scholarly journals The Potassium-Induced Decomposition Pathway of HCOOH on Rh(111)

Catalysts ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 675 ◽  
Author(s):  
Imre Kovács ◽  
János Kiss ◽  
Zoltán Kónya
Keyword(s):  
High Temperature ◽  
Binding Energy ◽  
Thermal Desorption ◽  
Negative Charge ◽  
Active Components ◽  
Surface Formate ◽  
Induced Decomposition ◽  
Decomposition Pathway ◽  
Formate Intermediate ◽  
Back Donation

Formic acid (FA) can be considered both a CO and a H2 carrier via selective dehydration and dehydrogenation pathways, respectively. The two processes can be influenced by the modification of the active components of the catalysts used. In the present study the adsorption of FA and the decomposition of the formed formate intermediate were investigated on potassium promoted Rh(111) surfaces. The preadsorbed potassium markedly increased the uptake of FA at 300 K, and influenced the decomposition of formate depending on the potassium coverage. The work function (Δϕ) is increased by the adsorption of FA on K/Rh(111) at 300 K suggesting a large negative charge on the chemisorbed molecule, which could be probably due to the enhanced back-donation of electrons from the K-promoted Rh into an empty π orbital of HCOOH. The binding energy of the formate species is therefore increased resulting in a greater concentration of irreversibly adsorbed formate species. Decomposition of the formate species led to the formation of H2, CO2, H2O, and CO, which desorbed at significantly higher temperatures from the K-promoted surface than from the K-free one as it was proven by thermal desorption studies. Transformation of surface formate to carbonate (evidenced by UPS) and its decomposition and desorption is responsible for the high temperature CO and CO2 formation.

The Role of Cr in H Desorption Kinetics in Rapidly Solidified Al

2014 ◽  
Vol 783-786 ◽  
pp. 264-269 ◽  
Author(s):  
Iya I. Tashlykova-Bushkevich ◽  
Keitaro Horikawa ◽  
Goroh Itoh
Keyword(s):  
High Temperature ◽  
Thermal Desorption ◽  
High Purity ◽  
Thermal Desorption Spectroscopy ◽  
Secondary Phase ◽  
Hydrogen Desorption ◽  
Oxide Surface ◽  
Desorption Kinetics ◽  
Hydrogen Trapping ◽  
Rapidly Solidified

Hydrogen desorption kinetics for rapidly solidified high purity Al and Al-Cr alloy foils containing 1.0, 1.5 and 3.0 at % Cr were investigated by means of thermal desorption analysis (TDA) at a heating rate of 3.3°C/min. For the first time, it was found that oxide inclusions of Al2O3 are dominant high-temperature hydrogen traps compared with pores and secondary phase precipitates resulted in rapid solidification of Al and its alloys. The correspondent high-temperature evolution rate peak was identified to be positioned at 600°C for high purity Al and shifted to 630°C for Al-Cr alloys. Amount of hydrogen trapped by dislocations increases in the alloys depending on Cr content. Microstructural hydrogen trapping behaviour in low-and intermediate temperature regions observed here was in coincidence with previous data obtained for RS materials using thermal desorption spectroscopy (TDS). The present results on hydrogen thermal desorption evolution indicate that the effect of oxide surface layers becomes remarkable in TDA measurements and show advantages in combinations of both desorption analysis methods to investigate hydrogen desorption kinetics in materials.

Xps Analysis of the Sapphire Surface as a Function of High Temperature Vacuum Annealing

1989 ◽  
Vol 159 ◽  
Author(s):  
E.D. Richmond
Keyword(s):  
High Temperature ◽  
Binding Energy ◽  
Photoelectron Spectroscopy ◽  
Vacuum Annealing ◽  
Xps Analysis ◽  
Chemical Changes ◽  
Cleaning Procedure ◽  
Sapphire Surface ◽  
X Ray ◽  
First Time

ABSTRACTFor the first time the (1102) surface of sapphire has been investigated by X-ray photoelectron spectroscopy to ascertain chemical changes resulting from annealing in vacuum at 1300° C and 1450° C. As received substrates had a substantial surface C contaminant. For substrates that were chemically cleaned before inserting them into the MBE system no trace of carbon is detected. A residual flourine contaminant results from the cleaning procedure and is desorbed by the vacuum annealing. Spectra of annealed substrates are compared to the unannealed chemically cleaned substrates. The annealed substrates exhibit 0.4 to 0.5 eV shift to higher binding energy of the Al peak and a 0.3 eV shift to higher binding energy of the O peak. In addition, a 2% depletion of oxygen from the surface occurs.

scholarly journals Development, Optimization and Validation of a Sustainable and Quantifiable Methodology for the Determination of 2,4,6-Trichloroanisole, 2,3,4,6-Tetrachloroanisole, 2,4,6-Tribromoanisole, Pentachloroanisole, 2-Methylisoborneole and Geosmin in Air

Processes ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 1571
Author(s):  
Patricia Jové ◽  
Marina Vives-Mestres ◽  
Raquel De Nadal ◽  
Maria Verdum
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
High Temperature ◽  
Thermal Desorption ◽  
Mass Spectrometric ◽  
Gas Chromatography Mass Spectrometry ◽  
Air Analysis ◽  
Good Linearity ◽  
Repeatability And Reproducibility

Compounds 2,4,6-trichloroanisole (TCA), 2,3,4,6-tetrachloroanisole (TeCA), 2,4,6-tribromoanisole (TBA) and pentachloroanisole (PCA), 2-methylisoborneol (2MIB) and geosmin (GSM) have been reported as being responsible for cork and wine taint. A sustainable method based on thermal desorption-gas chromatography–mass spectrometry (TD-GC/MS) has been developed and optimized, taking into account desorption parameters and chromatographic and mass spectrometric conditions. The combination of parameters that jointly maximized the compound detection was as follows: desorption temperature at 300 °C, desorption time at 30 min, cryo-temperature at 20 °C and trap high temperature at 305 °C. The proposed methodology showed a good linearity (R ≤ 0.994) within the tested range (from 0.1 to 2 ng) for all target compounds. The precision expressed as repeatability and reproducibility was RSD < 10% in both. The limits of quantification ranged from 0.05 to 0.1 ng. The developed methodology and the sampling rates (R-values) of all targeted compounds (from 0.013 to 0.071 m3 h−1) were applied to the air analysis of two wineries. The results showed that the developed methodology is a sustainable and useful tool for the determination of these compounds in air.

Characterization and Aging Test Methodology for Power Electronic Devices at High Temperature

2011 ◽  
Vol 324 ◽  
pp. 411-414 ◽  
Author(s):  
Ali Ibrahim ◽  
Zoubir Khatir ◽  
Laurent Dupont
Keyword(s):  
High Temperature ◽  
Energy Gap ◽  
Switching Frequency ◽  
Power Electronic ◽  
Active Components ◽  
Ambient Temperatures ◽  
Test Methodology ◽  
Aging Test ◽  
Wide Energy ◽  
Strategic Issue

Power electronic modules are key elements in the chain of power conversion. The application areas include aerospace, aviation, railway, electrical distribution, automotive, home automation, oil industry ... But the use of power electronics in high temperature environments is a major strategic issue in the coming years especially in transport. However, the active components based on silicon are limited in their applications and not suitable for those require both high voltages and high ambient temperatures. The materials with wide energy gap like SiC, GaN and diamond, have the advantage of being able to exceed these limits [1,2]. These materials seem adequate to extremely harsh temperature environments and allow the reduction of cooling systems, but also the increasing of switching frequency.

DFT Analysis of the Indium-Antimony-Vacancy Cluster in Silicon

2005 ◽  
Vol 245-246 ◽  
pp. 29-38 ◽  
Author(s):  
M.M. De Souza ◽  
Jonathan P. Goss
Keyword(s):  
High Temperature ◽  
Binding Energy ◽  
Vacancy Cluster ◽  
Antimony Atom ◽  
Teller Effect ◽  
High Temperature Anneal ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
Low Symmetry ◽  
Strong Binding Energy

A cluster comprising of indium, antimony and a vacancy in silicon is analysed using the planewave pseudopotential technique. This cluster has a strong binding energy that inhibits indium diffusion after high temperature anneal cycles. Difficulties associated with the simulation of a vacancy using the supercell approach are initially highlighted. In comparison, the indium-antimony-vacancy cluster reveals stronger distortions and reduction in relaxation volume. The indium atom in the relaxed cluster shows nearly six-fold coordination whereas the antimony atom acquires four neighbours. Due to the low symmetry of the centre, in constrast to the isolated vacancy there is no propensity for a Jahn-Teller effect. It gives rise to two defect levels in the bandgap.

scholarly journals Multiscale mechanisms of asphalt performance enhancement by crumbed waste tire rubber: Insight from molecular dynamics simulation

2021 ◽  
Author(s):  
Kui Hu ◽  
Caihua Yu ◽  
Yujing Chen ◽  
Wei Li ◽  
Chen Guixiang ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
High Temperature ◽  
Binding Energy ◽  
Dynamics Simulation ◽  
Tire Rubber ◽  
Modified Asphalt ◽  
Waste Tire ◽  
Temperature Performance ◽  
Waste Tire Rubber ◽  
Light Components

Abstract The recycling of crumbled waste tire rubber (CWTB) is a major environmental problem facing mankind, and the incorporation of CWTB as a modifier into asphalt is an extremely promising approach. However, the modification mechanism of CWTB to asphalt is not well understood, which restricts the development of CWTB-modified asphalt. In this study, the mechanism of CWTB modification of asphalt was explored in depth by dynamic mechanical analysis (DMA), fluorescence microscopy, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and molecular dynamics (MD) simulations. The results of the study showed that CWTB enhanced the high temperature performance of the base asphalt. The microscopic mechanism by which this phenomenon occurs is that CWTB has the largest binding energy with the aromatics (1100–1400 kcal/mol), followed by the saturates (700–900 kcal/mol), followed by the resins (200–450 kcal/mol), and the smallest binding energy with the asphaltenes (110–160 kcal/mol), which causes CWTB to absorb the light components of the asphalt (aromatics and saturates). In the process of absorbing the light components, CWTB will gradually swell, which causes CWTB to bind more and more tightly with the base asphalt, and eventually the good high temperature performance of CWTB is transferred to the base asphalt. The macroscopic manifestation of this process is that the rutting factor of CWTB modified asphalt is significantly higher than that of virgin asphalt. This study can provide basic theoretical support for the application of CWTB modified asphalt.

CO2 Laser-induced and BCl3-sensitized decomposition of hexafluoroacetone. Comparison with high temperature thermochemistry

1982 ◽  
Vol 47 (3) ◽  
pp. 912-917
Author(s):  
Josef Pola ◽  
Pavel Engst ◽  
Milan Horák
Keyword(s):  
Thermal Decomposition ◽  
Carbon Monoxide ◽  
High Temperature ◽  
Co2 Laser ◽  
Carbonyl Compounds ◽  
Total Pressure ◽  
Tungsten Filament ◽  
Reaction Progress ◽  
Induced Decomposition ◽  
Carbonyl Fluoride

The cw CO2laser-induced decomposition of hexafluoroacetone sensitized with boron trichloride (total pressure 5.3-8.0 kPa) yields along with perfluorinated hydrocarbons trifluoroacetyl fluoride, carbon monoxide and carbonyl fluoride. The same carbonyl compounds are also formed by conventional thermal decomposition of hexafluoroacetone on tungsten filament at temperatures 950-2 100°C but their distribution during reaction progress is different. Features of both reactions are discussed.

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