共查询到19条相似文献,搜索用时 78 毫秒
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在地聚合物体系中,浆体的组成及微观结构对于其硬化后的性能有着重要的影响。利用1H低场核磁共振仪对比研究了纯偏高岭土基(MK-100)及掺高钙粉煤灰(MK-85)的地聚合物的早期反应过程,探测了不同结合状态的水分子的质子信号,获得了水的纵向弛豫时间(T1)和横向弛豫时间(T2)。研究表明:1H低场核磁共振法适宜于研究地聚合物的早期反应过程,根据浆体纵向弛豫时间T1的加权平均值,可以将早期地聚合反应过程划分为加速期、减速期和稳定期3个阶段;高钙粉煤灰的加入使地聚合物浆体加速期缩短,减速期延长。早期地聚合反应过程中水的横向弛豫时间T2可以很好地表征毛细水或凝胶水的变化趋势。高钙粉煤灰的加入会延缓毛细水向凝胶水的转变过程。 相似文献
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采用低活性高硅尾矿预处理后作为硅铝原料(基质)与铝校正料偏高岭土复合,在碱硅酸盐溶液激发作用下制备地聚合物.通过ESEM和ATR-FTIR表征地聚合物净浆的早期水化反应机理,并对地聚合物砂浆试样后期的抗压强度及微观形貌进一步分析.结果表明:通过碱熔融与机械研磨复合的方式对尾矿进行预处理,可以有效促进地聚合物体系的早期水化反应进程,有利于铝硅酸盐凝胶相的形成,进而改善地聚合物后期的微结构及强度性能.本研究说明有可能通过改变硅铝原料性质的方式对地聚合物早期水化反应行为进行控制,从而调整地聚合物的后期性能(如强度性能、施工性能等),使其满足特定的工程应用需求. 相似文献
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地聚合物是硅铝质无机原料通过矿物缩聚生成的一种以离子键和共价键为主,范德华键为辅,由共用氧交替键合的硅、铝氧四面体组成的铝-氧-硅酸盐无定形网状结构的胶凝材料.地聚合物的水化反应是在碱性激发剂的作用下,硅氧键和铝氧键发生断裂-重组反应,再聚合生成地聚合物的过程.与硅酸盐水泥相比,地聚合物不仅可以充分利用工业固体废弃物为原料,而且可以在常温下反应制备,因此具有显著的利废节能特点.通过分析近年来国内外地聚合物的研究进展,重点论述了成分效应、外加剂和固化条件对地聚合物性能的影响,以及地聚合物混凝土的凝结和硬化特性、界面过渡区性质、钢筋粘结性质、耐高温性及耐久性,以期对地聚合物及其基材的深入认识和工程应用具有积极的参考作用. 相似文献
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根据单螺杆挤出机的聚合物挤出加工过程的混炼特性,提出一种新的形变混炼评定指标,并且结合常规单螺杆挤出机进行了计算分析,同时还与其它一些方法进行了比较。 相似文献
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Abdullah MM Jamaludin L Hussin K Bnhussain M Ghazali CM Ahmad MI 《International journal of molecular sciences》2012,13(4):4388-4395
This paper presents the results of a study on the effect of temperature on geopolymers manufactured using pozzolanic materials (fly ash). In this paper, we report on our investigation of the performance of porous geopolymers made with fly ash after exposure to temperatures from 600 °C up to 1000 °C. The research methodology consisted of pozzolanic materials (fly ash) synthesized with a mixture of sodium hydroxide and sodium silicate solution as an alkaline activator. Foaming agent solution was added to geopolymer paste. The geopolymer paste samples were cured at 60 °C for one day and the geopolymers samples were sintered from 600 °C to 1000 °C to evaluate strength loss due to thermal damage. We also studied their phase formation and microstructure. The heated geopolymers samples were tested by compressive strength after three days. The results showed that the porous geopolymers exhibited strength increases after temperature exposure. 相似文献
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To conduct a well‐planned plant shutdown, so as to reduce flare emissions for the sake of plant profitability and local environmental sustainability, one of the primary tasks is to perform comprehensive and precise accountings for flare emissions. Since the literature is still lacking systematic and quantitative studies, plant‐wide dynamic simulations are employed to simulate an ethylene plant shutdown and characterize its flare emission sources through which dynamic emission profiles of various emission species changing with respect to time are obtained. Plant shutdown emission inventories are enriched with details for point emission sources, and possible technical supports are provided to both industry and environmental agencies on evaluating and developing cost‐effective flare minimization strategies in the future. 相似文献
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Thomas Maischberger 《化学,工程师,技术》2019,91(12):1719-1723
The mass transfer coefficient (kL)and the value of the interfacial area (a) is used to characterize bioreactor systems for their oxygen transfer capability. The kLa value and the mixing time are amongst the most important performance indicators for bioreactors. Their calculation and modeling is extremely complex in highly aerated systems. This paper describes a new methodology for measuring the kLa value to accurately determine the coefficient. The valuable insights obtained allow for improved bioreactor characterization, thus, making it easier to meet regulatory requirements. Furthermore, examples outlining the benefits in the practical application of the new methodology are presented. 相似文献
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针对现浇混凝土结构早期变形开裂问题,设计了适用于轴向配筋试件的刚性框架端部约束收缩试验装置,进行不同配筋率和不同钢筋布置方式下C30混凝土干燥约束收缩试验,并以素混凝土试件和配筋试件端部自由收缩试验作为对比.测试配筋试件和素混凝土试件收缩变形、约束荷载、内部相对湿度随龄期的发展变化.结果表明:端部自由情况下,配筋试件干燥收缩小于素混凝土试件,约束率随配筋率增加而增大;端部约束情况下,配筋试件约束荷载远小于素混凝土试件,仅为素混凝土试件的1/8 ~1/17;干燥收缩过程中混凝土内部相对湿度呈"3阶段"规律变化.研究结果为混凝土早期变形开裂及防裂措施的研究提供参考. 相似文献
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