纳米铜孪晶的分子动力学模拟研究现状与展望

介绍了纳米铜中孪晶及其作用机理,综述了孪晶界对变形机制和变形行为的影响,描述了分子动力学模拟计算在纳米铜研究中的应用,概述了纳米铜孪晶的研究进展,并对其未来的发展方向做出了展望。     

纳米铜孪晶的分子动力学模拟研究现状与展望

介绍了纳米铜中孪晶及其作用机理,综述了孪晶界对变形机制和变形行为的影响,描述了分子动力学模拟计算在纳米铜研究中的应用,概述了纳米铜孪晶的研究进展,并对其未来的发展方向做出了展望。     

聚二硫二丙烷磺酸钠对电沉积纳米孪晶铜的影响

以聚二硫二丙烷磺酸钠(SPS)、明胶蛋白胨(GP)、氯离子为添加剂采用直流电镀制备了高度(220)择优取向的纳米孪晶铜，并探究了其形核机理。结果表明，加入SPS会使镀层由(111)和(220)取向转变为具有(220)择优取向的纳米孪晶铜，并且SPS浓度会强烈影响镀层的过渡层厚度。SPS和GP在铜表面竞争性吸附，使镀层的内应力比单一添加剂时更高，镀层通过形成(220)择优取向孪晶铜释放内应力。纳米孪晶铜的形核和生长受到电流密度和添加剂的共同影响，在合适的过电位下镀层才能通过形成孪晶来释放应变能。在20 mg/L SPS、4 A/dm²条件下，孪晶结构最完整，过渡层最薄。     

NdxY1-xAl3(BO3)4和NdxGd1-xAl3(BO3)4晶体中的孪晶结构

采用同步辐射形貌术结合化学腐蚀法,系统研究了ＮＹＡＢ和ＮＧＡＢ晶体中的孪晶结构。已经发现：ＮＹＡＢ晶体中的孪晶为反演孪晶,主晶和孪晶结构具有互为中心对称关系;而ＮＧＡＢ晶体中的孪晶为１８０°旋转孪晶,孪晶结构由主晶结构绕结构的三次对称轴旋转１８０°而成。     

电解抛光工艺对工业纯钛表面特性的影响

选用高氯酸与甲醇混合溶液作为电解液,在-32℃下对预压缩工业纯钛电解抛光3 min。探讨了电解抛光电压和电流密度对纯钛表面特性的影响。采用基于扫描电镜的电子背散射衍射(EBSD)和数字图像相关(DIC)原位法,研究了预压缩工业纯钛中的退孪晶变形。当电解抛光电压和电流密度分别为16 V和8.3～9.3 mA/mm~2时,EBSD花样标定率和DIC相关性均最好。工业纯钛退孪晶变形表现为较大尺寸孪晶的侧向变窄,部分小尺寸孪晶消失,孪晶附近应变集中。     

大尺寸Nd^3＋：YAP晶体中云层和孪晶的克服途径

本文报道用中频感应加热Czochralski法,在大的气-液温差场中生长大尺寸的Nd~(2+):YAP单晶,并在生长过程中采用“真空自然冷却法”退火工艺。即当大尺寸Nd~(3+):YAP单晶在高温下生成后,随即改变氮气氛成真空状态,由于真空状态下热辐射起主导作用,炉膛内温度梯度明显减少,使生成后的大单晶在这种由真空导致的低梯度的温场中自然冷却到室温。不仅可以克服云层的产生,而且可以克服孪晶的形成。     

电铸铜微观组织与织构的研究

采用扫描电镜、透射电镜和电子背散射衍射技术,研究了不锈钢上厚度约2.2 mm的电铸铜层的微观组织、晶粒取向和晶界特征.实验表明,其组织主要由柱状晶构成,靠近基体50～100 μm处的铸层由细小等轴晶和细小柱状晶构成.对于所有晶区,小角度晶界(<15°)的分布频率较小,大角度(>15°)晶界为电铸铜组织的主要晶界,在大角度晶界中,CSL晶界占有很大比例,其中∑3的分布频率较大.柱状晶由平行分布的层状孪晶构成,近似垂直于柱状晶长轴,层间孪晶界为∑3类型.铸层存在较显著的铜型织构,即<111>择优取向,并且随铸层厚度的增加而加强.     

提高工业X射线胶片扁平颗粒均一性的方法研究

本文重点研究了扁平颗粒双平行孪晶晶体结构，以及明胶组成和浓度、乳化P_Br、温度对颗粒晶型均一、单分散性的影响，通过扫描电镜、粒度分布仪检测、单分散性的计算，制得晶型均一、单分散性的扁平颗粒，并与现有产品进行性能对比测试，提高了胶片感光性能。     

Zn0.76Co0.24S/孪晶Mn0.5Cd0.5S同质异质结光催化产氢性能

采用水热法制备了孪晶Zn_0.76Co_0.24S (T-MCS)固溶体，随后借助原位水热法获得Mn_0.5Cd_0.5S/T-MCS纳米异质结光催化剂。结果表明：Zn_0.76Co_0.24S固溶体是六方纤锌矿Zn_0.76Co_0.24S (WZ-MCS)及立方闪锌矿Zn_0.76Co_0.24S (ZB-MCS)交替形成的孪晶同质结；引入Mn_0.5Cd_0.5S可增强体系光响应能力，提高表面载流子数量，其中3%Mn_0.5Cd_0.5S/T-MCS异质结在Na2S/Na2SO3混合溶液中的产氢速率可达132.9 mmol/(g·h)(300W氙灯，λ>420 nm)，分别是Mn_0.5Cd_0.5S和T-MCS的332.2倍和1.9倍。能带结构分析发现，WZ...     

周期性孪晶结构碳化硅纳米线改性环氧树脂的性能

通过超声分散和模具浇注成型法制备了周期性孪晶结构碳化硅(SiC)纳米线改性环氧树脂,探讨了SiC纳米线的周期性孪晶结构及含量对环氧树脂复合材料力学性能的影响。结果表明,周期性孪晶结构SiC纳米线的加入明显改善了环氧树脂基体的力学性能,孪晶结构有助于提高SiC纳米线与基体树脂之间的相互结合程度。随着孪晶SiC纳米线含量的增加,复合材料的拉伸性能和弯曲性能都呈现出先增加后减小的趋势。当SiC纳米线的含量为2%时,复合材料的拉伸强度、拉伸弹性模量、断裂伸长率、弯曲强度和弯曲弹性模量均达到最大值,相比于纯环氧树脂分别提高了90.6%,37.8%,38.3%,53.4%和24.5%。当SiC纳米线含量为3%时,弯曲应变达到最大值(6.72%),相比于环氧树脂提高了32.0%。     

On the Faceted and Inclined Twin Boundary of Titanium Carbide Derived from Nanolaminated Ti3AlC2

Due to its high twin boundary energy, the absence of Σ3{112} in covalently bonded TiC has been theoretically adjudged. Here, we report the observation of TiC twin boundaries that consist of Σ3{112} and Σ3{111} steps in a faceted and inclined manner. The twin interface in the transition region is not flat, wherein periodic contrasts resulting from overlapped twins were identified. Based on the microstructural analyses, a formation mechanism for the energy‐expensive Σ3{112} and inclined twin boundaries is elaborated.     

Arrowhead-like diamond crystals formed by hot-filament chemical vapor deposition

Arrowhead-like diamond crystals have been formed by using a simple method of hot-filament-assisted chemical vapor deposition. These are contact twins with {111} as the twin plane, of which each individual is composed of {100}, {110} and {111} faces. These twins flatten along {110} face and elongate parallel to {111} contact plane. The flattened {110} face consists of many {110} terraces sided by 〈110〉 and 〈112〉 steps. So the twinned crystal looks like an arrowhead. These twins are formed just underneath the uppermost substrate temperature for diamond growth.     

Structural Studies of Ordering in the (Pb1-xBax)(Mg1/3Nb2/3)O3 Crystalline Solution Series

The ordered structures of the (Pb_{1- x} Ba _x )(Mg_1/3Nb_2/3)O₃crystalline solution series were investigated by selected area electron diffraction (SAED) and high-resolution electron microscopy (HREM). At low Ba contents (e.g., x < 0.40), the ordered structure was found to be isostructural with Pb(Mg_1/3Nb_2/3)O₃, with a doubled unit cell characterized by 1/3{111} superlattice reflections. At higher Ba contents (e.g., x > 0.60), the ordered structure was characterized by 1/3{111} superlattice reflections. For intermediate Ba contents (e.g., x - 0.60), diffuse scattering along the {111} between diffuse 1/2{111} and 1/3{111} reflections was observed. The ordering is attributed to the distribution of the B-site cations between multiple sublattices. Strong fluctuations in the B-site cation ratio between ordered and disordered regions are believed not to exist; however, the possibility of weak fluctuations is consistent with the observed lattice images.     

Distribution of Grain Boundaries in SrTiO3 as a Function of Five Macroscopic Parameters

Measurements of the grain boundary population as a function of misorientation and boundary plane orientation show that the distribution is inversely correlated to the sum of the energies of the surfaces comprising each boundary. The observed correlation suggests that the difference between the energy of a high-angle grain boundary and the two component surfaces is relatively constant as a function of misorientation. Two exceptions to this correlation were identified: low-misorientation-angle boundaries and the coherent twin boundary, where the (111) planes in the adjoining crystals are parallel to each other, but rotated by 60° around the [111] axis. In these cases, the high degree of coincidence across this interface probably lowers the boundary energy with respect to that of the component surfaces. For all other boundaries, the anisotropy of the population is accurately predicted by the surface energy anisotropy, and in general, boundaries display a preference for {100} orientations, the planes of minimum surface energy.     

〈111〉 Rotation Twins in an Orthorhombic LaGaO3 Perovskite

Phase-transformation-induced twins in pressureless-sintered lanthanum gallate (LaGaO₃) ceramics have been analyzed using transmission electron microscopy. Twins are induced by solid-state phase transformation upon cooling from rhombohedral ( r , R 3 c ) to orthorhombic ( o , Pnma ) symmetry at 145°C. Domains with a 150°–60°–150° configuration were frequently detected when viewed along [210]. This observation representing the co-existence of the {121} and {123} twins is suggested by analyzing corresponding selected area diffraction patterns across the domain boundaries. The former, with the twin plane lying on {121}, is the reflection type whose twin variants are related by mirror plane symmetry. The latter, although its nature was confirmed by tilting experiments along an unsplit row of reflections, exhibits characteristic crystallographic orientation relationships that are distinctive from those of the {121} twins. The twin laws represented in the matrix form are also derived accordingly from corresponding orientation relationships. Crystallographic analysis indicates that these domains commonly possess an orientation relationship that can be described by the twofold rotation axis about 〈111〉 lost upon the rhombohedral→orthorhombic phase transition. They are therefore the 180° parallel-rotation twin, with the twin axis 〈111〉 lying in {123}. Twins generated by the r → o phase transition between crystals of non-group–subgroup relations are discussed in terms of an intermediate metastable cubic phase of the lowest common supergroup symmetry.     

双螺杆挤出机的进展及其应用

着重介绍日本新型双螺杆挤出机的最新研制和开发的机型,评述新型双螺杆挤出机的特点,特别是新近开发的SCR双螺杆挤出机、BIVOLAV双螺杆挤出机、HTM双螺杆挤出机、TEX双螺杆挤出机、高剪切型双螺杆挤出机、格子形叶的双螺杆挤出机、新AP型双螺杆挤出机的结构、性能及其应用,提出今后双螺杆挤出机发展前景及方向。     

Necessary Conditions for the Formation of {111} Twins in Barium Titanate

The experimental conditions for {111} twin formation in BaTiO₃ were investigated. When BaTiO₃ compacts without excess TiO₂ were sintered either in an oxidizing atmosphere (air) or in a reducing atmosphere (95N₂–5H₂), no {111} twins formed within the BaTiO₃ grains and no abnormal grain growth occurred. In contrast, many {111} twins were present within the abnormally grown grains in the excess-TiO₂-containing BaTiO₃ samples sintered in air, while no twins were observed in the excess-TiO₂-containing samples sintered in 95N₂–5H₂. X-ray diffraction analysis showed that excess TiO₂ forms a Ba₆Ti₁₇O₄₀ phase during sintering with the space group A 2/ a in air and a Ba₆Ti₁₇O_{40− x} phase with the space group C in 95N₂–5H₂. It appears therefore that excess TiO₂ and an oxidizing atmosphere are necessary for {111} twin formation in BaTiO₃. These results may also indicate that the interface structure between BaTiO₃ and Ba₆Ti₁₇O₄₀ influences the twin formation.     

双螺杆挤出技术在冻胶纺丝工艺中的应用

对双螺杆挤出机用于冻胶纺丝，其结构特性及相关设计多数进行了详细的分析和探讨，同时提出了一些参考建议，经特殊设计加工后的双螺杆挤出机应用在冻胶纺丝工艺上，成功地纺制出高强高模聚乙烯纤维。双螺杆挤出技术用于冻胶纺丝工艺已具备条件并切实可行。     

CVD法生长金刚石晶粒的形态

用ＳＥＭ研究了ＣＶＤ法生长金刚石晶体形态，观察到了单晶立方八面体、双晶立方八面体和两种不同形态的二十面体。晶粒上的三角形晶面多为凹坑，电有晶面上分层发育的晶层。在二十面体中，还直接地发现了倾角间隙，对于ＣＶＤ法生长的金刚石晶粒这些都是首次观察到，此外还首次观察到其它几种立方多面体晶形。     

Effect of Ba6Ti17O40/BaTiO3 Interface Structure on {111} Twin Formation and Abnormal Grain Growth in BaTiO3

A structural transition of Ba₆Ti₁₇O₄₀/BaTiO₃ interfaces from faceted to rough was induced by reducing oxygen partial pressure in the atmosphere. As the oxygen partial pressure decreased, the number densities of {111} twins and abnormal grain decreased. TEM observation showed that the twin formation was governed only by the faceting of the interface. Experimental evidence of {111} twin-assisted abnormal growth of faceted BaTiO₃ grains was also obtained.