Self-assembled microstructured polymeric and ceramic surfaces

Self-assembled microstructures were manufactured by dip coating of substrates with unfilled and filler-loaded preceramic polymer mixtures in the presence of a solvent and a non-solvent. The nature of the polymers was characterized by their solubility parameters. Variation of the polymer/polymer ratio and the volume fraction of the solvent and/or non-solvent led to different surface structures. Studies of the structure formation mechanism indicate that demixing processes of the polymers are responsible for self-assembly in filler-free mixtures. In filler-loaded mixtures the structure formation process, however, is more complex. The micro-structured polymeric coatings obtained from filler loaded systems were converted into polymer derived ceramic coatings under shape retention. High specific surface areas were measured after thermal conversion.     

Conformational,thermal, and ionic conductivity behavior of PEO in PEO/PMMA miscible blend: Investigating the effect of lithium salt

In this research, influence of incorporating LiClO₄ salt on the crystallization, conformation, and ionic conductivity of poly(ethylene oxide) (PEO) in its miscible blend with poly(methyl methacrylate) (PMMA) is studied. Differential scanning calorimetry showed that the incorporation of salt ions into the blend suppresses the crystallinity of PEO. The X‐ray diffraction revealed that the unit‐cell parameters of the crystals are independent of the LiClO₄ concentration despite of the existence of ionic interactions between PEO and Li cations. In addition, the complexation of the Li⁺ ions by oxygen atoms of PEO is investigated via Fourier transform infrared spectroscopy. The conformational changes of PEO segments in the presence of salt ions are studied via Raman spectroscopy. It is found that PEO chains in the blend possess a crown‐ether like conformation because of their particular complexation with the Li⁺ ions. This coordination of PEO with lithium cations amorphize the PEO and is accounted for suppressed crystallinity of PEO in the presence of salt ions. Finally, electrochemical impedance spectroscopy is used to characterize the ionic conductivity of PEO in the PEO/PMMA/LiClO₄ ternary mixture at various temperatures. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Local laser heat treatment of ultra high strength steels to improve formability

Ultra high strength steels are of enormous interest especially in the automotive industry due to their potential in realising light weight structures and improving the crash behaviour. However the poor formability of these steels limits their application for many parts in the car body. A solution to this limitation can be a local heat treatment using a laser beam to soften the material where a high formability is needed. Laser treatment was performed using a Nd:YAG laser with 3 kW maximum power. The output power was temperature controlled to achieve a constant temperature level during the heat treatment. Large areas are treated by scanning the surface with the laser beam. The materials under investigation are dual phase (DP), retained austenite (RA) and martensitic (MS) steels with a tensile strength of 600–1,200 MPa. The microstructure of DP steels consists of martensite and ferrite. RA steels contain ferrite, martensite and additionally a certain amount of retained austenite which transforms into martensite during plastic flow. MS steels are fully martensitic which gives them the highest yield strength of all UHS steels. The various steels were provided as not galvanised sheets (hot or cold rolled) with a thickness of 1.5 mm. Depending on material and process parameters tempering of martensite, formation of ferrite and transformation of retained austenite to martensite are observed as a result of the heat treatment. Tensile tests of DP 600, DP 1000 and MS-W 1200 reveal a significant reduction in yield and tensile strength and an increase in elongation after LHT. The effect is due to tempering of martensite and in the case of MS-W also due to an increase in volume fraction of ferrite. Tensile tests of RA-K 700 reveal a minor reduction in yield and tensile strength and a decrease in elongation. This can be attributed to the lower content of retained austenite which has transformed into martensite during LHT. From this result it can be expected that LHT is not beneficial for high deformation degrees. Deep drawing of a mock-up geometry using MS-W 1200 and RA-K 700 showed a significant decrease in slide force (~20%) compared to the initial condition. This results show that laser heat treatment has the potential to improve formability of UHS steels.     

Effect of oestrogen receptor status and time on the intra-tumoural accumulation of tamoxifen and N-desmethyltamoxifen following short-term therapy in human primary breast cancer

Chronic in utero methamphetamine treatment, throughout gestation in rats, resulted in alterations in both behavior and brain monoamine function in the adult offspring. The higher dose of methamphetamine (10 mg/kg/b.i.d.) caused a significant decrease in square crossing and rearing in an open field, as well as a regional increase of serotonin and dopamine uptake sites. In contrast, the lower dose of in utero methamphetamine (2 mg/kg/b.i.d.) resulted in a significant decrease in regional densities of serotonin and dopamine uptake sites, and only decreased rearing behavior. Across treatment groups, there were significant correlations between open-field square crossing activity and the number of uptake sites in specific brain areas. Other measured behaviors, such as the neonate righting reflex and the adult Morris water maze performance, were unaffected by either in utero drug regimen. These results are discussed in terms of the known neurotoxicity of amphetamines and the ability of the immature nervous system to compensate for fetal exposure to methamphetamine.