Supplementary material

The Supplementary Materials provide comprehensive information on the crystal structures of Ta-Sb binary phases, as well as precise data regarding their mechanical and thermal properties

How Does the Hydrogen Bonding Interaction Influence the Properties of Polybenzoxazine? An Experimental Study Combined with Computer Simulation

The formation of intra- or intermolecular hydrogen bonding and their influences on polybenzoxazine’s properties were investigated after the model benzoxazine monomers (<i>o</i>-AB-fbz, <i>o</i>-AF-fbz, <i>o</i>-AP-fbz, <i>p</i>-AB-fbz, <i>p</i>-AF-fbz, <i>p</i>-AP-fbz) were synthesized. Because of the different electron-donating abilities of bridging units (benzene, furan and pyridine) in isophthalic acid (IPA), 2,5-furandicarboxylic acid (2,5-FDCA) and 2,6-pyridinedicarboxylic acid (2,6-PDCA), the strength of intramolecular H-bonding involved with the oxygen atom in oxazine ring in <i>o</i>-AB-fbz, <i>o</i>-AF-fbz and <i>o</i>-AP-fbz followed the order of <i>o</i>-AB-fbz > <i>o</i>-AF-fbz > <i>o</i>-AP-fbz, and the strength of the overall H-bonding was arranged as follows: <i>o</i>-AB-fbz < <i>o</i>-AF-fbz < <i>o</i>-AP-fbz. While more intermolecular H-bonding was formed in <i>p</i>-AB-fbz and <i>p</i>-AF-fbz as well as <i>p</i>-AP-fbz. DSC and FT-IR results discovered the relationship between the H-bonding involved with the oxygen atom in oxazine ring and the curing activities of benzoxazines. After curing reaction, the cured systems showed varied glass transition temperature (<i>T</i>_g), and the influence of H-bonding on <i>T</i>_g was revealed by in situ FT-IR analysis. Molecular dynamics (MD) simulation was also applied to investigate the properties of synthesized polybenzoxazines and similar results were obtained. Not only the formation of H-bonding but also their effects on both the curing behaviors of benzoxazine monomers and the thermal properties of cured resins were systematically investigated, which would help us understand polybenzoxazines more deeply and might be a guideline for improving their comprehensive properties only by manipulating the H-bonding

Evolutionary Search for Novel Thorium Borides toward Advanced Nuclear Fuels

Thorium (Th)-based fuels are considered as promising candidates for generation-IV reactors. To explore potential thorium boride (ThxBy) structures and to obtain physical properties of these thorium borides, in our work, a variable-composition evolutionary algorithm prediction method implemented in the Universal Structure Predictor: Evolutionary Xtallography code was adopted to search stable binary compounds in the Th–B system. Six stable and metastable Th–B binaries with different chemical compositions were predicted, in which three hitherto-unknown phases ThB2, Th3B4, and ThB were discovered. The electronic, mechanical, and thermal properties of these thorium borides were studied in detail based on the first-principles method. ThB is the only ionic compound, and the other compounds exhibit metallic and covalent properties. All the thorium borides except for Th3B4 exhibit excellent thermal conductivity. In addition, ThB4 and ThB12 have outstanding mechanical properties. ThB2, ThB4, and ThB12 are expected to be promising candidates for new nuclear fuels due to their appropriate mechanical and thermal properties

Coordination Polymer-Derived Multishelled Mixed Ni–Co Oxide Microspheres for Robust and Selective Detection of Xylene

Multishell, stable, porous metal-oxide microspheres (Ni–Co oxides, Co₃O₄ and NiO) have been synthesized through the amorphous coordination polymer-based self-templated method. Both oxides of Ni and Co show poor selectivity to xylene, but the composite phase has substantial selectivity (e.g., <i>S</i>_xylene/<i>S</i>_ethanol = 2.69) and remarkable sensitivity (11.5–5 ppm xylene at 255 °C). The short response and recovery times (6 and 9 s), excellent humidity-resistance performance (with coefficient of variation = 11.4%), good cyclability, and long-term stability (sensitivity attenuation of ∼9.5% after 30 days and stable sensitivity thereafter) all show that this composite is a competitive solution to the problem of xylene sensing. The sensing performances are evidently due to the high specific surface area and the nano-heterostructure in the composite phase

Superlubricity Enabled by Pressure-Induced Friction Collapse

From daily intuitions to sophisticated atomic-scale experiments, friction is usually found to increase with normal load. Using first-principle calculations, here we show that the sliding friction of a graphene/graphene system can decrease with increasing normal load and collapse to nearly zero at a critical point. The unusual collapse of friction is attributed to an abnormal transition of the sliding potential energy surface from corrugated, to substantially flattened, and eventually to counter-corrugated states. The energy dissipation during the mutual sliding is thus suppressed sufficiently under the critical pressure. The friction collapse behavior is reproducible for other sliding systems, such as Xe/Cu, Pd/graphite, and MoS₂/MoS₂, suggesting its universality. The proposed mechanism for diminishing energy corrugation under critical normal load, added to the traditional structural lubricity, enriches our fundamental understanding about superlubricity and isostructural phase transitions and offers a novel means of achieving nearly frictionless sliding interfaces

Cytocompatibility of Ti₃AlC₂, Ti₃SiC₂, and Ti₂AlN: <i>In Vitro</i> Tests and First-Principles Calculations

Herein, the cytocompatibility of selected MAX phases, Ti₃AlC₂, Ti₃SiC₂, and Ti₂AlN, were systematically evaluated using <i>in vitro</i> tests for the first time. These phases were anoxic to preosteoblasts and fibroblasts. Compared with the strong viable fibroblasts, the different cellular responses of these materials were clearly distinguishable for the preosteoblasts. Under an osteoblastic environment, Ti₂AlN exhibited better cell proliferation and differentiation performance than Ti₃AlC₂ and Ti₃SiC₂. Moreover, the performance was superior to that of a commercial Ti–6Al–4V alloy and comparable to that of pure Ti. A possible mechanism was suggested based on the different surface oxidation products, which were determined from the binding energy of adsorbed Ca²⁺ ions using first-principles calculations. Compared with the partially oxidized TiC_<i>x</i>O_<i>y</i> layer on Ti₃AlC₂ and Ti₃SiC₂, the partially oxidized TiN_<i>x</i>O_<i>y</i> layer on the Ti₂AlN had a stronger affinity to the Ca²⁺ ions, which indicated the good cytocompatibility of Ti₂AlN

Facile and Efficient Decontamination of Thorium from Rare Earths Based on Selective Selenite Crystallization

The coexistence of radioactive contaminants (e.g., thorium, uranium, and their daughters) in rare earth minerals introduces significant environmental, economic, and technological hurdles in modern rare earth production. Efficient, low cost, and green decontamination strategies are therefore desired to ameliorate this problem. We report here a single-step and quantitative decontamination strategy of thorium from rare earths based on a unique periodic trend in the formation of crystalline selenite compounds across the lanthanide series, where Ce­(III) is fully oxidized in situ to Ce­(IV). This gives rise to a crystallization system that is highly selective to trap tetravalent f-blocks while all other trivalent lanthanides completely remain in solution when coexist. These results are bolstered by first-principles calculations of lattice energies and an examination of bonding in these compounds. This system is contrasted with typical natural and synthetic systems, where trivalent and tetravalent f-block elements often cocrystallize. The separation factors after one round of crystallization were determined from binary systems of Th­(IV)/La­(III), Th­(IV)/Eu­(III), and Th­(IV)/Yb­(III) to reach 2.1 × 10⁵, 1.2 × 10⁵, and 9 × 10⁴, respectively. Selective crystallization of thorium from a simulated monazite composite yields a separation factor of 1.9 × 10³ with nearly quantitative removal of thorium