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91.
92.
盐酸溶液中氯代十六烷基吡啶在锌表面上的吸附及其缓蚀作用 总被引:4,自引:0,他引:4
盐酸溶液中氯代十六烷基吡啶在锌表面上的吸附及其缓蚀作用杨春芬,白宇新(云南大学化学系昆明650091)关键词锌,氯代十六烷基吡啶,吸附,缓蚀作用在抑制金属腐蚀的方法中,缓蚀剂的应用是最受重视的一种,因为它具有用量少,不需附加设备和不改变金属制品本性等... 相似文献
93.
T. Balakrishnan E. Murugan 《Journal of polymer science. Part A, Polymer chemistry》2003,41(2):347-364
We prepared two batches of surface‐enriched (with active sites) polymer‐supported phase‐transfer catalysts (SE‐PSPTC) by fixing the crosslinking monomer divinylbenzene (DVB) at 2% (first batch) and 6% (second batch) through a free‐radical suspension copolymerization method with vinylbenzyl chloride (VBC; 25%) as a functionality and with styrene (St) as a supporting monomer, followed by the quaternization of the resulting terpolymer beads with triethylamine. The enrichment of the active sites on the surfaces of the beads was accomplished by a surface‐grafting technique through the delayed addition of the functional monomer (VBC) to the partially polymerized copolymer beads of poly(St/DVB). To bring the active sites fully onto the surfaces, we prepared six different types of terpolymer beads in each batch by varying the partial polymerization time (PPT) of St/DVB—0 h [0 VBC (conventional)], 3 h (3 VBC), 6 h (6 VBC), 9 h (9 VBC), 12 h (12 VBC), and 15 h (15 VBC)—and then gradually adding the functional monomer (VBC) to the partially polymerized poly(St/DVB) system. The resulting terpolymer beads, containing different concentrations of pendant benzyl chloride (? CH2Cl) on the surface in each batch, underwent facile quaternization [? CH2N+(C2H5)3Cl?] with an increase in the PPT of St/DVB and remained constant at 12 VBC and 15 VBC. To asses the superiority of the catalysts according to the surface enrichment of the active sites, particularly between conventional (0 VBC) catalysts and other PPT‐based SE‐PSPTCs, we characterized all the catalysts by estimating the chloride‐ion concentration, by using Fourier transform infrared (FTIR), scanning electron microscopy (SEM), EDAX, and ESCA, and by carrying out the dichlorocarbene addition to olefins. The chloride‐ion concentration by the Volhard method and the peak intensity of the C? N stretching absorbance concentration, that is, the quaternary onium group in the FTIR spectra of both batches, increased with the PPT of St/DVB in both batches of catalysts. In particular, the chloride concentration of a first‐batch catalyst of a representative mesh size (?120 + 140) had a twofold enhancement between the conventional catalyst (0 VBC; 1.88 m equiv g?1) and 9 VBC/SE‐PSPTC (3.74 m equiv g?1), although the same amount of the functional monomer was added in both preparations. These results showed the higher enrichment of the active site on the surface of 9 VBC, and the same trend was also maintained for second‐batch catalysts, regardless of the catalyst mesh size. SEM images of both batches showed that there was a higher concentration of nodules [due to the grafting of poly(VBC)] on the surfaces of the beads of 9 VBC/SE‐PSPTC and the aforementioned PPT catalysts than on the surfaces of the conventional catalysts (0 VBCs), which exhibited smooth surfaces (because of the simultaneous addition of all three monomers). This observation confirmed the enrichment of active sites on the surfaces. In the EDAX analysis, up to a depth of 0.5–1 μm, the surface chloride concentration increased from 0 VBC to 9 VBC/SE‐PSPTC and remained constant in 12 VBC and 15 VBC, first‐batch catalysts of a representative mesh size (?120 + 140). The same trend was also observed in second‐batch catalysts, indicating the enrichment of the onium group more on the surface in 9 VBC/SE‐PSPTCs. The ESCA analysis, to a depth of about 20–30Å, proved that the concentration of covalent chloride on the surface had increased from 0 VBC (15%) to 9 VBC/SE‐PSPTCs (29%) and remained constant thereafter in first‐batch catalyst; the trend was the same for second‐batch catalysts, also confirming the strong evidence of surface enrichment of the active sites. Similarly, the rate constants of different olefin addition reactions catalyzed by both batches of catalysts also increased from 0 VBC to 9 VBC and remained constant with 12 VBC and 15 VBC catalysts. The twofold increase of the rate constants, regardless of the olefins, for conventional catalysts to 9 VBC/SE‐PSPTCs confirmed the enrichment of the active sites on the surfaces. All these experimental observations proved that 50% of the active sites were successfully brought out from inside the poly(St/DVB) networks to the exterior surfaces, although same amount of VBC was added for the preparation of all the catalyst types. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 347–364, 2003 相似文献
94.
L. V. Levshin G. A. Ketsle G. V. Mel’nikov Yu. D. Lantukh 《Journal of Applied Spectroscopy》1997,64(5):639-641
Investigation of deactivation processes in triplet states of a series of aromatic hydrocarbon molecules (antracene, 1,2-benzantracene,
and 3,4-benzpyrene) made it possible to reveal the presence of triplet-triplet annihilation of the molecules in aqueous micellar
solutions of sodium dodecyl sulfate. It is shown that the effect of microheterogeneous solutions on the process of triplet-triplet
annihilation manifests itself in an increase in the probability of excimerization upon dissociation of triplet pairs of 1,2-benzantracene
and 3,4-benpyrene molecules compared to one-component solutions.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 5, pp. 626–628, September–October, 1997. 相似文献
95.
本文考虑一类半线性双曲系统的状态观测问题,给出了一个(求解)算法并证明了其在某种相当强的意义上的有效性. 相似文献
96.
Ze-Ping Wang 《Acta Mechanica Solida Sinica》1993,6(1):69-80
Based on meso-damage mechanics, a model of dynamic ductile damage under tensile stress is developed, in which work-hardening behavior, rate-dependent contribution and inertial effects are taken into account. Plate-impact test on pure copper under one-dimensional plane strain condition is conducted. Some significant mechanical phenomena are observed by means of microscopic observations of the spalled specimen. The mathematical model presented in this paper is incorporated in a hydrodynamic one-dimensional finite-difference computer code, to simulate the process of spallation in pure copper sample. Comparison of numerical calculations and experimental results shows that the model can describe spall damage successfully. 相似文献
97.
This paper solves a general continuous-time consumption and portfolio decision problem for a single agent for whom there exists, upon bankruptcy, a possibility of recovery from his bankruptcy. The main contribution of the paper is in the modeling of the recovery process. Moreover, it is shown that the model with recovery has a one-to-one correspondence with the model with terminal bankruptcy treated in the literature.This research was supported by Grants SSHRC-410-83-9888 and NSERC-A4619 to the first author and by Grants NSF-DMS-86-01510 and AFOSR-88-0183 to the second author. Comments from E. Presman are gratefully acknowledged. 相似文献
98.
Y. Isokawa 《Annals of the Institute of Statistical Mathematics》1983,35(1):201-213
Summary We consider the estimation of frequency ω of a sinusoidal oscillation contaminated by a stationary noise under a random sampling
scheme according to a stationary point processN. We prove the strong consistency and the asymptotic normality for a certain estimator of ω. Then we apply these results to
the case whereN is a stationary delayed renewal process. 相似文献
99.
Yngve Willassen 《Journal of multivariate analysis》1979,9(1):138-149
The paper consists of two parts. In the first part a previous result by Solari [(1969) J. Roy. Statist. Soc. Ser. B31] for a simplified two-variable model is generalized to the multivariate case. In the second part the behaviour of the likelihood surface is clarified when we have replications of observations. 相似文献
100.
Yuqing Yan 《Journal of Mathematical Analysis and Applications》2018,457(1):248-272
By a dual method, two Carleman estimates for forward and backward stochastic parabolic equations with Neumann boundary conditions are established. Then they are used to study a null controllability problem and a state observation problem for some stochastic forward parabolic equations with Neumann boundary conditions. 相似文献