Y. YU
,
X.X. Pan
,
Y.H. Rong
金属学报(英文版)
To simulate the mechanical behavior of the FCC crystal with the lower Peierls stress, the stiff property and physical meaning of the differential equation group consisted of dislocation evolution and mechanical state based on the 3-D discrete dislocation dynamics, the results indicate that the differential equation group is serious stiff, namely the external stress changes more quickly than dislocation evolution. Using the established numerical algorithm, we simulate the mechanical behavior of FCC crystal with the dislocations located in the parallel slip planes, and discuss the effect of strain rate on the dislocation configuration and mechanical behavior, and the saturation process of mobile dislocation. The simulation results indicate that our numerical algorithm can efficiently simulate the dislocation dipole and the low strain rate loading.
关键词:
FCC crystal
,
null
,
null
,
null
盛毅
,
张彩红
,
徐耀
,
吕春祥
,
吴刚平
,
吴忠华
,
李志宏
新型炭材料
利用二维小角X射线散射(2D-SAXS)方法,对PAN基炭纤维全部方位角进行微孔结构的研究.样品选取自制炭纤维MHS及日本东丽公司T300,T800产品.结果表明:MHS炭纤维微孔尺寸介于T300与T800之间,长径比t值小于T300和T800.T300中较小微孔(<9.1 nm)和较大微孔(>15.4nm)的含量大于MHS,T800含有大量的微孔短轴小于2nm的小尺寸微孔.MHS炭纤维的界面复杂程度较T300大,而小于T800.炭纤维内部存在由微孔散射导致的密度波动,其波动振幅F值和波动密度n值按MHS、T300和T800依次递减;电子密度波动越小,表明微孔结构越规整,T800的孔结构最规整.炭纤维内各个取向上均有一定结构的微孔分布,但总体上呈现沿纤维轴方向的定向排列.
关键词:
SAXS
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炭纤维
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孔结构
,
分形维数
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密度波动
马骁
,
白瑞成
,
任慕苏
,
孙晋良
,
秦显营
,
吕永根
材料科学与工程学报
应用二维小角X射线散射技术对PAN原丝、预氧丝、碳化丝纤维样品进行表征并采用Fankuchen切线法处理实验数据,得到微孔的平均结构信息.X射线散射集中在探测器平面赤道方向,原丝、预氧丝样品的散射强度相近并小于碳化丝散射强度,表明PAN基纤维在热处理过程中,纤维内部微孔一直沿纤维轴方向择优取向,在预氧化阶段微孔含量和大小基本保持不变,而在碳化阶段将产生大量微孔,并使微孔取向角增大.散射数据均呈现Porod正偏离,说明纤维内部还存在1nm以下的微结构起伏.
关键词:
碳纤维
,
小角X射线散射
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微孔
王琴
,
梁晓怿
,
吕春祥
,
张睿
,
乔文明
,
詹亮
,
刘鸿鹏
,
凌立成
,
陈中军
,
董宝中
高分子材料科学与工程
采用同步辐射小角X射线散射研究了PAN原丝制备过程中纤维轧结构的演变.结果表明,在水洗工艺中,纤维孔隙较多、较大,孔径分布较宽,近似圆形;在热水牵伸工艺中,纤维孔隙仍较多、较大,孔径分布较宽,近似椭圆形,长轴约17 nm-21 nm.短轴约4 nm～11nm;在干燥致密化工艺中,孔隙急剧减少、减小,孔径分布较窄,沿纤维轴向约7nm～9nm,垂直纤维轴向约2 nm;经过蒸汽牵伸,孔隙又增多、增大,孔径分布变宽,孔隙沿纤维轴向被牵伸得很长,近似梭形;但是随后的松弛热定型又使孔隙减小,孔径分布变窄.
关键词:
聚丙烯腈纤维
,
同步辐射小角X射线散射
,
孔隙结构
材料科学技术（英文）
The structure, specific heat, magnetic and electrical properties of MnTe(1-x)Sb(x) (x=0, 0.1, 0.15, 0.2 and 0.25) alloys have been investigated. The MnTe(1-x)Sb(x) alloys crystallize in a hexagonal NiAs-type structure, and the impurity of MnSb phase appears when x >= 0.15. The MnTe(0.9)Sb(0.1) compound exhibits ferrimagnetic behavior with hysteresis loops even at 350 K, showing that the magnetic properties of MnTe compound are very sensitive to little compositional change. The ferromagnetism in the MnTe(1-x)Sb(x) alloys with higher Sb contents may be attributed to the impurity of MnSb phase. Energy dispersive X-ray spectroscopy analysis on the MnTe(0.9)Sb(0.1) compound indicates that Sb is very difficult to dope into the lattice of MnTe. So the anomaly of resistivity at 300 K of MnTe(0.9)Sb(0.1) and the peak of specific heat around 304 K of all the alloys are thought to be related with the antiferromagnetic interactions of MnTe-based lattice.
关键词:
Electronic transport property;Hysteresis loop;Specific heat;manganese telluride;semiconductors;ferromagnetism;scattering;exchange
Powder Diffraction
The structure transitions and phase relationships of DyFe(3-x)Al(x) compounds have been investigated by X-ray powder diffraction. Our XRD results show that each of the compounds with x <= 0.45 crystallizes in the rhombohedral PuNi(3)-type structure with space group R (3) over barm and Z=9; for the 0.8 <= x<1.0 compounds, each has a hexagonal structure of the CeNi(3) type with space group P6(3)/mmc and Z=6; and each of the samples with 0.45<x<0.8 is a two-phase mixture of the PuNi(3)- and CeNi(3)-type structures. The calculated XRD intensities of the DyFe(3-x)Al(x) compounds with x=0.2, 0.33, 0.4, and 0.45 indicate that Dy occupies the 3a and 6c sites, Fe and Al distribute randomly on the 18h site, and the 3b and 6c sites are exclusively occupied by Fe, which agrees well with those of our experimental XRD patterns. The XRD intensities of the DyFe(3-x)Al(x) compounds with x=0.8 and 1.0 have also been calculated and found to agree with the experimental results with Dy on the 2c and 4f sites, Fe and Al at the 12k site, and Fe at the 2a, 2b, and 2d sites. In the two-phase region with x=0.45-0.8, the values of unit-cell parameters and phase compositions are linearly dependent on the value of x, indicating that the two phases are constituted by the same composition x with different stacking arrangements. This abnormal two-phase equilibrium is further confirmed by the structural analysis of the DyFe(2.33)Al(0.67) (or x=0.67) sample. The samples with x=1.1 and 1.2 were also analyzed, and each found to be a mixture of more than two phases. (C) 2010 International Centre for Diffraction Data. [DOI: 10.1154/1.3507088]
关键词:
X-ray powder diffraction;DyFe(3-x)Al(x) system;structure change;anomalous phase composition;magnetic-properties;intermetallic compounds;al substitution;rare-earth;fe;dy6fe23;refinement;aluminum;dy2fe17;co
Journal of Magnetism and Magnetic Materials
The ingot of Fe-(18-x) at% Ga-x at% Al (3 <= x <= 13.5) alloys was prepared from high purity elements using a high vacuum arc melting system. The X-ray diffraction patterns indicated that the alloys were disordered bcc A2 structure. The magnetostriction of the alloys was measured and the effect of partial substitution of Ga with Al on the magnetostriction of the alloys was investigated. Fe-9 at% Ga-9 at% Al alloy, the optimizing magnetostrictive alloy was found in Fe-(18-x) at% Ga-x at% Al (3 <= x <= 13.5) alloys. The saturated magnetostriction of the directional solidification Fe-9 at% Ga-9 at% Al rod is up to 135 ppm for 0 MPa and 221 ppm for 53 MPa. It was found that the alloy has the high linearity of the magnetostriction curve, the low hysteresis and saturated magnetic field, which suggests the directional solidification Fe-9 at% Ga-9 at% Al alloy is a potential candidate for magnetostrictive actuator and transducer applications. (C) 2010 Elsevier B.V. All rights reserved.
关键词:
Fe-Ga-Al alloy;Magnetostriction;Microstructure;fe-rich portion;phase-equilibria;system;elasticity;stability
Lizhi CHENG
,
Wei FENG
,
Xinquan DONG
,
Kuichang BAI and Kaiyuan HE (Dept. of Materials Science and Engineering
,
Northeastern University Shenyang 110006
,
China)
材料科学技术（英文）
The formation of nonequilibrium phase by mechanical alloying (MA) of Fe and B powders in a high energy vibration ball mill has been made for Fe100-xBx system with x=15. 30, 35, 45,55 and 70. By using the X-ray diffraction, magnetic measurement and M6ssbauer spectrummethods, it was revealed that the structure of the MA product varies with milling time and B contents.
关键词:
Physical Review B
NdCo(12-x)V(x) (2.2 <= x <= 2.6) crystallizes in the ThMn(12)-type structure and exhibits an unusual jump in the magnetization at a critical field B(C) that decreases with increasing V content. It was intriguing that the magnetization of the bulk samples below B(C) was very close to that of YCo(12-x)V(x) with the same V content. To investigate the nature of the magnetic order in these materials we have carried out powder neutron diffraction measurements as a function of temperature and magnetic field on the NdCo(9.5)V(2.5) composition. In zero field we find that both the Nd and Co ions have substantial ordered moments (similar to 2.9 and 0.4 mu(B), respectively) at low temperature (4 K), with the moments coupled ferromagnetically (T(C)=180 K) and aligned along the c axis. On a loose powder an applied field of 4 to 7 T rotates the particles so the c axis aligns with the field, indicating a strong uniaxial anisotropy that renders the system Ising-like. However, we find the same in-field magnetic structure and essentially the same values for the saturated magnetic moments as those in zero field. Magnetization data on magnetically prealigned samples reveal that for fields applied parallel to the (easy) c axis the magnetization saturates below 0.5 T at a magnitude that is in very good agreement with the moments determined from neutron diffraction. For fields applied perpendicular to the c axis, on the other hand, the magnetization data show a two-plateau behavior, explaining the original magnetization data on randomly oriented powders. The strong dependence of the magnetization on the direction of the applied magnetic fields indicates an occurrence of the first-order magnetization process due to the competing magnetocrystalline anisotropies of the Nd and the Co sublattices and of the higher-order terms of the anisotropy energy.
关键词:
rare-earth;intermetallic compounds;thmn12 structure;transition;anisotropy;crystal;fe;substitution;ndco9.5v2.5;compound
郭可信
金属学报
<正> X射线在金属学及金属物理这一学科中的应用日益广泛,它已经是从事金属研究的科学工作者所不可缺少的工具.同时,金属X射线学也已经成为一门新的边缘学科分支,是金属学及金属物理专业的必修课程.但是,在这方面,迄今为止尚无一本我国科学工作者编写的教材或参考书,仅有的几种译本亦都有内容贫乏与过时的缺点.因此,许顺生同志著的“金属X射线学”的出版是值得欢迎的.本书的内容范围相当广泛,并且是此较全面的.全书共26章,可以粗略地分五个部分:第一部分(1—5章):基本理论,包括X射线物理及晶体学基础,X射线衍射的几何及强度理论;第二部分(6—10章):各种实验方法,如劳厄、周转晶体、粉末及小角度散射法;第三部分(11—15章):X射线晶体学的一
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