Electrically conductive silicon oxycarbide thin films prepared from preceramic polymers

This work focuses on silicon oxycarbide thin film preparation and characterization. The Taguchi method of experimental design was used to optimize the process of film deposition. The prepared ceramic thin films with a thickness of c. 500 nm were characterized concerning their morphology, composition, and electrical properties. The molecular structure of the preceramic polymers used for the preparation of the ceramic thin films as well as the thermomechanical properties of the resulting SiOC significantly influenced the quality of the ceramic films. Thus, an increase in the content of carbon was found beneficial for the preparation of crack-free thin films. The obtained ceramic films exhibited increased electrical conductivity as compared to monolithic SiOC of similar chemical composition. This was shown to correlate with the unique hierarchical microstructure of the SiOC films, which contain large oxygen-depleted particles, mainly consisting of highly graphitized carbon and SiC, homogeneously dispersed in an oxygen-containing amorphous matrix. The matrix was shown to also contain free carbon and to contribute to charge carrier transport between the highly conductive large particles. The ceramic thin films possess electrical conductivities in the range from 5.4 to 8.8 S/cm and may be suitable for implementation in miniaturized piezoresistive strain gauges.     

Hybrid Self-Assembling Nanoparticles Encapsulating Zoledronic Acid: A Strategy for Fostering Their Clinical Use

Self-assembling nanoparticles (SANPs) promise an effective delivery of bisphosphonates or microRNAs in the treatment of glioblastoma (GBM) and are obtained through the sequential mixing of four components immediately before use. The self-assembling approach facilitates technology transfer, but the complexity of the SANP preparation protocol raises significant concerns in the clinical setting due to the high risk of human errors during the procedure. In this work, it was hypothesized that the SANP preparation protocol could be simplified by using freeze-dried formulations. An in-depth thermodynamic study was conducted on solutions of different cryoprotectants, namely sucrose, mannitol and trehalose, to test their ability to stabilize the produced SANPs. In addition, the ability of SANPs to deliver drugs after lyophilization was assessed on selected formulations encapsulating zoledronic acid in vitro in the T98G GBM cell line and in vivo in an orthotopic mouse model. Results showed that, after lyophilization optimization, freeze-dried SANPs encapsulating zoledronic acid could retain their delivery ability, showing a significant inhibition of T98G cell growth both in vitro and in vivo. Overall, these results suggest that freeze-drying may help boost the industrial development of SANPs for the delivery of drugs to the brain.     

Filled temperature‐sensitive poly(vinyl methyl ether) hydrogels

Temperature‐sensitive hydrogels based on poly(vinyl methyl ether) (PVME) with ferroelectric or ferromagnetic properties were synthesized by high‐energy irradiation. Barium titanate and poly(vinylidene fluoride) (PVDF) were used as ferroelectric filler and Ni as ferromagnetic filler. The filled PVME hydrogels were synthesized by electron beam or γ‐ray irradiation (of a suspension with 5–50 wt % of filler (with respect to polymer mass) in a 20 wt % aqueous PVME solution). Filling of the gel reduces the absolute swelling degree at low temperatures, but do not influence the phase‐transition temperature of the gel. The particle distribution of the fillers inside the gel was visualized by field emission scanning electron microscopy. The fillers were incorporated in the PVME network and fixed because of their size (inorganic particles), as well as by chemical bonds (PVDF). The ferroelectric or ferromagnetic properties of the filled gels were proved. Measurements in a corresponding alternating field provide the hysteresis loop, for both the ferromagnetic and ferroelectric gel. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2253–2265, 2005     

Stability and kinetics of iron-terephthalate MOFs with diverse structures in aqueous pollutant degradation

Synthesized iron-terephthalate metal–organic frameworks (MOFs), MIL-101 and MOF-235, with contrasting morphologies are examined to elucidate the role of structural arrangement in catalytic aqueous pollutant degradation. MIL-101 demonstrates a larger pseudo-first order rate constant than MOF-235 (3.5 ± 0.2 mol_Fe⁻¹ · s⁻¹ vs. 0.84 ± 0.07 mol_Fe⁻¹ · s⁻¹) toward oxidation of methylene blue (MB) dye with excess hydrogen peroxide at ambient temperature, likely due to intrinsic differences in ligand coordination at their metal nodes. However, despite continued activity upon reuse, both MOFs undergo structural alterations resulting in formation of leached species active for MB degradation that have been obfuscated in previous studies. Detailed stability testing and ex situ characterization of recovered catalyst, examinations that remain underreported in Fe-MOF studies for pollutant oxidation, indicate that water plays a prominent role in the breakdown of these frameworks. Collectively, this work informs the interpretation and use of common Fe-MOFs for aqueous applications, relating material changes to observed reaction phenomena.     

Application and automation of flow injection analysis (FIA) using fast responding enzyme glass electrodes to detect penicillin in fermentation broth and urea in human serum

An enzyme immobilization technique has been developed to determine the concentration of biological compounds. This technique has been applied to penicillinase and urease, which are crosslinked as very fine films directly onto the sensitive ends of pH glass electrodes, thereby dispensing with the need of an on-line enzyme reactor. The biosensor is incorporated in an FIA system within a magnetically stirred detection cell. Penicillin-V in fermentation broth and urea in human serum samples were detected and the results were compared with HPLC and spectrophotometric methods. On-line measurement is achieved through the automation of this FIA system.     

Electrochemical treatment of simulated ground water containing MTBE and BTEX with BDD anodes

BACKGROUND: Benzene, toluene, ethylbenzene, xylene (BTEX) and oxy‐fuels such as methyl tert‐butyl ether (MTBE) are typical contaminants of ground waters. Biological and physical techniques are often ineffective in removing these compounds, while promising results were obtained with advanced oxidation processes (AOPs), which are based on oxidation by hydroxyl radicals. Electrochemical oxidation with boron doped diamond (BDD) anodes occurs by OH radicals generated from water oxidation, so that it may be considered as an alternative to other AOPs. RESULTS: An experimental study on the electrochemical removal of MTBE and BTEX with BDD anodes from water with low organic concentrations and low conductivity is presented. The kinetics of the process was investigated by batch electrolyses: the removal of MTBE and benzene was controlled by the mass transfer towards the anode, while a further reaction bulk contribution was found for alkylbenzenes. The process was tested in continuous mode and the energy consumption was evaluated and compared with other AOPs. CONCLUSIONS: Removal of the pollutants higher than 95% was achieved under all the examined conditions, confirming the effectiveness of the process. The proposed electrochemical treatment was comparable with other AOPs in terms of energy consumption, and it can be considered as an alternative to other processes for ground water treatment. Copyright © 2010 Society of Chemical Industry     

Additive interactions in the stabilization of film grade high-density polyethylene. Part I: Stabilization and influence of zinc stearate during melt processing

The melt stabilization activity of some of the most commercially significant phenolic antioxidants and phosphites (alone and in combination), without and with zinc stearate, was studied in high-density polyethylene (HDPE) produced by Phillips catalyst technology. Multiple pass extrusion experiments were used to degrade the polymer melt progressively. The effect of stabilizers was assessed via melt flow rate (MFR) and yellowness index (YI) measurements conducted as a function of the number of passes. The level of the phenolic antioxidant remaining after each extrusion was determined by high-performance liquid chromatography (HPLC). Phenolic antioxidants and phosphites both improved the melt stability of the polymer in terms of elt viscosity retention; the influence of zinc stearate was found to be almost insignificant. However, phosphites and zinc stearate decreased the discoloration caused by the phenolic antioxidants. A correlation was found between the melt stabilization performance of phosphites and their hydroperoxide decomposition efficiency determind via a model hydroperoxide compound. Steric and electronic effects associated with the phosphorus atom influenced the reactivity towards hydroperoxides. Furthermore, high hydrolytic stability did not automatically result in lower efficiency. Besides phosphite molecular structure, stabilization activity was also influenced by the structure of the primary phenolic antioxidant and the presence of zinc stearate.     

Recycling the insoluble residue from titania slag dissolution (tionite) in clay bricks

Tionite is the insoluble residue from the titania slag dissolution process for TiO₂ manufacturing. It is a fine-grained sludge consisting of rutile, anatase, amorphous phase and bassanite. Chemical composition is TiO₂ (ca. 50%), SiO₂ (ca. 30%) and minor Al, Ca, Mg, and Fe, plus residual sulfur, implying an acidic pH of waste. Moisture is about 35% of dry weight. The potential of tionite as colouring agent in clay bricks was appraised by admixing (up to 9%) either as-produced or neutralized tionite to four industrial clay bodies. The effect on technological behaviour was assessed by laboratory simulation of the industrial brickmaking process and determining working moisture, drying sensitivity, shrinkage and bending strength, water absorption, bulk density, efflorescence, and colour. The use of tionite is technologically feasible, with little adjustment of industrial cycle, and resulting brick performances depend remarkably on the composition and properties of clay bodies. Carbonate-rich bodies seem to be affected by tionite more during drying than during firing; carbonate-poor bodies range from little changes to consistent worsening of brick performances. No relevant changes of process and product parameters were found up to 3% tionite. Additions over 5% induce significant variations, such as increase of working moisture and water absorption, decrease of bulk density and bending strength. A definite and consistent improvement of this technological behaviour is achieved by using neutralized tionite. The yearly output of tionite could be entirely recycled by approximately four average-size brickworks adding about 3% of residue (dry weight).     

Advantageous and detrimental effects of air sparging in membrane filtration: Bubble movement, exerted shear and particle classification

In various membrane applications air scour is applied to minimise fouling and to remove cake layers. Optimisation of module design and operating conditions (e.g., geometry and aeration intensity) requires knowledge of the most suited hydrodynamic conditions for the filtration task. However, many fundamentals of this multiphase flow in membrane modules are still unknown and difficult to access experimentally. Using experimental and numerical investigations it was shown that air sparging can have advantageous but also detrimental effects: depending on membrane plate spacing, wall shear can decrease with bubble size. Additionally, particle classification or segregation which increases the cake’s hydraulic resistance must be taken into account. Based on such findings, it will be possible to derive optimum bubble sizes, membrane spacing, aeration intensities and start-up strategies.     

Integrated Computational Materials Engineering in Solar Plants: The Virtual Materials Design Project

The high temperatures required for efficient operation of solar thermal power plants constitutes one of the major challenges of this technology. Gaining insight into materials behavior at very high temperatures is critical to improve their techno-economic feasibility. Standard material characterization approaches become inefficient, as extensive testing campaigns are required. We propose a multiscale–multiphysical approach that accounts for materials composition to (1) predict the behavior of both Inconel 625 and new solar salts, and (2) assess the thermomechanical performance of key components. We carried out a complete thermoelastic multiscale analysis that spans six time and length scales in a single simulation platform, combining discrete and continuum tools (from quantum to continuum mechanics). These applications show the substantial economic benefits that may be achieved by an ICME approach in the energy sector, reducing the cost of prototypes while decreasing development times and maintenance costs due to a better understanding of materials behavior.