scholarly journals On the Impact of the Degree of Fluorination on the ORR Limiting Processes within Iron Based Catalysts: A Model Study on Symmetrical Films of Barium Ferrate

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2532
Author(s):  
Stephan Wollstadt ◽  
Oliver Clemens
Keyword(s):  
Variable Temperature ◽  
Fluorine Content ◽  
Bulk Diffusion ◽  
Decomposition Temperature ◽  
X Ray Diffraction ◽  
Impedance Model ◽  
Degradation Temperature ◽  
Model Study ◽  
The Stability ◽  
The Impact

In this study, symmetrical films of BaFeO2.67, BaFeO2.33F0.33 and BaFeO2F were synthesized and the oxygen uptake and conduction was investigated by high temperature impedance spectroscopy under an oxygen atmosphere. The data were analyzed on the basis of an impedance model designed for highly porous mixed ionic electronic conducting (MIEC) electrodes. Variable temperature X-ray diffraction experiments were utilized to estimate the stability window of the oxyfluoride compounds, which yielded a degradation temperature for BaFeO2.33F0.33 of 590 °C and a decomposition temperature for BaFeO2F of 710 °C. The impedance study revealed a significant change of the catalytic behavior in dependency of the fluorine content. BaFeO2.67 revealed a bulk-diffusion limited process, while BaFeO2.33F0.33 appeared to exhibit a fast bulk diffusion and a utilization region δ larger than the electrode thickness L (8 μm). In contrast, BaFeO2F showed very area specific resistances due to the lack of oxygen vacancies. The activation energy for the uptake and conduction process of oxygen was found to be 0.07/0.29 eV (temperature range-dependent), 0.33 eV and 0.67 eV for BaFeO2.67, BaFeO2.33F0.33 and BaFeO2F, respectively.

scholarly journals Synthesis and Characterization of N-Substituted Polyether-Block-Amide Copolymers

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 773
Author(s):  
Jyun-Yan Ye ◽  
Kuo-Fu Peng ◽  
Yu-Ning Zhang ◽  
Szu-Yuan Huang ◽  
Mong Liang
Keyword(s):  
Titanium Isopropoxide ◽  
Decomposition Temperature ◽  
Phenyl Isocyanate ◽  
Cross Linking ◽  
Resonance Spectroscopy ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Degradation Temperature ◽  
Melt Polycondensation ◽  
Structural Regularity

A series of N-substituted polyether-block-amide (PEBA-X%) copolymers were prepared by melt polycondensation of nylon-6 prepolymer and polytetramethylene ether glycol at an elevated temperature using titanium isopropoxide as a catalyst. The structure, thermal properties, and crystallinity of PEBA-X% were investigated using nuclear magnetic resonance spectroscopy, Fourier-transform infrared spectroscopy, differential scanning calorimetry, wide angle X-ray diffraction, and thermogravimetric analysis. In general, the crystallinity, melting point, and thermal degradation temperature of PEBA-X% decreased as the incorporation of N-methyl functionalized groups increased, owing to the disruption caused to the structural regularity of the copolymer. However, in N-acetyl functionalized analogues, the crystallinity first dropped and then increased because of a new γ form arrangement that developed in the microstructure. After the cross-linking reaction of the N-methyl-substituted derivative, which has electron-donating characteristics, with poly(4,4′-methylenebis(phenyl isocyanate), the decomposition temperature of the resulting polymer significantly increased, whereas no such improvements could be observed in the case of the electro-withdrawing N-acetyl-substituted derivative, because of the incompleteness of its cross-linking reaction.

scholarly journals Chemical, Mineralogical, and Refractory Characterization of Kaolin in the Regions of Huayacocotla-Alumbres, Mexico

2018 ◽  
Vol 2018 ◽  
pp. 1-11
Author(s):  
L. M. Romero-Guerrero ◽  
R. Moreno-Tovar ◽  
A. Arenas-Flores ◽  
Y. Marmolejo Santillán ◽  
F. Pérez-Moreno
Keyword(s):  
Thermogravimetric Analysis ◽  
Decomposition Temperature ◽  
X Ray Diffraction ◽  
Polarization Optical Microscopy ◽  
Plagioclase Feldspar ◽  
X Ray ◽  
Mullite Phase ◽  
Significant Difference ◽  
The Stability

In the present work, the chemical, mineralogical, refractory, and microstructural characterizations of kaolinites from the Huayacocotla-Alumbres region, which is between Veracruz and Hidalgo border, by X-ray diffraction (XRD), polarization optical microscopy (POM), scanning electron microscopy (SEM), refractoriness proof (pyrometric cone equivalent), and thermogravimetric analysis (TGA) were carried out. The analysis by POM showed that the kaolinization degree in this region is variable due to the presence of primary minerals, such as plagioclase, feldspar, and quartz. Additionally, hydrothermal alteration of the epithermal type was determined by oxidation of sulfides (pyrite and galena) and chlorite association. With the X-ray diffraction technique, andalusite and kaolinite were identified as the majority phases in Huayacocotla and quartz was identified as the majority phase in Alumbres. The minority phases, such as dickite, kaolinite, and cristobalite, were observed in both zones. The SEM technique was useful in the determination of the morphology of kaolinite and impurities of Na, Mg, K, and Fe of the complex clay illite-andalusite-dickite group. Thermogravimetric analysis was useful to discover the decomposition temperature and reveal the significant difference between 400 and 800°C, which showcases the greatest mass loss due to dehydration and carbonates decomposition. The mullite phase was detected at approximately 1000°C in the kaolin samples. The refractoriness tests were important to determine the stability temperature of kaolin, which is between 1300 and 1600°C. This stability temperature makes it feasible to use the kaolin as a refractory material for both low and high temperatures. The variables that affect the kaolin stability temperature were determined by principal components with the XLSTAT free program.

scholarly journals Impedance Aggregation Method of Multiple Wind Turbines and Accuracy Analysis

Energies ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 2035 ◽  
Author(s):  
Liang Chen ◽  
Heng Nian ◽  
Yunyang Xu
Keyword(s):  
Stability Analysis ◽  
Reference Frame ◽  
Wind Turbines ◽  
Power Distribution ◽  
Wind Farm ◽  
System Level ◽  
Small Signal ◽  
Impedance Model ◽  
The Stability ◽  
The Impact

The sequence domain impedance modeling of wind turbines (WTs) has been widely used in the stability analysis between WTs and weak grids with high line impedance. An aggregated impedance model of the wind farm is required in the system-level analysis. However, directly aggregating WT small-signal impedance models will lead to an inaccurate aggregated impedance model due to the mismatch of reference frame definitions among different WT subsystems, which may lead to inaccuracy in the stability analysis. In this paper, we analyze the impacts of the reference frame mismatch between a local small-signal impedance model and a global one on the accuracy of aggregated impedance and the accuracy of impedance-based stability analysis. The results revealed that the impact is related to the power distribution of the studied network. It was found that that the influence of mismatch on stability analysis became subtle when subsystems were balanced loaded. Considering that balanced loading is a common configuration of the practical application, direct impedance aggregation by local small-signal models can be applied due to its acceptable accuracy.

Thermal and Chemical Stability of Micron Aluminum Powders Subjected to Gaseous Water

2016 ◽  
Vol 712 ◽  
pp. 241-245
Author(s):  
Sergey V. Zmanovskiy ◽  
Alexander M. Gromov ◽  
Valentina V. Smirnova ◽  
Vadim F. Petrunin ◽  
Jin Chun Kim
Keyword(s):  
Room Temperature ◽  
Gravimetric Analysis ◽  
X Ray Diffraction ◽  
Aluminum Powders ◽  
X Ray ◽  
The Stability ◽  
Heating Up ◽  
The Impact ◽  
Thermal And Chemical Stability ◽  
Composition Of Products

The paper studies the impact of gaseous water on the stability of micron aluminum powders in time at room temperature using the method of gravimetric analysis. The stability was studied using methods of thermal analysis during heating up to 1200 °С in air. The composition of products was analyzed using X-ray diffraction analysis. It was found out that the stability of micron aluminum powders depends on partial pressure of water vapor: the increase of pressure results in decreased stability of powders. The work gives recommendations for storing micron aluminum powders.

Synthesis and characterization of the pentazolate anion cyclo-N5ˉ in (N5)6(H3O)3(NH4)4Cl

Science ◽  
2017 ◽  
Vol 355 (6323) ◽  
pp. 374-376 ◽  
Author(s):  
Chong Zhang ◽  
Chengguo Sun ◽  
Bingcheng Hu ◽  
Chuanming Yu ◽  
Ming Lu
Keyword(s):  
Thermal Analysis ◽  
Single Crystal ◽  
Diffraction Analysis ◽  
Decomposition Temperature ◽  
Synthesis And Characterization ◽  
X Ray Diffraction ◽  
X Ray ◽  
Onset Decomposition Temperature ◽  
The Stability

Pentazole (HN5), an unstable molecular ring comprising five nitrogen atoms, has been of great interest to researchers for the better part of a century. We report the synthesis and characterization of the pentazolate anion stabilized in a (N5)6(H3O)3(NH4)4Cl salt. The anion was generated by direct cleavage of the C–N bond in a multisubstituted arylpentazole using m-chloroperbenzoic acid and ferrous bisglycinate. The structure was confirmed by single-crystal x-ray diffraction analysis, which highlighted stabilization of the cyclo-N5ˉ ring by chloride, ammonium, and hydronium. Thermal analysis indicated the stability of the salt below 117°C on the basis of thermogravimetry-measured onset decomposition temperature.

Mechanical and Thermal Properties of Reactable Nano-SiO2/polyoxymethylene Composites

2012 ◽  
Vol 535-537 ◽  
pp. 103-109 ◽  
Author(s):  
Xiang Min Xu ◽  
Li Ping Guo ◽  
Yu Dong Zhang ◽  
Zhi Jun Zhang
Keyword(s):  
Thermal Properties ◽  
Impact Strength ◽  
Decomposition Temperature ◽  
Silica Content ◽  
Mechanical And Thermal Properties ◽  
Scanning Calorimetry ◽  
Degradation Temperature ◽  
Melt Compounding ◽  
Air Atmosphere ◽  
The Impact

The polyoxymethylene-based composites containing reactable nano-SiO2were prepared in a twin-screw extruder by melt compounding, and mechanical and thermal properties of pure polyoxymethylene (POM) and composites were investigated. The results showed that reactable nano-SiO2could reinforce the tensile strength and Young’s modulus of composites. To the impact strength of composites, there was obvious improvement when a small amount of silica was added into POM. With the increase of silica content, the impact strength of composites showed a gradually decrease trend. It was worthy to note that reactable nano-SiO2could significantly increase the decomposition temperature of POM. When the content of reactaSubscript textble nano-SiO2was up to 5 wt%, the degradation temperature of composites could increase about 38.3°C under nSubscript textitrogen atmosphere and 43.8°C under air atmosphere, respectively, compared with pure POM. Furthermore, the differential scanning calorimetry (DSC) analysis showed that reactable nano-SiO2had a good heterogeneous nucleation capability in POM, and could increase crystallization temperature of POM, but surface structure of reactable nano-SiO2was not propitious to the growth of POM crystals, accordingly leading to the decreasing crystallinity of composites.

scholarly journals Boosting the Stability of Boron Peroxides through Subphthalocyanine Coordination

2021 ◽  
Vol 03 (02) ◽  
pp. 141-145
Author(s):  
Jorge Labella ◽  
Elisa López-Serrano ◽  
Tomás Torres
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Lewis Base ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
The Stability ◽  
The Impact ◽  
Structural And Optoelectronic Properties

The great potential of subphthalocyanines (SubPcs) to stabilize boron peroxides has been demonstrated. In particular, a subphthalocyanato boron (III) peroxide has been prepared in good yield via boron triflate. This derivative is remarkably stable under ambient conditions and can be fully characterized. The impact of the peroxide group on the structural and optoelectronic properties of SubPc was examined by NMR and UV/Vis spectroscopies, as well as single-crystal X-ray diffraction analysis. Moreover, density functional theory calculations were performed to explain the experimental results. The reactivity of this peculiar boron peroxide as an oxidant and a Lewis base was also studied.

scholarly journals Formation of ZrC–SiC Composites from the Molecular Scale through the Synthesis of Multielement Polymers

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3901
Author(s):  
Fabien Bouzat ◽  
Romain Lucas ◽  
Yann Leconte ◽  
Sylvie Foucaud ◽  
Yves Champavier ◽  
...  
Keyword(s):  
Ceramic Composites ◽  
Inorganic Materials ◽  
Oxide Ceramic ◽  
X Ray Diffraction ◽  
Preceramic Polymers ◽  
Fragmentation Mechanisms ◽  
Sic Composites ◽  
The Stability ◽  
The Impact ◽  
Polymeric Structures

In the field of non-oxide ceramic composites, and by using the polymer-derived ceramic route, understanding the relationship between the thermal behaviour of the preceramic polymers and their structure, leading to the mechanisms involved, is crucial. To investigate the role of Zr on the fabrication of ZrC–SiC composites, linear or hyperbranched polycarbosilanes and polyzirconocarbosilanes were synthesised through either “click-chemistry” or hydrosilylation reactions. Then, the thermal behaviours of these polymeric structures were considered, notably to understand the impact of Zr on the thermal path going to the composites. The inorganic materials were characterised by thermogravimetry-mass spectrometry (TG-MS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). To link the macromolecular structure to the organisation involved during the ceramisation process, eight temperature domains were highlighted on the TG analyses, and a four-step mechanism was proposed for the polymers synthesised by a hydrosilylation reaction, as they displayed better ceramic yields. Globally, the introduction of Zr in the polymer had several effects on the temperature fragmentation mechanisms of the organometallic polymeric structures: (i) instead of stepwise mass losses, continuous fragment release prevailed; (ii) the stability of preceramic polymers was impacted, with relatively good ceramic yields; (iii) it modulated the chemical composition of the generated composites as it led, inter alia, to the consumption of free carbon.

Thermal stability of Nb thin films on sapphire

1996 ◽  
Vol 11 (5) ◽  
pp. 1255-1264 ◽  
Author(s):  
Thomas Wagner ◽  
Marko Lorenz ◽  
Manfred Rühle
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Orientation Relationship ◽  
High Energy ◽  
X Ray Diffraction ◽  
Model Study ◽  
Transmission Electron ◽  
The Stability ◽  
Thermal Stability Of

The Nb/α−Al2O3 system has been used as a model study for investigating the stability of different MBE grown epitaxial Nb films on α−Al2O3 substrates. The films were grown at 800 °C in ultrahigh vacuum. The growth process was monitored in situ by reflection high energy electron diffraction (RHEED). After deposition the structure of the film was investigated by x-ray diffraction (XRD) and conventional transmission electron microscopy (CTEM) which encompasses also selected area diffraction (SAD). Both techniques revealed the following orientation relationship between the Nb film and the α–Al2O3 substrate: (0001)α–Al2O3‖ (111)Nb; [2110]α–Al2O3‖ [110]Nb. The stability of the niobium films was investigated by annealing the Nb-film/α–Al2O3 system to temperatures up to 1500 °C for different periods of time. Surprisingly, the orientation relationship between the Nb film and the substrate changed to (0001)α–Al2O3‖ (110)Nb; [0110]α–Al2O3‖ [001]Nb. A model will be developed which shows that above a critical film thickness the growth orientation is metastable with respect to its crystallographic orientation. Furthermore, high resolution transmission electron microscopy (HREM) was performed to investigate the defect structure of the annealed Nb/α–Al2O3 interface.

scholarly journals Preparation and Solid-State Characterization of Eltrombopag Crystal Phases

Molecules ◽  
2020 ◽  
Vol 26 (1) ◽  
pp. 65
Author(s):  
Vincenzo Mirco Abbinante ◽  
Massimo Zampieri ◽  
Giuseppe Barreca ◽  
Norberto Masciocchi
Keyword(s):  
Free Acid ◽  
Variable Temperature ◽  
Intermediate Species ◽  
X Ray Diffraction ◽  
Crystal Forms ◽  
X Ray ◽  
Crystal Phases ◽  
The Stability ◽  
Solid State Characterization

Eltrombopag, of C25H22N4O4 chemical formula, is a drug used against thrombocytopenia, marketed worldwide under different tradenames in the form of its bis-olamine salt. The free acid (CAS no. 496775-61-2) is an intermediate species used for the final drug isolation and is reported to crystallize in more than 20 distinct crystal forms, including a large number of hydrates and solvates. Their identification, and, ultimately, their quantification in industrial lots require the usage of accurately measured X-ray powder diffraction pattern, as well as the assessment of the metrical features (crystal symmetry and lattice parameters), nowadays accessible by powerful crystallographic software. Here, the complete indexing of 13 monophasic samples, prepared using literature or newly tailored crystallization methods, jointly to simultaneous thermogravimetric and calorimetric analyses and to variable temperature X-ray diffraction studies, provide a clear picture of the stability fields of the different crystal phases and their mutual interconversion processes, leading, in a few cases, to new and unexpected crystalline polymorphs or solvates of the pristine unsolvated Form I.

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