scholarly journals Oxidation of pyrite (FeS2) and troilite (FeS) impurities in kaolinitic clays after calcination

2021 ◽  
Vol 55 (1) ◽  
Author(s):  
Franco Zunino ◽  
Karen Scrivener
Keyword(s):  
Quality Control ◽  
Iron Sulfide ◽  
Negative Influence ◽  
Alkaline Media ◽  
Iron Sulfides ◽  
Clay Particles ◽  
Blended Cements ◽  
Complete Decomposition ◽  
Adequate Quality ◽  
The Stability

AbstractValorisation of locally available clays for producing blended cements is crucial for a widespread adoption of sustainable binders incorporating these materials. In some places, clays can be intermixed with small amounts of iron sulfides, which could eventually expand in the alkaline media of concrete and lead to cracking if clay particles are sufficiently fine. This study explored the stability of iron sulfides, namely troilite and pyrite, during calcination of clays and their influence in reactivity. It was found that both troilite and pyrite decompose and oxidize into hematite under typical calcination conditions for clays. Furthermore, there is no negative influence of the presence of iron sulfide phases on the reactivity of calcined clays. This shows that these clays are suitable for use in blended cements, provided that adequate quality control is conducted to ensure a complete decomposition of the iron sulfide phases.

scholarly journals Fe5S2 identified as a host for sulfur in Earth’s core

2021 ◽  
Author(s):  
Claire Zurkowski ◽  
Barbara Lavina ◽  
Abigail Case ◽  
Kellie Swadba ◽  
Stella Chariton ◽  
...  
Keyword(s):  
Iron Sulfide ◽  
Inner Core ◽  
Outer Core ◽  
Iron Sulfides ◽  
Earth’S Core ◽  
Earth's Core ◽  
Planetary Cores ◽  
Wide Range ◽  
Metal Metal ◽  
The Stability

Planetary habitability, as we experience on Earth, is linked to a functioning geodynamo which is in part driven by the crystallization of the liquid iron-nickel-alloy core as a planet cools over time. Cosmochemical considerations suggest that sulfur is a candidate light alloying element in rocky planetary cores of varying sizes and oxidation states; such that, iron sulfide phase relations at extreme conditions contribute to outer core thermochemical convection and inner core crystallization in a wide range of planetary bodies. Here we experimentally investigate the structural properties of the Fe-S system and report the discovery of the sulfide, Fe5S2, crystallizing in equilibrium with iron at Earth’s outer core pressures and high temperatures. Using single-crystal X-ray diffraction techniques, Fe5S2 was determined to adopt the complex Ni5As2-type structure (P63cm, Z = 6). These results conclude that Fe5S2 is likely to crystallize at the interface of Earth’s core and mantle and will begin to crystallize during the freezing out of Earth and Venus’ core overtime. The increased metal-metal bonding measured in Fe5S2 compared to the other high P-T iron sulfides may contribute to signatures of higher conductivity from regions of Fe5S2 is crystallization. Fe5S2 could serve as a host for Ni and Si as has been observed in the related meteoritic phase, perryite, (Fe, Ni)8(P, Si)3, adding intricacies to elemental partitioning during inner core crystallization. The stability of Fe5S2 presented here is key to understanding the role of sulfur in the multicomponent crystallization sequences that drive the geodynamics and dictate the structures of Earth and rocky planetary cores.

scholarly journals Superior FexN electrocatalyst derived from 1,1′-diacetylferrocene for oxygen reduction reaction in alkaline and acidic media

2020 ◽  
Vol 9 (1) ◽  
pp. 843-852
Author(s):  
Hunan Jiang ◽  
Jinyang Li ◽  
Mengni Liang ◽  
Hanpeng Deng ◽  
Zuowan Zhou
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Current Density ◽  
Active Sites ◽  
Reduction Reaction ◽  
Alkaline Media ◽  
Acidic Media ◽  
Onset Potential ◽  
Acidic And Alkaline Media ◽  
The Stability

AbstractAlthough Fe–N/C catalysts have received increasing attention in recent years for oxygen reduction reaction (ORR), it is still challenging to precisely control the active sites during the preparation. Herein, we report FexN@RGO catalysts with the size of 2–6 nm derived from the pyrolysis of graphene oxide and 1,1′-diacetylferrocene as C and Fe precursors under the NH3/Ar atmosphere as N source. The 1,1′-diacetylferrocene transforms to Fe3O4 at 600°C and transforms to Fe3N and Fe2N at 700°C and 800°C, respectively. The as-prepared FexN@RGO catalysts exhibited superior electrocatalytic activities in acidic and alkaline media compared with the commercial 10% Pt/C, in terms of electrochemical surface area, onset potential, half-wave potential, number of electrons transferred, kinetic current density, and exchange current density. In addition, the stability of FGN-8 also outperformed commercial 10% Pt/C after 10000 cycles, which demonstrates the as-prepared FexN@RGO as durable and active ORR catalysts in acidic media.

Quality assurance and quality control to ensure durability

2021 ◽  
Author(s):  
B. C. Roy ◽  
Tanmoy Guha ◽  
R. Ekambaram
Keyword(s):  
Quality Control ◽  
Quality Assurance ◽  
Service Life ◽  
Performance Standards ◽  
Full Compliance ◽  
Design Build ◽  
Adequate Quality ◽  
Structural Failures ◽  
High Level ◽  
Fundamental Requirement

<p>High level of quality during design, design-build and construction stages is a fundamental requirement to ensure that structure serves its intended purpose. Establishment of a quality assurance manual is prime necessity. Lack of quality control during design, review and approving design drawings are major reasons for structural failures. Designers and design checkers need to work in tandem to ensure more adequate Quality Assurance &amp; Control (QA/QC).</p><p>In structural design Durability is a key parameter and becomes critical for service life of 100/120 years. In design build and construction stages controlling work quality is important to maintain performance standards. Tailor made quality plan for Design-build Contract is essential. Quality procedures, inspection and testing needs implementation in practice to verify full compliance and prevent occurrence of faults and defects towards durability and service life. This paper deals with Quality with special emphasis on durability in design and construction through case studies of design build contracts.</p>

A New, Rapid and Simple RP-HPLC Method for Stability Quantification of a Protease Inhibitor in Tablets

2021 ◽  
Author(s):  
Rochele Cassanta Rossi ◽  
Josué Guilherme Lisbôa Moura ◽  
Vanessa Mossmann ◽  
Patrícia Weimer ◽  
Pedro Eduardo Fröehlich
Keyword(s):  
Quality Control ◽  
Protease Inhibitor ◽  
Degradation Products ◽  
Gradient Elution ◽  
Hplc Method ◽  
Array Detector ◽  
Forced Degradation ◽  
Control Analysis ◽  
Quality Control Laboratory ◽  
The Stability

Abstract Fosamprenavir calcium is a protease inhibitor widely used in the treatment and prevention of human immunodeficiency virus and acquired immunodeficiency syndrome. This protease inhibitor serves as a prodrug of amprenavir, offering better oral bioavailability. Although this drug was approved by the FDA in 2003, there are few methods established for quantifying the stability for quality control analysis of fosamprenavir-coated tablets. The purpose of the study was to develop and validate a method for determining the stability of fosamprenavir-coated tablets (Telzir®) that may be applied by any quality control laboratory. Chromatographic separation was performed using a Vertical RP-18 column programmed to run a gradient elution with sodium acetate buffer and acetonitrile. Flow rate was 1.2 mL min−1 for a total run time of 15 min. Ultraviolet detection was set at 264 nm and the use of a photodiode array detector in scan mode allowed selectivity confirmation by peak purity evaluation. The analyte peak was found to be adequately separated from degradation products generated during forced degradation studies. Thus, the proposed method was found to accurately indicate stability and was sufficient for routine quantitative analysis of fosamprenavir in coated tablets without interference from major degradation products and excipients.

scholarly journals A glycine-specific N-degron pathway mediates the quality control of protein N-myristoylation

Science ◽  
2019 ◽  
Vol 365 (6448) ◽  
pp. eaaw4912 ◽  
Author(s):  
Richard T. Timms ◽  
Zhiqian Zhang ◽  
David Y. Rhee ◽  
J. Wade Harper ◽  
Itay Koren ◽  
...  
Keyword(s):  
Quality Control ◽  
Protein Stability ◽  
Protein Degradation ◽  
E3 Ligase ◽  
Cleavage Sites ◽  
Caspase Cleavage ◽  
E3 Ligases ◽  
Ring E3 Ligase ◽  
The Stability ◽  
Ring E3

The N-terminal residue influences protein stability through N-degron pathways. We used stability profiling of the human N-terminome to uncover multiple additional features of N-degron pathways. In addition to uncovering extended specificities of UBR E3 ligases, we characterized two related Cullin-RING E3 ligase complexes, Cul2ZYG11B and Cul2ZER1, that act redundantly to target N-terminal glycine. N-terminal glycine degrons are depleted at native N-termini but strongly enriched at caspase cleavage sites, suggesting roles for the substrate adaptors ZYG11B and ZER1 in protein degradation during apoptosis. Furthermore, ZYG11B and ZER1 were found to participate in the quality control of N-myristoylated proteins, in which N-terminal glycine degrons are conditionally exposed after a failure of N-myristoylation. Thus, an additional N-degron pathway specific for glycine regulates the stability of metazoan proteomes.

Adsorption of Tetrathiomolybdate to Iron Sulfides and Its Impact on Iron Sulfide Transformations

2020 ◽  
Vol 4 (12) ◽  
pp. 2246-2260
Author(s):  
Nathan Miller ◽  
Maura Dougherty ◽  
Ruochen Du ◽  
Tyler Sauers ◽  
Candice Yan ◽  
...  
Keyword(s):  
Iron Sulfide ◽  
Iron Sulfides

scholarly journals Stability and Degradation Mechanismof Si-based Photocathodes for Water Splitting with Ultrathin TiO2 Protection Layer

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
Emanuel Ronge ◽  
Thorsten Cottre ◽  
Katharina Welter ◽  
Vladimir Smirnov ◽  
Natalie Jacqueline Ottinger ◽  
...  
Keyword(s):  
Water Splitting ◽  
Atomic Layer ◽  
Degradation Process ◽  
Alkaline Media ◽  
Semiconductor Surface ◽  
Nucleation Sites ◽  
Enhanced Solubility ◽  
High Structural Perfection ◽  
Protection Layer ◽  
The Stability

Abstract Using transmission and scanning electron microscopy, we study mechanisms which determine the stability of Silicon photocathodes for solar driven water splitting. Such tandem or triple devices can show a promising stability as photocathodes if the semiconductor surface is protected by an ultrathin TiO2 protection layer. Using atomic layer deposition (ALD) with Cl-precursors, 4–7 nm thick TiO2 layers can be grown with high structural perfection. The layer can be electrochemically covered by Pt nanoparticels serving as electro-catalysts. However, Cl-remnants which are typically present in such layers due to incomplete oxidation, are the origin of an electrochemical degradation process. After 1 h AM1.5G illumination in alkaline media, circular shaped corrosion craters appear in the topmost Si layer, although the TiO2 layer is intact in most parts of the crater. The crater development is stopped at local inhomogenities with a higher Pt coverage. The observations suggests that reduced Titanium species due to Cl−/O2− substitution are nucleation sites of the initial corrosion steps due to enhanced solubility of reduced Ti in the electrolyte. This process is followed by electrochemical dissolution of Si, after direct contact between the electrolyte and the top Si layer surface. To increase the stability of TiO2 protected photocathodes, formation of reduced Ti species must be avoided.

A theoretical study of adsorption on iron sulfides towards nanoparticle modeling

2020 ◽  
Vol 22 (40) ◽  
pp. 23258-23267
Author(s):  
Miroslav Kolos ◽  
Daniel Tunega ◽  
František Karlický
Keyword(s):  
Iron Sulfide ◽  
Theoretical Study ◽  
Sulfide Minerals ◽  
Adsorption Properties ◽  
Zero Valent Iron ◽  
Polar Molecules ◽  
Iron Sulfides ◽  
Iron Sulfide Minerals

The adsorption properties of two iron sulfide minerals (mackinawite and pyrite) and zero-valent iron with respect to two small polar molecules (H2O and H2S) and trichloroethylene (TCE) were modeled.

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