Oxidation Behavior of Amorphous Nano-Si3N4 Powders

2014 ◽  
Vol 602-603 ◽  
pp. 367-370 ◽  
Author(s):  
Jiang Bo Wen ◽  
Sheng Huang ◽  
Hong Jie Wang
Keyword(s):  
High Temperature ◽  
Partial Pressure ◽  
Mechanical Behavior ◽  
Low Temperatures ◽  
Traditional Method ◽  
Oxidation Behavior ◽  
Oxidation Process ◽  
Composite Ceramic ◽  
Intergranular Phase ◽  
Sintering Additives

The traditional method preparing Si3N4/Si2N2O composite ceramic is to sinter α-Si3N4 powder with additives at relatively high temperatures. But the intergranular phase transformed from the sintering additives can degrade the high-temperature mechanical behavior. Amorphous nanoSi3N4 is used to fabricate Si3N4/Si2N2O composite ceramic by its oxidation and nitridation without sintering additives at low temperatures. Thus, it is essential to study the oxidation behavior and mechanism of amorphous nanoSi3N4. Amorphous nanoSi3N4 powders were oxidized in different atmospheres, at varying temperatures and for various different length of time. The oxidation process and products was analyzed by means of XRD, TGA and FTIR. The results showed that amorphous nanoSi3N4 could be oxidized into SiO2 from 600°C to 1300°C. Below 1300°C, the oxidation became serious as the temperature increased. Besides, the longer the oxidation time and the lager the ratio of O2/N2 partial pressure was, the deeper the oxidation level was. When the temperature was above 1300°C, amorphous nanoSi3N4 was completely oxidized into SiO2.

scholarly journals Effect of ZrB2 addition on the oxidation behavior of Si-SiC-ZrB2 composites exposed at 1500°C in air

2017 ◽  
Vol 16 (1) ◽  
pp. 14-22
Author(s):  
Claudio D’Amico ◽  
Giovanni Bianchi ◽  
Elisa Padovano ◽  
Sara Biamino ◽  
Alberta Aversa ◽  
...  
Keyword(s):  
High Temperature ◽  
Oxidation Behavior ◽  
Oxidation Process ◽  
Oxidation Mechanism ◽  
Industrial Applications ◽  
Reactive Infiltration ◽  
Diffraction Patterns ◽  
Carbide Ceramics ◽  
Sic Composites ◽  
Silicon Carbide Ceramics

Background: Silicon carbide ceramics obtained by reactive infiltration of silicon (SRI) have many industrial applications especially involving severe and high temperature conditions. In this study, the oxidation behavior in air of Si-SiC-ZrB2 systems at a high temperature (1500°C) for dwelling times of up to 48 hours was examined. Methods: The oxidation process was analyzed on the basis of elemental maps and X-ray diffraction patterns taken, respectively, on the core and on the surface of the specimens, together with weight gains and the average thicknesses of the resulting scale. Further, flexural strength at room temperature was examined as a function of different oxidation times. Results: The main chemical reactions and phase transformations involved in the oxidation process are reported. Several oxides were detected on the surface: zirconia, silica, zircon and 3-zirconium monoxide. All of the samples showed a parabolic oxidation kinetics, suggesting that the controlling mechanism was the diffusion; however, even after 48 hours, the oxidation process was not finished – indeed, all of the samples continued to gain weight. Conclusions: The oxidation of Si-SiC-ZrB2 material produced via SRI was slower compared with previously investigated ZrB2-SiC composites processed with a different techniques and tested in similar conditions. The oxidation mechanism was found to be consistent with the convection cells model.

Effect of Mo on the Oxidation Behavior of NiTiAl Alloy

2007 ◽  
Vol 546-549 ◽  
pp. 1481-1484
Author(s):  
Jian Xu ◽  
Xin Qing Zhao ◽  
Sheng Kai Gong
Keyword(s):  
High Temperature ◽  
Oxide Scale ◽  
Oxide Layer ◽  
Oxygen Diffusion ◽  
Oxidation Behavior ◽  
Oxidation Process ◽  
Oxide Scales ◽  
Cross Sectional ◽  
Oxidation Layer ◽  
Poor Adhesion

The effect of Mo on the oxidation behavior of TiNiAl at 1073K has been investigated. It is found that 1at.% Mo addition can increase the diffusion of Al in the alloys and promote the formation of dense and continuous Al-rich oxide layer. Therefore the oxygen diffusion can be effectively impeded and the oxidation behavior of TiNiAl is improved. The observation of the cross-sectional oxidation layer showed that beneath the top oxide scale a Mo-rich oxide layer formed. Because the oxide of Mo is volatile at high temperature, voids formed in the oxide scales during the oxidation process. 3at.% Mo addition could cause cracks between the oxide scale and the substrate, resulting in poor adhesion of the oxide scale to the substrate.

Hot Corrosion Behavior of NiCoCrAlYSiHf Coating Deposited by Arc Ion Plating

2012 ◽  
Vol 472-475 ◽  
pp. 395-399
Author(s):  
Jia Hui Qu ◽  
Cean Guo ◽  
Jian Zhang
Keyword(s):  
High Temperature ◽  
Hot Corrosion ◽  
High Temperature Oxidation ◽  
Oxidation Behavior ◽  
Oxidation Process ◽  
Isothermal Oxidation ◽  
Temperature Oxidation ◽  
Arc Ion Plating ◽  
Ion Plating ◽  
Α Al2o3

Abstract: NiCoCrAlYSiHf coatings have been prepared by arc ion plating (AIP) on CrNi3MoVA steel ,which their microstructure and isothermal oxidation behavior at 950°C studied using SRD,SEM and EDAX. The results indicate that NiCoCrAlYSiHf coatings substantially increase the high-temperature oxidation resistance of CrNi3MoVA steel and the oxidation process was retarded mainly by the presence of α-Al2O3 oxide scale on the coating. Meanwhile, the major diffusion occured between the substrate element Fe and the coating element Co while Cr mainly distributed in the coating.

Crystal Growth of Aluminum Magnesium Borides from Al-Mg-B Ternary System Solutions and Properties of the Crystals

2004 ◽  
Vol 449-452 ◽  
pp. 365-368 ◽  
Author(s):  
Shigeru Okada ◽  
Kunio Kudou ◽  
T. Mori ◽  
Takaaki Shishido ◽  
I. Higashi ◽  
...  
Keyword(s):  
Crystal Growth ◽  
High Temperature ◽  
Ternary System ◽  
Low Temperatures ◽  
Oxidation Process ◽  
Anomalous Behavior ◽  
Optimum Conditions ◽  
Metallic Luster ◽  
Aluminum Metal ◽  
Metal Flux

Single crystals of AlMgB14and AlMgB22were grown from a high-temperature aluminum metal flux in an Ar atmosphere. The optimum conditions for growing AlMgB22and AlMgB14were established using the starting mixtures of B/Mg=0.5-1.0 and B/Mg=2.0-6.0. The AlMgB14and AlMgB22crystals obtained have well-developed {001} and {100} faces, and were black with a metallic luster. The maximum dimensions of these crystals were about 5.2 mm and 4.6 mm, respectively. The values of micro-Vickers hardness of the AlMgB14and AlMgB22crystals are in the ranges of 23.9±0.6-27.6±0.6 GPa. The oxidation process of AlMgB14and AlMgB22crystals were studied up to 1473 K by TG-DTA method. The susceptibility of AlMgB14 with an increase at low temperatures does not show any particular features, being indicative of a paramagnetic contribution, which is likely due to impurities. The susceptibility of the AlMgB22sample shows no apparent contribution from impurities and also does not have any anomalous behavior.

Application of TEM to Deformation, Wear, and Fracture of Ceramics

1974 ◽  
Vol 32 ◽  
pp. 472-473
Author(s):  
B. J. Hockey
Keyword(s):  
Wear Resistance ◽  
High Temperature ◽  
Mechanical Behavior ◽  
Brittle Materials ◽  
High Temperature Strength ◽  
Wide Range ◽  
Corrosive Environments ◽  
Further Development

Ceramics, such as Al2O3 and SiC have numerous current and potential uses in applications where high temperature strength, hardness, and wear resistance are required often in corrosive environments. These materials are, however, highly anisotropic and brittle, so that their mechanical behavior is often unpredictable. The further development of these materials will require a better understanding of the basic mechanisms controlling deformation, wear, and fracture.The purpose of this talk is to describe applications of TEM to the study of the deformation, wear, and fracture of Al2O3. Similar studies are currently being conducted on SiC and the techniques involved should be applicable to a wide range of hard, brittle materials.

Electron Microscopy of Silicon Nitride-Based Ceramics

1991 ◽  
Vol 49 ◽  
pp. 926-927
Author(s):  
Gareth Thomas
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
Silicon Nitride ◽  
World Wide ◽  
Sintering Temperature ◽  
Liquid Phase Sintering ◽  
High Temperature Strength ◽  
Sintering Additives ◽  
Glass Forming ◽  
Dense Product

Silicon nitride and silicon nitride based-ceramics are now well known for their potential as hightemperature structural materials, e.g. in engines. However, as is the case for many ceramics, in order to produce a dense product, sintering additives are utilized which allow liquid-phase sintering to occur; but upon cooling from the sintering temperature residual intergranular phases are formed which can be deleterious to high-temperature strength and oxidation resistance, especially if these phases are nonviscous glasses. Many oxide sintering additives have been utilized in processing attempts world-wide to produce dense creep resistant components using Si3N4 but the problem of controlling intergranular phases requires an understanding of the glass forming and subsequent glass-crystalline transformations that can occur at the grain boundaries.

Mechanical Behavior of High Temperature Composites

1994 ◽  
Author(s):  
Terry R. Barnett ◽  
H. S. Starrett
Keyword(s):  
High Temperature ◽  
Mechanical Behavior
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