Densification of Aluminum Nitride Ceramics with CaF2 Additive

2008 ◽  
Vol 368-372 ◽  
pp. 970-972 ◽  
Author(s):  
Yan Xiong ◽  
Zheng Yi Fu ◽  
Hao Wang
Keyword(s):  
Grain Size ◽  
Aluminum Nitride ◽  
Secondary Phase ◽  
Phase Evolution ◽  
Sintered Sample ◽  
Nitrogen Atmosphere ◽  
Microstructural Development ◽  
Secondary Phases ◽  
Nitride Ceramics ◽  
Sem Investigation

Effect of adding up to 5wt% CaF2 on the densification and microstructural development of hot pressed aluminum nitride (AlN) was investigated. SEM investigation showed that the grain size of the sintered sample decreases with the increasing content of CaF2. Secondary-phase evolution paths converge from CA6 to CA phase above 1650°C. TEM micrographs showed that formed secondary phases could evaporate from sintered bodies at higher temperatures in the carbon-containing nitrogen atmosphere and the residuals were mainly distributed at triple grain junctions, keeping direct connections of AlN grains. Translucnet AlN ceramics were prepared using CaF2 additive sintered at 1850°C for 5 h.

Synthesis, Characterization and Electrical Properties of Single Phase La0.9Sr0.1Ga0.8Mg0.2O3

2010 ◽  
Vol 636-637 ◽  
pp. 874-879
Author(s):  
Anna Gaki ◽  
G. Kakali ◽  
R.J. Wiglusz ◽  
W. Strek ◽  
Grzegorz Paściak
Keyword(s):  
Grain Size ◽  
Electrical Properties ◽  
Impedance Spectroscopy ◽  
Single Phase ◽  
Sintered Sample ◽  
Polymeric Precursor ◽  
Secondary Phases ◽  
Sem Images ◽  
Xrd Pattern ◽  
Precursor Route

Single phase La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM9182) was synthesized by a polymeric precursor route. The XRD pattern after calcination at 1300 °C for 6h indicates the formation of the perovskite without the presence of secondary phases. XRD, FTIR and TG-DTG measurements were used to examine the powder precursor as well as the intermediate and final products. SEM images indicated the small grain size of the final product. The conductivity of the sintered sample was examined by means of a.c. impedance spectroscopy and was found to be 9.10-2 S/cm at 800 °C similar to the typical value of LSGM materials.

scholarly journals The Early Stages of the Microstructural Development of the Colony Structure in Bi-2223 Tapes

2001 ◽  
Vol 689 ◽  
Author(s):  
T. G. Holesinger
Keyword(s):  
Liquid Phase ◽  
Texture Evolution ◽  
Secondary Phase ◽  
Primary Phase ◽  
Microstructural Development ◽  
Colony Structure ◽  
Secondary Phases ◽  
Phase Development ◽  
Multifilamentary Tapes

ABSTRACTThe current protocol for processing (Bi,Pb)2Sr2Ca2Cu3O10-x (Bi-2223) multifilamentary tapes involves the in situ formation of the primary phase from a suitable mixture of precursor phases. As such, the developments during the first few minutes of heat treatment determine to a large extent the efficiency of primary phase development, competing secondary phase development, texture evolution, and grain-to-grain connectivity. This work documents the development of the liquid phase, secondary phases, defects which may affect alignment and reaction kinetics, and the precipitation of Bi-2223 from the liquid phase.

Effect of Soaking Time on the Properties of Al2O3-C Refractory

2014 ◽  
Vol 602-603 ◽  
pp. 632-635
Author(s):  
Yong Liang Huang ◽  
Hong Xi Zhu ◽  
Cheng Ji Deng ◽  
Nai Peng ◽  
Wen Jie Yuan
Keyword(s):  
Grain Size ◽  
Compressive Strength ◽  
Thermal Shock Resistance ◽  
High Strength ◽  
Sintered Sample ◽  
Nitrogen Atmosphere ◽  
Soaking Time ◽  
Good Corrosion Resistance ◽  
Steel Making ◽  
Shock Resistance

Al2O3-C refractory has many advantages, high strength, good corrosion resistance and good thermal shock resistance, so Al2O3-C refractory is widely used in the steel-making process. In this paper, the effect of different soaking time on the properties of Al2O3-C refractory at 1450°Cin nitrogen atmosphere was studied. The phase composition of the sintered sample has little change when the soaking time was from 2h to 5h. Cylindrical sialon appeared as the soaking time being 3h, and its grain size increased and became uniform, about 2.5um when the soaking time being 4~5h. In the general performance, with the soaking time changing from 2h to 5h, the samples increment percentage in weight decreased gradually, and the compressive strength of the sintered was first increased, and then decreased, reaching the maximum when the soaking time is 4h. Both the apparent porosity and bulk density of the samples had little different changing.

Liquid Phase Sintering of SiC-Ceramics

2009 ◽  
Vol 624 ◽  
pp. 91-108 ◽  
Author(s):  
Koushik Biswas
Keyword(s):  
Mechanical Properties ◽  
Liquid Phase ◽  
Grain Boundary ◽  
Secondary Phase ◽  
Phase Evolution ◽  
Liquid Phase Sintering ◽  
Secondary Phases ◽  
Plasma Sintering ◽  
Carbide Ceramics ◽  
Silicon Carbide Ceramics

In view of considerable attention in the development of liquid phase sintered SiC, a comprehensive study of the data on processing, structure and properties seems highly relevant. This article provides a detailed and critical overview of liquid phase sintered silicon carbide ceramics with primary emphasis of grain-boundary/secondary phase evolution, their structure, distribution on the final properties of the sintered materials. The roles of individual additives in developing boundary microstructures will be identified and demonstrated to be critical in optimizing the mechanical properties, including fracture toughness, flexural strength and creep resistance. Numerous methods of structure-properties modification, like in-situ-toughening, -SiC phase transformation, volume of liquid phase, partial/full crystallization of grain-boundary and/or secondary phases are conclusively discussed. Apart from conventional pressureless sintering of SiC, enhanced spark plasma sintering with different oxide and non-oxide sintering additives are also discussed in terms of phase evolution, microstructure and their structure mechanical properties are correlated.

Effect of Calcination Temperature on the Breakdown Strength and Energy Density of CaCu3Ti4O12 Ceramic

2017 ◽  
Vol 888 ◽  
pp. 23-27 ◽  
Author(s):  
Mohd Fariz Ab Rahman ◽  
Mohamad Johari Abu ◽  
Rosyaini Afindi Zaman ◽  
Julie Juliewatty Mohamed ◽  
Mohd Fadzil Ain ◽  
...  
Keyword(s):  
Grain Size ◽  
Energy Density ◽  
Calcination Temperature ◽  
Single Phase ◽  
Breakdown Strength ◽  
Raw Materials ◽  
Sintered Sample ◽  
Xrd Analysis ◽  
Solid State Reaction Method ◽  
Secondary Phases

The effect of calcination temperature on the breakdown strength and energy density of CaCu3Ti4O12 (CCTO) ceramics was studied. CCTO ceramics were prepared via solid state reaction method. The raw materials of CCTO were wet mixed for 24 hours and then dried overnight in oven. CCTO mixtures were calcined at three different temperature which is at 900°C, 930°C and 950°C for 12 hours. The calcined powders were compacted at 250 MPa and then were sintered at 1040°C for 10 hours. X-Ray Diffractometer (XRD) analysis showed the formation of CCTO phase and secondary phases of CuO and CaTiO3 for C900 calcined powders but single phase of CCTO was obtained by C930 and C950 calcined powders. Single phase of CCTO also were seen for all sintered samples. Observation on Scanning Electron Microscopy (SEM) micrographs showed large grain size was seen in C900 sintered sample and finer grain size was observed for C930 and C950 sintered samples. C900 sintered sample obtained highest dielectric constant (8617), highest breakdown strength (7.92 kV/cm), highest energy density (2.392 J/cm3).

Fabrication of Nanocrystalline Dense Silicon Nitride Ceramics

2012 ◽  
Vol 715-716 ◽  
pp. 738-738
Author(s):  
Hai Doo Kim ◽  
Seong Hyeon Hong
Keyword(s):  
Grain Size ◽  
Silicon Nitride ◽  
Grain Growth ◽  
Oxygen Content ◽  
High Surface ◽  
Full Density ◽  
Microstructural Development ◽  
Nitride Powder ◽  
Nitride Ceramics ◽  
Silicon Nitride Powder

Since the properties of the bulk ceramics are dependent on the grain size the ceramic materials with nanoscale grain size is of interest. Sintering of nanosized powder compacts to full density with minimum grain growth is a difficult task to achieve due to its high surface energy. Two step sintering methode was developed to enhance densification with minimum grain growth for silicon nitride ceramics with liquid phase. Starting with nano-sized silicon nitride powder two step sintering methode gives rise to a very fine-grained b-Si3N4 matrix with large agglomerated Si2N2O grains due to its high surface oxygen content. Addition of Y2O3 shifts the composition point to a primary phase field with no Si2N2O, gives rise to b-Si3N4 with nano scale grain size and near full density. Carbothermal reduction method was employed to reduce the oxygen content in nano-sized silicon nitride powder to give nanocrystalline dense silicon nitride ceramics without Si2N2O formation. Use of SPS was effective to suppress the grain growth and to give near full density. Microstructural development and mechanical properties will be reported.

scholarly journals A Comparative Study of Spark Plasma and Conventional Sintering of Undoped SnO2 Sputtering Targets

2021 ◽  
Author(s):  
Levent Koroglu ◽  
Cem Aciksari ◽  
Erhan Ayas ◽  
Emel Ozel ◽  
Ender Suvaci
Keyword(s):  
Grain Size ◽  
Relative Density ◽  
Dwell Time ◽  
Sintering Temperature ◽  
Phase Evolution ◽  
Microstructural Development ◽  
Plasma Sintering ◽  
Average Grain Size ◽  
Conventional Sintering ◽  
Spark Plasma

Abstract SnO2 ceramics were fabricated by spark plasma sintering (SPS) and conventional (pressureless) sintering techniques by using undoped submicron SnO2 powders. The effect of sintering temperature and dwell time on the densification behavior, phase evolution and microstructural development of sintered ceramics were investigated. The relative density of SPSed ceramics increased when dwell time was raised from 1 to 10 min at 950ºC. However, full densification was prevented by the decomposition of SnO2 to Sn and O2(g). The decomposition starts after ~ 10 min at 950ºC. In parallel to this observations, as sintering temperature increases, amount of the elemental Sn in agglomerated form increases. On the other hand, the relative densities of conventionally sintered ceramics (at 1200ºC-1400ºC) were relatively low (i.e., 63 % relative density), and abnormal grain growth was observed due to the shift in sintering mechanisms to evaporation-condensation as a dominant mechanism. Since the undoped SnO2 ceramics, SPSed at 950°C for 5 min under 30 MPa exhibit 93 % relative density, high chemical purity, homogeneous grain size distribution and smaller average grain size, they demonstrate great potential as sputtering targets for production of high-quality thin film gas sensors.

Microstructural Design and Control of Silicon Nitride Ceramics

MRS Bulletin ◽  
1995 ◽  
Vol 20 (2) ◽  
pp. 38-41 ◽  
Author(s):  
Mamoru Mitomo ◽  
Naoto Hirosaki ◽  
Hideki Hirotsuru
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Phase Transformation ◽  
Silicon Nitride ◽  
Grain Growth ◽  
Processing Parameters ◽  
Microstructural Development ◽  
Nitride Ceramics ◽  
Microstructural Design ◽  
And Control

The improvement of mechanical properties by microstructural control has been one of the main topics of interest in the development of silicon nitride ceramics. Toughening, by developing an in situ composite or self-reinforced microstructure, has attracted particular attention.Microstructural design is a key factor in the optimization of processing parameters. The microstructures of sintered materials are composed of silicon nitride grains and grain boundaries, which can be either crystalline, amorphous, or partially crystalline, depending on the composition, amount of sintering additives, and processing parameters. Silicon nitride ceramics have been fabricated with an addition of metal oxides and rare-earth oxides that form a liquid phase during sintering and accelerate grain boundary diffusion. The effect of composition of the glassy phase on the mechanical properties of ceramics is presented by Becher et al. and Hoffmann elsewhere in this issue. This article focuses specifically on the design and control of grain size.As it is well recognized, many processing parameters affect grain growth behavior and the resulting microstructure. During sintering, the α- to β-phase transformation leads to a self-reinforcing microstructure on account of the anisotropic grain growth of the stable hexagonal β- Si3N4 phase. Therefore, α-rich powders are widely used for starting materials. Phase transformation accelerates anisotropic grain growth, resulting in an increase in the fracture toughness of Si3N4 ceramics. Kang and Han discuss the effect of phase transformation on nucleation and grain growth in an article in this issue. The effect of the grain-size distribution on microstructural development is described in this article, based on studies conducted mostly with β-Si3N4 powders.

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