In‐situ composite coating on powder metallurgy master alloy fabricated by vacuum hot‐pressing sintering technology

A material consisting of an in‐situ titanium carbide reinforced nickel‐aluminide (Ni₃Al) coating and a powder metallurgy master alloy was fabricated by vacuum hot‐pressing sintering technology. A metallurgical bonded, pores‐free interface between composite coating and powder metallurgy master alloy was formed at the sintering temperature of 1050 °C, pressure of 10^‐4 Pa and pressing pressure of 40 MPa. The phase, microstructure and wear behavior of composite coating were investigated. The results showed that polygonal titanium carbide particulates with various sizes were homogeneously distributed in nickel‐aluminide matrix. The sintering temperature, pressing pressure and heat from as‐reactions‐formed coating green compact facilitated the pore infiltration with transiently generated liquid phases and ensured the high‐intensity metallurgical bonding between composite coating and powder metallurgy master alloy. Due to the abnormal elevated‐temperature properties of nickel‐aluminide matrix, titanium carbide particulates reinforcement and the mechanically mixed layer protection, TiC/Ni₃Al‐coated parts demonstrated superior wear resistance and lower friction coefficient while compared with Ni₃Al‐coated parts and H13 steel.     

Auslegung von Sicherheitsventilen für Mehrzweckanlagen nach ISO 4126‐10

Multi‐purpose plants are frequently protected with safety valves or bursting disks. The sizing procedure can be very effortful if a relief of two‐phase gas/liquid mixtures is considered. Therefore energy specific relief areas (effective relief area per kW of energy input) have been determined for approx. 60 typical solvents. Results are based on the non‐equilibrium HNE‐DS method of the international standard ISO 4126 part 10. The data allow a quick check of the required relief area if the energy input of the reactor is known (external heating by a heat transfer medium, fire, chemical reaction). It leads to significantly smaller relief areas than according to the API 520.     

Chilling injuries in peaches during conventional and intermittent warming storage

Firm-breaker and firm-mature peaches (Prunus persica L. Batsch cv. ‘Paraguayo’) were conventionally stored for 4 weeks at 2°C and 90–95% relative humidity or subjected to intermittent warming cycles of 1 day at 20°C every 6 days of storage at 2°C. Warming periods induced ripening (reduced flesh firmness, extractable juice and titratable acidity), while during continuous storage abnormal values of these parameters were found. After 2 weeks at 2°C and particularly after the subsequent 3 days at 20°C, woolliness and to a lesser extent, vitrescence and dryness of the cortical tissue were detected. Severe levels of these disorders were found more frequently in firm-breaker than in firm-mature fruits, which mainly developed vitrescence. Three cycles of intermittent warming prevented chilling injuries but increased weight loss and senescence symptoms. Compared with conventional storage, intermittent warming increased the shelf-life of firm-mature and firm-breaker peaches by 1 and 2 weeks, respectively. Some considerations on the commercial application of the intermittent warming technique are included.     

Niedrigemittierende Außenoberflächen bei Wärmedämmverbundsystemen – ein Studie zur Vermeidung von Algenwuchs

Algae growth on the outside surface of thermal insulating composite systems (TICS) occurs because of long‐lasting wetting. The present techniques for its avoidance are without long‐term effect. Especially, dew and frost are an essential reason for its occurrence because of the highly thermal insulation of the TICSs. In the following report, it will be investigated by an algorithm on the basis of a worst case scenario for outside condensation whether outside condensation on TICSs can be counteracted by a low‐emissivity outside surface as it is well‐proven on highly insulating window glazing. The calculations showed that outside condensation on TICSs with heat transfer coefficients (U) values from 0.1 to 0.2 W/(m² K) cannot be avoided theoretically by thermal emissivity values ε in the range of 0.05 till 0.1. However, because the most critical scenario conditions for outside condensation are very stringent and, in addition, the calculations have shown that outside condensation is only possible for relative outdoor humidity rH_o ≥ 95%, it can be deduced that the occurrence of outside condensation will be very improbably in praxis for TICSs with U values from 0.1 to 0.2 W/(m² K) and ε values from 0.05 to 0.1. A weathering and soiling resistant surface with ε ≤ 0.1 can be realized by aluminum which may be additionally passivated by a titanium dioxide coating. Because of the hydrophilic property, this coating shows also self‐cleaning effect and quickly drying of the surface after rain. The latter may counteract algae growth, too.     

Diffusion and wetting on contaminated solids

The wetting dynamics of a drop of liquid (1) deposited on a solid on which there is already a thin layer of liquid (2) (contaminant, or maybe a wetting agent) is considered. Diffusion of liquid 2 into liquid 1 by Fickian diffusion leads to evolving effective solid/drop interfacial free energy, occurring during spreading, and modifying wetting kinetics. Spreading rate is increased. Strange behaviour is predicted near equilibrium conditions. The wetting line may “overshoot”, before receding asymptotically. The motion of a two‐dimensional drop is modelled, assuming it is given a slight push to one side after deposition. We expect a regime of spontaneous translational drop motion due to asymmetry in capillary conditions at the two triple lines. Diffusional wetting is compared to reactive wetting.     

Digitale Vision und gebaute Wirklichkeit — Über das Bauen von geometrisch anspruchsvollen Gebäudehüllen

Im letzten Jahrhundert haben Architekten für ihre Entwürfe vorwiegend geometrische Grundformen wie Würfel und Quader, Zylinder‐, Kegel‐ oder Torus‐Flächen verwendet. Seit den 60‐er Jahren des vorigen Jahrhunderts werden die digitalen Werkzeuge der Designer aber ständig weiterentwickelt (Nurbsflächen) und tragen nun zu einer quasi unbegrenzten Erweiterung des Formenvokabulars bei. Computer und entsprechende Software (CAD/CAM) dienen nicht nur zur Erstellung von technischen Zeichnungen oder zur Ansteuerung von CNC‐Maschinen in der Fertigung, sondern unterstützen vor allem auch die Konzeption neuartiger biomorpher Formen. Die Arbeit mit digitalen Werkzeugen und Inhalten ist zum globalen Industriestandard geworden. Die Tendenz, einfache lineare Formen aufzugeben, welche aus einer überschaubaren Anzahl einzelner ähnlicher Elemente bestehen, und diese durch einzigartige Skulpturen zu ersetzen, entstammt der schöpferischen Vision der Künstler und deren Willen, Dinge weit ab vom banalen Gebrauchsgegenstand zu schaffen. Diese Landmarks sind zu Sinnbildern von Eleganz, Anmut, Fortschritt und Innovation geworden. Computerized vision and built reality — About the designing of complex building shapes. For the past century, architects have been using cylinders, cones, rotational and ruled surfaces for their designs. Meanwhile computers and corresponding software are necessary for throughout the architectural design and planning of the construction industry. Whether it is the draft of drawings or the design of new complex building shapes, working with digital content has become the standard for the industry. There is a continuous tendency to give up linear forms with easily manageable numbers of the same elements. Free‐form structures originated by the creativity of architects beginning in the last decade of the previous millennium have developed to symbols of elegance, grace, progress, and innovation. The construction of arbitrarily shaped building envelopes necessitates the computerized design and calculation of large numbers of unique elements. This iconic or landmark architecture is commonly used to emphasize the brands of enterprises. To transfer the architectural concept into built reality, an intense collaboration of geometrical and structural engineers combined with production and material management experience is necessary to standardize complexity and hence increase the feasibility of the design.