磷灰石结构荧光粉Ba10(PO4)6F2:Ce3+,Tb3+的合成、发光和能量传递

采用高温固相法合成了系列Ce~(3+)和Ce~(3+)/Tb~(3+)激活的具有磷灰石结构荧光粉Ba_(10)(PO_4)_6F_2。用X射线衍射(XRD)、扫描电镜(SEM)、激发和发射(PLE和PL)光谱对样品进行了表征分析。研究结果表明:所合成的荧光粉Ba_(10)(PO_4)_6F_2∶Ce~(3+),Tb~(3+)具有氟磷灰石结构,样品微观呈现不规则形貌。荧光粉Ba10-x(PO4)6F2∶x Ce~(3+)的相对发射强度随着x增加而增强,当x=0.09时,荧光强度达到最大。荧光粉Ba_(10)(PO_4)_6F_2∶Ce~(3+),Tb~(3+)的激发光谱为240～330 nm的宽带,发射光谱呈现出Ce~(3+)的5d→4f跃迁紫外光(335和358 nm)发射和Tb~(3+)的4f→4f跃迁绿光(542 nm)发射。光谱特性表明,发光过程中存在Ce~(3+)→Tb~(3+)能量传递,能量传递效率可以达到60%。计算Ce~(3+)和Tb~(3+)的临界距离为0.79 nm,能量传递机理是偶极-偶极交互作用。此外,详细论述了Ce~(3+)和Tb~(3+)之间的能量传递和发光的过程。通过调节Tb~(3+)的掺杂浓度,对荧光粉发光色坐标与Tb~(3+)的掺杂浓度之间的关系也进行了研究,随着Tb~(3+)的掺杂量从0增加0.52,荧光粉Ba_(10)(PO_4)_6F_2∶Ce~(3+),Tb~(3+)的发射光谱色坐标可以从(0.149 4,0.045 1)蓝色区变化到(0.280 1,0.585 3)绿色区。     

Handedness inversion of chiral mesoporous silica: A diffuse-reflectance circular dichroism study

Temperature-depended handedness inversion in chiral mesoporous silica was investigated by diffuse-reflectance circular dichroism spectra.     

化学优质课3C-FIAS常模的建立研究

以全国优质课评比的90节化学课为常模样本,建立化学优质课3C-FIAS教学行为变量常模,并验证了常模的适用性、科学性和实用性。此外,根据弗兰德斯特殊序对,建立了3C-FIAS特殊序对常模。     

Synergistic effects of mono-component intumescent flame retardant grafted with carbon black on flame retardancy and smoke suppression properties of epoxy resins

Journal of Thermal Analysis and Calorimetry - A mono-component intumescent flame retardant named pentaerythritol phosphate melamine salt (PPMS) was grafted on the surface of carbon black (CB) to...     

Hybrid Organic–Inorganic Thermoelectric Materials and Devices

Hybrid organic–inorganic materials have been considered as a new candidate in the field of thermoelectric materials since the last decade owing to their great potential to enhance the thermoelectric performance by utilizing the low thermal conductivity of organic materials and the high Seebeck coefficient, and high electrical conductivity of inorganic materials. Herein, we provide an overview of interfacial engineering in the synthesis of various organic–inorganic thermoelectric hybrid materials, along with the dimensional design for tuning their thermoelectric properties. Interfacial effects are examined in terms of nanostructures, physical properties, and chemical doping between the inorganic and organic components. Several key factors which dictate the thermoelectric efficiency and performance of various electronic devices are also discussed, such as the thermal conductivity, electric transportation, electronic band structures, and band convergence of the hybrid materials.     

Vehicle–bridge interaction analysis under high-speed trains

The dynamic interaction between high-speed train and simply supported girders is studied by theoretical analysis and field experiment in this paper. The dynamic interaction model of the train–bridge system is established, in which the rigid-body dynamics theory, finite element method and wheel–rail displacement corresponding assumption are adopted for the vehicle model, bridge model and wheel–rail interaction model, respectively. The measured track irregularities are taken as the system excitation. The responses of a 24 m-span PC box girder bridge are calculated. The proposed analysis model and the solution method are verified through the comparison between the calculated results and the measured results.     

自呼吸式DMFC电堆构建与电池性能研究

本文报道了一种能驱动风扇工作的自呼吸式DMFC小型电堆,电堆主要南燃料储罐、膜电极(MEA)、集流体等组成.文中针对影响该电池性能的主要参数,如电堆的活化过程、甲醇浓度等因素进行了研究.同时,本文还对电堆的恒电流放电时的电流曲线特点以及阴极水的生成规律进行了初步考察和探讨.     

Langevin study of neutron emission in the reactions ^16O＋^181Ta and ^19F＋^178Hf^＊

The pre-scission neutrons measured in the reactions 16O 181Ta and 19F 178Hf are studied via a Langevin equation coupled with a statistical decay model. We find that because of the mass asymmetry of different entrance channels, the spin distributions of compound nuclei would be different, consequently, the measured neutrons in these two reactions would also different. This means that the entrance channel will affect the particle emission in the fission process of hot nuclei.     

Influence of angular momentum on evaporation residue cross section as a probe of nuclear dissipation

By calculating the excess of the evaporation residue cross sections of the ²⁰⁰Pb