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Morphology Studies (morphology + studies)

Distribution by Scientific Domains
Polymers and Materials Science50%

Selected Abstracts

Poly(vinyl acetate)/Silver Nanocomposite Microspheres Prepared by Suspension Polymerization at Low Temperature

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 1 2005
Jeong Hyun Yeum
Abstract Summary: High molecular weight (HMW) poly(vinyl acetate)/silver nanocomposite microspheres (PVAc/Ag), which are promising precursors of embolic materials with radiopacity, were prepared via a suspension polymerization approach in the presence of silver nanoparticles. It was found that a high yield and high molecular weight PVAc/Ag could be concurrently obtained even using a low-temperature initiator 2,2,-azobis(2,4-dimethylvaleronitrile) (,30,°C). In the case of presence of silver nanoparticles, the rate of polymerization was slightly slower than that without Ag. The suspension polymerization approach introduced could produce PVAc/Ag composite with conversion and viscosity-average molecular weight () up to 95% and 1,300,000, respectively, in spite of the low polymerization temperature (,30,°C), in sharp contrast with an only ,30% conversion of VAc under bulk polymerization. Morphology studies revealed that except normal suspension microspheres with a smooth surface, a golf ball-like appearance of the microspheres was observed, due to the migration and aggregating of the hydrophilic Ag nanoparticles at the sublayer beneath the microsphere's surface. [source]

Characterization and electrical properties of new perovskite films of Ba(Ti,Zr)O3 type doped with lanthanum (BLZT)

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2007
E. Delgado
Abstract In the current work, we characterized a new family of compounds with perovskite-type structure with the general formula: Ba1,yLa2y/3Ti1,xZrxO3 (BLZT). Through XRD on crystalline powder we detected a single perovskite cubic phase, Pm3m (221), for the compounds with zirconium content (x) lower than 0.15 and lanthanum content (La) lower than 0.17. Upon increasing the x value in BLZT compounds, the value of La falls to 0.13. Morphology studies through SEM revealed that the incorporation of lanthanum into the composition of Ba(Ti,Zr)O3 (BZT) compounds produces the formation of bigger grains and materials with greater density. The stoichiometry for each compound was corroborated by atomic emission spectroscopy (AES-ICP). The lanthanum-doped compounds demonstrated higher relative permittivity values with respect to the BZT and a decrease of the Curie temperature (Tc) with relation to the amount of La3+ ion present in the structure. Finally, we grew thin films by using a target of the compound Ba0.90La0.067Ti0.91Zr0.09O3 over three different substrates under two atmospheres (Ar and O2), using the Magnetron Sputtering technique by Radio Frequency (RF), showing the best results when growth is over the substrate SrTiO3.Nb 0.1% in the [00l] direction under an O2 atmosphere. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Morphology studies of doped polyaniline micro/nanocomposites containing TiO2 nanoparticles and Fe3O4 microparticles

POLYMER COMPOSITES, Issue 7 2009
Sook-Wai Phang
To produce polyaniline (PAni) nanodevices that display excellent microwave absorbing behaviors, novel hexanoic acid-doped PAni micro/nanocomposites containing TiO2 nanoparticles and Fe3O4 microparticles (PAni/HA/TiO2/Fe3O4) were prepared by template-free method, particularly to improve the dielectric and magnetic property of PAni. PAni/HA/TiO2/Fe3O4 synthesized at different polymerization temperatures and polymerization time by various TiO2 and Fe3O4 contents, and particles size of TiO2 were prepared. The aim of this research is to investigate the effect of synthesis condition on the morphology behaviors of nanorods/tubes. The resulted nanorods/tubes indicated that PAni micro/nanocomposites exhibited polymerization through elongation. PAni micro/nanocomposites synthesized at 0°C resulted in large amounts of nanorods/tubes compared with those synthesized at subzero temperature and above 0°C. PAni/HA/TiO2 and PAni/HA/TiO2/Fe3O4 synthesized using TiO2 with diameter (particles size) 180 nm resulted in large amounts of nanorods/tubes (diameter nanorods/tubes = 80,140 nm) compared with those synthesized using TiO2 with diameter of 30 and 6 nm. Increasing TiO2 and Fe3O4 content above 10% will significantly reduce the amount of nanorods/tubes. In conclusion, synthesis parameters mentioned above are the significant factors that might affect the morphology behaviors of PAni nanostructures. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source]

Molecular Modeling in Crystal Engineering for Processing of Energetic Materials

PROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 6 2003
Stéphane Bénazet
Abstract Nowadays molecular modeling is available to explain molecular phenomena. This approach helps to compute crystal surface property effects that can be used both for morphology studies and optimal design of "bonding agents" to prevent filler-binder detachment. The principles of crystal growth and of interaction energy computing have been applied to Hexanitrohexaazaisowurtzitane (HNIW). Crystallization experiments validate our calculations. Three families of additives of crystal growth are distinguished: the retarding (and inhibitor) agents, the promoters and finally the "tailor-mades". Retarding and inhibitor agents are the most interesting one to find bonding agents. HNIW is used to present our methodology, but engineering using molecular modeling could be generalized to other fillers. [source]