Scale-length optimising of short pulse Cu K-alpha laser plasma sources

The authors present experimental results showing how the use of a high contrast femtosecond laser system allows better optimization of K emission from a Cu target. The shorter scale-length preformed plasma is better optimized for resonance absorption of the laser light when the laser is moved away from best focus. The experimental data show a central peak of K emission at tight focus with strong secondary peaks at large offset. The use of these secondary peaks results in a much reduced hard x-ray background and should lead to shorter K pulses than at tight focus.

A density functional theory study of carbon monoxide oxidation on the Cu3Pt(111) alloy surface: Comparison with the reactions on Pt(111) and Cu(111)

Alloying metals is often used as an effective way to enhance the reactivity of surfaces. Aiming to shed light on the effect of alloying on reaction mechanisms, we carry out a comparative study of CO oxidation on Cu3Pt(111), Pt(111), and Cu(111) by means of density functional theory calculations. Alloying effects on the bonding sites and bonding energies of adsorbates, and the reaction pathways are investigated. It is shown that CO preferentially adsorbs on an atop site of Pt and O preferentially adsorbs on a fcc hollow site of three Cu atoms on Cu3Pt(111). It is also found that the adsorption energies of CO (or O-a) decreases on Pt (or Cu) on the alloy surface with respect to those on pure metals. More importantly, having identified the transition states for CO oxidation on those three surfaces, we found an interesting trend for the reaction barrier on the three surfaces. Similar to the adsorption energies, the reaction barrier on Cu3Pt possesses an intermediate value of those on pure Pt and Cu metals. The physical origin of these results has been analyzed in detail. (C) 2001 American Institute of Physics.

The preparation and properties of coprecipitated Cu-Zr-Y and Cu-Zr-La catalysts used for the steam reforming of methanol

A series of Cu-zirconia catalysts containing various additives (Y2O3, La2O3, Al2O3 and CeO2) have been prepared by coprecipitation and their activities and stabilities under operating conditions have been obtained for the steam reforming of methanol. It has been found that an yttria-promoted catalyst containing 30 mol% Cu and 20 mol% of Y2O3 is not only very active but is also very stable under reaction conditions. The yttria appears to stabilise a high copper surface area and may also have a slight promotional effect on the copper. The results obtained with this material compare very favourably with data for the best catalysts reported in the literature. (C) 2007 Published by Elsevier B.V.

Adsorption characteristics of Cu and Ni on Irish peat moss

Peat has been widely used as a low cost adsorbent to remove a variety of materials including organic compounds and heavy metals from water. Various functional groups in lignin allow such compounds to bind on active sites of peat. The adsorption of Cu²⁺ and Ni²⁺ from aqueous solutions on Irish peat moss was studied both as a pure ion and from their binary mixtures under both equilibrium and dynamic conditions in the concentration range of 5–100 mg/L. The pH of the solutions containing either Cu²⁺ or Ni²⁺ was varied over a range of 2–8. The adsorption of Cu²⁺ and Ni⁺² on peat was found to be pH dependent. The adsorption data could be fitted to a two-site Langmuir adsorption isotherm and the maximum adsorption capacity of peat was determined to be 17.6 mg/g for Cu²⁺ and 14.5 mg/g for Ni²⁺ at 298 K when the initial concentration for both Cu²⁺ and Ni²⁺ was 100 mg/L, and the pH of the solution was 4.0 and 4.5, respectively. Column studies were conducted to generate breakthrough data for both pure component and binary mixtures of copper and nickel. Desorption experiments showed that 2 mM EDTA solution could be used to remove all of the adsorbed copper and nickel from the bed.

TiK alpha radiography of Cu-doped plastic microshell implosions via spherically bent crystal imaging

We show that short pulse laser generated Ti K alpha radiation can be used effectively as a backlighter for radiographic imaging. This method of x-ray radiography features high temporal and spatial resolution, high signal to noise ratio, and monochromatic imaging. We present here the Ti K alpha backlit images of six-beam driven spherical implosions of thin-walled 500-mu m Cu-doped deuterated plastic (CD) shells and of similar implosions with an included hollow gold cone. These radiographic results were used to define conditions for the diagnosis of fast ignition relevant electron transport within imploded Cu-doped coned CD shells. (c) 2005 American Institute of Physics.

New Cu-Based Catalysts Supported on TiO2 Films for Ullmann SNAr-Type C-O Coupling Reactions

New routes for the preparation of highly active TiO2-supported Cu and CuZn catalysts have been developed for C-O coupling reactions. Slurries of a titania precursor were dip-coated onto glass beads to obtain either structured mesoporous or non-porous titania thin films. The Cu and CuZn nanoparticles, synthesized using a reduction by solvent method, were deposited onto calcined films to obtain a Cu loading of 2 wt%. The catalysts were characterized by inductively coupled plasma (ICP) spectroscopy, temperature-programmed oxidation/reduction (TPO/TPR) techniques, Cu-63 nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), scanning and transmission electron microscopy (S/TEM-EDX) and X-ray photo-electron spectroscopy (XPS). The activity and stability of the catalysts obtained have been studied in the C-O Ullmann coupling of 4-chloropyridine and potassium phenolate. The titania-supported nanoparticles retained catalyst activity for up to 12 h. However, catalyst deactivation was observed for longer operation times due to oxidation of the Cu nanoparticles. The oxidation rate could be significantly reduced over the CuZn/TiO2 catalytic films due to the presence of Zn. The 4-phenoxypyridine yield was 64% on the Cu/nonporous TiO2 at 120 degrees C. The highest product yield of 84% was obtained on the Cu/mesoporous TiO2 at 140 degrees C, corresponding to an initial reaction rate of 104 mmol g(cat)(-1) s(-1). The activation energy on the Cu/mesoporous TiO2 catalyst was found to be (144 +/- 5) kJ mol(-1), which is close to the value obtained for the reaction over unsupported CuZn nanoparticles (123 +/- 3 kJ mol(-1)) and almost twice the value observed over the catalysts deposited onto the non-porous TiO2 support (75 +/- 2 kJ mol(-1)).

Cu-Based Nanoalloys in the Base-Free Ullmann Heterocyle-Aryl Ether Synthesis

We report the first liquid-liquid Ullmann etherification process mediated not only by oxidatively stable Cu but also by CuZn and CuSn nanoparticle catalysts in conjunction with microwave heating that also avoids the use of solid and expensive bases. Conditions have led to improved turnovers and excellent yields in heteroaromatic Ullmann-type coupling reactions. Further enhancement is achieved upon the addition of 18-crown-6 as a kinetic promoter.

Rate-determining stage in NOSCR with propane on low-exchanged Cu-ZSM-5 catalyst

The kinetics of the NO SCR with propane has been studied on a low-exchanged Cu-ZSM-5 catalyst. The study of the kinetics of individual reaction stages (2-nitrosopropane isomerization to acetone oxime and reaction of adsorbed acetone oxime with gaseous NO) has shown that the NO reaction with acetone oxime is the rate-determining stage in the whole chain of transformations leading to the formation of molecular nitrogen in the low-temperature region below 300 C-degrees. The kinetic analysis of the reaction has revealed that at the temperatures above 300(degrees)C propane plays a more important role.