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Densification Process (densification + process)
Selected AbstractsMicrostructural Bases for the Superior Densification of Gels doped with Alumina NanoseedsADVANCED ENGINEERING MATERIALS, Issue 1-2 2006J. Tartaj The densification behavior of alumina gels has been studied. We have found that in addition to the effect of volume transformed, the thermal history of gels plays an important role in their densification process. Particularly, prior to the ,- to , transformation, the nanoseeded gels preserve a close packed and evenly distributed porous structure that helps to achieve full density at lower temperatures. [source] Spark Plasma Sintering Behavior of Nano-Sized (Ba, Sr)TiO3 Powders: Determination of Sintering Parameters Yielding Nanostructured CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2006Jing Liu Nano-powders of BaTiO3, SrTiO3, Ba0.6Sr0.4TiO3 (BST64), and a mixture of the composition (BaTiO3)0.6(SrTiO3)04 with particle sizes in the range of 60,80 nm were consolidated by spark plasma sintering (SPS). An experimental procedure is outlined that allows the determination of a "kinetic window," defined as the temperature interval within which the densification process can be kinetically separated from the grain growth one, enabling preparation of dense nanostructured ceramics. The width of this window varied from almost zero for BST64 to 125°C for the (BaTiO3)0.6(SrTiO3)0.4 mixture. During the densification (sintering) of the (BaTiO3)0.6(SrTiO3)04 mixture, BST64 is formed. The main part of this reaction occurs in a fully densified body through which suggesting that the constitutional phase(s) have a self-pinning effect on the grain growth. [source] Effect of Interface Structure on the Microstructural Evolution of CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2006Wook Jo The interface atomic structure was proposed to have a critical effect on microstructure evolution during sintering of ceramic materials. In liquid-phase sintering, spherical grains show normal grain growth behavior without exception, while angular grains often grow abnormally. 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 or singular interface structure. Coarsening of angular grains based on a 2-D nucleation mechanism could explain the abnormal grain growth behavior. It was also proposed that a densification process is closely related to the interface atomic structure. Enhanced densification by carefully chosen additives during solid state sintering was explained in terms of the grain-boundary structural transition from an ordered to a disordered open structure. [source] InSitu Densification Behavior in the Pyrolysis Consolidation of Amorphous Si-N-C Bulk Ceramics from Polymer PrecursorsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2001Julin Wan Insitu consolidation of amorphous Si-N-C ceramics during pyrolysis of polymer precursor provides a way to consolidate bulk silicon nitride based ceramics at lower temperatures. Porosity evolution during polymer-ceramic conversion has been investigated to clarify the densification process. A densification mechanism based on surface reaction and pyrolysis accommodated by viscous flow has been proposed. [source] Microstructure in Silicon Nitride Containing ,-Phase Seeding: III, Grain Growth and CoalescenceJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2001Horng-Hwa Lu The mechanical properties of Si3N4 materials depend mainly on the microstructure, which originates during the densification process. The microscopic evidence indicates that ,-Si3N4 seeds incorporated in the starting powders play an important role in microstructural development, especially in the heterogeneous grain growth of ,-Si3N4 grains during sintering. The growth of ,-grains is initiated from the ,-seeds, resulting in a core/shell microstructure. The presence of Moiré fringes and dislocations is attributed to misfit strain and compositional differences between the core and the shell. Coalescence can occur at the final stage of sintering. [source] The modeling of realistic chemical vapor infiltration/deposition reactorsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 5 2010John Ibrahim Abstract We describe the low Mach number equations as well as a second-order numerical integration procedure that are used to solve a realistic chemical vapor infiltration/chemical vapor deposition (CVI/CVD) problem. The simulation accounts for a homogeneous gas chemical reaction mechanism, a heterogeneous surface reaction mechanism, and an evolving pore structure model. The numerical solution of the model ultimately leads to the solution of a large system of stiff differential algebraic equations that are to be integrated over a long time. An operator splitting algorithm is employed to deal with the stiffness associated with chemical reactions, whereas a projection method is employed to overcome the difficulty arising from having to solve a large coupled system for velocity and pressure fields. Results show that the proposed integration procedure is very efficient for modeling long time CVI/CVD densification processes. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||