Nano powders are particulate materials that exhibit basic structural properties on a scale of 1-100 nm. The field of application of nanopowders is based on their unique properties, such as a very high specific surface area, increased chemical activity of atoms and molecules at the interface, and high absorption. Many of these properties are atoms and molecules on the surface versus the bulk state. Since the properties of nanoparticles are mainly related to their size, it is usually important to control the particle size in the smallest possible range. At present, there are a variety of physical and chemical methods that can be used to synthesize nanocrystalline materials, including gas condensation, high-energy ball mills, wet chemistry, and combustion synthesis. The gas condensation process uses various evaporation processes, such as laser ablation, thermal evaporation, chemical vapor condensation, and microwave plasma processes, to evaporate metal (or inorganic) materials in a low-pressure gas environment. When metal atoms collide with gas molecules, they lose energy and form a supersaturated area near the liquid surface. In this area, clusters form and grow with uniform nucleation. The average diameter of the aggregates is usually in the range of a few nanometers to a few hundred nanometers. The gas condensation method has a wide range of uses and has been successfully used to synthesize various materials, including metals, ceramics, semiconductors and other compounds. High-energy ball mill technology can also be used to produce nanoparticles. This is a sensitive process because "too little" (too short) will not lead to the formation of nanoparticles, and "too much" will increase product contamination. In colloidal chemistry, various chemical methods are used to obtain nano-sized metal particles, including reduction of salts in aqueous solutions, sol-gel methods, and hydrothermal methods. This chemical process is widely used due to its high productivity, good stoichiometric control and low cost.
The synthesis of combustion in solution involves self-sustaining reactions in homogeneous solutions of different oxidants (such as metal nitrates) and fuels (such as urea, glycine, and hydrazide). Depending on the type of precursor and the conditions used in the tissue process, SCS can occur through a combustion mode that spreads by volume or layer by layer. In a series of articles on SCS published in recent years, the synthesis of oxide ceramics, that is, luminescent materials and catalysts, dominates.
In recent years, research has been conducted on the production and evaluation of refractory metal nanopowders. Various methods have been developed, including gas condensation, high-energy ball mills, combustion synthesis, plasma treatment, and wire shot blasting. Suitable for all types of metal nanopowders. However, most of the methods described in the literature are not suitable for mass production. The main disadvantages of using these techniques are the relatively low power and relatively high levels of impurities (especially oxygen) inherent in the fabricated nanopowders. Moreover, most of these techniques are not suitable for rapid passivation of metal nanoparticles during processing, which can lead to fires in mass production. It is a manufacturing process that can produce refractory metal nanopowders of various sizes and high purity at low cost. All test results were obtained by mixing the reaction mixture with an alkali metal halide. During the combustion process, the metal halide acts as a coolant, lowering the combustion temperature and preventing particle formation. An active protective layer is formed around the individual particles to avoid fire and oxidation hazards during processing. As shown in Figure 1.28, the external design only describes the above mechanism. For example, fine metal oxide powder is reduced by a reducing agent. Magnesium, for example, dissolves in molten salts. As a result, nano-sized metal particles are formed in the molten salt. During the cleaning process, a thin oxide layer is formed on the particle surface to prevent further oxidation. According to chemical analysis, the oxygen content of the powder produced by the SACR process varies from 0.3 to 2.0% by weight depending on the mineral system investigated. In general, the highest oxygen concentrations (1.0–2.0%) were observed in Ti and Zr nanopowders and the lowest.