Taking copper nitrate as raw material and sodium hydroxide. The sodium carbonate mixed solution is a precipitating agent, and a direct precipitation method is employed, and a process for preparing nano-copper oxide by reaction precipitation, filtration, washing, drying, and calcination is feasible. Through single factor and orthogonal test analysis, considering the product particle size and copper yield in the preparation process, the suitable combination of process conditions for the precipitation reaction process is: reaction temperature 25 ° C, precipitant concentration O. 5 mol/L, reaction time 20 min, precipitant dosage 1.5:1; suitable calcination conditions are: calcination at 400 °C for 2 hours; at this time, the copper yield can reach over 97%, and the product particle size can reach 14 nm (2) The surface modification of nano-copper oxide powder was carried out with sodium stearate as modifier. The optimum range of process conditions was: the amount of modifier was 6-8%; the modification time was 20-30 min; modification Temperature 55 to 65 ° C: pH 7.5 to 8.0. The nano-copper oxide powder was surface-modified with sodium dodecylbenzenesulfonate as a modifier. The optimum range of the process conditions was: the amount of modifier was 6-10%; the modification time was 20~. 30 min; modification temperature 25 to 35 ° C; pH value 7.5 to 8.0.
1. The basic physical effects of nanoparticles
When the size of a particle enters the nanometer order (1~100m), it will have surface effect, volume effect, quantum size effect and macroscopic quantum tunneling effect, thus showing many peculiar physical properties that are not possessed by general solid materials, including Optical, electrical, magnetic, thermal, catalytic and mechanical properties. 1. The surface effect atoms of the surface effect particles are different from the environment of the internal atoms. When the particles decrease and the particle diameter enters the order of nanometers, the number and role of the surface atoms cannot be ignored, and the specific surface area, surface energy and surface binding energy of the particles at this time There will be big changes. The special effects caused by this are collectively referred to as surface effects.
In general, as the particle size decreases, the number of surface atoms of the particles increases rapidly, the specific surface area sharply increases, and the surface effect cannot be ignored. Physically speaking, the surface atoms are not like the atoms in the body. The surface atoms have higher energy than the atoms in the body, so the nano-powders have high surface energy. Taking nano-copper particles as an example, when the particle size of copper particles is gradually reduced from 100 m to 1 nm, the specific surface area, surface atomic fraction and specific surface energy of nano-copper particles vary with particle size, and the specific surface area and surface of nano-copper particles. Atomic number fraction and specific surface energy change with particle size
2. Volume effect
When the volume of the substance decreases, There will be two situations: one is that the nature of the substance itself does not change, but only the nature closely related to the volume changes, such as the semiconductor material, its electron free path becomes smaller; the other is the substance itself. The nature has also changed. Because nanoparticles are composed of a finite number of atoms or molecules, which change the properties of a substance originally composed of an infinite number of atoms or molecules, the properties of nanomaterials have changed greatly. This is called the volume effect of nanoparticles.
3. Quantum size effect
When the particle size is reduced to a certain value, the electron energy level near the metal Fermi level changes from quasi-continuous to discrete energy level and the semiconductor particles have discontinuous maximum occupied molecular orbital and lowest unoccupied molecular orbital energy. The phenomenon of widening the energy gap and the energy gap is called the quantum size effect. In nano-semiconductors, the existence of the quantum size effect causes the silver nanoparticles to change from a conductor to an insulator when reaching a certain scale; and the semiconductor titanium dioxide forbidden band width is significantly broadened when the particle size is as small as nanometer. In nanomagnetic materials, as the grain size decreases, the magnetic order state of the sample will change substantially. A ferromagnetic material in a coarse crystal state can be converted into a superparamagnetic state when the particle size is less than a certain critical value. This peculiar magnetic transformation is mainly caused by the quantum size effect, which makes the nano material and the conventional polycrystalline material have great differences in magnetic structure.
4. Macroscopic quantum tunneling macroscopic objects, when the kinetic energy is lower than the energy barrier of potential energy, can not exceed the barrier according to the classical mechanics law; for microscopic particles, such as electrons, even if the potential barrier is much higher than the kinetic energy of the particle, quantum mechanical calculations show that The state function of a particle is non-zero after a barrier or barrier, indicating that the microparticle has the ability to enter and cross the barrier, called tunneling. Macroscopic physical quantities, such as magnetization, will be affected by microscopic mechanisms at the nanoscale, that is, microscopic quantum effects can be expressed in macroscopic physical quantities, called macroscopic quantum tunneling.
In the early days, macroscopic quantum tunneling was used to explain that nickel ultrafine particles continue to maintain superparamagnetism at low temperatures. In recent years, people have discovered Fe. The velocity of the domain wall in the Ni film is substantially independent of temperature below a critical temperature. Therefore, it has been suggested that the zero-point vibration of quantum mechanics can play a similar thermal fluctuation effect at low temperatures, so that the reorientation of the magnetization vector of the microparticles near the thermodynamic zero degree maintains a finite relaxation time, that is, there is still a non-zero magnetization at the thermodynamic zero degree. Inversion rate, a similar viewpoint can be used to explain the high-magnetic crystal anisotropy single crystal at a low temperature to generate a stepped inversion magnetization mode, and one of the quantum interference devices
Some effects. The above-mentioned surface effects, volume effects, quantum size effects and macroscopic quantum tunneling effects are the basic characteristics of nano-particles and nano-solids, which make nano-particles and nano-solids exhibit many singular physical and chemical properties, thus making nano-materials very Broad application prospects.