Revealing local variations in nanoparticle size distributions in supported catalysts: a generic TEM specimen preparation method

The specimen preparation method is crucial for how much information can be gained from transmission electron microscopy (TEM) studies of supported nanoparticle catalysts. The aim of this work is to develop a method that allows for observation of size and location of nanoparticles deposited on a porous oxide support material. A bimetallic Pt‐Pd/Al₂O₃ catalyst in powder form was embedded in acrylic resin and lift‐out specimens were extracted using combined focused ion beam/scanning electron microscopy (FIB/SEM). These specimens allow for a cross‐section view across individual oxide support particles, including the unaltered near surface region of these particles. A site‐dependent size distribution of Pt‐Pd nanoparticles was revealed along the radial direction of the support particles by scanning transmission electron microscopy (STEM) imaging. The developed specimen preparation method enables obtaining information about the spatial distribution of nanoparticles in complex support structures which commonly is a challenge in heterogeneous catalysis.     

High-order volterra series analysis using parallel computing

This paper addresses the determination of high-order Volterra transfer functions of non-linear multiport networks containing multidimensional non-linear elements. A new method is developed for utilizing parallel computing which is very efficient for approximately 10–20 processors. The utilization of each processor may be as high as 80%–95%. The developed program is very flexible as it is ANSI C++ compatible and may run on both single- and multiprocessor computers. Using about eight processors it is possible to analyse rather complicated non-linear circuits up to ninth order in a few hours. © 1997 by John Wiley & Sons, Ltd.     

MODELING HEAT EFFICIENCY, FLOW AND SCALE-UP IN THE COROTATING DISC SCRAPED SURFACE HEAT EXCHANGER

A comparison of two different scale corotating disc scraped surface heat exchangers (CDHE) was performed experimentally. The findings were compared to predictions from a finite element model. We find that the model predicts well the flow pattern of the two CDHE's investigated. The heat transfer performance predicted by the model agrees well with experimental observations for the laboratory scale CDHE whereas the overall heat transfer in the scaled‐up version was not in equally good agreement. The lack of the model to predict the heat transfer performance in scale‐up leads us to identify the key dimensionless parameters relevant for scale‐up.