Control Of Particle Size Distribution Research Articles

Continuous Inhalation Exposure to Fungal Allergen Particulates Induces Lung Inflammation While Reducing Innate Immune Molecule Expression in the Brainstem.

Continuous exposure to aerosolized fine (particle size ≤2.5 µm) and ultrafine (particle size ≤0.1 µm) particulates can trigger innate inflammatory responses in the lung and brain depending on particle composition. Most studies of manmade toxicants use inhalation exposure routes, whereas most studies of allergens use soluble solutions administered via intranasal or injection routes. Here, we tested whether continuous inhalation exposure to aerosolized Alternaria alternata particulates (a common fungal allergen associated with asthma) would induce innate inflammatory responses in the lung and brain. By designing a new environmental chamber able to control particle size distribution and mass concentration, we continuously exposed adult mice to aerosolized ultrafine Alternaria particulates for 96 hr. Despite induction of innate immune responses in the lung, induction of innate immune responses in whole brain samples was not detected by quantitative polymerase chain reaction or flow cytometry. However, exposure did trigger decreases in Arginase 1, inducible nitric oxide synthase, and tumor necrosis factor alpha mRNA in the brainstem samples containing the central nervous system respiratory circuit (the dorsal respiratory group, ventral respiratory group, and the pre-Bötzinger and Bötzinger complexes). In addition, a significant decrease in the percentage of Toll-like receptor 2-expressing brainstem microglia was detected by flow cytometry. Histologic analysis revealed a significant decrease in Iba1 but not glial fibrillary acidic protein immunoreactivity in both the brainstem and the hippocampus. Together these data indicate that inhalation exposure to a natural fungal allergen under conditions sufficient to induce lung inflammation surprisingly causes reductions in baseline expression of select innate immune molecules (similar to that observed during endotoxin tolerance) in the region of the central nervous system controlling respiration.

Decorating platinum on nitrogen-doped graphene sheets: Control of the platinum particle size distribution for improved photocatalytic H2 generation

Nitrogen doping of graphene with systematically controlled dopant content and distribution of nitrogen species is demonstrated to improve the size distribution of the deposited platinum (Pt) nanoparticles. While the dopant content can be tuned by varying the urea dosage, the doped nitrogen species (namely pyridinic N, pyrrolic N, and graphitic N) can be controlled through the annealing temperature. Chemically reduced Pt nanoparticles were found to be evenly distributed on the nitrogen-doped graphene sheets (NRGO) with particle size centred at 2.7 nm. In comparison, the decoration of Pt on the non-doped graphene (RGO) yielded a composite material with larger Pt (7.8 nm) and poorer size distribution. The loading of Pt nanoparticles is shown to correlate with the concentration of the nitrogen dopant, in particular that of the graphitic N species. Owing to the smaller and better distributed Pt nanoparticles which facilitated more active sites for reaction, the Pt-loaded NRGO photocatalytically generated H2 gas ten times higher than that of Pt-loaded RGO when coupled with photoactive graphitic carbon nitride (g-C3N4).

Extraction of different phenolic groups from oats at a nonthermal pilot scale: Effect of solvent composition and cycles

AbstractThis article explores oat's polyphenols extraction in ethanol/water and methanol/water at a nonthermal pilot scale. Alcohol % (vol/vol) and cycles were controlled by response surface methodology. Eight polyphenols were evaluated (HPLC), together with antioxidant capacity (ORAC) and total polyphenol content (TPC). Model adjusted well in the majority of the cases. Highest TPC and ORAC were obtained with ethanolic mixtures. Vanillic acid and vanillin highest yields were at 14.6% (vol/vol) and 50% (vol/vol) in both alcohols. Hydrocinnamic acids were better extracted at high alcohol concentrations (98–100%, vol/vol), where p‐coumaric acid was the most present. Avenanthramides optimum alcohol extraction composition varied from 50 to 100% (vol/vol). Hence, different polarity behavior was observed (2c > 2f > 2p). Avenanthramide 2c showed the highest yield. Cycles effect varied depending on the polyphenol evaluated, they were more necessary for the extraction of p‐coumaric acid and avenanthramide 2f. Results aid to understand solvation process for a more efficient polyphenols extraction.Practical applicationsThe research fills the gap between reported laboratory work and the lack of experimental scale up data. It considers scale up aspects such as developing a simple and easy to scale process (ambient temperature and 8 bars pressure) and using food grade solvents. Extractions were run with a controlled particle size distribution rather than a specific particle size. A small solvent/solid ratio was kept, since excessive amount of solvent generates expensive downstream operations. Moreover, solvent was reused on each run until the necessary cycles were completed. The optimization here presented will allow a better understanding in the extraction of oat's polyphenols; individually, as group, and total. This will aid for a more robust polyphenols extractions from oat at the food industry.

Perspectives on the use of supercritical particle formation technologies for food ingredients

Numerous techniques have been developed for particle formation, encapsulation, impregnation and drying using supercritical carbon dioxide (SC-CO2), demonstrating the flexibility in such technologies while offering advantages in terms of the control of particle size, size distribution and morphology that cannot be matched by conventional technologies. A variety of food ingredients based on proteins, lipids, carbohydrates and minor components have been processed using SC-CO2 technologies and characterized in terms of their properties and functionality. Delivery of health benefiting food bioactives and their controlled release have been a major focus. It is important to better understand the relationships between product functionality and processing parameters so that optimal processes can be designed to produce ingredients with maximum functionality and bioavailability. Considering the growing demand for functional food ingredients, ingredients produced using SC-CO2 particle formation technologies show great potential for further development, targeting food and natural health product applications.

Development of polyester resin particles for toner with a controlled particle size distribution and shape

We developed new polyester resin particles for use in toner that are prepared by an advanced dissolution suspension method. The new resin particles have excellent characteristics, such as a narrow particle size distribution, a uniform and non-spherical particle shape and high melt elasticity at high temperature with low-temperature meltability. The narrow particle size distribution, which has a coefficient of variation (CV) under 20%, is obtained by using nanoscale styrene-acrylic particles during the particle formation of the dissolution suspension process. The styrene-acrylic particles are prepared by emulsion polymerization and act as a particle size control agent in the formation of the polyester particles by adsorption on the surface of the polyester solution droplets through the hetero-coagulation effect. The particle shape is controlled from spherical to non-spherical forms, such as spindle or dimple shapes, during the solvent removal process. Moreover, a melting property suitable for toner application is achieved by the elongation reaction of the polyester prepolymer proceeding simultaneously during the particle formation process. This review introduces the outlines of the technical features and the key processes. Novel polyester resin particles useful for toner with characteristics such as a narrow particle size distribution, a uniform and non-spherical particle shape, and high melt elasticity at high temperature with low-temperature meltability were developed. These characteristics were achieved by the application of three key technologies to the conventional dissolution suspension method, and they contribute to energy savings and high image quality for toner.

Particle size distribution control and related properties improvements of tungsten powders by fluidized bed jet milling

Fine grinding process of different particle size tungsten powders was carried out by fluidized bed jet milling. The results showed that the jet milling treatment caused deagglomeration of tungsten powders, which led to particles sufficient dispersion and narrow particle size distribution. Grinding gas pressure of 0.70Mpa made the particles achieve high speed which promoted the particles collision contributing to particle dispersion and shape modification. For tungsten powder with particle size of 3μmFSSS, a higher packing density with 5.54g/cm3 was obtained, compared with the 3.71g/cm3 of the original powder. For tungsten powder with particle size of 1μmFSSS, the big agglomerates disappeared and the particle size distribution become narrower, while small aggregates about 2–3μm still exist after the jet milling process. For tungsten powder with particle size of 5μm and 10μmFSSS, different medium diameter particle size and narrow particle size distribution of monodisperse tungsten powders can be produced by the optimized jet milling parameters. More important, the effective dispersion, favorable shape modification and precise classification have been achieved in the simple process.

Adaptive fault-tolerant shape control for nonlinear Lipschitz stochastic distribution systems

This paper addresses the problem of adaptive fault estimation and fault-tolerant control for a class of nonlinear non-Gaussian stochastic systems subject to time-varying loss of control effectiveness faults. In this work, time-varying faults, Lipschitz nonlinear property and general stochastic characteristics are taken into consideration in a unified framework. Instead of using the system output signal, the output distribution is adopted for shape control. Both the states and faults are simultaneously estimated by an adaptive observer. Then, a fault tolerant shape controller is designed to compensate for the faults and realize stochastic output distribution tracking. Both the fault estimation and the fault tolerant control schemes are designed based on linear matrix inequality (LMI) technique. Satisfactory performance has been obtained for a numerical simulation example. Furthermore the proposed scheme is successfully tested in a case study of particle size distribution control for an emulsion polymerization reactor.

Synthesis of nanosized 58S bioactive glass particles by a three-dimensional ordered macroporous carbon template

Nanosized 58S bioactive glass (BG) particles were synthesized by using a three-dimensional ordered macroporous carbon template (OMC) with a pore size of 400nm. The obtained 58S BG particles possessed a diameter of 300nm, narrow size distribution and uniform spherical morphology. 58S/gelatin composites were prepared and showed much better mechanical properties than pure gelatin. The narrow size distribution of the 58S particles replicated from OMC was confirmed crucial to the mechanical properties of the 58S/gelatin composite, comparing to the contrast sample prepared with polydispersed particles. The outstanding bioactivity of the 58S BG particles was confirmed by inducing the formation of carbonated hydroxyapatite on the 58S/gelatin composite surface. This work showed a successful example that OMC template could be used to synthesize particles requiring a robust reaction condition, and a particle synthesis method that could well control particle size distribution was important for preparing materials with outstanding mechanical properties.

Economically attractive route for the preparation of high quality magnetic nanoparticles by the thermal decomposition of iron(III) acetylacetonate

The thermal decomposition (TD) methods are among the most successful in obtaining magnetic nanoparticles with a high degree of control of size and narrow particle size distribution. Here we investigated the TD of iron(III) acetylacetonate in the presence of oleic acid, oleylamine, and a series of alcohols in order to disclose their role and also investigate economically attractive alternatives for the synthesis of iron oxide nanoparticles without compromising their size and shape control. We have found that some affordable and reasonably less priced alcohols, such as 1,2-octanediol and cyclohexanol, may replace the commonly used and expensive 1,2-hexadecanediol, providing an economically attractive route for the synthesis of high quality magnetic nanoparticles. The relative cost for the preparation of Fe3O4 NPs is reduced to only 21% and 9% of the original cost when using 1,2-octanediol and cyclohexanol, respectively.

Interaction of light with hematite hierarchical structures: Experiments and simulations

Mesocrystalline particles have been recognized as a class of multifunctional materials with potential applications in different fields. However, the internal organization of nanocomposite mesocrystals and its influence on the final properties have not yet been investigated. In this paper, a novel strategy based on electrodynamic simulations is developed to shed light on how the internal structure of mesocrystals influences their optical properties. In a first instance, a unified design protocol is reported for the fabrication of hematite/PVP particles with different morphologies such as pseudo-cubes, rods-like and apple-like structures and controlled particle size distributions. The optical properties of hematite/PVP mesocrystals are effectively simulated by taking their aggregate and nanocomposite structure into consideration. The superposition T-Matrix approach accounts for the aggregate nature of mesocrystalline particles and validate the effective medium approximation used in the framework of the Mie theory and electromagnetic simulation such as Finite Element Method. The approach described in our paper provides the framework to understand and predict the optical properties of mesocrystals and more general, of hierarchical nanostructured particles.

Preparation of Paraffin-Based Solid Combustible for Hybrid Propulsion Rocket Motor

Paraffin stands out as a promising solid combustible grain for the classical hybrid propulsion rocket motor. However, its low mechanical properties increase the risk of grain cracking and rupturing. The purpose of this experimental study is to address the existing drawbacks by formulating paraffin particles within a hydroxyl-terminated polybutadiene binder. Paraffin particles are prepared by crystallization in emulsion, which allows the control of particle size distribution, based on the droplets breakup and coalescence equilibrium. The paraffin particles are suspended in hydroxyl-terminated polybutadiene, and the maximum paraffin loading (62% volume fraction) is attained with the use of bimodal systems. A combustible grain (paraffin particles/hydroxyl-terminated polybutadiene) is cast with the maximum loading and submitted to thermal and mechanical tests. The results are compared to hydroxyl-terminated polybutadiene and paraffin wax counterparts, and they meet the criteria of performance and safety required for this kind of combustible. The crystallization in paraffin-in-water emulsion proves to be an efficient method to prepare spherical paraffin particles with controllable sizes, which may be used to get bimodal systems that improve the packing of paraffin particles. The resulting combustible grain exhibits adequate thermal and mechanical properties (ultimate elongation of 206%) for a hybrid propulsion rocket motor.

초음파 무화효과를 이용한 현탁액으로부터 나노입자의 분리포집법 제안

나노기술의 실제적인 응용을 위해 응집되지 않은 나노입자 상태를 얻는 것이 매우 중요하다. 나노입자를 사용하는 제품의 기능성을 향상시키기 위해, 그들의 합성 과정에서 입자 크기 분포의 더 정밀한 제어가 요구된다. 그러나 합성된 나노입자들은 물리적 혹은 화학적인 이유로 응집되기 쉬워 나노입자의 고유한 특성이 가려져 실제적인 응용에 있어서 문제를 일으킨다. 본 연구는 단분산된 나노입자만을 분리하기 위하여 초음파 무화 효과에 의한 무화입자를 분리장으로 사용한 나노입자 분리방법을 제안하였다. 0.002 wt. %의 농도를 갖는 <TEX>$TiO_2$</TEX> 나노입자 현탁액을 무화시켜 분리포집된 현탁액에 포합된 나노입자들의 입도분포를 측정하였다. 그 결과들로부터 제안된 방법을 이용하여 단분산 입자의 분리 포집이 가능함을 확인 할 수 있다. It is very important to obtain non-agglomerated nano particle state for practical application of nano technology. In order to improve the functionality of products using nano particles, more precise control of particle size distribution is required in their synthesis process. However, synthesized nano particles are agglomerated easily due to physical and chemical reasons, and it then veils unique properties of the nano particles and causes some troubles in their practical application. In this study, a separation method for nano particles from suspension by using the droplets as the separation space was proposed. Using the suspension of 0.002 wt. % with <TEX>$TiO_2$</TEX> powder, the particle size distribution of nano particles in the recollected suspension was measured. From the results, it was confirmed that it is possible to separate and to recollect the nano particles monodispersed by using the suggested method.

Size control of Au NPs supported by pH operation

Au NPs are expected to become useful functional particles, as particle gun used for plant gene transfer and also catalysts. We have studied PSD (particle size distribution) control of Au NPs by reduction crystallization. Previous study found out importance of seeds policy and also feeding profile. In this paper, effect of pH in the reduction crystallization was investigated to clarify the possibility of Au NPs PSD control by pH operation and also their growth process. Au NPs of size range 10–600nm were obtained in single-jet system using ascorbic acid (AsA) as a reducing agent with adjusting pH of AsA. Au NPs are found to grow in the process of nucleation, agglomeration, agglomeration growth and surface growth. Au NPs tend to grow by agglomeration and become larger size in lower pH regions, and to grow only by surface growth and become smaller size in higher pH regions.

Particle size distribution control of Pt particles used for particle gun

The purpose of this study is particle size distribution (PSD) control of submicron sized Pt particles used for particle gun. In this report, simple reaction crystallization is conducted by mixing H2PtCl6 and ascorbic acid. Without the additive, obtained Pt particles have broad PSD and reproducibility of experiment is low. With seeding, Pt particles have narrow PSD and reproducibility improved. Additionally, mean particle diameter of 100–700nm is controlled by changing seeding amount. Obtained particles are successfully characterized as Pt by XRD results. Moreover, XRD spectra indicate that obtained particles are polycrystals. These experimental results suggest that seeding consumed nucleation, as most nuclei attached on the seed surface. This mechanism virtually restricted nucleation to have narrow PSD can be obtained.

Activated lignin-chitosan extruded blends for efficient adsorption of methylene blue

This work investigates the production of activated lignin-chitosan extruded (ALiCE) pellets with controlled particle size distribution (almost spherical: dp ∼500–1000μm) for efficient methylene blue (MB) adsorption. The novel preparation method employed in this study successfully produced activated lignin-chitosan pellets. Structural and morphological characterizations were performed using BET, FTIR and SEM-EDX analyses. The influence of contact time, solution pH, ionic strength, initial adsorbate concentration and desorption studies was investigated. The experimental data fitted well with the Langmuir isotherm (R2=0.997), yielding a maximum adsorption capacity of 36.25mg/g. The kinetic data indicated that MB adsorption onto ALiCE can be represented by the pseudo second-order-model with intraparticle processes initially controlling the process of MB adsorption. Overall, these results indicate that the novel ALiCE offers great potential for removing cationic organic pollutants from rivers and streams.

A novel method for production of spherical Ti-6Al-4V powder for additive manufacturing

A novel method was developed to produce spherical Ti-6Al-4V powder for advanced near-net-shape manufacturing processes including additive manufacturing and powder injection molding. The new process synergistically integrates a few common low-cost processing techniques including granulation, sintering, and de-oxygenation to produce spherical Ti alloy powders without relying on costly melting and atomizing techniques. This new granulation-sintering-deoxygenation (GSD) process can use low-cost source powders such as scrap Ti as the raw material. The spherical Ti-6Al-4V powder produced using this process has controlled particle size distribution and low oxygen content (<0.15%), which meet the Aerospace Material Specification (AMS-4998) for spherical Ti-6Al-4V powder.

No Significant Effect of Phosphorous Doping on the Electrochemical Performance of Silicon-Carbon Composite Anodes for Li-ion Batteries

SUMMARY Using an industry-relevant method of production we have demonstrated production of doped silicon nanoparticles for Li-ion batteries. The particles have been characterized and tested in Li-ion battery half-cells for demonstration of the performance as Li ion storage material in the anode. In this presentation we will show the results regarding the characterization of the particles as well as the performance results of the material in Li-ion half cells. BACKGROUND The use of silicon as part of the anode in Li-ion batteries enhances the potential storage capacity greatly. While the graphite anode used in standard Li-ion batteries has a theoretical capacity of 372 mAh/g, the theoretical capacity for Si is 3,572 mAh/g [1]. However, to be able to absorb the sufficient amount of Li ions reversibly, the silicon material needs to be nanostructured [2]. EXPERIMENTAL IFE has earlier demonstrated production of silicon particles prepared using a silane-based free-space reactor, which allows control of particle size distribution and crystallinity and a high production capacity [3]. In this work, the setup was modified to allow for introduction of phosphine gas in the production process. The intention was to introduce phosphorous dopant atoms to modify the electrical conductivity of the silicon material. The current particles were produced with a silane flow rate of 5 slm, and 5 slm of 3% phosphine diluted in He. Thus, the P concentration in the process gases was 3% with respect to Si. The production rate at 100% yield would be about 400 g/h, while the product recovered from the process typically was between 100 and 200 g/h. The processing temperature was varied from 475 °C to 600 °C to produce particles with different properties. All electrochemical tests were performed in a crimped 2032 coin cell with lithium metal used as a counter electrode, with a polymer separator (Celgard 3401) and 1 M LiPF6 in 1:1 EC/DMC electrolyte (LP30, BASF). For some experiments, 10 wt% fluoroethylene carbonate (FEC) was used as electrolyte additive. The cells were cycled at 25 °C between 0.05 and 1.0 V with a constant C-rate of C/10 (after initial 3 cycles at C/20) using an Arbin Battery cycler (Arbin Instruments). RESULTS AND CONCLUSIONS The phosphorus content of the particles was by inductively coupled plasma mass spectrometry (ICP-MS) and energy-dispersive x-ray spectroscopy (EDS) measured to be in the range of 1.7-1.8% with respect to silicon. Thus, it seems that the utilization of the phosphine is not complete, or phosphorous binds to materials which are not recovered from the production process. The particle size distribution was centered around 600 nm as measured by laser scattering in a Malvern Mastersizer 2000. SEM and TEM revealed that the particles consisted of aggregates of spherical silicon particles with a primary particle size of 50-400 nm. X-ray diffraction showed that we could produce amorphous or crystalline particles depending on the temperature of the process. Cycling of the particles in lithium battery half cells showed a life time of about 300 cycles for doped and undoped particles. Some measurements indicate a better conductivity of the doped material but the results were not conclusive. The cells were cycled with a limited capacity regime where the capacity was set to 1000 mAh/g(Si) and thus the end-voltage could vary. The most pronounced difference in the cycling performance between doped and undoped silicon particles was a shift in the increase in end voltage for the doped particles: While end-voltage increased from 0.4 V to 0.6 V over the first 25 cycles, this development is stretched out over the first 50 cycles or more for doped particles. See the attached figure for further details.

Synthesis of SiO2-Modified Li2MnO3-LiMn1/3Ni1/3Co1/3O2 by Spray Pyrolysis with Acid Addition as Cathode Materials for Lithium Ion Batteries

Lithium-rich layered solid solutions of Li2MnO3 and LiMO2, where M denotes at least one 3d transition metal, has attracted much attention as a cathode material of lithium ion batteries because they offer high capacities of around 250 mAh g-1 within the potential range of 2.0 to 4.8 V (versus Li/Li+). However, most of the works on the material have reported the electrochemical performance at low current rates. Arranging the crystal structures and morphologies of the materials is particularly important for improving the cell performance. Spray pyrolysis is a simple one-step synthesis technique to obtain various kinds of functional oxide powders. The particles prepared by spray pyrolysis have some advantages such as small particle size distribution, high purity, and easy control in composition and morphology of multi-component metal oxides. In addition, powder morphology can be controlled by acid addition to the starting solution of spray pyrolysis. We have found that a small amount of SiO2 addition remarkably suppressed the capacity fade of Li2MnO3-LiMn1/3Ni1/3Co1/3O2 prepared by spray pyrolysis during charge and discharge cycling. In this study, we investigated the effect of acid addition to the starting solutions of unmodified and the SiO2-modified Li2MnO3-LiMn1/3Ni1/3Co1/3O2 of spray pyrolysis. Stoichiometric amounts of lithium nitrate, manganese nitrate hexahydrate, nickel nitrate hexahydrate, cobalt nitrate hexahydrate were dissolved in deionized water with the addition of citric acid or boric acid. SiO2 aerosol was added to the solution. The reaction furnace consisted of four independent heating zones. Cycling tests were performed galvanostatically at a 0.1 C rate (1 C = 314 mAh g-1) between 2.0 and 4.8 V at 30ºC. The rate tests were performed by charging and discharging the electrode at 0.1 C for 5 cycles, 0.2 C for 5 cycles, 0.5 C for 5 cycles, and 1 C for 5 cycles. Prior to the cycling, a stepwise pre-cycling treatment was carried out by increasing the upper potential limit by 0.1 V from 4.5 V every two cycles to 4.8 V [1]. We investigated the capacity retention for 0, 2 and 5 wt.% SiO2-modified Li2MnO3-LiMn1/3Ni1/3Co1/3O2 samples at 0.1C in 1 M LiPF6/EC+DMC (1:2) after the stepwise pre-cycling treatment. The capacity fade on the cycling was successfully suppressed for all SiO2-modified samples. The highest capacity retention was obtained for the 2 wt.% SiO2-modified sample. SEM images showed that the as-synthesized particles were not agglomerated and had spherical shapes. After heat-treatment, the particles retained their shapes. The spherical shapes were partially collapsed by SiO2 modification. The interior primary particle size was more grown than those of the unmodified particles. The specific surface area slightly decreased with SiO2 content to 2 wt.%. The specific surface area increased at a SiO2 content of 5 wt.% and this may be due to the collapsed shape compared with other particles. We synthesized the SiO2-modified Li2MnO3-LiMn1/3Ni1/3Co1/3O2 using the starting solutions containing various amounts of boric acid. SEM images showed that boric acid increased the densities of the materials by acting as a sintering agent. With more than 0.5 wt.% boric acid addition, Li2MnO3-LiMn1/3Ni1/3Co1/3O2 powders displayed aggregated structures and large sizes. Improvement of the densities of the materials means the decrease of the isolated particles observed in the case of the SiO2-modified Li2MnO3-LiMn1/3Ni1/3Co1/3O2, which may lead to the enhancing the electrochemical performance. Moreover, we synthesized the unmodified and SiO2-modified Li2MnO3-LiMn1/3Ni1/3Co1/3O2 using the starting solutions containing various amounts of citric acid. SEM images showed that most of the particles had spherical shapes but some particles were collapsed. The specific surface area of the synthesized Li2MnO3-LiMn1/3Ni1/3Co1/3O2 from the starting solutions containing citric acid is much higher than that of the unmodified and SiO2-modified Li2MnO3-LiMn1/3Ni1/3Co1/3O2. For example, the specific surface area of the as-synthesized Li2MnO3-LiMn1/3Ni1/3Co1/3O2 using the solution containing 0.93 mol l-1 of citric acid is 28 m2 g-1. Higher specific surface area is expected to favor the high rate capability. It can be found from the above results that boric acid and citric acid are effective in controlling the powder morphology. We will present the electrochemical properties including rate capability. [1] A. Ito, D. Li, Y. Ohsawa, Y. Sato, J. Power Sources 183 (2008) 344-346.

Effect of the pH of the preparation medium on the microstructure and electrocatalytic activity of carbon nanotubes decorated with PtSn nanoparticles for use in methanol oxidation

Carbon nanotubes (CNTs) decorated with PtSn nanoparticles (PtSn/CNT) were prepared by the microwave-assisted ethylene glycol reduction method and characterized by atomic adsorption spectroscopy, X-ray diffraction and transmission electron microscopy. Results indicated that the loading efficiency of the metal catalyst, and the degree of alloying and morphology of the PtSn nanoparticles were significantly affected by the solution pH value of the metallic ions in the ethylene glycol. The required composition of the PtSn/CNT catalysts could be obtained by adjusting the pH value to about 5, which is almost the isoelectric point of the acid-treated CNTs. The size of the PtSn nanoparticles decreased with the pH value in the range 2 to 7, but they became large and agglomerated when the pH value was greater than 7. Electrocatalytic activity tests indicated that the PtSn/CNTs prepared at pH 5 had the best catalytic performance towards methanol oxidation. The improvement in catalytic activity was mainly attributed to a high loading efficiency and control of particle shape and size distribution.

Optimising the bioreceptivity of porous glass tiles based on colonization by the alga Chlorella vulgaris

Green façades on buildings can mitigate greenhouse gas emissions. An option to obtain green facades is through the natural colonisation of construction materials. This can be achieved by engineering bioreceptive materials. Bioreceptivity is the susceptibility of a material to be colonised by living organisms. The aim of this research was to develop tiles made by sintering granular waste glass that were optimised for bioreceptivity of organisms capable of photosynthesis. Tiles were produced by pressing recycled soda-lime glass with a controlled particle size distribution and sintering compacted samples at temperatures between 680 and 740°C. The primary bioreceptivity of the tiles was evaluated by quantifying colonisation by the algae Chlorella vulgaris (C. vulgaris), which was selected as a model photosynthetic micro-organism. Concentrations of C. vulgaris were measured using chlorophyll-a extraction. Relationships between bioreceptivity and the properties of the porous glass tile, including porosity, sorptivity, translucency and pH are reported. Capillary porosity and water sorptivity were the key factors influencing the bioreceptivity of porous glass. Maximum C. vulgaris growth and colonisation was obtained for tiles sintered at 700°C, with chlorophyll-a concentrations reaching up to 11.1±0.4μg/cm2 of tile. Bioreceptivity was positively correlated with sorptivity and porosity and negatively correlated with light transmittance. The research demonstrates that the microstructure of porous glass, determined by the processing conditions, significantly influences bioreceptivity. Porous glass tiles with high bioreceptivity that are colonised by photosynthetic algae have the potential to form carbon-negative façades for buildings and green infrastructure.