Annealing and Leaching Studies With Natural and Artificial Obsidian Glass

1987 ◽  
Vol 112 ◽  
Author(s):  
T. D. MÄrk ◽  
G. Walder
Keyword(s):  
Temperature Dependence ◽  
Exponential Function ◽  
Annealing Time ◽  
Radiation Doses ◽  
Leaching Rate ◽  
Fission Tracks ◽  
Leaching Experiments ◽  
Induced Fission ◽  
Obsidian Glass ◽  
Kinetics Of

AbstractAnnealing kinetics of fission tracks (produced by induced fission of U235 in natural and artificial (doped) obsidian glass has been studied by etching microscopy as a function of annealing time and temperature. The observed annealing characteristics can be best decribed by a two term exponential function with an Arrhenius type temperature dependence of the annealing coefficients. The activation energies deduced are (0.94 ± 0.16)eV and (1.04 ± 0.15)eV for artificial obsidian and (0.83 ± O.13)eV and (0.60 ± 0.16)eV for natural (fossil) obsidian, respectively. In addition, leaching experiments of obsidian samples exposed to different radiation, doses and rates have been made at two different leachate temperatures. At a temperature of 60°C the leaching rate of irradiated samples is much larger than that of unirradiated samples, whereas at a temperature of 90°C observed leaching rates are similar.

Radiation Damage and Its Annealing in Sodium Silica Glass

1986 ◽  
Vol 84 ◽  
Author(s):  
T.D. Mark ◽  
W. Ritter
Keyword(s):  
Temperature Dependence ◽  
Radiation Damage ◽  
Absorption Spectroscopy ◽  
Exponential Function ◽  
Annealing Time ◽  
Silica Glass ◽  
Fission Fragments ◽  
Radiation Sources ◽  
Single Exponential Function ◽  
Single Exponential

AbstractAnnealing of radiation damage in artificial sodium silica glass has been studied by absorption spectroscopy for different radiation sources (fission fragments produced by n,f reactions, alpha decays produced by n, α reactions, and 2 MeV electrons) as a function of annealing time and temperature. The annealing observed can be described best by a single exponential functionA(t) = a exp (− αt)with an Arrhenius type temperature dependence of the annealing coefficient αα(T) = α0 exp (− EA/kT)For the three different radiation sources similar activitation energies EA were deduced from the data. Possible annealing processes are discussed.

Study on leaching kinetics of hexavalent chromium from aged calcium-free chromium slag

2021 ◽  
pp. 1-13
Author(s):  
Quan Qi ◽  
Liang Li ◽  
Liangyu Wei ◽  
Baoming Hu ◽  
Zheng Liu ◽  
...  
Keyword(s):  
Hexavalent Chromium ◽  
Resource Utilization ◽  
Scientific Basis ◽  
Diffusion Reaction ◽  
Leaching Kinetics ◽  
Leaching Rate ◽  
Chromium Slag ◽  
Leaching Solution ◽  
Main Components ◽  
Kinetics Of

To provide a scientific basis for the resource utilization of chromium slag, this article studies the release law of hexavalent chromium in the aged calcium-free chromium slag. XRD (X-ray diffractometer) and MLA (Mineral Liberation Analyzer) were used to analyze the composition of the chromium slag; using sulfuric acid-nitric acid as the leaching solution, the release law of hexavalent chromium in chromium slag and the leaching kinetics were studied. The results show that main components of the chromium slag are magnesioferrite, chromite, hematite, hydrargillite, and spinel; chromium is mainly present in chromite and magnesioferrite; the leaching rate of hexavalent chromium increases with the increase of temperature or the decrease of pH. The analysis of leaching kinetics shows the leaching rate is controlled by the internal diffusion reaction, and the apparent activation energy is 11.93 kJ·mol–1. The chromium slag is aged in high temperature seasons, which is conducive to the precipitation of hexavalent chromium in the chromium slag, can increase the yield of chromate in the roasting kiln, and is conducive to resource utilization; chromium slag should be stored in order to prevent acid rain erosion which leads to environmental pollution risk (e.g. drinking water).

scholarly journals Fluoride Leaching of Titanium from Ti-Bearing Electric Furnace Slag in [NH4+]-[F−] Solution

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1176
Author(s):  
Fuqiang Zheng ◽  
Yufeng Guo ◽  
Feng Chen ◽  
Shuai Wang ◽  
Jinlai Zhang ◽  
...  
Keyword(s):  
Activation Energy ◽  
Electric Furnace ◽  
Kinetic Equations ◽  
Surface Chemical ◽  
Leaching Rate ◽  
Surface Chemical Reaction ◽  
Mechanism And Kinetics ◽  
Semi Empirical ◽  
Kinetics Of ◽  
Furnace Slag

The effects of F− concentration, leaching temperature, and time on the Ti leaching from Ti-bearing electric furnace slag (TEFS) by [NH4+]-[F−] solution leaching process was investigated to reveal the leaching mechanism and kinetics of titanium. The results indicated that the Ti leaching rate obviously increased with the increase of leaching temperature and F− concentration. The kinetic equation of Ti leaching was obtained, and the activation energy was 52.30 kJ/mol. The fitting results of kinetic equations and calculated values of activation energy both indicated that the leaching rate of TEFS was controlled by surface chemical reaction. The semi-empirical kinetics equation was consistent with the real experimental results, with a correlation coefficient (R2) of 0.996. The Ti leaching rate reached 92.83% after leaching at 90 °C for 20 min with F− concentration of 14 mol/L and [NH4+]/[F−] ratio of 0.4. The leaching rates of Si, Fe, V, Mn, and Cr were 94.03%, 7.24%, 5.36%, 4.54%, and 1.73%, respectively. The Ca, Mg, and Al elements were converted to (NH4)3AlF6 and CaMg2Al2F12 in the residue, which can transform into stable oxides and fluorides after pyro-hydrolyzing and calcinating.

An Alternative Approach to Analyzing the Interstitial Decay from the End of Range Damage During Millisecond Annealing

2008 ◽  
Vol 1070 ◽  
Author(s):  
Renata Camillo-Castillo ◽  
Mark E Law ◽  
Kevin S Jones
Keyword(s):  
Annealing Time ◽  
Dwell Time ◽  
Extended Defects ◽  
Temperature Dependent ◽  
Temperature Regimes ◽  
Alternative Approach ◽  
Small Times ◽  
Conventional Annealing ◽  
Kinetics Of ◽  
Anneal Temperature

ABSTRACTFlash-assist Rapid Thermal Processing (RTP) presents an opportunity to investigate annealing time and temperature regimes which were previously not accessible with conventional annealing techniques such as Rapid Thermal Annealing. This provides a unique opportunity to explore the early stages of the End of Range (EOR) damage evolution and also to examine how the damage evolves during the high temperature portion of the temperature profile. However, the nature of the Flash-assist RTP makes it is extremely difficult to reasonably compare it to alternative annealing techniques, largely because the annealing time at a given temperature is dictated by the FWHM of the radiation pulse. The FWHM for current flash tools vary between 0.85 and 1.38 milliseconds, which is three orders of magnitude smaller to that required for a RTA to achieve similar temperatures. Traditionally, the kinetics of the extended defects has been studied by time dependent studies utilizing isothermal anneals; in which specific defect structures could be isolated. The characteristics of Flash-assist RTP do not allow for such investigations in which the EOR defect evolution could be closely tracked with time. Since the annealing time at the target temperature for the Flash-assist RTP is essentially fixed to very small times on the order of milliseconds, isochronal anneals are a logical experimental approach to temperature dependent studies. This fact presents a challenge in the data analysis and comparison. Another feature of Flash-assist RTP which makes the analysis complex is the ramp time relative to the dwell time spent at the peak fRTP temperature. As the flash anneal temperature is increased the total ramp time can exceed the dwell time at the peak temperature, which may play a significantly larger role in dictating the final material properties. The inherent characteristics of Flash-assist RTP have consequently required the development of another approach to analyzing the attainable experimental data, such that a meaningful comparison could be made to past studies. The adopted analysis entails the selection of a reference anneal, from which the decay in the trapped interstitial density can be tracked with the flash anneal temperature, allowing for the kinetics of the interstitial decay to be extracted.

scholarly journals Temperature Dependence of the Folding and Unfolding Kinetics of the GCN4 Leucine Zipper via 13Cα-NMR

2001 ◽  
Vol 80 (2) ◽  
pp. 939-951 ◽  
Author(s):  
Marilyn Emerson Holtzer ◽  
G. Larry Bretthorst ◽  
D. André d’Avignon ◽  
Ruth Hogue Angeletti ◽  
Lisa Mints ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Leucine Zipper ◽  
Unfolding Kinetics ◽  
Kinetics Of

scholarly journals Study on indium leaching from mechanically activated hard zinc residue

2011 ◽  
Vol 47 (1) ◽  
pp. 63-72 ◽  
Author(s):  
J.H. Yao ◽  
X.H. Li ◽  
Y.W. Li
Keyword(s):  
Activation Energy ◽  
Particle Size ◽  
Planetary Mill ◽  
Leaching Rate ◽  
Obvious Effect ◽  
Diffusion Controlled ◽  
Leaching Reaction ◽  
Kinetics Of ◽  
Positive Effect ◽  
Solution Kinetics

In this study, changes in physicochemical properties and leachability of indium from mechanically activated hard zinc residue by planetary mill were investigated. The results showed that mechanical activation increased specific surface area, reaction activity of hard zinc residue, and decreased its particle size, which had a positive effect on indium extraction from hard zinc residue in hydrochloric acid solution. Kinetics of indium leaching from unmilled and activated hard zinc residue were also investigated, respectively. It was found that temperature had an obvious effect on indium leaching rate. Two different kinetic models corresponding to reactions which are diffusion controlled, [1-(1- x)1/3]2=kt and (1-2x/3)-(1-x)2/3=kt were used to describe the kinetics of indium leaching from unmilled sample and activated sample, respectively. Their activation energies were determined to be 17.89 kJ/mol (umilled) and 11.65 kJ/mol (activated) within the temperature range of 30?C to 90?C, which is characteristic for a diffusion controlled process. The values of activation energy demonstrated that the leaching reaction of indium became less sensitive to temperature after hard zinc residue mechanically activated by planetary mill.

scholarly journals Leaching of Silver Contained in Mining Wastes Using the Thiosemicarbazide – Oxygen System

2018 ◽  
Author(s):  
Eleazar-Rodríguez Salinas ◽  
Juan Hernández-Ávila ◽  
Ma. Isabel Reyes-Valderrama ◽  
Eduardo Cerecedo-Sáenz ◽  
Demetrio Mendoza-Anaya ◽  
...  
Keyword(s):  
Partial Pressure ◽  
Effect Of Temperature ◽  
Mining Wastes ◽  
Leaching Rate ◽  
Partial Pressure Of Oxygen ◽  
Silver Recovery ◽  
Oxygen System ◽  
Stirring Rate ◽  
Kinetics Of ◽  
Representative Samples

The mining wastes generated during the last decades in the mining region of Pachuca-Real del Monte in Mexico, still contains silver values of interest. For this reason, the present work is a preliminary study of the leaching kinetics of silver contained in these residues, using as a leaching reagent the thiosemicarbazide-oxygen system, with the aim of proposing this leaching system as a less toxic alternative than cyaniding process. Previous the leaching process, representative samples were wholly characterized, finding 56 g of Ag and 0.6 g of Au per ton. For the kinetic study in the mentioned system, were evaluated the reagent concentration, temperature, partial pressure of oxygen, pH and stirring rate. According the experimental results found, it was observed that [CH5N3S] concentration showed a significant effect on the leaching rate, obtaining a reaction order of n = 0.93, in the range of 20 - 40 mol CH5N3S ⋅ m-3, getting so a silver recovery up to 76.9%. The effect of temperature gave an activation energy of Ea = 45.55 KJ mol-1, which was indicative of a chemical reaction control. Finally, partial pressure of oxygen has a notable effect on leaching rate, but pH and stirring rate have not apparent effect.

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