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51.
《Ceramics International》2016,42(8):9836-9843
Metals and alloys (such as Al, Si, Al–Mg and Al–Si) are commonly added to MgO–C refractory bricks as antioxidants due to their effectiveness to prevent carbon oxidation (in the 600–1400 °C range) and their low cost. These additives act at different temperatures and react with refractory components and gases in the environment, inducing significant changes in the resultant microstructure and affecting the overall thermo-mechanical performance of these products. This work addresses the evaluation of physical properties, cold and hot mechanical resistance, as well as in situ hot elastic modulus (E) measurements in the temperature range of 30–1400 °C for MgO–C bricks containing antioxidants (Al, Si or Al–Mg alloy) in a reducing atmosphere. Cured and fired samples of the designed formulations were evaluated throughout 1 or 2 heating-cooling cycles. Despite the improved mechanical behavior (higher cold crushing strength and hot modulus of rupture) of the antioxidant-containing formulations, compared to the additive-free MgO–C sample, the interaction of the selected additives with the refractory components and CO(g) led to a generation of phases (i.e., Al4C3, Al2O3, SiC, SiO2, MgAl2O4) that could not be well accommodated in the microstructure. Consequently, the in situ E drop was observed during cooling (mainly below 600 °C) of the antioxidant-containing sample due to crack and flaw formations. Si and Al–Mg were the most promising antioxidants, whereas the Al-containing composition showed the highest E damage level after two heating/cooling cycles up to 1400 °C for cured samples. Based on the elastic modulus profiles with the temperature, the results also indicated the best working conditions for these ceramic materials. 相似文献
52.
《Ceramics International》2016,42(5):5617-5622
We have synthesized a MgO transparent ceramic by spark plasma sintering (SPS) and studied the dosimeter properties for X-ray detections, in comparison with the single crystal form. Further, we have characterized the optical and scintillation properties. Despite the same material compositions, the photoluminescence (PL) of the ceramic sample showed dominantly around 450 nm whereas the single crystal sample had a dominant emission in the NIR range. The PL lifetime of 450 nm were measured to be ~10 and ~50 ns which were typical for emissions by F+ center in MgO. The scintillation spectra were similar to those observed in PL, but the lifetime was much longer on the micro-second scale. The TSL glow curves of MgO ceramic showed a main peak around 140 °C. The TSL spectrum at 140 °C had a broad emission band in the 300–400 range and around 600 and 750 nm, which approximately coincide with the scintillation spectra. The TSL response was confirmed to be linear to the irradiation dose for both samples over the dose range from 0.1 to 1000 mGy. 相似文献
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Shishuai Li Huanbei Chen Weide Wang Dongxu Yao Yongfeng Xia Yu-Ping Zeng 《International Journal of Applied Ceramic Technology》2022,19(5):2873-2882
In this work, the effects of Y2O3/MgO ratio on the densification behavior, phase transformation, microstructure evolution, mechanical properties, and thermal conductivity of Si3N4 ceramics were investigated. Densified samples with bimodal microstructure could be obtained by adjusting the ratio of Y2O3/MgO. It was found that a low Y2O3/MgO ratio facilitated the densification of Si3N4 ceramics while a high Y2O3/MgO ratio benefited the phase transformation of Si3N4 ceramics. Best mechanical properties (flexural strength of 875 MPa, and fracture toughness of 8.25 MPa·m1/2, respectively) and optimal thermal conductivity of 98.04W/(m·K) were achieved in the sample fabricated with Y2O3/MgO ratio of 3:4 by sintering at 1900°C for 4 h. 相似文献
56.
Dongqing Wang Mao Chen Yang Jiang Shuai Wang Zhixing Zhao Tim Evans Baojun Zhao 《Journal of the American Ceramic Society》2020,103(12):7299-7309
Phase equilibria and liquidus temperatures in the CaO–SiO2–Al2O3–MgO system at a CaO/SiO2 weight ratio of 0.9 in the liquid phase have been experimentally determined employing high-temperature equilibration and quenching technique followed by electron probe X-ray microanalysis. Isotherms at 1573, 1623, 1673, and 1773 K were determined and the primary phase fields of wollastonite, melilite, olivine, periclase, spinel, and corundum have been located. Compositions of the olivine and melilite solid solutions were analyzed and discussed. Comparisons between the newly constructed diagram, existing data, and FactSage predicted phase diagrams were performed and differences were discussed. The present study will be useful for guidance of industrial practices and further development of thermodynamic modeling. 相似文献
57.
北京放射性核束装置在线同位素分离器(BRISOL)采用100 MeV、200 μA回旋加速器提供的质子束打靶产生中、短寿命放射性核束,在线分析后供物理用户使用,其质量分辨率好于20 000。为开展20Na核的奇异衰变特性研究,研制了氧化镁靶,并采用100 MeV质子束轰击氧化镁靶在线产生了20~26Na+的钠同位素放射性核束。当质子束流强为8 μA时,20Na+离子束的最大产额为2×105 s-1,21Na+离子束的最大产额为4×108 s-1。完成了北京放射性核束装置首个放射性核束物理实验,累计供束近200 h。 相似文献
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Magnesia whiskers have been made by hydrolysis of MgCl2–KCl melt and conversion of magnesium hydroxide whiskers. The morphology of MgO whiskers was examined by SEM and TEM. Composition of products was identified by XRD. Comparisons have been made on the morphology and quality of the products by different methods. Discussions have been made on the efficiency, product quality control and scale-up feasibility of these methods. Whiskers prepared by hydrolysis have uniform diameter but other shapes of magnesia are often found. Conversion of Mg(OH)2 whiskers to MgO whiskers is simple and easy to scale-up, but the product often has many defects caused by decomposition. Nevertheless, the single crystal structure can be reserved as revealed by electron diffraction. XRD results show that the purity of products by hydrolysis is better than that by conversion. The conversion method is more hopeful for industrial production. 相似文献