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The mechanical properties and the life cycle assessment (LCA) of jute woven fabric composites and their hybrids are investigated. Jute woven fabric composites were sandwiched with glass woven composites with the epoxy matrix. The sandwiched composites were prepared using the resin infusion under flexible tooling method. The water absorption test was performed on jute woven composites and composite sandwiches. It shows that thin layers of glass woven composites in the composites sandwich decelerate water penetration to jute woven composites, which are the core materials. The water absorption process applied to jute woven composites and their sandwich was modeled using Fick’s second law. The glass woven composites at the outer surface of the sandwich can act as strong skins. The bending and impact (drop weight) properties of jute–glass woven composites are higher than those of jute woven composites. A commercial LCA software product was employed to evaluate the environmental impacts of manufacturing the jute woven composites and their hybrids. The manufacturing of jute–glass woven composites had more negative environmental impacts (global warming, ozone depletion, etc.) than that of jute fabric composites, because glass fibres are less environmental friendly than natural fibres.

Here we demonstrate a simple, template-free approach to the formation of spherical gold aggregates through the reduction of HAuCl4 by NaBH4, in the presence of cysteine (Cys) as a capping agent. The resulting aggregates are quite stable in solution. The pH of the solution and the molar ratio of Au:Cys are two key empirical factors in the formation of such highly ordered aggregates. At slightly alkaline pH (7-10) and with Au:Cys ratios ranging from 1:0.5 to 1:2, spherical Au aggregates of 30-80 nm are formed. At lower Cys ratios (Au:Cys> or =1:0.5) very loosely linked aggregates are formed; however, at very high Cys ratios (Au:Cys< or =1:3), highly dispersed Au particles of 2-4 nm are obtained, which are virtually indistinguishable from the original colloidal form. Aggregate size is influenced markedly by component concentration; a 3-fold increase in standard levels resulted in Au spherical aggregates of a larger size, 200-500 nm. In addition, we used a combination of Cys and lysine (Lys) as a capping agent/cross-linker and found that the morphology of the Au colloid aggregates can be easily manipulated from a linear to a spherical form by adjusting the proportions of Cys and Lys in the capping agent/cross-linker mixture. The introduction of mercapto (SH)-containing organic acids reduced the cross-linking ability of Cys, especially in the case of long-chain acids. Complete disruption of the spherical aggregates highlights the importance of Cys per se. An explanation of this ordered self-assembly process is proposed, in the context of the known surface chemistry of Au colloids.

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In this work, we aimed to tune the aggregation state of Au colloids by judicious regulation of their surface charges and by introduction of ultrasound irradiation. Au colloids were prepared by reduction of HAuCl 4 with NaBH 4 in the presence of 3-mercaptopropionic acid (MPA) as the stabilizing ligand. The Au colloids capped with MPA molecules possessing a single -SH terminal group, can form either linear or spherical Au colloid aggregates depending on the MPA : Au ratio, solution pH and Au colloid concentration. Adjustment of these parameters provides a convenient means of regulating surface charge on the Au colloid surface and, thus, the state and degree of aggregation. The spherical aggregates appeared to be thermodynamically stable, and ultrasound irradiation could promote their formation. Intense ultrasound irradiation resulted in the formation of well-crystallized nanospheres whilst mild irradiation tended to produce a more amorphous product. This is the first observation of a sonication effect on the crystallization state in freely suspended Au colloids in aqueous solution.