Magnetite core-shell nano-composites with chlorine functionality: preparation by miniemulsion polymerization and characterization

Magnetic composite particles with a magnetic core consisting of superparamagnetic iron oxide and a cover layer of hydrophobic polyvinylbenzylchloride are described. The magnetite was prepared by precipitation starting with mixed iron II and iron III salts and coating of the solid with oleic acid. The coating is conducted via the liquid–liquid phase transfer. Thereby oleic acid adsorbed on the magnetite surface. In a second step the oleic acid treated magnetite was coated with polyvinylbenzylchloride in a miniemulsion polymerization to get a protective layer. The obtained magnetite core-shell nano-composites with chlorine functionality were characterized by different methods: particle size measurement, acid treatment, iron content, morphology and elemental profiles across the composite particles diameter. The test result reveals the binding of the iron oxide inside the composites which can be also recognize in TEM pictures.     

Spray‐Coated Silver Nanowires as Top Electrode Layer in Semitransparent P3HT:PCBM‐Based Organic Solar Cell Devices

Silver nanowire (Ag NW) thin films are investigated as top electrodes in semitransparent inverted organic solar cells. The performance of semitransparent poly(3‐hexylthiophene‐2,5‐diyl):[6,6]‐phenyl‐C61‐butyric acid methyl ester (P3HT:PCBM) organic solar cells with Ag NW top electrode layers is found to match very closely the performance of reference devices based on thermally evaporated, highly reflective metal silver top electrodes. The optical losses of the semitransparent electrodes are investigated in detail and analyzed in terms of transmission, scattering, and reflection losses. The impact on an external back reflector is shown to increase the light harvesting efficiency of optically thin devices. Further analysis of transparent devices under illumination from the indium tin oxide (ITO) backside and through the Ag NW front electrode open the possibility to gain deep insight into the vertical microstructure related devices performance. Overall, Ag NW top electrodes are established as a serious alternative to TCO based electrodes. Semitransparent devices with efficiencies of over η = 2.0% are realized.     

Production process of wood-based materials for SiC Ceramics

The possibility of fabricating SiC ceramics using special wood-based materials has been shown in previous research. To form accurate SiC bodies from wood-based green templates, special shaping techniques are necessary to fulfill the requirements on the finished ceramic products. Due to the fact that wood-based green templates undergo shrinkage during carbonization, no suitable forming processes for the wood-based green templates have been presented so far. In this publication different raw materials and 3D shaping production processes and their influence on green body properties are described. It was possible to produce green bodies with a MOR higher than 15 N/mm² and a density in the range above 0.82 g/cm³. It is shown that reduction of resin content decreases the strength significantly and a reduction to 30 mass % resin content reduces the MOR of flat pressed panels to the defined limit. The extruded samples showed a significantly lower strength (mean 18.1 N/mm², standard deviation 8.6 N/mm²). Injection molding was not applied successfully. The findings show that shape pressing and extrusion were applied successfully, but the green body properties differed significantly from the results achieved by flat pressing.     

Is it only CO2 that matters? A life cycle perspective on shallow geothermal systems

Shallow geothermal systems such as open and closed geothermal heat pump (GHP) systems are considered to be an efficient and renewable energy technology for cooling and heating of buildings and other facilities. The numbers of installed ground source heat pump (GSHP) systems, for example, is continuously increasing worldwide. The objective of the current study is not only to discuss the net energy consumption and greenhouse gas (GHG) emissions or savings by GHP operation, but also to fully examine environmental burdens and benefits related to applications of such shallow geothermal systems by employing a state-of the-art life cycle assessment (LCA). The latter enables us to assess the entire energy flows and resources use for any product or service that is involved in the life cycle of such a technology. The applied life cycle impact assessment methodology (ReCiPe 2008) shows the relative contributions of resources depletion (34%), human health (43%) and ecosystem quality (23%) of such GSHP systems to the overall environmental damage. Climate change, as one impact category among 18 others, contributes 55.4% to the total environmental impacts. The life cycle impact assessment also demonstrates that the supplied electricity for the operation of the heat pump is the primary contributor to the environmental impact of GSHP systems, followed by the heat pump refrigerant, production of the heat pump, transport, heat carrier liquid, borehole and borehole heat exchanger (BHE). GHG emissions related to the use of such GSHP systems are carefully reviewed; an average of 63 t CO₂ equivalent emissions is calculated for a life cycle of 20 years using the Continental European electricity mix with 0.599 kg CO₂ eq/kWh. However, resulting CO₂ eq savings for Europe, which are between ?31% and 88% in comparison to conventional heating systems such as oil fired boilers and gas furnaces, largely depend on the primary resource of the supplied electricity for the heat pump, the climatic conditions and the inclusion of passive cooling capabilities. Factors such as degradation of coefficient of performance, as well as total leakage of the heat carrier fluid into the soil and aquifer are also carefully assessed, but show only minor environmental impacts.     

Microstructure and fracture mechanical response of wood

Investigations on the fracture properties of wood in relation to its microstructure are reported. The inhomogeneous and hierarchical structure of wood is addressed. Wood species, the influence of orientation, the role of structural features, like rays are considered and discussed. Likewise the mode of loading, which determines the mode of fracturing, and the influence of humidity have been studied by using new fracture mechanical techniques and ways of evaluation. The specific fracture energy has been determined under crack opening conditions. In-situ loading in an environmental scanning electron microscope (ESEM), which allows observation in moistured condition, has been performed in order to investigate the mechanisms of fracturing of wood on a sub-microscopic scale. In the nanometer range, especially the influence of the microfibril angle on deformation and fracture behaviour has been studied.     

Phase relations and homogeneity region of the hightemperature superconducting phase (Bi,Pb)2Sr2Ca2Cu3O10+d

For the nominal composition of Bi_2.27−xPb_xSr₂Ca₂Cu₃O_10+d, the lead content was varied from x < 0.05 to 0.45. The compositions were examined between 800 and 890‡C which is supposed to be the temperatue range over which the so-called 2223 phase (Bi₂Sr₂Ca₂Cu₃O_10+d) is stable. Only compositions between x < 0.18 to 0.36 could be synthezised in a single phase state. For x <0.36, a lead-containing phase with a stoichiometry of Pb₄(Sr,Ca)₅CuO_d with a small solubiliy of Bi is formed, for x > 0.18 mainly Bi₂Sr₂CaCu₂O_8+d and cuprates are the equilibrium phases. The temperature range for the 2223 phase was found to be 800 to 890‡C but the 2223 phase has extremely varying cation ratios over this temperaure range. Former single phase 2223 samples turn to multiphase samples when annealed at slightly higher or lower temperaures. A decrease in the Pb solubility with increasing as well as decreasing temperature with a maximum at about 850‡C was found for the 2223 phase.     

Colloidal Stability and Surface Chemistry Are Key Factors for the Composition of the Protein Corona of Inorganic Gold Nanoparticles

To study the influence of colloidal stability on protein corona formation, gold nanoparticles are synthesized with five distinct surface modifications: coating with citric acid, bis(p‐sulfonatophenyl)phenylphosphine dihydrate dipotassium salt, thiol‐terminated methoxy‐polyethylene glycol, dodecylamine‐grafted poly(isobutylene‐alt‐maleic anhydride), and dodecylamine‐grafted poly(isobutylene‐alt‐maleic anhydride) conjugated with polyethylene glycol. The nanoparticles are incubated with serum or bronchoalveolar lavage fluid from C57BL/6 mice (15 min or 24 h) to assess the effect of differential nanoparticle surface presentation on protein corona formation in the air–blood barrier exposure pathway. Proteomic quantification and nanoparticle size measurements are used to assess protein corona formation. We show that surface modification has a clear effect on the size and the composition of the protein corona that is related to the colloidal stability of the studied nanoparticles. Additionally, differences in the composition and size of the protein corona are shown between biological media and duration of exposure, indicating evolution of the corona through this exposure pathway. Consequently, a major determinant of protein corona formation is the colloidal stability of nanoparticles in biological media and chemical or environmental modification of the nanoparticles alters the surface presentation of the functional epitope in vivo. Therefore, the colloidal stability of nanoparticles has a decisive influence on nano–bio interactions.     

Processing of Aqueous Aluminum Nitride Suspensions with High Solid Loading

The impact of different additives on the hydrolysis of AlN powder in aqueous suspensions at room temperature was studied. The results show that citric acid and polyacrylic acid are most effective in chemically protecting AlN against hydrolysis. The protected powder is hydrophilic, which facilitates aqueous processing, and the chemical stability is retained when basic dispersing agents are added. Based on these results, the solid loading of the aqueous slurries was maximized by utilizing bimodal particle size distributions. Combining bimodal powders with the dispersants Dolapix and citric acid, colloidally stable slurries with solid loadings in excess of 50 vol% were obtained.