Jian Nong Wang

Organic−Inorganic Composite Nanocoatings with Superhydrophobicity, Good Transparency, and Thermal Stability

Superhydrophobic, highly transparent, and stable organic-inorganic composite nanocoating is successfully prepared by a simple sol-gel dip-coating method. This method involves control of the aggregation of inorganic colloid particles by polymerization and ultrasonic vibration to create the desired micro/nanostructure in the coating. Superhydrophobicity and transparency of the coating can be controlled by adjusting the initial concentration of monomer and the size of aggregates in the sol-gel. Thus, superhydrophobicity and high transparency can be concurrently achieved in a single coating. The prepared coating also possesses good thermal stability. Its superhydrophobicity can be maintained from 20 to 90 degrees C.

Large-diameter and water-dispersible single-walled carbon nanotubes: synthesis, characterization and applications

Single-walled carbon nanotubes (SWCNTs) with large diameters (LDs) (≥3 nm) have wide applications. But, up to now, the synthesis of these novel nanostructured carbon materials is still a great challenge, and exploration of a simple synthesis method suitable for economical and large-scale production is still an important task. The present study reports on the continuous synthesis of SWCNTs with a large average diameter of 5.8 nm and a maximum diameter of 10 nm. Raman spectroscopy is used to show the first observation of peaks at low frequencies of 45–85 cm−1 associated with the observed LD-SWCNTs but the peaks at higher frequencies of 200–270 cm−1 for the small-diameter (SD) counterparts. After purification by a non-destructive approach, the present LD-SWCNTs are found to be dispersible in water, a property which will benefit many applications. This observation is in contrast to that for conventional SD-SWCNTs which cannot be dispersed in any solutions without complicated functionalization. When LD-SWCNTs are used as a catalyst support for fuel cells, they show much better performance than SD-SWCNTs, multi-walled CNTs and the commercial catalyst from Johnson Matthey Co. It is suggested that the present approach may be immediately applied for large-scale production and the applications of LD-SWCNTs in a wide range of areas such as information technology, biomedicine, and environmental and energy industries may be investigated.

A novel self-cleaning coating with silicon carbide nanowires.

A novel self-cleaning glass was successfully achieved by coating macroscopical SiC nanowires (SiCNWs) in tetraethyl orthosilicate (TEOS) solution. The water contact angle (CA) was high, up to approximately 160 degrees, and the sliding angle was low, down to approximately 5 degrees, when SiCNWs were coated through 10 cycles, with a high roughness Ra of 1928.9 nm. High chemical stability was obtained even after immersing the sample in water for 14 days (336 h). The calculated data by using nano/micropillar composite structure model displayed a beneficial understanding on thehydrophobic property. The feasible coating on any substrate, high CA, and long lifetime make SiCNW a potential superhydrophobic material in various self-cleaning fields.

Superhydrophobic and transparent coatings based on removable polymeric spheres

Superhydrophobic and also highly transparent coatings can be prepared by a sol-gel dip-coating method. Polystyrene spheres (PSs) are used as a removable template and the coatings have a volcano-like micro/nano structure. The micrometer-sized pinnacles form by the assembly of PSs and silica particles, whereas the nanometer-sized peaks on individual pinnacles are created by the removal of PSs. Due to this particular structure the contact angle of a 4 µL water droplet on the prepared coating can reach 160° with the corresponding sliding angle being close to 0°. Additionally, the transmittance of the coated glass is as high as the uncoated glass.

Aligned Silicon Carbide Nanowire Crossed Nets with High Superhydrophobicity

Aligned silicon carbide nanowire crossed nets (a-SiCNWNs) were directly synthesized by using a vapor-solid reaction at 1100 degrees C. Zinc sulfide was used as catalyst to assist the growth of a-SiCNWNs with small size and crystal structure. After functionalization with perfluoroalkysilane, a-SiCNWNs showed excellent superhydrophobic property with a high water contact angle more than 156 +/- 2 degrees , compared to random nanowires (147 +/- 2 degrees ) and pure silicon wafers (101 +/- 2 degrees ). The topographic roughness and chemical modification with CF 2/CF 3 groups contributed the better superhydrophobicity. Furthermore, the as-grown SiCNWNs can be scraped off and coated on other substrates such as pure silicon wafers. The novel nanowire coating with good superhydrophobicity displays extensive applications in silicon-related fields such as solar cells, radar, etc.

Preparation of graphitic carbon with high surface area and its application as an electrode material for fuel cells

Nanostructured graphitic carbon materials have wide applications. However, the synthesis of such materials with a high surface area is still a great challenge. In this study, graphitic carbon nanocages with a surface area as high as 400–800 m2 g−1 were synthesized by pyrolysis of ethanol with dissolved iron carbonyl. This graphitic carbon was successfully applied as an electrode material for proton exchange membrane fuel cells and showed 40% improvement in fuel cell performance from amorphous carbon. The present method could be applied to large-scale production of graphitic carbon with a high surface area and would be practically relevant for fuel cell and many other technologies.

Influence of Preferred Orientation on the Electrical Conductivity of Fluorine-Doped Tin Oxide Films

Current development of high-performance transparent conductive oxide (TCO) films is limited with tradeoff between carrier mobility and concentration since none of them can be improved without sacrificing the other. In this study, we prepare fluorine doped tin oxide (FTO) films by chemical vapor deposition with inclusions of different additives and report that the mobility can be varied from 0.65 to 28.5 cm2 V−1 s−1 without reducing the achieved high carrier concentration of 4 × 1020 cm−3. Such an increase in mobility is shown to be clearly associated with the development of (200) preferred orientation (PO) but concurrent degradation of (110) PO in films. Thus, at a constant high carrier concentration, the electrical conductivity can be improved via carrier mobility simply by PO control. Such a one-step approach avoiding conventional post-deposition treatment is suggested for developing next-generation FTO as well as other TCO films with better than ever conductivities.

Ni-Ni3P alloy catalyst for carbon nanostructures

Abstract Carbon nanostructures were grown by using electroless Ni–P (Ni–Ni 3 P) alloys as catalysts. And the influence of the deposition structure on the as-grown nanostructures was examined. It reveals that traditional Ni–Ni 3 P alloy film on steel substrate could result in a preferred formation of carbon nanofibers, whereas, nanocrystalline Ni–Ni 3 P alloy catalysts could yield a formation of carbon nanotubes and especially those of nanotube junctions and double-helixed nanocoils. The successful use of these electroless alloys as catalysts here suggests wide catalysis applications of many binary or multinary alloys prepared through electroless plating and rapid quenching techniques.

Preparation of Large Area Double-walled Carbon Nanotube Macro-films with Self-cleaning Properties

Double-walled carbon nanotube (DWCNT) macro-films with large areas, excellent flexibility and superhydrophobicity are reported. The area of the macro-film is larger than 30 cm × 15 cm, and this large film can be bended, or folded without any damage, and even can be tailored freely. After a simple modification of perfluoroalkysilane, the surface of the macro-film shows excellent superhydrophobicity with a water contact angle of 165.7±2 deg. and sliding angle lower than 3 deg., the prepared superhydrophobic films showing excellent antifouling, self-cleaning and water-repellent functions. The topographic roughness and perfluoroalkysilane modification are found to contribute to the observed superhydrophobicity. Considering the outstanding electronic, chemical and mechanical properties of DWCNTs, it is expected that this multifunctional DWCNT macro-film has potential applications in many fields.

An investigation of the deformation mechanism in grain size-sensitive Newtonian creep

Creep of polycrystalline materials at low stresses often shows a linear relationship between strain rate and stress, and an inverse dependence on grain size squared or cubed. Attribution of this behavior to diffusional creep or grain boundary sliding (GBS) has evoked much confusion and controversy in the literature. A model is proposed to unify these two creep mechanisms. The model predicts a change in dominant mechanism from diffusional creep to GBS accommodated mainly by diffusion or by GBS itself as the amount of matter moved by diffusion decreases. Corresponding to this change, the model also predicts a spectrum of creep rate with the absolute value being dependent upon the extent of diffusion accommodation. Although experimental data exhibit scattering, most of them are in very good agreement with the prediction of the GBS model. Therefore, it is suggested that the Newtonian creep behavior with grain size dependence be induced by GBS rather than by conventional diffusional creep as believed before.