Thermoelectric generation is one of the strongest candidates for recovering the waste heat from industry and transportation. Some of oxides and silicides are considered to be promising thermoelectric materials because of their high oxidation resistance. Several types of modules using p-type Ca3Co4O9/n-type CaMnO3 and p-type MnSi1.75/n-type Mn3Si4Al2 have been prepared and shown around 4 kW/m2 of maximum power density. The present study described the challenging enhancement of the thermoelectric figure of merit ZT of both oxide and silicide compounds. Introduction of secondary phases and low bulk density using a partial melting method is found to be effective for reducing phonon thermal conductivity in the promising Bi2Sr2Co2Ox. The grain size and distribution of the secondary phases can be controlled by optimizing the parameters of the partial melting method. On the other hand, detailed crystallographic structure of a new n-type Mn3Si4Al2 is clarified and leads to the enhancement of the ZT values by elemental substitution.

All-polymer solar cells composed of binary blends of donor poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b]thiophene-)-2–6-diyl)] (PBDTTT-CT ), and acceptor polymers naphthalene diimide-selenophene copolymer (PNDIS-HD) and perylene diimide-selenophene copolymer (PPDIS) had power conversion efficiencies (PCEs) of 1.3 and 2.1%, respectively. Ternary blend solar cells composed of [PBDTTT-CT][PNDIS-HD]1−x[PPDIS]x at 75 wt% PPDIS had a PCE of 3.2%, which is about a 50%–140% enhancement compared with the binary blend devices. Equality of the ternary blend short-circuit current to the sum of those of the binary blend devices, among other results, provided evidence of a parallel-like bulk heterojunction mechanism in the ternary blend solar cells. These results provide the first example of enhanced performance in ternary blend all-polymer solar cells.

Material research and development is increasingly focusing on achieving specialized functionality in materials. For example, the ability to “self-heal (SH)”, or naturally repair accrued damage, is attractive because it extends the lifetime of the material by increasing resistance to damaging conditions and prolonging preservation of material properties. Additionally, shape memory (SM) materials, including SM polymers, are actively considered for their ability to change shape one or more times upon application of an external stimulus. Here, we present a polymer composite, composed of poly(vinyl acetate) (PVAc) and poly(ε-caprolactone) (PCL), exhibiting both SH and SM functionalities. In fact, the SM assists in the SH ability in a process developed by our group termed, shape memory-assisted self-healing (SMASH). The advantage of the SH composite presented here is its simple fabrication. Dual-electrospinning is used to simultaneously electrospin PVAc and PCL, achieving an interwoven polymeric composite of otherwise immiscible polymers. The dual-electrospinning method facilitates precise control of the relative weight fractions of the components, and thus allows for tuning of the material properties. Upon thermal activation, damaged PVAc–PCL composites exhibited SH under a variety of testing conditions. Furthermore, the composites exhibited impressive dual and triple SM capabilities in the dry and hydrated states, respectively. Together, the commercial availability of the components and the simplicity of preparation translate to a SMASH system that could be mass produced and used as a SH coating or alone, as a packaging material.

Several organisms possess a genetic program enabling them to form a mineral, a process termed biomineralization. The structure and composition of biominerals equip the biomineralizing organisms with functionalities that abiotic materials made of the same mineral do not necessarily possess. Even primary organisms such as bacteria are able to produce materials with properties superior to those of human-made equivalents. Magnetotactic bacteria represent a paradigm of such microorganisms. These organisms synthesize a hierarchical one-dimensional magnetic nanostructure based on the alignment of magnetosomes—organelles embedded in a vesicle dedicated to biomineralization and made of magnetic nanoparticles (magnetite (Fe3O4) or greigite (Fe3S4)). This article focuses on factors that play a role in the organization of these magnetosomes. The chains, which are based on aligned particles that have biologically controlled ultrastructure, size, morphology, organization, and orientation, serve as actuators and area means to align the bacteria with the Earth’s magnetic field lines when they swim in search of particular habitats in the aqueous environments they live in.

Modern materials design is largely based on composite structures aimed at a synergistic integration of multiple components with a diverse range of properties. Biologically grown minerals provide an intriguing example of sophisticated organic–inorganic nanocomposite structures resulting in excellent mechanical characteristics. Among the mineral phases utilized by living organisms to generate hard tissues, calcium carbonate—especially the calcite polymorph—is ubiquitous and has been studied intensively. Biogenic calcite crystals often show hierarchical organization spanning multiple length scales, and the occluded organic phases are now known to be intimately associated with the mineral host. Here, we discuss the internal micro- and nanostructure of two selected types of calcite biominerals—the sea urchin spine and prismatic single crystals extracted from mollusk shells. This article highlights recent advances in translating the key principles of biological mineralization into design strategies for synthetic materials and presents analogies between biogenic and synthetic calcite single crystals.

We demonstrate that fluorescence properties of organic fluors embedded in a porous polystyrene matrix are highly sensitive to the average pore size and pore-size distribution of the matrix. The effect can be understood as two different types of confinement imposed to the fluor molecules by the matrix. First, there is geometrical confinement that restricts the fluor oscillations due to its physical contact with a pore wall. Second, there is an electronic confinement due to a local polarization of the wall material by molecular dipoles. The effects lead to a spectral shift and enhancement of the fluorescence intensity of the material.

Additive manufacturing, also known as three-dimensional printing, has provided a promising solution to produce near-net shape components directly from metallic powder. However, their surface roughness still prevents them from immediate use; finish machining is usually required. This study has investigated the grain size variation and saw-tooth/shear-band spacing during the machining of titanium alloy (Ti–6Al–4V) printed using direct metal deposition. Grain refinement was observed within both the printed and substrate regions, and their grain structures retained the basket-weave Widmanstätten and bimodal structures, respectively. The saw-tooth spacing decreased as the build height increased.