scholarly journals Microstructure evolution during pressureless sintering of bulk oxide ceramics

2009 ◽  
Vol 3 (1-2) ◽  
pp. 13-17 ◽  
Author(s):  
Karel Maca
Keyword(s):  
Grain Size ◽  
Ceramic Materials ◽  
Oxide Ceramic ◽  
Oxide Ceramics ◽  
Final Density ◽  
Constant Rate ◽  
Final Microstructure ◽  
Injection Molded ◽  
Rate Controlled ◽  
Rate Of Heating

The author's experience concerning the influence of the choice of different pressureless heating schedules on the final microstructure of oxide ceramic materials is summarized in the paper. Alumina, ceria, strontium titanate, as well as tetragonal (3 mol% Y2O3) and cubic (8 mol% Y2O3) zirconia were cold isostatically pressed or injection molded and pressureless sintered with different heating schedules - namely with Constant-Rate of Heating with different dwell temperatures (CRH), with Rate-Controlled Sintering (RCS) and with Two-Step Sintering (TSS). It was examined whether some of these three sintering schedules, with the same final density achieved, can lead to a decrease of the grain size of sintered ceramics. The results showed that only TSS (and only for selected materials) brought significant decrease of the grain size. .

Strengthening of ZrO2 Ceramics due to Nano-Crystallization

2006 ◽  
Vol 45 ◽  
pp. 1674-1679 ◽  
Author(s):  
Koji Morita ◽  
Keijiro Hiraga ◽  
Byung Nam Kim ◽  
Hidehiro Yoshida
Keyword(s):  
Grain Size ◽  
Fracture Strength ◽  
Ceramic Materials ◽  
Flaw Size ◽  
Maximum Strength ◽  
Oxide Ceramic ◽  
Transformation Stress

The fracture strength σf of ZrO2-based ceramics tends to increase with decreasing grain size d. As compared with the data for submicrometer-grain-sized material with d ≈ 350 nm, nano-crystallization of ZrO2 ceramics less than d ≈ 90 nm can improve σf by a factor of 2.0-2.5. The maximum strength reaches σf ≈ 2500 MPa, which is classed as the highest σf of oxide ceramic materials. The high σf can be associated with an increase in the critical t →m transformation stress and a decrease in the flaw size due to nano-crystallization.

Effect of the Two-Step Sintering in the Microstructure of Ultrafine Alumina

2010 ◽  
Vol 62 ◽  
pp. 221-226 ◽  
Author(s):  
Adriana Scoton Antonio Chinelatto ◽  
Milena Kowalczuk Manosso ◽  
Elíria Maria Jesus Agnollon Pallone ◽  
Ana Maria Souza ◽  
Adilson Luiz Chinelatto
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
The Other ◽  
Ceramic Powders ◽  
Final Density ◽  
Final Microstructure ◽  
Conventional Sintering ◽  
Higher Temperature ◽  
Lower Temperature ◽  
Intermediate Density

Sintering in two-steps has been applied with success for densification of nanometric and submicrometer ceramic powders without grain growth. In this work the applicability of two-step sintering as a means of suppressing the grain growth of submicrometer alumina is verified. Experiments, in which the grain growth and densification were characterized after conventional sintering and two-step sintering, were conducted. Conventional sintering is used as a choice of the steps for two-step sintering. In the first two-step sintering studied, one hypothesis that the maximization of final density with minimum grain growth can be achieved by improving the narrowing of grain size distribution at a pre-densification sintering stage was assumed. And the other two-step sintering is based on works of Chen and Wang, in which the samples are first heated to a higher temperature to achieve an intermediate density, and then cooled down and held at a lower temperature until they are dense. The results showed that the choice of steps does not permit to suppress grain growth, but, the two-step sintering influenced in the development of the final microstructure, taking to microstructures which were finer grained than in alumina sintered conventionally.

The Influence of Dopants in the Grain Size of Alumina - A Review

2015 ◽  
Vol 820 ◽  
pp. 280-284 ◽  
Author(s):  
Pâmela Milak ◽  
Flávia Dagostim Minatto ◽  
Cristian Faller ◽  
Agenor de Noni Jr. ◽  
Oscar Rubem Klegues Montedo
Keyword(s):  
Grain Size ◽  
Wear Rate ◽  
Strong Influence ◽  
Wear Behavior ◽  
Erosive Wear ◽  
High Technology ◽  
Ceramic Materials ◽  
Final Microstructure ◽  
The Subject ◽  
Broad Understanding

Ceramic materials present interesting properties and generate products that meet engineering requirements referring to this class for several applications. Aluminum oxide is a very good example of this class of materials, being applied widely in high technology areas especially where the abrasive and erosive wear are strongly demanded. Many factors interfere on the wear of alumina: material composition, characteristics of the used oxides, and the manufacturing process that defines the final microstructure. It is know that the grain size of the alumina has a strong influence on the wear rate and is the focus of several studies. The grain growth during sintering as well as the diffusion process can be controlled by using dopants in the alumina composition. Thus the aim of this paper is to present a review about the dopants interference on the grain size of alumina, which in turn influences the wear behavior of the alumina. The results described allow broad understanding on the subject

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.

Energetic Materials in Ceramics Synthesis

1992 ◽  
Vol 296 ◽  
Author(s):  
J. J. Kingsley ◽  
L. R. Pederson
Keyword(s):  
Energetic Materials ◽  
Fine Particles ◽  
Impurity Content ◽  
Oxide Ceramic ◽  
Oxide Ceramics ◽  
Ceramic Powders ◽  
Metal Nitrates ◽  
Organic Fuels ◽  
Simultaneous Synthesis ◽  
Fuel Mixtures

AbstractCombustion of a proper combination of an oxidizer and a fuel can produce the exothermicity required for the simultaneous synthesis of oxide ceramic powders. Oxidizers include metal nitrates, ammonium nitrate, and ammonium perchlorate, while urea, carbohydrazide, glycine and others have been used successfully as fuels. Combustion methods are particularly well-suited to producing multicomponent metal oxides, yielding compositionally homogeneous, fine particles with low impurity content. Organic fuels, particularly those containing nitrogen, also serve as a complexant in the precursor, which inhibits inhomogeneous precipitation from occurring prior to combustion. The exothermic redox decomposition of these oxidizer-fuel mixtures is initiated at low temperatures, usually <250°C. Properties of the products are influenced by the nature of the fuel and the oxidizer/fuel ratio. Many technologically important oxide ceramics have been produced by these methods.

Effect of the Two-Steps Sintering in the Microstructure of Ultrafine Alumina

2008 ◽  
Vol 591-593 ◽  
pp. 611-615
Author(s):  
Adriana Scoton Antonio Chinelatto ◽  
Milena K. Manosso ◽  
Elíria Maria Jesus Agnolon Pallone ◽  
Adilson Luiz Chinelatto
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Image Analysis ◽  
Microstructural Analysis ◽  
Analysis Program ◽  
Constant Heating Rate ◽  
Heating Curve ◽  
Final Microstructure ◽  
Constant Heating ◽  
Scanning Electron

The control of the heating curve to manipulate microstructure during sintering is a way that has being studied and it presents advantages such as simplicity and economy. In this work, it was studied the sintering in two-steps of a commercial ultrafine alumina. For this, the alumina power was deagglomerated in milling ball and the specimens for sintering were pressed. Sintering was performed in a dilatometer, with constant heating rate of 15°C/min up to 1500°C. By these results, heat treatment temperatures for two-step sintering were defined. The sintering specimens were characterized through the apparent density measures using Archimedes method, the grain size measures using image analysis program and microstructural analysis using a scanning electron microscope. The results showed that the two-step sintering influence in the development of the final microstructure and permit the control of the grain size and density.

Oxide ceramic materials

2011 ◽  
Author(s):  
Karl Hauffe ◽  
Gundula Jänsch-Kaiser ◽  
David H. Sharp
Keyword(s):  
Ceramic Materials ◽  
Oxide Ceramic
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