Design of new systems for transfer hydrogenolysis of polychlorinated aromatics with 2-propanol using a Raney nickel catalyst

A multipurpose study deals with the transfer hydrogenolysis of 1,3,5-trichlorobenzene to benzene in the 2-propanol–Raney nickel system in the presence of KOH. At 70 °C, no reaction occurs without KOH or with weaker bases, e.g. amines or poorly soluble inorganic bases; however saturated KOH as well as water over 1% suppress the reaction rate, presumably due to the competitive adsorption of these species on the catalyst. The catalytic activity also drops with time because of the deposition of the solid KCl on the catalyst but can be recovered at washing the catalyst with water. The deactivation by KCl can be mitigated with the addition of promoters, e.g. quaternary ammonium salts (Aliquat 336, CTAC) or trioctylamine. Aliquat 336 also promotes hydrodechlorination in the hydrothermal system using a 10% solution of 2-propanol in water, Raney nickel and potassium carbonate as base at 150–200 °C and 10–20 bar. Under these conditions, hexachlorobenzene was also selectively dechlorinated to benzene.     

Linear chains of Ge/Si quantum dots grown on a prepatterned surface formed by ion irradiation

Semiconductors - The growth of Ge nanoclusters on a prepatterned Si (100) surface formed by imprint lithography in combination with subsequent irradiation with Ge+ ions is studied. The prepatterned...     

Ultra-Robust Flexible Electronics by Laser-Driven Polymer-Nanomaterials Integration

Polyethylene terephthalate (PET) is the most widely used polymer in the world. For the first time, the laser-driven integration of aluminum nanoparticles (Al NPs) into PET to realize a laser-induced graphene/Al NPs/polymer composite, which demonstrates excellent toughness and high electrical conductivity with the formation of aluminum carbide into the polymer is shown. The conductive structures show an impressive mechanical resistance against >10000 bending cycles, projectile impact, hammering, abrasion, and structural and chemical stability when in contact with different solvents (ethanol, water, and aqueous electrolytes). Devices including thermal heaters, carbon electrodes for energy storage, electrochemical and bending sensors show this technology's practical application for ultra-robust polymer electronics. This laser-based technology can be extended to integrating other nanomaterials and create hybrid graphene-based structures with excellent properties in a wide range of flexible electronics’ applications.     

Luminescence of Spatially Ordered Self-Assembled Solitary Ge(Si) Nanoislands and their Groups Incorporated into Photonic Crystals

Semiconductors - The luminescence properties of arrays of spatially ordered self-assembled solitary Ge(Si) nanoislands and their groups, including those embedded in two-dimensional photonic...     

Molar mass-dependent profiles of functional groups and carbohydrates in kraft lignin

Technical lignins are complex, irregular, polyphenolic compounds obtained in large quantities as by-products of the pulp and paper industries or according to current biorefinery setups. The availability of kraft lignin is increasing due to larger scale retrieval from process liquors, which opens new possibilities for further refining or new applications of such lignins. In the present study, sequential ultrafiltration of kraft lignin was performed to fractionate the lignin and to elucidate molar mass-dependent changes in lignin structure. Two industrial black liquors and three precipitated lignins were fractionated, and their functional groups were determined, providing molar mass-dependent profiles. Interrelations between structural parameters and functional groups, the molecular weight ranges, and the different lignin sources are discussed. This will help to establish structure-property-application relationships (SPARs) for technical lignins which are required for any future large-scale application.     

Commercial lignosulfonates from different sulfite processes as partial phenol replacement in PF resole resins

Four commercial spruce lignosulfonates representing the most common acidic, neutral, and alkaline sulfite pulping processes and varying significantly in molecular weight characteristics were tested as partial (40 wt %) phenol substitute materials for the manufacture of lignosulfonate‐phenol‐formaldehyde (LPF) resole resins. Similar as recently reported for technical lignins from nonsulfite pulping processes (kraft, soda, organosolv), all lignosulfonates of this study effectuated a faster viscosity gain during resole cooking compared to the lignin‐free reference resin (1000 mPa s after 120 min vs. 250 min to reach 1000 mPa s). Sodium lignosulfonate featuring the lowest weight average molecular weight (M_w 5780 g mol^?1) and dispersity (Ð 6.1) turned out to be superior to the other lignosulfonates with regard to curing rate (B‐time; 3:37 min vs. 6:41–9:08 min) and tensile shear strength development under hot pressing (120 °C; T_S,max = 5.64 N mm^?2 after 8 min) for beech veneer strips glued together with the respective LPF resins. Calcium and magnesium lignosulfonates are less suited with regard to phenol replacement due to the poor performance of the respective LPF adhesives in terms of tensile shear strength (T_S,max = 3.29–3.49 N mm^?2 after 12 min) most likely caused by considerable amounts of side products formed in the course of formose‐type reactions. Phenolation of the two promising lignosulfonates, that is, sodium and ammonium lignosulfonate, did neither considerably increase the rate of PF network formation during resin cooking and curing nor improve tensile strength development during hot pressing. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45893.     

SiGe quantum rings on the Si(100) surface

Results of experimental studies of forming SiGe nanometer-size rings on the Si(100) surface by the molecular-beam epitaxy method are presented. Detailed shapes and size distributions of the grown nanorings are studied by the atomic-force microscopy method. The elemental composition is determined by the Raman scattering method. The average germanium content in the nanorings was 37% for a forming temperature of 680°C. The obtained data on the geometry and composition of the produced nanostructures were used for calculations by the 6-band k × p-method of the energy spectrum and charge density distribution of hole states, localized on the SiGe quantum rings embedded in the Si-matrix. It is shown that the heterostructures with quantum SiGe rings are promising objects for creating devices that are capable of detecting electromagnetic radiation in terahertz and infrared wavelength ranges.     

Elastic Principal Graphs and Manifolds and their Practical Applications

Principal manifolds serve as useful tool for many practical applications. These manifolds are defined as lines or surfaces passing through “the middle” of data distribution. We propose an algorithm for fast construction of grid approximations of principal manifolds with given topology. It is based on analogy of principal manifold and elastic membrane. First advantage of this method is a form of the functional to be minimized which becomes quadratic at the step of the vertices position refinement. This makes the algorithm very effective, especially for parallel implementations. Another advantage is that the same algorithmic kernel is applied to construct principal manifolds of different dimensions and topologies. We demonstrate how flexibility of the approach allows numerous adaptive strategies like principal graph constructing, etc. The algorithm is implemented as a C++ package elmap and as a part of stand-alone data visualization tool VidaExpert, available on the web. We describe the approach and provide several examples of its application with speed performance characteristics.     

Ordered Arrays of Ge(Si) Quantum Dots Incorporated into Two-Dimensional Photonic Crystals

Semiconductors - Two different approaches to the integration of self-assembled Ge(Si) quantum dots into two-dimensional photonic crystals are considered. One approach includes the synthesis of an...