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硬硅钙石水热合成的形成历程及硝酸锶对它的影响 总被引:7,自引:2,他引:5
利用XRD,SEM,TEM等方法对动态水热法合成硬硅钙石的形成历程进行了研究,由C-S-H凝胶不能在高于200℃温度下稳定存在,使硬硅钙石在180℃和220℃时的形成历程不同,配料中加入硝酸锶,提高料浆的离子强度,产生原盐效应,降低了C-S-H凝胶的生成速率,延缓了硬硅钙石的形成,硬硅钙石合成过程中的料浆中固体粒子的ζ电位是不断变化的,加入硝酸锶,可以降低料浆固体粒子ζ电位的绝对值,有利于硬硅钙石纤维状晶体以及团聚体的长大。 相似文献
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硝酸锶对水热合成硬硅钙石球形团聚体的影响 总被引:4,自引:1,他引:3
硬硅钙石是一种用途广泛的保温材料,本工作以硝酸锶作为矿化剂,研究了在动态水热合成硬硅钙合成中,硝酸锶对硬硅钙石球形团聚体的影响。研究表明:在合成时添加硝酸锶,可以使水化硅酸钙(C-S-H)凝胶的ξ电位的绝对值减小,从而C-S-H胶团的凝聚长大,C-S-H凝胶粒度的增大是硬硅钙石球形团聚体增大的基础,Sr^2 进入到硬硅钙石晶体内引起其晶胞常数a和c的增大,促进硬硅钙石的纤维状晶体以及球形团聚体的长大,从而有利于得到轻质硬硅钙石材料。 相似文献
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用稻壳灰水热合成硬硅钙石的研究 总被引:7,自引:0,他引:7
研究了用稻壳灰作硅质材料水热合成硬硅钙石。结果表明,在合理选择钙硅比、水固比、搅拌时间,反应时间、反应温度等水热合成条件的情况下,稻壳灰中的SiO2能够与Ca(OH)2反应生成硬硅钙石晶体,并且这种纤维状的晶体还能相互交织成二次球形粒子。 相似文献
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采用动态水热法,以硅酸钠钙为原料合成硬硅钙石晶须,通过搅拌使晶须形成高孔隙率的球形颗粒. 考察了温度、时间和原料CaO/SiO2摩尔比等反应条件对硬硅钙石晶须及其球形颗粒孔隙率的影响. 结果表明,将CaO和SiO2按摩尔比0.90~1.15溶于Na2O浓度为20 g/L的NaOH溶液中,控制液固比为30 mL/g,以300 r/min的转速在220℃下水热反应7 h以上,可制备出直径约200 nm、长径比大于20的硬硅钙石晶须,晶须相互缠绕形成的球形颗粒孔隙率最高可达93%. 相似文献
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水热合成硅酸钙微孔球形颗粒 总被引:4,自引:2,他引:4
动态水热合成生成的硅酸钙微孔球形颗粒的空隙率可高达90%以上,颗粒由无数纤维状硬硅钙石晶体构成.讨论了合成工艺参数对形成球形颗粒的影响.反应物中SiO2 和CaO的比例需保持1∶1,否则反应最终产物中可能出现其它硅酸钙矿物.搅拌对形成球形颗粒起着决定性作用,在搅拌作用下C-S-H凝胶表面受到切向剪切力矩的作用,片状的凝胶被卷成为球形颗粒.在水热合成过程中加入矿化剂能够降低凝胶粒子ζ的绝对值,促进C-S-H凝胶形成大的团聚体,矿化剂的存在提高了由C-S-H凝胶团聚生成硬硅钙石的温度,从而保证C-S-H凝胶团聚有充足的时间形成大的球形团聚体. 相似文献
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The kinetics of solution of quartz and the crystallization of calcium silicate hydrate during hydro-thermal treatment of single crystals of quartz in saturated lime solutions were studied. Microscopic examination of sections of the product layer showed that the calcium silicate hydrate was of fibrous crystal habit and grew radially from nucleating centers in a general direction away from the quartz surface. X-ray diffraction established that the mineral was mainly xonotlite. The crystallization of the mineral did not follow the receding surface of the quartz; the product layer was extended only on the surface in contact with the lime solution. The silicate ions apparently diffused preferentially through the product layer although separate measurements proved that the membrane had no selective action against the diffusion of calcium ions. Plots of the weight of xonotlite versus square root of time gave straight lines indicating that the process was diffusion-controlled at 235° and 335°C. 相似文献
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Jung Sang Cho Jeong-Cheol Lee Shin Hye Chung Jeong Kon Seo Sang-Hoon Rhee 《Ceramics International》2014
The effect of grain size and density of hydroxyapatite particles, which were prepared by different spray-pyrolysis temperatures, on the sinterability of hydroxyapatite disk was investigated. Calcium phosphate solution (Ca/P ratio of 1.67 and 0.1 M concentration) was prepared by reacting calcium nitrate tetrahydrate and diammonium hydrogen phosphate solutions, and adding nitric acid. Spray-pyrolysis was carried out at 900 °C, 1200 °C, and 1500 °C at a carrier gas flowing rate of 10 L/min. The particles synthesized at 900 °C were large, hollow spheres with a hole at the outer surface, a broad size distribution, but had small grain sizes. Conversely, the particles synthesized at 1500 °C were small, solid spheres with a narrow size distribution, but had large grain sizes. The particles synthesized at 1200 °C had intermediate properties. A sinterability test conducted at 1100 °C for 1 h demonstrated that small and dense particles with large grain sizes showed a higher relative sintered density compared with large and hollow particles with small grain sizes. The results were explained in terms of the grain size and density of a particle, which were inversely and proportionally affected to sinterability. The practical implication of these results is that highly sinterable hydroxyapatite powders can be synthesized through spray-pyrolysis at a high temperature under a fixed initial concentration of calcium phosphate solution and flow rate of carrier gas. 相似文献
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从电石生产工艺出发,分析了氧化钙(俗称白灰)的杂质、生过烧、粒度和粉末率对电石生产节能降耗的影响,并介绍了采取的相应措施。严把白灰原料质量关,科学合理调整配比,可有效提高电石产品质量,降低电石生产成本。 相似文献
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以硬硅钙石作阻隔型填料,以金红石型二氧化钛和中空玻璃微珠为反射型功能填料,制备建筑外墙隔热涂料。研究了单掺硬硅钙石、金红石型二氧化钛、中空玻璃微珠以及复合添加3种填料对涂层隔热性能的影响。结果表明:单掺硬硅钙石、金红石型二氧化钛或中空玻璃微珠均可提高涂层隔热性能,硬硅钙石的适宜掺量为9%,金红石型二氧化钛的适宜掺量为30%,空心玻璃微珠的适宜掺量为20%;复合掺入硬硅钙石、金红石型二氧化钛和空心玻璃微珠可进一步提高涂层隔热性能,掺量为9%、30%和15%时,涂层的热反射率可达93.69%。按建筑行业标准JG/T235—2008《建筑反射隔热涂料》进行检测,涂料对波长为250~2 500 nm范围内的太阳反射比为0.85,半球发射率为0.87,隔热温差为13℃,符合标准要求;空心玻璃微珠、二氧化钛和硬硅钙石复合掺入后,发挥协同作用,能更加有效地提高涂层的隔热性能。 相似文献
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C. O. McHUGH T. J. WHALEN M. HUMENIK JR. 《Journal of the American Ceramic Society》1966,49(9):486-491
Finely divided molybdenum particles were dispersed in aluminum oxide to serve as inclusions for the inhibition of grain growth and secondary recrystallization during sintering. Conventional powder metallurgy techniques were used to fabricate compacts of aluminum oxide containing up to 16 vol% molybdenum. Three methods for developing a uniform dispersion of molybdenum particles in aluminum oxide are compared on the basis of the resulting microstructures. Specimens sintered in vacuum had densities approaching 98% of theoretical density with an average grain size of 2μ or less with no evidence of secondary recrystallization. The grain refinement is reflected in transverse rupture strength data with average strengths exceeding 80 kpsi and maximum strengths exceeding 100 kpsi. 相似文献