Dispersion of titania particles in water has been achieved thanks to the addition of two different compounds: (C(2)H(5))(4)NOH and Tiron. To compact particles using an electrophoretic deposition ...process, ethanol, up to 20 vol%, was added as cosolvent to prevent water electrolysis. Alcohol addition strongly affects zeta potential values of particles and increases suspension viscosity but without influence the surface charge. The more realistic interpretation is that integration of ethanol molecules into the water network moves the slipping plane away from the surface, reducing the repulsive potential between particles that leads to suspension destabilization.
Taigi, nuodugniai ištyrę kategorinių teiginių dalis, arba narius, iš kurių jie sudaromi, taip pat aptarkime ir tokių teiginių rūšių skirtumus. O pastaruosius galime svarstyti atsižvelgdami į ...predikato išsakymą ar subjekto suvokimą, arba į jų (ar visos ištaros) daugiareikšmiškumą, arba į veiksmažodžio laikų skirtingumą. Nuo predikato išsakymo priklauso tai, kad jį teigimu arba neigimu išreiškiantys teiginiai vadinami teigiamais arba neigiamais, taip pat vienuose teiginiuose jis išsakomas paprastai, o kituose – tam tikru būdu (modo), todėl pirmuosius įvardijame kaip paprastuosius, antruosius – kaip modalinius. Atsižvelgiant į subjektą, vieni teiginiai vadinami bendraisiais, kiti – daliniais, dar kiti – neapibrėžtaisiais, o likę – vieniniais. Terminų įvairumas lemia tai, kad vieni teiginiai būna vienareikšmiai, kiti – daugiareikšmiai, o laikų skirtingumas – jog vieni pasakomi apie dabartį, kiti – apie praeitį, dar kiti – apie ateitį.
Electrical measurement as a function of frequency is a non-destructive technique which has been applied on numerous ceramic based systems such as single crystals, heterogeneous materials or ...concentrated suspensions of ceramic powders. It is a method for looking at the dynamic response of the system under test. Several approaches have been developed by different authors to give the associated relaxation times based on a single or on a distribution of times. In order to support the interpretation of the dynamic signal, one has to vary the physical or chemical parameters such as temperature, time, concentration and so on. Application of high frequency measurements (1 MHz–1.8 GHz) on aluminous cement pastes (W/C=0.4) is described. The variations of the capacitance with respect to setting time (from 0 to a few hours after mixing water and cement) and temperature (20 and 30 °C) are related to hydration chronology and to the quantity of formed hydrates. The high frequency response of C
3AH
6, which has been prepared by a chemical route, is also discussed.
Dispersion of titania particles in water has been achieved thanks to the addition of two different compounds: (C
2H
5)
4NOH and Tiron. To compact particles using an electrophoretic deposition ...process, ethanol, up to 20 vol%, was added as cosolvent to prevent water electrolysis. Alcohol addition strongly affects zeta potential values of particles and increases suspension viscosity but without influence the surface charge. The more realistic interpretation is that integration of ethanol molecules into the water network moves the slipping plane away from the surface, reducing the repulsive potential between particles that leads to suspension destabilization.
A CFA cement from Lafarge prepared at 20°C, 100% relative humidity, and with water-to-cement weight ratio (W/C)=0.4, has been tested electrically between 10 Hz–1 MHz and 1 MHz–1 GHz. The samples have ...been measured at 20°C and 50% relative humidity from 8 h up to 150 h after mixing the water with the cement. For the first frequency range, the results presented here focus on the effect of the chemical nature of the electrode on the electrical response of the cement. Different electrode materials, namely, silver, gold or an indium–gallium mix, have been investigated. Silver leads to a major contribution of the cement–electrode interface to the global electrical response. This effect is less pronounced with gold and indium–gallium. Concerning the higher frequency range, measurements between 1 MHz and 1 GHz enable the evolution of the interface between cement and water during hydration to follow. An analysis of electrical data, namely, the permittivity and the conductivity, has been carried out using a procedure based on a continuous distribution of time constants. The corresponding relaxation frequencies are presented and related to the state of water inside the cement material. A comparison of the electrical behaviour between a cement and a silico-aluminous ceramic, in which water is not as reactive as in a cement, is also discussed.
The multiple light scattering in concentrated alumina suspensions adapted to stereolithography can be modeled using diffuse reflectance measurements coupled to the Kubelka–Munk model. The penetration ...depth of UV radiation can be related to the scattering coefficient allowing the prediction of the cure depth with an accuracy of 20%.
The degradation mechanism in PTC barium titanate ceramics under reduced atmospheres was investigated by the new method developed by authors. It was found that the potential barrier height in the ...lower temperature region (120°-180°C) was not affected by the degradation treatment, and that the height in the higher temperature region was reduced with the degradation time. It was suggested that the dominant factor in the degradation mechanism was the broadening of the distribution of interface states.
Ceramics suspensions composed of oppositely charged alumina and silica particles are studied experimentally and by means of Brownian dynamics simulations. Alumina and silica particles have quite ...similar sizes, the former having an average diameter larger by a factor 1.6. The suspension behavior is studied as a function of composition.
The aggregation process of a two-component dilute system (3 vol %), made of alumina submicrometer particles and silica nanoparticles, is studied by Brownian dynamics simulations. Alumina and silica ...particles have very different sizes (diameters of 400 and 25 nm, respectively). The particle−particle interaction potential is of the DLVO form. The parameters of the potential are extracted from the experiments. The simulations show that the experimentally observed aggregation phenomena between alumina particles are due to the silica−alumina attraction that induces an effective driving force for alumina−alumina aggregation. The experimental data for silica adsorption on alumina are very well reproduced.
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