Using reverse micelle processing, ZnAl2O4 nanopowders were synthesized from a mixed precursor(consisting of Zn(NO3)2 and Al(NO3)3). The ZnAl2O4 was prepared by mixing the aqueous solution at a molar ratio of Zn : Al = 1 : 2. The average size and distribution of the synthesized powders with heat treatment at 600 oC for 2 h were in the range of 10-20 nm and narrow, respectively. The average size of the synthesized powders increased with increasing water to surfactant molar ratio. The XRD diffraction patterns show that the phase of ZnAl2O4 was spinel(JCPDS No. 05-0669). The synthesized and calcined powders were characterized using a thermogravimetric - differential scanning calorimeter(TG-DSC), X-ray diffraction analysis (XRD), and high resolution transmission electron microscopy(HRTEM). The effects of the synthesis parameter, such as the molar ratio of water to surfactant, are discussed.

NiAl2O4 nanoparticle was synthesized by a reverse micelle processing for inorganic pigment. N (NO3)2·6H2O and Al(NO3)3·9H2O were used for the precursor in order to synthesize NiAl2O4 nanoparticles. The aqueous solution, which consisted of a mixing molar ratio of Ni/Al, was 1:2 and heat treated at 800~1100 oC for 2h. The average size and distribution of synthesized NiAl2O4 powders are in the range of 10-20 nm and narrow, respectively. The average size of the synthesized NiAl2O4 powders increased with an increasing water-to-surfactant molar ratio and heating temperature. The crystallinity of synthesized NiAl2O4 powder increased with an increasing heating temperature. The synthesized NiAl2O4 powders were characterized by X-ray diffraction analysis(XRD), a field emission scanning electron microscop (FE-SEM), and a color spectrophotometer. The properties of synthesized powders were affected as a function such as a molar ratio and heating temperature. Results indicate that synthesis using a reverse miclle processing is a favorable process to obtain NiAl2O4 spinels at low temperatures. The procedure performed suggests that this new synthesis route for producing these oxides has the advantage of being fast and simple. Colorimetric coordinates indicate that the pigments obtained exhibit blue colors.

Inorganic pigments have high thermal stability and chemical resistance at high temperature. For these reasons, they are used in clay, paints, plastic, polymers, colored glass and ceramics. CoAl2O4 nano-powder was synthesized by reverse-micelle processing the mixed precursor(consisting of Co(NO3)2 and Al(NO3)3). The CoAl2O4 was prepared by mixing an aqueous solution at a Co:Al molar ratio of 1:2. The average particle size, and the particle-size distribution, of the powders synthesized by heat treatment (at 900; 1,000; 1,100; and 1,200˚C for 2h) were in the range of 10-20 nm and narrow, respectively. The average size of the synthesized nano-particles increased with increasing water-to-surfactant molar ratio. The synthesized CoAl2O4 powders were characterized by X-ray diffraction analysis(XRD), field-emission scanning electron microscopy(FE-SEM) and color spectrophotometry. The intensity of X-ray diffraction of the synthesized CoAl2O4 powder, increased with increasing heating temperature. As the heating temperature increased, crystal-size of the synthesized powder particles increased. As the R-value(water/surfactant) and heating temperature increased, the color of the inorganic pigments changed from dark blue-green to cerulean blue.

Trivalent cerium-ion-doped Y3(Al, Ga)5O12 nanoparticle phosphor nanoparticles were synthesized using the reversemicelle process. The Ce doped Y3(Al, Ga)5O12 particles were obtained from nitrate solutions dispersed in the nanosized aqueousdomains of a micro emulsion consisting of cyclohexane as the oil phase and poly(oxyethylene) nonylphenyl ether (Igepal CO-520) as the non-ionic surfactant. The crystallinity, morphology, and thermal properties of the synthesized Y3(Al, Ga)5O12:Ce3+powders were characterized by thermogravimetry-differential thermal analysis (TGA-DTA), X-ray diffraction analysis (XRD),scanning electron microscopy (SEM), and transmission electron microscopy. The crystallinity, morphology, and chemical statesof the ions were characterized; the photo-physical properties were studied by taking absorption, excitation, and emission spectrafor various concentrations of cerium. The photo physical properties of the synthesized Y3(Al, Ga)5O12:Ce3+ powders werestudied by taking the excitation and emission spectra for various concentrations of cerium. The average particle size of thesynthesized YAG powders was below 1µm. Excitation spectra of the Y3Al5O12 and Y3Al3.97Ga1.03O12 samples were 485nmand 475nm, respectively. The emission spectra of the Y3Al5O12 and Y3Al3.97Ga1.03O12 were around 560nm and 545nm,respectively. Y3(Al, Ga)5O12:Ce3+ is a red-emitting phosphor; it has a high efficiency for operation under near UV excitation,and may be a promising candidate for photonic applications.

Fe/SiO2 core-shell type composite nanoparticles have been synthesized using a reverse micelle process combined with metal alkoxide hydrolysis and condensation. Nano-sized SiO2 composite particles with a core-shell structure were prepared by arrested precipitation of Fe clusters in reverse micelles, followed by hydrolysis and condensation of organometallic precursors in micro-emulsion matrices. Microstructural and chemical analyses of Fe/SiO2 core-shell type composite nanoparticles were carried out by TEM and EDS. The size of the particles and the thickness of the coating could be controlled by manipulating the relative rates of the hydrolysis and condensation reaction of TEOS within the micro-emulsion. The water/surfactant molar ratio influenced the Fe particle distribution of the core-shell composite particles, and the distribution of Fe particles was broadened as R increased. The particle size of Fe increased linearly with increasing FeNO3 solution concentration. The average size of the cluster was found to depend on the micelle size, the nature of the solvent, and the concentration of the reagent. The average size of synthesized Fe/SiO2 core-shell type composite nanoparticles was in a range of 10-30 nm and Fe particles were 1.5-7 nm in size. The effects of synthesis parameters, such as the molar ratio of water to TEOS and the molar ratio of water to surfactant, are discussed.

The preparation of Sm2O3 doped CeO2 in Igepal CO-520/cyclohexane reverse micelle solutions has been studied. In the present work, we synthesized nanosized Sm2O3 doped CeO2 powders by reverse micelle process using aqueous ammonia as the precipitant; hydroxide precursor was obtained from nitrate solutions dispersed in the nanosized aqueous domains of a micro emulsion consisting of cyclohexane as the oil phase, and poly (xoyethylene) nonylphenylether (Igepal CO-520) as the non-ionic surfactant. The synthesized and calcined powders were characterized by Thermogravimetry-differential thermal analysis (TGA-DTA), X-ray diffraction analysis (XRD), and Transmission electron microscopy (TEM). The crystallite size was found to increase with increase in water to surfactant (R) molar ratio. Average particle size and distribution of the synthesized Sm2O3 doped CeO2 were below 10 nm and narrow, respectively. TG-DTA analysis shows that phase of Sm2O3 doped CeO2 nanoparticles changed from monoclinic to tetragonal at approximately 560˚C. The phase of the synthesized Sm2O3 doped CeO2 with heating to 600˚C for 30 min was tetragonal CeO2. This study revealed that the particle formation process in reverse micelles is based on a two step model. The rapid first step is the complete reduction of the metal to the zero valence state. The second step is growth, via reagent exchanges between micelles through the inter-micellar exchange.

The preparation of Y2O3-doped ZrO2 nanoparticles in Igepal CO-520/cyclohexane reverse micelle solutions is studied here. In this work, we synthesized nanosized Y2O3-doped ZrO2 powders in a reverse micelle process using aqueous ammonia as the precipitant. In this way, a hydroxide precursor was obtained from nitrate solutions dispersed in the nanosized aqueous domains of a microemulsion consisting of cyclohexane as the oil phase, with poly (oxyethylene) nonylphenylether (Igepal CO-520) as the non-ionic surfactant. The synthesized and calcined powders were characterized by thermogravimetrydifferential thermal analysis (TGA-DTA), X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). The crystallite size was found to nearly identical with an increase in the water-to-surfactant (R) molar ratio. A FTIR analysis was carried to monitor the elimination of residual oil and surfactant phases from the microemulsion-derived precursor and the calcined powder. The average particle size and distribution of the synthesized Y2O3-doped ZrO2 were below 5 nm and narrow, respectively. The TG-DTA analysis showed that the phase of the Y2O3-doped ZrO2 nanoparticles changes from the monoclinic phase to the tetragonal phase at temperatures close to 530˚C. The phase of the synthesized Y2O3-doped ZrO2 when heated to 600˚C was tetragonal ZrO2.

A preparation of NixMn1-xFe2O4 nanoparticles produced via the reduction of Nickel nitrate hexahydrate, Manganese (II) nitrate hexahydrate and Iron nitrate nonahydrate with hydrazine in Igepal CO-520/cyclohexane reverse micelle solutions was investigated. Transmission Electron Microscope (TEM), X-ray Diffraction (XRD) and Vibration Sample Magnetometer (VSM) analyses showed that the resultant nanoparticles increased the molar ration of water to Igepal CO-520 as the concentrations of Nickel nitrate hexahyrate, Manganese (II) nitrate hexahydrate and Iron nitrate nonahydrate increased. The average size of the synthesized particles calcined at 600˚C for 2hrs was in the range of 20 nm to 30 nm, and the particle distribution was broadened. The phase of the synthesized particles was crystalline, and the magnetic behavior of the synthesized particles was superparamagnetism. The effect of the synthesis parameters of the molar ratio of water to surfactant and the calcination temperature was discussed.

Nanosized titania sol has been produced by the controlled hydrolysis of titanium tetraisopropoxide(TTIP) in sodium bis(2-ethylhexyl)sulfosuccinate(AOT) reverse micelles. The physical properties, such as crystallite size and crystallinity according to R ratio have been investigated by FT-IR, XRD and UV-DRS. In addition, the photocatalytic degradation of bromate has been studied by using batch reactor in the presence of UV light in order to compare the photocatalytic activity of prepared nanosized titania. It is shown that the anatase structure appears in the 300～600℃ calcination temperature range and the formation of anatase into rutile starts above 700℃. The crystallite size increases with increasing R ratio. In the photocatalytic degradation of bromate, the photocatalytic decomposition of bromate shows the decomposition rate increases with decreasing initial concentration of bromate and with increasing intensity of light.