Key Engineering Materials Vol. 655

Abstract: The Nb₂AlC powders were synthesized by high temperature solid state reaction method ,in which, the mixed powders of niobium (Nb), aluminum (Al) , graphite (C) were used as raw materials in an atomic ratio of 2.0:1.1:1.0, respectively. And the heating temperature was adjusted in a range of 1600–1650°C in order to investigate the effects of different preparing conditions on the synthesis of Nb₂AlC .The phase composition and morphology of the products were analyzed by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) respectively. The results indicated that all the XRD peaks can be indexed as Nb₂AlC with improved crystallization at 1610°C.And the SEM photographs show that the products are layered morphology.The reaction mechanism of Nb₂AlC synthesis was also studied.

Abstract: In this study, the yellow sand waste with enormous reserves in the Inner Mongolia Tengger desert was taken as the main raw material mixed with the same regional clays for the infrared functional low-temperature porcelained tile. The mineral composition and granule feature of Tengri yellow sand as well as the micro-structure and infrared property of the fired body were discussed by the means of various testing such as the grain fineness distribution analysis, the XRD diffraction analysis, the SEM scanning electron microscope analysis, the coefficient of thermal expansion measure and the infrared performance detection. The results revealed that the natural mineral could be replaced by the yellow sand waste in large for preparing the environmental protection functional porcelained ceramics with favorable properties. The flexural strength of porcelained tiles sintered at 1140°C~1160°Ckeeps from 40 to 55Mpa when the high addition of yellow sand varies 75wt% to 90wt%. And the body is composed of high quartz as the main phase and little wollastonite phase which meets with the thermal shock resistant standard of the present architectural material .

Abstract: The traditional architectural ceramic body is mainly molded by compression forming process with dry power. The study introduced the starch into the body formula and the feasibility and correlate technological means of the situ solidification forming of fly ash architectural ceramics body with full barren materials were discussed. The body with full barren materials has a low green strength which is less than 1MPa by the traditional compression forming with dry power. But it could be improved greatly by optimizing the kind and amount of starch and the heat holding technologies in the forming process. The research showed that the body’s green strength is higher by introducing modified potato starch. The sintered body’s porosity and water absorption will be increased and lower flexural strength will be obtained by more starch. The body’s properties show the best when the amount of the starch reached 4wt% and the holding time for demoulding is 70min under the holding temperature what is 80°C. Under that molding condition, the green strength reached 3.61MPa, the flexural strength and water absorption of the sintered body reached 49.01MPa and 0.17% separately.

Abstract: Due to low water absorption, high bending strength and abrasion resistance, and excellent chemical and frost resistance, porcelain building ceramic tiles are the highest increase in production and sales over all other kind of building ceramic tiles materials. In this paper, porcelain building ceramic tiles was prepared by a fast firing process of rare earth tailings as the main raw material, low fused sand and Zhuji porcelain sand et al mixture. Effects of firing temperature and forming pressure on the sintering behavior and mechanical property of porcelain building ceramic tiles were studied. The sintering behavior of the fired samples was evaluated by linear shrinkage and water absorption. The fired samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and bending strength measurements. The sample is pressured at 15 MPa and sintered at 1180 °C and endowed with 0.04% of the water absorption and 51 MPa of the bending strength, due to denser microstructure. The obtained results would contribute to save natural resources and protect environment.

Abstract: With the rapid development of the world's industrial, issues of energy and environment have increasingly been prominent. Currently, the cost of building ceramics production needs a large number of raw materials and fuel, how to save energy and reduce consumption in building ceramic process is still hot spot of domestic and international research and the main development trends. Reducing the sintering temperature is one of the most efficient ways for energy conservation and consumption. In order to reduce the sintering temperature, fluxing agents are often used in preparing ceramic products. In this paper, the ceramic green bodies were prepared by mixing clays, lithium China stone and grammite, equivalent to “K₂O-Na₂O-Li₂O-CaO” normally used as fluxing agents. The effects of grammite on the properties of ceramic body were studied. The sintering behavior of the samples was evaluated by water absorption and bulk density. The fired samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with an energy dispersive X-ray spectroscopy (EDS) and bending strength measurements. The results showed that the optimum sintering temperature range of 40 °C and bending strength of 60 MPa could be achieved in the presence of 3 wt % grammite. The obtained results are useful in low-temperature sintering porcelain ceramic application.

Abstract: Lead zirconate titanate (PZT) is one of the most widely used ferroelectric and piezoelectric materials. Its piezoelectricity is widely used in the applications of structural health monitoring (SHM). Here, we use PZT ceramics as sensors to detect the deformation of structure using guided Lamb waves. In order to well analyze the multi-modes of Lamb waves and achieve detection of deformation in superposed wave peaks, correlation and Fourier transform were used to extract peaks in both time and frequency domain. In this paper, a 7050 aluminum beam and three-point bending test machine were utilized to test the changes of waves when different deformations were introduced. With the adjustment of correlation index, change of time delay and new peaks occurring in time domain demonstrated the change of deformations. In frequency domain, the change of central frequencies and magnitudes also demonstrated the change of deformations. The study shows the potential applications of PZT sensors in detection of deformation.

Abstract: In this paper, the influence of synthetic conditions (the molar ratio of Mg²⁺ and Al³⁺; the concentration of cationic; the aging temperature and time) on the grain size and crystallinity of Mg-Al layered double hydroxide (LDH) has been investigated systematically based on the orthogonal experiment. Mg-Al LDH was prepared using magnesite through chemical precipitation and hydrothermal methods. The samples were characterized by X-ray diffraction (XRD). The grain size which along a and c axis were calculated through Scherrer formula. The experimental results showed that the grain size along a axis increased with the rise of synthesis temperature, while the grain size along c axis reduced. It was also found that the aging temperature and time had a great influence on the crystallinity of Mg-Al LDH.