Particle size reduction solution method

Physico-chemical methods for particle size reduction comprise methods wherein the substance is first dissolved and then precipitated in a finer form during further processing. This has the advantage that it is independent of the fineness of the starting material and that the formation of small agglomerating particles is largely prevented. Two methods are distinguished the solution method and the precipitation method. 

The solvent method basically distributes a small quantity of active substance (5 mg or less per dose unit) over a diluent. The active substance is dissolved in a suitable, volatile solvent, usually in a stainless steel mortar to be able to check if dissolution is completed. -Subsequently, the solution is mixed with a carrier that does not dissolve in the solvent. The moistened powder is triturated -until the solvent has completely evaporated. The powder mixture now consists of carrier particles with a coating of the active substance. This method is in fact a combination of simultaneous particle size reduction and mixing. Another advantage of this method is the reduced loss of the powder mixture during mixing. 

Suhtnicion nickel powders luive been synthesized successfully from aqueous NiCh at various tempmatuTKi and times with ethanol-water solvent by using the conventional and ultrasonic chemical reduction method. The reductive condition was prepared by flie dissolution of hydrazine hydrate into basic solution. The samples synthesized in various conditions weae claractsiz by the m ins of an X-ray diffractometry (XRD), a scanning electron microscopy (SEM), a thermo-gravimetry (TG) and an X-ray photoelectron spectroscopy (XPS). It was found that the samples obtained by the ultrasonic method were more smoothly spherical in shape, smaller in size and narrower in particle size distribution, compared to the conventional one. 

Herein we briefly mention historical aspects on preparation of monometallic or bimetallic nanoparticles as science. In 1857, Faraday prepared dispersion solution of Au colloids by chemical reduction of aqueous solution of Au(III) ions with phosphorous [6]. One hundred and thirty-one years later, in 1988, Thomas confirmed that the colloids were composed of Au nanoparticles with 3-30 nm in particle size by means of electron microscope [7]. In 1941, Rampino and Nord prepared colloidal dispersion of Pd by reduction with hydrogen, protected the colloids by addition of synthetic pol5mer like polyvinylalcohol, applied to the catalysts for the first time [8-10]. In 1951, Turkevich et al. [11] reported an important paper on preparation method of Au nanoparticles. They prepared aqueous dispersions of Au nanoparticles by reducing Au(III) with phosphorous or carbon monoxide (CO), and characterized the nanoparticles by electron microscopy. They also prepared Au nanoparticles with quite narrow... 

Competitive reduction of Au(III) and Ag(I) ions occurs simultaneously in solution during exposure to neem leaf extract leads to the preparation of bimetallic Au-core/Ag-shell nanoparticles in solution. TEM revealed that the silver nanoparticles are adsorbed onto the gold nanoparticles, forming a core/sheU structure. Panigrahi et al. [121] reported that sugar-assisted stable Au-core/Ag-shell nanoparticles with particles size of ca. 10 nm were prepared by a wet chemical method. Fructose was found to be the best suited sugar for the preparation of smallest particles. 

Some of the reports are as follows. Mizukoshi et al. [31] reported ultrasound assisted reduction processes of Pt(IV) ions in the presence of anionic, cationic and non-ionic surfactant. They found that radicals formed from the reaction of the surfactants with primary radicals sonolysis of water and direct thermal decomposition of surfactants during collapsing of cavities contribute to reduction of metal ions. Fujimoto et al. [32] reported metal and alloy nanoparticles of Au, Pd and ft, and Mn02 prepared by reduction method in presence of surfactant and sonication environment. They found that surfactant shows stabilization of metal particles and has impact on narrow particle size distribution during sonication process. Abbas et al. [33] carried out the effects of different operational parameters in sodium chloride sonocrystallisation, namely temperature, ultrasonic power and concentration sodium. They found that the sonocrystallization is effective method for preparation of small NaCl crystals for pharmaceutical aerosol preparation. The crystal growth then occurs in supersaturated solution. Mersmann et al. (2001) [21] and Guo et al. [34] reported that the relative supersaturation in reactive crystallization is decisive for the crystal size and depends on the following factors. 

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