金属直接氧化过程中的镁挥发机制

研究发现Al Mg Si合金直接氧化时存在层状Al/Al2 O3 复合结构 ,揭示了直接氧化过程的本质特征 ,证实了Mg挥发对直接氧化过程的重要作用 ,提出了Mg挥发机制并据此讨论了已有研究中尚未解决的几个重要问题。     

Ti-45Al合金的定向凝固组织

采用区域重熔定向凝固技术制备了Ti-45Al合金定向凝固试样,研究了不同参数下的凝固组织。结果表明,该合金在定向凝固过程中一次凝固可以以胞晶形式实现定向生长,胞晶内α2/γ片层方向与生长方向成45°或90°。凝固过程中稳定相β及亚稳相α同时存在,并以胞状生长,存在竞争而引起的交替现象。降速生长时定向组织比较理想。淬火实验表明,在大过冷度下亚稳α相作为领先相析出。     

脂质分子通过自组装合成不同形貌的介孔材料

主要描述了通过氨基酸分子自组装来制备四种不同形貌的介孔硅材料,并通过常用的检测仪器：电子显微镜进行结构解析。已经发现：（1）通过改变反应温度从0,10,15到20℃,可以制备得到不同形貌的介孔材料,即类似于蛋白质分子的螺旋飘带,空心球,飞碟状和手性棒状形貌的二氧化硅介孔材料;（2）在螺旋飘带和空心球形貌材料中介孔孔道排列是无序的,而在飞碟和手性棒状材料中介孔孔道是高度有序排列的;（3）螺旋飘带形貌的材料是纯左手的,而手性棒状形貌的材料是右手过剩的介孔材料。该研究将为在分子水平合成手性材料提供一种新的方法。     

化学沉淀-局部规整法制备棒状及片状BaFe12O19

以针状-γFeOOH为原料,采用化学沉淀-局部规整法制得棒状及片状BaFe12O19。通过控制搅拌速率调变γ-FeOOH的长径比和结晶有序程度,得到结晶有序程度较低但长径比为8～10和结晶有序程度较高但长径比为2～5的棒状BaFe12O19。受形成历程影响,900℃焙烧条件下所得BaFe12O19中含有少量α-Fe2O3和BaFe2O4杂相。前驱体加入少量NaCl,由于其起到提高γ-Fe2O3相变温度和助熔剂的双重作用,前驱体900℃焙烧物为纯相且结晶有序程度较高的BaFe12O19,且颗粒呈明显的二维近六角片状.     

温液固法制备纳米磷酸锌及其表征

用氧化锌、磷酸、氨水等为原料,室温下合成纳米级磷酸锌.该方法制备得到的磷酸锌,经XRD和TEM表征为纳米级片状晶体,产品粒径30～40nm.     

Influence of glycols on the formation of lamellar liquid crystals with an anionic surfactant,oleic acid,and water

The influence of glycol structures on the formation of lamellar liquid crystals with the physical appearance of transparent gels in formulations composed of an anionic surfactant, oleic acid, and water was investigated. The glycols studied belong to alkyl derivatives of ethylene glycol and diethylene glycol. The relationships between the ingredients of the so-called basic compositions—surfactant, oleic acid, and glycol—were optimized to form transparent gels when diluted with water. The ranges in which transparent gels existed were compared for the systems with different glycols. The most suitable glycols, as defined by the lowest surfactant content in the final transparent gels, were ethylene glycol methyl ether and especially methyl and ethyl derivatives of diethylene glycol. Formulations with 2–3% surfactant could be prepared with these glycols. These data were correlated with the polarity of the glycol structures described by means of log P (octanol/water partition coefficient). Transparent gel formation occurred for log P values ranging from approximately 0.5 to −0.5, whereas liquid crystal formation did not result from higher or lower values.     

聚苯胺/HNb_3O_8纳米复合材料合成及电化学性质研究

聚苯胺(PANI)/HNb3O8层状纳米复合材料通过原位聚合的方法合成,苯胺/HNb3O8插层型化合物作为前驱体。根据实验结果分析,苯胺插层到HNb3O8内层空间形成双相的苯胺/HNb3O8插层型化合物——单层和双层苯胺分子排列方式。通过聚合后,聚苯胺分子以单层方式排列在层间。实验得到的PANI/HNb3O8层状纳米复合材料通过XRD,SEM和IR表征,通过电化学修饰电极研究表明,复合材料具有很好的氧化还原活性和稳定性。     

A Study on the Relationship Between the Crystal Structure and Hard Elasticity of PVDF Fibers

Summary: Poly(vinylidene fluoride) (PVDF) fibers were prepared by melt-spinning process. The crystal structure of annealed PVDF fibers was characterized by wide- and small-angle X-ray diffraction (WAXD and SAXD) and scanning electron microscopy (SEM). Crystalline reflections of c-axis orientation of annealed PVDF fibers were illustrated by WAXD pattern. The stacked lamellar structure aligned in the direction normal to the fiber axis was found in SAXD pattern and the d-spacing of the lamellae was 13.4 nm. Such lamellar structure was supported by SEM micrographs as well. The elastic recovery of annealed PVDF fibers was above 80% from 50% extension, which was much higher than that of unannealed fibers on the first cycle. The initial elastic modulus of annealed fibers reached to a value of 3.5 GPa. The morphological and mechanical properties, all indicated that the annealed PVDF fibers had the characteristic of hard elasticity. A typical stress-strain curve at a very low strain rate indicated the deformation of crystal lamellae in the fibers and a suggested structural deformation mechanism detailed the characteristics of hard elasticity.

Cyclic loading to 50% extension of annealed PVDF fibers.     

轴承钢珠光体球化的研究现状及发展趋势

概述了轴承钢球化退火在轴承生产中的作用,分析了珠光体由片层状转变为颗粒状的变化规律,讨论了片层渗碳体的打断、短棒状向颗粒状转变以及颗粒状熟化长大的热力学机制。结果认为珠光体球化工艺的不足,一是存在碳化物分布不均匀、尺寸大小存在差异等问题;二是退火工艺固定化、格式化等问题,未能适应轴承钢的发展;三是球化退火后的组织检验粗糙化、不够细致。球化工艺的发展趋势,一是要在轧钢或锻压生产阶段通过引入塑性变形或增大冷却过冷度等方法来保证片层组织更加均匀、细化,无网状渗碳体;二是要开发新的球化工艺,例如在有可能的条件内引入电场、磁场以及高温高压应力场等方法来改善球化工艺;三是要将球化组织的定量化检验标准化。     

TC21钛合金的全片层组织和冲击性能研究

利用光学显微镜、场发射扫描电镜和示波冲击试验机等研究了TC21钛合金在不同退火温度下的全片层组织演化规律和冲击韧性。结果表明:TC21钛合金经980℃固溶处理后,再经720、770、820℃退火处理,均能获得具有多层次特征的全片层组织。随着退火温度升高,TC21钛合金组织中α片层厚度、晶界α相厚度、α丛域尺寸都增大,而β晶粒尺寸基本保持不变。合金显微组织中小角度界面的比例随退火温度的升高而逐渐增加,冲击断裂过程中的裂纹形成功和扩展功也逐渐增大,且扩展功所占比例提高;断裂机制从穿晶断裂为主逐渐向沿晶界和丛域界断裂为主转变。