Reaction Sintering Mechanism of Submicrometer Silicon Powder in Nitrogen

1992 ◽  
Vol 271 ◽  
Author(s):  
Yoshiyuki Yasutomi ◽  
Masahisa Sobue ◽  
Jiro Kondo
Keyword(s):  
Oxide Film ◽  
Oxide Films ◽  
High Strength ◽  
Silicon Powder ◽  
Reaction Sintering ◽  
Plasma Arc ◽  
Hollow Shell ◽  
Initial Stage ◽  
Near Net Shape ◽  
Higher Temperature

ABSTRACTKnowing the nitridation mechanism of Si is important to obtain near-net-shape high strength reaction bonded ceramics. In this report, comparison of nitridation mechanism of small spherical Si powder produced by plasma arc method and large faceted Si powder, is discussed on the basis of microstructural analyses by SEM and TEM. From the analyses, nitrogen diffuses through the oxide film of Si powder and forms Si3N4 under the oxide films during the initial stage of sintering. At higher temperature, the oxide film transform into fine Si3N4 grains when heated to the 1350°C. The Si3N4 has morphology of hollow shell and a size, which corresponds to that of the original Si particles.

Corrosion Behavior of High-Strength Low-Alloy Steel in High-Temperature Water with Zinc and Aluminum Simultaneous Injection

CORROSION ◽  
10.5006/3545 ◽  
2020 ◽  
Vol 76 (10) ◽  
pp. 918-929
Author(s):  
Shenghan Zhang ◽  
Chenhao Sun ◽  
Yu Tan
Keyword(s):  
Oxide Film ◽  
Corrosion Behavior ◽  
Electrochemical Impedance ◽  
Oxide Films ◽  
High Strength ◽  
Corrosion Current ◽  
Pressurized Water ◽  
Simultaneous Injection ◽  
Primary Water ◽  
Photocurrent Measurement

Oxide films were formed on A508-3 steel in simulated pressurized water reactor (PWR) primary water at the temperature of 561 ± 1 K for 168 h with zinc and/or aluminum injection. Corrosion behaviors of oxide films were analyzed by electrochemical polarization, electrochemical impedance spectroscopy, Mott-Schottky plots, photocurrent measurement, scanning electronic microscopy, and x-ray diffraction. The results showed that zinc and aluminum simultaneous injection technology decreased the corrosion current density, increased the impedance value, made the oxide film more compact, and affected the semiconductor properties of the oxide film. The increase in zinc concentration improved the corrosion resistance to some extent. ZnAl2O4 phase, with extremely low solubility and high stability, had been detected in the oxide film; this substance changed the composition of the oxide film and affected the corrosion behavior of A508-3 steel.

Oxidation Behavior of Cu Nanoparticles and Formation of Hollow Cu2O Spheres

2007 ◽  
Vol 561-565 ◽  
pp. 1703-1706 ◽  
Author(s):  
Ryusuke Nakamura ◽  
Daisuke Tokozakura ◽  
Jung Goo Lee ◽  
Hirotaro Mori ◽  
Hideo Nakajima
Keyword(s):  
Growth Rate ◽  
Oxide Film ◽  
Formation Process ◽  
Oxidation Behavior ◽  
Oxide Films ◽  
Volume Ratio ◽  
Oxidation Time ◽  
Cu Nanoparticles ◽  
Initial Stage

Oxidation behavior of Cu nanoparticles in the formation process of hollow Cu2O spheres was investigated by TEM. The thickness of Cu2O layers on Cu nanoparticles oxidized at 323 K in air was measured as a function of oxidation time. At the initial stage of oxidation until the oxide film with 2.5 nm in thickness is formed, the thickness of oxide films on Cu nanoparticles with the diameter of 10, 20 and 35 nm shows a nearly equal value regardless of diameter of Cu. After the formation of 2.5 nm layer, however, the growth rate of the oxide films on smaller nanoparticles becomes slower than that on larger nanoparticles. This result suggests that the voids formed at the Cu/Cu2O interface prevent Cu atoms from diffusing outward across the interface because the volume ratio of voids to inner Cu in smaller nanoparticles is much larger than that in larger nanoparticles.

Incorporation and Role of Nitrogen During Oxynitridation of Silicon Studied by Photoelectron Spectroscopy

1999 ◽  
Vol 567 ◽  
Author(s):  
Masayuki Suzuki ◽  
Yoji Saito
Keyword(s):  
Photoelectron Spectroscopy ◽  
High Vacuum ◽  
Oxide Films ◽  
Silicon Surfaces ◽  
Gaseous Mixtures ◽  
X Ray ◽  
Initial Stage ◽  
Thermal Stability Of

ABSTRACTWe tried direct oxynitridation of silicon surfaces by remote-plasma-exited nitrogen and oxygen gaseous mixtures at 700°C in a high vacuum. The oxynitrided surfaces were investigated with in-situ X-ray photoelectron spectroscopy. With increase of the oxynitridation time, the surface density of nitrogen gradually increases, but that of oxygen shows nearly saturation behavior after the rapid increase in the initial stage. We also annealed the grown oxynitride and oxide films to investigate the role of the contained nitrogen. The desorption rate of oxygen from the oxynitride films is much less than that from oxide films. We confirmed that nitrogen stabilizes the thermal stability of these oxynitride films.

Plasma Arc Spraying of Cu-Ti-Zr-Ni Amorphous Alloys

2000 ◽  
Author(s):  
D.J. Sordelet ◽  
P. Huang ◽  
M.F. Besser ◽  
E. Lepecheva
Keyword(s):  
Cross Sections ◽  
Metallic Glasses ◽  
High Strength ◽  
Amorphous Structure ◽  
High Fracture Toughness ◽  
Arc Spraying ◽  
Plasma Arc ◽  
High Fracture ◽  
Spray Coatings ◽  
Sprayed Coatings

Abstract A brief feasibility study was performed to produce thermal spray coatings using gas atomized powders of Cu47Ti34-xZr11Ni8Six, where x=0 and 1. These alloys have previously been shown to be capable of forming metallic glasses having thick (1-2 cm) cross sections because they can be cooled from the melt at relatively low cooling rates (e.g., 100-102Ks-1). The properties of these metallic glasses include high strength, high elasticity and high fracture toughness. Amorphous plasma arc sprayed coatings were produced which were close in composition to the starting powders, and exhibited comparable glass transition and crystallization behavior. The amorphous structure of the as-sprayed coatings was used as a source for forming a range of partially devitrified and fully crystallized structures. The average hardness of the coatings increased from around 6 GPa to near 10 GPa as the degree of crystallization increased.

scholarly journals Microstructure And Mechanical Properites Of Welded Advanced Materials For Automotive Applications

2021 ◽  
Author(s):  
Wen Xu
Keyword(s):  
Fiber Laser ◽  
Adhesive Layer ◽  
High Strength ◽  
Advanced Materials ◽  
Automotive Manufacturing ◽  
Bonding Length ◽  
Higher Temperature ◽  
Lower Temperature ◽  
New Generation ◽  
Steel Joints

Growing use of advanced materials (advanced high strength steel DP980 and ultralight-weight magnesium alloys) and innovative joining techniques (new-generation laser welding technology and weld bonding technique) is crucial for better fuel economy and lower CO2 emissions in automotive manufacturing. Microstructures and mechanical properties of fiber laser welded high strength low alloy and DP980 steel joints, weld-bonded Mg/Mg and Mg/steel joints and adhesive-bonded Mg/Mg joints were studied. Tempered martensite and welding concavity were observed in fiber laser welded DP980 joints which reduced fatigue resistance, while both HSLA and DP980 joints showed a superior tensile strength. Weld-bonded Mg/Mg and Mg/steel joints with an adhesive layer were significantly stronger than resistance spot welded Mg/steel joints. Reducing bonding length on weld bonded Mg/Mg joints led to a higher maximum tensile shear stress, both tensile and fatigue strength were slight lower than that of adhesive bonded Mg/Mg joints, while ability of energy absorption was equivalent. The tensile properties reduced at a higher temperature (90°C) but it increased at a lower temperature (-40°C).

scholarly journals A Superhydrophilic Aluminum Surface with Fast Water Evaporation Based on Anodic Alumina Bundle Structures via Anodizing in Pyrophosphoric Acid

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3497 ◽  
Author(s):  
Daiki Nakajima ◽  
Tatsuya Kikuchi ◽  
Taiki Yoshioka ◽  
Hisayoshi Matsushima ◽  
Mikito Ueda ◽  
...  
Keyword(s):  
Contact Angle ◽  
Oxide Film ◽  
High Speed ◽  
Porous Alumina ◽  
Aluminum Surface ◽  
Water Evaporation ◽  
Water Contact ◽  
Initial Stage ◽  
Angle Measuring ◽  
Pyrophosphoric Acid

A superhydrophilic aluminum surface with fast water evaporation based on nanostructured aluminum oxide was fabricated via anodizing in pyrophosphoric acid. Anodizing aluminum in pyrophosphoric acid caused the successive formation of a barrier oxide film, a porous oxide film, pyramidal bundle structures with alumina nanofibers, and completely bent nanofibers. During the water contact angle measurements at 1 s after the water droplet was placed on the anodized surface, the contact angle rapidly decreased to less than 10°, and superhydrophilic behavior with the lowest contact angle measuring 2.0° was exhibited on the surface covered with the pyramidal bundle structures. As the measurement time of the contact angle decreased to 200–33 ms after the water placement, although the contact angle slightly increased in the initial stage due to the formation of porous alumina, at 33 ms after the water placement, the contact angle was 9.8°, indicating that superhydrophilicity with fast water evaporation was successfully obtained on the surface covered with the pyramidal bundle structures. We found that the shape of the pyramidal bundle structures was maintained in water without separation by in situ high-speed atomic force microscopy measurements.

The Deposition of Silicon Oxide Films by LPCVD at Temperatures as Low as 100°C from a New Liquid Source

1992 ◽  
Vol 282 ◽  
Author(s):  
K. Hochberg ◽  
David A. Roberts
Keyword(s):  
Low Temperature ◽  
Silicon Oxide ◽  
Oxide Films ◽  
Temperature Sensitive ◽  
Oxide Layers ◽  
Low Temperature Deposition ◽  
Liquid Source ◽  
Temperature Deposition ◽  
Higher Temperature

ABSTRACTA precursor for the LPCVD of silicon oxide films has been developed that extends the low temperature deposition range to 100°C. The chemical, 1,4 disilabutane (DSB), produces silicon oxide depositions similar to those of the higher temperature silane and diethylsilane (DES) processes. Optimum DSB processes require pressures below 300 mTorr, similar to silane, in contrast to DES pressures above 600 mTorr at 350°C. This results in poorer conformalities than those of DES, but the step coverages are still superior to those from silane oxides. The DSB films are low stress, carbon-free oxide layers that are suitable for temperature-sensitive underlayers and substrates such as photoresist, plastics, GaAs, and HgCdTe.

Identification of the Initial Oxide Films on 18-8 Stainless Steel in High Temperature Water

CORROSION ◽  
1968 ◽  
Vol 24 (10) ◽  
pp. 336-337 ◽  
Author(s):  
T. NAKAYAMA ◽  
Y. OSHIDA
Keyword(s):  
Stainless Steel ◽  
High Temperature ◽  
Oxide Film ◽  
Oxide Films ◽  
Spinel Type ◽  
High Temperature Water ◽  
Temperature Water

Abstract Initial oxide film formed on 18–8 stainless steel in high temperature water at 300 C (572 F) for 1 hour was identical with corundum type crystals like (Cr, Fe)2O3 alone or its coexistence with α-Fe2O3. On the contrary, the oxide film produced by prolonged oxidation (24 hours) consisted mainly of the spinel type crystals containing nickel.

scholarly journals The cause of the colours shown during the oxidation of metallic copper

1927 ◽  
Vol 115 (772) ◽  
pp. 570-588 ◽  
Keyword(s):  
Thin Films ◽  
Oxide Film ◽  
Copper Oxide ◽  
Cupric Oxide ◽  
Metallic Copper ◽  
Oxide Films ◽  
Copper Surface ◽  
Considerable Time ◽  
Pass Through

During the initial stages of the oxidation of a clean metallic copper surface, and before the normal black colour of cupric oxide is finally attained, bright colours appear which pass through the first and second orders of the series of colours observed and tabulated by Newton as characteristic of thin films of air of increasing thickness. These facts have been known for a considerable time, but though the interference colours of thin films of air and those of the oxide film are produced in the same order, grave doubts have existed as to whether interference was the cause of the colours shown by the copper. This problem has been approached from measurements of the intensity of the light reflected from copper oxide films of known thickness, and the results show that interference is actually the cause of the production of the colour, though the result is complicated by the opacity of the film, the dispersion of the oxide, and the scattering of the light complementary to the film colour when the metal is burnished.

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