【作者】 郑坊平；

【导师】 陈立新；

【作者基本信息】 浙江大学 ， 材料学， 2006， 硕士

【摘要】 本文在对国内外BCC固溶体型储氢合金的研究进展进行全面综述的基础上,选择具有高吸氢量的Ti-V-Fe系储氢合金为研究对象,通过XRD、SEM、EDS分析以及吸放氢性能测试等手段,比较系统地研究了中V含量和高V含量的两种系列Ti-V-Fe三元合金的微结构和储氢性能,以及多元合金化和球磨改性处理对优选合金的微结构和储氢性能的影响规律,力求进一步提高Ti-V-Fe系储氢合金的综合性能。 对中V含量的Ti_100-x-yV_xFe_y（x=54,49,44;y=5,7,5,10）系三元合金的研究表明:该系列合金主要由体心立方（BCC）结构的固溶体相组成,其中Ti₄₁V₅₄Fe₅合金中还含有少量的α-Ti第二相。储氢性能测试表明:该系列合金的动力学性能很好,在室温和4MPa初始氢压条件下首次吸氢时,无需氢化孕育期就能快速吸氢;活化后的合金吸氢速度极快,只需3min左右即可吸氢饱和;随着Ti、Fe含量的增加和V含量的减少,合金的室温最大吸氢量、300℃有效放氢量以及放氢效率均随之增加。在所研究的合金中,Ti₄₆V₄₄Fe₁₀合金的综合性能相对较好:经4次吸放氢循环即可活化,室温最大吸氢量可达372.4 ml/g,300℃有效放氢量达到238.5 ml/g。 为了提高合金的最大吸氢容量及绝对有效放氢量,并降低合金的放氢温度,本文进一步系统研究了高V含量的(Zi_0.1V_0.9100-xFe_x（x=0,2,4,6）系三元合金的微结构和储氢性能。结果表明:该系列合金均由单一的BCC固溶体相组成;合金的点阵常数随着Fe含量的增加呈线性递减,晶胞体积也随之降低。随着Fe含量从x=0增加至x=6,合金的活化次数由4次降为2次,10℃最大吸氢量从509.5 ml/g逐渐降至424.8ml/g,而50℃有效放氢量先升后降,并在x=4时达到最高值255.6ml/g。在所研究的合金中,Ti_9.6V_86.4Fe₄合金具有较佳综合性能:经2次吸放氢循环即可活化,10℃最大吸氢量达到494.5 ml/g,50℃有效放氢量为255.6ml/g。对Ti_9.6V_86.4Fe₄合金在吸放氢过程中的物相分析表明,此类合金的有效放氢率偏低的主要原因是由于P-C-T放氢曲线的低平台压力较低、合金中VH_0.81基氢化物相难以分解脱氢造成的。 在三元合金的研究基础上,本文对优选出的Ti_9.6V_86.4Fe₄合金进行了复合球磨改性研究。研究表明,经1h真空机械球磨制备的Ti_9.6V_86.4Fe4+10wt%Ti_0.9Zr_0.1Mn_1.5复合物由BCC固溶体主相和C14型Laves第二相组成。与铸态Ti_9.6V_86.4Fe₄合金相比,球磨复合物的BCC主相晶胞体积略有增大;活化性能得到极大改善,首次吸氢即能活化:室温最大吸氢量有所降低（459.8 ml/g）,但P-C-T放氢平台特性和滞后现象有了一定改善,其50℃有效放氢量也有所提高（268.5 ml/g）。 在优选出的Ti_9.6V_86.4Fe₄合金的基础上,本文又进一步研究了Cr部分取代V对Ti_9.6V_86.4-xCr_xFe₄（x=11,12,13,14）系四元合金微结构和储氢性能的影响。研究表明:该系列合金均由单一的BCC固溶体相组成,合金的点阵常数随着Cr含量的增加呈更多还原

【Abstract】 In this thesis, the research and development of hydrogen storage alloys with BCC structure vanadium-based solid solution were exhaustively reviewed first. On this basis, Ti-V-Fe based alloys with high hydrogen absorption capacity were chosen as the objects of this study. By means of XRD, SEM, EDS analysis and hydriding/dehydriding characteristic measurements, the microstructures and hydrogen storage properties of Ti-V-Fe ternary alloys with middling and high V content have been investigated respectively. Then, the effects of multi-component alloying and mechanical ball-milling modification on the microstructures and hydrogen storage properties of the studied alloys have been investigated systemically. The purpose of such investigation is to improve the overall properties of Ti-V-Fe based hydrogen storage alloys.The study on the microstructures and hydrogen storage properties of Ti_100-x-yV_xFe_y （x= 54, 49, 44;y= 5, 7.5, 10） alloys with middling V content shows that Ti₄₁V₅₄Fe₅ alloy consists of a solid solution main phase with BCC structure and a little α-Ti secondary phase, Ti_43.5V₄₉Fe_7.5 and Ti₄₆V₄₄Fe₁₀ alloys consist of a single solid solution phase. It is found that all of these alloys have good kinetics, they can absorb hydrogen rapidly without hydrogenation gestation time at room temperature and under 4 MPa initial hydrogen pressure. All alloys can be activated after 4-5 cycles and absorb saturated hydrogen within 3 minutes. With the increase of Ti, Fe content and the decrease of V content, the maximum hydrogen absorption capacity at room temperature, the effective hydrogen desorption capacity at 300 ℃ and the efficiency of hydrogen desorption all increase. Among these alloys studied, Ti₄₆V₄₄Fe₁₀ alloy has a good overall property, such as the activation number of 4 cycles, the maximum hydrogen absorption capacity of 372.4 ml/g at room temperature and the effective hydrogen desorption capacity of 238.5 ml/g at 300℃.In order to enhance further the maximum hydrogen absorption capacity and effective desorption capacity besides reducing the temperature of hydrogen desorption, the microstructures and hydrogen storage properties of (Ti_0.1V_0.9)_100-xFe_x（x= 0, 2, 4, 6） alloys with high V content were investigated systematically. The results show that all of these alloys consist of a single vanadium-based solid solution phase with BCC structure. With the increase of Fe content, the lattice parameter descends linearly, the unit cell volume also decreases. As the Fe content increases from x=0 to x=6, the activation number decreases from 4 cycles to 2cycles, the maximum hydrogen absorption capacity at 10℃ decreases from 509.5 ml/g to 424.8 ml/g, and the effective hydrogen desorption capacity at 50℃increases first and then decreases while the maximum value of 255.6 ml/g is obtained at x=4. Among these alloys studied, Ti9.6V86.4Fe4 alloy has a good overall property, such as the activation number of 2 cycles, the maximum hydrogen absorption capacity of 494.5 ml/g at 10°C and the effective hydrogen desorption capacity of 255.6 ml/g at 50°C. The study on the change of phase structures of Ti9.6V86.4Fe4 alloy during hydrogenation/ dehydrogenation cycle shows that the main reason of low effective desorption capacity of the alloy is the very low pressure of lower plateau of P-C-T curve and the difficult dehydrogenation of VH0.8i-based hydride with high thermodynamic stability.The microstructure and hydrogen storage properties of Ti9.6Vg6.4Fe4 + 10 wt% Tio.9Zro.iMni.5 composite prepared by mechanical ball-milling for lh were investigated. The results show that the alloy has a C14 type Laves secondary phase besides the BCC solid solution main phase. Comparing with as-cast Ti9.6V86.4Fe4 alloy, the unit cell volume of BCC main phase of the ball-milled composite increases slightly, the activation behavior is improved evidently, the maximum hydrogen absorption capacity at room temperature decreases （459.8 ml/g）, and the effective hydrogen desorption capacity at 50°C increases （268.5 ml/g） due to the improved plateau characteristics of P-C-T curve.On the basis of the research on the ternary alloys, the microstructure and hydrogen storage properties of Ti9.6V86.4^Cr^Fe4 （x= 11, 12, 13, 14） alloys were investigated systematically. The results show that all of these alloys consist of a single vanadium-based solid solution phase with BCC structure. With the increase of Cr content, the lattice parameter descends linearly and the unit cell volume also decreases. It is found that all of these alloys have good kinetics, they can absorb hydrogen rapidly without hydrogenation gestation time at 10°C and initial hydrogen pressure of 4 MPa, but all alloys are activated after 3-4 cycles. As the Cr content increases from x=ll to x=14, both the maximum hydrogen absorption capacity and the effective hydrogen desorption capacity decrease. However, the Cr dopping is useful to improve the plateau characteristics of P-C-T curve for these alloys. Among these alloys studied, Ti9.6V75.4CrnFe4 alloy has a good overall property, such as the activation number of 3 cycles, the maximum hydrogen absorption capacity of 465.4 ml/g at 20°C, the effective hydrogen desorption capacity of 282.6 ml/g at 50 °C and the efficiency of hydrogen desorption of 60.72% .On the basis of the above work on the quadruple alloys, the changes in microstructure and hydrogen storage properties of Ti9.6V75.4CriiFe4 alloy after modification by mechanical ball-milling for different time （t = 0,1, 2,4, 8 h） were investigated. The results show that the alloys before and after ball-milling consist of a single V-based solid solutionphase with BCC structure. The lattice parameter and the unit cell volume descend with the increase of ball-milling time. It is found that the ball-milling can improve the activation behavior of the alloy effectively, and the activation number decreases from 3 cycles of the un-milled alloy to 1-2 cycles of the milled alloys. It is found that the alloys before and after ball-milling has good kinetics, they can absorb hydrogen rapidly without hydrogenation gestation time. The hydrogen absorption capacity of the activated alloy can get to 90 percent of the maximum hydrogen absorption capacity within 5 minutes. As the ball-milling time increases, the maximum hydrogen absorption capacity at room temperature decreases gradually, while the effective hydrogen desorption capacity increases first and then decreases. The Ti9.6V75.4CrnFe4 alloy ball-milled for 2 h has a good overall property, and the effective hydrogen desorption capacity at 50°C achieves 302.9 ml/g.更多还原