激光快速凝固法制备BaTi4O9微波介质陶瓷

采用激光快速凝固(LRS)法,制备四钛酸钡(BT4,BaTi4O9)微波介质陶瓷,使用X射线衍射仪(XRD)、扫描电子显微镜(SEM)分析晶相构成及显微组织,使用精密阻抗分析仪测试介电性能。结果表明,LRS制备BT4呈层片状结构,具有较高的致密度(相对密度99.6%),其晶粒沿c轴方向(平行于激光入射方向)择优生长,c轴方向择优取向度为0.46。在1 MHz下,介电常数为85,介电损耗为0.083,介电常数温度系数为1.96×10-4。由于在LRS过程中熔体产生极大的温度梯度,因而形成织构化的BT4,介电常数显著提高。     

TA7合金薄板冷轧织构的三维取向分析

建立了适用于表现六方系材料织构的取向分布函数(Orientation Distribution Function)的数学模型并编制了相应的计算程序(略)。提出利用最小二乘法,用r个极图级数系数Q_(lm)~i计算ODF级数系数W_(lmn)时的加权系数b~in的公式,论证了加权系数与被测试样织构类型无关。 实测并计算了TA7冷轧薄板的取向分布函数。通过分析ODF图确定;被测试样里绝大多数晶粒的轧面倾向于(0001),漫散可达40°,而轧向在各个方向上接近均匀分布;此外还有少数晶粒的取向为(2114)[0110]。     

冷轧TA7合金板材织构的完整ODF分析

依取向空间的等体积划分原理,将传统的六方晶系材料特征非对称子空间(等角法)予以改造。并按等面积投影法对 ODF 图进行重建。按此法对实测的冷轧 TA7 合金板材完整ODF 施行织构分析。结果表明,织构分析与原等角法的完全等效;此方法能清晰地建立起反极图与 ODF 图之间的关系。等面积投影法的采用使织构定量简便、易行。     

单轴晶体内非常光线与入射光线在法线同侧的条件

本文利用惠更斯原理和单轴晶体内的波面图 ,导出了单轴晶体界面上折射非常光和入射光在法线同侧的条件 ,用曲线表示出折射非常光和入射光在法线同侧时光轴取向与入射角之间的关系。求出了方解石晶体中e光和入射光在法线同侧时的最大入射角为 9.9°。     

阿干镇煤田中侏罗统阿干镇群底砾岩组的古流方向

本文通过砾石方位和其它沉积组构的分析,提出了判断底砾岩组沉积时期的古流方向的证据。底砾岩组内大多数砾石的c轴指向N22°—45°W,倾角65°—80°。因而砾石的最大扁平面(ab面)则向S22°—45°E倾斜,平均倾角20°左右。砾石的方位特征清楚地表示底砾岩组沉积时期的河流流向大约以N22°—45°W的方向自南东向北西流动的。此外,该组地层中粒度自南而北渐次变细和斜层理倾向北西的特征,与砾石方位所指示的古流方向是一致的。     

电铸超细晶材料的微观组织研究

应用电铸法制备超细晶粒金属Cu ,对电铸工艺参数与形成的材料的微观组织的关系进行了探讨。运用扫描电子显微镜 (SEM )和电子背散射衍射 (EBSP)等实验手段 ,对电铸Cu的显微组织及晶粒的生长方向进行了系统研究。研究表明 :电铸Cu材料晶粒十分细小 (晶粒尺寸在 1μm 3μm范围 ) ,且内部晶粒的晶体取向沿材料的法线方向存在择优取向 ,即有丝织构的存在 ;同时 ,通过对电子背散射所获得的极图与反极图进行分析可知 ,丝织构受电铸液成份的影响     

表面活性剂对合成羟基磷灰石晶体的影响

以Ca(NO_3)_2·4H_2O和H_3PO_4为前驱物,采用水热法制备羟基磷灰石(HA),着重研究水热体系中吐温80、十六烷基三甲基溴化铵(CTAB)、十二烷基硫酸钠(SDS)对合成羟基磷灰石晶体结构的影响。结果表明:添加不同的表面活性剂,对合成HA的晶体形貌与结构有一定的影响。添加非离子型表面活性剂吐温80合成的产物均为HA,HA晶体a、b轴方向上的生长受到限制,HA越向于c轴方向的生长,晶粒平均长度由79.13 nm增至89.60 nm。阳离子表面活性剂CTAB对HA晶体c轴上的生长基元Ca-P_6O_(24)有着一定的抑制作用,合成的HA晶粒平均长度较小,由79.13 nm降至73.84 nm。阴离子表面活性剂SDS与a、b轴上的生长基元OH-Ca_6的相互替代造成过饱和度的增加,促进了HA晶体长径比的增加,HA晶粒平均长度由79.13 nm增至133.08 nm,长径比由2.67增至3.34。     

羟基磷灰石/丝蛋白复合骨材料的生物相容性

以共沉淀法制备了羟基磷灰石/丝蛋白(HA/SF)复合骨修复材料,并对材料进行了XRD、TEM、SEM、孔径分布和孔隙率等相关的测试和表征。结果表明:该复合材料的无机组分为20~30 nm长、5 nm宽的棒状羟基磷灰石(HA)结晶,这些晶粒沿c轴自组装团聚成簇分散在丝蛋白基质中形成三维多孔结构,其孔径分布在0.3~115μm之间,开口孔隙率达66%。该材料植入动物体内,未出现明显的排异反应,在植入部位有连续的骨性连接和新生骨形成,说明HA/SF复合材料具有良好的生物相容性和骨诱导活性。     

织构对NiTi合金相变伪弹性的影响及其计算机模拟

近等原子比热轧态NiTi合金板材有较显著的择优取向,使该合金的相变伪弹性呈现明显的各向异性.拉伸实验表明拉伸轴沿与轧向成45°夹角的方向,相变伪弹性最好;沿轧向,次之;沿横向,最差.文中对NiTi织构进行了取向分布函数定量分析,并改进了NiTi单晶相变应变的晶格变形矩阵理论,以取向分布密度为加权因子,对该合金多晶的相变伪弹性进行了计算机模拟,所得结果与实测值吻合得较好.     

立方系材料织构精确分析方法

为了解决由于织构漫散度给织构分析带来的估算误差,以达到对材料织构进行更为精确的分析,采用从极图求算ODF(orientation distribution function)中的"二步法"作为基本原理,选择以1°为最小间隔单位划分欧拉空间,对欧拉空间所有取向点的取向密度进行了求算,并建立了相应的分析系统. 利用该分析系统对鞍钢生产的IF钢冷轧和退火样品进行了计算,并与已成熟的以欧拉角5°为最小间隔单位的ODF求算系统对比. 结果表明:以欧拉角1°为最小单位的ODF取向密度分析系统比以欧拉角5°为最小单位的ODF取向密度分析能更确切地表示织构的分布情况.     

Texture of the nano-crystalline AlN thin films and the growth conditions in DC magnetron sputtering

DC reactive magnetron sputtering technique has been used for the preparation of Al N thin fi lms. The deposition temperature and the fl ow ratio of N2/Ar were varied and subsequent dependency of the fi lms crystallites orientation/texture has been addressed. In general, deposited fi lms were found hexagonal polycrystalline with a(002) preferred orientation. The X-ray diffraction(XRD) data revealed that the fi lm crystallinity improves,with the increase of substrate temperature from 300 ℃to 500℃. The dropped in full width half maximum(FWHM) of the XRD rocking curve value further con fi rmed it. However, increasing substrate temperature above 500 ℃or reducing the nitrogen condition(from 60 to 30% in the environment) induced the growth of crystallites with(102) and(103) orientations. The rise of rocking curve FWHM for the corresponding conditions depicted that the fi lms texture quality deteriorated. A further con fi rmation of the variation in fi lm texture/orentation with the growth conditions has been obtained from the variation in FWHM values of a dominant E1(TO) mode in the Fourier transform infrared(FTIR) spectra and the E2(high) mode in Raman spectra. We have correlated the columnar structure in AFM surface analyses with the(002) or c-axis orientation as well. Spectroscopic ellipsometry of the samples have shown a higher refractive index at 500 ℃growth temperature.     

多晶TiNi和CuZnAl形状记忆合金中的织构转变

用X射线织构仪测定了TiNi和CuZnAl合金的母相奥氏体、产品相马氏体的极图,计算了测定极图各自的位向分布函数。分析结果表明,TiNi合金奥氏体具有一个弱的织构组元{4,0,3}〈0,1,0〉和一个α纤维织构,TiNiCu合金马氏体有6个主要的织构组元;CuZnAl合金奥氏体织构是一个纤维织构,其纤维轴为〈1,1,0〉平行于轧向,位向密度沿纤维轴从{001}〈1-10〉到{111}〈1-10〉扩展,在位向{001}〈1-10〉附近,获得最大位向密度为26.9。CuZnAl合金马氏体有10个主要的织构组元。从奥氏体与马氏体的织构分析发现,两者织构是相互关联的,一个奥氏体的织构组元对应多个马氏体的织构组元,此结果符合马氏体形成自适应形貌的要求。     

An off-normal fibre-like texture in thin films on single-crystal substrates

In the context of materials science, texture describes the statistical distribution of grain orientations. It is an important characteristic of the microstructure of polycrystalline films, determining various electrical, magnetic and mechanical properties. Three types of texture component are usually distinguished in thin films: random texture, when grains have no preferred orientation; fibre texture, for which one crystallographic axis of the film is parallel to the substrate normal, while there is a rotational degree of freedom around the fibre axis; and epitaxial alignment (or in-plane texture) on single-crystal substrates, where an in-plane alignment fixes all three axes of the grain with respect to the substrate. Here we report a fourth type of texture--which we call axiotaxy--identified from complex but symmetrical patterns of lines on diffraction pole figures for thin films formed by solid-state reactions. The texture is characterized by the alignment of planes in the film and substrate that share the same d-spacing. This preferred alignment of planes across the interface manifests itself as a fibre texture lying off-normal to the sample surface, with the fibre axis perpendicular to certain planes in the substrate. This texture forms because it results in an interface, which is periodic in one dimension, preserved independently of interfacial curvature. This new type of preferred orientation may be the dominant type of texture for a wide class of materials and crystal structures.     

多晶织构金属薄板的塑性各向异性分析

从晶体学理论出发 ,将多晶体看作是具有不同取向的单晶集合体 .认为单晶体各个滑移系的开动相互独立 ,从而简化计算模型 .同时利用从实测极图分析得到的三维晶粒取向分布函数作为权函数 ,对多晶织构圆板深拉延后径向应变进行平均化处理 ,得出薄圆板法兰部分的径向应变沿环向呈不均匀分布 ,其峰值个数及位置同已有实验结果相一致 ,表明模型正确 ,方法可行     

Crystallographic preferred orientation of akimotoite and seismic anisotropy of Tonga slab

The mineral akimotoite, ilmenite-structured MgSiO(3), exists at the bottom of the Earth's mantle transition zone and within the uppermost lower mantle, especially under low-temperature conditions. Akimotoite is thought to be a major constituent of the harzburgite layer of subducting slabs, and the most anisotropic mineral in the mantle transition zone. It has been predicted that if akimotoite crystals are preferentially oriented by plastic deformation, a cold subducted slab would be extremely anisotropic. However, there have been no studies of crystallographic preferred orientations and very few reports of plastic deformation experiments for MgSiO(3) ilmenite. Here we present plastic deformation experiments on polycrystalline akimotoite, which were conducted at confining pressures of 20-22 GPa and temperatures of 1,000-1,300 degrees C. We found a change in crystallographic preferred orientation pattern of akimotoite with temperature, where the c-axis maximum parallel to the compression direction develops at high temperature, whereas the c axes are preferentially oriented parallel to the shear direction or perpendicular to the compression direction at lower temperature. The previously reported difference in compressional-wave seismic anisotropy between the northern and southern segments of the Tonga slab at depths of the mantle transition zone can conceivably be attributed to the difference in the crystallographic preferred orientation pattern of akimotoite at varying temperature within the slab.     

Microstructure and heat treatment for Ni3Al-based single crystal alloy with different crystal orientations

Ni₃Al-based single crystal alloy IC6SX with different crystal orientations were prepared by seed crystal method. The microstructure and heat treatment of the alloy were investigated. The results showed that the microstructure of the alloy was in dendrite structure, and the crystal orientation had significant effect on the dendrite morphology of this alloy. The precipitated phases of (MoNi)₆C and NiMo appeared in the microstructure of the three alloys with different crystal orientations during solidification process. Compared with other two alloys, the volume fractions of precipitated phases of both (MoNi)₆C and NiMo was the most in the alloy with [111] orientation and the least in the alloy with [001] orientation. The solidus and liquidus temperatures of the alloy IC6SX tested by differential scanning calorimetry (DSC) were 1356 °C and 1387 °C, respectively. Meanwhile, the effect of different solution temperatures on the microstructure of the alloy with different orientations was studied. The results showed that the precipitated phases of (MoNi)₆C and NiMo were eliminated with the solid solution treatment under the condition of 1300 °C/10 h. However, the incipient melting of the alloys occurred due to the dissolution of low melting point phases. As the temperature dropped to 1280 °C, the area of incipient melting in the alloy with different orientations decreased gradually. However, there was no incipient melting appearing in the three alloys with different orientations when the solution treatment temperature dropped to 1260 °C.     

AlN压电薄膜微晶择优取向对其介电常数的影响

本文从声场理论出发,将各晶粒的电位移矢量D视作对有效介电常数有独立贡献的矢量,采用Bond矩阵法进行张量变换,并对各晶粒的贡献进行空间平均,得出AlN压电薄膜微晶择优取向对其介电常数影响的分析结果。     

立方晶体宏观织构取向分布函数的程序化

取向分布函数(ODF)从宏观整体上反映了多晶体各晶粒取向的统计分布,它突破了传统的极图法、反极图法用一维或二维图形来描述晶体的空间取向分布的局限性,可实现晶体取向分布的三维空间描述.针对具有立方结构的多晶体材料,采用级数展开法模型计算取向分布函数的理论模型,利用程序对ODF值进行了计算,并以Voronoi增量算法为基础生成包含有5000个晶粒的多晶体材料各晶粒的几何数据信息,与计算得到的ODF值一起导入OpenGL进行可视化处理,直观显示了多晶体材料中ODF值在各晶粒内的分布.通过对立方系多晶体材料的ODF测算,对该种材料的织构类型研究与分布规律分析具有重要的指导意义.     

射频磁控溅射制备c轴取向LiNbO3薄膜研究

采用射频磁控溅射技术,用富Li的LiNbO3靶材在Si(100)和Si(111)基底上制备了LiNbO3薄膜.通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)和X射线光电子能谱(XPS)对LiNbO3薄膜的结晶程度、晶体取向和表面形貌及薄膜与基底结合处的界面结构进行了研究.结果表明:样品在空气中经1 000℃退火1 h处理后,薄膜与Si基底界面处有SiO2生成,得到的LiNbO3薄膜结晶性好,具有高c轴取向,晶粒排列致密且粒径尺寸均匀.