Study On Hydrogen Storage Alloys PCT System And Its Experimental Analysis

Due to their characteristics of cleanness,safe transportation and high volumetric efficiency,hydrogen storage alloys have been applied for nickel/metal hydride battery and fuel cell vehicles.The alloys have been investigated in the science and engineering fields widely in the world.As their applications become more widely,there is a demand for automatic measurement instrument named Pressure-Composition-Temperature(PCT) equipment,an important apparatus for characterising the hydrogen absorption and desorption performance of hydrogen storage alloy.At present,homemade PCT instrument is rare,while most researchers are using imported ones(mainly GRC equipment from AMC).In addition,PCT measurement apparatus is required to be more accurate and reliable than before.On the bases of survey on the PCT measurement apparatus,the purpose of this thesis is to develope a new type of computer-controlled PCT measurement system for improving its data acquisition accuracy and its working reliability.On the basis of real gas state equation,the principle of PCT measurement for hydrogen storage alloys is analysed in detail.Then the schematic arrangement and main structure of the system is presented,including vacuum part,reactor,data acquisition and electronic control unit.In the automatic control unit,the high performance controller ADμC848 which incorporates 16-bit ADCs,62-kbyte on-chip Flash/EE program memory and 4-kbyte on-chip Flash/EE data memory is selected in the entire hardware circuits. The data acquisition part is made of pressure transducers,temperature sensor,sensor interface circuit,K type thermocouple matched circuit and LED display circuits.The executive parts are operated by the application of solid state relay to control open/close of the related electromagenatic valves.By using the controller ADμC848 and its peripheral circuit EMC design and its external 2.5V reference voltage,the accuracy and stability of the measurment are improved significantly.MCU program is compiled by C language,and application program on PC is developed with VC language.Their communication is carded out by RS232 serial interface.After debugging and testing,the whole system has the capability to measure PCT performance of hydrogen storage materials automatically,as well as to carry out absorbing-desorbing cycling test successfully.To verify the practical performance of the developed PCT measurement system,it is put into use with a typical LaNi₅ alloy.It is proved that with the increase of Ce content in the alloy,its equilibrium pressures of hydrogen absorption and desorption increase obviously,pressure hysteresis effect increases,hydrogen aborbtion capacity decreases though it increases initially.These results show that the developed PCT measurement system works accurately and reliably for the study of hydrogen storage alloys.It is hoped to use as an effective device for hydrogen storage alloy research.