Papers by Keyword: Secondary Phase

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Authors: S. Shibagaki, K. Ito, C. Akita, M. Tanaka, Hajime Haneda
Authors: Keisuke Teranishi, Tomohisa Azuma, Masakazu Hirose
Abstract: The effect of adding Al2O3 to the PZT-PMN solid solution material for use for ceramic resonator was investigated. It has been found that when the amount of Al2O3 added to PZT-PMN is 0.3 wt% or below, it exists inside the crystal lattice as Al3+ ion and increases the stability of oscillation frequency over application of heat (heat resistance). It has been found that when more than 0.3 wt% of Al2O3 is added, the Al3+ ion that remained undoped will exist at grain boundary as secondary phase, and increase the strength.
Authors: Kiyotaka Tanaka, Kenichi Kakimoto, Hitoshi Ohsato
Abstract: Various KNbO3 powders have been derived from sol-gel process by using different preparation and heating conditions. KNbO3 powder derived from ethanol solution and fabricated at 800oC was most suitable as the raw material of KNbO3 bulk ceramics, because of the small grain size of about 250 nm and its homogeneous size distribution.
Authors: Tatsuo Fujimoto, Noboru Ohtani, Shinya Sato, Masakazu Katsuno, Hiroshi Tsuge, Wataru Ohashi
Abstract: Sublimation-recrystallization processes occurring during PVT are investigated from the viewpoint of quasi-equilibrium phase transitions of SiC. In addition to the elemental reaction processes of PVT, other phenomena such as silicon droplet formation and in-situ etching are also discussed based upon the Si-C binary phase diagram, and possible mechanisms are proposed.
Authors: Li Hong Han, Derek O. Northwood, Henry Hu
Abstract: Mg-Al-Ca alloys with 1wt.% and 2 wt.% Ca additions (AC51 and AC52) were cast by the Permanent Mold technique. The microstructures of the as-cast Mg-Al-Ca alloys were observed by SEM with EDS analysis. The secondary phases were mainly precipitated along the grain boundaries and exhibited a continuous network microstructure for the AC52 alloy and a divorced microstructure for the AC51 alloy. EDS microanalysis showed that the solute (Ca) content in the grains of the AC52 alloy is higher than that in the AC51. A three-sided pyramidal (Berkovich) diamond indenter was used to characterize the local nano-creep behavior at room temperature within the α-Mg in grains. The nano-creep results showed that the AC52 alloy has better creep resistance than the AC51 alloy at all loads at room temperature. The creep exponent n, obtained from the indentation creep data, changes from 6.3 to 3.0 for AC51 alloy and from 6.6 to 3.2 for AC52 alloy at a critical stress (132 MPa for the AC51 and 145 MPa for the AC52). The transition in creep behavior at higher stresses is associated with a change in the deformation mechanisms.
Authors: Chun Ya Luo, Ming Zhe Hu, Quian Huang, Yang Fu, Hao Shuang Gu
Abstract: The influence of ZnO and Nb2O5 additions on the sinterability, microstructure and microwave dielectric properties of (Mg0.95Ca0.05)TiO3 (abbreviated as 95MCT hereafter) ceramic is investigated. XRD patterns indicate that MgTi2O5 secondary phase can be effectively suppressed by ZnO and Nb2O5 additions, which is beneficial for improving the microwave dielectric properties. Appropriate amount of Nb2O5 addition can effectively improve the Qf value of 95MCT ceramic, which is suggested to be ascribed to the reduced oxygen vacancies. When the ZnO: Nb2O5 mole ratio is 1.5 and the co-doping content is 0.25wt%, the optimal microwave dielectric properties can be obtained Qf=72730GHz(6.8GHz), εr=20.29 and τf=-6.84ppm/°C and the sintering temperature of 95MCT is lowered from 1400°C to 1320°C.
Authors: B. Matović, Snezana Bošković
Authors: Ming Lin Wang, Hui Zhang, Zheng Hai Zhu
Abstract: With development of theory on microalloy in steel, now there are trends of adding microalloy in many kinds of steels, making the production and application of microalloy-steel enlarge. The second phase in microalloy-steel is significant for quality of casting. During the periods of continuous casting, conveying and heating, different process may affect precipitation and dissolution behaviors of casting according to different heating profile, further affect state of precipitation and distribution of secondary phase. In this paper, secondary phase in micro-alloy steel J55 were studied. Results show that some secondary phase particulars in micro-alloy steel J55 steel distribute along the austenitic grain boundaries when the temperature of slab is below 805°C in roller conveying; The distribution of secondary phase particulars in different thermal history slab are comparatively similar after heating; Al, Ti, C and N elements which dissolute in J55 steel has the feature of austenitic grain boundary segregation.
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