Effect of coloring impurities on the absorption in neodymium phosphate laser glass at a lasing wavelength

This paper reports on the results of the investigation of KGSS 0180/35 neodymium phosphate glasses produced on an industrial scale under oxidizing conditions and glasses prepared under experimental conditions in which iron and copper in small amounts rather than neodymium are introduced into the glass composition. The experimental glasses are synthesized by varying the redox conditions of melting. The oxidation states of transition metal impurities (Cu, Fe, V, Ni, Co) and the nonactive absorption coefficients of glasses at the lasing wavelength are determined. It is revealed that the main contribution to the nonactive absorption coefficient of the KGSS 0180/35 glass produced on an industrial scale is made by Cu²⁺ ions at a concentration higher than 0.5 ppm. At a lower copper concentrations, the total contribution of Fe²⁺, V⁴⁺, Ni²⁺, and Co²⁺ impurity ions to the nonactive absorption coefficient is comparable to that of Cu²⁺ ions. It is demonstrated that a decrease in the concentration of coloring impurities in glasses and the optimization of redox conditions of melting make it possible to prepare phosphate laser glasses with a nonactive absorption coefficient of the order of 0.001 cm^?1. In terms of the nonactive absorption coefficient, these glasses are on a par with similar glasses of foreign manufacture and satisfy the requirements imposed on glasses by developers of high-power high-energy laser facilities.     

Effect of postreatment on the corrosion behaviour of tartaric-sulphuric anodic films

Unclad and clad AA2024 T3 specimens were anodised in a chromium-free tartaric-sulphuric acid bath (TSA) and subsequently postreated by different processes including impregnation in a cold, concentrated chromate solution, Cr-free hot-water sealing, and dichromate hot-water sealing. The purpose of this work is to evaluate the effectiveness of the classical postreatments used in the aircraft industry on the TSA-anodic films and their corrosion resistance behaviour. TSA-anodic films were characterised by scanning electron microscopy (SEM) and their thicknesses were measured by SEM and the eddy current method. Electrochemical impedance spectroscopy (EIS) was used to characterise the barrier and porous layers, and jointly with potentiodynamic polarisation allowed the evaluation of corrosion resistance parameters with immersion time in NaCl solution for anodised and postreated specimens. In all cases the postreatments increased the resistance of the barrier layer against degradation. However, the NaCl electrolyte easily penetrated TSA-anodised porous layers when they were not postreated, while penetration was slightly more difficult in cold-postreated specimens. The effective pore plugging was observed in the sealed TSA specimens resulting in an improved corrosion resistance. On the other hand, unsealed clad AA2024 specimens showed a self-sealing process of the TSA-anodic layer, which was slower for the cold chromate solution-postreated specimens.     

Effect of impurities on the electrochemical behaviour of aluminium electrodes anodized in phosphoric acid

The electrochemical behaviour of anodic films formed on pure aluminium (99.999% and 1100) and 6061-Al alloy substrates in phosphoric acid has been investigated in an aluminium saturated phosphate solution of pH 6.23. The polarization resistance data obtained after one day immersion in the electrolyte showed a strong correlation with the pit number, assessed from an outdoor atmospheric exposure test after 4 months. The cathodic polarization measurements of anodized aluminium in the electrolyte were also carried out. Electrochemical behaviour, eg corrosion, hydrogen evolution reaction, was interpreted in terms of “active sites” within the anodic film. It is suggested that the active sites were mainly formed in the presence of impurities or alloy constituents in aluminium substrates.     

衣康酸介质中杂质离子对两种不锈钢腐蚀行为的影响

针对发酵法生产衣康酸过程中的腐蚀问题研究了两种不锈钢在衣康酸工况介质（发酵液）中的腐蚀行为,探讨了介质中杂质离子Ｃｌ－、Ｆｅ３＋、ＳＯ２－４等对腐蚀的影响。结果表明,随衣康酸介质中Ｃｌ－含量增加,不锈钢的腐蚀速率也增大,而其点蚀电位则随Ｃｌ－浓度的对数值增加呈线性下降;Ｆｅ３＋浓度的增大可使不锈钢／发酵液由活化体系转变成活化 钝化体系;ＳＯ２－４对不锈钢稍有缓蚀作用;在含杂质的衣康酸介质中,Ｒ１双相不锈钢的耐全面腐蚀和耐点蚀性显著优于３１６Ｌ奥氏体不锈钢。     

稀土钕对镀锌层三价铬蓝白钝化膜耐蚀性的影响

在三价铬钝化液中添加稀土钕,以提高三价铬蓝白钝化膜的耐蚀性。研究了钝化温度、pH、时间以及钝化液中稀土钕含量对钝化膜耐蚀性的影响,得到镀锌层三价铬蓝白钝化的最优工艺条件为:Cr2(SO4)3 18.9 g/L,Nd(NO3)3·6H2O 4 g/L,NaNO32.2 g/L,C6H8O7·H2O 0.7 g/L,CoSO4·7H2O 7 g/L,NaH2PO2·H2O3.4 g/L,NH4HF2 0.2 g/L,温度30°C,pH 1.9,时间30 s。钝化液中添加稀土钕可有效提高钝化膜的耐蚀性。在最佳工艺条件下,钝化膜在3.5%NaCl溶液中的腐蚀电位、腐蚀电流密度和交流阻抗分别为-1.231 V、0.568μA/cm2和1 937?·cm2,中性盐雾试验出现白锈的时间为93 h。     

Effect of WC on electrodeposition and corrosion behaviour of chromium coatings

To study the effect of WC particles on corrosion behaviour of chromium coating steel samples were plated in Cr(VI) baths with various concentrations of WC. XPS, EPM and XRD were used to study the chemical composition, morphology and texture of the coatings. The corrosion behaviour was studied at different exposure times in solution containing 0.01 mol L^–1 H₂SO₄ + 0.5 mol L^–1 Na₂SO₄ using cyclic voltammetry and impedance spectroscopy. Cyclic polarization measurements suggest that WC particles slow down the processes of passive film dissolution and penetration of aggressive ions to the substrate. Electrochemical impedance spectroscopy (EIS) was used to reveal the details of the corrosion process at the solution/electrode interface. The simulation of EIS data with a proposed equivalent circuit model made it possible to obtain quantitative valuation of the Y₀ (Q_c), Y₀ (Q_s) and R_pore parameters, reflecting corrosion behaviour of samples at the solution/electrode interface. Samples plated in a Cr(VI) bath with WC provided better resistance to corrosion than those plated in a bath without WC. Analysis of the data obtained suggests that WC particles enhance corrosion resistance due to the microstructural features of the coatings.     

Effect of dodecylamine on the corrosion behaviour of zinc in ammonium chloride solution

Corrosion studies showed normal dodecylamine (NDDA) to be effective as an anodic inhibitor for zinc corrosion in ammonium chloride media. Its inhibiting effect was found to be associated with adsorption on active centres of the zinc surface. The adsorption is potential dependent and the inhibiting effect diminishes with positive shift of the zinc electrode during discharge. This feature makes it possible for NDDA to be used in zinc–manganese dry batteries as a substitute for the environmentally harmful mercury (salt) inhibitor.     

Crystallization behaviour of neodymium doped yttrium silicate nanophosphors

Sol-gel technique was used to prepare yttrium silicate powders doped with 0.01Nd³⁺. The crystallite sizes were determined to be 23 ± 0.5 nm from the XRD patterns of the powders annealed at 960 °C. The Y_4.67(SiO₄)₃O, Y₂Si₂O₇ and Y₂SiO₅ crystalline phases were observed upon heat treatment at 960 °C which is much lower than 1500-1650 °C are reported before.     

Effect of temperature on the corrosion behaviour of low-nickel duplex stainless steel bars in concrete

Stainless steel reinforcing bars can be a means for prolonging the service life of reinforced concrete structures exposed to tropical climates. To select a suitable grade of stainless steel according to exposure conditions and design service life, the definition of the chloride threshold for pitting corrosion initiation is required. This paper investigates the effect of temperature in the range 20–60 °C on the resistance to chloride-induced corrosion of low-nickel duplex stainless steel rebars and, for comparison, of traditional austenitic stainless steel rebars. Tests in concrete and in solutions simulating the concrete pore liquid were performed and an attempt to evaluate the chloride threshold levels for corrosion initiation was carried out. Results showed lower corrosion resistance and higher sensitivity to increase in temperature for low-nickel duplex stainless steel bars compared to traditional austenitic stainless steels.     

Effect of silicon alloying addition on the corrosion behaviour of aluminium in some aqueous media

The corrosion behaviour of three Al–Si alloys was studied after galvanostatic passivation in 0.1 M sodium tartrate, sulfate and borate solutions using EIS techniques. The degree of passivation depends on the anion type, the degree of polarization and the alloy composition. It was also found that increase in pH led to a decrease in polarization resistance R _p. The effect of formation voltage, V _f, on the growth and dissolution kinetics of the oxide grown on the alloys was studied. The polarization resistance value increases as V _f increases up to a certain value; above this the R _p value decreases. This critical V _f depends on the alloy composition and the test solution. The kinetics of oxide layer dissolution in the absence and presence of Cl^– ions was also studied. Increase in immersion time leads to a more severe attack by Cl^– ions as shown by the decrease in the value of R _p. At low Cl^– ion concentration the value of R _p is higher than that in chloride ion free sulfate solutions, because the rate of passive film repair is much higher than that of barrier layer dissolution. However, at high Cl^– ion concentration penetration of Cl^– through defects in the barrier layer leads to formation of an oxyhalide layer.     

Effect of some polymeric materials on the corrosion behaviour of tin in succinic acid solution

The anodic behaviour and corrosion of tin in various concentrations (0.05–0.7M) of succinic acid were studied using cyclic voltammetry. The potentiodynamic anodic polarization curves exhibit active/passive transition. The active dissolution of tin involves one anodic peak. The cathodic curve exhibits one cathodic peak corresponding to the reduction of the passive layer. The ratio of the anodic charge/cathodic charge is more than unity indicating that the passive layer is very thin and the dissolution products are mainly soluble species. Additions of some polyethylene glycols to the succinic acid solution decrease the anodic peak current and shift the peak potential in the negative direction. These changes depend on the concentration and molecular weight of the polyethylene glycol added. The effect of the inhibitors decreases in the following order: (PEG)₆₀₀₀ > (PEG)₄₀₀₀ > (PEG)₁₂₀₀. The inhibition efficiency decreases with increase in temperature, suggesting physical adsorption.     

Effect of biofouling on corrosion behaviour of grade 2 titanium in Mandapam seawaters

Titanium has the ability to withstand extremely high seawater velocities with negligible corrosion. The inherent passive nature of the metal favours the attachment of bio-organisms more. In this paper the biofouling characteristics and the influence of macrofouling on grade 2 titanium have been investigated in the Palk Bay waters of Mandapam (India) over a period of a year.This work comprises both field exposure as well as laboratory studies. The deposits on titanium were analyzed with the XRD technique. Green algae such as Cladophorapsis zoolengeri, Cheatomorpha area, Chlorodesmis hillibrandii, Enteromorpha intestinalis, Cladophora species and red algae species of Hypnea valentiae, and animals such as bryozoans and barnacles 4 mm in size were identified on the titanium metal surface. The effect of macrofouling on corrosion of titanium was investigated by both impedance and polarization techniques. Titanium experienced negligible corrosion in seawater exposure with an appreciable fouling load of 0.4527 kg.m⁻²y⁻¹.     

Effect of additives on electrodeposition of tin and its structural and corrosion behaviour

The present investigation deals with the electrodeposition of tin from chloride electrolytes. Gelatin, β-naphthol, polyethylene glycol, peptone and histidine were used as additives in the plating bath to improve the surface morphology, grain size, smoothness and corrosion resistance of the tin deposits. XRD data obtained for electrodeposited tin show polycrystalline nature with single β-phase and tetragonal structure. A uniform and pore free surface was observed under SEM analysis. AFM results indicate the grain refining brought about by the additives. Corrosion rate measurements using the Tafel extrapolation method and electrochemical impedance spectroscopy reveal the increased corrosion resistance from baths containing additives.     

Effect of water content on the corrosion behaviour of Ni in methanol (MeOH) solutions

The effect of water content on the corrosion behaviour of nickel in methanolic solutions have been investigated tracing the potentiostatic curves at room temperature in a standard electrochemical cell.Preliminary results reported in this communication, shown that the electrochemical behaviour of Ni in MeOH is strongly influenced by the water content of the solution and that traces of water (of the order of 0.5%) are able to guarantee the passivity of nickel.     

Influence of impurities on stainless steels corrosion in wet process phosphoric acid

The corrosion behaviour of stainless steels in wet process phosphoric acid was studied by means of polarization curves and corrosion tests; in this context the influence of impurities that enhance the corrosivity of the acid, such as chlorides, fluorides and sulphates, was evaluated. Moreover the efficiency of some corrosion inhibitors, present as impurities in wet-process phosphoric acid, was evaluated by means of polarization curves and corrosion tests. Inhibitors of fluoride aggressiveness such as compounds of silicon, aluminum, magnesium were tested both separately and together. Trivalent iron as an oxidizing agent was also evaluated in order to minimize chloride-induced corrosion. Different grades of stainless steels such as AISI 316 L, Alloy 20, Alloy 28 and a duplex stainless steel 22Cr5Ni type, were taken into consideration.     

Effect of chloride ions on the corrosion behaviour of steel in 0.1 M citrate

The corrosion behaviour of steel was studied in aerated near neutral citrate solutions without and with various concentrations of NaCl. The potentiodynamic anodic polarization curve in 0.1 M citrate solution exhibits four anodic peaks A1, A2, A3 and A4 prior to the oxygen evolution reaction. Addition of Cl⁻ ions to the solution enhances the four peaks currents, specially A3, which is followed by pitting corrosion. The negative going scans of the cyclic voltammograms show two anodic reactivation peaks A5 and A6 and one cathodic plateau P1. A diffusion controlled process in the potential range of A1, A2 and P1 was detected by RDE experiments. The potentiostatic current time transients, at different concentrations of NaCl and applied potentials E_a > A3, were studied. The pit nucleation rate (t_i⁻¹) is found to increase with increasing the concentration of NaCl and the applied anodic potential. The impedance spectra exhibit four different behaviours depending on the potential range used. They were fitted with a single time constant circuit at E_a < −700 mV. However, at −700 mV < E_a < −480 mV, they were fitted with a circuit with two time constants. At E_a > −480 mV, the second semicircle is replaced by negative polarization resistance which is disappeared at E_a > −300 mV. The electrode impedance was found to decrease with the applied potential.     

Effect of heat treatment on corrosion and electrochemical behaviour of AZ91D magnesium alloy

An AZ91D ingot in the as-cast condition was homogenized by solution treatment and then aged for various periods of time. The microstructures produced were studied in detail and the phase volume fraction was measured quantitatively. The Corrosion resistance of all the different microstructures was studied in 3.5% NaCl solution through weight loss measurement in constant immersion conditions and potentiodynamic polarization experiments. The corroded surfaces were analysed using SEM and XRD. The volume fraction of the phase was found to have a significant influence on the corrosion behaviour. The T4 condition improved the corrosion resistance of AZ91D alloy compared to the T6 heat treatment. The results support the idea of microgalvanic coupling between cathodic phase and anodic matrix.     

Engineering behaviour of soil materials on the corrosion of mild steel

Underground pipelines and steel structures are usually expected to have a long working life. The risk of corrosion should be estimated before installing such pipelines so this paper is aiming at the investigation of the surrounding and incorporating medium (soil filling materials).Many problems related to soil application are due to the unfavorable interaction between water and soil. Underground corrosion is primarily influenced by the following factors: the presence of soil moisture, the supply of oxygen, the redox potential, the pH value, the soil resistivity, and also by microbial activity.From engineering aspects an increase in soil water content has a number of disadvantages e.g. swelling, shrinkage and cohesion decreases which affect directly on the interaction of pipelines, causing deterioration of pipeline materials “corrosion” and also cause damage of infrastructure above this soil due to the occurrence of general and localized corrosion (pitting formation) which is present in different sites of steel structures. The presence of water is a prerequisite for the functioning of corrosion cells. Corrosion of mild steel is affected by grain size, swelling, shrinkage and clay mineral content. The finer soil particles, owing to the increase in swelling, shrinkage, and plasticity, are considered as corrosive medium for underground pipelines and steel structures. The clay mineral contents are also the main quality control to the mild steel corrosion for example montmorillonite and illite absorbed water more than kaolinite clay minerals so it is highly effective in the deterioration of metals.     

Sulfate-vanadate hot corrosion of neodymium cerate/yttria stabilized zirconia composite coating

Neodymium cerate (Nd₂Ce₂O₇) was laboratory synthesized by solid-state reactions of neodymia and ceria and spray dried to get the feedstock for plasma spraying. Hot corrosion behavior of air plasma sprayed 10% Nd₂Ce₂O₇/yttria stabilized zirconia (YSZ) topcoat was studied in the presence of V₂O₅ and Na₂SO₄ salts at 950°C for 10-60 hours. It was observed that due to the presence of relatively higher basic compounds Nd₂O₃ and CeO₂ (form Nd₂Ce₂O₇) than Y₂O₃ in YSZ changed the reaction dynamics during hot corrosion and the major part of corrosive (NaVO₃) was consumed by Nd of Nd₂Ce₂O₇, making NdVO₄. The Y₂O₃ of YSZ contributed in the corrosive reaction partially, relieving majority tetragonal zirconia (t-ZrO₂) in topcoat (YSZ). No remarkable cracking was developed in the topcoat even after 60 hours of accelerated hot corrosion, which was attributed to the retention of in-relief t-ZrO₂ in YSZ.