Papers by Keyword: Microparticle

Abstract: This paper presents the results of a analysis of rough thermo-elastohydrodynamic lubrication (TEHL) of line contact with non-Newtonian lubricant blended with Al₂O₃ nanoparticles and MoS2 microparticles. The simultaneous systems of time independent modified Reynolds equation, elasticity equation, load carrying with micro particle equation and energy equation were solved numerically using multigrid multilevel with full approximation technique. In this study, the effect of Al₂O₃ nanoparticle and MoS₂ microparticle additives and surface roughness were implemented to obtain film thickness, film pressure, film temperature, friction coefficient and load carrying with microparticle in the contact region. The simulation results showed that the maximum film temperature and friction coefficient increase slightly but the minimum film thickness decreases slightly with an increase in Al₂O₃ nanoparticle concentration due to thermal enhancement of nanofluid. For increasing of microparticle concentration, the minimum film thickness and friction coefficient decrease because the increasing of friction heating of MoS₂ microparticle.

Abstract: The present study reports that a sustained release profile could be transferred into a biphasic drug release profile when a hydrophilic polymer was encapsulated into the medicated microparticles. The multiple component composite microparticles were fabricated using a single fluid electrospraying process to treat a co-dissolving solution consisting of a polymer matrix (shellac), an active ingredient (FA), and an additional hydrophilic polymer (poly vinyl pyrrolidone, PVP). FESEM results showed that the microparticles M1 consisting of shellac and FA had an average diameter of 1.27 ± 0.38 μm, whereas the microparticles M2 consisting of shellac, FA and PVP had an average diameter of 1.51 ± 0.34 μm. Both the two types of microparticles were essentially amorphous composites due to the favourable secondary interactions between the components, as demonstrated by ATR-FTIR tests. In vitro dissolution tests demonstrated that the addition of PVP in the microparticles M2 made them give a typical biphasic drug release profile, whereas the double-component microparticles provided a sustained release profile. This study shows a simple way for developing advanced drug delivery systems through tailoring the components of polymer excipients using electrospraying.

Abstract: A novel free surface electrospining via a stepped pyramid-shaped spinneret was used to prepare composite nanofibers containing microparticles. We investigate the spinnability of Polyacrylonitrile (PAN) solution containing graphite powder microparticles. The influence of microparticle on fiber diameter has been studied. This method can be used to produce composite nanofibers containing microparticles structures by electrospinning in mass scale.

Abstract: Ultrasonic strengthening separation is a contactless separation technique, it is widely used in industrial processes, environmental assessment, biochemical analysis, clinical diagnosis and other fields. In this article, we deduced microparticle clustering in Z and X direction Coordinate equation, discussed in detail the various factors influencing particles equilibrium position in the liquid medium.

Abstract: An electrospraying process was developed for fabricating a new type of microparticulate third generation solid dispersions (SDs) composed of multiple components with ferulic acid (FA) as a model active pharmaceutical ingredient. The spraying fluids were the co-dissolving solutions of FA, polyvinylpyrrolidone K25 (PVP K25) and sodium dodecyl sulfate (SDS) in 95% ethanol aqueous solutions. Field emission scanning electron microscopic observations showed that the microparticles had an average size of 1.47 ± 0.75 μm. Results from the differential scanning calorimetry analyses suggested that FA and SDS were distributed in the polymer matrix in an amorphous status owing to the compatibility among components resulted from the second-order interactions, as verified by attenuated total reflectance Fourier transform infrared spectra. In vitro dissolution tests demonstrated that the microparticulate SDs could release all the contained FA within 1 minute, extremely faster than the raw FA particles. It can be concluded that electrospraying is a useful tool for creating new generation SDs composed of multiple components for enhancing the rapid dissolution of poorly soluble drugs.

Abstract: In order to protect carboniferous system layer in east Sichuan, it added microparticle filling agent in drilling fluid. It depended on the physical truth and principle of protecting hydrocarbon reservoir technology which used in drilling fluid. According to the property of filling agent, it studied fluid loss control agent CKH-1, calcium carbonate superfine powder, non-permeate pressure-bearing agent CY-1 and nanometer material. Dosage of CKH-1 was 1%, calcium carbonate superfine powder was 2%, CY-1 was 4% and nanometer material was 1% ,which were firmed via experiment of viscosity and fluid loss control. Microparticle filling agent was sequentially formed.

Abstract: This paper investigates characteristics of heat transfer in Fe micrometer and nanometer powder. The understanding for thermal properties of the powder is advantageous to the advancement of the processing technologies such as laser cladding, laser sintering, powder metallurgy and its other applications. Nanosized particles possess characteristic physical and chemical properties different from those of bulk materials due to the confinement of electrons, excitons, and photons into small volumes. Therefore it is valuable to discuss the thermal behaviours of powders constituted by nanometer-sized particles. The powder is wrapped up in the slender tube. One end of the slender tube filled with powder is connected to the low constant-temperature reservoir and the other end is kept at room temperature. The temperature histories at the 1cm location of the slender tube from the low constant-temperature reservoir are recorded using thermalcouples. Powders of particles with the diameter sizes 20nm and 5000nm are employed in this experiment. The results show that the thermal diffusion in the 20nm Fe powder is faster than that in the 5000nm Fe powder.

Abstract: This paper investigates effects of particle size on heat transfer in copper powders. The understanding for thermal properties of the powder is advantageous to the advancement of the processing technologies such as laser cladding, laser sintering, powder metallurgy and its other applications. Nanosized particles possess characteristic physical and chemical properties different from those of bulk materials due to the confinement of electrons, excitons, and photons into small volumes. Therefore it is valuable to discuss the thermal behaviours of powders constituted by nanometer-sized particles. The powder is wrapped up in the slender tube. One end of the slender tube filled with powder is connected to the low constant-temperature reservoir and the other end is kept at room temperature. The temperature histories at the 1cm location of the slender tube from the low constant-temperature reservoir are recorded using thermal couples. Powders of particles with the sizes 50nm and 5000nm are employed in this experiment. The results show that the thermal diffusion in the 50nm Cu powder is faster than that in the 5000nm Cu powder.

Abstract: Traditional materials processing in the nanometer range using laser technology is very difficult with conventional optics due to the diffraction limit of the beam wavelength, a near-field technology has been developed to circumvent the diffraction limit, permitting the spot size to be reduced down to 20 nm. In most near-field techniques, this technology is achieved by placing a small aperture or microparticle between the sample and the light source. Therefore this paper will analytically investigate the profile of the intensity for diffraction of laser irradiating an aperture or microparticle in nanostructure processing. Classical electromagnetic wave theory is employed to calculate the intensity for diffraction of laser irradiating a microparticle or aperture. The results will reveal the differences between an aperture and micoparticle for diffraction of laser. The effect of laser parameters on the intensity and distribution of diffraction will be also discussed.

Abstract: Carbon-MEMS (C-MEMS) have emerged as a new category of devices for micro/nano technology with many potential applications. Dielectrophoretic manipulation of micro/nanoparticles with C-MEMS is studied in this paper. Through electric field distribution modeling in carbon electrode array, we analyze the strongest simulation effect results of electric field in three dimensional (3-D) surface plots depicting the magnitude of electric field in various cross sections at different heights above the channel floor for 2, 10, 30 and 50 μm high carbon electrodes. It is represented here that maximum intensity of electric field generates with the equality between the height above the channel floor and the height of the electrodes. Simulation parameters involved are for dielectrophoretic manipulation of micro/nano particles based on 3-D C-MEMS. The advantages of using 3-D C-MEMS electrodes over other techniques of creating high-throughput systems for dielectrophoretic manipulation environment surrounded by micro/nano horizons are: (i) complex microscale 3-D electrodes with high-aspect ratios can easily be shaped and patterned using conventional lithography (ii) carbon has a high window of stability thus allowing application of higher voltages (iii) there is no need for bulk micromachining or patterning electrodes on multiple planes (iv) the distance between electrodes can precisely be controlled through the lithography process. FEMLAB 3.4 Multiphysics Modeling software (COMSOL, Stockholm, Sweden) is used for the modeling of electric fields and one-layer C-MEMS microelectrode array was fabricated with SU-8 photoresist.