The Reaction Mechanism Of Titanium-strong Alkaline Solution And Magnesium-water System

Titanium and titanium alloys are increasingly widely used asbiomedical and photocatalytic materials for their unique properties.However, titanium and its alloys can not meet all requirements. In order toimprove the biological, chemical, and mechanical properties, we need to dothe surface modification. In this paper,“alkali treatment”,“anodicoxidation” and “alkali-H₂O₂” were used to prepare the TiO₂nanowire filmon the surface of titanium. Meanwhile, titanium surface morphology, theelements and the elements chemical states of samples were characterizedsystematically by Scanning Electron Microscopy （SEM）, ElectronDiffraction Spectroscopy （EDS） and X-ray Photoelectron Spectroscopy（XPS）. Based on XPS and EDS results, we also discussed the formationmechanism of the oxide film under different experimental conditions. Thefollowing results were obtained.（1） From the morphology, nanowire films could be successfullyprepared by three methods. The type of the alkali （NaOH or KOH） didn’thave an effect on the morphology of the oxide films. Under the conditionsof low concentration of alkali solution, low temperature, the films tendedto form a net-like nanowire structure, whereas the band-like films with a porous structure or flower-like structure were formed under the conditionsof higher concentration of alkali solution and higher temperature.Different morphologies could be prepared with different anode voltages.After alkali-H₂O₂treatment, high concentration of H₂O₂was helpful forthe formation of nanowire structure films.（2） From XPS analysis results, the main components of the oxidationfilms were TiO₂. In alkali treatment，the relative amount of titanateincreased gradually with increasing of the temperature or alkaliconcentration. In addition, a little amount of sub-oxide Ti2O3was observedbecause partial oxidation happened under low reaction temperature.Sub-oxide titanium has more proportion under anodic treatment, and therewas a little amount of titanate. Furthermore, the surface took up mostpercentage of titanate in alkali treatment.（3） From the formation mechanism of the oxide film at80℃. In alkalitreatment, TiO₂was made from the hydrosis of the intermediate Ti（OH）₃.But TiO₂films were prepared by the oxidation of sub-oxide titanium inanodic treatment. For alkali-H₂O₂system, we mainly investigated theformation mechanism of titanate.Energy shortage and environmental pollution make people beinterested in exploring of green energy. The corrosion reaction happened onmagnesium scraps could gernerate both hydrogen and flame-retardantmaterial magnesium hydroxide, it is a win-win method. Surfacemorphology, the elements and the elements chemical states of the sampleswere characterized systematically by Scanning Electron Microscopy （SEM）,X-Ray Diffractometer （XRD）, Transmission Electron Microscopy （TEM）,Electron Diffraction Spectroscopy （EDS）. Based on XRD and EDS results,we also discussed the corrosion mechanism of magnesium or magnesium alloys which were immersed in NaCl solution or seawater. The followingresults were obtained.（1） Under different experimental conditions, the corrosion happenedon magnesium and magnesium alloys were radial epitaxial extension. Themorphology of the roughness and the protruding was quite different. Insimulated seawater, needle-like fibers were found. The honeycomb-like,even “Bird Nest”-like structure could be seen with the corrosion solutionconcentration increasing. With different reaction temperatures, flower-likeball appeared at40℃; spherical corrosion consisted of triangular at60℃,and flower bulb at80℃again. When the reaction between magnesium foilsand seawater happened, the typical two-dimensional film was appeared, butfor Mg-Cu alloy and Mg-Al alloy, we could found flower-like ball.（2） From XRD results which were obtained under our experimentalconditions, corrosion product grew along the crystalline phase （001）oriented. The particle size of the magnesium hydroxide increased withincreasing of the concentration and temperature.（3） From EDS results, the amount of magnesium chloride in thecorrosion process increased gradually with NaCl concentration increasing,but reduced with higher reaction temperature.（4） From the corrosion mechanism, the corrosion of magnesium andits alloys started from the reaction with water on the surface. The corrosionrate was related to the corrosive solution concentration and the reactiontemperature. While magnesium alloy has something to do with theelements contained in the alloys.