Papers by Keyword: Dispersibility

Abstract: By replacing the interface with sharp change properties with a functionally graded material with a gradually changing composition, a stable interface can be formed for mechanical and functional properties. In this study, the final goal is to functionally grade the interface between aluminum and alumina (Al₂O₃)/aluminum (Al) composites. First, the segmentation velocity of Al₂O₃ particles under gravity was measured to clarify the possibility of functional grading. The starting materials used were A356.0 Al alloy and α-type Al₂O₃ particles. The segmentation velocity obtained by the experiment was much faster than the theoretical velocity obtained by Stokes' law. It seems Stokes' law assumes that the particles are spherical and there is no interaction between particles, but the actual particle velocity was affected by the actual particle shape and interaction between particles. These factors affect the change in the segmentation velocity. The height of the mold was set to 40 mm, and an Al₂O₃ particle/Al composite with a particle size of 6.7 μm was placed on the top and an Al alloy was placed on the bottom in the mold, melted, and rapidly solidified after 12 sec., and an Al₂O₃ particle-dispersed Al alloy functionally graded composite was obtained under gravity.

Abstract: Microencapsulation of drugs is used for a long time to improve their properties. It was carried out a comparative assessment of the physical and physicochemical methods of microencapsulation on the example of some drugs. The spray drying method was selected from the physical methods. Physicochemical method based on simple coacervation was implemented by changing the solvent. A study and comparison of the properties of the products were obtained by UV and IR spectroscopy, liquid chromatography, electron microscopy. It was carried out a comparative assessment of the release profile of the active substance from microcapsules obtained by various methods. Using the example of furacilin microcapsules has been shown an increase in the biological activity of substances encapsulated in water-soluble polymers. The particle size distribution was determined by analyzing their trajectories. The main advantages and disadvantages of the two investigated encapsulation methods are outlined.

Abstract: Nanofibers have high cell affinity due to their fine structure and surface roughness, and are expected to be used as biomaterials. In particular, magnetic nanofibers containing magnetic particles are expected to be used for magnetically induced drug delivery systems and hyperthermia. However, due to the aggregation of the magnetic particles contained in the nanofibers, there is a problem that the aggregation location becomes a starting point of fracture and causes a decrease in tensile strength. In this study, to improve the dispersibility of magnetic particles in Magnetite/PLA nanofiber nonwoven fabrics for suppressing the decrease in tensile strength, magnetite is subjected to surface treatment with oleic acid or stearic acid and ultrasonic agitation. Magnetite/PLA nanofiber nonwoven fabric was prepared by the electrospinning method, and dispersion of magnetite in PLA nanofiber nonwoven fabric and tensile strength were evaluated. Magnetite dispersion was improved by the surface treatment and increasing the ultrasonic agitation time. In particular, by performing the stearic acid treatment and prolonging the ultrasonic agitation time, the magnetite dispersion tended to be improved. This treated Magnetite/PLA nanofiber nonwoven fabric showed higher tensile strength.

Abstract: The improvement of strength and ductility is a challenging task for application of oil well cement. As a 2D nanomaterial with high strength and toughness, graphene oxide (GO) was used as a reinforcing additive in oil well cement. The mechanical properties and micro-structure of oil well cement enhanced by GO were investigated. The compressive strength and flexrual strenghth of cement stone both showed a good enhancement effect when the content of GO was 0.02% -0.05%. The compressive strength and flexrual strength could increase by 15.8% and 33.5%, respectively. The results of SEM and MIP revealed that GO played a template role in promoting the formation of hydration products and further filled in the pores between the hydration products, which refined the micro-structure and improved mechanical properties of the cement consequently.

Abstract: The composite ZrB₂ powder coated A1₂O₃-Y₂O₃ prepared by co-precipitation method were densified via the spark plasma sintering (SPS) and then researched the oxidation resistance at high temperature. ZrB₂ powder must have the better dispersibility during the coating processing for obtaining the better coating effect. Effect of dispersant on the dispersibility of ZrB₂ powder in the liquid is researched in this paper, the results show ZrB₂ powder have the better dispersibility as the dispersant for PMAA and the content for 2vol%, which lay foundation for synthsising the better coating effect coated A1₂O₃-Y₂O₃-ZrB₂ composite powder.

Abstract: Graphene oxide (GO) was prepared by modified Hummer’s method, and reduced by solvothermal method using ethanol as the solvent and modified diethylene triamine (amine curing agent 593) as reducing agent and modifier. The effect of reduction time and temperature on the structure and conductive property of reduced graphene oxide (593-rGO) was investigated by SEM, FT-IR and XRD. The results show that the graphene modified by 593 is obviously improved in dispersibility and sedimentation stability in dichloromethane, as well as in conductivity. The optimal reduction processing is that the mass ratio of GO to 593 is 2:1, the reduction time and temperature is 6 h and 160°C, respectively.

Abstract: Pure aluminum (Al) has been used as high performance heat sink, electrical line and power supply line because of its light-weight, good thermal and electrical conductivities and high cost performance. On the other hand, the higher performance heat sink and eletrtorical line at room and high tempertture are reqired because of the increment of the power density and higher integration of semiconductor and LED. The use of Al matrix composites is one of suilable solution, because these parts needs multi functional propertes. In this study, titanium die-broide (TiB₂) particles was selected as the dispersant in Al matrix composites because of its good thermal and electrical conductivity, and good mechanical propertes. At first, the mixed power of Al and TiB₂ particles was obtained from six kinds of mixing process, which parameters are conventional boll milling, ultrasonic vibration after conventinal milling, planetary ball milling, which milling process was performed in wet process with ethanol and dry process. 20 vol. % TiB₂/ Al composites was obtained from spark plasma sintering. The dence comopsites with over 98% in relative density with highly dispersed TiB₂ particles was obtained from wet mixing process. But the tensile strength of the composites prepared from dry mixing process is higher than that of wet mixing process. The thermal conductivity of the composites is about 120 W/mK, and the obvious diferrence between the wet process and dry process was not observed.

Abstract: The widespread demand for light-weight materials in various emerging industrial sectors lead to the fabrication of aluminum- boron carbide composites. In this study, the B₄C particles were coated copper and Ni-B through electroless process using formaldehyde and sodium borohydride respectively as reducing agents under optimized condition. The microstructural and hardness behavior were investigated for powder metallurgy processed 20 vol. % of B₄C and coated B₄C particles in the aluminum matrix. Microscopic observation revealed that coating improved the dispersibility of B₄C particles in the matrix. The coated particles showed an increase in hardness and particle compaction with reduced porosity.

Abstract: 20vol% TiB₂ particle Al composites were fabricated by spark plasma sintering after blending TiB₂ and Al particles. The dispersibility of TiB₂ particles in composites was controlled by the blending method before sintering. Then the effect of the dispersibility on the electrical conductivity was estimated. As increasing the dispersibility, the electrical conductivity of the composites decreased. The dispersibility of TiB₂ particles in composites was estimated by two-dimensional local number (LN2D), quantitatively. The theoretical value of electrical conductivity considering LN2D was estimated by the simulation of finite volume method and the Laplace equation of electric potential distribution. The tendency of low electrical conductivity of the composite with uniform distribution of TiB₂ particles was confirmed by this simulation, but the experimental degradation of electrical conductivity for uniform distribution for clustering distribution was higher than that of theoretical value. The electrical conductivity of Al seems to be affected by the plastic deformation. There are the deformation regions around the interface between TiB₂ particle and Al because of the difference of thermal expansion. Therefore, the quantity of the deformation region is increasing for increasing the dispersibility, and then the electrical conductivity of the composites decrease.

Abstract: UV spectrophotometer was used to measure UV transmittance spectrum of pigment and photo-initiators to identify the light transmitting window of a pigment and photo-initiatorsabsorption peak , then later the types of photo-initiators was determined . In order to determine the optimal assignment of monomers, dispersing agent, defoaming agent and dispersing resin, the uniform design method was supplied to achieve the smallest particle diameter within the range of D95. After the excellent configuration of based ink, the orthogonal design methodwas used to determine the proportion of based ink, photo-initiators, film-forming resin, additives by regarding viscosity, surface tension, curing speed, and color fastness as indicators.