1 conventional preparation method
The traditional electrolytic copper powder because of the larger particles, generally more than 10um, is not suitable for the production of nano-superfine copper powder; atomization method because of difficult to solve the problem of antioxidant, difficult to promote. In addition to the traditional electrolysis and atomization method, the existing preparation methods are many, such as: physical method (ball mill method, vapor phase steam method, plasma method, y-ray irradiation a hydrothermal crystallization method, freeze-drying method, etc.) and liquid Phase chemical reduction method. The former is expensive, expensive equipment, complex process; the current study is more liquid chemical reduction method.
1.1 ball mill method
To coarse particles of copper powder as a sample, the use of improved vibration ball mill, high-energy ball mill. High-energy ball milling method is high, the process is simple, can be prepared by conventional methods difficult to prepare high melting point metal, immiscible system of solid solution, nano-metal compounds and nano-metal, ceramic composite material, the disadvantage is the grain is not uniform, Easy to introduce impurities.
Abroad, some people use the mechanical chemical synthesis of ultra-fine copper powder. The copper chloride and sodium powder mixed mechanical crushing, the occurrence of solid-state substitution reaction, the formation of copper and sodium chloride nanocrystalline mixture, cleaning to remove the grinding mixture of sodium chloride, ultra-fine copper powder. If only copper chloride and sodium as the initial mechanical crushing, the mixture will burn. If sodium chloride is added to the reaction mixture, the combustion is prevented and the resulting copper powder particles are finer and have a particle size between 20 and 50 nm.
Gas phase evaporation method
The method is the most direct and effective method for the preparation of ultrafine metal powder. France's L'air liquid company uses the induction heating method to prepare copper ultrafine powder with improved vapor-phase steam pulverization technology in a yield of 0.5 kg / H induction heating method is placed in the ceramic crucible in the high-frequency or medium frequency current induced by their own fever and evaporation, this heating method has a strong induction of stirring, heating speed, high temperature.
1.3 Plasma method
Plasma temperature is high, the reaction speed is fast, can get uniform, small particles of nano-powder. Easy to achieve mass production, can be prepared almost any nano-materials l. The plasma method is divided into DC arc plasma (DC) method, high frequency plasma (nv) method and hybrid plasma (Hybrid plasma) method. DC method using the equipment is simple, easy to operate, the production speed. Almost any fine metal powder can be prepared, but the electrode is easy to melt or evaporate at high temperature pollution products; RF method without electrode pollution, the reaction speed, the reaction area is large, widely used in the production of ultra-fine powder. The disadvantage is that the energy utilization is low and the stability is poor. The mixed plasma method combines the DC method with the RF method, which has both large plasma space, high production efficiency and purity, and good stability.
1.4 7 Radiation Irradiation A hydrothermal crystallization method
Chen Zuyao et al. Prepared the ultrafine particles by co-strong r-ray irradiation, and the nano-copper powder with average particle size of about 50 nlTl was obtained by the combination of r-ray irradiation and hydrothermal crystallization.
1.5 ultrasonic electrolysis
Zhu Xuebin, etc. to analyze the pure copper sulfate prepared into a lower concentration of 0.20-0.25 M solution, and add 1.8 to 2. O M sulfuric acid into an electrolyte. At room temperature, the electrolysis device is introduced into the ultrasonic device (ultrasonic frequency 20 ~ 60 kHz). During the electrolysis, an appropriate amount of organic solvent is added to prevent oxidation, such as ethanol, toluene, oleic acid and so on (both are pure). The solution after the completion of the electrolysis is subjected to high-speed centrifugation, vacuum filtration, alcohol washing and vacuum drying to obtain a powder product.
The effects of composition, particle size, morphology and structure on the preparation of nanometer powder were studied by XRD, TEM and so on. The main factors affecting the preparation of nano-powder were studied by ultrasonic electrodeposition. For analysis and optimization. The results show that the current density plays a role in the formation of nanometer powder, and the surfactant and ultrasonic field are more important for powder dispersion.
1.6 Supercritical Fluid Drying (SCFD)
The homogeneous nano - sized copper powder with high purity, high dispersibility and high oxidation resistance was prepared by a combination of homogeneous solution chemical reduction and supercritical fluid drying. The particle size of the powder particles is about 25 nm. Compared with the ordinary drying method, the supercritical fluid drying method achieves the drying and surface modification of the powder.
Preparation of nano - sized ultra - fine copper powder by chemical reduction method
2.1 formaldehyde method
Liao Rong and others, with formaldehyde direct reduction of copper sulfate, the copper particles are coarse, poor uniformity. Using glucose pre-reduction of copper sulfate, under alkaline conditions, with formaldehyde reduction to obtain purple super-fine copper powder, particle size in the 2O a 400 nm.
Wen Chuangeng and others with formaldehyde as a reducing agent, the use of liquid precipitation method of preparation of copper and sodium particles. The morphology of the particles is spherical, the average particle size is about 30nm, the particle size distribution is narrow, the particles are evenly distributed and no hard agglomeration is the cubic copper powder. The surface of the copper powder is passivated. Improve the ability of antioxidant. Can be stored in the air.
2.2 hydrazine hydrate method
Gao Yang, who will dissolve the dispersant of copper sulfate solution and hydrazine hydrate solution reaction, the particle size of about 10nm copper powder, particle size distribution.
(50-500 / lm) with different particle size were prepared by hydrazine hydrate as reducing agent. The preparation process of copper powder and the stability of copper powder with different particle size in air were studied. The use of glucose reduction method to improve the direct reduction of hydrazine hydrate to get the uniformity of copper powder. The author believes that gelatin as a dispersant, to prevent particle agglomeration, can control the particle size of copper powder.
SanoI and other hydrazine hydrate reduction of copper salt to get copper powder, adding polymer protective agent Polyvinylpyrrole (PVP) alkyl ketone is conducive to stabilize the grain, to prevent reunion. Lisicecki and other microemulsion method to hydrazine hydrate as a reducing agent to prepare the average diameter of 50 nm, monodisperse good nano-copper powder.
2.3 times sodium phosphite method
Zhang Zhimei et al. Reduced the CuSO4 complex solution with NaH2PO2 to obtain copper with a grain size of 30-50 nm. A certain concentration of sodium hypophosphite solution at a certain rate by adding a certain concentration of copper sulfate solution stirring, so that the two redox reaction occurs to produce elemental copper.
2.4 borohydride method
Huang Jun sound and others, with KBH4 reduction CuSO4, adding KOH and EDTA prepared nano-copper powder, adjust the concentration of reactants can eliminate Cu: O and other impurities, the preparation of nano-copper powder is still a certain reunion, the test need to add dispersant to improve.
Zhang Hong and so on with KBH4 solution reduction CuCI2 complex solution, get red and black copper powder, particle size of about 20-40nm.
2.5 zinc powder reduction method
Zhong Lianyun and other chemical synthesis method can be used to prepare ultra-fine copper powder. The effects of copper sulfate concentration, ammonia content and reaction temperature on the particle size of ultrafine copper powder were studied. The effects of copper sulfate concentration, ammonia concentration and reaction temperature on the particle size of ultrafine copper powder were studied. The results showed that the density of 0.1μm ultrafine Copper powder.
2.6 ascorbic acid method
Xiaojiang et al., CuSO4 · 5H2O as raw material, ascorbic acid as reductant and polyvinylpyrrolidine as protective agent to prepare 20 ~ 40 nm copper powder and explore the ratio of CuSO and ascorbic acid, the protective agent (dispersant) Dosage and its control of copper powder particles.

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