Analysis Of Micro-cracks Of Glass Surface And Ion-exchanged Surface Modification

Glass is a kind of high-strength inorganic non-metallic material,but because of the micro-crack in the surface,glass actual strength is less one- percent of its theoretical strength. In order to recover or increase glass strength,all kinds of strengthen methods came into being,one of which is ion-exchanged strengthen method that is the best method to strengthen 3-millimeter thick glass. But compressive surface stress layer gained through ion-exchanged is so thin that small surface scratch can decrease glass strength. Some scientific researchers had studied the mechanism through which the micro-crack affects glass strength. The experiment in the text will research how micro-crack affects glass strength and how to decrease or eliminate this influence to recover and rise glass strength.In the experiment,strength of a large number of strengthen specimen is measured. Through comparing strength dates obtained under different time and temperature,determine the ion-exchanged technology system and analyze the relationship of strength and ion-exchanged time and temperature. K+ ion diffusion depth and the relationship of ion-exchanged layer thickness and strength are determined by Auger electron spectrometer. Specimens are strengthened in the industrialized ion-exchanged furnace. Three-point bending test and double circle bending test are used to measure glass-bending strength. Strength dates is analyzed by statistical analysis method,to get the average strength and compare which method is better. By use of indentation cracks,determine the crack length that will result in strength decreased,at the same time,analysis the relationship of indenture load and crack length and depth. Collecting glass fragment,analysis fracture process and fracture morphology with fracture mechanics theory. Strengthening glass with indentation crack,to identify whether the crack will be remedied. Using SEM electron microscope to observe glass surface etched by HE Surveying glass strength after etched,to compare whether surface protecting raise strength or not. After etched and protected,the indentation crack is made up,and strength is recovered or heightened.The conclusion:the best technology system of ion-exchanged method is exchanging 16hours under 450 . Exchanged layer depth is in 20-30 m,and glass strength is nearly the maximum value and dispersity is notably improved. Double circle bending test is more suitable to measure glass strength. Through surface structure analysis and the experiment of indentation,it can be found that ion-exchanged can remedy indentation cracks. Through test,establish the relationship of crack length and glass strength,and point out the sizes ofsurface flaw affecting the strength of ordinary glass and ion-exchanged strengthen glass. Exceeding the sizes,glass strength will be decreased seriously,or lose the impression of ion-exchanged strengthen. Whether etching before ion-exchanged or after ion-exchanged,if the new surface is not protected right now,etching is none meaning. Having studied the affection that etching affects glass strength and surface flaws,because compressive surface stress layer is very thin,depth etched must be controlled precisely. Depth etched is up to surface microcrack size. Protected by SAR-08 after etched,glass surface is isolated from air,and glass strength is maintained.