Study On Preparation Of The Composited Film Of Hard Anodizing With Aluminum Alloys And PTFE

The paper developed a method to grow a larger aperture and thick alumina template by hard anodizing in sulfuric acid system and reaming in phosphoric acid,and then through the electrophoretic deposition method to introduce polytetrafluoroethylene (PTFE) in a porous template,ultimately prepared Al₂O₃-PTFE composite film.In order to prepare surface Al₂O₃-PTFE composites,the macroporous and thick alumina template is desired.So the effective factors such as the concentration H₂SO₄,the current density,the anodizing temperature,the oxidizing time by the hard anodizing of H₂SO₄ method are studied and then each effective factor on fabricating porous anodic aluminum oxide membrane is respectively discussed.Otherwise, anodic aluminum oxide membrane is characterized by scanning electron microscope (SEM).The result shows that oxide template has several unique structure properties such as symmetrical bores,almost same Size diameter(＜1μm),high thickness(about 75μm).The optimal technique is confirmed that the concentration H₂SO₄ is 16%, the current density is 6A/dm^-2,the temperature is -3℃,the oxidizing time is 120min Anodizing film was prepared on aluminum plate making use of anodizing film at constant voltage in phosphoric acid.The Al alloy plate coated with the anodizing film was them immersed in a diluted phosphoric acid(5%) for 5min～7min to allow the processing of pore-enlargement.The morphology and structure of the anodizing film after the processing of pore-enlargement were analyzed by means of scanning electron microscopy.It was found that,after being treated in diluted phosphoric acid,the tiny pores distributed uniformly in the anodizing film and the enlarged pores had a diameter about 1μm～2μm.In the end,electrodeposition pretreatment and electrodeposition technology factors which have influence on the properties of film were investigated,the later including electrophoresis voltage,electrophoresis time,electrophoresis temperature, concentration PTFE,firing temperature,firing time.The suitable cathodic electrophoresition technology conditions are optimized finally.When electrophoresis voltage is 45V,electrophoresis time is 2min,electrophoresis temperature is 30℃,concentration PTFE is 30%,firing temperature is 160℃,firing time is 30min,the pores of alumina film can be partly or wholly filled by nano-PTFE particles.The analysis of electron diffraction spectrum also shows that PTFE has been bound into the composite film,forming Al₂O₃-PTFE composite film.