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使用电熔镁砂、板状刚玉和分析纯氧化铁为原料,在1550℃埋石墨条件下高温烧成直径为20 mm厚10 mm的试样。使用X射线衍射仪分析试样的物相组成,使用Highscore Plus软件拟合试样中物相的衍射峰,根据特定晶面的晶面间距计算镁铁铝复合尖晶石的晶格常数和晶胞体积;用重铬酸钾容量法测试试样中氧化亚铁的含量;用扫描电子显微镜分析试样的微观结构;进行热力学计算阐述了镁铁铝复合尖晶石的生成机理。结果表明:制备的两种不同形貌的镁铁铝复合尖晶石,其晶格常数和晶胞体积均比标准卡片中MgO·Al_2O_3的大且其XRD谱中主强峰向左偏移;少量的MgO和Al_2O_3被C还原生成镁蒸气和铝蒸气,与CO和O_2发生气相沉积反应生成了针状MgO·Al_2O_3,高温下的液相促进了Al_(15.99)Mg_(7.64)Fe_(0.37)O_(32)相的生成。大量MgO与Al_2O_3反应生成了粒状MgO·Al_2O_3,Fe2+和Fe3+扩散进入MgO·Al_2O_3晶体内生成了Mg_(8.13)Al_(14.25)Fe_(1.13)O_(32)相;用重铬酸钾容量法测出,试样中FeO的含量为2.38%。 相似文献
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《中国粉体技术》2020,(3)
采用膜分散微反应器,利用共沉淀法研究镁铝尖晶石介孔材料的制备条件,考察合成条件对镁铝尖晶石纯度、晶粒尺寸、晶体相态和孔结构的影响,并成型得到Ni-Mo-MgAl_2O_4-γ-Al_2O_3催化剂;以质量分数为20%的小桐籽油为反应原料,在高温、高压加氢脱氧装置中对催化剂的加氢脱氧性能进行评价。结果表明:原料金属盐溶液浓度总和为0. 5 mol/L(其中镁、铝金属的物质的量比为1∶2)、反应pH为11、表面活性剂CTAB浓度为0. 001 mol/L、焙烧温度为1 000℃时,制备得到的镁铝尖晶石介孔材料具有较大的介孔面积和介孔体积;Ni-Mo-MgAl_2O_4-γ-Al_2O_3催化剂具有较大的比表面积和良好的机械稳定性、水热稳定性;在温度为360~390℃、压力为4. 0 MPa、空速为5. 0 h~(-1)、氢油质量比为200的工艺条件下,加氢脱氧油的收率大于79%。 相似文献
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《材料研究学报》2016,(2)
以无水氯化镁和无水氯化铝为原料,聚乙烯吡咯烷酮(PVP)为助纺剂,无水乙醇和N,N-二甲基甲酰胺(DMF)为溶剂,采用非水解溶胶-凝胶法制备纺丝前驱体溶液,利用静电纺丝技术获得镁铝尖晶石凝胶/PVP前驱体纤维,经900℃煅烧合成出镁铝尖晶石纤维。借助XRD,FTIR,SEM和TEM研究了凝胶化温度、凝胶用量和PVP用量等纺丝液参数对镁铝尖晶石纤维相组成及结构的影响。结果表明,直接添加混合溶液时,虽能合成出物相为镁铝尖晶石的纤维,但纤维交联严重,还出现了较多念珠状颗粒;当凝胶化温度为120℃时,纤维则出现了明显的断裂;纤维直径随凝胶用量和PVP用量的增加而增大。当凝胶化温度为100℃、凝胶用量为0.068 mol/L、PVP用量为0.045 g/m L时,纤维为镁铝尖晶石相,表面光滑、连续,直径均匀且细小,平均直径为121 nm,经1600℃煅烧后仍保持良好的纤维形貌。 相似文献
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以烧结板状刚玉和电熔镁铝尖晶石为原料、磷酸为结合剂,在1680℃下制备了刚玉-镁铝尖晶石复合耐火材料样品。在1500℃、0.2 MPa的条件下保温50 h测试试样高温蠕变性能,采用XRD、SEM和EDS分析蠕变前后试样的物相组成及显微结构,分析镁铝尖晶石添加量对刚玉-镁铝尖晶石复合耐火材料高温蠕变性能的影响。结果表明:刚玉-镁铝尖晶石复相材料较纯刚玉材料有着更好的抗蠕变性。镁铝尖晶石骨料在蠕变过程中会与氧化铝基质之间发生固溶反应而在尖晶石颗粒周围形成二次尖晶石层,有效连接了基质与骨料,提高了试样的抗蠕变性。在二次尖晶石层形成的过程中由于Mg;有着更高的迁移速率和在反应界面两侧较高的厚度比,会诱发柯肯达尔效应,导致界面处空位大量积累和孔隙的产生。 相似文献
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以Mg(NO3)2.6H2O、Al(NO3)3.9H2O为原料,Na2CO3、NaOH为沉淀剂,采用化学共沉淀法制得MgAl2O4尖晶石前驱体。用TG、XRD、TEM及物理吸附仪研究了试样的热稳定性、物相组成、显微形貌和表面性能。结果表明:前驱体经800℃处理后,几乎全部转变成粒径为10nm左右的MgAl2O4尖晶石超细粉末,并且颗粒分散性好,比表面积大,为136.35m2/g,比传统制备镁铝尖晶石粉末的温度低600~700℃。 相似文献
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以Mg、Al双金属正丁醇盐为原料,采用溶胶凝胶法合成一次粒子粒径在100~300nm之间的高纯镁铝尖晶石超微粉体。干凝胶在800℃煅烧开始出现镁铝尖晶石相,在1200℃保温2h,形成晶相完全的镁铝尖晶石粉体。 相似文献
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S. V. Gabelkov R. V. Tarasov N. S. Poltavtsev Yu. P. Kurilo M. P. Starolat N. F. Andrievskaya A. G. Mironova E. G. Ledovskaya L. M. Litvinenko F. V. Belkin 《Inorganic Materials》2007,43(4):398-405
Fine magnesium aluminate spinel powder has been synthesized at low temperatures (300–500°C) via thermal decomposition of hydroxide mixtures prepared by coprecipitation from nitrate solutions. The precipitates consisted of simple and mixed magnesium and aluminum hydroxides in crystalline and amorphous states. The effect of heat treatment (100–800°C) on the phase composition of the precipitates was studied. The synthesized fine spinel powder has three levels of structure: spherical conglomerates (1.2–2 μm), ellipsoidal and irregularly shaped agglomerates of medium (300–700 nm) or small (100–150 nm) size, and primary particles (30–60 nm). The size of coherently scattering domains in the powder is 4 ± 1 nm. 相似文献
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Al2O3/MgO composite powders were synthesized via a partially wet chemical method. The effects of precipitant agent on the morphology, size and chemical composition of the resultant powders were investigated. The structures of rod-like with polygonal prism surface, platelet-like and uniform spherical Mg-compound particles were successfully prepared by using ammonium hydrogen carbonate, sodium hydroxide and ammonia water as precipitant agents, respectively. Analysis results proved that using ammonium hydrogen carbonate as precipitant agent produced nesquehonite (MgCO3·3H2O) Mg-compounds but in the case of other two precipitant agents, Mg-compound particles with magnesium hydroxide (Mg(OH)2) chemical composition were obtained. The morphological features of MgO particles in Al2O3/MgO composite powders were the same as individual Mg-compound particles. Furthermore, conversion of the Al2O3/Mg-compound precursor synthesized with ammonia water to pure magnesium aluminate spinel particles was studied. The precursor converted to pure magnesium aluminate spinel phase with 220?nm particle size at 1200?°C. 相似文献
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V. A. Gorshkov P. A. Miloserdov V. I. Yukhvid N. V. Sachkova I. D. Kovalev 《Inorganic Materials》2017,53(10):1046-1052
Experimental data are presented on the high-temperature synthesis of cast inorganic materials in the MgO–Al2O3 system. Experiments were carried out in multipurpose self-propagating high-temperature synthesis (SHS) reactors at an argon pressure p = 5 MPa. The starting mixtures used in the experiments consisted of molybdenum(VI) and magnesium(II) oxides and aluminum. It has been shown that, varying synthesis parameters, one can control the phase composition and microstructure of the final oxide products. We have optimized synthesis conditions for the preparation of single-phase magnesium aluminate spinel, MgAl2O4. The SHS products have been characterized by X-ray diffraction and local microstructural analysis. 相似文献
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Stoichiometric MgAl2O4 spinel nanoparticles were synthesized by microwave assisted combustion reaction from aluminium nitrate nanohydrate(Al(NO3)3.9H2O) and Sol-Gel prepared magnesium hydroxide(Mg(OH)2) in the presence of urea((NH2)2CO) as a fuel,in about 20 min of irradiation.X-ray diffraction(XRD) studies reveal that mi-crowave assisted combustion synthesis route yields single-phase spinel nanoparticles with larger crystalline size(around 75 nm) than other conventional heating methods.Scanning electronic microscope(SEM) images show nanoparticles with spherical shape and homogenous morphology.The surface area measurements(SBET) show crystals with 2.11 m2/g and 0.0033 mL/g pore volume. 相似文献
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Fabrication of translucent magnesium aluminate spinel and its compatibility in sodium vapour 总被引:2,自引:0,他引:2
P. Hing 《Journal of Materials Science》1976,11(10):1919-1926
The sintering behaviour of magnesium aluminate spinel on both sides of the stoichiometry has been investigated. It is found that the composition close to the stoichiometric composition, but slightly enriched in magnesia can be sintered to translucency in a free flowing hydrogen environment. The grain size decreases with magnesia content; the addition of yttria, however, results in a highly bimodal grain structure. Prolonged exposure of the spinel in a high temperature sodium vapour environment forms Na2O · 5Al2O3 and some traces of Na2O · 11Al2O3 predominantely at the grain boundaries and near the surface of the specimen. Some possible sintering mechanism and factors affecting the in-line transmission are discussed. 相似文献
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J. C. Debsikdar 《Journal of Materials Science》1985,20(12):4454-4458
Transparent non-crystalline stoichiometric magnesium aluminate gel-monolith was prepared by chemical polymerization reaction between aluminium alkoxide and magnesium salt. The reaction mechanisms of gel formation are discussed. The ovendried gel was freed from residual organics by chemical treatment with hydrogen peroxide solution. X-ray analysis of organic-free gel powder after heat treatment for 4h at 2000 C did not show any indication of phase separation. It is suggested that the use of sol-gel-derived powders could largely eliminate most of the problems associated with the conventional method of fabrication of optically transparent stoichiometric magnesium aluminate spinel. 相似文献
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Influence of Electrolytes on the Microstructure of Microarc Oxidation Coatings on Ti—6Al—4V Alloy 总被引:3,自引:0,他引:3
Dense ceramic oxide coatings of about 50μm may be prepared on Ti-6Al-4V alloy surface by alternating-current microarc oxidation in aluminate and silicate solutions, respectively.Their phase constituent and microstructure sere characterized using X-ray diffraction (XRD) and scanning electron microscopy(SEM). The results show that the electrolytic ions have incorporated into the interior of the coatings.The coating formed in aluminate solution is composed of the rutile TiO2 and TiAl2O5 phases rather than the rutile, anatase and amorphous SiO2 phases for the coating formed in silicate solution.However,TiAl2O5 content in the outer layer of the two coatings is much higher than in the inner layer.It is suggested that all these oxides may result from a rapid solidification of the molten coating in the microarc discharge zone. 相似文献
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Cobalt aluminate/γ-alumina (CoAl(2)O(4)/γ-Al(2)O(3)) nanocomposite pigment with mesoporous structure has been synthesized. The method simply involves adsorption of Co(2+) ion on the surface of a commercially available boehmite (AlOOH) powder followed by the reaction of Co(2+) and AlOOH at relatively low temperature (500 °C) to obtain CoAl(2)O(4)/γ-Al(2)O(3) composite nanopowders. The formation of γ-Al(2)O(3) from boehmite induces the in situ generation of isostructural CoAl(2)O(4) (both crystallize as cubic spinel) at such a low temperature. The obtained intense blue powder of optimal composition (53.6 wt % CoAl(2)O(4) in γ-Al(2)O(3)) can be dispersed in glycerol and characterized by UV-visible, X-ray diffraction, Raman spectroscopy, TEM, and nitrogen sorption analyses. Raman studies confirm the formation of CoAl(2)O(4) phase in γ-Al(2)O(3). TEM studies reveal the formation of flake shaped (5-10 nm in width and 10-25 nm in length) nanopowders, and these flakes are assembled to form mesoporous structure. The specific surface area, total pore volume and average pore diameter of this powder are estimated to be ~118 m(2) g(-1), 0.1375 cm(3) g(-1), and 4.65 nm, respectively. This composite nanopowder has been used as an active catalyst for the decomposition of H(2)O(2) at room temperature and the decomposition follows the first order kinetics with rate constant value close to 2.3 × 10(-2) min(-1). This pigment nanopowder can be reused for several cycles without noticeable degradation of its original catalytic activity. 相似文献