Aluminum hydride (AlH3), and the complex aluminum hydrides (e.g., M3AlH6, MAlH5, M2AlH7, M(AlH4)n), make up a fascinating class of materials that have received considerable attention over the past 60 years for their use as explosives, reducing agents, solid rocket propellants, as well as a hydrogen source for portable power systems. The recent renaissance in hydrogen storage research, particularly for automotive applications, has generated renewed interest in aluminum-based hydrides due to their capacity to store up to 11 wt% hydrogen with volumetric capacities up to 150 g H2/L (more than twice that of liquid hydrogen). In addition, hydrogen can be released from these materials by low temperature thermolysis (<100°C), making them well-suited for proton exchange membrane fuel cells and other low temperature applications. This article covers recent research on aluminum-based hydrides, including crystal structures, thermodynamics, kinetics, hydrogenation conditions, and regeneration methods.

The development of safe, efficient, and economic hydrogen storage technologies is key for implementation of a hydrogen-based energy economy. In the search for high-hydrogen content materials, attention in the past decade has shifted to amides and borohydrides, two representative solid-state chemical sorption materials with high hydrogen capacities that had not been previously explored for hydrogen storage. A large number of new amide and borohydride systems have recently been developed that expand the material scope for hydrogen storage. This article reviews the current progress in amides and borohydrides with emphases on material design and kinetic improvement.

Watson and Crick’s discovery of the structure of DNA in 1953 and the near-simultaneous advent of the first silicon transistor in 1954 spurred parallel historic advances over the following decades in molecular biology and materials technology. As these two expansive fields of research have progressed, important areas of overlap have included the extensive use of materials innovations in biological research, such as in microscopy and measurement systems, while materials research has benefited from efforts to mimic design principles utilized in nature. Until relatively recently, however, the molecular mechanisms that underpin nature’s biological orchestra have remained largely outside the purview of materials research. Now, with new abilities to harness and modify biomolecular and cellular systems, evidence is mounting that biology can be fruitfully utilized to directly engineer technological materials. This article aims to highlight the importance of DNA-driven routes to new materials while providing a brief overview of the genetic engineering platforms that make these routes possible. Emphasis is placed on the fact that it is now possible to genetically evolve materials technologies in a manner that mimics the genetic evolution of biominerals in nature.

Rechargeable batteries are essentially unstable systems with respect to charging/discharging. The main electrode reactions of all battery chemistries are well known but are valid and reversible only at small currents. When batteries are used with nonzero current, gradients in voltage, current, and temperature will arise and initiate a number of less understood parasitic reactions. If all these rather complicated and interconnected reactions are not reversible upon charging/discharging, the battery will derail after a number of charging/discharging cycles. This article describes two ways to improve performance. One is to choose applications where the battery is not deeply discharged, such as in hybrid electric vehicles. In battery electric vehicle applications, this would correspond to working with a significantly oversized battery. The second way is to improve uniformity and quality of design and materials of metal hydride electrodes; however, this will also drastically increase cost, and for a battery application, the total throughput of available energy over the lifetime cost of the battery must be maximized. Uniform metal hydride particles with a large and uniform reaction surface are examples of how to increase battery performance by making the electrodes work under more ideal conditions, which slows down the deteriorating influence from the parasitic reactions.

This paper presents recent results of foam extrusion of thermoplastic cellulose acetate (CA) using HFO 1234ze as low global warming blowing agent and talc as nucleating agent. Foam extrusion behavior, physical foam properties, and foam morphologies were studied in detail with respect to blowing agent concentration and talc content. Depending on these parameters, thermoplastic CA exhibits excellent foam extrusion performance with good expansion behavior at the die. Talc as nucleating agent results in homogeneous fine foam morphologies with closed cells [i.e., Fig. 3(3)]. Depending on the blowing agent content and talc content, average cell size ranges from 1 to 0.12 mm and foam density ranges between 100 and 400 kg/m3.

The present work reports a soft-chemical pathway for preparing SnO–TiO2 composite nanocrystallites as photocatalyst through co-hydrolysis of tetrabutyl titanate and tin (II) chloride followed by acidic peptization of the hydrolysate under mild conditions. The procedure is simple and straightforward, from which a well-dispersed semitransparent hydrosol sample is obtained. The freestanding nanocrystallites observed in the as-prepared composite show diameters of 3–5 nm. TiO2 nanoparticles have almost entirely transformed into anatase phase, and the trace amounts of Sn in existence are mainly found in SnO crystals with tetragonal structure. The photocatalytic activity of the SnO–TiO2 composites is confirmed through the photodegradation of methyl blue dye under visible light irradiation (λ > 420 nm). As a p-type semiconductor, the incorporated SnO effectively improves the photocatalytic activity of TiO2 through promoting the separation of photo-generated charge carriers, inhibiting their recombination, and facilitating the reduction of O2 by the photo-generated electrons.

Sputter-deposited epitaxial (111) and (110) Ag films have high-density nanotwins with respective twin boundary orientations perpendicular and angled to the growth direction. Twin density in as-deposited (111) Ag films is much greater than in (110) films, leading to higher hardness in the (111) films. Annealing up to 800 °C (homologous temperature of 0.85 Tm) leads to increased twin thickness, although the average twin thickness remains <100 nm in both systems. Twinned volume fraction falls dramatically in annealed (110) films but remains constant at ∼50% in (111) films. The mechanisms leading to the elimination of nanotwins in (110) films and their remarkable stability in (111) films at elevated temperatures are discussed. Coarsening and elimination of twins result in hardness reduction after annealing. The variety of microstructures achieved via annealing allows for the introduction of a strengthening model considering both twin and grain boundaries.

To obtain highly dispersed and active Pd/C catalysts for formic acid electro-oxidation (FAEO), carbon supported Pd nanoparticles were prepared by three different synthesis methods. The first Pd deposition technique went through the ethylene glycol (EG)-assisted sodium borohydride (NaBH4) reduction process (Pd/C-EG-NaBH4). The second method was the polyol process (Pd/C-EG). The third method was the general NaBH4 reduction process (Pd/C-NaBH4). The results of x-ray diffraction and transmission electron microscopy (TEM) show that the Pd particles on carbon black prepared by the first method have the smallest average size of 3.5 nm with a narrow size distribution. Cyclic voltammetry was used to characterize the electrochemical performance. The peak current density (mass activity) of the Pd/C-EG-NaBH4 for FAEO is 1742 mA/mgPd, which is 1.45 times higher than that of Pd/C-EG and 1.48 times higher than that of Pd/C-NaBH4. Moreover, the experimental results show that the first method has no dependence on the pH value of the synthesis procedure, while the other two methods in the literature are greatly affected by the pH value.

A new theta geometry was developed for microscale bending strength measurements. This new “gap” theta specimen was a modification of the arch theta specimen that enabled microscale tensile testing. The gap theta specimen was demonstrated here on single-crystal silicon, microfabricated using two different etch processes. The resulting sample strengths were described by three-parameter Weibull distributions derived from parameters determined using established arch theta strengths, assuming a specimen-geometry and -size invariant flaw distribution and an approximate loading configuration.

Alternating layer-by-layer (LbL) deposition of polycations and polyanions on porous substrates is a convenient and versatile method for forming high-flux nanofiltration (NF) membranes. In this work, positively charged NF membranes were fabricated by the LbL assembly of poly(ethyleneimine) (PEI) and poly(sodium 4-styrenesulfonate) (PSS) on the modified polyacrylonitrile ultra-filtration substrate. The charge variation with each layer was characterized by zeta potential. ATR-FTIR, SEM, N2 adsorption and the weight changes with bi-layers were used to confirm the LbL deposition of the polyelectrolytes. NF performances of the prepared membrane with a number of bi-layers as well as solute concentrations were also investigated. The results of zeta potential showed that the whole multilayer films exhibited periodic variations in positive charge. NF results indicated that the rejection of Ni2+ and Cd2+ ions increased, while the permeate fluxes decreased with the number of bi-layers. And the rejections of the metal ion solutes were 98.02% for CuSO4, 95.53% for ZnSO4, 95.66% for NiCl2, 94.9% for CdCl2, along with permeation fluxes of 19.02, 19.72, 24.02, and 21.19 L/m2·h, respectively.

Nanocrystalline (NC) metals are known for having excellent strength but perceived to have poor ductility. Miniature tensile tests on NC Ni–Fe measured ultimate strengths of 2 GPa and elongations, by digital image correlation, of up to 10%. Detailed examination of the fracture surface revealed dimpled rupture and cross-section reduction up to 75%, suggesting an intrinsic ability for small grained Ni–Fe to accommodate plasticity. A survey of published studies on NC metals reveals that this behavior is quite common; despite low macroscopic elongation, NC metals often achieve extensive deformation suggesting good intrinsic ductility. Unfortunately, the common sheet-like configuration of NC tensile specimens muddies a simple evaluation of ductility based on elongation, since thin and wide geometries promote localized necking that expedites catastrophic failure. This paper presents a compact review of ductility concepts and literature to interpret the experimental ductility measurements of an electrodeposited nickel alloy.