Low-voltage Electrodeposition Of Diamond And Diamond-Like Materials Under Ambient Temperature And Pressure

Owing to their superior mechanical,electrical,chemical and optical properties, diamond and diamond-like carbon(DLC) have attracted considerable interests. Syntheses of diamond and DLC have been being a hot research topic.This paper first reviewed the important progresses in the synthesis of diamond with emphasis on electrodeposition of diamond and diamond-like materials from organic liquids.In this thesis,further research based on deposition of diamond from CCl₄-ionic liquids([BMIM]BF₄) system was carried out.By adding a third solvent and using ultrasonic-assisted reaction,the experimental conditions were improved.The possibility of electrodeposition of diamond and diamond-like carbon from acetonitrile (AN)-[BMIM]BF₄-CCl₄ and[BMIM]BF₄-CCl₄ using ultrasonic-assisted reaction system were testified using linear sweeping voltammetry(LSV),X-ray diffraction (XRD),and Raman spectroscopy.The product of AN-[BMIM]BF₄-CCl₄ system was sticky and soft,and that of the[BMIM]BF₄-CCl₄ ultrasonic-assisted reaction system was a yellow film.No characteristic diffraction peaks of diamond could be observed in the XRD patterns for both systems,and most of products were amorphous.This suggested that adding a third solvent make the system more complicated and changed the reaction mechanism.In addition,CCl₄,CHCl₃,and CH₃OH were also used as carbon sources for electrodeposition of diamond-like materials.Electroreduction of the CHCl₃—tetrabutylammonium chloride(TBAC)—propylene carbonate(PC) system was first examined by LSV using a three-electrode cell.A Ni-Co alloy electrode prepared by chemical deposition of Ni-Co alloy on a piece of nickel foil(1×1 cm) was used as the working electrode.The deposited product was studied using Raman spectroscopy and FTIR.The Raman spectrum showed four distinct broad characteristic peaks at ca.990, 1100,1290 and 1580 cm^-1,suggesting the formation of nanostructured DLC. Galvanostatic electrodeposition was also performed to evaluate the effect of current density(or deposition rate) on the crystallization of the product.Raman spectrum and XPS spectrum suggested that the products deposited at different current densities were composed of nanostructured DLC,and the products obtained at 1.0 mA·cm^-2 has the highest sp³ content.The results of CCl₄-TBAC—PC and(CCl₄+CHCl₃)—TBAC—PC systems were dissatisfactory,and the products were mainly amorphous materials.Direct current electrodeposition method with two electrodes was also adopted in the study of CH₃OH-TBAC,CHCl₃-TBAC and CCl₄-TBAC system.The ITO glass electrode was use as the cathode substrate for the CH₃OH-TBAC system.The product is a brown carbon film.The Raman spectrum of this film showed two broad peaks at ca.1349 and 1590 cm^-1 which are the characteristic absorbance peaks of DLC film. CHCl₃-TBAC and CCl₄-TBAC systems have also been studied using Ni-Co alloy as cathode substrates and no product was obtained.The products of the CHCl₃-TBAC system were amorphous materials and some polymers.No solid product was obtained from electrolysis of the CCl₄-TBAC system.