Molecule-confined modification of graphitic C3N4 to design mesopore-dominated Fe-N-C hybrid electrocatalyst for oxygen reduction reaction

To design inexpensive carbon catalysts and enhance their oxygen reduction reaction (ORR) activity is critical for developing efficient energy-conversion systems. In this work, a novel Fe-N-C hybrid electrocatalyst with carbon nanolayers-encapsulated Fe₃O₄ nanoparticles is synthesized successfully by utilizing the molecular-level confinement of graphitic C₃N₄ structures via hemin biomaterial. Benefiting from the Fe-N structure prevalent on the carbon nanosheets and large mesopore-dominated specific surface area, the synthesized catalyst under optimized conditions shows excellent electrocatalytic performance for ORR with an E_ORR at 1.08 V versus reversible hydrogen electrode (RHE) and an E_1/2 at 0.87 V vs. RHE, and outstanding long-term stability, which is superior to commercial Pt/C catalysts (E_ORR at 1.04 V versus RHE and E_1/2 at 0.84 V versus RHE). Moreover, the low hydrogen peroxide yield (<11%) and average electron transfer number (~3.8) indicate a four-electron ORR pathway. Besides, the maximum power density of the home-made Zn-air battery using the obtained catalyst is 97.6 mW cm⁻². This work provides a practical route for the synthesis of cheap and efficient ORR electrocatalysts in metal-air battery systems.     

Hydrogenation process in multiphase alloys of Ti-Zr-Mn-V system on the example of Ti42.75Zr27Mn20.25V10 alloy

The influence of phase composition and microstructure of Ti_42.75Zr₂₇Mn_20.25V₁₀ alloy on its hydrogenation kinetic and phase composition of hydrogenated product was studied. It is established that the process of dissociation of hydrogen molecules begins on the surface of Laves phase crystallites. The dissolution of atomic hydrogen in the material volume leads to the formation of cracks in the intermetallic crystallites, which further appear as additional centers of dissociation of hydrogen molecules and noticeably accelerate the diffusion of hydrogen into the bulk material. It was shown that the Laves phase acts as a donor of atomic hydrogen for the BCC solid solution during hydrogenation of two-phase structure, initiating intensive hydrogenation of the BCC phase at room temperature.     

Mechanical properties of Al2O3 and Al2O3/Al with Gyroid structure obtained by stereolithographic additive manufacturing and melt infiltration

To obtain both plasticity and toughness of the material at the same time, various manufacturing techniques of ceramic-metal composites and structures have been studied. In this work, a bio-inspired Al₂O₃ ceramic scaffold with Gyroid structure was designed and prepared by stereolithographic (SL) additive manufacturing, then the Al₂O₃/Al ceramic-metal hybrid structure was prepared by infiltrating molten Al into the Al₂O₃ ceramic structure. The performances of the Al₂O₃ ceramic scaffold and the Al₂O₃/Al ceramic-metal hybrid structure were compared and analyzed by a quasi-static compression experiment. The quasi-static compressive strength of the pristine Al₂O₃ scaffold was 14.36 MPa, while that of the Al₂O₃/Al ceramic-metal hybrid structure was up to 89.06 MPa. Moreover, the plasticity of the Al₂O₃/Al ceramic-metal hybrid structure was much higher than that of the Al₂O₃ scaffold. During compression, the Al₂O₃/Al ceramic-metal hybrid structure had excellent energy absorption, reaching up to 2569.16 KJ/m³, 15 times that of the Al₂O₃ scaffold. Therefore, this method can obtain materials with excellent ductility and toughness.     

Improvement in the properties of low carbon MgO-C refractories through the addition of graphite-SiC micro-composite

Graphite–SiC micro-composites have been prepared in–house by carbothermal reduction process. Controlling the process parameters including the weight ratio of SiO₂ to graphite as well as carbothermal reduction temperature during the micro-composite preparation favors the homogeneous formation of SiC with preferred morphologies like ribbons and whiskers/fibers. The micro-composite modified low carbon MgO-C refractories have exhibited significantly improved bulk properties over the standard composition. To understand the beneficial role of SiC reinforcement on hot strength performance under air oxidizing conditions, we propose a scaling parameter known as strength factor (fs) based on the ratio of hot strength (HMOR) to cold strength (CCS). Correlating the strength factor data (fs) with oxidative damage provides new insights into the reinforcing effects of distinct SiC morphologies in this new class of micro-composite fortified refractory systems over the standard compositions.     

Early hydration properties and microstructure evolutions of MgO-activated slag materials at different curing temperatures

This study reports on the early hydration properties and microstructure evolutions of MgO-activated slag at five curing temperatures (20 °C, 40 °C, 50 °C, 60 °C, and 80 °C) and three MgO types (S-MgO, M ? MgO, and R-MgO). The results indicated that high-temperature curing substantially increased the compressive strength of the specimens. Particularly, the highest strength was obtained at 40 °C and 60 °C for the S-MgO and M-MgO-activated slag specimens, respectively, and the high curing temperature for the R-MgO-activated slag specimen was 40 °C. We focused on the relationship between the mechanical properties, pore structure characteristics, and hydration products. The combination of calcium-silicate-hydrate (C-S-H) gel and Al increased under high-temperature curing conditions. XRD, FT-IR, TG-DTG, and ²⁷Al MAS-NMR results showed a high Al content in the formation of calcium silicate hydrate with Al in its structure (C-A-S-H gel) for the R-MgO-activated slag pastes under high-temperature curing; however, the microstructure was loose owing to the formation of excessive brucite. For the S-MgO-activated slag specimen, the Ca/Si ratio was high, with more Mg²⁺ penetrating the C-S-H gel interlayer, forming more hydrotalcite-like phases and increasing the chain length of the C-S-H gel. The microstructure showed good compatibility of the hydration products interweaving to form dense microstructures.     

Enhanced electromagnetic wave dissipation features of magnetic Ni microspheres by developing core-double shells structure

Readily oxidization of magnetic particles is a common drawback of these type of materials which reduce their electromagnetic wave dissipation performance. In this study, the magnetic core-double shells structured (Ni/SiO₂/Polyaniline) composite has been developed for protection of the core from oxidation and in consequent improvement the complex permittivity. Solvothermal and in-situ polymerization methods were utilized for decorating Ni micro-particles with SiO₂ and conductive polyaniline polymer respectively. All physico-chemical, magnetic and electromagnetic features were evaluated via XRD, FTIR, XPS, FESEM, VSM and VNA analysis. The double shells composite possesses significant performance in terms of reflection loss and effective absorption bandwidth. The results reveal that the maximum dissipation capacity of the double shells composite is – 32.5 dB at 16.5 GHz with 4.5 GHz effective absorption bandwidth and 1.5 mm thickness. Enhancement in microwave dissipation features are arises from synergistic influence of various phenomena such as interfacial polarization, multiple Debye relaxation, natural ferromagnetic resonance and proper impedance matching characteristic. Overall, developing double shells structure on magnetic Ni microsphere particles had a meaningful effect on tuning the microwave absorption performance.     

Structure and crystallization behavior of complex mold flux glasses in the system CaO-Na2O-Li2O-CaF2-B2O3-SiO2: A multi-nuclear NMR spectroscopic study

The structure of mold flux glasses in the system CaO-(Na,Li)₂O-SiO₂-CaF₂ with unusually high modifier contents, stabilized by the addition of ∼4 mol% B₂O₃, is studied using ⁷Li, ²³Na, ¹⁹F, ¹¹B, and ²⁹Si magic-angle-spinning (MAS), and ⁷Li{¹⁹F} and ²³Na{¹⁹F} rotational echo double-resonance (REDOR) nuclear magnetic resonance (NMR) spectroscopy. When taken together, the spectroscopic results indicate that the structure of these glasses consists primarily of dimeric [Si₂O₇]⁻⁶ units that are linked to the (Ca,Na,Li)-O coordination polyhedra, and are interspersed with chains of corner-shared BO₃ units. The F atoms in the structure are exclusively bonded to Ca atoms, forming Ca(O,F)_n coordination polyhedra. This structural scenario is shown to be consistent with the crystallization of cuspidine (3CaO·2SiO₂·CaF₂) from the parent melts on slow supercooling. The progressive addition of Li to a Na-containing base composition results in a corresponding increase in the undercooling required for the nucleation of cuspidine in the melt, which is attributed to the frustrated local structure caused by the mixing of alkali ions.     

Two Methods,One Goal: Structural Differences between Cocrystallization and Crystal Soaking to Discover Ligand Binding Poses

In lead optimization, protein crystallography is an indispensable tool to analyze drug binding. Binding modes and non-covalent interaction inventories are essential to design follow-up synthesis candidates. Two protocols are commonly applied to produce protein–ligand complexes: cocrystallization and soaking. Because of its time and cost effectiveness, soaking is the more popular method. Taking eight ligand hinge binders of protein kinase A, we demonstrate that cocrystallization is superior. Particularly for flexible proteins, such as kinases, and larger ligands cocrystallization captures more reliable the correct binding pose and induced protein adaptations. The geometrical discrepancies between soaking and cocrystallization appear smaller for fragment-sized ligands. For larger flexible ligands that trigger conformational changes of the protein, soaking can be misleading and underestimates the number of possible polar interactions due to inadequate, highly impaired positions of protein amino-acid side and main chain atoms. Thus, if applicable cocrystallization should be the gold standard to study protein–ligand complexes.     

利用菊池衍射花样鉴定晶体结构的方法研究

电子背散射衍射(Electron Backscatter Diffraction, EBSD)是研究材料显微结构的重要手段之一, 通过EBSD获取的菊池衍射花样是材料内部微观晶体结构的直观反映。本研究通过识别菊池花样中的对称轴, 结合晶体对称定律, 提出了一种利用菊池花样进行晶体对称性分析和晶体结构鉴定的方法。通过该方法成功对三个未知样品的对称性和晶体结构进行了判断。其中一个样品确定到所属晶系, 另两个样品锁定到部分点群, 通过确定晶系和点群排除了部分不符合对称性的相鉴定结果。研究结果表明, 利用菊池花样进行对称性分析是判断晶体结构的有效方法。同现有方法相比, 菊池衍射花样法大大缩小了相鉴定的检索范围, 显著提高了相鉴定的准确性和可靠性, 是一种有望用于新一代EBSD设备的标定技术。     

Structural Cues for Understanding eEF1A2 Moonlighting

Spontaneous mutations in the EEF1A2 gene cause epilepsy and severe neurological disabilities in children. The crystal structure of eEF1A2 protein purified from rabbit skeletal muscle reveals a post-translationally modified dimer that provides information about the sites of interaction with numerous binding partners, including itself, and maps these mutations onto the dimer and tetramer interfaces. The spatial locations of the side chain carboxylates of Glu301 and Glu374, to which phosphatidylethanolamine is uniquely attached via an amide bond, define the anchoring points of eEF1A2 to cellular membranes and interorganellar membrane contact sites. Additional bioinformatic and molecular modeling results provide novel structural insight into the demonstrated binding of eEF1A2 to SH3 domains, the common MAPK docking groove, filamentous actin, and phosphatidylinositol-4 kinase IIIβ. In this new light, the role of eEF1A2 as an ancient, multifaceted, and articulated G protein at the crossroads of autophagy, oncogenesis and viral replication appears very distant from the “canonical” one of delivering aminoacyl-tRNAs to the ribosome that has dominated the scene and much of the thinking for many decades.