The impact of pyrite variability, dispersive transport and precipitation of secondary phases on the sulphate release due to pyrite weathering

2008 ◽  
Vol 23 (12) ◽  
pp. 3783-3798 ◽  
Author(s):  
Claus Kohfahl ◽  
Paul L. Brown ◽  
Claire M. Linklater ◽  
Kai Mazur ◽  
Parviz Irannejad ◽  
...  
Keyword(s):  
Secondary Phases ◽  
Dispersive Transport ◽  
Pyrite Weathering ◽  
The Impact

Chemical Transport Facilitated by Multiphase Flow Systems1

1985 ◽  
Vol 17 (9) ◽  
pp. 1-12 ◽  
Author(s):  
Carl G. Enfield
Keyword(s):  
Organic Carbon ◽  
Boundary Conditions ◽  
Transport Equation ◽  
Fluid Phase ◽  
Chemical Transport ◽  
Facilitated Transport ◽  
Organic Fraction ◽  
Dispersive Transport ◽  
Transformation Of Variables ◽  
The Impact

Relatively immobile chemicals have been observed moving significantly faster than anticipated from hydrophobic theory. A theory is developed considering transport in three mobile fluid phases which can be used to describe this facilitated transport. The convective dispersive transport equation is solved utilizing a transformation of variables which permits utilizing existing solutions covering a wide variety of boundary conditions. The impact of the facilitated transport is demonstrated for one case where the soils organic carbon is 10%. If 2% of the fluid phase is an organic fraction, the theory developed projects that hydrophobic theory may underestimate mobility by more than 100 times. At concentrations of dissolved organic carbon normally observed in nature (5 - 10 mg/l), a measurable increased mobility is anticipated for the very immobile compounds like dioxins.

The Effect of Aging Heat Treatment on the Microstructure and Mechanical Properties of 10Cr20Ni25Mo1.5NbN Austenitic Steel

2016 ◽  
Vol 35 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Zhiyuan Liang ◽  
Wanhua Sha ◽  
Qinxin Zhao ◽  
Chongbin Wang ◽  
Jianyong Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Heat Treatment ◽  
Austenitic Steel ◽  
Treatment Time ◽  
Aging Treatment ◽  
Secondary Phases ◽  
Aging Heat Treatment ◽  
Microstructure And Mechanical Properties ◽  
The Impact

AbstractThe effect of aging heat treatment on the microstructure and mechanical properties of 10Cr20Ni25Mo1.5NbN austenitic steel was investigated in this article. The microstructure was characterized by scanning electron microscopy, energy dispersive spectrometry and transmission electron microscopy. Results show that the microstructure of 10Cr20Ni25Mo1.5NbN austenitic is composed of austenite. This steel was strengthened by precipitates of secondary phases that were mainly M23C6 carbides and NbCrN nitrides. As aging treatment time increased, the tensile strength first rose (0–3,000 h) and then fell (3,000–5,000 h) due to the decrease of high density of dislocations. The impact absorbed energy decreased sharply, causing the sulfides to precipitate at the grain boundary. Therefore, the content of sulfur should be strictly controlled in the steelmaking process.

scholarly journals A New Approach to the Study of Multi-Pass Welds–Microstructure and Properties of Welded 20-mm-Thick Superduplex Stainless Steel

2019 ◽  
Vol 9 (6) ◽  
pp. 1050 ◽  
Author(s):  
Maria Valiente Bermejo ◽  
Kjell Hurtig ◽  
Daniel Eyzop ◽  
Leif Karlsson
Keyword(s):  
Stainless Steel ◽  
Arc Welding ◽  
Gas Metal Arc Welding ◽  
Secondary Phases ◽  
Σ Phase ◽  
Flux Cored Arc Welding ◽  
Welding Sequence ◽  
Superduplex Stainless Steel ◽  
Secondary Austenite ◽  
The Impact

Type 2507 superduplex stainless steel 20 mm in thickness was multi-pass-welded with Gas Metal Arc Welding (GMAW) and Flux-Cored Arc Welding (FCAW) processes. Recommended and higher arc energies and inter-pass temperatures were used. Thermal cycles were monitored using a recently developed procedure involving the successive instrumentation of the multi-pass welds, pass by pass, by addition of thermocouples in each weld pass. The repeatability of temperature measurements and survival rate of more than 90% of thermocouples confirmed the reliability of the procedure. Reheating by subsequent passes caused a progressive increase in the austenite content of the weld metal. The as-deposited GMAW passes with higher-than-recommended arc energy showed the lowest presence of nitrides. Therefore, the cooling rate—and not the time exposed at the critical temperature range—seems to be the key factor for nitride formation. The welding sequence layout also plays an important role in the distribution of secondary phases. A larger amount and concentration of secondary austenite and σ-phase was found for a larger number of subsequent passes in the immediate vicinity of a specific weld pass. The impact toughness exceeded requirements for all welds. Differences in absorbed energies were related to the amount of micro-inclusions found with the FCAW weld showing the lowest absorbed energies and highest amount of micro-inclusions. Pitting corrosion preferentially initiated in locations with secondary austenite and σ-phase. However, in the absence of these secondary phases, the HAZ containing nitrides was the weakest location where pitting initiated. The results of this work have implications on practical welding for superduplex stainless steels: the current recommendations on maximum arc energy should be revised for large thickness weldments, and the importance of the welding sequence layout on the formation of secondary phases should be considered.

Influence of heat input and solubilizing heat treatment on the impact properties of SAW joints in SAF 2205 duplex steel

2012 ◽  
Vol 1381 ◽  
Author(s):  
M. Merlin ◽  
R. Vazquez-Aguilar ◽  
C. Soffritti ◽  
A. Reyes-Valdes
Keyword(s):  
Heat Treatment ◽  
Heat Input ◽  
Welding Process ◽  
Optical Microscope ◽  
Image Analyzer ◽  
Secondary Phases ◽  
Impact Properties ◽  
Steel Joints ◽  
Saf 2205 ◽  
The Impact

ABSTRACTIn this study the influence of heat input (HI) and heat treatment on submerged arc welded duplex SAF 2205 steel joints has been evaluated. In particular, multi-pass welding operations have been performed on 18 mm thick plates using four different heat inputs; a post-weld solubilizing heat treatment has been carried out in order to reduce the microstructural effects on the structure of the heat affected zone (HAZ). Instrumented impact strength tests have been performed on Charpy samples machined from the welded joints; the total absorbed energy and the two complementary contributions of initiation and propagation energies have been evaluated and correlated to the percentages of ferrite and austenite. The microstructures and the fracture profiles have been observed using an optical microscope (OM) and quantitatively analyzed by means of an image analyzer. A scanning electron microscope (SEM) equipped by energy dispersive X-ray spectroscopy (EDS) has been used to study the fractured surfaces. Hardness profiles have been performed across the joints in order to verify the hardness variations. A total absence of secondary phases has been found on the joints due to the performing of a suitable solubilizing heat treatment after the welding process. The results have shown that the impact properties of the samples have been mostly affected by the different heat inputs; in some cases a partial welding penetration has been found.

Property engineering in BaTiO3 films by stoichiometry control

2010 ◽  
Vol 25 (6) ◽  
pp. 1064-1071 ◽  
Author(s):  
J.F. Ihlefeld ◽  
P.R. Daniels ◽  
S.M. Aygün ◽  
W.J. Borland ◽  
J-P. Maria
Keyword(s):  
Thin Films ◽  
Grain Growth ◽  
High Resolution Electron Microscopy ◽  
Phase Assemblage ◽  
Secondary Phases ◽  
High Temperature Anneal ◽  
Resolution Electron ◽  
Electron Microscopy Analysis ◽  
Budget Systems ◽  
The Impact

BaTiO3 thin films were prepared on metallic foil substrates using chemical solution deposition. The impact of A to B site cation ratios on the phase assemblage and microstructural and dielectric properties was investigated by characterizing a sample set that includes stoichiometric BaTiO3 and 1, 2, 3, 4, and 5 mol% excess BaO. Each composition was subjected to a high-temperature anneal step with maximum dwell temperatures of 1000, 1100, and 1200 °C for 20 h. Excess barium concentrations greater than 3% lead to dramatic grain growth and average grain sizes exceeding 1 μm. Despite the large deviations from stoichiometry and the 20 h dwell time at temperature, x-ray diffraction, and high-resolution electron microscopy analysis were unable to detect secondary phases until films with 5% excess barium were annealed to 1200 °C. Thin films with 3% excess barium were prepared on copper substrates and annealed at 1060 °C, the practical limit for copper. This combination of BaO excess and annealing temperature produced an average lateral grain size of 0.8 μm and a room-temperature permittivity of 4000. This is in comparison to a permittivity of 1800 for stoichiometric material prepared using identical conditions. This work suggests metastable solubility of BaO in BaTiO3 that leads to enhanced grain growth and large permittivity values. This technique provides a new solid-state means of achieving grain growth in low thermal budget systems.

scholarly journals Improving Ultraviolet Responses in Cu2ZnSn(S,Se)4 Thin-Film Solar Cells Using Quantum Dot-Based Luminescent Down-Shifting Layer

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1166
Author(s):  
Woo-Lim Jeong ◽  
Junsung Jang ◽  
Jihun Kim ◽  
Soo-Kyung Joo ◽  
Mun-Do Park ◽  
...  
Keyword(s):  
Solar Cells ◽  
Quantum Dot ◽  
Wavelength Conversion ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Secondary Phases ◽  
X Ray Diffraction ◽  
Solar Cell Performance ◽  
The Impact ◽  
First Time

Quantum dot (QD)-based luminescent down-shifting (LDS) layers were deposited on Cu2ZnSn(S,Se)4 (CZTSSe) solar cells via the drop-casting method. The LDS layers can easily widen the narrow absorption wavelength regions of single-junction solar cells and enable improvement of the short-circuit current. The optical properties of LDS layers deposited on glass and containing different QD contents were analyzed based on their transmittance, reflectance, and absorbance. The absorber films to be used in the CZTSSe solar cells were determined by X-ray diffraction measurements and Raman spectroscopy to determine their crystal structures and secondary phases, respectively. The completed CZTSSe solar cells with LDS layers showed increased ultraviolet responses of up to 25% because of wavelength conversion by the QDs. In addition, the impact of the capping layer, which was formed to protect the QDs from oxygen and moisture, on the solar cell performance was analyzed. Thus, a maximal conversion efficiency of 7.3% was achieved with the 1.0 mL QD condition; furthermore, to the best of our knowledge, this is the first time that LDS layers have been experimentally demonstrated for CZTSSe solar cells.

The Impact of Increased Waste Loading on Vitrified HLW Quality and Durability

2009 ◽  
Vol 1193 ◽  
Author(s):  
Nick R Gribble ◽  
Rick Short ◽  
Edward Turner ◽  
Andrew D Riley
Keyword(s):  
Spent Nuclear Fuel ◽  
Liquid Waste ◽  
Operating Conditions ◽  
Incorporation Rate ◽  
Secondary Phases ◽  
Highly Active ◽  
Processing Line ◽  
Operational Envelope ◽  
The Uk ◽  
The Impact

AbstractThe Sellafield Waste Vitrification Plant (WVP) immobilises highly active liquid waste (HAL) arising from the reprocessing of spent nuclear fuel in the UK. In order to optimise WVP operations a full scale working replica of a WVP processing line, the Vitrification Test Rig (VTR), was constructed to processes non-active HAL simulants. Recently the VTR has been used to determine an operational envelope for the vitrification of HAL from Magnox reprocessing at a waste oxide incorporation rate in glass of up to 35wt% (compared to a “standard” incorporation rate of 25wt%). This paper discusses the differences in operating conditions necessary to achieve acceptable waste throughput at the increased incorporation rate. The chemical durability of the resulting vitrified product is also discussed, along with the formation of secondary phases, and a comparison is drawn between 35wt% incorporation glasses and products made at the standard 25wt% incorporation.

scholarly journals Reaction and Alteration of Mudstone with Ordinary Portland Cement and Low Alkali Cement Pore Fluids

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 588
Author(s):  
Keith Bateman ◽  
Yuki Amano ◽  
Mitsuru Kubota ◽  
Yuji Ohuchi ◽  
Yukio Tachi
Keyword(s):  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Mineral Dissolution ◽  
Initial Contact ◽  
Secondary Phases ◽  
Disturbed Zone ◽  
Flow Through ◽  
Alkaline Fluid ◽  
The Impact ◽  
Flow Experiments

The construction of a repository for the geological disposal of radioactive waste will utilize cement-based materials. Following closure, resaturation will result in the development of a highly alkaline porewater. The alkaline fluid will migrate and react with host rock, producing a chemically disturbed zone (CDZ) around the repository. To understand how these conditions may evolve, a series of batch and flow experiments were conducted with Horonobe mudstone and fluids representative of the alkaline leachates expected from a cementitious repository. Both ordinary Portland cement (OPC) and low alkali cement (LAC) leachates were examined. The impact of the LAC leachates was more limited than the OPC leachates, with experiments using the LAC leachate showing the least reaction and lowest long-term pH of the different leachate types. The reaction was dominated by primary mineral dissolution, and in the case of OPC leachates, precipitation of secondary calcium-silicate-hydrate (C-S-H) phases. Flow experiments revealed that precipitation of the secondary phases was restricted to close to the initial contact zone of the fluids and mudstone. The experimental results demonstrate that a combination of both batch and flow-through experiments can provide the insights required for the understanding of the key geochemical interactions and the impact of transport.

scholarly journals Mechanical Properties and Corrosion Characteristics of Thermally Aged Alloy 22

2002 ◽  
Author(s):  
Rau´l B. Rebak ◽  
Paul Crook
Keyword(s):  
Corrosion Resistance ◽  
Laboratory Data ◽  
Aged Alloy ◽  
Cubic Phase ◽  
Face Centered Cubic ◽  
Secondary Phases ◽  
Waste Container ◽  
Alloy 22 ◽  
High Level ◽  
The Impact

Alloy 22 (UNS N06022) is a candidate material for the external wall of the high-level nuclear waste containers for the potential repository site at Yucca Mountain. In the mill-annealed (MA) condition, Alloy 22 is a single face centered cubic phase. When exposed to temperatures on the order of 600°C and above for times higher than 1 h, this alloy may develop secondary phases that reduce its mechanical toughness and corrosion resistance. The objective of this work was to age Alloy 22 at temperatures between 482°C and 760°C for times between 0.25 h and 6,000 h and to study the mechanical and corrosion performance of the resulting material. Aging was carried out using wrought specimens as well as gas tungsten arc welded (GTAW) specimens. Mechanical and corrosion testing was carried out using ASTM standards. Results show that the higher the aging temperature and the longer the aging time, the lower the impact toughness of the aged material and the lower its corrosion resistance. However, extrapolating both mechanical and corrosion laboratory data predicts that Alloy 22 will remain corrosion resistant and mechanically robust tbr the projected lifetime of the waste container.

Sign in / Sign up

Export Citation Format

Share Document