YAG:Ce nano-sized phosphor particles prepared by a solvothermal method

Nano-sized Ce-doped YAG phosphor particles were synthesized by a mixed solvothermal method using the stoichiometric amounts of inorganic aluminum and yttrium salts. The formation of YAG:Ce was investigated by means of XRD and TG-DTA. The purified YAG crystalline phases was obtained under moderate synthesis condition (300 °C and 10 MPa), this indicated that ethanol replaced part of water as solvent favoring the formation of YAG. TEM images showed that YAG:Ce phosphor particles were basically spherical in shape, well dispersed and a mean grain size about 60 nm. The particle absorbed excitation energy in the range 403-510 nm, and the maximum excitation wavelength was near 470 nm. The crystalline YAG:Ce showed broad emission peaks in the range 480-650 nm and had maximum intensity at 528 nm. The excitation and emission intensity increased with increasing the synthesis temperature from 280 to 300 °C, and get the maximum brightness at 300 °C.     

Novel temperature controlled surface dissolution of excipient particles for carrier based dry powder inhaler formulations

The surface of lactose monohydrate was modified by solution phase variable temperature dissolution. Lactose monohydrate crystals were added to a known volume of a saturated solution of lactose monohydrate at 25°C. The temperature of the mixture was then ramped to either 30, 35, 40, or 50°C to produce lactose monohydrate batches with reduced levels of fines and lower surface roughness. A dramatic decrease in surface roughness with increasing dissolution temperature was visually observed using scanning electron microscopy. Particle size analysis suggested that the level of lactose fines was reduced after treatment at the lowest dissolution temperature, 30°C. Evaluation of the samples' drug aerosolization using a twin stage impinger, after blending with salbutamol sulphate, suggested that even though there were dramatic changes in roughness and particle size distribution after surface dissolution at 30°C, there was no significant difference in aerosolization as measured by fine particle fraction. However, after surface dissolution at 35°C, there was an increase in fine particle fraction. Surface dissolution at even higher temperatures did not result in any further increase in fine particle fraction. These observations suggest that surface roughness and fines play an important role in the aerosolization of salbutamol sulphate, but the inter-relationships are not straightforward.     

A novel mixing method for levitated particles using electrostatic fields

A continuous particle mixing system using electrostatic forces and vibrations was developed. The system consists of two symmetrically arranged devices. The same or different types of charged particles were continuously fed from each device in a dispersed state and mixed instantaneously in the space between devices. When charged particles with opposite polarities were fed from each device by changing the direction of the electric field, the particles were homogeneously mixed. The electric field and particle trajectories were numerically calculated to elucidate the particle-mixing mechanism. Furthermore, the mixing state of the particles was evaluated quantitatively using Shannon entropy.     

Morphologies and microstructures of nano-sized Cu(2)O particles using a cetyltrimethylammonium template

Hollow polyhedra and cubes of nanostructured Cu(2)O particles have been synthesized by reduction of CuSO(4) with ascorbate acid in the solution phase. The nanostructures were obtained when the cetyltrimethylammonium (CTAB) concentration ranged from 0 to 0.03?M in the presence of NaOH. Structural characterizations, by means of x-ray photoelectron spectroscopy (XPS) for measuring Cu valence states and by electron microscopy for microstructure and chemical analyses, suggest that most Cu(2)O nanoparticles are covered with a thin CuO shell arising possibly from reaction of the adsorbed oxygen on the Cu(2)O particle surface. The blue shift is observed as microstructures of Cu(2)O nanoparticles changed from cubic to hollow in ultraviolet and visible (UV-visible) absorption spectra. Both the Cu(2)O hollow and cubic nanostructures show certain quantum-confined effects. A cationic CTAB template mechanism is proposed to interpret the formation of the Cu(2)O nanoparticles.     

Protein crystal growth in microgravity using a liquid/liquid diffusion method

Crystallization of proteins by liquid liquid diffusion method was performed in microgravity using the MDA Minilab aboard the US Space Shuttle. Three proteins, namely lysozyme, trichosanthin, and a new lechin, were crystallized in the space experiment. In contrast to the results of space experiments with a tube-like vapor diffusion method, the crystallization conditions for growing better crystals in space are remarkably different from the conditions optimized on earth. This may be due to difficulties in ground optimization, which are caused by gravity-dependent phenomena, in particular the specific convective flow occurring with liquid liquid diffusion.     

Agglomeration process of dry ice particles produced by expanding liquid carbon dioxide

Formation of dry ice particles and their agglomeration process have been studied experimentally. The dry ice particles were produced by expanding liquid carbon dioxide at room temperature and pressure, and then introduced into an additional tube acting as an agglomeration chamber. In the experiments, the temperatures of the jet flow and the tube wall were measured by thermocouples, and dry ice particles in the jet flow were observed by a high speed camera with a zoom lens. It was found that two stages of temperature reduction occurred in the jet flow, corresponding to the agglomeration process. It was also found that the particle size of the agglomerates increased and the particle velocity decreased with increasing tube diameter. The agglomeration process of dry ice particles can be explained by the particle deposition and reentrainment, i.e. dry ice particles of several micrometers are deposited on the tube wall and form a deposition layer; then, agglomerates are reentrained from the layer into the jet flow.     

Synthesis of nano-sized ceria powders by two-emulsion method using sodium hydroxide

In the present study, nano-sized ceria powders were prepared by the two-emulsion method in the presence of aqueous sodium hydroxide. The effect of the ceria precursor concentration and the addition of an aqueous sodium hydroxide on the crystallite size, the size distribution and the morphology of the synthesized powders were investigated. The precipitates were obtained by mixing two water-in-oil emulsions with kerosene containing cerium nitrate aqueous solution and sodium hydroxide aqueous solution. The synthesized ceria powders were characterized by XRD and TEM. The synthesized ceria powders had nearly spherical shape and a uniform crystallite size in a range of 10 to 20 nm depending on the concentration of precursor solution and an addition amount of mineralizer.     

Mechanism of dispersing an active component into a polymeric carrier by the SEDS-PA process

Supercritical fluid anti-solvent precipitation has been attracting widespread attention due to its distinctive advantages, and has exhibited a great perspective of application in the production of polymer-based composite micro- and nanoparticles. In this study, based on the experiment results of production of carotene-loaded polymer PEG or l-PLA composite microparticles using solution enhanced dispersion by supercritical fluids through prefilming atomization (SEDS-PA) process, the possible mechanism of dispersing an active component in a polymeric carrier by the SEDS-PA co-precipitation was deduced. The mechanism is mainly the formation and growth of the active component (carotene) nuclei in the polymer-rich phase induced by mass transfer and phase transition, and the polymer capture/encapsulation of active component particles generated in an expanded solution droplet caused by the collision among these particles and polymer-rich phase. There are four factors that could influence the sizes and morphologies of the SEDS-PA precipitates. They are, respectively, atomization of solution, prompt and persistent super-saturation of the expanded droplets, breakup of the expanded droplets with interstices and the particle agglomeration caused by collision in the SEDS-PA process. The integrated effect of these factors dominates the sizes and morphologies of the SEDS precipitates.     

Formation of particles for dry powder inhalers

Inhalation therapy is widely employed to deliver drugs to the respiratory epithelium, predominantly for the treatment of local disorders. Recently aerosol therapy has become an attractive non-invasive way for systemic administration of biologically active components, because of the unique features of the lung, namely its large surface area, high permeability and wide blood supply. Success of a therapy depends on the effectiveness of particle delivery to a targeting site of the lungs. The paper explains mechanisms of particle transport, deposition and retention in the respiratory system coupled with the efficiency of the powder aerosolization with a dry powder inhaler (DPI) leading to the definition of the required particle structure. The most promising hollow or porous nanostructured particles have tapped density below 0.4 g/cm³ and mass medium aerodynamic diameter (MMAD) below 5 μm. Key features of the process leading to the formation of particles with the required structure are explained. Spray-drying, spray-freeze-drying and supercritical antisolvent precipitation are shown to be the most promising methods for efficient production of particles for inhalation. Examples of the production of therapeutic particles for delivery of peptides, antibiotics, anticancer drugs, and the structures of particles obtained with the above mentioned and other methods are presented. The paper concludes with brief information about a recent construction of DPIs for aerosolization of therapeutic particles.     

Development of a method for liquid xenon purification using a cryogenic centrifugal pump

We are developing a new type of photon detector for an experiment to search for muons decaying into a positron and a gamma ray. In this experiment, the photon detector will utilize liquid xenon (Xe) as the scintillation material. Good transparency of the liquid Xe is required in order to gain the highest performance out of the detector. Impurities like water and oxygen must be removed efficiently for this purpose. We have developed a new purification system, dedicated to removing water from liquid Xe, by employing a cryogenic centrifugal pump and molecular sieves. The performance of the system is described in this article.     

Estimation of effective refractive index of birefringent particles using a combination of the immersion liquid method and light scattering

A method to detect the effective refractive index and concentration of birefringent pigments is suggested. The method is based on the utilization of the immersion liquid method and a multifunction spectrophotometer for the measurement of back scattered light. The method has applications in the measurement of the effective refractive index of pigments that are used, e.g., in the paper industry to improve the opacity of paper products.     

Detection of micro- and nano-sized biocompatible particles in the blood

The research deals with new scanning electron microscopic evaluations of the interface between blood and explanted temporary vena cava filters from patients affected by blood disorders. The biological tissues adherent to the filter and the small thrombi formed in vivo were detached from the metallic structure of the device, fixed, dehydrated and prepared for the histological and the electron microscopy. The analyses showed that both samples (thrombus and newly formed tissue) contained foreign, in some cases nano-sized, bodies. The chemistry of these particles was different and varied, and unusual compounds containing non-biocompatible elements like bismuth, lead, wolfram, tungsten were also detected. The interaction between these debris travelling in the blood stream and the blood itself leads to suspect that the formation of the thrombus can originate from these inorganic and inert foreign bodies that act as triggering agent of the blood coagulation.     

液相沉淀法制备纳米AgO粉体影响因素的正交分析

采用正交试验法研究了液相沉淀法合成纳米 AgO 粉体的各影响因素,分析了影响规律和机理,并利用XRD、XPS 等测试手段对制备的粉体进行了测试表征.研究结果表明:AgO粉体的最佳制备条件是pH=0.7,Na2S2O8:AgNO2(摩尔配比)=1:0.5,m(NP20):m(AgNO3)为0.20,反应温度为60℃,反应时间为30min.在最佳工艺条件下,合成了晶粒度为32nm,含量为99.9%的高纯度纳米AgO粉体.     

Performance estimation of a Venturi scrubber using a computational model for capturing dust particles with liquid spray

A Venturi scrubber has dispersed three-phase flow of gas, dust, and liquid. Atomization of a liquid jet and interaction between the phases has a large effect on the performance of Venturi scrubbers. In this study, a computational model for the interactive three-phase flow in a Venturi scrubber has been developed to estimate pressure drop and collection efficiency. The Eulerian-Lagrangian method is used to solve the model numerically. Gas flow is solved using the Eulerian approach by using the Navier-Stokes equations, and the motion of dust and liquid droplets, described by the Basset-Boussinesq-Oseen (B-B-O) equation, is solved using the Lagrangian approach. This model includes interaction between gas and droplets, atomization of a liquid jet, droplet deformation, breakup and collision of droplets, and capture of dust by droplets. A circular Pease-Anthony Venturi scrubber was simulated numerically with this new model. The numerical results were compared with earlier experimental data for pressure drop and collection efficiency, and gave good agreements.     

A modelling and verification approach for soybean seed particles using the discrete element method

To build a discrete element method (DEM) model of soybean seed particles, the shape and size of soybean seed particles were measured and analysed. The results showed that the shape of a soybean seed particle could be approximated to an ellipsoid and that the dispersity in size could be approximated by a normal distribution. Additionally, a certain functional relationship between the primary dimension and secondary dimensions was determined. On this basis, an approach for modelling soybean seed particles based on the multi-sphere (MS) method was proposed. The soybean seed particle was simplified to an ellipsoid with the averaged size of one hundred randomly selected soybean seeds. The model of a single soybean seed particle was built by filling spheres within the ellipsoid. For modelling soybean seed assembly, the primary dimension was generated according to the normal distribution, and the other secondary dimensions were calculated based on their relationships with the primary dimension. In this way, the model of soybean seed assembly with different sizes and distributions was built. In this paper, four varieties of soybean seed were used. By comparing the simulated results and experimental results both in piling tests and “self-flow screening” tests, when the number of filling spheres was five, the simulated results were close to those obtained experimentally. Therefore, the feasibility and validity of the modelling method for soybean seed particles that we proposed were verified. Finally, an application case was employed to show how to use the soybean seed particle model and the discrete element method to analyse the discharging process of a silo.     

Improvement of the tool life of a micro-end mill using nano-sized SiC/Ni electroplating method

High mechanical properties of a tungsten carbide micro-end-mill tool was achieved by extending its tool life by electroplating nano-sized SiC particles (< 100 nm) that had a hardness similar to diamond in a nickel-based material. The co-electroplating method on the surface of the micro-end-mill tool was applied using SiC particles and Ni particles. Organic additives (saccharin and ammonium chloride) were added in a Watts bath to improve the nickel matrix density in the electroplating bath and to smooth the surface of the co-electroplating. The morphology of the coated nano-sized SiC particles and the composition were measured using Scanning Electron Microscope and Energy Dispersive Spectrometer. As the Ni/SiC co-electroplating layer was applied, the hardness and friction coefficient improved by 50%. Nano-sized SiC particles with 7 wt% were deposited on the surface of the micro-end mill while the Ni matrix was smoothed by adding organic additives. The tool life of the Ni/SiC co-electroplating coating on the micro-end mill was at least 25% longer than that of the existing micro-end mills without Ni/SiC co-electroplating. Thus, nano-sized SiC/Ni coating by electroplating significantly improves the mechanical properties of tungsten carbide micro-end mills.