Nano-sized particle

Furnish uniform highly dispersed nano-sized particles of Si or Sn ... 

The physical and chemical properties of MgO films prepared by the sol-gel technique were the area interest of the examinations presented by Shukla75. The aim of mentioned work was to produce films with nano size particles so as to employ them for the sensor applications, as adsorption in such films increases many folds due to the increase of surface area. Infra-red spectroscopic studies indicated the presence of solvent in the precursor, which helped in decomposition to nano-particles during nucleation of the film. The MgO sol-gel films were deposited on the glass rod bend in U-shape for humidity sensor. 

Making uniform nano-sized metal oxide particles is also of interest. Such particles could have a higher specific surface area and a higher density of surface defects than those made by conventional preparation methods. This could be beneficial to their catalytic properties. If the oxide particle is multi-component, then such nano-sized particles, each containing the various components would provide more intimate contact or... 

FIGURE 1.2. Formation of nanoparticles of metal oxide by reverse micelle method. A solution of inverse micelles is first formed by adding a long-chain alkylamine to a toluene solution. A small amount of water is trapped in the reverse micelle core. Mixing the reverse micelle solution with an aluminum alkoxy amine adduct results in hydrolysis of the aluminum alkoxide adduct and formation of nano-sized particles of aluminum oxyhydroxide after drying. These particles are shown in the SEM picture above. 

The ultimate strength and properties of many materials are dependent upon the intimate contact between the various members. Thus, for ceramics, nano-sized particles allow a more homogeneous structure resulting in stronger ceramic materials. 

FIGURE 11.7 The colour of the fluorescence from a nano-sized particle depends on its dimensions. 

Particles are known to scatter light as well as absorb it and this produces the white or pale appearance of fine powders. The even smaller nano-sized particles, however, are transparent because the scattering efficiency is reduced. This effect has led to the use of nanoparticles in sunscreens and cosmetics. These will still absorb ultraviolet light but will scatter less visible light. 

Synthesis of nano-sized particles from metal carbonates by the method of reversed mycelles... 

The nano-sized particles of calcium carbonate and barium carbonate have specific characteristics. They are important materials for the industry. The main object of this investigation is to obtain nanoparticles of calcium carbonate and barium carbonate by chemical reaction carried out in microemulsion of water in oil. The nanoparticles obtained are spherical. Their sizes vary from 20 to 30 nm. The shape and size of particles are determinated by electron microscopy. 

The investigations of materials obtained from nano-sized particles showed that they have unknown properties or enhanced characteristics compared to common materials. Many alkaline carbonates have take in especially application in practice. Calcium carbonate is widely used for production of toothpaste, binding agents, etc. [12,13]. Barium carbonate is used mainly in glass production industries, as well as water softening agent, etc. Both substances are crystalline, with rhombic lattice and practically insoluble in water [12]. 

Many methods have been used for synthesis of nano-sized particles vapour transport [2], precipitation of homogeneous solution [3], synthesis by sol-gel process [4], freeze-drying... 

Microemulsion is used as a special microreactor to limit the nano-sized particles growth. The shape of the microreactor depends on reaction conditions [9]. This method increases the homogeneity of the chemical composition at nano-level and facilitates the preparation of nano-particles with comparatively equal sizes [11]. The specific properties of the nano-particles make them suitable for microelectronics, ceramics, catalysis, medicine, cosmetics, as piezoelectric materials, conductors, etc. 

The aim of the present investigation is to synthesize nano-sized particles from CaCC>3 and BaCC>3 by the microemulsion method. 

The synthesis of nano-sized particles from CaCC>3 and BaCC>3 was carried out in a recurrent reactor equipped with stirrer and was close to reactor with ideal mixing. Chemical interaction between CO2 and the corresponding alkali suspension (dispersed in organic phase) takes place in the reactor. The process is endothermic so the device was equipped with cooling jacket. A diagram of the device is shown in Fig. 1. 

Fig. 1. Diagram of the facility for preparation of nano-sized particles. 1 Bottle with carbon dioxide, 2 rotameter, 3 recurrent reactior with jacket, 4 bubbler, 5 magnetic stirrers, 6 drecssel bottle.

Solid nano-sized particles of CaC03 and BaC03 were obtained from the experiments carried out using chemical re-... 

Fig. 2. Electron microscopy photographs of nano-sized particles of BaCC>3.

A technique and process for preparation of nano-sized particles from alkali carbonates was developed on the basis of the method of reversed micelles and a probable mechanism was suggested. 

Nano-sized particles of barium and calcium carbonate were obtained by a chemical reaction in a microemulsion. The particles were studied by electron microscopy and were found to possess spherical shape and diameters from 20 to 30 nm. 

The nano-sized particles were obtained at various ratios of the phases forming the microemulsion. They were about the same size, which confirmed the advantage of the method selected. 

Reactive crystallization, or precipitation, has been investigated by numerous research groups. Processes of industrial relevance include liquid-phase oxidation of para-xylene to terephthalic acid, the acidic hydrolysis of sodium salicylate to salicylic acid, and the absorption of ammonia in aqueous sulfuric acid to form ammonium sulfate (60). A very special type of reactive crystallization is diastereomeric crystallization, widely applied in the pharmaceutical industry for the resolution of enantiomers (61). Another fine example of reactive precipitation is the earlier-described production of nano-size particles of CaC03 in high-gravity fields (46). 

Reactive crystallization/precipitation can also be conducted in high-gravity (Higee) fields using rotating equipment. In China this technique has been used successfully for the production of nano-size particles of CaC03. Ultraline particles... 

Our studies of Ti02 and Zr02 nano-sized particles prepared by a sol-gel precipitation method [101] (titration with NH4OH and further stabilization of the precipitate with HNO3) showed interesting difference between titanium and zirconium dioxides [89, 90]. Fig. 8.1 performs a typical EPR spectrum of the N02 radical adsorbed on the surface of NC Ti02 thermally treated for 1 h at 200° (parameters are listed in Table 8.4). A similar one with lower intensity has been observed in the case of Zr02 [90],... 

V. V. Boldyrev, Structural and Morphological Changes during the Mechanical Activation of Nano-Size Particles, Mater. Res. Bull, 1995,... 

Fine solid particles adsorb at interfaces and can provide long-term kinetic stability of emulsions and foams.1"5 For more effective stabilization the particles must be much smaller than the dispersed droplets.1,2 For the production of microemulsions, nano-sized particles are therefore of particular interest. 

Abstract. The general alarm raised concerning the potential toxicity of inhaled nano-sized particles has moved several particle toxicology groups towards thorough investigations on the peculiar toxicity of ultrafine (nano) dusts. The new term Nanotoxicology has been proposed for these kinds of studies. An overview of the factors which may affect the toxicity of inhaled nano and micro-sized inhaled particles is herein presented. 

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