Model for the Prediction of the Time of Wetness from Average Annual Data on Relative Air Humidity and Air Temperature

The data of the program designed by the Economic Commission for Europe of the United Nations Organization (UN ECE) to estimate the effect of air pollution on materials, including historical and cultural heritage, were used to study the relation between the time of wetness (TOW), temperature (T), and relative air humidity (Rh). The new relation resulting from the analysis allows one to predict TOW from average annual T and Rh. The relation is a conceptual and prognostic improvement of the previous ones describing TOW as functions of T and Rh. The parameters of the equation were determined from the data of the UN ECE program and verified with the use of ISOCORRAG/MICAT and Russian data in the temperature range from –16 to 28°C. The new relation allows TOW to be easily calculated, including classification purposes.     

Effects of calcining temperature on SnO<Subscript>2</Subscript> sensors for CO and NO<Subscript>x</Subscript> gases

Nitrogen oxides (NO_x) and carbon monoxide (CO) are among the most dangerous chemical species to human health present in the atmosphere. Acute CO toxicity leading to unconsciousness, respiratory failure or death can occur after 1 hr of exposure when ambient CO levels reach 1000 ppm, whilst increase of NO_x emissions can contribute to acid deposition, pollution of groundwater, eutrophication of surface waters, and tropospheric ozone and ecosystem damage. In this work, pure SnO₂ sensors for CO and NO_x were prepared by spin coating solutions derived from a washed Gel-precipitate followed by a calcining step. SnO₂ sensors of nanometer grain size prepared by this process showed good sensitivity to CO and NO_x gases. The increase of calcining temperature not only affected grain size and surface morphology, but also caused a decrease in sensitivity of the SnO₂ sensors.     

Estimating and Mapping the Material Corrosion Losses in the European Part of Russia with Unified Doze—Response Functions

The unified doze—response functions (DRF) obtained according to the European Materials Exposure Program (EMEP) of the UN European Committee of Economics and describing the effect of acidic precipitates on materials are used for estimating the corrosion rates of metals, glass, and stones and the service lifetimes of alkyd-melamine coatings in the European part of Russia (EPR). The climate zones from cold (the Arctic) to subtropical (the Black Sea coast) including the areas with the heightened SO₂ levels are covered. In the EMEP scale (150 × 150 km), the maps of the average annual temperature (T), relative air humidity (Rh), estimated time of wetness (TOW), annual amount of precipitates (Rain), wet deposits (Rain · H⁺), and ozone level are shown. The TOW parameter is determined both by T and Rhfactors, although in the cold and northeast region, T produces the predominant effect. The maps of the corrosion rates of structural materials and alloys, the erosion of limestone and sandstone for ten years, and the service lifetimes of galvanized painted steel are considered. The effect of all the atmospheric factors, the scale and prospects of mapping the territory of Russia, the classification of the atmosphere corrosivity, and other aspects are discussed. The results indicate that the DRFs constructed can be used for mapping and estimating the cost of corrosion losses in cold regions even when the cold places are not directly involved in the test program. The effect of SO₂ on the corrosion is especially pronounced within the temperature zone of 9 to 11°C, which crosses the whole Europe and is characterized by the admissible pollution levels lower than in colder zones.     

MoS2颗粒表面包覆Al2O3及其在镀层中的应用

采用非均匀形核法将Al2O3包覆到MoS2颗粒表面,提高颗粒的亲水性能。研究了溶液pH值、Al(NO3)3的摩尔浓度和预处理工艺对包覆率的影响;采用SEM及EDS分析了包覆前后MoS2颗粒的微观形貌和表面成分;通过测量接触角研究了颗粒表面的亲水性。结果表明,颗粒表面均匀包覆了一层Al(OH)3;溶液pH值对包覆率的影响最大,Al(NO3)3的摩尔浓度次之。最佳工艺为:溶液pH值为5.5,Al(NO3)3浓度为0.15mol/L,预处理过程不添加表面活性剂。随着包覆率的提高,MoS2颗粒的亲水性提高。利用包覆Al2O3的MoS2制得了Ni-P-MoS2化学复合镀层,提高了镀层中沉积粒子的均匀致密性。     

Enhancement of photocatalytic activity of TiO2 film electrode by in situ photoelectro-generating active chlorine

The photoelectrocatalytic activity of TiO2 film electrodes in the degradation of nitrite ion was greatly enhanced in the presence of chlorine ion. The influences of NaCI concentration and initial pH value on the degradation rate of NO2^- and active chlorine production were studied. The results show that the decay rate of NO2^- and the accumulation rate of active chlorine increase with increasing NaCl concentration. At pH〈8, both the decay of increasing NaCl concentration, while at pH〉 10, they are suppressed NO2^- and active chlorine formation rates are enhanced with In addition, contrast to conventionally accepted view, in which an advantage of anatase over the rutile modification of TiO2 is in terms of photoactivity, it is found that a thermal oxidation futile TiO2 electrode is more suitable for both photogenerating active chlorine and degradingNO2^- in the presence of Cl^-. The correlative mechanism was also discussed in detail. Specific adsorption of Cl^- on the electrode causes its energy band edges to move towards positive value and also lower the photocurrent, thus less OH· radicals are produced. However, more active species of Cl that have longer lifetime are available to take part in the oxidation of NO2^- thus improving its degradation rate.     

Solvothermally synthesized tungsten oxide nanowires/nanorods for NO2 gas sensor applications

One-dimensional nanorods or nanowires of W₁₈O₄₉ were synthesized by solvothermal method at 200 °C with tungsten hexachloride (WCl₆) as precursor and cyclohexanol or 1-propanol as reaction solvent. Their morphology and structure properties were systematically characterized. The NO₂-sensing properties of the sensors based on nanowires and nanorods were investigated at 100 °C up to 250 °C over NO₂ concentration ranging from 1 ppm to 20 ppm. The results indicate that both nanowires and nanorods exhibit reversible response to different concentrations of NO₂, and the highest gas response is achieved at 150 °C. In comparison with nanorods, nanowires showed a much quicker response characteristic and a relative higher response value to the same concentration of NO₂ gas due to the smaller diameter and larger specific surface area.     

Application of NMR relaxometry for determining the concentration of nanopowder magnetite in aqueous media

The use of the effect of a decrease in the transverse relaxation time T ₂ of the NMR signal of water protons in the presence of magnetic particles has been suggested for the quantitative estimation of the concentration of magnetite (Fe₃O₄) nanopowder in water. A calibration dependence of the relaxivity T ₂ ^?1 on the iron concentration has been obtained for model suspensions of magnetite nanoparticles with sizes of approximately 20 nm in the concentration range of 0.15–70 mg/L. For comparison, the concentration dependences of T ₂ ^?1 for aqueous solutions of Fe(NO₃)₃ · 9H₂O and FeSO₄ · 7H₂O and paramagnetic salts Ni(NO₃)₂ · 9H₂O, Cr(NO₃)₃ · 9H₂O, and CuSO₄ · 5H₂O have been studied to show that they correlate with their paramagnetic susceptibilities.     

Mineralogical characterization and pretreatment for antimony extraction by ozone of antimony-bearing refractory gold concentrates

The mineralogical characterization of antimony-bearing refractory gold concentrates and the antimony extraction by ozone in HCl solution were investigated. The mineralogical study shows that there exist stibnite(Sb₂S₃), arsenopyrite(FeAsS), pyrite(FeS₂) and quartz in the concentrates, and the gold is mainly (67.42%) encapsulated in sulfides. The antimony extraction by ozone in hydrochloric acid was employed and the influences of temperature, liquid/solid ratio, HCl concentration and stirring speed on the extraction of antimony were investigated. High antimony extraction (93.75%) is achieved under the optimized conditions. After the pretreatment by ozone, the antimony is recovered efficiently and the gold is enriched in the leaching residue.     

硝酸根离子对U-0.79Ti合金腐蚀行为的抑制作用

采用电化学方法研究了硝酸根离子(NO3-)对U-0.79Ti合金在0.01mol/LNa Cl溶液中腐蚀的抑制作用。实验证明,NO3-对U-0.79Ti合金在含氯离子(Cl-)溶液中的腐蚀具有抑制作用,且与NO3-浓度密切相关。当NO3-与Cl-浓度比大于0.1时,NO3-能够有效抑制U-0.79Ti合金点蚀的发生;而低于这个比例时,NO3-对U-0.79Ti合金的腐蚀行为几乎无影响。从电化学过程来看,加入NO3-能够降低浓差极化并增大极限扩散电流密度。同时,NO3-能够降低氧化膜的阳极活性溶解速度,提高U-0.79Ti合金的点蚀电位。表面划痕实验则表明,NO3-的抑制作用很可能缘于其优先于Cl-在表面缺陷处吸附,阻碍了Cl-的点蚀成核。     

Tensile Properties and Fracture Behavior of Different Carbon Nanotube-Grafted Polyacrylonitrile-Based Carbon Fibers

The tensile properties and fracture behavior of different carbon nanotube (CNT)-grafted polyacrylonitrile-based (T1000GB) single carbon fibers were investigated. Grafting of CNTs was achieved via chemical vapor deposition (CVD). When Fe(C₅H₅)₂ (also applied via CVD) was used as the catalyst, the tensile strength and Weibull modulus of the carbon fibers were improved, possibly due to the growth of dense CNT networks on the carbon fibers, which may have led to a reduction in the number of strength-limiting defects. Separately, at lower concentrations of an Fe(NO₃)₃·9H₂O catalyst in ethanol, which was applied via dipping, the tensile strength of CNT-grafted fibers was nearly identical to that of the as-received fibers, although the Weibull modulus was higher. For higher concentrations of the Fe(NO₃)₃·9H₂O catalyst, however, the tensile strength and the Weibull modulus were lower than those for the as-received material. Although the density of the CNT network increased with the concentration of the Fe(NO₃)₃·9H₂O catalyst in the ethanol solution, heating of the ethanolic Fe(NO₃)₃·9H₂O catalyst solution generated nitric acid (HNO₃) due to decomposition, which damaged the fiber surfaces, resulting in an increase in the number of flaws and consequently a reduction in the tensile strength. Therefore, the tensile strength and Weibull modulus of CNT-grafted carbon fibers vary due to the combination of these effects and as a function of the catalyst concentration.     

Corrosion process of silver in environments containing 0.1 ppm H2S and 1.2 ppm NO2

The effects of sub‐ppm levels of nitrogen dioxide and hydrogen sulfide, and the adsorbed water on the corrosion of silver were studied in order to get a better understanding of the atmospheric corrosion process. An in situ mass balance was taken to monitor the kinetic behavior and the surface and the corrosion film were analyzed by X‐ray photoelectron spectroscopy (XPS). In H₂S environments, the tarnish film consisted of silver sulfide, and the corrosion rate depended upon oxygen as well as relative humidity. Silver was oxidized by only oxygen and the corrosion behavior conformed to a type of a parabolic law. In NO₂ environments, the corrosion film consisted of nitrate and oxide, and the corrosion rate depended upon oxygen as well as relative humidity. Compared to hydrogen sulfide, the formation of silver nitrate being strong hydroscopic reduced the effect of humidity on corrosion rate. In H₂S + NO₂ environment, the corrosion process was independent of both oxygen and humidity, and the kinetic behavior conformed to a linear law. The difference of corrosion process between H₂S or NO₂ environments and H₂S + NO₂ environments is thought to be due to the role of nitrogen dioxide as an ionic conductor and the presence of strong oxidizing species such as elemental sulfur which can be produced from the following reaction: H₂S + 2NO₂ → S + 2HNO₂. In addition, the role of adsorbed water affecting atmospheric corrosion process was mentioned based on the amount of adsorbed water from the three types of exposure environments.     

Phase Diagram for the System Cu(NO3)2-Al(NO3)3-H2O Ternary System Between 10 and 50?°C

The solid-liquid equilibria of the ternary system H₂O-Cu(NO₃)₂-Al(NO₃)₃ were studied by using a synthetic method based on conductivity measurements. Five isotherms between 10 and 50?°C were established and stoichiometric phases which appear are, respectively: At 10 and 20?°C: Al(NO₃)₃·9H₂O and Cu(NO₃)₂·6H₂O. At 30, 40, and 50?°C: Al(NO₃)₃·9H₂O and Cu(NO₃)₂·3H₂O.     

Preparation of self-healing protective films on a zinc electrode treated in a cerium(III) nitrate solution and modified with sodium phosphate and cerium(III) nitrate

Self-healing protective films were prepared on a zinc electrode previously treated in a Ce(NO₃)₃ solution by modification with Na₃PO₄ and Ce(NO₃)₃. The protective and self-healing abilities of the films were examined by polarization measurements and observation of pit formation after the electrode was scratched with a knife-edge crosswise and immersed in oxygenated 0.5 M NaCl at 30 °C for many hours. Mechanisms of the protective and self-healing activities were discussed using X-ray photoelectron spectroscopy and electron-probe microanalysis. The protective and self-healing abilities of the films prepared on the zinc electrode by treatment in the Ce(NO₃)₃ solution and modification with Na₃PO₄ plus Ca(NO₃)₂, Mg(NO₃)₂, Zn(NO₃)₂ or Ce(NO₃)₃ were summarized.     

Applications of porous silicon thin films in solar cells and biosensors

An overview of the applications of porous silicon (PS) thin films, as antireflection coatings (ARC) in silicon solar cells and transducers in biosensors, is presented. The reflectance spectra of PS films have been compared with other conventional ARCs (such as SiN_x TiO₂/MgF₂ and ZnS), and optimal PS ARC with minimum reflectance has been obtained. The implementation of PS into an industrially compatible screen-printed (SP) solar cell by both the electrochemical etching (ECE) and chemical etching (CE) methods are reviewed. Porous silicon films, formed via ECE for short anodization times, on textured n⁺ emitter ofc-Si solar cell having SP front and back contacts, lead to improvements in the performance of solar cells and demonstrate their viability in industrial applications.     

Phase Diagram of the Quaternary Al(NO<Subscript>3</Subscript>)<Subscript>3</Subscript>-Cu(NO<Subscript>3</Subscript>)<Subscript>2</Subscript>-Zn(NO<Subscript>3</Subscript>)<Subscript>2</Subscript>-H<Subscript>2</Subscript>O System

The phase diagram of the H₂O-Zn(NO₃)₂-Al(NO₃)₃-Cu(NO₃)₂ quaternary system at 30 °C has been established by using the conductivity measurements. The solid-liquid equilibria of the H₂O-Zn(NO₃)₂-Al(NO₃)₃, H₂O-Zn(NO₃)₂-Cu(NO₃)₂, H₂O-Al(NO₃)₃-Cu(NO₃)₂ ternary systems and two isoplethic sections were determined experimentally. The solid phases in equilibrium with the saturated solution are the tri- and hemipentahydrate of copper nitrate, the hexahydrate α and β of the zinc nitrate and the nonahydrate of aluminum nitrate. The copper and zinc nitrates are relatively soluble in opposition to the aluminum nitrate which presents some important precipitation domains.     

The ternary system: H2O–Fe(NO3)3–Co(NO3)2 isotherms −15 and −25 °C

The binary system H₂O–Fe(NO₃)₃ has been investigated at temperature ranging between –25 and 47 °C.The solid–liquid equilibria of the ternary system H₂O–Fe(NO₃)₃–Co(NO₃)₂ were studied at −15 and −25 °C by using a synthetic method based on conductivity measurements which allows all the characteristic points of the isotherms to be determined, and the stable solid phases which appear are respectively: ice, Fe(NO₃)₃·9H₂O, Fe(NO₃)₃·6H₂O, Co(NO₃)₂·9H₂O, Co(NO₃)₂·6H₂O and Co(NO₃)₂·3H₂O.     

Self-healing protective films prepared on zinc electrodes by treatment in a cerium(III) nitrate solution and modification with sodium phosphate and calcium or magnesium nitrate

Self-healing protective films were prepared on a zinc electrode by treatment in a Ce(NO₃)₃ solution and modification with Na₃PO₄ and Ca(NO₃)₂ or Mg(NO₃)₂. The protective and self-healing abilities of the films were examined by polarization measurements and observation of pit formation after the electrode was scratched with a knife-edge and immersed in aerated 0.5 M NaCl for many hours. The protective efficiency of the film modified with Ca(NO₃)₂ was higher than that of the film without Ca(NO₃)₂ but the self-healing ability of the former film was not sufficiently high during the prolonged immersion. Mechanisms of the protective and self-healing activities were discussed using X-ray photoelectron spectroscopy and electron-probe microanalysis.     

The preparation and gas sensitivity study of polypyrrole/zinc oxide

Polypyrrole (PPy) was prepared by chemical oxidation polymerization, analyzed by FT-IR, elemental analysis and HRTEM, and studied for gas sensitivity. It suggested that PPy had sensitivity to NH₃, H₂S and NO_x, and showed irreversibility to NO_x gas. The organic–inorganic hybrid materials PPy/ZnO with different PPy weight percents were prepared by mechanical mixing, and the sensitivity study of the materials to toxic gases NH₃, H₂S, NO_x was carried out at different operating temperatures 30, 60, and 90 °C. It was found that PPy/ZnO materials (PPy(1%)/ZnO, PPy(3%)/ZnO, PPy(5%)/ZnO, PPy(10%)/ZnO, PPy(20%)/ZnO) had better selectivity and reversibility to NO_x than pure PPy, and much lower working temperature than the reported working temperature of ZnO (about 350–450 °C). Their sensitivity increased with the increasing concentration of NO_x at particular working temperature, and among them PPy(10%)/ZnO had the maximum sensitivity to NO_x in the same condition. They showed no response to 1000, 1500, 2000 ppm NH₃ or H₂S. The response mechanism of PPy/ZnO materials to NO_x was discussed.     

Electrodissolution of 304 stainless steel in neutral electrolytes for surface decontamination applications

Brightening of 304 stainless steel in concentrated electrolytes of Na₂SO₄, Li₂SO₄, NaNO₃, LiNO₃, NH₄NO₃, and Ca(NO₃)₂ was studied. It is observed that the current efficiency and quality of the surface depend on the electrolyte concentration, ions present in the electrolyte and the operating current density. While sulfate electrolytes etch the electrodes, oxidizing electrolytes generally yield brightened surfaces. Surface brightening is achieved at the lowest current density in LiNO₃/Na₂Cr₂O₇ composite electrolyte at a pH of 5.2. The results are explained on the basis of salt film formation near the specimen surface.     

Kinetic and thermodynamic studies of AISI 4130 steel alloy corrosion in ethylene glycol-water mixture in presence of inhibitors

The electrochemical behavior of steel alloy in ethylene glycol-water mixture was investigated by electrochemical methods. The results obtained showed that corrosion rate was decreased with increasing ethylene glycol concentration. The effect of inorganic inhibitors including NO₃ ^?, NO₂ ^?, Cr₂O₇ ^2? and CrO₄ ^2? were studied using electrochemical techniques where the highest inhibition efficiency was obtained for CrO₄ ^2?. In the presence of chromate the inhibitor efficiency increased with its concentration. The inhibiting effect of the chromate was explained on the basis of the competitive adsorption between the inorganic anions and the aggressive Cl^? ions, and the adsorption isotherm basically obeys the Langmuir adsorption isotherm. Thermodynamic parameters for steel corrosion and inhibitor adsorption were determined and reveal that the adsorption process is spontaneous. Also, a phenomenon of both physical and chemical adsorption is proposed.