排序方式: 共有7条查询结果,搜索用时 0 毫秒
1
1.
In this work, forced convective heat transfer of nanofluid in the developing laminar flow (entrance region) in a circular tube is considered. The nanofluid thermal conductivity, as an important parameter, is considered as two parts: static and dynamic part. Simulated results show that the dynamic part of nanofluid thermal conductivity due to the Brownian motion has a minor effect on the heat transfer coefficients, on the other hand, static part of thermal conductivity including nanolayer around nanoparticle has an important role in heat transfer. 相似文献
2.
Shuwen Hu 《European Polymer Journal》2006,42(9):2053-2058
The perester silane t-butyl peroxy-11-trichlorosilylundecanoate was synthesized by hydrosilylation of t-butyl peroxy-10-undecanoate with trichlorosilane. These radical initiators were covalently bound to the surface of silicate substrates by self-assembled monolayer (SAM) techniques. Several hydrophilic and hydrophobic acrylate monomers were successfully grafted onto the silicate substrate by in situ polymerization from the surface bound perester initiators. The polymer brushes were characterized by the ATR-IR, XPS, AFM and water contact angles. The results of the study indicate this “grafting from” technique can be used for the preparation of polymer layers with high graft density. While these surface-bound initiators function similarly to surface-bound azo initiators, the preparation of the surface-active perester is a simple, two-step synthesis. 相似文献
3.
The demagnetization process for an exchange-coupled double-nanolayer system with perpendicular easy axes has been investigated within a micromagnetic model. The nucleation field, coercivity and angular distribution of the magnetization, have been obtained as functions of the thickness L of the misaligned layer, the layer with the easy axis perpendicular to the applied field. It is found that the coercivity is identical to the nucleation field only for very small L. For larger L (larger than a quarter of its Bloch wall width), the nucleation field is negative while the coercivity saturates at 0.414HK, where HK is the anisotropy field. Thus for larger L, the coercivity mechanism is self-pinning rather than pure nucleation. This self-pinning has both attributes of traditional nucleation and pinning. 相似文献
4.
Z. Messaï Z. Ouennoughi T. Mouet V. Harel N. Bouguechal 《Applied Surface Science》2010,257(2):616-621
In this paper we study nanocrystalline zinc oxide thin films produced by oxidation of electrodeposited zinc nanolayers on a monocrystalline p-Si(1 1 1) substrate.The electrolyte used is ZnCl2, an aqueous solution of 4 × 10−2 mol/l concentration. Several deposits were made for various current densities, ranging from 13 mA/cm2 to 44 mA/cm2, flowing through the solution at room temperature. A parametric study enabled us to assess the effect of the current density on nucleation potential and time as well as zinc films structure. The grazing incidence X-ray diffraction (GIXD) revealed that both Zn and ZnO films are polycrystalline and nanometric. After 1-h oxidation of zinc films at 450 °C in the open air, the structural analyses showed that the obtained ZnO films remained polycrystalline with an average crystal size of about 47 nm and with (1 0 0), (0 0 2) and (1 0 1) as preferential crystallographic orientations. 相似文献
5.
Synthesis of crosslinked polymer nanoparticles suitable for the formation of nanolayer organic films
Andrea Uveges John F. Hartmann Lajos Daroczi Janos Borbely 《Colloid and polymer science》2009,287(4):471-479
Free radical crosslinking copolymerization of styrene and ethylene glycol dimethacrylate (nST/nEGDM in feed = 5/5) has been investigated in toluene. Variation of the reaction conditions allows the formation of macromolecules
with low molecular weight (21.6 kDa and 12 nm in diameter), perfectly soluble branched particles in the early stage of the
polymerization. Elongation of the reaction time leads to the formation of soluble/swelling microgels with medium molecular
weight (156 kDa and 41–120 nm) and, finally, swelling/particularly soluble colloidal polymer particles with very high molecular
weight (3.6 MDa and 59–324 nm). Conversion, molecular weight [by gel permeation chromatography (GPC)], ratio of pendant vinyl
groups [by nuclear magnetic resonance (NMR)], size of nanoparticles in swollen [by dynamic light scattering (DLS)] and dried
state [by transmission electron microscopy (TEM)], morphology [by scanning electron microscopy (SEM)], and nanolayer film
formation (by SEM) were measured. The role of reaction conditions in producing different polymer structures and morphologies
was demonstrated. 相似文献
6.
Potentiometric sensors share unique characteristics that set them apart from other electrochemical sensors. Potentiometric nanoelectrodes have been reported and successfully used for many decades, and we review these developments. Current research chiefly focuses on nanoscale films at the outer or the inner side of the membrane, with outer layers for increasing biocompatibility, expanding the sensor response, or improving the limit of detection (LOD). Inner layers are mainly used for stabilizing the response and eliminating inner aqueous contacts or undesired nanoscale layers of water. We also discuss the ultimate detectability of ions with such sensors and the power of coupling the ultra-low LODs of ion-selective electrodes with nanoparticle labels to give attractive bioassays that can compete with state-of-the-art electrochemical detection. 相似文献
7.
Francesc Estrany David Aradilla Ramn Oliver Elaine Armelin Carlos Alemn 《European Polymer Journal》2008,44(5):1323-1330
Multilayered films formed by 3, 5 and 7 alternated layers of poly(3,4-ethylenedioxythiophene) and poly(N-methylpyrrole) have been prepared by chronoamperometry under a constant potential of 1.4 V using a layer-by-layer electrodeposition technique. In order to examine influence of the interface:bulk dimensional ratio, the thickness of the yielded films was reduced from the submicrometric to the nanometric scale by decreasing the polymerization time of each layer from 100 s to 10 s. The electroactivity, electrochemical characteristics and morphologies of the resulting multilayered films have been compared with those obtained for both single-component poly(3,4-ethylenedioxythiophene) films prepared using identical experimental conditions and previously reported multilayered films with thickness within the micrometric scale [Estrany F, Aradilla D, Oliver R, Alemán C. Eur Polym J 2007;43:1876]. 相似文献
1