Ein Natrium‐Oxocobaltat(II)‐Sulfat: Na8[CoO3][SO4]2

A Sodium Oxocobaltate(II) Sulfate: Na₈[CoO₃][SO₄]₂ Na₈[CoO₃][SO₄]₂ has been obtained from a redox reaction between cobalt metal and CdO in the presence of Na₂SO₄ and Na₂O at 550 °C (15 d) as red single crystals. The structure has been determined from single crystal data (IPDS‐data, T = 170 K, Cmcm, Z = 4, a = 806.88(9) pm, b = 2232.1(3) pm, c = 705.97(9) pm, R_all = 0.047). Magnetic properties and spectroscopic investigations are reported and discussed within the Angular‐Overlap‐Model.     

Rb吸附石墨烯纳米带电子性质和光学性质的研究

本文基于密度泛函理论的第一性原理方法了计算了Rb、O和H吸附石墨烯纳米带的差分电荷密度、能带结构、分波态密度和介电函数,调制了石墨烯纳米带的电子性质和光学性质,给出了不同杂质影响材料光学特性的规律.结果表明本征石墨烯纳米带为n型直接带隙半导体且带隙值为0.639 eV;Rb原子吸附石墨烯纳米带之后变为n型简并直接带隙半导体,带隙值为0.494eV;Rb和O吸附石墨烯纳米带变为p型简并直接带隙半导体,带隙值增加为0.996eV;增加H吸附石墨烯纳米带后,半导体类型变为n型直接带隙半导体,且带隙变为0.299eV,带隙值相对减小,更有利于半导体发光器件制备.吸附Rb、O和H原子后,石墨烯纳米带中电荷密度发生转移,导致C、Rb、O和H之间成键作用显著.吸附Rb之后,在费米能级附近由C-2p、Rb-5s贡献;增加O原子吸附之后,O-2p在费米能级附近贡献非常活跃,杂化效应使费米能级分裂出一条能带;再增加H原子吸附之后,Rb-4p贡献发生蓝移,O-2p在费米能级附近贡献非常强,费米能级分裂出两条能带.Rb、O和H的吸附后,明显调制了石墨烯纳米带的光学性质.     

甘油在氧化物/钯复合催化剂上的电氧化研究

应用交替微波加热法制备碳载氧化物和Pd的复合催化剂,并以电化学方法研究这一新型催化剂在碱性条件下对甘油的氧化性能.实验表明,Pd/C催化剂对甘油的电化学氧化有较好活性,但氧化物复合的非铂催化剂对甘油的电化学氧化显示出更高的活性,相对于Pd/C催化剂,其氧化起始电位发生负移及峰电流大幅度提高.本工作还优化了氧化物与Pd的比例.结果证明,氧化物的加入使复合催化剂对甘油氧化产生了协同效应.     

Free-standing nitrogen doped graphene/Co(OH)_2 composite films with superior catalytic activity for aprotic lithium-oxygen batteries

The recent boom in large-scale energy storage system promotes the development of lithium-oxygen batteries because of their high theo retical energy density.However,their applications are still limited by the sluggish kinetic,insoluble discharge product deposition and the undesired parasitic reaction.Herein,the free-standing nitrogen doped reduced graphene oxide/Co(OH)_2(NRGO/Co(OH)_2) composite films were prepared by a facile hydrothermal method,The NRGO/Co(OH)_2 composite films display interconnected three-dimensional conductive network,which can not only promote the diffusion of O_2 and the transport of electrolyte ions,but also provide abundant storage space for discharge products.Moreover,the introduction of nitrogen-containing functional groups results in improved conductivity and electron adsorption ability,which can facilitate electron transport and enhance the surface catalytic activity.Combining with excellent catalytic performance,the lithium-oxygen batteries with NRGO/Co(OH)_2 composite film cathodes deliver low charge overpotential and excellent cycling performance.     

氧化物纳米材料Y2O3:(Yb3+,Er3+)上转换发光性质的研究

以Y2O3,Yb2O3,Er2O3为原料,利用燃烧法分别制备了Y2O3:Er3 和Y2O3:(Yb3 ,Er3 )两种纳米材料和相应的体材料Y2O3:(Yb3 ,Er3 ).用发射波长为978 nm的半导体激光器和日立F-4500荧光分析仪测量了它们的上转换发光,得到纳米材料Y2O3:Er3 的上转换发光主要为绿色上转换发射而纳米材料Y2O3:(Yb3 ,Er3 )主要为红色上转换发射,而后者与激活离子掺杂浓度相同的体材料Y2O3:(Yb3 ,Er3 )的上转换发射相比较,体材料以绿色上转换发射为主、红色上转换发射很弱.     

Improved microstructure and mechanical properties in gas tungsten arc welded aluminum joints by using graphene nanosheets/aluminum composite filler wires

In the present study, different amounts of graphene nanosheets (GNSs) were added to the 4043 aluminum alloy powders by using the mechanical alloying method to produce the composite filler wires. With each of the produced composite filler wires, one all-weld metal coupon was welded using the gas tungsten arc (GTA) welding process. The microstructure, mechanical properties and fracture surface morphology of the weld metals have been evaluated and the results are compared. As the amount of GNSs in the composition of filler wire is increased, the microstructure of weld metal was changed from the dendritic structure to fine equiaxed grains. Furthermore, the tensile strength and microhardness of weld metal was improved, and is attributed to the augmented nucleation and retarded growth. From the results, it was seen that the GNSs/Al composite filler wire can be used to improve the microstructure and mechanical properties of GTA weld metals of aluminum and its alloys.     

Goos–Hänchen like shifts in graphene double barriers

We study the Goos–Hänchen like shifts for Dirac fermions in graphene scattered by double barrier structures. After obtaining the solution for the energy spectrum, we use the boundary conditions to explicitly determine the Goos–Hänchen like shifts and the associated transmission probability. We analyze these two quantities at resonances by studying their main characteristics as a function of the energy and electrostatic potential parameters. To check the validity of our computations we recover previous results obtained for a single barrier under appropriate limits.     

耦合氧化石墨烯的N掺杂Bi_2O_2CO_3微球光催化性能增强机制(英文)

光催化作为一种环境友好技术,在解决环境污染和能源匮乏问题方面展现出巨大应用潜力.TiO_2因其化学稳定性、无毒和低成本被广泛应用于能源转换和污染物降解等领域,但其快速的电子-空穴复合与低太阳能利用率等限制了其在光催化中的潜在应用.因此,寻找新的有优越可见光活性的催化剂是一个挑战.最近,(BiO)_2CO_3因其独特的形貌、化学稳定性和较高的催化效率成为有前景的光催化剂.然而,(BiO)_2CO_3较大的带隙限制了对太阳光的利用,快速的电子-空穴复合阻碍了光催化性能的提高.因此,提高(BiO)_2CO_3的光催化效率是当务之急.近期研究表明,通过与氧化石墨烯杂交提高载流子的分离能力,可有效增强光催化性能.基于此,我们设计并合成了一种氮掺杂的(BiO)_2CO_3与氧化石墨烯(GO)耦合的新型光催化剂(N-BOC-GO).首先,通过一步水热法合成了N-BOC-GO微球.N-BOC-GO光催化剂对NO可见光光催化去除性能达到62%.采用X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、紫外-可见漫反射光谱(UV-Vis)和光致发光光谱(PL)等表征手段研究了N-BOC-GO的光催化性能增强机制.从N-BOC-GO的XRD谱中没有发现GO的衍射峰,说明加入的GO分散度高;N-BOC-GO中的BOC晶格参数没有发生变化,说明GO没有进入BOC晶格,但加入GO增强了N-BOC的结晶度.XPS结果表明,与N-BOC相比,N-BOC-GO的峰位置发生了明显位移,表明N-BOC和GO之间存在强相互作用.此外,FT-IR和拉曼光谱证明了在复合物中存在GO.SEM表明,N-BOC规则地团聚成微球,且微球被固定在有褶皱的GO片上.这说明GO与N-BOC的作用是静电作用或物理作用,在光激发过程中有利于N-BOC微球上的电子转移到GO片上.UV-Vis图谱中,N-BOC-GO表现出明显增强的可见光吸收,说明加入GO会明显提高N-BOC的吸收能力.此外,3D分层结构会通过SSR效应提高光吸收.从PL图可以发现,N-BOC-GO的电子-空穴复合明显下降,说明GO可以转移电子从而提高光催化性能.结合前面的分析,我们提出了N-BOC-GO光催化剂3D分层结构的形成和性能增强机制.在水热过程中,通过分子间相互作用使N-BOC自组装成块,随后在表面能最小化的作用下转化成3D微球.加入GO后,N-BOC和GO通过物理吸附使得N-BOC微球均匀分散在GO上,最后N-BOC-GO的形貌类似于玫瑰花和其叶子的组合.在可见光照射下,N-BOC产生电子-空穴对,电子从N-BOC表面转移到GO表面,表明GO可作为电子的收集者和传递者以有效分离电子-空穴对,延长载流子寿命.N-BOC价带上的空穴可以直接氧化NO或产生?OH氧化NO.此外,由于GO独特的特征,光催化反应发生在N-BOC催化剂表面和GO片上,从而提高了反应空间位点.故引入GO于N-BOC体系中可有效分离光生载流子和提高反应活性位点,从而显著提高可见光催化性能.