measured from room temperature to 120 &#176;C. Measured free dielectric constants <img alt="Equation 1" src="/files/ftp_upload/53461/image001.jpg" /> and&#160;<img alt="Equation 2" src="/files/ftp_upload/53461/image002.jpg" /> were compared with calculated ones based on the measured full set data, and piezoelectric constants d15 and d33 were also calculated using different formulas. Excellent agreement was found in the entire range of temperatures, which confirmed the self-consistency of the data set obtained by the RUS.

This protocol describes the procedure of measuring the temperature dependence of the full set material constants of piezoelectric materials using resonant ultrasound spectroscopy (RUS).

全套材料常数表征及其温度依赖性的压电材料使用共振超声波谱

During the operation of high power electromechanical devices, a temperature rise is unavoidable due to mechanical and electrical losses, causing the ...

Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film synthesis) for the purpose of exploratory materials research. Certain materials pose a challenge wherein the traditional bulk Hall bar device fabrication method is insufficient to produce a measureable device for sample transport measurement, principally because the single crystal size is too small to attach wire leads to the sample in a Hall bar configuration. This can be, for example, because the first batch of a new material synthesized yields very small single crystals or because flakes of samples of one to very few monolayers are desired. In order to enable rapid characterization of materials that may be carried out in parallel with improvements to their growth methodology, a method of device fabrication for very small samples has been devised to permit the characterization of novel materials as soon as a preliminary batch has been produced. A slight variation of this methodology is applicable to producing devices using exfoliated samples of two-dimensional materials such as graphene, hexagonal boron nitride (hBN), and transition metal dichalcogenides (TMDs), as well as multilayer heterostructures of such materials. Here we present detailed protocols for the experimental device fabrication of fragments and flakes of novel materials with micron-sized dimensions onto substrate and subsequent measurement in a commercial superconducting magnet, dry helium close-cycle cryostat magnetotransport system at temperatures down to 0.300 K and magnetic fields up to 12 T.

We describe the methodology of mechanical exfoliation and deposition of flakes of novel materials with micron-sized dimensions onto substrate, fabrication of experimental device structures for transport experimentation, and the magnetotransport measurement in a dry helium close-cycle cryostat at temperatures down to 0.300 K and magnetic fields up to 12 T.

对于新材料的低温磁输运测量先进的实验方法

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film ...

Use of a Multi-compartment Dynamic Single Enzyme Phantom for Studies of Hyperpolarized Magnetic Resonance Agents

Imaging of hyperpolarized substrates by magnetic resonance shows great clinical promise for assessment of critical biochemical processes in real time. Due to fundamental constraints imposed by the hyperpolarized state, exotic imaging and reconstruction techniques are commonly used. A practical system for characterization of dynamic, multi-spectral imaging methods is critically needed. Such a system must reproducibly recapitulate the relevant chemical dynamics of normal and pathological tissues. The most widely utilized substrate to date is hyperpolarized [1-13C]-pyruvate for assessment of cancer metabolism. We describe an enzyme-based phantom system that mediates the conversion of pyruvate to lactate. The reaction is initiated by injection of the hyperpolarized agent into multiple chambers within the phantom, each of which contains varying concentrations of reagents that control the reaction rate. Multiple compartments are necessary to ensure that imaging sequences faithfully capture the spatial and metabolic heterogeneity of tissue. This system will aid the development and validation of advanced imaging strategies by providing chemical dynamics that are not available from conventional phantoms, as well as control and reproducibility that is not possible in vivo.

A multi-compartment dynamic phantom is used to simulate some biology of interest for metabolic studies using hyperpolarized magnet resonance agents.

一个多腔动态单一酶幻影超极化磁共振剂研究的用途

Imaging of hyperpolarized substrates by magnetic resonance shows great clinical promise for assessment of critical biochemical processes in real time. Due ...

Applying X-ray Imaging Crystal Spectroscopy for Use as a High Temperature Plasma Diagnostic

X-ray spectra provide a wealth of information on high temperature plasmas; for example electron temperature and density can be inferred from line intensity ratios. By using a Johann spectrometer viewing the plasma, it is possible to construct profiles of plasma parameters such as density, temperature, and velocity with good spatial and time resolution. However, benchmarking atomic code modeling of X-ray spectra obtained from well-diagnosed laboratory plasmas is important to justify use of such spectra to determine plasma parameters when other independent diagnostics are not available. This manuscript presents the operation of the High Resolution X-ray Crystal Imaging Spectrometer with Spatial Resolution (HIREXSR), a high wavelength resolution spatially imaging X-ray spectrometer used to view hydrogen- and helium-like ions of medium atomic number elements in a tokamak plasma. In addition, this manuscript covers a laser blow-off system that can introduce such ions to the plasma with precise timing to allow for perturbative studies of transport in the plasma.

X-ray spectra provide a wealth of information on high temperature plasmas. This manuscript presents the operation of a high wavelength resolution spatially imaging X-ray spectrometer used to view hydrogen- and helium-like ions of medium atomic number elements in a tokamak plasma.

运用X射线成像光谱水晶的使用为高温等离子体诊断

X-ray spectra provide a wealth of information on high temperature plasmas; for example electron temperature and density can be inferred from line ...

Studying Dynamic Processes of Nano-sized Objects in Liquid using Scanning Transmission Electron Microscopy

Samples fully embedded in liquid can be studied at a nanoscale spatial resolution with Scanning Transmission Electron Microscopy (STEM) using a microfluidic chamber assembled in the specimen holder for Transmission Electron Microscopy (TEM) and STEM. The microfluidic system consists of two silicon microchips supporting thin Silicon Nitride (SiN) membrane windows. This article describes the basic steps of sample loading and data acquisition. Most important of all is to ensure that the liquid compartment is correctly assembled, thus providing a thin liquid layer and a vacuum seal. This protocol also includes a number of tests necessary to perform during sample loading in order to ensure correct assembly. Once the sample is loaded in the electron microscope, the liquid thickness needs to be measured. Incorrect assembly may result in a too-thick liquid, while a too-thin liquid may indicate the absence of liquid, such as when a bubble is formed. Finally, the protocol explains how images are taken and how dynamic processes can be studied. A sample containing AuNPs is imaged both in pure water and in saline.

This protocol describes the operation of a liquid flow specimen holder for scanning transmission electron microscopy of AuNPs in water, as used for the observation of nanoscale dynamic processes.

使用扫描透射电子显微镜研究纳米大小的物体的动态过程中的液体

Samples fully embedded in liquid can be studied at a nanoscale spatial resolution with Scanning Transmission Electron Microscopy (STEM) using a ...

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia (YSZ) Scaffolds by In Situ Carbon Templating Xerogels

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) scaffolds with tunable specific surface areas up to 80 m2&#183;g-1. An aqueous solution of a zirconium salt, yttrium salt, and glucose is mixed with propylene oxide (PO) to form a gel. The gel is dried under ambient conditions to form a xerogel. The xerogel is pressed into pellets and then sintered in an argon atmosphere. During sintering, a YSZ ceramic phase forms and the organic components decompose, leaving behind amorphous carbon. The carbon formed in situ serves as a hard template, preserving a high surface area YSZ nanomorphology at sintering temperature. The carbon is subsequently removed by oxidation in air at low temperature, resulting in a porous, nanostructured YSZ scaffold. The concentration of the carbon template and the final scaffold surface area can be systematically tuned by varying the glucose concentration in the gel synthesis. The carbon template concentration was quantified using thermogravimetric analysis (TGA), the surface area and pore size distribution was determined by physical adsorption measurements, and the morphology was characterized using scanning electron microscopy (SEM). Phase purity and crystallite size was determined using X-ray diffraction (XRD). This fabrication approach provides a novel, flexible platform for realizing unprecedented scaffold surface areas and nanomorphologies for ceramic-based electrochemical energy conversion applications, e.g. solid oxide fuel cell (SOFC) electrodes.

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia YSZ Scaffolds by In Situ Carbon Templating Xerogels

A protocol for fabricating porous, nanostructured yttria-stabilized-zirconia (YSZ) scaffolds at temperatures between 1,000 &#176;C and 1,400 &#176;C is presented.

通过纳米氧化钇稳定的二氧化锆（YSZ）的支架的高温加工<em&gt;原位</em&gt;碳模板干凝胶

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) ...

Atomic Layer Deposition of Vanadium Dioxide and a Temperature-dependent Optical Model

Vanadium dioxide is a material that has a reversible metal-insulator phase change near 68 &#176;C. To grow VO2 on a wide variety of substrates, with wafer-scale uniformity and angstrom level control of thickness, the method of atomic-layer deposition was chosen. This ALD process enables high-quality, low-temperature (&#8804;150 &#176;C) growth of ultrathin films (100-1000 &#197;) of VO2. For this demonstration, the VO2 films were grown on sapphire substrates. This low temperature growth technique produces mostly amorphous VO2 films. A subsequent anneal in an ultra-high vacuum chamber with a pressure of 7x10-4 Pa of ultra-high purity (99.999%) oxygen produced oriented, polycrystalline VO2 films. The crystallinity, phase, and strain of the VO2 were determined by Raman spectroscopy and X-ray diffraction, while the stoichiometry and impurity levels were determined by X-ray photoelectron spectroscopy, and finally the morphology was determined by atomic force microscopy. These data demonstrate the high-quality of the films grown by this technique. A model was created to fit to the data for VO2 in its metallic and insulating phases in the near infrared spectral region. The permittivity and refractive index of the ALD VO2 agreed well with the other fabrication methods in its insulating phase, but showed a difference in its metallic state. Finally, the analysis of the films&#39; optical properties enabled the creation of a wavelength- and temperature-dependent model of the complex optical refractive index for developing VO2 as a tunable refractive index material.

Thin films (100-1000 &#197;) of vanadium dioxide (VO2) were created by atomic-layer deposition (ALD) on sapphire substrates. Following this, the optical properties were characterized through the metal-insulator transition of VO2. From the measured optical properties, a model was created to describe the tunable refractive index of VO2.

二氧化钒原子层沉积与温度依赖性光学模型

Vanadium dioxide is a material that has a reversible metal-insulator phase change near 68 &#176;C. To grow VO2 on a wide variety of substrates, with ...

Near-Infrared Temperature Measurement Technique for Water Surrounding an Induction-heated Small Magnetic Sphere

A technique to measure the temperature of water and non-turbid aqueous media surrounding an induction-heated small magnetic sphere is presented. This technique utilizes wavelengths of 1150 and 1412 nm, at which the absorption coefficient of water is dependent on temperature. Water or a non-turbid aqueous gel containing a 2.0-mm- or 0.5-mm-diameter magnetic sphere is irradiated with 1150 nm or 1412 nm incident light, as selected using a narrow bandpass filter; additionally, two-dimensional absorbance images, which are the transverse projections of the absorption coefficient, are acquired via a near-infrared camera. When the three-dimensional distributions of temperature can be assumed to be spherically symmetric, they are estimated by applying inverse Abel transforms to the absorbance profiles. The temperatures were observed to consistently change according to time and the induction heating power.

A technique utilizing wavelengths of 1150 and 1412 nm to measure the temperature of water surrounding an induction-heated small magnetic sphere is presented.

感应加热小磁球周围水近红外测温技术

A technique to measure the temperature of water and non-turbid aqueous media surrounding an induction-heated small magnetic sphere is presented. This ...

A 100 KW Class Applied-field Magnetoplasmadynamic Thruster

Applied-field magnetoplasmadynamic thrusters (AF-MPD thrusters) are hybrid accelerators in which electromagnetic and gas dynamic processes accelerate plasma to high speed; they have considerable potential for future space applications with the significant advantages of high specific impulse and thrust density. In this paper, we present a series of protocols for designing and manufacturing a 100 kW class of AF-MPD thruster with water-cooling structures, a 130 V maximum discharge voltage, a 800 A maximum discharge current, and a 0.25 T maximum strength of magnetic field. A hollow tantalum tungsten cathode acts as the only propellant inlet to inhibit the radial discharge, and it is positioned axially at the rear of the anode in order to relieve anode starvation. A cylindrical divergent copper anode is employed to decrease anode power deposition, where the length has been reduced to decrease the wall-plasma connecting area. Experiments utilized a vacuum system that can achieve a working vacuum of 0.01 Pa for a total propellant mass flow rate lower than 40 mg/s and a target thrust stand. The thruster tests were carried out to measure the effects of the working parameters such as propellant flow rates, the discharge current, and the strength of applied magnetic field on the performance and to allow appropriate analysis. The thruster could be operated continuously for significant periods of time with little erosion on the hollow cathode surface. The maximum power of the thruster is 100 kW, and the performance of this water-cooled configuration is comparable with that of thrusters reported in the literature.

The goal of this protocol is to introduce the design of a 100 kW class applied-field magnetoplasmadynamic thruster and relevant experimental methods.

一个100千瓦级的应用场磁等离子体动力学推进器

Applied-field magnetoplasmadynamic thrusters (AF-MPD thrusters) are hybrid accelerators in which electromagnetic and gas dynamic processes accelerate ...