Effect of Weight Loss on Liquid‐Phase‐Sintered Silicon Carbide

Grande, Tor; Sommerset, Hkon; Hagen, Eirik; Wiik, Kjell; Einarsrud, Mari‐Ann

doi:10.1111/j.1151-2916.1997.tb02945.x

Cited by 120 publications

(76 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This is an indication that porosity did not influence this microstructural characterization. The formation of SiC microstructure patterns sintered with Al 2 O 3 and Y 2 O 3 , as shown in Figure 3, has been previously observed 13 . These patterns are derived from heterogeneous segregation of the second phase 13 .…”

Section: Resultssupporting

confidence: 69%

Microstructural Characterization and Influence of Ceramography Method on the Microhardness of Sintering Agents Added Silicon Carbide

et al. 2017

View full text Add to dashboard Cite

This study carried out the microstructural characterization, by light microscopy, of sintered SiC in the presence of liquid phase at temperatures of 1800, 1850 and 1900 ºC, added with Al 2 O 3 and Y 2 O 3 as well with Al 2 O 3 -YAG composite in the proportions of 5, 10 and 15% by weight. It was possible to observe the formation of microstructural patterns resulting from the heterogeneous segregation of the additives, such observation is associated to the pulling of additives during the initial stage of ceramography. Two ceramographic paths were followed: method I -surface grinding followed by manual polishing and method II -automatic grinding and polishing. In order to compare the two techniques the analysis of 3D roughness by light interferometry and the Vickers microhardness test were used. It was concluded by the analysis of variance with 95% confidence that the degree of finishing obtained by both methods allowed the adequate microstructural characterization, as well as, to meet the requirements established by the ASTM C1327-15 standard for hardness test.

show abstract

Section: Resultssupporting

confidence: 69%

Microstructural Characterization and Influence of Ceramography Method on the Microhardness of Sintering Agents Added Silicon Carbide

et al. 2017

View full text Add to dashboard Cite

show abstract

“…The real vapor pressure falls in between these two extremes, but is most likely closer to the minimum estimate than the maximum. Considering previous work where weight loss during sintering could be detected at vapor pressures of ~10 -6 atm, 43 the estimations of the vapor pressure suggest that evaporation of alkali and coarsening due to evaporation-condensation mechanism does only take place at the sintering temperature and not during heating to the sintering temperature, in line with the insignificant dependence of the shrinkage with respect to the partial pressure of oxygen (Fig. 7).…”

Section: Discussionmentioning

confidence: 50%

Sintering of sub-micron K 0.5 Na 0.5 NbO 3 powders fabricated by spray pyrolysis

Haugen

Madaro

Bjørkeng

et al. 2015

Journal of the European Ceramic Society

Self Cite

View full text Add to dashboard Cite

K0.5Na0.5NbO3 (KNN)-based ceramics are promising lead-free piezoelectrics, but processing of these materials is an ongoing challenge. Here, we present a spray pyrolysis route to highquality KNN-based powders. Fine-grained (<100 nm as-prepared, ~130 nm calcined at 800 °C) and phase-pure KNN and Li0.03K0.485Na0.485Nb0.8Ta0.2O3 (KNNLT) powders were obtained from aqueous precursor solutions. Ceramics with 95 % of theoretical density and with normalized strain of 333 pm/V were obtained by conventional sintering. The sintering of KNN remained challenging even for the fine grained powders, and the origins of these processing challenges were investigated by dilatometry and electron microscopy. Coarsening into cuboidal grains, which strongly reduced the sinterability, was observed in alkali-oxide excess KNN, caused by the formation of a liquid phase at ~650 °C. We propose that the reactivity of alkali oxide with moisture and carbon dioxide at lower temperatures cause the formation of the liquid phase at the surface even for stoichiometric KNN powders.Evaporation, mainly of potassium oxide, at high temperatures was shown to cause the formation of a Nb-rich secondary phase. The segregation of a secondary phase and inhomogeneous distribution of K/Na are discussed in relation to sintering above the solidus temperature of KNN.

show abstract

“…However, SiO 2 impurities are detrimental when the sintering temperature is higher than 1900°C because chemical reactions between SiC and SiO 2 result in severe weight loss. 25) Although the free carbon content of powders B1 and B2 is similar (see Table 1) and B1 contained a higher amount of SiO 2 than the B2 powder, the B1 powder exhibited better sinterability, i.e., it possessed a higher sintered density when compared to the B2 powder. Thus, the difference in the sintered density between the specimens fabricated from the two powders was mostly affected by the difference in particle size.…”

mentioning

confidence: 99%

Influence of powder characteristics on the electrical resistivity of SiC ceramics

Lim

Kim

2012

J. Ceram. Soc. Japan

View full text Add to dashboard Cite

Four types of commercially available SiC powders were hot-pressed with 1 wt % Dy 2 O 3 AlN additives in a 3:2 molar ratio. Three submicron-sized SiC powders could be densified so as to have a relative density higher than 98%, whereas a micron-sized SiC powder showed limited densification up to 93.5%. SiC ceramics fabricated from ¢-SiC powders exhibited electrical resistivities (³10 ¹1 ³·cm) that were lower than those from ¡-SiC powders (³10 1 ³·cm). The lower electrical resistivity of the SiC ceramics fabricated from ¢-SiC powders could be attributed to a higher carrier density and enhanced charge mobility when compared to the SiC ceramics from ¡-SiC powders.©2012 The Ceramic Society of Japan. All rights reserved.Key-words : SiC, Sintering, Electrical resistivity [Received January 5, 2012; Accepted February 28, 2012] Silicon carbide (SiC) is considered to be a suitable material for various structural applications such as mechanical seals, bearings, cylinder liners, armor plates, and mirror materials for astronomical telescopes due to its superior properties of high hardness, high temperature strength, and excellent resistance to wear and corrosion.1)6) In addition, SiC ceramics with or without a small amount of additives have attracted considerable attention for use in semiconductor processing, nuclear fusion reactors, and high temperature thermomechanical applications because of their excellent chemical and thermal stability and good mechanical properties.7)11) In the mid 1970s, Lange 12) first reported on the successful densification of SiC by liquid-phase sintering with the addition of Al 2 O 3 as a sintering additive. Since this innovative work, interest in liquid-phase sintered (LPS)-SiC has grown continuously because such materials exhibit better mechanical properties than solid-state sintered SiC ceramics.2),6),13)17) Methods for the successful densification of SiC ceramics with a smaller amount of sintering additives via liquid-phase sintering include (1) the use of colloidal processing for the homogeneous distribution of sintering additives 18),19) and (2) the addition of in situsynthesized nano-sized SiC into submicron-sized SiC powders. 20) In this study, the sinterability of four different commercially available SiC powders was investigated with the addition of 1 wt % AlNDy 2 O 3 additives by hot pressing. The effect of the SiC powder characteristics on the electrical resistivity of the hot-pressed SiC ceramics was also investigated. The AlNDy 2 O 3 additive system was selected because of the success of previous research on the densification of SiC with AlN-rare earth oxide systems 4),11) and the good chemical stability of Dy 2 O 3 at high temperatures in the presence of SiC. 21)Four types of commercially available SiC powders were used as starting materials; their characteristics are shown in Table 1. The crystalline phase of powders A1 and A2 is ¡-SiC, while that of B1 and B2 is ¢-SiC. 22) The mixtures were dried, sieved (60 mesh), pressed uniaxially, and heat-treated at 200°C for 2 h in air so ...

show abstract

Effect of Weight Loss on Liquid‐Phase‐Sintered Silicon Carbide

Cited by 120 publications

References 2 publications

Microstructural Characterization and Influence of Ceramography Method on the Microhardness of Sintering Agents Added Silicon Carbide

Microstructural Characterization and Influence of Ceramography Method on the Microhardness of Sintering Agents Added Silicon Carbide

Sintering of sub-micron K 0.5 Na 0.5 NbO 3 powders fabricated by spray pyrolysis

Influence of powder characteristics on the electrical resistivity of SiC ceramics

Contact Info

Product

Resources

About