这项研究得到了院气候变化研究中心的支持 (格兰特 No。N11160012), 由科学、ICT 和未来规划部资助的韩国国家研究基金会领导的国外研究院招聘项目 (赠款 No. 2011-0030065), 主要的人力资源培训计划通过由科学、ICT 和未来规划部资助的韩国国家研究基金会 (NRF) 的区域新产业 (批准号:NRF-2016H1D5A1910603)。他们的支持得到了极大的赞赏。

1. 材料准备 <ol> <li> 复合材料的制备 注: 警告, 请在使用前查阅所有相关的材料安全数据表 (MSDS)。这些方法中使用的几种化学物质可能是有毒和致癌的。纳米材料与它们的散装相比可能有额外的危害。在进行试验时, 请使用所有适当的安全做法, 包括使用工程控制 (油烟罩、手套箱) 和个人防护用品 (安全眼镜、手套、实验室大衣、全长长裤、脚趾鞋). 
	注: 根据应用的不同, 增强纤维的类型可以是以下一种或多种: 单向纤维、梭织织物、无纺毡、切碎纤维。
	<ol> <li> 单向光纤类型 <ol> <li> 使用上复合材料 (预浸料), 因为它是最方便使用的. </li>
			<li> 将预浸料堆叠在包含0和 #176; 以及90和 #176 的堆叠序列中, 以避免分裂。例如, 堆叠到 [0 3 /90 3 ] s 。
		</ol> </li> <li> 梭织织物类型 <ol> <li> 准备编织的碳织物和膜型环氧树脂。如果使用预浸料, 请跳过步骤1.1.2.1 到 1.1.2.6. </li>
			<li> 用99.5% 丙酮或另一种溶剂清洗织物脱脂。清洗后要小心处理, 避免污染。将织物放在干净的表面或无绒的擦拭上. </li>
			<li> 在室温条件下干燥10分钟, 去除溶剂. </li>
			<li> 剥离环氧树脂的备份膜, 并将1层的薄膜型环氧树脂连接到碳织物1层. </li>
			<li> 将环氧连接的碳布放在预热70和 #176 的热板上; pre-impregnation 十年代的 C. </li>
			<li> 将准备好的预浸料在环境条件下冷却10分钟, 剥离其他备份胶片. </li>
			<li> 堆叠具有所需堆叠顺序的结构; 例如, 堆叠到 [0] 3 . </li>
		</ol> </li> <li> 无纺毡 <ol> <li> 准备无纺毡。
			<li> 用99.5% 丙酮或另一种溶剂清洁毛毡以进行脱脂。清洗后要小心, 避免污染。将毛毡放在干净的表面或无绒的擦拭上. </li>
			<li> 剥离环氧树脂的备份膜, 并将3层膜型环氧树脂连接到每一侧的1股碳毡上. </li>
			<li> 将环氧附着的碳毡放在预热70和 #176 的热板上; C 为 pre-impregnation 的十年代. </li>
			<li> 将准备好的预浸料在环境条件下冷却10分钟, 剥离其他备份胶片. </li>
		</ol> </li> </ol> </li> <li> 准备软层 注: 对于软层, 含氟聚合物如聚四氟乙烯 (PTFE) 或氟化乙烯丙烯 (FEP), 聚烯烃如聚乙烯或聚丙烯, 或合成橡胶, 如硅橡胶或氟可以使用。该方案采用了 FEP 膜, 其屈服强度大大超过120和 #176; C. 25 和 #181; m 厚 FEP 适用于单向纤维和无纺毡复合材料, 而厚的100和 #181; m 厚 FEP 适合于机织面料类型复合 10 。
	<ol> <li> 清除99.5% 丙酮的软层。小心处理, 避免皱纹和针孔. </li>
		<li> 用无绒抹布擦拭软层上的丙酮。确保软层上没有污染物, 因为在固化过程中它会被转移到复合材料中。始终保持软层远离灰尘和小颗粒, 因为这些可能不仅损害了复合材料, 而且还压缩模具. </li>
	</ol> </li> </ol> 2。复合制造 <ol> 压缩模具的安装 <ol> <li> 准备一个大小为120毫米和 #215 的空腔的压缩模具; 120 mm </li>
		<li> 将模具释放到压缩模具。只需粘贴或喷雾模具释放到模具, 并擦拭无绒抹布, 直到只有薄薄的一层的模具释放保持. </li>
		<li> 将准备好的复合板切割为118毫米和 #215 的尺寸; 118 mm </li>
		<li> 放置1层25和 #181; m 厚 FEP 膜在下部模具上. </li>
		<li> 将复合层压板放在 FEP 膜上, 并在层板上放置另一 FEP 膜. </li>
		<li> 拼合软层并去除在软层和复合层压板之间的气泡. </li>
		<li> 关闭模压成型模具. </li>
	</ol> </li> <li> 压缩成型 <ol> <li> 将热烫机加热到150和 #176; C. 
		注: 模具内的试样温度为140和 #176; C 在这种情况下。如果软层采用弹性体或聚烯烃, 也可以使用较低的温度。考虑复合材料的固化温度和软层软化温度, 以确定固化温度. </li>
		<li> 将模具放置在热压机中. </li>
		<li> 使用热压机施加压力; 固化时间和压力取决于复合类型。
		<ol> <li> 对于单向纤维复合材料, 在30分钟内施加20兆帕斯卡的恒定压力; 不需要其他进程. </li>
			<li> 对于梭织织物类型的复合, 应用20兆帕斯卡。4分钟和8分钟后, 将施加的压力释放到零, 并立即再次应用20兆帕斯卡. 
			注: 这个过程被称为清除, 其目的是去除过量的树脂和被诱捕的气泡。根据复合材料的大小, 清除步骤的数量可能会增加;尺寸复合材料需要更多的清洗。
			<ol> <li> 然而, 在树脂的黏度开始增加之后, 不要清除。治疗总共30分钟. </li>
			</ol> </li> <li> 无纺毡型复合物, 适用3兆帕斯卡30分钟. 当心压力过冲, 这将导致最终产品的空隙和缺陷。慢慢增加压力, 避免压力过大. </li>
		</ol> </li> <li> 在热压机中冷却压缩模具而不将压力释放到低于120和 #176; C, 这是预制复合材料的玻璃化转变温度. </li>
		<li> 释放压力并从热压机中取出压缩模具. </li>
		<li> 从压缩模具中脱模最终产品. </li>
	</ol>
	</li>
</ol>

<ol>
	<li>Hwang, I. U., 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=Bipolar+plate+made+of+carbon+fiber+epoxy+composite+for+polymer+electrolyte+membrane+fuel+cells.">Bipolar plate made of carbon fiber epoxy composite for polymer electrolyte membrane fuel cells.</a> J Power Sources. 184 (1), 90-94 (2008).</li><li>Avasarala, B., Haldar, P. <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+surface+roughness+of+composite+bipolar+plates+on+the+contact+resistance+of+a+proton+exchange+membrane+fuel+cell.">Effect of surface roughness of composite bipolar plates on the contact resistance of a proton exchange membrane fuel cell.</a> J Power Sources. 188 (1), 225-229 (2009).</li><li>Yu, H. N., Lim, J. W., Kim, M. K., Lee, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plasma+treatment+of+the+carbon+fiber+bipolar+plate+for+PEM+fuel+cell.">Plasma treatment of the carbon fiber bipolar plate for PEM fuel cell.</a> Compos Struct. 94 (5), 1911-1918 (2012).</li><li>Lim, J. W., Lee, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+composite-metal+hybrid+bipolar+plates+for+PEM+fuel+cells.">Development of composite-metal hybrid bipolar plates for PEM fuel cells.</a> Int J Hydrogen Energy. 37 (17), (2012).</li><li>Kim, B. G., Lee, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electromagnetic-carbon+surface+treatment+of+composite+bipolar+plate+for+high-efficiency+polymer+electrolyte+membrane+fuel+cells.">Electromagnetic-carbon surface treatment of composite bipolar plate for high-efficiency polymer electrolyte membrane fuel cells.</a> J Power Sources. 195 (6), 1577-1582 (2010).</li><li>Kim, B. G., Lim, J. W., Lee, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+single-type+aluminum/composite+hybrid+bipolar+plate+with+surface+modification+for+high+efficiency+PEMFC.">A single-type aluminum/composite hybrid bipolar plate with surface modification for high efficiency PEMFC.</a> Int J Hydrogen Energy. 36 (4), 3087-3095 (2011).</li><li>Yu, H. N., Lim, J. W., Suh, J. D., Lee, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+graphite-coated+carbon+fiber+epoxy+composite+bipolar+plate+for+polymer+electrolyte+membrane+fuel+cell.">A graphite-coated carbon fiber epoxy composite bipolar plate for polymer electrolyte membrane fuel cell.</a> J Power Sources. 196 (23), 9868-9875 (2011).</li><li>Kim, K. H., Kim, B. G., Lee, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+carbon+composite+bipolar+plate+(BP)+for+vanadium+redox+flow+battery+(VRFB).">Development of carbon composite bipolar plate (BP) for vanadium redox flow battery (VRFB).</a> Compos Struct. 109, 253-259 (2014).</li><li>Lee, D., Lim, J. W., Nam, S., Choi, I., Lee, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gasket-integrated+carbon/silicone+elastomer+composite+bipolar+plate+for+high-temperature+PEMFC.">Gasket-integrated carbon/silicone elastomer composite bipolar plate for high-temperature PEMFC.</a> Compos Struct. 128, 284-290 (2015).</li><li>Lee, D., Lee, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electro-mechanical+properties+of+the+carbon+fabric+composites+with+fibers+exposed+on+the+surface.">Electro-mechanical properties of the carbon fabric composites with fibers exposed on the surface.</a> Compos Struct. 140, 77-83 (2016).</li><li>Lee, D., Lim, J. W., Nam, S., Choi, I., Lee, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Method+for+exposing+carbon+fibers+on+composite+bipolar+plates.">Method for exposing carbon fibers on composite bipolar plates.</a> Compos Struct. 134, 1-9 (2015).</li><li>Lee, D., Lee, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Carbon+composite+bipolar+plate+for+high-temperature+proton+exchange+membrane+fuel+cells+(HT-PEMFCs).">Carbon composite bipolar plate for high-temperature proton exchange membrane fuel cells (HT-PEMFCs).</a> J Power Sources. 327, 119-126 (2016).</li><li>Lee, D., Choe, J., Nam, S., Lim, J. W., Choi, I., Lee, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+non-woven+carbon+felt+composite+bipolar+plates+using+the+soft+layer+method.">Development of non-woven carbon felt composite bipolar plates using the soft layer method.</a> Compos struct. 160, 976-982 (2016).</li><li>Lee, D., Lim, J. W., Lee, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cathode/anode+integrated+composite+bipolar+plate+for+high-temperature+PEMFC.">Cathode/anode integrated composite bipolar plate for high-temperature PEMFC.</a> Compos Struct. 167, 144-151 (2017).</li><li>Lee, D., Oh, Y., Nam, S., Choe, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adhesion+Characteristics+of+Fiber-exposed+Glass+Composites.">Adhesion Characteristics of Fiber-exposed Glass Composites.</a> Compos Struct. 165, 9-14 (2017).</li></ol>

作者没有什么可透露的。

与传统方法相比, 软层法具有明显的优越性, 且制造成本较低。软层法制备的三种复合材料的电学性能、力学性能、透气性、附着力等方面都具有独特的特性。
对于电学性能的测量, 采用了四点探针法。对 ASR 进行了5次测量, 平均值作为双极板的代表值。共测量了五双极板, 并对误差条使用了最大和最小的 ASR 值。
由于暴露的碳纤维 (图 2a</st...

双极板是能量转换系统和能量存储系统 (如燃料电池和电池) 的多功能关键部件。双极板的关键功能要求如下: 高电导率在穿过厚度方向, 以减少欧姆损耗, 高机械性能, 承受高压实压力和外部冲击, 以及高批量生产的生产率。
与传统上采用的石墨和金属作为双极板材料相比, 碳纤维/环氧树脂复合材料具有较高的比强度和刚度, 这表明系统的重量可以大大降低用复合材料取代传统的双极板材料1。然而, 传统的碳/环氧复合材料在穿透厚度方向上的导电性较差, 导致了大面积的电阻 (ASR), 这是由于复合表面上形成了树脂丰富的层。该绝缘树脂层防止导电炭纤维与相邻元件之间的直接接触, 如另双极板、气体扩散层 (GDL) 和碳毡电极。
许多研究是为了解决高 ASR 由于树脂丰富的层。第一种方法是表面处理方法, 以选择性地去除树脂丰富的层。例如, 机械磨损试图去除表面上的树脂2。然而, 碳纤维也被损坏, 导致了一个糟糕的 ASR。等离子体处理3、4和微波处理方法5、6也被开发以避免纤维损坏, 但它们导致生产率和均匀性低下。第二种方法, 导电层涂层方法, 包括膨胀石墨涂层7,8。该方法成功地降低了 ASR, 被认为是制造复合双极板的标准方法。然而, 它是昂贵的, 有耐久性和分层问题, 由于机械强度低。
在这项研究中, "软层法", 一种新的制造方法, 可以暴露碳纤维的复合双极板表面, 证明。该方法的主要目的是获得低的 ASR, 低的制造成本。软层法采用薄软层, 如在压缩模和双极板之间的聚合物释放膜。在压缩模和软层分离后, 制备的双极板显示在表面上暴露的碳纤维, 无任何 post-surface 处理。该方法不仅降低了 ASR, 而且大大提高了机械性能, 解决了气体渗透性问题。这种方法可用于许多其他用途: 发展一个导电板, 制造一个薄的复合材料, 和制造的粘合剂连接没有表面处理。

<table width="891">
	<tbody>
		<tr height="21" style="height:15.75pt">
			<td class="xl63" height="21" style="width:223pt;height:15.75pt" width="297">Unidirectional carbon/epoxy prepreg</td>
			<td class="xl63" style="width:72pt" width="96">SK Chemicals</td>
			<td class="xl63" style="width:110pt" width="146">USN020</td>
			<td class="xl66" style="width:264pt" width="352">Used to fabricate unidirectional carbon composite</td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl63" height="21" style="width:223pt;height:15.75pt" width="297">Plain weave carbon fabric/epoxy prepreg</td>
			<td class="xl63" style="width:72pt" width="96">SK Chemicals</td>
			<td class="xl63" style="width:110pt" width="146">WSN 1k</td>
			<td class="xl66">Used to fabricate fabric carbon composite</td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl63" height="21" style="width:223pt;height:15.75pt" width="297">Plain weave carbon fabric</td>
			<td class="xl63" style="width:72pt" width="96">SK Chemicals</td>
			<td class="xl63" style="width:110pt" width="146">C-112</td>
			<td class="xl66">Used to fabricate fabric carbon composite</td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl63" height="21" style="width:223pt;height:15.75pt" width="297">Non-woven carbon felt</td>
			<td class="xl63" style="width:72pt" width="96">Newell</td>
			<td class="xl63" style="width:110pt" width="146">Graphite felt 3 mm</td>
			<td class="xl66">Used to fabricated felt carbon composite</td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl63" height="21" style="width:223pt;height:15.75pt" width="297">Film type epoxy resin</td>
			<td class="xl63" style="width:72pt" width="96">SK Chemicals</td>
			<td class="xl63" style="width:110pt" width="146">K51</td>
			<td class="xl66">Used as a matrix of the composite</td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl63" height="21" style="width:223pt;height:15.75pt" width="297">Acetone 99.5%</td>
			<td class="xl63" style="width:72pt" width="96">Samchun</td>
			<td class="xl63" style="width:110pt" width="146">67-64-1</td>
			<td class="xl66">Used to cleanse the carbon fiber and the soft layers</td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl63" height="21" style="width:223pt;height:15.75pt" width="297">Mold release</td>
			<td class="xl63" style="width:72pt" width="96">ShinEtsu</td>
			<td class="xl63" style="width:110pt" width="146">KF-96</td>
			<td class="xl66">Used to coat the mold</td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl63" height="21" style="width:223pt;height:15.75pt" width="297">Release film</td>
			<td class="xl63" style="width:72pt" width="96">Airtech</td>
			<td class="xl63" style="width:110pt" width="146">A4000V</td>
			<td class="xl66">Used as a soft layer</td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl63" height="21" style="width:223pt;height:15.75pt" width="297">Compression mold</td>
			<td class="xl63" style="width:72pt" width="96">N/A</td>
			<td class="xl63" style="width:110pt" width="146">N/A</td>
			<td class="xl66">Machined in lab. Material: NAK80</td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl63" height="21" style="width:223pt;height:15.75pt" width="297">Hot press</td>
			<td class="xl63" style="width:72pt" width="96">Hydrotek 100</td>
			<td class="xl63" style="width:110pt" width="146">N/A</td>
			<td class="xl66">Used to apply pressure and heat</td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl63" height="21" style="width:223pt;height:15.75pt" width="297">Scanning electron microscope</td>
			<td class="xl63" style="width:72pt" width="96">FEI Compnay</td>
			<td class="xl63" style="width:110pt" width="146">Magellan 400</td>
			<td class="xl66">Used to investigate the surface of the composite</td>
		</tr>
	</tbody>
</table>

experimental implementation of a new composite fabrication method: exposing bare fibers on the composite surface by the soft layer method

双极板是质子交换膜燃料电池 (电池) 和钒氧化还原流电池 (VRFBs) 的关键部件。它是一种具有高导电性、高机械性能和高生产率的多功能元件。
在这方面, 碳纤维/环氧树脂复合材料可以是取代传统的石墨双极板的理想材料, 这往往导致整个系统的灾难性故障, 因为其固有的脆性。虽然碳/环氧树脂复合材料具有很高的机械性能, 易于制造, 但由于在其表面形成了富树脂层, 所以通过厚度方向的导电性较差。因此, 采用膨胀石墨涂层来解决导电问题。然而, 膨胀石墨涂层不仅增加了制造成本, 而且机械性能较差。
在本研究中, 展示了一种在复合表面上暴露纤维的方法。目前有许多方法可以暴露纤维的表面处理后, 复合材料的制造。然而, 这种新方法不需要表面处理, 因为纤维是在复合材料制造过程中暴露出来的。通过暴露表面裸露的碳纤维, 使复合材料的导电性和机械强度大幅度提高。

使用扫描电子显微镜 (SEM) (图 1) 观察制作的标本。因为覆盖纤维顶端的富树脂层只有几微米厚, 在标本顶部观察到的光学显微图像是不合适的。通过5倾斜标本观察到的 SEM 图像提供了更具代表性的图像。与传统的模压成型复合材料相比, 采用软层法制备复合材料, 其表面覆盖有树脂, 裸露纤维无缺陷。软层法适用于单向碳复合材料、炭纤维复合材料和?...

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Experimental Implementation of a New Composite Fabrication Method: Exposing Bare Fibers on the Composite Surface by the Soft Layer Method

提出了一种通过消除树脂富区来暴露复合材料表面裸露纤维的协议。纤维被暴露在复合材料的制造过程中, 而不是通过后表面处理。暴露的碳基复合材料在穿透厚度方向和高机械性能上表现出较高的电导率。

一种新的复合制备方法的实验实现: 用软层法对复合材料表面裸露纤维进行曝光

The bipolar plate is a key component in proton exchange membrane fuel cells (PEMFCs) and vanadium redox flow batteries (VRFBs). It is a multi-functional ...

experimental-implementation-new-composite-fabrication-method-exposing

Research

JoVE Journal

Engineering

8.2K 次观看.  Korea Advanced Institute of Science and Technology. 提出了一种通过消除树脂富区来暴露复合材料表面裸露纤维的协议。纤维被暴露在复合材料的制造过程中, 而不是通过后表面处理。暴露的碳基复合材料在穿透厚度方向和高机械性能上表现出较高的电导率。

视频: Experimental Implementation of a New Composite Fabrication Method: Exposing Bare Fibers on the Composite Surface by the Soft Layer Method

Fabrication and Characterization of Disordered Polymer Optical Fibers for Transverse Anderson Localization of Light

We develop and characterize a disordered polymer optical fiber that uses transverse Anderson localization as a novel waveguiding mechanism. The developed polymer optical fiber is composed of 80,000 strands of poly (methyl methacrylate) (PMMA) and polystyrene (PS) that are randomly mixed and drawn into a square cross section optical fiber with a side width of 250 &mu;m. Initially, each strand is 200 &mu;m in diameter and 8-inches long. During the mixing process of the original fiber strands, the fibers cross over each other; however, a large draw ratio guarantees that the refractive index profile is invariant along the length of the fiber for several tens of centimeters. The large refractive index difference of 0.1 between the disordered sites results in a small localized beam radius that is comparable to the beam radius of conventional optical fibers. The input light is launched from a standard single mode optical fiber using the butt-coupling method and the near-field output beam from the disordered fiber is imaged using a 40X objective and a CCD camera. The output beam diameter agrees well with the expected results from the numerical simulations. The disordered optical fiber presented in this work is the first device-level implementation of 2D Anderson localization, and can potentially be used for image transport and short-haul optical communication systems.

We develop and characterize a disordered polymer optical fiber that uses transverse Anderson localization as a novel waveguiding mechanism. This microstructured fiber can transport a small localized beam with a radius that is comparable to the beam radius of conventional optical fibers.

无序横向安德森本地化光聚合物光纤的制备和表征

We develop and characterize a disordered polymer optical fiber that uses transverse Anderson localization as a novel waveguiding mechanism. The developed ...

科研

工程学

Fabrication of Uniform Nanoscale Cavities via Silicon Direct Wafer Bonding

Measurements of the heat capacity and superfluid fraction of confined 4He have been performed near the lambda transition using lithographically patterned and bonded silicon wafers. Unlike confinements in porous materials often used for these types of experiments3, bonded wafers provide predesigned uniform spaces for confinement. The geometry of each cell is well known, which removes a large source of ambiguity in the interpretation of data.
Exceptionally flat, 5 cm diameter, 375 &#181;m thick Si wafers with about 1 &#181;m variation over the entire wafer can be obtained commercially (from Semiconductor Processing Company, for example). Thermal oxide is grown on the wafers to define the confinement dimension in the z-direction. A pattern is then etched in the oxide using lithographic techniques so as to create a desired enclosure upon bonding. A hole is drilled in one of the wafers (the top) to allow for the introduction of the liquid to be measured. The wafers are cleaned2 in RCA solutions and then put in a microclean chamber where they are rinsed with deionized water4. The wafers are bonded at RT and then annealed at ~1,100 &#176;C. This forms a strong and permanent bond. This process can be used to make uniform enclosures for measuring thermal and hydrodynamic properties of confined liquids from the nanometer to the micrometer scale.

A method for permanently bonding two silicon wafers so as to realize a uniform enclosure is described. This includes wafer preparation, cleaning, RT bonding, and annealing processes. The resulting bonded wafers (cells) have uniformity of enclosure ~1%1,2. The resulting geometry allows for measurements of confined liquids and gasses.

通过硅直接晶圆粘接制造均匀纳米级腔

Measurements of the heat capacity and superfluid fraction of confined 4He have been performed near the lambda transition using lithographically patterned ...

A Fabrication Method for Highly Stretchable Conductors with Silver Nanowires

Stretchable electronics are identified as a key technology for electronic applications in the next generation. One of the challenges in fabrication of stretchable electronic devices is the preparation of stretchable conductors with great mechanical stability. In this study, we developed a simple fabrication method to chemically solder the contact points between silver nanowire (AgNW) networks. AgNW nanomesh was first deposited on a glass slide via spray coating method. A reactive ink composed of silver nanoparticle (AgNPs) precursors was applied over the spray coated AgNW thin films. After heating for 40 min, AgNPs were preferentially generated over the nanowire junctions to solder the AgNW nanomesh, and reinforced the conducting network. The chemically modified AgNW thin film was then transferred to polyurethane (PU) substrates by casting method. The soldered AgNW thin films on PU exhibited no obvious change in electrical conductivity under stretching or rolling process with elongation strains up to 120%.

A simple synthesis method is used to chemically solder silver nanowire thin film to fabricate highly stretchable and conductive metal conductors.

对于高伸缩的导线与银纳米线制作方法

Stretchable electronics are identified as a key technology for electronic applications in the next generation. One of the challenges in fabrication of ...

Emission Spectroscopic Boundary Layer Investigation during Ablative Material Testing in Plasmatron

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution for future high-speed reentry missions. But despite the advancements made since Apollo, heat flux prediction remains an imperfect science and engineers resort to safety factors to determine the TPS thickness. This goes at the expense of embarked payload, hampering, for example, sample return missions. 
Ground testing in plasma wind-tunnels is currently the only affordable possibility for both material qualification and validation of material response codes. The subsonic 1.2MW Inductively Coupled Plasmatron facility at the von Karman Institute for Fluid Dynamics is able to reproduce a wide range of reentry environments. This protocol describes a procedure for the study of the gas/surface interaction on ablative materials in high enthalpy flows and presents sample results of a non-pyrolyzing, ablating carbon fiber precursor. With this publication, the authors envisage the definition of a standard procedure, facilitating comparison with other laboratories and contributing to ongoing efforts to improve heat shield reliability and reduce design uncertainties.
The described core techniques are non-intrusive methods to track the material recession with a high-speed camera along with the chemistry in the reactive boundary layer, probed by emission spectroscopy. Although optical emission spectroscopy is limited to line-of-sight measurements and is further constrained to electronically excited atoms and molecules, its simplicity and broad applicability still make it the technique of choice for analysis of the reactive boundary layer. Recession of the ablating sample further requires that the distance of the measurement location with respect to the surface is known at all times during the experiment. Calibration of the optical system of the applied three spectrometers allowed quantitative comparison. At the fiber scale, results from a post-test microscopy analysis are presented.

Development of new ablative materials and their numerical modeling requires extensive experimental investigation. This protocol describes procedures for material response characterization in plasma flows with the core techniques being non-intrusive methods to track the material recession along with the chemistry in the reactive boundary layer by emission spectroscopy.

烧蚀材料在试验过程中等离子体发生器发射光谱边界层研究

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution ...

Testing of Nanoparticle Release from a Composite Containing Nanomaterial Using a Chamber System

With the rapid development of nanotechnology as one of the most important technologies in the 21st century, interest in the safety of consumer products containing nanomaterials is also increasing. Evaluating the nanomaterial release from products containing nanomaterials is a crucial step in assessing the safety of these products, and has resulted in several international efforts to develop consistent and reliable technologies for standardizing the evaluation of nanomaterial release. In this study, the release of nanomaterials from products containing nanomaterials is evaluated using a chamber system that includes a condensation particle counter, optical particle counter, and sampling ports to collect filter samples for electron microscopy analysis. The proposed chamber system is tested using an abrasor and disc-type nanocomposite material specimens to determine whether the nanomaterial release is repeatable and consistent within an acceptable range. The test results indicate that the total number of particles in each test is within 20% from the average after several trials. The release trends are similar and they show very good repeatability. Therefore, the proposed chamber system can be effectively used for nanomaterial release testing of products containing nanomaterials.

Nanoparticle release is tested using a chamber system that includes a condensation particle counter, an optical particle counter and sampling ports to collect filter samples for microscopy analysis. The proposed chamber system can be effectively used for nanomaterial release testing with a repeatable and consistent data range.

从使用室系统一个复合含纳米材料的纳米颗粒释放测试

With the rapid development of nanotechnology as one of the most important technologies in the 21st century, interest in the safety of consumer products ...

Strain Sensing Based on Multiscale Composite Materials Reinforced with Graphene Nanoplatelets

The electrical response of NH2-functionalized graphene nanoplatelets composite materials under strain was studied. Two different manufacturing methods are proposed to create the electrical network in this work: (a) the incorporation of the nanoplatelets into the epoxy matrix and (b) the coating of the glass fabric with a sizing filled with the same nanoplatelets. Both types of multiscale composite materials, with an in-plane electrical conductivity of ~10-3 S/m, showed an exponential growth of the electrical resistance as the strain increases due to distancing between adjacent functionalized graphene nanoplatelets and contact loss between overlying ones. The sensitivity of the materials analyzed during this research, using the described procedures, has been shown to be higher than commercially available strain gauges. The proposed procedures for self-sensing of the structural composite material would facilitate the structural health monitoring of components in difficult to access emplacements such as offshore wind power farms. Although the sensitivity of the multiscale composite materials was considerably higher than the sensitivity of metallic foils used as strain gauges, the value reached with NH2 functionalized graphene nanoplatelets coated fabrics was nearly an order of magnitude superior. This result elucidated their potential to be used as smart fabrics to monitor human movements such as bending of fingers or knees. By using the proposed method, the smart fabric could immediately detect the bending and recover instantly. This fact permits precise monitoring of the time of bending as well as the degree of bending.

The integration of conductive nanoparticles, such as graphene nanoplatelets, into glass fiber composite materials creates an intrinsic electrical network susceptible to strain. Here, different methods to obtain strain sensors based on the addition of graphene nanoplatelets into the epoxy matrix or as a coating on glass fabrics are proposed.

基于多尺度复合材料的增强与石墨烯纳米片应变传感

The electrical response of NH2-functionalized graphene nanoplatelets composite materials under strain was studied. Two different manufacturing methods are ...

Flow-assisted Dielectrophoresis: A Low Cost Method for the Fabrication of High Performance Solution-processable Nanowire Devices

Flow-assisted dielectrophoresis (DEP) is an efficient self-assembly method for the controllable and reproducible positioning, alignment, and selection of nanowires. DEP is used for nanowire analysis, characterization, and for solution-based fabrication of semiconducting devices. The method works by applying an alternating electric field between metallic electrodes. The nanowire formulation is then dropped onto the electrodes which are on an inclined surface to create a flow of the formulation using gravity. The nanowires then align along the gradient of the electric field and in the direction of the liquid flow. The frequency of the field can be adjusted to select nanowires with superior conductivity and lower trap density. 
In this work, flow-assisted DEP is used to create nanowire field effect transistors. Flow-assisted DEP has several advantages: it allows selection of nanowire electrical properties; control of nanowire length; placement of nanowires in specific areas; control of orientation of nanowires; and control of nanowire density in the device. 
The technique can be expanded to many other applications such as gas sensors and microwave switches. The technique is efficient, quick, reproducible, and it uses a minimal amount of dilute solution making it ideal for the testing of novel nanomaterials. Wafer scale assembly of nanowire devices can also be achieved using this technique, allowing large numbers of samples for testing and large-area electronic applications.

In this paper, flow assisted dielectrophoresis is demonstrated for the self-assembly of nanowire devices. The fabrication of a silicon nanowire field effect transistor is shown as an example.

流动辅助介: 一种低成本的制备高性能溶液可纳米线器件的方法

Flow-assisted dielectrophoresis (DEP) is an efficient self-assembly method for the controllable and reproducible positioning, alignment, and selection of ...

A Fabrication and Measurement Method for a Flexible Ferroelectric Element Based on Van Der Waals Heteroepitaxy

Flexible non-volatile memories have received much attention as they are applicable for portable smart electronic device in the future, relying on high-density data storage and low-power consumption capabilities. However, the high-quality oxide based nonvolatile memory on flexible substrates is often constrained by the material characteristics and the inevitable high-temperature fabrication process. In this paper, a protocol is proposed to directly grow an epitaxial yet flexible lead zirconium titanate memory element on muscovite mica. The versatile deposition technique and measurement method enable the fabrication of flexible yet single-crystalline non-volatile memory elements necessary for the next generation of smart devices.

In this paper, we present a protocol to directly grow an epitaxial yet flexible lead zirconium titanate memory element on muscovite mica.

基于范德华 Heteroepitaxy 的柔性铁电元件制备及测量方法

Flexible non-volatile memories have received much attention as they are applicable for portable smart electronic device in the future, relying on ...

Magnet Assisted Composite Manufacturing: A Flexible New Technique for Achieving High Consolidation Pressure in Vacuum Bag/Lay-Up Processes

This work demonstrates a protocol to improve the quality of composite laminates fabricated by wet lay-up vacuum bag processes using the recently developed magnet assisted composite manufacturing (MACM) technique. In this technique, permanent magnets are utilized to apply a sufficiently high consolidation pressure during the curing stage. To enhance the intensity of the magnetic field, and thus, to increase the magnetic compaction pressure, the magnets are placed on a magnetic top plate. First, the entire procedure of preparing the composite lay-up on a magnetic bottom steel plate using the conventional wet lay-up vacuum bag process is described. Second, placement of a set of Neodymium-Iron-Boron permanent magnets, arranged in alternating polarity, on the vacuum bag is illustrated. Next, the experimental procedures to measure the magnetic compaction pressure and volume fractions of the composite constituents are presented. Finally, methods used to characterize microstructure and mechanical properties of composite laminates are discussed in detail. The results prove the effectiveness of the MACM method in improving the quality of wet lay-up vacuum bag laminates. This method does not require large capital investment for tooling or equipment and can also be used to consolidate geometrically complex composite parts by placing the magnets on a matching top mold positioned on the vacuum bag.

A new technique for applying consolidation pressure on the vacuum bag lay-up to fabricate composite laminates is described. The goal of this protocol is to develop a simple, cost-effective technique to improve the quality of laminates fabricated by the wet lay-up vacuum bag method.

磁铁辅助复合制造: 真空袋/糊化过程中实现高固结压力的一种柔性新技术

This work demonstrates a protocol to improve the quality of composite laminates fabricated by wet lay-up vacuum bag processes using the recently developed ...

Cutting Procedures, Tensile Testing, and Ageing of Flexible Unidirectional Composite Laminates

Many body armor designs incorporate unidirectional (UD) laminates. UD laminates are constructed of thin (&#60;0.05 mm) layers of high-performance yarns, where the yarns in each layer are oriented parallel to each other and held in place using binder resins and thin polymer films. The armor is constructed by stacking the unidirectional layers in different orientations. To date, only very preliminary work has been performed to characterize the ageing of the binder resins used in unidirectional laminates and the effects on their performance. For example, during the development of the conditioning protocol used in the National Institute of Justice Standard-0101.06, UD laminates showed visual signs of delamination and reductions in V50, which is the velocity at which half of the projectiles are expected to perforate the armor, after ageing. A better understanding of the material property changes in UD laminates is necessary to comprehend the long-term performance of armors constructed from these materials. There are no current standards recommended for mechanically interrogating unidirectional (UD) laminate materials. This study explores methods and best practices for accurately testing the mechanical properties of these materials and proposes a new test methodology for these materials. Best practices for ageing these materials are also described.

The goal of the study was to develop protocols to prepare consistent specimens for accurate mechanical testing of high-strength aramid or ultra-high-molar-mass polyethylene-based flexible unidirectional composite laminate materials and to describe protocols for performing artificial ageing on these materials.

柔性单向复合层压板的切割程序、拉伸测试和老化

Many body armor designs incorporate unidirectional (UD) laminates. UD laminates are constructed of thin (&#60;0.05 mm) layers of high-performance yarns, ...