一种弯曲主导型热膨胀点阵超材料的带隙特性研究

当前科技的发展对材料的多功能性提出了更高的要求。本文利用有限元法针对一种具有三角晶格的弯曲主导型热膨胀点阵超材料(JTCLM)进行了带隙研究,并讨论了几何参数对JTCLM单胞带隙的影响。结果表明,当JTCLM单胞存在弯曲曲率时将会产生带隙,且材料的几何参数对JTCLM点阵复合材料的带隙具有显著的影响。结果为实现热膨胀/带隙双目标的超材料设计提供了理论基础。通过合理的选材和形状设计,有望实现特定膨胀性质和带隙设计的双目标共赢,使材料具有更好的可调谐性和多功能性。     

二维BN材料中n型掺杂探索:基于第一性原理的带电缺陷计算

半导体材料的有效掺杂可为半导体器件的成功应用提供保障。理论上,通过计算缺陷形成能和电荷转移能级可以预测掺杂的难易性以及缺陷能级的深浅性。基于密度泛函理论,结合二维带电缺陷计算方法,系统计算二维BN材料中四种(C_B,Si_B,Ge_B,Sn_B)潜在n型掺杂体系的缺陷性质。结果表明,C_B(Sn_B)体系最稳定价态为+1价(-1价)和0价,而Si_B,Ge_B体系最稳定价态为+1价,0价和-1价,C_B,Si_B与Ge_B体系相应的施主离子化能为2.00 eV,3.57 eV和4.06 eV,均表现为深能级施主,很难为BN提供n型载流子。另外,C_B体系在宿主BN为p型掺杂时+1价态具有负形成能,将会严重降低BN p型掺杂效率及空穴导电率。该研究结果可为实验上对二维BN进行掺杂尝试提供理论依据。     

席夫碱共价有机框架的合成及对I‒的识别

设计合成了一种新型共价有机框架类荧光探针TpPa-COOH COF, 该探针在THF/H₂O(体积比1∶1)混合溶液中能够高选择性识别I^?. 向体系中加入I^?后, 溶液由浅红色变为黄色, 317 nm处荧光强度明显降低. 该探针具有良好的选择性, 抗干扰能力强, 检出限为0.028 μmol/L, pH适用范围广(1~13), 具有良好的应用前景.     

粉末压片-X-射线荧光光谱法分析砂岩型铀矿制样中粘结剂用量的探讨

由于砂岩型铀矿的成矿特性,样品粉末的内聚力小,采用直接压片法有时难以成型,样片表面常见裂纹,上机测量易碎裂。混合压片法适应性强,制样成功率高,但常见的问题是样品经粘结剂稀释会影响元素的检出限及结果的准确性。本文对粉末压片-X射线荧光光谱法测定砂岩型铀矿地质样品时,前期制样中添加粘结剂的比例进行了研究。试验按照不同比例在铀矿石标准物质GBW04101、GBW04102中添加粘结剂,在扫描电镜下观察到随着粘结剂用量的增加样片表面的光滑度及致密度都呈上升趋势,在X-射线荧光光谱仪上对主量元素进行测定后发现X射线强度在粘结剂添加量大于0.2 g时明显下降,经与GBW04101、GBW04102标准值进行对比后优选出粘结剂与样品的最佳比例为1：20,在此比例下制成的样片光滑平整,不易碎裂,用粉末压片-X射线荧光光谱法进行测定,标准物质测定结果的相对误差为0.56%～6.76 %,相对标准偏差(RSD,n=12)为0.013 %～7.68 %,均达到了《地质矿产实验室测试质量管理规范》DZ/T 0130-2006的要求。本文为粉末压片-X射线荧光光谱法分析砂岩型铀矿地质样品提供了可靠的实验参考依据。     

光纤中慢光群折射率限定特性研究

粒子在基态和亚稳态之间的振荡会导致探测光吸收的降低,而探测光束在很窄的频率范围内吸收的降低,会使介质的感生折射率在同样范围内迅速变化,从而改变群折射率ng=n(ω)+ωdn/dω。本文利用光纤慢光理论,对不同条件下的群折射率限定和群速度的变化特性展开讨论。群折射率随光纤长度的增加而降低,不同离子浓度的掺铒光纤中慢光的感生群折射率均随调制频率的增加而降低,同时在不同的调制频率条件下,群折射率随入射信号光强度的增大均有一个饱和的过程。     

Synthesis, characterization, and electrochemical application of Ca(OH)2-, Co(OH)2-, and Y(OH)3-Coated Ni(OH)2 tubes

We report on the synthesis, characterization, and electrochemical application of Ca(OH)2-, Co(OH)2-, and Y(OH)3-coated Ni(OH)2 tubes with mesoscale dimensions. These composite tubes were prepared via a two-step chemical precipitation within an anodic alumina membrane under ambient conditions. The morphology and structure of the as-synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM) equipped with energy dispersive spectroscopy (EDS). The results showed that the size of the tubes was of mesoscale dimension and the proportion of the tube morphology was about 95%. The as-prepared composite tubes were further investigated as the positive-electrode materials of rechargeable alkaline batteries. Electrochemical measurements revealed that the Ni(OH)2 tubes coated with Ca(OH)2, Co(OH)2, and Y(OH)3 exhibited superior electrode properties including high discharge capacity, excellent high-temperature and high-rate discharge ability, and good cycling reversibility. The mechanism analysis suggests that both the coated layers and the unique hollow-tube structures play an indispensable role in optimizing the electrochemical performance of nickel hydroxide electrodes.     

氯化钽在离子液体1-丁基-3-甲基咪唑六氟磷酸盐中电化学行为

采用循环伏安法,研究了0.25 mol/L TaCl₅在离子液体1-丁基-3-甲基咪唑六氟磷酸盐([Bmim]PF₆)中的电化学行为。 实验结果表明,电沉积钽是受扩散控制、两步骤的不可逆电极反应过程,首先是Ta(Ⅴ)还原为Ta(Ⅲ),其次是Ta(Ⅲ)还原为金属钽和形成其它低价钽氯化物。 Ta(Ⅴ)/Ta(Ⅲ)和Ta(Ⅲ)/Ta在离子液体[Bmim]PF₆中的阴极传递系数分别为0.155和0.406。 Ta(Ⅴ)在离子液体[Bmim]PF₆中的扩散系数为1.629×10^-9 cm²/s。 在100 ℃和-1.25 V条件下,采用恒电势法在铂片上电沉积钽,扫描电子显微镜照片和EDS分析表明,沉积物为钽和钽的低价氯化物。     

Indirect Electrochemical Determination of Ribavirin Using Boronic Acid-Diol Recognition on a 3-Aminophenylboronic Acid-Electrochemically Reduced Graphene Oxide Modified Glassy Carbon Electrode (APBA/ERGO/GCE)

A novel method for the indirect electrochemical determination of ribavirin based on boronic acid-diol recognition was developed using the platform as the sensing element. The device was constructed using a 3-aminophenylboronic acid (APBA)-electrochemically reduced graphene oxide (ERGO) modified electrode. When the electrode was immersed in a solution of ribavirin, complexation of boronic acid groups of APBA with ribavirin occurred at the surface of the electrode and simultaneously caused steric hindrance, resulting in a current decrease because the ferricyanide redox probe was unable access the surface. Under the optimized conditions, a linear relationship was obtained between the relative change in current (%Δi) of [Fe(CN)₆]^3?/4?and the concentration of ribavirin at levels from 10.0 to 7.50?×?10²?ng mL^?1. The proposed electrochemical sensor performed with acceptable sensitivity and reproducibility and was successfully used to determine the content of ribavirin in an injection with satisfactory results.     

(111)取向0.7PMN-0.3PT薄膜机电耦合性能

铁电薄膜由于其优异物理性能,而被广泛应用于微电子、光电子、微机电领域。在铁电薄膜理论研究方面,热力学理论可以有效地预测铁电薄膜的相结构、极化特性和机电性能等,且已在(001)取向铁电薄膜的研究中取得了较好的应用,而对于(111)取向铁电薄膜的研究报道非常少。因此,本文通过对序参量坐标转换的方法,构建了(111)取向薄膜的热力学势能函数及其机电性能计算方法。基于此,研究了(111)取向0.7PMN-0.3PT铁电薄膜的相结构及其机电性能。研究结果表明,(111)取向0.7PMN-0.3PT铁电薄膜的相结构主要存在沿晶轴方向三个极化可互换的对称相:顺电相PE、菱方相R和单斜相M_A(或M_B)。在应变和外电场的调控下,(111)取向0.7PMN-0.3PT薄膜展现出优良的机电性能,在R和M_A相变点处,介电常数ε11、ε22、ε33和面外压电系数d33取得了极大值。在外电场E₃分别为0、50 kV/cm、100 kV/cm和200 kV/cm时,面外介电常数ε33的峰值分别为4 382、2 646、2 102和1 600,面外压电系数d33的峰值分别为303.8 pm/V、241.9 pm/V、219.7 pm/V和195.1 pm/V。应变和外电场能够较好地调控薄膜的机电耦合性能,可为优异机电耦合性能的器件制备提供参考。     

Bi2WO6 photocatalytic films fabricated by layer-by-layer technique from Bi2WO6 nanoplates and its spectral selectivity

Bi₂WO₆ multilayer films have been fabricated successfully by a layer-by-layer (LbL) technique from Bi₂WO₆ nanoplates, which show higher visible-light photoactivity (λ>420 nm) than that of Bi₂WO₆ nanoplate powders and P25 TiO₂ films. The films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and UV-visible absorption spectroscopy. Photocatalytic activities of the films were evaluated by the rhodamine B (RhB) decomposition under UV and visible-light irradiation. Thickness and photoactivity of the film can be modified easily by changing the deposition cycles. Bi₂WO₆ films have the spectral selectivity of the photocatalytic degradation of RhB. Under the wavelength greater than 300 nm, the RhB molecules tend to be transformed to rhodamine over Bi₂WO₆ films selectively. However, in the case of shorter wavelength (λ=254 nm) light irradiation, the RhB molecules can be photodegraded completely.