Papers by Keyword: Master Sintering Curve

Abstract: Several models have been developed over the last years to study the microstructure development of ceramic and metal powders during sintering. Among the most utilized methodology one may find the Arrhenius and the so-called Master Sintering Curve (MSC). Both models involve manipulation of a large number of data, and repetitive and time-consuming calculations. In this work, was developed a versatile and friendly-user software for a PC-type computer encompassing both methodologies. The software is flexible allowing for kinetic data evaluation such as the activation energy for sintering and sintering maps. Details of the software along with its application to investigate the sintering process of 10 mol% gadolinia-doped ceria are described.

Abstract: The search for a simple, accurate model to predict the sintering behavior is still a valid challenge facing the particulate materials industry. In spite of the sophistication of the before proposed methods, most models have not yet attained a desirable level of applicability. All just describe the micro sintering process but fail in controlling the densification behavior. The master sintering curve (MSC) is a model in densification which can adequately predict sintering results and is independent of heating history. The MSC can give better understanding of arbitrary sintering process and be introduced into industry production successfully. This paper provides a detailed overview of the MSC, including the construction, application, complications and some improvements of the concept.

Abstract: The master sintering curve (MSC) of nanocomposite WC-MgO was constructed based on the combined-stage sintering model. Nano-sized WC-4.3wt%MgO powder with average particle size of 35nm was synthesized by high-energy ball milling, and then uniaxially pressed at the pressure of 500MPa to fabricate green compacts. The shrinkage response of the compacts, used to construct the master sintering curve, were studied by dilatometric runs at two constant heating rates of 5°C/min and 10°C/min up to 1900°C. Using the estimated activation energy, the master sintering curves were established and compared to acquire an optimum value (Q=361.8 kJ/mol). The obtained MSC was validated by non-isothermal sintering with the identical green compacts. The results demonstrate that the MSC can be applied successfully to predict and control shrinkage level and final density during heating up regardless of heating rates.

Abstract: With a view of simulating the dimensional changes during sintering of rectangle green bodies, the thermo-mechanical behavior of zirconium powder compacts at high temperature is investigated. In order to better describe the behavior of anisotropic shrinkage, the revised Master Sintering Curve is modified. Finite element calculations are then carried out on the green body according to the modified equation with the different shrinkages coefficients at the different stages of sintering. The possible causes of the anisotropic shrinkage are explained by macro-surface energy model. Numerical shape predictions have been compared with experimental data, which are considered to be in good agreement.

Abstract: Master sintering curve (MSC), in which the sintered density is a unique function of the integral of a temperature function over time, is insensitive to the heating path. In this paper, the densification of rutile TiO2 was continuously recorded at heating rates of 2 °C/min and 5 °C/min, respectively, by dilatometer. The MSC for rutile TiO2 was constructed for pressureless sintering using constant heating rate date based on the combined-stage sintering model. The construction and application of the MSC were described in detail for different thermal histories. The MSC can be used to predict and control the densification, final density, and microstructure evolution during the whole sintering. The final density can be predicted for an arbitrary temperature–time path. A good consistence exists between the predicted and experimental densification curve, confirming that it is possible to accurately predict and control the sintering behavior of TiO2 from the initial to final stage of sintering using MSC.

Abstract: A nano-sized CeO2 powder was synthesized by a modified glycine nitrate process (MGNP). The synthesized powder was characterized by X-ray diffraction (XRD), the Brunauer Emmett Teller (BET) method, and transmission electron microscopy (TEM). The lattice parameter and crystallite size were determined by the Rietveld refinement of X-ray diffraction patterns. The shrinkage kinetics of the green body was continuously monitored in air and in oxygen atmospheres using a high temperature dilatometer up to 1500°C. During the high temperature sintering in air a redox reaction occurred (Ce4+ was partially reduced to Ce3+, and oxygen gas was released). The redox reaction influenced the sintering behaviour of CeO2, resulting in a decrease in density. On the basis of shrinkage kinetics data in oxygen atmosphere a master sintering curve for CeO2 was constructed. Using the concept of the master sintering curve, the densification behaviour in oxygen atmosphere was successfully predicted from early to final stages of sintering. During sintering of CeO2 at lower temperature in air atmosphere a significant contribution of the surface diffusion was observed.

Abstract: The Master Sintering Curve (MSC) is quite useful for analyzing the shrinkage behavior of ceramics. It is possible to compare shrinkage behavior using MSCs that are obtained from different firing profiles. In this study, shrinkage behavior during sintering of green bodies of several kinds of Al2O3 based ceramics were evaluated, using an electric furnace equipped with a dilatometer to be controlled based on the MSC theory. Although all of the samples shrank monotonically, shrinkage behavior depended on the additive and heating rate. The MSC theory was applied to analyze shrinkage behavior. As a result, a different MSC could be obtained in Al2O3 with and without the addition of MgO. In the pure Al2O3, a single MSC could be obtained from shrinkage curves by firing at a heating rate of 7.5-20oC/min, though the shrinkage curve at a heating rate of 3-5oC/min did not correspond with the MSC. In contrast, shrinkage curves at heating rate of 5-20oC/min were converged in the case of the MgO doped Al2O3 to obtain a unique MSC independent of firing profile. Apparent activation energy for sintering was estimated as 555 kJ/mol in the pure Al2O3 and 880 kJ/mol in the MgO doped Al2O3. The firing profile to obtain a requested sintering shrinkage curve was predicted from the resultant MSC. A comparison between the predicted and the experimental shrinkage curves, showed good consistency, thus confirming that it is possible to control shrinkage behavior using the MSC.

Abstract: In this paper a practical approach to the analysis of sintering of BaTiO3 using the Master Sintering Curve concept has been presented. Non-isothermal sintering of high-purity non-doped BaTiO3 ceramics was monitored using a sensitive dilatometer at three different heating rates (10, 20 and 30 oC/min) up to 1380oC. Densification of BaTiO3 during sintering was analyzed using the Master Curve Sintering Theory. A MSC was defined characterizing the sintering behavior of barium-titanate regardless of the heating rate. Construction of the MSC enabled estimation of the process activation energy. Using defined MSC, densification behavior of BaTiO3 ceramics during sintering can be predicted for arbitrary temperature-time excursions and these predictions can be used in controlling and planning the sintering process of this material.