支持这项工作由海军研究办公室（N000141210603）和陆军研究办公室（W911NF1010381）深表感谢。来自美国国家科学基金会（CBET-0931290，CMMI-0926704，和CBET-0932573）的部分支持这项工作也承认。

1。实验过程<ol><li>收集样品。在这项工作中，人的头发样本是从一个30岁的健康的亚洲女性的收集。 </li><li>暂停两个铜电极之间的样品， 如图1A所示 。应用银糊剂在样品电极接触，以减少热和电的接触电阻到可以忽略的水平。 </li><li>使用显微镜做样品的初步检查，并确保该银膏也不会污染悬浮样品。 </li><li>因为人体头部的头发样本不导电的，涂层具有非常薄的一层金膜（〜40nm）的样品的外面，使其具有导电性。 </li><li>将样品在真空室中，并将其泵至1-3毫乇。 </li><li>喂养的工序直流电流通过样品引入电加热和感应电压-时间（V - t）的更新将通过使用示波器进行记录。 </li&gt; <li>得到的样品出腔室和外套它与另一薄层金膜（〜40nm）的，并重复步骤1.5和1.6。 </li><li>准备新的样品具有不同的长度，并重复步骤1.2-1.7。 </li><li>使用扫描电子显微镜（SEM）表征样品（长和短的）的长度和直径。 </li></ol> 2。数据处理第一正常化实验温度升高，并通过使用样品的热扩散率不同试验值进行的，该理论拟合。此过程在郭的详细工作1讨论。然后减去的辐射损失和寄生传导的热扩散的影响，并计算热导率。细节在下面给出。 <ol><li>确定有效的热扩散系数 在TET实验设置的示意图如图1A所示。在测量中，进料的工序的电流通过样品诱导焦耳加热。使用示波器来记录的感应电压-时间（V - 吨 ），其是在图1B的配置文件。有多快/慢温度的升高是由两个竞争的过程决定：一个是焦耳加热，另一种是来自样品的热传导到电极上。样品的更高的热扩散将导致更快的温度变化，即在较短的时间内达到稳定状态。因此，瞬态电压/温度变化可以用来确定热扩散率。当测定样品的热扩散率，没有真正的升温是必要的。事实上，只有根据该电压增加的归一化温度上升被使用。该过程用于确定热扩散率和热导率概述如下。 <ol><li>简化的热量传递到一维：取试样中沿一维传热<html>轴向移动。注意：该线的长度必须比其直径要长很多。更多详细信息可参阅郭的工作1。 <ol><li>求解归一化的温升（T *，也被称为空间平均温度在整个样品）在样本为使用下列公式的一维传热问题： <img alt="1" fo:content-width="1.8in" height="46" src="/files/ftp_upload/51144/51144_clip_image002.gif" width="260" /> （1） α和L是样品的热扩散系数和长度。 </li><li>求解归一化温度升高的电压变化（V 线 ）录得的示波器，并进行数据拟合，以确定热扩散率。在导线上的电压有关，其温度为： 0“/&gt;（2） R 0是样品加热前的电阻， 余电流通过样品和k的导热率。Q 0是每单位体积的电加热功率。很显然，所测量的电压变化是固有地关联到该样品的温度变化。的归一化温度上升T *根据实验数据判断可以计算为T * EXP =（V 线 - V 0）/（V 1 - V 0），其中V 0和V1 顷穿过的初始和最终电压样品（ 如图1B）。获得T * EXP后，用α不同的试验值来计算的理论T *通过应用公式1和拟合实验重sults（T * EXP）。利用MATLAB编程来通过应用最小二乘拟合技术比较实验值和理论值，并取该值给出的T * EXP最适合作为样品的热扩散率。 </li></ol></li></ol></li><li>减去的辐射损失和气体传导的影响 在TET热特性，的辐射损失的影响可能是显著如果样品具有非常大的纵横比（L / D，D：试样的直径），特别是对低导热率的样品。此外，如果真空室中的压力不是很低，热量传递到空气会影响测量到一定的程度。从样品表面辐射的热传递率可以表示为： <img alt="" fo:content-width="3.1in" height="29" src="/files/ftp_upload/51144/51144_clip_image002_0001.gif" width="390" /> ，（3） 磨片重ε是样品的有效发射率，A S的表面积，T的表面的温度，T 0的环境（真空室）的温度，θ= T - T 0在大多数情况下，θ&lt;&lt;波 0 ，则： <img alt="" fo:content-width="1.05in" height="23" src="/files/ftp_upload/51144/51144_clip_image002_0002.gif" width="138" /> （4） 通过将面辐射和气体传导到身体冷源，对样品的传热控制方程变为： <img alt="" fo:content-width="2.25in" height="49" src="/files/ftp_upload/51144/51144_clip_image002_0003.gif" width="345" /> ，（5） 其中 h为气体传导系数。在我们的物理模型中，由于电极是比样品大得多，具有优异的热传导，将样品的温度是在室温下进行一t为接触。因为θ（X，T）= T（X，T） - T 0，边界条件是θ（0，T）=θ（L，T）=θ（X，0）= 0。 以公式（5）的解决方案是： <img alt="" fo:content-width="3.5in" src="/files/ftp_upload/51144/51144_clip_image002_0004.gif" width="489" /> （6） 在这里，f的定义为- （16εδT0 3 / D +4 H / D）L 2 /π2 K，这是无量纲的。它是一种类型的Biot数，其大小表示从样品的两侧的热损失量。结合这个方程沿x方向和平均温度可以得到： <img alt="" fo:content-width="3in" src="/files/ftp_upload/51144/51144_clip_image002_0005.gif" width="408" /> （7） 因此，归一化大道愤怒的温度是： <img alt="" fo:content-width="4.2in" src="/files/ftp_upload/51144/51144_clip_image004_0005.gif" width="510px" /> （8） 经过仔细的数值和数学的研究中，与αEFF =α（1 - F），T *可以近似为 <img alt="" fo:content-width="2.2in" height="48" src="/files/ftp_upload/51144/51144_clip_image008.gif" width="288" /> （9） 数值计算已进行了研究上述近似的精度。请注意，当f为小于0时，在整个过渡状态下的最大绝对差值小于0.014（ 图2中示出）。最后： <img alt="" fo:content-width="1.7in" height="50" src="/files/ftp_upload/51144/51144_clip_image010.gif" width="218" /> （10） 因为实验是在非常低的压力（1-3毫乇）在真空室中进行，该气体传导的影响（ 小时）是可以忽略不计<html> BLE。所以简化公式10为： <img alt="" fo:content-width="1.4in" height="49" src="/files/ftp_upload/51144/51144_clip_image012.gif" width="173" /> （11） 这个公式表明，使用TET技术测量热扩散具有与辐射损失（4εσT0 3）的效果线性关系。使用这样的理论背景，以减去的辐射损失和气体传导的影响。 </li><li>确定真正的热扩散率和电导率 在公式11所确定的热扩散率（α）仍具有寄生传导的效果，如果测试样品上涂有薄金膜。造成涂层的热传输效果可使用威德曼 - 弗兰兹定律可以忽略不计的不确定性中减去。样品的实际热扩散率（α）被确定为1： 在“高度=”47“SRC =”/ files/ftp_upload/51144/51144_clip_image002_0006.gif .1“宽度=”134“/&gt;，（12） ρCp是基于体积的比热，这可以从校准时，非接触式光热技术或分别测量密度和比热以下方式获得：L 洛伦茨 ，T和A的洛伦兹数，样品的温度和截面积，分别。 因为<img alt="" fo:content-width="2.4in" height="46" src="/files/ftp_upload/51144/51144_clip_image004_0006.gif" width="343" /> ，但很明显，αEFF的与1 / R成线性关系，因此，在该实验中，涂覆1样品与金膜的两倍（这将导致1 / R的变化）和测试两次可通过消除寄生传导的影响曲线拟合。对于实际的热导率K，它可以很容易地通过采用k =ρCp评价45; </li></ol>

<ol>
	<li>Guo, J. Q., Wang, X. W., Wang, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermal+characterization+of+microscale+conductive+and+nonconductive+wires+using+transient+electrothermal+technique.">Thermal characterization of microscale conductive and nonconductive wires using transient electrothermal technique.</a> J. Appl. Phys. 101, (2007).</li><li>Lu, L., Yi, W., Zhang, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=3+omega+method+for+specific+heat+and+thermal+conductivity+measurements.">3 omega method for specific heat and thermal conductivity measurements.</a> Rev. Sci. Instrum. 72, 2996-3003 (2001).</li><li>Choi, T. Y., Poulikakos, D., Tharian, J., Sennhauser, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurement+of+the+thermal+conductivity+of+individual+carbon+nanotubes+by+the+four-point+three-omega+method.">Measurement of the thermal conductivity of individual carbon nanotubes by the four-point three-omega method.</a> Nano Lett. 6, 1589-1593 (2006).</li><li>Hou, J. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermal+characterization+of+single-wall+carbon+nanotube+bundles+using+the+self-heating+3-omega+technique.">Thermal characterization of single-wall carbon nanotube bundles using the self-heating 3-omega technique.</a> J. Appl. Phys. 100, (2006).</li><li>Kim, P., Shi, L., Majumdar, A., McEuen, P. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermal+transport+measurements+of+individual+multiwalled+nanotubes.">Thermal transport measurements of individual multiwalled nanotubes.</a> Phys. Rev. Lett. 87, (2001).</li><li>Kim, P., Shi, L., Majumdar, A., McEuen, P. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mesoscopic+thermal+transport+and+energy+dissipation+in+carbon+nanotubes.">Mesoscopic thermal transport and energy dissipation in carbon nanotubes.</a> Physica B Condens. Matter. 323, 67-70 (2002).</li><li>Shi, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measuring+thermal+and+thermoelectric+properties+of+one-dimensional+nanostructures+using+a+microfabricated+device.">Measuring thermal and thermoelectric properties of one-dimensional nanostructures using a microfabricated device.</a> J. Heat Transfer. 125, 881-888 (2003).</li><li>Li, D. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermal+conductivity+of+individual+silicon+nanowires.">Thermal conductivity of individual silicon nanowires.</a> Appl. Phys. Lett. 83, 2934-2936 (2003).</li><li>Shi, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermal+conductivities+of+individual+tin+dioxide+nanobelts.">Thermal conductivities of individual tin dioxide nanobelts.</a> Appl. Phys. Lett. 84, 2638-2640 (2004).</li><li>Feng, X. H., Wang, X. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermophysical+properties+of+free-standing+micrometer-thick+Poly+(3-hexylthiophene)+films.">Thermophysical properties of free-standing micrometer-thick Poly (3-hexylthiophene) films.</a> Thin Solid Films. 519, 5700-5705 (2011).</li><li>Feng, X., Wang, X., Chen, X., Yue, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermo-physical+properties+of+thin+films+composed+of+anatase+TiO2+nanofibers.">Thermo-physical properties of thin films composed of anatase TiO2 nanofibers.</a> Acta Mater. 59, 1934-1944 (2011).</li><li>Guo, J. Q., Wang, X. W., Zhang, L. J., Wang, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transient+thermal+characterization+of+micro/submicroscale+polyacrylonitrile+wires.">Transient thermal characterization of micro/submicroscale polyacrylonitrile wires.</a> Appl. Phys. A Mater. Sci. Process. 89, 153-156 (2007).</li><li>Hu, H. P., Wang, X. W., Xu, X. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Generalized+theory+of+the+photoacoustic+effect+in+a+multilayer+material.">Generalized theory of the photoacoustic effect in a multilayer material.</a> J. Appl. Phys. 86, 3953-3958 (1999).</li><li>Wang, X. W., Hu, H. P., Xu, X. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photo-acoustic+measurement+of+thermal+conductivity+of+thin+films+and+bulk+materials.">Photo-acoustic measurement of thermal conductivity of thin films and bulk materials.</a> J. Heat. Transfer. 123, 138-144 (2001).</li><li>Wang, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+zirconium(IV)+propoxide+concentration+on+the+thermophysical+properties+of+hybrid+organic-inorganic+films.">Effect of zirconium(IV) propoxide concentration on the thermophysical properties of hybrid organic-inorganic films.</a> J. Appl. Phys. 104, (2008).</li></ol>

没有什么可以透露。

在实验过程中，三个步骤[步骤2），3）和5）]是用于精确地表征热性能的成功很关键。步骤2）和3），备受关注需要在施加银膏只在样品电极接触支付。这是很容易污染的悬浮​​样品用银膏，和热性质将增加，如果发生这种情况。因此，在步骤3）中，检查样品与显微镜仔细，如果任何污染，银膏施加或延伸至悬浮样品被注意到的，一个新的样本需要进行的实验制备。 当式（10）简化为式（11）中，假定该实验是在真空室中以非常低的压力（1-3毫乇）进行的，所以该气体传导效果是微不足道的。做了一系列的测试在不同的压力后，可以确认的是，在公式10中，气体的行为离子系数 h正比于压力p为h =γP。系数γ是关系到一个叫做热协调系数反映的能量耦合/交换系数，当气体分子撞击材料表面参数。γ可以计算为ξπ2DρcP /（4L 2）其中，ξ是斜率对压力的热扩散系数γ的变化从样品到样品。该气体传导系数可以强烈影响，在TET表征该材料的表面结构和空间配置在腔室中。步骤5），进行实验在非常低的压力（1-3毫托）将确保这个复杂的气体传导效应可以忽略不计。 通过这种技术测量的样品的表面发射率（ε），也可以计算无线TH基于体积的比热（ρCP），它可以从校准获得，非接触式光热技术或13-15分别测量密度和比热的给定值。减去寄生传导的影响后，在图6所示的热扩散率（α+实弧度 ）仅具有辐射损失的影响， <img alt="" fo:content-width="2in" height="60" src="/files/ftp_upload/51144/51144_clip_image002_0011.gif" width="342" /> 。这是很容易知道： <img alt="" fo:content-width="1.7in" height="59" src="/files/ftp_upload/51144/51144_clip_image004_0010.gif" width="244" /> （13） 这里波 0为室温，L被测样品的直径，并且D中的样品的直径。 有在TET技术的一些局限性。一，特性时间ΔtC为日ermal运输 样品，相当于0.2026 L 2 /α1，应该比上升时间电流源（约2微秒）大得多。否则，电压变化的精度将会显著影响。因此，它要求样品长度 L不宜太小或热扩散系数α应该不会太大。第二，将样品的温度将约20-30°的实验上升。在此范围内，样品的电阻应该具有对温度的线性关系。这是因为，在理论背景的一部分，它是已知的测得的电压的变化是固有地关联到该样品的温度变化。如果样品的电阻值不必温度成线性关系，电压变化不能忍受的温度变化。第三，将样品的电压应具有线性关系的直流电流在实验期间喂食。这意味着，在一定的温度时，电阻也不会改变的直流电流的变化，当。这是众所周知，半导体就没有这个属性。 最后，该TET技术是一种非常有效和有力的方法来测量各种材料的热性能。对于相同的材料，只是测试两个样品具有不同的长度各两次，材料，如热扩散系数，导热性，和表面发射率（如果ρCp被给出）的所有重要的热性能，可被表征。

在TET技术图1是开发来测量固体材料的热扩散率，包括导电，半导电或不导电的一维结构的有效方法。在过去，单丝3ω方法2-4和微制造装置的方法5-9已经开发了在微/纳米尺度来衡量的1维结构的热性能。为了拓宽材料（导电和不导电）的测量范围，提高了精度和稳定性，瞬态电热（TET）技术已发展为微/纳米线的热物性的表征。该技术已成功地用于自由站立微米厚的聚（3 -己基噻吩）薄膜10的热特性，薄膜的锐钛矿相TiO 2纳米纤维11，单壁碳纳米管1，微/ submicroscale由聚丙烯腈导线12，和蛋白质纤维。消除（如果样品是涂有一层金，使其电子导电）和辐射损失寄生传导的影响后，实际的热扩散率可以得到。那么真正的热导率可以计算基于体积的比热（ρCP），它可以从校准时，非接触式光热技术，或者分别测量密度和比热来获得一个给定的值。

<table border="0" cellpadding="0" cellspacing="0" width="985">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:260px;">Digital Phosphor Oscilloscope</td>
			<td style="width:275px;">Tektronix</td>
			<td style="width:119px;">DPO 3052</td>
			<td style="width:331px;"> </td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:260px;">Sputter Coater</td>
			<td style="width:275px;">Denton Vacuum</td>
			<td style="width:119px;">DESK V</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:260px;">AC and DC Current Source</td>
			<td style="width:275px;">KEITHLEY</td>
			<td style="width:119px;">Model 6221</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:260px;">Laboratory Microscope</td>
			<td style="width:275px;">Olympus</td>
			<td style="width:119px;">BX41</td>
			<td></td>
		</tr>
		<tr height="27">
			<td height="27" style="height:27px;width:260px;">Dual Stage Rotary Vane Vacuum Pump</td>
			<td style="width:275px;">Varian</td>
			<td style="width:119px;">DS102</td>
			<td></td>
		</tr>
		<tr height="71">
			<td height="71" style="height:71px;width:260px;">Vacuum Chamber</td>
			<td style="width:275px;">Huntington Mechanical Laboratories</td>
			<td style="width:119px;">Customized Product</td>
			<td style="width:331px;">The pressure in the chamber should be as low as 1-3 mTorr 
			when working with the vacuum pump</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:260px;">Colloidal Silver Liquid</td>
			<td style="width:275px;">Ted Pella</td>
			<td style="width:119px;">16031</td>
			<td></td>
		</tr>
	</tbody>
</table>

characterization of thermal transport in one-dimensional solid materials

在TET（瞬态电 - 热）的技术是开发来测量固体材料的热扩散率，包括导电，半导电或不导电的一维结构的有效方法。这种技术拓宽材料（导电和非导电）的测量范围，提高了精确度和稳定性。如果样品（特别是生物材料，诸如人的头发，蜘蛛丝，和蚕丝）是不导电的，但将涂覆有金层，使电子导电。可以在数据处理过程中被减去寄生传导和热扩散率的辐射损失的效果。那么真正的热导率可以计算基于体积的比热（ρCP），它可以从校准时，非接触式光热技术或分别测量密度和比热来获得给定的值。在这项工作中，人的头发样本是使用d，来说明如何设置该实验中，处理实验数据，并减去寄生传导和辐射损失的效果。

拟合实验数据对人头部的头发样品1（长度0.788毫米，涂有金膜仅一次）示于图3。其热扩散率是在1.67×10 -7米2 /秒，它包括辐射损失和寄生传导的影响来确定。 图4是人的头发的典型SEM图像。中，短和长的样品都涂有金膜两次，并测试了两次分别根据公式12，寄生传导的效果，可以很容易地通过曲线拟合中减去， 如图5。其中拟合曲线相交的αEFF-轴的交点为αEFF的价值 当电阻是无穷大，即寄生传导的公式12中的效果是0。两个人的头发样本，不同长度进行测量，以获得两个相交。关于EXP详情erimental条件和测量结果列于表1。通过结合这两点，αEFF的关系 和L 2 / D可以被揭示。从测得的双（α1，L 1 2 / D 1）和（α2，L 2 / D 2），线性外推法（如在图6中示出），完成对L = 0的点（意味着没有的辐射损失在该点有效），并且热扩散系数为1.42×10 -7米2 /秒[=α1 - （α1 - α2）* L-1 2 / D 1 /（L 1 2 / D 1 - L 2 / D 2）]。此值反映了热DIF样品fusivity无辐射损失和寄生传导的效果。 对人的头发，密度为特征的加权几缕头发和测量其体积，并测得在1100千克/米3。比热是通过使用DSC（差示扫描量热法）测定，并测量在1.602千焦/千克K.所以真正的热传导率为0.25W /实验参数和结果对人类头发样品1米K.细节和图2是如表1所示。 <img alt="图1" fo:content-width="6in" fo:src="/files/ftp_upload/51144/51144fig1highres.jpg" src="/files/ftp_upload/51144/51144fig1.jpg" width="500px" /> 图1。 A）原理的TET实验设置和B）一个典型的V-T曲线。 <a href="https://www.jove.com/files/ftp_upload/51144/51144fig1highres.jpg" target="_blank">ç</a><html>舔这里查看大图。 <img alt="图2" fo:content-width="6in" fo:src="/files/ftp_upload/51144/51144fig2highres.jpg" src="/files/ftp_upload/51144/51144fig2.jpg" width="500px" /> 图2。 T *和它的近似使用公式9之间的差异。 <a href="https://www.jove.com/files/ftp_upload/51144/51144fig2highres.jpg" target="_blank">点击这里查看大图</a> 。 <img alt="图3" fo:content-width="6in" fo:src="/files/ftp_upload/51144/51144fig3highres.jpg" src="/files/ftp_upload/51144/51144fig3.jpg" width="500px" /> 图3。为归一化的温度上升与时间的关系（人的头发样品1）的实验数据和理论拟合结果之间的比较 。&gt;点击这里查看大图。 <img alt="图4" fo:content-width="6in" fo:src="/files/ftp_upload/51144/51144fig4highres.jpg" src="/files/ftp_upload/51144/51144fig4.jpg" width="500px" /> 图4。人类头发的典型的SEM图像 。 <a href="https://www.jove.com/files/ftp_upload/51144/51144fig4highres.jpg" target="_blank">点击这里查看大图</a> 。 <img alt="图5" fo:content-width="6in" fo:src="/files/ftp_upload/51144/51144fig5highres.jpg" src="/files/ftp_upload/51144/51144fig5.jpg" width="500px" /> 图5。拟合结果对1 / R热扩散系数的变化对人的头发样品1和2， <a href="https://www.jove.com/files/ftp_upload/51144/51144fig5highres.jpg" target="_blank">点击此处查看大图</a> 。 图6。拟合结果对人的头发样品的实际热扩散率。 <a href="https://www.jove.com/files/ftp_upload/51144/51144fig6highres.jpg" target="_blank">点击这里查看大图</a> 。 <table border="0" cellpadding="0" cellspacing="0" width="473"><colgroup><col /><col /><col /></colgroup><tbody><tr height="52"><td height="52" style="height:52px;width:249px;">人的头发样本</td><td style="width:111px;">示例1 （短） </td><td style="width:115px;">样品2 （长） </td></tr><tr height="21"><td height="21" style="height:21px;">长度（mm） </td><td> 0.788 </td><td style="width:115px;"> 1.468 </td></tr><tr height="21"><td height="21" style="height:21px;">直径（mm） </td><td> 74.0 </td><td style="width:115px;"> 77.8 </td></tr><tr height="25"><td height="25" style="height:25px;"> 真正的α+辐射 （×10 -7米2 /秒） </td><td> 1.48 </td><td style="width:115px;"> 1.62 </td></tr><tr height="25"><td height="25" style="height:25px;"> 真正的 α（×10 -7米2 /秒） </td><td colspan="2"> 1.42 </td></tr><tr height="25"><td height="25" style="height:25px;"> ρC P（×10 6焦耳/米3 K） </td><td colspan="2"> 1.76 </td></tr><tr height="25"><td height="25" style="height:25px;">实际的热导率（W /米K） </td><td colspan="2"> 0.25 </td></tr></tbody></table> 表1：实验参数和结果对人类头发的详细信息。

Watch this Scientific Journal Video about Characterization of Thermal Transport in One-dimensional Solid Materials at JoVE.com

Characterization of Thermal Transport in One-dimensional Solid Materials

该TET（瞬态电热）技术是开发测量固体材料的热扩散率的有效途径。

在一维固体材料的热传输的特性

The TET (transient electro-thermal) technique is an effective approach developed to measure the thermal diffusivity of solid materials, including ...

characterization-thermal-transport-one-dimensional-solid

Research

Education

JoVE Journal

JoVE Core

Physics

Engineering

Unit 1

Motion Along a Straight Line

SCIENTISTS IN ACTION

16.5K 次观看.  Iowa State University. 该TET（瞬态电热）技术是开发测量固体材料的热扩散率的有效途径。 

视频: Characterization of Thermal Transport in One-dimensional Solid Materials

Solid-state Graft Copolymer Electrolytes for Lithium Battery Applications

Battery safety has been a very important research area over the past decade. Commercially available lithium ion batteries employ low flash point (&lt;80 &deg;C), flammable, and volatile organic electrolytes. These organic based electrolyte systems are viable at ambient temperatures, but require a cooling system to ensure that temperatures do not exceed 80 &deg;C. These cooling systems tend to increase battery costs and can malfunction which can lead to battery malfunction and explosions, thus endangering human life. Increases in petroleum prices lead to a huge demand for safe, electric hybrid vehicles that are more economically viable to operate as oil prices continue to rise. Existing organic based electrolytes used in lithium ion batteries are not applicable to high temperature automotive applications. A safer alternative to organic electrolytes is solid polymer electrolytes. This work will highlight the synthesis for a graft copolymer electrolyte (GCE) poly(oxyethylene) methacrylate (POEM) to a block with a lower glass transition temperature (Tg) poly(oxyethylene) acrylate (POEA). The conduction mechanism has been discussed and it has been demonstrated the relationship between polymer segmental motion and ionic conductivity indeed has a Vogel-Tammann-Fulcher (VTF) dependence. Batteries containing commercially available LP30 organic (LiPF6 in ethylene carbonate (EC):dimethyl carbonate (DMC) at a 1:1 ratio) and GCE were cycled at ambient temperature. It was found that at ambient temperature, the batteries containing GCE showed a greater overpotential when compared to LP30 electrolyte. However at temperatures greater than 60 &deg;C, the GCE cell exhibited much lower overpotential due to fast polymer electrolyte conductivity and nearly the full theoretical specific capacity of 170 mAh/g was accessed.

Lithium ion batteries employ flammable and volatile organic electrolytes that are suitable for ambient temperature applications. A safer alternative to organic electrolytes are solid polymer batteries. Solid polymer batteries operate safely at high temperatures (&gt;120 &deg;C), thus making them applicable to high temperature applications such as deep oil drilling and hybrid electric vehicles. This paper will discuss (a) the polymer synthesis, (b) the polymer conduction mechanism, and (c) provide temperature cycling for both solid polymer and organic electrolytes.

接枝共聚物固态电解质的锂离子电池的应用

Battery safety has been a very important research area over the past decade. Commercially available lithium ion batteries employ low flash point (&lt;80 ...

科研

工程学

Probing and Mapping Electrode Surfaces in Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFCs) are potentially the most efficient and cost-effective solution to utilization of a wide variety of fuels beyond hydrogen 1-7. The performance of SOFCs and the rates of many chemical and energy transformation processes in energy storage and conversion devices in general are limited primarily by charge and mass transfer along electrode surfaces and across interfaces. Unfortunately, the mechanistic understanding of these processes is still lacking, due largely to the difficulty of characterizing these processes under in situ conditions. This knowledge gap is a chief obstacle to SOFC commercialization. The development of tools for probing and mapping surface chemistries relevant to electrode reactions is vital to unraveling the mechanisms of surface processes and to achieving rational design of new electrode materials for more efficient energy storage and conversion2. Among the relatively few in situ surface analysis methods, Raman spectroscopy can be performed even with high temperatures and harsh atmospheres, making it ideal for characterizing chemical processes relevant to SOFC anode performance and degradation8-12. It can also be used alongside electrochemical measurements, potentially allowing direct correlation of electrochemistry to surface chemistry in an operating cell. Proper in situ Raman mapping measurements would be useful for pin-pointing important anode reaction mechanisms because of its sensitivity to the relevant species, including anode performance degradation through carbon deposition8, 10, 13, 14 ("coking") and sulfur poisoning11, 15 and the manner in which surface modifications stave off this degradation16. The current work demonstrates significant progress towards this capability. In addition, the family of scanning probe microscopy (SPM) techniques provides a special approach to interrogate the electrode surface with nanoscale resolution. Besides the surface topography that is routinely collected by AFM and STM, other properties such as local electronic states, ion diffusion coefficient and surface potential can also be investigated17-22. In this work, electrochemical measurements, Raman spectroscopy, and SPM were used in conjunction with a novel test electrode platform that consists of a Ni mesh electrode embedded in an yttria-stabilized zirconia (YSZ) electrolyte. Cell performance testing and impedance spectroscopy under fuel containing H2S was characterized, and Raman mapping was used to further elucidate the nature of sulfur poisoning. In situ Raman monitoring was used to investigate coking behavior. Finally, atomic force microscopy (AFM) and electrostatic force microscopy (EFM) were used to further visualize carbon deposition on the nanoscale. From this research, we desire to produce a more complete picture of the SOFC anode.

We present a unique platform for characterizing electrode surfaces in solid oxide fuel cells (SOFCs) that allows simultaneous performance of multiple characterization techniques (e.g. in situ Raman spectroscopy and scanning probe microscopy alongside electrochemical measurements). Complementary information from these analyses may help to advance toward a more profound understanding of electrode reaction and degradation mechanisms, providing insights into rational design of better materials for SOFCs.

在固体氧化物燃料电池电极表面的探测和测绘

Solid oxide fuel cells (SOFCs) are potentially the most efficient and cost-effective solution to utilization of a wide variety of fuels beyond hydrogen ...

Characterization of Electrode Materials for Lithium Ion and Sodium Ion Batteries Using Synchrotron Radiation Techniques

Intercalation compounds such as transition metal oxides or phosphates are the most commonly used electrode materials in Li-ion and Na-ion batteries. During insertion or removal of alkali metal ions, the redox states of transition metals in the compounds change and structural transformations such as phase transitions and/or lattice parameter increases or decreases occur. These behaviors in turn determine important characteristics of the batteries such as the potential profiles, rate capabilities, and cycle lives. The extremely bright and tunable x-rays produced by synchrotron radiation allow rapid acquisition of high-resolution data that provide information about these processes. Transformations in the bulk materials, such as phase transitions, can be directly observed using X-ray diffraction (XRD), while X-ray absorption spectroscopy (XAS) gives information about the local electronic and geometric structures (e.g.&#160;changes in redox states and bond lengths). In situ experiments carried out on operating cells are particularly useful because they allow direct correlation between the electrochemical and structural properties of the materials. These experiments are time-consuming and can be challenging to design due to the reactivity and air-sensitivity of the alkali metal anodes used in the half-cell configurations, and/or the possibility of signal interference from other cell components and hardware. For these reasons, it is appropriate to carry out ex situ experiments (e.g.&#160;on electrodes harvested from partially charged or cycled cells) in some cases. Here, we present detailed protocols for the preparation of both ex situ and in situ samples for experiments involving synchrotron radiation and demonstrate how these experiments are done.

We describe the use of synchrotron X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) techniques to probe details of intercalation/deintercalation processes in electrode materials for Li-ion and Na-ion batteries. Both in situ and ex situ experiments are used to understand structural behavior relevant to the operation of devices

正极材料的同步辐射技术锂离子和钠离子电池表征

Intercalation compounds such as transition metal oxides or phosphates are the most commonly used electrode materials in Li-ion and Na-ion batteries. ...

Comprehensive Characterization of Extended Defects in Semiconductor Materials by a Scanning Electron Microscope

Extended defects such as dislocations and grain boundaries have a strong influence on the performance of microelectronic devices and on other applications of semiconductor materials. However, it is still under debate how the defect structure determines the band structure, and therefore, the recombination behavior of electron-hole pairs responsible for the optical and electrical properties of the extended defects. The present paper is a survey of procedures for the spatially resolved investigation of structural and of physical properties of extended defects in semiconductor materials with a scanning electron microscope (SEM). Representative examples are given for crystalline silicon. The luminescence behavior of extended defects can be investigated by cathodoluminescence (CL) measurements. They are particularly valuable because spectrally and spatially resolved information can be obtained simultaneously. For silicon, with an indirect electronic band structure, CL measurements should be carried out at low temperatures down to 5 K due to the low fraction of radiative recombination processes in comparison to non-radiative transitions at room temperature. For the study of the electrical properties of extended defects, the electron beam induced current (EBIC) technique can be applied. The EBIC image reflects the local distribution of defects due to the increased charge-carrier recombination in their vicinity. The procedure for EBIC investigations is described for measurements at room temperature and at low temperatures. Internal strain fields arising from extended defects can be determined quantitatively by cross-correlation electron backscatter diffraction (ccEBSD). This method is challenging because of the necessary preparation of the sample surface and because of the quality of the diffraction patterns which are recorded during the mapping of the sample. The spatial resolution of the three experimental techniques is compared.

The optical, electrical, and structural properties of dislocations and of grain boundaries in semiconductor materials can be determined by experiments performed in a scanning electron microscope. Electron microscopy has been used to investigate cathodoluminescence, electron beam induced current, and diffraction of backscattered electrons.

通过扫描电子显微镜在半导体材料的扩展缺陷的全面表征

Extended defects such as dislocations and grain boundaries have a strong influence on the performance of microelectronic devices and on other applications ...

High-resolution Thermal Micro-imaging Using Europium Chelate Luminescent Coatings

Micro-electronic devices often undergo significant self-heating when biased to their typical operating conditions. This paper describes a convenient optical micro-imaging technique which can be used to map and quantify such behavior. Europium thenoyltrifluoroacetonate (EuTFC) has a 612 nm luminescence line whose activation efficiency drops strongly with increasing temperature, due to T-dependent interactions between the Eu3+ ion and the organic chelating compound. This material may be readily coated on to a sample surface by thermal sublimation in vacuum. When the coating is excited with ultraviolet light (337 nm) an optical micro-image of the 612 nm luminescent response can be converted directly into a map of the sample surface temperature. This technique offers spatial resolution limited only by the microscope optics (about 1 micron) and time resolution limited by the speed of the camera employed. It offers the additional advantages of only requiring comparatively simple and non-specialized equipment, and giving a quantitative probe of sample temperature.

Europium thenoyltrifluoroacetonate (EuTFC) has an optical luminescence line at 612 nm, whose activation efficiency decreases strongly with temperature. If a sample coated with a thin film of this material is micro-imaged, the 612 nm luminescent response intensity may be converted into a direct map of sample surface temperature.

高分辨率热显微成像采用铕螯合物的荧光涂料

Micro-electronic devices often undergo significant self-heating when biased to their typical operating conditions. This paper describes a convenient ...

Characterization of Ultra-fine Grained and Nanocrystalline Materials Using Transmission Kikuchi Diffraction

One of the challenges in microstructure analysis nowadays resides in the reliable and accurate characterization of ultra-fine grained (UFG) and nanocrystalline materials. The traditional techniques associated with scanning electron microscopy (SEM), such as electron backscatter diffraction (EBSD), do not possess the required spatial resolution due to the large interaction volume between the electrons from the beam and the atoms of the material. Transmission electron microscopy (TEM) has the required spatial resolution. However, due to a lack of automation in the analysis system, the rate of data acquisition is slow which limits the area of the specimen that can be characterized. This paper presents a new characterization technique, Transmission Kikuchi Diffraction (TKD), which enables the analysis of the microstructure of UFG and nanocrystalline materials using an SEM equipped with a standard EBSD system. The spatial resolution of this technique can reach 2 nm. This technique can be applied to a large range of materials that would be difficult to analyze using traditional EBSD. After presenting the experimental set up and describing the different steps necessary to realize a TKD analysis, examples of its use on metal alloys and minerals are shown to illustrate the resolution of the technique and its flexibility in term of material to be characterized.

This paper provides a detailed method to characterize the microstructure of ultra-fine grained and nanocrystalline materials using a scanning electron microscope equipped with a standard electron backscatter diffraction system. Metal alloys and minerals presenting refined microstructures are analyzed using this technique, showing the diversity of its possible applications.

超细晶和纳米晶材料的表征采用透射菊池衍射

One of the challenges in microstructure analysis nowadays resides in the reliable and accurate characterization of ultra-fine grained (UFG) and ...

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

Electrically assisted deformation (EAD) is increasingly being used to improve the formability of metals during processes such as sheet metal rolling and forging. Adoption of this technique is proceeding despite disagreement concerning the underlying mechanism responsible for EAD. The experimental procedure described herein enables a more explicit study compared to previous EAD research by removing thermal effects, which are responsible for disagreement in interpreting previous EAD results. Furthermore, as the procedure described here enables EAD observation in situ and in real time in a transmission electron microscope (TEM), it is superior to existing post-mortem methods that observe EAD effects post-test. Test samples consist of a single crystal copper (SCC) foil having a free-standing tensile test section of nanoscale thickness, fabricated using a combination of laser and ion beam milling. The SCC is mounted to an etched silicon base that provides mechanical support and electrical isolation while serving as a heat sink. Using this geometry, even at high current density (~3,500 A/mm2), the test section experiences a negligible temperature increase (&#60;0.02 &#176;C), thus eliminating Joule heating effects. Monitoring material deformation and identifying the corresponding changes to microstructures, e.g. dislocations, are accomplished by acquiring and analyzing a series of TEM images. Our sample preparation and in situ experiment procedures are robust and versatile as they can be readily utilized to test materials with different microstructures, e.g., single and polycrystalline copper.

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

Isolating electrical and thermal effects on electrically assisted deformation (EAD) is very difficult using macroscopic samples. Metallic sample micro- and nanostructures together with a custom test procedure have been developed to evaluate the impact of applied current on the formation without joule heating and evolution of dislocations on these samples.

一种新的方法<em&gt;原位</em&gt;纳米级样品的机电表征

Electrically assisted deformation (EAD) is increasingly being used to improve the formability of metals during processes such as sheet metal rolling and ...

Focused Ion Beam Fabrication of LiPON-based Solid-state Lithium-ion Nanobatteries for In Situ Testing

Solid-state electrolytes are a promising replacement for current organic liquid electrolytes, enabling higher energy densities and improved safety of lithium-ion (Li-ion) batteries. However, a number of setbacks prevent their integration into commercial devices. The main limiting factor is due to nanoscale phenomena occurring at the electrode/electrolyte interfaces, ultimately leading to degradation of battery operation. These key problems are highly challenging to observe and characterize as these batteries contain multiple buried interfaces. One approach for direct observation of interfacial phenomena in thin film batteries is through the fabrication of electrochemically active nanobatteries by a focused ion beam (FIB). As such, a reliable technique to fabricate nanobatteries was developed and demonstrated in recent work. Herein, a detailed protocol with a step-by-step process is presented to enable the reproduction of this nanobattery fabrication process. In particular, this technique was applied to a thin film battery consisting of LiCoO2/LiPON/a-Si, and has further been previously demonstrated by in situ cycling within a transmission electron microscope.

Focused Ion Beam Fabrication of LiPON-based Solid-state Lithium-ion Nanobatteries for In Situ Testing

A protocol for the fabrication of electrochemically active LiPON-based solid-state lithium-ion nanobatteries using a focused ion beam is presented.

基于 LiPON 的固态锂离子 Nanobatteries 的聚焦离子束制备方法在原位测试中的研究

Solid-state electrolytes are a promising replacement for current organic liquid electrolytes, enabling higher energy densities and improved safety of ...

Electric-field Control of Electronic States in WS2 Nanodevices by Electrolyte Gating

A method of carrier number control by electrolyte gating is demonstrated. We have obtained WS2 thin flakes with atomically flat surface via scotch tape method or individual WS2 nanotubes by dispersing the suspension of WS2 nanotubes. The selected samples have been fabricated into devices by the use of the electron beam lithography and electrolyte is put on the devices. We have characterized the electronic properties of the devices under applying the gate voltage. In the small gate voltage region, ions in the electrolyte are accumulated on the surface of the samples which leads to the large electric potential drop and resultant electrostatic carrier doping at the interface. Ambipolar transfer curve has been observed in this electrostatic doping region. When the gate voltage is further increased, we met another drastic increase of source-drain current which implies that ions are intercalated into layers of WS2 and electrochemical carrier doping is realized. In such electrochemical doping region, superconductivity has been observed. The focused technique provides a powerful strategy for achieving the electric-filed-induced quantum phase transition.

Electric-field Control of Electronic States in WS2 Nanodevices by Electrolyte Gating

Here, we present a protocol to control the carrier number in solids by using the electrolyte.

用电解质浇注法对 WS2纳米器件电子态的电场控制

A method of carrier number control by electrolyte gating is demonstrated. We have obtained WS2 thin flakes with atomically flat surface via scotch tape ...

Ultrasonic Fatigue Testing in the Tension-Compression Mode

Ultrasonic fatigue testing is one of a few methods which allow investigating fatigue properties in the ultra-high cycle region. The method is based on exposing the specimen to longitudinal vibrations on its resonance frequency close to 20 kHz. With use of this method, it is possible to significantly decrease the time required for the test, when compared to conventional testing devices usually working at frequencies under 200 Hz. It is also used to simulate loading of material during operation in high speed conditions, such as those experienced by components of jet engines or car turbo pumps. It is necessary to operate only in the high and ultra-high cycle region, due to the possibility of extremely high deformation rates, which can have a significant influence on the test results. Specimen shape and dimensions have to be carefully selected and calculated to fulfill the resonance condition of the ultrasonic system; thus, it is not possible to test the full components or specimens of arbitrary shape. Before each test, it is necessary to harmonize the specimen with the frequency of the ultrasonic system to compensate for deviations of the real shape from the ideal one. It is not possible to run a test until a total fracture of the specimen, since the test is automatically terminated after initiation and propagation of the crack to a certain length, when the stiffness of the system changes enough to shift the system out of the resonance frequency. This manuscript describes the process of evaluation of materials' fatigue properties at high-frequency ultrasonic fatigue loading with use of mechanical resonance at a frequency close to 20 kHz. The protocol includes a detailed description of all steps required for a correct test, including specimen design, stress calculation, harmonizing with the resonance frequency, performing the test, and final static fracture.

A protocol for ultrasonic fatigue testing in the high and ultra-high cycle region in axial tension-compression loading mode.

拉伸压缩模式下的超声疲劳试验

Ultrasonic fatigue testing is one of a few methods which allow investigating fatigue properties in the ultra-high cycle region. The method is based on ...