CdBa2Cu3O7-x薄膜的涨落电导

测量了高质量的GdBa_2Cu_3O_(7-x)薄膜的电阻及磁阻曲线,应用Lawrence-Doniach理论对实验曲线进行了拟合,得到了一组自洽且合理的参数值,由ln(σ—σ_(?))-Int曲线可以明显地看到存在一个二维向三维的转变。 关键词：     

非超导的Bi2Sr2CuOy单晶的磁阻研究

铜氧化合物高温超导体正常态的电子输运一直是人们关注的焦点问题之一,根据最近研究的Bi₂Sr₂CuO_y单晶a-b平面内电阻率随温度的变化关系,发现许多直接生长的晶体在高温呈金属性而低温下出现电子局域化现象,对低温呈强局域化行为的样品进行了磁阻测量,发现在较低温区的低场,样品具有正磁阻效应,而高场下,样品具有负磁阻效应,最大正磁阻对应的磁场则随着温度的升高向低场漂移,在高温区,无论是低场和高场,样品不再具有正磁阻效应而只存在负磁阻效应,同时还发现样品的磁阻效应随着温度的增加而变得不明显,通过对横向磁阻与纵向磁阻的比较,发现这种磁阻主要是轨道效应的贡献。把实验结果与强局域化区域轨道磁阻的理论工作进行了比较,对正、负磁阻的起源进行了讨论。     

磁驱动加载装置负载区降温系统设计及应用

在材料物性研究中,压力和温度是两个基础的物理量,国内磁驱动加载装置具有压力调节能力,暂不具备样品降温控制技术,针对这一现状设计了一套配合磁驱动加载装置负载区的样品初始降温系统,结合设计的电极板结构和测试探针工装,使负载区电极板与样品、样品与探针固定于设定位置;通过往电极板和探针工装形成的密闭气室内注入压缩低温液氮达到对样品降温的目的;通过真空泵,抽出电极板和探针工装形成的密闭气室内的空气,避免测速探针由于低温凝结空气中的水汽而无法工作。基于该系统开展了低温下铋的斜波压缩实验,获得了?80 ℃初始温度下铋的动力学响应数据,验证了降温系统的可靠性。     

改进荧光法研究氟洛芬与牛血清白蛋白的相互作用

为解决经典荧光光谱法在研究药物与蛋白结合机理中存在的缺陷,以蛋白与兽用药氟洛芬(FF)的结合为例,在生理条件(pH=7.40的Tris-HCl缓冲溶液)下,以氟洛芬为荧光检测对象、牛血清白蛋白(BSA)为猝灭剂,通过改进荧光研究方法研究了药物与蛋白结合机理。结果表明,FF与BSA之间发生了静态猝灭,主要通过静电引力结合,其结合位点数约为1,Hill系数n H略大于1,表现为弱的正协同作用。同时运用紫外吸收光谱法对该方法进行了验证,表明改进荧光法能更准确和全面地表征蛋白和药物的相互作用。     

格列吡嗪与牛血清白蛋白相互作用的分子光谱法的改进实验

在pH 7.40的Tris-HCl缓冲溶液中,利用以蛋白荧光变化为考察对象的传统荧光光谱法和以药物荧光变化为考察对象的弹性散射荧光法,分别研究了293和303K温度下格列吡嗪(Gli)与牛血清白蛋白(BSA)之间的反应机理,两种方法所得结论均一致。即Gli与BSA之间猝灭方式为动态猝灭;两者主要通过疏水作用力结合,结合位点主要位于BSA的疏水区,结合位点数约为1;Hill系数nH小于1,表现为弱的负协同作用。弹性散射荧光法得到的Gli-BSA体系的结合常数均比传统荧光光谱法大,表明以药物荧光变化为考察对象的研究更准确、合理,并通过紫外光谱法对其所得结果的合理性进行了验证。结果表明:传统荧光光谱法利用蛋白为研究对象,研究药物与蛋白之间的相互作用存在一定的不足,其谱图只能反映蛋白分子与药物相互作用的部分信息,而弹性散射荧光法利用药物为研究对象,能够更全面、准确地表达药物与蛋白之间的作用信息。     

可溶性聚苯并咪唑的合成及性能表征

使用简单温和的方法合成了含醚键的聚苯并咪唑(PBI),通过控制反应时间与反应温度得到了4种重均分子量不同的PBI,考察了重均分子量对PBI溶解性和拉伸性能的影响,确定了PBI的最佳制备条件。采用热重分析仪分析了PBI的热稳定性,同时考察了磷酸浸泡时间对PBI膜性能的影响以及温度对磷酸掺杂PBI膜质子电导率的影响。结果表明:在140℃下反应2h,制得的PBI综合性能最优,重均分子量可达4.9×10~5,且具备优良的热稳定性。此外,磷酸未掺杂的PBI膜能吸收222%的磷酸,在170℃无水条件下的质子电导率达到16.3mS/cm,有望用作高温质子交换膜。     

陕西周原遗址出土西周原始瓷工艺特征的初步研究

南方地区原始瓷出土数量较多且出土地点较为集中,从而对它的工艺和产地研究较为深入;而北方原始瓷因出土地点分布零散和数量的限制,对它的科技分析比较少。随着陕西周原遗址出土了大量原始瓷,有必要对该遗址出土的原始瓷做一个整体分析。为了探讨陕西周原遗址出土西周时期原始瓷的工艺特征,采用超景深三维视频显微系统和能量色散X射线荧光光谱分别对原始瓷胎釉微观结构和化学元素组成进行了观察与测试。显微观察可见：原始瓷胎质粗糙,胎中未熔颗粒、孔隙较多;施釉不均,釉层较为浑浊,分布较多气泡。化学组成测试结果显示：胎中Al₂O₃含量集中在11.8%～17.21%,SiO₂含量分布在75%～80.5%, K₂O含量分布在3%～7.85%;釉中CaO含量分布在11.08%～23.94%, P₂O₅含量分布在1%～3.18%、MnO含量分布在0.24%～1%,而釉中P₂O₅,MnO,K₂O含量较胎相对提高。结果分析表明：原始瓷胎料可能选用含较高钾的瓷石;釉应是添加了草木灰的钙釉;周原遗址的原始瓷工艺尚处于制瓷技术初级阶段。     

Stability,electronic structures,and mechanical properties of Fe–Mn–Al system from first-principles calculations

The stability, electronic structures, and mechanical properties of the Fe–Mn–Al system were determined by firstprinciples calculations. The formation enthalpy and cohesive energy of these Fe–Mn–Al alloys are negative and show that the alloys are thermodynamically stable. Fe_3Al, with the lowest formation enthalpy, is the most stable compound in the Fe–Mn–Al system. The partial density of states, total density of states, and electron density distribution maps of the Fe–Mn–Al alloys were analyzed. The bonding characteristics of these Fe–Mn–Al alloys are mainly combinations of covalent bonding and metallic bonds. The stress-strain method and Voigt–Reuss–Hill approximation were used to calculate the elastic constants and moduli, respectively. Fe_(2.5)Mn_(0.5)Al has the highest bulk modulus, 234.5 GPa. Fe_(1.5)Mn_(1.5)Al has the highest shear modulus and Young's modulus, with values of 98.8 GPa and 259.2 GPa, respectively. These Fe–Mn–Al alloys display disparate anisotropies due to the calculated different shape of the three-dimensional curved surface of the Young's modulus and anisotropic index. Moreover, the anisotropic sound velocities and Debye temperatures of these Fe–Mn–Al alloys were explored.     

Effects of alloying element on stabilities,electronic structures,and mechanical properties of Pd-based superalloys

The thermodynamic stabilities, electronic structures, and mechanical properties of the Pd-based superalloys are studied by first principles calculations. In this work, we discuss the effect of Pd-based superalloys made from Al, Si, Sc, Ti,V, Cr, Mn, Fe, Cu, Zn, Y, Zr, Nb, Mo, Tc, Hf, Ta, W, Re, Os, Ir and Pt, and we also calculate a face centered cubic(fcc)structure 2 × 2 × 2 superalloy including 31 Pd atoms and one alloying element T M(Pd_(31)TM). The mixing energies of these Pd-Based superalloys are negative, indicating that all Pd-based superalloys are thermodynamically stable. The Pd_(31)Mn has the lowest mixing energy with a value of-0.97 eV/atom. The electronic structures of the Pd-based superalloys are also studied, the densities of states, elastic constants and moduli of the mechanical properties of the Pd-based superalloys are determined by the stress-strain method and Voigt–Reuss–Hill approximation. It is found that Pd_(31)TM is mechanically stable, and Pd_(31)Tc has the largest C_(11), with a value 279.7 GPa. The Pd_(31)Cr has the highest bulk modulus with a value of299.8 GPa. The Pd_(31)Fe has the largest shear modulus and Young's modulus with the values of 73.8 GPa and 195.2 GPa,respectively. By using the anisotropic index, the anisotropic mechanical properties of the Pd_(31)T M are discussed, and threedimensional(3 D) surface contours and the planar projections on(001) and(110) planes are also investigated by the Young modulus.