A new route of manipulation of poly(L‐lactic acid) crystallization by self‐assembly of p‐tert‐butylcalix[8]arene and toluene

A novel nucleating agent (TBC8‐t), self‐assembled with p‐tert‐butylcalix[8]arene (TBC8) and toluene, was used to manipulate the crystallization behavior of poly(L ‐lactic acid) (PLLA). Toluene molecules were used to adjust the crystallization structure of TBC8. Differential scanning calorimetry results show that the crystallization peak temperature (T_c) and crystallization rate (ΔH_c/time) of PLLA nucleated with TBC8‐t are 132.3 °C and 0.24 J/gs, respectively, which are much higher than that with conventional nucleating agent‐talc (T_c = 119.3 °C, ΔH_c/time = 0.13 J/gs). The results of polarized optical microscopy demonstrate that TBC8‐t could greatly enhance the crystallization rate of PLLA by increasing the nucleation rate rather than crystal growth rate. Along with an improvement of the crystallization rate, the crystalline morphology of PLLA is also affected by TBC8‐t. The addition of TBC8‐t transforms most of the original spherulite crystals into sheaf‐like crystals. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1235–1243, 2010     

Superconducting state parameters of ternary amorphous superconductors

The theoretical investigations of the superconducting state parameters (SSP) viz. electron-phonon coupling strength λ, Coulomb pseudopotential μ^?, transition temperature T_C, isotope effect exponent α and effective interaction strength N_OV of (Ni₃₃Zr₆₇)_1 − xM_x (x = 0, 0.05, 0.1, and 0.15, M = Cu) ternary amorphous superconductors have been reported using Ashcroft's empty core (EMC) model potential. Five local field correction functions proposed by Hartree (H), Taylor (T), Ichimaru-Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) are used in the present investigation to study the screening influence on the aforesaid properties. The T_C obtained from Sarkar et al. (S) local field correction function is found in excellent agreement with available theoretical data. Quadratic T_C equation has been proposed, which provides successfully the T_C values of ternary amorphous alloys under consideration. Also, the present results are found in qualitative agreement with other such earlier reported data, which confirm the superconducting phase in the superconductors.     

Hydrothermal synthesis of anatase flower‐like nanostructures for photocatalytic degradation of dye

Flower‐like hierarchical nanostructures of titanium dioxide (TiO₂) have been synthesized in large scale by a facile and controlled hydrothermal and after annealing process. The morphologies of flower‐like hierarchical nanostructures are formed by self‐organization of several tens of radially distributed thin flakes with a thickness of several nanometers holding a larger surface area. The materials are characterized by Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X‐ray diffraction (XRD). The ultraviolet photocatalytic degradation of R6G dyes has been studied over this flower‐like hierarchical nanostructures and the activity is compared with that of commercial P25 TiO₂ under same conditions. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of field emission property of carbon‐like nanofiber treated by using a fluorocarbon/oxygen plasma

Carbon‐like nanofiber (CNF) is synthesized using microwave plasma‐enhanced chemical vapor deposition. We present the effects of fluorocarbon and oxygen (CF₄/O₂) plasma‐treated on the microstructural, crystal, and field emission (FE) characteristics of CNF by SEM, transmission electron microscopy, micro‐Raman, and FE system. Results showed that the presence of the damaged CNF occurs at 2 min CF₄/O₂ plasma treatment and some amorphous carbon particles after 10 min CF₄/O₂ plasma treatment. One can also observe that turn‐on fields were enhanced (2.75 uA/cm²) at 2 min CF₄/O₂ plasma treatment; this indicates a remarkable FE enhancement of the local emission region in CNFs. Complementary information was obtained by thermal desorption atmospheric pressure ionization mass spectrometry and XPS. It can be found that the broken surface morphologies could be attributed to the chemical reaction exchanged via plasma excitation; a large number of bonding (C–F and C–O) in the CNF was detected. In addition, it is observed that the CNF has higher fluorine desorbed at 277.5 and 427 °C after CF₄/O₂ plasma treatment. Copyright © 2012 John Wiley & Sons, Ltd.     

二硝基甲苯低压加氢Ni-La-B非晶态合金催化剂的制备及结构表征

用化学还原法制备了Ni-La-B非晶态合金催化剂,并采用X射线衍射、透射电镜、差热分析、X射线光电子能谱、电感耦合等离子光谱和H2程序升温脱附技术对催化剂进行了表征,研究了La含量对催化剂微观结构及其催化二硝基甲苯(DNT)加氢制二氨基甲苯(DAT)性能的影响.结果表明,随着助剂La含量的增加,Ni-La-B催化剂中非晶态结构的长程无序程度增大,催化剂平均粒径逐渐由70nm左右减小至10nm左右,分布更加均匀;同时降低了Ni吸附H2的强度,使H2吸附物种更易于在催化剂表面流动并参与反应.另外,La助剂还显著提高了催化剂的热稳定性和抗氧化性.在二硝基甲苯加氢反应中,催化剂性能随着La加入量提高至6%(摩尔分数)时,1MPa低压条件下DNT转化率和DAT选择性均达100%.当La加入量为8%时,催化剂的Ni活性中心数明显减少,其活性下降.     

Synthesis, structure and optical features of single adamantanoid Hg-SePh-X anionic clusters stabilized by octahedral complexes (Ph = phenyl; X = Cl, Br, I)

The ligand dppmo₂ [CH₂{P(O)Ph₂}₂] (Ph = phenyl), MgCl₂·6H₂O, MgBr₂, MgI₂, FeBr₂, CoBr₂, NiBr₂ and Hg(SePh)₂ react one at a time to give the complex salt of the general formula [M(dppmo₂)₃][Hg₄X₄(SePh)₆]·4dmf·H₂O (M = Mg²⁺, Fe²⁺, Co²⁺, Ni²⁺; X = Cl, Br, I; dmf = dimethylformamide). The cations [M(dppmo₂)₃]²⁺ are predominantly octahedral with axial angles from 175° to 178°. The adamantane like anions [Hg₄X₄(SePh)₆]²⁻ are examples of single adamantanoid species, since these compounds normally appear as polymers or fused cages. Adamantanoid cages are the preferential thermodynamic configuration for this atomic aggregate. They appear as single molecules or ions however only in a halogen rich reactions milieu.     

光驱动多孔无定形TiO2的形成机制与光催化性能的研究

以钛酸正丁醇和乙二醇为原料,采用溶剂热法合成了钛乙二醇盐(TG)前躯体,在高压汞灯照射下制备出无定形TiO2。利用X射线衍射(XRD)、扫描电镜(SEM)和透射电镜(TEM)、紫外-可见吸收光谱(UV-Vis)、表面光电压谱(SPS)、N2吸附-脱附对所得材料进行了结构和性能的表征。借助X射线吸收精细结构(XAFS)对无定形TiO2的形成机制进行了分析,并通过硝基苯的还原反应考察了材料的光催化性能。结果表明:在紫外光驱动无定形TiO2的形成过程中,中心元素Ti4+的配位环境发生变化,由八面体结构转变为四面体结构;由于特殊的孔道结构使得多孔无定形TiO2显示出较好的光催化活性。     

Silicone oxidation for a‐Si:H passivation of wafers bonded to glass

A possible scenario for wafer‐based silicon photovoltaics is the processing of solar modules starting from thin silicon wafers bonded to glass. However, interactions between the adhesive used for bonding and the solar cell processing can affect the surface passivation of the bonded wafer and decrease cell performances. A method that suppresses these interactions and leads to state‐of‐the‐art a‐Si:H surface passivation is presented in this Letter. The method is based on an increase of the surface cross‐linking of a silicone adhesive by means of an O₂ plasma and it is successfully tested on three different silicones. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

High-Efficiency Silicon Solar Cells—Materials and Devices Physics

High-efficiency Si solar cells have attracted great attention from researchers, scientists, engineers of photovoltaic (PV) industry for the past few decades. Many researchers, scientists, and engineers in both academia and industry seek solutions to improve the cell efficiency and reduce the cost. This desire has drawn stronger support from major funding agencies and industry and stimulated a growing number of major research and research infrastructure programs, and a rapidly increasing number of publications in this filed. This article reviews materials, devices, and physics of high-efficiency Si solar cells developed over the last 20 years and presents representative examples of superior performances and competitive advantages. In this paper there is a fair number of topics, not only from the material viewpoint, introducing various materials that are required for high-efficiency Si solar cells, such as base materials (FZ-Si, CZ-Si, MCZ-Si, and multi-Si), emitter materials (diffused emitter and deposited emitter), passivation materials (Al-BSF, high-low junction, SiO₂, SiO_x, SiN_x, Al₂O₃ and a-Si:H), and other functional materials (antireflective layer, transparent conductive oxide and metal electrode), but also from the device and physics point of view, elaborating on physics, cell concept, development, and status of most types of high-efficiency Si solar cells, including passivated emitter and rear contact (PERC), passivated emitter and rear locally diffused (PERL), passivated emitter and rear totally-diffused (PERT), Pluto, PANDA, interdigitated back-contacted (IBC), emitter-wrap-through (EWT), metallization-wrap-through (MWT), heterojunction with intrinsic thin-layer (HIT), and so on. Finally, the technical data of these high-efficiency Si solar cells has been tabulated.     

Fractal Germanium Patterns: Annealing Strategies and Perspectives of Metal-Induced Crystallization

Semiconductor germanium (Ge) in contact with some metals, such as Al, Pd, and Au, etc., is a class of distinctive materials with non-integer dimensions (D) that differ from integer dimensional materials, such as nanoparticles (0D), nanowires/nanorods//nanotubes/nanoribbons (1D), and thin films (2D). In this article, we describe our efforts toward understanding the annealing strategies and perspectives of metal-induced crystallization for the amorphous Ge embedded in Al, Pd, and Au matrices prepared by high vacuum thermal evaporation techniques, highlighting contributions from our laboratory. First, we present the Al-induced crystallization of amorphous Ge and formation processes of fractal Ge patterns. In addition, the fractal Ge patterns induced by Pd nanoparticles with solid-state reactions will be summarized in detail. Temperature-dependent properties of resistance and fractal dimension in Pd/Ge bilayer films will be expounded. In particular, the nonlinear optical properties are discussed in detail. Finally, we will emphasize the in situ observations by transmission electron microscopy and multi-fractal analysis for the fractal Ge patterns induced by Au nanoparticles. Moreover, the polycondensation-type fractal Ge patterns with non-integer dimensions, thick branches and smooth edges, and metastable gamma-Au_0.6Ge_0.4 are further investigated. The computer simulation indicated that the experimental results are good agreement with the simulation patterns, which were carried out by a ripening mechanism of non uniform grains. This review may provide a novel insight to modulate their competent performance and promote rational design of micro/nanodevices.