Crystallization process of perovskite modified by adding lead acetate in precursor solution for better morphology and higher device efficiency

The power conversion efficiency of 15.20% is achieved in this study for planar perovskite solar cells fabricated in air from one-step spin-coating lead chloride (PbCl₂) based precursor modified by additional adding 1% lead acetate (PbAc₂), much higher than the reference one from pure PbCl₂ precursor without modification. A higher quality perovskite film with increased coverage is the reason for this improvement. The perovskite nucleation rate and start time of nucleation are key parameters of perovskite crystallization kinetics. By adding 1% PbAc₂ to the precursor, the density of perovskite crystal nucleuses is optimized to achieve the best film and then the highest device performance.     

FCBGA高铅凸块non-wet的失效机制及基于封装工艺的解决方案

FCBGA封装芯片中晶片凸块和基片凸块之间的non-wet问题是一个已知的能导致严重低良品率和引入可靠性隐患的问题。本文研究了FCBGA封装形式中non-wet的典型失效模式和揭示了其生成机制, 并确定了晶片凸块表面残留的铅和锡氧化物是导致晶片凸块和基片凸块之间non-wet的主要成因。晶片凸块回流工艺实验表明,优化后的回流时间和氢气流速能显著减少和去除晶片凸块表面的铅锡氧化物,从而能把non-wet引起的报废率降低90%左右。 失效分析结果和量产数据都验证了本文揭示的non-wet的失效机制是正确的。 研究确定的凸块回流工艺的优化参数显著降低了non-wet引起的报废率,从而大大地节省了制造成本和提高了产能利用率。     

扫描电镜血管内皮细胞硝酸银染色方法的改良

介绍一种简单适用的血管内皮细胞硝酸银染色方法,可使扫描电镜下内皮细胞的表面结构和反应血管通透性的形态改变得到良好展现。     

Copper lead frame: an ultimate solution to the reliability of BLPpackage

Copper lead frame was chosen as an on-board reliability enhancement for the BLP (bottom leaded plastic) package. Adopting the copper lead frame needed a verification process for the package reliability because of its high affinity with oxygen that degrades package reliability. A series of tests were performed to select the best copper material and to determine the adhesion index parameter. The experimental results showed that the adhesion strength between the copper lead frame and EMC (epoxy molding compound) was affected by alloy composition, oxide layer thickness, and cupric/cuprous oxide ratio, Among them, the adhesion index parameter proved to be the cupric/cuprous oxide ratio. When it falls between 0.2-0.3, the highest adhesion strength was obtained regardless of alloy composition and oxide thickness. From the adhesion test results, the Cr-Zr-Cu copper alloy was employed as the lead frame for the 54-pin BLP package. The package reliability and on-board reliability tests including surface mountability, mechanical robustness, and solder joint reliability were carried out to compare the 54-pin BLP package, with Cr-Zr copper alloy and alloy 42 lead frame     

磷化液改性片状FeCoZr合金粉末的电磁性能

采用机械球磨的方法,对气雾化FeCoZr软磁合金粉末进行了扁平化处理,以不同用量的MgBPO系磷化液对获得的片状合金粉末进行表面改性,考察了样品在3.95~12.40GHz时的复介电常数和复磁导率。结果表明:随着改性磷化液体积的增加,样品的复介电常数实部和虚部减小;改性后样品的复磁导率实部增大、虚部减小;计算的反射损耗曲线显示,样品的反射损耗峰相应地移向高频;磷化液用量为16mL时,样品具有最小的反射损耗峰值(–11.42dB)。     

Optical and structural properties of PbSe films obtained by ionic exchange of lead oxyhydroxicarbonate in a selenium-rongalite solution

In this work, starting from precursor films of Pb₁₀O(OH)₆(CO₃)₆, previously obtained by chemical bath deposition technique, we report the process to obtain PbSe films through ionic exchange. For this, after chemical deposition, several pieces of the precursor films were immersed in selenium ions solution in order to promote the transformation to PbSe films by ionic exchange. Instead using the conventional sodium selenium sulfite solution as the selenium ions solution, a new one is reported, which is based in rongalite (CH₃NaO₃S) and sodium citrate as reducing agents. Samples were removed after 30, 60 and 90 min to determine the effects of ionic exchange time on the phase transformation process. The complete set of samples was analyzed by X-ray diffraction, scanning electron microscopy and optical absorption measurements. The XRD results show a gradual crystalline transformation from the precursor phase to cubic PbSe crystalline phase. The gradual phase transformation is accompanied by surface morphologic changes as shown by SEM images. From the optical absorption spectrum of the PbSe films, it was calculated the energy band gap, being around 0.34 eV.     

Electron microscopic visualization of collagen aggregates without chemical staining.

Lateral, uni-directional aggregates of collagen, segment-long-spacing crystallites (SLS), were made by dialyzing collagen solutions against acetic acid containing ATP, and were examined by transmission electron microscopes without electron staining. There detected were at least 20 dark (electron dense) cross-striations within SLS. The banding pattern was compared with the biochemical and biophysical properties of the amino acid side chains along the collagen molecule. The banding pattern of unstained SLS was mostly correlated with the intramolecular distribution of basic amino acid residues. Since basic amino acids have relatively large side chains, the distribution of mass (molecular weight of amino acids) along the molecule (local density profile) partially explained the cross-striation. Addition of fractions of molecular weight of ATP to basic residues made the local density profile much better correlate to the banding pattern. We conclude that the electron microscopic banding pattern of unstained SLS was generated by the local amount of material or local density profile along the collagen aggregates, which was enhanced by ATP bound to positively charged basic residues. The concept that the electron density correlates with the amount of material is fundamental in electron microscopy, and it has been proven with biological materials in this paper.     

D.C. solution of bipolar-transistor circuits

The d.c. solution of bipolar-transistor circuits, from zero initial guess in a nodal-analysis program, is obtained effectively by controlled stepping of the d.c. excitation, exponential scaling of the linear resistors and using the Newton-Raphson algorithm with a simple damping factor in the iterative process.     

快速渗透测试系统的设计与实现

渗透测试人员通常使用扫描软件来检测网站是否存在安全漏洞,这些软件自动发送网络请求,分析网站返回的信息来确定安全风险。但是,随着越来越多的站点利用开源程序搭建,这些通用扫描软件就显得低效和费时。文中提出了一种结合Web程序指纹扫描和漏洞精确利用的方法来进行渗透测试扫描,并实现了Web漏洞扫描工具Zscan。经过与目前主流的漏洞扫描软件对比测试扫描开源程序,Zscan在扫描效率和准确度上有着明显的优势。     

关于防火墙渗透问题的分析与建议

介绍防火墙的分类,对比其原理及优缺点,同时,针对防火墙渗透问题的产生进行分析,并对建立防火墙网络安全防护体系提出几点建议。     

Transient analysis of modified t.t.l. gate

The letter derives expressions for the transient response of the modified t.t.l. NAND/NOR gate using a piecewise linear analysis. The expressions are presented in a form suitable for incorporation into a computer-aided circuit-analysis program based on the macromodelling concept and intended for the analysis of relatively large arrays of integrated-circuit logic gates. Results are compared with experimental observations.     

自动穿透测试框架的设计与实现

穿透测试是信息安全风险评估中的一个重要手段,本文针对其实现过程中的高度复杂性,设计并实现了一套自动穿透测试框架,着重阐述了该框架的体系结构和其中的一系列关键开发技术。     

黄铜-低碳钢异种金属激光深熔钎焊

采用1 kW Nd∶YAG激光器焊接2 mm厚H62黄铜和20#钢管材.聚焦激光作用在接头黄铜一侧形成深熔焊接熔池,熔化的黄铜浸润碳钢界面形成接头.因此,在焊缝的黄铜一侧为深熔焊,碳钢一侧为钎焊,这一方法称为激光深熔钎焊(LPB).采用光学显微镜、扫描电镜(SEM)和X射线能谱分析(EDS)对焊缝成形和接头界面进行观察,发现黄铜母材与焊缝界面是正常的激光深熔焊特征,同时碳钢母材与焊缝的界面形成了良好的冶金结合,相互作用区的宽度约为3μm.显微硬度结果表明焊缝硬度值高于黄铜母材.经爆破实验测试,断裂发生在黄铜一侧,表明H62黄铜-20#钢激光深熔钎焊接头力学性能满足工业使用要求.     

Modeling of Void-Mediated Cracking and Lithium Penetration in All-Solid-State Batteries

All-solid-state batteries (ASSBs) are expected to have an exceptional energy density and safety owing to the possibilities of direct usage of lithium as an anode and the suppression of dendrites by a solid-state electrolyte (SSE). However, recent experiments unveil discharging-induced voids in lithium-SSE interfaces and charging-induced cracks in SSE, wherein lithium penetration occurs. To avoid such cell failures, a theoretical model rendering high-credibility simulations is needed to assist ASSB designs. Herein, such a model coupling the electrochemical processes and mechanical responses of an ASSB are proposed, in which the kinetics of voids and cracks are the key ingredients. Numerical simulations based on the model reveal that void growth is the result of stripping with disparate diffusivity in the surface layer and the bulk of lithium. They bring about the non-uniform distribution of Li⁺ during electroplating, a damage zone near the interface, SSE cracking, and then lithium plating in the cracks. It is noted that the cracks and lithium dendrites revealed by the simulations are very similar to those observed in in situ experiments and that a high stack pressure cannot inhibit cracking and lithium penetration. Instead, suitable lateral compressive stresses can prevent SSE from cracking and therefore inhibit lithium dendrites.     

叶簇穿透UWB SAR的频段及极化特性选择

研究叶簇对电磁波传播的影响对于雷达穿透叶簇探测隐蔽目标具有重要意义,根据国外超宽带雷达的外场实验,总结出叶簇穿透衰减和后向散射特性与频率、极化、俯视角等系统参数之间的关系,为我国的叶簇穿透UWB－SAR系统的频段与极化参数选择提供依据。