Development of a Continuous Segmented Flow Tubular Reactor and the “Scale‐out” Concept – In Search of Perfect Powders

The synthesis of powders with controlled shape and narrow particle size distributions is still a major challenge for many industries. A continuous Segmented Flow Tubular Reactor (SFTR) has been developed to overcome homogeneity and scale‐up problems encountered when using batch reactors. Supersaturation is created by mixing the co‐reactants in a micromixer inducing precipitation; the suspension is then segmented into identical micro‐volumes by a non‐miscible fluid and sent through a tube. These micro‐volumes are more homogeneous when compared to large batch reactors leading to narrower size distributions, better particle morphology, polymorph selectivity and stoichiometry. All these features have been demonstrated on single tube SFTR for different chemical systems. To increase productivity for commercial application the SFTR is being “scaled‐out” by multiplying the number of tubes running in parallel instead of scaling‐up by increasing their size. The versatility of the multi‐tube unit will allow changes in type of precipitate with a minimum of new investment as new chemistry can be researched, developed and optimised in a single tube SFTR and then transferred to the multi‐tube unit for powder production.     

Mehrstrom-Wärmeaustauscher als gelötete Aluminium-Plattenapparate – Stand des Wissens

Multi-flow heat exchangers as soldered aluminium plate equipment – State of the art. Soldered aluminium plate heat exchangers are the most frequently used pieces of equipment for heat exchange between clean fluids in cryogenic and low temperature processes. Equipment of this type combines high flexibility in the flow arrangement, high heating surface densities (up to 1400 m²/m³), low pressure drops, and low production costs. This article provides a survey of the present state of the art of their manufacture and thermal dimensioning. In conclusion, new developments are treated.     

Vakuumgerechte Werkstoffe und Verbindungstechnik

In Part 1 (Henning, Materials used in Vacuum Technology), the application possibilities of different materials in vacuum technology were described. Part 2 describes the most important non-detachable connections of these materials to produce components that can be used in vacuum technology. The following processes are suitable for this purpose:

• ○ Welding

• ○ Soldering

• ○ Glueing

• ○ Fusion

For this reason, these four processes will be discussed in detail here; their advantages and disadvantages described and their worthiness for use in vacuum technology indicated. It should be noted here that other nondetachable connections such as rivets, point welding, projection seam welding or roll seam welding do not meet the demands of gas tightness made in vacuum technology and cannot, therefore, be used for such purposes.     

Catalysis with homogeneous membranes loaded with nanoscale metallic clusters and their preparation

Catalytically powerful, non-porous membranes were manufactured from two highly gas permeable poly(amide imides) consisting of structures with moieties of 3,3'-dimethylnaphthidine and hexafluoroisopropylidene (6F) or hexafluoroisopropylidene 2,2-bis(phthalic acid anhydride) (6FDA) and 6F. The catalysts are pure precious metals or precious metal alloys dispersed on a nanoscale uniformly throughout the membrane. The membranes are characterized by electron microscopy, gas permeability, hydrogen uptake and, as a model reaction, the decomposition of nitrous oxide by hydrogen to nitrogen and water catalyzed by Pd/Ag. The permeance to hydrogen and nitrous oxide is round 2–10^-6 cm³ (STP) /cm²·s·cmHg for membranes of 40–50μm in thickness.     

冠带层新平台技术

子午线轮胎出现不久，就采用钢丝带束层代替了纤维带束层，这对于实现子午线轮胎提高使用寿命和改善操纵性能的潜能是必要的。     

Cognitive load and instructionally supported learning with provided and learner-generated visualizations

This study investigated, whether learning from science texts can be enhanced by providing learners with different forms of visualizations (pictures) in addition to text. One-hundred-two 9th and 10th graders read a computer-based text on chemical processes of washing and answered questions on cognitive load (mental effort, perceived difficulty) and comprehension (retention, transfer, drawing). Instruction varied according to a 2 × 2-factorial design with ‘learner-generated pictures’ (yes, no) and ‘provided pictures’ (yes, no) as factors. Results indicate positive main effects of provided pictures on all three comprehension measures and negative main effects on both cognitive load measures. Additional analyses revealed a mediation effect of perceived difficulty on retention and transfer, that is learning with provided pictures decreased cognitive load and enhanced comprehension. Furthermore, results show a positive main effect of learner-generated pictures on drawing and mental effort, but no mediation effect. Taken together, computer-based learning with provided pictures enhances comprehension as it seems to promote active processing while reducing extraneous cognitive processing. Learners, generating pictures, however, seem to have less cognitive resources available for essential and generative processing, resulting in reduced comprehension. These results are in line with cognitive load theory, cognitive theories of multimedia learning, and generative theories of learning.