Nanomaterials synthesis, using productions

These different techniques have particularities regarding the type of material use, the production costs, the size distribution of the particle produced, the time to obtain the products and the purity of the final product. The application and the existence of adequate equipment help to select the best technique to obtain a certain nanomaterial. Table 1.1 compares de advantages e disadvantages of these different nanomaterials synthesis methods. 

Hydrothermal synthesis is a powerful method used for the fabrication of nanophase materials due to the relatively low temperature during synthesis, facile separation of nanopartides in the product, and ready availability of apparatus for such syntheses. Versatile physical and chemical properties of nanomaterials can be obtained with the use of this method that involves various techniques (e.g., control of reaction time, temperature and choice of oxidant and its concentration). Several extensive reviews are available that discuss the fundamental properties and applications of this method [2, 3]. These reviews cover the synthesis of nanomaterials with different pore textures, different types of composition [2, 4—6], and different dimensionalities in terms of morphology [6-8]. 

For example, Wuelfing et al. reported on the synthesis of Au NPs using the thiolated polymer, a-methoxy-co-mercapto-poly(ethylene glycol) (PEG-SH), as stabilizer in a modification of the Brust-Schiffrin method using a 1/12 polymer thiol/ AuC14 ratio. Transmission electron microscopy showed that the product had modestly polydisperse Au cores of average diameter 2.8 1 nm. This nanomaterial led to characteristics uniquely different from alkanethiolate MPCs, notably aqueous solubility, thermal and chemical stability, ligand footprint size, and ionic conductivity [66]. 

New spatial forms of carbon - fullerenes, nanotubes, nanowires and nanofibers attract significant interest since the time of their discovery due to their unique physicochemical and mechanical properties [1-3]. There are three basic methods of manufacturing of the carbon nanomaterials (CNM) - laser evaporation, electric arc process, and catalytic pyrolysis of hydrocarbons. However, the multi-stage manufacturing process is a serious disadvantage for all of them. For example, the use of organic solvents (benzol, toluene, etc.) for separation of fullerenes from graphite soot results in delay of the synthesis process and decrease in the final product quantity. Moreover, some environmental problems can arise at this. 

Abstract. Nanocarbon materials and method of their production, developed by TMSpetsmash Ltd. (Kyiv, Ukraine), are reviewed. Multiwall carbon nanotubes with surface area 200-500 m2/g are produced in industrial scale with use of CVD method. Ethylene is used as a source of carbon and Fe-Mo-Al- mixed oxides as catalysts. Fumed silica is used as a pseudo-liquid diluent in order to decrease aggregation of nanotubes and bulk density of the products. Porous carbon nanofibers with surface area near 300-500 m2/g are produced from acetylene with use of (Fe, Co, Sn)/C/Al203-Si02 catalysts prepared mechanochemically. High surface area microporous nanocarbon materials were prepared by activation of carbon nanofibers. Effective surface area of these nanomaterials reaches 4000-6000 m2/g (by argon desorption method). Such materials are prospective for electrochemical applications. Methods of catalysts synthesis for CVD of nanocarbon materials and mechanisms of catalytic CVD are discussed. 

The chemical methods for the preparation of nanomaterial could be categorized as either template-directed or template-free. The template synthesis methods commonly used for the production of one-dimensional nanostructured PANI are further subdivided into hard template (physical template) synthesis and soft template (chemical template) synthesis approach according to the solubility of the templates in the reaction media. Non-template routes for the synthesis of one-dimensional nanostructured PANI such as rapid-mixing reaction method, radiolytic synthesis, interfacial polymerization, and sonochemical synthesis have also been reported [56], Other approaches like combined soft and hard template synthesis are also known. An overview of hard-template, soft-template, and template-free procedures are presented in the following paragraphs. 

---