Transient Viscous Phase Reaction Sintered (Tvprs) Silicon Oxynitride Ceramics.

1992 ◽  
Vol 287 ◽  
Author(s):  
Kevin P. Plucknett ◽  
David S. Wilkinson
Keyword(s):  
Weight Loss ◽  
Silicon Nitride ◽  
Nitrogen Atmosphere ◽  
Silicon Oxynitride ◽  
Phase Reaction ◽  
Reaction Sintering ◽  
Sintering Aids ◽  
Powder Bed ◽  
Sintering Conditions ◽  
Composite Silicon

High density silicon oxynitride ceramics were fabricated by reaction-sintering a mixtureof silicon nitride and silica without the use of sintering aids. Precursor silicon nitride compacts were prepared by conventional means after which they were subjected to a lowtemperature oxidation heattreatment (∼1000ºC) producing a composite silicon nitride/silica compact. Oxidized compacts were then reaction-sintered in a nitrogen atmosphere at temperatures between 1400 and 1800ºC using a range of protective ‘powder-bed’ compositions. A ‘powder-bed’ comprising a mixture of boron nitride, silicon nitride and silica was found to be most effective in preventing decomposition and subsequent weight loss. Nearly complete reactive transformation to silicon oxynitride was observed under optimised sintering conditions.

Heterogeneous Formation of Oriented Silicon Oxynitride on α-Si3N4 Seed Crystals : Habits And Radiation Stability

1999 ◽  
Vol 5 (S2) ◽  
pp. 778-779
Author(s):  
R.W Carpenter ◽  
W Braue ◽  
M.J. Kim
Keyword(s):  
Silicon Nitride ◽  
Heterogeneous Nucleation ◽  
Radiation Stability ◽  
Silicon Oxynitride ◽  
Minor Constituent ◽  
Sintering Aids ◽  
Sintering Aid ◽  
Nucleation Sites ◽  
Heterogeneous Formation ◽  
A Minor

Lath-like silicon oxynitride crystals have often been observed in the microstructure of silicon nitride based ceramics after processing. They are usually located in glassy regions which are siliceous solidified sintering aid liquid, and usually contain a small (∼100nm) a-Si3N4 crystal. These nitride crystals are considered to be seeds, incompletely dissolved in the melt, that are heterogeneous nucleation sites for the oxynitride crystals. We present here the first observations of morphological and crystallographic habits between the seed nanocrystals and the host oxynitride laths.Fig. 1 shows a typical oxynitride lath containing a nitride seed crystal. The lath is surrounded by glass and ß-Si3N4 particles, and a small cristobalite particle (a minor constituent). This microstructure is from an Si02-Si3N4 ceramic processed with Al2O3 sintering aid. The same oxynitride lath/seed structures were observed when other sintering aids (eg. Y2O3, MgO, ZrO2) were used, so they are independent of sintering aid.

Mechanical and wear properties of Si3N4–W composites using tungsten boride powder

2003 ◽  
Vol 18 (9) ◽  
pp. 2262-2267 ◽  
Author(s):  
Hideki Hyuga ◽  
Mark I. Jones ◽  
Kiyoshi Hirao ◽  
Yukihiko Yamauchi
Keyword(s):  
Silicon Nitride ◽  
Sliding Wear ◽  
Nitrogen Atmosphere ◽  
Hot Press ◽  
Wear Properties ◽  
Tungsten Boride ◽  
Sintering Conditions ◽  
Hot Press Sintering ◽  
Boride Powder ◽  
Composite Disk

Silicon nitride–tungsten (Si3N4–W) composites were fabricated by reduction of tungsten boride under hot-press sintering in a nitrogen atmosphere. The fabricated composite consisted of mainly β–Si3N4 and W. The Si3N4 matrix grains were composed of an elongated and bimodal structure similar to conventional Si3N4. The mechanical properties of the composites in terms of fracture toughness and strength were almost the same as those of a monolithic Si3N4 produced under the same sintering conditions. The sliding wear properties of the composites were evaluated using a ball-on-disk machine under unlubricated sliding conditions against a commercial Si3N4 ceramic ball. The tungsten (W) content had a significant effect on the composite wear properties. In particular, for a composite disk with a W content of 8 vol% the specific wear rate of the opposing ball was decreased around ten times compared to the monolithic Si3N4. The composites had higher wear resistance compared with the conventional silicon nitride, which was attributed to the formation of debris consisting of W, Si, and O. The debris restricted the adhesion of the two surfaces.

Effects of Sintering Conditions and Additives on Translucent Silicon Nitride Ceramics

2012 ◽  
Vol 724 ◽  
pp. 282-286 ◽  
Author(s):  
Wen Wu Yang ◽  
Miki Inada ◽  
Yumi Tanaka ◽  
Naoya Enomoto ◽  
Junichi Hojo
Keyword(s):  
Silicon Nitride ◽  
Visible Region ◽  
Sintering Aids ◽  
Sintering Aid ◽  
Sintering Additives ◽  
Nitride Ceramics ◽  
Sintering Conditions

Translucent β-Si3N4 sintered ceramics have been fabricated by using AlN-MgO sintering additives. In the present study, the authors employed AlN-MgO as a standard sintering aid, and investigated the effects of sintering conditions on the translucency of Si3N4. Furthermore, various oxides such as HfO2, Sm2O3, Y2O3, Sc2O3, La2O3, Nd2O3, CeO2, CaO, ZrO2 etc. were used as the sintering aids of Si3N4, and the sintered β-Si3N4 ceramics exhibited different transmittances in the visible region. It was found that the transmittance of sintered ceramics was mainly affected by the sintering additives.

Crystallization of Zirconium Nitride in Silicon Nitride Ceramics with Nitrogen Pressures and Sintering Additives

2005 ◽  
Vol 287 ◽  
pp. 253-258 ◽  
Author(s):  
S.M. Lee ◽  
K.H. Park ◽  
Jung Whan Yoo ◽  
Hyung Tae Kim
Keyword(s):  
Mechanical Properties ◽  
Silicon Nitride ◽  
Surface Region ◽  
Nitrogen Atmosphere ◽  
Zirconium Nitride ◽  
Sintering Aids ◽  
Sintering Aid ◽  
Heat Treated ◽  
Nitride Ceramics ◽  
Sintered Silicon

We investigated grain boundary crystallization of gas-pressure-sintered silicon nitride with zirconia and magnesia as sintering aids. Cation compositions were mostly uniform throughout the specimen however, ZrO2 was crystallized in the surface region, while ZrN in the inside. When the specimen was heat-treated at 1 atm nitrogen atmosphere, ZrO2 in the surface region transformed to ZrN. The transformation, however, was suppressed when alumina was incorporated as an additional sintering aid. Based on these results, we propose a model describing the reaction among Si3N4, SiO2, ZrO2, ZrN and N2. Observed microstructures and measured mechanical properties were consistent with the model.

NITRIDATION OF SILICON WITH AMMONIA AND NITROGEN

2010 ◽  
Vol 09 (03) ◽  
pp. 169-174
Author(s):  
RENE CHAUSTOWSKI ◽  
YONG WANG ◽  
JIN ZOU ◽  
JISHENG HAN ◽  
SIMA DIMITRIJEV
Keyword(s):  
Silicon Nitride ◽  
Electronic Devices ◽  
Nitrogen Atmosphere ◽  
Silicon Oxynitride ◽  
Nitride Film ◽  
Heating Process ◽  
Ammonia Gas ◽  
Transmission Electron ◽  
Materials Used ◽  
Electron Energy Loss

Silicon nitride and silicon oxynitride are materials used extensively in mechanical and electronic devices due to their outstanding properties. Thin films of silicon nitride and silicon oxynitride can be deposited on a silicon surface. In this study, nitridation of silicon wafers by a rapid thermal heating process with both nitrogen and ammonia as precursors was investigated by transmission electron microscopy, electron energy loss spectroscopy, and ellipsometry analyses. It was found that, under ammonia gas, the growth of nitride film was limited to 0.5 nm, whilst under the nitrogen atmosphere, a nitride film of 5–10 nm could be formed at 1200°C. The limited growth in ammonia suggests formation of high-quality passivating layer.

Tensile Creep of Y-Si3N4: II. Cavitation

1991 ◽  
Vol 49 ◽  
pp. 972-973 ◽  
Author(s):  
B. J. Hockey ◽  
S. M. Wiederhorn
Keyword(s):  
Silicon Nitride ◽  
Creep Rupture ◽  
Tensile Creep ◽  
Sintering Aids ◽  
Microstructural Changes

ATEM has been used to characterize three different silicon nitride materials after tensile creep in air at 1200 to 1400° C. In Part I, the microstructures and microstructural changes that occur during testing were described, and consistent with that description the designations and sintering aids for these materials were: W/YAS, a SiC whisker reinforced Si3N4 processed with yttria (6w/o) and alumina (1.5w/o); YAS, Si3N4 processed with yttria (6 w/o) and alumina (1.5w/o); and YS, Si3N4 processed with yttria (4.0 w/o). This paper, Part II, addresses the interfacial cavitation processes that occur in these materials and which are ultimately responsible for creep rupture.

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