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In the present work, comparative study of the dielectric behavior of Mn_0.4Zn_0.6Fe₂O₄ ferrite synthesized with and without H₂O₂ (hydrogen peroxide) has been presented. The dc resistivity has been improved by the citrate precursor method as compared to the ceramic method, and it is further improved by the addition of H₂O₂, which acts as a strong oxidizing agent. We have shown by means of X-ray diffraction that the resulting ferrite is made up of nanocrystallites and the average size of these nanocrystallites–calculated by Scherrer's formula–depends on the polarizer. The average particle size was found to be ~70 nm with H₂O₂ and ~88 nm without H₂O₂. The particle size is further confirmed by scanning electron microscopy. Both the results are found to be in good agreement. The decrease in dielectric constant and dielectric loss factor by addition of oxidizing agent is justified by inverse proportionality between the resistivity and dielectric constant. Possible mechanisms contributing to these processes have been discussed.

Nanostructured alumina ceramic templates have been fabricated by anodizing annealed high-purity aluminium foil. Pore diameter, pore separation and thickness in these alumina ceramics can be controlled using a range of acid electrolytes and anodizing voltage profiles. Thermal development of the structure of these robust and optically clear templates have been compared using XRD, thermal analysis and ²⁷Al MAS NMR techniques, showing that species substituted in the alumina lattice from decomposition of the acid electrolyte play a major role in determining the chemical and physical stability of the ceramic template at elevated temperatures. Deposition of ultrathin palladium films on the surface of these alumina templates creates robust membranes that enable hydrogen separation from mixed gas streams at elevated temperatures. Gas permeability measurements through these membranes as a function of temperature have demonstrated their very high selectivity for hydrogen.

An experimental investigation was carried out to evaluate the fracture pressure and behaviors of ceramic materials for a dome port cover of an air breathing engine. The experiments were performed in a shock tube, which had a working section of 70 mm in diameter and a total length of 6 m in the shock tube. The response pressure transducers were used to measure expansion pressure and reflection pressure of working section near the end edge of the shock tube. Fractured specimens collected from the dump tank were investigated for the fracture phenomenon of ceramics after testing. The fracture pressure increases as a specimen thickness increases, and as the specimen diameter decreases, respectively. The driven gas pressures P₂ obtained from theory and experiment agree well. The reflection wave pressures P₅ agree well comparatively with both results of equation and experiment at low pressure of P₄, but they do not agree well at high pressure of P₄. The fracture phenomena of the plate and dome specimens at the same diameter are broken into small particles in various thicknesses, but the fracture phenomenon of the plate specimen is not broken into the particles as specimen diameter decreases.

The friction and wear of silicon nitride (Si₃N₄) against silicon nitride (Si₃N₄) and zirconia (Y–TZP) and chilled cast iron and Alumina sliding under dry friction at room temperature conditions were investigated with pin-on-disk tribometer at sliding speed of 0.56ms^-1 and normal load of 50N, 80N, respectively. Based on the variety regulation of the wear maps, the wear mechanisms of the two couples were analyzed. Get the result of friction coefficient and maps of wear Rate of the Pin and the Disk. The results of comparing this couple is Si₃N₄/ chilled cast iron < Si₃N₄/ ZrO₂< Si₃N₄/ Si₃N₄< Si₃N₄/ Al₂O₃.

The use of silicon-based ceramics and composites as combustor liners and turbine vanes provides the potential of improving next-generation turbine engine performance, through lower emissions and higher cycle efficiency, relative to today's use of super alloy hot-section components. As a series of research for FOD resistant, a particle erosion wear test was carried out for continuous Pre-SiC fiber-reinforced SiC matrix composites with a new concept of lab. scale fabrication by LPS process. The result shows that aperture (some form of porosity) between fiber and interface has a deleterious effect on erosion resistance. Aperture along the fiber interfaces consequently causes a severe wear in the form of fiber detachment. Wear rate increase proportional as contents of open porosity increases. For nearly full dense composite materials of about 0.5 % porosity, are about 200 % more wear-resistant than about 5 % porous composites. Grain growth and consolidate condition of matrix which directly affects to FOD resistant are also discussed.

Polycrystalline (1-x)YBa₂Cu₃O_7-y + xBaTiO₃–CoFe₂O₄(x = 0.0, 0.2, 0.4, 0.6 wt.%) superconductors were prepared by solid state route. XRD analysis reveals no significant change in "b" parameter and increase in "a" and "c" parameters. SEM micrographs show no change in grain size of the samples. With the increase of BaTiO₃–CoFe₂O₄ (BTO–CFO) addition it has been analyzed that the superconducting transition temperatures (T_c) determined from standard four-probe method was decreased and dropped sharply with higher wt.% addition. Excess conductivity fluctuation analysis using Aslamazov–Larkin model fitting reveals transition of two dominant regions (2D and 3D) above T_c. The decrease in 2D–3D crossover temperature T_LD (Lawerence–Doniach temperature) in the mean field region has been observed as a consequent dominance of 3D region to increase in wt.% in the composite. The increasing value of ρ_wl and ρ₀ and the decreasing trend in the value of zero-resistance critical temperature (T_c0) indicates that the connectivity between grains decreases gradually with the addition of magneto–electric composite BTO–CFO.

Electron paramagnetic resonance (EPR) spectra of 0.01, 0.1 and 1.0 molar percentage (mp) of CuO doped derivatives of layered Na₂Ti₃O₇ ceramic have been reported. The results show that copper substitutes as Cu²⁺ at Ti⁴⁺ octahedral sites. From the dependence of loss tangent (tan δ) and the relative permittivity (ε′) on temperature and frequency, it is concluded that all the derivatives are of polar nature. The relaxation peaks at lower temperatures have been attributed to the presence of different types of dipoles, whereas peaks in the higher temperature region indicate possible ferroelectric phase transition. The dependence of conductivity on temperature show that electron hopping (polaron) conduction exists in a wide span of temperature range. However, the associated interlayer ionic conduction exists in a small temperature range. Interlayer alkali ion hopping mechanism of conduction has been proposed toward higher temperatures. The conductivity versus frequency plots reveal that the polaron conduction plays a prominent role toward the lower temperature side that diminishes with the rise in temperature. The most probable relaxation times for 0.01 and 0.1 mp CuO doped derivatives are almost same but it records an increased value for 1.0 mp doped material. This again attributes to the possible change in the symmetry of copper environment.

The SOFC interconnect materials La${}_{0.75}$Sr${}_{0.25}$Cr${}_{1-x}$O${}_{3-\delta }$$(x=0$–$0.04)$ were prepared using an auto-ignition process. The influences of Cr deficiency on their sintering, thermal expansion and electrical properties were investigated. All the samples were pure perovskite phase after sintering at 1400${}^{\circ }$C for 4 h. The cell volume of La${}_{0.75}$Sr${}_{0.25}$Cr${}_{1-x}$O${}_{3-\delta }$ decreased with increasing Cr deficient content. The relative density of the sintered bulk samples increased from 93.2% $(x=0)$ to a maximum value of 94.7% $(x=0.02)$ and then decreased to 87.7% $(x=0.04)$. The thermal expansion coefficients of the sintered bulk samples were in the range of $10.60$–$10.98\times 10^{-6}{\mathrm{\text{K}}}^{-1}$ (30–1000${}^{\circ }$C), which are compatible with that of YSZ. Among the investigated samples, the sample with 0.02 Cr deficiency had a maximum conductivity of 40.4 Scm${}^{-1}$ and the lowest Seebeck coefficient of 154.8 $\mu$VK${}^{-1}$ at 850${}^{\circ }$C in pure He. The experimental results indicate that La${}_{0.75}$Sr${}_{0.25}$Cr${}_{0.98}$O${}_{3-\delta }$ has the best properties and is much suitable for SOFC interconnect material application.

The ceramics with the composition of $x{\mathrm{\text{Na}}}_{0.5}{\mathrm{\text{Bi}}}_{0.5}{\mathrm{\text{TiO}}}_3$–$(1-x){\mathrm{\text{Ba}}}_{0.66}{\mathrm{\text{Mg}}}_{0.04}{\mathrm{\text{Sr}}}_{0.3}{\mathrm{\text{TiO}}}_3$ (NBT–BMST) in which $x$ = 0.2, 0.3, 0.4 and 0.5 were prepared successfully by the solid-state reaction method. The effects of NBT-doping on phase structure, morphology, temperature stability and dielectric properties had been investigated in detail. The XRD results show that the composites are composed of tetragonal perovskite. The phase structure of NBT–BMST is observed by scanning electron microscopy. The dielectric constant of $0.3{\mathrm{\text{Na}}}_{0.5}{\mathrm{\text{Bi}}}_{0.5}{\mathrm{\text{TiO}}}_3$–$0.7{\mathrm{\text{Ba}}}_{0.66}{\mathrm{\text{Mg}}}_{0.04}{\mathrm{\text{Sr}}}_{0.3}{\mathrm{\text{TiO}}}_3$ ceramic is $\sim$4100, the temperature coefficients of capacitance are −15%, 15% and 22% at −55${}^{\circ }$C, 60${}^{\circ }$C and 200${}^{\circ }$C, respectively. And the dielectric loss is less than 0.13, which is obviously superior to other compositions. The results of this work showed that the component of $0.3{\mathrm{\text{Na}}}_{0.5}{\mathrm{\text{Bi}}}_{0.5}{\mathrm{\text{TiO}}}_3$–$0.7{\mathrm{\text{Ba}}}_{0.66}{\mathrm{\text{Mg}}}_{0.04}{\mathrm{\text{Sr}}}_{0.3}{\mathrm{\text{TiO}}}_3$ is a promising candidate to high-temperature stable materials.

Microstructures, electrical transport and magnetic properties of Sr${}_2$Ti${}_{1-x}$Co${}_x$O${}_4(0\le x\le 0.3)$ ceramics are investigated. With Co doping, the Sr${}_2$Ti${}_{1-x}$Co${}_x$O${}_4$ ceramics remain tetragonal structure while the grain size is decreased with doping. Magnetic moment is enhanced with Co doping and ferromagnetism is observed at low temperatures for Co-doped Sr${}_2$TiO${}_4$. The Sr${}_2$Ti${}_{0.9}$Co${}_{0.1}$O${}_4$ and Sr${}_2$Ti${}_{0.7}$Co${}_{0.3}$O${}_4$ show semiconductor-like transport properties, which can be well fitted by Mott variable range hopping model. The results will provide an effective route to synthesize Sr${}_2$Ti${}_{1-x}$Co${}_x$O${}_4$ ceramics as well as to investigate the physical properties.

Ceramic has a great broad application in high-temperature environment due to its favorable mechanical, antioxidant and corrosion resistance properties. However, it tends to exhibit severe crack or fail under thermal shock resulting from its inherent brittleness. Microstructure property is a vital factor and plays a critical role in influencing thermal shock property of ceramic. The present study experimentally tested and characterized thermal-shock crack and residual strength of ceramic under different quench temperature, while two kinds of alumina ceramics with different grain size are employed. A two-dimensional (2D) numerical model based on statistical mesoscopic damage mechanics is introduced to depict the micro-crack propagation of ceramic sheet under water quenching. The effects of grain size on critical thermal shock temperature, crack characteristics and residual strength are studied. And the microscopic mechanism of the influence of grain size on thermal shock resistance of ceramic is discussed based on the crack propagation path obtained from experimental and simulation results. The qualitative effect and evolution change of grain size on thermal shock property of alumina ceramic will be summarized.