Convection heat transfer of functionalized MWNT in aqueous fluids in laminar and turbulent flow at the entrance region

In this research, the convective heat transfer coefficients of water-based FMWNT nanofluid have been measured under both laminar and turbulent regimes flowing through a uniformly heated horizontal tube in entrance region. For the first time, we have compared effective parameters to measure the convective heat transfer coefficients for functionalized MWNT suspensions such as Re, mass fraction and temperature, altogether in entrance region. The experimental results indicate that the convective heat transfer coefficient of these nanofluids increases by up to 33–40% at a concentration of 0.25 wt.% compared with that of pure water in laminar and turbulent flows respectively and 20 °C.     

MWNTs/HDPE复合材料的结晶行为研究

采用超声分散溶液混合法制备出多壁碳纳米管(MWNTs)/高密度聚乙烯(HDPE)复合材料.通过场发射电镜观察了MWNTs在HDPE基体中的分散,采用X射线衍射(XRD)分析和差示扫描量热(DSC)分析研究了含碳纳米管的高密度聚乙烯的晶态结构和结晶行为,并利用Avrami方程描述了复合材料的等温结晶动力学.结果表明,MWNTs可以较好地分散在HDPE基体中并且作为一种有效的成核剂,用量较少(1%)和直径较大(60～100 nm)的MWNTs成核效果更明显;它们并没有改变HDPE的品型;随着MWNTs含量的增加和温度的升高,MWNTs/HDPE复合材料中HDPE主要是通过异相成核以球晶生长方式结晶的.     

不同激发波长下多壁碳纳米管光致发光特性

用化学气相沉积法(CVD)制备了多壁碳纳米管(MWNTs),并用扫描电镜(SEM)测量了纳米管的形貌。在室温条件下,测量了样品的拉曼光谱和吸收光谱:拉曼光谱表明样品含有较多缺陷,吸收光谱说明了该样品有光致发光的通道。测量了在不同波长光的激发下样品的光致发光光谱:当用550 nm的光激发多壁碳纳米管时,观察到峰值强度弱、峰值波长约为820 nm的带状光谱;当激发波长增加到580 nm时,发射光谱变为峰值波长约为868 nm、峰值强度较强、形状相似的光谱;当激发光波长增加到600 nm时,观察到峰值强度强、峰值波长约为900 nm的带状光谱。     

碳纳米管掺杂激光隐身涂层的制备及性能研究

以多壁碳纳米管(MWNTs)为填料,互穿聚合物网络(IPNs)为成膜物质,采用机械共混法制备了一种1.06μm波长处低反射率的激光隐身涂料。通过综合热分析(TG-DSC)、扫描电镜(SEM)分析了涂层的热稳定性和表面形貌。通过紫外-可见-近红外分光光度计(UVPC)和激光反射率测试,研究了MWNTs掺量对涂层1.06μm波长处反射率的影响。     

Preparation of MWNTs/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composites and their mechanical and electrical properties

Since their discovery by Iijima[1], carbon nanotubes (CNTs) have been the focus in novel materials research. Theoretical and experimental studies show[2-9] that CNTs have extraordinary mechanical and electrical properties. Krishnan et al.[2] have reported that the mean value of Young’s modulus of single-wall nanotubes (SWNTs) is 1.25 TPa. Yu et al.[3] measured Yang’s modulus of multi-wall nanotubes (MWNTs) between 270 and 950 GPa and breaking strength between 11 and 63 GPa. The ele…     

Carbon nanotube/polyaniline core-shell nanowires prepared by in situ inverse microemulsion

By the in situ inverse microemulsion, we prepared multi-walled carbon nanotubes/polyaniline composites (MWNTs/PANI). Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that the nanotubes were coated with a PANI layer. Fourier transform infrared (FT-IR) spectra suggested that the π-bonded surface of the carbon nanotubes (CNTs) interact strongly with the conjugated structure of the PANI shell layer. The thermal stability and electrical conductivity of the MWNTs/PANI composites were examined by thermogravimetric analysis (TGA) and conventional four-probe method. In comparison with the pure PANI, the decomposition temperature of the MWNTs/PANI (1 wt% MWNTs) composites increased from 360 to 400 °C and the electrical conductivity of MWNTs/PANI (1 wt% MWNTs) composites was increased by one order of magnitude.     

Investigation on adsorption and regeneration performances of multi-walled carbon nanotubes by supercritical water technique

In this paper,adsorption and regeneration characteristics of multi-walled carbon nanotubes (MWNTs) used as adsorbent were investigated for the removal of 1,3-benzenediol (BDO) from water by the supercritical water (SCW) technique. FTIR,XPS,SEM and dispersion stability tests were used to characterize the structure and surface morphology of CNTs. The results showed that CNTs surfaces were slightly activated and strongly etched in supercritical water system. The adsorption capacity of SCW-treated CNTs was higher than that of raw CNTs. The adsorbed amounts for treated CNTs and raw CNTs samples at the same initial concentration of 60 mg/L were ca. 16.42 and 7.30 mg/g,respectively. The BDO adsorption of treated CNTs was due to the physical adsorption. The experimental data fit Freundlich isotherm model better than Langmuir one. The loaded adsorbent could be efficiently desorbed and regenerated by SCW technique. Therefore,SCW is a promising and environmentally friendly technique for the improvement of adsorption and regeneration of CNTs.     

Nano-sized Sn/MWNTs and MWNTs Served as the Anode of Lithium Ion Battery

A chemical deposition was supposed to be an effwient method in preparation of nano-sized Sn/ MWNTs. The nanoconmposites of MWNTs and Sn/ MWNTs were both used as anodes of lithium ion battery. The special capacities and coulomb efficiencies of Snl MWNTs were studied by means of electrochemical methods. The coating of Sn on MWNTs observed by TEM was amorphous and nano-sized. The reversible capacity of Sn/ MWNTs , which was much larger than that of MWNTs , was 824 mAh/ g in the 1 st charge and discharge cycle. The coulomb efficiency of Sn/ MWNTs in the 1 st cycle was increased by 16% compared with that of MWNTs. The additional Sn, which was 37wt% of total Sn/ MWNTs＇ weight, introduced the additional reversible lithiation capacity at least 250 mAh/ g in the 40 charge and discharge cycles. The dispersing degree of Sn on MWNTs was the main reason for the influence of the electrochemical perfomance of the Sn/ MWNTs . Sn/ MWNTs is proved to be a promising candidate as an anode of lithium ion battery.     

多壁碳纳米管的球磨处理对其吸附储氢性能的影响

研究了球磨改性对多壁碳纳米管储氢性能的影响,球磨处理前后的碳纳米管微观结构采用TEM和XRD进行表征. 结果发现,球磨处理能使碳纳米管长度变短,管端口打开,缺陷增多,表面积增大,球磨处理12 h的碳纳米管的吸附量从未球磨的1.60%(w)提高到2.55%(w),表明球磨改性能明显提高碳纳米管的吸附量.