scholarly journals Revealing Hydrogen States in Carbon Structures by Analyzing the Thermal Desorption Spectra

2022 ◽  
Vol 8 (1) ◽  
pp. 6
Author(s):  
Yury S. Nechaev ◽  
Evgeny A. Denisov ◽  
Nadezhda A. Shurygina ◽  
Alisa O. Cheretaeva ◽  
Ekaterina K. Kostikova ◽  
...  
Keyword(s):  
Thermal Desorption ◽  
Atomic Hydrogen ◽  
Hydrogen Desorption ◽  
High Energy ◽  
Second Order ◽  
Main Research ◽  
Carbon Structures ◽  
Exponential Factors ◽  
Relationship Of ◽  
Preliminary Description

An effective methodology for the detailed analysis of thermal desorption spectra (TDS) of hydrogen in carbon structures at micro- and nanoscale was further developed and applied for a number of TDS data of one heating rate, in particular, for graphite materials irradiated with atomic hydrogen. The technique is based on a preliminary description of hydrogen desorption spectra by symmetric Gaussians with their special processing in the approximation of the first- and the second-order reactions. As a result, the activation energies and the pre-exponential factors of the rate constants of the hydrogen desorption processes are determined, analyzed and interpreted. Some final verification of the results was completed using methods of numerical simulation of thermal desorption peaks (non-Gaussians) corresponding to the first- and the second-order reactions. The main research finding of this work is a further refinement and/or disclosure of poorly studied characteristics and physics of various states of hydrogen in microscale graphite structures after irradiation with atomic hydrogen, and comparison with the related results for nanoscale carbon structures. This is important for understanding the behavior and relationship of hydrogen in a number of cases of high energy carbon-based materials and nanomaterials.

Effect of Nano Dispersant Additions to the Electrodes for Aluminum Electrolysis

2021 ◽  
Vol 875 ◽  
pp. 107-115
Author(s):  
Shahid Akhtar ◽  
Sten Yngve Larsen
Keyword(s):  
Aluminum Electrolysis ◽  
Metallurgical Industry ◽  
High Energy ◽  
Structure Property ◽  
Mixing Conditions ◽  
Carbon Structures ◽  
Technological Advances ◽  
Transmission Electron ◽  
Relationship Of ◽  
Global Carbon

Over the next half decade, significant changes expected in global carbon structures, carbon products and applications. Technological advances that improve the structure-property relationship of advanced carbon materials and breakthrough in manufacturing processes resulting in lower cost, leads to availability of carbon nano materials for applications in the metallurgical industry with a reference to electrodes for the metallurgical industry.In the current work we synthesized pitch-based C/C nano composite lab scale electrodes, partially replacing petroleum coke with nanofibers, by using a ball milling dispersion and high energy milling technique. The effect of different processing variables including the amount of binder and dispersants as well as mixing conditions is investigated. Low vacuum -SEM analyses of green pitch and dispersant samples show the pitch coating on dispersants. Field emission gun (FEG)-SEM is used to analyse dispersants, baked pitch/dispersant system as well baked electrodes. Transmission electron microscope (TEM) is applied to investigate in detail the primary structure of the dispersants, as well as the fiber/matrix interface and the alignment of binder with the fibres in graphitized and un-graphitized electrodes.

Silicon Nanofabrication and Chemical Modification by UHV-STM

1995 ◽  
Vol 380 ◽  
Author(s):  
J. W. Lyding ◽  
T.-C. Shen ◽  
G. C. Abeln ◽  
C. Wang ◽  
E. T. Foley ◽  
...  
Keyword(s):  
Chemical Modification ◽  
Field Emission ◽  
Thermal Desorption ◽  
Atomic Hydrogen ◽  
Molecular Hydrogen ◽  
Lower Energy ◽  
Vibrational Excitation ◽  
Hydrogen Desorption ◽  
Hydrogen Passivation ◽  
Electron Stimulated Desorption

ABSTRACTPatterning on the 10 Å size scale has been achieved with a UHV-STM for Si(100)-2×1:H surfaces. Hydrogen passivation serves as a monolayer resist which the STM locally desorbs, exposing clean Si(100)-2×1 for selective chemistry. Two mechanisms have been identified for hydrogen removal by STM electrons: in the field emission regime direct electron stimulated desorption of hydrogen occurs whereas, in the lower energy tunneling regime, hydrogen desorption results from vibrational excitation of the Si-H bond at high tunneling currents. Furthermore, we find that atomic hydrogen is liberated in contrast to molecular hydrogen evolved during thermal desorption. Selective oxidation and nitridation of the STM-patterned areas has been achieved.

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.

Synchronized Periodic Solutions of a Class of Periodically Driven Nonlinear Oscillators

1988 ◽  
Vol 55 (3) ◽  
pp. 721-728 ◽  
Author(s):  
Gamal M. Mahmoud ◽  
Tassos Bountis
Keyword(s):  
Periodic Solutions ◽  
Periodic Orbits ◽  
Nonlinear Oscillators ◽  
High Energy ◽  
Second Order ◽  
Multiple Time ◽  
Particle Beams ◽  
Periodically Driven ◽  
Time Scaling ◽  
A New Technique

We consider a class of parametrically driven nonlinear oscillators: x¨ + k1x + k2f(x,x˙)P(Ωt) = 0, P(Ωt + 2π) = P(Ωt)(*) which can be used to describe, e.g., a pendulum with vibrating length, or the displacements of colliding particle beams in high energy accelerators. Here we study numerically and analytically the subharmonic periodic solutions of (*), with frequency 1/m ≅ √k1, m = 1, 2, 3,…. In the cases of f(x,x˙) = x3 and f(x,x˙) = x4, with P(Ωt) = cost, all of these so called synchronized periodic orbits are obtained numerically, by a new technique, which we refer to here as the indicatrix method. The theory of generalized averaging is then applied to derive highly accurate expressions for these orbits, valid to the second order in k2. Finally, these analytical results are used, together with the perturbation methods of multiple time scaling, to obtain second order expressions for regions of instability of synchronized periodic orbits in the k1, k2 plane, which agree very well with the results of numerical experiments.

Trend surface analysis of major late Wisconsinan till sheets, Brantford–Woodstock area, southern Ontario

1978 ◽  
Vol 15 (6) ◽  
pp. 1025-1036 ◽  
Author(s):  
W. R. Cowan
Keyword(s):  
Strong Relationship ◽  
High Energy ◽  
Field Observations ◽  
Trend Surface Analysis ◽  
Southern Ontario ◽  
Niagara Escarpment ◽  
Regional Trends ◽  
Grade Material ◽  
Late Wisconsinan ◽  
Relationship Of

Linear and quadratic trend surfaces were computed for textural, carbonate, clast, and heavy mineral properties of the Catfish Creek (Nissouri Stadial), Port Stanley (Port Bruce Stadial), Tavistock (Port Bruce Stadial), and Wentworth (Port Huron Stadial) tills.Catfish Creek Till pebble grade material provided trend surfaces reflecting the underlying bedrock. However, an overall lack of regional trends in Catfish Creek Till is consistent with field observations that indicate remarkable uniformity for this till over several hundred square kilometres, a phenomenon that is believed to reflect the high energy of this ice sheet. Carbonates in Port Stanley Till were found to increase from east to west as the Silurian–Devonian contact was crossed. Tavistock Till was found to have increasing sand content and decreasing silt content from northwest to southeast owing to incorporation of underlying glaciofluvial sediments; pebble trends reflect the underlying bedrock for the most part. Wentworth Till trend surfaces for carbonates and pebbles show high dolomite near the Niagara Escarpment to the east and northeast with a dilution of dolomite and influx of limestone to the southwest.The strong relationship of the trend surfaces to substrate materials indicates the basal nature of the tills and the local origin of most glacial deposits. Pebble lithologies provide much information about local bedrock and drift prospectors should give close consideration to coarse fragments.

Synthesis by High-Energy Ball Milling of MgH2-TiFe Composites for Hydrogen Storage

2017 ◽  
Vol 899 ◽  
pp. 13-18 ◽  
Author(s):  
Ricardo Mendes Leal Neto ◽  
Rafael de Araújo Silva ◽  
Ricardo Floriano ◽  
Graziele Cristina Seco Coutinho ◽  
Railson Bolsoni Falcão ◽  
...  
Keyword(s):  
Ball Milling ◽  
Hydrogen Absorption ◽  
Hydrogen Desorption ◽  
High Energy ◽  
Control Agent ◽  
High Energy Ball Milling ◽  
Absorption Kinetics ◽  
Particle Size Reduction ◽  
Milled Sample ◽  
Energy Ball

The aim of this work is to investigate the influence of some processes variables on the microstructure and hydrogen absorption kinetics of MgH2 - X wt.% TiFe composites. Samples were synthesized by high-energy ball milling in a planetary (X = 40, 50, 60) and shaker mill (X = 40) under high-purity argon atmosphere. Commercial MgH2 instead of Mg powder was used in order to reduce adherence on the vial and balls. TiFe powder was previously produced by ball milling a mixture of TiH2 and Fe powders followed by a reaction synthesis at 600oC. Milled composites samples were characterized by XRD and SEM analysis. Milling time was preliminary investigated (X = 40) in the planetary ball mill (6 to 36h). TiFe particle size reduction was shown to be difficult since they are surrounded by MgH2 matrix. Strong particle reduction was obtained by using a shaker mill only for 2 hours and adding cyclohexane as process control agent. No reaction between MgH2 and TiFe compound was observed in any milled sample. Hydrogen absorption kinetics measurements of the as-milled samples were conducted on an Sieverts' type apparatus at room temperature after hydrogen desorption at 350oC under vacuum. The best hydrogen kinetics (3 wt% at the first hour) was attained by the planetary milled sample (36 h). Higher hydrogen capacity was observed for the sample milled in the shaker mill (4.0 wt.%), but only after 13h.

Sign in / Sign up

Export Citation Format

Share Document