Substrate effect on the structural and electrochemical properties of electrolytic manganese dioxide deposited from sulphate solutions

We studied the effect of anode substrates such as pure lead (Pb), lead antimony (Pb-Sb), and lead-silver (Pb-Ag) on the structural and electrochemical properties of electrolytic manganese dioxide (EMD). X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and chemical analyses were used to determine the structural and chemical characteristics of the EMD samples. The charge–discharge profile was studied in 9 M KOH using a galvanostatic charge-discharge unit. In all the substrates the current efficiencies were more than 99% except with Pb-Sb where it was 90%. Results revealed the nature of the substrate strongly affected the morphology of the deposited material which in turn affected the electrochemical properties of the EMD samples. XRD analyses revealed that the nature of the anode did not affect the crystal structure of the deposited EMD and all the samples were predominantly γ-MnO 2 , which is electrochemically active for energy storage applications. The EMD deposited on lead substrate showed superior discharge capacity of 245 mAhg -1 when compared with other substrates

System Dynamic Modeling for Quality Upgradation in Technical Education

The current research findings presented briefs about the dynamics of Infrastructure growth on quality of technical education system by developing the dynamic model with system dynamics as a methodology and Simulating the model for studying the behavior of the system for designing optimal policy for quality improvement of technical education system

Preparation and characterization of EMD from manganese cake — A byproduct of manganese nodule processing

Electrolytic manganese dioxide (EMD) was prepared from manganese cake, which is an oxide material and byproduct obtained during processing of manganese nodules. Manganese cake dissolution was carried out in sulfuric acid media using waste newspaper as a reductant. In the two-stage purification of leach liquor iron was initially removed by pH adjustment using lime slurry followed by sulfide precipitation using sodium sulfide. Effects of current density, Mn(II) and sulfuric acid concentrations were studied during the electrodeposition of EMD from purified solution. The EMD obtained was characterized by XRD, SEM and its discharge capacity was determined. The XRD pattern demonstrated that EMD was a mixture of γ- and ε-variety. The EMD produced from manganese cake showed a discharge capacity of 290 mAh/g, which is industrially acceptable

Preparation of electrolytic manganese dioxide (EMD) from low grade manganese ores/residues

A process flow sheet for processing low-grade manganese ores / residues has been developed to produce electrolytic manganese dioxide (EMD) as an end product that is suitable for battery industry. Maganese nodules leach residue having ∼ 25 % manganese and ∼ 8 % iron with other minor impurities such as Cu, Ni, Co and Zn was leached in H2SO4 medium using activated charcoal as reductant followed by purification and electrowinning of EMD. The leaching process was optimized for different parameters viz. pulp density, acid concentration and amount of charcoal. The optimal parameters for leaching of 20 % pulp density are 0.055 g charcoal per gram of Mn material with 2 M sulfuric acid at room temperature for 4 h showing ∼ 90 % Mn extraction. The leach liquor was purified in two stages - first step by addition of KMnO4 to oxidize ferrous to ferric and precipitation of iron by rising pH to 4 with addition of Ca(OH)2 followed by second step of addition of sodium sulphide for removal of Cu, Ni, Co and Zn. The purified liquor obtained after bringing down impurity levels was used for the preparation of EMD. The conditions for preparation of EMD, ie. concentration of Mn and acidity, temperature, current density have been optimized. The optimal parameters for EMD preparation are [Mn]: 48 g/L; [H2SO4]: 25 g/L; 90 °C at a current density of 200 A/m2. The deposited EMD was characterized for particle size and morphology by XRD & SEM. The EMD was of γ-varity with irregular and agglomerated particles having discharge capacity of 290 mAh/g

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Influence of alternative alkali reagents on Fe removal during recovery of Mn as Electrolytic Manganese Dioxide (EMD) from Mn sludge

Flow sheet for recovery of Mn values from Mn sludge, a by-product obtained during processing of the Mn nodules through ammonia-ammonium sulphate-sulphur dioxide leaching process route as Electrolytic Manganese Dioxide (EMD) was developed. The unit operations include dissolution of Mn sludge with sulphuric acid in presence of activated charcoal, purification of liquor in two stages - removal of Fe by adjusting pH to ~ 4 followed by precipitation of other impurities as sulphides by addition of Na2S. The purified liquor was electrowinned for producing EMD. During first stage purification, Fe precipitation was carried out with CaO that resulted in loss of Mn due to its entrapment in the gypsum. The paper discusses use of alternative alkali reagents MgO and NaOH to minimise the Mn loss. Physico-electrochemical characteristics of the EMD produced from the purified MnSO4 solutions obtained by using CaO, MgO and NaOH for Fe removal during stage I purification and subsequent stage II purification of other impurities as sulphides was investigated and the discharge capacities of the EMD samples were found to be 267, 260 and 250 mAhg- 1 respectivel

Investigation of molten fuel coolant interaction phenomena using real time X-ray imaging of simulated woods metal-water system

In liquid metal fast breeder reactors, postulated failures of the plant protection system may lead to serious unprotected accidental consequences. Unprotected transients are generically categorized as transient overpower accidents and transient under cooling accidents. In both cases, core meltdown may occur and this can lead to a molten fuel coolant interaction (MFCI). The understanding of MFCI phenomena is essential for study of debris coolability and characteristics during post-accident heat removal. Sodium is used as coolant in liquid metal fast breeder reactors. Viewing inside sodium at elevated temperature is impossible because of its opaqueness. In the present study, a methodology to depict MFCI phenomena using a flat panel detector based imaging system (i.e., real time radiography) is brought out using a woods metal-water experimental facility which simulates the UO2-Na interaction. The developed imaging system can capture attributes of the MFCI process like jet breakup length, jet front velocity, fragmented particle size, and a profile of the debris bed using digital image processing methods like image filtering, segmentation, and edge detection. This paper describes the MFCI process and developed imaging methodology to capture MFCI attributes which are directly related to the safe aspects of a sodium fast reactor

Exercise Volume Versus Intensity and the Progression of Coronary Atherosclerosis in Middle-Aged and Older Athletes: Findings From the MARC-2 Study.

BACKGROUND: Physical activity and exercise training are associated with a lower risk for coronary events. However, cross-sectional studies in middle-aged and older male athletes revealed increased coronary artery calcification (CAC) and atherosclerotic plaques, which were related to the amount and intensity of lifelong exercise. We examined the longitudinal relationship between exercise training characteristics and coronary atherosclerosis. METHODS: Middle-aged and older men from the MARC-1 (Measuring Athlete's Risk of Cardiovascular Events 1) study were invited for follow-up in MARC-2 (Measuring Athlete's Risk of Cardiovascular Events 2) study. The prevalence and severity of CAC and plaques were determined by coronary computed tomography angiography. The volume (metabolic equivalent of task [MET] hours/week) and intensity (moderate [3 to 6 MET hours/week]; vigorous [6 to 9 MET hours/week]; and very vigorous [≥9 MET hours/week]) of exercise training were quantified during follow-up. Linear and logistic regression analyses were performed to determine the association between exercise volume/intensity and markers of coronary atherosclerosis. RESULTS: We included 289 (age, 54 [50 to 60] years [median (Q1 to Q3)]) of the original 318 MARC-1 participants with a follow-up of 6.3±0.5 years (mean±SD). Participants exercised for 41 (25 to 57) MET hours/week during follow-up, of which 0% (0 to 19%) was at moderate intensity, 44% (0 to 84%) was at vigorous intensity, and 34% (0 to 80%) was at very vigorous intensity. Prevalence of CAC and the median CAC score increased from 52% to 71% and 1 (0 to 32) to 31 (0 to 132), respectively. Exercise volume during follow-up was not associated with changes in CAC or plaque. Vigorous intensity exercise (per 10% increase) was associated with a lesser increase in CAC score (β, -0.05 [-0.09 to -0.01]; P=0.02), whereas very vigorous intensity exercise was associated with a greater increase in CAC score (β, 0.05 [0.01 to 0.09] per 10%; P=0.01). Very vigorous exercise was also associated with increased odds of dichotomized plaque progression (adjusted odds ratio [aOR], 1.09 [1.01 to 1.18] per 10%; aOR, 2.04 [0.93 to 4.15] for highest versus lowest very vigorous intensity tertiles, respectively), and specifically with increased calcified plaques (aOR, 1.07 [1.00 to 1.15] per 10%; aOR, 2.09 [1.09 to 4.00] for highest versus lowest tertile, respectively). CONCLUSIONS: Exercise intensity but not volume was associated with progression of coronary atherosclerosis during 6-year follow-up. It is intriguing that very vigorous intensity exercise was associated with greater CAC and calcified plaque progression, whereas vigorous intensity exercise was associated with less CAC progression