微量沉积氯对焊点腐蚀过程的影响

不同金属间存在电位差,被硫、氯等污染的焊点易产生原电池腐蚀,这将降低焊接产品的可靠性,缩短产品的寿命。因此,焊点的腐蚀问题受到人们的高度重视。以镀钯铜线的球栅阵列(BGA)产品为研究对象,通过能谱仪(EDS)、X射线衍射(XRD)、X射线光电子能谱(XPS)等实验手段,首先分析了多焊点同时被氯腐蚀的影响因素,再将焊点表面划分为上表面、侧表面以及界面3个区域,并对各区域进行腐蚀分析和验证,最后得出氯腐蚀焊点的腐蚀机理。实验结果表明:1)氯腐蚀难易程度的主要影响因素为IMC的致密度和镀钯层上的铜露出面积,IMC的致密度越小,镀钯层上的铜露出面积越大,氯腐蚀越容易发生;2)焊点腐蚀路径表现为氯沿铜球表面向铜球与IMC的界面迁移的过程;3)焊点烘烤时间越短,焊点表层上钯的覆盖率越大,焊点被氯腐蚀的概率越低。

杭州湾沿岸大气中氯离子沉积速率检测与影响研究

目的 探究杭州湾沿岸工程设施的腐蚀严酷度水平。方法 选择3个临水检测点开展为期1 a的大气氯离子沉积速率检测,并分析季节、风向、方位、降雨量等对氯离子沉积速率的影响。结果 3个检测点的年均沉积速率都超过3mg/(m^(2)·d)。B检测点因方位、周围空间等原因,造成全年受到东部海洋大气的作用最为显著,氯离子沉积速率全年最高,其中7月份的氯离子沉积速率水平接近海南省中东部离海岸线350m处夏季水平。由于6月份降雨量比5月份增大了2.3倍,B检测点6月份氯离子沉积速率比5月下降了51%。B检测点附近服役15 a以上混凝土中,氯离子含量整体非常高,呈现典型的海洋腐蚀特征。结论 杭州湾沿岸大气符合海洋腐蚀环境特征,并且受到季节、风向、方位和降雨量等因素的影响。

海洋大气区氯离子在混凝土中的沉积与传输行为研究综述

海洋大气区氯离子对钢筋混凝土的侵蚀行为可分为两个阶段,首先,氯离子在风力作用下附着在混凝土表面,其次,从混凝土表面向混凝土内部侵蚀。基于海洋大气区氯离子对混凝土侵蚀的全过程,对已有研究进行归纳总结,阐述了各影响因素对沉积过程的影响规律。其中,海水含盐量、风速、暴露时间与混凝土氯离子沉积量呈正相关关系,距海岸距离与混凝土氯离子沉积量呈负相关关系;论述了各影响因素对传输过程的影响规律,水灰比越大、暴露时间越长、温度越高、内外湿度梯度越大、碳化越严重越容易形成对流区。目前,针对海洋大气区氯离子在混凝土中沉积和传输行为开展研究多基于单因素,多因素耦合作用下的沉积和传输行为尚需进一步研究。

空气中氯离子沉积速率的影响因素分析

目的分析空气中氯离子沉积速率的影响因素。方法采用灰色关联分析法、pearson相关系数法和spearman相关系数法分析了海南省中东部离海岸线350 m处监测的气温、相对湿度、风速、降雨量、海水有效波高、海水温度与氯离子沉积速率的相关性。结果3种方法的分析结果一致表明,与氯离子沉积速率的相关性最高的是海水有效波高,而与其他环境因素的相关性交替排序。结论海水有效波高与氯离子沉积速率呈现显著性正相关,表明海水有效波高越高,氯离子沉积速率越大。

东海海岛大气环境中氯离子沉积速率检测与影响分析

为了研究东海海岛大气环境中氯离子沉积速率的影响因素,开展了大气测试点氯离子沉积速率检测,分析了离海岸线距离、测试点方位、季节、降雨量、风向与风能等对氯离子沉积速率的影响。研究表明,氯离子沉积速率随离海岸线距离的增加而降低。摘箬山岛各测试点冬季氯离子沉积速率高于春、夏季,东北方向测试点氯离子沉积速率最大。氯离子沉积速率是风向、风能、降雨量等多因素影响的结果。

万宁地区近地面氯离子沉积速率的影响因素研究

目的 研究热带海洋大气环境中不同地貌下氯离子沉积速率的分布规律及主要影响因素。方法 通过挂片法采集万宁地区的氯离子沉积速率,并分析离海距离、地形地貌对氯离子沉积速率的影响,以及其与海水因素、自然环境因素间的相关性。结果 近海开阔区域氯离子沉积速率受离海距离和地貌的影响显著,在300 m处降低至90 m处的1/3左右,地貌的变化导致同一距离点处的氯离子沉积速率相差30倍。另外,高的海水有效波高、风速和东风占比使春季氯离子沉积速率高于夏季。结论 不同地貌下的氯离子沉积速率均与海水有效波高、风速间呈较强的正相关性。

海洋大气环境下Q235钢表面氯离子沉积量分布规律研究

目的 研究海洋大气环境下氯离子在Q235钢表面的沉积分布规律。方法 使用便携式X射线荧光光谱仪测试Q235钢在海南岛不同地点大气环境暴露后的表面氯离子沉积,然后采用插值算法绘制氯离子在Q235钢表面沉积分布图和海南岛不同地点氯离子在Q235钢表面平均沉积量分布图,并根据氯离子沉积分布图分析氯离子在Q235钢表面的沉积量分布规律。结果 氯离子在Q235钢表面呈不均匀分布特征。在环境暴露试验前6个月,Q235钢表面氯离子含量逐渐增加;暴露6~12个月,Q235钢表面的氯离子含量总体变化不大。从整个海南岛看,内陆地区氯离子在Q235钢表面的沉积量低,而在沿海环岛区域的沉积量高。在海南岛沿海地区,Q235钢表面氯离子沉积量随季风风向的变化而变化。结论 氯离子在Q235钢表面呈不均匀沉积分布,Q235钢表面氯离子沉积量在海南岛不同地点呈“中间低、两边高”的沉积分布规律,内陆地区沉积量低,而沿海环岛区域沉积量高,并且沿海地区的氯离子沉积易受季风风向的影响。

Electrochemical codeposition of Mg-Li-Gd alloys from LiCl-KCl-MgCl_2-Gd_2O_3 melts

Mg-Li-Gd alloys were prepared by electrochemical codeposition from LiCl-KCl-MgCl 2 -Gd 2 O 3 melts on molybdenum electrode with constant current density at 823 and 973 K. The microstructure of the Mg-Li-Gd alloys was analyzed by X-ray diffraction （XRD）, optical microscopy （OM） and scanning electron microscopy （SEM）. The results show that magnesium and gadolinium deposit mainly in the first 30 min, and the alloy obtained contains 96.53% Mg, 0.27% Li and 3.20% Gd （mass fraction）. Then, the reduction of lithium ions occurs quickly. The composition of alloy can be adjusted by controlling electrolysis time or Gd 2 O 3 concentration in LiCl-KCl melts. With the addition of Gd into Mg-Li alloys, the corrosion resistance of the alloys is enhanced. XRD results suggest that Mg 3 Gd and Mg 2 Gd can be formed in Mg-Li-Gd alloys. The distribution of Gd element in Mg-Li-Gd alloys indicates that Gd element mainly distributes at the grain boundaries of Mg-Li-Gd alloys.

Low-temperature Electrodeposition of Aluminium from Lewis Acidic 1-Allyl-3-methylimidazolium Chloroaluminate Ionic Liquids

Lewis acidic 1-allyl-3-methylimidazolium chloroaluminate ionic liquids were used as promising elec-trolytes in the low-temperature electrodeposition of aluminium.Systematic studies on deposition process have been performed by cyclic voltammetry and chronoamperometry.The surface morphology and X-ray diffraction(XRD) patterns of deposits prepared at different experimental conditions were also investigated.It was shown that the nu-cleation density and growth rate of crystallites had a great effect on the structure of aluminium deposited.The crys-tallographic orientation of deposits was mainly influenced by temperature and current density.Smooth,dense and well adherent aluminium coatings were obtained on copper substrates at 10-25 mA?cm?2 and 313.2-353.2 K.More-over,the current efficiency of deposition and purity of aluminium have been significantly improved,demonstrating that the ionic liquids tested have a prospectful potential in electroplating and electrorefining of aluminium.

Kinetic and Microstructure of SiC Deposited from SiCl_4-CH_4-H_2

Silicon carbide was prepared from SiCl4-CH4-H2 gaseous precursors by isothermal, isobaric chemical vapor deposition (CVD) at atmospheric pressure and temperatures ranging from 900°C to 1100°C. Kinetic studies showed that carbosilane of SiH2Cl2, SiHCl3 and SiCl2 formed from decomposition of SiCl4 and CH4 contributed to the deposition of hexangular facet and granular pebble structured SiC. An average apparent activation energy of 152 kJ·mol-1 was determined. The overall CVD process was controlled not only by the surface reactions but also by complex gas phase reactions. The as-deposited thin film was characterized using scanning electron microscopy, X-ray diffraction and transmission electron microscopy, these analysis showed that the deposited thin film consisted of pure phase of the β-SiC, the growth morphology of β-SiC differs from hexangular facet to granular pebble struc-tures, which varied with substrate length and CVD temperature.

Extraction of Organochlorine Pesticides in Sediments Using Soxhlet,Ultrasonic and Accelerated Solvent Extraction Techniques

The application of soxhlet, ultrasonic and accelerated solvent extractiontechniques to the analysis of six organochlorine pesticides (α-HCH, β-HCH, γ-HCH, o, p'-DDT,p,p'-DDT and p,p'-DDE) in Taihu Lake sediment samples is described. It was found that the limits ofquantification ranged from 0.002 μg g^(-1) to 0.004 μg g^(-1), and the recoveries oforganochlorine pesticides with the three extraction techniques were acceptable ( 】80.7%). With amass selective detector, better results were obtained by accelerated solvent extraction usinghexane-acetone (1:1) as compared with soxhlet and ultrasonic extraction. It was shown that theaccelerated solvent extraction was the optimum technique for the analysis of organochlorinepesticides in sediments. The general features of the three extraction techniques are also presented.

Spatial Distribution of Polychlorinated Biphenyls(PCBs)Contaminants in the Tidal-flat Sediments of Yangtze Estuary

PCBs pollutants are measured on tidal-flat sediments of Yangtze estuary by a high resolution capillary column gas chromatography ( HP6890 ) equipped with an 63Ni electron capture detector ( ECD ). The concentration tendency of PCBs is Phragmites zone > Scirpus zone > bare mudflats. There are linear relations between PCBs and TOC and > 63μm grain size percentage ( in volume ). The low chlorinated congeners may be more important than the high chlorinated congeners in this area. PCBs prefer to accumulate in the sediments near sewage outlets and Phragmites zone. The sediments’ PCBs pollution ( 10.7 ~ 28.6 ng/g, dry weight ) in the Yangtze estuary tidal-flat is less serious than that of the most of other areas in the world .But the detected ratio is 100%, even the Jiuduansha shoal has detected PCBs, so much attention should be paid to this area for PCBs.

Synthesis of Platin/Carbon XC72R Nanocomposite Using as Electrocatalyst for Direct Methanol Fuel Cells

Platinum/Carbon XC72R （Pt/C） nanocomposite was synthesized in-situ by polyol method. Precursor of hexahydrated chloroplatinic acid H2PtCI6-6H2O was reduced by EG （ethylene glycol） so as to form Pt nanoparticles which were deposited on the surface of carbon. Pt/C composites （treated or untreated carbon） were synthesized at pH - 6.5 and pH = 11. The XRD pattern of Pt/C showed peaks assigned to the crystalline structure of Pt and carbon. TEM images showed that Pt nanoparticles on carbon were ultrafine spheres and the particles obtained sizes from 2 to 6 nm which are mostly concentrated on size of 3 nm. The electrocatalytic activity of Pt/C catalysts toward methanol oxidation was examined by CV （cyclic voltammetry）. Pt/treated XC72R （pH = 11） at potential （0.69 V） exhibited better electroactivity （628 mA/mg Pt）.

Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in surface sediment and bivalve from the Changjiang Estuary, China

Surface sediments and bivalves were collected from the Changjiang Estuary in December 2003 and November 2004, respectively. Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in these samples were measured with high-resolution chromatography (HRGC)/High Resolution Mass Spectrometer (HRMS). The concentrations of total PCDD/Fs and toxic equivalent (TEQ) were 169.83±119.63 and 0.81±0.36 pg/g dry weight (dw) in sediments, and 580.33±240.17 and 7.24±3.65 pg/g dw in bivalves. The homolog compositions of PCDD/Fs were similar among samples, the most abundant congener was octa-chlorinated dibenzo-p-dioxin (OCDD) and then octa-chlorinated dibenzofuran (OCDF) and 1,2,3,4,6,7,8-hepta-chlorinated dibenzo-p-dioxin (HpCDD). The herbicide pentachlorophenol (PCP) and sodium pentachlorophenol (Na-PCP) were proved the main source of PCDD/Fs in this area.

Influence of NaCl deposition on atmospheric corrosion behavior of AZ91 magnesium alloy

Corrosion behavior of AZ91 magnesium alloy under NaCl particle deposition condition was investigated by gravimetric method and surface analysis technique.It was found that the mass gain increased rapidly at the beginning of exposure and then slowly with time.The corrosion morphologies were observed and the results showed that NaCl deposition resulted in the occurrence of localized corrosion.The composition of corrosion product was analyzed using X-ray photo electron spectroscopy.It was suggested that the corrosion product was a mixture of oxide and hydroxide of magnesium and aluminum.

Organochlorine pesticides in sediments from Honghu Lake, China

The levels of 13 organochlorine pesticides （OCPs） in sediments of Honghu Lake were investigated in order to evaluate their potential pollution and risk. A total of 30 sediment samples from 15 sampling locations were collected in the lake during July, 2005. The total concentrations in top-sediment samples and sub-sediment samples ranged from 3.52 ng/g to 69.71 ng/g and 0.49 ng/g to 97.37 ng/g, respectively. The HCH isomers, DDT congeners, aldrin, trans-chlordane, cis-chlordane, heptachlor and endrin-ketone were significant in these samples. The concentrations of OCPs in the lakeshore sediments were higher than those sampled across the lake. Distribution of HCHs, DDTs and other OCPs were different, indicating their various contamination sources. Composition analysis in sediments indicated recent usage or discharge of lindane, dicofol into the lake.

Effect of Boundary Layers on Polycrystalline Silicon Chemical Vapor Deposition in a Trichlorosilane and Hydrogen System

This paper presents the numerical investigation of the effects of momentum, thermal and species boundary layers on the characteristics of polycrystalline silicon deposition by comparing the deposition rates in three chemical vapor deposition （CVD） reactors. A two-dimensional model for the gas flow, heat transfer, and mass transfer was coupled to the gas-phase reaction and surface reaction mechanism for the deposition of polycrystalline silicon from trichlorosilane （TCS）-hydrogen system. The model was verified by comparing the simulated growth rate with the experimental and numerical data in the open literature. Computed results in the reactors indicate that the deposition characteristics are closely related to the momentum, thermal and mass boundary layer thickness. To yield higher deposition rate, there should be higher concentration of TCS gas on the substrate, and there should also be thinner boundary layer of HCl gas so that HCl gas could be pushed away from the surface of the substrate immediately.

Evaluating the performances of accelerated-solvent extraction, microwave-assisted extraction, and ultrasonic-assisted extraction for determining PCBs, HCHs and DDTs in sediments

Three extraction techniques have been recently used for the quantitative extraction of semi-volatile organic pollutants in sediments, i.e. accelerated solvent extraction （ASE）, microwave assisted extraction （MAE） and ultrasonic assisted extraction （UAE）. However, their extraction efficiencies have rarely been quantitatively compared using rigorous mathematical methods. In this paper, one-way analysis of variance （ANOVA） was employed to evaluate the performance of ASE, MAE and UAE in the overall extraction of PCBs, DDTs and HCHs by analysis of their recoveries from the Standard Reference Material IAEA-417, a sediment sample certified by many international laboratories. Conclusions were drawn at a significance level of P〈 0.05. No significant differences were found among the mean values for method recoveries using ASE, MAE and UAE. The mean values for real recoveries using ASE and MAE were nearly identical, but the real recovery using UAE was much lower. The concentrations of all PCBs, DDTs and HCHs except for CB52 and o,p＇-DDT using UAE were the lowest. Comparing the results obtained using ASE with MAE, the concentrations of CB28, CB52, CB138, ct-HCH, [3-HCH, p,p＇-DDE and p,p＇-DDD were nearly identical, while the concentrations of other compounds were significantly different. Based on the low recoveries, it was concluded that UAE is a relatively inefficient extraction method, while ASE and MAE are equivalent methods. Taking into consideration the relative standard deviation （RSD） values, solvent volume, extraction time, and purchasing costs of the apparatus, MAE was considered superior to ASE for extraction of PCBs, DDTs and HCHs.

PHASE ANALYSES FOR DUAL ION BEAM DEPOSITED ZrO_2 FILMS ON NaCl SUBSTRATE

ZrO2 films on NaCl(100) substrate produced by oxygen ion bombardment and argon ion sputtering of Zr are analysed using TEM, XRD and XPS. The result of TEM shows that only cubic phase exists for the ZrO2 film produced by oxygen ion bombardment with 30μA/cm2 and 200eV, while the XRD result shows that there seems to exhibit a small quanitity of monoclinic phase apart from cubic one under the production condition of oxygen ion of 25μA/cm2, 100eV.

Micromorphology and texture of niobium coating electrodeposited in NaCl−KCl−CsCl molten salt system

A low-toxicity and environment-friendly NaCl−KCl−CsCl−K_(2)NbF_(7) system was used to prepare Nb coatings on Mo substrates.The effects of temperature,current density and electrodeposition time on the micromorphologies and textures of the electrodeposited Nb coatings were studied.The results showed that Nb coatings obtained at 30−70 mA/cm^(2) in the temperature range of 700−750℃ were continuous and compact,with a hardness range of 2.16−2.45 GPa.As the columnar crystals grew with time,the preferential growth orientations of the Nb coatings changed from<200>to<211>and then became disordered.With increasing polarization,the morphologies of the Nb coatings changed from hexagonal star-like surface to conical or pyramid-like surface.