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1.
Monia Belhabri Jack Legrand Nathalie LeSauze Abdellah Arhaliass 《Particle & Particle Systems Characterization》2004,21(5):365-371
Emulsions are of great importance to industry. They are involved in many engineering operations, including chemical reactions, extraction, emulsification and suspension polymerization, etc. However, an important problem for these processes is how to control the size distribution of the dispersed phase. Indeed, off‐line analysis of the emulsion may generate uncertainties due to sampling and dilution of the product, which are likely to change the dispersion state and physico‐chemical properties. In this work, an on‐line optical method is proposed to characterize dispersed media in real flowing conditions. This method is based on the time‐analysis of back‐scattered light fluctuations. The present paper deals with the development of this method and its application to dispersions of alumina in water. The results obtained with the on‐line optical method are compared with those acquired by classical laser light scattering and microscopy. 相似文献
2.
3.
Diamy A.-M. Hochard L. Legrand J.-C. Ricard A. 《Plasma Chemistry and Plasma Processing》1998,18(4):447-460
Measurements of nitrogen atom density, by means of NO chemical titration, along with an evaluation of the densities of some excited species N
2
(B, v=11), N
2
(B, v=2), N
2
(C, v=0), and N
2
+
(B,v=0), by means of a spectroscopic study of some bands of dinitrogen, are achieved along the flowing afterglow of a dinitrogen microwave plasma (2450 MHz) for several pressures. The concentrations obtained are in the following range: [N]10
+15
, [N
2
(B, 2)]10
+9
–10
+10
, [N
2
(B, 11)]10
+8
–10
+9
, [N
2
(C, 0)]10
+6
–10
+7
, [N
2
+
(B,0)]10
+6
-10
+8
(cm-3). From a kinetic study of the formation and decay of excited and charged species, an estimation of N
2
(A, v), N
2
(X, v, and N
2
+
(X) densities can be derived: [N
2
(A, v)]10
+12
, [N
2
(X, v6)]10
+15
–10
+16
, [N
2
(X, v12)]10
+14
–10
+15
, [N
2
+
(X)]10
+10
(cm
-3
). 相似文献
4.
Summary A fumed silica surface was systematically modified by the grafting of n-alkyl chains with increasing carbon numbers. The samples
were characterized by the dispersive component of the surface energy, their specific interaction potential and enthalpies
of adsorption of polar, in particular, alcohol probes. It is shown that the variation of the surface properties and adsorption
capacities depend on the chain length of the graft. For instance, minimum values are recorded when the surface coverage by
methylene groups corresponds either to one or two CH2 surface layers. This behaviour is related to the mobility of the grafted alkyl chains, mobility which was examined by solid
state NMR. 相似文献
5.
J. Al Andari A. M. Diamy J. C. Legrand R. I. Ben-Aim 《Plasma Chemistry and Plasma Processing》1993,13(1):103-116
Electron temperature and ion density are measured in an air microwave-induced plasma (2450 MHz) by means of a floating double probe. A 'cinetic scheme for ion formation and decay is set up, and a relationship between atomic oxygen and ion densities is obtained. From this relationship an order-of-magnitude of atomic oxygen concentration in the discharge is derived and compared with results obtained by optical actinometry in another work. 相似文献
6.
H. Balard M. Sidqi E. Papirer J. B. Donnet A. Tuel H. Hommel A. P. Legrand 《Chromatographia》1988,25(8):712-716
Summary The surface properties of silicas modified with – diols having between 4 and 16 carbon atoms were investigated by inverse gas chromatography. It is shown, that the value of the dispersive component of the surface energy does not change monotonously: a minimum value is recorded when the surface is covered by a monolayer of methylene groups. Further, when measuring the adsorption enthalpies of polar probes, an alternation of their H values is observed: grafts having an odd number of carbon atoms systematically show higher H values than the others. A trans-trans configuration of the grafted chains which allows optimum interactions is proposed, suggesting a preferential diesterification reaction of both terminal hydroxyl groups of odd diols. 相似文献
7.
The rates of self-exchange electron transfer in the trimethylphosphine complex of cytochrome c have been measured by an NMR technique over a large range of ionic strengths. The rate constant is 1.56 x 10(4) M(-)(1) s(-)(1) at 23 degrees C (&mgr; = 0.34 M) at pH 6.9. Dependence on ionic strength of the rate constant is treated by van Leeuwen theory. Extrapolation of the rate constant to infinite ionic strength gives a rate constant of 3.9 x 10(5) M(-)(1) s(-)(1). This rate constant is compared with others reported for myoglobin and cytochrome b(5)(). The values for these systems range over 2 orders of magnitude with myoglobin-PMe(3) < cytochrome b(5)() < cytochrome c-PMe(3) < cytochrome c. Analysis of the data in terms of Marcus theory gives a reorganization energy, lambda, for self-exchange of 0.75 eV mol(-)(1) for cytochrome c-PMe(3). Substitution of Met-80 by PMe(3) appears to influence only weakly the rearrangement barrier to electron transfer. 相似文献
8.
The simultaneous determination of major impurities present in Antarctic snow and ice at ng g? (ppb) concentrations by ion chromatography is described. Calibration data are presented for ammonium, sodium, potassium, chloride, nitrate and sulphate ions. Special attention is paid to the different ways of removing field contamination from ice and snow cores and suitable equipment is described. The results provide evidence against the validity of published sets of concentration data for nitrogen-containing compounds (NO?3 and NH+4 in Antarctic snow, and demonstrate a crucial contamination problem in the determination of ammonium ions. 相似文献
9.
A. Oumghar J. C. Legrand A. M. Diamy N. Turillon R. I. Ben-Aïm 《Plasma Chemistry and Plasma Processing》1994,14(3):229-249
Conversion of CH4 with a N2 microwave plasma (2.45 GHz) is studied. The experiments cover the absorbed microwave power range 300–700 W with 17–62% of methane in the gas mixture, with pressures of 10–40 mbar and flow rates of 140–650 ml· min–1. The yields of C2 hydrocarbons and dihydrogen are analyzed by gas chromatography. The distance of methane addition downstream of the plasma plays an important role on the composition and the concentration of the products obtained. This distance mainly determines the energy concentrated in the active species of the plasma when they react with methane. Different behaviors for acetylene formation, on the one hand, and for ethane and ethene formation, on the other hand, have been observed, and this finding allows us to propose a kinetic mechanism for the decay of methane and for the formation of C2 hydrocarbons. 相似文献
10.
H. Balard M. Sidqi E. Papirer J. B. Donnet A. Tuel H. Hommel A. P. Legrand 《Chromatographia》1988,25(8):707-711
Summary Silica has been modified by an esterification reaction using either n-alcohols or - diols. The grafting ratios were evaluated by elemental analysis of carbon or by the weight loss of the grafted silica heated to 700°C. The grafting ratio can be easily fixed by changing the silica to reactant impregnation ratios. In the case of n-alcohols, the grafting ratios do not vary monotonously with the number of carbon atoms of the grafts and the density of the grafted layer is 25% higher for - diols than for n-alcohols. This observation needs further investigation. 相似文献