p‐TCOs für Transparente Elektronik

p‐type TCOs for use in transparent electronics In this article, a new type of semiconducting material is introduced. Transparent conducting thin films are already established in our everydaylife. But the type of these so‐called ?TCOs”? is dominated by electron transport, that means they are n‐type. To get transparent p‐n‐junctions and therefore transparent electronics, the missing part is a transparent p‐type material. Researchers all over the world have found different approach to produce this new generation of materials. At the Fraunhofer Institute for Surface Engineering and Thin Films (IST) in Braunschweig it is now possible to produce these kind of thin films as well.     

Air cargo scheduling: integrated models and solution procedures

Designing a profitable flight schedule is a highly complex planning problem. Both passenger and cargo airlines usually follow a decomposition approach and break this problem into several subproblems which are then solved consecutively and iteratively using specific but isolated models. At cargo airlines, the four major interdependent decision problems are flight selection, fleet assignment, rotation planning, and cargo routing. In our research, we have developed a planning approach which differs from other OR-based planning approaches in two aspects. The approach is based on integrated models and it is based on the pragmatic planning paradigm to optimally modify an existing schedule. For this purpose, the planner has to identify mandatory and optional flights. Then the planning goal is to identify the best combination of optional flights to be included into the schedule. Our integrated planning models comprise several additional important planning aspects for cargo airlines such as available capacities on external flights (e.g. belly capacities from passenger flights or road-feeder services), cargo handling costs and constraints, and aircraft maintenance regulations. There are two main aspects which we present in this paper. First, we describe the planning problem and the specific planning paradigm, develop a set of complex mixed-integer programs representing the different subproblems, and finally present integrated problem formulations as well as several model extensions. Thereafter, we develop a branch and price and cut approach for solving the mathematical programs and present extensive computational results obtained for a set of generated yet highly practical problem instances for different types of carriers. The results show that our approach is able to find high quality solutions to problem instances of realistic size and complexity within reasonable time.     

Designing block copolymer architectures for targeted membrane performance

Using a combination of block copolymer self-assembly and non-solvent induced phase separation, isoporous ultrafiltration membranes were fabricated from four poly(isoprene-b-styrene-b-4-vinylpyridine) triblock terpolymers with similar block volume fractions but varying in total molar mass from 43 kg/mol to 115 kg/mol to systematically study the effect of polymer size on membrane structure. Small-angle X-ray scattering was used to probe terpolymer solution structure in the dope. All four triblocks displayed solution scattering patterns consistent with a body-centered cubic morphology. After membrane formation, structures were characterized using a combination of scanning electron microscopy and filtration performance tests. Membrane pore densities that ranged from 4.53 × 10¹⁴ to 1.48 × 10¹⁵ pores/m² were observed, which are the highest pore densities yet reported for membranes using self-assembly and non-solvent induced phase separation. Hydraulic permeabilities ranging from 24 to 850 L m⁻² h⁻¹ bar⁻¹ and pore diameters ranging from 7 to 36 nm were determined from permeation and rejection experiments. Both the hydraulic permeability and pore size increased with increasing molar mass of the parent terpolymer. The combination of polymer characterization and membrane transport tests described here demonstrates the ability to rationally design macromolecular structures to target specific performance characteristics in block copolymer derived ultrafiltration membranes.     

Wachstumsmessungen von Kristallen in sauberen und verunreinigten Lösungen: Einzelkristall vs. Kollektiv

Information about crystal growth rates and the influence of impurities are essential for the design of industrial crystallization processes. Here, the influence of trivalent metal ions Fe³⁺ in solution and adsorbed in the crystal on the growth and dissolution rate is investigated. The results clearly show kinetic and thermodynamic effects caused by impurities which have to be taken into account in the equipment design. Furthermore, effects of growth rate dispersion must be excluded by investigation of crystal collectives. Additionally, the crystal growth data should be obtained from real starting solutions.     

Widely Tunable Morphologies in Block Copolymer Thin Films Through Solvent Vapor Annealing Using Mixtures of Selective Solvents

Thin films of block copolymers are extremely attractive for nanofabrication because of their ability to form uniform and periodic nanoscale structures by microphase separation. One shortcoming of this approach is that to date the design of a desired equilibrium structure requires synthesis of a block copolymer de novo within the corresponding volume ratio of the blocks. In this work, solvent vapor annealing in supported thin films of poly(2‐hydroxyethyl methacrylate)‐block‐poly(methyl methacrylate) [PHEMA‐b‐PMMA] by means of grazing incidence small angle X‐ray scattering (GISAXS) is investigated. A spin‐coated thin film of a lamellar block copolymer is solvent vapor annealed to induce microphase separation and improve the long‐range order of the self‐assembled pattern. Annealing in a mixture of solvent vapors using a controlled volume ratio of solvents, which are chosen to be preferential for each block, enables selective formation of ordered lamellae, gyroid, hexagonal, or spherical morphologies from a single‐block copolymer with a fixed volume fraction. The selected microstructure is then kinetically trapped in the dry film by rapid drying. This paper describes what is thought to be the first reported case where in situ methods are used to study the transition of block copolymer films from one initial disordered morphology to four different ordered morphologies, covering much of the theoretical diblock copolymer phase diagram.     

Versuchsplanerische Untersuchung der Umesterung von Sojaöl mit Ethanol im Mikroreaktor

Base‐catalyzed transesterification of fats and oils with primary alcohols in discontinuous operation is an established batch process for the biodiesel production. However, the application of microreaction technology and continuous flow process lead to an increase of process intensification. The ethanol/soy bean oil ratio at low flow rates as well as the reactor geometry have the most evident effects on the fatty acid ethyl ester yield of KOH‐catalyzed ethanolysis of soy bean oil in microreactors. The influence of the catalyst concentration is of a lower importance.     

Microstructure of the HMX‐Based PBX KS32 after Mechanical Loading

Non‐destructive X‐ray diffraction techniques were applied in order to monitor the influence of mechanical and shock‐loading on the microstructure of the plastic‐bonded high explosive KS32. The investigations uncovered damage to embedded coarse HMX crystals and to the binder system HTPB‐IPDI. Damage to the crystals occurred already during the kneading process in terms of deformation twinning. On higher loading between 400 MPa (static) and 480 MPa (dynamic) also crystal fracture was observed. The change in the binder structure was found after both static and dynamic loading, but not in the cured, differently kneaded samples. Moreover, the change in binder structure after dynamic loading was verified by dynamic mechanical analysis, and interpreted as a partial damage of the binder rubber shell around the explosive particles. The results are compared to literature data from imaging techniques.     

Energiedissipation und Energieflüsse während des Tablettiervorganges

The tableting process causes a temperature increase due to dissipation of energy. Therefore, with time the temperature of the tablets and the tablet press increases. Depending on the calculated tablet temperature, this temperature increase is discussed for different compression forces and lubricant concentrations. Two different measurement techniques are presented and compared.