熔融磷酸盐对石英玻璃侵蚀的机理及影响因素

采用分光光度计、偏光显微镜、扫描电镜、能谱仪等研究了磷酸氢二钠、磷酸钠、磷酸钾及混合磷酸盐对电熔透明石英玻璃的侵蚀,对侵蚀机理和影响因素作了探讨。实验证明混合磷酸盐对石英玻璃侵蚀严重,侵蚀后可形成均匀的半透明毛面。     

粒子浓度对C/C复合材料烧蚀行为的影响

为研究不同粒子浓度侵蚀条件下C/C复合材料的烧蚀机理及性能,采用自主研发的氧-煤油烧蚀实验系统对轴棒法编织的C/C复合材料进行烧蚀/侵蚀实验,实验的粒子浓度分别为0,1.37%,2.22%,2.64%。采用扫描电镜(SEM)观察实验后试样的微观形貌,测算了试样的烧蚀率,研究了粒子浓度对材料烧蚀率的影响规律,分析了材料的烧蚀机理。结果表明:不加粒子时试样的质量烧蚀率仅为0.159g/s,线烧蚀率为0.175mm/s,加入粒子后质量烧蚀率与线烧蚀率的最小值分别为0.432g/s和0.843mm/s,且随粒子浓度的增加,烧蚀率均加速增加。粒子的侵蚀作用加剧了试样的烧蚀,冲刷面上径向纤维的烧蚀梯度随粒子浓度的增加而增大。     

锶在粘土中吸附的影响因素研究

文章对锶在以伊利石含量为主粘土中吸附的影响因素:固液接触时间、液固比(ml/g)、锶离子的初始浓度等进行了研究.吸附实验用批实验方法进行,锶离子的初始浓度范围为10.1～10.6mol/L.实验中还对钙离子和钡离子对锶的咐附影响进行了研究,发现它们对锶吸附的影响与溶液中碱土金属的离子半径有关.最后运用Freundlich吸附等温曲线对实验数据进行了拟合,进而求出方程的相关参数.     

贫化过程铜熔渣型变化对炉衬侵蚀的特性

Al2 O3和MgO构成的耐火材料已被广泛运用到铜冶炼生产中.但由于熔池熔炼过程中高温及熔渣特性,耐火材料易被侵蚀和老化,尤其是耐火材料与铜熔渣直接接触处.本实验研究了Al2 O3坩埚和30％MgO-65％SiO2-5％Al2 O3坩埚对炉渣的抗侵蚀能力,探究了熔渣中碱度、Al2 O3含量对耐火材料侵蚀行为的影响.研究...     

基于相似性的海洋潮汐区环境混凝土抗氯盐侵蚀性能研究进展

随着我国"海洋强国"战略的实施,海洋工程结构基础设施建设规模空前,滨海环境下混凝土材料耐久性问题也逐渐引起人们的重视.氯离子侵蚀是导致海洋环境下钢筋混凝土结构耐久性能劣化的主要因素,因此,针对滨海环境下钢筋混凝土中氯离子侵蚀规律的试验研究引起了广泛关注.实海暴露试验存在受区域影响较大、推广性差、试验周期长和影响因素复杂等缺点,不能为寿命预测模型建立提供充足的数据基础,而室内模拟加速试验可有效弥补实海暴露试验的不足.以实海暴露试验为依据,通过研究二者之间的相似性,构建实际海洋工程结构的寿命预测模型,进而将室内模拟试验结果应用到现场实际情况中,可准确地实现海洋环境下基础设施建筑结构服役寿命的预测.目前,学者们已对海洋潮汐区环境混凝土抗氯盐侵蚀性能的实海暴露试验与室内模拟加速试验开展了大量的研究,并取得了丰富的成果.一方面,建立了相应的相似性模型,进而从理论方面分析实海暴露环境和人工模拟环境下混凝土中氯离子的侵蚀规律,为寿命预测模型的建立奠定理论基础;另一方面,试验设备得到不断的研发升级,为获取更加准确可靠的试验数据提供了一定技术支持.针对海洋潮汐区环境条件,对流区深度、表面氯离子浓度、扩散系数和氯离子浓度峰值等参数是建立寿命预测模型的关键要素,本文主要考虑这几方面的影响,分析总结了实海暴露环境下氯离子侵蚀规律,从实海暴露试验与室内模拟试验的角度出发,总结了海洋潮汐区环境混凝土抗氯盐侵蚀性能的研究进展,基于相似性理论分析探讨了氯盐侵蚀规律的相似性,并进行了讨论和展望.     

水泥基胶凝材料氧化物含量与氯离子结合量的定量关系

为揭示氯盐溶液及存在硫酸盐复合盐溶液中氯离子对水泥基材料的侵蚀特性,合理选用氯盐环境下水泥基材料组分,减小海洋环境和盐湖卤水对混凝土造成的氯离子侵蚀问题,本工作通过添加矿物掺合料(矿渣和粉煤灰)改变主要氧化物含量,研究水泥基材料氧化物含量与氯离子结合量的关系.采用等温吸附法测试样品的氯离子结合量,采用X射线衍射仪(XRD)和同步热分析仪(TG-DSC)表征侵蚀产物.实验结果表明,在氯盐溶液侵蚀下,水泥基材料的氯离子结合量与其Al2 O3、SiO2含量成正比,与CaO含量成反比.在硫酸盐存在的复合盐溶液侵蚀下,硫酸盐浓度较低(3.5％NaCl+0.5％Na2 SO4)时,氯离子结合量略有下降,测试结果表明Friedel盐的生成量不会因硫酸根离子的引入而降低,此时两种离子没有明显的竞争关系;当硫酸盐浓度提高到5％Na2 SO4时,氯离子结合量下降显著,实验结果表明Friedel盐的生成量降低,两种离子间竞争关系显著,但不影响氧化物含量与氯离子结合量之间的相关性.     

水泥混凝土TSA侵蚀研究进展

TSA侵蚀是水泥混凝土在低温、高湿、硫酸盐与碳酸盐长期作用下发生的一种特殊的硫酸盐侵蚀形式.它直接导致水泥石中CSH凝胶体的分解,生成无任何胶结性的硅灰石膏(thaumasite)晶体,使混凝土最终变为一种白色的烂泥状混合物.综述了国内外对此类侵蚀的研究现状和进展,包括破坏机理、影响因素和防治措施等,并指出应进一步的研究方向.     

影响不锈钢草酸侵蚀试验的有关因素

对不锈钢10％草酸电解试验的各参数进行了对比试验研究，试验结果表明，侵蚀电流和电解时间是影响实验结果的主要因素，电解液中草酸质量分数在12％－5％内变化时对试验结果无影响。     

水泥基材料硫酸盐侵蚀机理的研究进展

硫酸盐侵蚀是影响水泥基材料结构耐久性的重要因素。本文在分析硫酸盐侵蚀对水泥基胶凝材料铝相水化产物和C-S-H凝胶影响的基础上,归纳了现有水泥基胶凝材料硫酸盐侵蚀的作用机理,提出了硫酸盐侵蚀作用下水泥基材料微结构研究中存在的不足和进一步的研究方向。     

考虑温度时变效应氯离子侵蚀混凝土的格子Boltzmann数值模型

对于长期暴露在氯盐环境下的混凝土结构,在外界温度影响下氯离子的侵蚀作用非常复杂,会影响钢筋锈蚀进程及其耐久性.为此,基于格子Boltzmann方法,采用双分布函数分别描述混凝土温度场和氯离子浓度场的演化过程,考虑外界温度的时变效应,建立氯离子侵蚀混凝土的数值模型.在此基础上,讨论水灰比、饱和度和昼夜温差等因素对氯离子侵蚀机制以及混凝土服役寿命的影响.研究表明:随着水灰比的增大,氯离子扩散系数逐渐增大,从而加剧了氯离子的侵蚀作用.混凝土饱和度越大,氯离子的扩散速率越快,从而导致混凝土的服役寿命缩短,当饱和度超过75%时,混凝土的服役寿命变化趋势逐渐趋于稳定.此外,昼夜温差越大,其对扩散系数的影响越显著,但总体而言,昼夜温差的变化对混凝土服役寿命的影响并不突出.     

Prediction of plasma etching using a randomized generalized regression neural network

A new empirical technique to construct predictive models of plasma etch processes is presented. This was accomplished by combining a generalized regression neural network (GRNN) and a random generator (RG). The RG played a critical role to control neuron spreads in the pattern layer. The proposed R-GRNN was evaluated with experimental plasma etch data. The etching of silica thin films was characterized by a 2³ full factorial experiment. The etch responses examined include aluminium etch rate, silica etch rate, profile angle, and DC bias. Additional test data were prepared to evaluate model appropriateness. Compared to conventional GRNN, the R-GRNN demonstrated much improved predictions of more than 40% for all etch responses. This was illustrated over statistical regression models. As a result, the proposed R-GRNN is an effective way to considerably improve the predictive ability of conventional GRNN.     

Scanning electrochemical microscopy as a quantitative probe of acid-induced dissolution: theory and application to dental enamel

This Article reports the use of scanning electrochemical microscopy (SECM) for the quantitative study of acid-induced dissolution. An ultramicroelectrode (UME) is used to generate a flux of protons galvanostatically just above a sample surface, creating controlled acid challenges relevant to acid erosion. The electrochemical technique produces etch features in the sample, which are characterized by white light interferometry (WLI). The technique has been applied to bovine enamel where understanding the kinetics of dissolution is important in the context of acid erosion. Dissolution has been observed as a fast process, but the high rates of mass transport in SECM allow the surface kinetics of dissolution to be evaluated. Key attributes of SECM for these studies are the ability to deliver high, controllable, and local acid challenges in a defined way and that multiple dissolution measurements can be performed on one sample, eliminating intersample variability effects. A novel moving boundary finite element model has been designed to describe the etching process, which allows the etch kinetics to be evaluated quantitatively, simply by measuring the size and shape of etch features over time.     

TeO2晶体位错腐蚀形貌与晶体对称性

用化学腐蚀的方法研究TeO2晶体(110)面和(001)面位错蚀坑的形貌，结合晶面极图，并运用对称群理论进行分析论证，理论分析与实验结果相一致．实验结果同时显示，TeO2晶体位错腐蚀坑面由{110}面族构成，即{110}面族是晶体的习性面．     

On the use of a neural network to characterize the plasma etching of SiON thin films

Using a generalized regression neural network (GRNN), plasma etching of oxynitride thin films was modeled. The etch process was characterized by means of a statistical experiment. A genetic algorithm was employed to improve prediction performance by optimizing multiparameterized training factors. Compared to a conventional GRNN model, the constructed etch rate model demonstrated an improvement of about 60% in the prediction performance. 3-D plots were generated to qualitatively interpret etch mechanisms while validating the predictions with experimental data. In separating physical and chemical effects, both dc bias and profile angle variations were effectively utilized. The source power affected significantly the etch rate irrespective of changes in the bias power or C₂F₆ flow rate. For pressure variations, the etch rate was estimated to be dominated by chemical etching. The complex effect of C₂F₆ flow rate could be explained by dominant chemical etching or polymer deposition.     

Mechanism of dissolution of MgO crystals in acids

A simple model of dissolution of MgO crystals in acids involving chemical reactions and adsorption process on the crystal surface is used to derive expressions connecting rates of surface dissolution and selective etching with concentration, temperature and nature of an acid and with surface orientation. The experimental data of the dependence of etch rates of MgO on various etching parameters are then compared with the theory. The effect of acid viscosity and concentration are also briefly analysed and compared with the experimental observations. It is argued that the experimental results can be understood on the basis of the proposed mechanism if adsorption of the reactants and the complexes formed during dissolution on a perfect surface and at dislocation sites is taken into consideration. It is concluded that the adsorption processes play an important role in the formation of good, contrasting dislocation etch pits.     

16NiCo超高强度钢回火酸浸蚀检查EI

本文研究了１６Ｎｉｃｏ超高强度钢回火酸浸蚀行为，结果表明，１６Ｎｉｃｏ钢可以用硝酸酒精溶液进行回火酸浸蚀检查。     

Some aspects of electron beam welded and laser welded ferritic Fe-22Cr-3Mo-5Ni-0.3Ru alloy

Ferritic Fe-22Cr-3Mo-5Ni-0.3Ru alloy was welded by electron beam (EB) and laser techniques. Tensile tests, impact tests, oxalic acid etch, electrochemical potentiokinetic reactivation (EPR) and potential-time measurements were employed to investigate the mechanical properties, microstructural features and corrosion behaviour of the EB and laser welded metals. The oxalic acid etch tests revealed that the microstructure of the EB and laser welded metals consisted of columnar grains and cells, respectively. These structures were formed directly from the substrate by epitaxial solidification. Furthermore, the oxalic acid tests also showed that the EB and laser welded metals were immune to intergranular corrosion. Similar results were obtained by double loop EPR tests.     

Optimization of principal-component-analysis-applied in situ spectroscopy data using neural networks and genetic algorithms

A new model of multidimensional in situ diagnostic data is presented. This was accomplished by combining a back-propagation neural network (BPNN), principal component analysis (PCA), and a genetic algorithm (GA). The PCA was used to reduce input dimensionality. The GA was applied to search for a set of optimized training factors involved in BPNN training. The presented technique was evaluated with optical emission spectroscopy (OES) data measured during the etching of oxide thin films in a CHF(3)-CF(4) inductively coupled plasma. For a systematic modeling, the etching process was characterized by a face-centered Box Wilson experiment. The etch responses to be modeled include oxide etch rate, oxide profile angle, and oxide etch rate non-uniformity. In PCA, three types of data variances were employed and the reduced input dimensionality corresponding to 100, 99, and 98% are 16, 8, and 5. The BPNN training factors to be optimized include the training tolerance, number of hidden neurons, magnitude of initial weight distribution, gradient of bipolar sigmoid function, and gradient of linear function. The prediction errors of GA-BPNN models are 249 A/min, 2.64 degrees, and 0.439% for the etch rate, profile angle, and etch rate non-uniformity, respectively. Compared to the conventional and previous full OES models, the presented models demonstrated a significantly improved prediction for all etch responses.     

Analysis of etching mechanism and etched slope control of silicon for nanoimprinting lithography

In the nanoimprint lithography (NIL) process, profile control of imprint masters is a very important task. Therefore, we attempted to control the etched slope of imprint masters as a function of adding O2 to CF4 plasma. Etched profile mechanisms and relationships between the etch kinetics and plasma chemistry were explored using zero-dimensional-based modeling. O2 flow rate increased to 24 sccm, the Si etch rate increased in the range of 186-393 nm/min, while the etch rate rapidly decreased as the O2 flow rate increases beyond 24 sccm. Meanwhile, change in the etch rate of SiO2 followed a similar tendency as the etch rate of Si as a function of O2 flow rate in the CF4/O2 mixing gases. The Si and SiO2 etch rate were expected to be closely dependent on the F radical intensity in CF4/O2 mixing gases. Moreover, the results of simulated normalized lateral etch critical dimension (NLECD) are in agreement with the measured NLECD as a function of O2 flow rate in the CF4/O2 mixing gases.     

Chemical etching of (1 0 0) GaAs in the HNO3-HF-H2O system

This paper describes the action of solutions containing nitric acid, hydrofluoric acid and water on GaAs of (1 0 0) orientation. Single-crystal slices of the semiconductor were immersed in the etch and the rate of dissolution was measured. Results were taken over a wide range of composition of the solution. The results show a marked resemblance to the etch-rate data for silicon in the same etching solution, although the actual etching rates for GaAs were lower. The semiconductor surfaces were observed carefully after etching, using techniques of optical microscopy and scanning electron microscopy. Etch hillocks were observed for many compositions of the etch. It was found that the hillocks were covered by a layer of oxide: if any of this oxide covering came off, the hillock quickly disappeared. Sequential etching experiments showed that the hillocks were not associated with dislocations. Both the etch-rate data and the microscopic examination of the GaAs surfaces suggest that the system is probably diffusion-limited over the range of etch composition studied in this work.