Preparation of nano-materials

Abstract: Several physical and chemical nano-materials preparation, and the pros and cons of different methods were discussed.

Keywords: Nanomaterials; physical methods; chemical methods

1 Introduction

Nanomaterials and nanoTechnology is widely regarded as the twenty-first century's most important areas of new materials and Technology as early as the 1960s, the British chemist Thomas on the use of "gel" to describe the suspension as a 1nm-diameter 100nm particles .1992, < > Officially published, marking the nano-materials science as an independent science. Nanomaterials is an arbitrary one-dimensional scales less than 100nm crystal, amorphous, quasi-crystals and the interface layer structure of the material when the small particle size to nanometer time, will have its own surface and interface effects, quantum size effect, small size effect and macroscopic quantum tunneling, the effect of making nano-materials have many peculiar properties. Iijima for the first time since 1991 has been prepared by carbon nanotubes, one-dimensional nano-materials have many unique properties and potential applications and attracted wide attention. nanostructured inorganic materials due to a special electrical, optical, mechanical and thermal properties of the people more and more attention by the United States since 1991 began to include nanoTechnology, "the government of key technologies", the Natural Science Foundation of China and other projects and Research institutes regarded nanomaterials and nanoTechnology as a key Research project due to the morphology and size of nanomaterials with their performance important influence, therefore, nanomaterials synthesis of morphology and size control is very important as advanced nano-structured materials and nano-devices of the basic building blocks (Bui1ding Blocks), the synthesis and assembly of nanoparticles is an important part of nanoTechnology and infrastructure. This paper briefly reviews the preparation of nano-materials synthesis and several methods commonly used, and its merits compared.


2 nano-materials synthesis and preparation

 2.1 Physical Preparation
2.1.1 mechanical method 
Mechanical method of mechanical milling, mechanical grinding method and gravity techniques. Mechanical milling method does not derive from an external supply of heat, so the material by milling the material between the interface reaction, the large grains into small grains, to be nano-materials. Fan Jinglian prepared by ball milling and other uses tungsten-based alloy nano-powders. xiao other metal carbonyl powder using high energy ball milling to obtain nanoscale Fe-18Cr-9W alloy powder mechanical crushing method is to use a variety of mechanical grinding and spark an explosion ultrafine methods such as crushing the raw material directly into a superfine powder, especially for preparation of ultrafine brittle materials. gravity rotating packed bed technology uses high-speed rotation of the equivalent of a hundred times the centrifugal acceleration on the acceleration of gravity, the phase of mass transfer and micro-mixing to be greatly strengthened in order to prepare nano-materials. Liu Jianwei, etc. to ammonia and zinc nitrate as raw materials, the application of high gravity technology to prepare particle size 20nm-80nm, particle size distribution of ZnO nanoparticles.

2.1.2 fumed 
Gas law, including evaporation condensation method, the solution evaporation method, the depth of plastic deformation method. Evaporation condensation method in a vacuum or inert gas through the resistance heating, high frequency induction, plasma, laser, electron beam, arc sensors and other methods to feed gas or formation of plasma, and it reached saturation and then condensation in the gas medium in the form of high purity nano-materials. Takaki, etc. in an inert gas, the use of gas condensate prepared by suspension of nano-silver. Dufang Lin for preparing a copper, chromium, manganese, iron, nickel nanopowders in the 30nm-50 nm particle size range of control. Weisheng prepared by evaporation and condensation of nano-aluminum powder. solution to the solvent evaporation method is made after a small drop rapid evaporation, so that the smallest components of segregation, generally by spray drying, spray pyrolysis method or freeze-drying method to be addressed. depth of plastic deformation method is a quasi-static pressure under the effect of material plastic deformation to a great extent , leaving the size down to nanometer there reported in the literature, Φ82mm of Ge in 6GPa quasi-static pressure, and then heat-treated at 850 ℃, nanostructures begin to form, material from the equiaxed grain size composition of 100nm, while the temperature up to 900 ℃, the grain size increases rapidly to 400nm.

2.1.3 magnetron sputtering and plasma method 
Sputtering technique is the use of high-energy particles hit the target surface atoms or molecules to exchange energy or momentum, making the target surface atoms or molecules flying from the target surface to the substrate after deposition of the formation of nano-materials in the target material law no phase change, is not easy to change the composition of compounds present, sputtering technology has been great progress, commonly used cathode sputtering, DC magnetron sputtering, RF magnetron sputtering, ion beam sputtering and electron cyclotron resonance-assisted reactive magnetron sputtering technology. Plasma is used in an inert atmosphere or reactive atmosphere, the gas ionized by the DC discharge generates high temperature plasma, so that the raw material compound solution evaporates, cooling the steam to the formation of ultrafine particles around. Plasma high body temperature, can be prepared or refractory metal compound, the product of high purity, in an inert atmosphere, the plasma method can be prepared almost all of the metal nanomaterials.

Above describes several common physical preparation of nanomaterials, these preparation methods do not involve complex chemical reactions, therefore, control the synthesis of different morphologies of nano-structured materials has certain limitations.

 2.2 Chemical Preparation
2.2.1 sol - gel method 
Sol - gel process of chemical raw materials is first dispersed in a solvent, and then through the hydrolysis reaction of reactive monomers, reactive monomer polymerization, became a sol, and then generate a certain spatial structure of the gel. Stephen and so the use of high Molecular adduct (from alkyl and N-containing polymers, metals) in solution with H2S reaction of ZnS particle size distribution is narrow, and is evenly coated in the polymer matrix, particle size range can be controlled within 2nm -5nm between. Marcus Jones, etc. to CdO as raw material by adding Zn (CH  3)  2 and S [Si (CH  3)  3]  2 system had ZnS coated CdSe quantum dots, average particle size is 3.3nm, the quantum yield (quantum yield, QY) of 13.8%.

Ionic liquid method  2.2.2
Ionic liquid as a special kind of organic solvents, have unique physical and chemical properties such as viscosity, high ionic conductivity, high thermal stability, low toxicity, good liquidity, and has a wide liquid temperature range. Even at high temperatures, ionic liquid still has a low volatility, is not easy to cause environmental pollution, are a class of green solvents, therefore, ionic liquid synthetic nanostructures with different morphologies of a good medium. Jiang and sulfur such as to BiCl3 on behalf of the acetamide as raw materials, at room temperature in ionic liquid medium to synthesize a uniform size, the size of 3μm-5μm of Bi2S3 nanoflowers they think the solution pH, reaction temperature and time on the flower-shaped nano- appearance and crystal structure have a significant impact, they confirmed that these nano-flowers by the diameter of 60nm-80 nm nanowires form, with the aging time, the nanowires would take from the mother collapsed and eventually the formation of a single nano- line. Zhaorong Xiang and other bismuth nitrate and thiourea used as a pioneer of raw materials, the ionic liquid as reaction medium, Bi2S3 synthesized single-crystal nanorods.

Solvothermal  2.2.3
Solvothermal is in a closed reactor (eg autoclave), through a variety of solvent composition corresponding reaction heat, the reaction system to form a high temperature and pressure environment, so to achieve the controlled synthesis of nano-materials and preparation of an effective method. Lou and other single-source precursor Bi [S  2P (OC  8H   17) 2] 3 for reaction with a high degree of uniformity Solvothermal got the orthorhombic Bi  2S  3 nm stick, and that the method is suitable for mass production. Liu, etc. with Bi (NO3) 3 • 5H2O, NaOH and sulfur compounds as raw materials, glycerol and water as solvent, solvent-thermal method at 160 ℃ in the reaction autoclave 24-72 h system got up to several millimeters Bi2S3 nanoribbons.

2.2.4 Microemulsion 
Microemulsion nanoparticles prepared in recent years developed new areas of Research, has obtained a small particle size, particle size close to the monodisperse system, etc. .1943 years Hoar, who first reported the water, oil, surfactant agent, cosurfactant mixture, can spontaneously form a thermodynamically stable system, the system of dispersed phase by the 80nm-800nm ​​spherical or cylindrical particles, and the naming of this microemulsion system since then, microemulsion application of the theory has been developing rapidly .1982 years, Boutonnet, who applied Microemulsion was prepared by Pt, Pd and other metal nanoparticles. microemulsion preparation of nanomaterials, because of its unique process performance and relatively simple experimental setup, in practical applications by domestic and foreign Researchers attention. Links to free download http://www.hi138.com 4 Conclusion

Nano-materials have specific optical, electrical, magnetic, catalytic properties, can be widely used in military and civilian defense industrial fields. It is not only in high-tech fields have an irreplaceable role, but also to bring life and traditional industries vitality. With the preparation of nano-materials technology development and application of the continuous expansion of industrial production of nanomaterials is bound to the traditional chemical Industry and other industries have a significant impact, but so far, developed the product more difficult to achieve industrialization, trade scale. The main problem is: to control nanoparticle shape, size and distribution, performance, and other Research is far from adequate; nano-materials collection, storage, in particular nano-materials and nano-technology, bio-security is even more urgent solve these problems will not only accelerate the study and solution of nanomaterials and nanotechnology applications and development, and will greatly enrich and develop the basic theory of materials science.


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