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In this work, pronounced oscillations in the time-resolved reflectivity of Heusler alloy Co_2MnAl films which are epitaxially grown on Ga As substrates are observed and investigated as a function of film thickness, probe wavelength,external magnetic field and temperature. Our results suggest that the oscillation response at 24.5 GHz results from the coherent phonon generation in Co_2MnAl film and can be explained by a propagating strain pulse model. From the probe wavelength dependent oscillation frequency, a sound velocity of(3.85±0.1)×10~3m/s at 800 nm for the epitaxial Co_2MnAl film is determined at room temperature. The detected coherent acoustic phonon generation in Co_2MnAl reported in this work provides a valuable reference for exploring the high-speed magnetization manipulation via magnetoelastic coupling for future spintronic devices based on Heusler alloy films. 相似文献
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炭黑结合橡胶对天然橡胶性能的影响 总被引:1,自引:0,他引:1
本文研究了天然橡胶(NR)与五种不同类型炭黑的结合橡胶对其混炼胶的应力-应变、流变性质等的影响。结果表明,NR与炭黑的结合橡胶量随炭黑结构和表面积增加而增加。结合橡胶的增加使NR在低剪切下的本体粘度、弹性恢复性和强度增加,塑性和粘着性降低;在高剪切下流动性变差,挤出物收缩则有所下降。此外,结合橡胶的增加也增加了硫化胶的交联度,因此模量、硬度和耐磨性提高,抗张强度和伸长率却有所下降。 相似文献
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利用稀土钕催化体系合成窄相对分子质量分布的顺丁橡胶(NMWD-NdBR),研究了NMWD-NdBR的结构和性能,并与宽相对分子质量分布的稀土顺丁橡胶(WMWD-NdBR)进行对比。 结果表明,相同温度转速条件下NMWD-NdBR表现更为优异的流变行为;NMWD-NdBR与WMWD-NdBR相比,焦烧时间和硫化时间基本相似,但最小转矩(ML)降低,最大转矩(MH)提高,表现为更好的加工行为和更佳的物理机械性能;橡胶加工分析仪测试的数据可知,同样配方和加工工艺条件下,NMWD-NdBR具有与WMWD-NdBR相似的Payne效应和更低的滞后损失(tanδ),tanδ与碳黑分散性以及滚动阻力吻合性良好。 相似文献
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用均相的稀土催化剂进行丁二烯-异戊二烯本体共聚合的研究 总被引:1,自引:0,他引:1
本工作用均相的稀土催化体系Nd(naph)_3-Al(i-Bu)_2H-CH_3SiHCl_2进行了丁二烯和异成二烯的本体共聚合,研究了聚合规律和产物的结构性能.结果表明,在适当的催化剂组分比条件下,该催化体系具有较高的催化活性,用DSC测定了共聚物的玻璃化转变温度,~1H-NMR和IR分别测定了共聚物的组成和微观结构,证明共聚物的组成主要决定于单体原料的配料比,共聚物中两种单体单元都具有高顺式结构,生胶和硫化胶的性能测定表明,在丁二烯和异戊二烯两种单体的配料比为30比70时,得到的共聚胶的综合性能较好. 相似文献
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首先用Fourier红外吸收谱对p型掺杂的Si0.75Ge0.25/Si量子阱价带子带间跃迁的偏振特性进行了研究。实验表明TE和TM偏振光均能激发价带子带间跃迁,并在HH1→HH2跃迁中观察到很强的二向色性。同时分别在45°及垂直入射的情况下,对加有直流电场的样品进行Fourier红外电致吸收测量,首次得到样品在不同直流电场下吸收系数变化谱和折射率变化的电场依赖关系(Kerr效应)。在外电场作用下测得的较大△n(∝E2)及子带间跃迁的偏振特性表明,SiGe/Si半导体量子阱材料在焦平面阵式布列的集成线路及光电器件等应用方面具有潜在优势。 相似文献
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稀土催化剂本体聚合异戊二烯的生胶性能 总被引:5,自引:0,他引:5
本体聚合与溶液聚合相比,具有能耗低,反应平稳,转化率高等特点。杨彩云等用稀土催化剂对异戊二烯(Ip)进行本体聚合,聚合转化率达80%以上,聚合物中无疑胶,且分子量分布较窄(M_w/M?<2)。本文报道和讨论本体聚合放大试验胶样的生胶特性。 异戊二烯胶样(BLn-IR)本所自制。溶液钛催化聚异戊二烯IR-1Q为日本JSR生产。天然橡胶(NR)系海南岛3~#烟片。门尼粘度按GB1232测定。应力-应变性能(23℃),用DL-1000B型电子拉力机测定,拉速500mm/min。玻璃化温度(T_g)用PE DSC-2C型仪测定,升温速率 相似文献
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In this work, the spin dynamics of a centrosymmetric WSe_2 bilayer has been investigated by the two-color timeresolved Kerr rotation together with helicity-resolved transient reflectance techniques. Two depolarization processes associated with the direct transition are discovered at a low temperature of 10 K, with the characteristic decaying time of~3.8 ps and ~20 ps, respectively. The short decay time of ~3.8 ps is suggested to be the exciton spin lifetime of the WSe_2 bilayer, which is limited by the short exciton lifetime of the WSe_2 bilayer and the rapid intervalley electron–hole exchange interaction between K+and K-valley in the same layer as that of monolayer. The long decay time of ~20 ps is suggested to be the spin lifetime of photo-excited electrons, whose spin relaxation is governed by the rapid intervalley scattering from the K valley to the global minimum Σ valley and the subsequent interlayer charge transfer in WSe_2 bilayer.Our experimental results prove the existence of the spin-polarized excitons and carriers even in centrosymmetric transition metal dichalcogenides(TMDCs) bilayers, suggesting their potential valleytronic and spintronic device applications. 相似文献
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用均相的稀土催化剂进行丁二烯-异戊二烯本体共聚合的研究 总被引:3,自引:0,他引:3
本工作用均相的稀土催化体系Nd(naph)3-Al(i-Bu)2H-CH3SiHCl2进行了丁二烯和异成二烯的本体共聚合,研究了聚合规律和产物的结构性能.结果表明,在适当的催化剂组分比条件下,该催化体系具有较高的催化活性,用DSC测定了共聚物的玻璃化转变温度,1H-NMR和IR分别测定了共聚物的组成和微观结构,证明共聚物的组成主要决定于单体原料的配料比,共聚物中两种单体单元都具有高顺式结构,生胶和硫化胶的性能测定表明,在丁二烯和异戊二烯两种单体的配料比为30比70时,得到的共聚胶的综合性能较好. 相似文献