H. Altenburg

Bio: H. Altenburg is an academic researcher from Münster University of Applied Sciences. The author has contributed to research in topics: Electromagnetic shielding & Microstructure. The author has an hindex of 7, co-authored 12 publications receiving 198 citations.

Semiconductor ceramics for NTC thermistors : the reliability aspects

Abstract: Thermally induced processes in ceramic–electrode interfaces of CuxNi1–x–yCo2yMn2–yO4-based NTC thermistors as a function of their chemical compositions and quantitative parameters of low-temperature annealing at 400–800° C are studied. Thermal treatment of thermistors at 400-600° C during 15 h leads to degradation of the metallization layers for the majority of the investigated samples owing to the migration of electrode material (silver) into ceramic body. An accompanying anomalous increase of thermistors' electrical conductivity is observed. The following thermal treatment during 15 h at 800°C leads to an electrical conductivity regeneration to, approximately, the initial values. The reversible nature of this phenomenon is confirmed by Auger-spectroscopy method. Some of the studied NTC thermistors appear to be stable to low-temperature thermal treatment. These compositions are proposed for applications in devices operating at the temperatures up to 530° C.

Thick films of ceramic, superconducting, and electro-ceramic materials

Abstract: The use of thick films becomes more and more important in particular for elec- tronic and microelectronic applications. The term "thick film" does not relate so much to the thickness of the film but more to the kind of deposition. Thick films are made by low-priced processes such as doctor (dr) blading, screen-printing, or spraying methods, etc. The prepa- ration of thick films of ceramic material by these methods generally implies a processing sequence of the following steps: preparation of the oxide powders; preparation of pastes and slurries; painting/printing, etc. of the pastes onto a suitable substrate; drying at low tempera- ture; and sintering at high temperature to get a consolidated layer. These technologies and the fabricated thick films of thermoresistive and superconducting materials will be discussed.

Bimolecular relaxation kinetics observed in radiation-optical properties of Ge–As(Sb)–S glasses

Abstract: Numerical parameters of decaying bimolecular relaxation kinetics are analysed for radiation-optical properties of chalcogenide glasses within ternary stoichiometric As 2 S 3 –GeS 2 and Sb 2 S 3 –GeS 2 as well as non-stoichiometric As 2 S 3 –Ge 2 S 3 systems in dependence on their composition. It is shown, that the observed compositional dependences of bimolecular relaxation parameters have a monotonic character in the glasses of both stoichiometric systems, while the anomalous extremum-like behavior is observed in the vicinity of average coordination number close to 2.7 in non-stoichiometric glasses.

Controllable preparation of Bi-2223 phase through directed modification of precursors

Abstract: Microstructure of Bi-2223 precursor powders has a great influence on their reactivity and the properties of final product. Usually, to prepare precursors with different microstructure the different preparation techniques should be applied. Studies of particle size evolution upon synthesis and thermal treatment of oxide powders allowed to suggest a new method of fine and directed modification of precursor microstructure in frames of the same preparation technique. This method is based on mechanical and ultrasonic treatment of precursor powders at the intermediate stages of their synthesis.

Electrode materials and reaction mechanisms in solid oxide fuel cells: a brief review

Abstract: This work is focused on the comparative analysis of electrochemical and transport properties in the major families of cathode and anode compositions for intermediate-temperature solid oxide fuel cells (SOFCs) and materials science-related factors affecting electrode performance. The first part presents a brief overview of the electrochemical and chemical reactions in SOFCs, specific rate-determining steps of the electrode processes, solid oxide electrolyte ceramics, and effects of partial oxygen ionic and electronic conductivities in the SOFC components. The aspects associated with materials compatibility, thermal expansion, stability, and electrocatalytic behavior are also briefly discussed. Primary attention is centered on the experimental data and approaches reported during the last 10–15 years, reflecting the main challenges in the field of materials development for the ceramic fuel cells.

Electrospray droplet sources for thin film deposition

Abstract: Electrospraying utilises electrical forces for liquid atomisation. Droplets obtained by this method are highly charged to a fraction of the Rayleigh limit. The advantage of electrospraying is that the droplets can be extremely small, down to the order of 10’s nanometres, and the charge and size of the droplets can be controlled to some extent be electrical means. Motion of the charged droplets can be controlled by electric field. The deposition efficiency of the charged spray on an object is usually higher than that for uncharged droplets. Electrospray is, or potentially can be applied to many processes in industry and in scientific instruments manufacturing. The paper reviews electrospray methods and devices, including liquid metal ion sources, used for thin film deposition. This technique is applied in modern material technologies, microelectronics, micromachining, and nanotechnology.