Water jet guided laser as an alternative to EDM for micro-drilling of fuel injector nozzles: A comparison of machined surfaces

To characterize the inner surface of the fuel injector nozzle holes drilled by EDM and water jet guided laser drilling (Laser Micro-Jet) a specifically conceived scanning probe microscopy technique with true non-contact operating mode was used. A difference in morphology of the drilled surfaces is evident from the acquired surface topography along the hole axis for the two compared drilling techniques. Results showed that the surface texture can be characterized by (i) maximum peak-to-valley distance and (ii) periodicity. Acquired maps confirm that electro-eroded surfaces are an envelope of craters randomly distributed with total excursion up to 1.7 μm with a crater size of 15 μm. While, the efficient melt expulsion and immediate cooling of water jet guided laser generates a peak to valley distance of 800 nm with a periodicity of 18 μm. Average R_q derived from the measured cylindrical surfaces was 450 nm and 150 nm for EDM and Laser Micro-Jet, respectively. Water jet guided laser drilling has proved to be a reliable alternative to EDM from the point of view of repeatability of the results and surface quality to facilitate the atomization of the fuel jet.     

Effect of CO2 corrosion behavior of mild steel in oilfield produced water

The corrosion rates of API X65 mild steel alloy in CO₂ – containing produced water have been studied by weight loss technique, potentiodynamic polarization technique and characterization of the corroded surface techniques. The effect of temperature, speed of rotation, pH and acetic acid concentration were studied. The optimum condition in presence and absence of protective film were also addressed. The kinetic parameters and reaction behavior were discussed in details. Corrosion rates increases with increasing temperature, acetic acid concentration, and speed of rotation, and decreased with increasing solution pH. The primary corrosion product of API X65 mild steel is ferrous carbonate (FeCO₃) at high temperatures, high pH's (alkaline media) and absence of acetic acid, which could act as a protective film so that CO₂ corrosion rate can be reduced.     

Electrical performance of laser braze-welded aluminum–copper interconnects

The reported investigation is related to laser beam braze-welding technology for dissimilar aluminum–copper interconnects for Li-ion battery assembly. The correlation between the brittle and high-resistivity intermetallic compounds and the electrical contact resistance showed that a thin intermetallic layer is highly desirable. It was proved that highest shear strength and lowest contact resistance can be achieved within the same parameter set which is of particular interest to battery electrical vehicle applications requiring both high mechanical reliability and electrical performance.A study on the weld seam layout further showed that two parallel weld seams with optimized spacing and overlap design provide lowest contact resistance.     

用于应力腐蚀试验的飞机铝合金装配模拟件内部应力无损测定

目的 减少或避免服役飞机机体的应力腐蚀和腐蚀疲劳开裂.方法 采用短波长特征X射线衍射技术和仪器无损检测飞机铝合金装配模拟件的内部残余应力和装配应力的分布.结果 0.5 mm矩形间隙使下缘条根部上表层产生高达110 MPa及以上的拉应力;0.3 mm矩形间隙使下缘条根部上表层产生约80 MPa的拉应力;0.5 mm楔形间隙使下缘条根部上表层产生的拉应力平均值约55 MPa.结论 利用短波长特征X射线衍射技术能够无损测定和表征铝合金装配件内部应力及其分布,装配间隙使下缘条根部上表层产生较大拉应力,这与服役飞机机身螺接件出现较多非典型裂纹的部位吻合.矩形间隙装配件下缘条根部上表层的拉应力大于相同间隙值的楔形间隙装配件下缘条根部上表层的拉应力,并且,装配间隙越小,产生的拉应力越小.减小螺母靠根部处的装配间隙与螺母靠根部处到壁板距离的比值,将减小装配件的拉应力,减少或避免SCC&CFC的发生,以及非典型裂纹的产生.     

X射线结晶学在地学中的应用现状

本文概略地述评了X射线衍射方法在地学方面的应用现状:单晶结构分析和结构矿物学及其发展;X射线粉末法,特别是晶胞参数测定方法在造岩矿物研究中的应用;用单晶X射线照相研究造岩矿物调制结构;X射线粉末法在粘土矿物学及煤岩学上的应用,等等。 同时,还介绍了笔者在用X射线粉末法及单晶分析研究造岩矿物方面的主要成果。     

大气氢氧自由基测量技术研究进展

大气氢氧自由基在对流层大气化学中占有重要地位，但由于其浓度极低而活性极高，所以至今没有合适的测量方法。文章通过总结２０多年来大气氢氧自由基测量技术研究的成果，分析讨论了大气氢氧自由基浓度测量的研究现状和发展趋势。     

聚合硅酸铝铁的带电特征及X衍射分析

借助于微电泳技术研究了PSAF的带电特性，探讨了PSAF的絮凝机理，并与传统絮凝剂作了比较。结果表明：PSAF水解聚合形成物的电荷量随Al^3 ／Fe^3 摩尔比的减小以及SiO2浓度和碱化度B^ 的增大而逐渐降低，在酸性至中性范围内荷正电，在pH值大于7．5时荷负电。通过X射线衍射图谱的分析，证明在实验条件下，Al^3 、Fe^3 和SO4^2-均参与了反应，与聚硅酸形成了无定形高聚物。     

蒙脱石b轴有序度的测定及其实用意义

粉末X射线衍射测量蒙脱石结构有序度,采用v/p值法仅反映c轴方向有序度,不能代表a、b轴方向有序度。作者提出(02)反射带峰形不对称程度是b轴有序程度的直观反映,将该峰峰高(H)与2/3高宽(W)的比值定义为蒙脱石晶体结构的b轴有序度,H/W值越大,b轴有序度越高,反之,朽序度低。H/W值对蒙脱石原矿评价与应用研究有一定意义。     

碱性闪石12种阳离子占位度的X射线衍射测定

对所收集的４７个碱性闪石结构数据计算出理论Ｘ射线粉末图，同时实测出５个碱 性闪石样品的粉末图及其晶体化学占位，从这５２个样品的Ｘ射线衍射圈中选出１８条特征衍射 强度，将强度比值与各晶位各阳离子占位用多元统计分析统计出经验公式，以之作为估算未知 样品各阳离子占位的线性模型。回代实践表明，本线性模型具有较钙质闪石更高的可靠性与精 确度。预测５个实测样品的晶体化学类型与原定名对比完全符合，准确度达１００％。按国际分 类表纠正个别样品原定名的错误。在１２种阳离子占位中，估算的准确度有８种大于９０％，３种 近于９０％！唯有Ｔ位Ｓｉ的准确度仅６６％，这可能是因为所选样品中Ｔ位基本上为Ｓｉ占位，其 占位数均超过 ７．５，占位度均大于 ０.９，总变化幅度小从而降低其相关性。因 ５２个样品中，也包 含钠钙闪石亚族，故对整个闪石族用Ｘ射线衍射估算阳离子占位的问题已基本解决。     

蒙脱石矿物的结晶度及其地质意义初探

本文用X射线粉末衍射法研究蒙脱石矿物的结晶度与其埋藏深度之间的关系,并作出地质解释。 在X射线粉末衍射图上,V/P值的大小即C轴的有序程度是蒙脱石结晶度的标志。V/P值与其生成时的深度有相关性,其相关曲线呈一似抛物线形。似抛物线的顶点位于不同的生成深度,这主要是各地区地热增温率及成矿温度不同所引起。