Compositional effect on oxygen reduction reaction in Pr excess double perovskite Pr1+xBa1-xCo2O6-δ cathode materials

The kinetics of oxygen reduction reaction (ORR), being a prime requisite for electrode materials after the higher conductivity. Further, electrodes are observed to dissolute on reaction at triple phase boundary. However, the compositional effect on ORR is least understood. In order to inspect the ORR mechanism with substitution, a series of (1 + x) PrCoO₃ − (1 − x) BaCoO₃ (x = 0.2 to 1.0 with step of 0.2) compositions are prepared using conventional solid-state route method. The Rietveld refinement of X-ray diffractograms and specific heat curves confirms the formation of double phase comprising orthorhombic Pmmm phase corresponding to PrBaCo₂O_6-δ and Pnma phase corresponding to PrCoO₃ for x = 0.2 to 0.8 with well connected and porous microstructure. The triple phase boundary reactions suggest the formation of Co(OH)₃ along with H₂ gas on reaction of these composite electrodes with H₂O during electrochemical dissolution. However, chronoamperometric studies prove the suitability of x = 0.6 sample with higher ORR and liberation of H₂ gas at room temperature.     

Mid-infrared tunable magnetic response in graphene-based diabolo nanoantennas

The combination of metallic structure and graphene has become a promising platform for electrically controlled plasmonic devices. However, the current designs mainly utilize graphene as an active medium, which only modulate the devices performance slightly and the applications in tunable magnetic response have not been explored. Here, we explore the applications of graphene in the control of magnetic resonance in nanoantennas. By optimizing the design and parameter of the nanoantennas, gold–graphene hybrid diabolo antennas turn out to be the best candidate to achieve tunable magnetic response in mid-infrared wavelength range. The magnetic resonance of gold–graphene hybrid diabolo antennas has been significantly tuned from 32.3 μm to 19.8 μm, which is beyond one order of magnitude higher than conventional diabolo nanoantennas with graphene as active materials below the antenna structure. The corresponding absorption modulation and magnetic field enhancement can be as high as 12% and 1460%, respectively.     

A 3D Porous Coordination Polymer from Tetrazole Ligand and Cd(II): Crystal Structure,Luminescent Property and Adsorption of Methanol and Water

An unusual tetrazole-based Cd(II) coordination polymer, [Cd(4-tzba)(H₂O)]_n (tzba = 4-(tetrazolyl)benzenecarboxylic acid) (1), was synthesized by hydrothermal reaction and structurally characterized by single-crystal X-ray diffraction. The structure of 1 contains distorted octahedral cadmium centers coordinated by four different tzba^2? ligands and a water molecule. All the tzba^2? ligands display coordination of type, μ4-κN1:κN3:κN4:κO1, O2, which connects four Cd(II) atoms to form an intricate 3-D network. There are three kinds of apertures in the structure of 1; two helical channels and a hexagonal aperture are observed along different axes. Polymer 1 exhibits selective gas adsorption behavior for methanol, ethanol and water. In addition, 1 shows blue photoluminescence mainly arising from intraligand transitions of the aromatic rings in the tbza^2? ligand.     

Field emission properties and growth mechanism of In2O3 nanostructures

Four kinds of nanostructures, nanoneedles, nanohooks, nanorods, and nanotowers of In₂O₃, have been grown by the vapor transport process with Au catalysts or without any catalysts. The morphology and structure of the prepared nanostructures are determined on the basis of field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD), and transmission electron microscopy (TEM). The growth direction of the In₂O₃ nanoneedles is along the [001], and those of the other three nanostructures are along the [100]. The growth mechanism of the nanoneedles is the vapor-liquid–solid (VLS), and those of the other three nanostructures are the vapor-solid (VS) processes. The field emission properties of four kinds of In₂O₃ nanostructures have been investigated. Among them, the nanoneedles have the best field emission properties with the lowest turn-on field of 4.9 V/μm and the threshold field of 12 V/μm due to possessing the smallest emitter tip radius and the weakest screening effect.     

光纤熔接机高清显微物镜光学系统设计

在光纤熔接过程中,为了实现光纤高质量熔接,需要一个高清显微物镜来确保纤芯的准确对准。运用Zemax软件设计一款用于光纤纤芯对准的显微物镜,该物镜由6片透镜组成,放大率为8倍,数值孔径为0.25,工作距为13.4mm,共轭距为85mm,以CCD作为图像接收器件。显微物镜采用正向光路进行优化设计,正向光路设计的显微物镜更能贴近实际使用状态,能够更加清晰准确地检测到纤芯位置。该物镜工作波长为486~656nm,具有工作距离长、共轭距短、精度高等特点。     

高分辨率星载光学系统装调过程的偏心误差分析

针对影响光学系统成像质量的装调误差,分析了偏心误差对高分辨率光学系统成像的影响。基于一款自主设计的接近衍射极限的高分辨率星载相机光学系统,利用Zemax光学软件分析光学装调过程中偏心误差对光学传递函数的影响,得出光学系统中各个分离元件对成像质量影响的权重,为光学系统的装调方案设计和实施提供了依据,实现了该光学系统2 500万像素高分辨率成像。这种误差分析方法实现了对光学系统装调过程的有效控制,提高了光学装调的效率。     

Light absorption distribution of prostate tissue irradiated by diffusing light source

Determination of light absorption distribution in the prostate tissue irradiated by diffusing light source is important for the treatment planning.In this paper,a three-dimensional(3D)optical model of human prostate is developed,and the light absorption distribution in the prostate tissue is estimated by Monte Carlo simulation method.Light distribution patterns including 3D distributions in the tissue model irradiated by two diffusing light sources are obtained and compared.Also,the impacts of length and energy of cylinder diffusing light source on the irradiance volume are demonstrated.Those results will be significant for the nondestructive qualitative assessments of photodosimetry in biomedical phototherapy.     

Alkaline aluminum phosphate glasses for thermal ion-exchanged optical waveguide

Alkaline aluminum phosphate glasses (NMAP) with excellent chemical durability for thermal ion-exchanged optical waveguide have been designed and investigated. The transition temperature Tg (470 °C) is higher than the ion-exchange temperature (390 °C), which is favorable to sustain the stability of the glass structure for planar waveguide fabrication. The effective diffusion coefficient D_e of K⁺–Na⁺ ion exchange in NMAP glasses is 0.110 μm²/min, indicating that ion exchange can be achieved efficiently in the optical glasses. Single-mode channel waveguide has been fabricated on Er³⁺/Yb³⁺ doped NMAP glass substrate by standard micro-fabrication and K⁺–Na⁺ ion exchange. The mode field diameter is 9.6 μm in the horizontal direction and 6.0 μm in the vertical direction, respectively, indicating an excellent overlap with a standard single-mode fiber. Judd–Ofelt intensity parameter Ω₂ is 5.47 × 10⁻²⁰ cm², implying a strong asymmetrical and covalent environment around Er³⁺ in the optical glasses. The full width at half maximum and maximum stimulated emission cross section of the ⁴I_13/2 → ⁴I_15/2 are 30 nm and 6.80 × 10⁻²¹ cm², respectively, demonstrating that the phosphate glasses are potential glass candidates in developing compact optoelectronic devices. Pr³⁺, Tm³⁺ and Ho³⁺ doped NMAP glasses are promising candidates to fabricate waveguide amplifiers and lasers operating at special telecommunication windows.     

The synthesis,characterization and DFT calculations of highly volatile aminogermylene precursors and thin film investigation for CVD/ALD technology

Compared to the difficult volatilization for germanium (IV) precursors, germanium (II) precursors usually have better volatilization but difficult to synthesize. A series of diamine germanium (II) precursors were synthesized, characterized and investigated by DFT calculations. These germanium (II) precursors were tested by TG experiments and showed excellent volatilization, which were suitable as a potential membrane material. Moreover, the Ge film was deposited on Si wafer directly and characterized by SEM.