材料期刊网

MORPHOLOGY AND ORIENTATION CHARACTERISTICS OF DIRECTIONALLY SOLIDIFIED α(A1)-Mg_2Si EUTECTIC

S.P. Li , S.X. Zhao , M.X Pan , D.Q. Zhao , and X.C.Chen (Institute of Physics , Chinese Academy of Sciences , Beijing 100080 , China)

金属学报(英文版)

Dependence of the morphology of α(Al)-Mg2Si eutectic on the solidification velocity, and its orientation characteristics were investigated by thermoanalysis, directional solidification and electron diffraction techniques in this study.The eutectic morphology transformed from lamellae to rods with the increasing of the solidification velocity. Simultaneously, the orientation relationship changed from (100)Mg2Si/(100)Al;[110]Mg2si/[110]al to (011)Mg2si/(121)Al;[111]Mg2Si/[111]Al and (010)Mg2Si/(110)Al; [100]Mg2Si/[111]Al. Transformation of the eutectic morphology was related to the change of the preferred orientation of phase Mg2si.

关键词: :α(Al)-Mg_2Si eutectic , null , null

二维小角X射线散射法研究PAN基炭纤维内部微孔结构

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 , 炭纤维 , 孔结构 , 分形维数 , 密度波动

聚丙烯腈(PAN)基纤维中微孔的2维小角X射线散射

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 , 微孔

同步辐射小角X射线散射研究PAN原丝制备过程中孔结构的演变

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

MAGNETIC PROPERTIES OF Nd_2(Fe_(1-x)M_x)_(14)B(M=C,Si)ALLOYS

XING Feng JIANG Chao HE Wenwang Department of Physics , Peking University , Beijing , China [Originally published in ACTA METALL SIN (CHINESEEDN) 24 (5) 1988pp B348—B352 , received 22 October 1986:in revised form 8 May 1987]

金属学报(英文版)

The magnetic properties of Nd_2(Fe_(1-x)M_x)_(14)B(M=C and Si) compounds have been investi- gated.Substituting Fe by small amount of metalloid C and Si atoms,the compounds are in tetragonal structure and have uniaxial anisotropy.The substitution of C for part of Fe de- creases the Curie temperature of the compounds and the intrinsic coercivity of bond samples at low temperature.The replacement of Fe by Si makes the Curie temperature increase with a maximum at the vicinity of x=0.15.When the range of the content of Si is 0≤x≤0.10,the coercivity distinctly increases at room temperature.from 62.7 kA/m at x=0 to 138.7kA/m at x=0.06,where the residual magnetization has a maximum:in the mean time the saturation magnetization decreases only by a small amount.

关键词: Nd-Fe-B alloy , null , null

Nd_2(Fe_(1-x)M_x)_(14)B(M=C,Si)合金的磁性

邢峰 , 江潮 , 何文望

金属学报

本文研究了Nd_2(Fe_(1-x)M_x)_(14)B的磁性。少量类金属原子C和Si取代部分Fe,能形成四方结构,且具有单轴各向异性。碳取代Fe,使化合物的Curie温度降低,低温下粘结体样品的内禀矫顽力减少;而Si对Fe的取代可使Curie温度升高,并在x=0.15附近达到极大值。含Si样品在0≤x≤0.10范围内,矫顽力显著增加,室温下从x=0的62.7kA/m增加到x=0.06的138.7 kA/m,并且在x=0.06附近,剩磁有一个极值,饱和磁化强度减少不多。

关键词: Nd-Fe-B合金 , magnetic properties , Curie temperature

MnP_(1-x)M_x系列合金的磁热效应

门德 , 松林 , 伊博乐 , 刘璟芳 , 伊日勒图 , 特古斯

稀有金属 doi:10.3969/j.issn.0258-7076.2010.01.027

研究了1:1型MnP基系列合金MnP_(1-x)M_x(M=Si,Sb,Ge,Zn,Sn)(x=0,0.1)的结构及其磁热效应.室温X射线衍射表明该系列合金的主相结构均为正交MnP结构,空间群为Pnma.在用Ce,Sb,Zn,Sn作为替代元素的合金中存在少量第二相Mn_(5.64) P_3.磁性测量表明该系列合金MnP_(1-x)M_x(M=Si,Sb,Ge,Zn,Sn)(x=0,0.1)的存在由铁磁-顺磁的二级相变.其居里温度T_c分别为286,295,291,295,295 K.通过磁化曲线计算了MnP_(1-x)M_x(M=Si,Sb,Ge,Zn,Sn)(x=0,0.1)合金的最大等温磁熵变-△S_m,均在0.7-1.3 J·kg~(-1)·K~(-1)之间.

关键词: 合金 , 磁制冷 , 磁热效应 , 磁熵变

M_1-M_2-x-y系优势区相图的绘制及其应用

王龙章 , 黄克雄 , 骆如铁 , 姚渝 , 叶大陆 , 陈新民

金属学报

本文讨论了双金属共存体系M_1-M_2-x-y,当两种金属的化合物相互作用生成多金属化合物时,优势区相图的绘制原理、方法及计算机程序。通过绘制Zn-Fe-SO系的优势区相图,分析了ZnO·Fe_2O_3的生成及稳定条件,并说明了其在硫化锌矿焙烧中的指导作用。

关键词: M_1-M_2-x-y体系 , predominance diagram , roasting , zinc sulfide ore

DRAWING PREDOMINANCE DIAGRAM OF M_1—M_2—x—y SYSTEM AND ITS APPLICATION

WANG Longzhang HUANG Kexiong LUO Rutie YAO Yu YE Dalu CHEN Xinmin Central South University of Technology , Changsha , China

金属学报(英文版)

Discussions were made of the principle,method and computer program for drawing the pre- dominance diagrams of the bi-metal co-existed system M_1-M_2-x-y in which the multi-me- tallic compounds may be produced by interaction between compounds of both metals.The formation of zinc ferrite and its stable region have been analyzed through drawing Zn-Fe-S-O system predominance diagrams.The availability of the diagram is given the di- rection to roast the zinc sulfide ore as well.

关键词: system M_1-M_2-x-y , null , null , null

Ab initio elastic stiffness of nano-laminate (MxM '(2-x))AlC (M and M ' = Ti, V and Cr) solid solution

Journal of Physics-Condensed Matter

We have investigated the elastic stiffness and electronic band structure of nanolaminate (MxM2-x')AIC solid solutions, where M and M' = Ti, V and Cr by means of the ab initio pseudopotential total energy method. The second-order elastic constants, bulk moduli and anisotropic Young's moduli are computed for the solid solutions, in which x is changed from 0 to 2 in steps of 0.5. The bulk moduli of (MxM2-x')AIC is found to be approximately the average of the two end M(2)AIC and M-2'AIC phases as the substitution content x, as well as the valence electron concentration (VEC), varies in the compounds. On the other hand, the shear modulus c(44), which by itself represents a pure shear shape change and has a direct relationship with hardness, saturates to a maximum as VEC is in the range 8.4-8.6. It implies that solid solution hardening may be operative for alloys having VEC values in this range. Furthermore, trends in the elastic stiffness are interpreted in terms of the electronic band structure. We show that monotonically incrementing the bulk moduli is attributed to the occupying states involving transition-metal d-Al p covalent bonding and metal-to-metal dd bonding. The maximum in c44, on the other hand, originates from completely filling the shear resistive transition-metal d-Al p bonding states. Most importantly, we predict a method to optimize the desired elastic stiffness by properly tuning the valence electron concentration of (MxM2-x')AIC ceramics.

关键词: behavior;phases