Simulation of Iron Distribution after Crystallization of mc Silicon

2009 ◽  
Vol 156-158 ◽  
pp. 223-228 ◽  
Author(s):  
Jonas Schön ◽  
Holger Habenicht ◽  
Martin C. Schubert ◽  
Wilhelm Warta
Keyword(s):  
Defect Density ◽  
Iron Concentration ◽  
Experimental Studies ◽  
Total Iron ◽  
Extended Defects ◽  
Dimensional Model ◽  
Extended Defect ◽  
Recombination Lifetime ◽  
Block Height ◽  
Total Iron Concentration

Interstitial iron (Fei) and iron-boron pairs influence or even limit the recombination lifetime in industrial block cast multicrystalline (mc) silicon, though the proportions in the total iron concentration are generally small. Most of the iron in mc silicon is precipitated and less recombination active. This work aims for a better understanding of the distribution of iron in its different states (precipitated or dissolved) over the block height, as well as in regions of different crystal quality. In experimental studies several features of iron in mc silicon were observed, which occur due to the high extended defect density. In our 2-dimensional model for mc silicon, trapping of interstitial Fe at extended defects and precipitation at the extended defects are taken into account. The results are compared with NAA-data and spatial resolved measurements of the Fei concentration.

scholarly journals Mechanisms of Enhanced Ionic Conduction at Interfaces in Ceramics

1994 ◽  
Vol 357 ◽  
Author(s):  
D. Lubben ◽  
F. A. Modine
Keyword(s):  
Film Thickness ◽  
Ionic Conduction ◽  
Defect Density ◽  
Ionic Conductivities ◽  
Dislocation Motion ◽  
Extended Defects ◽  
Epitaxial Relationship ◽  
Extended Defect ◽  
Charge Layer ◽  
Fine Grained

AbstractA large enhancement in the ionic conductivity of certain compounds occurs when the compound is produced as a composite material containing a finely-dispersed non-conductor such as SiO2 or Al2O3 This effect has been reported on for more than 20 years, and it is well established that the enhancement is associated with the presence of interfaces. The popular explanation has been based on a model which contends that the enhancement is due to a space-charge layer which forms to compensate a net charge layer at an interface. A different model proposes that extended defects such as dislocations and grain boundaries, either resulting from or stabilized by the interface, are responsible for the enhancement. This paper describes recent experiments which strongly support the latter model. The ionic conductivities of LiI and CaF2 thin films grown on sapphire(0001) substrates were monitored in-situ during deposition as a function of film thickness and deposition conditions. LiI films grown at 27°C exhibited a region of enhanced conduction within 100 nm of the substrate and a lesser enhancement as the film thickness was increased further. This conduction enhancement was not stable but annealed out with a characteristic log(time) dependence. The observed annealing behavior was fit with a model based on dislocation motion which implies that the increase in conduction near the interface is due to extended defects generated during the growth process. LiI films grown at higher temperatures (100°C) in order to reduce the grown-in defects showed no interfacial conduction enhancement. X-ray diffraction measurements suggest that these high-temperature LiI films nucleate as faceted epitaxial islands with a stable misfit dislocation density defined by the epitaxial relationship between the substrate and film. CaF2 films grown at 200°C showed a behavior similar to the 27°C LiI films, with a region of thermally unstable enhanced conduction that occurs within 10 nm of the substrate. Amorphous Al2O3 films deposited over the CaF2 layers created no additional enhancement but did increase the stability of the conduction, consistent with an extended defect model. Simultaneous deposition of CaF2 and Al2O3 produced films consisting of very-fine-grained CaF2 and particles of amorphous Al2O23 (5-10 nm grain and particle size) and a high defect density which was stable even well above the growth temperature. Measured conduction in the composite at 200°C was approximately 360 times that of bulk CaF2.

Fecal total iron concentration is inversely associated with fecalLactobacillusin preschool children

2017 ◽  
Vol 32 (8) ◽  
pp. 1475-1479 ◽  
Author(s):  
Sasank Kalipatnapu ◽  
Sivaraman Kuppuswamy ◽  
Giriprasad Venugopal ◽  
Venkatesh Kaliaperumal ◽  
Balamurugan Ramadass
Keyword(s):  
Preschool Children ◽  
Iron Concentration ◽  
Total Iron ◽  
Total Iron Concentration

The Effect of Total Iron Concentration and Iron Speciation on the Rate of Ferrous Iron Oxidation Kinetics of Leptospirillum ferriphilum in Continuous Tank Systems

2007 ◽  
Vol 20-21 ◽  
pp. 447-451 ◽  
Author(s):  
Jochen Petersen ◽  
Tunde Victor Ojumu
Keyword(s):  
Oxidation Kinetics ◽  
Ferrous Iron ◽  
Ferric Iron ◽  
Iron Oxidation ◽  
Iron Concentration ◽  
Total Iron ◽  
Ferrous Iron Oxidation ◽  
Utilisation Rate ◽  
Kinetics Of ◽  
Total Iron Concentration

In this study the results from a systematic study of the oxidation kinetics of Leptospirillum ferriphilum in continuous culture at total iron concentrations ranging from 2 to12 g/L are reported. In all experiments the steady-state concentrations of ferrous iron were small and comparable, and at least 97% of was as ferric. Surprisingly, the specific ferrous iron utilisation rate decreased with increasing total iron concentration, while yield coefficients increased. It was noted that the biomass concentration in the reactor (as measured by both CO2 uptake rate and cell counts) dramatically increased with increasing total iron concentrations, whereas it stayed more or less the same over a wide range of dilution rates at a given total iron concentration. The experimental data was re-analysed in terms of ferrous iron kinetics using Monod kinetics with a ferric inhibition term. The results confirm that the maximum specific iron utilisation rate is itself a function of ferric iron concentration, declining with increasing concentration. It thus appears that high concentrations of ferric iron stimulate microbial growth while at the same time inhibiting the rate of ferrous iron oxidation. It is postulated that these phenomena are related, i.e. that more growth occurs to reduce the load on the individual cell, possibly by sharing some metabolic functions.

scholarly journals The number fraction of iron-containing particles affects OH, HO<sub>2</sub> and H<sub>2</sub>O<sub>2</sub> budgets in the atmospheric aqueous phase

2021 ◽  
Author(s):  
Amina Khaled ◽  
Minghui Zhang ◽  
Barbara Ervens
Keyword(s):  
Particulate Matter ◽  
Aqueous Phase ◽  
Aerosol Particles ◽  
Iron Concentration ◽  
Transition Metal Ions ◽  
Total Iron ◽  
Chemical Mechanism ◽  
Cloud Droplets ◽  
Iron Distribution ◽  
Total Iron Concentration

Abstract. Reactive oxygen species (ROS), such as OH, HO2, H2O2 affect the oxidation capacity of the atmosphere and cause adverse health effects of particulate matter. The role of transition metal ions (TMIs) in impacting the ROS concentrations and conversions in the atmospheric aqueous phase has been recognized for a long time. Model studies usually assume that the total TMI concentration as measured in bulk aerosol or cloud water samples is distributed equally across all particles or droplets. This assumption is contrary to single-particle measurements that have shown that only a small number fraction of particles contain iron and other TMIs (FN,Fe < 100 %) which implies that also not all cloud droplets contain TMIs. In the current study, we apply a box model with an explicit multiphase chemical mechanism to simulate ROS formation and cycling in (i) aqueous aerosol particles and (ii) cloud droplets. Model simulations are performed for the range of 1 % ≤ FN,Fe ≤ 100 % for constant pH values of 3, 4.5 and 6 and constant total iron concentration (10 or 50 . Model results are compared for two sets of simulations with FN,Fe < 100 % (FeN < 100) and 100 % (FeBulk). We find largest differences between model results in OH and HO2/O2− concentrations at pH = 6. Under these conditions, HO2 is subsaturated in the aqueous phase because of its high effective Henry's law constant and the fast chemical loss reactions of the O2− radical anion. As the main reduction of process of Fe(III) is its reaction with HO2/O2−, we show that the HO2 subsaturation leads to predicted Fe(II)/Fe(total) ratios for FN,Fe < 100 % that are lower by a factor of ≤ 2 as compared to bulk model approaches. This trend is largely independent of the total iron concentration, as both chemical source and sink rates of HO2/O2− scale with the iron concentration. The chemical radical (OH, HO2) loss in particles is usually compensated by its uptake from the gas phase. We compare model-derived reactive uptake parameters γ(OH) and γ(HO2) for the full range of FN,Fe. While γ(OH) is not affected by the iron distribution, the calculated γ(HO2) range from 0.0004 to 0.03 for FN,Fe = 1 % and 100 %, respectively. Implications of these findings are discussed for the application of lab-derived γ(HO2) in models to present reactive HO2 uptake on aerosols. As the oxidant budget in aerosol particles and cloud droplets is related to the oxidative potential, we also conclude that the iron distribution FN,Fe should be taken into account to estimate the ROS concentrations and health impacts of particulate matter that might be overestimated by bulk sampling and model approaches. Our study suggests that the number concentration of iron-containing particles may be more important than the total iron mass concentration in determining ROS budgets and uptake rates in cloud and aerosol water.

Kinetics of Ferrous Iron Oxidation by Leptospirillum Ferriphilum at Moderate to High Total Iron Concentrations

2009 ◽  
Vol 71-73 ◽  
pp. 255-258 ◽  
Author(s):  
K. Penev ◽  
D. Karamanev
Keyword(s):  
Ferrous Iron ◽  
Iron Oxidation ◽  
Iron Concentration ◽  
Total Iron ◽  
Effect Of Temperature ◽  
Leptospirillum Ferriphilum ◽  
Ferrous Iron Oxidation ◽  
High Concentrations ◽  
Kinetics Of ◽  
Total Iron Concentration

The effects of temperature, pH and iron concentration on the kinetics of ferrous iron biooxidation by a free suspended culture of Leptospirillum ferriphilum were studied in shake flasks and a circulating bed bioreactor at moderate to high total iron concentration. The kinetic study showed that there are two distinct modes of iron biooxidation: growth associated and non-growth associated, depending on the pH of the medium. There were also distinctive maxima of the effect of temperature and pH on the rate of biooxidation. A kinetic model of the process was proposed, based on an electrochemical-enzymatic model. The proposed model indicates that at moderate to high concentrations (above ~12 g/L), the total iron concentration becomes the single most prominent inhibiting factor.

scholarly journals Effect of Organic Substances on the Efficiency of Fe(Ii) to Fe(Iii) Oxidation and Removal of Iron Compounds from Groundwater in the Sedimentation Process

2017 ◽  
Vol 26 (3) ◽  
pp. 15-29 ◽  
Author(s):  
Izabela Krupińska
Keyword(s):  
Dissolved Oxygen ◽  
Iron Concentration ◽  
Total Iron ◽  
Organic Substances ◽  
Oxidizing Agent ◽  
High Concentration ◽  
Iron Compounds ◽  
Sedimentation Process ◽  
Groundwater Samples ◽  
Total Iron Concentration

Abstract One of the problems with iron removal from groundwater is organic matter. The article presents the experiments involved groundwater samples with a high concentration of total iron - amounting to 7.20 mgFe/dm3 and an increased amount of organic substances (TOC from 5.50 to 7.50 mgC/dm3). The water samples examined differed in terms of the value of the ratio of the TOC concentration and the concentration of total iron (D). It was concluded that with increase in the coexistence ratio of organic substances and total iron in water (D = [TOC]/[Fetot]), efficiency of Fe(II) to Fe(III) oxidization with dissolved oxygen decreased, while the oxidation time was increasing. This rule was not demonstrated for potassium manganate (VII) when used as an oxidizing agent. The application of potassium manganate (VII) for oxidation of Fe(II) ions produced the better results in terms of total iron concentration reduction in the sedimentation process than the oxidation with dissolved oxygen.

Study of the Effects of a Two-Step Anneal on the End of Range Defects in Silicon

2002 ◽  
Vol 717 ◽  
Author(s):  
Renata A. Camillo-Castillo ◽  
Kevin. S. Jones ◽  
Mark E. Law ◽  
Leonard M. Rubin
Keyword(s):  
Defect Density ◽  
Low Energy ◽  
Extended Defects ◽  
Dislocation Loops ◽  
Extended Defect ◽  
Enhanced Diffusion ◽  
Interstitial Concentration ◽  
Transmission Electron ◽  
Concentration Peak ◽  
Scale Down

AbstractTransient enhanced diffusion (TED) is a challenge that the semi-conductor industry has been faced with for more than two decades. Numerous investigations have been conducted to better understand the mechanisms that govern this phenomenon, so that scale down can be acheived. {311} type defects and dislocation loops are known interstitial sources that drive TED and dopants such as B utilize these interstitials to diffuse throughout the Si lattice. It has been reported that a two-step anneal on Ge preamorphized Si with ultra-low energy B implants has resulted in shallower junction depths. This study examines whether the pre-anneal step has a measurable effect on the end of range defects. Si wafers were preamorphized with Ge at 10, 12, 15, 20 and 30keV at a dose of 1x1015cm-2 and subsequently implanted with 1x1015cm-2 1keV B. Furnace anneals were performed at 450, 550, 650 and 750°C; the samples were then subjected to a spike RTA at 950°C. The implant damage was analyzed using Quantitative Transmission Electron Microscopy (QTEM). At the low energy Ge preamorphization, little damage is observed. However at the higher energies the microstructure is populated with extended defects. The defects evolve into elongated loops as the preanneal temperature increases. Both the extended defect density and the trapped interstitial concentration peak at a preanneal temperature of 550°C, suggesting that this may be an optimal condition for trapping interstitials.

Correlation of R2 with total iron concentration in the brains of rhesus monkeys

2005 ◽  
Vol 21 (2) ◽  
pp. 118-127 ◽  
Author(s):  
Peter A. Hardy ◽  
Don Gash ◽  
Robert Yokel ◽  
Anders Andersen ◽  
Yi Ai ◽  
...  
Keyword(s):  
Rhesus Monkeys ◽  
Iron Concentration ◽  
Total Iron ◽  
Total Iron Concentration

Reaction of Genotypes of Rice (Oryza sativa) to Iron Chlorosis in a Calcareous Soil

1986 ◽  
Vol 22 (1) ◽  
pp. 75-78
Author(s):  
B. P. Singh ◽  
M. K. Sinha ◽  
R. A. Singh ◽  
B. N. Singh
Keyword(s):  
Oryza Sativa ◽  
Calcareous Soil ◽  
Dry Matter ◽  
Iron Concentration ◽  
Total Iron ◽  
Iron Chlorosis ◽  
Dry Matter Accumulation ◽  
Matter Production ◽  
Rice Genotypes ◽  
Total Iron Concentration

SUMMARYNine rice genotypes were classed as tolerant, moderately tolerant, susceptible and highly susceptible, depending on their growth retardation and the intensity of lime-induced iron chlorosis. All except genotypes IET 7972 and IET 7973 showed varying degreees of chlorosis and corresponding decreases in shoot dry matter production. Chlorosis was negatively correlated with the orthophenanthroline reactive Fe2+ iron content of the leaves, the concentration of which accounted for 82% of the variability in chlorosis. However, total iron concentration in the leaves and the Fe/Mn, Fe/Cu and K/Fe ratios were not significantly correlated with dry matter accumulation in the plants.

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