Faceting behavior of Al2O3 in the presence of glassy phase

1987 ◽  
Vol 45 ◽  
pp. 152-153
Author(s):  
Y. Kouh Simpson
Keyword(s):  
Liquid Phase ◽  
Glass Phase ◽  
Glassy Phase ◽  
Liquid Phase Sintering ◽  
Sintering Process ◽  
Final Microstructure ◽  
Amorphous Glass ◽  
Glass Interface ◽  
Energy Consideration

It is well known that A1203 can reach near-theoretical density by a liquid-phase sintering process in which an amorphous glass phase containing SiO2, CaO and Al2O3 helps density Al2O3. Understanding the faceting behavior of Al2O3 in the presence of such a glass phase is important since the movement of the facets and the type of facets that form during the liquid-phase sintering process determine the final microstructure of the grain boundaries that ultimately control the properties of Al2O3 compacts. As a part of a larger study on the role of impurities in the sintering process of Al2O3 compacts, a new investigation has been carried out to examine the nature and the type (e.g. facet planes) of the crystalline Al2O3, / amorphous glass interface in systematic experiments in which densification aids such as SiO2, CaO and MgO are reacted with single crystal Al2O3. Substantial anisotropy, both from an energy consideration and a kinetics consideration, in the Al2O3/ glass interface is to be expected, and has been observed in this investigation.

Microstructures in Milli-Wave Sintered Silicon Nitride

2000 ◽  
Vol 6 (S2) ◽  
pp. 420-421
Author(s):  
M. E. Brito ◽  
M.C. Valecillos ◽  
K. Hirao ◽  
M. Toriyama
Keyword(s):  
Silicon Nitride ◽  
Liquid Phase ◽  
Microwave Absorption ◽  
Microwave Field ◽  
Liquid Phase Sintering ◽  
Wave Radiation ◽  
Sintering Process ◽  
Absorption Factor ◽  
Final Microstructure ◽  
Sintered Silicon

Expectations arised that unique microstructures could be attained by micro- or milli-wave processing of ceramics. To determine possible effects of milli-wave radiation on the microstructure evolution of silicon nitride, a detailed study has been carried out for silicon nitride sintered under conventional resistance heating and under milli-wave radiation (28 GHz). Densification of silicon nitride is achieved by liquid-phase sintering process. The additives such as yttria (Y2O3) and alumina (A12O3) are utilized to form a liquid phase during sintering. Considering the low microwave absorption factor of silicon nitride, heating in a microwave field is associated with the preferential microwave absorption of the additives. Differences in the nature and/or in the absorption factor of the additive will influence the sintering process and hence the final microstructure.

Upconversion luminescence properties of Li+-doped ZnWO4:Yb,Er

2008 ◽  
Vol 23 (8) ◽  
pp. 2078-2083 ◽  
Author(s):  
Xi-xian Luo ◽  
Wang-he Cao
Keyword(s):  
Liquid Phase ◽  
Calcination Temperature ◽  
Crystal Field ◽  
Lower Energy ◽  
Upconversion Luminescence ◽  
Peak Position ◽  
Liquid Phase Sintering ◽  
Red Shift ◽  
Luminescence Properties ◽  
Sintering Process

Upconversion luminescence (UPL) characteristics and effects of Li+ ion on the UPL of ZnWO4:Yb,Er polycrystalline phosphors were investigated. It was shown that introduction of Li+ ions could reduce the calcination temperature by about 200 °C and increase the crystallinity of ZnWO4:Yb,Er by a liquid-phase sintering process via formation of Li2WO4 and other intermediates. UPL efficiency is remarkably promoted by Li+ ions. Moreover, the UPL spectrum of Li+-doped ZnWO4:Yb,Er presents a red shift, and the strongest peak position shifts from 553 to 559 nm. These can be attributed to a shift in the 4f level barycenter to lower energy, which results from lowering of the symmetry of the crystal field around Er3+.

scholarly journals Role of Sintering Temperature in Production of Nepheline Ceramics-Based Geopolymer with Addition of Ultra-High Molecular Weight Polyethylene

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1077
Author(s):  
Romisuhani Ahmad ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
Wan Mastura Wan Ibrahim ◽  
Kamarudin Hussin ◽  
Fakhryna Hannanee Ahmad Zaidi ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Sintering Temperature ◽  
Ceramic Materials ◽  
Microstructural Properties ◽  
Sintering Process ◽  
Final Microstructure ◽  
Change Of Microstructure ◽  
Ultra High Molecular Weight

The primary motivation of developing ceramic materials using geopolymer method is to minimize the reliance on high sintering temperatures. The ultra-high molecular weight polyethylene (UHMWPE) was added as binder and reinforces the nepheline ceramics based geopolymer. The samples were sintered at 900 °C, 1000 °C, 1100 °C, and 1200 °C to elucidate the influence of sintering on the physical and microstructural properties. The results indicated that a maximum flexural strength of 92 MPa is attainable once the samples are used to be sintered at 1200 °C. It was also determined that the density, porosity, volumetric shrinkage, and water absorption of the samples also affected by the sintering due to the change of microstructure and crystallinity. The IR spectra reveal that the band at around 1400 cm−1 becomes weak, indicating that sodium carbonate decomposed and began to react with the silica and alumina released from gels to form nepheline phases. The sintering process influence in the development of the final microstructure thus improving the properties of the ceramic materials.

Effect of WC Addition on Phase Formation and Microstructure of TiC-Ni Composites

2008 ◽  
Vol 55-57 ◽  
pp. 353-356
Author(s):  
Nawarat Wora-uaychai ◽  
Nuchthana Poolthong ◽  
Ruangdaj Tongsri
Keyword(s):  
Liquid Phase ◽  
Tungsten Carbide ◽  
Phase Formation ◽  
Liquid Phase Sintering ◽  
Precipitation Process ◽  
Solid Solution Phase ◽  
Binder Phase ◽  
Sintering Process ◽  
X Ray Diffraction ◽  
X Ray

In this research, titanium carbide-nickel (TiC-Ni) composites, with tungsten carbide addition, were fabricated by using a powder metallurgy technique. The TiC-Ni mixtures containing between 0-15 wt. % tungsten carbide (WC), were compacted and then sintered at 1300°C and 1400°C, respectively. The phase formation and microstructure of the WC-added TiC-Ni composites have been investigated by X-ray diffraction and scanning electron microscopy techniques. Mechanical properties of these composites were assessed by an indentation technique. The X-ray diffraction patterns showed no evidence of tungsten rich phases in the sintered WC-added cermets. This indicates that during the sintering process, tungsten carbide particles were dissolved in metallic binder phase (Ni phase) via dissolution/re-precipitation process during liquid phase sintering. The liquid phase formed during sintering process could improve sinterability of TiC-based cermets i.e., it could lower sintering temperatures. The TiC-Ni composites typically exhibited a core-rim structure. The cores consisted of undissolved TiC particles enveloped by rims of (Ti, W)C solid solution phase. Hardness of TiC-Ni composites increased with WC content. Sintering temperature also had a slight effect on hardness values.

True Sedimentation and Particle Packing Rearrangement during Liquid Phase Sintering

2007 ◽  
Vol 534-536 ◽  
pp. 609-612
Author(s):  
Jong K. Lee ◽  
Lei Xu ◽  
Shu Zu Lu
Keyword(s):  
Liquid Phase ◽  
Concentration Gradient ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Liquid Phase Sintering ◽  
Particle Packing ◽  
Sintering Process ◽  
Second Stage ◽  
Packing Efficiency ◽  
Two Stages

When an alloy such as Ni-W is liquid phase sintered, heavy solid W particles sedimentate to the bottom of the container, provided that their volume fraction is less than a critical value. The sintering process evolves typically in two stages, diffusion-driven macrosegregation sedimentation followed by true sedimentation. During sedimentation, the overall solid volume fraction decreases concurrently with elimination of liquid concentration gradient. However, in the second stage of true sedimentation, the average solid volume fraction in the mushy zone increases with time, and oddly, no concentration gradient is necessary in the liquid zone. In this work, we propose that the true sedimentation results from particle rearrangement for higher packing efficiency.

Physical, Mechanical and Electrical Properties of W-20 wt.% Cu Composite Produced by Liquid Phase Sintering Process

2014 ◽  
Vol 879 ◽  
pp. 21-26
Author(s):  
Fauzi Ismail ◽  
Mohd Asri Selamat ◽  
Norhamidi Muhamad ◽  
Abu Bakar Sulong ◽  
Nurzirah Abdul Majid
Keyword(s):  
Particle Size ◽  
Liquid Phase ◽  
Electrical Properties ◽  
Microstructure Evolution ◽  
Sintering Temperature ◽  
Cold Isostatic Pressing ◽  
Liquid Phase Sintering ◽  
Sintering Process ◽  
Composite Powders ◽  
Mechanical And Electrical Properties

In this study, the effect of sintering temperature on the properties of tungsten-copper (W-Cu) composite produced by liquid phase sintering (LPS) process has been investigated. W-20 wt.% Cu composite powders with particle size less than 1 μm was prepared by cold compaction and followed by cold isostatic pressing. The green specimens were then sintered under nitrogen based atmosphere in the temperature range of 1100°C to 1300°C. The sintering studies were conducted to determine the extent of densification and corresponding to microstructure changes. In addition, the properties of the sintered specimens such as physical appearance, microstructure evolution, mechanical and electrical properties were presented and discussed.

The Influence of Production Process Parameters on the Properties W-Ag, Mo-Ag Composites

2007 ◽  
Vol 534-536 ◽  
pp. 1513-1516
Author(s):  
Jan Leżański ◽  
Marcin Madej
Keyword(s):  
Liquid Phase ◽  
Production Process ◽  
Process Parameters ◽  
Liquid Phase Sintering ◽  
Sintering Process ◽  
Powder Mixtures ◽  
Microstructure And Properties ◽  
Silver Additions

Attempts have been made to describe the influence of production process parameters on the microstructure and properties of W - Ag and Mo - Ag composites. The compositions of powder mixtures are W + 30% Ag and Mo + 30%Ag. Silver additions assists densification during sintering by a liquid phase sintering process. The main goal of this work is to compare properties and microstructure of as-sintered and as-infiltrated composites.

Sign in / Sign up

Export Citation Format

Share Document