Role of Double Oxide Film Defects in the Formation of Gas Porosity in Commercial Purity and Sr-containing Al Alloys

The role of double oxide film （bifilm） defects in the formation of gas porosity in commercial purity and Srcontaining AI alloys was investigated by means of a reduced pressure test （RPT） technique. The liquid metal was poured from a height into a crucible to introduce oxide defects into the melt. The melt was then subjected to different ＂hydrogen addition＂ and ＂holding in liquid state＂ regimes before RPT samples were taken. The RPT samples were then characterized by determining their porosity parameters and examining the internal surfaces of the pores formed in them by scanning electron microscopy. The results indicated oxide defects as the initiation sites for the growth of gas porosity, both in commercial purity and Sr-containing AI alloys. The results also rejected reduction of the surface tension of the melt, increase in the volumetric shrinkage and reduction in interdendritic feeding as the possible causes of an increase in the porosity content of the AI castings modified with strontium. The change in the composition of the oxide layers of double oxide film defects was suggested to be responsible for this behaviour.

Effect of Double Oxide Film Defects on Mechanical Properties of As-Cast C95800 Alloy

The morphology of double oxide film defects and their influence on the tensile mechanical properties of a commercial Cu-Al （C95800） alloy were investigated in this study. Plane castings were produced with two types of pouting systems, and their tensile properties were measured and then analyzed by means of Weibull statistics method. The fracture surfaces of the tensile specimens were examined using scanning electron microscopy equipped with energy-dispersive spectroscopy. A large amount of double oxide film defects were observed on the tensile fractured specimens of the topfilled plane castings, and their chemical composition is identified to be Al2O3. Weibull statistics analyses showed that the double oxide film defects significantly reduce mechanical properties of the castings investigated. Furthermore, the ultimate tensile strength is more obviously deteriorated by double oxide film defects than elongation.

Bauschinger and size effects in thin-film plasticity due to defect-energy of geometrical necessary dislocations

The Bauschinger and size effects in the thinfilm plasticity theory arising from the defect-energy of geometrically necessary dislocations （GNDs） are analytically investigated in this paper. Firstly, this defect-energy is deduced based on the elastic interactions of coupling dislocations （or pile-ups） moving on the closed neighboring slip plane. This energy is a quadratic function of the GNDs density, and includes an elastic interaction coefficient and an energetic length scale L. By incorporating it into the work- conjugate strain gradient plasticity theory of Gurtin, an energetic stress associated with this defect energy is obtained, which just plays the role of back stress in the kinematic hardening model. Then this back-stress hardening model is used to investigate the Bauschinger and size effects in the tension problem of single crystal Al films with passivation layers. The tension stress in the film shows a reverse dependence on the film thickness h. By comparing it with discrete-dislocation simulation results, the length scale L is determined, which is just several slip plane spacing, and accords well with our physical interpretation for the defect- energy. The Bauschinger effect after unloading is analyzed by combining this back-stress hardening model with a friction model. The effects of film thickness and pre-strain on the reversed plastic strain after unloading are quantified and qualitatively compared with experiment results.

OBSERVATION ON DEFECTS IN POLYCRYSTALLINE SILICON THIN FILMS

Polycrystalline silicon thin films were prepared by RTCVD (rapid thermal chemica l vapor deposition) method on several substrates such as SSP (silicon sheet from powder) ribbon, poly-Si wafer and mono-Si wafer. Intra-granular defects such as stacking faults, twins and microstructure defects were investigated on thin fil ms by scan electron microscopy (SEM) technique.

Influences of vacancy defects on thermal conductivities of Ge thin films

The effects of vacancy defects on the thermal conductivity of Ge thin films were investigated by employing molecular dynamics （MD） simula- tions and theoretical analysis based on the Boltzmann equation. Both the MD and theoretical results show that the lattice thermal conductivity dramatically decreases with the increasing of vacancy concentration at 400 and 500 K. In addition, the dependence of vacancy concentration on the thermal conductivity of Ge thin films becomes less sensitive as the temperature increases. Theoretical results also confirm that the major part of the lattice thermal conductivity reduction is associated with the point-defect scattering and phonon-phonon scattering processes.

Different Thermal Stabilities of Cation Point Defects in LaAlO_3 Bulk and Films

Using the first-principles method, we investigate the thermal stability of cation point defects in LaAlO3 bulk and films. The calculated densities of states indicate that cation vacancies and antisites act as acceptors. The formation energies show that cation vacancies are energetically favorable in bulk LaAIO3 under O-rich conditions, while the AILa antisites are stable in reducing atmosphere. However, the same behavior does not appear in the case of LaAlO3 films. For LaO-terminated LaAlOa fihns, La or AI vacancies remain energetically favorable under O-rich and O-deficient conditions. For an AlO2-terminated surface, under O-rich condition the La interstitial atom is repelled from the outmost layer after optimization, which releases more stress leading to the decrease of total energy of the system. An AI interstitial atom has a smaller radius so that it can stay in distorted films and becomes more stable under O-deficient conditions, and the Al interstitial atoms can be another possible carrier source contribution to the conductivity of n-type interface under an ultrahigh vacuum. La and Al antisites have similar formation energy regardless of oxygen pressure. The results would be helpful to understand the defect structures of LaAlOa-related materials.

基于稀疏成像的半导体薄膜材料界面缺陷检测

复杂背景下检测半导体薄膜材料界面微小缺陷具有一定的难度,为了精准检测半导体薄膜材料界面缺陷,提出一种稀疏成像下半导体薄膜材料界面缺陷检测方法。扫描采集半导体薄膜材料界面二维图像,对含有噪声的半导体薄膜材料界面实施小波分解,获取不同频带的子图像。低频图像保持不变,选择对应的模板对高频图像滤波处理,将滤波处理后的高频图像和低频图像两者合成,获取去噪后的图像。通过机器视觉定位薄膜材料界面的缺陷位置,提取缺陷区域特征,采用稀疏成像对特征参数修正,完成半导体薄膜材料界面缺陷检测。仿真结果表明,采用所提方法可以获取更加精准的检测结果,用时比较短,满足高效与高精度检测需求。

自成形硅表面微结构:表面特征及潜在应用

采用等离子体增强化学气相沉积法(Plasma Enhanced Chemical Vapor Deposition, PECVD)制备掺氢非晶硅膜,并对其表面结构学进行研究。该文发现在晶体硅衬底上沉积非晶硅薄膜时,会在表面形成非均匀分布的起泡缺陷。在已制备的非晶硅薄膜上进一步沉积了氮化硅/非晶硅的交替层,在起泡缺陷原位形成了一个完美的穹顶多壳的微结构,并且没有明显的结构坍塌。该文总结了自成形穹顶微结构的3个独特的结构特性,并进一步指出了该自成形穹顶微结构在纳米光学和微机电系统中的潜在应用。

反溶剂对CsPbBr_(3)太阳电池性能的影响

分别在钙钛矿前驱体中添加一系列的反溶剂乙酸乙酯(EA)和乙腈(ACN),制备出不同形貌的CsPbBr_(3)薄膜,探究薄膜质量与太阳电池性能的内在联系。结果表明,在大气制备环境中,反溶剂有助于CsPbBr_(3)晶粒的生长,薄膜表面缺陷明显减少,太阳电池各性能参数(短路电流密度、开路电压以及填充因子)均有所提升,尤其是添加乙腈(V(PbBr_(2)/DMF)∶V(ACN)=10∶1)后,光电转换效率(PCE)从3.16%提高到7.10%。

太阳电池阵电池基板PI薄膜黏结质量检测技术

航天器太阳电池阵电池基板上PI薄膜的黏结质量直接影响基板工作寿命。为有效、迅速、准确地检测PI薄膜黏结质量,通过热循环和热真空等环境试验,对PI薄膜黏结后微观尺度、非显性化的脱黏、气泡和凸起等典型缺陷进行充分暴露;利用基于偏振成像技术的视觉检测方法,对制备的4组试验样件进行正交试验,准确识别出PI薄膜黏结区域的典型缺陷及其具体尺寸范围。试验结果表明该技术对PI薄膜黏结质量缺陷的检测效果良好。

无菌生物护创膜在严重创伤致软组织缺损创面早期治疗中的应用效果分析

目的探讨无菌生物护创膜在严重创伤致软组织缺损创面早期治疗中的临床效果。方法选取2019年1月至2020年12月苏州大学附属第一医院收治的40例严重创伤致软组织缺损患者作为研究对象,按照不同治疗方法将其分为护创膜组(20例)与纱布组(20例),护创膜组患者在对症支持治疗的基础上局部创面早期行无菌生物护创膜联合负压封闭引流治疗,纱布组患者在对症支持治疗的基础上局部创面早期行灭菌凡士林纱布联合负压封闭引流治疗,对比观察两组患者创面疼痛评分、创面基底准备时间、创面愈合时间、住院时间、创面一次性愈合比值以及术后并发症发生情况。结果护创膜组患者治疗第7天时创面视觉模拟评分法(VAS)评分明显低于纱布组(Z=-2969,P=0003),创面基底准备时间、创面愈合时间及住院时间均明显短于纱布组(Z/t=-2394、-2782、3186,P=0017、0005、0003),而创面一次性愈合比值与纱布组无明显差异(χ^(2)=0173,P=0677);护创膜组患者术后并发症发生率为150%,与纱布组患者的术后并发症发生率200%无明显差异(χ^(2)=0173,P=0677)。结论无菌生物护创膜可有效减轻严重创伤致软组织缺损创面的疼痛程度,缩短创面基底准备时间、创面愈合时间及住院时间,具有较高的临床应用价值。

高分子薄膜表面缺陷检测系统的照明方案设计

阐述了高分子薄膜表面存在的缺陷类型及其可能造成的危害,着重介绍了工业视觉检测系统中光源对高分子薄膜表面缺陷特征成像的影响。为寻求能够最大程度呈现高分子薄膜表面缺陷特征的光源照明方案,通过分析高分子薄膜的光学特性和专用光源的相关特性,结合高分子薄膜表面缺陷的特点,设计了多组光源方案对比实验。实验结果显示,僵块和黑点类缺陷在红色、白色和绿色LED光源以正向背光、角度背光和侧向角度等照射方式均能较好地呈现特征;条纹和死皱类缺陷受光源颜色影响较小,当光源以侧向角度和角度背光照射时这两类缺陷特征较为明显,而以正向背光照射时几乎没有特征呈现;活皱缺陷仅在绿色光源以角度背光照射时特征较为清楚。综合各类缺陷在不同照明方案下的特征呈现效果,实现了高分子薄膜表面缺陷检测系统的照明方案设计。

热镀铝锌板黑线缺陷原因分析

为了查找薄规格热镀铝锌板黑线缺陷产生原因,采用ZEISS Merlin Compact场发射扫描电镜及其附带的OXFORD X-max N型能谱仪等分析技术对热镀铝锌钢板黑线缺陷表面、截面以及腐蚀去掉镀层后的钢铁基板表面进行了微观形貌观察和化学成分分析。结果表明:热镀铝锌钢板上表面黑线缺陷是由于钢铁基板划伤致使钝化膜较厚所致;热镀铝锌钢板下表面黑线缺陷是由于下表面镀层发生凹陷微变形致使钝化膜较厚所致。热镀铝锌钢板表面划伤以及镀层凹陷造成与周围其他位置对光的反射不同,形成了视觉上的黑线缺陷。

咪唑添加剂对钙钛矿太阳能电池性能的影响

为钝化钙钛矿薄膜中的缺陷并改善薄膜质量,将咪唑(Imidazole,IM)添加到钙钛矿前驱体中,并通过旋涂法制备钙钛矿薄膜;采用X射线光电子能谱仪、扫描电子显微镜、X射线衍射仪、紫外-可见分光光度计和稳态-瞬态荧光寿命光谱仪对钙钛矿薄膜形貌、结构和性能进行表征。结果表明:IM同时具有路易斯酸性与路易斯碱性,能够有效调控钙钛矿晶体生长,增大钙钛矿晶粒,改善钙钛矿薄膜质量;IM与钙钛矿中未配位的Pb2+和I-形成络合,协同钝化薄膜表面与晶界处的Pb2+和I-缺陷;经过IM修饰的电池器件,其光电转化效率从15.43%提高到17.02%;具有较大晶粒以及较低缺陷态密度的高质量钙钛矿薄膜,可以有效阻挡水分子的入侵,提高电池器件的稳定性。基于IM添加剂成功制备了低缺陷的高质量钙钛矿薄膜,为钙钛矿太阳能电池的商业化生产提供了理论指导。

铌酸锂晶体的缺陷结构

铌酸锂是集电光、声光、压电和非线性等性能于一体的人工晶体,在光子学及光电子学等领域具有广泛的应用前景,被誉为“光学硅”或“光子学硅”。近年来随着基于薄膜铌酸锂的集成光子学的迅猛发展,铌酸锂晶体受到更加广泛的关注。然而铌酸锂是一种典型的非化学计量比晶体,其含有大量的本征缺陷,严重影响了晶体性能;同时,铌酸锂晶格对众多杂质离子都有良好的固溶性,而且晶体的性质随着杂质离子的种类和浓度不同产生显著变化。如同单晶硅等半导体材料的缺陷工程,缺陷已经并且必将继续对晶体的性能及铌酸锂集成光子学产生重要影响。本文对铌酸锂晶体的缺陷结构做了一个简要的回顾,尤其是近期涉及薄膜铌酸锂晶体的相关内容,涵盖了本征缺陷结构、非本征缺陷结构、缺陷结构的表征、缺陷结构的理论计算、缺陷结构与晶体性能的构效关系等方面,以期对当前的铌酸锂集成光子学研究贡献微薄之力。

纸膜双层缺陷检测的视觉成像光场设计

为实现包装盒纸质基底层和透明膜层缺陷的同步检测,开展了对纸和膜缺陷的同步成像研究。首先,分别建立了标准球面积分光场、椭球面积分光场和弧面积分光场模型,并利用COMSOL Multiphysics 5.6对3类光场进行射线仿真,对比分析了球面积分光场下射线角度均匀性及辐照均匀性,通过正交仿真优化椭球面积分光场参数;其次,在椭球面积分光场环境、亮场前打光环境、暗场前打光环境下对包装盒成像。与此同时,对包装盒的油污、抵触、开口、泡皱、破损5项常见缺陷依次进行物理检测和机器视觉检测,验证缺陷成像的有效性。试验结果表明,在椭球面积分光场下成像,图像对纸质基底层缺陷特征、透明膜层缺陷特征均有较好的呈现效果,图像上油污、抵触、开口、泡皱、破损的物理检出率分别为96.2%、92.5%、100%、95%、92%,异常检出率分别为98.6%、97.5%、100%、100%、98.4%,缺陷类别检出率分别为97.6%、96%、100%、97%、96%。研究结果表明,椭球面积分光场光路角度和辐照强度均匀,覆透明膜包装盒的缺陷特征呈现清晰,满足工业生产的检测要求。

集磁器内壁轮廓形状对磁脉冲辅助半固态钎焊接头连接质量的影响

针对磁脉冲辅助半固态钎焊工艺中使用等内径集磁器连接铜、铝管件时存在的界面氧化膜去除效果不均、扩散层深度差异较大等问题,通过数值模拟方法分析了集磁器内壁轮廓形状及其结构参数对界面冲击应力及钎料剪切流变速率的影响。为实现连接区域内界面冲击及轴向剪切流变沿轴向分布的均匀性,对集磁器形状结构参数进行了优化,并针对性地制造了相应的集磁器,在特定的工艺参数下进行了系列钎焊实验。结果表明,相较于常规等内径集磁器,优化后的集磁器能够更好地去除母材表面氧化膜,促进界面扩散反应并减少连接缺陷,扩散层厚度增加且分布更为均匀,接头性能得到有效提升。

合金元素对耐酸钢耐蚀行为及表面缺陷的影响

耐酸钢具有比碳钢更强的耐酸性能,比耐酸不锈钢更低的合金成本,与涂镀产品相比又减少了电镀/热镀工序,在实际应用中体现出较大的应用价值。本文系统地介绍了合金元素对耐硫酸露点腐蚀钢耐蚀行为、表面质量的影响,对耐蚀钢实际生产中热轧表面缺陷产生原因进行了分析,并提出了有效改进措施。Cu、Sb、Sn、Cr元素的添加在耐硫酸腐蚀方面起着决定性作用,但是,Cu、Sb的选择性氧化会引起一系列表面质量问题,如“铜脆”和氧化铁皮色差,是工业生产的难题。研究发现,Ti能够以鳞片状富集在锈层内部,通过添加钛元素提高晶界密度;优化连铸工艺,避免铸坯在第三脆性区矫直开裂;缩短铸坯在加热炉时间、铸坯加热快速通过铜熔点区间和降低精除鳞温度等措施,在提高强度、有效消除“铜脆”缺陷的同时,还可以有效避免晶间腐蚀。在此基础上,探讨了微合金钛在耐酸钢中的作用及低成本耐酸钢的应用前景。认为,以Sn、Ti替代Sb,实现绿色环保生产,避免耐酸钢在使用过程中的全生命周期污染是新一代耐酸钢发展的趋势。

Effect of carrier gases on the entrainment defects within AZ91 alloy castings

An entrainment defect(also known as a double oxide film defect or bifilm) acts a void containing an entrapped gas when submerged into a light-alloy melt, thus reducing the quality and reproducibility of the final castings. Previous publications, carried out with Al-alloy castings, reported that this trapped gas could be subsequently consumed by the reaction with the surrounding melt, thus reducing the void volume and negative effect of entrainment defects. Compared with Al-alloys, the entrapped gas within Mg-alloy might be more efficiently consumed due to the relatively high reactivity of magnesium. However, research into the entrainment defects within Mg alloys has been significantly limited. In the present work, AZ91 alloy castings were produced under different carrier gas atmospheres(i.e., SF6/CO2, SF6/air).The evolution processes of the entrainment defects contained in AZ91 alloy were suggested according to the microstructure inspections and thermodynamic calculations. The defects formed in the different atmospheres have a similar sandwich-like structure, but their oxide films contained different combinations of compounds. The use of carrier gases, which were associated with different entrained-gas consumption rates, affected the reproducibility of AZ91 castings.

Micro-structure of PECVD Diamond Films by Slow Positron Beam

钻石电影的微观结构被慢正电子横梁和拉曼光谱学学习。为钻石电影的拉曼光谱学实验， sp 3 hybridized 契约的高部分在样品被检测。进一步照亮的正电子歼灭系列分析缺点的集中和类型在所有样品的每条 sample.2000 S-E 曲线是不同的，这证明钻石水晶结构在每件样品有明显的变化。这些结果显示那正电子歼灭光谱学是一个有效工具测量钻石电影的微观结构。