New dielectric ceramics are prepared by the conventional solid-state ceramic route. Effects of LZB glass on sintering, phase purity, microstructure, and dielectric properties of Li 2 ZnTi 3 O 8 ceramics have been investigated. Adding LZB lowers sintering temperature from 1050°C to 875°C, and does not induce much degradation of dielectric properties. The 1.0 wt% LZB glass-added ceramic has better properties of e r = 23.9, Q 9 f = 31,608 GHz, τ f = À14.3 ppm/°C. Additions of TiO 2 markedly improve microwave properties. Typically, the Li 2 ZnTi 3 O 8 + 1 wt%LZB + 3.5 wt%TiO 2 sintered at 900°C shows e r = 26.1, Q 9 f = 45,168 GHz, τ f = À4.1 ppm/°C. Compatibility with Ag electrode indicates that this material may be applied to LTCC devices.
The key problem about the application of TiC/Fe composite ceramics in high temperature is the oxidation resistance. With an aim to investigate oxidation properties, the high density TiC/Fe ceramics was produced by self-propagating high-temperature synthesis method combined with pseudo hot iso-static pressing (SHS/PHIP). The oxidation kinetics of TiC/Fe ceramics were investigated by means of conducting the isothermal oxidation experiments in air at temperature of 550°C 900°C for up to 150 hours, and measuring the variations of the weight gains of the composites with the oxidation times. The microstructure evolution of the composites during the oxidation processing was studied by using SEM/EDS and XRD. Experimental results show that TiC/Fe ceramics basically follows a parabolic rule at high temperature. A detailed characterization of the microstructure and distribution of the phases within the scale following oxidation studies has been undertaken to suggest the possible mechanism for the oxidation of TiC/Fe ceramics.
TiC-Mo-Ni and TiC-WC-Mo-Ni cermet blocks have been obtained in situ by reactive hot pressing sintering. The phase structure and microstructure of the two cermets were compared to investigate the effect of the addition of WC. The results show that the chemical reactions between Ti, Mo and C in TiC-Mo-Ni system are relatively complete. However, there is a small amount of unreacted C powder in TiC-WC-Mo-Ni system, which is associated with the reaction between Ti and WC. The in-situ carbide grains are very fine with the size range of 0.5-2µm. The boundary morphology between the carbide grains and the binder phase changes from an angular shape to an almost rounded shape with the addition of WC.
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