Detailed Chemical Characterization of the PEMFC Materials Aging: Identification of the Mitigating Role of an Anodic CO Contamination on Cathode Degradation

2010 ◽  
Keyword(s):  
Chemical Characterization ◽  
Cathode Degradation ◽  
Detailed Chemical

Structural role of copper in the minerals of the pearceite-polybasite group: the case of the new minerals cupropearceite and cupropolybasite

2007 ◽  
Vol 71 (06) ◽  
pp. 641-650 ◽  
Author(s):  
L. Bindi ◽  
M. Evain ◽  
P. G. Spry ◽  
K. T. Tait ◽  
S. Menchetti
Keyword(s):  
Chemical Characterization ◽  
Sample Space ◽  
The Other ◽  
Crystal Chemical ◽  
Structural Position ◽  
Space Group ◽  
Cu Content ◽  
Own Name

Abstract The pearceite-polybasite group of minerals, general formula [M6T2S7][Ag9CuS4] with M = Ag, Cu; and T = As, Sb, show a crystal structure which can be described as the succession, along the c axis, of two pseudo-layer modules: a [M6T2S7]2– A module layer and a [Ag9CuS4]2+ B module layer. Copper is present in one structural position of the B module layer and replaces Ag in the only fully occupied M position of the A module layer. When the Cu content is >4.00 a.p.f.u., the structural position of the A module layer becomes Cu-dominant and, consequently, the mineral deserves its own name. In this paper we report the crystal-chemical characterization of two Cu-rich members exhibiting the 111 unitcell type (corresponding to the Tac polytype). One sample (space group (P )m1, a 7.3218(8), c 11.8877(13) Å, V 551.90(10) Å3, Z = 1) having As >Sb and with the structural position of the A module layer dominated by Cu, has been named cupropearceite and the other sample (space group (P3̄)m1, a 7.3277(3), c 11.7752(6) Å, V 547.56(8) Å3, Z = 1) having Sb >As has been named cupropolybasite. Both the new minerals and mineral names have been approved by the IMA-CNMNC.

The Role of Temperature on Hydration of Binary System of Metakaolin/Portland Cement

2016 ◽  
Vol 851 ◽  
pp. 51-56 ◽  
Author(s):  
Martin Boháč ◽  
Radoslav Novotný ◽  
Jakub Tkacz ◽  
Miroslava Hajdúchová ◽  
Martin Palou ◽  
...  
Keyword(s):  
Binary System ◽  
Portland Cement ◽  
Isothermal Calorimetry ◽  
Chemical Characterization ◽  
Exothermic Peak ◽  
Early Hydration ◽  
Different Temperatures ◽  
C 50

The role of temperature of metakaolin/Portland cement binary system was studied by isothermal calorimetry. Sample with 50 % of metakaolin replacement were monitored at 30 °C, 40 °C, 50 °C and 60 °C. Structural and chemical characterization of hardened pastes was obtained by scanning electron and Raman microscopy. Paper deals with kinetics of main exothermal reactions during early hydration of the system. Activation energies were calculated for processes related to each exothermic peak. The nature of hydration products at different temperatures was revealed by microstructural studies.

Histolocalization and physico-chemical characterization of dihydrochalcones: Insight into the role of apple major flavonoids

2013 ◽  
Vol 90 ◽  
pp. 78-89 ◽  
Author(s):  
Matthieu Gaucher ◽  
Thomas Dugé de Bernonville ◽  
David Lohou ◽  
Sylvain Guyot ◽  
Thomas Guillemette ◽  
...  
Keyword(s):  
Chemical Characterization ◽  
Physico Chemical ◽  
Insight Into

scholarly journals Synthesis and Characterization of Chitosan/Agar/SiO2 Nano Hydrogels For Removal of Amoxicillin and of Naproxen From Pharmaceutical Contaminants

2021 ◽  
Author(s):  
Omid Moradi ◽  
Samira Mhdavi ◽  
Sajjad Sedaghat
Keyword(s):  
Aqueous Media ◽  
Environmental Pollutants ◽  
Chemical Characterization ◽  
Solution Ph ◽  
Physical And Chemical Characterization ◽  
Pharmaceutical Contaminants ◽  
Living Organisms ◽  
Physical And Chemical

Abstract Today, environmental pollutants pose a threat to human societies and all living organisms, which is why they have attracted the attention of environmental researchers. In this study, in order to remove pharmaceutical contaminants Naproxen and Amoxicillin from aqueous media with SiO2 nanoparticles based on Agar and Chitosan was investigated. The study of structural properties, physical and chemical characterization of synthesized nanocomposite was investigated by FTIR, XRD, TEM, FE-SEM, DLS and EDX analyzes. In addition, the role of parameters affecting the removal of pharmaceutical contaminants such as solution pH, contact time, contaminant concentration and temperature were studied. Nanocomposites prepared from Agar and Chitosan showed good performance in absorbing naproxen and amoxicillin. According to the studies performed to remove naproxen, the max adsorption efficiency was obtained at a concentration of 20 mg/l with an absorbent dose of 0.05 g and a pH of 8 and at an optimum temperature of 25 °C and 99% in 15 min. Also, for amoxicillin with nanocomposite prepared with an initial concentration of 20 mg/l and an adsorbent dose of 0.05 g, a time of 10 min, a temperature of 25 °C and a pH of 8, the max removal efficiency of 91.15% was obtained.

scholarly journals Measurement report: Effects of photochemical aging on the formation and evolution of summertime secondary aerosol in Beijing

2020 ◽  
Author(s):  
Tianzeng Chen ◽  
Jun Liu ◽  
Qingxin Ma ◽  
Biwu Chu ◽  
Peng Zhang ◽  
...  
Keyword(s):  
Chemical Characterization ◽  
Exposure Dose ◽  
Time Resolved ◽  
Increase Rate ◽  
Key Factor ◽  
Formation And Evolution ◽  
Photochemical Aging ◽  
Observation Period

Abstract. Atmospheric submicron aerosols have a great effect on air quality and human health, while their formation and evolution processes are still not fully understood. Herein, the crucial role of atmospheric oxidation capacity, as characterized by OH exposure dose in the formation and evolution of secondary submicron aerosols, was systematically investigated based on a highly time-resolved chemical characterization of PM1 in a southern suburb of Beijing in summertime from 25th July to 21st August 2019. The averaged concentration of PM1 was 19.3 ± 11.3 μg m−3, and nearly half (48.3 %) of the mass was organic aerosols (OA) during the observation period. The equivalent photochemical age (ta) estimated from the ratios of toluene to benzene was applied to characterize the OH exposure dose of the air mass. The relationships of NR–PM1 species, OA factors (i.e., one hydrocarbon-like (HOA) and three oxygenated (LO-OOA, SV-OOA and MO-OOA) organic aerosol factors) and elemental compositions (e.g., H / C, O / C, N / C, S / C, OM / OC, and OSc) to ta were analyzed in detail. It was found that higher PM1 concentration accompanied longer ta, with an average increase rate of 0.8 μg m−3 per hour. Meanwhile, the formation of SO42− and MO-OOA were most sensitive to the increase in ta, and their contributions to PM1 were enhanced from 19 % to 27 % and from 27 % to 48 %, respectively, as ta increased from 9.4 h to 19.6 h. In addition, OSc and the ratios of O / C and OM / OC increased with the increase in ta. These results indicated that photochemical aging is a key factor leading to the evolution of OA and the increase of PM1 in summertime.

Detailed chemical characterization of the composition and variability of soil gas at remediated residential heating oil discharges

2021 ◽  
Vol 413 ◽  
pp. 125372
Author(s):  
Xin Lu ◽  
Ellen Weiner ◽  
Elizabeth Smiley ◽  
Mark Widdowson ◽  
Gabriel Isaacman-VanWertz
Keyword(s):  
Chemical Characterization ◽  
Soil Gas ◽  
Residential Heating ◽  
Heating Oil ◽  
Detailed Chemical

scholarly journals Measurement report: Effects of photochemical aging on the formation and evolution of summertime secondary aerosol in Beijing

2021 ◽  
Vol 21 (2) ◽  
pp. 1341-1356
Author(s):  
Tianzeng Chen ◽  
Jun Liu ◽  
Qingxin Ma ◽  
Biwu Chu ◽  
Peng Zhang ◽  
...  
Keyword(s):  
Chemical Characterization ◽  
Exposure Dose ◽  
Time Resolved ◽  
Increase Rate ◽  
Key Factor ◽  
Formation And Evolution ◽  
Photochemical Aging ◽  
Observation Period

Abstract. Atmospheric submicrometer aerosols have a great effect on air quality and human health, while their formation and evolution processes are still not fully understood. Herein, the crucial role of atmospheric oxidation capacity, as characterized by OH exposure dose in the formation and evolution of secondary submicrometer aerosols, was systematically investigated based on a highly time-resolved chemical characterization of PM1 in a southern suburb of Beijing in summertime from 25 July to 21 August 2019. The averaged concentration of PM1 was 19.3 ± 11.3 µg m−3, and nearly half (48.3 %) of the mass was organic aerosols (OAs) during the observation period. The equivalent photochemical age (ta) estimated from the ratios of toluene to benzene was applied to characterize the OH exposure dose of the air mass, in which an observation period with the similar sources and minimal influence of fresh emission was adopted. The relationships of non-refractory PM1 species, OA factors (i.e., one hydrocarbon-like and three oxygenated organic aerosol factors) and elemental compositions (e.g., H∕C, O∕C, N∕C, S∕C, OM∕OC, and OSc) to ta were analyzed in detail. It was found that higher PM1 concentration accompanied longer ta, with an average increase rate of 0.8 µgm-3h-1. Meanwhile, the formation of sulfate and more oxidized oxygenated OA were most sensitive to the increase in ta, and their contributions to PM1 were enhanced from 22 % to 28 % and from 29 % to 48 %, respectively, as ta increased. In addition, OSc and the ratios of O∕C and OM∕OC increased with the increase in ta. These results indicated that photochemical aging is a key factor leading to the evolution of OA and the increase in PM1 in summertime.

scholarly journals Direct morpho-chemical characterization of elusive plant residues from Aurignacian Pontic Steppe ground stones

2020 ◽  
Author(s):  
G. Birarda ◽  
C. Cagnato ◽  
I. Pantyukhina ◽  
C. Stani ◽  
N. Cefarin ◽  
...  
Keyword(s):  
Direct Evidence ◽  
Homo Sapiens ◽  
Chemical Characterization ◽  
Chemical Imaging ◽  
Plant Residues ◽  
Chemical Profiles ◽  
Harsh Conditions ◽  
Shed Light

AbstractDirect evidence for the intentional processing of starch-rich plants during the Paleolithic is scant, and that evidence is often compromised by concerns over preservation and contamination. Our integrated, multimodal approach couples wear-trace analysis with chemical imaging methods to identify the presence of genuine ancient starch candidates (ASC) on ground stones used in the Pontic Steppe starting around 40,000 years ago. Optical and electron microscopy coupled with infrared spectromicroscopy and imaging provide morphological and chemical profiles for ASCs, that partially match the vibrational polysaccharide features of modern reference starches, highlighting diagenetic differences ranging from partial oxidation to mineralization. The results suggest the intentional processing of roots and tubers by means of mechanical tenderization and shed light on the role of dietary carbohydrates during Homo sapiens’ (HS) colonization of Eurasia, demonstrating a long acquaintance with predictable calorific foods, crucial to maintain homeostasis during the harsh conditions of the Late MIS 3 (40-25 ky).

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