Application of the surface potential data to elucidate interfacial equilibrium at ceria/aqueous electrolyte interface

Interfacial properties of ceria (CeO2) nanoparticles and highly organized ceria crystal planes {111} and {100} in the aqueous electrolyte solution were studied. It was confirmed by high resolution electron spectroscopy that a primary ceria nanoparticle consists mostly of two crystal planes {111} and {100} with different surface sites exposed to the aqueous electrolyte solution. Interfacial properties of ceria nanoparticles are directly related to the reactivity and surface densities of existing surface sites. However, surface characterization (potentiometric titrations and electrophoretic measurements) provides only some kind of average surface properties i.e. average surface charge densities and surface potentials. The point of zero charge (pHpzc) of ceria nanoparticles was measured to be between 6.4 and 8.7, depending on the electrolyte concentration, and the isoelectric point at pHiep = 6.5. With the purpose of understanding ceria nanoparticles surface charging the inner surface potentials of ceria macro crystal planes {111} and {100} were measured for the first time, by means of single crystal electrodes, as a function of pH and ionic strength. The inner surface potential directly affects the state of ionic species bound to a certain surface plane and is thus an essential parameter governing interfacial equilibrium. From the measured Ψ 0(pH) data and applying the Multi Site Complexation Model the thermodynamic equilibrium constants of doubly-coordinated ≡Ce2-OH (at the {100} ceria crystal plane) as well as singly-coordinated ≡Ce1-OH and triply-coordinated ≡Ce3-OH (at the {111} ceria crystal plane) were evaluated. The Ψ 0(pH) function differs for two examined ceria planes, however the inner surface potentials of both planes depend on ionic strength having a broad electroneutrality region between pH = 6 and pH = 9

Mechanochemical stability of hydrogen titanate nanostructures

Structural stability of nanostructured titanates was investigated for further processing and possible applications. With the aim to investigate their mechanochemical stability we applied highenergy ball milling and studied induced phase transitions. Hydrogen titanates having two different morfologies, microcrystals and nanotubes, were taken into consideration. During mechanochemical treatment of both morphologies, we observed the phase transition from hydrogen titanate to TiO2 anatase and then to TiO2 rutile. Anatase to rutile phase transition occurred without appearance of intermediate high pressure TiO2 II typically observed in the case of mechanochemical treatment of TiO2. In the case of microcrystals, phase transition from hydrogen titanate to anatase starts after longer milling time than in the case of nanotubes, which is explained by larger particles sizes of crystalline powder. On the contrary, further phase transition from anatase to rutile was occurred faster in crystalline powder than in the case of nanotubes. The sequence of phase transitions was studied by Raman spectroscopy and X-ray powder diffraction, while morphology and crystal structure at nanoscale were analyzed by high resolution electron microscopy

Value of Color-Doppler Imaging in Diagnosis of Intrabulbar and Intraorbital Tumors

Patients with intrabulbar and intraorbital tumours have been investigated by colour Doppler imaging. In the first group there were 20 patients with malignant melanoma of the uvea and in the second group there were 19 patients with cavernous hemangioma. The third group was a control group represented by 20 healthy individuals. In the group of patients with uveal melanoma it has been established that every patient, except one, has a blood flow inside of tumour tissue. Internal blood flow of intraorbital hemangioma was slower than inside the melanoma and the resistance index was lower. Comparison of blood flow in all patients has shown that there is no statistically significant difference between ophthalmic artery, central retinal artery and posterior ciliary arteries except in maximal blood flow in central retinal artery and posterior ciliary arteries

Fabrication and properties of the SITE-SiCf/SiC composite

Continuous SiC-fiber-reinforced SiC composite (SiCf/SiC) is an attractive candidate structural material for advanced concepts of future fusion power plants, mainly due to the favourable intrinsic properties of the SiC ceramics, i.e. high temperature- and chemical stability, low neutron activation and afterheat levels as well as due to the fact that it is the only nonmagnetic material proposed. Fabrication of such composites is a very challenging task due to limitations and requirements set for fusion-relevant structural materials

Saturated Ternary Systems. V. Solubility Isotherms of Organic Compounds in Water-Methanol Mixtures

Determined were the consta nts of solubility isotherms for the solutions of the following organic compounds in a mixture of methanol and water: benzen e (20° C), bromobenzene (0°), hexane (0°), tetrachloromethane (0°), toluene (0°), ethylbromide (0°), chloroform (0°) and heptane (0°). The authors show that the solubility of thenvestigated organic compounds at the intersections of the isotherms changes according to the same law for the systems methanol-water and the systems ethanol-water. Lower concentrations of water diminish the solubility of the organic compounds in the mixture alcohol-water relatively more tha n higher concentrations. The inner angles under which two isotherms intersect vary in the systems organic compound - water - methanol between 165 and 175° and in the systems with ethanol between 169 and 175° in the majority of the systems investigated

Saturated ternary systems. V. Solubility isotherms of organic compounds in water-methanol mixtures

Determined were the consta nts of solubility isotherms for the solutions of the following organic compounds in a mixture of methanol and water: benzen e (20° C), bromobenzene (0°), hexane (0°), tetrachloromethane (0°), toluene (0°), ethylbromide (0°), chloroform (0°) and heptane (0°). The authors show that the solubility of thenvestigated organic compounds at the intersections of the isotherms changes according to the same law for the systems methanol-water and the systems ethanol-water. Lower concentrations of water diminish the solubility of the organic compounds in the mixture alcohol-water relatively more tha n higher concentrations. The inner angles under which two isotherms intersect vary in the systems organic compound - water - methanol between 165 and 175° and in the systems with ethanol between 169 and 175° in the majority of the systems investigated

Dissolution of aluminium and iron oxo minerals in acetylacetone. Correlation of the digestion rate with mineral density

The series of aluminium oxo minerals such as gibbsite, boehmite, diaspore, and corundum as well as iron minerals lepidocrocite, goethite, and hematite dissolve in acetylacetone with decreasing extraction rate as the mineral density increases along each series listed above. The observed inverse dependence of the digestion rate on the mineral density for each series studied and the mechanism of digestion have been discussed

Dissolution of Aluminium and Iron Oxo Minerals in Acetylacetone. Correlation of the Digestion Rate with Mineral Density

The series of aluminium oxo minerals such as gibbsite, boehmite, diaspore, and corundum as well as iron minerals lepidocrocite, goethite, and hematite dissolve in acetylacetone with decreasing extraction rate as the mineral density increases along each series listed above. The observed inverse dependence of the digestion rate on the mineral density for each series studied and the mechanism of digestion have been discussed