Experimental Investigation And Thermodynamic Calculation Of Phase Diagram In Al-based Hydrolysis Hydrogen Production Alloy

The aluminum hydrolysis can produce hydrogen.However,aluminum is easily to generate dense Al2O3 oxide film,thus the aluminum hydrolysis reaction cannot be done consistently under room temperature and normal pressure.Doping with Ni,Co,Fe,Cu,Zn,Sn and Bi can effectively improve the hydrolysis hydrogen production performance.Phase diagram is the theoretical basis of materials design.Therefore,the experimental research and thermodynamic calculation of the phase diagram of the Al-based hydrolysis hydrogen production alloys have very important guiding value.The purpose of this paper is to experimentally determine the ternary system phase diagrams of the Al-based hydrolysis hydrogen production alloys through microstructure observation,electron probe probe-micro analysis and X-ray diffraction analysis techniques.Based on the obtained experimental results,the CALPHAD method was used to calculate the thermodynamic parameters and the phase diagrams of these Al-based hydrolysis hydrogen production alloys.The main results are listed as follows:(1)The isothermal sections of the Co-Sn-Ni ternary system at 700℃ and 1000℃ have been experimentally investigated.The experimental results showed that,there is an extensive region of mutual solubility existing between the βCo3Sn2 phase and the Ni3Sn2(h)phase,which is labeled as the(Ni,Co)3Sn2.A continuous solid solution phase(aCo,Ni)forms in the Co-Ni side.The maximum solid solubility of Co in the Ni3Sn(l)and Ni3Sn4 phases is about 6.9 at.%and 25.6 at.%,respectively.The maximum solid solubility of Ni in the CoSn phase is about 15.9 at.%.(2)The isothermal sections of the Co-Sn-Fe ternary system at 800℃ and 1000℃ have been experimentally investigated.The experimental results showed that,at 800 ℃,the maximum solid solubility of Fe in the CoSn and βCo3Sn2 phase is about 28 at.%and 32 at.%,respectively.And the maximum solid solubility of Co in the Fe5Sn3 phase is about 30 at.%.At 1000℃,a continuous solid solution phase(αCo,yFe)forms on the Co-Fe side.The maximum solid solubility of Fe in the βCo3Sn2 phase is about 52 at.%.(3)Based on the obtained experimental results,the CALPHAD method was used to calculate the thermodynamic parameters and the phase diagrams of the Al-Sn-Co,Al-Sn-Fe,Co-Sn-Ni,and Co-Sn-Fe ternary systems.The calculated results and experimental results have achieved good agreement.Using the thermodynamic parameters optimized obtained by the present study,the isothermal cross-sectional phase diagrams and longitudinal cross-sectional phase diagrams of Al-Sn-Co,Al-Sn-Fe,Co-Sn-Ni and Co-Sn-Fe ternary systems at more isothermal sections were extrapolated.It can provide basic thermodynamic parameters for the establishment of the thermodynamic database of Al-based hydrolysis hydrogen production alloys.