Formation of β‐iPP in isotactic polypropylene/ethylene–propylene rubber blends: Effects of preparation method,composition, and thermal condition

The effects of preparation method, composition, and thermal condition on formation of β‐iPP in isotactic polypropylene/ethylene–propylene rubber (iPP/EPR) blends were studied using modulated differential scanning calorimeter (MDSC), wide angle X‐ray diffraction (WAXD), and phase contrast microscopy (PCM). It was found that the α‐iPP and β‐iPP can simultaneity form in the melt‐blended samples, whereas only α‐iPP exists in the solution‐blended samples. The results show that the formation of β‐iPP in the melt‐blended samples is related to the crystallization temperature and the β‐iPP generally diminishes and finally vanishes when the crystallization temperature moves far from 125 °C. The phenomena that the lower critical temperature of β‐iPP in iPP/EPR obviously increases to 114 °C and the upper critical temperature decreases to 134 °C indicate the narrowing of temperature interval, facilitating the formation of β‐iPP in iPP/EPR. Furthermore, it was found that the amount of β‐iPP in melt‐blended iPP/EPR samples is dependent on the composition and the maximum amount of β‐iPP formed when the composition of iPP/EPR blends is 85:15 in weight. The results through examining the effect of annealing for iPP/EPR samples at melt state indicate that this annealing may eliminate the susceptibility to β‐crystallization of iPP. However, only α‐iPP can be observed in solution‐blended samples subjected to annealing for different time. The PCM images demonstrate that an obvious phase‐separation happens in both melt‐blended and solution‐blended iPP/EPR samples, implying that compared with the disperse degree of EPR in iPP, the preparation method plays a dominant role in formation of β‐iPP. It is suggested that the origin of formation of β‐iPP results from the thermomechanical history of the EPR component in iPP/EPR. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1704–1712, 2007     

A simple and general method for the synthesis of multicomponent Na2V6O16.3H2O single-crystal nanobelts

Multicomponent Na2V6O16.3H2O (barnesite) single-crystalline nanobelts were synthesized by a direct reaction-crystallization growth of bulk V2O5 and NaF powders under hydrothermal treatment without using any templates or catalysts. This new strategy could be extended to prepare other one-dimensional multicomponent nanomaterials including ammonium, alkali-metal or alkali-earth metal vanadium oxide bronzes and other transition metal oxyfluorides. This is an efficient and mild solution method with clear advantages over the traditional high-temperature approach for the large-scale production of 1D multicomponent nanomaterials. The applicability of this approach toward the preparation of other inorganic systems, such as tungstates and molybdates, will be explored.     

Characterization of mesoporous nanocrystalline TiO2 photocatalysts synthesized via a sol-solvothermal process at a low temperature

Nanocrystalline TiO₂ samples with mesoporous structure were prepared via a solvothermal treatment of surfactant-stabilized TiO₂ sols. The samples were obtained from media of different acidities including nitric acid, deionized water, and ammonia (denoted as HT-1, HT-2 and HT-3, respectively). These samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N₂-sorption (BET surface area), micro-Raman spectroscopy, infrared absorption spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of the samples were tested by the self-photosensitized degradation of an azo dye, Mordant Yellow 10 (MY), in aqueous solution under visible light irradiation. The results reveal that all three samples have high surface area and are pure anatase phase. The sample prepared in nitric acid medium possesses the most ideal mesoporous structure and also exhibits a blue shift in the Raman spectrum. All three samples show much higher photocatalytic activity than the commercial P-25. The activity order of the three samples is HT-1>HT-2>HT-3.     

稀土对38CrMoAl钢软氮化层抗冲蚀磨损性能的影响

研究了稀土元素对38CrMoAl钢软氮化层抗冲蚀磨损性能的影响. 结果表明: 与软氮化相比, 稀土软氮化提高了38CrMoAl钢的抗冲蚀磨损性能, 同时提高了软氮化层的硬度以及钢的冲击韧度. 由于软氮化时稀土的渗入, 改善了渗层组织, 从而提高了38CrMoAl钢的抗冲蚀磨损性能和机械性能. 扫描电子显微镜对冲蚀磨损试样表面形貌的观察发现, 普通软氮化层的磨损特征为塑性变形形成的犁沟剥落, 并伴随着萌生横向裂纹, 有大块磨屑剥落; 而稀土软氮化层则为塑性变形形成的犁沟剥落.     

A mesoporous Pt/TiO2 nanoarchitecture with catalytic and photocatalytic functions

A novel metal/semiconductor nanocomposite with catalytic and photocatalytic functions has been prepared. The new material consists of highly dispersed platinum (Pt) nanoparticles embedded in a cubic mesoporous nanocrystalline anatase (meso-nc-TiO2) thin film. The porous thin film possesses a narrow pore-size distribution and a large surface area. The diameter of the Pt cluster can be controlled to below 5 nm, and the high dispersion of these clusters gives rise to catalytic activity for the oxidation of carbon monoxide, an important reaction for automobile exhaust treatment. This novel ordered mesoporous Pt/TiO2 nanoarchitecture is also a promising photochemical material, as demonstrated by the photo-driven killing of Micrococcus lylae cells on the film.     

Experimental study of photocatalytic oxidation of formaldehyde and its by-products

Formaldehyde is one of the most harmful pollutants that endanger occupants' health and the way of its effective removal has become a focus in the field of air quality. This paper studies the static photocatalytic removal of formaldehyde experimentally and finds out that carbon monoxide, which is more harmful to occupants' health than the formaldehyde itself, is one of the by-products in the process of photocatalytic oxidation of formaldehyde. The increase of carbon monoxide concentration should be taken into consideration in the photocatalytic application. The photocatalyst surface at room temperature can weakly adsorb CO and CO₂, which can deactivate the photocatalysts.     

套索冠醚毛细管色谱柱的研制

用套索冠醚N,N′-双(2-甲基吡啶)-二氮杂-18-冠-6作为固定相,涂渍在弹性石英毛细管内,测其柱效、惰性、热稳定性、平均极性及选择性等性质.其结构由元素分析、红外光谱、核磁共振及质谱分析的试验数据所证实.试验表明,它具有良好的色谱性能、中等极性,适用于对醇、卤代烃、芳香烃等各类异构体的分离,并用分子结构观点探讨了保留机理.     

Preparation of a highly active nanocrystalline TiO2 photocatalyst from titanium oxo cluster precursor

Nanocrystalline TiO₂ (sample S1) was prepared from a titanium oxo cluster (Ti₇O₄(OEt)₂₀) precursor via a sol-gel route. This photocatalyst showed a higher photocatalytic activity than the TiO₂ (sample S2) obtained from titanium tetraisopropoxide. The samples were characterized by thermal analysis (TGA/DSC), X-ray diffraction, micro-Raman spectroscopy, transmission electron microscopy, N₂ adsorption (BET surface area), infrared absorption spectroscopy (FT-IR) and X-ray photoelectron spectroscopy. The characterization results show that both samples are anatase nanocrystals with particle sizes of about 12 nm, but the more photocatalytically active sample S1 has more surface hydroxyl groups and larger surface area and pore volume than sample S2.     

Preparation and evaluation of uniform-sized molecularly imprinted polymer beads used for the separation of sulfamethazine

Uniform-sized molecularly imprinted polymer (MIP) beads were prepared using a one-step swelling and polymerization method. The obtained sulfamethazine (SMZ)-imprinted polymer showed high affinity and selectivity toward SMZ and other structurally related sulfonamides in acetonitrile or water-acetonitrile mobile phases, particularly in high aqueous systems. The column performance of the MIPs for SMZ and its analogues could be improved by elevating the column temperature and optimizing the flow rate. The hydrogen-bonding effect plays a significant role in the recognition process of SMZ-imprinted polymer systems in organic media, while the ion-exchange effect, as well as hydrophobic effect, dominates the retention mechanism in aqueous-rich media, in addition to shape recognition.     

Interaction of zinc finger ZNF191(243—368) and its I323 W and R327W mutants with oligonucleotides by florescence spectrum

Two mutants of the zinc finger protein, ZNF191 (243–368) I323W and R327W, are successfully obtained by site-directed mutagenesis. The fluorescence spectrum is used to study the interaction between these two mutants and the oligonucleotides. The influence of the mutation on the interaction has been studied using ethidium bromide (EB) as the fluorescence probe. The binding constants of the I323W-DNA and R327W-DNA have been calculated and the possible binding models have been discussed.