Synthesis and characterization of nanocomposites …
Lanje  used the cost competitive and simple precipitation process for the synthesis of zinc oxide. The single step process with the large scale production without unwanted impurities is desirable for the cost-effective preparation of ZnO nanparticles. As a consequence, the low cost precursors such as zinc nitrate and sodium hydroxide to synthesize the ZnO nanoparticles ( 40 nm) were used. In order to reduce the agglomeration among the smaller particles, the starch molecule which contains many O-H functional groups and could bind surface of nanoparticles in initial nucleation stage, was used.
02/02/2012 · Polymer nanocomposites ..
Polymer brushes with multiwalled carbon nanotubes (MWNTs) as backbones were synthesized by grafting 2-hydroxyethyl methacrylate (HEMA) from the sidewall of MWNTs via surface reversible addition and fragmentation chain transfer (RAFT) polymerization using RAFT agent immobilized MWNTs as chain transfer agent. After immobilization of the RAFT agent, poly(2-hydroxyethyl methacrylate) (PHEMA) chains as water-soluble polymer chains were successfully grafted from the surface of MWNTs, resulting in the formation of core−shell nanostructures. Fourier transform infrared spectroscopy, thermal gravimetric analysis, and X-ray photoelectron spectroscopy were used to determine chemical structure and the grafted polymer quantities of the resulting product. Transmission electron microscopy (TEM) images indicated that the nanotubes were coated with a polymer layer. Gel permeation chromatography analyses showed that the molecular weight of cleaved PHEMA increased linearly with the grafted polymer content and the cleaved PHEMA chains had a narrow molecular weight distribution. The PHEMA grafted MWNTs can be hydrolyzed by HCl solution to yield poly(methacrylic acid) (PMAA) grafted MWNTs, which have higher loading capacities for metal ions, such as Ag+. TEM and energy dispersive spectroscopy measurements confirmed the nanostructures and the components of the resulting MWNT-PMAA/Ag hybrid nanocomposites.
In order to solve this problem, surface modification techniques are applied to improve the interaction between the nanoparticles and the polymer. In the work of Yuan , in order to prepare the silicone rubber with high thermal conductivity, pristine and surface-modified ZnO nanoparticles containing the vinyl silane group are incorporated into the silicone rubber via a hydrosilylation reaction during the curing process. The corresponding structure, morphology and properties of the silicone rubber/ZnO (SR/ZnO) and silicone rubber/SiVi@ZnO (SR/SiVi@ZnO) nanocomposites were investigated. Yuan synthesized ZnO nanoparticles (with an average size below 10 nm) by a sol-gel procedure. Next the silicone coupling agent VTES was successfully incorporated onto the surface of the nanoparticles. The SR/SiVi@ZnO nanocomposites showed better mechanical properties and higher thermal conductivity due to the formation of a cross-linking structure with the silicone rubber matrix and better dispersion in that matrix.
Nanocomposites: synthesis, structure, properties and …
Titanium dioxide, TiO2, an inexpensive and non-toxic semiconductor, exhibits very interesting characteristics that make its incorporation into polymeric matrices as nanoparticles an appropriate methodology to develop new nanocomposites with enhanced behavior. This chapter describes general features of TiO2, including its preparation protocols and disinfection capability, as well as itemizes different TiO2-polymer-based nanocomposites in order to learn how they can be prepared and about the improvement that TiO2 presence confers to the ultimate properties displayed by the final materials.
In situ synthesis of polymer-clay nanocomposites from ..
Stanković  extended their previous study to investigate mechanical-thermal synthesis (MTS)—mechanical activation followed by thermal activation of ZnO from ZnCl2 and oxalic acid (C2H2O4·2H2O) as reactants with the intention of obtaining pure ZnO nanopowder. The study also aimed to examine the effects of oxalic acid as an organic PCA, and different milling times, on the crystal structure, average particle size and morphology of ZnO nanopowders. The mixture of initial reactants was milled from 30 min up to 4 h, and subsequently annealed at 450 °C for 1 h. Qualitative analysis of the prepared powders was performed using X-ray diffraction (XRD) and Raman spectroscopy. The XRD analysis showed perfect long-range order and the pure wurtzite structure of the synthesized ZnO powders, irrespective of the milling duration. By contrast, Raman spectroscopy indicates a different middle-range order of ZnO powders. From the SEM images, it is observed that the morphology of the particles strongly depends on the milling time of the reactant mixture, regardless of the further thermal treatment. A longer time of milling led to a smaller particle size.
Synthesis, characterization and …
In processes of synthesis of nanopowders based on precipitation, it is increasingly common for surfactants to be used to control the growth of particles. The presence of these compounds affects not only nucleation and particle growth, but also coagulation and flocculation of the particles. The surfactant method involves chelation of the metal cations of the precursor by surfactants in an aqueous environment. Wang  obtained nanometric zinc oxide from ZnCl2 and NH4OH in the presence of the cationic surfactant CTAB (cetyltrimethylammonium bromide). The process was carried out at room temperature, and the resulting powder was calcined at 500 °C to remove residues of the surfactant. The product was highly crystalline ZnO with a wurtzite structure and with small, well-dispersed spherical nanoparticles in size of 50 nm. It was found that CTAB affects the process of nucleation and growth of crystallites during synthesis, and also prevents the formation of agglomerates.