Determination of functional groups of coal-derived liquids by n.m.r. and elemental analysis

A new method of structural analysis was applied to a group of hydroliquefied coal samples. The method uses elemental analysis and n.m.r. data to estimate the concentrations of functional groups in the samples. The samples included oil and asphaltene fractions obtained in a series of hydroliquefaction experiments, and a set of nine fractions separated from a coal-derived oil. The structural characterization of these samples demonstrates that estimates of functional group concentrations can be used to provide detailed structural profiles of complex mixtures and to obtain limited information about reaction pathways.     

0.1 μm Schottky-collector AlAs/GaAs resonant tunneling diodes

The Schottky-collector resonant tunneling diode (RTD) is an RTD with the normal N+ collector and ohmic contact replaced by a Schottky contact, thereby eliminating the associated parasitic resistance. With submicron Schottky contact dimensions, the remaining components of the parasitic series resistance can be greatly reduced, resulting in an increased maximum frequency of oscillation, f_max. AlAs/GaAs Schottky-collector RTDs were fabricated using 0.1 μm T-gate technology developed for high electron mobility transistors. From their measured dc and microwave parameters, and including the effect of the quantum well lifetime, f_max=900 GHz is computed     

Limitations of surface analytical techniques for determining the surface composition of bimetallic particles

Calculations of expected X-ray photoelectron spectroscopy intensity ratios for both homogeneous and segregated bimetallic particles demonstrate that a minimum particle size exists, below which reliable differentiation between homogeneous alloy particles and particles in which one component has segregated to the surface cannot be made. This minimum particle size varies between 3 and 8 nm depending on the specific metal combination in question. In cases of partial segregation of one component, the minimum particle size is even larger. The implications of these results for the study of surface segregation in supported bimetallic catalyst particles are discussed.This work was performed at Sandia National Laboratories for the US Department of Energy under contract DE-AC04-94AL85000.     

Analyses of PACTEL passive safety injection experiments with APROS, CATHARE and RELAP5 codes

The European Commission fourth framework programme project ‘Assessment of passive safety injection systems of advanced light water reactors’ involved experiments on the PACTEL test facility and computer simulations of selected experiments. The experiments focused on the performance of passive safety injection systems (PSIS) of advanced light water reactors (ALWRs) in small break loss-of-coolant accident (SBLOCA) conditions. The PSIS consisted of a core make-up tank (CMT) and two pipelines. A pressure balancing line (PBL) connected the CMT to one cold leg. The injection line (IL) connected it to the downcomer. The project involved 15 experiments in three series. The experiments provided information about condensation and heat transfer processes in the CMT, thermal stratification of water in the CMT, and natural circulation flow through the PSIS lines. The project included validation of three thermal-hydraulic computer codes (APROS, CATHARE and RELAP5). The analyses showed the codes are capable of simulating the overall behaviour of the transients. The codes predicted accurately the core heatup, which occurred when the primary coolant inventory was reduced so much that the core top became free of water. The detailed analyses of the calculation results showed that some models in the codes still need improvements. Especially, further development of models for thermal stratification, condensation and natural circulation flow with small driving forces would be necessary for accurate simulation of the phenomena in the PSIS.     

Study of the Influence of Xanthate Derivative Structures on Copper Sulfide Mineral Adsorption Under Acidic Conditions

Metallurgical and Materials Transactions B - Adsorption of commercial xanthate derivatives on copper sulfide mineral (covellite, CuS) was studied by kinetics and isotherm adsorption experiments....     

Montan wax extraction from Northern Ireland lignite

In preliminary studies of the extraction of wax from Northern Ireland (Crumlin deposit) lignite, a number of extractions were carried out with three solvents for different contact times and two extraction temperatures. Exhaustive extraction with toluene shows that Crumlin lignite contains 16.6 wt% wax on a dry basis.     

Petrography,textural, morphological and structural characteristics of tuffite for Cu(II) removal. Effect of adsorption process variables

Tuffite has been studied for Cu(II) adsorption from aqueous and ammoniacal solutions. Tuffite was characterized by mercury porosimetry, Brunnauer–Emmet–Teller (BET), scanning electron microscopy–energy X-ray dispersive spectroscopy (SEM-EDS), Fourier transform infrared spectra (FTIR), X-ray powder diffraction (XRD), inductively coupled plasma-atomic emission spectrometry (ICP-OES) and petrographic microscopy. The equilibrium time was 50 min. The second-order model is the best model to describe the process. It was determined that the intraparticle diffusion was not the only limited step. Process variables were studied to improve the adsorption process. The material washed contributes to increase the Cu(II) adsorption from 213.05 to 276 mg/g. The flow countercurrent system requires at least 6 g of tuffite to achieve 90% of removal.     

Two-dimensional oxide catalysts: propene oxidation on FeSbO4

FeSbO₄ catalysts used for selective propene oxidation/ammoxidation have been examined using a combination of XPS and TPD before and after ammonia reduction. These data indicate that the surface has a thin skin which is enriched in antimony oxide. This skin is shown to be important for selective oxidation. This two-dimensional oxide covering can be reduced to metallic antimony after only low pressure treatment in ammonia and the metallic layer can be desorbed upon heating above 600 K. The remaining surface is then covered with an Fe-rich layer which is not so easily reduced, and which is of lower selectivity in partial oxidation to acrolein.