We demonstrate the formation of metal alloys in Au–Ag, Au–Cu and Au–Pd systems and the experimental determination of their optical properties using optical transmission and reflection spectroscopy. The optical constants define the plasmon resonance wavelength and electromagnetic field local intensity. However, the optical constants behavior cannot be precisely modeled based on the data of pure metals due to unknown morphology and composition of the alloy. It has to be determined experimentally. We demonstrate the surface-enhanced Raman scattering using alloy metals. Depending on the metal to which molecules are adsorbed, we observe enhancement of different Raman modes. It is mainly due to the chemical enhancement effect between metal and molecules. 相似文献
The self-diffusion coefficient of Al in the B2-type intermetallic compound Fe-48 at.% Al has been determined using the intrinsic diffusion coefficients of Fe and Al and the self-diffusion coefficient of Fe with the help of the Darken-Manning relation. The self-diffusion coefficient of Al in Fe-48 at.% Al is estimated to be a factor of about 0.6 smaller than that of Fe, and the activation energy for the self-diffusion of Al is obtained to be 280 kJ mol?1 which is a little larger than the value of 262 kJ mol?1 for the self-diffusion of Fe, indicating that the diffusion mechanisms for both components are nearly equal. 相似文献
The γ-TiAl intermetallic compound with suitable alloying additions has shown considerable promise as a material for high-temperature applications. Diffusion studies in this alloy system are useful in assessment of their creep behaviour and structural stability in service conditions. Tracer diffusion coefficients of 51Cr and 54Mn in a γ-TiAl intermetallic compound containing 54.1 at. % aluminium were determined in the temperature range from 1095 to 1470?K. The temperature dependence of both the diffusing species follows a linear Arrhenius behaviour and can be expressed as DCr?=?4.4?×?10?3exp(?350?kJ?mol?1/RT)?m2?s?1 and DMn?=?1.2?×?10?3?×exp(?326?kJ?mol?1/RT)?m2?s?1. The data are analysed on the basis of empirical correlations between the diffusion and melting parameters applicable for conventional mono-vacancy diffusion mechanism in metals. It is concluded that impurity diffusion in γ-TiAl occurs through the migration of thermal vacancies via nearest-neighbour or next-nearest neighbour jumps. 相似文献
Hyperfine interactions were studied in the intermetallic compound GdRh2Si2 by perturbed angular correlation (PAC) technique using 181Hf(181Ta) probe nuclei. The measurements were performed in the temperature range 15–285 K. The PAC spectra above the antiferromagnetic ordering temperature of the GdRh2Si2 compound (TN ~ 106 K), were analyzed using a model that included only electric quadrupole interactions. The observed major fraction was assigned to the 181Hf(181Ta) probe substituting the Gd atoms. The PAC spectra below Néel temperature were analyzed using combined electric quadrupole and magnetic dipole interactions. The Bhf value at Gd, measured at 15 K was found to be 1.4(1) T which, is smaller, when compared with the values obtained in this compound using other nuclear probes, 155Gd (Bhf ~ 30 T) and 140Ce (Bhf ~ 26 T). The present result using 181Hf(181Ta) probe is quite interesting since it shows that the contribution to Bhf at Gd due the host is smaller than other components which contribute to the hyperfine field. The temperature dependence of Bhf shows an anomalous behavior. 相似文献
Abstract Liquid crystal materials having a decahydronaphthalene ring structure were designed for active matrix LCD and were prepared by hydrogenation of the ocatahydronaphthalenes obtained through the reaction of a fluorinated phenyl magnesium bromide with the 6-alkyl-decahydronaphthalen-2-ones and followed by dehydration. These compounds exhibit wide nematic temperature ranges with low melting points and very low birefringences. These results are useful for design of new liquid crystal mixtures for TFT-displays. 相似文献
Let (X, L) be a polarized manifold defined over the complex number field with dim X = n such that L is very ample. In this article, we will improve the classification of (X, L) with g2(X, L) = h2(𝒪X) + 1 which was obtained in Fukuma (Fukuma 2004
Fukuma , Y. ( 2004 ). On the sectional geometric genus of quasi-polarized varieties, I . Comm. Alg. 32 : 1069 – 1100 .[Taylor &; Francis Online], [Web of Science ®], [Google Scholar], Theorem 3.6), where g2(X, L) denotes the second sectional geometric genus of (X, L). 相似文献
When solid-state rhenium sulfide clusters with an octahedral metal framework are treated in a hydrogen stream above 300 °C,
a catalytic activity for condensation of butylamine to yield N-butylidenebutylamine develops. Primary amines such as ethylamine, pentylamine, and hexylamine are also converted to the corresponding
N-alkylidenealkylamines. Secondary amines such as diethylamine, dipropylamine, and dibutylamine are dehydrogenated to the corresponding
N-alkylidenealkylamines. When triethylamine is allowed to react, dealkylation proceeds to yield diethylamine and its dehydrogenated
product N-ethylideneethylamine. Trimethylamine is also dealkylated to dimethylamine. This series of catalytic behavior is the same as
that of palladium and platinum metals. The similarity in selectivity is attributable to the rhenium atom that accepts electrons
from the sulfur ligands leading to isoelectronic with the platinum group metals. 相似文献
Another way to dienes : The ruthenium‐catalyzed 6‐endo‐cycloisomerization of 1,5‐enynes gives the corresponding 1,3‐cyclohexadienes in high to excellent yields. This novel synthetic and catalytic method constitutes another way to selectively prepare 1,3‐cyclohexadienes, this cyclic diene skeleton being a core subunit in many natural products and a useful building block for a variety of organic transformations.
Xyloglucan in water solution turns into a gel with addition of alcohol such as methanol and ethanol. In regard to this phenomenon,
we investigated the adhesive property of alcohol to xyloglucan and proposed the mechanism of the gelation by molecular dynamics
(MD) simulation of a xyloglucan in water, water/methanol, and water/ethanol solution for 10 ns. The alcohol molecules showed
its adhesive property to the xyloglucan and made the swelling-shrinking motion of the xyloglucan slow. Alcohol molecules solvated
to the xyloglucan mainly in hydrophobic way so as to fill the void of water hydration shell, resulting in reformation of the
hydrogen-bond network of water molecules around the solute. We also found that alcohol molecules have strong tendency to hydrogen-bond
on xylose O3 in xyloglucan. According to these results, we proposed the gelation mechanism of xyloglucan in water/alcohol
solution. 相似文献
After Bénard's experiment in 1900, Rayleigh formulated heat convection problems by the Oberbeck-Boussinesq approximation in the horizontal strip domain in 1916. The pattern formations have been investigated by the bifurcation theory, weakly nonlinear theories and computational approaches. The boundary conditions for the velocity on the upper and lower boundaries are usually assumed as stress-free or no-slip. In the first part of this paper, some bifurcation pictures for the case of the stress-free on the upper boundary and the no-slip on the lower boundary are obtained. In the second part of this paper, the bifurcation pictures for the case of the stress-free on both boundaries by a computer assisted proof are verified. At last., Bénard-Marangoni heat convections for the ease of the free surface of the upper boundary are considered. 相似文献