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The c-axis preferred orientation of ZnO film is the most important factor for its successful application in piezoelectric devices. The effects of surface roughness of the substrate on the c-axis preferred orientation of ZnO thin films, deposited by radio frequency magnetron sputtering, were investigated. During sputtering, the oxygen content in the argon environment used was varied from 0 to 70% at a total sputtering pressure of 10 mTorr. Very smooth Si, smooth evaporated Au/Si, smooth evaporated-Al/Si, and rough sputtered-Al/Si were used as substrates. Their r.m.s. roughnesses, as measured by atomic force microscopy, were 1.27, 17.1, 21.1 and 65-118 Å, respectively. The crystalline structure and the angular spread of the (0 0* 2) plane normal to the ZnO films were determined using X-ray diffraction and X-ray rocking curves, respectively. The crystallinity and the preferred c-axis orientation of the ZnO films were strongly dependent on the surface roughness of the substrates rather than on the oxygen content of the working environment or on the chemical nature of the substrate. 相似文献
4.
Flame structure and NO emission characteristics in counterflow diffusion flame of blended fuel of H2/CO2/Ar have been numerically simulated with detailed chemistry. The combination of H2, CO2 and Ar as fuel is selected to clearly display the contribution of hydrocarbon products to flame structure and NO emission characteristics due to the breakdown of CO2. A radiative heat loss term is involved to correctly describe the flame dynamics especially at low strain rates. The detailed chemistry adopts the reaction mechanism of GRI 2.11, which consists of 49 species and 279 elementary reactions. All mechanisms including thermal, NO2, N2O and Fenimore are taken into account to separately evaluate the effects of CO2 addition on NO emission characteristics. The increase of added CO2 quantity causes flame temperature to fall since at high strain rates a diluent effect is prevailing and at low strain rates the breakdown of CO2 produces relatively populous hydrocarbon products and thus the existence of hydrocarbon products inhibits chain branching. It is also found that the contribution of NO production by N2O and NO2 mechanisms are negligible and that thermal mechanism is concentrated on only the reaction zone. As strain rate and CO2 quantity increase, NO production is remarkably augmented. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
5.
Nanocomposites based on poly(butylene terephthalate) (PBT) and an organoclay (Cloisite 30B) were prepared by melt blending using a twin‐screw extruder. Two kinds of PBTs, ie PBT‐A and PBT‐B, with different inherent viscosities (ηinh), were used for this study (ηinh of PBT‐A and PBT‐B were 0.74 and 1.48, respectively). Dispersion of the clay layers in the PBT nanocomposites was characterized by using X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Tensile and dynamic mechanical properties and non‐isothermal crystallization temperatures of the nanocomposites were also examined. Nanocomposites based on the higher‐viscosity PBT (PBT‐B) showed a higher degree of exfoliation of the clay and a higher reinforcing effect when compared to the composites based on the lower‐viscosity PBT (PBT‐A). The clay nanolayers dispersed in PBT matrices lead to increases in the non‐isothermal crystallization temperatures of the PBTs, with such increases being more significant for the PBT‐B nanocomposites than for the PBT‐A nanoocomposites. Copyright © 2004 Society of Chemical Industry 相似文献
6.
Grazing incidence reflection absorption Fourier transform infrared (GIRA-FTIR) spectroscopy was used to characterize the ferroelectric behavior of a thin poly(vinylidene fluoride–trifluoroethylene) P(VDF–TrFE) copolymer. The lab-built GIRA-FTIR apparatus allowed the heating and corona poling process to be carried out whilst collecting the GIRA spectra of the thin polymer film. The Curie transition from the ferroelectric to paraelectric phase was confirmed from the abrupt change in intensity of the 849 cm−1 band in the RA-FTIR spectrum. It was found that the Curie temperature dropped dramatically when the film thickness was lowered to below a certain critical value of approximately 100 nm. The switching of the CF2 dipoles in the ferroelectric crystals after applying the external electric field could be determined by monitoring the change in the 849 cm−1 band intensity. For the 600 nm thick P(VDF–TrFE) film, the switching of the dipoles appears to occur almost instantaneously, while the kinetics of dipole switching of the 75 nm thick film were significantly retarded. The repeated switchability of the CF2 dipoles upon the application of a bipolar cyclic electric field was also confirmed. The bistability of the film due to remnant polarization was also confirmed from the absorbance of the 849 cm−1 band after removing the applied voltage during corona poling. 相似文献
7.
Du Young Choi Long Mei Jin Dexian Wang Kyung Ho Row 《Korean Journal of Chemical Engineering》2005,22(3):465-469
High-performance frontal analysis (HPFA) was used for a protein binding study of isoflavones (daidzein, genistin, and genistein),
enantiomers of perillyl alcohol and S-ibuprofen to human serum albumin (HSA). The analyses were performed on a Develosil and
Inertsil 100-Diol-5 column (10 cm×4.6mm). Sodium phosphate solution (pH 7.4, ionic strength 0.17) was used as the mobile phase
at a flow rate of 1 ml/min. To ensure the drug to be eluted as a trapezoidal peak with a plateau, injection volumes were each
fixed up the zonal profile with an evident plateau appears. The unbound drug concentration was determined from a plateau height
of the plateau region after that experimental data were fitted by Scatchard equation. The binding constants (K) and total
binding affinities (nK) of drugs to HSA were calculated, respectively. 相似文献
8.
Byeong Il Noh Tae Kyung Yoon Byung Hyun Moon Jong Hyun Kim 《Korean Journal of Chemical Engineering》1995,12(1):18-22
Multicomponent mass transfer accompanied by instantaneous chemical reactions in a small drop has been modeled and simulated
for the case where two different solutes diffuse from a continuous phase into the drop and react rapidly with a third reactant
in the drop. The computational results obtained by Galerkin’s finite element method are reported in terms of concentration
profiles, the locations of reaction front, the cumulative mass flux, and the enhancement factor. The effects of physical parameters,
such as diffusivities of the solutes and the reactant, the interfacial concentration of solutes, and the relative amount of
the reactant, on the calculated quantities are discussed. 相似文献
9.
Seung-Yeop Kwak 《应用聚合物科学杂志》1995,55(12):1683-1690
The structural changes of poly(vinyl chloride) (PVC) plastisols during mixing of PVC with a plasticizer was investigated; as the temperature was increased, the system was found to transform from a suspension of solid particles in a liquid medium to a swollen gel and ultimately to a fused homogeneous matrix. The dynamic viscoelastic measurements were utilized to continuously monitor the changes of moduli under a controlled heating rate, employing a mechanical spectrometer. Characteristic changes in the viscoelastic behavior were associated with changes in particulate morphology as observed with a scanning electron microscope (SEM). Both viscoelastic and morphological observations were shown to provide details of structural changes in conjunction with the behavior of the PVC–plasticizer interaction, enabling a qualitative discrimination of the gelation and fusion processes. An in situ small-angle light-scattering (SALS) method was performed to make a quantitative estimate for the swollen particles of PVC while they were in the progress of gelation and fusion. From the manner of increase in correlation distances, along with the changes in viscoelastic moduli and morphology, the swelling behavior of the particulate structures were examined on the quantitative basis and brief insight into the complex behavior of the PVC–plasticizer interaction began to be unfolded. © 1995 John Wiley & Sons, Inc. 相似文献
10.
W. J. Kwak J. H. Lee S. M. Hwang Y. H. Kim 《Metallurgical and Materials Transactions A》2002,33(10):3255-3272
Investigated via a series of finite-element (FE) process simulations is the effect of diverse process variables on some selected nondimensional
parameters characterizing the thermomechanical behavior of the strip in hot-strip rolling. Then, on the basis of these parameters
an on-line model is derived for the precise prediction of roll force and roll power. The prediction accuracy of the proposed
model is examined through comparison with predictions from a FE process model and also with measurements. 相似文献