Decrease In Mean Particle Size Research Articles

Enhancing anaerobic digestion of lignocellulosic biomass by mechanical cotreatment

BackgroundThe aim of this study was to increase the accessibility and accelerate the breakdown of lignocellulosic biomass to methane in an anaerobic fermentation system by mechanical cotreatment: milling during fermentation, as an alternative to conventional pretreatment prior to biological deconstruction. Effluent from a mesophilic anaerobic digester running with unpretreated senescent switchgrass as the predominant carbon source was collected and subjected to ball milling for 0.5, 2, 5 and 10 min. Following this, a batch fermentation test was conducted with this material in triplicate for an additional 18 days with unmilled effluent as the ‘status quo’ control.ResultsThe results indicate 0.5 – 10 min of cotreatment increased sugar solubilization by 5– 13% when compared to the unmilled control, with greater solubilization correlated with increased milling duration. Biogas concentrations ranged from 44% to 55.5% methane with the balance carbon dioxide. The total biogas production was statistically higher than the unmilled control for all treatments with 2 or more minutes of milling (α = 0.1). Cotreatment also decreased mean particle size. Energy consumption measurements of a lab-scale mill indicate that longer durations of milling offer diminishing benefits with respect to additional methane production.ConclusionsCotreatment in anaerobic digestion systems, as demonstrated in this study, provides an alternative approach to conventional pretreatments to increase biogas production from lignocellulosic grassy material.

Emulsifying property, antioxidant activity, and bitterness of soybean protein isolate hydrolysate obtained by Corolase PP under high hydrostatic pressure

Enzymatic hydrolysis of proteins can enhance their emulsifying properties and antioxidant activities. However, the problem related to the hydrolysis of proteins was the generation of the bitter taste. Recently, high hydrostatic pressure (HHP) treatment has attracted much interest and has been used in several studies on protein modification. Hence, the study aimed to investigate the effects of enzymatic hydrolysis by Corolase PP under different pressure treatments (0.1, 100, 200, and 300 MPa for 1–5 h at 50 °C) on the emulsifying property, antioxidant activity, and bitterness of soybean protein isolate hydrolysate (SPIH). As observed, the hydrolysate obtained at 200 MPa for 4 h had the highest emulsifying activity index (47.49 m2/g) and emulsifying stability index (92.98 %), and it had higher antioxidant activities (44.77 % DPPH free radical scavenging activity, 31.12 % superoxide anion radical scavenging activity, and 61.50 % copper ion chelating activity). At the same time, the enhancement of emulsion stability was related to the increase of zeta potential and the decrease of mean particle size. In addition, the hydrolysate obtained at 200 MPa for 4 h had a lower bitterness value and showed better palatability. This study has a broad application prospect in developing food ingredients and healthy foods.

Influence of Particle Properties on Filter Cake Compaction Behavior under Oscillatory Shear

Filter cake compaction is a common method for mechanical deliquoring of compressible filter cakes. In addition to the conventional squeezing compaction method, applying oscillatory shear to filter cakes at low pressure is an alternative compaction process in cake filtration. While basic differences in terms of compaction success have already been identified for various materials, a systematic analysis of the influence of material properties on compaction behavior under oscillatory shear is missing. The present work addresses the influence of particle size distribution and increasing particle agglomeration on the compaction success of oscillatory shear to further clarify the process knowledge and applicability. The compressibility achieved by this technique was investigated for calcium carbonate materials with various particle size distributions. The results show that the compaction potential increases from 17.3% for the coarsest material (x50,3 = 23.5 μm) to 26.6% for the finest material (x50,3 = 2.3 μm) with decreasing mean particle size. The more widely distributed material exhibits a higher compaction potential of 21.7% compared to 18.4% for the narrowly distributed material. Increasing particle agglomeration to improve the slurry filterability does not affect the achievable compaction states of the material by vibration compaction at sufficiently high energy input.

Alkoxide-Decorated Copper Nanoparticles on Amidine-Modified Polymers as Hydrogenation Catalysts for Enabling H2 Heterolysis

Direct formation of Cu nanoparticles was accomplished on an amidine- and guanidine-functionalized polymer (polystyrene-bound 1,8-diazabicyclo[5.4.0]undec-7-ene (PS-DBU) and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (PS-TBD), respectively) by thermal treatment of Cu(acac)2 (acac = acetylacetonato) in methanol under pressurized H2. The immobilized structure was characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES), elemental analysis, and microscopic analysis. X-ray photoelectron spectroscopy (XPS) data indicated that the nanoparticles consisted of Cu(0) and oxygenated Cu(I). The Cu(0)/Cu(I) ratio was determined by X-ray absorption spectroscopy. In particular, X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) studies indicated the inclusion of alkoxides bound to Cu nanoparticles. Further 13C-labeled experiments allowed us to identify the Cu methoxide species by solid-state 13C nuclear magnetic resonance (NMR). A series of alkoxide-incorporated Cu nanoparticles were proven to facilitate H2 heterolysis and were applied in the catalytic hydrogenation of CO2 to formate salts in the presence of a nitrogen base. The catalytic activity increased with decreased mean particle size and increased Cu(I) content, indicating that the Cu(I) alkoxide species played an indispensable role in hydrogenation. The combination of Cu/PS-DBU and 2-tert-butyl-1,1,3,3-tetramethylguanidine (BTMG) achieved a maximum turnover number of 2450 at 100 °C without leaching or aggregation of the nanosized catalysts.

Ultrasonic modulated rice bran protein concentrate: Induced effects on morphological, functional, rheological, and thermal characteristics

The effect of low frequency (20 kHz) ultrasonication at varying amplitude (20%, 30%, 40% for 30 min) on the morphological, functional, rheological, and thermal characteristics of rice bran protein concentrate (RBPC) from three different rice varieties: Pusa Basmati- 1509, 1121 and Sugandha were undertaken for the study. Scanning Electron Microscopy images showed that sonication treatment changed the microstructure of RBPC as some pores appeared on the smooth particles surface and more disordered structures compared to the untreated sample. Sonication treatment decreased mean particle size, D[4,3] from 89.77 μm (untreated) to 64.34 μm (20% amplitude), and increased surface hydrophobicity significantly (p < 0.05), from 1.34 ± 0.0080 (untreated) to 1.65 ± 0.0081 (20% amplitude) of 1121 RBPC variety. The FTIR analysis showed that sonication treatment altered RPBC secondary structure as β sheets, and random coils increased while reducing α-helix and β-turns. Sonication treatment at a lower amplitude of 20% made RBPCs brighter in color as lightness, redness, and yellowness values increased. The results showed that sonication treatment has improved the foaming capacity (FC), foaming stability (FS), and oil binding capacity (OBC) of all RBPC varieties. The FC increased significantly from 34.10 ± 0.27 (untreated) to 50.13 ± 0.98 (30% amplitude), FS (60 min) from 21.19 ± 0.63 (untreated) to 44.20 ± 0.26 (30% amplitude), and OBC from 1.42 ± 0.05 (untreated) to 1.61 ± 0.01 (30% amplitude) of 1509 RBPC variety, respectively (p < 0.05). Furthermore, water binding capacity and emulsion activity were reduced for all RBPC varieties after sonication, while solubility and digestibility improved for the 1121 variety, whereas reduced for the 1509 and Sugandha RBPC varieties. Frequency sweep analysis showed that sonication treatment reduced both the storage modulus and loss modulus of RBPC dispersions. Moreover, protein gel linkages transformed from non-covalent to covalently cross-link with increasing % amplitude for the 1121 RBPC variety. Ultrasonication at a lower 20% amplitude, first decreased the denaturation temperature (Tp) of 1121 RBPC variety from 72.5 °C to 63 °C, then increased it to 77.3 °C at higher 40% amplitude. In conclusion, under the conditions investigated in this study, sonication treatment has the potential to modify the foaming and oil-binding properties of RBPCs.

Enhancement of room-temperature magnetoresistance in polyvinyl acetate encapsulated Fe3O4 nanoparticles

We report a facile method to enhance the magnetoresistance (MR) of magnetite (Fe3O4) nanoparticles assemblies using encapsulating with polyvinyl acetate (PVAc). Fe3O4 nanoparticles of various size distributions have been synthesized by a chemical co-precipitation method. X-ray diffraction study revealed the formation of cubic inverse spinel structure with Fd3¯m space group. Morphology and the particle size distributions were studied using FESEM and TEM. The films of smaller sized nanoparticles show higher resistivity, and a significant drop in resistivity was observed after the PVAc encapsulation over the film. Negative MR of 1.7–2.13% was observed with the decrease of mean particle size from ∼ 50 nm to 21 nm at room temperature under 0.5 T, which was increased to 4 – 8.4 % after the PVAc encapsulation. The large low field magnetoresistance is mainly attributed to the tunnelling of high spin polarized electrons in Fe3O4 grains through the spin disordered grain boundaries. The encapsulation of PVAc over the nanoparticles film reassembles the nanoparticles and reduce the interparticle distances by producing a compressive stress, which reduces the tunnelling barrier for the interparticle charge transport and improves the magnetoresistance.

Effect of secondary particle size of nickel oxide nanoparticles on cytotoxicity in A549 cells.

The effect of nanoparticle type, shape, as well as primary and secondary particle size on toxicity remains poorly characterized. In this study, suspensions of nickel oxide (NiO) nanoparticles with the same primary particle size (< 50 nm) but different secondary particle sizes were prepared, and their cytotoxicity was investigated. A planetary ball mill wet nanopulverizer with zirconium milling balls of decreasing sizes (φ: 0.5, 0.1, and 0.05 mm) yielded NiO nanoparticles of decreasing mean particle size (310.4 ± 6.7, 172.0 ± 2.8, and 102.0 ± 0.5 nm). Stock solutions were diluted to various concentrations in 10% heat-inactivated fetal bovine serum containing minimum essential medium, and shown to have the same primary particle size, but different secondary particle sizes. Tests with A549 cells revealed that cytotoxicity increased with increasing secondary particle size: milling ball diameter φ 0.05 mm (IC50: 148 μg/mL) < φ 0.1 mm (IC50: 83.5 μg/mL) < φ 0.5 mm (IC50: 33.4 μg/mL). Uptake experiments indicated that the intracellular amount of Ni increased with increasing secondary particle size. In summary, the present findings show that differences in secondary particle size affected the cytotoxicity of NiO suspensions, which could be ascribed at least in part to differences in the amount of NiO taken up by the cells.

Effect of Particle Size on the Dissolution of Pt3Co/C and Pt/C PEMFC Electrocatalysts

Potentiostatic and potentiodynamic Pt and Co dissolution were investigated for three Pt3Co/C catalysts with particle sizes of 4.9, 8.1, and 14.8 nm in aqueous electrolyte at potentials encountered by the PEMFC cathode. For all three Pt3Co/C catalysts under prolonged potentiostatic dissolution, the dissolved Pt steady state concentration increases from 0.85 V to reach a maximum at 1.1−1.15 V and decreases at higher potentials. The dependence of the dissolved Pt steady state concentration on particle size reveals that catalyst stability decreases with decreasing mean particle size, whereas the stability under potential cycling conditions is non-monotonic with particle size. Preferential dissolution of Co from all three Pt3Co catalysts was observed at all potentials, which increases at >1.1 V, the region over which Pt dissolution decreases, reflecting the opposing effects of Pt oxide formation on Pt and Co dissolution. Comparison of Pt3Co/C and Pt/C with similar mean particle sizes (4.9 vs 5.0 nm) and particle size distributions reveals that the Pt3Co/C has a higher potentiostatic dissolution rate (4–5 times), a higher steady state concentration of dissolved Pt (∼2 times), and a larger change in electrochemically-active surface area (ECA) (18 times) after prolonged cycling, indicating that Pt3Co has inferior stability. The higher rates of Pt dissolution for Pt3Co vs Pt have been attributed to higher extents of surface Pt oxidation, as determined using voltammetric oxide reduction charges and the white line intensities in Pt L3 X-ray absorption spectra.

Particle size reduction along the digestive tract of fat sand rats (Psammomys obesus) fed four chenopods.

It is generally accepted that microbial digestion contributes little to digesta particle size reduction in herbivores, and that faecal particle size reflects mainly chewing efficiency, and may vary with diet. Nevertheless, a decrease in mean particle size (MPS) along the gastrointestinal tract (GIT) has been reported, especially in hindgut fermenters. However, to what degree the very fine particle fraction (non-food origin, especially microbes) affects MPS is unclear. Fat sand rats (Psammomys obesus, diurnal herbivores, n = 23, 175 ± sd 24g) consumed one of four chenopods (natural dietary items in the wild) for 30days. Digestibility was related negatively to dietary fibre content. We determined digesta MPS in the forestomach, glandular stomach, small intestine, caecum, colon and faeces by wet sieving, including (MPSfines) or excluding (MPSnofines) particles < 0.25mm. The proportions of fines were higher and of MPSfines were correspondingly lower in GIT sections that harbour microbes (forestomach, hindgut), whereas MPSnofines did not differ between forestomach and glandular stomach. However, MPSnofines decreased along the GIT, indicating MPS reduction due to digestive (enzymatic and microbial) processes. The four different diets led to different MPS, but the magnitude of MPS reduction in the GIT was not correlated with dietary fibre fractions or dry matter digestibility. These results indicate that within a species, MPS cannot be used as a proxy for diet quality or digestibility, and raise the hypothesis that MPS reduction along the GIT may be more pronounced in smaller than in larger mammalian terrestrial herbivores, possibly due to the fine initial particles produced by chewing in small species.

Quality and productivity enhancement of sintering process using correlation-based online permeability by infrared-based flow measurement technique

ABSTRACT Sinter is the most preferred metallic burden for modern-day blast furnaces. It is produced by agglomeration of iron ore fines in sinter machine. Sintering process depends on airflow through the sinter bed under high suction. The airflow through the sinter bed is measured by sinter bed permeability and has direct correlation with sinter productivity. Permeability can be determined by different ways. Among these methods, permeability detection by measuring the airflow through granular sinter bed by placing the instrument in the static wind box is very well known. But there is a challenge due to multiphase and turbulent conditions in the wind box.Infrared-based flow measurement technique has been used to measure flow. Therefore, this flow has been used to get permeability in the form of JPU (Japanese Permeability Unit). Productivity increases by 4% in spite of decrease in mean particle size of iron ore by 3.4% for a fixed time duration.

Acoustic discrimination of fine surface textures by echolocating free-tailed bats

Surface texture is an integral cue used by echolocating mammals for characterizing and forming a mental representation of an ensonified target. Bats need to be able to recognize and discriminate between different target surface textures. Previous work showed that bats rely on spectral cues embedded in echoes to resolve textures, but the resolution limits for this behavior are unknown. Mexican free-tailed bats (Tadarida brasiliensis) are fast, high-flying insectivorous bats that emit broadband FM multi-harmonic sonar pulses. We trained three bats to perform a two-alternative forced-choice assay in which they compared and selected the coarser of two sandpaper samples of different grit size. Commercial sandpaper grits decrease in mean particle size following an exponential function. We tested the bats ability to discriminate between 10 different grit sizes varying from 40 to 240 grit, corresponding to mean particles diameters varying from 425 to 50 μm. Bats discriminated all grits from a smooth plexiglass control and almost all grits from each other up to 180versus 220 grit (82 vs 68 μm) but not 220 vs 240 (68 vs 54 μm), indicating an extraordinary minimum difference threshold of about 14 μm, which rivals human performance using tactile active sensing by finger touch.

Quantitative approach to realization of ultrasonic grain refinement of Al-7Si-2Cu-1Mg alloy

Ultrasonic melt treatment (UST) was applied to Al-7Si-2Cu-1Mg melt at various temperatures of 620, 650, 700 and 785 °C. MgAl2O4 particles which were often found to be densely populated along oxide films, became effectively dispersed and well-wetted by UST. Transmission electron microscopy work combined with crystallography analysis clearly indicates that MgAl2O4 particles can act as α-Al nucleation site with the aid of UST. However, with UST, grain refinement occurred only at temperature of 620 °C and the grain size increased from 97 to 351 μm with increase of melt temperature to 785 °C for UST. In quantitative analysis of grain size and MgAl2O4 particle diameter, it was found that ultrasonic de-agglomeration decreased mean particle size of the MgAl2O4 particles, significantly reducing size from 1.2 to 0.4 μm when temperature increased from 620 to 785 °C. Such a size reduction with increased number of MgAl2O4 particles does not always guarantee grain refinement. Thus, in this work, detailed condition for achieving grain refinement by UST is discussed based on quantitative measurement. Furthermore, we tried to suggest the most valid grain refinement mechanism among the known mechanisms by investigation of the relationship between grain size and particle size with variation of melt temperature.

Chemical separation in a binary liquid aerosol by filtration using electrospun membranes

Binary liquid aerosols were filtered using electrospun fiber membranes for the purpose of demonstrating the feasibility of changing aerosol composition through size selection. The impacts of filtration on the particle size distribution and the overall composition of the aerosols were studied and correlated to the filter properties. The binary liquid aerosols comprised di(2-ethylhexyl) sebacate and di(2-ethylhexyl) phthalate, with median mobility diameters between 200 nm and 300 nm. Droplet size-resolved measurements of aerosol composition, performed using a combination of cascade impactor and gas chromatography-mass spectrometry (GC–MS), revealed size-dependent compositional variation. Electrospun membranes of polyacrylonitrile with four different fiber diameters, ranging from 300 nm to 1 μm, were tested. The membranes with small fiber diameters were more likely to have significant impact on both the size and composition of the aerosols. Electrospun membranes consisting of 300 nm diameter fibers altered the median particle diameter by as much as 4%, and the overall composition of the aerosols by as much as 30%. Membranes with large fiber diameters, on the other hand, exhibited negligible effects on the aerosol systems with regard to both aerosol size and composition. Electrospun cellulose acetate membranes of different thicknesses were also tested on a binary aerosol system with the same components. Thicker filters resulted in greater decrease in mean particle size and greater change of aerosol composition, up to 16%. The changes in aerosol size distribution and composition upon filtration were correlated through the droplet size-dependence of the aerosol composition.

Effect of microfluidization on microstructure, protein profile and physicochemical properties of whole cowpea flours

Abstract Whole cowpea flours from three cultivars were microfluidized through a 200 μm “Z” type interaction chamber at room temperature for two passes. The confocal micrographs showed the microfluidization process could effectively disintegrate the structure of both cotyledon and seed coat, two major components of a cowpea seed. Disruption of cotyledon released the embedded starch granules and proteins, whereas disruption of seed coat generated large amounts of fiber fragments with amorphous and fluffy microstructure. Depending on the cultivars of cowpea, these effects significantly decreased mean particle size by up to 92.3% and bulk density by up to 68.7%, and increased specific surface area by up to 286.4%, swelling capacity by up to 107.7%, water-holding capacity by up to 16.1%, oil-holding capacity by up to 162.1%, and total water extractable proteins of whole cowpea by up to 39.7%. Reduced intensity of protein bands in SDS-PAGE was also observed. This indicated high pressure and high shear stress during microfluidization induced fundamental structural changes of cowpea proteins. Under the present experimental conditions, the microfluidization process had no apparent effects on both particle size and structure of cowpea starch granules present in the flours.

Combined Effects of Salt-related Variables on Qualitative Characteristics of Probiotic Fermented Milk

&lt;P&gt;Background: Doogh is a typical Iranian beverage based on fermented milk. The common salt used for Doogh is NaCl. Addition of salt in Doogh can take place before or after fermentation. The type of salt (NaCl or NaCl/KCl) and the sequence of salt addition in Doogh production can have significant impacts on biochemical characteristics of this product. &lt;/P&gt;&lt;P&gt; Methods: Nine probiotic Doogh treatments containing two probiotics (Lactobacillus acidophilus and Bifidobacterium lactis BB at the level of 107 cfu.mL-1) along with Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus, different salt percentages (0.5 and/or 1% (w/w)) in two ratios of NaCl/KCl (100:0 or 50:50) were prepared. Four samples were produced with the addition of salt before fermentation and four samples after fermentation (after cooling to 5°C). Apparent viscosity, phase separation, viability of probiotics and sensory properties of Doogh samples were studied during 21 days storage. &lt;/P&gt;&lt;P&gt; Results: The results showed that samples containing 1% (w/w) salt (NaCl or NaCl:KCl) had higher phase separation than treatments with 0.5% (w/w). The partial substitution of NaCl with KCl had a positive influence on the viability of probiotics. Treatments with 1% (w/w) NaCl:KCl and 0.5% (w/w) NaCl:KCl added before fermentation showed the maximum viability of probiotics. Addition of salt decreased the apparent viscosity of Doogh due to decreasing mean particle size of the dispersion system. From sensory point of view, the treatment with 0.5% (w/w) NaCl and those with 0.5% (w/w) NaCl:KCl before fermentation showed the highest acceptance. &lt;/P&gt;&lt;P&gt; Conclusion: A low-sodium Doogh with an acceptable probiotic viability was produced.&lt;/P&gt;

Strength Behaviors of Remolded Hydrate-Bearing Marine Sediments in Different Drilling Depths of the South China Sea

The mechanical behaviors of hydrate-bearing marine sediments (HBMS) drilled from the seafloor need to be understood in order to safely exploit natural gas from marine hydrate reservoirs. In this study, hydrates were prepared using ice powder and CH4 gas, and HBMS from the Shenhu area in the South China Sea were remolded using a mixed sample preparation method. A series of triaxial tests were conducted on the remolded HBMS to investigate the effects of soil particle gradation and the existence of hydrate on the mechanical properties of hydrate reservoirs. The results show that the stiffness and failure strength of HBMS decrease along with the decrease of mean particle size and soil aggregate morphology change at different drilling depths, and the reduction of failure strength is more than 20% when the drilling depth drops by 30 m. A better particle gradation of marine sediments may boost the stiffness and failure strength of HBMS. In addition, the existence of hydrate plays an important role in the strength behaviors of HBMS. The reduction of failure strength of HBMS with 30% initial hydrate saturation is more than 35% after complete hydrate dissociation.

Application of DRIFTS, 13C NMR, and py-MBMS to Characterize the Effects of Soil Science Oxidation Assays on Soil Organic Matter Composition in a Mollic Xerofluvent.

Chemical oxidations are routinely employed in soil science to study soil organic matter (SOM), and their interpretation could be improved by characterizing oxidation effects on SOM composition with spectroscopy. We investigated the effects of routinely employed oxidants on SOM composition in a Mollic Xerofluvent representative of intensively managed agricultural soils in the California Central Valley. Soil samples were subjected to oxidation by potassium permanganate (KMnO4), sodium hypochlorite (NaOCl), and hydrogen peroxide (H2O2). Additionally, non-oxidized and oxidized soils were treated with hydrofluoric acid (HF) to evaluate reduction of the mineral component to improve spectroscopy of oxidation effects. Oxidized non-HF and HF-treated soils were characterized by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), 13C cross polarization magic angle spinning (CP-MAS) nuclear magnetic resonance (NMR) spectroscopy, and pyrolysis molecular beam mass spectrometry (py-MBMS), and for particle size distribution (PSD) using laser diffractometry (LD). Across the range of soil organic carbon (OC) removed by oxidations (14-72%), aliphatic C-H stretch at 3000-2800 cm-1 (DRIFTS) decreased with OC removal, and this trend was enhanced by HF treatment due to significant demineralization in this soil (70%). Analysis by NMR spectroscopy was feasible only after HF treatment, and did not reveal trends between OC removal and C functional groups. Pyrolysis-MBMS did not detect differences among oxidations, even after HF treatment of soils. Hydrofluoric acid entailed OC loss (13-39%), and for H2O2 oxidized soils increased C:N and substantially decreased mean particle size. This study demonstrates the feasibility of using HF to improve characterizations of SOM composition following oxidations as practiced in soil science, in particular for DRIFTS. Since OC removal by oxidants, mineral removal by HF, and the interaction of oxidants and HF observed for this soil may differ for soils with different mineralogies, future work should examine additional soil and land use types to optimize characterizations of oxidation effects on SOM composition.

Tailoring the physical and catalytic properties of lanthanum oxycarbonate nanoparticles

The synthesis of lanthanum oxide and its carbonate analogues has been performed by flame spray pyrolysis (FSP). Two different feeds have been studied: an organic solution and an aqueous/organic microemulsion. A key experimental parameter of FSP, the O2 dispersion, i.e., the flow rate of the dispersing gas in the FSP nozzle, exhibits an effect on the properties of the materials prepared. Increasing the level of O2 dispersion led to an increase in surface area and a decrease in mean particle size and basicity when a lanthanum containing organic solution was used as FSP feed. Lanthanum can form different phases, such as oxides, hydroxides, oxycarbonates and carbonates. The increase of O2 dispersion also produced a phase change, going from a mixture of type Ia and type II La2O2CO3 and La2O3 to pure La2O3. The use of an aqueous/organic microemulsion feed, which had a higher viscosity than the organic feed, resulted in materials with a lower surface area and a higher mean particle size than those prepared using the organic solution at the same O2 dispersion. In this case a mixture of type II La2O2CO3 and La2O3 was obtained. The materials were tested for oxidative coupling of methane (OCM). We were able to demonstrate that the OCM performance of the materials could be modified by changing the synthesis parameters. For example, lower O2 dispersion produced the highest CH4 and O2 conversions. We also demonstrated that on ageing the mean particle size remain stable; however, the phases do not, showing a new phase, La(OH)3, formation and resulting in an increase in OCM activity. While the OCM performances are modest they do demonstrate the power of this approach for controlled synthesis of lanthanum materials.

Deagglomeration testing of airborne nanoparticle agglomerates: Stability analysis under varied aerodynamic shear and relative humidity conditions

ABSTRACTOccupational exposure to nanomaterial aerosols poses potential health risks to workers at nanotechnology workplaces. Understanding the mechanical stability of airborne nanoparticle agglomerates under varied mechanical forces and environmental conditions is important for estimating their emission potential and the released particle size distributions, which in consequence alters their transport and human uptake probability. In this study, two aerosolization and deagglomeration systems were used to investigate the potential for deagglomeration of nanopowder aerosols with different surface hydrophilicity under a range of shear forces and relative humidity conditions. Critical orifices were employed to subject airborne agglomerates to the shear forces induced by a pressure drop. Increasing applied pressure drop was found to be associated with decreased mean particle size and increased particle number concentrations. Rising humidity decreased the deagglomeration tendency as expressed by larger modal pa...

Characterization of ibuprofen microparticle and improvement of the dissolution

The objective of this study was to prepare ibuprofen (IBP) microparticles by pH-change method and enhance the dissolution rate in vitro. Tween80 and Cremophor RH40 were selected as stabilizers to change the microparticles morphology. The microparticles were evaluated by dissolution profiles and characterized by differential scanning calorimetry (DSC), powder X-ray diffraction (XRD), laser particle size analyzer, scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). IBP microparticle prepared with surfactants showed a significant increase in dissolution rate (more than three times within 10 min) and an obvious decrease in mean particle size. The morphology of microparticles was obviously changed. XRD and DSC results revealed that the crystalline state of the untreated IBP and the prepared IBP microparticles were similar. The crystallinity of microparticles produced might be lightly reduced by adding surfactants in preparation process. All results showed that it was useful to prepare high dispersion microparticle by adding surfactants in the preparation process for improving the dissolution.