195keV Ar^＋辐照非晶态合金表面损伤形貌的研究

用扫描电子显微镜观测研究了室温下１９５ｋｅＶＡｒ＋辐照非晶态合金Ｃｏ（６０）Ｆｅ（１２）Ｎｉ（１０）Ｓｉ６Ｂ（１２）和Ｆｅ（３９）Ｎｉ（３９）Ｖ２Ｓｉ（１２）Ｂ８在各剂量阶段的表面损伤形貌。结果表明，表面损伤是发泡和溅射相互竞争的过程。低剂量下，表面损伤以发泡为主；而在高剂量时，表面发泡消失，溅射造成的多孔粗糙表面损伤结构形成。对高剂量时表面发泡消失的可能机制作了探讨。     

离子注入碳对铀抗腐蚀性能影响的研究

利用离子注入技术分别用单能量和多能量叠加注入方式在铀表面注入碳形成表面改性层，并对改性层的形貌、注入元素的分布和相结构分别进行扫描电镜（SEM）、俄歇电子能谱（AES）及表面相结构衍射谱（XRD）分析，利用电化学极化法测试注入样品的抗腐蚀性能。结果表明：离子注入碳能够提高铀表面抗腐蚀的能力。     

锆合金表面缺陷引起氢致延迟开裂行为的研究

核反应堆用锆合金构件在服役过程中会发生氢致延迟开裂（HIDC）而失效,构件表面的微缺陷是否会引起HIDC是值得研究的问题。本文采用真空电子束焊接方法制备表面有微缝隙缺陷的样品,以研究这类微缝隙缺陷在400℃过热蒸汽中腐蚀以及在350℃高压水中热循环处理过程中的行为。由于这类缺陷处会形成尖劈状的氧化膜并镶嵌在金属中,在氧化膜前端将形成应力集中和应力梯度区,引起氢的扩散、富集和氢化物析出,即使样品中原先没有残余应力,也没有受到外加应力的作用,也会发生HIDC导致裂纹扩展而开裂。因此,在设计和加工制造核反应堆堆芯中锆合金的各种结构件时,需要重视如何避免锆合金构件表面可能生成这种缺陷的问题。     

离子束辅助沉积铌提高铀的抗腐蚀性能研究

利用离子注入技术在铀表面进行了离子束辅助沉积铌和离子注入铌形成表面改性层，并对改性层的厚度、注入元素的分布进行俄歇电子能谱（AES）分析和表面相及结构的X射线衍射谱（XRD）分析，用电化学极化法测试抗腐蚀性能。结果表明：离子束辅助沉积表面改性层比离子注入表面改性层明显增厚，铀的耐蚀性得到进一步改善。最后讨论了注铌改性层耐蚀性提高的原因。     

硅离子注入聚合物摩擦特性研究

采用金属蒸汽真空弧（MEVVA）离子注入机引出的Si离子进行了聚酯薄膜（PET）改性研究，注入后的聚酯膜表面结构发生了很大的变化。用透射电子显微镜观察了注入聚酯膜的横截面，结果表明，在注入层形成颗粒的沉积。红外吸收测量揭示这些颗粒为SiC和富集的碳颗粒。这些颗粒增强了注入层表面强化效果。用纳米硬度计测量显示，Si离子注入可明显地提高聚酯膜表面硬度和杨氏模量，从而极大地的增强了表面抗磨损特性。最后讨论了Si离子注入聚酯膜改善特性的机理。     

镧系裂变产物（La、Ce、Pr和Nd）在α-U表面偏析行为的第一原理研究 #br#

镧系裂变产物引起的燃料肿胀及包壳脆化是UZr金属燃料服役中的主要问题。其快速扩散通常借助于裂变气体释放通道,实验可观察到镧系裂变产物会在UZr金属燃料氙气泡处偏析。为理解裂变产物扩散机理及表面偏析现象,本文采用第一原理方法,对低温α-U中（100）、（112）、（001）、（021）、（110）、（010）表面的原子结构及形成能进行了研究,并讨论了常见镧系裂变产物La、Ce、Pr和Nd在不同表面的偏析行为。计算结果表明,（110）表面的形成能最低,为1.75 J/m²,（112）、（021）和（001）表面的形成能次之,为1.81~1.83 J/m²,（010）和（100）表面的形成能最高,分别为1.96 J/m²和2.04 J/m²。4种裂变产物在6种表面都表现出明显的偏析效应,对于同一种表面,其偏析驱动力排序为：La>Ce>Pr>Nd。对于同一种镧系裂变产物,偏析能随层间距的增加而减小。此外,采用Mc-Lean方程从热力学上评估了4种裂变产物在α-U表面的占据率,结果表明在服役温度范围内,4种镧系裂变产物均表现出明显的表面偏析。     

用等δ换算对压力容器部件进行缺陷评定

用等δ换算对压力容器部件进行缺陷评定邹广平，张正国，欧贵宝，何蕴增，潘信吉（哈尔滨工程大学）关键词等δ换算，等Ｋ换算，压力容器，缺陷评定１引言近年来，评价带有缺陷（裂纹）压力容器及管道结构部件的可靠性是一个重要问题。虽然已有几种对压力容器进行评定的规...     

SiC中离子植入诱导的化学和成分的变化以及由此引起的氢渗透特性

SiC晶体薄膜是科学技术感兴趣的材料，因为它有着多方面的潜在应用，如用于光电子学、高温半导体器上，用做核聚变装置第一壁材料（涂在不锈钢器壁表面上），以及用作高耐磨材料（也是涂在钢件表面上）。晶体SiC的大量用途也存在于非晶状态（α-SiC)。许多研究都侧重于研究这种非晶薄膜的结构和机械性能。然而，很少有人知道关于轰击诱导的化学和成分的变化。这里，我们综述与SiC和其它碳化物中轰击诱导的结构和成分变化有关的观测和解释。重点是放在N^-植入，N^ 植入导致用N逐渐代替C的 SiCxNy化合物。证明N植入通过促使在陶瓷－金属界面形成新的化学键大大增强了α-SiC与不锈钢之间的附着力。经过查考文献数据，我们或多或少地发现一些辐射诱导的迁移过程的明显证据。这些过程包括：(a)Gibbsian偏析；（b) 蒸发；（c）由不平衡电荷分布提供的长程 力；（d）缺陷诱导的迁移和（e）表面C的优先损失。这此现象有助于说明在SiC表面或其下面的成分的各种变化。当低能到中能的氢 碰撞碳化物表面时化学的和 与输 运相关的过程同时发生。在未来一低的聚变堆中大量氚能以被捕获的或游移的形式存在于壁上或其它内部部件。因此，甚至通过厚壁材料的氚渗透可能提出一 些难题。对α-SiC薄膜的氢渗透讨论表明，这种渗透受表面变化的强烈影响。     

GH3535合金表面渗铝层原位氧化工艺研究

高温工况下钍基熔盐堆中存在氚泄漏的风险，建立氚渗透屏障涂层有助于应对这一问题。采用包埋渗铝和原位氧化工艺，在GH3535合金表面制备了Al2O3/Ni-Al复合阻氚涂层，重点分析了氧化温度和真空度对氧化铝薄膜微观结构的影响。利用掠入射X射线衍射、扫描电子显微镜、透射电子显微镜等手段对氧化铝薄膜表面及截面的微观形貌、相构成进行了实验分析。实验结果表明：低氧分压能降低氧化铝薄膜的形成速度，促进形成更致密、表面平整的薄膜；高的氧化温度有利于形成α相氧化铝及更厚的氧化铝薄膜，但会大大增加表面缺陷。1.2 Pa真空度气氛、850℃氧化温度、72 h氧化时间是较优的原位氧化工艺参数，可以在GH3535合金基体表面获得性能较好的氧化铝薄膜，其相结构为γ和α相，厚度约为0.8μm，且表面致密无缺陷。     

探针组分对紫外光固化材料表面性能的影响

光固化快速成型技术（Stereolithography，SL）采用材料逐层固化累加法来形成三维实体模型，因此固化材料的表面性质对层与层之间的结合力有着非常大的影响。为了研究环氧丙烯酸酯类紫外光固化材料所形成表面的性质及影响因素，通过使用探针组分，对固化涂层进行接触角的测定和表面能的计算，并用衰减全反射-傅立叶变换红外光谱（Attenuated total reflectance-Fourier transforminfrared，ATR-FTIR）对固化膜的表面组成进行了表征。结果表明：固化过程中组分发生了迁移，其含量由表及里存在分布不均现象，最终对固化层的表面能产生了影响，且质量分数为0．01％的探针组分含量就能使表面能的变化显得相当敏感（Deuchem 467使涂层表面能由51．32mJ m^-2骤降至35．05mJm^2）.不同结构的探针组分迁移程度有差异，使涂层表面能发生了不同的改变。同时，组分的迁移程度也与涂层的两种接触介质（固化气氛与基材）的性质有关，引起涂层气氛面和基材面表面能的较大差异。     

The structural and dynamical properties of Al clusters adsorbed on Ni surface

The impact-induced deposition of Al₁₃ clusters with icosahedral structure on Ni(0 0 1) surface was studied by molecular dynamics (MD) simulation using Finnis–Sinclair potentials. The incident kinetic energy (E_in) ranged from 0.01 to 30 eV per atom. The structural and dynamical properties of Al clusters on Ni surfaces were found to be strongly dependent on the impact energy. At much lower energy, the Al cluster deposited on the surface as a bulk molecule. However, the original icosahedral structure was transformed to the fcc-like one due to the interaction and the structure mismatch between the Al cluster and Ni surface. With increasing the impinging energy, the cluster was deformed severely when it contacted the substrate, and then broken up due to dense collision cascade. The cluster atoms spread on the surface at last. When the impact energy was higher than 11 eV, the defects, such as Al substitutions and Ni ejections, were observed. The simulation indicated that there exists an optimum energy range, which is suitable for Al epitaxial growth in layer by layer. In addition, at higher impinging energy, the atomic exchange between Al and Ni atoms will be favourable to surface alloying.     

High resolution transmission electron microscopy of GeV heavy ion irradiated graphite

In this paper, we present some results relative to irradiations of natural and synthetic graphite with ∼1 GeV lead and uranium ions. High resolution transmission electron microscopy reveals no tracks in the bulk in either kinematic or diffraction contrast. Small surface patches are formed however random in distribution and proportional in number, but not equivalent to the total ion fluence. This suggests that some matter could be ejected from the entry and exit surfaces by electronic processes and are then redeposited on the surfaces.     

Silicon Wafer Bonding by Chemical Assembly of a Surface by Molecular Layering and Gas Cutting

It is suggested that chemical and heat treatment of surfaces under moist conditions (including also chemical assembly of a surface by molecular layering) and gas-cutting be used to fabricate silicon on insulator structures to obtain silicon wafer surfaces with prescribed chemical composition, activation, and surface modification.     

Neutralization of He ions scattered from Ca surface

The neutralization of He ions scattered from a Ca surface, as well as Al and Cu surfaces as references, is discussed on the basis of the incident energy dependence of low energy ion scattering (LEIS) spectra. The neutralization probability obtained for Ca is much higher than that expected on the basis of the Auger mechanism, indicating that the collision-induced (CI) process is dominant for the neutralization. The markedly large background component in the LEIS spectrum for Ca, corresponding to the re-ionization at the surface of He ions scattered and neutralized in the bulk, is consistent with the high probability of a CI process.     

Annihilation characteristics of positrons in free-standing thin metal and polymer films

Annihilation characteristics of positrons and positronium (Ps) in thin metal and polymer films were studied. Monoenergetic positrons were implanted into free-standing thin W and Au films and the annihilation γ-rays of positron-electron pairs were measured as a function of the incident energy of positrons. At the front-side surfaces of the films, an emission of Ps into vacuum and a resultant self-annihilation of ortho-Ps (o-Ps) were observed. At the backside surfaces, the Ps emission was found to be enhanced by an increase in the numbers of epithermal positrons and/or secondary electrons introduced by the impact of energetic positrons. For thin polymer films (polyester and polystyrene), the emission rate of o-Ps from the backside surfaces was higher than that from the metal films, which was attributed to the out-diffusion of o-Ps formed in the films. Those results suggested that the emission rate of Ps into vacuum was sensitive to the Ps formation process in the bulk and at the surface.     

Nanoscale self-affine surface smoothing by ion bombardment and the morphology of nanostructures grown on ion-bombarded surfaces

Surface smoothing by ion-bombardment with the concomitant formation of self-affine fractal surfaces at nanometer length scales is reviewed. Results of investigation of the dependence of surface smoothing on ion fluence and the threshold fluence for the formation of self-affine surfaces are presented. Finally, the morphology of self-assembled nanostructures grown by molecular beam epitaxy on surfaces of different fractal dimensions is investigated via studies of the roughness scaling exponent and the correlation length. While the self-assembled Ge islands grown on a pristine Si(1 0 0) surface are square or rectangular shaped, those on the ion-irradiated surface are nearly diamond-shaped.     

Results of steel corrosion tests in flowing liquid Pb/Bi at 420-600 °C after 2000 h

Corrosion tests were carried out on austenitic AISI 316L and 1.4970 steels and on MANET steel up to 2000 h of exposure to flowing (up to 2 m/s) Pb/Bi. The concentration of oxygen in the liquid alloy was controlled at 10⁻⁶ wt%. Specimens consisted of tube and rod sections in original state and after alloying of Al into the surface. After 2000 h of exposure at 420 and 550 °C the specimen surfaces were covered with an intact oxide layer which provided a good protection against corrosion attack of the liquid Pb/Bi alloy. After the same time corrosion attack at 600 °C was severe at the original AISI 316L steel specimens. The alloyed specimens containing FeAl on the surface of the alloyed layer still maintained an intact oxide layer with good corrosion protection up to 600 °C.     

Irradiation effects in an HfO2/MgO/HfO2 tri-layer structure induced by 10 MeV Au ions

In this report, we present radiation damage effects in a thin film, tri-layer structure, HfO₂/MgO/HfO₂. Irradiations were performed with 10 MeV Au ions in a recently developed medium energy ion irradiation facility at Los Alamos National Laboratory, which is described in this paper. Energy deposition by 10 MeV Au ions corresponds to a mixed regime, wherein electronic and nuclear stopping contribute to radiation damage. In this study, we investigated modifications of both surface and bulk properties in order to assess the structural stability of our oxide tri-layers under the severe irradiation conditions employed here. The most dramatic structural changes were observed to occur on the surfaces of the tri-layer samples. Surface features consisted of large craters and spires. The dimensions of these craters and spires exceed those of the individual ion tracks by almost three orders of magnitude. As for the bulk tri-layer structure, our conclusions are that this structure is stable in terms of: (i) resistance to amorphization; (ii) resistance to compositional mixing and (iii) resistance to pronounced nucleation and growth of extended defects. The main effect observed in the tri-layer structure was the transformation of the first HfO₂ layer from a monoclinic to either a tetragonal or cubic form of HfO₂.     

Characterization of atom and ion-induced “internal” electron emission by thin film tunnel junctions

Highly excited charge carriers are released when single or multiply charged ions impinge on metal surfaces. While electron emission into the adjacent vacuum phase is well investigated, one has only limited knowledge about the transport of excited electrons or holes into the bulk of a metal. This shortcoming can be reduced by studying the transport of these excited carriers over buried tunnel barriers in thin film metal-insulator-metal devices. The internal barriers can be tuned by a tunnel voltage which makes the device to a balance for excited electrons and holes. With a simple theoretical model we derive the balance function of different tunnel barriers and show their feasibility for the characterization of particle induced electronic excitations on metal surfaces.     

Turbulent transports by secondary flow vortices in a rod bundle

Experimental data on secondary flow vortices in a rod bundle with pitch-to-diameter ratio show weak vortices with the average velocity magnitude only about 0.1% of the mean bulk velocity. The question then arises, how important these weak vortices could still be as a transport mechanism in turbulent flows. The transport of axial momentum by these vortices is analysed quantitatively. While a minor importance is observed for the transport in radial direction, it is found that about half of the total transport in circumferential direction is due to the secondary flow vortex convection. Based on the analogy between the transport of momentum and heat, it is expected in nonisothermal situations that, in radial direction, the contribution can improve the heat transfer coefficient and contribute to better economy of heat transfer installations. In circumferential direction, the contribution helps to smooth out circumferential temperature differences, improves the heat removal from heated surfaces and, through a decrease of the maximum surface temperature, it contributes to passive safety of heat transfer installations.