The melting line for ethylene on graphite

Using the minimum in the nuclear magnetic spin-lattice relaxation time versus temperature as an indicator of melting we have mapped out the solid-fluid phase boundary for ethylene adsorbed on graphite. At low coverages the ethylene forms a self-bound monolayer solid with a melting temperature of about 68 K. The molecules in the solid retain orientational mobility down to 55 K, the lowest temperatures explored.     

Thermodynamic investigation of n-hexane thin films adsorbed on magnesium oxide

The thermodynamic properties of n-hexane adsorption on MgO(100) were determined using high-resolution volumetric adsorption isotherms in the temperature range 195-255 K. Two distinct layering transitions are observed in the isotherms. The isotherms are used to calculate the two-dimensional compressibility, the differential enthalpy and entropy, the heat of adsorption, and the isosteric heat of adsorption. Neutron Diffraction is used to identify where melting of the n-hexane monolayer takes place.     

TXRF analysis of aged three way catalysts

A methodology for the quantitative analysis of the elements present in car exhaust catalysts by TXRF is described. Some of the most relevant catalytic components (Zr, Rh, Pd) and contaminant elements (P, Pb, Zn, Pt, Ca and Ni) on car Three Way Catalysts were quantified during vehicle aging. The study was conducted along the main axis of a Ford Focus 1.6i catalytic cartridge, aiming to obtain the axial profile of the elements retained or eliminated after more than 59,000 km. The analysis of a fresh Three Way Catalysts (0 km) was also conducted for comparative purposes. The existence of a strong differences for elemental concentration in the interphase between the two blocks of the catalytic cartridge has been quantitatively measured for first time. In addition, the behaviour of the contaminant absorption capacity of both catalytic blocks has been obtained. Finally, the loss of the contaminant elements Pb and Zn to the environment has been proven.     

Thermodynamic investigation of thin films of ethane adsorbed on magnesium oxide

The layering properties of ethane on MgO(100) were measured between 91 and 144 K using high-resolution adsorption isotherms. In contrast to previous studies, the results demonstrate that only three layers are formed. The thermodynamic functions derived from the data (isosteric heat, differential enthalpy, and entropy of adsorption) compare well with literature values and show a steady trend toward the bulk properties as the number of layers increased. Phase transitions for two of the layers were identified by monitoring the changes in the two-dimensional isothermal compressibility as a function of chemical potential. Both of these phase transitions occur at approximately 127 K and within 1 K of each other. Through the use of neutron diffraction, it is possible to identify at least one solid surface phase that melts at approximately 75 K. The transition at 127 K is therefore a transition between a liquidlike phase and a hyper-critical fluid. A comparison is made between the present data and our recent study of methane on MgO.