pr3+掺杂透明氟氧化物玻璃陶瓷的光谱特性

根据pr3+掺杂透明氟氧化物玻璃陶瓷(Pr(0.2)∶FOV)样品在室温下的吸收光谱,分别采用了标准和修正的Judd-Ofelt理论拟合出J-O强度三参量Mn.结果表明,此修正的J-O理论应用到Pr(0.2):FOV材料的跃迁强度计算中是合理的和必要的.并由此修正理论计算了各个激发态之间跃迁的振子强度、自发辐射速率、荧...     

ChemInform Abstract: Valence Changes of Manganese and Structural Phase Transitions in Sr1‐xPrxMnO3 (0.1 ≤ x ≤ 0.6).

Fifteen perovskite manganites Sr_1‐xPr_xMnO₃ with x = 0.1—0.6 in steps of 0.025 are prepared by solid state methods and their crystal structures are determined by synchrotron powder XRD.     

Majorana zero modes in graphene with trigonal warping

We study the low energy properties of warped monolayer graphene, where the symmetry of the original honeycomb lattice reveals itself. The zero energy solutions are Majorana fermions, whose wave function, originating from the corresponding modified Dirac equation is spatially localized. Experimental consequences are discussed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

New implementation of composite fermions in terms of subgroups of a braid group

The new implementation of composite fermions and more generally — of composite anyons is formulated, exploiting one-dimensional unitary representations of appropriately constructed subgroups of the full braid group. The nature of hypothetical fluxes attached to the Jain's composite fermions is explained via additional cyclotron trajectory loops consistently with the braid subgroup structure. It is demonstrated that composite fermions are proper 2D particles (not an auxiliary construction), but associated with braid subgroups instead of the full braid group.     

Anyonic order parameters for discrete gauge theories on the lattice

We present a new family of gauge invariant non-local order parameters for (non-abelian) discrete gauge theories on a Euclidean lattice, which are in one-to-one correspondence with the excitation spectrum that follows from the representation theory of the quantum double D(H) of the finite group H. These combine magnetic flux-sector labeled by a conjugacy class with an electric representation of the centralizer subgroup that commutes with the flux. In particular, cases like the trivial class for magnetic flux, or the trivial irrep for electric charge, these order parameters reduce to the familiar Wilson and the ’t Hooft operators, respectively. It is pointed out that these novel operators are crucial for probing the phase structure of a class of discrete lattice models we define, using Monte Carlo simulations.     

Fabrication and characterization of superhydrophobic thin films based on TEOS/RF hybrid

Preparation of superhydrophobic silica-based thin film by adjusting different concentration of reverse (W/O) emulsion of resorcinol formaldehyde resin (re-RF) which was hybridised with silica sol has been developed. The hybrid films were coated by the mixing solution which included precursor solution (sol-gel process) and re-RF (sol-gel process). Rough surfaces were obtained by removing the organic polymer at high temperature and then the hydrophobic groups bonded onto the films were obtained by the reaction with trimethylchlorosilane (TMCS). Characteristic properties of the as-prepared cross-section and surface of the films were analyzed by scanning electron microscopy (SEM) and atom force microscopy (AFM). The experimental parameters are mainly varied the weight ratio of re-RF to silica sol from 0.2 to 4.0. The result showed that the contact angle of the modified silica film was greater than 160° when the weight ratio of re-RF to silica sol was 2.0.     

Photo-induced synthesis of DNA-templated metallic nanowires and their integration into micro-fabricated contact arrays

We report the synthesis of metallic nanowires accomplished by site-specific integration of single DNA duplexes into micro-fabricated contact arrays and their subsequent selective metallization. DNA interconnects between metallic contacts are formed by tethering the ends of DNA molecules, stretched in hydrodynamic flow into a linear conformation, at different gold contact pads via thiol functional groups. To transform the DNA interconnects into metallic cluster chains or nanowires, we use an electroless metal deposition technique where platinum ions bound along the DNA molecules from a salt solution are reduced to metallic clusters of less than 10 nm in diameter by applying UV light.     

The use of calcination in exposing the entrapped Fe particles from multi-walled carbon nanotubes grown by chemical vapour deposition

Multi-walled carbon nanotubes (MWCNTs) were synthesized a by chemical vapour deposition method. The effect of calcination at temperatures ranging from 300 to 550°C in exposing the metal nanoparticles within the nanotube bundles was studied. The degree of degradation of the structural integrity of the MWCNTs during the thermal process was studied by Raman spectroscopy, X-ray diffraction analysis, field-emission scanning electron microscopy, and transmission electron microscopy. The thermal behaviour of the as-prepared and calcined samples was investigated by thermogravimetric analysis. Calcination in air, at 400°C for 1 h, was found to be an efficient and simple method to extract metallic impurities from the amorphous carbon shells with minimal damage to the tube walls and lengths. The nanotubes were observed to be damaged at temperatures higher than 450°C.     

Pr3+,Tm3+共注入氮化铝薄膜的光谱特性

采用离子注入的方法在氮化铝薄膜中实现pr3和Tm3元素的单掺杂和共掺杂.以Raman光谱为主要表征手段,对离子注入过程中薄膜内部的应力变化进行研究;以阴极荧光为主要表征手段,对其低温和室温下的发光特性进行研究.Raman光谱的结果显示,离子注入过程使得薄膜内部应力下降,而退火过程使得薄膜内部应力升高.阴极荧光光谱结果显示,AIN:Pr3+主要跃迁峰位于528 nm;AIN:Tm3+主要跃迁峰位位于467 nm;AIN:Pr3+,Tm3+主要跃迁峰位位于528 nm和467 nm.AIN:Tm3+的低温光谱显示,与1I6和1D2两个能态相关的跃迁峰相对强度会随着温度出现急剧变化,由此表明在Tm3+之间存在与温度相关的相互作用.     

La(NO3)3和Pr(NO3)3对高岭石脱羟基动力学的影响

采用热重和微商热重(TG/DTA)综合热分析技术在不同升温速率下研究了掺入La(NO₃)₃和Pr(NO₃)₃的高岭石的热分解过程, 利用Coats-Redfern积分法和Achar微分法对热分析实验数据进行动力学计算, 得到了高岭石脱羟基反应过程中的控制机理函数、 活化能和指前因子等动力学参数; 分析了2种稀土掺入对高岭石脱羟基过程动力学参数的影响, 并用Ozawa法对活化能进行了验证. 结果表明, 未掺稀土和掺入Pr(NO₃)₃的高岭石的脱羟基反应过程均受化学反应模型F₃控制, 反应的活化能分别为307.94和282.86 kJ/mol, 指前因子lnA的值分别为47.8980和44.1718; 掺入La(NO₃)₃的高岭石脱羟基反应过程控制机理函数发生改变, 受化学反应模型F₂控制, 反应活化能为196.02 kJ/mol, 指前因子lnA的值为29.5551. 与未掺稀土的高岭石对比, 掺入Pr(NO₃)₃后活化能和指前因子略有降低; 而掺入La(NO₃)₃后则显著降低, 分别降低了36.34%和38.30%. 采用Ozawa法验证得到的活化能与Coats-Redfern积分法和Achar微分法结果一致.