A set of experiments investigating diffusion of alkali atoms in the noble gases is reported. A cesium gradient in the cell was induced by electrodeless pulse discharge. In the transient signal of absorption, corresponding to the ^2S_{1/2}-n^2P_J transitions, five diffusion modes were observed. The diffusion coefficient D of cesium in helium and argon has been measured in a spherical cell filled with a buffer gas of 2.5 to 30 hPa and for temperatures in the range from 275 K to 400 K.
A new method of simultaneous determining of the diffusion coefficient and the reflection coefficient of atoms from the reservoir walls is presented. The diffusion coefficient of cadmium atoms in the ground state in buffer noble gas atoms such as Ne, Ar, Kr, and Xe and reflection coefficient of Cd atoms from the quartz cell wall in the temperature range 350-550 K were determined. Experimental values of diffusion coefficient are compared with theoretical ones calculated from available potentials.
Magnetic resonance imaging was used for studies of the gelation and swelling processes of toluene-based bis-urea prepared in a form of cylindrical tablet and immersed in cyclohexane. The processes were investigated with the use of Bruker AVANCE (300 MHz) spectrometer equipped with a micro imaging probe head. The images were taken for cyclohexane protons within the bis-urea gel formed around the sample dry core at different intervals of the immersion. The mobility of the solvent molecules was estimated from the spatially resolved distribution of the spin-spin relaxation time T_2 and the spin densitiesρ, calculated on the basis of the images obtained. It was shown that the time-evolution of the thickness of the gel layer can be well described by the power equation with an exponent equal to 0.47 (±0.04), indicating the Fickian nature of the diffusion of cyclohexane molecules.
Efficient synthesis of antibacterial and antifungal titanium dioxide nano powders offers new advanced properties and opportunities for industrial applications. In the present study, TiO₂ nano particles were synthesized by sol-gel method using aqueous and alcoholic solutions of titanium tetraisopropoxide (TTIP). The effects of solvent type, support material (calcite, talk, zinc borate, silica) and drying temperature on antibacterial/antifungal and structural properties namely the average particle size and surface area of titania particles were investigated.
Novel simulation procedure of self-diffusion through model porous media is presented. The procedure is based on extensive use of molecular dynamic method. The introduced diffusion simulations have a potential to become a valuable design and development tool applications involving transport in porous media, e.g. filters or porous sensors. The porous membranes are created using phase-separating model with high surface tension and its properties are characterized and compared with existing porosimetry measurements and small angle scattering experiments. These membranes are then filled with a gas of diffusing particles. Relations between transport coefficients and material structure are discussed.
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.