additions on the mechanical properties of hydroxyapatite (HAp) were investigated. The addition of Ni 3 Al particles increased the strength as well as the fracture toughness of HAp. However, the improvements in the properties were limited because of the formation of microcracks around the metal particles. The microcracks were formed because of the large difference in the coefficients of thermal expansion between HAp and Ni 3 Al, and because of the relatively large size of Ni 3 Al particles (∼20 µm). The addition of submicrometer Al 2 O 3 powder was also effective in increasing the mechanical properties. The flexural strength and the fracture toughness were increased from about 100 MPa and 0.7 MPaؒm 1/2 , respectively, to 200 MPa and 1.5 MPaؒm 1/2 by the addition of 20 vol% Al 2 O 3 . When Ni 3 Al and Al 2 O 3 were added together, the fracture toughness was further increased to 2.3 MPaؒm 1/2 . This increase in the fracture toughness was attributed to the synergistic effect of matrix strengthening and crack interactions with the metal particles.

The random amphiphilic copolymers containing a large fraction (35−50 mol %) of ureidopyrimidinone (UPy) that can dimerize using a quadruple hydrogen bonding were synthesized to produce antifreeze and dynamic hydrogels. Directional packing of the UPy−UPy dimers provides nanosized aggregates, and the effective gap distance between the aggregates is narrow enough to inhibit the water crystallization by the confinement effect. The characteristic dimensions such as the aggregate size and gap distance depend on the polymer concentration and the UPy fraction in the polymers. Furthermore, the temperature-dependent dynamics of UPy allows the hydrogels to form the frozen structure at a lower temperature, while the injectability and self-healing property were achieved at room temperature. The antifreeze hydrogels also exhibit negligible cytotoxicity and thus expands the applicable area including the drug storage and cell cryopreservation.

mileage of electric vehicles (EVs). Although the operating voltage of Si is only slightly higher than that of its commercial graphite (Gr) counterpart, the theoretical specific capacity of Si (above 3000 mAh g −1 ) is far greater than that of its bare Gr counterpart (≈372 mAh g −1 ). [1] Nevertheless, the massive volume change (as much as 300%) Si undergoes during each charge-discharge cycle, has long been recognized as the origin of wrecking the integrity of the Si electrode at both the particle and electrode level as well as destabilizing the electrodeelectrolyte interface by accelerating the decomposition of the electrolyte. [2] These failure mechanisms shorten the cycle life of a Si-based electrode drastically and place a critical obstacle in the way of increasing the Si content of the LIB anodes.A variety of approaches have been introduced thus far to address the problems caused by the volume expansion of Si: diverse Si nanostructures represented by nanowires, [3] nanotubes, [4] and porous materials [5] as well as Si alloys with foreign atoms such as iron (Fe), [6] manganese (Mn), [7] and nickel (Ni) [8] turned out to be effective in buffering the volume expansion of Si. Carbon materials such as Gr, [9] graphene, [10] carbon nanofibers, [11] and carbon nanotubes [12] were also acknowledged to play a crucial role in stabilizing the electrodes over long-term cycling while supplementing the electrical conductivity. Although the exclusive use of Si as the active material would be the most ideal in terms of the energy density, blending Si with Gr would be a more realistic option in the near future to manage the aforementioned failure modes of Si.In addition to the various approaches mentioned above, the polymeric binder has also been identified as a critical electrode component that has to be taken into account when addressing the issues associated with the volume expansion of Si. [13] In this regard, it would be desirable to design the binder such that it outperforms conventional binders, which include carboxymethyl cellulose (CMC)-styrene butadiene rubber (SBR) blends, poly(vinylidene difluoride) (PVDF), and poly(acrylic acid) (PAA) in terms of preserving the electrode integrity during cycling. Beyond these established binders, various unconventional concepts were recently divulged, which include covalent crosslinking, [14] noncovalent supramolecular interactions with self-healing ability, [15] 3D networks, [16] and high elasticity. [15c,17] Most of these approaches were validated in treating bare Si active Maximizing the energy density of a lithium-ion battery cell by increasing the silicon content in the silicon-graphite (Si-Gr) composite anode is an ongoing research topic that is receiving much attention. However, the paradoxical surface characteristics of Si and Gr make it challenging to uniformly distribute the electrode components and maintain their adhesion during cycling accompanied with the immense volume change of Si. Here, an amphiphilic, tightly interlocked host-guest complex binder composed ...

For most of natural hybrid materials, the shape of mineral crystals is controlled by natural polymers (e.g., proteins) to provide designated and unique physical properties and functions. Synthetic hybrid materials, which show comparable performance to the natural ones, require well-controlled crystal growth. In particular, the dynamic process including adsorption of the polymers on the crystal surface plays a significant role. We investigated CaSO4·0.5H2O crystallization in the presence of linear or particulate charged macromolecules, which can interact electrostatically with the crystals. Not only the static factors such as concentration and charge fraction but also the diffusion dynamics of the charged macromolecules were found crucial to involve the complete inhibition of growth and the subsequent shape transition of the crystals. This leads to the elucidation of semiquantitative relationships between dynamic factors such as the diffusion of macromolecules and the rate of crystal growth to the growth inhibition. The diffusion-limited adsorption model was coherent with the experimental evidence, i.e., the effects of molecular weight of linear polyelectrolyte and the size of charged spherical micelles. This fundamental understanding of dynamic adsorption during the crystal growth would provide the basis for the kinetic control of polymer/inorganic hybrid assembly in both biological and engineering contexts.

No abstract