X射线线形的解卷分析与Bragg角的精确计算

采用解析函数模拟X射线线形, 在排除实验测试误差影响的条件下, 研究仪器宽化修正过程中各种因素如Kα双线、线形宽度和原点选取等对傅里叶系数和真实线形的影响;分析了从傅里叶系数或真实线形分离晶粒尺寸和微观应变的可靠性; 提出了无任何假设的前提下, 由实测线形的解卷计算求得精确Bragg角的方法. 关键词： X射线线形 傅里叶变换 真实线形 Bragg角     

机械球磨硒非晶化的XAFS研究

利用低温EXAFS和XANES方法研究了晶态Se在机械球磨过程中的结构变化—结果显示在球磨过程中引入链状分子间的中程无序，破坏了分子间的结合，而分子内Se原子以共价键结合，不易被打破．     

纳米孪晶纯铜的强度和导电性

强度和导电性是金属材料的两个至关重要的性能．常用的金属材料强化方式往往是在提高强度的同时使材料的导电性能明显损失，文章介绍了采用脉冲电解沉积技术制备出具有高密度孪晶片层结构的纯铜薄膜．这种具有纳米尺度的孪晶片层结构的纯铜材料不仅具有非常高的拉伸强度，同时还具有非常高的导电性．拉伸实验表明，当孪晶片层平均厚度小到15nm时，样品的拉伸屈服强度可达900MPa，断裂强度高达1068MPa(约为普通纯铜的10倍以上)，并具有与无氧高导铜相当(97％IACS)的室温电导率．     

金属纳米晶体的界面热力学特性

根据准协德拜近似从理论上计算了金属纳米晶体的界面热力学特性,包括界面过剩能、过剩焓、过剩熵、过剩Gibbs自由能等,着重讨论了界面过剩热力学参量与界面过剩体积和温度的关系.一些实验测量结果表明,理论计算与实验结果基本相符. 关键词：     

NUCLEATION AND GROWTH ACTIVATION ENERGIES DURING CRYSTALLIZATION OF AMORPHOUS ALLOYS (Ⅰ)——CALCULATION METHOD

A new method is developed for the determination of activation energies for nucleation(E_n) and for growth of nuclei (E_g) during crystallization of amorphous alloys. This methodis based on the crystallization kinetics theory and the experimental results of the variationrelationships of local activation energy E_c(x) and local Avrami exponent n(x) with the crys-tallized volume fraction (x) during crystallization of an amorphous Ni--P alloy. Calculationresults of E_n and E_g in tbe case of crystallization of the amorphous Ni--P alloy by thismethod show that this method is not only simple in the experimental procedures, but alsoaccurate in the quantitative results.     

ELECTRICAL RESISTIVITY OF NANOCRYSTALLINE Fe-Cu-Si-B ALLOYS

We have studied the room temperature and low-temperature electrical resistivities of nanocrystalline Fe-Cu-Si-B alloys with various grain sizes prepared by crystallization of amor-phous material. Experimental results showed that with the reduction of grain size both room temperature resistivity ρ_RT and residual reaistivity ρ₀ of the nanostructured alloys studied increased significantly. Based on the scattering effects from interfaces and lattice distortion, the above results were qualitatively discussed.     

受约束纳米铅薄膜的过热

利用叠层轧制的方法制备出夹在铝中的纳米铅薄膜,厚度约20nm,部分铅薄膜与铝基体形成外延取向关系,对此纳米铅薄膜溶化的原位X射线研究表明,部分铅薄膜的熔化温度超过普遍块体材料,首次实现了金属薄膜的过热。     

非晶态Se向纳米晶体Se的转变

采用水淬法制备出块状非晶态硒,通过非晶晶化法获得了六方晶型结构的、晶粒尺寸为6—45nm的块状纳米晶硒,X射线衍射及热分析研究表明非晶态硒向纳米晶硒的转变是由一步晶化完成的,激活能为54—60kJ/mol.并证实了非晶硒的短程序与六方晶型硒相同以及非晶硒的无规线团结构.根据不同方向的晶粒尺寸与晶化温度的关系,发现沿c轴的生长速率大于沿a轴的生长速率.采用无规线团形的分子链在晶界处折叠或延伸到相邻晶粒中的晶化机制解释了晶化过程中激活能低和生长速率沿c轴方向较大的实验结果. 关键词：     

非晶态合金晶化过程中的形核及核长大激活能——Ⅱ.与非晶态结构和温度的关系

本文利用第一部分提出的计算形核及核长大激活能(E_n和E_g)的方法分别测算了预退火热处理后非晶态Ni-P合金样品以及在不同温度区间内激冷非晶态Ni-P合金样品的E_n和E_g值.结果表明E_n和E_g值与非晶态合金微观结构和温度有密切的关系,非晶态合金有序程度越高,E_n和E_g值越小;晶化时的温度越高,E_n和E_g值越大.运用新近提出的晶化微观机制对这种用经典晶化机制难以解释的实验现象进行了合理的解释.     

NUCLEATION AND GROWTH ACTIVATION ENERGIES DURING CRYSTALLIZATION OF AMORPHOUS ALLOYS (Ⅱ)——RELATIONSHIP BETWEEN MICROSTFUCTURE OF AMORPHOUS STATE AND TEMPERATURE

By using the new method for determination of activation energies for nucleation andgrowth (E_n & E_g) developed in Part Ⅰ of this work, the E_n and E_g of some pre--annealedamorphous Ni--P alloys, as well as those of the as--quenched Ni--P glass within differenttemperature ranges are measured and studied. The results show that the values of E_n and E_gare closely related to the microstructure of amorphous alloys and the annealing temperature.The higher the ordering in the amorphous alloys, the smaller the values of E_n and E_g; thehigher the annealing temperature, the greater the E_n and E_g values. By means of the newlydeveloped crystallization micromechanism, such an experimental phenomenon which is diffi-cult to understand from the classical crystallization mechanism is reasonably explained.