Ralf Andreas Furche - Academia.edu (original) (raw)

Uploads

Papers by Ralf Andreas Furche

Physics and Chemistry of Minerals, 1998

Polarized electronic absorption spectra, Eka(kX), Ekb(kY) and Ekc(kZ), in the energy range 3000±5... more Polarized electronic absorption spectra, Eka(kX), Ekb(kY) and Ekc(kZ), in the energy range 3000±5000 cm ±1 were obtained for the orthorhombic thenardite-type phase Cr 2 SiO 4 , unique in its Cr 2+-allocation suggesting some metal-metal bonding in Cr 2+ Cr 2+ pairs with Cr-Cr distance 2.75 along [001]. The spectra were scanned at 273 and 120 K on single crystal platelets k(100), containing optical Y and Z, and k(010), containing optical X and Z, with thicknesses 12.3 and 15.6 mm, respectively. Microscope-spectrometric techniques with a spatial resolution of 20 mm and 1 nm spectral resolution were used. The orientations were obtained by means of Xray precession photographs. The xenomorphic, strongly pleochroic crystal fragments (X deeply greenish-blue, Y faint blue almost colourless, Z deeply purple almost opaque) were extracted from polycrystalline Cr 2 SiO 4 , synthesized at 35 kbar, above 1440 C from high purity Cr 2 O 3 , Cr (10% excess) and SiO 2 in chromium capsules. The Cr 2 SiO 4-phase was identified by X-ray diffraction (XRD). Four strongly polarized bands, at about 13500 (I), 15700 (II), 18700 (III) and 19700 (IV) cm ±1 , in the absorption spectra of Cr 2 SiO 4 single crystals show properties (temperature behaviour of linear and integral absorption coefficients, polarization behaviour, molar absorptivities) which are compatible with an assignment to localized spin-allowed transitions of Cr 2+ in a distorted square planar coordination of point symmetry C 2. The crystal field parameter of Cr 2+ is estimated to be 10 Dq910700 cm ±1. A relatively intense, sharp band at 18400 cm ±1 and three other minor features can, from their small half widths, be assigned to spin-forbidden dd-transitions of Cr 2+. The intensity of such bands strongly decreases on decreasing temperature. The large half widths, near 5000 cm ±1 of band III are indicative of some Cr-Cr interactions, i.e. d-d* transitions of Cr 4 2 , whereas the latter alone would be in conflict with the strong polarization of bands I and II parallel [100]. Therefore, it is concluded that the spectra obtained can best be interpreted assuming both dd-transitions of localized d-electrons at Cr 2+ as well as d-d* transitions of Cr 4 2 pairs with metal-metal interaction. To explain this, a dynamic exchange process 2 Cr 2 loc D Cr 4 2Ycpl is suggested wherein the half life times of the ground states of both exchanging species are significantly longer than those of the respective optically excited states, such that the spectra show both dd-and d-d*transitions.

Calcination of appropriate Cu/Zn hydroxycarbonates to the mixed oxides is a crucial step in the c... more Calcination of appropriate Cu/Zn hydroxycarbonates to the mixed oxides is a crucial step in the catalysts preparation of Cu/ZnO catalysts. Conventionally, calcination is performed in the presence of oxygen. It is assumed that during calcination at mild temperatures CuO and ZnO are modified by ad-mixed OH and CO3 groups [1, . These ad-mixed groups may serve as growth inhibitors of defect rich Cu particles in the final catalyst required for superior activity in methanol steam reforming. Therefore, calcination in the presence of CO2 may retain some particular ad-mixed carboxyl groups in the working Cu/ZnO catalyst in methanol steam reforming. Here, bulk structural investigation during calcination in different gas atmospheres (O2, CO2, He) on the microstructure of Cu/ZnO catalysts were investigated by using two complementary methods in situ X-ray diffraction (XRD) and in situ X-ray absorption spectroscopy (XAS) combined with online mass spectrometry.

This Deliverable, D7.2, is part of Work Package 7 "Training and Engagement" which aims ... more This Deliverable, D7.2, is part of Work Package 7 "Training and Engagement" which aims to expand the service portfolio and widen service coverage for new user communities. The new user communities include the fields of social sciences and humanities; built heritage; palaeontology and palaeoanthropology; and archaeology. These are widely varying and disparate groups, with different types of internal organisation and different degrees of coordination as well as different levels of engagement with scientific research. Here, we propose a plan for engagement with new communities. Some strategies are common to the four new user communities. This maximises effectiveness and impact, and minimises duplication. It will also allow us to easily extend our strategy to any further future new user groups. However, we recognise that the differences between the groups mean that we will need flexible strategies that take into account these dissimilarities. In all cases, we recognise the imp...

The essential aim of Task 7.1 is to provide targeted training to develop suitably skilled individ... more The essential aim of Task 7.1 is to provide targeted training to develop suitably skilled individuals and to raise awareness amongst potential users of the benefits of using IPERION HS facilities. To this purpose, it has been decided to organize two Doctoral Summer Schools (HS-DSS) and two Training Camps (HS-TC) aimed at developing highly skilled professionals in the wider heritage research community, fostering cooperation between the academic community and heritage and research institutions. Several online meetings have been organized in order to discuss and decide about the curricula and dates of the training activities. Given the uncertainty linked with the ongoing pandemic, it was decided that the first HS-DSS will be delivered virtually in July 2021, whereas the first HS-TC will be implemented in person in 2022 when it is expected the current travel restrictions will not be active anymore. The first HS-DSS will mainly report on successful TNA and JRA achieved during the IPERION...

Carbon, 2009

Carbon nanofibers (CNFs) were grown via the chemical vapor deposition of C2H4 on an activated car... more Carbon nanofibers (CNFs) were grown via the chemical vapor deposition of C2H4 on an activated carbon (AC)-supported Ni catalyst. The texture of the CNF/AC composites can be tuned by varying the growth temperature and by treatment in reducing atmosphere prior to C2H4/H2 exposure. The Ni-catalyzed gasification of the AC support increases the microporosity of the composite and shown to be dominant throughout the composite synthesis especially during reduction, subsequent treatment in reducing atmosphere, and CNF growth at low temperatures. N2 isotherm and scanning electron microscope were used to characterize the texture and morphology of the composites. Subsequent treatment in reducing atmosphere were shown to increase the Ni catalyst activity to grow CNFs. High resolution transmission electron microscope however did not reveal any microstructural difference for Ni catalyst with and without the subsequent reduction treatment. We propose in this paper that the carbon dissolutions during treatment of the catalyst might have an implication on the CNF growth. Controlling the yield and structure of carbon nanofibers grown on a nickel/activated carbon catalyst, A. Rinaldi et al.., Carbon 47 (2009), 3022-3033

Physics and Chemistry of Minerals, 1998

Carbon, 2009