Chemical Methods

CHEMICAL METHODS

Chemical Methods: Solvothermal synthesis is a method for preparing a variety of materials such as metals, semiconductors, ceramics, and polymers. The process involves the use of a solvent under moderate to high pressure (typically between 1 atm and 10,000 atm) and temperature (typically between 100 °C and 1000 °C) that facilitates the interaction of precursors during synthesis. If water is used as the solvent, the method is called “hydrothermal synthesis.” Nanoshel uses this method to prepare thermodynamically stable and metastable states including novel materials that cannot be easily formed from other synthetic routes.

Chemical Methods

Chemical Methods: The sol gel technique is a long-established industrial process for the generation of colloidal nanoparticles from liquid phase, Chemical Methods which has been further developed in last year’s for the production of advanced nanomaterials and coatings. Sol-gel-processes are well adapted for oxide nanoparticles and composites nanopowder synthesis. The main advantages of sol-gel techniques for the preparation of materials are low temperature of processing, versatility, and flexible rheology allowing easy shaping and embedding. They offer unique opportunities for access to organic-inorganic materials. The most commonly used precursors of oxides are alkoxides, due to their commercial availability and high liability of the M-OR bond allowing facile tailoring in situ during processing.

An aerosol-based process is a common method for the industrial production of nanoparticles. Aerosols can be defined as solid or liquid particles in a gas phase, where the particles can range from molecules up to 100 µm in size. Aerosols were used in industrial manufacturing long before the basic science and engineering of the aerosols were understood. For example, carbon black particles used in pigments and reinforced car tires are produced by hydrocarbon combustion; Titania pigment for use in paints and plastics is made by oxidation of titanium tetrachloride; fumed silica and titania formed from respective tetrachlorides by flame pyrolysis; optical fibers are manufactured by similar process.

Atomic or Molecular Condensation: This method is used mainly for metal containing nanoparticles. A bulk material is heated in vacuum to produce a stream of vaporized and atomized matter, which is directed to a chamber containing either inert or reactive gas atmosphere. Rapid cooling of the metal atoms due to their collision with the gas molecules results in the condensation and formation of nanoparticles. If a reactive gas like oxygen is used then metal oxide nanoparticles are produced.

Hydrothermal synthesis; a method to produce different chemical compounds and materials using closed-system physical and chemical processes flowing in aqueous solutions at temperatures above 100°C and pressures above 1 atm. The method is based on the ability of water and aqueous solutions to dilute at high temperature (500°C) and pressure (10-80 MPa, sometimes up to 300 MPa) substances practically insoluble under normal conditions: some oxides, silicates, sulphides and Nanoshel researchers preferably uses this technique to synthesize nanomaterials.

Spray drying; a method of removing solvent from solutions and suspensions based on the injection of liquid droplets in the stream of carrier gas, usually air, heated to temperatures of 100-300ºC, followed by separation of solid particles. This method mainly differs from the pyrolysis of aerosols in that it has a lower temperature of the carrier gas, which usually does not lead to a complete thermal decomposition of the saline components of the solution, and that nozzles are used instead of aerosol generators, creating droplets of a larger size, but with much better performance. Spray drying is one of the main methods for producing dry products and drugs in the food and (to a lesser extent) pharmaceutical industries.

Cryochemical synthesis; is a set of methods to synthesize substances and nano materials based on low-temperature chemical processes. The most widespread of such methods are cryochemical synthesis techniques with the use of aqueous solutions. In this case, solutions, suspensions or products of chemical co-precipitation of initial solution components containing cations of the synthesized material in a stoichiometric proportion are rapidly frozen and freeze dried in vacuum, after which thermal decomposition follows. The products of this synthesis are generally oxide powders with crystallite sizes of 40-300 nm