Experimental Evaluation of Thermal Conductivity and Other Thermophysical Properties of Nanofluids Based on Functionalized (-OH) Mwcnt Nanoparticles Dispersed in Distilled Water

A possible way to increase thermal conductivity of working fluids, while keeping pressure drop at acceptable levels, is through nanofluids. Nanofluids are nano-sized particles dispersed in conventional working fluids. A great number of materials have potential to be used in nanoparticles production and then in nanofluids;one of them is Multi-Walled Carbon Nano Tubes (MWCNT). They have thermal conductivity around 3000 W/mK while other materials used as nanoparticles like CuO have thermal conductivity of 76.5 W/mK. Due to this fact, MWCNT nanoparticles have potential to be used in nanofluids production, aiming to increase heat transfer rate in energy systems. In this context, the main goal of this paper is to evaluate from the synthesis to the experimental measurement of thermal conductivity of nanofluid samples based on functionalized (-OH) MWCNT nanoparticles. They will be analyzed nanoparticles with different functionalization degrees (4% wt, 6% wt, and 9% wt). In addition, it will be quantified other thermophysical properties (dynamic viscosity, specific heat and specific mass) of the synthetized nanofluids. So, the present work can contribute with experimental data that will help researches in the study and development of MWCNT nanofluids. According to the results, the maximum increment obtained in thermal conductivity was 10.65% in relation to the base fluid (water).

CNTs/Cu层状复合材料的制备及其组织和性能研究

采用扩散结合法将分散后的碳纳米管附着在铜箔表面,经裁剪、堆叠和预压后使用真空热压烧结炉进行烧结,制备出具有优良导电性的CNTs/Cu层状复合材料。使用SEM、EDS和XRD等对样品的微观形貌和成分进行表征,使用显微硬度计和导电率检测仪等对样品性能进行测试。结果表明:在热压烧结过程中,一定量铜扩散到CNTs层中,有效改善了碳纳米管层和铜层的结合能力。相比于纯铜,CNTs/Cu层状复合材料在硬度提高45%的同时,在平行于碳纳米管层方向导电率达到91%IACS,而垂直于碳纳米管层方向也仍具有80.6%IACS的导电率。

AuNP@Co_(3)(HITP)_(2)-CNT纳米结构的制备及电化学传感性能

利用一步水热法和化学还原法制备了基于金纳米颗粒负载Co_(3)(HITP)_(2)-碳纳米管(AuNP@Co_(3)(HITP)_(2)-CNT)的纳米复合材料。利用X射线光电子能谱仪(XPS)和扫描电子显微镜(SEM)对其表面微观形貌和元素组成进行表征。构建了前列腺特异性抗原(PSA)/牛血清蛋白(BSA)/PSA抗体(Ab)/AuNP@Co_(3)(HITP)_(2)-CNT/玻碳电极(GCE)电化学免疫传感器,并对PSA进行了检测,用循环伏安法(CV)、差分脉冲伏安法(DPV)和电化学阻抗谱(EIS)对其进行电化学性能分析测试。实验结果表明:基于AuNP@Co_(3)(HITP)_(2)-CNT纳米复合材料的电化学免疫传感器对PSA有较宽的检测范围,可达40 fg/mL~100 ng/mL,同时具有较好的特异性、稳定性和可重复性。

Optimal design of functionally graded Pm PV/CNT nanocomposite cylindrical tube for purpose of torque transmission

Carbon nanotube(CNT)/polymer nanocomposites have vast application in industry because of their light mass and high strength. In this work, a cylindrical tube which is made up of functionally graded(FG) PmP V/CNT nanocomposite, is optimally designed for the purpose of torque transmission. The main confining parameters of a rotating shaft in torque transmission process are mass of the shaft, critical speed of rotation and critical buckling torque. It is required to solve a multi-objective optimization problem(MOP) to consider these three targets simultaneously in the process of design. The three-objective optimization problem for this case is defined and solved using a hybrid method of FEM and modified non-dominated sorting genetic algorithm(NSGA-II), by coupling two softwares, MATLAB and ABAQUS. Optimization process provides a set of non-dominated optimal design vectors. Then, two methods, nearest to ideal point(NIP) and technique for ordering preferences by similarity to ideal solution(TOPSIS), are employed to choose trade-off optimum design vectors. Optimum parameters that are obtained from this work are compared with the results of previous studies for similar cylindrical tubes made from composite or a hybrid of aluminum and composite that more than 20% improvement is observed in all of the objective functions.

Synthesis and Application of Nanocomposite Reinforced with Decorated Multi Walled Carbon Nanotube with Luminescence Quantum Dots

Amidst the COVID-19 pandemic, environmental problems such as energy crisis, global warming, and contamination from pathogenic micro-organisms are still prevailed and strongly demanded progress in high-performance energy storing and anti-microbial materials. The nanocomposites are materials that have earned large interest owing to their promising applications for countering global issues related to sustainable energy and a flourishing environment. Here, polypyrrole coated hybrid nanocomposites of multi-walled carbon nanotube and cadmium sulfide quantum dots named MCP were synthesized using facile and low-cost in-situ oxidative polymerization method. Characterization techniques confirmed the synthesis. Electrochemical studies showed that the nanocomposite 1-MCP showed an impressively higher super capacitance behavior in comparison to f-MWCNT, 7-MCP and 5-MCP. The improved performance of the nanocomposites was attributed mainly to the good conductivity of carbon nanotubes and polypyrrole, high surface area, and stability of the carbon nanotubes and the high electrocatalytic activity of the cadmium sulfide quantum dots. Owing to the synergistic effect of MWCNT, CdS, and PPy the synthesized ternary nanocomposite also inhibited the growth and multiplication of tested bacteria such as S. aureus, and E. coli completely within 24 h. On the whole, the assimilated nanocomposite MCP opens promising aspects for the development of upcoming energy storage devices and as an antibacterial agent.

The Packaging Materials with Carbon Nanotube/Polymer Composites

A polymer-based carbon nano-tubes (CNTs) composite with high electromagnetic (EM) wave shielding effectiveness (SE) and with high mechanical property is developed for packaging of electronic modulus or devices.The liquid crystal polymers (LCP) and melamine formaldehydes (MF) polymer are used to study the orientation effect of CNTs in various polymeric matrix.The influences of orientation,aspect ratio,and mass fraction of CNTs upon the shielding effectiveness (SE) of CNTs-composites are investigated.The higher the orientation,aspect ratio,and weight percentages of nano-materials are, the higher the SE of the carbon composites.The highest SE for the CNTs/LCP nano composite obtained is more than 62 dB. This results may lead to the developing for CPU IC chip packaging.

MWCNTs/nano-CeO_2/PANI修饰的H_2O_2传感器

采用循环伏安和滴涂的方法在玻碳电极上制备出一种均匀且具有高电活性聚苯胺（PANI）/多壁碳纳米管（MWCNTs）/纳米氧化铈（nano-CeO2）复合膜.从膜的厚度、pH值、碳纳米管（CNTs）与nano-CeO2的质量比等方面系统地研究了复合膜探测H2O2浓度的各影响因素.结果表明：循环伏安聚合25圈的聚苯胺分散和固定CNTs,nano-CeO2,以及辣根H2O2酶的能力较好,且以CNTs与nano-CeO2的质量比为15∶1的复合膜在pH =6.4的缓冲溶液中具有较高的电活性.该复合膜修饰的电极对H2O2具有良好的响应电流,较快的响应时间（＜5 s）,较宽的检测范围为5.0 ×10-6～3.95 ×10-4mol/L,较低的检出极限7.6×10-7mol/L（S/N =3 dB）.

静电纺丝制备MWCNT_(s)/PVA定向导热复合纤维膜

将浓HNO_(3)和浓H_(2)SO_(4)酸化处理后的多壁碳纳米管(MWCNT_(s))加入聚乙烯醇(PVA)纺丝液中,通过静电纺丝法制备了不同MWCNT_(s)含量的MWCNT_(s)/PVA复合纤维膜。FT-IR分析表明,酸化后的MWCNT_(s)表面含有大量羟基和羧基。TEM分析表明,MWCNT_(s)在PVA内部呈定向线性排列。有效导热通道的形成,使得MWCNT_(s)/PVA复合纤维膜的水平导热系数显著增大,5%MWCNT_(s)/PVA的水平导热系数为1.32W/(m·K),为纯PVA纤维膜导热系数的6.6倍。同时,MWCNT_(s)的添加提高了复合纤维膜的热稳定性,5%MWCNT_(s)/PVA的热分解温度达到295.7℃,比纯PVA纤维膜提高了14.4℃。利用红外热像仪探测了MWCNT_(s)/PVA复合纤维膜应用于LED灯的散热效果,5%MWCNT_(s)/PVA纤维膜能有效降低LED灯珠的附近温度约11℃。

Natural Convection Melting in a Rectangular Heat Storage Tank of Carbon Nanotube Dispersed Latent Heat Storage Material

A dispersion system fluid can convect even if the dispersoid is a solid phase.Therefore,heat exchange performance can be improved while maintaining fluidity using a material with high thermal conductivity as the dispersoid.This study presents the melting performance evaluation results of a latent heat storage material with a carbon nanotube(CNT)dispersion system with high thermal conductivity,which enhances the thermal conductivity of the latent heat storage material and does not limit free convection.Increasing the thermal conductivity and enhancing the melting convection of the heat storage material result in increased latent heat storage speed.In this study,the thermal conductivity of the latent heat storage material was successfully increased by dispersing CNTs in the material.When 0.1%(in mass)of multi-wall CNT(MWCNT)was dispersed in a paraffin-based latent heat storage material,the shear stress increased by 1.5 times at a shear rate of 500 s^(-1),while taking into account the potential effects of convective inhibition.Therefore,a latent heat storage experiment was conducted in a rectangular heat storage tank using the CNT dispersion composition ratio as a parameter.A rectangular vessel with a heated vertical surface was used for the latent heat storage experiment.The melting speed was determined by comparing the amount of latent heat stored in a CNT-dispersed latent heat storage material and a single-phase latent heat storage material sample.The experimental results show that the time required for the latent heat storage material to completely melt in the heat storage tank was the shortest for the single-phase latent heat storage material sample.However,the fastest melting progress was observed for the sample with 0.02%(in mass)MWCNT content in the melting rate range of up to approximately 40%in the tank.The results indicate that this phenomenon is caused by the difference in the melting rates in the upper part of the tank.The generated data are useful for determining the shape and heat transfer surface arrangement of the latent heat storage tank.

Carbon Nano Material Synthesis from Polyethylene by Chemical Vapour Deposition

Three different types of Polyethylene family, High Density Polyethylene, (HDPE), Low Density polyethylene (LDPE) and Linear Low Density polyethylene (LLDPE) polymers having different molecular weight and density;were pyrolyzed in the temperature range of 550°C - 1050°C under H2, N2 and Ar gases. Taguchi Optimization technique was applied to find out the best operating conditions to get maximum yield of carbon nano material (CNM). For Taguchi op- timization, experimental set up was done in two different temperature ranges i.e. 550°C - 750°C and 850°C - 1050°C. CNMs synthesized were characterized by SEM, TEM, Micro Raman and XRD analysis. HDPE was found to yield maximum CNM. Its pyrolysis at 750°C under hydrogen atmosphere for 2h gave carbon nano beads and some carbon nano tubes. Whereas under same conditions at 1050°C more multi wall carbon nano tubes (MWCNT) were produced, with some carbon nano beads. XRD data confirmed the graphitic nature of carbon-nanotube. The intensities of G-band and D-band of Raman spectra suggested that CNM has more defect sites and spectra were similar for CNM obtained in both the temperature ranges. The TGA analysis of CNM obtained at 550°C - 750°C, indicated that they are not amor- phous carbon and CNM obtained at 850°C - 1050°C decomposed at 624°C - 668°C;suggesting that CNT synthesized at this temperature range were more crystalline than what was obtained at the 550°C - 750°C.

碳纳米管对RGO/CNT-CNP涂层吸光性能的影响

为获得对可见光到近红外光具有优异吸收性能的吸光涂层,以还原氧化石墨烯(reduced graphene oxide,RGO)作框架、碳纳米颗粒(carbon nano particles,CNP)和碳纳米管(carbon nano tubes,CNT)作附着物,采用高压静电喷涂技术制备了RGO/CNT_(x)-CNP吸光涂层(x为CNT的直径),研究了CNT的直径对RGO/CNT_(x)-CNP涂层形貌和吸光性能的影响。结果表明:RGO/CNP涂层对波长为400~1400 nm的光的平均吸收率为90.5%;加入CNT使RGO以一定角度倾斜堆叠,从而形成具有不同尺寸光学腔的复合结构,RGO/CNT_(x)-CNP涂层的光吸收性能显著改善;随着CNT直径的增大,CNT覆盖RGO框架的面积增加,RGO/CNT_(x)-CNP涂层的表面粗糙度增大,微米级和纳米级光学腔的数量增加,从而涂层的吸光率提高;采用直径为20 nm的CNT制备的RGO/CNT20-CNP涂层具有最佳的吸光性能,对可见光到近红外光的平均吸收率达94.1%。

CNT网络材料微观结构变化的数值模拟研究

为探究力学载荷作用对碳纳米管(carbon nano-tube,CNT)网络材料微观结构的影响,笔者建立了CNT网络材料的粗粒化模型,运用粗粒化分子动力学模拟方法对CNT网络在力学载荷作用下的微观结构变化行为进行仿真分析。结果表明:CNT网络材料的取向程度在拉伸应变增加初期增大速率较快,后续随着拉伸应变的增加取向程度趋于平稳,最终会趋近于稳定值0.95;在压缩载荷作用下,CNT网络材料的取向程度会随着应变的增大而减小,且最后减小至0.15;力学载荷速率不会影响CNT网络取向程度的变化规律。

CNTs/KClO_4复合材料的形貌特征及热行为

为有效避免点火药中纳米级氧化剂颗粒的团聚,进一步提高点传火稳定性,通过NH4ClO4溶液和KOH溶液的复分解反应制备了碳纳米管/高氯酸钾(CNTs/KClO4)复合材料。用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、差热分析(DSC)和比表面积(SSA)分析研究了CNTs/KClO4复合材料的形貌特征及热行为。结果表明:用这种方法制备的KClO4能有效涂敷在碳纳米管上。与纯CNTs相比,负载KClO4的碳纳米管管径明显增粗,CNTs/KClO4复合材料的比表面积降低了40.719 m2·g-1。与KClO4相比,CNTs/KClO4复合材料的热分解温度前移了75℃,晶型转变峰温前移了5℃。与以KClO4为原料制备的Mo/KClO4点火药相比,以CNTs/KClO4复合材料为原料制备的Mo/KClO4点火药的热导率提高了33.9%。

CNTs/KNO_3纳米粒子制备及表征

分别采用重结晶法和中和反应法制备了碳纳米管/硝酸钾(CNTs/KNO3)纳米复合粒子,运用扫描电镜(SEM)、X射线衍射能谱(XRD)、比表面积(SSA)和差热分析(DSC)等手段对复合粒子进行了表征。结果表明:两种制备过程实现了KNO3在CNTs外表面的负载,重结晶法制备的复合粒子的比表面积比CNTs降低了113.9 m2.g-1,热分解温度与KNO3相当;反应法制备的复合粒子的比表面积比CNTs降低了138.7 m2.g-1,热分解温度比KNO3降低了28℃。表明反应法制备的样品中,CNTs对KNO3的热分解过程具有催化作用。

正应力支配下混合顺序对PA6/HDPE/CNTs体系结构及性能的影响

利用自行研制的叶片式混炼装置,实现了正应力支配下聚合物复合体系的熔融共混。实验研究了混合顺序以及混合时间对高密度聚乙烯(HDPE)/尼龙6(PA6)/碳纳米管(CNTs)共混物的微观结构、流变特性、热性能及宏观力学性能的影响。结果表明:正应力支配作用能在短混合时间内实现PA6粒子和CNTs的均匀分散,分散效率高;相比于将HDPE,PA6,CNTs三者同时共混或者是先将PA6与CNTs混炼制成母料,再与HDPE共混这两种混合顺序,先将HDPE与CNTs混炼制成母料,再与PA6共混制得的共混物中分散相PA6粒径最小,分散更均匀,共混物的热性能以及力学性能更好。

机械球磨法制备CNTs/Al复合粉末的工艺过程研究

研究了用机械球磨法制备CNTs/Al复合粉末的工艺过程,分别选用不锈钢球、玛瑙球和氧化锆球在干磨和湿磨(乙醇介质)两种情况下进行球磨,研究了磨球材质对CNTs颗粒在Al基中分布均匀性的影响。结果表明:干磨有利于碳纳米管的断裂与分散;不同材质的磨球所获得的混合粉形态有很大差异,用玛瑙球可以获得最理想的分散效果。

多壁碳纳米管(MW-CNTs)表面纯化改性研究

采用浓HCl、浓HNO3、H2SO4/HNO3、溴水、K2Cr2O7/H2SO4等强酸及强氧化剂对多壁碳纳米管(MWNTs)进行纯化改性处理.采用X射线衍射(XRD)、傅立叶红外光谱(FTIR)和透射电镜(TEM)等手段对产物改性前后的结构及性能进行分析表征.结果表明:纯化改性处理能够除去杂质,截短碳纳米管,使其表面的羟基、羧基和羰基的含量明显提高.

钟罩压块铸造法制备CNTs/ZChPbSb15-5轴承合金复合材料

将碳纳米管(CNTs)、铅粉按质量比1∶5混合后压块,采用钟罩将制备好的预制块压入轴承合金熔体制备CNTs/ZChPbSb15-5复合材料。研究了该复合材料的微观组织和显微硬度,并测试了该复合材料在一定载荷下的摩擦因数和磨损量。结果表明:碳纳米管能明显细化复合材料的组织,使SnSb相分布密度增大、且更加均匀;相比基体合金复合材料的显微硬度显著提高,尤其是合金质点相的硬度提高了31.0%;在相同条件下,该复合材料的摩擦因数和磨损量均低于基体合金。

峰值电流密度对脉冲电沉积Ni-Co-CNTs复合镀层机械性能的影响

研究了峰值电流密度对脉冲电沉积Ni-Co-CNTs复合镀层机械性能的影响。结果表明:当峰值电流密度升高时,镀层表面变得粗糙;随着峰值电流密度的增加,镀层中碳的质量分数先增加后下降,当峰值电流密度为80 A/dm^2时,镀层中碳的质量分数达到最大值;镀层的显微硬度和抗拉强度均在峰值电流密度为100 A/dm^2附近时达到其最大值,且高于直流电沉积时所得镀层的显微硬度值和抗拉强度值。说明采用脉冲电沉积工艺可以提高镀层的机械性能。

MWCNT-WO_3薄膜双声路SAW NO_2气体传感器

以金属钨粉,H2O2,CH3OH和多壁碳纳米管(MWCNT)为原料,在双声路声表面波(SAW)器件的测量声路上制作了MWCNT-WO3薄膜,提出并实现了一种MWCNT-WO3薄膜双声路SAW NO2气体传感器。由于MWCNT和WO3对NO2气体都有敏感作用,而且碳纳米管的毛细作用、以及MWCNT的加入都增加了气体的接触面积,提高了NO2气体的吸附和敏感作用。同时,SAW器件的双声路结构消除了由于外界测量条件改变引起的测量误差,也进一步提高了传感器的可靠性和准确性。实验结果表明,该传感器对各种浓度的NO2气体具有好的响应特性,在31.2×10-9到20×10-6范围内,传感器的响应灵敏度为9.8kHz/1×10-6,比单一MWCNT或WO3薄膜对NO2气体具有更好的灵敏度和线性特性。