Porous Graphene-like Carbon from Fast Catalytic Decomposition of Biomass for Energy Storage Applications

A novel carbon material made of porous graphene-like nanosheets was synthesized from biomass resources by a simple catalytic graphitization process using nickel as a catalyst for applications in electrodes for energy storage devices. A recycled fiberboard precursor was impregnated with saturated nickel nitrate followed by high-temperature pyrolysis. The highly exothermic combustion of in situ formed nitrocellulose produces the expansion of the cellulose fibers and the reorganization of the carbon structure into a three-dimensional (3D) porous assembly of thin carbon nanosheets. After acid washing, nickel particles are fully removed, leaving nanosized holes in the wrinkled graphene-like sheets. These nanoholes confer the resulting carbon material with ≈75% capacitance retention, when applied as a supercapacitor electrode in aqueous media at a specific current of 100 A·g–1 compared to the capacitance reached at 20 mA·g–1, and ≈35% capacity retention, when applied as a negative electrode for lithium-ion battery cells at a specific current of 3720 mA·g–1 compared to the specific capacity at 37.2 mA·g–1. These findings suggest a novel way for synthesizing 3D nanocarbon networks from a cellulosic precursor requiring low temperatures and being amenable to large-scale production while using a sustainable starting precursor such as recycled fiberwood.Spanish Government Agency Ministerio de Economí a y Competitividad (MINECO) (grant number MAT2016-76526-R)

Microstructure, mechanical properties and cracking behaviour in a gamma'-precipitation strengthened nickel-base superalloy fabricated by electron beam melting

The influences of EBM processing and post-processing on microstructure, mechanical properties and cracking behaviour in a γ′ precipitation-strengthened nickel-base superalloy DZ125 are critically assessed. Results show that a solution treating and ageing (STA) is required to obtain γ′ precipitates with a cuboidal shape. The columnar grain width was found to gradually increase from the bottom to the top of the as-EBM sample having a total build height of 80 mm, whereas there was little gradient in γ′ size. The presence of EBM induced intergranular cracks can be closed by hot isostatic pressing (HIP), however reappearance of intergranular cracks with a much wider crack opening width was observed after STA treatment. EBM induced cracks are classified as liquid-state cracking, as the classic dendritic morphology were found on the cracked surfaces. The post-processing induced cracks can be attributed to the effect of γ′ dissolution and re-precipitation of fine γ′ during the cooling stage of solution treatment. The results suggest that HIP is not an effective approach in healing liquid-state cracks in EBM fabricated γ′ precipitation-strengthened superalloys

Digitale Teilhabe

Das Themenheft Digitale Teilhabe beschäftigt sich zentral mit den Potentialen der Nutzung der neuen Informations- und Kommunikationstechnologien durch benachteiligte Menschen. Im Leitartikel wird der Versuch unternommen, mögliche theoretische Anknüpfungspunkte und Forschungsfragen für weitere Studien- und Forschungsarbeiten in dem noch jungen Themenfeld der Digitalen Teilhabe zu identifizieren. Hierzu wird zunächst das zugrunde liegende Verständnis von Behinderung/Benachteiligung diskutiert und inklusive (Medien-)Bildung als Teil der Persönlichkeitsbildung skizziert. In verschiedenen Diskursen bzw. Disziplinen werden dann theoretische Anknüpfungspunkte für weitere Forschungsarbeiten benannt. Die Idee für das Themenheft ist im Rahmen des Projekts "Begleitforschung im PIKSL-Labor" des Zentrums für Planung und Evaluation Sozialer Dienste der Uni Siegen (ZPE) entstanden. Das PIKSL-Projekt zielt darauf ab, Menschen mit Behinderungen moderne Kommunikationstechnologien zugänglich zu machen, um ihnen Teilhabemöglichkeiten zu erleichtern und zugleich die personale Abhängigkeit von professioneller Unterstützung zu reduzieren. Der inter- und transdisziplinäre Ansatz von PIKSL wird durch die Vielfalt der Artikel in dem Heft deutlich: Digitale Teilhabe wird nicht alleine aus (medien-)pädagogischer bzw. sozialwissenschaftlicher Perspektive betrachtet. Die Besonderheit liegt in der Kooperation unterschiedlicher Disziplinen wie Soziale Arbeit, Kunst und Webdesign

Combining 2D and 3D characterization techniques for determining effects of HIP-rejuvenation after fatigue testing of SX microstructures

A hot isostatic pressing rejuvenation heat treatment is applied to a CMSX-4 type SX superalloy after it has been subjected to a low cycle fatigue test to rupture. The evolution of microstructural defects, such as pores and cracks which are present after fatigue, has been tracked in 3D by X-ray tomography before and after rejuvenation. From the rejuvenated specimen series of metallographic cross sections were prepared and investigated by scanning electron microscopy for getting complementary 2D information at high resolution. The micrographs were stitched to a panorama which was then matched into the 3D representation of the specimen volume. By combining 3D and 2D data, statistical volume related quantities were achieved while detailed characteristics have been assigned to individual defects present in the 2D panorama micrograph. This technique is in general appropriate for length-scale bridging microstructural investigations. Results of the performed investigations concerning the rejuvenation effect on the microstructure are presented and discussed

Assessment on the Use of High Capacity “Sn4_{4}P3_{3}”/NHC Composite Electrodes for Sodium-Ion Batteries with Ether and Carbonate Electrolytes

This work reports the facile synthesis of a Sn–P composite combined with nitrogen doped hard carbon (NHC) obtained by ball-milling and its use as electrode material for sodium ion batteries (SIBs). The “Sn$_{4}$P$_{3}$”/NHC electrode (with nominal composition “Sn$_{4}$P$_{3}$”:NHC = 75:25 wt%) when coupled with a diglyme-based electrolyte rather than the most commonly employed carbonate-based systems, exhibits a reversible capacity of 550 mAh g$_{electrode}$$^{−1}$ at 50 mA g$^{−1}$ and 440 mAh g$_{electrode}$$^{−1}$ over 500 cycles (83% capacity retention). Morphology and solid electrolyte interphase formation of cycled “Sn$_{4}$P$_{3}$”/NHC electrodes is studied via electron microscopy and X-ray photoelectron spectroscopy. The expansion of the electrode upon sodiation (300 mAh g$_{electrode}$$^{−1}$) is only about 12–14% as determined by in situ electrochemical dilatometry, giving a reasonable explanation for the excellent cycle life despite the conversion-type storage mechanism. In situ X-ray diffraction shows that the discharge product is Na$_{15}$Sn$_{4}$. The formation of mostly amorphous Na$_{3}$P is derived from the overall (electro)chemical reactions. Upon charge the formation of Sn is observed while amorphous P is derived, which are reversibly alloying with Na in the subsequent cycles. However, the formation of Sn$_{4}$P$_{3}$ can be certainly excluded

Assessment on the use of high capacity “Sn 4 P 3 ”/NHC composite electrodes for sodium‐ion batteries with ether and carbonate electrolytes

This work reports the facile synthesis of a Sn–P composite combined with nitrogen doped hard carbon (NHC) obtained by ball-milling and its use as electrode material for sodium ion batteries (SIBs). The “Sn4P3”/NHC electrode (with nominal composition “Sn4P3”:NHC = 75:25 wt%) when coupled with a diglyme-based electrolyte rather than the most commonly employed carbonate-based systems, exhibits a reversible capacity of 550 mAh gelectrode−1 at 50 mA g−1 and 440 mAh gelectrode−1 over 500 cycles (83% capacity retention). Morphology and solid electrolyte interphase formation of cycled “Sn4P3”/NHC electrodes is studied via electron microscopy and X-ray photoelectron spectroscopy. The expansion of the electrode upon sodiation (300 mAh gelectrode−1) is only about 12–14% as determined by in situ electrochemical dilatometry, giving a reasonable explanation for the excellent cycle life despite the conversion-type storage mechanism. In situ X-ray diffraction shows that the discharge product is Na15Sn4. The formation of mostly amorphous Na3P is derived from the overall (electro)chemical reactions. Upon charge the formation of Sn is observed while amorphous P is derived, which are reversibly alloying with Na in the subsequent cycles. However, the formation of Sn4P3 can be certainly excluded

Sozialmanagement - Professionalisierungsschub für die Soziale Arbeit oder feindliche Übernahme durch die BWL?

Der Begriff ‚Sozialmanagement‘ weckt auf den ersten Blick Assoziationen zu den klassischen Tugenden eines ehrbaren Kaufmannes. Doch selbst wenn sich innerhalb der Praxis Sozialer Arbeit an der einen oder anderen Stelle zutreffende Beispiele für solch einen Handlungstypus ausfindig machen lassen, verdeutlicht der Begriff ‚Sozialmanagement‘ vielmehr die folgende Entwicklung bzw. kann dafür als charakteristisch angesehen werden: „Wirtschaftlichkeit, d.h. die Beachtung ökonomischer Kriterien, Kosten-Nutzen-Abgleich u.ä, hat sich in den letzten Jahren zu einem zentralen Thema Sozialer Arbeit entwickelt“ (Lange 2000, S. 74)