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排序方式: 共有1934条查询结果,搜索用时 10 毫秒
91.
T.P. Nguyen P. Le Rendu V. H. Tran V. Parkhutik R. Fenollosa Esteve 《Journal of Porous Materials》2000,7(1-3):393-396
Electrical and optical properties of diode structures based on porous silicon (PS) and thin films of phenylene vinylene oligomer (PVO) have been studied. Steady-state photoluminescence spectroscopy show that the structure of the luminescence band depends on the PS morphology. We assign the observed effect to the morphology-dependent penetration of PVO material into the pores. Current-voltage characteristics of the PVO/PS diodes are studied and interpreted assuming Schottky emission and hopping transport of carriers aspossible mechanisms of d.c. electrical conduction. 相似文献
92.
Addition of zincate to the leach liquor for the preparation of skeletal copper increases the copper surface area; however it does not stabilize the structure against rearrangement. The leaching kinetics have been studied using a rotating disc electrode (RDE) at 269–293 K in 2–8 M NaOH and 0.0005–0.1 M Na2ZnO2. Zincate ions precipitate as zinc oxide, due to the local consumption of hydroxide ions near the leach front as the aluminium dissolves. This oxide hinders the aluminium dissolution, slowing the leaching rate. It also hinders copper dissolution/redeposition and prevents copper diffusion, thus reducing the structural rearrangement significantly, and causing the formation of a much finer copper structure with increased surface area. The zinc oxide redissolves as the leach front passes, releasing the copper to rearrange once more, thereby allowing the surface area to decrease with time. The activation energy for leaching was found to be 84 ± 6 kJ mol–1. 相似文献
93.
We report the surface modification of titania (TiO2) nanoparticles with azo-based radical initiator and vinyl (acrylate) polymerizable groups. This is achieved through the reaction
of the surface hydroxyl groups of the titania with acid halides. Polymer (specifically, polystyrene) was grafted “from” the
surface using the azo-modified titania, and “through” the surface of the vinyl-modified surface. Both conventional radical
and reversible addition-fragmentation chain transfer (RAFT) polymerizations were performed. The surface-modified titania and
the polystyrene-titania nanocomposites were characterized using IR spectroscopy, thermogravimetric analysis and gel permeation
chromatography. 相似文献
94.
Ammonium nitrogen removal characteristics of zeolite media in a Biological Aerated Filter (BAF) for the treatment of textile wastewater 总被引:3,自引:0,他引:3
Won-Seok Chang Hung-Thuan Tran Doo-Hyun Park Rui-Hong Zhang Dae-Hee Ahn 《Journal of Industrial and Engineering Chemistry》2009,15(4):524-528
The main objective of this study is to evaluate ammonium nitrogen removal characteristics of zeolite media in Biological Aerated Filter (BAF) process for treatment of textile wastewater. Several biofilters were conducted to compare the performance of natural zeolite with sand and granular activated carbon (GAC) as packing media. The removal of NH4+-N on the BAF reactor packed with natural zeolite media was more efficient than that with sand and GAC. After biofilm was well developed on the surface of zeolite media, the removal of NH4+-N by ion exchange, nitrification, and biological synthesis was estimated as 35.1%, 40.2%, and 22.3%, respectively. The natural zeolite pretreated with heat and HCl solution showed higher ammonium removal efficiency than that with NaOH solution. No significant difference on ammonium adsorption capacity was observed when nature zeolite was neither pretreated by heat nor hydrochloric acid solution. This study shows that natural zeolites has the feasibility to be chosen as a useful media in BAF process for the treatment of textile wastewater. 相似文献
95.
The ene-like reaction of naphtalen-1-ylamine and naphtalen-2-ylamine, and pyridin-2-ylamine with diethyl azodicarboxylate (DEAD) as well as that of naphthalen-2-ol with 4-phenyl-1,2,4-trizoline-3,5-dione is catalyzed by lithium perchlorate. Also conversion of ester function of (DEAD) to amide function in reaction with 2-aminopyridine and further rearrangement of ethyl N-pyridyn-2-ylcarbamoylazoformate into ethyl pyridin-2-ylcarbamate are catalyzed by LiClO4. 相似文献
96.
In this Account, we explore the role constant curvature structures play in amphiphilic small molecule crystals and extended coordination solids. A constant curvature structure is one in which there is a surface or interface that has the same curvature throughout its surface. Simple examples of such structures contain spheres (micelles), columns, or layers. Yet another family are cubic as is found in the gyroid topology. For amphiphilic systems, there are two domains, one generally hydrophobic and the other hydrophilic. We find that the interfaces between these two domains in small molecule structures resemble those in larger scale systems and adopt topologies related to constant curvature structures. The hydrophobic-to-total volume ratio, a molecular parameter, can be used to predict which type of constant curvature structure is adopted. In the case of three coordinate extended solids, constant curvature plays a role both in the extended net topology and in the hydrophobic-to-hydrophilic interface. 相似文献
97.
Kosuke Murata Tasuku Murata Hideyuki Nakanishi Tomohisa Norisuye Qui Tran‐Cong‐Miyata 《大分子材料与工程》2009,294(3):163-168
A method that combines UV irradiation and pausing was developed to manipulate the regularity and the length scales of the morphology generated by phase separation in full‐interpenetrating polymer networks of polystyrene and poly(methyl methacrylate). Upon increasing the pause time of photopolymerization and photo‐crosslink processes, the morphology gradually changes from hexagonal‐like packing to random structures. The width of the loss tan δ obtained for these phase‐separated materials changes with the morphological regularity, suggesting a potential technique for fabrication of mechanical bandgap materials.
98.
Jin S Li M Zhu C Tran V Wang B 《Chembiochem : a European journal of chemical biology》2008,9(9):1431-1438
Dopamine is an important neurotransmitter that plays important roles in various physiological and pathological processes, such as Parkinson's disease. Chemosensors for dopamine have a number of potential applications. On the basis both of the strong and reversible complexation between the boronic acid moiety and a diol functional group and computational chemistry studies, we have designed a series of four compounds for selective three-point recognition of dopamine, which include boronic acid-diol complexation, aromatic-hydrophobic interactions, and ionic interactions between a carboxylate and a protonated amino group. These compounds were synthesized in seven or eight linear steps and showed dopamine selectivity of up to tenfold over epinephrine. NMR spectroscopy experiments were conducted to probe the structures of the receptor-dopamine complexes. These receptors are the first to show such significant selectivity for dopamine over epinephrine in aqueous solution under near physiological conditions. 相似文献
99.
Polyethylene terephthalate (PET) is the most common plastic material used in injection stretch blow molding (ISBM) process for the manufacturing of bottles. The injection‐molded PET preform has to be preheated uniformly to a pliable state before the blowing stage of the process. Microwave technology offers a potentially more economical means for preheating the preform in place of the conventional infrared oven heating. For such applications, determination of dielectric properties of PET preform of a given geometry is essential. This article describes a novel approach of measuring the dielectric properties of PET preforms at microwave frequencies instead of the common experimental procedures used for such measurements. The dielectric properties are determined by using both CST Microwave Studio electromagnetic simulation software and the automatic network analyzer together. No complex mathematical solutions are required. Validation of this new approach has been made by comparing the measured dielectric properties of some polymers with those available in the published literature. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008 相似文献
100.
Fabio La Mantia Fabio Rosciano Nicolas Tran Petr Novák 《Journal of Applied Electrochemistry》2008,38(7):893-896
Li1+x
(Ni1/3Mn1/3Co1/3)1−x
O2 (NMC) oxides are among the most promising positive electrode materials for future lithium–ion batteries. A voltage “plateau”
was observed on the first galvanostatic charging curve of NMC in the extended voltage region positive to 4.5 V vs. Li/Li+ for compounds with x > 0 (overlithiated compounds). Differences were observed in the cycling stability of the overlithiated and stoichiometric
(x = 0) NMC oxides in this potential region. A differential plot of the charge vs. potential profile in the first cycle revealed
that, for the overlithiated compounds, a large irreversible oxidative peak arises positive to 4.5 V vs. Li/Li+, while in the same potential region only a small peak due to the electrolyte oxidation is detected for the stoichiometric
material. Differential Electrochemical Mass Spectrometry (DEMS) was used to investigate the high voltage region for both compounds
and experimental evidence for oxygen evolution was provided for the overlithiated compounds at potentials positive to 4.5 V
vs. Li/Li+. No oxygen evolution was detected for the stoichiometric compound. 相似文献