Enhanced efficiency of tri-layered dye solar cells with hydrothermally synthesized titania nanotubes as light scattering outer layer

In the present study dye sensitized solar cells (DSSCs) have been fabricated with a tri-layer photo anode consisting of hydrothermally prepared titania nano tubes (TNT) having a diameter of 9-10 nm and length of several micrometers as outer layer, P25 TiO₂ powder as transparent light absorbing middle layer and a compact TiO₂ inner layer to improve the adhesion of different layers on a transparent conducting oxide coated substrate. In comparison to cells fabricated using TNTs or P25 alone, the tri-layer DSSCs exhibit an enhanced efficiency of 7.15% with a current density of 17.12 mA cm^− 2 under AM 1.5 illumination. The enhancement is attributed to the light scattering generated by TNTs aggregates, reduction in electron transport resistance at the TiO₂/dye/electrolyte interface and an improvement in electron life-time.     

Synthesis of clay–carbon nanotube hybrids: Growth of carbon nanotubes in different types of iron modified montmorillonite

In the present study, montmorillonite–carbon nanotube hybrids were synthesized by catalytic decomposition of ethylene over iron montmorillonite surfaces modified by different experimental procedures. SEM and STEM analyses reveal the presence of carbon nanotubes attached to the clay layers and X-ray diffraction results indicate that sodium montmorillonite layers were intercalated with iron species during the ion-exchange processes and further delaminated due to the growth of carbon nanotubes. It is expected that montmorillonite–carbon nanotube hybrids will be beneficiary for improvement of mechanical properties in polymer nanocomposites due to their pre-exfoliated internal structure and the presence of surface carbon nanotubes which may significantly enhance reinforcing effect.     

高能球磨法制备的碳纳米管增强铝基复合材料的微观组织和力学性能

采用高能球磨法制备了不同体积分数的碳纳米管(CNT)与Al粉的混合粉末,用粉末冶金工艺制备了CNT/A1复合材料.微观结构分析表明.球磨可以分散一定含量的CNT到Al基体中,并与其产生良好结合.在适当的球磨工艺下.球磨不会造成CNT的严重损伤.拉伸实验表明,CNT体积分数为1.5%时,力学性能达到了最高值,屈服强度相对于纯A1基体提高了53.6%.而CNT体积分数为3%时,形成了大量的CNT团聚,力学性能迅速下降.CNT/A1复合材料的主要强化机制为细晶强化和载荷传递.     

基于碳纳米管的三维编织复合材料健康监测技术

分析了三维编织复合材料试件结构健康监测技术现状,结合三维编织复合材料编织工艺,提出了碳纳米管在三维编织复合材料试件健康监测方面的应用方法。结果说明碳纳米管应用于三维编织复合材料整体结构监测是可行的。碳纳米管传感器在三维编织复合材料试件结构健康监测中具有优异的应变传感特性,且嵌入的碳纳米管传感器对复合材料的力学性能影响不大。这为内置碳纳米管传感器应用于复合材料制件的健康检测提供了一种新的综合和分布式技术,为先进智能复合材料的研发与应用提供了依据。     

Enhancing hydrogen storage on carbon nanotubes via hybrid chemical etching and Pt decoration employing supercritical carbon dioxide fluid

Acidic etching and Pt particle decoration were applied to modify the hydrogen absorption behavior of carbon nanotubes (CNTs). Two different acidic solutions, namely H₂SO₄/HNO₃ and FeSO₄/H₂SO₄/H₂O₂, were used for etching treatment. A novel electroless deposition process, incorporating supercritical CO₂ (sc-CO₂) fluid, was used to decorate finely-dispersed nano-sized Pt particles on CNTs. The hydrogen storage capacities of various modified CNTs were measured by using a high pressure thermal gravimetric microbalance (HPTGA). The experimental results showed that acidic etching could increase the surface defect density and lead to open-up of the caps of CNTs, resulting in an increase in the active adsorption site for physical sorption of H_2. The electroless deposition of nano-Pt particles on CNTs, using conventional electrolyte, could promote chemical sorption of hydrogen via spillover mechanism. By employing sc-CO₂ bath, the Pt particle size became much finer and more uniformly distributed on the surfaces of CNTs, giving rise to a high hydrogen storage capacity. When a hybrid process including sc-CO₂ Pt decoration following acidic etching was applied to modify CNTs, a substantial enhancement of hydrogen storage capacity (about 2.7 wt%) was observed.     

Cu2O/Cu/TiO2 nanotube Ohmic heterojunction arrays with enhanced photocatalytic hydrogen production activity

Cu₂O/Cu/TiO₂ nanotube heterojunction arrays were prepared by assembling Cu@Cu₂O core-shell nanoparticles on TiO₂ nanotube arrays (NTAs) using a facile impregnation-reduction method. SEM and TEM results show that Cu@Cu₂O plate-like nanoparticles with tens of nanometers in size are confined inside TiO₂ NTAs. Only the outmost several nanometers of the nanoparticles are Cu₂O and the predominant inner of the nanoparticles are Cu metals. Cu L₃VV Auger spectra of Cu₂O/Cu/TiO₂ NTAs suggest that Cu metals are enveloped by at least several nanometers Cu₂O on the surface, which further confirms the Cu@Cu₂O core shell structure of Cu nanoparticles. The ability of light absorption of Cu₂O/Cu/TiO₂ NTAs is enhanced. The range of absorption wavelengths changes from 400 to 700 nm due to the surface plasmon response of Cu metals core and Cu₂O nanoparticles shell. The photocatalytic hydrogen production rate of Cu₂O/Cu/TiO₂ heterojunction arrays is enhanced when compared with those of Cu₂O/TiO₂ NTAs and TiO₂ NTAs under UV light. Moreover, a stable H₂ generation property was obtained under visible light (λ gt; 400 nm). The Cu metal core is believed to play a key role in the enhancement of photocatalytic properties of Cu₂O/Cu/TiO₂ nanotube heterojunction arrays.     

Improved carbon nanotube supported Pt nanocatalysts with lyophilization

The lyophilization was used to enhance platinum (Pt) nanoparticle distribution on carbon nanotube (CNTs). The results indicate that this method is very available to uniformly disperse nanotubes and effectively prevent Pt metal particles from agglomeration. The Pt nanoparticles ranging from 2 to 5 nm in diameter are uniformly deposited on CNTs characterized by both transmission electron microscopy (TEM) and X-ray diffraction (XRD). Instead, Pt/CNT catalysts fabricated by conventional drying method present a lower dispersion degree compared with that by lyophilization. The as-prepared catalysts have higher electrochemical active surface area and higher oxygen reduction reaction (ORR) activity as compared to that by drying method characterized through cyclic voltammetry (CV) and ORR.     

The influences of admixtures on the dispersion, workability, and strength of carbon nanotube-OPC paste mixtures

Carbon nanotubes (CNT) have excellent mechanical properties and have the potential, if combined with Ordinary Portland Cement (OPC), traditionally a brittle material in tension, to become a nano-composite with superlative mechanical properties. However, highly attractive van der Waals forces between CNTs create coherent agglomerates that prove difficult to disperse within the cement matrix and reduce the fluidity of the fresh mixture. Good dispersion of CNTs, while maintaining good workability of fresh OPC-CNT paste mixtures, is a prequalification before CNT-cement nanocomposites can be considered as a future building and construction material with enhanced mechanical properties. This paper reports the results of investigations of the dispersion, workability, and strength of CNT aqueous and CNT-OPC paste mixtures, with and without several generically different dispersants/surfactants that are compatible as admixtures in the manufacture of concrete. These include an air entrainer, styrene butadiene rubber, polycarboxylates, calcium naphthalene sulfonate, and lignosulfonate formulations. Aqueous mixtures were initially assessed for dispersion of CNTs, followed by workability testing of selected OPC-CNT-dispersant/surfactant paste mixtures. A broad range of workability responses were measured and the CNT dispersion within hardened pastes was qualitatively assessed by SEM analysis.     

改性碳纳米管对偏二甲肼的吸附热力学研究

对NaOH改性多壁碳纳米管吸附偏二甲肼的特性进行了研究,在温度为296～313K和浓度为44．51～211．41mg／L的范围内,多壁碳纳米管对偏二甲肼的吸附符合弗仑德利希（Freundlich）和兰缪尔（Langmuir）吸附等温式。不同温度下等温吸附曲线的测定和等量吸附焓的计算表明：多壁碳纳米管对偏二甲肼的吸附是吸热的。对偏二甲肼在多壁碳纳米管上的吸附焓、吉布斯自由能、吸附熵的计算表明,该多壁碳纳米管对偏二甲肼的吸附没有化学键生成,并对吸附行为作了机理性解释。