Characterization of in situ synthesized TiB2 reinforcements in iron-based composite coating

TiB₂ reinforced iron-based composite coatings can be fabricated on the mild steel substrate with a powder mixture of Ti and B₄C by plasma transferred arc (PTA) powder surfacing process. Characterizations of the TiB₂ reinforcements in the coated surface were investigated in this paper. The experimental work enables the following findings to be obtained: (i) acicular shaped and blocky formed TiB₂ phases could be synthesized in situ using PTA powder surfacing process in the iron-based composite coating. (ii) Gradient distributions of TiB₂ reinforcements appeared in the composite coating from both the vertical and horizontal direction of the coating's cross-section. Significant changes of the size, shape and volume fraction for TiB₂ particles appeared in different regions of the surface coating, due to the effects of the dilution rate and mass density. (iii) Values of coating dilution could have profound impacts on the characterization of TiB₂ reinforcements in the coated surfaces. With the increase of coating dilution, TiB₂ grain tends to be acicular shaped at the edge of the surface coating, while it remains to be granular formed in the center of the composite coating.     

二阶常微分方程组积分边值问题的正解

在借助于非负矩阵获得正解的先验估计的基础上,用不动点指数理论研究二阶非线性常微分方程组积分边值问题正解和多重正解的存在性.     

一种改进的视频超分辨率重建方法

针对目前无人机摄像、照相数据的特点,提出一种基于低分辨率视频重建高分辨率视频的改进方法;采用高斯金字塔光流算法对低分辨率视频及高分辨率图像进行运动估计利用小波频带分解方法提取图像的高频细节,并对视频进行运动补偿,采用凸集投影方法对补偿后视频进行迭代优化;并通过MATLAB仿真实现了以上算法,实验结果证明本文算法重建质量更好、处理速度更快。     

不同烧结温度对SnO2掺杂下的Y1Ba2Cu3O7-δ超导电性的影响

采用固相反应法制作了在不同烧结温度对Sn掺杂下的YBCO一系列样品.本文采用了X-射线衍射仪,电阻测量和SEM对样品物相形成,微观结构,晶格常数以及超导转变温度进行表征,测量结果表明:不同的烧结温度会影响Sn离子的形式,随着温度的升高,Y-123峰明显减弱,杂峰相增多.本文分析了晶格常数与超导性存在必然联系,SEM结果表明第二相粒子的形成以及表面形貌都与温度有关.     

Rutile TiO2 nanowires on anatase TiO2 nanofibers: a branched heterostructured photocatalysts via interface-assisted fabrication approach

A water-dichloromethane interface-assisted hydrothermal method was employed to grow rutile TiO(2) nanowires (NWs) on electrospun anatase TiO(2) nanofibers (NFs), using highly reactive TiCl(4) as precursor. The water-dichloromethane interface inhibited the formation of rutile NWs in water phase, but promoted the selective radial growth of densely packed rutile NWs on anatase NFs to form a branched heterojunction. The density and length of rutile NWs could be readily controlled by varying reaction parameters. A formation mechanism for the branched heterojunction was proposed which involved (1) the entrapment of rutile precursor nanoparticles at water-dichloromethane interface, (2) the growth of rutile NWs on anatase NFs via Ostwald ripening through the scavengering of interface-entrapped rutile nanoparticles. The heterojunction formed at anatase NF and rutile NW enhanced the charge separation of both under ultraviolet excitation, as evidenced by photoluminescence and surface photovoltage spectra. The branched TiO(2) heterostructures showed higher photocatalytic activity in degradation of rodamine B dye solution than anatase NFs, and the mixture of anatase NFs, and P25 powders, which was discussed in terms of the synergistic effect of enhanced charge separation by anatase-rutile heterojunction, high activity of rutile NWs, and increased specific area of branched heterostructures.     

Atomically Dispersed Zn-Pyrrolic-N4 Cathode Catalysts for Hydrogen Fuel Cells

To achieve practical application of fuel cell, it is vital to develop highly efficient and durable Pt-free catalysts. Herein, we prepare atomically dispersed ZnNC catalysts with Zn-Pyrrolic-N₄ moieties and abundant mesoporous structure. The ZnNC-based anion-exchange membrane fuel cell (AEMFC) presents an ultrahigh peak power density of 1.63 and 0.83 W cm⁻² in H₂-O₂ and H₂-air (CO₂-free), and also exhibits long-term stability with more than 120 and 100 h for H₂-air (CO₂-free) and H₂-O₂, respectively. Density functional calculations further unveil that the Zn-Pyrrolic-N₄ structure is the origin of high activity of as-synthesized ZnNC catalyst, while the Zn-Pyridinic-N₄ moiety is inactive for oxygen reduction reaction (ORR), which successfully explain the puzzle why most Zn-metal-organic framework -derived ZnNC catalysts in previous reports did not present good ORR activity because of their Zn-Pyridinic-N₄ moieties. This work offers a new route for speeding up development of AEMFCs.     

Redox-Bipolar Polyimide Two-Dimensional Covalent Organic Framework Cathodes for Durable Aluminium Batteries

Emerging rechargeable aluminium batteries (RABs) offer a sustainable option for next-generation energy storage technologies with low cost and exemplary safety. However, the development of RABs is restricted by the limited availability of high-performance cathode materials. Herein, we report two polyimide two-dimensional covalent organic frameworks (2D-COFs) cathodes with redox-bipolar capability in RAB. The optimal 2D-COF electrode achieves a high specific capacity of 132 mAh g⁻¹. Notably, the electrode presents long-term cycling stability (with a negligible ≈0.0007 % capacity decay per cycle), outperforming early reported organic RAB cathodes. 2D-COFs integrate n-type imide and p-type triazine active centres into the periodic porous polymer skeleton. With multiple characterizations, we elucidate the unique Faradaic reaction of the 2D-COF electrode, which involves AlCl²⁺ and AlCl₄⁻ dual-ions as charge carriers. This work paves the avenue toward novel organic cathodes in RABs.