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11.
M.G.?CarvalhoEmail author J.M.R.C.A.?Santos A.A.?Martins M.M.?Figueiredo 《Cellulose (London, England)》2005,12(4):371-383
In this work attention has been focused on the effects of papermaking beating, web forming and sizing operations on the physical/chemical
surface properties of bleached Eucalyptus globulus kraft fibres. Inverse gas chromatography (IGC) was used to determine the dispersive component of surface tension (γsd) as well as the acidic/basic character (according to the Lewis concept) of the solid surfaces (pulp fibres and pulp handsheets).
The results have shown that the main effect of beating is to increase the fibre's Lewis acidic character. Web forming caused
a strong decrease in γsd and significant increments in the adhesion works of both acidic and basic probes, lowering the ratio between the two. Nevertheless,
the surface of handsheets still exhibited a dominant acidic character. The sizing operation did not change the dispersive
component of the surface tension significantly but decreased the difference between the adhesion works of the acidic and basic
probes, rendering the handsheet surface less Lewis acidic and more Lewis basic. Thus, although internal sizing is expected
to strongly influence liquid spreading at the paper surface and liquid penetration of the fibre's network, it is concluded
that beating and web forming lead to important changes in the surface energetic properties of the Eucalyptus globulus kraft fibres. 相似文献
12.
ToF-SIMS analysis of the organometallic cluster Os3(μ-H)(CO)10(μ-SCH2CH2SH) chemically attached onto a silver or gold surface, and of the cluster fragment Os3(μ-H)(CO)10(μ-OSi) on a silica surface, allows for identification of the surface organometallic species, and also gives information on its reactivity. 相似文献
13.
Eckhard Spohr Andrij Trokhymchuk Douglas Henderson 《Journal of Electroanalytical Chemistry》1998,450(2):211
We report molecular dynamics (MD) simulations on the adsorption of water in attractive and repulsive slit pores, where the slit and a bulk region are in contact with each other. Water structure, surface force and adsorption behavior are investigated as a function of the overall density in the bulk region. The gas–liquid transition in both types of pores occurs at similar densities of the bulk region. 相似文献
14.
A master equation is used to study transitions between the stable limit cycle and stable focus in the two-variable bistable system. The distribution function of the mean first passage time between these attractors and the relative dispersion of the mean first return time from the stable focus to itself as a function of the intensity of fluctuations are calculated and discussed. A coherence resonance is observed for the return time from the focus to itself. 相似文献
15.
R.?Mitchell C.?M.?CarrEmail author M.?Parfitt J.?C.?Vickerman C.?Jones 《Cellulose (London, England)》2005,12(6):629-639
The surface chemical composition of raw unscoured cotton was successfully investigated by the surface analytical techniques
X-ray Photoelectron Spectroscopy (XPS) and Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS). The presence of non-cellulosic
material at the fibre surface was established and determined to be a complex mixture of fatty acids, alcohols, alkanes, esters
and glycerides. The effect of scouring and bleaching was to reduce the surface concentration of these materials but even after
aqueous processing some non-cellulosic material residue was still detected at the fibre surface. 相似文献
16.
Peter D. Dacre 《Theoretical chemistry accounts》1976,43(2):197-205
The direct CI method, which avoids explicit calculation of the Hamiltonian matrix, is presented in a new form. The method is linked with Davidson's algorithm for iterative evaluation of the ground state eigenvector. The viability of the method is indicated by the test calculations on water which are described. 相似文献
17.
一种新型的表面声波阻抗传感器及其在液相体系中的应用姚守拙,陈康,刘德忠,聂利华(湖南大学化学化工系,长沙,410082)关键词表面声波,阻抗传感器,液相应用表面声波传感器(SAWS)具有较高的灵敏度和检测精度,已广泛应用于气体微量组分分析、色谱检测和... 相似文献
18.
《Arabian Journal of Chemistry》2022,15(12):104329
To reduce the amount of hazardous chemical bottle waste in the environment, we report the optimization research of silica extraction in chemical bottle waste into silica gel. Alkali fusion and sol–gel process were utilised to prepare silica gel effectively. The alkali fusion process was carried out by adding sodium hydroxide to produce sodium silicate. Afterwards, silica gel was prepared by the sol–gel method using hydrochloric acid. Box-Behnken Design (BBD) was applied to Optimisation factors the poptimiseactors affecting the silica recovery. The factors that optimised mass ratio, particle size, and temperature. The optimum recovery of silica gel was obtained by SiO2: NaOH mass ratio of 1:3, the particle size of 63–74 µm, and a temperature of 800 °C. The purity of silica gel optimum is 63.74% characterised using X-ray fluorescence. The structure of silica gel is the appearance of amorphous peaks at 2θ 20-30° characterised using an x-ray diffractogram. The silica gel surface was characterises using scanning electron microscopy-energy dispersive x-ray. It showed an irregular surface and characteristic showed that silica gel had a radius of 15.74 nm and a specific surface area of 297.08 m2. 相似文献
19.
Cabaleiro-Lago EM Rodríguez-Otero J García-López RM Peña-Gallego A Hermida-Ramón JM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(20):5966-5974
A comprehensive B3LYP/6-31+G* study on the electrocyclization of 1,2,4,6-heptatetraene analogues was conducted. Starting from the cyclization of (2Z)-2,4,5-hexatrienal, a pericyclic disrotatory process favored by the assistance of a electron lone pair, we incorporated small modifications in its molecular structure to obtain a truly pseudopericyclic process. To this purpose electronegative atoms (fluorine and nitrogen) were added to give a more electrophilic character on the carbon atom which is attacked by the electron lone pair of the oxygen atom. The complete pathway for each reaction was determined, and changes in magnetic properties were monitored with a view to estimating the aromatization associated with each process. This information, together with the energetic and structural results, allowed us to classify the reactions as pseudopericyclic or pericyclic. Among all studied reactions only one was a truly pseudopericyclic process and another was a borderline case. The features of this unequivocally pseudopericyclic case were analyzed in depth. 相似文献
20.
Hiltrud Breitenfelder-Manske Friedrich Kohler 《Monatshefte für Chemie / Chemical Monthly》1985,116(11):1247-1261
The second virial coefficients of homonuclear three-centerLennard-Jones molecules are calculated with various parameters of the isosceles triangle connecting the three sites. A special effort is made to establish the reducedBoyle temperaturesT
B and the values of the second virial coefficients atT/T
B=0.3 for the sake of comparison with one- and two-centerLennard-Jones molecules. It is shown that it is possible to find parameter values of the interaction potential of one- and two-centerLennard-Jones molecules which give very similar values of second virial coefficients forT/T
B0.3, and the equivalence conditions are established. These conditions might not only give a basis for a microscopic scaling of state variables, but also some restrictions for the validity of the group contribution concept.Presented in part at the DFG-Colloquium at Paderborn, 19th April 1982, and at the 5th Conference on Mixtures of Nonelectrolytes and Intermolecular Interactions, April 18–22, 1983, at Halle (GDR). 相似文献