scholarly journals Surface conversion

2010 ◽  
Author(s):  
Anne Pichon
Keyword(s):  
Surface Conversion

Detection of Single Ions by Fulse Counting: Application to Ion Microprobe Mass Analyzer

1971 ◽  
Vol 15 ◽  
pp. 36-55
Author(s):  
L. A. Dietz
Keyword(s):  
Mass Spectra ◽  
Secondary Electron Emission ◽  
Target Surface ◽  
Mass Analyzer ◽  
Ion Microprobe ◽  
Ion Detection ◽  
Secondary Electrons ◽  
Electron Multiplier ◽  
Pulse Counting ◽  
Surface Conversion

The need to detect low intensity beams of resolved ions with keV energy is encountered frequently in mass spectrometry. It is most readily accomplished by using some form of pulse-counting detector in which ions are allowed to strike a target surface (conversion dynode) where each ion releases a pulse of low energy secondary electrons. The secondary electrons undergo further amplification in an electron multiplier or scintillator type of ion detector which is specially designed to detect single ions. Ion-to-electron conversion, amplification of the secondary electrons, efficiency of ion detection by pulse counting and dead-time corrections to observed random counting rates are all statistical processes which must be understood so that observed data can be corrected properly to obtain precise and accurate measurements. These processes are reviewed, along with some of the basic properties of ion-induced secondary electron emission from an amorphous Al2O3 thin film target. Ion detection in the ion microprobe is interpreted in light of these basic considerations, and several mass spectra are given for electron multiplier dynode surfaces.

Lysine-derivatized polyurethane as a clot lysing surface: conversion of adsorbed plasminogen to plasmin and clot lysis in vitro

Biomaterials ◽  
2001 ◽  
Vol 22 (13) ◽  
pp. 1919-1924 ◽  
Author(s):  
W.G. McClung ◽  
D.L. Clapper ◽  
S.-P. Hu ◽  
J.L. Brash
Keyword(s):  
Clot Lysis ◽  
Surface Conversion

Sub-Surface Equilibration of Hydrogen with the a-Si:H Network Under Film Growth Conditions

1993 ◽  
Vol 297 ◽  
Author(s):  
ILSIN An ◽  
Y.M. Li ◽  
C.R. Wronski ◽  
R. W. Collins
Keyword(s):  
Hydrogen Diffusion ◽  
Film Growth ◽  
Chemical Vapor ◽  
Growth Conditions ◽  
Emission Rates ◽  
Near Surface ◽  
Kinetic Information ◽  
Reaction Processes ◽  
Surface Conversion

In this study we characterize hydrogen diffusion and reaction processes in the near-surface (top 200 Å) of a-Si:H that lead to network equilibration under standard conditions of plasma-enhanced chemical vapor deposition (PECVD). Real time spectroscopic ellipsometry (SE) is used to provide continuous kinetic information on the near-surface conversion of Si-Si to Si-H bonds during exposure of in situ-prepared films at 250°C to filament-generated atomic H. We have found that for optimum PECVD a-Si:H, the formation of additional Si-H bonds is limited by the capture of H at trapping sites, and the rapid diffusion process (D>10-14 cm2/s) by which H reaches the site is not detected optically. Deep trapping occurs at a rate of ∼10 3 s-1 under our filament conditions, estimated to generate ∼1020 cm-3 mobile H in the near-surface of the film. Finally, more than 1021 cm-3 additional H atoms are trapped with emission rates <2×10-7 s-1, suggesting trap depths >2.0 eV. Shallower traps are also detected at lower concentration.

scholarly journals Conversion of Marine Structures to Calcium Phosphate Materials: Mechanisms of Conversion Using Two Different Phosphate Solutions

2016 ◽  
Vol 696 ◽  
pp. 36-39 ◽  
Author(s):  
Innocent J. Macha ◽  
David Grossin ◽  
Besim Ben-Nissan
Keyword(s):  
Calcium Phosphate ◽  
Metastable Phase ◽  
Crystal Formation ◽  
Ion Exchange Reaction ◽  
Marine Structure ◽  
Acidic Conditions ◽  
Surface Conversion ◽  
Phosphate Solutions ◽  
Diffusional Surface ◽  
Full Conversion

Marine structure, coralline materials were converted to calcium phosphate using two different phosphate solutions. The aim was to study the conversion mechanisms under acidic and basic environment at moderate conditions of temperature. Crystal growth and morphology of converted corals were characterized by XRD and SEM respectively. The results suggested that under acidic conditions (H3PO4), dissolution and precipitation control and direct the crystal formation and morphology in which transition from plate like to rod like hydroxyapatite structure was favoured. Metastable phase such as monetite formed and transformed to HAp during reaction. During the first hour of the dissolution a monetite and hydroxyapatite mixture precipitates and then the full conversion to hydroxyapatite is observed. On the other hand, under basic conditions (NH4)2HPO4, just diffusional surface conversion of the calcium carbonate structure of coralline materials to hydroxyapatite and a very small amount of tri-calcium phosphate is observed. The mechanism can be classified as the solid-state topotactic ion-exchange reaction mechanism.

First Results with a Surface Conversion H[sup −] Ion Source Based on Helicon Wave Mode-Driven Plasma Discharge

2009 ◽  
Author(s):  
O. Tarvainen ◽  
E. G. Geros ◽  
R. Keller ◽  
G. Rouleau ◽  
T. Zaugg ◽  
...  
Keyword(s):  
Plasma Discharge ◽  
Wave Mode ◽  
Ion Source ◽  
Helicon Wave ◽  
First Results ◽  
Surface Conversion

scholarly journals Effect of Low-Pressure Plasma Nitriding with Hollow Cathode Discharge on the Surface Microstructure of WC-Co Cermet

Coatings ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1149
Author(s):  
Jihua Peng ◽  
Yang Xiao ◽  
Yinglong Peng ◽  
Weiqiu Li ◽  
Jiwei Zeng
Keyword(s):  
Hollow Cathode ◽  
Photoelectron Spectroscopy ◽  
Plasma Nitriding ◽  
Chemical Vapor ◽  
Ion Source ◽  
Surface Microstructure ◽  
X Ray ◽  
Bombardment Energy ◽  
Hot Film ◽  
Surface Conversion

WC-Co cermet was plasma-nitrided with the assistance of a hollow cathode ion source at 400 °C under a vacuum of 3–8 Pa. Hot film chemical vapor deposition (HFCVD) of a diamond coating was carried out on the nitrided specimen, without chemical etching. Scanning electronic microscopy, electron probing microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were used to characterize the surface microstructure of the nitride specimens and the coatings. A thin surface conversion layer with a specific structure was formed, in which the primary Co binder was transformed into Co-rich particles. The Co-rich particles consisted of a γ-Co core and a Co4N outer layer. This specific surface conversion layer significantly suppresses the out-diffusion and catalytic graphitization of Co during HFCVD. The existent phase, morphology, and density distribution of Co compounds can be tuned by varying the nitriding parameters, such as gas media, ionization ratio, bombardment energy flux, and nitriding duration.

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