Laminated Si3N4/SiC Composites with Self-Sealed Structure

Self-sealed laminar Si3N4/SiC composites, with different cross-section shapes and various thickness ratios of Si3N4 to SiC, have been fabricated. The laminates consist alternately of thicker Si3N4 layers ranging from 100 to 500µm and thinner SiC layers ranging from 6 to 15µm after sintering. Preliminary results indicate that SiC thin layer forms during sintering according to the reaction Si3N4 + 3C ® 3SiC + 2N2, which is confirmed by X-ray diffraction. An excellent physical and chemical compatibility between Si3N4 and SiC layers was observed. The self-sealed Si3N4/SiC composites not only demonstrate a superb resistance to delamination, usually associated with the plate-form ones, but also show a high damage-tolerance behavior. The laminated Si3N4/ SiC composite with a layer thickness ratio of Si3N4 to SiC of approximately 40 gives the highest value of work of fracture (WOF) of approximately 406 kJ/m3, whereas the highest toughness of 21 MPam1/2 was achieved at the layer thickness ratio of 50. The effects of the relative thickness of Si3N4 and SiC layers on the densification of the laminates are examined and fracture behavior and microstructure of the Si3N4/SiC laminates discussed.

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Structural characterization and thermal stability of W/Si multilayers

Journal of Materials Research ◽

10.1557/jmr.1993.2600 ◽

1993 ◽

Vol 8 (10) ◽

pp. 2600-2607 ◽

Cited By ~ 12

Author(s):

M. Brunel ◽

S. Enzo ◽

M. Jergel ◽

S. Luby ◽

E. Majkova ◽

...

Keyword(s):

Thermal Stability ◽

Layer Thickness ◽

Thickness Ratio ◽

X Ray Diffraction ◽

Cross Sectional ◽

X Ray ◽

Layer Thickness Ratio ◽

Transmission Electron ◽

Thermal Stability Of ◽

Beam Deposition

Tungsten/silicon multilayers with tungsten layers of a thickness of 1–2 nm were prepared by means of electron beam deposition. Their structure and thermal stability under rapid thermal annealing were investigated by a combination of x-ray diffraction techniques and cross-sectional transmission electron microscopy. The crystallization behavior was found to depend on the interdiffusion and mixing at the tungsten/silicon interfaces during deposition as well as during annealing. The as-deposited tungsten/silicon multilayers were amorphous and remained stable after annealing at 250 °C/40 s. Interdiffusion and crystallization occurred after annealing all samples from 500 °C/40 s up to 1000 °C/20 s. By performing the same heat treatment in the tungsten/silicon multilayers, the formation of body-centered cubic W was observed with a layer thickness ratio δW/δsi = 1, whereas tetragonal WSi2 was detected in tungsten/silicon multilayers with a layer thickness ratio of δw/δsi ∼0.25. This dependence of the crystallization products on the layer thickness ratio δw/δsi originates from the different phenomena of interdiffusion and mixing at the tungsten/silicon interfaces. The possible formation of bcc tungsten as a first stage of crystallization of tungsten-silicon amorphous phase, rich in tungsten, is discussed.

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High-efficiency, flexibility and lead-free X-ray shielding multilayered polymer composites: layered structure design and shielding mechanism

Scientific Reports ◽

10.1038/s41598-021-83031-4 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Zefeng Li ◽

Wei Zhou ◽

Xianlong Zhang ◽

Yue Gao ◽

Shaoyun Guo

Keyword(s):

Polymer Composites ◽

Layer Thickness ◽

High Efficiency ◽

Thickness Ratio ◽

Lead Free ◽

X Rays ◽

X Ray ◽

Layer Thickness Ratio ◽

Number Of Layers ◽

Ethylene Octene Copolymer

AbstractTo overcome the severe toxicity and blind absorption zone of conventional lead-based shielding materials for X-rays in the 70–90 keV range, the lead-free multilayered polymer composites were designed and fabricated. The effects of the direction of incidence of the X-rays and number of layers as well as layer thickness ratio of the (tungsten/ethylene-octene copolymer)/(bismuth/ethylene-octene copolymer) layered composites on their shielding efficiency were studied systematically. Compared to the traditional polymer blending, the multilayered polymer composites exhibited the improved photon attenuation. The multilayered polymer composites (layer thickness ratio was 3:7) with 6 layers had the best X-ray shielding ability. Moreover, the X-ray shielding provided by the multi-layered interfaces and the multiple complementary effect of the absorption within the multilayered structure were firstly proposed based on computer simulations. The multilayered structural design effectively weakened the probability of the X-ray penetration. Therefore, the X-ray shielding capability can be effectively enhanced through increasing number of layers and the synergistic effect of multi-layered interfaces. The experimental results of this study can serve as guidelines for the fabrication of flexibility, lead-free, lightweight and high-efficiency X-ray shielding materials.

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High-Efficiency, Flexibility and Lead-Free X-ray Shielding Multilayered Polymer Composites

10.21203/rs.3.rs-116944/v1 ◽

2020 ◽

Author(s):

Zefeng Li ◽

Wei Zhou ◽

Xianlong Zhang ◽

Yue Gao ◽

Shaoyun Guo

Keyword(s):

Polymer Composites ◽

Layer Thickness ◽

High Efficiency ◽

Thickness Ratio ◽

Lead Free ◽

X Rays ◽

X Ray ◽

Layer Thickness Ratio ◽

Number Of Layers ◽

Ethylene Octene Copolymer

Abstract To overcome the severe toxicity and blind absorption zone of conventional lead-based shielding materials for X-rays in the 70-90 keV range, the lead-free multilayered polymer composites were designed and fabricated. The effects of the direction of incidence of the X-rays and number of layers as well as layer thickness ratio of the (tungsten/ethylene-octene copolymer)/(bismuth/ethylene-octene copolymer) layered composites on their shielding efficiency were studied systematically. Compared to the traditional polymer blending, the multilayered polymer composites exhibited the improved photon attenuation. The multilayered polymer composites (layer thickness ratio was 3:7) with 6 layers had the best X-ray shielding ability. Moreover, the X-ray shielding provided by the multi-layered interfaces and the multiple complementary effect of the absorption within the multilayered structure were firstly proposed based on computer simulations. The multilayered structural design effectively weakened the probability of the X-ray penetration. Therefore, the X-ray shielding capability can be effectively enhanced through increasing number of layers and the synergistic effect of multi-layered interfaces. The experimental results of this study can serve as guidelines for the fabrication of flexibility, lead-free, lightweight and high-efficiency X-ray shielding materials.

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Irregular Electrodeposition of Cu-Sn Alloy Coatings in [EMIM]Cl Outside the Glove Box with Large Layer Thickness

Coatings ◽

10.3390/coatings11030310 ◽

2021 ◽

Vol 11 (3) ◽

pp. 310

Author(s):

Lars Lehmann ◽

Dominik Höhlich ◽

Thomas Mehner ◽

Thomas Lampke

Keyword(s):

Layer Thickness ◽

Alloy System ◽

Liquid Solution ◽

Complexing Agents ◽

X Ray Diffraction ◽

X Ray ◽

Argon Stream ◽

Ionic Liquid Solution ◽

The Relationship ◽

Layer Composition

Thick Cu−Sn alloy layers were produced in an [EMIM]Cl ionic-liquid solution from CuCl2 and SnCl2 in different ratios. All work, including the electrodeposition, took place outside the glovebox with a continuous argon stream over the electrolyte at 95 °C. The layer composition and layer thickness can be adjusted by the variation of the metal-salts content in the electrolyte. A layer with a thickness of up to 15 µm and a copper content of up to ωCu = 0.86 was obtained. The phase composition was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray fluorescence (XRF). Furthermore, it was found that the relationship between the alloy composition and the concentration of the ions in the electrolyte is described as an irregular alloy system as according to Brenner. Brenner described such systems only for aqueous electrolytes containing complexing agents such as cyanide. In this work, it was confirmed that irregular alloy depositions also occur in [EMIM]Cl.

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Monitoring of Fluctuations in the Physical and Chemical Properties of a High-Calcium Fly Ash

MRS Proceedings ◽

10.1557/proc-113-107 ◽

1987 ◽

Vol 113 ◽

Cited By ~ 8

Author(s):

Scott Schlorholtz ◽

Ken Bergeson ◽

Turgut Demirel

Keyword(s):

Fly Ash ◽

Chemical Properties ◽

Operating Conditions ◽

Physical And Chemical Properties ◽

X Ray Diffraction ◽

X Ray ◽

Morphological Studies ◽

High Calcium ◽

Physical And Chemical ◽

And Chemical Properties

ABSTRACTThe physical and chemical properties of fly ash produced at Ottumwa Generating Station have been monitored since April, 1985. The fly ash is produced from burning a low sulfur, sub-bituminous coal obtained from the Powder River Basin near Gillette, Wyoming. One-hundred and sixty samples of fly ash were obtained during the two year period. All of the samples were subjected to physical testing as specified by ASTM C 311. About one-hundred of the samples were also subjected to a series of tests designed to monitor the self-cementing properties of the fly ash. Many of the fly ash samples were subjected to x-ray diffraction and fluorescence analysis to define the mineralogical and chemical composition of the bulk fly ash as a function of sampling date. Hydration products in selected hardened fly ash pastes, were studied by x-ray diffraction and scanning electron microscopy. The studies indicated that power plant operating conditions influenced the compressive strength of the fly ash paste specimens. Mineralogical and morphological studies of the fly ash pastes indicated that stratlingite formation occurred in the highstrength specimens, while ettringite was the major hydration product evident in the low-strength specimens.

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Fabrication of 239/238Pu-Zirconolite Ceramic Pellets by Natural Sintering

MRS Proceedings ◽

10.1557/proc-807-267 ◽

2003 ◽

Vol 807 ◽

Cited By ~ 2

Author(s):

T. Advocat ◽

F. Jorion ◽

T. Marcillat ◽

G. Leturcq ◽

X. Deschanels ◽

...

Keyword(s):

Grain Size ◽

Radioactive Waste ◽

Nuclear Waste ◽

Chemical Stability ◽

Minor Actinides ◽

Loading Capacity ◽

X Ray Diffraction ◽

X Ray ◽

Physical And Chemical ◽

Inorganic Matrix

ABSTRACTZirconolite is a potential inorganic matrix that is currently investigated in France, in the framework of the 1991 radioactive waste management law, with a view to provide durable containment of the trivalent and tetravalent minor actinides like neptunium, curium, americium and small quantities of unrecyclable plutonium separated from other nuclear waste. To confirm the actinide loading capacity of the zirconolite calcium site and to study the physical and chemical stability of this type of ceramic when subjected to alpha self-irradiation, zirconolite ceramic pellets were fabricated with 10 wt% plutonium oxide (isotope 239 or 238). The 55 pellets are dense (> 93.3% of the theoretical density on average) and free of cracks. They are characterized by a grain size of between 10 and 20 micrometers. X-ray diffraction analyses confirmed the presence of the zirconolite 2M crystalline structure.

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Macroscopic Fracture Behaviour of CrN Hard Coatings Evaluated by X-Ray Diffraction Coupled with Four-Point Bending

Materials Science Forum ◽

10.4028/www.scientific.net/msf.768-769.272 ◽

2013 ◽

Vol 768-769 ◽

pp. 272-279

Author(s):

Mario Stefenelli ◽

Angelika Riedl ◽

Juraj Todt ◽

Matthias Bartosik ◽

Rostislav Daniel ◽

...

Keyword(s):

Fracture Stress ◽

Fracture Behavior ◽

Fracture Behaviour ◽

Hard Coatings ◽

Relevant Parameter ◽

X Ray Diffraction ◽

X Ray ◽

Four Point Bending ◽

Macroscopic Fracture ◽

Crn Coatings

Fracture behavior of hard nanocrystalline coatings decisively influences the lifetime and performance of coated tools. In this work, residual stresses in as-deposited and annealed CrN coatings deposited at 350 °C using bias voltages of −40 V and −120 V were evaluated using synchrotron X-ray diffraction coupled with four-point bending. The stress development during the bending experiments was used to analyse fracture properties of the coatings. The results indicate that an annealing at 550 °C does not deteriorate the fracture behavior of the coatings prepared using −40 V bias. In the case of −120 V bias coatings, the residual stress relaxation after the thermal treatment is accompanied by a fracture strain decrease and a fracture stress increase. The as-deposited and annealed CrN coatings deposited using −120 V bias exhibit significantly large fracture strains in comparison with −40 V samples. Finally the results document that the fracture stress may not be the only relevant parameter when comparing different coating systems. Also the strain at fracture can be considered as significant indicator of the coating fracture response. Methodologically, the results indicate that in-situ X-ray diffraction coupled with four point bending can be effectively used to evaluate macroscopic fracture behaviour of hard coatings.

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