Correlation between micro-structural properties and ionic conductivity of Li1.5Al0.5Ge1.5(PO4)3 ceramics

We report on the structure and lithium ion transport properties of Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP). This material is commercially available and is prepared as amorphous powders via a flame spray technique called Flash Creation Method (FCM). We crystallize and sinter the amorphous powders at different temperatures in order to alter grain size and grain boundary properties. The structure is then characterized by means of powder X-ray diffraction, atomic force microscopy, scanning electron microscopy and transmission electron microscopy with energy dispersive X-ray spectroscopy. AC impedance spectroscopy is used to study lithium ion transport. A maximum total conductivity of 2 × 10⁻⁴ S cm⁻¹ at room temperature is found for a sample sintered at 750 °C for 2 h. In order to distinguish between grain and grain boundary contributions to the impedance spectra, equivalent circuit fits are carried out. The results are analysed in the framework of the classical brick layer model and of a finite-element approach taking into account non-ideal grain contacts. Our experimental results for the grain and grain boundary resistances are in good agreement with the predications of the finite-element approach.     

Glasdach Mensa und Rektorat der Technischen Universität Dresden

Glass Roof of the refectory and the rectorate at the Technische Universität Dresden. A Glass Roof has been erected during the modernisation of the refactory and the rectorate of the Technische Universität Dresden. The design and the planning process of the undirected glass roof with the structural use of glass beams are explained. This paper describes the tests for an individual approval for the use of glass in the roof construction that is not regulated in building codes. There are further emphasises the manufacture, the production and the assembly of the glass roof.     

Simulation of Mould Level Velocities During Continuous Casting of Round Bloom Strands With Mould-Electromagnetic Stirring

In modern continuous casting of round steel blooms rotating electromagnetic fields are commonly employed to improve the product quality.Mould-electromagnetic stirrers(M-EMS)are used to excite a rotary motion along the solidification front in the liquid core.These velocities lead to a better strand surface quality as well as enhancing the transition from columnar to equiaxed solidification.Although the usage of electromagnetic stirrers is widespread,not all effects are fully known or understood.Due to harsh conditions at the plant,measurements are scarce and limited.Water model experiments-an established alternative for investigating continuous casting of steel-cannot be used due to the low electrical conductivity of water.Experiments with liquid metals like mercury,Galinstan or Wood’s metal are either expensive or difficult to perform.Thus numeric simulations are essential to gain a better understanding of the processes involved in continuous casting with electromagnetic stirring.However numeric simulations should always be validated with experiments and/or measurements.While the velocity field inside the liquid core of the bloom cannot be measured at the caster,the velocity at the mould level can be measured by dipping a nail into it.The skull forming at the tip of the nail is directly linked to the occurring surface velocity.These measurements can then be compared with numeric simulations of the nail dipping process.The numeric model is restricted to the upper part of the strand.The lower part of the strand is also taken into account through adjusted boundary conditions(velocity field etc.taken from a simulation of the whole strand).In this work the influence of the stirring field strength on the simulation results will be investigated.In the future these nail dipping simulations will be validated with plant measurements.This can then to a certain extentvalidate the simulation of the strand with M-EMS too,as it serves as the basis for the nail dipping model.     

生产微合金化钢的几点考虑

在20世纪60～80年代,连续浇铸是钢铁工业的一项重要的工艺变革。这项技术无论对提高炼钢生产效率还是改善产品质量都产生了深刻的影响。然而,为保持产品竞争力和成本效益,需要一个统筹的炼钢方法。从铁水生产开始或者从冶炼开始,经过精炼到连铸,再到轧钢和后续工序,钢产品的整条生产路线应该整体可控。关于连铸,有2个实例可以说明这种发展趋势:改进中间包设计和冶金技术,优化浸入式水口和高水平的结晶器液面控制。无止境的洁净钢研究已经从连铸机本身转到钢包冶金。同样,无缺陷表面质量研究不再简单地专注于连铸技术,同时也将炼钢考虑进去。随着结构钢品种的合金设计转变,从普通的中碳锰钢到裂纹敏感的现代低碳微合金化HSLA钢,连铸机的设计和技术发展并驾齐驱。