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This paper reports on investigations of Ag-ZnO and Cu-ZnO interfaces, produced by internal oxidation. ZnO precipitates with the wurtzite structure were found showing mainly one orientation relationship( OR) with the matrix. However, closely related ORs were found, rotated by small angles from that orientation relation. The atomic structure of several interfaces surrounding these precipitates was studied and compared using high resolution transmission electron microscopy. This paper focuses on interfaces between low index facets of ZnO and vicinal planes of Ag. These interfaces clearly show relaxations. An interpretation of these relaxations in terms of dissociation of partial dislocations at the interface is put forward.

This paper concentrates on the transmission electron microscopy observations of different dislocation structures in laser nitrided Titanium. Equidistant edge dislocation in the bulk and periodic surface structures exhibit a periodicity within the same order of magnitude. An analysis is presented in which both periodic phenomena are explained by cellular growth.

The present paper concentrates on the applications of CO2 laser treatments to enhance fretting wear properties of stainless steel. Stainless steel 316 is used as substrate material. Powder particles of the various stellites with sizes ranging between 45 and 125 mu m are fed onto the surface. It was found that dilution of the substrate material with the clad material had a profound influence on the mechanical properties of the clad. The importance for this low level of dilution is that the powder blown onto the surface usually has an optimal alloy composition, which must not be altered. The overall pin-on-disc and fretting wear properties of Stellites are outstanding. The fact that the Stellite coatings tested are deposited using a high power laser beam seems to be a crucial improvement as far as the dense layer, low dilution, strong bonding and use of little material are concerned. Also, the laser depositing results in fine microstructures which may influence the oxidation rate and the oxide support from the substrate.

Internal oxidation of Ag-3at.%Mn resulted in Mn3O4 precipitates and of Cu-1at.%Mn gave rise to MnO and a minor amount of Mn3O4 precipitates. In Cu Mn3O4 transformed out of MnO, whereas in Ag Mn3O4 developed directly. Predominantly, precipitates with parallel topotaxy and an octahedron shape due to 8 (111) oxide facets are formed. Due to the tetragonality of Mn3O4 a tilt of 3.8 degrees can exist between the (111) of Mn3O4 and Ag on all 8 interfaces, but it appeared more favourable to align (ill) parallel for one pair of facets. Starting from a parallel topotaxy for MnO and Cu, the transformation out of MnO and the Pain-strain lattice correspondence with MnO determines largely for Mn3O4 the orientation relation with Cu. Tetragonal twinning is observed in Mn3O4 precipitates in both Ag and Cu. Coexistence in precipitates of MnO and tetragonal twinned Mn3O4, is frequently observed in Cu. Probably, tetragonal twinning reduces the misfit between Mn3O4 inclusions and the cubic matrix. This is verified by linear elasticity calculations pertaining to the inclusion problem.

Extruders are traditionally used in industry to melt, mix and shape polymeric materials. Due to their ability to process high viscous materials they can be used as a novel type of reactor. It is possible to use extruders as solvent free polymerisation or modification reactors. In situ compatibilisation during mixing of incompatible polymers is another interesting application of these machines. A third area, where extruders can be used as reactors is in the gelatinisation and modification of starches to use them as a base chemical from renewable resources. In this way it is also possible to produce copolymers between starches and synthetic polymers that can be used for packaging, disposables and controlled release.

The distribution of cationic vacancies in transition aluminas obtained by dehydration of boehmite has been investigated using HRTEM combined with an image simulation technique. Interstitial vacancies in a cubic-packed oxygen network have been found to be concentrated in an orderly fashion on low indexed lattice planes like the {110} and {100} planes of a spinel structure. Such arrangements of cationic vacancies on octahedral sites result in modified transition aluminas with lattice parameters a=a(gamma), b=a(gamma) or 2a(gamma), c=3a(gamma), where a(gamma)=0.79 nm is the lattice constant of the spinel structure of gamma-Al2O3.

A poly(butyl methacrylate) (PBMA) latex was coated with a thin polypyrrole (PPy) layer in a chemical in situ polymerization. Ammonium persulfate and Fenton's reagent were used as the oxidants. The influence of reaction time on the conversion of pyrrole and on the conductivity of the resulting coated latices was investigated. Furthermore, the influence of the reaction atmosphere was investigated. It was found that the ammonium persulfate-oxidized reaction was quite insensitive towards the reaction atmosphere, whereas the Fenton's reagent oxidized system was very sensitive. In the latter system, when kept in air the conductivity reached a maximum after 30 minutes. In a nitrogen reaction atmosphere the conductivity gradually increased. The maximum conductivity, which was about 20 times as high as in air, was reached after 90 minutes and remained stable.

ispartof: pages:3- ispartof: Proc. Euromat 97, 5th European Conference on Advanced Materials and Processes and Applications - Materials, Functionality & Design pages:3- ispartof: location:Maastricht, The Netherlands date:21 Apr - 23 Apr 1997 status: published