Alignment-retainable nitrogenation of cylindrical carbon nanotubes by thermal reaction with ammonia following UV oxidation: chemical alteration effects on electrical conductivity.

Cylindrical carbon nanotubes (CNTs) pretreated by UV irradiation were able to react with NH(3) to give nitrogen-containing CNTs without destroying their vertically aligned morphology. This process provided incorporation of nitrogen mostly at pyridinic and pyrrolic sites and promoted disordering, which was correlated with decreased electrical conductivity of CNT yarns.

Anti-agglomerating effect in vertically aligned carbon nanotubes derived by antisolvent precipitation of naphthalene.

We developed a novel anti-agglomeration method that enables preservation of the vertical alignment of carbon nanotubes (CNTs) during desiccation of wet CNTs by utilizing antisolvent precipitation and sublimation of naphthalene (Nap). Moreover, we succeeded in depositing Pt nanoparticles onto CNTs without collapse of the vertically aligned morphology by this method.

Growth of diameter-controlled carbon nanotubes from fe-v-o nanoparticles size-classified by ligand-exchanged fractional precipitation.

Colloidal Fe-V-O nanoparticles prepared as carbon nanotube (CNT) growth catalysts were precisely size-classified by fractional precipitation. Furthermore, the classification ability was improved by the fractional precipitation after ligand exchange process, which allowed us to obtain narrower size distributions of nanoparticles. CNTs were grown from the nanoparticles in order to investigate the dependence of diameter distribution of CNTs on that of nanoparticles. The results show that the diameter distribution of CNTs grown from classified nanoparticles was narrower than that of CNTs grown from as-prepared nanoparticles.

Ultrahigh-quality silicon carbide single crystals.

Silicon carbide (SiC) has a range of useful physical, mechanical and electronic properties that make it a promising material for next-generation electronic devices. Careful consideration of the thermal conditions in which SiC [0001] is grown has resulted in improvements in crystal diameter and quality: the quantity of macroscopic defects such as hollow core dislocations (micropipes), inclusions, small-angle boundaries and long-range lattice warp has been reduced. But some macroscopic defects (about 1-10 cm(-2)) and a large density of elementary dislocations (approximately 10(4) cm(-2)), such as edge, basal plane and screw dislocations, remain within the crystal, and have so far prevented the realization of high-efficiency, reliable electronic devices in SiC (refs 12-16). Here we report a method, inspired by the dislocation structure of SiC grown perpendicular to the c-axis (a-face growth), to reduce the number of dislocations in SiC single crystals by two to three orders of magnitude, rendering them virtually dislocation-free. These substrates will promote the development of high-power SiC devices and reduce energy losses of the resulting electrical systems.