Name: preparation and reactivity of gasless nanostructured energetic materials
Uploaded: 2015-04-02T13:00:00.000+00:00
Duration: 9 min 50 s
Description: Watch this Scientific Journal Video about Preparation and Reactivity of Gasless Nanostructured Energetic Materials at JoVE.com

This material is based upon work supported by the Department of&#160;Energy, National Nuclear Security Administration,&#160;under Award Number DE-NA0002377. Funding from the Defense Threat Reduction Agency (DTRA), Grant Number HDTRA1-10-1-0119. Counter-WMD basic research program, Dr. Suhithi M. Peiris, program director is gratefully acknowledged. This work was also supported by the Ministry of Education and Science and Education of the Russian Federation in the framework of Increase Competitiveness Program of NUST &#8220;MISIS&#8221; grant No. K2-2014-001.

1.高能球磨<ol><li>制备35克初始1:1的摩尔比Ni + Al混合物。在这种情况下，称量11.02克的Al和23.98克镍粉末。 </li><li>使用不锈钢研磨罐为这个系统的高能球磨。确保该罐具有更高的硬度比所述粉末被添加，否则粉末会损坏罐子和污染也会产生。注意:典型罐子选择包括钢，氧化锆，或碳化钨。 </li><li>使用5:1球:粉末（电荷比）为这个系统中， 即 ，175克10毫米钢球。确保球是由相同的材料构成的罐否则无论是球或罐子将被损坏。 注意:荷比定义粉末和研磨剂之间的相互作用的强度。 </li><li>添加球和粉末的瓶子。 </li><li>密封的罐子和瓶子泵大气气体由机械泵和吹扫氩。进行四个周期填充和用Ar气吹洗的（这确保有剩余的罐子没有氧气）。最后，充满氩气罐子略高于（0.13兆帕）的大气压力。 </li><li>插入罐子到行星式球磨机。 </li><li>选择每分钟（rpm）650革命罐的旋转速度和1400的转速的内旋（太阳轮）。 注意:在某些情况下，总和轮（1400转）和碾磨罐（从700至1300转）的转动比（k）中的变化，以调节复合粒子的微观结构。 </li><li>运行该高能球磨过程持续15分钟。注:系统有一个关键的时候，其中所描述的条件，等于17分钟。有研磨，可以在系统上之前反应发生在罐中进行有限数量。如果高能球磨进行长于临界时间，反应将发生在球磨罐，破坏实验。 </li><li>以下的研磨时间结束时，冷却该罐至RT，然后将罐转移到通风橱。<ol><li>发泄的jar删除从最初增压和铣削过程中释放的气体可能多余的气体压力。 </li><li>从通风橱下罐子取下盖子。一定要小心打开罐子时，所形成的粉末是非常活泼。打开罐子戴耐热手套和护目镜。 </li><li>之前收集粉末，将其暴露在空气中至少5分钟，使"钝化"。 注意:这可以防止在处理的混合物中可能出现的自发反应。 </li></ol></li></ol>含能材料2.反应表征<ol><li>收集瓶子的粉末。不要使用金属铲了此过程。 <ol><li>如果分级的颗粒和分离是需要的，利用分子筛。以确保适当的分离完成后，用筛子摇动器在延长的时间周期（12+小时）。分类粉末成各种尺寸的箱（不足10微米，10-20微米，20-53微米，一波夫53微米）。从这时开始，用20-53微米大小的颗粒。 </li></ol></li><li>按筛分成粉末用单轴按设定到1100公斤5毫米的不锈钢冲压模具（1,360兆帕）为2.0分钟的停留时间沉淀。记录与微米颗粒的高度（h）和直径（d）。记录样品（米）带刻度的重量。从这里，确定该粒料的密度。计算出的理论最大密度百分比（TMD％）由下式: <img alt="式（1）" src="/files/ftp_upload/52624/52624eq1.jpg" width="400" /> 其中A 铝 ，A 镍 -铝和镍原子重量; ρ 铝和镍 ρ -铝和镍的密度。假定粉末的化学计量比保持添加的初始粉末的比率。 <ol><li>如果圆柱形粒料被用来确定一个燃烧前缘的传播速度和温度分布在反应前，确保其足够高，由高度和直径之比来确定应≥2（ 例如，D =5毫米; H≥10mm）的。 </li><li>如果粒料被用来定义点火参数，使用一个薄的磁盘（ 例如，直径为5毫米，厚度为1毫米）。 </li></ol></li><li>要定义燃烧特性，将样品到石墨板。 </li><li>使附连到可变变压器一盘绕钨丝。 </li><li>定位在W线圈，使得所述丝的螺旋部分靠在所述粒料的顶部。如果反应系统是氧敏感，为此在无氧的反应室，否则执行在露天进行反应。 </li><li>为了确定燃烧波速，使用来自高速摄像机记录。位置和集中高速热敏相机的测试样品，并开始录制。这将使准确的温度和燃烧速度的信息来收集。 </li><li&gt;慢慢转动可调变压器上，使所述钨丝升温。该反应将开始，然后传播。 </li><li>以获得在燃烧过程中所需要的参数，通过所记录的红外电影的帧进行分析帧。 <ol><li>画出反应正面传播与时间的位置。获得的曲线的斜率平均燃烧速度。 </li><li>积在样品的中间的温度变化的一个点。使用所获得的曲线图，以获得有关反应波的温度时间曲线的信息。 </li></ol></li><li>以限定点火特性（点火温度和点火延迟时间）把薄盘在热板上预热到所需的温度（ 例如，800 K）。需要注意的是，从本实验所得到的精确值将变化显著如果任何参数改变，无论是颗粒的大小，将加热板的温度，或TMD。这个分析对于determinat有用离子的发展趋势。 <ol><li>为了确定点火参数使用高速摄像机。位置和聚焦高速热敏照相机，其中所述的样品将被放置在热板上并开始记录的区域。 注意:这将使过程中精确温度信息。 <ol><li>如果反应是氧敏感，在无氧的反应室执行此。重要提示:运行这个实验中多次赢得了良好的统计数据集。 </li></ol></li><li>把球成为焦点的区域。做这样的方式，所述粒子可以看出在每个帧 - 看到的第一帧，该粒料接触的热板是重要的。 </li><li>以获得所需的点火参数，通过所记录的红外电影的帧进行分析帧。 </li><li>为了确定点火延迟时间，确定第一帧之间的时间，当粒料接触的热板的表面上，以使反应开始。 </LI&gt; <li>为了确定点火温度，标绘在颗粒上的最高温度点。当时间 - 温度分布，从该一预热温度分布到该热炸药制度的开关，拐点匹配点火温度。 </li></ol></li></ol> 3.组织分析利用场发射扫描电子显微镜（FESEM）配备了聚焦离子束（FIB） <ol><li>暂停将0.1g制备的颗粒在10毫升乙醇中并沉积一滴悬浮液上扫描电子显微镜（SEM）样本保持器的表面上。 </li><li>干燥在90℃下将样品保持器5分钟。 </li><li>将样品放入双束FIB / SEM系统。 </li><li>进行抽样等离子体清洗5分钟。注意:这降低了损坏的样品将来自曝光经历于电子束（E-束）的量。 </li><li>把电子束（5千伏，3.5 NA），并专注于一个单个粒子。链接吨他z高度的工作距离，然后抬起样品eucentric高度。 </li><li>利用电子束与气体注射针，沉积铂（70纳米）的初始层样品上，以保护免于降解从使用镓离子束（工字钢）的。 </li><li>倾斜样品52°，然后打开I-横梁上。使用工字钢（5千伏，0.28 NA），再次与气体注射针，沉积铂（0.5微米）的附加层到样品进行保护。 </li><li>削减对样品受托痕迹。磨粒子为矩形形状。这极大地增加了机会，将有足够的信用，因为将有多个切口和角落使用。 </li><li>用程序的辅助下，切片与工字钢的粒子。 <ol><li>选择"文件"，然后"图像保存位置"，选择其中的图像将被存储在目录中。 </li><li>根据单个粒子，选择适当的宽度，LENGTH和深度;通过颗粒的整个体积选择这些完全粉碎。此外，选择的切片的数目，以及每个图像切片的数量。这些选项可以在"切片"选项卡中找到。 </li><li>通过选择"工具"，然后"建议电流"设置束电流。注意:这将允许该程序来选择合适的电子束电流，以磨样品在一个合理的时间，又要防止样品损坏。 </li><li>点击"查看"，软件将提供可视化铣网格，显示了该粒子的部分将被粉碎;确保该铣削网格放置准确在粒子中要被研磨的部分上。 </li><li>每片后，采取了高品质的电子束图像重建以后。要选择合适的电子束的参数，选择"设置"菜单，然后选择"E束图像扫描参数"。 注意:这将得到一种格选择分辨率和停留时间。停留时间越高，更多的时间才能收集的图像。 </li></ol></li><li>利用三维重建软件包，如先前所描述的25重建集从FIB / SEM采集图像。注意:此产生的颗粒，然后可将其用于计算表面区域接触，单个颗粒的孔隙率，漫射层的厚度，以及无数的其他有用的参数的完整三维虚拟副本。 </li></ol>

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该协议通过使用短期高能球磨法为制备活性高能（钛+ C的Ta + C的Ni + Al）的纳米复合材料与定制微结构的详细描述。的气腹异构混合物高能球磨涉及它们的处理在高速行星式球磨机，其中该混合物的颗粒进行机械冲击的力足以脆性组分的击穿（ 例如石墨）和变形的塑料部件（ 例如，铝，钛，钽，镍）。脆的反应物被研磨成较细的颗粒，并可能成为无定形的，而塑料的金属经受多种变?...

经典高能材料， 即，炸药，推进剂和烟火是一类材料，具有高含量的储存的化学能，可以在快速的放热反应1-5被释放的，例如，通常通过组合燃料和氧化剂组成生成炸药一个分子。这些材料的能量密度非常高。例如，在分解三硝基甲苯（TNT）释放7.22千焦耳/厘米3，并且形成为每100克（ 表1）气体的8.36摩尔的时间很短的时间。这些材料组成的微米级的有机和无机物质（燃料和氧化剂）的。 铝热剂系统，其中，反应取无机化合物之间发生， 即，还原性金属（ 例如，Al）和氧化物（的Fe 2 O 3，CuO的，铋2 O 3），属于另一类型的高能材料。能量密度（15-21千焦耳/厘米3）这样的系统中的超过的TNT，然而气体产物的量（每100g 0.15-0.6摩尔）典型地比对爆炸物（ 表1）少得多。另外，纳米thermites可能呈现极高速度的燃烧波的传播（&gt; 1,000米/秒）2 ​​-5。 它最近显示6-12，若干气腹异质反应系统（镍+铝，钛+ C的Ti + B）形成金属间或者难熔化合物的也可以被认为是高能材料。这些系统的能量密度（千焦耳/厘米3）的比的TNT（ 表1）的接近或更高。同时，在反应过程中不存在的气体的产品使得这种材料的优异候选者用于各种应用，包括合成的纳米材料，耐火材料和异种份的反应性粘接，气腹微发电机， 等等 11-17。然而，相对这些系统（900-3,000 K， 见表1）相比，thermites（〜1000 K）的atively高燃点温度阻碍了他们的应用程序。工程化纳米复合材料的制备中可以显著提高气腹异构系统12-14，17的点火与燃烧特性。 许多方法已被开发来制造工程改造高能纳米复合材料，如超声波混合18,19，自组装方法如图5所示 ，溶胶-凝胶20-22，气相沉积技术16,17,23,24，以及高能量的球磨（高能球磨）1,5。纳米粉末超声混合的缺点是厚（5-10纳米）氧化物壳上的金属纳米颗粒减小的能量密度，并降低反应混合物的燃烧性能。此外，燃料和氧化剂的分布是不均匀的，并且反应物之间的界面接触不是亲密。溶胶 - 凝胶的●自组装的策略是为编制具体的铝热剂纳米复合材料的发展。尽管是低成本的技术，这些战略都没有从绿色环保的角度来看。而且，大量的杂质被引入到制备复合材料。蒸镀或者磁控溅射用于制备反应性多层箔和芯 - 壳的高能材料。它提供了复合材料的无孔和良好定义的几何形状简化理论建模和提高精度。然而，这种技术是昂贵的并且难以扩大。此外，制备的层状纳米复合材料是不稳定的某些条件。 高能球磨（高能球磨）是一种环境友好，易于扩展的方法，使纳米结构复合材料精力充沛5,9 -14有效的制造。高能球磨便宜且可以与各种反应性材料的组合物（可以使用例如 ，在rmites，形成金属间化合物，碳化物，硼化物等 ）反应。 该协议通过使用短期高能球磨法为制备活性高能（镍+铝，钛+ C钽+ C）纳米复合材料与定制微结构的详细描述。它也描述了一种高速热成像技术来确定，为制造的​​高能材料的点火/燃烧特性。最后，它显示了使用场发射扫描电子显微镜（FESEM）配备了聚焦离子束（FIB）纳米复合材料的微观结构分析。该协议是对不同的精力充沛的纳米材料（无气和铝热剂系统），可以被用作高能量密度的来源或合成和先进的纳米材料的处理通过燃烧为基础的方法的制备方法的重要指南。

<table><tbody><tr><td>Titanium</td><td>Alfa Aesar</td><td>42624</td><td>Particle size: -325 mesh
&lt;br /&gt;Purity, 99.5%</td></tr><tr><td>Graphite</td><td>Alfa Aesar</td><td>46304</td><td>Particle size: 7-11 micron
&lt;br /&gt;Purity, 99%</td></tr><tr><td>Nickel</td><td>Alfa Aesar</td><td>10256</td><td>Particle size: 3-7 micron
&lt;br /&gt;Purity, 99.9%</td></tr><tr><td>Aluminum</td><td>Alfa Aesar</td><td>11067</td><td>Particle size: -325 mesh
&lt;br /&gt;Purity, 99.5%</td></tr><tr><td>Tantalum</td><td>Materion advanced chemicals</td><td>T-2017</td><td>Particle size: 325 mesh
&lt;br /&gt;Purity, 99.9%</td></tr><tr><td>Carbon lampblack</td><td>Fisher scientific</td><td>C198-500</td><td>Particle size: 0.1 micron
&lt;br /&gt;Purity, 99.9%</td></tr><tr><td>Tungsten wire</td><td>Mcmaster Carr</td><td></td><td>0.032&quot; diameter</td></tr><tr><td>Planetary Ball Mill</td><td>Retsch GmbH, Germany</td><td></td><td></td></tr><tr><td>Uniaxial press</td><td>Carver Hydraulic</td><td></td><td></td></tr><tr><td>Sieve shaker</td><td>Gilson performer</td><td></td><td></td></tr><tr><td>Cylindrical stainless steel press die</td><td>Action Machine</td><td></td><td></td></tr><tr><td>Stainless steel sieves</td><td>Mcmaster Carr</td><td>Type 304</td><td></td></tr><tr><td>High-speed thermal camera (SC6000)</td><td>FLIR</td><td></td><td></td></tr><tr><td>Helios NanoLab 600, Field Emission Scanning Electron Microscope (FESEM) Equipped by Focus Ion Beam (FIB)</td><td>FEI</td><td></td><td></td></tr><tr><td>Cylindrical reactor with a vacuum pomp</td><td>Action Machine</td><td></td><td></td></tr><tr><td>Autoslice and View (S&amp;amp;V)</td><td>FEI</td><td></td><td></td></tr><tr><td>Avizo Fire</td><td>FEI</td><td></td><td></td></tr></tbody></table>

preparation and reactivity of gasless nanostructured energetic materials

高能球磨（高能球磨）是其中的粉末混合物放入球磨机从球经受高能碰撞一个球磨处理。除其他应用中，它是一种通用的技术，其允许有效制剂的气腹活性纳米结构材料具有高能量密度的单位体积（镍+以Al，Ta + C的Ti + C）。反应介质的结构转变，其中高能球磨过程中发生的，确定的生产充满活力的复合材料的反应机制。改变加工条件允许制造复合颗粒的研磨引起的微观结构中的微调。反过来，反应性， 即 ，自燃温度，点火延迟时间，以及反应动力学，高能量密度的材料取决于其微观结构。铣削诱导的微结构的分析表明，的试剂之间新鲜无氧亲密高表面积接触形成我š负责它们的反应性的提高。这表现在降低点火温度和延迟时间，化学反应的速率增加，反应的有效活化能的整体下降。该协议提供了使用短期高能球磨法定制微结构反应性的纳米复合材料的制备方法的详细描述。它也描述了一种高速热成像技术来确定高能材料的点火/燃烧特性。该协议可以适于制备各种纳米结构的复合材料有活力和表征。

为了制备纳米结构的复合材料有活力，希望的粉末组分的混合物（通常是微米尺寸）的预设的研磨条件下进行机械处理。处理时间（通常为几分钟）被精确地控制，以产生组成上均化的纳米复合材料的颗粒，但不允许在自立化学反应研磨期间启动。 图1和视频1表明，在复合颗粒增加几个数量级的反应物之间的接触表面面积相比，初始混合物中。高能?...

Watch this Scientific Journal Video about Preparation and Reactivity of Gasless Nanostructured Energetic Materials at JoVE.com

Preparation and Reactivity of Gasless Nanostructured Energetic Materials

本协议描述的自保纳米结构的高能材料（镍+铝，钽+ C，钛+ C）使用短期高能球磨（高能球磨）技术的准备。它还描述研究的机械制造纳米复合材料的反应性的高速热成像方法。这些协议可以扩展到其它的反应性纳米结构的高能材料。

准备和无气腹纳米结构的反应含能材料

High-Energy Ball Milling (HEBM) is a ball milling process where a powder mixture placed in the ball mill is subjected to high-energy collisions from the ...

preparation-reactivity-gasless-nanostructured-energetic

Universidad San Sebastian

Research

JoVE Journal

Engineering

10.1K 次观看.  University of Notre Dame. 本协议描述的自保纳米结构的高能材料（镍+铝，钽+ C，钛+ C）使用短期高能球磨（高能球磨）技术的准备。它还描述研究的机械制造纳米复合材料的反应性的高速热成像方法。这些协议可以扩展到其它的反应性纳米结构的高能材料。 

视频: Preparation and Reactivity of Gasless Nanostructured Energetic Materials

Simultaneous Synthesis of Single-walled Carbon Nanotubes and Graphene in a Magnetically-enhanced Arc Plasma

Carbon nanostructures such as single-walled carbon nanotubes (SWCNT) and graphene attract a deluge of interest of scholars nowadays due to their very promising application for molecular sensors, field effect transistor and super thin and flexible electronic devices1-4. Anodic arc discharge supported by the erosion of the anode material is one of the most practical and efficient methods, which can provide specific non-equilibrium processes and a high influx of carbon material to the developing structures at relatively higher temperature, and consequently the as-synthesized products have few structural defects and better crystallinity.
 To further improve the controllability and flexibility of the synthesis of carbon nanostructures in arc discharge, magnetic fields can be applied during the synthesis process according to the strong magnetic responses of arc plasmas. It was demonstrated that the magnetically-enhanced arc discharge can increase the average length of SWCNT 5, narrow the diameter distribution of metallic catalyst particles and carbon nanotubes 6, and change the ratio of metallic and semiconducting carbon nanotubes 7, as well as lead to graphene synthesis 8. 
 Furthermore, it is worthwhile to remark that when we introduce a non-uniform magnetic field with the component normal to the current in arc, the Lorentz force along the J&times;B direction can generate the plasmas jet and make effective delivery of carbon ion particles and heat flux to samples. As a result, large-scale graphene flakes and high-purity single-walled carbon nanotubes were simultaneously generated by such new magnetically-enhanced anodic arc method. Arc imaging, scanning electron microscope (SEM), transmission electron microscope (TEM) and Raman spectroscopy were employed to analyze the characterization of carbon nanostructures. These findings indicate a wide spectrum of opportunities to manipulate with the properties of nanostructures produced in plasmas by means of controlling the arc conditions.

Anodic arc discharge is one of the most practical and efficient methods to synthesize various carbon nanostructures. To increase the arc controllability and flexibility, a non-uniform magnetic field was introduced to process the one-step synthesis of large-scale graphene flakes and high-purity single-walled carbon nanotubes.

同时合成单壁碳纳米管和石墨在电弧等离子体磁增强

Carbon nanostructures such as single-walled carbon nanotubes (SWCNT) and graphene attract a deluge of interest of scholars nowadays due to their very ...

科研

生物工程

Preparation and Evaluation of Hybrid Composites of Chemical Fuel and Multi-walled Carbon Nanotubes in the Study of Thermopower Waves

When a chemical fuel at a certain position in a hybrid composite of the fuel and a micro/nanostructured material is ignited, chemical combustion occurs along the interface between the fuel and core materials. Simultaneously, dynamic changes in thermal and chemical potentials across the micro/nanostructured materials result in concomitant electrical energy generation induced by charge transfer in the form of a high-output voltage pulse. We demonstrate the entire procedure of a thermopower wave experiment, from synthesis to evaluation. Thermal chemical vapor deposition and the wet impregnation process are respectively employed for the synthesis of a multi-walled carbon nanotube array and a hybrid composite of picric acid/sodium azide/multi-walled carbon nanotubes. The prepared hybrid composites are used to fabricate a thermopower wave generator with connecting electrodes. The combustion of the hybrid composite is initiated by laser heating or Joule-heating, and the corresponding combustion propagation, direct electrical energy generation, and real-time temperature changes are measured using a high-speed microscopy system, an oscilloscope, and an optical pyrometer, respectively. Furthermore, the crucial strategies to be adopted in the synthesis of hybrid composite and initiation of their combustion that enhance the overall thermopower wave energy transfer are proposed.

A protocol for conducting thermopower wave experiments is presented. The synthesis of hybrid composites of a chemical fuel and micro/nanostructured material, manufacturing of a thermopower wave generator, and methods for measuring the corresponding physical phenomena are described.

化学燃料和多壁碳纳米管的混杂复合材料的热电波的研究准备和评估

When a chemical fuel at a certain position in a hybrid composite of the fuel and a micro/nanostructured material is ignited, chemical combustion occurs ...

工程学

Preparation of Carbon Nanosheets at Room Temperature

Amphiphilic molecules equipped with a reactive, carbon-rich "oligoyne" segment consisting of conjugated carbon-carbon triple bonds self-assemble into defined aggregates in aqueous media and at the air-water interface. In the aggregated state, the oligoynes can then be carbonized under mild conditions while preserving the morphology and the embedded chemical functionalization. This novel approach provides direct access to functionalized carbon nanomaterials. In this article, we present a synthetic approach that allows us to prepare hexayne carboxylate amphiphiles as carbon-rich siblings of typical fatty acid esters through a series of repeated bromination and Negishi-type cross-coupling reactions. The obtained compounds are designed to self-assemble into monolayers at the air-water interface, and we show how this can be achieved in a Langmuir trough. Thus, compression of the molecules at the air-water interface triggers the film formation and leads to a densely packed layer of the molecules. The complete carbonization of the films at the air-water interface is then accomplished by cross-linking of the hexayne layer at room temperature, using UV irradiation as a mild external stimulus. The changes in the layer during this process can be monitored with the help of infrared reflection-absorption spectroscopy and Brewster angle microscopy. Moreover, a transfer of the carbonized films onto solid substrates by the Langmuir-Blodgett technique has enabled us to prove that they were carbon nanosheets with lateral dimensions on the order of centimeters.

We present the synthesis of an amphiphilic hexayne and its use in the preparation of carbon nanosheets at the air-water interface from a self-assembled monolayer of these reactive, carbon-rich molecular precursors.

碳纳米片在室温下准备

Amphiphilic molecules equipped with a reactive, carbon-rich "oligoyne" segment consisting of conjugated carbon-carbon triple bonds self-assemble into ...

化学

Synthesis and Functionalization of 3D Nano-graphene Materials: Graphene Aerogels and Graphene Macro Assemblies

Efforts to assemble graphene into three-dimensional monolithic structures have been hampered by the high cost and poor processability of graphene. Additionally, most reported graphene assemblies are held together through physical interactions (e.g., van der Waals forces) rather than chemical bonds, which limit their mechanical strength and conductivity. This video method details recently developed strategies to fabricate mass-producible, graphene-based bulk materials derived from either polymer foams or single layer graphene oxide. These materials consist primarily of individual graphene sheets connected through covalently bound carbon linkers. They maintain the favorable properties of graphene such as high surface area and high electrical and thermal conductivity, combined with tunable pore morphology and exceptional mechanical strength and elasticity. This flexible synthetic method can be extended to the fabrication of polymer/carbon nanotube (CNT) and polymer/graphene oxide (GO) composite materials. Furthermore, additional post-synthetic functionalization with anthraquinone is described, which enables a dramatic increase in charge storage performance in supercapacitor applications.

This video method describes the synthesis of high surface area, monolithic 3D graphene-based materials derived from polymer precursors as well as single layer graphene oxide.

合成和3D纳米石墨烯材料的功能化:石墨烯气凝胶和石墨烯宏组件

Efforts to assemble graphene into three-dimensional monolithic structures have been hampered by the high cost and poor processability of graphene. ...

Protocol of Electrochemical Test and Characterization of Aprotic Li-O2 Battery

We demonstrate a method for electrochemical testing of an aprotic Li-O2 battery. An aprotic Li-O2 battery is made of a Li-metal anode, an aprotic electrolyte, and an O2-breathing cathode. The aprotic electrolyte is a solution of lithium salt with aprotic solvent; and porous carbon is commonly used as the cathode substrate. To improve the performance, an electrocatalyst is deposited onto the porous carbon substrate by certain deposition methods, such as atomic layer deposition (ALD) and wet-chemistry reaction. The as-prepared cathode materials are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray absorption near edge structure (XANES). A Swagelok-type cell, sealed in a glass chamber filled with pure O2, is used for the electrochemical test on a battery test system. The cells are tested under either capacity-controlled mode or voltage controlled mode. The reaction products are investigated by electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, and Raman spectroscopy to study the possible pathway of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). This protocol demonstrates a systematic and efficient arrangement of routine tests of the aprotic Li-O2 battery, including the electrochemical test and characterization of battery materials.

Protocol of Electrochemical Test and Characterization of Aprotic Li-O2 Battery

A protocol for the electrochemical testing of an aprotic Li-O2 battery with the preparation of electrodes and electrolytes and an introduction of the frequently used methods of characterization is presented here.

电化学测试的协议及表征非质子锂的O<sub&gt; 2</sub&gt;电池

We demonstrate a method for electrochemical testing of an aprotic Li-O2 battery. An aprotic Li-O2 battery is made of a Li-metal anode, an aprotic ...

Nanothermite with Meringue-like Morphology: From Loose Powder to Ultra-porous Objects

The goal of the protocol described in this article is to prepare aluminothermic compositions (nanothermites) in the form of porous, monolithic objects. Nanothermites are combustible materials made up of inorganic fuel and an oxidizer. In nanothermite foams, aluminum is the fuel and aluminum phosphate and tungsten trioxide are the oxidizing moieties. The highest flame propagation velocities (FPVs) in nanothermites are observed in loose powders and FPVs are strongly decreased by pelletizing nanothermite powders. From a physical standpoint, nanothermite loose powders are metastable systems. Their properties can be altered by unintentional compaction induced by shocks or vibrations or by the segregation of particles over time by settling phenomena, which originates from the density differences of their components. Moving from a powder to an object is the challenge that must be overcome to integrate nanothermites in pyrotechnic systems. Nanothermite objects must have both a high open porosity and good mechanical strength. Nanothermite foams meet both of these criteria, and they are prepared by dispersing a nano-sized aluminothermic mixture (Al/WO3) in orthophosphoric acid. The reaction of aluminum with the acid solution gives the AlPO4 &#34;cement&#34; in which Al and WO3 nanoparticles are embedded. In nanothermite foams, aluminum phosphate plays the dual role of binder and oxidizer. This method can be used with tungsten trioxide, which is not altered by the preparation process. It could probably be extended to some oxides, which are commonly used for the preparation of high performance nanothermites. The WO3-based nanothermite foams described in this article are particularly insensitive to impact and friction, which makes them far safer to handle than loose Al/WO3 powder. The fast combustion of these materials has interesting applications in pyrotechnic igniters. Their use in detonators as primers would require the incorporation of a secondary explosive in their composition.

This manuscript describes the synthesis of combustible aluminophosphate matrices by the reaction of orthophosphoric acid (H3PO4) with aluminum nanopowder. When this reaction is carried out with excess aluminum in the presence of tungsten trioxide nanopowder, it leads to a solid, porous nanothermite foam.

Nanothermite 与蛋白酥样形态学: 从松散的粉末到超多孔物体

The goal of the protocol described in this article is to prepare aluminothermic compositions (nanothermites) in the form of porous, monolithic objects. ...

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We present methods for depositing and passively manipulating C60 molecules on rippled graphene that advance the pursuit of realizing applications involving 1D C60/graphene hybrid structures. The techniques applied in this exposition are geared towards high vacuum systems with preparation areas capable of supporting molecular deposition as well as thermal annealing of the samples. We focus on C60 deposition at low pressure using a homemade Knudsen cell connected to a scanning tunneling microscopy (STM) system. The number of molecules deposited is regulated by controlling the temperature of the Knudsen cell and the deposition time. One-dimensional (1D) C60 chain structures with widths of two to three molecules can be prepared via tuning of the experimental conditions. The surface mobility of the C60 molecules increases with annealing temperature allowing them to move within the periodic potential of the rippled graphene. Using this mechanism, it is possible to control the transition of 1D C60 chain structures to a hexagonal close packed quasi-1D stripe structure.

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Here we present a protocol for the fabrication of C60/graphene hybrid nanostructures by physical thermal evaporation. Particularly, the proper manipulation of deposition and annealing conditions allow the control over the creation of 1D and quasi 1D C60 structures on rippled graphene.

C 型60/石墨烯混合纳米结构的制备与表征

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We ...

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

This protocol presents both the synthesis method of the Ni single atom catalyst, and the electrochemical testing of its catalytic activity and selectivity in aqueous CO2 reduction. Different from traditional metal nanocrystals, the synthesis of metal single atoms involves a matrix material that can confine those single atoms and prevent them from aggregation. We report an electrospinning and thermal annealing method to prepare Ni single atoms dispersed and coordinated in a graphene shell, as active centers for CO2 reduction to CO. During the synthesis, N dopants play a critical role in generating graphene vacancies to trap Ni atoms. Aberration-corrected scanning transmission electron microscopy and three-dimensional atom probe tomography were employed to identify the single Ni atomic sites in graphene vacancies. Detailed setup of electrochemical CO2 reduction apparatus coupled with an on-line gas chromatography is also demonstrated. Compared to metallic Ni, Ni single atom catalyst exhibit dramatically improved CO2 reduction and suppressed H2 evolution side reaction.

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

Here, we present a protocol for the synthesis and electrochemical testing of transition metal single atoms coordinated in graphene vacancies as active centers for selective carbon dioxide reduction to carbon monoxide in aqueous solutions.

电化学 CO2还原的过渡金属单原子催化剂的合成及性能表征

This protocol presents both the synthesis method of the Ni single atom catalyst, and the electrochemical testing of its catalytic activity and selectivity ...

Optimization, Test and Diagnostics of Miniaturized Hall Thrusters

Miniaturized spacecraft and satellites require smart, highly efficient and durable low-thrust thrusters, capable of extended, reliable operation without attendance and adjustment. Thermochemical thrusters which utilize thermodynamic properties of gases as a means of acceleration have physical limitations on their exhaust gas velocity, resulting in low efficiency. Moreover, these engines demonstrate extremely low efficiency at small thrusts and may be unsuitable for continuously operating systems which provide real-time adaptive control of the spacecraft orientation, velocity and position. In contrast, electric propulsion systems which use electromagnetic fields to accelerate ionized gases (i.e., plasmas) do not have any physical limitation in terms of exhaust velocity, allowing virtually any mass efficiency and specific impulse. Low-thrust Hall thrusters have a lifetime of several thousand hours. Their discharge voltage ranges between 100 and 300 V, operating at a nominal power of &lt;1 kW. They vary from 20 to 100 mm in size. Large Hall thrusters can provide fractions of millinewton of thrust. Over the past few decades, there has been an increasing interest in small mass, low power, and high efficiency propulsion systems to drive satellites of 50-200 kg. In this work, we will demonstrate how to build, test, and optimize a small (30 mm) Hall thruster capable of propelling a small satellite weighing about 50 kg. We will show the thruster operating in a large space environment simulator, and describe how thrust is measured and electric parameters, including plasma characteristics, are collected and processed to assess key thruster parameters. We will also demonstrate how the thruster is optimized to make it one of the most efficient small thrusters ever built. We will also address challenges and opportunities presented by new thruster materials.

Here, we present a protocol to test and optimize space propulsion systems based on miniaturized Hall-type thrusters.

小型化霍尔推进器的优化、测试和诊断

Miniaturized spacecraft and satellites require smart, highly efficient and durable low-thrust thrusters, capable of extended, reliable operation without ...

Synthesis of Metal Nanoparticles Supported on Carbon Nanotube with Doped Co and N Atoms and its Catalytic Applications in Hydrogen Production

A method for facile synthesis of nanostructured catalysts supported on carbon nanotubes with atomically dispersed cobalt and nitrogen dopant is presented herein. The novel strategy is based on a facile one-pot pyrolysis treatment of cobalt (II) acetylacetonate and nitrogen-rich organic precursors under Ar atmosphere at 800 &#176;C, resulting in the formation of Co- and N- co-doped carbon nanotube with earthworm-like morphology. The obtained catalyst was found to have a high density of defect sites, as confirmed by Raman spectroscopy. Here, cobalt (II) nanoparticles were stabilized on the atomically dispersed cobalt- and nitrogen-doped carbon nanotubes. The catalyst was confirmed to be effective in the catalytic hydrolysis of ammonia borane, in which the turnover frequency was 5.87 mol H2&#183;molCo-1&#183;min-1, and the specific hydrogen generation rate was determined to be 2447 mL H2&#183;gCo-1&#183;min-1. A synergistic function between the Co nanoparticle and the doped carbon nanotubes was proposed for the first time in the catalytic hydrolysis of ammonia borane reaction under a mild condition. The resulting hydrogen production with its high energy density and minimal refueling time could be suitable for future development as energy sources for mobile and stationary applications such as road trucks and forklifts in transport and logistics.

Here, we present a protocol to synthesize Co nanoparticles supported on carbon nanotubes with Co- and N- dopants for hydrogen productions.

碳纳米管负载掺杂Co和N原子金属纳米粒子的合成及其在制氢中的催化应用

A method for facile synthesis of nanostructured catalysts supported on carbon nanotubes with atomically dispersed cobalt and nitrogen dopant is presented ...

准备和无气腹纳米结构的反应含能材料

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