A detailed thermal analysis of nanocomposites filled with SiO2, AlN or boehmite at varied contents and a review of selected rules of mixture

In order to investigate and compare the thermal and mechanical properties of nanocomposites filled with various nanoparticles multiple experiments have been carried out. The aim of this study was to enhance the thermal and mechanical properties of epoxy resin for fiber reinforces structures by the addition of nanoparticles. These altered properties were analyzed and reconciled with each other as well as compared to data developed from different rules of mixture. A hot curing epoxy system based on bisphenol-A (DGEBA) has been filled with different contents of silicon dioxide (SiO₂), aluminum nitride (AlN) and boehmite nanoparticles to examine the effects in the material’s thermal and mechanical behavior with variable filler materials and contents compared to the unfilled epoxy. The glass transition temperature fluctuates very little with varied filler content. The coefficient of thermal expansion can be reduced with increasing filler content. This improvement recurs also in thermal conductivity and during dynamic mechanical analysis. Several rules of mixture have been applied to be verified on the basis of varied materials and filler contents. The results did not always match the experiments. The deviations are ascribed to the influence of interphases that build up in the vicinity of the nanoparticles during the process of curing.     

Tunable White‐Light Emission from Conjugated Polymer‐Di‐Ureasil Materials

Conjugated polymer (CP)‐di‐ureasil composite materials displaying a tunable emission color from blue to yellow through white have been prepared using a simple sol–gel processing method. The tunability of the emission color arises from a combination of energy transfer between the di‐ureasil and the CP dopant and the excitation wavelength dependence of the di‐ureasil emission. Incorporation of the CP does not adversely affect the bulk or local structure of the di‐ureasil, enabling retention of the structural and mechanical properties of the host. Furthermore, CP‐di‐ureasils display superior thermal and photostability compared to the parent CPs. Thermogravimetric analysis shows that the onset of thermal decomposition can be increased by up to 130 °C for CP‐di‐ureasils, while photostability studies reveal a significant decrease in the extent of photodegradation. Steady‐state photoluminescence spectroscopy and picosecond time‐resolved emission studies indicate that the observed tunable emission arises as a consequence of incomplete energy transfer between the di‐ureasil and the CP dopant, resulting in emission from both species on direct excitation of the di‐ureasil matrix. The facile synthetic approach and tunable emission demonstrate that CP‐di‐ureasils are a highly promising route to white‐light‐emitters that simultaneously improve the stability and reduce the complexity of CP‐based multilayer device architectures.     

Evaluation of structural changes of HT-PEFC electrodes from in-situ synchrotron X-ray radiographs

One of the main goals for improvement of high-temperature polymer electrolyte fuel cells (HT-PEFCs) is the increase of the fuel cell performance under different operating conditions. We investigated the correlation between operating conditions and structural changes in the electrodes by means of in-situ through-plane synchrotron X-ray radiography. From the radiographs it is possible to clearly distinguish between the electrode crack structure beneath the ribs and beneath the channels of the flow field. We present a statistical method to analyze these crack structures. For this purpose a ‘radar’ method was developed in order to obtain the width of the cracks at many different locations and the distribution of crack widths. We found a different behavior of cracks located beneath the ribs and beneath the channels and an influence of the operating conditions on local regions of the crack structure.     

Shortcut Evaluation of Chemical Carbon Dioxide Utilization Processes

Chemical utilization of carbon dioxide seems to be an attractive option for the mitigation of greenhouse gas emissions. However, the respective processes themselves cause substantial greenhouse gas emissions. To achieve a good CO₂ balance, it is necessary not only to fix carbon but also to do this efficiently in terms of reactant supply and energy demand. An evaluation of the CO₂ balance requires detailed process simulation for the utilization reaction and the supply chain. To allow a quick evaluation of the potential to mitigate emissions, a number of estimation methods are presented.     

Stress corrosion cracking behaviour of stainless steels with respect to their use in architecture,part 1: corrosion in the active state

Unexpected failures on 18/8 CrNi and 17/12/2 CrNiMo steels in indoor swimming pool atmospheres made it necessary to reinvestigate chloride induced stress corrosion cracking (SCC). SCC in the active state was investigated on stainless steels 1.3974, 1.4301, 1.4303, 1.4439, 1.4462, 1.4522, 1.4539 and 1.4571 by testing under constant load at temperatures up to 50°C. Selected tests were performed on the material with the highest SCC susceptibility, 1.4301, in solutions with different concentrations of hydrochloric acid and sodium chloride. SCC was only observed in critical ranges of hydrogen-ion concentration and only in conjunction with pronounced general corrosion. In a solution with c(HCl) = 1.0 mol/l and c(NaCl) = 0.5 mol/l, which had proved to be highly SCC-inducing, the effects of different parameters on SCC behaviour were studied. Temperature, stress level and degree of cold deformation exerted only a secondary influence, in contrast to alloy composition: austenitic steels containing about 10% nickel (1.4301, 1.4303, 1.4571) exhibited very pronounced SCC. The other materials with nickel contents distinctively higher or lower proved, respectively, to be less susceptible or resistant to SCC. Thus, the same effect of nickel content was observed as is known for resistance to chloride induced SCC in the passive state. All materials were prone to pronounced general corrosion. The corrosion phenomena observed were completely different from the swimming pool failures reported.     

SAR of novel biarylmethylamine dopamine D4 receptor ligands

SAR for a novel series of dopamine D4 receptor ligands is shown. Very selective, highly potent compounds like 1-(2-pyrimidinyl)-4-(3-(3-thienyl)-benzyl)-piperazine (5f) and 2-(4-(1-fluorenylmethyl)-1-piperazinyl)-pyrimidine (8c) were obtained.     

Verfahrenstechnische Möglichkeiten zur Verringerung des Anstiegs von Kohlendioxid in der Luft

Engineering Solutions for Limiting the Increase of Carbon Dioxide in Air This article describes engineering solutions for limiting the increase of carbon dioxide in air. Fossile power plants are taken as a model for the source of CO₂. The global mass balance shows that the oceans play a most important role in the storage of the CO₂. The hypothesis is that it is not the absolute value of carbon dioxide concentration that is the real problem but rather its change. Keeping this in mind the present emissions should not be converted but stored for future times. This strategy is called ?hiding the CO₂“. The reduction of the emission is not very likely. It is believed that present actions to reduce the private power consumption will not really change the situation. A number of strategies for the sequestration of CO₂ are reported in the contribution. One proposal is to use shallow waters which form a thermohaline current for the sequestration. In this case, the injection of CO₂ is quite simple but the carbon dioxide travels hundreds of years in a deep sea current. Several scenarios are discussed for the fate of this CO₂‐enriched current. The environmental impact is briefly reported. This contribution describes the actual research needs, taking into account that similar research in Japan and in the U.S. is much more developed.