Quantitative Phase Analysis of the Hydrothermally Treated System γ-Ca2SiO4-CaO

A multiphase product of hydrothermal reaction in a system γ-Ca₂SiO₄-CaO, at a Ca/Si molar ratio of 2.25 and 200°C, was subjected to quantitative phase analysis by XRD and selective dissolution in a methanolic solution of salicylic acid. The step-wise procedure required by the general method of phase analysis included: (1) determination of the number of phases with overlapping XRD patterns, (2) determination of the individual XRO patterns from diffraction patterns of multiphase samples, and (3) determination of weight fractions for all coexisting crystalline constituents. The derived individual XRD patterns correspond to calciochondrodite, "γ-dicalcium silicate hydrate," and rankinite, a phase not hitherto reported to be formed at 200°C under saturated steam conditions. The method was checked on the model system xonotlitetobermorite-calcite.     

A Sulfur–Limonene‐Based Electrode for Lithium–Sulfur Batteries: High‐Performance by Self‐Protection

The lithium–sulfur battery is considered as one of the most promising energy storage systems and has received enormous attentions due to its high energy density and low cost. However, polysulfide dissolution and the resulting shuttle effects hinder its practical application unless very costly solutions are considered. Herein, a sulfur‐rich polymer termed sulfur–limonene polysulfide is proposed as powerful electroactive material that uniquely combines decisive advantages and leads out of this dilemma. It is amenable to a large‐scale synthesis by the abundant, inexpensive, and environmentally benign raw materials sulfur and limonene (from orange and lemon peels). Moreover, owing to self‐protection and confinement of lithium sulfide and sulfur, detrimental dissolution and shuttle effects are successfully avoided. The sulfur–limonene‐based electrodes (without elaborate synthesis or surface modification) exhibit excellent electrochemical performances characterized by high discharge capacities (≈1000 mA h g^?1 at C/2) and remarkable cycle stability (average fading rate as low as 0.008% per cycle during 300 cycles).     

Mapping of valence energy losses via energy-filtered annular dark-field scanning transmission electron microscopy

The advent of electron monochromators has opened new perspectives on electron energy-loss spectroscopy at low energy losses, including phenomena such as surface plasmon resonances or electron transitions from the valence to the conduction band. In this paper, we report first results making use of the combination of an energy filter and a post-filter annular dark-field detector. This instrumental design allows us to obtain energy-filtered (i.e. inelastic) annular dark-field images in scanning transmission electron microscopy of the 2-dimensional semiconductor band-gap distribution of a GaN/Al₄₅Ga₅₅N structure and of surface plasmon resonances of silver nanoprisms. In comparison to other approaches, the technique is less prone to inelastic delocalization and relativistic artefacts. The mixed contribution of elastic and inelastic contrast is discussed.     

跃变比判别热解Si-C-N陶瓷EELS定量分析的有效性

电子能量损失谱（EELS）分析方法的运用为材料研究领域提供了有力的定性和定量手段。通过对内壳层电子激发谱跃变比的计算,能够获得样品相对厚度的参考信息。这一方法弥补了实验条件在同步采集等离子激发谱和内壳层电子激发谱方面的局限性,并为辨别EELS定量的可靠性提供依据。本文以Si3N4为例,对跃变比随样品相对厚度的变化规律进行了研究,并在低于最佳样品厚度的范围内得到了可靠的定量结果。类似的跃变比变化规律能够运用于成份均一的Si-C-N热解样品,然而对于非均一的Si-C-N退火样品则不适用。     

SENSE OF COMMUNITY AND THE IMPORTANCE OF VALUES: COMPARISON OF TWO NEIGHBORHOODS IN SLOVENIA

ABSTRACT: Sense of community is analyzed in two very different types of neighborhoods in Ljubljana, Slovenia: a large housing estate and a middle‐class neighborhood of individual houses. The main research question posed is which individual characteristics are associated with sense of community in the two neighborhoods. A specific addition to current knowledge involves the inclusion of values as important characteristics associated with sense of community. The analysis was made on a quota sample of 337 individuals. Sense of community was shown to be comprised of three factors: (1) contact with neighbors; (2) social control; and (3) attachment. We observed this separately in the two neighborhoods. The analysis showed that values significantly increase the model's explanatory power and that the two neighborhoods differ significantly in terms of which variables are important for sense of community, therefore indicating that this could be highly context‐dependent. In addition, qualitative data are used to illustrate the sense of community in the two neighborhoods.     

Carbon incorporation and deactivation of MgO(0 0 1) supported Pd nanoparticles during CO oxidation

We have investigated the structure and composition of the model catalyst system Pd/MgO(0 0 1) during oxidation, CO reduction and CO oxidation at near atmospheric pressures by a combination of in situ X-ray diffraction and ex situ transmission electron microscopy and spectroscopy techniques. From the in situ X-ray experiments, we find: (a) the Pd nanoparticles with 9 nm in diameter transform into epitaxial PdO above 10⁻¹ mbar O₂ pressure at 570 K, (b) the oxidation process can be reverted by CO exposure, recovering Pd nanoparticles in their initial orientation, and (c) during CO oxidation in a mixture of 50 mbar O₂ and 50 mbar CO a new phase is evolving with lattice constant close to the MgO substrate value, which we assign to expanded Pd nanoparticles forming upon carbon incorporation. Ex situ transmission electron microscopy and different spectroscopy techniques uncover the CO₂ induced growth of a disordered overlayer containing C, Mg and O, which forms during CO oxidation and leads to an overgrowth of Pd nanoparticles thereby deactivating the catalyst.     

Natural Vermiculite Enables High‐Performance in Lithium–Sulfur Batteries via Electrical Double Layer Effects

Lithium–sulfur batteries with potentially high specific energy are viewed as very promising candidates for next‐generation lightweight and low‐cost rechargeable batteries. However, sulfur‐based cathodes suffer from dissolution of polysulfides causing shuttle effects. Here, in order to confine elemental sulfur and anchor the polysulfides, a novel host that is an inexpensive natural clay mineral, viz., vermiculite is proposed. When compared to regular carbon–sulfur composites, vermiculite–sulfur composites offer promising rate capability and much better cycling stabilities, displaying capacity retentions of ≈89 and ≈93% within 200 cycles at C/2 and 1 C, respectively, and ≈60 % at C/5 within 1000 cycles. Postmortem studies, advanced adsorption tests, density functional theory calculations, and zeta potential measurements in combination with intrinsic characteristics of the natural vermiculite provide insights into the new mechanism. The vermiculite contains naturally present surface cations which show a strong tendency to adsorb S_n^2? anions, hence protecting them from dissolution. The excess surface charge is most probably compensated by excess Li⁺ in the space charge zones which is beneficial for charge transfer and local conductivity. The reported results show that natural clay‐minerals are promising sulfur hosts being able to fixate sulfides via electrical double layer effects, thus enabling high‐performance in lithium–chalcogen batteries.