聚丙烯腈基碳纤维原丝在纺丝过程中纳米孔变化规律与机理研究

应用小角X射线散射等方法, 系统、定量地测试表征了聚丙烯腈基碳纤维原丝中纳米孔的尺寸、形状、体积分数、单位体积中纳米孔绝对数量以及纤维总孔洞率等形态结构参量, 并对这些参量在水洗、水洗牵伸、热致密化、高压蒸汽牵伸及热稳定化等工艺过程中的变化规律及原因进行了研究. 结果表明, 纺丝过程中牵伸及高温热处理均可使纤维总孔洞率逐步下降. 纳米孔尺寸体积分数V_i测试表明, 对于小于10 nm³的小纳米孔和大于10³ nm³的较大纳米孔, 两者的V_i在纺丝初期水洗牵伸工艺中分别为0.217和0.369, 而在纺丝后期热稳定化处理后发生大幅度改变, 分别为0.948 与0.015. 其原因并不是在高压蒸汽牵伸及热稳定处理中较小纳米孔含量的增加, 而是较大纳米孔含量的大幅度减少. 纳米孔形状研究表明, 纺丝工艺中的多次牵伸处理均使纳米孔的长短轴比加大, 而大于玻璃化温度的热处理均使纳米孔长短轴比收缩, 并且对于较小纳米孔来说这种收缩更为显著.     

Al-Li合金时效-回归-再时效析出δ′相的行为

应用小角X射线散射技术研究二元Al-Li(Li的质量分数为2.70%)合金时效-回归-再时效析出δ′相的行为.发现再时效8h析出的δ′相与基体之间存在明显的过渡界面层,再时效16h以后过渡界面层消失.表明δ′相粒子的长大首先是吞噬过渡界面层长大,然后是互相吞并长大. 关键词： Al-Li合金 时效－回归－再时效 过渡界面层     

NiTi合金的第一性原理研究

采用第一原理平面波方法,计算了NiTi合金B2相的体相性质,如晶格常数,形成能和结合能,弹性常数,计算的结果和实验数据以及别人的计算结果符合得很好.其次,计算了NiTi(100),(110)表面的几何结构和电子结构,计算结果表明,(100)表面具有表面振荡现象,(110)表面产生了表面波纹,最外层的Ti原子相对理想表面向真空层移动了0.198?,Ni原子向表面内移动了0.122?.比较表面的电子结构,NiTi(100)表面Ti端位较Ni端位更容易发生反应,而(110)表面较体相更稳定. 关键词： NiTi 第一性原理 电子结构 表面     

小角x射线散射确定TiNi薄膜中晶化粒子的长大激活能

用小角x射线散射技术研究以直流磁控溅射方法制备TiNi合金薄膜其退火生成的晶化粒子的长大行为.发现在室温下溅射的TiNi合金薄膜存在小于1nm尺寸的微空洞,将退火后薄膜的小角x射线散射强度扣除退火前微空洞产生的小角x射线散射强度,用这种方法得到的散射强度遵从Porod定律;而用通常方法扣除背底得到的散射强度结果不满足Porod定律.TiNi合金薄膜在733—793K之间退火晶化粒子的长大激活能Eg=301kJmol. 关键词： TiNi薄膜 晶化粒子 长大激活能     

Grain size and its distribution in NiTi thin films sputter-deposited on heated substrates

Grain size and its distribution in NiTi thin films sputter-deposited on a heated substrate have been investigated using the small angle x-ray scattering technique. The crystalline particles have a small size and are distributed over a small range of sizes for the films grown at substrate temperatures 370 and 420℃. The results show that the sizes of crystalline particles are about the same. From the x-ray diffraction profiles, the sizes of crystalline particles obtained were 2.40nm and 2.81nm at substrate temperatures of 350 and 420℃, respectively. The morphology of NiTi thin films deposited at different substrate temperatures has been studied by atomic force microscopy. The root mean square roughness calculated for the film deposited at ambient temperature and 420℃ are 1.42 and 2.75nm, respectively.     

Small-angle x-ray scattering study of the formation and growth of δ' in binary Al－7.87at% Li alloy

The formation and growth of δ' particles in an alloy of Al－7.87at% Li have been investigated using the small angle x-ray scattering technique. It has been shown that a transition zone, which exists between the δ' phase and the matrix after ageing for 16 h, disappears after ageing for 32 h. The existence of a transition zone indicates that the δ' phase is precipitated in the process of spinodal decomposition. This result also indicates that the growth of δ' particles should be divided into two stages. During the first stage, the δ' phase increases eating up the transition zone before ageing for 32 h, and in the second stage it grows by swallowing up each other after ageing for 32 h. In the latter stage, the larger and smaller δ' particles can coexist in the alloy.     

NiTi合金薄膜厚度对相变温度影响的X射线光电子能谱分析

采用X射线衍射和X射线光电子能谱实验手段对不同厚度的NiTi薄膜相变温度的变化进行了分析.结果表明在相同衬底温度和退火条件下,3?μm厚度的薄膜晶化温度高于18?μm厚度的薄膜.衬底温度越高,薄膜越易晶化,退火后薄膜奥氏体相转变温度As越低.薄膜的表面有TiO₂氧化层形成,氧化层阻止了Ni原子渗出;膜与基片的界面存在Ti₂O₃和NiO.由于表面和界面氧化层的存在,不同厚度的薄膜内层的厚度也不同,因而薄膜越薄,Ni原子的含量就越高.Ni原子的含量的不同会影响薄膜的相变温度. 关键词： NiTi合金薄膜 X射线衍射 相变 X射线光电子能谱