Influence of the Addition of Bi2O3 on the Grain Growth and Magnetic Permeability of MnZn Ferrites

Additions of Bi₂O₃ were used to promote grain growth and to increase magnetic permeability during sintering of MnZn ferrites. The results showed that small additions of Bi₂O₃ of <0.05 wt% remarkably increase the permeability of MnZn ferrites. On the other hand, addition of 0.05 wt% Bi₂O₃ induced the formation of a microstructure composed of giant grains with trapped pores embedded in a normal microstructure. The permeability of these samples showed a pronounced secondary maximum in permeability. At still higher Bi₂O₃ concentrations, above 0.2 wt%, the grain growth was retarded and a normal microstructure appeared; however, the magnetic permeability was strongly reduced.     

Slovenia: a new generation

During the Soviet era, Slovenia was renowned as an architectural oasis for experimentation on the western borders of eastern European greyness. Miha Desman describes how this small but significant nation has maintained its taste for design innovation, despite the shifting economic and political conditions of the past two decades. He outlines what present-day Slovenia has to offer a greater Europe and the special qualities of its contemporary architecture. Copyright © 2006 John Wiley & Sons, Ltd.     

Engineered invasive plant cellulose fibers as resources for papermaking

Seven fast-growing invasive plant species were harvested in Slovenia and tested for their valorisation potential in the pulp and paper industry with the aim of sustainable substitution of commercial cellulose fibres. Cellulose fiber materials were isolated by filtration after solubilizing extractives, lignin and hemicellulose in a kraft pulping process. The chemical structure was thoroughly studied, as well as the optical, morphological and mechanical properties. All examined species (Ailanthus altissima, Fallopia bohemica, Fallopia japonica, Rhus typhina, Robinia pseudoacacia, Rudbeckia laciniata and Solidago canadensis) contain relatively high amount of C6 polysaccharides (>?35%), have notable hemicellulose content (30–40%), low ash content (<?2%) and can be easily delignified, while manufactured natural fibers exhibit convenient morphology (fiber length 0.47–0.88 mm; width 14.4–20.9 μm), optical (ISO whiteness 19.0–36.0%) and mechanical characteristics (tensile index 18.0–58.0 Nm/g; tear index 0.8–4.1 mN m²/g; and burst index 0.5–2.4 kPa m²/g indices), which makes them applicable to sustainable paper production. The pulp yields varied between 34–44%, where both darker herbaceous and brighter woody fibers were morphologically comparable to typical hardwoods. According to the observed properties Robinia pseudoacacia and Rudbeckia laciniata seem to be superior raw material for commercial papermaking products. The ubiquitous invasive plants pose a huge potential for the circular economy, especially in terms of their cascade valorisation of biorefinery by the isolation and valorization of hemicellulose, sugars, and lignins into added-value aromatic and aliphatic building blocks. However, promising yield of cellulose fibers of decent morphology and mechanical properties are reported in this study.

     

Finite Element Multi-scale Modeling of Chemical Segregation in Steel Solidification Taking into Account the Transport of Equiaxed Grains

Metallurgical and Materials Transactions A - The transport of solid crystals in the liquid pool during solidification of large ingots is known to have a significant effect on their final grain...     

A Simplified Three-Phase Model of Equiaxed Solidification for the Prediction of Microstructure and Macrosegregation in Castings

Macrosegregation is a result of the interplay of various transport mechanisms, including natural convection, solidification shrinkage, and grain motion. Experimental observations also indicate the impact of grain morphology, ranging from dendritic to globular, on macrosegregation formation. To avoid the complexity arising due to modeling of an equiaxed dendritic grain, we present the development of a simplified three-phase, multiscale equiaxed dendritic solidification model based on the volume-averaging method, which accounts for the above-mentioned transport phenomena. The validity of the model is assessed by comparing it with the full three-phase model without simplifications. It is then applied to qualitatively analyze the impact of grain morphology on macrosegregation formation in an industrial scale direct chill cast aluminum alloy ingot.     

Recycling of waste Nd-Fe-B sintered magnets by doping with dysprosium hydride nanoparticles

Recycling of waste sintered Nd-Fe-B permanent magnets by doping DyH3 nanoparticles was investigated. The effect of the DyH3 nanoparticles on the microstructure and magnetic properties of the recycled m...     

PTCR anomaly in barium-titanate-based composites

We have identified a PTCR anomaly in undoped BaTiO₃ (BT) ceramics. This anomaly was ascribed to a disconnection of the semiconducting grains, due to dimensional changes of the BT grains at the Curie point, in a composite composed of two constituent BT phases, one with a low electrical resistivity and the other with a high electrical resistivity. The composite exhibits a significant PTCR effect of three orders of magnitude at the Curie temperature.     

Comparison Between Genetic Algorithm and Genetic Programming Approach for Modeling the Stress Distribution

This article compares genetic algorithm (GA) and genetic programming (GP) for system modeling in metal forming. As an example, the radial stress distribution in a cold-formed specimen (steel X6Cr13) was predicted by GA and GP. First, cylindrical workpieces were forward extruded and analyzed by the visioplasticity method. After each extrusion, the values of independent variables (radial position of measured stress node, axial position of measured stress node, and coefficient of friction) were collected. These variables influence the value of the dependent variable, radial stress. On the basis of training data, different prediction models for radial stress distribution were developed independently by GA and GP. The obtained models were tested with the testing data. The research has shown that both approaches are suitable for system modeling. However, if the relations between input and output variables are complex, the models developed by the GP approach are much more accurate.