Jens Klimke - Academia.edu (original) (raw)

Papers by Jens Klimke

2022 International Conference Laser Optics (ICLO)

The invention relates to a compact, electrodeless, low pressure gas discharge lamp which is chara... more The invention relates to a compact, electrodeless, low pressure gas discharge lamp which is characterised by a long shelf life and high light efficiency and light density. The inventive gas discharge lamp comprises a ball-shaped, ring-shaped, pear-shaped or ellipsoidal glass body which is used as a gas discharge receptacle, on the inner gas surface of which a layer containing at least two luminous substances is applied. The side of the glass bulb facing the gas discharge and/or the layer containing luminous matter and exposed to the gas discharge in the discharge receptacle are coated with a chemically, largely inert protective layer consisting of an oxide. The electrical energy is introduced into the discharge receptacle in an inductive manner using a ring-shaped closed ferrite core, preferably MnZn soft ferrite, which is partially located inside the discharge receptacle and is provided with a primary winding which is connected to an RF source in the frequency region of between 100...

The present invention relates to the field of ceramics and to a corundum which is due to its opti... more The present invention relates to the field of ceramics and to a corundum which is due to its optical properties to imitate colored Korundedelsteinen (rubies and sapphires), and a process for producing molded articles made of this material. The invention has for its object to develop a corundum having a lowest possible grain size of the corundum and a homogeneous distribution of the coloring doping. The object is achieved by a colored transparent corundum polycrystalline sub-micron microstructure an average particle size <1 micron, wherein the transmission spectrum of the one from the spectrum of not provided with color-providing doping at least 99.95% pure submicron-Korundmaterials by the occurrence of absorption due to reduced transmission in one or more parts of the visible spectrum differs, so that a visually recognizable colouration of the material is caused.

Verfahren zur Herstellung von redispergierbarem hochreinem Nanospinellpulver mit spezifischer Obe... more Verfahren zur Herstellung von redispergierbarem hochreinem Nanospinellpulver mit spezifischer Oberflache zwischen 50 und 125 m 2 /g und der Fahigkeit zur Herstellung hochtransparenter Sinterkeramik, bei dem Al- und Mg-enthaltende Ausgangsstoffe eingesetzt werden, wobei mindestens einer dieser Al- und/oder Mg-enthaltenden Ausgangsstoffe gelost wird, und der Losung komplexbildende Liganden zugegeben werden, der Ansatz dann unter Ruhren bei Temperaturen von 70–95°C hydrolysiert wird, danach eine Alterung durchgefuhrt werden kann, nachfolgend eine Trocknung der Materialien durchgefuhrt wird, dann die so erhaltenen Pulver bei Temperaturen von 900–1150°C kalziniert werden und diese dann einer Dispergierungsmahlung unterworfen werden.

Solid State Ionics, 1996

The influence of the oxidic boundary layer on the electrode potential behaviour of gold electrode... more The influence of the oxidic boundary layer on the electrode potential behaviour of gold electrodes with the solid electrolyte Zr0.86Y0.14O1.93 (YSZ) at temperatures ≤ 700 °C in gases containing oxygen and combustible components was investigated. The interface between gold and the solid electrolyte was chemically modified with TiO2 which was produced in two states (as a surface coating and dissolved

Materials Science Forum, 2000

SPIE Proceedings, 2011

ABSTRACT MgAl2O4 is a candidate for sintered windows, domes and lenses for UV, visible, and IR ap... more ABSTRACT MgAl2O4 is a candidate for sintered windows, domes and lenses for UV, visible, and IR applications. However, exact Mie calculation shows that for imaging uses with a window thickness of e.g. 5 mm even IR transmission will not tolerate smallest amounts of 0.01% of 50-100 nm small pores, and the impact of such pores is even worse at shorter wave lengths. Principles of solid state sintering suggest that smallest pores should be eliminated more easily than larger ones. It is, however, observed that a significant population of 50-100 nm small nanopores exists in undoped transparent spinel ceramics after hot-isostatic pressing with the higher concentration the finer the particles of the raw spinel powder are. On the other hand, it is demonstrated that sintering densification is governed not only by the size of the ceramic powder particles and the homogeneity of their mutual coordination but also by the state of the crystal lattice. Taking advantage of this latter effect, sintered spinel ceramics were derived by reactive sintering of undoped MgO/Al2O3 mixtures resulting in an in-line transmittance which fits comparable spinel single crystals from 200nm wave length up to the IR range.

$Research paper thumbnail of Investigation of titanium silicide formation in Ti+Si reactions using infrared spectroscopy and x-ray diffraction$

Journal of Applied Physics, 1995

Infrared (IR)-absorbance spectroscopy was investigated as a technique for monitoring titanium sil... more Infrared (IR)-absorbance spectroscopy was investigated as a technique for monitoring titanium silicide formation during the reaction of Ti films on (100) Si substrates. Films annealed to various stages of reaction were monitored by x-ray diffraction, film resistivity, and optical reflectance in order to relate the changes in the IR-absorbance spectra to reaction progress. Films at different stages of reaction showed distinctly different extinction coefficients α, and absorbance versus wave-number curves. IR absorbance was determined to be a useful indicator of reaction progress, especially in those cases where samples at different stages of the silicidation reaction have the same resistance but different absorbance behaviors.

Journal of the European Ceramic Society, 2018

Targeting higher toughness transparent ceramics, tetragonal (3 mol % yttria) and cubic (8 mol % y... more Targeting higher toughness transparent ceramics, tetragonal (3 mol % yttria) and cubic (8 mol % yttria) ZrO 2 starting powder mixtures were densified by spark plasma sintering (SPS) in vacuum at 1100°C and post hot isostatic pressing (HIP) in argon at 1100°C. The influence of the ultra-fine microstructure and phase composition on the fracture resistance and light transmission in the visible and infra-red range was assessed. Of special interest was the influence of a thermal annealing step in air on the transparency of the SPS and SPS-HIP ceramics.

Optical Materials, 2014

ABSTRACT

Journal of the European Ceramic Society, 2016

In order to increase the in-line transmission of fine transparent alumina in visible light the gr... more In order to increase the in-line transmission of fine transparent alumina in visible light the grain growth during sintering of alumina ceramics was supressed using a combined densification process. This process combines presintering of a green body by spark plasma sintering with final hot isostatic pressing. The presintering by spark plasma sintering provided bodies with a substantially smaller grain size than pressureless presintering. It is shown that the fine-grained presintered microstructure could be retained during final hot isostatic pressing and alumina ceramics doped with spinel and zirconia nanoparticles in particular could be sintered to full density with only minor grain growth during final hot isostatic pressing. The novel combined densification process enhanced by the unique nanoparticle doping approach provided fully dense alumina ceramics with an average grain size of 237 nm and an in-line transmission of 76.2% at a wavelength of 632.8 nm and a sample thickness of 0.8 mm.