金属中点缺陷的电子结构和缺陷谱

本文以胶体模型为基础,利用密度冷函理论和局域密度近似研究了过渡金属Cr,Fe,Ni和贵金属Cu中空位型缺陷、氢杂质、空位-杂质复合体的电子结构以及以正电子湮没寿命表征的缺陷谱。表明了用正电子湮没寿命谱研究金属点缺陷电子结构和缺陷尺度大小的可行性。 关键词：     

Fe-V-N稀合金中空位复合体特性的研究(Ⅱ)

本文利用离散变分法,集团模型和三维数值弛豫技术,研究了Fe-V-N稀合金中V-N-空位复合体的几何构型,正电子湮没特性和电子结构。根据正电子湮没寿命实验的结果和总能量极小原理,确定了V和N在V-N-空位复合体中的最佳占据位置。分析了V-N-空位复合体的成键特性和电荷转移情况。 关键词：     

AA 2037新型连铸铝合金热轧板退火的正电子湮没研究

应用正电子湮没等技术对AA 2037连铸铝合金热轧板不同温度退火下空位-溶质相互作用及沉淀相进行了研究， 研究表明：室温时效形成的主要是空位-铜复合体以及空位-镁-铜复合体；温度为200℃退火时由于过渡相的形成正电子平均寿命出现峰值，符合多普勒展宽谱的商谱中观察到锰信号的存在，表明形成了空位-镁-锰复合体或过渡相中可能存在锰；温度高于250℃时，随着过渡相变粗、溶解，锰信号消失，而铜信号增强，在350℃后铜信号达到饱和，温度为450℃左右时，稳定相形成. 关键词： 正电子湮没技术 空位-溶质复合体 沉淀 退火     

H,He,Kr杂质在过渡金属和贵金属中的行为

本文以胶体模型为基础,利用密度泛函理论,局域密度近似研究了H,He和Kr在过渡金属Ni,Fe,Cr和贵金属Cu中的空位团复合体的电子结构、正电子湮没寿命。结果表明:随着复合体尺寸的增加,杂质的束缚态电子能级变浅,散射态电子在复合体内的平均密度变小,正电子在复合体内的几率增大,正电子湮没寿命增加。 关键词：     

正电子湮没谱学在金属材料氢/氦行为研究中的应用

用于核反应堆的金属结构材料中氢/氦泡的前躯体——(氢/氦)-空位复合体的形成受到温度、辐照剂量等多方面因素的影响,研究其在材料中的形成和演化行为对气泡形核的理解及先进核反应堆材料的发展起着至关重要的作用.然而,受到分辨率的局限,这种原子尺度的微结构很难用电镜等常规方法进行表征,以致于该问题的研究上可利用的数据相对较少.正电子湮没谱学是一种研究材料中微观缺陷的特色表征方法,近些年来慢正电子束流和新型核探测谱仪技术的不断发展以及基于慢束发展起来的多种实验测试方法的改进,使正电子湮没技术应用已拓展到金属材料中氢/氦行为的研究领域,在金属材料表面氢/氦辐照损伤的研究中发挥了重要作用.本文结合国内外相关进展以及本课题组的一些研究成果评述了正电子湮没谱学在金属材料氢氦行为研究中的应用,着重讨论了正电子湮没寿命谱、多普勒展宽谱、符合多普勒展宽三种测量方法在如下金属材料氢/氦行为研究中的优势:1)氢/氦气泡尺寸和浓度的估算; 2)高能氢/氦离子辐照损伤缺陷及缺陷的退火、时效的演化行为; 3)不同形变程度样品中氢/氦与形变缺陷的相互作用; 4)不同能量或剂量氢/氦离子辐照对材料造成的损伤以及氢氦协同作用.     

化合物半导体材料的正电子寿命计算

在局域密度理论（LDA）和广义梯度理论（GGA）的基础上计算了ZnO,GaN,GaAs,SiC和InP五种化合物半导体材料中的正电子湮没信息,包括化合物半导体材料中的自由态正电子的湮没寿命;还有不同类型空位（单空位,双空位）附近俘获的束缚态正电子密度分布和湮没率分布,以及束缚态正电子的湮没寿命. 关键词： 半导体 正电子寿命     

用正电子湮没技术研究纯镍多晶体疲劳过程中的晶体缺陷

对充分退火纯镍多晶体样品分组进行了恒应变幅拉-压疲劳试验和冷轧形变后,测量了正电子湮没参数;并选少数疲劳试样进行了电子显微镜薄膜衍射象观察。用多指数拟合方法从疲劳试样的正电子湮没寿命谱中分解出与正电子在小空位团中湮没相应的成份。这些寿命值在不同疲劳阶段分别平均为209,255和>300ps。其相对强度的变化与小空位团浓度增加然后尺寸增大的趋势相符合。从而,本文根据正电子湮没技术提供了纯镍多晶体疲劳过程中除大量位错外空位聚集的实验证据。利用简单三态正电子捕获模型估算了上述缺陷浓度。本工作还提供了用多指数拟合方法分解复杂寿命谱和用于简单三态捕获模型的例证。 关键词：     

氢和温度对质子辐照硅的正电子捕获的影响

用正电子湮没寿命测量研究了在3.2×10¹⁷cm^-2和3.6×10¹⁶cm^-2质子辐照硅单晶中的正电子捕获,观测到辐照诱导的捕获正电子的缺陷主要是双空位,辐照过程中高剂量样品的双空位基本上都捕获了氢,低剂量样品还有一小部分未捕获氢,在高剂量样品的两轮和低剂量样品的第一轮升温测量中都观测到双空位进一步捕获氢,含氢双空位的荷电态随温度升高在145K附近发生由负荷电向中性转变,它的负荷电态正电子寿命比中性态正电子寿命长,无论 关键词：     

应用正电子湮没技术研究多晶形变镍中氢和缺陷的互作用

本文采用正电子湮没的多普勒展宽方法,研究冷轧形变镍中阴极充氢后氢与缺陷的互作用行为。实验结果表明:冷轧镍电解充氢以后其S参数显著上升,S参数上升量的大小取决于试样内部的空位浓度,与位错密度的大小关系不大。由此提出氢与空位互作用形成以氢为核心的空位团的机制,解释了实验中观察到的现象。     

Fe-V-N稀合金中空位复合体特性的研究(Ⅰ)

本文利用正电子湮没技术研究,Fe-V稀合金渗N后出现的V-N-空位复合结构。测定了这种复合结构的正电子湮没寿命值和估算了空位形成能。为解释Fe-V合金渗N后V的增强扩散机制提供实验依据。 关键词：     

协同显色反应测定粮食中铝(Ⅲ)

在ｐＨ６．５醋酸铵－醋酸缓冲液中,在ＯＰ存在下,铝（Ⅲ）和邻苯二酚紫与罗丹明６Ｇ形成紫红色离子缔合物。最大吸收波长λｍ ａｘ ＝ ５８０ ｎｍ ,表观摩尔吸光系数ε＝ ６．８×１０４ Ｌ·ｍ ｏｌ－ １ ·ｃｍ － １ 。铝（Ⅲ）在０～７ μｇ／２５ ｍ Ｌ范围内符合比耳定律。本法灵敏度高,选择性好,用于粮食中微量铝（Ⅲ）的测定,结果满意。     

Characteristics of large capacity ultrasonic complex vibration sources with stepped complex transverse vibration rods

Configurations of large capacity ultrasonic complex vibration sources with multiple longitudinal transducers are proposed and studied. The ultrasonic complex vibration systems are effective and essential for new applications in various industries. The complex vibration source of 27 kHz consists of a complex transverse rod with a welding tip (aluminum alloy, stainless steel and titanium alloy), a complex vibration rod with a flange and stepped part for holding the system, a circular longitudinal vibration disk (aluminum alloy) and six bolt-clamped Langevin type PLT transducers. Three transducer pairs are driven simultaneously using three driving systems at phase difference 120 degrees, and almost circular vibration locus is obtained.     

LaB6场发射阵列牺牲层制备工艺

 分析了传统牺牲层材料铝在制备LaB6场发射阵列时存在的问题,利用溅射及热蒸发工艺依次制备铝膜和氧化锌膜,制备出了一种新型的牺牲层——ZnO-Al复合牺牲层,并对所制备的阵列进行了测试。实验结果表明：ZnO-Al复合牺牲层能够有效地解决电化学腐蚀的问题,所制备出的LaB₆场发射阵列尖锥保持了完好的形貌,其发射特性也达到了最初制备场发射阵列的要求,说明ZnO-Al复合牺牲层是作为LaB₆场发射阵列牺牲层的理想材料。     

Passivation of an Al acceptor in silicon by hydrogen or muonium

We report on calculations of the electric field gradient at the site of the Al nucleus in the Si-H-Al complex in silicon. As a model for the surroundings of the complex we used a cluster consisting of 43 silicon and one aluminum atoms. The geometry of this cluster was fully optimized at the Hartree-Fock level. To discuss the dependence of our results on the level of theory, we studied a subcluster of four silicon and one aluminum atoms at the Hartree-Fock and CASSCF level.     

Infrared spectroscopic characterization of aluminized diphenyl carbazide

Infrared spectroscopy is used to determine the effect of a partial reaction of melted diphenyl carbazide (DPC) with pure aluminum cations during the formation of aluminized diphenyl carbazide (ADPC) complex by a new technique. For this purpose a detailed IR analysis is carried out for pure DPC, pure aluminum and ADPC in the range 400–4000 cm⁻¹. The analysis includes all of the internal fundamental modes of vibrations of symmetric and asymmetric stretching of N–H, aromatic C–H stretching, bending N–H, CO stretching absorption band, mono-substituted benzene and N–H oscillation using different mole aluminum concentration x. Changes in the spectral shape, mode frequency, mode shift, intensity are studied as a function of x and attributed to Al polarizability. The study revealed the presence of a critical value x=0.3 required for the formation of ideal ADPC complex which contains minimum traces of unreacted aluminum. The variations in transmittance, relaxation time, rotational energy barrier with mole concentration x are also studied and support the presence of critical mole concentration for ADPC complex formation. Detailed X-ray analysis is used to confirm and check the validity of the obtained results. Critical molar aluminum concentration value x=0.3 is determined. The absence of CN stretching mode and the presence of symmetric stretching and bending modes of N–H prove that ADPC complex is ketonic in nature. This conclusion is supported by the very little change in the IR absorption spectra of the carbonyl group.     

Synthesis and electroluminescent property of dinuclear aluminum 8-hydroxyquinoline complex

A new structural dinuclear aluminum 8-hydroxyquinoline complex (DAlq₃) with two aluminum chelate-center was designed and synthesized. It was assessed as light-emitting material in organic light-emitting device (OLED). The green light emission was observed in films and OLEDs. DAlq₃ has better electron mobility and also shows a higher electroluminescence (EL) efficiency than that of aluminum 8-hydroxyquinoline (Alq₃).     

Determination of Aluminum Ion with Morin in a Medium Comprised by Ionic Liquid?CWater Mixtures

In this study we have employed two ionic liquids (ILs) as a new media for the analysis of aluminum in aqueous solutions by spectrofluorimetric method. ILs are liquid salts and they have no measurable vapor pressure up to their thermal decomposition point, >300 ??C. This lack of vapor pressure makes these materials highly attractive for many studies as they can be used as clean solvents. Besides they are promising environments for analysis purposes and optical sensor designs. The results revealed that absorption, excitation and emission spectra of the morin?CAl complex exhibited considerable changes in moieties. The morin?CAl complex was stable at aluminum concentrations below 9.1?mg?L^?1 in 25% 1-butyl-3-methylimidazolium bromide (IL-I)-water binary mixtures. The higher concentrations of IL (>25% by volume) was not suitable for the complex formation thus in pure IL media the complex formation even at high aluminum concentrations was not observed. The complex stoichiometry ratio of aluminum:morin was 2:1 in IL-I-water binary mixtures. The linear concentration range was 0.045?C7.2?mg?L^?1 with a correlation coefficient of r?=?0.9909. The detection limit was found to be 0.036?mg?L^?1. Cu²⁺, Mn²⁺ and PO ₄ ^3? ions exhibited less interfering effect in presence of IL-I and the tolerance limit of Cu enhanced 10 times when compared with ethanol.     

Regularities of Structure Formation in AA2024 Alloy During High-Intensity Plastic Deformation Under Conditions of Adhesion-Diffusion Friction Interaction

Russian Physics Journal - The results of model experimental studies of structural-phase changes in an AA2024 aluminum alloy after friction with a counter-body of a complex configuration are...     

Facile fabrication of superhydrophobic surface with micro/nanoscale binary structures on aluminum substrate

The present work reports a simple method to produce the aluminum superhydrophobic surface based on an interface reaction between an aluminum foil and zinc aqueous solution. The products were characterized by field-emission scanning electron microscopy, X-ray powder diffraction and X-ray photoelectron spectrum. The field-emission scanning electron microscopy images show that the coating surface is composed of micro/nanoscale binary structure, which is similar to the structure of lotus leaf. The wettability of the coating surface was also investigated. It was found that after treatment with stearic acid, the wettability of the aluminum foil changed from superhydrophilic to water-repellent superhydrophobic. The complex micro/nanoscale binary structures along with the low surface energy lead to the high surface superhydrophobicity.     

Individual and collective vibrational modes of nanostructures studied by picosecond ultrasonics

We report on picosecond ultrasonic measurements obtained on aluminum and platinum nanostructures with variable dot size and lateral periodicity which realized a 2D phononic crystal. Performing investigations at different resolution scales, we have identified individual modes of vibration depending on the dot size, and mode of vibration strongly correlated with the bi-dimensional organization. The platinum dots sputtered on an aluminum layer have shown a behavior of isolated oscillators without any coupling between neighbor elements in this phononic crystal. The frequency of such normal modes, extracted from time resolved measurements are in good agreement with 3D finite element simulations. In contrast, with aluminum dot systems where the coupling is more efficient we observe a complex spectrum of vibrational modes related to the band structure induced by the bi-dimensional patterning.