Large-area Standing Diamond - Metal Composite Membrane Electroforming Applications

In this paper, the preparation, microstructure and micro-strain of diamond-metal composite film were studied. The composite films were prepared by using electrotyping method. The influence of electrotyping parameter on the characteristics of the film was discussed; Super-thin free-standing diamond grains-nickel composite films with large area were deposited, which have uniform distribution of diamond grains, uniform thickness and small micro-strain. These composite films were used to make super-thin cutting blades, and the continued machining process and cutting performance of the blades were also studied.The specific research works about the electrotyping diamond-metal composite film were as following:(1) The XRD and XPS spectra indicated that electrodeposited diamond grains-nickel composite films were composed of diamond and nickel, and there were no chemical bond between them, diamond grains were enwrapped in nickel during composite deposition.(2) Current density of cathode strongly affected the characteristics of the diamond grains-nickel composite films such as diamond grains content, the surface morphology, the micro-strain and deposition rate of the film. The deposition rate of the film increased with increasing of current density; The content of diamond grains in the film increased with increasing of current density at the beginning, and it reached the peak value when current density was at 1.3—2.5A/dm2, then it was slowly down. Further more, the micro-strain of the film decreased with increasing of current density according to our experiment condition. In order to deposite good composite films, the current density of cathode must be controlled strictly.(3) Diamond grains content of the film increased with increasing of the content of diamond grains in the electrolytic solution, but when it was greater than 18 g/L, diamond grains content of the film increased slowly and was close to saturation.(4) Agitation velocity and the place of impeller strongly affected the content and uniformity of diamond grains in deposited composite film when current density and diamond grains content in the solution were the same. The best film were deposited when agitation velocity was 180rpm-220rpm and the impeller was placed in the lower part of the solution.(5) The obliquity of cathode strongly affected the content of diamond grains in the film, and the content reached maximum when the obliquity was kept at 45 degree. The hanging orientation of cathode strongly affected the uniformity of the thickness of the film, and uniform films were deposited when cathode was intermissively circumrotated 90 degree in the plane itself during deposition.(6) The fluid field in solid-liquid stirred electrolytic solution was analysed by using Computational Fluid Dynamics(CFD). And the influences of agitation velocity, the place of impeller and the obliquity of cathode on the content of diamond grains in the film were explained. With Euler-Lagrange model, the just-suspended speed of impeller in solid-liquid stirred electrolytic tank was predicted using Zwietering formula, the predicted speed was 210r/min and it was consistent with experimental result.(7) Temperature affected diamond grains content, the size of nickel crystal grains, the micro-strain , deposition rate of the film and the oriented growth of nickel crystal grains. It was found that diamond grains content in the film increased initially with increasing of the temperature and reached a maximum at 50℃, then it decreased instead. The effect of temperature on the calculated micro-strain in the film was distinct, which indicated that the micro-strain in the film was the smallest at 50℃. Deposition rate of the film decreased with increasing of temperature. The size of nickel crystal grains also decreased with increasing of temperature. Furthermore, it was found that the growing of nickel crystal grains in the films was highly oriented when the temperature was under 40℃. These results suggest that in order to fabricate accurate diamond grains- nickel super-thin cutting blade, electrotyping temperature must be controlled at the range of 40—50℃.(8) Artificial neural network (ANN) was used to predict diamond grains content, thickness and micro morphology of the free-standing diamond grains-nickel composite film. It was found that the predicted results were near the measured values, and the comparative error was less than 9. 9%. This technique is useful to optimize the electrolytic parameters for preparation of free-standing diamond-nickel composite film.The specific research works about the application of electrotyping diamond-nickel composite film were as following:(1) The key factors which affected the application performance of the cutting blade were the content of diamond grains in the film, the uniformity of thickness of the film, distortion and the morphology of the blade. The main reason which determined the width of cut slot was the uniformity of thickness of the film.(2) The prepared super-thin cutting blade was tested for cutting silicon slice, which indicated that the blade can fulfil the need of cutting technics. The rotate speed of principal axis of the machine tool was 30000rpm, the walking velocity of the blade was 5mm/s, the depth of the cut slot was 0.35mm and the width of the slot was 0.048-0.053mm.(3) Electrical Discharge Machining (EDM) can efficiently remove the burr of the deposited film, it was a useful machining method of the super-thin cutting blade.The originality and innovations of this thesis are as follows:(1) The micro-strain was quantitatively analysised using X-ray diffraction method, and the influences of current density of cathod and temperature on it were studied. The results are valuable for the preparation of high quality diamond-metal composite film.(2) The rules of the fluid flow in solid-liquid stirred electrolytic solution and the moving of diamond grains in the fluid were analysed by using Computational Fluid Dynamics(CFD). The content and distribution of diamond grains in the film were controlled by choosing the best parameter according to the rules.(3) Artificial neural network (ANN) was used to predict the influence of electrolytic parameters on the deposited results and optimize the parameters for preparation of free-standing diamond-nickel composite film.