oxygen contamination
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Author(s):  
Shantanu V Madge ◽  
A Lindsay Greer

Abstract Bulk metallic glasses (BMGs), on account of their attractive properties, have now begun to witness a few commercial applications, e.g. in coatings and micro-gears. Additive manufacturing (AM) or 3D printing, although established for crystalline alloys, has only recently been used for synthesising BMG components. The issues arising in 3D printing of BMGs are of current relevance, and this review focuses on the key scientific aspects, namely vitrification (or crystallisation) during printing, mechanical properties of printed glassy alloys and the use of AM in identifying newer BMGs. Available data on crystallisation during printing of a variety of BMGs are analysed in terms of schematic TTT diagrams and the complex interplay between thermal cycles, the presence of quenched-in nuclei in the glass and oxygen contamination in a way that is hoped to be broadly applicable to most alloy systems. Also reviewed are three key factors influencing mechanical properties of printed BMGs, i.e. porosity, crystallinity and oxygen contamination and thereby potential strategies for improvement are suggested. The review concludes with a discussion on the use of AM for combinatorial alloy development aimed at identifying better glass-forming compositions, which may in turn facilitate greater use of AM in manufacturing glassy components with desired properties.


2021 ◽  
Vol 28 (6) ◽  
Author(s):  
Linda I. Vogt ◽  
Julien J. H. Cotelesage ◽  
Charles J. Titus ◽  
Samin Sharifi ◽  
Albert E. Butterfield ◽  
...  

Oxygen K-edge X-ray absorption spectroscopy is used routinely to study a range of solid materials. However, liquid samples are studied less frequently at the oxygen K-edge due to the combined challenges of high-vacuum conditions and oxygen contamination of window materials. A modular sample holder design with a twist-seal sample containment system that provides a simple method to encapsulate liquid samples under high-vacuum conditions is presented. This work shows that pure silicon nitride windows have lower oxygen contamination than both diamond- and silicon-rich nitride windows, that the levels of oxygen contamination are related to the age of the windows, and provides a protocol for minimizing the background oxygen contamination. Acid-washed 100 nm-thick silicon nitride windows were found to give good quality oxygen K-edge data on dilute liquid samples.


Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1186
Author(s):  
Igor Moravcik ◽  
Antonin Kubicek ◽  
Larissa Moravcikova-Gouvea ◽  
Ondrej Adam ◽  
Vaclav Kana ◽  
...  

One of the prevailing problems for materials produced by powder metallurgy is contamination from various sources. This work deals with the influence of process parameters and presence of process control agents (PCA) on the contamination level of materials produced by means of mechanical alloying (MA) technology, densified with spark plasma sintering (SPS). The equiatomic CoCrFeNi high-entropy alloy (HEA) was manufactured by the said methodology. For clear comparison, the 316L austenitic steel powder was milled and densified with identical conditions as a reference material. Both materials were milled in argon and nitrogen atmospheres for various times from 5 to 30 h. Chemical analysis of contamination by carbon, oxygen, and nitrogen within the powder and bulk materials was carried out using combustion analyzers. The microstructural analysis of powders and bulk samples was carried out using scanning electron microscopy (SEM) with focus on contaminant phases. The results show that carbon contamination increases with milling time. It is caused by wear of milling vial and balls made from high-carbon steels. Increase of carbon content within consolidation using SPS was also observed. The oxygen contamination also increases with milling time. It is more pronounced in the CoCrFeNi alloy due to higher oxidation of powder surfaces prior to milling. Milling of powders using nitrogen atmosphere also causes an increase of nitrogen content in both HEA and AISI 316L. The use of PCA (ethanol) during milling even for a short time (30 min) causes significant increase of carbon and oxygen contamination. The ways to decrease contamination are discussed in the paper.


2020 ◽  
Vol 1559 ◽  
pp. 012051
Author(s):  
A. Masi ◽  
C. Alvani ◽  
A. Angrisani Armenio ◽  
M. Bellusci ◽  
G. Celentano ◽  
...  

Author(s):  
Qurat-ul-ain Shamsi ◽  
Saeed Ahmad Buzdar ◽  
Shagufta Jabeen ◽  
Khalid Iqbal

Abstract The emergence of advanced radiotherapy techniques, such as intensity-modulated radiotherapy (IMRT), brachytherapy, conformal radiotherapy, magnetic resonance-guided radiotherapy (MRgRT), stereotactic synchrotron radiotherapy (SSRT) and microbeam radiotherapy (MRT), has increased the importance of the verification of volumetric dose distribution. The verification of dose distribution is usually done by 2D films and 3D gel dosimeters, but PRESAGE® due to its affordability, reproducibility, precision, accuracy, unique dosimetric and physical properties is considered as an effective candidate in providing 3D dose data. PRESAGE® is insensitive to oxygen contamination, machinable and can be molded to a variety of shapes and sizes. It is absorbing rather than scattering light which facilitates high-accuracy readout by optical computed tomography (OP-CT). This review focuses on the feasibility of using PRESAGE® in various complicated radiotherapy techniques by comparing its measured doses with 2D films and treatment planning system (TPS) calculated doses.


2020 ◽  
Vol 164 ◽  
pp. 108302 ◽  
Author(s):  
Martien Duvall Deffo Ayagou ◽  
Gaurav R. Joshi ◽  
Thi Tuyet Mai Tran ◽  
Bernard Tribollet ◽  
Eliane Sutter ◽  
...  

2019 ◽  
Vol 10 ◽  
pp. 20
Author(s):  
X. A. Aslanoglou ◽  
E. Evangelou ◽  
N. Konofaos ◽  
Ch. Dimitriades ◽  
E. Kossionides ◽  
...  

Multi layer structures consisting of TiN — SiO2 — Si layers operating as MOS devices were constructed and tested for their electrical properties. RBS and resonance reaction analysis were performed for the characterisation of the structure of the devices. The results show a correlation between the structure found by RBS and the electrical performance of the devices.


2018 ◽  
Vol 8 (1) ◽  
Author(s):  
Bung Uk Yoo ◽  
Young Jun Lee ◽  
Vladislav Ri ◽  
Seong Hun Lee ◽  
Hayk Nersisyan ◽  
...  

Author(s):  
Yutaro Aoki ◽  
Glenn Harvel ◽  
Toshiharu Sakura ◽  
Takeyoshi Sunagawa

In recent years, use of radiation beams or particle beams have been put to practical use for cancer therapy. In cancer radiation therapy, visualization of radiation patterns is absolutely necessary for precisely evaluating the dose distribution. Therefore, gel type or Fricke type dosimeters [1] are considered useful for visualization. In this study, we developed a new type of gel dosimeter using a doped polyvinyl alcohol (PVA) based solution. This gel uses a red color based chemical reaction that occurs when the active agent is separated. Irradiation of the gel with X-rays is sufficient to break the chemical bonds of the active agent. We irradiated different gel samples with X-rays from a Hitachi MBR-1520R-3 source under different configurations to test the gel performance. We used UV-VIS spectrometry to measure the absorbance of transmitted light through the gel. For the active agent, the absorbance is at a peak wavelength of 490 nm. The amount of absorbance is proportional to the number of interactions with X-rays. We irradiated the gel between 0.5Gy-10Gy with visualization of the gel by photography and spectrometry between each irradiation. The spectrometry was performed using a StellarNet Black Comet system observing the absorbance between 300nm and 600nm. The results show that as the X-ray dose increases, the gel transitions from a clear gel to a light pink gel and then to a red gel. All colors are translucent and allow for the passage of light. The first samples were done in clear plastic containers of 250 ml size. The containers were filled with gel to eliminate air and possible oxygen contamination. The second set of experiments repeated the first study but used metallic coins as X-ray shields. The regions covered by the coins were protected from the dose and remained clear. A sharp edge was observed at the edge of the coin. This implies that the gel does not diffuse and hence can represent a dose distribution as long as it is not mixed. The third samples were placed in disposable cells for measurement of absorbance. The absorbance had a peak in the vicinity wavelength of 490nm. The results confirmed the absorbance to be proportional for increasing applied dose. In summary, a color transition gel was developed for use in detecting irradiation dose from X-rays. This technique has potential application for visualization of dose during medical procedures.


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