Mechanism of catalytic reduction of NO by H2 or CO on a Pd foil; Role of chemisorbed nitrogen on Pd

The adsorption of NO and its reaction with H₂ over polycrystalline Pd were investigated using flash desorption technique and ultraviolet photoelectron spectroscopy under 10^?5 Pa pressure range of reactants and surface temperatures between 300 and 900 K. NO was adsorbed dissociatively onto the Pd surface above 500 K, and the heat of dissociative adsorption was ca. 126 kJ/mol. Atomic nitrogen was observed to accumulate on the Pd surface during the NO-H₂ reaction, whose desorption rate exhibited second order kinetics and is expressed as follows: V_d = 10^{?9.8 ± 0.3}exp(?67(kJ/mol)/RT) (cm²/atom·s). Hydrogenation of the adsorbed nitrogen proceeded rapidly at 485 K. It was confirmed from these results that formation of N₂ and NH₃ in the NO-H₂ reaction proceeds through this atomically adsorbed nitrogen. Pd-N bond energy and enthalpies of some intermediate states of the NO-H₂ reaction were estimated.     

Effect of solvent power on the adsorption of polystyrene onto a metal surface

The adsorption of linear polystyrenes from cyclohexane solutions onto a chrome plate of 35 (the theta temperature), 40, and 45°C was studied by ellipsometry. The adsorbance decreases with increasing temperature, while the extension of the adsorbed polymer layer increases. The adsorbance is almost independent of the molecular weight at these temperatures. The slope of a double logarithmic plot of extension versus molecular weight is 0.5 at the theta temperature, whereas at the higher temperatures the slope is a little larger. Both the adsorbance and the extension of the adsorbed layer change reversibly over a cycle of temperature change, indicating that a reversible conformational change has occurred. The expansion factor α_t of the adsorbed layer is compared with the theoretical predictions of Hoeve and of Jones and Richmond. The expansion factor α_t according to Hoeve's theory, was smaller than the measured value, whereas the expansion calculated by the Jones–Richmond theory is much larger than the measured value. It is concluded that the tail portions of adsorbed chains predominantly govern the extension of the adsorbed layer.     

Predicted effects of gamma and neutron irradiation on silicon solar cells

Numerical analysis of the characteristics of silicon solar cells under-ray or fast neutron irradiation is presented. The degradation of spectral response, short-circuit current, maximum power, open-circuit voltage and curve power factor are discussed. The calculation is based on estimating the minority carrier lifetime by the Shockley-Read equation, assuming the introduction rate, capture cross-section and the energy level to be equal to those of various predominant recombination centres, such as E-centre (phosphorus-vacancy complex), A-centre (oxygen-vacancy complex) and J-centre (boron-vacancy complex) in-irradiated silicon single crystals. The simulated results show good agreement with experiment for N-type F·Z and C·Z bulk crystals with E-centres, and for P-type C·Z bulk crystal with J-centres.     

Macroscopic observations of molecular recognition: discrimination of the substituted position on the naphthyl group by polyacrylamide gel modified with β-cyclodextrin

Macroscopic molecular recognition observations were realized using polyacrylamide-based gels modified with α-cyclodextrin (α-CD), β-cyclodextrin (β-CD), 1-naphthylmethyl (1Np), and 2-naphthylmethyl (2Np) moieties, which are denoted as αCD(x)-gel, βCD(x)-gel, 1Np(y)-gel, and 2Np(y)-gel, where x and y indicate the mol % of CD and Np moieties, respectively. The αCD(5)-gel did not adhere to either the 1Np(5)-gel or 2Np(5)-gel, whereas the βCD(5)-gel interacted with both to form alternating or checkered assemblies. Although the difference in the association constants of β-CD for the model polymers was small, the βCD(x)-gel successfully discriminated between 1Np(y)-gel and 2Np(y)-gel at the appropriate x and y.