Investigation on Design,Fabrication and Hydrolysis Properties of Al-(Bi,Sn) Based Composite Powders
Author:Liu Yu Heng
Supervisor:wang cui ping
Hydrogen generation using aluminum-water reaction has drawn a lot of attention for low cost,high efficiency,safety and environment-friendly.In practical uses,however,Al-based hydrolysis materials will react with oxygen in the air,forming dense Al2O3 passivation film on the surface and lose reactivity.In this paper,taking Al-based liquid-phase-separation system as research object,Al-(Bi,Sn)based powders are designed using CALPHAD method and fabricated by gas atomization method.The hydrolysis properties,oxidation resistance properties and mechanism are investigated,as well as the application on PEMFC.The main results are summarized as follow:(1)Using CALPHAD method,phase diagram and volume fraction are calculated,alloies are designed and Al-(Bi,Sn)based powders are fabricated using gas atomization method.In Al-Sn powders,Sn-rich phase segregates on Al-rich phase grain boundaries.In the Al-Bi and Al-Bi-Sn powders,by adjusting phase volume fraction,Bi-rich or(Bi,Sn)-rich phase can partially or entirely cover Al-rich phase.(2)Hydrolysis and oxidation resistance properties of Al-(Bi,Sn)based powders are investigated,as well as the influence of temperature,solution and composition.80Al-10Bi-10Sn wt.%powders have the best properties,the powders collected in air can react with distilled water at 30℃ with conversion yield of 91.3%within 16 min.Even at 0℃,the conversion yield gets 80%within 88 min.Partially covered structure,the difference of melting point and thermal expansion efficient are the key factors.(3)Hydrogen produced from Al-(Bi,Sn)based powders in this work has high purity of 99.98%,and can be directly used on PEMFC.Combining Al-(Bi,Sn)based powders and PEMFC,on-board hydrogen energy system are developed,2 g Al-(Bi,Sn)based powders can afford 3 W micro fan for 2 h.