Tailoring oxidation of Al particles morphologically controlled by carbon nanotubes

Aluminum powder is used for energetic materials due to high energy density. Controlling oxidation rate, oxidation temperature, and reaction enthalpy is important parameters prior to practical use. Here, we engineered static and dynamic properties of oxidation of Al particles by mixing CNTs (carbon nanotubes) having high thermal conductivity and large exothermic energy. Morphologies of Al/CNT mixture were engineered by a mechanical pulverization. Among various morphologies of Al/CNT mixture of i) CNTs adhered on the surface of Al particles, ii) CNTs partially embedded onto Al particles, forming an urchin type, and iii) CNTs fully embedded into aggregated Al particles, urchin type Al/CNT revealed the largest exothermic enthalpy at the lower oxidation temperature for both γ-Al2O3 and α-Al2O3 phases. This was attributed to the fast heat transfer into Al particles via partially embedded CNTs. Large exothermic enthalpy as well as the mass of alumina were obtained in oxidation of Al/CNT mixture compared to pure Al particles up to 1000°C oxidation. The exothermic enthalpy showed strong dependence on the CNT content, increasing to-188kJ/g at 20wt% CNT. The engineering ability of thermal properties in Al particles with CNTs opens a new research area for diverse use of solid fuel Al. © 2013.1891sciescopu

Induction of Thioredoxin Is Required for Nodule Development to Reduce Reactive Oxygen Species Levels in Soybean Roots

Nodules are formed on legume roots as a result of signaling between symbiotic partners and in response to the activities of numerous genes. We cloned fragments of differentially expressed genes in spot-inoculated soybean (Glycine max) roots. Many of the induced clones were similar to known genes related to oxidative stress, such as thioredoxin and β-carotene hydroxylase. The deduced amino acid sequences of full-length soybean cDNAs for thioredoxin and β-carotene hydroxylase were similar to those in other species. In situ RNA hybridization revealed that the thioredoxin gene is expressed on the pericycle of 2-d-old nodules and in the infected cells of mature nodules, suggesting that thioredoxin is involved in nodule development. The thioredoxin promoter was found to contain a sequence resembling an antioxidant responsive element. When a thioredoxin mutant of yeast was transformed with the soybean thioredoxin gene it became hydrogen peroxide tolerant. These observations prompted us to measure reactive oxygen species levels. These were decreased by 3- to 5-fold in 7-d-old and 27-d-old nodules, coincident with increases in the expression of thioredoxin and β-carotene hydroxylase genes. Hydrogen peroxide-producing regions identified with cerium chloride were found in uninoculated roots and 2-d-old nodules, but not in 7-d-old and 27-d-old nodules. RNA interference-mediated repression of the thioredoxin gene severely impaired nodule development. These data indicate that antioxidants such as thioredoxin are essential to lower reactive oxygen species levels during nodule development