嵌段共聚物薄膜快速自组装方法

嵌段共聚物 (BCP) 薄膜可通过不同的退火方法诱导其微相分离,从而获得大面积圆柱状、层状和球状等纳米图案。这些长程有序的纳米结构形态,已经广泛应用在纳米光刻和电子器件等多个领域中。目前,有效且快速的退火方法仍然是BCP薄膜自组装技术中的研究热点。本文首先介绍了制备BCP薄膜纳米结构图案常用的退火技术,然后综述了三种新型快速退火技术,最后分析总结了这些退火技术的优缺点。     

硅单粒子位移损伤多尺度模拟研究

本文结合分子动力学方法和动力学蒙特卡罗方法, 研究了单个粒子入射硅引起的位移损伤缺陷的产生和演化过程; 基于Shockley-Read-Hall理论计算了单个粒子入射引起的位移损伤缺陷导致的泄漏电流增加及其演化过程, 比较了缺陷退火因子与泄漏电流退火因子之间的差异, 并将计算结果与实验值进行了对比. 结果表明, 计算泄漏电流时, 仅考虑一种缺陷的情况下缺陷退火因子与泄漏电流退火因子相同, 考虑两种缺陷类型情况下二者在数值上有所区别, 但缺陷退火因子仍能在一定程度上反映泄漏电流的退火行为. 分子动力学模拟中采用Stillinger-Weber势函数和Tersoff势函数时缺陷退火因子和泄漏电流退火因子与实验结果一致, 基于Stillinger-Weber势函数的计算结果与实验值更为接近.     

浅析电子型掺杂铜氧化物超导体的退火过程

铜氧化物高温超导体的发现, 打破了基于电声子相互作用BCS理论所预言的超导转变温度极限, 掀开了高温超导材料探索和高温超导机理研究的序幕. 根据掺杂类型的不同, 铜氧化物超导材料可以分为空穴型掺杂和电子型掺杂两类. 受限于样品, 对电子型掺杂铜氧化物的研究工作远少于空穴型掺杂体系. 本文简要回顾有关电子型掺杂铜氧化物超导体近期研究成果, 通过对比电子型掺杂和空穴型掺杂铜氧化物的相图来阐明电子型掺杂铜氧化物的研究对探索高温超导机理的必要性, 并特别针对电子型掺杂样品制备中的关键因素“退火过程”展开讨论. 结合课题组最新实验结果和相关实验报道我们发现电子型掺杂铜氧化物超导体在制备过程中除受到温度和氧分压的影响外, 退火效果还受到界面应力的强烈调制. 在综合考虑样品生长过程中温度、气氛及应力等多种因素的基础上, 探讨了“保护退火”方法导致电子型体系化学掺杂相图变化的起因.     

钛表面生物活性榍石/氧化钛复合涂层的结构和磷灰石形成机理(英文)

采用微弧氧化和热处理复合技术,在钛表面制备了具有双层结构的榍石/氧化钛复合涂层。榍石/氧化钛复合涂层的外层是由微弧氧化涂层经热处理后晶化生成;而内层是由钛基底的氧化生成,并且氧化钛表现出不同的Ti,O原子比。由于钛基底的氧化,孔径在50~500 nm的微孔呈层状结构分布在涂层内层。与微弧氧化涂层相比,该复合涂层具有很好的磷灰石诱导能力,这是由于榍石沿着特定晶面和晶向与羟基磷灰石表现出良好的晶体学匹配关系,从而为磷灰石的成核和取向沉积过程提供良好的位点。     

聚集态的Fe氧化物在Fe/ZSM-5催化N_2O直接分解中的作用(英文)

研究了以离子交换法制备的Fe/ZSM-5上聚合态的Fe氧化物(FeOx)在催化N2O直接分解中的作用.Fe/ZSM-5催化剂利用600–900 ℃的高纯Ar处理,使催化剂中的FeOx发生聚合.利用一系列的表征手段(XRD,BET,DRIFTS,UV/vis-DRS,XAFS,N2O脉冲和O2-TPD)对催化剂进行了表征.结果发现,分子筛骨架外的FeOx在Fe/ZSM-5催化N2O分解中起重要作用;通过研究高温处理的Fe/ZSM-5催化剂中不同FeOx的比例与催化剂活性的关系,得到多核的FeOx是催化N2O分解的主要活性物种;并且,无定形态的FeOx中键长较长的Fe–O键((Fe–O)2)是参与反应的重要物种.     

Microstructure characterization of short-chain branching polyethylene with differential scanning calorimetry and successive selfnucleation/annealing thermal fractionation

A series of the copolymers of ethylene with 1-hexene(M1–M9) synthesized by metallocene catalyst Et[Ind]2ZrCl2/MAO was studied by differential scanning calorimetry and successive self-nucleation and annealing(SSA) thermal fractionation. The distribution of methylene sequence length(MSL) in the different copolymers was determined using the SSA method. The comonomer contents of samples M4 and M5 are 2.04 mol% and 2.78 mol%, respectively. Both M4 and M5 have low comonomer content and their MSL distribution profiles exhibit a monotonous increase trend with their MSL. The longest MSL of M5 is 167, and its corresponding molar percent is 43.95%, which is higher than that of M4. Moreover, the melting temperature(Tm) of M5 is also higher than that of M4. The comonomer contents of samples M7, M8, and M9 are 8.73 mol%, 14.18 mol% and 15.05 mol%, respectively. M7, M8, and M9 have high comonomer contents, and their MSL distribution profiles display unimodality. M7 has a lower peak value of 33 and a narrow MSL distribution, resulting in a Tm lower than that of M8 and M9. The MSL and its distribution are also key points that influence the melting behavior of copolymers. Sometimes, MSL and its distribution of copolymers have a greater impact on it than the total comonomer contents, which is different from traditional views.     

利用高压热处理技术提高Bi-2223/Ag高温超导带材临界电流

提高临界电流密度(Jc)对促进Bi-2223/Ag高温超导带材的应用有着重要意义.在常压热处理条件下所制备的带材中存在大量的裂纹、孔洞和第二相颗粒等,这些因素都会对带材的超导连接性能产生破坏作用.我们成功建立了一套可用氧气氛的热等静压设备,工作气压和温度可同时达到15MPa和850°C.通过引入裂纹愈合热处理过程,我们成功对带材进行了高压热处理,所得样品中第二相颗粒和裂纹数量大幅度降低,77K、自场下的临界电流相比常压热处理样品提高了20%左右.     

Effect of thermal-annealing on the magnetoresistance of manganite-based junctions

Thermal-annealing has been widely used in modulating the oxygen content of manganites. In this work, we have studied the effect of annealing on the transport properties and magnetoresistance of junctions composed of a La0.9Ca0.1MnO3＋6 film and a Nb-doped SrTiO3 substrate. We have demonstrated that the magnetoresistance of junctions is strongly dependent on the annealing conditions： Prom the junction annealed-in-air to the junction annealedin-vacuum, the magnetoresistance near 0-V bias can vary from ～-60% to N～0. A possible mechanism accounting for this phenomenon is discussed.     

Magnetic domain structures of precipitation-hardened SmCo 2：17-type sintered magnets： Heat treatment effect

The typical magnetic domains of Sm（CObalFe0.25Cuo.07Zr0.02）7.4 magnets quenched through various heattreatment steps have been revealed by using magnetic force microscopy （MFM）. For the specimens in which the nominal c-axis is perpendicular to the imaging plane, the domain configurations change from plate-like for the as-sintered magnet to corrugation and spike-like for the homogenized one, and then to a coarse and finally to a finer domain structure when isothermally aged at 830℃ and then annealed at 400℃. However, only plate-like domains can be detected on the surfaces with the nominal c-axis parallel to the imaging plane. The finer domain （so-called interaction domain） is a characteristic magnetic domain pattern of the SmCo 2：IT-type magnets with high coercivities. Domain walls in a zigzag shape are revealed by means of MFM in final bulk SraCo 2：17-type sintered magnets.