scholarly journals Mechanical Spectroscopy Investigation of Point Defect-Driven Phenomena in a Cr Martensitic Steel

Metals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 870 ◽  
Author(s):  
Alessandra Fava ◽  
Roberto Montanari ◽  
Alessandra Varone
Keyword(s):  
Point Defect ◽  
Cooling Rate ◽  
Point Defects ◽  
Martensitic Steel ◽  
Nucleation Mechanism ◽  
Hydrogen Attack ◽  
Mechanical Spectroscopy ◽  
Hydrogen Atoms ◽  
Slow Cooling ◽  
Cr Concentration

The paper presents and discusses results of mechanical spectroscopy (MS) tests carried out on a Cr martensitic steel. The study regards the following topics: (i) embrittlement induced by Cr segregation; (ii) interaction of hydrogen with C–Cr associates; (iii) nucleation of Cr carbides. The MS technique permitted characterising of the specific role played by point defects in the investigated phenomena: (i) Cr segregation depends on C–Cr associates distribution in as-quenched material, in particular, a slow cooling rate (~150 K/min) from austenitic field involves an unstable distribution, which leads to Cr concentration fluctuations after tempering at 973 K; (ii) hydrogen interacts with C–Cr associates, and the phenomenon hinders hydrogen attack (HA) because hydrogen atoms bound by C–Cr associates are not able to diffuse towards grain boundaries and dislocation where CH4 bubbles may nucleate, grow, and merge to form the typical HA cracks; (iii) C–Cr associates take part in the nucleation mechanism of Cr7C3 carbides, and specifically these carbides form by the aggregation of C–Cr associates with 1 Cr atom.

Detection of a point defect in a silicon single crystal by high-resolution TEM

1995 ◽  
Vol 53 ◽  
pp. 466-467
Author(s):  
M. Awaji
Keyword(s):  
High Resolution ◽  
Single Crystal ◽  
Point Defect ◽  
Point Defects ◽  
Noise Level ◽  
Dark Field ◽  
Silicon Single Crystal ◽  
High Resolution Image ◽  
Dark Field Imaging ◽  
Field Imaging

It is necessary to improve the resolution, brightness and signal-to-noise ratio(s/n) for the detection and identification of point defects in crystals. In order to observe point defects, multi-beam dark-field imaging is one of the useful methods. Though this method can improve resolution and brightness compared with dark-field imaging by diffuse scattering, the problem of s/n still exists. In order to improve the exposure time due to the low intensity of the dark-field image and the low resolution, we discuss in this paper the bright-field high-resolution image and the corresponding subtracted image with reference to a changing noise level, and examine the possibility for in-situ observation, identification and detection of the movement of a point defect produced in the early stage of damage process by high energy electron bombardment.The high-resolution image contrast of a silicon single crystal in the [10] orientation containing a triple divacancy cluster is calculated using the Cowley-Moodie dynamical theory and for a changing gaussian noise level. This divacancy model was deduced from experimental results obtained by electron spin resonance. The calculation condition was for the lMeV Berkeley ARM operated at 800KeV.

scholarly journals Correlation of Processing, Inner Structure, and Part Properties of Injection Moulded Thin-Wall Parts on Example of Polyamide 66

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Dietmar Drummer ◽  
Steve Meister
Keyword(s):  
Cooling Rate ◽  
Injection Moulding ◽  
Degree Of Crystallinity ◽  
Process Conditions ◽  
Thin Wall ◽  
Polyamide 66 ◽  
Slow Cooling ◽  
Cooling Conditions ◽  
Internal Structures ◽  
Wall Injection

In micro- and thin-wall injection moulding the process conditions affect the developed internal structures and thus the resulting part properties. This paper investigates exemplarily on polyamide 66 the interactions of different cooling conditions on the morphological and crystalline structures. The investigations reveal that a slow cooling rate of the melt results in a homogeneous morphology and a higher degree of crystallinity and also a favoured crystalline structure. Consequently, the dielectric behaviour and light transmitting part properties are affected.

Pts-Oi Complex Formation in Platinum Diffused Silicon

2005 ◽  
Vol 864 ◽  
Author(s):  
Wilfried Vervisch ◽  
Laurent Ventura ◽  
Bernard Pichaud ◽  
Gérard Ducreux ◽  
André Lhorte
Keyword(s):  
Thermal Treatment ◽  
Complex Formation ◽  
Cooling Rate ◽  
Point Defects ◽  
Diffusion Processes ◽  
Silicon Wafers ◽  
Doping Behaviour ◽  
Simulation Results ◽  
Dopant Atoms ◽  
P Type

AbstractWhen platinum is diffused at temperatures higher than 900°C in Cz or FZ low doped n-type silicon samples, which are then cooled slowly in the range [1-10]°C/min, a p-type doping leading to the formation of a pn junction can be observed by spreading resistance measurement. The lower the cooling rate, the deeper the junction is. This junction disappears after a second thermal treatment finishing with a quenching step. A platinum related complex formation is considered to explain this reversible doping behaviour. Different possible interactions between platinum and other impurities such as dopant atoms, intrinsic point defects, and common residual impurities (C, Oi, transition metallic atoms) are studied here. Experimental results from Pt diffusion processes in different qualities of silicon wafers, and simulation results, lead to the conclusion that the platinum related p-type doping effect is due to the formation of a Pts-Oi complex.

scholarly journals Reactivity of fluorographene is triggered by point defects: beyond the perfect 2D world

Nanoscale ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 4696-4707 ◽  
Author(s):  
Miroslav Medveď ◽  
Giorgio Zoppellaro ◽  
Juri Ugolotti ◽  
Dagmar Matochová ◽  
Petr Lazar ◽  
...  
Keyword(s):  
Point Defect ◽  
Point Defects

Understanding the links between nucleophilic/reductive strength of the environment, formation of radicals and point defect characteristics is crucial for achieving control over the functionalization of fluorographene.

Displacement cascade evolution in tungsten with pre-existing helium and hydrogen clusters: a molecular dynamics study

2020 ◽  
Vol 111 (8) ◽  
pp. 698-705
Author(s):  
Mohammad Abu-Shams ◽  
Jeffery Moran ◽  
Ishraq Shabib
Keyword(s):  
Molecular Dynamics ◽  
Point Defect ◽  
Radiation Damage ◽  
Point Defects ◽  
High Energy ◽  
Dynamics Simulation ◽  
Power Relationship ◽  
Hydrogen Clusters ◽  
Displacement Cascades ◽  
Hydrogen Defects

Abstract The effects of radiation damage on bcc tungsten with preexisting helium and hydrogen clusters have been investigated in a high-energy environment via a comprehensive molecular dynamics simulation study. This research determines the interactions of displacement cascades with helium and hydrogen clusters integrated into a tungsten crystal generating point defect statistics. Helium or hydrogen clusters of atoms~0.1% of the total number of atoms have been randomly distributed within the simulation model and primary knock-on-atom (PKA) energies of 2.5, 5, 7.5 and 10 keV have been used to generate displacement cascades. The simulations quantify the extent of radiation damage during a simulated irradiation cycle using the Wigner-Seitz point defect identification technique. The generated point defects in crystals with and without pre-existing helium/hydrogen defects exhibit a power relationship with applied PKA energy. The point defects are classified by their atom type, defect type, and distribution within the irradiated model. The presence of pre-existing helium and hydrogen clusters significantly increases the defects (5 - 15 times versus pure tungsten models). The vacancy composition is primarily tungsten (e. g., ~70% at 2.5 keV) in models with pre-existing helium, but the interstitials are primarily He (e. g., ~89% at 10 keV). On the other hand, models with pre-existing hydrogen have a vacancy composition that is primarily tungsten (more than 90% irrespective of PKA energy), and the interstitial composition is more balanced between tungsten (average 46%) and hydrogen (average 54%) interstitials across the PKA range. The distribution of the atoms reveals that the tungsten point defects prefer to reside close to the position of cascade initiation, but helium or hydrogen defects reside close to the positions where clusters are built.

X-Ray Diffuse Scattering Investigation of Defects in Ion Implanted and Annealed Silicon

1998 ◽  
Vol 524 ◽  
Author(s):  
C. H. Chang ◽  
U. Beck ◽  
T. H. Metzger ◽  
J. R. Patel
Keyword(s):  
Ion Implantation ◽  
Point Defect ◽  
Point Defects ◽  
Diffuse Scattering ◽  
Grazing Incidence ◽  
X Rays ◽  
Scattered Intensity ◽  
X Ray ◽  
Defect Clusters ◽  
Point Defect Clusters

ABSTRACTTo characterize the point defects and point defect clusters introduced by ion implantation and annealing, we have used grazing incidence x-rays to measure the diffuse scattering in the tails of Bragg peaks (Huang Scattering). An analysis of the diffuse scattered intensity will allow us to characterize the nature of point defects or defect clusters introduced by ion implantation. We have also observed unexpected satellite peaks in the diffuse scattered tails. Possible causes for the occurrence of the peaks will be discussed.

scholarly journals Modeling of Point Defects Annihilation in Multilayered Cu/Nb Composites under Irradiation

2016 ◽  
Vol 2016 ◽  
pp. 1-17 ◽  
Author(s):  
Sarah Fadda ◽  
Antonio Mario Locci ◽  
Francesco Delogu
Keyword(s):  
Point Defect ◽  
Point Defects ◽  
Surface Recombination ◽  
Multilayer Composite ◽  
Balance Equations ◽  
General Validity ◽  
Defect Diffusion ◽  
Temperature Radiation ◽  
General Tool

This work focuses on a mathematical modeling of the response to irradiation of a multilayer composite material. Nonstationary balance equations are utilized to account for production, recombination, transport, and annihilation, or removal, of vacancies and interstitials at interfaces. Although the model developed has general validity, Cu/Nb multilayers are used as case study. Layer thickness, temperature, radiation intensity, and surface recombination coefficients were varied systematically to investigate their effect on point defect annihilation processes at interfaces. It is shown that point defect annihilation at interfaces mostly depends on point defect diffusion. The ability of interfaces to remove point defects can be described by a simple map constructed using only two dimensionless parameters, which provides a general tool to estimate the efficiency of vacancy and interstitial removal in multilayer composite materials.

Point Defect Injection Kinetics by N2O Oxidation of Silicon

1997 ◽  
Vol 469 ◽  
Author(s):  
C. Tsamis ◽  
D. N. Kouvatsos ◽  
D. Tsoukalas
Keyword(s):  
Point Defect ◽  
High Temperatures ◽  
Point Defects ◽  
Silicon Substrate ◽  
Oxidation Process ◽  
Stacking Faults ◽  
Defect Injection ◽  
Dry Oxidation ◽  
Kinetics Of

ABSTRACTThe influence of N2O oxidation of silicon on the kinetics of point defects at high temperatures is investigated. Oxidation Stacking Faults (OSF) are used to monitor the interstitials that are generated during the oxidation process. We show that at high temperatures (1050°-1150°C) the supersaturation of self-interstitials in the silicon substrate is enhanced when oxidation is performed in an N2O ambient compared to 100% dry oxidation. This behavior is attributed to the presence of nitrogen at the oxidizing interface. However, at lower temperatures this phenomenon is reversed and oxidation in N2O ambient leads to reduced supersaturation ratios.

Enhancing the electrical conductivity of PP/CNT nanocomposites through crystal-induced volume exclusion effect with a slow cooling rate

2020 ◽  
Vol 183 ◽  
pp. 107663 ◽  
Author(s):  
Jun Wang ◽  
Yasamin Kazemi ◽  
Sai Wang ◽  
Mahdi Hamidinejad ◽  
Mayesha B. Mahmud ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Cooling Rate ◽  
Slow Cooling ◽  
Exclusion Effect

scholarly journals Effect of cooling rate on microstructure and mechanical properties of CB2 tempered martensitic steel

China Foundry ◽  
2020 ◽  
Vol 17 (2) ◽  
pp. 158-166
Author(s):  
Yu-lin Ma ◽  
Yue Liu ◽  
Li-ping Zhang ◽  
Xu Jiang ◽  
Chun-ming Liu
Keyword(s):  
Mechanical Properties ◽  
Cooling Rate ◽  
Martensitic Steel ◽  
Microstructure And Mechanical Properties
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