Calculation of cooling rate of amorphous aluminum alloy melt-spun ribbons

Based on the heat transfer theory and liquid solidification theory, the heat transfer during the rapid solidification process of amorphous ribbons prepared by melt spinning was approximately modeled by one-dimensional heat conduction equation. Besides, integration with the temperature gradient, the relationship between the ribbon thickness and solidification time was derived according to the boundary conditions of ribbon-copper wheel. A simply theoretical model was obtained to calculate the cooling rates of aluminum amorphous ribbons. According to the above theoretical model, the critical cooling rate of aluminum amorphous ribbons by melt spinning is above 10^6 K/s, which proves that the aluminum based alloys belong to the marginal glass forming ability of alloys. The calculated results are in good agreement with other estimated values reported previously.     

Mg65Cu25Y10非晶态合金的形成及其晶化行为

采用水淬法制备出厚度为2mm的片状Mg65Cu25Y10非晶态合金,衡量其非晶成形能力的参数过冷液态区域宽度△Tx（△Tx=58.3K）、约化玻璃转变温度Trg（Trg=0.56）均较高,表明此合金具有很强的非晶形成能力;并测出了它的硬度为263.2HV.通过恒速升温和等温晶化试验,采用差热分析、X射线衍射等研究了它的热行为,结果表明,此合金在433K以下还是稳定的,如进一步升高温度,材料将由非晶态结构逐步向晶态结构转变,当退火温度达到623K时,则完全转变为晶态结构.     

Mn含量对Mg2Ni型合金相形成及放电性能的影响

采用按比例混合合金粉末压制成圆柱试样，然后用低温烧结和随后机械球磨的方法制备了非晶态的Mg2Ni型合金。研究了烧结和球磨对不同Mn含量的Mg2Ni型合金的相形成过程及电化学性能的影响。实验表明：在Mg2Ni中采用第三组元Mn对Mg进行适量的替代后，通过烧结及球磨方法可以获得均匀的非晶相；微量替代可有效地提高其放电容量：随替代量的增加，合金最大放电容量和高速放电能力降低，而充放电循环稳定性提高。     

低翘曲玻纤增强PET复合材料的制备和性能研究

依据降低翘曲的机理，选用不同降低翘曲的方法，制备了系列翘曲玻纤增强PET复合材料，结果表明，具有较高形状对称性的填料，如滑石粉，云母粉和玻璃微珠都能不同程度地降低玻纤增强PET体系的翘曲，非晶聚合物也能有效改进该体系的翘曲性能。     

Structure development in amorphous starch as revealed by X‐ray scattering: Influence of the network structure and water content

The evolution of the amorphous structure of starch was characterized during the drying process by real‐time X‐ray wide‐angle scattering. The X‐ray diffractograms of injection‐molded starch show two superposed, rather broad, scattering maxima indicative of noncrystalline structures. The location of the two peaks has been associated to disordered starch single helices. A third maximum that arises upon drying the material in vacuum is associated to the scattering emerging from regions containing double helices. A model for the starch network is proposed, assuming a primary and a secondary component. The wider, temperature stable component appearing first, is correlated to the entanglement network of the melt. The narrower network component, which is created later, at lower temperature (secondary network), is explained by the formation of double helix regions that densify the wider primary network. The secondary network is increased strongly by the drying process. X‐ray experiments performed during the penetration of water, provoking a higher molecular mobility, reveal a better‐packed helical structure that becomes the precursor of a double helix crystalline formation. When temperature increases, the secondary network is dissolved and water molecules arrange themselves in better‐organized crystals as strongly bound crystal water. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1880–1886, 2006     

非晶态化学镀Ni-Sn-P合金镀层变温晶化的研究

研究了非晶态Ni-Sn-P合金镀层的变温化过程,由实验得出Ni-Sn-P合金约在350℃开始晶化,450℃左右晶化结束,并测得Ni-Sn-P合金变温晶化激活能为233KJ·moL~(-1)。     

非晶态NiB配位催化2-亚丁基环己酮的选择加氢动力学研究

以超细非晶态NiB为催化剂、乙醇为溶剂 ,研究了常压条件下 2 -亚丁基环己酮的选择催化氢化反应。确定了反应对 2 -亚丁基环己酮的反应级数n =1,80℃下准一级反应的速率常数为k =3.4× 10 -3 min-1。同时考察了氢化过程中外扩散的影响以及温度、催化剂用量对反应的影响。求得反应的活化能Ea =16 .391kJ/mol。     

电沉积非晶态合金镀层磁性的控制

磁性元件薄膜化促进了磁性镀层的开发与应用。综述了镀液及镀层成分、电沉积工艺、镀层厚度及热处理对电沉积非晶态镀层性能的影响，以便在实际应用中控制非晶态合金镀层的磁性。     

金属铝诱导法低温制备多晶硅薄膜

以氢气稀释的硅烷（SiH4）和硼烷（B2H6）为气源,利用等离子体增强化学气相沉积法（PECVD）制备出p型a-Si薄膜.采用铝诱导晶化技术对不同厚度的铝膜对a-Si薄膜晶化的影响进行了研究.实验中发现,铝膜溅射为10 s的非晶硅薄膜样品在450℃下退火10 min后,p型a-Si结构仍为非晶态,铝膜溅射为20 s的非晶硅薄膜在450℃下退火20 min后,p型a-Si薄膜开始晶化为polySi薄膜,并且铝膜厚度越厚,则a-Si薄膜晶化程度越强.     

Shape memory polymers based on uniform aliphatic urethane networks

Aliphatic urethane polymers have been synthesized and characterized, using monomers with high molecular symmetry, to form amorphous networks with very uniform supermolecular structures, which can be used as photo‐thermally actuable shape memory polymers (SMPs). The monomers used include hexamethylene diisocyanate (HDI), trimethylhexamethylenediamine (TMHDI), N,N,N′,N′‐tetrakis(hydroxypropyl)ethylenediamine (HPED), triethanolamine (TEA), and 1,3‐butanediol (BD). The new polymers were characterized by solvent extraction, NMR, XPS, UV/VIS, DSC, DMTA, and tensile testing. The resulting polymers were found to be single phase amorphous networks with very high gel fraction, excellent optical clarity, and extremely sharp single glass transitions in the range of 34–153°C. Thermomechanical testing of these materials confirms their excellent shape memory behavior, high recovery force, and low mechanical hysteresis (especially on multiple cycles), effectively behaving as ideal elastomers above T_g. We believe these materials represent a new and potentially important class of SMPs, and should be especially useful in applications such as biomedical microdevices. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007