Challenges and strategies of all-inorganic lead-free halide perovskite solar cells

Hybrid lead halide perovskite solar cells (PSCs) have experienced a rapid development in the past decade and a certified efficiency up to 25.5% has been achieved. However, the presence of toxic lead component and the inherent poor thermal stability of the organic cations in the hybrid lead halide perovskites obstruct the commercial applications of their corresponding photovoltaic devices. Therefore, fabricating high-efficient all-inorganic lead-free PSCs is a promising direction. This review summarizes the related research progress, which mainly focuses on the structural and optoelectronic properties of inorganic lead-free perovskites and devices. In particular, the strategies for improving the properties and stability of Cs–Sn perovskites, as well as enhancing the photovoltaic performance of the corresponding devices are highlighted. An outlook of challenges and future directions regarding to all-inorganic lead-free PSCs are also proposed.     

Hematite crystal growth in high-temperature lead-free multicomponent alkali borosilicate glass frit for red overglaze enamels

To elucidate the crystal growth process of hematite in high-temperature lead-free multicomponent alkali borosilicate glass, which is essentially important to control the color of red overglaze enamels, frit and hematite mixture is heat-treated and subjected to microscopic observations. Hematite particles slightly grew due to sintering at low temperature. Once the glass matrix formed near the softening point of frit, hematite dissolved into glass fluid. Hematite crystal growth concomitantly ensued with decrease in the number of hematite particles via Ostwald ripening as the temperature increased. The grown particles exhibited an anisotropic morphology with straight outlines reflecting crystal planes, the morphology of which is completely different from those grown by sintering and particles prior to heating. These results suggest that comprehensive understanding of frit and hematite from the perspectives of glass science and chemistry as well as powder technology are important to truly control the color of red overglaze enamels.     

Sensitivity of a solid Eu(III) complex towards acetonitrile vapor: Structural and spectroscopic characterization

The Eu(III) nitrate complex of the meso- N,N′-bis(2-pyridylmethylene)-1,2-(R,S)-cyclohexanediamine ligand was synthesized and characterized by single crystal and powder X-ray diffraction. The crystal lattice of the complex is capable of absorbing and desorbing selectively acetonitrile molecules, at 293 K upon an acetonitrile vapor pressure of ∼0.1 × 10⁵ Pa. This process, which is partially reversible, can be easily followed by both powder X-ray diffraction (P-XRD) and Eu(III) luminescence spectroscopy. The acetonitrile molecule, located in the outer coordination sphere of the metal ion, does not affect the radiative transition probability of ⁵D₀ level of Eu(III) and also it does not activate further non-radiative channels from this level. On the other hand, this molecule is capable of affecting the energy position and intensities of the crystal field components of the ⁵D₀→⁷F₂ transition. The complex in solid form can be considered a promising material for the optical sensing of acetonitrile vapors.     

Impact of gas formation on the transfer of Ti and O from TiO2-bearing basic-fluoride fluxes to submerged arc welded metals: A thermodynamic approach

Gas-slag-metal equilibrium calculations are performed to investigate the transfer of Ti and O to submerged arc welded metals with increasing TiO₂ addition in basic-fluoride fluxes. The results indicate that activities of TiO₂ and Ti₂O₃ considering slag-metal reactions alone do not account for Ti transfer behaviors since TiF₃ gas tends to form and reduce Ti-oxide activities. Thermodynamic simulation indicates that consideration of gases is essential to improve the prediction accuracy of Ti and O concentrations.     

铌硅基高温合金定向凝固铸造温度场模拟计算

以铌硅基高温合金定向凝固铸造过程为对象，通过实验测试和反求法确定了铌硅基高温合金和型壳的热物性参数，以及凝固过程各界面换热系数等边界条件；利用ProCAST软件对不同抽拉速率下铌硅基高温合金凝固过程温度场进行了模拟。结果表明，随着抽拉速率由5 mm·min?1增加到10 mm·min?1，固/液界面离液态金属锡表面的距离由12.1 mm下降到8.2 mm；平均糊状区宽度逐渐变窄，由11.5 mm减小到10.4 mm。针对抽拉速率为5 mm·min?1的实验结果表明，数值模拟结果与实际定向凝固实验获得的一次枝晶间距差异在6%以内，从一个方面验证了温度场模拟结果的正确性，相关结果可为铌硅基高温合金叶片定向凝固铸造参数的确定提供参考。      

Fabrication of dense Al2O3-FeAl composites by using solid-state sintering

Highly densified alumina-iron aluminide (Al₂O₃-FeAl) composites consisting of ubiquitous elements were fabricated by using pulse current sintering technique under a certain uni-axial pressure. The solid-state sintering without melting FeAl was the highlight in this study. The mechanical properties of the Al₂O₃-FeAl composites were much greater than previously reported ones fabricated by reaction sintering technique. The poor wettability of FeAl against Al₂O₃ strongly influenced the mechanical properties and made it difficult to be highly densified Al₂O₃-FeAl composites by liquid phase sintering especially when volume fraction of FeAl to Al₂O₃-FeAl was high (>30.5 vol%). However, highly densified Al₂O₃-FeAl composites were obtained by solid-state sintering with control of Al₂O₃ grain size and sintering temperatures. It was concluded that highly controlled powder metallurgy made it possible to fabricate dense ceramic-metal (intermetallic) composites from the combination of materials having poor wettability.     

Gas-assisted exfoliation of boron nitride nanosheets enhancing adsorption performance

A gas exfoliation strategy for controllable preparation of boron nitride (BN) nanosheets with few-layered structure were reported. The green exfoliation process provides the BN nanosheets remarkable increment of adsorption capacities to organic contaminants, which is ascribed to better exposure of active sites originating from the larger surface area and thinner layer. Moreover, the prepared BN also exhibits outstanding recyclability.     

树脂吸附铜锌离子的数值模拟

镀金原料氰化亚金钾的生产过程含氰废液中锌（Ⅱ）离子和铜离子（Ⅱ）浓度较高，为探究树脂吸附铜、锌离子的规律，运用Aspen Adsorption数值模拟软件对Φ10 mm×200 mm的树脂固定床吸附过程进行数值模拟，采用一阶迎风差分法作为偏微分方程的离散方法，研究不同条件下的吸附穿透曲线和吸附负荷分布曲线.结果表明:增加进料流量和进料浓度均可提高吸附效率，传质系数（K_S）大于临界值时，吸附穿透曲线不再受其影响，K_S（Zn2+）=4.3×10-3s-1, K_S（Cu2+）=1.00×10-2s-1.      

基于超材料的无标记光学生物传感

超材料(metamaterials)因为能够在亚波长尺度范围内精细调控电磁波而受到人们广泛关注。超材料具有丰富的电磁模态,在表面支持高度局域场增强且对周围介电环境极其敏感,可应用于无标记光学生物传感领域。与传统光学生物传感器相比,超材料生物传感器具有小型化、集成化、高度灵敏、多功能可定制等突出优点。本文总结了近年来超材料生物传感器在可见光、近红外、中红外以及太赫兹波段的研究进展,包括折射率生物传感、表面增强拉曼散射、表面增强红外吸收和太赫兹生物传感等。