1. Introduction
Recently, many research efforts have been made in developing polymer-silica hybrid nanocomposites.The combination of superior properties of polymers such as flexibility, dielectric, toughness and process ability, and that of oxides which have high thermal stability, good mechanical and optical properties, can lead to production of highly functionalized materials with desired properties to meet the demands of many industrial and high technology applications. The resulting materials exhibit someexcellent properties of its inorganic counterpart to beutilized in electrical, optical, structural, photoelectrical, andnon-linear optical applications.
Highly dispersed nanometer silica particles are essentialin the synthesis of nanocomposites in order to ensurehomogeneity, which is associated to the quality of the finalproducts. The most interesting and popular process inobtaining nanometer silica is through hydrolysis and condensationof silicon alkoxide at low temperature.During hydrolysis and condensation process, the silicate monomer nucleates in a supersaturated solution and grows to form dimeric, cyclic, spherical particles or gel network.Thus, different particles size and morphology of silica particles can be produced by sol–gel process through controlling parameters such as concentration of alkoxide,amount of water, concentration of ammonia or acid (pH),and solvent, aging time and admixture.
Kim et al. have reported that mono-valent electrolyte additives such as NaI can reduce the size of nanosized silica particles up to 17.5 nm. Based on our literature search, so far no studies have been reported on investigating the effect ofammonium salts in enhancing surface charge and thus reducing the size of silica particles through sol–gel process.When ammonium salts, NH4X dissolved in ammonia (act as catalyst in sol–gel process), the solution will contain ionic species of NH4
+ and X_. We believe that any changes in the morphology of the synthesized silica are caused solely by the anion presence. For the first time we use the conductivity profile to explain the effect of anion on the silica particle growth as alternative to the normally used zeta potential technique.
不要直接用有道翻译好么?