Materials and manufacturing technologies for solid oxide fuel cells

This article summarises recent developments in solid oxide fuel cell research regarding materials, processing and microstructure–property relationships. In the materials section, the various cell and stack materials are briefly described, i.e. electrolytes, electrodes, contact and protective layers, interconnects and sealing materials. The section on processing gives an overview of manufacturing technologies for cells including a view of different substrate materials and designs. Besides the widely used planar cell designs, the technologies for tubular designs are also described. In addition, the technologies are grouped with respect to the support, e.g. metal- or ceramic–metal (cermet anode substrate)-supported SOFCs. Finally, special emphasis is laid on the microstructure of functional layers which primarily govern the power output of the SOFC.     

Comparison and Applications of DPV-2000 and Accuraspray-g3 Diagnostic Systems

Comparative in-flight measurements of particles plasma sprayed by F4 and Triplex II guns were carried out using the diagnostic systems DPV-2000 and Accuraspray-g3. The comparison of mean particle velocities and temperatures as well as intensity profiles of the plume show a good agreement confirming their accuracy. However, the varying operating principles especially the deceased dimensions of the measurement volumes have to be considered carefully when evaluating the results. Furthermore, some applications of the diagnostic systems DPV-2000 and Accuraspray-g3 are shown. Finally some application limits, which were identified for certain powder compositions at higher plasma power levels will be discussed.     

Calculating nonlinear microwave circuits with undersampled time signals

An algorithm to reduce the computation time and storage space required during the analysis of microwave circuits with two or more nonharmonically related input frequencies is presented. It is very simple to implement in harmonic balance programs.<>     

Radiographic course after acetabuloplasty and femoral osteotomy in hip dysplasia

The radiographic course of 101 hips with residual dysplasia treated with roof plasty combined with intertrochanteric varus derotation osteotomy using the osteotomy wedge as a roof graft after Mittelmeier were reviewed. The average followup period was 8.8 years. The acetabular angle was improved by an average of 16 degrees (postoperative mean, 19 degrees; average at followup, 18 degrees). The center edge angle also was improved by 16 degrees and was stable at 25 degrees average at followup. The neck shaft angle, abnormal in 70% of hips preoperatively, was reduced by the varus osteotomies to a mean of 111 degrees and showed a spontaneous postoperative increase to normal values of an average of 129 degrees. There was no correlation of the postoperative of the neck shaft angle to patient age, preoperative valgus extension, correction angle, or length of followup. In nearly all cases, an almost anatomic joint shape was achieved. With a complication rate of only 1%, especially regarding the rate of necroses of the femoral head, the presented surgical technique can be recommended as highly effective, reliable, and safe for the treatment of congenital hip dislocation.     

Grain Size Control in Low-Voltage Varistors

Low-voltage ZnO varistors often suffer from a large spread in the current/voltage characteristics, due to discontinuously grown, inhomogeneous microstructures. Addition of seed grains to the ceramic powder is an effective means of preventing the growth of single large grains, thus making the control of final grain size and electrical properties much easier. Seed grains are generally single-crystalline particles of the same composition with a grain size which is considerably larger than the average grain size of the starting ZnO powder.     

Nutritional and toxicological study of rats fed a diet containing tin (author's transl)

A toxicological, nutritional and histological study of rats on a diet containing 0.5 g of tin (Sn Cl2) per 100 g of dry food for one month has been made. By gamma radioactivity measurements (with 113Sn used as a tracer) it is shown that this metal does not practically clear the digestive barrier. Otherwise the classical coefficients of nitrogen nutrition and the urinary parameters (volume, glucose, pH) are not influenced; but the growth of treated animals is obviously slower than control animals because of their reduced ingestion of food. Moreover after one month of treatment a marked anaemia results since the hematocrit and hemoglobin levels are perceptibly reduced. Lastly the histological investigations give evidence of notable irritation of the total gastrointestinal tract. This study, as that of many authors, raises the question of present permissible levels of tin (up to 250 ppm) in foods.