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1.
Hasan Guleryuz Ingeborg Kaus Claudine Filiàtre Tor Grande Mari-Ann Einarsrud 《Journal of Sol-Gel Science and Technology》2010,54(2):249-257
Deposition of silica thin films on silicon wafer was investigated by in situ mass measurements with a microbalance configured
for dip coating. Mass change was recorded with respect to deposition time when the substrate was fully immersed in the silica
sol. Mass gain during deposition was higher than predicted from monolayer coverage of silica nano particles. This implied
that deposition was facilitated by gelling of the nanoparticles on the substrate. The rate of deposition was enhanced by increasing
the particle concentration in the sol and by decreasing the particle size from 12 to 5 nm. Increasing the salt concentration
of the silica sol at constant pH enhanced the deposition of the silica particles. Reducing the pH of the sol from 10 to 6
decreased the deposition rate due to aggregation of the primary silica particles. 相似文献
2.
3.
A titanium dioxide sol with narrow particle size distribution was synthesized using TiCl4 as the starting material. The sol was prepared by a process where HCl was added to a gel of hydrated titanium oxide to dissolve it. The resulting aqueous titanic acid solution was heated to form titanium dioxide sol. The effects of preparation parameters were investigated. TiCl4 was slowly added to distilled water at 5°C. Aqueous solution of sodium hydroxide was added to adjust the pH of the system to 8–12. After aging for a period of time, the peptized sol was filtered and sufficiently washed. The filtered cake was repulped in water. Hydrochloric acid was slowly added to the solution with stirring. After condensation reaction and crystallization, a transparent sol with suspended TiO2 was formed. XRD results show that the crystalline phase was anatase. The suspended TiO2 particles were rhombus primary particles with the major axis ca. 20 nm and the minor axis ca. 5 nm. The TiO2 particles prepared at pH 8 had the largest surface area of 141 cm3/g and it was microporous. The compositions of the solution which yielded the smallest suspended TiO2 particles were TiO2:HCl (35% HCl) = 1:1 (molar ratio), concentration of TiO2 = 10%. Hydroxypropyl cellulose with viscosity of 150–400 cps was added as a dispersant. The sol was excellent in dispersibility and long-term stability. Transparent thin films could be obtained through dip-coating glass substrate in the sol. The dip-coating on glass can be less than three times to have one monolayer TiO2. The transparent TiO2 thin film had strong hydrophilicity after being illuminated by UV light. 相似文献
4.
I. A. Novakov F. S. Radchenko A. S. Ozerin E. V. Rybakova 《Polymer Science Series A》2011,53(5):364-368
The interaction of aluminum polyhydroxochloride sol and poly(4-vinylbenzene sulfonic acid) sodium salt is studied. It is found
that, in dilute aqueous solutions at pH 4.6, aluminum polyhydroxochloride sol and poly(4-vinylbenzene sulfonic acid) sodium
salt form insoluble polymer-colloid complexes of steady compositions. Potentiometric titration data show that the interaction
between particles of aluminum polyhy-droxochloride sol and linear macromolecules of the polyelectrolyte occurs via salt bonds
formed between unlikely charged groups on the surface of particles and units of the linear polyelectrolyte. The composition
of the polymer-colloid complex is determined, and the degree of conversion for the reaction of aluminum poly-hydroxochloride
sol and poly(4-vinylbenzene sulfonic acid) sodium salt is estimated. The influence of various polyelectrolytes on the stability
of the polymer-colloid complex is studied. 相似文献
5.
Influences of colloidal stability and electrokinetic property on electrodialysis performance in the presence of silica sol 总被引:1,自引:0,他引:1
Negatively charged silica sol is known to lead to fouling of anion exchange membranes during electrodialysis (ED) as a result of its deposition on the membrane surface. It is known that the fouling potential is related to the physical and electrochemical properties of the silica particles as well as those of the anion exchange membranes. In this study, the properties of the silica sol were characterized in terms of its particle size, turbidity, and zeta potential in order to predict their effects on the electrodialysis performance. In the stability of colloidal particles, the critical coagulation concentrations of silica sol were determined as functions of ionic strength, cation species, and solution pH. In the electrodialysis of NaCl solution containing silica sol with various concentrations of CaCl(2), the colloidal behavior related to deposition and transport was examined during and after electrodialysis. The electrodialysis experiments clearly showed that the deposition and transport of silica sol during electrodialysis were related to the colloidal stability of dispersion. 相似文献
6.
A. A. Antonova O. V. Zhilina G. G. Kagramanov K. I. Kienskaya V. V. Nazarov I. A. Petropavlovskii I. E. Fanasyutkina 《Colloid Journal》2001,63(6):662-667
Cerium dioxide hydrosols are synthesized by peptizing with nitric acid a precipitate obtained by hydrolyzing cerium(III) nitrate. The synthesized sols are stable with respect to aggregation in both acidic (pH 1.5–3.0) and alkaline media (pH 9.0–11.0). The mean hydrodynamic radius of particles is about 25 nm. The isoelectric point corresponds to pH 6.2. The phase composition of sol particles is determined by X-ray diffraction at pH of the dispersion medium ranging from 1.5 to 3.0. The sol coagulation thresholds are determined in the presence of sodium nitrate and sulfate, as well as of mixed magnesium salt at various pH values of the dispersion medium. Assumptions are made concerning the nature of the aggregative stability of sols. 相似文献
7.
Precipitation-redispersion of cerium oxide nanoparticles with poly(acrylic acid): toward stable dispersions 总被引:2,自引:0,他引:2
Sehgal A Lalatonne Y Berret JF Morvan M 《Langmuir : the ACS journal of surfaces and colloids》2005,21(20):9359-9364
We exploit a precipitation-redispersion mechanism for complexation of short chain polyelectrolytes with cerium oxide nanoparticles to extend their stability ranges. As synthesized, cerium oxide sols at pH 1.4 consist of monodisperse cationic nanocrystalline particles having a hydrodynamic diameter of 10 nm and a molecular weight of 400 000 g mol(-1). We show that short chain uncharged poly(acrylic acid) at low pH when added to a cerium oxide sols leads to macroscopic precipitation. As the pH is increased, the solution spontaneously redisperses into a clear solution of single particles with an anionic poly(acrylic acid) corona. The structure and dynamics of cerium oxide nanosols and their hybrid polymer-inorganic complexes in solution are investigated by static and dynamic light scattering, X-ray scattering, and chemical analysis. Quantitative analysis of the redispersed sol gives rise to an estimate of 40-50 polymer chains per particle for stable suspension. This amount represents 20% of the mass of the polymer-nanoparticle complexes. This complexation adds utility to the otherwise unstable cerium oxide dispersions by extending the range of stability of the sols in terms of pH, ionic strength, and concentration. 相似文献
8.
The dispersion and coagulation phenomena of iron(III) hydroxide sols were investigated as a function of pH in the absence and presence of amino acids. The amino acids used were glycine,L--alanine,DL--amino-n-butyric acid,L-valine,L-leucine,L- isoleucine,L-glutamic acid andL-arginine. The turbidity measurements of the iron-(III) hydroxide sols, which were prepared by pouring an aqueous iron(III) chloride solution into boiling distilled water, were carried out using a spectrophotometer with an addermixer device and an automatic recording system. The zeta potentials of sol particles were obtained by ultra-microelectrophoresis. The change in turbidity of the sol, as a measure in stability of the sol, increased with increasing pH in the region of pH 2–8, and reached a maximum at the isoelectric point of the particles. The coagulation at the isoelectric point was prevented by adding amino acids, and the stabilization had an optimum point at concentrations which depended upon the kinds of amino acids. The remarkable dispersing effect of amino acids which occurred near the isoelectric point of the particles at the suitable concentration of the ammo acids may be due to the steric protection by amino acid adsorbed. The protective action was explained according to a modified DLVO theory, the modification for London-van der Waals force being applied in order to take the effect of the adsorption layer into account. 相似文献
9.
This paper presents a low-cost method to coat polymer particles with silica nanoparticles from inexpensive sodium silicate solution, which is a less-common precursor compared with tetraethyl orthosilicate for coating of polymer particles. The method is based on deposition of active silicic acid in the presence of polymer particles, prepared by emulsion polymerization of styrene involving poly(N-vinyl-2-pyrrolidone), under conditions that a dilute silica sol can be formed from this active silicic acid. The whole process was conducted in aqueous media. The effects of different reaction parameters, such as reaction temperature, amount of active silicic acid and solution pH, on the morphology and size of composite particles were investigated. 相似文献
10.
The techniques of gamma-radiolysis, UV photolysis and hydrogen-induced reduction of aqueous palladium perchlorate to ultrafine particles of Pd, in the presence of alumina sol, have been studied. As compared to H2-induced reduction, both UV photolytic and gamma-radiolytic reduction methods lead to a very stable, brown colored Pd colloid with relatively less absorption in the higher wavelength region and possessing much smaller volume average particle size (62 and 61 nm, respectively). Higher concentration of alumina sol and increase in pH from 1.8 to 7.2, favour the formation of smaller sized particles as determined by the dynamic light scattering technique. 相似文献
11.
12.
Template-based sol electrophoretic deposition has been demonstrated as an attractive method for the synthesis of oxide nanorod
arrays, including simple and complex oxides in the forms of amorphous, polycrystalline, and single crystal. This paper systematically
studied a number of processing parameters to control nanorod growth by sol electrophoretic deposition. The influences of particle
and template zeta potentials, condensation rate, deposition rate (or externally applied electric field), the presence of organic
additives, and sol concentration on the growth of nanorod arrays were studied. It was found that higher zeta potential or
electric field resulted in higher growth rates but less dense packing. Templates with charge opposite to that of the sol particles
prevented formation of dense nanorods, sometimes resulting in nanotubes, depending on the field strength during electrophoresis.
In addition, the pH of the sol and chelating additives were also varied and likely affected the deposition process by affecting
the condensation reactions. 相似文献
13.
Manmohan Kumar 《Radiation Physics and Chemistry》2001,62(5-6):387-392
The spectral characteristics of the bimetallic sols produced by gamma and electron irradiation of mixed solutions of Tl+–Cu2+ ions in different ratios have been studied in aqueous medium. The intermediate transient species have also been characterized by the technique of pulse radiolysis. The rate constant for the reaction of Cu2+ion with the Tl+ ion reduction species was founded by 4×109 dm3 mol−1s−1. Developmental absorption spectra in gamma radiolytic reduction of the mixed ions indicated reduction of Tl+ ion on the surface of small copper particles, resulting in bimetallic-sol with core of copper. The presence of a small concentration of Cu2+ ion was found to restrict the agglomeration process of thallium particles at near neutral pH conditions. The reducing capability of the bimetallic sols was found to be proportional to the thallium content in the sol. The observed UV–Vis spectra of the mixed Tl/Cu sols produced on electron irradiation showed much lower absorption in the higher wavelength region and were more close to that of the pure sol of the ion, present in higher concentration in the feed solution. Thus, the high dose rate-assisted stabilization of smaller thallium particles. Size of all these bimetallic sol particles was much less than 50 nm. 相似文献
14.
V. I. Kuchuk E. V. Golikova Yu. M. Chernoberezhskii V. S. Grigor’ev 《Colloid Journal》2011,73(3):352-362
Electrosurface properties and aggregation stability of natural diamond sol in aqueous LiCl solutions at pH 6.0 and 9.0 are
studied. It is shown that the aggregation of particles occurs according to the barrierless mechanism in the potential minimum,
the depth of which is determined by the radius of structural forces. The ranges of the parameters of the structural forces
of natural diamond in these solutions are determined. It is revealed that the extension of the water boundary layers on natural
diamond decreases with an increase LiCl concentration and pH. 相似文献
15.
In this work, poly(acrylic acid-co-sodium acrylate) P(AA-SA) latex particles were prepared by inverse miniemulsion polymerization and used as a pH buffering agent for application. The polymerization was quickly initiated by a redox initiator (ammonium persulfate/sodium metabisulfite) at 0-5 degrees C. Thus the possibility of monomer dissolving in a solvent was reduced, which enhanced the degree of droplet nucleation. The effects of costabilizer and the ratio of SA/(AA+SA) in functional latex particles on the nucleation mechanism and emulsion stability were investigated. The apparent pK(a) values of the synthesized P(AA-SA) latex particles were determined by titration experiments. Their properties on pH buffering were also studied, including the pH temporal response and pH buffering ability. The results showed that sodium hydroxide, which was introduced as the costabilizer to enhance the osmotic pressure and to increase the deprotonation of acrylic acid, was effective in guaranteeing droplet nucleation predominantly. Meanwhile, the surfactant concentration was controlled to be less than its critical micelle concentration (CMC) value to avoid micellar nucleation. Furthermore, the P(AA-SA) latex particles thus synthesized were found to be an excellent material for pH buffering. The pH temporal response was very rapid and related to the crosslinking degree of the latex particles. The terminal range of pH buffering for latex particles was controllable by the ratio of SA/(AA+SA). 相似文献
16.
Polyaniline layers are produced by electrochemical polymerisation of aniline in the presence of small amounts of poly(2-acryalamido-2-methyl-propane-sulfonic acid) in an inorganic acid solution. Electroactivity and in situ conductance of the obtained polysulfonic acid-doped layers are studied in slightly acidic and neutral solutions. Electroless deposition of silver particles is carried out in silver-EDTA complex ion solutions at pH????.2 and pH????.6 by using the polyaniline layers as reductant. The amount of electroless-deposited silver is studied depending on: polymerisation charge used to synthesize the polymer layer, pH of the plating solution, metal ion concentration and dipping time. SEM shows in all cases a highly non-homogeneous distribution of the metallic phase over the surface, the most protruding fibrillar polymer structures favouring the electroless silver deposition. A linear dependence between amount of the polyaniline material and amount of deposited silver is found for the silver plating solutions with the highest investigated concentration (10?mmol?l??). At lower concentrations (2.0 and 0.4?mmol?l??), the same amount of silver becomes deposited on polymer layers with markedly different charges. The electroless deposition of silver in the solutions with lower acidity results in lower amounts of deposited silver at otherwise identical conditions. Effects such as charge transfer within the polymer phase and mass transport in the solution are addressed to explain the observed dependencies of the amount of deposited silver on concentration and pH in the different plating solutions. 相似文献
17.
Formation of individually dispersed nanoparticles or compactly aggregated nanoparticles from sols via a spray-drying route at low pressure was investigated experimentally. Silica sol was used as a sample material. Effects of operating temperature, colloid size, sol concentration, pressure, pH and zeta potential of sols on the morphology of product particles were investigated. From the experimental results, it was shown that dispersed nanoparticles could be obtained at a relatively low pressure (20 Torr) and low temperature (200 degrees C). The experiment also showed that dispersed nanoparticles could be achieved by careful control of the interfacial energy (pH value) of the colloidal precursor. A possible mechanism of sol-to-dry-particle formation in the spray-drying process at low pressure is suggested, based on the experimental results and the available theories. This mechanism was able to explain the experimental results well. 相似文献
18.
《Colloids and Surfaces》1983,6(1):1-16
The structure and properties of Schiller layers in β-ferric oxyhydroxide (β-FeOOH) sol are studied by microscopic observation. The structure is determined to be smectic. Rod-like particles of β-FeOOH sol gather to form mat-like assemblies, in each of which the rods are packed with their axes nearly perpendicular to the mat face. The mats are superimposed one on the other, to make up the whole structure. Two spatial periodicities in this structure would be the cause of the iridescence. This ordered structure coexisted in equilibrium with disordered suspension of the same sol. The Schiller layer systems usually have very low pH values (≲ 2) and in these cases attractive interaction or the effect of the secondary minimum is eminent. However, at moderately low pH (∼ 4), the interaction between the particles becomes repulsive, and, in spite of this, Schiller layers are formed when the sol is condensed to a certain extent. Formation of Schiller layers is a phase transition in monodisperse sol. 相似文献
19.
Blute I Pugh RJ van de Pas J Callaghan I 《Journal of colloid and interface science》2007,313(2):645-655
Surface characterization and foaming studies were carried out with nine industrially manufactured, colloidal silica dispersions with particles sizes from 5-40 nm. All the silica sols produced transient foams with short decay times and the dynamic foam generation (foamability) was found to vary according to the sol type with the greatest foamability occurring for the hydrophobically modified sol and the deionized hydrophilic sol. However, it was found that improved foamability of all the sols could be achieved by changing the pH to within the region of the pH(pzc) which corresponds to the region of lowest hydrophilicity. An increase in pH (and build-up of negative charge) enhances the surface hydrophilicity and caused a decrease in foamability. In addition, for selected hydrophilic sols, it was shown that the foamability (a) increased with decrease in particle size (within the 6-40 nm range) and (b) increased with particle concentration (within the range of 1-15 wt%). Overall, it was concluded that the foamability was primary controlled by hydrophobicity (and hence by pH) and also by the particle concentration, the particle size and the degree of agglomeration. 相似文献
20.
Silica and poly(l-lactic acid) (PLLA) are each a biocompatible polymer with many proven bio-applications. We describe a new hybrid made of these components in the form of submicron particles. The particles are prepared by entrapping PLLA in a forming sol–gel particle in an emulsion, the droplets of which are the micro-reactors in which the particles form. The dispersed phase is a hydrophobic solution of PLLA in tetraethoxysilane (TEOS) and chloroform and the dispersing phase is a water–ethanol solution of Triton X-100 at a basic pH, which acts also as the catalyst for the on-setting the sol–gel processes. The polyester@silica particles were fully characterized by scanning electron microscopies, by thermal gravimetric analysis and differential scanning calorimetry (DSC) by X-ray diffraction (XRD), and by ζ potential measurements. Another aspect of this report relates to the ability to dope these hybrid particles with a functional dopant, which is then used to follow up their degradation in acidic solution. 相似文献