Effect of Flowing Lead–Bismuth Eutectic on the Mechanical and Structural Properties of Stainless Steel 304L

Stainless steel 304L is being considered as a structural material for a component in a critical facility in an environment of molten lead–bismuth eutectic (LBE) at a temperature between 250 and 350 °C. This paper gives results on the effect, of 10,000 h exposure to non-isothermal liquid LBE at temperatures of 250 and 350 °C, on the mechanical and structural properties of SS 304L. The dissolved oxygen concentration in the molten eutectic was 4 × 10^?10 wt% and flow velocity was 16 cm/s. In order to assess the changes in mechanical properties tensile tests were carried out in air at 25 °C and fractography of fractured surface was observed by scanning electron microscopy. The results showed no change in the mechanical properties of SS 304L after 10,000 h exposure to LBE at 250 and 350 °C. Electron probe microanalysis of the interface of SS 304L with LBE showed that there was no penetration of LBE into the grain boundaries nor preferential dissolution of any of the components of steel in LBE after 10,000 h exposure at either temperature. No oxide layer was observed on the surface of SS 304L.     

Hydrometallurgical Process for Copper Recovery from Waste Printed Circuit Boards (PCBs)

Present paper focuses on the selective recovery of copper from the enriched ground printed circuit boards (PCBs) using leaching and solvent extraction. The metal-enriched ground sample obtained from the beneficiation of the sized PCBs in a laboratory scale column type air separator contained mainly 49.3% Cu, 3.83% Fe, 1.51% Ni, 5.45% Sn, 4.71% Pb, and 1.85% Zn. The leaching of the enriched sample with 3.5 mol/L nitric acid dissolved 99% copper along with other metals at 323 K temperature and 120 g/L pulp density in 1 h time. The composition of the leach liquor with wash solution was found to be 42.11 g/L Cu, 2.12 g/L Fe, 4.02 g/L Pb, 1.58 g/L Zn, and 0.4 g/L Ni. The McCabe–Thiele plot indicated the requirements of three counter-current stages for maximum extraction of copper from the leach liquor at pH 1.5 using 30, 40, and 50% (v/v) LIX 984 N at the phase ratios (A/O) of 1:3, 1:2, and 1:1.5, respectively. The counter-current simulation studies show the selective extraction of 99.7% copper from the leach liquor feed of 1.5 pH in three stages with 50% LIX 984 N at A/O phase ratio of 1:1.5. The stripping of copper from the loaded organic with sulfuric acid produced copper sulfate solution from which copper metal/powder could be recovered by electrolysis/ hydrogen reduction.     

Corrosion Compatibility Studies of Stainless Steel 304L in Flowing Liquid Lead Bismuth Eutectic

Stainless steel 304L is being considered as a structural material for some components in the lead–bismuth eutectic (LBE) target facility operating at a temperature of about 250°C. Data available on the corrosion of SS 304L in LBE for long duration exposure at these temperatures are scanty. This paper gives the corrosion behaviour of SS 304L after the exposure of 6500 h in LBE in a non-isothermal loop with oxygen concentration of ~4 × 10^?10 wt% at temperatures of 250 and 350°C and with flow velocity of 16 cm s^?1. The composition of the surface film was analysed by energy dispersive X-ray (EDAX) and X-ray photoelectron spectroscopy techniques. To record the changes in the mechanical properties of SS 304L upon exposure tensile tests of the tensile specimens exposed to LBE were performed in air at room temperature and the fractured surfaces were examined by scanning electron microscope (SEM). Changes in microstructure and elemental composition of the exposed surface of SS 304L were studied using SEM and EDAX. While no changes were observed in the mechanical properties and microstructure due to prolonged exposure to LBE at either temperature, the specimens exposed to 350°C after 6500 h showed a corrosion rate of 1.2 × 10^?3 μm h^?1. While no penetration of LBE into the grain boundaries was observed at either temperature after an exposure of 6500 h, a minor depletion of nickel was noted in specimens exposed at 350°C.     

Trace detection of Ce3+ by adsorption strip voltammetry at a carbon paste electrode modified with ion imprinted polymers

To develop a convenient method for sensitive and selective determination of Ce3+ in aqueous phase with complicated matrices, a carbon paste electrode(CPE) modified with ion imprinted polymers(IIPs) were fabricated. The polymers were prepared by precipitation polymerization using Ce3+ as template, allyl phenoxyacetate(APA) as monomer, ethylene glycol dimethacrylate(EGDMA) as crosslinker and azobisisobutyronitrile(AIBN) as initiator under the molar ratio of Ce3+, APA and EGDMA as 1:4:40, respectively. Ce~(3+) was detected directly by differential pulse adsorptive stripping voltammetry(DPASV) and its oxidation peak appears at about 0.93 V. All parameters affecting the sensor's response are optimized and a calibration curve is plotted at a linear range of 1.0 × 10~(-6)-1.0 x 10~(-5) mol/L and 1.0×10~(-5)-2.0 × 10~(-4)mol/L with the detection limit of 1.5 × 10~(-7) mol/L. All other rare earth ions have no interference with the determination of Ce~(3+) even at a concentration 500 times higher than that of Ce~(3+).This sensor was successfully applied to determination of Ce~(3+) in two catalyst sample solutions with RSD≤3.3%(n = 5)and recoveries in the range of 99.2%-106.5% at our optimal conditions.     

Surface Hardening of Powder Injection Molded 316L Stainless Steels Through Low-Temperature Carburization

The surface hardness of powder injection molded (PIM) 316L is generally low due to the inherited austenitic structure and large grains induced during high-temperature sintering. To increase the surface hardness and the wear resistance, low-temperature carburization (LTC) was applied to PIM 316L. With carburization at 773 K (500 °C) for 24 hours, the resulting hardness at the surface increases from 160 to 810 HV due to the “colossal” supersaturation of interstitial carbon and M₅C₂ carbide, and the corrosion resistance is not deteriorated. The carburized depth is about 40 μm, and the carbon content in this layer is about 3.25 wt pct or 13.5 at. pct, which causes lattice expansion of the austenite. When the carburization temperature increases to 823 K (550 °C), or the carburization time increases to 72 hours, chromium carbides are observed and the corrosion resistance is impaired. One distinct advantage of applying LTC to PIM 316L is that no acid cleaning process is required, unlike for wrought counterparts, because of the clean surface of the sintered materials.     

Effect of Ball Burnishing Treatment on the Fatigue Behavior of 316L Stainless Steel Operating Under Anodic and Cathodic Polarization Potentials

Corrosion fatigue (CF) behavior of AISI 316L was investigated in a 3 pct NaCl aqueous solution at an R = ? 1 stress ratio and a frequency of 60?Hz at room temperature. The test scale specimen was 7 cm². The passive (0 mV_Ref), pitting (120?mV_Ref), and cathodic (? 1400?mV_Ref) polarization potentials were statically applied and recorded during CF tests until the samples were broken. The shaft material surface was treated with a ball burnishing (BB) process. By the results, the fatigue behavior of AISI 316L was affected by polarization potential and surface treatment. Under 0?mV potential charged tests for 5?×?10⁵ cycles, BB treatment raised the CF strength of the shaft material from about 448 to 702?MPa with a percent 57 increase. Fractographic observations revealed that corrosion pits occurred during the experiments where anodic potential was applied and that transgranular surface fractures occurred in all cases.     

Effect of Annealing Temperature on Microstructure and Mechanical Properties of Bulk 316L Stainless Steel with Nano- and Micro-crystalline Dual Phases

Microstructures and mechanical properties of 316L stainless steels with dual phases austenite prepared by an aluminothermic reaction casting were explored. It is found that the steels consist of nano- and micro-crystalline austenite phases, a little δ ferrite and contaminations. Before and after annealing at 1073 K and 1273 K (800 °C and 1000 °C), average grain sizes of the nanocrystalline austenite phase are about 32, 31, 38 nm, respectively. Tensile strength increases first from 371 to 640 MPa and then decreases to 454 MPa. However, elongation ratio increases gradually from 16 to 23 and then 31 pct after annealing. The results illustrate that the steel after annealing at 1073 K (800 °C) has better properties, also indicating that combination of dual nano- and micro-crystalline austenite phase is conductive to improving tensile properties of materials.     

Effects of yttrium and phosphorus on growth and physiological characteristics of Microcystis aeruginosa

Yttrium is a main kind of rare earth elements (REEs) with wide applications in modern industry and farming. Phosphorus, an essential element of algae, is used as the nutrients and also one of the main factors of eutrophication. To investigate the effects of yttrium and phosphorus on Microcystis aeruginosa (M. aeruginosa), the growth and physiological changes were studied by lab cultured experiments. In the experiment, exogenous yttrium was tested by a concentration gradient (0.0, 0.1, 0.3, 0.5, 1.0 mg/L), meanwhile, phosphorus was tested by three concentrations (0.0, 0.02, 0.2 mg/L). The results show that the contents of chlorophyll a (chl-a) and soluble protein increase compared with the control and they have certain correlation with algal cells density. The growth status of algae is stimulated by initial yttrium concentration ≤0.3 and 0.2 mg/L phosphorus, while it is inhabited by 0.5 and 1.0 mg/L yttrium. Besides, the activity of superoxide dismutase (SOD) of algae increases with addition of yttrium dose (0–0.3 mg/L) when phosphorus dose is 0.2 mg/L. Furthermore, when yttrium dose is 0.5 and 1.0 mg/L, the vitality of SOD presents a sharp decline. The malondialdehyde (MDA) contents increase with time and addition of yttrium dose, 0.2 mg/L phosphorus weakens the accumulation of MDA.     

Voltammetric determination of venlafaxine as an antidepressant drug employing Gd2O3 nanoparticles graphite screen printed electrode

Graphite screen printed electrode modified with Gd_2 O_3 nanoparticles(Gd_2 O_3/SPE) was developed for the determination of venlafaxine(VF). The Gd_2 O_3 nanoparticles were thoroughly characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM) and X-ray diffraction(XRD) analyses. To study the electrochemical behaviour of venlafaxine cyclic voltammetry(CV), chronoamperometry(CHA)and differential pulse voltammetry(DPV) were employed. These studies reveal that the oxidation of venlafaxine is facilitated at Gd_2 O_3/SPE. After optimization of analytical conditions, analysis of venlafaxine using the modified electrode in 0.1 mol/L PBS(pH 7.0) demonstrates that the peak currents corresponding to venlafaxine vary linearly with its concentration in the range of 5.0 ×10~(-6)-9.0 × 10~(-4) mol/L. The detection limit(S/N = 3) of 2.1 × 10~(-7) mol/L is obtained for venlafaxine using DPV. The prepared modified electrode benefits from advantages such as simple preparation method, high sensitivity and low detection limit.Moreover, the evaluation of practical applicability of this proposed method is successful in the identification of venlafaxine in pharmaceutical formulations, urine and water samples.     

Effect of Temperature on the Fracture Toughness of Hot Isostatically Pressed 304L Stainless Steel

Herein, we have performed J-Resistance multi-specimen fracture toughness testing of hot isostatically pressed (HIP’d) and forged 304L austenitic stainless steel, tested at elevated (300 °C) and cryogenic (? 140 °C) temperatures. The work highlights that although both materials fail in a pure ductile fashion, stainless steel manufactured by HIP displays a marked reduction in fracture toughness, defined using J_0.2BL, when compared to equivalently graded forged 304L, which is relatively constant across the tested temperature range.     

Investigation of Degree of Undercooling of Fe-O Alloy on Al2O3 Substrate

An Fe-O drop of ~0.4 g in an alumina crucible was quenched from ~2200 K (~1927 °C) at a cooling rate of ?87 K/s by flowing He gas at a flow rate of 25 L/min STP. A deep undercooling of approximately 200 K was obtained regardless the oxygen content in the sample. According to the classical nucleation theory, the contact angle between a solid Fe nuclei and the Al₂O₃ substrate was estimated to be 53 (±4) deg.     

High-Temperature Oxidation Resistance of a Nanoceria Spray-Coated 316L Stainless Steel Under Short-Term Air Exposure

Nanoceria coatings using a spray method were implemented on a 316L stainless steel (SS). Coated and uncoated coupons were exposed to dry air at 1073 K to 1273 K (800 °C to 1000 °C) for short time periods (up to 24 hours) and in situ measurements of oxidation were carried out using a highly sensitive thermogravimetric balance. From the experimental outcome, activation energies were determined in both, coated and uncoated 316 SS coupons. The estimated exhibited activation energies for oxidation in the coated and uncoated conditions were 174 and 356 kJ/mol, respectively. In addition, the developed scales were significantly different. In the coated steel, the dominant oxide was an oxide spinel (Fe, Mn)₃O₄ and the presence of Fe₂O₃ was sharply reduced, particularly at 1273 K (1000 °C). In contrast, no spinel was found in the uncoated 316L SS, and Fe₂O₃ was always present in the scale at all the investigated oxidation temperatures. The coated steels developed a highly adherent fine-grained scale structure. Apparently, the nanoceria particles enhanced nucleation of the newly formed scale while restricting coarsening. Coarse grain structures were found in the uncoated steels with scale growth occurring at grain ledges. Moreover, the oxidation rates for the coated 316L SS were at least an order of magnitude lower than those exhibited by the steel in the uncoated condition. The reduction in oxidation rates is attributed to a shift in the oxidation mechanism from outward cation diffusion to inward oxygen diffusion.     

Adsorption of Oil onto API-X100 Pipeline Steel in CO2-Saturated Solutions

This research explores the validity of Langmuir adsorption theorem in analyzing the natural corrosion inhibition by an aromatic C₁₀H₁₂ compound, in a hydrocarbon fuel, in 1-bar CO₂-saturated solutions. The adsorption isotherms were constructed from the efficiencies of inhibition, by 10, 20, and 30 vol pct of the fuel, of the corrosion rates calculated from potentiodynamic polarization measurements, in 2 NaCl g/L solutions at 293 K, 323 K, and 353 K (20 °C, 50 °C, and 80 °C). The corrosion rates increased with temperature, and the hydrocarbon fuel, seemingly showing cathodic-inhibition characteristics, acted less efficiently accordingly; two main results the potentiodynamic polarization, electrochemical impedance spectroscopy and open-circuit measurements, demonstrated agreement on with each other.     

Design,Development, Analysis and Comparison of Instrumented Irradiation Capsule for Online Determination of Uniaxial Creep Behavior in Structural Specimen Out-of-Pile Test Results with Analytical Results in FBTR

The main intent of this work is to develop an instrumented capsule for online determination of uniaxial creep behavior of SS 316L structural specimen. The irradiation capsule has three different zones located one over the other. In the bottom zone of the capsule, the specimen is located, with one end fixed to the bottom portion of capsule and the other end connected to a central tube through a connecting plug. In the top zone a linear variable differential transducer (LVDT) is placed and its core is passed through the central tube. The end point of the LVDT core touches the plug connected to the specimen to measure the elongation of the structural specimen. In this capsule setup, bellows are used to apply a load on the structural specimen with the use of pressurized argon gas. With the application of pressure, the bottom bellow will expand and the top bellow will get compressed. During this expansion of the bottom bellow, tensile load will be applied on the specimen, and the elongation of the structural specimen will be measured by the movement of the core of the LVDT. This paper discusses the details of the design, assembly of an out-of-pile version of instrumented capsule and its experimental results are compared with literature results. The creep experiments have been carried out at three different temperatures and three different stresses (269 MPa at 450 °C, 287 MPa at 500 °C and 306 MPa at 550 °C). Initially the capsule is filled with pre-pressurized argon gas at 6 MPa at room temperature. We have observed that the force/load due to argon gas pressure is the major component for the tensile loading of the specimen and 95% of the total load acts on the SS 316L specimen and remaining 5% load only acts on the bellow. Design concept of instrumented capsule for uniaxial creep measurement has been validated.     

Selective Leaching-Recovery of Re and Mo from Out-Gas Dust of Molybdenite Roasting Furnace

Selective leaching and recovery of Mo and Re present in out-gas dust of molybdenite roasting furnace was quantitatively investigated. The effects of solid to liquid (S/L) phase ratio, sulfuric acid concentration and solution temperature on the selective extraction were determined. Considerable Mo and small amount of Re were detected in the out-gas dust of the industrial roasting furnaces. Recovery percentage of both Re and Mo increased by increasing acid concentration and solution temperature. The results also showed that the recovery percentage of Re decreased by increasing the S/L ratio. The best conditions for selective leaching was obtained as 20 min mixing in water (0 g/L sulfuric acid) with S/L ratio of 0.2 in the temperature range of 40–60 °C.     

SYNTHESIS OF COPPER METAL/SALTS FROM COPPER BLEED SOLUTION OF A COPPER PLANT

Copper bleed solution (CBS) generated during the electrorefining of anode copper contains 40 g/L Cu, 10–20 g/L Ni, and 170–200 g/L H₂SO₄, along with other impurities in different quantities. In order to get the valuable metals from this CBS, studies have been carried out to crystallize and recover metal salts on bench scale with/without partial decopperization from the point of view of reuse and the recycling of the sulphate salts and the acid recovered back to the system. Studies showed the possibility of recovering copper sulphate salt without affecting its purity with respect to nickel by controlling the extent of evaporation. In an alternative approach, a part of copper metal of purity 99.85% produced during partial decopperization of copper from 39.8 to 9.64 g/L Cu without affecting the current efficiency at a current density of 100 A/m². Subsequently, mixed salt containing 9.80% Cu and 13.19% Ni has also been produced from the partially decopperized solution. The mixed salt could be processed for metal recovery by solvent extraction. The mother and wash liquor could be recycled in the electrorefining plant for acid and copper make-up.     

Leaching of rare Earth elements from an Illinois basin coal source

The existence of rare earth elements(REEs) in coal sources at elevated concentrations has been the focus of several studies over the past decade. However, limited research has been conducted on methods to recover and refine the REEs. This paper reports the results of a detailed study into the potential of selectively recovering REEs in an Illinois basin coal source by leaching. Leaching characteristics are obtained for several segments obtained from a core sample as well as three different reject materials collected at a coal processing plant. Using a 1.2 mol/L sulfuric acid solution at 75 ℃,over 60% REE recovery is achieved from the direct floor and an inner parting material as well as the coal-rich core segments that are pretreated by low-temperature plasma oxidation to obtain access to the microdispersed mineral matter. In the leachable parting material, fluorapatite is detected by XRD analysis,which is one of the more soluble phosphate minerals with a documented association with REEs. For the three plant reject samples, the leaching recovery values obtained for the heavy REEs are higher than those obtained for the light REEs under the standard leaching conditions and when 0.1 mol/L(NH_4)_2SO_4 was used to extract REEs by an ion exchange mechanism. Thermal activation by roasting or chemical activation by pretreatment using 8 mol/L NaOH solution increases the total REE recovery with significantly higher gains obtained for the light REEs. Leaching kinetics are relatively fast within the first 2 h and then slow to provide relatively low overall recovery values under the standard test conditions for the coarse and fine reject samples. However, significantly higher recovery values are realized when treating mixed-phase(middling) particles existing within the coarse reject material.     

Influence of the Carbo-Chromization Process on the Microstructural,Hardness, and Corrosion Properties of 316L Sintered Stainless Steel

We report on the changes on the microstructural, hardness, and corrosion properties induced by carbo-chromization of 316L stainless steel prepared by Spark Plasma Sintering technique. The thermo-chemical treatments have been performed using pack cementation. The carburizing and chromization were carried out between 1153 K (880 °C)/4 h to 1253 K (980 °C)/12 h and 1223 K (950 °C)/6 h to 1273 K (1000 °C)/12 h in a solid powder mixture of charcoal/BaCO₃ and ferrochromium/alumina/NH₄Cl, respectively. The obtained layers were investigated using X-ray and electron diffraction, optical and scanning electron microscopies, Vickers micro-hardness, and potentiodynamic measurements. The thickness of the carbo-chromized layer ranges between 300 and 500 μm. Besides the host γ-phase, the layers are mainly constituted of carbides (Fe₇C₃, Cr₂₃C₆, Cr₇C₃, and Fe₃C) and traces of α′-martensite. The average hardness values decrease smoothly from 650 HV at the sample surface down to 200 HV at the center of the sample. The potentiodynamic tests revealed that the carbo-chromized samples have smaller corrosion resistance with respect to the untreated material. For strong chromization regimes, the corrosion rate is increased by a factor of four with respect to that of the untreated material, while the micro-hardness of the layer is three times larger. Such materials are suited to be used in environments where good corrosion resistance and wear properties are required.     

Reductive Leaching of Manganese Nodule Using Saw Dust in Sulphuric Acid Medium

Single-step reductive dissolution studies were carried out to extract Mn, Cu, Ni and Co values from manganese nodules of Indian Ocean using a cellulosic low-cost reductant (sawdust) in sulphuric acid medium. The leaching conditions were optimized for maximum extractions by varying experimental parameters such as time, amount of reductant, sulphuric acid concentration, temperature, and pulp density. It was observed that both acid as well as reductant were essential to successfully dissolve most of the desired metal values. 99.5% Mn, 99.1% Cu, 99.6% Ni, 93% Co and 64.6% Fe were dissolved under the conditions: pulp density 10% (wt/v), amount of sawdust 0.5 g/g of nodule, acid 5% (v/v), temp 105 °C, time 2 h. The enriched leach liquor was obtained following lock cycle technique. The composition of solution taken for purification was: 98.2 g/L Mn, 4.1 g/L Cu, 5 g/L Ni, 336 ppm Co with 12.3 g/L Fe. Precipitated bulk sulphides of Cu, Ni, Co and crystallized MnSO₄·H₂O were the two products obtained after Fe removal from the solution. A schematic flow sheet was suggested. The complete process comprised of simple hydrometallurgical unit operations.     

Microstructure and Magnetic Properties of Ni2(Mn,Fe)Ga Heusler Alloys Rapidly Solidified by Melt Spinning

The microstructure and magnetic properties of Ni₂MnGa base alloys with “Fe” substitution in place of “Mn” are studied. The processing technique used is melt spinning at wheel speeds of 20 m/s and 30 m/s followed by annealing at 1273 K (1000 °C) for 1 hour. Fe content is varied from 2 at. pct to 11 at. pct for alloys of Ni₅₀Mn_(25?x)Fe _x Ga₂₅ with Heusler stoichiometry. Austenite with B2 partial atomic ordering and premartensitic tweed structures were found at room temperature for all the alloys at different wheel speeds. After annealing at 1273 K (1000 °C) for 1 hour, austenite phase with L2₁ Heusler atomic ordering is stabilized in samples of all the processing conditions. Saturation magnetization, martensitic transformation temperature, and Curie temperature are measured. Martensite temperature and Curie temperature increase in proportion to iron content in the alloy. Saturation magnetization is sensitive to the phase content and compositional inhomogeneities.