Corrosion Behavior of 316LN and 316 Stainless Steels During Long-term Exposure to Aerated 0.5 M NaCl Using Electrochemical Noise Technique

In the present work 316LN as well as 316 stainless steel (SS) coupons each of dimensions (0.025 × 0.018 × 0.006 m³) in well-polished condition were used as two nominal electrodes which were immersed in the aerated solution of 0.5 M NaCl. Correlated current and potential electrochemical noise (EN) signals were collected at 1 Hz sampling frequency for 1 h daily over a period of 30 days. The detrended EN data were used to calculate the noise resistance (R _N) as well as the spectral noise resistance at zero frequency (R _SN^o) values and other statistical parameters. To study the nature of pits and distribution of their diameters as well as depths, extensive observations of the pitted and the blank specimens were carried out using Confocal Laser Scanning Microscopy (CLSM). The current and the potential records of the two alloys showed distinct differences in their corrosion behavior. It was observed that within less than 4 h of immersion, 316SS showed signals indicative of unstable pitting and onset of stable pitting was noticed after 48 h of exposure. However, until about 24 h, 316LN showed just the random signals and unstable pitting was observed after 28 h. The signals clearly indicated continuous growth of the stable pits in 316SS as against the repassivation of the unstable pits in 316LN after 7 days exposure. It was observed that R _N values showed a continuous decrease in the case of 316SS, but were quite stable in the case of 316LN over the exposure period. Concurrent to these observations it was observed that 316SS specimen was extensively pitted. The frequency distributions of pit diameters as well pit depths were observed to be highest at 10-20 μm and 5-10 μm, respectively. However, pits with as large as 70-80 μm diameter and as deep as 20-25 μm too were observed. No pits were observed in case of 316LN even after 30 days of exposure, an observation that corroborates well with the stable R _N values. Thus, in the present investigation, the long-term tests using EN technique coupled with CLSM studies conclusively prove that many unstable pits initiated in 316SS turn into stable ones resulting in insidious localized corrosion attack whereas the unstable pits initiated in 316LN get passivated in the simulated coastal environment.     

Filled Fibrous Sorbents Modified with Transition Metal Ferro- and Ferricyanides for Recovery of Americium and Rare-Earth Metals

Filled fibrous sorbents modified with transition metal ferro- and ferricyanides capable to recover americium(III) and rare-earth metals(III) from nitric acid solutions were prepared. The most complete and rapid recovery is attained on complex-forming and cation-exchange sorbents (as filled fibrous materials) saturated with nickel ions. The sorbents are characterized by good kinetic properties and can be used for recovery of the above metals.     

Factors of large graphite crucible life

Production methods used to prepare graphite crucibles with high operating properties are considered: use as a filler of good graphitizing acicular coke, vibration molding of the original coke mix, use of production cycles for impregnation with medium temperature coal-tar pitch — firing, firing of compacted billets in metal containers, graphitization of fired billets in graphite cylinders. The last two production methods make it possible to reduce the temperature drop throughout the volume of a billet during heat treatment, and as a consequence to reduce crack development to a minimum as a result of reducing thermal stresses. All of the production methods recommended may be entirely accomplished in existing electrode plants and may be used to increase markedly the quality crucible graphite. It is possible to achieve a quality for these materials at the best world level. Translated from Novye Ogneupory, No. 8, pp. 28–33, August 2008.     

Highly resistant dispensing nozzles based on zirconium dioxide for profiled CBCM. Part 1. Structure and physicomechanical properties of materials based on zirconium dioxide for producing CBCM dispensing nozzles

Technology is developed for preparing refractory components made of partially stabilized zirconium dioxide using an isostatic compaction press. Technology is provided for manufacturing dispensing nozzles using combined and separately stabilized zirconium dioxide, and also indices of the refractories obtained and imported materials are compared. __________ Translated from Novye Ogneupory, No. 3, pp. 127–131, March 2008.     

A light refractory concrete for thermal insulation

Compositions have been developed for nonshrinking vibrocast thermally insulating light refractory concretes with densities of 1.0, 1.3, 1.5, and 1.8 g/cm³ for temperatures of use up to 1400°C. The structure and properties have been examined for the concrete of density 1.3 g/cm³. __________ Translated from Novye Ogneupory, No. 4, pp. 29–32, April, 2008.     

Total and Fractional Performance of Granular Dust Traps in Refractory Production

Methods are proposed for designing interpolation models for the preliminary determination and subsequent forecasting of general and fractional breakthrough coefficients for dust used with granular filters, as employed in energy-saving and high-performance dust trapping from technological gases and ventilation discharges in refractory production. The models are supplied with nomograms, which makes them widely suitable for experts working in environmental protection at refractory-producing organizations. The main factors are identified that influence the performance. The results are of interest to experts in related areas of industry such as building materials and engineering ceramics and so on. Translated from Novye Ogneupory, No. 4, pp. 64–67, April, 2008.     

Optimizing the selective flocculation of coal by means of a selective reagent

The need to improve coal enrichment stems from the sharp deterioration in the coal being enriched (increasing ash and moisture content, content of small classes, rock content, etc.), which results from the widespread mechanization of mining operations, the development of high-ash deposits, and dust suppression [1].     

Dynamic modes of Ti combustion in a coflow of N<Subscript>2</Subscript>-Ar mixture

Combustion of bulk density Ti powder (containing 20 wt % TiN as a diluent) in a coflow of N₂-Ar mixture was investigated upon variation in the nitrogen content of the gaseous mixture. The obtained data are believed to open up new horizons for fabrication of layered and composite ceramics by infiltration-mediated combustion.