Regain Strain-Hardening in High-Strength Metals by Nanofiller Incorporation at Grain Boundaries.

Grain refinement to the nano/ultrafine-grained regime can make metals several times stronger, but this process is usually accompanied by a dramatic loss of ductility. Such strength-ductility trade-off originates from a lack of strain-hardening capacity in tiny grains. Here, we present a strategy to regain the strain-hardening ability of high-strength metals by incorporation of extrinsic nanofillers at grain boundaries. We demonstrate that the dislocation storage ability in Cu grains can be considerably improved through this novel grain-boundary engineering approach, leading to a remarkably enhanced strain-hardening capacity and tensile ductility (uniform elongation). Experiments and large-scale atomistic simulations reveal that a key benefit of incorporated nanofillers is a reduction in the grain-boundary energy, enabling concurrent dislocation storage near the boundaries and in the Cu grain interior during straining. The strategy of grain-boundary engineering through nanofillers is easily controllable, generally applicable, and may open new avenues for producing nanostructured metals with extraordinary mechanical properties.

High content reduced graphene oxide reinforced copper with a bioinspired nano-laminated structure and large recoverable deformation ability.

By using CuO/graphene-oxide/CuO sandwich-like nanosheets as the building blocks, bulk nacre-inspired copper matrix nano-laminated composite reinforced by molecular-level dispersed and ordered reduced graphene oxide (rGO) with content as high as ∼45 vol% was fabricated via a combined process of assembly, reduction and consolidation. Thanks to nanoconfinement effect, reinforcing effect, as well as architecture effect, the nanocomposite shows increased specific strength and at least one order of magnitude greater recoverable deformation ability as compared with monolithic Cu matrix.

Construction of a novel hierarchical structured NH4-Co-Ni phosphate toward an ultrastable aqueous hybrid capacitor.

Aqueous hybrid capacitors (HCs) suffer from sacrificed power density and long cycle life due to the insufficient electric conductivity and poor chemical stability of the battery-type electrode material. Herein, we report a novel NH4-Co-Ni phosphate with a stable hierarchical structure combining ultrathin nanopieces and single crystal microplatelets in one system, which allows for a synergistic integration of two microstructures with different length scales and different energy storage mechanisms. The microplatelets with a stable single crystal structure store charge through the intercalation of hydroxyl ions, while the ultrathin nanopieces store charge through surface redox reaction providing enhanced specific capacitance. Furthermore, the large single crystal can bridge the small nanopieces forming continuous electronic conduction paths as well as ionic conduction channels, and facilitate both electron and ion transportation in the hierarchical structure. The HC cell based on the as prepared material and a 3D hierarchical porous carbon delivers a high energy density of 29.6 Wh kg(-1) at a high power density of 11 kW kg(-1). Particularly, an ultralong cycle life along with 93.5% capacitance retention after 10,000 charge-discharge cycles is achieved, which is outstanding among the state-of-the-art aqueous HC cells.

Hybridized Phosphate with Ultrathin Nanoslices and Single Crystal Microplatelets for High Performance Supercapacitors.

A novel hybridized phosphate is developed through a mild hydrothermal method to construct high performance asymmetric supercapacitor. Single layered (Ni,Co)3(PO4)2·8H2O nanoslices (∼1 nm) and single crystal (NH4)(Ni,Co)PO4·0.67H2O microplatelets are obtained through a template sacrificial method and dissolution recrystallization approach respectively in one step. This unique hybridized structure delivers a maximum specific capacitance of 1128 F g(-1) at current density of 0.5 A g(-1). The asymmetric supercapacitor (ASC) based on the hybrid exhibits a high energy density of 35.3 Wh kg(-1) at low power density, and still holds 30.9 Wh kg(-1) at 4400 W kg(-1). Significantly, the ASC manifests very high cycling stability with 95.6% capacitance retention after 5000 cycles. Such excellent electrochemical performance could be attributed to the synergistic effect of the surface redox reaction from the ultrathin nanoslices and ion intercalation from the single crystal bulk structure. This material represents a novel kind of electrode material for the potential application in supercapacitors.

Nickel Cobalt Hydroxide @Reduced Graphene Oxide Hybrid Nanolayers for High Performance Asymmetric Supercapacitors with Remarkable Cycling Stability.

Nanolayered structures present significantly enhanced electrochemical performance by facilitating the surface-dependent electrochemical reaction processes for supercapacitors, which, however, causes capacitance fade upon cycling due to their poor chemical stability. In this work, we report a simple and effective approach to develop a stable, high performance electrode material by integrating 2D transition metal hydroxide and reduced graphene oxide sheets at nanometer scale. Specifically, a hybrid nanolayer of Ni-Co hydroxide @reduced graphene oxide (Ni,Co-OH/rGO) with an average thickness of 1.37 nm is synthesized through an easy one-pot hydrothermal method. Benefiting from the face to face contact model between Ni-Co hydroxide and rGO sheets, such unique structure presents superior specific capacitance and cycling performance as compared to the pure Ni-Co hydroxide nanolayers. An asymmetric supercapacitor based on Ni,Co-OH/rGO and three-dimensional (3D) hierarchical porous carbon is developed, exhibiting a high energy density of 56.1 Wh kg(-1) along with remarkable cycling stability (80% retention after 17 000 cycles), which holds great promise for practical applications in energy storage devices.

Enhanced Mechanical Properties of Graphene (Reduced Graphene Oxide)/Aluminum Composites with a Bioinspired Nanolaminated Structure.

Bulk graphene (reduced graphene oxide)-reinforced Al matrix composites with a bioinspired nanolaminated microstructure were fabricated via a composite powder assembly approach. Compared with the unreinforced Al matrix, these composites were shown to possess significantly improved stiffness and tensile strength, and a similar or even slightly higher total elongation. These observations were interpreted by the facilitated load transfer between graphene and the Al matrix, and the extrinsic toughening effect as a result of the nanolaminated microstructure.

Graphene-and-Copper Artificial Nacre Fabricated by a Preform Impregnation Process: Bioinspired Strategy for Strengthening-Toughening of Metal Matrix Composite.

Metals can be strengthened by adding hard reinforcements, but such strategy usually compromises ductility and toughness. Natural nacre consists of hard and soft phases organized in a regular "brick-and-mortar" structure and exhibits a superior combination of mechanical strength and toughness, which is an attractive model for strengthening and toughening artificial composites, but such bioinspired metal matrix composite has yet to be made. Here we prepared nacre-like reduced graphene oxide (RGrO) reinforced Cu matrix composite based on a preform impregnation process, by which two-dimensional RGrO was used as "brick" and inserted into "□-and-mortar" ordered porous Cu preform (the symbol "□" means the absence of "brick"), followed by compacting. This process realized uniform dispersion and alignment of RGrO in Cu matrix simultaneously. The RGrO-and-Cu artificial nacres exhibited simultaneous enhancement on yield strength and ductility as well as increased modulus, attributed to RGrO strengthening, effective crack deflection and a possible combined failure mode of RGrO. The artificial nacres also showed significantly higher strengthening efficiency than other conventional Cu matrix composites, which might be related to the alignment of RGrO.

Oxygen-rich hierarchical porous carbon derived from artemia cyst shells with superior electrochemical performance.

In this study, three-dimensional (3D) hierarchical porous carbon with abundant functional groups is produced through a very simple low-cost carbonization of Artemia cyst shells. The unique hierarchical porous structure of this material, combining large numbers of micropores and macropores, as well as reasonable amount of mesopores, is proven favorable to capacitive behavior. The abundant oxygen functional groups from the natural carbon precursor contribute stable pseudocapacitance. As-prepared sample exhibits high specific capacitance (369 F g(-1) in 1 M H2SO4 and 349 F g(-1) in 6 M KOH), excellent cycling stability with capacitance retention of 100% over 10 000 cycles, and promising rate performance. This work not only describes a simple way to produce high-performance carbon electrode materials for practical application, but also inspires an idea for future structure design of porous carbon.

High-Tc ferromagnetic semiconductor-like behavior and unusual electrical properties in compounds with a 2×2×2 superstructure of the half-Heusler phase.

Heusler phases, including the full- and half-Heusler families, represent an outstanding class of multifunctional materials on account of their great tunability in compositions, valence electron counts (VEC), and properties. Here we demonstrate a systematic design of a series of new compounds with a 2×2×2 superstructure of the half-Heusler unit cell in X-Y-Z (X=Fe, Ru, Co, Rh, Ir; Y=Zn, Mn; Z=Sn, Sb) systems. Their structures were solved by using both powder and single-crystal X-ray diffraction, and also directly observed by using high-angle annular dark-field imaging in a scanning transmission electron microscope (HAADF-STEM). The VEC values of these new compounds span a wide and continuous range comparable to those for the full- and half-Heusler families, thereby implying tunability in compositions and physical properties in the superstructure. In fact, we observed abnormal electrical properties and a ferromagnetic semiconductor-like behavior with a high and tunable Curie temperature in these superstructures.

Planar symmetry incompatibility in Ru-Sn-Zn pseudo-decagonal approximants composed of novel pentagonal antiprisms.

Two new ternary compounds in the Ru-Sn-Zn system were synthesized by conventional high-temperature reactions, and their crystal structures were analyzed by means of the single crystal X-ray diffraction: Ru(2)Sn(2)Zn(3) (orthorhombic, Pnma, Pearson symbol oP28, a = 8.2219(16), b = 4.1925(8), c = 13.625(3) Å, V = 469.66(16) Å(3), Z = 4) and Ru(4.15)Sn(4.96)Zn(5.85) (orthorhombic, Pnma, Pearson symbol oP60-δ, a = 8.3394(17), b = 4.2914(9), c = 28.864(6) Å, V = 1032.98(40) Å(3), Z = 4). With the increase in the Sn content, the half-decagon structure unit with a triangle center in Ru(2)Sn(2)Zn(3) grows up to a symmetry incompatible decagonal unit with a central triangle in the common plane in Ru(4.15)Sn(4.96)Zn(5.85). Both structures can be described by hexagonal arrays of Sn-centered novel pentagonal antiprisms. In light of their pseudodecagonal diffraction in the h0l section and point group mmm, both phases are considered as new quasicrystal approximants in the Ru-Zn-Sn ternary system. The temperature dependences of the electrical resistivity for both compounds exhibit metallic behavior, but their Seebeck coefficients are of opposite sign.

Complex alloys containing double-Mackay clusters and (Sb(1-δ)Zn(δ))(24) snub cubes filled with highly disordered zinc aggregates: synthesis, structures, and physical properties of ruthenium zinc antimonides.

A series of cluster-based ruthenium zinc antimonides with a large unit cell were obtained. Their structures were solved by the single crystal X-ray diffraction methods. They crystallize in the cubic space group of Fm3̅c (No. 226) with cell dimensions of 25.098(3), 24.355(3), 24.307(3), and 24.376(3) Šfor Ru(26)Sb(24)Zn(67) (CA), Ru(13)Sb(12)Zn(83.4) (CB), Ru(13)Sb(6.29)Zn(91.56) (CC), and Ru(13)Sb(17.1)Zn(74.8) (CD), respectively. By all indications, compounds CA and CB are two phases showing pronounced distinctions regarding compositions, lattice parameters, thermal and transport properties, but they are not members of an extended solid solution. Compounds CB, CC, and CD are three members of a same solid solution. Topologically, these four compounds contain face-centered cubic packing of double-Mackay type clusters and (Sb(1-δ)Zn(δ))(24) snub cubes filled with highly disordered zinc aggregates, with or without glue atoms between them. Both phases CA and CB are diamagnetic. There is a difference of ∼170 K between their thermally stable temperatures. CA exhibits rather low thermal conductivity with the value of ∼0.9 W m(-1) K(-1) at room temperature, which is about one-third that of CB. The electrical resistivity of CB is almost temperature independent. The Seebeck coefficient of CB is small and negative, while that of CA exhibits a complicated temperature dependence and undergoes a transition from p- to n-type conduction around room temperature.

Ru9Zn7Sb8: a structure with a 2 × 2 × 2 supercell of the half-Heusler phase.

The title compound Ru(9)Zn(7)Sb(8) was synthesized via a high-temperature reaction from the elements in a stoichiometric ratio, and its structure was solved by a single-crystal X-ray diffraction method. The structure [cubic, space group Fm3m, Pearson symbol cF96, a = 11.9062(14) Å (293 K), and Z = 4] adopts a unique 2a(hh) × 2a(hh) × 2a(hh) supercell of a normal half-Heusler phase and shows abnormal features of atomic coordination against the Pauling rule. The formation of this superstructure was discussed in light of the valence electron concentration per unit cell. It is a metallic conductor [ρ(300 K) = 16 µΩ·m], and differential scanning calorimetry revealed that Ru(9)Zn(7)Sb(8) undergoes a transformation at 1356(1) K and melts, by all indications, congruently at 1386 K. At room temperature, its thermal conductivity is about 3 W/m·K, which is only one-quarter of that of most normal half-Heusler phases. Ru(9)Zn(7)Sb(8) as well as its analogues of iron-, cobalt-, rhodium-, and iridium-containing compounds are expected to serve as a new structure type for exploring new thermoelectric materials.

Interpenetrating icosahedra chains based zinc-rich ternary phases Ru4.0Sn2.9Zn11.6 and Ru3.0Sb0.97Zn11.0: synthesis, structures and physical properties.

Substituting of Ru with Sn and Sb in the phase RuZn(3) led to two new zinc-rich ternary compounds: Ru(4)Sn(2.9)Zn(11.6) (SnRZ: Monoclinic, C2/m, Pearson symbol oC46-delta, a = 6.8011(14), b = 7.9760(16), c = 11.083(2) A, beta = 97.56(3) degrees, Z = 2) and Ru(3.0)Sb(0.97)Zn(11.0) (SbRZ: Orthorhombic, Cmcm, Pearson symbol oC60, a = 7.8936(16), b = 6.8347(14), c = 16.904(3) A, Z = 4). The structures of SnRZ and SbRZ are composed of four identical atomic layers but with different stacking sequences. They exhibit structural units of either three or two interpenetrating icosahedra fusing to form chains along the c axis. Their a and b lattice parameters are alike-interchanged in the chosen conventional setting-while the c parameters are related by c(SbRZ)/2 x (1 + tau) approximately = 2c(SnRZ) with tau = (1 + square root(5))/2 being the golden mean (known as tau-inflated phases). Both two compounds exhibit diamagnetic properties, and SnRZ and SbRZ congruently melt at 1296 K and 1233 K, respectively. Temperature-dependent resistivities reveal metallic behavior. The negative Seebeck coefficients indicate transport processes are dominated by electrons as carriers.

A borogermanate with three-dimensional open-framework layers.

A layered borogermanate with three-dimensional microporosity within the layers, K(4)[B(8)Ge(2)O(17)(OH)(2)] (monoclinic, space group: C2/c; a=12.095(2), b=6.7979(14), c=19.944(4) A; beta=93.04(3) degrees ; V=1637.6(6) A(3); Z=4), has been synthesized in a flux of potassium borate. Because of its three-dimensional pore structure and thermal stability, the compound has the potential to eventually form nanocomposites with polymers and to be processed into thin microporous films.

NH4[BGe3O8]: a new borogermanate framework made of infinite-chain building blocks.

A new microporous borogermanate NH4[BGe3O8] has been synthesized by a molten boric acid flux method with "reagent" quantities of water in which GeO2, ethylenediamine, H2O, and H3BO3 (5:8:14:25) were heated together at 513 K for 4 days. The structure consists of {Ge6O18}n chains, further linked together via BO4 tetrahedra, forming a three-dimensional open framework with intersecting channel systems including one-dimensional 10-membered-ring (MR) channels. Interestingly, the infinite chains {Ge6O18}n as building blocks, built of alternating 4- and 6-MRs made of vertex-sharing GeO4 tetrahedra, construct the borogermanate framework. It is noteworthy that the high viscosity of the reactive medium and the quantity of water play important roles in the formation of the compound.