定向生长碳纳米管阵列热界面材料技术研究

热界面材料技术是三维系统级封装中的关键技术。文章采用新型定向生长碳纳米管阵列方法制备了热界面材料,并研究了其导热性能。实验结果表明,通过采用50/100/100 nm厚的Ti/Ni/Au金属层和Sn64Bi35Ag1导热焊料,可成功实现碳纳米管阵列的100%转移;通过热释放胶带(Nitto Denko,Part Number:#3198MS)可获得悬浮碳纳米管阵列。文章还通过LFA 447激光导热仪分别测量了热界面材料在25℃、75℃和125℃下的热扩散系数,并计算了其表观热导率,还进行了热循环可靠性测试。结果表明,所选用碳纳米管阵列的表观热导率高于42 W/(m·K),200次热循环后的表观热导率高于41 W/(m·K);转移后的碳纳米管阵列的表观热导率高于28 W/(m·K),200次热循环后仍高于24 W/(m·K)。     

估算低压纯气体导热系数方法的评价及改进

导热系数是有机物的重要物性数据之一,也是化工过程模拟与优化建模中不可或缺的参数。尽管文献中有部分化合物导热系数的实验值,但很多物质的导热系数不能由实验获得,往往是通过建立数学模型来估算。这里主要对估算低压纯气体导热系数的方法进行了归纳和研究,并对一些方法存在的问题进行了说明及改进。主要介绍了Chung法、Eucken关系式法、改进的Eucken关系式法和Stiel-Thodos法的原理、优缺点及应用范围;并利用这些方法估算了100种化合物的导热系数值,将这些估算值再与温度关联式所计算的结果进行比较。结果表明Chung法是估算导热系数较之其它精确。同时对Chung法进行改进,得到Chung法的18种常用酸性化合物的k值,扩大了方法的应用范围。     

纳米技术涌动未来——极其微小的工艺，革命性的效应

技术引擎：碳纳米管碳纳米管碳纳米管的强度远远超过钢铁,并且拥有极好的导热与导电性,正因如此,其未来的应用涉及面极广,从CPU到电池,再到散热片等。碳纳米管是一种由单层碳原子构成的分子,其中的单壁碳纳米管直径只有1/10×10~(-8)～1/30×10~(-8)m,若将其放大后观察,人们会发现它看起来就像一卷铁丝网。碳纳米管有着不可思议的强度与韧性,重量却极轻、导电性极强,兼有金属和半导体的性能；把纳米管组合起来,比同体积的钢强度高100倍,重量却只有1/6。     

一种全自动的准稳态法导热系数测量装置

在对准稳态法测量导热系数原理分析的基础上,研制了一套用准稳态法测量导热系数的实验装置,克服了以往准稳态法导热系数测量装置中存在的一些不足,同时开发了运行于Windows环境下的全自动测量软件。最后利用已知热物性数据的标准试样有机玻璃对装置进行了检验。实验结果表明,所研制的实验装置能够准确地测得一定范围内固体试样的导热系数,并可满足实际工程导热系数测量的需要。     

修正型平面热源法导热系数测定仪的设计

在传统的瞬态平面热源法导热系数测定仪的基础上,改进设计了新型加热与温度测量探头,研究了半无限大平面在被加热时的瞬态热传导问题,建立了平面热源法的数学修正模型,并采用数学迭代与回归分析的数据处理方法,实现了采用修正型平面热源法的导热仪对材料吸热系数和导热系数的同时测定。测试实验数据表明:仪器测量精度可达5%,测量范围为0.003～40 W/(m.K),并且可以对单试件等不具备传统瞬态平面源法测定条件的材料进行测定和试件的在线测定。     

纳米技术涌动未来——极其微小的工艺，革命性的效应

技术引擎：碳纳米管 碳纳米管的强度远远超过钢铁，并且拥有极好的导热与导电性，正因如此，其未来的应用涉及面板广，从CPU到电池，再到散热片等。     

用微弱信号检测方法测量高导热系数

用热线法测量建筑、保温材料的导热系数是当前评价建材制品导热性能的一种快速、有效的方法,受到了各国的重视。针对该方法在测量高导热系数材料或制品时遇到热电势过小,干扰噪声影响测量精度的困难,采用微弱信号检测中一些行之有效的方法(包括多次积累平均方法),成功地解决了对高导热系数的测量,使导热系数的测量上限达到1W/m·K,满足了高导热系数建材及制品的测量要求。     

六方氮化硼导热复合材料研究进展

随着电子元器件、电力系统和通讯设备等领域的飞速发展,对散热要求也越来越高。六方氮 化硼是一种性能优异的绝缘导热填料,其导热复合材料受到了越来越多的关注。该文综述了近年来关 于六方氮化硼基导热复合材料的研究进展,简要介绍了其导热机理和研究现状,进一步总结了当前存 在的一些技术困难,并展望了未来六方氮化硼基导热复合材料的发展方向。     

碳纳米管在高电压设备在线监测领域的应用

阐述了高压电气设备绝缘故障在线检测的一些方法,介绍了碳纳米管气体传感器近期的研究动向和取得的成果。应用碳纳米管气体传感器监测电气设备绝缘故障特征气体时,重点介绍了纯SF6,SF6/N2混合气体中局部放电产生的气体分解组分在电压、气体压强、温度等因素下对气体传感器的影响。并提出了碳纳米管气体传感器在高电压设备在线检测领域研究中所存在的问题和未来的研究发展方向。     

基于SEM图像的碳纳米管薄膜均匀性表征方法研究

将多壁碳纳米管综合了超声处理和高速离心等分散工艺单分散后,采用喷射吸滤法制备碳纳米管薄膜,并研究超声时间对薄膜分布均匀性的影响.基于多重分形理论和SEM图像分析多壁碳纳米管薄膜的形态学特征.碳纳米管薄膜的分布均匀性主要取决于多重分形谱宽度Δa和最大、最小概率子集维数的差别ΔF等分形参数.多重分形分析弥补了传统的表面评价和统计分析的不足.该碳纳米管薄膜均匀性表征方法将为碳纳米管薄膜的制备提供指导.     

A simplified approach for heat conduction analysis of CNT-based nano-composites

The unique thermal properties of carbon nanotubes (CNT) may offer possibilities for the development of fundamentally new composite materials. Numerical simulation for such CNT-based composites usually demands extremely large and expensive computer resources. In preliminary computations, temperature distribution in the CNT has been turned out to be almost uniform, due to its exceptionally high heat conductivity in comparison with the host polymer. This feature allows us to considerably simplify the mathematical model of the heat conduction in CNT composites. In the proposed approach, the host polymer is the only domain which is modeled, while the CNTs are treated as heat superconductors with constant and unknown temperatures constrained at their surfaces. As a result, the computational scale is reduced substantially. The hybrid boundary node method is applied in this study. Numerical examples clearly demonstrate the efficiency and sufficient accuracy of the proposed approach.     

Development of CNT-ISFET based pH sensing system using atomic force microscopy

In recent years, there has been an increasing interest in the monitoring and controlling of pH. It has become an important aspect of many industrial wastewater treatment processes as well as a drinking water quality issue. At the same time, the demand for smaller electronic devices used for various industrial and commercial applications has greatly increased. Nanomaterials such as Carbon Nanotubes (CNTs) are well known for their excellent electrical, mechanical, and thermal properties. Therefore, CNTs are good candidates for the manufacturing of small devices. In this paper, a novel concept combining CNT and Ion Sensitive Field Effect Transistor (ISFET) is proposed for pH-sensing application. Atomic Force Microscope (AFM) based manipulation and electrical property measurements in nano level are involved. Nanochannels are created by AFM-based nanoscratching, and the electrical properties of both multi-walled and single-walled CNTs are tested using Current Sensing AFM. FETs are fabricated to test the possibility of the CNTs’ alignment between the source and the drain electrode using Dielectrophoresis (DEP). The experimental results reveal that CNT is a promising material for improving the performance and lowering the cost of existing pH chemical sensors.     

Computational fluid dynamics for effects of coolants on on-chip cooling capability with carbon nanotube micro-fin architectures

Carbon nanotubes (CNTs) have shown a broad promising application in high mechanical strength and electronic structure. In this work, the effects of coolants on heat transfer capability of on-chip cooling with CNTs Micro-fin Architectures was studied, and the two-dimensional computational fluid dynamics (CFD) simulations have been done for a series of material parameters of coolants in this paper. The influences of thermal conductivity, density, specific heat and viscosity on cooling have been obtained in the case studies. The results demonstrate that pressure drop between the inlet and outlet of the cooling device is dependent on coolant’s density and viscosity. Consequently, it will be necessary to find out a good balance between heat transfer capability and pressure drop. The simulation results also indicate that the heat sink capability will be better if there are more fin rows in the microchannel.     

碳纳米管/PDMS复合材料柔性阵列压力传感器制备与实验

以碳纳米管（CNTs）作为导电填料,聚二甲基硅氧烷（PDMS）为基体材料,采用溶液法制备出CNTs/PDMS导电复合材料。研究了碳纳米管浓度对复合材料的电学特性和压阻特性的影响规律,得到碳纳米管在PDMS中的渗滤区域。通过复合材料的压力灵敏度优化碳纳米管浓度。以制备的复合材料为敏感材料,FPCB工艺加工的柔性基板为电极,设计制备了一种简单结构和工艺的柔性阵列压力传感器。用零电势法设计了阵列电阻读出电路与LabVIEW实现的上位机配合,实现信号读取和显示。最后通过一个应用实例表明,该柔性阵列压力传感器及信号处理系统可以实现压力分布与大小的实时监测,可为柔性阵列压力传感器设计与制备提供参考。     

Carbon nanotubes in microfluidic lab-on-a-chip technology: current trends and future perspectives

Advanced nanomaterials such as carbon nanotubes (CNTs) display unprecedented properties such as strength, electrical conductance, thermal stability, and intriguing optical properties. These properties of CNT allow construction of small microfluidic devices leading to miniaturization of analyses previously conducted on a laboratory bench. With dimensions of only millimeters to a few square centimeters, these devices are called lab-on-a-chip (LOC). A LOC device requires a multidisciplinary contribution from different fields and offers automation, portability, and high-throughput screening along with a significant reduction in reagent consumption. Today, CNT can play a vital role in many parts of a LOC such as membrane channels, sensors and channel walls. This review paper provides an overview of recent trends in the use of CNT in LOC devices and covers challenges and recent advances in the field. CNTs are also reviewed in terms of synthesis, integration techniques, functionalization and superhydrophobicity. In addition, the toxicity of these nanomaterials is reviewed as a major challenge and recent approaches addressing this issue are discussed.     

利用DEP和流体驱动的碳纳米管组装研究

碳纳米管在微结构上的组装是实现纳器件的关键.本论文分别采用电泳和流体驱动方法对两种不同的多壁碳纳米管进行了排布组装研究.电泳过程中频率一定时,增加电压或电泳时间,碳管沉积的密度增加;流体排布组装过程中,适当的流体速度得到较好的排布效果;较直的碳管取得更好的排布组装效果.同时根据实验结果对电泳和流体驱动两种组装方法的优势和问题进行了比较,结果表明,介电电泳组装能实现在电极间的定位组装,流体排布组装可实现较大面积的均匀排布.     

Application of the Green function method to flow-thermoelastic forced vibration analysis of viscoelastic carbon nanotubes

In this paper, the Green function method (GFM) is implemented for forced vibration analysis of carbon nanotubes (CNTs) conveying fluid in thermal environment. The Eringen’s nonlocal elasticity theory is used to take into account the size effect of CNT with modeling the CNT wall–fluid flow interaction by means of slip boundary condition and Knudsen number (Kn). The derived governing differential equations are solved by GFM which demonstrated to have high precision and computational efficiency in the vibration analysis of CNTs. The validity of the present analytical solution is confirmed by comparing the results with those reported in other literature, and good agreement is observed. The analytical examinations are accomplished, while the emphasis is placed on considering the influences of nonlocal parameter, boundary conditions, temperature change, structural damping of the CNT, Knudsen number, fluid velocity and visco-Pasternak foundation on the dynamic deflection response of the fluid-conveying CNTs in detail.     

Rapid-manufacturing of micro-structured devices based on MWCNTs/PP composites by using hot embossing replication process

Carbon nanotubes have attracted the fancy of many scientists since their first discovery in 1991. Their small dimensions, strength and remarkable physical properties make them a very unique material with a whole range of promising applications. The most important application of carbon nanotubes based on their important mechanical properties will be as reinforcements in composite materials, especially nanotube-filled polymer composites are an obvious materials application area. In this work, the micro-structured devices in range of micro meter have been manufactured based on polymer/carbon nanotubes composites by using hot embossing replication process. Firstly, the carbon nanotubes with different loading rate (0.1, 1 and 10 %) have been mixed with polypropylene (PP) in molten state to obtain the composite, the rheological properties of MWCNTs/PP composites with different CNT loading ratios were investigated by means of rheometer with a cone-and-plate geometry, the improvement of dispersion of the CNT particles in polypropylene matrix were observed by scanning electronic microscopy. Afterwards, the obtained composite were granulated in particles and used in hot embossing process to realize the replication of micro structured; in this step, a Al mould with micro-motif on surface obtain by machining with computer numerical control machine tools has been used. Finally, the micro-structured motifs on the mould have been successfully transferred with the details on the MWCNTs/PP substrate under the embossing pressure.     

Ethanol gas sensors based on multi-wall carbon nanotubes on oxidized Si substrate

Microsystem Technologies - In this study, ethanol gas sensors were fulfilled by utilizing the vertically aligned carbon nanotubes (CNTs). CNTs were synthesized by thermal chemical vapor deposition...