高效率低功率抖动运转的Yb：Er共掺杂光纤激光器

通过理论计算分析了共掺Yb杂后掺Er光纤的有效泵浦率，证明了Yb：Er共掺杂可以提高有效泵浦率。使用这种光纤，可以使抑制光纤激光器中离子对导致的自脉冲效应所需的泵浦功率水平大大降低。说明这种共掺杂光纤激光器不仅可以提高效率还可以稳定激光输出。     

Electrocaloric Effect in Ferroelectric P(VDF-TrFE) Copolymers

The effect of multi-wall carbon nanotubes (MCNTs) addition on the electrochemical performance of Al/Ca codoped α-nickel hydroxide is studied. The microstructure and electrochemical performance of the prepared samples are characterized by XRD, SEM, electrochemical impedance spectroscopy, cyclic voltammetry, and charge-discharge tests. The results show that the addition of MCNTs could decrease the electrochemical reaction impedance dramatically, improve the electrochemical reaction reversibility, and increase the specific discharge capacity.     

Microporosity‐Controlled Synthesis of Heteroatom Codoped Carbon Nanocages by Wrap‐Bake‐Sublime Approach for Flexible All‐Solid‐State‐Supercapacitors

Heteroatom‐doped carbon nanomaterials with high surface area and tunable microporosity are important but they generally require difficult and multistep syntheses. Herein, a simple and straightforward strategy is introduced that involves a wrap‐bake‐sublime approach to synthesize microporosity controlled and heteroatom codoped carbon nanocages. A zinc‐containing zeolitic imidazolate framework (ZIF‐8) core is wrapped in a cross‐linked oligomer containing nitrogen and phosphorus, oligo(cyclotriphosphazene‐co‐hexahydroxytriphenylene) (OCHT). As‐synthesized core–shell ZIF‐8‐OCHT nanoparticles are baked at high temperatures to sublimate zinc through OCHT shell, resulting in a porous structure. Meanwhile, hollow cavities are introduced into N,P codoped carbon nanocages (NPCNs) via the sacrificial nature of ZIF‐8 template. The microporosity is finely tuned by controlling thickness of the OCHT shell during synthesis of the core–shell nanoparticles, since the sublimation tendency of zinc component at high temperatures depends on the thickness of OCHT shell. A systematic correlation between the electrochemical performance of NPCNs and their microporosity is confirmed. Furthermore, the electrochemical performance of the NPCNs is related to the degree of heteroatom codoping. The approach is successfully scaled‐up without compromising their electrochemical performance. Finally, a symmetric and flexible all‐solid‐state‐supercapacitor with high energy and power density, and a long‐term cycleability is demonstrated (75% capacitance retention after 20 000 cycles).     

水热-模板剂法制备纳米La(S,C)-TiO_2阵列膜

以多孔陶粒为载体,采用低温水热-模板剂法制备复合掺杂的La(S,C)-TiO_2阵列膜,研究水热反应温度、非离子型高分子模板剂用量和La、S复合掺杂的协同效应对纳米TiO_2膜性能的影响,并通过XRD、BET、EDS和SEM等手段进行表征.结果表明:水热反应温度为150 ℃,反应时间控制在10 h时可得到锐钛矿相的TiO_2膜;模板剂P123用量为0.03(与Ti的摩尔比)时,可以将TiO_2颗粒的比表面积从146 m~2/g提高到240 m~2/g,并形成有序排列的阵列膜;适量地复合掺杂La和S(C),可使TiO_2膜的光催化活性大大提高,在3 h内将甲基橙完全降解.     

Defective N/S‐Codoped 3D Cheese‐Like Porous Carbon Nanomaterial toward Efficient Oxygen Reduction and Zn–Air Batteries

Developing a facile and cost‐efficient method to synthesize carbon‐based nanomaterials possessing excellent structural and functional properties has become one of the most attractive topics in energy conversion and storage fields. In this study, density functional theory calculation results reveal the origin of high oxygen reduction reaction (ORR) activity predominantly derived from the synergistic effect of intrinsic defects and heteroatom dopants (e.g., N, S) that modulate the bandgap and charge density distribution of carbon matrix. Under the guidance of the first‐principle prediction, by using ultralight biomass waste as precursor of C, N, and S elements, a defect‐rich and N/S dual‐doped cheese‐like porous carbon nanomaterial is successfully designed and constructed. Herein, the intrinsic defects are artfully generated in terms of alkaline and ammonia activation. The electrochemical measurements display that such a material owns a comparable ORR activity (E_1/2 = 0.835 V) to the commercial Pt/C catalyst, along with splendid durability and methanol tolerance in alkali media. Furthermore, as cathode catalyst, it displays a high Zn–air battery performance. The excellent ORR activity of the catalyst can be attributed to its unique 3D porous architecture, abundant intrinsic defects, and high‐content active heteroatom dopants in the carbon matrix.     

Effect of Si, Mg, and Mg–Zn doping on structural properties of a GaN layer grown by metalorganic chemical vapor deposition

We have studied the structural properties of undoped, Si-doped, Mg-doped, and Mg–Zn codoped GaN using high-resolution X-ray diffraction (HRXRD) and transmission electron microscopy. When compared with undoped GaN, the dislocation density at the surface of the GaN layer decreases with Si doping and increases with Mg doping. In addition, we observed a reduction of dislocation density by codoping with Zn atoms in the Mg-doped GaN layer. The full width at half maximum of HRXRD shows that Si doping and Mg–Zn codoping improve the structural quality of the GaN layer as compared with undoped and Mg-doped GaN, respectively.     

Li~+共掺杂对掺Er~(3+):TiO_2上转换发光的增强作用·

采用非水性溶胶-凝胶法制备了0.1%Er~(3+)(摩尔分数,下同)、0%～2%Li~+共掺杂TiO_2粉末,在980nm半导体激光器(LD)激发下获得了中心波长526nm、550nm的绿色和663nm的红色上转换发光.Li~+共掺杂对掺Er~(3+):TiO_2的相结构未产生影响,但极大增强了上转换发光强度.随Li~+共掺杂摩尔分数的逐渐增大,绿色和红色上转换发光强度先增大后减小,当Li~+摩尔分数为1%时,上转换发光强度达到最大,绿色和红色上转换发光强度分别比掺Er~(3+):TiO_2提高了约330倍、30倍和60倍.Er~(3+)Li~+共掺杂TiO_2粉末的绿色和红色上转换发光均为双光子吸收过程.Li~+共掺杂不改变Er~(3+)的上转换发光机制,但破坏了Er~(3+)的局部晶体场对称性,影响了Er~(3+)内部4f能级的跃迁几率,导致上转换发光强度增强.     

MOCVD生长GaN材料p型掺杂最新进展

p型GaN薄膜的实现是发展光电器件的关键工艺.使用金属有机物化学气相沉积(MOCVD)方法已经获得实用性的p型掺杂,但是其电学和光学特性都不能让人满意.最近几年在掺杂工艺的改进和掺杂模型的理论研究方面都取得了显著进展.介绍了p型掺杂GaN中的自补偿模型、共掺杂工艺的原理和进展、PL谱的性质以及一些新的掺杂工艺.