The basic design idea when preparing nano-silver on the surface of stainless steel is to make nano-silver exist stably, uniformly and for a long time. Due to the poor binding force between nano-silver and stainless steel, it is difficult to exist stably on the surface of stainless steel alone. On the surface of stainless steel, according to previous studies, the carrier is usually holes, inorganic coatings, etc., combined with the preparation method of nano-silver and the preparation method of antibacterial stainless steel, it is found that electrochemical method and sol-gel method can be used to load nano-silver on the surface of stainless steel.
(1) Electrodeposition method
The traditional electrodeposition method to prepare nano-silver is to directly deposit silver on the cathode, and then peel off the metal powder of the cathode. The prepared powder has the advantages of high purity, large specific surface area, controllable powder particle size, and automatic production. Widely used in the preparation of nano-silver powder. However, this method can only be used to prepare powder, and cannot directly and stably prepare nano-silver on the surface of stainless steel.
The nano-silver preparation method selected in this paper is to use pulse electrodeposition technology to prepare nano-scale silver particles on the surface of stainless steel. Pulse electrodeposition technology is most commonly used to prepare nanocrystalline nickel coatings, and can also be used to prepare nano-silver. It has the advantages of chemicalization, reducing the need for additives, improving the quality of the coating, and improving the ability to resist discoloration. Regarding the research on the preparation of nano-silver by pulse electrodeposition, Fukumoto et al. studied the periodical reverse pulse electroplating silver technology from the silver-cyanide complex, and obtained a finely crystalline silver coating, and the current density, duty cycle, etc. Factors were studied and found that the current density of 1A/dm2 can get smooth silver coating. MariaS et al. used cyclic voltammetry to conduct silver polarization in an ethanol-saturated solution of NaNO3 degassed with argon, and obtained a simple and rapid method for preparing nano-silver. Zhang Bolin et al. used pulse electrochemical method to prepare nano-HA/Ag composite coating on the surface of biomedical titanium. The antibacterial rate of the prepared coating reached 99.9% and had good cytocompatibility.
No literature has been found about the preparation of nano-silver directly on the surface of stainless steel by pulse electrodeposition. Plating intermediate coatings and other complex operations, so when the predecessors used the electrochemical method to prepare antibacterial stainless steel, they usually first anodized the porous film layer on the surface of the stainless steel, and then deposited the antibacterial elements in the porous film layer. The antibacterial stainless steel prepared by this method is complicated. ,high cost.
When combining the pulse electrodeposition technology used in the preparation of nano-silver with the preparation of antibacterial stainless steel, it can be considered to use a periodic reverse pulse current. Under appropriate pulse current conditions, the surface of stainless steel is in an oxidized state when the anode is used, and the grain boundary Because of its high energy, it is in an activated and dissolved state. When stainless steel is used as a cathode, nano-silver is deposited in the grain boundary after corrosion. Under the action of periodic reverse pulse current, stainless steel will undergo different changes when it is in the cathode and anode. When stainless steel is in the anode, stainless steel will be oxidized at the anode as a reactant. The process is complicated, and there can be two states of anodic dissolution and passivation.
For metals, due to the higher grain boundary energy, the atoms are in an unstable state, and the grain boundary is rich in impurity atoms, the corrosion rate of the grain boundary is generally faster than that in the grain, so when the metal is in the anode activation area The grain boundaries will dissolve first.
When the stainless steel is at the cathode, the metal deposition process generally consists of the following unit steps in series: (1) Liquid phase mass transfer: the reaction particles in the solution migrate to the electrode surface. (2) Pre-conversion: The chemical conversion reaction occurs when the reaction particles migrate to the electrode surface, and the degree of hydration of hydration ions is reduced and rearranged. (3) Charge transfer: The reaction particles obtain electrons and are reduced to adsorbed metal atoms. (4) Electrocrystallization: The newly generated adatoms diffuse along the electrode surface to appropriate growth points and start to grow along the metal lattice, or gather with other adatoms to nucleate and grow to form crystals.
According to the above theory, the research in this paper considers the grain boundary of stainless steel as the carrier, and the pulse electrodeposition method is used to make the surface of stainless steel in a passivation state or the state where the surface oxide film will not be damaged when the stainless steel is used as an anode. Only the grain boundary is in an active state. Groove, when stainless steel is used as the cathode, the groove after grain boundary corrosion is used as the carrier for nano-silver deposition.
(2) Sol-gel method
The basic principle of the sol-gel method is to react an easily hydrolyzed metal compound with water in a certain solvent, gradually gel it through the process of hydrolysis and polycondensation, and then obtain the required material through drying and sintering.
The SiO2 film layer prepared by the sol-gel method has high mechanical strength, and has a good bonding force with the stainless steel base, and the film structure is loose and has certain holes, which is convenient for doping modification. Ag/SiO2 antibacterial coating It is often used in antibacterial glass and antibacterial ceramics. JeonHJ et al prepared Ag/SiO2 antibacterial coating by sol-gel method, studied the effect of Ag/SiO2 sol preparation process and heat treatment temperature on the microscopic morphology of the coating, and tested the antibacterial performance of the prepared antibacterial stainless steel, The antibacterial rate reaches 99.9%. Wang Ming prepared Ag/SiO2 antibacterial coatings on the surface of stainless steel by sol-gel dip coating method, studied the antibacterial properties of coatings with different Ag/SiO2 mass percentages, and found that when the Ag/SiO2 mass percentages reached 8%, the antibacterial rate reached 99.9%. SolmzBahang prepared nano silver silica composite coatings by sol-gel method, and studied the size and distribution of nano silver at different heat treatment temperatures. There are still few researches on the application of Ag/SiO2 antibacterial coating on the surface of stainless steel. Therefore, this paper prepares Ag/SiO2 sol system and coats it on the surface of stainless steel after aging polymerization. After heat treatment and calcination, a SiO2 film is formed on the surface. The silver loading on the SiO2 film achieves the purpose of stable existence on the surface of stainless steel, thus endowing stainless steel with excellent antibacterial properties.
Cherry
Website: www.jinyoumetal.com
Email: Cherry@jinyoumetal.com
WhatsApp/WeChat: +86 13373795593
#STAINLESSSTEELSHEEET #STAINLESSSTEELPLATE #SSCOIL #2BSTRIP #BASHEET #SHANKHESHWARSTEEL #stainlesssteelPIPE #SSSHEET #SSCOILS #SSPLATES #HOTROLLEDSHEET #COLDROLLEDSHEET #NO1SHEET #310SSHEET #201SHEET #304SHEET #316SHEET #SSBAR #SSPIPE
