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1.
聚丙烯腈原丝聚集态结构的长周期特征 总被引:1,自引:0,他引:1
采用小角X射线散射方法,通过模型计算将散射信号中聚丙烯腈(PAN)原丝长周期结构与微孔结构信息有效分离,建立了用小角X射线散射(SAXS)研究PAN纤维聚集态结构长周期特征结构的方法。通过对原丝湿法成型过程中的长周期特征结构演变的研究发现,PAN制备过程中凝固阶段纤维形成两相准晶体系,晶区和非晶区交替排列形成长周期结构,通过相关函数分析获得了PAN中准晶区、非晶区以及两相过渡层的统计尺寸信息,并结合广角X射线衍射数据讨论了凝固相分离过程和牵伸外场因素对长周期结构的影响。 相似文献
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利用小角X射线散射技术研究了淬火态Fe-Ni-Co-Al-Cu-Ti永磁合金在800℃保温不同时间时析出相的尺寸和比表面积的变化。初步分析了固溶淬火中形成的析出相的形状。揭示了析出相保温过程中的长大规律。 相似文献
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应用小角X射线散射技术确定了二元Al-2.70%Li合金在443-473K温度范围内的回火析出相长大激活能。 相似文献
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采用X射线小角散射方法,应用D/max2550型衍射仪,测量了国产高强炭纤维中的微孔为非单一尺寸散射体系,以及实验时选择不同的散射角范围,计算微孔尺寸时采用不同的微孔形状模型等因素,是导致不同实验者测得的微孔尺寸结果一致性不好的主要原因。 相似文献
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本文对几种稀土Al-Zn-Mg-Cu合金的小角X射线散射强度进行了分析,试验结果表明,在超塑变形过程中,合金中的微空洞产生的越多,材料的延伸率越好,稀土的含量对合金的超塑性也有一定的影响。 相似文献
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对不同成分(主要是钼含量不同)的油井管用调质态28CrMo钢的微观组织进行研究,采用物理化学相分析技术研究了碳化物析出相的类型、含量及结构,并用X射线小角散射分析碳化物析出相的粒径分布,研究了碳化物的溶解、析出规律及合金元素在基体与各相间的分配,探讨了它们同性能之间的关系,进而为合理的工艺制度的建立提供了理论依据。结果表明:碳化物类型为M_3C和MC型,颗粒尺寸在10~140 nm范围占80%以上,抗回火性能的差异由碳化物相中的Mo_3C和VC决定。 相似文献
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采用旋铸急冷工艺在大气环境中制备出(Ni0.75Fe0.25)78-xNbxSi10B12(x=0,5)非晶合金带材.X射线衍射(XRD)分析表明样品为完全非晶态.用差热分析仪(DTA)在高纯氩气保护下测量了非晶薄带的Tg、Tx、Tm,并分析了其热稳定性.根据DTA结果分析表明,(Ni0.75Fe0.25)78Si10B12非晶合金退火温度为695,715,745和765K,在715和745K退火时,非晶基体上析出了单一的γ-(Fe, Ni)固溶体,平均晶粒尺寸分别约为10.3和18.5nm;765K退火后的结晶相为γ-(Fe, Ni)固溶体,Fe2Si,Ni2Si和Fe3B.(Ni0.75Fe0.25)73Nb5Si10B12非晶合金的退火温度为720,750和800K,退火后不能在非晶基体上析出单一的晶化相,晶化析出相为γ-(Fe, Ni)固溶体,(Fe, Ni)23B6,Ni31Si12和Nb2NiB0.16. 相似文献
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Junming LIU 《材料科学技术学报》1998,14(3):193-199
Phase decomposition in amorphous Cu12.5Ni10Zr411Ti14Be22.5 alloy as annealed in the super-cooled liquid range was studied by applying small angle neutron scattering (SANS). As annealed between 600 K and 700 K, the alloy was observed to decompose into two new amorphous phases,with the second phase precipitates embedded in the matrix of the first. Long time annealing of the alloy results in crystallization in addition to evolution of the decomposed microstructure.The kinetic diagram of the decomposition and crystallization for this alloy is given. The second phase precipitates have several nanometers in size and occupy a quite low volume fraction. The decomposition of the supercooled liquid in overall temperature range exhibits the features of spinodal reaction. 相似文献
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Kozo Osamura Kazuhisa Shibue Paul Hideo Shingu Yotaro Murakami 《Journal of Materials Science》1979,14(4):945-952
The change in structure of an amorphous Fe-P-C alloy during ageing was examined using small-angle X-ray scattering (SAXS) measurement and transmission electron microscopy. The SAXS intensity was related to two different types of scattering regions depending on ageing time and temperature. The major scattering was from the crystalline particles, which had two-phase lamella structures. The average thickness of the lamellae remained constant at about 5 nm during ageing. The interlamella distance was three to five times the lamellar thickness in the regular packing region. Another minor scattering was interpreted as being caused by the local ordering of atomic configuration in the amorphous state. The average size of the scattering region was 1.8 to 2.4 nm and quite similar to the critical range proposed by Giessen and Wagner, beyond which the shortrange order disappears. 相似文献
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Weber CH Chiche A Krausch G Rosenfeldt S Ballauff M Harnau L Göttker-Schnetmann I Tong Q Mecking S 《Nano letters》2007,7(7):2024-2029
We present a complete analysis of the structure of polyethylene (PE) nanoparticles synthesized and stabilized in water under very mild conditions (15 degrees C, 40 atm) by a nickel-catalyzed polymerization in aqueous solution. Combining cryogenic transmission electron microscopy (cryo-TEM) with X-ray scattering, we demonstrate that this new synthetic route leads to a stable dispersion of individual PE nanoparticles with a narrow size distribution. Most of the semicrystalline particles have a hexagonal shape (lateral size 25 nm, thickness 9 nm) and exhibit the habit of a truncated lozenge. The combination of cryo-TEM and small-angle X-ray scattering demonstrates that the particles consist of a single crystalline lamella sandwiched between two thin amorphous polymer layers ("nanohamburgers"). Hence, these nanocrystals that comprise only ca. 14 chains present the smallest single crystals of PE ever reported. The very small thickness of the crystalline lamella (6.3 nm) is related to the extreme undercooling (more than 100 degrees C) that is due to the low temperature at which the polymerization takes place. This strong undercooling cannot be achieved by any other method so far. Dispersions of polyethylene nanocrystals may have a high potential for a further understanding of polymer crystallization as well as for materials science as, e.g., for the fabrication of extremely thin crystalline layers. 相似文献
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JingchengWANG FuqiangYOU JunlinYIN GuohuaGAO 《材料科学技术学报》2001,17(4):482-484
An amorphous alloy with Ni-(17~19) at. pct P prepared by electrodeposition process was studied using positron annihilation technique (PAT) associated with X-ray diffraction and the measurement of corrosion rate. It is suggested that defect or the interface between precipitates and matrix is one of the important factors which decrease corrosion resistance of the alloy after crystallization. 相似文献
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Peggy Cebe 《Journal of Materials Science》1988,23(10):3721-3731
Annealing of poly(etheretherketone), PEEK, has been studied for two materials cold crystallized from the rubbery amorphous state. The first material is a low molecular weight PEEK synthesized in our laboratory; the second is commercially available neat resin. Differential scanning calorimetry was used to monitor the melting behaviour of annealed samples. The effect of thermal history on melting behaviour is very complex and depends upon annealing temperature, residence time at the annealing temperature, and subsequent scanning rate. Thermal stability of both materials is improved by annealing, and for an annealing temperature near the melting point, the polymer can be stabilized against reorganization during the scan. Variations of density, degree of crystallinity, and X-ray long period were studied as a function of annealing temperature for the commercial material. Wide angle X-ray scattering was used to study the structure of annealed PEEK. An additional scattering peak was observed at higher d-spacing when annealed samples were cooled quickly. 相似文献
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B. Rashkova W. Prantl R. Grgl J. Keckes S. Cohen M. Bamberger G. Dehm 《Materials Science and Engineering: A》2008,494(1-2):158
The microstructural evolution of a Mg–Zn–Sn alloy was studied by combining X-ray diffraction (XRD), small angle X-ray scattering (SAXS), and transmission electron microscopy (TEM) in order to determine the individual phases, their size and volume fraction of the alloy. Solutionized and aged samples are analysed in detail concerning the nucleation, growth, morphology, and stability of precipitate phases. In the aged samples, firstly MgZn2 particles with a rod-like shape form, and secondly plate-like MgSn2 precipitates. The MgZn2 phase shows a well-defined orientation relationship with the Mg matrix. The formation of two types of precipitates is responsible for the occurrence of two pronounced hardness maxima. The growth behaviour of the MgZn2 phase is determined by combining TEM and SAXS measurements and the results are compared to the Lifschitz–Slyozov–Wagner (LSW) theory. 相似文献
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The structure of a Fe90Zr10 amorphous alloy was investigated by means of small angle X-ray scattering as well as large-angle diffraction measurements. For as-quenched specimens, SAXS was found to be relatively weak, but spread over a wide scattering angle. After quantitative analysis, it was concluded that a compositional fluctuation occurs on a fine scale of about 0.6 nm. When the specimen was heat treated below the crystallization temperature, the amorphous structure changed to a more stable dual structure consisting of pure iron and a structure similar to Fe3Zr. By prolonged heat treatment, the iron-rich regions crystallized initially from the amorphous state. An apparent correspondence was found to exist between the changes in the amorphous structure and in the mechanical properties. The microscopic phase separation within the amorphous state resulted in an increase of ultimate tensile strength and fracture toughness. The deterioration of mechanical properties was suggested to be attributed to the gradual crystallization of iron-rich regions. 相似文献
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Electro-spark deposition of Fe-based amorphous alloy coatings 总被引:3,自引:0,他引:3
A simple and effective surface coating technique, electro-spark deposition (ESD), has been used to produce amorphous alloy coatings. Fe-Cr-Mo-Gd-C-B amorphous alloy rods produced by copper mould casting were used as electrode to produce coatings onto 304 stainless steel substrate. Classical X-ray diffraction (XRD), glancing angle XRD (GAXRD), and scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis indicate that the coatings have an average thickness of ∼ 30 μm, show an amorphous structure, and are metallurgically bonded to the substrate. Microhardness tests showed that the coating layer has a high hardness of 1542 kg/mm2, implying a much improved wear resistance on surface of stainless steels. 相似文献
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B. Hammouda S. Krueger C. J. Glinka 《Journal of research of the National Institute of Standards and Technology》1993,98(1):31-46
The small angle neutron scattering technique is a valuable method for the characterization of morphology of various materials. It can probe inhomogeneities in the sample (whether occurring naturally or introduced through isotopic substitution) at a length scale from the atomic size (nanometers) to the macroscopic (micrometers) size. This work provides an overview of the small angle neutron scattering facilities at the National Institute of Standards and Technology and a review of the technique as it has been applied to polymer systems, biological macromolecules, ceramic, and metallic materials. Specific examples have been included. 相似文献