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Two yttria-doped zirconia powders (3Y-ZrO2) with identical bulk chemical composition and some differences in physical properties were characterized. Dispersibility of aqueous slips was evaluated by the measurement of zeta potential, apparent viscosity and particle size of the solid phase in slip. The results were in good agreement to indicate the pH range of stabilization and the state of dispersion...
New polymeric dispersing agents designed to stabilize and lower the viscosity of aqueous mineral suspensions have been synthesized and studied. These dispersants are made of a non-ionic hydrosoluble polymer (polyethylene oxide) with a functional group (diphosphonate) having a strong affinity for the mineral surfaces attached at one end of the macromolecular chains. This molecular architecture allows...
This study shows that microgel particles deswell in the presence of excluded free (i.e., non-adsorbing) polymer. The microgels investigated were poly(N-isopropyl-acrylamide-co-N,N′-methylene-bis-acrylamide (PNP-BA), poly (styrene-co-divinylbenzene) (PS-DVB) and poly(methylmethacrylate-co-methacrylic acid-co-ethyleneglycol dimethacrylate) (PMA-MAA-EM). The particles were characterized by scanning electron...
The interaction of hydrolysable lead ions with a thermosensitive, anionic microgel dispersion of N-isopropylacrylamide modified with acrylic acid comonomer has been investigated as a function of pH. The conformation of the anionic microgel was observed by dynamic light scattering to reversibly alter due to changes in either temperature or pH, or due to the presence of lead ions. The hydrodynamic diameter...
To further elucidate the changes in interparticle forces caused by polymers in ceramic slurries an aqueous barium titanate system was investigated using an atomic force microscope (AFM). Spherical barium titanate particles were sintered and then glued to an AFM-cantilever. A polished and cleaned barium titanate sintered body surface was used for the opposite site. Surfaceforce vs. distance curves...
The interfacial tension of a demixed colloid-polymer mixture is measured using the spinning drop technique. For a demixed system of colloidal silica (diameter 20 nm) and polydimethylsiloxane (Mw=97000) in cyclohexane a value of 1.5× 10−2 mN/m is obtained.
The adsorption kinetics of the polysaccharide xanthan from aqueous solution on zirconium oxide were studied as a function of pH and ionic strength. The adsorption was monitored by reflectometry in a stagnation-point flow setup. At intermediate pH and ionic strength, xanthan is present in a helical form and it can be viewed as a semi-flexible polymer under these conditions. By lowering the salt concentration...
The effect of urea on the stability of α-haematite hydrosols in the presence of various monovalent ions was studied on each side of the pzc (pH 8.2) by measurements of the critical coagulation concentration (CCC) of the hydrosol. It was observed that for pHs lower than the pzc, the effect of urea depends strongly on the nature of coagulating ion and on the pH:The CCC values of IO3 ...
A new approach to the characterization of polydispersed colloidal particles of silver iodide by light-scattering method was presented through the calculations from the Zimm plots.
An overview is given on measuring techniques for contact angles between smooth solids and liquids, solid-vapor surface tension of rough and porous solids, and wetting behavior of polymer melts. It has been shown that on non-inert polymer surfaces, such as maleimide copolymers and polystyrenes, Young contact angles can be obtained by dynamic contact angle measurements using liquids that do not swell...
Monitoring the pore structure is one of the most challenging objective in order to achieve optimal material properties in porous functional structures. The pore size obtained by stacking the particles followed by sintering is primarily affected by particle size and particle size distribution of the starting powder. Thorough slip preparation is a prerequisite in order to obtain controlled microstructure...
The local structure of titania/zirconia colloids has been investigated using small-angle neutron scattering (SANS). The colloids were produced by:• hydrolysing a mixture of titanium and zirconium alkoxides, and peptising the resulting hydrolysate with nitric acid (homogeneous); • hydrolysing a titanium alkoxide, and peptising the resulting hydrolysate with aqueous zirconium (IV) nitrate solution...
The stability of acid catalyzed alkoxide-based silica systems containing polyethylene glycol (PEG) of three different molecular weights (MPEG=4600 g/mol, MPEG=10000 g/mol and MPEG=35 000 g/mol) and concentrations (0–9 wt%) have been followed visually. There has been observed a macrophase separation visually which has been explained by the bridging effect between the...
Viscose fibres were finished with a blend of a nonionic fatty acid ethoxylate and a quarternary ammonium derivative. Zeta potential and static charging were investigated as a function of a cationic compound. There is strong evidence that the charging of the viscose fibres depends on the chemical nature of the surfactants side-groups.
A survey is made of published work on the location of oily soil on textile fabrics. There is evidence that such soil tends to build up at certain preferred sites in the fabric, such as between parallel fibres in the yarn. A theoretical explanation is developed which correlates these observations. Because the shape of a droplet of oil of given volume depends upon the local geometry and contact angle...
There is a cogent body of evidence showing that the physical properties of glass reinforced plastics (GRP) can be vastly improved, by pre-treatment of the glass fibers with appropriate coupling agents or sizes. This is the fourth part of a research series investigating different silanes with non-aqueous solvents and their effect upon silane deposition onto glass fibers. A sample of E-glass...
The application of supercritical fluids (SCF) to the technological processes of fibre treatment is becoming increasingly important. Therefore we investigated highly oriented semicrystalline unmodified poly(ethylene terephthalate) fibres by means of SAXS in order to study the influence of supercritical CO2 (critical data:Tc=304.2 K, pc=7.38 MPa), an environmentfriendly dyeing media, on the...
A mean field lattice (MFL) theory has been used to study the adsorption behaviour of nonionic surfactants in hydrophilic cylindrical pores. The theory predicts that with decreasing pore radius the absorbed amount decreases. Moreover, the step in the adsorption isotherm, which is a first-order phase transition in the mean field approximation, shifts to lower concentrations. Both effects have been observed...
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