Effects of Ion Implantation Conditions on the Tribology of Ferrous Surfaces

1991 ◽  
Vol 113 (1) ◽  
pp. 166-173 ◽  
Author(s):  
R. Wei ◽  
P. J. Wilbur ◽  
W. S. Sampath ◽  
D. L. Williamson ◽  
Li Wang
Keyword(s):  
Surface Temperature ◽  
Wear Test ◽  
Target Surface ◽  
High Dose Rate ◽  
304 Stainless Steel ◽  
High Dose ◽  
Near Surface ◽  
Wear Characteristics ◽  
Order Of Magnitude ◽  
Nitrogen Ion

The effects of implanted nitrogen ion dose and target surface temperature during implantation on the wear characteristics of iron (ferrite) and 304 stainless steel (austenite) have been studied systematically. Wear test results obtained using an oscillating pin-on-disk tester show that high dose rate, high dose implantation into these materials when they are being held at an elevated temperature (near 400°C) induce dramatic improvements in their wear characteristics. Surface and near-surface analysis techniques are used to demonstrate that implanted ion dose and surface temperature can be controlled to produce a desired microstructural state and thickness of the nitrogen-implanted layer. The most wear resistant surfaces are produced when γ’-Fe4N is formed in the ferrite and a concentrated solid solution of nitrogen is produced in the austenite. Implanted layer thicknesses greater than ~ 1 μm (an order of magnitude beyond the ballistic implantation depth) are observed in the austenite.

scholarly journals Surface composition and near-surface hardness studies on high dose boron-implanted 304 stainless steel

1990 ◽  
Vol 13 (5) ◽  
pp. 333-342 ◽  
Author(s):  
A K Goel ◽  
N D Sharma ◽  
R K Mohindra ◽  
P K Ghosh ◽  
M C Bhatnagar
Keyword(s):  
Stainless Steel ◽  
Surface Composition ◽  
Surface Hardness ◽  
304 Stainless Steel ◽  
High Dose ◽  
Near Surface

The Effects of Low-Energy-Nitrogen-Ion Implantation on the Tribological and Microstructural Characteristics of AISI 304 Stainless Steel

1994 ◽  
Vol 116 (4) ◽  
pp. 870-876 ◽  
Author(s):  
R. Wei ◽  
B. Shogrin ◽  
P. J. Wilbur ◽  
O. Ozturk ◽  
D. L. Williamson ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Elevated Temperatures ◽  
Wear Behavior ◽  
Plasma Nitriding ◽  
Low Energy ◽  
304 Stainless Steel ◽  
High Dose ◽  
Ion Energy ◽  
Wear Resistant ◽  
Nitrogen Ion

The effects of nitrogen implantation conditions (ion energy, dose rate, and processing time) on the thickness and wear behavior of N-rich layers produced on 304 stainless-steel surfaces are examined. Surfaces implanted at elevated temperatures (≈400°C) with 0.4 to 2 keV nitrogen ions at high dose rates (1.5 to 3.8 mA/cm2) are compared to surfaces implanted at higher energies (30 to 60 keV) and lower current densities (0.1 to 0.25 mA/cm2). The most wear-resistant surfaces are observed when the implanted-ion energy is near 1 keV and the dose is very large (> 2 × 1019 ions/cm2). Typically, surfaces implanted under these optimum conditions exhibit load-bearing capabilities at least 1000 times that of the untreated material. Some comparisons are also made to surfaces processed using conventional plasma-nitriding. Samples treated using either process have wear-resistant surface layers in which the nitrogen is in solid solution in the fcc phase. It is argued that the deep N migration (> 1 μm) that occurs under low-energy implantation conditions is due to thermal diffusion that is enhanced by a mechanism other than radiation-induced vacancy production.

The Influence of Implantation Conditions and Target Orientation in High Dose Implantation of Al+ into Si

1983 ◽  
Vol 27 ◽  
Author(s):  
F. Nam-Avar ◽  
J. I. Budnick ◽  
A. Fasihuddin ◽  
H. C. Hayden ◽  
D. A. Pease ◽  
...  
Keyword(s):  
Dose Rate ◽  
Surface Composition ◽  
High Vacuum ◽  
High Dose Rate ◽  
Ultra High Vacuum ◽  
High Dose ◽  
Polycrystalline Structure ◽  
Rutherford Back Scattering ◽  
Near Surface ◽  
Projected Range

ABSTRACTWe report the preliminary results of a study to determine the dependence of the near surface composition and structure on total dose, dose rate, vacuum condition and substrate orientation for Al implantation into Si (111) and Si (100) with doses up to 2 × 10l8 ions/cm2. Our studies include the results of Rutherford Back Scattering (RBS), Auger Electron Spectroscopy (AES) and x-ray diffraction measurements on samples implanted with a 100 keV energy in a diffusion pumped vacuum (DPV) system (10−6 Torr) with and without a LN2 trap and in an ultra high vacuum (UHV) system (2–4) x 10−8 Torr.Results of high dose rate (50 μA/cm2 ) implantation into Si (111) in an untrapped DPV system indicate that Al segregates with a preferred (111) orientation. For a dose of 1 × 1018 ions/cm2 the surface is Al-rich to a depth of 2500Å while for lower doses the surface is silicon-rich. A carbon build-yp occurred for samples prepared by low dose rate (5 μA/cm2 ) implantation. However, no Al segregation could be observed for doses of less than 1018 ions/cm2 . A similar behavior has been observed for Si (100) except that Al segregation occurs with a polycrystalline structure. Moreover, the segregated Al is present at depths greater than the projected range.When implantation was carried out in a DPV system with a LN2 trap, no carbon peaks could be observed by RBS regardless of the dose rate. For these conditions, as well as for the implantation of Al in an UHV system, we find Al segregation with a polycrystalline structure independent of the dose rates and target orientations we used. Al is observed at a depth greater by a factor of two than the expected value from the Rpcalculations. The Al depth penetration increases with the dose of implantation.

Absorbed dose simulations in near-surface regions using high dose rate Iridium-192 sources applied for brachytherapy

2014 ◽  
Vol 95 ◽  
pp. 299-301 ◽  
Author(s):  
E.S. Moura ◽  
C.A. Zeituni ◽  
R.K. Sakuraba ◽  
V.D. Gonçalves ◽  
J.C. Cruz ◽  
...  
Keyword(s):  
Dose Rate ◽  
Absorbed Dose ◽  
High Dose Rate ◽  
High Dose ◽  
Near Surface ◽  
Iridium 192

scholarly journals Megavolt Bremsstrahlung Measurements from Linear Induction Accelerators Demonstrate Possible Use as a FLASH Radiotherapy Source to Reduce Acute Toxicity

2021 ◽  
Author(s):  
Stephen Sampayan ◽  
Kristin Sampayan ◽  
George Caporaso ◽  
Yu-Jiuan Chen ◽  
Steve Falabella ◽  
...  
Keyword(s):  
Dose Rate ◽  
Rate Capability ◽  
High Dose Rate ◽  
High Repetition Rate ◽  
High Dose ◽  
Maximal Effect ◽  
Linear Induction ◽  
Order Of Magnitude ◽  
Tissue Sparing ◽  
Induction Accelerator

Abstract Recent studies indicate better efficacy and healthy tissue sparing with high dose-rate FLASH radiotherapy (FLASH-RT) cancer treatment. This technique delivers a prompt high radiation dose rather than fractional doses over a longer period of time. The threshold is >40 Gy-s-1 with a maximal effect at >100 Gy-s-1 that must be maintained in the treatment volume. Mechanisms are still widely debated, but toxicity is minimized while inducing apoptosis in malignant tissue. Delivery technologies to date show that a capability gap exists with clinic scale, broad area, deep penetrating, high dose rate capability. Based on present trends, if FLASH-RT is adopted, it may become a dominant approach except in the least technologically advanced countries. The linear induction accelerator (LIA) developed for high current, high repetition rate, species independent charged particle acceleration, has yet to be considered for this application. We briefly review the status of LIA technology, explore the physics of bremsstrahlung-converter-target interactions and our work on stabilizing the electron beam. While the gradient of the LIA is low, we present our preliminary work to improve the gradient by an order of magnitude, presenting a point design for a multibeam FLASH-RT system using a single accelerator for application to conformal FLASH-RT.

High-dose-rate effects in the radiolysis of water at elevated temperatures.

2021 ◽  
Author(s):  
Abida Sultana ◽  
Jintana Meesungnoen ◽  
Jean-Paul Jay-Gerin
Keyword(s):  
Dose Rate ◽  
Elevated Temperatures ◽  
General Pattern ◽  
Critical Time ◽  
High Dose Rate ◽  
High Dose ◽  
Dose Rates ◽  
Dose Rate Effects ◽  
Rate Effects ◽  
Order Of Magnitude

Monte Carlo track chemistry simulations were used to study the effects of high dose rates on the radical (e-aq, H•, and •OH) and molecular (H2 and H2O2) yields in the low linear energy transfer (LET) radiolysis of liquid water at elevated temperatures between 25–350 °C. Our simulation model consisted of randomly irradiating water by single pulses of N incident protons of 300 MeV (LET ~ 0.3 keV/μm), which penetrate at the same time perpendicular to this water within the surface of a circle. The effect of dose rate was studied by varying N. Our simulations showed that, at any given temperature, the radical products decrease with increasing dose rate and, at the same time, the molecular products increase, resulting from an increase in the inter-track, radical-radical reactions. Using the kinetics of the decay of hydrated electrons at 25 and 350 °C, we determined a critical time (τc) for each value of N, which corresponds to the “onset” of dose-rate effects. For our irradiation model, τc was inversely proportional to N for the two temperatures considered, with τc at 350 °C being shifted by an order of magnitude to shorter times compared to its values at 25 °C. Finally, the data obtained from the simulations for N = 2,000 generally agreed with the observation that during the track stage of the radiolysis, free radical yields increase, while molecular products decrease with increasing temperature from 25 to 350 °C. The exceptions of e-aq and H2 to this general pattern are briefly discussed.

scholarly journals Megavolt bremsstrahlung measurements from linear induction accelerators demonstrate possible use as a FLASH radiotherapy source to reduce acute toxicity

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Stephen E. Sampayan ◽  
Kristin C. Sampayan ◽  
George J. Caporaso ◽  
Yu-Jiuan Chen ◽  
Steve Falabella ◽  
...  
Keyword(s):  
Dose Rate ◽  
Irradiation Time ◽  
High Dose Rate ◽  
High Dose ◽  
Average Dose ◽  
Maximal Effect ◽  
Linear Induction ◽  
Order Of Magnitude ◽  
Tissue Sparing ◽  
Induction Accelerator

AbstractRecent studies indicate better efficacy and healthy tissue sparing with high dose-rate FLASH radiotherapy (FLASH-RT) cancer treatment. This technique delivers a prompt high radiation dose rather than fractional doses over time. While some suggest thresholds of > 40 Gy s−1 with a maximal effect at > 100 Gy s−1, accumulated evidence shows that instantaneous dose-rate and irradiation time are critical. Mechanisms are still debated, but toxicity is minimized while inducing apoptosis in malignant tissue. Delivery technologies to date show that a capability gap exists with clinic scale, broad area, deep penetrating, high dose rate systems. Based on these trends, if FLASH-RT is adopted, it may become a dominant approach except in the least technologically advanced countries. The linear induction accelerator (LIA) developed for high instantaneous and high average dose-rate, species independent charged particle acceleration, has yet to be considered for this application. We review the status of LIA technology, explore the physics of bremsstrahlung-converter-target interactions and our work on stabilizing the electron beam. While the gradient of the LIA is low, we present our preliminary work to improve the gradient by an order of magnitude, presenting a point design for a multibeam FLASH-RT system using a single accelerator for application to conformal FLASH-RT.

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