DECHEMA

About: DECHEMA is a nonprofit organization based out in Frankfurt am Main, Germany. It is known for research contribution in the topics: Corrosion & Oxide. The organization has 756 authors who have published 1307 publications receiving 25693 citations.

Cellulose solubilities in carboxylate-based ionic liquids

Abstract: The dissolution of cellulose allows easier processing of this important biogenic feedstock For this, ionic liquids have been proposed Carboxylate-based ionic liquids were identified as the most promising lead towards a high dissolution property Three homologous series of all 27 combination of the three cations: 1-ethyl-3-methylimidazolium, 1,3-dimethylimidazolium, and N,N-diethyl-N,N-dimethylammonium with nine carboxylates as anions were synthesised The cellulose solubilities of the 17 ionic liquid compounds (liquid below 373 K) were measured Up to 18 wt% for 1-ethyl-3-methyl-imidazolium propionate was achieved, slightly higher than when using acetate as the anion Generally, the solubilities determined for carboxylate-based ionic liquids with imidazolium cations were found to be in the same range, whereas those with quaternary ammonium cations were found to be poor solvents for cellulose Dicarboxylates gave higher solubilities compared to monocarboxylates Regenerated ionic liquids had no apparent difference to fresh ones

Development of a Comprehensive Oxide Scale Failure Diagram

Abstract: This paper describes a new approach towards the development of a comprehensive oxide scale failure diagram (OSFD) that delineates the mechanical limits of scales for the different types of failure mechanisms. While former diagrams of a similar type were based on relating the critical strain to scale failure to oxide scale thickness, the new approach replaces scale thickness with a comprehensive operational parameter ωo that summarizes in a multi-level treatment all contributing factors, e.g. physical defect size, interface roughness, scale thickness, Young’s modulus, fracture toughness, etc., that influence failure strain. While this approach should ideally be based on a comprehensive treatment of ωo using fully implemented coding, further considerations based on the identification of “low-impact” and “high-impact” parameters lead to a simplified OSFD where only the physical defect size is needed. This simplified approach can be used to assess the strain tolerance of oxide scales in industrial operation once the particular diagram has been established from laboratory data.

Role of growth stresses on the structure of oxide scales on nickel at 800 and 900°C

Abstract: The development and relief of intrinsic growth stresses in oxide scales on nickel of different purity have been investigated by combining the deflection test in monofacial oxidation (DTMO) with acoustic-emission analysis (AE). Parallel metallographic analysis gave information about the development of the physical- defect structure and all other structural features. The investigations were performed for 100 hr at 800 as well as 900°C in air. The assumption of elastic behavior led to the best correlation between models, literature data, and results of the present investigations. Microcracks are responsible for the relief of growth stress and inward oxygen penetration leads to the typical NiO duplex scale. The growth of the microcracks is initiated at large pore populations at the oxide–metal interface that most probably form due to outward cation-diffusion and vacancy condensation. The pore formation is increased by the presence of impurities. An equilibrium of microcracking and crack healing is finally reached, leading to a continuous growth of the inner and outer NiO layers of the duplex scale. The scale growth stresses are mainly compressive and can reach maximum values of −560 MPa at 900°C. An estimation of the fracture toughness of the oxide–metal interface assuming a wavy interface led to a KIc value of about 2 MNm-3/2 at 900°C