Combustion synthesis of yttria

Fine-particle, sinter-active yttria has been prepared by combustion of a redox compound, Y(N2H3COO)3·3H2O and mixtures of Y(N2H3COO)3·3H2O�NH4NO3 or NH4ClO4 as well as yttrium nitrate and hydrazine-based fuels. The fineparticle nature of the combustion-derived yttria has been investigated using powder density, particle size and BET surface area measurements. The uniaxially, cold-pressed fine-particle yttria when sintered at 1450�1500 °C achieved 98% theoretical density and showed a fine-grain (1�2 µm) microstructure.

Synthesis and properties of rare earth doped lamp phosphors

Red, blue and green emitting lamp phosphors such as EU(3+) doped Y2O3 (red phosphor), EU(2+) doped Ba0.64Al12O18.64, BaMgAl10O17 and BaMg2Al16O27 (blue phosphors) and Ce0.67Tb0.33MgAl11O19 and Eu2+, Mn2+ doped BaMgAl10O17 (green phosphors) have been prepared by the combustion of the corresponding metal nitrates (oxidizer) and oxalyl dihydrazide/urea/carbohydrazide (fuel) mixtures at 400 degrees-500 degrees C within 5 min. The formation of these phosphors has been confirmed by their characteristic powder X-ray diffraction patterns and fluorescence spectra. The phosphors showed characteristic emission bands at 611 nm (red emission), 430-450 nm (blue emission) and 515-540 nm (green emission). The fine-particle nature of the combustion derived phosphors has been investigated using powder density, particle size and BET surface area measurements.

Studies on Cu/CeO2: A new NO reduction catalyst

Fine particle and large surface area Cu/CeO2 catalysts of crystallite sizes in the range of 100-200 Angstrom synthesized by the solution combustion method have been investigated for NO reduction. Five percent Cu/CeO2 catalyst shows nearly 100% conversion of NO by NH3 below 300 degrees C, whereas pure ceria and Zr, Y, and Ca doped ceria show 85-95% NO conversion above 600 degrees C. Similarly NO reduction by CO has been observed over 5% Cu/CeO2 with nearly 100% conversion below 300 degrees C. Hydrocarbon (n-butane) oxidation by NO to CO2, N-2, and H2O has also been demonstrated over this catalyst below 350 degrees C making Cu/CeO2 a new NO reduction catalyst in the low temperature window of 150-350 degrees C. Kinetics of NO reduction over 5% Cu/CeO2 have also been investigated. The rate constants are in the range of 1.4 x 10(4) to 2.3 x 10(4) cm(3) g(-1) s(-1) between 170 and 300 degrees C. Cu/CeO2 catalysts are characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and electron paramagnetic resonance spectroscopy where Cu2+ ions are shown to be dispersed on the CeO2 surface. (C) 1999 Academic Press.

Synthesis and properties of La1-xSrxFeO3

Fine particle strontium substituted lanthanum ferrites La1-xSrxFeO3, where x = 0.0-1.0, have been synthesized by the solution combustion method using corresponding metal nitrates, oxalyl dihydrazide (ODH) or tetra formal tris azine (TFTA). Formation of La1-xSrxFeO3 was confirmed by the XRD and the fine particle nature of the ferrites investigated using SEM, particle size analysis and BET surface area measurements. La1-xSrxFeO3 (up to x = 0-0.4) exhibited low resistivity near the Neel temperatures. La1-xSrxFeO3 with x greater than or equal to 0.8 when used as bifunctional electrodes, showed oxygen evolution and reduction activity comparable with the orthoferrites prepared by the conventional solid state method. (C) 1999 Elsevier Science B.V. All rights reserved.

Potential Application of Adsorptive Media to Enhance Phosphorus Uptake in Stormwater Basins and Wetlands at Lake Tahoe : literature review. Report to the University of California Davis Tahoe Research Group

Phosphorus removal by wetlands and basins in Lake Tahoe may be improved through designing these systems to filter storm water through media having higher phosphorus removal capabilities than local parent material. Substrates rich in iron, aluminum and calcium oftentimes have enhanced phosphorus removal. These substrates can be naturally occurring, byproducts of industrial or water treatment processes, or engineered. Phosphorus removal fundamentally occurs through chemical adsorption and/or precipitation and much of the phosphorus can be irreversibly bound. In addition to these standard media, other engineered substrates are available to enhance P removal. One such substrate is locally available in Reno and uses lanthanum coated diatomaceous earth for arsenate removal. This material, which has a high positive surface charge, can also irreversibly remove phosphorus. Physical factors also affect P removal. Specifically, specific surface area and particle shape affect filtration capacity, contact area between water and the surface area, and likelihood of clogging and blinding. A number of substrates have been shown to effectively remove P in case studies. Based upon these studies, promising substrates include WTRs, blast furnace slag, steel furnace slag, OPC, calcite, marble Utelite and other LWAs, zeolite and shale. However, other nonperformance factors such as environmental considerations, application logistics, costs, and potential for cementification narrow the list of possible media for application at Tahoe. Industrial byproducts such as slags risk possible leaching of heavy metals and this potential cannot be easily predicted. Fly ash and other fine particle substrates would be more difficult to apply because they would need to be blended, making them less desirable and more costly to apply than larger diameter media. High transportation costs rule out non-local products. Finally, amorphous calcium products will eventually cementify reducing their effectiveness in filtration systems. Based upon these considerations, bauxite, LWAs and expanded shales/clays, iron-rich sands, activated alumina, marble and dolomite, and natural and lanthanum activated diatomaceous earth are the products most likely to be tested for application at Tahoe. These materials are typically iron, calcium or aluminum based; many have a high specific surface area; and all have low transportation costs. (PDF contains 21 pages)

Potential of a cyclone prototype spacer to improve in vitro dry powder delivery.

PURPOSE: Low inspiratory force in patients with lung disease is associated with poor deagglomeration and high throat deposition when using dry powder inhalers (DPIs). The potential of two reverse flow cyclone prototypes as spacers for commercial carrier-based DPIs was investigated. METHODS: Cyclohaler®, Accuhaler® and Easyhaler® were tested with and without the spacers between 30 and 60 Lmin−1. Deposition of particles in the next generation impactor and within the devices was determined by high performance liquid chromatography. RESULTS: Reduced induction port deposition of the emitted particles from the cyclones was observed due to the high retention of the drug within the spacers (e.g. salbutamol sulphate (SS): 67.89 ± 6.51% at 30 Lmin−1 in Cheng 1). Fine particle fractions of aerosol as emitted from the cyclones were substantially higher than the DPIs alone. Moreover, the aerodynamic diameters of particles emitted from the cyclones were halved compared to the DPIs alone (e.g. SS from the Cyclohaler® at 4 kPa: 1.08 ± 0.05 μm vs. 3.00 ± 0.12 μm, with and without Cheng 2, respectively) and unaltered with increased flow rates. CONCLUSION: This work has shown the potential of employing a cyclone spacer for commercial carrier-based DPIs to improve inhaled drug delivery.

Processible nanostructured materials with electrical conductivity and magnetic susceptibility: Preparation and properties of maghemite polyaniline nanocomposite films

We here present a versatile process for the preparation of maghemite/polyaniline (gamma-Fe2O3/ PAn) nanocomposite films with macroscopic processibility, electrical conductivity, and magnetic susceptibility. The gamma-Fe2O3 nanoparticles are coated and the PAn chains are doped by anionic surfactants of omega-methoxypoly(ethylene glycol) phosphate (PEOPA), 4-dodecylbenzenesulfonic acid (DBSA), and 10-camphorsulfonic acid (CSA). Both the coated gamma-Fe2O3 and the doped PAn are soluble in common organic solvents, and casting of the homogeneous solutions gives free-standing nanocomposite films with gamma-Fe2O3 contents up to similar to 50 wt %. The morphology of the gamma-Fe2O3 nanoparticles are characterized by transmission electron microscopy, UV-vis spectroscopy, and X-ray diffractometry. The gamma-Fe2O3/PAn films prepared from chloroform/m-cresol solutions of DBSA-coated gamma-Fe2O3 and CSA-doped PAn are conductive (sigma = 82-237 S/cm) and superpapamagnetic, exhibiting no hysteresis at room temperature. The zero-field-cooled magnetization experiment reveals that the nanocomposite containing 20.8 wt % gamma-Fe2O3 has a blocking temperature (T-b) in the temperature region of 63-83 K.

Activation of waste MDF sawdust charcoal and its reactive dye adsorption characteristics

This paper reports an experimental investigation of converting waste medium density fibreboard (MDF) sawdust into chars and activated carbon using chemical activation and thermal carbonisation processes. The MDF sawdust generated during the production of architectural mouldings was characterised and found to have unique properties in terms of fine particle size and high particle density. It also has a high content of urea formaldehyde resin used as a binder in the manufacturing of MDF board. Direct thermal carbonisation and chemical activation of the sawdust by metal impregnation and acid (phosphoric acid) treatment prior to pyrolysis treatment were carried out. The surface morphology of the raw dust, its chars and activated carbon were examined using scanning electron microscopy (SEM). Adsorptive properties and total pore volume of the materials were also analysed using the BET nitrogen adsorption method. Liquid adsorption of a reactive dye (Levafix Brilliant red E-4BA) by the derived sawdust carbon was investigated in batch isothermal adsorption process and the results compared to adsorption on to a commercial activated carbon (Filtrasorb F400). The MDF sawdust carbon exhibited in general a very low adsorption capacity towards the reactive dye, and physical characterisation of the carbon revealed that the conventional chemical activation and thermal carbonisation process were ineffective in developing a microporous structure in the dust particles. The small size of the powdery dust, the high particle density, and the presence of the urea formaldehyde resin all contributed to the difficulty of developing a proper porous structure during the thermal and chemical activation process. Finally, activation of the dust material in a consolidated form (cylindrical pellet) only achieved very limited improvement in the dye adsorption capacity. This original study, reporting some unexpected outcomes, may serve as a stepping-stone for future investigations of recycle and reuse of the waste MDF sawdust which is becoming an increasing environmental and cost liability. (C) 2004 Elsevier Ltd. All rights reserved.

Novel precipitated zirconia-based DGT technique for high-resolution imaging of oxyanions in waters and sediments

Water-sediment exchange is a fundamental component of oxyanion cycling in the environment. Yet, many of the (im)mobilization processes overlay complex spatial and temporal redox regimes that occur within millimeters of the interface. Only a few methods exist that can reliably capture these porewater fluxes, with the most popular being high-resolution diffusive gradients in thin films (HR-DGT). However, functionality of HR-DGT is restricted by the availability of suitable analyte binding agents within the sampler, which must be simple to cast and homogeneously distributed in the binding layer, exhibit adequate sorption capacities, be resistive to chemical change, and possess a very fine particle size (≤10 μm). A novel binding layer was synthesized to meet these requirements by in situ precipitation of zirconia into a precast hydrogel. The particle diameter ≤0.2 μm of zirconia in this precipitated gel was uniform and at least 50-times smaller than the conventional molding approach. Further, this gel had superior binding and stability characteristics compared with the commonly used ferrihydrite HR-DGT technique and could be easily fabricated as an ultrathin gel (60 μm) for simultaneous oxygen imaging in conjunction with planar-optodes. Chemical imaging of anion and oxygen fluxes using the new sampler were evaluated on Lake Taihu sediments.

Novel DGT method with tri-metal oxide adsorbent for in situ spatiotemporal flux measurement of fluoride in waters and sediments

Natural mineral-water interface reactions drive ecosystem/global fluoride (F−) cycling. These small-scale processes prove challenging to monitoring due to mobilization being highly localized and variable; influenced by changing climate, hydrology, dissolution chemistries and pedogenosis. These release events could be captured in situ by the passive sampling technique, diffusive gradients in thin-films (DGT), providing a cost-effective and time-integrated measurement of F− mobilization. However, attempts to develop the method for F− have been unsuccessful due to the very restrictive operational ranges that most F−-absorbents function within. A new hybrid-DGT technique for F− quantification containing a three-phase fine particle composite (Fesingle bondAlsingle bondCe, FAC) adsorbent was developed and evaluated. Sampler response was validated in laboratory and field deployments, passing solution chemistry QC within ionic strength and pH ranges of 0–200 mmol L−1 and 4.3–9.1, respectively, and exhibiting high sorption capacities (98 ± 8 μg cm−2). FAC-DGT measurements adequately predicted up to weeklong averaged in situ F− fluvial fluxes in a freshwater river and F− concentrations in a wastewater treatment flume determined by high frequency active sampling. While, millimetre-scale diffusive fluxes across the sediment-water interface were modeled for three contrasting lake bed sediments from a F−-enriched lake using the new FAC-DGT platform.

Development of composite particles for pulmonary delivery

In this work, biocompatible and biodegradable poly(D-L-lactide-co-glycolide) (PLGA) microparticles with the potential for use as a controlled release system of vaccines and other drugs to the lung were manufactured using supercritical CO2, through the Supercritical Assisted Atomization (SAA) technique. After performing a controlled variance in production parameters (temperature, pressure, CO2/solution flow ratio) PLGA microparticles were characterized and later used to encapsulate active pharmaceutical ingredients (API). Bovine serum albumin (BSA) was chosen as model protein and vaccine, while sildenafil was the chosen drug to treat pulmonary artery hypertension and their effect on the particles characteristics was evaluated. All the produced formulations were characterized in relation to their morphology (Morphologi G3 and scanning electronic microscopy (SEM)), to their physical-chemical properties (X-ray diffraction (XRD, differential scanning calorimetry (DSC), Fourier transform infrared (FTIR)) and aerodynamic performance using an in vitro aerosolization study – Andersen cascade impactor (ACI) - to obtain data such as the fine particle fraction (FPF) and the mass median aerodynamic diameter (MMAD). Furthermore, pharmacokinetic, biodegradability and biocompatibility tests were performed in order to verify the particle suitability for inhalation. The resulting particles showed aerodynamic diameters between the 3 and 5 μm, yields up to 58% and FPF percentages rounding the 30%. Taken as a whole, the produced microparticles do present the necessary requests to make them appropriate for pulmonary delivery.

HDPE-Ash Nanocomposites

Ash-based polymer composites are assuming increasing importance because of the pollutant potential, fine particle size, and low price of ash. Fly ash and rice husk ash are two prominent ash materials on which some investigations have already been done for potential use in polymer composites. This article highlights the results of a study on the use of wood ash in HDPE. Wood ash is mainly a mixture of various metallic compounds and some silica. Here, the characterization of wood ash has been done with the help of XRD, ICPAES, light scattering based particle size analysis, FTIR, and SEM. The results show that wood ash particle size has an average value of 293 nm, much lower than other categories of ash. When blended with HDPE in the presence of a compatibilizer, wood ash gives rise to vastly improved mechanical properties over that of the base polymer. The results prove that wood ash is a valuable reinforcing material for HDPE and the environmental pollution due to wood ash can be solved in a most profitable way by this technique.

Effect of air-drying pre-treatment on the characterization of forest soil carbon pools

Archived soils could represent a valuable resource for the spatio-temporal inventory of soil carbon stability. However, archived soils are usually air-dried before storage and the impact of a drying pretreatment on physically and chemically-defined C fractions has not yet been fully assessed. Through the comparison of field-moist and corresponding air-dried (at 25oC for 2 weeks) forest soil samples, we examined the effect of air-drying on: a) the quantity and the quality of cold- (CWEC) and hot-water (HWEC) extractable C and b) the concentration of C in physically isolated fractions (free- and intra-aggregate light and organo-mineral). Soil samples were collected from the organic (O) and mineral (A and B) horizons of three different forest soils from southeastern England: (i) Cambisol under Pine (Pinus nigra); (ii) Cambisol under Beech (Fagus sylvatica) and (iii) Gleysol under oak (Quercus robur). CWEC concentrations for dry samples were up to 2 times greater than for corresponding field moist samples and had significantly (p < 0.001) higher phenolic content. However, the effect of drying pretreatment on HWEC, its phenolic content was not significant (p > 0.05) for most samples. Dried soils had significantly (p < 0.001) higher concentrations of free light-C while having lower concentrations of intra-aggregate-C when compared to moist samples (p < 0.001). However, fine silt and clay fractions were not significantly affected by the drying pretreatment (p=0.789). Therefore, based on the results obtained from gleysol and cambisol forest soils studied here, C contents in hot-water extractions and fine particle size physical fractions (< 25µm) seem to be robust measurements for evaluating C fractions in dried stored forest soils. Further soil types should be tested to evaluate the wider generality of these findings.

Aerosol properties, in-canopy gradients, turbulent fluxes and VOC concentrations at a pristine forest site in Amazonia

Aerosol physical and chemical properties were measured in a forest site in central Amazonia (Cuieiras reservation, 2.61S; 60.21W) during the dry season of 2004 (Aug-Oct). Aerosol light scattering and absorption, mass concentration, elemental composition and size distributions were measured at three tower levels (Ground: 2 m; Canopy: 28 m, and Top: 40 m). For the first time, simultaneous eddy covariance fluxes of fine mode particles and volatile organic compounds (VOC) were measured above the Amazonian forest canopy. Aerosol fluxes were measured by eddy covariance using a Condensation Particle Counter (CPC) and a sonic anemometer. VOC fluxes were measured by disjunct eddy covariance using a Proton Transfer Reaction Mass Spectrometer (PTR-MS). At nighttime, a strong vertical gradient of phosphorus and potassium in the aerosol coarse mode was observed, with higher concentrations at Ground level. This suggests a source of primary biogenic particles below the canopy. Equivalent black carbon measurements indicate the presence of light-absorbing aerosols from biogenic origin. Aerosol number size distributions typically consisted of superimposed Aitken (76 nm) and accumulation modes (144 nm), without clear events of new particle formation. Isoprene and monoterpene fluxes reached respectively 7.4 and 0.82 mg m(-2) s(-1) around noon. An average fine particle flux of 0.05 +/- 0.10 10(6) m(-2) s(-1) was calculated, denoting an equilibrium between emission and deposition fluxes of fine mode particles at daytime. No significant correlations were found between VOC and fine mode aerosol concentrations or fluxes. (C) 2009 Elsevier Ltd. All rights reserved.

Ion dependence of magnetic anisotropy in MFe(2)O(4) (M = Fe, Co, Mn) nanoparticles synthesized by high-temperature reaction

The influence of different M(2+) cations on the effective magnetic anisotropy of systems composed of MFe(2)O(4) (M Fe, Co and Mn) nanoparticles was investigated. Samples were prepared by the high-temperature (538 K) solution phase reaction of Fe (acac) 3, Co (acac) 2 and Mn (acac) 2 with 1,2 octanodiol in the presence of oleic acid and oleylamine. The final particles are coated by an organic layer of oleic acid that prevents agglomeration. Transmission electron microscopy (TEM) images show that particles present near spherical form and a narrow grain size distribution, with mean diameters in the range of 4.5 - 7.6 nm. Powder samples were analyzed by ac susceptibility and Mossbauer measurements, and K(eff) for all samples was evaluated using both techniques, showing a strong dependence on the nature of the divalent cation. (C) 2008 Elsevier B.V. All rights reserved.