Diffusion of interstitial hydrogen atoms in α-iron was investigated using molecular dynamic simulation. In particular, hydrogen diffusivities in bulk, on (001) surface and within a Σ5 [100]/(013) symmetric tilt grain boundary (STGB) were estimated in a temperature range of 400 and 700 K. Furthermore, hydrogen diffusivities in a series of Σ5 [100] tilt grain boundaries with different inclinations were also determined as a function of temperature. The inclination dependence of activation energy for diffusion exhibits two local maxima, which correspond to two STGBs. Additional calculation of inclination dependence of boundary energy and boundary specific excess volume shows two local minima at the same STGBs. This suggests hydrogen diffusion into and within a grain boundary might be assisted by grain boundary excess volume and stress. Simulation of effects of hydrostatic pressure on diffusion shows tensile stress can promote hydrogen diffusion in lattice into grain boundary or surface traps, while compressive stress leads to a decrease in diffusivity, and a slower rate of filling these traps.

Tribological behavior of alumina-particle-reinforced aluminum composites made by powder metallurgy process has been investigated. The nanocomposite containing 15 vol% of Al2O3 nanoparticles exhibits excellent wear resistance by showing significantly low wear rate and abrasive wear mode. The wear rate of the nanocomposite is even lower than stainless steel. We have also demonstrated that such excellent wear resistance only occurred in the composite reinforced with the high volume fraction of nanosized reinforcing particles. The results were discussed in terms of the microstructure of the nanocomposite.

Highly graphitic carbons are obtained by precipitating carbon from molten steel inoculated with bismuth. Scanning electron microscopy images show that the products have a potato peel morphology. The inoculant leads to a breaking of the local symmetry of the graphitic structure as evidenced by Raman spectroscopic studies. The products exhibit flat charge–discharge profiles below about 200 mV versus Li+/Li, reversible capacities even exceeding the theoretical limit of 372 mAh/g for perfectly graphitic structures, low first-cycle irreversible capacities, and sustained hundreds of cycles.

Starch is an abundant, biodegradable, renewable, and low-cost commodity that has been explored as a replacement for petroleum-based plastics. By itself, starch is a poor replacement for plastics because of its moisture sensitivity and brittle properties. Using starch as a fermentation feedstock, various promising biodegradable plastic products have been developed that rival petroleum-based plastics and are poised to enter the marketplace or are already in production. Other starch-based plastics are blends with other compatible resins or are based on chemical treatments that improve the functional properties of various products. While these approaches are very promising, there are efforts under way to develop viable products from starch by using different processing technologies and by combining starch with other materials to make functional composites. This article focuses on different technologies for making starch-based foam materials and the use of reinforcing fibers and nanoparticles for making composites that can substitute for some petroleum-based foam products.

Bio-based plastics, in which the fossil carbon is replaced by bio/renewable-based carbon, offer the intrinsic value proposition of a reduced carbon footprint and are in complete harmony with the rates and time scale of the biological carbon cycle. Identification and quantification of bio-based content is based on the radioactive C-14 signature associated with (new) biocarbon. Using experimentally determined biocarbon content values, one can calculate the intrinsic CO2 emissions reduction achieved by substituting petrocarbon with biocarbon—the material carbon footprint value proposition. The process carbon footprint arising from the conversion of feedstock to final product is computed using life-cycle assessment methodology. Biodegradability in conjunction with selected disposal systems such as composting and anaerobic digestion offers an end-of-life solution to completely remove the plastic substrate from the environment. Not all bio-based polymer materials are biodegradable, and not all biodegradable polymers are bio-based. Most importantly, complete biodegradability (complete utilization of the polymer by the microorganisms present in the disposal environment) is necessary as per ASTM and ISO standards, otherwise there could be serious health and environmental consequences.

A significant change is occurring in the global polymer industries. Development of a new generation of bio-based polymers, polymers derived from renewable resources, is progressing rapidly. Complementing historical biopolymers such as natural rubber and cellulosics, these new bioplastics include a growing number of commercial successes, including polylactides and polyhydroxyalkanoates. Many more bioplastics are on the near horizon, made possible by rapid advances in biotechnology. The molecular specificity of biochemical transformations is ideally suited for producing high purity monomers needed for making high molecular weight polymer molecules. Some of the newest developments involve the creation of well-established polymers (polyethylene, polybutlylene, poly(ethylene terephthalate)) via new biochemical pathways that start with renewable, rather than fossil, resources. This article highlights some recent advances in bio-based polymers. Specifically, this review includes topics ranging from novel biopolymer synthesis, new bio-based nanocomposites, novel processing, and holistic assessments of sustainability through quantitative life-cycle analysis. It is demonstrated that greener plastic materials can be produced through ecologically responsible conversion of renewable resources using industrial biotechnology and enhanced by nanotechnology. This emerging approach represents a triple technological convergence that promises to significantly alter the value chains of the global plastics industries.