3 edition of Structure and grain coarsening during the process of engineering ceramics found in the catalog.
Structure and grain coarsening during the process of engineering ceramics
by National Aeronautics and Space Administration, For sale by the National Technical Information Service in [Washington, D.C.], [Springfield, Va
Written in English
|Statement||Nancy J. Shaw.|
|Series||NASA technical memorandum -- 100235.|
|Contributions||United States. National Aeronautics and Space Administration.|
|The Physical Object|
Synthesizing ceramics can require heating for long times at high temperatures, making the screening of high-through-put materials challenging. C. Wang et al. developed a new ceramic-sintering technique that uses resistive heating of thin carbon strips to ramp up and ramp down temperature quickly. This method allows for the quick synthesis of a wide variety of ceramics while mitigating the loss. The coarsening process of spherical grains with a disordered or rough interface atomic structure is diffusion‐controlled, because there is little energy barrier for atomic attachments. On the other hand, kink‐generating sources such as screw dislocations or two‐dimensional (2‐D) nuclei are required for angular grains having an ordered.
Structure-change processes for product property and quality enhancement require further development for ceramic materials and polymers. (Notable exceptions are the pyroceramic materials and polyethylen tenephthalate, which are well developed.). The templated grain growth (TGG) process [1, 2], which is a useful texturing method, has been applied to the fabrication of textured ceramics for various functional materials, such as Bi 4 Ti 3 O 12, Sr Ba Nb 2 O 7, BaBi 4 Ti 4 O 15, Pb(Mg 1/3 Nb 2/3)O 3-PbTiO 3, and (Na 1/2 Bi 1/2)TiO 3-BaTiO 3 [7–9] ceramics, etc. In this.
Zoran S Nikolic. University of Niš Fractal Nature in Ceramics Structure and New Modelling and Simulation Methods. Capillary liquid bridge and grain coarsening during liquid phase sintering. Since densification of powders requires high temperatures, grain growth naturally occurs during sintering. Reduction of this process is key for many engineering ceramics. Under certain conditions of chemistry and orientation, some grains may grow rapidly at the expense of their neighbours during sintering.
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Full text of "Structure and grain coarsening during the processing of engineering ceramics" See other formats. Get this from a library. Structure and grain coarsening during the process of engineering ceramics. [Nancy J Shaw; United States.
National Aeronautics and Space Administration.]. Studies have been made of three ceramic systems (Al2O3, Y2O3/MgO, and SiC/C/B), both to explore a surface area/density diagram approach to examining the coarsening processes during sintering and to explore an alternative coarsening parameter, i.e., the grain boundary surface area (raising it at a given value of the density) and not the pore surface area; therefore, pinning of the grain boundaries by solid Author: Nancy J.
Shaw. Coarsening of the pore‐grain structure appears to be the responsible process. Addition of 4 to 12 wt% C retards the coarsening and allows sintering to densities >97% at temperatures ≥°C. Abnormal grain growth accompanies this densification but can be inhibited by increased carbon by: During coarsening, the grain structure converges to a self-similar character seen in both the grain shape distribution and grain size distribution.
Coarsening behavior during sintering conforms to classic grain growth kinetics, modified to reflect the evolving by: Multi grain model represented by two dimensional contours defined as discrete set of points was used. Numerical method for simulation of grain coarsening was based on the interfacial concentrations as given by the Gibbs-Thomson equation and Author: Zoran S.
Nikolic, Kazunari Shinagawa, Branislav Randjelovic. He taught at the University of Michigan (Materials) during and MIT (Nuclear Engineering; Materials) during He began ceramic research studying martensitic transformations in zirconia nano crystals, which led to work on transformation plasticity, superplasticity, fatigue, grain growth and sintering in various oxides and nitrides.
Sintering is still the most important process in making bulk ceramics, but the process is not unique to ceramics. There is a large field known as “powder metallurgy” that considers many of the concepts and problems that we address for ceramics. Introduction to Materials Science, Chap Structure and Properties of Ceramics University of Tennessee, Dept.
of Materials Science and Engineering 9 NaCl structure: rC =rNa = nm, rA =rCl = nm ⇒rC/rA = From the table for stable geometries we see that C.N.
= 6 Crystal Structures in Ceramics Example: Rock Salt Structure. During ceramic fabrication, densification processes compete with coarsening processes to determine the path of microstructural evolution.
Grain growth is a key coarsening process. This paper examines grain boundary migration in ceramics, and discusses the effects of solutes, pores, and liquid phases on grain boundary migration rates. An effort is made to highlight work in the past Cited by: The critical-grain coarsening temperature also depends on the element added.
During Mechanical Deformation: As the initial austenite grain size (just above A 1) depends also on the initial structure of the steel, and thus, also on the amount of cold work to some extent, as it provides greater nucleation sites for austenite formation.
The. Ceramics can be organised into types or categories in terms of composition (oxide, carbide and so on). The characteristics of some of the more common are given below.
Alumina (aluminium oxide, Al 2 O 3) is by far the most commonly used engineering ceramic and is generally specified as the ceramic of first choice where operating conditions do. The abnormal grain growth (AGG, also referred to as discontinuous grain growth or exaggerated grain growth) during sintering of polycrystalline ceramics has been extensively studied.
During AGG, a few grains grow much faster than surrounding fine matrix grains so that the microstructure exhibits a bimodal distribution of grain size.
From the reviews: "Bengisu’s book clearly fills a gap in the current textbook literature on ceramic science and technology. Due to the well designed conception and the highly didactic style the present book may be expected to become a standard text in teaching ceramic science and engineering for the next decade.
the approx. references to original papers, including rather Brand: M. Bengisu. Journal of the Korean Ceramic Society Vol. 43, No. 11, pp. ~, −− Review Effect of Crystal Shape on the Grain Growth during Liquid Phase Sintering of Ceramics. During the initial stage of sintering, large pores are immobile and pin the grain boundaries, maintaining a small grain size.
During later sintering stage, fewer small pores are present, leading to larger grains. So, to maintain fine grain structure, sintering time should be lower. with decreasing grain size. Machinability is also affected; rough machining favors coarse grain size while finish machining favors fine grain size.
The effect of grain size is greatest on properties that are related to the early stages of deforma-tion. Thus, for example, yield stress is more dependent on grain size than ten-sile strength [2, 3].File Size: KB. Coarsening and grain growth accompany skeletal structure evolution during sintering of powder compacts [1,2].
In general, the sint ering process is driven by a decrease in the. The coarsening of polyhedral grains in a liquid matrix was calculated using crystal growth and dissolution equations used in crystal growth theories for faceted crystals.
The coarsening behavior was principally governed by the relative value of the maximum driving force for growth (Δ g max), which is determined by the average size and size Cited by: Ceramic engineering is the science and technology of creating objects from inorganic, non-metallic materials.
This is done either by the action of heat, or at lower temperatures using precipitation reactions from high-purity chemical solutions.
The term includes the purification of raw materials, the study and production of the chemical compounds concerned, their formation into components and the study of their structure, composition and properties.
Ceramic. The retardation of grain growth is shown to be associated with the segregation of filler additives into high energy grain boundary defects—a process that bears similarities to the segregation of impurity atoms within grain boundary structures in ceramics or metals.
The analysis of grain boundary energy, grain size distribution, and grain Cited by: 9.been the experimental demonstration that interface structure in general, and the roughening transition in particular, influence microstructural evolution during grain growth and coarsening . Furthermore, he has also identified a robust link connecting singular surfaces to abnormal coarsening and grain growth phenomena.
This phase structure is then used as an initial geometry in a two-phase moving-interface flow simulation to gauge into the phase structure coarsening process. Several case studies were performed, and the results show that the controllable generation of gradient-phase structures can be enabled by well-designed geometry and thermal boundary Author: Hangming Shen, Donggang Yao, Wei Zhang, Qian Ye.