This work provides a new binder system, i.e., nano-lakargiite (NL) [CaZrO3] for unshaped refractories. NL powder formulation is done through a green and facile route, i.e., solution mixing technique, which is easily capable of recycling the byproducts. The waste eggshells are practiced as a source of CaO for the preparation of NL. The characteristics such as differential thermal/thermogravimetric (DTA-TGA) analysis, X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM) of the synthesized NL powder are accomplished. The single phase orthorhombic crystal structure with the Pnma space group of nano CaZrO3 (avg. crystallite size ∼19 nm) is attained at 1100 °C. High alumina castable specimens are formulated through the replacement of calcium aluminate cement (CAC) by the NL and heat treated at 1600 °C. The different physico-mechanical properties of the prepared castables are comprehensively investigated. The corrosion resistance in the molten glass at 1400 °C is also examined. The properties are also equated with the different advanced bonding systems of high alumina refractory castables. Significant progress in terms of densification, hot strength, and thermal shock resistance is achieved for the NL bonded refractory castables. 相似文献
Ceramics in the system (1-x)[0.5K0.5Bi0.5TiO3-0.5Ba(Zr0.2Ti0.8)O3]-xBi(Zn2/3Nb1/3)O3 have been fabricated by a solid-state processing route for compositions x≤0.3. The materials are relaxor dielectrics. The temperature of maximum relative permittivity, Tm, decreased from 150 °C for composition x=0, to 70 °C for x=0.2. The x=0.2 sample displayed a wide temperature range of stable relative permittivity, εr, such that εr=805±15% from −20 to 600 °C (1 kHz). Dielectric loss tangent was ≤0.02 from 50 °C to 450 °C (1 kHz), but due to the tanδ dispersion peak, the value increased to 0.09 as temperatures fell from 50 °C to −20 °C. Values of dc resistivity were of the order of ~109 Ω m at 300 °C. These properties are promising in the context of developing new high temperature capacitor materials. 相似文献
Ceramic wear maps have been developed to elucidate the complex interactions of the operating parameters, environments, and wear mechanisms. This paper summarizes these interactions for four ceramics, alumina, yttria-doped zirconia, silicon carbide and silicon nitride. Wear maps of these ceramics are systematically constructed using measured data under dry sliding, water, and paraffin lubricated conditions. For each material, different wear level regions acid wear transition zones are identified as a function of operating conditions and lubrication conditions. Wear mechanism studies performed within each wear region give rise to the wear mechanism maps. These maps facilitate material comparison and selection. The knowledge of wear, wear transitions, and wear mechanisms for a material pair enables realistic wear model development. One outcome of this approach is the recognition that a single wear model for a material pair cannot cover all operating conditions and environments.
As wear maps are constructed today, they are material pair specific. Within a material pair, there are microstructural dependence and surface properties influence. These parameters can change substantially for a given chemical composition of the material. How to incorporate these factors into the wear map research remains an issue. The search for a universal parameter such as the “asperity temperature” in Ashby's wear map continues in spite of mounting evidence that this may not be practical or feasible. But the hope remains that some parameters can be identified to normalize a large number of materials, operating conditions, and environments for tribological applications. Systematic wear maps are the first steps in this direction. 相似文献