On the impact of post weld heat treatment on the microstructure and mechanical properties of creep resistant 2.25Cr–1Mo–0.25V weld metal

Creep resistant low-alloyed 2.25Cr-1Mo-0.25V steel is typically applied in hydrogen bearing heavy wall pressure vessels in the chemical and petrochemical industry. For this purpose, the steel is often joined via submerged-arc welding. In order to increase the reactors efficiency via higher operating temperatures and pressures, the industry demands for improved strength and toughness of the steel plates and weldments at elevated temperatures. This study investigates the influence of the post weld heat treatment (PWHT) on the microstructure and mechanical properties of 2.25Cr-1Mo-0.25V multi-layer weld metal aiming to describe the underlying microstructure-property relationships. Apart from tensile, Charpy impact and stress rupture testing, micro-hardness mappings were performed and changes in the dislocation structure as well as alterations of the MX carbonitrides were analysed by means of high resolution methods. A longer PWHT-time was found to decrease the stress rupture time of the weld metal and increase the impact energy at the same time. In addition, a longer duration of PWHT causes a reduction of strength and an increase of the weld metals ductility. Though the overall hardness of the weld metal is decreased with longer duration of PWHT, PWHT-times of more than 12 h lead to an enhanced temper resistance of the heat-affected zones (HAZs) in-between the weld beads of the multi-layer weld metal. This is linked to several influencing factors such as reaustenitization and stress relief in the course of multi-layer welding, a higher fraction of larger carbides and a smaller grain size in the HAZs within the multi-layer weld metal.

     

Rigorous electromagnetic analysis of dipole emission in periodically corrugated layers: the grating-assisted resonant-cavity light-emitting diode

We study the grating-assisted light-emitting diode, an LED design for high brightness based on a resonant cavity containing one- or two-dimensionally periodically corrugated layers (grating). We give in detail a generally applicable electromagnetic analysis based on the rigorous coupled-wave theory to calculate the extraction efficiency of spontaneous emission in a periodically corrugated layer structure. This general model is then specified on the grating-assisted resonant-cavity LED, showing simulated efficiencies of more than 40%.     

Bis(trifluoromethyl)carbinol polynorbornene as a pseudo-polyelectrolyte in multilayered films

Using weak, opposed to strong polyelectrolytes in multilayer polymer systems provides a convenient means of altering some of the physico-chemical properties of these thin films. Recently, we pushed the limits of the weak polyacids by the introduction of an additional class of polyelectrolytes, the pseudo-polyelectrolytes (pPE). This paper focuses on another pPE, poly[5-(2-trifluoromethyl-1,1,1-trifluoro-2-hydroxypropyl)-2-norbornene] (PNBHFA). As, with poly(4-vinylphenol), multilayer assembly with both a weak and a strong polycation was accomplished from aqueous media. However, this was achieved only at a high pH value of 12.0. The films that were produced were exceptionally thick, > 1.25 μm after only 30 total layers for the poly(allylamine hydrochloride)/PNBHFA system. The films were very hydrophobic with the contact angle of water increasing with the layer number; reaching a maximum of ~ 123° after 50 total layers of poly(diallyldimethylammonium chloride)/PNBHFA.     

Structure–Transport Correlation Reveals Anisotropic Charge Transport in Coupled PbS Nanocrystal Superlattices

The assembly of colloidal semiconductive nanocrystals into highly ordered superlattices predicts novel structure-related properties by design. However, those structure–property relationships, such as charge transport depending on the structure or even directions of the superlattice, have remained unrevealed so far. Here, electric transport measurements and X-ray nanodiffraction are performed on self-assembled lead sulfide nanocrystal superlattices to investigate direction-dependent charge carrier transport in microscopic domains of these materials. By angular X-ray cross-correlation analysis, the structure and orientation of individual superlattices is determined, which are directly correlated with the electronic properties of the same microdomains. By that, strong evidence for the effect of superlattice crystallinity on the electric conductivity is found. Further, anisotropic charge transport in highly ordered monocrystalline domains is revealed, which is attributed to the dominant effect of shortest interparticle distance. This implies that transport anisotropy should be a general feature of weakly coupled nanocrystal superlattices.     

Experiences from the implementation of a urine separation system: Goals,planning, reality

Over the last decade it has been ever increasing interest in developing alternative sanitary systems, which would be more sustainable than a conventional one is. In Sweden urine separation has been considered a promising approach towards increasing recycling of wastewater nutrients. Full scale trials are carried out and examined. This paper presents a study on implementation of urine separation system in urban environment. Technical and non-technical aspects of system performance are evaluated; system's interference with existing infrastructure is examined. Benefits and losses connected to urine separation system are analysed not only from environmental perspective but also system's owner point of view.     

Practical support for evaluating efficiency factors of a space heating system in cold climates

Plenty of technical norms, included in the EPBD umbrella, assesses the performance of buildings or its sub-systems in terms of efficiency. In particular, EN 15316 and its sub-sections determine the efficiency factors of a space heating system. This paper focuses on the estimation of efficiency factors for hydronic panel radiators. The assessment of efficiency factors occurs by evaluating the amount of heat emitted from the heat emitter and the thermal losses towards building envelope. A factor that influences the heat emitted is the location of radiator connection pipes. Connection pipes can be located on opposite side or at the same side of the radiator. To better estimate the heat emitted from the radiator with different location of connection pipes, a transient model with multiple storage elements is implemented in a commercial building simulation software and validated versus available experimental measurements. Sensitivity analysis encompasses the variations of heat losses due to the building location in different climates, the changing of the active thermal mass and the type of radiator local control. The final outcome of this paper is a practical support where designers and researchers can easily assess the efficiency factors for space heating system equipped with hydronic panel radiators of buildings located in Sweden. As main results, (i) the efficiency factor for control is higher in Northern climates (Luleå) than in Southern climates (Gothenburg), (ii) heavy-weight active thermal masses allow higher efficiency factors than light active thermal masses, and (iii) connection pipes located on the same side of the hydronic panel radiator enable higher efficiency factors than pipes located on opposite side.     

The influence of extensive vegetated roofs on runoff water quality

The influence of extensive sedum-moss vegetated roofs on runoff water quality was studied for four full scale installations located in southern Sweden. The aim of the study was to ascertain whether the vegetated roof behaves as a sink or a source of pollutants and whether the age of a vegetated roof influences runoff quality. The runoff quality from vegetated roofs was also compared with the runoff quality from non-vegetated roofs located in study areas. The following metals and nutrients were investigated: Cd, Cr, Cu, Fe, K, Mn, Pb, Zn, NO3-N, NH4-N, Tot-N, PO4-P, and Tot-P. The results show that, with the exception of nitrogen, vegetated roofs behave as source of contaminants. While in lower concentrations than normally found in urban runoff, some metals appear in concentrations that would correspond to moderately polluted natural water. Nitrate nitrogen is retained by the vegetation or soil or both. Apart from the oldest, the studied vegetated roofs contribute phosphate phosphorus to the runoff. The maintenance of the vegetation systems on the roofs has to be carefully designed in order to avoid storm-water contamination; for instance, the use of easily dissolvable fertilizers should be avoided.