魔芋葡甘聚糖及其油酸酯化物的体外抗氧化初步研究

对魔芋葡甘聚糖(KGM)和魔芋葡甘聚糖油酸酯(KGM酯)体外抗氧化性进行了研究。通过氧化诱导试验、清除DPPH自由基、清除ABTS自由基、对Fe~(2+)螯合能力、还原能力试验发现:KGM和KGM酯均有一定的抗氧化性,酯化度越高,抗氧化能力越强;当菜籽油中KGM和酯化度最高的KGM酯1添加量为0.8%时,与空白对照相比其氧化诱导时间分别延长5.94 h和2.56 h;在KGM酯与茶多酚、V_C、TBHQ协同试验中,KGM酯也表现出一定抗氧化性;质量浓度为0.5 mg/m L时,KGM和KGM酯1对DPPH自由基清除率分别为61.68%和36.93%;质量浓度为2.0 mg/m L时,KGM和KGM酯1对ABTS自由基清除率分别为20.31%和17.26%,对Fe~(2+)螯合率分别为17.58%和9.79%。虽然KGM酯化后其抗氧化能力稍有减弱,但仍具有抗氧化性,且与酯化程度呈正相关。     

快淬纳米晶/非晶Mg2-xLaxNi (x=0～0.6)合金的贮氢动力学

为了改善Mg2Ni型合金气态及电化学贮氢动力学性能,用La部分替代合金中的Mg,用快淬技术制备了Mg2-xLaxNi(x=0,0.2,0.4,0.6)合金,用XRD,SEM,HRTEM分析了铸态及快淬态合金的微观结构;用自动控制的Sieverts设备测试了合金的气态贮氢动力学性能,用程控电池测试仪测试了合金的电化学贮氢动力学.结果发现,快淬无La合金具有典型的纳米晶结构,而快淬含La合金显示了以非晶相为主的结构,表明La替代Mg提高Mg2Ni型合金的非晶形成能力.La替代Mg明显地改变Mg2Ni型合金的相组成.当La替代量x=0.4时,合金的主相改变为(La,Mg) Ni3+ LaMg3.合金的气态及电化学吸放氢动力学对La含量及快淬工艺敏感,La替代使合金的吸氢动力学降低,但适量的La替代可以明显改善合金的放氢动力学及高倍率放电能力.适当的快淬处理可以提高合金的气态及电化学贮氢动力学,但获得最佳贮氢动力学的快淬工艺与合金的成分密切相关.     

Structures and electrochemical performances of La_(0.75-x)Zr_xMg_(0.25)Ni_(3.2)Co_(0.2)Al_(0.1) (x=0-0.2) electrode alloys prepared by melt spinning

The La-Mg-Ni system A2B7-type electrode alloys with nominal composition La0.75-xZrxMg0.25Ni3.2Co0.2Al0.1(x=0,0.05, 0.1,0.15,0.2)were prepared by casting and melt-spinning.The influences of melt spinning on the electrochemical performances as well as the structures of the alloys were investigated.The results obtained by XRD,SEM and TEM show that the as-cast and spun alloys have a multiphase structure,consisting of two main phases(La,Mg)Ni3 and LaNi5 as well as a residual phase LaNi2.The melt spinning leads to an obvious increase of the LaNi5 phase and a decrease of the(La,Mg)Ni3 phase in the alloys.The results of the electrochemical measurement indicate that the discharge capacity of the alloys(x≤0.1)first increases and then decreases with the increase of spinning rate,whereas for x0.1,the discharge capacity of the alloys monotonously falls.The melt spinning slightly impairs the activation capability of the alloys,but it significantly enhances the cycle stability of the alloys.     

快淬对La-Mg-Ni系A_2B_7型电极合金循环稳定性的影响

用熔体快淬工艺制备了La-Mg-Ni系A2B7型La0.75-xZrxMg0.25Ni3.2Co0.2Al0.1（x=0,0.05,0.1,0.15,0.2）电极合金。用XRD、SEM、TEM分析了铸态及快淬态合金的微观结构,用程控电池测试设备测试了铸态及快淬态合金电极的电化学循环稳定性,研究了快淬工艺对合金结构及电化学循环稳定性的影响,探讨了电极合金的失效机理。结果表明,快淬态合金均具有多相结构,包括两个主相（La,Mg）Ni3及LaNi5和一个残余相LaNi2。快淬处理可以显著改善合金的电化学循环稳定性。导致合金失效的主要原因是电极表面被电解液剧烈腐蚀以及合金电极在电化学循环过程中的粉化。     

Co替代Ni对快淬纳米晶/非晶Mg_2Ni型合金吸放氢动力学的影响

为了改善Mg2Ni型合金的吸放氢动力学性能,用Co部分替代合金中的Ni。用快淬工艺制备了纳米晶和非晶Mg20Ni10-xCox(x=0,1,2,3,4)贮氢合金,分析了铸态及快淬态合金的微观结构,测试了合金的吸放氢动力学性能。研究了Co替代Ni及快淬工艺对合金吸放氢动力学性能的影响。结果表明,在快淬合金(x=0)中没有发现非晶相,但快淬合金(x=4)显示了纳米晶/非晶结构,表明Co替代Ni提高了Mg2Ni型合金的非晶形成能力。Co替代Ni不改变合金的Mg2Ni主相,但形成了第二相MgCo2。随Co替代量的增加,合金的吸氢量先增加而后减少,但其放氢量随Co替代量的增加而单调增加。     

Influences of stoichiometric ratio B/A on structures and electrochemical behaviors of Lao.75Mg0.25Ni3.5Mx （M=Ni,Co; x=0-0.6） hydrogen storage alloys

In order to investigate the influences of the stoichiometric ratio ofB/A （A： gross A-site elements, B： gross B-site elements） and the substitution of Co for Ni on the structures and electrochemical performances of the AB3.5-4.1-type electrode alloys, the La-Mg-Ni-Co system La0.75Mg0.25Ni3.5Mx （M=Ni, Co; x= 0, 0.2, 0.4, 0.6） alloys were prepared by induction melting in a helium atmosphere. The structures and electrochemical performances of the alloys were systemically measured. The results show that the structures and electrochemical performances of the alloys are closely relevant to the B/A ratio. All the alloys exhibit a multiphase structure, including two major phases, （La, Mg）2Ni7 and LaNis, and a residual phase LaNi2, and with rising ratio B/A, the （La,Mg）2Ni7 phase decreases and the LaNi5 phase increases significantly. When ratio B/A-3.7, the alloys obtain the maximum discharge capacities. The high rate discharge（HRD） capability of the alloy （M=Ni） monotonously rises with growing B/A ratio, but that of the alloy （M=Co） first mounts up then declines. The cycle stability of the alloy （M-Co） monotonously increases with rising B/A ratio, but it first decreases slightly then increases for the alloy （M=Ni）. The discharge potential of the alloy （M=Ni） declines with increasing B/A ratio （x〉0.2）, but for the alloy （M-Co）, the result is contrary. The substitution of Co for Ni significantly ameliorates the electrochemical performances. For a fixed ratio B/A=3.7, the Co substitution enhances the discharge capacity from 365.7 to 401.8 mA.h/g, the capacity retention ratio （S100） after 100 charging-discharging cycles from 50.32% to 53.26% and the HRD from 88.65% to 90.69%.     

模拟纤维增强复合材料的相似子域边界元法

根据夹杂相积分区域的相似性,提出了相似子域边界元法求解方案。把含随机分布夹杂相的固体归结为对一个含有内边界条件复连通域问题的求解,与传统的有限元和边界元分域解法相比,显著地提高了计算效率。应用相似子域边界元法,对含有随机分布圆形和椭圆形夹杂相的固体材料进行了大量数值计算,并把夹杂相与基体材料之间从理想粘结扩展到带有界面层的情况。这些计算为相应纤维增强复合材料宏观等效力学特性研究提供了有效的数值模拟方法。      

伊豆和小笠原弧北部可能有热液活动

目前,伊豆和小笠原弧的面貌类似于约15百万年前西黑泽期的东北日本弧。位于伊豆和小笠原北部火山前沿后部的弧后凹地是被正断层切割而形成的沉降性凹地。该弧后凹地可能有热液活动。进而,本文将它与在东北日本弧北鹿区域所形成的黑矿矿床条件的类似性进行了比较和研究。     

稀土钒钛高铬白口铸铁组织与性能的研究

高铬白口铸铁中加入适量钒钛和稀土复合变质处理后，可使基体组织细化，碳化物形态改善。适当的热处理可使组织性能进一步改善，获得耐磨性与韧性的良好配合