• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >Preparation of copper-bearing nanofluids for thermal applications .
【24h】

Preparation of copper-bearing nanofluids for thermal applications .

机译：用于热学应用的含铜纳米流体的制备。

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Stable suspension of nanometer solid particles in suitable solvents, so-called nanofluids, has shown enhanced thermal conductivity when compared with the fluid base; therefore, the preparation and characterization of these type of suspension will enable the development of more efficient and effective thermal management systems. In general, nanofluids hosting metal nanoparticles, (e. g., Ag or Cu) would exhibit better thermal conductivities than those bearing oxide nanoparticles. Accordingly, the present research addressed the optimization of the size-controlled synthesis conditions of copper nanoparticles, determination of the most suitable conditions to stabilize those nanoparticles in ethylene glycol and the reproducible measurement of the thermal conductivity as a function of nanoparticle volumetric load. The research work was also focused on the improvement of the stability and reliability of the system used to measure the thermal conductivity of copper-bearing nanofluids.;The synthesis of nanoparticles was achieved through the reduction of copper ions using hydrazine as well as by taking advantage of the reducing power of polyol solutions. The preparation of the copper-bearing stable nanofluid was attempted by treating nanoparticles with surfactant agents to disperse them in the base fluid (ethylene glycol). In the aqueous route, the rate of the Cu reduction reaction and the corresponding average crystallite size of the nanoparticles were strongly dependent on the copper ion and hydrazine concentration. From starting 0.016M Cu solution, the time at which the reduction of Cu was realized was shortened from 12 hours down to only 30 minutes when the concentration of hydrazine was increased from 0.059M to 0.7M. The corresponding average crystallite size decreased from 25nm to 17.8nm. In the polyol approach, the reaction time was as short as 30 seconds when a NaOH/Cu mole ratio = 50 was used. The corresponding average crystallite size, estimated at 21.2nm, went down to 12.7nm when a 5E-7M of Polyvinylpyrrolidone was used. The formation of Copper nanoparticles from starting Cu(II) species, in water and polyol solutions, involved the formation of precursor cuprous oxide (Cu2O), which underwent dissolution and subsequent reduction into elemental Cu. This dissolution-reduction step controls the average size of nanoparticles of elemental Copper.;The thermal conductivity of nanofluids produced was measured by using the transient hot-wire technique. The relationship between nanoparticle size, volumetric concentration in ethylene glycol and the relative thermal conductivity values are presented and discussed. The thermal conductivity of the base ethylene glycol was increased 32% when copper nanoparticles (7.5 %v/v), averaging 21nm, were suspended in the base fluid.
机译：与流体基料相比，纳米固体颗粒在合适的溶剂（所谓的纳米流体）中的稳定悬浮已显示出增强的导热性。因此，准备和表征这些类型的悬架将使开发更有效的热管理系统成为可能。通常，承载金属纳米颗粒（例如，Ag或Cu）的纳米流体将比带有氧化物纳米颗粒的纳米流体表现出更好的导热率。因此，本研究致力于优化铜纳米颗粒尺寸控制的合成条件，确定最合适的条件来稳定那些纳米颗粒在乙二醇中的含量以及可再现性的热导率随纳米颗粒体积负荷的变化。研究工作还集中在提高用于测量含铜纳米流体导热系数的系统的稳定性和可靠性上。纳米颗粒的合成是通过使用肼还原铜离子以及利用多元醇溶液的还原能力。通过用表面活性剂处理纳米颗粒以使其分散在基液（乙二醇）中来尝试制备含铜的稳定纳米流体。在水性途径中，Cu还原反应的速率和纳米颗粒的相应平均微晶尺寸强烈取决于铜离子和肼的浓度。当肼的浓度从0.059M增加到0.7M时，从开始添加0.016M Cu溶液开始，实现Cu还原的时间从12小时缩短到仅30分钟。相应的平均微晶尺寸从25nm减小到17.8nm。在多元醇方法中，当使用NaOH / Cu摩尔比= 50时，反应时间短至30秒。当使用5E-7M聚乙烯吡咯烷酮时，相应的平均微晶尺寸估计为21.2nm，降至12.7nm。在水和多元醇溶液中，由起始的Cu（II）物种形成的铜纳米粒子涉及前体氧化亚铜（Cu2O）的形成，该亚铜经过溶解并随后还原为元素Cu。该溶解-还原步骤控制元素铜的纳米粒子的平均尺寸。通过使用瞬态热线技术测量所产生的纳米流体的热导率。介绍并讨论了纳米粒径，乙二醇中的体积浓度与相对热导率值之间的关系。当平均粒径为21nm的铜纳米颗粒（7.5％v / v）悬浮在基础液中时，基础乙二醇的导热系数提高了32％。

著录项

  • 作者

    Velasco Abreo, Andres Felipe.;

  • 作者单位

    University of Puerto Rico, Mayaguez (Puerto Rico).;

  • 授予单位 University of Puerto Rico, Mayaguez (Puerto Rico).;
  • 学科 Engineering Mechanical.;Engineering Materials Science.
  • 学位 M.S.
  • 年度 2009
  • 页码 121 p.
  • 总页数 121
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 机械、仪表工业;工程材料学;
  • 关键词

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号