Papers by Keyword: Hollow Microsphere

Abstract: Resin-derived carbon foams with closed hollow spherical structure were prepared from mixtures of hollow phenolic microspheres and phenolic resin, followed by curing and carbonization. The resultant carbon foam had a bulk density of 0.45 g·cm^-3. Effects of hollow microsphere on the on the compressive property and thermal conductivity of carbon foams were investigated. The results revealed that the hollow microspheres played an important role in improving compressive fracture toughness and lowering the thermal conductivity of carbon foams. The compressive fracture characteristics of carbon foam exhibited gradient brittle fracture, and the compressive strength was 10.93 MPa. The thermal conductivity of the carbon foam was 0.907 W·m^-1·K^-1 at room temperature, which was lowered by 49.67 % in comparison with phenolic-based vitreous carbon.

Abstract: A novel hollow microsphere plastic pigment was prepared by the soap-free seeded emulsion polymerization. This pigment, with polyacrylate as core and with polystyrene as shell (PA/PSt) had hollow structure after dryness. The latex was characterized by transmission electron microscopy (TEM), Fourier transform infrared spectra (FTIR), and particle size analysis. The synthetic pigment was applied in the paper coating, and its influence on the printablility of the coated paper was investigated. The results show that the overall properties of the coated paper can be effectively improved when the clay in the base formulation is replaced by a small amount of hollow microsphere plastic pigment.

Abstract: Hollow microspheres with less than 1 millimeter in diameter and several micrometers in wall thickness are attractive for hydrogen storage and transportation. The hollow microspheres can be made by drop tower technique, microencapsulation and vapor deposition methods. By immersion in high pressure hydrogen for a period of time at elevated temperature, the hollow microspheres can be filed with hydrogen gas at pressures up to one hundred MPa. The hydrogen mass fraction can be varied from 1% to 10% for hollow microspheres with different membrane hoop stress at failure.

Abstract: The sulfonated polystyrene hollow microspheres (SPHS) with interpenetrated walls were used as templates. An in-situ growth of BaTiO₃ nanocrystals was conducted against SPHS templates at ambient pressure and 70°C. The structure and morphology of the resultant samples were investigated by XRD, SEM, TEM, FTIR and TGA. The results indicated that the composite hollow microspheres with diameter about 450 nm were double-shelled and composed of 30 nm cubic BaTiO₃ nanocrystals.

Abstract: The mixing required for post-mould gelatinisation of syntactic foams using starch as binder was studied. It was found that starch particles tend to adhere to hollow microspheres during mixing, forming agglomerates. A transition in the buoyancy of microsphere-starch phases was found at a particular volume fraction of starch. The transitional point was close to a volume fraction of starch at which a calculated relative density for a system consisting of multiple starch particles per microsphere was unity. Starch-microsphere inter-distance appears to be an important parameter affecting starch content in an agglomeration.

Abstract: Various manufacturing parameters involved in the ‘buoyancy method’ were inter-related. An equation based on unit cell models for a relation between volume expansion ratio (VER) of bulk microspheres in aqueous starch and microsphere size was derived. A good agreement between the equation and experimental data was found. The inter-microsphere distance (MID) concept was introduced and it was demonstrated that the MID can be calculated numerically for microspheres with known statistical data.

Abstract: Hollow microspheres of nickel hydroxide and nickel oxide were prepared with as-synthesized PS/Ni(OH)2 composite particles by sacrificing core method, respectively. The composite particles were synthesized by deposition of the Ni(OH)2 nanoflakelets formed by the hydrolysis of nickel nitrate onto the surfaces of polystyrene (PS) particles. The effects of different concentrations of nickel salt and urea on the deposition of the nanoflakelets of nickel hydroxide were studied. It was found that the uniform nanoflakelets were deposited on the polystyrene particles under the conditions of the 4╳10-3 M nickel salt and 0.667M urea. Compared with the directly calcinating of composite particles, Integral hollow microspheres of nickel hydroxide were attained by removal of cores of polystyrene in composite particles with toluene and NiO hollow microspheres by calcinating of these Ni(OH)2 hollow spheres in oven at 600°C for 2h.

Abstract: Chemically durable microspheres 20−30 µm in diameter containing a large amount of yttrium are useful for in situ radiotherapy of cancer as they can be activated by neutron bombardment to become β-emitters and can be injected in the vicinity of the cancer to provide a large localized dose of β-radiation. In this study, preparation of hollow Y2O3 microspheres using an enzymatic reaction was attempted, and the structure and chemical durability of the resulting microspheres were investigated. Hollow Y2O3 microspheres 20–30 &m in diameter were successfully prepared by this enzymatic method. The outer surface of the microspheres was smooth and dense, whereas the inner parts had a honeycombed structure. In simulated body fluids at pH 6 and 7, the hollow Y2O3 microspheres showed high chemical durability.

Abstract: We synthesized tricalcium phosphate (TCP) microspheres using an ultrasonic spray-pyrolysis technique, and investigated the effect of the concentrations of the starting solution on the powder properties. The XRD pattern showed that the crystalline phases of the resulting powders were β-TCP/HAp biphase in the case of pyrolysis temperature at 850 °C and TCP single phase at 1000 °C. The Ca/P molar ratios were determined by XRF to be at 1.50±0.03. The particle shapes of the powders were observed by SEM; the diameters of the microspheres were narrowly distributed from 0.5 to 4 µm. The mean particle diameters of the resulting powder increased with the concentration of the starting solutions and could be controlled in the range of 0.85-1.4 µm. When the compressed powder was sintered at 1050 °C for 5 h , the relative density of the sintered compact attained to 97%. The TCP microspheres had good sinterability.