scholarly journals Influence of Oxygen Admixture on Plasma Nitrocarburizing Process and Monitoring of an Active Screen Plasma Treatment

2021 ◽  
Vol 11 (21) ◽  
pp. 9918
Author(s):  
Jan Böcker ◽  
Anke Dalke ◽  
Alexander Puth ◽  
Christian Schimpf ◽  
Jürgen Röpcke ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Nitrogen Concentration ◽  
Compound Layer ◽  
Gas Composition ◽  
Reaction Products ◽  
Process Gas ◽  
Major Reaction ◽  
Oxygen Addition ◽  
Plasma Nitrocarburizing ◽  
Active Screen

The effect of a controlled oxygen admixture to a plasma nitrocarburizing process using active screen technology and an active screen made of carbon was investigated to control the carburizing potential within the plasma-assisted process. Laser absorption spectroscopy was used to determine the resulting process gas composition at different levels of oxygen admixture using O2 and CO2, respectively, as well as the long-term trends of the concentration of major reaction products over the duration of a material treatment of ARMCO® iron. The short-term studies of the resulting process gas composition, as a function of oxygen addition to the process feed gases N2 and H2, showed that a stepwise increase in oxygen addition led to the formation of oxygen-containing species, such as CO, CO2, and H2O, and to a significant decrease in the concentrations of hydrocarbons and HCN. Despite increased oxygen concentration within the process gas, no oxygen enrichment was observed in the compound layer of ARMCO® iron; however, the diffusion depth of nitrogen and carbon increased significantly. Increasing the local nitrogen concentration changed the stoichiometry of the ε-Fe3(N,C)1+x phase in the compound layer and opens up additional degrees of freedom for improved process control.

scholarly journals Influence of the Active Screen Plasma Power during Afterglow Nitrocarburizing on the Surface Modification of AISI 316L

Coatings ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1112
Author(s):  
Jan Böcker ◽  
Alexander Puth ◽  
Anke Dalke ◽  
Jürgen Röpcke ◽  
Jean-Pierre H. van Helden ◽  
...  
Keyword(s):  
Surface Modification ◽  
Surface Hardness ◽  
Additional Parameter ◽  
Gas Composition ◽  
Aisi 316L ◽  
Bias Power ◽  
Process Gas ◽  
316L Steel ◽  
Plasma Nitrocarburizing ◽  
Active Screen

Active screen plasma nitrocarburizing (ASPNC) increases the surface hardness and lifetime of austenitic stainless steel without deteriorating its corrosion resistance. Using an active screen made of carbon opens up new technological possibilities that have not been exploited to date. In this study, the effect of screen power variation without bias application on resulting concentrations of process gas species and surface modification of AISI 316L steel was studied. The concentrations of gas species (e.g., HCN, NH3, CH4, C2H2) were measured as functions of the active screen power and the feed gas composition at constant temperature using in situ infrared laser absorption spectroscopy. At constant precursor gas composition, the decrease in active screen power led to a decrease in both the concentrations of the detected molecules and the diffusion depths of nitrogen and carbon. Depending on the gas mixture, a threshold of the active screen power was found above which no changes in the expanded austenite layer thickness were measured. The use of a heating independent of the screen power offers an additional parameter for optimizing the ASPNC process in addition to changes in the feed gas composition and the bias power. In this way, an advanced process control can be established.

A Novel Approach of Plasma Nitrocarburizing Using a Solid Carbon Active Screen – a Proof of Concept

2017 ◽  
Vol 72 (5) ◽  
pp. 254-259 ◽  
Author(s):  
I. Burlacov ◽  
S. Hamann ◽  
H.-J. Spies ◽  
A. Dalke ◽  
J. Röpcke ◽  
...  
Keyword(s):  
Solid Carbon ◽  
Proof Of Concept ◽  
Novel Approach ◽  
Plasma Nitrocarburizing ◽  
Active Screen

scholarly journals Study of the Synchrotron Photoionization Oxidation of Alpha-Angelica Lactone (AAL) Initiated by O(3P) at 298, 550, and 700 K

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 4070
Author(s):  
Golbon Rezaei ◽  
Giovanni Meloni
Keyword(s):  
Atomic Oxygen ◽  
Fossil Fuels ◽  
Reaction Products ◽  
Photoionization Mass Spectrometry ◽  
Natural Substances ◽  
Primary Products ◽  
Major Reaction ◽  
Angelica Lactone ◽  
Significant Attention

In recent years, biofuels have been receiving significant attention because of their potential for decreasing carbon emissions and providing a long-term renewable solution to unsustainable fossil fuels. Currently, lactones are some of the alternatives being produced. Many lactones occur in a range of natural substances and have many advantages over bioethanol. In this study, the oxidation of alpha-angelica lactone initiated by ground-state atomic oxygen, O(3P), was studied at 298, 550, and 700 K using synchrotron radiation coupled with multiplexed photoionization mass spectrometry at the Lawrence Berkeley National Lab (LBNL). Photoionization spectra and kinetic time traces were measured to identify the primary products. Ketene, acetaldehyde, methyl vinyl ketone, methylglyoxal, dimethyl glyoxal, and 5-methyl-2,4-furandione were characterized as major reaction products, with ketene being the most abundant at all three temperatures. Possible reaction pathways for the formation of the observed primary products were computed using the CBS–QB3 composite method.

scholarly journals Oxidation of indolic bases by cytochrome P450 and ferrous picolinate

1997 ◽  
Vol 13 (2) ◽  
pp. 163-174
Author(s):  
K. Jankowski ◽  
M. Delaforge ◽  
M. Jaouen ◽  
H. Virelizier
Keyword(s):  
Cytochrome P450 ◽  
Reaction Products ◽  
Major Reaction ◽  
Hepatic Cytochrome

Oxidations performed on four indolic bases,β-carboline1, ibogaine2, reserpine3and ajmaline4, by hepatic cytochrome P450 (Cyt. P450) and ferrous picolinate (Fe(PA)2), lead to alicyclic hydroxylation as major reaction products.

GAS–LIQUID CHROMATOGRAPHY OF TERPENES: PART II. THE DEHYDRATION PRODUCTS OF α-TERPINEOL

1961 ◽  
Vol 39 (1) ◽  
pp. 1-12 ◽  
Author(s):  
E. Von Rudloff
Keyword(s):  
Liquid Chromatography ◽  
Oxalic Acid ◽  
Complex Mixture ◽  
Reaction Times ◽  
Gas Liquid Chromatography ◽  
Minor Components ◽  
Reaction Products ◽  
The Third ◽  
Major Reaction ◽  
Trace Constituents

The complex mixture of terpenes obtained on dehydrating α-terpineol with aqueous oxalic acid was almost completely separated by gas–liquid chromatography (GLC), using rapeseed oil as a new liquid phase. Terpinolene, dipentene, α- and γ-terpinene, Δ2,4(8)-p-menthadiene, and 1,8-cineole were identified as the major reaction products; three minor and seven trace constituents were also detected. One of the minor components was p-cymene, one an oxide, and the third an unidentified hydrocarbon. The yield of these components after different reaction times was determined by GLC. The initial dehydration gives terpinolene and dipentene in the ratio of approximately 2:1. Terpinolene is isomerized to α- and γ-terpinene, Δ2,4,(8)-p-menthadiene, and the unidentified hydrocarbon, but not to dipentene. 1,8-Cineole and the other oxide are formed in a reversible reaction. Dehydration of α-terpineol with several other acidic reagents yielded mixtures of products similar to that obtained with aqueous oxalic acid. With acetic acid or acetic anhydride, however, dipentene was formed preferentially and this reaction appears to proceed via the derived acetate.

Methods of Improving Glow-Discharge-Deposited a-Si1−xGex:H

1991 ◽  
Vol 219 ◽  
Author(s):  
Y. S. Tsuo ◽  
Y. Xu ◽  
E. A. Ramsay ◽  
R. S. Crandall ◽  
S. J. Salomon ◽  
...  
Keyword(s):  
Material Processing ◽  
Glow Discharge ◽  
Substrate Temperature ◽  
Gas Mixtures ◽  
Gas Composition ◽  
Processing Methods ◽  
Helium 4 ◽  
Process Gas

ABSTRACTWe have studied methods of improving glow-discharge-deposited a-Si1−x Gex :H alloys deposited using silane and germane gas mixtures. Material processing methods studied include (1) varying the substrate temperature from 170° to 280°C, (2) varying the process gas composition and pressure, (3) dilution of the feed gas by hydrogen, argon, or helium, (4) enhancing etching during deposition by adding small amounts of XeF2 vapor into the process gas, and (5) postdeposition annealing and/or hydrogenation.

Investigation of Compound Layer Structures after Nitriding and Nitrocarburizing of Quenched and Tempered Steels

2021 ◽  
Vol 76 (3) ◽  
pp. 219-236
Author(s):  
M. Sommer ◽  
S. Hoja ◽  
M. Steinbacher ◽  
R. Fechte-Heinen
Keyword(s):  
Surface Layer ◽  
Phase Composition ◽  
Bulk Material ◽  
Fatigue Behavior ◽  
Nitrogen Concentration ◽  
Maximum Level ◽  
Compound Layer ◽  
X Ray Diffraction ◽  
Treatment Processes ◽  
Layer Structures

Abstract A compound layer is formed by ingress of nitrogen from an external nitrogen source into the surface layer and the formation of nitrides when the solubility of nitrogen in the bulk material is exceeded. In the surface layer, where the nitrogen concentration is at its maximum level, the nitrides form a closed layer. The compound layer continues to contain alloy nitrides which have formed from the carbides and other precipitates from the bulk material. The properties of the compound layer have a decisive influence on the wear and fatigue behavior of the loaded surfaces. The current investigations deal with the extensive characterization of compound layers that have been produced in heat treatment processes with the aim of producing stress-resistant nitriding layers. The commonly used nitriding and quench and temper (Q&T) steels 31CrMoV9 and 42CrMo4 served as examination material. The structure of the compound layers was varied within the nitriding trials regarding the phase composition, porosity and layer thicknesses. The phase composition of the compound layers was determined by special etching, scanning electron microscopy (SEM), X-ray diffraction and GDOES.

scholarly journals Structural Characterization of Fine γ′-Fe4N Nitrides Formed by Active Screen Plasma Nitriding

Metals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1656
Author(s):  
Jaroslaw Jan Jasinski ◽  
Lukasz Kurpaska ◽  
Tadeusz Fraczek ◽  
Malgorzata Lubas ◽  
Maciej Sitarz
Keyword(s):  
Electron Microscopy ◽  
Surface Layer ◽  
Structural Characterization ◽  
Plasma Nitriding ◽  
Nitrogen Concentration ◽  
Grazing Incidence ◽  
Model Material ◽  
Active Screen Plasma Nitriding ◽  
Active Screen

The paper presents the structural characterization of γ′-Fe4N nitrides produced by active screen plasma nitriding (ASPN) processes. Experiments were performed on the Fe-Armco model material at 693, 773, and 853 K for 6 h. Investigation of the properties of the substrate was realized using scanning electron microscopy (SEM, SEM–EBSD/Kikuchi lines), energy-filtered transmission electron microscopy (TEM-EFTEM), X-ray diffraction (GID, grazing incidence diffraction, micro-XRD), and secondary ion mass spectroscopy (SIMS). Results have confirmed that the γ′-Fe4N nitrides’ structure and morphology depend considerably on the nitriding process’s plasma conditions and cooling rate. In addition to that, γ′-Fe4N nitrides’ formation can be correlated with the surface layer saturation mechanism and recombination effect. It has been shown that the γ′-Fe4N structure depends considerably on several phenomena that occur in the diffusive layer (e.g., top layer decomposition, nitrogen, and carbon atoms’ migration). Our research proves that the nitrogen concentration gradient is a driving force of nitrogen migration atoms during the recombination of γ′-Fe4N nitrides. Finally, realized processes have allowed us to optimize active screen plasma nitriding to produce a surface layer of fine nitrides.

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