Continuous‐Flow Asymmetric Hydrogenation of the β‐Keto Ester Methyl Propionylacetate in Ionic Liquid–Supercritical Carbon Dioxide Biphasic Systems

A continuous‐flow process for the asymmetric hydrogenation of methyl propionylacetate as a prototypical β‐keto ester in a biphasic system of ionic liquid and supercritical carbon dioxide (scCO₂) is presented. An established ruthenium/2,2′‐bis(diphenylphosphino)‐1,1′‐binaphthyl (BINAP) catalyst was immobilised in an imidazolium‐based ionic liquid while scCO₂ was used as mobile phase transporting reactants in and products out of the reactor. The use of acidic additives led to significantly higher reaction rates and enhanced catalyst stability albeit at slightly reduced enantioselectivity. High single pass conversions (>90%) and good enantioselectivity (80–82% ee) were achieved in the first 80 h. The initial catalyst activity was retained to 91% after 100 h and to 69% after 150 h time‐on‐stream, whereas the enantioselectivity remained practically constant during the entire process. A total turnover number of ∼21,000 and an averaged space‐time yield (STY_av) of 149 g L⁻¹ h⁻¹ were reached in a long‐term experiment. No ruthenium and phosphorus contaminants could be detected via inductively coupled plasma optical emission spectrometry (ICP‐OES) in the product stream and almost quantitative retention by the analysis of the stationary phase was confirmed. A comparison between batch‐wise and continuous‐flow operation on the basis of these data is provided.     

Reverted austenite in PH 13-8 Mo maraging steels

The mechanical properties of maraging steels are strongly influenced by the presence of reverted austenite. In this study, the morphology and chemical composition of reverted austenite in a corrosion resistant maraging steel was characterized using transmission electron microscopy (TEM) and atom probe tomography (APT). Two types of austenite, i.e. granular and elongated, are present after aging at 575 °C, whereby the content of the latter increases during aging. The investigations revealed that the austenite phase is enriched in Ni, which prevents the transformation to martensite during cooling. Inside and next to the austenitc areas, Mo and Cr-rich carbides, which form during the aging treatment, were found. Various aging treatments were performed to obtain the activation energy for the formation of reverted austenite. Additionally, the experimental data are compared with thermodynamic and kinetic simulations. Based on these results and the chemical composition changes of the phases, a model for the formation of reverted austenite is presented. It is concluded that precipitation of B2-ordered NiAl and formation of reverted austenite take place simultaneously during aging and that dissolution of precipitates is not essential for the initial formation of reverted austenite.     

Lyocell混纺——给纺织工业带来的附加效益

Ｌｙｏｃｅｌｌ具有迄今为止在其他纤维素纤维中从未有过的纤维强力特性,Ｌｙｏｃｅｌｌ的产品性能可以有与高质量的、长绒棉相媲美,甚至在某种情况下优于长绒棉。可以认为,在未来纺织工业中,针得到广泛的应用。介绍了Ｌｙｏｃｅｌｌ纤维与胶纤维、莫代尔纤维或棉混纺品的性能。     

Laboratory experiments and process modelling of the melting and dissolution of low‐density ferro‐molybdenum in steel melts

A low‐density sintered ferro‐molybdenum is presented as a new alloying agent. The paper describes laboratory studies about the dissolution in liquid iron of briquettes of this alloy and of classical high density ferro‐molybdenum pieces. It presents further a mathematical model of the melting and dissolution process. During dissolution, an approximately 1mm thick layer infiltrated by melt forms on the particle surface. The infiltrated melt solidifies in the plane where the temperature has reached the eutectic temperature in the system iron‐molybdenum. Internal dissolution of alloy material in the layer is weak, which means that the dissolution proceeds almost exclusively from the outer surface of the briquette. Dissolution rate increases with sinking briquette density. The lower molybdenum content per volume in the briquettes which is proportional to the density has the effect that the liquidus concentration and the liquidus temperature at the solid‐liquid interface decrease in comparison with compact material. This reduces the mass transfer rate and increases the heat transfer rate. The effect is a faster movement of the interface. Below a critical density of approximately 5200 kg/m³ for the alloy considered, the molybdenum concentration on both sides of the interface becomes equal. From this moment, the alloy is liquefied solely by melting of the moving interface. Mass transfer from the interface gets negligible and distribution of the molten alloy into the bulk melt takes place only by the outer mixing process. From the described behaviour it follows, that below the critical density the melting rate is solely determined by heat transfer. Since heat transfer is faster than mass transfer, melting of alloys with reduced density is correspondingly accelerated. The extremely slow dissolution rates of high melting alloys can thus, be overcome by giving the alloy a certain porosity. The mathematical process model describes the phenomena quantitatively.     

Microstructure and mechanical properties of the superalloy ATI Allvac 718Plus™

ATI Allvac^® 718Plus™ is a novel nickel-based superalloy, which was designed for heavy-duty applications in aerospace turbines. In the present study the high-resolution investigation techniques, atom probe tomography, electron microscopy and in situ high-temperature small-angle neutron scattering were used for a comprehensive microstructural characterization. The alloy contains nanometer-sized spherical γ′ phase precipitates (Ni₃(Al,Ti)) and plate-shaped δ phase precipitates (Ni₃Nb) of micrometer size. The precipitation kinetics of the γ′ phase can be described by a classical model for coarsening. The precipitation strongly influences the mechanical properties and is of high scientific and technological interest.     

Effect of persulfate on the oxidation of benzotriazole and humic acid by e-beam irradiation

These days, the use of persulfate in advanced oxidation processes (AOPs) has gained more attention as an emerging clean and efficient technology to degrade the organic pollutants. The objective of this study was to investigate the effect of the addition of persulfate on the oxidation of benzotriazole (BT) and humic acids (HAs) by irradiation. The degradation of BT (3.7 μM) was followed under the influence of persulfate addition (200-500 μM) in combination with a fixed radiation dose (15 Gy) in the absence and presence of HA (5 and 20mg/L) in deionized water. The main results obtained in this study on the degradation of BT in the presence of HA showed a different effect of S(2)O(8)(2-) addition during irradiation, depending on whether HA are oxidized or not-oxidized. (1) An inhibitory effect of S(2)O(8)(2-) was observed in the presence of non-oxidized HA. (2) The removal of BT was generally more important during irradiation in the presence of S(2)O(8)(2-) when HA is pre-oxidized. This could be explained by the different structures of humic acids. These differences of structures of HA were identified by physico-chemical parameters such as the absorbance in the UV (254 nm), the fluorescence and the SUVA measurement.     

Communication Maps: Exploring Energy Transport through Proteins and Water

Frequency-resolved communication maps provide a coarse-grained, global mapping of energy transport channels in a protein as a function of frequency of modes that carry energy. We illustrate the approach with a study of the homodimeric hemoglobin of Scapharca inaequivalvis, which exhibits cooperativity during ligand binding. We compare energy transport between the two hemes of the unliganded and oxygenated protein, which is mediated by water as well as residues forming a hydrogen-bonding network at the interface between the globules, and lies along the pathway for allosteric transitions observed in time-resolved X-ray studies. Non-equilibrium molecular simulations on energy transport from the heme corroborate the energy transport pathways identified by the communication maps.     

Machine learning in continuous casting of steel: a state-of-the-art survey

Journal of Intelligent Manufacturing - Continuous casting is the most important route for the production of steel today. Due to the physical, mechanical, and chemical components involved in the...     

On the Sensitivity of a Tool–Workpiece Thermocouple to Chemical Composition and Microstructure

Meeting the increasing demands on part quality and profitability of manufacturing processes despite difficult-to-machine materials is only possible with a deep understanding of the process. Herein, knowledge about the process temperature is of critical importance since it affects the material properties, such as hardness or forming behavior, as well as the chemical and physical interactions between the tool, workpiece, and lubricant. A proven thermoelectric method of temperature measurement in machining, forming, and blanking is a tool–workpiece thermocouple. Herein, instantaneous measurement of the temperature development is allowed in this setup during the manufacturing process in situ at the contact area of the tool and workpiece. The accuracy of this method is dependent on the calibration of the thermocouple, for which the Seebeck coefficients of the tool and workpiece material have to be determined. Usually, material samples from different batches are used for this purpose, although the resulting measurement errors due to slight changes in material properties are hardly known. The effects of small changes in the chemical composition and the transformation of the crystal lattice due to hardening on the Seebeck coefficient are investigated for the first time to allow precise quantification of the measurement error resulting from the calibration process.     

Catalytic Hydrogenation of CO2 to Formate Using Ruthenium Nanoparticles Immobilized on Supported Ionic Liquid Phases

Ruthenium nanoparticles (NPs) immobilized on imidazolium-based supported ionic liquid phases (Ru@SILP) act as effective heterogeneous catalysts for the hydrogenation of carbon dioxide (CO₂) to formate in a mixture of water and triethylamine (NEt₃). The structure of the imidazolium-based molecular modifiers is varied systematically regarding side chain functionality (neutral, basic, and acidic) and anion to assess the influence of the IL-type environment on the NPs synthesis and catalytic properties. The resulting Ru@SILP materials contain well-dispersed Ru NPs with diameters in the range 0.8–2.9 nm that are found 2 to 10 times more active for CO₂ hydrogenation than a reference Ru@SiO₂ catalyst under identical conditions. Introduction of sulfonic acid groups in the IL modifiers results in a greatly increased turnover number (TON) and turnover frequency (TOF) at reduced metal loadings. As a result, excellent productivity with TONs up to 16 100 at an initial TOF of 1430 h⁻¹ can be achieved with the Ru@SILP(SO₃H-OAc) catalyst. H/D exchange and other control experiments suggest an accelerated desorption of the formate species from the Ru NPs promoted by the presence of ammonium sulfonate species on Ru@SILP(SO₃H-X) materials, resulting in enhanced catalyst activity and productivity.